Advances In Aerogel Composites For Environmental Remediation 1st Edition Aftab Aslam Parwaz Khan Editor

Advances In Aerogel Composites For Environmental
Remediation 1st Edition Aftab Aslam Parwaz Khan
Editor download
https://ebookbell.com/product/advances-in-aerogel-composites-for-
environmental-remediation-1st-edition-aftab-aslam-parwaz-khan-
editor-46482962
Explore and download more ebooks at ebookbell.com

Here are some recommended products that we believe you will be
interested in. You can click the link to download.
Advances In Geology And Resources Exploration Ahmad Safuan Bin A
Rashid
https://ebookbell.com/product/advances-in-geology-and-resources-
exploration-ahmad-safuan-bin-a-rashid-44888202
Advances In Pattern Recognition And Artificial Intelligence Marleah
Blom
https://ebookbell.com/product/advances-in-pattern-recognition-and-
artificial-intelligence-marleah-blom-44899142
Advances In Communication Devices And Networking Proceedings Of Iccdn
2021 Sourav Dhar
https://ebookbell.com/product/advances-in-communication-devices-and-
networking-proceedings-of-iccdn-2021-sourav-dhar-45107982
Advances In Databases And Information Systems 26th European Conference
Adbis 2022 Turin Italy September 58 2022 Proceedings Silvia Chiusano
https://ebookbell.com/product/advances-in-databases-and-information-
systems-26th-european-conference-adbis-2022-turin-italy-
september-58-2022-proceedings-silvia-chiusano-45107984

Advances In Abdominal Wall Reconstruction Albert Losken Jeffrey Janis
https://ebookbell.com/product/advances-in-abdominal-wall-
reconstruction-albert-losken-jeffrey-janis-45210530
Advances In Oilwater Separation A Complete Guide For Physical Chemical
And Biochemical Processes Papita Das
https://ebookbell.com/product/advances-in-oilwater-separation-a-
complete-guide-for-physical-chemical-and-biochemical-processes-papita-
das-45285516
Advances In Smart Energy Systems Biplab Das Ripon Patgiri Valentina
Emilia Balas
https://ebookbell.com/product/advances-in-smart-energy-systems-biplab-
das-ripon-patgiri-valentina-emilia-balas-45334114
Advances In Biobased Fiber Moving Towards A Green Society Sanjay
Mavinkere Rangappa
https://ebookbell.com/product/advances-in-biobased-fiber-moving-
towards-a-green-society-sanjay-mavinkere-rangappa-45983380
Advances In Quantitative Economic Research 2021 International
Conference On Applied Economics Icqae Nicholas Tsounis
https://ebookbell.com/product/advances-in-quantitative-economic-
research-2021-international-conference-on-applied-economics-icqae-
nicholas-tsounis-46072866

Title page
ADVANCES IN AEROGEL
COMPOSITES FOR
ENVIRONMENTAL
REMEDIATION

Page left intentionally blank

Edited by
AFTAB ASLAM PARWAZ KHAN
Chemistry Department, Faculty of Science, and Centre of Excellence
for Advanced Materials Research, King Abdulaziz University, Jeddah,
Saudi Arabia
MOHAMMAD OMAISH ANSARI
Center of Nanotechnology, King Abdulaziz University, Jeddah,
Saudi Arabia
ANISH KHAN
Chemistry Department, Faculty of Science, and Centre of Excellence
for Advanced Materials Research, King Abdulaziz University, Jeddah,
Saudi Arabia
ABDULLAH M. ASIRI
Chemistry Department, Faculty of Science, and Centre of Excellence
for Advanced Materials Research, King Abdulaziz University, Jeddah,
Saudi Arabia
ADVANCES IN AEROGEL
COMPOSITES FOR
ENVIRONMENTAL
REMEDIATION

Elsevier
Radarweg 29, PO Box 211, 1000 AE Amsterdam, Netherlands
The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, United Kingdom
50 Hampshire Street, 5th Floor, Cambridge, MA 02139, United States
Copyright © 2021 Elsevier Inc. All rights reserved.
No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical,
including photocopying, recording, or any information storage and retrieval system, without permission in writing
from the publisher. Details on how to seek permission, further information about the Publisher’s permissions poli-
cies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing
Agency, can be found at our website: www.elsevier.com/permissions.
This book and the individual contributions contained in it are protected under copyright by the Publisher (other than
as may be noted herein).
Notices
Knowledge and best practice in this field are constantly changing. As new research and experience broaden our
understanding, changes in research methods, professional practices, or medical treatment may become necessary.
Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any
information, methods, compounds, or experiments described herein. In using such information or methods they
should be mindful of their own safety and the safety of others, including parties for whom they have a professional
responsibility.
To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for
any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any
use or operation of any methods, products, instructions, or ideas contained in the material herein.
Library of Congress Cataloging-in-Publication Data
A catalog record for this book is available from the Library of Congress
British Library Cataloguing-in-Publication Data
A catalogue record for this book is available from the British Library
ISBN: 978-0-12-820732-1
For information on all Elsevier publications
visit our website at https://www.elsevier.com/books-and-journals
Copyright
Publisher: Candice Janco
Acquisitions Editor: Marisa LaFleur
Editorial Project Manager: Mona Zahir
Production Project Manager: Punithavathy Govindaradjane
Designer: Victoria Pearson
Typeset by Thomson Digital

This book is dedicated to all the frontline workers who risked their life in fighting the deadly
COVID pandemic.

Page left intentionally blank

vii
Contents
Contributorsxv
Prefacexxi
1. Aerogel and its composites: fabrication and properties 1
Mohammad Omaish Ansari, Aftab Aslam Parwaz Khan, Mohammad Shahnawaze Ansari,
Anish Khan, Raviraj M. Kulkarni, and Vijaykumar S. Bhamare
1. Introduction 1
2. History and progress in the field of aerogels 2
3. Structure and properties of aerogels 4
4. Properties of aerogels 4
5. Synthesis of aerogels and its composites 6
5.1. Sol-gel process 6
5.2. Ageing of sol-gel 7
5.3. Drying of sol-gel 8
5.4. Carbonization 8
5.5. Silicon carbide aerogels by carbothermal reduction 9
6. Developments in aerogels and its composites 10
6.1. Silica aerogels 10
6.2. Organic aerogels 10
6.3. Carbon aerogels 11
6.4. Carbon nanotubes and graphene aerogels 11
6.5. Silicon carbide aerogels 12
6.6. Carbonaceous aerogels 12
7. Conclusions 12
References 13
2. Natural aerogels for pollutant removal 19
Sandeep R. Kurundawade, Ramesh S. Malladi, Raviraj M. Kulkarni,
and Aftab Aslam Parwaz Khan
1. Introduction 19
2. Properties 20
2.1. Porosity of aerogel 21
3. Types of aerogels 22
4. Important natural aerogels in pollutant removal 23
4.1. Noncellulose aerogel-type oil sorbents 23
4.2. Cellulose aerogel-type oil sorbents 23
4.3. Carbon aerogel extracted from pomelo peel 24
4.4. Nanocellulose-derived carbon aerogels 25

Contents viii
4.5. Carbon based aerogel 26
4.6. Carbon fiber aerogel (CFA) 26
5. Pollutant removal with cellulosic materials 27
6. Biomedical application of jackfruit aerogel 27
7. Advantages of natural aerogels in pollutant removal 27
8. Adsorption constants of some important natural adsorbents 28
9. Conclusions 29
References 29
3. Biomedical applications of aerogel 33
Varish Ahmad, Abrar Ahmad, Shah Alam Khan, Aftab Ahmad,
Mohammed F. Abuzinadah, Shahid Karim, and Qazi Mohammad Sajid Jamal
1. Introduction 33
2. Aerogel biomaterials for biomedical applications 34
2.1. Lignin-based aerogels 34
2.2. Pectin-based aerogels 35
2.3. Alginate-based aerogels 35
2.4. Starch-based aerogels 36
2.5. Chitosan-based aerogels 36
2.6. Protein-based aerogels 36
3. Bio-medical applications of aerogels 37
3.1. Antifungal and antibacterial activity 37
3.2. Aerogel in cancer treatment 39
3.3. Aerogel in drug development and delivery 39
3.4. Aerogel in diagnosis and bioimaging 40
3.5. Aerogel in orthopedics 42
3.6. Aerogel in implants 42
3.7. Aerogel in tissue engineering 43
3.8. Aerogel in identification of nucleic acid (DNA/RNA) 43
3.9. Aerogel as stem cell 45
4. Conclusions and future prospects 45
References 46
4. Carbon aerogel composites for gas sensing 49
Jamal Akhter Siddique, Shahid Pervez Ansari, and Madhu Yadav
1. Introduction 49
1.1. What is aerogel 49
1.2. Past to present aspects of aerogel 50
1.3. Carbon aerogel composite 51
2. Synthesis of carbon aerogel composite 52
2.1. Sol-gel transition (gelation) 52

Contents ix
2.2. Network perfection (aging) 52
2.3. Gel-aerogel transition (drying) 53
2.4. Carbonization process 54
3. Potential applications of carbon aerogel composite 54
3.1. Electronic and energy storage 55
3.2. Catalysts and catalytic supports 55
3.3. Water treatment 56
3.4. Thermal insulators and flame retardants 56
3.5. Gas storage and separation 56
4. Role of carbon-based aerogel composite in gas sensing 59
5. Mechanism of gas sensing by carbon aerogel composites 61
6. Conclusions 65
References 65
5. Conducting polymer-based aerogels for energy and environmental
remediation 75
Shahid Pervez Ansari, Ahmad Husain, Mohd Urooj Shariq, and Mohammad Omaish Ansari
1. Introduction 75
2. Conducting polymers 76
3. Conducting polymer aerogels (CPAs) 77
3.1. Synthesis of conducting polymer aerogels 77
3.2. Synthesis of gel precursors 77
3.3. PEDOT gel 78
3.4. PPy aerogel from PPy hydrogel 79
3.5. PANI aerogel from PANI hydrogel 79
4. Application of conducting polymer aerogels (CPAs) 79
4.1. VOC sensing 79
4.2. Adsorbing and separation 80
4.3. Electrochemical energy storage 81
4.4. Pressure sensing 82
4.5. Strain sensors 83
5. Outlook: challenges and prospects 84
References 85
6. Aerogels in photocatalysis 87
Jamiu O. Eniola, Mohammad Omaish Ansari, M.A. Barakat, and Rajeev Kumar
1. Introduction 87
2. Powdered photocatalysts 89
3. Aerogel photocatalyst 89
3.1. Metal-based aerogels 90
3.2. Organic-based aerogel 92

Contents x
3.3. Carbon aerogels 94
3.4. Silica aerogel 95
3.5. Hybrid aerogels 99
4. Properties of high-quality aerogel photocatalyst 100
5. The effect of various parameters on photocatalysis 102
5.1. The effect of solution pH 102
5.2. Concentration and nature of pollutants 102
5.3. Effect of dopant 103
6. Conclusions and future prospects 103
References 104
7. Aerogels for waterborne pollutants purification 109
Abdul Moheman, Showkat Ahmad Bhawani, and Abu Tariq
1. Introduction 109
2. Waterborne pollutants 110
2.1. Effects of waterborne pollutants on human health 110
3. Aerogels 114
3.1. Classification of aerogels 114
3.2. Application of aerogels in waterborne pollutants purification 115
References 120
8. Aerogel and its composites for sensing, adsorption, and photocatalysis 125
Akbar Mohammad, Mohammad Ehtisham Khan, Ahmed Abutaleb, Wahid Ali,
Mohd. Tauqeer, Taeho Yoon, and Moo Hwan Cho
1. Brief historical background and definition of aerogels 125
2. Aerogels and related materials 126
3. Water pollutions and remediation 126
4. Role of aerogels and its composites 128
5. Summary and future prospects 141
References 141
9. Metal and metal oxides aerogels in purification systems 145
Mohammad Ehtisham Khan, Jeenat Aslam, Akbar Mohammad, Ruby Aslam,
and Waleed Hassan Alhazmi
1. Overview of metal and metal oxides aerogels 145
2. Aerogels: classification and basics properties 148
3. Basic properties of metal and oxide-based aerogels 150
3.1. Porosity, hardness, and functionalization in aerogels 151
4. Fabrication of metal and metal oxides as an aerogel 151
5. Synthesis methods of aerogels 152
5.1. Brief elaboration 153

Contents xi
5.2. Sol-gel synthesis 153
5.3. Ageing of gels 154
5.4. Drying of gels 155
6. Role of metals, metal-oxides aerogels in purification system 156
6.1. Advances of aerogels in purification system 157
6.2. Metal oxides kinds of colorful aerogels 158
6.3. Metal, metal oxides-based aerogels in purification system 158
7. Conclusions 161
References 161
10. Adsorptive removals of pollutants using aerogels and its composites 171
Vijaykumar S. Bhamare, Raviraj M. Kulkarni, and Aftab Aslam Parwaz Khan
1. Introduction 171
2. Environmental air and water pollutants 173
3. Adsorptive removal of environmental air and water pollutants 175
3.1. Removal of CO
2
air pollutant 175
3.2. Removal of volatile organic compounds air pollutants 178
3.3. Removal of heavy metal ions from contaminated water 178
3.4. Removal of oil and toxic organic compounds from waste water 181
3.5. Adsorption and photocatalysis applications of aerogels for environmental
remediation 186
4. Conclusions 189
References 190
11. Aerogels as microbial disinfectant 201
Mohammad Oves, Mohd Ahmar Rauf, Mohinuddin Khan Warsi,
Fohad Mabood Husain, Mohammad Omaish Ansari, and Iqbal M.I. Ismail
1. Introduction 201
2. Aerogel synthesis 204
3. Aerogels for as antimicrobial agents 205
4. Aerogel for virus detection 207
5. Biocompatibility of aerogel 208
6. Aerogel intracellular uptake, biocompatibility, toxicity, biodegradability 208
7. Aerogel control release of drugs 209
8. Conclusion and prospects 209
References 210
12. Carbon aerogels for environmental remediation 217
Baljeet Singh and Mahak Dhiman
1. Introduction 217
2. Preparation of carbon aerogels 218

Contents xii
2.1. Synthesis of activated carbon aerogels 220
2.2. Synthesis of graphene aerogel 221
2.3. Synthesis of carbon nanotube aerogel 222
2.4. Synthesis of carbon fiber aerogel 223
2.5. Synthesis of nanocellulose aerogel 226
3. Application of carbon aerogels 230
3.1. Carbon aerogels for CO
2
capture 230
3.2. Carbon aerogels for VOC removal 232
3.3. Carbon aerogels for oil recovery from water 235
3.4. Carbon aerogels for heavy-metal ion removal from water 237
4. Conclusions 239
5. Challenges and future directions 239
References 240
13. Aerogels in the environment protection 245
Asim Jilani, Mohd Hafiz Dzarfan Othman, Mohsin Raza Dustgeer,
Ammar A. Melaibari, Imran Ullah Khan, and Ghani Ur Rehman
1. Introduction 245
2. Synthesis method 246
2.1. Sol-gel process 246
2.2. Critical drying method 246
3. Application in environmental protection 247
3.1. Metal and metal oxides based aerogels 248
3.2. Graphene-based aerogels 250
4. Conclusions 254
References 255
14. Carbon-based conducting polymers aerogels and their sensing behavior 259
Mohammad Shahadat, Asha Embrandiri, Parveen Fatemeh Rupani,
Rohana Adnan, T.R. Sreekrishnan, S. Wazed Ali, and Shaikh Ziauddin Ahammad
1. Introduction 259
1.1. Properties of conducting aerogels 260
1.2. Conducting aerogels for VOC’s sensing 265
2. Conclusions 271
Reference 271
15. Heavy metals scavenging using multidentate/multifunctional aerogels
and their composites 275
Mohammad Shahadat, Ajaz Ahmad Wani, Yahiya Kadaf Manea,
Rohana Adnan, Shaikh Ziauddin Ahammad, and S. Wazed Ali
1. Introduction 275
1.1. Synthesis of carbon aerogels 277

Contentsxiii
1.2. Sol-gel process 279
1.3. Resorcinol-formaldehyde (RF) carbon aerogel 280
1.4. Graphene aerogel 281
1.5. Comparative study of different drying techniques 283
2. Beneficent properties of aerogels/aerogel composites for heavy metal scavenging 284
2.1. Surface area and porosity 285
3. Functionalization and their relation with metal scavenging 286
4. Functional aerogels for metal removal 286
5. Conclusion and perspectives 291
References 292
16. Applications of nanocarbon-based aerogels in purifying industrial wastewater 297
Subia Ambreen, A. Dhivylakshmi, B. Shuruti, T. Dhivya, and Mohammad Danish
1. Introduction 297
2. Synthesis of carbon aerogels 299
2.1. Carbon nanotube-based aerogels 299
2.2. Graphene-based aerogels 300
2.3. Graphene oxide-based aerogels 301
3. Industrial wastewater 302
3.1. Domestic wastewater 302
3.2. Municipal wastewater 302
3.3. Industrial wastewater 303
4. Properties of industrial wastewater 303
4.1. Physical properties of industrial wastewater 303
4.2. Chemical properties of industrial wastewater 304
5. Treatment of industrial wastewater 304
5.1. Treatment of acids and alkalis present in wastewater 304
5.2. Treatment of other organics 305
5.3. Adsorption of metal ions 313
5.4. Adsorption of dyes 317
5.5. Absorption of oils/organic solvents 318
6. Conclusions 322
References 322
17. Bio-based aerogels for environmental remediation problems 329
Pankaj Bharmoria and Sónia P.M. Ventura
1. Introduction 329
2. Sol-gel synthesis of bio-based aerogels 333
3. Developments in bio-based aerogels post Kistler’s aerogels 334
4. Conclusions 340
References 341

Contents xiv
18. Bio-based aerogels and their environment applications: an overview 347
Fohad Mabood Husain, Altaf Khan, Rais Ahmad Khan, Jamal Akhter Siddique,
Mohammad Oves, Aftab Aslam Parwaz Khan, Mohammad Omaish Ansari,
and Hurija Dzudzevic Cancar
1. Introduction 347
2. Bio-based aerogels 348
2.1. Polysaccharide-based aerogels 348
3. Environmental applications of bio-based aerogels 352
4. Future prospects and outlook 354
References 354
19. Aerogel applications and future aspects 357
Naved Azum, Malik Abdul Rub, Anish Khan, Aftab Aslam Parwaz Khan,
and Abdullah M. Asiri
1. Introduction 357
1.1. Applications of aerogels 359
2. Future aspects of aerogels 364
3. Conclusions 364
References 364
Index 369

xv
Contributors
Ahmed Abutaleb
Department of Chemical Engineering, Jazan University, Jazan, Saudi Arabia
Mohammed F. Abuzinadah
Department of Medical Laboratory Technology, Faculty of Applied Medical Sciences,
King Abdulaziz University, Jeddah, Saudi Arabia
Rohana Adnan
School of Chemical Sciences, Universiti Sains Malaysia, USM, Penang, Malaysia
Shaikh Ziauddin Ahammad
Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology
IIT Delhi, New Delhi, India
Abrar Ahmad
Department of Biochemistry, Faculty of Science, King Abdulaziz University, Jeddah, Saudi
Arabia
Aftab Ahmad
Health Information Technology Department, Faculty of Applied Studies, King Abdulaziz
University, Jeddah, Saudi Arabia
Varish Ahmad
Health Information Technology Department, Faculty of Applied Studies, King Abdulaziz
University, Jeddah, Saudi Arabia
Waleed Hassan Alhazmi
Department of Mechanical Engineering, College of Engineering, Jazan University, Jazan, Saudi
Arabia
S. Wazed Ali
Department of Textile Technology, Indian Institute of Technology IIT Delhi, New Delhi, India
Wahid Ali
Department of Chemical Engineering Technology, College of Applied Industrial Technology
(CAIT), Jazan University, Jazan, Saudi Arabia
Subia Ambreen
Rajkiya Engineering College, Bijnore, Uttar Pradesh, India
Mohammad Omaish Ansari
Center of Nanotechnology, King Abdulaziz University, Jeddah, Saudi Arabia
Mohammad Shahnawaze Ansari
Center of Nanotechnology, King Abdulaziz University, Jeddah, Saudi Arabia
Shahid Pervez Ansari
Department of Applied Chemistry, Zakir Husain College of Engineering and Technology,
Aligarh Muslim University, Aligarh, Uttar Pradesh, India

Contributors xvi
Abdullah M. Asiri
Centre of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah,
Saudi Arabia; Chemistry Department, Faculty of Science, King Abdulaziz University,
Jeddah, Saudi Arabia
Jeenat Aslam
Department of Chemistry, College of Science, Yanbu, Taibah University, Al-Madina, Saudi Arabia
Ruby Aslam
Corrosion Research Laboratory, Department of Applied Chemistry, Faculty of Engineering and
Technology, Aligarh Muslim University, Aligarh, Uttar Pradesh, India
Naved Azum
Centre of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah,
Saudi Arabia
M.A. Barakat
Department of Environmental Sciences, Faculty of Meteorology, Environment and Arid Land
Agriculture, King Abdulaziz University, Jeddah, Saudi Arabia; Central Metallurgical R & D
Institute, Cairo, Egypt
Vijaykumar S. Bhamare
Centre for Nanoscience and Nanotechnology, Department of Chemistry, KLS Gogte Institute of
Technology, Belagavi, Karnataka, India
Pankaj Bharmoria
Chemistry Department, CICECO-Aveiro Institute of Materials, University of Aveiro, Aveiro,
Portugal
Showkat Ahmad Bhawani
Department of Chemistry, Faculty of Resource Science and Technology, Universiti Malaysia
Sarawak, Kota Samarahn, Sarawak, Malaysia
Hurija Dzudzevic Cancar
Department of Natural Sciences in Pharmacy, Faculty of Pharmacy, University of Sarajevo,
Sarajevo, Bosnia-Herzegovina
Moo Hwan Cho
School of Chemical Engineering, Yeungnam University, Gyeongsan-si, Gyeongbuk, South
Korea
Mohammad Danish
Department of Chemistry, Periyar Maniammai Institute of Science and Technology, Vallam,
Thanjavur, Tamil Nadu, India
Mahak Dhiman
Department of Chemistry & Chemical Biology, Rutgers, The State University of New Jersey,
Piscataway, NJ, United States
T. Dhivya
Department of Chemistry, Periyar Maniammai Institute of Science and Technology, Vallam,
Thanjavur, Tamil Nadu, India
A. Dhivylakshmi
Department of Chemistry, Periyar Maniammai Institute of Science and Technology, Vallam,
Thanjavur, Tamil Nadu, India

Contributorsxvii
Mohsin Raza Dustgeer
Department of Environmental Sciences and Engineering, Government College University
Faisalabad, Faisalabad, Punjab, Pakistan
Asha Embrandiri
Department of Environmental Health, College of Medicine and Health Sciences (CMHS),
Wollo University, Dessie, Ethiopia
Jamiu O. Eniola
Department of Environmental Sciences, Faculty of Meteorology, Environment and Arid Land
Agriculture, King Abdulaziz University, Jeddah, Saudi Arabia
Ahmad Husain
Department of Applied Chemistry, Zakir Husain College of Engineering and Technology,
Aligarh Muslim University, Aligarh, Uttar Pradesh, India
Fohad Mabood Husain
Department of Food Science and Nutrition, College of Food and Agriculture Sciences, King
Saud University, Riyadh, Saudi Arabia
Iqbal M.I. Ismail
Center of Excellence in Environmental Studies, King Abdulaziz University, Jeddah, Saudi
Arabia; Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah,
Saudi Arabia
Asim Jilani
Center of Nanotechnology, King Abdul-Aziz University, Jeddah, Saudi Arabia; Advanced
Membrane Technology Research Centre, Universiti Teknologi Malaysia, Johor Bahru, Johor,
Malaysia; School of Chemical and Energy Engineering, Faculty of Engineering, Universiti
Teknologi Malaysia, Johor Bahru, Johor, Malaysia
Shahid Karim
Department of Pharmacology, Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia
Altaf Khan
Department of Pharmacology and Toxicology, Central Laboratory, College of Pharmacy, King
Saud University, Riyadh, Saudi Arabia
Anish Khan
Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia;
Centre of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah,
Saudi Arabia
Imran Ullah Khan
Department of Chemical and Energy Engineering, Pak-Austria Fachhochshule, Institute of
Applied Sciences &Technology, Haripur, Khyber Pakhtunkhwa, Pakistan
Mohammad Ehtisham Khan
Department of Chemical Engineering Technology, College of Applied Industrial Technology
(CAIT), Jazan University, Jazan, Saudi Arabia
Rais Ahmad Khan
Department of Chemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
Shah Alam Khan
College of Pharmacy, National University of Science and Technology, Muscat, Sultanate of Oman

Contributors xviii
Raviraj M. Kulkarni
Centre for Nanoscience and Nanotechnology, Department of Chemistry, KLS Gogte Institute
of Technology, Belagavi, Karnataka, India
Rajeev Kumar
Department of Environmental Sciences, Faculty of Meteorology, Environment and Arid Land
Agriculture, King Abdulaziz University, Jeddah, Saudi Arabia
Sandeep R. Kurundawade
Department of Chemistry, KLE Technological University, Hubballi, Karnataka, India
Ramesh S. Malladi
Department of Chemistry, BLDEA’s V. P. Dr. P. G. Halakatti College of Engineering and
Technology, Vijaypur, Karnataka, India
Yahiya Kadaf Manea
Department of Chemistry, Aligarh Muslim University, Aligarh, Uttar Pradesh, India
Ammar A. Melaibari
Center of Nanotechnology, King Abdul-Aziz University, Jeddah, Saudi Arabia
Akbar Mohammad
School of Chemical Engineering, Yeungnam University, Gyeongsan-si, Gyeongbuk, South
Korea
Abdul Moheman
Department of Chemistry, Gandhi Faiz-e-Aam College (Affiliated to M. J. P. Rohilkhand
University), Shahjahanpur, Uttar Pradesh, India
Mohd Hafiz Dzarfan Othman
Advanced Membrane Technology Research Centre, Universiti Teknologi Malaysia, Johor
Bahru, Johor, Malaysia; School of Chemical and Energy Engineering, Faculty of Engineering,
Universiti Teknologi Malaysia, Johor Bahru, Johor, Malaysia
Mohammad Oves
Center of Excellence in Environmental Studies, King Abdulaziz University, Jeddah,
Saudi Arabia
Aftab Aslam Parwaz Khan
Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia;
Centre of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah,
Saudi Arabia
Mohd Ahmar Rauf
Use-Inspired Biomaterials & Integrated Nano Delivery (U-BiND) Systems Laboratory,
Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health
Sciences, Wayne State University, Detroit, MI, United States
Ghani Ur Rehman
Advanced Membrane Technology Research Centre, Universiti Teknologi Malaysia, Johor
Bahru, Johor, Malaysia; School of Chemical and Energy Engineering, Faculty of Engineering,
Universiti Teknologi Malaysia, Johor Bahru, Johor, Malaysia
Malik Abdul Rub
Centre of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah,
Saudi Arabia

Contributorsxix
Parveen Fatemeh Rupani
Department of New Energy, School of Energy and Power Engineering, Jiangsu University,
Zhenjiang, China
Qazi Mohammad Sajid Jamal
Department of Health Informatics, College of Public Health and Health Informatics, Qassim
University, Al Bukayriyah, Saudi Arabia
Mohammad Shahadat
School of Chemical Sciences, Universiti Sains Malaysia, USM, Penang, Malaysia; Department
of Biochemical Engineering and Biotechnology, Indian Institute of Technology IIT Delhi,
New Delhi, India
Mohd Urooj Shariq
Department of Chemistry, Aligarh Muslim University, Aligarh, Uttar Pradesh, India
B. Shuruti
Department of Chemistry, Periyar Maniammai Institute of Science and Technology, Vallam,
Thanjavur, Tamil Nadu, India
Jamal Akhter Siddique
Department of Chemistry, School of Basic and Applied Sciences, Lingaya’s Vidyapeeth,
Faridabad, Haryana, India
Baljeet Singh
CICECO—Aveiro Institute of Materials, Department of Chemistry, University of Aveiro,
Averio, Portugal
T.R. Sreekrishnan
Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology
IIT Delhi, New Delhi, India
Abu Tariq
Department of Chemistry, Aligarh Muslim University, Aligarh, Uttar Pradesh, India
Mohd. Tauqeer
Department of Chemistry, Aligarh Muslim University, Aligarh, Uttar Pradesh, India
Sónia P.M. Ventura
Chemistry Department, CICECO-Aveiro Institute of Materials, University of Aveiro, Aveiro,
Portugal
Ajaz Ahmad Wani
Department of Chemistry, Aligarh Muslim University, Aligarh, Uttar Pradesh, India
Mohinuddin Khan Warsi
Department of Biochemistry, Faculty of Science, University of Jeddah, Jeddah, Saudi Arabia
Madhu Yadav
Bio-organic Research Laboratory, Department of Chemistry, University of Allahabad, Allahabad,
Uttar Pradesh, India; Government Girls Inter College, Prayagraj, Uttar Pradesh, India
Taeho Yoon
School of Chemical Engineering, Yeungnam University, Gyeongsan-si, Gyeongbuk,
South Korea

Page left intentionally blank

xxi
Preface
Due to the burning of fossil fuels and industrial wastes, the pollution of the ecosystem
is increasing day-by-day. Thus, there is an immediate urge to educate the young masses
and professionals toward the newer materials capable of environmental remediation as
well as various advanced environmental remediation technologies. Aerogels, the light
yet mechanically strong material has the potential of being among the pioneer materials
for the above-mentioned field due to wide possibility such as large surface area, ease of
functionality, fabrication from natural and synthetic materials, etc. In spite of these quali-
ties, the aerogels have yet to gain attention and wide popularity, and this is the reason
for this book.
Advances in aerogel composites for environmental remediation provides a detailed innova-
tion in the field of fabrication of different types of aerogels such as traditional silica based
aerogels, polymeric aerogels, carbon aerogels, and composites aerogels. The wide contrast
in properties of the aerogels in contrast to the traditional materials is the main factor,
which makes it an exciting material for usage in newer and advanced technologies.
Being light weight, ease of functionality and fabrication as composites makes it highly
suitable material for different environmental remediation technologies such as adsorp-
tive removal of pollutants, vapor sensing of volatile organic compounds, microbial and
photocatalytic disinfection under natural and artificial systems, etc.
This book provides a wide-range exploration on the ongoing research and develop-
ments in the environmental remediation technologies using aerogel and its composites
written by from eminent writers of their field. The work discusses fabrication of various
aerogel composites along with their design and applications toward different environ-
mental remediation technologies. It will make a noteworthy appeal to scientists and
researchers working in the field of diverse aerogels for environmental sciences.
Advances in aerogel composites for environmental remediation consists of 19 chapters.
Chapter 1 deals with the basics of aerogels and their fabrication techniques. Rest of the
chapters deals with different types of aerogels and its composites, that is, natural aerogels,
carbon materials based aerogels, metal and metal oxide aerogels, conducting polymers
based aerogels, bio material based aerogels, and further their application in environmen-
tal remediation fields such as gas sensing, heavy metal removal, absorptive removal of
pollutants, microbial disinfection, biomedical application, etc.
Aftab Aslam Parwaz Khan
Mohammad Omaish Ansari
Anish Khan
Abdullah M. Asiri

Page left intentionally blank

1
Advances in Aerogel Composites for Environmental Remediation. http://dx.doi.org/10.1016/B978-0-12-820732-1.00001-1
Copyright © 2021 Elsevier Inc. All rights reserved.
CHAPTER 1
Aerogel and its composites: fabrication
and properties
Mohammad Omaish Ansari
a
, Aftab Aslam Parwaz Khan
b,c
, Mohammad Shahnawaze
Ansari
a
, Anish Khan
b,c
, Raviraj M. Kulkarni
d
, and Vijaykumar S. Bhamare
d
a
Center of Nanotechnology, King Abdulaziz University, Jeddah, Saudi Arabia
b
Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia
c
Centre of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah, Saudi Arabia
d
Centre for Nanoscience and Nanotechnology, Department of Chemistry, KLS Gogte Institute of Technology, Belagavi,
Karnataka, India
Chapter Outline
1 Introduction 1
2 History and progress in the field of aerogels 2
3 Structure and properties of aerogels 4
4 Properties of aerogels 4
5 Synthesis of aerogels and its composites 6
5.1 Sol-gel process 6
5.2 Ageing of sol-gel 7
5.3 Drying of sol-gel 8
5.4 Carbonization 8
5.5 Silicon carbide aerogels by carbothermal reduction 9
6 Developments in aerogels and its composites 10
6.1 Silica aerogels 10
6.2 Organic aerogels 10
6.3 Carbon aerogels 11
6.4 Carbon nanotubes and graphene aerogels 11
6.5 Silicon carbide aerogels 12
6.6 Carbonaceous aerogels 12
7 Conclusions 12
References 13
1 Introduction
The evolution of normal synthetic chemical methodologies has led to the deliberate syn-
thesis of porous materials. The porous materials have found large number of applications
in sensing, adsorption, catalysis, energy storage, etc. [1,2]. Among different porous materi-
als, aerogels are exciting owing to their peculiar properties such as low density, small pore
size, low optical index of refraction, etc. [3]. Aerogels, one of the most exciting material
of the 21st century that have been in use in space industry since 1960s, but recently have

Advances in Aerogel Composites for Environmental Remediation 2
also found newer applications in nowadays daily-used devices and all other industrial sec-
tors [4]. The aerogels are not one complete specific material or mineral with a definite set
of chemical formula, but rather, a material possessing unique porous specific geometrical
structure [5]. The fabrication strategy provides high porosity, high specific surface area,
low densities, and low thermal conductivities [6,7]. The aerogels are stretchable and high-
ly connected structures and thus can be easily fabricated into different forms and shapes.
Initially most of the work on aerogels was done on silica-based materials, but nowadays
many other materials such as polymers, carbonaceous materials, metal/metal oxides, etc.
have also been fabricated into aerogels [8–10]. The structure of aerogels consists of mostly
hollow space filled with air with very little solid material inside. This unique structure
gives it a ghostly appearance and hence is also called as a frozen smoke [11].
The first aerogels were created in 1931 by Samuel S. Kistler at the College of the
Pacific in Stockton, California. It was he who hypothesized that by using supercritical
drying (SCD) conditions it is possible to remove liquid out of gel without compact-
ing its shape and size [12]. He showed that at a critical point, the liquid phase can be
removed without disturbing the structure and the formation of liquid-vapor interfaces.
Apart from this, the capillary forces which lead to shrinkage during drying can also be
avoided by using SCD conditions. The Kistler method was tedious and went unnoticed
till merely 3 decades until Teichner and Nicolaon in 1960s prepared aerogels by com-
monly used sol-gel process [13]. The technique of Teichner and Nicolaon eliminated the
time-consuming salt removal and solvent-exchange steps. They produced silica aerogels
by using silicon alkoxide which speeded up the fabrication process and thus the final
aerogels can be made into few hours rather than days [14].
While the structure of aerogels is highly porous with pores in the range of nano-
meters, the incorporation of nanomaterials can further enhance their properties [15].
Carbon nanomaterials, metal, metal oxides, polymers, etc. based aerogels have shown ap-
plications in the field of sensors, energy storage, environmental remediation, etc. [16–18].
Thus, with the large number of possibilities of variety of aerogels-based composites,
this field is expected to be a big boom in near future for potential applications in vast
variety of areas. This chapter deals with the fabrication of aerogels and its composites,
their properties and applications in different areas. The work compiled here is far from
complete but covers most of the major developments and progress in this field.
2 History and progress in the field of aerogels
The pioneer discovery in the field of aerogels was done by Kistler who demonstrated
that the liquid part in the wet gel can be replaced by air under SCD conditions with-
out collapsing the original porous structure. Also, the capillary forces which dry the gel
into xerogel can also be avoided. The results got published in journal Nature in 1931
[19]. Due to the drying under supercritical conditions, the formation of liquid-vapor
meniscus at gel pores responsible for the mechanical tension in liquid and pore walls
responsible for gel shrinkage can be avoided [7]. This results in original porous structure,

Aerogel and its composites: fabrication and properties3
high surface area, and very low density in the aerogels. Besides silica, Kristler synthesized
alumina aerogels which was very weak and other aerogels of tungstic, ferric or stannic
oxide, and nickel tartrate.
The methodology of Kristler was cumbersome and the field was not much ex-
plored until in 1960s when Teichner and Nicolaon prepared aerogels from simple sol-gel
process. Teichner and Nicolaon eliminated the salt removal and solvent-exchange steps
which reduced time and fabricated silica aerogels by using silicon alkoxide. This process
initiated fast fabrication of aerogels from many days to few hours [20].
The advancement in technique resulted in scientist working in the design and fabrication
of aerogels using wide variety of materials such as: noble metal aerogels, that is, Ag, Au, Pt,
Pd [21], metal oxide aerogels, that is, SiO
2
, TiO
2
, ZnO, ZrO
2
[22], carbonaceous materials-
based aerogels, that is, CNT, graphene, nanodiamond-based aerogels [23–25], polymer-based
aerogels, that is, polyimide, polystyrene, conducting polymers, resorcinol-formaldehyde (RF)
[26], silica carbide-based aerogels [27], naturally occurring materials based aerogels, that is,
cellulose and proteins [28]. These developments have lead to a stage where the focus is on
their applications in advanced areas such as CO
2
trapping, coatings, energy storage, etc.
Due to wide potential possibilities of aerogels, the research in this field has grown
by leaps and bound in the last few decades. Fig. 1.1 demonstrates increase in the total
Figure 1.1 Total number of publications per year for the past 1 decade showing “aerogels composites”
in the content as per Science Direct record (Date of search: 09 January 2020).

Advances in Aerogel Composites for Environmental Remediation 4
number of publications per year for the past 1 decade showing “aerogels composites”
in the content as per Science Direct record (Date of search: 09 January 2020). Fig. 1.2
shows the evolution pattern of aerogels and its composites from 1930s by American
Scientist and chemical engineer Samuel Kistler.
3 Structure and properties of aerogels
Aerogels are solid with air pockets distributed throughout. Structurally they are large
number of particles fused together with lot of air in between. They can also be con-
sidered as foam having different shapes and sizes. The aerogels have very little solid
material and most of it, that is, approximately 99.8% of it is nothing but air. This gives
them ghostly appearance and thus is called as frozen smoke. Fig. 1.3 gives the represen-
tation of 3-dimensional network of silica aerogel. The well-connected different clusters
of SiO
2
can be clearly seen to be separated by large amount of void spaces with air in
between [29].
The aerogels of thermoset polyurea by Gu and coworkers [30] on scanning electron
microscopy characterization shows continuous structure of aerogel domains and large
pores. The pores are large enough and are in the micrometer range. This connectivity
and large void spaces in between gives aerogel their light weightlessness and compact
structure (Fig. 1.4).
4 Properties of aerogels
Low density and high porosity: Aerogels are highly porous solids and have extremely low
density which range from 0.0011 to ~0.5 g/cm
3
. The lightest aerogels prepared is silica
aerogel which is only 3 times heavier than air. The aerogels are open porous structure
Figure 1.2 Evolution pattern of aerogels and its composites.

Aerogel and its composites: fabrication and properties5
Figure 1.3 Three-dimensional network of silica aerogel with its detailed molecular structure. Repro-
duced with permission from Ref. [29].
Figure 1.4 SEM images of polyurea aerogels prepared using different content of Desmodur N3300A.
(A) PUA-0.1, (B) PUA-0.15 M, (C) PUA-0.2 M. Inset 1: fractured surface of aerogel domain, inset 2: skin
layer of aerogel domain. Reproduced with permission from Ref. [30].

Advances in Aerogel Composites for Environmental Remediation 6
and the air inside is not the trapped air, that is, not trapped inside solid pockets and the
diameters of pores range from <1–100 nm. They have huge internal surface of 10–2000
m
2
/g. This also gives low mean free path for the gas diffusion [31].
Acoustic properties: Aerogels have large sound absorption characteristics. Morettia
and coworkers [32] showed that small sized silica aerogels possessed transmission loss of
13 dB at 6400 Hz for 20 mm thickness.
Low thermal conductivity: The air inside aerogels has little space to move thus inhibiting
both convection and gas-phase conduction. This makes aerogels an excellent insulating
material. Yang and coworkers [33] showed that aerogel-enhanced hollow glass micro-
spheres insulation boards have thermal conductivity as low as λ=~ 0.0465 W/m K.
Color: The aerogels can be transparent, opaque, and can also be colored. Liu and
coworkers [34] prepared mechanically robust aerogel by self-organization of cellulose
nanofibers with polysiloxane cross-linking which were transparent to the visible light
spectrum. Similarly, virtually opaque aerogels can be prepared from graphene oxide to
yield spongy reduced graphene oxide aerogels [35]. Aerogels of various other colors
have also been reported such as silica, alumina, titania, zirconia are clear with rayleigh
scattering blue or white; iron oxide is rust red or yellow, opaque; chromia is deep green,
deep blue, or opaque; vanadia is olive green or opaque; neodymium oxide is purple or
transparent; samaria is yellow or transparent.
Functionalization: The surface of the aerogels offers possibilities for functionalization
with functional groups by chemical reaction (e.g., functionalization with OH, Cl, -CH
3
,
etc.) and physical deposition techniques (CVD deposition of magnetic layers, deposition
on surface by RF sputtering, pulsed laser deposition, atomic laser deposition, etc.). The
gel body on the other hand can be functionalized by embedding of particles inside or by
interpenetrating hybrid aerogel networks.
5 Synthesis of aerogels and its composites
Almost all the types of aerogels are synthesized using traditional sol-gel chemistry. A
synthetic procedure for preparation of aerogels consist mainly three steps: (1) Formation
of sol-gels; (2) Aging of the sol-gels; and (3) Drying of the sol-gels to form aerogels.
However, one more step is carried out to get carbon-based aerogels (carbon and carbide
aerogels) at high temperature of 600
o
C–2500
o
C under inert atmosphere of N
2
or Ar
gases to decompose H
2
and O
2
moieties [36].
5.1 Sol-gel process
Generally, aerogels of different types are synthesized using sol-gel reaction with different
starting precursors, operating and provision requirements [37]. Sol-gel process is simple,
economic, and effective. This process is found to be very useful in the manufacturing of
high standard materials which are used in different fields [38–42].

Aerogel and its composites: fabrication and properties7
Sol-gel process involves the synthesis of 3-dimensional network of inorganic aero-
gels in solution at low temperature. This synthesis takes place through the transition of a
colloidal sol (liquid) into a multiphase gel (solid) and thus it is called as sol-gel process.
During the formation of gel, liquid does not permit the solid network to get damaged
and the solid network does not permit the liquid to flow out [43]. The higher number
of cross-links present in the gel network offers greater mechanical strength to it.
The wet gels are named as alcogel and acetogel as the pore solvent is exchanged
for alcohol and acetone. The gels synthesized from natural-based precursors in aqueous
solution using sol-gel process are called as hydrogel. Precursors are starting materials
required for the synthesis of gels. Alkoxides are commonly used precursors for the gel
formation. Bradley and coworkers have thrown light on the important role of precursors
in the sol-gel process [44].
Generally, the synthesis of aerogel using alkoxide precursors takes place through sin-
gle-stage acid or base catalysis otherwise two-stage process involves first acid catalysis
and then base catalysis [45]. Reaction mechanism of sol-gel process shows that the OR
group of alkoxides is replaced by OH group to form silanol during hydrolysis reac-
tion. Silanol groups undergo polycondensation reactions to form siloxane bonds. The
polycondensation reaction in which water is formed as a side product is called as water
condensation. The polycondensation reaction in which alcohol is formed as a side prod-
uct is called as alcohol condensation. The different parameters such as variation in con-
centration of precursors, pH, temperature, solvent type, etc. affects the properties of gel
nanostructure [46,47]. Composite aerogels can be synthesized by incorporating either
dopant physically or organofunctional alkoxide derivatives chemically during the sol-gel
process. This will offer particular properties to the composite aerogels. Methyl functional
group offers the feature of stability to the composite aerogel against water. This is due
to hydrophobicity behavior of methyl functional group. The integration of polymeric
networks offers strong mechanical strength to composite aerogels [48,49]. During sol-
gel process, nanocatalysts or catalytically active elements can be incorporated into the gel
network structure to offer special features to composite aerogels [50–52].
5.2 Ageing of sol-gel
Ageing of the gel is done before drying step. The main aim of this step is to further growing
of gel network in the gelation solvent. Ageing offers strong mechanical strength to aero-
gels. The technique of ageing needs hours to days by soaking the gel in a suitable solvent
[46,53,54] at fixed conditions. Ostwald ripening phenomenon is taking place during the
ageing of sol-gel. In this phenomenon, the sol-gel network gets strengthened and coars-
ened [55]. The different factors such as variation in temperature, pH of the medium, and
time alters the kinetics of ageing step [54,56,57]. The textural properties, which include
porosity, surface area, and size of pores of sol-gel, will change during ageing of sol-gel. This
is a simple and robust step to offer excellent mechanical strength to sol-gel [58,59].

Advances in Aerogel Composites for Environmental Remediation 8
5.3 Drying of sol-gel
This is a very crucial step for the synthesis of aerogels. Drying of sol-gel involves the
cracking of the gel structure due to capillary forces which are set up in small pores. In
this process, gels are to be dried without disturbing their original porous structures.
There are main three methods of drying wet gels. These methods are SCD, ambient
pressure drying, and freeze drying.
SCD method involves the removal of liquid from pores by extraction at supercritical
conditions [60]. In this method, gels are dried at a critical point to remove the capillary
forces. The capillary forces do not exist in gel by SCD method. This method gives a solid
gel without disturbing its original porous structure. The conditions of SCD depend on
the solvent type [61,62]. SCD method is carried out using alcohol, acetone, and carbon
dioxide [48,49,63–65]. The drying of gels is safe and easy using supercritical CO
2
drying
as compared to supercritical alcohol drying [60,66].
Supercritical CO
2
drying reduces chemical durability of aerogels in the atmosphere.
Ambient pressure drying method is used to overcome the failure of SCD method. Am-
bient pressure drying is very prominent, easy, and convenient method to dry gels at am-
bient conditions. This is an appropriate method for mass industrial production [16,67].
Ambient pressure drying was introduced by Brinker for the synthesis of silica aerogels
[46]. This drying method involves the replacement of H from OH groups by hydro-
phobic functional groups. This is chemical modification of wet gel followed by ambient
pressure drying. Surface silanol groups undergo condensation reactions. As a result, non-
reversible shrinkage of gel structure takes place. This method produces surfaces with very
low energies. This decreases the surface tension. This method decreases the production
cost of aerogels.
Freeze drying is another method of drying gels. This method prevents phase bound-
aries between liquid and gas phase during drying of gels. This is an easy, cheaper, feasible,
and eco-friendly method to synthesize aerogels of high porosity [16]. In this approach,
the pore-liquid is first frozen and then sublimed at very low pressures [68–70]. The ma-
terials prepared by this drying approach are known as cryogels. The synthesized cryogels
are having maximum 80% porous structure. Cryogels are obtained in the form of pow-
ders. The freeze-drying approach is found to be suitable for fabrication of aerogels which
are used in medical studies. The higher temperature of other drying methods may break
the drug molecules present on the surface of aerogels.
5.4 Carbonization
Carbonization is an additional step used for the synthesis of carbon aerogels from car-
bonizable polymeric aerogels. Pekala introduced this method of carbonization in the
year 1989 after the synthesis of RF aerogels [71–73]. The organic aerogel is heated
above 600
o
C temperature and ambient pressure under nitrogen or argon inert gases.

Aerogel and its composites: fabrication and properties9
This heating at higher temperature decomposes oxygen and hydrogen moieties pres-
ent in the polymer chain. This develops and strengthens the carbon aerogel network
structure.
5.5 Silicon carbide aerogels by carbothermal reduction
Carbothermal reduction is another step used for the synthesis of highly porous mono-
lithic silicon carbide composite aerogels. These composite aerogels exhibits excellent
physical, thermal, and mechanical properties. Due to these properties, these composite
aerogels are used in many applications [74]. The porous monolithic silicon carbide com-
posite aerogels are synthesized from silica and carbon using carbothermal reduction.
SiO3CSiC2CO
2
+→ +

(1.1)
It was reported that the carbothermal reduction increases the thermal stability up to
650
o
C but also reduces the surface area of the aerogel. The flowchart for the synthesis of
aerogel is shown in Fig. 1.5.
SiO
2
+3C→SiC+2CO
Figure 1.5 Flowchart of the sol-gel process for the preparation of aerogels.

Advances in Aerogel Composites for Environmental Remediation 10
6 Developments in aerogels and its composites
6.1 Silica aerogels
The first inorganic aerogels fabricated accidently were silica gels [75]. Sodium metasili-
cate reacts with HCl to produce silica aerogels as per the following chemical equation.
NaSiO2HCl(x-1)HO SiOxHO2NaCl
23 22 2
++ →+

(1.2)
Sodium chloride is a side product and eliminated through dialysis process. The di-
alysis process was very complicated and time consuming. Kistler used this method to
prepare first aerogel [76]. Samuel Kistler synthesized aerogels using alumina, ferric oxide,
tungsten oxide, tin oxide, etc. Alkoxides are second generation precursors used for the
preparation of aerogels. Silica aerogels are very popular aerogels. Silica aerogels are prom-
inent materials with high porosity [5]. Silica aerogels possess nano porosity above 90%,
which exhibit very high thermal stability and very low thermal conductivity. Silica aero-
gels are very interesting materials for their applications in different fields [77–79]. Silica
aerogels exhibit poor mechanical stability. They have low strength and high brittleness.
Standeker and coworkers [80] reported that nanostructured silica aerogels having
open foam like structures exhibits low density around 5 kg/m
3
and large surface area
around 1000 m
2
/g. Aerogels using tetramethoxysilane (TMOS) exhibits hydrophilic be-
havior. This hydrophilic behavior is due to Si-OH groups present in silica aerogels which
promotes the adsorption of H
2
O. Hydrophobic silica aerogels can be synthesized by re-
placement of Si-OH groups with Si-R groups (R is alkyl group). This hinders the water
adsorption on the surface of hydrophobic silica aerogels.
Huijun Wu and coworkers [81] synthesized flexible silica aerogel composites rein-
forced with electrospun polyvinylidene fluoride web through electrospinning and sol-
gel procedure. In this context, aerogel composites were dried at temperature 70
o
C for
the period of 12 hours followed by further drying at temperature 100
o
C for the period
of 12 hours. This study reported the synthesis of three electrospun polyvinylidene fluo-
ride webs having different microstructures. This study revealed that electrospun poly-
vinylidene fluoride nanofibers are promising materials which offers better mechanical
strength and flexibility to silica aerogels. It also offers a low thermal conductivity to silica
aerogels for thermal insulation applications.
6.2 Organic aerogels
Organic precursors are used to synthesize organic polymers resting on strong (C-C)
covalent bonds and this is very easy as compared to silica precursors. Organic polymers
can be synthesized using sol-gel emulsion method with particle size varying from sub-
micrometers to a few hundred micrometers [82].
Organic aerogels such as melamine-formaldehyde (MF) and RF are widely investigat-
ed. MF aerogel can be synthesized by polycondensation of melamine and formaldehyde
in the presence of gelation catalysts such as NaOH or NaHCO
3
aqueous solution [72,83].
Na
2
SiO
3
+2HCl+(x-
1)H
2
O→SiO
2
xH
2
O+2NaCl

Aerogel and its composites: fabrication and properties11
Organic aerogels are also synthesized from precursors include phenolic-furfural
(PF) mixtures with polydimethylsiloxane (PDMS) [72,84], 2,3-didecyloxyanthacene
(DDOA) with C
2
H
5
OH or supercritical carbon dioxide as a solvent [85], polyacrylo-
nitrile (PAN) [86], polyisocyanates [87]. The latter gels which are mentioned here are
found to be very useful in many applications. They are used to fabricate heavily cross-
linked polyurethanes (PUR), polyureas, polyurethane imines, and polyisocyanurates
(PIR) aerogels. These aerogels offer better thermal insulation both under evacuated and
ambient conditions. Polyurethanes which are synthesized using CH
2
Cl
2
solvent are not
transparent. Therefore, aqueous MF solutions are used for obtaining optically transparent
aerogels [88].
6.3 Carbon aerogels
Carbon aerogels are novel and promising adsorbent materials having 3-dimensional net-
work of covalently bonded nanometer sized particles. They have large surface area and
highly porous structure. They are available in solid shapes, powder, and sheet forms. They
are considered as efficient and cheaper adsorbent materials for the purification of con-
taminated water [89].
Carbon aerogels are generally prepared by pyrolysis at higher temperature above
500
o
C of organic aerogels in inert atmosphere [83]. The organic aerogels are transformed
into an electrically conductive carbon network. RF is used to prepare carbon aerogels by
pyrolysis at higher temperature which possess large specific surface area (400–800 m
2
/g)
and higher mesoporous structure [90,91]. A huge amount of micro porosity is also ob-
served in carbon aerogels during pyrolysis at 1000
o
C. Shrinkage in aerogel structure was
also found [92,93]. Therefore, carbon aerogels are fabricated at the temperature 600
o
C
to get higher surface area. At this temperature, the pore radius is not severely affected
[94]. The parent RF aerogels can be doped with Ce or Zr to improve micro porous
structure of carbon aerogels. As a result, specific area of 2240 m
2
/g is obtained [95,96]
whereas graphitization above the temperature 1000
o
C is improved [97,98]. Barbieri and
coworkers reported that carbon aerogels show mass fractality which are obtained from
RF gelation in acetone and catalyzed by perchloric acid [99].
6.4 Carbon nanotubes and graphene aerogels
Carbon nanotubes (CNTs) and graphene aerogels are promising candidates for the re-
moval of contaminants and hence received considerable attention of the research com-
munities. CNTs and graphene aerogels have large surface area, higher electrical conduc-
tivity, resistivity to heat and fire, thermal stability, mechanical stability, well-defined and
controlled porous solid network. These prominent features furnish amazing benefits to
these aerogels for environmental remediation. These aerogels are used for the removal
of organic contaminants, toxic and non-biodegradable heavy metal ions and oils from
contaminated waste water. They are also used for the removal of toxic volatile organic
contaminants and CO
2
gas molecules from air [36].

Advances in Aerogel Composites for Environmental Remediation 12
Hong and coworkers [36] reported that CNT and graphene aerogels can be synthe-
sized by using various materials such as nanomaterials, solutions, and catalysts. Nanoma-
terials includes CNTs, graphene sheets, graphene flacks, graphene oxides (GO), reduced
graphene oxides (RGO), metal/metal oxide nanomaterials, and organic/polymers. Solu-
tions and catalysts include water and different sort of chemical compounds. Multiwall
carbon nanotubes (MWCNTs)—polyvinyl alcohol (PVA) hybrid aerogels are synthe-
sized using room temperature freeze gelation (RTFG) method. RTFG method is simple
and cheaper to produce hybrid CNTs and graphene aerogels on a large scale.
CNTs and graphene aerogels are lightest materials in the world [100]. CNTs and
graphene aerogels are having air packets in their network framework. They have large
surface area (400–1000 m
2
/g) and lowest thermal conductivity [36]. They are highly
elastic materials and exhibits strong mechanical strength. They can be easily recovered by
compression [101]. The graphene aerogels have lowest-density 0.16 mg/1 cm
3
which is
sevenfolds lighter than air (11.8 mg/1 cm
3
) [102,103]. These aerogels possess exceptional
features of hydrophobicity. They are very useful for the adsorptive removal of organic
contaminants, toxic heavy metal ions, harmful gases and oils from environment.
6.5 Silicon carbide aerogels
Silicon carbide aerogels were developed using carbothermal reduction process at very
high temperature (above 600
o
C) from a binary carbonaceous silica composite precur-
sor [104]. The highly porous monolithic silicon carbide aerogels were synthesized from
polyacrylonitrile [105] or RF cross-linked silica aerogels [104] at higher temperature. It
was reported that the carbothermal reduction increases the thermal stability up to 650
o
C
temperature but also reduces the surface area of the aerogel.
6.6 Carbonaceous aerogels
Adsorption technique is considered as a better approach due to its low cost and easy
operation as compared to other approaches for the removal of toxic organic contami-
nants and heavy metal ions [106]. The biomass-derived carbon materials are considered
as promising adsorbent candidate due to their large surface area and lighter in weight. Bi
and coworkers [107] fabricated twisted carbon fibers for the elimination of oil and or-
ganic solvents. Zhu and coworkers fabricated mesoporous magnetic carbon composites
to remove chromium (Cr
6+
) from contaminated water [108].
7 Conclusions
A large number of synthetic and natural materials has been fabricated into aerogels such
as metal, metal oxides, polymers, carbon materials, cellulose, etc. However, they are still to
be explored for real life applications. They offer huge prospects in environmental reme-
diation, energy storage due to their high porosity and possibilities of surface and internal

Aerogel and its composites: fabrication and properties13
functionalization. Efforts should be made to develop cost effective aerogels using natural,
synthetic materials, or by combination of both. Due to the wide fabrication and application
possibilities, the science of aerogels is expected to be a big boom for future technologies.
References
[1] A. Datt, N. Ndiege, S.C. Larsen, Development of porous nanomaterials for applications in drug delivery
and imaging, Nanomaterials for Biomedicine, 2012. ACS Symposium Series, vol. 1119.
[2] A. Bhaumik, Porous nanomaterials for energy, environment and biomedical applications, Mater. Sci.
Nanomater. 1 (2) (2017) e109.
[3] J.E. Amonette, J. Matyas, Functionalized silica aerogels for gas-phase purification, sensing, and catalysis:
A review, Microp. Mesop. Mat. 250 (2017) 100–119.
[4] N. Bheekhun, A. Talib, A. Rahim, M.R. Hassan, Aerogels in aerospace: an overview, Adv. Mater. Sci.
Eng. 2013 (2013) 406065.
[5] J. Fricke, T. Tillotson, Aerogels: production, characterization, and applications, Thin Solid Films 297
(1997) 212–223.
[6] S. Araby, A. Qiu, R. Wang, Z. Zhao, C.H. Wang, J. Ma, Aerogels based on carbon nanomaterials, J. Mater.
Sci. 51 (2016) 9157–9189.
[7] A.C. Pierre, History of aerogels, in: M. Aegerter, N. Leventis, M. Koebel (Eds.), Aerogels Handbook,
Advances in Sol-Gel Derived Materials TechnologiesSpringer, New York, NY, USA, 2011, pp. 3–18.
[8] L.A. Capadona, M.A.B. Meador, A. Alunni, E.F. Fabrizio, P. Vassilaras, N. Leventis, Flexible low-density
polymer crosslinked silica aerogels, Polymer 47 (2006) 5754–5761.
[9] C.T. Wang, S.H. Ro, Surface nature of nanoparticle gold/iron oxide aerogel catalysts, J. NonCryst. Sol-
ids 352 (2006) 35–43.
[10] Y. Bi, H. Ren, L. He, Y. Zhang, S. He, L. Zhang, Preparation and characterization of metallic copper-
based aerogel with the building block of nano-crystals, Mat. Lett. 139 (2015) 205–207.
[11] M. Najafpour, S. Salimi, S.E. Balaghi, M. Hołynska, T. Tomo, M.H. Sadr, et al. Nanostructured man -
ganese oxide on frozen smoke: a new water-oxidizing composite, Int. J. Hydrog. Ener. 41 (2016)
2466–2476.
[12] J.L. Gurav, I.K. Jung, H.H. Park, E.S. Kang, D.Y. Nadargi, Silica aerogel: Synthesis and applications, J.
Nanomater. 2010 (2010) 409310.
[13] S.J. Teichner, G.A. Nicolaon, M.A. Vicarini, G.E.E. Gardes, Inorganic oxide aerogels, Adv. Colloid In-
terface Sci. 5 (1976) 245–273.
[14] H. Tamon, T. Sone, M. Mikami, M. Okazaki, Preparation and characterization of silica–titania and
silica–alumina aerogels, J. Colloid Interface Sci. 188 (1997) 493–500.
[15] E. Barrios, D. Fox, Y.Y.L. Sip, R. Catarata, J.E. Calderon, N. Azim, et al. Nanomaterials in advanced,
high-performance aerogel composites: A review, Polymer (Basel) 11 (2019) 726.
[16] L. Zuo, Y. Zhang, L. Zhang, Y.E. Miao, W. Fan, T. Liu, Polymer/carbon-based hybrid aerogels: Prepara-
tion, properties and applications, Materials (Basel) 8 (2015) 6806–6848.
[17] W. Liu, A.K. Herrmann, N.C. Bigall, P. Rodriguez, D. Wen, M. Oezaslan, et al. Noble metal aerogels
synthesis, characterization, and application as electrocatalysts, Acc. Chem. Res. 48 (2015) 154–162.
[18] A. Benad, F. Jürries, B. Vetter, B. Klemmed, R. Hübner, C. Leyens, Mechanical properties of metal oxide
aerogels, Chem. Mater. 30 (2018) 145–152.
[19] S. Kistler, Coherent expanded-aerogels, J. Phys. Chem. 36 (1932) 52–64.
[20] P. Wagh, A. VRao, D. Haranath, Influence of molar ratios of precursor, solvent and water on physical
properties of citric acid catalyzed TEOS silica aerogels, Mat. Chem. Phys. 53 (1998) 41–47.
[21] H. Wang, Q. Fang, W. Gu, D. Du, Y. Lin, C. Zhu, Noble metal aerogels, ACS Appl. Mater. Interfaces 12
(2020) 52234–52250.
[22] D. Bianchi, T. Chafik, M. Khalfallah, S.J. Teichner, Intermediate species on zirconia supported methanol
aerogel catalysts V. Adsorption of methanol, Appl. Catal. A Gen. 123 (1995) 89–110.
[23] M. Zhang, S. Fang, A.A. Zakhidov, S.B. Lee, A.E. Aliev, C.D. Williams, et al. Strong, transparent, multi -
functional, carbon nanotube sheets, Science 309 (2005) 1215–1219.

Advances in Aerogel Composites for Environmental Remediation 14
[24] F. Meng, X. Zhang, B. Xu, S. Yue, H. Guo, Y. Luo, Alkali-treated graphene oxide as a solid base catalyst:
synthesis and electrochemical capacitance of graphene/carbon composite aerogels, J. Mater. Chem. 21
(2011) 18537–18539.
[25] P.J. Pauzauskie, J.C. Crowhurst, M.A. Worsley, T.A. Laurence, A.D. Kilcoyne, Y. Wang, et al. Synthesis and
characterization of a nanocrystalline diamond aerogel, Proc. Natl. Acad. Sci. 108 (2011) 8550–8553.
[26] D.A. Schiraldi, Polymer aerogels, Encyclopedia of Polymer Science and Technology, Wiley, New York,
(2015).
[27] Y. Kong, X. Shen, S. Cui, M. Fan, Use of monolithic silicon carbide aerogel as a reusable support for
development of regenerable CO
2
adsorbent, RSC Adv. 4 (2014) 64193–64199.
[28] M. Ahmadi, A. Madadlou, A.A. Saboury, Whey protein aerogel as blended with cellulose crystalline
particles or loaded with fish oil, Food Chem. 196 (2016) 1016–1022.
[29] H. Maleki, L. Duraes, A. Portugal, An overview on silica aerogels synthesis and different mechanical
reinforcing strategies, J. Non-Cryst. Solids 385 (2014) 55–74.
[30] S. Gu, S.C. Jana, Open cell aerogel foams with hierarchical pore structures, Polymer 125 (2017) 1–9.
[31] S. Gopi, P. Balakrishnan, V.G. Geethamma, A. Pius, S. Thomas, Applications of Nanocomposite Materials
in Drug Delivery, Woodhead Publishing Series in Biomaterials, 2018, pp. 75–95.
[32] E. Moretti, F. Merli, E. Cuce, C. Buratti, Thermal and acoustic properties of aerogels: Preliminary inves-
tigation of the influence of granule size, Energy Proced. 111 (2017) 472–480.
[33] W. Yang, J. Liu, Y. Wang, G. Sijia, Experimental study on the thermal conductivity of aerogel-enhanced
insulating materials under various hygrothermal environments, Energy Build. 206 (2020) 109583.
[34] Q. Liu, A.W. Frazier, X. Zhao, J.A.D.L. Cruz, A.J. Hess, R. Yang, et al. Flexible transparent aerogels as
window retrofitting films and optical elements with tunable birefringence, Nano Energy 48 (2018)
266–274.
[35] J. Zhang, C. Li, Z. Peng, Y. Liu, J. Zhang, Z. Liu, et al. 3D free-standing nitrogen-doped reduced gra -
phene oxide aerogel as anode material for sodium ion batteries with enhanced sodium storage, Sci.
Rep. 7 (2017) 4886.
[36] P.N. Hong, D.N. Minh, N.V. Hung, et al. Carbon nanotubes and graphene aerogels-The world’s 3D
lightest materials for environment applications: A review, IJMSA 6 (2017) 277–283.
[37] N. Husing, U. Schubert, Aerogels-airy materials: chemistry, structure, and properties, Angew. Chem. Int.
Ed. 37 (1998) 22–45.
[38] H. Matsuda, N. Kobayashi, T. Kobayashi, et al. Room-temperature synthesis of crystalline barium tita -
nate thin films by high-concentration sol-gel method, J. Non-Cryst. Solids 271 (2000) 162–166.
[39] D. Torikai, C.K. Suzuki, H. Shimizu, et al. Comparison of high-purityH2/O2 and LPG/O2 flame-
fused silica glasses from sol-gel silica powder, J. Non-Cryst. Solids 179 (1994) 328–334.
[40] H.C. Hamker, A general theory of lyophobic colloids I, J. R Netherlands Chem. Soc. 55 (1936) 1015.
[41] J. Lyklema, S. Levine, A.L. Smith, et al. General discussion, Discuss. Faraday Soc. 52 (1971) 312–323 .
[42] F. Schuth, K.S.W. Sing, J. Weitkamp, Wiley-VCH, Weinheim, Germany, (2002).
[43] C.J. Brinker, Hydrolysis and condensation of silicates: effects on structure, J. Non-Cryst. Solids 100
(1988) 31–50.
[44] D.C. Bradley, R.C. Mehrotra, D.P. Gaur, Metal Alkoxides, Academic Press, New York, NY, USA, (1978).
[45] C.J. Brinker, K.D. Keefer, D.W. Schaefer, et al. Sol-gel transition in simple silicates, J. Non-Cryst. Solids
48 (1982) 47–64.
[46] C.J. Brinker, G.W. Scherer, Sol-Gel Science, Academic Press, New York, (1990).
[47] A.V. Rao, G.M. Pajonk, U.K.H. Bangi, et al. Sodium silicate based aerogels via ambient pressure drying,
in: M.A. Aegerter, N. Leventis, M.M. Koebel (Eds.), Aerogels Handbook, Springer, 2011, pp. 103–124.
[48] H. Maleki, L. Duraes, A. Portugal, Synthesis of lightweight polymer-reinforced silica aerogels with im-
proved mechanical and thermal insulation properties for space applications, Micropor. Mesopor. Mater.
197 (2014) 116–129.
[49] H. Maleki, L. Duraes, A. Portugal, Synthesis of mechanically reinforced silica aerogels via surface-
initiated reversible addition-fragmentation chain transfer (RAFT) polymerization, J. Mater. Chem. A 3
(2015) 1594–1600.
[50] S. Liu, Q. Yan, D. Tao, et al. Highly flexible magnetic composite aerogels prepared by using cellulose
nanofibril networks as templates, Carbohyr. Polym. 89 (2012) 551–557.

Aerogel and its composites: fabrication and properties15
[51] X. Xiong, N. Ji, C. Song, et al. Preparation functionalized graphene aerogels as air cleaner filter, Procedia
Eng. 121 (2015) 957–960.
[52] S. Fun Chin, A.N. Binti Romainor, S. Cem Pang, Fabrication of hydrophobic and magnetic cellulose
aerogel with high oil absorption capacity, Mater. Lett. 115 (2014) 241–243.
[53] R.K. Iler, Soluble Silicates, ACS American Chemical Society, Washington, D.C., 1982.
[54] R.K. Iler, L.L. Hench, D.R. Ulrich (Eds.), Science of Ceramic Chemical Processing, Wiley, New York,
1986.
[55] H.S. Chen, R.V. Kumar, Sol–gel TiO
2
in self-organization process: growth, ripening and sintering, RSC
Adv. 2 (2012) 2294–2301.
[56] L.L. Hench, J.K. West, The sol-gel process, Chem. Rev. 90 (1990) 33–72.
[57] P.J. Davis, C.J. Brinker, D.M. Smith, Pore structure evolution in silica gel during aging/drying I. Tem-
poral and thermal aging, J. Non-Cryst. Solids 142 (1992) 189–196.
[58] D. Nadargi, S.S. Latthe, A.V. Rao, Effect of post-treatment (gel aging) on the properties of methyltrime-
thoxysilane based silica aerogels prepared by two-step sol–gel process, J. Sol- Gel Sci. Technol. 49 (2008)
53–59.
[59] R.A. Strom, M. Yasmine, A. Rigacci, et al. Strengthening and aging of wet silica gels for up-scaling of
aerogel preparation, J. Sol-Gel Sci. Technol. 41 (2007) 291–298.
[60] C.A. García-González, M.C. Camino-Rey, M. Alnaief, C. Zetzl, I. Smirnova, Supercritical drying of
aerogels using CO
2
: Effect of extraction time on the end material textural properties, J. Supercrit. Fluids
66 (2012) 297–306.
[61] K. Kawagishi, H. Saito, H. Furukawa, Superior nanoporous polyimides via supercritical CO2 drying of
jungle-gym-type polyimide gels, Macromol. Papid Commun. 28 (2007) 96–100.
[62] D.W. Matson, R.D. Smith, Supercritical fluid technologies for ceramic-processing applications, J. Am.
Ceram. Soc. 72 (1989) 871–881.
[63] G. Zhang, A. Dass, A.M.M. Rawashdeha, et al. Isocyanate-crosslinked silica aerogel monoliths: prepara -
tion and characterization, J. Non-Cryst. Solids 350 (2004) 152–164.
[64] M.A.B. Meador, Improving elastic properties of polymer-reinforced aerogels, in: M.A. Aegerter, N.
Leventis, M.M. Koebel (Eds.), Aerogels Handbook, Springer, New York, USA, 2011, pp. 315–334.
[65] N. Leventis, Three dimensional core-shell superstructures: mechanically strong aerogels, Acc. Chem.
Res. 40 (2007) 874–884.
[66] A. Soleimani Dorcheh, M.H. Abbasi, Silica aerogel; synthesis, properties and characterization, J. Mater.
Proc. Technol. 199 (2008) 10–26.
[67] H. Maleki, L. Duraes, A. Portugal, Development of mechanically strong ambient pressure dried silica
aerogels with optimized properties, J. Phys. Chem. C 119 (2015) 7689–7703.
[68] B. Mathieu, S. Blacher, R. Pirard, et al. Freeze-dried resorcinol-formaldehyde gels, J. Non- Cryst. Solids
212 (1997) 250–261.
[69] D. Klvana, J. Chaouki, M. Repellin-Lacroix, et al. A new method of preparation of aerogel-like materi -
als using a freeze-drying process, J. Phys. Colloq. 50 (1989) C4-29–C4-32.
[70] G.M. Pajonk, Drying methods preserving the textural properties of gels, J. Phys. Colloq. 50 (1989)
C413–C422.
[71] R.W. Pekala, Low Density Resorsinol-Formaldehyde Aerogels, U.S. Department of Energy, (Ed.), 4873
218, US, 1989.
[72] R.W. Pekala, Organic aerogels from the polycondensation of resorcinol with formaldehyde, J. Mater.
Sci. 24 (1989) 3221–3227.
[73] R.W. Pekala, C.T. Alviso, J.D. LeMay, Organic aerogels: microstructural dependence of mechanical
properties in compression, J. Non-Cryst. Solids 125 (1990) 67–75.
[74] Y. Kong, Y. Zhong, X. Shen, et al. Effect of silica sources on nanostructures of resorcinol-formaldehyde/
silica and carbon/silicon carbide composite aerogels, Micropor. Mesopor. Mater. 197 (2014) 77–82.
[75] A.C. Pierre, G.M. Pajonk, Chemistry of aerogels and their applications, Chem. Rev. 102 (2002) 4243–
4265.
[76] S.S. Kistler, Coherent expanded aerogels, J. Phys. Chem. 36 (1932) 52–64.
[77] R. Baetens, B.P. Jelle, A. Gustavsen, Aerogel insulation for building applications: a state-of-the-art re-
view, Energy Build. 43 (2011) 761–769.

Advances in Aerogel Composites for Environmental Remediation 16
[78] D.M. Smith, A. Maskara, U. Boes, Aerogel-based thermal insulation, J. Non-Cryst. Solids 225 (1998)
254–259.
[79] J.M. Schultz, K.I. Jensen, F.H. Kristiansen, Super insulating aerogel glazing, Sol Energy Mater. Sol C
89 (2005) 275–285.
[80] S. Standeker, Z. Novak, Z. Knez, Adsorption of toxic organic compounds from water with hydropho-
bic silica aerogels, J. Colloid Interface Sci. 310 (2007) 362–368.
[81] H. Wu, Y. Chen, Q. Chen, et al. Synthesis of flexible aerogel composites reinforced with electrospun
nanofibers and microparticles for thermal insulation, J. Nanomater. 2013 (2013) 1–8.
[82] H.J. Lee, J.H. Song, J.H. Kim, Synthesis of resorcinol/formaldehyde gel particles by the sol-emulsion-
gel technique, Mater. Lett. 37 (1998) 197.
[83] H. Tamon, H. Ishizaka, Influence of gelation temperature and catalysts on the mesoporous structure of
resorcinol-formaldehyde aerogels, J. Colloid Interface Sci. 223 (2000) 305–307.
[84] K.N. Lee, H.J. Lee, J.H. Kim, Synthesis of phenolic/furfural gel microspheres in supercritical CO2, J.
Supercrit. Fluids 17 (2000) 73–80.
[85] F. Placin, J.P. Desvergne, F. Cansell, Introduction to sol-gel processing, J. Mater. Chem. 10 (2000) 2147.
[86] P. Gouerec, D. Miousse, F. Tran-Van, et al. Preparation and modification of polyacrylonitrile microcel -
lular foam films for use as electrodes in supercapacitors, J. New Mater. Electrochem. Syst. 2 (1999) 221.
[87] G. Biesmans, D. Randall, E. Francais, et al. Proceedings of the fifth international symposium on aero -
gels (ISA 5), J. Non-Cryst. Solids 225 (1998) 36.
[88] M.H. Nguyen, L.H. Dao, Proceedings of the fifth international symposium on aerogels (ISA 5), J.
Non-Cryst. Solids 225 (1998) 51.
[89] A.K. Meena, G.K. Mishra, P.K. Rai, et al. Removal of heavy metal ions from aqueous solutions using
carbon aerogel as an adsorbent, J. Hazard. Mater. B122 (2005) 161–170.
[90] S.Q. Zhang, J. Wang, J. Shen, et al. The investigation of the adsorption character of carbon aerogels,
Nanostruct. Mater. 11 (1999) 375.
[91] H. Tamon, H. Ishizaka, T. Yamamoto, et al. Preparation of mesoporous carbon by freeze-drying, Car -
bon 37 (1999) 2049–2055.
[92] V. Bock, A. Emmerling, J. Fricke, Proceedings of the fifth international symposium on. aerogels (ISA
5), J. Non-Cryst. Solids 225 (1998) 69.
[93] R. Petricevic, G. Reichenauer, V. Bock, et al. Proceedings of the fifth international symposium on
aerogels (ISA 5), J. Non-Cryst. Solids 225 (1998) 41.
[94] H. Tamon, H. Ishizaka, T. Araki, et al. Control of mesoporous structure of organic and carbon aerogels,
Carbon 36 (1998) 1257–1262.
[95] E. Bekyarova, K. Kaneko, Microporous nature of Ce, Zr-doped carbon aerogels, Langmuir 15 (1999)
7119–7121.
[96] E. Bekyarova, K. Kaneko, Structure and physical properties of tailor-made Ce, Zr-doped carbon aero-
gels, Adv. Mater. 12 (2000) 1625.
[97] F.J. Maldonado-Hodar, C. Moreno-Castilla, J. Rivera-Utrilla, et al. Catalytic graphitization of carbon
aerogels by transition metals, Langmuir 16 (2000) 4367–4373.
[98] J. Kuhn, R. Brandt, H. Mehling, et al. Proceedings of the fifth international symposium on aerogels
(ISA 5), J. Non-Cryst. Solids 225 (1998) 58.
[99] O. Barbieri, F. Ehrburger-Dolle, T.P. Rieker, et al. Aerogels 6; Proceedings of the sixth international
symposium on aerogels (ISA6), J. Non-Cryst. Solids 285 (2001) 109.
[100] K. Araki, J.W. Halloran, New freeze-casting technique for ceramics with sublimable vehicles, J. Am.
Ceram. Soc. 87 (2005) 1859–1863.
[101] N. Van Hung, N. Ngoc Anh, P. Van Trinh, et al., Fabrication and characterization of carbon nanotubes
aerogel, 8th IWAMSN, Ha Long City,Vietnam, 2016.
[102] Z. Xu, H. Sun, C. Gao, Perspective: Graphene aerogel goes to superelasticity and ultraflyweight, APL
Mater. l (2013) 030901.
[103] H. Sun, Z. Xu, C. Gao, Multifunctional, ultra-flyweight, synergistically assembled carbon aerogels, Adv
Mater. 25 (2013) 2554–2560.
[104] Y. Kong, et al. Synthesis of monolithic mesoporous silicon carbide from resorcinolformaldehyde/silica
composites, Mater. Lett. 99 (2013) 108–110.

Aerogel and its composites: fabrication and properties17
[105] N. Leventis, et al. Click synthesis of monolithic silicon carbide aerogels from polyacrylonitrile-coated
3D silica networks, Chem. Mater. 22 (2010) 2790–2803.
[106] X.L. Wu, X.L. Tan, S.T. Yang, et al. Coexistence of adsorption and coagulation processes of both arse -
nate and NOM from contaminated groundwater by nanocrystallined Mg/Al layered double hydrox-
ides, Water Res. 47 (2013) 4159–4168.
[107] H.C. Bi, Z.Y. Yin, X.H. Cao, et al. Carbon fiber aerogel made from raw cotton: A novel, efficient and
recyclable sorbent for oils and organic solvents, Adv. Mater. 25 (2013) 5916–5921.
[108] J. Zhu, H. Gu, J. Guo, et al. Mesoporous magnetic carbon nanocomposite fabrics for highly efficient
Cr(vi) removal, J. Mater. Chem. A 2 (2014) 2256–2265.

Page left intentionally blank

19
Advances in Aerogel Composites for Environmental Remediation. http://dx.doi.org/10.1016/B978-0-12-820732-1.00002-3
Copyright © 2021 Elsevier Inc. All rights reserved.
CHAPTER 2
Natural aerogels for pollutant removal
Sandeep R. Kurundawade
a
, Ramesh S. Malladi
b
, Raviraj M. Kulkarni
c
, and
Aftab Aslam Parwaz Khan
d,e
a
Department of Chemistry, KLE Technological University, Hubballi, Karnataka, India
b
Department of Chemistry, BLDEA’s V. P. Dr. P. G. Halakatti College of Engineering and Technology, Vijaypur, Karnataka, India
c
Centre for Nanoscience and Nanotechnology, Department of Chemistry, KLS Gogte Institute of Technology, Belagavi,
Karnataka, India
d
Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia
e
Centre of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah, Saudi Arabia
Chapter Outline
1 Introduction 19
2 Properties 20
2.1 Porosity of aerogel 21
3 Types of aerogels 22
4 Important natural aerogels in pollutant removal 23
4.1 Noncellulose aerogel-type oil sorbents 23
4.2 Cellulose aerogel-type oil sorbents 23
4.3 Carbon aerogel extracted from pomelo peel 24
4.4 Nanocellulose-derived carbon aerogels 25
4.5 Carbon based aerogel 26
4.6 Carbon fiber aerogel (CFA) 26
5 Pollutant removal with cellulosic materials 27
6 Biomedical application of jackfruit aerogel 27
7 Advantages of natural aerogels in pollutant removal 27
8 Adsorption constants of some important natural adsorbents 28
9 Conclusions 29
References 29
1 Introduction
The presence of various organic compounds like pesticides, pharmaceuticals, dyes, and
oil leakages in the water bodies and ecology built around it during last few decades
is of serious concern. As the industrial revolution is at the highest pace, the industries
that use, process, or involve persistent organic compounds, oils, and other chemicals are
creating issues of the spill and leakage of various chemical reagents in the environment,
disturbing the ecology particularly around water bodies. This brings the importance of
the removal of such pollutants to the highest priority [1]. There are many techniques
already in practice to achieve the same. The important ones are filtration, centrifugation,

Advances in Aerogel Composites for Environmental Remediation 20
flotation, biodegradation, gravity separation, etc. Though these techniques serve the pur-
pose but they have their own limitations of being fairly less efficient, complicated, and
economically not efficient [2,3].
As an alternative, sorption was employed for the process of pollutant removal, which
has proved to be a good option [4,5]. So far, many natural organic sorbents and inor-
ganic sorbents have been explored [6]. As time and research progressed, it was found that
the inorganic sorbents have some limitations like poor oil sorption capacity and high
density [7,8], whereas, organic sorbents displayed lower water repelling ability and hence
they possess high water uptake. This made the researchers to look for natural sorbents
for pollutant removal. The basic requirements of sorbent are better selectivity toward
chemicals, recyclability, lipophilic, environmental friendly, and low density with best
sorption capacity [9].
Further developments discovered that aerogels can be a more effective option of
being sorbents for the removal of oil and chemical reagents from water. This chapter
discusses about the various natural aerogels available for pollutant removal in the cases
like oil spillage and similar. Aerogels were identified and brought to limelight early in
the 1930s by a scientist known as S. Kistler. He was able to extract aerogels mainly form
silica which resulted in depreciation of interest in the area of Aerogels for almost 30 years
[10,11]. Later as the new easy and effective methodologies were developed, new aerogels
were coming up. Even when many synthetic and efficient aerogels were made available
by extensive research, there were some natural aerogels also that hold their importance
in several applications, especially in pollutant removal. Starch, cellulose, other saccharides,
and proteins are the most important ones.
Aerogels are prepared by eliminating the liquid part present in gel by the process of
supercritical drying process [12]. This removes the liquid resulting in slow drying of the
material without allowing the solid matrix in the gel to undergo collapsing from result-
ing capillary action, as it normally happens in conventional evaporation.
2 Properties
Aerogel is a hard dry material that does not appear like a gel. Although they are rigid,
imposing a firm imprint will leave a permanent depression on the material. Pressing too
strongly causes the structure to deteriorate, making it shatter like glass. Modern aerogels
are very strong and they do not disintegrate easily. Even when the fact is that it is prone
to scattering, it is structurally strong. It has excellent load-bearing capabilities by the
virtue of dendritic microstructures. In such structure, spherical particles with the average
size between 2 and 5 nm are joined together in groups. Such groups form a 3-dimen-
sional, highly porous structure of nearly fractal chains with pores below 100 nm. The
average size of these groups as well as the density of holes can be controlled during the
process of manufacturing [13].

Natural aerogels for pollutant removal21
Aerogel is actually 99.8% air. They have a porous solid network with most of the
space within the material being air pockets. Lack of solid material makes aerogel virtu-
ally weightless. Aerogels show property of thermal insulation due to non-existence of
two out of three methods of heat transfer. They are: conduction—as they are mostly
made of insulating gas and convection—as the microstructure prevents pure gas move-
ment. Also, the inability of air to circulate through the lattice makes them good sensory
inhibitors. However, infrared radiation passes through the aerogels making them poor
radiative insulators [14,15].
As aerogels are hygroscopic in nature, they feel dry and act like a strong desiccant.
Exposure of skin to these aerogels for extended periods can cause dry brittle spots in the
skin. There it is advisable to wear gloves while handling the aerogels.
Aerogels possess light color due to Rayleigh scattering of short wavelengths in the
range of visible light which is actually due to nano-sized dendritic structure. They also
appear smoky blue for a dark background and yellow when they are put against a bright
background. Aerogels are hydrophilic in nature. When they absorb moisture, they usu-
ally undergo structural changes such as contraction and deterioration. However, they
can be made hydrophobic with the help of chemical treatment to prevent degradation.
It is desirable to have aerogels with hydrophobic layer instead of those with hydrophilic
interiors as they are more susceptible to degradation [10].
2.1 Porosity of aerogel
The versatile properties of aerogel carry various fields of applications. Porosity is a prop-
erty that provides filtering property to the aerogel. Porosity of aerogel can be determined
in different ways. The three important methods are mercury porosimetry, gas adsorption,
and scattering method. In the method of gas adsorption, nitrogen is absorbed into the
air sample at its boiling point.
Depending on the size of the pores and partial pressure of the gas relative to its satu-
ration pressure, the absorption of gas occurs. Then specific surface area of the sample
is calculated by knowing the amount of gas adsorption which is measured using the
Bruner, Emmitt and Taylor formula (BET). The Kelvin equation under high partial pres-
sure in adsorption/desorption gives the information about pore size distribution. In a
method known as mercury porosimetry, size of the mercury is determined by forcing
it into the aerogel porous system. However, this method is not that efficient since the
solid frame of the aerogel collapses for high compressive force. The process of scatter-
ing involves deflection of radiation within the aerogel sample. The sample can be solid
particle or holes. Radiation that passes through the material helps in determining the
fractal geometry of the aerogel orifice network. X-rays and neutrons are the radiation
wavelengths preferred for the study. Aerogel also possesses open porous network. In
open network, gases can enter and leave matter without any kind of limitation, whereas
in closed form of porous network gases are forced within. They have to live inside the

Advances in Aerogel Composites for Environmental Remediation 22
holes. The pores and surface area of aerogels enable them to be useful in a various areas
of environmental filtration applications.
3 Types of aerogels
The most common types of aerogels are metal oxide aerogels, silica aerogels, and carbon
aerogels (Fig. 2.1) [16]. Among the three, silica is widely used for various experimental
and practical applications. Therefore, when someone talks about aerogels, in many cases
they are talking about silica types [source: aerogel.org, silica]. Silica is different than sili-
con. Silica is actually a glass material which finds applications in insulation.
Metal oxide aerogels are made from metal oxides. These are used as catalysts for
chemical reactions, especially for chemical structure transformations. Apart from aero-
gels, they find uses in the manufacture of explosives and carbon nanotubes. Metal oxides
like iron oxide and chromia are different from their common silica cousins. In the form
of aerogel, iron oxide forms its trademark, which is like rust paint. Chromia aerogels are
dark green or blue by appearance. Different metal oxides in an airfield are of slightly
different color than each other.
On the other hand, there are carbon aerogels which are not glassy in appearance.
Instead they are carbon-based blacks and feel like charcoal. Though they lack a glossy
look, they have high surface area and good electrical conductive capacity. These proper-
ties make carbon aerogels suitable for fuel cells, supercapacitors, and most importantly
for desalination systems. Silica aerogel has characteristic blue color. Blue color occurs
as white light interacts with silica molecules of the aerogel. Aerogels scatter or reflect
light of shorter wavelengths as compared to longer wavelengths. Blue and violet have
shorter wavelengths and hence they should be visible to the viewers. However, human
eyes are more sensitive to blue light than violet and that is the reason we see blue color,
not violet [17].
Apart from these, there are many aerogels obtained from naturally available resources
like bamboo, fruit extracts, and similar saccharides and carbon sources. These mainly lead
Figure 2.1 Classification of aerogels.

Natural aerogels for pollutant removal23
to the extraction of cellulose aerogels and carbon aerogels. Due to their high hydropho-
bicity with water and oil, these are largely employed in separation of oil from water.
4 Important natural aerogels in pollutant removal
For effective removal of oil from water, it is important to select a suitable aerogel in the
form of oil sorbent. Ideally, oil sorbent has high adsorption capability and oil or water
selectivity. Also, it will show a high filtrate, a high purification rate, low density, financial
viability, eco-compatibility, and recyclability. These are characteristics of a good aerogel.
A perforated and lightweight is converted into aerogel by replacing the liquid content
from its frame by air. It will possess specific surface area, high porosity, and low density,
which gives a potential of being an ideal oil sorbent material [18].
4.1 Noncellulose aerogel-type oil sorbents
As on today, a variety of aerogel-type oil sorbents, for example, carbon nanotubes
(CNT), silica, and graphene aerogel are prepared and used. Pure silica aerogels capable
of absorbing oils, but it is impedent to separate the sorbent with oil from the water. The
mechanical brittleness cannot withstand capillaries seriously, and when the oils absorb
the mesopores in aerogels [19]. Whereas, newly obtained carbon-based aerogels such as
CNTs, carbon nanofibers, graphene, etc., show better sorption capacities ranging be-
tween 100 and 913 g/g and are reusable as well. However, the non-pragmatism of them
hinders their practicality [20]. Therefore, effort has been employed in developing a new
and stable aerogel material, with superior fusion properties and economical for oil-water
separation.
4.2 Cellulose aerogel-type oil sorbents
Cellulose aerogels, also known as sponges, are naturally found. Cellulose aerogels are
natural, renewable, biodegradable, and easy to modify the surface [21]. Hence, cellulose
aerogels are the most attractive natural oil sorbents after desired structural modifications
[16,22].
The cellulose aerogels are classified based on the nature of cellulosic materials. They
are
1. derived cellulosic aerogels,
2. regenerated cellulosic aerogels, and
3. nanocellulosic aerogels.
The mechanism of 3-dimensional network gelation process may involve physical or
chemical cross-linking [19].
Faraco in 2013 suggested that the best resource for the synthesis of cellulosic aerogel
can be obtained from lignocellulosic biomass. This is available in wood, waste cotton
linters, and agricultural residues [23].

Advances in Aerogel Composites for Environmental Remediation 24
Habibi and coworkers in 2010 reported that cellulose by nature is a homo-polysaccha-
ride and it comprises of straight chains of connected anhydro-glucose units. These are im-
mune to water dissolution and have a hierarchical structure which includes aligned as well
as misaligned chains that contribute to the ultimate chemical and physical properties [24].
The accumulation of molecules inside the cell architecture leads to the excellent
materials properties of these aerogels [25]. The concept of aggregation occurs principally
through inter as well as intramolecular hydrogen bonding that happens inside the cel-
lulosic chains [26,27].
Li and coworkers in 2011 reported that these organizations of chains are in parallel
way and they are also well sorted into a sheet-like structure. This is due to inter-chain
hydrogen bonds of OH–O and also weaker bonds in the form of CH–O hydrogen
bonds. As a result, Van der Waals dispersion forces stabilize the piling up of these cel-
lulosic sheets [19].
Lagerwall and colleagues in 2014 suggested that inside this layered structure, cel-
lulose molecules combine together into much larger units to form as elementary fibrils
or microfibrils [28].
Lavoine and colleagues in 2012 reported that the microfibrils further combine re-
sulting into bigger units, called as macrofibrils, which then gather into natural cellulose
fiber [29].
Anwar and colleagues in 2014 suggested that nanofibrillated cellulose or cellulos-
ic nanofibrils present in the structure provide strength and stiffness to the framework.
These are derived from the lignocellulosic biomass which are then termed as “nanocel-
lulose.” All these properties of these aerogels make them better agents for oil removal
when compared to other synthetic purifiers and are advantageous over other methods
of pollutant removal [30].
4.3 Carbon aerogel extracted from pomelo peel
Carbon aerogels were discovered in around the year of 1980 [31]. Pomelo peel is the
natural source of carbon. The peel has to undergo step by step process as explained
which will yield the pomelo peel carbon aerogel (PPCA) [9].
First the pomelo is peeled out the exocuticle, and the as-obtained raw pomelo peel
must be cut into tiny pieces of dimensions of about 3 × 3 × 1 cm
3
and they are then
washed with deionized water repeatedly to get rid of all the dirt particles adhering to
the material. Then they are placed in a stainless-steel autoclave with Teflon-lining. The
autoclave must be properly sealed and placed into the oven at temperature of 180°C
for 10 h. Subsequently, the spongy pomelo peel hydrogel is taken out and washed with
water maintained at around temperature of 70°C. Washing is repeated several times to
remove soluble impurities.
Then corresponding pomelo peel aerogel is made by freeze-drying at −20°C
for 24 h. The process is followed by drying the same at −80°C for about 48 h. The

Natural aerogels for pollutant removal25
obtained pomelo peel aerogel (PPA) is then pyrolyzed under nitrogen flow inside a tu-
bular furnace. It results in carbonization [32]. The furnace is heated up to 600°C, 700°C,
and 800°C at the rate of 5°C/min, respectively. The temperatures are held for 1 h each to
facilitate complete pyrolysis. Then they are cooled down to room temperature naturally.
The yield obtained at the end is ultra-light pomelo peel carbon aerogel (PPCA). Result-
ing aerogel is then used for pollutant removal in various scenarios. PPCA is an important
one being in the removal of oil and metal oxides from water and other sources.
4.4 Nanocellulose-derived carbon aerogels
This aerogel can be a more efficient, economic, and environmentally sustainable too. The
reason being, it is made from paper waste that goes in tones everyday [33]. The process
of obtaining this aerogel is as follows:
The cotton pads consisting of cotton fibers are commercially available now. The same
can be directly procured. Synthesis of these aerogels also requires motor oil (5w40) and
Singer machine oil. Then, analytical grade methyltrimethoxysilane (MTMS), acetone,
hexane, ethanol, and dichloromethane are the other chemicals required for the process
[34,35].
The process of making cellulose derived carbon aerogels is illustrated in Fig. 2.2.
First, the cotton pads are cut neatly into small strands of 0.5 × 4 cm dimensions. Then
the strands are mixed with cellulose fibers which are obtained by recycling from the pa-
per waste. For mixing 200 mL of deionized water is used as medium. The mass ratio of
cotton-to-cellulose is fixed at 1:0 (pure cotton), 1:1, 1:2, and 1:4. The concentration by
mass of fiber-to-water in aqueous dispersion is controlled with 0.25 wt%, 0.5 wt%, and
0.75 wt%, respectively. Further, with the help of a juice blender, the mixture dispersion
is homogenized for about 15 min. Then, through a sonication process, 66.6 µL of PAE
solution is poured in the dispersion, at 140 W for 5 min. Resulting homogenized disper -
sion is cooled to −18°C for 24 h where it gets frozen and then dried with the help of
vacuum at the temperature of −98°C. After 96 h of this treatment, monolith aerogels
are obtained. During the process of freezing, it is noticed that both cotton and cellulose
Figure 2.2 Preparation of cotton cellulose.

Advances in Aerogel Composites for Environmental Remediation 26
fiber are squeezed. This occurs due to the increase in volume as water converts to ice. As
a last step, the aerogels must be cured at 120°C for about 3 h [36,37].
4.5 Carbon based aerogel
Carbon based aerogels are another set of aerogels employed mainly in pollutant removal.
It is preferable to use ultra-low density carbon aerogels for efficient removal process.
Bamboo pulp makes a good source for obtaining such aerogels. The process is simple.
Bamboo pulp fibers produce ultra-low density carbon aerogels by freeze-drying and
pyrolysis methods [16,38].
Resulting carbon aerogels have high hydrophobicity at the contact angle of 135.9.
When tested, carbon aerogels showed absorption efficiency of 50–150 g/g for different
organic solvents and some oils. This number is superior compared to efficiency of any
other bio-based carbon aerogel. It is capable of lasting long. It is observed that, bamboo
pulp carbon aerogels maintain their efficiency with respect to absorption efficiency even
after 5 cycles of absorption process. That makes these carbon aerogels recyclable [39,40].
These factors give an impression that the carbon aerogels obtained by bamboo pulp
prove to be better choice for water treatment in future.
4.6 Carbon fiber aerogel (CFA)
Many industries that involve use of various chemicals release many kinds of chemicals in
the form of waste water. The chemicals released mainly are benzene, ethyl acetate, etha-
nol, oleic acid, toluene, tetrachloromethane, dimethylformamide, etc. These on joining
fresh water body spoil the ecosystem for living beings.
However, by experiments, it is evident that carbon fiber aerogels (CFA) have shown
good efficiency in absorbing such organic liquids. The adsorption efficiency of the aero-
gel is measured to be 23–51 g/g. This efficiency is quite higher when compared to the
counterparts like expanded vermiculite with 1–4 g/g, magnetic exfoliated graphite with
30–50 g/g, conjugated microporous polymers with 5–25 g/g of efficiency [41].
Considering the easy method of preparation and eco-friendly nature of these aero-
gels, they show more potential to be good pollutant removal candidates [42].
The adsorption test is normally carried out as explained further. The CFA is weighed
to start with the process. It is then placed in oil or organic solvent till the aerogel ad-
sorbs to its capacity. Time limit could be 10 min for oil and 3 min for organic solvents.
Final weight is measured and recorded [43]. Weight measurement must be happened
quickly as some of the solvents may have low boiling points and they evaporate. Now
for calculation, final weight is divided by initial weight. This entire process is repeated 5
times to assess the recyclability while monitoring the changes in adsorption efficiency
every time.
The adsorbates that are cheap and toxic are removed by combustion, low-viscosity
solvents are squeezed out, while expensive and high-viscosity solvents are extracted.

Natural aerogels for pollutant removal27
5 Pollutant removal with cellulosic materials
Cellulosic aerogels apart from being good oil sorbents at nano level, also are efficient in
various other relevant applications such as capture of gas, fire retardant, and electrical
storage applications [44,45].
Cellulosic aerogels are obtained by phase separation principles [22]. The aerogels are
of high porosity and high specific area which is essential for better efficiency at pollutant
removal [46]. As per the properties of cellulosic aerogels such as its texture properties
and surface chemistry they are employed in bacterial removal, air filtration, and electro-
chemical energy storage [47]. One main application of cellulosic aerogel is in capturing
the CO
2
.
6 Biomedical application of jackfruit aerogel
Study of natural aerogels obtained from jackfruit and sugarcane have shown their aniso-
tropic nature. With modification at nano level, current directing capability of G deco-
rated jackfruit aerogel is witnessed.
The anisotropy of the jackfruit and sugarcane aerogels gave them better absorption
capacity and electrical conductivity. Also, the antibacterial property of jackfruit aerogel
is significant when it is decorated with Ag-nanoparticles. By doing so, the antibacte-
rial property is enhanced to superior level which is beyond many medical polymer
absorbent materials. There are many electrical and biomedical applications yet to be
discovered along the research path. These aerogels surely show properties to be good
absorbents for pollutant removal or do some current driven action to aid medical needs
in the upcoming future [48].
7 Advantages of natural aerogels in pollutant removal
There are many aerogels available commercially which are employed for various applica-
tions as per their properties and capabilities.
Polypropylene is extensively used for oil pollutant treatment due to its high hydro-
phobicity of 15 g/g. Similarly there are other polymers such as polypyrrole, polyure-
thane, polydimethylsiloxane, etc. used for oil sorption. However, their suitability is not
so encouraging due to their poor environmental compatibility and poor absorption
capacity. Synthetic polymers being hard to degrade, they remain on the face of earth for
a long time. This results in serious issues [49,50].
Further improvisation was made possible with the help of nano carbon materials.
This sponge like material is prepared by chemical vapour deposition method. It has high
absorption capacity of 120 g/g with good reversibility. Then there are ultra-light gra-
phene aerogel bearing the absorption capacity of upto 200 g/g. Since pure cotton fibers
possess poor capacity of 30 g/g or less, they were subjected to pyrolysis to convert them

Random documents with unrelated
content Scribd suggests to you:

of Africa. I told him that I had entertained the idea, some years ago,
of presenting to his Minister of Marine a plan of a journey into the
interior of Africa; not a secret and adventurous excursion, but a
regular military expedition, in every respect worthy of the age and of
the Emperor. The Minister laughed in my face when I first conversed
with him on the subject, and looked upon the idea as an absurdity.
My plan was to have entered Africa at once on the north, south,
east, and west, and to have formed a junction in the centre; or, if
starting only from the east and west, I proposed that the two
divisions of the expedition should meet in the centre, separate again
and proceed, one to the north, the other to the south. I thought it
probable that, after obtaining from the Court of Portugal all the
information that could be procured, it would be found that there
already existed a communication from east to west, or that at all
events very little was wanting to effect it. The state of public feeling
at the time, our enthusiasm, our enterprizes, our prodigies, would
have rendered it easy to procure 5 or 600 good soldiers, with the
requisite number of surgeons, physicians, botanists, chymists,
astronomers, and naturalists, all willing to embark in the enterprize,
and we should undoubtedly have accomplished something worthy of
the age.
The necessary supply of beasts of burthen, small leathern boats for
crossing rivers, skins for conveying water through the deserts, and
light manageable field-pieces, would have rendered the execution of
the enterprize easy and complete.
“No doubt,” said the Emperor, “your idea would have pleased me. I
should have taken it up, submitted it to the consideration of a
committee, and brought it to a result.”
He said that he very much regretted his not having had time, during
his stay in Egypt, to accomplish something of this sort. He had
troops suited in every respect to brave the dangers of the desert. He
had received presents from the Queen of Darfour, and had sent her
some in return. Had he remained longer, he intended to have carried
to a great extent our geographical investigations in the northern

district of Africa, and that too by the simplest means, merely by
placing in each caravan some intelligent officers, for whom he would
have procured hostages.
The conversation then turned on the marine department. The
Emperor entered very deeply into the subject. He could not say that
he was satisfied with Decrès; and he even thought that the
confidence he reposed in him was not altogether irreproachable. The
difficulty of finding persons better qualified maintained him in his
post; for, after all, the Emperor said, Decrès was the best he could
find. Ganteaume was merely a sailor, and destitute of every other
talent. Cafarelli, he said, had forfeited his good opinion, because he
had been informed that his wife intrigued in political affairs, which
he regarded as an unpardonable offence. Missiessi was not a man to
be depended on; for his family had been one of those who
surrendered Toulon. The Emperor had, for a moment, cast his eye
on Emériau; but, on consideration, he did not think that he
possessed adequate capabilities. He had asked himself whether
T...... might not have filled the post; but he decided that he was not
qualified for it. He was a good man of business, it is true; but he had
plunged very deeply into the affairs of the revolution; and what had
confirmed the Emperor in his disapproval of him was that he had
subsequently seen some of his private letters, by which it was
evident that he still adhered to his old jacobinical sentiments.
“I had,” observed the Emperor, “rendered the duties of all my
ministerial posts so easy that almost any one was capable of
discharging them, if he possessed only fidelity, zeal, and activity. I
must however except the office of Minister of Foreign Affairs, in
which it was frequently necessary to exercise a ready talent for
persuasion. In fact,” continued he, “in the marine department but
little was required, and Decrès was perhaps, after all, the best man I
could have found. He possessed authority; and he discharged the
business of his office scrupulously and honestly. He was endowed
with a good share of understanding, but this was evinced only in his
conversation and private conduct. He never conceived any plan of
his own, and was incapable of executing the ideas of others on a

grand scale; he could walk, but he could never be made to run. He
ought to have passed one-half of his time in the sea-ports, or on
board the exercising squadrons. He would have lost none of my
favour by so doing. But, as a courtier, he was afraid to quit his
portfolio. This shews how little he knew me. He would not have been
the less protected by removing from my Court: his absence would
have been a powerful circumstance in his favour.”
The Emperor said he very much regretted Latouche-Tréville, whom
he regarded as a man of real talent. He was of opinion that that
Admiral would have given a different impulse to affairs. The attack
on India and the invasion of England would by him have been at
least attempted, and perhaps accomplished.
The Emperor blamed himself for having employed the pinnaces at
Bologne. He said it would have been better had he employed real
ships at Cherbourg. He was of opinion that had Villeneuve
manifested more vigour at Cape Finistèrre, the attack might have
been rendered practicable. “I had made arrangements for the arrival
of Villeneuve, with considerable art and calculation, and in defiance
of the opinions and the routine of the naval officers by whom I was
surrounded. Every thing happened as I had foreseen; when the
inactivity of Villeneuve ruined all. But,” added the Emperor, "Heaven
knows what instructions he might have received from Decrès,
[10]
or
what letters might have been privately written to him which never
came to my knowledge; for, though I was very powerful and fond of
searching into every thing, yet I am convinced that I was far from
knowing all that was passing around me.
"The Grand Marshal said, the other day, that it used to be remarked
in the saloon of the household that I was never accessible to any
one after I had given audience to the Minister of the Marine. The
reason was, because he never had any but bad news to
communicate to me. For my part I gave up every thing after the
disaster of Trafalgar; I could not be every where, and I had enough
to occupy my attention with the armies of the continent.

"I had long meditated a decisive expedition to India; but my plans
had been constantly frustrated. I intended to have fitted out a force
of 16,000 troops, on board ships of the line; each 74 to have taken
500 troops on board, which would of course have required thirty-two
ships. I proposed that they should take in a supply of water for four
months; which supply might have been renewed at the Isle of
France, or in any habitable spot of the desert of Africa, Brazil, or the
Indian Ocean. In case of need, they might have taken in water
wherever they chose to anchor. On reaching the place of their
destination, the troops were to be put ashore, and the ships were
immediately to depart, making up the number of their crews by the
sacrifice of seven or eight of the vessels which might be condemned
as unserviceable; so that an English squadron arriving from Europe
immediately afterwards would have found no trace of ours.
“As for the army, when abandoned to itself and placed under the
command of a clever and confidential chief, it would have renewed
the prodigies that were familiar to us, and Europe would have
beheld the conquest of India as she had already seen the conquest
of Egypt.”
I knew Decrès well; we had both commenced our career together in
the marine. I think he entertained for me all the friendship of which
he was susceptible, and I, on my part, was tenderly attached to him.
It was an unfortunate passion, as I used to say when I was rallied
on the subject, which was frequently the case, for Decrès was very
much disliked, and I have often thought that, from some motive or
other, he took pleasure in his own unpopularity. At St. Helena, as
elsewhere, I found myself almost his only defender. I saw a great
deal of him while the Emperor was at the island of Elba, and he was
occasionally favourable to Napoleon. We conversed candidly on the
subject, and I have every reason to believe that he observed full and
entire confidence with respect to me.
“No sooner had your Majesty returned to the Tuileries,” said I to the
Emperor, "than Decrès and I ran to embrace each other, exclaiming,
‘He has returned! we have him again!’ His eyes were suffused with

tears; I must bear this testimony to his feelings. ‘Well,’ said he to
me, in the presence of his wife, ‘I am now convinced that I have
often done you wrong, and I owe you reparation; but your old habits
and connections so naturally brought you in contact with those who
are now about to quit us that I doubted not but you would sooner or
later be perfectly reconciled with them, though you were perhaps
often offended at the expression of my real sentiments.’”—“And did
you believe this, you simpleton?" exclaimed the Emperor, bursting
into a fit of laughter. “This was an excellent piece of courtier-like art;
a touch for La Bruyère. It was really a good idea on the part of
Decrès; for if, during my absence, any thing offensive to me had
chanced to escape him, he would, you see, by this means, have
atoned for it once for all.”—"Well, Sire," continued I, "what I have
just told you is perhaps only amusing; but what I will now
communicate is of a more important nature:—During the crisis of
1814, before the taking of Paris, Decrès was sounded in a very artful
way as to his inclination to conspire against your Majesty, and he
honestly repelled the suggestion. Decrès was easily and often roused
to discontent; and he possessed a certain air of authority in his
language and manners which rendered him a useful acquisition to
any party he might espouse. He happened, at the unhappy period I
have just mentioned, to visit a person of celebrity; the hero of the
machinations of the day. The latter advanced to Decrès, and,
drawing him aside to the fire-place, took up a book, saying, I have
just now been reading something that struck me forcibly,—you shall
hear it. Montesquiou, in such and such a chapter and page, says,—
When the Prince rises above the laws, when tyranny becomes
insupportable, the oppressed have no alternative but....—‘Enough,’
exclaimed Decrès, putting his hand over the mouth of the reader; ‘I
will hear no more; close the book.’ And the other coolly laid down
the volume, as though nothing particular had occurred, and began
to talk on a totally different subject."
On another occasion, a certain Marshal, after his fatal defection,
alarmed at the unfavourable impression which his conduct was
calculated to produce on the public mind, and vainly seeking the

approbation and support of those who surrounded him, endeavoured
to interest Decrès in his favour. “I have always borne in mind,” said
he to Decrès, “one of our conversations in which you so energetically
painted the evils and perplexities that weighed upon the country.
The force of your arguments greatly influenced me in the step which
I took with the view of alleviating our misfortunes.”—"Yes, my dear
fellow," replied Decrès; “but did it not also occur to you that you
overshot your mark?”
“In order that these anecdotes may be appreciated as they deserve,”
said I to the Emperor, “I must inform your Majesty that they were
related to me by Decrès himself during your absence, and when he
certainly entertained no idea of your return.”
The Emperor kept up the conversation for nearly two hours in the
bath. He did not dine till nine o’clock, and he desired me to stay with
him. We discoursed about the military school at Paris. I left the
school only a year before Napoleon entered it, and therefore the
same officers, tutors, and comrades were common to us both. He
took particular pleasure in reverting with me to this period of our
youth: in reviving the recollection of our occupations, our boyish
tricks, our games, &c.
In this cheerful humour, he called for a glass of Champagne, which
was rather an unusual thing; for such is his habitual abstinence that
a single glass of wine is sufficient to flush his face, and to render
him very talkative. It is well known that he seldom sits longer than a
quarter of an hour, or half an hour, at table; but to-day we sat
upwards of two hours. He was very much surprised when Marchand
informed him that it was eleven o’clock. “How rapidly the time has
slipped away,” said he, with an expression of satisfaction. “Why can I
not always pass my hours thus agreeably! My dear Las Cases,” said
he, as he dismissed me, “you leave me happy.”
DANGEROUS ILLNESS OF MY SON.—REMARKABLE OBSERVATIONS.—THE
DICTIONARY OF WEATHERCOCKS.—BERTHOLET.

13th. Dr. Warden and two other medical gentlemen came to hold a
consultation on my son, whose indisposition alarmed me.
The Emperor, at my request, consented to receive Dr. Warden, our
old acquaintance of the Northumberland. He conversed for upwards
of two hours, familiarly taking a review of those acts of his
government which had drawn upon him the greatest share of
enmity, falsehood, and calumny. As the Doctor afterwards observed
to me, nothing could be more correct, clear, simple, curious, and
satisfactory, than these details.
The Emperor concluded with the following remarkable observations:
“I concern myself but little about the libels that have been written
against me. My acts and the events of my reign refute them more
completely than the most skilful arguments that could be employed.
I seated myself on a vacant throne. I arrived at supreme power
unsullied by the crimes that have usually disgraced the chiefs of
dynasties. Let history be consulted, let me be compared with others!
If I have to fear the reproaches of posterity and history, it is not for
having been too severe but perhaps for having been too indulgent!”
After dinner, the Emperor looked at the Dictionnaire des Girouettes
(Dictionary of Weathercocks) which is humourously conceived,
though not so well executed. It is an alphabetic collection of the
living characters who have figured on the stage of public events
since the Revolution, and whose language, opinions, and conduct
have followed the changes of the wind. Weathercocks are affixed to
their names, with an abstract of the speeches or a description of the
acts which have procured for them the distinction. On opening the
work, the Emperor inquired whether any of us were mentioned in it.
“No Sire,” some one present jokingly replied, “none save your
Majesty.” The name of Napoleon was indeed recorded in the work,
because, as it was affirmed, he had first sanctioned the republic and
then assumed the prerogative of royalty.
The Emperor read to us several articles from the Dictionary. The
contrast exhibited at different times in the language and conduct of
certain individuals was truly curious; and the transition was in some

instances performed with so much coolness and effrontery that the
Emperor several times suspended his reading and burst into a hearty
fit of laughter. However, after going through a few pages, he closed
the book, with an expression of disgust and regret, observing that,
after all, the publication was a disgrace to society, a code of
turpitude, and a record of our dishonour. One article seemed to
affect him deeply, namely, that concerning Bertholet, whom he had
so loaded with favour, and on whom, he said, he had every reason
to rely.
The following charming trait in the Emperor’s character may be
mentioned here, though it is pretty generally known. Bertholet had
sustained losses which involved him in difficulties, when, the
circumstance having come to the Emperor’s knowledge, he sent him
100,000 crowns, adding, that he had reason to complain of him,
since he seemed to have forgotten that he, Napoleon, was always
ready to serve his friends. Bertholet, however, behaved very
ungratefully to the Emperor, at the period of his disasters. His
conduct deeply affected Napoleon at the time, and he was often
heard to exclaim: “What Bertholet, on whom I thought I could rely
with such confidence!...”
On the Emperor’s return from Elba, Bertholet seemed again inclined
to manifest his former sentiments of attachment to his benefactor.
He ventured to show himself at the Tuileries, and desired Monge to
inform the Emperor that, if he did not obtain a sight of him, he
would put a period to his existence the moment he left the palace.
The Emperor could not refuse his request, and saluted him with a
smile as he passed by.
During his reign, the Emperor had conferred repeated favours on
several great manufacturers, among others on Oberkamp, Richard
Lenoir, &c. He wished to look for their names in the Dictionary, but
every voice was raised to bear witness to their good conduct.
RECEPTION OF THE PASSENGERS IN THE BENGAL
FLEET.

14th.—About four o’clock a great number of visitors came to
Longwood, They were passengers who had arrived by the East India
Fleet, and the Emperor had signified his willingness to receive them.
The party consisted of Mr. Strange, the brother-in-law of Lord
Melville, First Lord of the English Admiralty; a Mr. Arbuthnot; and Sir
William Burroughs, one of the Judges of the Supreme Court of
Calcutta; two of Lord Moira’s Aides-de-camp; and some others,
together with several ladies. We were all conversing together in the
ante-chamber, when the Emperor left his own room to proceed to
the garden. This circumstance excited the curiosity of our visitors,
who eagerly flew to the windows to see him pass by:—the scene
reminded us of Plymouth. The Grand Marshal conducted our visitors
to the presence of the Emperor, who received them with the most
perfect grace, and with that captivating smile which has exercised
such irresistible power. Curiosity and lively emotion were painted in
the countenances of all.
The Emperor conversed with each individual, and, according to
custom, instantly seized any circumstance that happened to be
connected with their names, as he heard them announced. He
discoursed with the Supreme Judge on legislation and the
administration of justice; with the Company’s officers on trade and
the internal Government of India. He questioned the military
gentlemen as to how many years they had served and how many
wounds they had received; he paid many flattering compliments to
the ladies, and remarked, that the climate of Bengal had not spoiled
the delicacy of their complexions, &c. Then, addressing himself to
one of Lord Moira’s aides-de-camp, he observed that the Grand
Marshal had informed him that Lady Loudon was on the Island, and
that, had she been within his limits, he should have had great
pleasure in paying his respects to her; but that, as she happened to
reside beyond the boundaries which had been prescribed to him, he
had no more opportunity of seeing her than if she were still in
Bengal.
During these conversations, in which I acted as interpreter, Mr.
Strange, with whom I had previously been talking, drew me aside by

the flap of my coat, and in a tone of surprise and satisfaction said:
—"What grace and dignity of manner the Emperor displays!—he
shows that he has been accustomed to the etiquette of holding a
levee!"
We conducted the company to the drawing-room, and curiosity led
them to take a peep at the Emperor’s apartments. Sir William
Burroughs, who, from the post he holds, may be supposed to have
some connection with the English ministry, on entering the drawing-
room asked me whether it was our dining-room. I informed him that
it was the drawing-room, or that we might more properly say, it was
the only room in the house; at this he was much astonished. I then
pointed out to him through the window, the two little chambers
which are all the Emperor has for his own use. His countenance
expressed regret, and he seemed, in his own mind to be drawing
comparisons between the present and the past. Remarking the
wretchedness of the furniture and the narrow limits of our abode, he
said, with an air of concern—"You will be better provided for
soon."—"How," said I, “is there any intention of removing us from
the Island?”—"No, but some elegant furniture and a commodious
house are to be sent to you."—"We do not," I replied, “complain of
the furniture, or the house; but of the rock to which we have been
banished, and the latitude in which it is situated. This latitude cannot
be changed and we can never be well here.”
I repeated to him literally what the Emperor had, a few days
previously said to the Governor on the same subject. Sir William was
amazed, and, pressing my hand, he said with a degree of warmth:
—"My dear Sir, he is too great and too gifted a man; we have too
much cause to dread and fear him."—"But," said I, in my turn, “why
not have driven the car of glory together, instead of mutually
destroying each other by dragging it different ways? What might not
then have been its course?” He looked at me, and again pressing my
hand, he said with a pensive air:—"Yes, that would doubtless have
been better; but...."

All were particularly struck with the Emperor’s freedom of manner,
and his tranquil expression of countenance. I know not what they
had expected to see. One remarked that he could scarcely form a
conception of the strength of mind necessary to enable Napoleon to
endure such wonderful reverses. “That is,” replied I, "because
nobody yet well knows the Emperor’s character. He told us the other
day that he had been like a block of marble during all the great
events of his life; that they had slipped over him without producing
any impression either on his moral or physical faculties."
After dinner, the Emperor asked us, as he often does, what we
should like to read. Some one proposed that we should resume the
Dictionary of Weathercocks; but this the Emperor objected to, on the
ground that it served but to render his evenings the more
unpleasant. “Rather let us amuse ourselves with fiction,” said he;
and, asking for Jerusalem Delivered, he read aloud several cantos of
that poem, occasionally translating passages into French. He then
read the chief part both of Phedre and Athalie, always expressing his
great admiration of the writings of Racine.

EQUALITY OF PUNISHMENTS.—THE EMPEROR REQUIRES ME TO GIVE HIM A
DETAILED HISTORY OF MY ATLAS.
15th.—The Emperor, during his walk, conversed on various subjects,
and at length happened to light on that of crimes and punishments.
He observed that the greatest jurists, even those who had been
influenced by the spirit of the age, were divided as to the principle of
the equalization of capital punishments. At the establishment of the
Code, he should have been averse to equalization, had not
circumstances obliged him to adopt a contrary course. He asked my
opinion: “I am,” said I, "decidedly favourable to the inequality of
punishments. Our notions demand a gradation in punishments,
analogous to that which we conceive in crimes. The harmony of our
sensations seems to require this. I can never bring myself to rank on
a level with each other the wretch who has murdered his father and
him who has merely committed a slight robbery accompanied by
violence. Should these two criminals be visited by the same
punishment?
“In this question the criminal himself is least of all to be considered.
The punishment is his business; and humanity discovers many
hidden modes of relieving his physical suffering. His ideas previously
to the commission of the crime, the feelings which his punishment
creates in the minds of the spectators, and the effect it produces on
society in general:—these are the points which must claim the
attention of the legislator in deciding the question of the equalization
of punishments. It is erroneous to suppose that death alone is
sufficient, and that the kind of death has no influence on the mind of
the criminal in the premeditation of his crime; for if there be
inequality of punishment, there is no culprit who would not make his
choice if he were permitted so to do. Let any member of society
consult his own feelings: he would shudder at the very idea of
certain punishments, while perhaps he would be totally indifferent to
certain modes of death. The inequality of punishments and the
solemnity of executions belong therefore to the justice and policy of

civilization. Yet I conceive that it would now be impossible to subdue
public opinion on this point.”
[11]
The Emperor entirely concurred in these ideas. Having mentioned
the crime of regicide, he observed that it might truly be said to be
the greatest of all crimes, owing to the consequences which it
produced. “The man,” said he, “who should have murdered me in
France would have subverted all Europe; and how many times have
I not been exposed to assassination!”
Lady Loudon, wife of Lord Moira, the Governor-General of India, has
been for several days at St. Helena, where she attracts general
attention. She is a lady of high rank, corresponding nearly with a
French Duchess under the old regime. The English officers treat her
with the utmost respect. To-day the Admiral invited her to a little
entertainment on board the Northumberland. He sent a messenger
on horseback to request me to lend him my Atlas for the evening, in
order that he might shew it to Lady Loudon, whose husband was
described in it as the first representative of the Plantagenets, and
consequently as the legitimate heir to the throne of England.
The Admiral and I were on a footing of perfect indifference; indeed
we had been nearly strangers to each other since the moment he
put me ashore. The request was not so much a mark of politeness to
me, as a compliment to the work itself. The Atlas had been the
subject of conversation, the lady had expressed a wish to see it, and
the Admiral felt a desire to shew it to her. However, I was unable to
satisfy this desire. The book was in the Emperor’s chamber, and such
was the answer I returned.
The Emperor smiled at the honour which the Admiral had intended
for me; and I could not help pitying the amusement that had been
prepared for the lady. This circumstance led the Emperor himself to
speak of the Atlas, and to repeat some observations which had fallen
from him before. He remarked that he heard my work spoken of at
all times and in all places; that he found it sought after by foreigners
as well as Frenchmen. He had heard it mentioned on board the
Bellerophon and the Northumberland, at the Island of St. Helena,

and, in short, every where, persons of information and rank either
knew the work, or expressed a wish to become acquainted with it.
“This,” said he, in a lively strain, “is what I call enjoying a real
triumph, a great reputation in the literary world. I wish you would
give me the history of this Atlas. Tell me when and how you
conceived the idea of it, the manner in which it was executed, and
its results: why you first of all published it under a fictitious name,
and why you did not afterwards affix your real name to it: in short,
give me a true and particular account; you understand, Mr.
Councillor of State?”
I replied that it would be a long story; though to me the recital
would not be devoid of pleasure; for, I added, that my Atlas was the
history of a great portion of my life, and that, above all, I was
indebted to it for the happiness of being now near the person of the
Emperor.
The following is the narrative, such as it appeared when corrected
after my first hasty notes. Its length, doubtless, requires indulgence;
but this I trust the reader will be inclined to grant, on consideration
that the details which I here enter into revive the recollection of my
happiest years, of the period of my youth, my health and strength,
in a word, of the dear but brief interval of the plenitude of life. I
once more entreat the reader to pardon the prolixity in which I have
indulged; but this statement so forcibly revives my recollections of
past happiness that even now, on reading it over, I cannot find it in
my heart to cancel any part of it.
"This Work was partly the fruit of chance; but above all, of necessity,
which, as the common proverb says, is the mother of industry.... At
the time of the first reverses of the French emigrants, I was cast by
the political hurricane in the streets of London, without friends,
without money, and without resources; but possessing the requisite
courage and willingness for exertion. To a man animated by such a
spirit, London, at that time, afforded certain sources of emolument.
"After having unsuccessfully made several applications, I determined
to rely on myself alone, and, like Figaro, I decided on turning author.

For a moment, I had thoughts of becoming a romance writer: this
idea was suggested to me by the proposals of a bookseller; but he
required too much and was inclined to pay too little. I then turned
my thoughts to writing history, which, at all events, was calculated
to procure for me a certain moral advantage, by storing my mind
with positive knowledge. It was then I conceived the first idea of my
Atlas, which I may truly regard as an inspiration from Heaven, for to
it I owed my life. The work was at first a simple sketch, a mere
nomenclature, very different from the form in which it now appears.
However, it sufficed immediately to relieve me from embarrassment,
and to secure to me what might be called a little fortune, in
comparison with the miseries endured by the other emigrants. Then,
Sire, came the Peace of Amiens, and the benefits conferred on us by
your amnesty. I was enabled to make a journey to France, merely as
a traveller, having no other object in view than to breathe my native
air and to see the French capital. There I found myself at liberty to
express my sentiments without restraint; investigation was easy; my
ideas and my judgment were enlarged; I was master of my time,
and I undertook to arrange my Atlas in the form in which it now
appears. I proposed publishing regularly four sheets per quarter. I
was now vastly improved both in my mind and circumstances.
Interest, attention, good offers, money and connexions, poured in
upon me; and I may confidently affirm that this was the happiest
period of my life.
"In England, I had published my Work under a feigned name, in
order to avoid compromising the honour of my own. I happened to
fix upon Le Sage, just as I might have decided on Leblanc, Legris, or
Lenoir. But I could not have made a more unlucky choice, or, at
least, I could not have assumed a more general appellation.
Sometime afterwards, a letter intended for me passed through all
the different colonies of French emigrants in London, and was
delivered by turns to twenty-two priests, who all bore the name of
Le Sage. At length one, who had apparently discovered that the
name did not belong to me, sent me the letter in a violent rage,
observing that, when people thought proper to change their names,

they should at least avoid taking those that belonged to other
persons.
"In France I still preserved the name of Le Sage, which had now
become identified with my Atlas. To have published it under a new
name might have led to the supposition that it was a new work.
Besides, I did not wish to expose my own name to the chance of
failure, to the attacks of the Journals, or to the bickerings of
criticism. Even though I had been assured of the complete success
of the work, I should not probably have felt the more inclined to
affix my real name to it, owing to a remnant of my old prejudices, of
which I could not easily divest myself.
"Certainly this literary fame flattered me not a little; but I had
sprung from a warlike race, and I conceived that I was in duty
bound to pursue fame of another kind. However, circumstances
rendered this impossible, and I think it proper to mention that at
least I was not unconscious of the duty. I never had cause to repent
of my double appellation. Independently of my real motive for
assuming it, it diffused around me an air of adventure and romance
which was by no means disagreeable, and which was moreover in
unison with my temper and character. It occasioned many mistakes
and humourous scenes which afforded me considerable amusement.
In England, for example, I have often, when in company, been
questioned in the most innocent way imaginable respecting the
merits of M. Le Sage’s work; and at a boarding-school I was once
addressed in very discourteous language, because I obstinately
persisted in condemning my own Atlas.
"So long as I continued myself to manage the publication of the
work, my method was to treat in person with all who offered to set
their names down as subscribers. I had now no favours to solicit; I
rather found it necessary in some instances to guard against
receiving those that were offered. In France particularly I was
overwhelmed with acts of kindness and flattering compliments.
Some paid me these attentions because they knew me, others
precisely because they did not know me; and all because I

conducted myself alike to each. For my part, I enjoyed the curious
spectacle that now presented itself to me. As every one who wished
to become a subscriber was obliged to give in his own name, I took
a review of many characters, whom I well knew, and observed them
in silence. I was thus enabled to meditate at my ease on the curious
diversity of opinion, judgment, and taste. The point which one
condemned was precisely that which another most admired, which a
third declared to be indispensable, and which a fourth pronounced to
be inadmissible. Each according to custom failed not to set forth his
own opinion as the prevailing one: it was the sentiment of all Paris
and of every body.
"I had now an opportunity of being convinced of the great
advantage that a man derives from superintending his own business
himself, and of the important influence of politeness and good
manners in all the affairs of life. I acceded to every thing that was
proposed, I received every hint that was suggested, and I was
repaid a hundred-fold for my complaisance. It frequently happened
that a person who had called on me, without any intention of
purchasing the work, was not only induced to carry it away with him,
but brought me ten, twenty, or even a hundred, additional
subscribers.
"One described my Atlas as a classic work to the Minister of the
Interior; another recommended it to the Minister for Foreign Affairs;
a third promised to procure for me the decoration of the Legion of
Honour, and a fourth wrote a flattering critique on the work, and got
it inserted in the public journals. Some carried their interest and
attachment for me even to a degree of enthusiasm. Of this the
following are instances. One of my provincial subscribers, who was
unacquainted with me, wrote to request, as a particular favour, that
I would get my portrait engraved to embellish the work, offering, in
case I acceded to the proposition, to defray half the expenses of the
engraving. Another, who was the owner of the Chateau de
Montmorency, paid me a visit every week under pretence of
enquiring whether I had got a new sheet of my Atlas ready for
publication, but in reality, as he himself assured me, to pass his

happiest hours in my society. He added that, if ever I should take a
fancy to sell my conversation as I did the sheets of my work, it was
in my power, if I chose, to ruin him. I afterwards learned that this
was a man of a very eccentric turn; one of La Bruyere’s characters;
quite after the manner of Jean-Jacques. For a considerable time he
seemed to rack his invention to make me offers of service in the
most delicate way imaginable: he even went so far as to throw out
paternal suggestions to me. ‘M. Le Sage,’ said he, oftener than once
‘you ought to marry. You possess qualities that are calculated to
insure the happiness of a wife, and still more that of a father-in-law.’
I must not omit to mention that the old gentleman had but one
daughter, and she was a rich heiress. However, the warmth of our
intimacy gradually abated, till at length I entirely lost the
acquaintance. It was not until a considerable time afterwards that,
being on a country excursion with a party of ladies, the sight of the
Chateau de Montmorency revived the recollection of my old friend. I
related the history of his eccentricities to the ladies who
accompanied me: their curiosity was excited, and we determined to
visit the chateau. The porter refused to admit us. On my enquiring
whether the gentleman was at his country residence, I received for
answer that he was there, and that this was precisely the reason
why we could not be admitted. I thought it very extraordinary that
he should thus immure himself and render himself totally
inaccessible. With considerable difficulty I prevailed on the servant to
announce M. Le Sage. The sound of the name operated like
enchantment; the affront offered to an elegant calash and rich
liveries was immediately repaired. The gates were thrown open,
apparently to the no small astonishment of the porter. The servants
received orders to show us over the building and to offer us every
kind of refreshment. We had brought with us in the carriage
provisions for a little rural repast; but a sumptuous dinner was laid
out for us in one of the best apartments; and we could not, with any
thing like a good grace, decline accepting what was so politely
offered. All this hospitality was perfectly disinterested on the part of
the worthy old gentleman, who was confined to his chamber by the
gout. He was overjoyed at seeing me; and he seemed to regard my

visit as the return of the prodigal son. He insisted on seeing the
ladies who accompanied me, and was carried into the dining-room
to do the honours of the dessert. One thing that amused us infinitely
was that he seemed to have no idea of the rank of the friends by
whom I was accompanied; and he treated them like persons of
inferior rank, though they were in reality ladies of distinction. The
old gentleman would now scarcely allow me to depart; he insisted
on my repeating my visit, and said, that I and all my friends should
ever be welcome to his residence. But alas! I could not avail myself
of his kindness; for a few days afterwards I read in the papers an
account of the death of this kind and sincere friend.
"From the commencement of my greatness, I may, under every
point of view, date the termination of the golden age of my Atlas.
When I was transplanted to Court and permitted to approach your
Majesty’s person, I conceived that I could not with propriety descend
to the details that had hitherto occupied me. I confided the
management of the copyright to one of my old college companions,
who had been an emigrant like myself, but who did not turn the
publication to so good an account as I had done.
"On entering upon my new post at Court, I was loaded with
compliments on my production; but to these I replied indifferently,
and just as one would do at a ball, after dropping one’s mask. When
it was found that I never alluded to my work, that I never quoted
from it, and that I avoided all discussion on it, I was never spoken to
on the subject; and at length people began to wonder how I had
ever written it, and indeed to doubt whether I had any right at all to
be considered as its author.
"On hearing these words, the Emperor said to me, ‘My dear Las
Cases, even this doubt has found its way to St. Helena. I have heard
it affirmed that the work was not written by you, that you purchased
the manuscript from the real author; and in support of this assertion
it has been remarked that you know nothing at all about the book,
because you never speak of it. To these observations,’ continued he,
‘I have merely contented myself with saying, Did you never know

any question to remain without a complete answer? Besides I
recognise throughout the whole work the style, the very expressions,
of Las Cases.’
“Many,” said I, resuming my narrative, "will think I injured myself by
this denial; but I preferred good taste to quackery, and I was only
acting according to the dictates of my natural disposition. Your
Majesty was the other day describing how Syees used to present
himself loaded with written plans, and at the very first word of
contradiction, as soon as he found it necessary to act on the
defensive, he would gather up his papers and be off in a moment.
This was precisely my feeling. I never could stand up publicly to
support my opinions. Before I could do this, I must enjoy the
authority of rank or the freedom of intimate friendship: otherwise I
prefer dooming myself to silence, that is to say, when I am not
interrogated and urged to the point. But to return to my subject.
"So long as I remained in obscurity I enjoyed the good-will of every
one; but my elevation rendered me an object of enmity, and I felt
the influence of that vague feeling of envy and malevolence which
ever follows the footsteps of fortune. The public journals, which for a
length of time had overflowed with flattery and agreeable
expressions in favour of the Historical Atlas, now inserted some very
ill-natured articles respecting the work, and when these were traced
to their source, the writers frankly avowed that they had been
occasioned solely by changes that had taken place in political
opinions and public affairs.
"A report was delivered to the Institute of all the works that had
appeared for several years past; and in this report the Atlas was very
severely treated. Happening to be one day in company with the
writer of this report, to whom I was known only by the name of Le
Sage, I expressed to him my dissatisfaction at what he had said of
the Atlas. He candidly confessed that the work and its author were
alike unknown to him; that, having found the labour of writing the
report too much for him, he had divided the task among several
other persons. He informed me that the article on Le Sage’s Atlas

was infinitely more severe when delivered to him than it appeared as
inserted in the report. He had softened it down considerably. ‘I can
easily perceive,’ continued he, ‘that you have enemies in the literary
world, and for these you are indebted to your habits and your
situation. You have connected yourself with a Count somebody, who
holds places at Court; but courtiers and authors never agree well
together. Those gentlemen are, for the most part, very unlike us. It
is said that, in this curious partnership, you supply the talent and he
provides the money. What is the use of that? The Count is only
making his profit of you; your work is good, and your bookseller
would have remunerated you for it. However, I am only repeating
what I have heard, and I advise you to what I conceive to be your
interest. If you wish to enjoy our suffrage, you must connect
yourself with us, you must identify yourself with our doctrines, and
leave the great folks to themselves.’
"I replied, with all possible civility, that I was certainly indebted to
him for his kind advice, though it was not just then in my power to
follow it. I assured him that he had formed an unfair opinion of my
friend; that our purses and our very lives were common to each
other; that our friendship and intimacy were indissoluble; that we
had vowed to live and die together, and that nothing could induce us
to break that vow. It was altogether a truly comic scene.
"Some time afterwards I was dining at the table of a Prince: I was
seated beside my illustrious host, and wore a uniform covered with
lace. The member of the Institute was one of the guests. Surprise
and embarrassment were portrayed in his countenance. I spoke to
him several times; but he always drew close to his neighbours,
whispering to them, and apparently making enquiries. After dinner,
he came up to me, and very good-humouredly begged me to relieve
him from his perplexity. He said that he perfectly recollected having
had the honour of meeting me before, but that he was quite at a
loss to comprehend the trick that I had played upon him. I
disclaimed any intention of hoaxing him. ‘All that you have seen,’
said I, ‘and all that I have told you, is nothing but reality and truth.
The mystery is easily solved. You then saw M. Le Sage who supplies

Welcome to our website – the perfect destination for book lovers and
knowledge seekers. We believe that every book holds a new world,
offering opportunities for learning, discovery, and personal growth.
That’s why we are dedicated to bringing you a diverse collection of
books, ranging from classic literature and specialized publications to
self-development guides and children's books.
More than just a book-buying platform, we strive to be a bridge
connecting you with timeless cultural and intellectual values. With an
elegant, user-friendly interface and a smart search system, you can
quickly find the books that best suit your interests. Additionally,
our special promotions and home delivery services help you save time
and fully enjoy the joy of reading.
Join us on a journey of knowledge exploration, passion nurturing, and
personal growth every day!
ebookbell.com

Advances In Aerogel Composites For Environmental Remediation 1st Edition Aftab Aslam Parwaz Khan Editor

About This Presentation

Slide Content

Tags

Categories

Download

Quick Actions

Statistics

Related Slideshows

Advances In Aerogel Composites For Environmental Remediation 1st Edition Aftab Aslam Parwaz Khan Editor

About This Presentation

Slide Content

Slide 1

Slide 2

Slide 3

Slide 6

Slide 7

Slide 8

Slide 9

Slide 10

Slide 11

Slide 12

Slide 13

Slide 14

Slide 15

Slide 16

Slide 17

Slide 18

Slide 19

Slide 20

Slide 21

Slide 22

Slide 23

Slide 24

Slide 25

Slide 26

Slide 27

Slide 28

Slide 29

Slide 30

Slide 31

Slide 32

Slide 33

Slide 34

Slide 35

Slide 36

Slide 37

Slide 38

Slide 39

Slide 40

Slide 41

Slide 42

Slide 43

Slide 44

Slide 45

Slide 46

Slide 47

Slide 48

Slide 49

Slide 50

Slide 51

Slide 52

Slide 53

Slide 54

Slide 55

Slide 56

Slide 57

Slide 58

Slide 59

Slide 60

Slide 61

Slide 62

Slide 63

Slide 64

Slide 65

Slide 66

Slide 67

Slide 68

Slide 69

Slide 70

Slide 71

Slide 72

Slide 73

Slide 74

Slide 75

Slide 76

Slide 77

Tags

Categories