aluminium extraction

this ppt is about aluminium extraction and applications.

1. Aluminum PROPERTIES, USES, EXTRACTION PROCESS, ALUMINUM ALLOYS Done By: Anubhav D. Kashyap (04) Anuj Sharma (05) Arushi Teotia (06)

2. DID YOU KNOW?

3. Aluminum

4. HIGHLIGHTS  History Ores Extraction Methods Properties Alloys Applications Pure Al Paste

5. Basic Information : Atomic number ? Electronic configuration? Density ? Atomic mass? Melting point? Boiling point ? 13 [Ne]3s 2 3p 1 2.7 g/cm 3 26.9g 2519 ∘ C 660 ∘ C

6. HISTORY Alum? is hydrated double sulphate salt of Al  Commander Archelaus discovered that wood was practically flame resistant if it was treated using an alum solution.  Scientist suspected an unknown metal in alum as early as 1787. 40 years Extraction Al

7. Humphry Davy : that aluminium could be produced by electrolytic reduction from alumina (aluminium oxide). Hans Christian Oersted ( Denmark) : Was successful in extracting but produced an aluminium alloy rather than pure aluminium. Friedrich Woehler [German] : continued Hans Christian’s work. 1808 1825 1827 1846 Friedric h created small balls of solidified molten aluminium (globules) 1856 Henri-Etienne Sainte-Claire Deville [French] : industrial applications. [ DEVILLE PROCESS] 1856-1890 200 tonnes of Al were produced in 36 years

8. But… … Chou-Chu general of ancient China during the third century. Upon digging his tomb, historians found a piece of jewellery. 85% of the material of the jewellery was actually aluminium

9. Introduction Aluminium is found in many rock minerals, usually combined with silicon and oxygen in compounds called Alumino silicates. Example: Kayanite ( Al₂O (SIO₄)), Topaz ( Al₂O (SIO₄)(OH,F)₂), Kaolinite ( Al₂Si₂O ₃(OH)₄) etc. Under certain types of tropical soil weathering these alumina-silicate compounds are separated into layers of hydrated iron oxide, hydrated alumina and silica. Example: Al(OH)₃, Al₂O₃.3H₂O etc. When such deposits are rich in alumina, this comprise the mineral bauxite. Bauxite is a mixture of gibbsite (Al(OH)₃), boehmite ( AlO (OH)) and diaspore ( AlO (OH)); and has a general formula of Al₂O₃.x2H₂O

10. Aluminum ores There are a large number of minerals and rocks containing aluminum; however, only a few of them can be used for extracting metallic aluminum. Bauxites are the most widely used raw materials for aluminum. Initially a semifinished product, alumina (A1 2 O 3 ) is extracted from the ores, and the metallic aluminum is produced electrolytically from the alumina. Nepheline-syenites as well as nepheline-apatites are also used as aluminum ores. These minerals are simultaneously used as a source of phosphates. Other minerals which can be used as a source of aluminum include alunites , leucitic lavas (the mineral leucite ), labradorites , anorthosites , and high-alumina clays and kaolins .

11. Bauxite Bauxite is the most important aluminium ore. It consists largely of the minerals gibbsite Al(OH)3, boehmite γ- AlO (OH), and diaspore α- AlO (OH), together with the iron oxides goethite and hematite. Bauxite does not have a specific composition. It is a mixture of hydrous aluminum oxides, aluminum hydroxides, clay minerals, and insoluble materials such as quartz, hematite, magnetite, siderite, and goethite. Bauxite is typically a soft (H:1-3), white to gray to reddish brown material with a pisolitic structure, earthy luster and a low specific gravity (SG: 2.0-2.5). Bayer’s Process is the main process for the production of bauxite.

12. Raw Material with uses for the extraction of aluminium RAW MATERIAL USE Alumina Source of Aluminium Crude Oil Making Coke Coal Making Pitch Coke, Pitch Electrode Manufacture Cryolite ( Na₃AlF ₆) Dissolving Alumina at 970⁰C (synthetically produced) Electricity Reduction of Alumina to Aluminium

13. EXTRACTION PROCESS 1.DEVILLE PROCESS 2.SERPECK’S PROCESS 3.HALL-HEROULT PROCESS 4.BAYERS PROCESS

14. 1.Deville process first industrial process. based on the extraction of alumina with sodium carbonate . Calcination of the bauxite at 1200 °C with sodium carbonate and coke. The alumina is converted in sodium aluminate. Iron oxide remains unchanged and silica forms a polysilicate .

15. sodium hydroxide solution is added , which dissolves the sodium aluminate, leaving the impurities as a solid residue. The solution is filtered off; carbon dioxide is bubbled through the solution, causing aluminium hydroxide to precipitate, leaving a solution of sodium carbonate The latter can be recovered and reused in the first stage. The aluminium hydroxide is calcined to produce alumina.

16. 2.Serpeck’s Process This process is used for the purification of bauxite ore containing silica (SiO2) as the main impurity . The powdered ore is mixed with coke and the mixture is heated at about 1800°C in the presence of Nitrogen gas, when aluminium nitride is formed. Al2O3 . 2H2O + 3C + N2 → 2AI N + 3CO+ 2H2O Aluminium nitride thus obtained is hydrolysed with water to get a precipitate of Al(OH)3. 2Al N + 6H2O → 2NH3 + Al(OH)3 The precipitate of Al (OH)3 is filtered, washed and dried. The silica present as impurity in bauxite is reduced to silicon which being volatile at high temperature. is removed easily. SiO2 + 2C → Si + 2CO

17. 3.Hall-Héroult process Aluminium's development changed with the discovery of a more cost-efficient electrolytic production method in 1886. It was developed by Paul Héroult , a French engineer, and Charles Hall, an American student, independently and at the same time. The method involved the reduction of molten aluminium oxide in cryolite . The process demonstrated excellent results, but required an enormous amount of electric power .

18. 4.Bayer’s Process STEP-1: Purification of bauxite - This is a two-step process called Bayer's process: a) First, we dissolve bauxite in aqueous sodium hydroxide( NaOH ) by digestion. Bauxite with higher hydroxide contents (Al(OH) 3 ) are treated at 120-140° C with dilute(3M) NaOH and bauxite with higher oxide content(' AlOOH ') is treated at a higher temperature(200-250° C) and a higher pressure (35 atm ) with 5-7M NaOH . b) The insoluble impurities are separated by filtration . Al(OH) 3 is precipitated by carbon dioxide and ignited to ~1200° C to obtain Al 2 O 3 .

19. STEP-2: Purified bauxite is then dissolved in cryolite (5-7% CaF 2 , 5-7% AlF 3 , 2-8% Al 2 O 3 ) and electrolyzed at 950° C in a carbon lined steel cathode with hard carbon rods as the anode. Li 2 CO 3 is used to ( i ) lower the melting point of the electrolyte (ii) permit larger current flow and (iii) reduce fluorine emission. The resulting reactions are produced: Al 2 O 3 → 2Al 3+ + 3O – At Cathode (positive electrode where reduction occurs by gain of electrons) : 2 Al 3+ + 6e - → 2Al At Anode (negative electrode where oxidation occurs by loss of electrons): 3O -- - 6e - → 3O

20. Alloys of aluminium Aluminium alloy  A luminium (Al) is the predominant metal . The typical alloying elements are copper, magnesium, manganese, silicon, tin and zinc. There are two principal classifications, namely casting alloys and wrought alloys, both of which are further subdivided into the categories heat - treatable and non-heat-treatable. The most important cast aluminium alloy system is Al–Si, where the high levels of silicon (4.0–13%) contribute to give good casting characteristics.

21. Alloys of Aluminium and it’s composition Alloy Name Al (%) Cu ( %) Mn ( %) Mg (%) Zn (%) Duralumin 95 4 0.5 0.5 - Magnalium 70-90 - - 30.10 - Elektron 9-10 - 0.5 87-86 3.5

22. Aluminium Alloys with their uses   Major alloy element   Content   Product   Some typical uses   Copper   Up to 4.5%   Sheet Extrusions Castings   High strength aircraft parts   Manganese   1.2%   Sheet   Sheet m etal work, pots etc.   Silicon   Up to 13%   Castings Motor parts etc.   Magnesium and Silicon   0.7% Mg , 0.4 % Si   Sheet Extrusions   Architectural extrusions   Magnesium   Up to 5%   Sheet   Marine, boats etc.   Zinc, Magnesium and Copper   5.8% Zn , 2.5 % Mg , 1.4 % Cu   Sheet Extrusions   High strength aircraft

23. Properties of aluminium It has low density, is non-toxic, has a high thermal conductivity, has excellent corrosion resistance and can be easily cast, machined and formed. It is the second most malleable metal and the sixth most ductile. It is cheaper than copper and weight for weight is almost twice as good a conductor. It is often used as an alloy because aluminium itself is not particularly strong.

24. These properties lead to a variety of specialised uses. 1.Lightness :- Use in aerospace and transport industries, as its lightness enables a greater volume of metal to be used, thus giving greater rigidity. Also used in pistons, connecting rods, etc. to give better balance, reduced friction and lower bearing loads . 2.Specific Strength: It is known as the strength to weight ratio of a material. Aluminium alloys have higher specific strength value (12 – 125kNm/Kg) than cast iron and steel . 3.Electrical conductivity : Used extensively for electrical conductors, especially in overhead Cables.

25. 4.Thermal conductivity : Extensive usage in heat exchangers, cooking utensils, pistons, etc. 5. Corrosion resistance : This is made use of in chemical plant, food industry packaging, building and marine applications. Aluminum paint is widely used. The oxide film can be thickened by anodizing, and the film can be dyed in a wide range of colors. This is done by making the article the anode of a direct current electrolysis cell using an electrolyte solution of approximately 15% sulfuric acid. 2Al + 3H₂O → Al₂O ₃ + 6H ₊ + 6e

26. 6.Linear expansion : Compared with other metals, aluminium has a relatively large coefficient of linear expansion. This has to be taken into account in some designs. 7.Non-magnetic material : Aluminium is a non-magnetic material. To avoid interference of magnetic fields aluminium is often used in magnet X-ray devices. 8. Machining : Aluminium is easily worked using most machining methods – milling, drilling, cutting, punching, bending, etc. Furthermore, the energy input during machining is low.

27. advantages Aluminum has three main advantages when compared with other metals. It has a low density, about one third that of iron and copper. Although it reacts rapidly with the oxygen in air, it forms a thin tough and impervious oxide layer which resists further oxidation. This removes the need for surface protection coatings such as those required with other metals, in particular with iron. Aluminum has a high corrosion resistance because of the tough oxide film always present on the surface of aluminum in the presence of air, water vapor, etc., and it has a strong affinity for oxygen.

28. disadvantages The disadvantages of aluminium are as follows: Aluminium can’t be used in such areas where heavy loads are required. Due to its ductile nature, it cannot take same stress like other elements, as in steel. Aluminium doesn’t give or bend as much as steel which means that it’s more prone to breaking out right. It also doesn’t absorb vibrations as good as steel, which can be good or bad depending on the situation.

29. APPLICATIONS OF AL

30. Aluminum is used in a huge variety of products including cans, foils, kitchen utensils, window frames, beer kegs and aero plane parts.

31. Aluminum is a good electrical conductor and is often used in electrical transmission lines.

32. When evaporated in a vacuum, aluminum forms a highly reflective coating for both light and heat. It does not deteriorate, like a silver coating would. These aluminum coatings have many uses, including telescope mirrors, decorative paper, packages and toys.

33. Biological Role of aluminum Aluminium has no known biological role . Our bodies absorb only a small amount of the aluminium we take in with our food. Cooking in aluminium pans does not greatly increase the amount in our diet Aluminium can accumulate in the body, and a link with Alzheimer’s disease (senile dementia) has been suggested but not proven.

34. THANKYOU…