Solution Purification and Metal Recovery

Purifikasi pada Hidrometalurgi

1. CHAPTER III
SOLUTION PURIFICATION AND
METALS RECOVERY FROM
PREGNANT LEACH SOLUTION

2. Remember thefollowinggeneralflowsheetof
hydrometallurgicalprocess:
Ore/concentrate
leaching
Solid-liquid separation
Solution purification
Precipitation
Pregnant Solution
Solid residu to waste
Leaching agentOxidant
Precipitant or
electric current
Pure compound Metals

3. Solution Purification
▪Leachingusuallynot100%selective.Once
thesolutionisseparatedfromthesolids,it
requirespurification.
▪Withoutpurificationthesubsequentprocess
ofmetalsrecoverywouldnotnotperform
effectively.
▪Oftenhighpuritysolutionsarerequiredto
producehighpurityproductsinmetals
recovery.

4. Four main methods of Solution
Purification
•Adsorption on Activated Carbon
•Ion Exchange (IX)
•Solvent Extraction (SX)
•Precipitation
–Precipitation by pH adjusment
–Precipitation by metals (cementation)
–Precipitation by gas
–Precipitation by electric current (electrodeposition)
–Precipitation by thermal treatment (cystallization)

5. Adsorption on Activated Carbon
•Adsorptiononactivatedcarbonisdonemainlyfor
concentratinggoldandsilverfromcyanideleach
solution.
•Activecarbonpreparedfromactivatedcharcoalis
muchcheaperadsorberthanIXresinsandSX
reagents.
•Theadsorptionofmetalionsbyactivatedcharcoalis
usuallyfavorableonlytoanionsandnottocations.
•Activatedcarbonisan“amorphous“formofcarbon;it
hasnoregularatomicstructure,hassosmallcrystal
sizethatitdoesnotgiveanX-raydiffractionpattern,
unlikethatofdiamond,graphite.

6. Preparation of Active Carbon
•Activatedcarboncanbemadefromawiderangeof
sourcematerials,suchascoal,coconutshells,wood,
peat,orbone.
•Therearetwotypesofamorphouscarbon,namely,
carbonblacksandcharcoals.
•Carbonblack:nonporousfineparticlesofcarbon
preparedbyincompletecombustionofgaseousor
liquidcarbonacesousmaterials(naturalgas,
acetylene,oils,tar)inlimitedsupplyofair.
•Carbonblacksareusedaspigmentsintherubber
industryandinkmanufacture.

7. Preparation of Active Carbon
•Heatingofsolidcarbonaceusmaterialssuchascoal,
woodandnutsheelsatabout600
o
Cintheabsenceof
airtovolatilizecomponentsotherthancarbon–the
processknownas“carbonization“.
•Furtherheatingto400-800
o
Cforlimitedtimewithair,
chlorineorsteamtoproducehighporousmaterialof
„activatedcharcoal“.
•Intheactivationstep,thesmallporestructureis
developedbyburningawaysomeremainingmaterial
tocreatenewporeandenlargeothers.
Active carbon is prepared as follow:

8. Preparation of Activated Charcoal
•Charcoalactivatedatlowtemperature(400
o
C)
areabbreviatedbyL-charcoalsandthose
activatedathightemperature(800
o
C)are
abbreviatedbyH-charcoals.
•Afteractivation,H-charcoalmustbecooledin
aninertatmosphere,otherwisetheywillbe
convertedtoL-charcoal.

9. Properties of Activated Carbon
•Thepropertiesofactivatedcarbondepend
primarilyonthetemperatureofactivation.
–Ithashighporosityandsurfaceareaper
unitweight.
–Itishydrophilic,meanswettedbywater
duetosurfacecomplexes.
–Itcontainsappreciableamountsof
hydrogenandoxygenintheirstructure
(boundintheformofsurfacecomplexes).

10. Tipical properties of L-charcoal and H-
charcoal activated at different temperatures
Activationtemperature
400
o
C 550
o
C 650
o
C 800
o
C
L-Charcoal H-charcoal
Analysis (%)
Carbon 75.7 85.2 87.3 94.3
Oxygen 19.0 10.4 7.4 3.2
Hydrogen 3.2 2.7 2.1 1.5
Ash 0.7 1.3 1.4 1.2
Surfacearea
[m
2
/g]
40 400 390 480

11. Typical microstructure of active carbon showing
the porous structure
•Ingoldextractionindustries,activatedcarbonis
usedintheformofpelletsorbreeze,having
diameterofabout2mm.

12. Adsorption of Au and Ag from pregnant
cyanide solution
-Theadsorptionconsistsoftwounitprocess:
-LOADING,and
-STRIPPING
StrippingdesorptionofAu,Agfromactivecarbonsurfaceby
meansofwashingwithasolutionsuchas20-25wt%ethyleneor
propyleneglycoland2wt%causticsoda).
recoveryofAuandAgisfurtherdonewithelectrowinning.
strippedcarbonmustbereactivated.

13. Industrial application of Active carbon
-Activecarbonareusedin:
-CarboninLeach(CIL)
-CarboninPulp(CIP),and
-CarbonInColumn(CIC)
-CarboninLeach(CIL):
-Appliediftheorescontainscarbonaceousmaterialssuchas
carbonate
-Carbonisaddedinleachingtanktoavoidgoldlossesinfine
carbonparticlesinoresthatarenotrecoveredbyscreening
-CarboninPulp(CIP):
-Carbonisaddedinthepulpafterleaching
-CarboninColumn(CIC):
-Carbonisplacedinacolumnandgold-bearingsolutionin
loadedtothecolumn

14. Block diagram of gold extraction applying
CIP method

15. Pictorial diagram of gold extraction
applying CIP method

16. Block diagram of gold extraction applying
CIL method

17. Solvent Extraction
•Extractionofmetalsfrompregnantaqueousleachsolution
byanorganicreagenttoformorganometalliccomplex
solution.
•Metalspeciesleavetheaqueousphaseandenterthe
organicphase
•Unitprocess:Extractionandstripping

18. Flow of material in metals extraction
by leaching-SX-electrowinning

19. ▪SXwasusedfirstlyforuraniumextraction
(Manhattanproject),followedbytheextractionsof
plutonium,thorium,niobium,tantalum,
zirconium,hafnium,boron,berrilium,molybdenum
▪Nowdays,SXisalsoindustriallyusedin
hydrometallurgicalextractiontoproducebase
metalssuchascopper(fromlowgradeore)and
nickelaswellasplatinumgroupmetalas(Pt,Pd,
Rh)
▪Mechanismofcopperextractionperformsbythe
followingreaction:[] []
aq
+
org2
Extraktion
stripping
aq
+2
org H2+CuRCu+H-R2
→
←

20. Copper extraction by heap leaching-SX-
electrowinning

21. Equipment of solvent extraction
▪Mixer-Settler
Consistsofamixingchamberwherethe
aqueousandorganicphasesaremixed
togetherbyarotatingimpeller
Certaintimeareprovidedformixedphases
toseparateinasettlingchamber
Themixersettlerrequireslargespace.
Manystagesareusuallyused(3to5)and
areoperatedincountercurrentflow.

22. Schematic of mixer settler phase separation
between liquid and aqueous phase

23. Equipment of solvent extraction
▪Column
Columndesigns:packedcolumn,pulsecolumn,
rotatingdiskcolumn
Packedcolumn:simplestdesign.Theorganic
solutionisintroducedfromthebottom,whereas
theaqueoussolutionfromthetop.
Pulsecolum:usingscreenpartitionsinsteadof
packing
Rotatingdiskcolumn:consistsofaverticaltower
withannulardiskattachedtothetowershell

24. Contactor columns in SX
Schematic
figure of
packed
column (left)
and pulsating
column (right)

25. ▪SX Extractant Selection Criteria
•Availabilityandcost
•Highsolubilityininorganicdiluentwhichisinsolublein
aqueousphase
–e.g.kerosene(i.e.,usually2to20%extractant)
•Easeofformationofmetal-organiccomplexwhichis
solubleinorganicphase
•Selectivetoimportantmetalsinaqueoussolution
•Goodseparationfromaqueousaftercontacting
densityisappreciablydifferent
lowviscosity
highsurfacetension
•Easeofmetalrecoveryfromorganicphase
•Easeofregenerationofextractantforrecycle

26. ▪SX Reagent Selection Criteria (cont.)
•Safetohandle
Nontoxic
Nonflammable
Non-volatile
•Stableduringstorageorwhenincontactwith
acidsoralkalinesanddoesnothydrolize
duringextractionorstripping

27. Diluent
•Anextractantisseldomusedinpureform.It
isusuallydilutedinacheaporganicsolvent
(calleddiluent)inorderalsotoimproveits
physicalpropertiessuchasitsdensityand
viscosity.
•Diluenthasnocapacitytoextractmetalions
fromsolution.
•Themostcommonly useddiluent:
hydrocarbonsandsubstitutedhydrocarbon
suchaskerosene.

28. Organicsolventextractanttypes
•Ethers and their derivatives
•Alcohols
•Aldehydes
•Ketones
•Oxime
•Organic acids
•Phenols
•Esters
•Amine and amine oxides
•Organic sulfides and sulfoxides
•Others

29. Some trade marks of extractants
•LIX
•Cyanex
•Kelex
•Versatic
•etc

30. Strippingand Distribution Coefficients
•Thetransportofmetalsfromaqueousphasetoorganic
phaseismeasuredbydistributioncoefficientD,in
which:
ThehigherDvalueatequilibrium,thehigheristhe
possibilityofasolventinextractingacertainmetalsin
aqueoussolution.phaseaqueous in ionconcentrat metals
phase organic in ionconcentrat metals
D=
Distribution coefficient

31. •Strippingcoefficient(D‘)isdefinedas:
SemakintingginilaiD‘padakesetimbangansemakin
besarkecenderunganionlogamditransferdarifasa
organikkefasaaqueous.
Ada2tujuanprosesstripping,yaitu:
1.Recoverylogamdarifasaorganik
2.Regenerasipelarut/extractantuntukdigunakan
kembali
StrippingCoefficientphase organic in ionconcentratmetals
phaseaqueous in ionconcentratmetals
=D'

32. Strippingdapatdengansalahsatucaraberikut:
a.Pencuciankembalifasaorganik
b.Pengendapanlogamsecaralangsungdarifasa
organik
c.Selectivestrippingjikapelarutorganikmelarutkan
lebihdarisatulogam.Dalamkasusini,stripping
dilakukandenganreagenyangberbedasecara
berurutan.

33. Nisbah (Rasio) Fasa
Nisbahvolumeorganik/aqueousbernilairendah,
mungkinbanyakpelarut(solvent)yanghilang.
Sebaliknyaapabilanisbahvolumeorganik/aqueous
bernilaibesar,kemungkinanberartikonsumsisolvent
tinggi(aspekekonomis).o
a
V
V
fasa Nisbah
V
a= Volume fasa aqueous
V
o= volume fasa organik

34. Persen Ekstraksi
•Apabilaberatsolute(zatterlarut)mula-muladalamfasa
aqueous=w,dansetelahekstraksiberkurangmenjadi
=w
1,maka
dimana,V
o=volumefasaorganik
V
a=volumefasaaqueousa
o
Vw
Vww
D
/
/)(
1
1

(1)1001
100
1
1










w
w
w
ww
ekstraksipersen

35. 100


oaV/VD
D
ekstraksipersen Daripersamaan(1)dapatdiperolehhubungan:ao
a
VDV
V
w
w


1
sehingga100x
VDV
V
- 1 ekstraksi persen
ao
a



36. Faktor Pengayaan dan Pemisahan
•Saat2ionlogamyangberbedadiekstrakdarisebuahlarutan
aqueousolehpelarutorganik,makaseparationfactor,β,untuk
2ionlogamtersebutdidefinisikansebagai:
dimana,D
AdanD
Bkoefisiendistribusimasing-masingion
logam.Agarpemisahanmungkinterjadi,makafaktor
separation,β,harustidaksamadengan1(β≠1).
Faktorpengayaan(enrichmentfactor),E,adalahB
A
D
D
 Bekstraksi
Aekstraksi
E
%
%


37. oaA
oaB
oaB
B
oaA
A
V/VD
V/VD
V/VD
D
/
V/VD
D
Bekstraksi%
Aekstraksi%
E

























100100 Untukmemilikifaktorenrichmentbesar,makatidakhanya
faktorseparationharusbesar,tetapijugaperlu
dipertimbangkanperbandinganvolumefasaaqueous/fasa
organikdimanavolumefasaorganikharussekecilmungkin
dibandingvolumefasaaqueous.

38. Contoh,
Jikasebuahlarutanmengandungsejumlahion-ionA
danBdiekstrakolehpelarutorganikdanperbandingan
distribusiuntukmasing-masingkomponenD
A=10dan
D
B=1,makaβ=10.pengayaandapatdihitungpada2
perbandinganvolumefasaaqueous/organikdengan
menggunakanpersamaandiatas:
SaatV
a/V
o=1:
PersenAyangditransferkefasaorganikadalah
PersenByangditransferkefasaorganikadalah%9,90100
110
10


 

 %50100
11
1 8,1
50
9,90
E

39. •SaatV
a/V
o=10:%50100
1010
10



PersenAyangditransferkefasaorganikadalah
PersenByangditransferkefasaorganikadalah%09,9100
101
1


 5,5
09,9
50
E
Inimenunjukkanbahwafaktorpengayaanmeningkat
denganmeningkatnyaV
a/V
o.

40. Multiple Extractions
•JikaVa=volumefasaaqueousyangmengandungw
gramzatterlarut,V
o=volumefasaorganik,dansetelah
extraksipertama,w
1=beratsisazatterlarutdalamfasa
aqueous,makakonsentrasikesetimbangandalamfasa
aqueous=w
1/V
a,dankonsentrasikesetimbangandalam
fasaorganik=(w–w
1)/V
o.Jadi:Vaww)DVoVa(
w.Vaw.VaVo.Dw
Vo
ww
Va
Dw
Va/w
Vo/)ww(
D






1
11
11
1
1 









Va/DVo
w
DVoVa
wVa
w
1
1
1

41. •Setelahekstraksikedua,w
2=beratsisazatterlarut
dalamfasaaqueous;konsentrasikesetimbangandalam
fasaaqueous=w
2/Va,dankonsentrasikesetimbangan
dalamfasaorganik=(w
1–w
2)/Vo.2
12
2
21
)/(1
1
)/(1
1
/
/)(












VaVoD
w
VaVoD
ww
Vaw
Voww
D

42. •Setelahekstraksike-n
dimana,w
n=beratsisadalamfasaaqueoussetelah
ekstraksike-n,atau:
dimana,C
n=konsentrasisetelahekstraksike-n,danC
1
=konsentrasiawaldalamfasaaqueous.n
n
VaVoD
ww








)/(1
1 n
n
n
n
VaVoD
CC
VaVoDVa
w
Va
w
















)/(1
1
)/(1
1
1

43. Diagram McCabe-Thiele

44. Diagram McCabe-Thiele
•DiagramMcCabe-Thielemencakup:
–Kurvakesetimbangandistribusiisothermal
•Ditentukansecaraempirikdengan cara
memvariasikannisbahaqueous(A)versusorganik
(O)untuklarutantertentu
–Garisoperasi(ditentukandarineracamaterial)
•Slopekurvamenunjukkan“nisbahfasa“(Va/Vo)
•Posisiawal(0,0)menunjukkankonsentrasiraffinate
(aqueousphase)dankonsentrasiorganikyang
sudahdistripping(strippedorganic)
•Posisiakhirmenunjukkankonsentrasifasaaqueous
umpandankonsentrasiloadedorganicphase

45. Diagram McCabe-Thiele
•DiagramMcCabe-Thielemencakup:
–Jumlahteoritiktahap(step)dalamproses
yangditentukansecaragrafis:
•Menentukankonsentrasifasaaqueousdan
fasaorganikyangmasukdankeluardalam
setiaptahap

46. ADSORPTION WITH
ION EXCHANGE RESIN (IX)

47. Ion Exchange Resin
•Ionexchangeresin:non-solublesolidmaterialwhich
canselectivelyandreversiblyadsorpmetalionsin
aqueoussolutionbymeansofionexchange
mechanism
•Structureofresin:M(PI)
n
–Matrix(M)
–Polarion(P)dancounterion(I)whichhas
oppositechargewiththepolarion
•IfPnegative,I=cationcationexchanger;I=anion
thentheresin=anionexchangerresin

48. Schematic of the interior structure of an ion exchange resin
(organic IX resin)

49. Ion Exchange
•The ion exchange reaction generally
can be formulated as follow:
M(PI)
n+ S

= M(PS)
n+ nI


50. Material of IX Resin
Based on the material use to prepare, IX resin can be
classified by inorganicand organicresin
InorganicResin
▪Natural:generallyhaswelldefinedcrystalstructure:
contoh:aluminosilicate,zeolite,chahabazite,analite
▪Synthetic:canbepreparedfrominorganicmaterials
suchasby:
Fusionofsoda,kaolin,feldspar,
Formation of gelatinous precipitates from Al-Na-Si
solutionand drying
Crystallization at high temp. and press. From aqueous
solutionscontainingSi, Al and alkalisuch as TiO
2•x H
2O,
zirconium phosphate

51. Advantages of Inorganic Resin
•Relatively has lower cost
•Operation at higher temperatures is
possible
•Inert to radioactivity

52. Organic Ion Exchange Resin
•Usuallypolystyrenebased
•Made byadditioncopolymerization
•Degree of crosslinkingis important
•If insufficient, resin with low capacity
Water absorbs and blocks sites
Resin soft and easily abraded
•If too much, resin capacity is reduced
-Slow to exchange ions, especially larger ones
•Typically capacities of 3-6 meq/g
•Researches have been done to prepare natural
organic IX from coal.

53. Types of Organic IX Resins

55. Characteristics of good IX Resin
•HighCapacityLargeamountof
exchangeableionsontheresinperunit
weight(expressedasmeq/g)
•HighSelectivity
•InsolubleinLeachSolution
•LowCost

57. Distribution Coefficient

62. Example

64. Teknik adsorpsi:
-Resin in Column
-Resin in Pulp

65. resin-in-pulp process

67. PRECIPITATION OF METALS
BY OTHER METAL
(CEMENTATION)

68. Cementation
•Precipitation of a metal from an aqueous solution
byanothermetal whichismoreelectronegative
M
1
z+
+ M
2
o
M
2
z+
+ M
1
o
•Application:
–Precipitationof copperwithiron scrap
–Precipitation of Au/Ag from cyanide solution with Zn
powder
–Removal of Cu, Cd, Fe byZn powderforpurification
of Zn-richsolutionfromZnOleaching
–Garemoval from aluminatesolutions with Al powder.

69. The purpose of cementation
1.Recovery of metals from pregnant-leach
solution:
–Example:
•Cu from Cu-rich solution resulted from Cu-oxide
leaching by iron scrapCu
2+
+ Fe Cu +
Fe
2+
•Au/Ag from cyanide solution by zinc powder[ ] [ ]→
-2
4
-
2 )CN(Zn+Au2Zn+)CN(Au2 [ ] [ ]→
-2
4
-
2 )CN(Zn+Ag2Zn+)CN(Ag2

70. Thepurposeof cementation
2.Purification of pregnant-leach solution:
–Example:
•Purification of Zn-rich solution from ZnO calcine
leaching
Removal of Cu, Cd by zinc powder
Cu
2+
+ Zn Cu + Zn
2+
Cd
2+
+ Zn Cd + Zn
2+
Iron at higher concentration is precipitated by oxidation
and pH adjusment as iron hydroxide (Fe(OH)
3)
Fe
2+
Fe
3+
+ e
Fe
3+
+ 3(OH)
-
Fe(OH)
3

71. Flowsheet of Merril-Crowe Process involving
gold/silver cementation by zinc powder

72. Gold/silver Cementation
•Gold/silvercementation(Merril-Crowe) ismoreeffective
forhigh ratioof Ag/Au in ore
•For Lowratioof Au/Ag, activatedcarbonadsorptionis
morepreferable
•Cementationmustbedonein clarifiedand deaerated
solution
•Thepurposeof clarification: avoidtheformationof passive
layeron thesurfaceof zinc.
•ThePurposeof deaeration
–Preventredissolutionof Au-Ag precipitate
–Increasestherate of Au-Ag precipitation

73. Equipment
•Small scale cementation process usually
conducted in agitation tank and rotating
drum
•Separation of precipitate is done by filtering
•For larger scale, cementation is done in
launder and inverted cone
•Launder: narrow tank, about 170 m long,
1.3 –3 m wide and 0.3 –1.3 m deep laid at
a slope of about 2%.

74. Rotating drum for cementation of copper

75. Rotating drum for cementation of copper
in Duisburg, Germany

76. Inverted cone for cementation of copper

77. ProblemsinCementation
•High reagent consumption
Causing factors: Consumed by unwanted side reactions
Example: Fe in Cu precipitation reacts with H
+
and Fe
3+
and
ions in solution
•Redissolution of precipitated metal
Example: In Cu cementation, Cu can be redissolved through
the following reactions:OHCuOHCu
CuCuCu
2
2
2
2
2/12
2



 2
2
2 HFeHFe 
 

23
32 FeFeFe
Iron consumption 2 –
4 of its theoretical
consumption
Precipitated must be
immediately
separated and over
agitation should be
avoided.

78. ProblemsinCementation(cont.)
•Formation of precipitates or alloys (impure product)
•Formation of hydrolytic product Solution pH must
be properly adjusted
•Formation of toxic gases, for example in Cu
cementation by iron scrap.3
2
23
236 AsHMHAsM 

M is divavent metal, AsH
3 is poisonous gas

79. PRECIPITATION OF
METALS
FROM SOLUTION BY GAS

80. Precipitation by gases
•Gases that are usually used
–H
2
–SO
2
–CO
–H
2S
•Except H
2S gas which results in metal sulfide
as a product, the other gases precipites
metals as metal powders

81. Precipitation by gases
•Reductionbygasisusuallydoneathightemperature
andpressureinapressurevesselsuchasautoclave.
•Itshouldbenoticedthat
–Solubilityofgasesdecreasesbytherisesof
temperatureupto100
o
Candre-increasesbythe
furthertemperaturincrease
–Solubilityofmostsaltsincreasesbytherisesof
temperatureupto100
o
C.
–Solubilityofcertainsaltsandgasesinfluencedby
thepresenceofothersaltsinsolution

82. Precipitation by hydrogen gas
•Theprecipitationofdivalentmetalperformsbythe
followingreaction
M
2+
+H
2M+2H
+
•Application:PrecipitationsofNi,Co,Cupowderfrom
solutionwithhighconcentrationsofthosemetals
•Precipitationofplatinumgroupmetals(PGMs)
•Precipitationcanbedoneeitherwithoutcatalyst
trhoughhomogenousreaction(i.e.nosolidsurfaceis
requiredforprecipitationsubstrate)and
heterogenouslybythepresenceofcatalyst.

83. Precipitation by hydrogen gas
•Theequilibriumconstantisgivenby
therefore,
Log[M
2+
]=-2pH–(logK+logpH
2)
Thismeansthatwhenprecipitationiscarriedoutat
constanttemperature,thenatequilibroumthereisa
linearrelationbetweenLog[M
2+
]andpHofsolution,
andtheslopethelineequals-2.[]
[]pHH
H
=K
2
+
2
+

84. Precipitation by hydrogen gas
•Precipitationofnickelproducedbyammonialeaching
(CaronProcess)
Ni
2+
+2NH
3+H
2Ni+2NH
4
+
Pictorial flowsheet of Ni HPAL plant in Murin-Murin, Western Australia
(involving H
2reduction)

85. Precipitation by SO
2 Gas
•Products:
–metal
–sulfate
•Example:DepositionofCuatroomtemperatureand
1atm,resultsinCuSO
4
SO
2+Cu
2+
+H
2O+1/2O
2CuSO
4+2H
+
•Attemperatureof100
o
Candpressureof50psi,Cu
metalwillbeprecipitated
SO
2+H
2OH
+
+HSO
3
-
Cu
2+
+HSO
3
-
+H
2OCu+HSO
4
-
+2H
+
Inthiscondition,Fe
3+
ionwillbereducedtoFe
2+
(not
-precipitated).

86. Precipitation by CO(Carbon Monoxide)Gas
•COgashasbeenusedforprecipitatingsilverfrom
AgNO
3solutionandcopperfrom[Cu(NH
3)
4]
2+
OBTAINEDfrombrassscrapleachinginammoniacal
ammoniumcarbonate.
[Cu(NH
3)
4]
2+
Cu
2+
+4NH
3
Cu
2+
+CO+H
2OCu+CO
2+2H
+