Hydrometallurgy A short walk through the history

HydrometallurgyA short overview of the history

and a primer of solvent extraction

Part of the curriculum in hydrometallurgyPresented by PRICE

Prepared by Dag Ø. EriksenApril 2020

Unless said differently: All pictures and figures are copyright Dag Øistein Eriksen

Use of metals - historically

• The first metals to be used were the ones whichare easy to find or make in elemental form:– Gold

– Silver

– Copper and later bronze

• Bronze requires the alloying of two metals: copper and tin– Brass is copper and zinc

– Both bronze and brass were impure with a lot of othercomponents present (Al, Mn, As, …)

PRICE - April 2020 2


• Gold and silver may be found in elemental form in nature– They are soft and easy to form, but

not useful as tools

• Copper and alloying metals maybe reduced by carbon in fires:Cu2S + C + 2O2 = 2Cu + CO2 + SO2

• Bronze is harder than copperand can be used in tools

Use of metals - historically

Minoan gold jewelery

Egyptian bronze axesPictures from The Natural Sapphire Company

• The carboreduction route for making metals was used for > 4 000 years

• Hydrometallurgical routes were not needed before the industrial revolution (18th century)– Based on alchemy – making gold, but founded the

basis for chemistry: mineral acids, distillation, …

– Needs understanding of chemistry as separation is essential

– Closely connected to understanding and knowledge of minerals, rocks and mining


Production of metals - historically

Mining – short history

• St Joachimsthal, Ertzgebirge

– Presently Jachymov, CzechRepublic

• Rich siver mine whichenabled Graf von Schlick, the owner, to mint Joachimsthaler

– Later the name was Thalerwhich is the origin of Dollar and in Norway: Daler (<1875)

• Georg Bauer, a Germanscholar, studied miningand founded mining as a field of science

– As scholars did in the16th century he tooka latin name: Georgius Agricola


When the silver mine was depleted, uraniumsalt was mined (19th century). U-salts were used as yellow color in glass.

Pictures from Wikipedia

Mining – short history

• The mine in St Joachimsthal has also a more tragic story:

• It was the site where the «Miners decease» was first recognized.

• It was not understoodbefore radon, Rn, wasdiscovered

• The decease is Lung cancer

• In the waste from themine Marie SklodowskaCurie separated first

• Polonium in July 1898, and

• Radium in December1898


Picture from Wikipedia

Radiochemistry is an important part ofhydrometallurgy


Teodora Retegan and Franz Schönhofer

From Lynas Investors presentation – March 2010

Example of steps in modern mining


Reason for crushing, grinding and milling

• Rocks consist of mixtures of minerals. A mineral is a (more or less) pure chemical compoundE.g.: Eudialyte Group: Na15Ca6(Fe,Mn,Ln)3Zr3SiO(O,OH,H2O)3(Si3O9)2(Si9O27)2(OH,Cl,F)2

• To access the interesting (valuable) mineral it is an advantage to mill down the rock so that the mineral grains are free, i.e. contain (almost) only one kind of mineral


Eudialyte

• Ores often contain only ca 1 % of the valuablemetal, e.g. NiS, Cu2S, REEs, CoS, Ta-, Nb-, W-oxides,…

• A pre-concentration step reduces sizes ofprocessing equipment and the consumptionof acid/base. Allows higher flow of valuethrough the system.


Beneficiation methods of ores

Beneficiation methods of ores• First crushing, grinding,

milling and sieving must be performed

• Flotation– Based on minerals

different hydrofobicity

– Uses surfactants like phosphonates

– Foam is separated and filtered

– Typically a particle size of50 µm is employed

– Milling consumes energy


Visit at a zinc & lead mine in Poland


Visit at a zinc-lead mine in Poland


Beneficiation methods of ores


• Gravitationalseparations– Uses differences in

density of minerals or rock materials

– Usually in aqueousslurries

• Magnetic separation– Many minerals possess

magnetic properties

– Usually slurries are used

Pictures from Wikipedia

A short history of radiochemistry• 1898: Marie and Pierre Curie discovered Po and Ra by

chemical separations of dissolved uranium ore– 1903 M. Curie has produced ca 100 mg pure Ra by

fractional crystallisation

• 1923: de Hevesy uses 212Pb as a tracer to follow the absorption in the roots, stems and leaves of the broad bean

• 1938: Otto Hahn proves fission of uranium as Ba is separated from irradiated uranium solution

• 1940: First transurane produced: Np by McMillan and Abelson

• Nuclear power requires separation of fission products– Requires methods remotely operated and with selective

chemistry


The cycle of nuclear energy


Hydrometallurgy needed

Figure ref.: DOI: 10.13140/RG.2.2.16166.78407 Figure from Wikipedia

60 80 100 120 140 160 180

1E-6

1E-5

1E-4

1E-3

0,01

0,1

1

Mass number

235

U

Thermal fission yields – 235U

90Sr 137Cs

Yield (%)


60 80 100 120 140 160 180

1E-6

1E-5

1E-4

1E-3

0,01

0,1

1

60 80 100 120 140 160 180

1E-6

1E-5

1E-4

1E-3

0,01

0,1

1

239

Pu

Mass number

235

U

Thermal fission yields – 235U and 239Pu

Data from T.R. England and B.F. Rider,

LA-UR-94-3106, ENDF-349

Yield (%)


Fission yields of 233U and 235U

60 80 100 120 140 160 180

1E-6

1E-5

1E-4

1E-3

0,01

0,1

1

60 80 100 120 140 160 180

1E-6

1E-5

1E-4

1E-3

0,01

0,1

1 235

U

Fis

sio

n y

ield

(%

)

Mass number

233

U

There are almost no differences in waste handling of fission products for 233U and 235U PRICE - April 2020 19

Radiochemistry has contributed to thedevelopment of hydrometallurgy

The need for safe, remote handling of thelaborious separations required in the nuclearsector boosted innovation in:

• Solvent extraction:– Continuous, counter current process enabled large

quantities to be processed

– Contactors like mixer-settlers were developed

• Ion exchange to perform difficult purificationsby chromatography


• Most ores contain traces of radioactivematerials, i.e. U- and Th-oxides

• Handling of radioactivity is therefore essentialas radioactive isotopes may be concentratedduring the separation process

• Knowledge of radioactivity, radiationprotection and dose assessment is importantcontribution to hydrometallurgical processdevelopment


Nuclear chemistry has contributed to thedevelopment of hydrometallurgy

Hydrometallurgy and nuclear chemistry

Nuclear (radio-)chemistry offers special methods useful in hydrometallurgy:• Use of radioactive tracers, i.e. radioactive isotopes of

the elements studied– Particularly important in liquid-liquid extraction

• Neutron activation can be used on all phases: solid, aqueous-, organic phases (and gas)

• AKUFVE-method very efficient in measuring extractionkinetics

• Many "hydrometallurgical" elements have suitableisotopes for use as tracers– In addition, e.g. Eu(III) can be used as tracer for Am(III), and

Nd3+ has equal ionic radius as Am3+


The natural radioactive series

92238𝑈

𝛼,4,5 109𝑦

90234𝑇ℎ

𝛽,24,1𝑑

91234𝑃𝑎

𝛽,1,2𝑚

92234𝑈

𝛼,2,5 105𝑦

90230𝑇ℎ

𝛼,8 104𝑦

88226𝑅𝑎

𝛼,1600𝑦

86222𝑅𝑛

𝛼,3,8𝑑

84218𝑃𝑜

𝛼,3,05𝑚

82214𝑃𝑏

𝛽,26,8𝑚

83214𝐵𝑖

𝛽,19,8𝑚

84214𝑃𝑜

𝛼,214µ𝑠

82210𝑃𝑏

𝛽,22𝑦

83210𝐵𝑖

𝛽,5,0𝑑

84210𝑃𝑜

𝛼,138,4𝑑

82206𝑃𝑏

92235𝑈

𝛼,7 108𝑦

90231𝑇ℎ

𝛽,25,6ℎ

91231𝑃𝑎

𝛼,3,3 104𝑦

89227𝐴𝑐

𝛽,22𝑦

90227𝑇ℎ

𝛼,18,7𝑑

88223𝑅𝑎

𝛼,11,4𝑑

86219𝑅𝑛

𝛼,3,9𝑠

84215𝑃𝑜

𝛼,1,8𝑚𝑠

82211𝑃𝑏

𝛽,36,1𝑚

83211𝐵𝑖

𝛼,2,15𝑚

81207𝑇𝑙

𝛽,4,8𝑚

82207𝑃𝑏

90232𝑇ℎ

𝛼,1,4 1010𝑦

88228𝑅𝑎

𝛽,5,7𝑦

89228𝐴𝑐

𝛽,6,13ℎ

90228𝑇ℎ

𝛼,1,9𝑦

88224𝑅𝑎

𝛼,3,64𝑑

86220𝑅𝑛

𝛼,55,6𝑠

84216𝑃𝑜

𝛼,0,15𝑠

82212𝑃𝑏

𝛽,10,6ℎ

83212𝐵𝑖

𝛽,60,6𝑚

84212𝑃𝑜

𝛼,0,3µ𝑠

82208𝑃𝑏 𝑎𝑛𝑑 83

212𝐵𝑖𝑎,60,6𝑚

81208𝑇𝑙

𝛽,3,05𝑚

82208𝑃𝑏


Challenges connected to thorium



Elements to be recovered throughhydrometallurgical methods


The rare earth containing mineral eudialyte

• Theoretical stoichiometric formula:Na15Ca6(Fe,Mn,Ln)3Zr3SiO(O,OH,H2O)3(Si3O9)2(Si9O27)2(OH,F)2

• Dissolvable in dilute acid

• Gives Na+ and F- in solution

• Gives also silicate/silicic acidand ferrous ions


Picture from Wikipedia

Think holistic!


Survey of rocks,

analyses of

minerals

Drilling for mapping

of the size of the

ore. Analyses of

minerals

Size big

enough?

No!

Ore

concidered as

resource

Decide

”Cut off”

Yes!

Drilling for

extraction of

ca100 kg samples

Test physical pre-

concentration

methods and

flotation

Conc.

Working?

Crushing,

Grinding and

milling

No

Leaching ,

calcining, baking,

etc.

Separation-

methodes:

SX, IX,

membranes,

Solid-liq. Sep.

Products with

high value

Good

economy?

Estimation of

potential income,

investment cost,

operation cost, etc.

Tailings,

gangue

materials

Tailings

Municipality

Stakeholders

Environmental

authorities

Policy

Production of high

technological,

environmentally

friendly products

Think holistic!

Production of

commercial

items

Distribution

of Items

Consumption

Sorting &

handling

of waste

Production of

feed

from waste

Depositories

Landfills

Virgin feed

from mineral

ores


From a visit at a tin mine in South Africa


Waste deposit

Dried out tailings dam


15 min break

Separation chemistry


• Imperative to have a change in phase

– Solid to liquid or gas

– Liquid to solid

– Liquid to liquid

– Gas to solid or liquid

– Liquid to gas – and back

• Membranes can be viewed as phase separators

Types of Separation chemistry

Chemical means:

• Precipitation, crystallisation

• Ion-exchange, IX

• Solvent Extraction (Liquid Liquid Extraction, LLX or SX)

• Membranes

• Mixing of methodes: impreg.resin, SLM, …

• Ionic liquids

Leaching:

• Alkaline

• Acid based

• Other: chlorination, baking, calcining, …

Phase separations:

• solid phase – liquid,

• liquid – gas,

• solid –gas,

• liquid – liquid,

• distillation, …


Basic theoryE.g.: Solvent Extraction – SX or LLX


• Basic SX– Acidic, alkaline and solvating

extractants

– Saponification

– D-, %E-, K-values

– Solvents and solvabilities

– Complexes

– Lewis’ acid-base concept(HSAB)

– Salting out effects

– Solubility curves

– Kinetics – extraction and strip

• Cation exchanging extractant:

Mn+(aq) + nHA(org) ↔ nH+(aq) + MAn(org)

𝐾 =𝑀𝐴𝑛 [𝐻+]𝑛

𝑀𝑛+ [𝐻𝐴]𝑛

𝐷 =𝑀𝐴𝑛𝑀𝑛+

logK = log𝑀𝐴𝑛

𝑀𝑛+ +n log[H+]-n log[𝐻𝐴]

logK = logD + nlog[H+] – nlog[𝐻𝐴]

logD = nlog[𝐻𝐴] + pK + npH(linear in log-log plot)log = log10, pK = - logK, pH = - log[H+]


Anion exchanging extractant:

MXyn-(aq) + nACl(org) ↔ nCl-(aq) + MXyAn(org)

𝐾 =𝑀𝑋𝑦𝐴𝑛 [𝐶𝑙−]𝑛

𝑀𝑋𝑦𝑛− [𝐴𝐶𝑙]𝑛

𝐷 =𝑀𝑋𝑦𝐴𝑛

𝑀𝑋𝑦𝑛−

logK = log𝑀𝑋𝑦𝐴𝑛

𝑀𝑋𝑦𝑛− + n log[Cl-] - nlog[𝐴𝐶𝑙]

logK = logD + nlog[Cl-] – nlog[𝐴𝐶𝑙]

logD = nlog[𝐴𝐶𝑙] + pK - nlog[Cl-] (linear in log-log plot)

Solvating extractant:

MXn(aq) + pA(org) ↔ MXnAp(org)

𝐾 =𝑀Xn𝐴𝑝

𝑀Xn [ ҧ𝐴]𝑝

𝐷 =𝑀Xn𝐴𝑝

𝑀Xn

logK = log𝑀Xn𝐴𝑝

𝑀Xn- p log[ ҧ𝐴]

logK = logD - p log[ ҧ𝐴]

logD = p log[ ҧ𝐴] - pK(linear in log-log plot)

Basic theoryE.g.: Solvent Extraction – SX or LLX

Extractants - examples

• Solvating extractants

– Tri-octylphosphine oxide, TOPO

– Tri-butylphosphate, TBP


• Cation exchangers– Di-2-ethylhexylphosphoric

acid: HDEHP or D2EHPA

– 2-ethylhexyl-(2-ethylhexyl)-phosphonic acid: PC88A, Cyanex 272, Ionquest 801, ..

Parts of the extractant is hydrophobic while one part is hydrophilic

Cation exchangers• Copper extraction is a major field in SX. Extractants are

usually oxime derivatives• Versatic acid is carboxylic acid R-COOH• Today there are also commercially available extractants

like R2POOH, R2POSH, R2PS(SH).Cytec is the main producer

• The acidity of the functional groups vary as:R2PSSH < R2POSH < R2POOH < (RO)RPOOH < (RO)2POOH < (RO)2POP(OH)(RO)2

• HDEHP forms dimers in aliphatic solvents:H(DEHP)2, making the capacity only half, but the acidity is larger than for the monomer

• The solubility of HDEHP can reach about 1 M


Extraction with HDEHP and PC88A of Eu and YData from MEGON

0,01 0,1 10,01

0,1

1

10

100

0.5M HDEHP/Shellsol D-70

0,01 0,1 10,01

0,1

1

10

100

1M PC88A/Shellsol D-70

D(E

u)

HCl konsentrasjon (M)

0,01 0,1 10,01

0,1

1

10

100

0,5M HDEHP/Shellsol D-70

Eu

Ford

elin

gsta

ll, D

0,01 0,1 10,01

0,1

1

10

100

Y

HCl-konsentrasjon (M)

n = - 3


0,1 1 10

0,01

0,1

1

10

100

.5M HDEHP S.D-70

1M HDEHP S.D-70

.5M HDEHP Solv150

1M HDEHP Solv150

1.5M HDEHP Solv150

.8M PC88A Solv150

1M PC88A Solv150

D(Y

)

HCl conc. (M)

0,01 0,1 1 10

0,1

1

10

100

.5M HDEHP S.D-70

1M HDEHP S.D-70

.5M HDEHP Solv150

1M HDEHP Solv150

1.5M HDEHP Solv150

1M PC88A Solv150

1M PC88A S.D-70

D(E

u)

HCl-conc. (M)

Extraction of Y and EuData from MEGON


Shellsol D-70: Aliphatic solventSolvesso 150: Aromatic solvent

0,01 0,1 1

0,01

0,1

1

10 .5M HDEHP S.D-70

1M HDEHP Solv150

1.5M HDEHP Solv150

1M PC88A Solv150

1M PC88A S.D-70

D(C

e3

+)

HCl-conc. (M)

0,01 0,1 1

1E-3

0,01

0,1

1 1M HDEHP Solv150

1M PC88A Solv150

1M PC88A S.D-70

D(C

a)

HCl-conc. (M)

Extraction of Ce(III) and CaData from MEGON


n = - 3 n = - 2

0,01 0,1 1 10

0,01

0,1

1

10

100

Y

Eu

Nd

Ce

Ca

log

D

HCl-conc. (M)

1M PC88A in Shellsol D-70

Extraction with 1M PC88A in Shellsol D-70

Summary: Extraction depends on• pKa of extractant• Solvent – aliphatic or aromatic• Concentration of extractant• Acid concentration


Traditional selective extractants for copper

• Oxime compounds have proven to be selective and stable compounds for recovery of Cu2+

• They only work for pH > 1, which makes them unusable for extraction from strong acids

• Well proven technology for Cu-extraction at industrial conditions

A = H

http://www.mining-solutions.basf.com/ev/internet/mining-solutions/en/download-center/redbook/index


Examples of extractions of REE with pure TBP

• TBP is a liquid at STP

• Chemically very stable

• REE can form complexes with nitrate


0,0 2,5 5,0 7,5 10,0 12,5 15,0 17,5

0,0

0,5

1,0

1,5

2,0

2,5

0,0 2,5 5,0 7,5 10,0 12,5 15,0 17,5

0,0

0,5

1,0

1,5

2,0

2,5

0,0 2,5 5,0 7,5 10,0 12,5 15,0 17,5

0,0

0,5

1,0

1,5

2,0

2,5

0,0 2,5 5,0 7,5 10,0 12,5 15,0 17,5

0,0

0,5

1,0

1,5

2,0

2,5

HNO3 (M)

Ce(III)

La

D 1

00

% T

BP

Pr

Nd

0,0 2,5 5,0 7,5 10,0 12,5 15,0 17,5 20,0

0,01

0,1

1

10

100

0,0 2,5 5,0 7,5 10,0 12,5 15,0 17,5 20,0

0,01

0,1

1

10

100

0,0 2,5 5,0 7,5 10,0 12,5 15,0 17,5 20,0

0,01

0,1

1

10

100

0,0 2,5 5,0 7,5 10,0 12,5 15,0 17,5 20,0

0,01

0,1

1

10

100

HNO3 (M)

Nd

HNO3 (M)

Eu

HNO3 (M)

Gd

D o

f 1

00

% T

BP

HNO3 (M)

Sm

0,0 2,5 5,0 7,5 10,0 12,5 15,0 17,5 20,0

0,01

0,1

1

10

100

0,0 2,5 5,0 7,5 10,0 12,5 15,0 17,5 20,0

0,01

0,1

1

10

100

0,0 2,5 5,0 7,5 10,0 12,5 15,0 17,5 20,0

0,01

0,1

1

10

100

0,0 2,5 5,0 7,5 10,0 12,5 15,0 17,5 20,0

0,01

0,1

1

10

100

0,0 2,5 5,0 7,5 10,0 12,5 15,0 17,5 20,0

0,01

0,1

1

10

100

D o

f 100%

TB

P

HNO3 (M)

Gd

Y

Tb

Dy

Ho

E. Hesford, E.E. Jackson, and H.A.C McKay “TRI-n-BUTYL PHOSPHATE AS AN EXTRACTING AGENT FOR INORGANIC NITRATES – VI” J. Inorg. Nucl. Chem. Vol.9, 279-289 (1959)D. Scargill, K. Alcock, J.M. Fletcher, E. Hesford, and H.A.C. McKay “TRI-n-BUTYL PHOSPHATE AS AN EXTRACTING AGENT FOR INORGANIC NITRATES – II” J. Inorg. Nucl. Chem. Vol.4, 304-314 (1957)

• Majority of anion extractants are amines

• Employed are:

– Primary amines: RNH2

– (Secondary: R2NH)

– Ternary amines: R3N

– Quarternary amines:R3R’NCl, R’ may be smaller than the other organic groups


Anion extractants - examples

• Primary to ternary amines must be activated:

R3N: + HCl = R3NH+ Cl-

• For large complexes quarternary amines may suffer from steric effects

Examples of use of amines

• Comparison of extraction of Th, Lu, La and Zr fra sulphuricacid environment, M(SO4)p

(n-2p), Mn+

• JM-T: primary amine, LA-1: secondary amine, TiOA: tertiaryamine (tri-isooctylamine)

Faglig pedagogisk dag 31.10.2019 45

0,01

1

100

10000

0.005 0.05 0.5 5

Acid conc. (M)

JM-T

LA-1

TiOA

0,00001

0,001

0,1

10

1000

0.005 0.05 0.5 5

Acid conc. (M)

JM-T

LA-1

TiOA

0,00001

0,001

0,1

10

1000

0.005 0.05 0.5 5

Acid conc. (M)

JM-T

LA-1

TiOA

0,1

1

10

100

1000

0.005 0.05 0.5 5

Acid conc. (M)

JM-T

LA-1

TiOA

Th

Lu

LaZr

Can we foresee which extractant will bind to which solute?

• The best theory is the Hard-Soft Acid Base theory – HSAB

• Based on Lewis acid-base theory

• Hard acids require hard bases and soft acids require soft bases

• Examples: Fe3+ is strongly extracted by HDEHPCd2+ needs R2PS(SH)


• Challenges with phase separations:

– Crud-formation, i.e. third phase or formation of solids at the interfacebetween the liquid phases

– Modifiers may be used to enhancephase separation. Often an alcoholthat replaces co-extracted water

– Interfacial tension and formation ofmicelles may make phasesdissolved in each other


In SX, Phase separation is imperative

Phase separation methodsavailable:• Gravitational

• Electrostatic

• Centrifuges

• One continuous phase –Electrodynamic contactor

Advantages and disadvantages ofLiquid-liquid (solvent) extraction

Advantages:• True continuous process• Can be run counter-currently• Washing and scrubbing is easy• Accepts fines and large flows• Can be stopped and restarted without changes in equilibrium

Disadvantages:• Every physical stage is less than a theoretical plate => Many stages

may be needed• Settlers contain a large volume of the product. Increases investment

cost.• Organic liquids will have some evaporation and dissolution• Organic liquids may have some negative environmental impact


Mixer-settlers


Counter current liquid-liquidextraction

In solvent extraction the key parameters to control are:• Flow rates• Concentrations, i.e. pH, extractant, feed

solutes etc. • Evaporation of diluent

• Densities of loaded and barren phases• Stirring speed• Presence of silicic acid, extractant’s

"poisons"


An example of copper extraction

• PLS = Pregnant Leach Solution

• Pregnant strip solution will accumulate Cu



Part of the former MCI-MEGON’s Y-plant


Another example of mixer-settlers


Documents

Hydrometallurgy A short walk through the history