This document discusses selective extraction of cobalt from nickel using ionic liquids. It begins with an introduction to ionic liquids, defining them and describing their properties. It then discusses different types of ionic liquids and their applications. The main body describes a study that used phosphonium-based ionic liquids to selectively separate cobalt and nickel via solvent extraction experiments. Key results showed the phosphonium ionic liquid achieved high separation factors for cobalt over nickel. The document concludes the method provides a greener approach to metal separation compared to conventional solvents. Future work is suggested to apply the technique to other metal separations.

1. Ionic Liquids in selective extraction
of Co from Ni
PUSHPA GAUTAM
16MS06004
MATERIALS SCIENCE & ENGG.
SMMME, IIT BBS
1

2. CONTENTS
• Introduction to Ionic Liquids- definition, properties.
• Types of ILs – TSIL, DES, MCIL
• Application of Ionic Liquids
• Literature review: Processing of metals in ILs
• Selective separation of Co from Ni by Solvent extraction with undiluted
Phosphonium Ionic liquids- Objective, chemicals used, Batch-scale
extraction experiment, Calculation, Results and discussion.
• Conclusion
• Future perspective
• Safety aspects
• References
2

3. 3
Ionic Liquids(ILs)
Definition: Ionic liquids are molten salts entirely composed of ions(+ve,-vely
charged) that are liquid at or below room temperature, i.e. MP ˂ 100°C.
Example: 1-ethyl-3-methyl imidazolium bis(trifluoro methyl sulfonyl) limide-
M.P.= -17°C.
Properties of ILs :
• Non- flammable
• Very low/negligible vapor pressure
• Wide liquid range, high thermal stability
• Wide electro-chemical window(> 4 V)
• High ion conductivity
• Designer solvents
• Green solvents
• Viscosity= 10cP to above 1000 cP
• Density = 0.8-3.3 g/cc

4. Types of ILs
1. Functional Ionic liquid/ Task-specific Ionic liquids (TSILs) :
• Possess functional groups covalently bonded to IL ions.
• Example- IL derived from anti fungal drug miconazol.
• Used to modify solvent parameters, improve bio- degradability , for catalytic
activation of certain dissolved substrate.
2. Deep eutectic solvents (DES):
• Mixtures of two components- a quaternary ammonium halide salt + a
hydrogen bond donor (like amine , alcohol, acid).
• Example- Mixture of choline chloride and urea
3. Metal-containing ionic liquid (MCILs):
• A metal ion or metal complex is part of either cation or anion.
• Example- Chloro- aluminate IL (N-ethyl pyridinium bromide + Aluminium
chloride)- moisture sensitive
• Used in spectroscopy, electro chemistry, organo metallic synthesis, catalyst,
electrolyte for electro deposition.
4

5. Application of ILs
• Electro deposition of metals/alloys
• Electrolytic extraction of active metals at room tempr
• Liquid-liquid extraction of metals
• Electro-refining of metals
• In electro chemical devices fuel cells, batteries
• Electrolyte in Lithium-ion battery
5

6. Literature review: Processing of
metals in ILs
1. Dai et al. (1997)- Investigated solubility of uranium(VI) oxide in
Imidazolium chloro-aluminate ionic liquids.
2. Bell et al. - reported dissolution of vanadium(V) oxide (V2O5) in
Imidazolium chloro-aluminate .
3. Abbott and co-workers- were able to dissolve wide variety of metal oxide
in Deep-Eutectic Solvent(DES). The reported solubility of copper(II) oxide,
zinc(II) oxide and iron(II, III) oxide in three different Deep-Eutectic Solvents
formed by mixture of Choline Chloride and a Carboxylic acid like Malonic
acid, Oxalic acid and Phenyl Propionic acid.
4. Nockemann et al. used betainium bis(tri-fluoro-methyl-sulfonyl) imide for
dissolution of metal oxides like rare-earth oxides, uranium(VI) oxide,
Zinc(II) oxide(ZnO), Copper(II) oxide(CuO) and Nickel(II) oxide(NiO).
6

7. Conti…..
5. White-head et al. used 1-butyl-3-methyl imidazolium hydrogen-sulfate as leaching
media for minerals like Pyrite and Chalcopyrite, in which an oxidative leach was
applied to selectively extract gold and silver with iron(III) sulfate as oxidant and
thio-urea as complexing agent.
6. Dong et al. used the same IL in (5) and its aqueous solution containing oxygen as
oxidant for leaching of chalcopyrite.
7. Rogers and co-workers first suggested the use of ILs as extraction phase for liq-liq
extraction in 1998.
8. Visser et al. in 2001- used ionic liquids for which thio-ether, thio-urea and urea
groups were substituted on alkyl-imidazolium cation combined with a hexa-
fluoro-phosphate anion and were able to extract heavy metal Hg2+ and Cd2+.
9. Rajendran investigated extraction behaviour of heavy metal ions
(Zn2+,Cu2+,Ni2+,Fe3+,Pb2+) to tri-methyl-capryl-ammonium in combination with
salicylate, benzoate and anthranilate anions.
10. Liu used (Cyphos IL 104) a combination of tri-hexyl (tetra decyl) phosphonium
with bis-(2,4,4-trimethyl pentyl phosphinate in Soybean oil, methyl-ester and
biodiesels as dilutant for rare earth extraction.
7

8. Selective separation of Co from Ni by Solvent
extraction with undiluted Phosphonium Ionic liquids
Objective:
Development of an efficient solvent extraction process for separation of Co &
Ni from a chloride medium by using Phosphonium ionic liquids.
Chemicals used :
1. Tri(hexyl)tetra decyl phosphonium chloride (Cyphos IL 101)
2. Tri(butyl) tetra decyl phosphonium chloride (Cyphos IL 167)
3. Tetra(octyl) phosphonium bromide (Cyphos IL 166)
4. Tri(hexyl) tetra decyl phosphonium bromide (Cyphos IL 102)
5. Methyl-tri octyl-ammonium chloride(Aliquat 336)
6. CoCl2.6H2O, NiCl2.6H2O, CaCl2.2HO , MgCl2.6H2O, MnCl2 .4H2O
7. Hydrogen chloride solution .
8

9. 9
Solvent Extraction:
1-Dissolution of metal source in acid/alkaline aqueous medium
2-Ionic Liquid brought in contact with metal-loaded aqueous solution
3-Metal ions enter ionic liquid phase preferentially
4-Separate/partition ionic liquid & aqueous phase layer
5-Loaded-organic phase introduced to another aqueous phase---STRIPPING
6-Unloaded organic phase after purification sent for reuse.
7-Metal is precipitated from metal-loaded aqueous phase.
Ion Exchange:
1-Solid synthetic resin(small hard porous
beads) made to absorb metal ion
2-Absorbed ion brought into solution-
ELUTION
3-Metal is recovered from solution by
precipitation.

10. Extraction batch test 1:
Aqueous solution of 8M HCl + Co & Ni mixture + 250 ml Ionic Liquid
[tri(hexyl)tetra decyl phosphonium chloride] poured in a jacketed reactor vessel
(500ml) → Intensively stirred at 1040 rpm for 10 min at 60°C→Equilibrium was
reached→ Phases were allowed to settle → Analysis of both phases.
Batch-scale extraction experiment:
Extraction batch test 2:
Aqueous solution of 8M HCl (250ml) + 250 ml Ionic Liquid
[tri(hexyl)tetra decyl phosphonium chloride] poured in a jacketed reactor vessel
(500ml)→Intensively stirred at 1040 rpm for 10 min at 60°C→ Equilibrium was reached
→Phases were allowed to settle→ organic phase (loaded with water & hydrochloride)
was reused as extraction phase→ extraction was repeated as in batch test 1→ Metal
content of 2 phases was analysed.
Extraction batch test 3:
Aqueous 8 M HCl soln containing CoCl2.6H2O, NiCl2.6H2O, CaCl2.2HO & MgCl2.6H2O with
a metal concentration of 5g/L was prepared (500 ml)→ Aqueous solution was poured in
a jacketed reactor vessel (1 L)→Extraction phase(500 ml) was added → Intensive
stirring at 1040 rpm for 10 min at 60°C → Equilibrium was reached →Phases were
allowed to settle→ Metal content of 2 phases was analysed.
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11. Batch scale reactor before extraction batch test 2 Batch scale reactor after extraction batch test 2 :
(upper phase = ionic liquid,
lower phase = aqueous soln phase): [2]
Cobalt(II) is extracted as the dark blue tetracobaltate(II) complex to the ionic
liquid phase, while the green hydrated Nickel(II) ions remains in the aqueous
phase.
11

12. Stripping conditions :
Water was poured in a jacketed reactor vessel (250 ml)→ Extraction phase from
extraction batch test-2 containing Co(II) (5 g/L, 80 ml ) was added→ Intensively stirred
at 1040 rpm for 10 min at 60°C→ Phases allowed to settle→ Cobalt-concentration in
aqueous phase was measured after centrifugation (3000 rpm, 10 min)→ Organic phase
recycled & reused.
Calculation :
Distribution coefficient for Cobalt :
where [Co]O = initial Co-concn in aqueous phase before extraction
[Co]aq=Co-concn in aqueous phase after extraction
Distribution coefficient for Ni :
where [Ni]O = initial Ni-concn in aqueous phase before extraction
[Ni]aq= Ni-concn in organic phase after extraction
Efficiency of separation of Co from Ni, β :
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13. Structure of tri (hexyl) tetra decyl phosphonium chloride
(P 66614Cl)
Distribution coefficient of cobalt(II) as a function of the
HCl concentration [2]
Extraction efficiency of Co increases with increasing Chloride concn, with a maximum
at a chloride concn of 8 M.
Results & Discussion
13

14. Absorption spectrum of the ionic liquid
phase after extraction,
containing
bis(tri(hexyl)tetradecylphosphonium)
tetrachlorocobaltate(II).
The absorption spectrum is typical for the
[CoCl4]2− anion. [2]
Distribution coefficient of Nickel(II) as a
function of the HCl concn. [2]
[CoCl4]2- + 2[P66614]Cl → [P66614]2 [CoCl4] + 2Cl-
Increases linearly, low absolute value
14
Anion Exchange mechanism

15. Results of the extraction after extraction batch tests 1 and 2 : [2]
Batch test 1 Batch test 2a
[Co]aq (mg L−1) 11 (±0.5) 14 (±1.4)
[Ni]org (mg L−1) 44 (±2.7) 43 (±3.6)
DCo 460 (±21) 360 (±32)
DNi 0.0088 (±0.0006) 0.0087 (±0.0007)
βCo
Ni 52 000 (±2800) 41 000 (±3300)
a --Using an ionic liquid phase, saturated with water and HCl.
Physical properties of the ionic liquid before and after extraction batch test 1 and
batch test 2 (at 60 °C) : [2]
Batch test 1 Batch test 2
Before-extrctn After-extrctn Before-extrctn After-extrctn
Water content (wt%) 0.1 7.7 8.7 6.9
HCl content (wt%) 0 5.2 6.0 5.8
Viscosity (cP) 280 101 95 101
Density (g mL−1) 0.87 0.91 0.90 0.91
Phase separation time (s) — 90 — 90
15

16. Distribution coefficients D for cobalt(II), nickel(II), manganese(II), magnesium(II), and
calcium(II) for Batch test-3 : [2]
Element D
Co 450
Ni 0.0062
Mn 30
Mg 0.0014
Ca 0.0056
Percentage of cobalt that is stripped to aqueous phase from IL : [2]
Stripping step Amount of cobalt stripped(%)
1 2.5
2 28
3 52
4 17.5
Total 100
16

17. Extraction results for extraction of cobalt and nickel from aqueous feed solutions
containing 4 M NaCl to tri(hexyl)- tetradecyl phosphonium chloride: [2]
[Co]aq (mg L−1) 21 (±3)
[Ni]org (mg L−1) 98 (±4.6)
DCo 240 (±29)
DNi 0.020 (±0.0010)
βCo
Ni 12 000 (±1000)
Extraction efficiency of Co & Ni increasing with increasing Chloride concn
Advantage of using NaCl soln in place of
HCl acid soln –
•less aggressive media
•cheaper
•lower concentrations of Chloride needed
17

18. Extraction results for the separation of cobalt and nickel using different ionic liquids
as the extractant phase : [2]
P8888Br P44414Cl P66614Br P66614Cl
[Co]aq (mg L−1) 11 180 11 11
[Ni]org (mg L−1) 23 300 39 44
DCo 450 27 450 460
DNi 0.0046 0.064 0.0078 0.0088
βCo
Ni 98000 420 58000 52000
Water content of
IL after
extraction(%O)
3.8 23.4 7.3 7.7
18

19. Extraction results after extraction using Aliquat 336 and Cyphos IL 101 as extraction
phase : [2]
Aliquat 336 Cyphos IL 101
[Co]aq (mg L−1) 60 11
[Ni]org (mg L−1) 160 44
DCo 80 460
DNi 0.03 0.0088
βCo
Ni 2500 52000
Separation factor is 20 times higher in Phosphonium IL than Aliquat 336 due to
increased hydrophobicity of Phosphonium IL.
19

20. Conclusion
• Co can be selectively separated from Ni, Mg & Ca with solvent extraction
using Phosphonium -based IL as extraction reagent.
• After extraction Co can be easily stripped using water in 4 stripping steps.
After stripping the IL can be reused as extraction phase which makes it
possible to do extraction in a Continuous process.
• Instead of Hydrochloric acid, Sodium Chloride can be used as a chloride
source.
• Advantage of using Phosphonium IL as extraction phase is that volatile
organic compounds are avoided and this offers a greener approach to
solvent extraction leading to environment friendlier and healthy working
conditions.
• By doing extraction on a Batch-scale setup, the practical implementation
of IL as extraction phase has been proved.
• 3 Phosphonium and 1 Ammonium ILs were compared for their extraction
capabilities where Tri(hexyl) tetra decyl phosphonium chloride seems to
be superior and the best option as the IL phase.
20

21. Future perspective
• Replacement of organic solvents by Ionic liquids can increase the metal
loading in extraction phase and lead to a clean technology.
• Platinum group metals (PGMs) are processed from a chloride medium
after leaching with hydrochloric acid with added chlorine. Here, Cyphos IL
101 could have potential as an extraction medium for separation of PGMs.
Feeds other than chlorides can also be used.
• By replacing chlorides with nitrates there are opportunities to selectively
extract lanthanides from a concentrated aqueous nitrate soln. This can be
used for Rare earth recycling.
• Ionic liquid technology can be applied in re-processing of spent nuclear
fuels for separation of residual Uranium and newly formed Plutonium
from fission products and higher actinides.
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22. Safety aspects
• Code of practice for Safety in lab should be followed while performing
experimental works with ILs .
• Specific caution is necessary for working with E4 products with clearance
and hazardous lab equipment (like Bromine).
• Co & Ni are carcinogenic and can cause genetic defects and allergic
symptoms; may damage fertility.
• Although ILs are green solvents still the safety of each individual IL should
be evaluated before use.
• The author has reported an accident in which the Protic Ionic Liquid,
Pyrrolidinium nitrate, exploded while drying it under reduced pressure at
110°C, using a rotary evaporator with an oil bath.
22

23. References
1. A. Stojanovic, C. Morgenbesser, D. Kogelnig, R. Krachler, and B.K. Keppler. Quaternary ammonium and
phosphonium ionic liquids in chemical and environmental engineering. In A. Kokorin, editor, Ionic Liquids:
Theory, Properties, New Approaches, volume 1, pages 657–680. InTech, 2011.
2. Sil Wellens, Ben Thijs and Koen Binnemans, An environmentally friendlier approach to hydrometallurgy:
highly selective separation of cobalt from nickel by solvent extraction with undiluted phosphonium ionic
liquids, Green. Chem.,2012.
3. Sil Wellens, Remi Goovaerts, ClaudiaMoeller, Jan Luyten, Ben Thijs and Koen Binnemans, Continuous ionic
liquid extraction process for the separation of cobalt from nickel , Green. Chem., 2013.
4. SilWellens, Tom Vander Hoogerstraete, Claudia Möller, Ben Thijs, Jan Luyten and Koen Binnemans,
Dissolution of metal oxides in an acid-saturated ionic liquid solution and investigation of the back-
extraction behaviour to the aqueous phase, Hydrometallurgy, 2014.
5. C.J. Bradaric, A. Downard, C. Kennedy, A.J. Robertson, and Y.H. Zhou. Industrial preparation of
phosphoniumionic liquids. Green Chem.
6. M.G. Freire, P.J. Carvalho, R.L. Gardas, L.M. Santos, I.M. Marrucho, and J.A. Coutinho. Solubility of water in
tetradecyltrihexylphosphonium-based ionic liquids. J. Chem. Eng. Data.
7. J. Rydberg, C. Musikas, and G.R. Choppin. Principles and Practices of Solvent Extraction, volume 1. Marcel
Dekker, inc., 1st edition, 1992.
8. A.P. Abbott, G. Frisch, J. Hartley, and K.S. Ryder. Processing of metals and metal oxides using ionic liquids.
Green Chem.
9. How safe are protic ionic liquids? Explosion of pyrrolidinium nitrate, Sil Wellens, Ben Thijsb and Koen
Binnemans
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24. THANK YOU.
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