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Selective PGM Extraction with Simple Ionic Liquids
Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University
Director Prof. Atsushi MURAMATSU
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Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, created in part from the former Research Institute of Mineral Dressing and Metallurgy, has been researching all sorts of things through many different approaches and viewpoints. Our institute promotes the development of cutting edge research and new areas of study, while also re-concentrating new comprehensive knowledge of metal resource processing. We aim to be a leader in future training and the continued development of the metallurgical industry, and have established the Center for Mineral Processing and Metallurgy (CMPM) in order to fulfill these goals. This center will recreate the expertise of processing and metallurgy that will support social infrastructure, and pursue new metal resource processing in the future, starting with the processes of dressing and refining metals, but also including the process of recovering resources from waste, nuclear fuel processes, resources circulation and disposal processing, and urban mining processes.
Founded on April 1st, 2018
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Research field
Hiroyuki FUKUYAMA High-temperature Physical Chemistry of Materials
Shin-ya KITAMURA Base Materials Processing
Junya KANO Powder Processing for Functional Materials
Nobuaki SATO Energy System
Itaru HONMA Chemistry of Energy Conversion Devices
Etsuro SHIBATA Metallurgy and Recycling System for Metal Resources Circulation
Atsushi MURAMATSU Hybrid Nano-particle
Takahisa OMATA Atomic Site Control in Inorganic Materials
Field of cooperative
research
Hiroshi NOGAMI Environmental-Conscious Materials Processing*
Hiroyuki SHIBATA Materials Separation Processing*
Manager of Center: Itaru HONMA
*Principal “DIVISION OF PROCESS AND SYSTEM ENGINEERING”
1st Step:
Separation of Pt and Pd
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Ionic Liquids:Novel Extraction media
Platinum Group Metals (PGMs)
Widely used in various fields (e.g. automobile catalyst, electronic materials) Platinum Group Metals (PGMs): Pd, Pt, Rh, Ir, Ru, Os
Problem: Depletion of PGMs Solution: recycle from urban mines
<Main recycle methods: Solvent Extraction with HCl solution>
H+ H+
Cl-Cl-PtCl62-
Cl-
Cl-
Cl-Cl-
Organicphase
Aq. phase
Solvent extraction system: Pt Extraction1)
[shaking]
NR R
R NR
RR
NHR
R
RPtCl62- HN
R
RR
PtCl62-NHR
R
RHN
R
RR
R : n-C8H17
High efficient extractionVolatile organic solvents (Non environmental friendly)Low selectivity
less toxic and high selectivity system is needed
1) B. Swain, J. Jeong, S. K. Kim and J. C. Lee, Hydrometallurgy, 104, 1 (2010).
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Solvent Extraction using Ionic Liquids
Ionic Liquids (ILs)Molten salts at room temperature
NS SO
CF3O
F3C
O
OPF6
BF4
Cl
( NTf2 )
cations anions
ILs have potential for new extraction media
ILs
Non-flammable, Non-volatile, and Non-harmful properties
Flexible molecular design
Suitable for extraction
Immiscible to water
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Basic scheme of IL synthesis
NNH3C
NNH3C
Cl−Cl
[C4mim][Cl]
LiTf2NR R Tf2N−
NNH3C
[C4mim][TFSI]
R
Evaluation of extraction
ICP-AES
Metal ions
Extract
Waterphase Shaking:
Temp. is kept.
Phase separation
*In the case of IL,extraction phase is under.
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The simpler, the better.
Cation Anion
Ionic Liquids
NS SO
CF3O
F3C
O
O PF6 BF4
OS
CF3O
O
Cl
Br
ClO4
( NTf2 )
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Design and synthesis of Ionic Liquids, which have phase separation against water, and have functions for extraction with affinity of target PGM.
Functionsfor extraction
Ionic Liquids+X-
PGMs +X-
TSILs, Task-Specific Ionic Liquids
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1st challenge IL-1
Shaking( 2600 rpm, 30 sec )
Pd, Au: Aqueous solution was changed to colorless.⇒Rapid and high extraction is expected.
Pd: red solid,Au: yellow solid.
Pt: no change in color and no precipitation.10
Pd Pt Au Pd Pt Au
Water phase
IL phase
ON NSO
NTf2
S
O
Extraction ( IL,2600 rpm, 30 sec )
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Proton NMR
IL1
IL2
ON NSO
NTf2
ON NSO
NTf2
S
O
PdPt
IL
Pt, PdH2O
PtH2O
Pd, IL
Pd-SelectiveTHP-Deprotection
IL1 or IL2 O
R
S
S
Pd
Cl
Cl
[PtCl6]2-
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ON N
NTf2
S
S
Pd
L
L
ON N
NTf2
SPd
L
Cl L
ON N
NTf2
SPd
L
S LO
N N NTf2
and
IL-1 - Pd
IL-2 - Pd
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Difficulty in Rh extraction by conventional method
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Next step:Extraction of Rh
Amino-substituted task-specific ILs
N N N
NTf2R
REffects of Alkyl chains on the PGM extraction
Effect of anions and cations on the hydrophobicity as solvent of extraction
Molecular Design of the ILs
Behave as Pd, Pt extractants1)
Expectation for Rh extractants2),the difficult element to extract
Amino-substituted organic extractants are useful forPGM extraction in organic solvent systems
NN
O
N
OC6H13
C8H17
C8H17
C8H17
C8H17
1) B. Swain, J. Jeong, S. K. Kim and J. C. Lee, Hydrometallurgy, 104, 1 (2010).2) H. Narita, K. Morisaku and M. Tanaka, Chem. Commun., 5921(2008).
NOct
Oct Oct
Extractants with Amino groupRhPt
Pd
Design and Synthesis of Amino-substituted Hydrophobic ILs Investigation of Rh Extraction Ability into the ILs
This Work
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A Synthetic Route of Amino-substituted ILsSynthesis of Amino-substituted ILs
IL2IL1
IL5
IL3
IL4
Various types of amino-substituted ILs were Prepared
IL6 IL7
N N N
NTf2N N N
NTf2
N N N
NTf2Oct
Oct
N N N
NTf2Hex
HexN N N
NTf2Bu
BuN N N
NTf2Pr
PrN N N
NTf2Et
Et
Br N N
NTf2
N N N
NTf2R
RR2NH
MeCN85 °C
LiNTf2
H2Or.t., 1 h
NN
Br(CH2)3Br
Acetone45 °C, 20 h
Br N N
Br
IL1: R = c-HexIL2: R = 2-EthylhexylIL3: R = OctIL4: R = HexIL5: R = BuIL6: R = PrIL7: R = Et
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A Extraction Procedure of PGMs into ILs
100 ppm Pd, Pt, RhHCl 2.0 mL (C0)
Shaking, 1500 rpm, 15 min
ILs (ILn (n = 1~7), 0.40 g)
Centrifuged, 6000 rpm, 5 min
Micro tube
ICP-AES (Aq. phase: C)Extraction efficiency E (%)E = 100 x (C0-C)/C0
before after
Aq. phaseILsphase
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HCl conc. was increased
E of Pd and Pt was decreasedRh was not extracted
PGM Extraction Experiment • Aq. phase: 100 ppm Pd, Pt, Rh HCl 2.0 mL• ILs phase: IL1, IL2, 400 mg• Shaking: 1500 rpm, 15 min, 25 oC
IL1: R = c-HexIL2: R = 2-Ethylhexyl
Pd Pt Rh
N N N
NTf2R
R
Pd, Pt1.0-4.0 M HCl: [PdCl4]2-, [PtCl6]2-
Because Cl- competed with [PdCl4]2-, [PtCl6]2-, Cl- blocked ion pairs
Rh 1.0 M HCl: Complex species were changed from [RhCl5 (H2O)]2- to [RhCl6]3-
Effect of Steric Hinderance on the PGM Extraction
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Less steric hinderance of the amino-group enhanced the PGMs extraction ability
IL1: R = c-HexIL2: R = 2-Ethylhexyl
IL2 extracted Pd and Pt efficientlyRh was slightly extracted
Pd Pt Rh
N N N
NTf2R
R
Less steric hinderancethan IL1
PGMs extraction in IL phase• Aq. phase: 100 ppm Pd, Pt, Rh HCl 2.0 mL• ILs phase: IL1, IL2, 400 mg• Shaking: 1500 rpm, 15 min, 25 oC
Effect of Steric Hinderance on the PGM Extraction
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Alkyl Chain Length (Oct-Bu) DependencePGMs extraction in IL phase• Aq. phase: 100 ppm Pd, Pt, Rh HCl 2.0 mL• ILs phase: IL3-IL5, 400 mg• Shaking: 1500 rpm, 15 min, 25 oC
IL3: R = OctIL4: R = HexIL5: R = Bu
Increase in the hydrophobicity that was turned by the alkyl chain length is a key factor for effective extraction of Rh ions
IL3-IL5 show high extraction ability toward Pd and Pt
The alkyl side chain enhanced hydrophobicity
Pd Pt
Rh
N N N
NTf2R
R
HCl conc. was increased
E of Pd and Pt was decreasedE of Rh was increased
IL3, IL4 exhibit high extraction ability to Rh
The amino-moiety was protonated, then captured PGM ions
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PGMs extraction in IL phase• Aq. phase: 100 ppm Pd, Pt, Rh HCl 2.0 mL• ILs phase: IL5-IL7, 400 mg• Shaking: 1500 rpm, 15 min, 25 oC
IL5: R = BuIL6: R = PrIL7: R = Et
N N N
NTf2R
R
At HCl 1.0-4.0 M, Increase of the hydrophobicity is the key factor to improve E
HCl 1.0- 4.0 M
High Hydrophobicity of the ammonium cation moiety is important
Non-protonated ILs coordinate with PGM ionsHCl 0.3 M
Rh
Pd
E of all elements tend to decreaseE: IL5 > IL6 > IL7
IL7 indicated extraction ability towards Pd and Rh
Pt
Alkyl Chain Length (Bu-Et) Dependence
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PGMs Extraction in the Presence of Multi Metal Ions
Cu, Ni, Al, Mg Basically Inactive
PGMs extraction in IL phase• Aq. phase: 100 ppm Pd, Pt, Rh, Zn, Fe, Cu,
Ni, Al, Mg HCl 2.0 mL• ILs phase: IL4, IL5, 400 mg• Shaking: 1500 rpm, 15 min, 25 oC
N N N
NTf2R
R
IL4 IL5
IL4: R = HexIL5: R = Bu
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IL4 Pd, Pt, Rh were selectively extracted
PGMs could be extracted with high selectivity
N N N
NTf2R
R
IL5 Only Pd and Pt were highly extracted
IL5
IL4: R = HexIL5: R = Bu
IL4
PGM solvent extraction• Aq. phase: 100 ppm Pd, Pt, Rh, Zn, Fe, Cu,
Ni, Al, Mg HCl 2.0 mL• ILs phase: IL4, IL5, 400 mg• Shaking: 1500 rpm, 15 min, 25 oC
Solvent Extraction for Multi Metal Ions
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Back Extraction of PGMs into HNO3 aq. Solution PGM back extraction• Aq. phase:HNO3 2.0 mL• ILs phase: IL3-IL5
(after 100 ppm Pd, Pt, Rh from 2.0 M HCl 2.0 mL extracted)• Shaking: 1500 rpm, 15 min, 25 oC
IL3: R = OctIL4: R = HexIL5: R = Bu
Back extraction efficiency Eback (%) Eback = 100 × Cback/(C0 – C)
Cback : Aq. phase PGM conc. afterback extraction
HNO3 conc. was increased
IL4, 1 M HNO3
PGMs can recover from ILs phaseChange in HNO3 conc. allow selective back extraction
IL5IL4IL3
N N N
NTf2R
R
Eback was increased
Only Rh and Pd could be extracted
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HNO3 ammonia
urea water
N N N
NTf2Hex
Hex
IL4: R = Hex
PGMs were successfully back-extracted into aq. HNO3 and ammonia.
Back Extraction of PGMs into aq. Solutions
PGM back extractionAq. phase:2.0 mLILs phase: IL4(after 100 ppm PGMs extraction)Shaking: 1500 rpm, 15 min, 25 oC
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【Extractant】 IL4 400mg
【Extraction】 100 ppm Pt, Pd, and Rh in 3.0 M HCl, 2.0 mL
【Back-extraction】 8 M HNO3 or 1% (wt%) NH3·H2O
N N N
NTf2Hex
Hex
IL4
Back-extraction: 8 M HNO3 Back-extraction: 1% (wt%) NH3·H2O
fresh C6 second-hand C6 third-hand C60
20
40
60
80
100
E (%
)
Pt Pd Rh
fresh C6 second-hand C6 third-hand C60
20
40
60
80
100
E (%
)
Pt Pd Rh
IL4 was recycled and exhibited high E after back-extraction with ammonia solution.The decrease in E was due to decrease in the IL4 amount by dissolution into the aqueous phase.
IL4 2nd-handIL4
3rd-handIL4
Recycle of Amino-substituted ILs for Extraction
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【Extractant】 IL4 400mg (fresh: 200 mg/used: 200 mg)
【Extraction】 100 ppm Pt, Pd, and Rh in 3.0 M HCl, 2.0 mL
【Back-extraction】 8 M HNO3 or 1% (wt%) NH3·H2O
fresh C6 fresh C6 (200 mg)+second-hand C6 (200mg)
fresh C6 (200mg)+third-hand C6 (200mg)
0
20
40
60
80
100
E (%
)
Pt Pd Rh
Back-extraction: 8 M HNO3 Back-extraction: 1% (wt%) NH3·H2O
fresh C6 fresh C6 (200 mg)+second-hand C6 (200mg)
fresh C6 (200mg)+third-hand C6 (200mg)
0
20
40
60
80
100
E (%
)
Pt Pd Rh
N N N
NTf2Hex
Hex
IL4
Usage of ammonia solution was an efficient back-extraction and recycle system.
Recycle of Amino-substituted ILs for Extraction
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1H-NMR Sprctra of IL4 After Treatment with HNO3
IL4
IL43.0 M HCl
IL4 after back-extraction
by HNO3(8 M)
IL4 after back-extraction
by ammonia(1 wt%)
water
8 M HNO3: Decomposition of IL4 was observed1 wt% NH3: IL4 was stable for the treatment with aq. NH3. 30
Towards Practical Usage of ILs for Extraction of PGMs
Kg-scale synthesis is readily possible.
Large-scale synthesis of ILs (500 g x 4 bottles)
A simple three-step route
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S. Ma, K. Funaki, A. Miyazaki, A. Muramatsu, K. Kanie, Chem. Lett., 46, 1422 (2017).
Synthesis of Amino-substituted IL with high hydrophobicity Investigation of PGM Extraction Ability into the ILs
ObjectivesSummary
Amino-substituted IL showed high extraction ability towards PGMmetals. Especially, the IL exhibits Rh extraction ability.
Only PGMs were selectively extracted from a model waste. Recycle of the ILs by the back extraction into NH3 phase was achieved.
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THANK YOU !Mr. Hanzawa, our graduate student, will present the recent results in our laboratory in his poster.
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