vg leaching zn use 060310_21streaken_presen_ohkawa

1060310 レアメタル研究会

New Extraction Processof

Precious Metals from Scrapby

Chemical Vapor Treatment

Chihiro OhkawaToru H. Okabe

Institute of Industrial Science The University of Tokyo, Tokyo, Japan


New Extraction Process ofPrecious Metals from Scrap by

Chemical Vapor Treatment1. Introduction

BackgroundPrevious researchPurpose of this study

2. New process using Mg and FeCl3 vapor3. New process using Li vapor and Cl2 gas4. Summary


Fig. Periodic table and applications of precious metals.

Precious metals

Chemical industry(Pt, Pd, Ru, Au, etc.)

http://www.nippon-nz.com/japanese/jigyo/pdct_220.html

• Textile industry

http://www.ishifuku.co.jp/Products/Industrial/intro7.htm

• Thermocouples

http://www.ishifuku.co.jp/Products/Industrial/intro7.htm

• Infusible electrodes

Catalysts (Pt, Pd, Rh, etc.)

http://www.ne-chemcat.co.jp/kagaku/noblemetal/index.html

• Petrochemical industry

• Automotive exhaust catalyst

Jewelry(Au, Pt, Ag, Rh, etc.)

http://www.ginzatanaka.co.jp/

http://www.inter-g7.or.jp/tanaka/products/products.html

Laboratory instruments (Pt, Ir, Au, etc.)

Electronic components,

Semiconductors(Au, Ag, Pd, Ru, etc.)

http://www.kkmisuzu.co.jp/

Dental alloys(Au, Pt, Pd, etc.)

http://www.tokuriki-kanda.co.jp/shika/index.html

IA IIA IIIA IVA VA VIA VIIA VIIIA IB IIB IIIB IVBVB VIBVIIB 01 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

1

2

3

4

5

6

7

1

H2

He3

Li4

Be5

B6

C7

N8

O9

F10

Ne11

Na12

Mg13

Al14

Si15

P16

S17

Cl18

Ar19

K20

Ca21

Sc22

Ti23

V24

Cr25

Mn26

Fe27

Co28

Ni29

Cu30

Zn31

Ga32

Ge32

As34

Se35

Br36

Kr37

Rb38

Sr39

Y40

Zr42

Mo43

Tc44

Ru45

Rh46

Pd47

Ag48

Cd49

In50

Sn51

Sb52

Te53

I54

Xe55

Cs56

Ba72

Hf73

Ta74

W75

Re76

Os77

Ir78

Pt79

Au80

Hg81

Tl82

Pb83

Bi84

Po85

At86

Rn87

Fr88

Ra104

Unq105

Unp106

Unh107

Uns108

Uno109

Une

57~71

*89~103

*** Lanthanoid** Actinoid

41

Nb


Other Jewelry:68 t(30%)

Autocatalysts:109 t (48%)

Chemicals:10 t (4%)

Electricals: 9 t(4%)

Autocatalysts:24 t (89%)

OtherChemicals: 1.3 t (5%)

Other

Northamerica:12 t (5%)

Other

South Africa:157 t (70%)

Russia:26 t (12%)

Recovery fromautocatalysts:

22 t (10%)

Russia:3 t (12%)

Other

Recovery fromautocatalysts: 4 t (16%)


America: 262 t (7%)

Other:1,601 t(42%)

Australia:258 t (7%)

Recoveryfrom scrap:828 t(22%)

Fig. Supply and demand of precious metals in the world (2004).

Pt227 t

Rh27 t 3,851 t

Au

Pt224 t

Rh27 t 3,851 t

Au

Jewelry:2,610 t (68%)


Demand

Net producerhedging: 442 t (11%)

Supply

*Johnson Matthey PLc: Platinum 2005 (2005).**Gold Fields Mineral Services Ltd.: Gold Survey 2005 (2005).

Officialsectors: 478 t (12%)

Supply and demand

Electricals:261 t (7%)


Fig. Transition and prediction of the world demand of platinum from 1900 to 2030.

*Johnson Matthey PLc: Platinum 2005 (2005).**U.S. Bureau of Mines: Minerals yearbook. etc…

Transition and prediction of Pt demand

The demand for Pt is increasing because of tightening environmental regulations.It is extremely important to develop a new recovery process for precious metals.

1900 1920 1940 1960 1980 2000 2020

400

300

0

Wor

ld d

eman

d, w

/ ton

100

200

500

600 Estimate

Total production of Pt since recorded history5,000 t

Current world production of Pt 200 t / year


Recovered precious metals

Scrap containing precious metals (M)

Pretreatment (Crushing, etc.)

Dissolution in acid

Separation and purification

Cu, Pb, Fe, etc.

Collector metal containing M

Fig. Typical recovery process for precious metals from scrap.

Extraction by collector metals

Dire

ctly

dis

solv

ed in

aci

d

Typical recovery process for precious metals

Pyrometallurgical process

○ High efficiency○ High speed

× High energy cost× Large-scale

facilities required

Hydrometallurgical process

○ Low energy cost○ Easy handling

× Long processing time

× Generation of a large amount ofwaste solution


Au

Pd

AgPt

Met

al c

onc.

in le

ache

d so

lutio

n / p

pm3000

2500

2000

1500

1000

500

00 30 60 90 120 150

Dissolution rate of precious metals

(Solution volume: 300 cm3, Sample form: 10 x 10 x 0.5 mm (1.07 g), Leaching temperature: RT)

*J. Shibata et al., Kagaku Kogaku Ronbunsyu, 27 (2001), pp. 367–372.

Fig. Dissolution behaviors of Au, Ag, Pt, and Pd with aqua regia as a function of time.

Time / min

Dissolution of precious metalsis very difficult, even by aqua regia.

Hydrometallurgical process requires a large amount of acid with a strong oxidant and involvesa long processing time.

If dissolution efficiency ofprecious metals is increased, hydrometallurgical processis expected to transform into a new energy saving process.

Leaching rate of Pt is extremely low.


New extraction process for platinum group metals (PGMs) from waste materials by using reactive metal vapor

*T. H. Okabe et al., Journal of Materials Research, 18, No. 8 (2003), pp. 1960–1967.

***Y. Kayanuma et al., Journal of Alloys and Compounds, 365 (2004), pp. 211–220.**T. H. Okabe et al., Materials Transactions, JIM, 44, No. 7 (2003), pp. 1386–1393.

Previous research

Fig. Concept of the metal vapor treatment of PGMs.

Metal vapor is supplied to PGMs dispersedon an oxide substrate.

Platinum group metals(PGMs)

R-PGM alloys are formed selectively.

R-PGM compounds

Surface area of PGMs is enlarged by selective dissolution of R.

This enables PGMs to react with acid effectively, and they dissolve faster than in their pure form.

ΔHcalcfor / kJ·(mol of atoms)–1

Mg3PtMgPt

MgPt3

Ca5Pt3Ca3Pt2CaPt2CaPt5

Li5PtLi2PtLiPt

LiPt2

Fe3PtFePt

FePt3

0 20 40 60 80A. R. Miedema et al.: Cohesion in Metals (1989).

Fig. Calculated enthalpy of formation ofbinary Pt compounds.


Previous research

Pt

0

50

100

Pt R-Pt

Mas

s% o

f di

ssol

ved

Pt

R: Mg R: Ca

Mass of sample: 0.05 - 0.1 gLeaching time: 1 - 4 hTemperature: RT

Rh

0

50

100

Rh R-Rh

Mas

s% o

f di

ssol

ved

Rh

R: Mg R: Ca

Mass of sample: 0.05- 0.1 g

Leaching time: 1 hTemperature: 323 - 333 K

Fig. Results of dissolution experiments of R-Pt and R-Rh samples using aqua regia.

New extraction process for platinum group metals (PGMs) from waste materials by using reactive metal vapor

*T. H. Okabe et al., Journal of Materials Research, 18, No. 8 (2003), pp. 1960–1967.

***Y. Kayanuma et al., Journal of Alloys and Compounds, 365 (2004), pp. 211–220.**T. H. Okabe et al., Materials Transactions, JIM, 44, No. 7 (2003), pp. 1386–1393.

Mg or Ca treatment of pure Pt or Rh was effective in enhancing the dissolution rate of Pt and Rh in aqua regia.

However, there still remains a problem: the generation of a large amount of waste solution containing heavy metals and strong acids.


(a) Pt-H2O system (aCl– = 0)

1.5

1.0

0.5

0.012840

PtO3

PtO2

PtH2

Pt2+

PtO

O2

pH

Pot

entia

l, E

/ V(b) Pt-H2O-Cl system (aCl– = 0.48)

1.5

1.0

0.5

0.012840

pH

Pot

entia

l, E

/ V PtO3

PtO2

Pt

[PtCl6]2–

PtO

O2

H2

Fig. E-pH diagram of (a) Pt-H2O and (b) Pt-H2O-Cl systems at 298 K.

*M. Pourbaix: Atlas of Electrochemical Equilibria in Aqueous Solution (1966).

E-pH diagram

Oxidizing agent is required for the dissolution of precious metals.However, when chloride compound is formed, it is possibleto dissolve precious metals in acid without using an oxidant.


(a) Conventional leaching processC

hem

ical

pot

entia

l of

chlo

rine

(or o

xyge

n)

Oxidation ・Dissolution

pCl2, pO2

Pt

PtCl62–

Processingtime, tprocess

Development of a new method for dissolving precious metalsby reactive metal treatment followed by chlorination

Long duration time

Purpose of this study

Long processing time and considerable amount of acidswith strong oxidants are required for the dissolution.

A large amount of waste solution containing heavy metals and strong acids is generated.


Che

mic

al p

oten

tial o

fch

lorin

e (o

r oxy

gen)

Oxidation ・DissolutionPtCl62–

Chlorination (or oxidation)RPtxCly (or RPtxOy)

R-PtCompound formation under reduced atmosphere

(b) Reactive metal treatment followed by chlorination (or oxidation)pCl2

, pO2

Pt Processingtime, tprocess

Short duration time

Development of a new method for dissolving precious metalsby reactive metal treatment followed by chlorination

Purpose of this study

• Pretreatment for selective and efficient dissolution of PGMs

• Higher dissolution efficiency• Lower amount of acids used for dissolution• High-speed dissolution

Discharge volume of waste solution can be reduced and chloride waste (e.g., FeCl3) can be utilized.




1. Introduction2. New process using Mg and FeCl3 vapor

3. New process using Li vapor and Cl2 gas4. Summary

Flowchart of this partSynthesis of Mg-M compoundsChlorination of Mg-M compounds using FeCl3Results


Fig. Precious metal recovery through the formation of complex chlorides(or oxides) by chloride vapor treatment.

Flowchart of this study

Chlorination (or oxidation)

Solution containing precious metals

Pure precious metals

Precious metal recovery

R vapor treatment

Dissolution Residue

R-M compounds

RMxCly (or RMxOy) compounds

HCl aq.

Reactive metal (R)(R: Mg, Li, etc.)

Chlorinationagent(or O2)

Scrap containing precious metals (M)(M: Pt, Rh, Au, etc.)

Pretreatmentshortens thedissolution time

Efficientdissolution


Temperature, T / K

Reciprocal temperature, 1000 T–1 / K–1

Vap

or p

ress

ure,

log

p i(a

tm)

-5

-10

-15

-20

0

0.8 1.0 1.2 1.4 1.6

1000 800 60012001400

FeCl3

AlCl3ZnCl2Zn

Mg

CaMgCl2NaCl

CaCl2Cu

Au

RhPt

KCl

FeCl2

Li

LiCl

Fig. Vapor pressure of selected metals and chlorides.

Supplying extraction medium in vapor form

Reactants can be supplied tothe entire quantity of scrap,irrespective of its complicated structure.

*I. Barin: Thermochemical Data of Pure Substances, 3rd edition (1995).

Selection of alloy former and chlorination agent

Chlorination

Alloy formation

Dissolution Residue

R-M compounds

RMxCly compounds

Acids

Mg

FeCl3vapor

Precious metals (M)(M: Pt, Rh, and Au)


Fig. Schematic illustration of the experimental apparatus forthe synthesis of Mg-M compounds.

Stainless steel reaction vessel

Ta crucible

Precious metal (Pt, Rh, or Au)

Stainless steel plate

Sponge Ti

TIG welding

Stainless steel cover

Mg

Synthesis of Mg-M compounds

• Pure precious metals were reacted with molten Mg at 1173 K for 12 h.→ XRD analysis: Mg-M compounds were formed

(but their phases were not identified).→ SEM/EDS analysis: Homogeneous compounds were obtained.


Quartz tube

FeCl3 M powder

Stainless steel reaction vessel

Stainless steel sample holder

Quartz crucible

Ar/vacuum

Stainless steel crucible

Powder of Mg-M compound(M = Pt, Rh, or Au)

Fig. Schematic illustration of the experimental apparatus forthe chlorination of Mg-M compounds.

Chlorination of Mg-M compounds using FeCl3

Heater

• Mg-M compounds were reacted with FeCl3 vapor at 673 K for 3 h.→ Mass change: The increase in the mass of Mg-M compounds

after chlorination was greater than that of pure precious metals.→ XRD analysis: Identification of the phases in the samples was difficult

due to the absence of relevant reference data.


Mas

s% o

f di

ssol

ved

Rh

Mas

s% o

f di

ssol

ved

Pt

Mas

s% o

f di

ssol

ved

Au

Dissolved in aqueous HCl solutionDissolved in aqua regia (HCl + HNO3)Not dissolved after leaching

0

50

100

Rh Mg-Rh ChlorinatedMg-Rh

Chlorinated Rh

0

50

100

Pt Mg-Pt ChlorinatedMg-Pt

Chlorinated Pt

0

50

100

Au Mg-Au ChlorinatedMg-Au

Chlorinated Au

PtT = RTt’’ = 1 h

RhT = 323–333 Kt’’ = 1 h

AuT = RTt’’ = 1 h

Fig. Percentage of dissolved precious metals after the leaching experiment.

Results of dissolution experiment

Dissolution efficiencies of Pt and Rh in aqua regia after alloy formation and chlorination were significantly enhanced.


Mas

s% o

f di

ssol

ved

Rh

Mas

s% o

f di

ssol

ved

Pt

Mas

s% o

f di

ssol

ved

Au


0

50

100


Chlorinated Rh

0

50

100


Chlorinated Pt

0

50

100


Chlorinated Au


RhT = 323 – 333 Kt’’ = 1 h

AuT = RTt’’ = 1 h



Chlorinated Rh and Mg-Rh compounds were dissolved in HCl aq. although pure Rh barely dissolved in acids.


Mas

s% o

f di

ssol

ved

Rh

Mas

s% o

f di

ssol

ved

Pt

Mas

s% o

f di

ssol

ved

Au


0

50

100


Chlorinated Rh

0

50

100


Chlorinated Pt

0

50

100


Chlorinated Au

PtT = RTt’’ = 1h

RhT = 323 – 333 Kt’’ = 1h

AuT = RTt’’ = 1h



Dissolution efficiencies of Au obtained from Mg-Au and chlorinated Mg-Au compounds decreased.→ The reason for these results

is under investigation.


(a) Before leaching (b) After HCl aq. leaching

Fig. Scanning electron micrograph of Mg-M compounds before and after leaching with HCl aq.

SEM analysis

10 µm

10 µm

10 µm

10 µm

10 µm

10 µm

Mg-Pt

Mg-Rh

Mg-Au

• Mg and Fe were dissolved,and their mass ratios becameless than 1 mass% after leaching.

• Grains of precious metals withseveral microcracks were obtained as residues afterleaching in HCl aq.

• Large surface areas of Pt and Rhthat formed after/during dissolution of Mg and Fe caused an increasein the dissolution efficiencies ofchlorinated Mg-M compounds.




1. Introduction2. New process using Mg and FeCl3 vapor3. New process using Li vapor and Cl2 gas

4. Summary

Flowchart of this partSynthesis of Li-M compoundsChlorination of Li-M compounds using Cl2 gasResults


Selection of alloy former

Temperature, T / K

Reciprocal temperature, 1000 T–1 / K–1

Vap

or p

ress

ure,

log

p i(a

tm)

-5

-10

-15

-20

0

0.8 1.0 1.2 1.4 1.6

1000 800 60012001400

FeCl3

AlCl3ZnCl2Zn

Mg

CaMgCl2NaCl

CaCl2Cu

Au

RhPt

KCl

FeCl2

Li

LiCl

Fig. Vapor pressure of selected metals and chlorides.*I. Barin: Thermochemical Data of Pure Substances, 3rd edition (1995).

Chlorination

Alloy formation

Dissolution Residue

R-M compounds

RMxCly compounds

Acids

Li vapor

Cl2 gas

Precious metals (M)(M: Pt and Rh)

• Readily-soluble chloride complexes ofLi and Pt or Rh were reported.(Li2[PtCl4]・6H2O, Li3[RhCl6]・12H2O)

• Li battery scrap can be utilized asLi source.


Synthesis of Li-M compounds

(a)

Stainless steel sheet

Precious metal (Pt or Rh)

Li shot

Stainless steel container

20 mm

73 m

m Mo crucible

Sponge Ti

(b)

Sponge Ti

Stainless steelcontainer (a)

TIG welding

Stainless steelreaction vessel

• Pure Pt and Rh were reacted with Li vapor at 1173 K for 6 h.→ XRD analysis: Li2Pt was obtained in Li-Pt system,

and LiRh was obtained in Li-Rh system.But some peaks were not identified.

Fig. Schematic illustration of the experimental apparatus forthe synthesis of Li-M compounds.


Chlorination of Li-M compounds using Cl2 gas

• Li-M compounds were reacted with Cl2 gas at 723~773 K for 1h.→ XRD analysis: RhCl3 was obtained in Li-Rh system. But identification of the phases

in other samples was difficult due to the absence of relevant reference data.

Fig. Schematic illustration of the experimental apparatus forthe chlorination of Li-M compounds.

Powder of Li-M compoundor M (M = Pt or Rh)

Ar

KMnO4 aq.

Light-proofbubbler

Na2S2O3 aq.H2O

P2O5

H2Oconc. KMnO4 aq.

conc. HCl aq.

Cl2 gas generator

Chlorination reactor

Cl2 absorber

Cl2 gas inlet

Gas outlet

Dehydrator

Heater


Dissolution efficiencies of Pt in aqua regia after alloy formation and chlorination were significantly enhanced.

Mas

s% o

f di

ssol

ved

Rh

Mas

s% o

f di

ssol

ved

Pt


0

50

100

Rh Li-Rh ChlorinatedLi-Rh

Chlorinated Rh

0

50

100

Pt Li-Pt ChlorinatedLi-Pt

Chlorinated Pt


RhT = 323–333 Kt’’ = 1 h




Dissolution efficiency of Rh in aqua regia after alloy formation was slightly increased.

Mas

s% o

f di

ssol

ved

Rh

Mas

s% o

f di

ssol

ved

Pt


0

50

100


Chlorinated Rh

0

50

100


Chlorinated Pt


RhT = 323–333 Kt’’ = 1 h




Dissolution efficiencies of Rhwere not improved after chlorination using Cl2 gas. → This is due to the formation of

RhCl3 which is insolublein acids.

Mas

s% o

f di

ssol

ved

Rh

Mas

s% o

f di

ssol

ved

Pt


0

50

100


Chlorinated Rh

0

50

100


Chlorinated Pt


RhT = 323–333 Kt’’ = 1 h




• Pt metal comprising micro grains with several cracks was obtained as residuesafter leaching of Li-Pt and chlorinated Li-Pt compounds by HCl aq.

• Large surface area of Pt formed after/during dissolution of Li caused an increasein the dissolution efficiencies of Li-Pt and chlorinated Li-Pt compounds.

• No major change of surface shape was observed in Li-Rh system.

SEM analysis

Fig. Scanning electron micrographof Li-M compounds before and after leaching with HCl aq.

(a) Before leaching (b) After HCl aq. leaching

10 µm

10 µm10 µm

10 µm

Li-Pt

Li-Rh


1. Reactive metal treatment followedby chlorination was conducted forincreasing the dissolution rate ofprecious metals.

2. Precious metals were reacted withmolten Mg at 1173 K for 12 h, andthen chlorinated using FeCl3 vaporat 673 K for 3 h.

After these treatments, dissolutionefficiencies of Pt and Rh in aqua regiawere significantly enhanced.

3. Precious metals were reacted with Li vapor at 1173 K for 6 h, and then chlorinated using Cl2 gas at 723~773 K for 1 h.

After these treatments, dissolution efficiency of Pt in aqua regia increased.Dissolution efficiency of Rh from Li-Rh compounds was slightly enhanced;however, those of chlorinated samples were not improved because of the formation of RhCl3 which is insoluble in acids.Optimization of chlorination condition is an important issue in the future.

Che

mic

al p

oten

tial o

fch

lorin

e (o

r oxy

gen)

Oxidation ・DissolutionPtCl62–

Chlorination (or oxidation)RPtxCly (or RPtxOy)

R-PtCompound formation

pCl2, pO2

Pt

Processingtime, tprocess

Short!

Summary

vg leaching zn use 060310_21streaken_presen_ohkawa

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