1. Recent developments in hydrometallurgical recovery of germanium
Sadegh Safarzadeh
Department of Materials and Metallurgical Engineering
South Dakota School of Mines and Technology
9/15/2014

2. Outline Germanium Chemistry Aqueous Processing Techniques
Solution Concentration and Purification
Reduction of Germanium Oxide to Metal

3. Atomic weight: 72.59
Density: 5.3 g/cm3 at 293 K
Melting point: 937 ˚C
Boiling point: 2830 ˚C
Valencies: +2 and +4
Crystal structure: fcc
Soluble in aqua regia and concentrated sulfuric acid
Germanium hydride (germane) is inflammable, toxic gas (GeH4)

4. Pourbaix diagram for Ge-H2O system at 298 K.

5. Sources of Ge Germanite: Cu3(Ge,Fe)S4 Renierite: a complex Cu-Fe-As-Ge
Zinc ores (associated with sphalerite ZnS): zinc concentrates contain ppm Ge
Combustion by-products (fly ash) of coal

6. Distillation &Hydrolysis
Apex Mine Process
Ore
Crushing/grinding
H2SO4
SO2
Leaching
CaF2
Filtration
Tailings
Cementation
Scrap Fe
Cu Cement
NaCl
NaClO3
H2S
Ge Precipitation
GeS2 leaching
Distillation &Hydrolysis
H2SO4
HCl
Ga Recovery
GeO2
Ga Metal

7. Leaching from other resources
T. ferrooxidants in H2SO4-Na2S2O3
USBM’s thermophilic ATCC53921
SiO2 issues during the leaching of zinc plant residues: polysilicic acid
HF leaching

8. Recovery of Ge from leach solution
Cementation onto zinc dust: redissolution followed by second cementation
Precipitation as Ge sulfide: H2S is used
Precipitation as germanates (CaGeO3): lime neutralization-Arsenic issues
Precipitation as basic germanates: Fe(III) added
Precipitation with polyhydroxycarboxylic acids (tannin and tannic acid)

9. Solvent Extraction Nitrobenzene CCl4 Chloroform MIBK TBP
Kelex 100: β-dodecenyl-8-hydroxyquinoline-molar ratios 5-10
Chelating α-hydroxyoxime extractants: LIX 26, LIX 63
Tertiary amines: Alamine 336
Synergistic extraction systems: LIX 26-Kelex 100

10. Kelex 100 Extraction reactions: pH<2
(3HL)org+(Ge(OH)i(4-i)++HSO4-+(i-3)H+)aq=
(GeL3+.HSO4-)org+(iH2O)aq
i=0,1,2
3<pH<8
(2HL)org+(Ge(OH)4)aq=(GeL2(OH)2)org+(2H2O)aq
Stripping reaction
(GeL3+.HSO4-)org+(4OH-)aq=(3HL)org+(H2GeO42-+SO42-)aq

11. Problems Very slow disengagement kinetics upon stripping
Poisoning of the organic phase with a hydrated precipitate Na2Ge2O7

12. Ion exchange Anionic exchange resins: Amberlite family of resins
IRA-400 (hydroxide and chloride forms) can extract anionic species of Ge such as GeO32-, HGeO3-, and Ge5O112-.
pH of around 9 is required for effective extraction
Fe (III) has poisonous effects and has to be removed

13. Electrowinning?
Cathode reactions: electrodepositionof Ge, hydrogen evolution, and GeH4 evolution
Ge can only be deposited from GeCl4 and GeI4 in ethylene and propylene glycol at high temperatures

14. GeO2 and Ge Fractionation of GeCl4 Concentrated HCl medium required
Arsenic is troublesome (AsCl3)-codistillation
AsCl3+Cl2=AsCl5
AsCl5+4H2O=H3AsO4+5HCl
Copper turnings in distillation column

15. GeCl4 hydrolysis GeCl4+3H2O=H2GeO3+4HCl H2GeO3=GeO2+H2O
Cold water required
Seeding required

16. Reduction of GeO2 CO, NH3, and Zn vapor
Hydrogen reduction is the most widely used
GeO2+H2=GeO+H2O
GeO+H2=Ge+H2O
Sublimation point of GeO is 700 ˚C

17. Recent developments
Complexation with catechol (C6H4(OH)2) or 1,2-dihydroxybenzene
Ge-cat complex formation:
Ge(OH)4+3C6H4(OH)2=Ge(C6H4O2)32-+2H++4H2O
Highly charged with high molecular weight
Ge-cat is extracted onto conventional anionic resins (AmberliteIRA-900, IRA 958)
2R2NR3Cl+GeCAT32-=(R2NR3)2GeCAT3+2Cl-
Ge is eluted from resin using HCl in 50% ethanol solution

18. Thank you for your attention!