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

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

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)

Pourbaix diagram for Ge-H2O system at 298 K.

Sources of Ge Germanite: Cu3(Ge,Fe)S4 Renierite: a complex Cu-Fe-As-Ge Zinc ores (associated with sphalerite ZnS): zinc concentrates contain 200-400 ppm Ge Combustion by-products (fly ash) of coal

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

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

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)

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

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

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

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

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

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

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

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

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

Thank you for your attention!