Study On The Recovery Of Germanium In Zinc-leaching Residue

As an important scattered metal element of making advanced technological material, germanium is needed more and more. In this paper, the high technology applications of germanium and the methods of recovering it from zinc-leaching residues are briefly reviewed. For the recovering difficulties of germanium from zinc-leaching residues combined with onsite production conditions, that "Two-stage hot acid-leaching—Reduction of zinc concentration—Solvent extraction" principal process was selected. A set of experimental studies of hot-leaching were carried out with thermodynamics and kinetics theoretical analysis. The synergistic extraction mechanism of germanium with P204-TBP-sulfonate kerosene system and extraction condition and stages of extraction as well as striping condition and stages were studied.The results of hot-leaching experiments showed that the dosages of sulfuric acid, leaching time and reaction temperature are the main factors influencing leaching rate. With the increase of the amount of sulfuric acid and reaction temperature and leaching time, leaching rate of germanium increases. The agitation intensity, liquid-solid ratio also has influence on the leaching process. The optimal leaching processing conditions were as follows:the mass concentration of sulfuric acid was188g/L, leaching temperature was95℃, leaching time was3h, leaching L/S ratio was5/1, and agitation speed was300r/min. Under suitable conditions, the leaching rate of germanium could reach to62%. Thermodynamics analysis of leach process suggests that acid leaching of germanium was exothermic reaction and equilibrium constant (25℃) was7.84×10-6. The kinetic study shows that the leaching process follows kinetic law of "shrinking of unreacted core" and is controlled by interface chemical reaction.Solvent extraction experiments were conducted from acidic solutions containing germanium(IV) using bi-(2-ethylhexyl) phosphoric acid (P204) as an extractant, tri-n-butyl phosphate (TBP) as modifier diluted in sulfonate kerosene. It is show in singel-batch experiments and cascade experiments that with30%P204and15%TBP combination, phase ratio O/A1/3, extraction intensity200r/min, extraction rate of germanium could reach86.7%in10min and it could reach to94.27%after two-stage countercurrent extraction under favorable conditions. Quantitative scrubbing (>99%) of iron with6mol/L hydrochloric acid concentration from the loaded organic phase without loss of quantitative germanium(IV).Sodium hydroxide aqueous solution was used to strip germanium(IV) from organic phase and get Na2Ge04aqueous solution, which is used to produce GeO2.