The solvent extraction of germanium and some heavy metals by commercial tri-octyl/decyl amine (Alamine 336), N-methyl-N, N-dioctyl chloride (Aliquat 336) and phosphine oxide (Cyanex 923) has been studied. In each extraction system, germanium was only extracted from a solution containing nickel, cadmium, cobalt, and zinc, which had a composition similar to gasification coal fly ash aqueous leach solutions. Under a comparable condition, the germanium extraction efficiency by the aforementioned extractants was in the order Aliquat 336 > Alamine 336 > Cyanex 923. The slope analysis method showed that 2 moles of Alamine 336 and Aliquat 336, as well as 4 moles of Cyanex 923, participated in the extraction of germanium. In amine extraction systems, tartaric acid was required as a complexant used to convert germanium to anionic species. As a result, the ratio of 2 (mole ration of tartaric acid to Ge) was required to complete anionic complexation. On the other hand, oxalic acid with a concentration of 0.1 M was chosen as a proper solvated complexant in the Cyanex 923 system. HCl solutions with concentrations of 1 and 2 M can properly strip germanium from the loaded Alamine 336 and Aliquat 336, respectively. In addition, 0.1 M NaOH was sufficient for germanium stripping from Cyanex 923. Consequently, it can be concluded that Aliquat 336 can be an economical and industry-friendly extractant for germanium solvent extraction from a mixed solution.Peer ReviewedPreprin

Transport process of germanium from an aqueous solution containing oxalic acid and 100 mg/L Ge was studied. Cyanex 923 immobilized in a polytetrafluoroethylene membrane was employed as a carrier in a flat-sheet supported liquid membrane (FSSLM) system. The speciation of the germanium ion in the oxalic acid medium and related diagrams were applied to study the transport of germanium. The effective parameters such as oxalic acid, carrier concentration, and strip reagent composition were evaluated in this study. Based on the experimental data, the oxalic acid and carrier concentrations of 0.075 mol/L and 20% v/v were the condition in which the efficient germanium transport was achieved, respectively. The concentration range of 0.04–0.1 mol/L was selected for sodium hydroxide (NaOH) as a strip reagent providing the best efficiency to transport germanium through the supported liquid membrane (SLM) system. Furthermore, the permeation model was obtained to calculate the mass transfer resistance of the membrane (Δ_m) and feed (Δ_f) phases. According to the results, the values of 1 and 1345 s/cm were found for Δ_m and Δ_f, respectively.