Co-Extraction and Stepwise Stripping of Indium and Germanium Using a BGYW–P204 System

To address the co-recovery of indium and germanium from sulfuric-acid systems containing indium and germanium together with their subsequent stepwise stripping, a hydroxamic-acid extractant-di-(2-ethylhexyl)phosphoric acid composite organic phase was investigated for the co-extraction and stepwise stripping of indium and germanium from sulfuric-acid solutions. The effects of extractant composition, aqueous acidity, O/A phase ratio, and extraction time were optimized, and HCl and NH4F were evaluated for stepwise stripping of In and Ge, respectively. Increasing hydroxamic-acid extractant significantly enhanced Ge extraction, while 25 vol% di-(2-ethylhexyl)phosphoric acid provided high extraction efficiencies for both metals. Tri-n-alkylphosphine oxide suppressed Ge extraction and reduced HCl stripping of In; therefore, the organic phase was selected as 15 vol% hydroxamic-acid extractant + 25 vol% di-(2-ethylhexyl)phosphoric acid + 60 vol% diluent. Under the optimized conditions of 15 g/L H2SO4, O/A = 2:1, and 5 min extraction, the extraction efficiencies of Fe, Ge, and In reached 99.9%, 99.7%, and approximately 100%, respectively. Using 3 mol/L HCl, the In stripping efficiency reached 99.8%, whereas Ge was scarcely stripped. Subsequent stripping with 2 mol/L NH4F achieved nearly 100% Ge recovery, although Fe co-stripping was approximately 95%. The hydroxamic-acid extractant-di-(2-ethylhexyl)phosphoric acid system therefore enables efficient co-extraction and stepwise stripping of In and Ge, while suppressing most coexisting impurities.