Recovery of Germanium from Zinc Smelting Leachate Using a Novel Hydroxamic Acid Extractant BGYW: Continuous Counter-Current Extraction and Process Optimization

Germanium is a critical rare-dispersed metal with irreplaceable applications in infrared optics, fiber-optic communications, and semiconductor industries, making its efficient recovery from secondary resources of great strategic importance. This study investigates the selective recovery of germanium from complex zinc smelting leachates using a novel hydroxamic acid extractant, BGYW, in synergistic combination with P204. The feed solution contained approximately 360 mg/L Ge, 10,790 mg/L Fe²⁺, and 98,530 mg/L Zn, representing a highly complex matrix. Continuous counter-current extraction was performed in a 30-stage miniature mixer-settler. Under optimized conditions of 10% BGYW + 5% P204 in white oil, an O/A ratio of 1:1, and 8 mol/L NH₄F as strippant, the single-stage germanium extraction efficiency reached 99.4%. Over 16 consecutive cycles, the extraction system maintained stable performance with average germanium extraction above 99%. A 3-stage scrubbing section using 50 g/L H₂SO₄ effectively removed co-extracted Zn, Cu, and Al impurities. Iron co-extraction, a major challenge, was successfully mitigated through a 2–3 stage iron scrubbing step using a chloride-containing scrubbing solution, which reduced the iron concentration in the strip liquor from approximately 600 mg/L to below 4 mg/L, and decreased the Fe/Ge mass ratio from 0.197 to below 0.01. The overall germanium recovery across the entire 30-stage continuous process reached 98.82%, and the dissolution loss of BGYW in the aqueous phase was reduced by over 85% compared to the conventional YW100 extractant. Third-phase formation caused by residual organic flocculants from the leaching step was eliminated through enhanced pre-treatment, while ferric fluoride precipitation in the stripping section was resolved by incorporating the iron scrubbing stage. This study demonstrates that the BGYW-P204 extraction system with the integrated iron scrubbing step offers an efficient, stable, and industrially viable approach for germanium recovery from zinc smelting leachates, providing a practical solution to the long-standing challenge of germanium–iron separation and contributing to the sustainable supply of this critical metal.