Recovery of Ge(IV) from synthetic leaching solution of secondary zinc oxide by solvent extraction using tertiary amine (N235) as extractant and trioctyl phosphate (TOP) as modifier

The N235–TOP–sulfonated kerosene system was applied for the recovery of Ge(IV) from a synthetic sulfuric acid leaching solution of secondary zinc oxide, containing Ge(IV), Zn(II), As(III), Fe(III), Si(IV), and Cd(II). The co-extraction of As(III) with Ge(IV) is a challenging problem in the extraction of Ge(IV) from aqueous solution by N235. However, TOP, as a modifier, suppressed the co-extraction of As(III) significantly. The effects of factors including N235 concentration, extraction time, tartaric acid to Ge(IV) molar ratio and temperature on the extractions of Ge(IV) and As(III) were studied. At an organic/aqueous (O/A) phase ratio of 1/1, aqueous phase pH of 1.2, extraction time of 10.5 min, tartaric acid-to-Ge(IV) molar ratio of 5.0, and temperature of 25 °C, the extraction efficiency of Ge(IV) reached 93.9%, whereas only 1.3% of As(III) was extracted by the 25%(v/v)N235–10%(v/v) TOP–sulfonated kerosene system in a single stage extraction. The Ge(IV) in the raffinate was less than 1.5 mg/L when employing a five-stage continuous countercurrent extraction at an O/A ratio of 1/10. In addition, aqueous NaOH solution of 0.5 mol/L was an appropriate reagent for the stripping of both Ge(IV) and As(III) at an O/A ratio of 1/1 and 25 °C for 10.0 min.