Extraction behavior of germanium from synthetic leaching solution of secondary zinc oxide in tertiary amine (N235)-trioctyl phosphate (TOP) system

In continuation with our previous work, in the present study, the tertiary amine-trioctyl phosphate-sulfonated kerosene system was employed to recover Ge(IV) from the synthetic leachate of secondary zinc oxide. The effects of different complexing agents (tartaric acid, citric acid, oxalic acid, gallic acid, and salicylic acid) and impurities (Zn(II), Fe(III), Cd(II), Si(IV), and As(III)) on the extraction of Ge(IV) were investigated. Under comparable conditions, the extraction of Ge(IV) with the aforementioned complexants had the following order in terms of extraction efficiency: tartaric acid > citric acid > gallic acid > oxalic acid, or salicylic acid. The reason for the low extraction efficiency of Ge(IV) with the addition of oxalic acid was revealed by an extraction comparison using pure germanium and polymetallic solutions. Furthermore, a stoichiometry analysis of the extracted complex indicated that the extracted Ge(IV)-organic species was R 3 NH·Ge(OH) 4 (HT)·0.5TOP with the addition of tartaric acid. The concentration of Ge(IV) in the loaded organic phase was less than 1 mg/L when three-stage countercurrent stripping was adopted at an O/A ratio of 1/3 and 25 °C for 10.5 min.