Precipitation of Germanium from Sulphate Solutions Containing Tin and Indium Using Tannic Acid

Abstract

The precipitation of tannin complex of germanium from sulfuric solutions obtained after dross leaching was investigated. The tested solutions contained mainly zinc, germanium, indium, and tin. The influence of temperature, time, amount of added tannic acid and its purity was determined. The application of pure tannic acid allowed the precipitation of >99% of germanium and decreased its concentration in a solution <0.015 g/dm3. It required ca. 11–13 g of pure tannic acid per each 1 g of dissolved germanium. The preferred process conditions for Ge precipitation using powder tannic acid were 90 °C, 90 min, whereas for 20% aq. solution—5 min. It was found that 40% to 50% of tin coprecipitated at these conditions. Therefore, a detinning operation using hydrogen peroxide was proposed. It allowed the removal of >99% Sn and reduced its concentration in the solution below 0.025 g/dm3.