The Recovery of Gallium and Germanium from Mine Tailings

Gallium (Ga), a posttranslational element, and germanium (Ge), a metalloid, are critical materials widely used in electronics, transport, defense, and renewable energy industries. The demand of these two elements far exceeds their supply, mainly due to these materials only being mined as by-products during the mining of other metals. This deficit will probably continue because these two materials are not found or produced in significant quantities. To address these supply challenges, attention is being given to secondary sources of Ga and Ge, such as electronic waste, coal fly ash, and mine waste. This study aimed to recover Ga and Ge from tailings from the Tsumeb mine in Namibia. Chemical and mineralogical characterizations using various analytical techniques were performed on the sample. The total dissolution of the tailings sample revealed that the sample comprised 1.870(5) % Ga and 0.0300(2) % Ge. Other notable elements in the sample were 23(2) % Zn, 9.01(12) % Cu and 0.740(5) % Pb. H2SO4 achieved the highest extraction of Ge of 40.63 % from four different mineral acids; H2SO4, H3PO4, HCl, and HNO3 were evaluated as a suitable extraction candidate, while H3PO4 was the most effective for Ga (25.00 %). The optimal dissolution conditions for Ga were determined to be 2 M H3PO4, solid-to- liquid ratio of 0.7 g:10 mL, at 90 °C, for one hour leaching with stirring speed of 100 rpm. For Ge, the optimal conditions were 3 M H2SO4, solid-to-liquid ratio of 0.1 g:10 mL, at 90 °C, for one hour leaching with 100 rpm stirring. Ge was isolated at pH 8 from the H2SO4 leachate, while Ga was isolated at pH 4 from the H3PO4 leachate. Products containing 5 % Ge and 25 % Ga were isolated.