Recovery of indium from sphalerite ore and flotation tailings by bioleaching and subsequent precipitation processes

摘要

Flotation tailings dump material of the former lead-zinc mine near Freiberg (Germany) consists of fine grained quartz, feldspar, mica as well as the sulphide- minerals pyrite, galena and sphalerite not recovered by flotation. Sphalerite contains, aside from iron, copper and cadmium, significant contents of indium (up to 0.38 % (w/w)) leading to indium contents up to 70 mg/kg in the mine tailings. Preliminary thermodynamic assessment showed a comparatively small Eh-pH-range where bioleaching is possible and indium is not hydrolytically precipitated. Shaking flask bioleaching of original polymetallic sphalerite ore from the Freiberg mining district (400 mg/kg In) showed maximum zinc and indium recovery rates of near 100 or 80 %, respectively. First tests on tailings material showed Zn and In yields of up to 80 %. A stepwise precipitation process is being developed for indium recovery from the PLS consisting of combined iron/indium precipitation and subsequent processing of the indium pre-precipitate.