Membrane treatment of leached mining waste - A potential process chain for the separation of the strategic elements germanium and rhenium

Microfiltration, nanofiltration, and reverse osmosis allow for separating multicomponent solutions. These membrane techniques are applied for the separation and concentration of several components on a scale of a micron down to an atomic range from aqueous solutions. This work showcases a potential process chain for the recovery of germanium and rhenium from an acidic bioleaching solution containing sludge particles. The focused feedstock is an anthropogenic mining waste (Theisen sludge) containing various valuable metals which were mobilized by bioleaching. For particle removal a rotating microfiltration (0.2 and 2.0 mu m) system was utilized, showing that > 99% of the leached sludge particles are retained. By nanofiltration > 99% of the cationic transition metals were removed and the target elements germanium and rhenium are separated in reverse osmosis, which follows suit. Thereby, germanium remains in the retentate and rhenium is separated in the permeate. The filtered streams are intended for further downstream processes such as solvent extraction and adsorption.