Ion flotation of germanium from fly ash aqueous leachates

The germanium – together with other metals and metalloids contained in the fly ash generated in the Integrated Gasification in Combined Cycle (IGCC) of Elcogas plant (Puertollano, Spain) – may be extracted by aqueous leaching. Here we report the study of the selective recovery of germanium from aqueous leachate by means of ion flotation, using a complexating agent and a surfactant as collector. The use of different ligands with dodecylamine as collector and the effect of the pH were evaluated. The optimal conditions found for germanium recovery are: catechol as complexating agent, triple stoichiometric ratio of the reagents and pH 4–7. In these conditions, germanium recovery was 100% and the extraction of impurities was reduced. The recovered froth was burned and characterized by thermogravimetric analysis (TGA), X-ray fluorescence (XRF) and X-ray diffraction (XRD). A high Ge product (53% GeO2) was obtained.