Selective recovery of germanium from iron-rich solutions using a supported ionic liquid phase (SILP)

© 2019 The Authors A supported ionic liquid phase (SILP) was developed to selectively recover germanium from iron-rich aqueous solutions. The SILP was synthesised by impregnating Amberlite XAD-16N with Aliquat 336, a mixture of quaternary ammonium salts. Characterisation was performed using elemental analysis, infrared spectroscopy, specific surface area, porosity and density measurements. Adsorption was preceded by the addition of citrate anions to the iron-rich aqueous solutions, to form germanium(IV) citrate complexes, which were extracted to the ionic liquid layer of the SILP. The reaction kinetics and several adsorption parameters, including pH, anion concentration and adsorbent mass, were investigated using synthetic single-element germanium solutions. The coordination of germanium(IV) to the citrate ligands was elucidated using Extended X-ray Absorption Fine Structure (EXAFS). Subsequently, the optimal adsorption parameters were tested on a multi-element solution with elemental concentrations resembling those of a leachate of goethite residue from the zinc industry. A high selectivity for germanium over iron could be achieved. Finally, the stripping and the reusability of the SILP were studied. A germanium solution of 44 mg·L −1 was obtained with a germanium-over-iron mass ratio of 39. This corresponds to a selectivity factor equal to 34 400, demonstrating the high potential of the reported process.status: publishe