Quantifying indium with ion chromatography in hydro- and biohydrometallurgical leaching solutions

A methodology has been developed to chromatographically quantify indium in polymetallic (bio)hydrometallurgical processing solutions using the Dionex IonPac CS5A column and pyridine-2,6-dicarboxylic acid eluent. Cu(II) and In(III) could be separated by elevating the column temperature to 45°C. The comparatively low stability constant of the In-eluent complex (log K₂  = 3.8) required typical leaching samples to be diluted in the eluent rather than acid or water to overcome ligand competition between components of the sample solution and the eluent. The methodology was applied to leachates from (bio)hydrometallurgical processing of oxidic flue dust residues and sulfidic zinc ores, where both are promising candidates for the recovery of indium from low grade ores and metallurgical wastes. Indium, ferrous iron, ferric iron, copper, zinc, nickel, and manganese concentrations could be simultaneously quantified. The method was found suitable for samples containing at least 0.25 mg/L indium and an iron to indium ratio of up to 100:1.