A validation experiment on indium recovery by electrowinning of aqueous electrolytes: Optimization of electrolyte composition

摘要

A batch-type and lab-scale indium recovery method was developed via electrowinning (EW) to prove mass production-capability and economic recovery of indium from InCl3 crystals precipitated from the solvent extraction using a suitable phosphoric acid-based extractant. More precisely, the InCl3 crystals thus precipitated were further dissolved in three different aqueous electrolyte mixtures for subsequent electrowinning experiments: 0.05 M InCl3 - 0.7 M LiCl; 0.05M InCl3; 0.05 M InCl3 - 0.7 M NaCl. The effect of adding LiCl and NaCl supporting electrolytes to InCl3 on overall EW efficiency was thus comprehensibly investigated. Direct electroreduction of InCl3 using 0.05 M InCl3 aqueous electrolyte resulted in the highest indium metal purity of 99.996 % deposited on the copper cathode. Thus, metallic contents obtained from the validation experiments were further characterized using various analytical tools such as inductively coupled plasma/atomic emission spectroscopy (ICP/AES), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) and X-ray fluorescence (XRF).