Selective Removal of Copper and Tin from Etching Waste by Cementation with cobalt: Subsequent Electro-winning

Abstract

Indium is one of the rare metals and 84% of it is mostly used as transparent electrodes of indium tin oxide (ITO) films of flat panel displays in 2007.  With recent trend of large sized flat panel displays and expanded market share of them, demand for indium has increased significantly and recycling should account for appropriate portion of indium supply.  On the other hand, significant portion of ITO etching waste solution is being discarded.  Therefore, appropriate portion of ITO etching waste solution has to be recycled to recover indium to comply with EU’s WEEE (Waste Electrical and Electronic Equipment) and RoHS
(Restriction of Hazardous Substances) directives.  In the present research, copper and tin were selectively removed by cementation with cobalt powders from indium-bearing etching waste solution.  The cobalt ions
were enriched by subsequent electro-winning process²⁾, where aluminum and indium ions were electrolytically reduced on Ir-coated Ti cathode.