Facile indium recovery from waste liquid crystal displays: Chloride-facilitated indium electroreduction and stepwise Cu/MoO2 and indium electrodeposition.

With a huge amount of waste liquid crystal displays (LCDs) generated annually, their proper recycling raises continuous concern to realize pollution control (heavy metal and liquid crystal) and resource recovery (indium). However, due to their multi-metal feature, traditional hydrometallurgy lacks of sufficient selectivity, which makes the recycling route lengthy, costly, and generate more waste. Electrodeposition acts as a promising technique for selective metal extraction from multi-metal system due to its high selectivity and electron as clean reagent. To fully develop its application in metal recovery, stepwise Cu/MoO2 and In electrodeposition from In-Cu-Mo-Fe waste LCD leachate is explored in depth. Electrochemical behavior analysis shows Cu and MoO2 can be first electrodeposited for their higher electroreduction potential. Cl- plays a key role in accelerating indium electroreduction kinetics, which largely shortens the extraction time without the sacrifice of current efficiency. This accelerating effect is attributed to the increased concentration of electroactive species or collision frequency. Under optimized condition, 99.41% of indium (> 99% purity) can be electrodeposited within 13 h with high current efficiency. This study provides a cleaner approach for waste LCDs recycling and gives implications for the potential application of electrochemical technique in e-waste recycling.