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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/MoO 2 and In electrodeposition from In-Cu-Mo-Fe waste LCD leachate is explored in depth. Electrochemical behavior analysis shows Cu and MoO 2 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. [Display omitted] • Stepwise electrodeposition of Cu/MoO 2 and In from LCD leachate was achieved. • Cl- can accelerate indium electrodeposition, improving recovery efficiency. • Increased surface concentration/collision frequency lead to the acceleration. • 99.41% of indium (> 99% purity) was recovered with current efficiency > 70%. [ABSTRACT FROM AUTHOR]

Recycling activity for waste electrical and electronic equipment is always accompanied with leaching solution containing copper. Its selective extraction is of environmental and economic significance, and is beneficial for subsequent resource purification procedure. Compared with techniques such as chemical precipitation and solvent extraction, potentiostatic electrodeposition is outstanding with the advantage of high selectivity, electron as clean reagent, and minimal chemical usage. However, key factors affecting copper electrodeposition behavior as well as its kinetic process remain unclear, which blocks its further application. In this study, selective copper electrochemical extraction from multi-metal leaching solution of waste liquid crystal display panels is explored. Copper electrodeposition is analyzed from electrochemical and mass transport point of view, and the main results are summarized: (i) copper can be first electrodeposited due to its higher reduction potential compared with indium; (ii) applied potential and agitation are the most influential factors towards space-time yield and current efficiency; (iii) a semi-empirical kinetic model could quantitatively describe the influence of agitation and the time-current-concentration relationship. The model-predicted extraction rate agreed well with experimental data throughout electrodeposition; (iv) electrodeposition experiments show over 95% of copper can be selectively extracted as ultrafine copper powder (~150 nm) at 0.05 V (vs. SHE). ga1 • Cu can be fully separated from In and Mo by electrodeposition. • Moderate applied potential and agitation are crucial for high efficiency. • Cu electrodeposition kinetics can be depicted by a semi-empirical model. • Deposited nanosized Cu can increase the risk of hydrogen evolution. [ABSTRACT FROM AUTHOR]

• Concurrent In leaching and Sn precipitation were achieved during acid leaching. • The leaching behavior and mechanism of In, Sn was studied in detail. • A kinetic model was deduced to depicting In leaching in thin film situation. • Pure Cu and In were separately extracted via electrodeposition. Since indium (In) was the most valuable resource in waste liquid crystal panels (LCDs), most researches only focused on preliminary recovery of In, while those coexisting metal elements (Cu, Sn, Al) raised little concern. This could lead to waste of resources, potential risk of heavy metal pollution, and also complexation of following In purification procedures. Besides, current hydrometallurgy processes for In purification are complicated, consume more reagents and generate more wastewater. Therefore, this research applied simple acid leaching and two-step electrodeposition for In-Sn and In-Cu-Al separation with minimum waste generation and input. Considering the special doping structure of indium-tin oxide (ITO), feasibility for concurrent In leaching and Sn precipitation was explored based on the unique Sn species' dissolution and precipitation behavior during acid leaching. Since the behavior of Sn was more sensitive to acidity and temperature, 97.07% of Sn removal and 99.25% of In recovery could be achieved using 1 mol/L H 2 SO 4 at 70 ℃ for 1 h. A specific kinetic model depicting In leaching in thin ITO film situation was developed referring to avrami equation. Then, the application of two-step electrodeposition enabled 95.32% extraction of Cu and deposition of In with a purity over 99 wt% at respective potential. [ABSTRACT FROM AUTHOR]