Efficient indium leaching and recovery from waste liquid crystal displays panels using microwave and ultrasound-assisted heating system

Abstract

Innovative approaches for recovery indium from waste liquid crystal displays (LCDs) has been continuously demanded with increasing concerns over its threat to human health and environment. In this work, we recycled indium from waste LCD panels based on acid leaching procedure (HCl, HClO4 and H3PO4) under microwave and ultrasound-assisted heating system. To optimize the leaching protocol, the method of full factorial experimental design was adopted to explore the influence of different parameters (microwave power, reaction time, acid concentration, and liquid to solid ratio). Results revealed that 100% leaching yield could be achieved as microwave power of 650 W, HCl concentration of 4 M, and liquid: solid ration of 2 within only 142 s. Overall, the leaching effect can be ranked as HCl > H3PO4 > HClO4. To further recovery indium from the acid solution after the microwave leaching by electrorefining, different electrolysis times (2 h, 4 h, 6 h, 8 h, 10 h), voltages (10 V, 15 V, 20 V) and currents (0.1 A, 0.3 A, 0.5 A, 0.7 A, 0.9 A, 1 A, 3 A, 4 A, 5 A) were investigated, the optimal indium recovery yield was accomplished by 93.41% with 1 A and 10 V for 10 h. The metal indium precipitate metalized at the cathode after electrolysis was found to be 99.14% for the purity. In addition, pareto chart analysis of standardized effect and regression mode were employed to testify the optimal leaching condition. This work demonstrates an effective and facile way to recovery indium from wasted LCDs with desirable leaching yield than conventional heating approach.