Ultrasound-assisted leaching and supported liquid membrane extraction of waste liquid crystal displays for indium recovery

Abstract

Indium recovery from waste liquid crystal displays (LCDs) was carried out by using ultrasound-assisted leaching (UAL) and supported liquid membrane (SLM) extraction. The leaching efficiency and purity of indium were approximately 97% and 94%, respectively, when using 0.75 M of sulfuric acid and 300 W of ultrasound power level. The highest extraction efficiency of indium was approximately 82%, obtained by using 20 vol% of D2EHPA fraction, 2 M of HCl concentration in the stripping solution and pH 3 of feed solution. The permeability coefficient, initial flux and reaction rate constant substantially increased with increasing D2EHPA fraction and feed solution pH, but HCl concentration provided little effect. If there is a synergistic effect occurring between the feed solution pH and the D2EHPA fraction, the permeability coefficient will be as high as 5.5 μm/s when using pH 3 of feed solution and 20 vol% of D2EHPA fraction. The overall recovery rate of indium can be close to 80%, and the indium purity of the final product solution can be almost 100%. If indium can be completely recovered in the extraction process, the final recovery rate of indium will be higher than 97%. Based on the findings of this study, indium can be efficiently recovered from waste LCDs by using the UAL and the SLM extraction methods.