Subcritical water extraction of indium from indium tin oxide scrap using organic acid solutions

Abstract

Environmental contextIndium is a metal increasingly used in high-technology industries, creating a demand for efficient recycling technology. We investigated extraction of indium from waste using a subcritical water extraction with organic acids. Compared with conventional methods employing concentrated mineral acids, the new method is less corrosive, more efficient and required shorter extraction times. AbstractSubcritical water extraction (SWE) was applied to extract indium (In) from indium tin oxide (ITO) scrap. Four organic acids, acetic acid, gluconic acid, citric acid (CA) and etidronic acid (EA), were used at a solid-to-liquid ratio (S/L) of 10gL−1. Neither acetic acid nor gluconic acid yielded significant extraction of indium. A total of 70.71% and 96.93% of indium was extracted using 1M of CA and EA respectively at 150°C and a final pressure of 18–19 bar within 30min. The extraction efficiency of In was shown to increase with the increase in acid concentration and in temperature. Compared with conventional extraction methods, SWE was more effective using less concentrated acids and required a shorter reaction time.