Ricerc@Sapienza

Since indium is considered a strategic material, a study for developing and optimizing a recovery process by electrowinning has been performed. The possibility of using electrolytic baths based on sulfates instead of chlorides has also been evaluated. Nowadays, chlorides are widely used because they generally present greater current efficiencies;however, the dangers of chlorine gasrequireexpensive-sealed systems to avoid human health and environmental issues. The use of sulfatesdoes not present the same problems;therefore the electrowinning process optimization can represent a definite indium recovery improvement. For this purpose, the effects of electrolyte composition, temperature, current density and pH on the quality of the deposit, specific energy consumption (SEC) and current efficiency (CE) have been assessed. The sulfate electrolytic solutionhas been then appropriately modified with organic additives, mineral salts and complexing agents to optimize the indium recovery by electrowinning. ACE of about80% and SEC equal to 2.7 kWh/kg have been obtained, operating with a pH in the range 2.2–2.3 at 40 °C and using 25 A/m2 current density with an electrolytic solution containing 60 g/l of In3+, 30 g/l of Na2SO4, 20 g/l of Al2(SO4)3 and 20 g/l of H3BO3.