Sorbent selection for the recovery of gallium and indium from aqueous solutions: a sustainable approach to the recovery of strategic metals from LED lamps

Abstract

Gallium and indium, metals present in LED lighting technology, were removed from aqueous solutions by sorption. Carbonaceous materials, such as activated carbon, beer bagasse, spent coffee grounds or peanut sells, and a low-cost zeolite as chabazite, were used. Chabazite protonated, under mild conditions, showed high sorption capacities for gallium (56 mg/g) and indium (92 mg/g), 10 to 30 times higher than carbonaceous materials. Sorption experiments with both metals in solution showed a competitive effect between gallium and indium for the sorption sites of the chabazite, showing more affinity towards gallium than indium. Ga3 + sorbed/In3 + sorbed molar ratio above 2 was achieved for the same initial concentration of both metals, increasing to almost 3 when the initial gallium concentration increased. However, the sorption capacity for both metals was always around 0.35 mmol Ga + In/g. The selectivity of the chabazite was conditioned by different behavior of both metals in aqueous solution at the sorption pH being the predominant species in solution Ga(OH)2+ for gallium and In3+ for indium. Sorption with protonated chabazite can be used in the treatment of spent light emitting diodes (LEDs) leachate for the dual purpose of water purification and selective metal separation.