Novel green hybrid acidic-cyanide bioleaching applied for high recovery of precious and critical metals from spent light emitting diode lamps

The spent light emitting diode (LED) lamp is a new type of electronic waste contains the large amount of valuable metals. In this study, a novel green hybrid acidic-cyanide bioleaching process was developed for the high efficiency recovery of valuable metals from spent LED lamps. The spent LEDs were biopretreated using biogenic ferric produced by Acidithiobacillus ferrooxidans to efficiently harvest all base and heavy metals, 93% Sn, 94% Ni, 80% Cu, 68% Al, 60% Ga, 51% Pb, 46% Cr, and 35% Fe were leached. Then the bio-pretreated residue was bioleached by Bacillus megaterium (B. megaterium). Under optimum conditions (pH 7; glycine 2.5 g/L; L. methionine 10 g/L), 15 mg/L cyanide was produced by B. megaterium in short time of 14 h. At 10 g/L bio-pretreated spent LED, under direct hybrid bioleaching, a 47% gold extraction efficiency was observed after 36 h. The better performance of direct hybrid bioleaching suggests the important role of extracellular polymeric substances (EPS) and the continuous production of CN-. Compared to single cyanide bioleaching with un-pretreated LEDs, the amounts of metals recovered through hybrid direct bioleaching were significantly high; 93% Au, 91% Ag, 98% Ni, 87% Cu, and 84% Ga were leached after 4 d. This study developed an approach for the efficient recycling of spent LEDs that will result in a huge economic interest and better environmental performance. (c) 2021 Elsevier Ltd. All rights reserved.