Mechanism of efficient selective separation and purification of Cu, In, and Ga in the deep eutectic solvents system

Conventional CIGS recycling primarily employs acid-base leaching methods. Since In and Ga in the leachate both belong to group IIIA elements with similar ionic radii and charge densities, the traditional process suffers from poor environmental friendliness and a high co-extraction rate of them. Based on the green and sustainable leaching properties of deep eutectic solvent (DES), this work developed a roasting-leaching process that not only allows for the simultaneous recovery of all elements from CIGS but also enables their effective separation. Through systematic experimental optimization, the key process parameters of DES, including solvent composition ratio, temperature, and leaching time, were accurately determined. Combined with leaching kinetics studies, the rate-controlling steps and interfacial reaction mechanisms were revealed. A multi-stage extraction-stripping coupling process was designed to achieve the deep separation of Cu, In, and Ga. Furthermore, density functional theory calculations were employed to decipher the leaching mechanism of DES and the mechanism of selective extraction within it. High-purity products, including CuO (99.36%), In 2 O 3 (99.59%), Ga 2 O 3 (99.43%), and SeO 2 , were successfully obtained through precipitation and calcination treatments. Moreover, the developed technique achieved high recovery efficiencies of 98.43% for Cu, 99.26% for In, 100% for Se, and 98.23% for Ga. Ultimately, a life cycle assessment revealed that the entire process is environmentally friendly, efficient, and sustainable. The advantages of this work over conventional methods include: (1) enhanced leaching efficiency, (2) highly selective separation of Cu, In and Ga, (3) the sustainable and environmentally benign nature of the DES.