A novel acid resource: Waste hydrochlorofluorocarbons refrigerants selective leaching Cu-In-Ga-Se (CIGS) and catalyzed mineralization under the hydrothermal atmosphere.

With the upgrading and obsoleting of electric refrigeration equipment, significant amounts of waste hydrochlorofluorocarbon (HCFCs) refrigerants are being generated, bringing serious ozone-depleting and global warming effects. HCFCs, containing chlorine and fluorine, have the potential to be converted into acids by mineralization. Hydrothermal technology possesses a tightly sealed environment and high thermal efficiency, providing significant advantages in treating volatile HCFCs. However, the stable C-F bonds and the by-product CClF=CH greatly impede the mineralization of HCFCs. Herein, an indium compound from waste CIGS (CuInGaSe) was introduced to promote the process, and this strategy successfully increased the mineralization rates of organic chlorine and fluorine to 99.2 % and 95.7 %, respectively. The acid produced from HCFCs degradation was utilized for the selective leaching of metals in CIGS. Meanwhile, the leaching product InOOH catalyzed further degradation of HCFCs. We revealed that InOOH can adsorb reactants and provide interfaces, resulting in (i) the elongation of C-X (F, Cl) bonds; (ii) a reduction in the energy barrier of the CClF=CH degradation reaction. This study provides a promising approach and theoretical basis for the harmless treatment and resourceful utilization of waste refrigerants containing Cl and F.