Natural sphalerite photocatalyst for treatment of oily wastewater produced by solvent extraction from spent lithium-ion battery recycling

Oily wastewater from solvent extraction is hard to be treated due to a large number of organic pollutants and high salt content. Here, we found a photocatalyst (natural sphalerite (NS), (Zn, Fe)S)) with great application potential for treating oily wastewater of solvent extraction, and studied its application in removal organics from actual solvent extraction wastewater of spent lithium-ion battery recycling. It found that doping Fe participated in the formation of new energy bands and accepted transferred-electrons from ZnS as electron acceptor, thus enhanced the visible-light absorption ability and carrier mobility. The photocatalysis activity of NS was further improved by adding hydrogen peroxide (H2O2), mainly because it prevented the recombination of photo-generated electron–hole pairs. Consequently, 86.20% removal of total organic carbon was achieved with H2O2-assisted NS under the optimum conditions. This work is expected to shed light on the application of photocatalysis in treatment of oily wastewater of solvent extraction.