Superoxide radical induced redox processes for simultaneous reduction of Cr (VI) and oxidation of ciprofloxacin in wastewater

Simultaneous removal of antibiotics and heavy metals from the wastewater is still a sophisticated task with great challenge. Interestingly, •O2- as a long-lived and highly active specie can simultaneously remove antibiotics and heavy metals. Herein, we design a S-type heterojunction photocatalyst, which can efficiently generate •O2-. Characterizations and DFT calculation demonstrate that internal electric field provides powerful propulsion for migration of photo generated carriers between Zn0.78Cd0.22S and g-C3N4, effectively extends electronic life, thereby enhances the production of •O2-. Photocatalytic reaction rate constants under optimal composite ratio conditions were 3.1-times (ciprofloxacin) and 5.9-times (Cr (VI)) higher than Zn0.78Cd0.22S under the coexisting pollutant system. Benefiting from the inbuilt electric field to stimulate electron transfer and utilization as well as the dual function of •O2-, it reveals the possibility of practical wastewater treatment in the internal circulating fluidized bed reactor.