Photocatalytic activation of oxalic acid over FeOOH loaded FeWO4/WO3 heterojunction for high-efficient degradation of tetracycline

Photocatalytic oxalic acid (OA) activation for pharmaceutical wastewater degradation based on Fe-based catalysts are usually limited by the cycle of Fe3+/Fe2+ and low conversion efficiency of OA. Herein, an effective OA activator, FeOOH loaded FeWO4/WO3 (FFW) heterojunction photocatalyst, were fabricated by electrostatic selfassembly for tetracycline (TC) degradation. Experimental results revealed that the introduction of FeOOH can greatly enhance the optical absorption and separation efficiency of photogenerated carriers of the FeWO4/WO3 (FW) composite. Moreover, optimized FFW heterojunction exhibited the excellent photocatalytic OA activation activity and the highest OA conversion rate for TC degradation, which exhibited 97.3% photocatalytic performance for TC within 30 min under 420 nm light irradiation. The FFW heterojunction still revealed high photocatalytic OA activation activity for TC degradation even after six cycles. The possible degradation pathway of TC and photocatalytic OA activation mechanism of FFW heterojunction were also presented by ESR spectroscopy results, quenching tests, and LC-MS analysis. This work not only provides a fresh perspective on the surface photo-Fenton chemistry of catalytic redox processes, but also presents a valid reference for designing highly efficient photocatalytic OA-activation systems for pharmaceutical wastewater treatment.