Novel Ag3PO4/ZnWO4-modified graphite felt electrode for photoelectrocatalytic removal of harmful algae: Performance and mechanism

A novel Ag3PO4/ZnWO4-modified graphite felt electrode (AZW@GF) was prepared by drop coating method and applied to photoelectrocatalytic removal of harmful algae. Results showed that approximately 99.21% of chlorophyll a and 91.57% of Microcystin-LR (MCLR) were degraded by the AZW@GF-Pt photoelectrocatalytic system under the optimal operating conditions with a rate constant of 0.02617 min-1 and 0.01416 min-1, respectively. The calculated synergistic coefficient of photoelectrocatalytic algal removal and MC-LR degradation by the AZW@GF-Pt system was both larger than 1.9. In addition, the experiments of quenching experiments and electron spin resonance (ESR) revealed that the photoelectrocatalytic reaction mainly generated •OH and •O2- for algal removal and MC-LR degradation. Furthermore, the potential pathway for photoelectrocatalytic degradation of MC-LR was proposed. Finally, the photoelectrocatalytic cycle algae removal experiments were carried out on AZW@GF electrode, which was found to maintain the algae removal efficiency at about 91% after three cycles of use, indicating that the photoelectrocatalysis of AZW@GF electrode is an effective emergency algae removal technology. The outbreak of harmful algal blooms (HABs) will cause a severe threat to the aquatic ecological environment and public health, which needs to be urgently addressed. Photocatalytic technology can effectively solve the problem of HABs, but there are certain shortcomings. For example, nano photocatalysts are easy to aggregate and precipitate in practical applications, and there are issues of recycling difficulties and secondary pollution. In addition, the electrons and holes generated by photocatalysis are extremely easy to be compounded, thus hindering the generation of ROSs and leading to their unsatisfactory removal efficiency in practice. In order to solve this problem, the AZW@GF-Pt photoelectrocatalytic composite system was constructed in this study to realize efficient algal removal as well as well solving the problem of difficult recycling of powder catalysts, which provides a new idea for the management of HABs.