Highly efficient photocatalytic Microcystin-LR elimination using magnetic recyclable nanocomposite ZnO/Fe3O4/Bi2WO6/RGO and its toxicity assessment

Photocatalysis offers an environment-friendly and sustainable strategy for Microcytin-LR (MC-LR) degradation in aquatic systems, and thus the exploitation of recyclable photocatalysts with high-efficiency is urgently needed. Herein, a magnetic photocatalyst ZnO/Fe3O4/Bi2WO6/RGO was developed to degrade MC-LR under visible light. The ZnO/Fe3O4/Bi2WO6/RGO achieved 97.4 % MC-LR degradation within 180 min under visible light, which was 2.2 and 2.5 times higher than those of Bi2WO6 and ZnO, respectively. The MC-LR removal efficiency decreased in the presence of algae cells, fulvic acid and coexisted anions (Cl-, CO32-, NO3-, and H2PO4-), which demonstrated a positive trend with the decrease of MC-LR initial concentration. The reactive radicals of h(+), center dot OH, and center dot O-2(-) participated in the degradation of MC-LR, and C-C bonds (C-3-C-4, C-4-C-5, and C-6-C-7) in Adda chain of MCLR was destroyed in degradation process. The result of ecological safety experiments indicated that ZnO-20 %/ Fe3O4/Bi2WO6/RGO (0.17 g/L) remaining in the solution after recovered by magnets had no toxic effects on Chlorella vulgaris, Daphnia magna, and zebrafish during the exposure period.