Visible light-driven photocatalytic degradation of Microcystin-LR by Bi 2 WO 6 /Reduced graphene oxide heterojunctions: Mechanistic insight, DFT calculation and degradation pathways

Developing heterostructure photocatalysts for removing Microcystin-LR (MC-LR) under visible light was of positive significance to control the risk of Microcystins and ensure the safety of water quality. Herein, the Bi WO /Reduced graphene oxide (RGO) nanocomposites were prepared via a simple one-spot hydrothermal method for the first time to degrade MC-LR. The optimized Bi WO /RGO (Bi WO /RGO ) achieved a removal efficiency of 82.3% toward MC-LR, with 1.9-fold higher efficiencies than Bi WO , and it showed superior reusability and high stability after 5 cycles. The degradation efficiency of MC-LR demonstrated a negative trend with the initial concentration of MC-LR, fulvic acid, and initial algal density increased, while MC-LR removal rate for the presence of anions was in the order of Cl > CO > NO > H PO . The degradation efficiency of MC-LR could reach up to 82.3% within 180 min in the neutral condition. The active species detection experiments and EPR measurements demonstrated that the holes (h ), hydroxide radicals (∙OH), and superoxide radicals (∙O ) participated in the degradation of MC-LR. The DFT calculations showed that 0.56 of electron transferred from Bi WO to RGO, indicating RGO introduction could prevent the recombination of photoelectrons and holes and was beneficial for MC-LR degradation. Finally, the possible intermediate products and degradation pathways were also proposed by the LC-MS/MS analysis.