One-step synthesis of a 3D/2D Bi2WO6/g-C3N4 heterojunction for effective photocatalytic degradation of atrazine: Kinetics, degradation mechanisms and ecotoxicity

Atrazine (ATZ), as a widely used s-triazine herbicide, has persistence and biological toxicity in the environment. Photocatalytic technique is considered as sustainable and promising strategy for the degradation of emerging organic pollutants. Thus, 3D/2D Bi 2 WO 6 /g-C 3 N 4 heterojunction photocatalysts were synthesized via one-step hydrothermal method for ATZ degradation. The Bi 2 WO 6 /g-C 3 N 4 -0.15 exhibited 99.96% removal efficiency for ATZ and the rate constant was approximately 25, 4.8 and 10 times greater than the rate constants of Bi 2 WO 6 , g-C 3 N 4 and “Bi 2 WO 6  + g-C 3 N 4 ”, respectively. The influence of synthesis reaction factors of Bi 2 WO 6 /g-C 3 N 4 and various environmental factors including catalyst dosage, ATZ concentration, pH, common anions and HA on photocatalytic property of Bi 2 WO 6 /g-C 3 N 4 were also investigated. The radical-quenching experiments proved that holes (h + ), 1 O 2 and O 2 – played pivotal roles in ATZ degradation in Bi 2 WO 6 /g-C 3 N 4 photocatalytic system. The ATZ degradation pathway involved dealkylation, alkyl hydroxylation, alkyl oxidation, dechlorination-hydroxylation and deamination-hydroxylation reactions, which was proposed by HPLC–MS/MS results and density functional theory (DFT) analysis. Moreover, quantitative structure–activity relationship (QSAR) evaluation showed that the ecotoxicity of many intermediates declined compared with ATZ. The 3D/2D Bi 2 WO 6 /g-C 3 N 4 heterojunction exhibited excellent photostability and pH adaptability, showing efficient practicality in the removal of refractory organic pollutants in wastewater.