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

Abstract

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 Bi2WO6/g-C3N4 heterojunction photocatalysts were synthesized via one-step hydrothermal method for ATZ degradation. The Bi2WO6/g-C3N4-0.15 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 Bi2WO6, g-C3N4 and “Bi2WO6 + g-C3N4”, respectively. The influence of synthesis reaction factors of Bi2WO6/g-C3N4 and various environmental factors including catalyst dosage, ATZ concentration, pH, common anions and HA on photocatalytic property of Bi2WO6/g-C3N4 were also investigated. The radical-quenching experiments proved that holes (h+), 1O2 and O2– played pivotal roles in ATZ degradation in Bi2WO6/g-C3N4 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 Bi2WO6/g-C3N4 heterojunction exhibited excellent photostability and pH adaptability, showing efficient practicality in the removal of refractory organic pollutants in wastewater.