Iron-tungsten oxides modified oxygen-rich carbon nitride with defects S-scheme heterojunction for boosting photo-Fenton like removal of pollutants

Owning to excellence of photocatalytic persulfate (PS)-based oxidation processes in pollutant removal, the iron-tungsten oxides modified oxygen-rich carbon nitride with defects (ITOs/OCNv) S-scheme heterojunction composites were successfully prepared, and the photo-Fenton like system (Vis/ITOs/OCNv/PS) was constructed to degrade antibiotic pollutants. Results indicated that the ITOs/OCNv composites exhibited large specific surface area and rich porous structure. In addition, the in-situ introduction of oxygen-rich functional groups and lots of N and O vacancy defects in the composites enhanced the absorption of visible light (Vis) and the electron transfer. Importantly, the formed S-scheme heterojunction improved the separation of photogenerated carriers. The degradation efficiencies of sulfamethazine (SMZ) and ciprofloxacin (CIP) in the optimal Vis/5% ITOs/OCNv/PS system were 99.6 % and 99.5 %, which were 1.69 and 2.34 times that of Vis/5% ITOs/OCNv system (SMZ 58.9 % and CIP 42.6 %) after 40 min, respectively. Results of quenching experiments showed that the main active species were h+, 1O2 and O2− for SMZ and CIP degradation. Moreover, this system exhibited better anti-interference of water substrates and applicability in actual water body. The degradation pathways of CIP were proposed by combining density functional theory calculation with intermediate analysis. Moreover, the ecotoxicities of CIP and its products were evaluated comprehensively. The system showed better broad-spectrum degradation of pollutants, including sulfamethoxazole, atrazine, sulfadimethoxine and bisphenol A, which would provide a new insight for persistent pollutant removal.