Construction of Ag3PO4/NiWO4 S-scheme heterojunction with enhanced sonocatalytic performance for the removal of tetracycline: Characterization, sonocatalytic mechanism and degradation pathways

In this study, Ag 3 PO 4 /NiWO 4 (AN) composites were synthesized by a two-step method. The sonocatalytic properties of Ag 3 PO 4 /NiWO 4 composites were investigated using tetracycline (TET) as a contaminant model, and the best sonocatalytic performance was obtained for AN-30. The removal of TET at pH= 8 with an initial concentration of 20 mg/L could reach 98.16 ± 0.37 % after sonication at 500 W for 5 min with 2 g/L of AN-30 and 3 mmol/L of K 2 S 2 O 8 added. Combined with the experimental results of active species capture and X-ray photoelectron spectroscopy, it was demonstrated that Ag 3 PO 4 formed an S-scheme heterojunction with NiWO 4 , which promoted the separation of electron-hole pairs and thus improved the sonocatalytic performance of NiWO 4 . The cycling experiments showed that the Ag 3 PO 4 /NiWO 4 catalysts also had good reusability and stability. Several transformation pathways of TET were deduced by liquid chromatography-mass spectrometry analysis. The biotoxicity test confirmed that the sonocatalytic technique could degrade TET into less toxic substances . This study would provide a research basis for the design and development of novel sonocatalysts for the sonocatalytic removal of pharmaceutical wastewater. Synthesis of Ag 3 PO 4 /NiWO 4 composites and removal of tetracycline (TET) by AN-30/K 2 S 2 O 8 /US system • Composite Ag 3 PO 4 could improve the sonocatalytic performance of NiWO 4 . • The addition of persulfate led to a further increase in TET removal. • Ag 3 PO 4 / NiWO 4 composite had good reusability and stability. • Several transformation pathways of TET were inferred through liquid-mass analysis. • Biotoxicity tests confirmed that TET was degraded to less toxic substances.