Double photoelectron-transfer mechanism in Ag AgCl/WO3/g-C3N4 photocatalyst with enhanced visible-light photocatalytic activity for trimethoprim degradation

Antibiotic contamination is increasing scrutinized recently. In this work, the AgAgCl/WO3/g-C3N4 (AWC) nanocomposites were successfully synthesized using a two-step process involving electrostatic self-assembly and in-situ deposition for trimethoprim (TMP) degradation. The as-prepared photocatalysts were investigated and characterized by XRD, FTIR, XPS, TGA, SEM, TEM, UV-vis, PL and EIS. The experimental results indicated that 99.9% of TMP (4 mg/L) was degraded within 60 min when the concentration of AWC was 0.5 g/L. Reactive species scavenging experiments and electron spin resonance (ESR) experiments illustrated that superoxide radical (center dot O-2(-)) and photogenerated holes (h(+)) were the main active species. The functional theory calculation and identification of intermediates via HPLC-MS revealed the possible degradation pathways of TMP. A double photoelectron-transfer mechanism in AWC photocatalyst was proposed. Five cycling photocatalytic tests and reactions under different solution matrix effects further supported that the AWC was a promising photocatalyst for the removal of TMP from the aquatic environment.