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

Antibiotic contamination is increasing scrutinized recently. In this work, the Ag-AgCl/WO/g-CN (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 (•O) 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.