Visible-NIR responsive Ag2O couple with MIL-53(Fe) on CS as S-scheme photocatalyst for efficient simultaneous removal of Cr(VI) and norfloxacin

This study addresses the urgent need to develop easily recoverable and efficient photocatalysts for the treatment of compound polluted wastewater. Herein, S-scheme MIL-53(Fe)/Ag2O heterojunctions on a charcoal sponge (CS) were constructed by solvothermal-chemical precipitation method, exhibiting high separation efficiency of photoinduced carriers and reduction–oxidation (REDOX) capacity. The synthesized CS/MIL-53(Fe)/Ag2O was characterized by SEM, TEM, XRD, and XPS, confirming the successful deposition and uniform distribution of MIL-53(Fe) and Ag2O nanoparticles on CS. Moreover, CS/MIL-53(Fe)/Ag2O exhibits an extensive light absorption range from visible to near-infrared (NIR) light, thereby significantly enhancing its photocatalytic activity. In present of H2O2, CS/MIL-53(Fe)/Ag2O demonstrated outstanding removal efficacy of norfloxacin (NFX, 96 %, pH=7) or Cr(VI) (100 %, pH=3) through the photocatalytic-Fenton reaction, which was notably superior to that of CS/MIL-53(Fe) (50.4 % NFX, 56.8 % Cr(VI)) and CS/Ag2O (44.3 % NFX, 38 % Cr(VI)). Importantly, when CS/MIL-53(Fe)/Ag2O was used to treat combined polluted wastewater containing both Cr(VI) and NFX, the removal efficiency of Cr(VI) and NFX showed a significant synergistic effect. Additionally, inhibition zone tests demonstrated that the toxicity of NFX intermediates to E. coli gradually decreased as the degradation of NFX progressed. Furthermore, density functional theory (DFT) calculation and relevant characterization were conducted to elucidate the reaction mechanism of S-scheme heterojunctions, highlighting the enhanced separation rate of photo-induced carriers and REDOX capability. This work not only offers a promising approach for construction of MOF-based S-scheme semiconductor heterojunctions, but also presents promising prospects for the purification of compound polluted wastewater containing norfloxacin and Cr(VI).