Design of S-O "highway" at Z-scheme heterojunction interface for efficient degradation treatment of lomefloxacin and actual pharmaceutical wastewater.

The charge transfer path and the resistance generated at the interface were crucial factors affecting the carrier separation efficiency in heterojunction photocatalysts. Herein, a novel Z-scheme Bi2Sn2O7/MoS2 heterojunction with covalent S-O interface was successfully synthesized by calcination and hydrothermal methods. Experimental evidence demonstrated that the prepared Bi2Sn2O7/MoS2 composite exhibited high photocatalytic efficiency for the degradation of lomefloxacin, and the antibacterial effects of lomefloxacin and its degradation products decreased during the process. An interfacial S-O bond-modified Z-scheme mechanism was proposed and investigated via systematic experimental characterization and theoretical calculations. The S-O bonds acted as a "highway" that, in conjunction with the Z-type charge transfer pathway, reduced interfacial resistance and enhanced the separation and transport efficiency of photoexcited charge carriers. Additionally, the decomposition pathway of lomefloxacin was explored using mass spectrometry and DFT techniques, and a toxicity analysis of the degradation intermediates was conducted via toxicological calculations. Notably, with the optimal Bi2Sn2O7/MoS2 sample, the COD of actual pharmaceutical wastewater decreased from 8327 mg/L to 1899 mg/L, achieving a removal rate of 77.2 %. The rapid transfer of charge transfer rates at the interfaces of heterojunction materials promoted the improvement of photocatalytic efficiency, thereby offering certain guidance for the practical treatment of antibiotic pollution.