Z型g-C_(3)N_(4)/Bi_(2)WO_(6)吸附-光催化降解左氧氟沙星:动力学、机制与降解路径

Z-scheme g-C_(3)N_(4)/Bi_(2)WO_(6) adsorption-photocatalytic degradation levofloxacin:Kinetics,mechanisms and degradation pathways

通过水热法制备了g-C_(3)N_(4)掺杂量为13%的g-C_(3)N_(4)/Bi_(2)WO_(6)复合光催化剂,并使用SEM、XRD、XPS、BET、UV-Vis DRS和电化学工作站等对其形貌、结构和光电化学性能进行表征.分析结果表明,g-C_(3)N_(4)均匀负载于Bi_(2)WO_(6)表面,形成了稳定的异质结结构.相比于g-C_(3)N_(4)和Bi_(2)WO_(6),g-C_(3)N_(4)/Bi_(2)WO_(6)具有更大的比表面积,在40 min的暗反应阶段对水中左氧氟沙星(LEV)的吸附效率为43.7%.g-C_(3)N_(4)/Bi_(2)WO_(6)对LEV的吸附行为符合准二级动力学模型,其初始吸附阶段颗粒内扩散是限速步骤.g-C_(3)N_(4)/Bi_(2)WO_(6)在120 min的可见光反应阶段对LEV的去除效率为85.8%,其光催化降解过程符合准一级动力学模型.g-C_(3)N_(4)/Bi_(2)WO_(6)吸附-光催化降解LEV性能增强的原因主要是增大的比表面积以及Z型异质结的形成拓展了催化剂的光谱响应范围,提高了光生电子-空穴的分离效率.h+和·O_(2)^(-)在g-C_(3)N_(4)/Bi_(2)WO_(6)光催化降解LEV过程中发挥主要作用,且经过光催化降解后LEV的急性毒性和致突变性均有所下降.

The g-C_(3)N_(4)/Bi_(2)WO_(6) composite photocatalyst with g-C_(3)N_(4) doping content of 13%was prepared by hydrothermal method,and its morphology,structure and photoelectrochemical properties were characterized by SEM,XRD,XPS,BET,UV-Vis DRS and electrochemical workstation.The results showed that g-C_(3)N_(4) was uniformly loaded on the surface of Bi_(2)WO_(6),forming a stable heterojunction structure.Compared with g-C_(3)N_(4)and Bi_(2)WO_(6),g-C_(3)N_(4)/Bi_(2)WO_(6) exhibited a larger specific surface area,and the adsorption efficiency of levofloxacin(LEV)in water was 43.7%after the dark reaction for 40 min.The adsorption behavior of g-C_(3)N_(4)/Bi_(2)WO_(6) to LEV conformed to the quasi-second-order kinetic model,and the intra-particle diffusion was the rate-limiting step in the initial adsorption stage.The removal efficiency of LEV by g-C_(3)N_(4)/Bi_(2)WO_(6) was 85.8%after visible-light reaction for 120 min,and the degradation process was in accordance with the quasi-first-order kinetic model.The enhanced performance for adsorptionphotocatalytic degradation of LEV was mainly due to the increased specific surface area and the formation of Z-scheme heterojunction,which extended the spectral response range of the photocatalyst and improved the separation efficiency of photogenerated electron-hole.The h+and•O_(2)-played the major role during the photocatalytic degradation of LEV by g-C_(3)N_(4)/Bi_(2)WO_(6).The acute toxicity and mutagenicity of LEV obviously declined after photocatalytic degradation by g-C_(3)N_(4)/Bi_(2)WO_(6).