介孔氮化碳光催化降解诺氟沙星的动力学机制

hotocatalytic degradation kinetics and mechanism of norfloxacin using mesoporous g-C_3N_4 under visible-light irradiation

采用一种简单高效的制备方法,利用Si O2为模板制备出具有更高催化活性的介孔氮化碳材料(mpg-C3N4),并通过透视电子显微镜(TEM)、X射线衍射(XRD)、氮气吸脱附测试(BET)、傅里叶变换红外光谱(FT-IR)、光电子能谱(XPS)对mpg-C3N4的形貌、组成结构进行表征.结果显示,mpg-C3N4表面存在大量直径约12nm的孔状结构,与g-C3N4相比,比表面积大幅度增大,并因此提供了更多的活性位点从而提高其光催化活性.使用紫外可见漫反射光谱(UV-vis DRS)和荧光光谱(PL)对其光电化学性能进行测试.结果表明介孔材料的引入使得氮化碳的吸收光谱发生红移,并降低了光生电子-空穴对复合率,从而提高对可见光利用效率.通过对诺氟沙星(NOR)的降解与吸附实验研究表明,NOR的光催化降解过程符合一级动力学和Langmuir-Hinshelwood动力学模型,而mpg-C3N4对NOR的吸附符合二级动力学,表明NOR的光催化降解主要发生在催化材料的表面且以化学吸附为主.吸附实验表明mpg-C3N4在30min内可以吸附56.78%的NOR,降解实验显示,光解1.5h后,超过90%的NOR可被降解.相比体相g-C3N4,mpg-C3N4表现出良好的吸附性能和光催化性能.pH值影响实验表明pH值约为7.41时达到最佳降解效果,主要归因于药物形态与材料表面电荷作用.淬灭实验表明O2·-和h+是降解体系中的主要活性物质.

Abstract:In this study,the photocatalytic degradation kinetics and mechanism of norfloxacin(NOR)were investigated in a sunlight-driven photocatalyst mesoporous g-C3N4(mpg-C3N4).The morphology and structure of mpg-C3N4 were studied by transmission electron microscope(TEM),X-ray diffraction(XRD),and nitrogen adsorption-desorption isotherms(BET).The results showed that mpg-C3N4 exhibited the mesoporous structure with the pore size of ca.12nm,which could provide more active site for photoreaction.Ultraviolet-visible DRS spectrum(UV-vis)showed that mpg-C3N4 exhibits high optical absorption capacity for visible light.Fluorescence pectrophotometer(PL)spectrum revealed that the mesoporous structure might restrain the recombination rate of photogenerated electrons and holes.The degradation of NOR followed the Langmuir-Hinshelwood(L-H)kinetics model,and the adsorption of NOR followed the second order kinetics,indicating that surface reactions and chemisorptions played the important roles during the photocatalysis process.mpg-C3N4 showed an enhanced reaction and adsorption for NOR degradation than g-C3N4.Almost 56.78%of NOR can be absorbed by mpg-C3N4 within 30 min absorption.Under 1.5h of simulated sunlight irradiation,around 90%of NOR can be decomposed.Effect of pH on photocatalytic degradation of NOR showed that mpg-C3N4 posed an optimal photocatalytic performance under neutral condition.Further study of reactive species(RSs)by RSs scavenging experiment showed that superoxide anion radical(O2·-)and photohole(h+)were responsible for the major degradation of NOR.