改性微管氮化碳的制备及光催化性能

Preparation of modified microtubule Carbon nitride and its photocatalytic performance

以三聚氰胺、固体亚磷酸H_(3)PO_(3)为原料,通过水热-煅烧法制备了不同质量比的磷掺杂且具有层状堆积结构的六方管状氮化碳(MTCN-x),x为固体亚磷酸与三聚氰胺的质量比.采用X射线衍射仪(XRD)、傅里叶变换红外光谱(FT-IR)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、比表面积分析仪(BET)、荧光光谱(PL)和紫外-可见漫反射光谱(UV-vis DRS)对最佳质量比X=1.2(MTCN-1.2)和不添加固体亚磷酸X=0(MTCN-0)催化剂形貌结构和光学性能进行了表征,结果表明,磷掺杂抑制了催化剂晶粒的生长,缩小了能带宽度,增加了可见光响应范围及可见光的利用率,有效的抑制了光生电子-空穴的复合,显著增强了光催化性能.通过光降解实验表明,MTCN-1.2在10min对抗生素环丙沙星(CIP)和四环素(TCL)的降解率分别为99.7%和97.8%,其反应速率常数分别是普通氮化碳(BCN)的10.5倍和6.8倍,表明改性的MTCN-1.2具有比MTCN-0、BCN更好的光催化降解性能.同时分别考察了溶液pH值、催化剂投加量、腐殖酸(HA)浓度等因素对光催化降解抗生素的影响,结果表明,CIP与TCL降解效果最佳的pH值分别为5和9.催化剂投加量的过高和HA浓度的升高,都会造成光催化效率的下降.自由基捕获实验证明,该催化体系降解过程中超氧自由基(·O^(2-))和空穴(h^(+))占主导作用.

Hexagonal microtubule carbon nitride(MTCN-x)with layered stacking structure was prepared by hydrothermal-calcination method by melamine and solid phosphite H_(3)PO_(3),where x represents the mass ratio of phosphite to melamine.Its structure,morphology,and photochemical properties were characterized using X-ray diffraction(XRD),fourier transform infrared spectroscopy(FT-IR),X-ray photoelectron spectroscopy(XPS),scanning electron microscope(SEM),transmission electron microscope(TEM),nitrogen adsorption-desorption isotherms(BET),fluorescence spectroscopy(PL)and ultraviolet-visible diffuse reflectance spectroscopy(UV-vis DRS).The results showed that the doping of phosphorus suppressed the growth of catalyst grains,reduced the energy gap,increased the response range of visible light and its utilization,inhibited the recombination of photoelectron and hole effectively and improved the photocatalytic performance significantly.The degradation rate of ciproloxacin(CIP)and tetracycline(TCL)for 10min was 99.7%and 97.8%,respectively.The degradation rate constants were 10.5 and 6.8 times of those by pure g-C_(3)N_(4)(BCN),respectively.The modified MTCN-1.2 exhibited better photocatalytic degradation performance than MTCN-0 and BCN.At the same time,the effects of pH,catalyst dosage,humic acid concentration on photocatalytic degradation of antibiotics were investigated,The results showed that the best pH values for CIP and TCL degradation were 5 and 9,respectively.The high dosage of catalyst and the increase of HA concentration would lead to the decrease of photocatalytic efficiency.The results of free radical capture experiment proved that superoxide radical(·O^(2-))and hole(h^(+))play a leading role in the catalytic system.