Ce/TiO2/g-C3N4异质结的制备及光催化降解PFOA反应机制  

Fabrication of a Ce/TiO2/g-C3N4 heterojunction and the photocatalytic decomposition mechanism of perfluorooctanoic acid with visible light

作　　者：唐力[1] 夏静芬[1] 杨国靖[1,2] 胡煜钗 常岩航 张妮 赵博 谢周云 王冬波[2] TANG Li;XIA Jingfen;YANG Guojing;HU Yuchai;CHANG Yanhang;ZHANG Ni;ZHAO Bo;XIEZhouyun;WANG Dongbo(College of Biological and Environmental Sciences,Zhejiang Wanli University,Ningbo 315100;College of Environmental Science and Engineering,Hunan University,Changsha 410082)

机构地区：[1]浙江万里学院生物与环境学院,宁波315100 [2]湖南大学环境科学与工程学院,长沙410082

出　　处：《环境科学学报》2020年第3期950-958,共9页Acta Scientiae Circumstantiae

基　　金：国家自然科学基金(No.51408551);浙江省基础公益研究计划项目(No.LGF19E090004,2017C33023);浙江省高校访问工程师校企合作项目(No.FG2018001);浙江省重中之重学科开放基金(No.KF2017006);宁波市“环境科学与工程”一流学科资助项目

摘　　要：采用溶胶凝胶-超声混合法制备了铈/二氧化钛/石墨相氮化碳(Ce/TiO2/g-C3N4)异质结催化剂,通过透射电子显微镜(TEM)、X-射线粉末衍射仪(XRD)、傅里叶变换红外光谱仪(FTIR)和紫外-可见分光光度计(UV-Vis)等表征了复合材料的结构、晶相、活性基团和光吸收性能,并考察了可见光下该催化剂对模拟全氟辛酸(PFOA)废水的降解效果.结果表明,Ce/TiO2/g-C3N4分散性好,粒径小于20 nm,金属Ce的掺入及TiO2/g-C3N4异质结的生成,有效抑制了光生电子和空穴对的复合,使复合光催化剂禁带宽度减小,光吸收范围增大,光催化性能得到明显提升.在pH值为2,PFOA浓度为4 mg·L^-1,催化剂投加量为1 g·L^-1的条件下,可见光照射180 min后,可降解94.4%的PFOA,脱氟率为38.6%.降解过程符合准一级反应动力学,速率常数为0.522 h^-1.通过HPLC-MS分析降解产物,同时结合氟元素物料平衡的计算结果,认为降解机制主要是以阴离子形式存在的PFOA吸附至表面带有大量正电荷的催化剂表面后,在光生空穴和活性自由基的作用下,以自由基机理逐步脱去CF2生成短链的PFCAs,同时生成氟离子.A novel Ce/TiO2/g-C3N4 heterojunction has been successfully fabricated using a sol-gel method combined with ultrasonic mixing.The photocatalysts were characterized using TEM,XRD,FTIR and UV-Vis spectroscopy.The photocatalytic activity was evaluated using the photocatalytic degradation of perfluorooctanoic acid(PFOA)under the illumination of a fluorescent lamp.The results reveal that the Ce/TiO2/g-C3N4 heterojunction had good dispersion with particle sizes<20 nm.The incorporation of Ce ions and the formation of heterojunction inhibited the recombination of photo-generated electron-hole pairs,reduced the band gap and expanded the absorption region to visible light.The composite photocatalysts show excellent photocatalytic activity.The degradation of PFOA followed pseudo-first order reaction kinetics and the rate constant was 0.522 h^-1.Using 1 g·L^-1 of this catalyst with an initial PFOA concentration of 4 mg·L^-1 at pH 2.0,the degradation rate of PFOA over 180 min could reached 94.4%,and the defluorination rate was 38.6%.The degradation products were separated and analyzed using HPLC-MS,and combined with the calculation results obtained for the fluorine element balance.The degradation mechanism involved the adsorption of PFOA anions onto the surface of the composite,which displayed a large amount of positive charge,and under the action of photogenerated holes and active free radicals,CF2 was gradually removed to form short-chain PCFAs and fluoride ions via a free radical mechanism.

关 键 词：光催化 全氟辛酸 二氧化钛 铈掺杂 氮化碳 

分 类 号：X703[环境科学与工程—环境工程]