为了探究分子印迹光催化剂的选择性降解行为,采用水热法,以钛酸丁酯为钛源、尿素为氮源、罗丹明B为模板分子,制备了分子印迹掺氮TiO2。FT-IR、XRD、低温N2吸附-脱附技术、UV-Vis DRS等表征结果显示,样品均为锐钛矿相;分子印迹一定程度地改善了光催化剂的孔隙结构,增大了孔容体积和比表面积,并且增强了可见光区的光吸收强度。可见光下催化剂对三苯甲烷类污染物罗丹明B、罗丹明6G和结晶紫的光降解表观速率常数(kap)分别提高1.97、1.21和1.26倍,说明分子印迹不仅提高了光催化剂的可见光活性,而且对目标污染物表现出良好的选择性。结合等温吸附实验,以Langmuir-Hinshelwood动力学积分模型探究吸附平衡常数(Ka)和降解反应速率常数(kr)对kap的贡献,发现罗丹明6G只与降解反应能力的提高有关,结晶紫同时归功于吸附和降解反应能力,罗丹明B则源于更为突出的吸附能力,该结果是由于模板分子印迹产生的特异识别位点所致。
In order to investigate selective photocatalytic activity,molecular imprinted N-doped TiO2 powders was synthesized by hydrothermal method using butyl titanate as the titanium source,urea as the nitrogen source and salicylic acid as the template molecule.The samples were characterized by FT-IR,XRD,N2 adsorption-desorption and UV-Vis diffuse reflectance spectrophotometer.The results indicated that all titania were anatase,the well-developed pore structure caused by molecular imprinted technique,which induced enlarged pore volume and specific surface area.The strengthened light absorption in the visible light area was also caused by molecular imprinting.In the visible light,the degradation apparent speed constant kap enhanced 1.97,1.21 and 1.26 times for rhodamine B,rhodamine 6G and crystal violet,respectively,which indicated not only the visible-light activity enlarged,but also the better selective photocatalytic activity for target pollutant by molecular imprinting.Combined with the isotherm adsorption experiment,the Langmuir-Hinshelwood kinetic integration model was used to investigate the contribution of the adsorption equilibrium constant Ka and the degradation reaction rate constant kr to kap.The results showed that rhodamine 6G was only related to the improvement of degradation reaction ability,crystal violet was attributed to both ability of adsorption and degradation reaction,and rhodamine B was derived more from the prominent adsorption capacity,which caused by the specific recognition site generated by template molecular imprinting.
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