活性炭负载TiO_2光催化剂的制备及光催化性能的研究

Preparation of activated carbon-supported TiO_2 and characterization of its photocatalytic property

采用溶胶-凝胶法制备了TiO_2/活性炭(TO_2/AC)复合光催化剂,并考察载体粒度、浸渍时间、煅烧温度对其光催化降解腐殖酸性能的影响,确定了最佳条件。利用XRD(X射线衍射)、氮吸附等手段对复合催化剂的物理特性进行了表征;探讨了催化剂投加量、重复使用次数等因素对光催化降解腐殖酸反应的影响。结果表明:试验制备的TiO_2/AC复合催化剂具有大的比表面积,纳米TiO_2晶粒为锐钛矿型且尺寸较小;催化剂投加量为2g/L、反应3 h,可去除腐殖酸溶液的UV_(254)值96%,具有比简单悬浮体系更高的光催化性能。

The present study is aimed at introducing the immobilized catalyst activated carbon supported Tie2 （TiO2/AC） initiated by us with a sol-gel method along with our characterization of its photocatalytic behavior by using humic acid （HA）. For our research purpose, we have done photocatalytlc experiments in a quartz glass reactor. The aqueous suspensions are magnetically stirred under the irradiation of a high pressure mercury lamp with full emission intensity at the wavelength of 365 nm, In order to have a better understanding of the properties and characteristic features of the catalyst, we have done analysis of the ultraviolet absorbency at the wavelength of 254 nm （UV254） of the solution, as well as the total organic carbon （TOC） content. So far, we have studied the following sub-topics on the catalyst： （1） As to the preparation of TiO2/AC, we have studied the TiO2 load, surface area, and Tie2 properties, concentration of Tie2 colloid, dipping time, calcination temperature and coating times; X-ray diffraction （XRD） tests for crystalline forms and particle size of Tie2, N2 adsorption-desorption analysis for BET surface areas and aperture distributions; （2） Our research goes on the degradation of HA under the photocatalytic action of TiO2/AC ： the direct photolysis of HA and the adsorption of HA on TiO2/AC in dark ; the effect of concentrations of TiO2/AC ; the activity of reused TiO2/AC ; the comparison of suspended and supported systems; TOC and SUVA （UV254/DOC） changes during the photocatalytic degradation of HA. As a result, the present study indicates that the supported TiO2 nanoparticle size has been worked out by using Scherrer formula. It is 11.7 nm, which means it is highly active photo-catalytically. And in the process of the photocatalytic degradation of HA, positive cooperativity between TiO2 and its supporter would be resulted from the synergistic reaction to the activated carbon, which helps to effectively enhance the degradation rate of HA. By the way, the supported TiO2/ AC can give 96% removal of UV254, with remarkable decrease of TOC and SUVA in 3 h irradiation time under the 2 g/L concentration of TiO2/AC. Thus, it can be concluded that the HA molecules arc decomposed into smaller and simpler molecules and then mineralized in the photocatalytic reaction.