光催化降解刚果红时TiO_2失活机理及再生方法研究

Deactivated mechanism and regeneration methods of TiO_2 during photocatalytic Congo Red

以刚果红作为模拟污染物,研究了Ti O2光催化剂的使用活性、失活及再生问题.Ti O2循环使用1、2、3、4、6、8次后,刚果红脱色率依次为86.0%、83.4%、79.1%、65.1%、46.0%、18.8%;失活Ti O2采用250℃、350℃、450℃、550℃进行焙烧再生,并考察其再生效果;通过SEM、XRD、紫外-可见漫反射光谱(UV-vis DRS)、傅立叶红外光谱(FTIR)对失活前后及再生Ti O2进行表征,分别分析了光催化剂的表面形态、晶体结构、光学特性及表面物种变化.结果表明:实验条件下,光催化剂反复使用8次后就基本丧失活性;造成Ti O2失活的主要原因,一是Ti O2颗粒的团聚;二是刚果红降解的中间产物,如硫酸盐,硝酸盐及含碳化合物累积在Ti O2表面占据催化剂的活性位,并阻碍光子和底物到达催化剂表面,使其光催化活性逐渐降低;失活Ti O2经最适温度450℃再生后,光催化活性恢复至81.4%.

This study aimed to investigate the activity,deactivation and regeneration of the Ti O2 photocatalyst using Congo Red as the reactant. The results showed that the decolorization rate of Congo Red were 86. 0%,83. 4%,79. 1%,65. 1%,46. 0%,and 18. 8% respectively after 1,2,3,4,6,and 8 times recycling by Ti O2. Deactivated catalysts were then roasted and regenerated under 250 ℃,350 ℃,450 ℃ and 550 ℃ separately. SEM,XRD,UV-vis diffuse reflectance spectra and FTIR spectra were used afterwards to determine the changing properties of the photocatalysts,including surface morphology,crystal structure,optical property and surface materials. The results indicated that fresh Ti O2 was inactivated after 8-time usage under lab conditions. There were two main reasons for the deactivation of Ti O2,the strong agglomeration of Ti O2 particles and the one caused by the intermediate products of Congo Red,such as sulphate,nitrate and carbon-containing compound. These intermediate products accumulated in the surface of Ti O2,occupied the active sites,and obstructed photons and substrates from reaching the catalyst surface. Ti O2 thus lost its photocatalytic activity gradually.Finally,the photocatalytic ability of the deactivated Ti O2 restored to 81. 4% at the optimum temperature of 450 ℃.