Immobilzed TiO_2 photocatalyst duriong long-term use:decrease of its activity

摘要

When TiO_2 is immobilized on organic fibres,pumice stone or polymer film,the photocatalytic efficiency decreases slowly durign logn-term use.The efficiency of immobilized photocatalysts were tested on 500 ml of a 5X10~(-5)M solution of acid orgnae-7 (a classical azo dye)before and after treatment of 10~(-3) M solutionof acid orgnae-7 durign 4 weeks.it was observed that the efficiency was reduced approxmately four,five and 10 times with polymer flm containing TiO_2,TiO_2 on organic fibres and TiO_2 on pumice stone,respectively,after 4 weeks of use.Volumes treated were 40,45 and 601,respecitvely.nevertheless,the decomposition rate staays a little higher with TiO_2 on pumie stone than with the two other catalysts tested.The photocatalytic activity of immobilized TiO_2 was significantly reduced also during treated with wastewaters.For immobilized photocatalysts used,the decrease of activity is considered to be caused by the elimination of some particles from the catalyst surface during use and also by fouling of catalyst surface by the formation of by-products during the course of degradation process.