Photocatalytic activity of transparent porous glass supported TiO2

A porous glass tube with a composition of 96SiO2·4B2O3 (wt%) supported TiO2 shows high photooxidation activity due to its transparency and large surface area. The surface area of the porous glass tube supported TiO2 is 10,000 times larger than that of conventional materials. TiO2 crystals supported are anatase type. Transparency of the porous glass tube is very important. Herein, sol–gel and chemical vapor deposition (CVD) processes were employed as TiO2 supporting processes. CVD process is more effective. For instance, an aqueous methylene blue solution with 1 ppm concentration almost thoroughly decomposes at a contact time of 300 s using porous glass tube supported TiO2 prepared by CVD process under irradiating with 10 W low-pressure mercury lamp, on the other hand, opaque porous alumina tube supported TiO2 was only 25%. The smaller the pore size of the porous glass tube, the larger the transparency and the permeation resistance through porous glass tube. Hence, porous glass tube with ca. 40 nm pore diameter is suitable from the standpoint of a practical use.