Solar photocatalytic decolorization of dyes in solution with TiO_2 film

摘要

Application of TiO_2 film to solar photocatalysis of organic dyes,including Methylene Blue (MB) (lambda_(max),660 nm),RR195 (lambda_(max),540 nm) and RY145 (gamma_(max),420 nm),was investigated.It was found that after 6-h solar irradiation,the extent of color degradation of dyes using solar photocatalytic system without TiO_2 film was quite limited.The color removal percentage for MB,RR195,and RY145 was found to be 23.3,-9.3,and -20.7%,respectively,resulting from competitions between the photosensitizing reaction and formation of colored intermediates during solar irradiation.However,as TiO_2 film was applied,the color degradation capability of solar photocatalytic system was significantly improved,in spite of the fact that only approximately 7% of solar irradiation belongs to the UV region.The color removal percentage for MB,RR195,and RY145 was up to 93.6%,85.3%,and 71.1%,respectively,after 6-h irradiation.We believed that in such a solar photocatalytic system immobilized with TiO_2 film,both the maximum absorbance wavelength of the dye and the adsorbability of the dye on TiO_2 film played significant roles on the rate and efficiency of color removal of the dye solutions.Moreover,the possible reaction mechanism was proposed.The solar photocatalytic process with immobilized TiO_2 film was found to follow the pseudo-first order reaction kinetics.Color removal rate of MB was almost twice of that of RY145.Accordingly,the photocatalytic degradation process using solar light as an irradiation source,and immobilized TiO_2 as a photocatalyst,showed potential application for the decolorization of wastewater.