Degradation of Hazardous Dyes in Wastewater using Nanometer Mixed Crystal TiO2 Powders under Visible Light Irradiation

Abstract

The partial phase transformation of nanometer TiO2 powder from anatase phase to rutile phase was realized by heat-treatment and a new TiO2 photocatalyst which could be excited by visible light was obtained. The heat-treated TiO2 powder at different stage of transition crystal was characterized and monitored by XRD, TEM, FT-IR and UV–vis DRS methods. The test of photocatalytic activity of the heat-treated TiO2 powder was carried out by the photocatalytic degradation of rhodamine B and acid orange II dyes, respectively, in aqueous solution under visible light irradiation. The results indicate that the nanometer TiO2 photocatalyst heat-treated at 500°C for 60 min shows the highest photocatalytic activity, that is, it can effectively degrade the rhodamine B and acid orange II under visible light irradiation. The remarkable improvement of photocatalytic activity of heat-treated TiO2 powder at 500°C for 60 min was mainly illustrated by the formation of special interphase between rutile and anatase phases, which not only restrains the recombination of photogenerated electrons and holes, but also reduces the adsorbability of nanometer anatase TiO2 powder properly for various dyes. Additionally, the effects of dye-assisting chemicals such as Na2CO3 and NaCl on the photocatalytic degradation were also studied.