Photocatalytic Degradation Of Dual Dyes By Titanium Dioxide Nano-scale Particles By Visible Light Irradiation

In this article, the photocatalystic degradation of Alizarin Red and Indigo Carmine-mixed dye solution was studied by visible light irradiation with P-25 nanosized titanium dioxide powders as photocatalyst. Samples were characterized by many analytic methods so that degradation condition was determined, degradation course was analyzed, intermediate products were deduced and the degradation rate of Alizarin Red and Indigo Carmine-mixed dye solution was got finally. In experiment, solvent of dye solution was quadratic distilled water. The photocatalytic process was carried out in homemade camera obscura. The illuminant was tungsten lamp, and light filter was used to filter ultraviolet radiation of it.The suitable conditions to degrade the dye-mixed solution by ultra violet (UV-vis) spectrum were that at room temperature, the using amount of P-25 was 2.0g/L and the pH of dye-mixed solution was lower than 6. In such conditions, the photocatalystic tests of Alizarin Red,Indigo Carmine and dye-mixed solution were carried out respectively and the UV-vis spectrum and degraded curves of these three solution were achieved. By analysis of these spectrums and curves, it had been determined and discovered that> C= O was ruptured and reset and the presence of AR accelerated the degradation of IC but inhibited that of itself which was named as synergy. After 8 hours reaction, in the reaction of single AR and single IC, the degradation rate of AR was 90.11% and that of IC was 84.2%, while in the reaction of dye-mixed solution, the degradation rate of AR was 86.1% and IC was 87.38%. The intermediates were ascertained by analysis of by fluorescence spectroscopy and nuclear magnetic resonance spectroscopy:there were new fluorescent matter by fluorescence spectroscopy; the conjugate degree was reduced and new intermediates with benzene circle emerged by NMR.There were two points had been used to the explanation of synergy:one was the absorption of dye on the surface of P-25; another was the effect of·H in degradation process. The study of adsorption kinetics showed that after mixed, the absorption amount of AR decreased which made the degradation rate of AR become low. The study of degradation process showed that·H produced in the beginning of reaction mainly reacted with IC, which impeded the degradation of AR; as the grow in account of·H, the amino reaction of IC was accelerated with which the chromophore was reorganized made the degradation rate raised.