Photoctalytic Efficiency of Silver Doped TiO₂-PC500 for Dyes Removal from Water under UV and Solar Radiations: Comparative Study

Abstract

Silver doped TiO 2 -Millenium-PC500 (Ag/TiO 2 -PC500) was prepared by wet chemical reduction method and characterized by X-ray diffraction, scanning electron microscopy, X-ray fluorescence, fourier transformed infrared and Brunauer-Emmett-Teller techniques. Ultraviolet (UV) and solar photocatalytic efficiency of Ag/TiO 2 -PC500 for the removal of congo red (CR) and crystal violet (CV) from water was investigated. The influence of several operational parameters (photocatalyst, dye concentrations, pH, H 2 O 2 ) was studied. Ag/TiO 2 -PC500 exhibits better performance under UV and solar irradiations for the discoloration of CR as compared to TiO 2 -PC500. In the presence of Ag/ TiO 2 -PC500, at free pH, CR was completely discolored within 15 min under UV (k = 0.064 min −1 ) and solar irradiation (k = 0.207 min −1 ). The discoloration rates of CV markedly improved under UV and solar irradiation, with Ag/TiO 2 -PC500 as compared to TiO 2 -PC500 albeit not complete (R ≤ 63.9%). Addition of H 2 O 2 (0.01 mol L −1 ) improved significantly the discoloration of CV (R ≤ 99.3%) with both photocatalysts whatever the light source. The better performance of Ag/TiO 2 -PC500 (84.87 m 2 g −1 ) as compared to TiO 2 -PC500 (287.09 m 2 g −1 ) confirms the positive contribution of silver during the photocatalytic process through its ability to absorb UV and solar light and slow the electron-hole (e − /h + ) recombination. The COD measurements show moderate mineralization rates for both dyes independently of the irradiation source.