Photoctalytic efficiency of silver doped TiO2-PC500 for dyes removal from water under UV and solar radiations: Comparative study

Abstract

Silver doped TiO2-Millenium-PC500 (Ag/TiO2-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/TiO2-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, H2O2) was studied. Ag/TiO2-PC500 exhibits better performance under UV and solar irradiations for the discoloration of CR as compared to TiO2-PC500. In the presence of Ag/ TiO2-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/TiO2-PC500 as compared to TiO2-PC500 albeit not complete (R ≤ 63.9%). Addition of H2O2 (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/TiO2-PC500 (84.87 m2 g-1) as compared to TiO2-PC500 (287.09 m2 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.