Spectral and Sorption Characteristics of Acid Orange II and Methylene Blue Dyes on TiO2 Photocatalyst

In this work, the characteristic spectral and sorption characteristics of Acid Orange II and Methylene Blue (MB) dyes was investigated. TiO₂ (P25) commercial catalyst was used as a semi-conductor photocatalyst. The work investigated the following; (i) amount of Acid Orange II dye adsorbed on TiO₂, (ii) the wavelength at which TiO₂ catalyst, Acid Orange II and Methylene Blue exhibit maximum absorbance (iii) determine the absorbance of Acid Orange II & Methylene Blue dyes to calibrate the spectrophotometer and compute the molar extinction coefficient for each dye. Several concentrations of the individual dyes were used for the experiments. Adsorption experiments were done in a UV panel, consisting of a rectangular frame, covered with a suitable cloth to shield natural light from the frame and a magnetic shaker. UV lamps emitting light at λ = 365 nm were used as a source of irradiation. To measure the spectral and sorption characteristics of the dyes, a UV/Vis spectrophotometer was used. From the absorbance measured, equilibrium concentrations and the amount of dye adsorbed on to n-TiO₂ (mol.g^-1) established. Adsorption significantly influences the degradation of dyes under UV light irradiation. The amount of dye adsorbed on the surface of TiO₂ catalyst was experimentally measured. This work concluded that the amount of Acid Orange II adsorbed on TiO₂ catalyst increased with higher initial dye concentrations. However, at initial dye concentration greater than 1×10^-4 mol.L^-1 the adsorption decreases significantly.