The effect of operational parameters on the photocatalytic degradation of three textile azo dyes in aqueous TiO2 suspensions

Photocatalytic degradation of three commercial textile diazo dyes, called (C.I. Direct 80, 3BL, C.I. Direct Blue 160, RL and C.I. Reactive Yellow 2, X6G) were investigated using commercial TiO2 in aqueous solution under 400 W high-pressure mercury lamp irradiation. The effect of oxygen, temperature, catalyst loading, UV-light irradiation time, solution pH and inorganic ions such as SO42−, Cl− and NO3− were studied and optimized values were obtained. Results show that the employment of efficient photocatalyst and selection of optimal operational parameters may lead to complete decolorization and to substantial decrease of the chemical oxygen demand (COD) of dye solutions.