Photocatalytic degradation of Crystal Violet (C.I. Basic Violet 3) on silver ion doped TiO2

The photocatalytic degradation of Crystal Violet, a triphenyl methane dye (also known as Basic Violet 3) in aqueous solutions was investigated with Ag+ doped TiO2 under UV and simulated solar light. The dye degradation using untreated TiO2 and Ag+ doped TiO2 was compared. It was found that Ag+ doped TiO2 is slightly more efficient. Ag+ doping was done also to separate the photocatalyst easily from the treated effluent just by settling or centrifuging and decantation thus avoiding the costly filtration process. Measurements of COD were done at regular intervals to have an idea of mineralization of the dye. The effects of pH, catalyst loading, substrate concentration, interfering substances such as Cl−, NO3−, SO42−, HPO42−, Ca2+, Fe3+ and humic acid on dye degradation were investigated. The degradation of the dye (20 ppm) was >97% on UV illumination for 105 min with TiO2 and >99% with Ag+ doped TiO2. The dye (20 ppm) was found to degrade about 88% after illumination for 10 h by a simulated solar light source in the presence of Ag+ doped TiO2. The degradation kinetics fit well to Langmuir-Hinshelwood rate law.