Photocatalytic degradation of Asucryl Red (GRL) in aqueous medium on heat-treated TiO2 powder – effect of analytical parameters and kinetic modeling

Water loaded with Asucryl Red (GRL) dye is frequently discharged into natural receiving environments at relatively high concentrations, which can have serious consequences on the ecosystem if adequate treatment operations are not undertaken. The adsorption and photocatalytic degradation of GRL, selected as a model organic pollutant, has been investigated in aqueous suspension of TiO 2 powder as photocatalyst under UV-lamp irradiation. The experiments were carried out to investigate the factors influencing the photocatalytic degradation, initial GRL concentration (5–25 mg/L), TiO 2 mass (0.2–1.2 g), pH 2–10 and NaCl ionic strength (0.2–1.6 g/L). The experimental results showed that the efficiency of the photocatalytic process strongly depends on the pH while the initial rate of the photocatalytic reaction is proportional to the catalyst dose, but above a certain value, it becomes constant and sometimes decreases. The adsorption is an important parameter controlling the apparent kinetic constant of the degradation. The photocatalytic degradation rate was favored for high concentrations of the solution in agreement with the Langmuir–Hinshelwood (L–H) model. The degradation rate was found to be pH and temperature-dependent with a high degradation rate at high temperatures. The TiO 2 photocatalyst has a better activity for GRL degradation, compared to the various commercial catalysts already available in the literature.