TiO2-photocatalyzed degradation of tetracycline: kinetic study, adsorption isotherms, mineralization and toxicity reduction

The photocatalytic degradation of tetracycline has been investigated in aqueous solutions using TiO2 as photocatalyst. The experiments were carried out to investigate the factors influencing the photocatalytic degradation, such as the previous adsorption in the dark, initial concentration of TC solution, TiO2 amount, and the system toxicity during TC photodegradation. The experimental results show that adsorption is an important parameter controlling the apparent kinetic constant of the degradation. The photocatalytic degradation rate was favored by a high concentration of solution with respect to Langmuir-Hinshelwood model. The chemical oxygen demand values at the end of the treatment indicated that the percentage mineralization is a function of the initial TC concentration. The acute toxicity increased at the beginning of TC photo-oxidation, and treatment times of around 6h are generally required for the toxicity to be lower than in the original solution.