Factors influencing the photocatalytic degradation of sulfonylurea herbicides by TiO2 aqueous suspension

The photocatalytic degradations of six sulfonylurea herbicides have been investigated in aqueous solutions containing TiO2 suspensions as photocatalyst, in order to assess influence of various parameters, such as adsorption, initial concentration and photon flux on the photocatalytic process. Results show that adsorption is an important parameter controlling the apparent kinetic order of the degradation (either one in the case of associative adsorption or a half in the case of dissociative adsorption). In respect to the Langmuir–Hinshelwood model, the photocatalytic reaction is favoured by a high concentration. A higher efficiency is observed under the lower photon fluxes, the limiting factor being the electron–hole pair recombinations.