The photoassisted oxidation of dilute aqueous solutions of 2-chlorophenol (2-CP) is investigated over a solid catalyst (TiO2) at laboratory level in an annular photocatalytic reactor. In order to characterise the reaction, different kinetic models are proposed, being related to the attack of the reagent by OH radicals. The model based on the competitive adsorption between oxygen and 2-chlorophenol does not lead to satisfactory results. For the other models it was assumed that oxygen adsorption occurs at different sites. The model with the adsorption isotherms of reagent and oxygen being proposed of a Langmuir type is the only one able to justify the observed dependence of the pollutant disappearance rate on dissolved 2-CP concentration, oxygen partial pressure and absorbed light intensity with adsorption parameters deduced from direct measurements.