Phenol is an organic compound used in the chemical industry for the manufacture of synthetic fibers, lubricating oils, adhesives, aspirin, mouthwashes and other drugs. Also is a recalcitrant compound and it has been detected in effluent from conventional water treatment plants. Therefore, phenol is used as a model compound in photocatalytic oxidation processes. In this paper, the results of the study of the oxidation of phenol solutions of high concentration in a reactor recirculation illuminated with UV light, TiO2, oxygen or ozone are reported. The results show that phenol is mineralized via formation of hydroquinone, benzoquinone, catechol and benzenetriol, which in turn are transformed to CO2. Although the degradation and mineralization reactions follow zero-order kinetic rate equation, injecting ozone instead of oxygen as an electron acceptor accelerates all the degradation reactions and favors the formation of catechol and benzoquinone. Illumination of the reactor system with the germicidal lamp favors the mineralization of phenol via formation of benzenetriol and increases degradation and mineralization reaction rate.