Laboratory-scale photodegradation of phenol in aqueous solution by photocatalytic membranes immobilizing titanium dioxides

The TiO2-mediated photodegradation of phenol was studied at 298 ± 2 or 308 ± 2 K (with the ratio between the hydrogen peroxide added and the stoichiometric amount (N) in the range 0–10), using PHOTOPERM® CPPI313 membranes containing immobilized 30 ± 3 wt.% TiO 2, with high or low pressure mercury arc lamps (radiant power in the absorption range, 145 and 8 W respectively). The initial rate of photodegradation was studied as a function of the initial concentration of substrate (1.0x10−5−0.12 M) using the linearized form of the Langmuir-Hinshelwood equation, from which the rate constants k and apparent equilibrium adsorption constants K were evaluated. The rationalization of k and K values on the basis of their dependency on N, the apparent reaction order, the advantages of the membrane process with respect to the use of colloidal suspensions of TiO2, also tested in comparable conditions, and the kinetic significance of K, on the basis of no measurable dark adsorption onto the photocatalytic membranes, are discussed.