LABORATORY-SCALE PHOTODEGRADATION OF PHENOL IN AQUEOUS-SOLUTION BY PHOTOCATALYTIC MEMBRANES IMMOBILIZING TITANIUM-DIOXIDE

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(R) CPP/313 membranes containing immobilized 30 +/- 3 wt.% TiO2, with high or low pressure mercury are lamps (radiant power in the absorption ra nge, 145 and 8 W respectively). The initial rate of photodegradation w as 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 ad sorption constants K were evaluated. The rationalization of k and K va lues on the basis of their dependency on N, the apparent reaction olde r, the advantages of the membrane process with respect to the use of c olloidal suspensions of TiO2, also tested in comparable conditions, an d the kinetic significance of K,on the basis of no measurable dark ads orption onto the photocatalytic membranes, are discussed.