Quantum efficiency of the photocatalytic conversion of 4-chlorophenol in a slurry reactor.

SATUF, M. L.; BRANDI, R. J.; CASSANO, A. E.; ALFANO, O. M.

Campinhas, Brasil

Otro; III Encuentro sobre Aplicaciones Ambientales de Procesos Oxidativos Avanzados (III EPOA).; 2005

UNICAMP

The knowledge of the quantum efficiency is fundamental in the study of photocatalytic reactions. It allows one to compare experimental results, to estimate the performance of a process and to find the optimal operating conditions. In the present work, we evaluate the quantum efficiency of the photocatalytic conversion of a model pollutant, 4-chlorophenol (4-CP), in an aqueous TiO2 suspension. 4-CP is a toxic, non biodegradable water pollutant that is involved in the synthesis of many pesticides, pharmaceuticals, and dyes. Experiments were carried out in a cylindrical reactor made of stainless steel and Teflon, with two borosilicate glass windows. It operates as a slurry reactor inside the loop of a batch recycling system. Radiation was supplied by two sets of UV, tubular lamps, placed at the sides of the reactor windows. Experimental runs were performed at different levels of TiO2 concentration (0.05-1.0 g L-1), incident radiation, and pH (2.5-11). Total organic carbon and chloride ions were monitored to assess the global mineralization process. The rate of photon absorption in the reactor is required to compute the quantum efficiency. It was obtained by solving the radiative transfer equation for the heterogeneous system, where radiation absorption and scattering take place. The effect of the different operating conditions on the 4-CP degradation rate and on the quantum efficiency of the process was evaluated.