Intermediate inhibition in the heterogeneous UV-catalysis using a TiO2 suspension system

Langmuir-Hinshelwood (L-H) kinetic expression was used to develop a basic m athematical model, which could describe the inhibition of intermediates in the photocatalysis of 2-chlorophenol (2-CP) in a suspended TiO2 system. Res ults showed that the photocatalytic oxidation of 2-chlorophenol followed th e L-H type behavior and the reaction by-products displayed an inhibiting ef fect on the degradation rate. The inhibition was estimated by comparing to observed and estimated half-lives. The higher the initial concentration of 2-chlorophenol, the higher the inhibition of photocatalytic reaction. The L -H kinetic has been modified slightly in this study to rationalize the cont rast of inhibited behavior and to improve in favor of a surface reaction. T he concentrations of 2-chlorophenol were investigated ranging from 7.78 x 1 0(-5) to 7.78 x 10(-4) mol l(-1). The degradation of 2-chlorophenol in this reaction condition approximates a first-order kinetics to near-complete de gradation. Calculated kinetic profiles are in an excellent agreement with t he experimental observation. The results of the theoretical analysis can be used to estimate reaction rates in different initial concentrations of tar get compound. (C) 2001 Elsevier Science Ltd. All rights reserved.