Kinetics and adsorption comparative study on the photocatalytic degradation of o-, m- and p-cresol

The kinetics and adsorption aspects of the photocatalytic degradation of three cresolic isomers were studied in aqueous suspension containing TiO2 (Degussa P-25). The Langmuir–Hinshelwood model (L–H) was applied to the kinetic results. Degradation kinetic constants were similar for the three compounds (o-cresol, 0.0188 ppm/s; m-cresol, 0.0166 ppm/s; p-cresol, 0.0182 ppm/s). However, the adsorption pattern of p-cresol is different from those of the other organics. Results from adsorption experiments carried out in darkness were modelized by using Langmuir and Freundlich isotherms. In general, the studied cresols showed little adsorption on TiO2 surface. The adsorbed species on the catalyst surface were identified by FITR spectroscopy. According to these results, only p-cresol forms cresolates. An important correlation between Langmuir constants and FTIR results was observed.