Physicochemical study of photocatalytic activity of TiO2 supported palygorskite clay mineral

Abstract

This study deals with the influence of physicochemical parameters, namely, the photocatalyst loading, dye concentration, and pH of polluted solutions, on the degradation efficiency of Orange G (OG) solutions containing TiOnanoparticles supported on palygorskite clay mineral (TiOPal). The TiOphotocatalyst attached to natural palygorskite fibers was elaborated by colloidal sol-gel route. It exhibits the anatase structure that is the most photoactive crystallographic form. The highest performances of supported photocatalyst on OG degradation were found using an optimum amount of TiOPal around 0.8 g·L-1, which corresponds properly to ca. 0.4 g·L-1 of TiO This amount is interestingly lower than the 2.5 g·L-1 generally reported when using pure unsupported TiOpowder. The photodegradation rate increases by decreasing OG initial concentration, and it was found significantly higher when the OG solution is either acidic (pH<4) or basic (pH≈11). For OG concentrations in the range 5×10-6- 5×10-4 M, the kinetic law of the OG degradation in presence of TiOPal is similar to that reported for unsupported TiOnanopowder. It follows a Langmuir-Hinshelwood model with a first-order reaction and an apparent rate constant of about 2.9×10-2 min-1. © 2013 Lahcen Bouna et al.