Photocatalytic degradation of phenol and isoproturon: Effect of adding an activated carbon to titania catalyst

An integrated process based on combination of adsorption, with a commercial activated carbon (AC), and heterogeneous photocatalysis, with a home-made titania catalyst (TiEt), has been studied in phenol and isoproturon removal. In this work, different physical mixtures of TiEt and AC catalysts were first studied in phenol photodegradation in order to optimize the TiEt/AC concentration ratio. In this sense, a higher degree of mineralization and an improvement of phenol photodegradation were reached with a 500/100 TiEt/AC mixture (500 mg L-1 TiO2: 100 mg L-1 AC) in the same photoassisted reactor in ambient conditions. The best photo-efficiency found with this TiEt/AC physical mixture can be well explained by means of a synergistic effect between both catalysts, where the activated carbon and titania particles interaction provides the formation of an active common contact interphase between both materials, and part of the adsorbed compounds on AC surface are photo-oxidized by the active species photogenerated in titania particles under irradiation conditions. Nevertheless, the higher photo-efficiency found during isoproturon photo-oxidation, when AC was combined with TiO2 in aqueous suspensions, is better related to an associative phenomena where an important adsorption step with the commercial AC is followed by photo-oxidation with the home-made titania catalyst, leading to a moderate improvement in TOC removal efficiency. (C) 2014 Elsevier B.V. All rights reserved.