TIO2-photocatalyzed degradation of phenol and ortho-substituted phenolic compounds

The photocatalytic degradation of phenol, guaiacol, 2-chlorophenol and cate chol in aqueous suspensions of TiO2 under different experimental conditions has been investigated. The photodegradation of the different organics foll ows a Langmuir-Hinshelwood kinetics, showing rate constants that decrease i n the order: guaiacol > 2-chlorophenol congruent to phenol > catechol. A si milar trend is also observed, except for catechol, for the stability of the a-complexes that may be formed between the aromatic ring and the OH. radic al. From different analytical techniques (HPLC, GC/MS and HPLC/MS), various hydroxylated intermediate compounds have been reported acid different mech anisms of degradation of the starting compounds have been proposed. From ex periments performed using aqueous solutions containing the four organics, i t is observed that the competitive Langmuir-Hinshelwood kinetics for the de gradation of each one of the phenolic compounds is obeyed. (C) 2001 Elsevie r Science B.V. All rights reserved.