Modeling the kinetics of UV/hydrogen peroxide oxidation of some mono-, di-, and trichlorophenols

The decomposition of a number of chlorophenols (CPs). namely 2-CP, 2,4-dichlorophenol and 2,4,6-trichlorophenol, has been studied in aqueous solution by UV-catalyzed oxidation with H2O2 under UV radiation emitted by a 125-W medium pressure Hg lamp in an immersion well-type quartz photoreactor, and the organic-bound chlorine has been converted into the environmentally harmless inorganic chloride. For oxidant/CP mole ratios between 1:1 and 16:1, the reaction kinetics were modeled and the corresponding rate constants found by periodically measuring the remaining CP, hydrogen peroxide and converted chloride in solution. A theoretical model for the degradation pathway is proposed expressing the rate as a linear function of the concentrations of CP and oxidant, The rate constants fur the pseudo-first order approximation of the CP degradation were compared. H2O2, when combined with UV, is an effective photoactivated oxidant. The photodegradation order in ter ms of the initial late of CPs destruction was: Cl-3 . Ph greater than or equal to Cl-2 . Ph > Cl . Ph. (C) 2000 Elsevier Science B.V. All rights reserved.