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In this work the intrinsic reaction kinetics of the degradation of a mixture of pollutants in aqueous solution employing the UV/H2O2 process was studied. The employed reactants were dichloroacetic acid (DCA) - a typical by product of chlorine disinfection - and formic acid, a very simple model compound. The main objective of this research to derive, from a mechanistic reaction scheme developed in a previous contribution, a mathematical model able to represent the kinetics of DCA and Formic Acid oxidation and validate its predictive quality with experiments. The kinetic model must be independent of the shape, size and configuration of the laboratory reactor in order to be apt for scaling up purposes. The experimental device consists of a cylinder sealed with two parallel, flat windows made of quartz. Each window was irradiated with a tubular, germicidal lamp (253.7 nm). The reactor is placed inside a recycle with includes: i) the centrifugal pump ii) a heat exchanger for temperature control iii) a storage tank (VTank=2000 cm3). Experiments were carried out changing the following variables: (i) hydrogen peroxide/pollutant mixture initial concentration ratio, ii) initial DCA and Formic Acid concentration, iii) incident radiation at the reactor wall. Using de mass action law and the micro steady state approximation, a kinetic model was developed. Working with a complete set of experimental runs, the unknown kinetics parameters of the mixture of pollutants degradation were obtained, upon application of the Levenberg-Marquardt optimization algorithm. Theoretical predictions of concentrations evolutions of DCA, Formic Acid and H2O2 are in very good agreement with experimental data. These results should allow us to nearing real problems of contamination aiming at reaching, as much as possible, a general kinetics development methodology. This is important, because wastewaters, particularly, have usually a rather complex chemical composition.

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