The photodegradation of a specific organic pollutant in aqueous solution using the photo-Fenton system has been modeled and experimentally verified. Kinetic and reactor models accounting for the decomposition rates of formic acid (the model compound) and hydrogen peroxide were developed. The experimental work was performed in a flat-plate, well-stirred reactor placed inside a batch recycling system having a high-flow-rate recirculating pump and a storage tank. The reactor was irradiated from both sides with two tubular lamps placed at the focal axis of two cylindrical reflectors of a parabolic cross section. When predictions of the theoretical model are compared with experimental results, a good representation of the formic acid and hydrogen peroxide concentration evolution in a rather wide range of their initial molar concentrations is obtained; within the range of explored variables, deviations between model predictions and experimental data were always smaller than 9%. Furthermore, model predictions and experimental results of the organic compound degradation show that UV irradiation improves the effectiveness of the Fenton system significantly. Under the adopted operating conditions, a pollutant conversion 63% greater than that obtained with the dark system was observed.

The effect of the reaction temperature on the degradation rate of formic acid, using the Fenton and photo-Fenton processes, is investigated. First, for both reactions, a stirred tank laboratory photoreactor irradiated from the bottom was used to evaluate the kinetic parameters between 298 and 328 K. Afterward, the proposed kinetic model was used to predict the conversion of the organic pollutant in a flat-plate solar photoreactor. The previously reported radiation field and mass balances have been used to compute the formic acid and hydrogen peroxide concentrations as a function of time in the solar reactor. Theoretical and experimental results show that UV solar radiation improves the effectiveness of the Fenton process. At lower temperatures, the pollutant conversion enhancement is significant, but this effect is less important at higher temperatures. For instance, experimental conversion enhancements after 20 min are 186.0, 74.0, and 7.4% for 298, 313, and 328 K, respectively.

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