Photo-Fenton Degradation of the Herbicide 2,4-D in Laboratory and Solar Pilot-Plant Reactors

Abstract

A theoretical and experimental study of a pilot-plant solar reactor for the photo-Fenton degradation of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) in aqueous solution is presented. Initially, a kinetic model is proposed to obtain the reaction rates of 2,4-D, the main intermediate (2,4-dichlorophenol), and the hydrogen peroxide. The kinetic study was performed in a well-stirred tank laboratory reactor. The effects of ferric salt initial concentrations, hydrogen peroxide to 2,4-D initial concentration ratios, reaction temperatures, and radiation levels are studied. The proposed kinetic model and the experimental data are used to estimate the kinetic parameters, applying a nonlinear regression procedure. Afterward,the kinetic model is used to predict the reactant concentrations during the photo-Fenton degradation in a pilot-plant solar reactor designed to capture the UV/visible/IR solar radiation. The solar reactor was able to reach a complete degradation of the 2,4-D and 2,4-dichlorophenol after 60 min, and a total organic carbon conversion of 98.9% after 210 min.