2,4-Dichlorophenoxyacetic acid degradation by catalyzed ozonation: TiO2/UVA/O3 and Fe(II)/UVA/O3 systems

The oxidative degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) by means of two different advanced oxidation technologies based on ozone activation has been studied. Ozonation of 2,4-D in presence of UVA light and TiO2, and in presence of UVA and Fe(II), has been carried out. Both treatment methodologies have been compared in terms of the dependence on several experimental parameters like reaction time, pH, light intensity and catalyst concentration on reaction efficiency. It is shown that the initial solution pH practically has no influence on the efficiency of the processes, due to the fact that the pH rapidly decreases during the first minutes of reaction, always attaining a final value close to pH 3. A linear variation of TOC removal with square root of light intensity has been observed. Some dependence of the amount of catalyst (TiO2 or Fe(II)) in solution on TOC degradation has been detected. The rapidness of substrate dehalogenation has also been examined by following the time course of chloride concentration in solution.