2,4-Dichlorophenoxyacetic acid degradation by catalyzed ozonation: TiO2/UVA/O-3 and Fe(II)/UVA/O-3 systems

The oxidative degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) by mean s of two different advanced oxidation technologies based on ozone activatio n has been studied. Ozonation of 2,4-D in presence of UVA Light and TiO2, a nd in presence of UVA and Fe(II), has been carried out. Both treatment meth odologies have been compared in terms of the dependence on several experime ntal parameters like reaction time, pH, light intensity and catalyst concen tration on reaction efficiency, It is shown that the initial solution pH pr actically has no influence on the efficiency of the processes, due to the f act that the pH rapidly decreases during the first minutes of reaction, alw ays attaining a final value close to pH 3. A linear variation of TOC remova l 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 exa mined by following the time course of chloride concentration in solution. ( C) 2000 Elsevier Science B.V, All rights reserved.