Photoinduced degradation of 2,4-dichlorophenol in water: influence of various Fe(III) carboxylates.

Fe(III)-carboxylate complexes were investigated with respect to tri-carboxylic (citric), di-carboxylic (tartaric) and mono-carboxylic (pyruvic) acids. In agreement with the chemical structure, results demonstrated that Fe(iii) was complexed by citric acid with a ratio of 1 : 1 (Fe/ligand), tartaric acid (d or l) with a ratio of 1 : 2 and by pyruvic acid with a ratio of 1 : 3. The iron concentration was fixed at 0.3 mmol L(-1) and the ligand concentration ranged from 0 to 1.0 mmol L(-1). The primary stage of 2,4-dichlorophenol (2,4-DCP) degradation photoinduced by these Fe(iii) complexes was investigated under monochromatic irradiation (lambda = 365, 313 and 296 nm). The values of initial quantum yields of 2,4-DCP disappearance (between 0.01 and 0.135) and Fe(ii) formation (between 0.002 and 0.47) were evaluated and are presented in detail. Short irradiation wavelength (296 nm), low pH (3.0) and high oxygen concentration favoured the pollutant degradation. The disappearance of 2,4-DCP was complete under these favourable conditions.