Degradation of sodium 4-dodecylbenzenesulphonate photoinduced by Fe(III) in aqueous solution

The Fe(III)-photoinduced degradation of 4-dodecylbenzenesulphonate (DBS) in aqueous solution was investigated. The mixing of DBS (1 mm) and Fe(III) (1 mm) solutions immediately led to the formation of a precipitate that contained DBS and monomeric Fe(OH)2+, the predominant Fe(III) species. Both species were also present in the supernatant. Irradiation of the supernatant solution resulted in a photoredox process that yielded Fe(II) and .OH radicals. The disappearance of DBS was shown to involve only attack by .OH radicals; the quantum yield of DBS disappearance is similar to the quantum yield of .OH radical formation. A wavelength effect was also observed; the rate of DBS disappearance was higher for shorter wavelength irradiation. Five photoproducts, all containing the benzene sulphonate group, were identified. .OH radicals preferentially abstract hydrogen from the carbon in the α position of the aromatic ring. The results show that the Fe(III)-photoinduced degradation of DBS could be used as an alternative method for polluted water treatment.