Photodegradation of surfactants: Part vi complete photocatalytic degradation of anionic, cationic and nonionic surfactants in aqueous semiconductor dispersions

Abstract

Various kinds of anionic ( e.g., C 12-DBS, C 12-DS, C 12-LES-3, C 14-AOS, and C 12-DG), cationic ( e.g., C 16-HTAB and C 12-BDDAC) and nonionic ( e.g., NPE n (n = 7, 9, 17, 50), C 18-PEA-15, C 12–14-BHA, C 12–14-PAE-10, C 12–14-NOE and C 14–16-NOE) surfactants have been photodegraded in a heterogeneous dispersion of TiO 2 semiconductor particles under UV illumination. These surfactants are ultimately converted to CO 2. A relationship between the structure of surfactants and the photodegradation rate is indicated in a comparison of the results with literature studies of biodegradation. CO 2 evolution from the photooxidation of anionic surfactants is faster than that observed from cationic surfactants in the initial stages of irradiation (2̃h). The nonionic surfactants photodegrade more slowly, evolving CO 2 at about 20% mineralization yield. UV-illuminated titanium dioxide affords strongly oxidizing catalytic sites, irrespective of the structure of surfactant.