Aqueous oxidation of dimethyl phthalate in a Fe(VI)-TiO2-UV reaction system

The application of a combined ferrate–photocatalysis process for the aqueous degradation of dimethyl phthalate (DMP) has been studied. The behaviour of the Fe(VI)-TiO2-UV process at pH 9 in the presence and absence of dissolved oxygen (DO) has been compared and significant differences have been found. In comparative tests under N2 and O2 bubbling, the chemical reduction rate of ferrate as conduction band electron acceptor was similar, but the resulting degradation of DMP was substantially lower in the presence of oxygen. It is speculated that the presence of oxygen leads to the formation of Fe–O–(organic) complex species that adsorb to, and deactivate, the surface of the photocatalyst. The presence of surface-adsorbed complex species was indicated by FTIR spectroscopy and a reduced TiO2 adsorption capacity for DMP. In the presence of typical environmental levels of DO (∼9 mg L−1), the Fe(VI)-TiO2-UV process achieved a modest degree of DMP degradation (40% in 120 min).