Enhanced photocatalytic degradation of maleic acid by Fe(III) adsorption onto the TiO2 surface

The role of Fe(III) on the TiO2-assisted photocatalytic degradation of maleic acid has been investigated. The study on the kinetics of the removal of organic matter, as well as the identification of all the stable mineralization intermediates, demonstrates that the presence of Fe(III), adsorbed onto the TiO2 surface, renders a more efficient process through a cleaner mineralization pathway compared to bare TiO2. Furthermore, the behaviour of the system does not depend on the iron source. On the other hand, the study of the Fe(III) influence on the interaction of maleic acid with TiO2 in the solid phase, by means of ATR–FT-IR technique, has been performed. From all the reported results, it is concluded that the Fe(III) effects are mainly due to surface phenomena. The enhanced photocatalytic activity is interpreted under different perspectives, including adsorbed Fe–maleic complexes, enhanced adsorption of oxygen and lower geminate recombination yields.