Optimization of H2O2 use during the photocatalytic degradation of ethidium bromide with TiO2 and iron-doped TiO2 catalysts

摘要

A series of nanosized iron-doped titania catalysts has been used for the photocatalytic degradation of ethidium bromide (EtBr) with oxygen. The study shows that EtBr surface adsorption is most favored over basic titania surfaces such as those present in undoped TiO2 and Fe-TiO2 with low iron content. This fact is shown to affect strongly the photocatytic mechanism of EtBr degradation. Based on EtBr adsorption and photocatalytic activity analyses, a titania catalyst with an iron content of 0.7 wt.% has been selected for subsequent studies using H2O2 as oxidant. Parameters as reaction pH and initial hydrogen peroxide concentration were analyzed to establish optimum operating conditions. It is shown that a new strategy based on dosing H2O2 in a controlled way could minimize radical self-scavenging reactions and improves final EtBr mineralization degree. Finally, the stability and durability of catalyst/activity have been examined through five consecutive cycles of H2O2 dosing. A constant activity level is maintained during at least four consecutive cycles in which total EtBr and 80% of Total Organic Carbon conversion is achieved.