Mineral iron oxides as iron source in electro-Fenton and photoelectro-fenton mineralization processes

Several low-soluble mineral iron oxides have been studied as an iron source for the production of hydroxyl radicals via H2O2 decomposition in the presence of ferrous ions (Fenton's reaction). In particular, this study focuses on electro-Fenton and photoelectro-Fenton processes, using aniline as a model pollutant. The aim of this work is to spread the use of iron minerals as catalyst in the different electrochemical wastewater treatments. Among all the iron oxides tested, magnetite (Fe3O4) and wustite (FeO) show the more promising results. The main advantages of these minerals are that they produce lower concentrations of iron in solution, ease of recycling the iron catalyst, and their ability to self-regulate the concentration of iron ions in solution. Wustite and magnetite behave purely as a source of iron ions in the electro-Fenton process. But, magnetite exhibits a heterogeneous photocatalytic effect when used as an iron source in the photoelectro-Fenton process. This new magnetite-photoelectro-Fenton process significantly improves the pollutant removal yield (16.7% more after 5 h of mineralization) compared to the conventional photoelectro-Fenton process. This effect is observed for two different wavelengths in the UV range, 254 and 360 nm. (c) 2007 The Electrochemical Society.