Improving the Fenton process by visible LED irradiation.

The effect of irradiation with visible light-emitting diode (LED) light on the efficiency of Fenton oxidation is investigated using phenol as the target compound (100 mg/L). The H2O2 dose and temperature are tested as operating variables with the aim of minimizing consumption of the reagents. At 50 °C, 10 mg/L Fe2+, and 60 % of the stoichiometric H2O2 amount, phenol was completely oxidized into CO2, H2O, and short chain organic acids, with oxalic acid completely degraded. Up to 95 % mineralization was achieved. This high efficiency can be attributed to the effect of LED radiation on the quinones/Fe2+/Fe3+/H2O2 cycle, which significantly increases the reaction rate, as well as on the photodecomposition of the iron complexes formed along the oxidation process, which also enhanced mineralization.