Activation of Photo-Fenton-like Process Catalyzed by Fe3+-IDS under Visible LED Light Irradiation

Abstract

This study is focused on the effect of the light source (LEDs emitting visible and UV-A light) on the activation of photo-Fenton processes for the Fe³⁺-iminodisuccinic acid/H₂O₂ catalytic system. The catalyst enables visible light for the hydroxyl radical’s formation by H₂O₂ conversion. This study shows, for the first time, the central role of visible light to accelerate the process kinetics favoring the complete degradation of a probe molecule ([gallic acid] = 25.0 mg L^–1 (0.147 mM)), in water solutions in 90 min using a [H₂O₂]/catalyst molar ratio (R) of 75, in comparison with data obtained under dark conditions (99% under visible radiation vs 67% in dark conditions). A kinetic model able to correlate the electrical nominal power of the used LEDs, the light absorption properties of Fe³⁺-iminodisuccinic acid (Fe-IDS), and LEDs emission spectra was developed to estimate the degradation kinetic constants for the process in dark conditions and in the presence of light. The accuracy of the calculated kinetic constants was tested under different R values to verify the predictive ability of the model. A very good agreement between the experimental data and the mathematical model calculations was achieved. These results highlight the promising use of the Fe-IDS catalyst for environmental remediation considering low energy consumption conditions. A reasonable explanation is that the presence of Fe-IDS significantly promoted the generation of reactive oxygen species using visible light and H₂O₂, which led to gallic acid removal.