Synergies, radiation and kinetics in photo-Fenton process with UVA-LEDs

• Published in: Journal of hazardous materials Vol. 380; p. 120882
• Main Authors: López-Vinent, N., Cruz-Alcalde, A., Romero, L.E., Chávez, M.E., Marco, P., Giménez, J., Esplugas, S.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15-12-2019
• Subjects: Intermediates; Kinetics; Photo-Fenton; Synergy wavelength; UV-A LED; Photo-Fenton; UV-A LED; Kinetics; Synergy wavelength; Intermediates
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2019.120882

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•Diphenhydramine (DPH) is degraded by UV-A LED photo-Fenton process.•The use of different wavelength ranges of UV-A LED (380–390, 390–400 nm) leads to similar results.•Potential synergy of two wavelengths ranges (380–390 nm and 390–400 nm) was found.•Kinetic constants were evaluated at initial time and during the rest of experiment.•Intermediates were identified and possible reaction pathways are proposed.
The photo-Fenton process, with UV-A LED (λ = 380–390, 390–400 and 380–400 nm) has demonstrated to be effective in the abatement of a target micropollutant, such as diphenhydramine hydrochloride (DPH). Different concentrations of iron (Fe2+) and H2O2 were tested and monitored, and the best results in DPH removal were obtained for the highest concentrations of both iron (II) and H2O2 (10 mg Fe2+/L - 150 mg H2O2/L). The evolution of iron and peroxide concentration was also monitored. Kinetic studies showed that dark Fenton process prevails at the beginning of the experiment, when Fe2+ concentration is higher. However, after these initial moments, the prevailing process is photo-Fenton and, in addition, wavelength radiation plays an important role. Concerning the effect of radiation, four LEDs (4.2 W total power) were used, emitting radiation in the wavelength range between 380–390 or 390–400 nm. Similar results were obtained in both cases in DPH removal by photo-Fenton (30 min for total elimination). However, a synergistic effect was observed when two LEDs of 380–390 nm and two LEDs of 390–400 nm were used. Total power was the same (4.2 W) in each experimental condition, but the increase in the wavelength range to 20 nm (380–400 nm) produces an increase in the rate of DPH removal, achieving its total elimination at 15 min. This fact, with the use of a simple radiation model, reveals the important role that radiation plays in the photo-Fenton process. Finally, the formed intermediates were determined and some reaction pathways were proposed.