Catalytic Degradation of 4-Ethylpyridine in Water by Heterogeneous Photo-Fenton Process.

In this work, the degradation of 4-ethylpyridine (4EP) in water by a heterogeneous photo-Fenton process (H₂O₂/Fe₃O₄/ultraviolet irradiation (UV)) was investigated. More rapid and effective 4EP degradation was obtained with H₂O₂/Fe₃O₄/UV than Fenton-like (H₂O₂/Fe₃O₄) and UV/H₂O_2, which is due to the larger production of hydroxyl radicals from the chemical and photolytic decomposition of H₂O₂. The operational conditions were varied during 4EP degradation experiments to evaluate the effects of pH, catalyst, concentration, and temperature on the kinetics and efficiency of H₂O₂/Fe₃O₄/UV oxidation. Under optimal conditions (100 mg/L 4EP, [H₂O₂] = 1000 mg/L, Fe₃O₄ = 40 mg/L, pH = 3 and room temperature, 300 rpm), 4EP was totally declined and more than 93% of the total organic carbon (TOC) was eliminated. Liquid chromatography analysis confirmed the formation of aromatic and aliphatic intermediates (4-hydroxypyridine, 4-pyridone, malonic, oxalic, and formic acids) that resulted in being mineralized. Ion chromatography analysis demonstrated the stoichiometric release of NH4⁺ ions during 4EP degradation by heterogeneous photo-Fenton oxidation. The reuse of the heterogeneous catalyst was evaluated after chemical and heat treatment at different temperatures. The heat-treated catalyst at 500 °C presented similar activity than the pristine Fe₃O₄. Accordingly, heterogeneous photo-Fenton oxidation can be an alternative method to treat wastewaters and groundwater contaminated with pyridine derivatives and other organic micropollutants. The combination of heterogeneous photo-Fenton oxidation with classical biological methods can be proposed to reduce the overall cost of the treatment in large-scale water treatment plants. [ABSTRACT FROM AUTHOR]