Application of a planar falling film reactor for decomposition and mineralization of methylene blue in the aqueous media via ozonation, Fenton, photocatalysis and non-thermal plasma: A comparative study

The efficiencies of ozonation and different advanced oxidation processes (AOPs) including photocatalytic ozonation, Fenton, photo-Fenton, photocatalytic oxidation, UVA/TiO2/H2O2, and non-thermal plasma generated by a dielectric barrier discharge (DBD) were compared in terms of the energy yield (G₅₀) for decolorization of MB and total organic carbon (TOC) removal using a planar falling film reactor. Fenton oxidation and ozonation were found to be the most efficient methods for the decolorization of MB, although these techniques attained rather low mineralization. A combination treatment of the ozonation with the photocatalysis demonstrates a synergistic effect on the mineralization efficiency. The photocatalytic oxidation and UVA/TiO2/H2O2 provide only a moderate MB decolorization. The degradation efficiency of the DBD plasma is significantly dependent on the composition of gas atmosphere. The addition of Fe2+ to the solution in the DBD plasma under argon atmosphere improves the degradation efficiency due to the occurrence of Fenton reaction. The energy yield for 50% conversion of MB is calculated between 0.13 and 20.5 g/kWh, and the maximum and minimum values were obtained by the ozonation and photocatalytic oxidation, respectively. Ozonation with the highest energy yield provided a moderate mineralization by only 19%, while the DBD plasma obtained the highest TOC removal by 88%.