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Water shortage and wastewater discharge into environment have led to significant research in the field of environmental engineering for developing high efficient, fast, and cheap wastewater treatment. In recent years, advanced oxidation processes (AOP) have been subjected to significant attention for wastewater treatment due to feasibility of the process in mild reaction conditions, requiring low cost equipment, and short time of the process. Electro-Fenton process addresses the potential drawbacks of Fenton reaction including transportation of H₂O₂ and regeneration of ferrous ions which act as catalyst. In the present study, ZSM-5 catalyst was synthesized by hydrothermal technique and promoter was introduced through wet impregnation method. Ir-ZSM-5 catalyst w::as char::acterized by XRD, FE-SEM, BET, FT-IR and NH₃-TPD techniques. The XRD patterns revealed the high crystallinity for the both parent and Ir impregnated ZSM-5 catalysts. FE-SEM images showed micro-spherical morphology. N₂-adsorption-desorption confirmed mesoporous structure for the synthesized catalyst including 321.1 and 327.3 m²/g specific surface area for the parent and Ir-ZSM-5 catalysts, respectively. FT-IR spectrum confirmed formation of ZSM-5 zeolite and also revealed presence of surface hydroxyl groups. NH₃-TPD revealed that acidity of the impregnated ZSM-5 catalyst was increased due to interaction of Ir with zeolite structure. Acidimetric-alkalimetric titration determined pH_PZC for the parent and Ir-ZSM-5 catalysts equal to 3.6 and 3.9, respectively. Catalytic performance of Ir-ZSM-5 catalyst for removal of methylene blue (MB) from wastewater in heterogeneous electro-Fenton like reaction was evaluated. Different operation conditions were tested including concentration of catalyst, pH of wastewater solution and applied current between graphite electrodes. The results showed that Ir-ZSM-5 catalyst had acceptable performance in near neutral pH level due to the improved adsorption of MB molecules on Ir-ZSM-5 structure. The stable catalytic activity resulted from formation of no sludge related to active phase. Detected OH groups at the surface of the catalyst attained positive charge at pHpzc and negative charge at pH>pH_pzc which influenced the adsorption capacity of the catalyst at different pH levels through electrostatic adsorption of ionized MB molecules on the catalyst. Blank test using no amount of Ir-ZSM-5 catalyst led to only 77% MB removal which was attributed to anodic oxidation on the surface of the graphite electrodes. Increasing applied current led to the improved MB removal owing to the faster degradation of the sacrificial graphite anode. The optimum operational conditions for the proposed system were pH=3, 0.2 gL^-1 of Ir-ZSM-5 catalyst and 100 mA applied current which resulted in the highest MB removal (100%). The reusability test of the catalyst was carried out by 3 consecutive runs at the optimum conditions. After each run, the used catalyst was regenerated at 550 °C to remove the adsorbed organic molecules due to adsorption of either MB or its oxidation intermediates. The regenerated catalyst showd the high catalytic performance with insignificant change of the removal efficiency as result of the high crystallinity and specific surface area of the synthesized catalyst. A pseudo first order kinetic was proposed for the reaction of removal which fitted the experimental data with the high correlation factor. The results confirmed the high potential of the heterogeneous electro fenton-like process for wastewater treatment.

Keywords: Dye removal, Advanced Oxidation Process, Electro Fenton like, Heterogeneous, Zeolite, Catalyst.

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