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Preparation of new iron–zeolite modified electrodes for the oxidation of pollutants via an electro-Fenton-like process is reported in this work. Alizarin Red S (ARS) is chosen as the model dye compound for anodic oxidation in an aqueous acidic medium. A minimal metal loading ranging from 0.2 to 0.8 wt% of ferrous/ferric (Fe2+/Fe3+) ions was introduced inside the ZSM-5 zeolite (Si/Al ratio of 15.0) via an ion-exchange process and the presence of iron species in the zeolite framework was determined using several physicochemical techniques. The iron–zeolite samples obtained under different experimental conditions were employed in order to study the textural and structural properties, and electrocatalytic activity. Cyclic voltammetry measurements showed that the textural properties of zeolite do not mainly affect the electrocatalytic reaction. However, the differences observed in catalytic peaks were a consequence of different iron ions present in zeolite. The structure–catalytic activity relationship is highlighted by the identification of the degradation products like oxalic acid (C2H2O4) and formic acid (HCOOH). Consequently, the degradation of ARS reached an optimum value of ca. 30% at 2 V vs. SCE for Fe(III)TTZSM-5 with a catalyst loading of 5.0 mg cm−2. This study shows that iron–zeolite modified electrodes are highly active for dye compound degradation without the addition of H2O2 and have potential application in the treatment of effluents. [ABSTRACT FROM AUTHOR]

Electrochemical oxidation, a powerful tool for the conversion of several of organic dye compounds using metal-exchanged zeolite modified electrodes, has shown great potential due to its capability of high efficiency degradation, a global priority for a sustainable environment. In this study, the role of the Fe(III)-exchanged-zeolite-modified electrodes using two different zeolite structures (such as FAU (Y) and MFI (ZSM-5)) on the Fenton-like oxidation of Congo Red dye (C 32 H 22 N 6 Na 2 O 6 S 2) was investigated at room temperature. To clarify the electrocatalytic trend observed by constant potential electrolysis, the surface acidity of the catalysts prepared by ion-exchange method was determined by microcalorimetric measurements of ammonia adsorption. The different acid properties deriving from the presence of different cations (NH 4 +, H+ and Na+) in the case of MFI structure were found to enhance the ion-exchange capacity as well as the oxidation reaction. MFI catalysts - Fe(Na)ZSM-5, Fe(H)ZSM-5 and Fe(NH 4)ZSM-5 - exhibited excellent activity and stability at the end of the electrolysis (within 60 min), with a total dye degradation and an higher mineralization on Fe(H)ZSM-5 (64% of TOC), compared with Fe(Na)Y nano , which takes twice as long (120 min) for total degradation, with 19% of TOC removal. This work provides an effective route for the development of stable Fe(III)-zeolite-modified electrodes for electro-Fenton oxidation, with a better stabilization of Fe3+ ions within the framework, without the aggregation of iron and the addition of H 2 O 2 , at room temperature. [Display omitted] • Easy preparation of Fenton-like catalysts based on zeolites, MFI and FAU. • Highly effective Fe(III)-zeolite-modified electrodes to electro-Fenton oxidation. • Electrochemical method allows faster mineralization of dye without redox agents at RT. • Eco-friendly Fenton-like oxidation was achieved with MFI-zeolite catalysts. [ABSTRACT FROM AUTHOR]