Oxidation of pollutants via an electro-Fenton-like process in aqueous media using iron-zeolite modified electrodes

Preparation of new ironzeolite 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 ironzeolite 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 structurecatalytic 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 cm2. This study shows that ironzeolite modified electrodes are highly active for dye compound degradation without the addition of H2O2 and have potential application in the treatment of effluents.
FCT (Fundação para a Ciência e a Tecnologia, Portugal) for the PhD grant to Marta Ferreira. This work was developed under the scope of the projects: BioTecNorte (operation NORTE-01-0145-FEDER-000004), supported by the Northern Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDF). This work also has been funded by national funds (FCT), through the projects: PTDC/AAG-TEC/5269/2014, Centre of Chemistry (UID/QUI/00686/2013 and UID/QUI/0686/2016). The authors also thank the graduate student João P. M. Fernandes for his contribution to the electrocatalytic tests.
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