The relevance of extra framework Al in the crystallisation of α-Fe2O3 nanocrystals over ZSM-5 as photo-Fenton catalyst

Abstract

Different crystal formation patterns of FexOy species over two zeolitic supports were observed. Starch was used in the synthesis of ZSM-5 to generate a zeolite with supplemented mesoporosity in addition to the traditional microporous structure. Fe was incorporated into the zeolitic matrices through hydrothermal synthesis of hematite nanoparticles. Two zeolitic catalysts with different activities in a photo-Fenton reaction were obtained. The materials were thoroughly characterised by XRD, UV–Vis DRS, TPR, FIT-IR, NMR, SEM, EDS, TEM, Mossbauer ¨ Spectroscopy and N2 adsorption-desorption isotherms. Methyl orange, a persistent anionic dye in water, was chosen for photocatalytic degradation testing. Promising results were obtained when hematite nanoparticles were supported onto hierarchical ZSM-5. The presence of extra-framework aluminium served as a nucleation site, leading to the formation of numerous smaller hematite crystals, enhancing the photocatalytic performance of the catalyst.