Enhanced Redox Properties of Cu-Exchanged Zeolite Synthesized from Fly Ash

Abstract

This study reports the synthesis of Cu-exchanged zeolite using coal fly ash as a low-cost silica–alumina source. Fly ash was first converted into zeolite through alkali fusion and hydrothermal crystallisation, followed by copper ion-exchange using Cu(NO₃)₂ solution and subsequent calcination. Structural and chemical characterisations were carried out by XRD, FTIR, and SEM/EDS. XRD analysis confirmed the preservation of the crystalline zeolite framework after Cu incorporation, along with weak reflections attributed to CuO species. FTIR spectra showed characteristic framework vibrations of Si–O–Al and additional bands related to Cu–O linkages, validating the presence of copper within the structure. SEM micrographs revealed agglomerated crystalline particles in the submicron range, while EDS confirmed uniform copper distribution. These results demonstrate that fly ash can be effectively transformed into a Cu-zeolite composite with a stable framework and redox-active Cu species, making it a promising candidate for catalytic and environmental applications such as NOx reduction and VOC oxidation.