Synthesis and properties of magnetic zeolite with good magnetic stability from fly ash

Magnetic fly ash-based zeolites (MFZ) with good magnetic stability were in situ synthesized from fly ash (FA) modified by Fe3O4 after alkali fusion, hydrothermal treatment, and followed by reduction. The effects of the synthesis parameters of MFZ, such as the loading amount of Fe3O4, NaOH/FA ratio, and SiO2/Al2O3 molar ratio, were investigated as well as its adsorption capacity for Cu2+ ions. The results indicated that MFZ were composed of zeolite A and sodalite phases and possessed excellent magnetic property. Fe3O4 nanoparticles were encapsulated in or covered below the as-synthesized zeolites, resulting in a good magnetic stability of MFZ. The magnetic property and crystal type of MFZ could be adjusted by controlling the synthesis parameters. High loading amount of Fe3O4 hindered the leaching of active SiO2 from FA and then limited the formation of zeolite A. MFZ exhibited a high adsorption capacity for Cu2+ ions and the latter increased with the amount and crystallinity of zeolite A in MFZ.