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. [Figure not available: see fulltext.].