Seeded-secondary growth synthesis of ZIF-8@porous mullite beads for adsorption of dyes

Zeolite imidazole framework-8 (ZIF-8), serving as a promising adsorbent for wastewater treatment, is limited in practical wastewater treatment due to its polycrystalline powder form resulting in poor recoverability. Herein, the millimeter-scale ZIF-8@porous mullite beads were prepared by the seeded-secondary growth method. The surface of the porous mullite beads is fully encapsulated by nanoscale ZIF-8 crystals, and the ZIF-8 crystals are anchored by mullite whiskers. This composition provides ZIF-8 with a stable macroscopic structure and maintains the exposure of its adsorption sites. Therefore, the ZIF-8@porous mullite beads exhibited good adsorption performance toward methyl orange (MO) and orange G (OG) in the aqueous solution. The analysis of adsorption kinetics indicating the adsorption efficiency of ZIF-8@mullite-w on MO and OG is influenced by the concentration of adsorbates and the adsorption sites. The maximum adsorption of ZIF-8@porous mullite beads on MO and OG was 16.5289 and 5.111 mg/g, respectively.