Template-additive-free synthesis of binary zeolite microspheres with tunable hierarchical architectures and their removal abilities for organic pollutants

Abstract

Binary zeolite microspheres (BZMs) with tunable hierarchical architectures, including particles (BZMs-PS, nanosheets-assembled microspheres (BZMs-NA), urchin-like microspheres with short nanorods (BZMs-US), and urchin-like microspheres with long nanorods (BZMs-UL) were prepared directly by self-crystallization via a facile and effective hydrothermal method without any additives from inorganic sources. The obtained BZMs were composed of hydroxyl sodalite (HS) and hydroxyl cancrinite (HC). The growth process of BZMs was explored and it was speculated that the tunable architecture formation was determined by the bi-phase crystallization differential. In addition, reversed crystal growth involving surface-to-core crystallization was detected, which was supposed to be the reason for the formation of hollow cores. The adsorption experiments indicated that the BZMs-NA exhibit the highest adsorption capacity of 45.6 mg g⁻¹, and all the BZMs showed a fast adsorption rate. All the factors that might influence the adsorption abilities of the BZMs, including surface area, pore sizes, zeta potentials, and intraparticle diffusion, were investigated. The results suggested that the adsorption was predominantly affected by the surface area accompanied by the electrostatic attraction, and intraparticle diffusion was excluded. Therefore, this work provides an effective strategy for the synthesis of spherical sodalite/cancrinite materials with tunable architectures, which can potentially be used in the field of separation and catalysis.