Hollow zeolite structures formed by crystallization in crosslinked polyacrylamide hydrogels

Abstract

Hollow zeolite structures including sodalite spheres and hollow zeolite NaA crystals were synthesized by introducing crosslinked polyacrylamide (C-PAM) hydrogels into zeolite synthesis gels. The synthesis gels with weight compositions of 0.8SiO2 : 1.0Al2O3 : 21.2Na2O : 86.0H2O : 7.4–28.7 acrylamide (AM) were used to produce hollow sodalite spheres. The synthesized hollow sodalite spheres had diameters of 1–5 μm and shell thicknesses of 0.5–1 μm, and the sphere diameters decreased from 5–10 μm to 1–3 μm as the amount of C-PAM increased. Hollow zeolite A crystals with sizes of 300–500 nm were grown from the synthesis gel with a weight ratio of 0.8SiO2 : 1.0Al2O3 : 2.6Na2O : 16.4H2O : 2.6–3.8AM. The experimental results suggest that the formation of hollow zeolite structures may involve a surface-to-core crystallization process induced by crosslinked polyacrylamide networks.