Study on using crystalline celluloses as templates for preparation of hierarchical LTA Zeolite for fast Cd(II) removal

Abstract

Crystalline celluloses, such as microcrystalline cellulose (MCC) and nanocrystalline cellulose (NCC), which are originated from biomass, were utilized as templates to prepare hierarchical LTA zeolites. The effect of both size and surface properties of crystalline cellulose on the zeolite synthesis were carefully discussed. As-prepared zeolite based on surface-modification NCC showed hierarchical porous structure with monolithic morphology inherited from nanocrystalline cellulose. Its specific surface area was measured to be 18.3 m2/g, which was approximately 3.4 times that of the traditional zeolite A (Z0, 5.4 m2/g). Owing to its unique structure, ZNSC facilitated fast Cd(II) adsorption with the adsorption equilibrium time shortened by 81.3%. Kinetics study revealed that intraparticle diffusion was significantly enhanced and the effective diffusion coefficient increased by near 5 times. Furthermore, the maximum adsorption capacity achieved by ZNSC was 324.3 mg/g at 283 K, as calculated from the Langmuir model, which was 1.3 times that of Z0. These results are obtained when the grain size of ZNSC is larger than that of Z0, reflecting the superiority of the hierarchical structure in enhancing adsorption performance and thus providing a facile yet robust strategy for designing hierarchically structured zeolites for rapid and efficient wastewater treatment.