Modification of crystal growth of NaA zeolite with steric hindrance agents for removing ammonium ion from aqueous solution

Abstract

The incorporation of steric effects into the hydrothermal synthesis system of NaA zeolite proves to be an effective method for modifying grain size, enhancing grain dispersion and obtaining single crystal products. In this study, three different molecular configurations, namely short-chain ethanolamine (MEA), long-chain polyethylene glycol (PEG), and ring-chain cyclohexanol (CyOH), were employed to investigate the impact of steric effects on the crystal growth of NaA zeolite. The crystal form, morphology, and particle size of NaA zeolite were characterized using XRD, FT-IR, and SEM techniques. The order of steric hindrance in terms of molecular configuration was found to be as follows: CyOH > PEG > MEA. NaA-CyOH exhibited a high dispersion of single crystal particles, the smallest grain size, and the largest specific surface area and pore volume. To evaluate the ammonium ion adsorption performance, NaA-CyOH-31, the zeolite with the best performance, was utilized for studying the reaction kinetics. The results indicated that the adsorption behavior of NaA zeolite towards ammonium ion could be better described by the quasi second-order equation and the Langmuir model. Furthermore, the evaluation of the regeneration ability of NaA-CyOH zeolite demonstrated that the recovered adsorbent still maintained a high level of adsorption performance.