Utilizing silica from rice husk ash to synthesize NaX zeolite for adsorbing Cr(VI) ions from water

Tóm tắt

This study aimed to use rice husk ash (RHA) as an agricultural by-product combined with heat treatment to recover silica and synthesize zeolite NaX through a hydrothermal method, optimizing the synthesis conditions. The molar ratio of reactants used in the synthesis was 4.2Na₂O:Al₂O₃:3SiO₂:18H₂O, with an aging time of 24 hours at room temperature and a crystallization time of 6 hours at 100°C. The adsorption of Cr(VI) ions in solution was optimized under conditions of pH 4.0, an initial Cr(VI) concentration of 120 mg/L, and a 30-minute adsorption time. The properties of the synthesized materials were characterized by X-ray diffraction (XRD) to identify characteristic diffraction peaks, and scanning electron microscopy (SEM) showed that the zeolite NaX had an average diameter of 113.16±0.12 nm. The study assessed the first-order and second-order adsorption kinetic models, as well as the Langmuir, Freundlich, and Dubinin-Radushkevich adsorption isotherms. Under the kinetic models, the adsorption of Cr(VI) ions onto the zeolite NaX followed the Langmuir isotherm model, with second-order kinetics and physical adsorption.