Adsorption Properties of Natural Zeolite Supported by Chitosan on Cd(II) in Micropolluted Irrigation Water

Abstract

This study utilized a 1% chitosan solution (dissolved in 2% acetic acid), with a chitosan-to-zeolite mass ratio of 0.005, to successfully prepare chitosan-loaded natural zeolite. The performance of chitosan-modified natural zeolite in the removal of low-concentration cadmium ions in the presence of micropollutants was investigated. The adsorbent was characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR), and scanning electron microscopy (SEM)/energy-dispersive spectroscopy (EDS) techniques. The impact of modified adsorbent dosage, pH value, contact time, temperature, and initial concentration on adsorption performance was discussed. Additionally, the adsorption kinetics, isotherms, and thermodynamics of cadmium on chitosan-modified zeolites were analyzed. The results indicated that the modified zeolite exhibited a dispersed and porous structure with increased surface area, average pore size, and total pore volume. Under the conditions of 25 °C, pH 6, a dosage of 8 g/L, and a 60 min adsorption reaction time, chitosan-loaded natural zeolite (CNZ) achieved a removal efficiency of over 94.51% for a 100 μg/L cadmium solution (in a 100 mL volume). The adsorption process followed the Langmuir model, suggesting monolayer adsorption. The adsorption kinetics followed a pseudo-second-order equation, indicating an exothermic process with an increase in entropy. Chitosan-loaded natural zeolite demonstrated improved adsorption capacity and effectively removed cadmium from water contaminated with micropollutants.