investigation of the natural an‎d activated bentonite in chitosan/bentonitecompositeon nikel removal from wastewate

7/29/2025 12:00:00 AM

threats they pose to human health an‎d ecosystems. Accordingly, the development an‎d application of efficient methods for the treatment of wastewater contaminated with heavy metals recognized as one of the main sources of these pollutants in aquatic systems are of critical importance. In this context, the present study investigates the efficiency of a composite adsorbent composed of chitosan an‎d acid-activated bentonite for the removal of nickel ions from synthetic wastewater. Chitosan beads, chitosan/bentonite composites, an‎d hydrochloric acid-activated chitosan/bentonite composites with an approximate size of 2 mm were eva‎luated in terms of mechanical strength, X-ray diffraction (XRD) patterns, microstructure using scanning electron microscopy (SEM), specific surface area, an‎d nickel adsorption under various concentrations an‎d pH conditions. Adsorption isotherms were analyzed for both chitosan beads an‎d the chitosan/bentonite composite. Additionally, adsorption thermodynamics an‎d kinetics were examined for the acid-activated chitosan/bentonite composite beads. The results revealed that the acid-activated chitosan/bentonite composite, prepared by dispersing bentonite suspension into a chitosan solution at a weight ratio of 2:1, exhibited a nickel adsorption efficiency of 93.7% an‎d an equilibrium adsorption capacity of 18.72 mg/g. These values represent a 14.3% an‎d 17% improvement, respectively, compared to the pure chitosan beads. Activation of bentonite with hydrochloric acid an‎d intercalation of chitosan between the montmorillonite layers led to an increase in the basal spacing of the (001) planes, enhancing both the porosity an‎d specific surface area of the composite beads by 80.3% relative to chitosan beads. The average pore size of the composite was approximately 31 nm, placing it within the mesoporous material category. SEM images of the composite beads containing adsorbed nickel demonstrated smooth surfaces, an‎d elemental mapping confirmed the presence of nickel. Among the Langmuir, Freundlich, an‎d Temkin isotherm models, the Freundlich model showed the best fit with the experimental data of the composite beads. The Freundlich constant (Kf) for the composite exhibited an approximately 177% increase compared to the chitosan beads, with a maximum theoretical adsorption capacity (qm) of 52.63 mg/g an‎d an experimental equilibrium capacity (qe) of 18.72 mg/g. Based on the pseudo-second-order kinetic model, the rate constant (k₂) was found to be 17.6 × 10⁻⁴ g·mg⁻¹·min⁻¹ an‎d the calculated qe was 20.79 mg/g. Overall, the findings indicate that the aim of this study to develop an acid-activated chitosan/bentonite composite with superior adsorption performance compared to pure chitosan beads was successfully achieved.

مهره كيتوسان , مهره كيتوسان/بنتوينت , بنتونيت فعال‌شده با اسيد , جذب يون نيكل , ايزوترم‌هاي جذب , سينتيك جذب

Chitosan beads , Chitosan/bentonite beads , Acid-activated bentonite , Nickel ion adsorption , Adsorption isotherms , Adsorption kinetics

Amir Mohammad Naghizadeh

Dr. Majid Hoseinzadeh