Effect of Thermal Activation of Iranian Bentonite on Nickel Adsorption Properties from Synthetic Wastewater by Chitosan/Bentonite Composite

Naghizadeh, Amirmohammad; Hosseinzadeh, Majid; Rezaei, Hamidreza

doi:10.30501/acp.2026.580021.1191

Effect of Thermal Activation of Iranian Bentonite on Nickel Adsorption Properties from Synthetic Wastewater by Chitosan/Bentonite Composite

Document Type : Original Research Article

Authors

Amirmohammad Naghizadeh ¹

Majid Hosseinzadeh ²

Hamidreza Rezaei ³

¹ MS Student, Department of Civil Engineering, Iran University of Science and Technology, Tehran, Iran.

² Assistant Professor, Department of Civil Engineering, Iran University of Science and Technology, Tehran, Iran.

³ Professor, Department of Materials and Metallurgical Engineering, Iran University of Science and Technology, Tehran, Iran.

10.30501/acp.2026.580021.1191

Abstract

Contamination of water by heavy metals and organics is a critical environmental issue, with adsorption being a key remediation strategy. Effective adsorbents include clays, zeolites, and biopolymers like chitosan. Chitosan excels at capturing metal cations, but its performance in acidic media, mechanical strength, and immersion behavior can be enhanced through compositing with other materials, such as bentonite. This study synthesized composite beads from chitosan and thermally activated bentonite. A 1.5% (w/v) chitosan solution in 2% acetic acid was mixed with bentonite suspensions at weight ratios of 3.75%, 7.5%, and 15% (w/v). The mixtures were dropwise introduced into an alkaline NaOH solution (pH 7-8) and solidified for 24 hours. Adsorption performance was evaluated using nickel solutions (40-100 ppm). The composite with a chitosan-to-bentonite ratio of 2:1 (CSB2) demonstrated optimal results, achieving 90.4% nickel removal and a capacity of 18.42 mg/g at an initial Ni²⁺ concentration of 80 ppm. This represents a 6.9% improvement in removal efficiency and an 8.9% increase in capacity compared to pure chitosan beads. Fourier-transform infrared spectroscopy (FTIR) confirmed the formation of Ni(RNH₂)₂⁺ complexes within the beads. Adsorption isotherm analysis indicated that the Freundlich and Temkin models best fit the experimental data. Freundlich parameters (Kf = 1.77 mg/L, 1/n = 0.909) confirmed multilayer adsorption on heterogeneous sites with linearly decreasing energy as adsorbate thickness increased. This composite shows enhanced potential for efficient nickel removal from wastewater.

Keywords

Thermally Activated Bentonite

Chitosan/Bentonite Composite

Freundlich Isotherm Model

Nickel-Chitosan Complex

Adsorbent Beads

Subjects

Composites

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