Fixed-bed adsorption studies using chitosan-coated bentonite (CCB) as adsorbent media were investigated for the simultaneous adsorption of Pb(II), Cu(II), and Ni(II) from a multimetal system. The effects of operational parameters such as bed height, flow rate, and initial concentration on the length of mass transfer zone, breakthrough time, exhaustion time, and adsorption capacity at breakthrough were evaluated. With increasing bed height and decreasing flow rate and initial concentration, the breakthrough and exhaustion time were observed to favorably increase. Moreover, the adsorption capacity at breakthrough was observed to increase with decreasing initial concentration and flow rate and increasing bed height. The maximum adsorption capacity at breakthrough of 13.49 mg/g for Pb(II), 12.14 mg/g for Cu(II), and 10.29 mg/g for Ni(II) was attained at an initial influent concentration of 200 mg/L, bed height of 2.0 cm, and flow rate of 0.4 mL/min. Adsorption data were fitted with Adams-Bohart, Thomas, and Yoon-Nelson models. Experimental breakthrough curves were observed to be in good agreement (R2>0.85andE%<50%) with the predicted curves generated by the kinetic models. This study demonstrates the effectiveness of CCB in the removal of Pb(II), Cu(II), and Ni(II) from a ternary metal solution.

In this study, the removal of Cu(II), Ni(II), Pb(II), and Zn(II) from aqueous solution in single and multi-metal system using chitosan-coated montmorillonite (ChiMC) beads was investigated. The non-crosslinked and crosslinked ChiMC beads were characterized using SEM–EDX, Fourier transform infrared, and Brunauer, Emmett, and Teller analysis. The effect of ionic strength and pH on the adsorption capacity and percent (%) removal of ChiMC was examined. Kinetic studies revealed that adsorption using ChiMC follows the pseudo-second-order equation with high correlation coefficient values (R² > 0.95). The equilibrium data were correlated with Langmuir and Freundlich isotherm models, where crosslinked ChiMC provided higher maximum adsorption capacity over ChiMC. The calculated Langmuir adsorption capacities for Cu(II), Ni(II), Pb(II), and Zn(II) using ChiMC in single-metal system are 13.04, 12.18, 29.85, and 13.50 mg/g, respectively. An increase in the calculated adsorption capacities derived from Langmuir isotherm was observed in multi-metal system, indicating a synergistic effect. The adsorption capacity in single- and multi-metal system followed the order: Pb(II) > Cu(II) > Zn(II) > Ni(II). The kinetic rate and adsorption capacity of the four metals were observed to increase in multi-metal systems. The removal of Cu(II), Ni(II), Pb(II), and Zn(II) from groundwater by adsorption onto ChiMC was also investigated.

In this study, fixed-bed adsorption of Pb(II) from an aqueous solution using chitosan-coated bentonite (CCB) was investigated. Characterization of CCB was performed using Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The effects of varying bed height (1.3 to 4.3 cm), flow rate (0.20 to 0.60 mL/min), and initial concentration (500 to 1500 mg/L) on the length of mass transfer zone (Z_m) and adsorption capacity at breakthrough (q_b) and exhaustion (q_e) were examined. Low flow rate and high bed height were determined to cause a longer time to reach breakthrough and exhaustion. Meanwhile, the fixed-bed system was observed to quickly attain breakthrough and exhaustion under high initial concentrations. Kinetic column models such as the Thomas, Yoon–Nelson, and Clark models were used to predict the breakthrough curves. High R² values (0.9758 ≤ R² ≤ 0.8087) were attained for the Thomas model, which indicates that there is good agreement between experimental data and linear plots generated by the Thomas model. Moreover, the Thomas model is best in describing the breakthrough curves of Pb(II) removal under a fixed-bed system.

In the present research, treatment of contaminated groundwater via adsorption of As(V) with an initial concentration of 50.99 µg/L using chitosan-coated bentonite (CCB) was investigated. The effect of adsorbent mass (0.001 to 2.0 g), temperature (298 to 328 K), and contact time (1 to 180 min) on the removal efficiency was examined. Adsorption data was evaluated using isotherm models such as Langmuir, Freundlich, and Dubinin-Radushkevich. Isotherm study showed that the Langmuir (R² > 0.9899; χ² ≤ 0.91; RMSE ≤ 4.87) model best correlates with the experimental data. Kinetics studies revealed that pseudo-second order equation adequately describes the experimental data (R² ≥ 0.9951; χ² ≤ 0.8.33; RMSE ≤ 4.31) where equilibrium was attained after 60 min. Thermodynamics study shows that the As(V) adsorption is non-spontaneous (ΔG⁰ ≥ 0) and endothermic (ΔH⁰ = 8.31 J/mol) that would result in an increase in randomness (ΔS⁰ = 29.10 kJ/mol•K) within the CCB-solution interface. FT-IR analysis reveals that hydroxyl and amino groups are involved in the adsorption of As(V) from groundwater. Results of the present research serve as a tool to determine whether CCB is an environmentally safe and cost effective material that could be utilized in a permeable reactive barrier system for the remediation of As(V) from contaminated groundwater.