Insight into copper and nickel adsorption from aqueous solutions onto carbon-coated-sand: Isotherms, kinetics, mechanisms, and cost analysis

This study investigated the use of carbon-coated-sand (CCS), as a more sustainable alternative to activated carbon (AC), for the removal of Ni²⁺and Cu²⁺ ions from an aqueous solution. The CCS was synthesized from sugar and sand without any additional binders and then activated using 0.1 M H₂SO₄ to form the modified version called MCSS. Activation increased the specific surface area by 15-folds from 0.409 (CCS) to 6.183 (MCCS) m²/g. Multi-linear regression was applied to evaluate the adsorption capacity as a function of three independent factors: pH of the solution; contact time; and initial concentration of the adsorbate. The optimum adsorption of Cu²⁺ and Ni²⁺ was achieved at pH 6.0 for both adsorbents. Activation enhanced the adsorption capacity by 68% for Cu²⁺and 54% for Ni²⁺. The adsorption behavior under different conditions was successfully modeled using multi-linear regression with high accuracy R² > 0.86 for CCS and R² > 0.96 for MCCS. Cost estimation provided encouraging evidence of the cost-effectiveness of CCS and MCCS compared to activated carbon. The results obtained in this study revealed that carbon-coating is a promising greener low-cost technique for water treatment.