Two Birds with One Stone: Fe/CS/CMSM Composite Membrane for the Removal of Pb(II) and Cr(VI)

With the rapid development of urban industrialization, heavy metal pollution has had serious impacts on human health and the environment. In response, this study introduces an iron-modified chitosan/carboxymethyl Salix powder composite membrane (Fe/CS/CMSM) for the adsorption of hazardous substances from water. The main findings are as follows. Fe/CS/CMSM exhibited optimal adsorption capacities for Pb²⁺ and Cr(VI), which were 377.49 and 367.10 mg g^-1, respectively. The processes of adsorption of Pb²⁺ and Cr(VI) by Fe/CS/CMSM fit the pseudo-second-order kinetic model and the Freundlich isotherm model, indicating that the adsorption is consistent with chemisorption on heterogeneous sites. Adsorption thermodynamics indicated that the adsorption process is spontaneous and exothermic and associated with a decrease in disorder. Additionally, the rates of desorption of Pb²⁺ and Cr(VI) from Fe/CS/CMSM reached 90.32% and 92.35%, respectively. After five adsorption-desorption cycles, the rates of desorption of Pb²⁺ and Cr(VI) remained above 80%, demonstrating the good reusability of Fe/CS/CMSM. This study presents an iron-modified chitosan/carboxymethyl Salix mongolica powder composite membrane, showcasing its efficiency and practicality in the adsorption of Pb²⁺ and Cr(VI).