Efficient selective adsorption of Cu2+ and Cd2+ by poly(hydroxyethyl methacrylate) polymer modified by polyfunctional groups

A novel polyfunctional group-modified poly(hydroxyethyl methacrylate) polymer, termed PFG-PHEMA, was synthesized for adsorption of Cu 2+ and Cd 2+ . Material characterization confirmed that the surface functional groups facilitated efficient adsorption of these ions. pH optimization experiments demonstrated that the adsorption capacities of Cu 2+ and Cd 2+ , reaching 162.2 and 150.3 mg·L −1 respectively, were maximized at a pH of 5, with an initial heavy metal concentration of 200 mg·L −1 . Kinetic and isotherm studies indicated that the adsorption process conformed to a monolayer, homogeneous, and chemisorption model, achieving equilibrium within 60 min. The maximum adsorption capacities were determined to be 500 mg·g −1 for Cu 2+ and 384.6 mg·g −1 for Cd 2+ . Competitive adsorption experiments showed that PFG-PHEMA exhibited superior selectivity for Cu 2+ over other metal ions. This selectivity was corroborated by X-ray photoelectron spectroscopy (XPS) analysis, which identified the sulfhydryl group as the crucial functional moiety responsible for Cu 2+ selectivity. Furthermore, the presence of low concentrations of fulvic acid (FA) enhanced adsorption via ternary complex formation, whereas higher concentrations impeded adsorption by forming FA-metal complexes that competed with the polymer. Overall, the strategic incorporation of multiple functional groups into PFG-PHEMA conferred a high adsorption capacity for Cu 2+ and Cd 2+ . The analysis further indicated that sulfhydryl groups exhibit high selectivity toward Cu 2+ , whereas amine and oxygen-containing groups preferentially bind to Cd 2+ , reinforcing the potential of PFG-PHEMA as a highly effective adsorbent for heavy metals.