Adsorption behavior and mechanism of Cu(II) by sodium alginate/ carboxymethylcellulose/magnesium hydroxide (SC-MH) hydrogel

In the present work, an environmentally-friendly, reusable hydrogel ball characterized by its great adsorption capacity to Cu(II) was synthesized. The preparation of this hydrogel drew on sodium alginate (SA) and carboxymethyl cellulose (CMC) as primary composition elements. The endeavor brought novelty by ingeniously infusing it with slurry magnesium hydroxide (MH). The factors (pH, SC-MH amount, initial concentration, adsorption time) that are critical to adsorption were also investigated. FTIR, SEM-EDS and XPS were used to reveal the adsorption mechanism of Cu on SC-MH. The results show that the surface of SC-MH is rough, and there are a large number of gully-like structures conducive to adsorption, which are rich in hydroxyl and carboxyl groups. Under the optimum conditions, the maximum adsorption capacity reached 215.68 mg/g. Based on its high R2 value (0.999), the Langmuir model is determined to be the most appropriate for describing the adsorption behavior, indicating monolayer homogeneous adsorption. The kinetic data align well with the pseudo-second-order kinetic model. Furthermore, thermodynamic analysis reveals the adsorption process to be spontaneous and endothermic, as demonstrated by a negative Delta G and positive Delta H (38.8859 KJ/mol). The mechanism involves electrostatic attraction, chelation, Mg(OH)2 adsorption and ion exchange.