Fabrication of a starch xanthate‐based reusable hydrogel for efficient removal of Co( <scp>II</scp> ) and Ni( <scp>II</scp> ) from wastewater

Abstract The elimination of harmful metal contaminants from wastewater remains a significant environmental challenge, necessitating the development of efficient and sustainable adsorbents. In this study, a starch xanthate‐based hydrogel (St@XA‐NH) was synthesized via free radical polymerization of N , N ‐dimethylacrylamide and 2‐hydroxyethyl methacrylate onto starch xanthate. The synthesized hydrogel was used for eliminating heavy‐metals from synthetic wastewater and was characterized using various techniques such as UV, FTIR, XRD, TGA, BET, and pH PZC analysis, confirming the formation of a porous three‐dimensional network with active binding sites. The St@XA‐NH‐2 hydrogel exhibited high swelling ratios of 245.78, 286.54, and 320.5 g/g in gray wastewater, tap‐water, and distilled water, respectively, after 670 min. For the St@XA‐NH‐2 hydrogel, water retention ratios were 85.99%, 83%, and 80.54% in gray, tap, and distilled water, respectively. The optimized adsorption studies revealed maximum removal efficiencies of 91.99 (±2.19) % for Co (II) and 89.33 (±1.93) % for Ni (II) ions, corresponding to maximum adsorption capacities (q m ) of 566.37 (±28.69) and 546.98 (±12.32) mg/g, respectively. Kinetic data followed the pseudo‐second‐order model, while equilibrium behavior was best described by the Langmuir and Redlich–Peterson isotherms, suggesting monolayer adsorption. Mechanistic analysis indicated that adsorption occurs through coordination, electrostatic interactions, and hydrogen bonding involving hydroxyl, amino, and xanthate groups. The hydrogel maintained high adsorption performance across five successive adsorption–desorption cycles, with efficiencies of 86.67% for Co (II) and 79.88% for Ni (II), demonstrating reusability and practical applicability. The synthesized St@XA‐NH‐2 hydrogel emerges as an efficient and eco‐friendly material for the adsorption‐based purification of metal‐ion contaminated water.