<p>The current study shows the synthesis of a novel sodium alginate-derived hydrogel (SMNA hydrogel) from acrylamide (AAm) and maleic acid (MA) monomers and of N,N-methylenebisacrylamide (MBA) crosslinker through free-radical graft copolymerization. Three grades of SMNA hydrogel were synthesized in all, viz., SMNA G-1, SMNA G-2, and SMNA G-3 hydrogels. The hydrogel has been characterized using analytical techniques such as FTIR (Fourier-transform infrared) spectroscopy, GPC (gel permeation chromatography), TGA (thermogravimetric analysis), point of zero charge (ΔpH_PZC) analysis, X-ray diffraction (XRD) analysis, and SEM (scanning electron microscopy). The synthesized hydrogel has been used to remove Cu²⁺ and Co²⁺ ions from synthetic wastewater. The swelling ratios and water retention properties have been studied for the hydrogel, and among the three grades, SMNA G-2 hydrogel demonstrated maximum swelling ratios of 225.86, 247.55, and 268.54&#xa0;g/g in gray wastewater, tap water, and distilled water, respectively. The removal efficiencies of 96.38% for Cu²⁺ and 94% for Co²⁺ ions were achieved with maximum adsorption capacities of 568.54&#xa0;mg/g for Cu²⁺ and 342.42&#xa0;mg/g for Co²⁺ ions by SMNA G-2 hydrogel. Further experiments were performed by varying adsorbent dosage, pH, time of contact, temperature, and concentration. Adsorption data were best described by the Langmuir isotherm model and kinetic studies revealed that the adsorption process follows a pseudo-second-order kinetic model. Thermodynamic analysis showed negative <i>ΔG</i> values, indicating a spontaneous adsorption process. The SMNA G-2 hydrogel also exhibited excellent desorption efficiency, with 97.51% for Cu²⁺ and 94.92% for Co²⁺ ions, and maintained its reusability for five consecutive adsorption–desorption cycles. SMNA hydrogel demonstrates high efficiency, cost-effectiveness, ease of use, low energy requirements, and significant potential for treating wastewater containing heavy metal ions.</p>