Magnetic Graphene Oxide/ NiO /Alginate Composite: Enhanced Adsorption Performance and Mechanistic Insights for Cationic Dye Removal

A novel ternary composite of magnetic graphene oxide (MGO), nickel oxide (NiO) nanoparticles, and sodium alginate (ALG) has been synthesized and evaluated for the adsorption elimination of malachite green (MG) and methylene blue (MB) cationic dyes from water. The composite was synthesized through the coprecipitation and ionic crosslinking of gel beads, and then milled into a powder to enhance the surface accessibility. Characterization of structural and physicochemical properties was performed using Fourier Transform Infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy‐dispersive X‐ray spectroscopy (EDS), and Brunauer–Emmett–Teller (BET)/Barrett–Joyner–Halenda (BJH) analysis. The systematic adsorption trials were conducted over a broad pH range (3–11), varying adsorbent doses (0.01–0.02 g per 25 mL; 0.4–0.8 g/L), initial dye concentrations (10–40 mg/L), contact durations (0–30 min), and temperature (25°C–45°C). The composite MGO/NiO/ALG demonstrated the greatest removal efficiencies of 94.87% and 79.11% for MG and MB, respectively, using only 0.01 g of the adsorbent per 25 mL of solution at pH 7 within 30 mins. The Freundlich isotherm model provided the best description of the adsorption equilibrium, yielding R 2 values of 0.956 and 0.929 for MG and MB, respectively, suggesting multilayer adsorption on a diverse surface. The pseudo‐second‐order kinetic model demonstrated the best fit for both MB and MG ( R 2 = 0.986 and 0.933, respectively). The maximum adsorption capacities according to Langmuir (112.5 mg/g (MG) and 127.7 mg/g (MB)) are reported here for comparative purposes with prior literature, though Freundlich remains the mechanistically preferred model. Following six continuous regeneration cycles, the composite achieved over 84% removal efficiency. These results emphasize the combined influence of NiO and the capacity of the ALG matrix as an eco‐friendly biopolymeric support, demonstrating the potential of MGO/NiO/ALG for large‐scale applications in wastewater management.