Synthesis and adsorption performance of carboxyl-functionalized magnetic agarose gel microspheres for Cu(II) removal

Succinic anhydride modified magnetic agarose microspheres (SA-MAM) were synthesized to develop a novel, high-performance, and highly efficient adsorbent for heavy metal ions. Fe3O4 magnetic nanoparticles (MNPs) were prepared via chemical co-precipitation. Magnetic agarose microspheres (MAMs) with different particle sizes and fast magnetic separation rates were prepared using an emulsion embedding method. MAMs with high specific surface area (10 μm, MAM-10) and high magnetic responsiveness (125 μm, MAM-125) were surface functionalized with carboxyl groups by using succinic anhydride (SA) in a non-homogeneous system. The results demonstrated that SA-MAM-10 exhibited a maximum Cu(II) adsorption capacity of 128.8 mg/g. This value was 60.4% higher than that of MAM-10 (80.3 mg/g), approximately 67.1% higher than that of commercial Magarose-COOH (10–30 μm, 77.1 mg/g), and comparable with that of commercial Magarose-NH2 (10–30 μm, 133.1 mg/g). By contrast, SA-MAM-125 maintained high magnetic responsiveness while achieving a maximum adsorption capacity of 76.3 mg/g, which was 21.7% higher than that of MAM-125 (62.7 mg/g) and surpassed the performance of Magarose-COOH (30–150 μm, 66.7 mg/g). Complete separation was achieved within 3 s under the influence of an external magnetic field. Overall, these two types of MAMs exhibited excellent performance in removing Cu(II) from water, highlighting their potential as adsorbents for wastewater purification.