Alginate-based nanocomposite hydrogel beads incorporating graphene oxide and magnetic CoMnFeO₄ nanoparticles for pirimicarb adsorption.

This study introduces novel magnetic nanocomposite-hydrogel beads composed of alginate (Alg), graphene oxide (GO), and CoMnFeO₄ nanoparticles for the efficient adsorption of Pirimicarb (a carbamate pesticide) from water. The beads were synthesized via ionotropic gelation and optimized using Response Surface Methodology (RSM) with a Box-Behnken design, achieving a predicted maximum adsorption capacity of 196 mg/g. Characterization through FT-IR, XRD, SEM, and VSM confirmed the successful integration of components, revealing enhanced surface functionality, magnetic properties, and porosity. Batch adsorption studies, optimized via Central composite design (CCD), yielded 99.28% removal under conditions of pH 7.69, 18.02 mg/L initial concentration, 1.06 g/L dosage, and 49.76 min contact time. Isotherm analysis favored the Freundlich model (R2 = 0.990), indicating heterogeneous multilayer adsorption, while kinetics followed the double-exponential model (R2 = 0.990), suggesting a two-stage diffusion process. Thermodynamic parameters (ΔH° = -100.275 kJ/mol, ΔS° = -297.34 J/mol·K) confirmed an exothermic, spontaneous physisorption-dominated mechanism. The beads exhibited excellent reusability over six cycles (retaining >80% efficiency with ethanol desorption) and robust performance in river water (89.7% removal). The synergistic roles of alginate's hydrogen bonding, GO's π-π stacking, and CoMnFeO₄'s magnetic separability position these beads as a promising adsorbent for pesticide remediation in environmental applications.