Magnetic chitosan-based biosorbents for phosphorus removal from wastewater: adsorption properties and mechanistic insights

To address the critical challenge of phosphorus pollution in surface waters, this study develops two chitosan-based magnetic biosorbents (denoted as Ce@mCS and Zr@mCS) for the efficient removal of phosphorus from wastewater. The biocomposites were engineered to provide a sustainable and high-performance solution, circumventing the limitations of existing phosphorus removal strategies. The successful fabrication of the biocomposites, including the incorporation of magnetic components (Fe 3 O 4 ) and dispersion of Ce/Zr active centers (i.e., CeCO₃OH, ZrO₂) with the chitosan scaffolds, was rigorously confirmed through SEM, XRD, XPS, FTIR, and zeta potential analyses. Batch adsorption experiments were carried out to optimize key parameters, yielding removal efficiencies of 88.3% for Ce@mCS and 85.7% for Zr@mCS ( C ₀ = 25 mg L −1 , dosage = 0.5 g L −1 , T  = 298 K, t  = 8 h). The adsorption isotherm data were best described by the Langmuir model, indicating monolayer adsorption with maximum capacities of 62.23 mg g −1 for Ce@mCS and 45.07 mg g −1 for Zr@mCS. Recycling performance analysis confirms the excellent capacity retention of both biocomposites over five consecutive cycles, validating their high practical potential promise. Post-adsorption characterization reveals that the mechanism for P capture lies in ligand exchange, Coulombic attraction, and H-bonding. This work exemplifies chitosan-based magnetic biocomposites for phosphate removal and underscores the promise of tailored biosorbents, providing a viable path for sustainable wastewater remediation and management.