Presentation: 2025 ND EPSCoR Annual conference 

October 21, 2025, NDSU Memorial Union, Fargo, North Dakota

Sustainable Removal of Phosphate from Water Using Iron–Chitosan Composite

Phosphorus-driven eutrophication creates serious environmental and economic challenges. In this study, iron–chitosan composite beads (FeCSB) were synthesized as eco-friendly adsorbents for phosphate removal from water. The Taguchi analysis identified pH, contact time, and initial phosphate concentration as key factors. Response surface methodology showed interaction effects and optimal removal conditions. The optimal FeCSB removed 90-97% phosphate within 120-180 min from waters containing 100 µg P/L to 5 mg P/L. The beads showed a maximum adsorption capacity of 57.75 mg/g at neutral pH, which increased to 117.66 mg/g at pH 2. The adsorption process followed the Freundlich isotherm and the pseudo-second-order kinetic model. The point-of-zero-charge was determined to be 6.8. Electrostatic interaction, complexation, and intra-particle diffusion were identified as the main mechanisms for phosphate removal. XPS analysis confirmed both inner-sphere Fe–O–P bonding and outer-sphere interactions involving Fe–OH and amine groups. The FTIR data supported these observations with spectra showing P–O stretching vibrations and shifts in OH and NH2 bands. EDX mapping verified phosphate incorporation into the FeCSB structure. The addition of glutaraldehyde (GA) as a crosslinker improved the beads’ mechanical strength and reusability over multiple cycles. Overall, the beads are robust and versatile with potential use for eutrophic water restoration and wastewater treatment.