CuO-modified chitosan beads: An efficient adsorbent for nitrate ion removal from aqueous solution for industrial applications

Nitrate contamination in water sources, primarily due to excessive fertilizer use and agricultural runoff, poses serious environmental and health risks. In this study, CuO-modified chitosan beads were developed as a sustainable, cost-effective, and eco-friendly adsorbent for efficient nitrate ion removal from aqueous solutions. Chitosan, a naturally derived biopolymer, was reinforced with varying concentrations of copper oxide nanoparticles (5 %, 25 %, and 50 % in wt %) to enhance active adsorption sites for nitrate ions. The synthesized beads were characterized using XRD, FTIR, and SEM-EDS to confirm structural parameters, functional groups, and surface morphology. The nitrate ion adsorption was a pH-dependent process with pH_PZC at 7.0. The highest nitrate ion adsorption efficiency was achieved at pH 4 of 93.85 % with an adsorption capacity of 9.16 mg/g for Chitosan beads with 25 % CuO. Under neutral pH, the nitrate ion adsorption efficiency was ∼82.2 % with an adsorption capacity of 8.2 mg/g. The isotherm and kinetic analysis revealed a combination of chemisorption at low concentrations (pseudo-second-order) and physisorption at higher concentrations (pseudo-first-order), with the Temkin model (R² = 0.97) indicating the decreasing adsorption energy on heterogeneous surface. FTIR analysis after nitrate ion adsorption confirmed the involvement of surface functional groups in the nitrate adsorption process. These results demonstrate that CuO-modified chitosan beads are effective, eco-friendly adsorbents for nitrate ion removal from water.