Plant-Assisted Synthesis of α-Fe₂O₃@Chitosan Nanocomposite for Highly Efficient Removal of Oxytetracycline from Aqueous Solution.

This work describes the production of α-Fe₂O₃@Chitosan (α-Fe₂O₃@Cs) composite using a simple plant-assisted route for the effective removal of oxytetracycline (OTC) from water. The formation of the hexagonal α-Fe₂O₃ phase with a 60 nm particle size, reduced to ≈27 nm after the CS addition, has been revealed by the XRD data. The purity of the samples and their composition of Fe, O, C, and N were proved by the EDX and XPS analyses, and the TEM indicated the anchoring of the α-Fe₂O₃ to the CS matrix. The adsorption study findings showed that OTC adsorption followed the pseudo-second-order (PSO) kinetic model and was well described by the Langmuir isotherm, indicating a chemisorption mechanism involving monolayer adsorption on energetically equivalent active sites of the composite. Batch tests demonstrated a peak OTC adsorption capacity of 185.9 mg/g at an optimum pH of 7. The impact of concurrent ions, including Na⁺, K⁺, Ca²⁺, Cu²⁺, NO₃⁻, and S₂O₃²⁻ revealed a competitive effect of the anions. The regeneration trials exhibited the composites' excellent reusability during five successive cycles. A potential adsorption mechanism for OTC elimination by the α-Fe₂O₃@CS composite, involving hydrogen bonding, n-π interactions, and complexation, was proposed. The outcomes establish a strong basis for utilizing plant extract-synthesized composites in the environmental cleanup of pharmaceutical contaminants. These findings highlight the potential of this composite for scalable wastewater treatment and pharmaceutical contaminant remediation.