Synthesis, characterization, and application of Fe₃O₄/PEG/HAp nanocomposite as an adsorbent for Pb(II)

This study presents the synthesis, characterization, and adsorption performance of a Fe₃O₄/PEG/HAp nanocomposite developed for the efficient removal of Pb2⁺ ions from aqueous solutions. The composite was fabricated through a co-precipitation and wet chemical method by integrating magnetite (Fe₃O₄), polyethylene glycol (PEG), and hydroxyapatite (HAp) to achieve a synergistic combination of magnetic recoverability, surface functionality, and structural stability. FTIR analysis confirmed the presence of Fe–O, PO₄3⁻, and C– O–C functional groups, verifying strong interfacial interactions among the components through coordination and hydrogen bonding. Adsorption experiments demonstrated optimal performance at a contact time of 12 hours, temperature of 25 °C, and adsorbent dosage of 0.1 g. The adsorption capacity decreased at elevated temperatures due to partial desorption and weakened electrostatic attraction, while higher adsorbent mass caused site overlapping and reduced surface efficiency. Kinetic data fitted well with the pseudo-second-order model (R2 = 0.9997), indicating chemisorption as the dominant mechanism. Thermodynamic parameters (ΔH° = 100.43 kJ mol⁻1, ΔS° = −3310 J mol⁻1 K-1) revealed an endothermic yet spontaneous process with decreased entropy at the solid–liquid interface. The Fe₃O₄/PEG/HAp nanocomposite showed excellent magnetic separability and reusability, retaining over 90 % of its adsorption capacity after multiple cycles. These findings highlight its potential as an eco-friendly, regenerable, and efficient adsorbent for Pb2⁺ removal.