Hybrid Materials Based on Protein-Modified Nano-Aluminum Hydroxide for Efficient Oxytetracycline Removal: Mechanism Insights

This study focuses on developing novel materials based on lysozyme, a protein derived from egg white, modified with aluminum hydroxide nanoparticles (γ-Al(OH)₃ and α-Al(OH)₃) via an adsorption technique to enhance oxytetracycline antibiotic (OTC) removal from water systems. The optimal parameters for lysozyme adsorption on both phases of Al(OH)₃ were determined to be a pH of 10, a contact time of 120 min, an Al(OH)₃ dosage of 10 mg/mL, and an ionic strength of 1 mM KCl. For OTC removal using lysozyme-modified γ-Al(OH)₃ (LGH) and α-Al(OH)₃ (LAH), the optimum conditions were identified as a pH of 6, an adsorbent dosage of 10 mg/mL, and a contact time of 90 min. The adsorption kinetics of OTC on both materials adhered to the pseudo-second-order model, while the Freundlich model provided the best fit for the adsorption isotherms. The LGH demonstrated a higher OTC adsorption capacity of 62.9 mg/g compared to LAH with 45.7 mg/g. The adsorption mechanism for OTC on LGH was primarily driven by nonelectrostatic interactions, whereas electrostatic forces predominantly governed OTC adsorption on LAH. Even after four regeneration cycles, the OTC removal efficiencies remained above 70.5% for LGH and 87.9% for LAH. These findings highlight that both lysozyme-modified aluminum hydroxides are environmentally friendly and highly effective materials for removing OTC from aquatic environments.