Recyclable tannic acid modified magnetic nanoparticles for ciprofloxacin adsorption

The rapid expansion of human and industrial activities has intensified antibiotic consumption, such as Ciprofloxacin (CIP), leading to the release of resistant compounds into aquatic systems and posing significant human health and environmental risks. In this study, tannic acid-functionalized magnetite nanoparticles (TA/Fe₃O₄ NPs) were synthesized via chemical precipitation and evaluated as efficient, magnetically separable, and recyclable adsorbents for CIP removal. Structural and morphological features were confirmed by XRD, BET, and SEM-EDS analyses. Key operational parameters, including pH, contact time, initial CIP concentration, and adsorbent dosage, were systematically optimized using response surface methodology (RSM). Under optimized conditions (pH = 10.47, adsorbent dosage = 1.43 g/L, contact time = 89.4 min, initial CIP concentration = 2 mg/L), the maximum removal efficiency reached 87.43%. Equilibrium modeling indicated that the Langmuir isotherm (R² = 0.9922) best described the adsorption process, with a maximum capacity of 4.27 mg/g, suggesting uniform monolayer coverage of CIP molecules. Kinetic analysis revealed that the Elovich model (R² = 0.9775) provided the most accurate fit, consistent with heterogeneous active sites and a physicochemical adsorption mechanism. Reusability tests demonstrated only an 8% decline in efficiency after five adsorption-desorption cycles, confirming the material's stability and durability. Mechanistic insights highlighted the role of tannic acid's hydroxyl and carboxyl groups, hydrogen bonding, π-π interactions, coordination effects, and ternary Fe-TA-CIP complexes in facilitating adsorption. Overall, TA/Fe₃O₄ NPs represent a cost-effective, sustainable, and environmentally benign strategy for antibiotic removal from aqueous environments, offering strong potential for practical application.