Green-synthesized Fe₃O₄/AC/zeolite nanocomposite for efficient tetracycline removal from real pharmaceutical wastewater

Tetracycline (TC), a commonly used antibiotic, frequently contaminates aquatic environments, raising concerns for ecological and public health due to its persistence and potential to promote antimicrobial resistance. In this study, a sustainable magnetic Fe₃O₄/activated carbon/zeolite (Fe₃O₄/AC/Zeo) nanocomposite was developed using Aloe vera extract to efficiently remove TC from synthetic solutions and real pharmaceutical wastewater. The nanocomposite was characterized using BET, SEM, FTIR, and XRD, confirming a high surface area (520.42 m 2 ·g −1 ), hierarchical porosity, and abundant surface functional groups. Process optimization using response surface methodology (RSM) with central composite design (CCD) identified pH and initial TC concentration as the most significant factors ( p < 0.0001). Within the experimental design range (adsorbent dosage: 0.2–1.0 g·L −1 ), optimal conditions were determined as pH 7, dosage 1.0 g·L −1 , temperature 35 °C, contact time 90 min, and initial TC concentration 100 mg·L −1 (85–87% removal). For practical pharmaceutical wastewater treatment, the dosage was strategically enhanced to 2.0 g·L −1 , achieving ~90% removal in synthetic solution and 82% in real wastewater under the same operational parameters. Kinetic studies revealed pseudo-second-order behavior (R 2 > 0.999), indicating rate-limiting surface interactions. Isotherm analysis showed favorable Langmuir monolayer adsorption with a maximum theoretical capacity of 80.65 mg·g −1 at 25 °C. Thermodynamic parameters indicated spontaneous (ΔG° = −2.26 to −0.25 kJ·mol −1 ) and exothermic (ΔH° = −22.34 kJ·mol −1 ) adsorption. The adsorption behavior is consistent with multiple interaction pathways, including electrostatic attraction, hydrogen bonding, π–π interactions, and possible coordination interactions. To the best of our knowledge, this is among the first studies to combine green Aloe vera –based synthesis with Fe₃O₄/AC/Zeo hybridization and application to real pharmaceutical effluent, highlighting its novelty and practical value. These findings demonstrate the potential of the developed nanocomposite as a cost-effective, magnetically recoverable, and environmentally sustainable solution for antibiotic-contaminated water. • Green synthesis using plant extract ( Aloe vera ) as a reducing and stabilizing agent. • High surface area (520.42 m 2 /g) and multi-mechanistic adsorption behavior. • ~90% removal in synthetic and 82% in real pharmaceutical wastewater. • Kinetics following pseudo-second-order model (R 2 > 0.999). • Thermodynamic validation of a spontaneous, exothermic, physisorption-dominated process. • Strong statistical optimization and model validation using RSM (R 2 = 0.9887).