Efficient removal of tetracycline from wastewater using chitosan-based aerogels functionalized with natural zeolite, Fe₃O₄, and MOF-808

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• Adsorbents: CS aerogel, CS/N-zeolite, and CS/N-zeolite/Fe₃O₄/MOF-808 were used. • Highest TC removal: 99.11 % by CS/N-zeolite/Fe₃O₄/MOF-808 at optimal conditions. • Adsorption followed Langmuir isotherm and showed favorable monolayer behavior. • Kinetics fit both PFO and PSO; α value was highest for the nanocomposite (6.002 mg/g·min). • Nanocomposite retained >90 % efficiency after 7 reuse cycles with minimal Fe/Zr leaching. In this study, chitosan (CS) aerogel, a CS/N-zeolite composite, and a magnetic nanocomposite (CS/N-zeolite/Fe₃O₄/MOF-808) were developed as efficient, eco-friendly adsorbents for tetracycline (TC) removal from pharmaceutical wastewater. Structural analysis confirmed successful synthesis, with surface areas of 5.908, 13.708, and 31.873 m²/g. XRD verified incorporation of MOF-808, N-zeolite, and Fe₃O₄ into the CS matrix. Under optimized conditions (pH 7, 50 °C, 10 mg/L TC, adsorbent doses of 2, 1.25, and 1 g/L, contact times of 90, 70, and 50 min), maximum TC removal rates were 98.94 %, 98.65 %, and 99.11 %, respectively. Thermodynamics indicated spontaneity and endothermic behavior, with negative Gibbs free energy and positive enthalpy values (26.326, 22.346, and 52.852 kJ/mol). Kinetic models fit well (R² > 0.95) to both pseudo-first and pseudo-second order, implying physical and chemical adsorption. The nanocomposite showed the highest initial adsorption rate (α = 6.002 mg/g·min). Equilibrium data fit Langmuir isotherm, indicating favorable, mainly physical adsorption. Maximum adsorption capacities for CS aerogel, CS/N-zeolite, and magnetic nanocomposite were 12.63, 23.21, and 31.69 mg/g, respectively. Reusability tests showed stable performance over multiple cycles. The CS/N-zeolite/Fe₃O₄/MOF-808 nanocomposite is a durable, recyclable adsorbent for TC removal from pharmaceutical effluents.