Iron-doped UiO-66 for Rapid Removal of Tetracycline Antibiotic from Water

Tetracycline antibiotics (TC) contamination in aquatic media poses serious environmental and public health concerns, necessitating the development of efficient, sustainable, and robust adsorbents for wastewater treatments. In this study, iron-doped UiO-66 metal organic frameworks (Fe-UiO-66) were synthesized via a modulator-free solvothermal method, with Fe/Zr molar ratio varied from 0 to 1.5 to enhance tetracycline adsorption efficiency. Iron was selected as a less toxic and eco-friendly dopant able to enhance the textural properties of UiO-66. Comprehensive characterization using PXRD, BET, SEM, FTIR, XPS, and AAS confirmed successful Fe incorporation into the UiO-66 framework while preserving structural integrity at moderate doping level. Among the prepared MOFs, FeU1 (Fe/Zr:1) exhibited the optimal adsorption performance, achieving complete removal of TC within 7 min under optimized conditions ([TC] = 5 ppm, MOF dosage = 200 ppm, T = 60 °C, pH = 10). The maximum adsorption capacity of FeU1 reached 204 mg/g. Adsorption kinetics followed pseudo-second-order model, while equilibrium data were best described by the Langmuir isotherm. Thermodynamic analysis confirmed an endothermic and spontaneous adsorption process suggesting chemisorption as the dominant mechanism, supported by spectroscopic features consistent with coordination and hydrogen-bond interactions between TC and Fe-modified Zr nodes. The FeU1 adsorbent maintained its adsorption efficiency over six consecutive cycles, indicating excellent structural stability. These findings demonstrate that controlled Fe doping in modulator-free UiO-66 enhances performance mainly by generating defect-driven adsorption sites, establishing a sustainable and efficient platform for the rapid removal of antibiotics from aqueous systems.