Simultaneous Adsorption of Ampicillin and Lead by a Highly Stable UiO-66-NH₂/TiO₂ Nanocomposite from Water: Mechanism, Kinetics, Equilibrium, Thermodynamics, and Regeneration Studies

A zirconium-based metal–organic framework (UiO-66-NH2) was fabricated, which was then hybridized with TiO2. The synthesized adsorbent was utilized for the adsorption of ampicillin (AMP) and lead (Pb(II)) from an aqueous solution. The main characterization analyses including Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), N2 adsorption/desorption isotherms, thermogravimetry (TG), energy-dispersive spectroscopy (EDS), elemental mapping, transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM), water contact angle, and XPS affirmed the correctness of the adsorbent synthesis. The nanocomposite UiO-66-NH2/TiO2 had a high crystallinity, high surface area (1050 m2/g), and high stability up to 600 °C. Adsorption experiments were performed to explore different parameters affecting adsorption. The results revealed the fast kinetics of this adsorbent. The majority of AMP and Pb(II) was adsorbed in 30 min, and pseudo-second-order kinetic model had a better agreement with the empirical data (R2 ≥ 0.993). Furthermore, the Langmuir isotherm (R2 ≥ 0.987) better fitted the data compared to the Freundlich isotherm (R2 ≥ 0.920). The maximum adsorption capacity of 625.7 mg/g was gained for AMP and 769.2 mg/g for Pb(II) (pH 7 ± 0.1 and T = 300 ± 1 K), which were 1.3 and 1.5 times greater, compared to the pristine UiO-66-NH2. Furthermore, the thermodynamic study demonstrated that the adsorption process of AMP/Pb(II) by UiO-66-NH2/TiO2 is spontaneous and exothermic. The high adsorption is allocated to the high surface area, large number of active sites, hydrogen bonding, hydrophobic forces, electrostatic interactions, and π–π interactions. Finally, the adsorbent had acceptable reusability in five regeneration cycles. With its sustainable and easy fabrication, remarkable adsorption performance, and excellent regeneration capability, UiO-66-NH2/TiO2 emerges as a highly effective adsorbent for industrial wastewater treatment applications.