Adsorption of Norfloxacin by Titanium-Doped Mesoporous Bioactive Glass: Kinetics, Isotherms, Thermodynamic and Regenerable Studies

Abstract—A series of Titanium-doped mesoporous bioactive glass with different Si-Ca ratios (MBG-Ti-1– MBG-Ti-5) were prepared by the sol-gel method. These materials were used to adsorb Norfloxacin (NOR) pollutant from aqueous solution. The morphology, microstructure and chemical properties of MBG-Ti-3 were characterized by transmission electron microscopy (TEM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The N₂ adsorption-desorption isotherm and pore size distribution of MBG-Ti-3 were investigated by the Brunauer–Emmett–Teller (BET) method and Barret–Joyner–Halenda (BJH) method. The specific surface of MBG-Ti-3 was 126.68 m²/g and the pore size was about 15 nm. The effect of time, initial concentration, pH and temperature on the adsorption of NOR were investigated. The maximum adsorption efficiency was 68% at 30°C, pH 8.0. Moreover, adsorption of NOR onto MBG-Ti-3 could be well fitted with the pseudo-first-order model and the pseudo-second-order model. Furthermore, adsorption was spontaneous, exothermic process of reduced entropy by analyzing thermodynamic model. Through the analysis of adsorption model, plausible adsorption mechanism was proposed. MBG-Ti-3 exhibited better adsorption efficiency after recycle 3 times. Additionally, bioactive glass was eco-friendly attribute to biological suitability which could not cause secondly pollution for aquatic environment. As an environmentally friendly adsorbent, Titanium-doped mesoporous bioactive glass showed promising potential application in NOR antibiotics removal from aquatic environment.