Tetracycline Adsorption from Aqueous Media by Magnetically Separable Fe3O4@Methylcellulose/APTMS: Isotherm, Kinetic and Thermodynamic Studies

Abstract

This study aimed to synthesize Fe3O4@Methylcellulose/3-Aminopropyltrimethoxysilane (Fe3O4@MC/APTMS) as a new magnetic nano-biocomposite by a facile, fast, and new microwave-assisted method and to be utilized as an adsorbent for tetracycline (TC) removal from aqueous solutions. Fe3O4@MC/APTMS was characterized by Fourier transform-infrared (FTIR), Field emission scanning electron microscopy (FESEM), Energy dispersive spectroscopy (EDS), Mapping, X-ray diffraction (XRD), Thermal gravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) and vibrating sample magnetometer (VSM). The point of zero charge (pHzpc) value of the nano-biocomposite was estimated to be 6.8 by the solid addition method. Optimum conditions were obtained in TC concentration: 10 mg L−1, adsorbent dosage: 80 mg L−1, contact time: 90 min, and solution pH 6 with the maximum TC removal of 90% and 65.41% in synthetic and actual samples, respectively. The kinetic and isotherm equations pointed to a pseudo-second order kinetic and Langmuir isotherm optimum fitting models. Based on the values of entropy changes (ΔS) (50.04 J/mol k), the enthalpy changes (ΔH) (9.26 kJ/mol), and the negative Gibbs free energy changes (ΔG), the adsorption process was endothermic, random, and spontaneous. The synthesized adsorbent exhibited outstanding properties, including proper removal efficiency of TC, excellent reusability, and simple separation from aqueous media by a magnet. Consequently, it is highly desirable that Fe3O4@MC/APTMS magnetic nano-biocomposite could be used as a promising adsorbent for TC adsorption from aqueous solutions.