[Synthesis of Magnetic Metal Organic Framework Fe3O4@NH2-MIL-53 (Al) Materials and Application to the Adsorption of Lead].

Metal organic framework, a novel class of organic inorganic hybrid functional materials, has been widely used in the fields of gas adsorption, catalysis, separation, and biological medicine due to its large specific surface area, diverse structural, and adjustable channel. In this work, a new amine-functionalized magnetic metal-organic framework material was synthesized. Nano-Fe3O4 was prepared by a solvothermal method, after which polyvinyl pyrrolidone was employed to modify Fe3O4. Finally, amino groups were introduced to prepare Fe3O4@NH2-MIL-53(Al). The crystal structure and functional groups of the material were characterized by means of X-ray diffraction (XRD) and Fourier transform infrared spectrometry (FT-IR). Combined with flame atomic absorption spectroscopy (FAAS), the adsorption of lead by the magnetic adsorbent was investigated. The magnetic adsorbent possesses high adsorption capacity because of the large specific surface area of Fe3O4@NH2-MIL-53(Al) and the coordination between amino group and lead. Experimental conditions affecting the adsorption percentage were discussed and the experimental operation parameters were optimized (pH value of 6.0 and adsorption time of 120 min). Kinetics and thermodynamics studies were conducted for the adsorption process. Langmuir/Freundlich and pseudo-first-order/pseudo-second-order models were applied to analyze the experimental data. Thermodynamic functions, i. e., changes of Gibbs energy, entropy, and enthalpy, were calculated from temperature experiments. In addition, the regeneration of the adsorbent was considered with hydrochloric acid as the desorption solution. Several adsorption and desorption experiments were carried out, illustrating that the Fe3O4@NH2-MIL-53(Al) adsorbent can be used repeatedly.