Preparation Of Magnetic Metal-organic Frameworks And Their Adsorption For Pollutants In Water

Global water resources are being polluted by various organic or inorganic chemicals that not only affect the growth of plants and animals,but also cause harm to human health through the accumulation of food chains.In face of serious water pollution problems,many methods have been taken to remove pollutants in water,such as flocculation,photocatalysis,adsorption and membrane separation technology,etc.Among these methods,adsorption method is widely employed because of its advantages of high efficiency,simplicity and no secondary pollution.The adsorption materials mostly are porous structure and large specific surface area.Among those adsorption materials,the magnetic metal organic framework materials attract researchers’interest.As environmental-friendly materials,magnetic metal organic framework materials combine the advantages of magnetic materials and metal organic framework materials.In this thesis,three different magnetic metal-organic framework materials were prepared and their structures were analyzed by XRD,FT-IR,SEM,TEM,VSM and other equipments.The prepared materials were used to adsorb typical pollutants in water.The influential factors,like adsorbent qualities,adsorption time,p H value and ionic strength,were investigated.Adsorption kinetics,isotherm and thermodynamic were studied to explore adsorption mechanism.The specific research contents are as follows:1.The binary magnetic metal organic framework material Fe₃O₄@MIL-53（Al）was prepared by solvothermal method using self-assemble of Fe₃O₄-COOH,aluminum nitrate and1,4-terephthalic acid under high temperature and pressure.Various characterization methods proved that Fe₃O₄@MIL-53（Al）with magnetic function had characteristic peaks and functional groups of MIL-53（Al）and Fe₃O₄.Fe₃O₄@MIL-53（Al）as adsorbent was used to adsorb CR,MB,TC and BPA.The experimental results showed that the adsorption on BPA,TC and CR followed pseudo-second-order model and Langmuir model,the adsorption on MB followed pseudo-second-order model and Freundlich model.The adsorption of BPA was spontaneous,exothermic and entropy reduction process.The adsorption of TC,CR and MB were spontaneous,endothermic and entropy increase process.The target pollutants adsorption processes inclued chemical and physical adsorption,but physical adsorption was predominant.The adsorbent had excellent adsorption performance.2.The 2-aminoterephthalic acid instead of 1,4-terephthalic acid as organic ligands to modify Fe₃O₄@MIL-53（Al）prepared aminated magnetic metal organic framework binary material Fe₃O₄@MIL-53（Al）-NH₂.The FT-IR characterization confirmed the presence of amino groups in Fe₃O₄@MIL-53（Al）-NH₂.The materials were used to remove BPA and TC.According to experimental results,the maximum adsorption capacities of BPA and TC were234.08 and 84.76mg/g,respectively,which were higher than those of non-amino modified adsorbents.Amine endowed with better adsorption performance for adsorbents.The pseudo-second-order model and Langmuir isotherm model were more suitable to illustrate the adsorption processes of Fe₃O₄@MIL-53（Al）-NH₂ on BPA and TC.Fe₃O₄@MIL-53（Al）-NH₂adsorption BPA and TC both were spontaneous,endothermic and entropic increase processes.After 5 cycles,Fe₃O₄@MIL-53（Al）-NH₂still had high adsorption capacities for BPA and TC,showing good recyclability.3.The three-layer core-shell magnetic metal organic framework material Fe₃O₄@Si O₂@Zn-TDPAT was prepared by combining Zn-TDPAT with Fe₃O₄@Si O₂ using coupling agents EDC and NHS.Fe₃O₄@Si O₂@Zn-TDPAT as adsorbent was used to adsorb CR and MB.The experimental fitting datum showed that Fe₃O₄@Si O₂@Zn-TDPAT on CR and MB adsorption followed pseudo-second-order model and Langmuir model.The CR and MB adsorption processes both were spontaneous,endothermic and entropic increase.After multiple cycles,the removal rate of CR and MB were over 80%.Fe₃O₄@Si O₂@Zn-TDPAT still remained crystal structure and functional groups,showing good chemical stability and reusability.