Study On Preparation And Adsorption Properties In Wastewater Treatment Of Metal-Organic Framework Materials

The rapid development of China’s industry has brought serious environmental pollution while improving the economic level.Water pollution is one of the three major environmental pollution problems,and it had been in the news for years.Among them,the discharge of non-ferrous organic dyes from textile,printing and dyeing industries,and the release of wastewater containing heavy metals from heavy industries such as leather and smelting industries are toxic and difficult to degrade.It not only endangers human health,but also causes serious damage to the ecological environment.To treat the pollutants in this kind of wastewater,it had gradually become the research focus at home and abroad by using simple,high-efficiency and low-cost technology.Metal-Organic Frameworks is a new type of porous material,which has the advantages of high specific surface area and porosity,adjustable structure and rich unsaturated metal sites.It has broad development prospects in the fields of adsorption,separation,energy storage,and catalysis.The indium-based MOF material is composed of octahedral units formed by In³⁺Ions and organic ligands which has good structural and thermal stability.However,the research on preparation of In-MOF series materials and the application of industrial wastewater pollutants was less.In this paper,the preparation of series materials and the effects of the introduction of different groups on the specific surface area and pore volume of the materials were studied.The effects of MIL-68（In）materials before and after modification on adsorption performance of methylene blue organic dye and heavy metal Cr⁶⁺ion in industrial wastewater were discussed.The main research contents are as follows:1.Two metal-organic framework materials named MIL-68（In）and NH₂-MIL-68（In）were prepared by solvothermal synthesis method.The structure and morphology of the materials were characterized by X-ray diffraction（XRD）,N₂adsorption and desorption（BET）,and Scanning electron microscopy（SEM）,Transmission electron microscopy（TEM）and Fourier infrared spectroscopy（TF-IR）.The effects of different synthetic conditions on the structure of materials were discussed.2.MIL-68（In）-SC was prepared by modifying the synthesized MIL-68（In）with Sodium Citrate as modifier.The optimum concentration and dosage of the modifier were determined by measuring the structure parameters of the modified material.The results showed that the addition of modifiers can apparently increase the specific surface area of synthetic materials.The specific surface area of MIL-68（In）-SC reached 1164.91 m²/g When 0.2 mL 0.5 mol/L sodium citrate solution was added.It was increased by 56.63%compared to specific surface areathe before modification.3.The adsorption properties of MIL-68（In）,NH₂-MIL-68（In）and MIL-68（In）-SC for methylene blue（MB）and heavy metal Cr⁶⁺ions in wastewater were investigated.The results showed that MIL-68（In）-SC had the best adsorption performance among the three synthetic materials.Compared with MIL-68（In）,the modified MIL-68（In）-SC has higher adsorption rate and quantity for methylene blue（MB）,the adsorption rate and quantity are96.63%and 204.16 mg/g,respectively.All three materials had an adsorption effect on heavy metal Cr⁶⁺ions,and the adsorption rate and adsorption capacity were 30.05%and24.04 mg/g.The adsorption kinetics of MB and Cr⁶⁺ions on the three materials were in accordance with the quasi-second-order kinetic model,and the adsorption thermodynamics was in accordance with the Langmuir adsorption model.The modified adsorption material retained good adsorption effect after 4 times reuse.4.The results showed that the prepared MIL-68（In）-SC material had better practical value for adsorbing organic dye Methylene blue in wastewater.