Preparation Of Metal Organic Framework Composite Materials And Study On Its Adsorption Properties

Metal organic framework materials(MOFs)are a class of three-dimensional porous crystal materials formed by metal ions or metal clusters and organic ligands.The MOFs have many advantages such as large surface area,uniform pore size distribution,unsaturated metal active sites and functional modification.The introduction of other functional materials through modification or doping can endow MOFs with more excellent properties,which is of great significance for improving the ability of single MOFs material to remove pollutants in water.In this paper,Cu-BTC and MIL-101(Cr)materials were prepared,and respectively doped with activated carbon(AC)and modified with polyethyleneimine(PEI)to prepare AC/Cu-BTC composite material and PEI-MIL-101(Cr)mater:ial.The XRD,FT-IR,SEM and BET were used to analyze the materials,and materials were applied to the adsorption of Cr6+and dye in simulated wastewater.The main research results are as follows:(1)The Cu-BTC is in the form of octahedron,the crystal surface is smooth and the crystal form is regular.The AC/Cu-BTC composite has the same octahedral structure as Cu-BTC'and its crystal morphology is relatively complete.The surface of AC/Cu-BTC is rough and more pore structure is formed.MIL-101(Cr)has an octahedral structure,good crystal formability and relatively uniform particles.The PEI was successfully introduced into MIL-lOl(Cr)material.PEI-MIL-101(Cr)maintained the crystal structure of MIL-lOl(Cr),but the regularity and integrity of crystallinity and crystal morphology decreased slightly.(2)The adsoqption experiments of Cu-BTC and AC/Cu-BTC adsorbents on methylene blue and methyl orange showed that the adsorption capacity of methylene blue by AC/Cu-BTC composite adsorbent with different proportion of AC was higher than that of Cu-BTC.The adsorption effect of 2%AC/Cu-BTC was best,the adsorption amount of methylene blue was increased from 34.94mg/g to 46.46mg/g.The adsorption of methylene blue by adsorbents is much higher than that of methyl orange,indicating that the surface of the adsorbent is negatively charged,which is more conducive to the adsorption of cationic pollutants.The adsorption amounts of Cu-BTC and AC/Cu-BTC adsorbents on methylene blue and methyl orange increased with time,and reached adsorption equilibrium after 180 min.The adsorption behavior of the adsorbent on methylene blue and methyl orange was more consistent with the Langmuir adsorption isotherm equation,the adsorption kinetics were more consistent with the second-order kinetic model.The adsorption process was a spontaneous exothermic reaction process.The adsorbents have good recycling performance and can be reused at least 3 times.(3)The adsorption experiments of MIL-101(Cr)and PEI-MIL-101(Cr)adsorbents on Cr6+ and methyl orange in simulated wastewater showed that the adsorption effect of PEI-MIL-101(Cr)adsorbent on Cr6+and methyl orange is significantly improved compared with MIL-101(Cr).The 30%PEI-MIL-101(Cr)adsorbent has the best adsorption effect,its adsorption capacity for Cr6+ was increased from 19.08mg/g to 31.45mg/g,the adsorption amount of methyl orange increased from 110.43mg/g to 136.48mg/g.The adsorption capacities of MIL-101(Cr)and PEI-MIL-101(Cr)adsorbents adsorbed Cr6+ and methyl orange increased with time,and the adsorption reached equilibrium after 180 min.The adsorption behavior of the adsorbent on Cr6+ and methyl orange accords with the Langmuir adsorption isotherm equation,the adsorption kinetics are consistent with the second-order kinetic model.The adsorption thermodynamics results show that the adsorption process of Cr6+ by adsorbent is a self-heating reaction process,and the adsorption process of methyl orange is a spontaneous endothermic reaction process.The adsorbents have good recyclability and can be reused at least 4 times.