Study Of Preparation Metal Organic Framework Composite And Its Application In Wastewater Treatment

With the increase of people’s living demands,the development of industrial technology and continuous progress of science and technology,heavy metal ions and organic dye wastewater pollution has become increasingly serious,resulting in a serious decline in water quality.The problem of environmental water treatment has always been concerned by researchers,and the synthesis of environmentally friendly materials for water treatment has become a research focus.Metal organic framework（MOFs）is a new kind of porous material.Its good adsorption property makes it suitable for wastewater treatment and quantitative detection.Based on this,this work synthesized three kinds of composite materials of MOFs and applied them to the treatment and detection of organic dye and heavy metal wastewater.The main research results of this work are as follows:（1）Use layer by layer self-assembly technology to carboxyl of ordinary filter paper as the carrier,on the surface of the filter paper growth Cu-MOFs materials（MOFs/CMFP）,the materials were characterized by the X-ray powder diffraction（XRD）,Fourier transform infrared scan（FT-IR）and scanning electron microscope（SEM）and element mapping（EDS）analysis and so on to confirm its structure.The adsorption properties of MOFs/CMFP on organic dyes（MB）,malachite green（MG）,rhodamine B（Rho B）and heavy metal ions(Pb²⁺and Cd²⁺)were investigated.The removal efficiency of organic dyes and heavy metal ions from before and after self-assembly Cu-MOFs filter paper was compared,and the selectivity of self-assembly Cu-MOFs filter paper in adsorption of heavy metal ions was discussed.It was found that the adsorption of organic dyes and heavy metal ions mainly came from the filter paper coated with MOFs.By controlling the layers of self-assembly MOFs to enhance the adsorption efficiency.The results showed that the removal efficiency of organic dyes and heavy metal ions was the best in the self-assembled 30-layer MOFs.It was also found that the material had selective adsorption for heavy metal ions(Pb²⁺and Cd²⁺).In addition,we analyzed the real samples（tap water）with self-assembled 30-layer MOFs.The experimental results showed that MB,Rho B,MG,Pb²⁺and Cd²⁺were not detected in the local tap water.After the addition of standard solution,the solution was analyzed and detected,the removal efficiency of dyes and heavy metal ions were over 87%.Through effective adsorption of dyes and metal ions in real water samples,it is proved that Cu-MOFs/CMFP is feasible to remove dyes and metal ion-contaminated in wastewater treatment.（2）The hybrid materials（CQDs/MOF）of carbon quantum dots and MOFs were prepared by hydrothermal synthesis method,and their structures were confirmed by XRD,FT-IR and TEM characterization.According to TEM analysis,the material has the surface structure of cubic phase,and it is found that carbon quantum dots are evenly distributed on the surface of MOFs.The fluorescence properties of the material were preliminarily investigated,and the fluorescence properties of CQDs,MOF and CQDs/MOF were compared,as well as the fluorescence changes after adding metal ions.It was found that the addition of CQDs could significantly enhance the fluorescence intensity of MOF hybrid materials,and the fluorescence quenching occurred after the addition of metal ions.Through experiments,it was found that CQDs/MOF hybrid materials had obvious selective quenching effect on Fe³⁺and Cu²⁺,and showed a good correlation in the range of 0-100 ppm.Based on this,Fe³⁺and Cu²⁺could be detected quantitatively by this method,and the detection limits of Fe³⁺and Cu²⁺by this method were 0.098 ppm and 0.129 ppm,respectively.In the simulated real sample analysis,the recoveries of Fe³⁺and Cu²⁺were between 95%and 105%,and the CQDs/MOF has little cytotoxicity to 4T-1 cells,indicating that CQDs/MOF material could be used to detect Fe³⁺and Cu²⁺in cells.（3）Magnetic Fe₃O₄and MOFs hybrid materials modified by L-cysteine（called Fe₃O₄/MOF/L-cysteine）were synthesized and characterized,the heavy metal Cd²⁺ions were removed and detected by adsorption,solid phase extraction-fluorescence sensing,respectively.The effects of adsorption time,the amount of adsorbent and the concentration of adsorbed substances on the adsorption performance were discussed.It was found that Fe₃O₄/MOF/L-cysteine had a good adsorption performance for Cd²⁺.After the adsorption reached equilibrium,the adsorption experiment was carried out after magnetic separation and acid analysis.The results showed that the adsorption efficiency remained above 90%after 5cycles and the maximum adsorption capacity was 248.24mg/g.Through the study of isothermal model and adsorption kinetics,the adsorption of Cd²⁺by Fe₃O₄/MOF/L-cysteine followed the Langmuir isothermal model and the second-order kinetic model.Based on the excellent adsorption performance,we used the inductively coupled plasma atomic emission spectrometry（ICP-AES）to detect trace heavy metal ions in water on the basis of magnetic solid phase extraction（MSPE）.The detection limit of this method for Cd²⁺was 10.6 ng/m L.At the same time,we also studied the performance of the material used in the detection of Cd²⁺by the fluorescence sensor.It was found that Cd²⁺had a fluorescence quenching effect on Fe₃O₄/MOF/L-cysteine,and the quenching degree was proportional to Cd²⁺,which could be used in the detection of Cd²⁺.The fluorescence detection limit was 0.94 ng/m L.