Preparation Of Mixed Matrix Membrane With High Water Stability MOFs And Its Nanofiltration Performance Research

In the field of membrane separation,MOFs materials are widely used in pervaporation,gas separation and organic solvent nanofiltration due to their excellent characteristics.Most MOFs have the problem of poor stability in water and there are relatively few application examples in the field of nanofiltration water treatment.In addition,in the preparation process of MOFs-based mixed matrix membrane,there are deficiencies such as large particle size,poor dispersion,and relatively complex preparation of fillers.In order to expand the application of MOFs materials in water treatment,two kinds of MOFs materials with high stability and good dispersion in water were selected in this thesis.A series of mixed matrix membranes were prepared by a simple method and used for nanofiltration removal of dyes in water.The specific work contents are as follows:(1)A series of Zr-abtc/PEI-HPAN-X mixed matrix membranes(where X represents the loading rate of Zr-abtc)were prepared by grinding and dispersing the synthesized Zr-abtc with 1D pore structure in water,which was blended with polyethyleneimine(PEI)aqueous solution,and then spin-coated on the pretreated polyacrylonitrile(HPAN)substrate.Among them,the mixed matrix membrane Zr-abtc/PEI-HPAN-80 showed ultra-high water permeability(2422.9 L/m~2·h·MPa)and good rejection to dye molecular methyl blue(98.0%).At the same time,it also had good nanofiltration separation performance for anionic dyes(congo red,acid fuchsin,chromium black T,acid orange-Ⅱ)and salts(sodium sulfate,magnesium sulfate,magnesium chloride,sodium chloride).A long-time nanofiltration test and anti-fouling experiment also showed that the membrane had good performance stability and anti-fouling.The microstructure analysis of the Zr-abtc/PEI-HPAN-80 membrane and the comparison of the nanofiltration performance between the Zr-abtc/PAM-HPAN-50membrane and other mixed matrix membranes in the literature show that the compatibility between polymers and MOFs and the loading of MOF have a great influence on the nanofiltration separation performance of the mixed matrix membrane.(2)A series of mixed matrix membranes PCN-250/PEI-HPAN-X(X represents the loading rate of PCN-250)were prepared by grinding MOF crystal and blending spin coating.The nanofiltration performance test showed that the mixed matrix membrane PCN-250/PEI-HPAN-75 prepared under the optimal ratio had a permeability of 1479.7L/m~2·h·MPa to water and a rejection rate of 97.3%to dye molecular methyl blue.In order to explore the reasons for the performance differences of several mixed matrix membranes,the nanofiltration performance of mixed matrix membranes prepared by Zr-abtc,BUT-28,and PCN-250 was compared.A series of characterization methods such as zeta potential,particle size analysis,SEM,and water contact angle were used to further explore.It was found that the electronegativity of MOF particle surface,dispersion in water,particle size,hydrophilicity and hydrophobicity were very important to the nanofiltration separation performance of the membrane.