Preparation And Purification Performance Of MOFs Nanofiltration Membrane

Nanofiltration separation technology has become the most promising and rapidly developing water purification technology because of its excellent performance of simple operation and energy saving,especially in the printing and dyeing,petrochemical and medical industries.So how to improve the performance and cost of separation membrane has become a hot topic in the field of environmental protection.Because in membrane separation,membrane materials need to be immersed in the raw material liquid environment for a long time,so its own mechanical properties,chemical stability,etc.,have higher requirements.Therefore,the membrane material selected in this experiment is polyvinylidene fluoride（PVDF）material with high mechanical strength and high chemical stability as the main membrane material,which provides strong support for the nanofiltration membrane prepared.However,polymers have limitations,and their application in material separation has been hampered by the lack of adjustable and ordered pores,low wettability and low porosity.In recent years,metal-organic matrix（MOF）materials are often used in membrane separation research due to their high porosity and regular porosity.In order to overcome the problems and limitations of polymer membrane preparation,the content of this study is to introduce MOFs materials as additives into a continuous polymer matrix to prepare mixed matrix membrane（MMMs）,so that it has good membrane performance in the treatment and separation of dye wastewater.In this study,a novel hybrid matrix membrane（MMMs）was prepared by adding metal-organic framework UIO-66 to polyethersulfone/polyvinylidene fluoride casting solution.Fourier transform infrared absorption spectrometer（FTIR）,atomic force microscopy（AFM）,scanning electron microscopy（SEM）,contact Angle and Zeta potential test were used to characterize the prepared UIO-66 material and THE nanofiltration membrane.During the preparation of nanofiltration membrane,the influence of pH and ratio of reactants on solvothermal synthesis of UIO66 material and the influence of adding amount of UIO-66 material on membrane properties were investigated.The results show that under the condition of 120℃,pH=8,the ratio of ZrCl₄to H₂BDC is 1.5:1,which makes the morphology of UIO-66 crystal uniform and high purity.The nanofiltration membrane prepared with 10%UIO-66 had the highest Mg SO₄ and Rhodamine B,reaching 41.23%and 93.49%,respectively,and the pure water flux reached 47.72 L·m^-2·h^-1.In the experiment,nanofiltration membrane with 10%UIO-66 content was used to conduct membrane separation test experiment on simulated wastewater containing Congo red,sunset yellow and carmine respectively.By changing the flow rate of raw material liquid,concentration of raw material liquid,operating pressure and other conditions,The membrane flux and retention of Congo red,sunset yellow and carmine were studied under different operating conditions.The experimental results show that there is a positive correlation between the feed liquid flow and the rejection rate and membrane flux.The concentration of the raw material liquid was negatively correlated with the membrane flux.From the perspective of operating pressure,operating pressure is positively correlated with membrane flux,but its influence on rejection rate is not obvious.In addition,the operation time has no obvious effect on the performance of nanofiltration membrane.The stability of nanofiltration membranes was investigated.The rejection rate of the prepared nanofiltration membranes decreased after treatment under acid and alkali conditions,but the decline rate remained within 22.3%.Therefore,the UIO-66nanofiltration membrane prepared in this study has a significant separation and purification function for printing and dyeing wastewater.