Study On Preparation And Properties Of Polyamide Composite Separation Membrane

Water scarcity is the most serious challenge in the 21st century,and open source methods such as seawater desalination and cost-saving methods such as wastewater treatment have become the way to solve the water scarcity problem.Membrane separation technology stands out from the crowd of water treatment technologies for its green,stable,durable and high energy efficiency.Membrane is the core of membrane separation technology,and thin film composite membrane is the mainstream of commercial separation membrane,which mainly consists of ultra-thin selective layer and porous support layer,among which selective layer is the key to determine the performance of thin film composite membrane.Investigating the interrelationship between the influencing factors and separation performance in the preparation of selective layer,it is important to break the Trade-off limitation to enhance the selective permeability of thin film composite membrane.In this paper,polyamide composite separation membranes are prepared under different conditions by interfacial polymerization.The specific research includes the following three parts.1.Polytetrafluoroethylene microfiltration membranes（pore sizes of 0.45μm,0.22μm and 0.1μm）,nylon microfiltration membranes（pore sizes of 0.22μm,0.1μm and 0.05μm）and polyethersulfone microfiltration membranes（pore sizes of 0.45μm,0.22μm and 0.1μm）are used as support layers.The effects of the physicochemical properties of the support layers on the surface morphology,hydrophilicity and properties of the polyamide composite separation membrane were discussed.The results show that the smaller the surface porosity of the support layer of the same material,the better the dye removal effect,but the lower the permeate flux.After weighing the permeate flux and dye retention performance,polyethersulfone microfiltration membrane with a pore size of 0.22μm is selected as the dominant support layer,and the permeate flux of the prepared polyamide composite separation membrane was 0.31 L·m^-2·h^-1·bar^-1,and the rejection of Congo red dye was 97.25%.2.Optimization of polyamide selective layer polymerization process.The effects of different organic phase volumes,reaction times and monomer concentrations on the performance of the polyamide composite separation membrane were investigated.The results show that the best performance of the polyamide composite separation membrane is prepared under the conditions of 1 m L organic phase volume,1 min reaction time,2 wt%amine concentration and 0.15 wt%chloride concentration,with a water flux of 0.79 L·m^-2·h^-1·bar^-1 and the rejection of Mg SO₄ was 91.25%.3.Design and modulation of polyamide molecular structure.The effects of aromatic amine monomers（m-Phenylenediamine,m-Xylylenediamine and p-Xylylenediamine）and alicyclic amine monomers（1,2-Cyclohexanediamine,1,4-Cyclohexanediamine with different cis-to-trans ratios）on the performance of the polyamide composite separation membrane were investigated,and the results show that the alicyclic amine monomers significantly enhanced the water flux of the composite separation membrane,in which the cis-to-trans ratio of 1,4-Cyclohexanediamine is 0.53:0.47,the water flux of the composite separation membrane is 11.12 L·m^-2·h^-1·bar^-1.