Synthesis And Characterization Of Polysulfone/Polyamide Composite Nanofiltration Membrane

Nanofiltration is a membrane separation process between ultrafiltration and reverse osmosis,compared with the traditional separation methods,nanofiltration membrane separation process has the advantages of high separation efficiency,low energy consumption,no phase change,no pollution,easy operation,easy recovery and utilization of products and many other advantages.The nanofiltration membrane technology has experienced a great development,and has been widely and effectively applied in various fields,especially in water treatment and other energy and environmental protection applications of great significance,forming an independent high-tech industry.The separation performance of the nanofiltration membrane is the result of the combination of the sieve effect and the charge effect of the membrane surface,and has good separation effect on the small molecular compound with molecular weight between 200 to 2000 and polyvalent charged ion.Since the development of membrane industry,anti-pollution performance has been restricting the commercialization of nanofiltration membrane development and application,therefore,how to improve the anti-pollution performance of nanofiltration membrane has been an important research direction in the field of membrane,which has attacted more and more attention of researchers.In this paper,based on the improvement of composite nanofiltration membrane anti-fouling properties,starting from improving the surface hydrophilicity of composite membrane,we synthesized a dendritic polymer of great hydrophilic as the water phase monomer,and terephthaloyl chloride is the oil phase monomer,then prepared the PAMAM/TC polyamide composite membrane successfully on the sufface of polysulfone ultrafiltration membrane by interfacial polymerization.The structure of the composite membrane was characterized by IR,NMR,contact angle and scanning electron microscopy,confirming the existence of polyamide functional layer successfully,also the separation and stability performance of the composite membrane has been investigated and studied.First of all,preparing a basement membrane through phase inversion method,meanwhile the effect of the preparation crafts on the membrane performances was studied,after that,a orthogonal test was designed to find the best preparation crafts of the basement membrane.In the following,the hydrophilic amino monomer PAMAM was synthesized by Michael addition and amidation reaction and the product was characterized through IR and NMR,the results showed that the obtained compound was the target product,then the Free-Standing lab showed that PAMAM has a good film-forming properties and can be used for the preparation of composite membranes.Later the polyamide composite nanofiltration membrane was prepared by the interfacial polymerization using the polysulfone ultrafiltration membrane as the base membrane and the dendrimer molecule PAMAM and terephthaloyl chloride TC as the biphasic monomers respectively,then the composite membrane was characterized by contanct angle,IR and SEM,the results showed that the contact angle of the composite films was significantly decreased and the hydrophilicity was improved,meanwhile the membrane surface covered with a layer of dense cross-linked layer,confirmed the presence of polyamide functional layer.At the same time,the separation performance of PAMAM/TC composite membrane was studied,the experimental results showed that PAMAM/TC composite membrane had a good separation performance,the rejection of the four kinds of inorganic salts were above 60%,especially the rejection of Na₂SO₄ reached 95.2%,and the flux was 21.4 L/m² h.From the performance of higher divalent anion retention and lower divalent cations interpenetration,the surface of PAMAM/TC composite membrane showed a negative electronegativity.Studying the effect of interfacial polymerization crafts on the preformances of composite membrane,The results showed that the concentration of water and organic phase,polymerization time,post-treatment temperature and time all had a great influence on the preformances of the composite membrane,there was a better technological range.At last,the stability properties of PAMAM/TC composite membrane was also investigated,the composite membrane was treated with acid,alkali solution,chlorine solution and high temperature aqueous solution respectively,the results showed that the composite membrane had a good alkali resistance,chlorine resistance and high temperature resistance,and can be used for the treatment of alkali,chlorine and high temperature solution,and the separation performances remaining stable.Then simulating methyl orange and bovine serum albumin as pollution sources,studying the anti-fouling property of the composite membranes through the static and dynamic test methods.The results of static test showed that the composite membrane had much less adsorption of contaminants than the basement membrane,and its anti-pollution performance was improved obviously,which has a great relationship with the molecular structure of PAMAM,meanwhile the dynamic experiments showed that the flux recovery rate of the composite membrane was 91.6%,which indicated that PAMAM/TC composite membrane had a good anti-pollution performance and can keep stable performance for a long time.