Preparation Of Antifouling Nanofiltration Membranes By Modifying Polyamide Layer Through Amino Acid

To improve the antifouling performance of nanofiltration membranes,small hydrophilic molecules were chosen to modify the surface of nanofiltration membranes,based on Whiteside's antifouling strategy of enhancing hydrophilicity.Inspired by bionic idea,different amino acid molecules and amino-metal complex were incorporated into the polyamide separation layer through the interfacial polymerization,which was to improve the hydrophilicity and antifouling performance of the membranes.The main content and conclusion were summarized as follows:Firstly,inspired by aquaporins,Lys,the simplest amino acid in nature,was incorporated into the dense polyamide separation layer.Based on the hydrogen bond effect between amino acid in aquaporins and water molecules,the hydrophilicity of the membranes was improved.The fouling resistant performance was enhanced toward negative charged foulants,attributing to the increased hydrophilicity and negative charges of the membrane surface.Meanwhile,the introduction of Lys increased the dense degree of the polyamide separation layer,leading to the decreased pure water flux and increased rejection level.Next,to certify the possibility of alkaline amino acid becoming a category of small molecule hydrophilic modification,Arg was incorporated into polyamide separation layer inspired by aquaporins1.The increasing of hydrophilicity and negative charge was achieved,and the antifouling performance of membranes was enhanced owing to the incorporation of Arg.However,Arg possessed multi-amino groups and interaction between guanidine groups.The resultant Arg-Arg dynamically disturbed the formation of PIP-TMC polyamide network.With the increasing of Arg addition,the pure water flux was ceaselessly increased and doubled,while the rejection presented the trend of decrease-increase-decrease.Finally,to overcome the trade-off effect of polyamide nanofiltration membranes modified by amino acid,the Arg-Fe complex was synthesized and incorporated into polyamide separation layer,which was inspired by the chelating effect of amino acid.The introduction of Arg-Fe complex eliminated the disturbing of Arg-Arg.When the pure water flux was ceaselessly increased,the rejection ratio still kept a high level.Meanwhile,the membranes modified by Arg-Fe complex still kept the same excellent hydrophilicity and antifouling performance as membranes modified by amino acid.Especially,after filtrating BSA foulants for 12 h,the flux recovery rate of the membranes reached 100%.