Polyetherimide Solvent-Resistant Nanofiltration Membrane Enhanced By Mixed-Amine Crosslinking

In the increasingly tense global energy resources and increasing pollution,low-energy and zero-pollution production processes are the inevitable choice for sustainable development.Membrane separation technology has the advantages of energy saving,no secondary pollution,high efficiency,and simple operation,which makes membrane separation technology widely used in seawater desalination,pharmaceutical industry,fine chemicals and other fields.Since organic solvents are widely used in petrochemical,fine chemical and pharmaceutical industries,the development of solvent-resistant nanofiltration membranes is increasingly important.In this paper,the stability and separation performance of polyamide solvent-resistant nanofiltration membrane in strongly polar aprotic solvent DMF was studied.The main work is as follows:First,the PEI support layer was prepared using different lengths of different mixed amines?EDA/DAB,EDA/HAD,EDA/XDA?as cross-linking agents.A composite nanofiltration membrane was prepared by interfacial polymerization of BTC n-hexane solution as the oil phase monomer and a cross-linked membrane surface free amine group.The effect of the composite membrane on the separation of DMF-RB was investigated.The reason for the difference in solvent resistance was analyzed from the chemical structure of the cross-linked support layer.The chemical structure,micro-morphology,and hydrophilic-hydrophobicity of the separation layer of the solvent-resistant composite membrane were used to analyze the reasons for the difference in separation performance.The composite membrane prepared by the crosslinker EDA/XDA has the best solvent resistance.In order to further explore the role of EDA and XDA amines in solvent resistance,the separation effect of composite nanofiltration membranes prepared with different ratios of EDA/XDA was analyzed in more detail,and the necessary characteristics of the composite membranes were characterized.Chemical structure and microstructure were analyzed.Finally,a composite nanofiltration membrane with a stability of more than 300 minutes in DMF,a flux of DMF of 1.0 Lm^-2h^-1MPa^-1,and an RB rejection of 98%was obtained.Secondly,the above composite membrane was modified with hydrochloric acid or ethylene glycol to obtain a thin composite membrane and the separation performance was improved.Ethylene glycol modification mainly utilizes ethylene glycol that does not react with the free amine groups in the pores of the cross-linked membrane,surrounds the amine groups in the pores with ethylene glycol,and prevents the reaction between the amine group and the interfacially polymerized BTC to make the membrane become loose,thinning the separation of the skin,and finally get a composite nanofiltration membrane with stability in DMF over 24 h,DMF flux of 6.1 Lm^-2h^-1MPa^-1,and RB rejection of 89%.