Regulation Of Basement Membrane Adhesion And Its Effect On Nanofiltration Membrane Structure And Performance

The results show that the surface properties such as the surface porosity of the base membrane have a significant influence on the interfacial polymerization process and membrane properties.However,the surface porosity of the existing base membrane is usually less than 10%,and the influence of the remaining 90%area on the adhesion of the monomer in the interfacial polymerization is often ignored.In this thesis,the negative segregation of SPSf in PES/SPSf ultrafiltration（UF）membrane prepared by different polymer concentration of PES/SPSf blend was studied.The influence of negative segregation of SPSf surface on the adhesion between base membrane and piperazine（PIP）was investigated.Because high concentration of reactive monomer may cover up the effect of base membrane on interfacial polymerization,the interfacial polymerization of 0.05 wt%PIP and trimethyl chloride（TMC）was carried out.The relationship between the reaction time and the thickness of PA layer was explored,finally,high performance ultra-thin PA composite NF membrane was prepared.The main research contents are as follows:（1）Preparation of PES/SPSf ultrafiltration membrane and negative segregation of SPSf on the membrane surface.PES/SPSf membrane was prepared by non solvent induced phase separation（NIPS）using PES/SPSf blend（fixed mass ratio of 5.25）as membrane material.It was found that when the concentration of polymer increased from 16%to 28%,the segregation degree of SPSf on the surface of PES/SPSf base membrane decreased,showing a negative segregation phenomenon.The content of sulfonate on the surface of PES/SPSf membrane decreased,resulting in the decrease of hydrophilicity and charge of PES/SPSf.Meanwhile,the adhesion of the membrane to PIP monomer in aqueous amine solution decreased from 17.9 to 2.6 n N.The pore size of the membrane also decreased from 23 to 11 nm.With the decrease of the pore size of the PES/SPSf membrane,the permeation flux decreased from 702.6 to 253.8 L·m^-2·h^-1·Bar^-1.When the concentration of polymer was 20%,the permeability of PES/SPSf₂₀ was still 559.8 L·m^-2·h^-1·bar^-1,and the retention of BSA was 99.5%.The polymer concentration has an important influence on the membrane structure and separation performance of PES/SPSf.（2）Preparation and process of composite nanofiltration membrane with high permeability and selectivity.The PA/PES/SPSf composite NF membrane with high perm-selectivity was prepared by IP with PES/SPSf as the support membrane,PIP and TMC as monomers.It was found that the roughness of NF membrane increased and the hydrophilicity and electronegativity decreased when the polymer concentration forming PES/SPSf membrane increased from 16%to 28%.At the same time,the separation layer thickness increased from 0.5 nm to 18 nm,IP reaction time decreased from 120 s to 10 s,and the pore size of NF membrane decreased from 0.51 nm to 0.38nm.It is preliminarily considered that the high adhesion force of the surface of PES/SPSf membrane has strong adhesion to PIP molecules,which reduces the activity of PIP molecules,decreases the number of PIP molecules participating in interfacial polymerization,and delays the interfacial polymerization time,resulting in the formation of thinner PA layer and longer polymerization time,and vice versa.When the concentration of polymer was 20%,the concentration of PIP and TMC was 0.05wt%,the performance of PA/PES/SPSf composite nanofiltration membrane was the optimal,the pure water flux reached 45.4 L·m^-2·h^-1·bar^-1,and the retention rate of Na₂SO₄ was 99.5%.The recovery rate of anti bovine serum protein membrane was100%.