Study On The Preparation Of Ionic Liquid Copolymer Modified PVC Blend Membrane And Its Anti-fouling Performance

Ultrafiltration has received widespread attention due to its economic and efficient technical advantages.Polyvinyl chloride（PVC）ultrafiltration membranes have attracted widespread attention due to its low cost and high efficiency.However,problems such as reduced flux,shortened life,and increased cost caused by membrane fouling have become bottlenecks in the use of ultrafiltration membranes.Antifouling modification of membranes and preparation of antifouling ultrafiltration membranes are hot topics of research.Firstly,we studied the preparation of PVC/BVIm BF₄ultrafiltration membrane by using PVC as the polymer matrix and 1-butyl-3-vinylimidazole tetrafluoroborate（BVIm BF₄）as an additive.Explore the effect of BVIm-BF₄on the structure and performance of PVC membrane.The addition of BVIm BF₄ can improve the porosity of the membrane surface and the size of the finger pores in the membrane cross section,and effectively improve the permeability of the membrane.When the content of BVIm-BF₄ is 3.85%,the pure water flux of PVC/BVIm BF₄ membrane can reach up to 390.5L/m²h（PVC original membrane 178.5 L/m²h）,BSA rejection rate is 79.4%,and contact angle is 77.3°.Tests on the antifouling performance of the membrane showed that the flux recovery rate of the PVC/BVIm BF₄ membrane was 50.1%,which was higher than 46.4%of the original PVC membrane.Secondly,a simple free radical polymerization method was used to synthesize the macromolecule PBVIm BF₄,and the content of PBVIm BF₄was changed to prepare different PVC/PBVIm BF₄ blended films.The effects of PBVIm BF₄ on the structure and properties of PVC films were investigated.The addition of PBVIm BF₄ can improve the porosity of the membrane surface and the size of the membrane and cross-section finger pores,effectively improving the permeability and hydrophilic properties of the membrane.When the content of PBVIm BF₄ is 3.85%,the pure water flux of PVC/BVIm BF₄ membrane can reach 358.3 L/m²h,the BSA rejection rate is 84.1%,and the contact angle is 66.5°.Testing of the membrane’s antifouling performance showed that the flux recovery rate of the PVC/BVIm BF₄ membrane was 71.2%,which had a good antifouling effect.Finally,the amphiphilic copolymer PMMA-b-PBVIm BF₄ was synthesized by radical polymerization.The copolymer was characterized by Fourier transform infrared spectroscopy（FTIR）,nuclear magnetic resonance hydrogen spectroscopy（¹HNMR）,and permeation gel chromatography（GPC）.Results The PMMA-b-PBVIm BF4copolymer was successfully synthesized.With the increase of PMMA-b-PBVIm BF4copolymer content,the surface of the membrane is positively charged,the average pore diameter increases,the pore size distribution becomes more uniform,and the hydrophilicity of the membrane surface is improved.When the PMMA-b-PBVIm BF4copolymer was added in an amount of 3.85%,the pure water flux of the membrane was360.4 L/m²h,and the BSA rejection rate was increased from 95.4%to 96.6%,achieving a simultaneous increase in permeability selectivity and a contact angle of 52.8°,at the same time the mechanical properties of the film have been greatly improved.The antifouling test results show that the flux recovery rate of the PVC/PMMA-b-PBVIm BF₄ blended membrane can reach 83.2%.After three repeated BSA pollution-cleaning cycles,the flux recovery rate can still be maintained above 73.2%.It has a good antifouling effect.