Preparation And Performance Study Of Ultra-high Separation Performance Nanofiltration Membrane

The efficient and convenient preparation of high-performance separation membranes with high permeability and high selectivity is of great significance for breaking the Robeson upper bound,improving separation efficiency and reducing separation energy consumption.In this paper,ultra-high perm-selective nanofiltration membranes were prepared by chitosan assisted interfacial polymerization to in-situ form an interlayer for the first time.The main research contents and results are as follows:?1?The preparation of CS-PIP aqueous solution:The property of aqueous phase solution is the key to in-situ form an interlayer during interfacial polymerization in this work because the viscosity of aqueous phase solution has an important influence on the diffusion rate of active monomer in interfacial polymerization process,which further affects the interfacial polymerization process.The aqueous solution containing chitosan nanoparticles?CSPs?was prepared by adding sodium polyphosphate?SPP?solution to piperazine?PIP?-chitosan?CS?blend solution by ionic crosslinking method.The results showed that the viscosity of aqueous solution increased significantly with the introduction of CS,and the viscosity of aqueous solution increased with the increase of CS concentration.The aging time had no significant effect on the solution viscosity and affected the composition of the aqueous solution.When the aging time is 0 h,CS mainly exists as free CS molecules in the aqueous solution;when the aging time is 6 h,CS mainly exists as CSPs in the aqueous solution.?2?The preparation of high perm-selective nanofiltration membrane by chitosan-assisted interfacial polymerization.High perm-selective PIP-CSP/TMC composite nanofiltration membranes were prepared by interfacial polymerization on polyethersulfone?PES?/sulfonated polysulfone?SPSf?supporting membrane.The CS-PIP solution containing SPP,CS,and PIP was used as the aqueous solution,and the n-hexane solution containing TMC was used as the organic phase,respectively.The results showed that the PIP-CSP₆/TMC composite membrane prepared with chitosan concentration of 0.5%and aging time of 6 h had the best permeability,whose pure water permeability was up to 45.2 L·m^-2·h^-1·bar^-1,and the rejection rate of Na₂SO₄ was 99.3%.And its permeability was equivalent to about 5-fold of the controlled PIP/TMC NF membrane,which was higher than the performance of the current literature reported and commercial nanofiltration membrane.?3?In order to further improve the comprehensive performance of the nanofiltration membrane,the PIP-CSP/TMC composite nanofiltration membrane was modified with copper sulfate solution.It was found that copper ions significantly improved the properties of the PIP-CSP₀/TMC composite nanofiltration membrane prepared by aging 0 h.The results showed that the pure water permeability of the PIP-CSP/TMC@Cu?II?composite nanofiltration membrane was increased from 28.1L·m^-2·h^-1·bar^-1to 50.0 L·m^-2·h^-1·bar^-1,the rejection rate of Na₂SO₄ was kept above99%,and the antibacterial rate of escherichia coli was 100%.This work provides a new design idea for the preparation of nanofiltration membrane with ultra-high perm-selectivity and high antibacterial property.