Self-doping And Copper Ion Enhanced Preparation Of Chitosan Composite Nanofiltration Membrane And Cr(?) Membrane Separation

The nanofiltration membrane is a pressure driven membrane having a performance between the ultrafiltration membrane and the reverse osmosis membrane,which has widely been used in the separation of divalent salts,dyes and organic solvents.The methods for preparing nanofiltration membrane include phase inversion,surface coating,interfacial polymerization and layer by layer self-assembly.Different membrane production methods produce different membrane properties and membrane applications.However,each method still has its own shortcomings,and the new nanofiltration membrane preparation method is still the current research hotspot.In this paper,a new method of homogeneous hybrid and copper ion(Cu(?))enhancement was used to prepare chitosan-based composite nanofiltration membrane.The main research contents are as follows:(1)Preparation of chitosan nanoparticle suspension.The sodium polyphosphate(SPP)was added to the chitosan(CS)solution to prepare a chitosan nanoparticle suspension by ion crosslinking.As a result,it was found that when the mass ratio of CS/SPP was in the range of 2.8 to 5.2,CS existed in the suspension in the form of chitosan nanoparticles(CSP)and fr-ee CS molecules.The size of CSP was about 40-50 um.(2)A new method of homogeneous hybrid and copper ion(Cu(?))enhancement to prepare chitosan-based composite nanofiltration membrane.The CSPs in the CSP suspension and tWi rtree(S molecules were simultaneously electrostatically adsorbed onto the surface of the alkalized polyacrylonitrile(mPAN)support,and the chitosan separation ayei(CSPM)was prepared by CSPs homogeneous hybrid.Finally,the CSPM/mPAN was immersed in a copper sulfate(CuSO4)solution for chelation crosslinking to obtain a CSPM-Cu(?)/mPAN.The results showed that the mass ratio of CS/SPP and Cu(?)chelation had a significant effect on properties of the membrane.When the ratio of CS to SPP was 3.4,the pure water flux of CSPM3.4-CLu(II)/mPAN was 74.8 L·-2·h-1.and Na2SO4 rejection was 93.3%.Compared with the CSPM3.4/mPAN,the pure water flux and Na2SO4 rejection of the CSPM3.4-Cu(II)/mPAN were simultaneously increased by 24.0%and 30.3%,respectively.Compared to the chitosan nanofiltration membrane prepared by interfacial polymerization,the CSPM3.4-Cu(?)/mPAN exhibited 3.6 times pure water flux and substantially the same rejection performance.The CSPM3.4-Cu(?)/mPAN had good stability.And the flux recovery rate after bovine serum albumin contamination reached 96.1%and the inhibition rate to E.coli was 100%,showing good anti-pollution and anti-bacterial properties.(3)Cr(?)separation by CSPM-Cu(?)/mPAN.Cr(?)separation with different pH and different concentrations of CSPM-Cu(?)/mPAN was tested.The results showed that when the pH was 9.0,Cr(VI)rejection with a concentration of 10 mmol/L was 93.6%,and the permeation flux was 53.9 L·m-2·h-1,which exhibited superior separation performance to high concentration C.r(?)compared to existing work.This work provides new ideas for the preparation,performance improvement and Cr(?)separation of nanofiltration membranes.