Preparation And Characterization Of Poly(N-hydroxyethyl Acrylamide) Functionalized Ultrafiltration Membranes And Loose Nanofiltration Membranes

N-Hydroxyethyl acrylamide?HEAA?is a kind of acrylamide type non-ionic water-soluble monomer.The poly?N-hydroxyethyl acrylamide??PHEAA?synthesized with excellent hydrophilicity,biocompatibility and low protein adhesion are widely used as antifouling coating materials.However,such polymers have rarely been reported in membrane modification.In this work,the amphiphilic triblock polymer,PHEAA-b-PMMA-b-PHEAA?PHMH?,containing polymethyl methacrylate?PMMA?and PHEAA was prepared via Radical Addition-Fragment chain Transfer?RAFT?polymerization and its application was explored in the modification of ultrafiltration membranes and the construction of loose nanofiltration membranes through functional assembly strategies.Firstly,PHMH as a kind of blending modifier to prepare PVDF/PHMH blend membranes via non-solvent induced phase separation method?NIPS?.The relationship between the content of PHMH and the structure and properties of the blend membranes were studied.The introduced of the modifier PHMH significantly improved the pore size,porosity,hydrophilicity,permeability and antifouling performance of the membrane surface.Due to surface segregation,the hydrophilic segment PHEAA in the modifier PHMH was enriched on the membrane surface.When the content of the modifier PHMH was 10%of the PVDF mass fraction,the performance of the blend membrane?M-2?was optimal.At the test pressure of 0.10 MPa,its pure water flux was221.55±8.91 L·m^-2·h^-1,and the rejection of BSA was 99.78%.After three cycles,the FRR was up to 94.70%,and the R_ir was as low as 4.28%.Compared with published literature,it showed that M-2 membrane has excellent antifouling performance while ensuring high flux and rejection.Secondly,the natural plant polyphenol tannic acid?TA?was added to the coagulation bath.During the NIPS process,amide bonds and hydroxyl groups in PHEAA and hydrogen bonds between the phenolic hydroxyl groups of TA caused the TA was enriched on the membrane surface because of the surface segregation.Unreacted phenolic hydroxyl groups in tannic acid can coordinate with Fe³⁺ions to form crosslinked network structure to prepare loose nanofiltration membrane to separate salt/dye wastewater effectively.The introduced of tannic acid and Fe³⁺,which changed the surface morphology of the membrane,caused the membrane surface pore size and porosity smaller,and formed a dense epithelial layer on the membrane surface.The membrane surface became smooth,the roughness was reduced,and the hydrophilicity was improved.At the test pressure of 0.10 MPa,the permeation flux of the M-TA/Fe membrane was 119.79±4.63 L·m^-2·h^-1,the rejection of Congo Red was99.92%,and the rejection for sodium chloride was 5.15%,this results indicated that the M-TA/Fe membrane can effectively separate salt/dye wastewater.In the cycle test,the flux recovery rate of the M-TA/Fe membrane was about 99%,which showed excellent antifouling performance.Compared with the membranes in the reported literature,the loose nanofiltration membranes we prepared had high flux while ensuring high rejection,and it provided new ideas to solve the"trade-off"effect between permeability and selectivity in the field of membrane separation and showed great application prospects in the efficient separation of salt/dye wastewater.