Preparation Of Antifouling Membranes Containing Guanidine-based Polymer

Reverse osmosis(RO)and ultrafiltration(UF)have been widely applied in various industrial fields including desalination of seawater and brackish water,treatment and reclamation of wastewater,preparation of ultrapure water,and so on.However,organic and microbial fouling can lead to irreversible deterioration of the membrane performance,which constrains the development of RO and UF technology.This work introduces the preparation of a novel hydrophilic guanidine-based polymeric bactericide and its application in surface modification of RO and UF membranes for organic fouling and biofouling control.The novel guanidine-based polymer,poly(guanidine-hexamethylenediamine-PEI)(poly(GHPEI)),was first synthesized by a melt polycondensation method and then grafted onto the RO membrane surface through the Michael-type addition or Schiff base reaction between poly(GHPEI)and polydopamine(PDA).A series of characterization was then conducted to evaluate the membrane performance.In comparison with the pristine polyamide(PA)membrane,the modified GHPEI-PA membrane possesses a surface with better hydrophilicity,lower roughness and approaching neutral charge at pH 6~7.Results indicate that the GHPEI-PA membrane exhibits superior antifouling property against BSA and SA foulants.After 48 h of BSA and SA fouling,the flux decline rates are 33.8% and 28.7%,respectively.Then after cleaning,the flux recovery rates are 88.9% and 90.3%,respectively.In addition,the GHPEI-PA2%1h membrane shows sterilization ratios of 98.6% and 96.5% against E.coli and B.subtilis respectively.The X-ray photoelectron spectroscopy(XPS)and inhibition zone test of membranes after long-term immersion in water also indicate the stability of poly(GHPEI)on the membrane surface.The hybrid UF membrane was fabricated by blending hydrophilic and antimicrobial nanoparticles with polyethersulphone(PES).The core-shell poly(GHPEI)functionalized silica nanoparticles(SNP@PG)were prepared by grafting poly(GHPEI)onto the surface of silica via PDA immobilization.The hydrophilicity of SNP@PG surface is beneficial to the formation of the membrane surface with improved surface pore size and pore density,as well as enhanced hydrophilicity.Thus the hybrid PES/SNP@PG membrane achieves an increased water flux around 2.6 times that of the pristine PES membrane and maintains the similar BSA rejection.The antifouling property during BSA filtration is enhanced as well.After three fouling-cleaning cycles,the flux decline rate and flux recovery rate are 21.6% and 84.4%,respectively.After 90 min of serious microbial fouling,the flux of the hybrid PES/SNP@PG membrane is almost stable and decreases by only 21.6%.Moreover,the PES/SNP@PG-1 membrane shows sterilization ratios of 92.7% and 92.0% against E.coli and B.subtilis,respectively.The sterilization ratios remain above 91% after long-term immersion in water.