| With the rapid growth of population and industrialization,the water crisis has devolved into one of the leading global environmental challenges facing mankind in the 21st century.Advanced materials and technologies present a promising solution to water scarcity.Particularly,membrane-based separation technology has been widely used in seawater desalination,wastewater treatment,brackish water recovery,drinking water treatment and purification,and other fields due to its advantages of energy-saving,environmentally friendly,and high efficiency.Among them,nanofiltration membrane separation technology with good selectivity can achieve selective separation of divalent ions and small organic molecules,and is widely used in contaminant removal,resource recovery,and reverse osmosis pretreatment.This study focused on the fabrication and application of novel nanofiltration membranes,through in-depth research on anti-fouling polyelectrolyte nanofiltration membranes and composite polyamide nanofiltration membranes,to achieve the control of antibiotic-resistant risk substances while mitigating membrane scaling and bio-fouling.Firstly,asymmetric polyelectrolyte nanofiltration membranes with excellent antibiotic and resistance gene retention performance and high permeability were prepared by layer-by-layer assembly.Asymmetric polyelectrolyte(PD ADMAC/PSS)nanofiltration membranes with loose bottom layers and dense top layers were fabricated on a PE S ultrafiltration substrate by adjusting the polyelectrolyte concentration and background ionic strength of the polyelectr olyte coating solution.This asymmetric polyelectrolyte membrane design scheme could combine the advantages of high permeability of the loose layer and excellent separation performance of the dense layer,with flexible and controllable pore size and surface potential.The optimized polyelectrolyte membrane with three loose bottom layers and two dense top layers exhibited pure water flux(15.4 LMH/Bar)comparable to commercial nanofiltration membrane NF270.Meanwhile,combining electrostatic exclusion and pore size sieving,the membrane exhibited excellent removal of a range of antibiotics and extracellular antibiotic resistance genes in water(>90%,>99.9%).In addition,the asymmetric polyelectrolyte membrane demonstrates favorable long-term operational stability.In addition,the results of pressure stability tests,longterm operational tests and pH stability tests show that this asymmetric polyelectrolyte membrane also demonstrates favorable stability.Secondly,novel antifouling thin-film composite polyamide nanofiltration membranes which could mitigate biofouling and gypsum fouling simultaneously were fabricated by introducing new quaternary ammonium compound monomers into interfacial polymerization.Amine-containing quaternary ammonium compounds(QAC)with excellent antibacterial properties were designed and synthesized as aqueous phase monomers,to fabricate defect-free QAC nanofiltration membranes by interfacial polymerization.The optimized membranes prepared using 0.5 wt%C12+ 0.5 wt%PIP aqueous phase solution exhibited the best overall performance.This membrane showed a larger pore size and enhanced negative surface charge compared to the control 1 wt%PIP membrane.It exhibited 51.3%flux enhancement and up to 84.4 Ca2+/SO42-selectivity without reducing the Na2SO4 retention rate,and effectively mitigated the concentration polarization on the membrane surface during nanofiltration operation.Meanwhile,owing to the great antibacterial property of QAC,0.5%C12 membrane showed 84.7%and 72.9%static antibacterial efficiency against Gram-negative E.coli and Gram-positive S.aureus,respectively.After 40 hours of gypsum scaling tests and E.coli dynamic biofouling tests,the 0.5%C12 membrane showed 78%and 25%reduction in flux loss compared to the control group,respectively,demonstrating good mitigation of biofouling and gypsum scaling. |
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