Preparation Of Copper-based Antibacterial Nanofiber Membranes And Their Application In Water Disinfection

Nowadays,pathogenic microbial contamination and transmission in drinking water is still a severe imperilment for the security of global public health.The traditional method responding to these challenges is the addition of chlorine disinfectants directly into water based on the oxidation mechanism.Although this treatment technology offers rapid bacteria-inactivating effectiveness,disadvantages like the irreversible consumption of disinfectants,as well as the generation of disinfection by-products spurred the development into other alternative strategies.By contrast,membrane separation technologies have attracted more attention owing to their high sterilization efficiency and simplicity of operation.However,relying on the dense porous structures of these membrane filters to effectively intercept pathogenic bacteria,almost all of them are ideal venues for the formation of biofilms due to the inevitable adhesion and accumulation of microorganisms and the lack of bactericidal properties,resulting in serious deterioration of filtration flux.Therefore,designing a water disinfection material with antibacterial function to extend its lifespan is highly demanded.CuO-doped polyacrylonitrile nanofiber membranes(CuO/PAN NMs)were prepared firstly.The prepared copper oxide nanoparticles(CuO NPs)were doped into the precursor spinning solution,and then CuO/PAN NMs were obtained by electrospinning technology.The antibacterial properties of CuO NPs and CuO/PAN NMs were tested,and the results revealed that CuO NPs displaied 99.9%antibacterial efficiency,while CuO/PAN NMs only showed a low antibacterial efficiency of 90%.This is because the CuO NPs in CuO/PAN NMs were embedded into the fibers and could not directly contact with bacteria,resulting in a decrease in their bactericidal performance.Therefore,it is unreliable to prepare water disinfection materials with high fluxes and antibacterial function by doping CuO NPs in precursor spinning solutions,and it is necessary to design new experimental schemes to prepare high-efficiency antibacterial water disinfection materials.To solve the above-mentioned problems,freestanding copper hydroxide(Cu(OH)₂)nanosheet-assembled polyvinyl butyral(PVB)nanofiber membranes(CNNMs)were further prepared.Then CNNMs were characterized through energy dispersive spectrometer(EDS)and X-ray photoelectron spectroscopy(XPS),confirming that the chemical composition of the nanosheets was Cu(OH)₂.Subsequently,the mechanical properties,pore size distribution and structural stability of CNNMs were tested.Little plastic deformation could be observed after80 cycles at a large buckling strain of 80%,indicating superior fatigue resistance of CNNMs.The average pore size of CNNMs was 0.5107?m,which was smaller than PVB nanofiber membranes(PVB NMs)with a 0.9897?m average pore size.The structural stability test results of the nanosheets indicated that the vertically aligned Cu(OH)₂ nanosheets were in-suit rooted on the surface of the nanofiber scaffold with high binding fastness,after being subjected to violent vortex forces and 80 bending cycles,the CNNMs still maintained the integrated nanosheet structure.Finally,the antibacterial performance and water disinfection properties of CNNMs were tested,and the safety of CNNMs for water disinfection was analyzed.In the case of chemical oxygen demand(COD)was 0,the CNNMs killed Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus)with the efficiency of 99.999%in 25 and 20 min,respectively.When the COD increased to 2000 mg/L,the CNNMs still realized the ultra-efficient antibacterial property(99.999%)within 40 min,suggesting the remarkable antimicrobial property of CNNMs.It is particularly worth noting that the CNNMs illustrated a high flux of 24000 L m^-2 h^-1 while the 4-log reduction was achieved,confirming eminent dynamic disinfection property of CNNMs.Inhibition zone experiments showed that CNNMs were non-leaching antibacterial materials.The concentration of Cu ions was highest at the beginning(0.5 mg/L)and then decreased gradually,which was lower than the drink water standard from World Health Organization(1.0 mg/L).Both experiments above indicated the sterilization mechanism and the safety of CNNMs for water disinfection.This facile strategy may throw light on manufacturing novel inorganic nanosheet-rooted nanofibrous membranes for water disinfection and public health.