Preparation?filtration And Antibacterial Properties Of Medical Stone/PLLA Based Composite Fibrous Membranes

Air quality problems caused by fossil fuel combustion,industrial emissions and vehicle exhaust emissions have posed a serious threat to human health.At present,most filter materials used in the personal protective equipment are non-degradable melt-blown polypropylene non-woven fabrics.Only one method,increasing the material thickness,can used to improve the filtration efficiency of those non-woven fabrics,due to their pore sizes of generally larger than 100 ?m.But this method will result in the increase of filtration resistance.In addition,the longer you use filter materials,the more and viruses accumulate in the filter materials,which will harm our health.So,the filter materials must be regularly replaced.As a result,discarded non-degradable filter materials will further lead to serious environmental pollution.The key to solve the above problems is to prepare a new type of filter material that can effectively filter suspended particles in the air,meanwhile the material have degradability.In this paper,a new type of biodegradable MS/PLLA composite fibrous filtration membrane was prepared by electrospinning.Polylactic acid?PLLA?is a biodegradable material,and natural Medical stone?MS?has large specific surface area and strong adsorption capacity.In order to furtherly solve the pollution problem caused by bacteria and viruses in the filter materials,Ag nanoparticles were loaded on the surface of MS particles to prepare MS@AgNPs/PLLA antibacterial filter membrane with stronger antimicrobial properties.This paper systematically studied the effect of MS content on the preparation,the microstructure and the filtration performance of MS/PLLA composite fibrous membrane.The morphology and structure of the MS/PLLA composite fibrous membranes were characterized by means of Field-Emission Scanning Electron Microscope?FE-SEM?,Energy-dispersive X-ray spectroscopy?EDS?and Fourier transform infrared spectroscopy?FT-IR?.The filtration performance test,Thermogravimetric Analysis?TGA?,antibacterial properties of MS/PLLA composite fibrous membrane were investigated.The results show that,the membrane is composed of fiber stacking,with a meandering but penetrating pore structure.The single fiber has a larger aspect ratio.The particles of the medical stone are randomly distributed on the fiber to form a thick “nodular” structure.As the MS content increases,the fiber become thinner and the nodules appear more likely.The filtration performance analysis showed that when the mass ratio of PLLA to MS was 100:80,the average filtration efficiency of the composite fibrous membrane was more than 95%,96.48% and 98.64%,respectively,when the average particle size was more than 1?m,2.5 ?m and 10 ?m.Filtration resistance stable at 47 Pa.TGA showed that the total adsorption rate of flue gas was more than 45.3 wt% of that of the composite membrane?PLLA/MS = 100:80?.Antibacterial performance test results show that the antimicrobial rate is 40%.In order to improve the antibacterial property of the composite fibrous membrane,the surface modification of MS was carried out by using polydopamine?PDA?.MS @ AgNPs were prepared by reduction of silver ions by PDA using AgNO₃ as precursor.Fourier transform infrared spectroscopy?FT-IR?,FieldEmission Scanning Electron Microscope?FE-SEM?,Energy-dispersive X-ray spectroscopy?EDS?and X-ray diffraction?XRD?,X-ray photoelectron spectroscopy?XPS?and Transmission Electron Microscopy?TEM?were used to characterize the molecular structure,morphology,and determine the best preparation process.The results show that the Ag loaded on the MS surface is mainly in the form of Ag⁰,which is a face-centered cubic pure phase of single-phase silver with good crystallinity and uniform distribution on the surface of the MS.The amount of silver increases with the increase of reaction time.After 20 h,the amount of silver reached the upper limit and stabilized,the percentage of silver was 3.2%,and the average diameter of silver nanoparticles was 56.25 nm.Based on the preparation of MS/PLLA fibrous membranes,MS@AgNPs/PLLA composite fibrous membranes were prepared.The microstructure and molecular structure of the prepared composite fibrous membranes were characterized by SEM and FT-IR.The hydrophilicity filtration performance and antibacterial property of MS@AgNPs/PLLA composite fibrous membranes were investigated.The results showed that the filtration efficiency of particles with diameters of ?1 ?m,?2.5 ?m and ?10 ?m were 95.58%,96.97% and 98.63% for PLLA/MS@AgNPs with the mass ratio of 100:80,respectively.The filtration resistance was 48 Pa,and the filtration efficiency reached the requirement of sub-high efficiency filter.The antibacterial rate of MS@AgNPs/PLLA fibrous membrane was above 98%.The antibacterial effect was obvious and the effect was still good after 24 h.