Human exposure to air pollution and especially to nanoparticles is increasing due to the combustion of carbon-based energy vectors. Fibrous filters are among the various types of equipment potentially able to remove particles from the air. Nanofibers are highly effective in this area; however, their utilization is still a challenge due to the lack of studies taking into account both nanoparticle collection efficiency and antibacterial effect. The aim of this work is to produce and evaluate novel silver/polyacrylonitrile (Ag/PAN) electrospun fibers deposited on a nonwoven substrate to be used as air filters to remove nanoparticles from the air and also showing antibacterial activity. In order to determine the optimum manufacturing conditions, the effects of several electrospinning process parameters were analyzed such as solution concentration, collector to needle distance, flow rate, voltage, and duration. Ag/PAN nanofibers were characterized by Xray diffraction (XRD), Transmission Electron Microscopy (TEM), Fourier Transform Infra-Red spectroscopy (FTIR), Energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and Scanning Electron Microscopy (SEM). In addition, filtration performances were determined by measuring the pressure drop and collection efficiency of sodium chloride (NaCl) aerosol particles (9 to 300 nm diameters) using Scanning Mobility Particle Sizers (SMPS). Filters with high filtration efficiency (≈100%) and high-quality factor (≈0.05 Pa -1 ) were obtained even adding different concentrations of Ag nanoparticles (AgNPs) to PAN nanofibers. The resultant Ag/PAN nanofibers showed excellent antibacterial activity against 10 4 CFU/ml E.coli bacteria.The crystallinity of the silver nanoparticles was analyzed using X-ray diffraction analysis and shown in Figure S1. The peak observed at 17° for the 0AgF samples corresponds to (110) plan of PAN. Crystalline peak corresponds to silver nanoparticles were absent in all samples (1AgF, 10AgF, and 50AgF) which is due to the small size (<5nm) of silver nanoparticles.

Often, solid matter is separated from particle-laden flow streams using electrospun filters due to their high specific surface area, good ability to capture aerial particulate matter, and low material costs. Moreover, electrospinning allows incorporating nanoparticles to improve the filter’s air filtration efficiency and bacterial removal. Therefore, a new, improved polyacrylonitrile (PAN) nanofibers membrane that could be used to remove air pollutants and also with antibacterial activity was developed. We engineered three different filters that are characterized by the different particles embedded in the PAN nanofibers: titanium dioxide (TiO2), zinc oxide (ZnO), and silver (Ag). Then, their filtration performance was assessed by quantifying the filtration of sodium chloride (NaCl) aerosol particles of 9 to 300 nm in diameter using a scanning mobility particle sizer. The TiO2_F filter displayed the smallest fiber diameter and the highest filtration efficiency (≈100%). Conversely, the Ag_F filter showed the highest quality factor (≈0.06 Pa−1) because of the lower air pressure drop. The resulting Ag_F nanofibers displayed a very good antibacterial activity using an Escherichia coli suspension (108 CFU/mL). Moreover, the quality factor of these membranes was higher than that of the commercially available nanofiber membrane for air filtration.

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Currently, scientific research in the field of nanotechnology has attracted growing interest because of its several applications. The metal oxides have high added value in industrial processes and in addition, human exposure to these nanoparticles can cause respiratory problems. Filtration using fibrous filters is among the various options that can be used to provide efficient elimination of nanoparticles. While it is known that fibrous filters can successfully remove microparticles present in the air, there has been little research concerning the removal of nanoparticles using nickel oxide nanoparticles. The aim of this study was to evaluate the efficiency of three HEPA (High-Efficiency Particulate Air) filter media with glass and micro-quartz fiber for the removal of nickel oxide nanoparticles. Two HEPA filter with glass fibers (H1 and H2) and one HEPA filter with micro-quartz fibers (H3). Nanoparticles were generated using an atomizer generator through a 0.1 g/L nickel oxide water suspension. The efficiency of filter media was measured using an electrical mobility particle analyzer (SMPS) coupled to the filtration line and particles were counted before and after the filter media in the size range between 7.4 and 289 nm. Both filter media had efficiency collection above 99% but H1 filter stand out among the others.

RESUMO -A filtração utilizando filtros fibrosos tem se mostrado útil na retenção de micropartículas expostas no ar. Como há poucas pesquisas sobre o comportamento desses filtros na remoção de nanopartículas, o objetivo desse estudo foi avaliar a eficiência do filtro de fibra de celulose HEPA (High Efficiency Particulate Air Filter), de Vidro e de Micro Quartzo na remoção de nanopartículas, através da variação do tempo em soluções de 5 g/L de cloreto de sódio e de 5 g/L de sacarose, pela técnica de mobilidade elétrica. Através do sistema experimental, foi possível simular uma contaminação das nanopartículas em uma corrente de ar ultrapuro a uma vazão de 1,59 L/min e velocidade de 5cm/s, na qual foi feito a contagem das partículas antes e após a passagem pelo meio filtrante. Durante a deposição das partículas nos filtros, a queda de pressão foi monitorada por um manômetro digital em função do tempo. O filtro de vidro foi o que apresentou menor permeabilidade, já o filtro HEPA a maior permeabilidade. De uma forma geral, todos os meios filtrantes foram muito eficientes na remoção de nanopartículas durante os tempos de filtração de 1 a 3 horas, sendo que o filtro HEPA apresentou uma pequena variação na eficiência na faixa de tamanho de partículas entre 80 e 200 nm, sobretudo para a solução de sacarose. INTRODUÇÃOCada dia mais os seres humanos estão expostos a nanopartículas, até mesmo no ambiente de trabalho. Estes fatores estão associados ao desenvolvimento urbano, industrial e à crescente utilização de veículos motorizados.Nanopartículas são partículas com uma ou mais dimensões na nanoescala (HANNAH, 2008). Diversas pesquisas na área da epidemiologia e toxicologia atribuem que, quanto menor a dimensão das partículas expostas no ar, maior é a ocorrência de doenças cardiorrespiratórias (HUANG et al., 2004). Segundo FEITOSA apud EPA, isto é explicado pelo fato de que partículas menores que 10 m geralmente não são removidas pelo sistema respiratório superior e, por consequência, acabam atingindo os alvéolos pulmonares e a corrente sanguínea.Com o rigor das leis, o setor industrial foi obrigado a controlar a emissão de seus poluentes. Uma das técnicas mais utilizadas para capturar partículas de uma corrente gasosa é a filtração, seu processo ocorre pela passagem do aerosol através do meio filtrante, na qual as partículas vão se depositando sobre a superfície do filtro. Essa operação possui alta Área temática: Engenharia de Materiais e Nanotecnologia 1