Efficient nanoparticles removal and bactericidal action of electrospun nanofibers membranes for air filtration

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 X-ray 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 10⁴ CFU/mL E. coli bacteria.