Evaluation of filter media with fiber layer produced by the centrifugal spinning method with biocidal effect

Abstract

This study aimed to evaluate the air filtration performance of the fiber layer, produced by centrifugal spinning equipment, adhered to the surface of a commercial filter media applied to the internal ventilation system. Also, to investigate the antimicrobial effect of the thyme essential oil added to the fiber layer for Escherichia coli and Staphylococcus aureus. For this purpose, filter media were produced varying the operating conditions of the equipment, the type of solvent and the substrate. The characteristics of the fiber layer (fiber diameter, porosity, pore size), filtration performance (pressure drop, permeability and collection efficiency of nano and microparticles) and the biocidal effect were analyzed. It was found that the combination of the use of VCS and substrates with different permeabilities led to the formation of a fiber layer with different characteristics; the more permeable the substrates, the lower the porosity of the formed fiber layer. The increase in the power of the VCS promoted an increase in production of fibers, with the decrease in the size of the fibers and the porosity of the fiber layer, consequently, increase in the pressure drop; the collection time had a strong effect on the fiber diameter, in which the longer collection time increased the fiber diameter. The addition of the fiber layer decreased the permeability of the filter medium, increased the pressure drop and the collection efficiency. The investigation of the substrate covered by PAN fibers produced from solutions with dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) indicated that the filter media DMF and DMSO had similar collection efficiency. This may indicate that the DMSO solvent promoted stronger and more consistent polarization of the PAN chains than the DMF solvent, increasing the collection of particles from the DMSO filter medium. The DMSO filter medium was expected to have less collection efficiency than DMF because the DMSO filter medium had a smaller fiber diameter and pore size than DMF and values close to surface porosity. In the study of the filtration performance of pure substrate and substrate covered by PAN fibers, the collection efficiency of micro and nanoparticles was evaluated. For the collection efficiency of nanoparticles, the collection efficiency had an increase of about 20% with the addition of PAN fibers. For the collection efficiency of microparticles, at the beginning of the experiment, the substrate showed a collection efficiency of 50.5% and the covered substrate of 71.0%. After 30 minutes of filtration, the substrate remains in deep filtration, while the addition of the fiber layer promoted surface filtration, which significantly increased the collection efficiency to 97.2%. Finally, the fibers were spun in the same operating conditions on the substrate with essential thyme oil. The filter medium was named 5THY when the thyme essential oil was added to the PAN solution and THY when the essential oil of thyme was sprayed on the filter medium after the production of the fiber layer. The filter media covered with fibers showed a greater pressure drop and collection efficiency of micro and nanoparticles and less permeability than the substrate. THY showed higher collection efficiency than the substrate and 5THY, 99% for microparticles and 58% for nanoparticles. Through the antimicrobial test, it was found that THY showed a 99.999% reduction for the bacteria Escherichia coli and Staphylococcus aureus. While 5THY had a reduction of 15.5 and 89.0%, respectively. In the 5THY filter, the essential oil was added to the fibers before spinning, this may have caused the trapping and/or evaporation of the essential oil and, thus, reduced the reduction of bacteria.