Sodium Chloride Aerosol Particles Research Articles

Development of Polydiacetylene Embedded Polyurethane Nanocomposites as a Mask for Sensing and Filtering Fine Dust

The importance of fine dust has been recognized around the world, and research has been conducted on various regulatory devices and protection devices. In this study, we prepared PU/PDA(polyurethane/polydiacetylene) nanofiber composite materials using 10,12-pentacosadiynoic acid (PCDA) and polyurethane (PU), which have color transition phenomena, to develop mask materials that can detect and block fine dust. PCDA was mixed with polyurethane as the supporting polymer, and the solution was electrospun to produce nanofiber composites on a polypropylene spunbond nonwoven substrate. Then, the nanocomposites were photopolymerized using UV irradiation to produce PU/PDA nanofiber composites with the diameters of the fibers ranging from 129–254 nm at various mass ratios of PU to PCDA. As the mass ratios increased from 4:1 to 6:1, the diameters of the nanofibers also increased. By using the PP spunbond nonwoven material, the PU/PDA fibrous membranes (basis weight: 3 g/m2) had tensile strengths approaching 3.0–3.5 kgf/cm2. The asprepared nanocomposites with comparable air permeability (112 mm/s) had surprisingly high filtration efficiencies (97.8–99.6 %) and low pressure drops (56.9–61.78 Pa) for sodium chloride aerosol particles in the range of 400–600 nm and paraffin aerosol particles with an average particle diameter of 400 nm. The colorimetric response was more sensitive in the nanofibers made with a high mass ratio of PU to PCDA, i.e., up to 80 µg/m3 of fine dust. A clear visual color transition was observed when the concentration of the fine dust was 100 µg/m3. It was confirmed that the visual color transition appeared clearly enough to be distinguished easily by the naked eye, even in the nanofibers with lower contents of PDA.

Effects of surface morphology of electrospun polystyrene fiber on its air filtration performance

A series of membranes, made from polystyrene microfibers and with different morphologies, were fabricated via electrospinning method in this study. In addition, not only porous fibers but also beaded fibers were obtained by adjusting the experimental temperature in a reasonable and appropriate way. Assisted by a high-speed camera, the images of jet behaviors at different experimental temperatures were captured for the purpose of in-depth and comprehensive understanding of formation mechanism of different fiber morphologies. Mono-disperse sodium chloride aerosol particles with different sizes and cigarette smoke were used, for the attainment of the objective of evaluation on the filtration performance of fabricated membranes. The experimental results showed that straight fiber with narrow pores on its surface can be obtained at 20°C spinning temperature because of the rapid jet motion and solvent evaporation, and also, beaded fibers can be fabricated in the situation of spinning temperature higher than 25°C due to the sudden change of surface tension resulted from the fast solvent evaporation. The porous straight fibers exhibited excellent filtration performance to cigarette smoke and aerosol containing particles of all sizes (99.76%, 99.92%, and 99.99% filtration efficiency for particles with sizes of 0.3 µm, 0.5 µm, and 1 µm, respectively).

A Miniature Aerosol Sensor for Detecting Polydisperse Airborne Ultrafine Particles.

Counting and sizing of polydisperse airborne nanoparticles have attracted most attentions owing to increasing widespread presence of airborne engineered nanoparticles or ultrafine particles. Here we report a miniature aerosol sensor to detect particle size distribution of polydisperse ultrafine particles based on ion diffusion charging and electrical detection. The aerosol sensor comprises a couple of planar electrodes printed on two circuit boards assembled in parallel, where charging, precipitation and measurement sections are integrated into one chip, which can detect aerosol particle size in of 30–500 nm, number concentration in range of 5 × 102–5 × 107 /cm3. The average relative errors of the measured aerosol number concentration and the particle size are estimated to be 12.2% and 13.5% respectively. A novel measurement scheme is proposed to actualize a real-time detection of polydisperse particles by successively modulating the measurement voltage and deducing the particle size distribution through a smart data fusion algorithm. The effectiveness of the aerosol sensor is experimentally demonstrated via measurements of polystyrene latex (PSL) aerosol and nucleic acid aerosol, as well as sodium chloride aerosol particles.

A Novel Hierarchical Structured Poly(lactic acid)/Titania Fibrous Membrane with Excellent Antibacterial Activity and Air Filtration Performance

Hybrid poly(lactic acid)/titania (PLA/TiO2) fibrous membranes exhibiting excellent air filtration performance and good antibacterial activity were prepared via the electrospinning technique. By varying the composition of the precursor solutions and the relative humidity, the morphologies of PLA/TiO2fibers, including the nanopores and nanometer-scale protrusions on the surface of the fibers, could be regulated. The distribution of nanopores and TiO2nanoparticles on the surface of PLA/TiO2fibers was investigated. Nitrogen adsorption-desorption analysis revealed that nanopores and nanometer-scale protrusions play an important role in improving the specific surface area and nanopore volume of the relevant PLA/TiO2fibrous membrane. Filtration performance tests conducted by measuring the penetration of sodium chloride aerosol particles with a 260 nm mass median diameter indicated that fibers with a high surface roughness, large specific surface area, and large nanopore volume greatly improved the particle capture efficiency and facilitated the penetration of airflow. Furthermore, the introduction of TiO2nanoparticles endows the relevant fibrous membrane with antibacterial properties. The as-prepared PLA/TiO2fibrous membrane loaded with 1.75 wt% TiO2nanoparticles formed at a relative humidity of 45% exhibited a high filtration efficiency (99.996%) and a relatively low pressure drop (128.7 Pa), as well as a high antibacterial activity of 99.5%.

Facile electrospun Polyacrylonitrile/poly(acrylic acid) nanofibrous membranes for high efficiency particulate air filtration

Polyacrylonitrile/poly(acrylic acid) (PAN/PAA with weight radios of 3/7, 4/6, 5/5, 6/4, 7/3 and 10/0) nanofibers (NFs) were prepared as filter medium by electrospinning. The tensile strength of blended nanofibrous mats increased as increasing PAA content, from 3.8 to 6.6 MPa, higher than pristine PAN. The mesoporous effect of nanofibrous mats was also investigated from the nitrogen physisorption isotherms, average pore size in the range of 17–44 nm. Air filtration efficiency and pressure drop of nanofibrous mats were evaluated. PAN/PAA (6/4) NFs showed high filtration efficiency (99.994 %) with lowest pressure drop (160 Pa) for 300–500 nm sodium chloride aerosol particles at a 5.3 cm/s airflow velocity, which suggested this material was appropriate as a promising candidate for high performance filters.

Tortuously structured polyvinyl chloride/polyurethane fibrous membranes for high-efficiency fine particulate filtration

Two-tier composite filtration medium exhibiting excellent filtration performance to airborne particulate was prepared by a facile deposition of electrospun polyvinyl chloride (PVC)/polyurethane (PU) fibers on a conventional filter paper support. The tortuous structure and composition of resultant fibrous membranes can be finely controlled by regulating the precursor solution composition. By employing the PU incorporation, the pristine PVC fibrous membranes were endowed with robust tensile strength approaching to 9.9MPa. The plausible correlation between resultant blended fibrous structure and mechanical property of relevant membranes was discussed, and a three-step break mechanism upon the external stress was proposed. Additionally, quantitative pore size and porosity distribution analysis using the capillary flow porometry method has confirmed the tortuous structure of PVC/PU fibrous membranes. Furthermore, the as-prepared membranes with high abrasion resistance (134 cycles) and comparable air permeability (154.1mm/s) showed fascinating filtration efficiency (99.5%) and low pressure drop (144Pa) performance for 300–500nm sodium chloride aerosol particles, suggesting their use as a promising medium for variety of potential applications in air filtration.

Measurements of Extinction by Aerosol Particles in the Near-Infrared Using Continuous Wave Cavity Ring-Down Spectroscopy

Cavity ring-down spectroscopy using a fiber-coupled continuous wave distributed feedback laser at a wavelength of 1520 nm has been used to measure extinction of light by samples of nearly monodisperse aerosol particles <1 μm in diameter. A model is tested for the analysis of the sample extinction that is based on the Poisson statistics of the number of particles within the intracavity laser beam: variances of measured extinction are used to derive values of the scattering cross section for size-selected aerosol particles, without need for knowledge of the particle number density or sample length. Experimental parameters that influence the performance of the CRD system and the application and limitations of the statistical model are examined in detail. Determinations are reported of the scattering cross sections for polystyrene spheres (PSSs), sodium chloride, and ammonium sulfate, and, for particles greater than 500 nm in diameter, are shown to be in agreement with the corresponding values calculated using Mie theory or Discrete Dipole Approximation methods. For smaller particles, the experimentally derived values of the scattering cross section are larger than the theoretical predictions, and transmission of a small fraction of larger particles into the cavity is argued to be responsible for this discrepancy. The effects of cubic structure on the determination of optical extinction efficiencies of sodium chloride aerosol particles are examined. Values are reported for the real components of the refractive indices at 1520 nm of PSS, sodium chloride, and ammonium sulfate aerosol particles.

Calibration and measurement uncertainties of a continuous-flow cloud condensation nuclei counter (DMT-CCNC): CCN activation of ammonium sulfate and sodium chloride aerosol particles in theory and experiment

Abstract. Experimental and theoretical uncertainties in the measurement of cloud condensation nuclei (CCN) with a continuous-flow thermal-gradient CCN counter from Droplet Measurement Technologies (DMT-CCNC) have been assessed by model calculations and calibration experiments with ammonium sulfate and sodium chloride aerosol particles in the diameter range of 20–220 nm. Experiments have been performed in the laboratory and during field measurement campaigns, covering a wide range of instrument operating conditions (650–1020 hPa pressure, 293–303 K inlet temperature, 4–34 K m−1 temperature gradient, 0.5–1.0 L min−1 flow rate). For each set of conditions, the effective water vapor supersaturation (Seff, 0.05–1.4%) was determined from the measured CCN activation spectra (dry particle activation diameters) and Köhler model calculations. High measurement precision was achieved under stable laboratory conditions, where the relative standard deviations of Seff were as low as ±1%. During field measurements, however, the relative deviations increased to about ±5%, which can be mostly attributed to variations of the CCNC column top temperature with ambient temperature. The observed dependence of Seff on temperature, pressure, and flow rate was compared to the CCNC flow model of Lance et al. (2006). At high Seff the relative deviations between flow model and experimental results were mostly less than 10%, but at Seff≤0.1% they exceeded 40%. Thus, careful experimental calibration is required for high-accuracy CCN measurements – especially at low Seff. A comprehensive comparison and uncertainty analysis of the various Köhler models and thermodynamic parameterizations commonly used in CCN studies showed that the relative deviations between different approaches are as high as 25% for (NH4)2SO4 and 12% for NaCl. The deviations were mostly caused by the different parameterizations for the activity of water in aqueous solutions of the two salts. To ensure comparability of results, we suggest that CCN studies should always report exactly which Köhler model equations and parameters were used. Provided that the Aerosol Inorganics Model (AIM) can be regarded as an accurate source of water activity data for highly dilute solutions of (NH4)2SO4 and NaCl, only Köhler models that are based on the AIM or yield similar results should be used in CCN studies involving these salts and aiming at high accuracy. Experiments with (NH4)2SO4 and NaCl aerosols showed that the conditions of particle generation and the shape and microstructure of NaCl particles are critical for their application in CCN activation experiments (relative deviations up to 18%).

Fast in situ sizing technique for single levitated liquid aerosols

A fast in situ sizing technique for single levitated aerosol particles is presented. It makes use of the analysis of fast-Fourier-transformed vertically polarized Mie scattering patterns from single liquid aerosols levitated in a Paul-trap-type electrodynamic balance. The technique is shown to give reliable results for a test sphere of known physical properties. A first application to aqueous sodium chloride aerosol particles that changed size on humidity variation is presented, yielding good agreement with the full Mie theory.

Response characteristics for four different condensation nucleus counters to particles in the 3–50 nm diameter range

The response characteristics of four condensation nucleus counters (CNC's) to monodisperse sodium chloride aerosol particles in the 3–50 nm diameter range are compared with concentrations that were measured with an aerosol electrometer. Measurements were conducted in a workshop that was held at the University of Minnesota Particle Technology Laboratory, 24–28 September 1984. The CNC's that were investigated included a variable expansion ratio CNC (Niessner et al., 1984), a commercial steady flow CNC (TSI, Inc., Model 3020), a modified version of the TSI Model 3020 CNC (Stolzenburg and McMurry, 1984), and a mixing type CNC (Kousaka et al., 1982). The latter two instruments were specifically designed for accurate measurements of aerosol concentrations for particles smaller than 10 nm. For particles of 24 and 50 nm, responses of all CNC's were within about ± 10% of values determined with the aerosol electrometer. For particles smaller than 10–20 nm, concentrations measured with the electrometer exceeded those measured by the CNC's. For 3 nm NaCl particles, average CNC counting efficiencies (CNC response/electrometer response) were 0.06 ± 0.03 (TSI, Inc. Model 3020), 0.60 ± 0.18 (Kousaka et al. mixing-type CNC) and 0.83 ± 0.17 (Stolzenburg and McMurry modified Model 3020 CNC). The size-dependent counting efficiency of the variable expansion CNC was similar to that for the TSI CNC. These data indicate that counting efficiencies for very small particles depend substantially on instrument design.