Filtration efficiency of nanometer-size aerosol particles

Wang, Hwa-Chi; Kasper, Gerhard

doi:10.1016/0021-8502(91)90091-u

Cited by 137 publications

(86 citation statements)

References 12 publications

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“…The mechanism of collision and sticking of small particles can be viewed as due to a balance between the particle kinetic energy and the mutual interaction between the particles (van der Waals forces) (Narsimhan and Ruckenstein 1985); when particles are in the free molecular regime, at high temperature such as that reached in flames, the particle kinetic energy may be higher than the interaction energy, resulting in a thermal rebound effect after collision (Wang and Kasper, 1991). Experimental results (Minutolo et al 1999;Sgro et al 2003;D'Alessio et al 2005) agreed with this simple model showing that flame-formed nanoparticles with 2-5 nm size possess a rate of coagulation lower than that of larger soot particles (20-50 nm) and well below the value predicted by the gas-kinetic theory, thus showing that the coagulation efficiency depends on particle size, morphology, and chemical structure.…”

Section: Introductionmentioning

confidence: 99%

Flame-Formed Carbon Nanoparticles: Morphology, Interaction Forces, and Hamaker Constant from AFM

Falco

Commodo

Minutolo

et al. 2015

Aerosol Science and Technology

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Interaction forces acting between combustion-generated carbon particles were studied by using atomic force microscopy (AFM). To this aim, carbon nanoparticles were produced in fuelrich ethylene/air laminar premixed flames with different equivalent ratios F, and analyzed at a fixed residence time in the flame. Particles were collected on mica substrates by means of a thermophoretic sampling system and then analyzed by AFM. A characterization of particle dimension and morphology were performed operating AFM in semicontact mode, showing that the shape of the particles collected on a sampling plate is never spherical. Increasing the flame-equivalent ratio, particle shape moves from an almost atomically thick object to thicker compounds, indicating the transformation from particles made of small, defective graphene-like sheets to particles containing stacked aromatic layers. Attractive and adhesive forces between a titanium nitride probe and sampled particles were calculated from force-distance curves acquired in AFM force spectroscopy mode. Assuming that van der Walls forces are the main contribution to attractive forces, the measurement of attractive forces allowed the evaluation of the Hamaker constant for the carbon particles as a function of the flame-equivalent ratio. The comparison of the measured Hamaker constants with the values for benzene and HOPG, suggests a continuous increase of the aromatic domains and the three-dimensional order within the particles when the flame-equivalent ratio increases.

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Section: Introductionmentioning

confidence: 99%

Flame-Formed Carbon Nanoparticles: Morphology, Interaction Forces, and Hamaker Constant from AFM

Falco

Commodo

Minutolo

et al. 2015

Aerosol Science and Technology

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“…Although there are some previous studies on fractional filtration efficiency in the size range of UFPs and MPPS Liu 1980, 1981;Wang and Kasper 1991;Hanley et al 1994;Hinds 1999;Ekberg and Shi 2009), studies for current intermediate ventilation air filters are still relatively scarce. One example is the study by Hanley et al (1994), which investigated fractional aerosol filtration efficiency of different contemporary filter media.…”

Section: Introductionmentioning

confidence: 99%

Intermediate Air Filters for General Ventilation Applications: An Experimental Evaluation of Various Filtration Efficiency Expressions

Shi

Ekberg

Langer

2013

Aerosol Science and Technology

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Neither the European standard nor the US standard for classification of intermediate class filters comprises testing of filter performance with respect to ultrafine particles (UFPs) or particles of the most penetrating size (MPPS). This could turn out to be a major lack in classification standards since UFPs have been pointed out as a serious health hazard. In this study, fractional efficiencies of eight new full-scale bag filters and twenty-three new filter medium samples were determined. The influence of air velocity and aerosol type was investigated, and correlations between efficiencies for UFPs (EF UFPs ), MPPS-sized particles (EF MPPS ) and 0.4 µm-sized particles (EF 0.4µm ) were established. The tested bag filters were challenged by four aerosol types: a neutralized atomized oil aerosol, the same oil aerosol but non-neutralized, a non-neutralized thermally generated oil smoke, and a "natural" indoor aerosol. The tests were carried out at different air velocities through the filter medium, ranging between 0.08 m/s and 0.22 m/s. The relationships that were observed between EF UFPs , EF MPPS, and EF 0.4µm appeared to be linear within the observed filtration efficiency ranges. These relationships were similar regardless of the test aerosol type used, but somewhat different for glass fiber filters than for charged synthetic filters. Generally, EF MPPS was 10-20% lower than EF 0.4µm . The influence of air velocity variations on the size resolved efficiency was determined. The glass fiber filters showed practically the same fractional efficiencies regardless of whether the test aerosol was neutralized or not. However, the charged synthetic filters showed substantially lower efficiencies when tested with the non-neutralized aerosol compared to the case when the aerosol was neutralized.

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“…The overall filtration performance of the membrane can be measured from Equation (15) [46,47], where E and P are the filtration and permeation in the membrane.…”

Section: Intrinsic Structural Properties and Their Relation To Depth mentioning

confidence: 99%

Simulation of Structural Characteristics and Depth Filtration Elements in Interconnected Nanofibrous Membrane Based on Adaptive Image Analysis

Pilehrood¹,

Heikkilä²,

Harlin³

2013

WJNSE

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Due to their unique structural features, electrospun membranes have gained considerable attention for use in applications where quality of depth filtration is a dominant performance factor. To elucidate the depth filtration phenomena it is important to quantify the intrinsic structural properties independent from the dynamics of transport media. Several methods have been proposed for structural characterization of such membranes. However, these methods do not meet the requirement for the quantification of intrinsic structural properties in depth filtration. This may be due to the complex influence of transport media dynamics and structural elements in the depth filtration process. In addition, the different morphological architectures of electrospun membranes present obstacles to precise quantification. This paper seeks to quantify the structural characteristics of electrospun membranes by introducing a robust image analysis technique and exploiting it to evaluate the permeation-filtration mechanism. To this end, a nanostructured fibrous network was simulated as an ideal membrane using adaptive local criteria in the image analysis. The reliability of the proposed approach was validated with measurements and comparison of structural characteristics in different morphological conditions. The results were found to be well compatible with empirical observations of perfect membrane structures. This approach, based on optimization of electrospinning parameters, may pave the way for producing optimal membrane structures for boosting the performance of electrospun membranes in end-use applications.

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Filtration efficiency of nanometer-size aerosol particles

Cited by 137 publications

References 12 publications

Flame-Formed Carbon Nanoparticles: Morphology, Interaction Forces, and Hamaker Constant from AFM

Flame-Formed Carbon Nanoparticles: Morphology, Interaction Forces, and Hamaker Constant from AFM

Intermediate Air Filters for General Ventilation Applications: An Experimental Evaluation of Various Filtration Efficiency Expressions

Simulation of Structural Characteristics and Depth Filtration Elements in Interconnected Nanofibrous Membrane Based on Adaptive Image Analysis

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