There is an on-going need for improved filtration media extending across a host of fields, industries and applications, including the microelectronics field, the medical device/pharmaceutical industries including health and hospital care applications, as well as food and cosmetic production facilities, and residential settings, e.g., in air purifiers and vacuum cleaners.
In U.S. Patent 7,645,327, New Jersey Institute of Technology (Newark, NJ) reveals systems and methods for achieving filtration that utilize agglomerates or granules of nanoparticles. The agglomerates or granules of nanoparticles may be used as and/or incorporated into a HEPA filtration system to remove solid or liquid submicron-sized particles, e.g., MPPS, in an efficient and efficacious manner.
According to NJIT Associate Director, New Jersey Center for Engineered Particulates Robert Pfeffer and team members Rajesh Dave, Stanislav Dukhin, Jose A Quevedo and Qun Yu, the filtration systems and methods utilize agglomerates or granules in a size range of about 100-500 microns. The agglomerates or granules of nanoparticles exhibit a hierarchical fractal structure.
In the case of agglomerates of nanoparticles, porosities of 0.9 or greater are generally employed, and for granules of nanoparticles, porosities that are smaller than 0.9 may be employed. Filter media formed from the agglomerates or granules may be formed from materials such as carbon black and fumed silica, and may be employed in baffled or non-baffled filtration apparatus.
The nano-filter media fills a need for filtration systems and methods that offer efficient and reliable filtration for sub-micron size particles, e.g., MPPS. The filtration systems effectively filter MPPS from feed streams that contain liquid and/or solid particles so as to prevent/reduce the potential for contamination and to protect systems/individuals from undesirable particulates, e.g., microorganisms such as bacteria, viruses and/or mold, pollen, asbestos, and the like.
FIG. 2 is a schematic illustration showing an exemplary hierarchical structure of fluidized agglomerates which are composed of sub-agglomerates (SA), which are in turn composed of primary agglomerates (PA).
FIG. 3B is an SEM image showing an agglomerate of nanosize fumed silica of about 140 micron (scale bar=20 micron magnification=1.13 K).
FIG. 4A is an SEM image showing clean agglomerates (granules) of carbon black of about 160 micron (scale bar=30 micron magnification=555).
FIG. 4B includes a pair of SEM images showing details of the surface of an agglomerate (granule) of carbon black of about 160 micron (scale bar=100 nm); the left image is at a magnification of about 185K and the right image is at a magnification of about 90K.
FIG. 5A is a schematic depiction of gas flow through an exemplary nanoagglomerate filtration media and FIG. 5B is a schematic diagram of gas flow through a conventional (prior art) HEPA fiber-based filter
FIG. 9 is a schematic depiction of an experimental filtration setup.
The improved setup included: (i) an aerosol generation system composed of an atomizer for the generation of submicron size droplets, a drier for removal of the solvent that contained the solid/liquid particles, and a neutralizer for removal of electrostatic charges; (ii) a particle counter located upstream of the filters composed of a Diluter and a Condensation Particle Counter (CPC); (iii) a system for measuring particle size distributions composed of a Scanning Mobility Particle Sizer (SMPS); and (iv) instruments for measuring typical variables related to filtration, such as flow and pressure drop.
A schematic illustration of the improved experimental setup is provided in FIG. 9. The experimental setup is generally effective for use with a clean air source, and the atomizer may be used to generate aerosols, e.g., solid aerosols using PSL spheres and liquid aerosols using oil.
A schematic illustration of the improved experimental setup is provided in FIG. 9. The experimental setup is generally effective for use with a clean air source, and the atomizer may be used to generate aerosols, e.g., solid aerosols using PSL spheres and liquid aerosols using oil.
The experimental setup is generally adapted to neutralize any electrostatic charges that may be generated/encountered, and includes a diluter for reducing the concentration of the aerosol feedstock. For purposes of particle size distribution measurements, the system includes classification functionality, i.e., an SMPS that classifies particles in the range of 15 to 800 nm, and detector functionality, i.e., a CPC that counts particles in the range of 0.015 microns up to 2 microns.
