Commercial Filter Media Research Articles

Functionalized Double‐Gradient Janus Filters for Full‐Scale Capture and Inactivation of Multiscale Aqueous Bioaerosols

AbstractExposure to bioaerosols can result in severe infection and even death, prompting the development of numerous air filters to capture and inactivate bioaerosols. Although the wettability of filter media determines its bioaerosol‐capture efficiency, the dynamic collision behavior of multiscale aqueous bioaerosols on most filter media is poorly understood. A double‐gradient Janus paper (Janus paper) with a pore‐size gradient, asymmetric wettability, and biocidal and bioadhesion properties is fabricated in this study using an industrially available papermaking process. The dynamic collision behavior at the micrometer and millimeter scales indicates that the Janus paper enables the full‐scale blocking and/or capture of aqueous aerosols by a two‐step mechanism where the water‐repellent top layer blocks large‐size aqueous aerosols, while the hydrophilic bottom layer permits the adherence of small‐size aerosols to its fibers. The Janus paper exhibits a higher capture and inactivation capacity (inactivation efficiency: 98.3%), better dust‐holding capacity (> 21 g m−2), and a longer lifetime than commercial filter media. Commercial air purifiers comprising the Janus paper exhibit high potential for large‐scale commercial applications owing to the facile, low‐cost, and scalable fabrication method. This study enables future research on efficient and practicable Janus‐paper filter media.

상업용 수처리 소재의 Cr(VI) 제거 비교 및 Ferox의 Cr(VI) 흡착 특성 규명

상업용 수처리 소재의 Cr(VI) 제거 비교 및 Ferox의 Cr(VI) 흡착 특성 규명

수중 박테리아 제거를 위한 상업용 여재의 특성 비교

수중 박테리아 제거를 위한 상업용 여재의 특성 비교

Performance and Influencing Factors of Phosphorus Removal in Two BAFs with Artificial Crystal Seed Media

The phosphorus removal from low concentration phosphorus wastewater in two BAFs with different artificial crystal seed meida and the influence of HRT, Ca/P and pH on the treatment performance were investigated. The results showed that the artificial crystal media BAFs was more efficient than that of the current commercial filter media for phosphorus removal and recovery, and the suitable pH range of wastewater was also enlarged. When the initial phosphorus concentration was 10 mg/L, the optimum operational condition of steel slag base composite meida filter was HRT=30 min, n (Ca)/n (P)=1 and pH=8, as well as the optimum condition of water slag base composite media filter was HRT=60 min, n (Ca)/n (P)=2.5 and pH=8. XRD analysis showed that the reaction products of phosphorus removal by the two artificial crystal seed media filters were all hydroxy calcium phosphate, but its crystallinity was not high, which might due to the production of calcium carbonate in the reaction of phosphorus removal simultaneously.

Preparation and Characterization of Porous Composite Filter Medium by Polytetrafluoroethylene Foam Coating

The high costs of ceramic and Teflon filter media for hot gas cleaning has limited their industrial applications. This paper presents a foam coating technology that can be used to produce an inexpensive and highly efficient filter for industrial applications. A new apparatus was designed and built that coats porous glass mats with liquid-phase polytetrafluoroethylene (PTFE). The machine generates bubbles, enables the formation of uniform micropores less than 45 μm in diameter, and produces a product with air permeability greater than 5.5 cm3/cm2/sec. The resulting filter was found to be thermally stable up to 270 °C without any visible distortion and was comparable in dust collection efficiency to other commercial filter media. In addition, its de-dusting efficiency was greater than 85%, which is similar to that of other test filter media.

Experimental study of nanoparticles penetration through commercial filter media

In this study, nanoparticle penetration was measured with a wide range of filter media using silver nanoparticles from 3 nm to 20 nm at three different face velocities in order to define nanoparticle filtration characteristics of commercial fibrous filter media. The silver particles were generated by heating a pure silver powder source via an electric furnace with a temperature of 870°C, which was found to be the optimal temperature for generating an adequate amount of silver nanoparticles for the size range specified above. After size classification using a nano-DMA, the particle counts were measured by an Ultrafine Condensation Particle Counter (UCPC) both upstream and downstream of the test filter to determine the nanoparticle penetration for each specific particle size. Particle sampling time continued long enough to detect more than 105 counts at the upstream and 10 counts at the downstream sampling point so that 99.99% efficiency can be detected with the high efficiency filter. The results show a very high uniformity with small error bars for all filter media tested in this study. The particle penetration decreases continuously down to 3 nm as expected from the classical filtration theory, and together with a companion modeling paper by␣Wang et al. in this same issue, we found no significant evidence of nanoparticle thermal rebound down to 3 nm.

Investigations of Particle Penetration in Fibrous Filters: Part I. Experimental

This article is the first of a two-part series. The second article titled "Investigations of Particle Penetration in Fibrous Filters, Part II. Theoretical" will appear in the upcoming March/April 1998 issue of the Journal of the IEST. The performance of high-efficiency filters is evaluated using a semiautomated test system. This system is used for accurate measurements of submicron particle penetrations and pressure drops of filters. The system is designed to minimize errors and uncertainties associated with filter testing procedures. New commercial filter media, rated from ASHRAE-grade to ULPA, are tested using this system. The particle penetration characteristics of these media are obtained at different face velocities, ranging from 2 to 20 cm/s (0.79 to 7.9 in/s), and the particle diameter is varied from 0.05 to 0.05μm. The efficiencies of these media range from 15 percent to 99.9999 percent. The particle penetration characteristics of the media are consistent with the theories of collection by diffusion and interception in the range of operating conditions studies. The presence of the most penetrating particle size is observed, varying from 0.1 to 0.3μm for the different media. The most penetrating particle size is shown to shift toward the smaller particle size for increasing face velocity.

Optimization of Pleated Filter Designs Using a Finite-Element Numerical Model

A numerical model has been developed to optimize the design of pleated filter panels. In this model, the fluid flow is modeled by a steady laminar flow and the filter media resistance is governed by the Darcy-Lapwood-Brinkman equation. A finite element method with a nine-node Lagrangian element is used to solve the governing equations. For the rectangularly pleated filter panel, the numerical results agree well with the analytical model of Yu and Goulding (1992) and with his experimental data. The pressure drop increases at small pleat count due to increased media face velocity, and at large pleat count due to increased viscous drag in the pleat spacings. Therefore, an optimal pleat count for minimum pressure drop exists at a certain pleat height for each filter media type. The optimization of rectangular pleated filters, e.g., mini-pleated filter panels, has been performed for six commercial filter media. The optimal pleat count is shown to increase with decreasing media permeability of the filter media....

“Worst-Case” Aerosol Testing Parameters: III. Initial Penetration of Charged and Neutralized Lead Fume and Silica Dust Aerosols through Clean, Unloaded Respirator Filters

The National Institute for Occupational Safety and Health (NIOSH) tests and certifies respirator filter media according to Title 30, Code of Federal Regulations, Part 11 (30 CFR 11). Subpart K of those regulations specifies that a silica dust test, silica mist test, and/or lead fume test will be used to test and certify dust and mist; and dust, fume, and mist particulate air-purifying respirator filter media. NIOSH studies have shown that an aerosol particle of a certain size can be identified as the most penetrating particle ("worst case") size. Commercial filter media of various types have been studied and the filter's performance against a worst-case sodium chloride (NaCl) and dioctyl phthalate (DOP) aerosol evaluated. This investigation was done to complement those previous studies by determining how one manufacturer's particulate filters performed against the existing certification aerosol challenges as compared with the worst-case size DOP and NaCl aerosols. Only initial penetration values were determined, and no loading effects were considered. Both neutralized (Boltzman charge distribution) and unneutralized aerosols were used in order to assess the contribution of charging. The results show the dramatic effect of particle size on filter efficiency, and they show that the present methods are not as sensitive as the worst-case aerosol method.