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1
Li, Xun Chao, e Cong Li. "The Development of Household Membrane Filters for Drinking Water Treatment". Applied Mechanics and Materials 535 (febbraio 2014): 446–50. http://dx.doi.org/10.4028/www.scientific.net/amm.535.446.
Testo completoAbstract (sommario):
The health risks and potential environment damage from unsafe municipal water have greatly accelerated the development of household water filter around the world. Similarly, the emergence of membrane technology in recently decades has greatly stimulated the rapid development and wide applications of membrane filter. The most widely used types of household membrane filters currently include RO membrane filter, UF membrane filter and MF membrane filter. Such filters are commercially available and of broad prospects in spite of membrane fouling. This review looks back over previous developments and applications of such three household membrane filters for better evaluation of their future development.
2
Alayande, Abayomi Babatunde, Yesol Kang, Jaewon Jang, Hobin Jee, Yong-Gu Lee, In S. Kim e Euntae Yang. "Antiviral Nanomaterials for Designing Mixed Matrix Membranes". Membranes 11, n. 7 (22 giugno 2021): 458. http://dx.doi.org/10.3390/membranes11070458.
Testo completoAbstract (sommario):
Membranes are helpful tools to prevent airborne and waterborne pathogenic microorganisms, including viruses and bacteria. A membrane filter can physically separate pathogens from air or water. Moreover, incorporating antiviral and antibacterial nanoparticles into the matrix of membrane filters can render composite structures capable of killing pathogenic viruses and bacteria. Such membranes incorporated with antiviral and antibacterial nanoparticles have a great potential for being applied in various application scenarios. Therefore, in this perspective article, we attempt to explore the fundamental mechanisms and recent progress of designing antiviral membrane filters, challenges to be addressed, and outlook.
3
Matlakh, Nikita, Dmytro Trushakov, Oleksandr Kozlovskyi e Marianna Fedotova. "Creation of a Multi-section Water Purification Filter With Automated Control of Membrane Pollution". National Interagency Scientific and Technical Collection of Works. Design, Production and Exploitation of Agricultural Machines, n. 52 (2022): 166–77. http://dx.doi.org/10.32515/2414-3820.2022.52.166-177.
Testo completoAbstract (sommario):
The article is devoted to the creation of a multi-section water purification filter, which can be made by hand at home. At the same time it is necessary to apply in the filter the automated control of pollution of membranes in sections of the filter. The main purpose of the study is to develop a simple and cheap multi-section filter for drinking water purification. The filter must have different cleaning technologies with the possibility of its own manufacture and with the possibility of automated control of membrane contamination. The task of the research is to develop and manufacture a working model of a multi-section filter for drinking water purification. The design of the filter should be multi-section with membranes containing various fillers for water purification; simple and cheap to make at home. The design of the filter should provide for automated control of the degree of contamination of the membranes in the filter sections. By analyzing the existing common household water filters, the most optimal solution for developing your own design of a household water filter has been determined. As a result of the analysis, a working model of a three-section water filter was created. The first section of the filter contains a membrane with quartz sand, the second section contains a membrane with activated carbon powder, the third section contains a membrane with small pieces of shungite (or with small pieces of silicon). As a result of an experimental study of the filtration of contaminated water using a three-section filter was determined next. The weight of water after passing through the filter decreases due to the retention of substances with a density greater than that of water (solid impurities). Also, the filtered water became clear and stopped foaming when shaken. This confirms the efficiency of the proposed filter. The developed three-section filter can be used as a separate stand-alone water filter or in addition with household polypropylene water filters for quality filtration of impurities up to 1 micrometer.
4
Papageorgiou, Georgios T., Laura Mocé-Llivina, Christina G. Christodoulou, Francisco Lucena, Dina Akkelidou, Eleni Ioannou e Juan Jofre. "A Simple Methodological Approach for Counting and Identifying Culturable Viruses Adsorbed to Cellulose Nitrate Membrane Filters". Applied and Environmental Microbiology 66, n. 1 (1 gennaio 2000): 194–98. http://dx.doi.org/10.1128/aem.66.1.194-198.2000.
Testo completoAbstract (sommario):
ABSTRACT We identified conditions under which Buffalo green monkey cells grew on the surfaces of cellulose nitrate membrane filters in such a way that they covered the entire surface of each filter and penetrated through the pores. When such conditions were used, poliovirus that had previously been adsorbed on the membranes infected the cells and replicated. A plaque assay method and a quantal method (most probable number of cytopathic units) were used to detect and count the viruses adsorbed on the membrane filters. Polioviruses in aqueous suspensions were then concentrated by adsorption to cellulose membrane filters and were subsequently counted without elution, a step which is necessary when the commonly used methods are employed. The pore size of the membrane filter, the sample contents, and the sample volume were optimized for tap water, seawater, and a 0.25 M glycine buffer solution. The numbers of viruses recovered under the optimized conditions were more than 50% greater than the numbers counted by the standard plaque assay. When ceftazidime was added to the assay medium in addition to the antibiotics which are typically used, the method could be used to study natural samples with low and intermediate levels of microbial pollution without decontamination of the samples. This methodological approach also allowed plaque hybridization either directly on cellulose nitrate membranes or on Hybond N+ membranes after the preparations were transferred.
5
Shin, Woo-Jin, Hyung-Seon Shin, Ji-Hun Hwang e Kwang-Sik Lee. "Effects of Filter-Membrane Materials on Concentrations of Trace Elements in Acidic Solutions". Water 12, n. 12 (12 dicembre 2020): 3497. http://dx.doi.org/10.3390/w12123497.
Testo completoAbstract (sommario):
Filtration is commonly used to separate liquids from solid materials before the determination of trace element concentrations in aqueous solutions. Therefore, it is important to determine how much elemental content is extracted from the filter itself or lost via absorption into the filter. In this study, we investigated three types of disposable syringe filters (polyvinylidene difluoride, PVDF; polytetrafluoroethylene, PTFE; PTFE with glass microfiber prefiltration media, GD/X) and their acid-cleaned versions using ammonium nitrate (NH4NO3) and acetic acid (HOAc) solutions. The concentrations of most trace elements (Li, Al, Cr, Mn, Co, Ni, Cu, Zn, Rb, Sr, Mo, Cd, Cs, Ba, Pb, and U) were higher in filtrates that had passed through acid-cleaned filters than those that had passed through uncleaned filters. In filtrates from PVDF and PTFE filters, many trace elements were below the detection limit. However, regardless of the filter type and acid cleaning, Li, Cu, Zn, Mo, and Ba concentrations in filtrates of NH4NO3 solutions, and Al, Cr, Mn, Cu, Zn, and Ba concentrations in filtrates of HOAc solutions were much higher than those of other trace elements. These differences were particularly noticeable in filtrates from GD/X filters containing glass microfiber layers. These data indicate that certain trace elements can be released from membrane materials by reacting with acid in the filtered solution. Furthermore, the amounts of each trace element were associated with the membrane type. These findings suggest that filter type should be carefully selected to obtain the required accuracy, in consideration of the target elements and whether an acid-cleaned filter is needed.
6
Zhang, Jinfeng, Guanyi Chen, Yanning Ma, Miao Xu, Songyan Qin, Xiaoliang Liu, Haijun Feng e Lian Hou. "Purification of pickling wastewater from the steel industry using membrane filters: Performance and membrane fouling". Environmental Engineering Research 27, n. 1 (29 dicembre 2020): 200486–0. http://dx.doi.org/10.4491/eer.2020.486.
Testo completoAbstract (sommario):
A new technique for treating pickling wastewater discharged from the steel industry using membrane filters was developed and membrane fouling was characterized in a full scale membrane filter. The morphological and chemical properties were examined through scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and inductively coupled plasma optical emission spectroscopy (ICP-OES) etc. The results showed that inorganic elements such as phosphates, chlorides, and sulfates were severely blocked in membrane surfaces and pores. The porosity, permeability, hydrophilic contact angle, and surface charge capacity of fouled membranes were all lower than those of new membranes, while the optimal neutralization reaction pH region for fouled membranes shifted and narrowed. Charge neutralization is a critical reason to membrane fouling. By increasing the Zeta potential of the pickling wastewater, the membrane fouling could be controlled. This method is proven to effectively improve the separation property of precipitates after pickling wastewater was neutralized. Moreover, Neutralization helped to reduce the unit number of treatment processes. This investigation could assist in obtaining a better understanding of the fouling properties and behavior in the full-scale membrane filters in the pickling wastewater treatment.
7
Afzal, Mohammad A., Joshua Peles e Andrew L. Zydney. "Comparative Analysis of the Impact of Protein on Virus Retention for Different Virus Removal Filters". Membranes 14, n. 7 (17 luglio 2024): 158. http://dx.doi.org/10.3390/membranes14070158.
Testo completoAbstract (sommario):
The performance of virus filters is often determined by the extent of protein fouling, which can affect both filtrate flux and virus retention. However, the mechanisms governing changes in virus retention in the presence of proteins are still not well understood. The objective of this work was to examine the effect of proteins on virus retention by both asymmetric (Viresolve® NFP and Viresolve® Pro) and relatively homogeneous (Ultipor® DV20 and PegasusTM SV4) virus filtration membranes. Experiments were performed with bacteriophage ϕX174 as a model parvovirus and human serum immunoglobulin G (hIgG) as a model protein. The virus retention in 1 g/L hIgG solutions was consistently less than that in a protein-free buffer solution by between 1 to 3 logs for the different virus filters. The virus retention profiles for the two homogeneous membranes were very similar, with the virus retention being highly correlated with the extent of flux decline. Membranes prefouled with hIgG and then challenged with phages also showed much lower virus retention, demonstrating the importance of membrane fouling; the one exception was the Viresolve® Pro membrane, which showed a similar virus retention for the prefouled and pristine membranes. Experiments in which the protein was filtered after the virus challenge demonstrated that hIgG can displace previously captured viruses from within a filter. The magnitude of these effects significantly varied for the different virus filters, likely due to differences in membrane morphology, pore size distribution, and chemistry, providing important insights into the development/application of virus filtration in bioprocessing.
8
Wohlsen, T., J. Bates, B. Gray e M. Katouli. "Evaluation of Five Membrane Filtration Methods for Recovery of Cryptosporidium and Giardia Isolates from Water Samples". Applied and Environmental Microbiology 70, n. 4 (aprile 2004): 2318–22. http://dx.doi.org/10.1128/aem.70.4.2318-2322.2004.
Testo completoAbstract (sommario):
ABSTRACT We evaluated the efficiency of five membrane filters for recovery of Cryptosporidium parvum oocysts and Giardia lamblia cysts. These filters included the Pall Life Sciences Envirochek (EC) standard filtration and Envirochek high-volume (EC-HV) membrane filters, the Millipore flatbed membrane filter, the Sartorius flatbed membrane filter (SMF), and the Filta-Max (FM) depth filter. Distilled and surface water samples were spiked with 10 oocysts and 10 cysts/liter. We also evaluated the recovery efficiency of the EC and EC-HV filters after a 5-s backwash postfiltration. The backwashing was not applied to the other filtration methods because of the design of the filters. Oocysts and cysts were visualized by using a fluorescent monoclonal antibody staining technique. For distilled water, the highest percent recovery for both the oocysts and cysts was obtained with the FM depth filter. However, when a 5-s backwash was applied, the EC-HV membrane filter (EC-HV-R) was superior to other filters for recovery of both oocysts (n = 53 ± 15.4 per 10 liters) and cysts (n = 59 ± 11.5 per 10 liters). This was followed by results of the FM depth filter (oocysts, 28.2 ± 8, P = 0.015; cysts, 49.8 ± 12.2, P = 0.4260), and SMF (oocysts, 16.2 ± 2.8, P = 0.0079; cysts, 35.2 ± 3, P = 0.0079). Similar results were obtained with surface water samples. Giardia cysts were recovered at higher rates than were Cryptosporidium oocysts with all five filters, regardless of backwashing. Although the time differences for completion of filtration process were not significantly different among the procedures, the EC-HV filtration with 5-s backwash was less labor demanding.
9
Sanaei, P., G. W. Richardson, T. Witelski e L. J. Cummings. "Flow and fouling in a pleated membrane filter". Journal of Fluid Mechanics 795 (13 aprile 2016): 36–59. http://dx.doi.org/10.1017/jfm.2016.194.
Testo completoAbstract (sommario):
Pleated membrane filters are widely used in many applications, and offer significantly better surface area to volume ratios than equal-area unpleated membrane filters. However, their filtration characteristics are markedly inferior to those of equivalent unpleated membrane filters in dead-end filtration. While several hypotheses have been advanced for this, one possibility is that the flow field induced by the pleating leads to spatially non-uniform fouling of the filter, which in turn degrades performance. In this paper we investigate this hypothesis by developing a simplified model for the flow and fouling within a pleated membrane filter. Our model accounts for the pleated membrane geometry (which affects the flow), for porous support layers surrounding the membrane, and for two membrane fouling mechanisms: (i) adsorption of very small particles within membrane pores; and (ii) blocking of entire pores by large particles. We use asymptotic techniques based on the small pleat aspect ratio to solve the model, and we compare solutions to those for the closest-equivalent unpleated filter.
10
Canalli Bortolassi, Ana Cláudia, Vádila Giovana Guerra, Mônica Lopes Aguiar, Laurence Soussan, David Cornu, Philippe Miele e Mikhael Bechelany. "Composites Based on Nanoparticle and Pan Electrospun Nanofiber Membranes for Air Filtration and Bacterial Removal". Nanomaterials 9, n. 12 (6 dicembre 2019): 1740. http://dx.doi.org/10.3390/nano9121740.
Testo completoAbstract (sommario):
Often, solid matter is separated from particle-laden flow streams using electrospun filters due to their high specific surface area, good ability to capture aerial particulate matter, and low material costs. Moreover, electrospinning allows incorporating nanoparticles to improve the filter’s air filtration efficiency and bacterial removal. Therefore, a new, improved polyacrylonitrile (PAN) nanofibers membrane that could be used to remove air pollutants and also with antibacterial activity was developed. We engineered three different filters that are characterized by the different particles embedded in the PAN nanofibers: titanium dioxide (TiO2), zinc oxide (ZnO), and silver (Ag). Then, their filtration performance was assessed by quantifying the filtration of sodium chloride (NaCl) aerosol particles of 9 to 300 nm in diameter using a scanning mobility particle sizer. The TiO2_F filter displayed the smallest fiber diameter and the highest filtration efficiency (≈100%). Conversely, the Ag_F filter showed the highest quality factor (≈0.06 Pa−1) because of the lower air pressure drop. The resulting Ag_F nanofibers displayed a very good antibacterial activity using an Escherichia coli suspension (108 CFU/mL). Moreover, the quality factor of these membranes was higher than that of the commercially available nanofiber membrane for air filtration.
11
Marsono, B. D., A. Yuniarto, A. Purnomo e ES Soedjono. "Comparison Performances of Microfiltration and Rapid Sand Filter Operated in Water Treatment Plant". IOP Conference Series: Earth and Environmental Science 1111, n. 1 (1 dicembre 2022): 012048. http://dx.doi.org/10.1088/1755-1315/1111/1/012048.
Testo completoAbstract (sommario):
Abstract Water treatment of river water is generally carried out conventionally, a rapid sand filter consisting of a coagulation unit, flocculation, sedimentation, and sand filtration. One of the disadvantages of sand filters is that it requires a large volume of water for washing, inconsistent quality, and escape of microorganisms less than 0.01 mm in size. Membrane technology can solve this problem with the advantages of including a more compact unit with a larger surface area per volume. The immersed membrane has another advantage that it is possible to integrate with sedimentation units so that it can save the land. This paper will study a comparison of the performance of the microfiltration membrane with sand filters in two drinking water treatment plants. The comparison method is based on technical specification, capacity, and quality performance. The results show that the quality of the microfiltration membrane filtrate is better than the sand filter. Overall immersed membrane microfiltration with pore size 0.05 µm had removal efficiency of E. Coli was 100%, turbidity 93 %, TSS 100%. Organic permanganate value 37%, and Microplastics 81.5%, whereas pore size 0.07 µm removal E. Coli was 99.8%, turbidity 52.9 %, Organic permanganate value 17.6%, and Microplastics 37.1%. The productivity of microfiltration membranes is more significant than rapid sand filters. The removal efficiency of WWTP Ngagel was better than Siwalan Panji.
12
Akimova, Olga V., Roman D. Svetogorov, Alexey V. Ovcharov e Nataliya R. Roshan. "The Structure Stability of Metal Diffusion Membrane-Filters in the Processes of Hydrogen Absorption/Desorption". Membranes 12, n. 11 (11 novembre 2022): 1132. http://dx.doi.org/10.3390/membranes12111132.
Testo completoAbstract (sommario):
The evolution of a nanostructured state of palladium—lead membrane alloys during their interaction with hydrogen was studied using precision X-ray diffraction with synchrotron radiation (SR) and scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDXS). The importance of this topic is due to the need and demand for improving the performance characteristics of dense metal diffusion filters for high purity hydrogen separation processes. Palladium-based membrane filters with lead concentrations of 5 and 20 wt.% were prepared via electric arc melting from high purity metals (99.95%). The thickness of the filters was 50 μm. Hydrogenation was carried out from a gas medium at 573 K and the pressure of 16 atm. within 150 min. The focus of the study is on the structural state of diffusion filter membranes depending on the content of the palladium-alloying element—lead—and on analysis of the substructure of alloys before and 5300 h relaxation after hydrogenation is carried out. Specific features of the surface morphology and the structure of the membrane filters depending on the concentration of lead in the alloys are determined. The formation and development of deformation processes in metal systems upon the hydrogenation is shown. The establishment of peculiarities of hydrogen interaction with metals will contribute to obtaining new potentially important characteristics of membrane filters.
13
Casino, Pablo, Asunción López, Sara Peiró, Santiago Rios, Aldous Porta, Gemma Agustí, Daniela Terlevich, Daniel Asensio, Ana María Marqués e Núria Piqué. "Polyethersulfone (PES) Filters Improve the Recovery of Legionella spp. and Enhance Selectivity against Interfering Microorganisms in Water Samples". Polymers 15, n. 12 (13 giugno 2023): 2670. http://dx.doi.org/10.3390/polym15122670.
Testo completoAbstract (sommario):
In the analysis of water samples, the type of filtration membrane material can influence the recovery of Legionella species, although this issue has been poorly investigated. Filtration membranes (0.45 µm) from different materials and manufacturers (numbered as 1, 2, 3, 4, and 5) were compared: mixed cellulose esters (MCEs), nitrocellulose (NC), and polyethersulfone (PES). After membrane filtration of samples, filters were placed directly onto GVPC agar and incubated at 36 ± 2 °C. The highest mean counts of colony-forming units and colony sizes for Legionella pneumophila and Legionella anisa were obtained with PES filters (p < 0.001). All membranes placed on GVPC agar totally inhibited Escherichia coli and Enterococcus faecalis ATCC 19443 and ATCC 29212, whereas only the PES filter from manufacturer 3 (3-PES) totally inhibited Pseudomonas aeruginosa. PES membrane performance also differed according to the manufacturer, with 3-PES providing the best productivity and selectivity. In real water samples, 3-PES also produced a higher Legionella recovery and better inhibition of interfering microorganisms. These results support the use of PES membranes in methods where the filter is placed directly on the culture media and not only in procedures where membrane filtration is followed by a washing step (according to ISO 11731:2017).
14
Rodrigue, Lynda, e Marc C. Lavoie. "Comparison of different membranes for use in the colony-immunoblot technique". Canadian Journal of Microbiology 36, n. 3 (1 marzo 1990): 231–35. http://dx.doi.org/10.1139/m90-040.
Testo completoAbstract (sommario):
We compared five different supports (Whatman paper filters Nos. 1, 5, and 40, nitrocellulose, and Nylon 66) for their suitability in the colony-immunoblot (CIB) technique. Results indicate that Whatman No. 5 filter paper recovered 94–98% of the bacterial colonies tested, were more resistant to tearing than the other Whatman papers tested, and showed reduced cross-reactions as compared with nitrocellulose membranes. Whatman No. 5 filters are 20 times less expensive than the nitrocellulose membranes usually used in the CIB technique. We thus adopted the former for our ecological studies of the murine oral cavity. Key words: colony-immunoblot, filter paper, nitrocellulose membrane, microbial ecology, oral cavity.
15
Schuerger, Andrew C., e William Hammer. "Use of Cross-Flow Membrane Filtration in a Recirculating Hydroponic System to Suppress Root Disease in Pepper Caused by Pythium myriotylum". Phytopathology® 99, n. 5 (maggio 2009): 597–607. http://dx.doi.org/10.1094/phyto-99-5-0597.
Testo completoAbstract (sommario):
Zoosporic pathogens in the genera Pythium and Phytophthora cause extensive root disease epiphytotics in recirculating hydroponic vegetable-production greenhouses. Zoospore cysts of Pythium myriotylum Drechsler were used to evaluate the effectiveness of cross-flow membrane filters to control pythiaceous pathogens in recirculating hydroponic systems. Four membrane filter brands (Honeycomb, Polypure, Polymate, and Absolife) were tested alone or in combination to determine which filters would effectively remove infective propagules of P. myriotylum from solutions and reduce disease incidence and severity. Zoospore cysts of P. myriotylum generally measured 8 to 10 μm, and it was hypothesized that filters with pore-sizes <5 μm would be effective at removing 100% of the infective propagules and protect pepper plants from root infection. Single-filter assays with Honeycomb and Polypure brands removed 85 to 95% of zoospore cysts when pore sizes were rated at 1, 5, 10, 20, or 30 μm. Single-filter assays of Polymate and Absolife brands were more effective, exhibiting apparently 100% removal of zoospore cysts from nutrient solutions on filters rated at 1 to 10 μm. However, plant bioassays with Honeycomb and Polymate single filters failed to give long-term protection of pepper plants. Double-filter assays with 1- and 0.5-μm Polymate filters significantly increased the protection of pepper plants grown in nutrient film technique systems but, eventually, root disease and plant wilt could be observed. Insect transmissions by shore flies were not factors in disease development. Scanning electron microscopy images of zoospore cysts entrapped on Polymate filters revealed zoospore cysts that were either fully encysted, partially encysted, or of unusually small size (3 μm in diameter). It was concluded that either the atypically small or pliable pleomorphic zoospore cysts were able to penetrate filter membranes that theoretically should have captured them.
16
Katrivesis, Fotios K., Varvara Sygouni, Christakis A. Paraskeva e Vagelis G. Papadakis. "A Performance Comparison of Pilot-Scale Sand Filtration and Membrane Filtration of Glafkos River Water". Journal of Marine Science and Engineering 9, n. 2 (16 febbraio 2021): 203. http://dx.doi.org/10.3390/jmse9020203.
Testo completoAbstract (sommario):
Surface-water treatment plants use the flocculation–precipitation method followed by gravity filters to remove suspended solids. In the present work, the replacement of gravity filters with ultrafiltration membrane units is suggested to improve the efficiency of water treatment and to reduce fixed and operational costs. A parametric pilot-scale study was conducted to compare the filtration efficiency of a deep bed and a membrane module for water-simulating river water of various turbidity degrees. Suspensions of kaolinite were prepared to simulate turbidity of the Glafkos River, Achaia Region of Greece and were filtered using a laboratory sand-bed column and a pilot ultrafiltration (UF) membrane unit. Operational parameters such as the particle concentration ratio, the flow rate, and the filter head loss were studied in the case of the granular bed. In the case of membrane filtration, the permeate flux, turbidity, and membrane permeability loss due to fouling were tested. A discussion in terms of the operational cost and environmental impacts was performed. Filtration capacity of the sand filter is a decreasing function of the flow rate and it was found less efficient than membrane ultrafiltration for increased turbidity or increased particle concentration values. Membrane ultrafiltration could achieve long-term economic profit while it is characterized by minimum environmental impact since the use of chemical reagents and the production of waste sludge are limited.
17
Persaud, Dave, Mikhail Smirnov, Daniel Fong e Pejman Sanaei. "Modeling of the Effects of Pleat Packing Density and Cartridge Geometry on the Performance of Pleated Membrane Filters". Fluids 6, n. 6 (5 giugno 2021): 209. http://dx.doi.org/10.3390/fluids6060209.
Testo completoAbstract (sommario):
Pleated membrane filters are widely used to remove undesired impurities from a fluid in many applications. A filter membrane is sandwiched between porous support layers and then pleated and packed into an annular cylindrical cartridge with a central hollow duct for outflow. Although this arrangement offers a high surface filtration area to volume ratio, the filter performance is not as efficient as those of equivalent flat filters. In this paper, we use asymptotic methods to simplify the flow throughout the cartridge to systematically investigate how the number of pleats or pleat packing density affects the performance of the pleated membrane filters. The model is used to determine an optimal number of pleats in order to achieve a particular optimum filtration performance. Our findings show that only the “just right”—neither too few nor too many—number of pleats gives optimum performance in a pleated filter cartridge.
18
Liu, Jing Xian, De Qiang Chang, Yue Xie, Ning Mao e Xi Sun. "Research on Fine Particles Capture of Baghouse Filter Media". Applied Mechanics and Materials 300-301 (febbraio 2013): 1293–97. http://dx.doi.org/10.4028/www.scientific.net/amm.300-301.1293.
Testo completoAbstract (sommario):
Industrial dust emission is one of the main sources of fine particle especially for PM2.5 in atmosphere. Filter media is the key component for baghouse. In the paper, several normal needle felt filters and membrane filter are studied through experiments. The performances of filter such as resistance, capture efficiency for total particle and number counting efficiency for fine particle are tested.The experimental results show that the resistance of filter increase after aging, the resisitance increasing rate of membrane filter is the smallest; The efficiencies for total particles of normal filter are above 99.9% at clean state, and 99.99% at stable state after aging; Although the filters have high efficiency for total particle, but the number counting efficiency for 10μm particle is 94%-99%, and 52%-92% for 2μm particles. New filters for fine particles are needed.
19
Shim, Euijin, Jeong-Phil Jang, Jai-Joung Moon e Yeonsang Kim. "Improvement of Polytetrafluoroethylene Membrane High-Efficiency Particulate Air Filter Performance with Melt-Blown Media". Polymers 13, n. 23 (23 novembre 2021): 4067. http://dx.doi.org/10.3390/polym13234067.
Testo completoAbstract (sommario):
Polytetrafluoroethylene (PTFE) membrane filters are widely used in low-load application areas, such as industrial cleanrooms, due to their low initial pressure drop. In this study, melt-blown (MB) nonwoven was introduced as a pre-filtration layer at the front end of a high-efficiency particulate air (HEPA) filter to improve the filter performance of the PTFE membrane. Pre-filtration reduces the average particle size, which reaches the PTFE membrane and reduces the dust load on the HEPA filters. A comparative analysis of the HEPA filters by composite MB and PTFE was conducted. Regarding the MB composite on the PTFE, low-weight and high-weight MB composites were effective in increasing dust filtration efficiency, and the dust loading capacity of the PTFE composite with high-weight MB increased by approximately three times that of the PTFE membrane. In addition, the filter was installed on an external air conditioner in an actual use environment and showed a high efficiency of 99.984% without a change in differential pressure after 120 days.
20
Ahluwalia, R. K., e H. K. Geyer. "Fluid Mechanics of Membrane-Coated Ceramic Filters". Journal of Engineering for Gas Turbines and Power 118, n. 3 (1 luglio 1996): 526–33. http://dx.doi.org/10.1115/1.2816679.
Testo completoAbstract (sommario):
Analytical models are formulated for evaluating the fluid mechanics of membrane-coated, dead-end ceramic filters. The models are applicable to forward flow as in the filtration mode and reverse flow as in the back-pulse cleaning mode. General criteria are derived to size the filter passages from considerations of Darcy pressure drop, friction pressure drop, and the dynamic head. These criteria together with Reynolds numbers are shown to provide measures of nonuniformities in face velocity and pressure that develop in the filter passages for atmospheric and high-pressure applications. A methodology is presented for optimizing the venturi geometry from the standpoint of minimizing pulse gas usage and controlling the thermal load imposed on the filter assembly.
21
Hong, Chuanxue, Patricia A. Richardson e Ping Kong. "Comparison of Membrane Filters as a Tool for Isolating Pythiaceous Species from Irrigation Water". Phytopathology® 92, n. 6 (giugno 2002): 610–16. http://dx.doi.org/10.1094/phyto.2002.92.6.610.
Testo completoAbstract (sommario):
Filter-based isolation is the primary approach for quantifying plant pathogens in irrigation water; however, the performance of various membranes is largely unknown. This study evaluated nine hydrophilic membranes for recovery of pythiaceous species, a group of very common and destructive pathogens on numerous ornamental plants and many agronomic crops. Three sources of water samples and three plating methods were used for the membrane comparison. Durapore5, Millipore5, and Osmonics5 filtered 100 ml of irrigation water or 50 ml of irrigation runoff in 10 s or less, whereas the other membranes required 34 s to 13.5 min or even a second membrane to filter the same water sample volume. Millipore5 and Durapore5 showed greater recovery rates than other membranes for all water sources when the membranes were directly inverted onto agar plates. Durapore5 was also one of the top two membranes for spore suspension and irrigation water samples when membrane washings were spread over the agar surface. Durapore5 was the only membrane that consistently performed well for both spore suspension and irrigation water samples. These data suggest that use of Durapore5 not only increases the sensitivity of filter-based isolation for quantifying pythiaceous species in irrigation water but also saves filtering time.
22
Ravnik, Jure, Gorazd Bombek, Aleš Hribernik, Timi Gomboc, Matej Zadravec, Aleks Kapun, Grega Hrovat, Jure Gradišek e Matjaž Hriberšek. "Energy Intake Models for Intermittent Operation of Dead-End Microfiltration Filling Line". Energies 15, n. 23 (23 novembre 2022): 8854. http://dx.doi.org/10.3390/en15238854.
Testo completoAbstract (sommario):
In filling lines equipped with membrane separation devices in the form of filters energy, consumption is only one of the important working parameters, the other being sustainable filter performance in terms of separation efficiency. As the filling line is typically equipped with a valve, intermittent operation of the filter is an important form of its use. Whereas the overall energy consumption of the filtration process is governed by the continuous operation mode, the intermittent mode, characterised by opening/closing of the valve, contributes most to problems of filter failure, i.e., the breakthrough of filtered particles through the membrane. A model for determination of the energy intake of a microfiltration membrane during the opening and closing of a valve is presented in this work. The model is based on computational analysis of the pressure wave signals recorded during the opening/closing of the valve using Fourier transform, and expressed in a nondimensional filter area specific energy intake form. The model is applied to a case of constant pressure dead-end microfiltration with three filter types: a single membrane filter, a stacked filter and a pleated filter with filtration surface areas ranging from 17.7 cm2 to 2000 cm2. Both clean filters, as well as partially clogged filter cases are taken into account. Second order polynomial models of the energy intake are developed and evaluated based on extensive analysis of the experimental data. The analysis of energy intake results show that the largest energy intake was observed for the clean filter case. When membrane fouling occurs at the constant flow rate values it leads to larger energy intake, however, due to a decreasing specific flow rate during fouling these values do not exceed the clean filter case.
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Yang, Xing, Joon Mo Yang, Yu-Chong Tai e Chih-Ming Ho. "Micromachined membrane particle filters". Sensors and Actuators A: Physical 73, n. 1-2 (marzo 1999): 184–91. http://dx.doi.org/10.1016/s0924-4247(98)00269-6.
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Sauvegrain, P., A. Tazi-Pain, F. Rogalla e F. Valter. "Anaerobic Biofiltration versus Aerobic Membrane Filtration: Comparison on a Difficult Substrate". Water Science and Technology 25, n. 10 (1 maggio 1992): 211–18. http://dx.doi.org/10.2166/wst.1992.0249.
Testo completoAbstract (sommario):
Several methods were compared to treat heat treatment liquor on a municipal wastewater treatment plant, to reduce loading and allow upgrading. To ensure low suspended solids in the return flows, granular anaerobic filters were chosen in parallel with membrane treatment:–an upflow wood-based charcoal anaerobic filter–an upflow floating polystyrene anaerobic filter–an aerobic reactor (activated sludge) coupled with microfiltration. Very similar loading rates and removal efficiency was obtained with the anaerobic filters; they allow to treat highly concentrated effluents in a detention time of 10 h but COD removal efficiency was limited to 60%. The higher contact time of up to 7 days in aerobic treatment, coupled with microfiltration, achieves elimination of 85% of COD and 95% of BOD. Nevertheless, loading rates and biomass concentrations remained low and flux on the membranes was heavily restricted.
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Fong, Daniel, e Pejman Sanaei. "Flow and transport in a pleated filter". Physics of Fluids 34, n. 9 (settembre 2022): 097102. http://dx.doi.org/10.1063/5.0102940.
Testo completoAbstract (sommario):
A pleated membrane filter consists of a porous membrane layer, which is surrounded by two supporting layers, and the whole structure is pleated and placed into a cylindrical cartridge. Pleated membrane filters are used in a variety of industrial applications, since they offer more surface area to volume ratio that is not found in equivalent flat filters. In this work, we introduce a novel three-dimensional model of a pleated membrane filter that consists of an empty region, a pleated region, and a hollow region. The advection diffusion equation is used to model contaminant concentration in the membrane pores along with Darcy's law to model the flow within the membrane and support layers, while the Stokes equation is used for the flow in the empty region and the hollow region. We further use the key assumptions of our model based on small aspect ratios of the filter cartridge and the pleated membrane to simplify the governing equations, which can be easily solved by numerical methods. By performing these steps, we seek to discover an optimal pleat packing density to find the optimum filter performance, while not exceeding a threshold for the particle concentration at the filter outlet.
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Mänttäri, M., e M. Nyström. "Ultrafiltration and nanofiltration in the pulp and paper industry using cross-rotational (CR) filters". Water Science and Technology 50, n. 3 (1 agosto 2004): 229–38. http://dx.doi.org/10.2166/wst.2004.0200.
Testo completoAbstract (sommario):
Ultra- and nanofiltration with high shear CR-filters have been utilized for cleaning of clear filtrates and effluents from the pulp and paper industry. The aim was to find out how different nanofiltration membranes operate at high shear conditions. The filtration efficiency of the membranes was evaluated by measuring flux, retention and fouling at various recovery and pH conditions. High fluxes (∼100 L/(m2h)) for nanofiltration membranes were measured when circulation waters from the paper machine were filtered at neutral conditions. In the filtration of discharge of external activated sludge treatment plants we measured fluxes around 150 L/(m2h) even at a concentration factor of 12. The best NF membranes removed over 80% of the organic carbon and of the conductivity and almost completely eliminated the color. With acidic waters fluxes and retentions were significantly lower. The NF270 membrane from Dow and the Desal-5 membranes from Osmonics had the highest flux and retention properties. However, the Desal-5 membrane lost its retention properties slowly, which restricts its use in the high shear CR-filter. CR-nanofiltration can be used in the pulp and paper industry without feed pre-treatment by ultrafiltration. This increases the attractiveness of high shear CR-nanofiltration.
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Hui-Feng, Sun, Miwa Takamori, Noriko Hata, Issei Kasahara e Shigeru Taguchi. "Application of Membrane Filters for Spectrophotometric Determination of Cationic Surfactants in River Water and Sediment". Journal of AOAC INTERNATIONAL 84, n. 6 (1 novembre 2001): 1781–85. http://dx.doi.org/10.1093/jaoac/84.6.1781.
Testo completoAbstract (sommario):
Abstract Cationic surfactant (CS+) in urban river water and sediment was extracted and determined spectrophotometrically with 2 membrane filters. The CS+ in the water samples, mostly in the form of an ion associate with the coexisting anionic surfactant (AS−), was collected on a polytetrafluoroethylene (PTFE) membrane filter and eluted with methanol. Bromphenol blue (BPB), hydrochloric acid, and water were added to the methanol solution successively, and the mixed solution was filtered through a mixed cellulose ester membrane filter. The CS+-BPB− ion associate, formed by a counter ion exchange, was collected on the filter and dissolved into N,N-dimethylformamide (DMF) together with the mixed cellulose ester membrane filter. After addition of 2 drops of triethanolamine, the absorbance of the DMF solution was measured. The CS+ in sediment samples was extracted with methanol by ultrasonic irradiation; the methanol solution was then passed through a PTFE membrane filter and evaporated to dryness. The CS+ was redissolved in a small amount of methanol. For water samples, recoveries and relative standard deviations for 0.30 μM benzyldimethyltetradecylammonium ion, a standard material, were ≥93 and ≤5%, with a detection limit of 0.02 μM. Concentrations of CS+ in sediments were much higher than those in water samples, indicating that CS+ is adsorbed on the surface of the sediment.
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SPEEGLE, LESLIE, MICHAEL E. MILLER, STEFFEN BACKERT e OMAR A. OYARZABAL. "Use of Cellulose Filters To Isolate Campylobacter spp. from Naturally Contaminated Retail Broiler Meat". Journal of Food Protection 72, n. 12 (1 dicembre 2009): 2592–96. http://dx.doi.org/10.4315/0362-028x-72.12.2592.
Testo completoAbstract (sommario):
Membrane filtration has been used to isolate Campylobacter spp. from feces, although ~5 log CFU/g must be present in the sample. Few studies have attempted to use filter membranes for the isolation of Campylobacter from foods. We investigated the minimum number of thermotolerant Campylobacter cells that pass through cellulose filters, the effect of different cell conditions on the rate of passage, and the minimum number of cells that could pass the filters from enriched broiler meat naturally contaminated with Campylobacter spp. Cellulose filters with 0.65-μm pore sizes retained fewer cells and were more effective than filters with 0.45-μm pore sizes. Scanning electron microscopy revealed that 15 min of contact of the filters with agar plates allowed for the passage of most bacteria. The minimum number of bacteria required to pass through the filters was contingent on cell conditions; nonmotile cells were retained more than motile cells (P < 0.05). The minimum number of motile bacteria from 24-h cultures and centrifuged cells were 2.2 and 2.1 log CFU, respectively, while the number of coccoid and nonmotile (flaA/B2 mutant) cells were 4.1 and 3.4 log CFU, respectively. Broiler meat samples enriched in Bolton's broth supplemented with 5% lysed blood showed that approximately 1.7 log CFU of Campylobacter can be filtered to pure colonies on agar plates. These results demonstrate that the motility of the bacteria influences passage through cellulose filters and that 0.65-μm-pore-size filters on agar plates help obtain pure Campylobacter colonies from enriched food samples.
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Ogbuoji, Ebuka A., Lauren Stephens, Amber Haycraft, Eric Wooldridge e Isabel C. Escobar. "Non-Solvent Induced Phase Separation (NIPS) for Fabricating High Filtration Efficiency (FE) Polymeric Membranes for Face Mask and Air Filtration Applications". Membranes 12, n. 7 (21 giugno 2022): 637. http://dx.doi.org/10.3390/membranes12070637.
Testo completoAbstract (sommario):
Protection against airborne viruses has become very relevant since the outbreak of SARS-CoV-2. Nonwoven face masks along with heating, ventilation, and air conditioning (HVAC) filters have been used extensively to reduce infection rates; however, some of these filter materials provide inadequate protection due to insufficient initial filtration efficiency (FE) and FE decrease with time. Flat sheet porous membranes, which have been used extensively to filter waterborne microbes and particulate matter due to their high FE have the potential to filter air pollutants without compromising its FE over time. Therefore, in this study, single layer polysulfone (PSf) membranes were fabricated via non-solvent induced phase separation (NIPS) and were tested for airflow rate, pressure drop and FE. Polyethylene glycol (PEG) and glycerol were employed as pore-forming agents, and the effect of the primary polymer and pore-forming additive molecular weights (MW) on airflow rate and pressure drop were studied at different concentrations. The thermodynamic stability of dope solutions with different MWs of PSf and PEG in N-methylpyrrolidone (NMP) at different concentrations was determined using cloud-point measurements to construct a ternary phase diagram. Surface composition of the fabricated membranes was characterized using contact angle and X-ray photoelectron spectroscopy (XPS), while membrane morphology was characterized by SEM, and tensile strength experiments were performed to analyze the membrane mechanical strength (MS). It was observed that an increase in PSf and PEG molecular weight and concentration increased airflow and decreased pressure drop. PSf60:PEG20:NMP (15:15:70)% w/w showed the highest air flow rate and lowest pressure drop, but at the expense of the mechanical strength, which was improved significantly by attaching the membrane to a 3D-printed polypropylene support. Lastly, the FE values of the membranes were similar to those of double-layer N95 filters and significantly higher than those of single layer of N95, surgical mask and HVAC (MERV 11) filters.
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Sanaei, P., e L. J. Cummings. "Flow and fouling in membrane filters: effects of membrane morphology". Journal of Fluid Mechanics 818 (6 aprile 2017): 744–71. http://dx.doi.org/10.1017/jfm.2017.102.
Testo completoAbstract (sommario):
Membrane filters are used extensively in microfiltration applications. The type of membrane used can vary widely depending on the particular application, but broadly speaking the requirements are to achieve fine control of separation, with low power consumption. The solution to this challenge might seem obvious: select the membrane with the largest pore size and void fraction consistent with the separation requirements. However, membrane fouling (an inevitable consequence of successful filtration) is a complicated process, which depends on many parameters other than membrane-pore size and void fraction; and which itself greatly affects the filtration process and membrane functionality. In this work we formulate mathematical models that can (i) account for the membrane internal morphology (internal structure, pore size and shape, etc.); (ii) describe fouling of membranes with specific morphology; and (iii) make some predictions as to what type of membrane morphology might offer optimum filtration performance.
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Li, Ting-Ting, Yujia Fan, Xixi Cen, Yi Wang, Bing-Chiuan Shiu, Hai-Tao Ren, Hao-Kai Peng, Qian Jiang, Ching-Wen Lou e Jia-Horng Lin. "Polypropylene/Polyvinyl Alcohol/Metal-Organic Framework-Based Melt-Blown Electrospun Composite Membranes for Highly Efficient Filtration of PM2.5". Nanomaterials 10, n. 10 (14 ottobre 2020): 2025. http://dx.doi.org/10.3390/nano10102025.
Testo completoAbstract (sommario):
Particulate matter 2.5 (PM2.5) has become a public hazard to people’s lives and health. Traditional melt-blown membranes cannot filter dangerous particles due to their limited diameter, and ultra-fine electrospinning fibers are vulnerable to external forces. Therefore, creating highly efficient air filters by using an innovative technique and structure has become necessary. In this study, a combination of polypropylene (PP) melt-blown and polyvinyl alcohol (PVA)/zeolite imidazole frameworks-8 (ZIF-8) electrospinning technique is employed to construct a PP/PVA/ZIF-8 membrane with a hierarchical fibrous structure. The synergistic effect of hierarchical fibrous structure and ZIF-8 effectively captures PM2.5. The PP/PVA composite membrane loaded with 2.5% loading ZIF-8 has an average filtration efficacy reaching as high as 96.5% for PM2.5 and quality factor (Qf) of 0.099 Pa−1. The resultant membrane resists 33.34 N tensile strength and has a low pressure drop, excellent filtration efficiency, and mechanical strength. This work presents a facile preparation method that is suitable for mass production and the application of membranes to be used as air filters for highly efficient filtration of PM2.5.
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Choi, Yong Ho, Moon-Ju Kim, Jia Lee, Jae-Chul Pyun e Dahl-Young Khang. "Recyclable, Antibacterial, Isoporous Through-Hole Membrane Air Filters with Hydrothermally Grown ZnO Nanorods". Nanomaterials 11, n. 12 (13 dicembre 2021): 3381. http://dx.doi.org/10.3390/nano11123381.
Testo completoAbstract (sommario):
Reusable, antibacterial, and photocatalytic isoporous through-hole air filtration membranes have been demonstrated based on hydrothermally grown ZnO nanorods (NRs). High-temperature (300~375 °C) stability of thermoset-based isoporous through-hole membranes has enabled concurrent control of porosity and seed formation via high-temperature annealing of the membranes. The following hydrothermal growth has led to densely populated ZnO NRs on both the membrane surface and pore sidewall. Thanks to the nanofibrous shape of the grown ZnO NRs on the pore sidewall, the membrane filters have shown a high (>97%) filtration efficiency for PM2.5 with a rather low-pressure (~80 Pa) drop. The membrane filters could easily be cleaned and reused many times by simple spray cleaning with a water/ethanol mixture solution. Further, the grown ZnO NRs have also endowed excellent bactericidal performance for both Gram-positive S. aureus and Gram-negative S. enteritidis bacteria. Owing to the wide bandgap semiconductor nature of ZnO NRs, organic decomposition by photocatalytic activity under UV illumination has been successfully demonstrated. The reusable, multifunctional membrane filters can find wide applications in air filtration and purification.
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Kaur, Satinderpal, Renuga Gopal, Wun Jern Ng, Seeram Ramakrishna e Takeshi Matsuura. "Next-Generation Fibrous Media for Water Treatment". MRS Bulletin 33, n. 1 (gennaio 2008): 21–26. http://dx.doi.org/10.1557/mrs2008.10.
Testo completoAbstract (sommario):
AbstractFibrous media in the form of nonwoven filters have been used extensively in water treatment as pre-filters or to support the medium that does the separation. Nonwoven media are composed of randomly oriented micron-size fibers and provide a one step separation as a substitute for conventional processes comprising chemical addition, flocculation, sedimentation, and sand filtration. At present the use of nonwoven filter media is limited to pre-filters and is not used further downstream as high performance filters. However it is expected that by reducing the fiber size in the nanometer range, higher filtration efficiency can be achieved. With the advent of nanotechnology, the ease of producing high quality nano scaled fibers is now a reality. Recent advancements in nanofibrous media through surface modifications have shown that nonwoven media can be used beyond the prefilter stage. Furthermore the pore size of the filter media can be controlled through modification of fiber size and thickness of membranes. These nanofibrous membranes possess high surface area and large porosity leading to high flux, low pressure membranes. This article highlights important opportunities and challenges associated with developing nanofibrous media for water treatment. In addition, we have attempted to capture a snapshot of this rapidly developing new area of fibrous media for water treatment for the benefit of the wider membrane community.
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Wang, Han, Zuo Yi Yang, Jin Yong Liu, Gao Feng Zheng e Ling Min Chen. "Explore on Pressure-Drop Performance of Nanofibrous Filtration Membrane". Advanced Materials Research 236-238 (maggio 2011): 1885–88. http://dx.doi.org/10.4028/www.scientific.net/amr.236-238.1885.
Testo completoAbstract (sommario):
High filtration efficiency of nanofibrous membrane has been proved in air filtration area, but, in addition to filtration efficiency, pressure drop is another important characteristic of fibrous filter. Because pressure-drop is related to energy wastage of filtration, it’s necessary to study. While there are not enough studies dedicated to pressure-drop of nanofibrous membrane filters. Here, different thickness PVA nanofibrous membranes were made by electrospinning, and they deposited on cotton scaffolds to form nanofibrous filter samples. Through testing these samples, we found as thickness of nanofibrous membrane increased, pressure-drop rose almost linearly, while filtration efficiency presented a different change trend. When thickness of nanofibrous membrane reaching a point, filtration efficiency attained extreme limit, even if increasing thickness nanofibrous membrane, filtration efficiency only rose limitedly, but pressure-drop still increased rapidly. At the same time, we found despite the thickness of nanofibrous membrane was thinner than conventional fibrous filter, pressure-drop of nanofibrous filter was obviously higher than conventional fibrous filter. So it’s remarkable phenomena. Through theoretical analysis and simulation, the causation of high pressure-drop of nanofibrous filter was discussed and provided. Decreasing diameter of fiber caused resistance performance change. It’s necessary to carry on a further research.
35
Sobsey, M. D., M. V. Yates, F.-C. Hsu, G. Lovelace, D. Battigelli, A. Margolin, S. D. Pillai e N. Nwachuku. "Development and evaluation of methods to detect coliphages in large volumes of water". Water Science and Technology 50, n. 1 (1 luglio 2004): 211–17. http://dx.doi.org/10.2166/wst.2004.0056.
Testo completoAbstract (sommario):
New and improved methods have been developed to detect somatic and male-specific coliphages in large volumes of water by single agar layer (SAL), enrichment and membrane filter methods. Somatic coliphages were detected efficiently on E. coli hosts C and CN13, male-specific coliphages were detected more efficiently on E. coli Famp than on Salmonella typhimurium WG49 and both types of coliphages were detected simultaneously on E. coli C3000. For water volumes of up to 100 ml, the SAL method was efficient and reliable. For water volumes of <1 L and as many as 10 multiple 1 L volumes, the enrichment method was efficient in detecting very low numbers of coliphages. Membrane filter methods, in which coliphages were adsorbed to and eluted from filters, also were relatively efficient, but they were less efficient than SAL and enrichment methods and were considered to be more cumbersome. For filter adsorption-elution methods, coliphage recoveries were most efficient for cellulose ester filters, less efficient for electropositive 1MDS filters and least efficient for a direct membrane filter method. Overall, the enrichment method was preferred because of its ability to easily and rapidly detect low levels of coliphages in large sample volumes by either presence-absence or most probable number quantification.
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Kopylova, Natalia, Alexei Kopylov e Yuri Salomatov. "Results of experimental studies and numerical modeling of multistage waveguide-slotted membranes filters with complex slots geometry". MATEC Web of Conferences 158 (2018): 01018. http://dx.doi.org/10.1051/matecconf/201815801018.
Testo completoAbstract (sommario):
The article contains the results of an experimental study and numerical simulation of the amplitude-frequency characteristics of one, three and four-stage filters on waveguide-slotted membranes with complex resonance slot geometry membranes located in a rectangular 35x15 mm waveguide. The design of filters and the topology of a complex slot in the membrane are shown. The results can be useful in the design of waveguide filters in the frequency range 5.5 … 8.5 GHz.
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Farsiyants, S. Yu, E. N. Verichev e L. S. Opaleichuk. "Ceramic filters with membrane coatings". Glass and Ceramics 47, n. 1 (gennaio 1990): 18–21. http://dx.doi.org/10.1007/bf00678256.
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Illi, H. "Hydrophobic grid membrane filters (HGMF)". Experientia 42, n. 1 (gennaio 1986): 101. http://dx.doi.org/10.1007/bf01975980.
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Wojcicki, J., W. Piatkiewicz, A. Werynski, J. Waniewski, H. Goch e M. Hay. "Membrane Plasma Fractionation: Effect of the Surface Area". International Journal of Artificial Organs 11, n. 5 (settembre 1988): 387–92. http://dx.doi.org/10.1177/039139888801100514.
Testo completoAbstract (sommario):
The influence of the surface area on the performance of plasma filters for dead-end mode of filtration is presented in this paper. Theoretical analysis of the dead-end filtration was performed and verified experimentally (using ENKA cellulose-diacetate PF-100 membranes) in respect to β-lipoprotein. The theoretical model allows to optimize the course of the transmembrane pressure during plasma fractionation procedure in dependence of the surface area, initial concentration of macromolecules, total volume of the feed and membrane structure. The results indicate that the surface area effect is an important factor in the operation of membrane plasma fractionation and should be considered in the design of the plasma fractionation filter.
40
Lyu, Chenxin, Peng Zhao, Jun Xie, Shuyuan Dong, Jiawei Liu, Chengchen Rao e Jianzhong Fu. "Electrospinning of Nanofibrous Membrane and Its Applications in Air Filtration: A Review". Nanomaterials 11, n. 6 (6 giugno 2021): 1501. http://dx.doi.org/10.3390/nano11061501.
Testo completoAbstract (sommario):
Air pollution caused by particulate matter and toxic gases is violating individual’s health and safety. Nanofibrous membrane, being a reliable filter medium for particulate matter, has been extensively studied and applied in the field of air purification. Among the different fabrication approaches of nanofibrous membrane, electrospinning is considered as the most favorable and effective due to its advantages of controllable process, high production efficiency, and low cost. The electrospun membranes, made of different materials and unique structures, exhibit good PM2.5 filtration performance and multi-functions, and are used as masks and filters against PM2.5. This review presents a brief overview of electrospinning techniques, different structures of electrospun nanofibrous membranes, unique characteristics and functions of the fabricated membranes, and summarization of the outdoor and indoor applications in PM filtration.
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Shelomentsev, Ivan G., e Ekaterina A. Gomzikova. "Prospects of analyzing of nanoparticles in the composition of aerosol by the method of electron microscopy". Hygiene and sanitation 102, n. 3 (31 marzo 2023): 259–64. http://dx.doi.org/10.47470/0016-9900-2023-102-3-259-264.
Testo completoAbstract (sommario):
Introduction. Control of distribution of aerosol particle by size in the workplace area is one of the important problems of hygiene. To assess health effect of aerosol particles in workers, it is necessary to improve existing and introduce new methods for analyzing the dispersion and chemical composition of aerosols, including their nanosized constituents.
Materials and methods. Generated lead oxide nanoparticles with an average diameter of 26.2±12.6 nm were sampled on 47-mm nylon membrane disc filters with a pore size of 0.2 µm and 1.2 µm. The experimental device represented a cascade system consisting of two membrane filters, where the first filter was intended for capturing nanoparticles while the second one was used for establishing the capture efficiency of the first. The sampling time for the cascade systems was 5, 10, 15, 20, 40, and 80 minutes for filters with a pore size of 0.2 µm and 5, 10, 20, and 120 minutes for those with a 1.2 µm pore size; in all cases, the volumetric flow rate was 1.5 L/min. The membrane surface was then analyzed by scanning electron microscopy.
Results. Lead oxide nanoparticles were found on all filters tested. They were evenly distributed over the entire effective filter area, their number increasing with air sampling duration. No nanoparticles were observed on the second level filters, regardless of the sampling period.
Limitations. The results cannot be extrapolated to all types of nanoparticles since the capacity of polyamide/nylon filters was studied only with respect to lead oxide nanoparticles.
Conclusion. The study proved that polyamide/nylon filters with the pore sizes of 0.2 µm and 1.2 µm have a high potential for nanoparticle capture and can be considered as a tool for developing new techniques of studying and controlling harmful factors.
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Tomas, Marija Kovač, Anto Mijatović, Mateja Bulaić Nevistić, Bojan Šarkanj, Jurislav Babić e Tihomir Kovač. "How different microfilters affect the recovery of eleven EU-regulated mycotoxins". Archives of Industrial Hygiene and Toxicology 74, n. 1 (1 marzo 2023): 8–15. http://dx.doi.org/10.2478/aiht-2023-74-3693.
Testo completoAbstract (sommario):
Abstract Microfiltration is a common step in liquid chromatography – tandem mass spectrometry (LC-MS), a method of choice in determining several mycotoxins in a solution at once. However, microfiltration may entail filter-analyte interactions that can affect the accuracy of the procedure, and underestimate exposure. The aim of our study was to assess how five different membrane materials for syringe filters (nylon, polytetrafluoroethylene, polyethersulphone, mixed cellulose ester, and cellulose acetate) affect microfiltration and recovery of EU-regulated mycotoxins, including aflatoxins B1, B2, G1, and G2, deoxynivalenol, fumonisins B1 and B2, zearalenone, T-2 and HT-2 toxins, and ochratoxin A. Polytetrafluoroethylene filters turned out to least affect microfiltration through mycotoxin loss, followed by more commonly used nylon filters, whereas the remaining three filter membrane materials had such a negative effect on recoveries that we found them incompatible with the procedure. Our findings clearly suggest that it is important to select a proper filter type that suits analyte properties and solution composition and to discard the first few filtrate drops to ensure the accuracy of the analytical procedure.
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Zhang, Yu Long, e Tao Dong. "A Membrane-Based Sample Preparation Kit for Waterborne Pathogens: Design and Manufacture". Applied Mechanics and Materials 281 (gennaio 2013): 75–79. http://dx.doi.org/10.4028/www.scientific.net/amm.281.75.
Testo completoAbstract (sommario):
Membrane-based microfluidic devices have been demonstrated in recent literature to show a significant potential in developing low-cost but high-efficient analytical devices. Usually, the step of sampling and sample preparation is the most importance processes in the whole analytical experiments. This study designed and manufactured a low-cost kit for water sampling and sample preparation of waterborne pathogens, especially protozoan parasites. Subsequently, Saccharomyces cerevisiae was employed as the model microbe to verify the function of kit. The concepts of green design and agile manufacturing were reflected throughout this work. In the devices, membrane filters were fixed and locked in a pair of disposable filter holders, and then the filter set would be assembled with a volumetric sample container to filter the microorganism in water samples. After the sampling process, the used filter holder with microbes on the membrane would be taken out and conserved in a preservation buffer, which could protect the DNA/RNA molecules inside the cells. When these filter holders were transported to a remote laboratory, the sample preparation cassette will be used in the on-site extraction of the DNA/RNA from the cells on the membrane. At last, the eluate was made for further identification, i.e. NASBA tests. Eight kinds of candidate membrane filters were evaluated in the kit, and the function of the kit was verified.
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Li, Ting-Ting, Xixi Cen, Hai-Tao Ren, Fei Sun, Qi Lin, Ching-Wen Lou e Jia-Horng Lin. "One-Step Bark-Like Imitated Polypropylene (PP)/Polycarbonate (PC) Nanofibrous Meltblown Membrane for Efficient Particulate Matter Removal". Polymers 11, n. 8 (4 agosto 2019): 1307. http://dx.doi.org/10.3390/polym11081307.
Testo completoAbstract (sommario):
A bark-like imitated polypr opylene (PP)/polycarbonate (PC) nanofibrous membrane was constructed by one-step meltblown technique for efficient particulate matter (PM) removal. The effects of PC content (0%, 1%, 3%, 5%, and 7%) on membrane thermal stability, microscopic characteristics, filtration performance, hydrophilicity, and water vapor transmission were investigated. The results demonstrated that using facile design of incompatibility and viscosity difference between PC and PP polymers decreases average fiber diameter, creating a bark-like groove appearance and increasing surface potential, making a new PP/PC membrane with high filtration performance. The resultant PP/PC membrane had finer average fiber diameter of 0.63 μm, which was nearly 89.41% lower than PP membranes (5.95 μm), and its quality factor (0.036 Pa−1) was nearly 2.12 times than that of PP membranes (0.017 Pa−1) with the die hole diameter of 0.5 mm. This fabrication technique of a special meltblown filter membrane saves the cost of die retrofitting and post-processing, which provides an innovative method for particulate efficient removal of high efficient filters.
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Engström, J. E., e C. Leck. "Determination of water-insoluble light absorbing matter in rainwater using polycarbonate membrane filters and photometric detection". Atmospheric Measurement Techniques Discussions 2, n. 1 (4 febbraio 2009): 237–64. http://dx.doi.org/10.5194/amtd-2-237-2009.
Testo completoAbstract (sommario):
Abstract. A method for determination of water-insoluble light absorbing matter in rainwater has been developed. After collection the rainwater samples were filtered using polycarbonate membrane filter in the laboratory. After drying the filter in filtered air, the amount of water-insoluble light absorbing matter (soot) on the filters was determined with photometry at a wavelength of 555 nm. The precision for the method was better than 10% calculated as relative standard deviation. The overall loss of soot due to adsorption during collection and filtration was 22±2%. The detection limit was estimated to 0.025 in optical density, or 2 ng/ml expressed as a concentration assuming a filtration volume of 30 ml. Analysis of environmental samples have been successfully performed with the described method at the Maldives Climate Observatory Hanimaadhoo and Nepal Climate Observatory. At Maldives the average soot concentration in rain was 0.048 μg/ml and at the Nepal obseravtory 0.086 μg/ml.
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Giglia, Sal, Anand Alembath e Joseph Hersey. "Defect Detection Sensitivity of Bubble-Point-Type Tests for Sterilizing-Grade Membrane Cartridge Filters". Membranes 13, n. 1 (10 gennaio 2023): 88. http://dx.doi.org/10.3390/membranes13010088.
Testo completoAbstract (sommario):
Bubble point tests are widely used for assessing the integrity of sterilizing-grade membrane cartridge filters. While many authors have considered the limitations of bubble point tests as applied to cartridge filters, the level of bacterial retention assurance provided by this test as conducted with automated integrity testers (AITs) has not, until now, been quantified. Contrary to the notion that filter leaks result in a depressed bubble point, it was shown that the bubble point as reported by AITs was insensitive to defect size up until the point where the AIT either determined a gross leak failure or was not able to return a valid result. For the three AITs used in this study, the minimum laser hole defect diameter in 10-inch (25.4 cm) sterilizing-grade cartridge filters that resulted in a failing bubble point test was between about 30 and 60 µm, depending on the filter type and test conditions. These defect sizes were associated with bacterial log reduction values in the 4.0 to 4.5 range. This study supports the generally recommended practice of pairing the bubble point test (which does confirm proper pore size rating) with a complementary gas–liquid diffusion test (better suited for detecting defects) to achieve a more comprehensive assessment of filter integrity.
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Ko, Kyujin, e Su-Chul Yang. "Magnetoelectric Membrane Filters of Poly(vinylidene fluoride)/Cobalt Ferrite Oxide for Effective Capturing of Particulate Matter". Polymers 12, n. 11 (5 novembre 2020): 2601. http://dx.doi.org/10.3390/polym12112601.
Testo completoAbstract (sommario):
In the last decade, particulate matter (PM) has gradually become a serious public health issue due to its harmful impact on the human body. In this study, we report a novel filtration system for high PM capturing, based on the magnetoelectric (ME) effect that induces an effective surface charge in membrane filters. To elucidate the ME effect on PM capturing, we prepared electrospun poly(vinylidene fluoride)(PVDF)/CoFe2O4(CFO) membranes and investigated their PM capturing efficiency. After electrical poling under a high electric field of 10 kV/mm, PM-capturing efficiencies of the poled-PVDF/CFO membrane filters were improved with carbon/fluorine(C/F) molar ratios of C/F = 4.81 under Hdc = 0 and C/F = 7.01 under Hdc = 700 Oe, respectively. The result illustrates that electrical poling and a dc magnetic field could, respectively, enhance the surface charge of the membrane filters through (i) a strong beta-phase alignment in PVDF (poling effect) and (ii) an efficient shape change of PVDF/CFO membranes (magnetostriction effect). The diffusion rate of a water droplet on the PVDF/CFO membrane surface is reduced from 0.23 to 0.05 cm2/s by covering the membrane surface with PM. Consequently, the PM capturing efficiency is dramatically improved up to 175% from ME membranes with the poling process and applying a magnetic field. Furthermore, the PM was successfully captured on the prototype real mask derived from the magnetoelectric effect induced by a permanent magnet with a diameter of 2 cm without any external power.
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Alonso-Echanove, Juan, Brian D. Sippy, Arthur E. Chin, Lisa Cairns, Rebecca Haley, Jay S. Epstein, Michael J. Richards et al. "Nationwide Outbreak of Red Eye Syndrome Associated With Transfusion of Leukocyte-Reduced Red Blood Cell Units". Infection Control & Hospital Epidemiology 27, n. 11 (novembre 2006): 1146–52. http://dx.doi.org/10.1086/508817.
Testo completoAbstract (sommario):
Objective.To characterize red eye reactions occurring within 24 hours after receipt of units of leukocyte-reduced red blood cells, determine their etiology, and investigate their potential link to transfusion.Methods.We conducted a survey of transfusion facilities nationwide to determine the scope and magnitude of the reactions; performed case-control and cohort studies among transfused patients at the facility where most reactions occurred; and performed animal experiments, using cellulose acetate derivatives extracted from leukocyte-reduction filters and filter precursors, to reproduce reactions.Results.From January 1, 1997, through January 15, 1998, we identified 159 reactions in 117 patients from 17 states. Reactions were characterized by conjunctival erythema or hemorrhage (in 100% of patients), eye pain (in 62%), photophobia (in 46%), and decreased visual acuity (in 32%). Symptom onset occurred 1-24 hours after initiation of transfusion and resolved within a median of 5 days. Reactions were associated with transfusion sessions that included units of red blood cells filtered with a specific brand of filter, the LeukoNet filter (HemaSure) (odds ratio, 100.4;P< .001). There was a dose-response relationship between the number of LeukoNet-filtered units transfused and the attack rate for reactions, ranging from 0.8% among sessions in which 1 unit was transfused to 27.3% among sessions in which 3 or more units were transfused (P< .001). A similar ocular syndrome was elicited in rabbits injected with cellulose acetate derivatives extracted from unused LeukoNet filters or filter precursors. No reactions were reported after LeukoNet filters were withdrawn from the market.Conclusions.This transfusion-associated red eye syndrome was linked to a specific brand of leukocyte-reduction filter and likely resulted from cellulose acetate derivatives leached from the filter membrane.
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Grant, Donald, Travis Lemke, Greg Duepner, Donna Wilkes e Norm Powell. "Measurement of Inorganic Contaminant Extraction from Fluid Handling Components By Dynamic Extraction". Journal of the IEST 39, n. 2 (31 marzo 1996): 29–37. http://dx.doi.org/10.17764/jiet.2.39.2.37v188215vww31lx.
Testo completoAbstract (sommario):
This paper addresses extraction of inorganic contamination from fluid handling components into semiconductor process chemicals. It presents a method of dynamic extraction that measures the rate at which inorganic contaminants are extracted from components as a function of time. The method overcomes many of the shortcomings of conventional techniques. It allows prediction of the amount of contamination added to chemical in a process tool with time. Examples of its use to measure extraction from all-Teflon 0.05-μm microporous membrane filters in 49 percent HF are included. Extraction from five different types of filters was measured. Each filter was tested for 2 to 8 weeks with multiple samples taken during the course of the extraction for metal analysis. Filters of the same type had similar extraction rates and similar contaminant "fingerprints." There were large differences between filter types. The use of an inappropriate O-ring on a filter cartridge was identified. The decrease in the rate of extraction from the filters was similar to theoretical predictions.
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Ensink, Jeroen H. J., Andy Bastable e Sandy Cairncross. "Assessment of a membrane drinking water filter in an emergency setting". Journal of Water and Health 13, n. 2 (11 ottobre 2014): 362–70. http://dx.doi.org/10.2166/wh.2014.025.
Testo completoAbstract (sommario):
The performance and acceptability of the NeroxTM membrane drinking water filter were evaluated among an internally displaced population in Pakistan. The membrane filter and a control ceramic candle filter were distributed to over 3,000 households. Following a 6-month period, 230 households were visited and filter performance and use were assessed. Only 6% of the visited households still had a functioning filter, and the removal performance ranged from 80 to 93%. High turbidity in source water (irrigation canals), together with high temperatures and large family size were likely to have contributed to poor performance and uptake of the filters.