Polypropylene Filter Research Articles

Filtration methodologies for the clarification and concentration of human mesenchymal stem cells

Currently human mesenchymal stem cells (hMSC) are expanded using microcarrier-based stirred culture systems from one to hundreds of liters of culture volume to guarantee the required cell numbers to be delivered to the clinic. Such culture volumes need to be clarified, ensuring efficient removal of microcarriers, and concentrated without compromising the cells׳ characteristics. The aim of this work was to evaluate the applicability of filtration methodologies, as dead end filtration and tangential flow filtration, for the clarification and concentration of hMSC, respectively.Different process variables and their impact on hMSC quality were evaluated, showing that polypropylene filters with pore sizes higher than 75μm can ensure the removal of microcarriers from the cell suspension bulk, without compromising cells׳ recovery or viability. Furthermore, hMSC could be successfully concentrated up to a factor of ten while maintaining their identity, potency and high cell viability, allowing for the recovery of over 80% of viable cells; an initial cell concentration higher than 2×105 cell/mL, and polysulfone membranes with pore sizes higher than 0.45μm were identified to be key conditions to obtain such concentration factors; shear rate and permeate flux were also shown to impact the cells׳ recovery yields, viability and quality.

Behavior of ambient concentrations of natural radionuclides (7)Be, (210)Pb, (40)K in the Mediterranean coastal city of Málaga (Spain).

During a 4-year period (January 2009-December 2012), the (7)Be, (210)Pb, and (40)K activity concentrations in airborne particulate matter were weekly determined at the Málaga (Spain) located in the southern Iberian Peninsula. Totally 209 polypropylene filters were analyzed in the mentioned period. In 100% of the filters, (7)Be and (40)K activity concentrations were detected while (210)Pb activity concentration was detected in 96% of the filters. The results from individual measurements of (7)Be, (210)Pb, and (40)K concentrations were analyzed to derive the statistical estimates characterizing the distributions. Principal components analysis (PCA) was applied to the datasets and the results of the study reveal that aerosol behavior is represented by two principal components which explain 73.2% of total variance. Components PC1 and PC2 respectively explain 46.0 and 27.2% of total variance. PC1 was related positively to dust content, (7)Be and (40)K concentrations and negatively to sunspot numbers. In contrast, PC2 was related positively to temperature and (210)Pb activity and negatively to precipitation and relative humidity. The (7)Be levels showed a significant correlation with sunspot numbers due to the cosmogenic origin. (40)K activities showed a good correlation with dust deposition in filters mainly because it was transported to the air as resuspended particle from the soil. An inverse relationship was observed between the (210)Pb concentrations and monthly rainfall, indicating washout of atmospheric aerosols carrying these radionuclides and a pronounced positive correlation with the average monthly temperature of air.

Characteristics of grey water filtration on polypropylene filters

Characteristics of grey water filtration on polypropylene filters

Separation of Nanoparticles from Air Using Melt-Blown Filtering Media

ABSTRACTOver the last few years, expectations have grown for the development of appropriate materials for separation of nanoparticles of different morphologies from air. Therefore, the objective of this work was to conduct a broad study of the process of filtration of polydisperse nanoaerosols in materials of our design and production. They were made using the modified melt-blown technology, a very promising technique that allows to produce large amounts of fibers with a wide range of diameters which when properly formed in mats or cores can be used in various filtering products, such as protective masks, car filters. The filtration efficiency for KCl solid nanoparticles and DEHS (di-ethyl-hexyl-sebacat) liquid nanoparticles in three polypropylene filters of different morphologies have been established. The obtained results show how the aerosol face velocity and the morphology of the nonwoven media affect the filtration efficiency and pressure drop. It turned out that fibrous filters of our own production can separate particles with very small diameters from the air. As the effectiveness of the separation grew with a decrease in diameter of filter fibers, a filter composed of nanoscale fibers proved to be the most effective. An increase in aerosol flow velocity through the filter negatively affected its filtering effectiveness. The observation of data for cubical KCl and spherical DEHS particles, showed no differences in filtering effectiveness, which proves that for the tested diameter range the morphology of particles removed from air does not play a significant role, as it does for larger particles. The results obtained from the filtration of polydisperse nanoaerosols were successfully interpreted using our Partially Segregated Flow Model which takes into account the polydisperse distribution of fiber diameters in the filter. What is more, it shows that the application of the classical theory of filtration significantly overvalues the results obtained in our experiments.

Filter media: Multilayer PP filters for the separation of O/W emulsions

Oil droplet coalescence and the separation of emulsions are industrially relevant processes. In this article, Dr Andrzej Krasinski of Warsaw University of Technology discusses his studies into the separation of oil-in-water emulsions by forced flow through meltblown polypropylene (PP) fibrous media. The research focuses on the structural design of the inlet layer and examines the effects of the fibre size, bed depth and flowrate.

Electreted polyetherimide–silica fibrous membranes for enhanced filtration of fine particles

Development of technologies for air filtration and purification is critical to meet the global challenges of threatened human health and accelerated greenhouse effect, especially for point-of-use applications. Here, we report a novel electreted polyetherimide–silica (PEI–SiO2) fibrous membrane by a single-step strategy to achieve effective filtration of fine particles. The hierarchical structured PEI–SiO2 membranes were endowed with promising superhydrophobicity with a water contact angle of 152°, allowing their better self-cleaning performance compared with commercial polypropylene (PP) filter media. Morphology, electric charge property, porous structure, and filtration performance could be regulated by tuning the type and concentration of electrets as well as the solution properties. Furthermore, unlike the commercial PP-based filter media, the as-prepared membranes can be treated at 200°C for 30min without sacrificing filtration efficiency (99.992%) and pressure drop (61Pa) owing to the combined contribution of polarization and space charges. We anticipate that this promising electreted fibrous medium will act as a core part of numerous air filtration systems, including ultra-low penetration air filters, clean room, respirator, and protective clothing.

Contenido de pigmentos en hojas de fresa (Fragaria sp) expuestas a diferente calidad de luz

Light is a very important environmental factor which affects plant growth and development in various important ways. Not only quantity, but also quality is very essential in determining the plant growth. The influence of light quality on chlorophyll and carotenoid content of strawberry leaves was examined. Plants were grown in a greenhouse under differing light qualities provided by polypropylene filter film (control without colored cover, yellow, green, blue, transparent, and red). The treatments were laid out in a randomized design, each treatment was replicated ten times. The filter films were set 1m above the crop canopy at the moment of transplanting and left until the end of the experiment. Eight months after transplanting both chlorophyll and carotenoid content in leaves were determined in alcoholic dilution using a spectrophotometer. The effect of different light qualities influenced chlorophyll content in leaves. The chlorophyll a content was highest in leaves under green and red light followed by blue, transparent and yellow light; the lowest chlorophyll a content was found in control plants. There were no differences in chlorophyll b content. The carotene / chlorophyll ratio was highest in leaves developed without cover, and lowest in leaves under green and red light. Results indicate that the use of colored covers for provision of selective light quality may be a used for increasing strawberry production.

Matrix Supported Poly(2-oxazoline)-Based Hydrogels for DNA Catch and Release

We describe the synthesis of matrix supported hydrogel structures based on amine containing poly(2-oxazoline)s and their use to bind and release genetic material for potential applications in diagnostics or pathogen detection. Amine containing poly(2-oxazoline)s were synthesized by copolymerization of 2-ethyl-2-oxazoline with a monomer bearing a tert-butyl oxycarbonyl (Boc) protected amine group in the 2-position and subsequent deprotection. The statistical copolymers were used to generate hydrogels and matrix supported hydrogels by cross-linking of a certain fraction of the amine groups with epichlorhydrin. Supported structures were prepared by soaking porous polyethylene (PE) or polypropylene (PP) filter materials in a copolymer/epichlorhydrin solution, which was cross-linked upon heating. Scanning electron microscopy (SEM) of the composites revealed a bead like structure of the gel phase, which could be attributed to a lower critical solution temperature (LCST) behavior of the initial polymer prior to gelation. The dependency of the LCST behavior on the content of amine groups was investigated. Swelling values and the ratio of hydrogel per composite was determined using water sorption analysis. Subsequently, the ability of the systems to absorb and release labeled DNA was tested. Uptake and stimulated release, triggered by changes in pH, temperature, and heparin concentration, were investigated using fluorescence microscopy. Polymerase chain reaction (PCR) proved the successful recovery of the DNA, demonstrating the potential of the presented system for a broad range of molecular biological applications.

Space-resolved extreme ultraviolet spectroscopy free of high-energy neutral particle noise in wavelength range of 10-130 Å on the large helical device.

A flat-field space-resolved extreme ultraviolet (EUV) spectrometer system working in wavelength range of 10-130 Å has been constructed in the Large Helical Device (LHD) for profile measurements of bremsstrahlung continuum and line emissions of heavy impurities in the central column of plasmas, which are aimed at studies on Zeff and impurity transport, respectively. Until now, a large amount of spike noise caused by neutral particles with high energies (≤180 keV) originating in neutral beam injection has been observed in EUV spectroscopy on LHD. The new system has been developed with an aim to delete such a spike noise from the signal by installing a thin filter which can block the high-energy neutral particles entering the EUV spectrometer. Three filters of 11 μm thick beryllium (Be), 3.3 μm thick polypropylene (PP), and 0.5 μm thick polyethylene terephthalate (PET: polyester) have been examined to eliminate the spike noise. Although the 11 μm Be and 3.3 μm PP filters can fully delete the spike noise in wavelength range of λ ≤ 20 Å, the signal intensity is also reduced. The 0.5 μm PET filter, on the other hand, can maintain sufficient signal intensity for the measurement and the spike noise remained in the signal is acceptable. As a result, the bremsstrahlung profile is successfully measured without noise at 20 Å even in low-density discharges, e.g., 2.9 × 10(13) cm(-3), when the 0.5 μm PET filter is used. The iron n = 3-2 Lα transition array consisting of FeXVII to FeXXIV is also excellently observed with their radial profiles in wavelength range of 10-18 Å. Each transition in the Lα array can be accurately identified with its radial profile. As a typical example of the method a spectral line at 17.62 Å is identified as FeXVIII transition. Results on absolute intensity calibration of the spectrometer system, pulse height and noise count analyses of the spike noise between holographic and ruled gratings and wavelength response of the used filters are also presented with performance of the present spectrometer system.

Seasonal ambient ammonia and ammonium concentrations in a pilot IMPROVE NHx monitoring network in the western United States

Ammonia and ammonium are important atmospheric trace constituents that affect particulate matter concentrations and contribute to reactive nitrogen deposition. We refer to and measure the sum of ammonia and ammonium as NHx. To better understand concentrations of NHx in remote areas, the Interagency Monitoring of Protected Visual Environments (IMPROVE) fine particulate matter (<2.5 μm) sampler was modified to measure NHx at a subset of locations in the routine IMPROVE network. To sample NHx, an additional IMPROVE PM2.5 sampler was installed. Samples were collected on phosphorous acid impregnated cellulose filters held in polypropylene filter holders. While the standard IMPROVE filter holder is made of Delrin (polyoxymethylene, POM), reactions between collected NHx and formaldehyde released by phosphorous acid degradation of the POM holder produced substantial amounts of artifact methylamine, especially during warm sampling periods. This artifact did not occur with the new polypropylene holder design, and no methylamine was measured above the method detection limit of 0.003 μg/m3. Samples collected using the new IMPROVE NHx sampling system were evaluated against samples collected with a collocated URG annular denuder/filter-pack module for 6 weeks; the observed bias was −7%. The NHx monitors were deployed at a total of nine sites in the U.S. Rocky Mountain and Great Plains regions and to the east, and at Bondville, Illinois, from April 2011 to August 2012. Collocated samplers at Rocky Mountain National Park, Colorado, and Bondville, Illinois, demonstrated excellent measurement precision. The data revealed a pattern of increasing NHx concentrations in late spring/early summer (June) and a decrease in winter, starting in September for most of the sites. This pattern is consistent with expected seasonal patterns in agricultural emissions of ammonia. Sites closer to agricultural sources at Bondville and Cedar Bluff (Kansas), however, still exhibit quite abundant winter NHx, which may reflect continued local agricultural emissions trapped within a shallower winter boundary layer. A probable impact of wildfires on NHx concentrations was observed for Bandelier NM, Chiricahua NM, and Yellowstone NP during summer/fall 2011.

Assessment of 226Ra and 228Ra activity concentration in west coast of India

An investigation on the distribution of 226Ra and 228Ra activity concentration in coastal surface sea water from Okha in Gujarat to Ratnagiri in Maharashtra state along the west coast of India was carried out. In-situ pre-concentration technique was used to measure radium isotopes by passing 1,000 L of seawater through MnO2 impregnated polypropylene filter cartridges at all the locations. 226Ra was estimated using gamma ray peak of its daughter radionuclides 214Bi and 214Pb. 228Ra was estimated from its daughter 228Ac. In the coastal waters, 226Ra and 228Ra activity concentration were observed to be in the range of 1.5–2.9 and 2.5–8.6 Bq m−3 with a mean of 2.2 and 4.9 Bq m−3 respectively. The activity of 228Ra was observed to be more than 226Ra in all the locations. The variation in spatial distribution of the radium isotopes activity concentration and its ratio with respect to location is discussed in the paper. The radioactive database obtained represents reference values for coastal environment of India.

Modification of polypropylene filter with metal oxide and reduced graphene oxide for water treatment

A hydrothermal method for the synthesis of reduced graphene oxide/titanium dioxide filter (RGO/TiO2) and reduced graphene oxide/zinc oxide filter (RGO/ZnO) by using polypropylene (PP) porous filter is reported. Field emission scanning electron microscopy illustrated that the nanoparticles were uniformly distributed on the reduced graphene oxide nanosheets. Flexural tests showed that the physical properties of the modified filters have greater strength than the original filter. Thermogravimetric analysis revealed that the thermal property of the modified filters is the same as that of the original filter. Under a halogen lamp, the modified filter exhibited excellent photocatalytic degradation of methylene blue. The RGO/TiO2 filter maintained its ability to degrade MB efficiently, even after five cycles of photocatalysis.

Larvicidal Activity and Click Synthesis of 2-Alkoxyl-2-(1,2,3-Triazole-1- yl)Acetamide Library

Heterogeneous copper-in-charcoal-catalyzed click synthesis in 96-well polypropylene filter plates is an efficient method for the rapid generation of sufficient pure 2-alkoxyl-2-(1,2,3-triazole-1-yl) acetamide derivatives library by simple filtration, which directly assay the products for larvicidal activity against mosquitoes. In this procedure, copper nanoparticles on charcoal were arrayed into each well on a 96-well plate, reagents were delivered using a pipette gun, and a constant temperature shaker bath was used to complete the click reaction in 24-72 hours under temperature-controlled conditions. The results of bioassays indicated that the target compounds possessed excellent larvacidal activities against mosquitoes. In particular, the larvacidal activities against mosquitoes of compounds 8[2,3] and 8[7,1] at 2 µg.mL⁻¹ were 100% and 73% respectively.

A Study on the Control of Bio-Aerosol for Prevention of Indoor Aerial Infection Using Antimicrobial Air Filter

Some indoor bio-aerosols trigger allergic reactions, including hypersensitivity pneumonitis, allergic rhinitis, and various types of asthma. Moreover, human influenza virus is one of the bio-aerosols that causes significant morbidity and mortality every year worldwide. Although vaccination is the most effective way to address the risk of airborne infection, they are not always feasible, available and practiced. An air cleaning device is effective and efficient in removing indoor bio-aerosols and thereby controlling or eliminating these airborne biological contaminants. An antimicrobial filter is developed and its antimicrobial activities against influenza viruses are measured. An extract from Gingko Biloba L. and Sumac (Rhus Javanica L.) possesses antifungal, antibacterial, and antiviral activities thus this class of natural products is used as an antimicrobial agent in this study. An antimicrobial air filters were prepared by coating the natural agent on polypropylene filter media. The antimicrobial rates of the filter against new influenza (H1N1) virus and A/PuertoRico/8/34 (A/PR/8) virus were greater than 99.9999%. The antimicrobial filters were effective in controlling the bio-aerosols by inhibiting bacterial and viral survival on the filter, thereby preventing secondary contamination of filter from breeding of bio-aerosols. An air cleaning device equipped with the antimicrobial air filter was tested for the inhibition effect on viruses and no virus was detected at the outlet of the purifier. Although the antimicrobial filters are developed and tested only for the inactivation of virus in this study, the filter could be also effective in removing other types of bio-aerosols, such as bacteria, fungi, and allergens. The antimicrobial filter appears to be promising application in air cleaning and biological protection fields.

Optimizing LC-MS-MS determination of microcystin toxins in natural water and drinking water supplies

The performance of a solid phase extraction (SPE) LC-MS-MS procedure for determining microcystins (MC) in water was investigated. Six MC, MCRR, MCYR, MCLR, MCLA, MCLF and MCLW, were determined using positive ion electrospray (+ESI) with separation on a C8 column eluted with a methanol–water gradient containing 15 mM ammonium formate and 0.006% acetic acid. Each MC, as well as the internal standard and surrogate, were detected by two transitions. Isocratic and gradient separations were examined to increase the resolution of MCRR and MCLF as all known naturally occurring MC elute between these two variants. Analysis of fortified laboratory reagent water as well as bloom samples from northern California provided performance information. Cell lysis, accomplished by freeze-thawing samples, was required to determine total sample toxins as 93 to 99% of the toxins were intracellular. Up to 98% of dissolved MC were lost by sorption in filter cartridges, but satisfactory recoveries were obtained with polypropylene filters after the filtrate was combined with a methanol rinse. C18 SPE required elution with trifluoroacetic acid (TFA) for acceptable recoveries of the arginine-containing MC. Freezing was required to preserve MC which degraded rapidly by microbial metabolism at 4 °C after an approximate 10 day lag period. With the optimized method the experimental Method Detection Limits (MDL) for both quantitation and confirmation transitions for the arginine-containing MC ranged from 0.03 to 0.04 μg L−1. Laboratory reporting limits (or LOQ) of 0.1 and 0.2 μg L−1 were confirmed by analyzing surface water samples where accuracy averaged 65 to 70%. Measurement of total MC in bloom samples was reproducible with relative standard deviations of 8.3 to 12%. The study demonstrates the importance of sample preservation, sample workup and quality control procedures in reliable MC determination using modern LC-MS-MS instruments.

Influence of Filtration Velocity on Cake Formation in Fibrous Filters

The filtration operation is one of the most widely used procedures in gas-solid separation due to its high removal efficiency, low cost and low sensitivity to variations in operating conditions. Therefore, the objective of this work is to study the effects of operating variables (pressure drop, filtration velocities and cleaning velocity) on the formation of filter cakes using gas-solid polypropylene filter media and particulate matter as for instance phosphate rock. The filtration velocities evaluated were 5, 7.5 and 10 cm/s with maximum pressure drops of 100, 200, 300 and 400mm H2O and filter cleaning velocities of 15 cm/s by the reverse air flow method. The cake filtration porosity was estimated using the classical Ergun equation (1952) in the literature. The results led to important correlations for the use of fibrous filters in the removal of particles suspended in in micrometer aerosols.

Growth, production and flower quality in calla lily (Zantedeschia aethiopica (L.) K. Spreng) exposed to different light quality

The quantity, quality and duration of light affect plant growth. Light quality refers to color, or wavelength, that reaches the plant. The spectral manipulation is aimed to specifically promote desired physiological responses. The influence of light quality on growth, production and flowers quality was studied in calla lilly plants (Zantedeschia aethiopica). Plants were grown in Tunja / Colobia, in a greenhouse, under different light qualities (control without colored cover, yellow, green, blue transparent and red) provided by polypropylene filter film. The colored films provided too different levels of shading to plants. The treatments were laid out in a randomized complete block design where each treatment was replicated ten times. The filter films were set 1m above the crop canopy at transplanting until the harvest of plants. The flowers quality related to the length of peduncle was positively affected by shading, however the number of flowers, the flowering time and the dry mass allocation to flowers were not influenced by the applied treatments. The response of plants in relation to growth rates were the result of joint action of both, the quantity and quality of incident light. Calla lily showed versatility to adapt to environmental conditions, which was manifested through physiological and morpho-anatomical changes in plants growing under manipulated spectra.

New Filtration Systems for Extra-Virgin Olive Oil: Effect on Antioxidant Compounds, Oxidative Stability, and Physicochemical and Sensory Properties

The purpose of this work was to evaluate some new filtration systems in relation to the quality of extra-virgin olive oil (EVOO). Filtration processes were undertaken using a polypropylene filter bag and two different inert gas flows as filter aids (argon and nitrogen). Qualitative and quantitative variations of the glyceride composition, antioxidant and pro-oxidant compounds, and water content were correlated with the oxidative stability to establish the effect on EVOO shelf life. The influence on physicochemical and sensorial properties was also evaluated. After filtration, the oxidative stability was reduced. The behavior of the polyphenols and water content on the filtration process could explain the lowest oxidative stability of filtered EVOO. Moreover, the results of the sensorial analysis confirmed that filtration using inert gases did not decrease the intensity of the main positive sensory attributes. The results could help olive-oil producers to improve EVOO quality and establish optimal storage conditions.

Removal of microbes and air pollutants passing through nonwoven polypropylene filters by activated carbon and nanosilver colloidal layers

Due to their high capacity, nonwoven textiles have been used for a long time as potential filters to remove harmful air pollutants. In this study, needle-punch polypropylene layers were treated with powder activated carbon and nanosilver particle through pad drying and spray techniques, respectively. The morphology of treated layers was observed by a scanning electron microscope and laboratory apparatus were used to evaluate effects of microbe elimination from samples of passing polluted air. The gas adsorption efficiency of fabricated filter was measured by an air pollution device. Results showed that samples treated with activated carbon absorbed 38%, 100% and 100% of CO, NO and NO2 gases, respectively, compared with pristine samples. Staphylococcus aureus and Escherichia coli were completely removed from passing air by nanosilver-coated layer.

Conductivity of Graphene-Like Thin Films Prepared from Chemically Exfoliated Carbon Nanotubes (CNTs), Highly Oriented Pyrolytic Graphite (HOPG), Natural Flake Graphite, and Carbon Powder

ABSTRACTThe use of super acids such as chlorosulfonic acid (CSA) has proven to be extremely effective at exfoliating different forms of graphite in high concentrations without covalently functionalizing the surface of the graphene. Once quenched, the acid solutions can then be vacuum filtered through acid resistant polypropylene filter paper with an average pore size of 0.2 μm to collect the exfoliated carbon into a free standing retentate film. These films can then be easily washed, removed, and redispersed into solution by sonicating the films in a surfactant solution. Films were deposited onto various substrates using a range of spin coating parameters. This study has found that exfoliated CNTs provide the best conductivity out of the four types of chemically exfoliated carbon structures studied. CNTs have also proven to be the easiest type of exfoliated carbon to disperse and are able to stay in solution with less than 1%wt surfactant. The findings have shown that the electrical conductivity of the spin coated films actually increases with RPM and is inversely proportional to the film thickness. It is possible to achieve electrical conductivities as high as 10,507 ± 3728.64 [S/m] while still maintaining the transparency of the thin films. The initial spin coating step is more efficient at low ramp rates around 100 rpm/s and results in very smooth films. High spin speeds of 1800 rpm during the casting stage are found to play a large role in improving the conductivity of the films. Lastly, drying the samples on a hot plate for 5 min. on high has significantly improved the films electrical properties and virtually eliminated the need for tedious and expensive plasma cleaning treatments.