Filtering Capacity Research Articles

Desorption efficiency and holding capacity of acid-treated filters for nicotine sampling in vape shops.

Efficient sampling materials are essential for assessing nicotine levels in vape shops and other settings where nicotine exposures may exist. Two different treatments of Whatman glass fiber type A (GF/A) filters (sodium bisulfate treated and citric acid treated) were evaluated for nicotine capture, desorption efficiency, and holding capacity using Gas Chromatography-Mass Spectrometry (GC-MS). The Filters were treated with 0.8mL of 0.1 M sodium bisulfate or citric acid solution and oven-dried (80 °C) for 30min. Nicotine was desorbed off the filters using a modified analytical method. The average nicotine desorption efficiency for sodium bisulfate-treated GF/A filters (98.4%) was significantly higher than that of citric acid-treated GF/A filters (60.9%) over a range of 1-100 µg nicotine. Sodium bisulfate-treated and citric acid-treated GF/A filters experienced a 10% nicotine breakthrough after being dosed with about 550 and 2,750 µg of nicotine, respectively compared to 75 µg for untreated GF/A filters. Citric acid-treated GF/A filters had a much greater nicotine-holding capacity, but nicotine desorption from citric acid-treated GF/A filters was below the recommended criteria. Therefore, we recommend that sodium bisulfate-treated GF/A filters are employed for sample of nicotine with the GC-MS method.

Effects of nanosilica and nanocellulose on poly(butylene adipate‐co‐terephthalate) nanocomposites for food packaging applications

AbstractPolymeric materials are highlighted in the global market due to their low cost, excellent properties, and diversity of applications, such as food packaging, which in addition to protecting packaged foods also promotes control and conservation against contaminants. Thus, the objective of this research is to investigate the effects of adding silica nanoparticles and cellulose nanofibers, alone and together, on the properties of poly(butylene adipate‐co‐terephthalate), aiming for application in food packaging. For this purpose, PBAT and the nanofillers were initially mixed in a rheometer to produce masterbatches, and, then, to be processed by a single screw extruder to generate the nanocomposites. The nanocomposites are analyzed by scanning electron microscopy, x‐ray diffraction, thermogravimetric analysis, differential scanning calorimetry, nuclear magnetic resonance, tensile testing, water contact angle, and microbial permeability. In low concentrations, it is observed that the system tends to be less heterogeneous. Nanoparticles do not interfere with thermal stability and present a barrier to microorganisms. Interestingly, in the two conditions studied, polymers with cellulose nanofibers or silica nanoparticles have filtering capacity, being effective as physical barriers to the growth of microorganisms within 60 days. However, the effect on mechanical properties is small, being more pronounced with the use of cellulose nanofibers.

Flux and fouling behavior during constant pressure sterile filtration of nanoemulsions

Nanoemulsions with droplet diameters from 20 to 200 nm have emerged as attractive adjuvants in the development of novel vaccines and as an advanced method of drug delivery for hydrophobic drugs. However, the large size of the nanoemulsion droplets leads to very low capacities during the final sterile filtration step used to ensure sterility of parenteral drug products. The objective of this study was to examine the sterile filtration of a model nanoemulsion made using squalene as the oil and Tween 20 and Span 85 as stabilizing surfactants. Data were obtained with different commercial sterile filters with different morphology and chemistry during constant pressure filtration. In each case, there was essentially no filtration until the transmembrane pressure exceeded a critical value related to the force required to push the deformable nanoemulsion droplets through the membrane pores. The filter capacity increased with increasing pressure, going from 700 g/m2 at 140 kPa to 1300 g/m2 at 280 kPa for a dual layer polyethersulfone sterile filter, with the flux decline well described by the complete pore blockage model. The dual layer asymmetric membranes showed much higher capacities than corresponding single layer filters due to the effectiveness of the upper layer in removing larger nanoemulsion droplets that would otherwise block the pores of the sterile filter. The capacity of the different sterile filters was also well-correlated with the initial filtrate flux, with both of these parameters governed by the pore size distribution and surface chemistry of the filters. These results provide important insights into factors controlling the sterile filtration of highly concentrated nanoemulsions used in the formulation of vaccines and drug products.

Bacterial Cellulose as a UVB Filter to Protect the Skin Microbiota.

Certain aerobic bacteria produce bacterial cellulose (BC) to protect themselves from UV radiation. Inspired by this natural function, the UV-filtering capacity of wet BC film (BC) and dried BC (BC-Dried) is evaluated and it is concluded that both samples hardly filter UVA, but filter UVB to some extent, especially BC-Dried. Moreover, this filtering capacity does not diminish but significantly increases with time, with efficiencies in the 145-160 min time range equal to or greater than most UV filters of the market. This increase in efficiency is due to the fact that the BC structure is modified by prolonged exposure to UVB radiation. Specifically, UVB causes sintering of the cellulose fibers, making the structure denser and increasing its reflection and scattering of UVB radiation. Remarkably, this UVB filtering ability of BC allows it to protect key skin probiotics, Lactobacillus fermentum (L. fermentum) and Cutibacterium acnes (C. acnes), against UVB damage. While the protection of healthy skin microbiota is not currently a regulatory requirement for sunscreens with UV filters, it may become a key differentiator for future UV filters given the increasing evidence on the role of skin microbiota in health.

Preparing and Assessment of Biocidal La Nano-complex Treated Filter Capacity against Isolated Microbes from Air Conditioning Systems in COVID-19 Rehabilitation Rooms

Mucormycosis is a severe fungal infection which mainly caused by filamentous fungi of the Absidia sp., Rhizopus sp., Cunninghamella sp, Mucor sp., and Rhizomucor sp. Moreover, the pandemic of the SARS-CoV-2 virus expands the need to interfere with spread of the airborne respiratory infections. Accordingly, developing cutting-edge solutions to restrict and/or prevent air contamination by infectious microbes are very warranted. The current work aims to prepare biocidal La-nano complex treated filters and assess their anti-fungal capacity against 20 Rhizopus oryzae, 10 Candida albicans, and 11 Aspergillus fumigatus. These fungi were isolated from the inside parts of the air conditioning systems in the rehabilitation rooms for COVID-19 patients. The obtained results demonstrated that the prepared were able to significantly decrease the invading microbes and eradicate Rhizopus, Aspergillus, Mucor, Candida albicans isolates at 0.64 mg/ml concentration. DFT study compares the electronic properties and reactivity of a ligand in its uncoordinated form with its lanthanum complex. The ligand exhibits lower binding energy, ionization potential, electron affinity, absolute electronegativity, and chemical potential when coordinated with lanthanum. In contrast, the lanthanum complex has a smaller energy gap, absolute hardness, and global softness.

Poly(vinylidene fluoride) membrane design for efficient oil-in-water emulsion separation: Integrating superhydrophilicity, photocatalysis and self-cleaning

To solve the increasingly serious wastewater problems, developing membranes with excellent filtration performance and anti-fouling property has been a research focus. Herein, hydrophilic tannic acid/cysteine/tyrosine@titanium (TA/Cys/Tyr@Ti) double crosslinked coating was constructed on the poly (vinylidene fluoride) (PVDF) microfiltration membranes by two-step coating method, while the mineralized titanium dioxide (TiO2) nanoparticles were utilized to produce superhydrophilic membranes. The synergistic effect of the multilayered nanostructure and hydrophilic groups enables excellent underwater superoleophobicity and anti-fouling property of modified membranes. The addition of TiO2 provides photocatalytic degradation and self-cleaning properties. The optimized modified membrane (MF-4) showed outstanding oil–water separation potential (emulsion flux of 2760 ± 30 L·m−2·h−1, oil rejection rate of 99.5 ± 0.3 %) and stable recycling filter capacity. Moreover, MF-4 was able to efficiently degrade methylene blue under UV light, which was 99.1 % at 90 min. The flux recovery rate (FRR) was 97.4 % following simulated contamination and regeneration with bovine serum albumin. After UV irradiation, the FRR appeared to be significantly enhanced, proving its great anti-fouling and self-cleaning properties. This modified membranes with superhydrophilic and self-cleaning properties have great application potential in oily wastewater and achieving automatic operation of wastewater treatment.

Assessment of filtration capacity of different filters used in the West Region of Cameroon for quality improvement of drinking water

Assessment of filtration capacity of different filters used in the West Region of Cameroon for quality improvement of drinking water

Periclase-magnesium aluminate spinel ceramics filter with excellent purification efficiency on molten steel prepared from Mg(OH)2: Effect of fused MgO content

Reticulated ceramic filters are widely used in the field of steel purification to improve the quality of steel products. In this work, periclase-magnesium aluminate spinel ceramic filters with microporous MgO coating were fabricated by using Mg(OH)2 as raw material. The effect of fused MgO content on the microstructures, mechanical properties and filtration capacity of filters on Al2O3 inclusions in molten steel was comparatively studied. The results indicate that the particle packing and liquid phase sintering cooperated to promote the formation of neck connections between microporous MgO particles, which increased the cold compressive strength and thermal shock resistance of the filters. Furthermore, the results from the immersion test in molten steel demonstrate that an appropriate amount of high-temperature liquid phase and the relatively microporous structure of filter skeleton were favorable for filters to filtrate Al2O3 inclusion in molten steel. Overall, the filter with 30 wt% fused MgO had the best comprehensive performance with a cold compressive strength of 0.68 MPa, a residual retention of cold compressive strength after three thermal shock recycles of 79.07 % and a filtration efficiency of 79.06 % in reducing the total oxygen content of the steel.

Prediction of the dynamic pressure drop of filter media loaded with water mists based on the deposited droplet mass distributions and pore network model

Predicting the pressure drop of a filter is necessary, especially regarding the jump in the dynamic pressure drop of a filter without pre-filters when clogged by rain or fog droplets. However, the efficient prediction method for the pressure drop in cylinder filters loading with water mists in the pore network faces limitations due to the high requirements for microscopic images of materials and the need to consider for the increasing holding droplet capacity of filters. In this study, a systematic method that takes into account the distributions of the deposited droplet mass within the water-absorbed filter medium layers in the pore network model (PNM) was developed. The pore geometry and distributions were determined from 2D microstructure images, and the dynamic deposited droplet mass and water-absorbing capacity of fibers were combined with the changing saturation to optimize the PNM for calculating the dynamic pressure drop of the filter media. Specifically, the empirical equation of the self-defined equivalent single fiber filtration efficiency (ESFFE) describes the relationship between the changing single fiber filtration efficiency and the deposited droplet mass. The optimized PNM is suitable for predicting the behavior of bibulous wood cellulose fiber filter media. The dynamic pressure drop shows a slight increase before surging, following the typical “channel and jump” model. Although the calculations deviate slightly from the experimental results with 25 % deviations, this systematic method effectively predict the jump in pressure drop of the tested filter medium. Therefore, this systematic method for predicting pressure drop of filters holds promise in anticipating unsafe pressure drop jumps in filters installed in coastal areas.

Airflow detailed analysis through a face mask using the schlieren technique

This work presents an exhaustive visualization of the airflow expulsed by a person while breathing, talking, exhaling, and blowing inside a closed room wearing a disposable face mask like those used in hospitals for patient protection and those who care for them. An optical schlieren experimental arrangement was used to obtain some of the relevant physical characteristics of the airflow, such as its refractive index gradient, the distribution of temperature, and the associated velocity field for all the tests developed. We tested three face masks, one of the surgical types and the others of the N95 series with denominations KN95 and 3MN95 (Aura TC-84A-8590). The results show appreciable differences between the masks evaluated; the surgical mask was the one that allowed the most abrupt output airflow through it in the field of view of the experimental setup. However, were also found some differences in the performance of the KN95 and 3MN95 masks. The KN95 face mask had the best performance since it expulsed to its surroundings the lowest airflow with different physical properties to the input airflow. The results obtained are relevant since it was possible to estimate the expulsed airflow velocity as a function of the distance for every face mask tested, which allows for understanding its filtering capacity by restricting the flow of potential pathogens from the mouth or nose of one person to another. Undoubtedly, the airflow behavior determination around a face mask can help to reduce the risk of spreading infectious airborne particles.

Development of a new modeling framework to describe sterile filtration of mRNA-Lipid nanoparticles

Sterile filtration is one of the critical steps in the production of lipid nanoparticle (LNP)-based biotherapeutics. However, LNP fouling can limit the overall capacity of the sterilizing-grade filter. Effective design and control of this unit operation enables a robust manufacturing process. The objective of this study was to examine the sterile filtration of mRNA-LNP through the dual-layer Sartopore 2 XLG membrane during both constant flux and constant transmembrane pressure (TMP) filtration experiments. The complete pore blockage model effectively described the fouling behavior at constant TMP, with the rate of pore blockage decreasing with increasing TMP. However, a novel modification of the complete pore blockage model was needed to describe the fouling behavior during constant flux operation, with the rate of pore blockage found to be a function of both the instantaneous TMP and the TMP gradient. This new model successfully describes the TMP profiles during constant flux operation at multiple fluxes and the flux profiles during constant TMP operation at multiple TMPs, all using the same model parameters. These findings establish a foundational framework that mathematically describes the fouling behavior of mRNA-LNP and can be used to design and optimize sterile filtration processes for this class of biotherapeutic.

Treatment efficiency and recovery in sand filters for on-site wastewater treatment: Column studies and reactive modelling

This study examined the adsorption capacity and treatment efficiency of sand filters in on-site treatment systems for cold climate regions. The effects of different operating conditions, porosity and kinetics parameters were investigated in column experiments and COMSOL Multiphysics® modelling, to comprehensively reveal the mechanisms and optimize treatment efficiency of nitrogen (N) and phosphorus (P) removal in a field tidal flow constructed wetland (TFCW), treating effluent from a package treatment plant with P filter material. The results from column experiments with sand showed that Total-P adsorption rate was dependent on feed water quality (Septic tank >0.77 ± 0.06 g kg−1; Biotreatment >0.41 ± 0.07 g kg−1; Reactive material Polonite® <0.18 ± 0.07 g kg−1). In the field TFCW trial, Total-P adsorption in the top layer (>1.42 ± 0.55 g kg−1) and middle layer (>1.06 ± 0.51 g kg−1) was twice that in laboratory columns, due to strong interaction with the air-water interface and use of fluctuated domestic wastewater solutions. The breakthrough curve (BTCs) of the coarse sand matched the physical behaviour of tracer electrical conductivity (EC) in effluent from the sand column experiments. The modelling results demonstrated that high filter porosity and low hydraulic load were significant factors for optimal removal of NH4–N, Total-N, PO4–P, Total- P in the top layer (>99.95 ± 0.03 %, 44.37 ± 28.75%, 70.89 ± 28.30%, 76.18 ± 20.3%), middle layer (>98.94 ± 1.77%, 18.23 ± 23.04%, 76.62 ± 28.73%, 65.40 ± 31.85%) and deep layer (>99.99 ± 0.02%, 65.50 ± 20.64%, 75.53 ± 23.16%, 41.54 ± 28.81%) in the TFCW system, respectively. The results show that on-site wastewater treatment in cold climate TFCW can be applied as a technology to polish effluent from a three-step pretreatment system. However, hydraulic optimization is an important factor for the design of the TFCW to receive a successful long-term operating system.

Improved sieving coefficient in perfusion cell culture with reduced effective filtration length of hollow fibers.

The hollow fiber filter is the primary cell-retention device used in high-density perfusion cell culture and often used in an alternating tangential flow (ATF) configuration. The limited commercially available diaphragm pumps for ATF prevent utilization of vertical space when scaling beyond 500 L. Stacking hollow fiber filters coupled with viscous cell culture imposes vacuum pressure exceeding facility capabilities. Additionally, the longer filter assembly increases the hold-up volume and exceeds the diaphragm pump's fluid exchange capacity. The conventional tangential flow filtration (TFF) configuration circumvents this issue by exchanging culture from the bioreactor and cell-retention device in a unidirectional recirculation loop; however, the increased filter length when scaled up exacerbates the TFF's inherent issue with product retention from Starling flow. Stacking commercially available 20 cm TFF filters to make up the similar single-module length TFF used for the platform 3 and 50 L perfusion process at 41.5 and 65 cm, respectively, attempts to reduce fouling caused by Starling flow. The permeate of a single-module filter is partitioned into short independent segments through serially stacked filters, each harvested separately. By partitioning the permeate, the sieving coefficient increased for both 3 and 50 L scales. Reduction of Starling flow was confirmed with lower total hydraulic membrane resistance throughout the culture. This work demonstrates a method for increasing sieving coefficient and filter capacity by stacking TFF filters with independent permeate streams.

Impact of functional coatings on microstructure and properties of periclase-magnesium aluminate spinel ceramic filter and its purification capacity on molten steel

Reticulated ceramic filters play an important role in the reduction of non-metallic inclusions in molten steel, which can improve the quality of steel products. In this work, periclase-magnesium aluminate spinel ceramic filters with Al2O3 and TiO2 functional coatings were fabricated by using microporous MgO powder, respectively. The effects of the functional coatings on their microstructure, properties and purification capacity on molten steel were studied. The filter with Al2O3 functional coating exhibited the best mechanical properties owing to the good rheological properties of the coating slurry, as well as the formation of in-situ spinel layer connection between the Al2O3 functional coating and the microporous MgO layer of the filter substrate. Compared with the filters without functional coating or with TiO2 functional coating, the filter with Al2O3 functional coating made more Al2O3 inclusions deposit on the filter surface by physical adsorption due to the same chemical composition between the functional coating and inclusions, which significantly improved the adsorption capacity of filter for Al2O3 inclusions in molten steel. Overall, the filter with Al2O3 functional coating had the highest cold compressive strength of 1.4 MPa, a residual retention of cold compressive strength after thermal shock of 65.71 % and an efficiency of 36.56 % in reducing the total oxygen content of the steel.

Inclined Tubes Clarifier for Effective Removal of Suspended Solids from Canal Water Prior to Groundwater Recharge

Groundwater recharge, through surplus supplies of canal water, may prove to be an important strategy for replenishing the rapidly depleting groundwater in Punjab and managing sustainably the groundwater resources. However, presence of suspended silt load in the canal water results in clogging of recharge wells and subsequent reduction in recharge rates and capacity of filters. In present study, an inclined tubes clarifier having filtration capacity of 1.8 L s-1 was designed and fabricated to filter the silt-loaded canal water. In the clarifier, tubes of poly vinyl chloride (PVC) media of 1-m length were attached one over the other to form an inclined honeycomb like structure through which canal water enters as inflow from the bottom and the clarified water exits as outflow from the top of the clarifier. Efficacy of the designed clarifier was tested at different total suspended solids ranging from 500 to 3000 mg L-1 in the canal water and at pumping rates varying from 0.3 to 2.1 L s-1. The results revealed more than 85% sediment-removal efficiency of the clarifier at flow rates above 0.8 L s-1. The results further indicated that efficiency of removing total suspended solids (TSS) reduced drastically at inflow rates more than 1.2 L s-1. Also, at all the flow rates, the efficiency was 6% higher for water samples having TSS more than 2000 mg L-1 in comparison to samples having TSS less than 1000 mg L-1. The clarifier makes no significant difference to the values of total dissolved solids, electrical conductivity, total solids and pH of the canal water.

Electrospun membrane of PLA/calendula with improved UV protection and stable filtration performance

The “dual carbon” strategy and the severe air pollution problem have spurred the development of environmentally friendly functional filters. However, the performance stability of degradable polymers under ultraviolet (UV) irradiation needs to be explored and addressed. Loading natural small molecules onto electrospun fibers can enhance their functionality and sustainability. This study explores the use of calendula extract to protect polylactic acid electrospun fibers from UV degradation and provide antibacterial properties. A double-layer filter was created using straightforward sequential electrospinning. Only one-third of the fiber membrane's thickness contains drugs, resulting in an 88 % inhibition rate against Staphylococcus aureus. Its UV protection capability has been significantly enhanced. The calendula filters exhibited a tensile strength loss rate of only 23 %, compared to 30 % for the unmodified filters. Furthermore, the calendula extract altered the morphology and porous structure of the fibers, leading to an enhancement in the stable filtration efficiency of the membrane. It maintains a filtration efficiency of over 99 % at a flow rate of 32–85 L/min. This study has enhanced the stable filtration capacity of biomass filters and showcased their potential for UV protection and antibacterial applications.

Improving Expressive Power of Spectral Graph Neural Networks with Eigenvalue Correction

In recent years, spectral graph neural networks, characterized by polynomial filters, have garnered increasing attention and have achieved remarkable performance in tasks such as node classification. These models typically assume that eigenvalues for the normalized Laplacian matrix are distinct from each other, thus expecting a polynomial filter to have a high fitting ability. However, this paper empirically observes that normalized Laplacian matrices frequently possess repeated eigenvalues. Moreover, we theoretically establish that the number of distinguishable eigenvalues plays a pivotal role in determining the expressive power of spectral graph neural networks. In light of this observation, we propose an eigenvalue correction strategy that can free polynomial filters from the constraints of repeated eigenvalue inputs. Concretely, the proposed eigenvalue correction strategy enhances the uniform distribution of eigenvalues, thus mitigating repeated eigenvalues, and improving the fitting capacity and expressive power of polynomial filters. Extensive experimental results on both synthetic and real-world datasets demonstrate the superiority of our method.

Filtration of a multi-serotype glycoconjugate vaccine drug product through sterilizing grade 0.2/0.22µm pore size filters.

Glycoconjugate vaccines containing multiple serotypes of a bacterial capsular polysaccharide can provide strong immune protection against pathogenic infections. Sterile filtration is an important component of the fill and finish operations in the preparation of these vaccines, with the capacity of the sterile filter limited by membrane fouling. The objective of this study was to examine the performance of a range of commercial 0.2/0.22µm nominal pore size sterilizing grade filters with both single-layer and dual-layer structures during filtration of a glycoconjugate vaccine drug product consisting of four polysaccharide serotypes. The highly asymmetric Millipore Express showed much higher capacity than the more homogeneous filters, with the support structure of the Express acting as a prefilter that was able to remove foulants thereby protecting the small pores in the size-selective skin layer. This behavior was confirmed by performing experiments with different batch prefilters and by examining the location of foulant deposition within the sterile filters using confocal microscopy. These results provide important insights into the factors controlling fouling by these multiserotype vaccines as well as a framework for increasing the capacity of the sterile filter.

DETERMINAÇÃO POR ESPECTROMETRIA DE MASSAS DO POTENCIAL DE BIOACUMULAÇÃO DE CONTAMINANTES EMERGENTES EM BIOFILME

DETERMINATION BY MASS SPECTROMETRY OF THE BIOACCUMULATION POTENTIAL OF EMERGING CONTAMINANTS IN BIOFILM. Personal hygiene products, such as UV filters, are consumed daily and released at sewage treatment plants. The presence of these compounds in aquatic environments may cause concern, as their impacts are not yet fully known. Biofilms can be an innovative and simple tool for monitoring the bioaccumulation of contaminants such as UV filters in aquatic environments. The present work aimed to determine and evaluate the potential of bioaccumulation of these compounds in biofilm and in the surface waters of the Barigui River. The determination of contaminants in environmental matrices was performed by liquid chromatography coupled to triple-quadrupole mass spectrometry (LC-MS/MS). The validation of the methodology used was based on the acceptance criteria of the National Institute of Metrology, Quality and Technology (Inmetro). The results obtained in the samples ranged from the maximums of 5.85 μg L–1 of benzophenone-1 for water samples to 1907.40 μg kg–1 of benzophenone-3 for biofilm. The study showed that biofilm is a very useful new tool in environmental monitoring, mainly due to the bioaccumulation capacity of UV filters.

РОЗРАХУНОК ПРОЦЕСІВ У ПЕРЕТВОРЮВАЧІ ЗА ТОПОЛОГІЄЮ LUO З ВИКОРИСТАННЯМ МЕТОДА УСЕРЕДНЕННЯ НА ОСНОВІ ТЕОРЕМ ЛАГРАНЖА

The electromagnetic processes in elementary dc converter according to the Luo topology with inverting output in modes of continuous and discontinuous conduction were studied. Using the method of averaging in the state space based on Lagrange theorems, mathematical models of converter for mentioned modes of operation have been devel-oped. The use of developed models made it possible to obtain analytical expressions for calculating the average and pulsation values of currents and voltages in the reactive elements of the converter, as well as their ripple coefficients. Graphical dependences of the mentioned parameters were calculated in the entire commutation range of converter, taking into account the conduction modes. It is shown that, in comparison with traditional topology of buck-boost con-verter, the output filter in elementary Luo converter with inverting output significantly reduces the ripple coefficient of output voltage. It was determined that the amount of voltage ripple reduction is proportional to the product of the in-ductance and filter capacity values, as well as the square of the switching frequency and does not depend on the con-ductivity mode of the converter. Ref. 13, fig. 5, table. Key words: dc voltage converters, Luo converter, averaging method in state space, Lagrange theorems.