جستجوی مقالات مرتبط با کلیدواژه « filtration » در نشریات گروه « پزشکی »

Protection of the respiratory system has been a vital, and for this purpose, various solutions have been proposed, including the use of masks. One of the most important parameters to measure the effectiveness of the mask against the penetration of microbial agents. The present study was conducted with the aim of evaluating the bacterial and particle filtration of medical masks.

To assess bacterial performance, the national standard 6138, compliant with EN14683, and Type I medical masks were utilized. Staphylococcus aureus bacterial suspension was prepared and passed through the mask using a nebulizer and through an impactor with a flow rate of 28.3 l/min. Plates containing soy agar were placed in the impactor. Subsequently, all plates were incubated, and the bacterial filtration efficiency (BFE) of the masks was determined by counting the bacterial colonies that passed through the mask’s media as a percentage of the total bacteria. It is worth noting that the pressure drop and particle filtration efficiency were also determined for all masks

Based on the results of the particle removal performance for the particle size of 3 µ, the masks were categorized into three groups with efficiency above 99%, above 95% and 90%. According to the standard, all masks had an acceptable pressure drop below 40 Pa. The acceptable bacterial filtration rate for type I masks should be above 95%. The results showed that type A and B masks have an acceptable bacterial filtration rate and there is a significant correlation between the types of masks examined in terms of bacterial and particle efficiency.

The results showed that different types of masks under investigation have significant differences in terms of particle capture efficiency and bacterial filtration performance. In addition, there is a significant correlation between bacterial and particle filtration efficiency.

In recent years, the manufacture of air purification media, especially nanofiber filters using polymeric materials and the electrospinning method, has received much attention in air pollution control. The production of high-performance media and low-pressure drops is an important issue in air filtration. This study aimed to investigate the feasibility of fabricating electrospinning polyethylene terephthalate (PET) media to abduct submicron and micron particles from the air stream.

To determine the optimal device conditions in the manufacture of PET media, different weight percentages of a PET polymer solution in a mixture of trifluoroacetic acid and dichloromethane solvents (70:30) were first prepared in a pilot study, and various parameters of the electrospinning device were examined and analyzed along with performing the electrospinning process. The surface and morphological characteristics of the media were evaluated using SEM. The pressure drop and efficiency of particle trapping were assessed using a mask and media pressure by a pressure drop test device.

The optimal electrospinning conditions of the PET polymer solution were obtained at a concentration of 20%. The average diameter of nanofibers PET was 163 ± 600 nm with a pressure drop of 26.33 ± 5.5 pa, and average efficiencies of 97.42 ± 1.67% and 99.85 ± 0.21 were obtained for submicron and micron particles, respectively, with a quality factor (QF) value of 0.1740.

The produced media can abduct and remove particles from the air stream for submicron and micron particles in ranges of 96-99% and 99-100%, respectively, with an average pressure drop of 26.33±5.5 pa.

Evaluation of the performance of these products is mainly based on their efficiency in numerical removal of particles in the range of different sizes. While the most important features of filters are the dust holding capacity, and the ability to remove the mass of particles with different densities, fewer studies have addressed this issue. Therefore, the present study evaluates the dust holding capacity of nanofiber media and its ability to capture synthetic dust to determine its ability to remove the mass of particles with different densities. At the same time, the initial efficiency of the fabricated media in the numerical removal of particles is also examined.

For producing nanofibers, a 16% w/w electrospinning solution of polyacrylonitrile polymer was prepared. The initial efficiency test in numerical removal of particles was performed according to ISO 29463 standard and the BS EN 779 standard was used for synthetic dust capture or arrestance test. Morphological characteristics, diameter, and surface porosity of the produced nanofibers were investigated using scanning electron microscopy.

The investigation of the numerical removal of particles by the produced media showed that the average initial efficiency for collecting particles from 10 to 1000 nm was 72.06 ± 19.62%. The results of the arrestance test showed that with increasing the mass of injected particles in different loading stages, the media pressure drop also increases. The dust holding capacity and the arrestance of the media for the final pressure drop of 265 Pascal were calculated to be about 180 mg and 99.86%, respectively. The total mean of arrestance was calculated to be about 99.86% after 6 loading steps. The morphological characterization of the produced nanofibers showed that the average diameter of the fibers was 380 nm with a coefficient of variation of 1.20, the morphology of nanofibers was non-uniform, and the surface porosity was determined to be 51%.

Proper collection efficiency and dust holding capacity, along with the low thickness of nanofiber media, make their applicability more specific in air filtration properties.

The present study aimed to compare the filtration performance between neat hybrid electrospun nanofibers consisting of polyacrylonitrile (PAN) polymer and magnesium oxide (MgO) nanoparticles and plasma treated ones in removing fine particles from the air stream.

The upper surface of the nanofibers were processed by cold-plasma with a radio frequency power supply (13.56 MHz with a power of 20 watts), argon gas and operating pressure of 0.2 torr. Initial efficiency tests for numerical removal of particles have been done in accordance with standards ISO 29463 and EN 779. Pressure drop and quality factor were determined for the fabricated media. In order to confirm the presence of magnesium oxide nanoparticles in the nanofibers, X-ray diffraction pattern (XRD) was prepared. Analysis algorithms of SEM images were used to calculate the porosity of filters using MATLAB software.

The mean initial efficiency of neat and plasma-treated media was 90.77 ± 6.7 % and 73.66 ± 8.86 % for collecting particles from 10 to 1000 nm, respectively. The initial mean pressure drop of the neat and treated media at the test face velocity was 78.22 ± 3.11 pa and 22.00 ± 2.33 pa, respectively, and their mean quality factor for collecting 10 to 1000 nm particles was 0.029 and 0.010 (Pascal/1), respectively.

By performing plasma treatment, collection efficiency of particle decreased, but with a significant decrease in pressure drop, so neat media ultimately presented the higher score of quality factor than treated one

In microbial contamination of food and water, identification of trace amounts of contaminating bacteria has always been an interest and concern for researchers. The most common way to remove of this problem is culture-based methods in order to increase and enrichment of bacteria samples, which extends the bacterial detection process to several hours or days. One of the smart strategies to solve this problem is concentrated of bacteria using physical methods. The aim of the present study was to enrich of Vibrio cholerae as the most important water polluting germs using filtration method and evaluation of its function by culture method and two detection methods ATP and PCR assay.

A certain concentration of V. Cholerae was added into a specified volume of sterile water, artificially. Then, the bacteria were extracted from the medium and filtered using 0.450µm separable filters. Finally, the performance of the pre- and post-filtration process was compared using bacterial cell culture (CFU), ATP and PCR assay with the specific primers for the ompW gene of V. cholerae.

The results of this work showed that this method shows high efficiency and recovery performance. So that, samples had no positive response before filtration in both methods, but after filtration in isolated and recovered samples, the presence of bacteria was detected in both ATP and PCR methods.

In conclusion, this strategy can detect V. cholerae in non-culture and in the least amount of time in contaminated water samples.

The importance of water and disease transmission has been known for a long time. One of the necessities of human life, both in times of peace and in times of crisis, is to drink "safe water". Drinking healthy, disease-free water plays an important role in preventing water-borne diseases such as acute and chronic diarrhea. Water-borne pathogens are abundant and include bacteria, viruses, protozoa, and parasitic worms.Adequate water supply and water purification in emergency situations and control and monitoring of water quality have particular importance. The United Nations recommends that each person needs 20-50 liters of healthy freshwater per day to meet basic human needs such as drinking, cooking, and cleaning, of which 2-4 liters per day is sufficient for drinking and should be provided from the best quality water sources. The minimum amount of drinking water consumption on the first day after the occurrence of a catastrophe to survive in a mild climate and mountain conditions is one liter per day and to survive in hot and dry conditions 3 liters per day.In the present review study, the practical and applied methods appropriate to the available technology for the drinking water supply of small communities have been presented.

Pulse jet systems are of interest due to their high filtration velocity,Theychr('39')re used as inlets from top and bottom. the purpose of this study was to compare the pressure drop and collection efficiency at the different inlet positions in a baghouse

In this experimental study, a pilot system was designed at 12ft/min permeability for MDF particles.For each inlet after several filtration-cleaning periods,pressure drop was measured by a manometer.Isokinetic sampling was also performed by Grimm1.108 monitor to determine the efficiency.To observe the behavior and Tyndall effect of particles, light and safety glass were used in one dimension of the baghouse

The mean pressure drop during the filtration-cleaning,the bottom inlet was 3CmWG, the top whit expansion inlet was 2.42CmWG,and the top flanged inlet was 2.57CmWG. but the particles settled on the expansion floor.The mean efficiency of top-expansion inlet was 99.995% and top-flanged 99.994%,significantly higher than the bottom inlet (99.974%).After several filtration-cleaning periods,The efficiency of  bottom inlet resulted 99.99%,top-expansion 99.97% and flanged 99.96%.There was no significant difference between the mean total efficiencies for different inlets.

The collection efficiencies were the same for baghouses with inlet from top and bottom.The pressure drop for baghouses with the top inlets was lower than the bottom inlet.It is recommended to use top inlets in case of predominantly fine particles with low density or in presence of a pre-separator,if  large particles,bottom inlet is recommended.Due to the slight difference of pressure drop and more functional limitation of the top inlet,bottom inlet in practice is preferred.

Before describing the structure and mechanism of action of a protein, it must first be subject to purification procedure. Protein purification is a set of processes in which one or a small number of proteins are purified from a complex compound that may be a complete cell, tissue, or organism. Understanding the functions, structural properties, and interactions of the protein are directly related to the degree of purity of the protein of interest. In the purification process, the protein and non-protein parts are separated. The biggest challenge is when the protein must be separated from other proteins. The purification procedure of an unknown protein is usually depends on the size, physicochemical properties, binding affinity, and biological activity. The end product of the purification process is called protein isolate. The protein purification process usually involves filtration and one or more chromatographic steps. Chromatography is a useful method for acquiring very pure protein for using in very accurate experiments. Therefore, by purifying the desired molecule, it can be used in various industries, such as medicine.

Nowadays, rapid growth of car wash industries has led to a demand for wastewater reclamation. In this study, the hybrid process including electrocoagulation/flotation, sedimentation, and filtration were used in treatment of real carwash wastewater. In this research, the sample was first entered into the ECF reactor, then entered the retention tank after specific times and eventually passed through filtration. COD was measured by closed reflux colourimetric method and turbidity was measured by Nephelometric method. To optimize the COD and turbidity removal efficiency, a central composite design was used based on response surface methodology (RSM) using Design-Expert version 7. According to the the RSM model, optimum conditions for pH, electrolysis time, and applied current were 7.67, 1.69 amps and 90 min, respectively, in which COD removal and turbidity removal efficiency were 94.5% and 95%, respectively. The most predicted efficiency for the COD and turbidity removals were 100% and 96.69%, respectively. Electric energy consumption and operating costs were found to be 4.2 kWh / m3 and 8820 Rials, respectively. The hybrid treatment process used in this study, seems to be an efficient and cost effective method compared to existing conventional treatment methods used in removing pollutants from carwash wastewater. Therefore, this method can be used to remove pollutants with high concentrations from car wash industry wastewater and in wastewater reclamation.

Electrospun nanofibers can be used to produce filter media in personal protective equipment for the military. The present study aimed to optimize the electrospinning process used to create polyurethane nanofiber substrates and compare the optimum substrate filtration performance with a typical commercial substrate used in the structure of N95 respirators. In this experimental study, polyurethane polymer solutions were prepared in a solvent system consisting of dimethylformamide and tetrahydrofuran with a mixing ratio of 3: 2 (v/v%). The main and interactive effects of electrospinning process parameters (polymeric solution concentration, applied voltage, electrospinning distance, and polymer injection rate) on the mean diameter and uniformity of electrospun nanofibers and their optimal values were studied using response surface methodology, specifically, a central composite design. The filtration efficiency and pressure drop of the electrospun polyurethane nanofiber filter media were compared with the commercial media used in the N95 respiratory mask structure using a prepared filtration test rig. Based on the results of the quadratic model, the optimal conditions for the electrospinning of polyurethane polymer were polymeric solution concentration, applied voltage, electrospinning distance, and polymer injection rate of 14 w/v%, 17 kV, 10 cm, and 0.4 ml/h, respectively. The results showed that despite having a lower base weight, the filtration efficiency and quality factor of four layers of polyurethane nanofiber filter media were higher than that of a three-layer N95 mask (98.24% % versus 98.1%, and a quality factor of 0.061 versus 0.084 Pa-1, respectively). It can be concluded that the electrospun polyurethane nanofiber media have acceptable filtration efficiency and quality factor values for filtration applications. In addition, the fabrication of nanofiber media with desired properties (nanofiber diameter, uniformity, etc.) for use in the filters of respiratory protection equipment is possible by optimizing the electrospinning process.

Nowadays, the greatest of process type used in treatment of beverage water is conventional treatment. That it cannot remove organic matter effectively. Filtration is one of the most important treatment processes used in water treatment plant.The one of approaches, modification of conventional rapid sand filters into dual or multimedia filters.
This study was results from of pilot study that with the purpose of assessment performance was using of GAC and Anthracite in dual media filter filters in Abadan water treatment plant in removal of TOC, Fe, Mn, No3-and NH4 in Drinking Water by GAC and Anthracite in dual - media filters in Abadan water treatment plant. All parameters were measured according to sections of Standard Methods APHA et al. The t-test and regression equations were calculated.
Samples were collected in summer from the inlet and outlet of each pilot filter and the outlet of the filtration unit. Turbidity, Total Organic Carbon (TOC), Fe, Mn, NO3- and NH4 were measured in each sample for three different low, medium, and high filtration rates. Pilot No.2 had a maximum efficiency in the removal of the parameters that removal average of turbidity, TOC, Fe, Mn, NO3-, NH4, respectively. So, the best performance of GAC-sand filter is in EBCT=20 min during loading rate of 35 l/d.
In general, both pilot filters performed better at low surface loading rate. More specifically, pilot scale No. 2 showed better removal of parameters and longer empty bed contact time (EBCT) in that surface loading rate.