Showing 9 results for Efficiency
Tahereh Mousavi, Farideh Golbabaei, Mohammad Reza Pourmand, Sasan Rezaei, Mostafa Hosseini, Mehrdad Helmi Kohneshahri, Ensieh Masoorian, Ali Karimi,
Volume 7, Issue 2 (6-2017)
Abstract
Introduction: Nowadays, HEPA filters is used in hospitals, clean rooms, microbiology hoods, ventilation of surgery rooms, and Pharmacy for removing microorganisms and reduce health hazard. The aim of this study is to increase the efficiency of HEPA filters with UVC radiation to reduce the density of airborne microorganisms.
Material and Method: The closed–loop chamber was made to evaluate Staphylococcus epidermidis, Bacillus subtilis bacteria and Aspergillus Niger, Penicillium fungi. The concentration of fungi and bacteria suspension Respectively was 106, 107 CFU/ml. After the suspension was prepared, it was sprayed into the closed loop chamber by nebulizer. Sampling was done with UVC radiation (1.8 mW/cm2 Illuminance) and no radiation (dark) that included time periods 60, 90 and 120 minutes. Microorganisms density was determined in term of CFU/m3.
Result: The result showed that there was a significant difference between UVC radiation and dark section for all the microorganisms (epidermidis, subtilis, Niger and Penicillium) at each time periods (P value< 0.05). This indicates that concentration of four microorganisms were decreased at all the time periods. UVC radiation could change the essential molecular substances for cellular factor. UVC can penetrate the cell walls of microorganisms. thus nucleic acids and other cellular vital material affected and will cause the destruction or inactivation of microorganisms.
Conclusion: UVC radiation is effectiveness to decrease concentration of four microorganisms. because UVC radiation could remove both bacteria and fungi. While the other studies in other countries, UVA radiation is only effective in reducing bacteria. Therefore, achieved greater efficiencies of HEPA filters, using HEPA filters with UVC will have a significant effect on reducing the density of microorganisms.
Majid Habibi Mohraz, Farideh Golbabaei, Il Je Yu, Asghar Sedigh Zadeh, Mohammad Ali Mansournia, Somayeh Farhang Dehghan,
Volume 8, Issue 1 (4-2018)
Abstract
Introduction: Electrospun nanofibers are suitable option to synthesize filtering mats for nanoparticles. This study was aimed to fabricate polyurethane nanofiber mats through electrospinning process and to investigate the effect of different parameters such as packing density, face velocity and particle type on the filtration efficiency and quality factor of electrospun polyurethane nanofiber mats.
Material and Method: The nanofiber mats were produced by electrospinning process. Polyurethane granules were dissolved (15w/w%) in a solvent system consisting of dimethylformamide and tetrahydrofuran (3:2). Then, the filtration performance testing system was made at the Fluid Mechanics Department of Hanyang University of South Korea and the filtration efficiency and pressure drop of prepared nanofiber mats were studied.
Result: Findings showed that by increasing the duration of electrospinning, the basis weight, thickness, packing density, initial pressure drop and filtration efficiency of the mats increased, and the quality factor of the mats decreased due to the increase of the pressure drop. The increase in electrospinning duration from 15 to 45 minutes was led to the increase in pressure drop from 7 to 32 Pa and the average filtration efficiency was increased about 9-10% for KCl and DEHS test particles. The filtration efficiency and quality factor of the prepared polyurethane nanofiber mats were declined with the increase of filtration face velocity from 2 to 5 and 10 cm/s. The reduction in filtration efficiency was more obvious for particles smaller than 425 nm.
Conclusion: The results demonstrated that prepared polyurethan naofiber mats provide acceptable filtration performance. What is more, such nanofiber mats can have other potential benefits such as light basis weight, low thickness and simple production.
Bahman Pourhassan, Farideh Golbabaei, Mohammad Reza Pourmand, Somayeh Farhang Dehghan, Ensieh Masoorian,
Volume 8, Issue 3 (9-2018)
Abstract
Introduction: Indoor air environments contain a wide variety of microorganisms such as bacteria, fungi, and viruses in which some of them can affect the human health. Filtration is considered as one of the most common methods to remove microorganisms in these environments. The purpose of current study was to investigation the neat and photocatalytic HEPA filters performance at different face velocities and various intensity of UVC light source on the reduction of airborne microorganisms.
Material and Method: After installation of the neat and photocatalytic HEPA filters in a closed–loop chamber, suspension of Staphylococcus epidermidis and Bacillus subtilis bacteria with a concentration of 107 CFU / ml were sprayed into the closed–loop chamber by nebulizer. Sampling of penetrated microorganisms from filters were performed using the NIOSH 0800 method under ambient temperature 22±3oC, relative humidity 35±5%, and different air velocity (0.1 m/s and 0.3 m/s) and UVC different radiation intensity (1 mW/cm2, 1.8 mW/cm2 and no radiation (dark)) at 30 minutes time period. penetrated microorganisms density from filters was determined in term of CFU/m3.
Result: There were no significant differences in the penetration rates of microorganisms at the dark mode between the two neat and photocatalytic HEPA filters (p>0.05). The penetration rate of bacteria was significantly decreased in the neat and photocatalytic HEPA filters at UVC radiation mode with various intensities than dark mode (p<0.05). In addition, comparison of the filters in the illuminance modes of 1 mW/cm2 and 1.8 mW/cm2 were statistically significant (P <0.05). Also, UVC radiation with the 1.8mW/cm2 illuminance compared to the 1 mW/cm2 illuminance resulted in a greater reduction in the bacterial penetration from both types of filters, which is statistically significant(p<0.05). The bacteria penetration rate dramatically increased by increasing the face velocity from 0.1 m/s to 0.3 m/s under UVC radiation at an illuminance of 1mW/cm2, 1.8mW/cm2 and as well as in no radiation mode in both types of HEPA filters (P <0.05).
Conclusion: Photocatalytic HEPA filters and increasing UVC illuminance, especially at lower surface velocities, have a significant positive effect on reducing airborne microorganisms and increasing the efficiency of HEPA filters
Roohollah Ghasemi, Farideh Golbabaei, Mohammad Javad Jafari, Mohammad Reza Pourmand, Sasan Rezaei, Ramin Nabizadeh, Ensieh Masoorian,
Volume 9, Issue 2 (6-2019)
Abstract
Introduction: Air pollution is now recognized as an important environmental and health concern. Biological control processes, due to their durable, cost-effective and eco-friendly, have become a good alternative to physic-chemical methods. Biotechnology is based on the activity of microorganisms.
The aim of this study was to compare the capability of Pseudomonas Putida PTCC 1694 (bacteria) and Polarotus Stratus IRAN 1781C (mushroom) in the removal of toluene from the air stream and its biodegradation under same operating conditions.
Material and Methods: To this purpose, a bio filter containing two parallel columns was designed and constructed on a laboratory scale and the experiments were carried out based on measuring the removal efficiency (RE), elimination capacity (EC) and pressure drop in these two columns. Thus, the bacteria were inoculated in one of the columns and in the other the fungus was inoculated.
Results: The bacterial testing lasted for 20 days and the fungal testing lasted for 16 days. The contaminant loading rates (LR) for bacterial and fungal bio filters were 11.65±2.26 and 11.94±2.56 g/m3.h, respectively. The results showed that the fungal bio filter was more capable of eliminating of toluene vapor than bacterial bio filter (9.65±3.53 vs 9.18±2.6 g/m3.h). However, the pressure drop in the bacterial bio filter was lower than the fungal bio filter (1±0.28 vs 1.1±0.32 cm water).
Conclusion: According to the results, fungal bio filtration appeared to be more successful than bacterial bio filtration in the removal of toluene.
Somayeh Farhang Dehghan, Farideh Golbabaei, Asghar Sedigh Zadeh, Hamzeh Mohammadi,
Volume 9, Issue 3 (9-2019)
Abstract
Introduction: Despite nanofibers have attracted great interests for filtering particulate matters from the air stream, fewer studies have been done on the feasibility of their use in the removal of gas pollutants, while the both pollutants are present in the most workplaces. Toluene is a toxic and mutagenic substance, and chronic exposure to its low levels can lead to a wide range of adverse health effects on people who exposed. The purpose of this study was to produce polymer /single-walled carbon nanotube hybrid nanofibers by electrospinning technique and doing plasma surface treatment and evaluating their removal efficiency of toluene from air stream.
Material and Methods: The nanofiber layers were fabricated by electrospinning solution containing polyacrylonitrile polymer (PAN) and single-walled carbon nanotube (SWNT) with a 99: 1 ratio under following conditions: applied voltage 20 kV, distance between needle and collector: 10 cm, injection rate: 1 ml / h; needle diameter: 18 gauge and drum speed ranging from 1000 to 500 rpm. The surface of the manufactured nanofibers was treated 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. Test conditions was prepared according to standard ISO 10121-1: 2014, which provides a method for testing the performance of gas-phase air filter for a variety of flat sheet media. In order to measure the concentration of toluene, the First check – handheld multi gas VOC detector equipped with a PID detector was used. The morphology characteristics of the fibers was performed using the analysis of scanning electron microscope images. Infrared spectroscopy-Fourier transform was used to identify organic compounds and functional groups in nanofibers.
Results: The results of the analysis of the images showed that the mean diameter of the fiber was 169.16 ± 7.19 nm and the mean coefficient of variation was 0.23. The uniform and bead nanofibers were obtained. The thickness, porosity and air permeability coefficient of test media was 0.15 mm, 43% and 5.75 Darcy, respectively. The mean removal efficiency of PAN / SWNT nanofiber treated with plasma was 98% and the mean pressure drop was 100 Pascal. The FTIR spectrum of the test filter media showed that the peaks appearing at certain wavelengths related to the vibration of C-H aliphatic groups of C-C and C=O bands related to PAN polymer and carbon nanotubes.
Conclusion: Removal of toluene was achieved through the fabrication of PAN/SWNT hybrid nanofibers treated with plasma. Uniform nanofibers were obtained and showed the proper removal efficiency and low pressure drop.
Zahra Tarin, Abdulrahman Bahrami, Mohsen Goodarzi, Farshid Ghorbani-Shahna,
Volume 12, Issue 2 (6-2022)
Abstract
Introduction: Generally, geometrical parameters of the cyclone have a profound effect on determining its performance. The air outlet (Vortex Finder) as one of the cyclone’s components has a significant impact on the cyclone’s internal flow pattern, pressure drop and even dust removal efficiency.
Material and Methods: Two different air outlets were designed in order to be easily installed and removed. The ribs (both in the opposite and the same swirl direction with the air flow) were inserted at the inner wall of the vortex finder. The step length of the blades was calculated to be 1.5. The dust feeder was injected the silica particles with a concentration about of 2.1 gr/m3 into the inlet air. The results of dust removal efficiency of the cyclone were calculated and compared for three groups of total dust, PM10 and PM2.5 in different experimental conditions.
Results: Installation of spiral blades in same swirl direction as the air flow inside the cyclone increased 7.75, 7.73 and 6.75 percent in total efficiency, PM10 and PM2.5, respectively. The dust removal efficiencies for total dust, PM10 and PM2.5 increased by 2.6%, 2.33% and 1.5%, respectively, when the swirl direction of ribs and air flow was the opposite. The effect of helical blades on pressure drop for the first experimental setup (same direction) decreased by (- 2.5%) and in the second one (opposite direction) increased by (+ 2.03%). The best quality factor was also calculated for the cyclone with the blade aligned with the air flow direction.
Conclusion: Use of ribs in the inner wall of the cyclone vortex finder, especially when the rotation direction of the ribs and airflow are the same, leads to a decrease in pressure drop and increase in dust collection efficiency which finally leads to improvement of cyclone performance.
Asghar Hadi, Aligholi Niaei, Azam Seifi, Yahya Rasoulzadeh,
Volume 12, Issue 3 (9-2022)
Abstract
Introduction: Rapid population growth and industrialization have increased chemical pollutants. Some studies show that employee exposure to formaldehyde in industrial places, hospitals, and laboratory settings is more than the allowed limits. Therefore, it is necessary to implement a proper control system to reduce this exposure. This study aimed to synthesize Ag3PO4/TiO2 nanocomposite, determine its morphological and structural characteristics, and test the degradation efficiency of this photocatalyst on formaldehyde.
Material and Methods: Ag3PO4/TiO2 composites were synthesized via an in-situ precipitation method. The physicochemical, morphological, and optical properties of the synthesized sample were investigated by employing the BET method, X-ray diffraction (XRD), UV–visible absorption spectroscopy, and scanning electron microscopy (SEM). The photocatalyst degradation efficiency test was performed on gaseous formaldehyde in a 3.2-liter photoreactor under visible light radiation.
Results: The UV–Vis absorption spectrum of the Ag3PO4/TiO2 sample noticeably shifted to the visible light region compared to that of the TiO2. The bandgap energy of the nanocomposite was 2.3 eV. The SEM image demonstrated that the average particle size of the nanocomposite was about 102 nm. The result of the degradation efficiency tests revealed that 63% of the formaldehyde was removed under visible light irradiation after 90 minutes by the Ag3PO4/TiO2 photocatalyst.
Conclusion: The adopted synthesis method adopted was highly efficient and appropriate for the synthesis of Ag3PO4/TiO2 nanocomposite according to the analyses. The Ag3PO4/TiO2 photocatalyst performed well under visible light radiation and could be used in pollution control systems.
Siavash Azad, Yousef Rashidi, Farideh Golbabaei,
Volume 13, Issue 2 (6-2023)
Abstract
Introduction: The important parameters for evaluating the performance of particle filtering respirators in international standards are the filtration efficiency and respiratory resistance of the mask filter against airflow passage. To improve nanofiber filtration efficiency while creating the least breathing difficulty for the wearer, various research has been or is being conducted worldwide. This study investigated the effect of using polyacrylonitrile (PAN) nanofiber composite membrane and montmorillonite clay nanoparticles (MMT) in enhancing particle-filtering respirators’ filter performance, achieving higher filtration efficiency while maintaining optimal respiratory resistance conditions.
Material and Methods: First, PAN polymer solution containing zero, 1%, 2%, 3%, and 5% MMT nanoparticles was prepared, and then PAN/MMT nanofiber composite membrane was synthesized in an electrospinning machine. Filtration efficiency was measured in diameter range of 0.3, 0.5, 1, and 3 microns using sodium chloride aerosol. Additionally, filter breathing resistance was measured at flow rates of 30, 85, and 95 liters per minute.
Results: The efficiency of synthesized composite nanofilters for particle purification can be improved by adding MMT nanoparticles to PAN nanofibers. Optimal MMT concentration was found to be 2%. This addition resulted in an increase in filtration efficiency for particles with sizes of 0.3, 0.5, 1, and 3 microns by 4.2%, 4.88%, 3.77%, and 2.75% respectively without causing significant difference in respiratory resistance. Improved filtration efficiency can be attributed to enhanced morphology of composite nanofilters resulting from addition of MMT nanoparticles. Adding 2% MMT nanoparticles to PAN nanofibers resulted in uniform distribution and smaller fiber dimensions which did not significantly affect Packing density and porosity.
Conclusion: If 2% of MMT nanoparticles are added to PAN nanofibers and used to produce particle respirators, resulting respirator will exhibit a 4.2% increase in particle filtration efficiency without increasing breathing difficulty for user. This result can help protect users from particulate pollutants in air pollution conditions.
Saba Kalantary, Mohammad Reza Pourmand, Ensieh Masoorian, Mirghani Seyd Someah, Zahra Barkhordarian, Sara Hajinejad, Farideh Golbabaei,
Volume 14, Issue 2 (6-2024)
Abstract
Introduction: 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.
Material and Methods: 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
Results: 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.
Conclusion: 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.
