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Considering the hazardous effects of particulate matter (PM) exposure on students and teachers and the high PM concentration issue in South Korea, air purifiers have recently been installed in most classrooms to improve air quality. However, some on-site challenges, such as operational costs and noise, have been issues with the continuous operation of air purifiers. Therefore, a guideline is needed to dynamically predict the indoor PM concentration based on the changes in outdoor PM concentration and activate the air purifiers only when necessary. This study develops a grey-box model that uses measured data and physical differential equations to perform the given objective and verifies its accuracy using ASTM D5157. Modeling and analysis results have obtained information that can form the basis for developing guidelines to address PM issues in schools: The air purifier should be operated during periods where the predicted values exceed the limit in closed windows and the air purifier is not operating. It was also confirmed that the need for the operation of the air purifier varies between schools and classrooms under the same outdoor PM concentration. Indoor PM concentration increased significantly after students' simultaneous mass movement, necessitating air purifiers' operation before and after the events. The pre-filter of the heater also aided in the removal of coarse PM. Additionally, the limitations and future development directions of the model were discussed. Copyright © 2023 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

Highlights: [•] Both amination and calcination, independently enhanced CO2 capacity and selectivity. [•] Dry phase modification such as amination favours coconut shell-based activated carbon while wet phase pre-treatment favours coal based activated carbon. [•] Nitride-like/aromatic N-imines, pyridinic and pyrollic nitrogen complexes were found to have high selective affinity towards CO2. [•] Integrating the two methods with Ca(NO3)2 impregnation produced the best treatment for both 0.3% and 10% CO2 selectivities. [Copyright &y& Elsevier]

Abstract: This paper reviews the concept of filter quality (q F) for dust filtration media composed of different structures: metal fiber beds (MFB), fabric filters (BF), and fly ash filters (FAF). Filter quality is a useful index of the filtration performance, which incorporates both pressure drop and filtration efficiency. Major parameters affecting the filter quality are filtration velocity in the range of 0.06–0.19 m/s, dust loading, porosity of the medium in the range of 75–93%, and internal structure of the medium. The experimental observation showed that filter quality decreased with increasing filtration velocity or dust concentration. A unique increase in filter quality during the initial stage of filtration appeared with the FAF as a result of the predominately surface filtration with less pore clogging. Nevertheless, the filter quality cannot be taken as an absolute indicator of filter performance, but rather it should be used just as a reference parameter depending on operating conditions. The results of this work show that fly ash filters are capable of providing more stable performance, particularly during the initial stage of filtration, and thereafter of a certain time filter quality initiates to decline as other filters. [Copyright &y& Elsevier]

The present work investigated various binders to assist the fly ash particles'' coagulation within the intermediate sintering temperature zone. In order to find the appropriate binding agents for fly ash pelletization, some common materials were examined with focus on the compressive strength. The main experimental variables were heat treatment temperature and the binder/fly ash proportions. As a result of the close investigation, alkali and acidic materials such as sodium hydroxide, potassium hydroxide and phosphoric acid were found quite acceptable based on the strength and cost effectiveness. A few organic materials also acted as desirable binders, but they revealed a few critical limitations when used in aqueous solution and at hot fluid environment. Inorganic binders, such as cement and lime, showed excellent cost effectiveness, but seemed to be disadvantageous for the high temperature process. [Copyright &y& Elsevier]

Volatile organic compounds (VOCs) generated in urban workplaces have been considered as significant air pollutants both indoors and outdoors. In order to reduce those harmful VOCs from urban emission sources, a non-thermal plasma reactor equipped with dielectric barrier discharge (DBD) using alternating current (AC) was investigated with a focus on process design including recirculation. Decomposition efficiency of low concentration VOCs was evaluated in terms of energy yield and conversion selectivity. At 20 ppm, the highest decomposition efficiency (97.3 %) was achieved in the treatment of n-hexane, followed by toluene at 96.6 %, MEK at 91.5 % and acetaldehyde at 90.4 %. A recirculation rate (Q R) of 50 % improved the system efficiency, particularly for acetaldehyde (49.47 %–63.86 %) and toluene (79.05 %–95.89 %). It also increased the complete energy yield and the selectivity for carbon monoxide (CO) and carbon dioxide (CO 2). By-product ozone concentration decreased significantly with increasing recirculation rate at the same input energy level. [ABSTRACT FROM AUTHOR]

Potassium sulfamate (PS) is an efficient starting material for the nitration reaction used in the synthesis of ammonium dinitramide (ADN), which is an environmentally friendly high-energy oxidizer for propellants that does not release chlorine-based compounds. PS is a core structure to form dinitramide, -N(NO2)2, by taking NO2−from nitric acid. In this work, five test batches of PS were prepared using a few solvents including ethanol, methanol, acetone, isopropanol, and their mixtures. The lab-made PSs matched well with the commercial PS in terms of the chemical structure. The use of acetone led to a high recovery of PS up to 97 w/w% and ultimately contributed to the formation of high-purity and (99.2%) and a high yield (57.3%) that are greater than those for commercial PS (87.3% purity and 31.3% yield). Therefore, we proved that the crystallinity and homogeneity of PS influenced the properties of ADN and the synthesis efficiency. [ABSTRACT FROM PUBLISHER]

Highlights: [•] K-based sites were stabilized on activated carbon by a novel post-amination method. [•] Achieved high CO2 adsorption amount for 10% and 0.3% levels compares with 100% feed. [•] Regeneration at 600°C achieved about 92% stable plateau from 2nd to 4th cycle. [•] Selectivity was respectively enhanced from 0.190 and 0.167 to 0.580 and 22.974 for 10 and 0.3% levels. [ABSTRACT FROM AUTHOR]

Highlights: [ • ] O3 oxidation enhanced both the textural and chemical properties of AC and the amination efficiency compared to H2O2. [ • ] UV-C reduced the amount of refractory SOFs, thereby increasing the proportion of those available for amination. [ • ] Carbonyl, carboxyl and hydroxyl aid the formation of pyridine and pyrrole groups, which showed high affinity toward CO2. [•] Narrower micropores achieved by O3 treatment enhanced the CO2 physisorption. [ABSTRACT FROM AUTHOR]

A pleated filter bag is often used to treat exhaust gas in many industrial applications, due to its fairly high dust collection efficiency and relatively low pressure drop. This work deals with the optimum pleating geometries of a pleated filter made with a newly developed PTFE/glass composite filter. It was found that pleating geometries, including pleat height and pleat pitch, directly affect the cleaning efficiency. The design index, α, which stands for the ratio of pleat height to pleat pitch, is 1.48 for optimum operation. When the α value was higher than 1.48, the pressure drop across the pleated filter medium increased, resulting in a decreased cleaning interval due to the difficulty of filter cleaning. Therefore, it is necessary that the optimum pleating geometry should be determined by employing the dimensionless parameter, α, in the design of cartridge filters. [ABSTRACT FROM AUTHOR]

Abstract The effectiveness of a surface dielectric barrier discharge (DBD) reactor was evaluated over a range of relative humidiy (RH), discharge areas and applied powers. Primary goals included maximizing toluene decomposition efficiency and CO 2 selectivity while maintaining a high specific energy density and energy yield. Humidity was a limiting factor, although it did not significantly increase the energy efficiency of the system. A RH of 20% was found to be optimal for toluene abatement, and large discharge areas decreased the energy yield by increasing the rate of power consumption. At a frequency of 60 Hz and an applied voltage of 4.3 kV, 8.4, 6.4 and 4.3 g/kWh of toluene was removed at discharge areas of 215, 430 and 645 cm2, respectively. Energy efficiency was also reduced at high applied power by ozone formation in the reactor. Graphical abstract Image [ABSTRACT FROM AUTHOR]

With its increasing value as a means of public transportation, the health effects of the air in subway stations have attracted public concern. In the current study, we investigated the pulmonary toxicity of dust collected from an air purifier installed on the platform of the busiest subway station in Seoul. We found that the dust contained various elements which are attributable to the facilities and equipment used to operate the subway system. Particularly, iron (Fe), chromium (Cr), zirconium (Zr), barium (Ba), and molybdenum (Mo) levels were more notable in comparison with those in dust collected from the ventilation chamber of a subway station. To explore the health effects of inhaled dust, we first instilled via the trachea in ICR mice for 13 weeks. The total number of pulmonary macrophages increased significantly with the dose, accompanying hematological changes. Dust-laden alveolar macrophages and inflammatory cells accumulated in the perivascular regions in the lungs of the treated mice, and pulmonary levels of CXCL-1, TNF-α, and TGF-β increased clearly compared with the control. The CCR5 and CD54 level expressed on BAL cell membranes was also enhanced following exposure to dust, whereas the CXCR2 level tended to decrease in the same samples. In addition, we treated the dust to alveolar macrophages (known as dust cells), lysosomal and mitochondrial function decreased, accompanied by cell death, and NO production was rapidly elevated with concentration. Moreover, the expression of autophagy- (p62) and anti-oxidant (SOD-2)-related proteins increased, and the expression of inflammation-related genes was dramatically up-regulated in the dust-treated cells. Therefore, we suggest that dysfunction of alveolar macrophages may importantly contribute to dust-induced inflammatory responses and that the exposure concentrations of Cr, Fe, Mo, Zr, and Ba should be considered carefully when assessing the health risks associated with subway dust. We also hypothesize that the bound elements may contribute to dust-induced macrophage dysfunction by inhibiting viability. • Dust was collected from the platform of the busiest subway station in Seoul. • Subchronic pulmonary exposure increased the total number of pulmonary macrophages. • Dust-laden alveolar macrophages accumulated in the perivascular regions in the lungs. • The dust up-regulated expression of inflammation-related genes in alveolar macrophages. • The bound elements may be responsible for dust-induced macrophage dysfunction. [ABSTRACT FROM AUTHOR]

The particle velocity model developed in this study described the dynamic motion of fine dust particles along the magnetized mesh wires in a low Stokes regime. The numerically evaluated velocity contour of the particles modeled the critical path lines indicating the threshold positions for magnetic collection. The velocity contour was determined using the parameters such as particle size, magnetic intensity, flow velocity, and mesh configuration including wire thickness and packing density. Particle size was one of the most significant parameters to determine the magnetic collection. The theoretical estimation matched well with the lab experiments, but the discrepancy increased for large particles with a fine filter. In consequence, application of magnetized mesh filters could contribute to the collection of the ferromagnetic dust or aerosols to a certain extent without any additional power or pressure resistance. Copyright 2015 American Association for Aerosol Research [ABSTRACT FROM PUBLISHER]

A catalyst of Ag with alumina has been widely used for the decomposition of odorous ammonia. In order to meet cost effectiveness, copper was added with five different doping ratios of Ag/Cu in this work, and NH3 decomposition was examined at 150-400 °C. Experimental results show that the catalyst doped with only Cu shows very weak potential to oxidize NH3 despite its excellent selectivity for nitrogen molecules than NO or N2O at temperatures over 300 °C. Analysis by X-ray photoelectron spectroscopy indicates that Ag0 is the major chemical functionality that determines the decomposition rate of NH3 at low temperature, e.g., 200 °C, while Ag+ and Ag2+ are efficient at higher temperatures. Among the five segregated copper functionalities, only Cu 2pa/2 appeared to be favorable for the activity of Ag particles. It was found from the experimental results that Ag/Cu = 1:9 could provide a cost-effective combination for the low temperature regime. [ABSTRACT FROM AUTHOR]

Capturing of odorous compounds such as toluene vapor by a particulate-activated carbon adsorbent was investigated in a gas-solid cyclone, which is one type of mobile beds. The test cyclone was early modified with the post cyclone (PoC) and a spiral flow guide to the vortex finder. The proposed process may contribute to the reduction of gases and dust from industrial exhausts, especially when dealing with a low concentration of odorous elements and a large volume of dust flow. In this device, the toluene capturing efficiency at a 400 ppm concentration rose up to 77.4% when using activated carbon (AC) particles with a median size of 27.03 μm. A maximum 96% of AC particles could be collected for reuse depending on the size and flow rate. The AC regenerated via thermal treatment showed an adsorption potential up to 66.7% throughout repeated tests. [ABSTRACT FROM PUBLISHER]

To control the levels of indoor CO2in public spaces, we investigated adsorption at room temperature onto zeolites and activated carbon (AC) modified by alkali and alkaline earth metals. A fixed-bed adsorption apparatus was used to obtain more information about the effects of impregnated cations. Cations impregnated into the supports had a significant influence on the adsorption of CO2. In particular, sorbents impregnated with Ca had the highest adsorption capacity. Moreover, modified zeolites (for all cations) had greater adsorption capacities than ACs, despite their smaller surface areas, because of the electrostatic interforces between zeolites. The presence of moisture in the mixed gas flow caused decreases in adsorption capacity. The results of the equations of Sips and Toth matched well with the CO2adsorptions of the present test sorbents. The presence of cations induced heterogeneous interactions between CO2and the sorbents. [ABSTRACT FROM AUTHOR]

Abstract: A newly developed PTFE foam coating filter was developed which can be used for hot gas cleaning at temperatures up to 250°C. The emulsion-type PTFE was coated onto a woven glass fiber using a foam coating method. The filter surface was closely examined using X-ray photoelectron spectroscopy (XPS) and contact angle measurements. The XPS results were used to determine the binding force between the carbon and fluorine of PTFE, which imparts coating stability to the filter medium. More than 95% of the bonds of the PTFE foam coating filter were between carbon and fluorine, and this filter demonstrated excellent hydrophobic and good oleophobic properties at the same time. The contact angles of liquid droplets on the filter surface were used to predict the potential wetability of the filter against water or oil. In addition, the very low surface free energy of the filter medium, which was evaluated using the Owens–Wendt method, demonstrates a very stable surface and a high de-dusting quality. [ABSTRACT FROM AUTHOR]

The incorporation of metal oxide nanoparticles (NPs) in fiber filters is an effective approach to enhance the specific surface area and surface roughness of the fiber, hence improving their efficiency for fine dust capture and other gas treatment or biological applications. Nevertheless, uneven distribution of NPs limits their practical applications. In this study, a commercial silane coupling agent (3-methacryloxypropyltrimethoxysilane) was used to improve the dispersion of zinc oxide (ZnO) NPs in thin polyacrylonitrile fibers. Scanning electron microscopy (SEM) revealed that the fibers incorporating the silane-modified NPs exhibited better distribution of NPs than those prepared with pristine ZnO NPs. The silane modification enhanced the specific surface area, surface roughness, and fiber porosity. In particular, the nanofiber filter incorporating 12 wt% ZnO NPs modified with 0.5 g silane per g of ZnO NPs maintained a filtration efficiency of 99.76% with a low pressure drop of 44 Pa, excellent antibacterial activity, and could decompose organic methylene blue dye with an efficiency of 85.11% under visible light. [ABSTRACT FROM AUTHOR]

To evaluate the level of fine particulate matters in elementary schools located in a high traffic area of Seoul and verify the emission source, a field study on the classrooms was conducted under the uncontrolled condition. The indoor PM 2.5 was lower than that of the outdoors as indicated by an I/O ratio of 0.52–0.92 based on mass concentration, and it was maintained below the National Guideline. Heavy metals such as Cr, Mn, Ni, Cu, Zn, As, Sn and Pb were lower in indoor PM 2.5 than outdoors. On the contrary, carbons including OC and EC were higher in indoor PM 2.5. As a result of source apportionment analysis, an outdoor emission source was responsible for 58.5% of the classroom PM 2.5. This study can contribute to urban planning and school design to keep children safe from harmful environments. [Display omitted] • Chemical composition was used to evaluate the emission source of urban school PM 2.5. • PM 2.5 levels in test classrooms were below the National Guideline (35 μg/m3). • Student activity and air purifier operation were significant factors to determine indoor PM 2.5. • Outdoor fine dust including traffic emissions contributed 58.5% to indoor PM 2.5. [ABSTRACT FROM AUTHOR]

In this study, we aimed to identify a toxic mechanism and the potential health effects of ambient dusts in an underground subway station. At 24 h exposure to human bronchial epithelial (BEAS-2B) cells (0, 2.5, 10, and 40 μg/mL), dusts located within autophagosome-like vacuoles, whereas a series of autophagic processes appeared to be blocked. The volume, potential and activity of mitochondria decreased in consistent with a condensed configuration, and the percentage of late apoptotic cells increased accompanying S phase arrest. While production of reactive oxygen species, expression of ferritin (heavy chain) protein, secretion of IL-6, IL-8 and matrix metalloproteinases, and the released LDH level notably increased in dust-treated cells (40 μg/mL), intracellular calcium level decreased. At day 14 after a single instillation to mice (0, 12.5, 50, and 200 μg/head), the total number of cells increased in the lungs of dust-treated mice with no significant change in cell composition. The pulmonary levels of TGF-β, GM-CSF, IL-12 and IL-13 clearly increased following exposure to dusts, whereas that of CXCL-1 was dose-dependently inhibited. Additionally, the population of cytotoxic T cells in T lymphocytes in the spleen increased relative to that of helper T cells, and the levels of IgA and IgM in the bloodstream were significantly reduced in the dust-treated mice. Subsequently, to improve the possibility of extrapolating our findings to humans, we repeatedly instilled dusts (1 time/week, 4 weeks, 0.25 and 1.0 mg/head) to monkeys. The total number of cells, the relative portion of neutrophils, the level of TNF-α significantly increased in the lungs of dust-treated monkeys, and the expression of cytochrome C was enhanced in the lung tissues. Meanwhile, the pulmonary level of MIP-α was clearly reduced, and the expression of caveolin-1 was inhibited in the lung tissues. More importantly, inflammatory lesions, such as granuloma, were seen in both mice and monkeys instilled with dusts. Taken together, we conclude that dusts may impair the host's immune function against foreign bodies by inhibiting the capacity for production of antibodies. In addition, iron metabolism may be closely associated with dust-induced cell death and inflammatory response. • Pulmonary toxicity of ambient dust in an underground subway station was tested. • The dust stimulated multiple cell death signals and disturbed immune balance. • Expression of ferritin (heavy chain) protein was notably enhanced. • The levels of IgA and IgM in the bloodstream was significantly reduced. • Inflammatory lesions, such as granuloma, were seen in both mice and monkeys. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the effect of a synthesis procedure of Sr hexaaluminate on catalytic performance during the decomposition of ionic liquid monopropellants based on ammonium dinitramide (ADN) and hydroxyl ammonium nitrate (HAN). Sr hexaaluminates were prepared via both coprecipitation and a sol–gel process. The surface area of hexaaluminate synthesized via the coprecipitation method was higher than that of hexaaluminate synthesized by the sol–gel process, and calcined at the same temperature of 1200 °C or more. This is because of the sintering of α-Al2O3 on the hexaaluminate synthesized via the sol–gel process, which could not be observed on the catalysts synthesized via the coprecipitation method. The hexaaluminate synthesized via coprecipitation showed a lower decomposition onset temperature during the decomposition of ADN- and HAN-based liquid monopropellants in comparison with the catalysts synthesized via the sol–gel process, and calcined at the same temperature of 1200 °C or more. This is attributed to the differences in the Mn3+ concentration and the surface area between the two hexaaluminates. Consequently, the hexaaluminate synthesized via coprecipitation which calcined above 1200 °C showed high activity during the decomposition of energetic ionic liquid monopropellants compared with the hexaaluminate synthesized via the sol–gel process. [ABSTRACT FROM AUTHOR]