Development of PM10 and PM2.5 cyclones for small sampling ports at stationary sources: Numerical and experimental study.

Air pollution caused by particulate matter (PM) has become a serious issue, and significant research has focused on managing large stationary emission sources, i.e., the primary sources of PM. Currently, the U.S. Environmental Protection Agency (EPA) Method 201A and ISO 23210 are predominantly employed to measure the PM emissions at large stationary sources. Method 201A is designated as a standard test method in Korea, but it is difficult to measure PM10 and PM2.5 simultaneously owing to the size of the full-set cyclone. In large stationary emission sources, the use of a serial connection of PM10 and PM2.5 cyclones is unsuitable for measurements at conventional sampling ports featuring diameters of approximately 100 mm. Therefore, in this study, PM10 and PM2.5 cyclones were developed to replace the cyclones currently used in Method 201A. The developed cyclones featured a cutoff diameter, which was confirmed by numerical and experimental analyses that were close to Method 201A. Moreover, there was an increase in the stiffness of collection efficiency. The hook adaptor, which is a key accessory used in Method 201A, was found to be applicable to the newly developed cyclones. This alternative method will help reduce the measurement time by simultaneously measuring TSP, PM10, and PM2.5 and eliminates the costs of installing or refurbishing additional sampling ports at existing large stationary sources.

Traffic-related particulate matter aggravates ocular allergic inflammation by mediating dendritic cell maturation.

The aim of this study was to determine the effects of traffic-related particulate matter (PM) on allergic inflammation of ocular surfaces. BALB/c mice were sensitized with ovalbumin (OVA) and aluminum hydroxide via intraperitoneal injection. Two weeks later, mice were challenged with eye drops containing OVA concomitant with either traffic-related PM2.5 or vehicle eye drops. Topical OVA challenges were administered following unilateral subconjunctival injection of magnetic-bead-sorted CD11c+ dendritic cells (DC). The following were assessed: (1) clinical signs, (2) infiltration of inflammatory cells into conjunctiva, (3) serum levels of OVA-specific IgE production, and (4) T-cell cytokine secretion with topical application of PM2.5, compared to saline vehicle. PM2.5 was found to increase production of OVA-specific IgE in serum and Th2 immune response-related cytokines including interleukin (IL)-4, IL-17A, and IL-13 compared to vehicle control. It is of interest that PM2.5 treatment also elevated the population of mature DCs in draining lymph nodes (LNs). Exposure with PM2.5 was associated with a significant rise in conjunctival expression of IL-1ß, IL-6, IL-17, and TNF. After subconjunctival injection of CD11c+DCs from PM2.5-treated allergic conjunctivitis (AC) mice into naïve mice, T cell responses and OVA-specific IgE were also enhanced. Data suggest that traffic-related PM2.5 exacerbated allergic conjunctivitis as evidenced by increased infiltration of inflammatory cells into the conjunctiva and Th2 responses in the draining LNs associated with enhanced maturation of DCs. Our findings provide new insight into the hazardous potential of traffic-related PM2.5 on allergic diseases, such as asthma or atopic dermatitis.

Characteristics of hydrogen production by photocatalytic water splitting using liquid phase plasma over Ag-doped TiO2 photocatalysts.

Hydrogen production from water was investigated by applying liquid plasma (LPP) to photocatalytic splitting of water. The optical properties of LPP due to water emission were also evaluated. The correlation between the optical properties of plasma and the formation of active species in water was investigated with the photocatalytic activity of hydrogen production. TiO2 was also doped with Ag to evaluate the effect of enhancing photocatalytic activity. The photocatalytic activity was evaluated by the rate of hydrogen production, and the effect of hydrogen formation was also investigated by injecting methanol as an additive. As a result of examining the luminescence properties of LPP, it showed high luminescence in the 309 nm UV region and the 656 nm visible region. The hydrogen doping rate was increased in the Ag-doped TiO2 photocatalyst. Ag-doped TiO2 has wider light absorption into the visible region and narrower band gap. Due to these properties, the rate of hydrogen generation is superior to TiO2 photocatalysts. The photochemical reaction with LPP and photocatalyst in aqueous solution with CH3OH showed a significant increase in hydrogen production rate. The increase in hydrogen production by injection of additives is because the optical properties of generating OH radicals are improved and CH3OH is decomposed to act as an electron donor to improve hydrogen production.

Study of stainless steel electrodes after electrochemical analysis in sea water condition.

For water electrolysis, a rare earth material (eg., platinum) is often used as an electrode, but because of the high cost and toxicity of chemicals, researchers are searching for cost effective and eco-friendly alternative materials. Various alloys and metals have been long explored for use as electrode materials in different media. Stainless steel (SS 304) electrodes are cost effective and have a large surface area; further their catalytic performance is comparable to that of carbon coated noble metals cathodes. Stainless steel has good mechanical properties and durability so it is widely used in desalination plants, oil and gas industries, ship building, etc. However, over a period of time it corrodes very quickly in saline water. To improve the stability and durability of the electrodes (i.e., to minimize corrosion), we anneal the samples under two different sets of conditions and test the electrodes in 3.5% NaCl solution. The anodic peak (-0.25 V) observed for bare stainless steel result from the formation of iron (II) hydroxide [Fe(OH)2]. The Raman bands observed at 210 and 274 cm-1 for bare stainless steel result from the formation of α-Fe2O3 owing to partial, anodic, and cathodic reactions occurring on the electrode which disrupts the surface layers. High intensity X-ray diffraction (XRD) and Raman peaks of Cr2O3 and MnCr2O4 observed in argon and hydrogen annealed sample after cyclic voltammetry reveal that this sample is more stable than bare and air annealed samples. XRD reveals mixed oxide phases in addition to eskolaite and magnetite phases. Scanning electron microscope (SEM) images show that although the air-annealed sample has a soft, spongy structure, Na and Cl ions are adsorbed in the voids on the outer surface of the electrode leading to quick degradation. For the air-annealed sample the oxide appears to adhere poorly to the stainless steel. Oxygen (ie., oxide composition) may play a key role in adherence and growth of Cr2O3 formed at high temperature. X-ray photoelectron spectroscopy (XPS) reveals that large amounts of Cr and Mn are dissolved/corroded into the electrolyte for air annealed sample which is in good agreement with the Raman and SEM results.

H2 Production from Yellow Poplar Gasification Over Ni/Spent FCC.

Ni/spent FCC catalyst was applied as the catalyst on the catalytic pyrolysis and gasification of yellow poplar (YP). Larger amount of gas (CO, CO2, H2, C1~C4) was produced by applying Ni/spent FCC catalyst to the catalytic pyrolysis and gasification of YP. Ni/spent FCC catalyst also increased the selectivity of phenols and aromatic hydrocarbons in oil product during the pyrolysis and gasification of YP. Overall catalytic performance of Ni/spent FCC catalyst was similar level with that of Ni/γ-Al2O3, suggesting its potential use.

Determination of the emission rate for ultrafine and accumulation mode particles as a function of time during the pan-frying of fish.

Particulate matter (PM) from cooking is considered one of the most harmful indoor air pollutants causing numerous adverse health effects, and it is essential to comprehend the characteristics of the particles generated from cooking to prevent these problems. In this study, we investigated PM from the pan-frying of salmon using number concentration and developed emission rates as a function of time for ultrafine particles (UFPs < 100 nm) and accumulation mode particles (AMPs 0.1-1 µm). The newly defined emission rates vary significantly with time and are very different from the conventionally determined rates that do not consider the variation of particle concentration with time. The emission rate of UFPs decreased over time after a sharp rise, whereas that of AMPs continued to increase, resulting in a change in the proportions of UFPs and AMPs in the total PM from 93 to 7% to 72 and 28%, respectively. Particle-particle interactions such as coagulation and coalescence were observed between primary particles via high resolution transmission electron microscopy (HR-TEM), which is a plausible reason for the decreasing emission rate of UFPs with time. The emission rate as a function of time can serve as a tool to estimate PM from cooking, as well as to monitor the change trends through phenomena such as agglomeration.

Acetaldehyde removal and increased H2/CO gas yield from biomass gasification over metal-loaded Kraft lignin char catalyst.

Acetaldehyde removal tests were performed to compare the catalytic activity of the Kraft lignin char (KC), KOH-treated Kraft lignin char (KKC), and activated carbon (AC) along with their impregnation with Mn in a plasma reactor. The gasification characteristics (syngas content, and H2/CO ratio) of yellow poplar were investigated using nickel catalysts supported on KC, KKC, AC, and γ-Al2O3 in a U-type quartz reactor. KKC and Mn/KKC improved significantly the surface area and contents of O and N functional groups over the raw char. In particular, Mn/KKC showed the highest acetaldehyde-removal efficiency. The catalytic activity of Ni-impregnated KC, KKC, AC, and γ-Al2O3 decreased in the order of Ni/KKC > Ni/AC > Ni/KC > Ni/γ-Al2O3 for the gas yield and Ni/γ-Al2O3 >Ni/KC > Ni/AC >Ni/KKC for the oil yield, respectively. The Ni/KKC provides a more conducive environment for gasification, resulting in larger amounts of syngas (H2 and CO) in the product gases. Moreover, Ni impregnated with char may be the most inexpensive and effective solution for achieving maximum tar reduction and syngas generation.

Assembling a supercapacitor electrode with dual metal oxides and activated carbon using a liquid phase plasma.

Developing supercapacitor electrodes at an affordable cost while improving their energy and/or power density values is still a challenging task. This study introduced a recipe which assembled a novel electrode composite using a liquid phase plasma that was applied to a reactant solution containing an activated carbon (AC) powder with dual metal precursors of iron and manganese. A comparison was made between the composites doped with single and dual metal components as well as among those synthesized under different precursor concentrations and plasma durations. The results showed that increasing the precursor concentration and plasma duration raised the content of both metal oxides in the composites, whereas the deposition conditions were more favorable to iron oxide than manganese oxide, due to its higher standard potential. The composite treated with the longest plasma duration and highest manganese concentration was superior to the others in terms of cyclic stability and equivalent series resistance. In addition, the new composite selected out of them showed better electrochemical performance than the raw AC material only and even two types of single metal-based composites, owing largely to the synergistic effect of the two metal oxides. Therefore, the proposed methodology can be used to modify existing and future composite electrodes to improve their performance with relatively cheap host and guest materials.

Low Frequency Ultrasonication of Degussa P25 TiO2 and Its Superior Photocatalytic Properties.

We report the simple and effective method for enhancing the photocatalytic properties of Degussa P25 TiO2 by low frequency ultrasonication. The improvement in the crystallinity of ultrasonicated TiO2 was confirmed by the X-ray diffraction and Raman spectroscopy studies. Further, the X-ray photoelectron spectroscopy was utilized to study the changes in chemical nature and band edge due to the effect of ultrasonication and H2O2 solvent. The transmission electron microscope (TEM) was used to analysis the surface distortion. The Moire fringes in TEM were examined to understand the partial transformation of amorphous to crystalline anatase structure and overlapping of rutile over anatase crystal. The photocatalytic results indicated improvement in the degradation of methylene blue dye. The degradation efficiency was estimated to be 86% for ultrasonicated TiO2, which is higher as compared to 40% of P25. The rate constant values revealed four times superior degradation property of ultrasonicated TiO2. The improvement in the photocatalytic efficiency was correlated to the formation of rutile/anatase TiO2 aggregation and its consequences on electron-hole recombination.

SiSe2 for Superior Sulfide Solid Electrolytes and Li-Ion Batteries.

Among the various existing layered compounds, silicon diselenide (SiSe2) possesses diverse chemical and physical properties, owing to its large interlayer spacing and interesting atomic arrangements. Despite the unique properties of layered SiSe2, it has not yet been used in energy applications. Herein, we introduce the synthesis of layered SiSe2 through a facile solid-state synthetic route and demonstrate its versatility as a sulfide solid electrolyte (SE) additive for all-solid-state batteries (ASSBs) and as an anode material for Li-ion batteries (LIBs). Li-argyrodites with various compositions substituted with SiSe2 are synthesized and evaluated as sulfide SEs for ASSBs. SiSe2-substituted Li-argyrodites exhibit high ionic conductivities, low activation energies, and high air stabilities. In addition, when using a sulfide SE, the ASSB full cell exhibits a high discharge/charge capacity of 202/169 mAh g-1 with a high initial Coulombic efficiency (ICE) of 83.7% and stable capacity retention at 1C after 100 cycles. Furthermore, the Li-storage properties of SiSe2 as an anode material for LIBs are evaluated, and its Li-pathway mechanism is explored by using various cutting-edge ex situ analytical tools. Moreover, the SiSe2 nanocomposite anode exhibits a high Li- insertion/extraction capacity of 950/775 mAh g-1, a high ICE of 81.6%, a fast rate capability, and stable capacity retention after 300 cycles. Accordingly, layered SiSe2 and its versatile applications as a sulfide SE additive for ASSBs and an anode material for LIBs are promising candidates in energy storage applications as well as myriad other applications.

Enhanced nanoscale friction on fluorinated graphene.

Atomically thin graphene is an ideal model system for studying nanoscale friction due to its intrinsic two-dimensional (2D) anisotropy. Furthermore, modulating its tribological properties could be an important milestone for graphene-based micro- and nanomechanical devices. Here, we report unexpectedly enhanced nanoscale friction on chemically modified graphene and a relevant theoretical analysis associated with flexural phonons. Ultrahigh vacuum friction force microscopy measurements show that nanoscale friction on the graphene surface increases by a factor of 6 after fluorination of the surface, while the adhesion force is slightly reduced. Density functional theory calculations show that the out-of-plane bending stiffness of graphene increases up to 4-fold after fluorination. Thus, the less compliant F-graphene exhibits more friction. This indicates that the mechanics of tip-to-graphene nanoscale friction would be characteristically different from that of conventional solid-on-solid contact and would be dominated by the out-of-plane bending stiffness of the chemically modified graphene. We propose that damping via flexural phonons could be a main source for frictional energy dissipation in 2D systems such as graphene.

Air-stable magnesium nanocomposites provide rapid and high-capacity hydrogen storage without using heavy-metal catalysts.

Hydrogen is a promising alternative energy carrier that can potentially facilitate the transition from fossil fuels to sources of clean energy because of its prominent advantages such as high energy density (142 MJ kg(-1); ref. 1), great variety of potential sources (for example water, biomass, organic matter), light weight, and low environmental impact (water is the sole combustion product). However, there remains a challenge to produce a material capable of simultaneously optimizing two conflicting criteria--absorbing hydrogen strongly enough to form a stable thermodynamic state, but weakly enough to release it on-demand with a small temperature rise. Many materials under development, including metal-organic frameworks, nanoporous polymers, and other carbon-based materials, physisorb only a small amount of hydrogen (typically 1-2 wt%) at room temperature. Metal hydrides were traditionally thought to be unsuitable materials because of their high bond formation enthalpies (for example MgH(2) has a ΔHf~75 kJ mol(-1)), thus requiring unacceptably high release temperatures resulting in low energy efficiency. However, recent theoretical calculations and metal-catalysed thin-film studies have shown that microstructuring of these materials can enhance the kinetics by decreasing diffusion path lengths for hydrogen and decreasing the required thickness of the poorly permeable hydride layer that forms during absorption. Here, we report the synthesis of an air-stable composite material that consists of metallic Mg nanocrystals (NCs) in a gas-barrier polymer matrix that enables both the storage of a high density of hydrogen (up to 6 wt% of Mg, 4 wt% for the composite) and rapid kinetics (loading in <30 min at 200 °C). Moreover, nanostructuring of the Mg provides rapid storage kinetics without using expensive heavy-metal catalysts.

α-Fe2O3 nanoparticles and hazardous air pollutants release during cooking using cast iron wok in a commercial Chinese restaurant.

Long-term exposure to fine particles (PM2.5), ultrafine particles (UFPs), and volatile organic compounds (VOCs) emissions from cooking has been linked to adverse human health effects. Here, we measured the real-time number size distribution of particles emitted when cooking two served food in Chinese restaurants and estimated the emission rate of UFPs and PM2.5. Experiments were conducted under a control hood, and both online measurement and offline analysis of PM2.5 were carried out. The measured emission rates of PM2.5 generated from deep-frying and grilling were 0.68 ± 0.11 mg/min and 1.58 ± 0.25 mg/min, respectively. Moreover, the UFPs emission rate of deep-frying (4.3 × 109 #/min) is three times higher than that of grilling (1.4 × 109 #/min). Additionally, the PM2.5 emission of deep-frying was comprised of a considerable amount of α-Fe2O3 (5.7% of PM2.5 total mass), which is more toxic than other iron oxide species. A total of six carcinogenic HAPs were detected, among which formaldehyde, acrolein, and acetaldehyde were found to exceed the inhalation reference concentration (RfC) for both cooking methods. These findings can contribute to future evaluation of single particle and HAPs emission from cooking to better support toxicity assessment.

Self-Healing Graphene-Templated Platinum-Nickel Oxide Heterostructures for Overall Water Splitting.

Electrocatalysts with dramatically enhanced water splitting efficiency, derived from controlled structures, phase transitions, functional activation, etc., have been developed recently. Herein, we report an in situ observation of graphene-based self-healing, in which this functional activation is induced by a redox reaction. Specifically, graphene on stainless steel (SUS) switches between graphene (C-C) and graphene oxide (C-O) coordination via an electrical redox reaction to activate water splitting. A heterostructure comprising Pt-NiO thin films on single-layer graphene directly grown on a SUS substrate (Pt-NiO/Gr-SUS) was also synthesized by electrodeposition. Pt-NiO/Gr-SUS exhibited water splitting activity with low Pt loading (<1 wt %). The findings provide valuable insight for designing robust electrodes based on reversible redox-induced self-healable graphene to develop more efficient catalysts.

Li-Compound Anodes: A Classification for High-Performance Li-Ion Battery Anodes.

Four main anode types are generally considered as typical anodes for Li-ion batteries (LIBs): Li-metal, carbon-based, alloy-based, and oxide-based anodes. Although they exhibit satisfactory electrochemical performance as LIB anodes, they cannot simultaneously satisfy all key requirements for LIB anodes: high reversible capacity, high initial Coulombic efficiency (ICE), long cycle life, fast rate capability, structural stability, and no safety concerns. Here, we suggest Li-compound anodes as a promising class of high-performance LIB anodes. Three binary (LiSn, Li2Sb, and LiBi) and three ternary (Li2ZnSb, Li5GeP3, and Li5SnP3) Li compounds were introduced as Li-compound anodes. LiSn and Li5SnP3 were selected and further modified into their nanocomposites by solid-state synthetic routes using carbon sources for high-performance LIB anodes. The Li-compound nanocomposite anodes exhibited excellent performance and simultaneously fulfilled all the key requirements for high-performance LIB anodes. Therefore, Li-compound anodes are expected to be a promising and innovative category of high-performance LIB anodes.

Analysis of VOCs Emitted from Small Laundry Facilities: Contributions to Ozone and Secondary Aerosol Formation and Human Risk Assessment.

Volatile organic compounds (VOCs) emitted to the atmosphere form ozone and secondary organic aerosols (SOA) by photochemical reactions. As they contain numerous harmful compounds such as carcinogens, it is necessary to analyze them from a health perspective. Given the petroleum-based organic solvents used during the drying process, large amounts of VOCs are emitted from small laundry facilities. In this study, a laundry facility located in a residential area was selected, while VOCs data emitted during the drying process were collected and analyzed using a thermal desorption-gas chromatography/mass spectrometer (TD-GC/MS). We compared the results of the solvent composition, human risk assessment, contribution of photochemical ozone creation potential (POCP), and secondary organic aerosol formation potential (SOAP) to evaluate the chemical species. Alkane-based compounds; the main components of petroleum organic solvents, were dominant. The differences in evaporation with respect to the boiling point were also discerned. The POCP contribution exhibited the same trend as the emission concentration ratios for nonane (41%), decane (34%), and undecane (14%). However, the SOAP contribution accounted for o-xylene (28%), decane (27%), undecane (25%), and nonane (9%), thus confirming the high contribution of o-xylene to SOA formation. The risk assessment showed that acrylonitrile, carbon tetrachloride, nitrobenzene, bromodichloromethane, and chloromethane among carcinogenic compounds, and bromomethane, chlorobenzene, o-xylene, and hexachloro-1, 3-butadiene were found to be hazardous, thereby excessing the standard value. Overall these results facilitate the selection and control of highly reactive and harmful VOCs emitted from the dry-cleaning process.

The interaction of Li+ with single-layer and few-layer graphene.

The interaction of Li(+) with single and few layer graphene is reported. In situ Raman spectra were collected during the electrochemical lithiation of the single- and few-layer graphene. While the interaction of lithium with few layer graphene seems to resemble that of graphite, single layer graphene behaves very differently. The amount of lithium absorbed on single layer graphene seems to be greatly reduced due to repulsion forces between Li(+) at both sides of the graphene layer.

Pd Nanocluster/Monolayer MoS2 Heterojunctions for Light-Induced Room-Temperature Hydrogen Sensing.

Developing sensing approaches that can exploit visible light for the detection of low-concentration hydrogen at room temperatures has become increasingly important for the safe use of hydrogen in many applications. In this study, heterostructures composed of monolayer MoS2 and Pd nanoclusters (Pd/MoS2) acting as photo- and hydrogen-sensitizers are successfully fabricated in a facile and scalable manner. The uniform deposition of morphologically isotropic Pd nanoclusters (11.5 ± 2.2 nm) on monolayer MoS2 produces a plethora of active heterojunctions, effectively suppressing charge carrier recombination under light illumination. The dual photo- and hydrogen-sensitizing functionality of Pd/MoS2 can enable its use as an active sensing layer in optoelectronic hydrogen sensors. Gas-sensing examinations reveal that the sensing performance of Pd/MoS2 is enhanced three-fold under visible light illumination (17% for 140 ppm of H2) in comparison with dark light (5% for 140 ppm of H2). Photoactivation is also found to enable excellent sensing reversibility and reproducibility in the obtained sensor. As a proof-of-concept, the integration of Pd nanoclusters and monolayer MoS2 can open a new avenue for light-induced hydrogen gas sensing at room temperature.

Quantification of tire wear particles in road dust from industrial and residential areas in Seoul, Korea.

In this study, we examined tire and road wear microparticles (TRWMPs) in road dust along the Seoul metropolitan area, from industrial and residential areas. The road dust samples were collected via vacuum sweep methods and then filtered to obtain particles with diameters less than 75 µm. To quantify the TRWMPs in road dust, we used the raw materials of tire components, natural rubber (NR), and styrene-butadiene rubber (SBR), as standard materials. We evaluated the usability of the pyrolyzer-gas chromatography/mass spectrometry py-GC/MS method introduced in ISO/TS 20593 by confirming the decomposition temperatures of the NR and SBR by thermogravimetric (TG) and evolved gas analysis (EGA)-MS. The average of TRWMPs in industrial and residential area road dust were 22,581 and 9818 µg/g, respectively, indicating that the industrial area has 2.5 times higher TRWMPs concentration. Further, the NR, the main component of truck bus radial, to SBR, the main component of passenger car radial, ratio was slightly higher in the industrial area than in the residential area. This presumably means that the high traffic volume, including heavy duty vehicles in industrial areas, affected the higher concentration of TRWMPs. This study reveals the growing evidence of the importance of TRWMPs in road dust and how TRWMPs quantity can impact the air quality of the Seoul metropolitan area.