Oxidation Ratio Research Articles

Study on the characteristics of zeolite-promoted thermal decomposition of H2O2 for efficient NO oxidation.

The H2O2 evaporation rate directly affected the oxidation of NO by H2O2. Green zeolite and synthetic mordenite were selected to promote H2O2 thermal decomposition and NO oxidation. The effects of different zeolites, evaporation conditions, temperatures, and reactant concentrations on the NO oxidation ratio were explored. The promotion mechanism of zeolite on NO oxidation by H2O2 thermal decomposition was explained. The results show that the zeolite surface can significantly accelerate the H2O2 evaporation rate to obtain a high NO oxidation ratio. The hydrophilicity and rich pore structure of zeolite enable the rapid diffusion and evaporation of droplets on the zeolite surface. Compared with the green zeolite with the mesoporous structure, the synthetic mordenite with the hierarchical pore structure has a more obvious promotion effect on the NO oxidation by H2O2 thermal decomposition. The reason is that the synthetic mordenite contains micropores, resulting in a larger specific surface area, and the mesoporous structure is conducive to the mass transfer and diffusion of H2O2 on its surface. The product of NO oxidation is mainly NO2, which proves that ·OH plays a major role in the process.

Highlighting the Compositional Changes of the Sm2O3/MgO-Containing Cellulose Acetate Films for Wound Dressings.

The development of wound dressing materials with appropriate specifications is still a challenge to overcome the current limitations of conventional medical bandages. In this regard, simple and fast methods are highly recommended, such as film casting. In addition, deliverable nanoparticles that can act to accelerate wound integration, such as samarium oxide (Sm2O3) and magnesium oxide (MgO), might represent a potential design with a novel compositional combination. In the present research, the casted film of cellulose acetate (CA) was mixed with different ratios of metal oxides, such as samarium oxide (Sm2O3) and magnesium oxide (MgO). The tests used for the film examination were X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The SEM graphs of CA films represent the surface morphology of Sm2O3@CA, MgO@CA, and Sm2O3/MgO/GO@CA. It was found that the scaffolds' surface contained a high porosity ratio with diameters of 1.5-5 µm. On the other hand, the measurement of contact angle exhibits a variable trend starting from 27° to 29° for pristine CA and Sm2O3/MgO/GO@CA. The cell viability test exhibits a noticeable increase in cell growth with a decrease in the concentration. In addition, the IC50 was determined at 6 mg/mL, while the concentration of scaffolds of 20 mg/mL caused cellular growth to be around 106%.

Relative contributions of fungi and bacteria to litter decomposition under low and high soil moisture in an Australian grassland

Fungi and bacteria differ in their sensitivity to soil moisture, but their activity and contributions to soil carbon (C) cycling under different soil moisture conditions remain unclear. We manipulated soil fungi and bacteria with the fungicide captan and bactericide bronopol, respectively, and examined their effect on C dynamics at low and high moisture levels (40 and 80 % water holding capacity) in a grassland soil over a 21-day incubation period in the laboratory. 13C-labeled ryegrass was added with and without biocide treatments to separate ryegrass from soil-derived C in respiration, dissolved organic C (DOC) and soil C. We also measured activities of four C-degrading enzymes. Soil total- and ryegrass-respiration rates and microbial biomass C (MBC) decreased, while ryegrass-derived C in DOC and soil increased with decreased soil moisture, suggesting reduced microbial activity with decreased soil moisture. Initially, ryegrass respiration rates were suppressed by both biocides and both soil moisture levels. However, at low soil moisture, ryegrass respiration no longer was suppressed by bronopol after eight days of incubation, but remained suppressed with captan, suggesting that with low moisture fungi played a more important role in decomposing ryegrass litter than bacteria. On the other hand, at high soil moisture, biocide effects on ryegrass respiration mostly disappeared after eight days, suggesting that more labile components of ryegrass litter were no longer present, and that the surviving microorganisms adapted similarly to decomposing the more recalcitrant litter. Bacteria preferred to decompose labile substrates early on during the incubation, and fungi played a greater role in decomposing more recalcitrant ryegrass left over in soil at the end of the incubation. At low moisture with captan, a reduction in oxidative enzyme production contributed to the increase in the hydrolytic:oxidative enzyme ratio, further indicating the importance of fungi for decomposing more recalcitrant substances under low moisture conditions.

Electrochemical properties depending on heteroatom and surface property of various carbon sources/NiO composites as supercapacitor electrode

AbstractThis study describes the creation and use of composites of nickel oxide and activated carbon as supercapacitor electrodes. A one‐pot reaction is used to synthesize composite materials of nickel oxide and activated carbon (microalgae, asphaltene, and wood). A precursor solution of Ni(OH)2 is blended with activated carbon through a precipitating method at a controlled weight ratio of nickel oxide and activated carbon, then the obtained powder is calcinated at 300°C for 3 hr. The composites are analyzed by X‐ray diffraction, scanning electron microscopy, and energy dispersive X‐ray analysis (EDX). It is confirmed that nickel oxide sprouted on activated carbon surface. At a nickel oxide activated carbon weight ratio of 1:20, the greatest specific capacitances at 1 A/g current density are 624.2, 487.1, and 403 F/g, respectively.

Investigation into the differences and relationships between gasSOA and aqSOA in winter haze pollution on Chongming Island, Shanghai, based on VOCs observation

To investigate the formation of secondary organic aerosol (SOA) under current atmospheric conditions, we conducted a field observation of SOA precursors in the downwind region of the Yangtze River Delta (YRD) in winter 2019 using a variety of offline and online instruments. During the entire observation period, the averaged fine particulate SOA was 7.9 ± 2.3 μg m−3, with precursor concentrations of 31 ± 11 ppbv for the measured volatile organic compounds (VOCs) and 16 ± 12 ppbv for NOx. Compared to those on the clean days, SOA on the haze days increased by a factor of 1.6, while the VOC and NOx increased by a factor of 1.3 and 2.0, respectively. Aerosol liquid water content (ALWC) and oxygenated VOCs (OVOCs, including acetaldehyde, formic acid, acetone, acetic acid, methyl ethyl ketone, and methylglyoxal) relationships suggested that the gasSOA and aqSOA occurred simultaneously on Chongming Island in winter. The gasSOA was primarily formed by the oxidation of aromatics and NOx at low RH (RH < 80%) conditions. In contrast, the aqSOA was formed under higher RH (RH > 80%) conditions via a combination of daytime photochemical aqueous phase processes of water-soluble OVOCs and nocturnal dark aqueous phase processes of primary emissions from biomass. The inversed higher mass ratio of NACs to (benzene + toluene) and nitrogen oxidation ratio (NOR) in the daytime during the gasSOA-dominated haze periods indicated that gasSOA could be transformed to aqSOA at high NOx levels. Our results also suggested the importance of NOx and VOC reduction measures in directly mitigating gasSOA and indirectly mitigating aqSOA during winter haze pollution.

Tannery Sludge Gasification in a Fluidized Bed for Its Energetic Valorization

The present article deals with the valorization of the organic content of tannery sludges to produce energy vectors. In this scenario, gasification is a viable option to obtain a flexible gaseous stream (syngas) of interesting energetic value, under operating conditions that do not favor the oxidation of Cr(III) (typically found in tannery sludges) to the more harmful Cr(VI) state. To this end, an industrial tannery sludge was characterized through proximate/ultimate analyses and determination of the heating value, showing its capability to act as a solid fuel in a gasification process, and metal analyses, showing that its Cr(VI) content was below the detection limit (2 ppm). The material was subjected to gasification tests in a lab-scale fluidized bed (FB) reactor. The reactor, with a 41 mm inside diameter and a 1 m height, was electrically kept at an operating temperature of 850 °C. The fluidization velocity was 0.30 m/s at 850 °C, i.e., 7.5 times the value of the minimum fluidization velocity. The gasifying stream was composed by O2 (3% vol.) diluted in N2. The adopted oxidant equivalence ratio (ER) levels were 0.15 and 0.24, to ensure substoichiometric (i.e., reducing) conditions in the FB atmosphere. Under the most reducing operating conditions, it was possible to produce syngas with a lower heating value of 12.0 MJ/N m3 (dry and N2-free basis). It contained, under these conditions, about 42% H2, 36% CO, and 4% CH4, plus 16% CO2 and other components. The tar produced from the process, fully characterized by gas chromatography–mass spectrometry, showed a favorably low concentration of about 25 g/N m3. FB bottom and fly ashes were analyzed for their carbon and metal contents. In bottom ash, the total Cr concentration resulted in the range of 8–12 g/kg, with a Cr(VI) concentration between 8 and 10 ppm. In the elutriated stream, the total Cr concentration was about 55 g/kg, with a Cr(VI) concentration between 4 and 7 ppm. The Cr(VI) concentration was higher when higher values of the ER were used, but it resulted in 3–4 orders of magnitude lower than the total Cr concentration, showing the appropriateness of the process to produce syngas with very limited oxidation of chromium in the solid residues.

Green synthesis of chitosan/erythritol/graphene oxide composites for simultaneous removal of some toxic species from simulated solution

In this study, chitosan (Ch) is adapted via green methodology including sonication induced crosslinking with different weight ratios of erythritol (Er) from (Ch-Er)1 to (Ch-Er)4. The products were casted in the form of thin films. The chemical modification was proved via FTIR spectroscopy. Then, the modified products were verified via an atomic force microscopy (AFM) investigation for their topography and surface properties. The data revealed that the optimized sample was (Ch-Er)3. This sample was further modified by different weight ratios of graphene oxide 0.1, 0.2, 0.4, and 0.8 wt./wt. (symbolized as (Ch-Er)3GO1, (Ch-Er)3GO2, (Ch-Er)3GO4, and (Ch-Er)3GO8 respectively). The prepared samples were investigated by different analytical tools. Then, the adjusted sample (Ch-Er)3GO2 was irradiated by electron beam (e-beam) at 10 and 20 kGy of irradiation doses to give samples (Ch-Er)3GO2R10 and (Ch-Er)3GO2R20, respectively. The AFM data of the irradiated samples showed that the pore size decreases, and surface roughness increases at higher energy e-beam due to the formation of more crosslinking points. The optimum samples of the prepared formulations were tested as sorbent materials for simultaneous elimination of methylene blue (MB) dye and mercury cation (Hg2+) from simulated solutions. The maximum removal of both MB dye and Hg2+ cation was achieved by (Ch-Er)3GO2R10 (186.23 mg g−1 and 205 mg g−1) respectively.Graphical abstract

Chemistry of PM2.5 in haze events in two East Asian cities during winter–spring 2019

East Asian experiences frequent severe haze episodes (EPs) during winter–spring, and their causes are not fully understood. Two EPs (daily average PM2.5 > 35 μg m−3) occurred at Tianjin (TJ), China, and Daejeon (DJ), Korea, during late February (EP-1) and early March (EP-2) 2019. The mean total PM2.5 concentrations at the TJ and DJ sites during these events (82.9 and 66.2 μg m−3, respectively) were approximately three times higher than those observed during non-haze events (27.3 and 23.0 μg m−3, respectively). MODIS satellite RGB images suggested that aerosols were transported regionally from east Asian countries to the DJ site during EPs. After NO3−, the major contributors to PM2.5 during the EPs at both sites were NH4+, SO42−, and organic carbon (OC), indicating that secondary aerosols were important in severe haze formation. During the EPs, the distributions of secondary chemical species were similar at the two sites, with coefficient of divergence (COD) values of <0.2, whereas primary chemical species had dissimilar distributions with COD values of >0.2. This suggests that secondary aerosols may be impacted by regional influences, whereas primary aerosols are subject to more local influence. The average COD values in the first two days (27–28 February) relative to the remaining days (1–7 March) were <0.2 at the DJ site during EP-2, indicating no additional local production of secondary and primary species. Sulfur oxidation ratios (SOR) were lower at the TJ site than at the DJ site, while nitrogen oxidation ratios (NOR) were higher. Gradual increases observed in SOR and NOR at the TJ site early in the EPs imply significant secondary formation of SO42− and NO3−. Strong correlations between aerosol liquid-water content (ALWC) and SOR and NOR at the TJ site indicate that aqueous-phase reactions were important in the formation of SO42− and NO3−. Although high concentrations of SO42− and NO3− were observed at the DJ site, correlations between ALWC and SOR/NOR were weak with low regression gradients, implying that SO42− and NO3− may have been associated with regional transport. Low COD values, and SOR and NOR values similar to those at the beginning of EP-2, imply that additional formation of SO42− or NO3− at the DJ site is not active, with stagnant atmospheric conditions prevailing.

Endurance training minimizing carbohydrate oxidation by targeting the optimal level of fat/carbohydrate oxidation ratio (OLORFOX)?

The effectiveness of endurance training at low to moderate intensities targeted at the level of maximal lipid oxidation (LIPOXmax) is confirmed by recent international work. It may seem paradoxical, given the low level of caloric expenditure involved. One of the explanations for this paradox is that LIPOXmax training has epigenetic effects and regulatory effects on eating behavior. Indeed, exercise at this level favors satiety and reduces the urge to snack, whereas at higher intensity, in the lipid oxidation zone, 30 to 60 minutes of endurance exercise favors food intake and may determine a paradoxical weight gain. In our previously published database of 3739 calorimetries we have recalculated the kinetics of the lipid/carbohydrate oxidation ratio and we observe that it peaks on average 12% below LIPOXmax (39.45% ± 0.20% vs. 44.87% ± 0.23% VO2max; P < 0.0001) at a level we propose to call “optimal level of fat/carbohydrate oxidation ratio” (OLORFOX) and that this level may present in many cases wide inter-individual variations, so that there are profiles of subjects in whom it is frankly disjointed from that of LIPOXmax. A preliminary series of 11 patients with this profile who were trained at OLORFOX confirms that this approach over 3 years is effective for weight loss (−11.5 ± 1.5% of initial weight P < 0.001), even though this level is set below the LIPOXmax which is itself located at a low to moderate intensity. These preliminary data lead us to study more widely this type of targeting of training in overweight individuals. L’efficacité de l’entraînement en endurance à des intensités faibles à modérées ciblée sur le niveau d’oxydation lipidique maximale (LIPOXmax) est confirmée par de récents travaux internationaux. Elle peut sembler paradoxale compte tenu du faible niveau de dépense calorique mis en jeu. Une des explications de ce paradoxe tient à des effets épigénétiques et à des effets régulateurs sur le comportement alimentaire. En effet l’exercice à ce niveau favorise la satiété et diminue les pulsions de grignotage tandis qu’à plus haute intensité, dans la zone d’oxydation lipidique, des exercices de 30 à 60 minutes en endurance favorisent la prise alimentaire et peuvent déterminer une prise de poids paradoxale. Dans notre base de données 3739 calorimétries (2490 femmes et 1249 hommes) nous avons recalculé la cinétique du rapport d’oxydations lipides/glucides et nous observons qu’il culmine en moyenne 12 % au-dessous du LIPOXmax (39,45 % ± 0,20 % vs 44,87 % ± 0,23 % de VO2max ; p < 0,0001) mais avec beaucoup de variations interindividuelles et qu’il y a des profils de sujets chez qui ce niveau est franchement disjoint de celui du LIPOXmax. Une série préliminaire de 11 patients présentant ce profil « biphasique » et entraînés au NOROLG confirme que cette démarche sur 3 ans est efficace pour perdre du poids (−11,5 ± 1,15 kg p < 0,0001) alors même que ce niveau est situé au-dessous du LIPOXmax qui est lui-même situé à une intensité faible à modérée. Ces premières données poussent à étudier plus largement ce type de ciblage du réentraînement dans les surcharges pondérales.

Curing Characteristics Based on the Mixing Ratio of MKP and Retardant in Phosphate-Based Rapid Hardening Repair Materials

Potholes in asphalt are phenomena in which a part or all of the surface layer is lost due to water, traffic load, and/or changes in temperature, which can lead to traffic accidents. Emergency repair materials used in pothole emergency repair work require different qualities such as suitable curing properties and fluidity, early strength development, high durability and adhesion strength, and moderate heat generation properties. Chemically bonded phosphate ceramic composites made of phosphate and magnesium oxide as main materials are recognized as rapidly hardening materials. This study evaluates the fluidity, hardenability, and mechanical properties of asphalt based on the magnesium oxide and phosphate ratio and retardant used to develop pothole repair materials. Experiments attempted to derive the optimal combination of phosphate and magnesium oxide, where the mixing ratio of phosphate and magnesium oxide and the curing time and curing characteristics based on increases in the contents of the retardant mixture were considered.

Pre-Treatment and Turbidity Reduction of Sea Waters Using New Composite Ceramic Microfiltration Membranes with Iron Oxide Additive

In this research, an experimental study was carried out on the pre-treatment and turbidity removal of Persian Gulf water using cross flow microfiltration by new composite ceramic membranes. Three types of tubular microfiltration composite ceramic membranes that consisted of Mullite, Mullite/SiC, and Mullite/SiC/Fe2O3 with different compositions were fabricated at relatively low temperature (1250 °C) with extrusion and sintering for this purpose. Furthermore, changes in porosity, pore size, and mechanical strength were compared in Mullite membranes and composite membranes to find the most suitable membrane for turbidity removal from seawater. According to the results, the most suitable synthetic membrane was M/SiC/Fe10 membrane with 60:30:10 ratios of mullite, silicon carbide, and iron oxide with 64.6 ± 2% porosity, average pore size of 0.54 μm, 95.4% turbidity removal, pure water permeability of 3811 L/m2.h, and higher mechanical strength (22.4 MPa) compared to other fabricated membranes. Results of Hermia’s models for fouling modeling indicated that the dominant mechanism of blocking in all membranes was standard pore blocking with the best compliance with experimental data. Therefore, results demonstrated that the addition of Fe2O3 to silicon carbide ceramic microfiltration membranes, with a specific weight percentage, improves their mechanical properties and membrane performance for pre-treatment of seawaters.

Quantitative monitoring and potential mechanism of the secondary corrosion risk of PAH-contaminated soil remediated by persulfate oxidation

The proportion of activated persulfate (PS) oxidation technology in the remediation of domestic organic contaminated sites has increased every year, and the potential corrosion risk of site reuse caused by residual oxidants and by-products has also attracted the attention of researchers. In this work, the potential corrosion degree such as the mass reduction rate and surface crack width of standard iron flakes under different conditions, including with different PS dosages and release times, was monitored quantitatively over a long period, and the corresponding corrosion risk was quantitatively assessed. The results showed that when n (Na2S2O8):n (PAHs) increased from 5:1 to 100:1, the higher the oxidizer dosage, the more severe the corrosion weight loss and surface crack width, indicating that the oxidizer dosage was positively correlated with the potential corrosion risk. In addition, the corrosion crack width of the standard iron flake had a significant positive correlation with the reaction time and a significant negative correlation with the mass change. According to the changes in the standard iron flake, the corrosion process could be divided into three stages, in which the corrosion risk from high to low followed the order of oxidant corrosion stage > oxidant and salt corrosion stage > salt and microbial corrosion stage. Therefore, the dosage of chemicals should be controlled, the molar ratio of oxidizer to contaminant should not exceed 25:1, and a natural recovery period of at least one year should be left post remediation. During the reuse of the remediation sites in the future, the potential corrosion risks should also be calculated based on the dosage and time, to avoid redevelopment and use of the restoration site in the high corrosion risk stage.

Using greenhouse gases in the synthesis gas production processes: Thermodynamic conditions

The work concerns the thermodynamic analysis of CH4 reforming with various oxidants (CO2, H2O, O2) in the technological variants DRM (Dry Reforming of Methane) and TRM (Tri-reforming of Methane) technological variants. Both processes of synthesis gas production (raw material for the production of value-added products) are problematic in terms of environmental protection. In the process, two components of greenhouse gases are used as a substrate: CO2 and CH4. The influence of temperature, pressure, and the molar ratio of oxidants to methane on the efficiency of both processes was analyzed using the deterministic method: raw material conversion, product efficiency and selectivity - H2 and CO, and the value of the H2/CO ratio characterizing the suitability of the synthesis gas for various syntheses. The problem of carbon deposition tendency in DRM was minimized through the selection of operational process conditions, and in the case of TRM, it was fully reduced. The deterministic method of non-linear programming by defining the objective function with constraints helped formulate allowed one the values of TRM parameters: complete reduction of the coking problem, maintaining the H2/CO ratio at the desired level - 2 and CO2 conversion equal to 90%, led to a hydrogen efficiency of over 90%. This efficiency can be obtained at the process temperature T = 273 K, with a pressure of 1 atm, and the molar ratios of oxidants to methane: CH4/CO2/H2O/O2 = 1/0.36/0.77/0.01.

Atmospheric sulfate formation in the Seoul Metropolitan Area during spring/summer: Effect of trace metal ions

Despite the effort to control SO2 emission, sulfate is still one of the major inorganic components of PM2.5 in urban area. Moreover, there is still a lack of understanding of the sulfate formation mechanism via SO2 oxidation under various ambient conditions. In this study, we focus on sulfate formation during a haze pollution episode in the spring/summertime of 2016 in Seoul Metropolitan Area (SMA). During the pollution episode, PM2.5 mass concentration exceeded over 60 μg m−3, and sulfate accounted for about 25% of the total PM2.5 mass concentration. A sharp increase of sulfur oxidation ratio (SOR) values along with aerosol liquid water content (AWC) under humid conditions could be ascribed to an apparent contribution of aqueous-phase oxidation of SO2 of sulfate formation during the pollution period. Comparisons of SOR values with four representative oxidants for the aqueous-phase oxidation (i.e., NO2, H2O2, O3, and TMIs) indicated that TMIs concentration, especially for Mn (II), showed the best positive correlation. Furthermore, for calculating the sulfate production rate, the contribution of TMIs concentration was found to be dominant within the pH range in SMA (2.1–3.0), which was determined by the chemical composition and derived AWC. These results imply that not only the SO2 emission but also other chemical components (e.g., TMI and nitrate) would play a critical combined role in sulfate formation under urban haze condition.

Oxidation and wetting characteristics of lead-free Sn-0.7Cu solder alloys with the addition of Fe and Bi

In this paper, the oxidation and wetting behaviour of Sn-0.7Cu and Sn-0.7Cu-0.05Fe-2Bi solder alloys has been investigated. The alloys were subjected to 200 °C in oxygen rich environment. Weight gain curves reveal that the oxidation behaviour obey the parabolic rate law. X-Ray photo electron spectroscopy (XPS) reveals the presence of SnO and SnO2 oxide layer on the surface of Sn-0.7Cu solder alloys. SnO was formed as the basic oxide layer. However, at higher temperature SnO transforms into SnO2. Addition of Bi results in the formation of Bi2O3. The Pilling-Bedworth ratio of SnO, SnO2 and Bi2O3 oxides are 1.28, 1.35 and 1.23 respectively. These ratios confirm the passive nature of oxide layers. Wetting behaviour of Sn-0.7Cu and Sn-0.7Cu-0.05Fe-2Bi were investigated on Cu substrate. The addition of Bi and Fe improves the wetting properties of Sn-0.7Cu solder alloys. Alloying with Bi and Fe results in growth suppression of intermetallic compound at the interface. Increase in spreading rate, decrease in wetting angle and solder height reveals better performance of the Sn-0.7Cu-0.05Fe-2Bi solder alloy.

Influence of sodium-based activators and water content on the fresh and hardened properties of metakaolin geopolymers

Several studies explore optimal molar oxide ratios for metakaolin geopolymer production. However, there is not a consensus on the optimal mix, and within similar range large differences in compressive strength are reported, and consequently in the overall performance. Hence, the present work selects a specific molar oxide ratio that leads to strengths above 30 MPa (SiO2/Al2O3 ratio of 3.19, a Na2O/Al2O3 of 1.00, and a water-to-solids ratio of 0.52), and investigates the individual effect of the sodium-based activators (NaOH and Na2SiO3) and the water content on fresh and hardened properties of metakaolin geopolymers. The tested properties include the rheology, setting time, mass loss, shrinkage, density and compressive strength. The test results show that an increase of water content (water-to-solids > 0.52) and increase of NaOH (Na2O/Al2O3 > 1.03) have the largest impact, showing a detrimental effect on both fresh and hardened properties. Moreover, the best results are obtained when using molar ratios of SiO2/Al2O3 at 3.14, Na2O/Al2O3 at 0.97 and a water-to-solids ratio of 0.51, which is within the range of optimum molar ratios from previous studies. The tests are further supplemented by Thermogravimetric analysis/Differential scanning calorimetry (TGA/DSC), scanning electron microscopy (SEM), and X-ray diffraction (XRD).

Analysis of methods used to identify combustible gas and vapour-related factors contributing to explosions in the context of assigning explosion and fire safety categories to premises

Introduction . The authors have classified numerous publications, addressing the assignment of explosion and fire safety categories to premises, buildings and outdoor facilities, into the three groups: 1) sources of information that are in effect (including in-house and region-wide documents), sources that were in effect; 2) manuals and guidelines on category assignment; 3) publications that confirm (refute) or clarify some provisions, specified in regulatory sources. This article can be included into the third group of publications. Goal. Analysis of different methods, used to identify the value of Z factor; identification of strengths and weaknesses of each method, development of recommendations on the application of these methods. Objectives . The objective is to identify the substance-related factor contributing to explosions, use particular cases to demonstrate the efficiency of this or other identification method. Results and discussion. The analysis of Z factor identification methods, describing the contribution of vapours of highly flammable liquids to an explosion, has proven that three types of procedures can be used to find the Z factor value: the method of tables (that uses the maximal possible tabular value of Z = 1; for gases and aerosols Z = 0.5; for vapours of highly flammable liquids Z = 0.3); the computational method based on a pattern of three-dimensional gas and vapour spreading on the premises; however, this method, if applied, may involve a high probability of errors due to numerous conditions limiting its applicability; hence, the unexplainable value of Z may exceed 1. Besides, the computational method is extremely laborious. Its application requires the clarification of conditions for its use; the graphical method (based on the dependency graph of Z on the X parameter). This method is the simplest and the most reliable one. When the graphical method is used to find the value of Z , the excess oxidant ratio must be taken as being equal to one, and the Х parameter must be calculated according to the following formula: Х = 0.99 Р s.v / С st.c . Conclusions. The graphical method, used to find the value of Z , is simple and reliable. When the Х parameter is identified, the excess air ratio is used: φ = 1.9, which leads to the underestimation of Z , the vapour-related factor contributing to explosions. To prevent the unreasonable underestimation of Z , the excess air ratio must be disregarded or taken as being equal to 0.99.

Optimal amorphous oxide ratios and multifactor models for binary geopolymers from metakaolin blended with substantial sugarcane bagasse ash

As a potential precursor, the utilization of sugarcane bagasse ash imparts enormous technical and environmental benefits to human society. However, its rich crystal content challenges the mix design of sugarcane bagasse ash-sourced geopolymers. The present study is aimed to contributing towards the substantial utilization of sugarcane bagasse ash in geopolymers and to developing a guideline for designing binary geopolymers from metakaolin and sugarcane bagasse ash. The experimental results show that when suitably designed, the compressive strength of metakaolin-sugarcane bagasse ash geopolymers satisfied the structural use for building materials, and the sugarcane bagasse ash proportion could substantially reach up to 50%. Moreover, through a combination of mechanical, economic and environmental assessments, the optimal mixing proportions fall into the following ranges: SiO2/Al2O3 = 4.63–5.60, Na2O/Al2O3 = 1.5–2.0 and H2O/Na2O = 8–10. Companion characterizations using XRD, FTIR and SEM show that the binary geopolymers produced within the above ranges register the greatest amorphicity, the highest degree of geopolymerization alongside the densest microstructure. Further, multi-factor models are proposed to regulate the mix design of binary geopolymers, with a R2 value beyond 0.9.

Responses of sulfate and nitrate to anthropogenic emission changes in eastern China - in perspective of long-term variations

We investigate responses of sulfate (SO42−) and nitrate (NO3−) to anthropogenic emission changes in 2006–2017 by fixing meteorology at the 2009 level using nested 3D chemical transport model GEOS-Chem. We find that sulfate concentration decreases following SO2 emissions, but with a relatively smaller reduction rate (by 16 % in North China Plain (NCP) and 28 % in Yangtze River Delta (YRD)) due to larger sulfur oxidation ratio (SOR) at lower SO2 level. SOR follows a power law with SO2 emissions in general except in winter in NCP, when and where both SO2 emission reduction and atmospheric oxidation capacity are critical to the inter-annual variations of SOR. Nitrate concentration ([pNO3−]) decreases along with NOx emission reduction in summer, but increases slightly in winter in 2011–2017. Equilibrium with gas phase HNO3, NO3− in particle phase (pNO3−) is determined by total HNO3 (TN = [pNO3−] + [gHNO3]) oxidized from NO2 and gas-particle partitioning (ε(NO3−) = [pNO3−]/TN). TN is decreasing faster in summer (~33 %) than in winter (~25 %) in 2011–2017. In contrast, ε(NO3−) changes marginally in summer (within 5 %) but increases by 36 % in NCP and by 51 % in YRD in winter in 2006–2017. The increasing of ε(NO3−) in winter is attributed to the strong reduction of [pSO42−], which increases the relative abundance of NH3 and thus favors partitioning of NO3− to the particle phase. The effect of increasing ε(NO3−) overcomes that of decreasing TN in winter. We suggest reduce SO2 emissions to further reduce [pSO42−] in eastern China. In addition, we recommend reduce NOx emissions in summer, and reduce atmospheric oxidation capacity and relative abundance of NH3 in winter to reduce [pNO3−].

Dilatometric characteristics of weakly sintered ceramics

Thermal expansion of refractory ceramics CaZrO3, MgAl2O4, La2Zr2O7 and YSZ-12 was studied. The samples of the complex oxides were synthesized by solution combustion synthesis with glycine; the fuel:oxidant ratio was varied depending on the character of redox reaction. The linear thermal expansion coefficient (LTEC) of ceramics was measured on the samples with an initial density 23–52%. The maximal sinterability of 89–92% after 6 h annealing at 1550 °С was demonstrated by La2Zr2O7 and YSZ-12, and the minimal values (78–82%) – by CaZrO3 and MgAl2O4. All materials have close LTEC values, from 9.0 to 9.6·10–6 K–1.