Search Results (105)

The SPICAV IR spectrometer aboard the Venus Express orbiter measured spectra of the 1.1 and 1.18 μm atmospheric transparency windows at the Venus night side in 2006–2014. The long-term measurements encompassed the major part of the Venus globe, including polar latitudes. For the first time, the H₂O volume mixing ratio in the deep Venus atmosphere at about 10–16 km has been retrieved for the entire SPICAV IR dataset using a radiative transfer model with multiple scattering. The retrieved H₂O volume mixing ratio is found to be sensitive to different approximations of the H₂O and CO₂ absorption lines’ far wings and assumed surface emissivity. The global average of the H₂O abundance retrieved for different parameters ranges from 23.6 ± 1.0 ppmv to 27.7 ± 1.2 ppmv. The obtained values are consistent with recent studies of water vapor below the cloud layer, showing the H₂O mixing ratio below 30 ppmv. Within the considered dataset, the zonal mean of the H₂O mixing ratio does not vary significantly from 60° S to 75° N, except for a 2 ppmv decrease noted at high latitudes. The H₂O local time distribution is also uniform. The 8-year observation period revealed no significant long-term trends or periodicities. Full article

Accurate measurements of upper troposphere humidity are essential to enhance understanding of contrail formation and guiding mitigation efforts. This study evaluates the ability of the IPRAL Raman Lidar, located south of Paris, to provide high-resolution water vapour mixing ratio (WVMR) profiles at contrail-relevant altitudes. Raman signals are screened on hourly bases, and a universal calibration method, independent of acquisition mode, is proposed towards operational Lidar water vapour profiles, using co-located ERA5 data. Calibration factors are derived from comparisons between 4 and 6 km, and nightly coefficients determined from hourly factors. Instrumental stability is monitored through the temporal evolution of calibration factors, and stable-period medians are adopted as final values. The uncertainty of calibrated WVMR profiles is assessed by comparison with GRUAN processed Meteomodem M10 radiosondes and ERA5 data. Results show a high agreement (>90%), with IPRAL exhibiting a small negative bias (~10%) below 8 km, reducing to ~5% up to 10.5 km to radiosondes. ERA5 systematically underestimates water vapour at cruise altitudes, with a dry bias increasing from 10% at 9 km to >20% at 11 km. Recent IAGOS corrections to ERA5, improving supersaturation representation, are validated over Paris. This calibrated Lidar data set supports improved atmospheric modelling and contributes to future air traffic management strategies. Full article

The Jiepailing deposit in southern Hunan is a typical large to super-large polymetallic tin deposit enriched in beryllium and other rare metals. To enhance the understanding of the mineralization processes of the Jiepailing deposit, detailed mineralogical, in situ geochemical, and sulfur isotopic analyses were conducted on pyrite closely associated with tin–polymetallic mineralization. Five types of pyrite have been identified in the deposit: (1) euhedral to subhedral medium- to coarse-grained pyrite (PyI) in tungsten–tin ore; anhedral fine-grained pyrite (PyII) in tin polymetallic–fluorite ore; anhedral fine-grained or aggregate pyrite (PyIII) in lead–zinc ore; euhedral to subhedral coarse-grained pyrite (PyIV) in beryllium–fluorite mineralization; and subhedral to anhedral fine-grained pyrite (PyV) in carbonate veinlets developed in the wall rock. Backscattered electron imaging indicates consistent structural features across the five types of pyrite. In situ trace element analysis reveals differences in trace element concentrations among the pyrite types. PyI is relatively enriched in Sn, Cu, and Co. In contrast, PyIII is enriched in Pb, Zn, Sn, and Ti, while PyIV and PyV are enriched in Ag and Sb. PyI has a Co/Ni ratio more than 1, while the Co/Ni ratios in the other four types of pyrite are less than 1. LA-MC-ICP-MS in situ sulfur isotope analysis shows δ³⁴S values ranging from 2.5‰ to 5.8‰ (average 4.3‰, PyI), 2.5‰ to 5.8‰ (average 4.3‰, PyII), −7.6‰ to 9.5‰ (average 3.9‰, PyIII), −3.7‰ to 10.6‰ (average 3.6‰, PyIV), and 6.8‰ to 14.1‰ (average 9.2‰, PyV). Based on previous studies, regional geological background, deposit characteristics, and the in situ trace element and sulfur isotope compositions of pyrite, it is inferred that the various ore bodies in the Jiepailing deposit are products of Late Cretaceous magmatic–hydrothermal activity. The early ore-forming fluid originated from magmatic sources and during the migration into the wall rock and shallow formations, mixed with fluids primarily derived from atmospheric precipitation. Temperature, pressure, and composition changed of the ore-forming fluid which carried a large amount of substances, leading to tungsten–tin, tin polymetallic–fluorite, lead–zinc, and beryllium–fluorite mineralization, followed by carbonation during the late-stage mineralization. Full article

Waste polymers composed of carbonaceous compounds can be converted into gases and oils by pyrolysis. Although pyrolysis char is generated continuously in the pyrolysis process, its high ash content limits its industrial application. In the present study, the use of pyrolysis char with a high ash content as a reductant for the reduction reaction of mill scale was investigated. The mill scale reduction behaviors were investigated by modifying the mixing ratio of oxygen in the mill scale and fixed carbon in the pyrolysis char at temperatures ranging from 1723 to 1873 K. The degree of reduction of molten iron oxide in the mill scale was obtained by measuring the amounts of CO and CO₂ gases generated during the reduction reaction in an Ar gas atmosphere. The degree of reduction increased with temperature and mixing ratio of the mill scale and pyrolysis char. In this study, the maximum degrees of reduction of mill scale at 1873 K were 0.32 and 0.65 for C/O ratios of 0.77 and 1.33, respectively. Based on a comparison of the rate constants for the overall mill scale reduction reaction with the previous rate constants, the rate-determining step in the present study was assumed to be the insufficient agitation effects owing to the limited gas evolution of CO and CO₂ caused by the low gases released during reduction resulting from the low initial carbon concentration. In addition, the potential use of pyrolysis char produced from the pyrolysis of waste materials composed of carbon compounds as an alternative carbon source was investigated. Full article

A new high-temperature allothermal gasification technology is used to process three types of oil waste: ground oil sludge (GOS), tank oil sludge (TOS), and petcoke. The gasifying agent (GA), mainly composed of H₂O and CO₂ at a temperature above 2300 K and atmospheric pressure, is produced by pulsed detonations of a near-stochiometric methane-oxygen mixture. The gasification experiments show that the dry off-gas contains 80–90 vol.% combustible gas composed of 40–45 vol.% CO, 28–33 vol.% H₂, 5–10 vol.% CH₄, and 4–7 vol.% noncondensable C₂–C₃ hydrocarbons. The gasification process is accompanied by the removal of mass from a flow gasifier in the form of fine solid ash particles with a size of about 1 μm. The ash particles have a mesoporous structure with a specific surface area ranging from 3.3 to 15.2 m²/g and pore sizes ranging from 3 to 50 nm. The measured wall temperatures of the gasifier are in reasonable agreement with the calculated value of the thermodynamic equilibrium temperature of the off-gas. The measured CO content in the off-gas is in good agreement with the thermodynamic calculations. The reduced H₂ content and elevated contents of CH₄, CO₂, and C_xH_y are apparently associated with the nonuniform distribution of the waste/GA mass ratio in the gasifier. To increase the H₂ yield, it is necessary to improve the mixing of waste with the GA. It is proposed to mix crushed petcoke with oil sludge to form a paste and feed the combined waste into the gasifier using a specially designed feeder. Full article

This study evaluates the impact of the addition of nanoparticles of anodic manganese dioxide (NAMD) on the mechanical properties and resistance to chemical attack of concrete. The research focused on nine concrete mixtures with water/cement ratios of 0.40, 0.45, and 0.50 and NAMD contents of 0, 5, and 10%. The properties of NAMD were analyzed, and fresh concrete properties such as temperature, unit weight, and consistency were measured. The compressive strength was determined at different ages (7, 14, 28, 56, and 90 days). The tensile and flexural strength were evaluated at 28 days, and the longitudinal change generated by the SO₄Mg attack was monitored until 90 days. In addition, an accelerated carbonation test was performed on concrete samples with 28 days of curing exposed to an atmosphere of 6% CO₂ for one week. The addition of NAMD did not significantly affect the temperature or unit weight of the fresh concrete, but it did influence the consistency. An increase in compressive, tensile, and flexural strength was observed, especially at early ages and for low w/c ratios. The addition of NAMD reduced the expansion of concrete exposed to magnesium sulfate, with 5% being the most effective dose, and reduced the carbonation rate of concrete by up to 40% in mixes with w/c ratios of 0.40 and 0.50. It was shown that the addition of 5% as an effective dose of NAMD improves the mechanical and durability properties of concrete, especially in mixtures with a low water/cement ratio, contributing to the improvement of the quality and strength of concrete. Full article

Mixed oxides featuring perovskite-type structures (ABO₃) offer promising catalytic properties for applications focused on the control of atmospheric pollution. In this work, a series of Ba_xMnO₃ (x = 1, 0.9, 0.8 and 0.7) samples have been synthesized, characterized and tested as catalysts for CO oxidation reaction in conditions close to that found in the exhausts of last-generation automotive internal combustion engines. All samples were observed to be active as catalysts for CO oxidation during CO-TPRe tests, with Ba_0.7MnO₃ (B0.7M) being the most active one, as it presents the highest amount of oxygen vacancies (which act as active sites for CO oxidation) and Mn (IV), which features the highest levels of reducibility and the best redox properties. B0.7M has also showcased a high stability during reactions at 300 °C, even though a slightly lower CO conversion is achieved during the second consecutive reaction cycle. This performance appears to be related to the decrease in the Mn (IV)/Mn (III) ratio. Full article

In the present work, deep eutectic solvents (DESs) were synthesized in a one-step process by heating the hydrogen bond acceptors (HBAs) tetrabutylammonium bromide and tetrabutylphosphonium bromide, along with two hydrogen bond donors (HBDs) ethanolamine and N-methyldiethanolamine, which were mixed in certain molar ratios. This mixture was then mixed with water to form a DES + water system. The densities of the prepared DES + water systems were successfully measured using the U-tube oscillation method under atmospheric pressure over a temperature range of 293.15–363.15 K. The CO₂ trapping capacity of the DES + water systems was investigated using the isovolumetric saturation technique at pressures ranging from 0.1 MPa to 1 MPa and temperatures ranging from 303.15 K to 323.15 K. A semi-empirical model was employed to fit the experimental CO₂ solubility data, and the deviations between the experimental and fitted values were calculated. At a temperature of 303.15 K and a pressure of 100 kPa, the CO₂ solubilities in the DES + water systems of TBAB and MEA, with molar ratios of 1:8, 1:9, and 1:10, were measured to be 0.1430 g/g, 0.1479 g/g, and 0.1540 g/g, respectively. Finally, it was concluded that the DES + water systems had a superior CO₂ capture capacity compared to the 30% aqueous monoethanolamine solution commonly used in industry, indicating the potential of DES + water systems for CO₂ capture. Full article

The use of industrial solid waste to capture and fix CO₂ is a promising technology for CO₂ sequestration. A thermogravimetric analyzer and CO₂ cement hydration mixing device were used to study the effects of mixing method, curing system, temperature, CO₂ concentration and other factors on the carbon fixation amount and performance of the circulating fluidized bed fly ash cement-based material system. The results showed that the carbon fixation and early strength of the cementitious materials could be improved by adding CO₂ in the stirring process and making CO₂ directly participate in the process reaction. The cementing materials samples prepared with CO₂ were cured in a standard curing box for 2 days and a carbon atmosphere for 1 day, the carbon fixation amount of the cementing material was increased by 33% and the compressive strength of the cementing material was also improved. This is because under the combined action of carbon mixing and carbon curing, the prepared binding materials produced more Ca(OH)₂ in the early stage, and it reacts with the introduced CO₂ to form CaCO₃. The strength of the calcium carbonate crystals is higher than the strength of the earlier stage of cement, and at the same time, the samples would solidify more CO₂. Considering the carbon fixation amount, sample performance and solid waste utilization rate, the best conditions for the cementing materials are as follows: the content of the circulating fluidized bed fly ash (CFA) was 35%, the concentration of carbon curing was 30%, the curing temperature was 40 ℃, the water-binder ratio was 0.4, and the carbon fixation amount of the cementing material could reach about 20%. The use of CFBFA to solidify and storge CO₂ is not only a new way to utilize high value-added fly ash resources, but also beneficial for reducing industrial carbon dioxide emissions. Full article

The increasing need for biodegradable polymers demands efficient and environmentally friendly extraction methods. In this study, a simple and sustainable method for extracting polyhydroxybutyrate (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate (PHB-co-HV) from Methylocystis hirsuta and a mixed methanotrophic consortium with different biopolymer contents was presented. The extraction of biopolymers with 1,3-dioxolane was initially investigated by varying the biomass-to-solvent ratio (i.e., 1:2 w v⁻¹, 1:4 w v⁻¹, 1:6 w v⁻¹, 1:8 w v⁻¹ and 1:10 w v⁻¹) and extraction time (6, 8 and 10 h) at the boiling point of the solvent and atmospheric pressure. Based on the results of the preliminary tests, and only for the most efficient biomass-to-solvent ratio, the extraction kinetics were also studied over a time interval ranging from 30 min to 6 h. For Methylocystis hirsuta, the investigation of the extraction time showed that the maximum extraction was reached after 30 min, with recovery yields of 87% and 75% and purities of 98.7% and 94% for PHB and PHB-co-HV, respectively. Similarly, the extraction of PHB and PHB-co-HV from a mixed methanotrophic strain yielded 88% w w⁻¹ and 70% w w⁻¹ recovery, respectively, with 98% w w⁻¹ purity, at a biomass-to-solvent ratio of 6 in 30 min. Full article

Key long-lived greenhouse gases (CO₂, CH₄, and N₂O) are perhaps among the best-studied components of the Earth’s atmosphere today; however, attempts to predict or explain trends or even shorter-term variations of these trace gases are not always successful. Infrared spectroscopy is a recognized technique for the ground-based long-term monitoring of the gaseous composition of the atmosphere. The current paper is focused on the analysis of new data on CO₂, CH₄, and N₂O total columns (TCs) retrieved from high resolution IR solar spectra acquired during 2009–2022 at the NDACC atmospheric monitoring station of St. Petersburg State University (STP station, 59.88°N, 29.83°E, 20 m asl.). The paper provides information on the FTIR system (Fourier-transform infrared) installed at the STP station, and an overview of techniques used for the CO₂, CH₄, and N₂O retrievals. Trends of key greenhouse gases and their confidence levels were evaluated using an original approach which combines the Lomb–Scargle method with the cross-validation and bootstrapping techniques. As a result, the following fourteen-year (2009–2022) trends of TCs have been revealed: (0.56 ± 0.01) % yr⁻¹ for CO₂; (0.46 ± 0.02) % yr⁻¹ for CH₄; (0.28 ± 0.01) % yr⁻¹ for N₂O. A comparison with trends based on the EMAC numerical modeling data was carried out. The trends of greenhouse gases observed at the STP site are consistent with the results of the in situ monitoring performed at the same geographical location, and with the independent estimates of the global volume mixing ratio growth rates obtained by the GAW network and the NOAA Global Monitoring Laboratory. There is reasonable agreement between the CH₄ and N₂O TC trends for 2009–2019, which have been derived from FTIR measurements at three locations: the STP site, Izaña Observatory and the University of Toronto Atmospheric Observatory. Full article

In recent decades, there has been growing interest in the thermal conversion of various alternative fuels, such as biomass and waste-derived fuels. One of the technological solutions for the so-called direct co-combustion of fuels is to create mixtures of various fuels, called mixed secondary fuel. However, mixed secondary fuel has different properties compared to primary fuels. Due to this, by properly selecting the types and proportions of mixtures, it is possible to eliminate their potentially negative impact on both combustion technology and the natural environment. In this paper, we decided to prepare mixed secondary fuel by mixing sunflower husk pellets with RDF (refuse-derived fuel) in a ratio of 1:1 and then analyze the combustion process of the produced fuel in fluidized bed conditions. The results obtained on the basis of the presented research indicate that the mixed secondary fuel eliminated the impact of alkali metal compounds on reducing the melting point of ash and, consequently, on the combustion process of the mixed secondary fuel. An additional benefit is the reduction of emissions of harmful compounds into the atmosphere occurring during the combustion of municipal waste and compliance with the concept of the circular economy. Full article

The thermodynamic modeling of waste oil (WO) gasification by a high-temperature gasification agent (GA) composed of an ultra-superheated H₂O/CO₂ mixture is carried out. The GA is assumed to be obtained by the gaseous detonation of fuel–oxidizer–diluent mixture in a pulsed detonation gun (PDG). N-hexadecane is used as a WO surrogate. Methane or the produced syngas (generally a mixture of H₂, CO, CH₄, CO₂, etc.) is used as fuel for the PDG. Oxygen, air, or oxygen-enriched air are used as oxidizers for the PDG. Low-temperature steam is used as a diluent gas. The gasification process is assumed to proceed in a flow-through gasifier at atmospheric pressure. It is shown that the use of the detonation products of the stoichiometric methane–oxygen and methane–air mixtures theoretically leads to the complete conversion of WO into a syngas consisting exclusively of H₂ and CO, or into energy gas with high contents of CH₄ and C₂-C₃ hydrocarbons and an LHV of 36.7 (fuel–oxygen mixture) and 13.6 MJ/kg (fuel–air mixture). The use of the detonation products of the stoichiometric mixture of the produced syngas with oxygen or with oxygen-enriched air also allows theoretically achieving the complete conversion of WO into syngas consisting exclusively of H₂ and CO. About 33% of the produced syngas mixed with oxygen can be theoretically used for PDG self-feeding, thus making the gasification technology very attractive and cost-effective. To self-feed the PDG with the mixture of the produced syngas with air, it is necessary to increase the backpressure in the gasifier and/or enrich the air with oxygen. The addition of low-temperature steam to the fuel–oxygen mixture in the PDG allows controlling the H₂/CO ratio in the produced syngas from 1.3 to 3.4. Full article

The sol–gel method, adapted to aqueous media, was used for the synthesis of BaMn_0.7Cu_0.3O₃ (BMC) and Ba_0.9A_0.1Mn_0.7Cu_0.3O₃ (BMC-A, A = Ce, La or Mg) perovskite-type mixed oxides. These samples were fully characterized by ICP-OES, XRD, XPS, H₂-TPR, BET, and O₂–TPD and, subsequently, they were evaluated as catalysts for CO oxidation under different conditions simulating that found in cars exhaust. The characterization results show that after the partial replacement of Ba by A metal in BMC perovskite: (i) a fraction of the polytype structure was converted to the hexagonal BaMnO₃ perovskite structure, (ii) A metal used as dopant was incorporated into the lattice of the perovskite, (iii) oxygen vacancies existed on the surface of samples, and iv) Mn(IV) and Mn(III) coexisted on the surface and in the bulk, with Mn(IV) being the main oxidation state on the surface. In the three reactant atmospheres used, all samples catalysed the CO to CO₂ oxidation reaction, showing better performances after the addition of A metal and for reactant mixtures with low CO/O₂ ratios. BMC-Ce was the most active catalyst because it combined the highest reducibility and oxygen mobility, the presence of copper and of oxygen vacancies on the surface, the contribution of the Ce(IV)/Ce(III) redox pair, and a high proportion of surface and bulk Mn(IV). At 200 °C and in the 0.1% CO + 10% O₂ reactant gas mixture, the CO conversion using BMC-Ce was very similar to the achieved with a 1% Pt/Al₂O₃ (Pt-Al) reference catalyst. Full article

Amorphous potassium sodium niobate (KNN) films were synthesized at 300 °C through the radio frequency magnetron sputtering method and subsequently crystallized by post-annealing at 700 °C in various alkali element atmospheres (Na and K). The as-deposited film is notably deficient in alkali metal elements, particularly K, whereas the loss of alkali elements in the films can be replenished through annealing in an alkali element atmosphere. By adjusting the molar ratio of Na and K in the annealing atmosphere, the ratio of Na/K in the resultant film varied, consequently suggesting the efficiency of this method on composition regulation of KNN films. Meanwhile, we also found that the physical characteristics of the films also underwent differences with the change of an annealing atmosphere. The films annealed in a high Na atmosphere exhibit large dielectric losses with limited piezoelectric vibration behavior, while annealing in a high K atmosphere reduces the dielectric losses and enhances the piezoelectric behavior. Furthermore, the results of vibration measurement demonstrated that the film annealed in a mixed powder of 25% Na₂CO₃ and 75% K₂CO₃ exhibits an optimal vibration displacement of ~400 pm under the sinusoidal excitation voltage of 8 V. This approach of altering the composition of KNN films through post-annealing may introduce the new concept of property design of KNN as well as other similar films. Full article