Search

Sonochemistry in combination with a combustion procedure was used to prepare superparamagnetic iron oxide nanoparticles. Two different iron precursors, ferrocene and iron(II)-acetate were dispersed...

The increase of fossil-fuel-derived CO2 in the atmosphere has led to the dilution of the atmospheric radiocarbon concentration, but due to the costly instrumentation, the continuous atmospheric 14C/12C data is incomplete in developing countries, such as in Indonesia. These data give useful information about the level of local and regional fossil emissions. In this study, 14C AMS measurements of local vegetation and woody plant species samples have been used to estimate the rate of fossil-fuel-derived carbon in the plants, which fix the CO2 from the atmosphere by photosynthesis. Evergreen leaf samples were collected in September 2018 on the island of Bali in different, diverse districts in local and urban areas. The samples from the densely populated areas show observable fossil fuel emissions and show that the Δ14C level is close to zero ‰, similar to the natural level.

Deciduous tree leaf and grass samples were collected in Debrecen, the second largest city in Hungary. The aim of the study was to determine the rate of fossil fuel-derived carbon in urban vegetation. At the locations sampled, C3 and C4 plants close to roads were collected in September 2017. In total, 82 tree and grass leaf samples were gathered at 36 different sampling points all over the city of Debrecen. The radiocarbon (14C) results of the samples were compared to the local urban background atmospheric 14CO2 data to determine the percentage of the fossil fuel-derived carbon in the plants. Based on our results, the average fossil carbon content in the tree and grass leaf samples were 0.9 ± 1.2% and 2.5 ± 2.5%, respectively. The highest fossil carbon content was 9.6 ± 0.6% in a grass and 4.7 ± 0.7% in a tree leaf sample. It appears that the negative fossil carbon content results obtained at urban sampling areas reflect modern carbon emission, where radiocarbon content is higher than the corresponding local background, presumably due burning of recent wood containing bomb 14C in the suburbs as well as other possible sources such as litter decomposition or soil CO2 emission.

In this study, a series of free-standing as well as controlled size Pt nanoparticles-loaded mesoporous metal oxides (NiO, Co3O4, CeO2 and MnO2) with high surface area and designed pore structure were prepared by hard template method and used as catalysts for CO2 hydrogenation together with dry reforming of CO2 with methane. The physicochemical properties of catalysts were analysed by N2 adsorption-desorption isotherm, XRD, TEM, and H2-TPR. Pt-free and Pt-loaded mesoporous NiO and Co3O4 performed with high catalytic activity and selectivity for both CO2 activation reactions. Pt-free NiO exhibited the highest catalytic activity and also showing 100% CH4 selectivity between 473–673 K and ˜1:1 H2/CO2 ratio between 673–973 K in CO2 hydrogenation and dry reforming with methane, respectively. The enhanced catalytic properties can be due to the existence of metallic Ni as well as the optimal dynamics of Ni/NiOx structure under reaction conditions.

The methane emissions from the Hungarian Pannonian Basin are not well qualified, due to a lack of measurements of CH4 mole fraction and δ13CCH4 in the air. This study reports methane measurements in air samples from Hungary, placing them in the context of regional and global background data, to investigate the inputs to the methane burden in Central Europe. CH4 mole fraction and δ13CCH4 from the Hungarian tall tower station, Hegyhátsál, and additional data from Mace Head (Ireland) and Zeppelin (Svalbard) are used with back-trajectory modeling to identify central European source areas and their seasonal variation between the summer vegetation and winter heating periods. Methane measurements in air masses sampled in the European interior, have significantly higher maxima and seasonal amplitudes than at the Mace Head and Zeppelin European background sites. The mean CH4 mole fraction value is about 80 ppb higher than the comparable marine background, and values above 2000 ppb were frequently observed between February 2013 and December 2015. The mean δ13CCH4 value -47.5±0.3 ‰ (2σ) was comparable to values at all three monitoring sites, but specific pollution events were detected at Hegyhátsál. Concentration weighted trajectory modeling, meteorological parameters, stable carbon isotopic composition (δ13CCH4), and Miller-Tans analysis show that the main factors influencing CH4 at the Hegyhátsál, apart from diurnal and seasonal changes in the Planetary Boundary Layer, are emissions from residential heating and industrial CH4 emissions during the winter.

In this paper, we present the time-dependent elemental composition and AMS radiocarbon dating results of 36 rape, sunflower and forest honey samples, collected between 1985 and 2018 in geographically close locations. Based on the elemental information, we conclude that bee products regardless the type provide useful environmental information of the previous decades, such as the decreasing trend of airborne Pb emission can be traced. However, radiocarbon results agree less with the atmospheric bomb peak. Random offsets were observed in the specific radiocarbon activity of the honey samples indicating that rape, sunflower and forest honey samples are not as reliable materials for radiocarbon dating as acacia honeys. The radiocarbon results show that the rape, sunflower and forest honey samples can contain non-photosynthetic carbon, presumably derived from the soil. Thus, the complex application of honey samples for environmental reconstruction requires the species-separated investigation of bee products to reveal their adaptability for assessment approaches.

A coupled accelerator mass spectrometer–gas interface system has been successfully operating at the Hertelendi Laboratory of Environmental Studies, Debrecen, Hungary, since 2013. Over the last 6 years more than 500 gas targets were measured below 100 µg carbon content for carbon isotopic composition. The system was tested with blanks, OxII, IAEA-C1, IAEA-C2, and IAEA-C7 standards. The performance of our instrumentation shows good agreement with other published gas-interface system data and also shows a quite good agreement with the nominal value of international standard samples. There is a measurable but quite small memory effect after modern samples, but this does not significantly affect the final results. Typical ion currents at the low energy side were between 10–15 µA with a 5% CO2 in He mixing ratio. The relative errors average ±6% for samples greater than or equal to 10 µgC sample with mean count rates of 300 counts per microgram C for OxII. The blank is comparable with other systems, which is 0.0050 ± 0.0018 F14C or 34,000–47,000 yr BP, which allows for the routine measurement of both of small environmental and archeological samples.

Considerable effort has been devoted recently to replace platinum-based catalysts with their non-noble-metal counterparts in the oxygen reduction reaction (ORR) in fuel cells. Nitrogen-doped carbon structures emerged as possible candidates for this role, and their earth-abundant metal-decorated composites showed great promise. Here, we report on the simultaneous formation of nitrogen-doped graphene and iron nitride from the lyophilized mixture of graphene oxide and iron salt by high-temperature annealing in ammonia atmosphere. A mixture of FeN and Fe2N particles was formed with average particle size increasing from 23.4 to 127.0 nm and iron content ranging from 5 to 50 wt %. The electrocatalytic oxygen reduction activity was investigated via the rotating disk electrode method in alkaline media. The highest current density of 3.65 mA cm–2 at 1500 rpm rotation rate was achieved in the 20 wt % catalyst via the four-electrode reduction pathway, exceeding the activity of both the pristine iron nitride and the undecorated nitrogen-doped graphene. Since our catalysts showed improved methanol tolerance compared to the platinum-based ones, the formed non-noble-metal system offers a viable alternative to the platinum-decorated carbon black (Pt/CB) ORR catalysts in direct methanol fuel cells.

A green and facile method has been developed for the preparation of in situ immobilized gold nanoparticles (AuNPs) using agarose as a reducing and stabilizing agent. The size of the synthesized AuNPs ranges between 10 and 100 nm, and their average size can be controlled by the concentrations of the agarose and gold salt. The agarose matrix as a mild and green reaction medium can provide a good dispersion environment for forming AuNPs, and the hydrogel can be well homogenized with polyacrylic macroporous microbeads as well, which can adsorb and stabilize the particles leading to the simultaneous synthesis and immobilization of AuNPs avoiding harmful inorganic compounds or organic solvents. The supported gold nanocatalyst was successfully applied as a catalyst in packed bed reactors for efficient NaBH4-mediated reduction of p-nitrophenol in continuous-flow mode.

Biomass is of growing interest as a secondary energy source and can be converted to fuels with higher energy density especially by pyrolysis or gasification. Understanding the mechanism and the kinetics of biomass pyrolysis (thermal decomposition) and gasification (conversion of organic material to gases) could be the key to the design of industrial devices capable of processing vast amounts of biomass feedstock. In our work real product components obtained in pyrolysis were took into consideration as well as char and oil as lumped components, and the kinetic constants for a biomass model compound (cellulose) pyrolysis and gasification were identified based on a proposed simplified reaction mechanism within a compartment model structure. A laboratory scale reactor was used for the physical experiments containing consecutive fast pyrolysis and gasification stages using alkali metal (K) containing feedstock, which has a significant effect on the cellulose pyrolysis and gasification. The detailed model was implemented in MATLAB/Simulink environment, and the unknown kinetic parameters were identified based on experimental data. The model was validated based on measurement data, and a good agreement was found. Based on the validated first principle model the optimal parameters were determined as 0.15 mL/min steam flow rate, and 4% K content.

In polymer technologies, various particle shapes and size distributions can be found. One of these are heterodisperse polymer beads. The capabilities of polymer swelling can be used in industries, e.g in the production of ion-exchange resins, to intensify specific technological steps such as sulphonation in the manufacturing process of ion-exchange resins. According to the literature different approaches can be used to create models for describing the behavior of disperse systems, of which the simplest models are the particle size distribution models for a given state of the solid phase. The aim of our examination was to compare and evaluate these simple models in terms of modeling polymer swelling. Hence, most of these models examine how each of the investigated models can be applied to approximately describe growth in a heterodisperse polymer system and how the identified model parameters in each time step could be interpreted. All the models were fitted to generate particle size distributions based on a swelling rate constant. The swelling of a styrene divinylbenzene-based copolymer was chosen as the basis of our examination. A model is proposed that is capable of describing the changes in the size of beads over time in this system.

The IFMIF-DONES (International Fusion Materials Irradiation Facility-Demo Oriented NEutron Source) test cell (TC) biological shielding is responsible of providing sufficient protection for the surrounding rooms and cells from intensive neutron irradiation and gamma radiation from inside of the TC. The TC biological shielding is composed of surrounding shielding walls, two top shielding plugs, six piping and cabling plugs (PCPs), TC floor, and removable shielding materials below the TC floor. Based on the previous TC configuration, the design of the lower shielding plug has been further developed by defining the specifications of embedded helium active cooling systems with the support of neutronic simulations, CFD analysis, and remote handling requirements. The PCP design is updated to provide sufficient space for pipe and cable connections. A preliminary piping of the water cooling system inside the heavy concrete shielding walls has been performed to qualify the capability of removing volumetric nuclear heating during irradiation experiments. The geometry of TC surrounding shielding walls are adjusted according to the latest design of PCPs and LSP as well as the requirements of the active cooling pipes which are embedded in the TC surrounding walls.

The biocomponent ratio in liquid fuels as well as the usage of renewable resources for fuel consumption in the transport sector needs to be increased as a result of EU directive 2003/30/EC. Based on radiocarbon (14C) measurements, it should be relatively simple and fast to measure the weight percentage of the fossil and biological sources by accelerator mass spectrometry (AMS) as recommended in the ASTM D 6866-12 and EN 16640 standards. In this study, a relatively easy and fast sample preparation and measurement method based on AMS measurements was developed at the Hertelendi Laboratory of Environmental Studies (HEKAL) using reference samples from the Hungarian MOL Nyrt. oil company. Considering the recent EU regulation for mixing rates of liquid fuels in the transport sector (0.7–2% biofuel content) and the projected higher rates (2–10% biofuel content), the method is applicable to determine fatty acid methyl ester (FAME) and/or hydrotreated vegetable oil (HVO) derived proportions of fuel blends with a 1σ uncertainty better than±0.3% m/m.

Nitrogen‐doped, bamboo‐like carbon nanotubes (BCNTs) were synthesized from butylamine by catalytic chemical vapor deposition (CCVD method). The nanotubes were oxidized by H2SO4/HNO3 treatment and used to prepare calcium alginate gelled BCNT spheres. These beads were first carbonized and then Pd, Rh and Ni nanoparticles were anchored on the surface of the spheres. These systems were then applied as catalysts in CO2 hydrogenation. The BCNT support was examined by Raman spectroscopy, dynamic light scattering (DLS) and X‐ray photoelectron spectroscopy (XPS). The prepared catalysts were characterized by HRTEM and SEM. The oxidation pretreatment of BCNTs was successful, with the electrokinetic potential of the water‐based dispersion of BCNTs measuring −59.9 mV, meaning the nanotube dispersion is stable. Pyridinic and graphitic types of incorporated nitrogen centers were identified in the structure of the nanotubes, according to the XPS measurements. The Pd‐containing BCNT sphere catalyst was the most efficient in the catalytic studies. The highest conversion was reached on the Pd catalyst at 723 K, as well as at 873 K. The difference in the formation rate of CO was much less at 873 K between the Pd and Rh compared to the 723 K values. Accordingly, the application of Pd‐containing BCNT/carbon‐supported catalyst favored the generation of CO. However, the Ni‐BCNT/carbon catalyst leads to the formation of CH4 as the major product.

Chlorine-free Platinum/nitrogen-doped graphene oxygen reduction reaction catalysts were synthesized by a one step method of annealing a mixture of platinum acetylacetonate and graphene oxide under ammonia atmosphere. Nanoparticles with close to the ideal particle size for oxygen reduction reaction (ORR) were formed, i.e., with diameter of 3–4 nm (500 and 600 °C) and 6 nm (700 °C). X-ray photoelectron spectroscopy confirmed the successful introduction of both pyridinic and pyrrolic type nitrogen moieties into the graphene layers, which indicates a strong interaction between the nanoparticles and the graphene layers. The electrocatalytic activity of glassy carbon electrodes (GCE) modified with the synthesized Pt/NG samples for oxygen reduction was compared to that of a platinum/carbon black catalyst modified electrode in acidic and alkaline media. Based on the measured limiting current densities and calculated electron transfer number, the highest activity was measured in acidic and alkaline media on the samples annealed at 600 and 700 °C, respectively.

Four Pd-Cu-based (2:1 wt.%) catalysts for water denitration, differing in physico-chemical characteristics and structural quality, were prepared, using carbon nanotubes (CNTs) as supports. The extent of lattice defects in the pristine CNTs turned out to govern resulting varieties of Pd nanoparticle size and the composition of the bimetallic (Pd:Cu) entities in the catalysts, playing an important role in nitrate reduction. Catalyst samples characterized by close proximity of Pd and Cu, as in an alloy, displayed the highest degree of nitrate conversion. At the same time, the size of the Pd particles, alone, or decorated to different extents with Cu atoms, was found to be critical for the second step of denitration reaction, directing the formed nitrite to either N2 or NH3. Water denitration is a structure sensitive reaction related to Pd particle size, and this effect is further emphasized in the decoration of the particle by the incorporation of Cu atoms into Pd particle corners and edges.

Alternative methods, including green synthetic approaches for the preparation of various types of nanoparticles are important to maintain sustainable development. Extracellular or intracellular extracts of fungi are perfect candidates for the synthesis of metal nanoparticles due to the scalability and cost efficiency of fungal growth even on industrial scale. There are several methods and techniques that use fungi-originated fractions for synthesis of gold nanoparticles. However, there is less knowledge about the drawbacks and limitations of these techniques. Additionally, identification of components that play key roles in the synthesis is challenging. Here we show and compare the results of three different approaches for the synthesis of gold nanoparticles using either the extracellular fraction, the autolysate of the fungi or the intracellular fraction of 29 thermophilic fungi. We observed the formation of nanoparticles with different sizes (ranging between 6 nm and 40 nm) and size distributions (with standard deviations ranging between 30% and 70%) depending on the fungi strain and experimental conditions. We found by using ultracentrifugal filtration technique that the size of reducing agents is less than 3 kDa and the size of molecules that can efficiently stabilize nanoparticles is greater than 3 kDa.

Our study shows a one-year-long, monthly integrated continuous monitoring campaign of gaseous radiocarbon emission and ambient air compared with 4 event-like, weekly (168 h) atmospheric aerosol radiocarbon data in every season of 2019, at 4 locations (n = 16 aerosol sample) around the Paks Nuclear Power Plant, Hungary. The study shows the first aerosol radiocarbon results around a nuclear power plant measured by accelerator mass spectrometry in Hungary. There was no dominant contribution detected in the atmospheric CO2 gas fraction, but we could detect excess radiocarbon in the total gaseous carbon fraction at almost every sampling point around the Paks Nuclear Power Plant. The highest Δ14C value in the total gaseous carbon form was 157.9 ± 4.6‰ in November and the highest Δ 14C value in the CO2 fraction was 86.1 ± 4.0‰ in December during 2019. Observed 14C activity excess is not higher than previously published values around the Paks Nuclear Power plant at the same sampling points (Molnar et al., 2007; Varga et al., 2020). Our aerosol radiocarbon measurements show that there is no significant contribution from the nuclear power plant to the atmospheric PM10 fraction. We could not detect a Δ 14C value higher than 0‰ in any season. The results show that the simple aerosol sampling, without pre-treatment of the filters, is appropriate for the measurement of excess radiocarbon at the vicinity of nuclear power plants. The applied preparation and measurement method can be applicable for detection of hot (14C) particles and early identification of radiocarbon emission from nuclear power plants in the PM10 fraction.

In the search for stable, visible light active photoelectrodes, hydrothermally synthesized tungsten oxide nanowires were modified via nitrogen incorporation into their structure. To this end, nanowires were heat-treated in ammonia/nitrogen atmosphere at different temperatures. This procedure caused transitions in their structure that were investigated along with the photoelectrochemical properties of the samples. Results were subsequently compared to the reference samples treated in inert nitrogen atmosphere. Morphological changes and structural transitions were followed by transmission and scanning electron microscopy and X-ray diffraction. Bandgap energies were determined from the UV–vis spectra of the materials, while photoelectrochemical properties were tested by linear sweep photovoltammetry and electrochemical impedance spectroscopy. Pristine tungsten oxide nanowires were first transformed into tungsten oxynitride and then tungsten nitride during high-temperature calcination in ammonia atmosphere. Electron microscopic investigation revealed that, along with phase transition, the initial fibrous morphology gradually converted into nanosheets. Simultaneously, bandgap energies significantly decreased in the calcination process, too. Photoelectrochemical measurements demonstrated that photoactivity in the treated samples was not improved by the decrease of the bandgap. This behavior might be explained with the deterioration of charge carrier transport properties of the materials due to the increased number of structural defects (acting as trap states), and current ongoing work aims to verify this notion.

The so-called “lumping approach” is widely used to study complex processes such as hydrocracking of vacuum residue. In order to describe the composition changes in such systems, not only must the kinetic parameters be determined, but the lumped reactions that occur should also be identified. In this study, the modeling of catalytic hydrocracking of vacuum gas oil has been carried out using six component lumps. Three different identification strategies have been developed to determine the reaction subnetwork containing a given number of reaction pathways that provides the data fit. The strategies were compared according to their tendency to provide increasingly better results, as a function of the number of reactions present. Although, in this way, 40% of the original reaction superstructure was eliminated from the system, the kinetic parameters of the remaining reactions still could not be identified with complete certainty. Hence, the linearized state-space model representations of the reaction networks ...

Scrubbing of hydrocarbon-based gases such as natural gas or biogas is essential prior to its use. These gas mixtures when contaminated with hydrogen sulfide cause safety, environmental, and corrosion problems in pipelines. There are several methods of reducing the content of hydrogen sulfide in sour gases, but few of these are selective as well. Selectivity is important to avoid unnecessary chemical usage. Chemisorption in sodium hydroxide solution by applying a special spray technique appears to be an efficient and selective method for hydrogen sulfide removal. This study aims to determine the characteristic of system and thereby facilitating the design of gas-cleaning parameters. The studied parameters include the contact time, concentration of sodium hydroxide, absorbent volumetric flow rate, and gas composition. Model gas mixtures of hydrogen sulfide, carbon dioxide, and nitrogen were used for experiments. To define the optimal experiment setup, the Box–Behnken design (BBD) method was applied. Based o...

Heterocatalytic oxidation of HCl into Cl2 (HCl conversion process) over a CeO2–CuO catalyst in a fixed-bed reactor has been optimized using four different objective functions and three different methods. For a given residence time, the HCl conversion could be maximized in various reactor configurations, namely with the application of a graded catalyst bed, with partitioning the reactor shell and using multistage temperature control, or with the combination of both methods. However, as the obtained temperature profiles differed considerably from each other, we considered three objective functions in order to smooth the reactor temperature profile. These implement a nonconventional approach since the proposed objective functions aim to deal directly with the temperature changes and HCl conversion is only taken into consideration as a nonlinear constraint. The different results from each method and objective function were compared using the apparent temperature gradients along the length of the reactor. The ...

Boron doped titanate nanoparticles were prepared from protonated (H-form) titanate nanotubes (TiONT) and nanowires (TiONW). The chemical nature and morphology of boron were monitored by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). XPS proved that significant part of the boron incorporated into interstitial position (Ti O B) of titanate nanotubes and nanowires, while a smaller part of the boron formed boron titanates via ion-exchange process. In the case of titanate nanotubes the presence of boron induced morphological (tubular to rod-like) and structural (trititanate to anatase) changes. These effects were not so pronounced on titanate nanowires.

A three-year-long methane mole fraction and d13CCH4 measurement campaign was performed at the Hungarian tall tower station, Hegyhátsál, between 2013-2016. The results were compared with that of two NOAA atmospheric monitoring sites Mace Head and Zeppelin to determine the continental methane excess and the relative isotopic shift. The data then were used for bac trajectory analyses to identify potential methane source regions in Europe coupled with d13CCH4 results. The Hungarian station can be separated from the coastal and polar areas based on the mole fraction results having higher maxima and seasonal amplitude, but the d13CCH4 results match well with the NOAA stations’ results. Our study shows that although the local, regional anthropogenic and natural sources are major influences, more distant regions can also influence the measured CH4 level and d13CCH4 signal in the Pannonian Basin.

Fine-fraction aerosol samples were collected, and air pollutants and meteorological properties were measured in situ in the regional background environment of the Carpathian Basin, a suburban area and central part of its largest city, Budapest, in each season for a 1-year-long time interval. The samples were analysed for PM2.5 mass, organic carbon (OC), elemental carbon (EC), water-soluble OC (WSOC), radiocarbon, levoglucosan (LVG) and its stereoisomers, and some chemical elements. Carbonaceous aerosol species made up 36 % of the PM2.5 mass, with a modest seasonal variation and with a slightly increasing tendency from the regional background to the city centre (from 32 % to 39 %). A coupled radiocarbon-LVG marker method was applied to apportion the total carbon (TC = OC + EC) into contributions of EC and OC from fossil fuel (FF) combustion (ECFF and OCFF, respectively), EC and OC from biomass burning (BB) (ECBB and OCBB, respectively), and OC from biogenic sources (OCBIO). Fossil fuel combustion showed rather constant daily or monthly mean contributions (of 35 %) to the TC in the whole year in all atmospheric environments, while the daily contributions of BB and biogenic sources changed radically (from  % up to 70 %–85 %) at all locations and over the years. In October, the three major sources contributed equally to the TC in all environments. In January, it was the BB that was the major source, with a share of 70 % at all sites. The contributions from biogenic sources in January were the smallest. In April, FF combustion and biogenic sources were the largest two contributors at all locations with typical shares of 45 %–50 % each. In July, biogenic sources became the major source type with a monotonically increasing tendency (from 56 % to 72 %) from the city centre to the regional background. The share of BB was hardly quantifiable in July. The ECFF made up more than 90 % of EC in April and July, while in October and January, the contributions of ECBB were considerable. Biomass burning in winter and autumn offers the largest and most considerable potential for improving the air quality in cities as well as in rural areas of the Carpathian Basin.

Recently, there has been an increasing interest in the application of nanotubular structures for drug delivery. There are several promising results with carbon nanotubes, however, in light of some toxicity issues, the search for alternative materials has come into focus. The objective of the present study was to investigate the influence of the applied solvent on the composite formation of titanate nanotubes (TNTs) with various drugs in order to improve their pharmacokinetics, such as solubility, stability, and bioavailability. Composites were formed by the dissolution of atenolol (ATN) and hydrochlorothiazide (HCT) in ethanol, methanol, 0.01 M hydrochloric acid or in ethanol, 1M sodium hydroxide, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), respectively, and then they were mixed with a suspension of TNTs under sonication for 30 min and vacuum-dried for 24 h. The structural properties of composites were characterized by SEM, TEM, FT-IR, differential scanning calorimetry (DSC), thermogravimetric (TG) analysis, and optical contact angle (OCA) measurements. Drug release was determined from the fast disintegrating tablets using a dissolution tester coupled with a UV&ndash, Vis spectrometer. The results revealed that not only the good solubility of the drug in the applied solvent, but also the high volatility of the solvent, is necessary for an optimal composite-formation process.

Catalytic systems prepared by controlled processes play an important role in the utilization of CO2 via catalytic hydrogenation to produce useful C1 chemicals (such as CO, CH4 and CH3OH), which will be vital for forthcoming applications in energy conversion and storage. Size controlled Pt nanoparticles were prepared by a polyol method and deposited on H-ZSM-5 (SiO2/Al2O3 = 30, 50, 80 and 280) zeolite supports. The prepared catalysts were tested for the CO2 hydrogenation in the temperature range of T = 473–873 K and ambient pressure, with CO2/H2 = 1:4. Size-controlled Pt nanoparticles boosted the catalytic activity of the pure H-ZSM-5 zeolites resulted in ~16 times higher CO2 consumption rate. The activity were ~4 times higher and CH4 selectivity at 873 K was ~12 times higher over 0.5 % Pt/ H-ZSM-5 (SiO2/Al2O3 = 30) compared to 0.5 % Pt/H-ZSM-5 (SiO2/Al2O3 = 280). In situ DRIFTS studies assuming the presence of a surface comlex in which the CO is perturbed by hydrogen and adsorbes via C-end on Pt but the oxygen tilts to the protons of the zeolite support.

In this study, PM2.5 aerosol samples collected continuously in Debrecen, Hungary from December 2011 to July 2014 were processed and analysed. Mass concentration and ratios of PM2.5 aerosol, organic and elemental carbon fractions, in addition, radio and stable carbon isotopes were evaluated together to obtain a better sight into the possible local and regional sources. For the studied period, the mean mass concentration of PM2.5 aerosol and the constituting total, organic and elemental carbon were 23.6, 5.8, 5.0 and 0.8 μg m−3, respectively. In all cases, the mean for the heating periods were on average 2–3 times that of the vegetation (i.e. heating-free) periods. The relatively high mean secondary organic carbon concentration of 4.1 μg m−3 and OC/EC ratio of 6.9 suggested the dominance of combustion processes in winter and, based on the higher contemporary carbon fraction of 0.77, wood fuels prevailed over coal or oil. The average δ13C of the tested wood fuels implies that combustion of black locust, oak and beech was a significant factor in forming the mean δ13C of PM2.5 of −25.6‰ during the heating months. The mean δ13C of −26.7‰ in summer was more influenced by emissions from transportation and the surrounding vegetation. In addition, using coupled backward trajectory modeling (HYSPLIT) and visualization of open fire events (FIRMS), we presume that the conspicuously enriched δ13C values of PM2.5 collected in October of the observation years were probably caused by long-range transport of particles derived from agricultural combustion of C4 plants close to the southern and eastern Hungarian borders.

The current article aims to study the influence of pH, temperature, and oxidant concentrations on the dissolution process of metals from liquid crystal display (LCD) boards in a Na2S2O8 environment...

Extremely high specific surface area mesoporous carbon-supported Pd nanoparticle catalysts were prepared with both impregnation and polyol-based sol methods. The silica template used for the synthesis of mesoporous carbon was removed by both NaOH and HF etching. Pd/mesoporous carbon catalysts synthesized with the impregnation method has as high specific surface area as 2250 m 2 /g. In case of NaOH-etched impregnated samples, the turnover frequency of cyclohexene hydrogenation to cyclohexane at 313 K was obtained ~ 14 molecules ∙ site − 1 ∙ s − 1 . The specific surface area of HF-etched samples was higher compared to NaOH-etched samples. However, catalytic activity was ~ 3–6 times higher on NaOH-etched samples compared to HF-etched samples, which can be attributed to the presence of sodium and surface hydroxylgroups of the catalysts etched with NaOH solution.

The purpose of this study is to provide an accurate kinetic description for the dissolution process of metals found in WEEE, such copper, zinc, and brass, using persulfate as a leaching oxidant. The factors affecting the performance and efficiency of the leaching process, such as stirring speed, persulfate concentration and temperature were separately investigated. It was observed that the leaching rate of the metals increased with the increase of temperature and persulfate concentration. We propose three models which accurately describe the variation in the surface of the solid for two kinds of geometries, a rectangular block, in the case of pure zinc dissolution, and a cylindrical rod for pure copper and brass dissolution. The apparent activation energy for the leaching of pure copper and zinc has been evaluated using Arrhenius expression and has been determined to be 5.2 × 10 4 J mol −1 for copper and 3.5 × 10 4 J mol −1 for zinc, in the range between 30 and 60 °C. The third model which describes the dissolution of brass has provided the best results.

Both animal and human studies suggest that in adulthood, plasma vasopressin level correlates well with anxiety. Little is known about the mood regulation during the perinatal period. Here, we aim to investigate the influence of vasopressin on anxiety during the early postnatal age. As a sign of distress, rat pups emit ultrasonic vocalizations (USVs) when they are separated from their mother. This USV was detected in 7- to 8-day-old vasopressin-deficient Brattleboro pups, and they were compared to their heterozygote littermates and wild-type pups. The results were confirmed by V1b antagonist treatment (SSR149415 10 mg/kg ip 30 min before test) in wild-types. Chlordiazepoxide (3 mg/kg ip 30 min before test)-an anxiolytic-was used to test the interaction with the GABAergic system. At the end of the test, stress-hormone levels were measured by radioimmunoassay. Vasopressin-deficient pups vocalized substantially less than non-deficient counterparts. Treatment with V1b antagonist resulted in similar effect. Chlordiazepoxide reduced the frequency and duration of the vocalization only in wild-types. Reduced vocalization was accompanied by smaller adrenocorticotropin levels but the level of corticosterone was variable. Our results indicate that the anxiolytic effect of vasopressin deficiency (both genetic and pharmacological) exists already during the early postnatal age. Vasopressin interacts with the GABAergic system. As mood regulation does not go parallel with glucocorticoid levels, we suggest that vasopressin might have a direct effect on special brain areas.

International audience; Pyrolysis of waste polymers looks attractive way for their transforming into valuable hydrocarbons. Due to the high number of reactions, the detailed kinetic modeling of the pyrolysis process is often not feasible. Hence the so-called lumping technique is often used to study these complex systems. In this study, the pyrolysis reactions were modeled in a two stage laboratory scale batch reactor using five component lumps. For pyrolysis the mixtures of real plastic waste were used. Kinetic parameters were identified and the model results were compared to the experimental results. It was found that the suggested model can properly describe the dynamic behavior of the reactor under semi batch conditions.

Recycling of waste electrical and electronic equipment (WEEE) is important not only to reduce the amount of waste requiring treatment, but also to promote the recovery of valuable materials. Implementation of the European Directive on WEEE and recycling targets imposed in the European Union will require new processes to be developed and applied to recover metals from WEEE. This study aims to provide an alternative process for the dissolution of metals from WEEE which contains Cu and Zn based on our previous research. The effects of leaching parameters, such as temperature, Na2S2O8 concentration, and leaching time, were separately investigated on leaching of copper, zinc, and brass (alloy composition −35% zinc and 65% copper) in Na2S2O8 solution (0.1, 0.2 and 0.3 M). Box–Behnken experimental design (BBD) method was used to determine the number and the condition of necessary leaching experiments. Statistical analysis of variance (ANOVA) was performed to see whether process parameters such as leaching time, ...

Atmospheric air samples were collected at 9 monitoring stations (A1 to A9) less than 2 km from the Paks Nuclear Power Plant (Paks NPP) and a background station (B24). The monthly integrated CO2 and total carbon (CO2+hydrocarbons (CnHm)) samples were collected to determine the excess 14C activity at the vicinity of the NPP. The measurements providing the 14C/12C ratio of the monthly integrated samples were carried out on a MICADAS type AMS at HEKAL. Due to the relatively low 14CO2 emission of PWR type Paks reactors and the local Suess effect, there was negligible excess 14C activity at the investigated stations in the pure CO2 fraction during the investigated 2 years period (2015–2016). On the contrary, there was a detectable (although minor) excess at every station in the CnHm fraction. In case of CO2, the average Δ14C excess was 3.8‰ and the highest measured value was 91.2‰ at the A3 station in February 2015. In case of CnHm, the average excess was 31.1‰ and the highest measured value was 319.1‰ at the A4 station in February 2016. We applied PC-CREAM 08 modelling to investigate the observed excess 14C activity at the environmental sampling stations, which depends on the distance from the NPP and the meteorological conditions, such as wind direction and wind speed. Meteorology data was collected at the operating area of the Paks NPP in a meteorology tower. The direct C-14 emission through the 120 m high stacks was measured in the NPP by liquid scintillation counting. These emission data and our model calculations explain the excess activity in the CnHm fraction at the A4 station, which is located only 915 m far from the NPP's stacks in the prevailing wind direction. The excess activity at A3 station (the farthest unit) probably came from the nearby NPP wastewater discharge point. The recently observed average excess and highest excess data is similar to the published data in former studies (Molnar et al., 2007; Veres et al., 1995) on Paks NPP, the highest 14CO2 and 14CnHm excess are just a little higher than it was in the earlier studies, but in these former studies, the A3 station was not equipped with a radiocarbon monitoring unit and the level of radiocarbon emission was almost invisible from the wastewater discharge point.

The leaching kinetics of copper and zinc from brass was investigated in sodium persulfate solution. The factors affecting the performance and efficiency of the leaching process, such as leaching time, acid concentration and temperature were separately investigated. The obtained results revealed that copper and zinc are successfully dissolved in a persulfate environment, especially for high temperature (60 °C) and oxidant concentration (0.3 M Na 2 S 2 O 8 solution). To define the exact geometry changes that appear a shrinking core model can be used. With the determination of pre- exponential constants, activation energies and reaction orders, the concentration and temperature dependence can be examined. The identified kinetic model can be used for describing similar processes involving dissolution of metals or alloys.

Intramolecular conjugate addition of the oxime from aldehyde 5 led to the formation of cyclic nitrone 6. 1,3-Dipolar cycloaddition of the latter with methyl acrylate gave the bicyclic 7 with high diastereoselection. Subsequent four-step transformation of 7 resulted in the tetrahydroxyindolizidine derivative 11.