Microwave (MW) assisted processes become more and more used in the synthesis and alteration of graphene materials. This technique brings some various advantages compare to the classical ones because it is a green, low-cost, environmentally-friendly process. Moreover, no toxic solvent is necessary for the production of high-quality graphene-based materials. This eco-friendly process has recently received important attention as uniform, fast, energy efficient and scalable approach to synthesis noble metals supported on graphene oxide. A facile, rapid, low cost and efficient method to prepare gold supported on reduced graphene oxide (Au/rGO) is presented in this paper. The Au/rGO samples were produced using the microwave power of 800 W and two temperatures, 60 and 80°C, for 30 minutes only. The physical characterization showed that the Au nanoparticles were grafting on the graphene surface. Additionally, the nitrogen adsorption–desorption isotherms show a high pore volume and specific surface suggesting that a larger mesoporous volume have been achieved. The presence of interconnections between micropores and mesopores is beneficial to the mass transport process in PEMFC by creating a facile access of the reactants. Moreover, the accelerated stability tests (AST) of the catalysts showed that the catalysts are stable and no remarkable change in the shape of the voltammetry curve could be observed after 200 cycles.
The clarity of the beer is essential to its marketability and good consumer approval. Moreover, the beer filtration aims to remove the unwanted constituents that cause beer haze formation. Natural zeolite, an inexpensive and widespread material, was tested as a substitute filter media for diatomaceous earth in removing the haze constituents in beer. The zeolitic tuff samples were collected from two quarries in Northern Romania: Chilioara, in which the zeolitic tuff has a clinoptilolite content of about 65%, and the Valea Pomilor quarry, containing zeolitic tuff with a clinoptilolite content of about 40%. Two-grain sizes, <40 and <100 µm, from each quarry were prepared and thermally treated at 450 °C in order to improve their adsorption properties and remove organic compounds and for physico-chemical characterization. The prepared zeolites were used for beer filtration in different mixtures with commercial filter aids (DIF BO and CBL3) in laboratory-scale experiments, and the filtered beer was characterized in terms of pH, turbidity, color, taste, flavor, and concentrations of the major and trace elements. The results showed that the taste, flavor, and pH of the filtered beer were generally not affected by filtration, while turbidity and color decreased with an increase in the zeolite content used in the filtration. The concentrations of Na and Mg in the beer were not significantly altered by filtration; Ca and K slowly increased, while Cd and Co were below the limits of quantification. Our results show that natural zeolites are promising aids for beer filtration and can be readily substituted for diatomaceous earth without significant changes in brewery industry process equipment and protocols for preparation.
ABSTRACT. The Lower Danube Basin covers the Romanian-Bulgarian sub-basin downstream from Cazane Gorge and the sub-basins of the Siret and Prut rivers. To extensively survey the Romanian nuclear power plant impact on the Danube water, tritium and radiocarbon baseline values are required. Therefore, the reported study tried to establish these values based on a 2-yr sampling campaign covering 975 km of the Danube from Cazane Gorge to Tulcea. The tributaries Cerna, Jiu, Olt, and Arges were also included in this study. During the sampling campaigns, tritium concentration of different sampling locations showed values between 7 ± 2.1 and 33.5 ± 2.3 TU. Measured 14 C activity for the same locations ranged between 88.45 ± 1.46 and 112.36 ± 1.56 pMC. Lower values were recorded for tributaries: between 8.3 ± 2.1 and 12.2 ± 2.2 TU for tritium and between 67.3 ± 1.29 and 86.04 ± 1.42 pMC for 14 C. Despite the nuclear activity in the observed areas, tritium and 14 C activities presented slightly higher values for specific locations without any influence on Danube River water. INTRODUCTIONRivers are important freshwater sources, and much of the world's population has relied on rivers for its development. In recent years, many international and national hydrology research programs have focused on large river basins. In humid basins, precipitation processes are the primary signal traced by river discharge. Evidence that precipitation input signals are not static is found from long-term isotope records of European rivers. Interannual variations of these processes reflect the inherent decadal variability of precipitation processes. Comparing tritium levels in the Danube River with tritium levels in precipitation at Vienna (Rank et al. 1998) reveals that not only short-term signals but also long-term changes in the isotope ratio of precipitation are transmitted through the catchments and can be detected in river water. A comparison of measured and modeled 3 H contents in the Danube River revealed that the best fit that could be obtained (mean residence time of 3 yr) is still not satisfactory (Rank et al. 2005).The Danube River Basin is the second largest river basin in Europe, covering 801,463 km 2 (ICPDR 2005). It lies west of the Black Sea in central and southeastern Europe. Due to its geological and geographical conditions, the Danube River Basin can be divided into 3 main parts: the Upper, Middle, and Lower Danube Basin. About 65% of the Lower Danube Basin forms the natural border between Romania and Bulgaria. Two important nuclear power plants (NPP) for both countries are found in this region: Kozloduy NPP and Cernavoda NPP. Both countries consider nuclear energy to be a potential energy solution for future economic development. In fact, nuclear power generates between 10% and 45% of the electricity for the Danube riparian countries. Therefore, Romania has already built a new CANDU (CANada Deuterium Uranium)-type unit in Cernavoda, which was put into operation in 2007, and Bulgaria started negotiations for a new NPP in Belene...
The quenching properties of nitromethane, nitric acid, acetone and saturated solutions of chloroform, carbon tetrachloride, dichloro-methane, and a blend of carbon tetrachloride and chloroform mixed with an Ultima Gold uLLT liquid scintillation cocktail were investigated by using a Quantulus 1220 as well as TRICARB 2800TR liquid scintillation counters. With respect to all investigated quenching agents, nitromethane showed higher quenching action and solubility as well as a remarkable time stability. The implications of this finding for further routine tritium determinations are presented and discussed.
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