Functional groups of the activated carbon play the major role in metals removal from aqueous solutions and, for this reason, different treatments can be used to modify the adsorbent surface improving ...the adsorption capacity for a particular pollutant. In this research, oxidation with nitric acid, heating under an inert atmosphere, and ammonia treatment were applied to modify the activated carbon surface. The modified adsorbents were used for the removal of hexavalent chromium (Cr(VI)) from aqueous solutions at different concentrations (10–500 mg L−1), pH 6, and 25 °C. Adsorption mechanisms of Cr(VI) on the activated carbon were proposed based on the surface chemistry, adsorption/reduction, and desorption experiments. Findings demonstrate that acid functional groups of the activated carbon had an important effect on the hexavalent chromium removal. For instance, a high reduction of Cr(VI) to Cr(III) (50%) was obtained by the oxidized adsorbents, whereas the heat treated adsorbents achieved a low reduction (35%), but the ammonia-treated activated carbon achieved the lowest reduction (20%). The heat-treated adsorbent showed the best Cr(VI) adsorption capacity (48 mg g−1), especially at equilibrium Cr(VI) concentration lower than 200 mg L−1, and the fastest adsorption kinetics among the studied adsorbents. Furthermore, the highest Cr(VI) desorption (90%) was achieved with 0.1 N NaOH-NaCl solutions. In summary, an anionic/reduction coupled adsorption mechanism of Cr(VI) seems to be feasible, and the heat-treated activated carbon is an interesting option for sequestering Cr(VI) species from aqueous effluents.
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•Acid functional groups play the major role in the reduction of Cr(VI) to Cr(III).•Heat-treated adsorbent showed the best Cr(VI) adsorption and desorption capacity.•Basic functional groups enhance the adsorption of Cr(VI) species by electrostatic interactions.•Cr(VI) removal is carried out by anionic/reduction coupled adsorption mechanisms.
Since global reanalysis datasets first appeared in the 1990s, they have become an essential tool to understand the climate of the past. The wind power industry uses those products extensively for ...wind resource assessment, while several climate services for energy rely on them as well. Nowadays various datasets coexist, which complicates the selection of the most suitable source for each purpose. In an effort to identify the products that best represent the wind speed features at turbine hub heights, five state‐of‐the‐art global reanalyses have been analysed: ERA5, ERA‐Interim, the Japanese 55‐year Reanalysis (JRA55), the Modern Era Retrospective Analysis for Research and Applications‐2 (MERRA2), and the National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) Reanalysis 1 (R1). A multi‐reanalysis ensemble approach is used to explore the main differences amongst these datasets in terms of surface wind characteristics. Then, the quality of the surface and near‐surface winds is evaluated with a set of 77 instrumented tall towers. Results reveal that important discrepancies exist in terms of boreal winter seasonal means, interannual variability (IAV), and decadal linear trends. The differences in the computation of these parameters, which are mainly concentrated inland, reach up to the order of magnitude of the parameters themselves. Comparison with in situ observations shows that the ERA5 surface winds offer the best agreement, correlating and reproducing the observed variability better than a multi‐reanalysis mean in 35.1% of the tall tower sites on a daily time‐scale. However, none of the reanalyses stands out from the others when comparing seasonal mean winds. Regarding the IAV, near‐surface winds from ERA5 offer the values closest to the observed IAV.
The coexistence of several global reanalysis products challenges the selection of the most appropriate product to satisfy the reanalysis user needs. Here we consider a set of five state‐of‐the‐art global reanalyses to intercompare their wind data and eventually select the product that better represents the near surface wind speeds. The verification has been done using a set of 77 tall towers distributed worldwide, whose data have been exhaustively quality controlled for that purpose. Which reanalysis best represents near‐surface wind speeds?
► An increase in the degree of crosslinking affected the mechanical properties of films. ► The addition of essential oil improved the antimicrobial and barrier properties of films. ► Modifying the ...degree of crosslinking, it is possible to obtain an effective antibacterial alginate film.
Alginate films with different degrees of crosslinking obtained by internal gelation, and alginate films incorporated with oregano essential oil (OEO) were prepared. The impact of the degree of crosslinking caused by the use of calcium carbonate as crosslinking agent and the incorporation of OEO into the alginate films on their antibacterial, optical, mechanical, microstructural and water vapour barrier properties was evaluated.
An increase in the degree of crosslinking produced alginate films that were significantly thicker (0.031–0.038mm) and stronger (51.9–52.9MPa) but less elastic (2.3%) than those non-crosslinked films (0.029mm; 39.7MPa; 4.4%). The water vapour permeability (WVP) of the films decreased significantly only with the highest level of crosslinking.
The incorporation of OEO in alginate films affected significantly their physical properties. Thickness and percent elongation at break of the films were increased by the addition of OEO (0.036–0.042mm and 2.7–3.7%), while the tensile strength and water vapour permeability decreased (31.1–55.5MPa and 2.7–3.0×10−9g/msPa).
Films incorporated with OEO were more effective against Gram-positive bacteria (Staphylococcus aureus and Listeria monocytogenes) than Gram-negative bacteria (Escherichia coli and SalmonellaEnteritidis). A minimum concentration of 1.0% of OEO was necessary to ensure their antibacterial efficacy.
Diarylprolinol silyl ethers are among the most utilized stereoselective organocatalysts for the construction of complex molecules. With their debut in 2005, these catalysts have been applied in ...numerous method developments primarily leveraging enamine and iminium-ion catalysis. These strategies have extended into the preparation of complex molecules in both academic and industrial settings. This Review intends to give an overview of the application of the diarylprolinol silyl ether catalysts in total synthesis. Furthermore, integration of these catalysts in patent literature is also disclosed highlighting the versatility of the catalytic system.
Non-alcoholic fatty liver disease has become the leading liver disease in North America and is associated with the progressive inflammatory liver disease non-alcoholic steatohepatitis (NASH). ...Considerable effort has been made to understand the role of resident and recruited macrophage populations in NASH however numerous questions remain. Our goal was to characterize the dynamic changes in liver macrophages during the initiation of NASH in a murine model. Using the methionine-choline deficient diet we found that liver-resident macrophages, Kupffer cells were lost early in disease onset followed by a robust infiltration of Ly-6C+ monocyte-derived macrophages that retained a dynamic phenotype. Genetic profiling revealed distinct patterns of inflammatory gene expression between macrophage subsets. Only early depletion of liver macrophages using liposomal clodronate prevented the development of NASH in mice suggesting that Kupffer cells are critical for the orchestration of inflammation during experimental NASH. Increased understanding of these dynamics may allow us to target potentially harmful populations whilst promoting anti-inflammatory or restorative populations to ultimately guide the development of effective treatment strategies.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Improving Ammonia Production Using Zeolites Matito-Martos, I; García-Reyes, J; Martin-Calvo, A ...
Journal of physical chemistry. C,
08/2019, Letnik:
123, Številka:
30
Journal Article
Recenzirano
Odprti dostop
Ammonia is one of the most important compounds in the chemical industry as it is the main raw material in the production of fertilizers. Its production is achieved using the Haber–Bosch process, ...where nitrogen and hydrogen react in the presence of a catalyst producing a mixture containing ammonia. In this work we use molecular simulations to study the effect of confinement on the ammonia synthesis reaction in pure silica zeolites FER, MOR, MFI, BEA, LTA, and FAU. We calculated adsorption isotherms and isobars of the components resulting from the reaction for a wide range of values of pressure and temperature. The removal of the resulting ammonia will keep the equilibrium of the reaction favoring ammonia formation at lower values of pressure than in conventional plants. Among the studied zeolites, FAU and ITQ-29 are preferred for ammonia storage because of their higher adsorption capacity. The effect of confinement is proven to increase ammonia production, being the zeolites with the narrowest pores (FER and MFI) the ones that exhibit the highest conversion of the reactants. Besides, we found that the optimal working conditions for the production process in confinement are 573 K and 200 bar. At these particular conditions, the production of ammonia increases without the addition of any extra operational costs to the process.
A novel strategy for the direct enantioselective oxidative homocoupling of α‐branched aldehydes is presented. The methodology employs open‐shell intermediates for the construction of chiral ...1,4‐dialdehydes by forming a carbon–carbon bond connecting two quaternary stereogenic centers in good yields and excellent stereoselectivities for electron‐rich aromatic aldehydes. The 1,4‐dialdehydes were transformed into synthetically valuable chiral pyrrolidines. Experimental mechanistic investigations based on competition experiments combined with computational studies indicate that the reaction proceeds through a radical cation intermediate and that reactivity and stereoselectivity follow different trends.
Homocoupling? That's radical! A novel strategy for the direct enantioselective oxidative homocoupling of α‐branched aldehydes is presented. Studies indicate that the reaction proceeds through a radical cation intermediate and that reactivity and stereoselectivity follow different trends.
We are considering the propagation of circularly polarized light normally impinging on a cholesteric elastomer slab doped with metallic spheres. The slab is composed of two layers: the first layer is ...a right-handed chiral structure, and the second one is a helix with left-handedness; however, the pitch of the chiral structure remains constant. We performed a theoretical model to find numerically, reflection and transmission spectra for circularly polarized light impinging on the slab. We considered the effects of mechanical strains along the helical axis since the force exerted on the structure can tilt the mesogens in the slab along the helical axis. The Photonic Band-Gap(PBG) of the elastomer slab becomes narrowed because of the strain; there we also observe high reflectance (hyper-reflectivity) that depends on the filling factor of the silver doping and on whether the defect is located at a position that contains complete periods of the structure. Additionally, the spectra display reflection bands for both right- and left-polarized light. We expressed the PBG edges in terms of material parameters; this allows us to select the region of the electromagnetic spectrum for the reflection bands. This medium exhibits a hyper-reflective photonic band when the pitches of both right- and left-handed helical layers are identical.
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