Solid-state cross-polarization magic-angle spinning (CP/MAS) NMR spectra were recorded for the compounds [Ag(NH3)2]2SO4, [Ag(NH3)2]2SeO4 and [Ag(NH3))]NO3, all of which contain the linear or nearly linear two-coordinate [Ag(NH3)2]+ ion. The 109Ag CP/MAS NMR spectra show centrebands and associated spinning sideband manifolds typical for systems with moderately large shielding anisotropy, and splittings due to indirect 1J(109Ag,14N) spin-spin coupling. Spinning sideband analysis was used to determine the 109Ag shielding anisotropy and asymmetry parameters Deltasigma and eta from these spectra, yielding anisotropies in the range 1500-1600 ppm and asymmetry parameters in the range 0-0.3. Spectra were also recorded for 15N and (for the selenate) 77Se. In all cases the number of resonances observed is as expected for the crystallographic asymmetric units. The crystal structure of the selenate is reported for the first time. One-bond (107, 109Ag,15N) coupling constants are found to have magnitudes in the range 60-65 Hz. Density functional calculations of the Ag shielding tensor for model systems yield results that are in good agreement with the experimentally determined shielding parameters, and suggest that in the solid compounds Deltasigma and eta are reduced and increased, respectively, from the values calculated for the free [Ag(NH3)2]+ ion (1920 ppm and 0, respectively), primarily as a result of cation-cation interactions, for which there is evidence from the presence of metal-over-metal stacks of [Ag(NH3)2]+ ions in the solid-state structures of these compounds.
The focus of this study was the notched impact property of high-density polyethylene (HDPE)-organoclay composites and the resultant morphology of impact-fractured surfaces. Composites with a different organoclay content and degree of organoclay dispersion were compared with neat HDPE under identical conditions. The degree of organoclay dispersion was controlled through the use of a compatibilizer, maleic anhydride grafted polyethylene. It was found that the addition of organoclay can slightly increase the elastic modulus and notched impact strength of the composite. When the level of organoclay dispersion was improved by using compatibilizer, elastic modulus and toughness further increased. A significant increase in yield strength was also notable. The presence of organoclay was found to suppress strain hardening of the matrix during tensile testing. The impactfractured surfaces of failed specimens were studied with scanning electron microscopy. The micromechanism for the increased toughness of HDPE-organoclay composites was discussed.
Activated carbon can be prepared from any kind of hydrocarbon-based material, and that from agricultural wastes is attractive for many reasons. The use of natural fiber in various industries gives rise to some associated waste streams. In this work, activated carbon, produced from the non-fibrous material waste from pineapple leaf fiber production, was studied for its heavy metal adsorption behavior. The material was carbonized at different temperatures and chemical activation was carried out using phosphoric acid. Pore size and pore volume of the adsorbent were determined using the Brunauer–Emmett–Teller (BET) method, and surface morphology by scanning electron microscopy (SEM). Fourier Transform Infrared Spectrophotometry (FT-IR) was used to identify the functional groups in the material. It was found that the surface area, pore volume and morphology of the surface depended on the carbonization temperature. The best adsorbent was obtained using a carbonization temperature of 500 °C and an activation temperature of 600 °C. Adsorptions of several heavy metals were studied over the concentration range of 4 - 800 mg L−1 and pH 2-10. The optimum amount of the adsorbent was found to be 1.20 g per 100 ml of solution, removing up to 92.67% of lead ions. The adsorption behaviour was closer to the Freundlich isotherm than to the Langmuir isotherm. So this waste could be a useful bio-source for activated carbon production.
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