The effect of flame coal oxidation on the solid and soluble products of its extraction

Solid and soluble products of THF and CH₂Cl₂ extraction of flame coal oxidised by four different oxidising agents (peroxyacetic acid (PAA), 5% HNO₃, O₂/Na₂CO₃, air/125 °C) were studied by elemental analysis and FTIR. The extraction yield with THF was much higher than that with CH₂Cl₂ for all samples. The greatest changes in elemental composition were in the extracts from coal oxidised by nitric acid. The sulphur content was lowest in extracts from coal oxidised with 5% HNO₃ and PAA. FTIR confirmed that coal treatment with nitric acid incorporates nitrogen into the coal structure.     

Determination of chemical shift parameters from zeeman nuclear quadrupole resonance in single crystals

The components of the chemical shift tensor of the ³⁵Cl nuclei in paradichlorobenzene single crystal have been determined directly from Zeeman-split NQR spectra, with the magnetic field applied parallel to the principal axes of the electric-field-gradient tensor. The results are compared with values obtained by NMR in the pure quadrupole regime.     

The use of microwave radiation for obtaining carbonaceous adsorbents from biomass and their use in elimination of inorganic pollutants

A new technology of obtaining activated carbons by physical and direct activation of biomass with the use of microwave radiation is described. The effect of activation temperature (700 and 800 °C) and two periods of time (15 and 30 min) on the textural parameters, acid–base character of the surface and sorption properties of activated carbons was tested. The resulting carbons were characterized by low-temperature nitrogen sorption and determination of pH as well as the number of surface oxygen groups. The sorption properties of the activated carbons obtained were characterized by determination of nitrogen dioxide and hydrogen sulphide adsorption in dry and wet conditions as well as by iodine removal from aqueous solution. The final products were adsorbents of surface area ranging from 291 to 368 m²/g and pore volume from 0.20 to 0.26 cm³/g, showing basic character of the surface. The results obtained in our study have proved that suitable choice of the pyrolysis and activation procedure for hay with the use of microwave radiation permit producing adsorbents with good capacity toward toxic gases of acidic character as well as inorganic pollutants of molecules of size similar to that of iodine molecules.     

Parent,Unsubstituted Hemiporphycene: Synthesis and Properties

Among seven possible nitrogen‐in constitutional isomers of porphyrin only one, porphycene, has been obtained so far in the free, unsubstituted form. Herein, the synthesis of another isomer, parent hemiporphycene ( HPc ), and its thorough structural, spectral, photophysical, electrochemical, and theoretical characterization are reported. Most of the properties of HPc are intermediate between those of porphyrin and porphycene, as evidenced by the values of inner‐cavity dimensions, orbital‐energy splittings, absorption coefficients, magnetic circular dichroism parameters, NH‐stretching frequencies, fluorescence quantum yields, tautomerization rates, and redox potentials. The largest differences arise with respect to tautomerism, due to the low symmetry of HPc and inequivalence of the four nitrogen atoms that define the inner cavity. Two trans tautomers are observed, separated in energy by about 1 kcal mol^?1. Tautomerization from the higher‐ to the lower‐energy form is detected in the lowest‐excited singlet state and occurs at a rate that is about four orders of magnitude lower than that observed for porphycene. Hemiporphycene is a very good model for the investigation of inequivalent intramolecular H‐bonds present in one molecule; two such bonds in HPc reveal unusual characteristics, and the bond strength results from the interplay between the N ??? N distance and the N?H?N angle.     

Deuterium isotope effects on 13C chemical shifts of negatively charged NH…N systems

Deuterium isotope effects on ¹³C chemical shifts are investigated in anions of 1,8‐bis(4‐toluenesulphonamido)naphthalenes together with N,N‐(naphthalene‐1,8‐diyl)bis(2,2,2‐trifluoracetamide) all with bis(1,8‐dimethylamino)napthaleneH⁺ as counter ion. These compounds represent both “static” and equilibrium cases. NMR assignments of the former have been revised. The NH proton is deuteriated. The isotope effects on ¹³C chemical shifts are rather unusual in these strongly hydrogen bonded systems between a NH and a negatively charged nitrogen atom. The formal four‐bond effects are found to be negative indicating transmission via the hydrogen bond. In addition, unusual long range effects are seen. Structures, ¹H and ¹³C NMR chemical shifts and changes in nuclear shieldings upon deuteriation are calculated using density functional theory methods. Copyright © 2013 John Wiley & Sons, Ltd.     

Influence of inner transducer properties on EMF response and stability of solid-contact anion-selective membrane electrodes based on metalloporphyrin ionophores

The performance of solid-contact coated-wire-type electrodes with plasticized poly(vinyl chloride) membranes containing metalloporphyrins as anion-selective ionophores is reported. The membranes are deposited on transducers based on graphite pastes and graphite rods. The hydrophobicity of the underlying conductive transducer surface is found to be a key factor that influences the formation of an aqueous layer beneath the polymer film. Elimination of this ill-defined water layer greatly improves the electrochemical properties of the ion-sensors, such as electromotive force stability and lifetime. Only highly lipophilic electrode substrates, namely graphite paste with mineral oil, were shown to prevent the formation of aqueous layer underneath the ion-sensing membrane. The possibility of employing Co(III)-tetraphenylporphyrin both as NO₂ ⁻ selective ionophore and as electron- and ion-conducting species to ensure ion-to-electron translation was also discussed based on the results of preliminary experiments.     

MgO/CaO-loaded porous carbons for carbon dioxide capture

Nanoporous carbons loaded with both MgO and CaO were prepared by a simple heating of mixtures consisting of poly(ethylene terephthalate) and natural dolomite. Preparations were carried out at temperatures ranging from 850 to 1,000 °C that ensured complete thermal decomposition of the dolomite contained in the mixtures to the oxides. An influence of the PET/dolomite weight ratio and temperature of the preparation process on the porosity of the obtained composite products and on CaO and MgO crystallite sizes are discussed using the results of nitrogen adsorption/desorption at 77 K and X-ray diffraction analyses, respectively. Performances of the hybrid materials as sorbents for carbon dioxide were examined using thermogravimetric analyses. Finally, possibility of regeneration of the spent sorbent materials together with a side—effect accompanying this process are discussed on the basis of thermogravimetric measurements. As found, a part of CO₂ captured by the hybrid sorbents gets adsorbed weakly and another portion is fixed strongly. During thermal regeneration, the strongly fixed CO₂ reacts with carbon material. In this way small fraction of a sorbent is lost.     

Solid Contact Nitrate Ion‐selective Electrode Based on Cobalt(II) Complex with 4,7‐Diphenyl‐1,10‐phenanthroline

Nitrates are a group of compounds widely distributed in the natural environment with many applications in various industries. Due to their ambiguous impact on the human body and suspicions of their carcinogenic activity, they have been very popular for decades and are the subject of research by many scientists in the field of medicine, biology and chemistry. Due to the need to monitor their content in environmental and food samples, various methods for their determination are developed. This paper proposes the use of a nitrate ion‐sensitive ion selective electrode with a membrane containing as the active ingredient a new cobalt(II) complex with 4,7‐diphenyl‐1,10‐phenanthroline (Bphen) of the formula Co(Bphen)₂(NO₃)₂(H₂O)₂. The obtained sensor showed the theoretical slope of the characteristic curve, a wide measuring range, as well as short response time and very good potential stability. It was successfully used for the determination of nitrates in real samples: in mineral water, tap water and river water from eastern Poland.