Resorcinol–formaldehyde aerogels (five samples, three of them with addition of nitrogen containing precursors—3-hydroxypyridine, 3-aminophenol and melamine) have been prepared by sol–gel polycondensation, subcritical drying and pyrolysis. The pyrolysis of prepared organic aerogels has been studied by non-isothermal TG at constant heating rate. The process of pyrolysis has been found to consist of three steps with the total mass loss 40.2–61.7% (room temperature—1,000 °C). The resulted carbon aerogels have been tested as sorbents of Ni(II), Pb(II) and Cu(II) ions from aqueous solutions. Various relations have been found among the results obtained from the pyrolysis experiments and properties affecting adsorption. Besides the expected correlation between the mass loss gained from TG (isothermal step at 500 °C was applied) and from heating in the laboratory oven, the relationship between the mass loss during pyrolysis and sorption capacities for all three metal ions has been found. Other relations among pyrolysis behaviour, surface area and content of nitrogen have been also examined. Batch adsorption experiments show (with an exception of one sample) that N-doped samples have higher adsorption capacity for metal ions. In addition, changing of nitrogen functionalities during the pyrolysis has been considered and pyridinic-N (N-6) functionality has been contemplated as a suitable structure for the adsorption process.
The process of oxygen chemisorption on coal in the temperature range ≈150–300 °C was studied under different experimental
conditions using TG-DSC apparatus. As changing experimental conditions, oxygen flow (20 or 200 cm3 min−1), material of crucible (α-Al2O3 or Pt–Rh alloy), and initial sample mass (2–13 mg) were examined with respect to reliability and reproducibility of the parameters
derived from TA curves. As parameters quantifying coal oxidation, temperatures of minimal Tmin and maximal Tmax sample mass, mass changes (mass loss WH below Tmin and mass increase WO above Tmin), heat evolution during oxygen chemisorption QO (related to the coal mass increase), and kinetic parameters (activation energy E and frequency factor A) were evaluated. Values of Tmax, E, and A were found to lie in very close intervals independently on experimental conditions (95% confidence intervals were Tmax = 270.2 ± 0.7 °C, E = 81 ± 3 kJ mol−1, log10A = 5.9 ± 0.3 s−1). Thus, these parameters can be used as actual characteristics of oxygen chemisorption stage of coal oxidation irrespective
on conditions of TA measurements. Opposite, parameter QO was confirmed to depend clearly on initial sample mass. The dependence is different for crucible materials used; however,
it tends to the same value (≈50 kJ g−1) with increasing sample mass. Further, precision of values WH, WO, and Tmin determined from TG was found to be poor. This fact complicates evaluation of the effect of experimental conditions. Finally,
the effect of oxygen flow on all above parameters was found to be negligible. Its influence (if any) was hidden by common
Authors:D. Hovorka, Z. Farkaš, J. Spišiak, J. Krištín, L. Števula, I. Túnyi, and A. Kaplíková
keramiky. In: Praehistorica 22. Varia Archaeologic a 7. Praha 1997, 9–40.
2005 = D. Hovorka
: Metamorphosis of industrial and postindustrial age — Technometamorphosis. (in Slovak with English abstract). 1
events of the S. Slovakia depressions in the light of the stress-field analyses). - Mineralia slovaca, 25, pp. 79-92.
Sled paleogénnych a neogénnych tektonických udalosti v juhoslovenských kotlinách vo svetle napätových analýz
An influence of inorganic compounds (Fe2O3, ZnO, PbO, CaCO3 and K2CO3) on the blast furnace coke thermal oxidation in the air and in the CO2atmosphere was investigated by means of thermal analysis. A catalytic effect showed itself at the oxidation in the air, especially
with PbO and K2CO3. These compounds bring the oxidation starting temperature and activation energy down and increase the reaction rate constant
most distinctly. The PbO and K2CO3 actions differ in their mechanisms. K2CO3 accelerates particularly the amorphous coke fractions oxidation. In the CO2 atmosphere an important catalytic effect occurred only with K2CO3. The PbO catalytic influence is less distinct.
Authors:P. Beneš, M. Kuncová, J. Slovák, and P. Ramos
Use of laboratory model experiments for analysis of interaction of radionuclides with surface water solids is connected with methodical problems concerning selection of solid phase, sampling, storage and pretreatment of solid phase, concentration of radionuclide, selection of liquid to solid ratio, adsorption of radionuclide on vessel walls, choice of experimental procedures and change in radionuclide speciation in the solid phase. These problems are discussed on the basis of literature data and of experiments with radiocobalt or radiocesium in a system river water-suspended solids or bottom sediments. Possible ways of solution of the problems are shown. Two modifications of batch method are described in detail and their merits or drawbacks evaluated. Comparison of the modifications shows their possible use as complementary methods for the study of radionuclide behaviour in surface waters.
Authors:Daniela Šátková-Jakabová, J. Trandžík, Ľudmila Hudecová-Kvasňáková, Erika Hegedüšová-Zetochová, A. Bugarský, J. Buleca Jr., L. Zöldág, F. Jakab, and P. Fľak
Genetic variation at six microsatellite loci was analysed for five Thoroughbred subpopulations to determine the magnitude of genetic differentiation and the genetic relationships among the subpopulations. Significant deviations from Hardy-Weinberg equilibrium were shown for a number of locus-population combinations, with all subpopulations. The genetic diversities and relationships of five Thoroughbred subpopulations were evaluated using six microsatellites recommended by the International Society of Animal Genetics (ISAG). The allele frequencies, the effective numbers of alleles, and the observed and expected heterozygosities were calculated. POPGENE v. 1.31 (Yeh et al., 1997) was used to test for deviations from the Hardy-Weinberg (H-W) equilibrium and to assign FIS estimates (Weir, 1990). The utility of microsatellites for evaluating genetic diversity of horses is discussed.