Search

The article presents the results of tests performed on fly ash with a high content of ammonium (up to 400 ppm) from the NOx reduction process. The main properties of fly ash were tested according to EN 450-1 and the results were compared with fly ash without ammonium. The comparison showed that fly ash with high concentration of ammonium suits the requirements of the European standard. Although the requirements do not limit the ammonium content, using such material as an additive for cement composites causes the emission of gaseous ammonium during mixing and from the final product. For this reason, the emission of ammonium from mortars containing fly ash were tested. The results have shown that using high ammonium fly ash might pollute indoor air and affect the health of users.

The paper presents the results of research on the properties of fly ashes from the process of flue gas denitrification by selective non-catalytic reduction (SNCR), consisting of dosing urea into the coal combustion chamber. The research was carried out on two types of fly ash: Silica fly ash from flue gas denitrification and ash from a traditional boiler without the flue gas denitrification process. The scope of comparative studies included physicochemical and structural features of ashes, as well as slurries and mortars with the addition of ashes. Fly ash from denitrification, whose ammonia content at the time of sampling was 75 mg/kg at the maximum, was examined. Our own research has shown that fly ash from flue gas denitrification is characterized by a higher value of losses on ignition and ammonia content in comparison to ashes without denitrification. It was shown that the ammonia content in the analyzed range does not limit the use of fly ash as an additive to cement and concrete.

Analytical precision for Pb isotope measurement by thermal and plasma source mass spectrometry has improved by an order of magnitude in the last 20 years. Much of this improvement relates to a shift away from the external method of correcting instrumental mass fractionation – where samples are assumed to fractionate to the same extent as an average value of a working measurement standard. Implementation of a variety of techniques, including thallium spiking, sample–standard bracketing and double/triple spiking has provided more robust methods of fractionation correction. Isotope laboratories use one or more of these procedures, but an assessment of the measurement precision and relative merits of each system is needed to determine which is the most appropriate for the purpose. This study reviews each of these methods and provides a comparison based on an extensive analytical record covering 18 years, and using a variety of mass spectrometers. As two or three of the methods have been applied to most measurements, direct and robust comparisons can be made between correction protocols. In particular the effects of sample purity and variable sample matrices on measurement precision and accuracy have been examined. Data acquired from the measurement of rock, soil and metal are used to provide a statistical comparison of the analytical uncertainty of each technique, guiding the choice of the most appropriate method. Isotope standard data acquired over this period is also compared with other high-precision laboratories to generate a set of concordant working ratios for the NIST SRM 981 Pb standard: 206Pb/204Pb = 16.9412; 207Pb/204Pb = 15.4988; 208Pb/204Pb = 36.7233.

This work reports tests performed to evaluate the stability of aqueous dispersions of inorganic oxide pigments with different specific surface areas, with the use of anionic and non-ionic surfactants and concentrators. Color mixtures of oxide compounds of blue, green, olive and brown with the unit cell spinel structure were used as pigments. The sodium salt of sulfosuccinic acid monoester, oxyethylenated nonylphenol and ethoxylated derivatives of lauryl alcohol, fatty alcohol and fatty amine were used as surfactants. The concentrators used were: poly(vinyl alcohol), the sodium salt of carboxymethyl cellulose as well as a water-based polyurethane oligomer. The highest dispersion efficiency was found for dispersed systems in which surfactant and concentrator were incorporated in the formula. The one containing the sodium salt of carboxymethyl cellulose or polyurethane oligomer with ethoxylated saturated fatty alcohol or fatty amine was found to be the most efficient. It was discovered that a higher dispersion efficiency corresponds to pigments with larger specific surface. The efficiency is also found to improve when the concentrator is an acrylic polymer or copolymer made up of two acrylic species. In this case, the concentrator interaction with the surfactant is more effective if the value of its boundary viscosity number is higher. This observation confirms the existence of interactions between macro-chains of the concentrator and surfactant molecules forming micelles with the pigment particles.

The novel iminosugar (1R,2S,3R,5R,8aR)-3-(hydroxymethyl)-5- methyloctahydroindolizine-1,2-diol (steviamine) was isolated from leaf material of Stevia rebaudiana and leaves and bulbs of Veltheimia capensis. This is the first report of an indolizidine iminosugar alkaloid from the Asteraceae and Hyacinthaceae. Steviamine may occur in some Stevia products and influence taste. © 2010 Phytochemical Society of Europe.

X-ray crystallographic analysis of the title hydrobromide salt, C10H20N+·Br−, of (1R,2S,3R,5R,8aR)-3-hydroxymethyl-5-methyloctahydroindolizine-1,2-diol defines the absolute and relative stereochemistry at the five chiral centres in steviamine, a new class of polyhydroxylated indolizidine alkaloid isolated from Stevia rebaudiana (Asteraceae) leaves. In the crystal structure, molecules are linked by intermolecular O—H...Br and N—H...Br hydrogen bonds, forming double chains around the twofold screw axes along the b-axis direction. Intramolecular O—H...O interactions occur.