Search Results
Abstract
Instrumental neutron activation analysis (INAA) has been applied for the simultaneous determination of up to 33 elements including major, minor and trace elements in the environmental reference materials soil and coal fly ash from China. The procedure involves both short and long irradiations followed by the measurement of the gamma spectra with a Ge(Li) detector. The analytical results are presented and discussed.
Abstract
Palladium/II/ in aqueous solution can be selectively extracted by bismuth diethyl-dithiocarbamate into chloroform at pH around 3.5. This preconcentration procedure combined with neutron activation analysis provides an extremely sensitive method for measuring low levels of Pd in natural samples. Applications of this method to Pd determination in natural water and in coal fly ash are described.
Abstract
The results of pozzolanic activity determination using DTA-TG method are presented. This feature was characterised by Ca(OH)2 residue determination in cement pastes admixtured with siliceous earth, consuming the calcium ions from hydrolysis of cement clinker minerals. The rate of pozzolanic reaction was thus estimated. Some results for fly ash containing pastes were also given.
TheI i=E i/RT i dimensionless evaluation is very suitable for describing the TG measurements according to theE i/RT i=lnA +n[ln(1−α)i]−ln(dα/dr)i equation. TheI i andE i functions make the comparison of the different TG measurements possible quantitatively in the case of more DTG peaks as well.
Abstract
The chemical composition of brown coal fuels and several sedimental type atmospheric particulate pollutants of industrial origin (e.g. fly-ash, bottom-ash, dust particulates from foundry-halls and casting-halls) was studied in relation to their toxic and their natural radioactive contents. In addition, some agricultural crops (e.g. soya bean, sunflower, rape, barley and luceme) sampled, in the near vicinity within a radius of about 10 km of the industrial centre were also analysed for significant distributions of any toxic components. Because of the high uranium and thorium concentrations in Hungarian coal fuels and, consequently, in various fly-ash particulate pollutants, the natural gamma activities of the samples were also measured and the relevant equilibriu states of the232Th and238U natural decay series were studied.
Abstract
Fly ashes from the combustion of coal thermal power stations are commonly incorporated into portland cements and/or concretes and mortars. The chemical and morphological composition of fly ashes, together with their particle size, make them suitable as pozzolanic(non-calcic) or pozzolanic/hydraulic(highly calcic) additions to manufacture such building materials. This work focuses on the incorporation of two different fly ashes (non-calcic but of very different Fe2O3(%) contents, fineness and morphology) to two ordinary portland cements (of very different mineralogical composition as well), to determine the effects those have and the interactions they produce in the hydration reactions of portland cement. The main techniques employed for this study have been: conduction calorimetry and Frattini test; secondary techniques applied have also been: determination of setting times and analysis by X-ray diffraction and SEM. Analysis of the results obtained permitted to find different effects of fly ash addition on the hydration reactions of portland cements. Thus, dilution and stimulation effects augment with the increased fly ash percentage. Delay and acceleration of the reactions depend mainly on the type of portland cement and are accentuated with increased fly ash contents. Their behaviour as concerns heat dissipation mainly, depends on the type of fly ash used and is more pronounced with increased cement replacement. On the other hand, the pozzolanic activity of these fly ashes has been revealed at 7 and 28 days, but not at 2 days. Finally, pozzolanic cements can be manufactured using different portland cements and/or types of fly ashes, in the appropriate proportions and compatible qualities, depending on the effect(s) one wish to enhance at a specific age, which is according to previous general conclusions drew out of sulphate attack and chloride attack researches.
Abstract
Fly ash of a waste incineration facility in Berlin, Germany has been found to be a very useful multielement reference material. It can be used for a large number of matrices to be analyzed. It has served as a reference material particularly for environmental multielement analyses. Components which have been recognized as environmental pollutants are present in higher concentration levels than in any other multielement reference material commercially available.
Abstract
A rapid and comprehensive method has been developed for the determination of ppm to sub-ppb amounts of Ru, Pd, Ag, Os, Ir, Pt and Au, based on thermal neutron irradiation, dissolution of samples, selective absorption on Srafion NMRR ion exchange resin and high resolution γ-ray spectrometry. Two noble metals “specific” resins were tested for their absorption behaviour. The method has been used for analysis of standard rocks, ores, minerals, lunar samples, coal, coal fly ash, and several biological materials.
Abstract
Improvements have been made in the rabbit system used for multielement fast-neutron activation analysis at the Lawrence Livermore National Laboratory Rotating Target Neutron Source, RTNS-I. Procedures have been developed for the analysis of 20–25 elements in samples with an inorganic matrix and 10–15 elements in biological samples, without the need for prohibitively expensive, long irradiations. Results are presented for the analysis of fly ash, orchard leaves, and bovine liver.
Abstract
Information about the sorption of radionuclides on natural materials used for cementation of liquid radioactive wastes (RAW) is important for predictions of migration rates of radionuclides in the products of fixation. Cementation process for conditioning liquid RAW uses, besides cement, materials which improve quality of products. In Czechoslovakia technology among these materials are clinoptilolite tuffit, mordenite tuff, tobermorite and fly ash. Liquid RAW issued from nuclear power plants contains the principal radionuclides60Co,134Cs and137Cs, therefore, a sorption study of these radionuclides was carried out. pH of liquid RAW was 12.5–13.7 and salt content ca. 200 g·dm–3. Results of sorption are given by distribution coefficients. The best results for cesium in those pH region and salt content had mordenite tuff DCs=100 dm3·kg–1 and the worst results had fly ash DCs=4.1 dm3·kg–1. The best results for cobalt in those solutions had tobermorite DCo=38 dm3·kg–1 and the worst results had fly ash DCo=6.9 dm3·kg–1.
