S. S. Grazhulene

Adsorption properties of carbon nanotubes depending on the temperature of their synthesis and subsequent treatment

A correlation between the temperature of the synthesis of carbon nanotubes (CNT) by method of catalytic pyrolysis from ethanol on a nickel catalyst and their ability for the modification of oxidation under various conditions and also their adsorption capacity to a number of metal ions is demonstrated. The study of infrared spectra in correlation with the total acidity of the CNT synthesized and modified under various conditions has shown that the samples synthesized at 400°C possess the maximum ability for modification. This can be explained by the higher deficiency of their structures at low synthesis temperatures. Adsorption isotherms of silver, copper, lead, cadmium, zinc, iron, and magnesium ions under batch and dynamic modes were studied, depending on pH and element concentration in the solution. It was found that CNT synthesized at 400°C and treated with conc. HNO3 in an autoclave at 110–120°C possess the maximum adsorption capacity of all the studied elements, which exceeds the capacity of active coal, traditionally used for these purposes, by several times. The attained adsorption capacity is 5–10 times higher than that reported in the literature for carbon nanotubes in relation to the same elements. Prospects of using CNT as collectors for the preconcentration of trace impurities in spectroscopic methods of analysis are considered.

Quartz crystal microbalance determination of vapors of volatile organic compounds on carbon nanotubes under batch conditions

Specific features of the sorption of vapors of monoatomic aliphatic alcohols and aromatic compounds on coatings formed from carbon nanotubes of various genesis studied by the method of piezoelectric micro weighing are considered. The morphology of the coatings is considered in dependence on the conditions of synthesis and aftertreatment of carbon nanotubes. A new method of the processing of signals from an array piezoelectric sensors is proposed; it allows an increase in the selectivity of the determination of volatile organic compounds in an equilibrium gas phase by 2–2.5 times. The advantages of the application of carbon nanotubes as sorption coatings in comparison to the standard polymeric sorbents for piezoelectric micro weighing are demonstrated: the detection limit decreases by 4–15 times and the duration of measurement by 5–55 times.

Neutron activation analysis of PbxSn1-xTe using extraction chromatography

A simple procedure of neutron activation analysis for the determination of 16 impurities in PbxSn1−xTe with detection limits from 1×10−4% for Ni and Zr to 2×10−9% for Sc has been developed. The procedure is based on extraction chromatographic separation of impurities from the irradiated sample.

Neutron activation analysis of CdxHg1-xTe

A procedure has been developed for the analysis of CdxHg1-xTe samples; the elements to be determined /Na, K, Cr, Mn, Cu, Co, Zn, As, La/ are separated by chromatography after neutron activation. The detection limit varies between 1×10−5% and 5×10−8%. A comparison of the calculation and semiempirical methods of the screening effect determination has been made.

Study of carbon nanomaterials as potential sorbents to concentrate admixtures in the atomic spectroscopy analysis methods

Carbon nanomaterials (CNM) obtained by the catalytic pyrolysis of ethanol vapors are characterized with respect to their morphology, chemical purity, and sorption capacity. The efficacy of their usage to concentrate metal ions by sorption is demonstrated. The change in the sorption capacity of CNM in different treatments of materials is explained by the surface modification by the oxygen-containing functional groups and their destruction upon annealing. This is confirmed by chemical and thermogravimetric analysis methods. The optimal conditions to concentrate a series of metal ions from water solutions for determining further flame atomic adsorption are found. This allowed the reduction of the detection limits by one to two orders of magnitude. The correctness of the determination is confirmed by the method of additions and the analysis of standard samples.

Extraction-chromatographic system TBP-HBr in radiochemical neutron activation analysis of high-purity materials

The extraction and extraction-chromatographic behaviour of a variety of elements in the TBP-HBr system with concentrations from 0.1 to 7M HBr has been studied. The results allowed the development of simple procedures for radiochemical neutron activation determination of 22 impurity elements (Na, K, Sc, Cr, Mn, Fe, Co, Ni, Cu, Ga, As, Se, Rb, Sr, Zn, Mo, Ag, Sb, Te, Ba, La, Hf and W) in high-purity cadmium and indium samples with detection limits from 1 μg g−1 for Fe and Zr to 0.01 ng g−1 for Na, Sc, Mn with relative standard deviations < 0.15. To increase the selectivity of the extraction-chromatographic separation, use was made of extraction suppression and co-extraction effects. The procedure for the extraction-chromatographic separation of scandium from a number of other elements is described as an example. The procedure can be used for simultaneous quantitative separation of impurity radionuclides from radiation produced long-life scandium radionuclides in the neutron activation analysis of titanium and vanadium.

Analysis of mo and its high-purity compounds, with preconcentration of impurities

SummaryA procedure for concentrating microimpurities (especially W) in high-purity Mo by extraction chromatography (stationary phase trioctylammonium hydrochloride) has been developed. Extraction with 1-phenyl-3-methyl-4-benzoylpyrazol-5-one in molten naphthalenediphenyl mixture was also examined, but proved less useful. The extraction of W in the presence of macroamounts of Mo is suppressed in the extraction chromatography, allowing quantitative separation of these two elements. The electrochemical behaviour of Mo and W in each others presence has been studied and a polarographic technique for determination of 10−6 M developed. The polarographic results for W are not affected by the presence of a 100-fold ratio of Mo. If the extraction chromatography and polarographic analysis are combined, the detection limit for W in Mo appears to be 10−5%.ZusammenfassungAnreicherungsverfahren für Mikrobeimengungen (in erster Linie von Wolfram) in hochreinem Molybdän mit Hilfe der Extraktions-Chromatographie (unbewegliche Phase Trioktylammoniumchlorid) und der Extraktion mit leicht schmelzenden Extraktionsmitteln (PMBP-Naphthalin-Diphenyl) wurden untersucht. Die Unterdrückung der Wolfram-Extraktion durch Makromengen Molybdän wurde bei der Trennung ausgenützt. Das elektrochemische Verhalten von Mo und W bei gemeinsamer Anwesenheit wurde untersucht und die Methodik der polarographischen Bestimmung von 10−6 M Wolfram ausgearbeitet. Die Anwesenheit eines 100fachen Überschusses an Molybdän beeinflußt die Ergebnisse für Wolfram nicht. Bei Kombination des extraktions-chromatographischen Verfahrens mit der Polarographie beträgt die Bestimmungsgrenze für Wolfram in Molybdän 10−5%.

Study of correlations between the physicochemical properties of carbon nanotubes and the type of catalyst used for their synthesis

It is found that carbon nanotubes (CNTs) obtained by the catalytic pyrolysis of ethanol vapor with Ni-, Co-, and Fe catalysts vary in their ability to oxidative modification and, finally, in adsorption capacity, dispersion, and the texture of the synthesized powders. The adsorption capacity of the modified CNTs varies in the order Ni > Co > Fe. The material obtained with a Ni catalyst has good bulk and hydrodynamic properties, which is essential for use in chromatographic columns. Using a Fe catalyst, a loose, cotton wool-like product was obtained that is unsuitable for column chromatography, and with a Co catalyst, a material with intermediate properties was synthesized. Differences in the physicochemical properties of CNTs are related to the morphology of the products.

Broadening of linear dynamic range of photoelectric registration of emission spectra

A method for broadening the linear dynamic range of measurements (LDRM) for a developed photoelectron system of registering emission spectra using series of charge-coupled devices (CCDs) was suggested. The method is based on creation of virtual spectrum scanning channels with different sensitivity and corresponding mathematical processing of measurement results. The possibility of increasing the LDRM by three orders of magnitude as compared with the standard scanning mode for different elements was shown by example of determination of admixtures in artificial mixtures based on graphite powder. Analysis of carbon nanopipes in wide range of content of impurity elements was performed using the obtained data.

Application of extraction chromatography for analysis of high-purity CdTe and ZnSe

SummaryThe possibilities of extraction chromatography are investigated for the separation of impurities from high-purity CdTe and ZnSe. The conditions of a quantitative separation of the impurities are determined. As a result of the investigations the techniques are developed for neutron activation analysis of CdTe and spectral analysis of ZnSe, the impurity-detection limits being from 10−5% to 10−7%.ZusammenfassungDie Möglichkeiten der Extraktions-Chromatographie für die Anreicherung von Mikrobeimengungen in hochreinem CdTe und ZnSe wurden untersucht. Dazu wurden die Bedingungen der quantitativen Trennung von Mikrobeimengungen in Cd, Te und Zn ermittelt.Als Ergebnis der Untersuchungen wurden Methoden der Neutronen-Aktivierungsanalyse von ZnSe ausgearbeitet. Bei der Kombination der extraktions-chromatographischen Anreicherung mit diesem Analyseverfahren beträgt die Bestimmungsgrenze für Mikrobeimengungen 10−5−10−7%.