Elzbieta Stefaniak

Combined SEM/EDX and micro-Raman spectroscopy analysis of uranium minerals from a former uranium mine

Samples of the secondary uranium minerals collected in the abandoned uranium mine at Pecs (Hungary) were investigated by two micro-techniques: scanning electron microscopy (SEM/EDX) and micro-Raman spectroscopy (MRS). They were applied to locate U-rich particles and identify the chemical form and oxidation state of the uranium compounds. The most abundant mineral was a K and/or Na uranyl sulphate (zippeite group). U(VI) was also present in the form showing intensive Raman scattering at 860 cm(-1) which can be attributed to uranium trioxide. This research has shown the successful application of micro-Raman spectroscopy for the identification of uranyl mineral species on the level of individual particles.

Study of Chromium(VI) Adsorption from Aqueous Solution on to Activated Carbon

The adsorption of chromium(VI) from dilute aqueous solutions on to activated carbons at natural pH values was investigated. The activated carbons were modified to obtain materials with a well-defined surface containing inorganic impurities at ppb or ppm level. Measurements of the adsorption kinetics relative to the degree of granulation were undertaken. It was found that the reaction rate of the ions on the surface of the activated carbon rather than diffusion was the major process influencing the equilibrium. Surface reduction of CrVI to CrIII appeared to be the principal mechanism for the adsorption of chromium on the activated carbons studied. It was demonstrated experimentally that the presence of oxidizing agents dramatically changed the adsorption capacity of CrVI on the studied carbons. The influence of the ionic strength (controlled by the addition of NaCl) on the adsorption capacity was also studied. Variable and complex influences of the ionic strength on the adsorption capacity were observed.

Determination of chemical composition of individual airborne particles by SEM/EDX and micro-Raman spectrometry: a review

The strategies for sampling and analysis by SEM/EDX and micro-Raman spectrometry for individual airborne particles analysis as applied at the University of Antwerp (Belgium) by the MITAC group have been reviewed. Microbeam techniques provide detailed information concerning the origin, formation, transport, reactivity, transformation reactions and environmental impact of particulate matter. Moreover, some particles of certain chemical properties have been recognized as a threat for human health and cultural heritage objects. However, the small sizes of particles result in specific problems with respect to single particle analysis. Development of equipment and software for improvement of analysis and quantification are reported.

On the Adsorption of Chromium(VI) Ions on Dolomite and ‘Dolomitic Sorbents’

The sorption capability of raw and thermally treated dolomite samples with respect to toxic ions was estimated through the adsorption of chromium(VI) from aqueous solutions. The adsorption isotherms were shown to fit the well-known Freundlich equation. The results confirm the weak adsorption of chromium(VI) on raw dolomite relative to the other dolomite-derived sorbents. The influence of ionic strength on the adsorption was also determined.

Investigation of inclusions trapped inside Libyan desert glass by Raman microscopy

Several specimens of Libyan desert glass (LDG), an enigmatic natural glass from Egypt, were subjected to investigation by micro-Raman spectroscopy. The spectra of inclusions inside the LDG samples were successfully measured through the layers of glass and the mineral species were identified on this basis. The presence of cristobalite as typical for high-temperature melt products was confirmed, together with co-existing quartz. TiO2 was determined in two polymorphic species rutile and anatase. Micro-Raman spectroscopy proved also the presence of minerals unusual for high-temperature glasses such as anhydrite and aragonite.

Study of the surface adsorption properties of feldspar

The adsorption properties of Polish feldspar towards hydrocarbons from the gaseous phase have been studied and the adsorption energy distribution functions for n-octane, benzene and toluene are presented. It appears that there are three types of adsorption sites present on the feldspar surface examined. Treatment of feldspar with aqua regia led to the elimination of low-energy interaction centres. The adsorption properties of the raw and leached feldspar with respect to CrVI ions have also been studied. The kinetic curves for the sorption of CrVI ions exhibited two stages which suggest two different mechanisms of sorption. The adsorption capacity depended on the pH with a maximum for pH = 4.8. The excess adsorption isotherm of CrVI on the raw feldspar surface showed a maximum value at 20 mmol/dm3 equilibrium concentration of CrVI ions.

Physicochemical study of 'dolomitic' sorbents prepared under different thermal conditions. Part III. The influence of carbon dioxide content over a heated sample

The physicochemical properties of ‘dolomitic’ sorbents formed through the partial decomposition of dolomite have been discussed in two papers published previously dealing with the influence of temperature and the time of heating. When carried out at 800°C, the newly formed solid consisted of spongelike calcite and finely powdered magnesium oxide which was resistant mechanically and exhibited considerably greater porosity than the raw material. Long-term heating led to a decrease in the porosity and to the partial elimination of pores. The corresponding ‘dolomitic’ sorbents prepared in an inert atmosphere showed even greater porosity and a different internal structure when compared to those formed in the presence of carbon dioxide. However, no changes were observed as far as the chemical composition was concerned.

Investigations of physicochemical properties of Polish dolomites

Physicochemical investigations of thermal decomposition and adsorption properties of dolomite samples originating from the Oldrzychowice-Romanowo deposit (Poland) were made using differential thermal analysis and gas chromatography. The derivatographic measurements showed a two-step thermal decomposition of the tested mineral. The adsorption isotherms of n-octane, toluene, and water were determined using GC. The components of the free surface energy were calculated from the Bangham-Razouk equation. The amounts of selected metals contained in dolomite samples were measured by absorption atomic spectroscopy. From the results obtained, the adsorption properties of the investigated mineral were determined.

The physicochemical surface properties of feldspar and some attempts of its purification

In this paper the results of the qualitative analysis of the basic elements and impurities of the domestic feldspar are presented. From n-octane and toluene adsorption measurements the components of the free surface energy were calculated and from the porosity investigations the pore size distribution curves were obtained. The adsorption and mercury porosimetry data showed the energetical and structural heterogeneity of the examined material. Having in consideration the industrial application of this mineral, preliminary tests of the chemical purification from iron additives by some acids were carried out. It appeared that the best results were achieved after etching it with aqua regia (nitrochloric acid).