Hunting colours: origin and reuse of glass tesserae from the Wierum terp

Mosaic glass tesserae were imported to Dutch sites during the Early Medieval period, probably to address the demand for coloured glass needed in ornamental bead manufacture. Although challenging, because of the uncertainty of the material’s context, the Wierum Early Medieval collection represents an extraordinary opportunity, being the most significant find of glass tesserae in the Netherlands to date. The combined use of electron microprobe analysis (EMPA) and hand-held X-ray fluorescence spectrometry (HH XRF) allowed us to examine glass tesserae and other vitreous samples from the site. Low levels for magnesium and potassium oxides (<1.5 wt%) and the chemical components linked with the silica source, fluxes, opacifiers and chromophores are compatible with an older Roman soda-lime-silica glass production. Alumina and calcium oxide contents together with the adoption of antimony-based opacifiers are compatible with mosaic tesserae of a first to third century AD Roman tradition. We assume that these tesserae were collected during the spoliation of a lavish building and reused for glass objects produced locally. The hypothesis seems to be confirmed by the presence in the collection of tesserae still embedded in mortar, stone tesserae fragments and a rounded fragment of Egyptian blue.

RESEARCH OF THE POSSIBILITY OF REDUCING THE CIRCULATION OF SULFUR OXIDE IN THE PRODUCTION OF WHITE CEMENT

The article discusses the possibility of reducing the circulation of sulfur oxide in the production of white cement by introducing alkaline potassium oxides K2O and sodium Na2O. A decrease in the circulation of sulfur oxide SO3 is achieved by increasing its yield in the clinker by transferring SO3 from a more sublimated compound of calcium sulfate CaSO4 to less sublimated potassium sulfates K2SO4 and sodium Na2SO4. Potassium and sodium oxides are introduced in the composition of carbonates and feldspar. The amount of introduced alkali oxides is controlled by the molar ratio A/S between sulfur oxide SO3 and alkaline oxides K2O and Na2O. It is shown that with the same molar ratio between sulfur oxide and alkaline oxides, the amount of SO3 removed with clinker depends on the ratio between potassium and sodium oxides. The higher the sodium oxide content, the more sulfur oxide comes out with the clinker and less remains to circulate in the kiln. The sublimation of sulfur oxide decreases from 70.5% - without the introduction of alkaline oxides, to 38,5 % at the maximum A/S ratio with the addition of potassium and sodium oxides in a ratio of 80:20 %. When potassium and sodium oxides are added in a ratio of 20:80%, the sublimation of sulfur oxide is reduced to 7,7 % at the same A/S ratio.

Correlation between the material constitution components in apatite-nepheline ores of the Khybiny Rock Massif (the Kola Peninsula)

Raw apatite-nepheline ores of the Khibiny alkaline massif are similar in terms of the set of ore-forming minerals and differ in their quantitative ratio. A special place among apatite-nepheline ores is occupied by ores of tectonically destroyed zones, which are widespread in the Khibiny apatite-nepheline deposits. Destruction zone ores are product of secondary changes in raw ores and are characterized by the presence of finely dispersed secondary minerals represented by hydrated micas, zeolites and clay minerals. In the aquatic environment they form colloidal sediments with active surface properties. This fact, as well as thin films of clay and other minerals formed on the surface of apatite grains, cause a decrease in the degree of hydrophobicity of fluorapatite and deterioration of the selectivity of apatite flotation. According to the analytical determinations of the chemical components of the ores and their mineralogical composition, a correlation-regression analysis of the ratio of the components of the material composition of the ores has been performed. The results of correlation-regression analysis have shown that the presence of hypergenically changed ores related to difficult-to-treat ones can be identified by lower ratios of sodium and potassium oxides, as well as sodium and aluminum relative to their average. The presence of products of nepheline change in all ores processed has allowed revealing the most stable correlation between nepheline and sodium oxide, rather than aluminum oxides, in contrast to the earlier opinion. The very high correlation relationship between fluorapatite, nepheline, and titanite and the oxides of phosphorus, sodium, and titanium, respectively, and the statistical significance of the correlation and regression coefficients allow determining the content of these minerals using the regression equations presented in the paper.

The Purification of Electroplating Industry Effluents with Agricultural Waste

The article suggests the usage of ash from sunflower husk combustion, which is constantly considered to be production waste, as a treating agent for electroplating industry wastewater purification. The chemical and mineral composition of ash waste has been researched by means of X-ray diffraction method with an X-ray fluorescent spectrometer. The structure of waste has been studied with a high-resolution scanning electron microscope. The ash contains calcium, magnesium and potassium oxides, so this waste can be used as a chemical treating agent in purifying water from heavy metals. The acid leaching of ash has been performed to determine the degree of its components transition. The trial purification of real electroplating wastes with the ash has been carried out. The purification efficiency for nickel and copper amounts to 62.0 and 48.0 % at the ash consumption 3.0 g/dm3.

Characterization of FeCo based catalyst for ammonia decomposition. The effect of potassium oxide

FeCo fused catalyst was obtained by fusing iron and cobalt oxides with an addition of calcium, aluminium, and potassium oxides (CaO, Al2O3, K2O). An additional amount of potassium oxide was inserted by wet impregnation. Chemical composition of the prepared catalysts was determined with an aid of the XRF method. On the basis of XRD analysis it was found that cobalt was built into the structure of magnetite and solid solution of CoFe2O4 was formed. An increase in potassium content develops surface area of the reduced form of the catalyst, number of adsorption sites for hydrogen, and the ammonia decomposition rate. The nitriding process of the catalyst slows down the ammonia decomposition.

Use of Ash from Coffee Wood into Clayey Ceramic

This work has as its objective to evaluate effect of the incorporation of an ash, obtained from burning wood from coffee plant, in the physical and mechanical properties of incorporated clayey ceramic. The ash has undergone characterization tests by the techniques of XRF, DTA / TG and XRD. Formulations were prepared with 5, 10, 20 and 30 wt% of ash incorporated into clay bodies that were then homogenized, dried and finally moistened. Rectangular test specimens were prepared by uniaxial pressing in a steel mold at 20 MPa, followed by firing at 700 °C. The fired ceramics were subjected to physical and mechanical tests for determining the bulk density, linear shrinkage, water absorption and tensile strength. The results indicate that the ash is composed predominantly of calcium, magnesium and potassium oxides. The incorporation of ash up to 20 wt% decreased the water absorption and notably increased the ceramic mechanical strength in the temperature investigated.