Technologically significant properties of municipal solid waste compost

The paper presents the results of studies of the technologically significant properties of municipal solid waste (MSW) compost produced by MSW processing enterprises in St. Petersburg (Russia) where the Dano drum process is implemented. The chemical and microbiological composition of compost, as well as heat during ripening, are investigated. The chemical composition of industrial compost produced in St. Petersburg does not make it possible to use it as fertilizers and soil in agriculture. From the microbiological point of view, NSW compost is not dangerous, but the content of indicator groups of microorganisms classifies it as contaminated soil. The heat generation of compost during ripening is uneven - the largest share of heat 78.5% is released in the first year of maturation. In absolute terms, this value is 3250 kJ/kg by dry weight. To ensure the process is carried out during a period when the compost temperature is higher than the ambient temperature, toxic substances must be added to the compost in an amount not more than 400 times the pollutant content in waste of the 4th hazardclass

Complex Study of a Painted Gypsum XVIII Century Bas-Relief by Optoelectronic Methods to Develop a Combined Cleaning Technique

In this work, a painted gypsum bas-relief from the facades of the inner courtyard of the St. Petersburg Academy of Arts building was examined using UV and visible light photography and optical and electron scanning microscopy, which showed the heterogeneous layers of white painting on the surface of the bas-relief that covered the historical ones. These undesirable layers should be removed during the restoration work, but it was found that the traditional method of removing surface layers of painting with the help of chemical solvents and mechanical cleaning does not solve the problem to the full extent. A cross-section of all the painting layers was prepared to investigate the stratigraphy of the paint layers. These studies were conducted using optical and electron scanning microscopy in order to determine the structure of the paint layers more properly and study the chemical composition of every layer. After this study, a complex cleaning technique was developed. This technique combines chemical and laser cleaning, making it possible to effectively remove the upper dense layers of paint without damaging the historical paint layers

Structural Engineering of Photocatalytic ZnO-SnO₂-Fe₂O₃ Composites

The ZnO-SnO2-Fe2O3 composites containing flower-like particles were prepared by the non-isothermal polymer-salt method. Thermochemical processes proceeding during composites synthesis was studied by DTA/TG method. The structure and morphology of obtained composites were studied by the SEM and XRD analysis. Prepared composites containing small amounts of SnO2 and Fe2O3 demonstrate the high adsorption and photodecomposition of the organic dye Rhodamine 6G in its solutions. Obtained materials show the ability of the photogeneration of the chemically active singlet oxygen under the visible irradiation. The synergistic effect of the flower structure and Fe2O3 doping can significantly improve the photocatalytic and adsorption activities

Long-Term Aging of Chernobyl Fuel Debris: Corium and “Lava”

Samples of Chernobyl fuel debris, including massive corium and “lava” were collected inside the Chernobyl “Sarcophagus” or “Shelter” in 1990, transported to Leningrad (St. Petersburg) and stored under laboratory conditions for many years. In 2011 aged samples were visually re-examined and it was confirmed that most of them remained intact, although some evidence of self-destruction and chemical alteration were clearly observed. Selected samples of corium and “lava” were affected by static leaching at temperatures of 25, 90 and 150 °C in distilled water. A normalized Pu mass loss (NLPu) from corium samples after 140 days was noted to be 0.5 g/m2 at 25 °C and 1.1 g/m2 at 90 °C. For “lava” samples NLPu was 2.2–2.3 g/m2 at 90 °C for 140 days. The formation of secondary uranyl phases on the surface of corium and “lava” samples altered at 150 °C was confirmed. The results obtained are considered as an important basis for the simulation of fuel debris aging at Fukushima Daiichi nuclear power plant (NPP)

Long-Term Aging of Chernobyl Fuel Debris: Corium and “Lava”

Samples of Chernobyl fuel debris, including massive corium and “lava” were collected inside the Chernobyl “Sarcophagus” or “Shelter” in 1990, transported to Leningrad (St. Petersburg) and stored under laboratory conditions for many years. In 2011 aged samples were visually re-examined and it was confirmed that most of them remained intact, although some evidence of self-destruction and chemical alteration were clearly observed. Selected samples of corium and “lava” were affected by static leaching at temperatures of 25, 90 and 150 °C in distilled water. A normalized Pu mass loss (NLPu) from corium samples after 140 days was noted to be 0.5 g/m2 at 25 °C and 1.1 g/m2 at 90 °C. For “lava” samples NLPu was 2.2–2.3 g/m2 at 90 °C for 140 days. The formation of secondary uranyl phases on the surface of corium and “lava” samples altered at 150 °C was confirmed. The results obtained are considered as an important basis for the simulation of fuel debris aging at Fukushima Daiichi nuclear power plant (NPP)

Phase Transformations upon Formation of Transparent Lithium Alumosilicate Glass-Ceramics Nucleated by Yttrium Niobates

Phase transformations in the lithium aluminosilicate glass nucleated by a mixture of yttrium and niobium oxides and doped with cobalt ions were studied for the development of multifunctional transparent glass-ceramics. Initial glass and glass-ceramics obtained by isothermal heat-treatments at 700–900 °C contain YNbO4 nanocrystals with the distorted tetragonal structure. In samples heated at 1000 °C and above, the monoclinic features are observed. High-temperature X-ray diffraction technique clarifies the mechanism of the monoclinic yttrium orthoniobate formation, which occurs not upon high-temperature heat-treatments above 900 °C but at cooling the glass-ceramics after such heat-treatments, when YNbO4 nanocrystals with tetragonal structure undergo the second-order transformation at ~550 °C. Lithium aluminosilicate solid solutions (ss) with β-quartz structure are the main crystalline phase of glass-ceramics prepared in the temperature range of 800–1000 °C. These structural transformations are confirmed by Raman spectroscopy and illustrated by SEM study. The absorption spectrum of the material changes only with crystallization of the β-quartz ss due to entering the Co2+ ions into this phase mainly in octahedral coordination, substituting for Li+ ions. At the crystallization temperature of 1000 °C, the Co2+ coordination in the β-quartz solid solutions changes to tetrahedral one. Transparent glass-ceramics have a thermal expansion coefficient of about 10 × 10−7 K−1