[en] Silica nanoparticles were successfully extracted from the rice husk ash. The obtained SiO₂ powders had monoclinic crystal system, large specific surface area (258.3 m2/g), and particle size (10 to 15 nm). Nano SiO₂ prepared from rice husk ash increased the chloride resistance of fly ash cement concrete. The ability to resist chloride penetration increases with the content of using nano-SiO₂. When the content of nano-SiO₂ is 2 %, the chloride resistance of concrete is optimized (25 % reduction of charge passed compared to concrete not using nano-SiO₂). (author)

[en] Short communication

[en] The large rapid ashing apparatus consists of a special ashing furnace, oxidation-reduction gas supply system and temperature-programming cabinet. The following advantages have been showed by ashing experiment with apparatus above-mentioned. Because nitrogen and mixed gases of oxygen and nitrogen dioxide were supplied for charring and ashing of samples respectively, the total time of charring and ashing was shortened significantly and electric energy was saved. In comparison with the method of typical muffle furnace, the total time of the rapid ashing method for eight biological samples might be reduced by a factor of 6-53, and electric energy might be saved by a factor of 1.6-13, depending on different properties of biomaterials. This appratus can ash a large amount of samples a batch. For example, it may ash 3.8 kg fresh rabbits muscle a batch and 1.6-2 kg rice or wheat a batch. The fresh sample can also be charred and ashed directly. The apparatus is suitable for rapid ashing of a large amount of environmantal samples containing low level radioactivity and trace elements

[en] Estonian oil shale ash contains chemically active compounds which would undergo different spontaneous transformations in the atmosphere of air. For explaining these processes the system ash-water-air was studied storing moisture samples of ash in laboratory in open-air as well as hermetic conditions. The samples of dry ash formed at pulverized combustion of oil shale at the Baltic Power Plant, and samples obtained from ash storing plateau from different depth of different boreholes were under investigation. Storing conditions as well as the properties of initial samples have a great influence upon the processes taking place at storing of ashes. The results obtained could be used to explain and control the processes taking place at storing of ashes under atmospheric (wet) conditions

[en] Ash from the combustion of powdered Estonian oil shale in power plants has a high chemical reactivity and ability to bind hazardous components in the waste from the Sillamaee plant. This characteristic suggests that the ash should be considered as a component of a barrier system for remediation of the tailings pond. Different types of ash, collected in different parts of a power plant, show different reactivities

No abstract available

[en] Short communication. 2 refs, 1 fig

[en] The possibility of biological wastes treatment is discussed by using a RAF-3 type rapid ashing apparatus and the immobilization of ash with cement is studied. This apparatus, developed by China Institute for Radiation Protection (CIRP), is used for pretreatment of samples before chemical analysis and physical measurement. The results show that it can ash 3 kg of animal corpora by a batch, ashing time is 5-7 h and the ash content, <4%(wt). The ashing temperature not exceeding 450 deg. C is used without any risks of high losses of radionuclides. The ash can be immobilized with cement using an in-drum mixing procedure. The optimum formulation of cemented waste form is 35 ± 5% (wt) of the Datong Portland cement, 29 ± 2% (wt) of water and 36 ± 6% (wt) of ash. The cemented waste forms are homogeneous and dense. Its density is ∼ 1.78g/cm³, compressive strength is >7.7MPa. At the 42nd day the leaching rate of ¹³⁴Cs and ⁸⁵Sr is 2.5 x 10^-4 cm/d and 9.0 x 10^-4 cm/d respectively. The coefficient of volume reduction is about 1.6 for ash immobilization with cement. 100 kg of biological wastes becomes a less than 11.2 kg of cemented waste from after ashing and solidifying. (author). 8 refs, 2 figs, 3 tabs

[en] The coal unburned in flying ashes obtained in the processes of coal combustion is the main disadvantage for its use in the industry of the construction. This material normally has a size of particle greater than the mineral material, therefore it is possible to be separated in a considerable percentage, obtaining double benefit: the reusability of unburned like fuel or precursor for the activated charcoal production and the use of the mineral material in the industry of the construction since the organic matter has retired him that disables its use. In this work it is experienced with a sifted technique of separation by for three obtained flying ash samples with different technology (travelling Grill, pneumatic injection and overturning grill), were made grain sized analyses with meshes of a diameter of particle greater to 0,589 mm, the short analyses were made to them next to the retained material in each mesh and the unburned percentage of removal was determined of. The technique was compared with other developing.

[en] One of the most important parts of any analytical procedure is the initial decomposition of the sample. Not only must the sample matrix be dissolved but the element sought must be converted reliably to the proper ionic form before chemical reactions characteristic of that element can be obtained. Fusion with molten potassium fluoride is one of the simplest and most effective methods for dissolving metallic as well as siliceous refractories because of the stability of the fluoride complexes and the high reaction rates available at its melting point of 846⁰C. Inclusion of a small quantity of potassium nitrate even permits rapid and complete dissolution of refractory carbides such as Carborundum. The cake then be transposed either with sulfuric acid to a pyrosulfate fusion with simultaneous volatilization of both hydrogen fluoride and silicon tetrafluoride, or with nitric and boric acids to give a solution free of sulfate. The procedure is neither difficult nor time-consuming as is generally supposed. Extremely serious problems can be introduced by evaporating solutions of quadrivalent elements to dryness or by neutralizing them to too high a pH. Powerful sequestering agents can be produced from orthophosphates in the sample that will completely change the course of the analysis unless recognized and provided for. Standardizations are frequently carried out in a careless and inaccurate manner. Contamination is one of the greatest problems in trace analysis and needs to be avoided by good management and understanding of the causes. Preservation of both samples and standards can be vastly improved by application of a little more fundamental chemistry