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[en] The binder gypsum, with a content of constitutional water of 4.7 to 6.6% and a carbonate content smaller than 1%, is mixed with water glass. After this, one adds the waste-containing solution with HF, H2SO4, HClO4, HCl, HNO3, or KOH, NaOH, NE3, CaOH up to content of 40% by weight or with water-soluble organic compounds. (DG) 891 HP/DG 892 MBE
[de]Das Bindemittel Gips mit dem Kristallwassergehalt von 4,7 bis 6,6% und einem Karbonatgehalt kleiner 1% wird mit Wasserglas vermischt. Daraufhin erfolgt die Zugabe der die Abfallstoffe enthaltenden Loesung mit HF, H2SO4, HClO4, HCl, HNO3 oder KOH, NaOH, NE3, CaOH bis zu einem Gehalt von 40 Gew.% bzw. mit wasserloeslichen organischen Verbindungen. (DG)
[en] The international Phosphogypsum Working Group (PGWG) has its origins in joint meetings of the Stack Free project and the IAEA (2006). These led to formal joint meetings of the IAEA and FIPR (2006, 2007) and to a number of collaborative activities. Out of these activities came two IAEA sponsored meetings on PG, in 2008 and 2009. Another is planned for 2010. The PGWG has adopted the following vision and mission statements. 1. Vision. PG is a resource not a waste. 2. Mission. Find the point of equilibrium between PG production and consumption based on safe, sustainable use. (author)
[en] Full text: In salines the gypsum is deposited as impurity and after being subjected to the treatment process can be made possible its application in the cement industry. The great interest in the gypsum is assigned to a peculiar characteristic who consists in the ease of dehydration and rehydration. The calcination of the gypsum may occur in furnaces under atmospheric pressure or in autoclave, obtaining the types known as β and α plaster, respectively, both with a wide variety of industrial applications. The aim of this study consists on the optimization of the calcination of gypsum process, of the factors of temperature and time of calcination what were evaluated of accordance with design Box - Behnken (BBD), giving a solution for gypsum that is discarded on the ground without any isolation of the area or discarded at sea or river. The response surface methodology (RSM) of the response variable are the mechanical tests of resistance to compression set by NBR-13207. From the design was possible to obtain the chart predicted values for the observed values satisfying a mathematical model adjustment factor of 95%, obtained values of compression strength of 10 MPa higher than that required by the norms of the construction (> 8 40), analyzes of DRX with the predominant presence of quartz and of the beta plaster in the conditions. (author)
[en] This paper presents the results of a study to characterize the raw materials (ilmenite and slag), residue (red gypsum) and co-products (ferrous sulphate monohydrate and heptahydrate) associated with titanium dioxide production, in particular their elemental composition (major, minor and trace elements), mineralogy and radioactive content, with the objective of applying this knowledge to facilitate the use of some of these materials in applications such as construction and civil engineering. Obviously, the environmental and health impact of the co-products should comply with existing regulations. In particular, the main properties of cement produced with different proportions of red gypsum and the improvements obtained in relation to ordinary Portland cement have been studied. It is demonstrated that the levels of pollutants in the red gypsum cement remain within safety limits. (author)
[en] Natural radionuclides were analyzed in samples of phosphogypsum. The activity mass concentrations of these radionuclides and their decay products in both Togo and Palfos gypsum were higher than those observed in ordinary soil in the Philippines. The activity mass concentration of 238U and its daughters in Togo (325.8 Bq/kg wet weight) was relatively higher than that in Palfos (58.2 Bq/kg wet weight). In contrast, the activity concentration of 232Th and its daughters in Palfos (225.6 Bq/kg wet weight) was significantly higher than that in Togo (29.4 Bq/kg wet weight). Based on these results, it would appear that higher radon concentrations would emanate from Togo than from Palfos. Measurements of mass exhalation rate of radon in Togo indicated an average exhalation of 4.65 m Bq/kg/s while that in Palfos, 1.64 m Bq/kg/s. (author). 6 refs., 3 tabs
[en] A partition coefficient (λ) for Ra in gypsum was determined from coprecipitation experiment using oversaturation method. The λ-value derived for Ra was: λRa = 0.32±0.15. Saturation state was estimated with the initial concentration of Ca and SO42- in an experiment of the present study. Saturation index was calculated to be (0.49±0.02). This value was similar to those corresponds to analogous case where slow precipitation rate was kept in coprecipitation experiment for Sr in gypsum. Therefore, derived λ-value is thought to describe partition of Ra and Ca in solid phase and solution under an equilibrium condition without the effect of kinetic of precipitation. Determined λ-value was compared with those of other alkaline elements in sulfate minerals. The derived λ-value is smaller than that of Ra in barite and is similar to those of Sr in gypsum. This trend agrees with mechanical understanding for the size effect against partition coefficient. (author)
[en] Scaling formed by calcium sulfate dehydrate are often met in water desalination processes. Membranes scaling with gypsum are one of the problems met in reverses osmosis process. In a first place, the temperature influence on the induction time of gypsum nucleation (homogeneous and heterogeneous) was studied. The zone gypsum homogeneous nucleation witch take place at supersaturation values superior than 4 is distinguished from heterogeneous one witch occurred at low supersaturation. Gypsum nucleation chemical inhibition was also studied at different temperatures. The MPA (Nitrilotri (methyl-phosphonic acid) efficiency against gypsum precipitation was tested by following the induction time determined by the Quartz-microbalance. The MPA presents a very good efficiency as inhibitor against CaSO4.2H2O formation. Indeed, at low concentration (approximately 6 ppm), the MPA delay considerably gypsum germination and slow down its kinetics.
[en] As you know, the concentration of radon in buildings built with different building materials also varies. Wood and concrete houses can be considered satisfactory in terms of radon concentration. Thus, widespread construction materials such as trees, bricks and concrete produce relatively small radon radiation.In wooden houses, this radiation is minimal (up to 0.5 mZv / year), while brick and reinforced concrete houses are slightly larger (up to 1.5 mZv / year).It should be noted that the increase in radon concentrations inside buildings is not only building materials, but also soil below the building.Therefore, despite the fact that wood is less radiant than other building materials, in some cases wooden homes have more radon levels than brick houses.For example, studies in Norway have shown that concentration of radon in wooden houses is higher than that of brick houses, and it is found that these trees are usually smaller floors and closer to the radon source.During the development of phosphorus sources, calcium-silicate slag is formed as a by-product.This slag, which has long been used as a building material and concrete component in North america (Idaho and Florida) and Canada, has been found to have a sufficiently high radioactivity.Phosphorus mining uses a different technology to produce additional products called phosphogips.