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Beneficiation of Denizli - Acıgöl sodium sulphate ore by exploiting its structural properties
Published in Gülhan Özbayoğlu, Çetin Hoşten, M. Ümit Atalay, Cahit Hiçyılmaz, A. İhsan Arol, Mineral Processing on the Verge of the 21st Century, 2017
Sodium sulphate is an important industrial chemical. The main uses of sodium sulphate are in the pulp and paper, powder detergent, glass and textile dying industries. Sodium sulphate is widespread in occurrence and is a common constituent of many mineral waters, as well as seawater. Many of the saline lakes throughout the world contain varying amounts of sodium sulphate (Weisman, 1983). Sodium sulphate in its natural form is found as the hydrous salt mirabilite (commonly called glauber’s salt), and as thenardite, the anhydrous variety, mirabilite, Na2SO4.10H2O, contains 55,9 % water of crystallisation. It is efflorescence or spontaneous loss of water. On dehydration it changes to anhydrous form, Na2SO4. Thenardite, the anhydrous mineral, Na2SO4, contains 43,68 % Na2O and 56,32 % SO3.
Deterioration of Brickwork Retaining Walls as a Result of Thaumasite Formation
Published in Christer Sjöström, Durability of Building Materials and Components 7, 2018
Salts were collected from either on or below the surface of the garage retaining walls and three different compounds were detected using XRD analysis. These were (i) sodium sulphate (thenardite), (ii) a double salt containing potassium and sodium sulphate (aphthitalite) and (iii) a double salt containing potassium and calcium sulphate (syngenite). Whereas the precipitation of sodium or calcium salts as crypto-efflorescence is relatively harmless, the occurrence of crypto-efflorescent salts containing potassium can seriously damage the front face of brickwork [1] [2].
Characterization of lime mortar additivated with crystallization modifiers
Published in International Journal of Architectural Heritage, 2018
Sanne J.C. Granneman, Barbara Lubelli, Rob P.J. Van Hees
In the case of sodium sulfate, the identification of a modifier which can be effective in mortar is more difficult. Phosphonates are a group of crystallization modifiers for sodium sulfate often mentioned in literature (Rodriguez-Navarro and Benning 2013; Ruiz-Agudo, Rodriguez-Navarro, and Sebastián-Pardo 2006; Selwitz and Doehne 2002). However, phosphonates are not very well suited to be added to building materials, as their effect is strongly dependent on pH. A suitable alternative for modification of sodium sulfate crystallization was found in borax (Na2B4O7 · 10H2O) (Granneman et al. 2014; Ruiz-Agudo and Rodriguez-Navarro 2010). Borax is supposed to work as promoter of mirabilite in (bulk) solution (Ruiz-Agudo and Rodriguez-Navarro 2010; Schiro, Ruiz-Agudo, and Rodriguez-Navarro 2012; Telkes 1952), also at highly alkaline pH values, as those present in fresh mortar (Granneman et al. 2014). However, recent research by the authors on the crystallization of sodium sulfate from solution additivated with borax has pointed out that its modification mechanism is not so straightforward. It was shown that the effect of borax depends on the borax concentration and the experimental conditions. Depending on borax starting concentration, two phases of borax can crystallize, leading to a different effect on sodium sulfate crystallization. When borax crystallizes as the decahydrate, the precipitating sodium sulfate phase is the decahydrated mirabilite. However, when borax crystallizes as the pentahydrated tincalconite, the sodium sulfate crystallizes as anhydrous thenardite with {153} as the dominant crystal form (Granneman et al. 2017).
Application of X-ray diffractometry and scanning electron microscopy to study the transformation of carnallite and thenardite to schoenite at 25 °C
Published in Chemical Engineering Communications, 2020
Qingyu Hai, Huaide Cheng, Haizhou Ma, Jun Li, Xiwei Qin
From Table 3 and Equation (1), we find that (1) the double-decomposition of carnallite and mirabilite exists (Figure 4), but this reaction is unlikely and (2) the water required for the double-decomposition is negative because lots of structural water exists in carnallite and mirabilite. Mirabilite is unstable and dehydrates rapidly in dry air, the prismatic crystals convert to a white powder, thenardite. Therefore, we replaced mirabilite with thenardite, and the double-decomposition of carnallite and thenardite is described as follows:
Sulfate attack on residential concrete foundations in Japan
Published in Journal of Sustainable Cement-Based Materials, 2019
Figure 1 shows the appearance of deteriorated concrete. The common natures of the deterioration phenomenon observed in our investigations are the surface scaling of continuous footing and collapse of a floor post footing. The surface of the concrete was deteriorated along with white crystals. The white crystals were identified as sodium sulfate (thenardite and/or mirabilite) by using XRD (X-ray diffractometer).