Concentration- and pH-dependence of highly alkaline sodium silicate solutions

Nordström, Jonas; Nilsson, Erik; Jarvol, Patrik; Nayeri, Moheb; Palmqvist, Anders; Bergenholtz, Johan; Matic, Aleksandar

doi:10.1016/j.jcis.2010.12.085

Cited by 57 publications

(30 citation statements)

References 27 publications

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“…The behavior of Na 2 SiO 3 in aqueous solutions have been intensively investigated: depending on the pH of the solution and the total silica concentration, the silica tetrahedral (SiO 4 ) can be under SiO 4− 4 , SiO 3 (OH) 3− , SiO 2 (OH) 2− 2 , SiO(OH) − 3 , and Si(OH) 4 forms (Engelhardt et al, 1975;Marinakis, 1980;Marinakis and Shergold, 1985;Bass and Turner, 1997;Halasz et al, 2007;Jansson et al, 2015). Furthermore, the pH, total silica concentration, and SiO 2 :Na 2 O ratio affect the polymerization degree of silica tetrahedra, a high ratio inducing a high polymerization degree (Lentz, 1964;Marinakis, 1980;Bass and Turner, 1997;Dimas et al, 2009;Nordström et al, 2011;Jansson et al, 2015). In the froth flotation process, according to the SiO 2 :Na 2 O ratio and the total silica concentrations commonly used, the main species of Na 2 SiO 3 are Si(OH) 4 for pH < 9.4 and SiO(OH) − 3 for 9.4 < pH < 12.6 (Marinakis, 1980;Han et al, 2016) (Figure 11).…”

Section: Sodium Silicatementioning

confidence: 99%

The Challenge of Tungsten Skarn Processing by Froth Flotation: A Review

et al. 2020

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Recently, tungsten has drawn worldwide attention considering its high supply risk and economic importance in the modern society. Skarns represent one of the most important types of tungsten deposits in terms of reserves. They contain fine-grained scheelite (CaWO 4) associated with complex gangue minerals, i.e., minerals that display similar properties, particularly surface properties, compared to scheelite. Consistently, the froth flotation of scheelite still remains, in the twenty first century, a strong scientific, industrial, and technical challenge. Various reagents suitable for scheelite flotation (collectors and depressants, mostly) are reviewed in the present work, with a strong focus on the separation of scheelite from calcium salts, namely, fluorite, apatite, and calcite, which generally represent significant amounts in tungsten skarns. Albeit some reagents allow increasing significantly the selectivity regarding a mineral, most reagents fail in providing a good global selectivity in favor of scheelite. Overall, the greenest, most efficient, and cheapest method for scheelite flotation is to use fatty acids as collectors with sodium silicate as depressant, although this solution suffers from a crucial lack of selectivity regarding the above-mentioned calcium salts. Therefore, the use of reagent combinations, commonly displaying synergistic effects, is highly recommended to achieve a selective flotation of scheelite from the calcium salts as well as from calcium silicates.

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Section: Sodium Silicatementioning

confidence: 99%

The Challenge of Tungsten Skarn Processing by Froth Flotation: A Review

et al. 2020

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“…A similar mechanism is not likely to take place in silicate-based AAS systems, as the increase in hydroxide concentration due to recrystallisation of CLDH in sodium silicate solution would have much less effect on increasing its alkalinity, mainly due to the complexity of the silica speciation in concentrated sodium silicate solutions which buffers the apparent pH changes. 30,31 Hence, the changes in reaction kinetics identified in the modified AAS cements assessed may be associated with a combination of fillertype and nucleation templating effects, both speeding up the reaction and favouring precipitation of larger amounts of reaction products. However, to enable the clear identification of the roles played by both CLDH and HT additions in the AAS system, it is important to correlate the reaction kinetics with the reaction products forming in these cements.…”

Section: Kinetics Of Reactionmentioning

confidence: 99%

Layered double hydroxides modify the reaction of sodium silicate-activated slag cements

Bernal

Provis

2019

Green Materials

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The impact of adding two types of layered double hydroxides (LDHs), commercial hydrotalcite (HT) and its thermally treated form (CLDH), on the reaction kinetics and phase assemblage development of a sodium silicate-activated slag cement was investigated. The reaction kinetics of LDH-modified cements was assessed by isothermal calorimetry, and the results were correlated with in situ attenuated total reflection Fourier transform infrared spectroscopy results collected over the first days of reaction, to identify the structural evolution of the main binding phase forming in these cements: a sodium-containing calcium aluminosilicate hydrate (C-(N)-AS -H)-type gel. The addition of either HT or CLDH into sodium silicate-activated slag paste accelerates the precipitation of reaction products and increases the formation of HT in these cements, without causing significant changes to the C-(N)-AS -H binding phase. This is extremely relevant in terms of the durability of alkali-activated slag cements, as a higher content of the HT-like phase has the potential to reduce their chloride permeability and enhance carbonation resistance. 52 Cite this article Ke X, Bernal SA and Provis JL (2019) Layered double hydroxides modify the reaction of sodium silicate-activated slag cements.

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“…The Q 4 structure almost disappeared, and the small peak at −83 ppm was attributed to the Q 2 structures, i.e. cyclic trisilicate . In addition, the spectrum of the Sol solution showed only two broad signals centered at the regions of (−95)–(−100) and (−100)–(−105) ppm, corresponding to the Q 3 and Q 4 anionic structures, respectively.…”

Section: Resultsmentioning

confidence: 98%

Effect of formulation of silica‐based solution on corrosion resistance of silicate coating on hot‐dip galvanized steel

Zhang

Kong

Sun

et al. 2016

Surface & Interface Analysis

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Several silica-based solutions with 50 g/l of SiO 2 were prepared from sodium silicate solutions and silica sol; the silicate conversion coatings were obtained by immersing hot-dip galvanized steel sheets in these solutions. These solutions were characterized using high-resolution transmission electron microscopy and 29 Si nuclear magnetic resonance; the morphology of the coatings was observed by SEM and atomic force microscopy while the corrosion resistance was evaluated by electrochemical measurements as well as neutral salt spray tests. The results show that the coatings obtained from the single silica sol solution had poor adhesion and the coating obtained from the sodium silicate solution with low SiO 2 /Na 2 O molar ratio was uneven. By adding the silica sol to the silicate solution with low molar ratio, uniform coatings with better protection property were obtained. According to the results of 29 Si nuclear magnetic resonance spectra, the effects of the distribution of silicate anions with various polymerization degrees in the silica-based solutions on the microstructure and corrosion resistance of the silicate coatings are discussed.

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Concentration- and pH-dependence of highly alkaline sodium silicate solutions

Cited by 57 publications

References 27 publications

The Challenge of Tungsten Skarn Processing by Froth Flotation: A Review

The Challenge of Tungsten Skarn Processing by Froth Flotation: A Review

Layered double hydroxides modify the reaction of sodium silicate-activated slag cements

Effect of formulation of silica‐based solution on corrosion resistance of silicate coating on hot‐dip galvanized steel

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