Equilibrium and Structural Studies of Silicon(IV) and Aluminium(III) in Aqueous Solution. 11. Polysilicate Formation in Alkaline Aqueous Solution. A Combined Potentiometric and 29Si NMR Study.

Sjöberg, Staffan; Öhman, Lars‐Olof; Ingri, Nils; Andersen, Leif Percival; Lindqvist, Oliver; Žemlička, Milan

doi:10.3891/acta.chem.scand.39a-0093

Cited by 55 publications

(39 citation statements)

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“…These efforts were based on potentiometric titrations as well as infrared, Raman and 29 Si NMR spectroscopy [11][12][13][14][15][16][17]. From these studies, it became clear that aqueous silicate solutions is a mixture of anions and that the distribution of various silicate species mainly depended on the SiO 2 :Na 2 O ratio, SiO 2 concentration, pH, temperature and aging.…”

Section: Introductionmentioning

confidence: 99%

A study of sodium silicate in aqueous solution and sorbed by synthetic magnetite using in situ ATR-FTIR spectroscopy

Yang

Roonasi

Holmgren

2008

Journal of Colloid and Interface Science

167

105

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The sorption of sodium silicate by synthetic magnetite (Fe 3 O 4 ) at different pH conditions (pH 7-11) and initial silicate concentrations (1 × 10 −3 and 10 × 10 −3 mol L −1 ) was studied using in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. The analysis of infrared spectra of sodium silicate in solution as well as adsorbed on magnetite nano-particles clearly showed the evolution of different silicate species depending on pH and silica concentration. The silicate concentration studied (10 × 10 −3 mol L −1 ) contained polymeric or condensed silicate species at lower pH as well as monomers at high pH, as evident from infrared spectra. Condensation of monomers resulted in an increased intensity of absorptions in the high frequency part (>1050 cm −1 ) of the spectral region, which contains information about both silicate in solution and sorbed silicate viz. 1300 cm −1 -850 cm −1 . In the pH range studied, infrared spectra of sorbed silicate and sorbed silicate during desorption both indicated the presence of different types of surface complexes at the magnetite surface. The sorption mechanism proposed is in accordance with a ligand exchange reaction where both monodentate and bidentate complexes could exist at low surface loading level, the relative proportion of the complexes being due to both pH and concentration in solution. Oligomerization occurred on the magnetite surface at higher surface loading.

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Section: Introductionmentioning

confidence: 99%

A study of sodium silicate in aqueous solution and sorbed by synthetic magnetite using in situ ATR-FTIR spectroscopy

Yang

Roonasi

Holmgren

2008

Journal of Colloid and Interface Science

167

105

View full text Add to dashboard Cite

show abstract

“…One study assumed only the monomer and the dimer, but it allowed all possible ionizations of each (Sef5iK et al, 1997). Most other modelers (Svensson et al, 1986;Caullet et al, 1989;Grenthe et al, 1992;Eikenberg et al, 1990;Sjoberg et al, 1985) have included higher polymeric species as well. This study has also included the higher polymers since it is more comprehensive.…”

Section: Solubilities In Neutr4l Salt Solutionsmentioning

confidence: 99%

“…Initially, the exact set of silicate species (Sjoberg et al, 1985) was selected for this study since the results comprise more than half of the data used in this study. The optimal parameter fits were obtained for the same formation constants.…”

Section: Solubilities In Neutr4l Salt Solutionsmentioning

confidence: 99%

Prevention of solids formation: Results of the FY 1999 studies

Hunt¹,

Beahm²,

Chase³

et al. 1999

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Additional components such as nitrite and carbonate will be added to the test matrix. The results will be used to develop safe operating windows for safe waste transf=s at Hadord. In addition to the waste transfer, unwanted solids formation can occur during waste processing activities such as the Enhanced Sludge Washing (ESW). Previous work has shown that phosphate gels and particles are formed as the hot leach solutions from the ESW process are permitted to cool. In another study, insoluble aluminosilicates apparently formed during the hot caustic leaching, which significantly reduced the pefiormance of &e ESW process. The aluminosilicates, as well as the phosphate gels from the ESW process, could also forma pipeline plug. This study confirmed the formation of alurninosilicates during the ESWprocess and demonstrated the importance of a thorough water wash prior to the caustic leaches. The water wash improves the performance and the reproducibility of the ESW process. A key difference in the leach tests with washed sludge and unwashed sludge was the higher ionic strength in the unwashed tests due to the presence of water-soluble salts. In response to the alurninosilicate plug at Savannah River, an equilibrium model on the solubilities of silicate vii species at 25 'C was developed. After the solubilities of silicon and aluminum species at higher temperatures are incorporated into the model, safe operating windows for the evaporator system will -be provided to the tank farm operators. Finally, a simulated chemical plug based on the sodium phosphate plug was developed and provided to the Retrieval Program of the Tanks Focus Area to test recovery methods. Additional simulated plugs have been requested.

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“…Under highly basic conditions Si(IV) can form a wide range of monomeric and polymeric species ranging from simple monomers to cubic octamers (Sjoberg et al 1985;Svensson et al 1986). These, species, which often are highly charged, have also been shown to interact strongly with environmentally important species such as Sr and Eu (a trivalent actinide analog), thus increasing the solubility of the important solid phases of these elements [i.e., SrCO 3 (c) and Eu(OH) 3 ].…”

Section: Understanding the Formation Of Polymerized Species Under Extmentioning

confidence: 99%

Computational Studies in Molecular Geochemistry and Biogeochemistry

Felmy¹,

Bylaska²,

Dixon³

et al. 2006

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Equilibrium and Structural Studies of Silicon(IV) and Aluminium(III) in Aqueous Solution. 11. Polysilicate Formation in Alkaline Aqueous Solution. A Combined Potentiometric and 29Si NMR Study.

Cited by 55 publications

References 0 publications

A study of sodium silicate in aqueous solution and sorbed by synthetic magnetite using in situ ATR-FTIR spectroscopy

A study of sodium silicate in aqueous solution and sorbed by synthetic magnetite using in situ ATR-FTIR spectroscopy

Prevention of solids formation: Results of the FY 1999 studies

Computational Studies in Molecular Geochemistry and Biogeochemistry

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