Abstract
In this study, a thermodynamic model for silica and aluminum in high ionic strength solutions at elevated temperatures up to 100 °C is constructed. Pitzer equations are utilized for the thermodynamic model construction. This model is valid up to ionic strengths of ~24 molal (m) in NaOH solutions with silicate concentrations up to ~1.5 m. The speciation of silica (including monomers and polymers) and aluminum at elevated temperatures is taken into account. Also, the equilibrium constants for silicic acid and its polymer species (H4SiO4, H5Si2O7- , H4Si2O72-, and H5Si3O73-) at elevated temperatures up to 100 °C, are obtained based on theoretical calculations. Using this thermodynamic model, thermodynamic properties, including equilibrium constants, and respective reaction enthalpies are obtained for sodium silicates, zeolite A, and the amorphous form of zeolite A, based on solubility experiments at elevated temperatures. The equilibrium constants for zeolite A and amorphous precursor of zeolite A regarding the following reactions up to 100 °C,
where T is temperature in Kelvin. The enthalpy of formation from elements, Gibbs free energy of formation from elements, and standard entropy derived for zeolite A and the amorphous form of zeolite A with the chemical formulas mentioned above at 25 °C and 1 bar are -2738 ± 5 kJ/mol, -2541 ± 2 kJ/mol, 373 ± 10 J/(K·mol); and -2642 ± 3 kJ/mol, -2527 ± 2 kJ/mol, and 648 ± 10 J/(K·mol), respectively. The enthalpy of formation from elements for zeolite A derived in this study based on solubility experiments in hydrothermal solutions agrees well with those obtained by calorimetric measurements and by theoretical calculations.
© 2015 by Walter de Gruyter Berlin/Boston
Articles in the same Issue
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Articles in the same Issue
- H/D isotope effects in brucite at low temperatures
- Coupled H and Nb, Cr, and V trace element behavior in synthetic rutile at 600 °C, 400 MPa and possible geological application
- Dissolution-reprecipitation vs. solid-state diffusion: Mechanism of mineral transformations in sylvanite, (AuAg)2Te4, under hydrothermal conditions
- Compression and structure of brucite to 31 GPa from synchrotron X-ray diffraction and infrared spectroscopy studies
- Full analysis of feldspar texture and crystal structure by combining X-ray and electron techniques
- Correlating planar microstructures in shocked zircon from the Vredefort Dome at multiple scales: Crystallographic modeling, external and internal imaging, and EBSD structural analysis
- A spectroscopic and carbon-isotope study of mixed-habit diamonds: Impurity characteristics and growth environment
- Thermal infrared and Raman microspectroscopy of moganite-bearing rocks
- Mineralogical characterization and formation of Fe-Si oxyhydroxide deposits from modern seafloor hydrothermal vents
- Cathodoluminescence properties of quartz eyes from porphyry-type deposits: Implications for the origin of quartz
- Microbeam X-ray analysis of Ce3+/Ce4+ in Ti-rich minerals: A case study with titanite (sphene) with implications for multivalent trace element substitution in minerals
- Aluminum ordering and clustering in Al-rich synthetic phlogopite: The influence of fluorine investigated by {19F/1H} 29Si CPMAS NMR spectroscopy
- DFT+U investigation of the catalytic properties of ferruginous clay
- A thermodynamic model for silica and aluminum in alkaline solutions with high ionic strength at elevated temperatures up to 100 °C: Applications to zeolites
- Nanopores in hematite (α-Fe2O3) nanocrystals observed by electron tomography
- Berthierine-like mineral formation and stability during the interaction of kaolinite with metallic iron at 90 °C under anoxic and oxic conditions
- An X-ray diffraction study of the pressure-induced hydration in cordierite at 4–5 GPa
- Natural occurrence of keatite precipitates in UHP clinopyroxene from the Kokchetav Massif: A TEM investigation
- High-pressure Raman spectroscopy, vibrational mode calculation, and heat capacity calculation of calcium ferrite-type MgAl2O4 and CaAl2O4
- First-principles study on the high-pressure phase transition and elasticity of KAlSi3O8 hollandite
- Zircon growth and recrystallization during progressive metamorphism, Barrovian zones, Scotland
- Saltonseaite, K3NaMn2+Cl6, the Mn analogue of rinneite from the Salton Sea, California
- Rongibbsite, Pb2(Si4Al)O11(OH), a new zeolitic aluminosilicate mineral with an interrupted framework from Maricopa County, Arizona, U.S.A.
- Quadratite, AgCdAsS3: Chemical composition, crystal structure, and OD character
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- Crystal chemistry of layered Pb oxychloride minerals with PbO-related structures: Part II. Crystal structure of vladkrivovichevite, [Pb32O18][Pb4Mn2O]Cl14(BO3)8·2H2O
- Amorphous materials: Properties, structure, and durability: Acceleration and inhibition effects of phosphate on phase transformation of amorphous calcium carbonate into vaterite
- Letter: Implications of equilibrium and disequilibrium among crystal phases in the Bishop Tuff
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