Thermodynamic study of alkali and alkaline-earth cation-exchanged natrolites

Wu, Lili; Navrotsky, Alexandra; Lee, Yong Jae

doi:10.1016/j.micromeso.2012.09.003

Cited by 12 publications

(10 citation statements)

References 28 publications

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“…Using the C p° = 359.2±0.7 J/mol/K and S° = 359.7±1 J/mol/K of Johnson et al (1983), the measured increase of natrolite solubility as a function of temperature is described well. The Δ f H° calculated from Δ f G° and S° (Table 4) is with -5728±10 kJ/mol in good agreement with the Δ f H° = -5719±5 kJ/mol measured by Johnson et al (1983) and the -5724±6 kJ/mol measured by Wu et al (2013). Figure 7: Solubility products for A) zeolite P(Ca):…”

Section: Solubility Of Natrolite and Zeolite P(ca)supporting

confidence: 83%

Zeolite formation in the presence of cement hydrates and albite

Lothenbach

Bernard

Mäder

2017

Physics and Chemistry of the Earth, Parts A/B/C

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Zeolite formation caused by interactions between cement hydrates and rock forming minerals was investigated by two sets of batch experiments and supported by thermodynamic modelling. The first set of batch experiments investigated the interaction between calcium silicate hydrates (C-S-H) (Ca 0.8 SiO 2.8 •32H 2 O) and ettringite (Ca 6 Al 2 (SO 4) 3 (OH) 12 (H 2 O) 26) as cement hydrate minerals and albite (NaAlSi 3 O 8) as a rock forming mineral at 20, 50 and 80°C. The dissolution of C-S-H, ettringite and albite led to relatively high calcium and low silicon and sodium concentrations and to the formation of zeolite P(Ca) (Ca 2 Al 2 Si 2 O 8 4.5H 2 O) and natrolite (Na 2 Al 2 Si 3 O 10 2H 2 O). The second set of experiments used ettringite and silica fume as cement phases and NaAlO 2 to represent a rock forming mineral. High initial sodium, hydroxide and aluminium concentrations were observed leading to the precipitation of zeolite X (Na 2 Al 2 Si 2.5 O 9 6.2H 2 O) and C-S-H gel at 20 and 50°C where only 40 to 60% of the silica had reacted after 3 years. At 80°C where more silica fume had reacted, the formation of SiO 2-rich zeolite Y (Na 2 Al 2 Si 4 O 12 8H 2 O) and chabazite (CaAl 2 Si 4 O 12 6H 2 O) was observed. Solubility products for the zeolite P(Ca), natrolite, chabazite, zeolite X and zeolite Y were obtained from the measured concentrations. Comparison with values published in the literature shows a high

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Section: Solubility Of Natrolite and Zeolite P(ca)supporting

confidence: 83%

Zeolite formation in the presence of cement hydrates and albite

Lothenbach

Bernard

Mäder

2017

Physics and Chemistry of the Earth, Parts A/B/C

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“…This implies that the chemical nature and crystallographic distribution of charge-compensating cations may be crucial factors governing the stability of ion-exchanged zeolites. Although they may be less obvious for high silica zeolites, − such differences are clearly obvious for zeolites with low Si/Al ratio, such as zeolite A.…”

Section: Results and Discussionmentioning

confidence: 99%

“…The energetics of several ion-exchanged zeolites, including zeolite β, Y, and natrolite, have been investigated by direct calorimetric measurement of heats of formation. − Very recently, we studied the energetics of Na–Ca ion-exchanged zeolite A with different calcium contents using high temperature oxide melt solution calorimetry . We found that the overall energetics and degree of hydration of Na–Ca ion-exchanged zeolite A are tightly correlated with the average ionic potential of guest cations ( Z / r , defined as ∑ X i ( Z / r )/∑ X i ), where X is mole fraction, Z is charge, and r is ionic radius .…”

Section: Introductionmentioning

confidence: 99%

Energetics of Alkali and Alkaline Earth Ion-Exchanged Zeolite A

Sun

Liu

et al. 2016

J. Phys. Chem. C

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Alkali and alkaline earth ion-exchanged zeolite A samples were synthesized in aqueous exchange media. They were thoroughly studied by powder X-ray diffraction (XRD), electron microprobe (EMPA), thermogravimetric analysis and differential scanning calorimetry (TG-DSC), and high temperature oxide melt solution calorimetry. The hydration energetics and enthalpies of formation of these zeolite A materials from constituent oxides were determined. Specifically, the hydration level of zeolite A has a linear dependence on the average ionic potential (Z/r) of the cation, from 0.894 (Rb-A) to 1.317 per TO2 (Mg-A). The formation enthalpies from oxides (25 °C) range from −93.71 ± 1.77 (K-A) to −48.02 ± 1.85 kJ/mol per TO2 (Li-A) for hydrated alkali ion-exchanged zeolite A, and from −47.99 ± 1.20 (Ba-A) to −26.41 ± 1.71 kJ/mol per TO2 (Mg-A) for hydrated alkaline earth ion-exchanged zeolite A. The formation enthalpy from oxides generally becomes less exothermic as Z/r increases, but a distinct difference in slope is observed between the alkali and the alkaline earth series.

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“…This positive linear trend is consistent with previous studies on zeolites Y, beta, and natrolite, all of which show less exothermic formation enthalpies from oxides for both hydrated and dehydrated zeolites as the average ionic potential increases. [35][36][37][38] This reflects the fundamental acid-base chemistry of ternary oxide formation, with alkali ternary oxide compounds showing more exothermic enthalpies of formation than alkaline earth compounds.…”

Section: Discussionmentioning

confidence: 99%

Energetics of sodium–calcium exchanged zeolite A

Sun

Guo

et al. 2015

Phys. Chem. Chem. Phys.

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A series of calcium-exchanged zeolite A samples with different degrees of exchange were prepared. They were characterized by powder X-ray diffraction (XRD) and differential scanning calorimetry (DSC). High temperature oxide melt drop solution calorimetry measured the formation enthalpies of hydrated zeolites CaNa-A from constituent oxides. The water content is a linear function of the degree of exchange, ranging from 20.54% for Na-A to 23.77% for 97.9% CaNa-A. The enthalpies of formation (from oxides) at 25 °C are -74.50 ± 1.21 kJ mol(-1) TO2 for hydrated zeolite Na-A and -30.79 ± 1.64 kJ mol(-1) TO2 for hydrated zeolite 97.9% CaNa-A. Dehydration enthalpies obtained from differential scanning calorimetry are 32.0 kJ mol(-1) H2O for hydrated zeolite Na-A and 20.5 kJ mol(-1) H2O for hydrated zeolite 97.9% CaNa-A. Enthalpies of formation of Ca-exchanged zeolites A are less exothermic than for zeolite Na-A. A linear relationship between the formation enthalpy and the extent of calcium substitution was observed. The energetic effect of Ca-exchange on zeolite A is discussed with an emphasis on the complex interactions between the zeolite framework, cations, and water.

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Thermodynamic study of alkali and alkaline-earth cation-exchanged natrolites

Cited by 12 publications

References 28 publications

Zeolite formation in the presence of cement hydrates and albite

Zeolite formation in the presence of cement hydrates and albite

Energetics of Alkali and Alkaline Earth Ion-Exchanged Zeolite A

Energetics of sodium–calcium exchanged zeolite A

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