Solubility and Solvation Parameters of Calcium Carbonate in Mixed Ethanol-water Mixtures at 301.15 K

Gomaa, Esam A.

doi:10.5923/j.scit.20120201.10

Cited by 8 publications

(5 citation statements)

References 10 publications

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“…By replacing a significant portion of water with ethanol, the relative saturation state will increase. Gomaa shows that the calcite solubility product decreases by 1 log unit with every ∼25 mol % increase of ethanol solution. However, increases in the saturation state along could not drive the formation of Ca–Mg carbonate, which has been demonstrated by Land .…”

Section: Discussionmentioning

confidence: 99%

Low-Temperature Synthesis of Disordered Dolomite and High-Magnesium Calcite in Ethanol–Water Solutions: The Solvation Effect and Implications

et al. 2021

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How dolomite [CaMg(CO 3 ) 2 ] forms is still underdetermined, despite over a century of efforts. Challenges to synthesizing dolomite at low temperatures have hindered our understanding of sedimentary dolomite formation. Unlike calcium, magnesium’s high affinity toward water results in kinetic barriers from hydration shells that prevent anhydrous Ca–Mg carbonate growth. Previous synthesis studies show that adding low-dielectric-constant materials, such as dioxane, dissolved sulfide, and dissolved silica, can catalyze the formation of disordered dolomite. Also, polar hydrophilic amino acids and polysaccharides, which are very common in biomineralizing organisms, could have a positive role in stimulating Mg-rich carbonate precipitation. Here, we show that disordered dolomite and high-magnesium calcite can be precipitated at room temperature by partially replacing water with ethanol (which has a lower dielectric constant) and bypassing the hydration barrier. Increasing the ethanol volume percentage of ethanol results in higher Mg incorporation into the calcite structure. When the ethanol volume percentage increases to 75 vol %, disordered dolomite (>60 mol % MgCO 3 ) can rapidly precipitate from a solution with [Mg 2+ ] and [Ca 2+ ] mimicking seawater. Thus, our results suggest that the hydration barrier is the critical kinetic inhibitor to primary dolomite precipitation. Ethanol synthesis experiments may provide insights into other materials that share similar properties to promote high-Mg calcite precipitation in sedimentary and biomineral environments.

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Section: Discussionmentioning

confidence: 99%

Low-Temperature Synthesis of Disordered Dolomite and High-Magnesium Calcite in Ethanol–Water Solutions: The Solvation Effect and Implications

et al. 2021

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“…This is explained by the mass loss during PT (Y SR = 56 wt%), where Y SR is solid residue yield after pretreatment (wt%), and hints that an organic solvent‐ (e.g. ethanol)‐based PT is not an effective tool for calcium removal, which is easily explained by the poor solubility of calcium salts, such as calcium carbonate, 27 in water‐ethanol mixtures. The spent liquor was also only mildly acidic, pH = 4.2, whereas a pH < 3 is deemed necessary to remove calcium from biomass significantly 28 …”

Section: Resultsmentioning

confidence: 99%

Cellulosic glycols: an integrated process concept for lignocellulose pretreatment and hydrogenolysis

Molder

Kersten

Lange

et al. 2021

Biofuels Bioprod Bioref

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Lignocellulose is the most abundant source of saccharides and it is therefore a promising feedstock for glycols, such as ethylene-glycol, via catalytic hydrogenolysis of the polysaccharides that it contains. However, this catalytic hydrogenolysis step is hampered by the presence of lignin and other biomass contaminants, such as ash, which need to be removed in a pretreatment step. We propose an organosolv-like pre-treatment that can delignify and de-ash lignocellulose to a level that allows it to be upgraded to glycol with comparable yields to pure cellulose under demanding hydrogenolysis conditions. This work identifies the main design constraints of the integrated process and provides an initial experimental validation of it. Pretreatment of biomass in water/ethanol/acetic acid solutions at 180-200 °C can reduce the lignin content of the solid residue to ≤6 wt%. The addition of an organic acid, such as acetic acid, appears important to improve the removal of the recalcitrant Ca 2+ , which is a known inhibitor of the tungstate catalyst typically used in this process. The pretreatment medium is designed to use the by-product(s) of the process as organic solvent, to reduce the need for fresh solvent input. However, the process still needs a high solvent recovery (between 93.5 and 99.9 wt%). This can be achieved by selecting volatile component as organic solvent, as it allows recovery by evaporation from the dissolved lignin and ashes.

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“…The Gibbs free energies of association were calculated by applying equation (9) [20][21][22][23] in absences and presences of Kryptofix 221 in mixed MeOH-DMF solvents at different temperatures and their values are shown also in Tables (2) and (3).…”

Section: Resultsmentioning

confidence: 99%

Conductometric Studies of Calcium Ions with Kryptofix 221 in Mixed MeOH-DMF Solvents at Different Temperatures

Gomaa¹,

Al-Jahdali²

2012

EDU

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On using conductometric technique, the apparent association constant (K A ) of Ca (NO 3 ) 2 were measured in mixed MeOH-DMF mixed solvents at 0,20, 40 , 60 ,80 and 100% MeOH (by volume) and different temperatures (298.15, 303.15, 308.15 and 313.15K) in absence and presence of . 7,13,16,8,5) tricosane]. From the experimental results, the molar conductivities (∧) were calculated and limiting molar conductivities (∧ 0 ) were calculated by using Shedlovsky and Fouss -Kraus extrapolation methods. The molar solvated (∨), Van der Waals (∨ w ) and electrostriction (∨ e ) were evaluated. The association constants K A for Ca(NO 3 ) 2 were calculated by using simple equation derived from Ostwald, Arrhenius and Fuoss-Shedlovsky theories. From the association constants the different thermodynamic parameters were evaluated and the results obtained were discussed. The free energy of association ( A G ∆ ), free energy necessary for complexation ( complex G ∆ ) and enthalpy ( ΔH ) were determined. It was concluded that the maximum complexation between calcium ions and Kryptofix-221 were by using 80% and 100%. MeOH in the mixtures. Where as the least complexing ability at 40% and 60% by volume of MeOH .This work give data can help for the analytical determination of calcium in blood and water samples.

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Solubility and Solvation Parameters of Calcium Carbonate in Mixed Ethanol-water Mixtures at 301.15 K

Cited by 8 publications

References 10 publications

Low-Temperature Synthesis of Disordered Dolomite and High-Magnesium Calcite in Ethanol–Water Solutions: The Solvation Effect and Implications

Low-Temperature Synthesis of Disordered Dolomite and High-Magnesium Calcite in Ethanol–Water Solutions: The Solvation Effect and Implications

Cellulosic glycols: an integrated process concept for lignocellulose pretreatment and hydrogenolysis

Conductometric Studies of Calcium Ions with Kryptofix 221 in Mixed MeOH-DMF Solvents at Different Temperatures

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