Arun2642
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What factors contribute most to solubility of ionic substances in highly polar solvents, esp. ionic liquids and DESs?
I am trying to determine a method to dissolve a mineral salt with a lattice energy of β18000 kJ/mol. I know that lattice energy is the most
significant factor affecting solubility of an ionic substance in highly polar solvents, and my general understanding is that the more polar (or
locally polar), the greater the ability of the solvent to dissolve materials with higher lattice energies, by contributing more hydrogen bonding
and/or more efficient charge distribution.
Hence I have been testing solubility in an array of Deep Eutectic Solvents (DES) and doing research into solubility of this and similar compounds in
other ionic liquids, and reached out to an expert in the field.
I have found that while these solvents are typically able to dissolve compounds with lattice energies unto around 12000 kJ/mol. in great quantity,
solubility quickly drops off around 15000 kJ/mol. and the professor I contacted said that their research indicated that without other agents, this
material would be insoluble in the ionic liquids they worked with because of it's high lattice energy.
My question then is what other factors would be most important in increasing the solubility of this compound in ionic liquids, anything from adding
highly soluble cations, chelating agents, type of ionic liquid I might use, or any other other factors that play into solubility, and could be tuned
to optimal conditions?
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AJKOER
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This may just be an oversight on your part, but you did not mention temperature or pressure (for gases, primarily).
In general, if you can find something that helps to induces a chemical reaction, the solubility could benefit (chelating agents fall into this
category). Increasing surface area is sometimes cited (for example, if possible, create a nano suspension). For solids, ball milling explained below,
to quote:
"It is a ball milling process where a powder mixture placed in the ball mill is subjected to high-energy collision from the balls. This process was
developed by Benjamin and his coworkers at the International Nickel Company in the late of 1960. It was found that this method, termed mechanical
alloying, could successfully produce fine, uniform dispersions of oxide particles (Al2O3, Y2O3, ThO2) in nickel-base superalloys that could not be
made by more conventional powder metallurgy methods. Their innovation has changed the traditional method in which production of materials is carried
out by high temperature synthesis. Besides materials synthesis, high-energy ball milling is a way of modifying the conditions in which chemical
reactions usually take place either by changing the reactivity of as-milled solids (mechanical activation β increasing reaction rates, lowering
reaction temperature of the ground powders)βor by inducing chemical reactions during milling (mechanochemistry). It is, furthermore, a way of
inducing phase transformations in starting powders whose particles have all the same chemical composition: amorphization or polymorphic
transformations of compounds, disordering of ordered alloys, etc."
Link: http://www.understandingnano.com/nanomaterial-synthesis-ball...
My speculation being, that ball milling the mineral salt to be dissolved may favorably alter the lattice energy.
[Edit] See also "Microstructural changes and effect of variation of lattice strain on positron annihilation lifetime parameters of zinc ferrite
nanocomposites prepared by high enegy ball-milling" where the full text is available at http://www.scielo.br/scielo.php?pid=S1516-14392012000600028&...
[Edited on 7-7-2015 by AJKOER]
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Metacelsus
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What's the salt? Aluminum nitride? Not many compounds have lattice energies that high. You probably know this, but you need to think in terms of
making the solvated state have a lower free energy.
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