I am trying to find out an environmentally friendly alternative to organic solvents, like liquid/gaseous CO2, for my following application.
I have been working to change the surface property of some powdered compounds like Inorganic 0xides and pigmnts using some liquid surface active
agents (SA). In this process, a mixture of solvent + SA is prepared and the insoluble powder is suspended and fully dipped (soaked) into this liquid
mixture. After a few minutes the slurry is mixed slowly to homogeneously impregnate the powder and then the solvent is removed thoroughly under
reduced pressure, living behind the powder fully covered/coated with the SA.
Although this has given me the desired results, due to some specific reasons and restrictions I am being forced to obsolete the use of ANY organic
solvent and replace it with an environmentally friendly alternatives like liquid CO2 and alike.
My question is :
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Is it possible to use gaseous CO2 or dry ice in place of organic solvents in a pressurized vessel/autoclave along with starting Powder (99% by wt.) +
SA (1% by wt.) mixture, then changing pressure/temperature conditions for creating CO2 liquid media, mixing for a short while and then finally
releasing the CO2 gas living behind only the coated powder??
Are there any practically viable suggestions for this and some others like this?
Please note: Here role of the solvent is only to create a liquid media giving a quantitative coating solution for the SA. There is only soaking, no
extraction is involved.
P.S. : The credit of this idea of using CO2 in place of organic solvents goes fully to AvBaeyer.
[Edited on 20-3-2014 by enertech]jwpa17 - 20-3-2014 at 05:10
Is it possible? Probably.
Suggestions - call Dionex and speak with an application specialist for their supercritical fluid (SCF) extraction system. Yes, you're not trying to
extract. But the Dionex Corp is the only source I know of SCF technology. It's not that there aren't others; I just don't know of others. (BTW -
Dionex is now part of Thermo-Fisher.)
I suspect (but have no real experience with SCF) that you'll need to verify that you can actually dissolve the surfactant in the liquid CO2 - you may
need some small amount of additive, like methanol (sorry). Also, based on making old-style packed column GC packings, you'll need to agitate the
mixture while you're releasing the SCF, and probably you'll need to control the release-rate of the SCF to prevent really exciting "bumping."
Interesting engineering problems ahead. I'll bet that there's a reasonable amount of chemical engineering literature on the use of liquid CO2 - it's
been used industrially since the mid-60's, I believe.
Sincerely - good luck.
[Edited on 20-3-2014 by jwpa17]enertech - 20-3-2014 at 20:27
Dear jwpa17,
Actually the problem with SCF is it's too expensive to go on. I am looking for another alternative in which I can use conventional CO2 gas/liquid/dry
ice and maintain some specific temp+pressure conditions to change the phase from liquid to gas or vice versa. Is this possible?
Will be looking forward if I could receive some suggestions and advises for this.....
Propane / Butane as solvent media
enertech - 16-4-2014 at 04:09
Besides CO2, can the Propane OR Butane as compressed gas - (liquid form) be used for this?
confused - 16-4-2014 at 06:12
you might want to consider supercritical methanol Etaoin Shrdlu - 16-4-2014 at 09:39
