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Author: Subject: How to remove a surfactant combo
JibbyDee
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[*] posted on 9-12-2011 at 23:40
How to remove a surfactant combo


How would you go about removing two synergistic surfactants from a mixture in which one surfactant is soluble in non polar solvents (in this case its stearyl alcohol) and the other surfactant is soluble in polar solvents (in this case its hydroxyethylcellulose)? I hear that adding salt to an emulsion, forces the aqueous phase and organic phase to properly separate into 2 layers. If I was to dilute the solution enough to bring it below the critical micelle concentration, would there be a way to overcome the effects of the surfactants and force two phases to form? In a situatation like that, I'm guessing the stearyl alcohol would go into the organic phase while the hydroxyethylcellulose would stay in the aqueous phase.

UPDATE: I added the substance to acetone to see if it would dissolve but it exhibited the same dissolution properties as it did in water, i.e. end up with insoluble, clumps floating around in the solvent. This time though, I suspect that its the hydroxyethyl cellulose that is insoluble in the acetone, instead of the stearyl alcohol which was insoluble in water. To test this theory I added water to the mixture and the mixture instantly turned cloudy then a large amount of foam formed in the solvent and rose to the top of the mixture. There are still solid particles floating around the bottom of the mixture but now there is a layer of foam on the top of the liquid. Any idea whats going on here? Why did the mixture foam up when I added water? Water or acetone alone don't produce foam like that, it was only when I mixed the 2 solvents.

UPDATE2: This happens every time I add water to acetone, but not the other way around. My theory is that when the water mixes with the acetone, the acetone forces the dissolved oxygen out of the water, the oxygen bubbles rise and the stearyl alcohol traps some of it and forms a foam at the top. I can see bubbles rising as soon as I add the water. Something doesn't add up though. Why doesn't this happen when I add acetone to water? It only happens when I add water to acetone.

[Edited on 10-12-2011 by JibbyDee]
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Panache
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[*] posted on 15-12-2011 at 08:00


remember there is no such thing as a thermodynamically stable emulsion, only a kinetically stable one, so victory is assured if you have enough time. There is a bag of tricks but time works best.
My advice, chill it to round 10C, then microwave it (all in the sep funnel). I tend to take the partial victories as i get them, so if there's a small discrete layer thats removable, then remove it.
The acetone thing is weird, what's exactly in the mix?

edit-when microwaving make sure the funnel isn't sealed and do it in 10sec bursts checking each time. Use the one in the lunch room and become everyone best friend.

[Edited on 15-12-2011 by Panache]




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turd
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[*] posted on 15-12-2011 at 13:13


Quote: Originally posted by Panache  
remember there is no such thing as a thermodynamically stable emulsion, only a kinetically stable one

The argument falls on its face once you realize that you aren't thermodynamically stable either.
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Panache
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[*] posted on 19-12-2011 at 13:01


Quote: Originally posted by turd  
Quote: Originally posted by Panache  
remember there is no such thing as a thermodynamically stable emulsion, only a kinetically stable one

The argument falls on its face once you realize that you aren't thermodynamically stable either.


that quip is mercurial, easily the best thing i've heard all year.




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