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Author: Subject: Removal of Na2SO4 from Mg(OH)2
soma
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[*] posted on 14-5-2018 at 02:59
Removal of Na2SO4 from Mg(OH)2


After reacting MgSO4 with NaOH I want to remove the Na2SO4. I've tried filtering which was very slow and now just mixing the products with water and waiting for them to separate and then removing the clear supernatant with a turkey baster. But it takes a long time for the clear layer to appear.

Any suggestions?

Thanks.
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CobaltChloride
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[*] posted on 14-5-2018 at 03:43


What you did is a a good separation method. Mg(OH)2 is insoluble, but sodium sulfate is quite soluble. Any method of removing the precipitate and keeping the solution will work. So you can either filter or decant the liquid, but please be more patient with both methods. Chemistry takes time.

[Edited on 14-5-2018 by CobaltChloride]

[Edited on 14-5-2018 by CobaltChloride]
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fusso
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[*] posted on 14-5-2018 at 09:48


u need suction filtration if u want faster separation.



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RogueRose
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[*] posted on 14-5-2018 at 21:08


Mg(OH)2 is a major PITA to filter and even allowing to seperate. I'd find a large vessel and add a lot of water which will dilute the Na2SO4 as much as possible. Allow to settle and decant. Repeat as many times as you see fit.

Time is your best ally in this endeavor and while it may seem like a PITA to wait, it provides the best results.

You don't happen to have a centrifuge by any chance do you? I've wanted to get/make one for some time for this type of situation so the precipitate will just stick to the wall and the liquid will flow out. It seems a better solution when working with difficult precipitates such as this and others like CaSO4.
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AJKOER
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[*] posted on 18-5-2018 at 14:51


My experience is that freezing (or near freezing) a solution with a fine suspension, and then allowing to warm, appears to assist in the settlement process.

Another path, best with a well sealed plastic vessel containing the suspension, is to employ a centrifuge or a home version (like a spin only setting on the washing machine).
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clearly_not_atara
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[*] posted on 18-5-2018 at 15:00


You might want to look up Sorel cements. MgO and MgSO4 form an insoluble double salt. Separation is likely to be very hard.



[Edited on 04-20-1969 by clearly_not_atara]
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Melgar
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[*] posted on 20-5-2018 at 19:35


You might actually consider using a centrifuge if it's annoying enough. I have a friend who build his own centrifuge, and he actually uses it all the time.



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soma
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[*] posted on 23-5-2018 at 03:24


Any information on how to build a centrifuge? I'd be interested.
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LearnedAmateur
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[*] posted on 23-5-2018 at 06:11


I’ve always thought an easy to make one would be from an old bike, change the pedals to handles or use as is, and high torque is converted to a fast spin with large gears with the sample secured to the edge of the wheel and with bits removed so it doesn’t hit the frame. Alternately, there’s this if you want to prep something on the micro-micro scale for less than a dollar/pound/[insert currency here]:

https://www.nature.com/articles/s41551-016-0009

[Edited on 23-5-2018 by LearnedAmateur]




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