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Author: Subject: How do I make Lactic Acid from Polylactic Acid?
9CWAI
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[*] posted on 8-1-2022 at 21:49
How do I make Lactic Acid from Polylactic Acid?


I have lots of PLA waste from a 3d printer and no hotplate so I cannot temperature control enough to not burn it when melting it. I want to make Lactic acid from it but boiling for a while did little but warp it. How can I encourage the water to attack the PLA?
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DraconicAcid
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[*] posted on 8-1-2022 at 22:10


You should be able to hydrolyze it with strong base to get lactate ion, then acidify to get lactic acid.



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SaccharinSlayer157
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[*] posted on 8-1-2022 at 22:24


Well, I was going to say something about that but apparently I'm wrong, so nevermind :P

[Edited on 9-1-2022 by SaccharinSlayer157]
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[*] posted on 9-1-2022 at 14:19


Quote: Originally posted by DraconicAcid  
You should be able to hydrolyze it with strong base to get lactate ion, then acidify to get lactic acid.

What would you recommend out of the easily obtainable 3, Ca(OH)2, NaOH, or KOH? which one would be the easiest to get rid of?
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[*] posted on 9-1-2022 at 14:24


I really don't wanna use H2SO4.
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[*] posted on 9-1-2022 at 16:48


If you use calcium hydroxide, then you can neutralize with sulphuric or phosphoric acid, filter out the calcium salts, and have a fairly pure solution of lactic acid. If you acidify with a different acid (such as hydrochloric), then regardless of which base you use, you'll want to have an excess of base so that you can distill the lactic acid (ew!) without any excess acid coming over.

Just hypothesizing here, but you might also be able to hydrolyze the polymer by refluxing it in aqueous acid for a while, adding just enough bicarbonate to neutralize the acid that you've added, and then distilling.




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[*] posted on 10-1-2022 at 17:05


Quote: Originally posted by DraconicAcid  
If you use calcium hydroxide, then you can neutralize with sulphuric or phosphoric acid, filter out the calcium salts, and have a fairly pure solution of lactic acid. If you acidify with a different acid (such as hydrochloric), then regardless of which base you use, you'll want to have an excess of base so that you can distill the lactic acid (ew!) without any excess acid coming over.

Just hypothesizing here, but you might also be able to hydrolyze the polymer by refluxing it in aqueous acid for a while, adding just enough bicarbonate to neutralize the acid that you've added, and then distilling.

Yeah, I did the math and sulfuric is the best option unfortunately. Even compared to buying lactic acid. 24 a gallon and a half at Home Depot, the PLA is waste anyway, and eggshells are a fine source of calcium. less than a cent per gram if I do it that way rather than like a dollar per gram on eBay.
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