Hector
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sodium permissive membrane
In the chlor-alkali process a membrane is used to make the production of sodium hydroxide possible. For an amateur who is trying to get the said NaOH
from brine electrolysis, where do i get this "membrane" (what is it made of and where to find one)
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18thTimeLucky
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Mood: 0 Kelvin and still won't crystallise from solution
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Funnily enough 'CaCl2' asked a very similar question a few days ago over in Reagents and Apparatus Acquisition.
http://www.sciencemadness.org/talk/viewthread.php?tid=77879
I made a reply there mentioning a blog post I have recently done on my own experience of the chlor-alkali process using cotton from cotton balls as
the membrane. If you check out my blog post (there is a link in my signature) the post is called 'Synthesis of alkali metal hydroxides via
electrolysis'.
Expensive commercial membranes are obviously going to be better in everyway but I had a good amount of success using cotton, and I doubt the
availability of these commercial membranes compares to cotton for the amateur, so I do have to recommend it. The post is a bit long but it hopefully
will cover every problem you will have and give you some insight into the process (it is less of a how-to and more of a story of my experiences).
I have heard of various other salt bridges and membranes, but I have no experience with them, just with cotton, so maybe somebody more knowledged will
stop by and help out. Saying that, I am interested if anybody on SM has done a synthesis paper on this process. I will put it on my to do list to have
a quick look on the archive.
I hope this helps.
[Edited on 4-11-2017 by 18thTimeLucky?]
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macckone
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obligatory UTFSE warning.
https://www.sciencemadness.org/whisper/viewthread.php?tid=77...
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Hector
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nice vlog man
so if i use cotton it would be ok for the purpose then
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18thTimeLucky
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Mood: 0 Kelvin and still won't crystallise from solution
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Thank you! I'm glad I could be of help.
Yes, cotton should work as it did multiple times for me. I know you are new to Sciencemadness, but like macckone said please use the search engine and
dig around a bit before posting a question in the future as people have asked very similar or the same questions before.
Yep, I have a chemistry blog!
18thtimelucky.wordpress.com
"Amateur chemistry does seem like being in a relationship with someone very beautiful and seductive but has expensive taste, farts a lot and doesn't
clean up after themselves, but you love them anyway" - a dear friend |
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Melgar
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I'd expect polyester fabric (PET plastic) to work better than cotton, however I posted a paper recently in this forum about using cross-linked
polyvinyl alcohol as an alkali-stable divided-cell membrane. Cross-linking can be done with gluteraldehyde solution (used to disinfect medical
devices) or by using periodate to cleave its occasional diol sites into aldehydes. PVA is subsidized by the Chinese government because it can be made
from coal instead of oil, so it's in practically everything. Clear dollar-store glue contains nothing else besides water, most of the time.
The first step in the process of learning something is admitting that you don't know it already.
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mysteriusbhoice
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Quote: Originally posted by Melgar  | | I'd expect polyester fabric (PET plastic) to work better than cotton, however I posted a paper recently in this forum about using cross-linked
polyvinyl alcohol as an alkali-stable divided-cell membrane. Cross-linking can be done with gluteraldehyde solution (used to disinfect medical
devices) or by using periodate to cleave its occasional diol sites into aldehydes. PVA is subsidized by the Chinese government because it can be made
from coal instead of oil, so it's in practically everything. Clear dollar-store glue contains nothing else besides water, most of the time.
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Can i use sodium borate which is stable in alkaline conditions as a cross linking agent or will it slowly dissolve in the soln..
another thing is im using this to create sulfuric acid from sodium sulfate where the cathode side electrolyte is a paste of calcium sulfate and the
anode side is a soln of sodium sulfate.
i want dat sodium to pass through in order to attack the calcium sulfate and convert it into insoluble calcium hydroxide.
this process worked using cotton but the membrane bridge started to heat up because the sulfuric acid conc got high that it started to react with some
product from the other side.
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mysteriusbhoice
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I tested pva glue and sodium borate mix and it seems to hold up in both acidic and alkaline mediums
bad news is that its incompatible with HCl because the mix dissolves in HCl but not H2SO4 so using sodium sulfate as the electrolyte can work for my
purposes if at all it works as an exchange membrane.
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Melgar
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| Quote: Originally posted by mysteriusbhoice |
this process worked using cotton but the membrane bridge started to heat up because the sulfuric acid conc got high that it started to react with some
product from the other side. |
No, it's heating up because of electrical resistance. you need to increase the area of the interface between the half cells.
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