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Author: Subject: Removal of Chlorides from H2SO4 electrolyte
gsd
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[*] posted on 13-11-2005 at 05:51
Removal of Chlorides from H2SO4 electrolyte


As per my lead-Acid battery supplier's specs, the Chloride content of the electrolyte should be below 4 ppm.

The electrolyte is essentially 50 % H2SO4.

I have diluted the commercial grade 98 % H2SO4 to 50 % using distilled water which gives Chloride content of about 120 ppm.

Is there any way this can be reduced to 4 ppm ( Short of distilling off the acid!) preferably by chemical means ?
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[*] posted on 13-11-2005 at 06:58


Maybe precipitation with AgNO3?

Why do you need such a low Cl-content?:o
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neutrino
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[*] posted on 13-11-2005 at 07:51


Have you tried heating the concentrated acid? The HCl formed from chloride + sulfuric acid should be driven out with heat without too much trouble. (Remember that anhydrous HCl is a gas.) I'm not sure how low you could get the chloride content like this, but it's worth a try.
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[*] posted on 13-11-2005 at 09:11


Adding AgNO3 won't work as the solubility of AgCl greatly increases in the presence of H+.



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MadHatter
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[*] posted on 13-11-2005 at 09:50
Chloride


I'll go with neutrino's suggestion on this one. It will drive out HCl. However, there will
be sulphate leftover, and hopefully, this is not a problem for you.




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neutrino
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[*] posted on 13-11-2005 at 19:49


>Adding AgNO3 won't work as the solubility of AgCl greatly increases in the presence of H+.

Unless I'm mistaken, that only happens with the salts of weak acids.
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garage chemist
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[*] posted on 14-11-2005 at 06:07


Even the tiniest bit of silver ions in the electrolyte of a lead- acid accumulator will kill it. It's been used as a method of sabotage for vehicles!
Precipitating the chloride using silver would therefore be like fighting a house fire by blowing the house up.:)

Heating the commercial 98% sulfuric acid to over 200°C under reflux for some time and maybe simultaneously blowing filtered + dried air through it to sweep out the HCl would be the most obvious solution, at least that's what I would try.
However, I don't know how the manufacturers of electrolyte grade sulfuric acid solve this problem. Contacting them would be a good idea (assuming that the process isn't a secret).

[Edited on 14-11-2005 by garage chemist]
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