haveagojoe
Well-known member
- Joined
- Aug 1, 2014
- Messages
- 238
I have tried to recover HCl from used Copper Chloride solution using electrolysis, see thread here:
https://goldrefiningforum.com/threads/copper-chloride-ap-cleanup-experiment-writeup.35323/
The experiment seemed to produce reasonable results in depositing Copper from solution at the cathode, but I wasn't happy with the amount of Chlorine gas produced, and I was not able to test the strength of the resulting acid. I suspect that it was significantly weakened by the release of Chlorine and resulting production of water by the electrolysis.
In my ongoing quest to find a workable method to renew my acid I came across this excellent and thorough video which came out a few days ago, which I'm sure will be of interest to members:
Video
Distilling off the HCl from the Copper Chloride salts seems to be a much more practical and effective approach than electrolysis.
The video creator performs the extra steps of fractional distillation to bring the concentration of the acid up to its azeotope, and then bubbling Hydrogen Chloride gas through it to increase the concentration further. However for reuse in Copper Chloride etches, I think it would be sufficient to simply reuse without fractional distillation or further concentration, at low strength ~10%.
The drawback of this approach is that, as the creator notes around the 1:40 mark, only free HCl can be recovered. In heavily saturated solutions, the Chloride is bound to the Copper ions and remains behind in the Copper (ii) Chloride salts.
I am wondering if there is any way to address this in order to recover Chlorides which are bound up with Copper? I was thinking that prior electrolysis might help by removing metallic Copper, but I think the release of Chlorine gas during oxidation simply depletes the HCl, producing water.
Would there be any benefit in dropping the Copper out with Iron first instead to create Iron Chloride solution, and distill that to recover the HCl?
This video details the process of HCl recovery from Iron Chloride solution, but it seems far too advanced to replicate at the hobby level... Video
https://goldrefiningforum.com/threads/copper-chloride-ap-cleanup-experiment-writeup.35323/
The experiment seemed to produce reasonable results in depositing Copper from solution at the cathode, but I wasn't happy with the amount of Chlorine gas produced, and I was not able to test the strength of the resulting acid. I suspect that it was significantly weakened by the release of Chlorine and resulting production of water by the electrolysis.
In my ongoing quest to find a workable method to renew my acid I came across this excellent and thorough video which came out a few days ago, which I'm sure will be of interest to members:
Video
Distilling off the HCl from the Copper Chloride salts seems to be a much more practical and effective approach than electrolysis.
The video creator performs the extra steps of fractional distillation to bring the concentration of the acid up to its azeotope, and then bubbling Hydrogen Chloride gas through it to increase the concentration further. However for reuse in Copper Chloride etches, I think it would be sufficient to simply reuse without fractional distillation or further concentration, at low strength ~10%.
The drawback of this approach is that, as the creator notes around the 1:40 mark, only free HCl can be recovered. In heavily saturated solutions, the Chloride is bound to the Copper ions and remains behind in the Copper (ii) Chloride salts.
I am wondering if there is any way to address this in order to recover Chlorides which are bound up with Copper? I was thinking that prior electrolysis might help by removing metallic Copper, but I think the release of Chlorine gas during oxidation simply depletes the HCl, producing water.
Would there be any benefit in dropping the Copper out with Iron first instead to create Iron Chloride solution, and distill that to recover the HCl?
This video details the process of HCl recovery from Iron Chloride solution, but it seems far too advanced to replicate at the hobby level... Video
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