# Can HCL bath be reused?



## Metaphore (Oct 25, 2015)

`Is there a way to reuse HCL after using it to dissolve non value metals? Any way to drop the metals so it can be used again?

I'm not so much worried about the cost of HCL, it's cheap. I am trying to minimize the volume of waste material.


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## NobleMetalWorks (Oct 25, 2015)

So your concern is not really to re-use the HCl, but instead to neutralize your waste.

This is the go to thread on this particular subject http://goldrefiningforum.com/phpBB3/viewtopic.php?f=47&t=1300

It takes time and effort, but if you follow as this thread directs, you will be able to reduce your waste to basically salt water, which can be disposed of safely.

SCott


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## jason_recliner (Oct 26, 2015)

Slight elaboration, as I think in the way you've framed the question, reusing the HCl is a slightly different topic to waste.

Let's say you're using your HCl bath to pre-soak tin and others before going to, for example, copper chloride leach ("AP"). Yes, you can definitely keep using it until it won't dissolve any more, or until it becomes too slow to be productive. Store it in an airtight container, as you would HCl.

But then, once it's saturated with tin, you will treat the waste as described. For the only practical way to remove the metals from the solution will also neutralise the acid.


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## butcher (Oct 26, 2015)

Using HCl on metals, by looking at the reactivity series of metals we see that reactive metals above hydrogen in the reactivity series, displace hydrogen from the acid as gas when the more reactive metal reacts with the acid, to make a chloride salt of the metal. without the hydrogen you no longer have HCl acid to reuse.
Metals below hydrogen the less reactive metals the hydrogen in the acid forms water in the reaction with metals as we make the metal chloride salt solution in the reaction. so again we no longer have HCl to reuse.
So without free HCl in solution, if all of the acid is used in the reaction we no longer have HCl acid.

Again by looking at the reactive series of metals, we see we can displace a less reactive metal from solution using another metal that is more reactive (in a displacement reaction, like we do with using copper to displace gold from solution). In this reaction we are changing the chloride salt in solution (or which metal chloride is involved).

Then there there are other places where we can use a reaction so that we can reuse a solution, like where we make a copper chloride solution, and rejuvenate the solution changing the CuCl back into a CuCl2solution so we are able to dissolve more copper.

We can also change one metal salt to another metal salt, example say we have a copper chloride solution, we can add sulfuric acid and distill out HCl gas (which can be collected if we wished for reuse) and make copper sulfate from that reaction in the process.

If you have a soup of reactive metals in solution (several different metals dissolved as chloride salts) in one soup of a solution you can use the reactivity series to displace the ones below the metal your using in the series of reaction.

Basically we cannot reuse HCl acid once we use it on metals, but we can convert it once used to another chemical, that can possibly be reused, or reform HCl from a salt. 
Gaining an understanding of the chemical reactions through educating yourself in the chemical reactions, and what happens is really the only way you can learn how to reuse the solution or make another solution from your used HCl.


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## Metaphore (Oct 26, 2015)

NobleMetalWorks said:


> So your concern is not really to re-use the HCl, but instead to neutralize your waste.
> 
> This is the go to thread on this particular subject http://goldrefiningforum.com/phpBB3/viewtopic.php?f=47&t=1300
> 
> ...



Thanks! That's some procedure! Easy enough to understand, though. I'll have to get some 15 gal drums and give it a go.


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## upcyclist (Oct 27, 2015)

Metaphore said:


> NobleMetalWorks said:
> 
> 
> > So your concern is not really to re-use the HCl, but instead to neutralize your waste.
> ...



Note that they don't _have _to be _15 gallon _drums--only if that's the size appropriate to your operation


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