Cementing copper with iron

[Ayham Hafez]

How we can control dissolving iron in AR solution when we cementing copper, Iron is dissolved in HCl and usually AR has a lot of free HCL so how to know when all copper is cemented so we remove the iron to prevent it from dissolving?

Last week I put about 10 Kg iron bar in 60 liters AR solution collected from different refining processes, I forgot it at all, today I noticed that the iron bar totally dissolved and I got only about 1 Kg of copper powder so I believe that iron dissolved by HCl not by cementation.

 

[Yggdrasil]

How we can control dissolving iron in AR solution when we cementing copper, Iron is dissolved in HCl and usually AR has a lot of free HCL so how to know when all copper is cemented so we remove the iron to prevent it from dissolving?

Last week I put about 10 Kg iron bar in 60 liters AR solution collected from different refining processes, I forgot it at all, today I noticed that the iron bar totally dissolved and I got only about 1 Kg of copper powder so I believe that iron dissolved by HCl not by cementation.

When no more Copper cements out, it is done.

 

[Ayham Hafez]

When no more Copper cements out, it is done.

So there is no way to stop HCl dissolving iron while use it in cementing.

 

[Golddigger76]

There's no method I know of other than removing the iron when the copper stops cementing out.
This is a stage in the waste treatment that you need to keep a close eye on to stop the reaction manually.

 

[Alondro]

Calculating roughly how much AR you need to dissolve the scrap, and only using a small amount of excess acid is the only way to control it. If you don't have much acid remaining, then it won't dissolve much iron.

I try to limit the volumes of acids to only slightly over what is needed to dissolve the scrap. As a result, my copper recovery doesn't consume much iron beyond what is needed to exchange for the copper ions.

 

[andu]

If your solution is saturated with copper, they'll essentially exchange, so you'll always have iron in solution, I might be wrong.

 

[Yggdrasil]

If your solution is saturated with copper, they'll essentially exchange, so you'll always have iron in solution, I might be wrong.

In his case he wants the Copper out and the Iron in for waste treatment I guess.

 

[Yggdrasil]

So there is no way to stop HCl dissolving iron while use it in cementing.

Not if you want the Copper out.
But make sure there is not an excess of Nitric so you can keep the Copper from re-dissolving.

 

[D-dog]

Don't mean to hijack the thread. If you used iron powder like rust instead a iron bar. Would that result in copper grains precipitate? Ie, copper powder instead of copper plate?

 

[Yggdrasil]

Don't mean to hijack the thread. If you used iron powder like rust instead a iron bar. Would that result in copper grains precipitate? Ie, copper powder instead of copper plate?

Rust is not Iron powder it is Iron Oxide powder and no that will not work.

 

[Flying Farmer]

Please forgive the ignorance on my part. I would have thought the acid eventually saturates with iron and would then stop digesting. There must be some limit to the amount of iron that can be dissolved in a set volume of acid, yes?

 

[Yggdrasil]

Please forgive the ignorance on my part. I would have thought the acid eventually saturates with iron and would then stop digesting. There must be some limit to the amount of iron that can be dissolved in a set volume of acid, yes?

The purpose is not to digest the Iron, it is to let the Iron and the Copper ions swap place in a process called cementing.
In this process the Copper salt becomes metallic Copper and the Iron metal becomes an Iron salt.

 

[4metals]

The iron in solution will come out in waste treatment at about pH 3 but it is difficult to filter so it's best to let as little as possible go into solution.

When I used this process on a large scale, 50-100 gallons a day, I set it up for a continuous flow into and out of the "iron" drum. I also used a large plating barrel for the iron I used, which was cut up rebar. The tumbler kept breaking off the bits of cemented metal and the iron dissolved at a controlled (predictable) rate based on the inflow. The tank with the tumbler had an inlet and an outlet so if we had a 55 gallon drum to treat, we started it trickling in and when the drum was empty we raised the barrel full of iron out until next time.

We routinely added more rebar. Probably every 3 to 4 weeks we emptied the iron drum and collected the copper. Tumbling made a nice easy to settle (and rinse) flake that we shipped to a copper refiner.

 

[FrugalRefiner]

Please forgive the ignorance on my part. I would have thought the acid eventually saturates with iron and would then stop digesting. There must be some limit to the amount of iron that can be dissolved in a set volume of acid, yes?

Yes and no...

Consider our friend, the copper chloride leach (aka AP). The chloride ions combine with the copper ions from oxidized copper to create CuCl₂. CuCl₂ will then dissolve copper metal, creating two CuCl. Oxygen will then further oxidize the CuCl, which combines with chloride ions to create more CuCl₂. The cycle can continue almost indefinitely as long as there are no metals other than copper and there is ample oxygen. The reason this works is that the copper ions can easily move from an oxidation state of Cu¹⁺ (CuCl) to Cu²⁺ (CuCl₂) and back again.

Ferric chloride can act similarly. The iron ions can easily move between oxidation states, consuming more iron as they do.

Dave

 

[BGDOCK]

I learn something new every day then promptly forget it .

 

[D-dog]

Rust is not Iron powder it is Iron Oxide powder and no that will not work.

I have used HCL to clean rusty parts before and the Iron stays in solution. So I thought it might displace pm's in solution. Thanks much for the response.

Edited by moderator:
You made a post indicating I had said the above but I had not.
Please make sure your posts are correctly formatted.

 

[D-dog]

Sorry about my reply to Yggdrasil. I deleted the first couple words of it. And the cursor jumped up and merged the two. Didn't realize it it would post that way.

 

[galenrog]

Sorry about my reply to Yggdrasil. I deleted the first couple words of it. And the cursor jumped up and merged the two. Didn't realize it it would post that way.

ALWAYS preview posts. Doing so reduces embarrassment.