Dropping copper (again) and other interogations

[Ditto]

Bonsoir, good evening.

I have been getting my feet wet by dissolving my silver scrap (I am a bench jeweller by profession) and recovering the silver, and that all went outstanding well. I have read Hooke's once from start to finish, and keep reading and revisiting things. Ultimately, I don't know if I continue to refine my metals, or just parts, or none, but it's a great experience for a precious metal-guy.

So I was left with my silver cemented out and a nitric solution of copper. Originally, I just wanted to get rid of it, environmentally correct, and dumped scrap iron into it. It sat for a month or two. I changed my mind telling me that it would be a nice exercise to collect the copper as well.

I filtered a good amount of that brown mud that settled, but I am at a loss of what I have at hand now. Reading the forum (and it's posting about that subject) are still over my head, so excuse my stupid questions.

1. If I assume for the moment that I had no idea what I have here in front if me, would I be able to tell if this is copper or iron oxide (rust) ?

2. My intention is to wash the mud a couple of times with HCl to get rid of any Zn, Pb, ... or whatever I have left. Then washing with distilled. Good thinking ?

3. The 'brown soup and mud' (tm) did actually leave a coloration on glass and porcelain I used in the process. It doesn't go away with simple washing under running water. Side question : How to take care of my dishes ? Is tap water "allowed" for household tasks ?

Sorry for the stupidness, I can only hope this helps the next guy on the same road.

 

[Martijn]

Hi Ditto, the brown mud will be mostly if not only copper. What do you intend to use it for once recovered?
Your questions led me to another evening of searching and studying. I did not find all the answers, but gave me more insight.

I'm not sure if any iron oxide on the scrap iron will displace the copper nitrate from solution and will have went into solution or if it stays in oxide form along with the copper powder. >>Jedi's? Proffessors? please enlighten us.
Or the fact that you have left the iron in there for two moths, I don't know if that will create any iron oxide that could remain in the copper mud.

Adding/rinsing with HCL of the copper mud should dissolve any iron present, forming (Cuprous, pardon me, I meant Ferrous Chloride (FeCl2), which will slowly transform to Ferric Chloride (FeCl3) when left exposed to air. This in turn can dissolve elemental copper and you'll be back at step one, so don't leave the mud too long in the HCL what other ingredients like Pb Ni Zn etc. will do not sure. Pb will form lead chloride e.g. soluble in hot water. Hokes could shed some light on that maybe.

I guess it all comes down to what you've started with. pure silver and copper in your sterling scrap? Or some other metals in the mix? Any PM's would have been left behind after the nitric digestion of your sterling. Make sure you save that.

Bon chance mon ami.

P.S. if you live close to Lille, I would love to come by and see your workplace, maybe i can get some jewelers tips and tricks or even use a rolling mill for a piece of silver or Gold hammer and anvil do not give the best results.

Martijn.

Edited to correct Cuprous Chloride into Ferrous chloride and Pd into Pb... it was a stressy day at work.

 

[Ditto]

Hi Martijn, thanks for chiming in!

I started out with sterling silver scrap and some lemel, so if there was anything more precious than Ag it wasn't much.

The metal scrap wasn't rusted, but it certainly had that black scale of hot rolled steel - so technically, it wasn't iron. That's for sure. But if I am confronted with rust now, it has produced in the nitric.

I had some commercial rust remover (which I believe is mostly phosphoric acid) and it did dissolve a trial of that brown mud. From some basic research, I believe that phosphoric doesn't attack copper. So even if there were rust in the mud, it shouldn't have dissolved all of it. I am confused.

I might dissolve everything again in nitric, then drop the copper with zinc or maybe brass. It's not about the copper, but about learning something and getting better at this.

You're welcome to come to my shop, but I fear it's a little farther away than Lille. I am near Toulouse in the south-west, which means I am nearer to Barcelona than Paris or Brussels from your point of view.

Doei doei.

Ditto

 

[Martijn]

Thats not really close to home no. But not far from Perpignan, our favorite vacation area. Wish i lived in southern France. Beautiful country.

 

[goldenchild]

A really crude way to test if you have any iron oxide mixed in with your cemented copper is to mix your precipitate very thoroughly. Take a small sample and dry it. Put it in a dry container and use a strong magnet. By the way, your copper will ALWAYS have iron contamination unless you pull the steel you're using to cement the copper before all the copper has been displaced out of solution. It's exactly like cementing silver out of solution with copper.

 

[kurtak]

By the way, your copper will ALWAYS have iron contamination unless you pull the steel you're using to cement the copper before all the copper has been displaced out of solution. It's exactly like cementing silver out of solution with copper.

That is correct

If you use a bubbler when cementing copper with iron - & you run it to long you can actually end up with quite a lot iron oxide in your cemented copper - you can rid the iron oxide with HCl or phosphoric (after first washing the nitrate out)

with HCl don't leave the HCL in to long or it will start to dissolve copper again (as already mentioned) & you want to get the HCl well washed out before drying - not sure about phosphoric

or you can just dry it (after getting the nitrate "well" washed out) & then smelt it with flux (borax & soda ash) the flux will slag the iron oxide off

Kurt

 

[Geo]

Another thought, there is an alloy called palladium sterling. 92.5% silver and 3% palladium. When you cement the silver with copper, unless you adjusted the PH and took pains to compensate for it, the palladium will either stay in solution or redissolve quickly back into solution. Are you stannous chloride testing your spent solution? Your cemented copper may also contain any palladium that was present in the sterling.

"PALLADIUM + STERLING SILVER (SPD) - white alloy - 0.925 silver, copper, palladium
Palladium Sterling is a 92.5% sterling silver alloy which contains 3.0% palladium to give your jewelry that little extra edge. It has been formulated to perform to the highest standards for all jewelry applications and can be cast, formed and fabricated just like traditional sterling silver. Palladium enhances the luster of your sterling silver jewelry and gives your pieces added value. Palladium sterling has been formulated for optimum tarnish resistance. Palladium Sterling can be hallmarked as sterling.

Recommended Uses: SPD is suited for all general fabrication techniques. It is intrinsically harder than standard sterling silver and has improved tarnish resistance."

 

[gagan7741]

By the way, your copper will ALWAYS have iron contamination unless you pull the steel you're using to cement the copper before all the copper has been displaced out of solution. It's exactly like cementing silver out of solution with copper.

That is correct

If you use a bubbler when cementing copper with iron - & you run it to long you can actually end up with quite a lot iron oxide in your cemented copper - you can rid the iron oxide with HCl or phosphoric (after first washing the nitrate out)

with HCl don't leave the HCL in to long or it will start to dissolve copper again (as already mentioned) & you want to get the HCl well washed out before drying - not sure about phosphoric

or you can just dry it (after getting the nitrate "well" washed out) & then smelt it with flux (borax & soda ash) the flux will slag the iron oxide off

Kurt

Hi Kurt
I run a small electrical contacts manufacturing business in North India and have setup a small silver refinery here to deal with the scrap our unit generates.For the past 2 years we have been throwing away the copper that is consumed when cementing silver in the form of copper hydroxide (generated by adding sodium hydroxide to copper nitrate solution).Someone advised me to start cementing copper with iron scrap and so we did.We have an oven to dry silver powder.But How do you dry the Copper powder thus obtained without letting it turn black(copper oxide)? Need the copper dry to put it in the melting furnace.

Thanks
Gagandeep Singh

 

[Geo]

Ahhh. Sorry, I'm not Kurt but I can tell you that the black copper oxide is good and preferable. It helps stop the attack of the copper powder by SO2 in the atmosphere as long as the copper stays dry. The black copper oxide will not pose a problem when melting the copper. Add a 10th of a portion of sodium carbonate to your flux. During the melt, the oxygen in the oxide will react to the carbonate producing carbon dioxide and reducing the copper oxide to copper metal. The slag will also be black from the small amount of copper oxide that did not convert. Also, stir the melt with a steel bar, such as reinforcing steel or rebar. This will help reduce the copper oxide to copper metal. This is for large melts of several kilos at a time. If it is small melts, just add the sodium carbonate.

 

[kurtak]

You need a reducer "mixed in" with your flux to rob the oxygen from the copper oxide (thereby reducing the copper oxide to copper)

Carbon works as a reducer so try mixing charcoal (powder) in with your flux

Or you can try using flour or sugar in the flux as the flour or sugar will turn to carbon which then acts as the reducer

Also "fine" iron shavings/powder can be used as a reducer

When drying the copper it is likely to "cake" into a hard but brittle cake --- for the flux (with reducer mixed in) the flux/reducer needs to make contact with the "fine" copper - so you need to crush/mill the copper/copper oxide back to a powder then mix that powder with the flux

It does not take a lot of reducer to rob the oxygen from the copper oxide - so I would start by mixing 1 part reducer with 4 parts flux (flux should be 50/50 borax/soda ash)

I would start the actual smelt with 2 parts flux/reducer to 1 part cemented copper powder

Depending the smelt results you will likely need to make adjustments (up or down )to the flux/reducer/metal components of the smelt (including maybe adding a thinning agent like fluorspar)

In other words - there is "a bit" of a learning curve to find what fits you particular situation

Like anything else in this business - a few small smelts will dial you into move on to the larger ones

Kurt

 

[kurtak]

Geo's post is good advice as well :mrgreen:

Kurt

 

[gagan7741]

Sorry for the very late reply guys. Thanks to you guys, i used to dispose off 15-25 kgs of copper in form of copper nitrate to the disposal company every month , now we recover copper as well in house.

 

[kurtak]

Sorry for the very late reply guys. Thanks to you guys, i used to dispose off 15-25 kgs of copper in form of copper nitrate to the disposal company every month , now we recover copper as well in house.

Good to here it has worked out for you 8)

It good to here that our help - helps others :!:

Kurt