Electrochemistry au,ag,cu,mixture how to recover thru electrolysis

[acpeacemaker]

ElectricAngel, I didn't suggest to melt silver plate, anyone going after silver plate will spend a lot of time and money chasing very little money. Probably spending more on chemicals than earning in silver.
There is nothing strange with refining copper and recovering silver, every copper refinery is doing it. But to think you could do it on a hobby basis and making money is just wrong.

I was talking about thicker silver contact points, where the silver could be 1-2 mm thick on top

/Göran

Don't forget about cadmium and fumes when doing stuff like this.

Andrew

 

[ElectricAngel]

It seems like to me most people try to run their cells with too little dissolved metal in solution, and too high volts and/or amps.

Yes, precisely calibrating the electricity is where my cell when awry. It worked well when I used 4 AA batteries putting out 6V, but using the old cell phone charger did not work as well. I am seeking a controllable power source: do you have a recommendation?

Before I start my copper cell, the solution is totally saturated, then as the copper plates out on the cathode it makes room for more to dissolve into solution, or at least that's the idea. If you start off with a solution that isn't saturated, you are going to dissolve other things into solution. Since I was running silver/copper in the cell that were not melted into an anode bar but rather just attached to each other, any silver that did get dissolved was forced back out again. And like I said above, running a pure copper anode after, then taking a small amount and testing with HCl to see if silver chloride is formed, I was able to ensure my solution was just copper 2 sulfate.

I never thought to run pure copper through the cell (what's the point, right? It's already electrorefined pure.) to recharge the solution. I will have to do this. Thanks. As to saturated, I sued the formula given previously. I am sure that I depleted it over time while using it, no doubt due to electric levels. One question: according to the electrorefining sources (I have Ammen's book), any metal more noble than copper should not go into solution, but should drop out at the anode. Did you ever record silver going into solution in your refining cell?

There are a lot of reasons why I am leaning strongly towards electrolytic refining, I like the idea of reduced amounts of waste solution, and I love the idea of paying for silver and getting a little Au and other PGMs, rather than paying for gold and getting a little silver and other PGMs. Just makes more sense to me.

Scott

A man after my own heart. I will work on perfecting this over coming months; we see the same thing, a MUCH lower cost to part silver and copper, with no nitric, no silver nitrate, no consumable chemicals needed. Gold is worth the cost of nitric and the labor, silver, barely, copper, no. The fascinating thing, however, is that if done in large enough volume, the copper recovered from electrorefining coins that are 50/50 Cu/Ag (or Kennedy Halves at 60/40 Cu/Ag) can pay for the refining process; mixed silver coins sell for their silver value, and the copper is free.

 

[g_axelsson]

Yes, Göran, that's why I called it the "white whale" of refining, after Moby Dick: this great allure that drags you to your doom. The big problem in silverplate is zinc in the brass: it will boil at a lower temperature than silver melts, so melting down a bunch of silverplate to form an ingot for electrorefining can ruin your electromelt furnace! If the silverplate is simply silver over copper, however, it should be possible to heat the plate to 1850 Degrees F, hot enough to melt silver but not hot enough to melt copper, to get the silver off it. With my electromelt furnace, that would cost me 30 minutes, about half a kWh, and 10 cents. Too labor intensive to make any money; one something does for the joy of experimentation.

Sorry, I misunderstood you on the Moby Dick citate. My bad!
I don't think you could melt the silver plate off a copper object. Surface tension would keep it in place and when molten it will start to form an alloy with copper making it even harder to remove from the surface.

Do you have a recommended electrical power supply that is less than $200 and would allow me to control amperage and/or voltage? I think what I am building towards is a future article here on "building a copper electrorefining cell," and my early experiments were proof that the cell works; now to get the cell to work RIGHT.

One way to regulate the cell voltage is to run a number of identical cells in serie, then each cell only sees part of the voltage. The problem here is that you need identical electrolyte, electrode area, temperature. pH, ... and so on, else you get an imbalance between the cells.
Another way is to use a variac and then a simple unregulated power supply. (most DC wall warts with a transformer is unregulated)
For a small cell you could buy a bench supply for $90 on eBay, http://www.ebay.com/sch/i.html?_odkw=regulated+power+supply&_nkw=variable+regulated+power+supply&_sacat=0

I'm looking forward to see how it goes for you.

/Göran

 

[ElectricAngel]

Sorry, I misunderstood you on the Moby Dick citate. My bad!
I don't think you could melt the silver plate off a copper object. Surface tension would keep it in place and when molten it will start to form an alloy with copper making it even harder to remove from the surface.

Well, when you cite a famous Swedish writer and I miss it, be gentle! I'm honored you know the reference.

I did actually roast one spoon in my furnace. I took it out, glowing red. The silver did not run off of it while hot, as you said it would not, but it did oxidize to silver oxide in the open air, and I could thereafter just brush it off. Too hard, but it would be one way to get silverplate off without chemicals or much cost.

Another way is to use a variac and then a simple unregulated power supply. (most DC wall warts with a transformer is unregulated)
For a small cell you could buy a bench supply for $90 on eBay, http://www.ebay.com/sch/i.html?_odkw=regulated+power+supply&_nkw=variable+regulated+power+supply&_sacat=0
/Göran

Thanks, I ordered a small power supply. I'll perfect a small electrorefining cell for copper and report back in a few weeks, with cross-ref here.

 

[element47.5]

Screaming beauty of a power supply:
http://www.ebay.com/itm/Lambda-Regulated-Power-Supply-LM-G5-OVM-RV-CS-/350617952109?pt=LH_DefaultDomain_0&hash=item51a2755f6d

5 volts, 80 amps.

 

[goldsilverpro]

Yes, Göran, that's why I called it the "white whale" of refining, after Moby Dick: this great allure that drags you to your doom. The big problem in silverplate is zinc in the brass: it will boil at a lower temperature than silver melts, so melting down a bunch of silverplate to form an ingot for electrorefining can ruin your electromelt furnace! If the silverplate is simply silver over copper, however, it should be possible to heat the plate to 1850 Degrees F, hot enough to melt silver but not hot enough to melt copper, to get the silver off it. With my electromelt furnace, that would cost me 30 minutes, about half a kWh, and 10 cents. Too labor intensive to make any money; one something does for the joy of experimentation.

It is a common error for beginners to think that metal separation will occur by choosing a temperature in between the melting points of the the 2 metals. This doesn't work for 2 main reasons.

(1) Note the silver-copper phase diagram below. Note that molten alloys of Ag-Cu are formed at temperatures well below 1850F (1010C). Also note that at a little below 800C (1472F), much below the melting point of silver (962C), a 28%/72%, Cu/Ag alloy will form. In other words, as you heat this up, various alloys will form between the 2 metals. At some early point, all of the thin silver will be combined with copper. This thin alloy layer will be held tight to the copper by surface tension. Also, copper oxides will come into play. Even if the layer were thick enough for some to drip off, it would be heavily contaminated with copper.

I did a poor job of explaining that. Maybe someone can do better.

(2) Surface tension. Once we had a few drums of silver aircraft bearings. They were made of mild steel and the silver coating on one side was about 1/16", or more, thick. Since silver and iron don't form alloys at the silver melting point and higher (I think they start alloying about 2250F), the first thing we tried was to sweat off the silver. It beaded up but, even at that thickness, only 1/2 of the silver dripped off. The rest was held on by surface tension. We tried using a stainless toothbrush, while it was molten, to remove more but about 1/4 was still stuck on the surface.

 

[butcher]

silver can be soldered onto copper these two metals can dissolve together where they meet to stick together, this is done below the melting point of the copper, heating this with a torch will not make the silver melt and fall off of the copper, the silver will just spread out thinner into the outer layer of copper, If we heated this even hotter trying to melt off the silver from the copper we would melt both of these metals into a new alloy.