Use for wastes other than waste? A copper processing Q

[MacMasterMike]

My question is essentially what options are out there for things to do with the waste from the process. Not asking where to dispose of it but rather what other forms of chemistry can you do with the stuff. Like say recycling acids. From what I've been told by the guy helping me out and get me interested in precious metal refining/recycling was that to hold on to the spent nitric acid. I'm assuming with just copper in the solution he told me that recovery of the nitric was possible with distillation glassware. Now I've only ever done silver refining so please keep that in mind.

I was talking to him about some silver refining and basically filled me in on some more info i found pretty interesting. I'll paraphrase the silver refining process some so bare with me. The best way is to dissolve it all(the silver bronze i have) in nitric acid, adding only enough nitric to dissolve it all, then you can precipitate it out with salt, filter off the AgCl, and keep the copper and sodium nitrate and told me to remember that you can get every drop of your nitric acid back. The lab prof I've done my test with is willing to let me give him my waste and have the lab dispose of it. A very nice service of his but I'll have to try this next step

Take that copper sodium nitrate and mix it with sulfuric acid and then distill it at about 80 degrees Celcius. Very pure, red, fuming nitric acid will come over. You are left with copper sulfate (great for plating) and sodium hydrogen sulfate (good for removing stains) Also if I didn't want that stuff you can add a bunch of aluminum shavings or aluminum foil to it and drop out pure copper powder. I wondered how to get the copper sulfate and sodium hydrogen sulfate separate and if distilling acids is a little much for a novice like myself. The response to those questions were crystallization and using the NaHSO4 with the CuSO4 and makes a great plating salt out of it. Also it appears this isn't that hard assuming you have the proper setup which i would figure is a distillation glass setup of some sizable amount. So I ask the veterans here is the processing of the copper on my hobby scale to perhaps get my nitric back and perhaps get into copper platting a worth while endeavor?

 

[lazersteve]

In theory your process paraphrased sequence of reactions is feasible.

The labor of the recycling process is not going to be offset by the value of the copper and nitric produced. Harold has recommended using iron or steel instead of aluminum to percipitate the copper if my memory serves me correctly.

As for distilling the nitric acid in glassware, I wouldn't put the task to anyone who doesn't have hands on lab experience and an excellent labware setup. Larger scaled distillations would definitely be out of the question for most home experimenters.

The idea of recycling is always good. I've been tinkering with the exact situation you have referenced here. I'll keep you posted on my progress.

Steve

 

[MacMasterMike]

Yeah thats pretty much what I thought Steve. The guy helping me out is a Chem grad student and I think he forgets I'm an amateur at times. Anyways the consensus is that despite processing of the waste for 3 very usable items doing so would still not be as cost effective as ditching the waste and buying new nitric? Assuming you had the safe apparatus to work with.

 

[Harold_V]

Harold has recommended using iron or steel instead of aluminum to percipitate the copper if my memory serves me correctly.

Before moving to Washington, I was a resident of Utah, where I was born and raised. One of the largest producers of copper was very near my home-----Kennecott Copper Corp. They have, literally, created a hole in the ground that is miles in diameter, and stands where there was once a mountain, a part of the Oquirrh Mountain range.

Kennecott Copper uses scrap steel to recover copper from leach solutions, which they accumulate from their tailings. It's cheap and does an excellent job. The only problem with the entire operation is that it requires melting to be marketable. For them, that's not a problem. If you have a small cupola and can operate it without problems, you could recycle extracted copper, but it's not economical to do the melting in a crucible. The cost of operation quickly exceeds the value of the copper, due in part to the necessary fluxing. You're better off to remove the copper from solutions with scrap steel, then dispose of it. Even with that large copper producer in my back yard, I found on one that was interested in two 55 gallon drums of copper concentrate.

Do keep in mind that was back in the early 90's, when copper was depressed. With today's high value, it's entirely possible you could find someone willing to accept it. I can't help but think China! :wink:

Harold

 

[goldsilverpro]

I'm not familar with silver bronze. I Googled it and found no listing. I assume you're talking about a silver copper alloy, such as sterling silver, coin silver, etc. Do you know exactly what you have? It could make a difference as to advice.

To do what you want to do, I think you should keep things as simple as possible and try not to introduce any new things to the mix. To start with, you only have copper, silver, and nitrate, assuming you're starting with one of the common silver/copper alloys. Of course, there is water and hydrogen ion (H+) but, you really don't have to worry about these last two.

There are 3 basic ways to drop silver but, only one doesn't introduce anything new.
(1) You can use NaCl, common table salt, to form silver chloride - AgCl. To me, this is the worst choice. You are adding sodium, Na, which is unnecessary. Also, it is almost impossible to drop all of the silver chloride without adding too much NaCl, even with practice. Therefore, you are adding Cl to the mix, which I think would track over during the distillation. You would end up with nitric contaminated with a little hydrochloric, a weak form of aqua regia. Unless you're using the distilled nitric for aqua regia, Cl is one of the worst contaminants you could have.

(2) HCl = hydrochloric acid or muriatic acid. This will drop silver chloride the same as table salt. The key ingredient is Cl, which is common to both. This would be better than NaCl because no sodium is introduced. You are adding the H+ ion but, that is good. The reason you add sulfuric to the distillation is for the H+ ions it provides. If you notice the chemical symbols for acids, they always start with H. When you dissolve the silver/copper you rid the nitric of H+ ion and need to provide more.

The Cl problem using HCl is the same as with using salt.

Muriatic acid is a less pure form of hydrochloric acid. It usually contains a little iron

(3) The only way to not add anything new is to cement the silver out of the spent nitric with solid copper. You simply put the copper into the solution and all the silver plates out on it, in a lumpy cement-like form. The purest forms of scrap copper are those used to carry electricity - copper wire or copper buss bar. Wire doesn't work as well because the cemented silver hangs up among the strands of wire and is much harder to rinse out. The buss bar should be clean, not plated, with no solder or connectors. Cut the buss bar so it sticks an inch or two out of the container, so you can remove it easily. The more pieces of buss bar , the faster the silver will cement out. Another advantage in using copper to drop out the silver is that the silver doesn't end up as silver chloride, which requires a fairly difficult process to convert it to silver metal. The cement silver is fairly pure silver metal. If you rinse it well, it can be 99% pure.

When using copper to drop the silver, you don't add anything new. You do add a little more copper to the solution from the buss bar, about 1/3 oz for every ounce of silver cemented out. Also, if you didn't use up all the nitric, when dissolving the silver, the extra nitric will dissolve some copper.

I'm still thinking about the distillation.

 

[MacMasterMike]

Thanks I had no idea about the copper method for silver precip. What i ment by silver bronze was its copper with silver in it. Around 20% silver. I have 7 pounds of the stuff I cast into shot which was a pain for too many reasons to mention. There may also be some zinc in the metal too would that interfere with the copper method? Also i added the little bit of gold to the metal that i had only about a penny weight when taking the karat into account. That wont be an issue i just gotta make sure I get it out of there before I would start with the copper. I will deffinatly test that method when I get the chance next to do this. I have the perfect bus bars even, as i got some ends from some 400watt fuses with those zinc cores(forgive me if I used the wrong wording.) I have converted some AgCl to Ag using the lye/dextrose method. Another negative that i could add is how for me at least how small some of the silver particles are. They would go right though my filter papers. Not all of it of course but still there is some value there. Have to dry it out or something to retrieve it is all.

 

[goldsilverpro]

Really nothing will interfere with the copper method. It's very selective. The only things it will drop is silver, gold, and the platinum group. Everything else stays in solution.

I think copper will also drop mercury but, it's never or rarely present

At one place I worked, we dissolved large volumes of stuff with aqua regia - maybe 15 drums per month. There was gold, platinum, palladium, and a lot of base metals in the solution. We added urea and dropped the gold. Then we used buss bar to drop the Pt and Pd. Worked great.

Be careful when melting stuff with zinc in it. When you do, if you see white cobwebs floating around, get away from it. It's very bad to breathe.

 

[MacMasterMike]

Another question i got for you when rereading your long post. Is the copper method your choice method? Also by rinse it well how does that help purity? My experience with the cement silver is that from C.W. Ammen's book where he suggests using Zinc foil/powder to precip the silver after disolving the AgCl if i recall it correctly. Anyways he said that purity would be about 97% give or take a few but could get better over time. by 99% do you mean fine 99.99% silver? I understand even getting that with some methods is tough depending on how clean you operate but I just want to make sure.

I know all about zinc fume fever as i have a background in metal casting. Have that glass of milk ready!

 

[goldsilverpro]

Good questions

I actually base my method on the type material I'm running. I use the copper method when I have little or no free nitric acid present, as in when I dissolve contact points in nitric.

One time, I setup to dissolve the silver braze off of about 50,000# of jet engine stators, the big fan blade like parts that you see in the engine in photos. The silver only ran 1% to 2% of the total weight. We had about 500 gallons of 50/50 nitric to do this and we wanted to use the same solution over and over. We harvested the silver every few days. When we harvested, the nitric still had about 90% of it's original strength. If I had used copper 2 things would happen. First, I couldn't reuse the solution. Second, there was so much free acid left that we would eaten about 500# of copper before the silver even started dropping. So, I used HCl to drop the silver.

Cement silver is hard to rinse. About the only source of contamination is the copper solution. If you could get it all out, you would have silver that is close to pure. Sometimes, slivers of copper fall off into the silver but, this doesn't usually add up to much. If you were to dry and melt with copper solution still in the silver, the result would not be very pure. Each rinse gets rid of more copper. Hot tap water is best.

Zinc, iron, aluminum - all of these things work on silver chloride. Harold had a good write up on using aluminum. Converting silver chloride to metal is not as easy as you might think. Look for the posts that Lazersteve and I made on the subject.

99% = 99.00% = 990 Fine. The number of 9's is always the same

 

[Harold_V]

I don't have as many years of silver refining under my belt as does GSP, but I, too, used copper. Messing with silver chloride is nothing short of a waste of time, and should be used only when you have no other options.

The small amount of gold you combined with your metals will be recovered if you use your head. It will be left behind as a black powder and will readily settle out of solution given an opportunity.

If, by chance, you managed to get any tin in the mix, you could have problems filtering, but you should be able to allow solutions to settle well, then decant using a short length of vinyl hose. It's the fastest, easiest and most efficient way to transfer fluids without disturbing the bottom.

A dilute solution of silver nitrate will work better than a concentrated one when it comes to recovering the silver. If the solution is too concentrated, it's not uncommon for the silver to plate out so dense that it doesn't shed from the copper. I would liken the end result to electroless nickel plating, but with silver. My vessel of choice for this operation was a plastic container, which I don't usually recommend, although GSP used such containers routinely. Different strokes! I see no right or wrong. If you use plastic buckets, it's real easy to stir the cement silver once it's down, so you can introduce water and stir it well, then allow the mess to settle before decanting.

Washing the silver well after you've recovered it is always a good idea. Wash it until it has no traces of blue coming off, and make your final rinse one with hot water, which will dissolve any lead nitrate that may have managed to get through the process. If you wash and decant quickly, the lead will go with the hot water. It will precipitate as a white substance if allowed to cool. If you wash and rinse until your wash water is clear, you can usually filter the cement silver in a Buchner with no trouble. It will compact down to a nice, thick layer that readily gives up moisture. You can compress it with a flat object and continue washing if you see color coming from the filter. Filtering without proper washing before introducing the cement silver to the filter is usually a difficult task. My procedure was to do a final drying of the cement silver in an evaporating dish at low heat. It was then melted and cast as an anode for the silver cell.

As an aside, if your silver has been cemented from a very dirty solution and you find it's not very silvery, it does no harm to do a wash with dilute HCL, which will usually liberate a lot of contaminants. It does no harm to the silver.

Harold

Edit: added the word "if"

 

[MacMasterMike]

Any thoughts on the further steps to do to the waste?

 

[Harold_V]

A lot depends on your waste, as far as I'm concerned. I had a unique situation in that my waste water, once processed by a waste handling plant (sewage disposal), ended up in the Great Salt Lake, so there was little fear of hurting anything. I removed all heavy metals and neutralized anything harmful, but it was comfortable knowing that my discharge wasn't going in a river that became someone's drinking water downstream. If you don't know, the Great Salt Lake supports almost no life forms. The lake is devoid of any plant life, and has only brine shrimp and some kind of small fly that lives out of the water. There is precious little one can do to harm anything, and any minerals you add to the lake are eventually harvested by industry. There's a thriving magnesium industry, along with many other industries that mine the lake through the use of huge evaporation ponds. Fact is, they're harvesting the minerals at such a rate that the salt flats are slowly disappearing.

I may have mentioned at some point along the way that I am not really a refiner. My refining was nothing more than a hobby that got out of control, due in part to being in the right place at the right time, but, more importantly, due to my honesty with those that became my customers. Once I refined for a jeweler, word traveled fairly quickly.

Anyway, the point here is that I was a toolmaker/machinist before I started refining full time. I did a serious amount of defense work, which always includes finishing of materials, anything from passivation of stainless to hard chrome plating and anything in between. I was very familiar with my plating source, and often toured their facility, having free run of the place. As OSHA started tightening the noose on the plating industry, they were forced to install a large precipitation device that neutralized their chemicals, precipitated them, then collected them in a filter press, discharging all the solutions and leaving only the solids from the press for hazardous waste disposal.

You could do something on that order if you so desired. I recall that all fluids from plating were combined, with the basic solutions and acid solutions coming close to neutralizing each of them. In most (maybe all-----I'm not a chemist) situations, when you shift from acid to base, or the reverse, anything in solution will automatically precipitate, so just a shift in pH was all that was required for all but a few of their discharges. Cyanide can be neutralized with chlorine------and likely other ways, too, but, then again, I'm not a chemist. Sue claims to have very good credentials, but has been reluctant to speak about much to do with refining. Perhaps he could seize this opportunity to expound on the matter. I am clearly not qualified.

Harold