Using Aqua Regia to Refine Silver

has this method been cost effective so far?

interesting topic, some might be helped with this

If this is a "pretty quick question", I shudder to think what a complicated question would look like.

What is the scale of your salvage operation? I see 55 gallon drums of scrap mylar to yield a gram of gold.

Waste disposal is also troubling me.

I do not claim to be able to offer you any meaningful help. My only contact with HCl is when I pour it in my swimming pool.

My best advice is to hire a pro in the field of inorganic chemistry. He / she will design the easiest, most efficient, safest and environmentally friendly process for you to implement. At my company we deal with both: organic and inorganic compounds, and I went that way to improve some obsolete and inefficient processes (also had to struggle against prejudice, cause they have "always" been done that way). The results have been highly rewarding!

If you prefer electroplating, try a graphite electrode. Otherwise, copper sulfate mixed with con. sulfuric acid and a little heat will yield nitric acid and leave copper sulfate.

Good luck. GH

Friend,

I don't see where the nitrate comes from in your verbal equation. Please advise us.

--JMM

You are right, I mis-spoke. I should have said copper nitrate plus con. sulfuric acid. The OP indicated he had lots of copper nitrate. Sometimes my brain takes a break when I start typing.

GH

Have you looked at the "gold refining forum"? They specialize in gold and precious metal recovery. They are also safety Nazis, so anything that looks like a dumb question will get you flamed, tarred and feathered, whipped and rolled in salt, and given a tongue lashing by someone who makes Lyn look tame.

But they seem to know their stuff.

There is also a book available on line by Hoke, called something like "refining of precious metals" It's a free download, and you can find it on that same forum.

Jon.

PS: The link is:http://www.goldrefiningforum.com/

I couldn't get the link tool to work in the editor.

Suggest you do a cost analysis on your present process and any future ones. You seem to be generating a lot of waste chemicals. The USA is the most costly place to correctly dispose of direct process waste and also secondary process waste. For all the work and chemicals being used you might be giving the stuff away and not know it. The fines for illegal disposal are real steep and only one incident for a violation you never heard of could put you in the poor house.

Another more important item is the personal protective equipment that everyone needs to wear. Nitric and Hydrochloric acids are real bad ones requiring some expensive PPE and personnel must be protected. Same with these fines.

Good Luck, Old Salt

You could start out with a keyboard mylar, attach it to positive electrode of voltage supply, and a silver foil attached to the negative (ground) electrode. There has to be an electrolyte and HCl is OK, as long as you do not overdrive the voltage through electode polarization and make chlorine. Electrowinning has many side benefits: (1) it helps purify the metals (this is how raw smelted copper is purified to high grade copper), (2) does not involve aqua regia that is extremely hazardous to work with, and will poison you with NOx if you breathe the brown gas that is emitted, and (3) can be applied to metals containing both silver and gold, where sometimes the gold simply drops out of suspension near one of the electrodes.

With some fine tuning you might learn that you have less work to do cleaning up and separating the yield. I think there are even companies out there that specialize in selling the equipment for this. Be aware that electrowinning may consume considerable electric power, and may be slower than you are used to dealing with.

I thought about electroplating it off but found that the plating would take the silver off unevenly. It would break contact with the part hooked up to power and leave over half the silver on the mylar. I usually try to electroplate when really needed such as when I purify copper or cobalt as well as the molten salt plating for calcium, sodium, lithium and aluminum. I will after getting this silver shot done pour it into an anode and then plate it over to increase the purity. It is just the process of getting it off the mylar that is the kicker.

As for the original question I found the aqua regia does work a little bit but isn't any more cost effective. Also I re-read an earlier post and I should have said 15-30ml not 150-300ml for a half ounce.
I have since decided to move in the direction of making nitric acid to use on the silver rather than finding an alternative way of stripping it. It isn't so hard to make and sodium nitrate is much cheaper than buying straight nitric.

Half an ounce (14g) of silver from 15ml (three teaspoons) of reagent? Really?

Give or take, yea. Nitric can hold quite a bit of silver in it. I also said 15-30ml as well.

Have you even considered destroying the mylar?

Total glycolysis, methanolysis, and hydrolysis[edit]

The treatment of polyester waste through total glycolysis to fully convert the polyester to bis(2-hydroxyethyl) terephthalate (C₆H₄(CO₂CH₂CH₂OH)₂). This compound is purified by vacuum distillation, and is one of the intermediates used in polyester manufacture (see production). The reaction involved is as follows:

[(CO)C₆H₄(CO₂CH₂CH₂O)]_n + n HOCH₂CH₂OH → n C₆H₄(CO₂CH₂CH₂OH)₂

This recycling route has been executed on an industrial scale in Japan as experimental production.

The above was copied and pasted from a Wikipedia article on PET, of which mylar is a particular sub-class. Sometimes the Mylar is modified by coating or treatment to make the polymer less crystalline (makes it more flexible and is more resistant to cracking). If you wish to recycle the Mylar, it makes about as much sense to break it down, filter off the silver (and any other metals if they are present), and then sell the clean "monomer blend". IF you only wish to destroy the Mylar, then try using caustic soda bath at high concentration, to (a) partially hydrolyze the Mylar and slough off the silver, or (b) totally dissolve the Mylar, and if insoluble have the monomers float off, and the silver sink to the bottom. I think it could be worth an experiment. I would like to get a cut of the action on this if it works.! Good luck.