Washing process and no ice available.

[nickvc]

You can use salt to precipitate silver chloride and converting that back to silver metal is very easy, I like Lou's method add some sulphuric a few piece of iron and tumble or use a mixing rod attachespd to a drill.
You need to filter all your gold solutions, it's so easy to contaminate your gold at the final stage or pour a little silver chloride into your solution from the dregs at the bottom.
With filter papers you simply save them until you have enough to process then it's a careful incineration a good HCl wash and then into AR, very simple.
Hoke is an old book but gives you the basics for recovery and refining and how to test your solutions, remember it was written for those with little or no chemistry background, that's the reason we try to get newbies to read it, it gives you the basic understanding of most processes.
With high 14k+ scrap you can go direct to AR but will be left with silver chloride and a few rogue pieces that always seem to crop up, the one good thing in some ways are that any PGMs present should also be in solution, solid pieces of Pt are not likely to dissolve completely but if you melt and cornflake the metal first it helps to dissolve the Pt into the rest of the metals.

 

[butcher]

autumnwillow
To be honest with you, I have read Hoke's book so many times that I think it is already outdated and the processes there generate too much waste. I already have about 25gallons of copper nitrate, 5 gallons has already been processed with iron (which is a pain to do). I would go for HCl addition to make silver chloride this time, then just process the solution remaining in the stock pot. The remaining 20 gallons, I'll just save it and I believe I could use it somewhere sometime.



Copper nitrate can be reused, to make nitric acid, in recovery to dissolve base metals, to make other copper salts, you can also recover gold and make another useful copper salt or solution in the same process, for me copper nitrate is almost as valuable as nitric acid, I do not consider copper nitrate a waste, I consider it a useful byproduct.

If you precipitate silver from a solution of silver/copper nitrate with NaCl or HCl acid, you will still have a waste product to deal with. This time it will be a mixture of copper chloride and nitrates, which I see as less useful as a byproduct than the copper nitrate. Unless if you were dealing with a more pure solution of AgNO3 where the byproduct with Nacl would be sodium nitrate and sodium chloride, that could be separated as salts, or with HCl and a byproduct of HNO3.

I have to disagree, I do not see Hokes book as outdated at all, in my opinion it is as relevant today as it was almost a hundred years ago, besides maybe in a few minor areas or details, there may be better or safer options in some instances, or processes for some materials, that we know more about now. Hokes book was not written today, so it will not reflect the times it was written in. Not what we know or use today. The chemistry, basics or principles have not changed in all of these years, I am sure if she would have been able to re-write her book today it would have most of the things we discuss today, or at least mention or touch on them. She did not write her book on mining or recovery of values from mining, but she did touch on the subject. She would not have written the book on recovery of electronics if written today although I am sure she would touch on the subject, if she was to rewrite her book "Refining Precious Metal Waste" today. Her book was written mostly for jewelers to help them in that trade to recover and refine their scrap.

 

[Anonymous]

I agree Richard

The chemistry doesn't change, and it's wholly valid when taken within that perspective. The added metals involved in e-waste do put a different perspective on things though because as you rightly pointed out the book was written to help jewellers.

 

[autumnwillow]

Okay. I agree. Let me re-state that. Hoke's book is just a little bit outdated. Books get revised all the time. I think it should be re-written by Lou/4metals whom I find is very experienced and knowledgeable in this field.

The 20 gallons that I saved is for your killing with two birds in one stone method. Which I will do once I get my hands on materials to process. Nitric is cheap in my place, distilling it would cost more as electricity is very expensive here.

My silver nitrates from inquarted gold contains trace PGMs which I think could be recovered after removing the silver chloride thru HCL then stock pot copper cementation.

 

[autumnwillow]

The contaminant is primarily iridium with a little silver chloride.

How does one go about setting aside iridium so it does not keep on being part of your refining cycle?

 

[nickvc]

Are you sure it's iridium?
I ask because it's not normally associated with karat jewellery, it can and has been used in platinum alloys, if it's dissolved you can cement it out with copper, when I actually had some in my system it really wasn't keen to dissolve if I remember correctly, very like rhodium, I think HCl and hydrogen peroxide will have a better chance at dissolving it, check for gold before cementation and if present precipitate that first and then cement.

 

[autumnwillow]

A theory perhaps.

Gold chloride readily vaporizes when incinerated.

By putting all the filter papers containing trace amounts of gold chloride and silver chloride in a ferrous sulphate solution, we are able to convert gold chloride to metallic gold and silver chloride to silver in the presence of iron.

Wash, dry then incinerate.

Proceed with nitric digest, then hot AR. Drop Platinum, then drop Gold.
Whats left should be iridium and trace amounts of other metals.

I'll try these next week on my free time.

 

[g_axelsson]

I don't think ferrous sulfate will turn silver chloride back into silver.

Göran

 

[4metals]

Take the silver out as a chloride with salt.

 

[autumnwillow]

I don't think ferrous sulfate will turn silver chloride back into silver.

Göran

Correct me if I am wrong.

Iron and 10 percent sulfuric acid will. Ferrous sulfate.

Take the silver out as a chloride with salt.

Thank you for the advice, if it wasn't for the advice I could have lost some silver.

My theory worked.
The process was:

Put all the used filter papers in a beaker.
Add recycled ferrous sulphate. Mix until the filter paper crumbles to pieces.
Add HCL to precipitate any dissolved silver as AgCl. Mix.
Add iron, mix.
Filter the sludge until pH is equal with wash water. I used tap water here.
Incinerate.
Digest in Nitric.
Filter again in a filter paper.
Melt.
Digest in AR.
Wash and Melt.

I would prefer this method over immediate incineration as gold chloride is easy to vaporize and no accidental AgCl fumes to deal with.

 

[g_axelsson]

I don't think ferrous sulfate will turn silver chloride back into silver.

Göran

Correct me if I am wrong.

Iron and 10 percent sulfuric acid will. Ferrous sulfate.

Yes, that is a well known method.

What I think is that some silver is dissolved and then it is cemented on the iron. Iron and sulfuric acid is not the same thing as ferrous sulfate.

I haven't tried this yet but what I think is happening is that the iron will form an electrolytic cell. When the iron goes into solution the silver chloride is turned into silver and chloride ions.
From what I have heard, the transformation starts at the iron and moves outward. (Unless it is tumbled.)

Göran

 

[autumnwillow]

I wonder if just iron in a chloride solution will convert silver chloride to silver metal. I will try and test this on a test tube.

Are you the same Goran from the finishing website?

 

[Topher_osAUrus]

I wonder if just iron in a chloride solution will convert silver chloride to silver metal. I will try and test this on a test tube.

Are you the same Goran from the finishing website?

I dont think it would?

Since its above silver in the reactivity series, i think it would be a fruitless venture.

Not trying to be a nay-sayer, or negative nancy. But, trying to think pragmatically.

FeCl + AgCl would end up with the exact same things i believe, as there isnt anything to give up an electron or to catalyze the conversion.

Maybe i misunderstood the "iron in a chloride solution" though.
As i know iron has many oxidation states.

 

[g_axelsson]

I wonder if just iron in a chloride solution will convert silver chloride to silver metal. I will try and test this on a test tube.

Are you the same Goran from the finishing website?

No, I've never registered there.

Göran

 

[upcyclist]

I wonder if just iron in a chloride solution will convert silver chloride to silver metal. I will try and test this on a test tube.

I wouldn't think so. For the reactivity series to come into play, the solid has to be soluble in the solution. Copper will dissolve in nitric, thus you can cement out silver or gold in solution when the copper replaces those metals in the solution itself. Because the silver chloride is insoluble in nitric and hydrochloric acid, there is no option for it to be in solution at all, which means no cementation.

That's why the iron & sulfuric acid works--AgCl is slightly soluble in sulfuric, and once it's in solution, the iron knocks it back out, and it cements onto the iron. (usual caveat: I think so, and the big brains will tell me if I'm off or not, hehe)

--Eric