# Assistance in process for precious metals recovery



## Anonymous (May 23, 2008)

I work at a computer repair store, and we literally got tons of material we cant do anything with. I am looking into possibility of us doing a precious metal recovery, but have to be careful in how we do it. Been studying on possible processes for 6 months, and then found this site.

First, thanks for being a place that can keep others straight.

So this is what ive come up with in my studies so far.

1. Silver recovery is easierand safer than gold or platinum recovery, but still potentially dangerous

2. byproducts of most of the processes are hazmat items.

3. leave it to the professionals

Meh, ok, so im ignoring number three.

My goal is to determine a way to do what i need with little pollution or byproducts as possible.

this is what i got so far...

6H2SO4 + 6NaNO3 -> 6NaSO4 + 6HNO3 + 3H2
6 Sulferic Acid + 6 Sodium Nitrate = 6 Nitric Acid + 6 Sodium Sulphate + 3 Hydrogen Gas

Hydrogen gas will bubble out. Place containor in freezer to force the sulphate salt to drop out. seperate salt and liquid (50% nitric Acid)

4Ag + 6HNO3 -> 4AgNO3 + 3H2O + NO + NO2
4 Silver + 6 Nitric Acid = 4 Silver Nitrate + 3 Water + 1 Nitric Oxide + 1 Nitrogen Dioxide

Nitrogen oxides bubble out, leaving Silver Nitrate diluted in water. seperate liquid and sludge

2Cu + 4AgNO3 -> 2Cu(NO3)2 + 4Ag
2 Copper + 4 Nitric Acid = 2 copper Nitrate + 4 Silver

Silver drops out, leaving with Copper Nitrate


End result after this first process should be as follows

Hydrogen gas
Nitric Oxide Gas
Nitrogen Dioxide Gas

Sodium Sulphate Solid
Silver Solid
"Sludge" Solid

Copper Nitrate Liquid

So here are the questions

1. Anything wrong with what i see so far?
2. Best way of pulling copper out of Copper Nitrate, or how to convert to a disposable liquid
3. The "Sludge" should contain a mess of hydrocarbons, Polymers, and metals that Nitric Acid can not break down, such as gold and platinum. Best way of further processing this sludge aiming for minimum waste?
4. I read that Sodium Suphate has been used in recovering gold, can i use that to further process the sludge?
5. Effect of Nitrogen Oxide gasses? (locally and Globally)
6. Any changes needed to minimize pollution?

Thanks in advance


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## Irons (May 23, 2008)

Dilute Sulfuric +H2O2 doesn't fume, leaves the lead as an insoluble sulfate and dissolves the copper, iron, some if not all the silver and some of the palladium. It's cheap and won't corrode your garage and everything in it.

If you use Nitric, it will dissolve the lead, corrode, and leave you with an expensive to dispose of waste.


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## Anonymous (May 23, 2008)

Sulpheric acid and hydrogen peroxide....

hmmm 

H2SO4+H2O2 -> SO4 + 2H2O

SO4+2Ag -> Ag2SO4

Keep Liquid

Ag2SO4+Cu = CuSO4+Ag2

ok.. I like this... very clean.. copper sulphate is a pesticide

add zinc to drop copper back out for further use, leaves us with

Zn+CuSO4=Cu + ZnSO4

Pull out copper.. hmm Zinc Sulphite still a biohazard but not as bad as others...

Anyway of dropping the zinc out and replacing with say H2 to get sulpheric acid back? 

Answers many questions, I still will have a sludge left that most likely has gold/platinum in it. best way of processing it?


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## Lou (May 23, 2008)

No hydrogen is formed from combining sodium nitrate and sulfuric acid.


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## Anonymous (May 23, 2008)

Lou said:


> No hydrogen is formed from combining sodium nitrate and sulfuric acid.



Hmm.. can you then requalify for me the results from that mix? i cant make it balance without having extra H molecules left over..

looking over math right now...

6H2SO4 + 6NaNO3 -> 6NaSO4 + 6HNO3 + 3H2

left side has 12 H, 6 S, 42 O, 6 Na, 6 N
right side has 12H, 6 S, 42 O, 6 Na, 6 N

so as far as a balanced equation, it works. so if no hydrogen gas is produced, where does the extra go?


Edit: HNO3 is classic nitric acid... is H2NO3 another variety of nitric acid???


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## banjags (May 23, 2008)

Irons said:


> Dilute Sulfuric +H2O2 doesn't fume, leaves the lead as an insoluble sulfate and dissolves the copper, iron, some if not all the silver and some of the palladium. It's cheap and won't corrode your garage and everything in it.
> 
> If you use Nitric, it will dissolve the lead, corrode, and leave you with an expensive to dispose of waste.



Do I understand correctly that Diliute sulfuric and peroxide would be an alternative to hcl and peroxide?


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## Anonymous (May 23, 2008)

banjags said:


> Irons said:
> 
> 
> > Dilute Sulfuric +H2O2 doesn't fume, leaves the lead as an insoluble sulfate and dissolves the copper, iron, some if not all the silver and some of the palladium. It's cheap and won't corrode your garage and everything in it.
> ...



That would match what ive seen other places..

HCL+Peroxide would create silver chloride that has to be seperated
Sulferic acid + sodium nitrate will create silver nitrate that has to be seperated
sulferic acid + peroxide will create silver sulphide that has to be seperated

many avenues to same goal


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## Irons (May 23, 2008)

Valareos said:


> banjags said:
> 
> 
> > Irons said:
> ...



Silver sulfate is soluble in the low concentrations that you would be seeing.

I've already tested the H2SO4 peroxide on copper/lead and the copper goes in solution quite nicely and the lead precipitates as Lead Sulfate or passivates with a coating of Lead sulfate.
Solder would behave according to the alloy with Tin.

You can warm the solution without corroding everything in sight.

Don't use Sodium Nitrate because that will make Nitric Acid which defeats the whole point of using Sulfuric/H2O2.

Don't use concentrated acid and high strength peroxide on circuit boards. All that organic material can have some nasty consequences. I speak from experience.


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## Irons (May 23, 2008)

Honestly, I don't think you know what you're doing and need to find some other way to waste your money.

Tell your boss to man up and pay for the disposal of the scrap.


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## Anonymous (May 23, 2008)

its also more of a personal challenge. I know enough about the chemical reactions to see benefit in what you suggested.

I also know enough to be willing to study it for months before doing any live tests, get a method in place, present it for possible issues, and have exact amounts of chemicals to do precicely what i want.. before i do anything.

Irons, your suggestions is wonderful, and solved an issue saw as potential waste. 

If it wasnt for your input, id never tought of using a sulphide instead of a nitrate.

Please dont take my asking of questions and verifications of formulas as lack of knowledge, but instead as an understanding on how dangerous this can be


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## goldsilverpro (May 23, 2008)

Valareos,

I think you should totally forget about the chemistry, for now. You need zero knowledge of chemistry to be a good refiner. What you need is a knowledge and a feeling of what happens when various chemicals come in contact with various metals and other materials. You need to develop a knack for these things. You're mistakenly using the chemistry as a short cut. Refining is much more of an art than a science. 

Chemical equations are great when you have single materials and chemicals. When you have several chemicals working on several different materials, you can pretty much throw the chemistry out the door. Harold says that he knows no chemistry, but I bet he could refine rings around any of you. Learn how to refine first. The knowledge of how to refine will eventually teach you a lot of the chemistry, by osmosis.

Read Hoke first. Then start playing around with very, very small quantities (100 mL beakers are a good size). The more small experiments you run, the more you'll know. Keep notes. Ask a lot of specific questions. Study the forum.

I will admit that chemistry is helpful is the refining of the Pt.Gp. metals. You don't need it, but it is helpful.


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## Anonymous (May 23, 2008)

i fully understand that concept 

Im just ensuring on the chemestry side i know what im supposed to get vs what i actually get.

i actually plan to attempt gold and silver recovery by first using "pure" samples.

For example, the cheap, easy to get gold flakes in reflectorol I can get my hands on from my local gemology shops.

im hoping that by working first with known items and seeing what results should be in a perfect situation, i wont miss something important later on.

Biggest part for me on the chemest side is to limit byproducts mostly. Major safety issues i refuse to mess with, so i want to have a method where at least 75% of the waste can be disposed of easilly.

which reminds me of a question...

can i take the solution of copper sulfide that develops near the end and "replate" a copper rod to recover the copper out of it, leaving me with the same SO4 solution i started with?


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## banjags (May 23, 2008)

Irons, or whom ever can answer this. I am assuming by what you are saying I could go to nearest battery shop, buy some battery electrolite aka dilute sulfuric acid and use standard 3% peroxide as a substite for AP? and the h2so4 & peroxide will not corode everything metal with in 20ft? I this is infact true I think I will use this method to process the 5 pounds of fingers I am going to process next weekend.


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## Lou (May 23, 2008)

Yes banjags, that actually works, and no it doesn't really produce much in the way of corrosive gases at those *low* concentrations. I should mention that straight sulfuric and concentrated hydrogen peroxide forms a very dangerous and highly corrosive mixture that will violently decompose with impurities. That said, don't use any peroxide stronger than 6%.


As for Valareos, your equation is incorrect because you are reducing H+ to ground. Is that likely to happen with two oxidising acids? Your equation is wrong.

"6H2SO4 + 6NaNO3 -> 6NaSO4 + 6HNO3 + 3H2 "

You made a simple error--sodium is always +1 in oxidation in aqueous solution. Always.

It should be this:
H2SO4 + 2Na/KNO3 ---> 2HNO3 + (Na)2SO4 if excess H2SO4 is used.

In reality:
H2SO4 + NaNO3 --> HNO3 + NaHSO4 + NO2 

Worry not! Although your chemistry may be lacking, as GSP said, it is possible to do this without knowing a whole lot of chemistry (if any). While I feel strongly that having an idea of what the hell is actually happening is extremely important, it is not integral to successfully refining gold and silver and some of the PGMs. Basically if you can bake a cake, you can refine gold....generally.


Lou


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## Harold_V (May 24, 2008)

goldsilverpro said:


> You need zero knowledge of chemistry to be a good refiner.



I'm afraid I'd have to agree. I just posted on this very thing a few minutes ago. 

I took no chemistry in high school, and no math classes. 

I founded and ran a VERY successful refining business, operated for years, and sold it to retire. I still know almost nothing about chemistry, but my gold quality was outstanding, something I'm very proud to proclaim. I attribute my success to faithfully following prescribed procedures. 

Again, the often seen picture of some of my gold shot, below.

Harold


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## markqf1 (May 24, 2008)

There are many different recipes for baking the same cake. I suggest that a combination of a basic understanding of the chemistry involved, coupled with the trial and error others are willing to share, as well as what you are able to figure out for yourself, would serve you best in your refining endeavers. Nothing like a little OJT to create a database!
You obviously know more about chemistry than I do.

Mark


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## Bernie Foley (Jun 12, 2008)

I still would like to try a spoonfull of those golden flakes!!
One could dream about those!..Bernie


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## cerise (Jul 25, 2008)

So what is the mix .What ratio of Sulfuric to peroxide ?


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