For the LIFE of me I cannot get my gold to drop! šŸ˜­

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kurtak said:
Cementing with copper should give him back ALL his gold and it should come down as at least 98 % (with some copper contamination) & if done right should come down at (plus/minus) 99.5 %
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No one disputed the convenience of precipitating gold by cementation with copper ā€œat home.ā€
The main advantage is the absence of the need for acidic multi-stage precipitate treatment.
That's all. Not everyone here is collecting gold from e-waste and scrap jewelry.
In most industrial cases, the precipitation time is much more important (!) than the subsequent complexity of cleaning. Especially when we are talking about thousands of liters of solution.

All gold is NOT equal "at least 98%".

The duration of cementation by copper has well-researched and documented reasons that are described in the scientific literature on electrochemistry. It is quite logical that with a high concentration of gold in the solution, a significant part of it will be deposited quite quickly with a sufficiently large fresh contact surface of copper.

But it will take considerable time to precipitate ALL the gold (100%). Not two hours, but about a week. This is exactly what I wrote about. You have blurred my thesis and given it a completely different meaning.

You did not agree (B.S. :)) with my assessment of 100% cementation time by copper, so I asked you to refer to scientific sources to confirm your words.

kurtak said:
I do not need to waste my time "looking for" authoritative scientific papers on this matter of cementation (actually ion exchange)

So - I most certainly do not need to provide you with scientific references to prove my point - nor is what I am telling you just a matter of my opinion

It is a MATTER OF FACT - with100% certainty - verified - by the almost daily (if not daily) employment of cementation in my (about) 10 years of making a living at the recovery & refining of PMs

Your turn

Kurt
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Unfortunately, I don't know how to continue a scientific discussion based on the formulations you propose, so I propose to close this dispute :)
 
Ultrax said:
Unfortunately, I don't know how to continue a scientific discussion based on the formulations you propose, so I propose to close this dispute :)
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I applaud both Ultrax and Kurtak for expressing their perspective on this issue. And I appreciate both sides. And like everything chemistry there are exceptions.

This forum was originally started by a young college student who wanted to learn about refining. In the beginning it attracted people who had little to no information about refining. It has since evolved into a much more informed group but it still has many members who are green, so to speak.

Typically answers here start by assessing the refining skills of the member posting and tailoring the response to fit.

It is obvious that Ultrax has a great deal of experience in refining and I personally am grateful for his participation. And a lot of what he said applies to large volumes of solution.
Ultrax said:
In most industrial cases, the precipitation time is much more important (!) than the subsequent complexity of cleaning. Especially when we are talking about thousands of liters of solution.
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In large vats of solution the factors of retention time to allow exposure of the values in solution to come into contact with the metallic copper, as well as appropriate agitation weigh heavily. It is easy to see how an air agitation setup can be much more effective on a pail of acid than on a large vat of acid. That is where the majority of the time comes into play to effect a complete recovery.

For most refiners, not the large Metalor's of the world, but for small to mid sized refiners, the cementation on reasonable sized solution volumes is relatively quick. I say relatively because it depends on the concentration of the values in solution, lower concentrations take longer.

So for this discussion, which I see as a friendly discussion, nothing else, both Ultrax and Kurtack have expressed valid points. We (all of the forum members) are lucky to have the knowledge that both Ultrax and Kurtack bring to these discussions as they bring together both practical hands on experience with a technical education who has also had practical experience.

Again thank you both for your participation.
 
As far as process is concerned, both are correct. Because both come from different backgrounds in recovery and refining of precious metals, there will be differences of opinion.

Time for more coffee.
 
Ultrax said:
All gold is NOT equal "at least 98%".
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You and Kurt are both heavyweights in my book with tons of experience and very helpful posts.

But to clear something up: I think Kurt meant to say: all the gold will come down(100% of the present gold), with some impurities, making it at least 98% pure gold. With no traces of gold in solution.
 
I should note that larger refiners have analytical labs capable of verification of 100% removal of the values from solution. Smaller operators who do not have similar capabilities often rely of stannous chloride.

A solution that does not indicate values on stannous chloride is still capable of holding a few PPM of values which will remain undetected.
 
Just to be fair to both sides of this discussion below are the numbers calculated for a retention of 1 PPM of Gold at today's prices for 5 gallons (20 liters) and 528 gallons (2000 liters)
ppmgramslitersgallonscontent (g)gold pricegold per gramloss
1​
0.001​
20​
5.28​
0.02​
$2,025.00​
$65.11​
$1.30​
1​
0.001​
2000​
528.40​
2​
$2,025.00​
$65.11​
$130.21​
As you can plainly see, larger refiners have incentive to recover down to the last PPM. This is usually accomplished with resin columns or, depending on the feedstock for the waste generated, waste treatment.
 
As cementation to recover values is an important concept in refining for both the big players and the small players, I should note that I labeled the right column as loss. By that I mean it is lost to the process lot it came from, but it is not a loss.

To a small refiner proper cementation with copper in basic waste treatment should bring that back as a mixed concentrate. To the larger refiner there are more (costly) options.

But it is mislabeled as a loss for the refiner. It is a loss to the customer expecting payout. Because it is non quantifiable lot by lot. And to be fair to the refiner, if they had to charge you for recovering every milligram of your material, the refining costs would be much higher. The best deal for the customer will allow for that "accountability" loss. But make no mistake the refiner can get the values recovered but at that point the profit goes to the house.
 
Yggdrasil said:
More or less.
Do not add too much, if a ml or two has not fixed it, it is something else.
And the liquid need to be cold not warmed.
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Sooooooo ... I tested the pH and it was at around 2.5 ... so yeah - Never gonna even test with urea again šŸ˜…

That said, I decanted back and forth until I had a "clean" solution, and added a splash of HCl. INSTANTLY I found the Silver that we were looking for šŸ¤£šŸ¤£šŸ¤£šŸ¤£šŸ¤£šŸ¤£

So now what šŸ¤£

I'm thinking siphon the liquid to not disturb the precipitant, then wash it in HCl and put that rinse in with the siphoned colloidal solution.

As for the precipitant itself ... is it silver sulfate? If so, I can use table salt to convert it to silver chloride ... or is it already silver chloride? If so then do the lye and sugar method for the AgCl to turn it back to metal... Then should I proceed to do the dropwise bleach for the liquid as before?
 

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OldManSam said:
Sooooooo ... I tested the pH and it was at around 2.5 ... so yeah - Never gonna even test with urea again šŸ˜…

That said, I decanted back and forth until I had a "clean" solution, and added a splash of HCl. INSTANTLY I found the Silver that we were looking for šŸ¤£šŸ¤£šŸ¤£šŸ¤£šŸ¤£šŸ¤£

So now what šŸ¤£

I'm thinking siphon the liquid to not disturb the precipitant, then wash it in HCl and put that rinse in with the siphoned colloidal solution.

As for the precipitant itself ... is it silver sulfate? If so, I can use table salt to convert it to silver chloride ... or is it already silver chloride? If so then do the lye and sugar method for the AgCl to turn it back to metal... Then should I proceed to do the dropwise bleach for the liquid as before?
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If HCl instantly "found" your Silver it could be Silver Chloride, the only strange thing is there was plenty Chloride from before.
I'd add a few drops of Bleach or pool Chlorine if that clears the solution filter well and cement out the PMs.
Then deal with the White stuff later, test it by adding a crystal of NaOH to a tea spoon with the material.
 
Yggdrasil said:
If HCl instantly "found" your Silver it could be Silver Chloride, the only strange thing is there was plenty Chloride from before.
I'd add a few drops of Bleach or pool Chlorine if that clears the solution filter well and cement out the PMs.
Then deal with the White stuff later, test it by adding a crystal of NaOH to a tea spoon with the material.
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My hunch was correct... It appears to be silver sulfate because it is easily soluble in water.

I'm gonna wash it and let it settle and process it later tonight.
 
OldManSam said:
Who has two thumbs and finally got his gold to fall out of solution???

THIS GUY!

My math said to expect 7.01 grams. I achieved 6.93! Not bad for a cluster____!!! Thank you all for your help!
View attachment 61450
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Congrats, but you should have refined it a second time before you melted it.
Anyway you now have a button :)
 
Yggdrasil said:
Congrats, but you should have refined it a second time before you melted it.
Anyway you now have a button :)
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I was just ready for this one to be done šŸ˜…šŸ˜…šŸ˜…

I learned a lot about working with low karat scrap. I figured I could get away with 8k not being inquarted but the passivation of the silver just made it a nightmare. That's what I get for trying to take shortcuts. Next time I'll alloy it down and stop being so lazy, because that ten minutes I saved cost me the next four days trying to fix it.
 
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