Topher_osAUrus
Well-known member
This was a discussion initiated back in the "determining the contaminant" thread awhile back. About using sulfuric and agitation for gold powder cleanup.
Seen here :arrow: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=25309&hilit=Sulfuric+sonification&start=30
If you dont want to read through it, here's the highlights on the process
:arrow:
I didn't want to completely derail that thread, but I haven't had time to make its own until now with my questions on the matter.
Lou used a 70% hot concentrated sulfuric solution with magical agitation by sound. 4metals used an oblique barrel, most likely 55 gallons or something incredibly huge like the size of my garage with a blade mixer that was probably the propeller off a ship from WWII.
Also a noted difference, 4metals used 25% sulfuric acid.
The solubility of some metals changes substantially in the concentration differences of sulfuric acid. Some things stay in solution when concentrated sulfuric is used, some stay when dilute is used. Is the concentration on one of yours a typo? Or is it no matter, just hot acid and agitation?
The precipitation was done with SO2. The usual culprits are copper, palladium, silver chloride, and I suppose lead sulfate if poorly filtered.
Would a copperas precipitation be the same? Or would is specifically require the dilute pulping leach because of the iron?
Is the traditional washing done firstly? HCl, water, etc? If so, what point is the sulfuric done? Or is it hearty enough to run as a stand alone leach, followed by water to get neutral pH?
Is multiple sulfuric washes done? First with concentrated, then with diluted? Or first diluted then concentrated?
Imagine a small time refiner, what practical way to integrate this method is there? Is a magnetic stirrer "good enough"? Or a good simmer with constant stirring sufficient?
When you say the sonification needs a longer leach, how much longer are we talking here? Until noteable color change in the acid, then decant and add fresh acid? Or decant, add water, and begin the dilute leach?
I am trying a simmer of dilute (maybe 30%) sulfuric on gold powder now. The sulfuric being the only leach after precipitation, the followed by water, drying and melting in a new dish. I don't think I want to try boiling strong sulfuric acid...
If you made it this far, your patience and perseverance is astounding
Seen here :arrow: http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=25309&hilit=Sulfuric+sonification&start=30
If you dont want to read through it, here's the highlights on the process
:arrow:
4metals said:I mentioned a method I had used which I called pulping. Basically it involves tumbling in a violently agitated tumbler, gold sponge and adding 25% concentrated sulfuric acid to 75% hot distilled water. I was working on a large project and looking to gas gold in a single pass from direct aqua regia digestions and get a purity of .9999.Lou said:A final sonication with 70% hot sulfuric acid can be used to clean up the gold markedly in purity.
...
I took a sample of the sponge before treatment and then used the pulping process in a large oblique barrel with a blade mixer and did the sulfuric water thing and ran it for 15 minutes. Filtered, rinsed, and resampled the gold. The gold before the process was .999+ and the gold after the process was .99999.
.....
Lou had never heard of this before and since he has a well equipped lab with all of the big boys toys he gave it a try. The thing is he didn't have the oblique barrel and he didn't have the gold quantity to require the big barrel anyway so he used ultrasonics to provide the agitation. ....
I didn't want to completely derail that thread, but I haven't had time to make its own until now with my questions on the matter.
Lou used a 70% hot concentrated sulfuric solution with magical agitation by sound. 4metals used an oblique barrel, most likely 55 gallons or something incredibly huge like the size of my garage with a blade mixer that was probably the propeller off a ship from WWII.
Also a noted difference, 4metals used 25% sulfuric acid.
The solubility of some metals changes substantially in the concentration differences of sulfuric acid. Some things stay in solution when concentrated sulfuric is used, some stay when dilute is used. Is the concentration on one of yours a typo? Or is it no matter, just hot acid and agitation?
The precipitation was done with SO2. The usual culprits are copper, palladium, silver chloride, and I suppose lead sulfate if poorly filtered.
Would a copperas precipitation be the same? Or would is specifically require the dilute pulping leach because of the iron?
Is the traditional washing done firstly? HCl, water, etc? If so, what point is the sulfuric done? Or is it hearty enough to run as a stand alone leach, followed by water to get neutral pH?
Is multiple sulfuric washes done? First with concentrated, then with diluted? Or first diluted then concentrated?
Imagine a small time refiner, what practical way to integrate this method is there? Is a magnetic stirrer "good enough"? Or a good simmer with constant stirring sufficient?
When you say the sonification needs a longer leach, how much longer are we talking here? Until noteable color change in the acid, then decant and add fresh acid? Or decant, add water, and begin the dilute leach?
I am trying a simmer of dilute (maybe 30%) sulfuric on gold powder now. The sulfuric being the only leach after precipitation, the followed by water, drying and melting in a new dish. I don't think I want to try boiling strong sulfuric acid...
If you made it this far, your patience and perseverance is astounding