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hissingnoise
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If you send me the top layer of clay, I'll be only too glad to do the separation!   
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watson.fawkes
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Quote: Originally posted by Traveller  | | I am attempting to recover ultra-fine gold particles from the top surface of a deposit of clay. It is a fairly rich deposit of gold a few millimeters
thick on the upper surface of the clay. |
How much clay is it, exactly. What's the percentage of gold by mass?
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Traveller
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There is a few miles of this clay. The assay results are on a need to know basis only. Suffice it to say it is worth putting considerable effort into.
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Traveller
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http://www.freepatentsonline.com/3957505.html
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watson.fawkes
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| Quote: Originally posted by Traveller | | There is a few miles of this clay. The assay results are on a need to know basis only. Suffice it to say it is worth putting considerable effort into.
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And you do know this is a forum for amateur science, right? Your secrecy is utterly characteristic
of money-making mining operations.
Stripping a few miles of streambed (since you specified a linear length, rather than an area, I'll assume it's an alluvial deposit) is just not at the
amateur scale. As an estimate, take 10 km of stream, 5 mm of surface thickness, 2 m of width, and 1% gold by mass. I'll take the density of wet
excavated clay at 1.8 kg/m3. That's 100 m3 of clay. I don't know anyone with a garage large enough to hold the raw material.
Gold content estimated at 1.8 kg, or about 58 troy ounces. At USD 1700 per ounce, that's just shy of USD 100,000.
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Traveller
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Well, I don't know of many people who mine gold just for the fresh air and exercise. At some point, the novelty of seeing the yellow metal wears off
and one likes to see a slight return on one's efforts.
You assumed, when I stated there was a few miles of this clay, I had the means and authority to strip mine miles of clay at a time. Nothing could be
further from the truth. I am limited to the tools I can pack in on my back to a very remote and isolated locale and it would take several lifetimes
for me to successfully exploit this entire deposit. Also, it is not a stream. Beaches are measured in miles, as well, and this deposit sits atop a
layer of marine clay a few feet below the surface of an ocean beach. The gold is deposited by waves during winter storms.
As you can see, I am not a large mining corporation. If I were, I likely wouldn't be asking for advice on this forum but would, instead, hire
engineers and chemists to work out the leaching problems. I am just a person trying to supplement his income in these troubled times by trying to
recover an ounce or two of gold when time permits.
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watson.fawkes
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| Quote: Originally posted by Traveller | | I am just a person trying to supplement his income in these troubled times by trying to recover an ounce or two of gold when time permits.
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Are you planning to do leaching on site, then? Or to haul back clay and process in the lab? My guess is that
you'll get better mass / unit-transportation efficiency by hauling clay rather than hauling a portable lab around.
I think you'll also find that iodine in any form is fairly expensive and recovery of spent iodine is difficult. Cyanide leaching is well understood,
much less expensive, and importantly for your concerns, and be remediated before discharge. Oxidation to cyanate is quite common, but electrowinning
of gold has the side effect of regenerating the cyanide in ionic form, where it can be reused. Search on "cyanide remediation" for lots of hits.
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Traveller
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| Quote: Originally posted by watson.fawkes | | Quote: Originally posted by Traveller | | I am just a person trying to supplement his income in these troubled times by trying to recover an ounce or two of gold when time permits.
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Are you planning to do leaching on site, then? Or to haul back clay and process in the lab? My guess is that
you'll get better mass / unit-transportation efficiency by hauling clay rather than hauling a portable lab around.
I think you'll also find that iodine in any form is fairly expensive and recovery of spent iodine is difficult. Cyanide leaching is well understood,
much less expensive, and importantly for your concerns, and be remediated before discharge. Oxidation to cyanate is quite common, but electrowinning
of gold has the side effect of regenerating the cyanide in ionic form, where it can be reused. Search on "cyanide remediation" for lots of hits.
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Correct. And as leaching takes time, a person would be tied to the site until the gold was dissolved and precipitated. My basic plan is to scrape off
the minimal amount of clay I can, break it down to a liquid form in a bucket and screen it down to -30 mesh. At this point, it should be a manageable
volume for packing out.
As for recovering and recycling iodine, I posted the patent by Richard Homick for everyone's perusal of his plan for recycling.
I know cyanide is very economical, straightforward to use and can be neutralized to prevent it harming the environment. However, when things go bad,
they go bad in a big way. I'm not sure what country you are in but, in Canada, there does not appear to be a legal method for a small time operator,
such as myself, to obtain cyanide.
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Traveller
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Another question about Lugol's Solution, is it particularly volatile? What I mean is, the patent requires the leaching process to be agitated. I was
thinking of the smallest cement mixer I could find to keep the clay and Lugol's constantly mixed and moving. Would it be necessary to cover the top to
prevent evapouration losses of iodine?
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Vargouille
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Well, there are a few points to be told to answer that. Lugol's solution, as a whole, is not particularly volatile at standard temperatures. The
conversion of iodine to triiodide keeps it in solution unless something happens to separate the iodine (or the iodide) from the triiodide. For iodine,
it can be either a reducing agent, or heat. A mixer of the type you describe will certainly produce at least some amount of heat, from friction,
although I'm not certain whether or not that amount is enough to liberate iodine from triiodide. When in doubt, however, I find it best to err on the
side of caution. So, unless you're a gambling man, you may want to consider keeping it covered during operation, or use something to keep the
temperature down.
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zed
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Other Halogens will do. Beside liberating Halogens via the action of Oxone on Halide salts....More economical routes are available.
Herein, someone is suggesting Sodium Hypochlorite plus HCl....to produce Cl2.
http://www.ehow.com/how_10075085_leach-gold-ore-chlorination...
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Traveller
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The sodium hypochlorite/hydrochloric acid leach is very effective at dissolving gold. However, it is even more effective at dissolving iron (the HCl
turns oxides such as haematite and magnetite into ferric chloride) and actually preferrs iron to gold. Because there are large amounts of magnetite
and haematite found in the top layer of clay, it would be necessary to remove the iron from the clay before leaching; unless a way could be found to
make the NaClO/HCl leach selective for gold. Perhaps by ph adjustment?
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Traveller
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The sodium hypochlorite/hydrochloric acid leach is very effective at dissolving gold. However, it is even more effective at dissolving iron (the HCl
turns oxides such as haematite and magnetite into ferric chloride) and actually preferrs iron to gold. Because there are large amounts of magnetite
and haematite found in the top layer of clay, it would be necessary to remove the iron from the clay before leaching; unless a way could be found to
make the NaClO/HCl leach selective for gold. Perhaps by ph adjustment?
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Traveller
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The sodium hypochlorite/hydrochloric acid leach is very effective at dissolving gold. However, it is even more effective at dissolving iron (the HCl
turns oxides such as haematite and magnetite into ferric chloride) and it actually prefers iron to gold. Because there are large amounts of magnetite
and haematite found in the top layer of clay, it would be necessary to remove the iron from the clay before leaching; unless a way could be found to
make the NaClO/HCl leach selective for gold. Perhaps by ph adjustment?
[Edited on 27-10-2012 by Traveller]
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zed
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Ummm. The Iron bearing components of sand are often magnetic. To the best of my knowledge, Gold is not magnetic.
I would suggest removing as much Iron as possible via magnets, prior to Cl2 treatment.
Other salts of Iron, may be soluble via less extreme conditions. The idea of using Halogens to dissolve Gold... is due to few other things being
able to.
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Traveller
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| Quote: Originally posted by zed | Ummm. The Iron bearing components of sand are often magnetic. To the best of my knowledge, Gold is not magnetic.
I would suggest removing as much Iron as possible via magnets, prior to Cl2 treatment.
Other salts of Iron, may be soluble via less extreme conditions. The idea of using Halogens to dissolve Gold... is due to few other things being
able to.
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Sounds really simple, doesn't it? Yes, magnetite is quite magnetic (gee, I wonder if that's how it got its name?) and, with the new N42 and N52
neodymium magnets, even haematite can be removed magnetically.
The problem is this. When particles of iron or "black" sand, as we call it, are attracted to a magnet, they move towards that magnet in a tightly knit
wave. Any particles of gold in the way of this "wave" get snowploughed by the black sand and end up being stuck to the magnet with the black sand.
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AndersHoveland
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The use of bromine in the extraction of gold was proposed by R. Wagner (Dingler's Journal, 218, p253)
Encyclopaedia Britannica, Volume 4 p633
Interestingly, the reaction of iodine upon gold is reversible:
Action of Iodine on Gold.
At ordinary temperatures pure dry iodine is without action on gold ; between 50° C. and the melting point of iodine combination takes place with the
formation of amorphous iodide; above that temperature crystalline aurous iodide is formed. The direct reaction is always limited by the inverse
decomposition of the iodide formed, but in the presence of excess of iodide pure aurous iodide may be obtained; this in excess is then best removed by
subliming the mixture at a temperature of 30° ... In the presence of water, gold and iodine react in a closed vessel to form aurous iodide, but the
reaction is limited, and, at normal temperatures, if the iodine can escape, the iodide is entirely decomposed. — F. Meyer (Comptes rend., 1904, 139,
733).
Pharmaceutical journal; A weekly record of pharmacy and allied sciences, Volume LXXIV, Great Britain, 1905
For more information about the chemistry of iodine and gold, see "Hand-book of chemistry", Leopold Gmelin, Volume 6, p211
One of the more obscure ways to reduce gold(III) chloride back to elemental gold is to use an alkaline solution of hydrogen peroxide. Although usually
oxidizer, in some reactions H2O2 can act as a reducing agent.
(2)AuCl4[-] + (3)H2O2 + (6)OH[-] --> (2)Au + (8)Cl[-] + (6)H2O + (3)O2
The gold from this reaction usually separates out in a finely divided state, and appears brown by reflected light and greenish blue by transmitted
light. If very dilute solutions are used, the gold sometimes separates out forming a yellowish film on the sides of the test tube.
I'm not saying let's go kill all the stupid people...I'm just saying lets remove all the warning labels and let the problem sort itself out.
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zed
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The process you are going to use to extract your Gold and remove other unwanted metals, needn't involve a total reinvention of the wheel. There will
be a lot of literature on the subject. It's all been done before. Don't like magnets.....try something else. Or, try rinsing your magnetized iron
ores to remove adherent Gold. It won't matter what you try; no method will be 100% effective in recovering ALL of the Gold that is actually present.
I'm merely suggesting Cl2, because it is inexpensive and it might scale up easily. Iodine is expensive. And, its purchase in quantity might attract
unwanted attention. Nosy folks could show up...demanding permits, mining claim documentation, a cut of the take, and/or tax payments.
There is nothing more offensive to people in general, than seeing someone else make an buck. Makes 'em crazy.
I suggest the two famous Bogart films...."Treasure of The Sierra Madre" and "Beat the Devil".
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rustbucketguy
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leaching of gold with iodine
I realize this is an old thread, but I have not seen a whole lot of answers except outright, untested, negative responses. If you have (or suspect
you have) material with micron gold, pm me or check www.blacksand2gold.com I do not intend to post details openly, but I welcome the opportunity to test your material for you. Most people have a
very poor understanding of the iodine chemistry when used with gold. It is very simple, fast, and not nearly as expensive as people think.
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