Diluted HCL bleach.

Anonymous · Oct 26, 2009

Hey Guys,
I got some powder that contains very fine gold (as in small particles) and was thinking of using diluted
HCL and bleach to effect recovery. I have 16 ounces of powder that I suspect contains 2.5 - 3 grams of gold
I am thinking of the dilute solution because of the volume of powder, HCL & bleach because the particles are
super fine. I however do not have data on the amount of HCL to dilute, and the amount of bleach to useto extract the
3 grams of gold.

Any help would be appreciated.

thanks
Jim

lazersteve · Oct 26, 2009

Jim,

Diluting HCl-Cl should not hurt it's effectiveness up to about 50% dilution of the acid (15% HCl conc). The extra water will actually allow the solution to hold more chlorine gas which is what actually does the work.

I would also recommend heating the reaction to 60-90C to speed the reaction. Stirring will also be necessary to make sure the chlorine water comes in contact with the fine gold.

Steve

Anonymous · Oct 26, 2009

Steve do you know how much HCL should be needed to dissolve 3 grams of gold?
The reason is this opperation is on a very tight budget to determine profitability.

thanks
jim

lazersteve · Oct 26, 2009

I did some theoretical math on this one a few weeks ago and posted it here:

Auric Chloride in HCl

In reality many factors will influence the maximum amount the HCl can hold. One of these factors is the salt formed from the reaction of HCl with NaOCl. This salt will eat up the HCl so it is not able to absorb gold. Since the reaction is an equilibrium the actual figures depend on many variables: temperature, dilution, pressure, other dissolved salts, etc. Changes in these variables favor one form of the solution or another.

As you can see from the previous post I cited, theoretically about 3 grams of gold will fit in 1 mL of 38% HCl. In reality, the HCl must come in contact with the gold and react with it in the presence of Cl2 at a suitable temperature to become soluble. This requires a medium, which is HCl in water in this case.

The more water you have in the mix and the more material that is not gold in the mix, limits the exposure of the HCl to the gold. For these reasons it is a trade off between dilution and exposing the gold to the reactive part of the solution (ie the gold has to come in contact with the HCl and chlorine), this is where stirring and heat come in.

Basically you can't just calculate the required amount of HCl and use that amount in the reaction as the reaction conditions will dictate the exposure and reaction rates. Ultimately you want to increase the odds in favor of the HCl and chlorine coming in contact with the gold, without saturating the solution with salts that rob the dissolving power of the mix.

You also do not want to dilute the reagents (HCl and chlorine) to such a level that the probability of them encountering a particle of gold is reduced to virtually nil.

The trick is to control the reaction conditions to favor the desired outcome. Just enough water to allow the HCl-Cl to penetrate the feed material and just enough HCl-Cl and temperature to assure all the gold that comes in contact with a reactive species is digested.

I hope I haven't confused you more with this explanation.

Steve

Anonymous · Oct 26, 2009

Steve
Do you think a dilute AR would be better? I notice you use it effectively in your CD on cats.
My feed stock is the plastic from IC chips that I have greatly concentrated by mechanical means.
I was worried that the Nitric in the AR might form some gloppy type stuff and give me issues.
I am trying to not incenerate at this time, but having reduced the volume of the chips by a factor
over 22:1 it my be something considered in the future. I know that after inceneration things would be
much easier.
I also kept in my estimation 90 percent of the base out by mechanical seperation.

Thanks
Jim

lazersteve · Oct 26, 2009

Dilute AR is more reactive towards gold at room temperature so it would require less control of the reaction conditions on your part. It would also be faster for this reason.

Needless to say, incineration first would work best with this feedstock. You would reduce the volume of your material again and hence increase the exposure of the values to the reactive part of the solution.

Steve

Anonymous · Oct 26, 2009

I am in the process of building a super fine sluice box to try and cut the plastic
down to 40:1, I would not feel bad about incinerating then.

I may do 1 oz with AR and 1 oz with HCL-bleach to gauge results.

thanks
you have given me much to consider.
Jim

core · Feb 12, 2013

Hey guys and gals,

So... I am having a different problem that relates to this. I am trying to recover the gold from my first ever parts run.

Not Knowing better at the time, I used the a/p process to try to recover values from all kinds of computer parts with gold on them. I figure that I do have lead and tin from solder as well as iron salts. I cemented the solution that I was having problems with.

I did recover and refine with sucess a portion of the total. Thanks to you folks.

OK. So in this mixture of salts that i cemented out of solution with copper- when I try to dissolve the gold in the hcl/cl solution I get a nice golden solution that is to be expected, but for the second time I have experienced a major loss into the atmosphere. The next day it has rained aucl3 both on the front side and back side of my vent fan (small puddles of thick honey). Yeah, it is a little humorus that it is literaly raining gold around here. But not that funny.

I tried slowing the reaction down by adding small amounts of clorox at a time. I was wondering if im too aggressive still or if it may be that I accidently bought super concentrated clorox.

I would appreciate some advice as to how to be more graceful at this. I was even considering building a condensing unit and catching it in another jar of water or something.

I thought that it may be a point of interest for other new aspiring refiners in the future.

Thank you for your thoughts!

butcher · Feb 13, 2013

core,
This does not make much sense to me, Clorox bleach normally 3 to 6% sodium hypochlorite, sodium hypochlorite added in very small amounts and letting it react, maybe you are using some stronger 12% solution (which you could dilute with water), but even then I cannot see how you forcing gold to leave the vessel.

You should only have a very small amount of chlorine gas leaving solution, not any gold, I cannot imagine how you would have gold leave the solution unless you were doing something very wrong.

A yellow solution does not necessarily mean it is gold, iron can also make a yellow solution, what did the stannous chloride test reveal?

I would go back and study the process again; you must be missing some of the details of the process.

Diluted HCL bleach.

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