Refining placer cons- bromide electrolytic leaching

[The Refiner49er]

Hi All!

I have been researching methods for refining placer gold with Black Sands (BS, I like the abbreviation- LOL!) and other native gold concentrates.

I found a process designed specifically for these types of materials that utilizes a water/sodium bromide solution, but had to edit this post, as recently several local individuals are trying to run their materials in house, rather than using my services.

John
AKA- The Refiner49er
[email protected]

 

[OMG]

I would keep the reaction covered.
Bromine will make your nose burn.
In wiki it says bromine reacts with gold at 140*C.

I'm interested in the results. Keep posting.

 

[Irons]

Selenium Arsenic and Germanium form volatile compounds when reacted with Bromine and HBr.
Unless you do the reaction in sealed apparatus where these volatiles can be collected safely, you risk some severe health issues.
You have to assume that black sands contain Arsenic unless you know otherwise.

 

[The Refiner49er]

Thanks, Irons!

In processing placer concentrates, I was thinking that a preliminary assay is advisable, and with regards to unknown toxicology; it now seems mandatory. An assay also serves well to justify the refineability of the material, and provides a definition of the expected values, to the benefit of both customer and refiner.

Thanks again, Everyone!

 

[Irons]

No point in wasting valuable resources on barren material.

Set up a small version and test for values before investing more.

It's always good practice not to vent fumes into the atmosphere for many reasons. Your health and the health of your family and friends is number one on the list.

 

[Lino1406]

gives bromine vapors immediately

 

[The Refiner49er]

Hi All!

Thanks for the input! I will keep posting on this as progress is forged.

John
AKA- The Refiner49er

 

[The Refiner49er]

One more factor..

I have discussed this primarily as a leach process, but the method is also used in an immersion application, with the feasibility of processing other gold content materials, including E scrap.

Just a theory...

 

[OMG]

I did some experiments with bromine a while ago. In one of the containers I had bromine and chlorine and their salts and HCl, and the "bromine activator" (which I think does the same action as sulfuric acid would). That was a few months ago, and I opened it up the other night and it still reeks of bromine. (made my nose burn a bit and my eyes watered).
That batch was left in a sealed container in the dark.
The other batch I tried on gold plated computer parts - just a bunch of random stuff. I didn't put HCl in this time. It has sat for about a month (open to the air). It doesn't smell much anymore, but I don't know if it dissolved gold. It dissolved most of the copper though. the solution is looks like a green watery paste. It showed no result when testing with stannous.

You should do a test to see how cold you have to keep bromine so it doesn't fume. You should be able to make bromine by adding a bit of that NaBr to HCl and add bleach. Normally HCl + bleach makes Cl2, but with the NaBr there, the Br2 should be given off instead.

I think you'll be surprised at how strong a little bit of bromine is, even if its below its boiling point.

It would be nice if you could keep the bromine almost at its freezing point.
The reaction would probably be very very slow though.

 

[Lou]

It sounds like you want to have a bromine water solution. That is very easy to do. Bromine is exceedingly easy to make with sodium or potassium bromate and hydrobromic acid. But since most of you probably don't have HBr or don't want to make it (distill H2SO4 with NaBr) I'll tell you the easiest way to make bromine. It's about a 98% yield, depending on technique.

The best way to make bromine is:

NaClO3 + 6NaBr + 6HCl --> 3Br2 + 3H2O + 7NaCl

it requires distillation to get the near perfect yields.

Electrolysis of sodium bromide solution doesn't really give bromine in appreciable levels, believe me, I've tried it. This is because there are competing reactions occurring (in particular the formation of bromate, BrO3(-1) ).

Remember, bromine formed via electrolysis depends highly on temperature. What actually happens is that some of the NaBr forms NaOBr in solution, the bromine analogue of hypochlorite (bleach). This OBr(-1) is what actually oxidises the bromide anion in solution to Br2. Unfortunately for you lot, this is a reversible reaction, meaning it can go backwards! That's why electrolysis sucks for making a bromine solution. Sorry to burst your bubble.


Attached is a photo of about 450g of bromine I made a few evenings back (for use in my catalytic converter project!).

EDIT: PS, bromine is preferable to work with in the cold. It freezes at 19F, so keeping it about the f.p. of water means its vapour pressure is low, which means your eyes are smarting! Invest in a gas mask if you really want to pursue this.
Also, that price on sodium bromide is about what I paid (a little more, I got mine for 5USD/kg as a 12kg pail) so it's a good price.

 

[The Refiner49er]

Hey Lou!

Thanks for posting on this subject.

From the details, it looks like a great way to extract the PM's and leave the base metals behind.

Thanks!

John

 

[Lou]

Interesting. As I thought, this process relies upon the hypobromite to do the oxidation work. This is somewhat similar to the acid-''chlorox'' method used by some here in dissolving gold.

I've heard about this method before and thought of it independently before but for me, I thought it would be easier to use chlorine instead. I am 95% sure that you can substitute chlorine for bromine in this situation and have the same recovery. I can't see why this is patented, as chlorine will do the same thing (which is used as a leach, HCl+sodium hypochlorite or just chlorine water). The only thing I can think of is that if we substituted sodium chloride for sodium bromide, the formation of the hypohalite might not be as favored. Wait, and perhaps bromine is more selective at PMs and not introducing in extraneous ions.

My thoughts are that the process will work, but that it is not really suitable for being a patent as there is an identical process which uses chlorine. The chemistry is the same.

This is something I would try on the small scale, perhaps by precipitating some gold onto silica sand or perhaps making some gold and silver sulfides and seeing if this could work.


Lou

 

[The Refiner49er]

Hey-

If anyone out there has a surplus of placer black sands, I would definitely be interested in running it. Substantial size/value batches will have a preliminary assay done, to statistically verify the efficiency of extraction.

Please E mail me if you are interested.

Thanks!

John
AKA The Refiner49er
[email protected]

 

[The Refiner49er]

Hey Lou!

You are using bromine as a component in processing cats? May I assume Br3 or HBr dissolves PGM's? A guy inquired as to the ability of this process to extract Pt from placer sands a few days ago, and I would like to know the specifics. Especially the procedure to selectively precipitate from the solution (separate from the other PM's).

Thanks again!

 

[Lou]

There is no stable Br3. It is diatomic, Br2.

Dry and wet bromine gas will attack platinum, rhodium, and palladium, but it is at a high temperature.

Wet, aqueous bromine will not dissolve any platinum, at least not to a noticeable extent. That is why platinum electrodes are used in the production of bromine and chlorine.


Lou

 

[skippy]

Neat method of making bromine Lou! Is chlorine contamination a problem?

I've made bromine with approximately %60 yield by the H2SO4+H2O2+2NaBr ->Na2SO4 + Br2.
I used a spa sodium bromide solution. I dripped in sulfuric acid drain cleaner slowly, to avoid heat and thus HBr evaporating. Then I put the solution in an ice bath and slowly (one drop every 6-8 seconds or so) added 35% peroxide. I used a 10% excess of peroxide because I was worried that some might decompose into O2 pre reaction. The solution solution turns a turbid red by the end and the Bromine settled out overnight. For drying, I pipetted the bromine out (avoid pipetting the aqueous phase) and then injected it into concentrated H2SO4 in a storage bottle. Anyhoo, another way to make bromine - and without a fancy distillation apparatus. It doesn't make too much smell
either. Yield can probably be better with some care and tweaking, but I just wanted to test it out and was pleased that it worked.

 

[Lou]

That method will work as well (and it's self heating if you decide to distill for better yields). The only problem is that you are using Caro's Acid which is extremely corrosive.


As far as chloride and water contamination goes, there is a simple solution. Shake the bromine you make with conc. sulfuric acid. This removes any dissolved water. To remove any bromine halides, you simply distill the bromine over KBr. Alternatively, you can agitate the bromine with alkaline KBr solution, decant, and then separatory funnel dry it with sulfuric.

 

[Lino1406]

In the beginning of that thread
someone was planning to use bromide
which can be reused (instead of chloride)...

 

[The Refiner49er]

Hi Lou!

I would like your recommendation on where to get sodium bromide. The company I got a quote from has a large minimum order, and the material must be shipped from Texas. 12 lbs sounds way better than 200 lbs at this point in time!

Thanks!

John
AKA TheRefiner49er
(previously "honemaster")

 

[DNIndustry]

Bromine is nasty stuff. It does complex to the Br-3 ion. Just like Iodine
In the present of an alkaliearth metal like Na or K
NaBr/Br2-> Na+ Br- Br-3