Iodine leach

[kurtak]

Come on in Kurt the water is fine...[emoji23][emoji1787][emoji16]

Sent from my SM-G950U using Tapatalk

:lol: :lol: :lol:

Thanks for the encouragement - but the problem is not jumping in to give it a go - the problem is not having material to jump in on

When I made my move I brought a trailer load of higher grade material with me & last year I went through the trailer & pulled out the vast majority of the plated stuff & processed it - got 52 grams out of that run - if I dug "deep" back into the trailer I "might" come up with another pound of plated material - just not worth chasing for a gram or two

Where I now live there just is not a lot of material available because grant county (which is like the 4th or 5th largest county in Oregon) only has about 7,500 people in the county (there is only one stop light in the whole county) so finding scrap is hard to even find - the county is like 70 - 80 % national forest

I do have like 60 - 70 pounds IC chip I hope to process this year but that's an incinerate/smelt process

As well I have a few hundred pounds of HIGH chip pop boards - but again - those are an incinerate/smelt process

Also have a few hundred pound of some "good" silver recovery stuff (contact points)

Just don't really have any (or much) gold plated to play with - or I would certainly jump in to play :mrgreen:

That all said - I sure am enjoying watching you all play :G :mrgreen:

Kurt

 

[patnor1011]

I wonder (and will try this) if this is not a way to get silver out of keyboard mylar sheets. I have saved up about 15 kilogram of them. Seems like a next project but I will have to find a way to get hydroxylamine

 

[patnor1011]

Pat
I believe the crust is precipitated/crystallized base metal salts and the reduced efficiency of the leach are caused by increasing amount of base metals in the solution.

That is what I thought so that is why I think that I will remove iodine and start fresh after every use, or every other one.

 

[philddreamer]

I finally had some time today and melted a .2g buttom... … I think I dissolved more base metals than gold. So, I've been doing some reading and I found this:
https://www.sciencedirect.com/science/article/abs/pii/0304386X9190029L
which reads:

Several oxidants (hypochlorite, iodine and hydrogen peroxide) were used to evaluate the dissolution of gold in iodide electrolytes at ambient temperatures. Evans diagrams constructed for the two half cells involved in the dissolution process show that hydrogen peroxide is not a suitable oxidant for the iodide system.
The gold dissolution rate in an iodine-iodide mixture is dependent upon the concentration of iodide, iodine and the solution pH. An optimum iodine-iodide mole ratio of 0.35–0.4 was found for 0.1 M KI solutions, with pH ranging from 2.7 to 11.5; these are capable of dissolving gold at a maximum rate of 17 mg/cm2h.
If a small addition of hypochlorite is made (< mM for 0.1 M KI solutions), gold will be dissolved faster than with iodine as oxidant. However, the gold dissolution rate in a hypochlorite-iodide mixture is strongly dependent upon the solution pH. The optimum hypochlorite-iodide mole ratio is 0.25 for KI solutions of 0.02 to 0.1 M at pH 2.7.
Cyanidation, using the same concentration of cyanide yielded gold dissolution rates within the range of 1.3 (at pH 12.5) and 3.5 mg/cm2h (at pH 8.5).

I'll make another batch and check the pH, and maybe bring it to pH6 (or higher) if need be!?
Maybe then, it will dissolve more gold and less base metals!?
Just wondering... :|

Thank you!
Phil

 

[patnor1011]

Key here may be in using uniform stock. Like if the material is the same it is easy to observe when gold is dissolved and material can be removed before any significant amount of base metals start dissolving. Also agitation. When I did it I used smaller amount of material going up and down in solution. THat way it was all exposed more or less equally.
I would love to try like 5l of solution in a RVEC. :mrgreen:

 

[philddreamer]

patnor wrote:

Key here may be in using uniform stock.

I just started doing that last night... while looking for more material to process, I came across 11 pounds of the same material, so I've been sorting it, and prioritizing... which one will be processed first and so on!
I still would like to know, though, that if by adding some lye and bringing up the pH, if that would help keep base metals from dissolving too readily... :|

phil

 

[patnor1011]

Don't know Phil all we can do is to try
I picked up 50 laptops so when I tear them apart I will have some more material to experiment with.

 

[philddreamer]

Well, here's an update on my iodine leach process...
I made a new batch, I checked the pH = 6.7; so I added 2 pounds of low yield plated material, and it de-plated quickly; I decanted the solution and added another 2 pounds. As I swished the solution, the solution quickly became clear!!! :shock:
So... I thought, that means I de-pleated the iodine!?
So I added some 12% peroxide, and the iodine color came back, BUT, that's when things went BLAHHH! :?
The solution started to foam up, so I added a bit of water, proceeded to decant the solution and add some SMB in order to drop the gold.
The gold didn't drop, but the base metals did, resembling silver chloride, (though no silver was in material). :roll:
I suspected that the gold cemented, so I inspected the left over material and it seems so.
I need to go back to the drawing board, sit down and evaluate things... :mrgreen:

Pat mentioned about the thio cell, is it this one?
https://goldrefiningforum.com/phpBB3/viewtopic.php?f=86&t=28686#p302362

phil

 

[nickvc]

Phil what you experienced is very similar to what happens if you overload a cyanide solution which is very easy with plated materials as the leach prefers copper and nickel, so you strip the gold and it cements back out as it prefers to dissolve them, weak solutions are much more selective but also more time consuming and produces much more waste solutions.
I think you are going to have to play with your solution and different ph levels to find the optimum balance, I remember talking to our much missed GSP about this and also recall him saying he made good money buying other refiners stripped material and doing the job properly

 

[philddreamer]

Nick wrote:

Phil what you experienced is very similar to what happens if you overload a cyanide solution which is very easy with plated materials as the leach prefers copper and nickel, so you strip the gold and it cements back out as it prefers to dissolve them, weak solutions are much more selective but also more time consuming and produces much more waste solutions.
I think you are going to have to play with your solution and different ph levels to find the optimum balance, I remember talking to our much missed GSP about this and also recall him saying he made good money buying other refiners stripped material and doing the job properly

Thanks, Nick!
Yes, I'm afraid I have overloaded the solution... It's obvious that we need to find a balance.
I have been thinking of diluting and/or raising the pH levels, then run some tests until we figure it.
Yeap, I miss Chris, too!

I will be trying the thiourea/citric cell soon... lets see how that works out with big batches!!!
I know, I know... "we donee no stinking baachess!" :mrgreen:

phil

 

[kurtak]

Ok - so recently I have had a couple people tell me they have "several" buckets full of black sands & asked if I could recover the "traces" of gold in the sands - these would be the traces remaining in the sands "after" other concentration methods (running the sands through a gold spinner &/or over a shaker table)

we know that even a shaker table or gold spinner does not get all the gold from black sands

So I am just wondering if iodine/iodide leaching the black sands would work to recover the traces of gold in the black sands ?

Hopefully Deano can chime in on any pros/cons

out the gate I can likely get my hands on 10 - 15 buckets full & if it's a viable leach method I can likely get who knows how much more - being as where I live it's just a matter of putting the word out to get more

Kurt

 

[Deano]

Most gold in black sands is present as free gold particles, it is rare for any quantity of gold to be locked up in the sands themselves.

As most of the black sands cons have been recovered by sluicing you are looking to gravity recover the gold by a system which is at least as efficient as a sluice system.

Most, if not all, of this free gold can be recovered by use of a table, provided the feed has been properly sized and the table is operated correctly, I had a section on tabling on my earlier thread.

The amount of gold which is not recovered by a properly run table is small enough that it is only viable to use cyanide as a leach system to recover this gold.

You can certainly recover any fine residual gold from table tailings with most gold leaches but it usually is not viable to do so due to the cost of running these leaches.

Most acid based or high redox leaches will also have a lot of the leach components lost in the digestion of the iron sands themselves, so you are looking at low redox or neutral to alkaline based systems to minimise reagent consumption.

My first approach would be to set up a properly made Wilfley type table and run feed which has been well sized, it is impossible to recover all < 50 micron gold from a coarse feed which has a higher inertial component.

Deano

 

[DNIndustry]

I2 leach can also be used with organic solvents, including DBC.

The gold is recovered by boiling wherein the iodine sublimates, AuI3 decomposes and metallic gold left behind.

I previously did this alot both KI and NH4I.
KI is very acidic is very hungry for base metals. NH4I is nearly neutral easy virtually no base metals

1 gallon of this KI/I3 (depending on I2 concentration) can hold upto 4 ozt of Gold

Lou..
I believe that unless you use a some form of liquid cooled coiled condenser you are going to loose values. I know this for a fact. I have lost a decent amount For reference they use iodine to refine Titanium, Niobium, Halfnium, And a bunch of other metals as an Iodine gas.
Chemical Mass transport
Van Arkel Deboer process

Any apparatus ideas?

 

[DNIndustry]

The HCl or Nitric wash is to clean the Iodine after it have been dropped out of the dirty Iodide solution.
The document uses the phrase "mineral acid" so I guess HCl might be the goto solution for most of us.

I'm going to test Ammonium Iodide because then I'm not confined to buy new KI.
I will then just generate the NH4I needed by adding NH4OH and H2O2 to the I2.
That is my plan at least :wink: :mrgreen:

Look back through my old posts. You will find alot of what you will need.

 

[DNIndustry]

House hold nh4oh is not the same.
A
Has other ingredients if its the cleaner.
Tech grade NH4OH is 28 to 29%. 1 gallon will last for ever

Make sure to follow directions on lingering smell if it occurs. Add h2o2 as delineated.

I believe I used sulfuric for the regenerating. Have to look back.

Hydroxylamine hcl is on eBay.

Don't forget you can do palladium platinum and rhodium as well.

I advise against the oxalic acid drop ....nano spherical metalic gold that glazes your beaker.

You will know if you cleaned the mud well when you melt an purple or blue smoke comes out. Your losing gold if so.

 

[Lou]

Do not add ammonia (ammonium hydroxide) to elemental iodine!!

 

[Yggdrasil]

Hi Lou.
Can you please elaborate a bit more?

 

[patnor1011]

Hi Lou.
Can you please elaborate a bit more?

It will produce highly unstable explosive nitrogen triiodide. That stuff if dried can be set off with a feather.
I do not mind a bit of base metals in solution or to recover iodine after every leach and to start over. It is more labour-intensive but well offset any hazard of trying to use iodine with ammonia.
I like the peace of mind when doing my stuff and as little hazard or problems as possible. To this day I am scared to go close to concentrated sulfuric or lye and I do not plan to add iodine leach to that list so no ammonia for me. :mrgreen:

 

[Yggdrasil]

Aah I rest my case.
There was no such mention in the patent document.
Can this be counteracted by adding peroxide first or using a lower concentration ammoniun hydroxide?

 

[DNIndustry]

The patent doesn't give the warning Lou does.
It expects you to follow the directions explicitly. If you follow them it works wonderfully.
Remember your reading a patent. Pretty sure the patent office reviews and checks the claims very carefully.
They are not going to publish what not to do
Ammonium iodide it self is not flammable.