problem of extracting gold from cyanide solution

[avalanche]

hallo
I used 100g of NaCN dissolve in 15 liter of water with strong presence of oxygen in an alkaline environment PH = 12 (I dissolve 25 grams of calcium hydroxide) to dissolve 25 grams of gold (10 KG motherboard mobile phone) everything goes very well
in the phase of recovery of gold from cyanide solution I use zinc in reality this is not a very fine powder because I did not find but I scrape a zinc plate for powder in the size of sand or a little less but it gives no result
I tried electrolysis with stainless steel electrodes it gives me that rust (corrision the electrode) a note the color of the solution is a clear yellow problemme I doubt that problemme this is due to excess NaCN in solution
I dont know exactly
can you help me please
thank you

 

[Gratilla]

First, I'd suggest that you test for gold with stannous chloride. Unfortunately, we've seen too many members chasing values that don't exist. Stannous chloride is usually used for testing in acid leaches, but Hoke gives a description of testing for values in cyanide leaches. The process will give off toxic hydrogen cyanide gas, so please only use a small quantity and a fume cupboard or well-ventilated area.

Zinc cementation first requires that you extract the oxygen from your cyanide solution; this would otherwise interfere with the redox. The usual way for this is with a vacuum pump.

 

[avalanche]

how I can transform my basic solution in acid solution the addition of sulfuric acid may do the trick?
elimination of oxygen from the solution prevents the oxidation of gold rushes butt there is no precipitate despite the color of the solution changes from colorless to light yellow and I can even clear that the Gold is totally removed from the motherboard I want to know is what Présance ions CN - influences the result is that the size of dust zinc influences I have not seen in any items that need to be heated after your experiances what is the color of good gold cyanide solution
I need your help

 

[skullsbox01]

You can recovery the gold by electrowinning cell, but the ph in the solution must be > 12 and your anode and cathode must be stainless Aisi 316 or Aisi 354, otherwise the anode will be corroded by the current.

 

[jeneje]

how I can transform my basic solution in acid solution the addition of sulfuric acid may do the trick?
elimination of oxygen from the solution prevents the oxidation of gold rushes butt there is no precipitate despite the color of the solution changes from colorless to light yellow and I can even clear that the Gold is totally removed from the motherboard I want to know is what Présance ions CN - influences the result is that the size of dust zinc influences I have not seen in any items that need to be heated after your experiances what is the color of good gold cyanide solution
I need your help

I would not add any kind of acid to the solution, until you know what you are doing. I would wait to hear from GSP, or another Mod before moving on with this. You may live longer.
Ken

 

[Gratilla]

Hmmmmm, avalanche, in the short time that you've been here, you've successfully (and unwisely) shown that:

1. You haven't read Hoke (available for download at a number of places on the forum). <see Hoke page 90> and
2. You haven't done a search of the msgs/resources of the forum.

Both/either of which would've given you the answers that you seek. Fortunately, Gratilla is such a nice guy.

See thread:

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=41&t=16887 and

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=60&t=19043

 

[goldsilverpro]

I use about 3 or 4 times more cyanide, per gallon, and I use, to start, about 25ml of 30-35% hydrogen peroxide - I tumble about 20-40 pounds in 1 - 2 gallons of hot tap water in a cheap cement mixer. More peroxide (often) and, more cyanide (rarely) might later be needed. The idea is to blast the gold off fast, 2 to 3 minutes usually - 10 sometimes - before it starts to eat the copper - heat and strength. If you start off with 140F water, the peroxide can get it to where it's steaming. It always (well, almost always - very rarely you have to use a fresh solution) works and you can get all the gold you can see. On copper or on a very thin nickel barrier layer that mechanically and chemically (slowly) wears off in the tumbling, thus exposing the copper, it can take longer. The solution is only good once.

I then combined all the solutions and rinses into a 55 gallon plastic drum with the top cut out, elevated on a stand taller than the drum, to allow siphoning into another drum. Three or four hundred pounds of material, about a day's work, might generate 40 gallons of solution. I then adjusted the pH of the solution to 12-12.5 with sodium hydroxide and added an extra 10g of NaCN per gallon. I then stirred vertically, slowly up and down, with a plunger stirrer I made from a 5" diameter plastic disk on the end of a 5' length of plastic pipe. Stir continuously. While stirring, I added zinc dust in small increments though a flour sifter. At first, you will see brown gold power being brought to the surface by the stirrer. Keep stirring. After 1 or more further additions, the powder will start to turn gray. When it's all gray, with no hint of brown, stop adding. Hang 2 zinc bars, near the top of the solution, and let it settle overnight.

Next morning, I siphoned off the solution into another drum, filtered and rinsed the sludge very well with hot water, put the sludge plus paper in a plastic bucket, covered it with water, and added nitric acid in small increments until I got no more fizzing. It got hot. I prefer full strength nitric because it will dissolve silver and copper, which will usually be there. Finally, after filtering and rinsing very well, I dissolved the impure gold in aqua regia with a minimum amount of nitric, and dropped the gold with sodium sulfite.

_______________________________________________________________

The zinc you're using is a big problem. When gold deposits on the Zn surface, it packs tightly. To deposit gold, you must dissolve some zinc. Therefore, when the zinc is completely covered with gold, it stops depositing and the zinc stops dissolving. You end up with gold coated pieces of zinc. Unless you used a lot of zinc, most of the gold is still in solution. The idea is to use really finely divided zinc powder. The best is a 325 mesh product called "Zinc Dust". It has a diameter of .0017" or .043mm. It's the only fine powder I know of that doesn't contain the undesirable silica product, Cab-O-Sil, which is added to prevent clumping of the zinc.

_______________________________________________________________

What is your oxygen source?

I can't imagine that excess oxygen will cause any problem in the zincing, whether using peroxide or pumping in oxygen, at all. Any great excess that might cause problems will be consumed by its reaction with the cyanide. Hundreds of times, I have observed the total destruction of a pound of cyanide when I had to use a lot of peroxide. Also, the cyanide + oxygen will dissolve zinc, consuming both.

__________________________________________________________________

The Hoke test involves, under a fume hood, the treating of a very small amount of solution with a small amount of hydrochloric (muriatic) acid. This destroys the cyanide and the gold forms a chloride, which can be tested with stannous chloride. It only tests the presence of gold and not the amount. Sulfuric (dihydrogen sulfate) can't be used because gold can't form a sulfate, at least not under normal conditions.
EDIT:The Hoke test used copperas (ferrous sulfate) and not stannous chloride after adjusting with hydrochloric.

Does someone know the page this test is on?

 

[butcher]

Hoke's book page 90, teat for gold in alkaline or cyanide solutions.

Pay note to page 81, all cyanides are poisonous, when mixed with acids they are doubly so, the fumes are deadly...

 

[avalanche]

I Thank You all for the very interesting information
I have 3 questions to conclude my dear mr for GSP and other expert
- What is the right concentration of sodium cyanide at the beginning (your real experiance)
- What is the right color of the solution after leaching
- How you can get gold from 10kg motherboard mobile phone
thank you

 

[avalanche]

I do not use peroxide seulmenet fresh air pumping

the process was a slow is about 30 minutes but the result Were satisfactory

 

[muhammad Shahzad]

I use about 3 or 4 times more cyanide, per gallon, and I use, to start, about 25ml of 30-35% hydrogen peroxide - I tumble about 20-40 pounds in 1 - 2 gallons of hot tap water in a cheap cement mixer. More peroxide (often) and, more cyanide (rarely) might later be needed. The idea is to blast the gold off fast, 2 to 3 minutes usually - 10 sometimes - before it starts to eat the copper - heat and strength. If you start off with 140F water, the peroxide can get it to where it's steaming. It always (well, almost always - very rarely you have to use a fresh solution) works and you can get all the gold you can see. On copper or on a very thin nickel barrier layer that mechanically and chemically (slowly) wears off in the tumbling, thus exposing the copper, it can take longer. The solution is only good once.

I then combined all the solutions and rinses into a 55 gallon plastic drum with the top cut out, elevated on a stand taller than the drum, to allow siphoning into another drum. Three or four hundred pounds of material, about a day's work, might generate 40 gallons of solution. I then adjusted the pH of the solution to 12-12.5 with sodium hydroxide and added an extra 10g of NaCN per gallon. I then stirred vertically, slowly up and down, with a plunger stirrer I made from a 5" diameter plastic disk on the end of a 5' length of plastic pipe. Stir continuously. While stirring, I added zinc dust in small increments though a flour sifter. At first, you will see brown gold power being brought to the surface by the stirrer. Keep stirring. After 1 or more further additions, the powder will start to turn gray. When it's all gray, with no hint of brown, stop adding. Hang 2 zinc bars, near the top of the solution, and let it settle overnight.

Next morning, I siphoned off the solution into another drum, filtered and rinsed the sludge very well with hot water, put the sludge plus paper in a plastic bucket, covered it with water, and added nitric acid in small increments until I got no more fizzing. It got hot. I prefer full strength nitric because it will dissolve silver and copper, which will usually be there. Finally, after filtering and rinsing very well, I dissolved the impure gold in aqua regia with a minimum amount of nitric, and dropped the gold with sodium sulfite.

_______________________________________________________________

The zinc you're using is a big problem. When gold deposits on the Zn surface, it packs tightly. To deposit gold, you must dissolve some zinc. Therefore, when the zinc is completely covered with gold, it stops depositing and the zinc stops dissolving. You end up with gold coated pieces of zinc. Unless you used a lot of zinc, most of the gold is still in solution. The idea is to use really finely divided zinc powder. The best is a 325 mesh product called "Zinc Dust". It has a diameter of .0017" or .043mm. It's the only fine powder I know of that doesn't contain the undesirable silica product, Cab-O-Sil, which is added to prevent clumping of the zinc.

_______________________________________________________________

What is your oxygen source?

I can't imagine that excess oxygen will cause any problem in the zincing, whether using peroxide or pumping in oxygen, at all. Any great excess that might cause problems will be consumed by its reaction with the cyanide. Hundreds of times, I have observed the total destruction of a pound of cyanide when I had to use a lot of peroxide. Also, the cyanide + oxygen will dissolve zinc, consuming both.

__________________________________________________________________

The Hoke test involves, under a fume hood, the treating of a very small amount of solution with a small amount of hydrochloric (muriatic) acid. This destroys the cyanide and the gold forms a chloride, which can be tested with stannous chloride. It only tests the presence of gold and not the amount. Sulfuric (dihydrogen sulfate) can't be used because gold can't form a sulfate, at least not under normal conditions.
EDIT:The Hoke test used copperas (ferrous sulfate) and not stannous chloride after adjusting with hydrochloric.

Does someone know the page this test is on?

hi gsp

in your post. There is no any mention about extracting oxygen from cyanide solution. iam confused because of gritilla wrote in his post that
zinc cementation first requires extract oxygen from cyanide solution. otherwise it would interfere redox. the usual way for this is with caccum pump.
so. is it necessary to eliminating the oxygen from cyanide solution to percepitating gold or not ?
please help me.
thanks

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[4metals]

If there is an excess of Cyanide, as GSP described in his post, there is not going to be any issue with oxygen.

 

[muhammad Shahzad]

If there is an excess of Cyanide, as GSP described in his post, there is not going to be any issue with oxygen.

may u tell me the estimated value of cyanide

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[4metals]

As GSP posted above, the parts were stripped quickly and the solution was transferred into a drum so it could all be processed together. When you have the parts in the strip solution you can see visually that the gold has been stripped. The issue is while there was enough cyanide to strip the gold, you have no idea if you had an excess of cyanide.

The zinc process works best when there is an excess of cyanide, to assure an excess, as GSP stated in his post;

I then adjusted the pH of the solution to 12-12.5 with sodium hydroxide and added an extra 10g of NaCN per gallon.

 

[muhammad Shahzad]

As GSP posted above, the parts were stripped quickly and the solution was transferred into a drum so it could all be processed together. When you have the parts in the strip solution you can see visually that the gold has been stripped. The issue is while there was enough cyanide to strip the gold, you have no idea if you had an excess of cyanide.

The zinc process works best when there is an excess of cyanide, to assure an excess, as GSP stated in his post;

I then adjusted the pH of the solution to 12-12.5 with sodium hydroxide and added an extra 10g of NaCN per gallon.

thanks a lot for your post.
you explain extra quantity of cyanide. Now let's talk about main quantity of synide by which gold strips from gold plated item. gsp wrote above ( I use about 3 or 4 times more cyanide, per gallon, and I use, to start about 25 ml of 30-35% hydrogen proxide-i tumble about 20-40 pounds in 1-2 gallons of hot tap water in a cheap cement mixer )
so one gallon equal 3.785 liter.
3.785 ×3 =11.355 syanide
it's too much out from limit. then what is the Wright volume
and how calculate

thanks




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..

 

[nickvc]

With the use of cyanide like many processes it’s a balancing act, too much cyanide and it will strip base metals as well as gold or silver, a weak solution is much more selective but you need bigger volumes or be able to strip the solution as you work so it keeps dissolving your values, if you overload your solution with values it will plate back out onto the base metals as I learnt :shock: :evil:

 

[anachronism]

Weak + minimal oxidant = more selective + slower
Strong + lots of oxidant = less selective + faster

Movement = increased leach speed
Raise of temperature = increased leach speed

 

[4metals]

Unfortunately in the real world application you have to play this by eye. In a perfect world, it you knew the exact weight of gold and it was all the exact same thickness, it would be a simple calculation.

But then the real world raises it's ugly head and you realize that all plating deposits vary, the edges have more thickness than the center, and pieces on edges of a rack have more thickness than pieces in the center. And that is just on a lot plated together. As refiners we get mixed lots of material plated in different shops by different bath types so there is no way it is all uniform.

If you hit copper it will consume chemistry at a different rate than if the under-plate was nickel so as different metals are exposed your chemical consumption changes.

As Jon says, week solutions are more selective, and mixing and heat are your friend. And learn to trust your eyes, keep checking to see when there is no more gold color showing.

 

[tesaygo]

You can use activated carbon to absorb gold ion from your cyanide solution. Then ash the carbon and smelt it

 

[Swissgoldrefiner]

Hello,
we recived a solution which is used in jewellery to dissolve small part of watch to get back the diamound.
It contain KCN, Au, Pd, ...pH more than 13. Solution is red/orange. It should contain around 300-400 gram of gold in 10-15 Liters.
First time we handle this material. We did on few mL some test.
So first we tryed electrolysis, with Pt anode and Ti cathode. It works and some material comes out.
However, the solution stay yellow/orange. It dosent change color even if we let the reaction run.
Addition of Zn dust, dosent give any reaction. There is no buble and no precipitate. It's maybe because of lack of free KCN.
Under fume hood, we add HCl to the solution which contain Zn. There is some buble and at some point the solution become colorless.
After letting it stand overnight, the pH go back to around 11-12, which we understand why and the color become light orange which we dont understand why.
We push the addition of HCl and Zn, until there is no more buble and pH is around 2. The solution dont become colorless again. It seems some copper fine powder or gold fine powder.

Off curse, we have some precipitate. So, we were thinking about this ways to hanlde this:
1. Take out most of metal with electrolysis and then wash the solution with activated carcoal to get everything. (we didnt try the carcoal yet)
2. Build a fume scrubber which contain NaOH or bleach and acidify the solution and heat it to get ride of the HCN. Then add Zn dust. But it seems we need to finish it with carcoal as well.

Any suggestion?