Thiosulphate Dropped--Testing for PM?

[renatomerino]

Blast! It loaded my post without letting me do the rest of the pictures. I'm probably doing something wrong, but I'll try again. These will be in order, but it's possible the uploading tool could show them reversed. You want to start viewing from the point the tank/leach is clear.

Looks like I can only do 5 at a time, so I'll put the rest in another post.

Hi Ferrell:
Like this is your tests with thiosulfate?.
I have some doubts with your annotations as the composition of the leaching solution you buy, the concentrations of different salts per liter, the consumption of reagents per ton, leaching time and rate of dissolution.
I tested for leaching of gold and I would like to exchange data on the subject.

 

[Ferrell]

Hi Everybody!

Great respect and thanks to everybody here on this site! I think that the results shown in the photos say alot. I was also perplexed about the gold depositing semi-reduced at the positive electrode. But it's an interesting discovery, one must admit. I think it's not all that hard to try. Proof is always in the pudding!
I am very interested in seeing the developing results in this process. Soon I will be going off to an African country to work dissolving and refining gold for my friends in a Russian company. They were not at all pleased with their own experiments with mercury and want a more effective and safe technology. It looks like blue/grey clay, so I'm afraid of preg robbing. Looks like this thiosulfate process is the way to go for me.
Thank you very much for all that you have already shared in this thread, Mrs. Ferrell and Dr. Poe!

Best Regards,
Paul

Paul, we're still in the experimenting stage, ourselves, but do feel that we're making progress. We don't like the more dangerous chemicals and want to use thiosulfate to recover the majority of our gold and silver. We're looking at possibly purchasing an electrowinning machine rather than continuing to try to make a homemade job work effectively, as we're still working out the kinks in that process. But the steel wool in the leach did show us that we have a substantial amt of gold that can be recovered.

I don't blame the people in Africa. Mercury can be nasty to work with and I'd be urging them to get away from it if possible, as well. I'll definitely update this forum when we have more to report.

 

[Ferrell]

Blast! It loaded my post without letting me do the rest of the pictures. I'm probably doing something wrong, but I'll try again. These will be in order, but it's possible the uploading tool could show them reversed. You want to start viewing from the point the tank/leach is clear.

Looks like I can only do 5 at a time, so I'll put the rest in another post.

Hi Ferrell:
Like this is your tests with thiosulfate?.
I have some doubts with your annotations as the composition of the leaching solution you buy, the concentrations of different salts per liter, the consumption of reagents per ton, leaching time and rate of dissolution.
I tested for leaching of gold and I would like to exchange data on the subject.

You have doubts on which aspect? We're still in the experimental stage and still figuring it all out, so can't promise I'll have answers for you.

 

[renatomerino]

Hello friends:
I have closely followed the comments on the leaching with thiosulphate to use it in auriferous minerals but have not got any particular value.
I have the impression that the tests have been performed only with metals.
Currently silver ores leached by agitation and electrowinning and welcome, I can guide on the subject because I have work values.
In messages sent on leaching with thiosulfate have read only vague comments that can be learned from any book or paper patent.
I personally will try to establish the most suitable composition for leaching gold-bearing ores and carries out the relevant tests and share experiences with you.
In the sites mentioned can be obtained theoretical fundamentals of the leaching with thiosulphate now lack the practical development.
(Translation of Spanish with google)

 

[renatomerino]

Ahh sorry:
At the mention of any metallurgical testing on the most important thing is to present a metallurgical balance and has not submitted comments on the subject.
Unless the dosage of reagents from there my doubts.

 

[patnor1011]

Renato, that may be it. You cant find many ore leaching topics here as forum main aim is about PM recovery from electronics or karat gold.

 

[renatomerino]

Renato, that may be it. You cant find many ore leaching topics here as forum main aim is about PM recovery from electronics or karat gold.

Among the topics of conversation developed in this forum and samples in which we share experiences and views this: Prospecting, Mining, Ore Concentrates & Geochemical and others.
This gives an idea about the variety of topics in this forum and is the reason that unites us all.

 

[patnor1011]

I only suggest that what is not here, may be found on some mining forum or site. This area of recovery is not that much pursued on this particular forum.

 

[butcher]

Many old mining books are great resources of information.
But I do not know how much they will discuss thiosulfate as a leach, I believe it is a more modern leach to try and find an alternative for cyanide, but the chemistry of photography has been studied for many centuries now, I am not sure how long they have used thiosulfate in their art, but it should be a great resource for your study of this. I would look into the chemistry of photography as well as mining, most of it will most likely speak of silver and thiosulfate, but gold has also had its use in photography.

Renatomerino,
I would be interested in what you learn from your search on this topic.
If someone has a strong interest in a subject, and works hard to find the answer to his questions, and He does not give up on his search for the answer, he will learn the answer to his question, this will usually lead to more questions and more answers, just do not give up looking.

 

[renatomerino]

Many old mining books are great resources of information.
But I do not know how much they will discuss thiosulfate as a leach, I believe it is a more modern leach to try and find an alternative for cyanide, but the chemistry of photography has been studied for many centuries now, I am not sure how long they have used thiosulfate in their art, but it should be a great resource for your study of this. I would look into the chemistry of photography as well as mining, most of it will most likely speak of silver and thiosulfate, but gold has also had its use in photography.

Renatomerino,
I would be interested in what you learn from your search on this topic.
If someone has a strong interest in a subject, and works hard to find the answer to his questions, and He does not give up on his search for the answer, he will learn the answer to his question, this will usually lead to more questions and more answers, just do not give up looking.

You're right, I have thirty years experience in mineral flotation and leaching of gold and silver cyanide.
The change of cyanide to thiosulfate is very interesting and this requires a specialization similar to cyanide where you can understand all the chemical mechanisms of the process.
The first provides some background on the use of thiosulfate is photography.
According to this, first of all I've bought liquid fixative and silver chloride dissolved to 24 g / l.
But all photographic liquids are sold with a denomination without informing their composition.
A typical formulation is:
250 g / l ammonium thiosulfate.
25 g / l sodium sulphite
The presence of sodium sulphite prevents the decomposition of thiosulfate to sulfate.
The formation of thiosulfate is by replacing an atom of oxygen by sulfur in a sulfate ion.
In the process of photography there is a change of silver ionized species therefore does not require a metal oxidation.
In the case of minerals auriferous this generally occurs in metallic state in an infinite number of sizes.
In the oxidation of gold is used as Cu +2 amide as catalyst in the absence of oxygen.
Oxygen degrades to thiosulfate.

 

[renatomerino]

Many old mining books are great resources of information.
But I do not know how much they will discuss thiosulfate as a leach, I believe it is a more modern leach to try and find an alternative for cyanide, but the chemistry of photography has been studied for many centuries now, I am not sure how long they have used thiosulfate in their art, but it should be a great resource for your study of this. I would look into the chemistry of photography as well as mining, most of it will most likely speak of silver and thiosulfate, but gold has also had its use in photography.

Renatomerino,
I would be interested in what you learn from your search on this topic.
If someone has a strong interest in a subject, and works hard to find the answer to his questions, and He does not give up on his search for the answer, he will learn the answer to his question, this will usually lead to more questions and more answers, just do not give up looking.

You're right, I have thirty years experience in mineral flotation and leaching of gold and silver cyanide.
The change of cyanide to thiosulfate is very interesting and this requires a specialization similar to cyanide where you can understand all the chemical mechanisms of the process.
The first provides some background on the use of thiosulfate is photography.
According to this, first of all I've bought liquid fixative and silver chloride dissolved to 24 g / l.
But all photographic liquids are sold with a denomination without informing their composition.
A typical formulation is:
250 g / l ammonium thiosulfate.
25 g / l sodium sulphite
The presence of sodium sulphite prevents the decomposition of thiosulfate to sulfate.
The formation of thiosulfate is by replacing an atom of oxygen by sulfur in a sulfate ion.
In the process of photography there is a change of silver ionized species therefore does not require a metal oxidation.
In the case of minerals auriferous this generally occurs in metallic state in an infinite number of sizes.
In the oxidation of gold is used as Cu +2 amide as catalyst in the absence of oxygen.
Oxygen degrades to thiosulfate.

Personally I think the study of the leaching of minerals begins performing laboratory tests with solutions and for pure metals can then continue with the minerals.
I found this site which is leached by thiosulfate, discarded cell phones to extract the gold they contain.
http://tainguyenso.vnu.edu.vn/xmlui/bitstream/handle/123456789/13130/HN_U233.pdf?sequence=1

According to this reference I have prepared the following solution:
125 g / l Sodium thiosulfate + 5H2O
12 g / l Sodium Meta Bisulfite
20 cc / l Ammonia (25%)
7.5 g / L Copper as sulphate +5 H2O
pH 5.5 aprx.

In the first solutions with sodium thiosulfate and copper sulfate or silver chloride sulfide was formed of these metals.
Probably under certain conditions in a solution of sodium thiosulfate ion is produced sulfide and sulfides of these metals such conditions might be pH or ORP (redox potential).
In this solution is not precipitated copper sulfide and gold is dissolved obtained by precipitation with sodium metabisulfite.
The acid pH of the formulation occurs metabisulfite.
I the amount of ammonia added to present a similar balance of ammonium thiosulfate.
In the case of cyanide is possible to increase the speed of dissolution of gold by hydrogen peroxide but thiosulfate solutions is difficult to achieve since the conditions required for the reaction are very limited.

Example of solution of gold cyanide:

1 200cc beaker
3 g of sodium cyanide
50 cc of water
0.02 grs of gold precipitated with sodium metabisulfite

When carefully add a few drops of hydrogen peroxide of 10 v/v can see the dissolution of gold with great speed.
Thiosulfate have not yet obtained the information to increase the speed of dissolution.
Found in published papers, as noted 10 hrs dissolution times but do not indicate the size of the particles of gold.
Sorry for the translation from Spanish.

 

[renatomerino]

Hi butcher:
On this site:
http://www.ejmpep.com/rath_et.al.pdf
Is a summary that allows to prepare a solution of sodium thiosulfate using thiosulphate, ammonia and copper.
The interesting thing that gives values ​​of thiosulfate, ammonia and copper, which responds to the doubts that may have.
I prepared a solution with:

Sodium thiosulphate (Na2S2O3•5H2O)
0.4 M (S2O3)-2 >> PM Na2S2O3+5H2O=248
>> PI S2O3=112 >> % =45.16 Thiosulfate ion
0.4x112=44.8 >> 44.8/0.4516=99.2 grs Na2S2O3

Ammonia water (25%NH3)
2 M NH3 >> PM NH3 = 17
>> 17x2= 34/0.25 = 136 cc NH3

Cupric sulphate (CuSO4•5H2O)
0.0001 M Cu >> PM CuSO4+5H2O= 249.5
>> P Cu=63.6 >> % =25.49 >> 0.0001x63.6=0.00636
0.00636/0.2549=0.02495 grs CuSO4+5H2O

Water
To make 1000 cc.

This solution dissolved in 6 hours a gold precipitate obtained with metabisulphite,I hope to complete with photos.
I believe that this solution can be done dissolution testing.
Then you could continue with auriferous minerals.
I hope your comments to improve the matter.

 

[butcher]

renatomerino,

I like your approach of study and experimenting, the powders are fine, would they be about what size the gold would be in ore?

And as we know the ore will also change the chemistry of the solution, but by your experimenting with a more pure gold, and preparing a base line for the latter experiments, I feel you are taking a well-planned scientific approach to this study.

it will also be interesting if you experiment with different ore samples later with known contents of gold, maybe some of the members who have samples of ore can help you out and send you a few rocks later, when you get to that stage.

Very interesting please do keep the forum posted of your results.

I really cannot give any advice, but I am very interested in following your work in this.

Most of the papers I read about this leaching process seem to be studies (looking for alternative to cyanide), and in the lab they do seem to have good results, have you read anything of the use of this in the gold fields? And the results they are getting? Any of the bigger gold mines in my area do not use leaching as they only get the free gold with mechanical means, although there are shipments of black sands and ore going to other counties like china, I am not sure how they recovering the values there, or what type of leaching they use.

Keep up the good work.

 

[renatomerino]

butcher:
It is possible that someone could repeat the test?.
This is a test solution of gold with thiosulfate solution type.
I prepared a solution with:
20 g Na2S2O3 + 5 H2O
0.05 g CuSO4 + 5H2O
0.01 g Na4EDTA
3 cc NH3 20% + 3cc NH3 20%
200 cc Water
pH 9
To this solution I added 0.4 grams of gold precipitate obtained from a gold chloride solution with sodium citrate.
The precipitate of gold I have screening through 325 mesh before placing in the solution of thiosulfate.
In 48 hours it has dissolved about 0.3 g.
The amounts of reagents are very high and I think it is possible to download all concentrations proportionately.
The leaching operation that I do use concentrations of 30 g/L of NaCN equivalent to 60 g / L of Na2S2O3 + 5H2O.
I added 2 times NH3 because I have a atmospheric pressure of 490 mmHg.
Surely the time it takes to dissolve gold is due to the particle size which is about 0.04mm.
The test is being performed in an open beaker without agitation.

 

[butcher]

I do not see air or oxygen involved are you bubbling air into solution?, I really do not know much about the leach, but I thought oxygen played a role.

What is the purpose of Na4EDTA?

from what I understand the leach is normally slow, but I thought they got 90-95% gold dissolution in ore, being you do not have the ore involved to effect or change the chemistry of the solution, your leach values seem a bit low (about 75% of gold leached).

Renatomerino,

I really do not know if I can help with this, but I do wish you to keep us informed on your progress, it is fascinating, and the experimentation you are working on would be an invaluable tool for anyone working with this leach.

A thought and I do not know if is worth anything:

This Thiosulfate leach is dependent on the copper sulfate acting as a catalyst as far as I understand and the ammonia in solution regenerates for lack of better term the thiosulfate, and forms alkaline copper ammines for catalyst for gold dissolution, (again if I understand).
Can you tell by color of solution what the copper is doing? Copper thiosulfate, copper ammines, or what ever, is this masked by gold or other solutions?

Sorry I can not be any help, I would have to learn much more first.

keep up the good work.

 

[renatomerino]

butcher
Your comments are important as well as other forum members which enriquese us all.
You can use oxygen in the leaching with thiosulfate but for this via the decomposition of this reagent is important to producing sulfate.
I think the gold solution is favored in an ammoniacal medium intermediate form after gold thiosulfate.
The oxidation of gold is achieved that through Cu +2 dissolved in ammoniacal medium is reduced to Cu +1 and gold is oxidized to Au +1 Au probably.
The Na4EDTA is a scavenger of copper to prevent the decomposition of thiosulfate.
The dissolution of gold with thiosulfate is faster than cyanide and lack a test of leaching with agitation.
Dr. Poe said in a recent message that it is possible to form thiosulfate, heating a solution of sodium hydroxide with sulfur.
Look for patents on the subject and prepare 500 ml of a solution with 40 g of NaOH and 28 grams of sulfur, warm to 89 ° C for one hour and filter.
Then use the same dosage above and the results are similar.
Carries out, slag leaching tests with thiosulfate in similar concentrations.
The gold in the thiosulfate solution I precipitated with fine steel wool.
I invite everyone to duplicate the tests and publish the results.

 

[AztekShine]

Renatomerino,

I am considering this process in my next experiment. Thank you for all of your input on this topic. It is much apreciated!

Will

 

[renatomerino]

Hi butcher:
I have continued leaching tests with thiosulfate to the quantities of reagents indicated and a gold concentrate of 1000 g/ton.
I noticed that with an agitation of 500 rpm evaporates or moves the ammonia with air or oxygen injected into the pulp.
I think it is important to control the pH close to 9.
In my particular case the increase of the concentration of gold in solution takes place for 2 hours then stops. This coincides with decreasing pH.
For this reason I am correcting the pH and the solution continuously.
In short my gold concentration in solution is currently 0.3 g / l for 50% pulp solids and froth flotation concentrate of 1000 g/ton.
It is likely that I can reach a solution significant considering the above.
It is likely that some experiences with thiosulfate leaching carried out in sealed agitators for this reason.

 

[butcher]

Renatomerino,
I enjoy discussing this leaching process with you, as it helps me learn, I also like the fact you report your results from your process as it helps all of us.

I have no experience with the thiosulfate leach, besides reading, and my understanding of it is very limited, although I would like to learn as much as possible about it.

Also I cannot say I understand as much as I read, as it sometimes seems they use a language I am also learning.

From looking at the equations in the document lined below, if I understand them correctly.

Gold oxidizes in this caustic solution with high volumes of air/oxygen to gold hydroxides.
Gold oxidation in the presence of ammonia, and oxygen to form gold ammine complex.

Gold oxidation in the presence of oxygen and thiosulfate to form gold thiosulfate complex’s.

Oxidation by oxygen
Au +0.25O2 + OH- + O.5 H2O --> Au(OH) 2
Au + 0.25 O2 + 2NH3 + 0.5 H20 --> Au(NH3)2 + OH-
Au + 0.25O2+ 2S2O3+ 0.5H2O --> Au(S2O3 )2 + OH-

These reactions above, I believe are only part of the reactions involved, and air injection also helps to agitate the ore and solutions, assisting in the reaction.

Copper solutions are also a big part of the reactions as the copper in ammonium solutions is the catalyst that helps to put gold into solution as a thiosulfate complex.


Notice in the reactions below, most of them ammonia evolves from leach, I believe this to be part of the process as gold forms thiosulfate complex with ore, this ammonia would need replaced for the reaction to proceed, (I do not know if it can be contained in solution)

Oxidation by copper (II)

Au + Cu(NH3)4 --> Au(NH3)2+ Cu(NH3)2
(Here both form diammine compounds)

Au + 2S2O3 + Cu(NH3)4 --> Au(S2O3)2 + Cu(NH3)2 + 2NH3
(Here gold thiosulfate forms, copper ammine and ammonia)

Au + 5S2O3+ Cu(NH3)4 --> Au(S2O3)2+ Cu(S2O3)3+ 4NH3 ********
(Gold in thiosulfate solution, copper thiosulfate and ammonia gas)


Au + 2S2O3 + Cu(OH)2 --> Au(S2O3)2+ Cu(OH)
(Notice hydroxide of copper and gold thiosulfate)

Au + 2OH- + Cu(OH)2 --> Au(OH)2+ Cu(OH)2

Au + 5S2O3+ Cu(OH)2 à Au(S2O3)2+ Cu(S2O3)3+ 2OH- *********
(Gold in solution, and copper formed thiosulfate complex and freed hydroxides)

Disproportionate of gold (I)
3Au(I)(NH3)2 --> 2Au + Au(III)(NH3)4+ 2NH3

I also believe if pH was allowed to get towards acidic gold would precipitate back int the leaching solutions.


This seems to be a very complicated leach, and keeping ammonium and copper complexes in balance would seem extremely difficult to me, If these could be monitored easily it would should help, but this leach to me looks like trying to walk on a tight rope with a big monkey on your back pulling on your hair,
Look like it would be very difficult to maintain a balance in this leach.

Equations are from this document:
http://www.springerlink.com/content/51787642774g1020/fulltext.pdf

 

[renatomerino]

Butcher:
Thanks for the article of Gold Bulletin.
According to everything we have studied, I prefer to think that the solution of gold in thiosulfate solutions using copper and ammonia is mainly due to the latter using copper as the oxidant.
The amount of ammonia used is sufficient to produce the amide of copper in addition to allowing a exedente dissolve gold.
They are interesting patents: US5308381, US5114687.
The solution of gold with ammonia requires high pressures and closed reactors to prevent volatilization.
In the case of ammonium thiosulfate solutions can better manage the gold solution with ammonia.
It seems important to your opinion and other members of the forum.