# sodium thiosulphate And hypochloride leaching



## labalkeny (Oct 15, 2016)

Hi all.
i am new to the forum, and dont seem to find any info on thipsulphate leaching / hypochloride leaching of a sulphide gold ore.
could someone point me in the correct direction!
i need to choose one of 2methods above based on its simplicitu.


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## g_axelsson (Oct 15, 2016)

labalkeny said:


> a sulphate gold ore.


I can't help you with the leach, but I'm curious, I've never heard about a sulphate gold ore before. Sure it isn't a sulphide gold ore?

Göran


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## Barren Realms 007 (Oct 15, 2016)

labalkeny said:


> Hi all.
> i am new to the forum, and dont seem to find any info on thipsulphate leaching / hypochloride leaching of a sulphate gold ore.
> could someone point me in the correct direction!
> i need to choose one of 2methods above based on its simplicitu.



This thread should help you out. Read the posts by Deano.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=85&t=22668


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## labalkeny (Oct 15, 2016)

Thank u very much Goran,for that correction. i wil check the link. 
thanks


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## labalkeny (Oct 15, 2016)

Barren R, am checking out the thread! big up(thanks)


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## labalkeny (Oct 19, 2016)

Hello, this place is surely a sea of vital chemistry information. I managed to go through threads given, but would still need asistance with the following.
1-i bought a 500g sodium thiosulphate marked 99%, how many grams of this 99%thio do i mix in how much water, to make what concentration to be able to leach economically and succesfully?
what is the recomended concentration of thiosulphate needed to do leaching?

2-rapid fixer(photo fixing ammonium thiosulphate) ,how much water is mixed to have it do gold ore leaching.
Can some one throw more light on the numbers as regards concentration in thio leach, together with time taken for the process to completely leach .
I thank u all.
labalkeny


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## Barren Realms 007 (Oct 19, 2016)

labalkeny said:


> Hello, this place is surely a sea of vital chemistry information. I managed to go through threads given, but would still need asistance with the following.
> 1-i bought a 500g sodium thiosulphate marked 99%, how many grams of this 99%thio do i mix in how much water, to make what concentration to be able to leach economically and succesfully?
> what is the recomended concentration of thiosulphate needed to do leaching?
> 
> ...



The thread I listed a couple of posts above this one gives all of that information. All you have to do is read closely and put the information together.


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## labalkeny (Oct 19, 2016)

"My preference is for pH 7, 200 grams per litre plain salt, calcium hypochlorite starting at 1 gram per litre.
The lower you can keep the hypochlorite levels the less attack on metals apart from gold.
This also makes a good silver leach if the solution is circulated through a cannister of activated carbon so that the silver level in solution is always kept low.
The silver will load on the carbon to the point where it can actually be burnished, similarly to gold.
Recover the precious metals by ashing "
This i picked.from Deano's explanation of chlorine leach method.
May U direct me to information showing me details about thiosulphate leach like the.one above for chlorine leach.
what thiosulphate concentration in moles per liter is recomended for the thio leach?
awaiting a responce.
Labalkeny


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## labalkeny (Oct 19, 2016)

Barren R thanks,.but it looks like i there only is a detailled info on the chlorine leach, like theone written by Deano.
I cant seem to find a page stating the concentration of the thiosulphate needed to leach may u pliz quote one!
Bigup.


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## Barren Realms 007 (Oct 19, 2016)

labalkeny said:


> Barren R thanks,.but it looks like i there only is a detailled info on the chlorine leach, like theone written by Deano.
> I cant seem to find a page stating the concentration of the thiosulphate needed to leach may u pliz quote one!
> Bigup.



I was thinking it was in that thread but I didn't find it. That thread has been condensed from it's original version but I don't think that information was left out of the original thread.

Do a search on Deano's posts and see what you can find out. I'm pretty sure he has a written more on the subject you are asking about.

http://goldrefiningforum.com/phpBB3/search.php?author_id=40539&sr=posts


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## Deano (Oct 19, 2016)

Thiosulfate leaching is not a preferred method for several reasons.

The leach solutions are generally in the range 5 to 30 grams per litre ammonium thiosulfate, around 7 grams per litre blue copper sulfate with ammonium hydroxide added to pH 9.5 to 10.

This is a fairly narrow pH slot in which to operate.

This is a relatively expensive leach solution which will consume high levels of thiosulfate during leaching.

The gold/silver thiosulfate complexes load very poorly onto carbon and resin.

Recovery is by precipitation onto either zinc, copper or iron filings.

No de-aeration is required prior to the precipitation step.

The recovered precious metals will always contain copper from the leach solution which is co-precipitated with the precious metals.

The major problems with commercial use apart from cost are the ammonia fumes and corrosion of any steel in the plant.

The leach system has been heavily researched over the years, best of luck in finding a better way to run it.


Deano


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## labalkeny (Oct 21, 2016)

Very vital info,thanks Deano.
1-what about precipitating the gold ans silver using sodium sulfide, and regenerating the thiosulphate to reuse in the leaching process.
2-how much time does it take the thiosulphate to leach an ore?
3-is there away to go around a ph meter? i dont seen to see one around !
labalkeny


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## anachronism (Oct 21, 2016)

I may be incorrect however I think what Deano was trying to say politely was "reasons not to use it." 

From your reply you seem to have discounted the parts of the post that you didn't want to hear. Why ask for advice if you're not prepared to listen to the advice given?

Edit for three words missing.


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## nickvc (Oct 22, 2016)

I will echo anachronisms last post, if Deano advises for or against a process listen very carefully he really is the expert at this type of processing.


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## labalkeny (Oct 25, 2016)

No,no,no. gentle men, i do not dispute anachronism,ruther iam.saying, can sodium sulfite drop both gold and silver so the leachant can be regenersted for reuse!
look at my situation, plenty of ore, extremly complicated hypochloride process , cynide is highly restricted not even seen anyway.
only option left is probably thio.
if sodium sulfite generates leach and drops Ag& Au, under what consitions some texts say under acidic thio conditions & others say just drops. how does one proceed from here?
I am an rf(radio frehency) technician , not a chemist. just suggested so we can share and if am wrong be corrected!
if it were u (by u i mean every person who cares) what would be the best method to employ?
thnks


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## goldsilverpro (Oct 25, 2016)

http://goldrefiningforum.com/phpBB3/search.php?keywords=thiosulfate&terms=all&author=deano&sc=1&sf=all&sr=posts&sk=t&sd=d&st=0&ch=300&t=0&submit=Search


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## Deano (Oct 25, 2016)

Gold can be precipitated from a thiosulfate leach at slightly acid pH by many precipitants.

Why does the mining industry not use this form of recovery ?

The chemical costs associated with the pH shifts, you have to both lower and then raise the pH back into the leaching slot make it totally not viable.

You also have the problem of the copper precipitating out and thus needing to be redissolved with the ammonia.

This redissolving only occurs in the presence of aqueous ammonia so you now have to cope with the high level of ammonia fumes.

Recovery from this type of leach has always been by metal displacement with no pH shift and even this method has too many costs , filtration being the major one, for commercial practice.


Deano


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## Deano (Oct 25, 2016)

If you are looking to run a commercial leach plant you really have only two options.

One is to use a chloride leach, the other is to use a cyanide leach.

The pH 7 saline hypochlorite leach will work well but it will attack any metal parts of the plant it comes in contact with.

It can be run as CIL or as a vat leach with separate carbon canister.

This leach type is difficult to use with an ore having appreciable levels of sulfides. These sulfides will consume hypochlorite and lower the pH, this means needing more care with process control.

Especially if run as a vat leach it is a commercial contender for leaching of ores, depending on the ore.

For cyanide leaches you have two options, you can use commercial sodium or calcium cyanide at pH11 in CIL or vat leach.

Recovery is by carbon or, after filtration, zincing.

The second option is to use potassium ferrocyanide to generate potassium cyanide.

The only reason you use this method is that the potassium ferrocyanide has virtually no restrictions on transport or storage.

The conditions for use are virtually the same as for sodium cyanide, the only qualifier is that the formation of the cyanide complex is catalysed by UV and thus either sunlight or UV lights at night are required.


Deano


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## labalkeny (Oct 26, 2016)

Goldsilver pro and Deano thanks alot i appreciate the positive effort !
Let me get down to those links and check them out . Also the chlorine /hypochloride method i shal check once again.
thanks


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## labalkeny (Oct 27, 2016)

goldsilver pro i have gone through the links and i think like Deano sugested, chloride leaching looks good.
With the battle lines drown,lets begin!
Deano, within the hypochlorous acid leach 'zone', confirm;
1- a 200litre air tight highdensity plastic tank can be openned for regular ph checks.
2- silt fine ore/ concentrate particle size is no problem with leac.
Now the survivalist way, stuck kilometers away in gold desert with a dead ph meter. how can a litmus paper with all its colour chart coresponding to ph 1 to 14 be used to save the leach thats already in water?


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## labalkeny (Oct 27, 2016)

Aquiring the ideal concentration from calcium hypochloride 90% available chlorine, do we use the molecular mass ? 
what if we had sodium hypochloride 75% available chlorine?
how do we get the concentration required from the 2 species of different hypochloride concentrations?
Activated carbon.
i already said it before, this is a battle and we are out gunned! the survivalist way, i happen to cook my meals using a charcoal, in a charcoal stove. And Deano says, activated carbon is what he recpmends for recovery. my charcoal and acticated carbon are all carbon.
can i add the hot charcoal to the leach, just afew minutes into the leach proces?
thanks 
oh, by the way i am already on my way to gold desert.
5 buckets of hypochloride are in the car. no activated carbon, in uganda its restricted i think. not seen just like cynide and ph meter that can only be got at the main referal hospital.And they wont lend me one!


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## Deano (Oct 27, 2016)

Hypochlorite leaching at pH 7 evolves very little chlorine, if run outdoors there is no need to seal the leach vessel.

As in all leaching you have to get movement of the liquor through the particles of ore.

This can be done by agitating the pulp physically or by moving the liquor through the pulp solids as in a vat leach.

Any metal coming into contact with the leach will be attacked so you are looking to have all wetted surfaces made of plastic, this includes any pump internals.

Usually in a vat leach you would have a peristaltic pump with plastic hosing pumping through a plastic canister containing activated carbon.

If using mechanical agitation either a recirculating peristaltic pump with a carbon screen or air agitation is used, carbon rates are around 5 grams per litre in an agitated system or around 10 times the carbon volume as clean liquor in a vat system.

This means that if you had 1 litre of carbon in a canister you could pump 10 litres of liquor per hour through this carbon, this is scaleable.

Silt and other fines present no problem with this type of leach.

Concentrate particle size can present a problem if the particles encapsulate the gold, if the leach cannot contact the gold it cannot leach it.

Always keep in mind that if you have sulfides present in the ore you have to keep a close eye on the leach pH.

Litmus papers will work as well as a pH meter for this type of leach.

If using a pH meter keep in mind that the reading will be depressed by about 1 unit by the salt, so if the meter is reading pH 7 the actual pH is 8.

If using a meter you usually run the leach at a reading of pH 6 - 7, this gives an actual leach pH of 7 - 8.

pH 8 is about the top end of your leaching range.

Hypochlorite is usually added dry as calcium hypochlorite unless there are sulfides present where the formation of gypsum in quantity would present a problem.

Liquid sodium hypochlorite contains much higher proportional quantities of caustic than dry calcium hypochlorite, so is not commercially used because of the extra acid required to get the pH back into range.

If you do not have a high consumer of hypochlorite in the ore then you just add around 5 grams per litre of dry calcium hypochlorite to start the leach.

If you do have a high consumer of hypochlorite present you would start around 10 grams per litre and keep a closer eye on the pH.

The obvious consumers of hypochlorite are sulfides and organics. The pH shift from organics is much less than from sulfides.

The level of hypochlorite in the leach is usually monitored with an Eh meter, this is usually a single meter with separate probes for pH and Eh.

Start with your known level of hypochlorite in the leach at ph 7 and take the Eh reading, this is around the value you want to have.

If you do not have an Eh meter you can approximate the level by smell, the level of free chlorine is very small and presents little danger if sniffed carefully.

This is not a recommended method but is used in emergencies.

Usually the pH and Eh move together over extended periods of time.

In the short term a drop in pH will lead to the evolution of free chlorine to the point where the Eh is very high.

While this chlorine is being evolved the Eh will be very high but as the available chlorine level is depleted the Eh will drop substantially to the level where gold in solution levels cannot be maintained.

Sodium hypochlorite is sold by weight percent, do the maths to get the equivalent grams needed.

Sodium hypochlorite degrades fairly rapidly in storage, unless the supplier moves a lot of well rotated stock you may not get what you expect.

Generally charcoal will have some gold adsorption properties, it will not be anywhere as good as specialised activated carbon.

It also has the unfortunate property of being brittle and will attrition readily.

As the gold is actually reduced to metal on the outer surface of the carbon any attrition losses of carbon result in the higher than expected losses of gold.

If you do have to use charcoal make sure that you pre-attrition it before use to lessen the losses.

Deano


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## labalkeny (Oct 29, 2016)

Deano thanks a big deal!
i shall be doing my first extraction process late next week God willing.
I surely appreciate the support man!
labalkeny


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## labalkeny (Dec 15, 2016)

Hello. Deano or any other person who can be of help.
I got this concern.
1_ for a highly sulpfide ore, when leaching with calcium hypochlorite and salt at Ph 7or 8, isn't gold and silver dropped due to the formation of sulphates?
2_ uniodized salt is not seen on the market .how can iodized salt be used for this leach?
I thank you all.
labalkeny.


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## labalkeny (Dec 15, 2016)

Regarding the loss of values due to formation of sulphates,
is there anything one can do to avoid such a loss if any?
If iodized salt can't be used, what else would replace salt and how can one tell that all the gold and silver has been leached with the hypochlorite Leach system?
can one tell the leach has reached its peak?


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## Goldcat (Mar 4, 2017)

Hey ya'll here's a good pdf. article on thiosulfate vs. cyanide leaching studies. :arrow: https://www.doria.fi/bitstream/hand...e Leaching for Gold Production.pdf?sequence=2

Hope this contributes!


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## labalkeny (Mar 11, 2017)

thanks a lot gold cat, for those links. very useful indeed. 
Labalkeny


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## Goldcat (Mar 12, 2017)

No problem. Let me know how your thio leaching goes. I been trying it on river concentrates to extract micron gold. So far, acid-chlorox works much better.


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