process for thiourea and thiosulphate leaching

[gurudatta]

i am using sodium cyanide for gold leaching ,i know that it is very dangerous and harmful to envoirnment,so i want to know about other chemical which can leach gold and silver also.so i want to know how about thioleaching.

 

[Lino1406]

Thiosulphate solution with air bubbling are replacement for cyanidation

 

[gurudatta]

can you explain exact procedure and rate of dissolution of gold .
Thanks

 

[Lino1406]

Given the principles, optimization of the process is up to you.
Depends on concentration, heating, exploitation of oxygen, stirring...

 

[Wyndham]

If I might ask , since thiosulphate leaching is a relatively quick & safe leach. If it is used on blk sands concentrates, will the iron in the blk sands hamper the leaching of gold from the concentrate?
Thanks Wyndham

 

[sawmill]

Wyndham

If you roast the sand ,then grind the sand in a ball mill,
or rod mill with citric acid,it gets rid of iron and sulfides.
Rinse the sand well with water and you are good to go.
It is always a good idea to eliminate all the junk you can,
before leaching.

 

[qst42know]

I expect Iron content will have a profound effect on a thiosulfate leach.

When thiosulfate is used for dissolving silver chloride encrusted karat gold, it is then cemented with steel wool.

I would assume nothing will go into solution until all the iron is gone.

 

[Lino1406]

will interfere, except for contamination?

 

[butcher]

I suspect iron with thiosulfate would form ferrous sulfate and precipitate the gold, while your trying to leach, basically not leaching the gold into solution (at least to any extent).

qst42know is this your thought?

 

[sawmill]

I think you guys are missing some very important details.
The first one is that Thiosulfate is a very selective leach.
You have to work at it to make it take iron into solution,as
it will ignore iron if used right. Any loss due to iron is due
to operator error,and excessive leach times.

Excessive copper is the worst for preg robbing the solution.
That can even be dealt with too.

 

[butcher]

Thank you, sawmill,
I really did not know for sure, I have never used the thiosulfate leach, that is why I said I suspect, it was just based on an assumption, of how easily iron forms sulfates. That is what I get for assuming.

This crow ain't that bad mmm kinda tastes like an old chicken.

 

[sawmill]

Butcher
No problem,I use Thio for leaching ore,and black sand.
Once you understand it,the thiosulfate is a fantastic leach.

 

[Platdigger]

It is refreshing to have some one with a working knowledge of thiosufate on here... 8)
Thank you for sharing Sawmill.

 

[sawmill]

Thanks Platdigger

I wish I knew a lot more. This Thio thing has became a quest
of sorts. I have been working on the process for awhile. It is
amazing how such a small amount of chemicals can work so fast,
and made to work,for the job at hand.

 

[qst42know]

I suspect iron with thiosulfate would form ferrous sulfate and precipitate the gold, while your trying to leach, basically not leaching the gold into solution (at least to any extent).

qst42know is this your thought?

Sorry for the long delay Butcher, I'm having computer problems and borrowing time on another.

Though I can't explain the chemistry involved, iron drops both silver and gold from a thiosulfate solution with a potent sulfurous rotten egg odor. Isn't hydrogen sulfide a strong precipitant, or is my memory playing tricks again? If that is the case PH may be the key.

 

[sawmill]

Sodium sulfide,and ferrous sulfate will both precipitate
gold from solution. I run high iron content ore with Thiosulfate.
The only time there is ever a smell of rotten eggs is after the
addition of sulfide as the reductant. Even then if you haven't
dropped the PH to 8 ,the precipitation will be real slow and in
very fine particles.

The only smell present during the leach time is ammonia. PH
has every thing to do with using thiosulfate.
If you let your leach run too long,and let the PH drop too much
during run time ,it will then pull in some iron. Run time,PH,and
temperature are the keys to using thiosulfate.

P.S. All of my observations are with sodium thiosulfate.
Ammonium thiosulfate will react differently,with different ores.
Although the ammonium thiosulfate leaches faster,it is not as
stable to work with.

 

[gurudatta]

hi ,sawmill
i am using cyanide leaching process,thisulphate has better dissolurion rate to agcl,but what about the gold?it takes so much time to dissolve,please guide me.

 

[sawmill]

gurudatta

What are you trying to leach? Is it an ore,black sands,
or scrap? Some more information about your project and
the thio process you have tried would help a lot.

 

[gurudatta]

Respected sir ,
I dont know about thioleach but I tried it as a fixer for agcl dissolution.Recently I am doing cyanide leaching for dust comes from jewellery refining.I treat it first by aqua regia than i treat it by sodiumcyanide.Sir, can you explain me details of thioleach,because cyanide is very dengerous to health.

 

[nickvc]

Respected sir ,
I treat it first by aqua regia than i treat it by sodiumcyanide.Sir, can you explain me details of thioleach,because cyanide is very dengerous to health.

Thats an understatement mixing cyanide with any acid containing powder is as dangerous as it gets.
I doubt very much you have removed all the AR when you then add cyanide to the mix, I hope you have excellent extraction and even better fume scrubbing in place......