# Thiosulfate leach



## kjavanb123 (Apr 4, 2013)

All,

I did the search on thio leach and read all 304 results, but in none of them there is an explanation of how it is done on e-scrap. Is it possible members with more knowledge on this matter to post here to discuss this method of leach in details, like thio solution concentration?

Thanks
Kevin


----------



## kjavanb123 (Apr 7, 2013)

All,

I found what it seems to be a treasure in thio leaching, please advise.

View attachment ammonium thiosulfate cupric ammonia leaching.pdf


Regards,
Kj


----------



## solar_plasma (Apr 7, 2013)

Thanks for sharing, just what I am looking for! 

I wished,I had such good information about iodine leaching!


----------



## FrugalRefiner (Apr 7, 2013)

Interesting documents Kevin. From a real quick read, it looks like you need to crush your material to nearly a powder to get acceptable recovery. Let us know how it goes.

Dave


----------



## kjavanb123 (Apr 17, 2013)

In the article it said, they got 78% recovery if they just leach the boards as they were without any crushing. Also I tried to find the grams per liter of water in the leach based on the article, please kindly advise if this is correct calculation:

0.1M ammonium thiosulfate in 250cc water, how many grams of ammonium thiosulfate is this?

moles of ammonium thiosulfate = M ( ammonium thiosulfate ) x volume of solution = 0.1M x 0.25 liter = 0.025 moles
0.025 moles x ( 148.21 g / moles ) = 3.7 grams of ammonium thisulfate needed to be added to 250 cc water.

48mM copper sulfate base on the above calculation means 0.04 grams of it needed to be added to the above solution.

I haven't tried this test yet, but I read somewhere this is faster than sodium thiosulfate leach but lower recovery rate.

Regards
Kevin


----------



## solar_plasma (Apr 17, 2013)

I think the main problem not time and not recovery rate, but selectivity. What does the leach solution do to basemetals and how does it handle cementation? There is often said, it is selective - but no hard facts.

When I get great amounts of basemetals, then AR would be as fine....or bad

Until now, I didn't find anything about that anywhere. As far as I understood the basemetals are still problematic in both iodine, thio and cyan leaching. Only the organic leaching methods seem to take the gold only. Tell me I am wrong and make me happy...


----------



## kjavanb123 (Apr 18, 2013)

solar_plasma,

I believe your presumption on those leaches are not selective is incorrect, that is their main characteristic to select only precious meals from a load of base metals.

Regards,
Kj


----------



## solar_plasma (Apr 18, 2013)

Yes, but I cannot find much about the *special conditions *to gain this selectivity and nothing about how large the selectivity is in fact. With my first* iodine leaching* I got much copper iodide and gold plated back. Next time I will be able to measure the ORP to be between 300 and 800 mV. Maybe I will be more optimistic thereafter.


----------



## kjavanb123 (Apr 18, 2013)

solar,

I believe if you read the pdf file, it clearly states the optimum conditions as for pH, copper sulfate, and temperature to reach the highest recovery rate.


Regards,
Kevin


----------



## solar_plasma (Apr 18, 2013)

I can first say that I understand a recovery process, when I also know,what will happen, if I would get out of the right parameters.
when will gold cementate back and why or why not?
how much base metals will dissolve at optimal conditions?
I can't find any informations about that.
I am not satisfied only to know the "right" conditions, because then I don't know to handle unexpected situations.

I am very interested in leaching.


----------



## bswartzwelder (Apr 19, 2013)

I read (or should I say I tried to read) the PDF file about thiosulfate leaching. Evidently, my chemistry background is extremely weak. But to me, trying to understand what they are saying is almost impossible. It's like they wrote it in a foreign language. The processes involved also sound more like something out of a commercial process rather than something that could or should be attempted by people recovering and refining PM's as a hobby. At the very least, it sounds much more complicated than using AP, AR, or poormans AR where normally you mix the chemicals and let them do the work. The AR and AP systems are old, accepted, and if done properly, relatively simple. They also provide quite a good return on your chemical and time investments. And while AR and AP are not foolproof, and they do have disadvantages, they are generally accepted as tried and proven. Maybe if I understood the thio leach process, I might give it a try, but for now, I'll stick with the old methods.


----------



## butcher (Apr 19, 2013)

It has been quite a while since I studied much on the Thiosulfate leach, which seems better suited for ore, I forgot most of what I had learned, but from what I do remember, it seems to be hard to keep the solution in balance, copper sulfate/ copper amine as the catalyst, pH also seemed to be very critical, I am not sure how selective it would be, but I suspect more selective when dealing with preprocessed ore than if dealing with electronic scrap where you have a rainbow of metals, I know for ore it is an option and there is quite a bit of information, but for electronic scrap it seems to me it has just been investigated and a few studies done (I could be wrong but I do not remember seeing much of any information on leaching electronic scrap beside some study's written up).

The Iodine leach also seems to be geared more for ore.

No doubt these leaches would work, but they do seem to me to be complicated and harder to deal with, and when we work with such small batches, it seems to me to be more trouble than it is worth, trying to walk a tight rope and keep your balance in such small batches, I believe it would be much harder trying to do this on a small scale, than working with large volumes on a larger scale.


----------



## kjavanb123 (Apr 20, 2013)

Hi

I was interested since I am scaling up to 100 kg PCBs per day so instead of sufiric acid cell i could use thio leach. 



Thanks


----------

