thio based solution with e-waste @ large scale

[future gold refiner]

hello refining-guys...I need some help.
I have a experience (4 years) with AR and HCl / H2O2 (with high Karat-Au) but I want to process very large quantities of e-scrap because now i have access to large quantities of PCB´s / chemicals / equipment. I to deal with this over one year - read tons of information and made my experiments (without superior success :lol: ) .

NOW THE PROBLEM: I am looking for a leaching/etching solution to recover precious metals from PCB´s.
cyanide -> is out of the question because the known risks, environmental requirement´s and legal constraints (in germany)
Br2 and I2 -> read interesting things about it but to process it in 1000 Liter´s or more it seems not practical.

So my preferred system is ones of the THIO-based systems.
I know there are some different types with:

ammonium thiosulfate / sodium thiosulfate / thiourea as complexing agent
oxygen / copper / ferric (sulfate/nitrate/oxalic) as catalyst or Oxidizing agent
acidc or alkaline environment

......what I need is a solution composition that really works - not only on the paper.
[preferred: ambient temperature, fast leach rate]

needed information:

1. the solution composition ( g / litre )
2. about redox potential range ( mV ) and how to adjust ( chemicals )
3. about the pH value and how to adjust ( chemicals )
4. about leachtime
5. solution decomposition
6. loading capacity

I would prefer an answer from guys who had experience with the suggested solution.
Answers like: i read that xyz use that .... did not help. -> I need information from reliable sources.

additional information:
that other metals are also leached by thio**** is known but is not so serious.
all chemicals and wastes will be disposed by a certified company.

thanks a lot in advance

 

[future gold refiner]

Does no-one have experience with the THIO technology?
Most of my experiments focused on the Thiosulfate -Ammonia- copper system.
All my tests ended, that either sulphite is precipitate or my "fingers" are coated with copper or coppersulfite.

I have used differend concentrations and ratios of ammonium thiosulfate // sodium thiosulfate / Ammonia / copper - with and without bubbling air in it.
the pH value was 9-10 .

I can´t believe that no-one in this forum can´t help me.

(I read the GRF book 1 & 2, hooks book and hundreds of pages of thioleaching - I am not lazy -> but I do not make progress.)

 

[Lino1406]

anyhow must include oxygen (air) bubbling

 

[Anonymous]

Small test sample for electronics, it worked I would say fair but not great and would not work when metals other than copper were in the batch and the copper had to be limited to less than 2 percent of the bulk material.

I used 1 liter water, 4 grams ammonioum hypo, .5 grams copper sulfate, ammonium hydroxide to make ph 10. bubbled pure oxygen, then tried sealed unit on tumbler to mix in the oxygen so I would not have to continously bubble.

any iron, aluminum, zinc, tin used up the chemicals and prevented good progress.

I processed in test batches of 200 grams of ground materials that did not contain the pcb board, only ground up components.

hope that helps.

Jim

edit+
I do not have redux measurer.
I used unscented dollar store ammonia for PH controld and it helps with the reaction.
Worked better with less chemicals than more.
let the batches run 24 hours.

Most importantly the material has to be ground up real fine, never tried it on fingers.

I did find that preleaching the base metals with warm dilute HCL improved the process significantly, but, I also found that after you do that you can use used the HCL/Bleach or my favorite HCL/chlorine gas plattner process to recover the gold.


I have been just way to busy for anything gold related other than some small testing and online research keeping up with the friends.

 

[Lino1406]

With HCl will precipitate sulphur

 

[Anonymous]

not with HCL, after HCL

 

[future gold refiner]

how woud you lower the pH (because it rises with leaching time- despite ammonia buffer) i use H2SO4
why to use copper-sulfate and not copper-hydroxide -> to lower the sulfat-ion concentration

does thiosulfate leaches pgm´s ( platinum and palladium ) in elemental form or only from salts ???

...and how to drop all (!) [without Na, K] metals out for analysis not for commercial application

1. use sodium/potassium phosphate filter the precipitate and glow it -> dissolve it in AR analyze it with atom absorption spectroscopy
2. use sodium borohydride filter the precipitate and glow it -> dissolve it in AR analyze it with atom absorption spectroscopy

does it work ?

 

[Anonymous]

the test batches I did were done in a basic solution. copper sulfate is a catalyst and you only need a small amount.

This solution needs to be dilute to use, does not work very fast, chlorine based leaches work much better and yield gold chlorides which are easier to deal with.

I only did test, to see if it would be viable for me, it is not.

Jim