# Indium Extraction from CIGS in Aqua Regia to DEHPA



## zephler (Apr 3, 2014)

Hi everyone!

I have some CIGS material mixed with other misc. Indium containing scrap, the analysis of the CIGS was:

Cu 28%
Ga 7.8%
In	52%
Se 0.03%

With the introduction of the other scrap, some Ni and some Fe has been introduced. 

The whole batch has been digested in Aqua Regia, producing a dark green solution, with loads of either precipitate or material that has not gone into solution (due to solid liquid ratio not being optimal at this point).

I have access to DEHPA, and would like to know if someone has a reference or can comment on using it to extract Indium from this soup of Metals, from a AR media. In particular, what pH should I get to, in order to get DEHPA selective enough to just pull out the Indium? Should I just use NaOH to adjust the pH up to that level?

Thanks!


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## necromancer (Apr 3, 2014)

you crushed your solar panels & other scrap and it all went straight into Aqua Regia solution ??

no other pre-process ??


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## zephler (Apr 3, 2014)

material was mixed together already.


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## necromancer (Apr 3, 2014)

do you have experience with precious metal extraction ?


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## freechemist (Apr 3, 2014)

Zephler,

Apparently you are very fond of short language, and thus expect everybody to be familiar even with almost all 4-letter-abbreviations. - What concerns me, I am not, and so I need explanations. For one term, "DEHPA", - a 5-letter-term, - I did a short Google-search myself and found it referring to a chemical used in uranium-extraction from aqueous solutions into an organic phase. May be, that this could be of some relevance, to help to solve your indium-problem.

However, this forum is concerned with recovering and refining of precious metals, and thus doesn't cover indium, not regarded as a precious metal. Secondly, doing a serious search on the indium-topic yourself, should provide you with appropriate answers in reasonable time.


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## joubjonn (Apr 3, 2014)

If you can understand this paper on using DEHPA
http://www.tdx.cat/bitstream/handle/10803/6439/02Mrb02de14.pdf?sequence=2
For palladium extraction

Then you don't need our help anyway. Seems pretty advanced and you would need a lot of experience and equipment. 
I would send that material out to a refiner. By asking us it would seem you need a lot of help. Dangerous.


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## necromancer (Apr 3, 2014)

joubjonn said:


> If you can understand this paper on using DEHPA
> http://www.tdx.cat/bitstream/handle/10803/6439/02Mrb02de14.pdf?sequence=2
> For palladium extraction
> 
> ...



thank you for the paper joubjonn !!


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## joubjonn (Apr 3, 2014)

No problem. It was way over my head. Maybe someone here can explain it better. If it's even worth explaining.


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## necromancer (Apr 3, 2014)

me to but so are 1/2 the books i get from the thrift store, $100.00 books for $3.99

and google is great for guys like me :lol:


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## Geraldo (Apr 3, 2014)

I'll take a quick crack at it. It will be in general terms, since I am going by memory from stuff I last looked at at least a decade ago.

1. Please use D2EHPA in your research and reference. "DEHPA" isn't correct.

2. Indium extraction commercially is usually done from single acid solutions (typically sulfuric or hydrochloric systems). It can also be extracted from nitric solutions. The mix of nitric and hydrochloric complicates things. I guess if you are extracting from aqua regia and that is your only choice, realize that ion bleed through (chloride AND nitrate ions) and speciation (indium forms a lot of different complexes depending on pH and counter-ion, and having both chloride and nitrate acids makes for a mess) will make generalizations very difficult.

3. indium extraction improves at "higher pH" generally, when extracted from HCL or H2SO4 or HNO3. For nitrate and chloride acids, high pH is still below 1. A better description might be g/L of free acid, since pH measurement is iffy below pH 1. If I was testing this, I would start at maybe 10 g/L free acid.

4. D2EHPA is a fantastic general purpose extractant, and works very well for indium. By that, I mean fairly good kinetics and decent equilibrium recovery level. Still, a typical extraction circuit would require 3 mixer-settlers for extraction (running loaded organic and loaded feed solution counter-current) and then at least 2 stripping cells (again, running counter current). It might be possible to use a column SX unit since the kinetics are pretty good for indium extraction, but I suspect that a person would have to test that. Also be aware that loading indium onto D2EHPA releases acid into the aqueous solution, and depending on the initial concentration of indium this may require you to neutralize the solution between extraction unit operations e.g. mixer settler #1, re-neutralize pregnant leach solution, mixer settler #2, re-neutralize solution, etc etc.

5. I would strip with HCL at perhaps 50 g/L to start, depending on the acidity level at loading. So, if you loaded at 5-10 g/L acid, you might try stripping at 50 g/L. If you end up having to load at 20 g/L acid, you might need to strip at 100 g/L. Obviously don't go too high in stripping acidity, or you will destroy your organic solution. You could then recover the indium by sponging with zinc, drying the sponge, melting the indium sponge and casting cathodes, electro-refining, remelting anodes with ammonium chloride to purify, and casting final product. You could end up with 99.9% indium if done carefully.

About selectivity - you are right that it will depend on loading (feed) pH/acidity. Generally speaking, at pH below 1, you can selectively extract indium versus most base metals (like zinc, nickel, cobalt and cadmium). I can't say for sure how selective D2EHPA is for indium vs. the PGMs on the basis of pH. What I DO know is that PGMs are experimentally separated using D2EHPA by changing the concentration of D2EHPA in the organic phase. Platinum can be separated from some other PGMs by using LOW D2EHPA concentrations in the organic phase. This will complicate things since you will also have to tune the D2EHPA concentration for indium extraction efficiency.

Also remember that you will have to play with dilution (D2EHPA must be diluted in kerosene) and possibly phase modifiers (such as octanol or decanol) in order to get organic/aqueous phase separation. If you don't get that part right, you will just end up with acidic mayonnaise, which you won't appreciate.

Just thoughts dragged out from my ailing memory.

Best Regards, Geraldo


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## zephler (Apr 4, 2014)

freechemist: I wasn't aware that Ruthenium and Osmium were precious metals either - why are they covered here if the forum is only for precious metals? I apologize for posting about Indium in the forum, I also apologize for the acronym use. I do appreciate the apprehension in providing information on topics like these, as you are quite correct, it is dangerous work. The paper provided me with an answer to another question I had about pH for Pd SX extractions, so thank you! 

necro: I do not have experience with precious metals extraction, however I do have years of experience as an (organic) chemist.

Geraldo: Thank you so much!!!!!!!!! Exactly the information I was looking for!!! :lol:


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## zephler (Apr 4, 2014)

Geraldo - are you sure about DEHPA not being correct? lol! :lol: Thanks again !!!


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## necromancer (Apr 4, 2014)

zephler said:


> freechemist: I wasn't aware that Ruthenium and Osmium were precious metals either - why are they covered here if the forum is only for precious metals? I apologize for posting about Indium in the forum, I also apologize for the acronym use. I do appreciate the apprehension in providing information on topics like these, as you are quite correct, it is dangerous work. The paper provided me with an answer to another question I had about pH for Pd SX extractions, so thank you!
> 
> necro: I do not have experience with precious metals extraction, however I do have years of experience as an (organic) chemist.
> 
> Geraldo: Thank you so much!!!!!!!!! Exactly the information I was looking for!!! :lol:



you have experience as an (organic) chemist, good ! i never know, there is so many new people here, a background in chemistry gets you points !!
my only chemistry experience is from what i have learned here on this forum, links from here & studying online over the last 3 years.

Platinum, Palladium, Rhodium, Iridium, Osmium, & Ruthenium are the 6 platinum group metals. so they fit together.

as for the indium, its talked about here, i have about 49 grams myself.


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