How can I use iodine to recover gold from circuit boards?

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Discussion Overview

The discussion revolves around the recovery of gold from circuit boards using iodine as a solvent. Participants explore various methods, challenges, and chemical processes involved in dissolving and precipitating gold while aiming to reuse the iodine solution. The conversation includes theoretical and practical considerations related to chemistry and materials science.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant is experimenting with iodine to dissolve gold from circuit boards but seeks methods to precipitate the gold from the iodine solution for reuse.
  • Another participant expresses skepticism about iodine's ability to dissolve gold, suggesting that copper could be used to precipitate the gold but may render the iodine solution ineffective for further use.
  • A suggestion is made to consider bisulfite as a potential method for recovering gold, although details are not fully recalled.
  • Concerns are raised about the selectivity of iodine, with some participants questioning whether it might dissolve other materials instead of just gold.
  • A participant proposes a specific mixture of iodine, potassium iodide, and water, believing it to be selective enough to target gold without damaging underlying materials.
  • There is a discussion about the volatility of iodine and whether heating the solution could aid in recovering iodine, though some participants caution against potential losses.
  • Several participants discuss the cost and practicality of using alternative methods, such as ascorbic acid or other weak acids, to reduce gold from the iodine solution.
  • One participant mentions previous experiences with aqua regia and expresses a desire for a more selective method that avoids the use of cyanide.

Areas of Agreement / Disagreement

Participants express a mix of skepticism and support regarding the use of iodine for dissolving gold, with no consensus on its effectiveness or the best method for precipitating gold from the solution. Various competing views and suggestions are presented without a clear resolution.

Contextual Notes

Participants acknowledge limitations in their knowledge and the complexity of the chemical processes involved. There are references to specific chemical reactions and the need for further research to clarify methods and outcomes.

Who May Find This Useful

This discussion may be of interest to individuals involved in gold recovery, chemistry enthusiasts, and those exploring alternative methods for metal extraction from electronic waste.

glondor
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I am working on a pilot project to recover gold from circuit boards. I have tried several methods and am interested in giving iodine a try. I know it will dissolve the gold but I cannot find an answer on how to get the iodine solution to drop the gold. Any ideas? Thanks.
 
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I am a bit sceptical that iodine actually dissolves gold but if you are correct I'd suggest that you use copper to precipitate the gold.
 
Bisulfite? I don't remember details and I don't plan to Google, but from what I have read similar project was described at tomshardware.com.
 
Thanks. Yes I believe copper will drop the gold, but it would render the iodine solution infective for further use. I would like to reuse the iodine solution. I am trying to cut down on chem use during the process.
 
This can be tricky. You want to reduce gold not reducing iodine, but most reducing agents will probably reduce both.
 
Again, I am sceptical if the iodine dissolves gold properly. Are you sure? Where do you have it from? It goes against what I have learned. Either aqua regia or base + cyanide dissolves gold. However, is it possible that you are dissolving everything else and get some kind of gold suspension? Then you only need to centrifuge or filter off the gold to recover the iodine.
 
Thanks for the link Borek. Here is a quote>>>>

Originally Posted by Mapes
Good point. G01, what is the underlying sample made of?

Potassium iodide is another good selective etchant for gold.
Yes. In the mean time I have done some research and decided that a 1:2:10 mix of I2, KI, and H2O are best for my purposes. I here it's very selective and won't attack the material underneath.

Thanks for the advice!

RE: The 1/2/10 mix. I understand I2 as Iodine. 1 part. H20 of course is water.10 parts. Is K I some type of potassium? Thanks Mike.
 
  • #10
Why dissolve the gold? Might just be easier to separate out everything not-gold.
 
  • #11
glondor said:
Is K I some type of potassium?

Potassium iodide.
 
  • #12
alxm said:
Why dissolve the gold? Might just be easier to separate out everything not-gold.


Many of the parts we work with are plated. Copper, nickel, Kovar base metals that must be removed or separated. Iodine is reported to be selective enough to just remove the gold. I am still looking for a way to "drop" the gold from the Iodine and still be able to reconstitute the Iodine solution for reuse.
 
  • #13
Iodine is volatile. Is there any economy in heating the solutions to dryness? The iodine will collect on any cold surface.
 
  • #14
Nemus said:
Iodine is volatile. Is there any economy in heating the solutions to dryness? The iodine will collect on any cold surface.

You are going to loose way too much.
 
  • #15
Why? Iodine is rather insoluble in pure water. I think I did something like this when I was a kid and made iodine from seaweeds. But it will cost a lot of energy, that's for sure.
 
  • #16
I have used Aqua regia to disolve gold, but it is not as selective as I would like for some of the parts I do. I know that iodine will work, I just have not found the method to drop the gold and regenerate the solution for reuse. I know it was used commercially for a while before cyanide displaced it due to cost as cyanide was much cheaper. I will not use cyanide. I can still use Aqua Regia as well as HCL/bleach to recover the gold, however there are many steps that can be eliminated if I do not have to remove the base metals first. I can remove the base metals with HCL/peroxide solution but it takes time. I can also use dilute nitric acid, however nitric is very expensive for this task.

If anyone can shed more light on this I would be very grateful. I do have some friends working on this aspect of recovery as well, and they have developed it to a point but solid info would help to break some road blocks. It is all well and good to be able to dissolve the gold, but if we cannot drop it out of solution, it is a loosing proposition.

We will keep at it! Thanks for your help so far. I will refer people from another forum to this post.

Feel free to come visit at goldrefiningforum.com. It is a fascinating place and we have some great people there.
 
  • #17
Nemus said:
Why? Iodine is rather insoluble in pure water. I think I did something like this when I was a kid and made iodine from seaweeds. But it will cost a lot of energy, that's for sure.

Iodine is very volatile, so it will try to run as a gas. IMHO it is better to look for a way of recycling solution, than to recycle iodine getting it out from the solution first.
 
  • #18
Can anyone add anything further to this?
 
  • #19
Nemus said:
Why? Iodine is rather insoluble in pure water.
But it's soluble in I- water solution, for example in KI w. solution. It forms I3-.
 
  • #21
Vitamin c is relatively expensive for this process. I am looking for a way to cut the cost factor and reuse as much as possible.

That is a very good link to the patent. Thank you Lightarrow. Not being a chemist it will take me a while to decipher tho...
 
Last edited:
  • #22
glondor said:
Vitamin c is relatively expensive for this process. I am looking for a way to cut the cost factor and reuse as much as possible.
The documents says to use "a weak acid, e.g. ascorbic acid" so you can use another weak acid, maybe citric acid, maybe oxalic, there are many (I would choose a non oxidant one, however).
 
  • #24
This patent is so unclear it doesn't make any sense to me. Ascorbic acid is often used as a reducing agent, no idea whether is will be able to reduce gold (quite possible). However, I am more than sure it will reduce the iodine

titrations.info/iodometric-titration-Vitamin-C

which is a thing you want to avoid.
 

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