help with gold adsorbed on activated carbon.

[Anonymous]

First of let me just say what a great forum this is. There is a real sharing of factually correct information. I am actually a chemistry instructor at a small community college so feel free to send me questions. Please keep in mind though that although I teach chemistry for a living my expertise is in organic chemistry and not inorganic or analytical chemistery.

Recently i have come across a sizeable amount of 5-10% gold adsorbed on activated carbon that I am trying to purify. I was wondering if anybody had any first hand knowledge of dealing with this material?

Basically I think I am going to try an iodine extraction but am still considering other options
Please let me know if you think this is a sound plan.

1. First place the activated carbon in a iodine/sodium iodide solution to oxidize the gold which will then be soluble.

2. Filter away the carbon leaving the gold in solution.

3. Use zinc to reduce the cationic gold back to its elemental form and then filter the gold particles to collect.

I do have a couple of specific questions to those of you that have done something similiar.

A. What are typical reaction times/temperatures for gold and iodine in this situation?
B. Are any measures needed to prevent the oxidized gold from readsorbing on to the activated carbon?
C. Is there a better way to precipitate the gold besides zinc?

thanks again.

 

[Lou]

Burn it.

Make provisions for collecting the gold. This also works for Pd/C, Pt/C, Rh/C etc. I use a tube furnace and air or O2 to do it--put what you want to oxidise in a large tube, pack both ends with kaowool, test gas flow, then heat. Easy.



Nice to see another chemist on the board!

 

[Harold_V]

Unless you desire to recover the carbon, I agree with Lou.

The bureau of mines has publications that deal with stripping activated carbon by various means. It is one of the commonly applied recovery systems from heap leaching. Sorry, I am unable to provide any titles, but that's a good place to start looking if you wish to save the carbon.

Welcome to the forum.

Harold

 

[Lino1406]

In my opinion, is too weak
and slow for that stuff

 

[Blacktoadd]

Carbon has the most porous surface which is why it is used. What was discribed in the article said a tall colum of carbon is used, solution slowly allowed to fall through the column (collector). When gold laden solution started to exit the collector the carbon was full. Remove carbon, burn, and refill.