Potassium Iodide-Iodine gold etchant

[usernameguy]

Hi All,
GSP, I finally got around to precipitating the gold plating solution I asked about bd10 I think the name was. It's in this thread a previous post. Anyway, you're brilliant. you're memory served you very well. I added just a bit of sulfuric, and dropped out pure gold sponge. It was a beautiful thing. Very easy to folter also since it's almost like putty. very cool Thanks a lot man. I just came across some gold plating solution that has hardly been used at all. It's "old" so the professor who comes back here like once a year wants to buy fresh every year. It again is just going to be thrown out. This solution is cyanide based, so its not the same as the last one. I'll search through the forum to see if I can find anything about this, but if your memory serves you as well as this time, let me know if there's something that will work as good as the sulfuric did on the cyanide free stuff. I know I must be even more careful with this solution as it is the cyanide that kills people. We have a well ventilated fume hood I have access to that goes through a chemical scrubber.

Thanks again,
Guy

 

[DNIndustry]

Just thought Id mention this...
The danger of cyanide (outside of ingestion) is when the solution becomes acidic. The CN- Ion bonds with the disassociated H+ from the acid, forming HCN gas. Now if cyanide is ingested their is an "antedote" but A.) good luck getting it fast enough B.) dont see how a liquid in your stomach could stop a gas diffusing into your lungs.
(Thiosulfate is the antedote..supposedly)

If you are playing with H2S04 you should know that H2S gas is just deadly with no antedote.

 

[usernameguy]

Yeah,
Thanks DNI. One good thing about H2S is it's very low odor detection concentration also though. I do head your warning. I actually have access to very good fume hoods that are qualified by OSAH, and are exhaused through rain scrubbers before being diluted something like 10,000 to 1 before release. Does anyone know about HCN gas detection threshhold? Is it one of thsoe super nasty's? ie., if you smell it your dead? We haves some gases here in the mustard family that are like that. arsine and phosphine. Yikes. HCN is almond smell, yes?

 

[EVO-AU]

Juan Manuel: I have just gone thru all the posts on this thread and quite impressed with the high exponent of knowledge with which you gentlemen indulge. I have been experimenting with 7 % Iodine on natural ores for about two years now. Very limited experience I grant you. Leaching is quite new to me in this regard.

However, my question to you is do you work with natural ores at all ? And if so, do you have anything to offer in this regard. I don't care for electronic scrap. There are just too many steps involved and I like natural things anyway. Sincerely, Phill

 

[usernameguy]

EVO,
I very much enjoy prospecting (placer), and have used the iodine based etchant I have access to to disolve some of my flour gold, which obviously works well. I don't have any experience with hard rock ores, but if it helps, I do know the Iodine etchant I use will dissolve up to 100g of Au per gallon. Have you had the ores assayed? I'm curious if you have free gold or sulfide complexes, etc. I do have a B.S. in geology, but not much experience. Got into the electronics/semiconductor field professionally (go figure)
-Guy

 

[Juan Manuel Arcos Frank]

EVO-AU:

This process was originally done in ores.It works lovely with ores but could be more expensive than cyanide process.The problem is making potassium iodide.

Regards.

Manuel

 

[DNIndustry]

Thats where NH4I comes in. With out looking is their anything it could complex in said ores that could create an issue?
I hate to beat a dead horse but the NH4OH method destroys KI from a $ as well as simplicity, just make more.
Juan, any insite?
It works wonders for electronics but what about ore.
It does not attack base metals which could actually be a negative, depening on the fineness of your dirt

 

[donnybrook]

I live within an old goldfield. More than 100 years ago the miners were only interested in the free yellow metal. They had little time and had to make a living. Things such as mecury on copper plates were used with a stamper battery and they usually hung a bag of cyanide at the water inlet to prevent flouring of gold if they were working with hardrock.

I have a Recovery Table. I concentrate and furnace but took an interest in leaching the metals as I realized (after assaying my tailings and middlings) that even the recovery table was losing precious metals .

I have experimented with 10% iodine in 5 parts water. I add a small amount of muriatic acid (or brick cleaning acid)to keep the pH at 4. This also keeps the ORP at good levels (between 400 and 900). I have had some success with this.

After about 24 hours using a plastic rotating drum with a length of pvc pipe weighted with concrete and sealed at either end with a cap and epoxy glue as a grinder. I process about 10 kilos or 22 pounds each time. The solution should turn a red brown.

I have been adding chrlorine or homemade liquid using dry powder for swimming pools to convert the gold from gold iodide to gold chloride. I then adjust the pH to 7 using sodium hydroxide and the metals precipitate as a black powder. Filter after 24 hours using a large nylon cooking strainer (say 8") and tissue papers over a 5 gallon bucket. Dry in an oven for about 5 hours. Roast to convert the metals from oxides to gold and then furnace or smelt.

I have never worked with circuit boards or computer scrap using this leaching method. There is supposed to be a way to recover your iodine which costs me about $40-00 (AU) to buy. I have kept the clear iodine solutions as I intend to reclaim my iodine when I know how. I think this is probably just a pH adjustment and taking the iodine back up to use again.

Base metals such as tin etc in scrap boards can cause all sorts of problems and it is best to try and eliminate these with something like brick cleaning acid before beginning the process.

Donnybrook

 

[donnybrook]

I am new to the web site "Gold Refining Forum". Not sure how to use it properly and have made two attempts to contact other members without success the story of my life.

A couple of references have been made to using Iodine (9%) solution to extract PM's from ores. There is a web site I am also familiar with and a link is shown within the Forum Site. I have experminted with other possible sources such as computer scrap etc in the past. Decided to use iodine as opposed to the old CLS system or another using salt and an acid. Probably for safety and health reasons.

Can someone tell me how to recover the iodine after conversion to gold chloride and precipitation. How do you recover it and then bring it back up for reuse? It seems to be the way to go from an economic point of view.

A member named Phill also had a similar inquiry.

I also table, furnace and refine.

donnybrook

 

[AKDan]

Donnybrook,
I am thinking based on your description that you can "recharge" and then re-use your existing solutions with the addition of Hydrogen Peroxide. If you go through the process of recovering your iodine out of solution, then you will likely need to mix back the elemental iodine into a solution of potassium iodide that you prepair to start a new leach. I believe that eventually you will need to do this anyway as every time you use the leach your volume increases and eventually becomes unmanageable.

I may be corrected on a couple of points here as I am talking from memory.

 

[Palladium]

http://www.freepatentsonline.com/5026420.html

The excess iodide formed during the process is reoxidized to iodine electrochemically in a special diaphragm cell to regenerate the lixiviant. :arrow: http://www.freepatentsonline.com/4557759.html



The solubility of elemental iodine in water can be vastly increased by the addition of potassium iodide. The molecular iodine reacts reversibly with the negative ion, creating the triiodide anion. :arrow: Au3+ and I- ions = AuI3, gold(III) triiodide

 

[Palladium]

Have you thought about bromide. Now that's interesting. :mrgreen: :mrgreen: :mrgreen:

 

[solar_plasma]

That one little oxygen molecule is what prevents making the bad stuff.

What is the "bad stuff"? I do not dare to experiment with NH4I until I completely understand the dangers. NH4OH is something I normally never would bring together with iodine or silver unless I really know, what I am doing. So, would anyone like to comment this further or give a hint, what to look for?

 

[kjt124]

I could be mistaken, but "the bad stuff" is likely NI3 (nitrogen triiodide) which is the product of elemental iodine and aqueous ammonia. When I was younger and dumber I used to play with this stuff a bit. When it dries it makes a very touchy contact explosive. Type nitrogen triiodide into youtube for any number of demonstrations. It is rather powerful and VERY dangerous. If you believe at any point you've accidentally made some, please keep it wet (reduces the chance of deflagration). I am not certain what would deactivate it entirely. Perhaps someone else can chime in on that.

Kevin

 

[solar_plasma]

Yes, I know it as an experiment in ancient schoolbooks. One of the things I never felt the need to make, - even when I was a kid. I guess, my modest mind and my blood pressure has enough to do with the better documented methods. :lol:

Thanks for the answer!