An alternative passive stripping system

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UPDATE!!

Hot dang! it seems to work! The gold on the substrate is completely gone, and the pins are getting a bit "silvery", showing the metal inder the plating. So I guess I jumped the gun a bit, but my test shows it takes a hell of a lot more than two hours. My count is nearly 60 hours for the process to eat away the gold, and there's still a bit left on the pins.

But I'm not in a rush. My next step will be a small bucket (one liter) containing all my collected gold trimmings from pins, processors and board edges. Since the process is very slow, no heat seems to be generated and no gases either so it seems safe to do it indoors.

Hopefully, I'll be able to recover some gold precipitate, then add more iodine as the solution gets depleted. I'll then filter out the solution of AuI and keep it safe for the next batch.

Robert
 
Hey Don,

I just saw your reply, don't worry 'bout it... I guess I was a bit hasty in my declaration that my experiment was a dud... And I understand what you're saying... I shouldn't have melded the results of two distinct processes in one post, and I shouldn't have refered to the results of the original poster, but as I say, I'm not a chemist, and any experiment that doesn't involve cyanide, fuming nitric acid or mercury is fine by me! LOL :mrgreen:

Time to pull out the 1L beaker! :twisted:

Robert
 
Robert,

I have not tried any of the iodine methods yet, but I can tell you that you should try to follow the directions to a 'T' until you understand what's going on and what variables affect the reaction. Once you can reproduce a chemical reaction and understand the fundamental chemistry involved, then you can add your own touch.

I can also tell you that if the formula calls for elemental iodine, you will not have the same luck using povidone. Povidone is a non-staining form of iodine tincture that uses a polymer-like structure to slowly release elemental iodine. For this reason you should liberate the iodine from the Povidone before using it in any formulations that call for elemental iodine.

I have seen a reaction for removing iodine from povidone somewhere years ago, I think it involves dehydrating the povidone, then subliming the iodine from the resulting residue.

Good luck with your experiments.

Steve
 
I am sorry about this but I forgot to add that I add a small amount of HCl to get the pH slightly acidic. That and iodine water. And I don't care if it take takes 60 hours -- that is the whole idea of passive stripping. Mix it up and ignore it for awhile. And yet I do do it indoors.

Randy
 
Hi Randy,

Aah! So we had a missing ingredient! LOL :lol: So your recipe actually produces a mixture of AuI and AuCl. :!: Is the HCl helping or provoking the metal precipitation? Could you recommend quantities of the various ingredients? Is the HCl concentrated (20 Be-32%) or diluted?

So far, I have tried your process with a twist: Au + H2O•C2H5OH:I = AuI + H2O•C2H5OH and it seems to work but rather slowly. Upon reading the details of that formula, I understand that my initial mix had too little iodine so I added a little and the process seems to be chugging along just fine. Next weekend, i'll try to process a boxful of parts and fingers.

So let me know about the proportion of your ingredients and i'll try a small batch of that to see if the process is a bit faster.

Thanks

Robert
 
Water is harder to make it go bang. :p
Randy, would peroxide help or hinder the reaction? Just wondering
Wyndham

Edit: Here's the page on Basement chemistry that talks about Iodine, hope this helps
http://webpages.charter.net/kwilliams00/bcftp/docs/halides.htm
 
eeTHr said:
Robert;

Also (you probably already know this), be very careful with using alcohol in refining. Personally I don't even keep it around the area---
Click to expand...

Indeed, no nitrates or nitric acid anywhere near my bucket-o-gold :mrgreen:
Robert
 
Hey guys,
I'm something of a noob but wanted to let you guys know that iodine is toxic and releases toxic vapours(not like regia but toxic nonetheless). This method works because iodine is a halide like chlorine and releases toxic vapours during reactions,always make sure you have some form of ventilation, wear gloves and eye protection.
 
Yes, the pins seem to remain relatively intact, the other metals don't seem affected at all. I've put the experiment aside for a few days because i've had busy days and evenings lately, but my next test will include more gold plated material including board fingers as well as solder-contaminated pins to see if the lead will be eaten away or remain unaffected. So far it seems like it works, but a chemist friend of mine suggested that I increase the amount of iodine in my solution. I'll resume the experiment next weekend if I have time.
 
Shecker said:
As the iodine is exhausted tiny bits of metal will fall to the bottom of whatever vessel you would use. There will also be a golden yellow solution left over which still contains gold. I recover most of that on carbon but I am still working on the residue gold left in solution.

Randy in Gunnison
Click to expand...
I would like to know how you recover the tiny bits and is this tiny bits of metal gold?
all info I can find on iodine say the pm's precipate after lye is added i wonder if this Povidone has something to do with this.
 
I live 8 miles from nowhere, but when I get somewhere that I can buy iodine, I will try this and post the results.
 
Is this the right stuff?

http://cgi.ebay.ca/250g-IODINE-CRYSTALS-99-8-PRILLED-LAB-GRADE-USP-ACS-EP_W0QQitemZ220711807221QQcategoryZ63512QQcmdZViewItemQQ_trksidZp4340.m263QQ
 
I don't think the stuff Shrecker used was near that concentrated, more like maybe 10%. He said he used Povidone iodine, which I think is generally 9%-12%.

I'm thinking something like Wal-Mart sells here:
http://www.walmart.com/ip/Dynarex-Corporation-Povidone-Iodine-Solution/15648976
 
Method for removing electrically conductive materials containing silver from electrodeposited parts

In the case of a method for removing electrically conductive materials containing silver from electrodeposited parts, in particular, electroformed dental parts, the part is treated with iodine and/or at least one compound containing iodine under at least one processing step. The iodine/compound containing iodine is/are preferably present in the form of a solution or a dispersion in at least one polar solvent. Inorganic iodides and iodophores are prime candidates as the compound containing iodine.
Click to expand...


View attachment Process for refining gold and apparatus employed therefor.txt


Here's a relevant patent.
United States Patent 5026420: Purification process for gold-bearing iodine lixiviant



Another ineresting patent

I'm finding that this process is very useable!... Investigtion time... :twisted:
 
Ok... I used a half gallon apple juice bottle (top half cut and used as funnel...) as the lixivant chamber and a plastic sobe bottle with its bottom pepper punctured to allow flow in and from its insides to react with plated metal values I filled it with.

I used pm metal plate content from A/V, Comm, Sat, Game console, pc, and telephone, crushed monolithic resistors and caps, pins from various connector types, cut up flatpacks, etched and cut to size, cut up pcb's bearing gold boards, plated jewelry, etc. 980 grams total...

The solvent went clear after 5 minutes, so I added water, shook content, added hcl, stirred content. Added additional iodine.

By the way, was I supposed to use distilled water? I used tap water that had previously been used to break down some of my polymetallic ore from it's solid state into mud, which turned the water light blue. I figured I'd try using it as I'm sure it contains pm values leached fom the ore it was used to break down into componant segmentations.

The red coloration dissipated entirely, leaving what I feel is a very pregnant solution. I added 1 teaspoon of lye and stirred - drk blue elements appeared, then settled at the bottom of the solvent... showing a heaviness in volumn. was the precipitant actully black sludge in blue water?

I think my solutions are saturated, so I'll siphon off the first batch tomorrow and put the leachant in fresh solution... hopefully the pcb boards will then get stipped...

all pm values seem to have been successfully stripped, except pcb boards. Will report back in the morning, after I check the overnight pogress.
 

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