An alternative passive stripping system

[Aristo]

"Ariso, I have no doubt you can recover your gold, the question should be just how to do it."
"and I am also sure you will recover your gold, just do not do something you are not sure of."
Was that being referred to me ?
I made no reference regarding losing gold or not being able to recover gold personally.I have not used the iodide method nor do I plan to.
Your assertions are not accurate.
Please govern yourself accordingly.

I visit the board from time to time and I try to stay in touch with some members. I try not to get immersed in the actual refining since I handle relatively large volumes of e waste. I usually solicit those who are trained and have the necessary resources and licences to take care of my processing.
I agree with many things that you have written.

 

[TheGarbageManCan]

I have read that Naoh (lye) should drop gold.

 

[patnor1011]

I have seen some members of this forum reprimanded, censured or had their priviledge revoked for a variety of reasons ranging from obscene and rude behaviour or to lesser infractions.
I would ,politely, like to question the moderators as to why the OP has not been reprimaned for apparently leading on falsely or misleading unsuspecting and honest enthusiasts who are simply trying to learn.
I do believe that there is a wealth of information and experience to be gleaned from this forum, however, there should be some examination of the posts by the "proven experts" prior to its publication or use. In the science of chemistry and metallurgy, there is no magic or as someone put it, witchcraft. Whether it is electronic scrap, ore or related precious metal bearing products, they are all governed by known science.
I would like to kindly urge those that are responsible to review this matter and, if there are no known scientific proof to what is being presented, some action should follow.
Thank you.

I thought idea of the use of iodine (at least in this post) was to selectively strip the gold without using strong acids or cyanide, not to dissolve the base metals & leave the gold behind, which every other process described here does, easier & cheaper.

The thread's title said as much... but it appears the title is misleading!

An alternative passive stripping system
by Shecker » September 15th, 2009, 2:27 pm

I have been experimenting with another passive stripping approach to e-scrap that seems well suited for such things as cpu's, pins, fingers, monolithic capacitors, etc. I've been using a dilute solution of veterinarian grasde Povidine Iodine. I make an iodine solution that has a thin red color (iodine water). This dissolves gold, silver, platinum, palladium, but does not react with lead, tin, aluminum, or copper. As the solution begins to become saturated it starts dropping out some discrete particles of precious metals. It will continue to do until the solution looses it stability and goes clear. I ran some CPU's today and after about two hours the precious metals were laying in the bottom of the container. No precipitation was required. Forum members working with iodine may give this try and report their observations.

Randy in Gunnison

Nowhere in this post - the post starting this topic - did Randy mention using "a small amount of hcl". In his third post, Randy was asked if it worked. He replied:

Just enough to make the water reddish-brown but you can still see through the solution. If the mixture becomes opaque add more water.

Water to reconstitute the iodine.Water to reconstitute the iodine?! This is where I changed 'water (H2O)' to 'Hydrogen Peroxide 3% (H2O2)'. This is how to get your "opaque" mixture back to the active reddish-brown it needs to be to work.

In his 4th post Randy states:

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

This is where I got the info on using activated carbon to get my pm values out. I never saw ny 'bits of metal' as Randy described it.

After several people scrutinize his method (one person even including alohol in thier attempt) and report failures... all of them... Randy reappears and says:

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

Now Randy comes back with this 'oops...'. After my little attempt, Oz informs us that this is now no longer an iodine leach but now an AP solution.

This thread, at this point IMHO, is irrelevant, costly, and dangerous. It provided partial info that has cost several folks, including myself, time, money, and now possibly my gold.

If I cant find a viable method in recovering it after ashing and smelting my charcoal I'm going to flag this thread and ask for it to be removed so that other newbies like myself wont be fooled by it, or worse even, be harmed by it.

"Ariso, I have no doubt you can recover your gold, the question should be just how to do it."
"and I am also sure you will recover your gold, just do not do something you are not sure of."
Was that being referred to me ?
I made no reference regarding losing gold or not being able to recover gold personally.I have not used the iodide method nor do I plan to.
Your assertions are not accurate.
Please govern yourself accordingly.

I visit the board from time to time and I try to stay in touch with some members. I try not to get immersed in the actual refining since I handle relatively large volumes of e waste. I usually solicit those who are trained and have the necessary resources and licences to take care of my processing.
I agree with many things that you have written.

You contradict yourself. You stated what is marked in red and then when Butcher tried to help you talk about assertions and governing.

 

[Aristo]

The quote in red that you pointed out is a quote from DarkspARCS. Please read carefully.

 

[DarkspARCS]

lol... the part you highlighted in red is a quote to something I said pat...

Anywho, sorry that I havent posted much lately to this thread as I've had a couple of issues come up needing my attention that took me away from this.

I haven't ashed my carbon due to the volatility possibility as well as the loss issue in gold going up in the smoke. I believe that I'm going to have to somehow ash the carbon in a sealed container, however I may also be able to prevent values from being lost in the smoke by just skipping the ashing, grinding my carbon, mixing it with flour, possibly covering the mix heavily with a boron flux (as an added measure to insure loss prevention) and then just smelting it outright, capturing any values within boron glass. I may instead crush up a crt screen and mix my boraxo with the leaded silicate, captuing values in lead and discarding the borosilicate waste.

Regards any values still in the solution (I need to create some stanous and check), I may just let it slowly evaporate though a coffee filter and then smelt any leftover salts with the filter (yes, I have goggles and half-face respirator utilizing chemical filters) mixed with flour and heavily fluxed (just like the carbon) and catch any values in borosilicate glass.

I'm weighing my options. Til then I'm capturing resources to work the next 1000 grams of material with, this time using distilled water and iodine, instead of the copper polluted wter I used with this batch...

 

[patnor1011]

My bad... I need break for a while I guess. :lol:

 

[donnybrook]

Many posts have been made on the various leaching processes which is why I write this, such as the Swan Leach (SSN?),Iodine Leach and the Chlorine Leach.I have looked at and used with success these latter three processes.

I have worked with computer components and mineral sands. The most important thing to do is to remove the base metals.

With mineral sands from old mine workings using the chlorine leach I roast until the concentrates are red, then remove what base metal I can (such as iron) with a 10% HCL solution using a plastic pale or drum. I filter my concentrates in calico bags and then give this a further roast before the addition of the leach. I found that making my own liquid chlorine using the late Mr Williams method effective producing a stronger form than some of the commercial products sold here. I add this to my concentrate and then adjust my pH to 8.5 using HCL and mix ( agitate) it for one to two days adjusting the pH etc as required. When I believe the leach has done its job I adjust the pH to 7 using Lye and HCL. The precipitate will begin to drop. I have also added SMB when the pH was adjusted to 7.

The SWAN Leach (SSN) using saltwater and nitric and a small amount of iodine was also as effective. After leaching is complete (use an ORP meter) I remove the nitric (expel it) using urea and then precipitate my PM's out using SMB.

Iodine and its use on mineral sands containing PM's is the third most effective method to recover these. I use a 10% solution then add 10 parts water. Adjust the pH to 2 and maintain it during the leaching process. I then filter the solution and mineral sands using a calico filter bag; it should be red brown. Adjust the pH to 7 using Lye and HCL and your precipitate will drop. It could take 1 or 2 days to fully settle on the bottom. Decant or siphon the clear solution off (this contains your iodine) and precipitate (or drop your iodine or iodide) using clorox. Take it up again using Lye ready for use again. There will be some loss of iodine.

I am not a chemist and like others new to the Forum I found many things confusing. I thank the more experienced members on it for their advice at times. Whatever you do or whatever process you use remember your safety using proper protective clothing and known processes. Your health is a priority. If you are not sure get advice as mixtures of chemicals and sometimes admixtures can be disastrous.

I hope the above helps in some way for those wanting to recover PM"s using these leaching processes.

donnybrook

 

[dtectr]

I, for one, have done even more research & experimentation on this process & I believe that there may have been some holes in cited methodology.
And, I was speaking without understanding when I criticized the use of HCl & H2O2, as their proper use seems to be key for keeping the process working. For that, i apologize.

However, some things I've gleaned:
1. Elemental iodine strips the gold, but only dissolves in sodium/potassium iodide. Elemental iodine is converted to the iodide my dissolution of small amounts of iodine in lye water.
2. As the process proceeds (clears) iodine is converted to an iodide. The leach stalls here. The VERY SMALL addition of HCl converts this back to elemental iodine, and the leach starts up again.
3. The ph is critical, 4-5, small additions of lye water or HCl (monitored by litmus test or ph meter, or orp meter, let you know when. Too much deviation seems to result in at least partial dissolution of base metals.
4. Agitation seems to be extremely helpful, preventing a passivating layer from forming on the objects to be stripped.
5. The -Cl ion is necessary for the leach to work (see #2)
6. Addition of clorox when too much HCl is in solution causes dissolution of precipitate. So, an extended evaporation seems to help "regulate" this balance prior to precipitation.
7. H2O2 can also be used to oxidize the solution, precipitating the iodine - but since all I have is 3%, this results in a considerable increase in volume for me, without measurable success, yet. But, it may sidestep the HCl-Cl dissolution problem

As relatively expensive as iodine is, I'm not sure that this process is the most economical. You are supposed to be able to recover your iodine, but some, at times quite a bit of iodine is lost to evaporation/oxidation/? (I don't know complete cause - these are guesses on my part as to "why").

Butcher -
You, as well as others, seem to be of the mind, based on your experiences, that the effectiveness of many types of selective stripping/leaching (like Plattner's Process, using chlorine, for example) will be limited/hindered as long as base metals are still present resulting in cementation of values, and this seems to be grounded completely in fact/practice. Much of my limited experience thus far also seems to bear this out. In your opinion, would that factor in with iodine/iodide leaching?

According to the good Dr. from Costa Rica, all the halides, including chlorine & iodine, behave basically the same, with the exception of flourine. Since I'm no chemist, clearly, this sounds perfectly logical. If so, wouldn't the same base metal issue affect the entire group, to varying degrees?

I am very interested in the ongoing nature of this experimentation & welcome any feedback.
dtectr
EDIT: grammar

 

[butcher]

I cannot be much help as this is a halide that I have very little experience with.

From what I understand it is the Tri Iodide that dissolves the gold.
I2 (Iodine) + I- (Iodide) ---> I3 (tri Iodide)
the tri-Iodide (I3) is the oxidant for gold, and with Iodide (I-) forms AuI4,
2 Au + 3 I3 ---> 2 AuI4 + I-
after gold is dissolved ascorbic acid (vitamin C) could be used to precipitate the gold and reduce the Iodine (I2) to Iodide (I-)
this results in a deficiency in tri Iodide (I3), and then the halide is a poor solvent for the gold.
Tri-Iodide has a dark brown color, when tri Iodide is depleted in solution it will turn clear-ish, showing a loss of tri Iodide, and gold will precipitate.

As you stated hydrogen peroxide can be used as an oxidizer for reuse of solution.
Try going to spa and pool supply house for more concentrated H2O2.

Chlorine is more reactive than Iodine in the series of halogens,
Cl2 + NaI ---> 2NaCl + I2
here chlorine is oxidizing Iodide to Iodine

I2 + 2NaOH ---> 2NaI-
here sodium hydroxide is reducing Iodine to Iodide

I cannot understand your loss of Iodine is it as gas or is it locked up with base metals or gangue materials?

As far as base metals since they would also form iodides of these metals, eliminating them only makes sense to me.

Sorry I do not have experience with this leach, and can only go by what I have read, and played with in test tube.
And as you know until you get your hands dirty your not much help.
my hands do not have much to do with Iodine.

Keep up the good work you are helping me, and others to understand this.

edit spell check

 

[glondor]

I asked about this process in a general way on another forum I used to frequent in the past. http://www.physicsforums.com/showthread.php?t=491186

The inquiry resulted in this link to a patent. Not being a chemist however makes it a bit over my head as far as understanding. Is there any info in this patent that is usable to us?

http://www.freshpatents.com/Recovery-of-gold-from-potassium-iodide-iodine-etching-solution-dt20070920ptan20070217976.php

I am interested in this method for various reasons. I would like to see someone have success with it.

 

[dtectr]

glondor,
Thanks for your interest & input. The fact that they referred you to the patent without an explanation, sounds to me like they have had similar results to those posted. As I researched, the physics was clear, but the application of it was problematic.

Applying some of butcher's suggestions - i set up 2 test batches, very small, not meant to quantify PM recovery, but to see how easy it would be to control the processes - A) one with a bubbler/screen apparatus in a small glass container; B) another in a small glass container, planning only to use frequent shaking to provide agitation, as some sources suggested.

Results were less than satisfactory on many levels, but did pinpoint some specific problem areas -
1. Cementation - B) was clearly worse than A) in this regard, but neither avoided it completely. It even appeared that with B) that the iodine cemented onto the exposed base metals, as well. If this wasn't the actual case, then it must have become trapped in the thick layer of cement.
2. Recovery of iodine - the additions of lye & H2O2 must be in very accurate increments, stochiometric even, for this to work smoothly.
3. Process in general - Also, ph seems to need to be monitored very closely, as I suggested above but wasn't successful in accomplishing without a ph meter.

After reading several related patents using Halides, & my very limited experimenting so far, I believe that if someone had specific knowledge of sites/materials where either iodine or chlorine was used as a leach without the complete removal of base metals first or sophisticated controls, someone with the right set-up & know-how (maybe cyanide?) may be able to extract what was left behind, as I feel strongly that those smaller scale processors were satisfied to get "most of the gold".

If someone is able to do so, please don't forget ol' dtectr when you make some $$$ 8)

I have other ideas to follow up on, & will try to keep all apprised of my discoveries & ask that all of you following this please do the same.

EDIT: grammar

 

[Hamish]

Iodine & Gold solubilization & re-precipitation.

After 20yrs of manipulating iodine compounds to generate stable compounds its capacity to get outside the box still amazes me - iodine is not easy to manipulate and requires a solid understanding of the background chemistry that is occuring during use.

While Iodine shares many of the halide properties of Chlorine its single biggest draw is its sensitivity to other competing reactions - you will have upwards of 15 competing reactions present in a vial containing iodine and metals - more if organics are also present - pH amplifies some reactions & supresses others.

Theoretically Iodine provides a range of possibilities - practically controlling/minimizing the multiple side reactions takes time and experience.

Finally the vapours generated from Iodine systems are not to be taken lightly.

 

[butcher]

Hamish thank you for your post maybe you can help the forum out more about this Iodine leach.

 

[Goldfinger4]

I found the following (german): http://www.microchemicals.de/technische_infos/gold_aetzen.pdf

They say that a sollution of 4g KI, 1g I and 40ml water can dillute 1 micrometer of gold per minute. The KI does not react but increases the solubility of AuI in water.

 

[Hydroxide]

Okay. I stumbled upon this forum today as I searched for a refining method utilizing Iodine and peroxides. After reading five pages of posts in this particular thread, I am left with only more questions.
1) [assumption] there is no literature stating clear balanced reactions/side reactions and steps/reagents because everyone here seems completely ignorant [question] why is there not published research about this so you all don't have to guess and I don't have to work it out for myself a.k.a why no easily accessible knowledge? this is refining METALS. we have done this for thousands of years. what the hell?
2) (kind of relates to 1) why has not a pro inorganic chemist or amateur know-it-all come along and drop their knowledge bombs and lulz directed at us for not knowing/figuring the chemistry out on our own?

Anyone care to take a crack at those- or write a half-worthy method of getting this done...?

 

[butcher]

Good Idea, can not wait to see it when your done. :lol:

 

[Anonymous]

Anyone care to take a crack at those- or write a half-worthy method of getting this done...?

Yeh I will take a crack at solving your problem......and I will solve one more problem for the forum,
Are you "Anders Hoveland"? Can I please get a mod to check his IP? Whether you are or not......you need to learn some respect,or go find your information somewhere else!
You have read 5 pages,on a forum that contains thousands upon thousands,of pages of information,then you have the audacity to redicule us?And STILL ask us to help? You have a lot of nerve,and a lot of unwelcome comments. If I catch you making anymore comments like this again,I WILL make sure that those comments are forwarded to a moderator,and I will ask them to take action.A lot of us have been here for years,trying the best we can to help others for free.Even some of the people that have only been here a few months help as much as they can with the newbies.Noone on this forum deserves,or needs,your insults.

 

[stihl88]

Okay. I stumbled upon this forum today as I searched for a refining method utilizing Iodine and peroxides. After reading five pages of posts in this particular thread, I am left with only more questions.
1) [assumption] there is no literature stating clear balanced reactions/side reactions and steps/reagents because everyone here seems completely ignorant [question] why is there not published research about this so you all don't have to guess and I don't have to work it out for myself a.k.a why no easily accessible knowledge? this is refining METALS. we have done this for thousands of years. what the hell?
2) (kind of relates to 1) why has not a pro inorganic chemist or amateur know-it-all come along and drop their knowledge bombs and lulz directed at us for not knowing/figuring the chemistry out on our own?

Anyone care to take a crack at those- or write a half-worthy method of getting this done...?

I'll say this politely as i can, go and get stuffed...

 

[Harold_V]

It appears that this individual made one showing and has not returned. If he does, and runs his mouth, he's gone. Not to worry.

Harold

 

[capt_dugout]

Well as with quite a bit of our supplies, http://www.usdoj.gov/ndic/pubs1/1467/index.htm..

this would be a good point to mention the keeping of records.
I try to keep a record of all chemicals in inventory and the amounts used in each of my experiments. At some point we should all expect a visit from our local LEOs due to the ilicit use of many of the chemicals used to refine PMs.

A little time done on keeping notes could prevent a lot of notes on doing time.