Using SSN Leach--ORP Levels?

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GoldHappy

Active member
Joined
Jul 8, 2012
Messages
33
We're leaching ore (ground down to 100-200 mesh) that came from a volcanic mud flow and using SSN/butyl/oxalic for leach/recovery. We sent a 3 lb sample to a company in Idaho that leaches/extracts/tests for large companies to see if any gold could be recovered. They sent results back and said SSN was the best leach to use for our ore and they did recover gold. We've had poor results, but recently discovered the ORP is supposed to stay above 800 and preferably above 900 to put the gold into solution and keep it there. We checked and the ORP was around 600+, but never above 700. In doing a little more research we've discovered a pre-leach/pre-wash with HCL might be beneficial and enable us to get the ORP up where it needs to be. We're going to do the pre-wash today.

Has anyone had experience with getting the ORP up on SSN and keeping it up? We'd love to hear any other comments/suggestions you might have on using SSN. Thanks!
 
1) First (if you haven't already done so) get yourself a copy of the standard SSN PDF available at a number of locations on this site, including here:

http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=44&t=11738#p123484

If you look at the graphs verrry carefully, you can see residual shaded patches of the "sweet spot/area" for Eh(ORP)/Ph for most of the PGMs. Although these areas are verrry indistinct, you can generally work them out by cross-referencing with the text.

2) I believe Eh decreases with time (and use), so instead of making your SSN in bulk, mix up a fresh batch each time you need it.

3) Do a search of SSN on this site using the GRF (Google Custom) Search ie NOT the standard forum search (which doesn't work for TLA's - Three Letter Acronyms). Lots of good stuff.
 
Thanks so much. We've read the PDF a couple of times in the past as well as doing a lot of research other places. From what we've discovered, for gold ORP/Eh needs to be above 800 and the pH at around .8. Our problem in the past has been getting the ORP up to the 800+ mark. We'll see what happens this time after doing a pre-wash with HCL, and if it improves the ORP I'll post an update.

Yes, we agree. We never mix SSN in advance, always only when we need it, but thanks for the reminder.

I didn't know about the Google search on the forum. I've been trying to use the standard forum search with little to no results, so I very much appreciate your instruction on that aspect.

Thanks for chiming in!!

Gratilla said:
1) First (if you haven't already done so) get yourself a copy of the standard SSN PDF available at a number of locations on this site, including here:

http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=44&t=11738#p123484

If you look at the graphs verrry carefully, you can see residual shaded patches of the "sweet spot/area" for Eh(ORP)/Ph for most of the PGMs. Although these areas are verrry indistinct, you can generally work them out by cross-referencing with the text.

2) I believe Eh decreases with time (and use), so instead of making your SSN in bulk, mix up a fresh batch each time you need it.

3) Do a search of SSN on this site using the GRF (Google Custom) Search ie NOT the standard forum search (which doesn't work for TLA's - Three Letter Acronyms). Lots of good stuff.
 
If you look at the Pourbaix diagram on page 6 of the PDF, you'll see a minimum Eh of 0.89 (at a pH of between around 0.1 and 1.6) is required to "encourage" Au into solution. At a lower pH, a higher Eh is required.

IMO, it's well worth the learning curve time to get your head around Pourbaix diagrams.
 
With the SSN document you are referring to it also states that the most gold they obtained in their experiments 1600 mg was at a ph of 0.8 and at a temperature of 80 degrees celcious. Are you heating your leech solution?. Just a thought :mrgreen:
 
golddigger2 said:
With the SSN document you are referring to it also states that the most gold they obtained in their experiments 1600 mg was at a ph of 0.8 and at a temperature of 80 degrees celcious. Are you heating your leech solution?. Just a thought :mrgreen:

We were heating it to 120 to 130 F....we got that suggestion from a scientist who actually works for the company who makes Butyl Diglyme and has done a lot of work with SSN, recovering with Butyl and then oxaylic acid.

It was mentioned here by Gratilla that the Eh should be .89....we're more familiar with ORP numbers....so is .89 similar to 890 ORP, or something else entirely? Everything we've read has said the ORP must be above 800 while keeping the pH down to under 1 (around .8) also stated by the chemist from the Butyl company. It's been impossible to have the ORP up while keeping the pH that low. That's what we're hoping someone can help us figure out how to do.
 
Platdigger said:
What ratio of nitric to saturated salt water are you starting with? Looks like the orp should go up as well as the ph going down with additions of nitric.

7 to 1, which is supposed to be the optimum ratio. We've tried adding more nitric but it doesn't bring the ORP up enough to help, and you don't want to add to much, or it alters the ratio to where it's not working as effectively. The only thing we've found that works at all is hydrogen peroxide, but even it won't get the ORP up to anywhere near 600, much less 800.
 
I,ll ask the idiot question Lou, is this a leech that basically needs a full lab to make it work efficiently or can any fairly well informed refiner get this working in their shed?
 
Yes, iodine will bring it up if you can get your hands on the real thing. We've only been able to purchase the weak, regulated version that's on the market now. If anyone knows where to find the old iodine that is strong, we'd love to know.

Nickvc--we have made it work but it's tricky and not consistent. We've felt that the ORP being too low might be the main issue. We've had it up to 650 before.

As to dropping the pH lower, we've had it down to .2 and still not been able to get the ORP above 700.
 
I have tried to search for stateside manufacturers or suppliers but I'm not sure I'm searching the right thing but there must be suppliers there, you just need to find them. Surely the chemical supply houses would have it or could get it.
 
In former times, 18th and 19th century, they made iodine from the ashes of kelp.Those ashes contain 0,1-0,5wt% iodine, bound as iodide and iodate. I will have eyes open if I can find an old book with descriptions, - could be a nice experiment, if one lives near the sea.
 
nickvc said:
I have tried to search for stateside manufacturers or suppliers but I'm not sure I'm searching the right thing but there must be suppliers there, you just need to find them. Surely the chemical supply houses would have it or could get it.

Everyone we called said it's been banned due to meth labs using it to make illegal drugs. It can now only be sold super diluted, at least here in the states. Getting it in Mexico would be a great option if you lived near the border.
 
eastky said:
99.9% ACS grade elemental iodine crystals. 250 grams for $125.00 on ebay. Would that work?

Whew! I'm sure it would, but that's spendy! Thanks for finding it. Nice to know there's an option. Just a little richer than I want to spend not knowing for sure it's going to work after the ORP goes up.
 
I would avoid buying the iodine--not necessary and not even worth getting put on The List.

Suggestion: forget the SSN.

I'd like to know where all these ore processing companies in Idaho or Utah or Nevada are coming up with their suggestions. For small operators, if it doesn't pan, it doesn't pay.

Nick,

I think the leach is acceptable for dilute amounts of PMs when there are special circumstances (like a really clean feed on silica or ceramic). But even then, I'm not a big believer in using lots of solution for little amount of values on material that's in a porous substrate. Can you say solution volume escalation?

To be honest, I really believe that physical/mechanical upgrading (milling, floatation, etc) and pyrometallurgy (smelting) are the best ways to do ore. Otherwise you're making a bunch of kitchen sink solutions containing dilute amounts of precious metals as well as nasty base metals...just a mess. It really shouldn't be done on complex ores.
 
Thanks Lou that's what I thought.
To paraphrase what your saying, this is a total waste of time on most material.
I'm with you on low level concentrations of values in big volumes, a pain to recover all the values and a headache to safely treat for disposal.
I'm sure the big boys are playing with various ideas to recover values more efficiently but physical concentration of the values first is almost mandatory to make recovery and eventual refining possible and economical.
 
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