Using SSN Leach--ORP Levels?

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That's the conclusion I've come to, as well....I originally posted this before getting interested in and researching froth flotation as the best means for concentration since we have a sulfide ore. Trying to learn more about the process, chemicals, etc., but there's not a lot of super specific info out there.
 
Goldhappy I don't know anything about ores so I cant help you on that. If I understand you right you want to collect small particle gold after you crush it to a fine powder? Is that right or are you trying to get the gold into solution to recover.

I got interested in recovering fine gold from mud and did some searching on the net to see how people were collecting flour gold.

If you do a search for " micro flood gold " on the net you will find a post on a gold prospecting forum. The post is quite long 17 pages. There is a guy that posted in that topic that uses fish oil to recover fine gold from dirt gravel sand and such. Might point you in the right direction.

He doesn't give out the whole setup details but he gives out enough that you should be able to figure it out through trial and error.
 
From what I understand about sulfide ore (which isn't much), the gold is locked up as sulfides and not as "free gold". A quick Google search for "concentrate sulfide ores" got me http://electrochem.cwru.edu/encycl/art-m02-metals.htm that gives different methods of extracting metals from sulfide ores. I don't know if it might help any but thought I'd post it just in case it might be useful.

bmgold2
 
I've just been wading through one of the Intec patents:

http://www.google.com/patents/US7858056 - Recovering metals from sulfidic materials

and came across this:

"To achieve a higher solution Eh ..., it may be necessary to add additional oxidant such as oxygen, air, chlorine gas, hydrogen peroxide etc

FWIW.

Hmmm.
 
Lou said:
If you have to add more oxidizer, why not just skip this lixiviant all together?
In preference to what, exactly? A little extra air/oxygen sparging (if necessary) is hardly excessive.

Lou said:
Suggestion: forget the SSN.
Is it just SSN you're against or is it all halide leaches?

Lou said:
To be honest, I really believe that physical/mechanical upgrading (milling, floatation, etc) and pyrometallurgy (smelting) are the best ways to do ore.
The mining industry as a whole, though, disagrees. Over 90% of ore is (cyanide) leached; the vast majority of low grade ores is (cyanide heap) leached - much without any preprocessing apart from possibly milling

Moves against cyanide though are turning to other leaches with the current favourite being halide leaches - for many reasons - not least of which are their ability to handle refractory ores (including sulfides, arsenates, etc), with the possible exception of high-carbon preg-robbing ores (for which preprocessing would be necessary).

If you add solvent extraction (SX) to leaching, you have the minimum number of unit processes from ore to high-purity metals. And a number of large names in the industry are already predominantly using SX (for which a pre-leach is necessary) for all their PGMs (except Rhodium).
 
In preference to not doing it on the small scale.

I'm against halide leaches for reducing ores (all of the chalcogenides). I'm against them for ores containing larger quantities of heavy elements. I'm against them for amateur use. We're talking context here.
Agreed that air is cheapest (I meant that more in the sense of peroxide). That's why it's used in mass to roast ores and why most of the large players in SA have sulfuric acid plants integrated with the refinery.


FYI, the cyanidation was implied as that happens after comminution but before smelting of the Merril-Crowe cementate.

As for SX...I've used pretty much all of them. Only one I've ever been impressed with are the carbitols and the longer chain alcohols favored by Mintek.
They all have issues and are really specific to the feed you're running.

Don't fool yourself into thinking you're going to load up a lixiviant and pull out the PMs in pure form and have not a care in the world. It might be possible to get 4N Pd/Pt out of such a leach, but unless you have dedicated recycle loops, it will not be profitable.
 
Obviously we disagree on a number of points (but not all).

The main significant difference between small and large scale is attention to detail. Large Scale needs it to be viable; Small Scale too often unrealistically expects to be fed a by-the-numbers optimum process.

Case in point is SX where an understanding of partition coefficients is in order. And sometime back I uploaded a graph to show exactly this. Appreciation of the "sweet spot" for optimum partitioning and again for the acid scrub CAN successfully produce high quality separations.

BTW, Mintek's favourite organic solvent as used in their flagship Minataur process is neither a carbitol/diglyme nor an alcohol. It's an ester.
 
It's OK to disagree--I'm interested in your thoughts on why SSN or halide leaches should be used. My thoughts on reducing ores would be that you'd have too much gas formation. Not sure that we're entirely on the same page.

Sure it's not a long chain alcohol? I would have guessed it would be ethylhexanol or something like that, but please enlighten me.

I guess my concern really is the waste volume produced from leaching. Sure, all of it is surmountable, but I think for the small operator it's too easy to get mired in getting the value out without looking down stream to all the raff treatment.


As for the SX, yes, you can scrub out a lot of the junk but it requires some pretty advanced technology (i.e. continuous, counter-current centrifugal separation--Rousselet Robatel is one manufacturer whose components are in common employ). Certain conditions must be employed given different contaminant levels. One thing I've noticed with the carbitols--high iron/selenium, you're going to have a lot of scrubbing. Sure, that waste acid can be re-used but you're just moving contaminants around at that point and have to deal with them eventually.
 
My thoughts on why halide leaches should be used?

A major reason is that they're "broad spectrum". That is, they can (potentially) dissolve pretty much all the metals etc in the ore (if it has been properly preprocessed) as opposed to, say, cyanide, which is more targetted - towards gold (and silver). Some may consider this a disadvantage, but with available ores becoming increasingly low grade and increasingly contaminated, I believe a "cover all" leach is attractive, particularly if viable separation technologies are available at the preprocessing and post-refining stages. (see Intec [Refractory] Gold Process at http://www.intec.com.au and patent US7858056.)

This makes possible additional income streams from sale of commodity "contaminants" and can decrease tailings disposal costs by converting toxic products to inert minerals.

In addition hydrometallurgical pre/leach/post processing make synergies possible where (particularly halide leach) processes can be combined (ie run in parallel).

In short, a totally hydro process makes for potentially elegant solutions BUT a broad appreciation of the science is vital.

SX techniques (if you're familiar with the background) are fairly straight-forward and needn't be technologically advanced. For example, centrifugal separation is only really necessary where the densities of the organic solvent and aqueous fraction approach each other; if they are equal, separation becomes pretty much impossible. The Minataur solvent doesn't have this problem!

Ethylhexanol is a good guess. It is superior to DBC (see patent WO2011/154603A1) in that:
- the [Au loaded] DBC phase settles very slowly from the aquaeous phase,
- the solubility of DBC is extremely high (approx 3 g/l @25 deg C), leading to reagent losses [to the aqueous fraction],
- the flashpoint of DBC is relatively low
- etc

Mintek's organic solvent has all these advantages, plus one virtually unique one, which they let slip in their Minataur description, namely it does not suffer from phase inversion. The answer should now be easy to determine for those with a reasonable grasp of chemistry. I won't post the answer on a public forum, but will let you (ie Lou) know, if necessary <g>, in PM.
 
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