Bioleaching arsenopyrite and other sulphide based ores.

[oregonmp03]

I hope you guys figure this out. Your way past my understanding of chemistry on this. I was working an area near me and came across some of this arsenopyrite. I was exploring some old mines and didn't bother, at the time, to read up on if it was free gold or sulfides. After I found the mine i decided to do some reading and of course everything I've read is it's just plain bad stuff. I had my detector on me at the time and packed out the hardest hitting rocks I could find. They all hit high in the 70's and 80's on my detector. Reading a little more on old reports the mine assayed at .75 to 3.5 ounces per ton back in the day. So that said if you need some good samples let me know as I have some good stuff but will never deal with it myself as it's too dangerous for me. It's pretty much coal black with rusty quartz running through it. Good luck,

 

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[SaltwaterServr]

I hope you guys figure this out. Your way past my understanding of chemistry on this. I was working an area near me and came across some of this arsenopyrite. I was exploring some old mines and didn't bother, at the time, to read up on if it was free gold or sulfides. After I found the mine i decided to do some reading and of course everything I've read is it's just plain bad stuff. I had my detector on me at the time and packed out the hardest hitting rocks I could find. They all hit high in the 70's and 80's on my detector. Reading a little more on old reports the mine assayed at .75 to 3.5 ounces per ton back in the day. So that said if you need some good samples let me know as I have some good stuff but will never deal with it myself as it's too dangerous for me. It's pretty much coal black with rusty quartz running through it. Good luck,

View attachment 1417830

If you crack one of those rocks open, what does it smell like?

 

[oregonmp03]

If you crack one of those rocks open, what does it smell like?

My sniffer is broken due to a cold so I honestly couldn't tell you.

 

[SaltwaterServr]

My sniffer is broken due to a cold so I honestly couldn't tell you.

View attachment 1418077

I can see the what may be some siderite, limonite, and hematite. I don't really see any arsenopyrite. The easy way to tell is to crack it open. If there's arsenopyrite you'll be able to smell the garlic.

 

[Mad Machinist]

Bump back to the top for further research.

 

[Twobrothers]

Heres my knowledge dump on sulfides. Some material for brainstorming and food for thought.
Sulfide ores in order of prevalence in my district:

Iron sulfides ~50%
Lead sulfides ~17.5%
Zinc sulfides ~ 12.5 %
Arsenic sulfides ~ 10%
Copper sulfides ~ 10%

In order of reactivity to natural oxidative processes (sunlight, water, oxygen, bacteria) Most reactive to least reactive:
1) Iron Sulfides (FeS) "Iron pyrite"
2) Arsenic Sulfides (AsS, FeAsS) "Arsenopyrite"
3) Zinc Sulfides (ZnS) "Sphalerite"
4) Copper Sulfides (Cu[SUB]x[/SUB]S[SUB]y[/SUB], and Cu5FeS4) X and Y values range a broad spectrum from 1 to 39 " chalcocite, covellite, bornite, others, ect"
5) Lead sulfides (PbS) "Galena" Almost always contains traces of silver disseminated within the matrix ranging from trace values to 1% by weight


Sulfide ores react slightly differently when exposed to oxygen, water, and natural processes based on my observation.
When I mean react I mean, rot, or oxidize. Some sulfides crumble, crack and exfoliate, opening up the inner un-oxidized layers causing it to rot.
Others form a passivization layer after the outer surface oxidizes leaving the inner sulfide encased in a water proof, oxygen proof environment.

-Iron and Arsenic sulfides react fairly similarly. They appear to decompose at similar rates and rot through quite thoroughly with enough exposure to the natural processes (O2, H20, sunlight, natural bacterial processes). As long at they are not encased in water proof, airtight host rock they crumble and exfoliate all the way and do not form impenetrable passivization layers
Lead sulfides

-Zinc sulfides. Not a lot of experience observing them but it appears they also form a passivization layer to some extent but not to the same extent as lead sulfides. Zinc sulfides appear to crumble apart (rot) eventually, but much more slowly.

-Copper sulfides. I don't have enough observation to say definitively but it appears that all factors equal they oxidize at a less rapid rate than iron and arsenic sulfides. Can't say definitively based on my observation but I don't think they form impenetrable passivization layers.

-Lead sulfides DO form a passivization layer. Once the exposed sulfide layer rots away a layer of metallic/ oxidized layer of lead is leftover that effectively inhibits further oxidation.

 

[Twobrothers]

Thoughts on Bi oxidation of sulfides:

Thoughts on Bi oxidation of sulfides:

Based on the natural processes I've observed You need the right balance of:
-water,
-oxygen,
-bacteria,
-and to some degree sunlight.
Sunlight isn't a must and I don't know if its the UV or the heat but it seems to help. Under naturally occurring circumstances the process to thoroughly oxide ore can take years.

My thoughts on the subject of artificially increasing the speed of oxidation are fairly conservative, low tech, and low investment:
1.) Crush material. Maximum diameter size dependent on the host rock and what it takes to expose the sulfides.
2.) Lay down an impermeable layer of plastic in a shallow pit.
3.) Combine the crushed ore leach material with a mixture of charcoal and organic material ("circulation-" "rotting-" or "bulking-" material). What for to wick water moisturizing the layer and provide air circulation. Charcoal to help absorb, lock up/ re-mediate nasty byproducts. Charcoal won't bacterial decompose. Shredded mulch, straw, wood chips, something for bacteria to culture on. Rotting organic material releases humic acids which assist in decomposition/ weathering of rock. 50-50 ratio of ore to circulation/ bulking material. 30-70 for the charcoal to organic material mix.
4.) Layer six to eight inches thick, wetted down enough to keep things moist, but not soggy.
5.) Raked once or twice a week.

Kind of like a modified patio process, leaning more towards a bacterial, rather than chemical process
Provided warm, moist conditions can be maintained 6-9 months of the year you may expect complete oxidation turn around in 1 year.
Float/ wash off organic material. Need to formulate appropriate disposal plan for the used "circulation-" "rotting-" or "bulking-" material. Hopefully by using natural processes any hazardous compounds generated will be in a stable less toxic form. Re-use it? Mulch organic material away leaving charcoal? Dispose of charcoal as hazardous material?

Other thoughts:
-Periodic additions of mild nutrient solutions (nitrate) to speed bacterial action.
-A mild freeze-thaw cycle would be beneficial if environmental conditions are available for that. Not too cold for prolonged periods because that will slow down the process. 60-70 Fahrenheit daytime temperatures to low 30 Fahrenheit nighttime would be nice.
-Site selection is important. Wherever however an area/ contingency to absorb any acid, and-or iron/arsenic runoff.
-The particle size is somewhat dependent on the host material. As long as the sulfides are at some point in contact with oxygen and water. Not all the sulfide minerals are applicable to the process. I would say Iron and Arsenic sulfides are most amenable to the process.
-Lead Sulfides probably have to be crushed to quite a fine size. Probably not real practical for profitable bio leaching.

Thats my brainstorm. Something sweet about the the smell wafting from my sulfide pile after it rains. Mmmm. Smells like money!

 

[Mad Machinist]

Thought you all would find this interesting. Seems the "toxic legacy" of mining is coming to an end.

http://www.biomining.ca/elements-bi...oration-aims-turn-mine-waste-valuable-metals/

 

[Mad Machinist]

http://www.sgs.pt/~/media/Global/Do... Recovering refractory resources EN 13 09.pdf

Put this link here from another thread to keep this all in one place

 

[Mad Machinist]

Back to the top. I am still working on this.

 

[AnnaMountain]

Excellent thread guys, thanks for sharing

 

[Mad Machinist]

Excellent thread guys, thanks for sharing

Your welcome. I hope you find it useful. If you get a chance read the other thread I posted on recovering lead and elemental sulfur. I also have one to post on pressure oxidizing arsenopyrite when I get more time.