# Working with bacteria to extract Silver from ore samples



## TROBISON (Feb 27, 2012)

Hi I am new to the forum so I hope this is an interesting topic for the group.

I am an avid rock hound and I have a mountain of high grade ore that was not suitable as a samples (wide variety but mostly chalcopyrite and acanthite/argentite on a quartz matrix).

My wife has been hounding me to do something with the pile so I decided to try an experiment with microbal leaching techniques. 

Equipment:

Built reaction chanber out of plastic drum by installing drain on bottom of drum then filling bottom with inert plastic beads providing a porous substrate that allows fluid (lixiviant) and oxygen to pass.

Installed 6" perforated pvc pipe with grate on each end standing on end in the center of the drum to maximize air available to the center of the ore heap.

Installed heat exchanger (coiled plastic pipe connected to solar water heater) goal is to raise internal heap temprature to 100-120 def F. Cheap timer on circulating pump runs 7 hours a day from 10 am to 5 pm (hottest part of the day.

Crushed ~ 500 lbs of samples to a uniform 1 inch size and filled drum layering fine material from crushing activity on top of heap.

Set up tub under reaction chamber to catch fluid that passes through the ore heap.

Filled tub with water (15 gallons). 

Hooked up circulating pump (Swamp cooler pump) and cheap timer to pump the water from the holding tank over the ore in the reaction chamber. Pump is set to run every 6 hours for 6 minutes.

Current Status:

Got permission from BHP Copper corporation to gather water and solid samples from the tailing ponds at pinto creek refinery. 

Mixed (Innoculated) water in holding tank with tailings and started lixiviant circulation. 

Started solar heater.

At startup internal heap temperature was 51 deg f and pH of lixiviant was 8.2

Experiment has been running for 7 days. 

Internal heap temperature now 88 deg f and pH has gone acidic @ 5.1 and mild Sulfur Odor can be detected. 

This material (ore mixture) should contain minimum 15 to 17 onces of silver per ton

The microbes should convert the metal Sulfides to Sulfates going into solution in the lixiviant. This appears to be happening because Copper easly cements out of the solution using scrap iron but I am not getting any silver when I throw in the copper scrap.

Question for Forum:

Does anyone have experiance with bioleaching for Silver in a complex argentiferrous ore? Will the silver leach out when the pH gets lower or is heating of the lixiviant required to cement the silver out of the solution.

I am worried that mixing the ore made it too complex (Antamony, mercury, trillium, barium will also be present in small quantities) and this is retarding the microbes ability to use Ferrous Iron to catalyze the silver sulfide.

Thoughts?


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## DONNZ (Mar 16, 2012)

My search / microbe miners:

Been going on a long, long, time. Just barely scratched the surface on the subject. And I'm not very keen on chemicals that can kill you.

Gaining speed in S. America due to low water supply. When using this system one just keeps using the water over and over. 
A three vat system I would think. Month one, two, and three. 

Read a paper out of Hawaii a couple months back on this subject. Can't lay my hands on it or remember the my search.

The one thing that stood out in this paper was the fact those little microbe's love to party. Binge drinkers. They thrive and multiply and are very happy swimming around in, 

wait for it:

Wood Alcohol. 

Also read an article in Omni Mag. / Life by Dr. Bernard Dixion.

This was published in Sept. 1979. I have that copy.
In it he touches on copper,nickel, gold, and uranium. I'm sure silver would be no problem. If you have the raw material you have the micro.

So many ongoing projects, I'll scan it and pull out the goodies. 

Later.


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## AztekShine (Mar 16, 2012)

I don't kno much about this subject but I am a Mycologist. 110-120 seems like a high temp. Especially sense you gathered the microbes from a creek I would match the creek temp. But like I said don't kno about these bacteria. Any links would be helpful. I gota go but I'll be back, this is very interesting


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## AztekShine (Mar 17, 2012)

Here's a link look at the patents...
http://yestech.com/tech/gold1.htm


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## jack_burton (Mar 17, 2012)

It sounds interesting, but patents have been on file for almost 2 decades and it doesn't seem like this has hit the mainstream. Truly viable? I dunno.


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## DONNZ (Mar 17, 2012)

http://www.yestech.com/tech/gold1.htm

*Cyanide-free Biocatalyzed Leaching of  Gold and Silver Ore*
These bacteria can use wood alcohol, grain alcohol or vinegar as food,

I should start a folder for my searches. Usually I save the search instead of individual articles as in this case. 

http://www.bing.com/search?q=leaching+silver+oar&qs=SC&sk=&pq=leching%2520sil&sp=1&sc=4-11&form=QBLH

And as Dr. Dixion points out in his article:

"A typical application, as pioneered in the US by Rio Tinto, is heap leaching. Pieces of ore are simply placed on an impervious surface and sprayed with water. There's no need to add T.ferroxidans; it will be there already."

We have a recipe for growing microbes, where to find them, and their name. 
This would be an interesting experiment, One million microbes can produce one gram of gold or silver, but I fine no time line. 
Wonder what a billion can do.

I have a scan of Dr. Dixion's article but not wishing to infringe on copy writes I can't post it. 

Then again, no one might want it.


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## AztekShine (Mar 17, 2012)

Yeah when I mentioned the patents I was refering to the fact that they were a dead end. Maby if you found a super strain of bacteria it could work. The 100-120F temps you mentioned are what I don't understand. After extended periods at 120F most microbes will be pasteurized.


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## DONNZ (Mar 18, 2012)

Here's what I got:

I'm very sure heat is not necessary, grow many microbes, and set up 3 tanks or trays about 2 to 3 months apart to establish some kind of timeline. Feed them wood alcohol, grain alcohol or vinegar periodically. Might add a circulation pump. Maybe a small electric charge, that might excite them, it would excite me. Find out what temperature they prefer and perform best at. Experiment on a small or micro scale. Who knows, someone here may come up with a brake throw. 

This is being used in Bolivia and Peru according to the TV program aired within the last 30 days. Can't remember the program, World News, PBS, Euro News? 

excerpts from: LIFE by Dr. Bernard Dixion (Sept. 1979 OMIN Mag.)

A typical application, as pioneered in the US by Rio Tinto, is heap leaching. Pieces of ore are simply laced on an impervious surface and sprayed with water. There's no need to T. farroxidans; it will be there already. the bacteria promote a variety of chemical reactions. solubilizing iron and copper and generating sulfuric acid. Copper, for example appears as copper sulfate. 
There are several ways of recovering the metals afterward. One of the easiest is "cementation," in which copper-rich waters are circulated over bits of iron and can be scraped off from time to time.
The Western Mining Corp. in Australia, has announced a microbiological method for extracting another valuable metal, nickel, from low-grade ores. the rock is sprayed with a diluted solution of sulfuric acid containing T. ferroxidans. Percolating through the ore, the liquid extracts high concentrations of nickel, which in this case is removed form solution by electrolysis. 
In the USSR, researchers at the Irkutsk Institute of Rare Metals have claimed similar success in microbial mining for gold. 
Uranium leaching is even more promising, in view of the rapidly escalating cost of this matal and the ease with which bacteria scavenge it from the most unpromising materials. Although most uranium is extracted with chemicals, less rich ores are already being treated with microbial methods is apparent throughout the industry. 
Work at the Elliot lake area in Canada is typical. about 30 percent of the ore there is left behind to support the roof of the workings. Afterward, water is pumped down, T. ferroxidans begins work, and, eventually, over 90 percent of the residual uranium dissolves. 
Taking this stage further, mining engineers are beginning to see microbial mining as a total replacement for orthodox techniques. Water containing the mini-miners can be pumped into deep rocks and then can be brought back the surface for metal recovery. Miners' lives are not put at risk, damage to the environment is negligible, and there are enormous savings in transporting, crushing, and grinding the ore.


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## AztekShine (Mar 18, 2012)

This is a wonderful idea. I would like to do my own test on this. If just for sh!ts and giggles. 

This bacteria may be capable of acting faster at higher temps I don't kno. But if it's natural and aerobic prolly not much above 86 degrees. Anaerobic bacteria thrive at higher temps tho. 

My big question is that if the ore is not crushed how can it penatrate te rock in any Ammount of time? Seems crushing to atleast 1" pieces would be called for.


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## DONNZ (Mar 19, 2012)

Would like to hear back from TROBISON. 

Hope he wasn't discouraged when he received no feedback on his experiment.
Feb. 27 - Mar 16 was a bit long for a reply. 
It took me that long to remember and where to fine something that might help.

AztekShine: I would say the smaller the faster.

If I had some paydirt, I do believe I'd give it a shot.


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## Barren Realms 007 (Mar 19, 2012)

You might want to look into the organizams found in the hot spings at Yellow stone and see if that gets you any where.


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## AztekShine (Mar 19, 2012)

That's a brilliant idea, 007!


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## AuExplorer (Apr 5, 2012)

Hello, 
I have been briefly fringing this subject for years now. My interest has been in decomposing Fe/Cu/Au sulphide deposits similar to the bio leech program going on in Arizona. It has been my understanding that the micro-organism is obtained from the source material and then given the ultimate favorable environment for reproduction. I have no practical experience in bio-leeching but have always been fascinated by the concept. Let me know if you have success in your extremophile cultures. I just might try :idea:


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## AztekShine (Apr 5, 2012)

So the bacteria are extremeophyle's? Then they would be high temp. Makes sense.


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## AuExplorer (Apr 12, 2012)

You might want to consider a roasting process , that is milled to the optimum classification and then introduce the colony since you have it established. I would use this as trials and start a couple of different lab quality runs if possible. The elements present in the material can be driven off. I have not handled the material and I am "flying blind" at the best of my ability under the circumstances. This is only an avenue to investigate.


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