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Group of Microbes Change Dissolved Gold to Solid
option8 writes " National Geographic, has a an article about a newly discovered strain of bacteria that might be used (though, as the article says, not cost-effectively) to harvest gold and other metals from seawater - a longtime fantasy of science fiction."
A lot of bacteria that are found in exotic environments, such as hydrothermal vents, aren't horribly happy when moved far away from those environments. (After all if they were competitive in other places, you'd expect them to show up more widely in the ocean).
The article doesn't say, but they may require high temperature, high pressure, or unusual mineral solutions in order to grow and do their thing. This naturally leads to higher costs, at the very least causing you to pump water through some tank designed to keep them happy. Some of the bacteria used in environmental cleanup etc, are actually genetically modified versions meant to survive in environments other than where the trait developed. Of course on the other hand we might get lucky and they do like sitting on the beach churning out gold.
If it can be made profitable I'm sure someone will do it.
You couldn't just let the bacteria escape into the ocean. It's not simply a matter of lowering a cage of bacteria into the ocean - you'd need to put the seawater in with the bacteria, leave it to work for a few days at least, then filter out the millions of tiny bacteria and put them in a box. (It's much similar to the technique used to produce insulin with genetically modified bacteria, only with gold instead of insulin.)
After all that, you're left with a tank maybe the size of a swimming pool full of sea water - and there's maybe only a milligram (or LESS) of gold in the whole thing.
Suffice to say, it's rarely worth it unless you're sure there's a whole bunch of Au dissolved in your patch of the Atlantic.
jd
Everyone seems to think these bacteria are simply coagulating dissolved gold metal, something you could do by simply by letting water settle.
They're not.
The bacteria are reducing the gold from an ionized salt form (Ag+) to solid gold. That would take a bit more effort (and a ton of water pollution) for a laboratory to accomplish.
Cyanide Heap Leeching is not necessarily dangerous to the environment until it is released to a tailings storage facility (A big pond containing the refuse cyanide solution from the process). The beauty of (hopefully) running gold ore through a microbe solution instead of a cyanide solution is that if it were pumped a similar TSF-style pond, the ore would continue to break down (not just gold, but iron and other metals too) whilst it is in the pond.
Enormous potential.
I swear, if I see another Slashdot comment with "It will be interesting to see"...