Golden Bacterial “Do”…

OK, sometimes you run into something that just makes you push back from the keyboard and say “No Way! It just CAN’T be!!” yet “The facts just are. -E.M.Smith” so you look at it again. And again.

Well, two days into it. I’m thinking this is starting to look like at a minimum a “partial answer”, and maybe the major answer. Folks have found bacteria at great depths in the earth, living on what looks like mineral soup. Now this. Could there be bugs living in the earth “do”ing This?

So, do we need to redefine “Gold Bug”?

I’ll leave that for you to decide….

http://www.communityhill.com/PolymetallicNodule/index.htm

Gold ores have also been located along the mid-ocean ridges of the Atlantic and Pacific Oceans. One such deposit was found in association with the TAG hydrothermal field at 26o North latitude on the mid-Atlantic Ridge at the 3,670 meter water depth (Herzig 1991). The gold ores in these locations are associated with sulfide deposits formed by hydrothermal vents. These vents occur when the spreading seafloor allows water to percolate down in the crustal rocks and reach hot regions deep beneath the seafloor. The heated seawater dissolves mineral in much higher concentrations than can occur in cold water.
[…]
Much about the process of precipitation of gold and other metals from these solutions is unknown, however, it is believed that some sulfur-oxidizing bacteria of the genera Beggiatoa, Thiothrix or Thiovulum play an active role in this precipitation (Zierenberg 1990).

So far, so good. Mixed metals in a bulk of sulphide, and some sulphur eating bacteria remove it, concentrating the metals. OK, I’d heard of that bit before. Now comes the “hard left turn”…

These chemosynthetic bacteria derive energy unlike their surface dwelling relatives (assuming that they are related). Instead of deriving energy from the oxidation of organic mater, or from photosyntheses, they oxidize sulfide compounds directly from the scorching hot hydrothermal liquids. How these bacteria can live and even thrive at 200o C is a matter of much discussion and investigation, but evidence suggest that these bacteria can efficiently remove gold, silver, copper, and other metals and minerals from dilute aqueous solutions.

Other theories have been proposed regarding the role of gold precipitation from ore solutions by bacteria. Recent evidence suggests that most of the placer gold found in Alaska originated from bacterial scavenging. An analysis of the microstructure of Alaskan placer gold, and that of many of the epithermal deposits around the world, has revealed a fine structure of nearly pure gold microtubuals approximately 1 micrometer in diameter. It has been proposed that these hollow gold structures are the exact shape and size of the cellwall of bacterium genus Pedomicrobia (Watterson 1992). These bacteria are believed to derive energy from the precipitation of gold around themselves. A close examination of the microtubuals reveals branching structures of smaller diameters connected to the larger diameters. This observation is remarkable similar to the observed method of reproduction for Pedomicrobia. Instead of reproducing my fission, the splitting of the cell in two, these bacteria often reproduce by budding, a process remarkable similar in appearance to the gold microtubuals (Rennie 1992). The gold casings around the Pedomicrobia are extraordinary because of their high degree of purity, in excess of 98% gold (Pain 1988). It has been argued by these researchers that much of the Earth’s placer gold deposits, have originated from similar biological processes with these or other bacteria. It is believed that the bacteria can concentrate the gold around themselves in such massive amounts because of an electrochemical reaction whereby the gold is gathered on pecifically adapted membrane receptors to which the bacteria discharges excess electrons from its biological processesthus precipitating the gold out of solution (Watterson 1992).

The possibility that certain bacteria can concentrate gold in amounts sufficient to comprise a major share of the Earth’s gold ores suggest that with the right application, these or similar bacteria may be employed in the extraction of gold from low grade deposits or solutions. Already, there are commercial applications of bacteria in the mining of gold. Specifically, the bacteria Bacillus cereus is being used by the Canadian Genprobe Company to increase the yield of gold from pyrite ores (Anonymous 1989). In this case the bacteria are after the pyrite matrix that binds the gold and prevents economic recovery otherwise. Bacterial processing of these pyrite ores is relatively inexpensive and has increased yields from an average of about 65% to as much as 96% (Dworetzky 1988). Given the affinity that some bacteria have for the concentration of gold, the question arises as to whether it might be feasible to employ such a bacterium, or one specifically engineered for the task, to scavenge gold directly from the dilute concentrations present in sea water.

Conclusion:
Even at the conservative estimates of 10 ppb of gold in seawater, there is a great deal of gold in solution in the oceans. Humankind has unearthed perhaps a total of 3.3 billion ounces of gold over the course of history, an amount equivalent To a cube of gold 55 feet on a side (Dworetzky 1988), but the sea water of the Earth’s oceans contain about 25 billion ounces of gold (Burk 1989). If the ability of some of these bacteria to concentrate gold around their cell membranes to the degree that they form massively dense agglomerations of hollow gold microtubuals, as the evidence suggests, then perhaps a similar bacterium may find a practical application in sea water.
[…]

So I’m sitting here with this mental image of a bacteria making its own gold jewelry…

That, and the pondering of what my spouse will say when I tell her that her gold is made of bug, er, um, “leavings”…
;-)

This is truly a very strange world…

Plastics. There’s a future in Plastics!

OK, so what brought me to that place? I was looking to see if anyone had done similar work on gold, as that done with Uranium, to extract it from the sea via a customized plastic. (Little did I now that bacteria had beaten us to the punch some billions of years ago…)

http://onlinelibrary.wiley.com/doi/10.1002/(SICI)1099-0518(20000115)38:2%3C269::AID-POLA1%3E3.0.CO;2-E/full

New macroporous polymers for the selective adsorption of gold (III) and palladium (II). I. The synthesis, characterization, and effect of spacers on metal adsorption
J. M. Sánchez1, M. Hidalgo1, M. Valiente2, V. Salvadó1,*

Article first published online: 21 JAN 2000

DOI: 10.1002/(SICI)1099-0518(20000115)38:23.0.CO;2-E

Copyright © 2000 John Wiley & Sons, Inc.

Keywords:
polymer functionalization;spacer arm;Cyanex 471;triisobutylphosphine sulphide;heteroatoms;metal adsorption

Abstract

New macroporous polymers with a functional group based on triisobutylphosphine sulphide are synthesized and characterized for the selective adsorption of gold and palladium. Five coordinating polymers are prepared from chloromethylated divinylbenzene polystyrene, by either direct attachement of the phosphine sulphide to the polymer or through a spacer chain that is modified to introduce O and S heteroatoms. The influence of the length and composition of the spacer chain on resin capacities is studied. The presence of O and S heteroatoms in the spacer increases the hydrophilicity of the polymers, and it is found to be essential for the adsorption of Au(III) and Pd(II). This is attributed to the coordination of the metal with the heteroatoms of the spacer.
© 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 269–278, 2000

OK, it’s not QUITE purely gold. You have to accept some palladium “contamination” as well ;-)

INTRODUCTION

Ion exchange resins have been extensively used for the separation of noble metals.1–7 Unfortunately, the low selectivity of most commercially available ion exchange resins does not allow for effective separation without the use of elution solutions.

The use of coordinating resins solves the problem when the most suitable functional group is selected, as their selectivity is higher than that of conventional resins. Over the last few years there has been considerable research into the synthesis of coordinating resins with functional groups based on ligands presenting a high level of liquid–liquid extraction efficiency.8, 9

Polymers with covalently bonded functional groups containing donor sulphur atoms (such as thiol,10–14 thiourea,8, 15–20 dithizone,8, 21–23 thioglicolate,8 thiooxime,8 thiosemicarbazide,24, 25 and 2-mercaptobenzotiazol26) have been applied for the selective sorption of noble metals. Triisobutylphosphine sulphide (TIBPS, Cyanex 471) has demonstrated a high level of selectivity for gold and palladium in solvent extraction,27–34 supported liquid membranes,35–38 and solvent-impregnated resins.39 This ligand, bound to a microporous matrix,40, 41 can selectively separate gold, palladium, and silver from base metals. The use of a microporous matrix to prepare coordinating polymers presents some problems, as the swelling of this kind of matrix is highly dependent on the composition of the solution, thus making it difficult for data to be reproduced. Macroporous polymers, on the other hand, have higher capacities and are more highly selective than microporous resins, and they are not affected by the concentration of the external solution nor by the solvent.42

The reaction between the functional group and the metal, and the diffusion43 of the metals into the polymer, determine the success of coordinating resins in adsorbing metals. Steric hindrance by the polymeric matrix and the hydrophobic nature of the polymeric ligand sometimes limit the coordinating reaction.

This article describes the preparation and characterization of different waterinsoluble macroreticular polystyrenedivinylbenzene polymers functionalized with diisobutylphosphine sulphide groups (Fig. 1), which are selective towards Pd(II) and Au(III) ions.

For the rest, hit the link. The “bottom line”, though, it that it can be done. At $1500 an ounce, I think we’ll see folks doing it. This work was likely done back when gold was about $300 an ounce. A 5 fold jump can really boost your cost / benefit ratio ;-)

Silver

As a “sidebar” note, I also ran into an interesting approach to mining silver. Don’t know yet whatever came of it, but with current prices it would likely be a ‘winner’. Maybe someone ought to test the sediments of the Colorado in the Gulf of California and the sediments of the Sacramento where it dumps into the Delta / SF Bay for metal content… I know that at one point the silver from millions of folks photographs was washing into the SF Bay in quantities high enough they warned about silver poisoning in the area around Alviso…

http://www.saudiaramcoworld.com/issue/198205/silver.from.the.sea.htm

No, not absorption, but mud concentration. This article is from 1982, so there has been a lot of price action since then.

Silver from the Sea

Written by Glyn Ford and Jonathan Simnett

In the Red Sea three years ago, Saudi Arabia and The Sudan jointly launched an experiment that, in the Middle Ages, might have been called alchemy: the transmutation of a common, worthless substance – mud – into a rare and valuable substance: silver. In the Red Sea, however, the process depends on technology rather than magic, and is extraction rather than transmutation.
[…]
What the commission is investigating are thick layers of mud – up to 30 meters (98 feet) – that have been collecting over the last 10,000 years in the deep depressions along the center of the Red Sea 90 kilometers from land (56 miles). Found beneath pools of dense, extremely hot brines-60°C (140°F)-that have formed in depressions two kilometers deep, these muds are rich in zinc and copper, smaller amounts of other metals, including gold, and — the main target-silver.

Since the 1880s, oceanographers have suspected that the Red Sea had hidden secrets. It was not until 1948, however, as the post-war boom in ocean research got underway, that the strange, high-temperature brines were found and recorded by the Swedish vessel Albatross. And it was not until about 1963 that scientists, in a burst of exploratory activity, obtained samples of the metalliferous muds.

Since then, 18 brine pools and associated mud deposits have been discovered. But from a commercial viewpoint only one of these is important: the Atlantis II Deep. The largest found so far, the Atlantis II Deep, named after the survey ship which discovered it, has a surface area of 60 square kilometers (23 square miles) and vast deposits of multi-colored muds, the consistency of soft toothpaste, containing, in the southwest basin, six percent zinc, one percent copper and 100 parts per million of silver.

The formation of these deposits came about, partially, as a result of the split in the earth’s crust between Africa and Arabia – the continuation of which may eventually turn the Red Sea into a full fledged ocean; it widens at the rate of 10 kilometers (six miles) every million years. When this thin ocean crust cracked, sea water poured onto the molten rocks below and formed salt solutions rich in metallic compounds. Carried upwards by convection currents, these solutions mingled with the colder water closer to the surface, where -since solubility is temperature dependent – the salts with the metallic components were precipitated – i.e. forced out of the solution – within the muds.

To be of commercial interest these deposits must, of course, be recovered economically. To determine costs, therefore, the governments of Saudi Arabia and The Sudan, in September 1975, established the Saudi-Sudanese Red Sea Commission to sponsor research into, and development of, these resources (See Aramco World, July-August 1981), and engaged Preussag to carry out a $28 million, five-year feasibility study.

Preparations for the study took time, of course, but by March, 1979, Preussag had readied the Sedco 445, a large mining ship equipped with a 2,200-meter steel drill-string (7,200 foot) with a suction head attached to the end of a standard oil drilling pipe. Lowered into the deeps, the suction head, with a motorized vibrating attachment, broke up the mud and pumped it to the surface; between March and June 1979, 15,000 cubic meters (68,190 cubic feet) of muds and brines were pumped to the surface for processing.
[…]
Engineers, therefore, had to be sure that the process could function in the Red Sea’s frequently rough weather. This was assured by tests run by the Warren Spring Laboratory in Britain, in which a ship’s motion simulator reproduced Red Sea conditions on land-so successfully that the commission’s pre-pilot test achieved concentration factors of eight to10 times, with an overall recovery rate of up to 70 percent and a final product containing 32 percent zinc, 5 percent copper and 0.07 percent silver.
[…]
Technical optimism aside, Saudi Arabia and The Sudan must also consider the economics – and they are as tricky as the technology. To be sure, the latest estimates of Atlantis II Deep suggest a tremendous potential: 1.95 million metric tons of zinc, 400,000 metric tons of copper, 4,000 metric tons of silver and 60 tons of gold worth some $4 billion at current prices. But metal markets are highly volatile. At today’s prices, for example, almost half the revenue would come from zinc – which has recently been steadily rising in price – while copper revenues would be much smaller.

As for silver, the target metal, commission experts have to keep in mind such upsets as the 1980 fiasco when prices gyrated wildly during an attempt to corner the market – and then crashed. On the other hand, the silver market is usually less vulnerable than other metals and now seems assured of a long-term upward trend.
[…]
So far, fortunately, detailed environmental monitoring has shown little adverse reaction. During the tests, the German research vessel Valdivia tracked the tailings plume as they were pumped down to 400 meters (1,300 feet) through a steel sewage pipe attached to Sedco 445’s bow anchor line – to be sure the tailings neither contaminated the water nor reduced light penetration, an important factor in the biology of the sea. In addition, LANDSAT satellite-sensors that have been monitoring the tailings (See Aramco World, March-April 1982) and post-test investigations showed that so far neither the coral reefs nor the fauna within the surface layers have been affected. Recently, the commission also received a report – from a Saudi doctoral candidate studying in San Francisco – saying that fine zinc particles discarded in the Red Sea develop a thin layer of oxide that makes them sink faster than originally thought-virtually eliminating danger to marine life from this source.
[…]
Glyn Ford and Jonathan Simnett are members of a research group at Manchester University in England, now studying the future usages of oceans.

This article appeared on pages 22-25 of the September/October 1982 print edition of Saudi Aramco World.

I find it interesting that they are simply discarding the zinc …

At any rate, it looks like there’s another place with loads of metals to mine.

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