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By subhajit_waugh
#8691
Sea water contains about 0.1-2 mg/tonne of gold dissolved in water (average 1 mg/tonne). But considering the amount of seawater available, it is a really huge goldmine! Theoretically fine, but problems were practical (which prevented profitable extraction till now). This can however become possible with the old electrolysis technique, with the only difference that the voltage difference between the electrodes must be maintained slightly less than the minimum potential difference required for electrolysis of water (yes, there is a minimum pot. difference, say 1.48 volts, below which water won't be hydrolysed. But since gold lies below hydrogen in electrochemical series, it will get deposited on the cathode!). Since it is impractical to pump millions of gallons of water, it is more practical to move the electrodes over vast regions of oceans.

With a slight modification, the propellors of ships can be designed to form the electrodes! Each of the 3 blades will be a stack of 3 blades (like a sandwich) with the sandwiched blade maintained +ve and the other two forming cathode (of course they won't be touching each other. There will be a gap of a few cm between each blade, supported by rubber/cork). The tilt of each blades will be much less than conventional propellor, so that it makes much more revolution per advancement, and hence scan the volume of water more effectively. It is practical to make each blade 1.7 metre in length, so that cross sectional area of circle formed on revolution of blades will be 10 metre square. This will scan 10 tonne of water per 1 metre moved by the ship. Considering that efficiency of extraction is only 0.1 mg/tonne, it comes to 1 mg/metre of distance covered (or 1 gram per k.m. or 1 k.g gold per 1000 k.m.) So, this may not be profitable if ship is designed only for gold hunt. But it can be a real bonus for commercial ships which has to cover thousands of k.m. anyway.

Reward: calculate it yourself (please consider this idea, it is an earnest appeal. I require your help. At least you can forward this idea to more people).
By Rishi
#8985
nydave wrote:I like this idea, i looked around on the internet some and everyone says it seems unfeasable. Will electrolysis really work becaue most people mention that using a membarane or some micro organisims are the only way that worked. check out this article: http://www.hinduonnet.com/thehindu/2002 ... 831200.htm


While electrolysis is an established process it will not work at the low levels of gold in the sea water. Separation of gold from sea water by any means will prove more expensive than the value of the metal recovered. This is the same dilemma as with alternate energy options.
rishi
#22535
subhajit_waugh wrote:But since gold lies below hydrogen in electrochemical series, it will get deposited on the cathode!). Since it is impractical to pump millions of gallons of water, it is more practical to move the electrodes over vast regions of oceans.


Sorry about reviving a very old post.

One problem with the idea is that you wont be getting gold alone, but a whole lot of other stuff. A whole lot of elements and compounds found in sea water are below hydrogen in the electrochemical series. Many of these are present in sea water in much higher concentrations than gold.
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By swimmer
#22834
The elctrolysis methos is not efficient. But the ship cruising with a collecting device is a genius one.

What needs to be done is find a chemical material which binds to gold or makes gold bind together. Maybe on a vibration frequency bases as every atom has its frequency.
By bluarc1
#23725
Your new gold from sea water(new technique) is neither genius nor new. I am 68 yrs old now and when I was 25 yrs old a friend of mine had a patent that belonged to his father. My friend being about my age so if were still alive his father would be well into his mid nineties. The patent was for a "Gold Amalgamator" I saw the blue prints it looked like a big upright tank with some electrodes in it and a charge of mercury in the bottom of the tank that could be drained off and more clean mercury added to replace that which was drained for processing. There was a very low voltage involved like 1.5 volts to excite the mercury and to cause an attraction to it in the sea water inside the tank. My friends plan was to build a boat and install the Gold Amalgamator on board and put to sea with sea water circulating through this unit collecting the gold from the sea water. This is a much better plan than yours as this unit can be mounted onto any boat or ship to work weather they were moving or not. Any type of pump could be used to move the water such as a wind or motion pump to save on electricity. You do not have anything new here and your idea pales in comparison to the one I saw in the drawings. You can get these drawings from the US patents office. I know because many years ago I did just that.
If this were a good way to get rich many others would have done this years ago. And further you would not have to go anywhere nor would you even need any sort of pump in a running river in gold country. Just save your money and buy some land with such a river going through or even a gold claim. Just set up the machine and sit back. Much better than running a ship all over the ocean.
By Joe Skulan
#25558
A problem with all of these ideas based on electrochemical deposition of gold is that gold in seawater is not ionized, but appears to exist primarily as a covalently bonded monohydroxide, with a net charge of zero. Thus gold will not move toward a cathode. This suggests another approach to extracting gold. As most metals in seawater are ionized, it may be possible to filter these out using a positively charged dialysis membrane made of a suitably corrosion resistant material, like nickel, with a molecular weight cutoff sufficiently low to prevent the passage of proteins and other organic goo. Nickel also is toxic to algae and other organisms that might colonize and clog the membrane. The filtrate would be free of ionized metals other than those found in the rare metal containing anions. Filtrate metals would primarily consist of rare (in seawater) uncharged atoms of complexes of metals, including gold and also iron, nickel, vanadium, platinum group elements. The concentrations of these elements in the filtrate would be no higher than in unfiltered seawater, but if they could be selectively removed there still would be a concentration gradient driving their continued diffusion across the membrane. Even if all the metals were removed, the concentration of gold in the resulting mix would be millions of times greater than in seawater. I do not know if AuOH(H2O) is soluble in mercury, but there may be/probably are molecular sieves that could trap it.

In an actual device, the filtrate would have to be processed rapidly so that a sufficient volume of seawater could be processed to extract significant amounts of gold and other metals, but also to prevent the buildup of a large electrical potential between the filtrate and seawater. I'm operating at the very limits of my competency here, but it seems to me that the energy requirements of such a setup would be modest, with the work being maintaining a concentration gradient in an extremely dilute solution. Energy would be needed to supply current to the dialysis membrane and, probably, to operate a pump to force the filtrate through a molecular sieve. A one square meter solar electric panel should be enough. If the device were simply left to drift in an ocean gyre for a few years and then collected, the fact that it only operated 40% of the time wouldn't matter.

The question, of course, is whether enough gold could be recovered to make the operation profitable. A dialysis device with its power supply probably could be built for $1000, and placing and retrieving them from the ocean would add to that cost. But let’s say the break even point would be on oz of gold per device. The concentration of gold in seawater is about 13 ug/m^3 (not 1.3 mg), so to extract one troy oz of gold you would have to process about 2.3 million M^3 of seawater. If the device could average 10 liters/second it would do that in about 7 years. That's a tall order.

But why all the emphasis on gold? There are other valuable metals in seawater. From the same amount of water needed to produce one oz of gold you could extract 21,500 oz of silver, worth 200 times more than an oz of gold. A silver extraction device operating at a much more reasonable 0.5 liters/second would break even in about 1.5 years. If you put the devices in places heavily polluted by silver, such as the south end of San Francisco Bay, yields could be much higher, and break even times much shorter. Sediments in the area contain ore-grade Ag concentrations, from years of dumping by photographic industry. Plus, the dominant species of silver in seawater is an anion, AgCl-, which is ideal for a dialysis technique.
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By emil.ekdahl
#25707
Clorox in the bay area manufactured chlorine bleach from sea water using mercury cells (until outlawed). Gold was a byproduct of these mercury cells. Since mercury was on the bottom of these electrochemical cells. All metal cations would collect into the mercury forming amalgam - primarily sodium, but over time plenty of gold would collect. Though if gold were the primary product it would not be economically feasible. As a secondary by product the first being chlorine bleach and second being sodium hydroxide then it was profitable.

It may be possible to invent some electrochemical device. Remember Fritz Haber's 1920's prediction that it is not economically possible (thus shutting the door on all serious research) is based upon pumping cost. Eliminate the pumping and it might be profitable. like large surface area placed in an ocean current...
#25831
Hello, I am Subhajit Waugh. It's me who made the original post. I want to add something more (after doing a lot of study & research, I feel that this post needs to be updated):
This process can be made much more profitable by a simple process.
Consider this: there are 3 primary ways of separating U235 from U238. Forget the diffusion & centrifugal processes. 3rd method: You shine a laser light of exactly matching wavelength to selectively excite U235 (it is easy nowadays, since we wave Cu vapor laser & dye-lasers for fine tuning)
Plan: Just like a Sodium vapor lamp, it is possible to make a gold vapor lamp, which will selectively excite Au ions, thus requiring even lesser voltage (I believe it will be lesser than the critical voltage which starts breaking H2O into Hydrogen & oxygen). ....the gold vapor lamp would shine directly on the propeller blades of the ship (which would act like electrodes). It will to possible to filter/scavenge through billions of tonnes of seawater that way. This process/step is critical because as the concentration of ions (Au in this case) start decreasing, the voltage required. to extract starts increasing. But selective excitation should help a lot
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