Extraction of gold from seawater

A. Hi, Rider

You have assumed that none of the gold will get through the ultrafiltration membranes of the desalination plant. That may be true, but I'm not so sure. Thanks.

Regards,

 Once saw a Micky mouse comic where the pump just made enough gold to pay for the fuel. (45 years ago) Gyro Gearloose cleverly decided to use the pump to push his boat through the water. Obviously I was impressed by the lateral thinking of the comic book writer. Sometimes it's just a matter of looking at things in a new way. We will extract gold from seawater when it is economical to do so.

A. I may have misunderstood. I thought that seawater gold was bound to a salt, and the desalination process was designed to remove salts. UCLA has developed a new reverse osmosis process they are calling M3. They claim this process is 95% efficient in removing salts downstream from agricultural runoff. They also say this is a very portable unit, in that it can be carried in a van. My questions to the board is; what is the minimum parts per million for seawater gold extraction to be practical/profitable, and how close are we today to that concentration? I am not looking for a get rich scheme, I just think that as filter technology improves, we will discover new ways to apply those filters. This does include mass production of the various components of seawater. To the detriment of the commodities markets for sure, but to the gain of nearly everyone else.

 Hi, Kevin. This site is for technical information, camaraderie, and fun. If you have any info which you are willing to divulge, please do. But this isn't the right site for postings advertising products & services (we get several hundred spams every day), nor for complaining about other posters ("Render unto Facebook..."). Thanks. Good luck!

Regards,

A. Re. Gold from seawater. My understanding is that when gold enters seawater it converts to gold chloride and is chemically locked into the salt, therefore I doubt that filtering is viable. The gold must then be extracted from the salt chemically or electrically. There are various chemical precipitants available that do that task, such as iodine, trisulphates, etc. Many ships have systems that convert seawater to freshwater by evaporation. The resultant salt sludge is returned to the sea. How much gold chloride is being dumped every day? I have seen gold extracted from coarse rock salt using trisulphate. Google will provide many links for gold precipitants and methods. Good luck. Bob.

A. I have been following the mining gold from seawater since 2009. Gold at $1700 per oz., makes it seem as if there should be some way to do this economically. I have thought of using a bio-degradable ion such as lactic acid and sending the seawater thru an electronically charged magnetized container, and vibratory system. My question is would this would help solidify the gold and attach itself to the magnetic surface for a minute time to facilitate harvesting?

A. I think the point is still being missed. I don't see any way to economically "mine seawater". I think the only way to extract the gold is to use the concentrate from a desalination process. I have looked at the attempts of getting gold from harvesting sea salts, and the concentrations just aren't there, but the slurry from modern desal might work, as it is enormously concentrated already. I am not doing the math, but the equation should be pretty straight forward: the price point of gold, the cost of extraction, economy of scale, the concentration needed to break even. Some bright person is going to graph this out. I also wonder if there are other uses for the concentrate, or ways to take out more of the unwanted, leaving just the gold bearing salts. I did a school project(25 years ago) that put a small DC current through metal screens and calcium solidified on the screens, sort of like concrete board. Just a thought.

A. Of course the metal screens were in seawater, and the electrolysis produced a calcium deposit that was pretty uniform, and very strong. I always thought there might be something useful there as this seems to be a slow but green way to make a pre-fabbed building panel. I said before I am not looking for the get rich quick scheme, I am just following a thought experiment from my high school days. LOL. I also am not working on any of this, just thinking. Sometimes I sit and think, and sometimes I just sits.

A. I have an Idea for deep ocean in the pacific. It involves Biospheres for providing food for the planet and fuel they could use the temperature difference between surface and the deep to run heat engines. Extraction of nutrients and desalination of water could lead to gold as by product. landfills and the garbage it contains are an immediate investment because there is currently technology for separating out metals while creating the fuel we use in most vehicles today and or make other crude oil products. all powered by the natural gas it also creates. It's called a thermal conversion unit and it could scale up or down as needed.

A. Gold attaches to Polymers...

www.cleanwayusa.com/index-metalzorb.php

www.dynaphore.com/

If the water being treated contains for example 1 ppm gold, 8200 gallons will have to run through the bed of absorbent to produce one troy ounce of gold. At saturation, a cubic foot of the Sponge will hold about 4-5 ounces of gold.

This is the patent and info on the polymer sponges...

www.freepatentsonline.com/5096946.html

Hi Nick. Thanks! I wasn't familiar with shaping ion exchange resin into dice cubes and moth ball shapes like that so that it can serve as self-filtration and be retained in simple mesh bags. That is very good to know.

But it's a long way from a practical way to recover gold from sea water :-)

For one thing, there is nowhere near 1 ppm of gold in seawater, so instead of needing to process 8200 gallons to produce an ounce of gold, you'd need to process 6,800,000 gallons. And the resin would be filled with other metals and ions, and fouled beyond recognition long before you approached even a tiny fraction of a percent. The gold in seawater seems safe from our technology for a little more while.

Regards,

A. I believe that if gold extraction from seawater is ever used it would be as an offshoot from purification of seawater, and then only as a cost offset. More than a need for gold, there is a very large need for purified drinking water. One method of obtaining purified drinking water is through a desalinating process, which is also expensive. The effluent brine solution that results is currently considered a waste product. While the concentration of gold in seawater is impractical for mining, the concentration would be higher in said effluent. At some point the price of gold may be high enough that the possible electrolysis of gold may offset a substantial percentage of the cost of the whole water purification process.

A. Hi Adriel. Please give us a link to the technical article that you read that proposed it for gold extraction. All I see are a bunch of ads for desalination equipment. Thanks.

Regards,

A. Hi, Guglielmo Marconi developed experiments to extract gold from sea water; here's the link:
http://lateralscience.blogspot.co.uk/2013/04/marconi-gold-from-seawater.html

He used coal in a bag of copper wires, cables with electric waves (which type and tension is unknown) and plunged into the sea from the boat. Several hours, he showed his daughter the gold particles attached to the bag.

He apparently abandoned the test; apparently by its many responsibilities, and died a year later.

I hope that is helpful.

A. Why don't you try to google "Gold Fractionation". The kind of gold in the sea is called a nano particle, it is not dissolved; nano particles behave differently than regular small bits of a substance. Gold nano particles are used extensively industrially and as such their manufacture and suspension is quite well documented. You might be better off to try and gather the small bits of gold at the delta of a river where there have been gold placer operations. Alternatively if you go to youtube there are videos about placer mining bags of sand obtained from various big box home building stores. Some good success has been obtained and you could try using electrolysis on the wash water to get the nano gold if home panning actually works out.

A. A METHOD OF EXTRACTING GOLD FROM SEA WATER was patented 1n 1900

(Application filed Feb, 5, 1900.)
"Patent US679215 - Method of extracting gold from sea-water"
-- visit https://www.google.com/patents/US679215

A. 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 hydrolyzed. 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. This process can be made much more profitable by another simple process (which I explain later).

With a slight modification, the propellers 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 propeller, 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 meter in length, so that cross sectional area of circle formed on revolution of blades will be 10 meter square. This will scan 10 tonne of water per 1 meter moved by the ship. Considering that efficiency of extraction is only 0.1 mg/tonne, it comes to 1 mg/meter 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 have to cover thousands of k.m. anyway.

This process can be made much more profitable by another simple process.
Consider this practical concept: 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)
https://en.wikipedia.org/wiki/Atomic_vapor_laser_isotope_separation
PLAN: Just like a Sodium vapor lamp, or Copper vapor lamp/laser
(https://en.wikipedia.org/wiki/Copper_vapor_laser)
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). 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. And besides, it will help to dissociate (charge) neutral covalently bonded gold-monohydroxide.
[Let me explain and elaborate about the gold vapor light. It can be built using same technique as that of a copper vapor lamp. Actually, copper vapor laser is one of the few lasers that can be home built!
Since using pure gold vapor lamp is difficult to construct, because of the extremely high temperature, necessary to create gold vapor, therefore, gold halides, like gold chloride or gold bromide or gold iodide may be substituted, since they form vapors at much lower temperatures]

A. That's true; the separation voltage of gold is under the hydrogen -- but this voltage is in relation with the concentration too.
Mining only gold from sea water no, impossible but perhaps possible more metals together. And important you must collaborate with other industries too -- for example, PVC.

  Good point, Istvan. We wouldn't be able to electrodeposit brass if it were solely a matter of potential, because zinc is about 1 volt more negative than copper. The zinc portion can be electrodeposited only because the copper is complexed to such a strong degree that the free ion concentration is ridiculously low so zinc plates out instead.

I believe the Nernst Equation will explain the truth of your assertion to readers.

Regards,