When will mining seawater for elements be affordable?

[Ophiolite]

Reading through the third of the links I was interested to learn that, in addition to salt, some substances are already being extracted from sea water. (Comments below, in italics, taken from the link) It seems the answer to the OP is "mineral extraction is affordable now and is practised. However, it is not widespread."

Bromine:
Large quantities of bromine were extracted from seawater in the early to middle 20th century using the ‘blow out method’.

Magnesium:
There are several forms of magnesium that have historically or are currently being extracted from seawater including magnesium metal and various magnesium compounds. Magnesium metal was once predominantly produced from seawater . . .there are a number of facilities around the world that produce magnesium compounds from seawater including facilities in Ireland, Japan, Norway, and the USA.

Potassium:
Potassium compounds are currently produced from seawater as a byproduct from solar salt operations, which makes up a small percentage of worldwide potassium compound production.

 

[Sherwood Botsford]

The issue is cost.

Example: My well provides water that has 120 ppm Na, 25 ppm Fe, 74 ppm Ca...

The iron is easy to separate: Expose it air, and ferrous oxide goes to ferric oxide, and plates out on my toilet bowl. (I may have ous and ic reversed) Sodium requires removing the water, then separating the sodium from the carbonate/bicarbonate ions. This process would also yield calcium, minor amounts of magnesium. (My aquifer is glacial till/sandstone/limestone.)

Sea water runs about 3 percent salt, a quarter of that is sodium, so the sea runs about 7,000 ppm Na. At 60 times the concentration, you can guess where people are going to go for it. Not my well.

There are very small quantities of gold, platinum, iridium etc in sea water. But very is the key word. Really really tiny amounts. Look for metals that cost bucks per pound instead of cents per pound. Chromium. Copper. Vanadium.

So three things are needed:
* Ways to passively get the ions out of water. You need a chemical that binds specifically to the ion you're chasing, or to a cluster of ions you'd like, without getting it filled with junk. E.g. a Copper/Silver selector would be fine, as long as it doesn't pick up something really common like iron.
* A way to bind this chemical onto a surface.
* A way to very cheaply move LOTS of water past this surface.

Ideally it could work like this:

Build a raft and anchor it in a fairly slow ocean current. Make sure it's hurricane proof.
Coat some form of sheet or mesh with the ion selector material.
Hang the sheets in the current.
Periodically process the sheets, removing the ion and process the concentrate.

The scale of this is immense. You are filtering cubic miles of water.

While this is certain extraction, I'm not sure if I would call it mining.

 

[Nik_2213]

IMHO, there are a very-few locations where multiple-mineral extraction from sea-water *may* prove cost effective. Isn't there a plausible proposal to pipe sea-water to the Dead Sea, use the 'hydraulic head' to desalinate part of the stream by reverse osmosis, send the brine 'waste' to the existing salt-pans and chemical works ??

IIRC, a lot of the sea-water 'mining' notions came to grief when initial laboratory deposition rates of 'sea-crete' failed to scale. FWIW, I've since read of the process being used on a small scale to remediate coral reefs, stabilise and 'seed' storm-bared sea-beds. A combination of solar & wind power suits the current requirements, and natural interludes allow diffusion to equilibrate the 'sea-crete' internals...

 

[r8chard]

Before you bet your rent money on mining seawater or asteroids you should consider the last half-century of the Silver mining and marketing.

And how the Hunt brothers turned a billion dollar inheritance into millions playing the corner-the-market game. Silver was booming between coinage and film. However governments decided to screw with coins. And technical progress such as digital cameras made film obsolete.

That sound you heard was the silver market crashing. You might want to rethink betting on centralized fusion power and check out what's new in decentralized power systems.

Maybe not as productive or efficient as fusion power. However, do you want to depend for your energy needs on a distant monopoly or on something you yourself can control?

 

[Drakkith]

Maybe not as productive or efficient as fusion power. However, do you want to depend for your energy needs on a distant monopoly or on something you yourself can control?

I like to pay a company to provide me with electricity and to take care of all the maintenance, upgrades, and other things that I either can't do or don't want to do. In thirty-plus years the absolute worst thing that has ever happened to me has been that I've lost power for, at most, perhaps a day or two. I'd say that's a pretty good track record for the various power companies. I can't imagine how having control over my own power generation would be any better.

 

[jim mcnamara]

@r8chard do you have citations for any of the claims in your post? @Drakkith simply said what he personally would like, not that electric companies are monopolies. Some are, yes. Can you name several hundred companies in the US that are owned by the customers? Come back when you can do that. Time to learn!

Please do not express flat statements that are not correct. Thanks.

 

[jim mcnamara]

This thread is off track. Closed.