[syhprum (OP)]

It is often suggested that a small amount of gold is dissolved in sea water with all industry shut down could the surplus electrical power be used to extract it 

[Bored chemist]

If I was going to shift gigatonnes of sea water to extract stuff from it, I don't think I'd be looking at gold.
There's something like a gram of gold (About £45) in a hundred million tons of water.

[evan_au]

could the surplus electrical power be used to extract it?

For the past century, it has been mostly surplus human lives that have extracted gold.

There are better things to do with surplus electricity - pumped hydro storage is well-proven.
- Researchers are looking at Hydrogen storage
- Reducing greenhouse emissions is another useful thing to do with surplus electricity from wind power and solar

[alancalverd]

The most useful thing to extract from seawater would be clean water. Nothing else has any real value.

[hattielucas]

I believe there is 4mg of gold/ton of water or 4mg/m3

[Bored chemist]

The most useful thing to extract from seawater would be clean water. Nothing else has any real value.

You could almost literally get your salary from sea water by evaporation, though the water is probably quite valuable too.
Both salt and water are extracted from sea water.

I believe there is 4mg of gold/ton of water or 4mg/m3

For a long time, many people thought that. That figure was widely quoted, but it's wrong.

https://www.newscientist.com/article/mg12717242-800-science-gold-in-sea-water-not-enough-to-get-rich/