Lithium and uranium are basically the only two things that could be worth extracting from ocean water besides salt itself. It’s not crazy expensive to do it. A

Lithium and uranium are basically the only two things that could be worth extracting from ocean water besides salt itself. It’s not crazy expensive to do it. And you save a bunch of money by using the brine left over from desalination. But you can find naturally occurring brines with higher lithium concentration, so why bother with ocean water? ...in other words, lithium is plentiful, and the cheapest is from places like South America where it is extracted from brines similar to how sea salt is extracted, so the process is cheap, too (which is why we don’t really do hard rock mining of lithium any more... sea salt like evaporation ponds are just much cheaper). (Another interesting source is the brines from geothermal power stations... there are some at power stations I California that are rich in lithium and there are efforts to extract it... two birds and one stone. Example: https://www.azocleantech.com/article.aspx?ArticleID=1066 https://www.azocleantech.com/article.aspx?ArticleID=1066 )