There is a fundamental minimum amount of energy needed to desalinate: you can't take less energy to do it,than you could gain back (from osmotic pressure) if you allowed the desalinated water to expand a cylinder containing the residual brine. This is large. This paper is a thermal method, so it doesn't have an electricity input, but to justify their efficiency claim, they should really compare against what you could do by using the same surface area for solar panels, driving a conventional setup. My (limited) understanding is that conventional reverse osmosis is not far from the theoretical optimum, energy-wise, the main difficulties being operational (the membranes need declogging). And of course RO is more expensive than rain.

This paper is interesting, however, in directly producing crystalline salt, which is lower volume than brine and easier to dispose of, maybe even valuable.

This appears to be the same New Rochester article as 4 days ago with 20 comments.

https://news.ycombinator.com/item?id=48349507

They are talking about lithium recovery, but there is a less exotic byproduct I'm interested in. One tonne (≈ 1 m^3) of seawater contains about 1.3 kilograms of magnesium, equivalent to about 4 kg of magnesite ore. Typical desal prices are on the order of $1 per tonne. Magnesite ore goes for about $100 per tonne, so the crude magnesium in a tonne of seawater is worth about $0.40, which could account for a substantial fraction of the desalination cost. (These numbers are very rough.)

Now you ask: why don't we just recover magnesium from brines if it's so great? Magnesium recovery from seawater isn't that easy: typically you have to treat it with some kind of alkali (often Ca(OH)2), so the cost is dominated by the extraction process (your alkali is consumed!), and you're competing with a pretty cheap ore. But if you have a solid byproduct, instead of a liquid, the options for magnesium recovery might be a lot more efficient, potentially offsetting the cost.

The fourth-most-prevalent ion, sulfate, might also be interesting, at least in a hypothetical post-petroleum future where sulfur as a byproduct of fossil fuel extraction is no longer "free". Sulfate is also annoying to extract from seawater, but again if we have a solid, the rules change.

As for the "table" salt itself, I think we'd quickly saturate (!) the market.

Awesome, love seeing stuff out of Rochester - RIT or UofR or any of the nearby schools.

Totally underrated area for academic pursuits.

> without waste

...except for the huge piles of salt.

If the salt was not waste, surely people would already be extracting it from the brine and the existing methods would also be "without waste".

What about removing oil from water, have we conquered that yet?

"in mice". No, wait, that auto-reply is for cancer breakthrough.

Let me check, is that a wonderful battery ? Nope.. A promising fusion ? Neither...

Ok, so this must be the fourth kind of pseudo-wonder discovery that will maybe make it out of the lab in 20 years, if the research team managed to get scraps of funding while VC pick the next way to waste pensioners money.

Anyway, whenever they have desalinated enough water to get each researcher a pint, the round is on me.

This reads like hyperbole:

> The brine byproduct wreaks havoc on sea life when it’s deposited back into the ocean by raising the salt level and lowering oxygen in the water.

Managing return of concentrated brine should be entirely tractable in the literal ocean.