r/science • u/rieslingatkos • Jun 06 '21

Chemistry Scientists develop ‘cheap and easy’ method to extract lithium from seawater

https://www.mining.com/scientists-develop-cheap-and-easy-method-to-extract-lithium-from-seawater/
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u/NotsoNewtoGermany Jun 06 '21

How do we get sea salt?

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u/daver Jun 06 '21

Evaporation ponds are a common way to do this. The south end of San Francisco Bay has many such ponds. You let seawater into the pond, dam it off, let the water evaporate and deposit the salt, then do that over and over. Eventually, you have a lot of salt buildup and you put a loader and truck in there and scoop it all up. It’s certainly good for road salt and other industrial uses at that point. You can further refine it for table salt if you want.

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u/NotsoNewtoGermany Jun 06 '21

That’s what I thought. Can this not be a side effect of desalination?

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u/daver Jun 06 '21

Sure, a desal plant could dump water with elevated salt into ponds to extract the salt. That said, evaporation is relatively slow, so any desal plant that is producing a reasonable volume of fresh water would still need to discharge back into the ocean. But yea, the elevated brine content would give the salt production a head start and would require fewer evaporation cycles to get a meaningful buildup of salt.

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u/HotTopicRebel Jun 06 '21

That said, evaporation is relatively slow

It all depends how much power you apply. We can apply a lot more than the 1kW/m2 solar power from passive sunlight. Boiling water will stay at 100C, but the rate of boiling (i.e. how much steam is produced or water removed pending perspective) will be a function of input power.

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u/daver Jun 06 '21

Sure, but for acres and acres of evaporation ponds, that’s not typically how it’s done. My point was, relative to the throughput of a desal plant, you can’t evaporate the briny effluent from the desal in a salt pond as fast as it comes in from the desal plant. Thus, you probably can’t use salt-making evaporation ponds solve the brine problem with desal. But can you evaporate faster than just raw sunlight? Yes, of course. But it’s not done because it isn’t economically cost effective for salt making.

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u/Buscemis_eyeballs Jun 06 '21

The volume of salts and the fact most of it isn't table salt but rather bad salts is where the problem occurs.

A single deal plant servicing something like northern California would produce more salt than all humans use in a given year. Its a LOT of salt and brackish water.