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Comment by 867-5309 | Hacker News Reader

strange how calcium and sodium are omitted

Sodium is not "mined" per se, as, you know, just get some sea water

Calcium is, but maybe because it's not processed as most metals it is not included in the graph

At least half of all NaCl that's used world wide is mined from salt mines. For many places in the world it's not feasible to rely on solar evaporation of sea water. Using other energy sources to evaporate sea salt is not cost effective and many places have large salt deposits.

https://salt-partners.com/pdf/Santorini2006Paper.pdf

Would it be feasible to use the sodium from desalination wastewater?

desalination wastewater contains a number of other chemicals used in the desalination process (e.g. pH adjusters, coagulants and flocculants, antiscalants, dispersants, biocides, and reducing chemicals)

So the next question: would those contaminants significantly degrade the performance of the battery?

I mean... pH adjusters would definitely significantly alter things. The other major problem (I'd guess) is just the health implications of working with toxic wastewater. Is it safe?

For context, as of 2019, we produced enough of this "brine" to cover Florida with 30 centimeters of brine every year. That means, as a whole, desalination plants actually produce even more toxic wastewater than they do clean drinking water.

As a result figuring out ways we could utilize this _product_ ("byproduct" feels like the wrong term here considering it's the primary thing produced) is a major area of interest

Didn't gasoline start out as a byproduct of kerosene production?

Sure but it's alternative uses were already known. It just so happened that a world-altering invention (the consumer automobile) came along to dramatically raise already existing demand for it. There is currently no demand/use for desalination brine. For every "this byproduct is actually useful" story there's likely 10 byproducts that simply stay byproducts. Still, it's urgent we figure out something to do with it since it's damaging our ocean ecosystems

I looked up your claim that desalination plants produce "toxic wastewater" and I found nothing to support it. The output appears to be simple concentrated ocean water, and that's it.

Can you cite your claim?

I'm more interested in what you possibly looked up that made it hard to find...

> Furthermore, chemicals such as biocides, surface−active agents, anti-scale additives, and solid residues from filter backflushing may be present in the effluent discharge on a continuous or periodic basis, posing a risk to the environment

> Brine effluents from RO desalination plants not only have a high salt content but typically also contain compounds from the desalination process, such as phosphonate-based antiscalants and ferric (or alum) sulphate-based coagulants

[1] https://www.frontiersin.org/articles/10.3389/fmars.2022.8451...

[2] https://www.sciencedirect.com/science/article/abs/pii/S00431...

> However, concern also exists regarding the use and release of toxic anti-foulants and anti-scalants to maintain plant infrastructure

[3] https://www.sciencedirect.com/science/article/abs/pii/S00431...

> The super-salty substance is made even more toxic by the chemicals used in the desalination process, researchers reported in the journal Science of the Total Environment.

> Copper and chlorine, for example, are both commonly used.

[4] https://phys.org/news/2019-01-brine-highlights-toxic-problem...

They can be removed in purification steps.

Go from the super high salinity brine through to crude salt, then chloralkali process to get sodium (which can be cleaned up) and chlorine gas (industrially useful).

I am aware of this, but mining (or salt water processing) for the specific extraction of sodium metal from NaCl or others is really small

Mined salt is probably more valuable as table salt (and cattle feed) than as source of metallic Na

Sodium is also mined for sure. There's a reason there are many expressions about salt mines :-)

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