Hydrophilic disc uses solar power to separate salt from water

https://newatlas.com/solar-steam-generator-water-desalination/60726/

by HillaryBriss • 7 years ago

126 59 7 years ago

beat• 7 years ago

One cool thing about this is that it looks inexpensive and simple, as well as functional. If a square meter can generate enough clean water for a person per day, islands of it could support entire cities.

jbob20003• 7 years ago

This doesn't make for a good drinking water, this creates distilled water that would drain your body of minerals if you drank it.

You now need to expend energy to gather those minerals from somewhere else and then put them in the water. Is the energy spent gathering those minerals more than other desalination processes?

option_greek• 7 years ago

You now need to expend energy to gather those minerals from somewhere else and then put them in the water

Did you mean the white stuff coming out :)

jbob20003• 7 years ago

Is that just salt? Or a heterogeneous mixture of salt and minerals? You want just the minerals, no salt. How do you separate the salt from the minerals in that "white stuff"?

DennisP• 7 years ago

Does reverse osmosis retain the minerals?

And wouldn't the minerals in food compensate for their lack in water?

jbob20003• 7 years ago

No, reverse osmosis filters out most minerals. But reverse osmosis filters aren't always used for drinking water. And yes, minerals in food can compensate.

wrycoder• 7 years ago

People pay good money for “sea salt” to use on their food. That’s just the dried residue from this process, assuming clean sea water to begin with.

It’s common to add a bit of salt and Epsom salts to water when brewing - the harder water improves the taste.

You get your minerals from food, not water. I doubt your premise about leaching body minerals by drinking distilled water (or rainwater!).

HillaryBriss• 7 years ago

People pay good money for “sea salt”

true. and if the salt produced by this process if free of micro plastics, people might pay even more

driverdan• 7 years ago

That's an urban legend. We get nutrients and minerals from the food we eat.

DanBC• 7 years ago

the World Health Organistion seems to think that it's important (but also reasonably easy to fix). https://www.who.int/water_sanitation_health/dwq/nutrientscha...

robocat• 7 years ago

The first sentence is probably true, the second seems false.

"Results of experiments in human volunteers evaluated by researchers for the WHO report (3) are in agreement with those in animal experiments and suggest the basic mechanism of the effects of water low in TDS (e.g. < 100 mg/L) on water and mineral homeostasis. Low-mineral water markedly: 1.) increased diuresis (almost by 20%, on average), body water volume, and serum sodium concentrations, 2.) decreased serum potassium concentration, and 3.) increased the elimination of sodium, potassium, chloride, calcium and magnesium ions from the body"

sitharus• 7 years ago

A very large number of people get their water from captured rain water stored in tanks. I do myself. It's not mineral-free but it's certainly very low in dissolved minerals. I appear to be alive, as do many others.

jjtheblunt• 7 years ago

https://en.wikipedia.org/wiki/Solar_still

is a lower tech solar solution?

goda90• 7 years ago

One cool application of solar stills is when you can't find any liquid water, no matter how salty or dirty, but you can cut up parts of plants and seal them in plastic to collect the moisture from the plants. Obviously not scalable, but it can be a useful survival technique.

aidenn0• 7 years ago

Actually the Navy survival kit still seems to even have similar space efficiency if a 1/3m^2 footprint allowed for 2.4L per day. That would translate to 7.2L per M^2 per day which is right around the 6-8L mentioned in the article.

Retric2• 7 years ago

“This device can produce six to eight liters (1.6 to 2.1 gal) of clean water per square meter (of surface area) per day”

That’s really bad from a density standpoint. You’re talking ~8,000 gallons per day per acre of land. Solar powered reverse osmosis is something like 1/500th the space.

If the can get installed costs below 1$ per square meter it might be interesting, but even just land costs are likely to be an issue.

SCAQTony2• 7 years ago

But what do you do with the salt and brine that is toxic to soil used in the farming? The wind will scatter the salt in all directions.

wbl• 7 years ago

You dump the brine into well-mixed ocean areas.

8note• 7 years ago

pull out the lithium and make batteries?

mulmen• 7 years ago

Can it be installed at sea?

fian• 7 years ago

The researchers are in Australia, where we have abundant coastal land that is not suitable for agriculture. Indeed there are many salt lake systems already being used for large scale salt production via sea water evaporation (https://www.riotinto.com/australia/dampier-salt-4644.aspx).

Should this type of technology scale out, some of these salt production operations might also be able to produce desalinated water either for domestic or industrial use (in the case it is still too brackish for drinking).

newguy12342• 7 years ago

This is research, so the final production will most likely be boosted with refinements.

p1necone• 7 years ago

I feel like there almost needs to be a bot that posts this on everything. So many people comment on things on here saying effectively "in the current state this would not be good enough for practical application", it's like no shit, that's why it's still in the research stage. Explain why you think this can't improve otherwise your comment is worthless.

noselasd• 7 years ago

Hopefully you can fold the surface in 3d space so you don't need a full square meter of 2d space.

inflatableDodo• 7 years ago

Reminds me of dye chromotography, I wonder if you can get different salts to turn up at different places on the edge? Might be able to get useful concentrations of lithium out of it that way.

wollstonecraft• 7 years ago

Hydrophilic anything in the environment quickly fouls to hydrophobic.

ncmncm2• 7 years ago

Even when supplied via wicking?

tom_mellior2• 7 years ago

Do I understand it correctly that this doesn't actually produce liquid water but only somewhat more humid air in the general area above the device? I wonder how much additional effort it takes to actually get the water into a container.

carapace• 7 years ago

To me it looked like moisture was condensing inside the column and maybe collecting in the bottom.

tom_mellior2• 7 years ago

Yeah, I saw the condensation in the column, but since that's where the salt water comes in I figured it would be related to that. The article talks about "steam that builds up on the disc", which I understood to mean its upper surface.

The university's press release at https://www.monash.edu/news/articles/water-solutions-without... says: "Researchers created a disc using super-hydrophilic filter paper with a layer of carbon nanotubes for light absorption. A cotton thread, with a 1mm diameter, acted as the water transport channel, pumping saline water to the evaporation disc. The saline water is carried up by the cotton thread from the bulk solution to the centre of the evaporation disc. The filter paper traps the pure water and pushes the remaining salt to the edges of the disc."

My best guess at what this means is that some of the water is turned into vapor (not really steam at 100 C, I guess?) and that this evaporation drives the capillary effect that keeps bringing in new water. Some other part of the water, the part that "the filter paper traps", could then drip out into the column. Maybe? Or maybe this prototype is really more about just demonstrating that salt can be collected, and doesn't care about capturing the water.

Here's the original article, paywalled at UKP 42.50: https://pubs.rsc.org/en/content/articlelanding/2019/ee/c9ee0...

Hydrophilic disc uses solar power to separate salt from water

Related Stories