Desalination Breakthroughs?

[GordMay]

The scientific community is reporting back-to-back breakthroughs, in their ongoing efforts to find effective means of "desalination," the process of removing salt from water, to create a drinkable supply.

A recent breakthrough made by a startup in South Korea, called Capture6 [1], boasts the ability to address the environmental concerns of desalination plants, by using "carbon capture" technology. This process aims to reduce greenhouse gases, produce fresh water, and mitigate pollution, by taking carbon dioxide from the air, and storing it in brine, from desalination.
The company plans to build a facility, called Project Octopus, at the Daesan Industrial Complex, an oil and gas park, in an area stricken by drought.

In another new milestone, a team of researchers, from New York University, discovered a method of desalination, that uses the speed of liquid flow, to make the process more efficient, describing the results in the journal Cell Reports Physical Science [2].
They investigated how water flow rate impacts the performance of a system called redox flow desalination (RFD), which uses chemicals to remove salt from seawater.
The study found that higher flow rates of these chemicals improved the system's ability to remove salt and reduced the energy needed. The researchers suggested that adjusting flow rates can make RFD more effective and affordable.

Yet another innovation was reported [3], by scientists at Nankai University, in China, who developed a more efficient system for desalinating seawater using solar power.
The system uses structures called "DNA hydrogels" that absorb sunlight and therefore reduce the energy needed to evaporate water, according to the team's findings [3], published in the journal Science Advances.
The solar-powered desalination process also has the potential to simultaneously extract uranium from seawater or treat nuclear wastewater.

In 2023, The Los Angeles Times reported on a project [4], underway off the coast of Southern California, that aims to create the country's first-ever "blue water farm."
The pilot project would create drinking water from "desalination pods" on the ocean floor, and California-based company OceanWell [4] said it would combat environmental challenges associated with traditional land-based plants.
The project could produce 10 million gallons of fresh water per day.

[1] “Water Positive Carbon Removal” ~ Capture6
➥ https://capture6.org/

[2] “Investigation of flow rate in symmetric four-channel redox flow desalination system” ~ by Stephen A. Maclean et al
➥ https://www.sciencedirect.com/scienc...069?via%3Dihub

[3] “Solar-powered simultaneous highly efficient seawater desalination and highly specific target extraction with smart DNA hydrogels”~ by Hanxue Liang et al
➥ https://www.science.org/doi/10.1126/sciadv.adj1677

[4] “Seafloor desalination” ~ L.A. Times
➥ https://www.latimes.com/environment/...wer-to-drought
OceanWell ➥ https://www.oceanwellwater.com/

See also:
“Global Water Desalination Market Size is Estimated to Reach USD 43.03 billion by 2031, Growing at a CAGR of 9.12%” ~ Straits Research
➥ https://www.globenewswire.com/news-r...-Research.html

[MicHughV]

They'll get my attention when they can make beer from salt water

[wholybee]

Originally Posted by MicHughV

They'll get my attention when they can make beer from salt water

If after desalinization you mix in malt barley, hops, and yeast, you have made beer from salt water. Some boats do this already.

[MicHughV]

I've tried making my own beer before....it was ok is about as best I can describe it. Would it sell ?? probably not.

On the other hand I know some guys that have taken to making their own beer to a new art form making a stupendous product worthy of international accolades, but such skills allude me

[hpeer]

Gord,

Thanks for the report.

I keep hearing about exciting new technologies, but have not seen any mature yet. Fingers crossed. It is clearly a big problem.

[catalystcat]

Numbers 2 and 3 are interesting.

Reference 2 less so than reference 3.
It uses FeCn (yep, that’s got cyanide in it) as sort of a catalyst to improve ionic diffusion across a membrane (in addition to the electrical potential that does so). Note that this is a refinement of something that has been in development for a while now. These guys are mostly working on improving rate and performance by controlling the relative flow rates on opposite sides of the membrane. Their system improves on some other approaches, but, still struggles with actual seawater, as opposed to brackish. Given the difficulties in maintaining such electric potential plus pressure drive ionic membranes, (see, e.g., fuel cells which don’t deal with the crap you find in seawater) and the size of the system vs membrane area, it seems a long way from maritime viable.

Reference 3 is pretty interesting, though perhaps for land based systems. Again, this one is an improvement on something that has been discussed for a few years now. Though these guys have added a dynamic control to do things like selectively isolate metals in the water.
The basic concept is great. It’s super simple (evaporation) and uses a very cheap medium (basic hydrogels). Hydrogels have huge effective surface areas for a given area/volume. That means a huge impact on evaporation rate. So, you get an effective evaporative distillation system that doesn’t require much more than sunlight to do the conversion. Of course, the problem with boat based systems is the tradeoff between production rate and real estate. To see that, let’s take a quick look at what you get for a 4 gallon an hour system.
From the paper – “water evaporation rate reached a high level of 3.54 kilograms per square meter per hour” That’s about a gallon an hour per square meter of surface area. If you are willing to give up about 4 sq meters of deck space, this could give you about 30 gals a day. (assuming an effective solar day of 8 hours, because their number is based on a kilowatt per sq meter of illumination and early mornings and late afternoons aren’t full illumination.) Note that I have assumed the saltwater is magically transported to the hydrogel with zero power and the fresh water falls into the tank with zero power.
As a comparison, that deck space would produce around 800W of power with high end solar panels (about 6.4kWh/8hr day). That would drive something like 4 hrs on a 1.6kW watermaker that produces about 50gals/hr – or 200gal of water vs 30.
That’s not competitive – yet. But, with some improvement and some clever architecting, it could get there. e.g., if you place the hydrogel beneath the solar panels and let the IR light through, you can get the evaporation and keep your solar panels. This takes advantage of the fact that solar panels use mid-visible light, mostly, and the heat for evaporation comes mostly from the IR part of sunlight.
Lots of engineering needed to make that work and it has some poor assumptions. But, it does show that there are paths to make this basic approach work.
In a completely different context - deserts near oceans, or open water near islands, this gets a lot more interesting. I could see inexpensive desalination platforms taking advantage of this geography, especially in island areas and in several locations in Africa.