Materials

Mixed up membrane desalinates water with 99.99 percent efficiency

Mixed up membrane desalinates ...
A new membrane production process could improve water desalination
A new membrane production process could improve water desalination
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A new membrane production process could improve water desalination
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A new membrane production process could improve water desalination
A diagram demonstrating the new co-axial electrospun membrane compared to traditional ones
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A diagram demonstrating the new co-axial electrospun membrane compared to traditional ones

That ancient mariner was onto something when he said “water, water everywhere, nor any drop to drink” – the vast majority of water on Earth is undrinkable. Desalination could be a vital technology to meet the world’s drinking water needs, and now Korean engineers have developed a new nanofiber membrane that can operate efficiently for long periods.

There are a few different ways to desalinate water, but this study focuses on membrane distillation. In this process, the salty brine on one side of the membrane is heated, while the fresh water on the other side remains cold. The membrane is hydrophobic to repel the liquid water, but water vapor from the hot side can still pass through the pores. Due to a vapor pressure difference it drifts over to the cold side, where it recondenses as fresh water.

The problem is, the buildup of salts and other pollutants on the membrane can affect its hydrophobicity. Eventually the brine leaks through and makes the freshwater less fresh, requiring the membrane to be replaced.

So for the new study, researchers at the Korea Institute of Civil Engineering and Building Technology (KICT) created more advanced membranes. Often they’re made through a process called electrospinning, where an electric force is used to draw charged nanofibers out of nozzles. The KICT team used a version called co-axial electrospinning, where two different materials are mixed together during the printing process.

A diagram demonstrating the new co-axial electrospun membrane compared to traditional ones
A diagram demonstrating the new co-axial electrospun membrane compared to traditional ones

In this case, those two materials were a polymer called PVDF-HFP and silica aerogel. The rough surface helps to repel the water, while the silica aerogel acts like a thermal insulator, keeping the hot side from warming up the cold side. That in turn keeps the difference in vapor pressure high and makes the membrane more efficient.

In tests, the team ran the new membrane for 30 days, and found that it still filtered out 99.99 percent of the salt after that time. That’s a far longer runtime than other electrospun nanofiber membranes, which the team says struggle to last more than 50 hours of continuous use before they begin to leak.

"The co-axial electrospun nanofiber membrane have strong potential for the treatment of seawater solutions without suffering from wetting issues and may be the appropriate membrane for pilot-scale and real-scale membrane distillation applications,” says Dr. Yunchul Woo, lead researcher on the study.

The research was published in the Journal of Membrane Science.

Source: KICT via Newswise

6 comments
6 comments
guzmanchinky
This tech seems to be getting better and better. And just in time...
CraigAllenCorson
These need to be put on every lifeboat and in every survival kit in the world.
HoppyHopkins
As things get worse in the world and fresh water gets more scarce, this could be a life saver. Water is the new oil rush; why else do you think China has been trying to buy up or conquer every water resource it can get
2Hedz
Just waiting for LG to acquire this, and I'll invest. Could be a game changer!
VicCherikoff
But it still needs an energy source to heat the seawater. Perhaps Star Scientific's HERO® process could provide the heat from the cold fusion of hydrogen and oxygen that comes from the freshwater side. Incidentally, we can't drink water devoid of all solutes as it leaches minerals from our bones and teeth. So some of the (filtered) brine would need to be put back in the freshwater and in appropriate doses.
lon4
Most of the energy required to operate existing Reverse Osmosis membranes for seawater desalination is for a pump that produces 55 to 80 bar (800-1000PSI) pressures. Since the Journal Abtract is all can read, and all I can see is a very low input pressure (1.75 bar) it looks promising. Depending on how much heat is required per liter of product fresh water, and how much energy rquired to cool the ouput, this really might be a game changer. If a vaccuum - negative pressure - were to be applied on the product side, perhaps the heat inpiut could be reduced further.