Scientists claim to have developed a new technology that can remove nearly all of the salt from seawater, potentially resolving one of the world’s most serious health issues.
The coaxial electrospun nanofiber membrane was developed by researchers at the Korea Institute of Civil Engineering and Building Technology (KICT).
The membrane not only removes 99.9% of the salt from seawater, but it also lasts up to a month, whereas previous solutions only lasted about 50 hours before needing to be replaced.
Because of its low sliding angle and thermal conductivity, the membrane was able to operate without wetting or fouling. However, because of how it conducts heat, it has some drawbacks, most notably temperature polarization and a decrease in water vapor flux.
According to the World Health Organization, good drinking water should have a total dissolved solid (TDS) level of less than 600 parts per million (ppm).
Previous technologies had a high water vapor flux performance despite operating for less than 50 hours.
‘The co-axial electrospun nanofiber membrane has 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,’ said Dr Yunchul Woo, the study’s lead author. The potential solution is enormous, given that approximately 785 million people do not have access to safe drinking water, according to World Health Organization data from 2019.
Furthermore, according to the WHO, approximately 2 billion people worldwide drink water that is contaminated with feces.
Diarrhea, cholera, dysentery, typhoid, and polio can all be caused by contaminated water.
According to the WHO, by 2025, “half of the world’s population will live in water-stressed areas.”
The membrane was created using alternative nanotechnology, also known as electrospinning, to help prevent the membrane from becoming too wet and to improve its long-term stability. The nanofibers in the membranes enable higher surface roughness and water repellency, also known as hydrophobicity.
Other solutions have struggled with membrane wetting, which is why they need to be replaced so frequently, and that filtration system had not been feasible for long-term operations until now.
The KICT researchers developed this technology by starting with poly (vinylidene fluoride-co-hexafluoropropylene) as the core and mixing it with silica aerogel and a low concentration of polymer as the sheath, which allows the team to achieve the hyper-repellent membrane surface.
The findings were published in the Journal of Membrane Science in April. Previous attempts to convert seawater into drinking water included desalinating it with a metal-organic framework and using sunlight as a power source.
Other attempts have included using temperature differences between surface and deep sea water to make sea water drinkable, as well as using graphene to create a membrane to filter sea water into drinking water.
Although water covers 71% of the Earth’s surface, 96.5 percent of that is ocean water, according to the US Geological Survey. As a result, only 2.5 percent of the world’s water is drinkable.
Saline water contains high concentrations of dissolved salts. In this case, the concentration is the amount of salt in water (by weight), expressed in “parts per million” (ppm).
If the concentration of dissolved salts in water is 10,000 ppm, then dissolved salts account for one percent of the water’s weight.
The salt content of ocean water is approximately 35,000 ppm.
Freshwater scarcity and the need for additional water supplies are already critical in many arid regions around the world.
Many arid areas lack freshwater resources in the form of surface water, such as rivers and lakes.
They may have only limited underground water resources, some of which are becoming brackish as water extraction from aquifers continues. Solar desalination evaporation is used by nature to produce rain, which is the main source of freshwater on earth.