A sea to drink
"Blue gold" is becoming increasingly scarce, and to meet our water needs, we must look to the open sea… Desalinating seawater to turn it into fresh water is now a global challenge. This process has just taken a major step forward thanks to researchers atthe European Membrane Institute.
According to the UN, by 2030 the planet will face a 40% shortage of drinking water, while the population continues to grow. But where can we get water when the aquifers that supply us are no longer enough to meet our needs? The answer: from the sea.“Today, 20% of the water we use is seawater that has been desalinated,” explains Mihail Barboiu ofthe European Membrane Institute (IEM). But as our freshwater resources dwindle, in 50 years, 60 to 70% of our water is expected to come from the sea. This is a major challenge to which the researcher has just made a significant contribution.
Reverse osmosis
Because separating salt from water is no easy task.“The ions that make them up are the same size, so we can’t simply filter them out.”To get around this problem, researchers use reverse osmosis: “We pass the water through a specialmembrane that traps the salt,” explains Mihail Barboiu. But even here, the solution isn’t obvious.“When a permeable membrane separates two solutions withdifferentsalt concentrations, water naturally flows through the membrane until the concentrations on both sides are balanced—this is what we call osmosis,”explains the specialist.
Once there is an equal amount of salt in both solutions, what is known as osmotic equilibrium is reached.“To continue moving water across the membrane after this point ,we must apply pressure to force the flow—this is reverse osmosis.” It’s an effective technique, but one that requires a great deal of energy to generate this pressure.“Reducing the amount of energy required is a real challenge for improving seawater desalination capabilities.”
Permeability and Selectivity
That’s where researchers at theIEM come into play by developing a new type of membrane that allows water to pass through more easily while effectively retaining salt. Their formula? “A polyamide membrane into which we’ve inserted artificial water channels.” These channels are synthetic compounds that form pores permeable to water molecules while rejecting ions. “This results in a membrane with greater permeability and good selectivity, ”explains Mihail Barboiu. Because itis more permeable, it allows water to pass through more easily, so less energy is required to drive the flow. Challenge met.
An innovation that has already proven itself, backed by the numbers.“It is three times more permeable than the membranes currently in use, without losing any selectivity,” explains Mihail Barboiu. These super membranes therefore allow for a water flow that is 75% higher than that observed with current industrial membranes.“They thus reduce the amount of energy needed to desalinate seawater by 12%—a considerable improvement, ” says the researcher. This also means that more freshwater can be produced using the same amount of energy. Already patented, this research was published in *Nature Nanotechnology* on November 9.