A long way to go
"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. A process that has just taken a major step forward thanks to researchers atthe European Membrane Institute.
According to the UN, by 2030 the world will face a 40% shortage of drinking water, even as the population continues to grow. But where can we find water when the aquifers that supply us are no longer enough to meet our needs? The answer: the sea.“Today, 20% of the water we use is desalinated seawater,” explains Mihail Barboiu ofthe European Membrane Institute (IEM). But with the decline in our freshwater resources, in 50 years, 60 to 70% of our water is expected to come from the sea. A real 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 simple filtration won’t work.”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 ,pressure must be applied 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 is where researchers at theIEM step in with the development of a novel type of membrane that allows water to pass through more easily while effectively retaining salt. Their secret? “A polyamide membrane into which we have 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. Being 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 its worth, backed by hard data.“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 rate 75% higher than that observed with current industrial membranes.“They thus reduce the amount of energy needed to desalinate seawater by 12%, which is a significant improvement,” the researcher notes. 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.