Many wars have been fought over water. And we are likely to fight many more in the coming decades. Already one-tenth of humanity lives in areas where water is scarce, and, according to the United Nations, our rapidly changing climate is going to double that number by 2025.
A solution to this problem is converting sea water into drinkable water. This, however, is expensive. The most energy-efficient method available to us right now is reverse osmosis, but the technology still has severe limitations.
Now researchers from the University of Illinois at Urbana-Champaign have developed a new filter that they claim might be cheaper and more effective than the filters used today. Their results have been published in Nature Communications.
The principle of reverse osmosis is simple. It consists of two chambers separated by a membrane, which has holes only big enough to let water molecules through. When pressure is applied on the saltwater side, salt and other impurities, which are usually much bigger in size, are blocked and pure water is filtered through to the other chamber.
The limitation with current reverse-osmosis filters is that, while the membranes appear thin to the naked eye, at the microscopic level they are still too thick. The passage of water molecules through those filters is like that of moving through a tunnel. Thus it takes more energy to push the water to the other side and there are greater chances of blockages happening.
So University of Illinois researchers set about building a better filter. Their solution is to create a single-layer sheet of molybdenum disulphide (MoS2) with nanopores in them. The sheet is only a billionth of a meter thick.
Membranes made of graphene—which consists of a single layer of carbon atoms—are thinner than MoS2 filters, but MoS2 seem to be better. A slightly thicker filter gives MoS2 more physical strength to withstand pressure, and, unlike graphene filters, they are more easily manufactured.
Beyond that, however, it will take a lot more effort to bring this lab-built filter to reality. Lab inventions aren’t always easy to manufacture at a large scale. But let’s hope it works because nobody wants people fighting over water.