“Water, water everywhere, and not a drop to drink.” This classic proverb explains the conundrum of being surrounded by seawater — there's more than enough to drown in, but none of can quench your thirst. The high salt content of seawater can cause the body to go into shock if it's consumed, so it's unwise to drink seawater, especially if you're already dehydrated.
The other problem is that this salt is often extremely difficult to remove from water. Simple filters like the LifeStraw can remove bacteria and other pathogens, but are unable to trap the dissolved salt on a molecular basis. Seawater can be desalinated through distillation or reverse osmosis filtration, but both of these processes are time-consuming and require large amounts of energy input. However, researchers have recently announced the development of a graphene nano-membrane filter which can efficiently remove salt from seawater.
Graphene is a cutting-edge material composed of a flat hexagonal lattice of Carbon atoms. Each layer of graphene is two-dimensional on an atomic scale, meaning it's only one atom thick. This structure generates some very interesting properties — it exhibits tensile strength higher than steel, it's nearly transparent, and it's a highly efficient conductor of heat and electricity. One form of graphene, graphene oxide, has a microscopic structure which enables it to form a filter with extremely small pores.
Scientists at the University of Manchester recently announced research which demonstrates the effectiveness of graphene oxide for desalination. These filters can reportedly be produced easily in the lab, and the membrane pore size can be precisely controlled to less than one nanometer in size. Common salt molecules found in seawater are about one nanometer in size, so the membrane efficiently strips salt from water molecules while retaining a high flow rate.
Until now, this level of control over graphene membrane pore size was not possible. Researchers say more work needs to be done to prove these filters work on an industrial scale, and to document the filter cleaning or replacement intervals, but this study still represents a major step forward in seawater desalination. The initial testing shows these graphene oxide filters can reject 97% of common salt (NaCl) in water.
In layman's terms, this presents the possibility of simple, portable, high-flow molecular filters which can convert seawater into drinkable water. For survivalists, especially those who live near the coast, that's an exciting prospect. For more info, check out this article from the BBC or read this University of Manchester press release.