Sheet of graphene. Credit: Wikimedia Commons.
With the development of a new, thinner membrane, defense contractor Lockheed Martin could revolutionize the process of desalination, providing fresh water across the globe at higher efficiency and lower costs.
Traditionally, the best way of taking salt out of water has been through vacuum distillation. The salt water is enclosed at a low pressure to reduce its boiling point, making it easier to vaporize to separate the salt from the water. A more efficient but more energy-intensive way is through the process of reverse osmosis: A membrane separates two chambers, and the side holding the salt water is subjected to pressure, forcing the water to pass through the membrane and leave the salt, which is too large to cross the barrier.
Lockheed's new Perforene membranes, made of graphene (sheets of pure carbon only one atom thick), are 500 times thinner than filters currently on the market. This means less energy is required to push water through the membrane, making reverse osmosis more efficient. John Stetson, head engineer for the project, told Reuters that it would require approximately 100 times less energy than other membranes.
But working with such a thin material presents new problems, and engineers are still trying to find the best way to produce nanometer-wide holes in the membranes quickly and on a large scale without tearing the product. The added difficulties of manufacturing will probably factor into cost, but Lockheed says desalination plants wouldn't need to change their infrastructure to use Perforene. The prototype expected by the end of this year will be a drop-in replacement for filters currently in use.
If Lockheed Martin engineers can make large-scale production of Perforene feasible, it could make a huge difference to the 780 million people living without access to fresh water. The company also hopes to find applications in healthcare, where the material could replace current dialysis membranes, and in environmental cleanup.