Imagine a cross-section of a hair. That tiny surface about one millionth of a meter in diameter is huge compared to the pores in a new type of filter developed at the University of Tokyo in Japan.
In a research published Thursday in the peer-reviewed journal Science, scientists unveiled their new method of desalinating water with fluorine rings measuring about one to two nanometers in diameter. The chemicals'' hydrophobic properties contributed to its remarkable ability to filter salt molecules with exceptional speed and performance.
It would take roughly 100,000 rings to spread throughout the cut surface of a human hair, laying them out end-to-end.
According to one of the papers co-authors, the less wet testing channels perfectly rejected incoming salt molecules, while the larger ones were still an improvement over other dealination techniques and even cutting-edge carbon nanotube filters.
Fluorine is the perfect solution for the unimaginable small pores.
Fluorine, a hydrophobic element that has long been recognized for wanting to stay home, is a major component in Teflon, which is used on non-stick pans to keep fried eggs from sticking and inside pipes more efficiently. Fluorine is also used to combat negatively charged ions, including the chlorine in salt (NaCl). Its electric properties also break down clumps of water molecules that can keep the liquid from flowing as freely as possible.
The researchers created membranes by stacking several fluorous rings around each other to form tubes. The tubes were embedded side by side in a water-tight layer of lipid molecules, creating something that resembles a cell membrane. Water molecules are welcome to pass through, and salt molecules are not.
The real surprise for me was how fast the process took place. Our sample was more efficient than most industrial equipment, and nearly 2,400 times faster than experimental carbon nanotube-based desalination methods.
A long way to commercialization
The development of sea water into something that humans can eat is a vital technological asset that is becoming more and more important.
Water is desalated daily, using heat to evaporate seawater so it condenses as pure water, or by reverse osmosis, which uses pressure to force water through a membrane that blocks salt, according to Itoh.
Although these technologies are proven to be effective at large scales, they require a lot of energy. These early findings suggest fluorine nanostructures may be the key to desalination techniques that are far more efficient. According to Itoh, fluorous nanochannels require little effort.
The majority of the energy costs associated with the process of making the new material are required, but scientists believe they can lower those costs. And given the longevity of the membranes and their low operational costs, the overall energy costs will be significantly lower than with current methods, according to Itoh.
The current study is impressive, but it is far from a functional prototype that a community can rely on. Despite our factual measurements being single nanochannels, it is possible to develop a membrane across the scales in years, according to Itoh. And the researchers are able to look beyond water desalination.
Itoh claims that similar membranes may be used to reduce carbon dioxide or other unwanted waste materials released by the industry.