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Hot brines used in traditional membrane distillation systems are highly corrosive, making the heat exchangers and other system elements expensive, and limiting water recovery (a). To improve this, UCR researchers developed a self-heating carbon nanotube-based membrane that only heats brine at the membrane surface (b), where the porous carbon nanotube layer acts as a Joule heater (c).



In modern days, water deficiency is a big issue to all over the world. Today, 1 billion people affect from every continent around the world and more than 1.2 billion people lack access to clean drinking water. But recently scientists at the University of California have developed a new way to recover the 100 percent water from waste brine or highly concentrated salt solutions.

Now, scientists are very much confident about this system. They said it will reduce the water shortage in arid regions. This research is based on a development of carbon nanotube-based heating element. Moreover, during membrane distillation processes it will improve the recovery of fresh water.

Osmosis process is a vital process for the biological system but reverse osmosis process is a common method to remove the salt from seawater or wastewater. Sometimes, it is not capable of treating highly concentrated salt solution such as brine. Brines are generated, during reverse osmosis and hydraulic fracturing. Phys.Org reported.

Furthermore, in the case of hydraulic fracturing, the water is often disposed of underground in injection wells. But as a result, it may increase the chances of an earthquake. There is only one way to treat brine, which is membrane distillation. Membrane distillation is a thermally driven separation program in which heat drives water vapor across a membrane, allowing further water recovery while the salt stays behind.

The hot brines are highly corrosive and making the heat exchanger while the other system elements expensive in traditional membrane distillation systems. Actually, this process relies on the heat capacity of water and single pass recoveries are very low(less than 10 percent), Science Daily reported.

Currently, membrane distillation processes rely on a constant feed of hot brine, which limits water recovery across the membrane to about 6 percent. To avoid this problem, the researcher developed this elf-heating carbon nanotube-based membrane that only heats the brine at the membrane surface.

The whole project leads by David Jassby, an assistant professor of chemical and environmental engineering at UCR's Bourns College of Engineering. His team also investigated how the application of alternating currents to the membrane heating element and how it could prevent degradation of the carbon nanotubes in the saline environment.

During the experiment, a threshold frequency was also found by scientists where electrochemical oxidation of the nanotubes was prevented. It allows the nanotube films to be operated for significant lengths of time with no reduction in performance. However, this particular work will allow carbon nanotube-based heating elements to be used in other applications where electrochemical stability of the nanotubes is a concern.