Due to a newly designed technique, almost 100% of the water from the highly concentrated salt solutions can be recovered.
Engineers from the University of California have developed this system that can lessen the water shortages in arid places along with decreasing concerns about the high salinity salt water disposal like the hydraulic fracturing waste.
The study published in Nature Nanotechnology includes the development of a carbon nanotube-based heating component which will greatly improve the revival of fresh water through the process of membrane distillation.
Though the common method of reverse osmosis removes salt from wastewater, seawater or brackish water, the process can not treat the highly concentrated salt solutions. These solutions which are also known as brines are produced in great quantities as waste products during the reverse osmosis and as produced water during hydraulic fracturing. In order to avoid environmental damage, these products ought to be disposed of properly. In hydraulic fracturing, the produced water is frequently disposed in underground injection well but they can result in increased number of earthquakes, informs Science Daily.
One way to treat brine is through membrane distillation. Membrane distillation is a thermal desalination technology in which heat generates water vapors across a membrane which in turn allows water recovery as it leaves the salt behind. However, the process contains few drawbacks which make it not so perfect to be used.
David Jassby, the lead researcher informed, “In an ideal scenario, thermal desalination would allow the recovery of all the water from brine, leaving behind a tiny amount of a solid, crystalline salt that could be used or disposed of. Unfortunately, current membrane distillation processes rely on a constant feed of hot brine over the membrane, which limits water recovery across the membrane to about 6 percent.”
For improving this, Jassby and his team created a self-heating carbon nanotube-based membrane which heats the brine at the membrane surface only. The system was able to reduce the heat required during the procedure and improved the yield of recovered water to about 100%.
Along with this, the team also observed how altering currents that are applied to the membrane heating element can possibly prevent degradation of carbon nanotubes in saline surroundings. A threshold frequency was detected where electrochemical oxidation of the nanotubes was blocked which further permitted the nanotube films to be operated for noticeable time with no performance drop, reported Science Blog.