UC Riverside: Squeezing every drop (almost 100%) of fresh water from waste brine (salt solutions)


squeezingeveHot 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 …more

Engineers at the University of California, Riverside have developed a new way to recover almost 100 percent of the water from highly concentrated salt solutions. The system will alleviate water shortages in arid regions and reduce concerns surrounding high salinity brine disposal, such as hydraulic fracturing waste.

The research, which involves the development of a carbon nanotube-based heating element that will vastly improve the recovery of fresh during membrane distillation processes, was published today in the journal Nature Nanotechnology. David Jassby, an assistant professor of chemical and environmental engineering in UCR’s Bourns College of Engineering, led the project.

While reverse osmosis is the most common method of removing salt from seawater, wastewater, and brackish water, it is not capable of treating highly concentrated salt solutions. Such solutions, called brines, are generated in massive amounts during reverse osmosis (as waste products) and hydraulic fracturing (as produced water), and must be disposed of properly to avoid environmental damage. In the case of , produced water is often disposed of underground in injection wells, but some studies suggest this practice may result in an increase in local earthquakes.

One way to treat brine is membrane distillation, a thermal desalination technology in which heat drives water vapor across a membrane, allowing further water recovery while the salt stays behind. However, hot brines are highly corrosive, making the heat exchangers and other system elements expensive in traditional membrane distillation systems. Furthermore, because the process relies on the heat capacity of water, single pass recoveries are quite low (less than 10 percent), leading to complicated heat management requirements.

“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,” Jassby said. “Unfortunately, current processes rely on a constant feed of hot brine over the membrane, which limits water recovery across the membrane to about 6 percent.”

To improve on this, the researchers developed a self-heating carbon nanotube-based membrane that only heats the brine at the membrane surface. The new system reduced the heat needed in the process and increased the yield of recovered water to close to 100 percent.

In addition to the significantly improved desalination performance, the team also investigated how the application of alternating currents to the heating element could prevent degradation of the carbon nanotubes in the saline environment. Specifically, a threshold frequency was identified where electrochemical oxidation of the nanotubes was prevented, allowing the nanotube films to be operated for significant lengths of time with no reduction in performance. The insights provided by this work will allow carbon nanotube-based heating elements to be used in other applications where electrochemical stability of the nanotubes is a concern.

Explore further: Researchers develop hybrid nuclear desalination technique with improved efficiency

More information: Frequency-dependent stability of CNT Joule heaters in ionizable media and desalination processes, Nature Nanotechnology, nature.com/articles/doi:10.1038/nnano.2017.102

 

UC Riverside: Lithium-ion batteries made from recycled glass bottles – Video



Lithium-ion batteries made from recycled glass bottles – UC Riverside 

Researchers  at the University of California, Riverside’s Bourns College of Engineering are using waste glass bottles and a low-cost chemical process to create nanosilicon anodes for lithium-ion batteries that will extend the battery life of electric vehicles and personal electronics.

UC Riverside Research Teams have developed a low-cost way of turning discarded glass bottles into lithium-ion batteries that can store almost 4 times more energy and last much longer than conventional batteries.

The three-step process of producing the anodes starts by crushing and grounding glass bottles into fine white powder, silicon dioxide is then converted into nanostructured silicon, followed by coating the silicon nanoparticles with carbon.

This could mean significantly fewer charges for laptops, cell phones and electric cars, while reducing waste.

Watch The Video:

 

Researchers at UC Riverside Make Magnetic Graphene


Graphene Mag researchersmGraphene, a one-atom thick sheet of carbon atoms arranged in a hexagonal lattice, has many desirable properties. Magnetism alas is not one of them. Magnetism can be induced in graphene by doping it with magnetic impurities, but this doping tends to disrupt graphene’s electronic properties.

Now a team of physicists at the University of California, Riverside has found an ingenious way to induce magnetism in while also preserving graphene’s electronic properties. They have accomplished this by bringing a graphene sheet very close to a magnetic insulator – an electrical insulator with magnetic properties.

“This is the first time that graphene has been made magnetic this way,” said Jing Shi, a professor of physics and astronomy, whose lab led the research. “The magnetic graphene acquires new so that new quantum phenomena can arise. These properties can lead to new electronic devices that are more robust and multi-functional.”

Graphene Mag researchersm

Graphene is a one-atom thick sheet of carbon atoms arranged in a hexagonal lattice. UC Riverside physicists have found a way to induce magnetism in graphene while also preserving graphene’s electronic properties. Credit: Shi Lab, UC Riverside.

Read more at: http://phys.org/news/2015-01-magnetic-graphene.html#jCp

The finding has the potential to increase graphene’s use in computers, as in computer chips that use electronic spin to store data.

Study results appeared online earlier this month in Physical Review Letters.

The magnetic insulator Shi and his team used was yttrium iron garnet grown by laser in his lab. The researchers placed a single-layer graphene sheet on an atomically smooth layer of yttrium iron garnet. They found that yttrium iron garnet magnetized the graphene sheet. In other words, graphene simply borrows the from yttrium iron garnet.

Magnetic substances like iron tend to interfere with graphene’s electrical conduction. The researchers avoided those substances and chose yttrium iron garnet because they knew it worked as an electric insulator, which meant that it would not disrupt graphene’s electrical transport properties. By not doping the graphene sheet but simply placing it on the layer of yttrium iron garnet, they ensured that graphene’s excellent electrical transport properties remained unchanged.

In their experiments, Shi and his team exposed the graphene to an . They found that graphene’s Hall voltage – a voltage in the perpendicular direction to the current flow – depended linearly on the magnetization of yttrium iron garnet (a phenomenon known as the anomalous Hall effect, seen in magnetic materials like iron and cobalt). This confirmed that their had turned magnetic.

Explore further: Researchers find magnetic state of atoms on graphene sheet impacted by substrate it’s grown on