Sep. 20, 2018
NewsScientific News

A New Way to Quickly Filter Water

  • A liquid metal droplet with flakes of aluminium oxide compounds grown on its surface. Each 0.03mm flake is made up of about 20,000 nano-sheets stacked together. Credit: RMIT UniversityA liquid metal droplet with flakes of aluminium oxide compounds grown on its surface. Each 0.03mm flake is made up of about 20,000 nano-sheets stacked together. Credit: RMIT University

Australian researchers have designed a rapid nano-filter that can clean dirty water over 100 times faster than current technology.Simple to make and simple to scale up, the technology harnesses naturally occurring nano-structures that grow on liquid metals.

The RMIT University and University of New South Wales (UNSW) researchers behind the innovation have shown it can filter both heavy metals and oils from water at extraordinary speed. RMIT researcher Dr Ali Zavabeti said water contamination remains a significant challenge globally - 1 in 9 people have no clean water close to home.The liquid metal chemistry process developed by the researchers has potential applications across a range of industries including electronics, membranes, optics and catalysis. The groundbreaking technology is sustainable, environmentally-friendly, scalable and low-cost. The researchers created an alloy by combining gallium-based liquid metals with aluminium. When this alloy is exposed to water, nano-thin sheets of aluminium oxide compounds grow naturally on the surface.

These atomically thin layers - 100,000 times thinner than a human hair - restack in a wrinkled fashion, making them highly porous. This enables water to pass through rapidly while the aluminium oxide compounds absorbs the contaminants. Experiments showed the nano-filter made of stacked atomically thin sheets was efficient at removing lead from water that had been contaminated at over 13 times safe drinking levels, and was highly effective in separating oil from water. The process generates no waste and requires just aluminium and water, with the liquid metals reused for each new batch of nano-structures. The method developed by the researchers can be used to grow nano-structured materials as ultra-thin sheets and also as nano-fibres. These different shapes have different characteristics - the ultra-thin sheets used in the nano-filter experiments have high mechanical stiffness, while the nano-fibres are highly translucent. The ability to grow materials with different characteristics offers opportunities to tailor the shapes to enhance their different properties for applications in electronics, membranes, optics and catalysis.
Original publication: DOI: 10.1002/adfm.201804057

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