Chemical engineers develop 'outstanding alternative' to clean water

Thursday, 4 October 2018

As water contamination remains a significant problem world-wide, Australian engineers have designed a nanofilter that can clean dirty water more than 100 times faster than current technology.

Researchers from RMIT University in Melbourne and The University of NSW in Sydney have developed the technology that they say harnesses naturally occurring nanostructures which grow on liquid metal.

RMIT’s Dr Ali Zavabeti, an automation engineer, said heavy metal contamination causes serious health problems, with children particularly vulnerable.

“We’ve shown it works to remove lead and oil from water, but we also know it has potential to target other common contaminants,” Dr Zavabeti said. “Previous research has already shown the materials we used are effective in absorbing contaminants like mercury, sulphates and phosphates.”

Project leader, Professor Kourosh Kalantar Zadeh, is a professor of chemical engineering at UNSW and an honorary professor at RMIT. He revealed that the liquid metal chemistry used in the process enabled differently shaped nanostructures to be grown – as atomically-thin sheets for the nanofilter or as nanofibrous structures.

“Growing these materials conventionally is power intensive, requires high temperatures, extensive processing times and uses toxic metals,” he said. “Liquid metal chemistry avoids all these issues, so it’s an outstanding alternative.”

The team created an alloy by combining gallium-based liquid metals with aluminium. When this was exposed to water, nano-thin sheets of aluminium oxide compounds grew naturally on the surface.

“These atomically -layers restack in a wrinkled fashion, making them highly porous,” Prof Kalantar Zadeh said. “This enabled water to pass through rapidly while the aluminium oxide compounds absorbed the contaminants.”

Experiments showed the nanofilter 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 team said the process does not generate any waste and only requires aluminium and water, with the liquid metals reused for each new batch of nanostructure.

Dr Zavabeti said the team’s new nanofilter is sustainable, environmentally-friendly, scalable and low cost, and has the potential for a range of applications across electronics, membranes, optics and catalysis. The findings are published in the journal Advanced Functional Materials.

 

Image: A liquid metal droplet with flakes of aluminium oxide compounds grown on the surface; each flake represents 20,000 nanosheets. Source: RMIT University.

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