An inexpensive new gadget makes contaminated water drinkable in minutes. (stock image)
Credit: © Vasily Merkushev / Fotolia
UNSW and RMIT researchers have
discovered a revolutionary and cheap way to make filters that can turn
water contaminated with heavy metals into safe drinking water in a
matter of minutes.
Recent UNSW SHARP hire Professor Kourosh Kalantar-zadeh and his
former colleagues at RMIT showed that nano-filters made of aluminium
oxide could be cheaply produced using virtually no energy from a fixed
amount of liquid metal gallium.
In a paper published in Advanced Functional Materials, lead
author Dr Ali Zavabeti (RMIT) and Professor Kalantar-zadeh explained
that when a chunk of aluminium is added to the core of liquid gallium at
room temperature, layers of aluminium oxide are quickly produced at the
surface of the gallium.
The authors discovered that these aluminium oxide nano-sheets were
highly porous and went on to prove they were suitable for filtering both
heavy metal ions and oil contamination at unprecedented, ultra-fast
rates.
Professor Kalantar-zadeh, who was recently awarded an ARC Australian
Laureate Fellowship soon after joining UNSW's School of Chemical
Engineering, said that low cost and portable filters produced by this
new liquid metal based manufacturing process could be used by people
without access to clean drinking water to remove substances like lead
and other toxic metals in a matter of minutes.
"Because it's super porous, water passes through very rapidly," Professor Kalantar-zadeh said.
"Lead and other heavy metals have a very high affinity to aluminium
oxide. As the water passes through billions of layers, each one of these
lead ions get attracted to one of these aluminium oxide sheets.
"But at the same time, it's very safe because with repeated use, the
water flow cannot detach the heavy metal ions from the aluminium oxide."
Professor Kalantar-zadeh believes the technology could be put to good
use in Africa and Asia in places where heavy metal ions in the water
are at levels well beyond safe human consumption. It is estimated that
790 million people, or one in 10 of the Earth's population, do not have
access to clean water.
"If you've got bad quality water, you just take a gadget with one of these filters with you," he said.
"You pour the contaminated water in the top of a flask with the
aluminium oxide filter. Wait two minutes and the water that passes
through the filter is now very clean water, completely drinkable.
"And the good thing is, this filter is cheap."
There are portable filtration products available that do remove heavy
metals from water, but they are comparatively expensive, often costing
more than $100.
By contrast, aluminium oxide filters produced from liquid gallium
could be produced for as little as 10 cents, making them attractive to
prospective manufacturers.
"Up until now, to produce aluminium oxide, you need to process
aluminium at above 1000 degrees or use other energy intensive
processes," Professor Kalantar-zadeh said.
"It would normally consume so much energy to make anything like this filter, making it hugely expensive.
"Now we're talking about something you can do even under the sun in summer at 35 degrees."
While aluminium is a plentiful and cheap metal, gallium is relatively
expensive. But what makes gallium the hero in the process is the fact
that it remains pure and unchanged after each production of aluminium
oxide.
"You just add aluminium to the gallium and out comes aluminium oxide
when its surface is exposed to water. You can use gallium again and
again. Gallium never participates in the reaction," Professor
Kalanter-zadeh said.
Professor Kalantar-zadeh said the manufacture process is so cheap and
requiring such low expenditure of energy, these filters could even be
made out of a kitchen.
"We are publishing this concept and releasing it to the public
domain, so people around the world can use the idea for free and
implement it for enhancing the quality of their lives," he said.
"This is all about a new paradigm. We haven't even begun to explore
how we can use liquid metals as a base for manufacturing things that are
cheap, green and safe for humans."
The work led by Professor Kalantar-zadeh and Dr Zavabeti was funded
by The ARC Centre for Future Low-Energy Electronics Technologies
(FLEET).