How To Make Toxic Water Safe And Drinkable

In Australia, 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.