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Australian researchers develop ultrathin nanosheets to separate lead from water

In a world-first for water treatment processes, researchers have created an ultrathin porous membrane to completely separate harmful ions such as lead and mercury from water.

Led by Monash University and Australia's Nuclear Science and Technology Organisation (ANSTO), the research team may have found a way to enhance the desalination process and transform dirty water into something potable for millions of people across the world.

The novel membrane performed for more than 750 hours using limited energy and has the potential to be manufactured on a global scale, pending further testing.

Monash University Department of Chemical Engineering’s Professor Xiwang Zhang, who led the study, said the membrane offered plenty of advantages as a water purification tool, but there was still work to be done.  

“Owing to the rich porosity and uniform pore size, Metal Organic Frameworks (MOFs) offer significant advantages over other materials for the precise and fast membrane separation,” Professor Zhang said.

“However, it remains a daunting challenge to fabricate ultrathin MOFs membranes (less than 100 nanometres) for water-related processing, since most reported MOFs membranes are typically thick and suffer from insufficient hydrolytic stability.

“In this world-first study, we were able to use these ultrathin Al-MOFs to create a membrane that is permeable to water, while achieving maximum porosity with nearly 100% rejection of ions.”

Traditional polymeric membranes for ion separation usually contain a dense selective layer, leading to limited selectivity. Nanoporous membranes may overcome this limitation.

ANSTO Principal Scientist Dr Qinfen Gu said the research confirmed that the intrinsic nanopores of Al-MOFs nanosheets facilitate the ion-water separation by creating vertically-aligned channels as the main transport pathway for water molecules.

“We use an instrument called the Powder Diffraction beamline at ANSTO’s Australian Synchrotron, to understand the difference between the molecular structure of nanosheet samples, and samples at different temperatures, in order to test water purification performance,” Dr Gu said.

“The technique, called in-situ, high temperature powder X-ray diffraction characterisation, was conducted on the nanosheets, and during the process there were no obvious variations in the samples at increasing temperature, demonstrating their robustness.”