Water filtration with a 'molecular sieve'

Deakin University scientists have used cutting-edge nanomaterials to create a chemical filter capable of industrial-grade water purification, in a study described in the journal Nature Communications.

Researchers from Deakin’s Institute for Frontier Materials (IFM) made the filter with layered flakes of hexagon-shaped chemical compound boron nitride, creating a stable and highly resistant membrane that can filter and block out more than 99% of nanoparticles. The team was led by Dr Weiwei Lei, whose previous work has included a boron nitride nanosheet sponge capable of absorbing oil from water.

A Senior Research Fellow at IFM, Dr Lei said the membrane, which contains microscopic parts, could be used to provide clean drinking water, while also being effective at purifying organic solvents such as acetone and alcohol. He explained, “Small molecules can pass through the nanochannels of the membrane, but the larger molecules and impurities are blocked.

“This forms an excellent filtration membrane, and it will be a good candidate for purification such as separating organic material and removing toxic dyes from water and organic solvents, which has huge potential for applications across water, chemical and pharmaceutical industries.”

Dr Lei said this is the first time chemically stable boron nitride has been used to create a functional membrane, meaning it is much more effective than commercial filter membranes and others based on 2D nanomaterials.

“Our new membrane has an adjustable thickness and high durability — and unlike commercial membranes currently on the market it is stable under harsh conditions, such as in acidic and basic solutions,” he said.

“It also has more nanochannels for small molecules to pass through, offering unprecedented transport performance and filtering at levels more than 1500 times higher than those of commercial membranes.”

Dr Lei added that the separation and recovery of organic solvents is currently a global problem for chemical and pharmaceutical companies, accounting for 40–70% of operating costs. Any new efficient separation process or materials will thus minimise the cost and consumption of energy, he said.

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