A team of Australian and US scientists today announced a world advance in the use of membrane technology to filter and separate various gases and vapours.

The breakthrough has implications for many activities, ranging from water purification and environmental cleanup, to better fuels and petrochemicals, purer medicines and desalination of seawater for drinking.

A team from CSIRO, University of Texas at Austin, North Carolina State University and MTR, Menlo Park California, reports in the latest issue of Science (April 19) the discovery of a new type of nanoparticle-enhanced filter for separating compounds at the molecular level.

"Just as astrophysicists are exploring 'wormholes' in space-time through which people might one day be able to pass, we're looking at ways to create wormholes at the tiniest level, just millionths of a millimeter in size, in a filter medium so that we can control precisely what passes through and what doesn't," explains CSIRO's Dr Anita Hill.

The new filtration media are created by combining organic polymers normally used to make membrane filters with inorganic substances - in this case a mist of silica nanoparticles.

The team discovered that this combination gives the membrane a quite extraordinary ability to separate large organic molecules from the gases in which they might be floating.

This new class of organic/inorganic materials, known as nanocomposites, have already been shown to be remarkable for enhanced conductivity, being extremely tough, having valuable optical properties and acting as catalysts.

The US-Australian team has now demonstrated a new and potentially even more useful trait - the ability to filter gases and organic vapours at the molecular level.

"This is a diverse field affecting processes such as biomolecule purification, environmental remediation, seawater desalination and petroleum chemicals and fuel production," Dr Hill says.

"Traditionally, this sort of filtering has mostly been done by distillation, which is often very costly in terms of equipment and energy use.

"Membranes are attractive as filters because they are a low-cost, energy-efficient, green technology - but their uses for separating gases have so far been limited by the lack of the right sort of membranes to yield pure products, with high speed and low operating cost while remaining stable."

As a rule, the more selective a polymer is at extracting a pure gas, the less permeable it tends to be - and the more expensive it is to use.

The new nanoparticle-enhanced polymers promise to deliver both high filtering efficiency and high throughput, making them much more cost-efficient, she says.

While the work has so far only been demonstrated in laboratory and pilot-scale trials, further down the track she is confident it offers the prospects of greater efficiency to industries such as Australia's $2.6 billion natural gas export sector - or in the production of hydrogen, now seen by leading CSIRO scientists as Australia's primary energy source of the future.

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