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Fantastic plastic could cut CO2 emissions and purify water

15.10.2007

A new membrane that mimics pores found in plants has applications in water, energy and climate change mitigation.

Announced today in the international journal Science, the new plastic membrane allows carbon dioxide and other small molecules to move through its hourglass-shaped pores while preventing the movement of larger molecules like methane. Separating carbon dioxide from methane is important in natural gas processing and gas recovery from landfill.

The new material was developed as part of an international collaboration involving researchers from Hanyang University in Korea, the University of Texas and CSIRO, through its Water for a Healthy Country Flagship.

“This plastic will help solve problems of small molecule separation, whether related to clean coal technology, separating greenhouse gases, increasing the energy efficiency of water purification, or producing and delivering energy from hydrogen,” Dr Anita Hill of CSIRO Materials Science and Engineering said.

“The ability of the new plastic to separate small molecules surpasses the limits of any conventional plastics.

“It can separate carbon dioxide from natural gas a few hundred times faster than current plastic membranes and its performance is four times better in terms of purity of the separated gas.”

The secret to the new plastic lies in the hourglass shape of its pores, which help to separate molecules faster and using less energy than other pore shapes. In plant cell membranes, hourglass-shaped pores known as aquaporins selectively conduct water molecules in and out of cells while preventing the passage of other molecules such as salt.

The research shows how the plastics can be systematically adjusted to block or pass different molecules depending on the specific application. For example, these membranes may provide a low energy method for the removal of salt from water, carbon dioxide from natural gas, or hydrogen from nitrogen.

Each of these small molecule separations has impact on Australia’s interrelated issues of water scarcity, clean energy, and climate change mitigation.

“The new plastic is durable and can withstand high temperature, which is needed for many carbon capture applications. Heat-stable plastics usually have very low gas transport rates, but this plastic surprised us by its heightened ability to transport gases,” Dr Hill said.

The research is a partnership between Hanyang University Korea, led by Professor Dr Young Moo Lee and, the University of Texas, led by Professor Benny Freeman, and CSIRO.

Dr Hill and her team analysed the material, which was initially engineered by Ho Bum Park at Hanyang University, to show how it worked.

“Because it is so much more efficient than conventional plastic membranes, this material has huge potential to reduce the environmental footprint of water recycling and desalination,” Director of the Water for a Healthy Country Flagship Dr Tom Hatton said.

“Our Flagship, with state governments, water utilities and university partners, is working overtime to improve the sustainability of our water resources. We know how to desalinate and we know how to recycle and the challenge is to do this more efficiently and reliably without adding to greenhouse gas emissions.

“This global partnership has the goal of generating scientific understanding that underpins the development and implementation of new membrane technologies for energy and the environment.

“It is also a demonstration of how collaboration across boundaries can produce transformational science with potential societal benefits."