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Environment, Health, Safety & Security

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Chementator: This Membrane Mimics Mother Nature to Separate CO2

| By Dorothy Lozowski

A plastic membrane that allows CO2 and other small molecules to move through its pores while largely preventing the movement of larger molecules like CH4, has been developed by a team of researchers from CSIRO Materials Science and Engineering and the Water for a Healthy Country Flagship (Melbourne, Australia; edlinks.chemengonline.com/6902-537); the Center for Energy and Environmental Resources, the Department of Chemical Engineering from the University of Texas (Austin) and the School of Chemical Engineering of Hanyang University (Seoul, South Korea). The membrane can separate CO2 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, says Anita Hill, a scientist at CSIRO.

The team has worked with polymers with a cavity size intermediate to those of polyimides, polysulfones, and polycarbonates and those of the most permeable polymer, poly(1-trimethylsilyl-1-propyne). The team’s approach for preparing intermediate-sized cavities is controlled cavity formation through spatial rearrangements of the rigid polymer-chain segment in the glassy phase. Polymers with an intermediate cavity size, a narrow cavity size distribution, and an hourglass shape, such as those found in nature in the form of ion channels and aquaporins — hourglass-shaped pores in plant membranes, which selectively conduct water molecules into cells while preventing the passage of ions — have been shown to yield both high permeability and high selectivity for CO2. The secret of the new plastic lies in the hourglass shape of its pores, which helps to separate molecules faster and using less energy than other pore shapes.