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Molecular ‘sieves’ harness ultraviolet irradiation for greener power generation

Posted on June 14, 2013
Image shows fluorescence of solution (left) and membrane (right) made of a polymer of intrinsic microporosity (PIM-1) under irradiation of ultraviolet (UV) light. The ultraviolet irradiation induces oxidation and surface densification of the polymeric molecular sieve membranes. Credit: Nature Publishing Group

Image shows fluorescence of solution (left) and membrane (right) made of a polymer of intrinsic microporosity (PIM-1) under irradiation of ultraviolet (UV) light. The ultraviolet irradiation induces oxidation and surface densification of the polymeric molecular sieve membranes. Credit: Nature Publishing Group

New research shows that exposing polymer molecular sieve membranes to ultraviolet (UV) irradiation in the presence of oxygen produces highly permeable and selective membranes for more efficient molecular-level separation, an essential process in everything from water purification to controlling gas emissions.

Published in the journal Nature Communications, the study finds that short-wavelength UV exposure of the sponge-like polymer membranes in the presence of oxygen allows the formation of ozone within the polymer matrix. The ozone induces oxidation of the polymer and chops longer polymer chains into much shorter segments, increasing the density of its surface.

By controlling this ‘densification’, resulting in smaller cavities on the membrane surface, scientists have found they are able to create a greatly enhanced ‘sieve’ for molecular-level separation – as these ‘micro-cavities’ improve the ability of the membrane to selectively separate, to a significant degree, molecules with various sizes , remaining highly permeable for small molecules while effectively blocking larger ones.

The research from the University of Cambridge’s Cavendish Laboratory partly mirrors nature, as our planet’s ozone layer is created from oxygen hit by ultraviolet light irradiated from the sun.

Researchers have now demonstrated that the ‘selectivity’ of these newly modified membranes could be enhanced to a remarkable level for practical applications, with the permeability potentially increasing between anywhere from a hundred to a thousand times greater than the current commercially-used polymer membranes.

Scientists believe such research is an important step towards more energy efficient and environmentally friendly gas-separation applications in major global energy processes – ranging from purification of natural gases and hydrogen for sustainable energy production, the production of enriched oxygen from air for cleaner combustion of fossil fuels and more-efficient power generation, and the capture of carbon dioxide and other harmful greenhouse gases.

Read more at: Phys.org

   
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