December 14, 2015

Faster, finer filtration

A blend of block copolymers creates a nanofiltration material to produce
a cheap way of removing contaminants from water.
Reproduced with permission from Ref 1.© 2015

(December 14, 2015)  A method of fabricating polymer membranes with nanometer-scale holes that overcomes some practical challenges has been demonstrated by KAUST researchers.

Porous membranes can filter pollutants from a liquid, and the smaller the holes, the finer the particles the membrane can remove. The KAUST team developed a block copolymer membrane with pores as small as 1.5 nanometers but with increased water flux, the volume processed per hour by a membrane of a certain area.

A nanofilter needs to be efficient at rejecting specific molecules, be producible on a large scale, filter liquid quickly and be resistant to fouling or the build-up of removed micropollutants on the surface.

Block copolymers have emerged as a viable material for this application. Their characteristics allow them to self-assemble into regular patterns that enable the creation of nanoporous materials with pores as small as 10 nanometers.

However, reducing the size further to three nanometers has only been possible by post-treating the membrane (depositing gold, for example2). Moreover, smaller holes usually reduce the water flux.

Klaus-Viktor Peinemann from the KAUST Advanced Membranes & Porous Materials Center and Suzana Nunes from the KAUST Biological and Environmental Science and Engineering Division formed a multidisciplinary team to find a solution.

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