06 April 2010

New Desalination Membrane Self-Cleaning

A new method of fabricating nano-membranes for desalinating and purifying water, is described in the current issue of Journal of Materials Chemistry. The new membrane structure was devised by UCLA researchers, and incorporates nano-fibrous "brushes" which self-clean the membrane to prevent fouling. This self-cleaning should reduce the maintenance costs of reverse osmosis desalination and water purification appreciably.
The highly permeable, surface-structured membrane can easily be incorporated into today's commercial production system, the researchers say, and could help to significantly reduce desalination operating costs. Their findings appear in the current issue of the Journal of Materials Chemistry.

...The new membrane was synthesized through a three-step process. First, researchers synthesized a polyamide thin-film composite membrane using conventional interfacial polymerization. Next, they activated the polyamide surface with atmospheric pressure plasma to create active sites on the surface. Finally, these active sites were used to initiate a graft polymerization reaction with a monomer solution to create a polymer "brush layer" on the polyamide surface. This graft polymerization is carried out for a specific period of time at a specific temperature in order to control the brush layer thickness and topography.

...In this new membrane, the polymer chains of the tethered brush layer are in constant motion. The chains are chemically anchored to the surface and are thus more thermally stable, relative to physically coated polymer films. Water flow also adds to the brush layer's movement, making it extremely difficult for bacteria and other colloidal matter to anchor to the surface of the membrane. _PO

It is now a matter of finding economic ways to scale the process for fabricating large surface areas of material cheaply.


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