• Dai, Jane
• Duke, Mikel
• Orbell, John
• She, Fenghua
• Winther-Jensen, Bjorn
• Dumée, Ludo
• Reis, Rackel

Abstract

Surface modification of thin film composite (TFC) membranes has been widely explored as one of the pathways to design improved reverse osmosis desalination membranes. The membrane’s urface charge plays an important role in rejecting water-born contaminantsdue to strong nanoscale electrostatic interactions . Plasma treatments are rapid and cost-effective techniques to tune surfaces to achieve desirable surface properties. Such treatments lead to the design of unique surfaces with cotrollable physical and chemical properties. Here, two different routes using plasma tecnique were explored for tuning TFC surface. The first one was performed by using reactant gases, such as argon, to chemically etch and modify the texture of the membranes, while the second involved the plasma polymerization of monomers across the surface to increase carboxylic and amine functional groups densities and therefore alter surface charge. A simple argon plasma treatment at low power increased fresh water transport through the membrane by up to 36% without loss of the cirtical salt-rejecting property. Also negative surface charge, when characterised by the streaming potential, was dramatically increased from -20 to -65 mV between 10 and 50 W plasma power. Likewise, plasma polymerization of maleic acid monomers significantly increased negative charges reaching up to -80 mV without compromising membrane performance. On the other hand, plasma polymerization of 1-vinyl(imidazole) increased amine groups and therefore, positive charges reached +30 mV and isoelectric point was formed around pH 7. Analysis of resultant film homogeinity and thickness was performed by FTIR mapping at the Australian Synchrotron. Membrane film uniformity and thickness was increased with increasing plasma duration up to 15 min. This presentation demonstrates the potential of plasma as a fine tunning tool and versitile technique to design smart next generation desalination membranes that deliver fresh potable water from contaminated sources to the community.

Topics

• surface
• thin film
• composite
• texture
• amine
• surface energy