NAMS 2002 Workshop - ICOM 2008

Membrane and Surface Modification I – 6
Tuesday July 15, 5:00 PM-5:30 PM, Wai’anae
Dopamine: Biofouling-Inspired Anti-Fouling Coatings for Water Purification
Membranes
B. McCloskey (Speaker), The University of Texas at Austin, Austin, Texas, USA
H. Park, University of Ulsan, Korea
B. Freeman, The University of Texas at Austin, Austin, Texas, USA – freeman@che.utexas.edu
One of the main issues facing water purification membrane technology is
membrane fouling, which is the deposition of organic contaminants on the
membrane surface or in its pore structure. Fouling leads to a catastrophic
decrease in water flux which, in turn, results in high operating costs and short
membrane lifetime. Many methods have been studied to combat membrane
fouling, most of which focus on two general techniques: introducing high fluid
shear on the feed stream side, such as backpulsing, dean vortices, and air
sparging, and altering the surface properties of the membranes, either through
surface grafting/coating, plasma treatment, or other chemical modifications.
Although feed flow instabilities increase flux in some MF and UF membrane
applications, fouling is still a concern. Furthermore, combining surface modified
membranes with increased surface shear will lead to higher membrane efficiency
over using one of the two techniques. Therefore, this study focuses on producing
a simple chemical modification technique that uses a strongly bound, hydrophilic
ad-layer, which is stable under even the most extreme fluid shear environments.
Dopamine has been recently used to mimic a mussel s adhesive plaque. In
alkaline solutions, dopamine will self-polymerize (polydopamine) and deposit on
virtually any surface with which it comes into contact. By using this simple
deposition technique, polydopamine is “coated” onto polysulfone (PSf)
ultrafiltration (UF) membranes and polyamide (PA) reverse osmosis (RO)
membranes. Polydopamine was found to increase a membrane s surface
hydrophilicity and therefore increase its resistance to fouling. After one day of oilemulsion
fouling, the polydopamine-coated PSf membrane showed a flux over 8
times higher than that of the unmodified PSf membrane, and a polydopaminemodified
PA RO membrane exhibited a 30% flux increase over the unmodified
membrane. Furthermore, organic rejection of the modified membranes is similar
to that of the unmodified membranes.