A new class of stimuli responsive nanofiltration and ultrafiltration membranes for water treatment will be developed with superior fouling resistance compared to current membranes. More hydrophilic membranes resulting from surface modification demonstrates better anti-fouling properties. The research proposed here involves grafting polymer nanobrushes known to be highly fouling resistant, from the surface of commercially available nanofiltration and ultrafiltration membranes. The research is extremely novel in that these nanobrushes can be magnetically activated. In an oscillating magnetic field they will rotate like the cila of microorganisms leading to mixing at the membrane fluid interface. Preliminary particle-image velocimetry data indicate that nanobrush movement causes mixing in the liquid layer up to 0.5 mm from the membrane surface. Thus unlike previous work, surface modification is used not only to create an anti-fouling surface layer on the membrane, but also, to suppress fouling by hydrodynamic mixing at the actual membrane fluid interface.
Membrane based separations for water treatment applications are often limited due to membrane fouling especially by colloidal particles. This proposal aims to develop a new class of low fouling selfcleaning nanofiltration and ultrafiltration membranes. Fouling resistant nanobrushes will be grown from the surface of commercially available nanofiltration and ultrafiltration membranes. Atom transfer radical polymerization (ATRP) will be used to grow the nanobrushes. ATRP allows fine control over the thickness and density of the nanobrushes. Using ATRP a single reactive functional group may be added to the chain ends. Here an amine group is added to the chain ends, which allows covalent and therefore permanent attachment of superparamagnetic nanoparticles coated with carboxylic groups. In an oscillating magnetic field, the polymer chains move like the cilia of microorganisms. This movement will cause local mixing at the membrane surface which will suppress colloidal fouling. Development of practical magnetically responsive nanofiltration and ultrafiltration membranes will require optimization of nanobrush length and density as well as the superparamagnetic particle size and the external magnetic field strength and oscillation frequency. These parameters also govern energy usage, and heat production, thus optimization requires the ability to predict mixing characteristics for any given configuration. A fluid-structure computational model will be developed using computational fluid dynamics to study mixing as a function of particle size, spacing, and nanobrush length. Parallel theoretical studies will be used to predict the force that acts on the particles as a function of superparamagnetic particle size, and magnetic field strength and frequency. The fundamental scientific knowledge gained could transform the approaches currently used to impart fouling resistance to membranes. Results will be published in journals such as Journal of Membrane Science, Environmental Science & Technology and Macromolecules.
This multidisciplinary international collaborative research project will contribute to the development of highly skilled US workforce that is able to operate in an increasingly global environment. Graduate and undergraduate students will gain from unique international research and training experiences as well as access to equipment and expertise not available at Colorado State University. Colorado State University provides a ?water rich? research and educational environment for graduate and undergraduate students. Students will learn about the many complex water related issues in the western United States. Students from underrepresented groups in science and engineering will be recruited through the existing programs at CSU such as the Colorado AEGP. Undergraduates will work in a team on subprojects that match their educational level. Project meetings will be held with the German collaborators via web-conferencing. Development of fouling resistant membranes for water treatment will have tremendous societal impacts and benefits. Further by focusing on nanofiltration and ultrafiltration membranes, the research will establish the scientific knowledge and feasibility for development of responsive reverse osmosis and microfiltration membranes. Successful completion of the proposed research will lead to a new class of fouling resistant membranes that could find applications in other area such as bioseparations.
