Institute: Rhode Island
Year Established: 2011 Start Date: 2011-03-01 End Date: 2012-02-28
Total Federal Funds: $15,856 Total Non-Federal Funds: $34,605
Principal Investigators: Geoffrey Bothun
Abstract: Fouling of polymeric membranes used in water treatment represents the major challenge to employing membrane-based treatment processes at the state, regional, and global levels. Stimuli responsive membranes represent a novel means of mitigating fouling by, for example, changing their surface adhesion properties, morphology, and roughness during operation. Temperature-stimulated polymers, such as poly(n-isopropylacrylamide) or polyNIPAAM, exhibit a lower critical solution temperature (LCST) where the polymer chains undergo a coiled to globule transition with increasing temperature. Associated with this transition is a decrease in polymer volume (as a hydrogel) or thickness (as a film), and a transition from hydrophilic to hydrophobic. This proposal seeks to exploit this property to inhibit membrane fouling and manipulate flux and solute rejection by depositing polyNIPAAM brush films on cellulose acetate ultrafiltration membranes. Rather than utilizing bulk heating to cross the LCST, which is energy intensive and yields thermal pollution, the modified membranes will be thermally-activated by heating embedded superparamagnetic iron oxide (SPIO) nanoparticles using alternating current electromagnetic fields (EMFs). This mode of activation will provide direct and localized heating to control surface roughness and surface hydrophobicity. Because heating is localized within the NIPAAM film, the activation response time will be rapid and frequent cycling between activated and non-activated states will be achieved. This approach to inhibiting fouling and manipulating separation performance is novel, and could have a broad impact in the field of surface engineering and membrane modification. This proposal leverages an ongoing collaboration between PI Bothun and Prof. Isabel Escobar at the University of Toledo. It is driven by the central hypothesis that temperature activation in a NIPAAM/cellulose acetate nanocomposite membrane can be reversibly triggered through alternating current electromagnetic field heating of embedded SPIO nanoparticles without comprising membrane integrity. To test these hypotheses we will (Objective 1) characterize chemical and morphological changes of the stimuli-responsive membranes as a function of nanoparticle concentration and temperature via scanning electron microscopy and x-ray photoelectron spectroscopy; (Objective 2) determine the effects of EMF temperature activation on membrane water flux by developing an testing unit capable of in situ membrane heating; and (Objective 3) determine the effects of temperature activation on film stability and fouling via dynamic contact angle analysis and fluorescence microscopy.