Decline in water quantity and quality has accelerated the adoption of desalination as a reliable source of potable water. Widespread implementation of membrane-based desalination technologies, however, is constrained by the high energy requirement. A fundamental redesign of reverse osmosis (RO) membranes will be needed to meet water resource needs in an energy constrained environment. The overarching aim of the proposed research is to reduce the energy demands of membrane-based desalination by increasing membrane permeability and reducing fouling. This project exploits the unique properties of carbon nanotubes (CNTs) in the design of novel RO membranes with high flux and resistance to biofouling. The first objective is to improve permeability and reduce biofouling of conventional thin-film composite (TFC) RO membranes by incorporating single-walled carbon nanotubes (SWNTs) into the thin-film barrier. They hypothesize that SWNTs will perturb the polymer packing structure of the thin-film polyamide layer, thereby enhancing the permeability of conventional TFC membranes. The antimicrobial characteristics of SWNTs also offer novel strategies for the prevention of membrane biofouling. The proposed research will optimize SWNT incorporation into TFC RO membranes, evaluate the impact of SWNTs on membrane permeability and selectivity, quantify microbial inactivation at the SWNT-TFC membrane surface, and elucidate the mechanistic pathways for permeability enhancement and bacterial cytotoxicity. The second objective of the proposed research is to fabricate an aligned SWNT membrane. Theory predicts high flux and high salt rejection through aligned CNT membranes, but current fabrication techniques cannot produce membranes that meet theoretical requirements for desalination through a size exclusion mechanism. Post-synthesis alignment of SWNTs using liquid crystalline agents will yield a membrane with SWNT diameters small enough to reject hydrated salt ions. Their research will involve the preparation and characterization of SWNTs, optimization and characterization of the liquid crystalline system, demonstration of SWNT alignment, characterization of aligned SWNT membranes, and optimization of membrane porosity. The proposed research will develop the scientific base for the fabrication of robust RO membranes with high permeability and reduced biofouling propensity. These next generation RO membranes will substantially reduce the energy use and cost of desalination, thereby providing a viable avenue for augmenting and diversifying global water supplies via seawater desalination. Knowledge gained from this research can be readily applied to the development of highly selective carbon nanotube-based ultrafiltration and nanofiltration membranes that can be used in biomedical, chemical, analytical, and environmental separation processes. The majority of requested funds will be applied toward the training of a doctoral student on an emerging and interdisciplinary research topic. The student will have the opportunity to serve as a TA on a newly developed Polymer Physics course that features a lab module on experimental techniques heavily utilized in the proposed work. Additionally, two undergraduate students will carry out their senior theses research as part of this project. Both the PI and co-PI are committed to recruitment of underrepresented groups in science and will further that goal in this project. The proposed work will be used as the basis for the design and implementation of high school science projects, as part of the New Haven Science Fair for students and a Research Experience for Science Teachers (REScT) program. Critically, these outreach efforts advance K-12 science education and increase awareness of water quality and environmental issues. Beyond the research and educational benefits, the proposed work has the potential for profound, tangible societal impact, as it directly addresses the advancement of science and development of technology to tackle a pressing concern.
