The goal of this proposal is to enhance understanding of the fundamental mechanisms of particle size separation and the processes that control metal ion species adsorption by biopolymer gel micro and nanoparticles, with the aim of guiding the next generation of biosorbent design. Specifically, the work will examine multiphase flow in complex geometries that serve as models for water purification devices in order to discover the mechanisms driving particle size separation phenomena during flow and subsequent adsorption processes. Utilization of abundant and biocompatible natural biopolymers with outstanding sorbent properties and low energy cross-linking routes offers a unique opportunity for effective heavy metal contaminant removal from industrial wastewater streams, a leading environmental concern. Improved insight into the multiphase transport aspects of water purification is essential for improving the efficacy and speed of water treatment. Intellectual Merit: The novelty of this research derives from the proposed experimental study of heterogeneous particle suspensions in complex geometry flows, and mass transfer at the micro and nanoscale in resulting fixed particle beds formed from such flows. During the filling of a typical fixed bed geometry, the flow field is tightly coupled to the nonuniform spatial distribution of particles. Hence, it is beyond the predictive power of current suspension models to anticipate the resulting flows of bimodal suspensions (two particle sizes). In addition, the particle materials, specifically biopolymer gels, are known to have strong complexation and electrostatic interactions with metal ions in solution, but a combined multiscale structure including biopolymer nanoparticles has not been considered. The powerful experimental technique of nuclear magnetic resonance imaging (NMRI) will be used to gather detailed information on several features of particle and species transport. Experimental results will also be compared with state of the art calculations based on continuum modeling of monomodal suspension flows. The specific aims of this research program include: (1) Synthesizing biopolymer microbeads coated with complementary biopolymer nanoparticles and characterizing equilibrium heavy metal ion uptake. (2) Understanding mechanisms of particle size separation in a bimodal suspension flowing through model filtration bed geometries. (3) Quantifying the kinetics of metal ion adsorption in flow through a fixed bed of biopolymer micro-nanoparticle structures. Broader Impact Technology: The fundamental research results can be implemented as long-term practical guidelines for the utilization of complementary biopolymer micro and nanoparticle structures in the next generation of wastewater purification units, in order to improve purification efficiency and employ naturally abundant and environmentally benign materials. Educational Impact: Education and outreach activities will focus on incorporating concepts and results from the research into hands-on, active laboratory experiences for students at multiple educational levels. Hands-on laboratory experiences involving fluid mechanics and rheology will energize programs ranging from an academic enrichment program for disadvantaged high school students to a graduate laboratory course helping to prepare students for doctoral research. Intensive research training in the P.I.?s laboratory, for high school, undergraduate, and graduate students, is also a key component of the educational activities. This unified research and education project will enhance the understanding of multiphase transport issues that are crucial for achieving efficient removal of toxic metal contaminants from water while simultaneously it will engage and train the next generation of scientists in the study of fluid flows and material properties.
