(179d) Functionalized Membranes for Water Treatment: An Overview (Invited Keynote Speech)

Functionalization of membranes with appropriate macromolecules or nanoparticles provides water treatment applications such as, tunable water flux and separations at low pressure, toxic metal capture, toxic organics destruction, etc. Traditionally, microfiltration membranes have been used for filtration of suspended solids, bacteria, viruses, etc. However, microfiltration membranes (eg, cellulosics, silica, polysulfone, polycarbonate, alumina) can be functionalized with a variety of reagents. Depending on the types of functionalized groups (such as, chain length, charge of groups, biomolecule, etc.) and number of layers, these types of membranes could be used in applications ranging from environmental applications to biocatalysis. In addition, electrostatic self assembly in pores (layer-by-layer, LBL) can also be achieved through alternate adsorption of cationic and anionic poly-aminoacids under convective flow conditions. Non-stoichiometric immobilization of charged multilayers within a confined pore geometry leads to an enhanced volume density of ionizable groups in the membrane phase. For example, the use of polypeptides with helix-coil transitions allows nano-domain interactions in membrane pores for selective environmental separations (using layer-by-layer nano-assembly in pores), and for the capture of various toxic metals. Multilayer assemblies of polyelectrolytes provide excellent platform for protein/enzyme immobilization by providing reusability and high reactivity. The presentation will include the role of nano-domain interactions for selective separations, polypeptide assembly in membrane pores for water treatment applications, in-situ synthesis methods of nano-structured bimetallic systems in membrane domain for chloro-organic detoxification from water. The use of nanostructured metals immobilized in membrane phase is expected to have significant positive impact on pollution remediation through compact and flexible dechlorination technology development with high reaction rates at room temperature, significant reduction of metals usage, and improvement in water quality. The authors would like to thank NIEHS-SBRP, US EPA, and NSF-IGERT program for funding various aspects of this work.