CBET-EPSRC A Game-Changing Approach for Tunable Membrane Development: Novel Covalent Organic Framework Active Layers Supported by Solvent Resistant Materials

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

Title: CBET-EPSRC A Game-Changing Approach for Tunable Membrane Development: Novel Covalent Organic Framework Active Layers Supported by Solvent Resistant Materials 1706219 Marinas Surface and groundwater may be purified to drinking water quality standards via nanofiltration, a pressure-driven process which relies on a membrane as a physical barrier to remove contaminants from water. The membrane allows water to pass through its nanometer size pores at a higher rate compared to dissolved and/or suspended solutes, resulting in purification of the water that passes through the membrane. To achieve even higher water quality, more selective reverse osmosis membranes have sub-nanometer pores, which require higher applied pressure to facilitate water transport across the membrane. There is a general trade-off between permeability of the membrane to water versus impermeability to contaminants: smaller pore sizes retain a broader range of contaminants but decrease water throughput per unit time and/or increases energy consumption; in contrast, larger pore sizes lead to less contaminant rejection but higher water permeability or lower energy consumption. State of the art membranes are made from polymers, for which the spaces between the polymeric chains act as the pores that filter the contaminants. As these pores are formed via the three-dimensional arrangement of polymer chains, the pore size is not easily controlled on a molecular level. Current membranes have a limited lifetime, due to the negative effects of biofouling, mechanical compaction, and chemical degradation. Biofouling is a result of the deposition of organic contaminants and nutrients on the membrane and the subsequent growth of a biofilm that creates a barrier for subsequent water permeation through the membrane; polymer compaction results in pore tightening in the amorphous portion of membranes that leads to reduced water permeability; and chemical degradation is a process exacerbated by the use of harsh chemicals during cleaning of fouled membranes that ultimately results in higher permeability to contaminants. To address these concerns, this project will develop novel membranes that enable a molecular-level design of pore size and shape and the incorporation of fouling-resistant chemical functional groups. The project capitalizes upon a new interfacial polymerization process that synthesizes covalent organic frameworks in a high-surface area thin polymeric film. Unlike other polymeric materials, these frameworks are highly crystalline with well-defined surface chemistry and a regular pore structure, this regularity enables molecular level design, which in turn will allow for optimized retention of particular solutes combined with high water permeability across the membrane. The frameworks could also be modified to incorporate anti-fouling surface chemistry and to decrease pore size. The key advance of this collaborative project is to develop the thin active covalent organic framework layer in concert with a polymeric support that is stable in the solvents used for the polymerization process and during membrane cleaning. The project scope of work includes synthesis of novel membranes with various building blocks, tuning of pore size and surface chemistry by altering the covalent organic framework, and the identification of solvent stable support media. Various surface analysis techniques will be used for the physicochemical characterization of the resulting membranes, and optimization of the interfacial polymerization process to control the interface between the covalent organic framework and the support. The resulting membranes will be tested for performance with aqueous solutions of model contaminants. This international collaboration, facilitated by an inter-agency agreement between the U.S. and U.K., brings together membrane and polymer synthesis experts from two countries to develop this new class of membranes while building an international research network and providing students with a unique international educational opportunity.