Miguel Jaimes, “Continuous Covalent Organic Framework Membranes for Dye/Salt Separation”
Mentors: Xiaoli Ma, Junwei Wang, & Zhiqin Qiang, Materials Science & Engineering
Covalent organic frameworks (COFs) are an emerging class of porous membrane materials constructed from organic building blocks via strong covalent bonds. They possess a wide range of unique properties including high crystallinity, ordered two or three-dimensional pore structure, tunable pore size and functionality, and excellent thermal and chemical stability. With a pore size in the range of 1-3nm, COF membranes are well suited for nanofiltration applications such as the separation of dye molecules. In this work, we will present the synthesis and dye/salt separation properties of COF membranes based on ketoenamine-linked two dimensional (2D) COFs. Their pore structures are constructed by aldehydes and diamines through a Schiff base reaction followed by irreversible enol-keto tautomerism. These 2D COFs can be synthesized as continuous membranes on polymeric substrates using a facile and scalable interfacial crystallization method. In a cross-flow filtration setup, measurements using single dye or salt solution, the membranes showed a high water permeance of >50 L m-2 h-1 bar-1 with a high rejection of dye molecules (e.g., 100% rejection of Congo Red) and low rejection rates (<5%) for mono- and divalent salts (e.g., NaCl and MgSO4). The dye/salt mixture separation properties of these membranes at different separation conditions will also be discussed in this poster presentation.
As an Environmental Science major, this topic is very exciting! I remember seeing images of neon purple and pink rivers in India flowing near textile plants. Any company would be delighted to hear about the reuse of dyes, except for the current dye producers I suppose. Your diagrams and graphs are very clear and easy to understand. Very interesting work and positive results, thank you for sharing!