Electro-conductive porous materials (membranes) for electrosorption / -desorption of natural organic matter from water
Final Report Abstract
Natural water sources including surface water contain a variety of organic and inorganic compounds, with natural organic matter (NOM) posing significant challenges for water treatment. Removing specific NOM fractions, particularly larger molecular weight compounds like humic substances (HSs), is essential to reduce the formation of disinfection by-products (DBPs) such as trihalomethanes (THMs) and haloacetic acids (HAAs) in chlorinated water. The best approach to decrease DBP potential is to remove NOM before the disinfection step. In this project, the concept of electro-conductive (EC) membranes was explored with the aim to increase selectivity of a porous ultrafiltration (UF) membranes for NOM, using electrical potential to drive the filtration process, while keeping the membrane fouling potential low. Virgin and modified polyacrylonitrile (PAN) UF membranes with diverse chemical functional groups were used to establish EC membranes. A porous thin conductive metal (Pt) nanolayer was applied on both side of the membrane using a plasma-based magnetron sputtering process. These porous EC membranes were tested in a flow-through electrode configuration in dead-end filtration plant. The membrane's selective layer acted as the working electrode, and the conductive supporting layer served as the counter electrode, simplifying the design by eliminating the need for an additional counter-electrode. An electrical potential difference ranging from 0.5V to 2.5V was applied across the electrodes to drive the electro-sorption and electro-desorption processes. During the project, electro-sorption processes were studied on EC membranes. Positive potentials were applied to the working electrode for electro-sorption, and polarity was switched to negative for electro-desorption. UF membrane materials with high polarizability and positive zeta potential proved to be effective for electro-sorption, aiding in efficient NOM removal without severe fouling. The performance of EC membranes improved with increasing positive potential and was not significantly affected by the speed of filtration (contact time). The electro-sorption process efficiently removed HSs and the removal of NOM fractions decreased with decreasing molecular weight compounds at applied filtration pressure of < 0.2 bar. Moreover, up to 25% of NOM, primarily uncharged fractions, remained in the water. The NOM electro-sorption process on EC membranes was largely reversible. EC membranes showed high NOM separation efficiency (up to 75%) without losing performance, thus allowing for membrane regeneration and consistent performance. An additional advantage of the counter electrode configuration of EC membranes is a significant increase in filtration flux due to the electro-osmotic phenomenon. Additionally, the energy demand for electro-filtration was very low (20 Wh/m3), making it an efficient approach for treating water with high NOM content.
Publications
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Amine‐Terminated PAN Membranes as Anion‐Adsorber Materials. Chemie Ingenieur Technik, 93(9), 1396-1400.
Glass, Sarah; Mantel, Tomi; Appold, Michael; Sen, Sitashree; Usman, Muhammad; Ernst, Mathias & Filiz, Volkan
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Modification of Polyacrylonitrile Ultrafiltration Membranes to Enhance the Adsorption of Cations and Anions. Membranes, 12(6), 580.
Kishore, Chand Anthony Arvind; Bajer, Barbara; Schneider, Erik S.; Mantel, Tomi; Ernst, Mathias; Filiz, Volkan & Glass, Sarah
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Conductive membranes for removal of organic water constituents in drinking water treatment. Center for Molecular Water Science (CMWS) Water Days, 26-28 Feb. 2024, Hamburg.
Usman, Muhammad
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Electro-sorption and -desorption characteristics of electrically conductive polyacrylonitrile membranes to remove aqueous natural organic matter in dead-end ultrafiltration system. Journal of Water Process Engineering, 58, 104733.
Usman, Muhammad; Glass, Sarah; Mantel, Tomi; Filiz, Volkan & Ernst, Mathias
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Elucidating the Mechanism of Electro-Adsorption on Electrically Conductive Ultrafiltration Membranes via Modified Poisson-Boltzmann Equation. Membranes, 14(8), 175.
Usman, Muhammad; Vahedi, Shahrokh; Glass, Sarah; Filiz, Volkan & Ernst, Mathias
