Macromolecules Innovation Institute (MII)

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Browsing Macromolecules Innovation Institute (MII) by Department "Civil and Environmental Engineering"

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    Exceptional capacitive deionization rate and capacity by block copolymer–based porous carbon fibers
    Liu, Tianyu; Serrano, Joel; Elliott, John; Yang, Xiaozhou; Cathcart, William; Wang, Zixuan; He, Zhen; Liu, Guoliang (American Association for the Advancement of Science, 2020-04-17)
    Capacitive deionization (CDI) is energetically favorable for desalinating low-salinity water. The bottlenecks of current carbon-based CDI materials are their limited desalination capacities and time-consuming cycles, caused by insufficient ion-accessible surfaces and retarded electron/ion transport. Here, we demonstrate porous carbon fibers (PCFs) derived from microphase-separated poly(methyl methacrylate)-block-polyacrylonitrile (PMMA-b-PAN) as an effective CDI material. PCF has abundant and uniform mesopores that are interconnected with micropores. This hierarchical porous structure renders PCF a large ion-accessible surface area and a high desalination capacity. In addition, the continuous carbon fibers and interconnected porous network enable fast electron/ion transport, and hence a high desalination rate. PCF shows desalination capacity of 30 mgNaCl g⁻¹ PCF and maximal time-average desalination rate of 38.0 mgNaCl g⁻¹ PCF min⁻¹, which are about 3 and 40 times, respectively, those of typical porous carbons. Our work underlines the promise of block copolymer–based PCF for mutually high-capacity and high-rate CDI.
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    Mitigation of bidirectional solute flux in forward osmosis via membrane surface coating of zwitterion functionalized carbon nanotubes
    Zou, Shiqiang; Smith, Ethan D.; Lin, Shihong; Martin, Stephen M.; He, Zhen (Elsevier, 2019-07-08)
    Forward osmosis (FO) has emerged as a promising membrane technology to yield high-quality reusable water from various water sources. A key challenge to be solved is the bidirectional solute flux (BSF), including reverse solute flux (RSF) and forward solute flux (FSF). Herein, zwitterion functionalized carbon nanotubes (Z-CNTs) have been coated onto a commercial thin film composite (TFC) membrane, resulting in BSF mitigation via both electrostatic repulsion forces induced by zwitterionic functional groups and steric interactions with CNTs. At a coating density of 0.97 gm⁻², a significantly reduced specific RSF was observed for multiple draw solutes, including NaCl (55.5% reduction), NH₄H₂PO₄(83.8%), (NH₄)₂HPO₄ (74.5%), NH₄Cl (70.8%), and NH₄HCO₃ (61.9%). When a synthetic wastewater was applied as the feed to investigate membrane rejection, FSF was notably reduced by using the coated membrane with fewer pollutants leaked to the draw solution, including NH₄⁺-N (46.3% reduction), NO₂⁻₋N (37.0%), NO₂⁻₋N (30.3%), K⁺ (56.1%), PO₄³⁻₋P (100%), and Mg²⁺ (100%). When fed with real wastewater, a consistent water flux was achieved during semi-continuous operation with enhanced fouling resistance. This study is among the earliest efforts to address BSF control via membrane modification, and the results will encourage further exploration of effective strategies to reduce BSF.