Browsing by Author "Nnorom, Njideka C"

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    Functionalized Polymeric Coatings for Enhanced Selective Removal of Ions in Electric-Field Driven Processes
    (2023-04-20) Nnorom, Njideka C; Verduzco, Rafael
    More than 80% of the world’s wastewater flows back into the environment without any treatment or reuse and in developing regions, that number can reach up to 95%. This means, a significant percentage of available water in the world is inaccessible to fulfill everyday needs. To combat water contamination, there is a need to utilize various water treatment methods. Electrified membrane-based technologies (i.e., membrane capacitive deionization (MCDI) and electrodialysis (ED)) are actively utilized to extract ions for water purification purposes. These electrified filtration systems have ion-exchange membranes placed in front of each electrode, or chamber, to prevent the passage of co-ions which leads to enhanced salt removal and charge efficiencies. Despite the efficiencies of these methods, these systems cannot selectively target and remove ionic contaminants from mixed feed streams. In this work, we look to modify these electrified processes by incorporating polymeric coatings, equipped with functional groups, that can selectively extract target ions. We first looked to improve Ca2+/Na+ selectivity by using a sulfonated polymer (PEDOT:PSS). Through membrane transport property studies and MCDI experiments we determined that selective transport, through PEDOT:PSS, is driven by higher ion diffusivities of Ca2+ relative to Na+ and we can achieve Ca2+/Na+ selectivity as high as 8 (molar basis) under optimized conditions. This dissertation lays a framework to enhance the removal of target ions in electrified membrane-based technologies through the implementation of polymeric materials. Utilizing fabrication methods and tuning parameters we can qualify more polymer materials containing broader functional groups, such as iminodiacetic acid for the selective removal of copper and covalent organic frameworks as a newly emerging class of porous materials for water purification.