Electrically conductive membranes (ECMs) are of significant research interest for their ability to mitigate fouling, enhance separation capacity, and induce electrochemical degradation of contaminants. Most ECM development has been in flat sheet format suitable for laboratory studies; in industrial applications, formats such as hollow fiber (HF) are preferred for their high packing density. While ECMs in HF format are emerging in research, these techniques typically employ the same methods proven for flat sheet, often involving direct deposition of conductive material onto a support membrane with no further investigation into how the deposition process affects ECM properties. This is a significant challenge for long (~1 m) HF membranes where coating uniformity is essential to ensure consistent performance. The goal of this project was to fabricate conductive HF membranes, ensuring uniform performance along the fiber. In this work, we have developed a “crossflow deposition” technique to deposit a uniform layer of single walled/ double walled carbon nanotubes (SW/DWCNTs) onto the interior surface of commercial polyether sulfone HF membranes. In a design-of-experiments model, feed pressure and crossflow velocity were shown to directly impact composite membrane conductivity and permeability. The highest permeability (~2900 LMH/bar) and conductivity (~670 S/m) were both achieved at the high pressure (0.2 bar) and high crossflow velocity (1.06 cm/s) condition. An inverse relationship was identified between conductivity and permeability for 29 different HF membranes coated under various flow and particle loading conditions. Similar trends were evident in ECM literature when comparing 80 membranes across 38 papers, covering various conductive materials, separation types, configurations, and applications. Metallic-based ECMs outperformed graphitic nanomaterial or conductive polymer-based ECMs with conductivities three orders of magnitude higher. This review also revealed a wide variation in performance testing with 35 unique pollutants in 63 total tests, indicating a need for standardization to accurately compare ECMs and a need for testing with more realistic feed sources. Finally, electrochemical degradation of methyl orange using the CNT-coated HF membranes was evaluated in batch and continuous removal experiments. Although no significant MO removal was detected in either configuration, these modules can be used for further optimization in terms of targeted conductivity, contact time, and electrochemical parameters such as applied voltage. This work highlights the existence of a conductivity/ permeability trade-off in ECM development and how manipulation of flow parameters during deposition can impact this trade-off in HF membrane development. / Thesis / Master of Applied Science (MASc) / Membrane separation technologies are a common purification strategy in many fields due to their simplicity and low energy requirements. Membranes operate by rejecting particles from feed water based on their chemical or physical properties such as size or charge. Long-term membrane operations are limited by fouling, incurring large operating costs for frequent cleaning cycles and downtime. Furthermore, traditional membrane separations only physically remove particles, presenting a risk for contaminant re-introduction into the environment. Electrically conductive membranes are an emerging strategy for addressing these concerns due to their demonstrated antifouling, enhanced selectivity, and redox capabilities. To date, these membranes have almost exclusively been developed as flat sheets with limited research into other membrane formats. Hollow fiber membranes resemble thin tubes ~1 mm in diameter and up to ~1 m in length where filtration occurs through the tubular wall of the fiber; the small diameter allows for hundreds of fibers to pack into an individual module, thus maximizing throughput. In this thesis, several issues with hollow fiber conductive membrane fabrication are addressed to ensure consistent performance along the length of the fiber. A key trade-off between membrane surface conductivity and throughput was found to exist universally in the conductive membrane field. This knowledge can be used to select fabrication methods and parameters to target certain performance ranges.

Le travail reporté dans ce manuscrit concerne l’élaboration de matériaux conducteurs protoniques et anioniques destinés à une application en tant que membrane ou liants d’électrodes. Tout d’abord, la première approche consiste en la formation de polymères pour la conception de membranes anioniques. Pour cela, 2 types de fonctions amine tertiaire ont été greffés le long de la chaîne des polysulfones, puis transformés en ammonium pour leur donner un caractère conducteur anionique. Les fonctions greffées sont de types diméthylamino et N,N diméthylaminométhyle. Différentes séries de polysulfones ont été élaborées en faisant varier le taux de fonctions amine greffées. Pour les polysulfones comportant les fonctions diméthyalmino, les résultats montrent que la stabilité thermique des fonctions ammonium est trop faible pour les utiliser pour la conception de membranes conductrices anioniques. Pour le deuxième type de fonctions amine, des membranes ayant une conductivité maximum de 40 mS.cm-1 pour un taux d’humidité de 95% et une température de 100°C ont été obtenu. Par ailleurs, pour la conception de liants d’électrodes, la synthèse de polyarylènes éthers fluorés conducteurs anioniques a été effectuée. Là encore, une série de polymères a été réalisée en faisant varier le taux de fonctions amine introduit. Les masses molaires ont été controlées pour permettre aux polymères d’être suffisamment soluble pour la mise en solution. Les valeurs de conductivités sont de l’ordre de 35 mS.cm-1. Enfin, pour la conception de membrane protonique, les polymères synthétisés précédemment avec les fonctions diméthylamino ont été utilisés. Ces polymères ont été par la suite dopés à l’aide d’acide phosphorique et la conductivité des membranes obtenues a été testée en condition anhydre. Les résultats obtenus pour ce genre de matériaux est de 160 mS.cm-1 pour un taux de dopage de 50%. En revanche, pour des forts taux de dopage, la conductivité obtenue était plus forte (260 mS.cm-1) mais les membranes perdaient de leurs propriétés mécaniques alors que pour de faibles taux de dopage (environ 18%), les conductivités obtenues étaient faibles. / The work reported in this thesis is the development of proton and anion conducting materials for applications such as membrane or binders electrodes. The first approach is the formation of polymers for the anionic membranes design. To perform it, two types of tertiary amine functions have been grafted along the polysulfones chain, then converted to ammonium rendering data anionic conductive. The grafted functions types are dimethylamino and N, N dimethylaminomethyl. Different series of polysulfones were prepared by varying the rate of amine functions grafted. For polysulfones with dimethyalmino functions, the results show that the thermal stability of ammonium functions is too low to be used in anion conductive membranes design. In the second type of amine, membranes having a maximum conductivity of 40 mS.cm-1 to a moisture content of 95% and a temperature of 100 °C have been obtained. In addition, for the electrodes binders design, the synthesis of fluorinated ethers polyarylenes anionic conductors has been completed. Then, a series of polymers was carried out by varying the rate of amine introduced. The molar masses were controlled to allow polymers to be sufficiently soluble for the dissolution. Conductivity values are around 35 mS.cm-1. Finally, the design of membrane proton polymers synthesized with previously dimethylamino functions has been chosen. These polymers were subsequently doped with phosphoric acid and the conductivity of the resulting membranes has been tested in anhydrous condition. The results obtained for this kind of material is 160 mS.cm-1 for a doping level of 50%. However, for high doping level, conductivity obtained was higher (260 mS.cm-1) but the membranes lost their mechanical properties, while for low doping levels (about 18%), the conductivities obtained were low.

In the past 30 years zero-valent iron (ZVI) has become an increasingly popular reducing agent technology for remediating environmental contaminants prone to chemical degradation. Azo dyes and chlorinated organic compounds (COCs) are two classes of such contaminants, both of which include toxic compounds with known carcinogenic potential. ZVI has been successfully applied to the surfaces of permeable reactive barriers, as well as grown into nanoscale particles (nZVI) and applied in-situ to chemically reduce these contaminants into more environmentally benign compounds. However, the reactivity of ZVI and nZVI in these technologies is limited by their finite supply of electrons for facilitating chemical reduction, and the tendency of nZVI particles to homo-aggregate in solution and form colloids with reduced surface area to volume ratio, and thus reduced reactivity. The goal of this project was to combine reactive nanoparticle and membrane technologies to create an electro-catalytic permeable reactive barrier that overcomes the weaknesses of nZVI for the enhanced electrochemical filtration of azo dyes in solution. Specifically, nZVI was successfully grown and stabilized in a network of functionalized carbon nanotubes (CNTs) and deposited into an electrically conductive thin film on the surface of a polymeric microfiltration support membrane. Under a cathodic applied voltage, this thin film facilitated the direct reduction of the methyl orange (MO) azo dye in solution, and regenerated nZVI reactivity for enhanced electro-catalytic operation. The electro-catalytic performance of these nZVI-CNT membrane surface composites to remove MO was validated, modelled, and optimized in a batch system, as well as tested in a dead-end continuous flow cell system. In the batch experiments, systems with nZVI and a -2 V applied potential demonstrated synergistic enhancement of MO removal, which indicated the regeneration of nZVI reactivity and allowed for the complete removal of 0.25 mM MO batches within 2-3 hours. Partial least squares regression (PLSR) modelling was used to determine the impact of each experimental parameter in the batch system and provided the means for an optimization leading to maximized MO removal. Finally, tests in a continuous system yielded rates of MO removal 1.6 times greater than those of the batch system in a single pass, and demonstrated ~87% molar removal of MO at fluxes of approximately 422 lmh. The work herein lays the foundation for a promising technology that, if further developed, could be applied to remediate azo dyes and COCs in textile industry effluents and groundwater sites respectively. / Thesis / Master of Applied Science (MASc)