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A database is being developed by the NWMO that will be capable of predicting sorption for key elements of interest onto crystalline and sedimentary rocks in the highly saline groundwaters and porewaters at DGR depths in Ontario, Canada. Pd(II), Np(IV), and Np(V) have all been identified as elements of interest by the NWMO. Sorption experiments of Pd(II) were conducted on illite, bentonite, and shale to investigate the effects that ionic strength (I), and pH have on sorption. Na-Ca-Cl solutions ranging from 0.01 – 6.0 M I with pH values between 3 and 9 were considered under aerobic conditions at 25°C for sorption testing conditions. Sorption data for Pd(II), Np(IV), and Np(V) was used with 2SPNE SC and 2SPNE SC/CE models developed in PHREEQC to model sorption onto illite and montmorillonite at different values of I and pH. These models were also used to test proposed reaction constants from various sources in the existing literature, and to establish and propose optimized surface complexation constants of our own. Optimized reaction constants were compared with the LFER to determine its validity across all test conditions. The LFER was found to not adequately describe sorption of Pd(II), Np(IV), or Np(V) on either illite or montmorillonite. The JAEA TDB, R04, and R07 THEREDA were all tested along with the Davies, Debye-Hückel, SIT, and Pitzer computational methods in order to determine their overall accuracy. The JAEA TDB using the SIT computational method was found to not be capable of modelling Np(IV) onto illite or montmorillonite in 4.0 M I. / Thesis / Master of Applied Science (MASc)

Ionic electroactive polymer (IEAP) actuators are a class of electroactive polymer devices that exhibit electromechanical coupling through ion transport in the device. They consist of an ionomeric membrane coated with conductive network composites (CNCs) and conductive electrodes on both sides. A series of experiments on IEAP actuators with various types of CNCs has demonstrated the existence of a direct correlation between the performance of actuators and physical and structural properties of the CNCs. Nanostructure of CNC is especially important in hosting electrolyte and boosting ion mobility. This dissertation presents a series of systematic experiments and studies on IEAP actuators with two primary focuses: 1) CNC nanostructure, and 2) ionic interactions. A novel approach for fabrication of CNC thin-films enabled us to control physical and structural properties of the CNC thin-films. We, for the first time, facilitated use of layer-by-layer ionic self-assembly technique in fabrication of porous and conductive CNCs based on polymer and metal nanoparticles. Results were porous-conductive CNCs. We have studied the performance dependence of IEAP actuators on nano-composition and structure of CNCs by systematically varying the thickness, nanoparticle size and nanoparticle concentration of CNCs. We have also studied influence of the waveform frequency, free-ions and counterions of the ionomeric membrane on the performance and behavior of IEAP actuators. Using the LbL technique, we systematically changed the thickness of CNC layers consisting of gold nanoparticles (AuNPs) and poly(allylamine hydrochloride). It was observed that actuators consisting of thicker CNCs exhibit larger actuation curvature, which is evidently due to uptake of larger volume of electrolyte. Actuation response-time exhibited a direct correlation to the sheet-resistance of CNC, which was controlled by varying the AuNP concentration. It was observed that size and type of free-ions and counterion of ionomeric membrane are also influential on the actuation behavior or IEAP actuators and that the counterion of ionomeric membrane participates in the actuation process. / Ph. D.

Ionic polymer transducers comprise a class of active material that exhibit interesting chemoelectromechanical coupling capabilities. With the ability to convert energy between chemical, electrical and mechanical domains, these materials offer potential for use in numerous engineering applications. The research presented in this dissertation focuses primarily on the electromechanical coupling that exists within these ionic polymer materials. When plated with a conductive surface electrode, these ionomeric membranes function effectively as either sensors or actuators. Mechanically compliant, these transducers demonstrate large strain, but limited force, capabilites while operating at low excitation voltages. The objective of this research is to improve understanding of the transduction properties inherent in the ionic polymer. Most of the existing work in this area has focused on the actuation response, therefore the focus of this research is on providing a better understanding of the sensing and impedance responses of the ionic polymer transducer. Using transport theory as the basis, a set of analytical models are developed to characterize the charge motion that develops within an ionomer when subject to either mechanical or electrical loading. These models characterize the internal potential and charge density responses of the membrane, as well as the expected surface current that would be measured as the result of external loading. In addition to the analytical work, numerous experimental characterizations of the membrane are also presented. The ionic polymer's actuation, sensing and impedance responses are each considered as a function of the counterion and solvent type present within the ionic polymer. These studies demonstrate the importance of the ionomer's impedance response in understanding the electromechanical capabilites of an ionic polymer transducer. Most sample-to-sample variation can be attributed to the voltage to current conversion that occurs within the ionic polymer. By relating these experimental results to the analytical models, it is possible to characterize these changes in performance in terms of the effective diffusion and permittivity parameters of the transducer. A final series of experiments are also considered to determine the effectiveness of the model in predicting the impedance response as a function of temperature, solvent viscosity and preloading of the membrane. / Ph. D.

Ionomeric polymer transducers consist of an ion-exchange membrane plated with conductive metal layers on its outer surfaces. Such materials are known to exhibit electromechanical coupling under the application of electric fields and imposed deformation (Oguro et al., 1992; Shahinpoor et al., 1998). Compared to other types of electromechanical transducers, such as piezoelectric materials, ionomeric transducers have the advantage of high-strain output (> 9% is possible), low-voltage operation (typically less than 5 V), and high sensitivity in the charge-sensing mode. A series of experiments on actuators with various ionic polymers such as Nafion and novel poly(Arylene ether disulphonate) systems (BPS and PATS) and electrode composition demonstrated the existence of a linear correlation between the strain response and the capacitance of the material. This correlation was shown to be independent of the polymer composition and the plating parameters. Due to the fact that the low-frequency capacitance of an ionomer is strongly related to charge accumulation at the electrodes, this correlation suggests a strong relationship between the surface charge accumulation and the mechanical deformation in ionomeric actuators. The strain response of water-hydrated transducers varies from 50 μstrain/V to 750 μstrain/V at 1Hz while the strain-to-charge response is between 9 ^μstrain_{^c_m²} and 15 ^μstrain_{^c_m²}. This contribution suggests a strong correlation between cationic motion and the strain in the polymer at the ionomer-conductor interface. A novel fabrication technique for ionic polymer transducers was developed for this dissertation for the purpose of quantifying the relationship between electrode composition and transducer performance. It consists of mixing an ionic polymer dispersion (or solution) with a fine conducting powder and attaching it to the membrane as an electrode. The Direct Assembly Process (DAP) allows the use of any type of ionomer, diluent, conducting powder, and counter ion in the transducer, and permits the exploration of any novel polymeric design. Several conducting powders have been incorporated in the electrode including single-walled carbon nanotubes (SWNT), polyaniline (PANI) powders, high surface area RuO2, and carbon black electrodes. The DAP provided the tool which enabled us to study the effect of electrode architecture on performance of ionic polymer transducers. The DAP allows the variation in the electrode architecture which enabled us to fabricate dry transducers with 50x better performance compared to transducers made using the state of the art impregnation-reduction technique. DAP fabricated transducers achieved a strain of 9.4% at a strain rate of 1%/s. Each electrode material had an optimal concentration in the electrode. For RuO2, the optimal loading was approximately 45% by volume. This study also demonstrated that carbon nanotubes electrodes have an optimal performance at loadings around 30 vol%, while PANI electrodes are optimized at 95 vol%. Extensional actuation in ionic polymer transducers was first reported and characterized in this dissertation. An electromechanical coupling model presented by Leo et al. (2005) defined the strain in the active areas as a function of the charge. This model assumed a linear and a quadratic term that produces a nonlinear response for a sine wave actuation input. The quadratic term in the strain generates a zero net bending moment for ionic polymer transducers with symmetric electrodes, while the linear term is canceled in extensional actuation for symmetric electrodes. Experimental results demonstrated strains on the order of 110 μstrain in the thickness direction compared to 1700 μstrain peak to peak on the external fibers for the same transducer, could be achieved when it is allowed to bend under +/-2V potential at 0.5 Hz. Extensional and bending actuation in ionic polymer transducers were explained using a bimorph active area model. Several experiments were performed to compare the bending actuation with the extensional actuation capability. The active area in the model was assumed to be the high surface area electrode. Electric double layer theory states that ions accumulate in a thin boundary layer close to the metal-polymer interface. Since the metal powders are evenly dispersed in the electrode area of the transducer, this area is expected to actuate evenly upon voltage application. This active area model emphasizes the importance the boundary layer on the conductor-ionomer interfacial area. Computing model parameters based on experimental results demonstrated that the active areas model collapses the bending data from a maximum variation of 200% for the strain per charge, to less than 68% for the model linear term. Furthermore, the model successfully predicted bending response from parameters computed using thickness experimental results. The prediction was particularly precise in estimating the trends of non-linearity as a function of the amount of asymmetry between the two electrodes. / Ph. D.

Ionic polymer transducers are a class of electroactive polymer materials that exhibit coupling between the electrical, chemical, and mechanical domains. With the ability for use as both sensors and actuators, these compliant, light weight, low voltage materials have the potential to benefit diverse application areas. Since the transduction properties of these materials were recently discovered, full understanding of their dynamic characteristics has not yet been achieved. This research has the goal of better understanding the actuation response of ionic polymers. A specific emphasis has been placed on investigating the observed nonlinear behavior because the existing proposed models do not account for these characteristics. Employing the Volterra representation, harmonic ratio analysis, and multisine excitations, characterization results for cantilever samples showed that the nonlinearity is dynamic and input-dependent, dominant at low frequencies, and that its influence varies depending on the solvent. It was determined that lower viscosity solvents trigger the nonlinear mechanisms at higher frequencies. Additionally, the primary components of the harmonic distortion appear to result from quadratic and cubic nonlinearities. Using knowledge gained from the characterization study, the utility of different candidate system structures was explored to model these nonlinear response characteristics. The ideal structure for modeling the current-controlled voltage and tip velocity was shown to consist of an underlying linear system with a dynamic input nonlinearity. The input nonlinearity is composed of a parallel connection of linear and nonlinear terms, where each nonlinear element has the form of a Hammerstein system. This system structure was validated against data from measured time and frequency responses. As a potential application, and consequently further validation of the chosen model structure, a square-plate polymer actuator was considered. In this study, the plate was clamped at the four corners where a uniform input was applied, measuring the center-point displacement. Characterization and modeling were performed on this system, with results similar to the cantilever sample. Applying output feedback control, in the form of proportional-integral compensation, showed that accurate tracking performance could be achieved in the presence of nonlinear distortions. Special attention was extended here to the potential application in deformable mirror systems. / Ph. D.

This dissertation explores the properties of sulfonated poly(arylene ether sulfone)s for desalination membrane applications. A multi-scale approach is used to understand the relationships between the chemical structure of the polymer, the equilibrium water content, and the bulk properties. The polysulfones investigated here are aromatic polymers with relatively high ion contenremain in the glassy state at room temperature even when fully hydrated. In order to better understand the effects of water on these ionic polysulfones molecular dynamics (MD) simulation is used to investigate ion aggregation and hydration at the atomic scale. MD simulations show that the sulfonate and sodium ions are not simply paired. Instead, they form an ionic network. The molecular nature of melting water within sulfonated polysulfones is also examined by combining differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and MD simulation. Experimental evidence shows that at high ion contents, the spacing between the ionic groups impacts the amount of melting water present in the polymer. We conclude that the amount of melting water in the polymer is more closely related to geometric clustering effects than electrostatic effects. Finally, molecular-scale insight is used to understand the trends in hydrated tensile modulus and hydrated glass transition (Tg) temperatures in sulfonated polysulfones. Polymers with a more rigid backbone show different trends compared to those with a more flexible backbone. The modulus and Tg trends for the more flexible backbone are qualitatively consistent with the increase in intra-chain ionic associations (loops) predicted by the sticky Rouse model. / Doctor of Philosophy / This dissertation investigates new materials that could be used to make better membranes that can remove ions (salt) from water. Existing materials are too soft or too brittle when they are fully immersed in water. Consequently, they must be combined with more durable materials in order to make useful membranes. We would like to design durable ionic polymers (large chain-like molecules with ions attached) that interact with water and other ions in a very specific way in order to make membranes that can remove salt efficiently. The goal of this research is to create tools that can describe how changes to the chemical structure of the polymer impact how the polymer, water, and ions interact with each other so that we can improve membrane properties. We find that the ions on the polymer chain interact with each other to form threads, which can form a network inside of the polymer under the right conditions. When the ions are located far apart on the polymer chain, the ion threads link one polymer chain to another polymer chain. These ionic links strengthen the polymer network. However, when the ions are located closer together on the polymer chain, the chain starts to form loops between neighboring ions. As the number of loops increases, the polymer quickly becomes softer and more gel-like. We also find that water molecules are distributed within the polymer and are not always located next to the ions. When there is more water inside the polymer, the water molecules begin to group together to form clusters. At low temperatures, water molecules that have fewer than four neighboring molecules cannot freeze. However, water in a cluster of five molecules or more can freeze into an ice crystal. The insights gained from this research will help the community to design better polymers for desalination membrane applications.

Rare earth elements (REE) exhibit particular and unique properties that render them essential to technological applications. Of particular interest is their involvement in the transition toward global sustainability and their military applications. The magnetic properties of the rare earth elements is of primordial importance to sustainable development. More specifically, terbium and dysprosium are two elements with no known substitutes in critical applications and with no domestic or allied sourcing available. These elements are currently mined by in-situ leaching of ion-absorbed clays, mostly from illegal operations in Myanmar financed by Chinese companies. The demand from both elements, and for the other magnet rare earths is projected to growth at very high rates through 2035 while the world undergoes a transition toward sustainability, and a drastic reduction in greenhouse gases emissions. Our team has been evaluating the potential of acid mine drainage (AMD) as a source of rare earth elements and critical materials (CM). Acid mine drainage is the result of in-situ generation of sulfuric acid due to the weathering of sulfide ores. It is a significant legacy environmental issue and one of the largest pollutants in many mining districts throughout the world. The objective of the present work is to provides a roadmap for the utilization of AMD as a critical material feedstock to preserve the independence of the United States of America with regards to these materials. To that effect, a fundamental economic assessment of REE/CM recovery from AMD using a network sourcing strategy in addition to a robust, flexible feedstock separations and refining facility was undertaken. A techno-economic analysis of the extraction, refining, separation and reduction to metal is presented along with a sensitivity analysis.The results of this analysis show that, with the exception of the minimum price scenario, all operational configurations have positive economic indicators with rates of return varying from 25% to 32% for the contemporary price scenario. This is primarily due to the very high enrichment in terbium and dysprosium of AMD. The optimal configuration was determined to be production of Co, Mn, and all REEs except for mischmetal, which is not recovered. Sensitivity analysis and Monte Carlo Simulation show that capital cost and HCl consumption are the two major factors influencing rate of return, thus indicating opportunities for future technology development and cost optimization. In order to reduce both the capital and operation cost of the facility, alternative ionic liquids extractants based on conventional acidic extractants where synthesized and investigated. The results show that the ionic liquids varied in performance, with [c101][D2EHP] and [c101][EHEHP] performing poorer than their conventional counterparts and [c101][c572] performing better. The performance of [c101][c572] was 13% superior to Cyanex 572, 20% superior to EHEHPA and 27% superior to D2EHPA the current commercially used extractants. Recommendations for further study on [c101][c572] include stripping tests, continuous pilot testing, and techno-economic analysis. The test work revealed that zinc and to a lesser extent calcium were significant deleterious elements in the solvent extraction circuit, and that selective removal would significantly reduce the acid-base consumption of the separation circuit. A process was developed to selectively remove calcium and zinc from AMD-derived feedstock and from REE products. The ammonium chloride leach process offer many advantages, including the possibility of closing the cycle by using carbon dioxide sequestration as a step to regenerate the ammonium chloride in a zero-discharge process. / Doctor of Philosophy / A younger me: - What are these elements in the bottom of the periodic table? My high school chemistry teacher: - "Don't waste time there, these are of no concern." Twenty years later, technological developments and the imperative to transition away from fossil energy to mitigate climate change have brought the rare earth elements, a series of 17 elements with unique properties to the forefront of the conversation. In addition to an organic increase in demand, the recent supply chain consolidation by China is adding a geopolitical risk to the equation. The magnetic properties of the rare earth elements is of primordial importance to sustainable development and to our military technology. More specifically, terbium and dysprosium are two elements with no known substitutes in critical applications and with no domestic or allied sourcing available. These elements are currently mined from illegal operations in Myanmar, with the support of Chinese companies. The demand from both elements, and for the other magnet rare earths is projected to growth at very high rates through 2035 while the world undergoes a transition toward sustainability, and a drastic reduction in greenhouse gases emissions. Given the important of the rare earth elements, and the absence of significant deposits in the united states, with the exception of the Bear Lodge and Elk Creek deposits, the Department of Energy has mandated academic institution of evaluating alternative sources of rare earth elements. Our team has been evaluating the potential of acid mine drainage as a source of rare earth elements and critical materials. Our team has surveyed many acid mine drainage sources and determined that many sites are highly enriched in terbium and dysprosium. Acid mine drainage is a legacy environmental issue related to past problematic mine development techniques. In the problematic mines. these acidic mine waters are permanently generated and if not treated can have severe impacts on water streams in which they flow. The toxicity of the acid mine drainage on the environment is due to its high acidity and significant levels of toxic metals. Acid mine drainage can be recognized by their yellow to red tint. It is treated by reacting it with a neutralization agent, which results in treated water and a sludge. The sludge is dewatered and stored in tailing impoundments. I have designed a process for the economical recovery of rare earth elements and critical materials from acid mine drainage. The cost to build and operate the facility was derived and it was determined that the project could be further enhanced by reducing the plant chemical reagent consumption. One specific category of chemical referred to as extractant, is central to the rare earth separation process. A novel variation on the standard extractants has been evaluated and promises to provide significant savings. While the extractants were investigated, it was noticed that some impurities such as zinc and calcium created issues in the circuit. I then developed a process for their selective removal. The process also provide a net carbon dioxide sequestration potential.