A technique to measure the cation-transference number of salts in fully hydrated ion-selective membranes has been developed and demonstrated on Nafion 117 for LiCl and Li 2 SO 4 . Dilute solution theory is used to identify experimental conditions that reduce the propagation of uncertainties in membrane properties to transference number estimates. This technique has advantages over commonly used methods, including the elimination of the need for the analysis of electrode potentials in approaches that exploit electroanalytical methods or the need for additional information required to reconcile NMR-based methods with the bulk transport property. It additionally allows for numerous measurements per day and offers the possibility to relate trace measurements of either cations or anions to values of transference number. For LiCl both modes of the technique were employed; the anion-tracer method is more precise and gives t + = 0.936 ± 0.010. The experimental procedure was repeated using the cation-tracer method for Li 2 SO 4 , and t + = 0.95 ± 0.06 was estimated. The 21 st century presents a key challenge in energy storage due to the intermittency of wind and solar energy sources. Lithium ion batteries, fuel cells, and redox flow batteries are promising technologies for energy storage since they have high energy densities, are environmentally friendly, and have an array of other desirable properties. [1][2][3][4][5][6] Solid electrolytes are ubiquitous for these energy storage systems since they serve the important function of mechanical separation between electrodes. In addition, solid electrolytes circumvent several problems associated with liquid electrolytes such as the leakage of electrolyte solution and the reaction of volatile organic solvents.7 Of the solid electrolytes, polymer electrolytes have garnered the most interest in recent years. [8][9][10][11] These membranes facilitate ionic transport between electrodes, inhibit electron flow between electrodes, prevent direct contact between electrodes, and minimize mixing of the anolyte and catholyte.In recent decades, researchers have sought to understand the relationship between the molecular structure of polymer electrolytes and their performance. These structure-property relationships have been developed for two major types of polymer electrolytes: (I) mixtures of salts in high molecular weight polymers and (II) polymerized ionic liquids (single ion conductors). Polyethylene oxide (PEO), polypropylene oxide (PPO), and 4 poly[bis(methoxy-ethoxyethoxy) phosphazene] (MEEP) are all promising Type I polymer electrolytes.12-16 The electron-donating groups incorporated into the polymer architecture are responsible for solvating the lithium ion while the fast segmental dynamics promote high ionic conductivities through fluctuation-driven diffusion. [17][18][19] However, Type I polymer electrolytes typically suffer from poor mechanical properties, which is an unfortunate compromise for the fast segmental dynamics. Furthermore, Type I polymer electrolytes have relative...

Direct contact membrane distillation (DCMD) is an emerging water treatment technology that has high salt rejection; however, its commercialization potential for applications such as seawater desalination or industrial wastewater reuse may be limited by low rejection of volatile and semivolatile contaminants. In this manuscript, a contaminant concentration (CC) model describing the transport of volatile and semivolatile contaminants for DCMD systems was developed and validated using data from the bench-scale DCMD treatment of synthetic wastewaters. The DCMD tests showed that the more volatile contaminants (methyl-tert-butyl ether, acetone, pentanone, butanol, and hexanol) accumulated in the permeate collection stream at greater concentrations than in the feed stream. The validated CC model (average normalized root mean squared error ≤11.3%) was then used to evaluate the product water quality from the large-scale DCMD treatment of oil and gas produced waters. The modeled product water contaminant concentrations exceeded the Environmental Protection Agency limits for discharging to publicly owned treatment works. This indicated that DCMD treatment of produced waters may require additional processing to meet discharge requirements.

Crossover in Vanadium Redox Flow Batteries (VRFB) has an important impact on performance and is dependent on several physical properties, including the transference number. In this work, model-guided design of experiment was used to determine vanadium transference number in fully-hydrated ion-selective membranes, while minimizing uncertainties related to unknown or unmeasured properties. The transference number of VO2+ in Nafion 117 for varying ratios of H2SO4 to VOSO4 was measured, and the analysis showed that the transference number estimate can be obtained with 5% or less uncertainty. The VO2+ transference number sharply decreased as acid was added to the electrolyte. The variation in the transference number with the ratio of H2SO4 to VOSO4 was fit to a model to obtain the product of the ratio of vanadium-to-proton partition and diffusion coefficients.

Polymer electrolytes, which are commonly used as separator materials in electrochemical devices, have ionic conductivity that is thought to be controlled by segmental mobility. Thus, any improvements made toward increasing ionic mobility come at the expense of mechanical integrity. However, selectively solvating the ionic domain, the region responsible for ion conduction, with water or polar organic solvents presents a potential opportunity to circumvent this physical constraint. Here, we explore the role of hydration on the transport properties of membranes formed from randomly sulfonated polystyrene (PS-r-sPS). We find that the water volume fraction underpins an intrinsic trade-off between separator permselectivity (Ψm) and ion conductivity (κ)thus, improvements in ion diffusion because of increased water content come at the expense of charge density in the membrane which yields a reduced Ψm. We provide a summary of the Ψm–κ trade-off for a suite of commercially available separators to elucidate structure–property relationships and present methodologies for improving both Ψm and κ.

Microbially influenced corrosion (MIC) results in significant damage to metallic materials in many industries. Anaerobic sulfate-reducing bacteria (SRB) have been well studied for their involvement in these processes. Highly corrosive environments are also found in pulp and paper processing, where chloride and thiosulfate lead to the corrosion of stainless steels. Acidithiobacillus ferrooxidans is a critically important chemolithotrophic acidophile exploited in metal biomining operations, and there is interest in using A. ferrooxidans cells for emerging processes such as electronic waste recycling. We explored conditions under which A. ferrooxidans could enable the corrosion of stainless steel. Acidic medium with iron, chloride, low sulfate, and pyrite supplementation created an environment where unstable thiosulfate was continuously generated. When combined with the chloride, acid, and iron, the thiosulfate enabled substantial corrosion of stainless steel (SS304) coupons (mass loss, 5.4 ± 1.1 mg/cm2 over 13 days), which is an order of magnitude higher than what has been reported for SRB. There results were verified in an abiotic flow reactor, and the importance of mixing was also demonstrated. Overall, these results indicate that A. ferrooxidans and related pyrite-oxidizing bacteria could produce aggressive MIC conditions in certain environmental milieus. IMPORTANCE MIC of industrial equipment, gas pipelines, and military material leads to billions of dollars in damage annually. Thus, there is a clear need to better understand MIC processes and chemistries as efforts are made to ameliorate these effects. Additionally, A. ferrooxidans is a valuable acidophile with high metal tolerance which can continuously generate ferric iron, making it critical to copper and other biomining operations as well as a potential biocatalyst for electronic waste recycling. New MIC mechanisms may expand the utility of these cells in future metal resource recovery operations.