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In this study, we explored the extent to which hydrotropes can be used to increase the aqueous solubilities of redox-active compounds previously used in flow batteries. We measured how five hydrotropes influenced the solubilities of five redox-active compounds already soluble in aqueous electrolytes (≥0.5 M). The solubilities of the compounds varied as a function of hydrotrope type and concentration, with larger solubility changes observed at higher hydrotrope concentrations. 4-OH-TEMPO underwent the largest solubility increase (1.18 ± 0.04 to 1.99 ± 0.12 M) in 20 weight percent sodium xylene sulfonate. The presence of a hydrotrope in solution decreased the diffusion coefficients of 4-OH-TEMPO and 4,5-dihydroxy-1,3-benzenedisulfonate, which was likely due to the increased solution viscosity as opposed to a specific hydrotrope-solute interaction because the hydrotropes did not alter their molecules' hydraulic radii. The standard rate constants and formal potentials of both 4-OH-TEMPO and 4,5-dihydroxy-1,3-benzenedisulfonate remained largely unchanged in the presence of a hydrotrope. The results suggest that using hydrotropes may be a feasible strategy for increasing the solubilities of redox-active compounds in aqueous flow batteries without substantially altering their electrochemical properties.

LHD’s are expensive vehicles; therefore, it is important to accurately define the financial consequences associated with the investment of purchasing the mining equipment. This study concentrates on long-term incremental and sensitivity analysis to determine whether it is feasible to incorporate current battery technology into these machines. When revenue was taken into account, decreasing the amount of haulage in battery operated equipment by 5% or 200 kg per h amounts to a $4.0 × 104 loss of profit per year. On average it was found that using battery operated equipment generated $9.5 × 104 more in income annually, reducing the payback period from seven to two years to pay back the additional $1.0 × 105 investment of buying battery powered equipment over cheaper diesel equipment. Due to the estimated 5% increase in capital, it was observed that electric vehicles must possess a lifetime that is a minimum of one year longer than that of diesel equipment. Keywords: Sensitivity analysis, Underground mining vehicles, Battery power, Battery mining equipment, Economic evaluation

As deeper wells drilled for oil and gas extraction encounter higher pressures, temperatures, and concentrations in the downhole environment, it becomes increasingly important to consider the integrity of the casing that provides both support and isolation of the well. These casings are commonly cemented to provide better sealing, and the alkaline environment provided by the pore water at the cement-casing interface typically puts the steel in a passive region. However, exposure to acid gases can cause degradation of the cement and thus lower the pH at the steel surface. Further, many formation waters are brines containing high concentration of chlorides. This increases the risk of corrosion and failure of the well casing. With these issues in mind, a corrosion study was initiated to investigate the corrosion behavior of grade L-80 casing steel in cement synthetic pore solutions in contact with CO2 and H2S. Experimental approaches consisted of two stages. In the first stage, a Class H well cement was exposed to a 5 wt% NaCl brine in contact with CO2 and H2S at 85 °C for 200 hours. At the end of the exposure time, the pore water of the exposed cement was sampled and analyzed qualitatively and quantitatively. This chemical analysis was used for preparing a cement synthetic pore solution (CSPS) for corrosion testing. In situ electrochemical measurements, performed for the L-80 steel samples in the CSPS at 85 °C, included linear polarization resistance, electrochemical impedance spectroscopy, cyclic voltammetry, and Tafel analysis. Additionally, ex situ surface analyses using scanning electron microscopy, X-ray energy dispersive spectroscopy, and X-ray diffraction were performed for the corroded samples. Mass loss measurement coupons were also used to confirm the electrochemical results.

A comprehensive picture of the interface between aqueous solutions and the (110) surface of rutile (alpha-TiO2) is being developed by combining molecular-scale and macroscopic approaches, including experimental measurements, quantum calculations, molecular simulations, and Gouy-Chapman-Stern models. In situ X-ray reflectivity and X-ray standing-wave measurements are used to define the atomic arrangement of adsorbed ions, the coordination of interfacial water molecules, and substrate surface termination and structure. Ab initio calculations and molecular dynamics simulations, validated through direct comparison with the X-ray results, are used to predict ion distributions not measured experimentally. Potentiometric titration and ion adsorption results for rutile powders having predominant (110) surface expression provide macroscopic constraints of electrical double layer (EDL) properties (e.g., proton release) which are evaluated by comparison with a three-layer EDL model including surface oxygen proton affinities calculated using ab initio bond lengths and partial charges. These results allow a direct correlation of the three-dimensional, crystallographically controlled arrangements of various species (H2O, Na+, Rb+, Ca2+, Sr2+, Zn2+, Y3+, Nd3+) with macroscopic observables (H+ release, metal uptake, zeta potential) and thermodynamic/electrostatic constraints. All cations are found to be adsorbed as "inner sphere" species bonded directly to surface oxygen atoms, while the specific binding geometries and reaction stoichiometries are dependent on ionic radius. Ternary surface complexes of sorbed cations with electrolyte anions are not observed. Finally, surface oxygen proton affinities computed using the MUSIC model are improved by incorporation of ab initio bond lengths and hydrogen bonding information derived from MD simulations. This multitechnique and multiscale approach demonstrates the compatibility of bond-valence models of surface oxygen proton affinities and Stern-based models of the EDL structure, with the actual molecular interfacial distributions observed experimentally, revealing new insight into EDL properties including specific binding sites and hydration states of sorbed ions, interfacial solvent properties (structure, diffusivity, dielectric constant), surface protonation and hydrolysis, and the effect of solution ionic strength.