Showing papers by "Mark L. Dietz published in 2010"
TL;DR: In this article, the authors examined the extraction of pertechnetate and related tetra-oxo anions from aqueous solutions into IL-based solvents incorporating tetraalkylphosphonium bis[(trifluoromethyl)sulfonyl]imide and a crown ether.
Abstract: Hydrophobic ionic liquids (IL) have the potential to simplify certain separations by serving as both an extraction solvent and an electrolyte for subsequent electrochemical reductions. While IL-based solvents are known to be efficient media for metal ion extraction, separations employing these solvents are frequently complicated by the loss of constituent IL ions to the aqueous phase, resulting in deteriorating performance. In this study, we have examined the extraction of pertechnetate and related tetra-oxo anions from aqueous solutions into IL-based solvents incorporating tetraalkylphosphonium bis[(trifluoromethyl)sulfonyl]imide and a crown ether. In contrast to various previously studied IL-based cation extraction systems, facile anion extraction without significant transfer of the IL ions to the aqueous phase has been observed. In addition, the solvents exhibit high distribution ratios (100-500 for pertechnetate), significant electrical conductivity (>100 ?S/cm), and a wide (4 V) electrochemical window. The results suggest that these solvents may provide the basis for improved approaches to the extraction and recovery of a variety of anions.
39 citations
01 Jun 2010
TL;DR: In this article, a volume-averaged model based on the work by Quintard and Whitaker is employed for the nonlinear species-transport equation inside the fully saturated porous medium.
Abstract: Modeling flow, evaporation and transport of multicomponent liquids remains one of the most challenging problems in porous media studies. Slow evaporation under isothermal conditions of a non‐dilute multi‐component liquid mixture from a cylindrical porous wick made of sintered polymer beads is studied in this paper. Since the rate of mass evaporation from wick top is much smaller than the rate of capillary‐pressure‐driven liquid imbibition, the wick is considered fully saturated while the evaporation from wick top is modeled as a boundary effect. A volume‐averaged model based on the work by Quintard and Whitaker is employed for the nonlinear species‐transport equation inside the fully‐saturated porous medium. An implicit finite‐difference method is employed to solve the governing equations in a one‐dimensional domain representing the cylindrical wick. The Darcy velocity inside the wick is determined from the evaporation rate at the wick‐top, which in turn is a function of mole‐fractions of all components at the gas‐liquid interface. A flux‐balance condition, based on the overall mole‐balance for each component, is employed to develop a mole‐fraction boundary‐condition at the wick‐bottom interface with a liquid container. Results of this simulation are compared with experiments for a mixture of n‐Decane, n‐Dodecane and n‐Hexadecane; reasonable agreement is observed for the evaporation rate at the wick top, and the component concentration distributions along the wick.