Non-Ideal Behavior in Solvent Extraction

This report presents a summary of the work performed to meet FCR&D level 3 milestone M31SW050801, 'Complete the year-end report summarizing FY11 experimental and modeling activities.' This work was carried out under the auspices of the Non-Ideality in Solvent Extraction Systems FCR&D work package. The report summarizes our initial considerations of potential influences that non-ideal chemistry may impose on computational prediction of outcomes in solvent extraction systems. The report is packaged into three separate test cases where a robustness of the prediction by SXFIT program is under scrutiny. The computational exercises presented here emphasize the importance of accurate representation of both an aqueous and organic mixtures when modeling liquid-liquid distribution systems. Case No.1 demonstrates that non-ideal behavior of HDEHP in aliphatic diluents, such as n-dodecane, interferes with the computation. Cases No.2 and No.3 focus on the chemical complexity of aqueous electrolyte mixtures. Both exercises stress the need for an improved thermodynamic model of an aqueous environment present in the europium distribution experiments. Our efforts for year 2 of this project will focus on the improvements of aqueous and non-aqueous solution models using fundamental physical properties of mixtures acquired experimentally in our laboratories

Thermodynamics and Kinetics of Advanced Separations Systems ? FY 2010 Summary Report

This report presents a summary of the work performed in the area of thermodynamics and kinetics of advanced separations systems under the Fuel Cycle Research and Development (FCR&D) program during FY 2010. Thermodynamic investigations into metal extraction dependencies on lactate and HDEHP have been performed. These metal distribution studies indicate a substantial deviation from the expected behavior at conditions that are typical of TALSPEAK process operational platform. These studies also identify that no thermodynamically stable mixed complexes exist in the aqueous solutions and increasing the complexity of the organic medium appears to influence the observed deviations. Following on from this, the first calorimetric measurement of the heat of extraction of americium across a liquid-liquid boundary was performed

Toward understanding the thermodynamics of TALSPEAK process. Medium effects on actinide complexation

The ingenious combination of lactate and diethylenetriamine-N,N,N’,N”,N”-pentaacetic acid (DTPA) as an aqueous actinide-complexing medium forms the basis of the successful separation of americium and curium from lanthanides known as the TALSPEAK process. While numerous reports in the prior literature have focused on the optimization of this solvent extraction system, considerably less attention has been devoted to the understanding of the basic thermodynamic features of the complex fluids responsible for the separation. The available thermochemical information of both lactate and DTPA protonation and metal complexation reactions are representative of the behavior of these ions under idealized conditions. Our previous studies of medium effects on lactate protonation suggest that significant departures from the speciation predicted based on reported thermodynamic values should be expected in the TALSPEAK aqueous environment. Thermodynamic parameters describing the separation chemistry of this process thus require further examination at conditions significantly removed from conventional ideal systems commonly employed in fundamental solution chemistry. Such thermodynamic characterization is the key to predictive modelling of TALSPEAK. Improved understanding will, in principle, allow process technologists to more efficiently respond to off-normal conditions during large scale process operation. In this report, the results of calorimetric and potentiometric investigations of the effects of aqueous electrolytes on the thermodynamic parameters for lactate protonation and lactate complexation of americium and neodymium will be presented. Studies on the lactate protonation equilibrium will clearly illustrate distinct thermodynamic variations between strong electrolyte aqueous systems and buffered lactate environment

Understanding the solution behavior of minor actinides in the presence of EDTA(4-), carbonate, and hydroxide ligands

Understanding the solution behavior of minor actinides in the presence of EDTA(4-), carbonate, and hydroxide ligand

Randomized clinical trial of a brief and extensive dyadic intervention for advanced cancer patients and their family caregivers

Background Few intervention programs assist patients and their family caregivers to manage advanced cancer and maintain their quality of life (QOL). This study examined (i) whether patient–caregiver dyads (i.e., pairs) randomly assigned to a brief or extensive dyadic intervention (the FOCUS Program) had better outcomes than dyads randomly assigned to usual care and (ii) whether patients' risk for distress and other factors moderated the effect of the brief or extensive program on outcomes. Methods Advanced cancer patients and their caregivers ( N  = 484 dyads) were stratified by patients' baseline risk for distress (high versus low), cancer type (lung, colorectal, breast, or prostate), and research site and then randomly assigned to a brief (three‐session) or extensive (six‐session) intervention or control. The interventions offered dyads information and support. Intermediary outcomes were appraisals (i.e., appraisal of illness/caregiving, uncertainty, and hopelessness) and resources (i.e., coping, interpersonal relationships, and self‐efficacy). The primary outcome was QOL. Data were collected prior to intervention and post‐intervention (3 and 6 months from baseline). The final sample was 302 dyads. Repeated measures MANCOVA was used to evaluate outcomes. Results Significant group by time interactions showed that there was an improvement in dyads' coping ( p  < 0.05), self‐efficacy ( p  < 0.05), and social QOL ( p  < 0.01) and in caregivers' emotional QOL ( p  < 0.05). Effects varied by intervention dose. Most effects were found at 3 months only. Risk for distress accounted for very few moderation effects. Conclusions Both brief and extensive programs had positive outcomes for patient–caregiver dyads, but few sustained effects. Patient–caregiver dyads benefit when viewed as the ‘unit of care’. Copyright © 2012 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/96760/1/pon3036.pd

Non-Ideal Behavior in Solvent Extraction

This report presents a summary of the work performed to meet FCR&amp;D level 3 milestone M31SW050801, 'Complete the year-end report summarizing FY11 experimental and modeling activities.' This work was carried out under the auspices of the Non-Ideality in Solvent Extraction Systems FCR&amp;D work package. The report summarizes our initial considerations of potential influences that non-ideal chemistry may impose on computational prediction of outcomes in solvent extraction systems. The report is packaged into three separate test cases where a robustness of the prediction by SXFIT program is under scrutiny. The computational exercises presented here emphasize the importance of accurate representation of both an aqueous and organic mixtures when modeling liquid-liquid distribution systems. Case No.1 demonstrates that non-ideal behavior of HDEHP in aliphatic diluents, such as n-dodecane, interferes with the computation. Cases No.2 and No.3 focus on the chemical complexity of aqueous electrolyte mixtures. Both exercises stress the need for an improved thermodynamic model of an aqueous environment present in the europium distribution experiments. Our efforts for year 2 of this project will focus on the improvements of aqueous and non-aqueous solution models using fundamental physical properties of mixtures acquired experimentally in our laboratories

TALSPEAK CURVE: AN ILLUSTRATION OF A SEE-SAW EFFECT IN SEPARATIONS

A superbly balanced thermodynamic struggle for metal ion coordination by aqueous aminopolycarboxylate reagent, DTPA, and non-aqueous organophosphorous phase transfer reagent, HDEHP, affords the separation of trivalent actinides from trivalent lanthanides under the umbrella of the Talspeak liquid-liquid distribution process. This thermodynamic relationship has been linked to an analogous “see-saw” behavior, where the balance is distorted when either of the key complexing players is subject to adverse conditions that interfere with their optimal operation. The thermodynamic balance is tipped in favour of HDEHP whenever increased acidity of the aqueous solution out-competes the metal ion complexation by aqueous complexing agent. Also enhanced steric crowding may switch-off efficient coordination of the metal ion. When HDEHP is depolymerised due to the presence of aliphatic alcohol in the organic phase its phase transferring power is diminished. Such complication paves way for DTPA to establish its dominance on the distribution of trivalent metal ions in the 2-phase system. The illustrated sensitivity of the thermodynamic balance between DTPA and HDEHP in Talspeak-type systems may serve as informative tool when studying less-predictable realms of Talspeak chemistry

CONTRIBUTING TO THE DISCUSSIONS ON THE FUNDAMENTAL ASPECTS AND COMPLEXITIES OF TALSPEAK CHEMISTRY

When liquid-liquid distribution of lanthanides was monitored at Talspeak-related conditions a characteristic drop in the extraction efficiency was observed at high lactate concentrations. The lactate dependency trend also appears to be directly affected by the increasing complexity of the non-aqueous environment. Some considerations of the non-ideal solution behavior in aqueous and organic environment are presented here in an attempt to explain the observed metal partitioning trends. While the mechanism of metal ion phase transfer appears to adhere to the conventional thermodynamic struggle between HDEHP and DTPA, the diminished metal distribution and suppressed slopes for the extractant dependencies suggest further build-up in the complexity of the non-aqueous environment in Talspeak systems

First calorimetric determination of heat of extraction of 248Cm in a bi-phasic system

This report presents a summary of the work performed to meet FCR&amp;D level 2 milestone M21SW050201, 'Complete the first calorimetric determination of heat of extraction of 248Cm in a bi-phasic system'. This work was carried out under the auspices of the Thermodynamics and Kinetics FCR&amp;D work package. To complement previous work undertaken under this work package we have extended out heat of extraction studies by di-2-ethyl-hexyl-phosphoric acid to curium. This report also details the heat of extraction of samarium in the same system. This work was performed to not only test the methodology but also to check for consistency with the heats of extraction obtained with those in the prior literature. The heat of extraction for samarium that was obtained in this study was -9.6 kJ mol-1, which is in reasonable agreement with the previously obtained value of -10.9 kJ mol-1. The curium heat of extraction was performed under two sets of conditions and the obtained heats of extraction were in reasonable agreement with each other at -16.0 {+-} 1.1 and -16.8 {+-} 1.5 kJ mol-1