Heats of dilution of sodium chloride temperature dependence

The recent increase of interest in high temperature thermodynamic data has revealed that very little precise data exists. Also, the data that does exist contains some large uncertainties. An efficient and accurate method is needed by which high temperature thermodynamic data can be obtained. This is essential not only for extending the present knowledge of aqueous electrolyte solutions, but also to remove the uncertainties now existing in published data. The heats of dilution of sodium chloride have been measured over a concentration range of 0.1 m to 6.0 m at 40°, 50°, 60°, 70°, and 80° . These measurements were made using a micro-degree calorimeter. The experimental data was extrapolated to infinite dilution using the extended Debye-Hückel equation. The partial molal heat contents of solute and solvent were calculated from the experimental heats of dilution. These values in turn were used to correct existing activity coefficients and osmotic coefficients at 25° to higher temperatures. The calculated values were found to be in excellent agreement with existing data. The apparent molal heat capacity of solute was also calculated from partial molal heat content of solute; however, no real conclusions as to the accuracy of these values could be reached. It is concluded that use of heat of dilution data to correct existing values of thermodynamic quantities to higher temperatures is an efficient and precise technique

Recommended Guanidine Suppressor for the Next-Generation Caustic-Side Solvent Extraction Process

The guanidine recommended for the Next-Generation Caustic-Side is N,N ,N -tris(3,7-dimethyloctyl)guanidine (TiDG). Systematic testing has shown that it is significantly more lipophilic than the previously recommended guanidine DCiTG, the active extractant in the commercial guanidine product LIX -79, while not otherwise changing the solvent performance. Previous testing indicated that the extent of partitioning of the DCiTG suppressor to the aqueous strip solution is significantly greater than expected, potentially leading to rapid depletion of the suppressor from the solvent and unwanted organic concentrations in process effluents. Five candidate guanidines were tested as potential replacements for DCiTG. The tests included batch extraction with simulated waste and flowsheet solutions, third-phase formation, emulsion formation, and partition ratios of the guanidine between the solvent and aqueous strip solution. Preliminary results of a thermal stability test of the TiDG solvent at one month duration indicated performance approximately equivalent to DCiTG. Two of the guanidines proved adequate in all respects, and the choice of TiDG was deemed slightly preferable vs the next best guanidine BiTABG

Next Generation Solvent Development for Caustic-Side Solvent Extraction of Cesium

This report summarizes the FY 2010 and 2011 accomplishments at Oak Ridge National Laboratory (ORNL) in developing the Next Generation Caustic-Side Solvent Extraction (NG-CSSX) process, referred to commonly as the Next Generation Solvent (NGS), under funding from the U.S. Department of Energy, Office of Environmental Management (DOE-EM), Office of Technology Innovation and Development. The primary product of this effort is a process solvent and preliminary flowsheet capable of meeting a target decontamination factor (DF) of 40,000 for worst-case Savannah River Site (SRS) waste with a concentration factor of 15 or higher in the 18-stage equipment configuration of the SRS Modular Caustic-Side Solvent Extraction Unit (MCU). In addition, the NG-CSSX process may be readily adapted for use in the SRS Salt Waste Processing Facility (SWPF) or in supplemental tank-waste treatment at Hanford upon appropriate solvent or flowsheet modifications. Efforts in FY 2010 focused on developing a solvent composition and process flowsheet for MCU implementation. In FY 2011 accomplishments at ORNL involved a wide array of chemical-development activities and testing up through single-stage hydraulic and mass-transfer tests in 5-cm centrifugal contactors. Under subcontract from ORNL, Argonne National Laboratory (ANL) designed a preliminary flowsheet using ORNL cesium distribution data, and Tennessee Technological University developed a chemical model for cesium distribution ratios (DCs) as a function of feed composition. Inter Laboratory efforts were coordinated in complementary fashion with engineering tests carried out (and reported separately) by personnel at Savannah River National Laboratory (SRNL) and Savannah River Remediation (SRR) with helpful advice by Parsons Engineering and General Atomics on aspects of possible SWPF implementation

Thermal stability study of a new guanidine suppressor for the next-generation caustic-side solvent extraction process

<p>Cesium stripping performance of thermally stressed solvent worsens slowly over time in batch tests of the Next-Generation Caustic-Side Solvent Extraction (NG-CSSX) process. NG-CSSX is currently used in full-scale equipment at the Savannah River Site for the selective removal of caesium from high-level salt waste. Recently, a new guanidine, <i>N,N</i>’,<i>N</i>”-tris(3,7-dimethyloctyl)guanidine (TiDG), was chosen for use as the suppressor, a lipophilic organic base needed for stripping, and the present study was undertaken to address the question of its stability. The NG-CSSX process solvent was evaluated for a period of three months under a variety of temperature and storage conditions. The performance of the solvent was tested at 30-day increments using an extraction, scrub, strip and extraction (ES₂S₃E) sequence. The results provide insights into the effects of storage and process conditions, the stripping behaviour of TiDG and the stability of the new solvent composition.</p

Separation of ²⁴¹Am³⁺ from ¹⁵⁴Eu³⁺ Using 3,3’-Butyloxy-Bis-1,2,4-Triazinyl-2,6-Pyridine as a Potent Receptor

The effective partitioning and transmutation of the minor An from the Ln in spent nuclear fuel in a non-proliferative manner is critical to lowering potential impact to the environment, moderating concern over the increase of nuclear power as a green alternative to fossil fuels, and solving a grand challenge in separation science. Although present in less than .1 wt.%, Am and Cm represent half-lives of over 400 years and significantly contribute to heat load through radioactive decay. Separation of the minor An from the neutron-poisoning Ln can advance the nuclear fuel cycle further toward closure and decrease the volume and radiotoxicity of daughter nuclides stored in a geologic repository. Similar physical properties and metal-complexant binding phenomena render this separation difficult. In this work, a comprehensive liquid-liquid separations study using the recently discovered 3,3’-butyloxy-bis-1,2,4-triazinyl-2,6-pyridine in the polar aprotic solvent trifluoromethylphenyl sulfone is presented. Unlike contemporary bis-1,2,4-triazinyl-2,6-pyridine complexants, the current system is stable and performs well in highly acidic systems. Separation of 241Am3+ from 154Eu3+, acid range tolerance, complexant concentration, and decomplexation studies are presented herein.</p

Separation of Americium from Europium using Camphor-BisTriazinyl Pyridine: A Fundamental Study

<p>Among the different components present in spent nuclear fuel, long-lived trivalent actinides are particularly difficult to separate from the shorter-lived lanthanide fission products due to their similar chemical properties. Selective extraction of americium from acidic solution (up to 2M HNO₃) containing tenth molar quantities of lanthanides has been achieved using neutral pyridine-based ligands dissolved in polar diluents. Nitrogen-based Bis Triazinyl Pyridine (BTP) ligands are desirable for both their excellent An/Ln selectivity and incinerability. Results pertaining to ligand solubility, kinetics, hydrolytic stability, and extraction performance in various nitric acid environments are presented.</p