The separation of adjacent lanthanides continues to be a challenge worldwide because of the similar physical and chemical properties of these elements and a necessity to advance the use of clean-energy applications. Herein, a systematic structure−performance relationship approach toward understanding the effect of N-alkyl group characteristics in diglycolamides (DGAs) on the separation of lanthanides(III) from a hydrochloric acid medium is presented. In addition to the three most extensively studied DGA complexants [N,N,N′,N′-tetra(n-octyl)diglycolamide, TODGA; N,N,N′,N′-tetra(2-ethylhexyl)diglycolamide, TEHDGA; N,N′-dimethyl-N,N′-di(n-octyl)diglycolamide, DMDODGA], 12 new extracting agents with varying substitution patterns were designed to study the interplay of steric and electronic effects that control rare-earth element extraction. Subtle changes in the structure around diglycolamide carbonyl oxygen atoms result in dramatic shifts in the lanthanide extraction strength and selectivity. The effects of the chain length and branching position of N-alkyl substituents in DGAs are elaborated on with the use of experimental, computational, and solutionstructure characterization techniques.

Industrial rare earth element (REE) separation facilities utilize acidic cation exchange ligands such as 2ethylhexylphosphonic acid mono-2-ethylhexyl ester (PC88A) for solvent extraction processes. REE separations are costly and difficult due to their chemical similarities and subsequent low separation factors. Several empirical correlations are available in the literature to predict steady state extraction equilibria for various solvent systems. However, complete solvent extraction flow sheet design for REE separations requires complex scrubbing and stripping circuits to separate and produce individual pure species. Furthermore, dynamic modeling of extraction, scrubbing, and stripping in REE separations circuits will aid in process design, optimization, and management of process fluctuations. A dynamic MATLAB/SIMULINK REE equilibrium model has been coupled with dynamic acid balances to predict REE solvent extraction processes using laboratory equilibrium data. The model was used to predict a flow sheet that produced high purity neodymium from a 25 wt % praseodymium and 75 wt % neodymium feed. Laboratory mixer−settlers were used to verify and validate model performance.Results indicated that the model reasonably predicts the dynamic behavior of a countercurrent REE separation process, and accurately predicts the steady state REE concentration profiles across the cascade. Transient concentration predictions exhibit more deviation from experimental results due to the initial assumption of a homogeneous, well-mixed stage. The model was revised to account for variations in mixer−settler holdup volumes for future validation efforts. Current model limitations assume complete equilibrium is achieved in each stage. The model can be applied to any REE separation or solvent system provided adequate laboratory equilibrium data are available.

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2,2'-Oxybis(N,N-divinylacetamide):To a mixture of diallylamine (32.7 g, 128 mmol, 2.2 equiv.) in THF (0.3 M) was added Et3N (2.1 equiv.). The reaction mixture was cooled in an ice-water bath prior to slow addition of 2,2-oxydiacetyl chloride (1 equiv.) then stirred at room temperature for 2 h. The solvent was evaporated under reduced pressure. To the crude material, Et2O (~0.3 M) was added, the precipitate was removed by filtration through a short Celite  plug and rinsed with Et2O (2x). The filtrate was concentrated under reduced pressure to yield crude product (23.6

Previous research studies have shown that INL-developed engineered form sorbents are capable of capturing both xenon and krypton from various composite gas streams. The existing experimental test bed provided the capability of single column testing for capacity evaluations over a broad temperature range. To advance research capabilities, the employment of an additional column to study selective capture of target species to provide a defined final gas composition for waste storage was warranted. The second column addition also allows for compositional analyses of the final gas products to provide for final storage determinations.The INL krypton capture system was modified by adding an additional adsorption column to create a multi-column test bed. The purpose of this modification was to allow for the investigation of the separation of xenon from krypton supplied as a mixed gas feed. An extra (upstream) column was placed in a Stirling Ultra-low Temperature Cooler, capable of controlling temperatures between 190 and 253K and the column was filled with AgZ-PAN sorbent to capture the xenon from the feed gas. The effluent from this column would then be routed to the column in the cryostat filled with HZ-PAN to capture the krypton. Additional piping and valves were incorporated into the system to allow for a variety of flow path configurations.A limited scope of testing was performed to evaluate the performance of this updated test bed and to determine xenon and krypton separation, adsorption selectivity, desorption, and final concentrations in the desorbed gas streams. Sampling and analysis methods used in these tests included on-line GC-TCD analysis of the AgZ-PAN column outlet gas for xenon and krypton, as has been used in prior tests, and the addition of GC-MS evaluation of evacuated sample bombs. The sample bombs were analyzed after each test completion to measure xenon and krypton desorption from the columns as they were heated to above room temperature, with no purge gas flow.Two separation tests were performed utilizing a feed gas consisting of 1000 ppmv xenon and 150 ppmv krypton with the balance made up of air. The AgZ-PAN column temperature was held at 295 or 253K while the HZ-PAN column was held at 191K for both tests. The effluent from the AgZ-PAN column was monitored for xenon and krypton via GC-TCD during the tests. No xenon was detected exiting the AgZ-PAN column during the adsorption phase of either test.During the desorption phase of each test, gas samples from each column were taken via evacuated sample bombs and were analyzed by GC-MS analysis. No purge gas flowed during the sample bomb collection; the sample collection relied only on the evacuated bombs that drew gas from the sorbent beds when the connecting valve was opened.Results of these evaluations verified that the system operated as designed and demonstrated that AgZ-PAN exhibits excellent selectivity for xenon over krypton in air at or near room temperature, and that krypton with only small amounts of xenon was captured in the HZ-PAN column ...