Extraction of Trivalent Lanthanides and Americium by Tri-n-octylphosphine Oxide from Ammonium Thiocyanate Media

Abstract

An investigation of the solvent extraction of trivalent lanthanides and Am³⁺ from ammonium-thiocyanate media by tri(n-octyl)phosphine oxide (TOPO) in toluene has been completed. This system is of interest both for its potential as a means of separating transplutonium actinides from fission-product lanthanides and for inherent interest in thiocyanate-based solvent extraction systems. Partitioning was monitored using radiotracer techniques where appropriate, and ICP-OES or ICP-MS for others. The extraction behavior of all members of the lanthanide series (except for Pm) plus Y have been investigated. Conditional enthalpies (all exothermic) were determined (for selected systems) from the temperature dependence of the extraction reaction. A comparison with nitrate media shows higher extractive power of TOPO in contact with thiocyanate media, arising at least in part from the lower heat of the phase transfer of thiocyanate (relative to nitrate). The moderate tendency of HSCN to partition into the extractant phase has been profiled. Slope analysis indicates that TOPO solvation decreases from four (M(SCN)₃TOPO₄) for the light members of the series to three (or less) for the heavy lanthanide ions; Am³⁺ is extracted with four TOPO molecules. Despite the decrease in Ln:TOPO stoichiometry across the series, extraction is generally flat for the light lanthanides and increases from Gd³⁺ to Lu³⁺. The extraction of Am³⁺ from mildly-acidic ammonium-thiocyanate media was found to be at least 10 times stronger than that of the lanthanides between La³⁺ and Gd³⁺.     

In-Silico Calculations as a Helpful Tool for Designing New Extractants in Liquid-Liquid Extraction

Due to new challenges, new extraction solvents based on innovative extractants are needed in hydrometallurgy for specific tasks. Thus, the aim of the present article is to discuss the potential and limits of Quantitative Structure–Properties Relationship (QSPR) and molecular modeling for identifying new extractants. QSPR methods may have useful applications in such a complex problem as the design of ligands for metal separation. Nevertheless, the degree of reliability of the predictions is still limited and, in the present state of the art, these techniques are likely more useful for optimization within a given family of extractants than to build in-silico new reagents. The molecular modeling techniques provide binding energies between target metals and given ligands, as well as optimized chemical structures of the formed complexes. Thus, in principle, the information, which can be deduced from the molecular modeling computations are richer than that provided by QSPR methods. Nevertheless, an effort should be made to establish more tangible links between the calculated binding energies and the physical parameters used by the hydrometallurgists, such as the complexation constants in aqueous phase (β_MAn) or better the extraction constants (K_ex).     

Low energy helium ion texturization of titanium and relevance to biomedical applications

Helium irradiation of metals has long been studied in efforts to understand the damaging aspects associated with applications in fusion reactors and tritium storage. This work examines the possibility of using low energy helium ion bombardment as a method of producing a beneficial surface texturization to promote bone growth on orthopedic implants. Using 300 eV helium ions, two unique porous titanium surfaces were created when substrates were held at temperatures of roughly 450 °C and 600 °C. The surfaces were physically characterized by scanning electron microscopy (SEM) and scanning white light interferometry. A week long hFOB 1.19 cell culture was performed using an untreated titanium control to evaluate the suitability of these surfaces for orthopedic implants. Cell health and viability were evaluated by calcein AM live cell staining, MTT assay, and SEM. The results show that helium texturizations promote cellular activity and have no detrimental effect on cell health.     

PANI–LDPE composites: Effect of blending conditions

A composite based on polyaniline (PANI) and low density polyethylene (LDPE) with electrical conductivity was developed. Polyaniline was polymerized by chemical oxidation and doped with dodecyl‐benzene‐sulfonic acid (DBSA). PANI–LDPE composites were prepared via melt blending and the films were obtained by compression molding. The influence of three variables of the blending (temperature, [PANI], rotor speed) on conductivity, microstructure and mechanical properties of the composites was studied by means of statistical tools and a 2³ experimental design. The results show that the PANI concentration is the most influential variable, which mainly affects the conductivity and the elongation at break of the composites. These changes are related to the microstructure of the composites. Statistically, the other variables don't show significant influence on conductivity and mechanical properties in the studied range. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers.     

Fast Hartley transforms for spectral analysis of ultrasound Dopplersignals

Spectral analysis of Doppler ultrasound is known to yield valuable information to assess the state of circulation in the peripheral blood vessels. In the past, the raw Doppler data have been directly input into a dedicated spectrum analyzer or transformed on a microcomputer using the fast Fourier transform (FFT) technique. In the present study, the first Hartley technique is used to transform on a microcomputer to the digitized Doppler data obtained from a normal common carotid artery is presented and the resulting spectra are compared to those obtained by using the Cooley-Tukey FFT algorithm. The Hartley transform has the advantages of being a purely real-numbered transform; therefore, for real Doppler data, it is not only more conceptually straightforward, but also requires less computer memory, is simpler to calculate, and is better suited to large-scale integration implementation. The raw Doppler data were input into a digital oscilloscope from the analog Doppler unit, digitized in real time with 12-b resolution, and displayed on the computer monitor. These data were then stored in a file, on floppy or hard disk, using software provided with the digitizing oscilloscope, and then transformed to the spectral domain using either transform technique. In this application, the transforms were performed using a compiled BASIC language     

A Fast Production Scheduler for Generation Expansion Planning in a Hydro-Thermal System

A fast production scheduling algorithm suitable for generation expansion studies is described in this paper. It can handle several independent rivers, thermal plants, pumped storage plants, import, export, and internal non-firm markets. Inflows and load are deterministic and a one-reservoir limit is imposed on each river. The scheduling problem is formulated as a generalized network problem which is efficiently solved by an adaption of the simplex method. The algorithm is part of a program developed by Hydro-Québec to conduct preliminary evaluations of alternative expansion plans. The program and the scheduling algorithm are presented.     

Lack of method variance in self-reported affect and perceptions at work: Reality or artifact?

Spector (1987) recently concluded that there is little evidence of method variance in multitrait-multimethod studies of self-reported affect and perceptions at work. In this article we propose that this conclusion was incorrect and was the result of improper analytical procedures. Spector's data were reanalyzed by using a more powerful approach: confirmatory factor analysis. Model comparisons and variance partitioning indicated that method variance is present and accounts for approximately 25% of the variance in the measures examined by Spector. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Field test and evaluation of residential sprinkler systems: Part II

A series of National Fire Protection Association full-scale tests involving sprinkler installations was conducted in a two-story residence in Los Angeles, CA, and in a mobile home in Charlotte, NC. Previous laboratory tests, including full-scale room fire tests, had indicated that a prototype “quick-response” sprinkler was effective in controlling residential home fires. More full-scale fire tests under less controlled and more operational conditions were considered necessary to confirm or deny this conclusion. Part I of this three-part series (November 1983) explained the objectives of the tests and the test procedures that were to be followed. This second part describes the criteria used to evaluate the effectiveness of sprinkler systems using the “quick response” sprinkler in the series of seventy-six tests and the results of those tests. Part III will cover that phase of the test program that focused on a comparison of sprinkler and smoke detector activation times in the mobile home test structure. National Fire Protection Association Mr. Cote is Assistant Vice President (Engineering & Technical Services) for the NFPA. He served as project manager for the test series insofar as the NFPA had overall management responsibilities for the program. Reference: Cote Arthur E., “Field Test and Evaluation of Residential Sprinkler Systems: Part II” Fire Technology, Vol. 20, No. 1, February 1984, p. 48.     

College drinking game participation within the context of other predictors of alcohol use and problems.

One hundred and fifty-one alcohol-using college students completed a questionnaire on their frequency of drinking game participation, usual amount drunk during these games, and their own and perceived others' reasons for playing. Respondents also reported on their levels of alcohol use, moderate to severe problems with alcohol use, expectancies of the effects of alcohol on their moods and behaviors, perceived norms of significant others for levels of alcohol use, and reasons for drinking and not drinking alcohol. They completed the Eysenck I.7 measure of impulsivity, venturesomeness, and empathy. Reported frequencies of drinking game participation were very high in this sample and were significantly associated with several known predictors of alcohol use and problems. Game playing was a highly significant predictor of heavy alcohol use over and above other predictors. The influence of game playing on alcohol problems was found to be mediated by heavy alcohol use. (PsycINFO Database Record (c) 2010 APA, all rights reserved)