Atom-at-a-time studies of the transactinide elements

Some of the techniques used in atom-at-a-time investigations of both nuclear and chemical properties of transactinide elements will be discussed. Constraints on the systems that are valid for exploring chemical properties when only a few atoms at a time are available and recent developments in instrumentation are considered. The current status of investigations of the chemical properties of the transactinides is summarized and prospects for additional studies are evaluated.     

Development of a micro-mixer-settler for nuclear solvent extraction

Nuclear solvent extraction was traditionally performed with packed columns, pulse columns, mixer-settlers and centrifugal extractors. However for rapid separations at micro-flow level, micro mixer-settlers were desired and in the past, few of them were actually designed and operated in nuclear solvent extraction research. In the current era of micro-reactor and microchannel devices, there is a renewed interest for micro-mixer-settlers for costly solvents and specialty solutes where small flow-rate is not an issue. In this article, development of a simple but effective micro-mixer-settler for nuclear solvent extraction is reported. The developed unit was tested with 30% TBP/n-dodecane/nitric acid system and in both the regimes of mass transfer c → d (mass transfer from continuous phase to dispersed phase, also written as c → d) and d → c (mass transfer from dispersed phase to continuous phase, also written as d → c) nearly 100% efficiency was observed in extraction as well as stripping modes of operation.     

Application of fast solvent extraction processes to studies of exotic nuclides

The nucleus²³Na has been investigated by studying the primary γ-rays emitted from 53 keV neutron capture in it using a high resolution and high efficiency (100%) HPGe detector and NaI(T1) detector for anti-Compton. 24 primary γ-rays were placed in the²⁴Na, in which 3 primary γ-rays were new ones from a (n, γ) reaction, and reported for the first time. In order to obtain an exact energy calibration within 7 MeV,⁵⁶Fe(n,γ)⁵⁷Fe reaction was used at thermal neutron energy. Intensity calibration was obtained from the²⁷Al(p,γ)²⁸Si reaction atE _p=2046 keV. The neutron binding energy of²⁴Na was determined to be 6959.75 keV.     

Development and publication of solvent extraction methods

Guidelines are set for the development of solvent extraction separation methods and for their preparation for publication. The necessity of establishing the novelty of and need for the new method is emphasized. The various items that require specification are discussed, and the criteria for successful application of the method, viz. completeness of extraction, selectivity and freedom from interference, are laid down.     

The use of trioctylphosphine oxide for solvent extraction recovery and purification of transplutonium elements

Extraction of trivalent curium, berkelium, californium, einsteinium, and europium with trioctylphosphine oxide (TOPO) from nitric acid solutions as well as extraction of curium and cerium from lactic acid solutions containing DTPA depending on aluminium nitrate concentration have been studied. The distribution of cobalt, nickel, chromium, iron, aluminium, titanium, zirconium, and niobium ions has been studied and coefficients of berkelium purification from the elements studied have been determined under the conditions of extraction-chromatographic recovery of berkelium. The influence of weighed amounts of the same impurities on the yield of berkelium in its extraction-chromatographic separation has been studied. Some examples of the practical application of the extraction-chromatographic techniques using TOPO are given.     

Development of a miniature Taylor-Couette extractor column for nuclear solvent extraction

Miniature annular centrifugal contactors are nearly perfect for shielded hot-cell applications during flowsheet evaluation but these contactors require complex maintenance of electrical drive-motors during radioactive experiments. To reduce the number of electrical drives in the shielded cell, an indigenous design of miniature Taylor Couette (TC) mixing based countercurrent differential extraction column has been developed. In this paper, results of mass transfer experiments for an indigenously developed TC column with 30% TBP/aqueous nitric acid solutions are reported. The developed device worked perfectly in counter–current differential mode and demonstrated equivalence to multiple-extraction stages while working with a single electrical drive. The developed TC unit demonstrated operation with a reduced efficiency without flooding even in absence of rotor rotation. This observation is a vital step towards designing of robust contactors, which do not flood during temporary power failure or failure of drive mechanism.     

Separation of rhodium from ruthenium and iridium by fast solvent extraction with HDEHP

Solvent extraction of rhodium, ruthenium and iridium with di(2-ethylhexyl)phosphoric acid (HDEHP) has been investigated. Under the conditions [Cl^–1]=0.20M, [(HDEHP)₂]=0.30M, pH 4.05, phase contact time 1 minutes, Rh(III) is extracted 90.7%, Ru(III) and Ir(III) 20.0% and 11.5%, respectively, at phase ratio 11. The distribution ratio of rhodium is proportional to [(HDEHP)₂]³ for a freshly prepared aqueous phase with low chloride concentration but might drop to [(HDEHP)₂]^1to2 for an aqueous phase high in chloride concentration and after standing. The spectroscopic studies indicate that the extracted compound of rhodium is Rh(H₂O)_6–x Cl _x [H(DEHP)₂]_3–x (x=0, 1, 2).     

Development of a standardized sequential extraction protocol for simultaneous extraction of multiple actinide elements

Sequential extraction is a useful technique for assessing the potential to leach actinides from soils; however, current literature lacks uniformity in experimental details, making direct comparison of results impossible. This work continued development toward a standardized five-step sequential extraction protocol by analyzing extraction behaviors of ²³²Th, ²³⁸U, ^239,240Pu and ²⁴¹Am from lake and ocean sediment reference materials. Results produced a standardized procedure after creating more defined reaction conditions to improve method repeatability. A NaOH fusion procedure is recommended following sequential leaching for the complete dissolution of insoluble species.     

Separation of rare earth elements from uranium by solvent extraction and ion exchange

The detection limit of⁹⁹Tc in (,) radio-activation analysis was determined in the presence of molybdenum and compared with that of⁹⁹Tc in pure materials in the previous paper. The isotopic ratio of molybdenum in a⁹⁹Mo–^99mTc generator column could be simultaneously determined by photon activation analysis.     

AAS determination of trace elements in high-purity gold after matrix separation by solvent extraction

Summary A method is described for the determination of 20 trace elements in gold of a qualification of about 4–5 N. The matrix is separated by solvent extraction into methylethylketone/chloroform and the trace elements are determined in the aqueous phase by AAS (flame or graphite furnace). The procedure is optimized as to minimize the number of contamination sources.     

3-Thianaphthenoyltrifluoroacetone: A new reagent for the solvent extraction of zirconium and hafnium

Summary A method for the solvent extraction of mg quantities of zirconium(IV) and hafnium(IV) from 3-molar perchloric acid with 3-thianaphthenoyltrifluoroacetone is described. The effects due to acidity, choice of acid, time, heating, solvents and reagent concentration are reported.

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Zusammenfassung Eine Methode zur Losungsmittelextraktion von mg-Mengen Zr(IV) und Hf(IV) aus 3-m Perchlorsäure mit 3-Thianaphthenoyltrifluoraceton wurde beschrieben. Der Einfluß der Acidität, der Art der Säure, der Zeit, des Erhitzens, der Lösungsmittel und der Reagenskonzentration wurde erörtert.

     

A new analytical method for 32P: Liquid scintillation counting with solvent extraction

⁵⁷Fe Mössbauer spectroscopy has been applied to the ultramafic rocks collected from the Jinchuan nickel deposit in China to elucidate their mineralization process. Their Mössbauer spectra consisted of two sextets ascribable to magnetite, two doublets ascribable to Fe²⁺ and Fe³⁺ in chromite, and one doublet ascribable to olivine. The closest sample to the ore body did not contain chromite and contained a doublet ascribable to pyrite and a sextet ascribable to pyrrhotite. The valence and site distribution of iron species suggested low oxygen fugacity for the formation of the Jinchuan nickel deposit.     

Comparison of solvent mixtures for pressurized solvent extraction of soil fatty acid biomarkers

The extraction and transesterification of soil lipids into fatty acid methyl esters (FAMEs) is a useful technique for studying soil microbial communities. The objective of this study was to find the best solvent mixture to extract soil lipids with a pressurized solvent extractor system. Four solvent mixtures were selected for testing: chloroform:methanol:phosphate buffer (1:2:0.8, v/v/v), chloroform:methanol (1:2, v/v), hexane:2-propanol (3:2, v/v) and acetone. Soils were from agricultural fields and had a wide range of clay, organic matter and microbial biomass contents. Total lipid fatty acid methyl esters (TL-FAMEs) were the extractable soil lipids identified and quantified with gas chromatography and flame ionization detection. Concentrations of TL-FAMEs ranged from 57.3 to 542.2 n mole g⁻¹ soil (dry weight basis). The highest concentrations of TL-FAMEs were extracted with chloroform:methanol:buffer or chloroform:methanol mixtures than with the hexane:2-propanol or acetone solvents. The concentrations of TL-FAMEs in chemical groups, including saturated, branched, mono- and poly-unsaturated and hydroxy fatty acids were assessed, and biological groups (soil bacteria, mycorrhizal fungi, saprophytic fungi and higher plants) was distinguished. The extraction efficiency for the chemical and biological groups followed the general trend of: chloroform:methanol:buffer ≥ chloroform:methanol > hexane:2-propanol = acetone. Discriminant analysis revealed differences in TL-FAME profiles based on the solvent mixture and the soil type. Although solvent mixtures containing chloroform and methanol were the most efficient for extracting lipids from the agricultural soils in this study, soil properties and the lipid groups to be studied should be considered when selecting a solvent mixture. According to our knowledge, this is the first report of soil lipid extraction with hexane:2-propanol or acetone in a pressurized solvent extraction system.     

Determination of seven trace elements in natural waters after separation by solvent extraction and anion-exchange chromatography

A method is described for the determination of cadmium, cobalt, copper, manganese, lead, uranium, and zinc in samples of natural waters. After acidification with hydrochloric acid the water sample is filtered and the diethyldithiocarbamates of the trace elements are isolated by extraction with acetone—chloroform (2:5) at pH 5. Following this preconcentration step the metal ions are adsorbed on a column of the strongly basic anion-exchange resin Dowex 1-X8 (chloride form) using as sorption solution a mixture (5:4:1, $\text{v}\text{v}$) of tetrahydrofuran, methyl glycol and 6 M hydrochloric acid. Successive elution is effected with 6 M hydrochloric acid (Co, Cu, Mn and Pb), 1 M hydrochloric acid (U) and 2 M nitric acid (Cd and Zn); the metal ions in the eluates are determined by atomic absorption spectrophotometry (except uranium, which is determined fluorimetrically). The procedure was used to determine the trace-metals in water and snow samples collected in Austria and to analyse a sample of sea water from the Adriatic Sea.     

A new solvent extraction scheme for the separation of platinum,palladium, rhodium and iridium

A new scheme is proposed for the separation of platinum, palladium, rhodium and iridium in hydrochloric acid solutions, by solvent extraction. Platinum and palladium are complexed with 2-mercaptobenzothiazole and potassium iodide and simultaneously extracted into chloroform, thus separating them from rhodium and iridium. Palladium is separated from platinum by extracting its dimethylglyoxime complex into chloroform, while rhodium is separated from iridium by extracting its 2-mercaptobenzothiazole complex into chloroform after reduction with tin(II) chloride.     

A simple and fast micromethod for the analysis of polychlorinated biphenyls in air by sorbent enrichment and ultrasound-assisted solvent extraction

A combination of sorbent enrichment and ultrasound-assisted solvent extraction has been used to determine polychlorinated biphenyls in air. Analytes were sampled by pumping a known volume of air through a porous polymer (Tenax TA). The enriched adsorbent was transferred into a glass vial, and ultrasound-assisted extraction of the analytes was then performed in n-hexane. Quantification was carried out by using gas chromatography coupled to tandem mass spectrometry. Breakthrough volume of the sampling step was studied, indicating that 10 m³ of air could be processed without losses of the most volatile compounds. Good recoveries (75–96%) were obtained, and limits of detection at the sub ng m^–3 were achieved for all the analytes. The proposed method is very simple and fast, avoiding the use of large solvent volumes and time-consuming preconcentration steps.     

A new method for fast chitin extraction from shells of crab,crayfish and shrimp

A new method for quick chitin isolation from the shells of crab, crayfish and shrimp is described. The main difference between the new method and the conventional method is two sodium hypochlorite (NaClO) treatments for 10 min each before the processes of demineralisation and deproteinisation. After the NaClO treatment, only 15 min is adequate for the demineralisation and 20 min for the deproteinisation processes. Newly extracted chitin from crab, crayfish and shrimp shells and commercial chitin were characterised using FT-IR, TGA, X-ray diffractometry and elemental analysis. From the results, it was observed that the chitins isolated with the new method and the commercial chitin had almost the same physicochemical properties. The advantage of the new method compared to traditional methods is the relatively rapid chitin extraction. When compared to the traditional chitin extraction method, the proposed method appears to be promising regarding its time and energy saving nature.