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.     

Organic solvent extraction of uranium from alkaline nuclear waste

There are proliferation issues with the Plutonium Uranium Redox Extraction process due to the possibility of recovering plutonium. The objective of this research was to evaluate different organic extraction ligands that can remove uranium from the nuclear waste and to determine the most effective organic solvent for extracting uranium only, from alkaline media. The results indicate that Alamine 336 in xylene has zero (0%) extraction capability for surrogate fission products at an optimum extraction time of 15 min. Aliquat 336 in xylene has an extraction percentage of 72% for uranium in 60 min. However, Aliquat 336 in toluene extracted 82% of the uranium from the feed solution after 30 min, decreasing to 76% after 60 min.

     

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.     

Development of new centrifuges for fast solvent extraction of transactinide elements

Inductively coupled plasma-mass spectrometry (ICP-MS) was used to concurrently determine multiple long-lived (t_1/2>10⁴ y) actinide isotopes in soil leachates. Ultrasonic nebulization was found to maximize instrument sensitivity. Instrument detection limits for actinides in solution ranged from 50 mBq L^–1 (²³⁹Pu) to 2Bq L^–1 (²³⁵U). Hydride adducts of²³²Th and²³⁸U interfered with the determinations of²³³U and²³⁹Pu; thus, extraction chromatography was used to concentrate the analytes and separate uranium from the other actinides in advance of mass spectrometric determination. Alpha spectrometric determinations of²³⁰Th,²³⁹Pu, and the²³⁴U/²³⁸U activity ratio in soil leachates compared well with ICP-MS determinations; however, there were some small systematic differences (ca. 10%) between ICP-MS and -spectrometric determinations of²³⁴U and²³⁸U activities. These differences were attributed to the use of different isotope dilution spikes for ICP-MS and -spectrometry.     

Separation of strontium from nuclear waste solutions by solvent extraction with crown ethers

The possibilities of strontium separation from medium activity waste (MAW) solutions have been investigated. MAW originates from the PUREX process and contains NaNO₃ and HNO₃ in a large excess. By solvent extraction with the crown ether dicyclohexano-18-crown-6 (DC-18-C-6) in 1,1,2,2-tetrachloroethane, separation is possible. The distribution ratio for Sr²⁺ depends on the concentration of HNO₃, NaNO₃ and Pb(NO₃)₂. The extraction system is employed in a continuous counter-current process. After use, the extraction agent can easily be regenerated by reextraction with pure water.     

Ionic liquids as a novel solvent for lanthanide extraction.

Octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide (CMPO) dissolved in an ionic liquids, 1-butyl-3-methyl-imidazolium hexafluorophosphate, greatly enhances extractability and selectivity of lanthanide cations compared to that dissolved in conventional organic solvents; further, the recovery of lanthanides extracted into ionic liquids can be accomplished using several stripping solutions containing complexing agents. The possibility of utilizing ionic liquids as novel separation media in an industrial liquid-liquid extraction process was demonstrated.     

柴胡中柴胡皂甙a的超声辅助溶剂提取

以溶剂提取法为基础,以超声波为辅助手段,对柴胡中的有效成分进行了提取.通过对提取液中柴胡皂甙a量的测定,研究了超声功率、提取温度、提取时间和样品浸渍时间等条件对提取效果的影响,优选出超声辅助溶剂提取的最佳条件为超声功率50%、提取温度50 ℃、提取时间20 min、样品浸渍时间24 h.实验结果表明,超声辅助溶剂提取比普通的溶剂提取具有更高的提取效率.     

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.     

Advance of computational technology for simulating solvent extraction.

Due to recent significant enhancement of computer performance as well as computational techniques, molecular modeling and molecular simulations using computational chemistry can be achieved at the level of practical applications. Even in solvent extraction, the application of computational chemistry to simulations of extraction processes and the molecular design of high-performance extracting agents have gradually been increasing during the last decade. With combining the quantitative structure-property relationship between the molecule properties calculated by the computational chemistry methods and the thermodynamic properties obtained from experiments, researchers can precisely predict the next-generation of extracting agents and novel extraction processes. In this review, the concept of computational chemistry, such as molecular mechanics, molecular orbitals and molecular dynamics calculations, frequently used in the filed of solvent extraction, are outlined. Our systematic research on the solvent-extraction process utilizing MM, MO and MD calculations is also presented.     

Some solvent effects on the solvent extraction of 8-quinolinol

The distribution constants of 8-quinolinol between water and a series of substituted aliphatic hydrocarbons, at 25 degrees , are reported. The results are discussed in terms of dielectric constant and solubility parameter of the solvents. For 8-quinolinol, and possibly for its chelates, bromochloromethane, dibromomethane and chloroform seem to be about the best solvents, in that order. Among the solvents studied, chloroform shows significantly higher values than expected; the deviation may be explained as a specific interaction of the hydrogen- bonding type.     

Catalytic effects in solvent extraction

Catalytic phenomena in solvent extraction of metals with hydrophobic chelating extractants are reviewed. Interface modification by adsorption of additives, phase transfer catalysis, formation of micelles, reversed micelles and microemuslions are discussed and examples are given.     

In-line phase separator for microfluidic solvent extraction of uranium

Experiments are carried out to study the separation of liquid-liquid dispersion generated at a microfluidic junction by using an in-line phase separator. The phase separator comprises a metallic mesh sandwiched between two flow channels. Dispersion generated at the microfluidic junction is fed to the upper flow channel of the in-line phase separator. Continuous phase permeates through the metallic mesh into the lower flow channel and gets separated from the dispersed phase. The effects of operating parameters (flow rates of the aqueous and organic phases), flow channel geometry and mesh properties (pore size and thickness) on phase separation are studied. After identification of operating window in which complete phase separation is achieved, mass transfer experiments are performed to demonstrate intensified uranium extraction using a micromixer and in-line phase separator.

     

Anomalous solvent extraction behavior of astatine

We studied the solvent extraction behavior of astatine and found the anomalous behavior of this element similar to radioiodine. Astatine was extracted into CS₂ from acidic solution over a wide range of carrier iodine concentration. The distribution ratios of astatine were determined by measuring the -ray from 210 At with a Nal(TI) detector. A drastic change was observed around at 10^–4 mol/l as in the case of 131 I. This tendency is well explained by the kinematics of the chemical reactions concemed.     

Speciation of arsenic in a contaminated soil by solvent extraction

Soil collected from a disused cattle dip in northern New South Wales was studied with the aim of developing an inexpensive, yet effective method for quantitative determination of arsenic(III), arsenic(V) and total organic arsenic in a contaminated soil. Hydrochloric acid extractions were used as a method for removal of the arsenic from the soil in a form suitable for speciation. It was found that the extraction efficiency varied with the ratio of soil to acid, and the concentration of the acid. Arsenic(III), as arsenic trichloride, was selectively extracted into chloroform from a solution highly concentrated in hydrochloric acid. This was followed by back-extraction of the arsenic into water. Total inorganic arsenic was determined in a similar manner after the reduction of arsenic(V) to the trivalent state with potassium iodide. Arsenic(V) was determined by the difference between the results for arsenic(III) and total inorganic arsenic. All analyses for the various arsenic species were performed by hydride generation-atomic absorption spectroscopy; concentrations of total arsenic in the soil were confirmed using X-ray fluorescence spectrometry. It was found that all the arsenic in the soil was present as inorganic arsenic in the pentavalent state. This reflects the ability of arsenic to interchange between species, since the original species in cattle dipping solution is arsenic(III).     

New macrocycles derived from biphenyl for pH-switched solvent extraction

Four new fluorescent macrocyclic ligands derived from biphenyl are described. The new compounds have been used in liquid-liquid extraction experiments and the influence of pH has been studied in those ligands containing carboxylic groups. The results obtained for the latter ligands have been compared with those observed in the presence of an external acid.     

Pressurised solvent extraction for organotin speciation in vegetable matrices

Because organotin compounds (OTC) are widely used in many fields of activity, they have become an ubiquitous environmental presence. The presence of organotins in the environment impacts upon food safety, making it important to monitor the levels of organotin pesticides in fruits and vegetables. Nevertheless, only a few studies have been published on organotin speciation in plants. The objective of the present study was to evaluate and optimise a specific procedure based on pressurised solvent extraction (PSE) that is suitable for monitoring organotin content in vegetables. In ASE, solvents are used at elevated temperatures and pressures to increase the rate and efficiency of the extraction process. The results from this procedure were compared to those from the technique usually employed, solid/liquid extraction (SLE) performed in an acidic solvent by mechanical shaking. Three extracting solutions were tested—methanol, ethyl acetate and a mixture of methanol and ethyl acetate—and the mixture was found to give the most quantitative results while preserving the speciation. French bean and lettuce leaves as well as potato tubers were used as the plant materials. These vegetables were considered because they are the vegatables consumed in the most quantities in Europe. The study focuses on trisubstituted OTCs, which are the most toxic tin species. The samples were spiked with four trisubstituted organotins: tributyltin (TBT), triphenyltin (TPhT), tricyclohexyltin (TcHexT) and trioctyltin (TOcT). The influence of the pressure and the temperature of the PSE on the quantitativity of the process and on species preservation was evaluated using the experimental design methodology. The optimised PSE allowed detection limits down to 1–2 ng (Sn) g^–1 to be reached. These are higher than those obtained by SLE (0.1–1 ng (Sn) g^–1). Although the repeatability is similar for both PSE and SLE (2–12% for triorganotin compounds), this appears to be highly time-dependent in the case of SLE. Comparison with SLE confirms that PSE is an interesting tool for vegetable analysis considering the satisfactory OTC preservation and repeatability obtained for a relatively short extraction duration (only 15 min against 2–12 h for SLE).