Search

This article demonstrates possible separation of Pd(II), Pt(IV), and Rh(III) ions from chloride solutions by solvent extraction in rotating coiled columns (RCC). The most common reagents used for extraction of platinum metals were selected as extractants: trioctylamine (TOA), methyltrialkylammonium chloride (MTAA), tributyl phosphate (TBP), and relatively new reagent—N,N,N',N'-tetra-n-octyldiglycolamide (TODGA). The completeness of extraction of platinum metals from individual and mixed hydrochloric acid and chloride solutions has been analyzed as a function of the essence and concentration of extractant, acidity of the analyzed solutions, and other factors. Optimum conditions of quantitative extraction of the metals from model hydrochloric acid and chloride solutions into the extractant phase have been determined, including subsequent selective separation at the re-extraction stage. A flowchart has been proposed for multistage extraction of Pd(II), Pt(IV), and Rh(III) using 0.05 M MTAA solution in toluene as a stationary phase in RCC. The flowchart includes extraction of Pd(II) and Pt(IV) ions from the solution (0.1 M HCl + 30 g/L Cl–) into the organic phase upon simultaneous separation of Rh(III) remaining in the aqueous phase and consecutive re-extraction of Pd(II) and Pt(IV) from the organic phase using 0.01 M solution of thiourea in 0.1 M HCl and 1 M solution of thiourea in 0.5 M HCl, respectively. The flowchart has been verified for separation of platinum metals in the production process of preset composition. The degree of metal extraction after processing by 0.05 M solution of MTAA in in toluene and consecutive re-extraction by solutions of thiourea is 99.5% for rhodium(III), 99.9% for palladium(II), and 97.4% for platinum(IV). The extracted aqueous phases of rhodium and platinum after output from the column did not contain impurities of other platinum metals. In the aqueous fraction of palladium, the platinum content was 0.5%.

For efficient extraction of cyclic amino acids, it has been proposed to use polymers based on N-vinylformamide. The extraction of phenylalanine, tyrosine, histidine, and proline in two-phase systems based on poly-N-vinylformamide and N-vinylformamide–N-vinylimidazole copolymer has been studied for the first time. Systems with the maximum recovery rate of individual amino acids have been found. The mechanism of intermolecular interactions in polymer–amino acid systems has been proposed. The results of extraction of a phenylalanine–tyrosine mixture by a N-vinylformamide–N-vinylimidazole copolymer are reported. An electrophoretic method for determining amino acids in extracts is proposed.

Actively developing “unconventional” methods for the solid-phase extraction (SPE) of organic substances, for example, solid-phase microextraction, solid-phase dynamic extraction, dispersive solid-phase extraction, matrix solid-phase dispersion, microextraction in a packed syringe, etc., are characterized. The main distinctive features of the methods and the fields and prospects for their application are considered. Solid-phase microextraction is most popular, mainly because of a possibility of the full automation of the separation and determination of analytes and the ease of combination with gas and liquid chromatography, as well as with other analytical methods.

The development and use of instrumental methods for the determination of a wide range of trace elements in oil is considered. Special attention is paid to methods of the direct introduction of samples into spectrometers. It is shown that preliminary sample preparation is in certain cases necessary for the determination of trace elements in oil. The main methods of sample preparation of oils, including methods of extraction of a series of trace elements from crude oil (extraction, membrane, sorption, etc.), are described.

A combined approach to the analysis of volcanic ash (VA) was proposed. Ash particles were separated by size using a combination of vibration sieving on sieves (140, 70, 40 μm) and field-flow fractionation in a rotating coiled column (for separation of nano- and submicron particles). Initial samples and obtained fractions were characterized using scanning electron microscopy and static light scattering. Their elemental composition was determined using ICP-MS and ICP-AES methods. The radionuclide composition of the VA was studied by the low-background gamma spectrometry. The studies were carried out by the example of ashes from Puyehue volcano, the Puyehue Cordon Caulle volcanic group, Andes (Santiago, eruption on June, 2011), which were taken immediately after eruption and after first rain. It was shown that up to 15% of major elements (such as P, Ca, and К) and trace elements (such as Be, Hg, Tl, As, Sb, and Bi) could be extracted from the ash by rain and migrate into environment. It was also found that the content of radionuclides (U235, Th234, Pb214, Bi214, Be7) after rain decreases by 30–40%. Of special interest are ash nanoparticles (up to 200 nm), in which the contents of Cu, Pb, Tl, Bi, Sn, As, and Sb are over an order of magnitude higher than the bulk contents of these elements in the ash. This regularity was found in samples taken both prior to and after rain. The proposed methodology of fractionation, study, and analysis of ash particles may be applied for a wide range of soil, ash, and dust samples of different nature.

The properties of a Diasorb-130-IDK sorbent based on silica gel with a grain size of about 6 µm were studied in order to choose conditions for the separation of the rare-earth elements from the samples of natural wine and their subsequent determination by inductively coupled plasma mass spectrometry. The possibility of the quantitative separation of the elements with the use of an ultrasonic flow suspension column was demonstrated. The results were compared with data obtained with the use of other sample preparation methods. A procedure was proposed for the determination of the rare-earth elements and yttrium in the samples of wines.

It is demonstrated that field-flow fractionation using a rotating coiled column (RCC) can be used for the separation and purification of the polydisperse sorbents based on polystyrene–divinylbenzene. The behavior of the sorbent at different operating parameters of RCC was studied. The mobile phase composition, column rotation speed, and the initial flow rate of the mobile phase were selected, optimized for the isolation of a monodisperse fraction with the particle size 4.5 µm and the separation of particles 0.5–2 µm in size, particle fragments, and residues of sorbent synthesis. It is shown that a 15-mL analytical RCC ensures the efficient fractionation of 100 mg of the sorbent in one experiment taking less than one hour with the yield of the desired fraction greater than 95%. The perspectives for scaling up the fractionation in RCC are evaluated; the possibility of using the method for the preparative separation of particles of different nature is discussed.

A method is proposed for the luminescence determination of neptunium in natural waters with the removal of interfering iron. For the separation of iron ionic and colloidal species, solid-phase extraction with N-benzoyl-phenylhydroxylamine as a complexing reagent is used. The method makes possible the reduction of iron concentration in samples by more than two orders of magnitude without noticeable losses of neptunium and, therefore, the attainment of a detection limit for neptunium equal to its value in samples containing no iron.

Nanodiamonds that are obtained during cavitation synthesis in toluene [E. M. Galimov et al., Doklady Phys. 49 (3), 150 (2004)] are investigated. The procedure of chemical purification of nanodiamonds allowing for isolating a chemically pure product is developed, and diamond nanoparticles less than 10 nm in size are obtained. New data indicating that the fcc modification of carbon appears along with the diamond phase under cavitation synthesis and raising the question on the account of interaction types of carbon precursors are represented.

The paper presents the first comparative study of the fractionation of heavy metals, arsenic, antimony, and selenium in soils, sludge and bottom sediments using two systems for dynamic extraction, rotating coiled columns (RCC) and cylindrical microcolumns (MC). It has been revealed that the results of the fractionation of the forms of elements are related with the physicochemical properties of soils, sludge, and bottom sediments and the special features of mixing the sample and eluent in RCC and MC. In particular, it has been demonstrated that, as compared to MC, RCC provides more efficient recovery of the most mobile (ecologically relevant) forms of arsenic, antimony, and selenium from samples rich with organic matter. However, in the majority of cases, despite the different efficiency of the recovery of individual fractions, RCC and MC provide comparable diagrams of the distribution of the extracted forms of elements. The influence of the rate of the eluent flow on the processes of the dynamic extraction of heavy metals, arsenic and antimony in RCC and MC has been estimated. The directions of research for the further harmonization of the methods of dynamic fractionation of forms of elements in soils, sludge, and bottom sediments with different physicochemical mobilities and potential biological availabilities are outlined.

The recovery and separation of plutonium(IV) and americium(III) by solid-phase extraction (SPE) on alkylated silica gel S16 modified with N-benzoylphenylhydroxylamine (BPHA) and with its derivatives was studied. BPHA was modified by introducing into the p-position of the phenyl ring of electronactive substituents that differ in their hydrophobicity: CH3, Ph, Cl, F, and NO2. The SPE of plutonium(IV) and americium(III) was studied in the range of acidities from pH 8 to 1 M HNO3. The recovery and separation of these elements was shown to depend on the nature of the substituent, aqueous acidity, and the preparation of S16 to SPE experiments.

We studied the influence of synthesis parameters and the composition of the reaction mixture on the size and morphology of copper nanoparticles (NPs). Use of a surfactant (polyoxyethylenesorbitan monooleate) is promising for confining NP growth and stabilizing NPs. Concentration ranges of existence were determined for copper NP dispersions stable to aggregation and sedimentation. Scanning electron microscopy and dynamic light scattering were used to show that: the NP size varied from 10 to 65 nm, the average diameter was 25–35 nm, and the shape was spherical. The sizes of copper NP aggregates were determined.

A method for the continuous-flow fractionation of particles in a transverse centrifugal field in a rotating conoidal coiled (RCC) column has been developed. A model of a planetary centrifuge with a conoidal drum of a special construction has been tested. The effects of the rotation and revolution speed of the conoidal RCC, as well as the direction and pumping rate of the mobile phase on the behavior of particles smaller than 1 μm have been studied. The conditions have been selected and optimized for the retention and elution of spherical particles of the ‘150 nm’, ‘400 nm’, and ‘900 nm’ standard samples of silica gel (Polyscience Inc.). The possibility of using RCC for the analysis and production of monodisperse standard particle samples has been demonstrated. In particular, the ‘900 nm’ particles have been separated from admixtures of small (100–200 nm) particles and nonspherical 1–2 μm particles present in the sample. The separated fractions have been characterized by electron microscopy.

Comparative elemental analysis of the Tengiz oil and diesel fuel is performed by inductively coupled plasma mass-spectrometry with autoclave digestion, digestion, dilution with organic solvents, and also rotating coiled columns (RCCs). The advantages and drawbacks of each of the listed sample preparation techniques for the separation of microelements are discussed. In contrast to the other versions, the use of RCCs is shown to provide a unique opportunity to preconcentrating microelements from oil and petroleum products into tiny volumes of aqueous solutions (10 mL of 0.5 M HNO3). The eluate prepared can be used in the subsequent analysis by ICP MS with no extra sample preparation steps. The RCC preconcentration of elements from oil and petroleum products makes it possible to determine metals in concentrations from μg/kg to ng/kg.

Recovery of Np(V), Pu(IV), and Am(III) by solid-phase extraction with supported N-benzoylphenylhydroxylamine (BPHA) from simulated groundwater with pH 8.5 was studied. DIAPAK C16 cartridges modified with BPHA can be used for preconcentration of these elements from natural waters by solid-phase extraction.

Reinforced track membranes are used for the first time to study element distribution between particles of various sizes and other water components. The properties of the reinforced track membranes are considered. Factors affecting the quality of water in the Volga River in the region of the water intake of the city of Dubna in the Moscow region and potable water in various districts of the city in are characterized by the fractional composition of macro- and microcomponent.