Modeling of analytical, preparative and industrial scale counter-current chromatography separations.

Analytical, preparative and industrial scale counter-current chromatography (CCC) processes differ in the volumes of the loaded solution of components to be separated and in the design of the equipment. Preliminary mathematical modeling is necessary for selection of the optimal design and operation mode of these CCC separations. This study aims to compare simulations of CCC separations at different scales, using an exact description based on the model of equilibrium cells and a much simpler approximate solution based on the Gaussian distribution.

Modelling and Comparative Analysis of Different Methods of Liquid Membrane Separations.

This article is devoted to a brief review of the modelling of liquid membrane separation methods, such as emulsion, supported liquid membranes, film pertraction, and three-phase and multi-phase extraction. Mathematical models and comparative analyses of liquid membrane separations with different flow modes of contacting liquid phases are presented. A comparison of the processes of conventional and liquid membrane separations is carried out under the following assumptions: mass transfer is described by the traditional mass transfer equation; the equilibrium distribution coefficients of a component passing from one of the phases to another are constant.

Extraction of Copper from Sulfuric Acid Solutions Based on Pseudo-Liquid Membrane Technology.

Pseudo-liquid membranes are extraction devices in which a liquid membrane phase is retained in an apparatus consisting of two interconnected chambers while feed and stripping phases pass through the stationary liquid membrane phase as mobile phases. The organic phase of the liquid membrane sequentially contacts the aqueous phases of the feed and stripping solutions in the extraction and stripping chambers, recirculating between them. This extraction separation method, called multiphase pseudo-liquid membrane extraction, can be implemented using traditional extraction equipment: extraction columns and mixer-settlers.

Three- and Multi-Phase Extraction as a Tool for the Implementation of Liquid Membrane Separation Methods in Practice.

To promote the implementation of liquid membrane separations in industry, we have previously proposed extraction methods called three- and multi-phase extraction. The three-phase multi-stage extraction is carried out in a cascade of bulk liquid membrane separation stages, each comprising two interconnected (extraction and stripping) chambers. The organic liquid membrane phase recycles between the chambers within the same stage.

Intermittent sample loading technique as a tool for obtaining high- concentration elution bands in recycling liquid-liquid chromatography: Theoretical study of periodic and semi-continuous separation processes.

To improve the efficiency of countercurrent chromatography (CCC) separations, we have previously proposed a new sample loading method called intermittent sample loading (ISL), in which continuous sample feed alternates with short periods of "clean" mobile phase feed to the CCC device. In semi-continuous separation processes, during sample feed periods, the sample is loaded in separate batches, each consisting of a series of intermittent sample loads. It was shown that the application of the intermittent sample loading method in the conventional isocratic CCC separations significantly increased process productivity and the concentration of compounds in the separated fractions.

Closed-Loop Recycling Dual-Mode Counter-Current Chromatography with Specified Sample Loading Durations: Modeling of Preparative and Industrial-Scale Separations.

We previously reported on a new counter-current chromatography (CCC) operating mode called closed-loop recycling dual-mode counter-current chromatography (CLR DM CCC), which incorporates the advantages of closed-loop recycling (CLR) and dual-mode (DM) counter-current chromatography and includes sequential separation of compounds in the closed-loop recycling mode with the mobile -phase and in the inverted-phase counter-current mode with the mobile -phase. The theoretical analysis of several implementations of this separation method was carried out under impulse sample injection conditions. This study is dedicated to the further development of CLR DM CCC theory applied to preparative and industrial separations, where high-throughput operation is required.

Large exchange bias in Cr substituted FeO nanoparticles with FeO subdomains.

Tuning the anisotropy through exchange bias in bimagnetic nanoparticles is an active research strategy for enhancing and tailoring the magnetic properties for a wide range of applications. Here we present a structural and magnetic characterization of unique FeCr-oxide nanoparticles generated from seed material with a Fe : Cr ratio of 4.71 : 1 using a physical aerosol method based on spark ablation.

A simple and highly efficient counter-current chromatography method for the isolation of concentrated fractions of compounds based on the sequential sample loading technique: Comparative theoretical study of conventional multiple and intermittent sample loading counter-current chromatography separations.

A new modification of the conventional multiple sample loading (MSL) mode - sequential sample loading (SSL) - is suggested to enhance further the performance of the counter-current chromatography (CCC) separation processes. The sequential sample loading technique is simple and easy to implement: the continuous sample solution supply to a CCC column is alternated (interrupted) with short periods of the "pure" mobile phase supply. Periodic (batch) and continuous SSL CCC separations can be designed and implemented.

Magnetic hysteresis and strong ferromagnetic coupling of sulfur-bridged Dy ions in clusterfullerene DyS@C.

Two isomers of metallofullerene DyS@C with sulfur-bridged Dy ions exhibit broad magnetic hysteresis with sharp steps at sub-Kelvin temperature. Analysis of the level crossing events for different orientations of a magnetic field showed that even in powder samples, the hysteresis steps caused by quantum tunneling of magnetization can provide precise information on the strength of intramolecular Dy⋯Dy inter-actions. A comparison of different methods to determine the energy difference between ferromagnetic and antiferromagnetic states showed that sub-Kelvin hysteresis gives the most robust and reliable values.

Analytical, Preparative, and Industrial-Scale Separation of Substances by Methods of Countercurrent Liquid-Liquid Chromatography.

Countercurrent liquid-liquid chromatographic techniques (CCC), similar to solvent extraction, are based on the different distribution of compounds between two immiscible liquids and have been most widely used in natural product separations. Due to its high load capacity, low solvent consumption, the diversity of separation methods, and easy scale-up, CCC provides an attractive tool to obtain pure compounds in the analytical, preparative, and industrial-scale separations. This review focuses on the steady-state and non-steady-state CCC separations ranging from conventional CCC to more novel methods such as different modifications of dual mode, closed-loop recycling, and closed-loop recycling dual modes.

Chromatographic behavior of six lanthanides on a centrifugal mixer-settler extractor cascade.

This work furthers the development of counter-current chromatography as an industrial separation process method. It was demonstrated that the industrial counter-current chromatography methods, in particular, for the separation groups of rare earth metals, can be implemented in a modified cascade of centrifugal mixer-settler extractors. The retention behavior of rare earth elements (samarium, europium, gadolinium, terbium, dysprosium and yttrium) on the pilot chromatographic unit consisting of 70 serially connected centrifugal mixer-settler extractors was experimentally studied under isocratic elution conditions using the mixture of 30 vol.

Theoretical study of industrial scale closed-loop recycling counter-current chromatography separations.

Industrial separation technologies can be improved and greatly simplified by using the methods of counter-current chromatography (CCC). We have previously proposed the use of currently available solvent extraction equipment (a series of multistage columns, a cascade of centrifugal mixer-settler extractors) as large-scale CCC devices. For industrial separations, the application of closed-loop recycling counter-current chromatography (CLR CCC) methods seems to be the most promising.

[The role of actual demographic trends in improving state health policy].

The decreasing of demographic security level is a global social economic trend in both developed and developing economies. Hence there is an urgent need in improving state social policy, including health care. The key target of this study is to evaluate the role of modern demographic trends in improving state social economic policy in health care.

Modeling of two semi-continuous methods in liquid-liquid chromatography: Comparing conventional and closed-loop recycling modes.

Two high throughput steady-state methods of counter-current chromatography separations: conventional (SS CCC) and closed-loop recycling (SS CLR CCC) are proposed, evaluated and compared. The methods are based on the application of semi-continuous sample loading technique: the CCC setup includes two mobile phase tanks - one with the pure mobile phase and the second - with the sample solution in the mobile phase. The mobile phase pump is periodically switching from one tank to another.

Single-Molecule Magnets DyM N@C and Dy MN@C (M=Sc, Lu): The Impact of Diamagnetic Metals on Dy Magnetic Anisotropy, Dy⋅⋅⋅Dy Coupling, and Mixing of Molecular and Lattice Vibrations.

The substitution of scandium in fullerene single-molecule magnets (SMMs) DySc N@C and Dy ScN@C by lutetium has been studied to explore the influence of the diamagnetic metal on the SMM performance of dysprosium nitride clusterfullerenes. The use of lutetium led to an improved SMM performance of DyLu N@C , which shows a higher blocking temperature of magnetization (T =9.5 K), longer relaxation times, and broader hysteresis than DySc N@C (T =6.

Modeling of closed-loop recycling dual-mode counter-current chromatography based on non-ideal recycling model.

Closed-loop recycling dual-mode counter-current chromatography (CLR DM CCC) includes two separation stages: 1 - closed-loop recycling separation of solutes with mobile x-phase (CLR CCC); 2 - separation of solutes with the mobile y-phase in the opposite flow direction. Previous analysis of CLR DM CCC separations has been limited to the ideal recycling model, which neglects extra-column dispersion. In this study, the analysis of CLR CCC separations is based on the non-ideal recycling model, which takes into account the extra-column dispersion caused by the recycling system.

Air-stable redox-active nanomagnets with lanthanide spins radical-bridged by a metal-metal bond.

Engineering intramolecular exchange interactions between magnetic metal atoms is a ubiquitous strategy for designing molecular magnets. For lanthanides, the localized nature of 4f electrons usually results in weak exchange coupling. Mediating magnetic interactions between lanthanide ions via radical bridges is a fruitful strategy towards stronger coupling.

Closed-loop recycling dual-mode counter-current chromatography. A theoretical study.

Closed-loop recycling dual-mode counter-current chromatography (CLR DM CCC) processes consist of two successive separation stages: separation of solutes in the recycling closed-loop with mobile x-phase and separation of solutes in the counter-current mode with mobile y-phase. Several variants of the implementation of this separation method can be developed: the closed-loop recycling stage may consist of one or several successive separation steps; all components of a mixture can pass through both stages of separation or individual components may be withdrawn from the system at different stages. In this study, such separation processes are theoretically investigated, and simple equations for simulation presented.

Industrial countercurrent chromatography separations based on a cascade of centrifugal mixer-settler extractors.

In hydrometallurgy, traditional extraction technologies, in particular, for isolation and purification of rare-earth metals include a number of processing steps using up to hundreds of mixer-settler extractors. These technologies could be greatly simplified by using the methods of countercurrent chromatography (CCC) separation. However, the current CCC equipment cannot process large volumes of feed material formed during the industrial production of these metals.

Partial magnetic ordering in one-dimensional arrays of endofullerene single-molecule magnet peapods.

The magnetic ordering and bistability of one-dimensional chains of endofullerene Dy2ScN@C80 single-molecule magnets (SMMs) packed inside single-walled carbon nanotubes (SWCNTs) have been studied using high-resolution transmission electron microscopy (HRTEM), X-ray magnetic circular dichroism (XMCD), and ab initio calculations. X-ray absorption measurements reveal that the orientation of the encapsulated endofullerenes differs from the isotropic distribution in the bulk sample, indicating a partial ordering of the endofullerenes inside the SWCNTs. The effect of the one-dimensional packing was further investigated by ab initio calculations, demonstrating that for specific tube diameters, the encapsulation is leading to energetically preferential orientations of the endohedral clusters.

Strong carbon cage influence on the single molecule magnetism in Dy-Sc nitride clusterfullerenes.

Magnetic properties of endohedral metallofullerenes with nitride clusters DySc2N and Dy2ScN and different carbon cages are studied by SQUID magnetometry. All molecules behave as single molecule magnets (SMMs) and exhibit magnetic hysteresis. It is found that the blocking temperature of magnetization and relaxation times strongly depend on the fullerene cage, with the C80-Ih isomer offering the best SMM properties.

Simultaneous concentration and separation of target compounds from multicomponent mixtures by closed-loop recycling countercurrent chromatography.

Closed-loop recycling countercurrent chromatography (CLR CCC) with multiple sample injection has been shown to provide simultaneous concentration and separation of target compounds from multicomponent mixtures. Previous analysis of CLR CCC with multiple sample injections has been limited to the ideal recycling model, which neglects the effects caused by the pump and connecting lines. In this study, an analysis of the process is carried out based on the non-ideal recycling model: recycling chromatograms at two points of the closed-loop - the inlet of the column (A) and the outlet of the column (B) - are considered.

An easy-to-use calculating machine to simulate steady state and non-steady-state preparative separations by multiple dual mode counter-current chromatography with semi-continuous loading of feed mixtures.

Multiple dual mode counter-current chromatography (MDM CCC) separation processes with semi-continuous large sample loading consist of a succession of two counter-current steps: with "x" phase (first step) and "y" phase (second step) flow periods. A feed mixture dissolved in the "x" phase is continuously loaded into a CCC machine at the beginning of the first step of each cycle over a constant time with the volumetric rate equal to the flow rate of the pure "x" phase. An easy-to-use calculating machine is developed to simulate the chromatograms and the amounts of solutes eluted with the phases at each cycle for steady-state (the duration of the flow periods of the phases is kept constant for all the cycles) and non-steady-state (with variable duration of alternating phase elution steps) separations.

Electro-optical characteristics of a liquid crystal cell with graphene electrodes.

In liquid crystal devices (LCDs) the indium tin oxide (ITO) films are traditionally used as transparent and conductive electrodes. However, today, due to the development of multichannel optical communication, the need for flexible LCDs and multilayer structures has grown. For this application ITO films cannot be used in principle.

Switching Molecular Conformation with the Torque on a Single Magnetic Moment.

For the endohedral fullerene molecule HoLu_{2}N@C_{80}, it is shown that the endohedral HoLu_{2}N unit may be oriented in a magnetic field. The Ho magnetic moment is fixed in the strong ligand field and aligns along the holmium-nitrogen axis. The torque of a magnetic field on the Ho magnetic moment leads to a hopping bias of the endohedral unit inclining to an orientation parallel to the externally applied field.