Separation Of Mixture Components Research Articles

Zeolite Properties, Methods of Synthesis, and Selected Applications.

Zeolites, a group of minerals with unique properties, have been known for more than 250 years. However, it was the development of methods for hydrothermal synthesis of zeolites and their large-scale industrial applications (oil processing, agriculture, production of detergents and building materials, water treatment processes, etc.) that made them one of the most important materials of the 20th century, with great practical and research significance. The orderly, homogeneous crystalline and porous structure of zeolites, their susceptibility to various modifications, and their useful physicochemical properties contribute to the continuous expansion of their practical applications in both large-volume processes (ion exchange, adsorption, separation of mixture components, catalysis) and specialized ones (sensors). The following review of the knowledge available in the literature on zeolites aims to present the most important information on the properties, synthesis methods, and selected applications of this group of aluminosilicates. Special attention is given to the use of zeolites in agriculture and environmental protection.

Diffusion mechanisms of convective instability in liquid and gas mixtures

AbstractA review of publications on stability of mechanical equilibrium of multicomponent mixtures in gases and liquids under non‐isothermal and isothermal conditions is given. Studies where diffusion in binary and multicomponent mixtures led to the occurrence of instability of mechanical equilibrium of the system have been analyzed. The main attention is paid to the description of approaches predicting the areas where there are increasing convective disturbances, as well as the determination of the spectrum of thermophysical parameters where the contribution of convection to heat and mass transfer is negligible. At the same time, the problems determining the role of diffusion, thermodiffusion, and double diffusion mechanisms in the separation of mixture components at the boundary of convective instability were given priority in the description. The results of investigations related to the study of the evolution of flows arising due to instability at the initial stage of mixing were also discussed.

Nonlinear liquid-liquid chromatography: Beyond a constant distribution coefficient

Liquid-liquid chromatography (LLC) is a technique in which the separation of mixture components is achieved due to their different distribution between the two phases of a pre-equilibrated biphasic solvent system. In this work, the LLC operation in the nonlinear range of the distribution isotherm was systematically examined for the first time. The influence of the feed concentration on the elution profiles of a model component (cannabidiol, CBD) was studied in three LLC units of different types and sizes ranging from ∼20 mL to ∼2 L. A series of pulse injections with CBD concentrations varying from 1 to 300 mg/mL was performed with n-hexane/methanol/water 5/4/1 (v/v/v) in descending mode (lower phase as the mobile phase). The elution profiles were simulated using the equilibrium-cell model and an anti-Langmuir-like equation for describing the CBD distribution equilibria. The distribution equilibria equation parameters were fitted to the CBD elution profiles using the peak fitting method. The model was validated and provided good predictions of the CBD elution profiles in the entire concentration range for all three LLC units.

Discontinuous Galerkin scheme for solving non-isothermal and non-equilibrium model of liquid chromatography

A total variation bounded (TVB) Runge–Kutta local-projection discontinuous Galerkin (RK-LDG) finite element method is applied for numerically approximating the non-isothermal and non-equilibrium model of liquid chromatography. The model comprises a system of convection-diffusion partial differential equations (PDEs) coupled with algebraic and ordinary differential equations (ODEs). The suggested numerical scheme is explicit in nature and has the potential to capture sharp peaks and abrupt changes in the solution profiles. A number of case studies are carried out for single and two-component elution. The influence of temperature on the column efficiency and separation of mixture components is analyzed. Furthermore, important parameters are identified that influence the performance of the column. The results of the proposed method are authenticated against the high-resolution finite-volume scheme (HR-FVS).

Influence of a variable thermal diffusion coefficient on convection of a binary mixture in rectangular cavities

This paper presents the results of numerical simulation of nonlinear convection regimes of a NaCl aqueous solution in square and horizontally elongated rectangular cavities with hard and impermeable boundaries. The vertical boundaries of the cavities are thermally insulated, and the horizontal ones are maintained at different constant temperatures, which corresponds to heating from below. Calculations are carried out within the non-stationary approach using of Boussinesq approximation and taking into account the polynomial temperature dependence of the thermal diffusion coefficient. According to this approximation, at T*≈285.4 K, the thermal diffusion coefficient changes sign, and thus the direction of the concentration gradient also changes. The temperature gradients on the horizontal boundaries are chosen so that the thermal diffusion coefficient changes sign inside the cavity. Other transport coefficients are considered to be constant. Simulations were performed under Earth-gravity and reduced-gravity conditions. Based on the results of simulations, the local and integral characteristics of non-linear regimes were obtained, and the structure of the emerging flow and the distribution of NaCl concentration were determined. It is shown that the temperature dependence of the thermal diffusion coefficient only slightly affect the structure and intensity of the emerging flow but significantly reduces the degree of separation of mixture components. Under the influence of the Earth’s gravitational field, an oscillatory four-vortex flow with reconnection of vortices occurs in the square cavity, and a multi-vortex flow - in the rectangular cavity. The characteristics of the multi-vortex flow vary irregularly. At reduced gravity, a stationary flow is observed in both square and rectangular cavities. Under microgravity conditions, the concentration isolines are “frozen” into the stream function field, i.e., the similarity between the fields is pronounced.

On a class of repulsive mixture models

Finite or infinite mixture models are routinely used in Bayesian statistical practice for tasks such as clustering or density estimation. Such models are very attractive due to their flexibility and tractability. However, a common problem in fitting these or other discrete models to data is that they tend to produce a large number of overlapping clusters. Some attention has been given in the statistical literature to models that include a repulsive feature, i.e., that encourage separation of mixture components. We study here a method that has been shown to achieve this goal without sacrificing flexibility or model fit. The model is a special case of Gibbs measures, with a parameter that controls the level of repulsion that allows construction of d-dimensional probability densities whose coordinates tend to repel each other. This approach was successfully used for density regression in Quinlan et al. (J Stat Comput Simul 88(15):2931–2947, 2018). We detail some of the global properties of the repulsive family of distributions and offer some further insight by means of a small simulation study.

Representational Rényi Heterogeneity.

A discrete system’s heterogeneity is measured by the Rényi heterogeneity family of indices (also known as Hill numbers or Hannah–Kay indices), whose units are the numbers equivalent. Unfortunately, numbers equivalent heterogeneity measures for non-categorical data require a priori (A) categorical partitioning and (B) pairwise distance measurement on the observable data space, thereby precluding application to problems with ill-defined categories or where semantically relevant features must be learned as abstractions from some data. We thus introduce representational Rényi heterogeneity (RRH), which transforms an observable domain onto a latent space upon which the Rényi heterogeneity is both tractable and semantically relevant. This method requires neither a priori binning nor definition of a distance function on the observable space. We show that RRH can generalize existing biodiversity and economic equality indices. Compared with existing indices on a beta-mixture distribution, we show that RRH responds more appropriately to changes in mixture component separation and weighting. Finally, we demonstrate the measurement of RRH in a set of natural images, with respect to abstract representations learned by a deep neural network. The RRH approach will further enable heterogeneity measurement in disciplines whose data do not easily conform to the assumptions of existing indices.

MODELING AND CALCULATION OF GRINDING AND CLASSIFICATION OF MIXTURE OF DISSIMILAR COMPONENTS IN CLOSED MILLING CIRCUIT

It is shown that the developed earlier model of joint grinding of dissimilar particulate solids based on the discrete models of the Boltzmann equation does not take into account the possible size and density classification of particles and the operating of technological equipment in a closed milling circuit. It is substantiated that the problem of improving the efficiency of separation of mixture components, based on the analysis of their treatment in a closed milling circuit is an actual problem in the field. Theoretical investigations were based on the discrete models of the Boltzmann equation and the methods of their solution related to the technology of treatment of dissimilar components mixture. A special program for measurements and experimental data treatment obtained at the laboratory fluidized bed jet mill and the impact mill was developed for the experimental investigations. In the course of computational and experimental study a mathematical model of classification of dissimilar components was proposed and tested as well as the algorithm of its implementation into the general model of a closed milling circuit. The computational investigations were carried out to estimate the model sensitivity to the input parameters disturbance.  The directions of improving the efficiency of the objective component separation in the closed milling circuit with the fluidized bed jet mill are found. The developed model the closed milling circuit for grinding dissimilar particulate solids can be used in engineering practice with acceptable accuracy. It can be used to estimate the possible enrichment of particulate solids mixtures and to define the optimal technological conditions of their separation with taking into account the limitations on the objective product impurity. The paths are outlined and the order of selection of the parameters of the grinding processes and the classification for effective separation of the components of the mixture are shown.

Experimental Investigation of the Effect of Pressure on Separation of a Carbon Dioxide-Containing Gaseous Mixture

Experimental investigations have been carried out to estimate the effect of pressure on the intensity of separation of mixture components with enrichment of the resultant mixture in a heavy component for the 0.082CO2 + 0.918N2– N2 system. It is shown that the penetrability of carbon dioxide increases with pressure. For the system considered, the separation coefficient has been determined, and the stability map has been constructed within the linear theory of stability.

Separation Capacity of an Extraction System with a Phase Transition of Mixture Components

The relationship between the separation capacity and a change in the Gibbs energy of an extraction system with a phase transition of one mixture component is established. A thermodynamic interpretation of the optimum conditions for the separation of mixture components is proposed.

Method for performing a single act of the reversible separation of ideal solution components

A method for performing a single act of separation of the components contained in a liquid solution of optical isomers in a reversible process is proposed. Mechanisms that allow the reversible separation of mixture components at least in theory are discussed.

Thermal gravitational separation of ternary mixture n-dodecane/isobutylbenzene/tetralin components in a porous medium.

Our present work focuses on the coupling between thermal diffusion and convection in order to improve the thermal gravitational separation of mixture components. The separation phenomenon was studied in a porous medium contained in vertical columns. We performed analytical and numerical simulations to corroborate the experimental measurements of the thermal diffusion coefficients of ternary mixture n-dodecane, isobutylbenzene, and tetralin obtained in microgravity in the international space station. Our approach corroborates the existing data published in the literature. The authors show that it is possible to quantify and to optimize the species separation for ternary mixtures. The authors checked, for ternary mixtures, the validity of the "forgotten effect hypothesis" established for binary mixtures by Furry, Jones, and Onsager. Two complete and different analytical resolution methods were used in order to describe the separation in terms of Lewis numbers, the separation ratios, the cross-diffusion coefficients, and the Rayleigh number. The analytical model is based on the parallel flow approximation. In order to validate this model, a numerical simulation was performed using the finite element method. From our new approach to vertical separation columns, new relations for mass fraction gradients and the optimal Rayleigh number for each component of the ternary mixture were obtained.

EFFECT OF SALT MAGNESIUM CHLORIDE ON VAPOUR - LIQUID EQUILIBRIA OF BINARY AZEOTROPIC LIQUID MIXTURE: ETHYL ACETATE – ETHANOL

Separation of azeotropic liquid mixtures using distillation is a challenging task for process engineers. A straight distillation is not useful for complete separation of mixture components for azeotropic liquid mixtures. The conventional process using liquid entrainer is energy intensive and involves running extra distillation column. The salt which dissolve in liquid mixture but has different solubility in components of liquid mixture can be used as the extracting agent like that of liquid entrainer. The added salt can hold the component in equilibrium liquid phase which has more solubility and hence can enrich the equilibrium vapour phase with the other component. Therefore the added salt has the capability to alter the relative volatility of liquid mixture. The Vapour – Liquid Equilibrium data indicates the relative amount of components in liquid and vapour phase and hence indicates extend up to which liquid mixture can be separated using distillation. In this paper we have studied the separation of one of the important azeotropic liquid mixture Ethyl Acetate –Ethanol in presence of salt Magnesium Chloride. The Vapour – Liquid Equilibrium (VLE) data of binary liquid mixture Ethyl Acetate (A)- Ethanol (B) without salt and with salt is obtained experimentally by using modified Othmer’s still. The system found to forms the minimum boiling azeotrope at 0.550 mole fraction of ethyl acetate at 71.7 0 C under the normal atmospheric pressure. The effect of addition of salt Magnesium Chloride (MgCl 2) has been studied on the vapour - liquid equilibria of ethyl acetate- ethanol. Two different compositions of salt (20% and 25% by weight of ethanol in mixture) have been tried and corresponding shift in azeotropic point towards the higher composition of ethyl acetate than without salt is noted.

Frame dependence of stationary heat transfer in an inert mixture of ideal gases

This paper is devoted to the study of a stationary heat transfer problem in an inert binary mixture of ideal gases. The mixture is enclosed between two coaxial cylinders, kept at two different constant temperatures and at rest in a non-inertial frame. In particular, the frame is assumed to rotate with a constant angular velocity around the cylinder axes. The phenomenon is described by the linearized equations of extended thermodynamics with 13 moments. Integration of the field equations requires the assignment of non-controllable boundary values, which are determined through a fluctuation principle. It turns out that the temperature field presents boundary layers. Moreover, in agreement with the predictions of the kinetic theory, the tangential components of the heat and of the diffusion fluxes cannot vanish. We also show that the mixture and its constituents cannot be at rest in the rotating frame. An analysis is proposed concerning the combined effects of thermo-diffusion and rotation in the separation of mixture components. A comparison between classical and extended thermodynamics predictions is also proposed.

THEORETICAL MATTERS OF REVERSE OSMOSIS AND ADSORPTION AT PURIFICATING MULTICOMPONENT SOLUTIONS

Traditional modern chemical technology methods for solution and liquid mixture component separation are based on the difference between physical and chemical parameters of components being separated (boiling point, solubility). The methods use the phenomenon of phase change. Thus to install the equipment for the processes is quite complicated and power-consuming.As the world population grows we face new problems,i.e. the shortage of drinking water. Different methods are applied for getting drinking water such as distillation and freezing out. Half of all the desalinated water is got by distillation. To solve the arisen problems by using the traditional methods of chemical technology is becoming more and more complicated. Methods of membrane separation have turned out to be promising in this respect.

Gibbs energy change in the symmetric separation of the components of an initial equimolar binary mixture in an extraction cascade

The change in Gibbs energy in the process of separation of mixture components by multistep liquid extraction with two extragents in a rectangular cascade with the central input of an initial mixture is calculated. An interpretation of the difference between the performed thermodynamic separation work and the minimum required work is proposed.

Producing Highly Charged Ions without Solvent Using Laserspray Ionization: A Total Solvent-Free Analysis Approach at Atmospheric Pressure

First examples of highly charged ions in mass spectrometry (MS) produced from the solid state without using solvent during either sample preparation or mass measurement are reported. Matrix material, matrix/analyte homogenization time and frequency, atmospheric pressure (AP) to vacuum inlet temperature, and mass analyzer ion trap conditions are factors that influence the abundance of the highly charged ions created by laserspray ionization (LSI). LSI, like matrix-assisted laser desorption/ionization (MALDI), uses laser ablation of a matrix/analyte mixture from a surface to produce ions. Preparing the matrix/analyte sample without the use of solvent provides the ability to perform total solvent-free analysis (TSA) consisting of solvent-free ionization and solvent-free gas-phase separation using ion mobility spectrometry (IMS) MS. Peptides and small proteins such as non-β-amyloid components of Alzheimer's disease and bovine insulin are examples in which LSI and TSA were combined to produce multiply charged ions, similar to electrospray ionization, but without the use of solvent. Advantages using solvent-free LSI and IMS-MS include simplicity, rapid data acquisition, reduction of sample complexity, and the potential for an enhanced effective dynamic range. This is achieved by more inclusive ionization and improved separation of mixture components as a result of multiple charging.

Simultaneous removal of copper, nickel and zinc metal ions using bulk liquid membrane system

One of the novel techniques of mixture component separation is an application of liquid membranes. This paper reveals the ability of liquid membrane in simultaneous transport of mixture components in which a liquid membrane (LM) constitutes a separate phase which separates mixture from an internal receiving phase. In the present work, the experiments were performed for determining the distribution coefficient and Cu, Ni and Zn metal ion removal measurements. Metal distribution coefficients were obtained by simply equilibrating an aqueous solution of the metal ions with an organic liquid membrane containing a complexing agent (D2EHPA), in a separating funnel at 25 °C. Initially, to assure mass balance, samples of both the phases were analyzed by an atomic absorption spectrophotometer. Routinely, only the aqueous phase was analyzed. Distribution coefficients were measured over a broad range of metal ion concentration. The separation of metal ions was analyzed for bulk liquid membrane–cylinder in cylinder setup, by varying the source metal ion concentration. Maximum extraction of 98.8% of zinc, 95.8% of copper and 95.0% of nickel metal ion was achieved at the optimum conditions and maximum removal of the metal ions was in the order Zn > Cu > Ni.

Using perdeuterated surfactant micelles to resolve mixture components in diffusion‐ordered NMR spectroscopy

Diffusion-ordered NMR spectroscopy resolves mixture components on the basis of differences in their respective diffusion coefficients or molecular sizes. However, when components have near-identical diffusion coefficients, they are not resolved in the diffusion dimension of a diffusion-ordered spectroscopy (DOSY) spectrum. Adding surfactant micelles to these mixtures has been shown to enhance resolution when the component molecules interact differentially with the micelles. This approach is similar to that used in electrokinetic chromatography (EKC) where modifiers like micelles or polymers are used to enhance the separation of mixture components. In this study, perdeuterated surfactants are added to analyte mixtures studied with the DOSY technique. Since no micelle resonances appear in the mixture spectra, the difficulty associated with performing biexponential analyses in spectral regions where analyte and surfactant resonances overlap is avoided. The approach is demonstrated using mixtures of peptides with near-identical diffusion coefficients.

A thermodynamic interpretation of optimum conditions of the separation of mixture components by distillation of dilute solutions

A condition for the maximum thermodynamic efficiency of distillation of dilute solutions in a multistep cascade was obtained from the condition of a maximum change in the entropy of a mixture. These conditions were shown to correspond to a maximum degree of separation of mixture components. A thermodynamic equation was derived to describe the relation between a decrease in the Gibbs energy and the mixture value increment during distillation of a dilute ideal solution.