Activity Coefficients Of Components Research Articles

Activity Coefficient of Solution Components and Salts as Special Osmolyte from Kirkwood-Buff Theoretical Perspective

Background: There has been different interpretation of kosmotropes and chaotropes without concern for the physicochemical characteristics of the macromolecule and for the link between Hofmeister phenomena with solution structure. The objectives of this research are: 1) To investigate different ways of determining activity coefficient and activity of ionic osmolyte 2), to present a common theoretical basis for the interaction between reaction mixture components and Hofmeister phenomena and 3) determine the preferential interaction parameters and the Kirkwood-Buff integrals.
 Methods: A major theoretical research and partly experimental.
 Results and Discussion: Some equations in literature gave different values of activity coefficient and activity of solution components. The preferential interaction by binding is positive with ethanol only and at its higher concentration in the presence of ideal solution of different concentration of calcium chloride. There was positive m-value with ethanol. It was negative m-value in the presence of preferentially binding species, calcium ion and ethanol as against the excluded chloride ion. There was negative and positive change of solvation preference and interaction parameter due respectively to ethanol only and a mixture of it and the salt.
 Conclusion: Selected equations in literature may not give the same values of activity coefficient and activity of solution components. The presence of stabilising osmolyte, salt, and ethanol may not always yield positive m-values. The sign of the change of solvation preference with either binary or ternary mixture of osmolytes and, the cognate interaction parameter, may be a better indicator of the stability of a macromolecule. The kosmotropes and chaotropes may be cationic or anionic and their deficit or otherwise around the macromolecule and consequence, depend largely on net charge on the macromolecule at a given pH.

Investigation of surface tension and surface properties of alkanolamine–alcohol mixtures at T = 313.15 K and P = 90.6 kPa

Alkanolamine compounds are especially useful in the adsorption of acid–gases from gas streams. In this work, surface tension for nine binary systems containing an alkanolamine (monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA)) and a short chain alcohol (methanol, ethanol and isopropanol) were measured over the entire concentration range at 313.15 K and 90.6 kPa by means of the ring detachment method. From these data, the surface tension deviations were computed. The maximum deviation in nine systems was <1%. Then these surface tension data were correlated using Myers–Scott (MS) and Fu et al. (FLW) polynomial expansions. Also, the surface tension data have been predicted based on the Sprow–Prausnitz (SP) equation. The results show that good agreement is obtained between experimental and predicted data of surface tension, a fact which confirms the applicability of the SP equation in the binary mixtures with polar components. The modified UNIFAC group contribution method is used for calculation of activity coefficients of components in mentioned systems. Finally, surface mole fraction of alcohol at the (air + liquid) interface were calculated from (SP) equations. The results show that the surface concentration of alcohol in binary mixtures increase with increasing the alkyl chain length of alcohol.

Aqueous two-phase systems for cephalexin monohydrate partitioning using poly ethylene glycol and sodium tartrate dihydrate: Experimental and thermodynamic modeling

The partitioning of cephalexin monohydrate in aqueous two-phase system (ATPS) of polyethylene glycol (PEG) with different molecular weights (1000, 2000, 6000, and 8000) and sodium tartrate dihydrate salt was investigated. Equilibrium compositions of two liquid phases were obtained in each system. The experimental data were correlated using the extended NRTL and a modified UNIQUAC (UNIQUAC+DH) models by adding a Debye-Huckel term (DH) to original models for taking into account the long range forces term of activity coefficient of components. The results show that the molecular weight of the polymer has a considerable effect on the partition coefficient of cephalexin monohydrate. The comparison of results for presented models with the experimental data demonstrates that the investigated thermodynamic models can correlate the equilibrium composition very well. The extended NRTL model with AARD of 0.099 is superior to UNIQUAC+DH.

NEAT—NMR Spectroscopy for the Estimation of Activity Coefficients of Target Components in Poorly Specified Mixtures

Mixtures of which the composition is not fully known are important in many fields of engineering and science, for example, in biotechnology. Owing to the lack of information on the composition, suc...

Refining of Diesel and Ship Fuels by Extraction and Combined Methods. Part 1. Use of Ionic Liquids as Extractants

Modern and perspective environmental requirements to the quality of diesel and ship fuels are considered. Data on the selectivity and solvency of ionic liquids with respect to aromatic hydrocarbons and heterocyclic sulfur- and nitrogen-containing compounds, obtained using gas-chromatographic data on the limiting activity coefficients of model mixture components in ionic liquids, are discussed. Experimental data on the liquid-liquid phase equilibrium in model systems consisting of a saturated hydrocarbon, an aromatic sulfur- or nitrogen-containing compound, and an ionic liquid and on the component distribution ratios and separation factors are presented. The advantages and drawbacks of ionic liquids as extractants in selective refining of diesel fractions and vacuum gasoils to obtain raffinates meeting perspective environmental requirements to diesel and ship fuels are considered.

Droplet evaporation characteristics of aviation kerosene surrogate fuel and butanol blends under forced convection

A droplet evaporation model for blends of aviation kerosene surrogate fuel (n-decane and toluene) and butanol (a promising bio-jet fuel) was presented and validated by conducting droplet suspension experiments. The model incorporates the non-ideal effects of blended fuels using the component activity coefficient, which turns out to greatly deviate from unity for test fuels and thus significantly influence their evaporation rate. The effects of recirculation inside the suspended droplet on the heat and mass diffusion were also considered. The experimental data were largely consistent with simulated results under different ambient temperatures and different convention velocities. With increasing butanol content, the droplet evaporation rate increased and the micro-bubble phenomenon was more likely to occur. The convection velocity exhibited a significant influence on the evaporation process as Reynolds number and Sherwood number rose under forced convection conditions. The discrepancy between experimental data and simulated results at the convection velocity of 0.05 m/s was small and comparable with that at the convection velocity of 0.1 m/s and 0.5 m/s, which implies the model could reflect the convection effect reasonably. Temporal evolutions of component concentrations at the liquid surface demonstrated that butanol and toluene were likely to evaporate at a faster rate than n-decane.

Study of aggregation behavior between N-lauryl sarcosine sodium and Dodecyltrimethylammonium bromide in aqueous solution, using conductometric and spectrophotometric techniques

The micellization behavior of N-Lauryl sarcosine sodium (NLS, an anionic surfactant) and Dodecyltrimethylammonium bromide (DOTAB, a cationic surfactant) in aqueous solution is investigated by UV–vis spectrophotometric and conductometric methods at 298.15 K. A critical micelle concentration (CMC) were obtained for pure NLS and DOTAB as well as mixed micelles [NLS(1) + DOTAB(2)]. The CMC values of the studied system at different mole fractions (yi) are much less than that of individual surfactants (due to the strong electrostatic attraction between components after mixing). In this work, the tautomers of 1-phenyl-1, 3-butadione (or benzoylacetone) were used to obtain the mixed CMC of anionic surfactant systems by UV–Vis technique. The deviations of critical micelle concentration (CMC) from the ideal values show the interaction between NLS and DOTAB. The micellar mole fraction values (X1m and X2m) according to Rubingh approach were calculated and the results obtained reveal the same composition in the mixed micellization at most mole fraction(y1) even when the initial mixing ratio is far from equimolar. The activity coefficients of components were less than unity (f1m < < 1 and f2m < < 1) and the values of the interaction parameter (βm) are negative in all compositions, which indicate the strong synergistic interaction between NLS and DOTAB. The Gibbs free energy of micellization (ΔGmic0) and the excess free energy of micellization (GmicE) values are found to be negative in this system demonstrated the stability of the mixture. All of the evaluated results imply a strong synergism between components.

Introducing sorption coefficient through extended UNIQAC and Flory-Huggins models for improved flux prediction in forward osmosis

A 2D computational fluid dynamic-based finite element model was developed to describe water flux and concentration polarization in forward osmosis (FO) under steady-state conditions. The extended UNIQAC equation in the feed and the Flory Huggins equation on the membrane side were solved simultaneously to calculate the activity coefficients of the diffusion components. The ratio of the feed component activity coefficient to that on the membrane surface was defined as the sorption coefficient. Employing the sorption coefficient led to a significantly improved accuracy of the developed model in estimating water flux. The membrane structural parameter determining internal concentration polarization (ICP) should be maintained at reasonable values. Otherwise, it may significantly increase the reverse salt flux and external concentration polarization (ECP) on the active layer. This suggests the tradeoffs between the membrane structural parameter and membrane selectivity, between ECP and ICP. Water fluxes were similar in counter-current and co-current flow modes. ICP had the most significant resistance to flow, reducing the water flux up to 75%. ECP on the feed side had a limited effect on FO water flux, particularly at high flow velocity. ECP on the draw side and reverse salt flux had negligible effects on FO water flux in our modeling. Our study provides important insights into developing high-performance FO membranes with reasonably low structural parameters and improving FO water flux by reducing the key limiting factor (e.g. ICP).

Liquid balance - steam for methanol mixing - Benzen using the Peng Robinson and Van-Laar models

This paper is related to the procedure for calculating curves dew point and bubble point of a binary system, consisting of the methanol and benzene mixture to 45°C, using the Peng-Robinson cubic equation to calculate the fugacity coefficient of gas i in the mixture, and Van Laar model to calculate the activity coefficient of component i in the liquid mixture. Then a comparison between the theoretical data with the experimental data and later with the commercial simulator Hysys-Aspen, which applies the model of Wilson. The simulation was validated with experimental data,in addition to comparing the results with a commercial simulator.

SB-PB-AG ALLOY PROCESSING BY VACUUM DISTILLATION

The paper relevance is determined by the need to create an environmentally safe, high-performance and cost-efficient integrated vacuum distillation technology for the processing of lead-containing middling products and wastes, in particular, a Sb-Pb-Ag (SPA) alloy resulting from the recovery of silicate slag from copper anode slime melting to obtain sellable mono-element concentrates of an­timony, lead and silver. Laboratory studies were carried out on SPA alloy processing with the calculations of «T—x» temperature-com­position VLE (vapor liquid equilibrium) diagrams to analyze the behavior of Sb-Pb and Pb-Ag binary alloys during processing, select preliminary system temperature and pressure, and assess component separation efficiency in the following conditions: T = = 900+2100 K, P = 1+133 Pa, т = 8+16 hours. The aim of the study was to investigate the effect of temperature and pressure in the system, the duration of sublimation on the completeness of extraction and the degree of antimony, lead and silver separation from the SPA composition. Activity coefficients of binary alloy components when constructing VLE diagrams were calculated using the MI- VM (molecular interaction volume model). The information is obtained regarding the effect of temperature and vacuum level on the degree of sublimation and separation of metals from Sb—Pb and Pb—Ag compositions of different contents. Saturated vapor pressures were calculated for Sb (p* = 273.664+ 67436.9 Pa), Pb (0.149+485.9), Ag (5.05440 -5 -6.558) at T = 1073+1773 K. It was demonstrat­ed that the high values of the pSb /PPb = 1832.98+138.79, рр ь /pA g = 2948.16+74.09 ratio and lgPsb = 2.099+3.33 and lgPp b = 1.813+ +3.944 separation factor create theoretical prerequisites for a selective isolation of these metals by vacuum distillation, when anti­mony and lead are successively enriched in the gas phase (Ps^ > 1, Pp b > 1), and silver — in the liquid phase. The molar fraction of hard-to-sublimate lead/silver in the gaseous phase ур Ь /уA g = (1.55+982)T0 -3 /(36+772)T0 -3 is increased with rising temperature 894+1601/1399+2099 K, pressure 1.33+133 Pa and metal content in the alloy x Pb /x Ag = 0.9+0.9999/0.9+0.99. The MIVM model was used to calculate the activity factors of antimony Ysb = 0.832+0.999, lead yp b = 0.474+1.0, YA g = 0.331+0.999 for Sb/Pb and Pb/Ag al­loys with the following composition 0.1+0.9/0.9+0.1 in the investigated temperature range. The found dependences of the amount and composition of polymetallic alloy sublimation products on the process parameters are important for practical application due to the development of a principal technology for SPA processing by vacuum distillation.

NMR Spectroscopic Method for Estimating Activity Coefficients of Target Components in Poorly Specified Mixtures in Bioprocess Engineering

NMR Spectroscopic Method for Estimating Activity Coefficients of Target Components in Poorly Specified Mixtures in Bioprocess Engineering

Method for Estimating Activity Coefficients of Target Components in Poorly Specified Mixtures

Mixtures that contain a known target component but are otherwise poorly specified are important in many fields. Previously, the activity of the target component, which is needed, e.g., to design separation processes, could not be predicted in such mixtures. A method was developed to solve this problem. It combines a thermodynamic group contribution method for the activity coefficient with NMR spectroscopy, which is used for estimating the nature and amount of the different chemical groups in the mixture. The knowledge of the component speciation of the mixture is not required. Test cases that are inspired by bioprocess engineering applications show that the new method gives surprisingly good results.

Solubility and Ionic Interaction of the CaF2–CaSO4–H2O System at 298.1 K

Solubility isotherms of the sparingly soluble salts CaF2(s) and CaSO4·2H2O(s) in their mixed aqueous solutions have been measured at 298.1 K. It was found that the CaF2(s) solubility decreases with increasing CaSO4 concentration in the solution and reaches about 1/3 of the CaF2(s) solubility in pure water in the CaSO4·2H2O(S) saturated solution. A thermodynamic model was developed to predict the CaF2(s) solubility isotherm in this system, in which the short range interactions of the species in the aqueous solution are represented by ion-association constants reported in literature, and the long range interaction, i.e., the electrostatic term, is represented by the well known Davies equation. The predicted solubility isotherm reasonably agrees with the experimental results. The contributions of the long-range term and the short-range term to the calculated solubility isotherm were investigated. It was concluded that the ionic association combining with the Davies equation is sufficient to represent the excess interaction of the CaF2 + CaSO4 aqueous solution at 298.15 K. This model approach could be applicable for other dilute mixed electrolyte systems in which component activity coefficients are lacking and model parameters are difficult to determine.

Phase equilibria calculations of electrolyte solutions containing water- polymer- salt using a new thermodynamic model, applicable in aqueous two phase systems

In current paper a new thermodynamic model has been suggested for prediction of phase equilibria of binary and ternary systems containing polymer, salt and water. To calculate the activity coefficient of components three different terms of long range, middle range and short rang for excess Gibbs energy is considered. For long range forces between components a modified form of Debye-Hückel theory has been used. Moreover, to represent the middle range term of excess Gibbs energy a new expression of VERS model has been extended using the van der Waals volume parameter of the molecule. Also, UNIFAC-Freed-FV model has been employed for computation of short range part of activity coefficient. To determine the binary interaction parameters of the model, 12 binary systems of water + PEG or salt and 11 ternary data set of water- PEG- Salt have been used. The regressed binary parameters have been applied for phase equilibria calculations of 54 aqueous two phase systems. It can be seen that the new model can predict the phase composition of ATPS very well.

Surface properties and surface thickness of aqueous solutions of alcohols

Surface properties and surface concentrations of binary mixtures of aliphatic alcohols (methanol, ethanol, 1-propanol and 2-propanol) with water have been calculated by surface tension data at various temperatures (293.15–323.15)K. The surface tension data over the entire concentration range are correlated by the Fu et al. (FLW) and Myers-Scott (MS) models. The average relative error obtained from the comparison of experimental and calculated surface tension values for 28 binary systems (the four systems at seven temperatures) with two models is <2%. Also, the UNIFAC group contribution model is applied for calculation of activity coefficients of components in solution. The adsorption isotherms of binary aqueous solutions of alcohols are determined using Gibbs adsorption equation with experimental surface tension data and the calculated activities of alcohols. The obtained results show that the values of adsorption for mixtures of alcohols/water increase with increasing the alkyl chain length of alcohol and decreasing temperature. In addition to find more information about surface structure of binary mixtures, the thickness of surface layer as a function of composition and temperature has been obtained by relative Gibbs adsorption and surface mole fraction (from EL model).

(Vapor + Liquid) Equilibrium (VLE) for Binary Lead-Antimony System in Vacuum Distillation: New Data and Modeling Using Nonrandom Two-Liquid (NRTL) Model

In this work, new experimental vapor–liquid equilibrium (VLE) data of lead-antimony alloy (Pb-Sb alloy) in vacuum distillation are reported. The activity coefficients of components of Pb-Sb alloy were calculated by using the NRTL model. The calculated average relative deviations were ±0.1425 and ±0.2433 pct, and the average standard deviations were ±0.0009 and ±0.0007, respectively, for Pb and Sb. The VLE phase diagrams, such as the temperature composition (T-x) and pressure composition (P-x) diagrams of Pb-Sb alloy in vacuum distillation were predicted based on the NRTL model and VLE theory. The predicted results are consistent with the new experimental data indicating that VLE phase diagrams obtained by this method are reliable. The VLE phase diagrams of alloys will provide an effective and intuitive way for the technical design and realization of recycling and separation processes. The VLE data may be used in separation processes design, and the thermodynamic properties as the key parameters in specific applications.

Pressurized metallurgy for high performance special steels and alloys

The pressure is one of the basic parameters which greatly influences the metallurgical reaction process and solidification of steels and alloys. In this paper the history and present situation of research and application of pressurized metallurgy, especially pressurized metallurgy for special steels and alloys have been briefly reviewed. In the following part the physical chemistry of pressurized metallurgy is summarized. It is shown that pressurizing may change the conditions of chemical reaction in thermodynamics and kinetics due to the pressure effect on gas volume, solubility of gas and volatile element in metal melt, activity or activity coefficient of components, and change the physical and chemical properties of metal melt, heat transfer coefficient between mould and ingot, thus greatly influencing phase transformation during the solidification process and the solidification structure, such as increasing the solidification nucleation rate, reducing the critical nucleation radius, accelerating the solidification speed and significant macro/micro-structure refinement, and eliminating shrinkage, porosity and segregation and other casting defects. In the third part the research works of pressured metallurgy performed by the Northeastern University including establishment of pressurized induction melting (PIM) and pressurized electroslag remelting (PESR) equipments and development of high nitrogen steels under pressure are described in detail. Finally, it is considered in the paper that application of pressurized metallurgy in manufacture of high performance special steels and alloys is a relatively new research area, and its application prospects will be very broad and bright.

Erratum to: Measurement and prediction of solid–liquid phase equilibria for systems containing biphenyl in binary solution with long chain n-alkanes

Solid–liquid equilibria of the n-alkanes (n-octadecane, n-eicosane, n-tetracosane, n-pentacosane, n-triacontane) in biphenyl were measured by DSC 7 (Perkin-Elmer). It was found that all systems are simple eutectic. The solubility of the biphenyl in n-alkanes was studied in the temperature range 301–370 K. The experimental results were correlated using modified UNIFAC (Larsen and Gmehling versions) and ideal models. Good representation of solubility diagrams was obtained using partly readjusted UNIFAC parameters of Larsen version. Taking into account the large range of applicability of UNIFAC and the predictions of the activity coefficients for many other components in different classes of mixtures, we can conclude that the new experimental data for the systems mentioned in this work should be included in the database used by UNIFAC in order to evaluate better interaction parameters and to improve predictions.

Vapor–liquid phase equilibria of binary tin–antimony system in vacuum distillation: Experimental investigation and calculation

Vacuum distillation experiments were conducted for tin-antimony alloy (Sn–Sb alloy) under the system pressure of 5 Pa. The content of Sb (mole fraction) in crude Sn, viz., xSb was reduced from 0.5000 to 0.0619 in a single stage distillation process under the condition of residual pressure of 5–10 Pa, distillation temperature of 1373 K and distillation time of 60 min. The activity coefficients of components of Sn–Sb alloy were calculated by using the molecular interaction volume model (MIVM), and the calculated average relative deviation and the average standard deviation were ±0.00039 and ± 0.173%, respectively for both Sn and Sb. The vapor–liquid equilibrium (VLE) phase diagrams, including the temperature-composition (T-x) and pressure-composition (p-x) diagrams of Sn–Sb alloy in vacuum distillation were calculated based on VLE theory and the MIVM. A reasonable agreement between the calculated results and the experimental data indicates that VLE phase diagrams obtained by this method are reliable. The VLE phase diagrams of alloys will provide an effective and convenient way for the designing of the process parameters of industrial production of vacuum metallurgy, and for the prediction of the needed product component dependence of temperature and pressure during the process of vacuum distillation.

Study of the surface properties and surface concentration of ionic liquid–alcohol mixtures

ABSTRACTSurface properties for three binary mixtures containing a 1-butyl-3-methylimidazolium thiocyanate ([BMIM][SCN]) and a long-chain alcohol (1-butanol, 1-pentanol and 1-hexanol) were determined by surface tension data at the following temperatures: (298.15, 308.15, 318.15, 328.15 and 338.15) K. The surface tension data over the entire mole fraction range are correlated by the Fu et al.(FLW) and Myers-Scott (MS) models. There is good agreement between the experimental data and the results of correlations for 15 binary systems (the three systems at five temperatures) with an average relative error below 1.5%. In addition, the UNIFAC group contribution method is applied for calculation of activity coefficients of components in solution. Moreover, the relative adsorptions of alcohol at the air/liquid interface are determined using Gibbs adsorption isotherm. The obtained results show that the values of adsorption for mixtures of alcohols/[BMIM][SCN] increase with increasing the alkyl chain length of alcohol and decreasing temperature.