Equilibrium Distribution Coefficients Research Articles

Recovery of copper(II) and chromium(III) from nitrate medium with salicylideneaniline dissolved in 1-octanol

The solvent extraction of copper(II) and chromium(III) from nitrate medium with salicylideneaniline (HL) is studied as a function of various parameters: pH, concentration of salicylideneaniline, contact time and the nature of anoin (nitrate and sulfate) in aqueous phase. Chromium(III) is not extracted by salicylideneaniline diluted in 1-octanol. Copper(II) is only extracted by salicylideneaniline and it was found that the highest extractability achieved to 95 % at pH 4.9, The stoichiometry of the extracted species was determined by using the method of slope analysis. Elemental analysis, UV–vis and IR-spectra were used to confirm the structure. It is found that the copper (II) is extracted as CuL 2 .2H 2 O Their equilibrium constant, distribution coefficient, percentage extraction ( %E ) and free energy are also calculated.

Sodium Chloride Diffusion in Low-Acid Foods during Thermal Processing and Storage.

This study aimed at modeling sodium chloride (NaCl) diffusion in foods during thermal processing using analytical and numerical solutions and at investigating the changes in NaCl concentrations during storage after processing. Potato, radish, and salmon samples in 1% or 3% NaCl solutions were heated at 90, 105, or 121°C for 5 to 240 min to simulate pasteurization and sterilization. Selected samples were stored at 4 or 22°C for up to 28 d. Radish had the largest equilibrium NaCl concentrations and equilibrium distribution coefficients, but smallest effective diffusion coefficients, indicating that a greater amount of NaCl diffused into the radish at a slower rate. Effective diffusion coefficients determined using the analytical solution ranged from 0.2 × 10(-8) to 2.6 × 10(-8) m²/s. Numerical and analytical solutions showed good agreement with experimental data, with average coefficients of determination for samples in 1% NaCl at 121°C of 0.98 and 0.95, respectively. During storage, food samples equilibrated to a similar NaCl concentration regardless of the thermal processing severity. The results suggest that sensory evaluation of multiphase (solid and liquid) products should occur at least 14 d after processing to allow enough time for the salt to equilibrate within the product.

Sulfonated Magnetic Nanocomposite Based on Reactive PGMA-MAn Copolymer@Fe3O4 Nanoparticles: Effective Removal of Cu(II) Ions from Aqueous Solutions

Chelating magnetic nanocomposites have been considered as suitable materials for removal of heavy metal ions for water treatment. In this work poly(glycidyl methacrylate-maleic anhydride) copolymer (PGMA-MAn) is modified with 4-aminobenzenesulfonic acid (ABSAc) and subsequently the product reacted with modified Fe3O4 nanoparticles and 1,2-ethanedithiol (EDT) in the presence of ultrasonic irradiation for preparation of tridimensional chelating magnetic nanocomposite. Synthesized magnetic nanocomposite was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), vibrating sample magnetometer (VSM), energy dispersive X-ray analysis (EDX), elemental mapping analysis (EMA), Brunauer-Emmett-Teller (BET), and thermal gravimetric analysis (TGA). The adsorption behavior of Cu(II) ions was investigated by synthesized nanocomposite in various parameters such as pH, contact time, metal ion concentration, and adsorbent dosage. The equilibrium distribution coefficient (kd) was determined and the findings prove that the kd value is approximately high in the case of all selected metal ions. The synthesized nanocomposite exhibited good tendency for removing Cu(II) ions from aqueous solutions even at an acidic pH.

Phase Equilibria of Ternary and Quaternary Systems Containing Dibutyl Ether with Water at T = 298.15 K

In this study (liquid + liquid) equilibrium (LLE) data were measured at 298.15 K under atmospheric pressure for the {water + 2,2,4-trimethylpentane (TMP) + dibutyl ether (DBE)} ternary system, and the (water + ethanol + TMP + DBE) and (water + 2-propanol + TMP + DBE) quaternary systems. The experimental LLE data show good correlations with the modified and extended UNIQUAC models. The solubility of alcohol and TMP in the aqueous and organic phases is represented by an equilibrium distribution coefficient calculated from the LLE data. The influence of different alkyl groups on the solubility of alcohols in liquid phases is discussed.

Establishing the Concept of Buffer for a High-level Radioactive Waste Repository: An Approach

The buffer is a key component of the engineered barrier system in a high-level radioactive waste (HLW) repository. The present study reviewed the requirements and functional criteria of the buffer reported in literature, and also based on the results, proposed an approach to establish a buffer concept which is applicable to an HLW repository in Korea. The hydraulic conductivity, radionuclide-retarding capacity (equilibrium distribution coefficient and diffusion coefficient), swelling pressure, thermal conductivity, mechanical properties, organic carbon content, and illitization rate were considered as major technical parameters for the functional criteria of the buffer. Domestic bentonite (Ca-bentonite) and, as an alternative, MX-80 (Na-bentonite) were proposed for the buffer of an HLW repository in Korea. The technical specifications for those proposed bentonites were set to parameter values that conservatively satisfy Korea's functional criteria for the Ca-bentonite and Swedish criteria for the Na-bentonite. The thickness of the buffer was determined by evaluating the means of shear behavior, radionuclide release, and heat conduction, which resulted in the proper buffer thickness of 0.25 to 0.5 m. However, the final thickness of the buffer should be determined by considering coupled thermal-hydraulic-mechanical evaluation and economics and engineering aspects as well.

Equilibrium distribution of samarium and europium between fluoride salt melts and liquid bismuth

The extraction of samarium and europium from a melt of a molar composition 73LiF–27BeF2 into liquid bismuth with additions of lithium as a reducing agent at a temperature of 600–610°С was studied. The equilibrium distribution coefficients of samarium and europium were measured. In the metal fluoride salt melt under study, the valence of samarium and europium was shown to be equal to two.

Microwave assisted hydrothermal synthesis of MnO2·0.5H2O ion-sieve for lithium ion selective adsorption

ABSTRACTLi1.6Mn1.6O4 (LMO) synthesized by microwave assisted hydrothermal method were used to obtain MnO2·0.5H2O ion sieves (HMO) after acid treatment. The HMO-1 prepared with a Li/Mn molar ratio of 4, at 100ºC for 1 h under microwave irradiation, exhibits an effective Li+ adsorption capacity of 5.6 mmol·g−1 and a high selectivity to Li+ with an equilibrium distribution coefficient of 12366.44 mL·g−1. Moreover, it shows almost saturated ion-exchange capacity (> 95%) for Li+ extracted/inserted process. Thus HMO ion-sieves with high adsorption capacity and selectivity to Li+ are expected to be a promising application for Li+ selective adsorption from brine, seawater, and aqueous lithium generated in industries.

Combinatorial Methodology for Screening Selectivity in Polymeric Pervaporation Membranes.

Combinatorial methodology is described for rapid screening of selectivity in polymeric pervaporation membrane materials for alcohol-water separations. The screening technique is demonstrated for ethanol-water separation using a model polyacrylate system. The materials studied are cross-linked random copolymers of a hydrophobic comonomer (n-butyl acrylate, B) and a hydrophilic comonomer (2-hydroxyethyl acrylate, H). A matrix of materials is prepared that has orthogonal variations in two key variables, H:B ratio and cross-linker concentration. For mixtures of ethanol and water, equilibrium selectivities and distribution coefficients are obtained by combining swelling measurements with high-throughput HPLC analysis. Based on the screening results, two copolymers are selected for further study as pervaporation membranes to quantify permeability selectivity and the flux of ethanol. The screening methodology described has good potential to accelerate the search for new membrane materials, as it is adaptable to a broad range of polymer chemistries.

Kinetic modeling of pH-dependent antimony (V) sorption and transport in iron oxide-coated sand

Understanding the mechanisms and kinetics controlling the retention and transport of antimony (Sb) is prerequisite for evaluating the risk of groundwater contamination by the toxic element. In this study, kinetic batch and saturated miscible displacement experiments were performed to investigate effects of protonation–deprotonation reactions on sorption–desorption and transport of Sb(V) in iron oxide-coated sand (IOCS). Results clearly demonstrated that Sb(V) sorption was highly nonlinear and time dependent, where both sorption capacity and kinetic rates decreased with increasing solution pH. Breakthrough curves (BTCs) obtained at different solution pH exhibited that mobility of Sb(V) were higher under neutral to alkaline condition than under acidic condition. Because of the nonlinear and non-equilibrium nature of Sb(V) retention and transport, multi-reaction models (MRM) with equilibrium and kinetic sorption expressions were utilized successfully to simulate the experiment data. Equilibrium distribution coefficient (Ke) and reversible kinetic retention parameters (k1 and k2) of both kinetic sorption and transport experiment showed marked decrease as pH increased from 4.0 to 7.5. Surface complexation is suggested as the dominant mechanism for the observed pH-dependent phenomena, which need to be incorporated into the kinetic models to accurately simulate the reactive transport of Sb(V) in vadose zone and aquifers.

Theoretical and experimental investigation of interdiffusion in MF-4SC sulfonated cation-exchange membranes

Theoretical approaches to describe the interdiffusion of aqueous solutions of inorganic 1: 1 electrolytes having a common anion across a cation-exchange membrane have been discussed. A new method to characterize the interdiffusion of cations across an MF-4SC sulfonated cation-exchange membrane in terms of the “fine-pore membrane” homogeneous model taking into account the physicochemical properties of the membrane has been proposed. It has been theoretically found that the interdiffusion coefficient of the membrane with respect to a pair of electrolytes is inversely proportional to the difference in the reciprocals of the diffusion coefficients of the cations and depends on the ratio between the fixed charge density and the electrolyte concentration and on the equilibrium distribution coefficients of the cation-anion ionic pairs in the membrane matrix. The adequacy of the proposed approach has been confirmed via comparing theoretical calculations and experimental results on the interdiffusion permeability of the MF-4SC membranes.

Experimental studies and modeling of clinoptilolite and vermiculite fixed beds for Mn2+, Zn2+, and Cr3+ removal

In the present study, batch and fixed bed experiments were conducted in order to compare clinoptilolite and vermiculite for the removal of Mn2+, Zn2+, and Cr3+ from aqueous solutions under the same experimental conditions. Ion-exchange equilibrium is examined by use of batch equilibrium isotherms, distribution coefficients, and maximum exchange levels (MEL). Fixed bed experiments were conducted, and breakthrough curves and operational capacity were determined. Furthermore, diffusion coefficients were estimated by use of simplified fixed bed models. Concerning the comparison of the two minerals, in all experiments, for both batch (distribution coefficients and MEL) and fixed bed (breakthrough points and operating capacity (OC)), vermiculite showed better performance than clinoptilolite for all metals. Vermiculite selectivity series derived from batch distribution coefficients as well as in fixed beds is Cr3+ > Zn2+ > Mn2+ and is the same for clinoptilolite for liquid-phase equilibrium at relative concentration of X < 0.2. For more concentrated equilibrium solutions, the clinoptilolite selectivity changes for Cr3+ and remains the same for the other two metals, i.e. Zn2+ > Mn2+ > Cr3+. MEL are 14.4–26.9 mg/g and 34.2–43.6 mg/g for clinoptilolite and vermiculite, respectively, and OC is found to be 3.6–7.9 mg/g and 12.8–29.3 mg/g for clinoptilolite and vermiculite, respectively, 25–75% lower than MEL. The application of the simplified fixed bed model is successful for Zn in both minerals and Cr3+-vermiculite system. For Cr3+-clinoptilolite system, the model is not applicable due to the sigmoidal shape of the isotherm while for Mn, the model fails in low concentrations for both minerals, and it seems to approach experimental data only for X > 0.2–0.3. Solid-phase diffusion coefficients were estimated to be in the order of magnitude of 10−8 cm2/s for clinoptilolite and 10−9 cm2/s for vermiculite.

Effect of calcium-oxide on the removal of calcium during industrial directional solidification of upgraded metallurgical-grade silicon

Directional solidification is often used to remove metallic impurity in the photovoltaic industry for the low equilibrium distribution coefficient between solid and melt. However, in our present experiments, compared with other impurities, the removal of calcium is variable at the low height of ingot, which is caused by the existence of insoluble CaO particle. CaO exists as insoluble particle in the feedstock. During directional solidification stage, CaO motions with the melt convection, and it is likely to envelop in solid. Consequently, the content of calcium is relatively high if many CaO particles are just contained, which is verified by the analysis of SEM-EDS. In a word, the removal efficiency depends upon the chemical state of calcium. The reason why CaO exists is studied, and the envelopment of the particle is mainly discussed by means of thermodynamics, especially on gravitational force, repulsive force, and drag force.

Separation of (+)-catechin and quercetin on mesoporous MCM-41 composites: Dynamics of the sorption of flavonoids

An analysis of conditions for chromatographic separation of quercetin and (+)-catechin based on experimental data and using the equations of an asymptotic model of sorption dynamics for substances characterized by convex isotherms of sorption is presented. The effects of the equilibrium (distribution coefficient) and kinetic (diffusion coefficient) factors on the dynamics of the sorption of flavonoids by ordered mesoporous material of the MCM-41 type and its composites with grafted organosilane groups is considered. The effects of kinetic and equilibrium parameters on the broadening of adsorption fronts is demonstrated with allowance for the inner and outer diffusion limitations of the sorption process.

Humic acid transport in saturated porous media: Influence of flow velocity and influent concentration

Understanding the transport of humic acids (HAs) in porous media can provide important and practical evidence needed for accurate prediction of organic/inorganic contaminant transport in different environmental media and interfaces. A series of column transport experiments was conducted to evaluate the transport of HA in different porous media at different flow velocities and influent HA concentrations. Low flow velocity and influent concentration were found to favor the adsorption and deposition of HA onto sand grains packed into columns and to give higher equilibrium distribution coefficients and deposition rate coefficients, which resulted in an increased fraction of HA being retained in columns. Consequently, retardation factors were increased and the transport of HA through the columns was delayed. These results suggest that the transport of HA in porous media is primarily controlled by the attachment of HA to the solid matrix. Accordingly, this attachment should be considered in studies of HA behavior in porous media.

Theoretical study of interdiffusion of aqueous solutions of 1 : 1 electrolytes having the same anion through a cation-exchange membrane

The interdiffusion of aqueous 1: 1 electrolytes having the same anion through a negatively charged (cation-exchange) membrane has been studied without taking into account the diffusive layers. It has been established that the interdiffusion coefficients of the cations depend (in addition to their own diffusion coefficients in the membrane) on the ratio of the diffusion coefficients of both cations to the diffusion coefficient of the anion and the ratio of the density of charges fixed in the membrane to the equal concentration of the electrolytes on both sides of the membrane, as well as the equilibrium distribution coefficients of cationanion ion pairs in the membrane matrix. The conditions have been found under which the membrane plays the role of a “blocking system” (like a diode) that is impenetrable to cations located on both sides of the membranes in spite of the existence of their concentration gradients. The developed approach can be used to describe the interdiffusion of 1: 1 electrolytes through any uniformly charged membrane.

Phase Equilibria of Ternary and Quaternary Systems Containing Diethyl Carbonate with Water

In this study liquid phase equilibrium compositions were measured at 298.15 K under atmospheric pressure for (water + propan-1-ol + diethyl carbonate (DEC) + benzene or cyclohexane or heptane) quaternary systems and (water + DEC + propan-1-ol or benzene or cyclohexane) ternary systems. Good correlation of the experimental LLE data was seen for the measured systems by both modified and extended UNIQUAC models. The solubility of DEC in aqueous and organic phases is shown by equilibrium distribution coefficients calculated from the LLE data.

Transport of p-nitrophenol in an agitated bulk liquid membrane system – Experimental and theoretical study by network analysis

A predictive mathematical model has been developed to simulate the pertraction of phenolic compounds in the agitated bulk liquid membrane system (ABLM). A bond-graph method, based on pseudo-thermodynamic network analysis, was applied for the detailed description of the three steps pertraction mechanism, i.e., extraction, diffusion, and re-extraction with the neutralization reaction in the stripping solution. The corresponding mathematical model (a set of ordinary differential equations) was solved to predict the time evolution of local fluxes and concentrations of p-nitrophenol (PNP) in the experimental system: PNP aq. soln.|tolunene|NaOH soln. The calculations were carried out mainly with the data accessible in literature (diffusion coefficients, thickness of diffusion layers) or measured in independent experiments (extraction and re-extraction kinetic constants, equilibrium distribution coefficient). The results of numerical calculations were compared with the experimental PNP transport data. It was found that the model and calculation procedures allow the prediction of time dependent-concentration or fluxes profiles of the transported species in the feed, membrane, and stripping solution as a function of operating parameters (volumes, concentrations), as well as pertraction mechanism parameters (distribution coefficients, diffusion coefficients, kinetic constants).

Radiochemical Study of Re/W Adsorption Behavior on a Strongly Basic Anion Exchange Resin

Abstract Rhenium-186g is a radionuclide with a high potential for therapeutic applications. It emits therapeutic β − particles accompanied by low energy γ-rays, which allows for in-vivo tracking of the radiolabeled compound and dosimetry estimates. The current reactor production pathway 185Re(n, γ)186gRe produces low specific activity 186gRe, thereby limiting its therapeutic application. Work is underway to develop an accelerator-based, charged particle induced production method for high specific activity 186gRe from targets of enriched 186W. To optimize the chemical 186gRe recovery method, batch studies have been performed to characterize the adsorption behavior of Re and W on a strongly basic anion exchange resin. An in-depth physicochemical profile was developed for the interaction of Re with resin material, which showed the reaction to be endothermic and spontaneous. Basic (NaOH) and acidic (HNO3) matrices were used to determine the equilibrium distribution coefficients for Re and W. The resin exhibits the best affinity for Re at slightly basic conditions and little affinity above moderately acidic concentrations. Tungsten has low affinity for the resin above moderately basic concentrations. A study was performed to examine the effect of W concentration on Re adsorption, which showed that even a high ionic WO4 2– strength of up to 1.9 mol kg –1 does not significantly compromise ReO4 – retention on the resin.

Experimental and Correlational Study of Phase Equilibria in Aqueous Solutions of Formic and Butyric Acids with Isoamyl Acetate and Methyl Isoamyl Ketone at T = 298.15 K

This study demonstrates the experimental solubility and tie-line data for {water + formic acid or butyric acid + solvents} ternary systems at T = 298.15 K and p = 101.32 kPa for the first time. The selected organic solvents were isoamyl acetate and methyl isoamyl ketone. Despite structural similarity, however, they belong to two different C7 chemical classifications. The phase diagrams for all of the studied ternary systems are of type-1. Solubility curves were experimentally determined using the cloud point method. The experimental tie-line data were determined by acidimetric titration, the Karl–Fischer technique, and refractive index measurements. The experimental tie-line data were correlated using the UNIQUAC and NRTL models. The quality of the experimental tie-line data was determined through the Othmer–Tobias and Hand correlation plots. From the experimental equilibrium data, distribution coefficients and separation factors were obtained through the regions of immiscibility.

Study on Equilibrium Distribution Coefficients during Osmotic Dehydration of White Gourd Slices

Equilibrium distribution coefficients were obtained to understand osmotic dehydration mechanism and to optimize and control osmotic dehydration process. The equilibrium distribution coefficients of white gourd slices were determined during osmotic dehydration at different temperatures (30–50C) and maltose syrup concentrations (40–60%, w/w). Equilibrium distribution coefficients as a function of temperature and maltose syrup concentration were modeled using nine nonlinear models. The results showed that the equilibrium distribution coefficients of water and solids ranged from 0.3411 to 0.8406 g/g and from 1.2392 to 1.5754 g/g, respectively. The best models for the equilibrium distribution coefficients of water and solids are, respectively, λse = −0.8345 + 0.0281T + 6.5665C − 0.0627CT + 0.0001T2 − 4.9081C2 + 0.0004T2C2 [R2 = 0.9899, sum of squared error (SSE) = 2.0511 × 10−4, root mean square error (RMSE) = 0.0143, χ2 = 9.2299 × 10−4, P = 2.10%], λse = −0.8345 + 0.0281T + 6.5665C − 0.0627CT + 0.0001T2 − 4.9081C2 + 0.0004T2C2 (R2 = 0.9734, SSE = 3.0827 × 10−4, RMSE = 0.0176, χ2 = 0.0014, P = 1.09%). Practical Applications Osmotic dehydration of white gourd slices in maltose syrup solution was investigated experimentally in different solution concentrations and at different temperatures. The equilibrium distribution coefficients of water and solids were calculated during osmotic dehydration of white gourd in maltose syrup solution. The equilibrium distribution coefficients of water and solids for white gourd slices as a function of maltose syrup concentration and temperature were investigated.