Equilibrium Aqueous Phase Research Articles

Application of Date Palm Tree Branch-Based Activated Carbon for Aqueous Toxicity Reduction

The Kingdom of Saudi Arabia (KSA) has millions of date palm trees for commercial scale date-fruit production. The respective industry also generates agricultural waste including date palm tree branches. This rich bio-resource can be used for several beneficial applications. The present study therefore investigated the application of granular activated carbon (GAC) produced using date palm tree branches to successfully remove phenol, p-cresol, and copper from synthetic wastewater. The respective adsorption equilibrium results fitted well to the Langmuir-type adsorption isotherm. Furthermore, the pH-dependent adsorption results both for phenol and p-cresol appeared to follow an anionic-type adsorption behavior (i.e., decreasing adsorption with an increase in aqueous phase equilibrium pH). However, the pH-dependent adsorption finding for copper showed a cationic-type adsorption behavior. These adsorption trends were explained employing the pH-dependent speciation of the respective pollutants. In general, findings from the present work indicate that a high-specific-surface-area (SSABET) GAC material from the date palm tree branches can be successfully employed for aqueous phase pollution control.

Study of complexation of Li, Na and K trichloroacetates in extraction systems with benzo-15-crown-5 ether and its lipophilic analog

The extraction of Li, Na and K trichloroacetates by benzo-15-crown-5 ether and its lipophilic analog in chloroform has been studied. Extraction isotherms were obtained and the transition of extractants into the equilibrium aqueous phase was determined. The metal: crown ether ratios in the extracted compounds were determined by the slope analysis method. The thermodynamic extraction parameters of Li, Na and K trichloroacetates in systems with benzo-15-crown-5 ether (B15C5) and 3-tert-pentylbenzo-15-crown-5 ether (tPB15C5) were determined. The complexes [Li3(B15C5)(TCA)3], [Na(B15C5)(TCA)] and [K(B15C5)2](DCA)·H2O were isolated in crystalline form and characterized by IR spectroscopy and X-ray diffraction.

In uence of the nature of the diluent on the extraction capacity of N,N,N',N'-tetrabutyldiglycolamide to Eu(III), Am(III) and Cm(III)

The in uence of HNO3 concentration on the extraction of Eu(III), Am(III) and Cm(III) by N,N,N',N'tetrabutyldiglycolamide in 5 diluents (nitrobenzene, toluene, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane and chloroform) was studied. The dependence of the distribution ratios of the listed metals on the nature of the diluent was examined. The extraction of Eu(III), Am(III) and Cm(III) decreases in the following order: nitrobenzene > m -tri uoromethylnitrobenzene > mixture of n -dodecane and decanol-1 (90 : 10 vol/vol) > tetrachloromethane > 1,2-dichloroethane > benzene > 1,1,2,2-tetrachloromethane > toluene > chloroform. The conditions for the separation of Eu(III)/Am(III) and Am(III)/Cm(III) pairs were determined. The explanation of the observed increase of the Am(III)/Cm(III) separation factors with the increase of the nitric acid concentration in the equilibrium aqueous phase was suggested.

Monomer Transport in Emulsion Polymerization IV Gaseous Monomers

AbstractMethods for the evaluation of the Damkohler number for monomer transport during emulsion homopolymerization and copolymerization are extended to the analysis of gaseous monomers. Results indicate that the monomer transport limitation of gaseous monomers in both homo and copolymerization is strongly dependent on overall pressure through Henry's law relationship governing the concentration of monomer in the aqueous phase in equilibrium with monomer bubbles. At low pressures, most monomers studied exhibit monomer transport limitations; however, even at very high pressures, some gaseous monomers still exhibit monomer transport limitations.

Contributions of partition and adsorption to polycyclic aromatic hydrocarbons sorption by fractionated soil at different particle sizes.

Partition and adsorption of polycyclic aromatic hydrocarbons (PAHs) are critical mechanisms determining their fate at the solid-liquid interface. The complexity of soil composition makes it difficult to distinguish between partition and adsorption, and bates the accuracy of the research results. This study found that the composition and structure of the soil particles (SAs) of varying particle sizes were significantly different. Partition contributed significantly to phenanthrene (Phe) sorption in SAs over 0.002mm. However, PAHs had the highest sorption coefficient (Kd) in SA less than 0.002mm (SA-3), and the lower aqueous phase equilibrium concentration of Phe, the greater the adsorption effect. According to morphology and structural analysis, Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS), interactions of micropores, soil organic matter (SOM) and minerals enhanced the sorption of PAHs. Additionally, thermogravimetry and mass spectrometry (TG-MS) results proved that SOM could inhibit the release of PAHs adsorbed in SAs during heating process. We observed that the Log Koc of PAHs was the most important factor in determining the Kd in SAs applying principal component analyses (PCA), and they have significant linear relationships (R2=0.79-0.93). These findings provide new understandings on interface reactivity of PAHs sorption to soils and the development of interface model.

Extraction behavior of Pu(IV), Th(IV), and fission product elements with hexapropyl and hexabutyl phosphoramides

Abstract Hexapropyl phosphoramide (HPPA) and hexabutyl phosphoramide (HBPA) were examined for the macrolevel extraction and stripping of tetravalent metal ions such as Pu(IV) and Th(IV). The solvation number of Pu(IV) with both the phosphoramides were measured. The number of stages was evaluated for the quantitative extraction and stripping of Pu(IV) and Th(IV) in cross-current mode with 1.1 M phosphoramides in xylene from the nitric acid medium. The distribution ratios for the extraction of Th(IV) were measured with 1.1 M phosphoramides in xylene as a function of equilibrium aqueous phase Th(IV) and nitric acid concentration. In addition, distribution ratios for the extraction of fission product elements such as Zr, Tc, Ru, lanthanides (La, Pr, Nd and Gd) and activation product Am were also measured with 1.1 M HPPA and HBPA in n-Dodecane (n-DD) system as a function of aqueous phase nitric acid concentration. The extraction data generated with phosphoramides were compared with a 1.1 M TBP/n-DD system.

Effects of Polydispersity on the Phase Behavior of Additive Hard Spheres in Solution.

The ability to separate enzymes, nucleic acids, cells, and viruses is an important asset in life sciences. This can be realised by using their spontaneous asymmetric partitioning over two macromolecular aqueous phases in equilibrium with one another. Such phases can already form while mixing two different types of macromolecules in water. We investigate the effect of polydispersity of the macromolecules on the two-phase formation. We study theoretically the phase behavior of a model polydisperse system: an asymmetric binary mixture of hard spheres, of which the smaller component is monodisperse and the larger component is polydisperse. The interactions are modelled in terms of the second virial coefficient and are assumed to be additive hard sphere interactions. The polydisperse component is subdivided into sub-components and has an average size ten times the size of the monodisperse component. We calculate the theoretical liquid–liquid phase separation boundary (the binodal), the critical point, and the spinodal. We vary the distribution of the polydisperse component in terms of skewness, modality, polydispersity, and number of sub-components. We compare the phase behavior of the polydisperse mixtures with their concomittant monodisperse mixtures. We find that the largest species in the larger (polydisperse) component causes the largest shift in the position of the phase boundary, critical point, and spinodal compared to the binary monodisperse binary mixtures. The polydisperse component also shows fractionation. The smaller species of the polydisperse component favor the phase enriched in the smaller component. This phase also has a higher-volume fraction compared to the monodisperse mixture.

Extraction of REE(III), U(VI), and Th(IV) from Perchloric Acid Solutions with 2,6-Bis(diphenylphosphorylmethyl)pyridine N-Oxide

The extraction of microamounts of REE(III), U(VI), and Th(IV) from HClO4 solutions with solutions of 2,6-bis(diphenylphosphorylmethyl) pyridine N-oxide (I) in 1,2-dichloroethane was studied depending on the HClO4 concentration in the equilibrium aqueous phase. The stoichiometry of the extracted complexes was determined. It was shown that compound I extracts REE(III), U(VI), and Th(IV) from dilute HClO4 solutions with much higher efficiency than from HNO3 solutions. With an increase in the concentration of acids, the magnitude of the “perchlorate” effect upon extraction of REE(III) and U(VI) decreases, and Th(IV) is extracted by compound I from HClO4 solutions with lower efficiency than from HNO3 solutions.

Solvent extraction of lithium ions using benzoyltrifluoroacetone in new solvents

This work studies the solvent extraction of lithium ions from alkaline aqueous solutions by chelating agent 3-benzoyl-1,1,1-trifluoroacetone (HBTA). To develop a more eco-friendly extraction system for lithium than currently used, various hydrophobic room-temperature ionic liquids were investigated as diluents. The influence of several experimental parameters on lithium extraction was examined, including aqueous phase pH, the nature of lithium counter-ion, extractant concentration, the addition of electrically neutral co-extractant.It was found that contrary to the traditional extraction systems with molecular diluents, HBTA alone dissolved in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid extracts efficiently lithium ions from the aqueous solution. The addition of co-extractant, tri(n-octyl)phosphine oxide (TOPO) to HBTA did not result in a synergetic effect. To confirm the mechanism of lithium extraction by HBTA dissolved in ionic liquid (IL), the measurements of IL constituent ions and deprotonated HBTA concentrations in the equilibrium aqueous phase were carried out. Analysis of the results suggests that an electrically neutral lithium-HBTA extractant complex is extracted into the IL phase.The system combining HBTA extractant and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid has high selectivity for lithium over sodium but poor selectivity over calcium. We have shown also that a high stripping ratio can be obtained using relatively concentrated aqueous solutions of hydrochloric acid. Finally, it was found that the use of some deep eutectic solvents as diluents is much less efficient compared with ILs.

Composition of Hydrosolvates during the Extraction of Nitric Acid in the HNO3–H2O–EHEHPA System

The role of water in the extraction of nitric acid in the HNO3–H2O–EHEHPA (PC88-A, P507, or Ionquest 801) system and the composition of the resulting hydrosolvates are studied for further use of the data obtained in modeling industrial extraction processes. Dependences of the solubility of water in the extractant on the activity of water in the aqueous phase are calculated, along with the content of dissolved and hydrate water in the organic phase at different concentrations of nitric acid in the equilibrium aqueous phase, and the IR spectra of extracts are recorded. Compositions of hydrosolvates in the HNO3–H2O–EHEHPA system are calculated. It is found that water participates in the extraction of nitric acid, but its involvement in the range of high concentrations is negligible. The compositions of hydrosolvates (HL)2 · 2HNO3 · Н2О ( 5 M nitric acid in the aqueous phase) are determined.

Phase equilibrium data for semiclathrate hydrates formed with tetra-n-butylammonium (bromide or chloride) and tetra-n-butylphosphonium (bromide or chloride) under hydrogen + carbon dioxide pressure

Semiclathrate hydrates are host–guest materials that can be used for CO2 capture due to their unique gas selectivity. CO2 capture from H2 + CO2 mixed gas is possible by semiclathrate hydrates formed by tetra-n-butylammonium (TBA) and tetra-n-butylphosphonium (TBP) salts. TBA bromide (TBAB), TBA chloride (TBAC), TBP bromide (TBPB) and TBP chloride (TBPC) are widely available ionic substances for semiclathrate hydrate formation. In order to understand their gas capture properties, phase equilibrium data of these materials are necessary. Here we report experimental three phase (gas–hydrate–aqueous phase) equilibrium data measured in (TBAB, TBAC, TBPB or TBPC) + H2 + CO2 + H2O systems. The comparison with the literature data suggested that H2 can be incorporated in the TBAB and TBAC hydrates together with CO2, but TBPB and TBPC hydrates reject H2. The hydrate phases were identified by single crystal X-ray diffraction analyses. The TBAB, TBPB and TBPC form the same or similar hydrate phases, i.e., orthorhombic and hexagonal phases. The TBAC formed the tetragonal hydrate phase. The present results suggest that different CO2 capture properties are obtained by these semiclathrate hydrates.

Analysis of the mixture of rare earth elements by atomic spectroscopy

The authors of this paper give the characteristic and the principle of operation of the ICPE-9000 spectrometer, proposed for the chamber residue analysis that is one of the products of ion flotation, for individual rare earth elements and their mixture content by atomic spectroscopy. The chamber residue was obtained by conducting the ion flotation from nitrate solutions, containing individual rare earth elements of the cerium group and their mixture. The results of the analysis of the solutions by optical emission spectroscopy are shown in the form of molar concentration. According to the obtained experimental data, a tendency for the change of distribution coefficients, separation factors and pH values of maximum recovery at the different values of equilibrium aqueous phase pH value was identified. The possibility of the most effective separation of rare earth elements of the cerium group at different concentrations of indifferent ions was revealed, as well as the forms of recovered compounds were determined.

DETERMINATION OF TYPE OF SOLVATE OF PHOSPHORIC ACID DURING ITS EXTRACTION BY TRIBUTYL PHOSPHATE

The extraction of phosphoric acid with a solution of tri-n-butyl phosphate (TBP) in toluene from its individual aqueous solutions in a concentration range of 0-11 M is investigated. The experiments are performed at room temperature (20 ± 1 °С). The isotherms of extraction of phosphoric acid under conditions of equality of the volumes of the saturating aqueous phase and the receiving organic phase are constructed. The extraction isotherm is nonlinear, but to an acid concentration in the aqueous phase of ~ 8 M, it is close to linear, and at higher concentrations, the amount of extracted acid increases harshly. To establish the mechanism of acid extraction in the system phosphoric acid – 0.1 M solution of TBP in toluene the method of combining a laboratory and computational experiment is proposed. The optimal parameters describing the extraction of phosphoric acid from natural aqueous solutions are determined. Calculations performed in two approximations were made. In the first approximation the condition of ideality of systems is accepted. In the second approximation the deviations of the properties of phosphoric acid solutions in aqueous solution are taken into account. For the two approximations the preferential extraction of phosphoric acid molecules in the form of H3PO4 ∙ nTBP type solvates (where n = 1, 3) is shown. In the range of concentrations of phosphoric acid in the aqueous phase from 6 to 11 M, the values of equilibrium constants are estimated, which describe the processes and reactions occurring in the system: stepwise dissociation of acid, distribution of TBP, formation of solvates of phosphoric acid, distribution of the resulting solvates of acid, displacement of ionic equilibria in aqueous phase. Mathematically these processes are taken into account using the law of mass action and the equations of material balance. It is believed that the system has established an equilibrium corresponding to a given temperature and pressure. The calculated values of solvate concentrations are in satisfactory agreement with experimental data.

In Situ Monitoring and Kinetic Analysis of the Extraction of Nitric Acid by Tributyl Phosphate in N-Dodecane Using Raman Spectroscopy

ABSTRACTUnderstanding the fundamental rates of transfer and complex formation is crucial in maintaining optimal efficiency and effectivity in solvent extraction. Methodologies to analyze solvent extraction systems are lacking in that they are commonly performed off-line in subsequent experiments. Thus, a method to proficiently investigate solvent extraction systems in a Lewis cell using in situ Raman spectroscopy paired with chemometric modeling has been developed to allow for on-line analysis and monitoring. Forward and reverse interfacial transfer coefficients for the extraction of nitric acid by tributyl phosphate, a process crucial to used nuclear fuel reprocessing, were measured by spectroscopic monitoring of both phases simultaneously in a two-phase solvent extraction system. Concentration data was derived from the chemometric modeling using Raman spectra. The concentration data was fit to a nonlinear least squares regression model to allow for the calculation of the transfer coefficients in the system. The reverse interfacial transfer coefficient, kr, was determined along with the parameter 95% confidence intervals and 95% prediction intervals. The forward interfacial transfer coefficient, kf, was then back calculated from kr and the aqueous phase and organic phase equilibrium concentrations. The average calculated values of kr and kf were 2.56 (± 0.50) × 10−5 m s−1 and 4.75 (± 1.13) × 10−6 m s−1, respectively. The information obtained regarding solvent extraction parameters and transfer can be applied in the study of systems of higher complexity, involving complex formation and their transfer across a liquid:liquid interface.

A new efficient algorithm to determine three-phase equilibrium conditions in the presence of aqueous phase: Phase stability and computational cost

Three-phase flash calculation is a crucial part of the modeling and simulation of the transport phenomenon in various chemical and petroleum processes. To obtain the compositions of phases in equilibrium, utilization of Equations of State (EOSs) and thermodynamic phase equilibria rules/laws (e.g., Henry's law, Lewis/Randall rule, and modified Raoult's law) seem inevitable to model phase behaviors of liquid, vapor, and aqueous phases. This study plans to develop two thermodynamic modeling approaches (on the basis of Henry's law and EOS) to conduct three-phase flash calculations in the presence of water. It is found that both developed algorithms are capable of determining the equilibrium conditions in the three-phase region such that a desired precision is obtained. In this research study, a new stability algorithm based on a negative flash procedure is introduced to forecast the formation and/or condition of the stable phases. The modeling results reveal that the aqueous phase equilibrium calculations by using EOS lead to an inaccurate prediction of stable phases in a vicinity of phase change regions. Improving the accuracy and reliability of the phase equilibria calculations, a new analytical derivative of fugacity coefficient with respect to mole fraction is obtained so that a better convergence and less runtime (compared to numerical derivatives) are achieved. An appropriate method to guess the initial equilibrium ratio is presented in this research investigation. The best roots of the cubic EOS are then selected for all three phases by minimizing Gibbs free energy. The proposed procedure can be implemented in different multiphase systems (and simulation softwares) to increase the accuracy of multiphase equilibrium calculations with an acceptable computational cost.

On the use of ionic liquids as adjuvants in PEG-(NH4)2SO4 aqueous biphasic systems: Phase diagrams behavior and the effect of IL concentration on myoglobin partition

Abstract The introduction of ionic liquids (ILs), either as phase forming components or as adjuvants, in the implementation of aqueous biphasic systems (ABS) enabled to finely tune the properties of the two aqueous phases in equilibrium thus providing the opportunity to increase extraction efficiencies and selectivities of biomolecules. Nevertheless, the effect of ILs addition on the phase diagram behavior and partitioning of biomolecules changes depending on the polymer, salt, ILs and biomolecules used and is still not fully understood. In this context, the influence of the addition of 7 different ILs based on imidazolium, pyrrolidinium or pyrydinium cation on PEG 3350 + ammonium sulfate ((NH4)2SO4) ABS at 25 °C is studied in this work. In terms of phase equilibrium, it was observed that the chemical nature of the IL leads to either a decrease or increase of two-phase region, therefore in the latter affording a decrease in concentrations of phase forming compounds needed for the liquid-liquid demixing. It is shown, that the IL anion affinity for water or the anion’s hydrogen-bond basicity controls the phase splitting behavior and thus [C4mim][N(CN)2] is able to greatly enhance two-phase region. Moreover, these PEG 3350 + (NH4)2SO4 + IL ABS were tested in the extraction/concentration of myoglobin from aqueous solutions. The obtained results indicate that the myoglobin partition is strongly influenced by its hydrophilicity and pH of the phases in equilibrium. Consequently, it preferentially partitions to the salt-rich phase. However, partitioning studies in presence of ILs as adjuvants show that these compounds can tune the polarity of the PEG-rich phase thus offering a tunable platform for the purification of myoglobin. This ability greatly depends on the chemical structure of the IL used and closely follows the IL hydrogen-bond basicity (β), enabling the most hydrophilic IL – [C4mim][CH3CO2] – to change the myoglobin partitioning behavior from salt-rich to the PEG-rich phase.

Phase equilibrium for argon clathrate hydrate at the temperatures from 197.6 K to 274.1 K

Abstract The phase equilibrium conditions of clathrate hydrate of argon were measured by the isochoric procedure at the temperatures from 197.6 K to 274.1 K. Argon hydrate would have industrial applications including a working medium of the hydrate-based heat pump systems as well as influence the analysis of the past climate change on the Earth. Nevertheless, the equilibrium conditions of argon hydrate were limited in the literatures and not reported below the temperature 264 K. The lowest and the highest measured equilibrium pressure is the pressure 0.825 MPa at the temperature 197.6 K and the pressure 9.881 MPa at the temperature 274.1 K. The equilibrium pressure increases with an increase in temperature. The reliability of the measured equilibrium conditions is supported by the internal consistency of those and the coincidence of the experimentally determined quadruple point (vapor + hydrate + ice + aqueous phases in equilibrium) temperature with the water freezing temperature theoretically predicted. The discussion is given on the comparison of the equilibrium data measured in this study and those reported in the literature.

Technical Note: Characterization of Corrosion Films Formed on Austenitic Stainless Steel in Supercritical CO2 Containing H2O and O2

Future technologies require structural alloys resistant to corrosion in supercritical CO2 (sCO2) fluids containing impurities such as H2O and O2. Traditional pipeline steels are potentially unsuitable for these environments and more corrosion resistant alloys such as stainless steels might be required. Little is known about the corrosion products formed on, and hence the processes which control corrosion of, stainless steels in impure sCO2 environments. In this study, austenitic stainless steel 347H (UNS S34709) was exposed to sCO2 containing H2O and O2 at 8 MPa and 50°C or 250°C, and separately to the aqueous phase in equilibrium with the sCO2 at 50°C, to simulate conditions expected in sCO2-based power cycles and carbon capture and storage pipelines. Only thin (<20 nm) surface films formed after 500 h resulting in small mass changes and corrosion rates <10−4 mm/y, suggesting the material resists significant degradation in these environments. X-ray photoelectron spectroscopy and transmission electron microscopy were used to characterize the corrosion films in detail. Exposure to the aqueous phase resulted in a thin (<5 nm) Cr-oxide and/or -hydroxide passive film, while exposure to sCO2 phases resulted in a multilayer Fe-rich oxide structure characteristic of a gas-phase oxidation process.

Extraction of U(VI), Th(IV), and REE(III) from Nitric Acid Solutions with 2,6-Bis(diphenylphosphorylmethyl)pyridine N-Oxide

The extraction of microamounts of U(VI), Th(IV), and REE(III) from HNO3 solutions in the form of complexes with 2,6-bis(diphenylphosphorylmethyl)pyridine N-oxide (I) was studied in relation to the kind of organic diluent and to the HNO3 concentration in the equilibrium aqueous phase. The stoichiometry of the extractable complexes was determined. With respect to the ability to extract Th(IV) and REE(III), compound I considerably surpasses tetraphenylmethylenediphosphine dioxide and tetraalkyl-substituted analogs of I.

Effects of temperature on the extraction of U(VI) and Pu(IV) by tris(2-methylbutyl) phosphate from nitric acid media

Abstract Extraction behavior of tris(2-methylbutyl) phosphate (T2MBP), a higher homologue of tri-n-butyl phosphate (TBP), in the extraction of U(VI) and Pu(IV) from nitric acid media has been evaluated in the present study. Distribution ratios for the extraction of these metal ions by T2MBP were measured as a function of equilibrium aqueous phase nitric acid concentration, extractant concentration and temperature to understand the temperature effects on extraction. Enthalpies of extraction of T2MBP/n-dodecane-U(VI)-HNO3 and T2MBP/n-dodecane-Pu(IV)-HNO3 systems were calculated from the distribution ratio data using “second law” method. The data reveal that the extraction of U(VI) by T2MBP is exothermic in nature, whereas that of Pu(IV) is endothermic.