Simulation of the properties of a binary carbon dioxide-water mixture under sub- and supercritical conditions

A method for determining the multiphase thermodynamic equilibriums of a binary mixture expressed in pressure-enthalpy-mixture composition variables is suggested. The use of such variables, in contrast to the classical thermodynamic pressure-temperature-composition variables, makes it possible to determine not only the two-phase, but also three-phase states of a mixture. The method can be used to describe real properties of mixtures in a wide range of pressure and temperature values containing critical points; it can be helpful in modeling of the mixture flows in a porous medium. The suggested problem of calculating the multiphase equilibrium can be visually interpreted in terms of geometry by constructing a convex envelope for the thermodynamic potential of the mixture. This method is used to study the phase diagram of the carbon dioxide-water mixture.     

Measurements of the virial coefficients and equation of state of the carbon dioxide+ethane system in the supercritical region

Gas-phase densities of the system carbon dioxide+ethane were measured with a Burnett apparatus at 320 K and at pressures up to approximately 10 MPa. Measurements were made on systems having carbon dioxide mole fractions of 0, 0.25166, 0.49245, 0.73978, and 1. Second and third virial coefficients were determined for each composition, and the cross virial coefficients were calculated. Comparisons were made with other recent high-quality measurements on this system. For each mixture compositionPT measurements were made on five isochores having densities within ±30% of the critical density. Temperatures varied from 288 to 320 K. The two-phase boundary was determined and estimates are given forT _c andP _c for each composition.     

Determination of the interaction second virial coefficients for the carbon dioxide-ethane system from refractive index measurements

The compressibility behavior of the CO₂-C₂H₆ system was investigated experimentally. In this work, the refractive indexes of the pure gases and the mixtures were measured using an optical apparatus. On the basis of these data, density and compressibility factors were computed using the Lorentz-Lorenz law. For the pure components, carbon dioxide and ethane, the data from the optical system were slightly adjusted by a fit to Burnett apparatus data measured separately. The experiments produced very accurate virial coefficients and refraction virial coefficients. This paper reports on the effect of temperature on the second and third virial coefficients. For the first refraction virial coefficient, no influence of temperature was found with the equipment used. The interaction second virial coefficient B ₁₂ (as a function of temperature) was computed from experimental data for the CO₂-C₂H₆ binary system. The data, for which an accuracy of ±1.5 cm³ · mol^–1 was estimated, are in agreement with the data published by Holste et al.     

Removal of gallium (III) ions from acidic aqueous solution by supercritical carbon dioxide extraction in the green separation process

Supercritical carbon dioxide extraction, which is a feasible "green" alternative, was applied in this study as a sample pretreatment step for the removal of gallium (III) ions from acidic aqueous solution. The effect of various process parameters, including various chelating agents, extraction pressure and temperature, dimensionless CO(2) volume, the concentration of the chelating agent, and the pH of the solution, governing the efficiency and throughput of the procedure were systematically investigated. The performance of the various chelating agents from different studies indicated that the extraction efficiency of supercritical CO(2) was in the order: thiopyridine (PySH)>thenoyltrifluoroacetone (TTAH)>acetylacetone (AcAcH). The optimal extraction pressure and temperature for the supercritical CO(2) extraction of gallium (III) with chelating agent PySH were found to be 70 degrees C and 3000psi, respectively. The optimum concentration of the chelating agent was found to be 50ppm. A value of 7.5 was selected as the optimum dimensionless CO(2) volume. The optimum pH of the solution for supercritical CO(2) extraction should fall in the range of 2.0-3.0.     

Combined supercritical fluid extraction/solid-phase extraction with octadecylsilane cartridges as a sample preparation technique for the ultratrace analysis of a drug metabolite in plasma.

Supercritical fluid extraction was coupled with solid-phase extraction using octadecylsilane cartridges for the selective isolation of ultratrace levels of a drug metabolite, mebeverine alcohol, from plasma. Plasma was directly applied to the extraction cartridge, the cartridge was washed to remove protein and then extracted under supercritical conditions using CO2/5% methanol. The effluent from the extraction cell was bubbled through a small volume of 2-propanol to trap the extracted mebeverine alcohol. The effects of extraction pressure and temperature on analyte recovery were examined. The absolute recovery, selectivity, precision, and accuracy of the combined supercritical fluid extraction/solid-phase extraction approach were compared to those of conventional solid-phase extraction using gas chromatography/mass spectrometry in the selected-ion monitoring mode. Mebeverine alcohol was used as a model compound, and dog plasma was employed as the biological matrix for these studies.     

Dynamical analysis of a compressible elastic rod in the current configuration

The dynamical behavior of a compressible elastic rod, left in a nonequilibrium state, is described in the current configuration in a context of large strains and velocities. The phenomenon is governed by a nonlinear hyperbolic system of differential equations in which the unknown are the mass density, the velocity and the stress fields. Some particular cases are simulated from the solution of the associated Riemann problems.     

Mixing in a system of plane cocurrent jets of an incompressible liquid over the main portion

We consider mixing in a periodic system of plane subsonic jets of an incompressible liquid for laminar and turbulent flows. Asymptotic expressions for the change in the velocity defect are obtained. A comparison with a numerical calculation and with existing experimental data is carried out. We show that under the conditions considered the accuracy of the expressions derived is rather high and they can be used for evaluating the mixing velocity over the main portion of mixing.     

超临界流体快速膨胀法分散碳纳米管

利用超临界状态下CO2的快速膨胀(RESS)来分散碳纳米管,为可放大化且无挥发性有机化合物的新方法。将碳纳米管在超临界CO2悬浮液中经由微细喷嘴快速膨胀使其均匀分散。电子显微镜(SEM)表征证实RESS可有效地实现碳纳米管的分散。同时,为了解决再团聚难题,提出利用小分子包覆法和将碳纳米管嵌入高分子基体法来防止其再团聚,均起到良好的效果。     

Thermodynamic analysis of phase equilibria in the Sm-Cu-O system

This paper presents thermodynamic analysis of the Sm-Cu-O system and its constituent binaries using available experimental data. Analytical expressions are derived for the Gibbs energy of Sm₂CuO₄, SmCuO₂, and the liquid; the invariant points in the ternary system are located; and the CuO-SmO_1.5 phase diagram at an oxygen partial pressure of 21 kPa is calculated.     

Design for on-line coupling of supercritical fluid extraction with liquid chromatography: quantitative analysis of polynuclear aromatic hydrocarbons in a solid matrix

Supercritical fluid extraction (SFE) was directly coupled with high-performance liquid chromatography (LC) via the simplest interface--only one six-port injection valve. By using water to eliminate decompressed CO2 gas in the solid-phase octadecylsilica trap, high extraction recovery (> or = 95%) of polynuclear aromatic hydrocarbons (PAHs) from a sand matrix was achieved under optimized conditions. The volume of rinse water had little influence on the recovery, due to the very low solubility of PAHs in water and the sorption properties of the C-18 trap. Different amounts of sand matrix with a fixed mass of analytes have also been tested. No decrease in recovery was found when the matrix (sand) increased from 1 to 10 g. Methanol and acetone were used as a CO2 modifier to enhance the extraction efficiency. Finally, PAHs in naturally contaminated soil were successfully extracted and quantitatively determined by this hyphenated system. Compared to the EPA method (Soxhlet extraction following by GC/MS), on-line SFE-LC gave precise results in a much shorter time.     

磁性多壁碳纳米管固相萃取-气相色谱质谱联用快速测定食用油中的苯并[a]芘

建立以磁性多壁碳纳米管(Fe3O4/MWCNTs)作为磁固相萃取吸附剂,气相色谱-质谱联用检测食用油中苯并[a]芘(Ba P)的方法。实验优化萃取时间、洗脱溶剂的种类和用量、洗脱时间等影响萃取效率的主要参数。最佳样品处理条件为:萃取时间5 min、4 m L甲苯作为洗脱剂超声洗脱3 min。在最佳条件下,该方法具有较高的准确性和灵敏度,其回收率为95.3%~100.5%,检出限(3倍信噪比)为0.15μg/L。检测市售食用油中的Ba P时,实际样品加标回收率为77.2%~89.1%,相对标准偏差为1.1%~6.0%,检出限为0.19%~0.29μg/L,该方法操作简便、耗时短、有毒试剂用量少、准确灵敏。     

Air/light-free hyphenated extraction/analysis system: supercritical fluid extraction on-line coupled with liquid chromatography-UV absorbance/electrospray mass spectrometry for the determination of hyperforin and its degradation products in Hypericum pertoratum

Hyperforin, which is a major active constituent of the antidepression herbal medicine-Hypericum pertoratum (St. John's wort), is very sensitive to oxygen and light. Our paper reports for the first time an air/light-free extraction-separation-detection hyphenated system and its application to St. John's wort. It involves on-line coupling of supercritical fluid extraction with liquid chromatography-UV absorbance/electrospray ionization mass spectrometry (SFE-LC-UV/ESI-MS). Mass spectral data on the extract that was produced on-line suggested the presence of the major degradation compound of hyperforin-furohyperforin and two of its analogues. Thus, some degradation process must have already occurred in our sample during plant drying or storage. The feasibility of quantitative extraction and analysis of hyperforin by on-line SFE-LC was made possible by optimizing the extraction pressure, temperature, and CO(2) modifier content. High recovery ( approximately 90%) relative to liquid-solid extraction was achieved under optimized conditions.     

Generalized algorithm for the unified analysis and simultaneous evaluation of geometrical spin-redirection phase and Pancharatnam phase in a complex interferometric system

To permit unified analysis and simultaneous evaluation of geometrical spin-redirection phase and Pancharatnam phase, the conventional 2 x 2 Jones matrix calculation is generalized and a new scheme of 3 x 3 matrix calculation is proposed. With the proposed algorithm one can trace the polarization state changes and the geometric phase shifts caused by beam propagation along an arbitrary optical path that involves both reflection and refraction at surfaces with Fresnel shift and birefringence.     

Application of the radial basis function interpolation to phase extraction from a single electronic speckle pattern interferometric fringe

In this paper, we introduce the radial basis function (RBF) interpolation method to electronic speckle pattern interferometry (ESPI) and propose the RBF interpolation method to obtain unwrapped phase values based on a skeleton map. Because of the excellent approximation properties of the RBF interpolation, the proposed method can extract accurate phase values from a single fringe pattern effectively, even using a simple 3×3 mean filter as preprocessing. Using our method, both special filtering methods for ESPI fringes as preprocessing and postprocessing, including a dilatation and erosion algorithm for pruning and connecting and the smooth algorithm for improving the phase values are not needed. We test our method on a computer-simulated and two experimentally obtained poor-quality fringe patterns. The results have demonstrated that our RBF interpolation method works well even under a seriously disconnected skeleton map where it is impossible to apply the widely used, Matlab function grid data interpolation or the backpropagation neural networks method [Appl. Opt. 46, 7475 (2007)].     

Synthesis of a new cubic phase in the B-C-N system

Phase formation in the B-C-N system has been studied at pressures from 6 to 15 GPa and temperatures from 1000 to 1600°C using mixtures of carbon nitride (C₃N₄) nanospheres and boron. A new ternary phase with the structure of cubic boron nitride in which some of the nitrogen and boron atoms are replaced by carbon has been obtained at p ? 8 GPa and t ? 1500°C. According to the Rietveld refinement results, its composition is BC_0.47N_0.85.     

Thermodynamics of the migration of a liquid phase in a three-phase dispersed system with one dissolving solid phase

An expression describing a change in the Gibbs potential in a liquid phase migration in a three-phase dispersed system with one dissolving solid phase has been derived. The conditions have been defined, at which the structure formation is possible either without a change in the initial skeleton structure of a refractory phase, or due to a total or partial deconsolidation of the skeleton structure.     

Consolidation thermodynamics of the nanoparticles in a solid-mobile phase two-phase system

Thermodynamic functions have been derived that describe the processes of the nanoparticle consolidation in a solid-mobile phase two-phase dispersed system and the deconsolidation of a polycrystalline body that is accompanied by the spontaneous formation of a nanodispersed system. An expression for the shrinkage pressure has been deduced, which allows one to calculate stresses occurring in the bulk of heterophase composite materials in the course of the nanoparticle consolidation.     

Heat and mass transfer in the condenser-evaporator of a dynamic system for water extraction from an electrochemical energy generator

A system of transfer equations over the length of the apparatus is considered, taking account of the electrolyte-concentration gradient in a porous phase separator. The results of computer calculation are given.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 4, pp. 640–648, October, 1985.