Liquid—liquid coexistence curves for binary systems

The liquid—liquid coexistence curves of polar+non-polar binary systems have been determined experimentally. The polar compounds studied were ethanenitrile, methanol and N-methylpyrrolidone, whereas the non-polar compounds were chosen from the n-alkane series. The upper critical solution temperature for each set of mixtures increases with increasing n-alkane chain length, and the critical composition of the polar component also increases in this fashion.     

Liquid—liquid—vapor phase equilibria behavior of certain binary ethane + n-alkylbenzene mixtures

The liquid—liquid—vapor loci for the binary mixtures ethane + n-nonylbenzene, ethane + n-decylbenzene and ethane + n-undecylbenzene were experimentally studied. The pressure, temperature, and compositions and molar volumes of the liquid phases are reported along the loci. n-Nonylbenzene was found to be the first member of the n-alkylbenzene homologous series to exhibit liquid—liquid—vapor immiscibility with ethane. For the three alkylbenzenes studied, the liquid—liquid—vapor loci have the same type of behavior: they extend from a lower critical end point (LCEP) to an upper critical end point (K-point).     

Liquid–solid extraction of butyltin compounds from marine samples

Environmental damage due to organotins (TBT, DBT, MBT) released from antifouling paints is well documented. The concentrations of these compounds in seawater are usually at ppt (parts per 10¹²) levels. Many analytical techniques, including chromatographic and spectrophotometric ones, have been presented in the literature to detect organotins at these low levels. Liquid-liquid extraction is commonly employed as a concentration method. However, it presents some disadvantages during sampling campaigns and requires large volumes of toxic and expensive solvents. In this paper we propose an analytical method based on a liquid-solid extraction procedure that can be easily performed in the field and is characterized by good recoveries and high enrichment factors. Three different solid phases (Carbopack, LC 8 and LC 18) and five different eluting agents (methanol/tropolone, methanol, dichloromethane, hexane and diethyl ether) were evaluated. Carbopack and LC 18 were the most suitable solid phases. Inorganic tin was not retained on these solid phases and a separation of TBT from DBT and MBT was achieved, performing the elution in two steps with methanol and methanol/tropolone. In this way GF AA was suitably employed to obtain butyltin speciation data.     

An investigation of gold adsorption from a binary mixture with selective mesoporous silica adsorbents

Gold-selective adsorbents were prepared from mesoporous MCM-41 silica by grafting organic amine groups (i.e., RNH2, R2NH, and R3N; R=propyl). NH2-MCM-41, NRH-MCM-41, and NR2-MCM-41 displayed strong affinity for gold and at 1 mmol/g loading adsorbed 0.40, 0.33, and 0.20 mmol/g of gold. Copper and nickel were not adsorbed on these adsorbents. Grafting surface chemical moieties introduces heterogeneity on an otherwise uniform MCM-41 pore surface and metal adsorption is best described by the Freundlich adsorption model. A series of binary adsorption equilibrium studies with NH2-MCM-41 containing 2.2 mmol RNH2/g shows that NH2-MCM-41 adsorbs only gold from solutions containing copper and nickel with an adsorption capacity of 0.6 mol of Au/mol of RNH2 (1.1 mmol of Au/g of NH2-MCM-41). Copper and nickel were not adsorbed by NH2-MCM-41 regardless of the solution concentration, composition, and pH (i.e., 2 to 4) in the presence of gold. The LeVan and Vermeulen adsorption model based on a single component Freundlich isotherm and corrected for the anion effect accurately predicted the binary adsorptions. The adsorbed gold was completely recovered by a simple acid wash and the recovered gold solution is 99% pure. The regenerated NH2-MCM-41 remained 100% selective for gold removal and exhibited the same adsorption capacity even after several uses.     

Thermal equation for the adsorption of a binary gas mixture

Conclusions An equation proposed previously has been generalized to the case of the adsorption of binary gas mixtures. Based on this equation, the partial thermal equations of adsorption of the components of a mixture have been derived, and the critical parameters of the adsorbed phase have been calculated.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2418–2421, November, 1987.     

Molecular simulation of binary mixture adsorption in buckytubes and MCM-41

MCM-41 and buckytubes are novel porous materials with controllable pore sizes and narrow pore size distributions. Buckytubes are carbon tubes with internal diameters in the range 1–5 urn. The structure of each tube is thought to be similar to one or more graphite sheets rolled up in a helical manner. MCM-41 is one member of a new family of highly uniform mesoporous silicate materials produced by Mobil, whose pore size can be accurately controlled in the range 1.5–10 nm. We present grand canonical Monte Carlo (GCMC) simulations of single fluid and binary mixture adsorption in a model buckytube, and nonlocal density functional theory (DFT) calculations of trace pollutant separation in a range of buckytubes and MCM-41 pores. Three adsorbed fluids are considered; methane, nitrogen and propane. The GCMC studies show that the more strongly adsorbed pure fluid is adsorbed preferentially from an equimolar binary mixture. Ideal adsorbed solution theory (IAST) is shown to give good qualitative agreement with GCMC when predicting binary mixture separations. The DFT results demonstrate the very large increases in trace pollutant separation that can be achieved by tuning the pore size, structure, temperature and pressure of the MCM-41 and buckytube adsorbent systems to their optimal values.     

Liquid–solid helium interface: some conceptual questions

I raise, and discuss qualitatively, some conceptual issues concerning the interface between the crystalline solid and superfluid liquid phases of ⁴He emphasizing, in particular, the fact that the ground-state wave functions of the two phases are prima facie qualitatively quite different, in that the superfluid liquid phase possesses off-diagonal long-range order (ODLRO), while the crystalline solid does not. The fact that the statics and dynamics of the interface do not appear to be particularly sensitive to the presence of ODLRO in the liquid is tentatively explained by the fact that because of a subtlety associated with the Bose statistics obeyed by the atoms, the solid and liquid wave functions are not locally very different.     

Selective and sequential adsorption of bovine serum albumin and lysozyme from a binary mixture on nanosized magnetic particles

Magnetic particles about 10 nm in size were prepared by chemical precipitation under nitrogen and used for the selective and sequential adsorption of bovine serum albumin (BSA) (pI = 4.7) and lysozyme (LSZ) (pI = 1.1) under different conditions, such as pH and initial protein concentration. The separation ratio of BSA over LSZ at pH 4.6 is about 5, which is about 1.5 times the separation ratio of LSZ over BSA at pH 11.0. Only 10% of the preadsorbed BSA could be displaced by the sequential adsorption of LSZ at pH 11.0. On the other hand, 60% of the preadsorbed LSZ was desorbed due to the sequential adsorption of BSA at pH 4.6. Over 50% desorption of BSA or LSZ could be achieved either by 0.5 M Na(2)HPO(4) or 0.5 M NaH(2)PO(4) after 2 h. Over 80% of the enzymatic activity of LSZ was preserved when it was desorbed from magnetic particles.     

Prediction of adsorption of organic component and water vapour mixture onto activated carbon

A simple isotherm equation is derived for the adsorption of an organic component onto activated carbon in presence of water vapour. The theoretical results are compared with experimental data for toluene-water vapour-activated carbon, which were published byRipperger andGermerdonk [10].

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Vorhersage der Adsorption einer organischen Komponente und Wasserdampf an Aktivkohle

Zusammenfassung Es wird eine einfache Adsorptionsisotherme abgeleitet, welche die gleichzeitige Adsorption eines organischen Stoffes und Wasser an Aktivkohle beschreibt. Die theoretischen Ergebnisse werden mit experimentellen Resultaten vonRipperger undGermerdonk [10] für Toluol-Wasser-Aktivkohle verglichen.

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Symbols a _i adsorbate concentration in adsorbent, kg/kg of carbon - a _0i monolayer capacity, kg/kg of carbon - b _i kinetic parameter of theLangmuir equation - E _j adsorption energy in thej-th layer - i i-th component (1 — water vapour, 2 — organic compound) - j j-th layer - m number of layers - n number of adsorbed components - p partial pressure, Pa - p* saturation partial pressure, Pa - p _C water vapour partial pressure at begining of capillary condensation, Pa - surface coverage     

The remarkable reaction of N2O with a binary component lanthanide oxide mixture

The interaction of N2O with a Sm2O3-PrO(2-x) mixed oxide proceeds via the unexpected production of a new bulk phase that has been tenatively assigned to a new cis-hyponitrite compound.     

Effect of a third component on the interactions in a binary mixture determined from the fluctuation theory of solutions

The Kirkwood–Buff (KB) theory of solution is applied to a ternary mixture by deriving explicit expressions for the various Kirkwood–Buff integrals (KBIs) and the corresponding excesses of the number of molecules around central ones. However, the ideal solution should be considered non-aggregated, and the above expressions for the excesses provide non-zero values for such a case. For this reason, in order to obtain information about clustering one must subtract from the traditional excesses those which correspond to a reference state, thus ensuring that for an ideal mixture the excesses are zero. The expressions derived for the latter excesses have been applied to the investigation of the N,N-dimethylformamide–methanol–water mixture, to conclude that: (i) in the vicinity of the water molecules there are excesses of water and N,N-dimethylformamide molecules and a deficit of methanol molecules; (ii) in the vicinity of the methanol molecules there are excesses of methanol and N,N-dimethylformamide molecules and a deficit of water molecules; (iii) in the vicinity of the N,N-dimethylformamide molecules there are excesses of methanol and water molecules and a deficit of N,N-dimethylformamide molecules; (iiii) the excesses of N,N-dimethylformamide around water and methanol molecules and those around N,N-dimethylformamide are weakly dependent on the concentration of the third component in a large range of concentrations of the latter, and these results are compatible with the existence of N,N-dimethylformamide–water and N,N-dimethylformamide–alcohol complexes.     

Pervaporative separation of ethanol from an alcohol—ester quaternary mixture

As part of a research project focusing on the development of a sustainable biocatalytic process for production of chiral secondary alcohols, the pervaporative separation of ethanol from ethanol/ethyl acetate/1-methoxy-2-propanol/1-methoxy-2-propyl acetate-mixtures through a commercial PVA-based membrane was investigated. Separation behavior of this mixture was studied in a range of mol fractions (10–70%), temperatures relevant for biocatalytic conversions (35–55 °C) and downstream pressures (35–200 mbar).

Pervaporation of the non-diluted multicomponent mixture was shown to be strongly influenced by interactions between the permeants and the membrane. Investigation of these interactions contributed to the understanding of the mass transport mechanism of this mixture. Overall, high fluxes were obtained, but small differences between the fastest permeating species were found. The fastest permeating species was ethanol, ethyl acetate or 1-methoxy-2-propanol depending on the feed composition.     

Light scattering from a binary mixture with internal relaxation

The hydrodynamic modes of a binary liquid mixture are investigated for two cases: (1) the bulk viscosity contains a frequency dependent part, and (2) an additional internal variable is introduced. The consequences for the light scat- tering spectrum are discussed and comparisons are made with previous investigations by other authors.     

Electric field-induced component dynamics in a binary liquid crystal mixture studied using two-dimensional Raman scattering

The intermolecular interactions in a mixed, binary liquid crystal system are probed using two-dimensional Raman scattering. The sample is a 50/50 by weight blend of 4-pentyl(4-cyanophenyl)cyclohexane (PCH5) and 4-methoxybenzylidene-4-butylaniline (MBBA). The response of the Raman anisotropy of the individual components to step voltages is identical. Furthermore, cross correlation analysis of oscillatory electric field experiments shows only synchronous reorientation between the two constituents. Since neat MBBA aligns perpendicular and neat CH5 aligns parallel to the applied field, the data imply strong intermolecular interactions. Additionally, as previously observed for PCH5, frequency sweep experiments indicate that the flexible parts of the molecules can reorient independently of the rigid cores.     

Chromatographic study of adsorption from binary and ternary solutions

Adsorption of benzene, anisole, and nitrobenzene on hydroxylated silica gel from binary and ternary solutions (adsorbate--n-hexane and adsorbate--n-hexane--terahydrofuran) was studied by HPLC. The equation that describes the adsorbate retention as a function of its concentration in binary and ternary solutions was proposed. The equation makes it possible to calculate the adsorption isotherms and adsorption equilibrium constants directly from chromatograms using the retention parameters and equilibrium concentrations of the adsorbate in the mobile phase.     

Modelling adsorbent heterogeneity for adsorption from binary liquid mixtures

It is demonstrated that the detailed structure of the surface energy or selectivity distribution function is not critical to obtaining adequate analytical expressions for surface excess isotherms for adsorption from binary liquid mixtures on heterogeneous adsorbents. The gamma and the uniform selectivity distribution functions, which are very different in form, were successfully used in conjunction with the monolayer-pore filling model for adsorption on a homogeneous site to describe adsorption of various binary liquid mixtures on silica gel. Both models described the salient features of the surface characteristics of the silica gel.