Chemical interactions between aqueous and organic phases in a reactive extraction process

Partitioning of lactic acid between aqueous phase and kerosene containing trin-octyl phosphine oxide (TOPO) as a reactive agent was measured and analyzed in terms of an association model between lactic acid and TOPO. Equilibrium association was calculated to involve 1.1 mol of lactic acid/mol of TOPO.³¹P-NMR and FTIR analyses found no evidence of covalent bond formation between lactic acid and TOPO in solutions in kerosene, and pointed to hydrogen bond formation between the two chemicals. In a hydrophobic, microporous, hollow-fiber-membrane module, the simultaneous presence of lactic acid, TOPO, and the back-extractant NaOH resulted in drastic membrane fouling as evidenced by the loss of kerosene flux through the membrane. The membrane could be restored back to the original kerosene flux after extensive washing.

     

A method for measuring infinite-dilution partition coefficients of volatile compounds between the gas and liquid phases of aqueous systems

Vejrosta, J., Novák, J. and Jönsson, J.Å., 1982. A method for measuring infinite-dilution partition coefficients of volatile compounds between the gas and liquid phases of aqueous systems. Fluid Phase Equilibria, 8: 25–35.A method has been developed for measuring the partition coefficients of volatile compounds between the gas and liquid phases of aqueous systems, based on the direct analysis of both phases. A gas mixture containing a known proportion of a volatile compound is drawn through the liquid (water) until equilibrium is established. A defined volume of the liquid phase is then withdrawn through a porous-polymer trap while maintaining the system at equilibrium. The residual water in the trap is then expelled by a stream of nitrogen gas, and the deposit remaining is thermally desorbed and analyzed by gas chromatography. This approach, together with an experimental technique for producing gas mixtures containing an accurately known concentration of hydrocarbon at low values, makes it possible to determine accurately the partition coefficients of low-solubility compounds, such as for hydrocarbons in aqueous systems, at very low solute concentrations in the system. The method has been verified by measuring the partition coefficient of hexane between the gas and liquid phases of an aqueous system at various concentrations and temperatures.     

Features of the distribution of dicarboxylic acids between organic and aqueous phases

Water-organic distribution constants are determined for oxalic, succinic, and glutaric acids. The constants can be related to the physicochemical characteristics of extractants by linear many-parameter equations that account for the ability of the extractants to specific and nonspecific solvation; therewith, the most important factor is basicity.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 8, 2004, pp. 1306–1312.Original Russian Text Copyright © 2004 by Makitra, Vasyutyn, Polyuzhin.This revised version was published online in April 2005 with a corrected cover date.     

Thermodynamics of the partition of 8-quinolinol between several organic solvents and aqueous buffers

The partition coefficients of 8-quinolinol between water and benzene, nitrobenzene, toluene and chloroform have been determined as a function of temperature, and values of DeltaH and DeltaS determined for each. Values of the dissociation constant for protonated 8-quinolinol are reported as a function of temperature.     

Solute partition study in aqueous sodium dodecyl sulfate micellar solutions for some organic reagents and metal chelates

The partition constants (K _d) have been estimated for nitrophenols, thiazolylazo dyestuffs and metal chelate compounds into the sodium dodecyl sulfate (SDS) micellar phase at an ionic strength of 0.10M [(H⁺, Na⁺)Cl^–] and at 20 °C. The equilibrium partition data obtained by batch-wise solution spectrophotometry (equilibrium shift method) agree well with those by the micellar electrokinetic capillary chromatography (MECC) with the SDS micellar pseudo-stationary phase. The MECC clearly discriminates a very small difference (0.03) in the logK _d values of some metal chelates. The plot of theK _d values with the van der Waals volume of the solute molecules obviously shows the leveling-off of theK _d values over solute size near 110 ml/mol, which seems to be consistent with the results obtained in the Triton X-100 micellar system. This phenomenon arises most probably from the rigidity of the micellar pseudo-phase (a micellar volume-constraint effect) in sharp contrast with true two-phase partitioning such as solvent extraction systems.     

Temperature-induced transport of thermosensitive hairy hybrid nanoparticles between aqueous and organic phases

This paper reports on the temperature-induced transport of thermosensitive polymer brush-grafted silica nanoparticles between aqueous and organic phases. Poly(methoxytri(ethylene glycol) methacrylate), a thermosensitive water-soluble polymer with a cloud point of approximately 48 degrees C in H2O, was grown on silica nanoparticles by surface-initiated atom transfer radical polymerization in the presence of a free initiator. These hairy particles were found to quantitatively transfer from aqueous to ethyl acetate phases upon heating at 60 degrees C under the stirring condition. Cooling in an ice/water bath caused the particles to move from ethyl acetate to the aqueous layer. The concentrations of the particles in the original phases during the transport processes were monitored by UV-vis spectrometry. When mutually saturated water and ethyl acetate were used, the transport rates of the particles between the two phases were enhanced. The faster transport was attributed to the solvent phase separation, which produced liquid droplets, dramatically increased the interfacial area, and hence facilitated the transport of the particles. The reversible transfer of the particles between the aqueous and ethyl acetate phases upon heating at 60 degrees C and cooling in an ice/water bath can be repeated consecutively at least 10 times. The hairy particles can also be quantitatively transported from 1-butanol and toluene to H2O by stirring in an ice/water bath. However, only 60% of the particles transferred from water to 1-butanol and no particles to toluene upon heating at 60 degrees C. The reasons are discussed.     

A new apparatus for the extraction of organic compounds from aqueous solutions

A new apparatus for the extraction of organic compounds from sea water is described. With this apparatus it is possible to extract 54 standard compounds with high recovery percentages from 9 1 of sea water with 3 ml ofn-hexane. The analysis time (about 1 h) is appreciably lower than those of the extraction methods based on RP-18 and Carbopack-B adsorption (about 15 h). Furthermore, it is possible to analyze samples without filtration. An application of this method to the analysis of Tirreno sea water is reported.     

Deposition of small organic molecules by the displacement of two immiscible supercritical phases

A new coating process is described (deposition from two immiscible supercritical phases, or DISP) in which a solution of supercritical carbon dioxide (scCO2) with a desired solute is displaced by supercritical helium (scHe). After depressurization, the solute is deposited on substrates initially submerged in the coating solvent. Micron-sized particles and thin films of sucrose octaacetate (SOA) were formed on silicon wafer substrate coupons from DISP at relatively low temperatures and pressures (< or = 6500 psi and < or = 60 degrees C). The particle size, film thickness, and morphology of SOA were characterized as a function of coating conditions-solution concentrations, withdrawal velocities, and pressures. Particles in the range of 1-14 microm in diameter were deposited at low solute concentrations (< or = 0.2 wt % at 4500 psi), whereas films in the range of 0.1-0.5 microm in thickness were deposited at higher solute concentrations (> or = 1.5 wt % at 4500 psi). Particle sizes decreased with increasing displacement velocity and increasing pressure. Estimates of characteristic times for diffusion and nucleation indicate that DISP is a diffusion-limited process. Optical microscopy and atomic force microscopy (AFM) were used to characterize film morphology, including defect formations and film roughness. Highly uniform films with low root-mean-square (RMS) roughness (approximately 10 angstroms) were obtained at a low displacement velocity of 0.0035 cm/s, while ring-like defect structures were observed in films deposited at a higher displacement velocity of 0.035 cm/s. The film thickness and morphology of the films deposited from DISP were compared with films from normal dip coating with typical organic solvents (acetone and toluene). Films deposited from scCO2 by DISP were much thicker, more uniform, and exhibited much fewer drying defects and lower RMS roughness compared with films from the organic solvents.     

Distribution of metal chelates between aqueous and surfactant phases separated from a micellar solution of a nonionic surfactant

A dilute micellar solution of poly(oxyethylene) 4-nonylphenyl ether with oxyethylene units 7.5 (PONPE-7.5) was separated into two phases (aqueous and surfactant phases) at room temperature. The partition constants of several chelating reagents and their metal chelates between the two phases were determined at 293 K and ionic strength 0.1 (NaClO₄). The partition constants of the neutral metal chelates depend on the kind of metal ions and were considerably smaller than those expected from the regular solution theory. These facts suggested that the chelates were incorporated into a hydrocarbon environment in the surfactant phase, whereas the chelating reagents were distributed in the poly(oxyethylene) part of PONPE-7.5. A brief review was also presented on the analytical applications to the extraction of metal ions and organic compounds.     

Calculations on partition equilibria in liquid-liquid extraction systems,applied to the separation of metal ions from aqueous solutions

A program has been developed for the calculation of partition equilibria in the case when metal ions are extracted from an aqueous phase into an immiscible organic solvent containing a chelating reagent. Given the extraction constants and the initial concentrations, titration curves are constructed which show the extraction percentage of each ion in the presence of the others. The program is applied to hypothetical situations both in activation analysis and isotope dilution analysis.     

Substoichiometry for multielement separation by metal chelate extraction and its application in activation analysis

The method of substoichiometric separation is completed for radioactivity measurements using special nuclear measurement methods in a way that along with the substoichiometric extraction of a given metal the simultaneous quantitative separation of other metals can also be effected. Some general relationships have been derived for the substoichiometric multielement separation of MA _m -type metal chelates. Particularly, the primary dithizonates of silver and copper(II) have been studied, and the application of the method is demonstrated by the separation of silver and copper from cobalt.     

Selectivity assessment of a sequential extraction procedure for metal mobility characterization using model phases

This study considers the selectivity of the extractants used in a sequential extraction scheme for metals mobility assessment by analyzing individual mineral phases previously coprecipitated or sorbed with trace metals. The scheme evaluated was a modification of the Tessier et al. [A. Tessier, P.G.C. Campbell, M. Bisson, Anal. Chem. 51 (1979) 844] sequential procedure proposed by the authors. The phases studied were calcite, amorphous iron oxide, hausmannite, humic acid, kaolinite and illite. Selective extractions were obtained for As, Cr, Cu, Ni, Pb and Zn in metal-coprecipitated phases whereas NH(2)OH-HCl was not selective for the extraction of Hg and Cd coprecipitated in hausmannite and amorphous iron oxide, respectively. Otherwise, Cd, Hg, Ni and Zn sorbed on the different phases were released with MgCl(2) and NaOAc/HOAc, but stronger reagents were needed to release As, Cr, Cu and Pb.     

A self-assembled supramolecular organic material for selective extraction of uranium from aqueous solution

Journal of Radioanalytical and Nuclear Chemistry - A supramolecular organic material MA-IPA containing melamine and isophthalic acid was prepared by low-temperature hydrothermal reaction, with an...     

Density of organic phases in the extraction system tributyl phosphate-phosphoric acid

Data on the density of phosphoric acid solutions in crude TPB and TBP-based commercial extractant for purification of wet-process phosphoric acid are tabulated over the phosphoric acid concentration range 0.62–27.74 wt% (recalculated to P₂O₅).     

A method for enlarging the Kerr constant of polymer-stabilised blue phases

Polymer-stabilised blue phase (PSBP) is one of the most promising materials for display devices because of its superior electro-optical properties compared with conventional nematics. However, the application of the PSBP has a serious practical issue in that the driving voltage required is too high to drive with thin film transitors, that is, the magnitude of the Kerr constant of PSBPs is insufficient. We present a useful method for increasing the Kerr constant based on the control of polymer aggregation structure using a cross-linker with a chiral structure. The director distortion arising from polymer networks in the PSBP seems to be responsible for the resulting improvement.     

In-tube extraction for enrichment of volatile organic hydrocarbons from aqueous samples

In-tube extraction (ITEX) is a novel solventless extraction technique in which a headspace syringe with a needle body filled with a sorbent (here: Tenax TA) is used. The analytes are extracted from sample headspace by dynamic extraction. The needle body is surrounded by a separate heater, which is used for thermal desorption of analytes into the injection port of a GC system. We report here for the first time the optimization and evaluation of a fully automated analytical method based on ITEX. As target analytes, 19 common groundwater contaminants such as halogenated volatiles and monoaromatic compounds have been chosen. Method related parameters such as extraction temperature, number of extraction cycles, extraction and desorption volume as well as extraction and desorption flow rates were investigated in detail. The linear dynamic range of the ITEX method ranged over six orders of magnitude between 0.028 microg/L and 1218 microg/L with linear correlation coefficients between 0.990 and 0.998 for the investigated compounds. Method detection limits for monoaromatic compounds were between 28 ng/L (ethylbenzene) and 68 ng/L (1,2,4-trimethylbenzene). For halogenated volatile organic compounds, method detection limits between 48 ng/L (chloroform) and 799 ng/L (dichloromethane) were obtained. The precision of the method with external calibration was between 3.1% (chloroform ethylbenzene) and 7.4% (1,2,3-trimethylbenzene).