Separation of zinc(II) from europium(III) by using hollow fiber membrane

Extraction and separation of Eu3+ and Zn2+ in sulfuric acid solution was investigated by hollow fiber membrane with cyanex 302 (bis (2,4,4-trimethylpentyl) monothiophosphinic acid) in counter-currently circulating operation. Reaction mechanism of membrane extraction and effect of extractant concentration and H+ concentration in aqueous phase on the mass transfer coefficient were discussed. It can be concluded that Zn2+ can be extracted completely from Eu3+ sulfate solution according to the kinetics competing difference. In one extractor process, extraction percentage of Zn2+ was not completely and Eu3+ was not extracted. Extraction percentage of Zn2+ reached 94.92%, but Eu3+ only reached 8.59% after 100 minutes extraction in two series connectors and that of Zn2+ and Eu3+ reached 99.9% and 6.53% respectively after 40 minutes extraction in three series connectors.

The effect of KSCN on the partition of proteins in polyethylene glycol/(NH4)(2)SO4 aqueous two-phase system

The effect of potassium thiocyanate on the partitioning of lysozyme and BSA in polyethylene glycol 2000/ammonium sulfate aqueous two-phase system has been investigated. As a result of the addition of potassium thiocyanate to the PEG/ammonium sulfate system, the PEG/mixed salts aqueous two-phase system was formed. It was found that the potassium thiocyanate could alter the pH difference between the two phases, and, thus, influence the partition coefficients of the differently charged proteins. The relationship between partition coefficient of the proteins and pH difference between two phases has been discussed. It was proposed that the pH difference between two phases could be employed as the measurement of electrostatic driving force for the partitioning of charged proteins in polyethylene glycol 2000/ammonium sulfate aqueous two-phase system.

Mixing enthalpy and phase behavior of PEO/PVAc blends

Phase behaviors and heats of mixing of the miscible blends of poly(ethylene oxide) (PEO) and poly(vinyl acetate) (PVAc) with different molecular weights were investigated by DSC. A method proposed by Natasohn and Ebert et al. was adopted to estimate the binodal temperatures and the enthalpies of mixing from onset temperatures and values of areas of a series of endothermic peaks (corresponding to heats of demixing), respectively, in their heating scanning thermograms obtained with different heating rates. Phase diagrams and heats of mixing of this blending system were also predicted by using Sanchez-Lacombe lattice fluid theory. A very good agreement was obtained for both. phase behaviors and heats of mixing obtained with two different methods.

Separation of Th4+ and RE3+ with hollow fiber extraction

Separation of Th4+ and RE3+ was investigated by hollow fiber membrane extraction with N1923 in countercurrent recirculating operation. The effect of Hf concentration in aqueous phase and flow rates of aqueous and organic phases on mass transfer coefficient was tested. Then the extraction of Th4+ from RE sulfate obtained from Baotou ore was carried out. The results obtained show that the mass transfer coefficient of Th4+ changes with the flow rate of aqueous phase, but does not change with the flow rate of organic phase and H+ concentration in aqueous phase, which suggests that the mass transfer rate of Th4+ is controlled bg that in the water critical layer, The mass transfer rate of RE3+ does not change with the flow rate of water phase, changes a little with the flow rate of organic phase, and changes with H+ concentration, which suggests that the mass transfer rate is controlled by their reaction rate with N1923. Th4+ could be extracted completely in 8 h from RE sulfate solution of Baotou ore with relatively less extraction of RE3+. So the separation of radioactive element under the sealed condition could be done.

Novel morphology in ring-banded spherulites from single-phase mixtures of poly(epsilon-caprolactone) with poly(styrene-co-acrylonitrile)

Novel morphology of ring-banded spherulites in the surface of poly(epsilon-caprolactone)/poly(styrene-co-acrylonitrile) (PCL/SAN) blends was discovered and studied by SEM and TEM. The ring-banded spherulites separate into those exhibiting a very dark contrast, of relatively regular bundles of lamellae and others appearing with a much brighter intensity, of a coarse and irregular aggregates of lamellae. The origin of the novel morphology is not due to different crystalline structures as in the case of isotactic polypropylene because only one crystal structure exists in PCL/SAN blends. The formation may reflect whether spherulites in PCL/SAN blends are nucleated at the bottom surface or at the top (free) surface.

A study of ion kinetic energy spectrometry of o(-), m(-), and p(-) diol benzene doubly charged ions and singly charged ions in gas phase

With Mass Analyzed Ion Kinetic Energy Spectrometry (MIKES), Collisional Induced Dissociation(CID), and Electron Capture Induced Decomposition(ECID) technigues, the doubly charged ions and singly charged ions from o(-), m(-), and p(-) diol benzene in the EI source have been studied. In terms of the values of the kinetic energy releases(T) of the charge separation reactions of the doubly charged ions and the estimated intercharge distances(R) of the exploding doubly charged ions the transition structures were proposed. Some structural information about the transition states was also obtained. It is of interest that the MIKES/CID spectra of singly charged ions [C6H6O2](+) from the three isomers are of significant differences.

Rheological studies on the phase dissolution in a block copolymer

The microphase transition in a styrene-butadiene-styrene triblock copolymer was studied by rheometric mechanical spectroscopy. A high-temperature-melt rheological transition from the highly elastic, nonlinear viscous behavior typical of a multiphase structure to linear viscous behavior with insignificant elasticity typical of a single-phase structure was observed. The transition temperature is determined according to the discontinuity of the rheological properties across the transition region, which agrees well with the results obtained from the small angle X-ray scattering data and the expectation of the random phase approximation theory. Maybe for the first time, microphase dissolution was investigated theologically. The storage modulus (G') and the loss modulus (G '') increase with time during the process. An entanglement fluctuation model based on the segmental density fluctuations is presented to explain the rheological behavior in this dissolution process. (C) 1997 John Wiley & Sons.

Study of semicrystalline-amorphous diblock copolymers .1. Microphase separation, glass transition and crystallization of tetrahydrofuran methyl methacrylate diblock copolymers

The microphase separation, glass transition and crystallization of two series of tetrahydrofuran-methyl methacrylate diblock copolymers (PTHF-b-PMMA), one with a given PTHF block of M(n) = 5100 and the other with a given PTHF block of (M) over bar(n) = 7000, were studied in this present work. In the case of solution-cast materials, the microphase separation of the copolymer takes place first, with crystallization then gradually starting in the formed PTHF microphase. The T-g of the PMMA microphase shows a strong dependence on the molecular weight of the PMMA block, while the T-g of the PTHF microphase shows a strong dependence on the copolymer composition. The non-isothermal crystallization temperature (T-c) of the diblock copolymer decreases rapidly and continuously with the increase in the amorphous PMMA weight fraction; the lowest T-c of the copolymer is ca. 35 K lower than the T-c of the PTHF homopolymer. There also exists a T-c dependence on the molecular weight of the PTHF block. In addition, when the major component of the copolymer is PMMA, a strong dependence of the crystallizability of the copolymer on the molecular weight of the PTHF block is observed; the higher the molecular weight, then the stronger its crystallizability. The melting temperature of the block copolymer is dependent on the copolymer composition and the molecular weight of its crystallizable block. Copyright (C) 1996 Elsevier Science Ltd.

Compositional dependence of the microphase separation transition in styrene-butadiene-styrene triblock copolymer/polystyrene blends

The change in the microphase separation transition (MST) temperature of a styrene-butadiene-styrene (SBS) triblock copolymer induced by the addition of polystyrene (PS) was investigated by small-angle X-ray scattering. It was found that the transition temperature was determined from the molecular weight (M(H)) Of the added PS in relation to that of the corresponding blocks (M(A)) in the copolymer. The MST temperature decreased with added PS if M(H)/M(A) < 1/4, while it increased with added PS when M(H)/M(A) > 1/4 Analysis of the theoretical expression based on the random phase approximation showed exactly the same tendency of change in the transition temperatures as that observed experimentally. The interaction parameter, chi(SB), obtained by nonlinear fitting of the scattering profiles of SBS/PS blends in the disordered state, was found to be a function of temperature and composition. Composition fluctuations were found to exist in SBS/PS blends, increasing with increasing addition of PS but diminishing with increasing molecular weight of the added PS.

Phase behavior in mixtures of a homopolymer and a block copolymer .4. SALS and SAXS studies

Phase behavior of blends of poly(vinyl methyl ether) (PVME) with four styrene-butadienestyrene (SBS) triblock copolymers, being of various molecular weights, architecture, and compositions, was investigated by small-angle light scattering. Small-angle X-ray scattering investigation was accomplished for one blend. Low critical solution temperature (LCST) and a unique phase behavior, resembling upper critical solution temperature (UCST), were observed. It was found that the architecture of the copolymer greatly influenced the phase behavior of the blends. Random phase approximation theory was used to calculate the spinodal phase transition curves of the ABA/C and BAB/C systems; LCST and resembling UCST phase behavior were observed as the parameters of the system changed. Qualitatively, the experimental and the theoretical results are consistent with each other. (C) 1996 John Wiley & Sons, Inc.

Chromatographic separation and C-13 NMR characterization of aromatic diester-diacids isomers

Reverse phase high performance liquid chromatography (HPLC) was used to separate and quantify aromatic diester-diacids isomers which arise from the opening selectivity of anhydride rings towards methanol. C-13 NMR spectroscopy was a supplementary tool to characterize the isomer structure. It was found that a meta-position attack is slightly preferred in pyromellitic dianhydride (PMDA), while the preferred position of an attack in bridged dianhydrides is determined by the chemical nature (donors or accepters) of the bridged group. The stronger its electron-withdrawing abilities, the lower the probability of a meta-position attack.

SIMULTANEOUS DETERMINATION OF GUANINE, URIC-ACID, HYPOXANTHINE AND XANTHINE IN HUMAN PLASMA BY REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH AMPEROMETRIC DETECTION

A reversed-phase high-performance liquid chromatographic method with amperometric detection is described for the separation and quantification of uric acid, guanine, hypoxanthine and xanthine. The isocratic separation of a standard mixture of the compounds was achieved in 5 min on a Spherisorb 5 C-18 reversed-phase column, with a mobile phase of NaH2PO4 (300 mmol dm(-3) pH 3.0)-methanol-acetonitrile-tetrahydrofuran (97.8 + 0.5 + 1.5 + 0.2). Uric acid, guanine, hypoxanthine and xanthine were completely separated, with detection limits in the range 2-20 pmol per injection. The effect of pH and the composition of the mobile phase on the separation are described. The hydrodynamic voltammograms of these compounds were recorded at a glassy carbon electrode. The linear range of the calibration graph for each compound was: uric acid; 1-5000 mu mol dm(-3); guanine, 0.5-2000 mu mol dm(-3); hypoxanthine, 0.1-500 mu mol dm(-3) and xanthine, 0.5-5000 mu mol dm(-3). The within- and between-day precision was good. The uric acid and hypoxanthine content in human plasma was measured using the proposed method. Good recoveries of uric acid (97.9-103%), hypoxanthine (98.0-99.2%), guanine (96.0-98.3%) and xanthine (96.0-102%) were obtained from human plasma. The results of electrochemical detection were in good agreement with those of UV detection.

UNIMOLECULAR DISSOCIATION REACTIONS OF DOUBLY-CHARGED IONS [C12H12N2O](2+) AND [C12H12N2S](2+) IN GAS-PHASE

The unimolecular dissociation reactions of doubly charged ions were reported, which resulted from a tandem mass spectrometer and a reversed geometry double focusing mass spectrometer by electron impact, Mass analyzed ion kinetic energy spectrometry (MIKES) was used to obtain the kinetic energy releases in charge separation reactions of doubly charged ions, The intercharge distances between the two charges at transition states can be calculated from the kinetic energy releases, Transition structures of unimolecular dissociation reactions were infered from MIKES and MS/MS.

PHASE-BEHAVIOR IN MIXTURES OF A HOMOPOLYMER AND A BLOCK-COPOLYMER .1. FTIR AND DSC STUDIES

Miscibility in blends of three styrene-butadiene-styrene and one styrene-isoprene-styrene triblock copolymers containing 28%, 30%, 48%, and 14% by weight of polystyrene, respectively, with poly(vinyl methyl ether) (PVME) were investigated by FTIR spectroscopy and differential scanning calorimetry (DSC). It was found from the optical clarity and the glass transition temperature behavior that the blends show miscibility for each kind of triblock copolymers below a certain concentration of PVME. The concentration range to show miscibility becomes wider as the polystyrene content and molecular weight of PS segment in the triblock copolymers increase. From the FTIR results, the relative peak intensity of the 1100 cm-1 region due to COCH3 band of PVME and peak position of 698 cm-1 region due to phenyl ring are sensitive to the miscibility of SBS(SIS)/PVME blends. The results show that the miscibility in SBS(SIS)/PVME blends is greatly affected by the composition of the copolymers and the polystyrene content in the triblock copolymers. Molecular weights of polystyrene segments have also affected the miscibility of the blends. (C) 1995 John Wiley & Sons, Inc.