Influence of isooctanol on the interfacial activity and mass transfer of ytterbium(III) using 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester as an acidic extractant

BACKGROUND: Introducing an adduct into an extractant system is an effective method of improving extraction performance. The effect of additives upon extraction is very important, especially in the case of interfacial behaviour. In most work published in the literature, there is little data on the interfacial behaviour of extractants and modifiers. As the mass transfer must pass through an interface, the influence of isooctanol on the interfacial activity and mass transfer of ytterbium(III) using 2-ethylhexylphosphonic acid mono-2-ethlhexyl ester has been investigated.RESULTS: With increasing amounts of isooctanol, the interfacial tension and surface excess (Gamma(max)) of the 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester(HEHEHP)-isooctanol system decreased, and the area of the absorbed HEHEHP molecule (Amin) increased. The interfacial activity of the HEHEHP-isooctanol system varied significantly depending on ionic strength and temperature and the mass transfer flux decreased with increasing isooctanol content.

Interfacial activity of sec-nonylphenoxy acetic acid and kinetics of yttrium extraction

The interfacial behavior of sec-nonylphenoxy acetic acid (CA-100) at various diluents/(H, Na)Cl interfaces was examined using the Du Nouy ring method. Different adsorption isotherms such as the Gibbs and Szyszkowski were in good agreement with the experimental data. The values of interfacial excess at saturated interface increase in the following order: n-heptane > kerosene > cyclohexane > CCl4 > toluene > benzene > chloroform. The effects of temperature, acidity, and ionic strength of the aqueous phase on the interfacial activity of CA- 100 were also examined. The interfacial-activity data were used to discuss the mechanism and kinetics of yttrium (Y) extraction.

Interfacial behavior of primary amine N1923 and the kinetics of thorium(IV) extraction in sulfate media

The influences of additive, diluents, temperature, acidity of the aqueous phase on the interfacial behavior of primary amine N1923 in sulfate media have been investigated using the Du Nouy ring method. In addition, the effect of concentration of thorium(IV) loaded in the organic phase on the interfacial tension has also been studied. The interfacial tension isotherms are processed by matching different adsorption equations such as the Gibbs and the Szyszkowski. The surface excess at the saturated interface (Gamma (max)) and the minimum bulk concentration of the extractant necessary to saturate the interface (C-min) under different conditions are calculated according to two adsorption equations to be presented in comprehensive tables and figures. It appears that primary amine N1923 has strong interfacial activity and behaves very differently in various diluents systems. The surface excess at saturated interface increase with the type of diluerits in the following order: chloroform < aromatic hydrocarbons < aliphatic hydrocarbons. The relationship between the interfacial activity and kinetics of thorium extraction by primary amine N1923 has been discussed by considering different factors. However, the interfacial activity of primary amine N1923 is only a qualitative parameter suggesting the interfacial mechanism for thorium extraction, it cannot give strong evidence quantitatively supporting this mechanism.

Interfacial behavior of DEHEHP and the kinetics of cerium(IV) extraction in nitrate media

The effects of diluents, temperature, acidity, and ionic strength of the aqueous phase on the interfacial properties of DEHEHP have been extensively investigated using the Du Nouy ring method. In addition, the effect of cerium(IV) concentration loaded in the organic phase on the interfacial tension has also been studied. With the increase of DEHEHP concentration, the value of interfacial tension (gamma) decreases in the studied system, which shows that DEHEHP has interfacial activity as a kind of surfactant. The surface excess at the saturated interface (Gamma(max)) and the minimum bulk concentration of the extractant necessary to saturate the interface (C-min) under the different conditions are calculated according to two adsorption equations such as the Gibbs and Szyszkowski functions to be presented in comprehensive tables and figures. The relationship between the interfacial activity of DEHEHP and cerium(IV) extraction kinetics by DEHEHP has been discussed by considering different factors such as the effects of diluents and temperature. However, the interfacial activity parameter of extractant only is a qualitative parameter, but cannot provide strong enough evidence to quantitatively explain the relationship between extraction kinetics and interfacial properties of an extractant.

Mass transfer kinetics of yttriium(III) using a constant interfacial cell with laminar flow. Part I. Extraction with Cyanex 302

The interfacial tension is measured for Cyanex 302 in heptane and adsorption parameters are calculated according to Gibbs equation and Szyskowski isotherm. The results indicate that Cyanex 302 has a high interfacial activity, allowing easy extraction reaction to take place at the liquid-liquid interface. The extraction kinetics of yttrium(III) with Cyanex 302 in heptane are investigated by a constant interfacial cell with laminar flow. The effects of stirring rate, temperature and specific interfacial area on the extraction rate are discussed. The results suggest that the extraction kinetics is a mixed regime with film diffusion and an aqueous one-step chemical reaction proposed to be the rate-controlling step. Assuming the mass transfer process can be formally treated as a pseudo-first-order reversible reaction with respect to the metal cation, the rate equation for the extraction reaction of yttrium(III) with Cyanex 302 at pH <5 is obtained as follows:R-f = 10(-7.85)[Y(OH)(2)(+)]((a))[H(2)A(2)]((o))(1.00)[H+]((a))(-1.00)Diffusion parameters and rate constants are calculated through approximate solutions of the flux equation.

Interfacial self-assembly of a bacterial hydrophobin

The majority of bacteria in the natural environment live within the confines of a biofilm. The Gram-positive bacterium Bacillus subtilis forms biofilms that exhibit a characteristic wrinkled morphology and a highly hydrophobic surface. A critical component in generating these properties is the protein BslA, which forms a coat across the surface of the sessile community. We recently reported the structure of BslA, and noted the presence of a large surface-exposed hydrophobic patch. Such surface patches are also observed in the class of surface-active proteins known as hydrophobins, and are thought to mediate their interfacial activity. However, although functionally related to the hydrophobins, BslA shares no sequence nor structural similarity, and here we show that the mechanism of action is also distinct. Specifically, our results suggest that the amino acids making up the large, surface-exposed hydrophobic cap in the crystal structure are shielded in aqueous solution by adopting a random coil conformation, enabling the protein to be soluble and monomeric. At an interface, these cap residues refold, inserting the hydrophobic side chains into the air or oil phase and forming a three-stranded β-sheet. This form then self-assembles into a well-ordered 2D rectangular lattice that stabilizes the interface. By replacing a hydrophobic leucine in the center of the cap with a positively charged lysine, we changed the energetics of adsorption and disrupted the formation of the 2D lattice. This limited structural metamorphosis represents a previously unidentified environmentally responsive mechanism for interfacial stabilization by proteins.

Extraction and separation of cadmium(II), iron(III), zinc(II), and europium(III) by Cyanex302 solutions using hollow fiber membrane modules

The mass transfer behaviors of Cd(II), Fe(III), Zn(II), and Eu(III) in sulfuric acid solution using microporous hollow fiber membrane (HFM) containing bis(2,4,4-trimethylpentyl)monothiophosphinic acid (commercial name Cyanex302) were investigated in this paper. The experimental results showed that the values of the mass transfer coefficients (K-w) decreased with an increase of H+ concentration and increased with an increase of extractant Cyanex302 concentration. The mass transfer resistance of Eu3+ was the largest because K-w value of Eu3+ was the smallest. The order of mass transfer rate of metal ions at low pH was Cd > Zn > Fe > Eu. Mixtures of Zn2+ and Eu3+ or of Zn2+ and Cd2+ were well separated in a counter-current circulation experiment using two modules connected in series at different initial acidity and concentration ratio. These results indicate that a hollow fiber membrane extractor is capable of separating the mixture compounds by controlling the acidity of the aqueous solution and by exploiting different mass transfer kinetics. The interfacial activity of Cyanex302 in sulfuric acid solution was measured and interfacial parameters were obtained according to Gibbs adsorption equation.

Morphology, tensile strength and thermal behavior of isotactic polypropylene/syndiotactic polystyrene blends compatibilized by SEBS copolymers

The effects of three triblock copolymers of poly [styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) of different molecular weight (MW) on the morphology, tensile strength and thermal behavior of isotactic polypropylene/syndiotactic polystyrene (iPP/sPS, 80/20) blend are investigated. Morphology observation shows that both the medium MW and the lower MW SEBS are more effective than the higher MW SEBS in compatibilizing the blends. Tensile tests revels both the medium and low MW compatibilizer lead to a significant improvement in tensile strength, while the higher MW compatibilizer is efficient in increasing the elongation at break of the blends. The localization of compatibilizers in the blends is observed by mean of SEM and the correlation between the distribution of the compatibilizers and mechanical properties of the blends is evaluated. The mechanical properties of the iPP/sPS blends depend on not only the interfacial activity of the compatibilizers but also the distribution of the compatibilizer in the blend. Addition of the compatibilizers to the blend causes a remarkable decrease in the magnitude of the crystallization peak of sPS at its usual T-c. Vicat softening points demonstrate that the heat resistance of iPP/sPS blend is much higher than that of the pure iPP.

Compatibilization effects of block copolymers in high density polyethylene/syndiotactic polystyrene blends

Three triblock copolymers of poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) of different molecular weights and one diblock copolymer of poly[styrene-b-(ethylene-co-butylene)] (SEB) were used to compatibilize high density polyethylene/syndiotactic polystyrene (HDPE/sPS, 80/20) blend. Morphology observation showed that phase size of the dispersed sPS particles was significantly reduced on addition of all the four copolymers and the interfacial adhesion between the two phases was dramatically enhanced. Tensile strength of the blends increased at lower copolymer content but decreased with increasing copolymer content. The elongation at break of the blends improved and sharply increased with increments of the copolymers. Drop in modulus of the blend was observed on addition of the rubbery copolymers. The mechanical performance of the modified blends is strikingly dependent not only on the interfacial activity of the copolymers but also on the mechanical properties of the copolymers, particularly at the high copolymer concentration. Addition of compatibilizers to HDPE/sPS blend resulted in a significant reduction in crystallinity of both HDPE and sPS. Measurements of Vicat softening temperature of the HDPE/sPS blends show that heat resistance of HDPE is greatly improved upon incorporation of 20 wt% sPS.

Mass transfer of Er(III) between HBTMPTP dissolved in n-heptane and HAc-NaAc

The rate of extraction of Er(III) from aqueous acetate solutions at 0. 2 mol/L ionic strength by HBTMPTP in n-heptane was studied by using a constant interfacial area cell with laminar flow at (30+/- 0. 5)degrees C. The interfacial activity of HBTMPTP was investigated at n-heptane/0. 2 mol/L (H, Na)Ac (pH=5. 00) interface, The rate of Er(III) extraction was measured at different chemical compositions by varying hydrogen ion, HBTMPTP, Cyanex 302 and chlorine ion concentrations, The effect of stirring speed, temperature and special interfacial area on the rate of extraction was also studied. The results showed that, under the conditions of the experiments, the overall rate is diffusion controlled, that the impurities of Cyanex 302 have the effect of synergistic extraction.

Preparation of the HIPS/MA graft copolymer and its compatibilization in HIPS/PA1010 blends

The graft copolymer of high-impact polystyrene (HIPS) grafted with maleic anhydride (MA) (HIPS-g-MA) was prepared with melt mixing in the presence of a free-radical initiator. The grafting reaction was confirmed by infrared analyses, and the amount of MA grafted on HIPS was evaluated by a titration method. 1-5% of MA can be grafted on HIPS. HIPS-g-MA is miscible with HIPS. Its anhydride group can react with polyamide 1010 (PA1010) during melt mixing of the two components. The compatibility of HIPS-g-MA. in the HIPS/PA1010 blends was evident. Evidence of reactions in the blends was confirmed in the morphology and mechanical behavior of the blends. A significant reduction in domain size was observed because of the compatibilization of HIPS-g-MA in the blends of HIPS and PA1010. The tensile mechanical properties of the prepared blends were investigated, and the fracture surfaces of the blends were examined by means of the scanning electron microscope. The improved adhesion in a 15% HIPS/75% PA1010 blend with 10% HIPS-g-MA copolymer was detected. The morphology of fibrillar ligaments formed by PA1010 connecting HIPS particles was observed. (C) 1999 John Wiley & Sons, Inc.

Effect and mechanism in compatibilization of poly(styrene-b-2-ethyl-2-oxazoline) diblock copolymer in poly(2,6-dimethyl-1,4-phenylene oxide) poly(ethylene-ran-acrylic acid) blends

The compatibilization effect of poly(styrene-b-2-ethyl-2-oxazoline) diblock copolymer, P(S-b-EOx), on immiscible blends of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and poly(ethylene-co-acrylic acid) (EAA) is examined in terms of phase structure and thermal, rheological and mechanical properties, and its compatibilizing mechanism is investigated by Fourier-transform infrared spectroscopy. The block copolymer, synthesized by a mechanism transformation copolymerization, is used in solution blending of PPO/EAA. Scanning electron micrographs show that the blends exhibit a more regular and finer dispersion on addition of a small amount of P(S-b-EOx). Thermal analysis indicates that the grass transition of PPO and the lower endothermic peal; of EAA components become closer on adding P(S-b-EOx), and the added diblock copolymer is mainly located at the interface between the PPO and EAA phases. The interfacial tension estimated by theological measurement is significantly reduced on addition of a small amount of P(S-b-EOx). The tensile strength and elongation at break increase with the addition of the diblock copolymer for PPO-rich blends, whereas the tensile strength increases but the elongation at break decreases for EAA-rich blends. This effect is interpreted in terms of interfacial activity and the reinforcing effect of the diblock copolymer, and it is concluded that the diblock copolymer plays a role as an effective compatibilizer for PPO/EAA blends. The specific interaction between EAA and polar parts of P(S-b-EOx) is mainly hydrogen bonding. (C) 1998 Elsevier Science Ltd. All rights reserved.

Switchable biosensor controlled by biocatalytic process

The poly(dimethylamino methacrylate) (PDMAEMA) brush-modified indium tin oxide (ITO) electrode was used to test the switch properties of interfacial activity caused by bioelectrochemical signals. The swelling of the polymer brushes increased when the medium's pH changed from alkaline to acid after glucose was added to the system. A pH change generated in situ by means of biocatalytic reactions enabled bioelectrocatalytic interface's reversible activation. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Estudo da formação de domínios em bicamadas lipídicas induzidos por peptídeos antimicrobianos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Neue Methoden zur Darstellung von Blockcopolymeren unter Beteiligung radikalischer Polymerisationsmechanismen

Im Rahmen dieser Dissertation wurden die Synthese und die Charakterisierung verschiedener, zum Teil neuartiger Blockcopolymere beschrieben, wobei die Einbeziehung radikalischer Polymeri-sationsmechanismen den konzeptionellen Kern ausmachte. Mit einer auf die jeweilige Kombination von Monomeren zugeschnittenen Syntheseroute gelang die Verknüpfung von Segmenten, die allein mittels der herkömmlich zur Synthese von Blockcopolymeren genutzten, ionischen Mechanismen nur mit hohem Aufwand oder gar nicht zu verbinden sind. Auf materieller Seite stand die Herstellung amphiphiler Strukturen im Vordergrund. Diese wurden entweder direkt beim Aufbau der Blockcopo-lymere oder nach anschließender polymeranaloger Umsetzung eines ihrer Segmente erhalten. Solche amphiphilen Substanzen besitzen aufgrund ihrer Grenzflächenaktivität Anwendungspotential z. B. als Stabilisatoren in der Dispersionspolymerisation oder als Flokkulantien. Es wurden drei Verfahren zum Aufbau von Blockcopolymeren untersucht:1. Die Transformation von anionischer zu freier radikalischer Polymerisation für die Synthese von Polystyrol-b-poly(N-vinylformamid) (PS-b-P(VFA)).2. Die Transformation von anionischer zu kontrollierter radikalischer Polymerisation (ATRP) für den Aufbau von Blockcopolymeren aus Poly(dimethylsiloxan) PDMS und Segmenten von t-Butylacrylat (t-BuA) bzw. (2-(Trimethylsiloxy)ethyl)methacrylat (TMS-HEMA).3. Die kontrollierte radikalische Polymerisation unter Einsatz von Triazolinyl als Gegenradikal zur Synthese von Poly[(2-(trimethylsiloxy)ethyl)methacrylat]-b-polystyrol (P(TMS-HEMA)-b-PS) als alternative Route zur anionischen Polymerisation.