Search results for "Two-phase"
showing 10 items of 98 documents
Aqueous nonionic copolymer-functionalized laponite clay. A thermodynamic and spectrophotometric study to characterize its behavior toward an organic …
2006
The affinity of functionalized Laponite clay toward an organic material in the aqueous phase was explored. Functionalization was performed by using triblock copolymers based on ethylene oxide (EO) and propylene oxide (PO) units that are EO(11)PO(16)EO(11) (L35) and PO(8)EO(23)PO(8) (10R5). Phenol (PhOH) was chosen as organic compound, which represents a contaminant prototype. To this purpose, densities and enthalpies of mixing as well as PhOH UV-absorption spectra were determined. The enthalpy and the spectrophotometry revealed PhOH-Laponite interactions whereas the volume did not. It emerged that the area occupied by PhOH on the Laponite surface is equal to that computed from the partial m…
ZrO2SiO2 mixed oxides: surface aspects, photophysical properties and photoreactivity for 4-nitrophenol oxidation in aqueous phase
1996
Abstract Mixed oxides of ZrO2 and SiO2 were synthesized by a sol-gel technique by using zirconyl chloride and commercial silica gel as starting materials. The paper reports some surface features of the powders and the photoreactivity results obtained in the oxidation of 4-nitrophenol in aqueous suspensions of powdered photocatalyst. The optical characterization of the suspension was also performed by measuring the photon flows reflected and absorbed by the reacting system. The photoactivity exhibited by the ZrO2SiO2 samples is very scarce especially if compared with that shown by a TiO2 sample tested at equal experimental conditions. The low photoreactivity can be justified on the basis of…
Synthesis of 3-substituted isoindolin-1-ones via a tandem desilylation, cross-coupling, hydroamidation sequence under aqueous phase-transfer conditio…
2015
A simple and expedient method for the synthesis of 3-methylene-isoindolin-1-ones 4 under aqueous phase-transfer conditions has been developed. Starting from 2-iodobenzamides 1 and (silyl) alkynes, the products are obtained in high yields and short reaction times (30 min) with the use of inexpensive CuCl/PPh3 catalyst system in the presence of n-Bu4NBr (TBAB) as a phase-transfer agent. Terminal alkynes are conveniently "unmasked" upon in situ desilylation under the reaction conditions. Alkynes possessing heterocyclic moieties were also found as amenable substrates. Furthermore, a one-pot process starting from 2-iodobenzamides 1, aryl halides (bromides or iodides) and trimethylsilylacetylene …
Aqueous two-phase system cold-set gelation using natural and recombinant probiotic lactic acid bacteria as a gelling agent
2016
The present study aimed to entrap probiotic lactic acid bacteria (LAB) in a sodium alginate and sodium caseinate aqueous two-phase gel system. The natural acidifying properties of two therapeutic probiotic LAB were exploited to liberate calcium ions progressively from calcium carbonate (CaCO3), which caused the gelation of the co-existing phases. Bi-biopolymeric matrix gelation of GDL/CaCO3 or LAB/CaCO3 was monitored by dynamic rheological measurements, and the final gels were characterized by frequency dependence measurements and confocal laser scanning microscopy. Weak to strong gels were formed with an elastic modulus G' from 10 to 1.000Pa, respectively. After cold-set gelation of our sy…
Dimensional analysis and upscaling of two-phase flow in porous media with piecewise constant heterogeneities
2004
Dimensional analysis of the traditional equations of motion for two-phase flow in porous media allows to quantify the influence of heterogeneities. The heterogeneities are represented by position dependent capillary entry pressures and position dependent permeabilities. Dimensionless groups quantifying the influence of random heterogeneities are identified. For the case of heterogeneities with piecewise constant constitutive parameters (e.g., permeabilities, capillary pressures) we find that the upscaling ratio defined as the ratio of system size and the scale at which the constitutive parameters are known has to be smaller than the fluctuation strength of the heterogeneities defined, e.g.,…
Hydrodynamics of a co-current three-phase solid-bed reactor for foaming systems
2001
The objective of the present study was to evaluate the parameters, which characterize the pulsing flow of the gas and liquid through a bed, namely the frequency of pulsation, the velocity of the pulses and the pulse structure, for foaming systems. The paper presents the results of experiments aimed at determining the effect of the foaming power and the surface tension of liquid phase on the values of the measured parameters.
Incorporation of Pd nanoparticles in mesostructured silica
2009
Monodisperse Pd nanoparticles were prepared by controlled reduction in organic phase and subsequent transfer to aqueous phase. A systematic study was carried out to finely tune nanoparticle size and optimize particle size distribution. The use of 4-dimethylaminopyridine as a transfer agent allowed for the easy and quantitative extraction of the Pd to the aqueous phase. The quaternary amine-functionalized metal nanoparticles were then used as metallic micelle replicas to grow silica around them. This novel and facile metal incorporation method provided an excellent dispersion and homogeneity of Pd nanoparticles on silica supports. In addition, cationic surfactants, such as cetyltrimethylammo…
Electrodeposition methods in superheavy element chemistry
2008
To prepare electrodeposition experiments with superheavy elements (SHE), their homologs were investigated. In the experiments, various electrode materials and electrolytes were used. Critical potentials (E crit ) where the electrodeposition starts and potentials for the deposition of 50% of the atoms in solution (E 50% ) were determined. Underpotential deposition was observed in most cases. An electrolytic cell for a fast electrochemical deposition was developed and the time for the deposition of 50% of the atoms in solution (t 50% ) was determined. Short lived α-emitting isotopes were produced at Gesellschaft fur Schwerionenforschung (GSI), Darmstadt, transferred to the aqueous phase with …
Liquid–liquid equilibria in the system H3PO4–KCl–H2O–tri-n-butyl phosphate: experiments and modelling
2004
Abstract The liquid–liquid equilibria of the system H3PO4–KCl–H2O–TBP was studied experimentally in the concentration range 0–6 mol/kg. The obtained data were modelled using the Pitzer equation for the aqueous phase and the Sergievskii–Dannus relationship for the organic phase. A fairly good agreement was observed between the model and the experimental data.
Eucalyptol-based green extraction of brown alga Zonaria tournefortii
2018
Abstract A green extraction method, based on the use of 1,8-cineole (eucalyptol) as biosolvent, has been developed to prepare crude extracts from the brown alga Zonaria tournefortii characterized by chemical composition, particularly dominated by phenolic compounds derived from phloroglucinol. The main advantage of the developed technique are the recovery of eucalyptol, based on multistep liquid-liquid extraction with distilled water, followed by centrifugation and elimination of the aqueous phase, and the complete recycling of biosolvent by steam distillation. A comparative study between the proposed green extract and the conventional extract, prepared by solvent maceration using the mixtu…