Ganzuo Li

A cyclic voltammetric technique for the detection of micro-regions of bmimPF6/Tween 20/H2O microemulsions and their performance characterization by UV-Vis spectroscopy

As green solvents, ionic liquids (ILs) can be substitutes for traditional organic solvents, and form useful microemulsions with water. Microemulsions consisting of the IL, 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6), the non-ionic surfactant Tween 20 and water were formed at 30.0 °C, and the phase behavior of the ternary system was investigated. Three regions of the microemulsions: water-in-bmimPF6 (W/IL), bicontinuous, and bmimPF6-in-water (IL/W) were identified by cyclic voltammetry using potassium ferrocyanide K4Fe(CN)6 as an electroactive probe. The polarity of the microemulsion environment was investigated by UV-Visible spectroscopy using methyl orange as a probe. Use of the ionic compound K3Fe(CN)6 in UV-Visible measurements revealed that the bmimPF6/Tween 20/H2O microemulsions could solubilize salt species into the microemulsion droplets. Moreover, the solubilization of riboflavin in the microemulsions was also shown by UV-Visible spectra. These results show that these IL-based microemulsions have potential in the production of metal nanomaterials, in biological extractions or as solvents for enzymatic reactions.

Formation of Water‐in‐CO2 Microemulsions with Non‐fluorous Surfactant Ls‐54 and Solubilization of Biomacromolecules

The solubility of Ls-54 surfactant in supercritical CO(2) was determined. It was found that the surfactant was highly soluble in SC CO(2) and the water-in-CO(2) microemulsions could be formed, despite it being a non-fluorous and non-siloxane nonionic surfactant. The main reasons for the high solubility and formation of the microemulsions may be that the surfactant has four CO(2)-philic groups (propylene oxide) and five hydrophilic groups (ethylene oxide) and its molecular weight are relatively low. The results of this work provide useful information for designing CO(2)-soluble non-fluorous and non-siloxane surfactants. The phase behavior of the CO(2)/Ls-54/H(2)O system, solvatochromic probe study, and the UV spectrum of lysozyme proved the existence of water domains in the SC CO(2) microemulsions. The method of synchrotron radiation small-angle X-ray scattering was used to obtain the structural information on the Ls-54 based water-in-CO(2) reverse micelles. By using the Guinier plot (ln I(q) versus q (2)) on the data sets in a defined small q range (0.022-0.040 A(-1)), the radii of the reverse micelles were obtained at different pressures and molar ratio of water to surfactant, W(0), which were in the range of 20.4-25.2 A.

An experimental study on alkaline/surfactant/polymer flooding systems using nature mixed carboxylate

Abstract The orthogonal-test-design method was used to determine the optimal formula by phase behavior and transient interfacial tension (IFT) studies, respectively. The results indicate the major components are cheap, naturally mixed carboxylate SDC (0.5%), alkaline NaHCO 3 /Na 2 CO 3 weight ratio of 1 (1.0%), and HAPM (1000 mg dm −3 ). In the coreflood experiment, their oil recovery will be increased by a factor of 25.2 and 26.8% the original oil in place (OOIP).

Studies on cetyltrimethylammonium bromide (CTAB) micellar solution and CTAB reversed microemulsion by ESR and 2H NMR

Abstract ESR spectroscopy was used in this study to monitor the aggregation behavior of cationic surfactant [cetyltrimethylammonium bromide (CTAB) in aqueous solution by measuring the rotational correlation time τ of a nitroxide labeled fatty acid probe (5-doxyl stearic acid) as a function of the surfactant concentration. The critical micelle concentration (CMC) of CTAB micelle in aqueous solution was obtained. The CMC value of CTAB micelle solution obtained by ESR spectroscopy is in good accordance with that obtained by the surface tension method. ESR studies on CTAB/n-butanol/octane/H2O reversed microemulsion showed that the probe motion becomes more anistropic with increase in water content W 0 = [ H 2 O ] t [ CTAB ] t . From 2H NMR spectra it is concluded that the free water content becomes larger with increase in W0, and five water molecules are tightly bound to one CTAB molecule.

CURRENT TERTIARY OIL RECOVERY IN CHINA

I . Introduction 2. Microemulsion/Polymer Flooding 2.1 General Situation of the L Reservoir of Laojunmiao Oil Field 2.2 Properties of Fluid in the Reservoir 2.3 Sodium Petroleum Sulfonate 2.4 Study of Optimum Flooding Fornulation 2.5 Pseudo-tertiary Diagram of YM-3A 2.6 Phase Behavior and Synergism among the Compositions of YM-3A 2.7 Study of Adsorption Losses of Petroleum Sulfonate and the Inhibitor 2.8 Study of Matching Property between Surfactant Flooding System and Polymer Solution 2.9 Oil-Displacing Test of MicroemulsionPolymer in Physical Model 3. PolymerFlooding 3.1 Polymer Solution Behavior 3.2 Thickening Property

pH-induced spontaneous vesicle formation from NaDEHP

Abstract A new pH-induced vesicle composed of single surfactant, sodium bis-(2-ethyl hexyl) phosphate (NaDEHP), was prepared. Spontaneous vesicles form by varying the initial pH value from 6.0 to 3.0 in the NaDEHP aqueous solution which has been demonstrated by negative-staining transmission electronic microscopy (TEM) and dynamic light scattering (DLS) methods. The monodispersity of the vesicle system is quite well and the polydispersities are almost lower than 0.10. The vesicle formation is the consequence of charged and uncharged surfactant molecules coexisting at a certain pH values that form dimers through hydrogen bond, which have the appropriate geometry structure to engender bilayer vesicle.

Effect of benzyl alcohol on the rheological properties of CTAB/KBr micellar systems

Abstract The effect of benzyl alcohol on the rheological properties of cetyltrimethylammonium bromide (CTAB)/potassium bromide (KBr) micellar systems has been investigated. The addition of the alcohol induces the viscosity of 0.01 mol l−1 CTAB/KBr micellar system to go through a marked maximum. These results have been discussed in terms of 1H-NMR spectra of CTAB molecules in the aqueous systems included benzyl alcohol and KBr salt. It is argued that benzyl alcohol will be located in the interfacial region of CTAB/KBr micelles and promotes these micelles to be bigger with lower concentration of alcohol. This process makes the viscosity of the system rise. With increasing alcohol content continuously, it will be solubilized in the palisades of the micelles and induce these worm-like micelles to be transformed into rod and spherical ones.

Kinetic studies of lipase-catalyzed esterification in water-in-oil microemulsions and the catalytic behavior of immobilized lipase in MBGs

Abstract The esterification kinetics of octanoic acid with 1-octanol, catalyzed by Candida lypolytical (CL) lipase, was studied in water-in-oil microemulsions formed by water/bis-(2-ethylhexyl)sulfosuccinate sodium (AOT)/isooctane. Kinetic studies showed that the reaction follows a Ping-Pong Bi Bi mechanism with inhibition by excess of 1-octanol. The values of all apparent kinetic parameters were determined to be vmax=4.7×10−3 mmol l−1 min−1 mg−1, Km acid=49.3 mmol l−1, and Km alcohol=47.6 mmol l−1, respectively. CL lipase has also been immobilized in gelatin-containing AOT microemulsion-based organogels (MBGs) with retention of catalytic activity. These lipase-containing MBGs were proved to be a novel solid-phase catalyst for use in apolar organic solvents. The behavior of this novel, predominantly hydrophobic matrix as an esterification catalyst was also examined.

Determination of the first and second CMCs of surfactants by adsorptive voltammetry

Abstract The first and second critical micellar concentrations (CMCs) of sodium dodecylsulfate and cetyltrimethylammonium bromide were determined by adsorptive voltammetry with an electrochemical probe. The distribution of probe inside and outside the micelle at the second CMC was calculated. The electrode reaction mechanism of the probe on the hanging mercury drop electrode is also discussed.

Effect of Complexation on the Zeta Potential of Titanium Dioxide Dispersions

Abstract The present paper deals with the surface charge properties and the dispersion stability of an aqueous titania suspension. Generally the titania powder surface is negatively charged. The dispersion stability of TiO2 suspension is governed by the value of zeta potential. The zeta potential was measured as a function of barium acetate and zinc acetate concentrations, at pH 6.0, and the addition of electrolytes caused sharp decrease of surface charge. Ethylenediaminetetraacetic acid (EDTA) was used to chelate the bivalent metal ions, so that the charge of counterions was reduced. The complexation of bivalent counterions favors the increase of the negative zeta potential and the dispersion stability of aqueous TiO2 suspension.