Journal of Colloid And Interface Science (v.299, #1)


The physics of moving wetting lines by Terence D. Blake (1-13).
Scientists tend to think in terms of their most familiar models. It is not accidental that the earliest descriptions of the moving wetting line and its associated dynamic contact angle were in terms of displaced equilibria (chemists), friction (physicists) and viscous bending of the liquid–vapour interface (engineers and mathematicians). Each of these approaches has progressed since its inception, but, while each reflects a different facet of the underlying physical mechanism, and each offers at least a semi-empirical route to its description, none is complete. There is, as yet, no fully agreed treatment that is consistent with all three viewpoints and provides an effective basis for prediction—though at least one new hydrodynamic approach has emerged that goes some way in this direction. This paper seeks to offer a status report: to briefly review each of the current approaches, to illustrate their successes and limitations as revealed by experiment and simulation, and to suggest ways in which the different aspects of wetting dynamics might be investigated in the future.A review of our understanding of dynamic wetting, which surveys current approaches, illustrates their successes and limitations as revealed by experiment and simulation, and suggests future directions.
Keywords: Dynamic wetting; Contact angle; Hydrodynamics; Molecular dynamics; Coating;

A nonlinear parametric model for phenanthrene sorption by Philippe Blanc; Alain Saada; Philippe Baranger (14-21).
Two models for phenanthrene sorption prediction are discussed and checked against experimental data. The first model, based on a two-site Langmuir expression, displays too large uncertainties. The second is based on a modified Langmuir relation and provides a better description of the whole dataset. It includes an experimentally derived relation between the site maximal concentration and chemical parameters of the substrate: TOC amount and polarity index (O + N)/C. The model is tested against sorption isotherms of phenanthrene acquired with six different substrates. Calculated values display satisfying accordance with experimental data. Validity of the model is tested with an isotherm that does not belong to the set of data used for the regression, with good results. Some discrepancies may arise from analytical uncertainty and structural aspects not included within the model.Sorption reaction proceeds in two stages: (1) coating of the organic substrate, (2) sorption onto the absorbed phenanthrene molecules.
Keywords: Phenanthrene; PAH; Sorption; Langmuir; Isotherm;

The effects of an anionic (sodium 4-octylbenzenesulfonate, NaOBS) and a cationic (1-dodecylpyridinium chloride, DPC) surfactant on the detachment of colloidal hematite particles adhered to glass beads was studied using the packed column technique. Both additives induced particle removal at concentrations above those necessary for the reversal of charge either on particles or on beads, in order to induce a repulsion between interacting surfaces. The amount of detached hematite was substantially increased as the surfactant concentrations exceeded the corresponding critical micellization concentrations (CMC). Particle removal was shown to follow first order kinetics with two distinctively different rate constants. The value of the constant for rapid removal, k r , was substantially higher than that established in earlier studies for detachment of the same particles with NaOH solutions.
Keywords: Adhesion of particles; Hematite monodispersed; Particle removal; Surfaces in adhesion;

Surface complexation of Pb(II) on amorphous iron oxide and manganese oxide: Spectroscopic and time studies by Ying Xu; Thipnakarin Boonfueng; Lisa Axe; Sungmin Maeng; Trevor Tyson (28-40).
Hydrous Fe and Mn oxides (HFO and HMO) are important sinks for heavy metals and Pb(II) is one of the more prevalent metal contaminants in the environment. In this work, Pb(II) sorption to HFO (Fe2O3nH2O, n = 1 – 3 ) and HMO (MnO2) surfaces has been studied with EXAFS: mononuclear bidentate surface complexes were observed on FeO6 (MnO6) octahedra with Pb―O distance of 2.25–2.35 Å and Pb―Fe(Mn) distances of 3.29–3.36 (3.65–3.76) Å. These surface complexes were invariant of pH 5 and 6, ionic strength 2.8 × 10 −3 to 1.5 × 10 −2 , loading 2.03 × 10 −4 to 9.1 × 10 −3   mol Pb / g , and reaction time up to 21 months. EXAFS data at the Fe K-edge revealed that freshly precipitated HFO exhibits short-range order; the sorbed Pb(II) ions do not substitute for Fe but may inhibit crystallization of HFO. Pb(II) sorbed to HFO through a rapid initial uptake (∼77%) followed by a slow intraparticle diffusion step (∼23%) resulting in a surface diffusivity of 2.5 × 10 −15   cm 2 / s . Results from this study suggest that mechanistic investigations provide a solid basis for successful adsorption modeling and that inclusion of intraparticle surface diffusion may lead to improved geochemical transport depiction.EXAFS spectra and Fourier transform (magnitude and imaginary part) of Pb/HFO samples at pH 5 and IS 10−2 as a function of time at Pb LIII-edge. FT was performed over range 2.8–9.5 Å−1, fitted over range 0.45–3.58 Å. Dashed lines represent fits.
Keywords: Lead; Adsorption; Hydrous ferric oxide; Hydrous manganese oxide; Amorphous oxide; EXAFS; XANES; Intraparticle diffusion modeling;

Lectin–carbohydrate affinity measured using a quartz crystal microbalance by Kateryna Lebed; Andrzej J. Kulik; László Forró; Małgorzata Lekka (41-48).
The association of two molecules is described by two parameters, association equilibrium and association rate constants, which are characteristic for a given type of interaction. Usually, they are determined for interacting molecules dissolved in solution. However, for many applications one type of molecules is immobilized on a substrate, which may influence the binding kinetics. The studied complex of concanavalin A and carboxypeptidase Y belongs to the lectin–carbohydrate type of interaction involving the recognition of oligosaccharide moieties. The concanavalin A was immobilized on a gold electrode of quartz crystal, while carboxypeptidase Y was added to a buffer (Tris-buffered saline). The constants describing the association of the investigated molecules were determined on the basis of measurements performed using a quartz crystal microbalance in liquid. The obtained values were ( 0.59 ± 0.01 ) × 10 6  M −1 for the association equilibrium constant and ( 5.6 ± 0.1 ) × 10 4  M −1 s −1 for the association rate constant. The saturation binding experiment gave another value of the association constant, ( 2.7 ± 0.02 ) × 10 6  M −1 . The comparison of obtained values with previously published ones verifies that the molecule orientation and binding site accessibility for specific ligands could influence the association equilibrium constant value. The presented measurements demonstrate the ability of a quartz crystal microbalance to detect and to evaluate the association process occurring between molecules.
Keywords: Quartz crystal microbalance; Concanavalin A; Lectin–carbohydrate interaction; Association equilibrium constant;

The aim of the present study was to propose a simplified experimental–theoretical method for estimating the kinetic and thermodynamic parameters for the solid–liquid separation of pollutants by using kinetic studies with batch reactors, i.e., the removed quantity of dissolved ion as a function of time at different initial concentration. This method was applied to the removal of uranyl ion (UO2+ 2) from aqueous solutions onto synthetic manganese oxide (birnessite). The pseudo-second-order kinetics and one-site saturation models were proposed to fit the experimental and calculated data, the fitting parameters being estimated by nonlinear regression, using the least-squares method. For initial concentration range 0.2–11.8 μM, the results showed that the uranyl removal process in dispersed batch reactors can be efficiently modeled by the proposed models. Then, several kinetic and thermodynamic parameters were calculated, such as maximal removed quantity of uranyl, q r , max , half-removal time, t 1 / 2 , initial rate of uranyl-ion removal, v 0 , initial uranyl-removal coefficient, K, maximal rate of uranyl removal, v 0 , max , mass transfer coefficient, D transfer , equilibrium Langmuir constant, K L , and constant separation factor, K s . These parameters make it possible to demonstrate that the removal of U onto birnessite is favorable, and that the maximum surface coverage of the uranyl ions represents about 3% of vacant sites in the Mn layer.Removal of uranyl ion from aqueous solution onto synthetic manganese oxide.
Keywords: Removal; Uranyl ions; Manganese oxide; Pseudo-second-order kinetics; One-site saturation models; Batch reactors;

Three model proteins, bovine serum albumin, hen's egg lysozyme and bovine serum fibrinogen, were adsorbed from aqueous solution onto finely dispersed ceramic particles, namely different kinds of alumina and hydroxyapatite particles. The influence of adsorption on protein secondary structure was investigated. The FTIR spectroscopic findings were compared with the results of DSC measurements. In almost all cases it was found that adsorption results in destabilisation and structural loss of the bound protein. A decrease in transition enthalpy is correlated with a loss in α-helical structure, which seems to be the most sensitive structure on adsorption-induced rearrangements. A total collapse of structure in the adsorbed proteins was not determined on any ceramic surface. Some residual structure is always retained. Structural changes in the D- or E-domains of fibrinogen could be independently observed by two different calorimetric signals. The two techniques applied in the present study—micro-DSC and FTIR spectroscopy—can be concluded to provide complementary information on adsorption-induced structural changes on both the molecular (thermal stability, overall structure) and the sub-molecular level (secondary structure).The influence of adsorption on protein secondary structure is investigated by FTIR spectroscopy and micro-DSC on serum albumin, lysozyme and fibrinogen, adsorbed onto finely dispersed ceramic particles.
Keywords: Adsorption; Protein; Ceramic particles; FTIR; Differential scanning calorimetry; Structural changes;

Poly(ethylene oxide)s hydrophobically modified. Adsorption and spreading at the air–water interface by Angel Leiva; Marcela Urzúa; Ligia Gargallo; Deodato Radić (70-75).
A comparative study of spread and adsorbed monolayer of poly(ethylene oxide)s of different molecular weight hydrophobically modified with alkyl isocyanates of different length chain is reported. The modification of the polymer was carried out according to reported procedures. The polymers obtained were studied at the air–water interface by Langmuir isotherms for spread monolayers and by Gibbs isotherms for the adsorption process. Isotherms obtained are interpreted in terms of the hydrophobic and hydrophilic balance of the polymers. Limiting area per repeating unit ( A 0 ) and collapse pressure ( π c ) from spread monolayers were obtained. Spread monolayers of the hydrophobically modified polymers show larger collapse pressure values than unmodified polymer monolayers. In the adsorption process the excess surface concentration Γ ∞ , area per repeat unit σ, and efficiency of the adsorption were determined. The values of the area occupied per repeat unit in adsorbed monolayer (σ) were larger than those of the spread monolayer. The efficiency of the adsorption of poly(ethylene oxide)s increases with the hydrophobic modification and with the alkyl chain length.
Keywords: Biodegradable polymer; Air–water interface; Monolayer; Adsorption;

Acid mine drainage (AMD) has long been a significant environmental problem resulting from the microbial oxidation of iron pyrite in the presence of water and air, affording an acidic solution that contains toxic metal ions. The main objective of this study was to remove metal ions [Fe(II), Fe(III), Mn(II), Zn(II)] from AMD using lignite, a low-cost adsorbent. The lignite sorbent was utilized for the sorption of ferrous, ferric, manganese, zinc, and calcium ions in aqueous solutions. Studies were performed at different pH to find optimum pH. Equilibrium isotherms were determined to assess the maximum adsorption capacity of lignite for different metal ions. Sorption capacities were compared in single, binary, ternary, and multicomponent systems. The sorption data are correlated with Freundlich and Langmuir isotherms in each system. Both Freundlich and Langmuir isotherms fit the data reasonably well in terms of regression coefficients. Sorption studies were also performed at different temperatures to obtain the thermodynamic parameters of the process. The maximum lignite adsorption capacities at 25 °C were 34.22, 25.84, and 11.90 mg/g for Fe(II), Mn(II), and Fe(III), respectively. Adsorption of Fe2+ (24.70 mg/g at 10 °C and 46.46 mg/g at 40 °C) increased with increased temperature, while Mn2+ adsorption (28.11 mg/g at 10 °C and 7.70 mg/g at 40 °C) decreased with increased temperature.Lignite, a low cost sorbent was utilized for the remediation of various metal ions viz., ferrous, ferric, manganese in single, binary, and multicomponent aqueous systems in reference to acid mine drainage (AMD). The sorption capacity of this adsorbent is comparable/higher than adsorbents/carbons/biosorbents employed for the removal of Fe(II), Fe(III), and Mn(II) from water/wastewater/AMD. This study demonstrates the use of lignite as a value added adsorbent over its fuel value.
Keywords: Adsorption; Heavy metals; Adsorbent; Lignite; Acid mine drainage;

Adsorption of atrazine on soils: Model study by Ilias D. Kovaios; Christakis A. Paraskeva; Petros G. Koutsoukos; Alkiviades Ch. Payatakes (88-94).
The adsorption of the widely used herbicide atrazine onto three model inorganic soil components (silica gel, γ-alumina, and calcite (CaCO3) was investigated in a series of batch experiments in which the aqueous phase equilibrated with the solid, under different solution conditions. Atrazine did not show discernible adsorption on γ-alumina ( θ = 25 ° C , 3.8<pH<12.1) or calcite ( θ = 25 ° C , 7.7<pH<11.7). Significant and completely reversible adsorption from solutions was found for silica gel suspensions. The adsorption isotherms obtained for atrazine uptake on silica gel particles were best fitted with the Freundlich model. An increase of the ionic strength of the electrolytic solution induced an increase of the surface concentration of atrazine on silica gel, indicating significant electrostatic interactions between atrazine and silica gel particles, possibly through interaction with the surface silanol groups of the solid substrate. Increase of the pH value of the electrolyte solution from 6 to 9 considerably decreased the amount of atrazine adsorbed on the silica gel substrate. Decrease of the solution pH from 6 to 3 had only a slight effect on the surface concentration of the adsorbed atrazine. The adsorption of atrazine on silica gel increased when the temperature was decreased from 40 to 25 °C, an indication that the adsorption is exothermic. The calculated enthalpy of adsorption (∼10 kJ/mol) indicates that the uptake at the solid–liquid equilibrium pH (6.1) was largely due to physisorption.Adsorption of atrazine on silica surfaces at different ionic strength values.
Keywords: Atrazine; Adsorption from solution; Thermodynamics of adsorption; Adsorption isotherms; Silica; Alumina; Calcium carbonate;

Adsorption of 2,4,5-trichlorophenol (TCP) and picric acid (PA) by montmorillonite preloaded with crystal violet (CV) up to 80, 100, and 125% of the cation exchange capacity was studied. The adsorption isotherms indicated a strong interaction of TCP and PA with the organoclay. While the adsorption isotherms of both pollutants can be described by the Langmuir model with relatively good fit, the adsorption of TCP is more adequately described by the dual-mode model (DMM), which combines the Langmuir equation with a partition mechanism. Competitive adsorption experiments and adsorption experiments in water:ethanol mixed medium as a solvent confirmed the assumption that the removal of TCP from water by the organoclay follows two different mechanisms: site-specific adsorption occurs in the low concentration range, whereas a partition mechanism dominates the high concentration range. This double mechanism in organoclays exhibits both complete removal at low pollutant concentrations and high sorption capacity in the high concentration range, and therefore may be effective in water treatment for a wide range of pollution levels.Adsorption isotherm of TCP to M100 from: water (circles), water:ethanol 50:1 V/V (triangles) and water:ethanol 10:1 V/V (squares). Adsorption is strongly influenced by the composition of the solvent, indicating a partition mechanism with the sorbent.
Keywords: Adsorption; Organoclays; Langmuir equation; Dual-mode model;

Adsorption of nonionic surfactant micelles onto ultrafiltration (UF), membranes was studied. Two homologous series of nonionic surfactants, namely, Tritons (alkylphenol ethoxylates) and Neodols (alcohol ethoxylates), were used to characterize surface properties of two polymeric ultrafiltration membranes with 20,000 nominal cutoff. Particularly, a cellulose acetate and a polysulfone membrane were investigated. Static adsorption experiments were carried out using surfactant solutions at concentrations above their critical micelle concentration. The characterization of surface properties of UF membranes was based on the adsorption behavior of surfactant species. The adsorption extent on UF membranes was affected by the hydrophobicity-to-hydrophilicity ratio mainly determining the interactions developed at the membrane–surfactant species interface. Adsorption experimental data seem generally to fit the Langmuir isotherm model. Atomic force microscopy was used to examine the alteration of the top membrane surface morphology.Adsorption of nonionic surfactant micelles on ultrafiltration membranes (cellulose acetate and polysulfone) was investigated. Atomic force microscopy was used to examine the alteration of the top surface morphology.
Keywords: UF membrane; Surfactant; Adsorption; Interaction; AFM;

Granular activated carbon was used for the removal of 18-crown-6 from aqueous solution by adsorption. The influence of two experimental parameters, initial 18-crown-6 concentration and temperature, on the adsorption kinetics was evaluated. The kinetics data obtained were modeled by pseudo-first-order and pseudo-second-order models, respectively. The process of adsorption follows a pseudo-second-order rate model. The most important result of the present study is that the correlation coefficient is not a sufficient criterion for selection of a kinetic model, and therefore several criteria are suggested for its selection.
Keywords: Adsorption; Kinetics; 18-Crown-6; Pseudo-first-order; Pseudo-second-order; Granular activated carbon;

The removal of tannin from aqueous media by cationic surfactant-modified bentonite clay was studied in a batch system. The surfactant used was hexadecyltrimethylammonium chloride. Adsorbent characterizations were investigated using X-ray diffraction, infrared spectroscopy, surface area analysis, and potentiometric titration. The effects of pH, contact time, initial solute concentration, adsorbent dose, ionic strength, and temperature on the adsorption of tannin onto modified clay were investigated. The adsorbent exhibited higher tannin removal efficiency ( > 99.0 % ) from an initial concentration of 10.0 μmol/L at pH 3.0. Adsorption capacity decreased from 90.1 to 51.8% with an increase in temperature from 10 to 40 °C at an initial concentration of 25.0 μmol/L. The adsorption process was found to follow pseudo-first-order kinetics. Film diffusion was found to be the rate-limiting step. Tannin adsorption was found to decrease with increase in ionic strength. The tannin equilibrium adsorption data were fitted to Langmuir and Freundlich isotherm models, the former being found to provide the best fit of the experimental data. The maximum monolayer adsorption capacity for tannin was 69.80 μmol/g at 30 °C. Comparison of adsorption capacity of the modified clay with reported adsorbents in the literature was also presented. Adsorbed tannin on modified clay can be recovered by treatment with 0.1 M NaOH solution. Regeneration experiments were tried for four cycles and results indicate a capacity loss of < 10.0 % . From the results it can be concluded that the surfactant-modified clay could be a good adsorbent for treating tannin-contaminated waters.Surfactant-modified bentonite clay was developed, characterized, and utilized as an adsorbent for the removal of tannin from aqueous solutions. The effects of various operating variables on tannin adsorption were investigated.
Keywords: Organoclay; Bentonite; Tannin; Adsorption kinetics; Isotherm; Desorption;

A new titanium(IV) oxide–hectorite nanofilm photocatalyst was prepared on quartz slides. It was evaluated in the photooxidation of dibenzothiophene (DBT) in nonpolar organic solution (tetradecane), as a model for diesel fuel. A removal regimen was developed consisting of catalytic photooxidation followed by adsorption of products on silica gel. Photooxidation of DBT was performed with and without catalyst, at 254 and 300 nm. Comparison was made with a commercially available TiO2 catalyst, Degussa P25. The catalyst was analyzed by nitrogen adsorption, XRD, SEM, and TGA-DTA. DBT concentrations were measured by HPLC and UV spectrophotometry. Preliminary qualititative analysis of products was performed by UV and HPLC. Results indicated that the outlined process was effective in reducing sulfur levels to below 10 ppm sulfur.Changes in the color of DBT solutions exposed to photooxidation (2) and silica adsorption (3).
Keywords: Titanium oxide; Dibenzothiophene; Photooxidation; Desulfurization;

The extension of the Ψ function developed by Tóth from equilibria taking place at gas–solid interfaces to those taking place at liquid–solid interfaces was investigated. The results were applied to conventional liquid–solid systems used in reversed-phase liquid chromatography (RPLC). The adsorbents in these systems are made of porous silica having a hydrophobic solid surface obtained by chemically bonding C18 alkyl chains to a porous silica gel then endcapping the surface with trimethylsilyl groups. The liquid is an aqueous solution of an organic solvent, most often methanol or acetonitrile. The probe compound used here is phenol. Adsorption data of phenol were measured using the dynamic frontal analysis (FA) method. The excess adsorption of the organic solvent was measured using the minor disturbance (MD) method. Activity coefficients in the bulk were estimated through the UNIFAC group contributions. The results show that the Ψ function predicts 90% of the total free energy of immersion, ΔF, of the solid when the concentration of phenol is moderate (typically less than 10 g/L). At higher concentrations, the nonideal behavior of the bulk liquid phase becomes significant and it may contribute up to about 30% of ΔF. The high concentration of adsorbed molecules of phenol at the interface decreases the interfacial tension, σ, by about 18 mN/m, independently of the structure of the adsorbed phase and of the nature of the organic solvent.The calculation of the surface Gibbs free energy (●) at the silica-C18/methanol–water or C18-silica/acetonitrile–water interfaces versus the solute concentration in the solution using the experimental Tóth Ψ function previously defined and applied to gas–solid equilibria predicts accurately the true surface free energy (♦) at low concentrations and gives a fair estimate at high concentrations.
Keywords: Liquid–solid equilibrium; Integral isotherm equations; Gibbs equation; Free energy of the surface; Ψ function; Reversed-phase liquid chromatography; Adsorption isotherms; Measured isotherms; Frontal analysis; Minor disturbance method; Methanol–water liquid phase; Acetonitrile–water liquid phase; Silica-C18; Phenol;

Equilibrium and kinetics for the sorption of promethazine hydrochloride onto K10 montmorillonite by Gürhan Gereli; Yoldaş Seki; İ. Murat Kuşoğlu; Kadir Yurdakoç (155-162).
This study presents the adsorption of cationic drug, promethazine hydrochloride from aqueous solution onto K10 montmorillonite. The effects of pH and temperature on adsorption process were investigated. Maximum adsorption pH was obtained to be about 7.5. Thermodynamic parameters found in this study depict the exothermic nature of adsorption. The process was favorable and spontaneous. From kinetic studies, it was found that adsorption process obeyed the pseudo-second-order kinetic model. The Langmuir, Freundlich, Dubinin–Radushkevich (DR) models were applied to describe the equilibrium isotherms and the isotherm constants were determined. The fit of the Langmuir and DR models appeared to be good. Physisorption mainly controls the whole adsorption process but chemisorption also shows a particular contribution.Adsorption of promethazine hydrochloride from aqueous solution onto K10 montmorillonite was investigated as a function of ionic strength, pH and temperature.
Keywords: K10; Adsorption; Kinetic; Thermodynamic parameters; SEM;

Evaluation of zirconocene-based silica phases in organochloride pesticides preconcentration by Ana Maria Geller; Fernanda C. Stedile; Maria do Carmo R. Peralba; Tânia M. Pizzolato; João Henrique Z. dos Santos (163-171).
Silica was chemically modified with zirconocenes, namely Cp2ZrCl2, (MeCp)2ZrCl2, (iBuCp)2ZrCl2 and (nBuCp)2ZrCl2 by grafting. Hybrid silica bearing surface indene groups was synthesized by the sol–gel method, followed by metallation with ZrCl4⋅2THF. According to RBS measurements, metal content was 0.2–0.3 wt% Zr/SiO2 for the grafted systems and 4.5 wt% Zr/SiO2 for the phase prepared by the sol–gel method. The solid phases were evaluated in the adsorption/preconcentration of organochloride (hexachlorobenzene, lindane, heptachlor, heptachlor epoxide, dieldrin and endrin) pesticides from aqueous solution. For comparative reasons, commercial LC-18 phase was also evaluated. Analyte concentration was monitored by GC-ECD. For the grafted phases, the coordination sphere around the metal center seems not to influence the adsorption/desorption properties of these phases vis-à-vis the studied analytes. Recoveries results for both analytes were comparable to those observed in the case of LC-18 in the case of the phases prepared by the sol–gel method. Experiments using ZrO2 and ZrO2/SiO2 phases led to lower recovery results.Silica was chemically modified with Cp2ZrCl2, (MeCp)2ZrCl2, (iBuCp)2ZrCl2 and (nBuCp)2ZrCl2 by grafting. Hybrid silica bearing surface indene groups was synthesized by the sol–gel method, followed by metallation with ZrCl4⋅2THF. The solid phases were evaluated in the adsorption/preconcentration of organochloride pesticides from aqueous solution.
Keywords: Organochlorine compounds; Solid-phase extraction; Pesticides; Extraction methods; Silica;

This is the first of a two-part study focusing on a novel dispersion method which enables increasing the crystallization rate of polypropylene (PP) through the incorporation of nucleating agent HPN-68 into the molten polymer using a microemulsion as a nanovehicle. The cycle time for processing the PP is significantly reduced and thus the effectiveness of its production is increased. Our concept is based on creating an advantage in dispersion capability of the nucleator that is dissolved in a nanoreactor vehicle in comparison with its conventional introduction as a crystalline powder. The microemulsions were introduced to the target PP using a mixer. By the end of the mixing, when the water phase had evaporated, only the nucleator and the surfactant remained in the matrix. The microemulsion components that solubilized the HPN-68 were mineral oil, alcohol, surfactant, and water. DSC results showed a 24% improvement in nucleation efficiency of PP by this method. WAXS results showed that HPN-68 is a γ-nucleator. It causes polymorphism by significantly raising the γ-phase concentration in the PP. SEM results showed a four-fold decrease in the PP spherulite size due to the improved dispersion of HPN-68 within the matrix via microemulsion compared to conventional nucleator incorporation.This paper is the first part of a two-part study that focuses on a novel dispersion method which enables increasing the crystallization rate of polypropylene (PP) through the introduction of nucleating agent HPN-68 by microemulsion technology.
Keywords: Microemulsion; Nucleating agent; Solubilization; Phase diagram; Dispersion; Crystallization; Polypropylene; Copolymers;

Direct measurement of forces between a colloidal particle and a phospholipid bilayer by Jeffrey M. Sharp; Randolph S. Duran; Richard B. Dickinson (182-190).
Colloidal interaction forces between a silica particle and a solid-supported Langmuir–Schaefer phospholipid bilayer were directly measured using a gradient optical trap and evanescent wave light scattering. A small custom-built Langmuir trough was integrated with an optical trapping microscope to allow force measurements on a single particle within the subphase of the trough after the dip of the substrate was completed. The novel method allows the force measurements to be conducted without transferring the substratum across an air/water interface. The fluctuating particle position near the bilayer was tracked by evanescent wave light scattering to determine the deflection due to surface forces, and the relaxation time of particle fluctuations was measured to simultaneously determine the viscous forces. Measured equilibrium and viscous force–distance profiles of silica microspheres with diameters of 1 and 5 μm on bilayers of dipalmitoyl phosphatidyl choline (DPPC) were markedly different than force–distance on bare mica and DPPC monolayers under the same electrolyte conditions.A method is reported for direct measurement of colloidal forces on a phospholipid bilayer using an optical trap force transducer and evanescent-wave light scattering.
Keywords: Optical trap; Phospholipid bilayer; DPPC; Colloidal force measurement; Adhesion; Evanescent wave light scattering;

Study of electrolyte induced aggregation of gold nanoparticles capped by amino acids by Santosh Aryal; Remant Bahadur K.C.; Narayan Bhattarai; Chul Ki Kim; Hak Yong Kim (191-197).
This work reports the electrolyte induced aggregation of gold nanoparticles directly conjugated to amino acid by chemical reduction in aqueous solution. The study was focused on three different classes of amino acids depending on the nature of α substituent, viz. l-cysteine, l-leucine, and l-asparagine. The band broadening and the red shift of surface plasmon band with increase in flocculation parameter showed the aggregation of gold nanoparticles with increase in electrolyte concentration and decrease in pH as monitored by UV–visible spectrophotometer. The 1H NMR spectrum demonstrates that the sulfide bond of cysteine and α amino group of leucine and asparagine interact with nanoparticles surface. Furthermore, transmission electron microscope (TEM) and thermogravimetric analysis (TGA) were performed to characterize and to support the fate of stabilization of the gold nanoparticles by amino acid.This work reports the electrolyte induced aggregation of gold nanoparticles directly conjugated to amino acid by chemical reduction in aqueous solution. The study was focused on three different classes of amino acids depending on the nature of α substituent, viz. l-cysteine, l-leucine, and l-asparagine. The band broadening and the red shift of surface plasmon band with increase in flocculation parameter showed the aggregation of gold nanoparticles with increase in electrolyte concentration and decrease in pH as monitored by UV–visible spectrophotometer. The 1H NMR spectrum demonstrates that the sulfide bond of cysteine and α amino group of leucine and asparagine interact with nanoparticles surface. Furthermore, transmission electron microscope (TEM) and thermogravimetric analysis (TGA) were performed to characterize and to support the fate of stabilization of the gold nanoparticles by amino acid.
Keywords: Amino acid; Gold; Nanoparticles; Biomaterial; Surface modification;

Diffusion coefficients of water in Na-montmorillonite (Na-mon) suspensions have been determined by pulsed-field gradient spin–echo (PGSE) NMR spectroscopy for three directions (x, y, and z), where x and y mean the directions perpendicular to the static magnetic field, and z the direction parallel to it. Diffusion anisotropy was observed in the suspensions with Na-mon weight fractions of 0.63, 1.82, and 3.32%; i.e., the diffusivity of water in the z direction is faster than that in the x or y direction. The largest diffusion anisotropy of water was observed at the Na-mon fraction of 3.32%. However, diffusion anisotropy disappeared in the suspensions with Na-mon fraction more than 5.02%. The fast diffusivity in the z direction was slightly enhanced in a stronger static magnetic field (14.1 T). These results indicate that the platelike Na-mon particles are aligned with their platelike faces parallel to the static magnetic field of NMR. We also measured diffusion coefficients of water for the z direction in the temperature range from 24 to 85 °C. The plot of diffusion coefficients of water against reciprocal temperature showed a refraction point at 65 °C. This phenomenon explicitly means that the alignment is gradually relaxed at higher temperatures.Alignment of Na-montmorillonite particles in magnetic fields ( B 0 ) was revealed based on the diffusion anisotropy of water detected by pulsed-field gradient spin–echo (PGSE) NMR method.
Keywords: Montmorillonite; Diffusion anisotropy; PGSE NMR; Alignment; Magnetic field;

A rapidly convergent series for calculation of the interaction energies between two similar plane double layers for Na2SO4 type asymmetric electrolytes at positive surface potential was obtained by introducing a parameter λ into an elliptical integral. When the dimensionless surface potential is less or equal to 20, the number of the series terms required to obtain the interaction energies with six significant digits is not more than 2. The accurate numeral results were given and they can be used to check up the validity of approximate expressions obtained. The present results are also fit for CaCl2 type asymmetric electrolytes at negative surface potential. V z − z ′ and V ′ in the figure are the interaction energies of symmetric and Na2SO4 type asymmetric electrolytes at y > 0 , respectively. V z − z ′ must intersect V ′ at a certain ξ d . When ξ d is smaller, V ′ > V z − z ′ ; when ξ d is larger, V ′ < V z − z ′ . The difference value ( V − V z − z ′ ) increases with the increase of y 0 .
Keywords: Double layers; Interaction energies; Asymmetric electrolytes; Elliptical integral;

The flocculation behavior of poly(N-isopropylacrylamide) (pNIPAM) microgels containing polar ―(―OCH2CH2 ―)3 ―OH chains, incorporated by the copolymeric components (triethyleneglycol methacrylate, TREGMA), in aqueous NaCl solution was investigated. Determination of the critical flocculation temperatures (CFTs) and the critical flocculation concentrations (CFCs) of the microgels at 45 °C shows that polar ―(―OCH2CH2 ―)3 ―OH chains have different influence on the flocculation behavior of the microgels at temperatures below and above their volume phase transition temperatures (VPTTs). The flocculation of the microgels becomes more difficult with the increase of ―(―OCH2CH2 ―)3 ―OH chains below the VPTT. In contrast, the microgels flocculate more easily with more ―(―OCH2CH2 ―)3 ―OH chains above the VPTT. Preliminary investigation on the flocculation kinetics of the microgels further shows that ―(―OCH2CH2 ―)3 ―OH chains have different effects on the flocculation rate at temperatures below and above the VPTT. The flocculating rate of the microgels at 25 °C decreases with the increase of ―(―OCH2CH2 ―)3 ―OH chains. While the flocculation rate at 45 °C increases with the increase of ―(―OCH2CH2 ―)3 ―OH chains due to their enrichment on the surface of the microgels as a result of the temperature-induced volume-phase transition, which was verified by variable temperature 1H NMR spectroscopy. The polar ―(―OCH2CH2 ―)3 ―OH chains rich in the surface increase the attractive force between the microgels, promoting the flocculation.The effect of polar side chains, i.e., ―(―OCH2CH2 ―)3 ―OH, on the CFTs of the microgels in NaCl solutions from 0.02 to 1 M were investigated using turbidity method. The result shows that the CFTs of p(NIPAM-co-TREGMA) microgels increase with the increase of the polar side chains in the microgels, as the existence of the polar side chains strengthens the H-bonding between the microgels and water molecules, restrains the increase of the Hamaker constant of the microgels. As a result, the CFTs of the microgels increase with the increase of the polar side chains.
Keywords: Microgels; Flocculation; Temperature-sensitive; N-Isopropylacrylamide; Volume-phase transition;

Water-soluble CdSe and CdSe/CdS nanocrystals: A greener synthetic route by Da-Wei Deng; Jun-Sheng Yu; Yi Pan (225-232).
We report a new green synthetic route of CdSe and core–shell CdSe/CdS nanoparticles (NPs) in aqueous solutions. This route is performed under water-bath temperature, using Se powder as a selenium source to prepare CdSe NPs, and H2S generated by the reaction of Na2S―H2SO4 as a sulfur source to synthesize core–shell CdSe/CdS NPs at 25–35 °C. The synthesis time of every step is only 20 min. After illumination with ambient natural light, photoluminescence (PL) intensities of CdSe NPs enhanced up to 100 times. The core–shell CdSe/CdS NPs have stronger photoactive luminescence with quantum yields over 20%. The obtained CdSe NPs exhibit a favorable narrow PL band (FWHM: 50–37 nm) with increasing molar ratio of Cd/Se from 4:1 to 10:1 at pH 9.1 in the crude solution, whereas PL band of corresponding CdSe/CdS NPs is slightly narrower. The emission maxima of nanocrystals can be tuned in a wider range from 492 to 592 nm in water by changing synthesis temperature of CdSe core than those reported previously. The resulting new route is of particular interest as it uses readily-available reagents and simple equipment to synthesize high-quality water-soluble CdSe and CdSe/CdS nanocrystals.Absorption and photoluminescence spectra of CdSe (—) and CdSe/CdS (- - -) nanoparticle solutions. The strong luminescence of CdSe/CdS NPs can been observed with naked eye under normal indoor light without UV irradiation, which suggest that H2S generated by the reaction of Na2S―H2SO4 can be used as a sulfur source to prepare CdSe/CdS NPs.
Keywords: CdSe; CdSe/CdS; Water-soluble nanocrystals; A green synthetic route;

Effects of cleaning procedures of silica wafers on their friction characteristics by Bogdan C. Donose; Elena Taran; Ivan U. Vakarelski; Hiroyuki Shinto; Ko Higashitani (233-237).
Silicon wafers with thermal silicon oxide layers were cleaned and hydrophilized by three different methods: (1) the remote chemical analysis (RCA) wet cleaning by use of ammonia and hydrogen peroxide mixture solutions, (2) water-vapor plasma cleaning, and (3) UV/ozone combined cleaning. All procedures were found to remove effectively organic contaminations on wafers and gave identical characteristics of the contact angle, the surface roughness and the normal force interactions, measured by atomic force microscopy (AFM). However, it is found that wafers cleaned by the RCA method have several times larger friction coefficients than those cleaned by the plasma and UV/ozone methods. The difference was explained by the atomic-scale topological difference induced during the RCA cleaning. This study reveals the lateral force microscopy as a very sensitive method to detect the microstructure of surfaces.Frictional force for wafers cleaned by the RCA procedure is significantly larger than those for wafers cleaned by the plasma and UV/ozone procedures.
Keywords: Friction; AFM; Silica; Surface cleaning; Hydrophilic surface;

Study of nickel nanoparticles supported on activated carbon prepared by aqueous hydrazine reduction by R. Wojcieszak; M. Zieliński; S. Monteverdi; M.M. Bettahar (238-248).
Nickel nanoparticles were obtained by the reduction in hydrazine aqueous media of nickel acetate as a precursor supported on activated carbon of high surface area. Classical catalysts using nickel acetate or nitrate were prepared for comparison. The catalysts were characterized by N2 physisorption, H2-TPR, H2-adsorption, TPD, TEM, and XRD, and tested in the gas phase hydrogenation of benzene. Hydrazine catalysts were found much more active in benzene hydrogenation than corresponding classically prepared catalysts. Remarkably, their reactivity is comparable (turn-over frequency of 0.2001–0.2539 s−1 at 393 K) to that of Pt classical catalysts supported on activated carbon in the same conditions. Evidence is given for the existence of the hydrogen spillover effect in benzene hydrogenation, not reported before in the literature. As a result of the hydrogen spillover effect, catalysts performances can be explained by a combination of surface metal atom reactivity, metal–support interaction strength, and specific surface area extent. Maximum effect is observed with hydrazine preparation method, for 1% Ni content and nickel acetate as a precursor. Unexpectedly, it was also found that hydrazine preparation increases the specific area of the catalysts.Hydrazine preparation method gives Ni/activated carbon catalysts highly performing in benzene hydrogenation due to combination of highly reactive nickel nanoparticles formed, strong metal–support interaction and wide specific surface area.
Keywords: Nickel; Hydrazine; Catalysts; Activated carbon; Hydrogen chemisorption; Benzene hydrogenation;

More than 85% of 10 mg L−1 of pentachlorophenol (PCP) was removed by magnesium/silver (206/1.47 mM) bimetal system in the presence of acetic acid. Dechlorination was found to be sequential and phenol was identified as the ultimate hydrocarbon skeleton along with some accumulation of tetra-, tri-, and dichlorophenols. The dechlorination reaction was found to follow second-order kinetics. Lower PCP removal efficiency (35%) was observed when the reaction was carried out in the absence of acid using Mg0/Ag system. When the reaction was conducted using Mg0 alone in the presence of acid, substantial sorption of PCP occurred with very low efficiency of PCP dechlorination. Dechlorination studies on 10 mg L−1 initial concentrations of 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP) and 2,4,5-trichlorophenol (2,4,5-TCP), under identical conditions as to PCP, revealed that dechlorination efficiency and reaction rate constants decrease with decreasing number of chlorine atoms on the target compound. A correlation ( R 2 > 0.9 ) between the dechlorination rate constants and E LUMO for chlorophenols was obtained.Dechlorination of pentachlorophenol was achieved by Mg0/Ag system in the presence of acid. Dechlorination was sequential and phenol was identified as the product with accumulation of tetra-, tri-, and dichlorophenols.
Keywords: Chlorophenol; Dechlorination; Silver; Magnesium; Pentachlorophenol; Zerovalent;

Troilite oxidation by hydrogen peroxide by Paul Chiriţǎ; Michaël Descostes (260-269).
Both experimental results and theoretical considerations illustrate the importance of temperature, pH, and [H2O2] for the kinetics and mechanisms of troilite oxidation. The amounts of dissolved iron strongly increase with temperature and [H+], whereas an increase of H2O2 concentration seems to reduce the troilite oxidation. The reaction orders with respect to [H+] are variable, pointing out notable modifications of reaction mechanism with experimental conditions. The estimated value E a = 25.4 ± 0.9   kJ mol −1 ([H2O2] = 0.4 mol L−1 and pH 1) points to dissolution kinetics controlled by a mix regime of surface reaction and diffusion.The changes with experimental conditions in reaction orders with respect to [H+] point out that troilite oxidation by hydrogen peroxide proceeds through different reaction mechanisms.
Keywords: Troilite; Hydrogen peroxide; Dissolved iron; Oxidation reaction mechanism; Diffusion;

A glass plate was coated with calcium hydroxyapatite (CaHAp) by a dip-coating method and employed for the removal of aqueous cadmium. Sol obtained from alcoholic solution of (NH4)2HPO4 and Ca(NO3)2⋅4H2O was employed for the precursor of the CaHAp layer. The preparation of CaHAp from the sol needed a rather low calcination temperature of 573 K and the resulting solid mainly contained CaHAp. It was shown that the glass plate coated with CaHAp with the sol could be employed for the removal of aqueous cadmium. Furthermore, it was found that cadmium immobilized on the coated plate could be regenerated into weak acidic solution. A dissolution–precipitation mechanism was suggested for the removal–regeneration of aqueous cadmium.Removal–regeneration of aqueous Cd2+ with hydroxyapatite-film prepared by a sol–gel technique is reported, although it had been accepted that the regeneration of heavy metal immobilized on hydroxyapatite is essentially impossible.
Keywords: Aqueous cadmium; Calcium hydroxyapatite; Sol–gel; Thin layer; Removal–regeneration process;

Stability of triglyceride liquid films on hydrophilic and hydrophobic glasses by Rosa Vazquez; Rui Nogueira; Marta Orfão; José Luís Mata; Benilde Saramago (274-282).
Wetting and dewetting of solid surfaces by oily fluids were investigated in terms of the stability of the liquid film formed between an air bubble and the solid surface. With the objective of understanding how molecules with low polarity but relatively complex molecular structure behave at the solid/liquid interface, three liquid triglycerides with different chain length and saturation were chosen, namely, tributyrin, tricaprylin, and triolein. Tributyrin and tricaprylin exist in milkfat while triolein is present in vegetable oils. The stability of the liquid films may be inferred from the shape of the disjoining pressure isotherms, which represent the dependence of the disjoining pressure on the film thickness. Disjoining pressure isotherms for films of the three triglycerides on hydrophilic and hydrophobic glasses were obtained using a recently developed apparatus, based on the interferometric technique. The experimental curves are compared with the theoretical predictions of London–Hamaker. The deviations between theory and experiment are interpreted in terms of a structural component of the disjoining pressure. All triglycerides form metastable films on both hydrophilic and hydrophobic glasses which means that for disjoining pressures higher than a critical value, π c , a wetting transition occurs and the film ruptures. The mechanisms for film rupture are discussed and a correlation between film stability and the apolar (Lifshitz–van der Waals) and the polar components of the spreading coefficient is proposed.
Keywords: Disjoining pressure isotherms; Triglycerides; Film stability; Structural forces; Dewetting;

Aqueous foam films stabilized by sodium naphthenates by Shawn D. Taylor; Jan Czarnecki; Jacob Masliyah (283-290).
Stratification of a foam liquid film drawn from aqueous solutions of sodium naphthenate at relatively high concentration is likely due to a lamellar liquid crystal-like structure within the film. Film stratification, resulting in stepwise thinning, has been observed in foam films formed from systems containing either moderate to high concentrations of surfactant or in films formed from solutions containing solid particles. At moderate surfactant concentrations, film stratification is likely due to layers of ordered spherical micelles as postulated in Wasan and Nikolov's model of film stratification [A.D. Nikolov, P.A. Kralchevsky, I.B. Ivanov, D.T. Wasan, J. Colloid Interface Sci. 133 (1989) 13]. At high surfactant concentrations, stepwise thinning of the films and occurrence of domains of uniform color within the film suggest a lamellar liquid crystal-like structure within the film, potentially up to hundred or more oriented layers. The LLC-like structure inside the film can occur at concentrations below the lower limit of the LLC existence as a bulk phase.Stratification observed in foam films drawn from aqueous solutions of sodium naphthenate at relatively high concentrations likely due to a lamellar liquid crystal-like structure within the film.
Keywords: Thin films; Sodium naphthenates; Stratification; Stepwise thinning;

Sol–gel processing of a bimetallic alkoxide precursor confined in a porous glass matrix: A route to novel glass/metal oxide nanocomposites by Willian G. Menezes; Pedro H.C. Camargo; Marcela M. Oliveira; David J. Evans; Jaísa F. Soares; Aldo J.G. Zarbin (291-296).
In this work we present the utilization of the heterometallic alkoxide [FeCl{Ti2(OPr i )9}] as the first sol–gel single-source precursor to achieve nanocomposites made of iron and titanium oxides incorporated into Porous Vycor Glass (PVG). The nanocomposites were prepared by the impregnation of the precursor in a PVG plate followed by hydrolysis reactions. Different samples were obtained by further thermal treatment of the hydrolyzed sample. The nanocomposites were characterized by UV–vis-NIR, Raman and EPR spectroscopies, XRD and TEM. The results indicate that the room-temperature hydrolyzed samples are formed by nanoparticles of FeOOH and brookite-TiO2 embedded on a glassy matrix. After the heat treatment at temperatures above 900 °C, a pseudobrookite Fe2TiO5 was formed. All samples present high transparency and homogeneity. The results showed here indicate that the sol–gel process using the single-source precursor [FeCl{Ti2(OPr i )9}] should be a novel and efficient approach to the preparation of nanometric Fe/Ti oxides incorporated into a glassy matrix.The picture represents a TEM image showing spherical iron–titanium oxide nanoparticles homogeneously incorporated in a glass mass.
Keywords: Nanocomposites; Sol–gel process; Iron oxide; Titanium oxide; Porous glasses;

Phase behavior and preparation of mesoporous silica in aqueous mixtures of fluorinated surfactant and hydrophobic fluorinated polymer by Suraj Chandra Sharma; Hironobu Kunieda; Jordi Esquena; Carlos Rodríguez Abreu (297-304).
The phase behavior and formation of self-assemblies in the ternary water/fluorinated surfactant (C8F17EO10)/hydrophobic fluorinated polymer (C3F6O) n COOH system and the application of those assemblies in the preparation of mesostructured silica have been investigated by means of phase study, small angle X-ray scattering, and rheology. Hexagonal (H1), bicontinuous cubic (V1) with Ia3d symmetry, and polymer rich lamellar ( L α ′ ) are observed in the ternary diagram. C8F17EO10 molecules are dissolved in polymer rich aggregates, whereas (C3F6O) n COOH molecules are practically insoluble in the surfactant lamellar phase due to packing restrictions. Hence, two types of lamellar phases exist: one with surfactant rich ( L α ) and the other with polymer rich ( L α ′ ) in the water/C8F17EO10/(C3F6O) n COOH system. As suggested by rheological measurements, worm-like micelles are present in C8F17EO10 aqueous solutions but a rod-sphere transition takes place by solubilization of (C3F6O) n COOH. C8F17EO10 acts as a structure directing agent for the preparation of hexagonal mesoporous silica by the precipitation method. The addition of (C3F6O) n COOH induces the formation of larger but disordered pores.
Keywords: Fluorinated surfactant; Polymeric oil; Phase behavior; Rheology; Mesoporous silica; Liquid crystals;

Adsorption of reactive dyes on titania–silica mesoporous materials by Paula V. Messina; Pablo C. Schulz (305-320).
This paper presents a study on the adsorption of two basic dyes, methylene blue (MB) and rhodamine B (RhB), from aqueous solution onto mesoporous silica–titania materials. The effect of dye structure, adsorbent particle size, TiO2 presence, and temperature on adsorption was investigated. Adsorption data obtained at different solution temperatures (25, 35, and 45 °C) revealed an irreversible adsorption that decreased with the increment of T. The presence of TiO2 augmented the adsorption capacity ( q e ) . This would be due to possible degradation of the dye molecule in contact with the TiO2 particles in the adsorbent interior. The adsorption enthalpy was relatively high, indicating that interaction between the sorbent and the adsorbate molecules was not only physical but chemical. Both Langmuir and Freundlich isotherm equations were applied to the experimental data. The obtained parameters and correlation coefficients showed that the adsorption of the two reactive dyes (MB and RhB) on the adsorbent systems at the three work temperatures was best predicted by the Langmuir isotherm, but not in all cases. The kinetic adsorption data were processed by the application of two simplified kinetic models, first and second order, to investigate the adsorption mechanism. It was found that the adsorption kinetics of methylene blue and rhodamine B onto the mesoporous silica–titania materials surface under different operating conditions was best described by the first-order model.Wastewater containing pigments and or dyes can cause serious water pollution problems. In this work, adsorption on titania–silica mesoporous materials surface from aqueous reactive dyes has been studied. The focus of the present research is to characterize the sorption properties of these material to evaluate their possible use as decontaminants.
Keywords: Adsorption; TiO2 nanoparticles; Silica–titania mesoporous materials; Surfactant templates; Reactive dyes; Energetic surface heterogeneity; Decontamination; Isotherms; Kinetics; Thermodynamic;

Widely used traditional Parachor model fails to provide reliable interfacial tension predictions in multicomponent hydrocarbon systems due to the inability of this model to account for mass transfer effects between the fluid phases. In this paper, we therefore proposed a new mass transfer enhanced mechanistic Parachor model to predict interfacial tension and to identify the governing mass transfer mechanism responsible for attaining the thermodynamic fluid phase equilibria in multicomponent hydrocarbon systems. The proposed model has been evaluated against experimental data for two gas–oil systems of Rainbow Keg River and Terra Nova reservoirs. The results from the proposed model indicated good IFT predictions and that the vaporization of light hydrocarbon components from crude oil to gas phase is the governing mass transfer mechanism for the attainment of fluid phase equilibria in both the gas–oil systems used. A multiple linear regression model has also been developed for a priori prediction of exponent in the mechanistic model by using only the reservoir fluid compositions, without the need for experimental measurements. The dynamic nature of interfacial tensions observed in the experiments justifies the use of diffusivities in the mechanistic model, thus enabling the proposed model predictions to determine dynamic gas–oil miscibility conditions in multicomponent hydrocarbon systems.The newly proposed mechanistic Parachor model in this study for prediction of dynamic interfacial tension and miscibility in multicomponent hydrocarbon systems is given by σ 1 / 4 = ( D os D so ) n ( ρ M L ∑ x i P i − ρ M V ∑ y i P i ) .
Keywords: Interfacial tension; Mass transfer; Diffusivity; Miscibility; Phase equilibria; Vaporization; Condensation;

Wettability of nano-epoxies to UHMWPE fibers by S. Neema; A. Salehi-Khojin; A. Zhamu; W.H. Zhong; S. Jana; Y.X. Gan (332-341).
Ultra high molecular weight polyethylene (UHMWPE) fibers have a unique combination of outstanding mechanical, physical, and chemical properties. However, as reinforcements for manufacturing high performance composite materials, UHMWPE fibers have poor wettability with most polymers. As a result, the interfacial bonding strength between the fibers and polymer matrices is very low. Recently, developing so-called nano-matrices containing reactive graphitic nanofibers (r-GNFs) has been proposed to promote the wetting of such matrices to certain types of fiber reinforcements. In this work, the wettability of UHMWPE fibers with different epoxy matrices including a nano-epoxy, and a pure epoxy was investigated. Systematic experimental work was conducted to determine the viscosity of the epoxies, the contact angle between the epoxies and the fibers. Also obtained are the surface energy of the fibers and the epoxies. The experimental results show that the wettability of the UHMWPE fibers with the nano-epoxy is much better than that of the UHMWPE fibers with the pure epoxy.Based on development of nano-matrices containing reactive graphitic nanofibers (r-GNFs), the wettability of UHMWPE fiber with different epoxy matrices including a nano-epoxy and a pure epoxy was investigated.
Keywords: UHMWPE fibers; Reactive graphitic nanofibers (r-GNFs); Epoxies; Wetting; Surface energy; Viscosity; Contact angle;

Pore-scale modelling and tomographic visualisation of drying in granular media by Martin Kohout; Zdeněk Grof; František Štěpánek (342-351).
Spatio-temporal evolution of liquid phase clusters during drying of a granular medium (realised by random packing of cylindrical particles) has been investigated at the length-scale of individual pores. X-ray microtomography has been used to explicitly resolve the three-dimensional spatial distribution of the solid, liquid, and gas phases within the wet particle assemblies. The propagation of liquid menisci through the granular medium during drying was dynamically followed. The effect of contact angle on the degree of dispersion of the drying front has been studied by observing drying in a layer of untreated (hydrophilic) and silanised particles; the drying front was found to be sharper in the case of the silanised (less hydrophilic) particles. This observation was confirmed by direct numerical simulations of drying in a digitally encoded porous medium identical in structure to the experimental one. The simulations also revealed that the average gas–liquid interfacial area in a given porous microstructure strongly depends on the contact angle.
Keywords: Drying front; Porous media; Particle packing; Contact angle; Meniscus; Interfacial area; X-ray microtomography; Volume-of-fluid method;

Celecoxib (clxb) is an important drug for treatment of rheumatoid arthritis and osteoarthritis by specifically inhibiting the enzyme cyclooxygenase-2 (COX-2). Clxb is a type 2 drug characterized by low water solubility (<5 μg/ml) and fast transmembrane transport. The present formulations require high dosage since the transmembrane transport fluctuates and is very difficult to control. Dissolving the drug within an oil phase was not practical since its dissolution was very small and its dispersion in water was impossible. In our recent studies, we learned to construct U-type phase diagrams and to formulate reverse microemulsions (oil-based concentrates) that are progressively and fully dilutable with aqueous phase. In the present study, we solubilized clxb in nanostructures of reverse micelles of U-type nonionic microemulsions that consisted of R(+)-limonene, alcohol, propylene glycol (PG), and hydrophilic surfactant (Tween 60). The solubilization capacity of the drug in these systems is many times higher than in either the oil or the aqueous phase. The clxb solubilized microemulsions are fully diluted with aqueous phase without phase separation. The solubilization capacity decreases as the water content increases. Electrical conductivity, viscosity, and self-diffusion (SD) coefficients of the microemulsion components were measured along a suitable water dilution line. The three major microemulsion regions were detected and the transitions between the W/O to bicontinuous phase and from this phase to the O/W droplets were identified (at 30 and 70 wt% aqueous phase, respectively). From the SD coefficients, it was found that the drug is initially solubilized at the interface of the W/O droplets and there are no significant structural changes. The transition to a bicontinuous phase occurs at the same water content as in the empty (i.e., without drug) system. From the viscosity profiles, we concluded that the drug affects the structure of the bicontinuous phase as reflected in the water content at which the oil-continuous network is destroyed and full inversion occurs (50 vs 55 wt% in the drug-loaded system). Upon further dilution the drug remains solubilized at the interface and is oriented with its hydrophilic part facing the water, and is strongly affects the inversion to O/W droplets. From Small Angle X-ray Scattering (SAXS) measurements we learned that the drug effects the structure of microemulsion droplets and forms “ill-defined structures,” probably less spherical. Yet, the overall droplet sizes at the high dilutions did not change very much.Microemulsions are excellent vehicles for solubilization of Celecoxib. Electrical conductivity, viscosity, diffusion coefficient (SD-NMR), SAXS, and QELS are suitable methods to clarify the interfacial behavior of the Celecoxib and its effect on the interfacial partitioning of the surfactant, cosurfactant, cosolvent, and the oil phase.
Keywords: Celecoxib; Drug delivery; Solubilization; SD-NMR; Nanosized self-assembly vehicles; Microemulsions; Nanostructures; Self-microemulsifying drug delivery system (SMEDDS);

The effect of steric interactions on the stability of oil-in-water emulsions is studied here by means of emulsion stability simulations (ESS). For this purpose, a new steric potential based on a modification of the one formerly proposed by Vincent et. al. [Colloids Surf. 18 (1986) 261] is employed. The parameters of the calculation correspond to hexadecane in water emulsions stabilized with nonylphenol ethoxylated surfactants of different chain lengths (NPEm). Stability ratios (W) were calculated using the half life time of the number of drops per unit volume of these systems. A functional relationship between W and the repulsive potential barrier, (ΔV), similar to the one previously found by Prieve and Ruckenstein for electrostatically stabilized suspensions [J. Colloid Interface Sci. 73 (1980) 539] was obtained. However, according to our simulations there exists a threshold for the stability of emulsions with respect to coalescence which is approximately located around 12.7 k B T .
Keywords: Nonionic; Stability; Steric; Emulsions;

Incorporation of substituted acrylamides to the lamellar mesophase of Aerosol OT by Isabel E. Pacios; Carmen S. Renamayor; Arturo Horta; Björn Lindman; Krister Thuresson (378-387).
The structure and stability of the lamellar liquid crystal formed by the surfactant sodium bis-2ethylhexyl sulfosuccinate (AOT) in water is perturbed by small amounts of the substituted acrylamides N-isopropyl, N,N-diethyl, N-acryloylmorpholine, and N,N-dimethyl methacrylamide, as revealed by small angle X-ray scattering (SAXS), deuterium NMR, and microscopy. These molecules are water soluble and stay mostly in the water layers between lamellae, but a small fraction of them (5–19%) are incorporated into the AOT bilayers, thereby producing dramatic changes. Both, the degree of anisotropy in the water molecules hydrating AOT (quadrupolar splitting in 2H NMR) and the long period spacing between lamellae (SAXS), decrease with addition of this molecules at low concentrations, which is attributed to the lower average headgroup density at the AOT/water interface when the acrylamide is incorporated. The strength of these perturbations depends on the acrylamide, and goes in parallel with the hydrophobic character of the alkyl side groups in its molecule, which suggests that the acrylamides incorporated to the bilayer enter into contact with the lipophilic tails of the AOT molecule. An interaction with the hydrated heads of AOT is also suggested in the particular case of N-isopropylacrylamide. On increasing the molecule concentration an incipient melting of the lamellar phase towards an isotropic solution takes place, first at the microscopic level, then macroscopic. Near this phase transition, the ordered domains lose the random orientation prevailing at lower acrylamide concentrations, and adopt a preferred orientation, perpendicular to the magnetic field.
Keywords: Substituted acrylamides; AOT; Lamellar mesophase; Deuterium NMR; SAXS;

Effects of counterion species on the aggregate structure of tetradecyldimethylamine oxide (C14DMAO) accompanying the protonation were examined by viscoelastic properties and phase behavior observations. Different extents of the synergetic behavior between protonated and non-protonated amine oxides were observed depending on the counterion species, which follow the Hofmeister, or the lyotropic, series. The efficacy of monovalent anions with respect to the increasing the surfactant packing parameter was as follows: salicylate > perchlorate > nitrate > bromide > chloride, formate. Vesicle formation was found in the case of salicylate and perchlorate anions and elongation of rodlike micelles was observed for nitrate, bromide, sulfate, tartronate and tartrate anions but little effects in the case of chloride and formate anions. The observed ionic specificity is well correlated with the free energy of hydration of counterions.Note that a 20% protonation with HCl on a 100 mM C14DMAO solution leads to a decrease of the viscosity while the same protonation with HSCN leads to an increase of the viscosity by almost a factor of 1000.
Keywords: Hofmeister ion series; Phase diagrams of protonated tetradecyldimethylamine oxide surfactants; Vesicles from single chain surfactants; Rheological behavior; Shear thinning behavior;

Manufacture of large uniform droplets using rotating membrane emulsification by Goran T. Vladisavljević; Richard A. Williams (396-402).
A new rotating membrane emulsification system using a stainless steel membrane with 100 μm laser drilled pores was used to produce oil/water emulsions consisting of 2 wt% Tween 20 as emulsifier, paraffin wax as dispersed oil phase and 0.01–0.25 wt% Carbomer (Carbopol ETD 2050) as stabilizer. The membrane tube, 1 cm in diameter, was rotated inside a stationary glass cylinder, diameter of 3 cm, at a constant speed in the range 50–1500 rpm. The oil phase was introduced inside the membrane tube and permeated through the porous wall moving radially into the continuous phase in the form of individual droplets. Increasing the membrane rotational speed increased the wall shear stress which resulted in a smaller average droplet diameter being produced. For a constant rotational speed, the average droplet diameter increased as the stabilizer content in the continuous phase was lowered. The optimal conditions for producing uniform emulsion droplets were a Carbomer content of 0.1–0.25 wt% and a membrane rotational speed of 350 rpm, under which the average droplet diameter was 105–107 μm and very narrow coefficients of variation of 4.8–4.9%. A model describing the operation is presented and it is concluded that the methodology holds potential as a manufacturing protocol for both coarse and fine droplets and capsules.A novel rotating membrane emulsification system using a stainless steel membrane with 100 μm laser drilled pores was used to produce monodisperse oil/water emulsions.
Keywords: Membrane emulsification; Monodisperse emulsion; Rotating membrane emulsification; Stainless steel membrane;

Lyophilic properties of surfactant-rich phases of polyethoxylated alkylphenols formed at cloud point temperature by Volodymyr O. Doroschuk; Sergey O. Lelyushok; Olga O. Rakhilchuk; Sergey A. Kulichenko (403-409).
The influence of the concentration conditions, solutions acidity, and electrolyte additions on the lyophilic properties of the surfactant-rich phases of polyethoxylated alkylphenols OP-7 and OP-10 formed at cloud point temperature were studied. The lyophilic properties of surfactant-rich phases were determined by estimating of their effective hydration values and solvation free energy of methylene and carboxyl groups at cloud point extraction of aliphatic monocarboxylic acids. It was shown that the surfactant-rich phases formed from the dilute surfactant solutions have more hydrophobic properties than the phases formed from the high concentrated solutions. The possibility of changing the lyophilic properties of surfactant-rich phases by electrolyte additions was shown: complex formation between electrolyte cation and the polyoxyethylene chain of the surfactant increases the hydrophilic properties of the surfactant-rich phases. Calculations of the solvation free energy of methylene and carboxylic fragments of the aliphatic carboxylic acids at micellar extraction showed the uniqueness of the surfactant-rich phases which are able to energetically advantageously extract both hydrophilic and hydrophobic molecules of substrates.Dependence of the solvation free energy of methylene and carboxyl groups of aliphatic carboxylic acids at cloud point extraction via the OP-7 concentration in the solution. Calculations of the solvation free energy of methylene and carboxylic fragments of the aliphatic carboxylic acids at micellar extraction showed the specificity of the surfactant-rich phases. These phases are able to energetically advantageously extract both hydrophilic and hydrophobic molecules of substrates.
Keywords: Cloud point extraction; Non-ionic surfactants; Lyophilic properties;

Phase behavior of gemini surfactant hexylene-1,6-bis(dodecyldimethylammonium bromide) and polyelectrolyte NaPAA by Yingying Pi; Yazhuo Shang; Changjun Peng; Honglai Liu; Ying Hu; Jianwen Jiang (410-415).
The phase behavior of aqueous mixtures of gemini surfactant hexylene-1,6-bis(dodecyldimethylammonium bromide) (12-6-12) and oppositely charged polyelectrolyte sodium polyacrylate (NaPAA) has been studied experimentally. Compared to the mixtures of the traditional surfactant dodecyltrimethylammonium bromide (DTAB) and NaPAA, the gel phase region in the 12-6-12/NaPAA solution is larger. Element analysis reveals that NaPAA in the gel phase tends to replace the counterions of surfactant micelle and to release its own counterions. Spherical aggregates are observed in either top or bottom gel phase as detected by transmission electron microscopy. The addition of sodium bromide (NaBr) leads to a decrease in the gel phase region and the occurrence of a new cream phase.Phase diagrams of (A) 12-6-12/NaPAA and (B) DTAB/NaPAA aqueous solution.
Keywords: Gemini surfactant; Polyelectrolyte; Phase behavior; Gel; Aggregate;

Variation of saturated surface density of ovalbumin on bubble surface in continuous foam separation by Hideo Maruyama; Hideshi Seki; Akira Suzuki; Norio Inoue (416-420).
The adsorption of ovalbumin (OA) onto the bubble surfaces was studied with various pHs (3.5, 4.6, 6.0 and 8.0) by a continuous foam separation technique. From the value of the saturated surface density of adsorbed OA, the variation of effective diameter (D) of an OA molecule on the bubble surface was estimated for various pHs (3.5, 4.6, 6.0 and 8.0) of the OA solutions, assuming that the cross section of the OA molecules be circular and that the OA molecules adsorb on the bubble surface in a closest packing structure. The estimated variation of D with pH was attempted to explain based on a model modified from that proposed by Pujar and Zydney [N.S. Pujar, A.L. Zydney, J. Chromatogr. A 796 (1998) 229–238]. The modified model could well reproduce the variation of the effective diameter with pH; the values of D calculated on the basis of the modified model almost agreed with that estimated from the saturated surface density in the present experimental pH range. From these, conclusion was drawn that the modified model presented in this study can express the variation in the effective diameter with pH.In this work, variation of sphere-equivalent diameter of ovalbumin adsorbed on bubble surface in saturated state with pH was attempted to explain based a model modified from that proposed by Pujar and Zydney (1998).
Keywords: Foam separation; Saturated surface density; Ovalbumin; Effective diameter; Surface charge;

Reduction of methylene blue by thiocyanate: Kinetic and thermodynamic aspects by Surojit Pande; Sujit Kumar Ghosh; Sudip Nath; Snigdhamayee Praharaj; Subhra Jana; Sudipa Panigrahi; Soumen Basu; Tarasankar Pal (421-427).
This article reports the reduction of methylene blue (MB) by thiocyanate ions (SCN) in aqueous and micellar solutions. Thiocyanate ions are found to be an effective reducing agent for the decolorization of methylene blue under ambient condition. Effects of salting-in and salting-out agents have been investigated for real-time application in the reduction process. The salting-in agent urea has been found to uniquely enhance the rate of the reduction of MB by thiocyanate ion in the presence of micelles. Again, the catalytic activity of nanoparticles in the reduction of MB has also been studied. Detailed kinetic and thermodynamic aspects have been considered to realize the interaction between methylene blue and thiocyanate. Kinetic studies revealed that the reaction is reversible and follows first-order reaction kinetics.
Keywords: Methylene blue; Thiocyanate; Catalysis; Micelle; Salting-in and salting-out agents; Nanoparticles;

Charge number effect on the miscibility of inorganic salt and surfactant in adsorbed film and micelle: Inorganic salt–octyl methyl sulfoxide mixtures by Hidemi Iyota; Takako Tomimitsu; Kazuko Shimada; Norihiro Ikeda; Kinsi Motomura; Makoto Aratono (428-434).
Adsorption and micelle formation of a surfactant in the presence of inorganic salts with different charge numbers of cations were investigated from the viewpoint of mixed adsorption and micelle formation of salt and surfactant. Surface tension of aqueous solutions of the mixtures of octyl methyl sulfoxide (OMS) with calcium chloride and lanthanum chloride was measured as a function of the total molality of the mixture and the mole fraction of OMS in the mixture at 298.15 K under atmospheric pressure. Composition of the adsorbed film and micelle was numerically evaluated from the dependence of the total molality at a given surface tension and the mixture CMC on the bulk composition to draw phase diagrams of adsorption and micelle formation. Judging from the phase diagrams together with the ones of the sodium chloride system, miscibility of inorganic salt and OMS in the adsorbed film and micelle increases with an increase in the charge number of inorganic cation, which is attributable to the attractive interaction between inorganic cation and the polar head group of OMS molecule in the adsorbed film and micelle.Attractive interaction between inorganic cation and OMS in the adsorbed film and micelle increases with increasing charge number and decreasing hydration of the cation.
Keywords: Charge number of inorganic ion; Mixture of inorganic salt and nonionic surfactant; Surface tension of a mixture; Miscibility in adsorbed film and micelle; Phase diagrams of adsorption and micelle formation;

Nonionic ortho ester surfactants as cleavable emulsifiers by Kristina Mohlin; Krister Holmberg (435-442).
Acid labile surfactants containing an ortho ester link are used as emulsifiers for an aliphatic oil, squalane. The emulsions were made in the presence of a cationic polymer, either polyamine or the corresponding hydrophobically modified polyamine. Spontaneous hydrolysis of the surfactant resulted in emulsions stabilized by polymer together with degradation products from the surfactant. The effect of breakdown of the surfactant on the emulsion was evaluated by means of droplet size measurements and kinetic stability. One linear and one branched nonionic ortho ester surfactant with the same number of oxyethylene units were characterized and used for the purpose. The ortho ester surfactants are complex mixtures of components, ranging from very hydrophilic to very hydrophobic species. The chemical shift of the central methine proton in the ortho ester link is extremely sensitive to the substitution pattern and it was possible to identify by 1H NMR the components that make up the surfactants, as has been reported earlier [P.E. Hellberg, K. Bergström, M. Juberg, J. Surf. Deterg. 3 (2000) 369]. The change in emulsion stability, the change in droplet size and the rate of surfactant hydrolysis were studied at acidic pH at room temperature. Both gas chromatography and 1H NMR were used in order to monitor the surfactant degradation. The presence of a polymer gave a more sluggish breakdown of the surfactants, probably due to hydrophobic shielding by the polymer. There was a good correlation between increase of droplet size and degree of surfactant decomposition.Nonionic surfactants, which are cleaved by acid, are used together with polymers to stabilize an oil-in-water emulsion.
Keywords: Ortho ester surfactant; Emulsion; Squalane; Acid-catalyzed hydrolysis; Polymer;

Diffusiophoresis of concentrated suspensions of spherical particles subject to a small electrolyte gradient is analyzed theoretically at arbitrary levels of zeta potential and double-layer thickness. The Kuwabara unit cell model is adopted to describe the system under consideration. The effect of double-layer polarization is taken into account. It is found that the diffusiophoretic mobility exhibits a local maximum as well as a local minimum with varying zeta potential or double-layer thickness, similar to the corresponding dilute dispersion. The direction of the particle movement may even change back and forth. The previous low-zeta-potential approach is found to significantly overestimate the diffusiophoretic mobility as the zeta potential goes high. The deviation may be several fold sometimes. The effect of the volume fraction ratio of colloids is also examined. The higher the ratio, the lower the mobility.Polarization effect in diffusiophoresis.
Keywords: Diffusiophoresis; Polarization effect; Kuwabara unit cell model; Arbitrary zeta potential;

Non-equilibrium molecular dynamic (NEMD) simulations have been used to study heat and mass transfer across a vapor–liquid interface for a one-component system using a Lennard-Jones spline potential. It was confirmed that the relation between the surface tension and the surface temperature in the non-equilibrium system was the same as in equilibrium (local equilibrium) [A. Røsjorde, D.W. Fossmo, S. Kjelstrup, D. Bedeaux, B. Hafskjold, J. Colloid Interface Sci. 232 (2000) 178]. Interfacial transfer coefficients were evaluated for the surface, which expressed the heat and mass fluxes in temperature and chemical potential differences across the interfacial region (film). In this analysis it was assumed that the Onsager reciprocal relations were valid [A. Røsjorde, S. Kjelstrup, D. Bedeaux, B. Hafskjold, J. Colloid Interface Sci. 240 (2001) 355]. In this paper we extend the number of simulations such that we can calculate all four interface film transfer coefficients along the whole liquid–vapor coexistence curve. We do this analysis both for the case where we use the measurable heat flux on the vapor side and for the case where we use the measurable heat flux on the liquid side. The most important result we found is that the coupling coefficients within the accuracy of the calculation are equal. This is the first verification of the validity of the Onsager relations for transport through a surface using molecular dynamics. The interfacial film transfer coefficients are found to be a function of the surface temperature alone. New expressions are given for the kinetic theory values of these coefficients which only depend on the surface temperature. The NEMD values were found to be in good agreement with these expressions.
Keywords: Onsager's reciprocal relations; Non-equilibrium molecular dynamics (NEMD) simulation; Non-equilibrium thermodynamics; Kinetic theory;

The dynamic mobility of a spherical dispersion of soft particles, where a particle comprises a rigid core and a membrane layer, is evaluated for the case when the shear stress across the membrane layer–liquid interface is discontinuous, the so-called stress-jump condition. We show that, due to the effect of double-layer deformation, the magnitude of the dynamic mobility of a particle has a local maximum and the corresponding phase angle has a negative (phase lead) local minimum at a low to medium level of the frequency of the applied electric field. This effect becomes insignificant if the frequency of the applied electric field is sufficiently high. The stress-jump condition may lead to a significant influence on the drag, and consequently the mobility of a particle. The degree of influence depends upon the sign of the stress-jump coefficient and the charged conditions of the membrane layer of the particle.Dynamic electrophoresis of a spherical dispersion of soft particles subject to a stress-jump condition modeled by cell model.
Keywords: Dynamic electrophoresis; Spherical dispersion; Soft particles; Stress-jump condition;

Effect of mass transfer on the film drainage between colliding drops by J.-P. Chevaillier; E. Klaseboer; O. Masbernat; C. Gourdon (472-485).
The influence of mass transfer on the drainage behaviour of the thin liquid film between two drops immersed in another liquid colliding at constant approach velocity has been studied experimentally. The liquid–liquid system used is glycerol in silicone oil. The transferred solute is acetone and the volume concentration difference across the interface ranges from 1 to 5%. The film thickness evolution has been measured using a laser interferometry technique. The direction of mass transfer (from the drops towards the film phase and inversely) has been investigated and the results compared to the case with no mass transfer [E. Klaseboer, J.P. Chevaillier, C. Gourdon, O. Masbernat, J. Colloid Interface Sci. 229 (2000) 274–285]. When the solute transfers from the drops towards the continuous phase, the drainage rate is significantly higher than in the case with no mass transfer. This result is interpreted as a consequence of the mass transfer induced surface mobility in the film region (the so-called Marangoni effect) due to localized surface tension differences. This effect has been demonstrated by the visualization of the flow patterns in the drops and in the film phase (using a particle tracer technique). In this case, the slope of the film height as a function of time seems to be independent of the approach velocity condition imposed on the drop and appears to be controlled by the interfacial tension gradient. In the opposite case, when the solute transfers from the continuous phase towards the drops, the film drainage rate is lowered with respect to the case of no mass transfer, goes to zero or even changes its sign depending on the mass transfer intensity. The results also show that in the range of solute concentration studied, the effect of mass transfer on the film drainage process takes place at large distances compared to the scales at which lubrication theory is valid.Visualization of mass transfer induced Marangoni flows between two approaching liquid drops. Glycerol drops with 5% acetone into silicone oil (47V50).
Keywords: Marangoni effect; Experiments; Drops; Mass transfer; Film drainage; Solute; Interference pattern;

Electrophoretic mobility equation for protein with molecular shape and charge multipole effects by Jae Young Kim; Se Hyuk Ahn; Seung Tae Kang; Byung Jun Yoon (486-492).
We derive a simple formula for the free solution electrophoretic mobility of protein by including both molecular shape and charge distribution effects. The molecular shape of protein is described by a deformed sphere model, while the charge distribution is represented in terms of net charge, charge dipole, and charge quadrupole. The deformed sphere model approximates the radial coordinate of the protein surface as a simple quadratic equation based on the atomic coordinate data. Charge dipole does not affect the mobility of protein. Combined with the quadratic coefficients of the surface equation, charge quadrupole affects the mobility. When the charge quadrupole contribution is negligible, the mobility equation simplifies to the Henry equation in which the sphere radius is replaced with the hydrodynamic radius of protein. The deformed sphere model predicts correctly the hydrodynamic radius of protein from the atomic coordinate data. The hydrodynamic radius is not the radius of sphere of equal volume but the effective radius that correlates with the translational diffusivity of protein. To illustrate the utility of our mobility equation we study the electrophoresis of lysozyme and compare our results with previously published works.An electrophoretic mobility equation is derived for protein by including both molecular shape and charge distribution effects.
Keywords: Capillary electrophoresis; Continuum electrostatics; Lysozyme; Poisson–Boltzmann equation; Protein charge; Protein diffusivity;

Initial growth process of polystyrene particle investigated by AFM by Tetsuya Yamamoto; Yoichi Kanda; Ko Higashitani (493-496).
We carried out molecular-scale and in situ investigations of the initial growth process of polystyrene particles in soap-free polymerization, where a cationic initiator, V-50, was used to make the formed particles transfer onto the mica plate in sampling, using an atomic force microscope. It was found that the particles coagulated soon after the nucleation process. Such coagulation was estimated from a macroscopic research, however; microscopic evidence was not enough. This study verifies it from a microscopic view.Coagulation process in the initial stage of the growth process.
Keywords: Polystyrene particle; AFM; Coagulation; Soap-free polymerization;