Surface Electrokinetic Properties Research Articles

Self-organized, free-standing TiO2 nanotube membranes: Effect of surface electrokinetic properties on flow-through membranes

In the present work we investigate the effect of the surface electrokinetic properties and presence of background ions on the flow of a marker dye through TiO2 nanotube membranes. We believe the results to be of high significance not only for filtration but also for the design of microphotoreactor application based on photoactive TiO2 nanotubes membrane. First, both-side open, high aspect ratio TiO2 nanotube membranes were obtained by fast anodization of Ti to self-aligned TiO2 nanotube layers, followed by a lift-off process. Then we investigated the permeation through the TiO2 nanotube membranes by diffusion of acid orange 7 (AO7) and extracted the dye diffusion rates. The effects of pH, ionic concentration, and size of ions were investigated, and the results were compared with theoretical modeling of the surface charge of TiO2 and the neighbouring electric double layer as a function of different species of ions; the modeling confirms the experimental data. We observed a remarkable influence of the background ion species, as well as of ion concentrations and pH in the feed solution on the diffusion rate of AO7. The results of modeling are well in line with the observed influence of TiO2 nanotube inner surface charge and effective size (hydrodynamic radius) of the ions in the background solution. It is also observed that the absolute permeate flux and the membrane's permeability strongly depend on the electric and wetting conditions of the membrane surface.

Dispersion of nanosized ceramic powders in aqueous suspensions

Seven commercially available dispersants have been applied to produce high concentrated aqueous suspensions of the nanosized alumina and partially stabilized zirconia powders processed by the plasma technique. Simultaneously, the electrokinetic behaviour of powders has been investigated in diluted suspensions by microelectrophoresis method. Zeta potential measurements are used to estimate the influence of selected dispersants on the electrokinetic properties of the powder surface. On the basis of obtained data the correlation between the surface electrokinetic properties in dilute suspensions and reached maximal suspension concentration is discussed.

Bacterial quorum sensing and cell surface electrokinetic properties

The hypothesis tested in this paper is that quorum sensing influences the microbial surface electrokinetic properties. Escherichia coli MG1655 and MG1655 LuxS- mutant (lacking quorum-sensing gene for Autoinducer synthase AI-2) were used for this study. AI-2 production (or lack of) in both strains was analyzed using the Vibrio harveyi bioassay. The levels of extracellular AI-2 with and without glucose in the growth medium were consistent with previously published work. The surface electrokinetic properties were determined for each strain of E. coli MG1655 by measuring the electrophoretic mobility using a phase amplitude light-scattering (PALS) Zeta potential analyser. The findings show that the surface charge of the cells is dependent upon the stage in the growth phase as well as the ability to participate in quorum sensing. In addition, significant differences in the electrophoretic mobility were observed between both strains of E. coli. These findings suggest that quorum sensing plays a significant role in the surface chemistry of bacteria during their growth.

Preparation of concentrated aqueous suspensions from nanosized plasma-processed zirconia powder

Four commercially available dispersants have been compared for their ability to produce high-concentrated suspensions of the partially stabilized nanosized zirconia powder, processed by the plasma technique. Zeta potential measurements are used to study the influence of these dispersants on the electrokinetic properties of the powder surface. The highest solid loading (up to 70 wt%) is achieved using Atsurf 3222 and KD7 as dispersants. The optimal amounts of the dispersant (2-3 wt% of the dry mass of the solid) have been determined by adsorption and viscosity measurements. On the basis of obtained data, the correlation between the surface electrokinetic properties and maximal suspension concentration reached is discussed.

Analysis of electrokinetic flow in microfluidic networks

A general model for electrokinetic flow in a one-to-multi-branch microchannel system is developed. This model can be extended to more complex microfluidic networks. The liquid flow may be generated by applying pressure gradients (pressure-driven flow) or electric fields (electro-osmotic flow) to the microchannels. Phenomenological coefficients in non-equilibrium thermodynamics are employed to describe the effects of channel size and surface electrokinetic properties on microfluidic characteristics. Analytical solutions of the flow rate and the streaming potential (for pressure-driven flow) or the electric current (for electro-osmotic flow) are obtained for each branch-channel, in addition to the distributions of pressure and electric potential. The flow behaviors in such a microchannel network can thus be predicted by these analytical solutions. As examples, a two-section heterogeneous microchannel and a one-to-two-branch microchannel system are analyzed using the derived model.

Fiberglass Surface and Its Electrokinetic Properties

The surface charge of fiberglass is an important variable for fiber dispersion and web formation in a wet-laid process. This paper presents an overview of the glass surface electrokinetic properties as well as their applications for improving the quality of wet-laid nonwovens through good fiber dispersion and uniform web formation. The paper addresses the basic concepts used in electrokinetic characterization of glass surface and briefly discusses the available techniques for zeta potential measurement.

Electrokinetic effects on expression characteristics of clay slurries

This paper provides the first report of the particle surface electrokinetic properties effects on expression characteristics in clay slurries. As solution pH decreases or ionic strength increases, the zeta potential becomes less negative. Consequently, the resistance to filtration decreases while the residual moisture in the cake after filtration increases also. The expression data are interpreted by the combined Terzaghi‐Voigt rheological model, from which the model parameters are evaluated. The particle surface electrokinetic properties have only a mild effect on the primary consolidation process, but has, nevertheless, a substantial influence on the secondary consolidation characteristics. Both the easiness of creeping of constituting particles within the sludge cake and the fraction of moisture removal by the secondary consolidation increase when the zeta potential becomes less negative.

Electrokinetic properties of human cryopreserved platelets.

A method for the cryopreservation of human platelets with glycerol/glucose is described which was a simplified modification of the method of Dayian and Pert (1979). The effect of cryoinjury of the platelet surface membrane was investigated by studying the surface electrokinetic properties of the platelet. A significant increase in platelet electrophoretic mobility was found after cryopreservation. The fresh platelets had a mean electrophoretic mobility of 1.04 +/- 0.05 microns s-1 V-1 cm-1 and cryopreserved platelets 1.18 +/- 0.05 microns s-1 V-1 cm-1, P < 0.05. However, the total platelet sialic acid of fresh platelets was 62.5 +/- 5.6 nmol 10(-9) platelets compared to 47.2 +/- 4.6 nmol 10(-9) platelets after cryopreservation, P < 0.001. Similarly, the neuraminidase-labile sialic acid was 26.4 +/- 4.3 nmol 10(-9) platelets for fresh platelets and 17.6 +/- 4.0 nmol 10(-9) platelets after cryopreservation, P < 0.001. Using polyacrylamide gel electrophoresis with Western blotting, we showed a reduction in the platelet glycoprotein Gp Ib after cryopreservation, this was confirmed by using crossed immunoelectrophoresis. Electron microscopy revealed a significant change in platelet morphology after the cryopreservation procedure with disruption of the platelet membrane and also platelet shape change. These features may explain the changes in platelet electrokinetic properties.

Platelet surface charge heterogeneity: characterization of human platelet subpopulations separated by high voltage continuous flow electrophoresis.

Washed formol-fixed normal human platelets have been separated into surface charge-dependent subpopulations using high voltage continuous flow electrophoresis. The procedure is highly reproducible and the heterogeneity profile extends over 20-25 fraction tubes on the anodal side of the entry port to the separation chamber. Fractions have been subdivided into subpopulation pools A, B and C which have mean mobilities by analytical cytopherometry extending over the range 0.81-0.91 micron/s/V/cm from the least (C) to the most (A) electronegative cells. Coulter volume differences across the profile from 5.0 to 12.8 fl correlated well with electrophoretic mobilities whereas buoyant density appeared to be an independent parameter. Analysis of surface neuraminidase-labile sialic acid of the platelets in pools A and C correlated well with differences in electrophoretic mobility, whereas a similar relationship for the alkaline phosphatase-labile phosphate moieties (also believed to be contributory to cell surface electrokinetic properties) could not be established even though in both cases the profiles of the enzyme-treated platelets showed significant shifts towards the cathode when compared with untreated cells. Titration of surface DTNB-reactive sulphydryl (-SH) groups revealed an inverse relationship between electronegativity and membrane -SH group status. This electrophoretic expression of subpopulation heterogeneity within the circulating platelet pool may have advantages in studying clinical conditions where the profiles may reflect cell surface interactions 'in vivo'.

Influence of mono- and multivalent cations on the electrokinetic properties of normal human lymphoid and burkitt lymphoma cells.

Various mono- and multivalent cations, at constant ionic strength, affected the surface electrokinetic properties of normal human lymphoid and Burkitt lymphoma cells in a manner which reflected more the physicochemical properties and binding affinities of the cation than its valence. The effect was expressed in the changes of the magnitude of the net surface charge and in the shift of the isoelectric point of the surface. These changes were greater at the surface of Burkitt's lymphoma cells than at the surface of their normal cell-line counterparts.

Erythrocyte Surface Membrane Alterations

Electrophoretic mobility measurements were made of red blood cells obtained from patients with Duchenne and myotonic muscular dystrophy, from dystrophic mice and chickens, and from corresponding controls. Alterations in the erythrocyte surface electrokinetic properties were found in dystrophic mice and chickens and in many, but not all, patients with muscular dystrophy. The results are consistent with the concept of muscular dystrophy as a systemic membrane disease not limited to muscle.

Surface electrokinetic properties of two strains of Staphylococcus aureus during their cell growth cycle

Two strains of Staphylococcus aureus were investigated: S. aureus H, a normal wild-type strain, and 52A5, a mutant strain whose cell wall contains no teichoic acid but is made up entirely of mucopeptide. S. aureus H cells in the lag or stationary phase of growth had an electrophoretic mobility of −1.10 μm/s/V/cm while those in the logarithmic phase had a mobility of −0.80 μm/s/V/cm in saline at pH 7.2, 0.6 mM NaHCO 3, 25°C (I = 0.145 g-ions/l). S. aureus 52A5 cells in the same solution had a mobility of −0.87 μm/s/V/cm in lag and stationary growth phases but a mobility of −1.30 μm/s/V/cm in the logarithmic growth phase. The S. aureus H cell surfaces at lag phase had pKs of 3.2 and 9.5; at logarithmic phase, 4.2 and 9.0; and at stationary phase, 3.0 and 9.5. The 52A5 cell surfaces at lag phase had pKs of 2.3 and 10.3; at logarithmic phase, 1.7 and 8.5; at stationary phase, 2.6 and 10.2.

Electrokinetic properties of nuclear surfaces A comparison of nuclei from normal and regenerating rat liver

1. 1. Studies of various isolation procedures for nuclei were found to yield nuclear surfaces with significantly different electrokinetic properties. Citric acid-extracted nuclei have surface properties similar to those of the intact liver cell; citric acid-sucrose-extracted nuclei also have similar characteristics although these may be masked by variable irreversible DNA adsorption especially when using low ionic strength media for their isolation or electrophoretic examination. Sucrose extracted nuclei displayed considerable electrokinetic instability consistent with the gradual desorption of surface cytoplasmic components. 2. 2. A comparison of nuclei from normal and regenerating liver revealed no difference in their surface electrokinetic properties despite the probable adsorption of DNA at the nuclear surface in both groups when citric acid-sucrose-isolated nuclei were examined. 3. 3. In no instance was sialic acid demonstrable on the nuclear surface.

Relation between the zeta potential of rutile and its flotation with sodium dodecyl sulphate

AbstractThe influence of pH on the surface electrokinetic properties of the rutile‐solution interface has been studied; below pH 3.5 the surface is positively charged and above this pH value it is negatively charged. Adsorption of dodecyl sulphate anions from aqueous solution on to the rutile surface is influenced profoundly by the electrokinetic properties of the mineral‐solution interface, the surface showing decreased adsorption of anions with increase in pH. Flotation tests have shown that at constant pH, the flotation rate increases with collector concentration and that for a fixed collector concentration, a decrease in flotation rate occurred as the pH increased from 3 to 7.