Electrokinetic Properties Research Articles

The effect of CuO coatings on the electrokinetic properties of stone wool fibres determined by streaming potential measurements

Commercial stone wool fibres were modified with copper(II) oxide coatings. This oxide is widely used in processes of surface modification for filter materials to improve its bacterial retention. The microorganisms are already susceptible to low concentrations of copper in contrast to humans for which copper is an inert material in the concentration range. Additionally, the coatings changed the electrokinetic properties of the fibres. As a result, the isoelectric point (IEP) of the untreated fibres was shifted from acidic towards a more basic pH range. A positive or no charge on the surface of the fibres allows them to be a substrate for the positively charged adsorbents of negatively charged waterborne contaminants with the use of electrostatic adsorption. The coatings were prepared by dip coating with the use of two different coating precursors: the aqueous suspension of CuO nanoparticles and aqueous solutions of copper(II) nitrate trihydrate or copper(II) acetate or a mixture of thereof. The zeta potential of the modified fibres was determined by a streaming potential method. The adhesion of the coatings was tested by flushing and ultrasonication of the modified fibres. The isoelectric point of the fibres was shifted towards a more basic pH range for all precursors with the largest impact of the copper(II) nitrate trihydrate precursor. This coating changed the IEP of the fibres from 4.1 to 8.3 pH value. The highest calculated coverage of the coatings was in the range of 54% and was obtained by using copper(II) nitrate trihydrate/CuO nanoparticles precursor. Although, we do not predict such modified fibres to act as a standalone water filter, we believe they have the potential to be an excellent support material for active adsorbents.

Adsorbing behavior of polycarboxylate superplasticizer in the presence of the ester group in side chain

ABSTRACTThe effect of the ester group in side chain on adsorbing behavior and dispersion of polycarboxylate superplasticizer (PC) was studied by comparing the performance of two types of PC. The fluidity of cement paste was tested to discuss the dispersing ability and dispersing retention ability of PC. The total organic carbon analyzer was used to measure the adsorption amount, and the adsorption layer was obtained by x-ray photoelectron spectroscopy. Fourier-transform infrared spectroscopy, nuclear magnetic resonance, and pH value were used to verify the stability of the ester group, and the electrokinetic properties of cement particle were confirmed using the zeta potential measurement. The results show that the ester group in side chain reduces the initial dispersing ability while it increases the dispersing retention ability. The dispersing retention ability depends on the increase of adsorption amount and adsorption layer in 5–60 minutes, and the greater increase leads to the better dispersing retention ability. The ester group can be decomposed to release carboxyl group to enhance the adsorbing ability of PC under the condition of cement hydration, which is the main reason for the greater increase of adsorption amount and adsorption layer and the improvement in dispersing retention ability. It suggests that grafting the ester group is a good way to enhance the dispersing retention ability.

Simektit Süspansiyonlarının Bazı Elektrolit ve Polimer Solüsyonları İçerisinde Sedimantasyon ve Elektrokinetik Özellikleri

Simektit Süspansiyonlarının Bazı Elektrolit ve Polimer Solüsyonları İçerisinde Sedimantasyon ve Elektrokinetik Özellikleri

Lignosulfonate as a byproduct of wood pulp production: A potential precursor for the preparation of functional hybrid materials

<p>Functional hybrid materials based on magnesium lignosulfonate and silica were obtained and characterized. Magnesium lignosulfonate is a common waste product of the wood pulp industry, while silica is a well-known inorganic material with exceptional physicochemical properties. In this study, silicas with a spherical particle shape were synthesized using a sol-gel method and alternatively in a nonpolar medium. Silica was found to improve the thermal and electrokinetic properties of the final products. The resulting lignosulfonate/silica hybrid materials were analyzed with the use of advanced techniques and measuring methods: scanning electron microscopy, a laser diffraction method enabling particle size measurements, Fourier transform infrared spectroscopy, elemental analysis, thermogravimetry, electrophoretic light scattering, zeta potential measurements, low-temperature nitrogen sorption, and colorimetric analysis. The results enabled the hybrid materials to be characterized from the point of view of potential applications in various branches of industry (for example as polymer fillers, electroactive blends and biosorbents). We additionally indicate new methods for the utilization of waste products, a category to which lignosulfonate certainly belongs.</p>

Comparison of the Poly(vinyl alcohol) Adsorption Behaviour on the Mixed Oxides with Different Surface Structure

The adsorption and electrokinetic properties, as well as the stability of the mixed oxide suspensions in the absence and presence of poly(vinyl alcohol) – PVA were studied. Two alumina-silica-titania (AST) oxides were used: AST50 (TiO2 : 50 %, SiO2 : 28 %, Al2O3 : 22 %) and AST71 (TiO2 : 71 %, SiO2 : 8 %, Al2O3 : 21 %). All measurements were carried out in the pH range 3 – 9 as a function of the polymer molecular weight (72 000 and 100 000 Da) and degree of PVA hydrolysis (86 % and 98 %). The obtained results indicated that the PVA adsorption strongly depends on the solution pH – for AST50 it decreases and for AST71 increases with the pH rise. This is caused by various PVA chains conformation on the solid surfaces with different structures. The adsorption of poly(vinyl alcohol) influences on the stability of the mixed oxides suspension. The greatest effects were observed in the presence of PVA 100 000 at pH 3 for AST50 suspension and at pH 9 for AST71 system. In these cases, polymer addition leads to significant improvement of stability conditions of examined systems.DOI: http://dx.doi.org/10.5755/j01.ms.22.2.7778

Electrokinetic properties of iron-containing microporous glasses

The electrokinetic properties of the particles of microporous borosilicate glass powder containing the magnetite phase in its composition on the background of an indifferent electrolyte (NaCl) have been studied. It is found that the modification of two-phase sodium borosilicate glass with iron oxide leads to a shift in the position of the isoelectric point from pH 0.5 for alkali borosilicate (ABS) porous glass (PG) to pH 4.1 ± 0.1 for iron-containing ABS PG. The observed changes in the behavior of modified PG open up new prospects for their practical application.

The adsorption of uranium (VI) onto colloidal TiO 2 , SiO 2 and carbon black

The adsorption behavior of uranium (VI) onto colloidal hydrophobic carbon black and the hydrophilic, hydrous metal oxides, silica and titanium dioxide, was studied as a function of pH using quantitative adsorption isotherms and electrokinetic measurements of the suspended particles. Adsorption isotherms and micro-electrophoresis results were used in conjunction with uranium (VI) hydrolysis equilibrium data to identify the metal ion species adsorbing onto the various substrate surfaces as a function of pH. The study focuses on the solution conditions of metal ion concentration and pH, below the precipitation edge of solid uranium hydroxide. The adsorption of the uranium significantly modifies the electrokinetic properties of the colloidal adsorbent. The initial uranium (VI) species adsorbing at low pH on the different adsorbent surfaces is the uranyl ion (UO22+). For all adsorbents, the adsorption of the uranium (VI) renders the surfaces more positive compared to the native surface, over the pH range examined.

Molecular Characterization and Design of CMP Pads

Together with slurries, pads play an important role in the mechanical and chemical processes used to polish and planarize wafers. Pads are typically characterized based on their bulk physical, mechanical, and microstructural properties as they correlate to polishing performance. Surface interactions at the pad-slurry interface can be characterized using contact angle and zeta potentiometry to measure surface energy and electrokinetic properties. The molecular structure of the polyurethane material is a critical factor that defines many of the aforementioned pad characteristics. For example, the stiffness of a chain and the degree of cross-linking are important factors in targeting hardness, elasticity, temperature resistance, and chemical affinity. The ability to measure and understand the polymer structure and bond composition of a pad is a critical tool to rationalize performance and to design new materials that address future polishing needs. In this paper, a fundamental molecular study on the polymer structure and network formation will be described. The work was performed using Fourier Transform infrared spectroscopy coupled with a thermally controlled attenuated total reflection (ATR) accessory. After an overview of the main polyurethane infrared absorption bands, the investigation will provide important molecular formation insights related to the polymerization reaction (gelation), curing, and final structure of the polymer.

Electrokinetic Properties of the Pristine and Oxidized MWCNT Depending on the Electrolyte Type and Concentration.

Electrostatic stabilization is reduced in its efficiency in an electrolyte-containing environment. The effect of electrolyte concentration is mostly described as negative factor for dispersion stabilization. Usually, zeta potential and physical stability decrease at increasing electrolyte concentration. The purpose of the present study was to measure the surface properties of nanotubes in aqueous solution of monovalent electrolytes at different concentration. Characteristics such as size distribution, surface chemistry, surface charge, and dispersability in aqueous phase have been identified. Hydrodynamic size and zeta potential in aqueous multiwalled carbon nanotube (MWCNT) suspensions were determined at different pH with the desired concentrations of electrolyte of the cationic group (NaCl, KCl, CsCl) and the anionic group (NaClO4). The correlations between the response of the surface functionality of pristine and oxidized multiwalled carbon nanotubes and electrical double layer (EDL) forming at different ionic environments in the vicinity of a nanotube surface were determined. The nanotube dispersion stabilization was found to be more affected by ion size and pH medium then electrolyte concentration. The data obtained confirms the predominant role of surface reactions. The most stable dispersion of nanotubes was achieved in KCl electrolyte solution at less negative charge of the surface.

A Comparative Study on Electrokinetic Properties of Boronic Acid Derivative Polymers in Aqueous and Nonaqueous Media

A Comparative Study on Electrokinetic Properties of Boronic Acid Derivative Polymers in Aqueous and Nonaqueous Media

Interfacial layer effects on surface capacitances and electro-osmosis in electrolytes

Many properties of the interfacial layer of water at surfaces differ significantly from those of bulk water. The consequences are most significant for the double-layer capacitance and the electrokinetic properties. We model the interfacial hydration layer by a modified dielectric constant and a modified local viscosity over a single interfacial width. Analytic expressions in the low-charge Debye-Hückel approximation are derived and shown to describe experimental surface capacitance and electro-osmotic data in a unified framework.

Charge regulation phenomenon predicted from the modeling of polypeptide electrophoretic mobilities as a relevant mechanism of amyloid-beta peptide oligomerization.

Electrophoretic mobilities of amyloid-beta (1-40) and (1-42) peptides and their aggregates are modeled to study the amyloidogenic pathway associated with Alzheimer´s Disease. The near molecule pH generated by the intraparticle charge regulation phenomenon during the oligomerization of amyloid-beta (1-40) and (1-42) peptides is evaluated and discussed as a relevant mechanism supporting the "amyloid cascade hypothesis" proposed in the literature. A theoretical framework associated with the oligomerization of amyloid-beta peptides including simple scaling laws and the consideration of electrokinetic and hydrodynamic global properties of oligomers is presented. The central finding is the explanation of the near molecule pH change toward the pI when the oligomerization number increases. These results allow one to rationalize consecutive physical stages that validate the amyloid cascade hypothesis. Concluding remarks involving mainly the effects of pair and intraparticle charge regulation phenomena on the amyloidogenic pathway with some suggestions for future research are provided.

Electrokinetic Properties of Lubricin Antiadhesive Coatings in Microfluidic Systems

Lubricin is a glycoprotein found in articular joints which has long been recognized as being an important biological boundary lubricant molecule and, more recently, an impressive antiadhesive that readily self-assembles into a well ordered, polymer brush layer on virtually any substrate. The lubricin molecule possesses an overabundance of anionic charge, a property that is atypical among antiadhesive molecules, that enables its use as a coating for applications involving electrokinetic processes such as electrophoresis and electroosmosis. Coating the surfaces of silica and polymeric microfluidic devices with self-assembled lubricin coatings affords a unique combination of excellent fouling resistance and high charge density that enables notoriously "sticky" biomolecules such as proteins to be used and controlled electrokinetically in the device without complications arising from nonspecific adsorption. Using capillary electrophoresis, we characterized the stability, uniformity, and electrokinetic properties of lubricin coatings applied to silica and PTFE capillaries over a range of run buffer pHs and when exposed to concentrated solutions of protein. In addition, we demonstrate the effectiveness of lubricin as a coating to minimize nonspecific protein adsorption in an electrokinetically controlled polydimethylsiloxane/silica microfluidic device.

Analysis of electrokinetic properties of NiFe2O4 nanoparticles synthesized by DC thermal plasma route and its use in adsorption of humic substances

The paper reports the influence of electro-kinetic properties of nanoparticles of NiFe2O4 on the adsorption of humic substances (HS); with an aim of understanding their adsorption behavior. Crystalline single phase magnetic nanoparticles of NiFe2O4 are synthesized by gas phase condensation method using DC thermal plasma reactor. Due to the high temperature and steep temperature gradient this method helps in producing highly crystalline nanoparticles with sufficiently large number of surface states suitable for adsorption. These particles possessed high value of zeta potential, reducing their agglomeration and resulting into an enhanced adsorption capacity. However no significant influence of plasma parameters is observed on their zeta-potential and iso-electric values. The adsorption kinetics is studied and fitted to non-linear kinetic models and the best fit is observed for the pseudo first-order model. The analysis of adsorption isotherms suggests that the non-linear Langmuir model fits better as compared to Freundlich adsorption model. The adsorption of HS onto the nanoparticles is seen to depend on the pH value of the solution. A maximum adsorption of 5.2mg/g is obtained at pH value of 3.64. These results suggest that plasma synthesized nanoparticles of NiFe2O4 have high colloidal stability and can be employed as efficient adsorbents for the removal of humic substances from water sources.

Study of electrokinetic properties of nanofillers used for the preparation of nanocomposites

The aim of the studies was to determine, how the zeta potential and particle size of nanofillers affect the stability of the dispersion of nanoparticles in the electroinsulating varnish, and consequently can influence the varnish properties. We have investigated the nanofillers that had been used for the preparation of nanocomposites in our earlier works. It has been found that in toluene the zeta potential of all nanofillers is much increased. It enables modifying of nanofillers. Correlation between the properties of the nanocomposite and the results of the particle size measurements has been observed. Thus studies of electrokinetic properties can be used during the preparation of nanocomposites, as well to determine the factors affecting the nanoparticles deagglomeration and a preliminary determination of the optimal technological parameters of process of preparing of nanocomposites.

Zeta potential and surface charge of DPPC and DOPC liposomes in the presence of PLC enzyme

Zeta potential of liposomes is often measured in studies of their properties and/or applications. However, there are not many papers published in which zeta potential was determined during enzymatic reaction of a lipid. Therefore in this paper size, polydispersity index, and zeta potentials of 1,2-dipalmitoylsn-glycero-3-phosphatidylcholine (DPPC) and 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC) liposomes were investigated in 1 mM NaCl (pH 6.2) and phosphate buffer (pH 8.1) during 60 min of phospholipase C action at 20 and 37 °C. The hydrocarbon chains saturation differ these two phospholipids what appears in some differences in the zeta potential changes during the hydrolysis reaction run. The polydispersity index of the liposomes indicates that they are relatively stable and monodisperse, except for DPPC in phosphate buffer where up to 30 % of the initial amount forms larger size moieties, possibly aggregates of the liposomes, enzyme and the hydrolysis products. However, in this buffer zeta potential of the liposomes practically does not change during PLC action. Also the changes of zeta potential of DOPC liposomes are minor, although their negative values are much smaller than those of DPPC at both temperatures. These small changes of the potential may be due to compression of the diffuse double layer by present phosphate buffer. However, distinct changes of the zeta potentials in the presence of PLC take place in NaCl solution. The observed changes can be explained by reorientation of the phospholipid polar heads and their different density on DPPC and DOPC surface of the liposomes. Although it appeared that the zeta potential is not a very sensitive parameter for tracking the hydrolysis reaction in phosphate buffer, generally zeta potential enables the characterization of such reactions through determination of electrokinetic properties of liposomes as well as the polydispersity and size distribution of the liposomes do.

Glycobiology of the cell surface: Its debt to cell electrophoresis 1940-65.

This Review describes how in the period 1940-1959 cell electrophoresis (in the earlier literature often referred to as 'microelectrophoresis') was used to explore the surface chemistry of cells. Using the erythrocyte as a suitable model for the study of biological membranes, the early investigators were agreed on the presence of negatively charged groups at the surface of this cell. The contemporary dogma was that these were phosphate groups associated with phospholipids. Work in the 1960s, particularly on changes in the electrokinetic properties of erythrocytes following treatment with proteolytic enzymes, lead to the realization that the negatively charged groups at the red cell surface are predominantly due to sialic acids carried on glycoproteins. It quickly became apparent from cell electrophoresis that sialic acids have a ubiquitous presence on the surface of animal cells. This finding required that any complete model of the plasma membrane must include glycosylated molecules at the cell periphery, thus laying the foundations for the field termed 'Glycobiology of the Cell Surface'.

Zeta potentials of polydimethylsiloxane surfaces modified by polybrene of different concentrations.

Zeta potential is an important parameter for characterizing the electrokinetic properties of a solid-liquid interface. In this paper, zeta potentials of polydimethylsiloxane surfaces modified by polybrene (PB) solutions of different concentrations in Phosphate buffer solution and pure water were reported. The zeta potentials were measured by an induction current method. The measurements were validated both by a calibration curve based on the data reported in the published papers and by comparing the zeta potential determined by using the Smoluchowski equation and the measured velocity of the electrokinetic motion of particles in a microchannel.

Adsorption and Electrokinetic Properties of Catalase onto Perlite Samples

Adsorption and Electrokinetic Properties of Catalase onto Perlite Samples

Synthesis, surface characterization and electrokinetic properties of colloidal silica nanoparticles with magnetic core

In order to obtain functionalized silica colloids with magnetic properties, the three-step reaction, was carried out. The aqueous suspension of iron oxide nanoparticles as magnetic core (maghemite—γ-Fe2O3) was synthesized according to the Massart’s method (Massart in IEEE Trans Magn 17:1247–1248, 1981). A silica shell was obtained onto maghemite employing a modified sol–gel method by Salgueirino (Salgueirino-Maceira et al. in Adv Mater 19:4131–4144, 2006). As-synthesized magnetic silica core/shell nanocomposites were further functionalized by the post-grafting approach, using (3-Aminopropyl)-trimethoxysilane (APTMS) (Pham et al. in Langmuir 18:4915–4920, 2002). The obtained materials were characterized by nitrogen adsorption/desorption measurements, X-ray powder diffractometry (XRD), transmission electron microscopy (TEM). Particle sizes were measured by diffraction laser (DL). In order to establish colloidal stability of the system, zeta potential were measured. The syntheses routes led to obtain both, good purity of maghemite particles (more than 90 %) and their good coverage by outer silica shell. Thanks to their nanometer size and surface properties (especially, presence of amino groups which can ensure the electrostatic interaction between surface of adsorbent and adsorbate molecules), as-prepared nanocomposites can be considered as promising adsorbents. It can be found in the literature, that such systems are used in medicine as targeted drug delivery systems (Chen et al. in J Magn Magn Mater 322:2439–2445, 2010; Bele et al. in J Chromatogr B 867:160–164, 2008) or in environment protection as magnetically removable adsorbents (Giakisikli and Anthemidis in Anal Chim Acta 789:1–16, 2013; Tural et al. in J Phys Chem Solids 72:968–973, 2011).