Article

Measurement and interpretation of electrokinetic phenomena. J Colloid Interface Sci

University of Granada, Granada, Spain.
Journal of Colloid and Interface Science (Impact Factor: 3.37). 06/2007; 309(2):194-224. DOI: 10.1016/j.jcis.2006.12.075
Source: PubMed

ABSTRACT

In this report, the status quo and recent progress in electrokinetics are reviewed. Practical rules are recommended for performing electrokinetic measurements and interpreting their results in terms of well-defined quantities, the most familiar being the zeta-potential or electrokinetic potential. This potential is a property of charged interfaces and it should be independent of the technique used for its determination. However, often the zeta-potential is not the only property electrokinetically characterizing the electrical state of the interfacial region; the excess conductivity of the stagnant layer is an additional parameter. The requirement to obtain the zeta-potential is that electrokinetic theories be correctly used and applied within their range of validity. Basic theories and their application ranges are discussed. A thorough description of the main electrokinetic methods is given; special attention is paid to their ranges of applicability as well as to the validity of the underlying theoretical models. Electrokinetic consistency tests are proposed in order to assess the validity of the zeta-potentials obtained. The recommendations given in the report apply mainly to smooth and homogeneous solid particles and plugs in aqueous systems; some attention is paid to nonaqueous media and less ideal surfaces.

Download full-text

Full-text

Available from: Fernando González-Caballero
  • Source
    • "The various labelled diamonds in (a) show data obtained using natural or synthetic formation brine (FMB). studies have suggested that the two methods may yield different results (e.g., [52,10]). To test this, we compare zeta potential measurements obtained using both methods on the Portland Limestone , varying pCa in 0.05 M NaCl electrolyte (Fig. 10). "
    [Show abstract] [Hide abstract]
    ABSTRACT: We report measurements of the zeta potential on intact limestone samples obtained using the streaming potential method (SPM), supplemented by the more ubiquitous electrophoretic mobility method (EPM). The effect of the potential-determining ions (PDI) Ca, Mg and SO4, and the total ionic strength controlled by NaCl concentration, is investigated over the range typical of natural brines. We find that the zeta potential varies identically and linearly with calcium and magnesium concentration expressed as pCa or pMg. The zeta potential also varies linearly with pSO4. The sensitivity of the zeta potential to PDI concentration, and the IEP expressed as pCa or pMg, both decrease with increasing NaCl concentration. We report considerably lower values of IEP than most previous studies, and the first observed IEP expressed as pMg. The sensitivity of the zeta potential to PDI concentration is lower when measured using the SPM compared to the EPM, owing to the differing location of the shear plane at which the zeta potential is defined. SPM measurements are more appropriate in natural porous samples because they reflect the mineral surfaces that predominantly interact with the adjacent fluids. We demonstrate that special cleaning procedures are required to return samples to a pristine zeta potential after exposure to PDIs. We apply our results to an engineering process: the use of modified injection brine composition to increase oil recovery from carbonate reservoirs. We find a correlation between an increasingly negative zeta potential and increased oil recovery.
    Full-text · Article · Jan 2016 · Colloids and Surfaces A Physicochemical and Engineering Aspects
  • Source
    • "Gouy[7]and Chapman[8]developed a diffuse layer (DL) theory. Stern extended that theory by proposing a model in which the interfacial layer is divided into two parts[9], the inner Helmholtz plane and the outer Helmholtz plane[10]. It has been shown[11]that the Stern model is applicable away from the surface, but cannot be taken literally near the surface. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Aluminum oxide-hydroxide nanolayer with a thickness of approximately 1.2 nm is electroadhesively deposited onto silicious support material with large surface area of about 50 m2/g, forming a highly electropositive composite of boehmite nanolayer in the form of monocrystalline oxide/hydroxide (α-Al2O3·H2O) on the second electronegative solid. The composite can be viewed as a sphere with a rough surface and charge density of approximately 0.08 C/m2. This creates a significant electric field with negligible screening (ka ≪ 1) in the region close to the surface of the nanocomposite. This field attracts nano- and micron-sized particles from as far as 200 μm in a few seconds, many orders of magnitude greater than conventional Derjaguin–Landau–Verwey–Overbeek (DLVO) theory, which predicts only nanometer-scale effects arising from the presence of the surface. The strong electric field on the surface is then able to retain small particles such as viruses, atomically thin sheets of graphene oxide, RNA, DNA, proteins, dyes as well as heavy metals such as cobalt, arsenic, and lead. Alumina’s nanolayer surface can be further functionalized by adding other sub-micron or nano-sized particles to target a specific contaminant. An example is shown where alumina nanolayer is coated with nano-sized iron monohydrate to yield an arsenic sorbent that shows high sorption capacity.
    Preview · Article · Oct 2015 · International Journal of Smart and Nano Materials
    • "The solutions used for pH titration were 0.1 M HCl and 0.1 M NaOH. The electrophoretic mobilities were converted into zeta potential using Smoluchowski's formula [20] [21]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Bovine serum albumin (BSA) and zinc oxide nanoparticles (ZnO NPs) are chosen as a model system to investigate NPs-protein corona complex formation. ZnO NPs with average size of ∼20nm are coated with BSA using covalent and non-covalent conjugation at temperatures of 4°C and 20°C. The interaction mechanism between ZnO NPs and BSA is studied by using UV-vis absorption, fluorescence, synchronous fluorescence and Raman spectroscopy. Raman spectra of BSA in the presence of ZnO NPs are registered for the first time and confirm decreased α-helix content, increased unstructured folding and β-sheet content in BSA structure. The synchronous fluorescence spectra revealed that the hydrophobicity of the tyrosine residue is decreased and that of the tryptophan is increased. The relation of elucidated changes in BSA structure of BSA-coated ZnO NPs cytotoxicity is tested for CHO cell viability and reactive oxygen species (ROS) generation in vitro. Covalent and non-covalent binding of BSA to ZnO NPs reduces ZnO NPs cytotoxicity and ROS generation, however changes in BSA conformation makes corona less protective against ZnO NPs. Copyright © 2015 Elsevier B.V. All rights reserved.
    No preview · Article · Jul 2015 · Colloids and surfaces B: Biointerfaces
Show more