Colloid potential measurements

Contaminated bed sediments exist at numerous locations in the United States and around the world. These result mainly from past indiscriminate pollution of our aquatic environments and consist of freshwater and marine bodies including streams, lakes, wetlands, and estuaries. The bed sediments contain many hydrophobic organic compounds and metal ions that in the course of time act as sources of pollutants of the overlying aqueous phase. There are a number of transport pathways by which pollutants are transferred to the aqueous phase from contaminated sediments. One of the lesser known, but potentially important, modes of transport of pollutants from bed sediments is by diffusion and advection of contaminants associated with colloidal-size dissolved macromolecules in pore water. These colloids are measured in the aqueous phase as dissolved organic compounds (DOCs). (These are defined operationally as particles with a diameter smaller than 0.45 micrometer.)... 

One of the applications of zeta potential measurements is in the determination of surface charges of colloids such as proteins. We look into this briefly in Section 12.10 and derive the equation connecting the surface charge to the zeta potential under some simplifying assumptions. 

Surface polarity can also be independently evaluated by physical means. deMayo and coworkers have assigned surface polarity of silica gel particles by observing shifts in the absorption spectra of absorbed spiropyrans which are sensitive to solvent polarity . Darwent and coworkers have shown that kinetic salt effects follow surface charge on colloidal titanium dioxide and, with zeta potential measurements, that surface area and charge could be separately evaluated... 

R.H. Yoon and J.L. Yorden, Zeta-potential measurements on microbubbles generated using various surfactants, J. Colloid Interface Sci. 113 (1986) 430-438. 

In addition, the surface charge (or zeta potential) of suspended colloids was measured on separate pH-adjusted aliquots using a laser micro-electrophoretic instrument. These measurements were made between the pH range of 2 to 12. 

Temperature- and pH-sensitive core-shell microgels consisting of a PNIPAAm core crosslinked with BIS and a polyvinylamine (PVAm) shell were synthesized by graft copolymerization in the absence of surfactant and stabilizer [106] The core-shell morphology of the microgels was confirmed by TEM and zeta-potential measurements. Other examples of core-shell microgel systems are PNIPAAm-g-P(NIPAM-co-styrene) colloids [107] or PS(core)-g-PNIPAAm (shell) particles [108],... 

The work of Larson et al. (62) represented the first detailed study to show agreement between AFM-derived diffuse layer potentials and ((-potentials obtained from traditional electrokinetic techniques. The AFM experimental data was satisfactorily fitted to the theory of McCormack et al. (46). The fitting parameters used, silica and alumina zeta-potentials, were independently determined for the same surfaces used in the AFM study using electrophoretic and streaming-potential measurements, respectively. This same system was later used by another research group (63). Hartley and coworkers 63 also compared dissimilar surface interactions with electrokinetic measurements, namely between a silica probe interacting with a polylysine coated mica flat (see Section III.B.). It is also possible to conduct measurements between a colloid probe and a metal or semiconductor surface whose electrochemical properties are controlled by the experimenter 164-66). In Ref. 64 Raiteri et al. studied the interactions between... 

Physical techniques for evaluating surface polarity led deMayo and coworkers to assign relative rates of reaction on silica gel particles from shifts in the absorption spectra of absorbed spiropyrans [76, 77]. Similarly, Darwent and coworkers demonstrated that kinetic salt effects correlate with surface charge and with zeta potential measurements on colloidal titanium dioxide [80]. 

The study of the electric field strength effect on the shape of the density gradient formed in the TLF cell indicated an important difference compared with the first approximation theoretical model. A series of experimental data and the theoretically calculated curves are shown in Figure 6. The difference can be caused by the interactions between the colloidal particles of the binary density forming carrier liquid. Moreover, the electric field strength across the cell or channel thickness was estimated from the electric potential measured between the electrodes, but the electrochemical processes at both electrodes can contribute to this difference. 

Barratt, G. Characterization of colloidal drug carrier systems with zeta potential measurements. Pharmaceutical Technology Europe 1999, 25-32. 

The practical significance of zeta-potential measurement lies in the fact that strong empirical correlation exists between the measured zeta potential of the system and the properties of the system which are the manifestation of the electrostatic interfacial phenomenon. Since the measurement of zeta potential can be conveniently performed, it becomes an ideal parameter for use in routine testing. Zeta-potential control has been successfully applied to various technical fields involving colloidal and non-colloidal systems. 

The physical stability of a colloidal system is determined by the balance between the repulsive and attractive forces which is described quantitatively by the Deryaguin-Landau-Verwey-Overbeek (DLVO) theory. The electrostatic repulsive force is dependent on the degree of double-layer overlap and the attractive force is provided by the van der Waals interaction the magnitude of both are a function of the separation between the particles. It has long been realized that the zeta potential is a good indicator of the magnitude of the repulsive interaction between colloidal particles. Measurement of zeta potential has therefore been commonly used to assess the stability of colloidal systems. 

Zeta-potential measurement has long been recognized as an excellent tool for characterizing colloidal systems. Its practical significance stems from the fact that... 

Nishimura, S. et al., Zeta potential measurement of muscovite mica basal plane-aqueous solution interface by means of plane interface technique, 7. Colloid Interf. Sci., 152, 359, 1992. 

Smit, W. and Stein, H.N., Electroosmotic zeta potential measurements on single crystals, 7. Colloid Interf. Sci., 60, 299, 1977. 

Moritz, T. et al.. Investigation of ceramic membrane materials by streaming potential measurements. Colloids Surf. A, 195, 25, 2001. 

Avena, M.J., Camara, O.R., and de Pauh, C.P., Open circuit potential measurements with Ti/TiOj electrodes, Colloids Sutf, 69, 217, 1993. 

Zhang, J.S., Stanforth, R., and Pehkonen, S.O., Proton-arsenic adsorption ratios and zeta potential measurements Implication for protonation of hydroxyls on the goethite surface, 7. Colloid Interf. Sci., 315, 13, 2007. 

Ricq, L. et al., Use of electrophoretic mobility and streaming potential measurements to characterize electrokinetic properties of ultrafiltration and microfiltration membranes, Colloids Surf. A, 138, 301, 1998. 

Hussain, S.A., Demirci, S. and Ozbayoglu, G., Zeta potential measurements on three clays from Turkey and effects of clays on coal flotation, J. Colloid Interf. Sci., 184, 535, 1996. 

Carlson, K. and Hall, M.. Streaming potential measurements performed on silicate and calcium aluminate glass microspheres, Colloids Surf. A, 325, 101. 2008. 

Limousy, H. et al.. Determination by zetametry and streaming induced potential measurements of the amounts of catalytic precursors necessary to saturate a support. Colloids Surf. A, 181, 91, 2001. 

Labib, M.E. and Williams, R., The use of zeta-potential measurements in organic solvents to determine the donor-acceptor properties of solid surfaces, 7. Colloid Intetf. Sci., 91, 356, 1984. 

Zhukov, A.N., Duda, L.V., and Fedorova, I.L., Effect of the surface conductance on electrokinetic potential measured in nonaqueous media. Colloid J., 63, 301, 2001. 

Zeta potential measurements show that particles coated with NOM have the greatest negative charge (results not shown). This supports the hypothesis that salts present in the NOM allow the colloids to... 

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