Influence of surface conductivity on the apparent zeta potential of TiO2 nanoparticles

Abstract

Zeta potential is a physico-chemical parameter of particular importance in describing ion adsorption and electrostatic interactions between charged particles. Nevertheless, this fundamental parameter is ill-constrained, because its experimental interpretation is complex, particularly for very small and charged TiO(2) nanoparticles. The excess of electrical charge at the interface is responsible for surface conductance, which can significantly lower the electrophoretic measurements, and hence the apparent zeta potential. Consequently, the intrinsic zeta potential can have a larger amplitude, even in the case of simple 1:1 electrolytes like NaCl and KCl. Surface conductance of TiO(2) nanoparticles immersed in a NaCl solution is estimated using a surface complexation model, and this parameter and particle size are incorporated into Henry's model in order to determine a constrained value of the zeta potential from electrophoresis. Interior conductivity of the agglomerates is calculated using a differential self-consistent model. The amplitude of estimated zeta potential is greater than that derived from the von Smoluchowski equation and corresponds to the electric potential at the outer Helmholtz plane calculated by our surface complexation model. Consequently, the shear plane may be located close to the OHP, contradicting the assumption of the presence of a stagnant diffuse layer at the TiO(2)/water interface.

Influence of surface conductivity on the apparent zeta potential of calcite

“…where a is the mean radius (in m) and s Σ is the specific surface conductivity (in S) of the crystals, which can be computed by an electrostatic surface complexation model [25,29,36]. Eq.…”

Modeling the evolution of complex conductivity during calcite precipitation on glass beads

“…Eq. (20) holds for small electrical potentials at the onset of the diffuse layer of magnitude <k b T /e but remains accurate for larger electrical potentials (Hunter 1981;Lyklema 1991;Revil & Glover 1997;Leroy et al 2011). As we are interested to interpret the complex conductivity experiment of Wu et al (2010) involving pore water containing saline water (I ∼ = 0.03 mol L −1 ) where the diffuse layer is compressed and zeta potential is low, eq.…”

Molecular dynamics simulations of the electrical double layer on smectite surfaces contacting concentrated mixed electrolyte (NaCl–CaCl2) solutions

“…Water and solute diffusion coefficients near solid-water interfaces are fundamental parameters that influence solute mass fluxes in nanoporous media, such as natural or engineered clay barriers [54], the electrophoretic mobility of nanoparticles [11], and the rates of transport-limited interfacial reactions [120]. At the molecular level, the diffusion coefficient can be calculated using the well-known Einstein relation [121]:…”

“…This view is adopted, for example, as the molecular basis for the widely-applied triple-layer model (TLM [3][4][5]), on which the distribution of ions near a charged planar solid surface is calculated under a set of simplifying assumptions that include assigning all ISSCs to a plane at the solid surface (0-plane), all OSSCs to a second plane lying farther into the aqueous phase (β-plane), and all DS species to a region lying beyond a third plane farther out than the β-plane (d-plane) ( Inferences about EDL surface speciation and molecular structure from experimental data on proton and ion adsorption [6,7,8], salt filtration efficiency [9], second harmonic generation [10], electrophoretic mobility [11], or interparticle forces [12] are necessarily sensitive to simplifying EDL model assumptions such as those just described for the TLM [13][14][15][16]. Models of the EDL that approximate liquid water as a uniform dielectric continuum (such as the Poisson-Boltzmann equation [17,18], hypernetted chain theory [19,20], or the primitive model [18,21]) inherently cannot describe surface complexes [17,18].…”