Induced polarization and surface electrochemistry

Abstract

Induced-polarization (IP) responses arising from activation overvoltage are investigated, with the goal of relating established electrochemical properties and processes to IP time constants. In activation overvoltage, an electrical double layer with a well-defined areal capacitance forms at the mineral-electrolyte interface. This study shows that the known capacitance of the interface is compatible with observed initial time constants for the decay of electrode polarization. Furthermore, because the electrical double-layer capacitance is determined largely by the electrolyte and not the mineral, the conclusion is that, although the polarization is caused by the presence of the mineral, the time constants of the decay are determined primarily by the electrolyte and not the mineral. The dependence of the capacitance on the sign and magnitude of the potential implies that the effective decay time constant will be small at the start of depolarization and will progress to larger values as the decay proceeds.

Geophysical Monitoring of Coupled Microbial and Geochemical Processes During Stimulated Subsurface Bioremediation

“…S11; R ct 1 ), facilitating greater rates of electron transfer and a phase response reflective of a diffusion-controlled process (13,14,21). Under such conditions, the composition of the mineral(s) facilitating electron transfer is of minimal importance and in agreement with recently reported results (14) and previous studies investigating the electrochemical nature of the IP response (13).…”

“…Among these methods, the induced polarization (IP) technique has shown excellent sensitivity to enhanced microbial activity (5,7,(9)(10)(11)(12). Such studies, combined with theoretical investigations exploring the electrochemical mechanisms underlying the IP response (13,14), suggest it is well suited to monitoring stimulated subsurface bioremediation under field conditions. Analogous to laboratory electrochemical approaches, the IP method involves injection of variable frequency currents into the ground and the measurement of resulting voltage potentials via electrodes located above and below the ground surface.…”

On the pore water chemistry effect on spectral induced polarization measurements in the presence of pyrite

“…Such studies mainly focus on the role of the metal content (total weight or volume fraction percentage) and physical (textural) properties such as the metallic particle grain size and surface area on the spectral induced polarization (SIP) response. In contrast, relatively few studies have examined the significance of the physical and chemical characteristics of the metal-electrolyte interface controlling the IP-effect (e.g., Flekkøy, 2013;Gurin et al, 2015;Hubbard et al, 2014;Merriam, 2007;Placencia-Gómez and Slater, 2014) in such systems.…”

“…1b. The faradaic conduction path provides an additional charge transport process in the EDL (Merriam, 2007), giving rise to a charge-transport conductivity (σ * ct ) in addition to the surface conductivity (σ* surf ), where the latter accounts for the ionic space charge which is not engaged by redox reactions with the metallic mineral, i.e., a non-faradaic conduction path. Thus, when redox reactions take place at the interface, the real conductivity will be determined by the superposition of different conduction paths σ′ = f (σ w , σ′ surf , σ′ ct , σ e ), where i ct may drive electronic conduction (σ e ) through isolated metallic particles.…”

Supercooled interfacial water in fine-grained soils probed by dielectric spectroscopy

“…The mostly negative surface charge of the mineral surface (silicates) in contact with an aqueous electrolyte solution results in the formation of a boundary layer (electrical double layer -EDL). In principle, the interface layer consists of the surface charge of the mineral and an equivalent number of so-called counterions in the free electrolyte (Merriam, 2007). Tieleman and Berendsen (1996) stated that water molecules are ordered at the mineral surface according to two principles: (i) they effectively compensate for the local dipolar charge distribution of the surface molecules, and (ii) they reorient themselves due to the geometric constraints of the surface.…”