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Interfacial Catalysis at Oil/Water Interfaces
Published in Alexander G. Vdlkdv, Interfacial Catalysis, 2002
In ion-association extraction systems, hydrophobic and interfacially adsorbable ions are included. Complexes of Fe (II), Cu (II), and Zn (II) with 1,10-phenanthroline (phen) and its hydrophobic derivatives exhibited remarkable interfacial adsorptivity, although the ligands themselves can hardly adsorb at the interface, unless protonated [28-30]. Solvent-extraction photometry of Fe (II) with phen is widely used for the determination of trace amounts of Fe (II). The extraction-rate profiles of Fe (II) with phen and its dimethyl (DMP) and diphenyl (DPP) derivatives into chloroform were investigated by the HSS method. In the presence of 0.1MNaClO4, both the formation rate of the phen complex and its interfacial adsorption were remarkably dependent on the anions of Cl- and ClO4-. The initial extraction rate was described by the equation:
Dielectric Thermoscopy Characterization of Water Contaminated Grease
Published in Tribology Transactions, 2018
Nicholas Dittes, Anders Pettersson, Pär Marklund, Defeng Lang, Piet M. Lugt
There is more than one physical property that contributes to the functionality of this measurement. Research shows that the dielectric constant of water rises rapidly as the frequency of measurement becomes lower (Angulo-Sherman and Mercado-Uribe (25)). This is due to two properties of water: the first results from the ability of water to separate into ion pairs that can move toward the charged electrodes, decreasing reactance and increasing capacitance. Reactance is the imaginary part of impedance, meaning that a smaller magnitude capacitive reactance results in a higher opposition of the capacitor to a change in voltage or current. The ions increase ionic conduction, allowing electrons to move more easily and, additionally, with a lower frequency the ion pairs can separate farther resulting in more stored energy (“Ion Association” (26)). The second involves the dipole pairs of water molecules that polarize according to the direction of the electric field (Lewowski (23)). This happens only with low frequencies (in the range of tens or hundreds of Hertz, not megahertz or higher) because there is a greater time between alternating electric fields, thus allowing for a charge to be stored in either polarized dipoles or ion pairs due to it being a “slow” process (Trout and Parrinello (22)). Normally, dielectric properties are measured at frequencies above 1 MHz (i.e., radio frequency–based techniques) to reduce the mentioned increases in dielectric constant but are more complicated than low-frequency measurements (Dean, et al. (20)). In other words, more typical dielectric measurements use high frequencies (in the range of megahertz to gigahertz), so the contribution to the impedance of the measurement from ionic conduction is less than that of the impedance due to the capacitance (Lewowski (23); Bonanos, et al. (27); Flaschke and Trankler (28)).