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Electrokinetically Enhanced In Situ Soil Decontamination
Published in Donald L. Wise, Debra J. Trantolo, Remediation of Hazardous Waste Contaminated Soils, 2018
Sibel Pamukcu, J. Kenneth Wittle
Another effect that retards the ionic velocity is the relaxation effect.47 This phenomenon comes about as the central ion is suddenly moved in its atmosphere; the atmosphere will tend to attain a asymmetrical shape about the central ion due to time lapse between the responses of the central ion and the ionic atmosphere. If the central ion moves steadily in the applied electric field, the effect of a permanent distortion of the ionic atmosphere will tend to retard the ionic velocity. The average charge density will tend to decrease in front of the moving ion, and it will increase behind it. The excess charge behind the ion induces an electrostatic retardion on the moving ion. The magnitude of ion velocity retardation by the electrophoretic and the relaxation effects are directly proportional to the ionic concentration. As the ionic concentration increases, the charge density of the ionic atmosphere increases; therefore, the forces associated with the electrophoretic and electrostatic retardation increase.
Associations of Impurity Atoms
Published in Victor I. Fistul, Impurities in Semiconductors, 2004
The Debye-Huckel theory suggests that a dense atmosphere of oppositely charged ions is formed, with time, around every ion in an electrolytic solution. So, the interaction of ions is actually an interaction of ionic atmospheres. The charge of an ionic atmosphere grows with total ion concentration in the solution and decreases with distance from the atmosphere center. In an external electric field, cations and anions move in opposite directions, together with their atmospheres slightly lagging behind, thereby retarding the movement of ions. Ions are also retarded because of the attrac-tion between oppositely charged ionic atmospheres. These retarding effects decrease ion mobility. So the internal energy of an electrolytic solution appears to be the sum of two components: one is U0 characterizing the inter-nal energy of the uncharged particle subsystem and the other is Ue charac-terizing the subsystem of electrical charges. All thermodynamic functions are thought to consist of two parts corresponding to the uncharged and char-ged components of the solution. The behavior of uncharged particles is des-cribed fairly rigorously by well-known thermodynamic relations. But in order to describe the behavior of charged particles, one has to find the Helmholtz free energy due to the action of charges, or to inter-ion interactions.
Biothermodynamics
Published in Marc J. Assael, Geoffrey C. Maitland, Thomas Maskow, Urs von Stockar, William A. Wakeham, Stefan Will, Commonly Asked Questions in Thermodynamics, 2022
Marc J. Assael, Geoffrey C. Maitland, Thomas Maskow, Urs von Stockar, William A. Wakeham, Stefan Will
Here, mi, L, ρA, and kB are the molality of the ion i, the Avogadro constant, the density of the solvent A and the Boltzmann constant, respectively. For water at 25°C, the parameter α = 1.172 mol1/2 kg−1/2. Note that this activity coefficient refers to the molality and not the mole fraction (as in Question 4.6) for reasons that are explained in Question 8.4. Details on the use of molality are provided in Question 5.4.2.1. Debye and Hückel used the following approximations to derive Equation 8.6:In highly dilute solutions strong electrolytes dissociate completely into ions.Electrostatic interactions impose some degree of order over random thermal motions.Non-ideality is only a result of electrostatic interactions.Ions are considered as non-polarizable point charges.The solvent is considered to be a structureless, continuous medium characterized by a bulk macroscopic property with relative permittivity, ε.No electrostriction (i.e. no shape changes under the application of an electric field) is allowed.Each ion is assumed to have an ionic atmosphere owing to all other ions in the electrolyte solution. The charge of each ion has to be balanced by the charge of the ionic atmosphere owing to the electro-neutrality condition. Although the ions of the ionic atmosphere are discrete charges, the ionic atmosphere itself is described as though it would be a smeared-out cloud of charge whose density varies continuously throughout the solution.
Relationships of pulsed frequency and anammox bacteria growth rate, at low temperatures
Published in Environmental Technology, 2022
Chi Zhang, Chao Wang, Ze Lv, Xiaomin Hu
In an aqueous solution, positive or negative ions existed as hydronium ions causing the movement of hydration ions through the movement of charged ions. According to the Debye-Huckel theory, the ion distribution in the solution can be regarded as the composition of the ionic atmosphere. However, the ionic atmosphere had a negative effect on the movement of the central ion. The central ion of the ionic atmosphere would be removed from the ionic atmosphere with the effect of the electric field, and this result caused these ions to be rearranged. Besides, the rearrangement of the surrounding water molecules was also due to the rearrangement of these ions. However, with the effect of the electric field, the equilibrium status of the ionic atmosphere was broken. The new ionic atmosphere of the central ion was not built up, meanwhile the previous ionic atmosphere was also not completely damaged. Hence, the ionic atmosphere was not symmetry, and this asymmetric ionic atmosphere had a resistance force for the movement of the central ion, causing the ion migration rate lower.