Spontaneous crystallization of potassium chloride from aqueous and aqueous‐ethanol solutions Part 2: Mechanism of aggregation and coalescence of crystals

Abstract

Published data on aggregation kinetics of potassium chloride crystals at its spontaneous crystallization from supersaturated aqueous and aqueous-ethanol solutions were analysed. It was found that the crystals coalesced through contact nucleus-bridges according to the mechanism proposed by Polak. The kinetics of aggregation were described by the Smoluchowski equation for coagulation of colloidal particles. The kinetic coefficient of aggregation process depended on supersaturation, temperature of solution and other characteristics of system. The specific surface energy of potassium chloride 0.98 mJ/m 2 was found.

Spontaneous crystallization of sodium chloride from aqueous‐ethanol solutions – Part 2: Mechanism of aggregation and coalescence of crystals

“…Earlier [14] it was shown that kinetics of aggregation of potassium chloride crystals at spontaneous crystallization from aqueous and aqueous-ethanol solutions in sympathy with coagulation of colloidal particles were describes by the famous Smoluchowski equation [15]. That equation for this case was transformed into [7,14]:where τ is the time (s); K a is the aggregation constant; τ 0 is the length of the induction period of crystallization (s); N 0 , N are the total numbers of crystals of salt in solution at the end of the induction period of crystallization and at time τ , respectively. During the crystallization of potassium chloride the aggregation constant K a decreased as result of drop in supersaturation of solution, and was determined by expression [7,14]:…”

“…But at present theoretical models of the crystallization describe this process only on a quality level [8][9][10][11][12][13]. Earlier [14] it was shown that kinetics of aggregation of potassium chloride crystals at spontaneous crystallization from aqueous and aqueous-ethanol solutions in sympathy with coagulation of colloidal particles were describes by the famous Smoluchowski equation [15]. That equation for this case was transformed into [7,14]:…”

“…During the crystallization of potassium chloride the aggregation constant K a decreased as result of drop in supersaturation of solution, and was determined by expression [7,14]:…”

The role of dielectric constant in sodium chloride solution chemistry: Magnitude of super saturation

“…Crystallization of sodium chloride was investigated in several works (Birchall and Davey, 1981;Mohameed et al, 1997;Kubota et al, 2000;Al-Jubbouri andUlrich, 2001, 2002;Doki et al, 2002;Linnikov, 2004;2006a, b;2007). It was reported that the overall growth, dissolution rates and the surface integration step are linear with respect to supersaturation of solution (Mohameed et al, 1997;Al-Jubbouri andUlrich, 2001, 2002).…”

“…The kinetics of spontaneous crystallization of potassium and sodium chlorides have been extensively studied by Linnikov (2004Linnikov ( , 2007, who determined the growth rates and activations energies and found that the earlier was proportional to supersaturation. He described the kinetics of the observed crystals aggregation by the famous Smoluchowski equation for coagulation of colloid particles.…”