KINETICS OF RAPID COAGULATION OF MONODISP ERSE SILICON DIOXIDE SUSPENSION

Using the Single Particle Optic Sizer method the kinetics of rapid coa gulation of monodisperse SiO2 (r = 265 nm) suspension in KCl and CaCl2 solutions was studied. The rate constant of the process (K-11) is 1,9 . 10(-12) cm(3)/sec, which is only about one third of Smoluchowski's value for the overall rate constant. This discrepancy is explained by the retardation effect of hydrodynamic interactions. For suspensions w ith particle number between 2,5 . 10(8) and 1,9 . 10(9) the k(11) valu e is independent of the initial particle number and of the pH of the s olution (between pH 6.8 and 10). The ratio of coagulation values of mo novalent and bivalent counterions both in perikinetic and orthokinetic conditions is 50, which means that the suspension studied (at pH = 6. 8 - 10) is electrostatically stabilized. The role of particle size in the mechanism of stabilization of SiO2 suspensions at different pH val ues is discussed.