Kinetics of magnetic flocculation. II. Flocculation of coarse particles

Abstract

For pt.I see ibid., vol.23, p.1447 (1990). In theoretical studies of flocculation kinetics one usually assumes that the flocculation process reaches a steady state very rapidly. This assumption is invalid when a long-range attraction between the particles is present. In this paper the authors show that such a situation occurs for magnetic flocculation, provided that the particles are not too small. A full mathematical description of such a process is very difficult. As an alternative, a modified version of von Smoluchowski's model for rapid flocculation is presented, which describes the qualitative features of their experimental observations of aqueous Mn2O3 colloids with a particle diameter of about 0.8 mu m quite well. In particular this model suggests that the deviations from the 'steady-state' predictions increase very rapidly with increasing particle size, making these results almost always incorrect for many practical applications of magnetic flocculation.