DISPERSION MECHANISM OF COAGULATED PARTICLES IN LIQUID FLOW

This paper reviews our recent research results for the dispersion mech anisms of agglomerated colloidal particles in acceleration flow and sh ear flow, using latex particles of 1.1-5.2 mu m in diameter. (1) Exper imental results of the dispersion of coagulated particles by an accele rating suspension in a convergent nozzle are well correlated by a disp ersibility DS, which is defined as the ratio of the separation force t o the interaction force between particles (van der Waals force and ele ctrostatic force). (2) The dispersion is enhanced by an increase of th e surface potential and electrolyte concentration under a constant ext ernal force, which can be explained on the basis of the DLVO theory. ( 3) In a shear flow field, both dispersion and shear coagulation occur simultaneously. A definition of dispersibility is proposed as DM = M(b )/M(t), where M(b) is the bending moment induced by the drag force on the doublet, and M(t) is the moment required to separate the two adher ing spheres. For DM>1, doublets in the shear flow of a concentric rota ting cylinder become dispersed. For DM<1, shear coagulation overcomes dispersion and new doublets are formed.