KINETICS OF COLLOIDAL PARTICLE DEPOSITION ON PULP FIBERS .1. DEPOSITION OF CLAY ON FIBERS OF OPPOSITE CHARGE

The rate of deposition of clay particles on oppositely charged fibers was measured in five systems where the negative surface charge of either the fibers or the clay was reversed by adsorption of cationic polyethylenimine or pH control. A theoretical model of particle deposition kinetics derived from Langmuir analysis is presented, which is also applicable to a system containing fewer particles than required for full coverage by introducing a new parameter. It is observed that the rate of deposition of dispersed clay particles is considerably slower than the deposition of clay aggregates. The maximum mass coverage of fibers by dispersed clay particles is also less than the coverage by clay aggregates. The experimental rates are comparable to those calculated theoretically and thus consistent with Smoluchowski's kinetics.