Diffusion-controlled flocculation kinetics

The fast flocculation kinetics was investigated by Smoluchowski [12], who considered the process to be represented by second-order kinetics and the process to be simply diffusion-controlled. The number of particles n at any time t may be related to the initial number (at t = 0) by the following expression ... 

However, if the ionic strength is enhanced, the thickness of the electrolyte cushion is rendered thinner. A larger fraction of particles may then collide per unit time, leading to a coagulation of the particles to a dense sediment. For a O.l-mol/dm 1 1 electrolyte solution, the repulsive electrostatic barrier (Tables 8.3 and 8.4) may be considered to be effectively removed and the particle coagulation is controlled by diffusion alone. Sometimes a balance is reached at intermediate distances (3 to 5 nm), which is characterized by a weak negative minimum. Then, the particles form a loose flocculated structure that is easily redispersed. To a great extent the association kinetics follows the same principles as for the ions discussed above, but at a slower rate. - - " ... 

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