Mini-Encyclopedia of Papermaking Wet-End
Part Three: Equipment & Unit Operations
The word coagulation refers to the coming together and sticking of finely divided particles or droplets due to the addition of ionic materials. The principle mechanisms used to bring about coagulation are (a) neutralization of surface charges, and (b) screening of electrostatic repulsions by increasing the electrical conductivity of the solution. Coagulated dispersions or emulsions tend to settle or cream. The coagulation mechanism by itself is seldom sufficient to ensure retention of fine particles during paper manufacture. The word "flocculation" is more often used when one is referring to treatment with retention aids that are capable of forming shear-resistant bonds between fine particles, fiber-fines, and fibers.
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