In order to realistically model the behavior of Brownian particles in water, collision efficiency factor in Brownian coagulation (αBr) should be included. αBr is calculated by solving the diffusion equation including the detailed mathematical description of hydrodynamics and interparticle forces. αBr is found to be a function of several parameters: particle size and ratio, Hamaker constant, ionic strength of liquid, surface potential of particle. Ionic strength and surface potential significantly affect αBr. The graphical plane of ionic strength and surface potential is divided into two regions by a curve: above this curve, no coagulation is expected, however, below this curve, coagulation is expected. αBr values in this region are the same as those predicted for no electric repulsion. The model qualitatively explains the change of coagulation efficiency at estuary or water treatment plant. Better prediction of suspensions at both stabilized and destabilized system can be made possible incorporating the collision efficiency factors of the other coagulant mechanisms such as differential sedimentation and fluid shear.

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