Abstract
Abstract
In this study, we treat the dirty (small) and the adsorbing (large) particles, which are both of approximately micron-order or smaller, as charged and oppositely charged spheres and investigate the behavior of these particles under the gravity field by means of Brownian dynamics simulations. We have here mainly discussed the dependence of the adsorption rate on the particle diameter ratio, the volumetric fraction of large particles, and the input amount of large particles. Large particles adsorb much more small particles, per large particle, but the total number of small particles adsorbed by the large particles more significantly increases for large particles with smaller diameter if the same input amount of adsorbing agents (large particles) is used. This is because large particles with small diameter more actively perform random motion and move more extensively to adsorb small particles, although the surface area of large particles increases with decreasing diameter, leading to more opportunity to contact small particles. Hence, it is seen that putting numerous adsorbing particles with smaller diameter into water is more effective for removing suspended substances or dirty particles. Even if the input amount of large particles is increased, an adsorption performance cannot significantly be improved because the number of inefficient large particles that do not contribute to the adsorption performance increases. From these results, we understand that an optimal input amount of adsorption agents, from a commercial point of view, should be determined by various factors in the application of the adsorption technique to actual situations.
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