Deposition Behavior of Latex Particles In Filtration Process Through Glass Packed Column
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The mechanisms of the filtration have been investigated for subjects such as water treatment or transport of colloidal contaminants in groundwater. In the case of colloid transport in porous media, colloidal particles, which are very small relative to the porous media grain (collector) size, are retained only if attractive forces dominate when the particles collide with the collector [7]. This phenomenon is termed deposition. Deposition is the process whereby particles are transported to a solid collector surface, where they become attached. The overall deposition process is divided into two sequential steps: transport and attachment [8]. The transport step is a particle transport process from bulk fluid to the vicinity of a solid collector surface which can be quantitatively described by convective-diffusion and trajectory equations. The attachment step is controlled by the chemical characteristics of the particle and the surface and by the solution chemistry. Whether the transported particle is attached or not depends on the interactions between the particle and the collector surface which operate at short distances of separation (usually several tens of nanometers). The interactions are the van der Waals and electrical double layer interactions which form the basis of the Detjaguin-Landau [9] and Verwey-Overbeek [10] (DLVO) theory of colloid stability. The behavior of the colloid deposition onto solid collector surface can be observed by conducting column experiments. The results are presented as particle breakthrough curves (BTCs). The effluent concentration of particles, C, as a function of time or effluent volume, is presented as a fraction of the influent concentration, CG, in the BTCs. Because of the difference of retention mechanisms, the shape of a colloid BTC is quite different from that of a solute BTC. For example, a colloid BTC could have a tailing or plateau which can not be seen in a solute BTC. Flow rate has significant effects on the colloid deposition behavior in filtration process, however, there is not much data available in the literature. Although the effect was investigated 743 Mat. Res. Soc. Symp. Proc. Vol. 556 © 1999 Materials Research Society
through column experiments with pulse input of colloid solutions [I 11, such studies with step input have not been conducted enough. The objective of the present work is to explain the typical colloid deposition behavior in filtration process and to observe the effect of the flow velocity on it through column experiments with polystyrene latex particles and glass beads which are similarly charged. The deposition behavior is discussed through the concept of a single collector efficiency.
EXPERIMENT Materials Spherical soda lime glass beads (Toshin Riko) with diameter of 0.35-0.40 mm were used as
solid collectors in column experiments. They were cleaned by soaking for 30 minutes in an ultrasonic bath with 0.3 M HCI solution and distilled deionized water (Barnstead, Fistreem I , Epure) successively, then dried in an oven at 60 `C. Distilled deioniz
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