Yoshihiro Fukui

Collection of submicron particles in electro-flotation

Abstract A theoretical analysis is presented to describe the deposition of Brownian particles onto hydrogen bubbles under surface interactions. Single collection efficiency has been numerically calculated for zeta potentials, having assumed that the effective Hamaker constant is equal to 3.0 × 10−14erg though our choice of Hamaker constant is rather arbitrary. From a mass balance, total collection efficiency or the rate of flotation has been determined. In this way, electro-flotation process is quantitatively described. Experimentally, the electro-flotation of polystyrene latices of mean diameter 0.6 μm has been studied to examine the effect of the charge on both particles and bubbles on the total collection efficiency. The bubbles were of mean diameter 20 μm. The electrolyte was AlCl3. To measure the charge on the bubbles, we directly sampled solution including very small bubbles with a glass tube from a flotation vessel and poured into a micro-electrophoresis cell. The horizontal velocity measured when the bubbles rose up a “stationary level” in the cell under the known potential gradient gave the electromobility. The charge on the latex particles were found to change its sign from negative to positive as flotation time went on. The theoretical total collection efficiency has been in close agreement with the experimentally determined one.

Electroosmotic flow in rectangular microelectrophoresis cells

Abstract This paper presents a rigorous solution of asymmetric profile of fluid velocity in microelectrophoresis cells from which electrophoretic particle velocity can be estimated. The asymmetrical profile in the cell is a common problem and prevents accurate measurement of the electrophoretic velocity of particles. An analytical solution of the Navier—Stokes equations for electroosmotic flow in a rectangular cell has been developed for realistic boundary conditions allowing horizontal and vertical asymmetry. The solution provides a theoretical basis for the conventional method in which the average of the two electrophoretic velocities at the Komagatas stationary levels may be used as an approximation. The solution also requires that, for application of the conventional method, the aspect ratio is larger than 20.

Development of apparatus for electro-flotation

Abstract A new apparatus for electro-flotation has been developed by using the impeller of stirred tank as electrode(s). The principle of this apparatus reported is that the gas bubbles generated by electrolysis float the flocs while flocculation is promoted by the rotation of electrode(s). The collection efficiency of this apparatus for tap water containing blue ink of 10 −3 m 3 /M 3 in concentration has been discuss by using various electrode(s) and changing the rotation speed of the electrode(s).

Collection of submicron particles by H2 bubbles

Abstract A theoretical analysis is presented to describe the deposition of Brownian particles onto H 2 bubbles (flotation) by analogy with classical filtration theory. Experimentally, it is shown that submicron and smaller particles of MnO 2 are collected by H 2 bubbles without using the special collector or chemicals usually employed in flotation. The experimental technique for determining the total collection efficiency is described. A comparison between the theory and our experiment makes it clear that there are cases in which the simpler filtration theory is adaptable to a complicated flotation analysis. In addition, we find that the collection mechanisms of submicron particles of MnO 2 is predominantly characterized by interception and Brownian diffusion.

Turbulent disruption and agglomeration of fly ash particles in a stirred tank

We have measured the change of size distribution and number concentration of fly ash particles suspended in a stirred tank. Disruption of aggregates is dominant for the dilute suspension (3.3 × 1012/m3). On the other hand, agglomeration of particles is dominant for high concentration (8.2 × 1013/m3). In both cases, the rapid changes of particle size distributions occur for the initial 2 min and the equilibrium states that the amounts of disruption and agglomeration are in balance have been reached after about 15 min from the starting point of rotation. Also, it has been found that for the intermediate concentration the amounts of agglomeration and disruption are in balance and cancel out each other from the starting point of rotation.