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 AlCl 3. 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.