抄録
A novel microbubble flotation using a spiral-liquid-flow type microbubble generator was developed to recover the iron oxide fine particles from the suspension containing dilute surfactants. Although the suspended iron oxide particles were hardly removed from suspension using other aerators such as a single orifice and a glass ball filter, the microbubble generator achieved 90% recovery of the particles in 60 minutes. In bulk liquid, both surfaces of microbubbles and iron oxide particles became electrically charged. When pH was controlled between 4.4 and 7.8, the surface of microbubbles was charged negatively and the surface of iron oxide particles was charged positively. Therefore, the microbubbles and the particles were attracted each other. At pH = ca. 5 the microbubbles adsorbed well the iron oxide particles. In the foam layer at the top of flotation column, the particles were trapped and removed from the bulk liquid. The recoverability depended on the degree of ionization and the concentration of added surfactant. In the present system, the concentration of surfactant was suitable to be only 1 to 2 % of the critical micelle concentration to achieve the highest recoverability of suspended particles from the suspension. Moreover, to understand the mechanism of the iron oxide particle separation using microbubble flotation, the novel kinetic model which considers the adsorption and the release coefficients was proposed. The microbubble flotation model could estimate well the removal of iron oxide particles from the suspension.
