Effect on surface charges of bubbles and fine particles on air flotation process

Abstract

The adhesion of fine particles onto bubbles in flotation was studied on the basis of surface charge measurement3 of the bubbles and particles.The surface charges of the bubbles were measured by the use of a micro-electropheresis apparatus devised in our previous study and the mechanism of the bubble charging was studied under various experimental conditions. In distilled water, the bubbles were negatively charged and the iso-electric point appeared at pH = 2.5. The surface charges of the bubbles in the surfactant solution were determined by the surfactant molecules adsorbed at the surface and depend strongly on the values of pH.The flotation efficiency of latex particles (0.923 pin) was found to be strongly influenced by the surface charges of both the particles and the bubbles. The force between the particle and the bubble was estimated from the observation of the particle attachment to the bubble surface, and a simple equation including the effects of the hydrodynamic and surface charge interactions was proposed to determine the floatability limit.L'adhCsion de particules fines dans des bulles en tlottation a Ct C etudiee sur la base de mesures de charge de surface des bulles et des particules.Les charges de surface des bulles ont kte mesurees au nroyen d'un appareillage de micro-dectrophorese c o n y danr nos etudes anterieures, et on a Ctudit le mecanisme de chargement des bulles dans des conditions experimentales variees. Dans de I'eau distillte, les bulles ont CtC chargees negativement et le point iso-blectrique est apparu au pH de 2.5. Les charges de surface de bulles dans la solution de surfactant ont ttC dkterminees par les molkcules de surfactant adsorbkes B la surface et elles dCpendent fortement des valeurs du pH. On a trouve que I'effcacitC de flottaison des particules de latex (0,923 pm) Ctaient fortenient influencee par les charges de surface a la fois des particules et des bulles. La force entre les particules et les bulles a cte estimee 2 partir de I'observation de la liaison des particules a la surface des bulles, et on propose une equation simple incluant les effets des interactions des charges de surface et de I'hydrodynamique pour determiner la limite de flottabilitk.

Hydrophobic Forces in Thin Water Films Stabilized by Dodecylammonium Chloride

“…As the surfactant concentration is further increased, the double-layer is compressed, causing a decrease in Ј 1 . Note also that the -potentials of air bubbles measured in RNH 3 Cl solutions by Okada et al (31) are substantially lower than the calculated Ј 1 values.…”

Strategy for selection of methods for separation of bioparticles from particle mixtures

“…The latter typically lies between 10 À21 and 10 À19 J (Fielden, 1996;Han, 2002;Hayashi et al, 2001b;Koliadima, 1999;Okada et al, 1990b;Shaw, 1966).…”

“…8) or by specific adsorption of surfactants or ions on their surface (Chang and Hshieh, 1991). The latter strategy has been shown to work successfully for air-water interfaces with aluminium (Li and Somasundaran, 1992) and magnesium ions (Li and Somasundaran, 1991) as well as for polystyrene particles with surfactants (Okada et al, 1990b). Addition of polymers or polyelectrolytes can also lower the electrostatic repulsion, but more importantly these compounds may form bridges between the particles by adsorbing onto the particle surface.…”

Measurement of the Zeta Potential of Gas Bubbles in Aqueous Solutions by Microelectrophoresis Method

“…The presence of a charge on the bubble liquid surface causes a spatial distribution of ions in the solution, leading to the formation of an electric double layer (EDL) (2). The EDL of a gas bubble plays an important role in bubble-solid and bubbleoil droplet attachment and bubble coalescence (4)(5)(6)(7)(8), which are commonly encountered in many industrial processes such as froth flotation, waste and potable water treatment, and wetting 1 To whom correspondence should be addressed. phenomena (9).…”