Hydrophobic Flocculation of Fine Hematite, Siderite, and Rhodochrosite Particles in Aqueous Solution

The hydrophobic flocculation of fine hematite, siderite, and rhodochrosite particles rendered hydrophobic by the adsorption of surfactants in aqueous solution has been studied. The effects on hydrophobic flocculation of the contact angle of the particle surface, the zeta potential of the particles, the temperature of the suspension, and the duration of agitation have also been investigated. The mechanism of this flocculation has been studied by measuring the hydrophobic adhesion force with the slope method. The results reveal that this flocculation cannot be interpreted by classical DLVO theory and is closely correlated with the change of the contact angle of particles and the hydrophobic adhesion force. A theoretical approach to hydrophobic flocculation, which is a modification of classical DLVO theory, has been put forward. The calculation of the interaction potential energies between particles related to the hematite-sodium oleate system demonstrated that the hydrophobic interaction potential energy between hydrophobic particles is one or two orders of magnitude larger than that of the van der Waals and electrical double-layer interaction potential energies. Therefore, it was concluded that hydrophobic interaction plays a dominant role in the hydrophobic flocculation of fine mineral particles in aqueous solution.