SURFACE PROPERTIES AND SELECTIVE FLOTATION OF INHERENTLY HYDROPHOBIC MINERALS

Surface properties of a number of minerals including talc, graphite and sulphides such as chalcopyrite and galena were investigated. A new method of surface preparation for the layer- type, inherently hydrophobic minerals was developed. A correlation has been shown between contact angle, zeta potential and flotation behaviour. The hydrophilic-to-hydrophobic ratios of various minerals were estimated and their role in this correlation discussed.;Critical surface tensions of wetting ((gamma)(,c)) were determined using pure liquids as well as aqueous solutions. Adsorption densities of methanol ((GAMMA)(,Lv)) and viscosities were used to explain the mechanism of wetting and the frequently observed (gamma)(,c) value of (TURNEQ) 30 mN/m for a number of hydrophobic samples. The adhesion tension diagrams were used to identify the critical surface tension range within which preferential wetting occurs between two inherently hydrophobic minerals. This range has been exploited for the flotation separation of binary mixtures of the minerals. Induction periods estimated as a function of surface tension ((gamma)(,Lv)) have been discussed with reference to the separation tests. The separations employing the methanol solutions have been compared with those obtained using a more conventional system of Lignosol-MIBC solutions.;The effect of sulphur formation and hydrocarbon chain length of the wettability and floatability of sulphides were also determined as a function of (gamma)(,Lv).