Abstract
Froth flotation is the most used physical beneficiation process capable of producing sufficiently purified fluorspar for use in fluorochemical industries. The processing requirements of fluorspar orebodies depend on their gangue constituents. Lower than expected recoveries are often encountered in commercial flotation plants, most notably in fluorspar ores with unique gangue constituents. This study investigated the required flotation process adaptations when hematite is the main gangue mineral, and oleic acid is used as the collector.
The mineral fluorite is part of the semi-soluble salt mineral grouping. These minerals are characterised by their ionic bonding and limited solubility in water. They slowly dissolve when immersed in water, developing a charged particle surface. The surface charge is generated by charged ions, like the potential determining ions of fluoride, calcium, hydroxide and hydrogen in the fluorite system, transferred onto or away from the surface. The charged fluorite surface can also attract colloidal particles with opposite charges.
The ore was analysed by mineral liberation analysis to reveal the process mineralogy of the ore and gangue components. The physical separation was investigated using bench scale flotation testing using different sources for the make-water and altering the conditioning parameters. Electrophoretic measurements to determine the zeta potential confirmed the mechanism of heterocoagulation of sericite and hematite slime particles onto the fluorite grains, thereby inhibiting collector adsorption onto the fluorite surfaces resulting in poor bubble-particle adhesion and thereby lowering the recovery of fluorite to the final flotation concentrate.
General strategies to counter heterocoagulation include the removal of the slime particles ahead of flotation, chemical treatment during the conditioning through pH control of the suspension and dispersant usage to change the attraction force between the slime coating and valuable mineral. This study illustrated that increased mixing intensity and high % solids during the conditioning pretreatment achieved the highest recovery of fluorite in the rougher and cleaner flotation processes.
Keywords: Process mineralogy, froth flotation, hydrolysis interactions, zeta potential, slimes, heterocoagulation and conditioning pretreatment.