Effect of clay minerals on the mechanical entrainment in the flotation of copper ore

Processing of ores with high clay causes some problems such as slime coating, mechanical entrainment and change of foam stability in flotation, due to fine particle size, layer structure and anisotropic load of clay minerals. Although the importance of air flow rate and foam height is still not fully understood when compered with other parameters affecting flotation, it is known that mechanical entrainment and gangue gain are significantly affected by these two factors. In study, the effects of clay species (Kaolinite- Montmorillonite) commonly found in Cu ores were anvestigated on flotation performance and mechanical entrainment. Clay type/ amount (5- 10- 15 %), foam height (1,2,3 cm) air flow rate (8,10,12 l/min) are studied as experimental parameters. In the evaluation of mechanical entrainment, the actual efficiency (RG) values were determined from the total flotation efficiency (RT) and mechanical entrainment efficiency (RM) difference by using flotation test data with collector and without collector. With increasing clay content, it was determined that the grade of concentrate did not show a significant change in kaolin while it decreased in montmorillonite. Montmorillonite significantly increases the apparent viscosity of the pulp and consequently affects the bubble-particulate collision, resulting in grade of concentrate decreases. It was obtained with lower efficiency concentrate with montmorillonite containing ore than kaolin containing ore. The efficieny values increased after 10% clay content due to the mechanical entrainment of clay minerals to the concentrate. When working with high air flow rate, it was found that the grade decreases and yield increases. The increase in the air flow rate increases the stirring effect and the rate of foam rise in the flotation and increases the mechanical entrainment and reduces the valuable mineral grade. In term of mechanical entrainment efficiency, the foam height did not show a significant effect on the kaolin-containing ore but decreased with increasing foam height in montmorillonite. With increasing foam height, the actual efficiency values increased in montmorillonite but decreased in kaolin. Decreasing of grade with increasing of foam height in kaolin has been related with the transport the foam phase of suspended fine-sized kaolin particulate in the pulp. Keywords: Copper, Flotation, Clay, Mechanical Entrainment, Foam depth, Air flow rate