| Fine particles pose two challenging problems in the froth flotation process. The first problem is the difficulty in effectively floating and recovering hydrophobic particles, mainly due to their small mass and high surface area. The second problem involves the high mechanical entrainment of fine hydrophilic particles due to their small size. Much research has been conducted to improve the flotation rate of fine hydrophobic particles, while the hydrophilic particles are kept highly dispersed in these systems. As a result not only does the problem of mechanical entrainment still remain, but it is also further aggravated by the techniques developed by such research. The resulting consequence of such techniques is an improved recovery but lower grade of the hydrophobic particles; the lower grade being attributed to the entrainment of the hydrophilic (gangue) particles.; The objective of this thesis was to verify the positive correlation between particle size of hydrophilic particles and mechanical entrainment, and to use polymeric depressants to flocculate and thus increase the particle sizes of these hydrophilic particles so that their entrainment and recovery into the froth would be minimized. Using a number of various dispersants and polymeric depressants, tests were performed to minimize the mechanical entrainment of hematite and hydroxylapatite, each separately, in the flotation of quartz. Sodium silicate dispersant in conjunction with corn starch depressant appeared to be the most effective in minimizing the entrainment of these minerals, particularly hematite. |
