The poor flotation of coarse particles is attributed to their detachment from gas bubbles in the high turbulent regions of flotation cells. Particle detachment increases, and therefore flotation deteriorates, with increasing particle size or with decreasing particle hydrophobicity, such as with composite particles. Generally, most of the coarse particles in ores are composite of valuable minerals and hydrophilic silicate gangue minerals.
The objective of this study is to relate the hydrophobicity of composite particles with their mineral composition. Synthetic composite particles were fabricated in this study as they allow a better control of the proportion and distribution of mineral phases than with natural particles. Composite particles of quartz particles in a lead borate matrix were fabricated in six size fractions between 75 and 600 μm. By changing the size of the quartz particles in the composite particles, simple and complex locking textures could be obtained. Backscattered scanning electron microscopy of the composite particles imbedded in epoxy resin was used to measure the particle size and the degree of quartz liberation. Selective quartz hydrophobisation was achieved with addition of trimethylchlorosilane. The contact angle of the composite particles was measured with the Washburn technique and was found to increase with the percentage of quartz.