Some researchers [16–19] studied the kinetics and chemistry of
phosphate flotation from its siliceous gangue by fatty acids. Most
of these studies emphasised that the formation of calcium dioleate
by the reaction between apatite and oleate is responsible for the
chemisorptions of collector on the apatite surface. However, the
presence of calcium divalent in the flotation pulp either by the dissolution
of apatite or due to the process water, precipitate more
calcium oleate on the surface of the silica (gangue) which activate it
and render it hydrophobic. The study recently conducted by Brown
et al. [20] showed that the maximum hydrophobicity of the silica
occurswhenexcess collector (2:1 oleate to calcium) is present in the
solution. This may emphasis the role of sodium silicate in depressing
silica by precipitating some of the solution calcium cations as
calcium silicate.