Adsorption, contact angle and flotation of anionic Atrac and non-ionic ethaloxylated nonylphenol surfactant,
and their mixture on apatite and magnetite were studied. The effect of calcium ions and sodium silicate on Atrac adsorption
was investigated. The effect of Atrac adsorption on the contact angle data of apatite and magnetite in the presence and
absence of sodium silicate was also examined. Wettability of solids depends on solids surface free energy and the surface
energies of apatite and magnetite powders were calculated from polar and non-polar liquid contact angle data.
A decrease in particle size increased the polar contribution to surface free energy due to unsaturated broken bonds on the
surface. Atrac is seen to adsorb equally on apatite and magnetite, and the adsorption increased in the presence of calcium
ions. The presence of water glass decreased the Atrac contact angle data on magnetite and also the flotation response
demonstrating its role as magnetite depressant in flotation. The presence of non-ionic surfactant enhanced the Atrac flotation
of apatite with no flotation of magnetite. Bench-scale flotation tests showed that 50% of Atrac can be replaced with
non-ionic collector without impairing the flotation results. Results also illustrate that the non-ionic adsorbs on apatite in
equal amount of Atrac collector signifying 1:1 composition of anionic and non-ionic collector on apatite surface. Nonionic
head group sitting in between anionic head groups screens the electrostatic repulsion and forms compact adsorbed
layer on apatite surface thereby increasing the hydrophobicity and flotation.