XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2291
we may argue that no perturbation on the second solvation
shell stems from the introduction of the cation.
Modeling the interfacial calcite/collector system
Finally, we made our first attempts at modeling the adsorp-
tion of the collector on mineral surface. In this regard, a
quite challenging topic in flotation deals with the libera-
tion mechanism of apatite from calcite (Wang 2022). It is
known that the hydrophobization mechanism of apatite
results from solubilization of fatty acid at basic pH followed
by a chemical reaction fixing the collector on the apatite
surface. However, the fatty acid may also adsorb on the cal-
cite making the latter hydrophobic and thereby eliminating
the selectivity of the direct apatite flotation process. As a
matter of fact, the understanding of the principles involved
in the apatite/calcite separation is still far from having
reached the maturity which would allow an a priori choice
of surface conditioning. Hence, improvement on apatite
flotation process nowadays still arises from trial and error,
rather than a fundamental analysis of the physicochemical
processes of activation and depression of the gangue miner-
als accompanying the apatite.
We started challenging this topic by simulating oleic
acid C18H34O2 on calcite. Oleic acid (OA) is soluble in
water in the presence of a base such as caustic soda. The pro-
ton then reacts with the hydroxide to give carboxylate ion,
whereas the radical chain confers the hydrophobic charac-
ter to the collector. The adsorption of OA on the surface of
the calcite may result either from an electrostatic interac-
tion (attraction as opposed to electric charge), or from a
chemical reaction (Somasundaran 1969). Yet, the adsorp-
tion energy of –221 kJ·mol–1 per collector monitored dur-
ing the MLFF simulation (Figure 7) is strong enough to
support the idea that the collector is adsorbed on the calcite
by a chemical reaction, in particular a chelation reaction
with the calcium ions on the calcite. Next simulation steps
will involve the addition of starch in solution to investigate
the mechanism by which the latter prevents the hydropho-
bic action of OA.
Figure 6. (a) Hydrogen and oxygen profile densities at the silica/water interface as a function of the axial distance. The quartz
slab is settled at 0 Å, which corresponds to the position of the outermost oxygens belonging to the fully hydroxylated slab. (b)
Profiles after introduction of the cation M+ (M =Li, Na, K) the red dash line points out the position of the slab surface
we may argue that no perturbation on the second solvation
shell stems from the introduction of the cation.
Modeling the interfacial calcite/collector system
Finally, we made our first attempts at modeling the adsorp-
tion of the collector on mineral surface. In this regard, a
quite challenging topic in flotation deals with the libera-
tion mechanism of apatite from calcite (Wang 2022). It is
known that the hydrophobization mechanism of apatite
results from solubilization of fatty acid at basic pH followed
by a chemical reaction fixing the collector on the apatite
surface. However, the fatty acid may also adsorb on the cal-
cite making the latter hydrophobic and thereby eliminating
the selectivity of the direct apatite flotation process. As a
matter of fact, the understanding of the principles involved
in the apatite/calcite separation is still far from having
reached the maturity which would allow an a priori choice
of surface conditioning. Hence, improvement on apatite
flotation process nowadays still arises from trial and error,
rather than a fundamental analysis of the physicochemical
processes of activation and depression of the gangue miner-
als accompanying the apatite.
We started challenging this topic by simulating oleic
acid C18H34O2 on calcite. Oleic acid (OA) is soluble in
water in the presence of a base such as caustic soda. The pro-
ton then reacts with the hydroxide to give carboxylate ion,
whereas the radical chain confers the hydrophobic charac-
ter to the collector. The adsorption of OA on the surface of
the calcite may result either from an electrostatic interac-
tion (attraction as opposed to electric charge), or from a
chemical reaction (Somasundaran 1969). Yet, the adsorp-
tion energy of –221 kJ·mol–1 per collector monitored dur-
ing the MLFF simulation (Figure 7) is strong enough to
support the idea that the collector is adsorbed on the calcite
by a chemical reaction, in particular a chelation reaction
with the calcium ions on the calcite. Next simulation steps
will involve the addition of starch in solution to investigate
the mechanism by which the latter prevents the hydropho-
bic action of OA.
Figure 6. (a) Hydrogen and oxygen profile densities at the silica/water interface as a function of the axial distance. The quartz
slab is settled at 0 Å, which corresponds to the position of the outermost oxygens belonging to the fully hydroxylated slab. (b)
Profiles after introduction of the cation M+ (M =Li, Na, K) the red dash line points out the position of the slab surface