The fresh surface exposed by the broken and ground mineral is not the same as the internal structure. This is because the molecules of the mineral surface layer are affected by water dipoles, water-soluble gases (such as oxygen, carbon dioxide) and ions (such as [H 3 O] + , OH - etc.), which are dissolved, hydrolyzed, and adsorbed. And so on, the mineral surface changes. Because the water dipole acts differently on the various ions on the mineral surface, the ion surface ions are transferred into the solution or transferred from the solution to the mineral surface, which forms a layer of excess positive ions on the surface of the mineral. (or negative ions). This ion is also known as a localization ion. Under the attraction of surface-localized ions, some of the ions in the solution are close to the surface of the mineral, and the surface is electrically balanced, which causes a layer of ions on the surface to form an electric double layer.
Calcite and quartz are used as examples to illustrate:
Calcite (CaCO 3) particles in water, since the surface layer of Ca 2+ attracted water molecules into the solution, results in the surface of the calcite have extra CO 3 2- ions, since the surface of the calcite ions excesses occur, so The positive ions in the solution are densely packed toward the surface of the calcite, forming an electric double layer.
Broken quartz particles (SiO) particles, due to the cleavage of silicon-oxygen bonds, have positively charged silicon atoms on the surface of water, and can combine with OH- in water to form surface silicic acid. The surface oxygen atoms are negatively charged and can combine with H+ in water to form surface silicic acid. When the pH is greater than 2.3-3.7, the surface silicic acid loses part of H + and forms a surface with negative charge. The above process can be expressed by the following formula:
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Obviously, this process is closely related to the pH of the water.
Thus, under the negative attraction of the quartz surface, some of the positive ions in the solution are close to the surface of the quartz and densely formed to form an electric double layer.
The following figure shows a general schematic of the electric double layer structure. The figure shows that the mineral surface is negatively charged, and the hydrated counter ion is an anion whose concentration increases with increasing distance from the surface of the ore particle until it is equal to the anion concentration in the solution.
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