Calcium lime can be used to increase the pH value of pulp during the flotation process; adjust the activity of thio compound collectors and other inhibitors (such as cyanide); can be used to inhibit the iron sulfide minerals, natural gold particles Flotation; precipitation of heavy metal ions that are harmful to flotation; it has the effect of condensing slime into larger aggregates.
Adjusting the pH value of pulp
Calcium lime is cheap and easily available and has strong alkalinity. In the flotation process of sulfide minerals, it is usually used as the pH when it is necessary to increase the pH value of the pulp or in alkaline or weakly alkaline media. Value modifier. In general, its role is as follows:
(1) Adjust the concentration of heavy metal ions in the pulp to form insoluble compounds. This is important to eliminate certain harmful ions to adjust the method. For example, the addition of OH- ions can cause many metal cations to form insoluble hydroxides. Common flotation and insoluble hydroxides are: Al (OH) 3, Cu (OH) 2, Fe (OH) 2, Fe (OH) 3, Pb (OH) 2, Zn (OH) 2, etc.
(2) Adjust the ion concentration of the collector. The presence of the collector in molecular or ionic state in water is closely related to the pH of the medium. Adjusting the pH value can adjust the ratio of the collector in the molecular or ionic state in water. In fact, the dissociation degree of the collector is adjusted.
(3) Adjust the effect between collector and mineral. The interaction between the collector ion and the mineral surface is closely related to the pH value of the pulp. The collector anion and OH- can compete on the mineral surface. The higher the pH value, the higher the OH- ion concentration, the more the Can repel the role of collector anions.
(4) Adjust the concentration of the inhibitor. Some inhibitors are salts composed of strong bases and weak acids, such as the commonly used inhibitor water glass (also known as sodium silicate, which has a chemical composition of NaO2SiO2), that is, it can be hydrolyzed in water to make the pulp alkaline, pH The level directly affects the degree of its hydrolysis. When pH <9, silicic acid (H2SiO3) molecules are dominant; when pH = 9 ~ 13, HSiO-3 is dominant; when pH> 13, SiO-3 is dominant.
(5) Adjust the foaming ability of the foaming agent. The pH value has a certain effect on the foaming ability of the foaming agent. For example, the foaming ability of pinitol oil (2 # oil) increases as the pH of the medium increases.
(6) Adjust the dispersion and reunion of the slime. The pH adjuster used in practice is often a dispersant or agglomerating agent of the slime, which plays the role of dispersing or agglomerating the pulp. For example, Ca2 + in lime can weaken the negative charge of the quartz surface, reduce the electrostatic repulsion, and facilitate the adsorption of ionic flocculants.
For gold flotation, when processing simple ores containing simple metal sulfide ore (such as most ore mines in Shandong), which contain few harmful substances to cyanide, lime is generally used to control the flotation pH = 7 ~ 9.