Application and Storage of Xanthates

The collecting capacity and selectivity of xanthates for various minerals are closely related to the solubility product of their corresponding metal xanthates. Common metal minerals are usually classified into three categories based on the solubility product of their metal ethyl xanthates:

(1) Chalcophile Element Minerals

The solubility product of their metal ethyl xanthates is less than 4.9×10⁻⁹. Metals in this category include Au, Ag, Hg, Cu, Pb, Sb, Cd, Co, Bi, etc. Xanthates exhibit the strongest collecting capacity for native metals (such as Au, Ag, Cu) and metal sulfide minerals of these elements.

(2) Siderophile Element Minerals

The solubility product of their metal ethyl xanthates is greater than 4.9×10⁻⁹ but less than 7×10⁻². Metals in this category include Zn, Fe, Mn, etc. Xanthates have a certain collecting capacity for the metal sulfide minerals of these elements, but it is relatively weak. If xanthates are used as collectors, flotation separation between chalcophile element sulfide minerals and siderophile element sulfide minerals can be easily achieved. Although the solubility product of cobalt and nickel ethyl xanthates is less than 10⁻¹ (classifying them as chalcophile elements), they are often closely associated with iron sulfide minerals and thus tend to be floated together with iron sulfide minerals.

(3) Lithophile Element Minerals

The solubility product of their metal ethyl xanthates is greater than 4.9×10⁻². Metals in this category include Ca, Mg, Ba, etc. Due to the high solubility product of their metal ethyl xanthates, a hydrophobic film cannot form on the surface of these metal minerals under normal flotation conditions, so xanthates have no collecting effect on them. Therefore, xanthates are not used as collectors when separating alkali metal, alkaline earth metal minerals, oxide minerals, or silicate minerals.

In general, the solubility product of metal sulfide minerals is smaller than that of their corresponding metal ethyl xanthates. According to chemical principles, xanthate anions (X⁻) cannot react with the surface of metal sulfide minerals to replace sulfide ions (S²⁻). Only when the surface of metal sulfide minerals undergoes slight oxidation—where S²⁻ on the mineral surface is replaced by ions such as OH⁻, SO₄²⁻, S₂O₃²⁻, and SO₃²⁻—and the solubility product of the metal xanthate is smaller than that of the corresponding metal oxide, can xanthate anions (X⁻) replace the anions corresponding to the metal oxides on the surface of metal sulfide minerals.

Xanthates are commonly used as collectors for native metals (e.g., Au, Ag, Cu) and metal sulfide minerals among chalcophile and siderophile elements.

To prevent hydrolysis, decomposition, and excessive oxidation of xanthates, they should be stored in airtight containers. Avoid contact with moist air and water; pay attention to water and moisture resistance. Xanthates should not be exposed to direct sunlight or stored for long periods. They are best stored in a cool, dry, and well-ventilated area. Prepared xanthate aqueous solutions should not be left standing for too long, and hot water should not be used to prepare such solutions. Generally, xanthate aqueous solutions are prepared and used within the same shift. For production purposes, the concentration of prepared xanthate solutions is usually 5%.