Lead and zinc are among the earliest metals extracted from ores. They are widely used in the electrical, mechanical, military, metallurgical, chemical, light, and pharmaceutical industries. Additionally, lead has significant applications in the nuclear and petroleum sectors. Among lead-zinc ores, there are 11 industrially significant lead minerals and 6 zinc minerals, with galena and sphalerite being the most important.
Galena (PbS)
Galena has an isometric crystal structure, where sulfur ions form a cubic close-packed arrangement, and lead ions occupy all octahedral sites. Fresh galena surfaces are naturally hydrophobic, making them highly floatable in the absence of oxidation; however, oxidation reduces floatability. Xanthates and dithiophosphates (e.g., aerofloats) are typical collectors for galena, with xanthates chemically adsorbing onto the mineral surface. Ethyl xanthate and sodium diethyldithiocarbamate are also commonly used, while ammonium dibutyl dithiophosphate offers selective collection for galena.
Dichromates are effective depressants for galena, though their efficiency decreases when galena is activated by Cu²⁺ ions. Galena depressed by dichromates is difficult to re-activate unless treated with hydrochloric acid or sodium chloride in an acidic medium. Cyanides do not suppress galena flotation. Sodium sulfide strongly affects galena floatability, and excess sulfide ions can inhibit flotation. Sulfur dioxide, sulfites, lime, zinc sulfate, and combinations with other reagents can also depress galena.
Sphalerite (ZnS)
Sphalerite also has an isometric crystal structure, with Zn ions located at the corners and face centers of the unit cell, and S ions at the centers of four of the eight smaller cubes within the unit cell. At low concentrations (4–6 × 10⁻⁵ mol/L), potassium permanganate strongly depresses activated sphalerite, but at higher concentrations, it promotes flotation. The mechanism: at low concentrations, KMnO₄ reacts with the surface activation film and lattice ions to form metal hydroxy compounds that depress flotation and desorb xanthate; at higher concentrations, redox reactions occur on the mineral surface, generating elemental sulfur.
Cyanides are strong depressants for sphalerite. Other depressants include zinc sulfate and thiosulfates.
Post time: Apr-09-2026
