Classification and Mechanism of Depressants in Froth Flotation

Classification and Mechanism of Depressants in Froth Flotation

To improve selectivity in the flotation process, enhance the effectiveness of collectors and frothers, reduce the mutual content of valuable minerals, and optimize pulp conditions, regulators are commonly used in flotation. These regulators include various reagents, which can be classified based on their functions as depressants, activators, pH modifiers, defoamers, flocculants, dispersants, and more.

In froth flotation, depressants are reagents that prevent or reduce the adsorption or interaction of collectors on the surface of non-target minerals, thereby forming a hydrophilic film on their surfaces.

Based on their chemical composition, depressants are divided into two major categories: inorganic compounds and organic polymers.

Mechanism of Depressants

The depression mechanism of these reagents includes:

1. Forming a hydrophilic compound film on the surface of non-target minerals, e.g., dichromates depressing galena.
2. Forming a hydrophilic colloidal adsorption film on the surface of non-target minerals, e.g., zinc sulfate forming zinc hydroxide (or zinc carbonate) adsorbed on sphalerite (or marmatite) surfaces in alkaline pulp, or silicate starch.
3. Forming a hydrophilic ionic adsorption film on the surface of non-target minerals, e.g., HS⁻ or S²⁻ ions dissociated from sodium sulfide in alkaline pulp adsorbing on non-target sulfide mineral surfaces.
4. Certain strong oxidizing agents decomposing the collector film adsorbed on non-target sulfide mineral surfaces, thereby exposing their hydrophilic surfaces.