Froth Modifiers

The list of modifying or conditioning agents used in flotation is long and varied. It generally includes all reagents whose principal function is neither collecting nor frothing. Modifying agents may act as depressants, activators, pH regulators, dispersants, etc.

A depressant is any reagent which inhibits or prevents the adsorption of a collector by a mineral particle and thereby prevents its flotation. Activators function to enhance the adsorption of the collector. Frequently, several functions may be performed by a single compound. For example, soda ash (Na₂CO₃) may be an activator (for pyrite) and a depressant (for calcite), as well as functioning both a pulp dispersant and a pH regulator.

The classification of modifying agents in Table 2, page 8, is based on the direct – rather than the end – result of their addition to the ore pulp. As the table shows, modifiers may function as:

 pH modifiers
 Resurfacing agents
 Precipitants for soluble salts

Again, a single product, such as lime, way fall into more than one grouping.

The following subsections discuss the several modifying agent groups. The information should help understanding of the basic principles of differential flotation, and its application to a large number of mineral separations.