Activators can promote the interaction between collectors and minerals. The main types are as follows:
(1) Certain metal ions. These ions, when used as activators, must be able to adsorb onto the surface of the activated mineral and form insoluble salts with the collector. For example, when using xanthate to collect sphalerite, Cu²⁺ can be used as an activator. On the one hand, Cu²⁺ can adsorb onto sphalerite through ion exchange; on the other hand, Cu²⁺ can form insoluble copper xanthate with xanthate, promoting the adsorption of xanthate on sphalerite. When using xanthate to collect sulfide minerals, Cu²⁺, Ag⁺, Pb²⁺, etc., can all be used as activators. Reagents used include copper sulfate, silver nitrate, and lead nitrate. When using fatty acid collectors, alkaline earth metal ions that can form insoluble salts with carboxylic acids, such as Ca²⁺ and Ba²⁺, can be used as activators. Reagents used include calcium chloride and barium chloride.
(2) Inorganic acids and bases. They are mainly used to clean oxide-contaminated films or adhering slime from the surface of minerals that are to be floated, which affect the action of collectors. Commonly used agents include hydrochloric acid, sulfuric acid, hydrofluoric acid, and sodium hydroxide. For example, the ferric hydroxide film formed on the surface of pyrite can be reacted with sulfuric acid to form ferric sulfate, which dissolves in water, thereby re-exposing the fresh surface of the pyrite to facilitate the action of xanthate.
(3) Organic activators. For example, industrial oxalic acid can activate pyrite that has been inhibited by lime.