A flotation operator has two areas of control over his circuit, physical, and chemical. By physical controls I mean things such as the density, grind and the pulp levels of the cells. The chemical controls are normally only the amount of reagent flow, the type of reagent, and the point oe addition. To verify the operator’s effectiveness, assays are performed on key areas of the flotation circuit. By continually comparing previous results with the current assay, it is possible to judge the degree of flotation success.

The reason that I have mentioned these two types of control now is to indicate that as important as reagent control is on the assays, physical control is equally so. The two do have an impact upon one another and one cannot be adjusted without a reaction from the other.

I suppose the best place to start explaining reagent control is with the first reagent to be added to the circuit. In many mills the nature of the ore requires that the depressant be added first. If you think about it you can see why. The collector has a direct contact with the surface of the mineral for a depressant to work it would have to come in between, the mineral and the collector to prevent that surface contact being made.

As depressants are used to prevent unwanted minerals from floating, COLLECTORS could be considered their opposite. They collect the minerals together to allow them to float. It wasn’t until the 1950’s that reagents were developed that could be selective in the minerals that were collected. These reagents are called XANTHATES. They are basically long molecules that are attracted to both the chemical makeup of the mineral and the air of the air bubble that is injected into the flotation cell. As the mineral comes into contact with the xanthate molecule the two stick together. When the collected mass of minerals bumps into the air bubble. The xanthate molecule attaches itself to the air of the bubble which gives the mineral a ride to the surface of the cell and separates it from the unwanted rock.