Lime is a commonly used modifier in the flotation of sulfide ores. It can adjust the pulp to be alkaline, inhibit iron sulfide ore, and has a coagulating effect on slime. It is widely available and inexpensive, making it one of the main reagents in sulfide ore flotation.

When using xanthate to collect sulfide ores, an alkaline pulp is often required, and lime is generally used to adjust the pH value of the pulp.

Lime is a depressant for iron sulfide ores (pyrite, pyrrhotite, marcasite). Pyrite and arsenic sulfide are often associated with copper sulfide, lead sulfide, and zinc sulfide ores. To better float copper, lead, and zinc minerals, lime is added to inhibit iron sulfide minerals. When the content of inhibited iron sulfide minerals is relatively low, lime can be used to adjust the pulp pH to above 9. If the iron sulfide content is relatively high, lime should be used to adjust the pulp pH to above 11.

It should be noted that lime also has a certain inhibitory effect on galena, especially galena with a slightly oxidized surface. Therefore, when flotating galena from polymetallic sulfide ores, sodium carbonate is generally used to adjust the pH value instead of lime. If lime must be used to inhibit pyrite content, the amount of lime used should be carefully controlled to minimize its impact on galena.

Lime itself is also a coagulant, which can cause ore slime to agglomerate and, to some extent, eliminate the harmful effect of ore slime on ore particle adhesion. When the amount of lime is appropriate, it can maintain a certain viscosity and appropriate stability in the froth. However, if the amount is too large, it will cause fine particles to agglomerate in the froth, causing the froth to stick and expand, or even run off the slurry, resulting in operational chaos and a decrease in separation indicators. Therefore, the amount used must be carefully controlled.

In production, lime is generally added in the form of lime slurry, or it can be added in powder form. Its amount is generally controlled by adjusting the pH value of the slurry. However, when a large amount of lime is used, it is necessary to measure the free CaO content in the slurry to reflect the amount used.