Sodium sulfide (Na2S) is a commonly used reagent in the flotation of sulfide ores. Its functions are as follows:
1. Sodium sulfide is the inhibitor of most sulfide ores.
When the dosage is large, it can inhibit the vast majority of sulfide ores. It inhibits the decline of sulfide ore in the order of galena, sphalerite, chalcopyrite, bornite, copper blue, pyrite and chalcopyrite. Because molybdenite has good natural floatability, sodium sulfide can not inhibit it. Using this, Na2S can be used to suppress other sulfide ores when molybdenite is flotation.
2. Sodium sulfide is a sulfide agent for non-ferrous metal oxides
Nonferrous metal oxides can not be directly collected by xanthate. But if sodium sulfide and non-ferrous metal oxides are added before xanthate flotation, a layer of sulfide film can be formed on the surface of minerals, and xanthate can be collected. This effect of sodium sulfide is called sulfidation, so it can be used as a sulfidating agent for non-ferrous metal oxides.
The surface color of lead ore changed from white to dark after it was treated with sodium sulfide. After the interaction of malachite and sodium sulfide, the surface color changes from green to dark, which indicates that sulfide films different from minerals are formed on the surface of these two minerals after sulfuration.
3. Sodium sulfide is a reagent for removal of mixed concentrate of sulfide ore
When the dosage of sodium sulfide is large, xanthate collectors adsorbing mineral surface can be resolved. Therefore, sodium sulfide can be used as a depressant before separation of mixed concentrate. For example, before separation of lead-zinc mixed concentrate or copper-lead mixed concentrate, the pulp can be concentrated, a large amount of sodium sulfide can be added to remove the drug, then washed, and fresh water is added to the slurry for separation and flotation.
In addition to the above three main functions, because sodium sulfide can form insoluble sulfide precipitation with many metal ions, sodium sulfide also has the effect of eliminating some harmful ions in the pulp for flotation.