1. Vulcanization process and essence

The surface of the copper oxide has an ionic bond, and the electrostatically attracted water molecules are polarized to form a relatively directional aligned hydrated film, which is hydrophilic, and it is difficult for the collector to act on the copper oxide mineral through the hydrated film. s surface. After addition of sodium sulfide, copper oxide or HS- rapid adsorption surface S2-, presenting a metal sulfide film. Sodium sulphide is a strong base weak acid salt that is first hydrolyzed in aqueous solution and then ionized in two steps:

Na2S+2H2O H2S+2NaOH

H2S HS-+H+

HS- H++ S2-

According to the solution balance calculation, when the pH value is less than 7, H2S is dominant in the solution, and a small amount of HS- is present. At pH values ​​below 7-12, HS- dominates the solution with a small amount of H2S. Only when the pH is equal to 11-13, there is a small amount of S2-, HS- still dominates, and when the collector is adsorbed on the surface of the sulfided mineral, the adsorption amount is the highest when the pH is 7-10, and the recovery rate is the highest. The highest, indicating that Na2S is mainly HS-vulcanized by malachite, and the surface reaction is:

CuCO3 (surface) + HS- → CuS (surface) + HCO3-

Cu(OH)2 (surface) + HS- →═CuS(surface)+H2O+OH-

It can be seen that mastering the pH value of flotation and controlling the amount of Na2S are important factors that are interrelated and mutually restrictive.

When the amount of sodium sulfide is suitable, after vulcanization, the contact angle of the surface of the copper oxide mineral is increased, the floatability is enhanced, and the amount of the required collector is also minimized, and the effective flotation of the copper oxide ore can be successfully achieved; If the amount of sodium is too large, it will be inhibited.

Second, the inhibition of excessive vulcanization

As mentioned earlier, sodium sulphide is an activator of copper oxide ore when used in an appropriate amount, but is a strong inhibitor in excess. Therefore, while studying the activation process and mechanism of sodium sulfide, more attention has been paid to the problem of excessive sulfur ions inhibiting the sulfided copper oxide mineral. So far, four more representative views have been proposed for the reasons for the suppression:

(1) Excessive sulfur ions cause inhibition by themselves; studies have shown that a small amount of sulfur ions can also inhibit the flotation of malachite; for vulcanized chrysocolla, the influence of excessive sulfur ions is more complicated. Only when a certain amount of sodium sulfide is used, the cyanite can be floated; when the sodium sulfide is excessive, the cyanite will be irreversibly inhibited, that is, the buoyancy will not recover when the excess sodium sulfide is washed by fresh water.

(2) The product formed by the oxidation of excess sulfur ions causes inhibition; in addition to the inhibition of excess sulfur ions in the solution itself, the oxides adsorbed on the surface of the mineral, such as sulfite, thiosulfate, etc., also have a strong inhibitory effect. This is because the hydrogen price of sulfur in the hydrogen sulfide molecule is -2, and it is the lowest among the eight valence states of sulfur and has a reducing property. That is, sulfur ions and sulfur ions are easily oxidized. Once they are oxidized, they lose their inherent ability to activate. Moreover, these oxidation products together with excess sulfur ions in the solution constitute the cause of the inhibition of copper oxide ore flotation.

(3) Excessive sodium sulfide causes the decrease of the adsorption amount of the collector to cause inhibition; it has been found that an excessive amount of sodium sulfide reduces the adsorption amount of the collector, and thus the flotation of the mineral is suppressed. After the copper oxide mineral is vulcanized, a copper sulfide film is formed on the surface of the copper sulfide. The properties are similar to those of the copper sulfide mineral, so that when the sodium sulfide is excessive, the excess HS- and S2- in the slurry are oxidized and consume free in the solution. Oxygen, due to the absence of free oxygen in the flotation slurry, causes the collector to not adsorb on the sulfide minerals, forming inhibition.

(4) Excessive sodium sulfide causes the formed copper sulfide film to be loose and unstable, and is easily detached to cause inhibition. It is also believed that due to the excess of sodium sulfide, the pH of the slurry is increased, causing the copper sulfide film to be loose and unstable, falling off into colloidal copper sulfide, and the xanthate itself is consumed, resulting in insufficient collector to achieve effective flotation. The vulcanized film formed by malachite in the vulcanization process was analyzed by X-ray diffractometer, electrochemical and electron microscopy equipment. It was found that the composition of the vulcanized film formed on the surface of the sulfide and the copper sulfide of the domain were similar, and the vulcanized product was a layer. The loose sediment with irregular character is easy to fall off during the pulp mixing process, and the loss of the adsorbed xanthate is caused after falling off, resulting in insufficient inhibition of the amount of the collector.

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