Oxygen, the role of flotation
Xanthate is a metal sulfide ore beneficiation floating main collector, but only under the conditions of the presence of oxygen, xanthate will play a role. Test was done, the galena grinding water in absence of oxygen, and mineral flotation, the collector can not be galena xanthate. Oxygen plays a very important role in the action of xanthate and metal sulfide ore. There are different opinions on the mechanism of action of oxygen, which is summarized into two points.
(1) The formation of semi-oxides on the surface of minerals shows that in the process of flotation and beneficiation, the surface of the sulfide minerals will be favored for the flotation process after slight oxidation, and the over-oxidation will reduce the floatability. Most of the sulfide ore is oxidized on the surface after oxidation. For example, galena PbSO4 formed surface oxide film, a surface oxide film ZnSO4 generated sphalerite, as represented by the reaction formula:
PbS+2O2→PbSO4
ZnS+2O2→ZnSO4
Pyrite oxygen process is quite complicated, and the final result is:
2FeS2+7O2+2H2O→2FeSO4+FeSO4
Oxidation brass ore is:
CuFeS2+4O2→CuSO4+FeSO4
Because the solubility of sulfate is much larger than that of the corresponding sulfide, it is beneficial to the collector of xanthate.
Ion conversion is performed between. For example, the surface of galena is slightly oxidized. When it is collected by xanthate, the following replacement reactions exist:
In the reaction formula, X- represents a xanthate anion, and A- may be SO2-4 or SO2-3.
Before X- adsorption on the surface of galena, oxygen first reacts with sulfur to oxidize a part of sulfur ions on the surface of galena.
or
, as shown in Figures 6-16. The xanthate anion is then replaced with Pb2+ to form a less soluble lead xanthate PbX2.
However, the ore dressing practice proves that the oxidation is too deep due to the formation of a thick lead sulfate shell on the surface, and the solubility of lead sulfate is too large, and the collector ions cannot be strongly adsorbed, so the leaching of the galena is too deep, but the floatability is reversed. It is getting worse.
The semi-oxides of galena and related products obtained by the action of xanthate anions are now shown in Figures 6-17.
Figure 6-17 shows only the components of the outermost two layers of the solid phase. The deeper meaning is:
On the left side (inside the solid phase) all S are not oxidized;
Many layers S on the left side (inside the solid phase) have been oxidized to sulfate.
The above studies indicate that the effect of xanthate anion on the surface of galena is related to the degree of mineral oxidation. Slight oxidation is mainly formed on the surface of galena minerals. It is mainly a monolayer of lead xanthate. It has good hydrophobicity. It covers a certain degree on the surface of minerals and is enough to form a multi-molecular layer of lead xenthate on its surface. The lead phase of the yellow acid is less hydrophobic than the monolayer lead film, so the oxidized galena has a decrease in floatability.
The degree of oxidation is affected by the following factors: slurry temperature, application of oxidant, presence of oxidation products on the surface of the mineral, pH of the slurry, aeration time and aeration intensity, oxygen content in water, and the like. For example, in the separation operation of copper-sulfur (Cu-S) mixed concentrate, in order to smoothly carry out the sulfur-reducing copper, the method of strengthening oxidation is adopted, which makes the discriminability of chalcopyrite-pyrite more discriminating. Copper and sulfur separation can get better indicators. The slurry is subjected to strong agitation and strong aeration under high pH conditions (pH > 11.5). Since pyrite is more susceptible to oxidation than chalcopyrite, this deepens the oxidation of pyrite surface and inhibits the floatability of pyrite. The chalcopyrite is slightly oxidized, which acts better with xanthate and its floatability is improved.
(2) The presence of oxygen eliminates the potential grid of the mineral surface and promotes the electrochemical reaction of the mineral surface. Since the sulfide mineral contains more or less impurities, there are various lattice defects, which make it have semiconductor properties, and have both a cathode region and Anode zone. For example, galena generally contains silver . In a cyanide-containing slurry, silver reacts as follows:
Free electrons are generated and transported to the cathode region, causing more electrons in the vicinity of the cathode region to accumulate, resulting in a negative potential gate, as shown in Figure 6-18.
In this way, it is bound to generate an electrostatic repulsion to the xanthate anion X- near it, hindering its adsorption on the mineral surface. If oxygen is present in the slurry, the following reactions can occur:
Therefore, the repulsion of negative electricity can be eliminated, which is beneficial to the adsorption of floating mineralizer on the mineral surface.
The role of galena and xanthate can be written as:
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