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Inhibition and removal of non-molybdenum sulfide minerals in molybdenum ore - inhibition of sulfides such as lead and iron
Molybdenum ore or copper -molybdenum ore contains, in addition to copper sulfide, impurities such as lead sulfide and iron sulfide. In some molybdenum ores, iron sulfide and lead sulfide are also higher than copper sulfide, and become the main non-molybdenum sulfide impurities.
Means for inhibiting agent or composition of copper, almost all-round to inhibit iron sulfide, zinc sulfide; and addition of cyanide inhibitors also could inhibit lead sulfide, bismuth sulfide. It makes it easy to remove sulfide impurities such as lead and iron.
The common lead sulfide is galena (Pbs), and the iron sulfide is pyrite (FeS 2 ). Their crystal structures are shown in Fig. 1 and Fig. 2.
Figure 1 Crystal structure of galena
Figure 2 Crystal structure of pyrite
Inhibition except that a sulfide galena outside, and also with a heavy chromate Knox agents.
Sodium dichromate (Na 2 Cr 2 O 7 ) is an orange-red monoclinic prismatic crystal or a fine needle-shaped dihydrate (Na2Cr20, · 2H, 0), which is easily deliquescent and easily soluble in water. (Compared with the solubility of potassium dichromate: OC, sodium salt 63 intestine, potassium salt only 5%; 100'C, sodium salt 80%, potassium salt only 45% and potassium salt is more expensive than sodium salt, dressing Common sodium salt). The aqueous solution is acidic:
Na 2 Cr 2 O 7 â†â†’2Na + +Cr 2 O 7 2-
Cr 2 O 7 2- +H 2 Oâ†â†’2H + +2CrO 4 2-
In acidic media, dichromate is a strong oxidizing agent. And barium, lead, silver, mercury and Other metals hardly water-soluble chromate. For example, the solubility product of PbCrO 4 is 1.77×10 -14 . [next]
In molybdenum selection, sodium dichromate is sometimes used to inhibit minerals containing lead and antimony.
Inhibition mechanism: It is generally believed that in a weakly alkaline medium, sodium dichromate is converted to sodium chromate, and a poorly soluble, hydrophilic lead chromate (PbCrO 4 ) is formed on the surface of the oxidized galena. In addition, the strong oxidizing property of sodium dichromate in an acidic medium can not only oxidize the surface of the galena, but also oxidize the hydrophobic film of the collector adsorbed on the surface.
Sodium dichromate acts only with oxidized galena. Therefore, in the weakly acidic (pH=7.4) medium, the human sodium chromate and the slurry are fully stirred to exert the new chemical properties, so that the surface of the galena and the surface collector are oxidized and then reacted. Here, the pH control is very important, the acidity is too strong, the oxidation is too fast to lose the inhibition effect; the alkalinity is too strong, the oxidation is too slow, and it is not conducive to inhibition.
The amount of sodium dichromate is about 1~1.25kg/t based on the crude concentrate (sorting material).
Sodium dichromate can also inhibit pyrite, barite, and the like. However, when the material to be separated contains secondary copper minerals, the amount of Cu + and Cu 2+ ions in the medium is large, and these copper ions will adsorb on the surface of galena and pyrite, and the inhibition will be invalid. Knox or sodium sulphide should be used at this time. Phosphonium is often used to inhibit galena.
The effect of using phosphonox to inhibit galena and its comparison with sodium cyanide are shown in Figures 3 and 4.
Obviously, sodium cyanide can hardly inhibit galena, and phosphonox can better inhibit lead sulfide.
The bismuth ore (Bi 2 S 3 ) is similar to galena, and the effect of inhibition with sodium cyanide and phosphonox is shown in Figure 5.
The effect of Phonon Knox and potassium dichromate on the inhibition of galena is shown in the table below.
Figure 3 Phosphonium on the anti-lead effect of Jinduicheng molybdenum ore
Figure 4 Inhibition effect of different inhibitors on lead minerals in Jinduicheng molybdenum beneficiation
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Figure 5 Effect of different inhibitors on Jinduicheng molybdenum beneficiation
Table Yangjiazhangzi K 2 Cr 2 O 7 Phospho Knox lead inhibition (production)
Raw ore containing lead (%)
Pharmacy consumption (g/t)
Coarse concentrate grade (%)
Molybdenum concentrate grade (%)
K 2 CrO 7
P-Nokes
Mo
Pb
Mo
Pb
0.05
0.05
0.05
53.6
48
twenty four
5.62
6.60
7.85
1.16
1.23
1.38
46.22
45.40
45.58
0.461
0.0946
0.117
Obviously, the effect of Phonon Knox on inhibiting galena is much better than that of chromate. This may be more difficult with Phonon Knox and Pb 2+ ions to form insoluble lead thiophosphate (solubility product 1.5×10 -32 ), which is much harder than lead chromate (solubility product 1.77 × 10 -14 ) Dissolved. Therefore, the Knox agent also has a much better effect on the chromate inhibition.
The inhibition of pyrite is related to its intramolecular ratio of sulfur to iron (S/Fe). When the ratio of sulfur to iron is closer to 2, the flotation or inhibition of pyrite is easier; when the ratio of sulfur to iron is smaller, the farther away from 2, the inhibition It has become difficult. The Jinduicheng pyrite is measured, and its S/Fe ratio is 1.97~2.02, so the inhibition is relatively much easier.
Abramov et al. believe that during the grinding and flotation aeration process, the surface of the pyrite in the slurry will oxidize to form iron carbonate or iron hydroxide. When the pH is lowered (<7) and inflated, the hydroxide will dissolve and fall off. Therefore, the recovery of pyrite is often carried out in an acidic medium. When the pH is ≥ 9, the hydrophilic coating of iron hydroxide on the surface of the pyrite is inhibited.
The iron hydroxide differs depending on the oxidation-reduction potential of the slurry. When the oxidation potential is high, it is mainly Fe(OH) 3 ; when the oxidation potential is low, it is Fe(OH) 2 or FeCO 3 .
Therefore, molybdenum flotation often adds lime water Ca(OH) 2 to increase the pH of the medium to inhibit pyrite.
For the pulp with pH=9~12, with or without inhibitor, the inhibition rate of pyrite does not change much (see Figure 6).
Figure 6 Inhibition effect of inhibitor on Jinduicheng molybdenum ore