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(2)
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The main characteristics of fine-grained minerals are small mass, large specific surface and high surface energy. The small mass causes the hydrophobic ore particles to have small momentum in the slurry, and the collision probability with the bubbles is small, and it is difficult to overcome the energy between the ore particles and the bubbles and adhere to the surface of the bubbles. However, if the gangue mineral particles adhere to the surface of the bubble, it is difficult to fall off, and the fine-grained gangue mineral is greatly affected by the water medium, and easily enters the foam layer to form inclusions. The large specific surface area and high surface energy cause serious non-selective agglomeration between gangue ore particles; the adsorption amount of the agent increases, and the selectivity of drug adsorption decreases, and the viscosity of the slurry increases greatly, which is not conducive to flotation. There are many researches on flocculation theory, typical of DLVO flocculation theory, as well as the former Soviet scholar BVDeryagin, L. Landau and Dutch scholar EJ Verwey, JTGOverbeek studied the interaction between the colloidal particles caused by the diffusion double layer and the van der Waals interaction. The energy of action, the proposed mutual attraction energy between particles of various shapes, explains the reason for the reversible aggregation (flocculation) of particles. Wang Yumin et al., Guo Jizhi et al. also elaborated on the action energy of colloidal particles in the electric double layer. Flotation aspects of research on low-grade ore of platinum, palladium, Tang Min, etc. on the flotation of the mine Serpentine analyzed and discussed, at present more and more research has focused on new hydrometallurgical process aspects, such as yellow Kun, Chen Jing, etc. conducted a series of cyanide leaching experiments on the mine.
In this paper, the properties of a fine-grained platinum-containing palladium- copper- nickel sulfide ore were investigated by conventional hydrophobic flocculation flotation. According to the characteristics of fine-grain mineral processing , the influencing factors were analyzed in detail.
   First, the experiment
(a) sample
This experiment iron ores collected from a qualitative ultrabasic rocks, metal sulfide minerals are pyrrhotite, pyrite, chalcopyrite, pentlandite, purple sulfur pentlandite the like, containing a small amount of platinum, palladium mineral ; metal oxides mainly magnetite, chromium, limonite, a small amount of platinum group minerals; gangue minerals are serpentine, hornblende stone, mineral carbonates, pyroxenes, chlorite, biotite .
The pure mineral test is mainly applied to observe the microscopic morphology between minerals in water, from the Jinchuan copper-nickel sulfide deposit, which is selected from the crystallization of pentlandite. After grinding through a mortar, it is sieved and classified by a 200,300,400 mesh sieve. After the fine-grained grade is passed through a 400-mesh sieve, it is further ground for a long time, and it has been ensured that most of the ore pellets are tested below -400 mesh. . Serpentine also comes from Jinchuan and is sampled in the same way.
(2) Test conditions
The flotation agent is butyl xanthate, butyl ammonium black drug, water glass, CMC, 2 # oil, Na 2 SO 3 , OC, KN is a self-made agent. The flotation test used XPY1-63 jaw crusher , 200Y120 roller mill, XMQ-67 type Ф240×90mm grinding machine, XF-D type single tank flotation machine (1.5 and 0.5L). Improved test uses pure mineral Harry Mond 50ml tube, magnetic stirrer, a mercury barometer and the like.
(3) Test methods
1. Ore test method
Each time, 500 g of mineral sample and 500 ml of water were weighed and added to a mill for grinding. After grinding, the slurry was poured into a 1.5 L flotation tank, and the flotation agent was added to stir for flotation. The specific process is shown in Figure 1. Grinding and flotation routine tests are carried out in conventional laboratory mills and flotation machines.
Figure 1 A copper-nickel sulfide ore stage grinding stage selection process
2. Nickel pyrite test method
Weigh 1g of pentlandite mineral, add it to the beaker, wash it with acid, clean it, add water and flotation agent together, then transfer the sample and solution together to the single bubble tube, and start the electromagnetic stirrer. Rotate to make the ore particles in suspension. After purging, the nitrogen gas is pressed into the flotation tube at a constant speed. The nitrogen gas is introduced into the flotation tube at 30-40 ml·min -1 , and the flotation is stopped after 6 minutes. The collected ore particles are collected in a beaker and are observed under a microscope, and the remaining weighing is performed. And calculate the recovery rate.
(4) Test content
Extraction of nickel pyrite flotation test samples, sample size: -20μm particle size particles: test conditions and results are as follows:
1. The flotation test was carried out with butyl xanthate (100g·t -1 ) alone, and the upper concentrate was taken for observation.
2. The flotation test was carried out by using the butyl ammonium black drug (100g·t -1 ) alone, and the floating concentrate was taken for observation.
3. The change of the amount of the combined collector is changed: (1) 24 g·t -1 , (2) 60 g·t -1 , (3) g·t -1 , and the upper concentrate is taken for observation.
4. No collector test, direct observation of fine-grained nickel pyrite in water.
5. The same nickel mineral concentration and combined collector concentration test as the ore flotation (0.28g of ore, combined collector 0.002g·ml -1 ), and the upper concentrate is taken for observation.
6. Manually mix ferronickel and serpentine gangue minerals, add appropriate amount of collector, and flotation concentrates are observed under water microscope using OLYMPUS microscope.
   Second, the results and analysis
(1) Flotation of ore and tailings water and metal determination results
Compare Figure 2 to analyze the recovery of each fraction of each useful mineral in the sulphide ore flotation. It can be seen that according to the conventional flotation experience, the useful minerals of the coarser grade should be better than the fine fraction, but the actual results are reversed. The recovery of the useful minerals of the coarser grade is not good, but it should be difficult to recycle. The recovery of fine-grained sulfide minerals is very good. It shows that the fine-grain metal sulfide ore is satisfactory under the reasonable oxidation control atmosphere. However, the content of MgO in the concentrate is as high as 20.11%, and it is shown that the MgO in the concentrate is difficult to be effectively removed during the intensive dispersion and inhibition test, which may be closely related to the mechanical inclusion of the gangue mineral.
Figure 2 Water analysis results and metal distribution determination of ore and tailings and metal recovery of each grade in concentrate
(II) Analysis of ore sedimentation test results
Test conditions: Weigh 25g sample into a 500ml measuring cylinder, add only water to the 500ml mark in the blank test, stir evenly, start timing, and record the height of the clear layer; the difference in the sedimentation test of adding the combined collector is more A collector (butyl ketone 100 g·t -1 + butyl ammonium black drug 50 g·t -1 ) was added, and after the action was completed, the sedimentation test was started.
Table 1 Flotation results of fine-grained nickel pyrite
Name of project
Feed/g
The float fraction/%
Residue/%
(1)
(2)
(3)1
2
3
1.0
1.0
1.0
1.0
1.0
70
71
20
50
78
30
29
80
50
twenty two
Table 2 Ore sedimentation test results
Time of
Sedimentation/min
High of clear layer
Density of head ore 5%
Density of concentrate 5%
(1)
(2)
(1)
(2)
2
4
8
12
16
20
twenty four
1×60
┇
10×60
48.0
100.8
189.6
213.6
216.0
217.0
218.6
219.0
┇
220.8
81.6
168.0
211.2
213.5
215.9
217.2
218.0
220.0
┇
220.0
55.2
148.8
206.4
208.8
213.6
216.0
217.5
219.0
┇
220.5
108.0
204.0
210.4
215.0
216.5
218.8
219.0
220.0
┇
220.9
From the ore sedimentation test, it can be seen that in the first 8 min, the sedimentation velocity of the collector sample is faster than that of the blank sample. Since only the combined collector is added, it is suggested that there may be hydrophobic flocculation between the fine-grained mineral particles, so that the partially sulfided minerals and their contiguous bodies form flocs, which leads to an increase in sedimentation speed. From the phenomenon, the clear layer added to the collector mineral sample is more turbid than the blank ore, and a large number of gangue micro-materials are suspended therein, indicating that the precipitated mineral is mainly the floc of the copper-nickel sulfide mineral, and most of the remaining The gangue minerals are retained in the clear layer and have not yet settled down, so they appear turbid. From the concentrate reprocessing settlement test, it can be seen that the height difference is about 50 mm in the first 4 minutes, especially in the first 2 minutes. The content of copper-nickel sulfide minerals in the concentrate is very high. Therefore, after the collector is added, the flocculation effect between the fine-grained copper-nickel sulfide mineral particles is remarkable, and the sedimentation speed is relatively fast. Moreover, its clear layer is more turbid than without the collector.
Figure 3 Observation results of flotation concentrates of different grades of nickel pyrite
(3) Particle size and concentration of fine-grained minerals and hydrophobic flocs
Only when the particles are small to a certain extent, the influence of the cohesive force on the dynamic characteristics of the particles exceeds the gravity, and the phenomenon of flocculation is highlighted. Therefore, particle size is an important factor affecting flocculation. At the same time, mineral concentration may also be a factor affecting flocculation.
Through the analysis of the ore grinding fineness test results, it is found that the fineness of the grinding has a great influence on the hydrophobic flocculation flotation of the fine particles with sulfide minerals, as shown in Fig. 4.
Figure 4 Effect of grinding fineness on concentrate quality (a ~ c)
As can be seen from Figure 4, as the fineness of the grinding increases, the yield of the concentrate increases sharply (from 17.12% to 29.72%), while the nickel grade in the concentrate decreases drastically (from 0.72% to 0.44%). ), fine grinding can dissociate minerals from more useful mineral monomers, which should be more conducive to this hydrophobic flocculation. However, the possibility that the gangue slime mechanical inclusions enter the concentrate cannot be ignored. From the single-bubble test of ferronickel, it is found that there is little or no hydrophobic flocculation between the coarse mineral particles, and the possibility of mechanical inclusions in the gangue slime is small. Of course, it affects the recovery of useful minerals with coarser grades. Factors should also consider the cover of the slime, and some of the muddy gangue may be covered on the useful minerals or their connected organisms, reducing their floatability, causing some minerals to be lost with the inhibition of gangue. . The mineral concentration also affects the flocculation results of the fine-grained copper-nickel sulfide minerals. It is found in Fig. 5(d) and (e) that a small amount of small flocs appear at low mineral concentrations, while large concentrations of large flocs occur at high concentrations. group. This is consistent with the results of the ore test.
Figure 5 Test results of different combinations of collectors and used alone
(4) Strengthening the effect of collector on the hydrophobic flocculation of fine minerals
It can be seen from Fig. 6(a) that when the amount of the combined collector is small, the recovery rate of the useful mineral is low but the grade is high. It is indicated that the amount of the combined collector is not sufficient to cause a part of the fine particles to be used for the mineral particles to overcome the repulsion energy barrier between them, and the number of flocs is reduced, and the recovery rate of the useful mineral is lowered. Of course, the possibility that the serpentine gangue mud is mechanically mixed is greatly reduced. As the amount of combined collectors continues to increase, the hydrophobic flocculation between the fine particles and the minerals is intensified, forming more, larger, and looser flocs, which increases the chance of mechanical inclusions in the gangue. The concentrate yield has increased dramatically, but the grade of nickel in the concentrate has also dropped dramatically. From Fig. 6(b), it was found that the hydrophobic flocculation phenomenon between the fine particles using the butylammonium black drug was strong, and almost no monomer or small floc was present, and most of them formed a loose, reticulated large floc. The hydrophobic flocculation phenomenon between the fine particles of butyl xanthate is not as strong as the former, and most of the medium-sized flocs are between 100 and 200 μm, which is consistent with the test results of the butyl ammonium black dose of the ore flotation. .
Fig.6 Effect of combined collectors on ore flotation on concentrate grade and recovery rate
(5) Effects of dispersants and inhibitors on the selection index and hydrophobic flocs
From the above test results, it was found that the combined inhibitor of CMC and KN has a certain inhibitory effect on serpentine gangue slime. The grades and recovery indexes of Ni and Cu in the concentrate are good, but the minimum MgO content in the concentrate is 20.11%. Although the combination inhibitor has obvious inhibition on the serpentine gangue, the veins in the concentrate Stone is still difficult to remove effectively, which means that the gangue mine entering the concentrate is most likely due to the mechanical entrainment of the useful mineral hydrophobic flocs.
Table 3 Test results of serpentine gangue inhibitor CMC+KN
Type and dosage
Of depressant
Product of cleaner
Output/
(g·t -1 )
Grade/%
Recovery/%
Ni
Cu
MgO
Ni
Cu
KN50+KN50
Concentrate к
Middling л 1
Middling л 2
Tailing Ñ…
The head
2.74
3.60
9.44
84.82
100.00
2.71
0.69
0.17
0.126
0.218
4.00
0.156
21.03
34.06
9.05
7.36
49.08
100.0
70.26
KN150+KN150
Concentrate к
Middling л 1
Middling л 2
Tailing Ñ…
The head
3.04
4.22
8.33
84.22
100.00
2.71
0.69
0.17
0.126
0.218
3.76
0.156
20.92
35.42
11.03
6.64
46.91
100.0
73.27
CMC50+CMC50
Concentrate к
Middling л 1
Middling л 2
Tailing Ñ…
The head
3.32
4.16
8.98
83.56
100.00
2.54
0.57
0.17
0.121
0.218
3.61
0.156
22.42
40.82
7.71
6.60
46.83
100.0
76.83
CMC150+CMC150
Concentrate к
Middling л 1
Middling л 2
Tailing Ñ…
The head
2.76
3.74
9.02
84.38
100.00
2.97
0.52
0.17
0.12
0.218
4.45
0.156
22.23
37.60
8.92
7.03
46.65
100.0
78.73
KC(KN+CMC)+KC50+50
Concentrate к
Middling л 1
Middling л 2
Tailing Ñ…
The head
3.78
4.12
9.01
82.92
100.00
2.21
0.48
0.15
0.122
0.218
3.19
0.156
22.14
38.32
9.07
6.20
46.41
100.0
77.30
KC+KC150+150
Concentrate к
Middling л 1
Middling л 2
Tailing Ñ…
The head
3.26
3.84
6.96
83.94
100.00
2.38
0.62
0.20
0.118
0.218
3.5
0.156
20.14
35.59
10.92
8.05
45.44
100.0
73.14
KC+KC100+200
Concentrate к
Middling л 1
Middling л 2
Tailing Ñ…
The head
2.44
4.22
10.98
82.36
100.00
3.11
0.52
0.19
0.12
0.216
4.55
0.29
0.078
0.028
0.156
20.11
34.81
10.07
9.57
45.55
100.0
71.64
7.85
5.63
14.88
100.0
Figure 7 Flotation test results of dispersant
By sodium silicate and sodium hexametaphosphate dispersing agent, the kind and amount of test results show that the inhibition of serpentine sodium silicate gangue weak, but its good dispersion of the slurry, clay slurry to avoid a certain role of . On the one hand, water glass enhances the strength and hydrophilicity of the hydration layer on the surface of the slime, so that the mutual agglomeration is hindered by space; on the other hand, the absolute value of the negative potential on the surface of the slime is greatly improved, and the same-sex charge between the fine particles is enhanced. The electrostatic repulsion forces make them difficult to approach each other and close together, indicating that the use of the dispersant can improve the mechanical entrainment of the gangue slime on the hydrophobic flocs to a certain extent, but does not fundamentally solve the problem.
   Third, research on hydrophobic flocculation mechanism
According to DLVO theory, the interaction potential between particles in the system is:
E T =E W +E B (1)
Among them: E W is the van der Waals potential energy, E B is the electric double layer repulsive potential energy, and E B is the electric double layer repulsive potential energy. The extended DLVO theory holds that the interaction potential E T should include the hydrophobic potential energy E H , the hydrophilic interaction energy E′ H and the spatialized repulsion energy E P of the macromolecule on the basis of E W and E B . The combined drug system is a hydrophobic system, so the extended DLVO theory is:
Where: R is the nickel pyrite particle size, set to 10×10 -6 m; A is Hamaker constant, K is Debye constant, taking 0.104; A is 2.28×10 -19 J; at pH=6.7, ψ=-17.5 mV,h is the attenuation length, taking 10×10 -9 m; H is the interaction distance between particles, C H =(0.14±0.02)N·m -1 . Let the radius of the two particles be equal to R 1 =R 2 and the thickness of the adsorbed layer is uniform δ 1 =δ 2 . The thickness δ of the adsorption layer is obtained by the formula ξ=φdexp[-k(δ-Δ)], and Δ is the thickness of the Stern layer, which is 0.3 nm, k=1.38×10 -23 J·K -1 is substituted into (2) to obtain a curve. Figure 8.
Fig.8 Potential energy curve of intergranular interaction of hydrophobic system nickel pyrite
It can be seen from Fig. 8 that in the hydrophobic system, the potential energy of the interaction between the particles of nickel pyrite is between 0 and 100 nm, indicating that the hydrophobic interaction is spontaneous and the hydrophobic flocs are spontaneously formed. . This is consistent with our test results.
   Fourth, the conclusion
The results of flotation concentrate microscopic observation of fine-grained nickel pyrite and copper-nickel sulfide ore show that hydrophobic flocculation flotation is the main flotation mechanism of fine-grained copper-nickel sulfide minerals. Under the action of a powerful combined collector, the fine-grained copper-nickel sulfide mineral particles are hydrophobized and flocculate into agglomerates, increasing the "apparent" particle size of the mineral and increasing the recovery rate of the flotation. It was also found from the flotation test of pentlandite that the size and quantity of the hydrophobic flocs and the degree of flocculation showed a positive relationship with the change of the amount of the combined collector. This just explains the increase in the yield of concentrates in the sulphide ore flotation due to the increase in the amount of combined collectors, and the recovery of nickel in concentrates is gradually increasing. The hydrophobic floc structure formed between the fine-grained copper-nickel sulfide mineral particles is not compact and compact, but a loose porous network structure. In the ore flotation, these pores become a hydrophobic hydrophobic serpentine gangue slurry. Convenient location.