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A arsenic-bearing gold ore flotation technology
A gold mine belonging to the metal sulfide deposits, ore composition less complicated. Metallic minerals natural gold, pyrite and arsenopyrite, and a small amount of copper, lead, zinc and other metal sulfides, metal only for the recovery of gold. The main carrier minerals of gold are pyrite, arsenopyrite and quartz . The gold minerals have a fine grain size and are mostly in the form of fissure gold and interstitial gold. The symbiotic relationship between gold and carrier minerals and arsenopyrite and pyrite is extremely close. Therefore, it is difficult to achieve gold and arsenic separation by flotation. Through the selection and combination test of various inhibitors, the arsenic content of gold concentrate was reduced to 0.27% and the removal rate of arsenic reached 92.68% by using the stage selection and phase-inhibition beneficiation process, reaching the arsenic content of gold concentrate. Less than 0.4% quality requirement. The gold concentrate grade is 82.30g/t, and the gold recovery rate is 87.01%.
First, the nature of the ore
(1) Material composition and embedding characteristics of ore
Ore raw material composition is not complicated, metal metal sulfide minerals pyrite, arsenopyrite, chalcopyrite, and small amounts of lead and zinc, and gold NATURAL; gangue minerals are quartz, sericite followed carbonate mineral salts and chlorite, plagioclase, tremolite and the like. The multi-element chemical analysis of the ore and the determination results of the main mineral inlaid particle size are shown in Table 1 and Table 2, respectively.
Table 1 Multi-element chemical analysis results of raw ore %
element
Au
Ag
As
Cu
Pb
Zn
content
7.50
8.00
0.27
0.071
0.054
0.059
element
Fe
S
SiO2
Al 2 O 3
CaO
MgO
LOS
content
0.67
2.33
69.36
11.54
3.93
1.12
7.73
Note: The unit content of Au and Ag is g/t.
Table 2 Inlaid particle size distribution of major minerals
Size/mm
content/%
Pyrite
Arsenopyrite
quartz
+0.5
-0.5+0.1
-0.1+0.074
-0.074+0.056
-0.056+0.037
-0.037
total
23.64
39.97
15.82
9.62
6.42
4.53
100.00
21.45
31.42
21.19
13.34
6.68
5.83
100.00
12.94
28.85
17.37
25.56
9.04
6.24
100.00
Metallic minerals are mostly in the form of disseminated and agglomerated in ores, and the symbiotic relationship between metal minerals is close. Pyrite is often replaced by toxic sand and is produced by continuous crystal. The phenomenon that pyrite is filled and fractured along the fissures of natural gold, chalcopyrite, sphalerite and galena is also obvious. In addition to its close relationship with pyrite, the poisonous sand is also closely produced with metal sulfides such as natural gold, sphalerite and chalcopyrite. Therefore, improving the fineness of grinding makes the dissolving of the poisonous sand and its associated minerals fully, which is the premise of reducing the arsenic grade in gold concentrate.
(2) The occurrence state of gold minerals
There are two main types of gold minerals in ore, namely natural gold and silver gold, of which natural gold accounts for more than 94%. Most of the gold minerals are produced in the intergranular or fissures of other minerals. The gold minerals are less encapsulated, and the particles are mostly granular, plate-like or fine veins. Gold minerals are closely related to metal minerals. About 40% of gold minerals are found in pyrite. The gold minerals in arsenopyrite and quartz account for 10% and 25% of the impulse, respectively. Pyrite, arsenopyrite and quartz are The main carrier of gold minerals. Other gold minerals are found in minerals such as sphalerite, chalcopyrite, galena, or in the interstices between metal minerals and gangue minerals. The gold minerals have a finer grain size, and their distribution in each grain size is shown in Table 3.
Table 3 Embedding grain size of gold minerals
Size/mm
+0.037
-0.037
-0.01
-0.005
-0.001
+0.01
+0.005
+0.001
Distribution rate /%
21.75
42.45
24.08
9.62
2.10
Second, the beneficiation test
According to the study of ore properties, gold minerals and metal sulfides, especially with pyrite and arsenopyrite, are closely related. The arsenopyrite is not only the main carrier mineral of gold minerals, but also an important factor causing high arsenic content in gold concentrates. . Therefore, it is a prerequisite to achieve the separation of gold and arsenic by increasing the fineness of grinding and dissociating the poisonous ore and yellow iron from the gold mineral monomer. Studies have shown that the floatability of gold minerals is better than that of pyrite and arsenopyrite, selecting suitable collectors and inhibitors, strengthening the inhibition of arsenic-containing minerals, increasing the single floating probability of gold minerals, and floating gold to reduce arsenic. research focus.
(1) Mineral floatability test
First, the floatability of the ore was tested by the sorting process of Fig. 1. The test results are shown in Table 4.
Figure 1 Mineral optional test procedure
Table 4 Results of mineral floatability test
product name
Yield
As grade
S grade
As recovery rate
S recovery rate
section
accumulation
section
accumulation
section
accumulation
section
accumulation
section
accumulation
Concentrate
Middle mine 1
Middle mine 2
Middle mine 3
Middle mine 4
Tailings
Raw ore
0.46
0.90
1.32
3.22
1.88
92.22
100.00
0.46
1.36
2.68
5.90
7.78
100.00
0.81
1.70
2.24
3.48
1.91
0.085
0.27
0.81
1.40
1.81
2.72
2.53
0.27
19.87
36.60
33.84
29.31
12.57
0.21
2.24
19.87
30.94
32.37
30.70
26.32
2.24
1.36
5.57
10.75
40.76
13.05
28.51
100.00
1.36
6.93
17.68
58.43
71.49
100.00
4.08
14.70
19.93
42.11
10.54
8.64
100.00
4.08
18.78
38.71
80.82
91.36
100.00
As can be seen from Table 4, the arsenopyrite has good floatability, and its content in the concentrate increases rapidly with the increase of the amount of the collector. This also shows that the use of butyl xanthate as a collector to achieve arsenic reduction in gold concentrate difficult. Agents that have weak trapping ability for arsenopyrite and have a strong selective harvesting effect on gold minerals, such as butylammonium black medicine, should be selected.
(2) Selection of arsenopyrite inhibitors
In addition to improving the monomer dissociation degree of gold arsenic minerals by increasing the fineness of grinding, it is an important link to reduce the arsenic grade in gold concentrate by determining the reasonable type and amount of inhibitor. (1) Lime is a common inhibitor of arsenopyrite. The experiment found that the amount of lime in the rough selection operation increased, and the arsenic grade in the coarsely selected concentrate decreased significantly. When the amount of lime was 3000g/t, the arsenic grade in the coarse concentrate decreased to 0.35%, and the arsenic recovery rate was only 13.29%. (2) Cyanide is also a potent inhibitor of arsenic minerals. The proper amount of cyanide can increase the arsenic reduction effect. A small amount of cyanide can reduce the arsenic content of gold concentrate to less than 0.30%, but because cyanide has a strong inhibitory effect on gold and sulfide ore, it has a great influence on the yield of gold concentrate. Therefore, the amount of cyanide should not exceed 10g / t. (3) Sodium bisulfite also has a certain effect on improving the effect of gold and arsenic sorting. In the rough selection operation, 1000g/t of sodium hydrogen sulfite is added, and the arsenic grade ratio in the gold concentrate is not decreased by 0.01%. The arsenic recovery rate was reduced by 2.53 percentage points, the gold recovery rate was not affected, and the gold grade was increased by 8.75 g/t. Tests have shown that the combination of lime, sodium bisulfite and a small amount of cyanide has a significant effect on the inhibition of arsenopyrite.
(III) Determination of the process of mineral processing
Although lime, sodium bisulfite and cyanide can effectively inhibit arsenopyrite, these three agents also have a strong inhibitory effect on gold minerals. If the arsenic-containing minerals are strongly inhibited in the rough selection, the yield and recovery rate of the gold concentrate will be greatly affected. Therefore, in the development of the sorting process, it is necessary to take advantage of the natural floatability of natural gold, and to use a reasonable pharmaceutical system to expand the floatability difference of gold and arsenic minerals, so that gold minerals can be fully recovered. The ore dressing test process as shown in Fig. 2 was finally determined through experiments, and the test results are shown in Table 5. The process can effectively achieve the separation of gold and arsenic minerals, and obtain a good index of gold concentrate gold grade 82.30g / t, gold recovery rate 87.01%, arsenic grade 0.27%, arsenic inhibition rate of 92.68%.
Table 5 Results of mineral processing test
product name
Yield/%
grade/%
Recovery rate/%
Au
As
S
Au
As
S
Concentrate
Tailings
Raw ore
8.01
91.99
100.00
82.30
1.07
7.58
0.27
0.30
0.30
2.81
1.96
2.03
87.01
12.99
100.00
7.32
92.68
100.00
11.10
88.90
100.00
Figure 2 Process of mineral processing test
Third, the conclusion
(1) The ore used for the test belongs to the quartz vein type sulfide-depleted gold ore, the useful mineral is natural gold, and the main harmful mineral is poisonous sand. The gold minerals in the ore are closely related to the symbiosis of pyrite, arsenopyrite and quartz, and the metal sulfides such as arsenopyrite and pyrite are also closely symbiotic. Arsenopyrite is not only the main carrier mineral of gold, but also an important factor causing high arsenic content in gold concentrate.
(2) Selecting reasonable inhibitors and sorting processes, making full use of the difference in floatability of minerals such as gold and arsenopyrite is the key to achieving gold-arsenic separation. In the test, lime, sodium bisulfite and a small amount of cyanide were used as inhibitors of arsenopyrite, and the process of phase inhibition and stage selection was adopted to make the gold concentrate contain arsenic of 0.27% and the arsenic inhibition rate of 92.68%. However, the range of the amount of the inhibitor should be strictly controlled, otherwise it is difficult to ensure that gold concentrate containing less than 0.4% arsenic can be obtained, and a higher gold recovery rate can be obtained.
(3) The ore contains a certain amount of mica minerals. Although it has the characteristics of easy muddy and harmful flotation process in the flotation, due to the presence of mica, it can stabilize the flotation mineralized foam layer and become gold. Flotation carrier. Under the condition that the main carrier of gold minerals, pyrite and arsenopyrite, is fully inhibited, it is possible for natural gold to float alone and rely on new carrier floatation. The gold concentrate contained in the test contains more mica minerals. at this point.