Sulfide ore flotation electrochemical and collectorless flotation

1 Introduction
Since the discovery of electrochemical regulation of sulfide ore-free collector flotation in the 1940s, a large number of theoretical research results have been obtained. The fundamental characteristic of the electrochemically controlled flotation of sulfide ore is that the surface of the sulfide mineral is hydrophobized and hydrophilized by the matching, adjustment and control of potential-pH, thereby achieving flotation and separation. The hydrophobicization of the collector on the surface of the sulfide ore and the hydrophobicization of the collector-free agent are an electrode reaction process. The interfacial potential of the sulfide mineral-liquid phase determines the flotation and inhibition of the sulfide ore. Therefore, the macroscopic effect of electrochemical regulation is to adjust the potential to a certain value to produce a hydrophobized electrode reaction (flotation); or to another value so that the electrode reaction that produces the hydrophobic body does not occur (inhibit). The theoretical study of collector-free flotation under electrochemical regulation is divided into two aspects:
1.1 Hydrophobicization mechanism of non-collector flotation without electrochemical modifier
There are three kinds of influential views:
   
(1) It is considered that under electrochemical control, moderate anodization of the surface of the sulfide ore produces neutral sulfur (S 0 ), resulting in flotation.
MS+H 2 O←→S 0 +MO+2H + +2e
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(2) that the regulation of the electrochemical, anodic surface oxidation of sulphide minerals generated initial lack of sulfur-rich metal compound is a hydrophobic material. When the surface oxidation of the sulfide ore begins, the metal ions preferentially leave the mineral lattice and enter the liquid phase, leaving a metal-deficient sulfur-rich layer, which is considered to be hydrophobic. As the oxidation process continues, the metal ions are increasingly leaving the mineral crystals, entering the liquid phase, and the sulfur content is getting higher and higher, eventually producing neutral sulfur on the mineral surface. The total reaction formula is:
MS+xH 2 O ←→ M 1-X S+xMO+2xH + +2xe
(3) It is considered that the solubility of sulfide minerals is very small and is not easily wetted by water, which determines the flotation of minerals without collectors. The smaller the solubility, the better the floatability of the collector. In essence, this view belongs to the traditional natural floatability category.
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1.2 Hydrophobization Mechanism of Non-collector Flotation with Electrochemical Conditioner
Some sulfide ore (e.g. pyrite) does not have the neutral sulfur (S 0) generated by self-oxidation, it is necessary to add an electrochemical adjuster, i.e. without flotation collector electrochemically induced adjusting agent. In one case, neutral sulfur is generated on the surface of the sulfide ore to promote flotation without collector; in another case, as a reduction potential regulator, the slurry potential is lowered, and the collector-free flotation of certain sulfide ore is inhibited.
1.3 Methods of electrochemical regulation
(1) External control potential method The electrode is added to the flotation cell. For example, the Outokumpu Company of Finland has developed an externally controlled potential flotation machine, which has been successfully applied to the flotation of low-grade copper- nickel sulfide ore. This method eliminates the influence of chemical factors on the flotation of sulfide minerals, and can obtain a single dependence of the flotation behavior of sulfide minerals on the potential. However, there are still some difficulties in implementing the site at present, and the potential value in the slurry cannot be uniform.
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Our school started this research in 1998 and proposed a collector-free flotation process that is only regulated by adding a small amount of electrochemical modifier. This process has been successfully applied to the sulfur flotation of a large iron ore and to a certain The experimental results of copper and sulfur flotation of large copper-bearing magnetite have been obtained.
2 No collector flotation under the control of electro-chemical I
Studies on the non-collector flotation of sulfide minerals such as chalcopyrite, chalcopyrite and pyrite show that the addition of a small amount of electro-chemical I can reduce the amount of collector (xanthate) by 80-90%, significantly reducing the float. The cost of selecting the drug; Electrochemical I, the source of raw materials is wide, the price is cheap, the amount of addition is small, the use is convenient, and there is no harmful effect on the flotation process; no change to the original production process and equipment is required to adopt this process. [next]
2.1 Application of sulfur flotation in a large iron ore mine
The company's annual production capacity (original ore) is 1.2 million t/a, the original mine TFe grade is 50-52%, and the S grade is about 3%. The float-magnetic process is used to float the sulfur to obtain the sulfur concentrate, and then use the weak magnetic separation. Recover iron concentrate. Sulfur flotation was added with butyl xanthate at 100 g/t or higher, and No. 2 oil at 60 g/t. The results of the non-collector flotation laboratory test and the on-site industrial test are shown in Tables 1 and 2, respectively. The original production conditions in the table: butyl xanthate 100g / t, No. 2 oil 60g / t; test agent conditions: Electrochemical I No. 100g / t, butyl xanthate 20g / t, No. 2 oil 60g / t.
Table 1 Laboratory test results without collector flotation
condition
product
Yield(%)
Grade (S) /%
Recovery rate (S) /%
Original conventional flotation
Concentrate
Middle mine
Tailings
Raw ore
7.76
1.46
90.78
100.00
39.24
14.28
0.32
3.54
85.92
5.88
8.20
100.00
No collector flotation
Concentrate
Middle mine
Tailings
Raw ore
8.60
1.25
90.15
100.00
38.55
8.58
0.31
3.70
89.55
2.90
7.55
100.00
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Table 2 Industrial test results without collector flotation
condition
product
Yield/%
Grade (S) /%
Recovery rate (S) /%
Original conventional flotation
Concentrate
Tailings
Raw ore
5.60
94.40
100.00
37.54
0.39
2.47
85.10
14.90
100.00
No collector flotation
Concentrate
Tailings
Raw ore
6.38
93.62
100.00
37.23
0.42
2.77
85.80
14.20
100.00
Laboratory and industrial test results show that no collector flotation can replace the original conventional flotation. The plant has applied the new process of flotation-free flotation to the production in the second half of 1999, and the annual production cost of pharmaceuticals can reach more than 1 million yuan. [next]
2.2 Flotation test results of a large copper-bearing magnetite copper and sulfur non-collector
The main metal minerals in the ore are chalcopyrite, cobalt -bearing pyrite and magnetite. The float-magnetic process is used. The copper-sulfur mixed-separation flotation produces copper concentrate and sulphur-cobalt concentrate, and then the floating tail magnetic Choose to recover iron concentrate. Copper-sulfur mixed flotation was added with ethyl xanthate 70g/t, No. 2 oil 72g/t; copper-sulfur mixed concentrate was separated from flotation by Φ50M thickener, and flotation was added to separate lime and Z-200 agent. According to the non-collector flotation test, the dosage of ethyl yellow can be reduced from 70g/t to 7g/t under the condition of adding electro-chemical I No. 90g/t, which is 90% lower than conventional flotation; due to mixed flotation The amount of collector is greatly reduced, thus improving the separation of copper and sulfur. The mixing and flotation can be carried out directly without separation, and the Z-200 agent added by the original separation and flotation can be omitted, and the amount of lime can be greatly reduced ( 50%). Tables 3 and 4 show the mixed flotation comparison test and the full-process flotation closed-circuit test results, respectively.
Table 3 Mixed flotation open circuit comparison test results
condition
product
Yield(%)
grade/%
Recovery rate/%
Cu
S
Cu
S
Originally
Regulation flotation
Mixed
Floating tail
Raw ore
7.86
92.14
100.0
8.20
0.081
0.719
23.52
0.20
2.03
89.62
10.38
100.00
90.94
9.06
100.00
No capture
Flotation
Mixed
Floating tail
Raw ore
8.61
91.39
100.0
7.02
0.051
0.651
21.10
0.215
2.02
92.81
7.19
100.00
90.26
9.74
100.00
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Table 4 Results of the whole process without collector flotation closed circuit test
product
Yield(%)
grade/%
Recovery rate/%
Cu
S
Cu
S
Copper essence
Sulfur
Floating tail
Raw ore
2.71
3.63
93.66
100.0
22.13
0.55
0.052
0.668
29.88
33.94
0.21
2.24
89.72
2.99
7.29
100.00
36.17
55.04
8.79
100.00
  
Experimental studies have shown that the non-collector flotation using the electrochemical I control can also be used for copper-sulfur mixed flotation, which not only reduces the cost of the agent but also improves the separation of copper and sulfur.
3 Investigation on the mechanism of action of electrification I
The effects of Electrochemical I on slurry potential, pH value and mineral wetting contact angle were investigated by using PXD-2 universal ion meter and JJO-2 type wetting angle measuring instrument. [next]
3.1 Electrochemical No. I concentration and slurry potential
Figure 1 shows the potential measurement results of clean water and slurry filtrate under different electrochemical concentrations of I. The slurry filtrate is a filtrate obtained by filtering after the action of the electrochemical ion No. I at the concentration of the flotation slurry.
     
Fig.1 Potential value of clear water and slurry filtrate under different electrification No.1 concentration
It can be seen from Fig. 1 that the potential value of the clean water and the filtrate is the same without adding the electrochemical I, indicating that the ore is oxidized during the fine grinding process, but it does not affect the dissolved oxygen concentration in the water, and its oxidation potential and clean water The oxidation potential caused by dissolved oxygen is similar; the gradient of the clear water curve reflects the effect of the reducing oxidized species such as oxidized I and dissolved oxygen in water; there is a big difference between the gradient of the clear water curve and the filtrate curve, reflecting As a result of the adsorption and chemical action of the Ionization No. I on the mineral surface, since the concentration range of the Electrochemical I is very low, the decrease in the filtrate potential is small. [next]
   
Fig. 2 is a graph showing the change in the filtrate potential in the case where the concentration of the electro-chemical I is relatively high.
                  
  
When the concentration of the electrochemical I reaches 900mg/l, the potential of the slurry is reversed (from positive to negative), and the concentration of the electrochemical I is continuously increased, and the decrease of the slurry potential is slowed down. It indicates that the oxidizing substances in the pulp have been basically reduced, and the pulp has shown strong reducibility. Considering that Ethylene I was retained in the slurry for a long time in use, the slurry potential value of the slurry with an ionization I concentration of 30 mg/l at different stirring times was determined, as shown in Table 5. [next]
 
Table 5 Potential values ​​of the filtrate of the slurry with an concentration of 30 mg/l at different stirring times
Stirring time (min)
5
10
20
40
80
Potential value (mV)
130
131
132
130
132
The data in Table 5 indicates that the electrochemical I number still exhibits stable chemical properties under stirring for a long time in the slurry.
3.2 Electrochemical No. I concentration and pulp pH
  See Figure 3
The electrolysis I was hydrolyzed to be alkaline. Due to the adsorption and chemical action of the electrochemical I on the mineral surface, the two curves of the clear water and the filtrate showed different gradients. [next]
3.3 Electrochemical I concentration and mineral wetting contact angle
JJO-2 type using a contact angle meter measured the contact angle wetting chalcopyrite, pyrite and galena sheet of pulp and water at different electrochemical No. I concentration measurement result in FIG. 4, FIG. 5 Show.

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It can be seen from Figures 4 and 5 that the three mineral contact angles show similar trends in different concentrations of electrochemical solution No. 1; at the same concentration, the contact angles of chalcopyrite and galena are larger, and pyrite contact The angle is small; in the absence of electrification No. 1, the contact angle of pyrite with chalcopyrite and galena is very different, and the addition of electrification No. 1 can greatly reduce this difference; in the clear aqueous solution, When the concentration of electro-chemical No. 1 is 10~30mg/l, the contact angle of each mineral is larger, and in the slurry filtrate, the concentration of electro-chemical No. 1 when the contact angle of mineral is large is 20~40mg/l (it can be considered that The adsorption and action of the surface of the ore particles leads to the consumption of the agent). The addition amount corresponding to this concentration range is 50-100g/t, which is completely in harmony with the selection test phenomenon. At this time, the contact angle of chalcopyrite is more than 50 0 , and the contact angle of pyrite is more than 45 0 . Has a good natural floatability. According to Fig. 1 and Fig. 3, the pH value of the slurry is about 8 and the potential value is 127~132mV. Both chalcopyrite and pyrite may be in a moderate oxidation range, and the surface may form a hydrophobic substance S 0 .
   
Through the investigation and study of the mechanism of Electrochemical No. 1, it can be considered that the regulation of the potential of the slurry by the Electrochemical No. 1 is an important reason for the flotation of copper and sulfur minerals without collectors. It also confirmed the phenomenon that Electrochemical No. 1 adsorbed or reacted on the mineral surface. Since the change of the composition of the mineral surface was not analyzed, the induction activation mechanism of Electrochemical No. 1 could not be explained. [next]
4 Conclusion
(1) Using the electrochemical regulator-Electronization No. I regulator-free flotation process, it can successfully replace the traditional copper and sulfur flotation process, and the yellow drug dosage can be reduced by 80-90%, significantly reducing flotation The cost of the medicament does not require any modification to the original flotation process and equipment. It is also beneficial to improve the subsequent separation of copper and sulfur after the use of non-collector flotation for copper-sulfur mixed flotation.
(2) Study on the mechanism of action of Electrochemical I No. I showed that Electrochemical I is alkaline in the solution and its properties are stable. It will not change significantly under the stirring for a long time; when the addition amount is 50-100g At /t, chalcopyrite, galena and pyrite can obtain large contact angles, showing good floatability, which is completely consistent with the experiment; regulation of slurry potential is an important mechanism of action of electrification I.

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