Separation test between siderite and hematite

Siderite ore (including single and siderite and hematite, limonite Ore) Reserves Although accounting for less than 10% of the world's total proven reserves of iron ore, but it is predicted that the global iron ore resource potential , siderite accounts for about 40%. China's siderite resources are relatively abundant, and reserves are among the highest in the world. The proven reserves are 1.834 billion tons, accounting for 3.4% of the proven reserves of iron ore, and the reserves are 1.821 billion tons. Although the siderite is widely distributed and has a large proven reserves, it is mainly associated with hematite and magnetite, and there is very little single siderite resources.

Since the density of siderite and hematite is similar, the magnetic rate is similar, and the siderite is easily muddy, strong magnetic separation and re-election cannot effectively separate the two minerals; magnetization roasting of siderite-hematite It is a more effective method, but the magnetization roasting consumes a large amount of energy and the processing cost is high. In comparison, in various beneficiation processes for treating siderite-hematite-type iron ore, flotation and its combined process are more economical and rational process plans. However, in the existing reverse flotation practice of siderite-hematite type iron ore, due to the presence of siderite, the impact on the anti-flotation index is great. As the content of siderite increases, the The flotation indicator deteriorated sharply, eventually leading to a fine tail, and the siderite could not be recycled, resulting in low iron recovery. However, if the mixed flotation of siderite and hematite is also carried out, there is also a problem that the concentrate grade is low, which affects economic benefits.

Therefore, the study of new flotation methods to enable high-efficiency separation of siderite and hematite has become an urgent problem to be solved in the development and utilization of siderite-hematite type iron ore. Separating siderite from hematite not only helps to eliminate the influence of iron carbonate on the flotation process, but also obtains higher grade hematite concentrate at a lower cost, and the siderite can be separately recovered to increase iron. Recovery rates allow resources to be fully utilized. In this study, a flotation method for the effective separation of two minerals was developed from the flotation properties of single minerals of siderite and hematite. The separation effect of this method was verified by artificial mixing. The actual ore sorting provides a theoretical basis.

I. Test materials and research methods

(1) Test materials

The raw material used to prepare the hematite single mineral is the spiral chute concentrate of the Angang Steel Tundish Concentrator. The raw material for preparing the single mineral of the siderite is the siderite ore of Jilin Tonggang Da Lizi Mining Company. The hematite raw materials are first sorted by laboratory chamber type magnetic separator for several times to remove the ferromagnetic minerals. After several times of shaking, the iron concentrates with a grade of more than 69% are obtained, and then the laboratory standard is used. The particles with a particle size larger than 0.1 mm were removed by sieve, and the slime of -10 μm was removed by water filtration, filtered, and dried at a low temperature to obtain a single mineral of hematite, which was more than 97% pure by microscopic examination. After the raw material of the siderite is crushed and ball-milled to -0.076mm for 80%, the magnetic iron is removed by multiple weak magnetic separation, the gangue is removed by strong magnetic separation, and the chernorite is removed by multiple shakers to obtain the final The single mineral of the siderite is examined under the microscope, and its purity is greater than 95%. The iron phase analysis shows that the iron carbonate iron accounts for 97% of the total iron.

The collectors used in the test included sodium oleate, dodecylamine, 250 ^# collector, MP, TS, sodium oleate and dodecylamine for chemical purity, and the rest were made in the laboratory. The adjusting agent includes starch, ferric nitrate, ferrous chloride, calcium chloride, water glass, modified water glass, the water removal glass is industrial product, the modified water glass is made by the laboratory, and the others are all chemically pure. The test water is deionized water.

(2) Research methods

First, investigate the effects of different collectors and modifiers on the floatability of hematite and siderite minerals, determine the appropriate collectors and regulators for the separation of the two minerals; then use the selected collectors and adjust The separation and flotation of the artificial minerals of the two minerals were carried out to verify the separation effect. Finally, the mechanism of action of the selected agents on the two minerals was investigated by photoelectron spectroscopy (XPS).

The flotation test was carried out on an SFG hanging tank flotation machine with a spindle speed of 1650 r/min; the flotation temperature was controlled at 30 °C. The pH value of the flotation pulp was measured by a pH-25 type acidity meter manufactured by Shanghai Weiye Instrument Factory, and the XPS analysis was carried out by using an ESCALAB 250 photoelectron spectrometer manufactured by Thermo-VG Scientific, USA.

Second, the study of single mineral flotation properties

(1) Flotation effect of different collectors on two minerals

Sodium oleate, dodecylamine, 250* collector, MP and TS were selected as collectors to investigate their effect on the capture of two minerals at different pulp pH values. Among them, 250# collector is a fatty acid type anion collector, MP is an amphoteric collector, and TS is a novel anion collector with sulfur as the main bonding atom.

According to the appropriate dosage of each collector determined by the exploratory test, the two single minerals were floated at different pulp pH values. The test results are shown in Figures 1 to 5.

Figure 1 Recovery of two minerals by 250# collector at different pH

(250# collector dosage 80mg/L, flotation 3min)

â– -hematite; â—‹-rite iron ore

Figure 2 Recovery of two minerals by MP at different pH

(MP dosage 160 mg/L, flotation for 3 min)

â– -hematite; â—‹-rite iron ore

Figure 3 Recovery of two minerals by dodecamine at different pH

(dodecylamine dosage 40mg/L, flotation 3min)

â– -hematite; â—‹-rite iron ore

It can be found from Fig. 1 to Fig. 5 that when 250# or MP is used as the collector, the flotation property of hematite and siderite is similar in the whole test pH range; when dodecylamine is used as the collector, In the range of pH=6～8, the recovery rate of hematite is more than 85%, the recovery rate of siderite is about 45%, and the floatability of the two minerals is different. When sodium oleate is used as the collector, In the range of pH less than 11, the hematite floatability is superior to that of siderite. The flotation recovery rate is about 40% difference between pH 4 and 11. When the pH is greater than 11, the hematite floatability is reduced. The floatability of the siderite is increased. When TS is the collector, both minerals exhibit good floatability in the weakly acidic medium, but the hematite does not float under strong alkaline conditions. At this time, the recovery rate of the siderite flotation is close to 90%, and the flotation properties are quite different.

Figure 4 Recovery of two minerals by sodium oleate at different pH

(Sodium oleate dosage 40mg/L, flotation 3min)

â– -hematite; â—‹-rite iron ore

Figure 5 Recovery of two minerals by TS at different pH

(TS dosage 320mg/L, flotation 5min)

â– -hematite; â—‹-rite iron ore

The above test results show that in the strongly alkaline medium, the difference in the flotation recovery rate of TS for the two minerals is the largest among the five collectors examined. Therefore, TS can be used as a collector for siderite in the separation of hematite and siderite flotation.

(B) the effect of modifiers on the floatability of two minerals

Using TS as a collector and adding different kinds of modifiers for flotation experiments, it is hoped that the difference in flotation properties between the two minerals will be further increased to effectively separate the two minerals. The selected adjusting agents include starch, iron nitrate, ferrous chloride, calcium chloride, water glass, and modified water glass. In the test, the amount of collector TS was 300 mg/L, and the amount of adjusting agent was 40 mg/L. The effects of various modifiers on the floatability of the two minerals at different pulp pHs are shown in Figures 6-11.

Fig. 6 Effect of ferric nitrate on the floatability of two minerals at different pH

â–  - siderite, no inhibitor; â—‹ - siderite, plus ferric nitrate;

â–³-hematite, no inhibitor; â—‹-hematite, iron nitrate

Figure 7 Effect of starch on the floatability of two minerals at different pH

â–  - siderite, no inhibitor; â—‹ - siderite, plus starch;

â–³-hematite, no inhibitor: â–¼-hematite, starch

Figure 8 Effect of ferrous chloride on the floatability of two minerals at different pH

â–  - siderite, no inhibitor; â—‹ - siderite, plus ferrous chloride;

â–³-hematite, no inhibitor: â–¼-hematite, ferrous chloride

Figure 9 Effect of calcium chloride on the floatability of two minerals at different pH

â–  - siderite, no inhibitor; â—‹ - siderite, plus calcium chloride;

â–³-hematite, no inhibitor: â–¼-hematite, plus calcium chloride

Figure 10 Effect of water glass on the floatability of two minerals at different pH

â–  - siderite, no inhibitor; â—‹ - siderite, water glass;

â–³-hematite, no inhibitor: â–¼-hematite, water glass

Figure 11 Effect of modified water glass on the floatability of two minerals at different pH

â–  - siderite, no inhibitor; â—‹ - siderite, water glass;

â–³-hematite, no inhibitor; â–¼-hematite, water glass

It can be seen from Fig. 6 to Fig. 11 that starch is an effective inhibitor of hematite, which can strongly inhibit hematite in the whole pH range of the test, but it is in the neutral and alkaline conditions on the siderite. It also has a certain inhibitory effect; ferric ions, ferrous ions and calcium ions have a certain activation effect on hematite, but have little effect on the floatability of siderite; water glass starts to red at pH 7 Iron ore has a strong inhibitory effect, and it has a certain inhibitory effect on the siderite after the pH is higher than 8, but the inhibitory effect on the siderite is weak in the strong alkaline medium; after the pH of the modified water glass reaches 9 It can maintain a strong inhibitory effect on hematite, while at the same time has little effect on the flotation properties of siderite.

Third, artificial mixed ore flotation separation test

Based on the single mineral flotation test, the flotation separation characteristics of the siderite and the hematite artificial mixed ore were studied. In the test, hematite and siderite were mixed in a ratio of 1:1, and 20 g of mixed ore samples were taken each time for flotation.

(1) Comparative test of different separation schemes

The results of single mineral flotation test show that the following three conditions are beneficial to the separation of siderite and hematite. Therefore, these three conditions are used as a test scheme for artificial mixed ore flotation separation:

Scheme 1—using TS as a collector and starch as an inhibitor to inhibit hematite and floating siderite in a weakly acidic to neutral medium;

Scheme 2: Using TS as a collector and water glass as an inhibitor, inhibiting hematite and floating siderite in a neutral to strong alkaline medium;

Scheme 3 - Using TS as a collector and modified water glass as an inhibitor, hematite and planktonite are inhibited in a strong alkaline medium.

A series of exploration experiments were carried out on the flotation effects of the above three separation schemes, and the optimal indicators obtained are listed in Table 1. The sorting efficiency in the table is calculated as follows:

In the formula, ε _red is the recovery rate of hematite in the hematite concentrate; γ _k is the hematite concentrate yield; M _red is the content of hematite in the ore.

Table 1 Comparison of the best results of the three kinds of program exploration experiments

It can be seen from Table 1 that the separation effect of Scheme 3 (using modified water glass as an inhibitor under strong alkaline conditions and using TS as a collector) is significantly better than the other two schemes. Therefore, it is determined that this scheme is used for further conditional testing.

(2) Scheme 3 conditional test

Conditional tests were carried out on the pH value of the slurry, the amount of the collector TS and the amount of the modified modified water glass. The test results are shown in Figures 12 to 14.

Figure 12 Scheme 3 slurry pH test results

(Modified water glass dosage 45mg/L, TS dosage 600mg/L)

â– -Sorting efficiency; â—‹-hematite concentrate iron grade; â–³-hematite concentrate hematite recovery rate

Figure 13 Scheme 3 TS dosage test results

(Modified water glass dosage 45mg/L, pH=11)

â– - sorting efficiency; â—‹-hematite concentrate iron grade; â–³-hematite concentrate hematite recovery rate

Figure 14 Scheme 3 modified water glass dosage test results

(TS dosage 720 mg/L; pH=11)

â– -Sorting efficiency; â—‹-hematite concentrate iron grade; â–³-hematite concentrate hematite recovery rate

According to Fig. 12 to Fig. 14, it can be determined that the suitable conditions for the artificial mixed ore flotation separation according to the scheme 3 are slurry pH=11, TS dosage 720 mg/L, and modified water glass dosage 48 mg/L. The test results obtained under these conditions are shown in Table 2. It can be seen that the siderite and hematite are effectively separated. The iron grade and hematite recovery rate of the hematite concentrate reached 64.57% and 94.0%, respectively, and the sorting efficiency reached 78.0%.

Table 2 % of final sorting results of artificial mixed mines

Fourth, the mechanism analysis

The temperature was controlled at 30 ° C and the pH was 11. The single mineral was stirred in a solution of deionized water and an additive (TS 720 mg/L, modified water glass 48 mg/L) for 3 min, then settled and dried at a low temperature. The photoelectron spectroscopy was carried out to trace the relative content of mineral surface elements and the changes of non-carbonate Cls, carbonate Cls, S2p, Ca2p, Ols, Fe2p3/2, Si2s and Si2p orbital electron binding energy before and after the action of the agent. Table 3, Table 4.

Table 3 % change of relative content of mineral surface elements before and after the action of the agent

Table 4 Changes in atomic orbital electron binding energy of mineral surface before and after the action of the agent

It can be seen from Table 3 that after the action of hematite with TS and modified water glass, the relative content of S and non-carbonate C on the surface increased by 62.9% and 27.4% respectively before the effect, indicating that the red iron There is a certain amount of TS adsorption on the surface of the ore, but it is not enough to float the hematite; the relative content of Si is 32.7% before the effect, indicating that the adsorption of modified water glass on the surface of hematite is obvious. After the effect of siderite and modified water glass, the relative content of S and non-carbonate C on the surface increased by 227.3% and 26.5% respectively, indicating that there is a large amount of surface of the siderite. TS adsorption; while the relative content of Si did not change much, indicating that the modified water glass was not adsorbed on the surface of the siderite.

Since the maximum system error of the XPS test is 0.2 eV, when the measured change in electron binding energy is greater than 0.2 eV, the chemical environment of the element is significantly changed, otherwise it may be physical adsorption. It can be seen from Table 4 that the electron binding energy of the Sits, S2p and Ca2p orbitals on the surface of the hematite has a significant change before and after the action of the agent, and the electronic binding energy of the S2p and Fe2p orbitals on the surface of the siderite has a significant change. It is indicated that the chemical agent may be chemisorbed on the surface of hematite through the action of Ca element on the surface of hematite; while TS is chemically adsorbed on the surface of siderite by its bonding of atomic sulfur to ferrous action on the surface of siderite. So that the siderite floats up.

V. Conclusion

(I) Under strong alkaline conditions, TS is used as the collector of siderite, and modified water glass is used as an inhibitor of hematite to realize effective flotation of the siderite of hematite-hematite. Separation.

(2) Modified water glass can be selectively adsorbed on the surface of hematite to be inhibited, and has little effect on the floatability of siderite.

(3) Under strong alkaline conditions, the TS collector is adsorbed on the surface of the mineral mainly through the chemical interaction of the bonded atomic sulfur with the ferrous ion on the surface of the siderite, so that it has good buoyancy.

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