Study on separation process of feldspar-quartz flotation

1 Introduction quartz sand resources, since it contains more impurities such as feldspar, aluminum, high iron content, the SiO2 content in the raw sand sometimes only 74%, the glass industry can not meet the requirements of purity quartz sand. The use of beneficiation methods to improve the purity of quartz sand is of great significance for the development and utilization of quartz sand resources.

In this experiment, the flotation experiments of a certain potassium and sodium feldspar were successfully carried out, and the effective separation of impurity minerals such as K-feldspar and quartz was successfully realized, and the mechanism of flotation separation was studied.

The phase analysis of the potassium and albite ore samples from the ore properties is shown in Table 1.

Table 1 Analysis of feldspar multi-element (%)

Through the systematic test of the ore samples, the two kinds of feldspar ore can not be effectively separated under the conventional acidic and alkaline conditions, and the qualified feldspar and quartz concentrate products are not obtained. Only when HF is used as an inhibitor, the fine feldspar and quartz concentrate products can be finally obtained by coarse refining. The small test results are shown in Table 2.

Table 2 Small test results (%)

Both quartz and feldspar belong to the framework of silicate minerals, which have the same crystal structure: silicon (aluminum) oxygen tetrahedron and four silicon tetrahedral co-angled tops are connected to each other to form an infinitely extending frame structure in three-dimensional space. . The charge of the two in the aqueous solution is basically the same: after the mineral is broken, the crystal is broken, the silicon (aluminum) oxygen bond is broken; the adsorbed and positioned ions in the aqueous solution form the hydroxyl surface; and the dissociation occurs under different pH conditions of the medium. Or adsorption, forming different surface potentials.

Due to the high degree of polarization and high hydrophilicity in the fracture section of the mineral, quartz and feldspar are negatively charged in a wide pH range, and the zero point is very low.

Due to the substitution of the aluminoxy tetrahedron to the siloxane tetrahedron in the feldspar structure, the two have different characteristics in many aspects:

Al3 + and Si4 + price different, to compensate for Al3 + of electricity Si4 substituted + caused by the imbalance, and the introduction of K +, Na + and the like alkaline earth metal ion, a bond between the metal ions and O2- strong low, coupling is weak, It is easy to dissociate in water, leaving the surface of the mineral with a negatively charged character, which makes the feldspar usually have a lower zero point than quartz. At the same time, since the Al-O bond is stronger than the Si-O bond, the Al-O bond is more likely to be broken during the crushing, and the surface of the feldspar is exposed to a large amount of the chemical active region of Al3+. These differences lead to slightly different floatability of quartz and feldspar, providing a basis for the flotation separation of quartz and feldspar.

3 Experimental research (1) Iron ore removal test

The iron-containing impurity minerals in feldspar are mainly magnetite, biotite and limonite. Magnetite is magnetic, and biotite and limonite have weak magnetic properties, so they can be separated by high gradient magnetic separation. In the grinding process, the black mica flakes are not screened out for different fineness screening, so the biotite and feldspar cannot be separated by screening or grading, and the iron ore can only be separated by high gradient magnetic separation. Object. In order to remove iron-containing impurities, the Slon-100 experimental pulsating high gradient magnetic separator was used for the test. The process is shown in Figure 1, and the results are shown in Table 3.

Figure 1 Raw iron removal test procedure

Table 3 - 200% of the 200% of the magnetic field strength of different magnetic field (%)

From the results of Table 3, as the strength of the magnetic field increases, the yield of iron minerals decreases at 1.0 T, but at 1.2 T, the yield increases by about 0.3% from 0.8 T. Therefore, the best condition is the ore fineness - 200 mesh accounted for 81% and the magnetic field strength was 1.2T.

Figure 2 pH condition test procedure

(2) Sulfuric acid feldspar-quartz separation test

1, pH condition test face

The test procedure is shown in Figure 2 and the results are shown in Table 4.

Table 4 Test results of pH value of sulfuric acid method (%)

2, the amount of collector test

The test procedure is the same as in Figure 2, using sulfuric acid as the inhibitor and the pH value is 2, and the amount of different combination collectors is changed. The test results are shown in Table 5.

Table 5 Test results of combined dosage of sulfuric acid method (%)

The method is to preferentially float feldspar with an anion-cation mixed collector under the condition of strong acid (generally H2SO4) (pH=2~3). According to research by KH Rao, the pH value is near the zero point of quartz and higher than the zero point of feldspar (pH = 1.5). Therefore, under this condition, the surface of the feldspar is negatively charged and the surface of the quartz is not charged. It is important to point out that the key to achieving flotation selectivity is the pH of the slurry solution, ie, at this pH, the charge on the surface of the feldspar and quartz is different, so the amine collector is adsorbed on the surface of the feldspar without Adsorbed on the surface of quartz, the anion collector is complexed with the cationic collector to co-adsorb and increase the hydrophobicity of the mineral surface; while the quartz is close to neutral due to the surface, it does not adsorb the anion and cation, so it is difficult to float. . It has also been pointed out that the anion-cation mixed collector greatly enhances the hydrophobicity of the surface of the feldspar. At this pH, the surface of the feldspar has both the adsorption of the active Al3+ on the anion collector and the surface hydration of the metal ion. K+ or Na+ is a positive charge cavity formed on the mineral surface due to dissolution in the slurry. The electrostatic and molecular adsorption of the cationic collector, various adsorptions promote each other and synergistically, so that the feldspar floatability is much better than quartz.

It can be seen from Tables 4 and 5 that using sulfuric acid as an inhibitor, quartz and feldspar cannot be effectively separated regardless of the amount of the collector, which may be caused by insufficient dissociation of the ore monomer.

(III) HF method potassium feldspar-quartz sorting test

The test procedure is shown in Figure 3 and the results are shown in Table 6.

Figure 3 HF feldspar-quartz sorting test procedure

Table 6 K-feldspar-quartz HF method for sorting (%)

(4) HF method sodium feldspar-quartz separation test

The test procedure is the same as in Figure 3, and the test results are shown in Table 7.

Table 7 Sodium feldspar-quartz HF method sorting test results (%)

It can be seen from Tables 6 and 7 that the SiO2 content of the obtained quartz product is still low due to the fine grain size of the ore dressing, even if the feldspar-quartz cannot be effectively separated by the HF method.

(5) Two-stage grinding feldspar-quartz separation test

In order to obtain qualified quartz products, in view of the characteristics of fine feldspar and quartz in the ore, the fineness of the quartz and the complex embedding characteristics, the quartz obtained after the flotation is added for the second stage grinding, and then the second selection by the HF method. The test process is shown in Figure 4 and the results are shown in Table 8.

Figure 4 Two-stage grinding HF feldspar-quartz separation process

Table 8 Two-stage grinding HF feldspar-quartz separation results (%)

From the results of Table 8, the quartz coarse concentrate is re-milled and then sorted by HF method. The obtained Sio2 content of the quartz product reaches 96.74%, which meets the user quality requirements; the feldspar product can also meet the requirements of the first grade product. The method is to add HF acid to quartz and feldspar pulp. When the pH is 2-3, the cations are preferentially floated with cation collector amines.

As the pH of the slurry decreases, the dissociation balance of the quartz and feldspar surfaces in the above slurry is broken. The concentration of [H+] is increased, and the dissociation equilibrium is shifted to the left, and the surface charge of quartz and feldspar is reduced. When pH=2~3, the surface potential of quartz surface is close to zero; due to the etching of Si-O bond by HF acid, Al3+ on the surface of feldspar protrudes and becomes the active center. At the same time, the [SiF6]2- complex ion formed in the solution can form a stable complex with Al3+, K+ and Na+ on the surface of the feldspar, and attaches to the surface of the feldspar, which in turn forms a considerable negative charge on the surface of the feldspar. When the cation collector RNH3+ is added to the system, it will be electrostatically adsorbed on the surface of the feldspar, which will make the surface of the feldspar hydrophobic and preferentially float out.

4 Analysis of refractory factors of ore 1. The similarity in physical properties, chemical composition, structure and structure of potassium feldspar and quartz is the main reason for the difficulty of separation. They are all silicate frame structures, except that 1/4 of Si4+ in the quartz structure is replaced by Al3+, which becomes feldspar. Since Al3+ replaces Si4+, K+ or Na+ is added as a metal counter ion in the corresponding tetrahedral structural unit to maintain the methanoelectricity of the mineral. Therefore, according to the content of K+ or Na+, feldspar can be divided into potassium feldspar and albite.

2. Since the mineral itself contains trace amounts of carbonate, some Ca2+ and Mg2+ will be dissolved in the acidic medium. When the concentration of Ca2+ and Mg2+ in the slurry is high, it will affect the static charge of the collector on the surface of the feldspar. And molecular adsorption, which ultimately affects the priority of feldspar. Therefore, acid elution water is required in the test.

3. In the test, when pH>4.5 or <1.5, feldspar and quartz can not be effectively separated even if the anion-cation mixed collector is added, which indicates that the slurry pH is very important for flotation: when the pH is controlled at 2.0-3.0 At the same time, the addition of an anion or a cationic collector alone does not effectively float the feldspar. This shows that the effect of the collector on the feldspar is: 1) strong acidity shifts the dissociation equilibrium of the feldspar surface to the left and decreases the electronegativity; 2) the voids in the feldspar lattice are tared with metal ions K+ or Na+ Dissolved in the slurry, the surface forms a positive charge cavity. When the anion-cation mixed collector is added to the slurry, only weak electrostatic and molecular adsorption is formed on the quartz surface, while active Al(s)3+ is formed on the surface of the feldspar. The characteristic adsorption of the anion collector and the electrostatic and molecular adsorption of the positive charge cavity on the cationic collector, these several kinds of adsorption promote each other and work together, so that the adsorption amount of the collector on the surface of the feldspar is much larger than that of the quartz surface, resulting in a long Stones are preferred.

5 Conclusions 1) The test ore belongs to a material composition with complex composition and fine grain size.

2) Under neutral conditions, the general acid method and the alkali method can not effectively separate the quartz-feldspar, and the qualified feldspar and quartz concentrate products cannot be obtained.

3) Qualified feldspar and quartz concentrate can be obtained by HF method plus coarse concentrate re-grinding.

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