A method for removing iron mineral impurities from quartz sand by reverse flotation

Abstract

This invention discloses a method for removing iron mineral impurities from quartz sand using reverse flotation, belonging to the field of mineral processing technology. The method includes the following steps: adjusting the pH of the quartz sand slurry to 5-5.5, sequentially adding a citric acid analog and an oxalic acid analog, stirring, then adding a quartz inhibitor and stirring; subsequently, adding a collector to the quartz sand slurry under aeration and stirring, stirring, then adding a frother for reverse flotation, stirring and skimming the bubbles, and washing to obtain the product quartz sand. This invention first achieves the separation of quartz and iron minerals under weakly acidic conditions using a specially formulated chelating agent, and then uses a specific reverse flotation method to remove iron mineral impurities. The quartz sand obtained after reverse flotation has high purity, with the iron impurity content reduced to below 10 ppm.

Description

Technical Field

[0001] This invention belongs to the field of mineral processing technology, and specifically relates to a method for removing iron mineral impurities from quartz sand by reverse flotation. Background Technology

[0002] High-purity quartz products possess excellent physicochemical properties such as high temperature resistance, corrosion resistance, low thermal expansion, high insulation, and light transmittance, making them widely used in high-tech industries such as fiber optic communication, solar photovoltaics, aerospace, electronics, and semiconductors. High-purity quartz sand is an irreplaceable basic material in the preparation of high-purity quartz products, and its preparation and purification are currently the focus of research.

[0003] Quartz sand is generally obtained through the crushing and purification of silicate minerals such as quartz. In the quartz sand purification process, the presence of mineral impurities is a significant factor affecting the purity of quartz. In particular, residual iron mineral impurities such as hematite and ilmenite in quartz ore will severely impact the quality of high-purity quartz sand, thereby reducing the performance of the final quartz products. For example, the iron content is a key factor determining the light transmittance of glass. Ordinary glass, due to its high iron content, often appears green and has low light transmittance. Photovoltaic glass, characterized by high light transmittance and high transparency, has strict requirements for iron content. Quartz sand is a major raw material for photovoltaic glass, and its iron content directly determines the quality of the photovoltaic glass. According to relevant standards, the ferric oxide content of low-iron quartz sand used in photovoltaic glass is required to be no higher than 60 μg / g, far lower than that of quartz sand used in flat glass.

[0004] Chinese patent document CN115417414A discloses a method for synergistic removal of iron impurities from quartz sand using sodium and ammonium salts. This invention involves adding a mixed solution of sodium and ammonium salts to the quartz sand, stirring and washing for 30-100 minutes. After washing, potassium permanganate solution is added to the mixture, and the reaction is carried out for 10-30 minutes. Solid-liquid separation is then performed, and the resulting solid is the quartz sand after iron removal. This invention uses a mixed solution of sodium and ammonium salts instead of traditional acid washing solutions for synergistic iron removal from quartz sand. Chinese patent document CN108298545A discloses a method for iron removal and purification of quartz sand using sulfuric acid and metal chloride media. This invention mixes quartz sand with sulfuric acid solution and metal chloride solution, and leaches impurities such as Fe under heating and stirring. After the reaction, solid-liquid separation is performed to obtain a solid and mother liquor. The solid is washed and dried to obtain the quartz sand product. In this invention, hydrogen ions can react with sulfate ions to form HSO4. - The composite ions increase the activity of hydrogen ions, which can improve the leaching rate of iron and reduce its volatility.

[0005] As a crucial step in the purification process, flotation can effectively remove a series of iron mineral impurities from quartz ore. For example, Chinese patent document CN102600982A discloses a fluorine-free, low-acid anionic and cation-anionic reverse flotation process for quartz sand. This invention employs a two-stage reverse flotation process. In the first stage, sulfuric acid is added first, followed by a propylene diamine cationic collector, and then a frother is added, followed by stirring and skimming. In the second stage, sodium carbonate is added first, followed by an anionic collector composed of sodium petroleum sulfonate and octyl hydroxamic acid, and then a frother is added, followed by stirring and skimming. In this invention, the flotation process can efficiently remove metallic impurities such as Fe and Al. However, during the reverse flotation process to remove iron mineral impurities from quartz ore, these iron mineral impurities can act as activators for quartz, causing it to float and resulting in poor flotation impurity removal and low recovery rate. Summary of the Invention

[0006] This invention provides a method for removing iron mineral impurities from quartz sand by reverse flotation. The steps are simple and efficient. First, quartz and iron minerals are separated under weakly acidic conditions using a special chelating agent. Then, a specific reverse flotation method is used to remove the iron mineral impurities. After reverse flotation, the content of iron impurities in the quartz sand is reduced to below 10 ppm.

[0007] The specific technical solution adopted is as follows:

[0008] A method for removing iron mineral impurities from quartz sand by reverse flotation includes the following steps:

[0009] Adjust the pH of the quartz sand slurry to 5-5.5, add citric acid analogue and oxalic acid analogue in sequence, stir, then add quartz inhibitor and stir; then add collector to the quartz sand slurry under aeration and stirring, stir, then add frother for reverse flotation, stir and skim the bubbles, and wash to obtain the product quartz sand.

[0010] The citric acid analogue is citrate, the oxalic acid analogue is oxalate, and the mass ratio of the citric acid analogue to the oxalic acid analogue is 0.2 to 2:1.

[0011] Preferably, the quartz sand in the quartz sand slurry is obtained by pretreatment of quartz ore, wherein the SiO2 content in the quartz ore is ≥90%, and the pretreatment is: crushing, grinding, washing and magnetic separation of the quartz ore.

[0012] More preferably, the quartz ore contains 90.27-95.19% quartz, 3.16-4.30% feldspar, and other iron minerals (hematite, magnetite, ilmenite, etc.).

[0013] Preferably, the quartz sand particle size in the quartz sand slurry is 50-100 mesh, and the mass concentration of the quartz sand slurry is 60-70 wt%.

[0014] Preferably, sulfuric acid is used to adjust the pH of the quartz sand slurry to 5-5.5, and the citric acid analogue is trisodium citrate; the oxalic acid analogue is disodium oxalate.

[0015] Under weakly acidic conditions, trisodium citrate, which is tridentate and has certain steric hindrance, can chelate with iron ions to form an iron-citric acid complex. At this time, the iron atom still has empty 3d orbitals. The addition of disodium oxalate, which has low steric hindrance, can saturate the coordination of iron atoms, thus forming a more stable iron metal complex. This allows iron mineral impurities to enter the water more efficiently and float with the foam, resulting in a good separation effect between iron mineral impurities and quartz.

[0016] Furthermore, the order in which citric acid analogues and oxalic acid analogues are added is crucial. To ensure the maximum effectiveness of these two chelating agents, trisodium citrate should be added to the slurry first to form an iron-citric acid complex, followed by disodium oxalate. However, if disodium oxalate is added first, it will cause the iron ions to complex with the two disodium oxalates, causing the citric acid to lose its coordination space, which in turn leads to the instability of the final iron mineral impurities and affects their separation from quartz.

[0017] Adjusting the pH of the quartz sand slurry to 5-5.5 with sulfuric acid can better enhance the flotation effect of trisodium citrate and disodium oxalate on iron minerals. Excessive acidity will lead to the formation of citric acid and oxalic acid, which have poor coordination ability with iron. Under alkaline conditions, the empty 3d orbitals of iron atoms are easily occupied by hydroxide ions, resulting in poor floatability of iron minerals.

[0018] Further preferably, the amount of citric acid analog added is 20–60 g / t based on the solid mass of the quartz sand slurry, and the amount of oxalic acid analog added is 20–40 g / t based on the solid mass of the quartz sand slurry. Insufficient addition of the chelating agent will result in poor separation of iron mineral impurities from quartz, while excessive addition will cause some quartz sand to float to the surface along with the iron mineral impurities, affecting the recovery rate.

[0019] Preferably, the quartz depressant is water glass, and the amount of quartz depressant added is 200-400 g / t based on the solid mass of the quartz sand slurry. The quartz depressant can reduce quartz flotation and increase the flotation difference with iron minerals.

[0020] Preferably, the collector comprises sodium fatty acid and sodium dodecyl sulfonate, with a mass ratio of sodium fatty acid to sodium dodecyl sulfonate of 0.2–3:1; the amount of collector added is 100–140 g / t based on the solid mass of the quartz sand slurry; the frother is pine oil, with an amount of frother added of 10–20 g / t based on the solid mass of the quartz sand slurry. The above-mentioned collector can selectively capture iron mineral impurities while having virtually no capturing effect on quartz, and the frother pine oil can further improve the frothing properties and enhance the flotation effect.

[0021] Preferably, the method of removing iron mineral impurities from quartz sand by reverse flotation is repeated at least once to further improve the purity of the product quartz sand.

[0022] Preferably, the obtained product, quartz sand, has a purity of ≥97% and an iron content of ≤10ppm.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] (1) Under weakly acidic conditions, the present invention utilizes the chelation effect of citric acid analogues and oxalic acid analogues with iron ions to form iron metal complexes with good stability, thereby initially achieving the separation of iron mineral impurities and quartz. Subsequently, iron mineral impurities are removed through a specific reverse flotation process, which can ensure the recovery rate of quartz while achieving good removal of iron mineral impurities.

[0025] (2) The present invention utilizes reverse flotation to remove iron mineral impurities from quartz sand. This method has a good effect on removing iron mineral impurities, high iron dissolution efficiency, and the resulting quartz sand has high purity and low Fe content. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The present invention will be further described below with reference to specific embodiments.

[0028] Example 1

[0029] 1. Mineral raw materials:

[0030] The quartz ore contains 90.27% quartz, 3.62% feldspar, 0.59% hematite / magnetite, and 0.95% ilmenite. Phase analysis shows that the ore mainly contains quartz, feldspar, hematite / magnetite, and ilmenite.

[0031] 2. Flotation reagents and operating conditions:

[0032] Pretreatment process: The above-mentioned quartz ore is crushed into particles using a crusher; the particles are then ground in a wet mill to a mesh size of 50-100; water glass washing agent and water are added to the quartz sand, and the sand is then washed in a washing machine; after washing, the sand is dried in a vacuum dryer; the dried quartz sand is then magnetically separated in a magnetic separator to remove magnetic impurities, resulting in preliminarily purified quartz sand.

[0033] Reverse flotation process: First, the preliminarily purified quartz sand is rinsed once with hot water to prepare a quartz sand slurry with a mass concentration of 70wt%. Then, the pH of the slurry is adjusted to 5 with sulfuric acid. Trisodium citrate and disodium oxalate are added sequentially, with addition amounts of 40g / t and 20g / t respectively. The mixture is stirred for 5 minutes. Next, 400g / t of water glass, a quartz inhibitor, is added and stirred for 5 minutes. Under aeration and stirring, sodium oleate and sodium dodecyl sulfonate collectors are added to the slurry, with addition amounts of 90g / t and 30g / t respectively. After a small amount of foam is generated by stirring, 20g / t of frother pine oil is added. Quartz reverse flotation is then performed on the ore for 10 minutes, with stirring and skimming of bubbles during the process. After flotation, the obtained quartz sand is rinsed two to three times with deionized water to remove reagent residues from the mineral surface. The above process is repeated once more to obtain the product quartz sand.

[0034] The test results show that the above process parameters and reagent conditions can effectively recover quartz minerals with a recovery rate of 79.25%, and obtain quartz sand with a grade (purity) of 97.23%, with the iron impurity content reduced to below 10 ppm.

[0035] Example 2

[0036] 1. Mineral raw materials:

[0037] The quartz ore contains 95.19% quartz, 3.16% feldspar, 0.23% hematite / magnetite, and 0.44% ilmenite. Phase analysis shows that the ore mainly contains quartz, feldspar, hematite / magnetite, and ilmenite.

[0038] 2. Flotation reagents and operating conditions:

[0039] The pretreatment process is the same as in Example 1;

[0040] Reverse flotation process: First, the preliminarily purified quartz sand is rinsed once with hot water to prepare a quartz sand slurry with a mass concentration of 60wt%. Then, the pH of the slurry is adjusted to 5.5 with sulfuric acid. Trisodium citrate and disodium oxalate are added to the slurry at amounts of 20g / t and 20g / t, respectively, and stirred for 5 minutes. Next, 200g / t of water glass, a quartz inhibitor, is added and stirred for 5 minutes. Under aeration and stirring, sodium oleate and sodium dodecyl sulfonate, collectors, are added to the slurry at amounts of 50g / t and 50g / t, respectively. After a small amount of foam is generated by stirring, 10g / t of frother, pine oil, is added to the slurry. Quartz reverse flotation is then performed on the ore for 10 minutes, with stirring and skimming of bubbles during the process. After flotation, the obtained quartz sand is rinsed two to three times with deionized water to remove reagent residues from the mineral surface. The above process is repeated once more to obtain the product quartz sand.

[0041] The test results show that the above process parameters and reagent conditions can effectively recover quartz minerals with a recovery rate of 83.77%, and obtain quartz sand with a grade of 98.06%, and reduce the content of iron impurities to below 10 ppm.

[0042] Example 3

[0043] 1. Mineral raw materials:

[0044] The quartz ore contains 93.27% quartz, 4.30% feldspar, 0.38% hematite / magnetite, and 0.49% ilmenite. Phase analysis shows that the ore mainly contains quartz, feldspar, hematite / magnetite, and ilmenite.

[0045] 2. Flotation reagents and operating conditions:

[0046] The pretreatment process is the same as in Example 1;

[0047] Reverse flotation process: First, the preliminarily purified quartz sand is rinsed once with hot water to prepare a quartz sand slurry with a mass concentration of 65wt%. Then, the pH of the slurry is adjusted to 5.5 with sulfuric acid. Trisodium citrate and disodium oxalate are added to the slurry at amounts of 40g / t and 20g / t, respectively, and stirred for 5 minutes. Next, 300g / t of water glass, a quartz inhibitor, is added and stirred for 5 minutes. Under aeration and stirring, sodium oleate and sodium dodecyl sulfonate, collectors, are added to the slurry at amounts of 60g / t and 40g / t, respectively. After a small amount of foam is generated by stirring, 15g / t of frother pine oil is added to the slurry. Quartz reverse flotation is then performed on the ore for 10 minutes, with stirring and skimming of bubbles during the process. After flotation, the obtained quartz sand is rinsed two to three times with deionized water to remove reagent residues from the mineral surface. The above process is repeated once more to obtain the product quartz sand.

[0048] The test results show that the above process parameters and reagent conditions can effectively recover quartz minerals with a recovery rate of 80.45%, and obtain quartz sand with a grade of 97.34%, and reduce the content of iron impurities to below 10 ppm.

[0049] Comparative Example 1

[0050] The only difference between this comparative example and Example 1 is that the chelating agent used is trisodium citrate instead of trisodium citrate and disodium oxalate.

[0051] The experimental results show that although adding trisodium citrate alone as a chelating agent can effectively recover quartz minerals with a recovery rate of 81.30% and obtain quartz sand with a grade of 90.93%, the content of iron impurities in it exceeds 100 ppm.

[0052] Comparative Example 2

[0053] The only difference between this comparative example and Example 1 is that the chelating agent used is disodium oxalate instead of trisodium citrate and disodium oxalate.

[0054] The experimental results show that although the addition of disodium oxalate as a chelating agent can effectively recover quartz minerals with a recovery rate of 81.34% and obtain quartz sand with a grade of 91.22%, the content of iron impurities in the product exceeds 100 ppm.

[0055] Comparative Example 3

[0056] The only difference between this comparative example and Example 1 is that the amounts of trisodium citrate and disodium oxalate added are 10 g / t and 10 g / t, respectively.

[0057] The test results show that although the above method can effectively recover quartz minerals with a recovery rate of 79.25% and obtain quartz sand with a grade of 95.23%, the content of iron impurities in it exceeds 50 ppm.

[0058] Comparative Example 4

[0059] The only difference between this comparative example and Example 1 is that the amounts of trisodium citrate and disodium oxalate added are 70 g / t and 70 g / t, respectively.

[0060] The test results show that although the above method can effectively recover quartz minerals, the recovery rate is only 61.99%, and the product quartz sand with a grade of 97.03% is obtained, with an iron impurity content of 7 ppm.

[0061] The embodiments described above provide a detailed explanation of the technical solutions of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, or similar substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for removing iron mineral impurities from quartz sand by reverse flotation, characterized in that, The process includes the following steps: adjusting the pH of the quartz sand slurry to 5-5.5, adding citric acid analogue and oxalic acid analogue in sequence, stirring, adding quartz inhibitor, and stirring; then adding collector to the quartz sand slurry under aeration and stirring, stirring, adding frother for reverse flotation, stirring and skimming the bubbles, and washing to obtain the product quartz sand. The citric acid analogue is citrate, the oxalic acid analogue is oxalate, and the mass ratio of the citric acid analogue to the oxalic acid analogue is 0.2 to 2:

1.

2. The method for removing iron mineral impurities from quartz sand by reverse flotation according to claim 1, characterized in that, The quartz sand in the quartz sand slurry is obtained by pre-treatment of quartz ore, wherein the quartz ore has a SiO2 content of ≥90%, and the pre-treatment includes crushing, grinding, washing and magnetic separation of the quartz ore.

3. The method for removing iron mineral impurities from quartz sand by reverse flotation according to claim 1, characterized in that, The quartz sand in the quartz sand slurry has a particle size of 50-100 mesh and a mass concentration of 60-70 wt%.

4. The method for removing iron mineral impurities from quartz sand by reverse flotation according to claim 1, characterized in that, The pH of the quartz sand slurry is adjusted to 5-5.5 using sulfuric acid. The citric acid analogue is trisodium citrate, and the oxalic acid analogue is disodium oxalate.

5. The method for removing iron mineral impurities from quartz sand by reverse flotation according to claim 1, characterized in that, The amount of citric acid analogue added is 20-60 g / t based on the solid mass of the quartz sand slurry, and the amount of oxalic acid analogue added is 20-40 g / t based on the solid mass of the quartz sand slurry.

6. The method for removing iron mineral impurities from quartz sand by reverse flotation according to claim 1, characterized in that, The quartz inhibitor is water glass, and the amount of quartz inhibitor added is 200-400 g / t based on the solid mass in the quartz sand slurry.

7. The method for removing iron mineral impurities from quartz sand by reverse flotation according to claim 1, characterized in that, The collector includes sodium fatty acid and sodium dodecyl sulfonate, with a mass ratio of sodium fatty acid to sodium dodecyl sulfonate of 0.2 to 3:1; the amount of collector added is 100 to 140 g / t based on the solid mass in the quartz sand slurry.

8. The method for removing iron mineral impurities from quartz sand by reverse flotation according to claim 1, characterized in that, The foaming agent is pine oil, and the amount of foaming agent added is 10-20 g / t based on the solid mass of the quartz sand slurry.

9. The method for removing iron mineral impurities from quartz sand by reverse flotation according to claim 1, characterized in that, The method of removing iron mineral impurities from quartz sand by reverse flotation shall be repeated at least once.

10. The method for removing iron mineral impurities from quartz sand by reverse flotation according to claim 1, characterized in that, The obtained product, quartz sand, has a purity of ≥97% and an iron content of ≤10ppm.