Method for producing low-iron high-whiteness quartz sand by using fluorine-containing waste sulfuric acid

Abstract

The invention provides a method for producing low-iron high-whiteness quartz sand by using fluorine-containing waste sulfuric acid, and belongs to the technical field of quartz sand purification. The method comprises the following steps: diluting fluorine-containing waste sulfuric acid, and adding hydrogen peroxide or sodium hydrosulfite to obtain a pickling solution; and adding the coarse quartz sand into a pickling solution, and sequentially soaking, pickling and washing to obtain the low-iron high-whiteness quartz sand. According to the method, the low-concentration hydrofluoric acid solution in the fluorine-containing waste sulfuric acid is used for carrying out soaking pretreatment on the coarse quartz sand, then oxalic acid is added as a catalyst for pickling, and the low-iron high-whiteness quartz sand is prepared, so that resource recycling of the fluorine-containing waste sulfuric acid is realized, waste is turned into wealth, the fluorine-containing waste sulfuric acid can be efficiently digested, and the production cost is reduced. And cost reduction and efficiency increase of the quartz sand industry are facilitated, and the method is worthy of vigorous popularization and large-scale industrialization.

Description

Technical Field

[0001] The invention relates to the technical field of quartz sand purification, in particular to a method for producing low-iron and high-whiteness quartz sand by utilizing fluorine-containing waste sulfuric acid. Background Art

[0002] The new energy industry is booming. During the production of lithium hexafluorophosphate, a key component of its batteries, a large amount of fluorine-containing waste sulfuric acid is produced, which contains F2-6%, H 2 SO 4 80%、H 2 O14~18%, and with the continuous development of new energy vehicles, the output of this fluorine-containing waste sulfuric acid will further increase. According to statistics, the current annual production of fluorine-containing waste sulfuric acid exceeds 500,000 tons, and it will exceed 1 million tons in three years. The harmless treatment and resource utilization of this fluorine-containing waste sulfuric acid is very difficult. There are two reasons for this: First, the conventional technology of heating and concentrating ordinary waste sulfuric acid and cracking and circulating sulfuric acid cannot be implemented because of the fluorine content; second, because the fluorine content is relatively high, it cannot be used in the production of superphosphate. Therefore, it is urgent to develop a technology for large-scale treatment and resource utilization of fluorine-containing waste sulfuric acid to cooperate with the healthy development of the new energy industry.

[0003] At present, there are two production processes used in the quartz sand pickling industry for pickling and refining: one is to use 15-17% hydrochloric acid to wash iron; the other is to use hydrofluoric acid plus oxalic acid to wash iron. These two processes have their own advantages and disadvantages. Method one can ensure the quality and cost advantages of pickling, but many places prohibit the discharge of chloride ion wastewater and cannot be used. Method two can be used in areas where the use of hydrochloric acid is prohibited, but it has no advantages in quality and cost. The quartz sand refining industry urgently needs to develop a new pickling and refining process that can ensure quality and cost advantages, does not require the participation of hydrochloric acid, and avoids the discharge of chlorine-containing wastewater. This is a strategic process problem that affects whether the entire quartz sand industry can develop smoothly. Summary of the invention

[0004] The object of the present invention is to provide a method for producing low-iron and high-whiteness quartz sand by utilizing fluorine-containing waste sulfuric acid, so as to solve the problem of high cost of preparing low-iron and high-whiteness quartz sand by pickling in the prior art.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for producing low-iron and high-whiteness quartz sand by utilizing fluorine-containing waste sulfuric acid, comprising the following steps:

[0007] (1) diluting the fluorine-containing waste sulfuric acid, adding hydrogen peroxide or hydrosulfite to obtain a pickling solution;

[0008] (2) Adding coarse quartz sand into the pickling solution, soaking, pickling and washing in sequence, to obtain low-iron and high-whiteness quartz sand.

[0009] Preferably, in step (1), the concentration of sulfuric acid in the diluted fluorine-containing waste sulfuric acid is 20-40%.

[0010] Preferably, in the step (1), the amount of hydrogen peroxide or sodium hydrosulfite added is 0.5-1.5% based on the mass of the fluorine-containing waste sulfuric acid.

[0011] Preferably, in step (2), the mass ratio of coarse quartz sand to pickling solution is 2.5 to 3:1.

[0012] Preferably, in step (2), the soaking temperature is 30 to 50° C., and the soaking time is 4 to 6 hours.

[0013] Preferably, in the step (2), oxalic acid is added before pickling, and the amount of oxalic acid added is 1 to 2% based on the mass of the pickling solution.

[0014] Preferably, in step (2), the pickling temperature is 80 to 95° C., and the pickling time is 4 to 6 hours.

[0015] Preferably, in step (2), the number of water washings is 5 to 6 times.

[0016] Beneficial effects of the present invention:

[0017] (1) The present invention utilizes a low-concentration hydrofluoric acid solution in fluorine-containing waste sulfuric acid to pre-treat coarse quartz sand by soaking it, and then adds oxalic acid as a catalyst for pickling to obtain low-iron and high-whiteness quartz sand.

[0018] (2) In the prior art, the traditional high-concentration hydrofluoric acid pickling process contains a large amount of HF, which is SiO 2 Nemesis, when the two meet SiO 2 will dissolve, and the dissolved substance is H 2 SiF 6 If the quartz sand is not thoroughly cleaned with pure water, a trace amount of H 2 SiF 6 Ultrafine powder wrapping will generate a large number of microbubbles when producing quartz crucibles, quartz ingots, and gas-refined quartz drawn tubes, causing their quality to decline or fail to meet quality and technical standards. After diluting the fluorine-containing waste sulfuric acid, the present invention reduces the concentration of hydrofluoric acid in the pickling solution. The soaking pretreatment can improve the wettability of low-concentration hydrofluoric acid on coarse quartz sand, so that the lattice system of quartz sand is gradually in an "open" state, which is conducive to the hydrofluoric acid solution in the pickling process to penetrate into the quartz sand lattice system, dissolve the internal impurities, and expand the quartz sand lattice cracks in the microscopic state, which is conducive to improving the purity of the quartz sand after subsequent high-temperature pickling.

[0019] (3) The present invention uses fluorine-containing waste sulfuric acid to pickle quartz sand, which can be almost all except SiO 2 The impurities react with the pickling tank, and at the same time, the quartz sand crystals are protected from damage, and the generation of chloride ion wastewater is eliminated, which is beneficial to environmental protection. During the pickling process, the temperature of the pickling tank is controlled at 80-95°C. At this time, the quartz sand is in a fluffy state in the pickling tank, and its lattice system will expand. The cracks of the quartz sand "torn" by the hydrofluoric acid are further enlarged, and the sulfuric acid in the pickling tank is changed from a low energy level to a high energy level by the high temperature. The high energy level sulfuric acid molecules enter the cracks of the quartz sand lattice for circulation, and react violently with the impurity trace elements Al, Ca, Cu, Fe, K, Li, Na, Cr, Mn, Ti, etc. contained in the quartz sand, thereby removing a large amount of impurity elements contained in the solid quartz sand inclusions. The present invention utilizes the change of the temperature difference expansion coefficient to fully expose the impurities in the quartz sand, so that the high energy level sulfuric acid molecules are fully immersed in the quartz lattice system to react with harmful elements, thereby achieving the purpose of purifying quartz sand.

[0020] (4) The present invention uses fluorine-containing waste sulfuric acid to prepare the pickling solution, which reacts with the impurity elements in the quartz sand to almost completely generate metal sulfate. The quartz sand after the pickling is cleaned with industrial water (pure water) and can be dissolved in an aqueous solution and discharged in the form of waste water. The addition of slaked lime facilitates neutralization treatment, reduces environmental pollution, and meets environmentally friendly requirements.

[0021] (5) The pickling process technology of the present invention is matched with the production of phosphorus hexafluoride, a key component of the battery industry in the field of new energy, to achieve the resource recycling of a large amount of fluorine-containing waste sulfuric acid generated in its production process, turning waste into treasure, and efficiently digesting fluorine-containing waste sulfuric acid, which is beneficial to cost reduction and efficiency improvement in the quartz sand industry and is worthy of vigorous promotion and large-scale industrialization. DETAILED DESCRIPTION

[0022] The present invention provides a method for producing low-iron and high-whiteness quartz sand by utilizing fluorine-containing waste sulfuric acid, comprising the following steps:

[0023] (1) diluting the fluorine-containing waste sulfuric acid, adding hydrogen peroxide or hydrosulfite to obtain a pickling solution;

[0024] (2) Adding coarse quartz sand into the pickling solution, soaking, pickling and washing in sequence, to obtain low-iron and high-whiteness quartz sand.

[0025] In the present invention, in the step (1), the concentration of sulfuric acid in the diluted fluorine-containing waste sulfuric acid is 20-40%, preferably 25-35%, and more preferably 30%.

[0026] In the present invention, in the step (1), the amount of hydrogen peroxide or sodium hydrosulfite added is 0.5-1.5%, preferably 1%, based on the mass of the fluorine-containing waste sulfuric acid.

[0027] The hydrogen peroxide added in the present invention can oxidize divalent iron ions to oxidize divalent iron into trivalent iron. The hydrolysis pH value of trivalent iron is low, and it is easier to remove the iron element in quartz sand. In addition, the fluorine-containing waste sulfuric acid contains a small amount of phosphite, and the addition of hydrogen peroxide can oxidize the phosphite into phosphate.

[0028] In the present invention, the mixture is preferably stirred after adding hydrogen peroxide or hydrosulfite, and the stirring time is 24 to 48 hours.

[0029] In the present invention, in the step (2), the mass ratio of coarse quartz sand to pickling solution is 2.5 to 3:1.

[0030] In the present invention, the coarse quartz sand is added into the pickling solution, preferably the pickling solution can immerse the coarse quartz sand.

[0031] In the present invention, in the step (2), the soaking temperature is 30 to 50°C, preferably 35 to 45°C, more preferably 40°C, and the soaking time is 4 to 6 hours, preferably 5 to 6 hours.

[0032] In the present invention, after the coarse quartz sand is added, the pickling liquid overflows from the pickling tank into the pickling liquid buffer tank. During the soaking process, the pickling liquid is preferably circulated by a pump so that the pickling liquid is in a flowing state during the soaking process.

[0033] In the present invention, in the step (2), oxalic acid is added before pickling, and the amount of oxalic acid added is 1-2% by mass of the pickling solution, preferably 2%.

[0034] In the present invention, after oxalic acid is added before pickling, it is preferably circulated by pump for 1 hour before pickling.

[0035] In the present invention, in the step (2), the pickling temperature is 80 to 95°C, preferably 85 to 95°C, more preferably 90 to 95°C, and the pickling time is 4 to 6 hours, preferably 5 to 6 hours.

[0036] In the present invention, during pickling, the pickling liquid is preferably circulated by a pump so that the pickling liquid is in a flowing state during the pickling process.

[0037] In the present invention, in step (2), the water washing is performed 5 to 6 times, and the water washing is terminated when the washing water becomes neutral.

[0038] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0039] Example 1

[0040] Put fluorine-containing waste sulfuric acid (the mass concentration of sulfuric acid is 80%, and the mass concentration of hydrogen fluoride is 4%) in a pickling tank, add industrial water to dilute it, the mass concentration of sulfuric acid after dilution is 30%, then add hydrogen peroxide (wherein the addition amount of hydrogen peroxide is 1%), stir for 40 hours, and obtain a pickling solution;

[0041] Add coarse quartz sand into the pickling solution. The mass ratio of coarse quartz sand to pickling solution is 2.5:1. The pickling solution should be able to immerse the coarse quartz sand. The overflowing pickling solution is circulated by a pump to keep the pickling solution in a flowing state during the immersion process. The immersion temperature is 40℃ and the time is 6h.

[0042] After soaking, add 2% oxalic acid based on the mass of the pickling liquid, circulate it with a pump for 1 hour, then raise the temperature of the pickling tank to 90°C and pickle for 6 hours. During the pickling process, the pickling liquid is kept in a flowing state by circulating it with a pump.

[0043] After the pickling is completed, the pickling liquid is pumped back to the pickling liquid buffer tank for recycling. The quartz sand after pickling is filtered through a high-position vertical water filter tank. Finally, the quartz sand after pickling is washed with clean water for 6 times until the washing water is neutral to obtain low-iron and high-whiteness quartz sand.

[0044] Transfer the low-iron and high-whiteness quartz sand to the drying equipment for drying, and then use the screening machine to divide it into quartz sand below 20 mesh, 20-40 mesh, 40-70 mesh, and 70-120 mesh, and then pack it.

[0045] Since the washing water contains fluoride ions and sulfate ions, the pH value is adjusted to 12 by adding lime slurry. Fluoride ions react with calcium ions to form calcium fluoride, and sulfate ions react with calcium ions to form calcium sulfate. Both are precipitated and separated by a bag filter press. The clarified water can be recycled.

[0046] Example 2

[0047] Put fluorine-containing waste sulfuric acid (the mass concentration of sulfuric acid is 80%, and the mass concentration of hydrogen fluoride is 4%) in a pickling tank, add industrial water to dilute it, the mass concentration of sulfuric acid after dilution is 30%, then add hydrogen peroxide (wherein the addition amount of hydrogen peroxide is 1.5%), stir for 48 hours, and obtain a pickling solution;

[0048] Add coarse quartz sand into the pickling solution. The mass ratio of coarse quartz sand to pickling solution is 3:1. The pickling solution should be able to immerse the coarse quartz sand. The overflowing pickling solution is circulated by a pump to keep the pickling solution in a flowing state during the immersion process. The immersion temperature is 50℃ and the time is 4h.

[0049] After soaking, add 1% oxalic acid based on the mass of the pickling liquid, circulate it with a pump for 1 hour, then raise the temperature of the pickling tank to 95°C and pickle for 5 hours. During the pickling process, the pickling liquid is kept in a flowing state by circulating it with a pump.

[0050] After the pickling is completed, the pickling liquid is pumped back to the pickling liquid buffer tank for recycling. The quartz sand after pickling is filtered through a high-position vertical water filter tank. Finally, the quartz sand after pickling is washed with clean water for 5 times until the washing water is neutral to obtain low-iron and high-whiteness quartz sand.

[0051] Transfer the low-iron and high-whiteness quartz sand to the drying equipment for drying, and then use the screening machine to divide it into quartz sand below 20 mesh, 20-40 mesh, 40-70 mesh, and 70-120 mesh, and then pack it.

[0052] Since the washing water contains fluoride ions and sulfate ions, the pH value is adjusted to 14 by adding lime slurry. Fluoride ions react with calcium ions to form calcium fluoride, and sulfate ions react with calcium ions to form calcium sulfate. Both are precipitated and separated by a bag filter press. The clarified water can be recycled.

[0053] Example 3

[0054] Put fluorine-containing waste sulfuric acid (the mass concentration of sulfuric acid is 80%, and the mass concentration of hydrogen fluoride is 4%) in a pickling tank, add industrial water to dilute it, the mass concentration of sulfuric acid after dilution is 30%, then add hydrogen peroxide (wherein the addition of hydrogen peroxide is 0.5%), stir for 30 hours, and obtain a pickling solution;

[0055] Add coarse quartz sand into the pickling solution. The mass ratio of coarse quartz sand to pickling solution is 2.8:1. The pickling solution should be able to immerse the coarse quartz sand. The overflowing pickling solution is circulated by a pump to keep the pickling solution in a flowing state during the immersion process. The immersion temperature is 30℃ and the time is 5h.

[0056] After soaking, 1.5% oxalic acid is added to the pickling liquid by mass. After circulating with a pump for 1 hour, the temperature of the pickling tank is increased to 85°C and pickling is carried out for 5 hours. During the pickling process, the pickling liquid is kept in a flowing state by circulating with a pump.

[0057] After the pickling is completed, the pickling liquid is pumped back to the pickling liquid buffer tank for recycling. The quartz sand after pickling is filtered through a high-position vertical water filter tank. Finally, the quartz sand after pickling is washed with clean water for 5 times until the washing water is neutral to obtain low-iron and high-whiteness quartz sand.

[0058] Transfer the low-iron and high-whiteness quartz sand to the drying equipment for drying, and then use the screening machine to divide it into quartz sand below 20 mesh, 20-40 mesh, 40-70 mesh, and 70-120 mesh, and then pack it.

[0059] Since the washing water contains fluoride ions and sulfate ions, the pH value is adjusted to 13 by adding lime slurry. Fluoride ions react with calcium ions to form calcium fluoride, and sulfate ions react with calcium ions to form calcium sulfate. Both are precipitated and separated by a bag filter press. The clarified water can be recycled.

[0060] The iron content and blue light whiteness value of the low-iron and high-whiteness quartz sand of Examples 1 to 3 were tested, and the test results are shown in Table 1:

[0061] Table 1 Test results of iron content

[0062] serial number Iron content (ppm) Blue light whiteness value (%) Example 1 48 85 Example 2 52 82 Example 3 56 80

[0063] As can be seen from Table 1, the use of fluorine-containing waste sulfuric acid to treat quartz sand can remove the iron element in the coarse quartz sand, and the content of iron element can be as low as 48ppm, while the whiteness of the quartz sand can be improved.

[0064] From the above implementation, it can be seen that the present invention provides a method for producing low-iron and high-whiteness quartz sand using fluorine-containing waste sulfuric acid. First, the fluorine-containing waste sulfuric acid is diluted, and hydrogen peroxide or hydrosulfite is added to obtain a pickling solution; then the coarse quartz sand is added to the pickling solution for soaking, pickling and washing in sequence to obtain low-iron and high-whiteness quartz sand. The present invention uses a low-concentration hydrofluoric acid solution in fluorine-containing waste sulfuric acid to soak the coarse quartz sand for pretreatment, and then adds oxalic acid as a catalyst for pickling to obtain low-iron and high-whiteness quartz sand.

[0065] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for producing low-iron and high-whiteness quartz sand using fluorine-containing waste sulfuric acid, characterized in that: The steps include: (1) diluting the fluorine-containing waste sulfuric acid, adding hydrogen peroxide or hydrosulfite to obtain a pickling solution; (2) Adding coarse quartz sand into the pickling solution, soaking, pickling and washing in sequence, to obtain low-iron and high-whiteness quartz sand.

2. The method for producing low-iron and high-whiteness quartz sand using fluorine-containing waste sulfuric acid according to claim 1, characterized in that: In the step (1), the concentration of sulfuric acid in the diluted fluorine-containing waste sulfuric acid is 20-40%.

3. The method for producing low-iron and high-whiteness quartz sand using fluorine-containing waste sulfuric acid according to claim 1 or 2, characterized in that: In the step (1), the amount of hydrogen peroxide or hydrosulfur powder added is 0.5-1.5% based on the mass of the fluorine-containing waste sulfuric acid.

4. The method for producing low-iron and high-whiteness quartz sand using fluorine-containing waste sulfuric acid according to claim 3, characterized in that: In the step (2), the mass ratio of coarse quartz sand to pickling solution is 2.5 to 3:

1.

5. The method for producing low-iron and high-whiteness quartz sand using fluorine-containing waste sulfuric acid according to claim 2 or 4, characterized in that: In the step (2), the soaking temperature is 30 to 50° C. and the soaking time is 4 to 6 hours.

6. The method for producing low-iron and high-whiteness quartz sand by utilizing fluorine-containing waste sulfuric acid according to claim 5, characterized in that: In the step (2), oxalic acid is added before pickling, and the amount of oxalic acid added is 1-2% based on the mass of the pickling solution.

7. The method for producing low-iron and high-whiteness quartz sand using fluorine-containing waste sulfuric acid according to claim 2, 4 or 6, characterized in that: In the step (2), the pickling temperature is 80 to 95° C., and the pickling time is 4 to 6 hours.

8. The method for producing low-iron and high-whiteness quartz sand using fluorine-containing waste sulfuric acid according to claim 7, characterized in that: In the step (2), the number of water washings is 5 to 6 times.