Fluorine-containing silicon slag resource utilization method

Abstract

The invention discloses a fluorine-containing silicon slag resource utilization method, and relates to the field of fluorine-containing silicon slag resource utilization. The method comprises the following steps: washing fluorine-containing silicon slag, and filtering to obtain crude silicon dioxide; adding excessive crude silicon dioxide into the ammonium bifluoride solution, stirring and dissolving, and filtering after reaction to obtain first filtrate; mixing and stirring part of the first filtrate with first ammonia water, and aging to obtain silicon dioxide gel seed crystals; mixing and stirring the silicon dioxide gel seed crystal and the remaining first filtrate, adding second ammonia water under the stirring condition, continuously stirring for ammonolysis reaction until crystallization is completed, and filtering to obtain a silicon dioxide filter cake and second filtrate; the fluorine-containing silicon slag is used as a raw material in the whole process route, and the raw material source is wide; the white carbon black product is synthesized by preparing the seed crystal, so that the product quality is high; the reaction conditions are mild, the raw materials are recycled, the comprehensive utilization degree is high, and no secondary waste is generated.

Description

Technical Field

[0001] This invention relates to the field of resource utilization of fluorinated silicon slag, and in particular to a method for resource utilization of fluorinated silicon slag. Background Technology

[0002] Fluorosilicone slag is a byproduct generated during the production of fluoride products from fluorosilicic acid or fluorosilicates as raw materials. Its main components include silicon dioxide, fluorosilicic acid, and water.

[0003] Currently, the resource utilization of fluorinated silica slag includes converting the low specific surface area silica in the fluorinated silica slag into silica. The commonly used method is to react the fluorinated silica slag with a strong alkaline solution to prepare an alkali metal ion silicate solution, and then react the alkali metal ion silicate solution with an acid to prepare silica.

[0004] However, sulfuric acid is highly corrosive, reacts violently, and is difficult to control; hydrochloric acid is highly volatile and corrosive, reacts rapidly, and makes it difficult to control particle size and morphology; carbonic acid reacts slowly and has poor precipitation. In addition, the introduction of alkali metal ions not only promotes the aggregation of silica particles through charge shielding or salt effects, leading to a decrease in specific surface area, but also the corresponding byproducts—alkali metal ion salts—have limited added value. Summary of the Invention

[0005] In view of the shortcomings of the above-mentioned related technologies, the present invention provides a method for the resource utilization of fluorinated silicon slag.

[0006] The present invention provides a method for the resource utilization of fluorine-containing silicon slag, which adopts the following technical solution: A method for the resource utilization of fluorine-containing silicon slag includes the following steps: S1: Take fluorine-containing silicon slag, wash it, and filter it to obtain crude silicon dioxide and an aqueous solution of fluorosilicic acid; S2: Add excess crude silicon dioxide to ammonium bifluoride solution and stir to dissolve. After the reaction is complete, filter to obtain the first filtrate. S3: Take a portion of the first filtrate and mix it with the first ammonia solution, stir and age to obtain silica gel seed crystals; S4: Mix the silica gel seed crystals with the remaining first filtrate and stir. Add the second ammonia water while stirring, and continue stirring to carry out the ammonolysis reaction until crystallization is complete. Filter to obtain silica filter cake and second filtrate. S5: Take the second filtrate, evaporate to remove ammonia, and reuse the resulting ammonia gas in steps S3 and / or S4. Reuse the resulting ammonium bifluoride gas in step S2.

[0007] By adopting the above scheme, in step S1, silicon dioxide and fluorosilicic acid are separated from the fluorinated silicon slag. In step S2, crude silicon dioxide is converted into an aqueous solution of ammonium fluorosilicate containing fluoride ions (first filtrate) through the reaction 4NH4HF2 + SiO2 = (NH4)2SiF6 + 2NH4F + 2H2O. In step S3, ammonium fluorosilicate is converted into silicon dioxide gel seed crystals through the reaction (NH4)2SiF6 + 4NH3·H2O = SiO2 + 6NH4F + 2H2O. In step S4, the remaining first filtrate is... Ammonium fluorosilicate in the liquid crystallizes under the induction of silica gel seed crystals to obtain silica filter cake (the purity and specific surface area of ​​silica meet the requirements of precipitated silica) and a second filtrate whose main component is ammonium fluoride aqueous solution. In step S5, the ammonium fluoride in the second filtrate is converted into ammonium hydrogen fluoride and ammonia water and recycled to the above steps. The entire process route uses fluorinated silica slag as raw material, and the raw material source is wide. The precipitated silica product is synthesized through the preparation of seed crystals, and the product quality is high. The reaction conditions are mild, the raw materials are recycled, the comprehensive utilization rate is high, and no secondary waste is generated.

[0008] Preferably, the concentration of the ammonium bifluoride solution is 17 wt.%-20 wt.%.

[0009] Preferably, in step S3, the weight ratio of the first ammonia solution to the first filtrate is 1.6-1.7:1.

[0010] Preferably, in step S3, the weight ratio of the first ammonia solution to the first filtrate is 1.68:1.

[0011] Preferably, the mass fraction of the solute in the first ammonia solution is 2%-5%.

[0012] Preferably, in step S4, the weight ratio of the second ammonia solution to the first filtrate is 0.27-0.29:1.

[0013] Preferably, in step S4, the weight ratio of the second ammonia solution to the first filtrate is 0.272:1.

[0014] Preferably, the mass fraction of the solute in the second ammonia solution is 10%-20%.

[0015] Preferably, the first filtrate used in step S3 accounts for 20%-30% of the total mass of the first filtrate.

[0016] Preferably, in step S3, the stirring speed is 280-320 r / min and the stirring time is 10-20 s.

[0017] Preferably, the stirring and aging temperature in step S2 is 30-55℃.

[0018] Preferably, the stirring rate during the ammonolysis reaction in step S3 is 150-250 r / min and the temperature is 40-70℃.

[0019] In summary, the present invention has the following beneficial technical effects: This invention converts low-value-added silica in fluorinated silica slag into ammonium fluorosilicate solution using ammonium bifluoride solution. Then, after preparing silica gel seed crystals, the ammonium fluorosilicate is converted into high-value-added silica products. Fluorosilicic acid in the fluorinated silica slag is recovered and reused in the form of an aqueous solution. The ammonium fluoride solution generated during the reaction is converted into ammonium bifluoride and ammonia water for reuse in the previous steps. The overall process has mild reaction conditions, recycled raw materials, high comprehensive utilization, and no secondary waste is generated. Attached Figure Description

[0020] Figure 1 This is the process flow diagram of Example 1. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to the embodiments. The following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, specific conditions in the following embodiments were performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the methods used are conventional methods known in the art, and the consumables and reagents used are commercially available. Unless otherwise stated, the technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be applied to the present invention.

[0022] Example 1 Embodiment 1 of the present invention provides a method for the resource utilization of fluorine-containing silicon slag, referring to... Figure 1 The steps are as follows: S1: Weigh 220.00 grams of fluorinated silicon slag (mainly composed of silicon dioxide, fluorosilicic acid and water), add 660.00 grams of water and wash in two batches. After filtration, obtain 218.92 grams of crude silicon dioxide and fluorosilicic acid aqueous solution with a water content of 40%. S2: Weigh 310.20 g of 98% ammonium bifluoride and add it to 1378.68 g of distilled water. Dissolve the solution in 1688.89 g of ammonium bifluoride under stirring. Add crude silica in batches. After the reaction is complete at room temperature, filter to obtain 1888.89 g of the first filtrate. S3: Take 377.78 g of the first filtrate and 634.67 g of the first ammonia solution with a mass fraction of 3%, heat them to 40°C, and then quickly add the first filtrate and the first ammonia solution to a stirring beaker at the same time. Stir at 300 rpm for 15 seconds, stop stirring, and then age for 15 minutes to obtain silica gel seed crystals. S4: Add silica gel seed crystals to the remaining first filtrate and stir at 200 r / min while heating to 60℃. While maintaining the stirring speed and temperature, add 411.02 g of second ammonia water with a mass fraction of 18% for 45 minutes. After the addition is completed, continue stirring at the same speed for 15 minutes until the ammonolysis reaction is complete. Filter to obtain 200.78 g of silica filter cake and 2734.58 g of second filtrate. Add 600.00 g of water to the silica filter cake in two batches, stir and separate, and dry to obtain the silica product. Analyze the purity and specific surface area of ​​silica. S5: Take the second filtrate, evaporate to remove ammonia, and reuse the resulting ammonium bifluoride in step S2. The resulting ammonia gas is used to prepare ammonia water and reused in steps S3 and S4.

[0023] Example 2 Embodiment 2 of the present invention provides a method for the resource utilization of fluorine-containing silicon slag, the steps of which are as follows: S1: Weigh 500.00 grams of fluorinated silicon slag, add 1500.00 grams of water in two batches and stir and wash. After filtration, obtain 500.15 grams of crude silica and fluorosilicic acid aqueous solution with a water content of 40%. S2: Weigh 697.96 grams of 98% ammonium bifluoride and add it to 2722.04 grams of distilled water. Dissolve the solution in the solution under stirring to obtain 3420.00 grams of ammonium bifluoride. Add crude silica in batches. After the reaction is complete at room temperature, filter to obtain 3871.73 grams of the first filtrate. S3: Take 774.00 g of the first filtrate and 1428.00 g of the first ammonia solution with a mass fraction of 3%, heat them to 40°C, and then quickly add the first filtrate and the first ammonia solution to a stirring beaker at the same time. Stir at 300 rpm for 15 seconds, stop stirring, and then age for 15 minutes to obtain silica gel seed crystals. S4: Add silica gel seed crystals to the remaining first filtrate and stir at 200 r / min while heating to 60℃. While maintaining the stirring speed and temperature, add 924.80 g of second ammonia water with a mass fraction of 18% over 45 minutes. After the addition is completed, continue stirring at the same speed for 15 minutes until the ammonolysis reaction is complete. Filter to obtain 453.12 g of silica filter cake and 5772.80 g of second filtrate. Add 1350.00 g of water to the silica filter cake in two batches, stir and separate, and dry to obtain the silica product. Analyze the purity and specific surface area of ​​the silica. S5: Take the second filtrate, evaporate to remove ammonia, and reuse the resulting ammonium bifluoride in step S2. The resulting ammonia gas is used to prepare ammonia water and reused in steps S3 and S4.

[0024] Example 3 Embodiment 3 of the present invention provides a method for the resource utilization of fluorine-containing silicon slag, the steps of which are as follows: S1: Weigh 1000.00 grams of fluorinated silicon slag, add 3000.00 grams of water and wash in two batches. After filtration, obtain 1003.25 grams of crude silica and fluorosilicic acid aqueous solution with a water content of 40%. S2: Weigh 1395.92 grams of 98% ammonium fluoride and add it to 5804.08 grams of distilled water. Dissolve the solution in 5804.08 grams of distilled water under stirring to obtain 7200.00 grams of ammonium fluoride solution. Add crude silica in batches. After the reaction is complete at room temperature, filter to obtain 8100.00 grams of the first filtrate. S3: Take 1620.00 g of the first filtrate and 2856.00 g of the first ammonia solution with a mass fraction of 3%, heat them to 40°C, and then quickly add the first filtrate and the first ammonia solution to a stirring beaker at the same time. Stir at 300 rpm for 15 seconds, stop stirring, and then age for 15 minutes to obtain silica gel seed crystals. S4: Add silica gel seed crystals to the remaining first filtrate and stir at 200 r / min while heating to 60℃. While maintaining the stirring speed and temperature, add 1849.60 g of second ammonia water with a mass fraction of 18% over 45 minutes. After the addition is completed, continue stirring at the same speed for 15 minutes until the ammonolysis reaction is complete. Filter to obtain 896.57 g of silica filter cake and 11905.60 g of second filtrate. Add 2700.00 g of water to the silica filter cake in two batches, stir and separate, and dry to obtain the silica product. Analyze the purity and specific surface area of ​​the silica. S5: Take the second filtrate, evaporate to remove ammonia, and reuse the resulting ammonium bifluoride in step S2. The resulting ammonia gas is used to prepare ammonia water and reused in steps S3 and S4.

[0025] Comparative Example 1 Comparative Example 1 provides a method for the resource utilization of fluorine-containing silicon slag, the steps of which are as follows: S1: Weigh 484.69 grams of 98% ammonium bifluoride and add it to 2681.97 grams of distilled water. Dissolve the solution in the solution under stirring to obtain 3166.67 grams of ammonium bifluoride. Add 2000.00 grams of fluorinated silicon slag in batches. After the reaction is complete at room temperature, filter the solution to obtain 3583.33 grams of the first filtrate. S2: Take 716.67 g of the first filtrate and 1983.33 g of the first ammonia solution with a mass fraction of 3%, heat them to 40°C, and then quickly add the first filtrate and the first ammonia solution to a stirring beaker at the same time. Stir at 300 rpm for 15 seconds, stop stirring, and then age for 15 minutes to obtain silica gel seed crystals. S3: Add silica gel seed crystals to the remaining first filtrate and stir at 200 r / min while heating to 60℃. While maintaining the stirring speed and temperature, add 1284.44 g of second ammonia water with a mass fraction of 18% over 45 minutes. After the addition is completed, continue stirring at the same speed for 15 minutes until the ammonolysis reaction is complete. Filter to obtain 625.91 g of silica filter cake and 6226.11 g of second filtrate. Add 1875.00 g of water to the silica filter cake in two batches, stir and separate, and dry to obtain silica product. Analyze the purity and specific surface area of ​​silica. S4: Take the second filtrate, evaporate to remove ammonia, and reuse the resulting ammonium bifluoride in step S1. The resulting ammonia gas is used to prepare ammonia water and reused in steps S2 and S3.

[0026] Comparative Example 2 Comparative Example 2 provides a method for the resource utilization of fluorine-containing silicon slag, referring to Figure 1 The steps are as follows: S1: Weigh 1211.73 grams of 98% ammonium bifluoride and add it to 6704.93 grams of distilled water. Dissolve the solution in 6704.93 grams of distilled water under stirring to obtain 7916.67 grams of ammonium bifluoride solution. Add 5000.00 grams of fluorinated silicon slag in batches. After the reaction is complete at room temperature, filter to obtain 8958.33 grams of the first filtrate. S2: Take 1791.67 g of the first filtrate and 4958.33 g of the first ammonia solution with a mass fraction of 3%, heat them to 40°C, and then quickly add the first filtrate and the first ammonia solution to a stirring beaker at the same time. Stir at 300 rpm for 15 seconds, stop stirring, and then age for 15 minutes to obtain silica gel seed crystals. S3: Add silica gel seed crystals to the remaining first filtrate and stir at 200 r / min while heating to 60℃. While maintaining the stirring speed and temperature, add 3211.11 g of second ammonia water with a mass fraction of 18% over a period of 45 minutes. After the addition is completed, continue stirring at the same speed for another 15 minutes until the ammonolysis reaction is complete. Filter to obtain 1562.50 g of silica filter cake and 15565.28 g of second filtrate. Add 4687.50 g of water to the silica filter cake in two batches, stir and separate, and dry to obtain silica product. Analyze the purity and specific surface area of ​​silica. S4: Take the second filtrate, evaporate to remove ammonia, and reuse the resulting ammonium bifluoride in step S1. The resulting ammonia gas is used to prepare ammonia water and reused in steps S2 and S3.

[0027] Comparative Example 3 Comparative Example 3 provides a method for the resource utilization of fluorine-containing silicon slag, referring to Figure 1 The steps are as follows: S1: Weigh 220.00 grams of fluorinated silicon slag, add 660.00 grams of water and wash in two batches. After filtration, obtain 219.37 grams of crude silica and fluorosilicic acid aqueous solution with a water content of 40%. S2: Weigh 310.20 g of 98% ammonium bifluoride and add it to 1378.68 g of distilled water. Dissolve the solution in 1688.89 g of ammonium bifluoride under stirring. Add crude silica in batches. After the reaction is complete at room temperature, filter to obtain 1888.89 g of the first filtrate. S3: Take 1888.89 g of the first filtrate, stir at 200 r / min, and simultaneously heat to 60℃. While keeping the stirring speed and temperature constant, add 516.80 g of the second ammonia solution with a mass fraction of 18% for 45 minutes. After the addition is completed, continue stirring at the same speed for 15 minutes until the ammonolysis reaction is complete. Filter to obtain 199.62 g of silica filter cake and 2734.58 g of the second filtrate. Add 600.00 g of water to the silica filter cake in two batches, stir and separate, and dry to obtain the silica product. Analyze the purity and specific surface area of ​​the silica. S4: Take the second filtrate, evaporate to remove ammonia, and reuse the resulting ammonium bifluoride in step S2. The resulting ammonia gas is used to prepare ammonia water and reused in step S3.

[0028] Testing and Inspection (1) The specific surface area of ​​the silica products obtained in Examples 1-3 and Comparative Examples 1-3 was tested according to GB / T 20020-2013; the purity of the silica products obtained in Examples 1-3 and Comparative Examples 1-3 was tested according to HG / T 3062-2008, and the results are shown in Table 1.

[0029] Table 1:

[0030] Results Analysis The present invention will be described in detail below with reference to the experimental results provided in Table 1.

[0031] Referring to Table 1, where Examples 2 and 3 are scaled-up experiments of Example 1, the silica specific surface area obtained in Examples 1-3 reaches 125 m². 2 The purity of the silica was above 98.8% (g / g), meeting the requirements for use as a silica product. When the fluorinated silica slag was not washed and filtered, Comparative Example 2 was a scaled-up experiment of Comparative Example 1. The silica specific surface area obtained in Comparative Examples 1-2 was only 92 m². 2 / g; when a portion of the first filtrate is not taken first to prepare silica gel seeds, the specific surface area of ​​silica obtained in Comparative Example 3 is only 89.56%, and the specific surface areas of silica obtained in Comparative Examples 1-3 are all much lower than those of silica obtained in Examples 1-3. The analysis is due to the following reasons: On the one hand, in Examples 1-3, the fluorinated silicon slag is first washed with water to remove the fluorosilicic acid impurities from the raw materials. Then, excess crude silicon dioxide is reacted with ammonium bifluoride solution, with the reaction formula being: 4NH4HF2 + SiO2 = (NH4)2SiF6 + 2NH4F + 2H2O. In Comparative Examples 1-2, fluorosilicic acid is not separated, and excess fluorinated silicon slag is directly reacted with ammonium bifluoride solution, with the reaction formula being: H2SiF6 + 6NH4HF2 + 2SiO2 = 3(NH4)2SiF6 + 4H2O. When preparing silicon dioxide gel seeds, the addition of low-concentration ammonia water (first ammonia water) and the presence of free fluoride ions are beneficial to establishing the dynamic nucleation of silicon dioxide and fluorosilicate ions in the early stage of nucleation. The presence of fluoride ions helps to maintain a state of equilibrium, slow down the nucleation rate of silica, inhibit homogeneous nucleation, and promote heterogeneous nucleation, which is beneficial to improving the uniformity and stability of crystal nuclei. Furthermore, the presence of fluoride ions helps to activate silanol groups to form more stable gel seed crystals, avoiding the agglomeration of silica particles caused by explosive precipitation during ammonolysis. On the other hand, during the growth stage after mixing gel seed crystals, the remaining first filtrate, and high-concentration ammonia water (second ammonia water), fluoride ions regulate the dissolution of unstable silica particles generated in the system and transfer to and deposit them under the induction of the seed crystals, inhibiting the agglomeration of silica particles generated under high-concentration ammonia water, thereby improving the uniformity and stability of the prepared silica and achieving the effect of increasing the specific surface area of ​​silica.

[0032] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of the present invention.

Claims

1. A method for the resource utilization of fluorine-containing silicon slag, characterized in that: Includes the following steps: S1: Take fluorine-containing silicon slag, wash it, and filter it to obtain crude silicon dioxide and an aqueous solution of fluorosilicic acid; S2: Add excess crude silicon dioxide to ammonium bifluoride solution and stir to dissolve. After the reaction is complete, filter to obtain the first filtrate. S3: Take a portion of the first filtrate and mix it with the first ammonia solution, stir and age to obtain silica gel seed crystals; S4: Mix the silica gel seed crystals with the remaining first filtrate and stir. Add the second ammonia water while stirring, and continue stirring to carry out the ammonolysis reaction until crystallization is complete. Filter to obtain silica filter cake and second filtrate. S5: Take the second filtrate, evaporate to remove ammonia, and reuse the resulting ammonia gas in steps S3 and / or S4. Reuse the resulting ammonium bifluoride gas in step S2.

2. The method for resource utilization of fluorinated silicon slag according to claim 1, characterized in that: The concentration of the ammonium bifluoride solution is 17 wt.%-20 wt.%.

3. The method for resource utilization of fluorinated silicon slag according to claim 1, characterized in that: In step S3, the weight ratio of the first ammonia solution to the first filtrate is 1.6-1.7:

1.

4. The method for resource utilization of fluorinated silicon slag according to claim 1, characterized in that: The mass fraction of the solute in the first ammonia solution is 2%-5%.

5. The method for resource utilization of fluorine-containing silicon slag according to claim 1, characterized in that: In step S4, the weight ratio of the second ammonia solution to the first filtrate is 0.27-0.29:

1.

6. The method for resource utilization of fluorine-containing silicon slag according to claim 1, characterized in that: The mass fraction of the solute in the second ammonia solution is 10%-20%.

7. The method for resource utilization of fluorinated silicon slag according to claim 1, characterized in that: The first filtrate used in step S3 accounts for 20%-30% of the total mass of the first filtrate.

8. The method for resource utilization of fluorine-containing silicon slag according to claim 1, characterized in that: In step S3, the stirring speed is 280-320 r / min and the stirring time is 10-20 s.

9. The method for resource utilization of fluorine-containing silicon slag according to claim 1, characterized in that: The stirring and aging temperature in step S3 is 30-55℃.

10. A method for resource utilization of fluorinated silicon slag according to claim 1, characterized in that: The stirring rate during the ammonolysis reaction in step S4 is 150-250 r / min, and the temperature is 40-70℃.

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