Preparation method of high-purity boric acid

Abstract

The invention discloses a preparation method of high-purity boric acid, and belongs to the technical field of preparation of high-purity boric acid. The invention relates to a preparation method of high-purity boric acid, which adopts borax as a raw material to prepare the high-purity boric acid through a series of precise processes. The method comprises the specific steps of borax pretreatment, boric acid extraction through an electrolytic method, solid-phase extraction treatment, boric acid crystallization and recrystallization. The preparation method comprises the following steps: firstly, dissolving borax and deionized water, adjusting the pH value, and filtering to remove impurities, so as to obtain a pretreated borate solution; secondly, boric acid is extracted through an electrolytic method, then solid-phase extraction is carried out to remove impurities, and a high-purity boric acid solution is obtained; finally, the purity of boric acid is further improved through crystallization and recrystallization. The method has the advantages of simple and convenient process, thorough impurity removal, high purity and the like, is particularly suitable for industrial production of high-purity boric acid, and meets high-end application requirements. By adopting the method, the purity of boric acid can be effectively improved, the environmental pollution is reduced, the energy consumption is lower, and the method has higher industrial popularization value.

Description

Technical Field

[0001] The present invention relates to the technical field of high-purity boric acid preparation, and more specifically, to a method for preparing high-purity boric acid. Background Art

[0002] Boric acid, as an important chemical raw material, is widely used in glass manufacturing, ceramics, pesticides, fertilizers, metallurgy, and the electronics industry, especially playing an irreplaceable role in semiconductor and optical fiber manufacturing. High-purity boric acid is particularly crucial for certain high-end applications, with extremely high purity requirements, usually reaching over 99.9%. Conventional methods for preparing boric acid include extraction from minerals such as borax, through chemical reactions, crystallization, and post-treatment processes. However, existing preparation methods have disadvantages such as low purity, complex production processes, high energy consumption, and prominent environmental protection issues.

[0003] Traditional methods for producing boric acid usually rely on wet processing. Preliminary borate solutions are obtained through acidolysis or alkaliolysis reactions of borax, and then further purified through steps such as crystallization. However, these methods often have problems such as impurities being difficult to completely remove during the purification process and the crystallization process being difficult to control, resulting in the product purity being difficult to meet high requirements. At the same time, heavy metals and other impurities in traditional methods are difficult to completely remove, which may affect the quality of the final boric acid product.

[0004] With the progress of technology, modern methods for producing boric acid are gradually developing towards the direction of high efficiency, environmental protection, and energy conservation. New technologies such as electrolysis and solid-phase extraction have been introduced into the field of boric acid preparation, which can remove impurities more efficiently and improve the product purity. The electrolysis method can precisely control the precipitation process of boric acid by adjusting electrolysis conditions, and the solid-phase extraction method can further remove harmful impurities in the solution and improve the final purity of boric acid.

[0005] However, existing high-purity boric acid preparation technologies still face problems such as how to improve purity, reduce energy consumption, and simplify the process flow. Future development trends will focus on more efficient separation technologies, intelligent control, and green and environmentally friendly production methods, aiming to achieve the maximum utilization of resources and the minimum environmental impact during the production process. At the same time, with the continuous growth of the demand for high-purity boric acid, future technologies will develop towards more efficient and refined directions to meet the strict requirements for material purity in high-end applications. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for preparing high-purity boric acid, which has the advantages of simple process, thorough impurity removal, high purity, can effectively improve the purity of boric acid, reduce environmental pollution, and has low energy consumption.

[0007] A method for preparing high-purity boric acid, characterized by comprising the following steps: (1)Pretreatment of borax: Add deionized water solvent and borax into the reaction vessel, stir and dissolve at 40 - 60 °C for 2 - 4 h, adjust the pH of the solution to 8 - 10 with 1 mol / L sodium hydroxide solution, continue stirring and reacting for 80 - 120 minutes, filter to remove impurities by vacuum filtration method, cool to room temperature, and obtain a clear pretreated borate solution; (2)Extraction of boric acid by electrolysis method: Add the pretreated borate solution into the electrolytic cell, add electrolyte for electrolysis, then heat and stir at 60 - 80 °C for 40 - 60 minutes, filter to remove impurities by vacuum filtration method, cool to room temperature, and obtain a clear electrolyzed borate solution; (3)Solid-phase extraction treatment: Pass the electrolyzed borate solution through an activated ion exchange resin for solid-phase extraction treatment, use 1 mol / L sodium chloride solution as the eluent to elute the impurities in the resin in the reverse direction, repeat the solid-phase extraction treatment 2 - 4 times, and obtain a solid-phase extraction-treated borate solution; (4)Crystallization of boric acid: Heat the solid-phase extraction-treated borate solution at 60 - 80 °C to a saturated solution, then maintain at this temperature for 120 - 180 minutes, then lower the temperature to 10 - 14 °C and maintain for 6 - 8 h. After crystallization, filter to remove impurities by vacuum filtration method to obtain boric acid crystals; (5)Recrystallization of boric acid: Add deionized water solvent and boric acid crystals into the reaction vessel, stir and dissolve at 60 - 80 °C for 80 - 120 minutes, then lower the temperature to 10 - 14 °C and maintain for 5 - 7 h. After crystallization, filter to remove impurities by vacuum filtration method to obtain recrystallized boric acid.

[0008] Preferably, in the step (1), the mass ratio of the deionized water solvent to borax is 6 - 10:1.

[0009] Preferably, in the step (2), the added electrolyte is sodium chloride, and its weight is 6 - 10% of the weight of the borate solution.

[0010] Preferably, in the step (2), the electrolysis conditions are that the voltage in the electrolytic cell is 4 - 6 V, the current density is 60 - 100 A / m 2 , and electrolyze at 50 - 70 °C for 4 - 6 h.

[0011] Preferably, in the step (3), the activated ion exchange resin is a weakly acidic activated ion exchange resin, and the usage amount of the resin is 3 - 5 times the mass of the solution.

[0012] Preferably, in the step (3), the conditions for solid-phase extraction treatment are that the flow rate is 1 - 2 L / h·g and the temperature is 25 - 45 °C.

[0013] Preferably, the cooling rate of the solution in step (4) is 2-3 °C / min.

[0014] Preferably, the mass ratio of deionized water solvent to borax crystallization in step (5) is 4-6:1.

[0015] Preferably, the cooling rate of the solution in step (5) is 1-2 °C / min.

[0016] Compared with the prior art, the advantages of the present invention are as follows: (1) The present invention can significantly improve the purity of boric acid Through a fine process flow, such as pretreatment, extraction by electrolysis, solid-phase extraction, crystallization and recrystallization, etc., this method can effectively remove impurities and ensure high purity of the final boric acid. Especially in the electrolysis and solid-phase extraction processes, metal ions, inorganic impurities and organic substances can be fully removed, so that the purity of boric acid can reach more than 99.9%, meeting the requirements of high-end applications.

[0017] (2) The method of this invention patent is green and environmentally friendly Using deionized water as a solvent reduces the need for a large amount of acidic and alkaline chemical reagents in traditional preparation methods, helping to reduce environmental pollution. At the same time, by combining solid-phase extraction and electrolysis, this method reduces the dependence on harmful chemical substances, meets the requirements of green chemistry, and conforms to the trend of sustainable industrial production.

[0018] (3) The process control of the method of this invention patent is precise In the method of this patent, the electrolysis conditions (voltage, current density, temperature, etc.) of the electrolysis method and the process parameters such as the flow rate and temperature of solid-phase extraction are strictly controlled, which helps to more precisely control the extraction and purification process of boric acid, avoids the extensive operation in traditional methods, and can more stably obtain high-purity boric acid products.

[0019] (4) The method of this invention patent can reduce energy consumption and costs Compared with traditional chemical treatment methods, the electrolysis method and solid-phase extraction method adopted in this patent not only improve the purity of boric acid, but also can complete the extraction and purification of high-purity boric acid in a shorter time, reducing energy consumption and reaction time, thus reducing production costs and energy consumption.

[0020] (5) The method of this invention patent has strong adaptability The electrolysis method and solid-phase extraction technology adopted in this method can be widely applied to borax from different sources, have strong adaptability, and can effectively remove different types of impurities, making this method have strong potential for industrial application.

[0021] (6) The method of this invention patent improves the quality of boric acid through recrystallization The recrystallization step further improves the purity of boric acid, effectively removing residual impurities and trace harmful substances, and ensuring the quality stability of the final boric acid product. This process not only improves the product purity but also effectively removes trace amounts of insoluble substances, enabling the boric acid product to meet higher standards.

[0022] (7) The method of this invention patent can improve the yield Through reasonable pretreatment and electrolysis condition settings, this method can achieve efficient extraction of boric acid within a short reaction time, ensuring a higher yield. The optimization of the crystallization and recrystallization processes further ensures the crystallization efficiency and the recovery rate of boric acid.

[0023] (8) The process of the method of this invention patent is simplified and easy to be applied industrially The method steps of this patent are clear and the process is simplified, suitable for large-scale industrial production. Each step such as filtration, extraction, crystallization, etc. adopts common operation methods, facilitating automation and process management, and meeting the operation requirements of modern production lines. Detailed implementation manners

[0024] Example 1: (1) Pretreatment of borax: Add 600 deionized water solvents and 100 g of borax to the reaction vessel, stir and dissolve at 40 °C for 2 h, adjust the pH of the solution to 8 using 1 mol / L sodium hydroxide solution, continue stirring and reacting for 80 minutes, filter out impurities by vacuum filtration method, cool to room temperature, and obtain a clear pretreated borate solution; (2) Extraction of boric acid by electrolysis method: Add the pretreated borate solution to the electrolytic cell, add 6% of the electrolyte sodium chloride by weight of the borate solution, set the voltage in the electrolytic cell to 4 V and the current density to 60 A / m 2 , electrolyze at 50 °C for 4 h, then heat and stir at 60 °C for 40 minutes, filter out impurities by vacuum filtration method, cool to room temperature, and obtain a clear electrolyzed borate solution; (3) Solid-phase extraction treatment: Pass the electrolyzed borate solution through a weakly acidic activated ion exchange resin for solid-phase extraction treatment. The usage amount of the resin is 3 times the mass of the solution, the flow rate is 1 L / h·g, the temperature is 25 °C, use 1 mol / L sodium chloride solution as the eluent to reverse-elute the impurities in the resin, and repeat the solid-phase extraction treatment 2 times to obtain the solid-phase extraction-treated borate solution; (4) Crystallization of boric acid: Heat the solid-phase extraction-treated borate solution to a saturated solution at 60 °C, then maintain at this temperature for 120 minutes, then reduce the temperature to 10 °C at a cooling rate of 2 °C / min, maintain for 6 h. After crystallization, filter out impurities by vacuum filtration method to obtain boric acid crystals; (5) Recrystallization of boric acid: Add 400 g of deionized water solvent and 100 g of boric acid crystals to the reaction vessel, stir and dissolve at 60 °C for 80 minutes, then lower the temperature to 10 °C at a cooling rate of 1 °C / min, hold for 5 h. After crystallization, filter to remove impurities by vacuum filtration to obtain recrystallized boric acid.

[0025] Example 2: (1) Pretreatment of borax: Add 700 g of deionized water solvent and 100 g of borax to the reaction vessel, stir and dissolve at 45 °C for 2.5 h, adjust the pH of the solution to 8.5 with 1 mol / L sodium hydroxide solution, continue stirring and reacting for 90 minutes, filter to remove impurities by vacuum filtration, and cool to room temperature to obtain a clear pretreated borate solution; (2) Extraction of boric acid by electrolysis: Add the pretreated borate solution to the electrolytic cell, add 7% by weight of the electrolyte sodium chloride based on the weight of the borate solution, set the voltage in the electrolytic cell to 4.5 V and the current density to 70 A / m 2 , electrolyze at 55 °C for 4.5 h, then heat and stir at 65 °C for 45 minutes, filter to remove impurities by vacuum filtration, and cool to room temperature to obtain a clear electrolyzed borate solution; (3) Solid-phase extraction treatment: Pass the electrolyzed borate solution through a weakly acidic activated ion exchange resin for solid-phase extraction treatment. The amount of resin used is 3.5 times the mass of the solution, the flow rate is 1.25 L / h·g, the temperature is 30 °C, use 1 mol / L sodium chloride solution as the eluent to reverse-elute the impurities in the resin, and repeat the solid-phase extraction treatment 2 times to obtain a solid-phase extraction-treated borate solution; (4) Crystallization of boric acid: Heat the solid-phase extraction-treated borate solution to a saturated solution at 65 °C, then hold at this temperature for 135 minutes, then lower the temperature to 11 °C at a cooling rate of 2.25 °C / min, hold for 6.5 h. After crystallization, filter to remove impurities by vacuum filtration to obtain boric acid crystals; (5) Recrystallization of boric acid: Add 450 g of deionized water solvent and 100 g of boric acid crystals to the reaction vessel, stir and dissolve at 65 °C for 90 minutes, then lower the temperature to 11 °C at a cooling rate of 1.25 °C / min, hold for 5.5 h. After crystallization, filter to remove impurities by vacuum filtration to obtain recrystallized boric acid.

[0026] Example 3: (1) Pretreatment of borax: Add 800 g of deionized water solvent and 100 g of borax into the reaction vessel, stir and dissolve at 50 °C for 3 h, adjust the pH of the solution to 9 with 1 mol / L sodium hydroxide solution, continue stirring and reacting for 100 minutes, filter out impurities by vacuum filtration method, cool to room temperature to obtain a clear pretreated borate solution; (2) Extraction of boric acid by electrolysis method: Add the pretreated borate solution into the electrolytic cell, add 8% of the electrolyte sodium chloride by weight of the borate solution, set the voltage in the electrolytic cell to 5 V and the current density to 80 A / m 2 , electrolyze at 60 °C for 5 h, then heat and stir at 70 °C for 50 minutes, filter out impurities by vacuum filtration method, cool to room temperature to obtain a clear electrolyzed borate solution; (3) Solid-phase extraction treatment: Perform solid-phase extraction treatment on the electrolyzed borate solution through weakly acidic activated ion exchange resin. The usage amount of the resin is 4 times the mass of the solution, the flow rate is 1.5 L / h·g, the temperature is 35 °C, use 1 mol / L sodium chloride solution as the eluent, reverse elute the impurities in the resin, repeat the solid-phase extraction treatment 3 times to obtain the solid-phase extraction treated borate solution; (4) Boric acid crystallization: Heat the solid-phase extraction treated borate solution to a saturated solution at 70 °C, then keep at this temperature for 150 minutes, then lower the temperature to 12 °C at a cooling rate of 2.5 °C / min, keep for 7 h. After crystallization, filter out impurities by vacuum filtration method to obtain boric acid crystals; (5) Recrystallization of boric acid: Add 500 g of deionized water solvent and 100 g of boric acid crystals into the reaction vessel, stir and dissolve at 70 °C for 100 minutes, then lower the temperature to 12 °C at a cooling rate of 1.5 °C / min, keep for 6 h. After crystallization, filter out impurities by vacuum filtration method to obtain recrystallized boric acid.

[0027] Example 4: (1) Pretreatment of borax: Add 90 g of deionized water solvent and 100 g of borax into the reaction vessel, stir and dissolve at 55 °C for 3.5 h, adjust the pH of the solution to 9.5 with 1 mol / L sodium hydroxide solution, continue stirring and reacting for 110 minutes, filter out impurities by vacuum filtration method, cool to room temperature to obtain a clear pretreated borate solution; (2) Extraction of boric acid by electrolysis method: Add the pretreated borate solution into the electrolytic cell, add 9% of the electrolyte sodium chloride by weight of the borate solution, set the voltage in the electrolytic cell to 5.5 V and the current density to 90 A / m 2, electrolyze at 65 °C for 5.5 h, then heat and stir at 75 °C for 55 minutes, filter out impurities by vacuum filtration, cool to room temperature to obtain a clear electrolyzed borate solution; (3) Solid-phase extraction treatment: Pass the electrolyzed borate solution through a weakly acidic activated ion exchange resin for solid-phase extraction treatment. The usage amount of the resin is 4.5 times the mass of the solution, the flow rate is 1.75 L / h·g, the temperature is 40 °C, use 1 mol / L sodium chloride solution as the eluent, elute the impurities in the resin in the reverse direction, and repeat the solid-phase extraction treatment 3 times to obtain the solid-phase extraction treated borate solution; (4) Boric acid crystallization: Place the solid-phase extraction treated borate solution at 75 °C and heat it to a saturated solution, then maintain at this temperature for 165 minutes, then lower the temperature to 13 °C at a cooling rate of 2.75 °C / min, and maintain for 7.5 h. After crystallization, filter out impurities by vacuum filtration to obtain boric acid crystals; (5) Boric acid recrystallization: Add 550 g of deionized water solvent and 100 g of boric acid crystals to the reaction vessel, stir and dissolve at 75 °C for 110 minutes, then lower the temperature to 13 °C at a cooling rate of 1.75 °C / min, and maintain for 6.5 h. After crystallization, filter out impurities by vacuum filtration to obtain boric acid recrystallization.

[0028] Example 5: (1) Pretreatment of borax: Add 1000 g of deionized water solvent and 100 g of borax to the reaction vessel, stir and dissolve at 60 °C for 4 h, use 1 mol / L sodium hydroxide solution to adjust the pH of the solution to 10, continue to stir and react for 120 minutes, filter out impurities by vacuum filtration, cool to room temperature to obtain a clear pretreated borate solution; (2) Extraction of boric acid by electrolysis method: Add the pretreated borate solution to the electrolytic cell, add 10% of the electrolyte sodium chloride by weight of the borate solution, set the voltage in the electrolytic cell to 6 V, and the current density to 100 A / m 2 , electrolyze at 70 °C for 6 h, then heat and stir at 80 °C for 60 minutes, filter out impurities by vacuum filtration, cool to room temperature to obtain a clear electrolyzed borate solution; (3) Solid-phase extraction treatment: Pass the electrolyzed borate solution through a weakly acidic activated ion exchange resin for solid-phase extraction treatment. The usage amount of the resin is 5 times the mass of the solution, the flow rate is 2 L / h·g, the temperature is 45 °C, use 1 mol / L sodium chloride solution as the eluent, elute the impurities in the resin in the reverse direction, and repeat the solid-phase extraction treatment 4 times to obtain the solid-phase extraction treated borate solution; (4)Boric acid crystallization: The borate solution after solid-phase extraction treatment is heated to a saturated solution at 80 °C, then maintained at this temperature for 180 minutes, and then the temperature is reduced to 14 °C at a cooling rate of 3 °C / min and held for 8 h. After crystallization, impurities are removed by vacuum filtration to obtain boric acid crystals; (5)Recrystallization of boric acid: Add 600 g of deionized water solvent and 100 g of boric acid crystals to the reaction vessel, stir and dissolve at 80 °C for 120 minutes, then reduce the temperature to 14 °C at a cooling rate of 2 °C / min and hold for 7 h. After crystallization, impurities are removed by vacuum filtration to obtain recrystallized boric acid.

[0029] Performance test Purity test of boric acid Take 5 g from the finally obtained recrystallized boric acid samples in Examples 1-5, dry them thoroughly to a constant weight, and use an Agilent 1260 Infinity II high-performance liquid chromatograph to test the purity of the samples by high-performance liquid chromatography. Referring to the national standard GB / T 602-2002, the following table shows the test results: Impurity content test Take 5 g from the finally obtained recrystallized boric acid samples in Examples 1-5, dissolve them fully in 1000 g of deionized water solvent, and use a PerkinElmer AA800 atomic absorption spectrometer to detect the heavy metal content by atomic absorption spectrometry. Set the wavelength according to the target metal element, and the burner gas is an acetylene / air mixture. Referring to the national standard GB / T 12694-2008, the following table shows the test results:

Claims

1. A method for preparing high-purity boric acid, characterized in that: The steps include: (1) Pretreatment of borax: add deionized water solvent and borax to a reaction container, stir and dissolve at 40-60° C. for 2-4 hours, adjust the pH of the solution to 8-10 with 1 mol / L sodium hydroxide solution, continue stirring and reacting for 80-120 minutes, filter and remove impurities by vacuum filtration, cool to room temperature, and obtain a clear pretreated borate solution; (2) Extraction of boric acid by electrolysis: Add the pretreated borate solution to an electrolytic cell, add electrolyte for electrolysis, then heat and stir at 60-80°C for 40-60 minutes, filter and remove impurities by vacuum filtration, and cool to room temperature to obtain a clear electrolyzed borate solution; (3) Solid phase extraction treatment: The electrolyzed borate solution is subjected to solid phase extraction treatment by passing it through an active ion exchange resin, using a 1 mol / L sodium chloride solution as an eluent to reversely elute impurities in the resin, and the solid phase extraction treatment is repeated 2-4 times to obtain a borate solution after solid phase extraction treatment; (4) Boric acid crystallization: The borate solution after solid phase extraction is heated at 60-80°C to a saturated solution, and then maintained at this temperature for 120-180 minutes, and then the temperature is reduced to 10-14°C and maintained for 6-8 hours. After the crystallization is completed, impurities are removed by vacuum filtration to obtain boric acid crystals; (5) Boric acid recrystallization: Add deionized water solvent and boric acid crystals to a reaction vessel, stir and dissolve at 60-80°C for 80-120 minutes, then lower the temperature to 10-14°C and maintain for 5-7 hours. After the crystallization is completed, vacuum filtration is used to remove impurities to obtain boric acid recrystallization.

2. The method for preparing high-purity boric acid according to claim 1, wherein: In the step (1), the mass ratio of the deionized water solvent to borax is 6-10:

1.

3. The method for preparing high-purity boric acid according to claim 1, wherein: The electrolyte added in step (2) is sodium chloride, and its weight is 6-10% of the weight of the borate solution.

4. The method for preparing high-purity boric acid according to claim 3, characterized in that: The electrolysis conditions in step (2) are as follows: the voltage in the electrolytic cell is 4-6V and the current density is 60-100A / m 2 , electrolyze at 50-70℃ for 4-6h.

5. The method for preparing high-purity boric acid according to claim 1, characterized in that: The active ion exchange resin in step (3) is a weakly acidic active ion exchange resin, and the amount of the resin used is 3-5 times the mass of the solution.

6. The method for preparing high-purity boric acid according to claim 1, characterized in that: The conditions for the solid phase extraction treatment in step (3) are a flow rate of 1-2 L / h·g and a temperature of 25-45°C.

7. The method for preparing high-purity boric acid according to claim 1, characterized in that: The cooling rate of the solution in step (4) is 2-3°C / min.

8. The method for preparing high-purity boric acid according to claim 1, characterized in that: In the step (5), the mass ratio of the deionized water solvent to the borax crystals is 4-6:

1.

9. The method for preparing high-purity boric acid according to claim 1, characterized in that: The cooling rate of the solution in step (5) is 1-2°C / min.

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