CN104150499A - Preparation method of high-purity boric acid and nuclear grade high-purity boric acid - Google Patents

Abstract

The invention relates to a preparation method of high-purity boric acid and nuclear-grade high-purity boric acid, belonging to the technical field of fine chemicals. The method includes the following process steps: 1) mixing industrial boric acid with water, stirring to remove calcium, magnesium, and sodium impurities, and obtaining a high-purity boric acid precursor after solid-liquid separation; 2) dissolving the high-purity boric acid precursor Prepare a boric acid solution containing H ₃ BO ₃ 180g/L～280g/L in hot pure water, remove iron and heavy metals with compound additives, then filter, crystallize by cooling, separate solid-liquid, wash, and dry , to obtain high-purity boric acid product. The high-purity boric acid product is dissolved in pure water, and after 1-2 times of recrystallization, dehydration, and drying, the nuclear-grade high-purity boric acid product is obtained. The invention not only can obtain high-purity boric acid products of different grades, but also has simple process, easy operation and control, good reproducibility, low production cost and environmental friendliness.

Description

A kind of preparation method of high-purity boric acid and nuclear-grade high-purity boric acid

technical field

The invention relates to the technical field of fine chemical production, in particular to a method for preparing high-purity boric acid and nuclear-grade high-purity boric acid.

Background technique

Boric acid is widely used. In addition to being widely used in glass manufacturing industry, it is also used in enamel, ceramics, metallurgy and other industrial sectors. In addition to being used as raw materials for chemical reagents, fluorescent materials and high borosilicate glass, high-purity boric acid can also be used as a neutron moderator, collector and coolant, and is widely used in the nuclear industry. With the further development of the nuclear power industry in the world, especially in China, the consumption of nuclear grade boron products will increase rapidly. Nuclear-grade boric acid has high requirements on the content of impurities such as Ca ²⁺ , Fe ³⁺ , Pb ²⁺ , SO ₄ ^2- , Cl ^-, etc., and domestic reagent-grade boric acid cannot meet the requirements.

The world's largest producers of boric acid, such as the United States and Turkey, use natural borax and colemanite as raw materials. Due to the high content of raw material B ₂ O ₃ (about 45%) and less impurities, the preparation process of boric acid and high-purity boric acid is relatively simple. And the main raw material that our country is used to produce boric acid is magnesite and magnesite, because of its B ₂ O ₃ content is low, impurity kind is many, the content is high, so that the preparation process of boric acid is comparatively complicated, the produced industrial boric acid Fe, Ca, Mg, SO ₄ ^2- and other impurities are relatively high, and some industrial boric acids also contain heavy metal impurities (about 10×10 ^-6 in terms of Pb). The preparation of high-purity boric acid from industrial boric acid usually uses hydrogen peroxide to oxidize Fe ²⁺ in the boric acid solution to Fe ³⁺ , and then iron is precipitated and removed. However, due to the limited ability of this method to remove iron, heavy metals cannot be precipitated and removed, resulting in a long process for preparing high-purity boric acid.

At present, the domestic preparation of nuclear-grade high-purity boric acid mainly adopts the following methods: one is to use industrial boron trifluoride-10 ether complex as raw material, calcium chloride is used as deoxidizer, and methanol is used as medium to react to obtain boric acid tris methyl ester, and then hydrolyze trimethyl borate to obtain nuclear-grade boric acid; the other is to use industrial boric acid as raw material to prepare nuclear-grade high-purity boric acid by oxidation-esterification crystallization method. For example, Dalian University of Technology disclosed in the article "Preparation and Crystal Morphology of Photoelectric/Nuclear Power Grade High-purity Boric Acid", using industrial boric acid as raw material, proposed an oxidation-esterification crystallization method to prepare nuclear power grade high-purity boric acid.

It can be seen that the above two preparation methods of nuclear-grade boric acid both use organic compounds, which not only has an impact on the environment, but also consumes high energy consumption, and at the same time makes the product cost relatively high.

Although my country is a country rich in boron resources, due to the limitation of boron ore grade and preparation technology, the high-purity boric acid used in China's nuclear industry is almost all imported from abroad. Conducive to the development of the domestic nuclear power industry.

Contents of the invention

The object of the present invention is to provide a kind of method that takes domestic industrial boric acid as raw material to prepare high-purity boric acid and nuclear grade high-purity boric acid. The method has abundant and economical sources of raw materials, simple process, easy operation and control, and good reproducibility. When removing iron, heavy metal impurities can be removed at the same time; and no organic reagents need to be added during the preparation process, the production cost is low, and the method is environmentally friendly.

Realize above-mentioned purpose of the invention, the concrete technical scheme that the present invention adopts is:

A preparation method for high-purity boric acid is characterized in that it comprises the following processing steps:

1) Slurry industrial boric acid with water, stir to remove calcium, magnesium, and sodium impurities, and obtain high-purity boric acid precursor after solid-liquid separation;

2) Dissolve the high-purity boric acid precursor in pure water at a temperature of 80°C to 100°C to prepare a boric acid solution containing 180g/L to 280g/L of H ₃ BO ₃ . After filtration, cooling and crystallization, solid-liquid separation, washing and drying, the high-purity boric acid product can be obtained.

The high-purity boric acid that has not been dried in step 2) is dissolved in pure water, and after 1 to 2 times of recrystallization, dehydration, and drying, the nuclear-grade high-purity boric acid product is obtained.

The high-purity boric acid precursor described in step 2) can be replaced by high-quality industrial boric acid, which has a Ca content of <0.032%, Mg content of <0.015%, Fe content of <0.002%, and Na content of <0.03%.

The composite additive is a combination of sulfide and ammonia water, which are used after pulping.

The sulfide is any one of ammonium sulfide, barium sulfide, strontium sulfide, potassium sulfide, sodium sulfide, or a combination of any two or three; the dosage is 10 to 30 times the stoichiometric amount.

The volume ratio concentration of the ammonia water is 5%, and its consumption is 30-60 times of the sulfide by mass ratio.

The specific preparation process of the high-purity boric acid precursor is: weigh the industrial boric acid, add 1.5 to 4 times of water according to the mass ratio, stir at a temperature of 10 to 35°C for 20 to 60 minutes, and obtain High-purity boric acid precursor.

The mother liquor after solid-liquid separation contains H ₃ BO ₃ 35g/L-75g/L, which can be returned to the water immersion pretreatment process for recycling. When the Ca content in it accumulates to nearly 500mg/L, it can be used as Raw materials for the preparation of industrial boric acid or calcium borate.

The specific preparation process of the high-purity boric acid product is: add the high-purity boric acid precursor prepared in step 1) into pure water at a temperature of 80-100°C, stir and dissolve to obtain a boric acid solution, and then add ammonia water to adjust the pH value of the solution 4.6 to 5.3, then add compound additives to react for 15 to 30 minutes, filter to obtain the purified solution; then maintain the temperature of the purified solution at 70 to 95°C, add hydrogen peroxide, and stir for 15 to 30 minutes to convert excess ^S2- into elemental Sulfur or SO ₄ ^2- , after filtering, add nitric acid with a mass concentration of 40-45% to the filtrate, adjust the pH value of the solution to 2.5-4.0, stir, cool and crystallize until the temperature is 10°C-30°C, and separate the solid and liquid. Wash the boric acid crystals with pure water, dehydrate and dry at 60°C to 70°C to obtain high-purity boric acid products.

The purification solution contains 180-280 g/L of H ₃ BO ₃ , 18-140 mg/L of Ca, 14-60 mg/L of Mg, 0.10-0.3 mg/L of Fe, and 0.06-0.2 mg/L of Pb. Before the compound additive is added to remove impurities, the iron content of the solution is 1-13 mg/L, and the lead content is 0.4-3 mg/L Pb.

The added amount of the hydrogen peroxide is 0.2-1.0% of the volume of the boric acid solution.

The high-purity boric acid product has Na content <40×10 ^-6 , Fe content <5×10 ^-6 , and Pb content <1×10 ^-6 .

The specific preparation process of the nuclear-grade high-purity boric acid is: first dissolve the high-purity boric acid that has not been dried in pure water at a temperature of 80°C to 100°C to prepare 180g/L to 280g/L of H ₃ BO ₃ L of boric acid solution, then add ammonium nitrate or ammonium acetate at 1.5~2.5g/L into the solution, heat-retain and filter, cool and crystallize under stirring conditions to a final temperature of 10°C~30°C, and then separate solid and liquid; recrystallize in this way 1 to 2 times, drying and packaging to obtain nuclear-grade high-purity boric acid products.

Compared with the prior art, the present invention has the advantages of:

1. Due to the high content of impurities such as iron, calcium, and sulfate in many domestic industrial borates, their uses are severely limited and their market competitiveness is not strong. However, the present invention can directly use domestic industrial boric acid with high impurity content such as iron, calcium, sulfate, and heavy metals as raw material, and adopt water immersion to remove impurities such as part of calcium, magnesium, and sodium in industrial boric acid to obtain the next step of preparing high-quality boric acid. The precursor of pure boric acid has rich and economical sources of raw materials; at the same time, the mother liquor after solid-liquid separation can be returned to the water immersion treatment process for recycling one to three times, or used as raw materials for the preparation of industrial boric acid and calcium borate. The process of removing some calcium, magnesium and sodium impurities in industrial boric acid is simple and easy to operate.

2. The present invention removes part of calcium, magnesium, and sodium impurities in industrial boric acid by water immersion to obtain a precursor for preparing high-purity boric acid, and then uses compound additives to remove iron and heavy metals in depth, and obtain high-purity boric acid after cooling and crystallization. Boric acid, with sodium content <40×10 ^-6 , iron content <5×10 ^-6 , lead content <2×10 ^-6 , meets the requirements for analyzing pure boric acid for impurities. This process not only removes iron and heavy metals thoroughly, but also does not need to use organic reagents during recrystallization. While reducing environmental pollution, it fundamentally solves the technical problem of using industrial boric acid as raw material to prepare nuclear-grade high-purity boric acid. And achieved better economic results.

3. The present invention can simultaneously prepare high-purity boric acid and nuclear-grade high-purity boric acid by using domestic industrial boric acid as a raw material. The content of boric acid in the solution reaches 180g/L-280g/L, and the high-purity boric acid can be recrystallized 1-2 times. The nuclear-grade high-purity boric acid product is obtained, and the subsequent purification process is very simplified and easy to operate.

The present invention can economically prepare high-purity boric acid and nuclear-grade high-purity boric acid by using domestic industrial boric acid as a raw material. Compared with the existing method for preparing nuclear-grade high-purity boric acid using industrial boric acid as a raw material, the present invention has the advantages of simple process and easy operation. The control is relatively easy, the recrystallization does not use a large amount of high-purity organic reagents, and the production cost is low. Since high-purity boric acid with extremely low content of impurities such as iron and heavy metals is prepared first, the subsequent purification process for preparing nuclear-grade high-purity boric acid is simplified, and the entire process is easier to implement industrially.

Description of drawings

Fig. 1 is the process flow chart of the inventive method

Figure 2 is the scanning electron microscope image of various grades of boric acid

Wherein: a is the microscopic image of industrial boric acid, b is the microscopic image of a certain imported high-purity boric acid, and c and d are the microscopic image of nuclear grade high-purity boric acid of the present invention.

Detailed ways

The above-mentioned contents of the present invention are described in further detail below through the specific implementation of the examples, but this should not be interpreted as the scope of the above-mentioned subject of the present invention is limited to the following examples, all high-purity products realized based on the above-mentioned contents of the present invention The preparation technology of boric acid all belongs to the scope of the present invention.

The preparation method of embodiment 1 high-purity boric acid

The process steps include: 1) leaching industrial boric acid with water to remove part of the calcium, magnesium, and sodium impurities to obtain a high-purity boric acid precursor; 2) dissolving the high-purity boric acid precursor in pure water at a temperature of 80°C to 90°C , to prepare a boric acid solution containing H ₃ BO ₃ 180g/L～220g/L, remove iron and heavy metals with composite additives, and then filter, cool and crystallize, separate solid-liquid, wash, and dry to obtain high-purity boric acid products.

The composite additive is a combination of sulfide and ammonia water, which are used after pulping.

The sulfide is any one of ammonium sulfide, barium sulfide, strontium sulfide, potassium sulfide and sodium sulfide, and its dosage is 15 to 30 times the stoichiometric amount.

The volume ratio concentration of the ammonia water is 5%, and its consumption is 40-50 times of the sulfide by mass ratio.

The specific preparation process of the high-purity boric acid precursor is: weigh the industrial boric acid, add 2 to 4 times the water according to the mass ratio, stir at a temperature of 10 to 20°C for 40 to 60 minutes, and obtain High-purity boric acid precursor.

The mother liquor after solid-liquid separation contains H ₃ BO ₃ 35-49g/L, which can be returned to the water immersion treatment process for recycling. When the Ca content in it accumulates to 450-500mg/L, it can be used as a preparation industry Raw materials for boric acid or calcium borate.

The specific preparation process of the high-purity boric acid product is: dissolving the high-purity boric acid precursor in pure water, stirring and dissolving the boric acid solution at a temperature of 80-90° C., adding ammonia water to adjust the pH value of the solution to 4.6-5.0 , then add compound additives to react for 15-30 minutes, filter to obtain a purified solution; then maintain the temperature of the purified solution at 80-95°C, add hydrogen peroxide, and stir for 25-30 minutes to convert excess S ^2- into elemental sulfur or SO ₄ ^2- After filtering, add nitric acid with a concentration of 40-45% to the filtrate by weight, adjust the pH value of the solution to 3.5-4.0, stir, cool and crystallize until the temperature is 10°C-20°C, separate the solid and liquid, and then use The boric acid crystals are washed with pure water, dehydrated, and dried at 65°C to obtain high-purity boric acid products.

The purification solution contains H ₃ BO ₃ 180-223g/L, Fe 0.05-0.1mg/L, and Pb 0.05-0.15mg/L. The leaching solution before iron removal contains 3-9 mg/L of iron and 1.5-2.5 mg/L of Pb.

The added amount of the hydrogen peroxide is 0.4-1.0% of the volume of the boric acid solution.

The high-purity boric acid product has Na content <40×10 ^-6 , Fe content <5×10 ^-6 , and Pb content <1×10 ^-6 .

The preparation method of embodiment 2 nuclear grade high-purity boric acid

First, the high-purity boric acid obtained in Example 1 without drying treatment is dissolved in pure water at a temperature of 80°C to 90°C to prepare a boric acid solution containing H ₃ BO _180g /L to 220g/L, and then in Add ammonium nitrate at 2.5-3.5g/L to the solution, heat-preserve and filter, cool and crystallize under stirring conditions to a final temperature of 10°C-20°C, and then separate solid and liquid; recrystallize in this way for 1-2 times, dry and package get the product.

The preparation method of embodiment 3 high-purity boric acid

The process steps include: 1) leaching industrial boric acid with water to remove part of the calcium, magnesium, and sodium impurities to obtain a high-purity boric acid precursor; 2) dissolving the high-purity boric acid precursor in pure water at a temperature of 80°C to 90°C , to prepare a boric acid solution containing H ₃ BO ₃ 240~280g/L, remove iron and heavy metals with composite additives, and then filter, cool and crystallize, separate solid-liquid, wash, and dry to obtain high-purity boric acid products .

The composite additive is a combination of sulfide and ammonia water, which are used after pulping.

The sulfide is a combination of any two of ammonium sulfide, barium sulfide, strontium sulfide, potassium sulfide and sodium sulfide, and its dosage is 10 to 15 times the stoichiometric amount.

The volume ratio concentration of the ammonia water is 5%, and its consumption is 50-60 times of the sulfide by mass ratio.

The specific preparation process of the high-purity boric acid precursor is: weigh the industrial boric acid, add 1.5 to 3 times of water according to the mass ratio, stir at a temperature of 20 to 30°C for 30 to 40 minutes, and obtain High-purity boric acid precursor.

The mother liquor after solid-liquid separation contains H ₃ BO ₃ 46-68g/L, which can be returned to the water immersion treatment process for recycling. When the Ca content in it accumulates to 500mg/L, it can be used to prepare industrial boric acid or Raw material of calcium borate.

The specific preparation process of the high-purity boric acid product is: Dissolving the high-purity boric acid precursor in pure water, stirring and dissolving at a temperature of 90-100°C to obtain a boric acid solution, adding ammonia water to adjust the pH value of the solution to 4.8-5.3 , then add compound additives to react for 20-30 minutes, filter to obtain a purified solution; then maintain the temperature of the purified solution at 85-95°C, add hydrogen peroxide, and stir for 25-30 minutes to convert excess S ^2- into elemental sulfur or SO ₄ ^2- After filtering, add nitric acid with a concentration of 40-45% to the filtrate by weight, adjust the pH value of the solution to 2.5-3.5, stir, cool and crystallize until the temperature is 20°C-30°C, separate the solid and liquid, and then use Wash boric acid crystals with pure water, dehydrate and dry at 70°C to obtain high-purity boric acid products.

The purification solution contains 240-283 g/L of H ₃ BO ₃ , 0.10-0.3 mg/L of Fe, and 0.15-0.22 mg/L of Pb. The leaching solution before iron removal contains 1-6 mg/L of iron and 0.5-1.0 mg/L of Pb.

The added amount of the hydrogen peroxide is 0.2-0.5% of the volume of the boric acid solution.

The high-purity boric acid product has Na content <30×10 ^-6 , Fe content <5×10 ^-6 , and Pb content <2×10 ^-6 .

The preparation method of embodiment 4 nuclear grade high-purity boric acid

First, the high-purity boric acid obtained in Example 3 without drying treatment is dissolved in pure water at a temperature of 90°C to 100°C to prepare a boric acid solution containing _{H BO} 220g/L to 280g/L, and then in Add ammonium acetate to the solution at 3.0-3.5g/L, heat-preserve and filter, cool and crystallize under stirring conditions to a final temperature of 20°C-30°C, and then separate solid and liquid; recrystallize in this way for 1-2 times, dry and package get the product.

The preparation method of embodiment 5 high-purity boric acid

The process steps include: 1) leaching industrial boric acid with water to remove part of calcium, magnesium, and sodium impurities to obtain a high-purity boric acid precursor; 2) dissolving the high-purity boric acid precursor in pure water at a temperature of 90°C to 100°C , to prepare a boric acid solution containing H ₃ BO ₃ 240~280g/L, remove iron and heavy metals with composite additives, and then filter, cool and crystallize, separate solid-liquid, wash, and dry to obtain high-purity boric acid products .

The composite additive is a combination of sulfide and ammonia water, which are used after pulping.

The sulfide is a combination of any three of ammonium sulfide, barium sulfide, strontium sulfide, potassium sulfide, and sodium sulfide, and its dosage is 15 to 20 times the stoichiometric amount.

The volume ratio concentration of the ammonia water is 5%, and its consumption is 35-45 times of the sulfide by mass ratio.

The specific preparation process of the high-purity boric acid precursor is: weigh the industrial boric acid, add 2 to 3 times the water according to the mass ratio, stir at a temperature of 25 to 35°C for 20 to 30 minutes, and obtain High-purity boric acid precursor.

The mother liquor after solid-liquid separation contains H ₃ BO ₃ 55-75g/L, which can be returned to the water immersion treatment process for recycling. When the Ca content in it accumulates to nearly 500mg/L, it can be used to prepare industrial boric acid Or the raw material of calcium borate.

The specific preparation process of the high-purity boric acid product is: Dissolving the high-purity boric acid precursor in pure water, stirring and dissolving at a temperature of 90-100°C to obtain a boric acid solution, adding ammonia water to adjust the pH value of the solution to 5.0-5.3 , then add compound additives to react for 15-20 minutes, filter to obtain a purified solution; then maintain the temperature of the purified solution at 85-95°C, add hydrogen peroxide, and stir for 25-30 minutes to convert excess S ^2- into elemental sulfur or SO ₄ ^2- After filtering, add nitric acid with a concentration of 40-45wt% to the filtrate, adjust the pH value of the solution to 3.5-4.0, stir, cool and crystallize until the temperature is 25°C-30°C, separate solid-liquid, and then wash with pure water The boric acid crystals are dehydrated and dried at 65°C to obtain high-purity boric acid products.

The purification solution contains 240-280 g/L of H ₃ BO ₃ and 0.10-0.2 mg/L of Fe. Pb 0.10～0.15 mg/L. The leaching solution before iron removal contains 4-8 mg/L of iron and 1.0-2.0 mg/L of Pb.

The added amount of the hydrogen peroxide is 0.6-0.8% of the volume of the boric acid solution.

The high-purity boric acid product has Na content <30×10 ^-6 , Fe content <5×10 ^-6 , and Pb content <1×10 ^-6 .

The preparation method of embodiment 6 nuclear grade high-purity boric acid

First, the high-purity boric acid obtained in Example 5 without drying treatment is dissolved in pure water at a temperature of 80°C to 95°C to prepare a boric acid solution containing H ₃ BO _180g /L to 250g/L, and then in Add ammonium nitrate or ammonium acetate at 2.5-3.5g/L to the solution, heat-preserve and filter, stir mechanically, cool and crystallize to a final temperature of 15°C-30°C, recrystallize 1-2 times, then centrifuge, dry, and pack. get the product.

The preparation of embodiment 7 high-purity boric acid precursor

Raw material industrial boric acid contains Ca 0.06%, Mg 0.05%, Na 0.035%, Fe  0.0052%, Pb  0.001%. Used in Examples 7.1 to 7.4 below.

Example 7.1 Take 1000.0g of industrial boric acid, add it to 4000mL of water at a temperature of 10°C, stir for 60 minutes, filter, and dry at 65°C to obtain 867.1g of high-purity boric acid precursor; after analysis, its Ca content is 0.03%, and its Mg content is 0.009%, the Na content is 0.021%, and the Fe content is 0.0043%. The Ca removal rate was 56.65%, the Mg removal rate was 84.39%, the Na removal rate was 47.97%, the Fe removal rate was 28.30%, and the B ₂ O ₃ recovery rate was 86.71%.

Example 7.2 Take 1000.0g of industrial boric acid, add it to 2000mL of water at 20°C, stir for 20 minutes, filter, and dry at 65°C to obtain 909.6g of high-purity boric acid precursor; after analysis, its Ca content is 0.028%, and Mg content is 0.010%, the Na content is 0.024%, and the Fe content is 0.0045%. The Ca removal rate was 57.55%, the Mg removal rate was 81.81%, the Na removal rate was 37.63%, the Fe removal rate was 18.14%, and the B ₂ O ₃ recovery rate was 90.96%.

Example 7.3 Take 1000.0g of industrial boric acid, add it to 1500mL of water at 35°C, stir for 40 minutes, filter, and dry at 65°C to obtain 914.1g of high-purity boric acid precursor; after analysis, its Ca content is 0.031%, and Mg content is 0.011%, Na content is 0.025%, and Fe content is 0.0046%. The Ca removal rate was 52.77%, the Mg removal rate was 79.89%, the Na removal rate was 34.71%, the Fe removal rate was 15.90%, and the B ₂ O ₃ recovery rate was 91.41%.

Example 7.4 Take 1000.0g of industrial boric acid, add it to 3000mL of water at 15°C, stir for 30 minutes, filter, and dry at 65°C to obtain 881.2g of high-purity boric acid precursor; after analysis, its Ca content is 0.029%, and Mg content is 0.010%, the Na content is 0.023%, and the Fe content is 0.0043%. The Ca removal rate was 55.48%, the Mg removal rate was 82.38%, the Na removal rate was 42.09%, the Fe removal rate was 27.13%, and the B ₂ O ₃ recovery rate was 88.12%.

The preparation of embodiment 8 high-purity boric acid product

Take 850.0 g of the high-purity boric acid precursors prepared in Examples 7.1-7.4 in Example 7, and mix them thoroughly. Sampling analysis showed that the content of H ₃ BO ₃ was 99.53%, the content of Ca was 0.030%, the content of Mg was 0.010%, the content of Na was 0.023%, the content of Fe was 0.0044%, and the content of Pb was 0.0008%. Used in Examples 8.1 to 8.4 below.

Example 8.1 Take 400.0g of the above mixed high-purity boric acid precursor and dissolve it in pure water at a temperature of 80°C to obtain H ₃ BO ₃ content of 180.05 g/L, Fe content of 8.0 mg/L, and Pb content of 1.5 mg /L solution 2210ml. At a temperature of 80°C to 85°C, add an appropriate amount of ammonia water to adjust the pH value of the solution to 5.3, and then add 0.87g of industrial barium sulfide with a BaS content of 66% (10 times the chemical reaction formula, adjust with 26ml of 5% ammonia water) slurry), stirred and reacted for 30min, then heated to 95°C, filtered to obtain 2185ml of purified solution.

The purification solution contains H ₃ BO ₃ 182.1g/L, Fe 0.22mg/L, and Pb 0.21mg/L. At a temperature of 80°C to 85°C, add 4.5ml of hydrogen peroxide, stir for 20min, and filter. Add dilute nitric acid with a concentration of 42% to the filtrate to adjust the pH value of the solution to 4.0, stir, cool and crystallize to 15°C, filter, wash boric acid with 160ml of pure water, then dehydrate, and dry at 68°C to obtain high-purity boric acid product 320.6 g, the high-purity boric acid contains Fe 2.6×10 ^-6 , Pb 1.7×10 ^-6 , and Na 15×10 ^-6 .

The yield of boric acid crystallization in this example was 80.16%.

Crystal mother liquor 1749ml, containing H ₃ BO ₃ 41.7g/L. Product lotion 165ml, containing H ₃ BO ₃ 41.2g/L.

Example 8.2 Take 400.0g of the above-mentioned high-purity boric acid precursor and dissolve it in pure water at a temperature of 90°C to obtain a compound with a H ₃ BO ₃ content of 240.16 g/L, a Fe content of 10.7 mg/L, and a Pb content of 1.9 mg/L. Solution 1658ml. At a temperature of 90°C to 95°C, add an appropriate amount of ammonia water to adjust the pH value of the solution to 5.0, and then add 2.61g of industrial barium sulfide with a BaS content of 66% (30 times the chemical reaction formula, adjust with 105ml of 5% ammonia water) slurry), stirred and reacted for 15min, filtered to obtain 1660ml of purified solution.

The purification solution contains Fe 0.10mg/L and Pb 0.11mg/l. At a temperature of 90°C to 95°C, add 16ml of hydrogen peroxide, stir for 20 minutes, and filter. Add dilute nitric acid with a concentration of 42% to the filtrate to adjust the pH value of the solution to 2.5, stir, cool and crystallize to 20°C, filter, wash boric acid with 160ml of pure water, then dehydrate, and dry at 65°C to obtain high-purity boric acid product 328.1 g, the high-purity boric acid contains Fe 1.0×10 ^-6 , Pb 0.7×10 ^-6 , and Na 16×10 ^-6 .

The yield of boric acid crystallization in this example was 82.03%.

Crystallization mother liquor 1290ml, containing H ₃ BO ₃ 48.22g/L. Product lotion 166ml, containing H ₃ BO ₃ 47.56g/L.

Example 8.3 Take 400.0g of the above-mentioned high-purity boric acid precursor, dissolve it in pure water at a temperature of 95°C, and obtain a compound with a H ₃ BO ₃ content of 280.0 g/L, a Fe content of 12.5 mg/L, and a Pb content of 2.3 mg/L. Solution 1421ml. At a temperature of 90°C to 95°C, add an appropriate amount of ammonia water to adjust the pH of the solution to 5.1, and then add 0.88g of industrial sodium sulfide with a Na ₂ S content of 60.0% (20 times the chemical reaction formula, and 53ml of 5% Ammonia water mixing), stirring and reacting for 20 minutes, and filtering to obtain 1406ml of purified solution.

The purification solution contains Fe0.21mg/L and Pb0.15mg/L. At a temperature of 90°C to 95°C, add 10ml of hydrogen peroxide, stir for 20min, and filter. Add dilute nitric acid with a concentration of 42% to the filtrate to adjust the pH value of the solution to 3.0, stir, cool and crystallize to 30°C, filter, wash boric acid with 160ml of pure water, then dehydrate, and dry at 68°C to obtain high-purity boric acid product 324.1 g, the high-purity boric acid contains 1.8×10 ^-6 Fe, 0.9×10 ^-6 Pb and 33×10 ^-6 Na.

The yield of boric acid crystallization in this example was 81.03%.

Crystallization mother liquor 1035ml, containing H ₃ BO ₃ 62.85g/l. Product lotion 165ml, containing H ₃ BO ₃ 62.60g/l.

Example 8.4 Take 400.0g of high-quality industrial boric acid (the main impurities are Ca 0.019%, Mg 0.010%, Na 0.022%, Fe 0.0015%, Pb 0.0007%), and dissolve it in pure water at a temperature of 90°C to obtain H ₃ BO ₃ 1660ml of a solution with a content of 240.20 g/L, a Fe content of 3.6 mg/L, and a Pb content of 1.7 mg/L. At a temperature of 90°C to 95°C, add an appropriate amount of ammonia water to adjust the pH of the solution to 5.1, and then add 0.86g of industrial barium sulfide with a BaS content of 66% (30 times the chemical reaction formula, adjust with 35ml of 5% ammonia water) slurry), stirred and reacted for 15min, filtered to obtain 1660ml of purified solution.

The purification solution contains Fe 0.15mg/L and Pb 0.12mg/l. At a temperature of 90°C to 95°C, add 6ml of hydrogen peroxide, stir for 20 minutes, and filter. Add dilute nitric acid with a concentration of 42% to the filtrate to adjust the pH value of the solution to 3.0, stir, cool and crystallize to 20°C, filter, wash boric acid with 150ml of pure water, then dehydrate, and dry at 65°C to obtain high-purity boric acid product 328.7 g, the high-purity boric acid contains Fe 1.4×10 ^-6 , Pb 0.7×10 ^-6 , and Na 14×10 ^-6 .

The output rate of boric acid crystallization in this example was 82.18%.

Crystallization mother liquor 1293ml, containing H ₃ BO ₃ 48.19g/L. Product lotion 155ml, containing H ₃ BO ₃ 47.70g/L.

Example 8.5 Referring to the experimental conditions and methods of Example 8.1, high-purity boric acid precursors were used as raw materials, and different sulfides and their combinations were used to prepare high-purity boric acid products. The main impurities of the high-purity boric acid products are shown in Table 1.

It can be seen that in the high-purity boric acid products prepared by using different composite additives described in the present invention, the Na content of the boric acid product is <40×10 ^-6 , the Fe content is <3×10 ^-6 , and the Pb content is <2×10 ^-6 .

Example 9 Preparation of nuclear-grade high-purity boric acid product by recrystallization of high-purity boric acid

Each of the 8 high-purity boric acid products obtained in Example 8.1-8.3 and Example 8.5 in Example 8 is 300g, 2400g in total, and fully mixed. Its H ₃ BO ₃ content is 99.85%, and the main impurities are Fe 1.9×10 ^{-6 ,} Na 19×10 ^-6 , Ca 18×10 ^-6 , Mg 6×10 ^-6 , Pb 1.0×10 ^-6 , SO ₄ ^2- 22×10 ^-6 , used in Examples 9.1-9.3.

Example 9.1 Preparation of nuclear-grade high-purity boric acid by one recrystallization

Take 333.0g of high-purity boric acid and 6.5g of ammonium nitrate (analytically pure), and dissolve them in 1590ml of pure water at a temperature of 90°C to 95°C. The resulting boric acid solution contains H ₃ BO ₃ 180.02g/L, NH ₄ NO ₃ 3.5 g/L. After filtration, the temperature is 80°C, add an appropriate amount of nitric acid to adjust the pH of the solution to 4.0, mechanically stir, cool and crystallize until the temperature is 10°C, stir, cool and crystallize for 10 hours, filter, and wash twice with 200ml of pure water. Dry the boric acid crystals at 70°C to obtain 271.52 g of boric acid product ((No. 1 ^# product), the content of Fe is 1.2×10 ^-6 , the content of Ca is 3.5×10 ^-6 , and the content of Mg is 1.0×10 ^-6 , Na content is 3.0×10 ^-6 , SO ₄ ^2- content is 2.5×10 ^-6 , and Cl ^- content is 1×10 ^-6 .

The output rate of boric acid recrystallization in this example was 81.54%.

The above-mentioned impurity indicators in this case have met the requirements of my country's nuclear power plant users for high-purity boric acid.

Example 9.2 Preparation of nuclear-grade high-purity boric acid by secondary recrystallization

Take 333.0g of high-purity boric acid and 6.5g of ammonium acetate (analytically pure), and dissolve them in 1375ml of pure water at a temperature of 90°C to 95°C. The resulting boric acid solution contains H ₃ BO ₃ 204.3g/L, NH ₄ NO ₃ 4.0 g/L. After filtration, at a temperature of 85°C, add an appropriate amount of nitric acid to adjust the pH of the solution to 3.5, stir it mechanically, cool and crystallize to a temperature of 20°C; stir, cool and crystallize for 8 hours, filter, and wash twice with 200ml of pure water. Dry the boric acid crystals at 65°C to obtain 258.7g of boric acid product, with Fe content of 1.2×10 ^-6 , Ca content of 3×10 ^-6 , Na content of 4×10 ^-6 , SO ₄ ^2- content of 2.2 ×10 ^-6 .

Take 235.0g of primary recrystallized high-purity boric acid and 2.1g of ammonium nitrate (analytically pure), and dissolve them in 665ml of pure water at a temperature of 90°C to 95°C. The obtained boric acid solution contains H ₃ BO ₃ 280.0g/L, NH ₄ NO ₃ 2.5g/L. It was mechanically stirred, cooled and crystallized to 20°C (time 6h), filtered, and washed twice with 150ml of pure water. The product was dried at 68°C to obtain 197.5 g of boric acid product (coded as 2 ^# product), with Fe content of 0.7×10 ^-6 , Ca content of 0.9×10 ^-6 , Mg content of 0.5×10 ^-6 , Na The content is 0.8×10 ^-6 , the SO ₄ ^{2 -} content is 1.0×10 ^-6 , and the Cl ^- content is 0.7×10 ^-6 . The above impurity indicators all meet the requirements of my country's nuclear power plant users for high-purity boric acid.

Example 9.3 Treatment of recrystallization mother liquor and washing solution

The initial H ₃ BO ₃ content of the solution used in the recrystallization tests of Examples 9.1 and 9.2 was about 180g/L-280g/L, and the H ₃ BO ₃ content of the mother liquor was about 48g/L when cooled to 20°C. After washing and drying, the single yield of boric acid is about 77.0%, and about 20% of H ₃ BO ₃ exists in the mother liquor, and about 3% of H ₃ BO ₃ exists in the washing solution. In order to improve the recovery rate of boric acid, the crystallization mother liquor and lotion should be returned for use.

The contents of main impurities in each crystallization mother liquor and lotion are shown in Table 2.

Return each mother liquor to use once, that is, raise the temperature of each mother liquor to about 95°C to dissolve the corresponding boric acid raw material, then cool and crystallize according to the aforementioned method, and use the corresponding crystallization washing liquid to wash the product for the first time, and the new washing water consumption is the same as before , carry out secondary recrystallization, and the high-purity acid product produced (No. 3 ^# product) has Fe content of 0.8× ^10-6 , Ca content of 1.3× ^10-6 , Mg content of 0.8× ^10-6 , Na The content is 1.0×10 ^-6 , and the SO ₄ ^2- content is 1.5×10 ^-6 . The above-mentioned impurity content also meets the quality requirements of nuclear power users for high-purity boric acid.

After recycling twice, the first crystallization mother liquor and the first crystallization washing solution can be used as the medium for the preparation of the boric acid precursor (the first crystallization mother liquor can also be used as the raw material for the preparation of low-iron boric acid), and the first recrystallization mother liquor can be used as the next Circulate the solvent medium for the first crystallization; the primary recrystallization washing solution and the secondary recrystallization mother liquor are used as the solvent medium for the first recrystallization in the next cycle; the secondary recrystallization is carried out, and the high-purity acid product produced ( No. 4 ^# product) its Fe content is 0.8×10 ^-6 , Ca content is 1.6×10 ^-6 , Mg content is 1.0×10 ^-6 , Na content is 1.5×10 ^-6 , SO ₄ ^2- content is 1.7 ×10 ^-6 . Such a reciprocating cycle operation, the recrystallization process of boric acid produces high-purity boric acid, and the direct recovery rate of H ₃ BO ₃ can reach about 80%.

The nuclear grade high-purity boric acid product quality index that embodiment 9 makes is shown in Table 3.

It can be seen from Table 3:

1. The impurity content of the prepared high-purity boric acid is in line with the quality requirements of my country's nuclear industry users for high-purity boric acid.

2. It is known that the nuclear-grade high-purity boric acid imported from abroad has an abundance of ¹⁰ B > 19.6%. After testing, the ¹⁰ B abundance of the nuclear-grade high-purity boric acid prepared by the present invention is 19.61% to 19.65%, and ^{the 10} B content of the product meets the requirements.

Claims (10)

1. a preparation method of high-purity boric acid is characterized in that: comprise the following processing steps: 1) Slurry industrial boric acid with water, stir to remove calcium, magnesium, and sodium impurities, and obtain high-purity boric acid precursor after solid-liquid separation; 2) Dissolve the high-purity boric acid precursor in pure water at a temperature of 80°C to 100°C to prepare a boric acid solution containing 180g/L to 280g/L of H ₃ BO ₃ . After filtration, cooling and crystallization, solid-liquid separation, washing and drying, the high-purity boric acid product can be obtained. 2. The preparation method of high-purity boric acid according to claim 1, characterized in that: the high-purity boric acid that has not been dried in step 2) is dissolved in pure water, and recrystallized, dehydrated, and dried for 1 to 2 times, That is to obtain nuclear-grade high-purity boric acid products. 3. according to the preparation method of the described high-purity boric acid of claim 1, it is characterized in that: described composite additive is the combination of sulfide and ammoniacal liquor, and both are used after pulping. 4. according to the preparation method of the described high-purity boric acid of claim 1, it is characterized in that: described sulfide is any one in ammonium sulfide, barium sulfide, strontium sulfide, potassium sulfide, sodium sulfide, or any two or A combination of the three, and the amount of sulfide is 10 to 30 times the stoichiometric amount. 5. The method for preparing high-purity boric acid according to claim 1, characterized in that: the volume ratio concentration of the ammonia water is 5%, and its consumption is 30 to 60 times that of the sulfide by mass ratio. 6. according to the preparation method of the described high-purity boric acid of claim 1, it is characterized in that: the concrete preparation process of described high-purity boric acid precursor is: industrial boric acid is weighed, add 1.5～4 times pure water by mass ratio, Stir at a temperature of 10-35° C. for 20-60 minutes, and obtain a high-purity boric acid precursor after solid-liquid separation. 7. The preparation method of high-purity boric acid according to claim 1, characterized in that: the specific preparation process of the high-purity boric acid product is: adding the high-purity boric acid precursor prepared in step 1) at a temperature of 80°C to 100°C After stirring and dissolving the boric acid solution in pure water at ℃, add ammonia water to adjust the pH value of the solution to 4.6-5.3, then add compound additives to react for 15-30 minutes, filter to obtain the purified solution; then maintain the temperature of the purified solution at 70- Add hydrogen peroxide at 95°C and stir for 15-30 minutes to convert excess S ^2- into elemental sulfur or SO ₄ ^2- . After filtering, add nitric acid with a mass concentration of 40-45% to the filtrate to adjust the pH of the solution to 2.5 ~4.0, stirring, cooling and crystallization until the temperature is 10°C-30°C, solid-liquid separation, then washing boric acid crystals with pure water, after dehydration, drying at 60°C-70°C to obtain high-purity boric acid products; The pure boric acid product has Na content <40×10 ^-6 , Fe content <5×10 ^-6 , and Pb content <2×10 ^-6 . 8. The method for preparing high-purity boric acid according to claim 7, characterized in that: the high-purity boric acid precursor described in step 2) is replaced by superior industrial boric acid, the Ca content of the superior industrial boric acid is <0.032%, Mg content<0.015%, Fe content<0.002%, Na content<0.03%. 9. The method for preparing high-purity boric acid according to claim 7, characterized in that: the amount of hydrogen peroxide added is 0.2-1.0% of the volume of the boric acid solution. 10. The preparation method of high-purity boric acid according to claim 2, characterized in that: the specific preparation process of the nuclear-grade high-purity boric acid product is: first dissolve the high-purity boric acid product in pure water at a temperature of 80°C to 100°C In the process, a boric acid solution containing H ₃ BO ₃ 180g/L～280g/L was prepared, and then ammonium nitrate or ammonium acetate was added to the solution at a rate of 1.5～2.5g/L, and then filtered under heat preservation, and cooled and crystallized under stirring conditions until the final Warm at 10°C to 30°C, and then separate solid and liquid; recrystallize in this way for 1 to 2 times, dry and pack to obtain nuclear-grade high-purity boric acid products.