A method for the precipitation conversion of barium sulfate radium into soluble radium salts

Abstract

The present application relates to nuclear chemical engineering and radionuclide extraction technical field, and disclose a kind of barium sulfate radium precipitation conversion into soluble radium salt method, the method is first to the radium-containing aqueous solution is added soluble barium salt and sulfate radical provider, form barium sulfate radium coprecipitation;The obtained barium sulfate radium solid is mixed with adjuvant and then placed in quartz boat, and reducing gas is introduced, so that insoluble barium sulfate radium is reduced to soluble barium sulfide radium solid, continue to dissolve barium sulfide radium solid in hot water, under alkaline conditions, carbon dioxide is introduced, so that soluble barium sulfide radium is converted into insoluble barium carbonate radium precipitate;Finally, barium carbonate radium solid is dissolved in dilute acid solution under stirring condition, and soluble radium salt solution is obtained, the present application is reduced by using reducing gas, so that soluble radium salt is completely converted and no carbon residue, its process is green and environmentally friendly, suitable for rare earth slag removal dissolving solution, tantalum niobium ore extraction residual liquid and oilfield barite scale in a variety of radium-containing raw materials.

Description

Technical Field

[0001] This invention relates to the fields of nuclear chemical engineering and radionuclide extraction technology, specifically a method for converting barium sulfate radium precipitation into soluble radium salts. Background Technology

[0002] Alpha nuclides, due to their high linear energy transport (LET) and short range, exhibit significant advantages in targeted tumor therapy (TAT) with high lethality, good efficacy, and high safety, and are considered to be the next generation of highly promising nuclides. Among them, Ac-225, due to its suitable half-life and decay characteristics, is expected to become the most promising alpha nuclide, with a projected market size of tens of billions of dollars in the future. However, the global supply of Ac-225 is extremely limited, and no domestic company has yet achieved mass production. The current production level severely restricts the research and development and commercialization of related radiopharmaceuticals. One of the key raw materials for the preparation of Ac-225 is Ra-226, and the stable supply of Ra-226 is one of the critical bottlenecks that urgently need to be solved.

[0003] In industrial production, soluble barium salts are often added during rare earth radium removal processes, along with sulfates, for co-precipitation to form barium radium sulfate (Ba(Ra)SO4) precipitate. Similarly, tantalum and niobium raffinate also contains significant amounts of radium, and the scale produced by oil and gas industry plugging agents is primarily composed of barium radium sulfate. These radium-containing tailings are currently mostly stored as waste in specialized storage facilities, resulting in a significant waste of valuable resources. Barium radium sulfate utilizes the similarity in radius, charge, and crystal structure between radium and barium ions to effectively enrich radium through a eutectic process. However, how to convert insoluble barium radium sulfate back into soluble radium salts remains a key technical challenge in the process.

[0004] Currently, there are two main existing technologies for achieving this conversion: (1) Carbonate conversion method: Barium sulfate radium is added to a high-concentration sodium carbonate solution to convert the sulfate into barium carbonate radium (Ba(Ra)CO3), and then the carbonate is dissolved in hydrochloric acid or nitric acid to obtain a soluble radium salt. (2) Carbon reduction method: Barium sulfate radium is reduced with carbon at high temperature to generate barium radium sulfide (Ba(Ra)S), and then the barium radium sulfide is dissolved in hydrochloric acid or nitric acid to obtain a soluble radium salt.

[0005] However, both of the above methods have significant drawbacks. The carbonate conversion method easily leads to scaling on the reactor walls, incomplete conversion, and requires repeated treatment of insoluble substances, resulting in low efficiency. The carbon reduction method produces toxic hydrogen sulfide (H2S) gas with a strong odor, posing a significant environmental burden, and unreacted carbon is mixed with the products, making post-treatment difficult. Therefore, developing a new barium sulfate-radium conversion method that achieves complete conversion, is environmentally friendly, and produces pure products is of great significance. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] To address the shortcomings of existing technologies, this invention provides a method for converting barium sulfate radium precipitation into soluble radium salts. This method offers advantages such as thorough conversion, avoidance of toxic gas generation, simple post-processing, high product purity, and environmental friendliness. It effectively solves the problems of incomplete reaction, easy scaling, and repeated treatment required in existing carbonate conversion methods, as well as the problems of highly toxic hydrogen sulfide gas, severe odor, significant environmental pressure, and difficulty in separating the product from carbon impurities produced by carbon reduction methods.

[0008] (II) Technical Solution

[0009] To achieve the above objectives, the present invention provides the following technical solution: a method for converting barium sulfate radium precipitate into soluble radium salt, comprising the following steps:

[0010] Step 1: Preparation of barium sulfate-radium coprecipitate: Add soluble barium salt and sulfate donor to a radium-containing aqueous solution to form barium sulfate-radium coprecipitate, i.e., barium sulfate-radium solid;

[0011] Step 2, gas-solid reduction of barium sulfate and radium: After the barium sulfate and radium solid obtained in Step 1 are mixed evenly with the additives, they are placed in a quartz boat. A reducing gas is introduced into a high-temperature tube furnace to reduce the insoluble barium sulfate and radium to soluble barium radium sulfide solid.

[0012] Step 3, hot water dissolution of barium radium sulfide and conversion of barium radium carbonate: The barium radium sulfide solid obtained in step 2 is dissolved in hot water, and then under alkaline conditions, carbon dioxide is introduced to convert the soluble barium radium sulfide into insoluble barium radium carbonate precipitate.

[0013] Step 4: Acid dissolution of barium carbonate and radium: Add the barium carbonate and radium solid obtained in step 3 to a dilute acid solution while stirring until the solid is almost completely dissolved, to obtain a soluble radium salt solution.

[0014] Preferably, in step one: the radium-containing aqueous solution is a rare earth slag removal and conversion dissolving solution, tantalum-niobium ore extraction residue, radium-containing wastewater from phosphate production, or radium-containing wastewater after non-ferrous metal extraction.

[0015] Preferably, in step one: the soluble barium salt is one or more of barium chloride and barium nitrate; the sulfate donor is one or more of sulfuric acid and sulfate; and the alkaline solution is one or more of sodium hydroxide solution, ammonia water, and potassium hydroxide solution.

[0016] Preferably, the preparation process of barium sulfate-radium coprecipitation in step one is as follows:

[0017] S1.1 Heat the radium-containing aqueous solution to 50-90°C, add a soluble barium salt solution and sulfate donor, so that radium and barium form a barium sulfate-radium coprecipitate;

[0018] S1.2 Add alkaline solution to adjust the pH value to 0.5-3.0, maintain the temperature of 50-90℃ for 3-6 hours to allow the eutectic particles to gradually grow, then cool to room temperature at a rate of 1-5℃ / h and stir for 10-20 hours, and filter to obtain barium radium filter cake;

[0019] S1.3 The obtained barium radium filter cake is dried at 50-80℃ for 12-24 hours, and then ground and passed through a 20-40 mesh sieve to obtain barium radium solid.

[0020] Preferably, in step S1.1, radium and barium form a barium sulfate radium coprecipitate, and the chemical equation for this process is as follows:

[0021] (1) Main reaction formula:

[0022]

[0023] In the formula, Barium ions are formed from the ionization of soluble barium salts. Sulfate ions provided for sulfuric acid or sulfates;

[0024] (2) Eutectic reaction:

[0025]

[0026] In the formula, It refers to radium-226 ions in radium-containing aqueous solutions. It is a sulfate ion. Substitution into the BaSO4 lattice , Enter Lattice substitution ;

[0027] (3) The overall reaction equation is expressed as:

[0028]

[0029] In the formula, product It is a barium sulfate-radium mixed crystal coprecipitation.

[0030] Preferably, in step two: the barium radium sulfate solid obtained in step one is mixed evenly with the additive and placed in a quartz boat, which is then placed in a tube furnace. A reducing gas is introduced, with a flow rate controlled at 50-1000 mL / min. The temperature is increased to 800-1200℃ at a heating rate of 10-30℃ / min. After holding at this temperature for 1-4 hours, heating is stopped, and the mixture is allowed to cool naturally to room temperature to obtain barium radium sulfide solid.

[0031] Preferably, the auxiliary agent is alum stone, and the amount used is 0.05% to 0.2% of the mass of barium sulfate radium solid; the reducing gas is one or more of methane, hydrogen, carbon monoxide, and synthesis gas.

[0032] Preferably, the hot water dissolution of barium radium sulfide and the conversion of barium radium carbonate in step three are as follows:

[0033] S2.1 Dissolve the solid barium radium sulfide obtained in step 2 in hot water at 50-100℃ with a liquid-to-solid ratio of (3-8):1. Stir at 100-200 rpm for 2-4 hours and filter while hot to obtain an alkaline filtrate containing soluble barium radium sulfide.

[0034] S2.2. Keep the filtrate at 50-80℃, add sulfide, and adjust the pH to 10.0-12.0 with ammonia.

[0035] S2.3 Finally, carbon dioxide gas is introduced and the reaction is allowed to proceed for 3 to 5 hours. Then, sodium hydroxide is added to adjust the pH value to 12.5 to 14.0. The mixture is then aged at room temperature for 20 to 30 hours. The filter cake obtained after filtration is washed with water and dried to obtain barium carbonate solid.

[0036] Preferably, the sulfide is ammonium sulfide; the mass concentration of ammonia water ranges from 25% to 28%; and the mass concentration of sodium hydroxide ranges from 20% to 30%.

[0037] Preferably, the dilute acid solution in step four is selected from dilute hydrochloric acid or dilute nitric acid solutions with a mass concentration of 2 to 4 mol / L.

[0038] Compared with the prior art, the present invention provides a method for converting barium sulfate radium precipitation into soluble radium salt, which has the following beneficial effects:

[0039] 1. This invention utilizes reducing gases (such as methane and hydrogen) to reduce barium sulfate radium at high temperatures, achieving high reduction efficiency and yielding high-purity barium radium sulfide with no insoluble carbon impurities, thus achieving complete conversion of barium sulfate radium. In subsequent processing, carbon dioxide is introduced under alkaline conditions to generate barium carbonate radium, completely avoiding the problem of highly toxic and malodorous hydrogen sulfide gas generated in traditional acid dissolution processes. Furthermore, the process is safe to operate, has low environmental pressure, and boasts significant green and environmental advantages. Simultaneously, the conversion under alkaline conditions can remove heavy metal impurities such as lead, copper, and zinc, significantly improving the purity of the final radium salt product. This invention has a wide range of applications, capable of treating various radium-containing raw materials such as rare earth slag dissolution solutions, tantalum and niobium ore extraction residues, radium-containing wastewater from phosphate production, and barite scale from oil fields, with a radium recovery rate of 82%–95%. Attached Figure Description

[0040] Figure 1 This is a flowchart of the soluble radium salt conversion process of the present invention. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] Please see Figure 1 A method for converting barium sulfate radium precipitate into soluble radium salt includes the following steps:

[0043] Step 1: Preparation of barium sulfate-radium coprecipitate: Soluble barium salt and sulfate donor are added to a radium-containing aqueous solution. Taking advantage of the similar crystal structure, ionic radius and charge of radium sulfate and barium sulfate, radium ions enter the barium sulfate lattice in a co-crystal form to form an insoluble barium sulfate-radium coprecipitate. This achieves efficient enrichment and separation of radium from dilute solution, obtaining barium sulfate-radium solid, which provides raw material for subsequent gas-solid reduction.

[0044] Step 2, Gas-solid reduction of barium sulfate and radium: After the barium sulfate and radium solid obtained in Step 1 are mixed evenly with the additives, they are placed in a quartz boat. A reducing gas is introduced into a high-temperature tube furnace to reduce the insoluble barium sulfate and radium. ) is reduced to soluble barium radium sulfide ( This process transforms the sparingly soluble sulfate into a readily soluble sulfide, laying the foundation for subsequent hot water dissolution and alkaline conversion.

[0045] Step 3: Hot water dissolution of barium radium sulfide and conversion of barium radium carbonate: The barium radium sulfide solid obtained in Step 2 is dissolved in hot water. Taking advantage of the water solubility of barium radium sulfide, it is separated from alum, unreacted raw material barium sulfate, and insoluble impurities such as lead sulfide and copper sulfide. Then, under alkaline conditions, carbon dioxide is introduced to convert the soluble barium radium sulfide into insoluble barium radium carbonate precipitate. This process is carried out entirely in an alkaline environment, which can effectively avoid the generation of toxic hydrogen sulfide (H2S) gas, and at the same time remove metallic impurities such as lead, copper, and zinc, achieving further purification and enrichment of radium.

[0046] Step 4: Acid dissolution of barium carbonate and radium: The barium carbonate and radium solid obtained in Step 3 is slowly added to a dilute acid solution under stirring until the solid is almost completely dissolved, thus obtaining a soluble radium salt solution.

[0047] Specifically, in step one: the radium-containing aqueous solution is a rare earth slag removal and conversion dissolving solution, tantalum-niobium ore extraction residue, radium-containing wastewater from phosphate production, or radium-containing wastewater after non-ferrous metal extraction; the soluble barium salt is one or more of barium chloride and barium nitrate; the sulfate provider is one or more of sulfuric acid and sulfate; and the alkaline solution is one or more of sodium hydroxide solution, ammonia water, and potassium hydroxide solution.

[0048] Specifically, in step one: the soluble barium salt is one or more of barium chloride and barium nitrate; the sulfate donor is one or more of sulfuric acid and sulfate; and the alkaline solution is one or more of sodium hydroxide solution, ammonia water, and potassium hydroxide solution.

[0049] Specifically, the preparation process of barium sulfate-radium coprecipitation in step one:

[0050] S1.1. The radium-containing aqueous solution is heated to 50–90°C, and a soluble barium salt solution and sulfate donor are added to form a barium sulfate-radium coprecipitate. The main chemical equation for this process is:

[0051] (1) Main reaction formula (barium precipitation):

[0052]

[0053] In the formula, Barium ions are the ions produced by the ionization of soluble barium salts (such as barium chloride and barium nitrate). Sulfate ions provided for sulfuric acid or sulfates;

[0054] (2) Eutectic reaction (radium entering the crystal lattice):

[0055]

[0056] In the formula, It refers to radium-226 ions in radium-containing aqueous solutions. It is a sulfate ion. Substitution into the BaSO4 lattice , Enter Lattice substitution ;

[0057] (3) The overall reaction equation is expressed as:

[0058]

[0059] In the formula, Barium ions, It is a radium ion. It is a sulfate ion, and the product is... It is a co-precipitation of barium sulfate and radium;

[0060] S1.2 Add alkaline solution to adjust the pH value to 0.5-3.0, maintain the temperature of 50-90℃ for 3-6 hours to allow the eutectic particles to gradually grow, then cool to room temperature at a rate of 1-5℃ / h and stir for 10-20 hours, and filter to obtain barium radium filter cake;

[0061] S1.3 The obtained barium radium filter cake is dried at 50-80℃ for 12-24 hours, and then ground and passed through a 20-40 mesh sieve to obtain barium radium solid.

[0062] The advantages are: by adjusting the pH value to a weakly acidic environment of 0.5 to 3.0 and using a slow cooling and stirring process, barium sulfate and radium sulfate can be effectively promoted to form uniform and dense eutectic particles. The precipitated particles are large and easy to filter, and the co-precipitation enrichment rate of radium can reach more than 95%. By using the barium salt co-precipitation method, extremely low concentrations of radium ions (ppm or even ppb level) can be efficiently enriched from complex aqueous solutions to the solid phase, thus providing a high-concentration and high-purity raw material basis for subsequent conversion. Moreover, the process is simple to operate, has low equipment requirements, and can be applied to a variety of radium-containing industrial waste liquids.

[0063] Specifically, in step two: the barium radium sulfate solid obtained in step one is mixed evenly with the auxiliary agent and placed in a quartz boat, which is then placed in a tube furnace. A reducing gas is introduced, with the flow rate controlled at 50–1000 mL / min. The temperature is increased to 800–1200℃ at a rate of 10–30℃ / min. After holding at this temperature for 1–4 hours, heating is stopped, and the mixture is allowed to cool naturally to room temperature to obtain barium radium sulfide solid. The auxiliary agent is alum stone, and its dosage is 0.05%–0.2% of the mass of the barium radium sulfate solid. The reducing gas is one or more of methane, hydrogen, carbon monoxide, and synthesis gas.

[0064] The advantages are: by adopting the gas-solid reduction method, using reducing gases such as methane and hydrogen instead of traditional solid carbon reducing agents, there is no solid carbon residue after the reaction, and the product, barium radium sulfide, has higher purity, making it easier to dissolve in hot water later; the reduction reaction is carried out in a closed tube furnace, making the gas flow controllable and ultimately greatly improving the reduction efficiency (conversion rate can reach over 90%). Because the reaction temperature inside the tube is uniform, local overheating or incomplete reduction can be effectively avoided; compared with the carbon reduction method, the method of this invention does not produce mixed solid residues, and there is no need to separate carbon powder from the subsequent solution, simplifying the post-processing process.

[0065] Specifically, the hot water dissolution of barium radium sulfide and the conversion of barium radium carbonate in step three:

[0066] S2.1 Dissolve the barium radium sulfide solid obtained in step two in hot water at 50-100℃ with a liquid-to-solid ratio of (3-8):1. Stir at 100-200 rpm for 2-4 hours and filter while hot to remove insoluble impurities (mainly alum stone residue, a small amount of unconverted barium sulfate, lead sulfide, and copper sulfide, etc.) to obtain an alkaline filtrate containing soluble barium radium sulfide (main components are Ba²⁺, Ra²⁺, HS⁻, S²⁻ and OH⁻).

[0067] S2.2. Keep the filtrate at 50-80℃, add sulfide, and adjust the pH to 10.0-12.0 with ammonia.

[0068] S2.3 Finally, carbon dioxide gas is introduced and the reaction is allowed to proceed for 3 to 5 hours. Then, sodium hydroxide is added to adjust the pH value to 12.5 to 14.0. The mixture is then aged at room temperature for 20 to 30 hours. The filter cake obtained after filtration is washed with water and dried to obtain barium carbonate solid.

[0069] Specifically, the sulfide is one or more of sodium sulfide, potassium sulfide, and ammonium sulfide, preferably ammonium sulfide; the mass concentration of ammonia water is in the range of 25% to 28% (this range is concentrated ammonia water); and the mass concentration of sodium hydroxide is in the range of 20% to 30%.

[0070] The advantages are: this invention does not directly dissolve barium radium in acid after it has dissolved, but instead first introduces carbon dioxide under alkaline conditions to convert it into barium radium carbonate precipitate, thus completely avoiding the production of highly toxic and foul-smelling hydrogen sulfide by direct acid dissolution of barium radium in traditional processes. The gas problem ensures high operational safety and low environmental pressure. At the same time, alkaline conditions can promote the formation of sulfide or hydroxide precipitates of heavy metal impurities such as lead, copper, and zinc, which can be filtered out and removed, thereby effectively purifying radium products, which is in line with the concept of green chemical industry.

[0071] In step four, the dilute acid solution is selected from either dilute hydrochloric acid or dilute nitric acid solution with a mass concentration of 2-4 mol / L. During the operation, barium carbonate radium solid must be added slowly while stirring to control the reaction rate and prevent boiling or splashing caused by the large amount of carbon dioxide generated. After the solid is almost completely dissolved, a soluble radium salt solution (radium chloride or radium nitrate) is obtained. This solution can be directly used for further enrichment and purification of radium or as a raw material for the preparation of Ac-225 nuclide target material.

[0072] The method of this invention can be effectively applied to the treatment of various radium-containing raw materials such as rare earth slag removal dissolution liquid, tantalum and niobium ore extraction residue, radium-containing wastewater from phosphate production, and barite scale from oil fields.

[0073] The present invention will be verified below with reference to the embodiments:

[0074] Example 1 (Extraction of radium from rare earth slag conversion solution)

[0075] Take 1L of rare earth slag removal and conversion solution, heat to 50-90℃, add barium chloride dihydrate solution (12g dissolved in 40mL of pure water), then add sulfuric acid solution (volume ratio 1:1). A white precipitate will continuously form. Then add alkaline solution (sodium hydroxide solution, ammonia water, potassium hydroxide solution, etc.) to adjust the pH value to between 0.5 and 3.0. Maintain the reaction at this temperature for 3-6 hours to allow the eutectic particles to gradually grow. Then slowly cool to room temperature and stir for 16 hours. Filter. The main component of the obtained solid is barium sulfate and radium. Dry the filter cake in a forced-air drying oven at 50-80℃, then transfer it to a desiccator to cool to room temperature. After drying, the solid is ground and passed through a 30-mesh sieve and then used directly in the next reaction.

[0076] Take 10g of barium sulfate radium solid and 10mg of alum stone, mix them well and add them to a quartz boat. Then place the boat in a tube furnace, connect a gas flow meter and a gas cylinder, and start to introduce reducing gas (methane, hydrogen, etc.). Set the flow rate to 50mL to 1000mL / min, open the gas valve of the gas cylinder, and heat the tube furnace to 900℃ (heating rate controlled at 20℃ / min). After reaching the temperature, keep it at that temperature for 1-4 hours, then stop heating and let it cool to room temperature.

[0077] Remove the quartz boat and dissolve the obtained solid in water at 50-100℃ (preferably 60℃) with a liquid-to-solid ratio of 5:1. After stirring for 3 hours, filter while hot to remove insoluble impurities. Keep the filtrate at 60℃ and add sulfides (sodium sulfide, potassium sulfide, ammonium sulfide, etc., preferably ammonium sulfide). Add ammonia to adjust the pH to 11.0, then introduce carbon dioxide and react fully for 4 hours. Then add sodium hydroxide to adjust the pH to 13.5, cool to room temperature and age for 24 hours. Filter, wash the filter cake with water, dry, and weigh to obtain 6.4g.

[0078] The obtained solid was dissolved in 3 mol / L hydrochloric acid or 3 mol / L nitric acid. During the process, a large number of bubbles will emerge. The solution needs to be added slowly while stirring until the solid is almost completely dissolved. A total of 32 mL of radium-containing solution was obtained, which can be used for further enrichment and purification.

[0079] After dilution, the radon was measured using an HD-2012 fully automated radon and radium analyzer. 0.2 mL of the filtrate was taken, diluted to 20 mL (100-fold dilution), and sealed in a diffuser. After seven days of sealing, the generated radon gas was transferred to a scintillation chamber and tested using an HD-2012 fully automated radium and radon analyzer (N240046). After two experimental verifications, the radium recovery rates were 93% and 94.5%, respectively, which is quite satisfactory.

[0080] Table 1: Results of Radium Content Test in Parallel Experiments of Rare Earth Slag Removal Dissolving Solution

[0081]

[0082] Results Analysis: Example 1 shows that the method of the present invention has excellent radium recovery effect on radium-containing waste liquid in the rare earth industry, with a recovery rate of over 93%, proving that the process has good applicability and stability in the field of rare earth waste liquid treatment.

[0083] Example 2 (Extraction of radium from low specific activity tantalum-niobium ore extraction residue)

[0084] Take 5L of tantalum-niobium ore extraction residue (low specific activity), heat to 50-90℃, add barium chloride dihydrate solution (24g dissolved in 80mL of pure water), then add sulfuric acid solution (volume ratio 1:1). A white precipitate will continuously form. Then add alkaline solution (sodium hydroxide solution, ammonia water, potassium hydroxide solution, etc.) to adjust the pH value to between 0.5 and 3.0. Maintain the reaction at this temperature for 3-6 hours to allow the eutectic particles to gradually grow. Then slowly cool to room temperature and stir for 16 hours. Filter. The main component of the obtained solid is barium sulfate and radium. Dry the filter cake in a forced-air drying oven at 50-80℃, then transfer it to a desiccator to cool to room temperature. After drying, the solid is ground and passed through a 30-mesh sieve and then used directly in the next reaction.

[0085] Take 10g of barium sulfate radium solid and 10mg of alum stone, mix them well and add them to a quartz boat. Then place the boat in a tube furnace, connect a gas flow meter and a gas cylinder, and start to introduce reducing gas (methane, hydrogen, etc.). Set the flow rate to 50mL to 1000mL / min, open the gas valve of the gas cylinder, and heat the tube furnace to 900℃ (heating rate controlled at 20℃ / min). After reaching the temperature, keep it at that temperature for 1-4 hours, then stop heating and let it cool to room temperature.

[0086] Remove the quartz boat and dissolve the obtained solid in water at 50-100℃ (preferably 60℃) with a liquid-to-solid ratio of 5:1. After stirring for 3 hours, filter while hot to remove insoluble impurities. Keep the filtrate at 60℃ and add sulfides (sodium sulfide, potassium sulfide, ammonium sulfide, etc., preferably ammonium sulfide). Add ammonia to adjust the pH to 11.0, then introduce carbon dioxide and react fully for 4 hours. Then add sodium hydroxide to adjust the pH to 13.5, cool to room temperature and age for 24 hours. Filter, wash the filter cake with water, dry, and weigh to obtain 6.6g.

[0087] The obtained solid was dissolved in 3 mol / L hydrochloric acid or 3 mol / L nitric acid. During the process, a large number of bubbles will emerge. The solution needs to be added slowly while stirring until the solid is almost completely dissolved. A total of 32 mL of radium-containing solution was obtained, which can be used for further enrichment and purification.

[0088] After dilution, the radon and radium were measured using an HD-2012 fully automated radon and radium analyzer. A 0.2 mL sample of the filtrate was diluted to 20 mL (100-fold dilution) and sealed in a diffuser. After seven days of sealing, the generated radon gas was transferred to a scintillation chamber and tested using an HD-2012 fully automated radium and radon analyzer (N240046). The radium recovery rate was 89.4%.

[0089] Table 2: Results of Radium Content Test in Low Specific Activity Tantalum-Niobium Ore Extraction Residue

[0090]

[0091] Results Analysis: Example 2 shows that the method of the present invention is also applicable to the extraction residue of tantalum-niobium ore with low specific activity. Although the radium concentration of the raw material is low, a recovery rate of nearly 90% can still be achieved, proving that the method has a good enrichment ability for low-concentration radium-containing wastewater.

[0092] Example 3 (Extraction of radium from high specific activity tantalum-niobium ore extraction residue)

[0093] Take 2L of tantalum-niobium ore extraction residue (with high specific activity), heat it to 50-90℃, add barium chloride dihydrate solution (12g dissolved in 40mL of pure water), then add sulfuric acid solution (volume ratio 1:1). A white precipitate will continuously form. Then add alkaline solution (sodium hydroxide solution, ammonia water, potassium hydroxide solution, etc.) to adjust the pH value to between 0.5 and 3.0. Maintain the reaction at this temperature for 3-6 hours to allow the eutectic particles to gradually grow. Then slowly cool to room temperature and stir for 16 hours. Filter. The main component of the obtained solid is barium sulfate and radium. Dry the filter cake in a forced-air drying oven at 50-80℃, then transfer it to a desiccator to cool to room temperature. After drying, the solid is ground and passed through a 30-mesh sieve before being used directly in the next reaction.

[0094] Take 10g of barium sulfate radium solid and 10mg of alum stone, mix them well and add them to a quartz boat. Then place the boat in a tube furnace, connect a gas flow meter and a gas cylinder, and start to introduce reducing gas (methane, hydrogen, etc.). Set the flow rate to 50mL to 1000mL / min, open the gas valve of the gas cylinder, and heat the tube furnace to 900℃ (heating rate controlled at 20℃ / min). After reaching the temperature, keep it at that temperature for 1-4 hours, then stop heating and let it cool to room temperature.

[0095] Remove the quartz boat and dissolve the obtained solid in water at 50-100℃ (preferably 60℃) with a liquid-to-solid ratio of 5:1. After stirring for 3 hours, filter while hot to remove insoluble impurities. Keep the filtrate at 60℃ and add sulfides (sodium sulfide, potassium sulfide, ammonium sulfide, etc., preferably ammonium sulfide). Add ammonia to adjust the pH to 11.0, then introduce carbon dioxide and react fully for 4 hours. Then add sodium hydroxide to adjust the pH to 13.5, cool to room temperature and age for 24 hours. Filter, wash the filter cake with water, dry, and weigh to obtain 6.3g.

[0096] The obtained solid was dissolved in 3 mol / L hydrochloric acid or 3 mol / L nitric acid. During the process, a large number of bubbles will emerge. The solution needs to be added slowly while stirring until the solid is almost completely dissolved. A total of 31 mL of radium-containing solution was obtained, which can be used for further enrichment and purification.

[0097] After dilution, the radon was measured using an HD-2012 fully automated radon and radium analyzer. A 0.2 mL sample of the filtrate was diluted to 20 mL (100-fold dilution) and sealed in a diffuser. After seven days of sealing, the generated radon gas was transferred to a scintillation chamber and tested using an HD-2012 fully automated radium and radon analyzer (N240046). The radium recovery rate was 91.2%.

[0098] Table 3: Results of Radium Content Test in High Specific Activity Tantalum-Niobium Ore Extraction Residue

[0099]

[0100] Results Analysis: Example 3 shows that for tantalum-niobium ore extraction residue with high specific activity, the method of the present invention can still stably achieve a radium recovery rate of over 91%, indicating that the method has good adaptability and stability to raw materials with different levels of radioactivity.

[0101] Example 4 (Extraction of radium from barite scale in oil fields)

[0102] Take 20g of oilfield barite scale (mainly composed of barium sulfate and radium), add 40mL of purified water, stir for 1 hour and then filter. Dry the filter cake in a forced-air drying oven at 50-80℃, then transfer it to a desiccator to cool to room temperature. After drying, the solid is ground through a 30-mesh sieve and then used directly in the next step of the reaction.

[0103] Take 10g of the treated barite scale solid and 10mg of alum stone, mix them well and add them to a quartz boat. Then place the boat in a tube furnace, connect a gas flow meter and a gas cylinder, and start introducing reducing gas (methane, hydrogen, etc.) at a flow rate of 50mL to 1000mL / min. Open the gas valve of the gas cylinder and heat the tube furnace to 900℃ (heating rate controlled at 20℃ / min). After reaching the temperature, keep it at that temperature for 1-4 hours, then stop heating and let it cool to room temperature.

[0104] Remove the quartz boat and dissolve the obtained solid in water at 50-100℃ (preferably 60℃) with a liquid-to-solid ratio of 5:1. After stirring for 3 hours, filter while hot to remove insoluble impurities. Keep the filtrate at 60℃ and add sulfides (sodium sulfide, potassium sulfide, ammonium sulfide, etc., preferably ammonium sulfide). Add ammonia to adjust the pH to 11.0, then introduce carbon dioxide and react fully for 4 hours. Then add sodium hydroxide to adjust the pH to 13.5, cool to room temperature and age for 24 hours. Filter, wash the filter cake with water, dry, and weigh to obtain 6.3g.

[0105] The obtained solid was dissolved in 3 mol / L hydrochloric acid or 3 mol / L nitric acid. During the process, a large number of bubbles will emerge. The solution needs to be added slowly while stirring until the solid is almost completely dissolved. A total of 32 mL of radium-containing solution was obtained, which can be used for further enrichment and purification.

[0106] After dilution, the radon was measured using an HD-2012 fully automated radon and radium analyzer. A 0.2 mL sample of the filtrate was diluted to 20 mL (100-fold dilution) and sealed in a diffuser. After seven days of sealing, the generated radon gas was transferred to a scintillation chamber and tested using an HD-2012 fully automated radium and radon analyzer (N240046). The radium recovery rate was 82.5%.

[0107] Table 4: Results of Radium Content Test in High Specific Activity Tantalum-Niobium Ore Extraction Residue

[0108]

[0109] Note: The specific activity test results of barite scale solids were obtained from high-purity germanium gamma spectrometer measurements.

[0110] Results Analysis: Example 4 shows that the method of the present invention is not only applicable to aqueous system, but can also directly treat solid radium-containing waste residue (such as barite scale in oil fields). Although the recovery rate is slightly lower than that of aqueous system (mainly because the radium in the solid raw material is wrapped in a dense lattice, making reduction and dissolution more difficult), it can still achieve a recovery rate of more than 82%, which can provide a feasible way for the resource utilization of radium-containing waste residue in oil fields.

[0111] In summary, this invention successfully converts sparingly soluble barium radium sulfate into soluble radium chloride or radium nitrate solution through four steps: co-precipitation enrichment → gas-solid reduction → hot water dissolution and alkaline conversion → acid dissolution. This not only provides a feasible, efficient, and environmentally friendly technical solution for the resource utilization of radium-containing waste and the preparation of high-purity radium salts, but also provides a stable and reliable radium-226 raw material guarantee for the preparation of α nuclides such as Ac-225.

[0112] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for converting barium sulfate radium precipitate into soluble radium salt, characterized in that, Includes the following steps: Step 1: Preparation of barium sulfate-radium coprecipitate: Add soluble barium salt and sulfate donor to a radium-containing aqueous solution to form barium sulfate-radium coprecipitate, i.e., barium sulfate-radium solid; Step 2, gas-solid reduction of barium sulfate and radium: After the barium sulfate and radium solid obtained in Step 1 are mixed evenly with the additives, they are placed in a quartz boat. A reducing gas is introduced into a high-temperature tube furnace to reduce the insoluble barium sulfate and radium to soluble barium radium sulfide solid. Step 3, hot water dissolution of barium radium sulfide and conversion of barium radium carbonate: The barium radium sulfide solid obtained in step 2 is dissolved in hot water, and then under alkaline conditions, carbon dioxide is introduced to convert the soluble barium radium sulfide into insoluble barium radium carbonate precipitate. Step 4: Acid dissolution of barium carbonate and radium: Add the barium carbonate and radium solid obtained in step 3 to a dilute acid solution while stirring until the solid is almost completely dissolved, to obtain a soluble radium salt solution.

2. The method for converting barium sulfate radium precipitate into soluble radium salt according to claim 1, characterized in that, In step one: the radium-containing aqueous solution is a rare earth slag removal and conversion dissolving solution, tantalum and niobium ore extraction residue, radium-containing wastewater from phosphate production, or radium-containing wastewater after non-ferrous metal extraction.

3. The method for converting barium sulfate radium precipitate into soluble radium salt according to claim 1, characterized in that, In step one: the soluble barium salt is one or more of barium chloride and barium nitrate; the sulfate donor is one or more of sulfuric acid and sulfate; the alkaline solution is one or more of sodium hydroxide solution, ammonia water, and potassium hydroxide solution.

4. The method for converting barium sulfate radium precipitate into soluble radium salt according to claim 1, characterized in that, The preparation process of barium sulfate-radium coprecipitation in step one: S1.1 Heat the radium-containing aqueous solution to 50-90°C, add a soluble barium salt solution and sulfate donor, so that radium and barium form a barium sulfate-radium coprecipitate; S1.2 Add alkaline solution to adjust the pH value to 0.5-3.0, maintain the temperature of 50-90℃ for 3-6 hours to allow the eutectic particles to gradually grow, then cool to room temperature at a rate of 1-5℃ / h and stir for 10-20 hours, and filter to obtain barium radium filter cake; S1.3 The obtained barium radium filter cake is dried at 50-80℃ for 12-24 hours, and then ground and passed through a 20-40 mesh sieve to obtain barium radium solid.

5. The method for converting barium sulfate radium precipitate into soluble radium salt according to claim 1, characterized in that, In S1.1, radium reacts with barium to form a barium sulfate radium coprecipitate. The chemical equation for this process is: (1) Main reaction formula: ； In the formula, Barium ions are formed from the ionization of soluble barium salts. Sulfate ions provided for sulfuric acid or sulfates; (2) Eutectic reaction: ； In the formula, It refers to radium-226 ions in radium-containing aqueous solutions. It is a sulfate ion. Substitution into the BaSO4 lattice , Enter Lattice substitution ; (3) The overall reaction equation is expressed as: ； In the formula, product It is a barium sulfate-radium mixed crystal coprecipitation.

6. The method for converting barium sulfate radium precipitate into soluble radium salt according to claim 1, characterized in that, In step two: the barium radium sulfate solid obtained in step one is mixed evenly with the additive and placed in a quartz boat, which is then placed in a tube furnace. A reducing gas is introduced, with the flow rate controlled at 50-1000 mL / min. The temperature is increased to 800-1200℃ at a rate of 10-30℃ / min. The temperature is maintained for 1-4 hours, and then heating is stopped. The mixture is allowed to cool naturally to room temperature to obtain barium radium sulfate solid.

7. The method for converting barium sulfate radium precipitate into soluble radium salt according to claim 6, characterized in that, The auxiliary agent is alum stone, and the dosage is 0.05% to 0.2% of the mass of barium sulfate radium solid; the reducing gas is one or more of methane, hydrogen, carbon monoxide, and synthesis gas.

8. The method for converting barium sulfate radium precipitate into soluble radium salt according to claim 1, characterized in that, The hot water dissolution of barium radium sulfide and the conversion of barium radium carbonate in step three are as follows: S2.1 Dissolve the solid barium radium sulfide obtained in step 2 in hot water at 50-100℃ with a liquid-to-solid ratio of (3-8):

1. Stir at 100-200 rpm for 2-4 hours and filter while hot to obtain an alkaline filtrate containing soluble barium radium sulfide. S2.

2. Keep the filtrate at 50-80℃, add sulfide, and adjust the pH to 10.0-12.0 with ammonia. S2.3 Finally, carbon dioxide gas is introduced and the reaction is allowed to proceed for 3 to 5 hours. Then, sodium hydroxide is added to adjust the pH value to 12.5 to 14.

0. The mixture is then aged at room temperature for 20 to 30 hours. The filter cake obtained after filtration is washed with water and dried to obtain barium carbonate solid.

9. The method for converting barium sulfate radium precipitate into soluble radium salt according to claim 8, characterized in that, The sulfide is one or more of sodium sulfide, potassium sulfide, and ammonium sulfide, preferably ammonium sulfide; the mass concentration of ammonia water is in the range of 25% to 28%; and the mass concentration of sodium hydroxide is in the range of 20% to 30%.

10. The method for converting barium sulfate radium precipitate into soluble radium salt according to claim 1, characterized in that, In step four, the dilute acid solution is selected from either dilute hydrochloric acid or dilute nitric acid solution with a mass concentration of 2–4 mol / L.

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