A deep processing technology for purifying crude sodium pyroantimonate

Abstract

The present application relates to inorganic chemical material preparation technical field, disclose a kind of crude sodium pyroantimonate purification deep processing technology, including crude sodium pyroantimonate is deployed into slurry and is applied ultrasonic wave and is carried out physical activation treatment;Reducing stabilizer and composite organic acid complexing agent are added to the slurry after activation;Afterwards, lye is added to carry out pH neutralization and back adjustment;Finally, product is obtained by solid-liquid separation, washing and drying.The present application breaks particle agglomerates by ultrasonic wave, creates interface for chemical impurity removal;Then, by the synergistic effect of reduction-complexation, high-valence metal impurities are first converted into low-valence state which is easy to react, and then composite organic acid complexing agent forms stable water-soluble complex with them;The final pH neutralization and back adjustment step inhibits the hydrolysis of the complex and prevents the contamination of impurities.This process effectively solves the problem of removing encapsulated impurities and high-valence impurities, and improves the product purity and process stability.

Description

Technical Field

[0001] This invention relates to the field of inorganic chemical material preparation technology, specifically a deep processing technology for the purification of crude sodium pyroantimonate. Background Technology

[0002] Sodium pyroantimonate is an important inorganic fine chemical product with wide applications in glass clarifying agents, high-efficiency flame retardants, and catalysts. These applications place stringent requirements on the purity of sodium pyroantimonate, particularly the content of harmful metal impurities such as iron, lead, and arsenic. In industrial production, crude sodium pyroantimonate, obtained directly through wet synthesis, typically contains various metal impurity ions. The presence of these impurities directly affects the whiteness, optical properties, and flame retardant performance of the final product; therefore, it must undergo further purification and processing to meet high-end application standards.

[0003] Existing purification methods for sodium pyroantimonate mostly employ wet chemical processing, but they generally face bottlenecks in achieving deep impurity removal. A core challenge stems from the physical morphology of crude sodium pyroantimonate. During synthesis and crystallization, the tiny crystals of sodium pyroantimonate easily form tightly packed aggregates. Some metallic impurities are not simply attached to the particle surface but are physically encapsulated within these aggregates. Conventional acid washing or complexation treatments struggle to penetrate these aggregates, failing to effectively contact the encapsulated impurities. This results in the residue of these impurities, becoming a fundamental obstacle to improving product purity.

[0004] Furthermore, the chemical valence state of impurities also poses challenges to purification. Metallic impurities such as iron and lead in crude sodium pyroantimonate often exist in high valence states, such as ferric iron and tetravalent lead. These high-valence ions are chemically stable, exhibit low reactivity with conventional organic acid complexing agents, and result in slow reaction rates. Simply increasing the concentration of acid or complexing agent to enhance removal is not only costly but also introduces excessive acid radicals, burdening subsequent treatments, and offers limited improvement in impurity removal efficiency.

[0005] Even if some impurities are successfully dissolved and released into the liquid phase through acid leaching or complexation, the entire purification process remains unstable. The stability of metal impurity complexes formed in acidic media is highly dependent on the pH of the solution. During subsequent washing and neutralization processes, the pH of the slurry system fluctuates. This fluctuation disrupts the stable structure of the complexes, triggering hydrolysis and causing impurity ions that have already entered the liquid phase to precipitate again as hydroxides or oxides, depositing on the surface of the purified sodium pyroantimonate product, resulting in secondary contamination. This impurity back-contamination phenomenon makes it difficult to consistently control the purification effect, affecting the uniformity of the final product quality. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a deep processing technology for the purification of crude sodium pyroantimonate, which solves the problems of difficult removal of encapsulated impurities caused by the agglomeration of sodium pyroantimonate particles, low efficiency of complex removal of high-valence metal impurities due to their stable chemical properties, and back pollution caused by hydrolysis of impurity complexes due to environmental changes during the process.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a deep processing technology for purifying crude sodium pyroantimonate, comprising: The crude sodium pyroantimonate raw material is prepared into a slurry, and the slurry is subjected to ultrasonic physical activation treatment to break the agglomerates of sodium pyroantimonate particles and expose the encapsulated impurities. A composite organic acid complexing agent and a reduction stabilizer are added to the slurry that has undergone physical activation treatment under stirring conditions. The reduction stabilizer is used to convert high-valence metal impurity ions into low-valence ions that are easy to complex. Then, the composite organic acid complexing agent and the converted low-valence impurity ions form a water-soluble complex, thereby realizing the transfer of impurities from the solid phase to the liquid phase. An alkaline solution is added to the slurry containing the water-soluble complex to neutralize and adjust the pH, thereby inhibiting the hydrolysis of the water-soluble complex and blocking the path of impurities returning to the sodium pyroantimonate solid phase. The slurry that has undergone pH neutralization and adjustment is subjected to solid-liquid separation. The resulting solid phase is washed and dried to obtain high-purity sodium pyroantimonate product.

[0008] By adopting the above technical solution, the effectiveness of the process of this invention stems from the synergistic effect of physical activation and multi-stage chemical purification. A key challenge the process must first address is that a large number of impurities are not attached to the particle surface, but are physically encapsulated within the agglomerates of sodium pyroantimonate. To address this, the initial physical activation treatment utilizes the cavitation effect of ultrasound to generate strong microscopic mechanical forces, breaking up these agglomerate structures and exposing the previously inaccessible impurities, thus creating the necessary contact interface for subsequent chemical reactions.

[0009] After the impurities are fully exposed, the process enters a dual synergistic chemical removal phase. This phase does not employ a single complexation method, but rather actively controls the chemical valence state of the impurities.

[0010] Impurity valence state regulation: The added reducing stabilizer functions to neutralize the chemically stable, non-complexing ferric ions (Fe3+) in the system. 3+ ) or tetravalent lead ions (Pb) 4+ High-valence metal impurities such as ferrous ions are in situ reduced to ferrous ions (Fe2+) with higher complexing activity. 2+ or divalent lead ions (Pb)2+ This pretreatment step is a prerequisite for efficient impurity removal in the subsequent process.

[0011] Complexation transfer: After the impurity ions are converted into easily reactive low-valence states, the hydroxyl and carboxyl groups in the complex organic acid complexing agent act as polydentate ligands, chelating with these low-valence metal ions to form structurally stable water-soluble metal-organic acid complexes. Through this process, impurities in the solid matrix are stripped and transferred to the liquid phase.

[0012] However, simply transferring impurities to the liquid phase does not signify complete purification, as these formed complexes can be unstable under certain conditions. If the process environment changes, the complexes can hydrolyze, causing impurities to redefine as hydroxides, resulting in secondary contamination of the product surface, known as "re-contamination." To block this failure path, this invention introduces a pH neutralization and reversion step. By adding alkali to precisely control the pH of the slurry to a near-neutral range, the stability of water-soluble complexes in the liquid phase can be significantly improved, inhibiting hydrolysis and ensuring that impurities are thoroughly and stably removed from the solid phase system.

[0013] In summary, this invention achieves deep removal of surface, deep, and encapsulated impurities from crude sodium pyroantimonate through a triple action of physical activation, reduction-complexation, and stabilization to prevent back-contamination, ultimately obtaining a high-purity sodium pyroantimonate product.

[0014] Preferably, the composite organic acid complexing agent is composed of component A1 and component A2, and the mass ratio of component A1 to component A2 is 1:(1-4). Component A1 is selected from at least one of tartaric acid and citric acid; component A2 is selected from at least one of sodium gluconate and sodium lactate.

[0015] By adopting the above technical solution, component A1 (hydroxycarboxylic acid) provides the main acidic environment and complexing functional groups, while component A2 (hydroxycarboxylic acid salt), as its conjugate base, constitutes a buffer system that can stabilize the pH of the system during the complexation reaction. At the same time, it also participates in the complexation. The combination of the two enhances the complexation ability of various metal impurities and the process stability.

[0016] Preferably, the reducing stabilizer is selected from at least one of sodium sulfite and ascorbic acid. By adopting the above technical solution, both sodium sulfite and ascorbic acid are mild and efficient reducing agents, the reduction products are easy to handle, and no new harmful impurities are introduced into the system.

[0017] Preferably, the total amount of the composite organic acid complexing agent added is 5-15% of the dry weight of the crude sodium pyroantimonate; the total amount of the reducing stabilizer added is 0.5-2% of the dry weight of the crude sodium pyroantimonate.

[0018] By adopting the above technical solution, this dosage range is an optimized result that balances the impurity removal rate with the control of production costs.

[0019] Preferably, in the physical activation treatment by applying ultrasound, the frequency of the ultrasound is 20 to 40 kHz, and the ultrasound treatment time for the physical activation treatment is 15 to 30 minutes.

[0020] By adopting the above technical solution, this parameter range ensures sufficient energy input to break up particle agglomeration, while avoiding energy waste or excessive particle breakage caused by over-processing.

[0021] Preferably, in the step of forming the water-soluble complex, the complexation reaction temperature is 40–60°C and the complexation reaction time is 10–18 hours.

[0022] By adopting the above technical solution, moderate heating is beneficial to increasing the rate of reduction and complexation reactions, while the set reaction time ensures that the reaction proceeds sufficiently.

[0023] Preferably, in the process of adding alkali solution for pH neutralization and adjustment, the pH value of the slurry is adjusted to 6.8 to 7.2.

[0024] By adopting the above technical solution, this pH range is the optimal range for the stability of most organometallic acid complexes, and can most effectively prevent the hydrolysis of complexes.

[0025] Preferably, the step of preparing crude sodium pyroantimonate raw material into a slurry includes a pre-washing and desalting step: mixing the crude sodium pyroantimonate raw material with pure water at a solid-liquid mass ratio of 1:(1.0-1.5), wherein the pre-washing temperature of the mixture is 40-60°C, the pre-washing stirring time is 0.5-1.5 hours, and then performing solid-liquid separation.

[0026] By adopting the above technical solution, the pre-washing step can remove some of the soluble salt impurities attached to the raw materials in advance, reducing the load on the subsequent chemical purification steps and improving the overall process efficiency.

[0027] Preferably, after adjusting the pH value of the slurry to 6.8-7.2, the aging process further includes continuing to stir and age the slurry at the pH value, wherein the aging temperature is 40-60°C and the aging time is 0.5-1.5 hours.

[0028] By adopting the above technical solution, the aging step makes the chemical balance in the system more stable, which helps the trace impurities that are not fully complexed to react further, or makes the structure of the formed complex more stable, thus ensuring the final separation effect.

[0029] This invention provides a process for the purification and deep processing of crude sodium pyroantimonate. It has the following beneficial effects: 1. This invention utilizes ultrasonic waves for physical activation, breaking down the particle agglomerates of crude sodium pyroantimonate raw materials and exposing the encapsulated metallic impurities. This treatment method allows subsequent chemical agents to directly contact and act on these internal impurities, solving the problem of incomplete removal of such impurities in traditional wet processes and contributing to the acquisition of higher purity sodium pyroantimonate products.

[0030] 2. This invention establishes a synergistic chemical purification pathway by combining a reducing stabilizer with a complex organic acid complexing agent. The reducing stabilizer first converts high-valence metal impurities into lower-valence states with higher chemical activity, and then the complex organic acid complexing agent complexes them. This effectively overcomes the limitation of single complexing agents in removing some stable-valence impurities, and improves the efficiency of impurity transfer from the solid phase to the liquid phase.

[0031] 3. After the complexation reaction is complete, this invention adjusts the slurry environment from acidic to near neutral by adding alkali solution to neutralize and restore the pH. This step aims to stabilize the metal impurity complexes in the liquid phase, effectively inhibiting the hydrolysis of the complexes and their re-precipitation onto the product surface. This ensures the durability of the purification effect and improves the stability and yield of the entire deep processing technology. Attached Figure Description

[0032] Figure 1 This is a comparison chart showing the removal rates of the main impurity elements Fe, Pb, and As obtained from the products of Examples 1-3 of the present invention. Figure 2 This is a graph showing the trend of dissolved Fe concentration in the supernatant of Example 2 and Comparative Examples 3-4 of the present invention at different pH values; Figure 3 This is a comparison chart of the residual Fe and Pb impurities in the products obtained in Example 2 and Comparative Examples 1-2 of the present invention; Figure 4 This is a comparison chart of the Sb recovery rate and pH value of the aqueous extract of the products obtained in Example 2 and Comparative Examples 3 and 5 of the present invention. Detailed Implementation

[0033] The technical solutions in 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.

[0034] Preparation Examples 1-3: Preparation Example 1: This preparation example provides a method for preparing a composite organic acid complexing agent (pharmaceutical A) in which the mass ratio of component A1 to component A2 is 1:1, comprising the following steps: (1) Add the calculated amount of purified water to a clean container equipped with a stirring device.

[0035] (2) Start stirring, weigh tartaric acid as component A1 and sodium gluconate as component A2 in a mass ratio of 1:1, and slowly add the weighed solid materials to the pure water that is being stirred.

[0036] (3) Stir continuously at room temperature (20-30℃) until all solid components are completely dissolved to form a homogeneous and clear solution.

[0037] (4) By adjusting the amount of pure water added, the mass fraction of the solute (total mass of tartaric acid and sodium gluconate) in the final solution is precisely controlled to be 20%. The resulting solution is the composite organic acid complexing agent (reagent A) of this preparation example, and is sealed for later use.

[0038] Preparation Example 2: This preparation example provides a method for preparing a composite organic acid complexing agent (reagent A) with a mass ratio of component A1 to component A2 of 1:2.5, comprising the following steps: (1) Weigh out equal amounts of tartaric acid and citric acid, mix them physically until homogeneous, and use them as component A1 for later use.

[0039] (2) Add the calculated amount of purified water to a clean container equipped with a stirring device and turn on the stirring.

[0040] (3) According to the mass ratio of component A1 to sodium gluconate (as component A2) of 1:2.5, the two pre-weighed components are slowly added to the purified water that is being stirred.

[0041] (4) Stir continuously at room temperature (20-30℃) until all solid components are completely dissolved to form a homogeneous and clear solution.

[0042] (5) By adjusting the amount of pure water added, the mass fraction of the solute (total mass of component A1 and component A2) in the final solution is precisely controlled to be 35%. The resulting solution is the composite organic acid complexing agent (reagent A) of this preparation example, and is sealed for later use.

[0043] Preparation Example 3: This preparation example provides a method for preparing a composite organic acid complexing agent (reagent A) in which the mass ratio of component A1 to component A2 is 1:4, comprising the following steps: (1) Weigh out citric acid as component A1; weigh out equal amounts of sodium gluconate and sodium lactate, and mix them evenly as component A2.

[0044] (2) Add the calculated amount of purified water to a clean container equipped with a stirring device.

[0045] (3) Start stirring and slowly add the weighed materials to the stirred pure water according to the mass ratio of component A1 to component A2 of 1:4.

[0046] (4) Stir continuously at room temperature (20-30℃) until all solid components are completely dissolved to form a homogeneous and clear solution.

[0047] (5) By adjusting the amount of pure water added, the mass fraction of the solute (total mass of component A1 and component A2) in the final solution is precisely controlled to be 50%. The resulting solution is the composite organic acid complexing agent (reagent A) of this preparation example, and is sealed for later use.

[0048] Examples 1-3:

[0049] Example 1: This embodiment provides a method for purifying and further processing crude sodium pyroantimonate, including the following steps: (1) Pre-washing and desalination: Weigh 1000g of wet-basis crude sodium pyroantimonate raw material with a moisture content of 25.2% (equivalent to 748g on a dry basis) and place it in a 2L reactor. Add 748g of purified water at a dry basis solid-liquid mass ratio of 1:1.0, start stirring, and set the speed to 100rpm. Start heating to raise the slurry temperature to and maintain it at 40℃, and stir continuously for 0.5 hours under this condition. Subsequently, the slurry is subjected to solid-liquid separation, and the resulting filter cake is washed 8 times with purified water to obtain the primary washed filter cake.

[0050] (2) Ultrasonic pretreatment of slurry: All the primary washed filter cake obtained in step (1) is re-mixed with pure water to prepare a slurry with a solid content of 30% (mass percentage). The slurry is pumped into an ultrasonic reactor, the ultrasonic generator is started, the ultrasonic frequency is set to 20kHz, and the slurry is treated for 15 minutes.

[0051] (3) Complexing and leaching with composite organic acids: The ultrasonically treated slurry was transferred to a clean reactor, stirring was started, the speed was set to 100 rpm, and the temperature was raised to and maintained at 40°C. Based on the calculation that the total amount of pure solute added to the composite organic acid complexing agent (reagent A) is 5% of the dry weight of crude sodium pyroantimonate (748 g), i.e., 37.4 g of pure solute is required, 187 g of the 20% solute mass fraction composite organic acid complexing agent (reagent A) solution prepared in Preparation Example 1 was weighed and slowly added to the slurry. After addition, the pH of the system stabilized at 4.0. Subsequently, based on 0.5% of the dry weight of crude sodium pyroantimonate, 3.74 g of sodium sulfite was added to the slurry as a reducing stabilizer (reagent B). The reaction was continuously stirred at a constant temperature of 40°C for 10 hours.

[0052] (4) pH neutralization and complex stabilization: After completing the reaction in step (3), keep stirring and temperature constant. Slowly add a 10% sodium hydroxide solution by mass through a metering pump to adjust and stabilize the pH of the slurry at 6.8. Stop adding alkali and continue stirring and aging at this pH and temperature for 0.5 hours.

[0053] (5) Refining and washing and obtaining the product: The slurry after aging in step (4) is subjected to solid-liquid separation, and the obtained refined sodium pyroantimonate filter cake is washed three times with pure water. The qualified filter cake is placed in an oven at 100°C for drying until the physical water content of the product is less than 0.3%, and the final high-purity sodium pyroantimonate product is obtained, which is denoted as S1.

[0054] Example 2: This embodiment provides a method for purifying and further processing crude sodium pyroantimonate, including the following steps: (1) Pre-washing and desalination: Weigh 1000g of wet-basis crude sodium pyroantimonate raw material with a moisture content of 25.2% (equivalent to 748g on a dry basis) and place it in a 2L reactor. Add 935g of purified water at a dry basis solid-liquid mass ratio of 1:1.25, start stirring, and set the speed to 150rpm. Start heating to raise the slurry temperature to and maintain it at 50℃, and stir continuously for 1.0 hour under this condition. Subsequently, the slurry is subjected to solid-liquid separation, and the resulting filter cake is washed 9 times with purified water to obtain the primary washed filter cake.

[0055] (2) Ultrasonic pretreatment of slurry: All the primary washed filter cake obtained in step (1) is re-mixed with pure water to prepare a slurry with a solid content of 40% (mass percentage). The slurry is pumped into an ultrasonic reactor, the ultrasonic generator is started, the ultrasonic frequency is set to 30kHz, and the slurry is treated for 22.5 minutes.

[0056] (3) Complexing and leaching with compound organic acids: The ultrasonically treated slurry was transferred to a clean reactor, stirring was started, the speed was set to 200 rpm, and the temperature was raised to and maintained at 50°C. Based on the calculation that the total amount of pure solute added to the compound organic acid complexing agent (reagent A) is 10% of the dry weight of crude sodium pyroantimonate (748 g), i.e., 74.8 g of pure solute is required, 213.7 g of the 35% solute mass fraction compound organic acid complexing agent (reagent A) solution prepared in Preparation Example 2 was weighed and slowly added to the slurry. After addition, the pH of the system stabilized at 3.3. Subsequently, based on 1.25% of the dry weight of crude sodium pyroantimonate, 9.35 g of sodium sulfite was added to the slurry as a reducing stabilizer (reagent B). The reaction was continuously stirred at a constant temperature of 50°C for 14 hours.

[0057] (4) pH neutralization and complex stabilization: After completing the reaction in step (3), keep stirring and temperature constant. Slowly add a 15% sodium hydroxide solution by mass through a metering pump to adjust and stabilize the pH of the slurry at 7.0. Stop adding alkali and continue stirring and aging at this pH and temperature for 1.0 hour.

[0058] (5) Refining and washing and obtaining the product: The slurry after aging in step (4) is subjected to solid-liquid separation, and the obtained refined sodium pyroantimonate filter cake is washed 4 times with pure water. The qualified filter cake is placed in an oven at 105°C for drying until the physical water content of the product is less than 0.3%, and the final high-purity sodium pyroantimonate product is obtained, which is denoted as S2.

[0059] Example 3: This embodiment provides a method for purifying and further processing crude sodium pyroantimonate, including the following steps: (1) Pre-washing and desalination: Weigh 1000g of wet-basis crude sodium pyroantimonate raw material with a moisture content of 25.2% (equivalent to 748g on a dry basis) and place it in a 2L reactor. Add 1122g of purified water at a dry basis solid-liquid mass ratio of 1:1.5, start stirring, and set the speed to 200rpm. Start heating to raise the slurry temperature to and maintain it at 60℃, and stir continuously for 1.5 hours under this condition. Subsequently, the slurry is subjected to solid-liquid separation, and the resulting filter cake is washed 10 times with purified water to obtain the primary washed filter cake.

[0060] (2) Ultrasonic pretreatment of slurry: All the primary washed filter cake obtained in step (1) is re-mixed with pure water to prepare a slurry with a solid content of 50% (mass percentage). The slurry is pumped into an ultrasonic reactor, the ultrasonic generator is started, the ultrasonic frequency is set to 40kHz, and the slurry is treated for 30 minutes.

[0061] (3) Complexing and leaching with composite organic acids: The ultrasonically treated slurry was transferred to a clean reactor, stirring was started, the speed was set to 300 rpm, and the temperature was raised to and maintained at 60°C. Based on the calculation that the total amount of pure solute added to the composite organic acid complexing agent (reagent A) is 15% of the dry weight of crude sodium pyroantimonate (748 g), i.e., 112.2 g of pure solute is required, 224.4 g of the 50% solute mass fraction composite organic acid complexing agent (reagent A) solution prepared in Preparation Example 3 was weighed and slowly added to the slurry. After addition, the pH of the system stabilized at 2.5. Subsequently, based on 2% of the dry weight of crude sodium pyroantimonate, 14.96 g of ascorbic acid was added to the slurry as a reducing stabilizer (reagent B). The reaction was continuously stirred at a constant temperature of 60°C for 18 hours.

[0062] (4) pH neutralization and complex stabilization: After completing the reaction in step (3), keep stirring and temperature constant. Slowly add a 20% sodium hydroxide solution by mass through a metering pump to adjust and stabilize the pH of the slurry at 7.2. Stop adding alkali and continue stirring and aging at this pH and temperature for 1.5 hours.

[0063] (5) Refining and washing and obtaining the product: The slurry after aging in step (4) is subjected to solid-liquid separation, and the obtained refined sodium pyroantimonate filter cake is washed 5 times with pure water. The qualified filter cake is placed in an oven at 110°C for drying until the physical water content of the product is less than 0.3%, and the final high-purity sodium pyroantimonate product is obtained, which is denoted as S3.

[0064] Comparative Examples 1-5: Comparative Example 1: Compared with Example 2, the difference is that the ultrasonic pretreatment of the slurry in step (2) is omitted. Instead, the primary washing filter cake obtained in step (1) is re-mixed with pure water to prepare a slurry with a solid content of 40% (mass percentage), and then the composite organic acid leaching and complexation in step (3) are carried out directly. The rest are the same.

[0065] Comparative Example 2: Compared with Example 2, the difference is that sodium sulfite was not added as a reducing stabilizer (reagent B) in step (3), but the rest are the same.

[0066] Comparative Example 3: Compared with Example 2, the difference is that the complex organic acid complexing agent (agent A) in step (3) is replaced with an equal mass and mass fraction of conventional industrial-grade sulfuric acid solution, and all other aspects are the same.

[0067] Comparative Example 4: Compared with Example 2, the difference is that the complex organic acid complexing agent (agent A) in step (3) is replaced with a single sodium gluconate solution of equal mass and equal solute mass fraction, and all other aspects are the same.

[0068] Comparative Example 5: Compared with Example 2, the difference is that the pH neutralization and complex stabilization process in step (4) is omitted. That is, after the reaction in step (3) is completed, the solid-liquid separation and purification washing in step (5) are carried out directly. The rest are the same.

[0069] Test Examples 1-4: Test Example 1: Verification of Core Purification Effect and Process Range Accurately weigh 2.0000 g each of the dried crude sodium pyroantimonate raw material and the sodium pyroantimonate products S1, S2, and S3 prepared in Examples 1-3, and place them separately in polytetrafluoroethylene digestion vessels. Slowly add a mixed solution of 15 mL high-purity hydrochloric acid and 5 mL high-purity nitric acid to each digestion vessel, and let the reaction stand until no obvious bubbles are generated.

[0070] Cover the digestion vessel but do not tighten it completely to maintain a slightly open, low-pressure venting state. Then place it on a corrosion-resistant heating plate and heat it to 90–100°C according to the set temperature program, maintaining this temperature for 1.5 hours to ensure the solid sample completely dissolves into the liquid phase, while ensuring safety. After digestion, cool to room temperature, open the digestion vessel lid, and pour the solution onto the corrosion-resistant heating plate at 120°C to remove acid until approximately 2 mL of solution remains.

[0071] After removing the acid, the extract was quantitatively transferred to ultrapure water and diluted to a volumetric flask of 50 mL. After shaking well, it was filtered through a 0.22 μm aqueous microporous membrane, and the filtrate was collected as the sample to be tested.

[0072] The emission spectral intensities of iron, lead, and arsenic in each sample were measured sequentially using an inductively coupled plasma optical emission spectrometer (ICP-OES). The mass concentration (ppm) of the corresponding impurity element in each sample was calculated using the standard curve method, and the removal rate was calculated based on the initial concentration of the raw material.

[0073] Table 1. Test data on impurity content and removal rate of raw materials and products from Examples 1-3 crude raw materials 1856.42 - 941.15 - 428.67 - Example 1 (S1) 24.51 98.68 17.38 98.15 9.62 97.76 Example 2 (S2) 8.27 99.55 5.14 99.45 3.01 99.30 Example 3 (S3) 4.19 99.77 2.36 99.75 1.15 99.73 Note: "-" in Table 1 indicates that there is no corresponding calculation data for this item, because the crude raw material is used as the initial reference for the entire purification process and does not have an impurity removal rate as an indicator.

[0074] Figure 1This is a comparison chart of the impurity removal rates of the products obtained in Examples 1 to 3 of this invention. The horizontal axis in the chart represents the three main impurity element categories of interest in the test, and the vertical axis represents the removal rate values ​​of each impurity after purification by the corresponding embodiment of this invention.

[0075] According to the data in Table 1, the crude sodium pyroantimonate raw material contained high concentrations of iron, lead, and arsenic impurities. These associated elements readily occupy lattice defects or undergo surface physical adsorption with the antimony matrix during conventional smelting and crystallization, resulting in initial detection concentrations as high as 1856.42 ppm, 941.15 ppm, and 428.67 ppm, respectively. In the product S1 obtained in Example 1, the concentrations of each impurity showed a significant decrease, with an iron removal rate of 98.68%. This indicates that even under relatively conservative ultrasonic frequencies and low acid concentration ratios, the composite organic acid can still release sufficient coordination functional groups into the liquid phase, effectively stripping free impurities from the solid-liquid interface. Examples 2 and 3 exhibited even more thorough impurity removal trajectories. The increasing ultrasonic cavitation intensity physically disintegrated the spatial barrier of sodium pyroantimonate aggregates, further exposing stubborn impurities within the micropores. Combined with data from Example 3, it can be observed that the absolute residual amounts of iron, lead, and arsenic were drastically reduced to trace levels of 4.19 ppm, 2.36 ppm, and 1.15 ppm, respectively. This significant increase in impurity removal depth confirms the chemical coupling effect occurring within the mixed system. Specifically, organic acid molecules with different carbon chain lengths and spatial configurations collaboratively construct a multi-dimensional complexation and trapping network. Within the stable reducing field created by sodium sulfite or ascorbic acid, interfering ions such as ferric ions are maintained in a low valence state, readily complexing, and subsequently firmly locked by organic ligands to form water-soluble complexes. No decline in removal rate was observed during the neutralization and aging stage, confirming that the desorbed metal complex at the interface still maintains an extremely high thermodynamic stability constant in a near-neutral solution. This completely blocks the reverse reaction path of impurity ion hydrolysis and re-contamination, providing strong data support for the scientific nature of the purification mechanism and the rationality of the process boundary setting in this scheme.

[0076] Test Example 2: Verification Test of Hydrolysis Resistance and Complexation Stability Mechanism Take 200 mL of each of the acidic leachate slurries obtained after completing step (3) in Examples 2, 3 and 4, and use a 0.45 μm aqueous microporous filter membrane for filtration and separation to retain all suspended solid particles and collect the clear acidic leachate mother liquor in its initial state.

[0077] The three leaching mother liquors were transferred to constant-temperature titration reactors equipped with water bath jackets, and the circulating water was turned on to maintain the system temperature at a constant 50°C. Composite pH electrodes calibrated with standard buffer solution were inserted into each reactor and connected to an automatic potentiometric titrator.

[0078] Start the stirring device to mix the liquid. Use an automatic potentiometric titrator to slowly add a 10% sodium hydroxide solution through a capillary tube, and dynamically monitor and record the real-time pH value of the system.

[0079] When the pH of the system reaches 3.5 (near the initial baseline), 4.0, 5.0, 6.0, and 7.0, respectively, stop the dropwise addition and immediately extract 5 mL of reaction solution from each reactor. Transfer the extracted reaction solution into centrifuge tubes and centrifuge at 8000 rpm for 10 minutes to forcibly separate the newly formed hydrolyzed colloidal precipitate under these pH conditions.

[0080] The supernatant from each centrifuge tube was poured out and diluted with 2% dilute nitric acid at a volume ratio of 1:50. The mass concentration of dissolved iron in each supernatant sample was accurately determined using an inductively coupled plasma optical emission spectrometer (ICP-OES).

[0081] Table 2. Data on the concentration of dissolved iron in the supernatant of each system under different pH conditions Example 2 Leachate 468.23 467.05 464.81 462.19 459.74 Comparative Example 3 Leachate 471.56 118.42 22.15 3.84 0.67 Comparative Example 4 Leachate 463.89 428.14 317.52 204.68 139.21 Figure 2 This is a graph showing the change in dissolved iron concentration as a function of pH during the neutralization and rebalancing process of the leaching mother liquors from Example 2, Comparative Examples 3, and 4 of this invention. The horizontal axis indicates the pH value nodes of the system dynamically adjusted by adding alkali solution, and the vertical axis reflects the concentration of dissolved iron ions remaining in the supernatant after centrifugation at the corresponding pH. The broken lines and markings in the graph represent the test trajectories of Example 2 (complex organic acid system), Comparative Example 3 (conventional sulfuric acid system), and Comparative Example 4 (single sodium gluconate system), respectively.

[0082] According to the data in Table 2, the leaching mother liquors of Example 2, Comparative Examples 3 and 4 all exhibited high iron ion leaching concentrations in the initial slightly acidic environment (pH=3.5), ranging from 463.89 to 471.56 mg / L. As the neutralization and adjustment process progressed, the liquid-phase metal ion behavior of the three systems showed significant differentiation. Comparative Example 3 used a conventional inorganic sulfuric acid system for impurity removal. After leaving the high-acidity environment, the free iron ions rapidly crossed their solubility product constant critical point. When the pH slightly increased to 4.0, the dissolved iron concentration in the supernatant plummeted to 118.42 mg / L, and only a trace amount of 0.67 mg / L remained at the neutral pH of 7.0.

[0083] A large amount of iron is irreversibly converted into ferric hydroxide colloidal precipitate. This typical inorganic salt hydrolysis characteristic directly leads to impurities re-attaching to the solid surface of the product in actual industrial production, forming secondary pollution that is difficult to wash off. Comparative Example 4 used sodium gluconate as a single complexing agent. In the initial stage of the test, it showed a certain ability to mask metal ions. However, during the evolution of pH increase, the original complexation equilibrium was gradually broken due to the limitations of the single ligand's spatial configuration and the saturation of coordination sites.

[0084] Some iron ions broke free of the coordination network and underwent hydrolysis, causing the liquid iron concentration to drop to 139.21 mg / L at pH 7.0, revealing a significant shortcoming in the hydrolysis resistance of a single reagent over a wide pH range. The composite organic acid system represented in Example 2 exhibited excellent thermodynamic stability in this test. In the preliminary formulation screening and long-term material purification observation, we found that the complementary synergy of multiple partitions can effectively close the coordination vacancies of free metal ions, and the experimental data accurately confirmed this judgment. During the complete titration cycle from acidic to neutral, the iron ion concentration in the supernatant of Example 2 only experienced very slight fluctuations, ultimately remaining stable at a high level of 459.74 mg / L.

[0085] This indicates that, with the assistance of a reducing agent, complex organic acids composed of different carbon chain structures form extremely robust multidentate cyclic complexes with iron ions. These complexes have extremely low dissociation constants, effectively resisting coordination competition from hydroxide ions in a neutral environment. This ensures that the stripped metallic impurities are effectively locked in the liquid phase, fundamentally cutting off the material transfer pathway for impurities to return to the solid sodium antimonate pyroplatin matrix. This constitutes the core technological barrier for achieving purification and deep processing in this process.

[0086] Test Example 3: Comparison of the synergistic effects of physical activation and chemical reduction on impurity removal efficiency Weigh 5.0000 g each of the dried sodium pyroantimonate product prepared in the final step (5) of Example 2, Comparative Example 1, and Comparative Example 2, and place them into 250 mL stoppered conical flasks. Add 50 mL of a mixed extract containing tartaric acid and hydrochloric acid to the conical flasks and seal the flasks tightly.

[0087] Place the conical flask in a constant temperature shaker, set the temperature to 60℃ and the shaking frequency to 150r / min, and continuously extract and desorb for 4 hours to fully transfer the adsorbed or residual impurity elements on the product's lattice defects and surface into the liquid phase.

[0088] After extraction, remove the conical flask and cool it to room temperature. Transfer the suspension in the flask to a centrifuge tube and centrifuge at 10,000 rpm for 15 minutes to achieve complete solid-liquid separation.

[0089] Accurately transfer 10–100 mL of the supernatant after centrifugation into a volumetric flask, dilute to the mark with 2% dilute nitric acid, and mix well. Determine the concentrations of iron and lead in the diluted solution using inductively coupled plasma optical emission spectrometry (ICP-OES). Calculate the residual impurity content (ppm) in each solid product, and then calculate the corresponding impurity removal rate based on the initial iron content (1856.42 ppm) and lead content (941.15 ppm) in the raw material.

[0090] Table 3. Test data on residual iron and lead impurities and removal rates of products obtained under different process conditions Example 2 8.27 99.55 5.14 99.45 Comparative Example 1 (without ultrasound pretreatment) 134.61 92.75 78.42 91.66 Comparative Example 2 (without reducing stabilizer) 367.28 80.21 6.53 99.30 Figure 3 This is a distribution chart of residual iron and lead impurities in the products obtained in Example 2 of this invention and Comparative Examples 1 and 2. The horizontal axis in the chart indicates the three specific experimental subjects participating in the comparative test, and the vertical axis represents the absolute concentration of residual metal impurities in the final solid product after treatment with different purification process parameters. The solid and dashed lines in the chart respectively delineate the abnormal fluctuation trends of residual iron and lead elements when specific physicochemical intervention conditions are missing.

[0091] According to the data in Table 3, Example 2, under the conditions of combining ultrasonic physical dispersion and reducing agent chemical regulation, significantly improved the purification depth, reducing the residual iron and lead content in the product to 8.27 ppm and 5.14 ppm, respectively. In contrast, in Comparative Example 1, which lacked the ultrasonic pretreatment step, the residual iron and lead content rebounded to 134.61 ppm and 78.42 ppm, respectively. Crude sodium pyroantimonate generally exhibits severe particle agglomeration during crystallization and precipitation, forming numerous closed or semi-closed microporous structures. Without the cavitation tearing effect of specific frequency ultrasound, conventional mechanical stirring is insufficient to break the spatial barrier of the agglomerates, preventing free impurities encased within the grains and deep within the micropores from fully contacting the complex organic acids in the liquid phase. This limited reaction interface directly hinders the mass transfer efficiency of the impurity removal system, leaving a large number of associated impurities untouched within the solid matrix. In Comparative Example 2, which examined the chemical reduction conditions, we observed more differentiated element retention behavior. Even after omitting reducing stabilizers such as sodium sulfite, the lead removal rate remained at a relatively high level of 99.30%, while the residual iron content surged to 367.28 ppm, resulting in a significant drop in the removal rate to 80.21%. Under uncontrolled redox potentials, the iron impurities in the purification system primarily existed as high-valence ferric ions (Fe3+). Compared to ferrous or lead ions, ferric ions readily reach their solubility product critical point and undergo hydrolysis and precipitation in complex solution systems. Without a reducing agent to pre-convert them to a more stable, complexed ferrous state, the free or weakly complexed ferric ions underwent an irreversible phase transition during subsequent acid reduction and neutralization steps, re-coating the surface of the sodium antimonate pyroantimonate particles as ferric hydroxide. The asymmetric decrease in the removal rate of specific impurities reveals the rule that conventional acid leaching or single physical washing cannot fully cover the various complex ion hydrolysis characteristics within the system. This, from both positive and negative perspectives, confirms the necessity and scientific validity of this process in integrating spatial structure disintegration and specific valence state regulation to construct a purification microenvironment.

[0092] Test Example 4: Comparison Test of Product Physicochemical Quality and Matrix Loss Sb Recovery Determination: Accurately record the total mass of the final dried products obtained in Examples 2, 3, and 5. Weigh approximately 0.5000 g of each sample into a 500 mL Erlenmeyer flask, add 10 g of potassium sulfate and 25 mL of concentrated sulfuric acid, and heat in a fume hood until the solution is clear. After cooling, dilute with 100 mL of water, add 10 mL of concentrated hydrochloric acid, and heat to boiling for 5 minutes. After cooling, add 2–3 drops of methyl orange indicator and titrate with 0.05 mol / L standard potassium bromate solution until the solution changes from red to colorless and does not fade for 30 seconds, which is the endpoint. Record the volume consumed. Calculate the antimony content in the product based on the titration results, and calculate the total recovery rate of antimony based on the initial feed amount (equivalent to 748 g on a dry basis).

[0093] pH determination of aqueous extract: Weigh 10.00 g of each of the three dried products mentioned above and place them in a beaker containing 100 mL of freshly boiled and cooled deionized water. Stir continuously at 300 rpm for 30 minutes using a magnetic stirrer to ensure thorough dispersion and leaching equilibrium. Stop stirring and let stand for 5 minutes. Then, measure the pH of the supernatant using a pH meter calibrated with a standard buffer solution (accuracy 0.01).

[0094] Table 4. Test data on Sb recovery rate and pH value of aqueous extract obtained under different process conditions Example 2 98.73 7.08 Comparative Example 3 (Sulfuric Acid Washing) 85.19 7.15 Comparative Example 5 (without pH neutralization) 97.94 4.62 Figure 4 This is a comparison chart of the recovery rate of the main element and the pH value of the aqueous extract of the products obtained in Example 2, Comparative Examples 3 and 5 of this invention. The horizontal axis of the chart indicates the three specific experimental subjects participating in the comparative test, the left vertical axis represents the recovery rate of the main element antimony, and the right vertical axis represents the pH value of the aqueous extract of the product. The gray filled bars and black broken lines in the chart correspond to the test results of the above two physicochemical indicators, respectively.

[0095] According to the data in Table 4, the process in Example 2, while ensuring product quality, also effectively protected the sodium antimonate pyroantimonate matrix, achieving an ideal Sb recovery rate of 98.73%, and the product's aqueous extract was neutral (pH=7.08). In stark contrast, Comparative Example 3 used a conventional strong acid (sulfuric acid) instead of the complex organic acid for leaching. Although it also performed a pH neutralization step, resulting in a final product pH of 7.15, its Sb recovery rate plummeted to 85.19%.

[0096] This significant matrix loss exposes the non-selective attack defect of inorganic strong acids during the purification process. While sulfuric acid decomposes impurities, it also irreversibly damages the structure of sodium pyroantimonate (Na[Sb(OH)6]), causing a large amount of the main component to dissolve and be lost in the mother liquor, resulting in substantial economic losses and resource waste. Another key process deviation is the omission of the pH neutralization and adjustment step in Comparative Example 5. Although the mild organic acid used had less matrix erosion and the Sb recovery rate remained high at 97.94%, the final physicochemical quality of the product suffered severe deterioration.

[0097] Test results showed that the pH value of its aqueous extract was only 4.62, exhibiting obvious acidity. The underlying mechanism of this phenomenon is that after the acidic leaching reaction, a large amount of acidic mother liquor, along with the formed metal impurity complexes, is physically encapsulated in the capillary channels of the filter cake, which cannot be completely replaced and removed by conventional water washing alone.

[0098] In practical applications, such acidic residues will severely affect its performance compatibility and thermal stability when used as a flame retardant or glass clarifying agent. Comprehensive analysis shows that the process innovation of this invention lies in precisely controlling the chemical environment. This utilizes the mild complexing properties of the complex organic acid to avoid excessive erosion of the main material, while ensuring the complete elimination of acidic residues through a key pH neutralization and stabilization step. This achieves a synergistic unity between high purity, high recovery rate, and excellent physicochemical properties.

Claims

1. A deep processing technology for purifying crude sodium pyroantimonate, characterized in that, Includes the following steps: The crude sodium pyroantimonate raw material is prepared into a slurry, and the slurry is subjected to ultrasonic physical activation treatment. A composite organic acid complexing agent and a reduction stabilizer are added to the slurry that has undergone physical activation treatment under stirring conditions. The reduction stabilizer is used to convert high-valence metal impurity ions into low-valence ions that are easy to complex. Then, the composite organic acid complexing agent and the converted low-valence impurity ions form a water-soluble complex. An alkaline solution was added to the slurry containing the water-soluble complex to neutralize and adjust the pH. The slurry that has undergone pH neutralization and adjustment is subjected to solid-liquid separation. The resulting solid phase is washed and dried to obtain high-purity sodium pyroantimonate product.

2. The deep processing technology for purifying crude sodium pyroantimonate according to claim 1, characterized in that, Under the stirring conditions, a composite organic acid complexing agent and a reducing stabilizer are added. The composite organic acid complexing agent is composed of component A1 and component A2, and the mass ratio of component A1 to component A2 is 1:(1-4). Component A1 is selected from at least one of tartaric acid and citric acid; component A2 is selected from at least one of sodium gluconate and sodium lactate.

3. The deep processing technology for purifying crude sodium pyroantimonate according to claim 1, characterized in that, Under the stirring conditions, a complex organic acid complexing agent and a reducing stabilizer are added, wherein the reducing stabilizer is selected from at least one of sodium sulfite and ascorbic acid.

4. The deep processing technology for purifying crude sodium pyroantimonate according to claim 1, characterized in that, In the step of adding the composite organic acid complexing agent and the reducing stabilizer, the total amount of the composite organic acid complexing agent added is 5-15% of the dry weight of the crude sodium pyroantimonate; The reducing stabilizer is added, and the total amount of the reducing stabilizer added is 0.5 to 2% of the dry weight of the crude sodium pyroantimonate.

5. The deep processing technology for purifying crude sodium pyroantimonate according to claim 1, characterized in that, In the physical activation treatment of the slurry by applying ultrasound, the frequency of the ultrasound used is 20-40 kHz, and the treatment time of the ultrasound is 15-30 minutes.

6. The deep processing technology for purifying crude sodium pyroantimonate according to claim 1, characterized in that, In the step of forming the water-soluble complex, the complexation reaction temperature is 40–60°C, and the complexation reaction time is 10–18 hours.

7. The deep processing technology for purifying crude sodium pyroantimonate according to claim 1, characterized in that, In the process of adding alkali solution for pH neutralization and adjustment, the pH value of the slurry is adjusted to 6.8-7.

2.

8. The deep processing technology for purifying crude sodium pyroantimonate according to claim 1, characterized in that, The step of preparing crude sodium pyroantimonate raw material into a slurry further includes a pre-washing and desalting step, wherein the pre-washing and desalting step is as follows: The crude sodium pyroantimonate raw material is mixed with pure water at a solid-liquid mass ratio of 1:(1.0-1.5). The pre-washing temperature of the mixture is 40-60°C, and the pre-washing stirring time is 0.5-1.5 hours, followed by solid-liquid separation.

9. The deep processing technology for purifying crude sodium pyroantimonate according to claim 8, characterized in that, After adjusting the pH of the slurry to 6.8–7.2, the method further includes: The slurry is further stirred and aged at a pH of 6.8 to 7.2, at a temperature of 40 to 60°C, for a time of 0.5 to 1.5 hours.

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