A method for preparing high-purity sodium pyroantimonate from antimony-containing waste

Abstract

This invention relates to a method for preparing high-purity sodium pyroantimonate from antimony-containing waste, belonging to the field of sodium pyroantimonate preparation technology. Specifically, the method includes: crushing and ball milling the antimony-containing waste, followed by sulfidation-alkali leaching in the presence of modified inorganic mineral additives. Antimony enters the solution as Na3[SbS3], while lead, copper, and iron precipitate as sulfides in the slag phase. The additives improve the settling and filtration performance of the leaching slag and assist in the adsorption of colloidal arsenic. After deep purification of the leachate with sodium sulfide, the mother liquor is cooled and crystallized to remove arsenic, which is separated as sodium arsenite crystals. The purified liquid undergoes air oxidation precipitation under seed crystal induction, followed by liquid-solid separation, washing, and drying to obtain high-purity sodium pyroantimonate product. This invention meets the quality requirements of electronic-grade glass clarifying agents, and features strong process compatibility, controllable additive costs, and recyclable mother liquor.

Description

Technical Field

[0001] This invention belongs to the field of sodium pyroantimonate preparation technology, specifically relating to a method for preparing high-purity sodium pyroantimonate from antimony-containing waste. Background Technology

[0002] In the process of antimony smelting and deep processing, a large amount of antimony-containing secondary resources are generated, such as antimony alkali slag, antimony-containing flue dust, and antimony refining slag. Refining alkali slag is a product of the alkali refining process for removing arsenic from crude antimony. The slag contains 20%–40% Sb, 3%–5% As, and a total basicity (calculated as Na₂CO₃) of 20%–30%. Antimony and arsenic mainly exist in the form of antimonates and arsenates. It also contains small amounts of SiO₂, CaO, Al₂O₂, S, Pb, and Fe. How to efficiently and selectively recover antimony from these complex materials and prepare high-purity sodium pyroantimonate, while properly handling associated impurities, is a key technical challenge facing the industry.

[0003] The existing wet processes for preparing sodium pyroantimonate from antimony-containing waste mainly include the following technical routes:

[0004] Chinese patent CN107858521A discloses a method for preparing sodium pyroantimonate from antimony-containing flue dust, which involves leaching with an alkaline solution containing oxalate reducing agent, followed by purification with sodium sulfide and oxidation with hydrogen peroxide. In this method, sodium sulfide may undergo a side reaction with antimony, resulting in antimony loss. Furthermore, excess sulfiding agent entering the oxidation process is oxidized to sulfate, affecting product purity.

[0005] Chinese patent CN113371757B discloses a method for preparing sodium pyroantimonate from high-arsenic antimony white and recycling the mother liquor. The mother liquor is reused after arsenic removal through cooling crystallization and lead-zinc removal through sulfidation. This method is mainly for high-arsenic antimony white raw materials and has limited applicability to antimony-containing wastes with more complex compositions, such as antimony alkali slag. Arsenic in the mother liquor mainly exists in the form of sodium arsenate, which is separated by low-temperature cooling crystallization.

[0006] In addition, the air oxidation method involves leaching sodium thioantimonate solution from sodium sulfide and then blowing air into it to generate sodium pyroantimonate product. This method has the advantage of low cost. However, the traditional air oxidation method has limited effectiveness in removing impurity ions from the solution, and the purity of the product is difficult to meet the standard requirements for electronic-grade glass clarifying agents.

[0007] The existing technology has the following main shortcomings:

[0008] (1) There is a contradiction between the deep removal of heavy metal impurities and the high recovery rate of antimony. When sodium sulfide removes impurities such as lead, excessive sodium sulfide will react with antimony and cause antimony precipitation loss; insufficient sulfiding agent will result in incomplete impurity removal.

[0009] (2) There is a lack of efficient means for the separation of arsenic. During the sulfide leaching process, arsenic partially enters the solution in the form of sodium thioarsenite. During the subsequent antimony oxidation precipitation, it may co-precipitate into the product. The arsenic separation efficiency of relying solely on the mother liquor circulation cooling crystallization is limited.

[0010] (3) During the oxidation precipitation stage, it is difficult to effectively control the problems of impurity entrainment and fine crystal agglomeration during crystal growth, which affects product purity and filtration performance.

[0011] (4) The leaching residue has poor settling and filtration performance and low liquid-solid separation efficiency, which affects production efficiency.

[0012] Therefore, there is an urgent need to develop a method for preparing sodium pyroantimonate from antimony-containing waste that can effectively improve the settling performance of leaching residue, inhibit impurity entrainment during the oxidation and precipitation stage, and comprehensively improve product purity. Summary of the Invention

[0013] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing high-purity sodium pyroantimonate from antimony-containing waste. This method introduces a modified inorganic mineral additive to effectively improve the settling and filtration performance of the leaching residue during the leaching stage, and slightly inhibits fine crystal agglomeration during the oxidation and precipitation stage. Combined with a synergistic impurity removal strategy of sulfide precipitation to remove heavy metals and mother liquor cooling crystallization to remove arsenic, a high-purity sodium pyroantimonate product is ultimately obtained.

[0014] The technical solution of the present invention is as follows:

[0015] A method for preparing high-purity sodium antimonate pyroantimonate from antimony-containing waste includes the following steps:

[0016] (1) Crush and ball-mill the antimony-containing waste to a particle size of -200 mesh or more (85%), and dry it for later use;

[0017] (2) Preparation of modified inorganic mineral additives: Chitosan quaternary ammonium salt is dissolved in acetic acid solution, and sepiolite or bentonite is added at a mass ratio of chitosan quaternary ammonium salt to inorganic mineral matrix of 1:(3-8). The modification reaction is carried out in a water bath at 50-70℃ with mechanical stirring at 200-300r / min for 2-4 hours. After centrifugation, washing, drying and grinding, the modified inorganic mineral additives are obtained.

[0018] (3) Mix the pretreated antimony-containing waste with the composite leaching agent at a liquid-solid mass ratio of (3-6):1 to make a slurry. Then add the modified inorganic mineral additive prepared in step (2) to the slurry. The amount added is 1%-4% of the dry weight of the antimony-containing waste. Heat the slurry to 75-95°C and mechanically stir and leach for 2-4 hours. Separate the liquid and solid to obtain the antimony-containing leachate.

[0019] (4) Cool the antimony-containing leaching solution to 60-75°C, detect the residual Pb and Cu concentrations in the solution, calculate the theoretical amount of sodium sulfide required for precipitation, add sodium sulfide at 1.0-1.3 times the theoretical amount, stir mechanically for 30-60 minutes, and filter to obtain the purified solution.

[0020] (5) Heat the purified liquid to 80-95℃, add high-purity sodium pyroantimonate seed crystals, the amount of seed crystals added is 2%-8% of the theoretical mass of sodium pyroantimonate produced, at a concentration of 0.8-2.0m 3 / (h·m 3 The flow rate is increased to allow air or oxygen-enriched air to pass through for an oxidation and precipitation reaction for 2 to 4 hours;

[0021] (6) Liquid-solid separation: after washing and drying, the solid is used to obtain high-purity sodium pyroantimonate product.

[0022] Furthermore, in step (3), the composite leaching agent is composed of sodium hydroxide and sodium sulfide, wherein the concentration of sodium hydroxide is 40-80 g / L and the concentration of sodium sulfide is 60-120 g / L.

[0023] Further, in step S4, when the arsenic content in the purified liquid is higher than 500 mg / L, the purified liquid is cooled to 5-15°C using an industrial chiller and kept at 100-150 r / min for 1-3 hours for cooling crystallization. The liquid and solid are separated to obtain the arsenic-removed liquid and the arsenic-containing crystal product. The arsenic-removed liquid is then processed through steps (5) and (6) to obtain a high-purity sodium pyroantimonate product.

[0024] Furthermore, the oxidized liquid after solid-liquid separation in step (6) is returned to step (3) for recycling. During the recycling process, the concentration of NaOH in the mother liquor is monitored to maintain 40-80 g / L and the concentration of Na2S is maintained to maintain 60-120 g / L.

[0025] Furthermore, in step (4), the concentrations of residual Pb and Cu in the solution are detected by ICP-OES.

[0026] Furthermore, the degree of substitution of the chitosan quaternary ammonium salt in step (2) is 0.6–0.9, and the molecular weight is 5 × 10⁻⁶. 4 ~1.5×10 5 Da.

[0027] Furthermore, the inorganic mineral matrix mentioned in step (2) is sepiolite or sodium bentonite; the purity of sepiolite is ≥85% and the specific surface area is ≥150m² / g, and the purity of sodium bentonite is ≥90% and the cation exchange capacity is 80~120mmol / 100g.

[0028] Furthermore, in step (2), the mass ratio of chitosan quaternary ammonium salt to inorganic mineral matrix is ​​1:(4-6), the modification reaction temperature is 60℃, the reaction time is 3 hours, and the mechanical stirring speed is 250r / min.

[0029] Furthermore, in step (5), the amount of seed crystals added is 3% to 6% of the theoretically generated sodium pyroantimonate mass, the oxidation precipitation temperature is 85 to 90°C, and the air flow rate is 1.0 to 1.5 m³ / h. 3 / (h·m 3 The reaction time is 2.5 to 3.5 hours.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] 1. The modified inorganic mineral additive used in this invention—based on sepiolite or bentonite and modified with chitosan quaternary ammonium salt—has a clear functional positioning: in the leaching stage, its surface quaternary ammonium salt groups adsorb colloidal arsenic sulfide and other fine particles through electrostatic interaction, and its layered or fibrous structure improves the settling and filtration performance of the leaching residue; in the oxidation and precipitation stage, trace residual components slightly inhibit the agglomeration of fine crystals.

[0032] 2. This invention achieves effective separation of various impurities through a four-pronged synergistic strategy: in-situ precipitation of lead, copper, and iron during the sulfidation and alkaline leaching stage; adsorption of colloidal arsenic by additives; arsenic removal through mother liquor cooling and crystallization; and inhibition of impurity entrainment by seed crystals. Under optimized process conditions, the arsenic removal rate is ≥92%, the lead removal rate is ≥98%, the iron removal rate is ≥97%, and the copper removal rate is ≥97%.

[0033] 3. In this invention, after the leachate is deeply purified, it undergoes oxidation precipitation under seed crystal induction. The resulting sodium pyroantimonate product has a main component content of ≥99.5%, Fe≤180ppm, Pb≤8mg / kg, As≤4mg / kg, and Cu≤5mg / kg, which meets the quality requirements of electronic grade glass clarifying agent.

[0034] 4. Chitosan quaternary ammonium salt is a bulk industrial product, while sepiolite and bentonite are inexpensive natural minerals. The additive preparation process is simple, and the addition amount is only 1% to 4% of the raw material amount, making the overall cost controllable. The additive is added once in the leaching stage, and the subsequent processes are fully compatible with the existing wet process, without the need to add complex equipment units, resulting in low cost for upgrading existing wet production lines.

[0035] 5. The addition of additives increases the settling speed of leaching residue by 30% to 60%, significantly improving the efficiency of liquid-solid separation, which is beneficial for continuous industrial production.

[0036] 6. The oxidized liquid is returned to the leaching process for recycling, reducing alkali consumption and wastewater discharge; arsenic is separated in the form of sodium arsenite crystals, which can be sold as a raw material for glass clarifying agent, realizing the resource utilization of arsenic and meeting the requirements of clean production and circular economy. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0038] 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.

[0039] like Figure 1 As shown, a method for preparing high-purity sodium pyroantimonate from antimony-containing waste includes the following steps;

[0040] Example 1

[0041] This embodiment uses antimony alkali slag from an antimony smelter as raw material. The main components and their mass percentages are: Sb 41.2%, As 3.8%, Pb 2.5%, Fe 1.9%, Cu 0.5%, Cd 0.03%, with the remainder being sodium salts and gangue components. Antimony and arsenic in the raw material mainly exist in the form of antimonates and arsenates.

[0042] (1) Raw material pretreatment: The antimony alkali slag is crushed and ball-milled to a particle size of -200 mesh accounting for 88%, and dried at 90℃ for later use. The -200 mesh is the particle size that can pass through a 100 mesh sieve but is intercepted by a 200 mesh sieve.

[0043] (2) Preparation of modified inorganic mineral additives: Take 10g of chitosan quaternary ammonium salt, wherein the degree of substitution of chitosan quaternary ammonium salt is 0.8 and the molecular weight is about 8×10 4 Da was dissolved in 500 mL of a 1.5% acetic acid solution and stirred until completely dissolved to prepare a 2% chitosan quaternary ammonium salt solution. 50 g of sepiolite was added at a chitosan quaternary ammonium salt to sepiolite mass ratio of 1:5, wherein the sepiolite purity was ≥87% and the specific surface area was 180 m². 2 / g, in a 60℃ water bath, mechanically stirred at 250r / min for 3 hours to modify the reaction. After the reaction, centrifuge, wash with deionized water until neutral, dry at 70℃ for 8 hours, and grind to a particle size of -200 mesh to obtain the modified inorganic mineral additive for later use.

[0044] (3) Co-leaching of antimony-alkali residue with additive-assisted sedimentation: 100g of pretreated antimony-alkali residue was mixed with a composite leaching agent at a liquid-to-solid mass ratio of 4:1 to form a slurry. The NaOH concentration in the composite leaching agent was 60g / L, and the Na2S concentration was 90g / L. 2.5g of the modified inorganic mineral additive prepared in step (2) was added to the slurry. The slurry was heated to 85℃ and leached for 3 hours under mechanical stirring. After leaching, the liquid and solid were separated by plate and frame filtration while hot to obtain antimony-containing leachate and leaching residue. The antimony leaching rate was 96.8%, the sedimentation rate of the leaching residue was increased by about 45% compared with that without the additive, and the filtration time was shortened by about 35%.

[0045] (4) Sulfide Depth Removal: The antimony-containing leaching solution was cooled to 70°C. ICP-OES analysis revealed a residual Pb concentration of 32 mg / L and a Cu concentration of 18 mg / L. Based on this, the theoretical amount of sodium sulfide required for precipitation was calculated. Considering that trace amounts of other heavy metal ions such as Cd and Zn might remain in the solution and consume sulfide ions, to ensure complete precipitation of lead and copper ions, the actual amount of sodium sulfide added was 1.1 times the theoretical amount. The reaction was carried out under mechanical stirring for 45 minutes. After the reaction, plate and frame filtration was used to separate the purified solution and heavy metal sulfide residue. Analysis showed that the Pb content in the solution decreased to 0.6 mg / L and the Cu content decreased to 0.4 mg / L.

[0046] The calculation of the theoretical amount of sodium sulfide required for precipitation is as follows:

[0047] The residual Pb and Cu concentrations (mg / L) in the solution were determined using inductively coupled plasma optical emission spectrometry (ICP-OES), and the volume V1 (L) of the antimony-containing leachate was measured. The residual lead and copper in the solution mainly existed as soluble hydroxyl complexes, such as [Pb(OH)4]. 2- [Cu(OH)4] 2- It exists in a certain form, and upon the addition of sodium sulfide, the following precipitation reaction occurs:

[0048] Lead removal reaction: [Pb(OH)4] 2- + S 2- → PbS↓ + 4OH⁻;

[0049] Copper removal reaction: [Cu(OH)4] 2- + S 2- → CuS↓ + 4OH⁻;

[0050] According to the above chemical reaction equation, 1 mole of lead ions consumes 1 mole of sulfide ions, and 1 mole of copper ions consumes 1 mole of sulfide ions. The theoretically required mass of sodium sulfide, m1 (in g), is calculated using the following formula:

[0051] m1= [ (C1 / M1) + (C2 / M2) ] × V × M3 × 10 -3 ;

[0052] In the formula:

[0053] C1—Residual lead concentration in solution as detected by ICP-OES, mg / L;

[0054] C2—Residual copper concentration in the solution as detected by ICP-OES, mg / L;

[0055] M1—Molar mass of lead, 207.2 g / mol;

[0056] M2—Molar mass of copper, 63.5 g / mol;

[0057] V1 — Volume of antimony-containing leachate, in L;

[0058] M3 – Molar mass of sodium sulfide, 78.0 g / mol.

[0059] (5) Arsenic Removal by Cooling and Crystallizing Mother Liquor: This step was performed because the As content in the leachate reached 1850 mg / L. The purified liquid was cooled to 10°C using an industrial chiller and kept at that temperature for 2 hours under mechanical stirring at 120 r / min. Some of the sodium thioarsenite and sodium arsenite in the solution were converted into sodium arsenite crystals and precipitated, with the sodium arsenite crystals mainly being Na3AsO3·5H2O. Liquid-solid separation was performed to obtain the arsenic-removed liquid and the arsenic-containing crystalline product. The As content in the solution was reduced to 320 mg / L, and the arsenic removal rate was approximately 82.7%.

[0060] (6) Seed-induced oxidation precipitation: The arsenic-removed solution is heated to 88°C. Under mechanical stirring, high-purity sodium pyroantimonate seed crystals are added first, with the amount added being 5% of the theoretical mass of sodium pyroantimonate to be generated from antimony in the solution; then, according to 1.2m 3 / (h·m 3 Air is introduced at a flow rate of 100% to initiate an oxidation precipitation reaction, which lasts for 3 hours. Sodium thioantimonite in the solution is oxidized, and antimony crystallizes and precipitates on the seed crystal surface as sodium pyroantimonite.

[0061] The theoretically generated sodium pyroantimonate mass is calculated using the following method:

[0062] First, the concentration C of antimony in the purified liquid or arsenic-removed liquid was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). Sb(Unit: g / L), and measure the solution volume V2 (unit: L). Antimony in the solution mainly exists as sodium thioantimonyate. Under conditions of air oxidation and the addition of sodium hydroxide, sodium thioantimonyate is oxidized and reacts with sodium hydroxide to form sodium pyroantimonyate precipitate. The chemical reaction equation is:

[0063] 2Na3[SbS3] + 5H2O2+ 2NaOH + 9H2O → 2Na[Sb(OH)6]↓ + 6S↓ + 6NaOH;

[0064] In the actual oxidation process, oxygen from the air is introduced as the oxidant, and the overall reaction can be simplified to:

[0065] 2Na3[SbS3] + 5O2 + 2NaOH + 11H2O → 2Na[Sb(OH)6]↓ + 6S↓ + 6NaOH;

[0066] As can be seen from the reaction equation, when all the antimony in the solution is converted into sodium pyroantimonate, 1 mole of antimony atoms (Sb) generates 1 mole of sodium pyroantimonate.

[0067] The molar mass of sodium pyroantimonate is 246.8 g / mol, where Na = 23.0, Sb = 121.8, O = 16.0 × 6 = 96.0, H = 1.0 × 6 = 6.0, and the molar mass of antimony is 121.8 g / mol.

[0068] The total mass of antimony in the solution m Sb (Unit: g) Calculate using the following formula:

[0069] m Sb = C Sb ×V2;

[0070] The theoretical mass of sodium pyroantimonate produced, m 理论 (Unit: g) Calculate using the following formula:

[0071] m 理论 = m Sb × (M 焦锑酸钠 / M 锑 ) = m Sb ×(246.8 / 121.8) ≈ m Sb ×2.026;

[0072] Theoretically, the mass of sodium pyroantimonate produced is approximately 2.026 times the total mass of antimony in the solution.

[0073] Seed addition amount m 晶种 (Unit: g) represents 2% to 8% of the theoretically produced sodium pyroantimonate mass, i.e.:

[0074] m晶种 = m 理论 ×(2%~8%);

[0075] (7) Post-processing: The reaction slurry was centrifuged and filtered to separate the liquid and solid, resulting in wet sodium pyroantimonate and oxidized liquid. The wet sodium pyroantimonate was washed three times with deionized water and then dried at 110°C for 5 hours to obtain high-purity sodium pyroantimonate product. The oxidized liquid contained 52 g / L NaOH, 78 g / L Na2S, 15 g / L sodium carbonate, and 8 g / L sodium thiosulfate. It was recycled back to step (3) and NaOH and Na2S were replenished to the initial concentration.

[0076] (8) Product testing results: The obtained sodium pyroantimonate product has a main component content of 99.6% and a total impurity content of 0.36%. Heavy metal content: Pb 5mg / kg, As 3mg / kg, Cd 0.5mg / kg, Cu 3mg / kg, Fe2O3 150ppm. The product quality meets the standard requirements for high-purity sodium pyroantimonate.

[0077] Example 2

[0078] This embodiment uses antimony-containing flue dust produced by a lead-antimony smelting plant as raw material. The main components and their mass percentages are: Sb 28.5%, Pb 8.6%, As 6.2%, Fe 2.3%, Cu 0.8%, and Cd 0.05%.

[0079] (1) Raw material pretreatment: antimony-containing flue ash is ball-milled to a particle size of -200 mesh accounting for 90%, and dried at 85℃ for later use.

[0080] (2) Preparation of modified inorganic mineral additives: Bentonite was used as the matrix material. 10g of chitosan quaternary ammonium salt was taken, wherein the degree of substitution of chitosan quaternary ammonium salt was 0.6 and the molecular weight was about 5×10. 4 Da was dissolved in 400 mL of a 1.5% acetic acid solution. 30 g of bentonite was added at a chitosan quaternary ammonium salt to sodium bentonite mass ratio of 1:3, wherein the sodium bentonite had a purity ≥90% and a cation exchange capacity of 80 mmol / 100 g. The mixture was mechanically stirred at 200 r / min in a 50°C water bath for 2 hours for modification. Subsequent treatment was the same as in Example 1.

[0081] (3) Sulfide-alkali leaching synergistic leaching and additive-assisted sedimentation: 100g of pretreated antimony-containing fly ash was mixed with a composite leaching agent at a liquid-to-solid mass ratio of 3:1 to form a slurry. The NaOH concentration in the composite leaching agent was 40g / L, and the Na2S concentration was 60g / L. 1g of modified inorganic mineral additive was added to the slurry. The slurry was heated to 75℃ and leached for 2 hours under mechanical stirring. After leaching, liquid-solid separation was performed by plate and frame filtration while still hot. The antimony leaching rate was found to be 95.8%, and the sedimentation rate of the leaching residue was increased by approximately 30% compared to the result without additives.

[0082] (4) Sulfide Depth Removal: The residual Pb and Cu concentrations in the antimony-containing leachate were detected by ICP-OES. Sodium sulfide was added at 1.0 times the theoretical amount, and the reaction was mechanically stirred at 60°C for 30 minutes. Plate and frame filtration was used for separation. The Pb content in the solution was reduced to 0.9 mg / L, and the Cu content was reduced to 0.6 mg / L.

[0083] (5) Arsenic removal by cooling and crystallization of mother liquor: This step is performed because the As content in the leachate is 1850 mg / L. The purified liquid is cooled to 5°C using an industrial chiller and kept at 100 r / min for 1 hour under mechanical stirring. The liquid and solid are separated to obtain the arsenic-removed liquid and the arsenic-containing crystallized product. The arsenic removal rate is about 78.5%.

[0084] (6) Seed-induced oxidation precipitation: Heat the arsenic-removed solution to 80°C, add seed crystals, wherein the amount added is 2% of the theoretical mass of sodium pyroantimonate to be generated from antimony in the solution, according to 0.8m 3 / (h·m 3 The air flow rate is increased to allow for oxidation and precipitation reaction, with a reaction time of 2 hours.

[0085] (7) Post-processing: Centrifuge and filter to separate liquid and solid, wash twice, and dry at 100℃ for 4 hours to obtain the finished product. The oxidized liquid is returned for recycling, and NaOH and Na2S are added according to the monitored concentration.

[0086] (8) Product test results: The obtained sodium pyroantimonate product has a main component content of 99.5% and a total impurity content of 0.45%. Heavy metal content: Pb 8mg / kg, As 4mg / kg, Cd 0.7mg / kg, Cu 5mg / kg, Fe2O3 180ppm.

[0087] Example 3

[0088] This embodiment uses antimony refining slag produced by antimony smelting as raw material. The main components and mass percentages are: Sb 35.8%, Pb 3.8%, As 2.5%, Fe 4.2%, Cu 0.6%, and Cd 0.04%.

[0089] (1) Raw material pretreatment: The antimony refining slag is ball-milled to a particle size of -200 mesh, accounting for 86%, and dried at 95℃ for later use.

[0090] (2) Preparation of modified inorganic mineral additives: Sepiolite was used as the matrix material. 10g of chitosan quaternary ammonium salt was taken, wherein the degree of substitution of chitosan quaternary ammonium salt was 0.9 and the molecular weight was approximately 1.5×10. 5 Da is dissolved in 500 mL of 2% acetic acid solution. 80 g of sepiolite is added at a chitosan quaternary ammonium salt to sepiolite mass ratio of 1:8, wherein the sepiolite has a purity ≥85% and a specific surface area of ​​150 m². 2 / g, and mechanically stirred at 300r / min in a 70℃ water bath for 4 hours for modification. Subsequent treatment was the same as in Example 1.

[0091] (3) Sulfide-alkali leaching synergistic leaching and additive-assisted sedimentation: 100g of pretreated antimony refining slag was mixed with a composite leaching agent at a liquid-to-solid mass ratio of 6:1 to form a slurry. The NaOH concentration in the composite leaching agent was 80g / L, and the Na2S concentration was 120g / L. 4g of modified inorganic mineral additive was added to the slurry. The slurry was heated to 95℃ and leached for 4 hours under mechanical stirring. After leaching, liquid-solid separation was performed by plate and frame filtration while the slag was still hot. The antimony leaching rate was found to be 97.5%, and the sedimentation rate of the leached slag was increased by approximately 60% compared to the leaching without additives.

[0092] (4) Sulfide Depth Removal: The residual Pb and Cu concentrations in the antimony-containing leachate were detected by ICP-OES. Sodium sulfide was added at 1.3 times the theoretical amount, and the reaction was carried out with mechanical stirring at 75°C for 60 minutes. Plate and frame filtration was used for separation. The Pb content in the solution was reduced to 0.3 mg / L and the Cu content was reduced to 0.2 mg / L.

[0093] (5) Arsenic Removal by Cooling Crystallization of Mother Liquor: In this embodiment, the As content in the raw material is 2.5%, and the As concentration in the leachate is approximately 1100 mg / L. Arsenic removal by cooling crystallization is performed. The purified liquid is cooled to 15°C using an industrial chiller and kept at this temperature for 3 hours under mechanical stirring at 150 r / min. Liquid-solid separation yields the arsenic-removed liquid and arsenic-containing crystalline products, primarily sodium arsenite crystals. The arsenic removal rate is approximately 86.2%.

[0094] (6) Seed-induced oxidation precipitation: Heat the arsenic-removed liquid to 95°C, add seed crystals, wherein the amount of seed crystals added is 8% of the theoretical amount, at a concentration of 2.0m 3 / (h·m 3 The flow rate of oxygen-enriched air is introduced to carry out an oxidation and precipitation reaction, which takes 4 hours.

[0095] (7) Post-processing: The liquid and solid components are separated by centrifugation and filtration, washed 3 times, and dried at 120°C for 6 hours to obtain the finished product. The oxidized liquid is returned for recycling, and NaOH and Na2S are added according to the monitored concentration.

[0096] (8) Product test results: The main component content of the obtained sodium pyroantimonate product was 99.7%, and the total impurity content was 0.28%. Heavy metal content: Pb 3mg / kg, As 2mg / kg, Cd 0.3mg / kg, Cu 2mg / kg, Fe2O3 120ppm.

[0097] Comparative Example 1

[0098] The difference from Example 1 is that no modified inorganic mineral additives are added in step (3), while the other conditions are the same as in Example 1.

[0099] Results: The antimony leaching rate was 96.5%. However, the settling speed of the leaching residue was significantly slower, and the liquid-solid separation time was extended by about 50%. The final sodium pyroantimonate product contained: 99.0% main component, 12 mg / kg Pb, 8 mg / kg As, and 250 ppm Fe2O3. Neither the product purity nor the impurity content met the high-purity standard requirements.

[0100] Comparative Example 2

[0101] The difference from Example 1 is that step (5) of cooling and crystallizing the mother liquor to remove arsenic is omitted, while other conditions are the same as in Example 1. It should be noted that the arsenic content of the leachate in this comparative example is the same as in Example 1, but since the cooling and crystallization step to remove arsenic is not performed, the arsenic cannot be separated in crystal form and directly enters the subsequent oxidation and precipitation process.

[0102] Results: Because arsenic was not separated by cooling crystallization, it gradually accumulated during the recycling of the oxidized solution. After 5 cycles, the As content in the product increased from 3 mg / kg to 15 mg / kg, exceeding the standard requirements. This indicates that when the arsenic content in the leachate exceeds 500 mg / L, cooling crystallization of the mother liquor to remove arsenic is a crucial step in ensuring that the arsenic content in the product meets the standards.

[0103] Comparative Example 3

[0104] The difference from Example 1 is that no seed crystals are added in step (6), and oxidation precipitation is carried out directly.

[0105] Results: The obtained sodium pyroantimonate product had a main component content of 98.8%, a Pb content of 18 mg / kg, and a Fe2O3 content of 320 ppm. The product purity was significantly lower than that of Example 1. Furthermore, the product particles were finer, resulting in poor filtration and washing performance.

[0106] Comparative analysis of the effects of each embodiment and comparative example

[0107] Antimony leaching rate (%) 96.8 95.8 97.5 96.5 96.8 96.8 Main product content (%) 99.6 99.5 99.7 99.0 99.3 98.8 As content (mg / kg) 3 4 2 8 15 (after 5 cycles) 6 Pb content (mg / kg) 5 8 3 12 6 18 <![CDATA[Fe2O3 content (ppm)]]> 150 180 120 250 160 320 Filtration performance of leaching residue excellent good excellent Difference excellent — Does it meet the standard (≥99.5%)? yes yes yes no no no

[0108] The comparison results show that:

[0109] (1) Examples 1 to 3 respectively verified the feasibility of the middle value, the value near the lower limit endpoint, and the value near the upper limit endpoint of the scope of protection of the claims. All examples can produce products that meet the high purity standard, which fully proves that the technical solution of the present invention has feasibility and beneficial effects throughout the entire scope of protection.

[0110] (2) The addition of modified inorganic mineral additives significantly improved the settling and filtration performance of the leaching residue, and at the same time had an auxiliary adsorption and removal effect on trace amounts of arsenic.

[0111] (3) Cooling and crystallizing the mother liquor to remove arsenic is a key step in controlling arsenic accumulation and ensuring that the arsenic content of the product meets the standards under long-term circulating conditions;

[0112] (4) Seed induction can effectively suppress impurity entrainment, improve product purity and enhance filtration performance;

[0113] (5) Only through the synergistic effect of the four can the goal of preparing high-purity sodium pyroantimonate from antimony-containing waste be stably achieved.

[0114] Example 4

[0115] This embodiment verifies the continuous impact of mother liquor recycling on the process. Based on the conditions of Example 1, all the oxidized liquid from each batch was returned to step (3) for the preparation of the composite leaching agent, and a total of 10 cycles were performed. The concentrations of NaOH and Na2S in the circulating mother liquor were monitored for each batch, and reagents were added to maintain the NaOH concentration at 55-65 g / L and the Na2S concentration at 85-95 g / L. Modified inorganic mineral additives were added fresh for each batch at 2.5% of the dry weight of the raw materials. The mother liquor cooling crystallization arsenic removal step was performed for each batch (10°C, heat preservation for 2 hours, 120 r / min).

[0116] After 10 cycles, the antimony leaching rate remained between 95.5% and 97.0%, the main component content of the sodium pyroantimonate product remained between 99.3% and 99.6%, the Fe₂O₃ content ranged from 145 to 175 ppm, the As content ranged from 2.5 to 4 mg / kg, and the Pb content ranged from 4 to 7 mg / kg. The arsenic concentration in the mother liquor was 320 mg / L in the first batch, 385 mg / L in the fifth batch, and 415 mg / L in the tenth batch, without any sustained large-scale accumulation, verifying the long-term cyclic stability of the process.

[0117] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing high-purity sodium pyroantimonate from antimony-containing waste, characterized in that: Includes the following steps: (1) Crush and ball-mill the antimony-containing waste to a particle size of -200 mesh or more (85%), and dry it for later use; (2) Preparation of modified inorganic mineral additives: Chitosan quaternary ammonium salt is dissolved in acetic acid solution, and sepiolite or bentonite is added at a mass ratio of chitosan quaternary ammonium salt to inorganic mineral matrix of 1:(3-8). The modification reaction is carried out in a water bath at 50-70℃ with mechanical stirring at 200-300r / min for 2-4 hours. After centrifugation, washing, drying and grinding, the modified inorganic mineral additives are obtained. (3) The pretreated antimony-containing waste is mixed with a composite leaching agent composed of sodium hydroxide and sodium sulfide at a liquid-solid mass ratio of (3-6):1 to form a slurry. Then, the modified inorganic mineral additive prepared in step (2) is added to the slurry, with the amount added being 1%-4% of the dry weight of the antimony-containing waste. The slurry is heated to 75-95°C and mechanically stirred for 2-4 hours to leach. The liquid and solid are separated to obtain the antimony-containing leachate. The concentration of sodium hydroxide in the composite leaching agent is 40–80 g / L, and the concentration of sodium sulfide is 60–120 g / L; (4) Cool the antimony-containing leaching solution to 60-75°C, detect the residual Pb and Cu concentrations in the solution, calculate the theoretical amount of sodium sulfide required for precipitation, add sodium sulfide at 1.0-1.3 times the theoretical amount, stir mechanically for 30-60 minutes, and filter to obtain the purified solution. (5) heating the purified solution to 80-95℃, adding high-purity sodium pyroantimonate crystal seeds, the amount of crystal seeds added being 2%-8% of the theoretical mass of sodium pyroantimonate generated, and passing air or oxygen-rich air at a flow rate of 0.8-2.0 m 3 / (h·m 3 ) to carry out the oxidation precipitation reaction for 2-4 hours; (6) filtering the solution to obtain sodium pyroantimonate crystals; (6) Liquid-solid separation: after washing and drying, the solid is used to obtain high-purity sodium pyroantimonate product.

2. The method for preparing high-purity sodium pyroantimonate from antimony-containing waste according to claim 1, characterized in that: In step (4), when the arsenic content in the purified liquid is higher than 500 mg / L, the purified liquid is cooled to 5-15°C using an industrial chiller and kept warm for 1-3 hours under mechanical stirring at 100-150 r / min for cooling crystallization. Liquid-solid separation is performed to obtain arsenic-removed liquid and arsenic-containing crystal products. The arsenic-removed liquid is then processed through steps (5) and (6) to obtain high-purity sodium pyroantimonate product.

3. The method for preparing high-purity sodium pyroantimonate from antimony-containing waste according to claim 1, characterized in that: The oxidized liquid after solid-liquid separation in step (6) is returned to step (3) for recycling. During the recycling process, the concentration of NaOH in the mother liquor is monitored to maintain 40-80 g / L and the concentration of Na2S is maintained to maintain 60-120 g / L.

4. The method for preparing high-purity sodium pyroantimonate from antimony-containing waste according to claim 1, characterized in that: In step (4), the concentrations of residual Pb and Cu in the solution are detected by ICP-OES.

5. The method for preparing high-purity sodium pyroantimonate from antimony-containing waste according to claim 1, characterized in that: The degree of substitution of the chitosan quaternary ammonium salt in step (2) is 0.6–0.9, and the molecular weight is 5 × 10⁻⁶. 4 ~1.5×10 5 Da.

6. The method for preparing high-purity sodium pyroantimonate from antimony-containing waste according to claim 1, characterized in that: The inorganic mineral matrix mentioned in step (2) is sepiolite or sodium bentonite; the purity of sepiolite is ≥85% and the specific surface area is ≥150m² / g, and the purity of sodium bentonite is ≥90% and the cation exchange capacity is 80~120mmol / 100g.

7. The method for preparing high-purity sodium pyroantimonate from antimony-containing waste according to claim 1, characterized in that: In step (2), the mass ratio of chitosan quaternary ammonium salt to inorganic mineral matrix is ​​1:(4-6), the modification reaction temperature is 60℃, the reaction time is 3 hours, and the mechanical stirring speed is 250r / min.

8. The method for preparing high-purity sodium pyroantimonate from antimony-containing waste according to claim 1, characterized in that: In step (5), the amount of seed crystals added is 3% to 6% of the theoretical mass of sodium antimonate pyroantimonate, the oxidation precipitation temperature is 85 to 90°C, and the air flow rate is 1.0 to 1.5 m³ / h. 3 / (h·m 3 The reaction time is 2.5 to 3.5 hours.

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