A method for preparing sodium antimonate based on multi-stage leaching and deep oxidation

Abstract

The present application relates to the field of comprehensive recovery of non-ferrous and strategic metal resources and preparation of chemical products, and particularly relates to a method for preparing sodium antimonate based on multi-stage leaching and deep oxidation. The method comprises water leaching arsenic pretreatment and open circuit, multi-stage countercurrent leaching treatment of arsenic removal residue, sodium sulfite tellurium precipitation, and antimony precipitation by oxidation. The present application synchronously realizes high leaching rate of antimony and high utilization rate of sodium sulfide reagent through the multi-stage countercurrent leaching system with real-time potential regulation, thereby reducing production cost and impurity interference from the source, so as to stably prepare high-purity sodium antimonate with sulfur content lower than 0.15%.

Description

Technical Field

[0001] This invention relates to the field of comprehensive recycling of non-ferrous and strategic metal resources and preparation of chemical products, specifically to a method for preparing sodium antimonate based on multi-stage leaching and deep oxidation. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Antimony is an important strategic minor metal, listed as a critical mineral by many countries. It has irreplaceable applications in flame retardants, photovoltaic glass clarifying agents, lead-acid batteries, and the military industry. However, antimony is extremely rare due to its very low abundance in the Earth's crust and limited global reserves. With the rapid development of emerging fields, especially the photovoltaic industry, the demand for high-quality antimony products continues to grow, making the recovery of antimony from secondary resources crucial.

[0004] Arsenic-antimony slag is a typical type of antimony-containing hazardous waste generated during the smelting of non-ferrous metals such as copper and lead, and the recovery of precious metals. Traditionally, antimony recovery from complex antimony-containing materials such as arsenic-antimony slag has primarily employed pyrometallurgical processes, such as volatilization roasting, vacuum distillation, and high-temperature reduction smelting. These methods suffer from high energy consumption, environmental pollution from the volatilization of toxic substances like arsenic, and unsatisfactory metal recovery rates. In recent years, hydrometallurgical processes have become the mainstream research approach due to their environmental advantages. However, the main problem with this approach is the significant contradiction between leaching efficiency and reagent consumption: constrained by the industry bottleneck of 'difficult solution preparation,' excessive amounts of sodium sulfide are often added to ensure leaching rates. This not only wastes reagents but also creates a double challenge of 'competition from high background antimony ions' and 'interference from free sulfur' in the subsequent tellurium precipitation step, becoming a primary obstacle to product purity.

[0005] Therefore, developing an integrated wet process that can efficiently and cleanly recover antimony from arsenic-antimony slag and stably produce low-sulfur, high-purity antimony is of great significance for enhancing the value of secondary resources and meeting the needs of high-end industries. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing sodium antimonate based on multi-stage leaching and deep oxidation. Through the multi-stage countercurrent and real-time potential-controlled leaching system, the present invention simultaneously achieves a high antimony leaching rate and a high utilization rate of sodium sulfide reagent, thereby reducing production costs and minimizing impurity interference from the source, and thus enabling the stable preparation of high-purity sodium antimonate products with low sulfur content.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: A method for preparing sodium antimonate based on multi-stage leaching and deep oxidation includes at least two processes of preparing sodium antimonate using arsenic-antimony slag; wherein the Nth process of preparing sodium antimonate using arsenic-antimony slag includes the following steps: Arsenic compounds in arsenic-antimony slag were dissolved by water leaching to obtain arsenic-containing liquid and arsenic-removed slag; The arsenic-removed slag is treated using a multi-stage countercurrent leaching method. The treatment process is as follows: the leaching agent obtained from the (N-1)th process of preparing sodium antimony from arsenic-antimony slag is used to perform a first-stage leaching treatment on the arsenic-removed slag to obtain a first-stage leachate and a first-stage leaching residue; the first-stage leaching residue is then treated with a sodium sulfide solution to perform a second-stage leaching treatment to obtain a second-stage leachate; the first-stage leaching treatment is performed once; the second-stage leaching treatment is performed at least once, and the leachate obtained from the last leaching treatment is the second-stage leachate; sodium sulfide solution is added to the second-stage leachate and mixed evenly until the oxidation-reduction potential (ORP) reaches a preset value, which is the leaching agent used to treat the (N+1)th process of preparing sodium antimony from arsenic-antimony slag. The first-stage leachate was treated with sodium sulfite to precipitate tellurium in the leachate, yielding crude tellurium and tellurium-free liquid. The solution after tellurium removal is oxidized to produce sodium antimonate precipitate. N is a natural number greater than 1.

[0008] In some implementations, the default value for ORP is -650 to -500 mV.

[0009] In some implementations, the amount of sodium sulfite added is 2.5 to 3 times the amount of sodium sulfite required for theoretical precipitation of tellurium in a first-stage leachate.

[0010] In some implementations, the pH of the reaction system is 12-14 and the temperature is 80-90°C during the oxidation reaction.

[0011] Compared with the prior art, the present invention has the following significant advantages: 1. This invention achieves highly efficient and selective leaching of soluble arsenic through a mild water leaching method, while simultaneously and effectively inhibiting the co-dissolution of associated tellurium. This step thus achieves clean arsenic extraction and initial enrichment of valuable metals at the source, providing a crucial "clean" raw material foundation for subsequent core processes such as "multi-stage countercurrent-ORP controlled" leaching.

[0012] 2. By constructing an intelligent leaching system of "multi-stage countercurrent-ORP precise control", this invention not only achieves efficient antimony leaching and reagent saving, but more importantly, it stably produces the leaching solution used for subsequent purification, laying a decisive foundation for the optimization of the entire process.

[0013] 3. In response to the "high antimony and low tellurium" system caused by raw material differences, this invention overcomes the dual consumption bottleneck of high antimony competition and residual free sulfur ions by optimizing the amount of sodium sulfite added. This invention achieves efficient and selective removal of tellurium, cutting off the impurity migration pathway from the core link.

[0014] 4. This invention forms a complete product deep purification path through the synergistic design of "deep tellurium precipitation" and "high pH high temperature deep oxidation", which can stably produce high-purity sodium antimonate with a sulfur content of less than 0.15%, meeting the standards of high-end applications such as photovoltaic glass.

[0015] 5. This invention integrates the stabilization and opening of arsenic, the high-value recovery of valuable metals, the resource utilization of mother liquor, and the reuse of wastewater, thus constructing a complete clean production system for comprehensive resource utilization and near-zero pollution emissions, and solving the environmental problems left by existing technologies. Attached Figure Description

[0016] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0017] Figure 1 This is a process flow diagram of Embodiment 1 of the present invention; Figure 2 This is a comparison of the macroscopic appearance of sodium antimonate obtained in Example 1 of the present invention (left) and the product obtained in Comparative Example 10 (right). Detailed Implementation

[0018] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0019] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0020] Existing wet processes for recovering antimony from arsenic-antimony slag suffer from problems such as extensive leaching process control, high reagent consumption, severe impurity interference, high sulfur content in the product, and a lack of systematic solutions for the treatment of high-arsenic raw materials and high-salt wastewater. This invention proposes a method for preparing sodium antimonate based on multi-stage leaching and deep oxidation.

[0021] A typical embodiment of the present invention provides a method for preparing sodium antimonate based on multi-stage leaching and deep oxidation, comprising at least two processes of preparing sodium antimonate using arsenic-antimony slag; wherein the Nth process of preparing sodium antimonate using arsenic-antimony slag includes the following steps: Arsenic compounds in arsenic-antimony slag were dissolved by water leaching to obtain arsenic-containing liquid and arsenic-removed slag; The arsenic-removed slag is treated using a multi-stage countercurrent leaching method. The treatment process is as follows: the leaching agent obtained from the (N-1)th process of preparing sodium antimony from arsenic-antimony slag is used to perform a first-stage leaching treatment on the arsenic-removed slag, obtaining a first-stage leachate and a first-stage leaching residue; the first-stage leaching residue is then treated with a sodium sulfide solution to perform a second-stage leaching treatment, obtaining a second-stage leachate; the first-stage leaching treatment is performed once; the second-stage leaching treatment is performed at least once, and the leachate obtained from the last leaching treatment is the second-stage leachate; sodium sulfide solution is added to the second-stage leachate and mixed evenly until the ORP reaches a preset value, thus obtaining the leaching agent used to treat the (N+1)th process of preparing sodium antimony from arsenic-antimony slag. The first-stage leachate was treated with sodium sulfite to precipitate tellurium in the leachate, yielding crude tellurium and tellurium-free liquid. The solution after tellurium removal is oxidized to produce sodium antimonate precipitate. N is a natural number greater than 1.

[0022] In some embodiments, the solvent used to dissolve arsenic compounds in arsenic-antimony slag by water leaching is water or a sodium hydroxide solution with a mass concentration not exceeding 10%. Studies have shown that the treatment effect is better under these conditions. Specifically, the mass concentration of the sodium hydroxide solution is 3-10%, or it can be 3-5%.

[0023] In some embodiments, the water immersion method is used to dissolve arsenic compounds in arsenic-antimony slag at a temperature of 85-90°C for 1-2 hours.

[0024] In some embodiments, when dissolving arsenic compounds in arsenic-antimony slag using the water leaching method, the solid-liquid ratio of arsenic-antimony slag to solvent is 4.5~5.5:1, kg / L. Studies have shown that the treatment effect is better under these conditions.

[0025] In some embodiments, during a single leaching treatment, the temperature is 93~97°C and the time is 1.8~2.2 h.

[0026] In some embodiments, during the two-stage leaching process, the temperature is 93~97°C and the time is 1.8~2.2 h.

[0027] In some embodiments, during the two-stage leaching treatment, the concentration of the sodium sulfide solution is 85–95 g / L. Studies have shown that the treatment effect is better under these conditions.

[0028] In some embodiments, the concentration of the sodium sulfide solution mixed with the second-stage leachate is not less than 105 g / L. Specifically, a sodium sulfide solution of 105~115 g / L is first mixed with the second-stage leachate, and then a sodium sulfide solution of 190~210 g / L is used for adjustment until the ORP reaches the preset value.

[0029] In some embodiments, the default value of ORP is -650 to -500 mV. Specifically, the default value of ORP is -600 to -550 mV.

[0030] In some embodiments, the amount of sodium sulfite added is 2.5 to 3 times the amount of sodium sulfite required for theoretical precipitation of tellurium in a first-stage leachate.

[0031] In some embodiments, the leachate is treated with sodium sulfite for 25-35 minutes. Specifically, the treatment temperature is 25-35 °C.

[0032] In some embodiments, during the oxidation reaction, the pH of the reaction system is 12-14, and the temperature is 80-90°C. Specifically, the pH of the reaction system is 13-14. Specifically, the temperature is 80-85°C. Specifically, the pH of the reaction system is adjusted using a sodium hydroxide solution. The concentration of the sodium hydroxide solution is 10-50%.

[0033] In some embodiments, the oxidant added during the oxidation reaction is hydrogen peroxide. Specifically, the hydrogen peroxide is added dropwise, with the addition time being one-half to two-thirds of the total reaction time, and the addition rate being 10~25 ml / min.

[0034] In some embodiments, during the initial preparation of sodium antimonate from arsenic-antimony slag, the leaching agent used in the first stage of leaching is a sodium sulfide aqueous solution of 65-85 g / L. The concentration of the sodium sulfide aqueous solution can also be 70-80 g / L.

[0035] In some embodiments, after the oxidation reaction, the slurry undergoes solid-liquid separation, and the solid is washed and dried to obtain a sodium antimonate product with a sulfur content of <0.15%; the separated mother liquor containing sodium sulfate is subjected to deep resource utilization treatment.

[0036] Specifically, it includes the following sequential steps: S0) Water leaching arsenic removal pretreatment and open circuit: Arsenic antimony slag is mixed with water or dilute alkaline solution, stirred and reacted, and then the solid and liquid are separated to obtain arsenic-containing solution and arsenic-removed slag. The arsenic-containing solution is treated by sodium sulfide precipitation to achieve stable open circuit of arsenic. S1) Sodium sulfide multi-stage countercurrent leaching: The arsenic-removed slag is subjected to two-stage countercurrent leaching to obtain an antimony-rich leachate; S1a) First stage leaching: The arsenic-removed residue obtained in step S0 is mixed with fresh sodium sulfide solution for leaching. Solid-liquid separation is performed to obtain a first stage leaching solution and a first stage leaching residue. The first stage leaching solution is used in step S2. S1b) Second stage leaching: The first stage leaching residue is leached a second time with fresh sodium sulfide solution, and after solid-liquid separation, a second stage leaching residue and a second stage leaching solution are obtained. S1c) Countercurrent circulation: After the second-stage leachate is mixed and prepared with fresh sodium sulfide solution, it returns to step S1a to leach a new batch of arsenic-removed slag. During the preparation process, ORP is monitored and adjusted to reach a preset target value.

[0037] S2) Sodium sulfite precipitation of tellurium: Sodium sulfite is added to a section of leachate obtained in step S1. After the reaction is completed, solid and liquid are separated to obtain crude tellurium and tellurium-free liquid. S3) High pH and high temperature oxidation precipitation of antimony: After adjusting the pH of the detellurized solution obtained in step S2 to 12~14, hydrogen peroxide is added at 80~90℃ to carry out an oxidation reaction to generate sodium antimonate precipitate. S4) Product separation and deep resource utilization of mother liquor: The slurry obtained in step S3 is separated into solid and liquid components. After washing and drying the solid, sodium antimonate product with sulfur content < 0.15% is obtained. The separated mother liquor containing sodium sulfate is subjected to deep resource utilization treatment.

[0038] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0039] In the following examples, arsenic-antimony slag produced during the smelting and impurity removal process of a copper smelter was used as raw material, and its composition is shown in Table 1 below: Table 1. Test data of raw materials used in the experiment (%)

[0040] Example 1 A method for preparing sodium antimonate based on multi-stage leaching and deep oxidation, such as Figure 1 As shown, the main steps include: 1. Step S0 (Water leaching arsenic removal pretreatment): Take 1 kg of the above-mentioned arsenic-antimony slag and mix it with 5 L of 5% sodium hydroxide solution (liquid-solid ratio 5:1). Stir and react at 90℃ for 2 h. After the reaction, perform solid-liquid separation to obtain arsenic-removed slag and arsenic-containing liquid. The arsenic-containing liquid enters the waste acid treatment process and is treated by sodium sulfide precipitation to achieve stable open-circuit arsenic removal. Testing showed that the arsenic removal rate was 96.21%, and the tellurium loss rate was 5.21%.

[0041] 2. Step S1 (Sodium sulfide multi-stage countercurrent leaching): (1) S1a (first stage leaching): The above-mentioned arsenic-removed residue was mixed with fresh sodium sulfide solution for the first stage leaching, and the total effective liquid volume of the leaching system was controlled to be 5L, with a Na2S concentration of 78 g / L. The leaching was carried out at 95℃ for 2 hours. After solid-liquid separation, a first stage leachate and a first stage leachate residue were obtained.

[0042] (2) S1b (Second stage leaching): The first stage leaching residue is leached a second time with 3L of fresh sodium sulfide solution with a concentration of 85 g / L (under the same conditions as the first stage) to obtain the second stage leaching solution and the second stage leaching residue. This residue is enriched with most of the lead and bismuth in the form of insoluble sulfides or oxides in the raw materials, as well as a small amount of residual antimony and tellurium. Its phase composition is compatible with conventional lead smelting feedstocks and can be returned to the upstream lead smelting system as an intermediate product for comprehensive recovery.

[0043] (3) S1c (Countercurrent Circulation and ORP Control): To ensure that the first stage leaching of each batch is carried out in a constant volume system of 5L, the second stage leaching solution is mixed with a fresh sodium sulfide solution with a concentration of 110 g / L (at 25°C) and brought to a final volume of 5L. During the mixing process, the oxidation-reduction potential (ORP) is monitored online, and fine-tuned by adding a fresh sodium sulfide solution with a concentration of 200 g / L, so that the ORP of the mixture is precisely controlled and stabilized at -580 mV (with a standard hydrogen electrode as a reference). This prepared solution is used as the starting leaching agent for the first stage leaching of the next batch, realizing countercurrent circulation.

[0044] Leaching effect: According to calculation (based on leaching residue, the same below), the antimony leaching rate is 95.29%, and the antimony-tellurium mass ratio in the leachate is about 10.7:1, showing a typical "high antimony and low tellurium" characteristic.

[0045] 3. Step S2 (Sodium sulfite precipitation of tellurium): Take a portion of the above leachate, stir it at 30°C, and add sodium sulfite. The amount added is calculated based on an excess coefficient of 2.5 for the theoretical precipitation amount of tellurium in the solution. After reacting for 0.5 hours, separate the solid and liquid phases to obtain crude tellurium and the tellurium-removed liquid. Analysis showed that the tellurium removal rate was 98.69%.

[0046] 4. Step S3 (High pH, ​​High Temperature Oxidation and Antimony Precipitation): The pH of the above-mentioned tellurium-depleted solution was adjusted to 13.5 with a 30% sodium hydroxide solution, and then the temperature was raised to 85°C. Under stirring at 400 r / min, 30% hydrogen peroxide was slowly added dropwise at a rate of 25 mL / min for a total reaction time of 3 h (2 h of which was the addition time). After the reaction was completed, a large amount of white precipitate was formed.

[0047] 5. Step S4 (Product separation and deep resource utilization of mother liquor): The oxidized slurry was decanted and filtered. The obtained solid was washed three times with hot water and dried at 105°C to obtain sodium antimonate product. The supernatant mother liquor from the decantation was combined with the filtrate and fed into an evaporation crystallization system to recover sodium sulfate decahydrate. The condensate was returned to step S0 as process water for water leaching arsenic removal.

[0048] After the above-described complete process, the system reaches steady-state operation. The key chemical components of the intermediate products in each major step are shown in Tables 2-4 below, clearly illustrating the direction of valuable metals and the removal pathways of impurity elements.

[0049] Table 2. Liquid test data (mg / L) during the experiment.

[0050] Table 3. Analysis data of slag produced during the experiment (%)

[0051] Table 4. Experimental data on sodium antimonate produced (%)

[0052] The results in Tables 2-4 show that: (1) Excellent product purity: The main component (calculated as Sb2O5) of the obtained sodium antimonate product is ≥64.5%, which meets the industry standard YS / T1459-2021. More importantly, the sulfur content of the product is stable below 0.15%, which meets the stringent requirements of high-end applications for low sulfur impurities.

[0053] (2) High efficiency in metal recovery: According to calculations, the antimony leaching rate was 95.29%; the overall antimony recovery rate reached 93.2%; and the effective utilization rate of sodium sulfide was greater than 94%. This confirms that the "multi-stage countercurrent-ORP regulation" leaching system achieves efficient utilization of reagents while ensuring a high leaching rate.

[0054] (3) Resource utilization and clean production closed loop: The whole process realizes the safe opening of arsenic stabilization, lead / bismuth enrichment and refining, sodium sulfate crystallization recovery and process water recycling, and constructs a complete resource comprehensive utilization system, solving the treatment problems of high arsenic hazardous waste and high salinity wastewater from the source.

[0055] Example 2 A method for preparing sodium antimonate based on multi-stage leaching and deep oxidation, such as Figure 1 As shown, the main steps include: 1. Step S0 (Water leaching arsenic removal pretreatment): Take 1 kg of the above-mentioned arsenic-antimony slag and mix it with 5 L of 3% sodium hydroxide solution (liquid-solid ratio 5:1). Stir and react at 80℃ for 3 h. After the reaction is completed, perform solid-liquid separation to obtain arsenic-removed slag and arsenic-containing liquid. The arsenic-containing liquid enters the waste acid treatment process and is treated by sodium sulfide precipitation to achieve stable open-circuit arsenic.

[0056] 2. Step S1 (Sodium sulfide multi-stage countercurrent leaching): (1) S1a (first stage leaching): The above-mentioned arsenic-removed residue was mixed with fresh sodium sulfide solution for the first stage leaching, and the total effective liquid volume of the leaching system was controlled to be 5L, with a Na2S concentration of 70 g / L. The leaching was carried out at 95℃ for 2 hours. After solid-liquid separation, a first stage leaching solution and a first stage leaching residue were obtained.

[0057] (2) S1b (Second stage leaching): The first stage leaching residue is leached a second time with 3L of fresh sodium sulfide solution with a concentration of 85 g / L (under the same conditions as the first stage) to obtain the second stage leaching solution and the second stage leaching residue. This residue is enriched with most of the lead and bismuth in the form of insoluble sulfides or oxides in the raw materials, as well as a small amount of residual antimony and tellurium. Its phase composition is compatible with conventional lead smelting feedstocks and can be returned to the upstream lead smelting system as an intermediate product for comprehensive recovery.

[0058] (3) S1c (Countercurrent Circulation and ORP Control): To ensure that the first stage leaching of each batch is carried out in a constant volume system of 5L, the second stage leaching solution is mixed with a fresh sodium sulfide solution with a concentration of 105 g / L (at 25°C) and brought to a final volume of 5L. During the mixing process, the oxidation-reduction potential (ORP) is monitored online, and fine-tuned by adding a fresh sodium sulfide solution with a concentration of 200 g / L, so that the ORP of the mixture is precisely controlled and stabilized at -600 mV (with a standard hydrogen electrode as a reference). This prepared solution is used as the starting leaching agent for the first stage leaching of the next batch, realizing countercurrent circulation.

[0059] 3. Step S2 (Sodium sulfite precipitation of tellurium): Take a portion of the above leachate, stir it at 30°C, and add sodium sulfite. The amount added is calculated based on an excess coefficient of 3.0 for the theoretical precipitation amount of tellurium in the solution. After reacting for 0.5 hours, separate the solid and liquid phases to obtain crude tellurium and the tellurium-depleted liquid.

[0060] 4. Step S3 (High pH, ​​High Temperature Oxidation and Antimony Precipitation): The pH of the above-mentioned tellurium-depleted solution was adjusted to 13 using a 30% sodium hydroxide solution, and then the temperature was raised to 80℃. Under stirring at 400 r / min, 30% hydrogen peroxide was slowly added dropwise at a rate of 10 mL / min for a total reaction time of 3 h (2 h of which was the addition time). After the reaction was completed, a large amount of white precipitate was formed.

[0061] 5. Step S4 (Product separation and deep resource utilization of mother liquor): The oxidized slurry was decanted and filtered. The obtained solid was washed three times with hot water and dried at 105°C to obtain sodium antimonate product. The supernatant mother liquor from the decantation was combined with the filtrate and fed into an evaporation crystallization system to recover sodium sulfate decahydrate. The condensate was returned to step S0 as process water for water leaching arsenic removal.

[0062] After the above-described complete process, the system reaches steady-state operation. The key chemical components of the intermediate products in each major step are shown in Tables 5-7 below, clearly illustrating the direction of valuable metals and the removal pathways of impurity elements.

[0063] Table 5. Liquid test data (mg / L) during the experiment.

[0064] Table 6. Analysis data of slag produced during the experiment (%)

[0065] Table 7. Experimental data on sodium antimonate produced (%)

[0066] Example 3 A method for preparing sodium antimonate based on multi-stage leaching and deep oxidation, such as Figure 1 As shown, the main steps include: 1. Step S0 (Water leaching arsenic removal pretreatment): Take 1 kg of the above-mentioned arsenic-antimony slag and mix it with 5 L of 10% sodium hydroxide solution (liquid-solid ratio 5:1). Stir and react at 95℃ for 1 h. After the reaction is complete, perform solid-liquid separation to obtain arsenic-removed slag and arsenic-containing liquid. The arsenic-containing liquid enters the waste acid treatment process and is treated by sodium sulfide precipitation to achieve stable open-circuit arsenic.

[0067] 2. Step S1 (Sodium sulfide multi-stage countercurrent leaching): (1) S1a (first stage leaching): The above-mentioned arsenic-removed residue was mixed with fresh sodium sulfide solution for the first stage leaching, and the total effective liquid volume of the leaching system was controlled to be 5L, with a Na2S concentration of 85 g / L. The leaching was carried out at 95℃ for 2 hours. After solid-liquid separation, a first stage leaching solution and a first stage leaching residue were obtained.

[0068] (2) S1b (Second stage leaching): The first stage leaching residue is subjected to a second leaching with 3L of fresh sodium sulfide solution with a concentration of 95 g / L (under the same conditions as the first stage) to obtain the second stage leaching solution and the second stage leaching residue. This residue is enriched with most of the lead and bismuth in the form of insoluble sulfides or oxides in the raw materials, as well as a small amount of residual antimony and tellurium. Its phase composition is compatible with conventional lead smelting feedstocks and can be returned to the upstream lead smelting system as an intermediate product for comprehensive recovery.

[0069] (3) S1c (Countercurrent Circulation and ORP Control): To ensure that the first stage leaching of each batch is carried out in a constant volume system of 5L, the second stage leaching solution is mixed with a fresh sodium sulfide solution with a concentration of 115 g / L (at 25°C) and brought to a final volume of 5L. During the mixing process, the oxidation-reduction potential (ORP) is monitored online, and fine-tuned by adding a fresh sodium sulfide solution with a concentration of 200 g / L, so that the ORP of the mixture is precisely controlled and stabilized at -550 mV (with a standard hydrogen electrode as a reference). This prepared solution is used as the starting leaching agent for the first stage leaching of the next batch, realizing countercurrent circulation.

[0070] 3. Step S2 (Sodium sulfite precipitation of tellurium): Take a portion of the above leachate, stir it at 30°C, and add sodium sulfite. The amount added is calculated based on an excess coefficient of 2.5 for the theoretical precipitation amount of tellurium in the solution. After reacting for 0.5 hours, separate the solid and liquid phases to obtain crude tellurium and the tellurium-depleted liquid.

[0071] 4. Step S3 (High pH, ​​High Temperature Oxidation and Antimony Precipitation): The pH of the above-mentioned tellurium-depleted solution was adjusted to 14 using a 50% sodium hydroxide solution, and then the temperature was raised to 85°C. Under stirring at 400 r / min, 30% hydrogen peroxide was slowly added dropwise at a rate of 25 mL / min for a total reaction time of 3 h (2 h of which was the addition time). After the reaction was completed, a large amount of white precipitate was formed.

[0072] 5. Step S4 (Product separation and deep resource utilization of mother liquor): The oxidized slurry was decanted and filtered. The obtained solid was washed three times with hot water and dried at 105°C to obtain sodium antimonate product. The supernatant mother liquor from the decantation was combined with the filtrate and fed into an evaporation crystallization system to recover sodium sulfate decahydrate. The condensate was returned to step S0 as process water for water leaching arsenic removal.

[0073] After the above-described complete process, the system reaches steady-state operation. The key chemical components of the intermediate products in each major step are shown in Tables 8-10 below, clearly illustrating the direction of valuable metals and the removal pathways of impurity elements.

[0074] Table 8. Liquid test data (mg / L) during the experiment.

[0075] Table 9. Analysis data of slag produced during the experiment (%)

[0076] Table 10. Experimental data on sodium antimonate produced (%)

[0077] Comparative Example 1 This comparative example is the same as Example 1, except that: in step S1, a single-stage leaching is performed, using only a 60 g / L Na2S solution to leach the arsenic-removed residue in the first stage.

[0078] Comparative Example 2 This comparative example is the same as Example 1, except that: in step S1, a single-stage leaching is performed, using only an 80 g / L Na2S solution for the first stage leaching of the arsenic-removed residue.

[0079] Comparative Example 3 This comparative example is the same as Example 1, except that: in step S1, a single-stage leaching is performed, using only a 100g / L Na2S solution to perform the first stage leaching of the arsenic-removed residue.

[0080] Comparative Example 4 This comparative example is the same as Example 1, except that: in step S1, a single-stage leaching is performed, using only a 120 g / L Na2S solution for the first stage leaching of the arsenic-removed residue.

[0081] Comparative Example 5 This comparative example is the same as Example 1, except that: in step S1, a single-stage leaching is performed, using only a 140 g / L Na2S solution to perform the first stage leaching of the arsenic-removed residue.

[0082] Comparative Example 6 This comparative example is the same as Example 1, except that: in step S1, a single-stage leaching is performed, using only a 160 g / L Na2S solution for the first stage leaching of the arsenic-removed residue.

[0083] Comparative Example 7 This comparative example is the same as Example 1, except that: in step S1, a single-stage leaching is performed, using only a 180 g / L Na2S solution to perform the first stage leaching of the arsenic-removed residue.

[0084] Comparative Example 8 This comparative example is the same as Example 1, except that: in step S1, a single-stage leaching is performed, using only a 200 g / L Na2S solution for the first stage leaching of the arsenic-removed residue.

[0085] Comparative Example 9 This comparative example is the same as Example 1, except that in step S1, no fresh sodium sulfide solution was added for fine-tuning during the mixing of the second-stage leachate and the fresh sodium sulfide solution, and its redox potential (ORP) was monitored online to be -540 mV (with the standard hydrogen electrode as a reference).

[0086] The key chemical components of the intermediate products in steps S1 and S2 are shown in Table 11 below.

[0087] Table 11 Key chemical components of some intermediate products in steps S1 and S2

[0088] Comparative Example 10 This comparative example is the same as Example 1, except that in step S1, during the mixing of the second-stage leachate and the fresh sodium sulfide solution, an excess of fresh sodium sulfide solution is added for fine-tuning, so that the online monitored redox potential (ORP) is -615 mV (with the standard hydrogen electrode as a reference).

[0089] The key chemical components of the intermediate products in steps S1 and S2 are shown in Table 12 below.

[0090] Table 12 Key chemical components of some intermediate products in steps S1 and S2

[0091] The results of the antimony leaching effect comparison between Example 1 and Comparative Examples 1-10 are shown in Table 13.

[0092] Table 13 Comparison of single-stage leaching effects under different initial concentrations

[0093] The data from Comparative Examples 1-8 show that when the sodium sulfide concentration is 60 g / L, the utilization rate of sodium sulfide is the highest, reaching 98.5%, but the leaching rate of antimony is severely insufficient, at only 60.23%. As the sodium sulfide concentration increases, the utilization rate of sodium sulfide decreases, while the leaching rate of antimony increases. When the sodium sulfide concentration increases to 200 g / L, the leaching rate of antimony is the highest, reaching 96.82%, but the utilization rate of sodium sulfide is as low as 44.16%.

[0094] The data from Comparative Examples 9-10 and Example 1 show that when the ORP value is too low, the system's reducing power is too strong. While this is beneficial for antimony leaching, excessive free sulfide ions not only lead to ineffective consumption and reduced utilization of sodium sulfide, but also severely interfere with the subsequent tellurium precipitation process, resulting in incomplete tellurium precipitation. When the ORP value is too high, the system's reducing power is insufficient, and the antimony leaching rate is significantly reduced. Meanwhile, the comparison between the sodium antimonate products prepared in Comparative Example 10 and Example 1... Figure 2As shown, adding an excessive amount of fresh sodium sulfide solution during the mixing process of the second-stage leachate and the fresh sodium sulfide solution also leads to an excessively high concentration of sulfur ions in the material, resulting in poor appearance quality of the final product.

[0095] Experimental conclusion: Traditional single-stage leaching processes contain inherent contradictions that are difficult to reconcile. Within a wide concentration range of 60-200 g / L, the antimony leaching rate and Na₂S utilization rate consistently exhibit a significant negative correlation. To achieve a high leaching rate, extremely high concentrations must be used, resulting in reagent utilization rates below 50% and extremely poor economic efficiency; conversely, if high utilization rates are pursued, the leaching rate will fall below 85%, leading to incomplete resource recovery. This invention, through a system innovation of "multi-stage countercurrent-ORP regulation," simultaneously elevates both the antimony leaching rate and Na₂S utilization rate to high levels and achieves synergistic optimization. Through process reengineering and precise process control, it overcomes the technical and economic bottlenecks of traditional processes.

[0096] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing sodium antimonate based on multi-stage leaching and deep oxidation, characterized in that, The process includes at least two steps in preparing sodium antimonate using arsenic-antimony slag; wherein the Nth step in preparing sodium antimonate using arsenic-antimony slag includes the following steps: Arsenic compounds in arsenic-antimony slag were dissolved by water leaching to obtain arsenic-containing liquid and arsenic-removed slag; The arsenic-removed slag is treated using a multi-stage countercurrent leaching method. The treatment process is as follows: the leaching agent obtained from the (N-1)th process of preparing sodium antimony from arsenic-antimony slag is used to perform a first-stage leaching treatment on the arsenic-removed slag, obtaining a first-stage leachate and a first-stage leaching residue; the first-stage leaching residue is then treated with a sodium sulfide solution to perform a second-stage leaching treatment, obtaining a second-stage leachate; the first-stage leaching treatment is performed once; the second-stage leaching treatment is performed at least once, and the leachate obtained from the last leaching treatment is the second-stage leachate; sodium sulfide solution is added to the second-stage leachate and mixed evenly until the ORP reaches a preset value, thus obtaining the leaching agent used to treat the (N+1)th process of preparing sodium antimony from arsenic-antimony slag. The first-stage leachate was treated with sodium sulfite to precipitate tellurium in the leachate, yielding crude tellurium and tellurium-free liquid. The solution after tellurium removal is oxidized to produce sodium antimonate precipitate. N is a natural number greater than 1.

2. The method as described in claim 1, characterized in that, The solvent used to dissolve arsenic compounds in arsenic-antimony slag by water leaching is water or a sodium hydroxide solution with a mass concentration not exceeding 5%; preferably, the mass concentration of the sodium hydroxide solution is 3-5%. Alternatively, when using the water leaching method to dissolve arsenic compounds in arsenic-antimony slag, the solid-liquid ratio of arsenic-antimony slag to solvent is 4.5~5.5:1, kg / L.

3. The method as described in claim 1, characterized in that, During the first leaching treatment, the temperature is 93~97℃ and the time is 1.8~2.2 h; Alternatively, during the two-stage leaching treatment, the temperature is 93~97℃ and the time is 1.8~2.2 h.

4. The method as described in claim 1, characterized in that, During the two-stage leaching process, the concentration of sodium sulfide solution used is 85~95 g / L; Alternatively, the concentration of the sodium sulfide solution mixed with the second-stage leachate shall not be less than 105 g / L; preferably, a sodium sulfide solution of 105~115 g / L shall be mixed with the second-stage leachate first, and then a sodium sulfide solution of 190~210 g / L shall be used for adjustment until the ORP reaches the preset value.

5. The method as described in claim 1, characterized in that, The preset value for ORP is -650 to -500 mV; the preferred value is -600 to -550 mV.

6. The method as described in claim 1, characterized in that, The amount of sodium sulfite added is 2.5 to 3 times the amount of sodium sulfite required for theoretical precipitation of tellurium in the first stage of the leachate.

7. The method as described in claim 1, characterized in that, During the oxidation reaction, the pH of the reaction system is 12-14 and the temperature is 80-90℃; preferably, the pH of the reaction system is 13-14; preferably, the temperature is 80-85℃.

8. The method as described in claim 1, characterized in that, During the oxidation reaction, the added oxidant is hydrogen peroxide; preferably, the hydrogen peroxide is added dropwise, the addition time is one-half to two-thirds of the total reaction time, and the addition rate is 10~25 ml / min.

9. The method as described in claim 1, characterized in that, In the first process of preparing sodium antimonate using arsenic-antimony slag, the leaching agent used in the first stage of leaching was an aqueous solution of sodium sulfide with a concentration of 65-85 g / L.

10. The method as described in claim 1, characterized in that, After oxidation, the slurry is separated into solid and liquid components. The solid is washed and dried to obtain sodium antimonate product with a sulfur content of <0.15%. The separated mother liquor containing sodium sulfate is subjected to deep resource utilization treatment.

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