High-purity bismuth oxide and a method for preparing the same

Abstract

The application relates to the technical field of hydrometallurgical gold and rare metal purification, and particularly relates to a preparation method of high-purity bismuth oxide. + The bismuth concentration in the bismuth-containing feed liquid is 80-100 g / L, the H concentration is 1-1.5 mol / L, and the NaCl concentration is 2-2.5 mol / L; an organic phase extraction is added to obtain a loaded organic phase; the organic phase comprises 25-30% of trialkylamine, 15-20% of isooctanol and kerosene in terms of volume percentage; impurities are removed through washing to obtain a purified loaded organic phase, oxalic acid solution is added for back extraction to obtain a bismuth-containing back extraction liquid; heating is carried out, ammonia water is used to adjust the pH to 3-3.5, precipitation is carried out, and after heat preservation, suction filtration is carried out to obtain large-granularity bismuth oxalate crystals; high-temperature calcination is carried out to obtain 99.999% high-purity bismuth oxide; and the core technical contradiction that an amine extraction system needs to be extracted under low acidity and bismuth ions are extremely easy to hydrolyze and precipitate under low acidity is solved.

Description

Technical Field

[0001] This invention relates to the field of hydrometallurgical gold and rare metal purification technology, specifically to the field of bismuth extraction and purification technology, and particularly to a high-purity bismuth oxide and its preparation method. Background Technology

[0002] Bismuth (Bi) is an important rare metal with high purity, low toxicity, and excellent thermoelectric and nuclear properties. It is widely used in pharmaceuticals, cosmetics, low-melting-point alloys, the nuclear industry, the electronics industry, and high-temperature superconducting materials. High-purity bismuth oxide (Bi₂O₃) is a key raw material for preparing these advanced materials, and its purity directly affects the performance of the final product.

[0003] Currently, the preparation methods for high-purity bismuth oxide mainly fall into two categories: pyrometallurgical refining and hydrometallurgical purification. Pyrometallurgical refining suffers from high energy consumption, significant bismuth volatilization loss, and severe environmental pollution. Hydrometallurgical purification primarily includes electrolysis and solvent extraction. Solvent extraction, in particular, offers advantages such as high separation efficiency, good selectivity, and continuous operation, making it an important method for preparing high-purity bismuth compounds. N235 (trialkylamine) is a commonly used basic anion-exchange extractant, widely applied in the separation of precious and rare metals.

[0004] For example, CN108796220B discloses a method for separating bismuth and iron from a bismuth-iron mixed solution through extraction-sulfidation phase inversion. First, high-valence ions in the solution are reduced with iron powder; then, trivalent bismuth is selectively extracted using a quaternary ammonium salt (such as N235). After washing, the bismuth-loaded organic phase is directly passed through a sulfide for selective sulfidation, producing high-purity bismuth sulfide. This process is mainly for bismuth-iron separation; for complex solutions containing other impurities (such as Cu, Zn, Pb, etc.), its selectivity and product purity (>99.9%) are limited. CN101376929A discloses a method for extracting bismuth from bismuth concentrate or bismuth-containing materials. This involves hydrochloric acid leaching, leaching solution purification and reduction, and bismuth extraction using an amine extractant (such as N235, with TBP added as a modifier). A complexation-back-extraction method is used, employing EDTA, tartaric acid, and other complexing agents to back-extract bismuth from the organic phase. The bismuth-rich solution is used to produce bismuth chemicals or electrolyze metallic bismuth, but the composition of the back-extraction solution is complex. Subsequent extraction of bismuth from solutions containing high concentrations of complexing agents (such as electrolysis or reprecipitation) is very difficult, the reagent costs are high and difficult to recover, causing economic and environmental pressures on the process. In summary, the existing N235 extraction and purification process for bismuth has the following technical problems: (1) Improper control of extraction conditions leads to low extraction rate or severe emulsification; (2) Poor selectivity of back-extraction and severe co-extraction of impurities; (3) Poor control of precipitation conditions makes it difficult to achieve a product purity of 99.999%; (4) Discontinuous process flow and large loss of organic phase.

[0005] Based on this, the present invention develops a method for preparing high-purity bismuth oxide by N235 extraction and purification, which has high extraction rate, good separation selectivity and high product purity. Summary of the Invention

[0006] This invention provides a high-purity bismuth oxide and its preparation method, the purpose of which is to solve the above-mentioned problems existing in the background art.

[0007] To achieve the above objectives, embodiments of the present invention provide a method for preparing high-purity bismuth oxide, comprising the following steps: S1: Industrial-grade bismuth raw material is pretreated to obtain a bismuth-containing liquid; the bismuth concentration in the bismuth-containing liquid is 80-100 g / L, H + The concentration is 1–1.5 mol / L, and the NaCl concentration is 2–2.5 mol / L; ensuring that bismuth exists in the form of a highly coordinated anionic chloride complex ([BiCl6)). 3 [BiCl5] 2 The existence of ) inhibits Bi 3+ Hydrolysis also satisfies the subsequent N235 pair ([BiCl6)). 3 [BiCl5] 2 Extraction requirements for complex anions; S2: An organic phase is added to the bismuth-containing feed solution for extraction to obtain a loaded organic phase. The organic phase, by volume percentage, comprises 25%–30% trialkylamine N235, 15%–20% isooctanol, and kerosene. This ensures that under high phase ratios and high loading, the organic phase remains a single phase with low viscosity and rapid phase separation, which is crucial for the industrialization of countercurrent extraction. The isooctanol acts as a viscosity modifier for the organic phase, improving its viscosity and phase separation properties. N235 is a trialkyl tertiary amine that forms an ammonium salt after extracting the anionic bismuth complex. This salt has limited solubility in kerosene and easily aggregates to form a third phase. Isooctanol is a long-chain alcohol; its -OH groups can form a larger solubilization layer with the extractant-metal complex through hydrogen bonding. The steric hindrance significantly improves the solubility of the extract in the organic phase, preventing micelle aggregation.

[0008] S3: Wash the supported organic phase to obtain a purified supported organic phase and impurities; S4: Oxalic acid solution is added to the purified supported organic phase for back-extraction to obtain a bismuth-containing back-extraction solution; simultaneously, the organic phase is washed with 2 mol / L hydrochloric acid to regenerate N235; the oxalic acid solution forms a stable [Bi(C2O4)2] with bismuth. - or [Bi(C2O4)3] 3-The soluble complex has a complexation stability constant much higher than that of [BiCl6]. 3 [BiCl5] 2 This enables efficient and selective back-extraction of bismuth; S5: The bismuth-containing back-extraction solution is heated, and the pH is adjusted to 3-3.5 with ammonia water to induce precipitation. After being kept at the temperature for a period of time, it is filtered to obtain large-particle bismuth oxalate crystals. During the heat preservation and aging process, the bismuth oxalate crystals grow completely, with large particles and excellent filtration performance. The filtration speed is 3 to 5 times higher than that of bismuth oxalate colloidal precipitate, and impurities such as Fe are separated by leaving them in the mother liquor. S6: The bismuth oxalate crystals are calcined at high temperature to obtain high-purity bismuth oxide; the purity of the bismuth oxide is 99.999%. During the calcination process, bismuth oxalate decomposes into bismuth oxide, carbon dioxide, and carbon monoxide, and the decomposition reaction formula is: Bi2(C2O4)3→ Bi2O2+ 3CO2↑ + 3CO↑.

[0009] Preferably, in step S1, the industrial-grade bismuth raw material is bismuth concentrate or bismuth smelting slag.

[0010] Preferably, in step S2, the molar ratio of the trialkylamine to bismuth is 1.5 to 3:1 to ensure complete extraction and appropriate excess; the extraction process is carried out in two stages of countercurrent extraction at room temperature above 25°C and with a ratio of O:A of 2 to 3:1.

[0011] Preferably, in step S2, the single-stage extraction rate is 96% to 99%, and the total extraction rate of the two-stage countercurrent extraction is greater than 99.5%.

[0012] Preferably, in step S3, the washing process involves two-stage countercurrent washing using a 1-1.5 mol / L hydrochloric acid solution with an O:A ratio of 2-3:1; the impurities include one or more of Fe, Sb, Sn, Cu, and Pb.

[0013] Preferably, in step S4, the amount of oxalic acid solution used is 5%-7%; the back-extraction process: compared with O:A of 3 to 2:1, two-stage countercurrent back-extraction is performed.

[0014] Preferably, in step S5, the bismuth oxalate crystal particles have a particle size of 50–200 μm; and the iron content in the bismuth oxalate crystals is less than 1 ppm.

[0015] Preferably, in step S5, the volume ratio of the bismuth-containing back-extraction solution to ammonia is 1:1; the heating temperature is 80-90℃; and the holding time is 20-30 min.

[0016] Preferably, in step S6, the high temperature is 800-950°C and the calcination time is 3 hours.

[0017] The embodiments of the present invention also provide high-purity bismuth oxide obtained by the above preparation method.

[0018] The above-described solution of the present invention has the following beneficial effects: (1) This invention optimizes the aqueous phase composition (Bi 80-100 g / L, H) + With a concentration of 1–1.5 mol / L NaCl and an organic phase ratio of 25%–30% N235 and 15%–20% isooctanol, single-stage extraction achieves a single-stage extraction rate of 96%–99%, and two-stage countercurrent extraction achieves a total extraction rate greater than 99.5%, with high bismuth recovery and high extraction efficiency. This method solves the core technical contradiction that amine extraction systems require low acidity, while bismuth ions are easily hydrolyzed and precipitated under low acidity.

[0019] (2) This invention uses hydrochloric acid washing to effectively remove impurities such as Fe, Sb, Sn, Cu, and Pb, and selective back-extraction with oxalic acid to further separate Bi from the impurities; then, by adjusting the pH of the back-extraction solution to 3-3.5, the bismuth oxalate is effectively precipitated completely, leaving the main impurity Fe in the mother liquor, and the final bismuth oxide product has a purity of 99.999%. The acidity of oxalic acid is used to displace bismuth from the organic phase, simultaneously generating bismuth oxalate precipitate. Heating reduces the supersaturation of the solution, and ammonia is used to adjust the pH to near the isoelectric point of bismuth oxalate, promoting the growth of crystals into large particles through the Ostwald ripening mechanism. Simultaneously, at this pH, Fe... 3+ No ferric oxalate precipitate (Fe) will be formed. 3+ At this pH, it is more likely to form soluble oxalic acid complexes [Fe(C2O4)3]. 3 [Fe(C2O4)3] 3 (Or remain in a dissolved state), achieving crystallization purification. This decouples back-extraction, precipitation, crystal growth, and deep impurity removal (especially Fe) into two precisely controlled steps, achieving high purification results.

[0020] (3) By controlling the precipitation temperature of bismuth oxalate to 80-90℃ and the pH to 3-3.5, the present invention obtains large bismuth oxalate crystals of 50-200μm, the filtration speed is 3-5 times higher than that of colloidal bismuth oxalate precipitation, the washing efficiency is high, and the mother liquor carries fewer impurities.

[0021] (4) This invention adopts a continuous process of two-stage countercurrent extraction-two-stage countercurrent washing-two-stage countercurrent back-extraction, with the organic phase recycled, ensuring stable operation and suitability for industrial production. Furthermore, this method can process various bismuth-containing raw materials, including bismuth concentrate and industrial-grade bismuth-containing slurry from bismuth-containing smelting slag, demonstrating good raw material adaptability. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the process flow for a method of preparing high-purity bismuth oxide according to the present invention; Figure 2 This is a photograph of bismuth oxalate crystals prepared in Example 1 of the present invention, using a method for preparing high-purity bismuth oxide. Detailed Implementation

[0024] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0025] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0026] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0027] In the following text, "v / v" refers to the volume ratio; "6% (g / V) oxalic acid solution" means 6g of oxalic acid is added to 100ml of water.

[0028] This invention addresses existing problems by providing a high-purity bismuth oxide and its preparation method.

[0029] The following description uses specific examples and comparative models to illustrate the points. Example 1 An embodiment of the present invention provides a method for preparing high-purity bismuth oxide, the process flow diagram of which is shown below. Figure 1 As shown, the specific steps include the following: (1) Pre-treat bismuth-containing smelting slag to obtain a bismuth-containing liquid; the bismuth concentration in the bismuth-containing liquid is 95 g / L, Fe 1.2 g / L, Sb 0.8 g / L, Sn 0.3 g / L, H + The concentration is 1.2 mol / L, and the NaCl concentration is 2.3 mol / L; (2) An organic phase was added to the bismuth-containing feed solution, and a two-stage countercurrent extraction was performed at room temperature (28°C) with a ratio of O:A = 2.5:1 to obtain a loaded organic phase. The organic phase, by volume percentage, included 28% (v / v) of trialkylamine N235, 18% (v / v) of isooctanol, and 54% (v / v) of kerosene. The raffinate contained 0.15 g / L of Bi, and the total extraction rate was 99.8%.

[0030] (3) The loaded organic phase was washed in two stages of countercurrent washing with 1.2 mol / L hydrochloric acid with a ratio of O:A = 2.5:1 to obtain a purified loaded organic phase. The Fe content in the organic phase was reduced to 0.015 g / L and the Sb content was reduced to 0.008 g / L.

[0031] (4) Add 6% (g / V) oxalic acid solution to the purified loaded organic phase, with a ratio of O:A = 2.5:1, and perform two-stage countercurrent back-extraction to obtain a bismuth-containing back-extraction solution, wherein Bi 92 g / L and Fe 0.012 g / L; (5) The bismuth-containing back-extraction solution was heated to 85°C, and ammonia was added dropwise while stirring to adjust the pH to 3.2 for precipitation. After keeping it warm for 20 minutes, it was filtered to obtain large-particle bismuth oxalate crystals. The actual photograph is shown in Figure 2. The Fe content is 0.2 ppm. (6) The bismuth oxalate crystals were calcined at 900°C for 3 hours to obtain high-purity bismuth oxide; the purity of the bismuth oxide was 99.999% and the total impurities were <1ppm, as determined by ICP-MS.

[0032] Example 2 An embodiment of the present invention provides a method for preparing high-purity bismuth oxide, the process flow diagram of which is shown below. Figure 1 As shown, the specific steps include the following: (1) Bismuth concentrate is pretreated to obtain a bismuth-containing liquid; the bismuth concentration in the bismuth-containing liquid is 82 g / L, Fe 0.5 g / L, Cu 0.2 g / L, Pb 0.1 g / L, H + The concentration is 1.0 mol / L, and the NaCl concentration is 2.0 mol / L; (2) Add an organic phase to the bismuth-containing feed solution, and perform two-stage countercurrent extraction at room temperature (30°C) with a ratio of O:A = 3:1 to obtain a loaded organic phase; the organic phase comprises, by volume percentage, 25% (v / v) trialkylamine, 20% (v / v) isooctyl alcohol, and 55% (v / v) kerosene; the raffinate contains 0.14 g / L Bi, and the total extraction rate is 99.83%.

[0033] (3) The loaded organic phase is washed in two stages of countercurrent washing with 1.0 mol / L hydrochloric acid with a ratio of O:A=3:1 to obtain a purified loaded organic phase.

[0034] (4) Add 5% (g / V) oxalic acid solution to the purified loaded organic phase, with a ratio of O:A=3:1, and perform two-stage countercurrent back-extraction to obtain a bismuth-containing back-extraction solution, wherein Bi 92g / L and Fe 0.012g / L; (5) Heat the bismuth-containing back-extraction solution to 88°C, add ammonia water dropwise while stirring to adjust the pH to 3.5, precipitate, keep warm for 30 min and then filter to obtain large bismuth oxalate crystals; (6) The bismuth oxalate crystals were calcined at 850°C for 3 hours to obtain 99.999% high-purity bismuth oxide.

[0035] Example 3 The difference between this embodiment and Embodiment 1 is that the NaCl concentration in step (1) is 2.0 mol / L, while the other steps and parameters are the same as in Embodiment 1.

[0036] Example 4 The difference between this embodiment and Example 1 is that the NaCl concentration in step (1) is 2.5 mol / L, while the other steps and parameters are the same as in Example 1.

[0037] Example 5 The difference between this embodiment and embodiment 1 is that in step (1) H + The concentration was 1.0 mol / L, and all other steps and parameters were the same as in Example 1.

[0038] Example 6 The difference between this embodiment and embodiment 1 is that in step (1) H + The concentration was 1.5 mol / L, and all other steps and parameters were the same as in Example 1.

[0039] Comparative Example 1 The difference between this comparative example and Example 1 is that the NaCl concentration in step (1) is 1.0 mol / L.

[0040] Comparative Example 2 The difference between this comparative example and Example 1 is that the NaCl concentration in step (1) is 1.5 mol / L.

[0041] Comparative Example 3 The difference between this comparative example and Example 1 is that the NaCl concentration in step (1) is 3.0 mol / L, while the other steps and parameters are the same as in Example 1.

[0042] Comparative Example 4 The difference between this comparative example and Example 1 lies in step (1) H + The concentration is 0.1 mol / L.

[0043] Comparative Example 5 The difference between this comparative example and Example 1 lies in step (1) H + The concentration is 0.5 mol / L.

[0044] Comparative Example 6 The difference between this comparative example and Example 1 lies in step (1) H + The concentration was 2.0 mol / L, and all other steps and parameters were the same as in Example 1.

[0045] Comparative Example 7 The difference between this comparative example and Example 1 is that the N235 concentration in step (2) is 15% (v / v), while the other steps and parameters are the same as in Example 1.

[0046] Comparative Example 8 The difference between this comparative example and Example 1 is that the N235 concentration in step (2) is 20% (v / v), while the other steps and parameters are the same as in Example 1.

[0047] Comparative Example 9 The difference between this comparative example and Example 1 is that the N235 concentration in step (2) is 40% (v / v).

[0048] Comparative Example 10 The difference between this comparative example and Example 1 is that the pH in step (5) is 2.0, while the other steps and parameters are the same as in Example 1.

[0049] Comparative Example 11 The difference between this comparative example and Example 1 is that the pH in step (5) is 4.5, while the other steps and parameters are the same as in Example 1.

[0050] Comparative Example 12 The difference between this comparative example and Example 1 is that the pH in step (5) is 6.0, while the other steps and parameters are the same as in Example 1.

[0051] The extraction process and results of the above-described embodiments and comparative examples are recorded in Table 1 below.

[0052] Table 1

[0053] As shown in Table 1, the present invention designs a high-chlorine, low-acid bismuth-containing feed system to regulate the bismuth morphology. Using N235 and isooctanol as the main extractants (25% (v / v) ~ 30% (v / v) N235 + 15% (v / v) ~ 20% (v / v) isooctanol), countercurrent extraction with an O / A ratio as high as 2-3:1 is used at room temperature to achieve a high extraction rate of 96-99%. Then, through the synergistic effect of multiple steps such as back-extraction-precipitation integration, crystallization purification, and calcination, bismuth oxide with a purity of 99.999% is prepared.

[0054] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing high-purity bismuth oxide, characterized in that, Includes the following steps: S1: Industrial-grade bismuth raw material is pretreated to obtain a bismuth-containing liquid; the bismuth concentration in the bismuth-containing liquid is 80-100 g / L, H + The concentration is 1–1.5 mol / L, and the NaCl concentration is 2–2.5 mol / L; S2: An organic phase is added to the bismuth-containing liquid for extraction to obtain a loaded organic phase; the organic phase comprises, by volume percentage, 25%–30% trialkylamine, 15%–20% isooctanol and kerosene; S3: Wash the supported organic phase to obtain a purified supported organic phase and impurities; S4: Add oxalic acid solution to the purified supported organic phase for back-extraction to obtain a bismuth-containing back-extraction solution; S5: The bismuth-containing back-extraction solution is heated, and the pH is adjusted to 3-3.5 with ammonia water to induce precipitation. After keeping it at the temperature for a period of time, it is filtered to obtain large-particle bismuth oxalate crystals. S6: The bismuth oxalate crystals are calcined at high temperature to obtain high-purity bismuth oxide; the purity of the bismuth oxide is 99.999%.

2. The method for preparing high-purity bismuth oxide according to claim 1, characterized in that, In step S1, the industrial-grade bismuth raw material is bismuth concentrate or bismuth smelting slag.

3. The method for preparing high-purity bismuth oxide according to claim 1, characterized in that, In step S2, the molar ratio of trialkylamine to bismuth is 1.5 to 3:1; the extraction process is carried out in two stages of countercurrent extraction at room temperature above 25°C and with a ratio of O:A of 2 to 3:

1.

4. The method for preparing high-purity bismuth oxide according to claim 3, characterized in that, In step S2, the single-stage extraction rate is 96% to 99%, and the total extraction rate of the two-stage countercurrent extraction is greater than 99.5%.

5. The method for preparing high-purity bismuth oxide according to claim 1, characterized in that, In step S3, the washing process involves two-stage countercurrent washing using a 1-1.5 mol / L hydrochloric acid solution with an O:A ratio of 2-3:

1. The impurities include one or more of Fe, Sb, Sn, Cu, and Pb.

6. The method for preparing high-purity bismuth oxide according to claim 1, characterized in that, In step S4, the amount of oxalic acid solution used is 5%-7%; the back-extraction process: compared with O:A of 3 to 2:1, two-stage countercurrent back-extraction is performed.

7. The method for preparing high-purity bismuth oxide according to claim 1, characterized in that, In step S5, the bismuth oxalate crystal particles have a particle size of 50–200 μm; the iron content in the bismuth oxalate crystals is less than 1 ppm.

8. The method for preparing high-purity bismuth oxide according to claim 1, characterized in that, In step S5, the volume ratio of the bismuth-containing back-extraction solution to ammonia is 1:1; the heating temperature is 80-90℃; and the holding time is 20-30 min.

9. The method for preparing high-purity bismuth oxide according to claim 1, characterized in that, In step S6, the high temperature is 800-950℃, and the calcination time is 3 hours.

10. High-purity bismuth oxide obtained by the preparation method according to any one of claims 1-9.

Images