Oriented crystal form product of high-purity bismuth oxide and preparation method thereof

Abstract

The invention belongs to the technical field of bismuth oxide preparation, and particularly relates to an oriented crystal form product of high-purity bismuth oxide and a preparation method thereof. The method comprises the following steps: 1) carrying out acid liquor replacement on a bismuth-containing raw material, adding an auxiliary agent metal, carrying out a reaction, and filtering to remove solids to obtain a filtered mother liquor; 2) carrying out gradient heating distillation to obtain a concentrated and purified solution; 3) heating and distilling until high-purity bismuth salt crystals are separated out; 4) adding the high-purity bismuth salt crystal into excessive water to react to obtain an oxygen-containing bismuth salt crystal; 5) adding the oxygen-containing bismuth salt crystal into a weak base salt solution for anion replacement to obtain a BiOaXb solid; 6) calcining the obtained BiOaXb solid to obtain a bismuth oxide product with a target crystal form. The method for preparing the high-purity bismuth oxide has the advantages that the process is simple, complicated processes and related equipment are not needed, the raw materials are easy to obtain, the cost is low, the energy consumption in the separation process is low, the direct recovery rate of the materials is high, and the obtained product has the advantages of being high in purity, less in agglomeration, uniform and fine in particle and controllable in crystal form.

Description

Technical Field

[0001] The invention belongs to the technical field of bismuth oxide preparation, and in particular relates to a directional crystal product of high-purity bismuth oxide and a preparation method thereof. Background Art

[0002] Bi 2 O 3 There are seven crystal forms, namely α-type (monoclinic), β-type (tetragonal), γ-type (body-centered cubic), δ-type (face-centered cubic), ε-type (orthorhombic), ω-type (triclinic) and hexagonal. Among these crystal forms, the stable phase α-type and the metastable phase β-type are more common and are more widely used. 2 O 3 It has high conductivity and photocatalytic activity. Therefore, it is widely used in the fields of electronic devices and photocatalysis. It can also be used as anode material in solar cells and photoelectrocatalytic hydrogen production. 2 O 3 It has lower conductivity and is often used in the preparation of ceramic materials and catalysts. It is also often used in the preparation of light absorption layers of optoelectronic devices to absorb visible light and convert it into electrical energy.

[0003] High purity is the material requirement for electronic devices, semiconductors, optics and other fields. Compared with ordinary metallurgical-grade bismuth oxide, high-purity bismuth oxide has significantly fewer impurities and has better chemical stability, electronic properties, catalytic activity and optical properties. High-purity bismuth oxide can be directly prepared into high-purity metallic bismuth through hydrogen reduction. High-purity bismuth is widely used in many fields such as nuclear energy, semiconductors, electronics, and superconductors due to its excellent properties.

[0004] As the demand for high-purity bismuth oxide and metallic bismuth continues to increase, the related purification and preparation technologies are becoming more and more diverse, such as vacuum distillation, zone smelting, electrolytic distillation and other methods. However, these preparation methods often have some limitations when used alone. For example, the metallic bismuth oxide prepared by the electrolytic process will contain a high level of impurity elements, such as lead, iron and arsenic, and may also produce AsH 3 and SbH 3 And other highly toxic gases. In addition, although zone melting and vacuum distillation can remove many impurity elements, the removal effect of arsenic, antimony and other impurity elements of the same family is not ideal, and multiple cycles of purification are required, and the energy consumption is high. In addition, wet methods such as ion exchange and adsorption are also used to remove some impurities, but there are problems such as low efficiency, strict operating conditions, and high cost. In addition, the existing technology cannot achieve the direct preparation of high-purity directional crystalline products. Therefore, the development of an efficient and clean high-purity bismuth oxide preparation process is crucial to promote the development of the high-purity bismuth industry. Summary of the invention

[0005] In view of the problems of existing bismuth oxide purification technology in terms of low removal efficiency of similar elements and elements of the same family, complex purification process, low efficiency, low recovery rate, high energy consumption, and inability to directly and effectively produce oriented crystal products, the present invention provides an oriented crystal product of high-purity bismuth oxide and a preparation method thereof.

[0006] The main purpose of the present invention is: 1. It can economically and efficiently realize the preparation of high-purity bismuth oxide above 5N grade; Second, it is possible to prepare high-purity bismuth oxide with different crystal forms to meet different application scenarios; 3. It is possible to control the crystal form of high-purity bismuth oxide.

[0007] To achieve the above objectives, the present invention adopts the following technical solutions.

[0008] A method for preparing a directional crystal product of high-purity bismuth oxide, The method comprises: 1) placing the bismuth-containing raw material in an acid solution and heating it to replace the acid solution, adding an auxiliary metal to react, filtering and removing solids to obtain a filtered mother liquor; 2) The filtered mother liquor is subjected to gradient temperature distillation to obtain a concentrated purified liquid; 3) The concentrated purified solution is further heated and distilled until high-purity bismuth salt crystals are precipitated; 4) adding high-purity bismuth salt crystals to excess water, stirring to react, obtaining oxygen-containing bismuth salt crystals, and washing with water until they are nearly neutral; 5) Prepare a weak alkaline salt solution, add oxygen-containing bismuth salt crystals into the weak alkaline salt solution for anion replacement, and filter and dry to obtain BiO a X b Solid, wherein X is a weak acid ion provided by a weak base salt solution; 6) The obtained BiO a X b The solid is calcined, and the calcination treatment adopts low-temperature calcination and / or high-temperature calcination to obtain a target crystal form of bismuth oxide product; in: β-crystalline bismuth oxide is obtained by low-temperature calcination; The α-crystalline bismuth oxide is obtained by high-temperature calcination; The alpha-beta mixed crystal bismuth oxide is obtained by combining low-temperature calcination with high-temperature calcination.

[0009] As a preference, Step 1) the bismuth-containing raw material is crude bismuth ore and / or crude bismuth oxide and / or crude bismuth salt and / or crude bismuthate; Step 1) The acid solution is a strong acid aqueous solution capable of dissolving the bismuth-containing raw material, and the bismuth ion concentration in the solution after dissolution is 100 to 500 g / L.

[0010] As a preference, Step 1) The heating is to raise the temperature to 45-60°C; Step 1) the auxiliary metal is copper with a mesh size of ≥200 mesh, and after the auxiliary metal is added, the mixture is stirred at a speed of 300 to 800 r / min for 25 to 35 minutes; Step 1) The amount of the auxiliary metal is calculated according to the arsenic content in the bismuth-containing raw material, and the amount is at least 5 times the molar amount of the arsenic content in the bismuth-containing raw material. If the arsenic in the bismuth-containing raw material cannot be detected, the amount of the auxiliary metal is controlled to be 2-5 wt% of the bismuth-containing raw material; The filtering process of step 1) uses a microporous filter membrane, and the pore size of the microporous filter membrane is 0.2-0.8 μm.

[0011] As a preference, Step 2) During the gradient temperature distillation, the temperature is raised to 102-108°C and 245-255°C respectively, and after reaching the target temperature, the temperature is kept until no distillate is produced in the solution system and the temperature begins to rise sharply from the macroscopic performance.

[0012] As a preference, Step 3) The distillation temperature during the heating distillation is controlled to be 447-460°C.

[0013] As a preference, Step 4) the water is deionized water, and the solid-liquid volume ratio is controlled to be 1: (7-25) when added; Step 4) The stirring reaction time is ≥ 1 h.

[0014] As a preference, Step 5) the weak base salt solution is an ammonium carbonate aqueous solution, the concentration of the ammonium carbonate aqueous solution is 10-25 wt%, and the amount of the ammonium carbonate aqueous solution is 8-12 mL / g of oxygen-containing bismuth salt crystals; Step 5) In the anion replacement process, the solution temperature is controlled to be 30-80°C, and the stirring reaction time is ≥45 min.

[0015] As a preference, Step 6) The low-temperature calcination process controls the calcination temperature to be 320-380°C; Step 6) The high temperature calcination process controls the calcination temperature to be 450-550°C; Step 6) The total duration of the calcination treatment is 2.5 to 5 hours.

[0016] The oriented crystalline product of high-purity bismuth oxide prepared by the method, The oriented crystal product of the high-purity bismuth oxide is an α crystal phase or a β crystal phase, or an α+β mixed crystal phase composed of the α crystal phase and the β crystal phase in a target ratio.

[0017] like Figure 1 As shown, for the technical solution of the present invention, the core is divided into two aspects. On the one hand, it is the impurity removal process required to obtain high-purity bismuth oxide, and on the other hand, it is the calcination process for controlling the crystal form of the product after deep impurity removal. Among the two, the impurity removal process is the basis. It is necessary to ensure effective deep impurity removal before the crystal form of the product can be efficiently and directly controlled through calcination treatment.

[0018] As for the impurity removal process, the impurity removal focus of the present invention is arsenic and antimony. The removal of arsenic and antimony, the same group elements in bismuth, is one of the difficulties in bismuth purification. Step 1) By introducing auxiliary metals, the copper replacement method can be used to selectively and efficiently remove impurities such as arsenic and antimony in the raw materials, and the introduced copper impurities can be removed by subsequent distillation. The copper replacement process for removing arsenic and antimony requires controlling the appropriate temperature, copper powder particle size and reaction time to achieve a higher removal rate for arsenic and antimony impurities. Arsenic and antimony exist mainly in the form of As[III] and Sb[III] ions in acid solutions. The potential difference between copper arsenic and copper antimony is greater than that between copper and bismuth, so they can be selectively removed by the replacement method.

[0019] The acid used in the present invention is mainly hydrochloric acid. The initial distillation is kept below the azeotropic point of water and hydrochloric acid, and the bismuth chloride solution is concentrated mainly by distilling a large amount of water, and the distillation of HCl is suppressed as much as possible. In this way, the solution can maintain a high acidity and avoid BiCl 3 The second distillation temperature range can ensure that the low-boiling chloride impurities are evaporated. If the temperature is not too high, BiCl 3 distillation loss.

[0020] Step 3) The medium-high temperature distillation temperature is 447~460℃. Too high a temperature may cause some high-boiling point chloride impurities to distill out and enter BiCl 3 In the molten salt. In this temperature range, it can be ensured that the impurity chlorides such as copper and lead with large saturated vapor pressure remain in the distillation residue.

[0021] Based on the above-mentioned deep impurity removal process, the present invention can ensure that the product can eventually reach a purity level of 5N and above. In conventional processes, the presence of impurities will affect the crystal structure of the intermediate crystal when it is precipitated, affecting the nucleation and growth of the crystal, and impurity atoms will cause lattice distortion. Due to the fan-shaped segregation effect of impurities, the impurity content in different fan-shaped areas will be different. This difference makes the stress more obvious at the boundary of the fan-shaped area, affecting the integrity of the crystal structure. At the same time, impurity atoms can form defects, causing changes in the lattice constant in the crystal lattice. These changes may promote the symmetry of certain crystal forms, thereby affecting the morphology of the crystal.

[0022] After deep impurity removal, the present invention introduces oxygen ions to form oxygen-containing bismuth salts through step 4), and replaces anions through step 5), which can fully dechlorinate and effectively change the trend of bismuth salts to bismuth oxide, and achieve a certain degree of crystal pre-construction. 2 CO 3 It can reach a semi-stable state so that it can be transformed into the target crystal form more efficiently. During the transformation process, the calcination temperature has a decisive influence on the crystal form of the product. Because during the calcination process, it will undergo a thermal decomposition process, which will remove carbon dioxide, and the calcination temperature itself will affect the crystallization process of the substance, and will also affect the rate of the thermal decomposition reaction. The decomposition rate also affects the crystal form of the product to a certain extent. But in general, the commercially available bismuth oxycarbonate will form impurities or incomplete transformation during the transformation process. For example, the conversion rate to bismuth oxide at 350 °C will be relatively low, only about 91-96%, while the conversion rate at 400 °C is relatively high, but the low-temperature target product β-BiO 3 Part of α-BiO 3 Similarly, under high temperature conditions such as 600 °C, the transformation from β phase to α phase is incomplete. Although the conversion rate is also high, a small amount of β phase will inevitably remain. On the one hand, it may be due to the structural differences of the precursors. On the other hand, it is mainly because the commercially available bismuth oxycarbonate contains impurity elements such as arsenic and antimony that are difficult to completely and effectively remove. These elements will hinder the formation and transformation of bismuth oxide, making it difficult to effectively and stably obtain the target phase of bismuth oxide.

[0023] The beneficial effects of the present invention are: (1) The preparation method of the present invention utilizes a high-acid chloride system, and through copper powder replacement and step-by-step distillation, the efficient separation of the same group and similar elements that are difficult to remove in electrolysis and zone melting is achieved. At the same time, the impurities can be redistributed between the solid and liquid phases through the hydrolysis process, further improving the purity. The entire process has less pollution and does not introduce elements such as sodium that are difficult to remove in the crystallization process; (2) The process for preparing high-purity bismuth oxide of the present invention is simple, does not require complicated processes and related equipment, the raw materials are easily available, the cost is low, the energy consumption of the separation process is low, and the direct recovery rate of the material is high. The obtained product has the advantages of high purity, less agglomeration, uniform and fine particles, and controllable crystal form. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a flow chart of the program of the present invention; Figure 2 The different crystal forms of Bi prepared in Example 2 of the present invention 2 O 3 XRD pattern of Figure 3 Bi is obtained by calcining at 350 °C in Example 2 of the present invention. 2 O 3 SEM images of Figure 4 Bi is obtained by calcining at 500 °C in Example 2 of the present invention. 2 O 3 SEM image of . DETAILED DESCRIPTION

[0025] The present invention is further described in detail below in conjunction with specific embodiments and the accompanying drawings. A person of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are generally only embodiments of a part of the present invention, rather than all embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without making creative work should fall within the scope of protection of the present invention.

[0026] In the description of the present invention, it should be understood that the terms "thickness", "upper", "lower", "horizontal", "top", "bottom", "inner", "outer", "circumferential" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In the description of the present invention, "multiple" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined, and "several" means one or more.

[0027] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] Unless otherwise specified, the raw materials used in the examples of the present invention are all commercially available or available to those skilled in the art; unless otherwise specified, the methods used in the examples of the present invention are all methods known to those skilled in the art.

[0029] Examples 1 to 6 A method for preparing high-purity bismuth oxide powder with different crystal forms, Including the following raw materials: Bi 2 O 3 powder, HCl solution, copper powder, high purity water, (NH 4 ) 2 CO 3 Crystals; The method for preparing high-purity bismuth oxide powder with different crystal forms comprises the following process steps: Step 1: Acid dissolution replacement, the crude Bi 2 O 3 The powder is placed in a reaction container, and then an HCl solution is added to completely dissolve the bismuth oxide to obtain a crude bismuth chloride solution containing arsenic. The solution is heated to 50° C. under a protective atmosphere, and copper powder is added to the solution. The solution is continuously stirred during the reaction process. The reaction time is 30 minutes, and the tail gas is collected and purified. Finally, the mixed solution is filtered; The specific parameters of different instances are as follows: Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Stoichiometric ratio 15 35 35 35 35 35 HCl concentration 6mol / L 6mol / L 4mol / L 6mol / L 6mol / L 6mol / L Main metal dosage 100g / L 100g / L 100g / L 100g / L 400g / L 100g / L Stirring speed 600rpm 600rpm 600rpm 600rpm 600rpm 300rpm In the table: the stoichiometric ratio is the stoichiometric ratio (molar ratio) of the added copper powder to the arsenic content in the crude bismuth chloride solution; the HCl concentration is the concentration of hydrochloric acid in the crude bismuth chloride solution after acid dissolution in step 1; the main metal concentration is the concentration of main metal bismuth in the crude bismuth chloride solution after acid dissolution in step 1; and the stirring rate is the stirring rate controlled during the reaction process in step 1.

[0030] The arsenic removal results are as follows: Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Arsenic content (mg / L) 22.8 4.91 35.2 7.41 29.2 5.8 Arsenic removal rate 92.98% 98.37% 34.13% 98.22% 46.22% 98.22% Step 2: gradient temperature distillation. The filtered mother liquor in step 1 is transferred into a distillation kettle, heated to 105°C for the first time, the distillation rate is controlled to evaporate most of the water, and then heated to 250°C to evaporate the low-boiling impurities.

[0031] Step 3, secondary distillation, further heating the concentrated bismuth chloride crystals in step 2 to a boiling point of 447° C., and collecting the distillate, which is high-purity bismuth chloride crystals; Step 4: hydrolysis. Pour the high-purity bismuth chloride in step 3 into a reaction vessel, add high-purity water for hydrolysis, the solid-liquid ratio of hydrolysis is 1:20, stir and react for 1 hour, filter after the reaction to obtain high-purity BiOCl, and rinse it until the rinse liquid is near neutral; Step 5: Transformation, (NH 4 ) 2 CO 3 The crystals were placed in a reaction vessel and high-purity water was added to dissolve them to obtain 20% (NH 4 ) 2 CO 3 The high-purity BiOCl in step 4 was poured into the ammonium carbonate solution, and the mixed solution was heated to 60°C and stirred for 1 hour. After the reaction, it was filtered and dried to obtain (BiO) 3 CO 3 solid; Step 6: calcination to convert (BiO) 3 CO 3 The solid was calcined at different temperatures, the calcination temperature was 350℃, and the calcination time was 3h to obtain high-purity β-Bi 2 O 3 Powder. The calcination temperature is 500℃ and the calcination time is 3h to obtain high-purity α-Bi 2 O 3 powder.

[0032] It is worth noting that in the present invention, the bismuth concentration of the bismuth chloride solution in step 1 is about 100-500 g / L, the copper-arsenic molar ratio is 5:1-40:1, the HCl concentration is 3-8 mol / L, the copper powder particle size is 200 mesh, the stirring rate is 300-800 r / min, and the protective atmosphere used is nitrogen.

[0033] It is worth noting that in the present invention, the filter paper for filtration is a microporous filter membrane with a diameter of 80 mm and a pore size of 0.44 μm.

[0034] From the above results, it can be seen that the relative amount of metallic copper and the concentration of the strong acid used will have a significant effect on the overall arsenic removal rate. In more experiments, when the stoichiometric ratio (molar ratio) of copper to arsenic is 5:1, the arsenic removal rate of more than 85% can still be maintained, but if it is lower, the arsenic removal rate will drop sharply, and excessive addition of too much metallic copper may cause waste of resources or introduce new impurities. Therefore, in general, controlling the stoichiometric ratio of copper to arsenic and / or antimony impurities within the range of 5 to 50 can produce relatively good results. Similarly, for the strong acid used, hydrogen chloride is used in the embodiments of the present invention, and the concentration of hydrogen chloride in the range of 3 to 8 mol / L can play a relatively good effect, but also from the above arsenic removal results, the effect of 6 mol / L hydrogen chloride is also significantly better than 4 mol / L, and in more experiments, 6 to 8 mol / L hydrogen chloride can show better use effects. In addition, the amount of main metal will also significantly affect the arsenic removal effect. Because a higher concentration of the main metal also means the introduction of more impurities, and in the system of the present invention, impurities such as bismuth ions and arsenic ions have a high similarity, the introduction of too much main metal will make it more difficult to remove impurities such as arsenic, because controlling the main metal dosage at 100 to 500 g / L has a better effect.

[0035] In addition, the products prepared in Example 2 were characterized by XRD and SEM, respectively, to characterize the products calcined at 350 °C and 500 °C. Figure 2 From the characterization results shown, both low-temperature calcination and high-temperature calcination can obtain products with a single and controllable crystal form. Figure 3 and Figure 4 From the characterization results, the two crystalline forms of the products have significant differences in structure.

[0036] Comparative Example 1 A method for preparing high-purity bismuth oxide powder with different crystal forms, Including the following raw materials: Bi 2 O 3 powder, HCl solution, copper powder, high purity water, (NH 4 ) 2 CO 3 Crystals; The method for preparing high-purity bismuth oxide powder with different crystal forms comprises the following process steps: Step 1: Acid dissolution replacement: the crude Bi 2 O 3The powder is placed in a reaction container, and then an HCl solution is added to completely dissolve the bismuth oxide to obtain a crude bismuth chloride solution containing arsenic. The solution is heated to 50° C. under a protective atmosphere, and copper powder is added to the solution. The solution is continuously stirred during the reaction process. The reaction time is 30 minutes, and the tail gas is collected and purified. Finally, the mixed solution is filtered; Step 2: gradient temperature distillation. The filtered mother liquor in step 1 is transferred into a distillation kettle, heated to 105°C for the first time, the distillation rate is controlled to evaporate most of the water, and then heated to 250°C to evaporate the low-boiling impurities.

[0037] Step 3, secondary distillation, further heating the concentrated bismuth chloride crystals in step 2 to a boiling point of 447° C., and collecting the distillate, which is high-purity bismuth chloride crystals; Step 4: hydrolysis: pour the high-purity bismuth chloride in step 3 into a reaction vessel, add high-purity water for hydrolysis, and stir the reaction for 1 hour. After the reaction is completed, filter to obtain high-purity BiOCl, and rinse it until the rinse liquid is near neutral; Using different hydrolysis ratios, the experimental results are as follows: Hydrolysis ratio 1:8 1:9 1:10 1:11 1:12 1:15 1:20 Hydrolysis rate 68.4% 71.2% 75.1% 79.6% 82.3% 88.2% 95.7% Step 5: Transformation, (NH 4 ) 2 CO 3 The crystals were placed in a reaction vessel and high-purity water was added to dissolve them to obtain 20% (NH 4 ) 2 CO 3 The high-purity BiOCl in step 4 was poured into the ammonium carbonate solution, and the mixed solution was heated to 60°C and stirred for 1 hour. After the reaction, it was filtered and dried to obtain (BiO) 3 CO 3 solid; Step 6: calcination to convert (BiO) 3 CO 3 The solid was calcined at different temperatures, the calcination temperature was 350℃, and the calcination time was 3h to obtain high-purity β-Bi 2 O 3 Powder. The calcination temperature is 500℃ and the calcination time is 3h to obtain high-purity α-Bi 2 O 3 powder.

[0038] It is worth noting that in the present invention, the bismuth concentration of the bismuth chloride solution in step 1 is about 100-500 g / L, the copper-arsenic molar ratio is 5:1-40:1, the HCl concentration is 3-8 mol / L, the copper powder particle size is 200 mesh, the stirring rate is 300-800 r / min, and the protective atmosphere used is nitrogen.

[0039] It is worth noting that in the present invention, the filter paper for filtration is a microporous filter membrane with a diameter of 80 mm and a pore size of 0.44 μm.

[0040] Comparative Example 2 A method for preparing high-purity bismuth oxide powder with different crystal forms, Including the following raw materials: Bi 2 O 3 powder, HCl solution, copper powder, high purity water, (NH 4 ) 2 CO 3 Crystals; The method for preparing high-purity bismuth oxide powder with different crystal forms comprises the following process steps: Step 1: Acid dissolution replacement: the crude Bi 2 O 3 The powder is placed in a reaction container, and then an HCl solution is added to completely dissolve the bismuth oxide to obtain a crude bismuth chloride solution containing arsenic. The solution is heated to 50° C. under a protective atmosphere, and copper powder is added to the solution. The solution is continuously stirred during the reaction process. The reaction time is 30 minutes, and the tail gas is collected and purified. Finally, the mixed solution is filtered; Step 2: gradient temperature distillation. The filtered mother liquor in step 1 is transferred into a distillation kettle, heated to 105°C for the first time, the distillation rate is controlled to evaporate most of the water, and then heated to 250°C to evaporate the low-boiling impurities.

[0041] Step 3, secondary distillation, further heating the concentrated bismuth chloride crystals in step 2 to a boiling point of 447° C., and collecting the distillate, which is high-purity bismuth chloride crystals; Step 4: hydrolysis. Pour the high-purity bismuth chloride in step 3 into a reaction container, add high-purity water at a solid-liquid ratio of 1:20 for hydrolysis, and stir the reaction for 1 hour. After the reaction is completed, filter to obtain high-purity BiOCl, and rinse it until the rinse liquid is near neutral. Step 5: Transformation, (NH 4 ) 2 CO 3 The crystals were placed in a reaction vessel and high-purity water was added to dissolve the obtained (NH 4 ) 2 CO 3 The high-purity BiOCl in step 4 was poured into the ammonium carbonate solution, and the mixed solution was heated to 60°C and stirred for 1 hour. After the reaction, it was filtered and dried to obtain (BiO) 3 CO 3 solid; Using different mass fractions (NH 4 ) 2 CO 3Solution, the experimental results are as follows: Quality score 5% 10% 15% 20% 25% Dechlorination efficiency 87.8% 95.94% 98.34% 99.05% 99.99% Step 6: calcination to convert (BiO) 3 CO 3 The solid was calcined at different temperatures, the calcination temperature was 350℃, and the calcination time was 3h to obtain high-purity β-Bi 2 O 3 Powder. The calcination temperature is 500℃ and the calcination time is 3h to obtain high-purity α-Bi 2 O 3 powder.

[0042] It is worth noting that in the present invention, the bismuth concentration of the bismuth chloride solution in step 1 is about 100-500 g / L, the copper-arsenic molar ratio is 5:1-40:1, the HCl concentration is 3-8 mol / L, the copper powder particle size is 200 mesh, the stirring rate is 300-800 r / min, and the protective atmosphere used is nitrogen.

[0043] It is worth noting that in the present invention, the filter paper for filtration is a microporous filter membrane with a diameter of 80 mm and a pore size of 0.44 μm.

[0044] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that numerous changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a directional crystal product of high-purity bismuth oxide, characterized in that: The method comprises: 1) placing the bismuth-containing raw material in an acid solution and heating it to replace the acid solution, adding an auxiliary metal to react, filtering and removing solids to obtain a filtered mother liquor; 2) The filtered mother liquor is subjected to gradient temperature distillation to obtain a concentrated purified liquid; 3) The concentrated purified liquid is further heated and distilled until high-purity bismuth salt crystals are precipitated; 4) adding high-purity bismuth salt crystals to excess water, stirring to react, obtaining oxygen-containing bismuth salt crystals, and washing with water until they are nearly neutral; 5) Prepare a weak alkaline salt solution, add oxygen-containing bismuth salt crystals into the weak alkaline salt solution for anion replacement, and filter and dry to obtain BiO a X b Solid, wherein X is a weak acid ion provided by a weak base salt solution; 6) The obtained BiO a X b The solid is calcined, and the calcination treatment adopts low-temperature calcination and / or high-temperature calcination to obtain a target crystal form of bismuth oxide product; in: β-crystalline bismuth oxide is obtained by low-temperature calcination; The α-crystalline bismuth oxide is obtained by high-temperature calcination; The α-β mixed crystal bismuth oxide is obtained by combining low-temperature calcination with high-temperature calcination.

2. The method for preparing a directional crystal product of high-purity bismuth oxide according to claim 1, characterized in that: Step 1) the bismuth-containing raw material is crude bismuth ore and / or crude bismuth oxide and / or crude bismuth salt and / or crude bismuthate; Step 1) The acid solution is a strong acid aqueous solution capable of dissolving the bismuth-containing raw material, and the bismuth ion concentration in the solution after dissolution is 100 to 500 g / L.

3. A method for preparing a directional crystal product of high-purity bismuth oxide according to claim 1 or 2, characterized in that: Step 1) The heating is to raise the temperature to 45-60°C; Step 1) the auxiliary metal is copper with a mesh size of ≥200 mesh, and after the auxiliary metal is added, the mixture is stirred at a speed of 300 to 800 r / min for 25 to 35 min; Step 1) The amount of the auxiliary metal is calculated according to the arsenic content in the bismuth-containing raw material, and the amount is at least 5 times the molar amount of the arsenic content in the bismuth-containing raw material. If the arsenic in the bismuth-containing raw material cannot be detected, the amount of the auxiliary metal is controlled to be 2-5wt% of the bismuth-containing raw material; The filtering process of step 1) uses a microporous filter membrane, and the pore size of the microporous filter membrane is 0.2-0.8 μm.

4. The method for preparing a directional crystal product of high-purity bismuth oxide according to claim 1, characterized in that: Step 2) During the gradient temperature distillation, the temperature is raised to 102-108° C. and 245-255° C. respectively, and after reaching the target temperature, the temperature is kept until no distillate is produced in the solution system.

5. The method for preparing a directional crystal product of high-purity bismuth oxide according to claim 1, characterized in that: Step 3) The distillation temperature during the heating distillation is controlled to be 447-460°C.

6. The method for preparing a directional crystal product of high-purity bismuth oxide according to claim 1, characterized in that: Step 4) the water is deionized water, and the solid-liquid volume ratio is controlled to be 1: (7-25) when added; Step 4) The stirring reaction time is ≥ 1 h.

7. The method for preparing a directional crystal product of high-purity bismuth oxide according to claim 1, characterized in that: Step 5) the weak base salt solution is an ammonium carbonate aqueous solution, the concentration of the ammonium carbonate aqueous solution is 10-25 wt%, and the amount of the ammonium carbonate aqueous solution is 8-12 mL / g of oxygen-containing bismuth salt crystals; Step 5) In the anion replacement process, the solution temperature is controlled to be 30-80°C, and the stirring reaction time is ≥45 min.

8. The method for preparing a directional crystal product of high-purity bismuth oxide according to claim 1, characterized in that: Step 6) The low-temperature calcination process controls the calcination temperature to be 320-380°C; Step 6) The high temperature calcination process controls the calcination temperature to be 450-550°C; Step 6) The total duration of the calcination treatment is 2.5 to 5 hours.

9. An oriented crystalline product of high-purity bismuth oxide obtained by the method of any one of claims 1 to 8.

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