Crude arsenic purification method and application

Abstract

The present invention provides a crude arsenic purification method and application; the crude arsenic purification method comprises: placing the crude arsenic raw material in a vacuum environment with a pressure of no more than 1Pa, a hot end temperature of 600-900°C, and a cold end temperature of 400-700°C, and performing vacuum sublimation by adding a reducing agent and a purifying agent to obtain a sublimation product; cooling the obtained sublimation product to room temperature, and crushing it under the protection of an inert gas to obtain a purified elemental arsenic product, wherein the impurity content of the obtained arsenic product is greatly reduced and the purity is significantly improved. The present invention reduces the sublimation temperature of arsenic under high vacuum conditions, utilizes the difference between the saturated vapor pressure, volatilization rate and boiling point of arsenic and impurity metals at low sublimation temperatures; converts low-value metallic crude arsenic into a low-impurity content, high-value elemental arsenic product, and has a wide range of applications in crude arsenic purification.

Description

Technical Field

[0001] The present invention relates to the field of arsenic extraction, and in particular to a crude arsenic purification method and application. Background Technology

[0002] Smelting processes such as lead and zinc smelting and copper smelting will produce a large amount of arsenic-containing waste slag. Crude arsenic is usually a by-product from the non-ferrous metal smelting process. Among them, the output of crude arsenic increases with the increase of non-ferrous metal output. Therefore, in areas with large non-ferrous metal output, the output of crude arsenic is particularly significant. As a toxic heavy metal element, arsenic will cause serious damage to soil, water sources and ecosystems if it is discharged directly into the environment without treatment.

[0003] Elemental arsenic is an important semiconductor material that is widely used in electronic and optoelectronic devices; however, arsenic has high chemical activity and is easily contaminated by impurities during the preparation process, especially the doping of elements such as antimony, which not only affects the performance of arsenic, but also seriously restricts its application in the field of high-end technology. At present, traditional crude arsenic purification methods, such as pyrolysis, can effectively remove certain low-melting point impurities, but have limited effects on certain high-melting point metal impurities, and the energy consumption caused by high-temperature operation makes its cost relatively high. In addition, the overall processing efficiency of wet extraction is low, and the solubility differences of most components are small, which makes it difficult to purify crude arsenic in depth.

[0004] In view of the technical challenges of crude arsenic treatment and purification, as well as the dual needs of environmental protection and industrial application, the present invention aims to propose a crude arsenic purification method and application to solve or at least alleviate the technical problems of the difficulty in deep processing and purification of crude arsenic materials and the difficulty in removing impurity elements. SUMMARY OF THE INVENTION

[0005] The main purpose of the present invention is to provide a crude arsenic purification method and application, so as to solve the technical problems that the crude arsenic material is difficult to be deeply processed and purified, and the impurity elements are difficult to remove, especially the elements of the same family are difficult to remove; the innovative method is based on the addition of a purifying agent and a reducing agent in a vacuum environment to synergistically purify the crude arsenic, improve the purity and quality of the elemental arsenic, and meet the demand of modern industry for high-purity arsenic products.

[0006] To achieve the above purpose, the present invention provides a method for purifying crude arsenic, comprising:

[0007] Crude arsenic, reducing agent and purifying agent are mixed to obtain mixed arsenic material;

[0008] Place the mixed arsenic material in a sealed high vacuum environment, which includes a hot end and a cold end. The mixed arsenic material sublimates at the hot end and condenses at the cold end. The condensate at the cold end is collected to obtain arsenic element. The vacuum pressure in the high vacuum environment is no more than 1Pa;

[0009] The temperature of the hot end is 600 - 900 °C, and the temperature difference between the hot end and the cold end is not less than 200 °C; the temperature of the cold end is 400 - 700 °C.

[0010] Furthermore, the vacuum pressure in the high-vacuum environment is 0.001 - 0.1 Pa.

[0011] Furthermore, the reducing agent includes one or more of zinc powder, iron powder, magnesium powder, and carbon powder.

[0012] Furthermore, the purifying agent includes one or more of copper powder, cadmium powder, lead powder, and sulfuric acid.

[0013] Furthermore, the purity of the crude arsenic is 1N - 3N; the impurity elements in the crude arsenic include antimony and sulfur; the oxygen content of the crude arsenic > 5%.

[0014] Furthermore, the addition amount of the reducing agent is 1 - 5% of the mass of the crude arsenic.

[0015] Furthermore, the addition amount of the purifying agent is 2 - 10% of the mass of the crude arsenic.

[0016] Furthermore, during the process of sublimating the mixed arsenic material at the hot end, condensing it at the cold end, and collecting the condensate at the cold end to obtain elemental arsenic, the sublimation duration at the hot end is not less than 2 h.

[0017] Furthermore, the process of sublimating the mixed arsenic material at the hot end, condensing it at the cold end, and collecting the condensate at the cold end to obtain elemental arsenic further includes transferring the elemental arsenic to an inert atmosphere and successively performing a crushing process and a screening process; wherein, the duration of the crushing process is 5 - 30 min, and the particle size of the screening process is 200 - 400 mesh.

[0018] The present invention provides an application of the crude arsenic purification method as described in any one of the above in the production of elemental arsenic and arsenic compounds.

[0019] The beneficial effects of the present invention are as follows:

[0020] The present invention controls the vacuum pressure in the vacuum environment to be no greater than 1 Pa, reducing the sublimation temperature of arsenic. By utilizing the differences in the saturated vapor pressures, volatilization rates, and boiling points between arsenic and the main impurity antimony at low sublimation temperatures, the separation of the two is achieved, effectively alleviating the problem of difficult impurity separation during the sublimation of crude arsenic and obtaining high-purity elemental arsenic. In addition, by adding external reducing agents and purifying agents, arsenic oxides are reduced to elemental arsenic, and at the same time, a reducing environment is maintained at high temperatures to prevent the re-oxidation of arsenic, avoiding the escape of arsenic oxide to the cold end due to its larger saturated vapor pressure and diffusivity. This process not only improves the volatilization efficiency of arsenic but also enhances its dissociation ability from oxides. On the other hand, purifying agents such as copper powder and cadmium powder effectively separate these impurities from arsenic by forming non-volatile compounds with sulfur. These compounds remain in the solid residue during the sublimation process, preventing the volatilization of impurities. The use of purifying agents also enhances the chemical stability of the system, avoids the occurrence of side reactions, and ensures the specificity and efficiency of the purification process. During the sublimation process, since arsenic directly changes from a solid state to a gaseous state, its particles or molecules have greater mobility and a wider distribution range in the gaseous state. Coupled with the fact that the temperature at the hot end is sufficient to provide the activation energy required for the oxidation process of arsenic, at this time, the control of high-vacuum conditions is necessary. High-vacuum technology significantly reduces the introduction of impurities, reduces the oxidation risk, and improves the chemical purity and crystal quality of elemental arsenic.

[0021] In the present invention, crude arsenic is mixed with a reducing agent. On the one hand, the negative impacts of oxidized impurities (such as arsenic oxides in high valence states) on the sublimation efficiency of arsenic and the purity of the product are avoided. The addition of an appropriate amount of reducing agent can reduce these oxidized impurities to lower-valence arsenic that is more easily sublimated. At the same time, an external purifying agent is added to fix the impurities and purify arsenic, thereby making the purification of arsenic relatively thorough. On the other hand, the reducing agent can create a reducing atmosphere to ensure that arsenic is not oxidized during the sublimation process.

[0022] The present invention realizes the high-efficiency purification of arsenic resources by purifying arsenic elements from crude arsenic or other arsenic-containing by-products. This method not only improves the value of arsenic resources but also reduces the environmental risks brought about by the abandonment of arsenic elements, having both economic and environmental benefits. Brief Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following-described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the structures shown in these drawings.

[0024] Figure 1 It is a schematic flow chart of the purification of crude arsenic in the embodiment of the present invention;

[0025] Figure 2 It is the elemental analysis diagram of the crude arsenic raw materials in Embodiments 1-9 and Comparative Examples 1-5 of the present invention;

[0026] Figure 3 It is the purity analysis diagram of the crude arsenic raw materials in Embodiments 1-9 and Comparative Examples 1-5 of the present invention;

[0027] Figure 4 It is the XRD diagram of the crude arsenic raw materials in Embodiments 1-9 and Comparative Examples 1-5 of the present invention;

[0028] Figure 5 It is the full-element determination and analysis diagram of the purity of the pure arsenic prepared in Example 4 of the present invention.

[0029] The realization, functional features and advantages of the object of the present invention will be further described in conjunction with the embodiments with reference to the accompanying drawings. Specific Embodiments

[0030] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0031] In addition, the descriptions such as "first" and "second" in the present invention are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features.

[0032] Moreover, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0033] As Figure 1 shown, the present invention provides a method for purifying crude arsenic, comprising the following steps:

[0034] S1, mixing and proportioning crude arsenic, a reducing agent and a purifying agent to obtain a mixed arsenic material.

[0035] Crude arsenic is an arsenic product prepared by the carbon reduction process route of arsenic oxide. It has a high impurity content and low economic value, and usually comes from by-products in non-ferrous metal smelting processes, such as lead-zinc smelting, copper smelting, etc. These smelting processes will produce a large amount of arsenic-containing waste residues. The output of crude arsenic increases with the increase in the output of non-ferrous metals. Therefore, in regions with a large output of non-ferrous metals, the output of crude arsenic is particularly high.

[0036] The utilization of crude arsenic has important environmental significance. Arsenic is a toxic heavy metal element. If directly discharged into the environment without treatment, it will cause serious damage to the soil, water source and ecosystem. Secondly, the reuse of crude arsenic helps to reduce the exploitation of natural resources, promotes the recycling of resources, and conforms to the concept of sustainable development. In addition, by converting crude arsenic into valuable purified arsenic products, it can bring economic benefits to relevant enterprises, and at the same time promotes the development and application of environmental protection technologies.

[0037] The main impurity of crude arsenic is antimony. Since arsenic and antimony belong to the same Group V A elements and have similar chemical properties, it is difficult to separate them under conventional conditions. However, by controlling the reaction temperature under high vacuum conditions and using the significant differences in the saturated vapor pressure and the maximum evaporation rate between arsenic and antimony under high vacuum and low temperature conditions, the residual amount of antimony can be effectively reduced. At this temperature, the evaporation rate of arsenic is significantly higher than that of antimony, enabling arsenic to preferentially sublime to the cold end and improving the purity of the product, which reflects the innovation of the present invention.

[0038] The calculation formula for the saturated vapor pressure of each metal is:

[0039]

[0040] According to the above formula, the saturated vapor pressure of each metal is calculated as:

[0041]

[0042] The present invention controls the vacuum pressure in the vacuum environment to be no greater than 1 Pa, and utilizes the differences in the saturated vapor pressure, evaporation rate and boiling point between arsenic and the main impurity antimony to separate the two, effectively alleviating the problem of difficult impurity separation during the sublimation process of crude arsenic, thereby obtaining high-purity elemental arsenic.

[0043] The high vacuum environment provides a preparation condition with almost no interference from gas molecules, which helps to reduce the introduction of impurities and improve the purification efficiency. Under high vacuum conditions, elemental arsenic can be purified through the sublimation process. During the sublimation process, solid substances directly turn into gaseous state without passing through the liquid state; in the high vacuum environment, due to the reduction of the interference of gas molecules on the sublimation process, the sublimation process can proceed more effectively.

[0044] During the purification process, elemental arsenic is heated to the sublimation point, and the arsenic molecules will detach from the solid surface and enter the vacuum environment. Due to the different sublimation temperatures of arsenic and antimony, arsenic and antimony can be separated by precisely controlling the temperature of the hot end. In addition, a high vacuum environment also helps to reduce the oxidation and hydrolysis of arsenic during the sublimation process, thereby ensuring the chemical purity of the purified elemental arsenic. High vacuum sublimation purification technology combined with precise temperature control and atmosphere management provides a new way to prepare high-purity elemental arsenic, which can not only improve the purity of elemental arsenic, but also reduce by-products and operational risks in the preparation process, which is of great significance for promoting the development of semiconductor material technology.

[0045] In some embodiments of the present invention, the particle size of crude arsenic can be 0.5~3cm, and the purity of crude arsenic can be 1N~3N. For example, the purity of crude arsenic can be 1N~2N; for example, the purity of crude arsenic can be 2N; it should be noted that, taking 2N grade crude arsenic as an example, 2N grade crude arsenic is an arsenic element with an impurity content of ≤1% and >0.1%.

[0046] The crude arsenic is subjected to quantitative element analysis. The Sb content in the crude arsenic can reach 1~1500ppm, for example, the antimony content in the crude arsenic can be 500~1500ppm; for example, the antimony content in the crude arsenic can be 1000~1500ppm. Antimony is the impurity element with the highest content in the crude arsenic. Other impurity elements include Si, S, and B, and the contents can be 40~60ppm, 4~5ppm, and 1~2ppm respectively; the impurities in the crude arsenic can specifically include Sb and S, and the contents are described above; the oxygen content of the crude arsenic is >5% or ≤5%; further, the oxygen content in the crude arsenic can be 5~10%. It should be noted that the oxygen content of the crude arsenic here refers to the mass fraction of oxygen in the crude arsenic.

[0047] In some embodiments, the reducing agent does not include aluminum powder; exemplary, the reducing agent may include one or more of zinc powder, iron powder, magnesium powder, and carbon powder. Exemplary, the reducing agent may include one or more of zinc powder, iron powder, and carbon powder.

[0048] In some embodiments, the particle size of the reducing agent may be 200 mesh.

[0049] The present invention mixes crude arsenic with a reducing agent, which, on the one hand, avoids the negative impact of oxidized impurities (such as high-valent arsenic oxides) on the sublimation efficiency of arsenic and the purity of the product. The addition of an appropriate amount of reducing agent can reduce these oxidized impurities to low-valent arsenic that is easier to sublimate, thereby making the purification of arsenic relatively thorough. On the other hand, the reducing agent can create a reducing atmosphere to ensure that the arsenic is not oxidized during the sublimation process.

[0050] In some embodiments, the amount of reducing agent added may be 1-5% of the mass of crude arsenic.

[0051] In some specific embodiments, crude arsenic, purifying agent and reducing agent can be placed in an inert atmosphere in proportion and fully ground and mixed by a mixer to obtain a mixed arsenic material, and then the mixed arsenic material is placed in a vacuum container, and after being sealed and evacuated to 0.001~0.1Pa, it is placed in a furnace structure with a hot end and a cold end.

[0052] In the present invention, the purifying agent may include one or more of copper powder, cadmium powder, lead powder, and sulfuric acid.

[0053] In some embodiments of the present invention, when the purifying agent is sulfuric acid, the concentration of sulfuric acid can be 90-95%.

[0054] In some embodiments of the present invention, the purifying agent may include copper powder and / or sulfuric acid.

[0055] In the present invention, the amount of the purifying agent added can be 2-10% of the mass of the crude arsenic.

[0056] In some preferred embodiments, the reducing agent may be one of carbon powder, zinc powder, and iron powder, and the purifying agent may be one of copper powder and sulfuric acid;

[0057] In some preferred embodiments, the reducing agent may be one of carbon powder and iron powder, and the purifying agent may be copper powder;

[0058] In some preferred embodiments, the reducing agent is carbon powder and the purifying agent is copper powder;

[0059] In some preferred embodiments, the reducing agent is carbon powder and the purifying agent is sulfuric acid.

[0060] S2, place the mixed arsenic material in a closed high vacuum environment, which includes a hot end and a cold end. The mixed arsenic material sublimates at the hot end and condenses at the cold end. The condensate at the cold end is collected to obtain arsenic element.

[0061] In some embodiments, the vacuum pressure in the high vacuum environment is no greater than 1 Pa.

[0062] In some embodiments, the vacuum pressure in a high vacuum environment may be 0.001-0.1 Pa. It should be noted that the vacuum pressure here is equivalent to the vacuum degree, that is, the specific apparent pressure value of the gas in a vacuum environment.

[0063] In some embodiments, the temperature of the hot end is 600-900°C, and the temperature difference between the hot end and the cold end is not less than 200°C; the temperature of the cold end is 400-700°C.

[0064] When the cold end temperature is lower than 300°C, the adsorption energy will be too low, and it will be difficult for arsenic gas molecules to adhere to the cold end medium.

[0065] In some specific embodiments, the temperature of the hot end can be 600 - 800 °C, and the temperature of the cold end can be 400 - 600 °C. In some more specific embodiments, the temperature of the hot end can be 600 - 700 °C, and the temperature of the cold end can be 400 - 500 °C.

[0066] Exemplarily, in the case of a vacuum degree of 0.001 Pa, the temperature of the hot end can be set to 650 °C, and the temperature of the cold end is 450 °C.

[0067] In the present invention, the sublimation duration at the hot end is not less than 2 h; further, the sublimation duration at the hot end can be 2 - 8 h; exemplarily, the sublimation duration at the hot end can be 6 - 8 h.

[0068] The steps of sublimating the mixed arsenic material at the hot end, condensing it at the cold end, and collecting elemental arsenic further include transferring the elemental arsenic to an inert atmosphere and successively performing crushing treatment on the elemental arsenic; wherein, the duration of the crushing treatment is 5 - 30 min, and the particle size for screening is 200 - 400 mesh.

[0069] The inert atmosphere can be one of nitrogen or argon. The crushing process is to crush the material using a crushing and grinding machine to obtain purified arsenic powder.

[0070] The crushing process can be to crush the material using a crushing and grinding machine to obtain purified arsenic powder. The crushing time is 5 - 30 min, and the particle size for screening can be 200 - 400 mesh.

[0071] The preparation method of the present invention has high impurity removal efficiency and deoxidation performance. By precisely controlling the ratio of additives and reaction conditions, high-purity elemental arsenic can be prepared on a large scale to meet the market demand for high-quality arsenic products. At the same time, the standardized process of this method is also convenient for implementation in industrial production, ensuring the consistency and reliability of product quality.

[0072] The present invention also provides an application of the crude arsenic purification method as described in any one of the above in the production of elemental arsenic.

[0073] For further understanding of the present invention, examples are given below for illustration:

[0074] It should be noted that the crude arsenic in Examples 1 - 9 and Comparative Examples 1 - 5 all comes from the crude arsenic products produced by a certain enterprise in Henan through the reduction of arsenic oxide.

[0075] Example 1

[0076] This example adopts the following experimental steps:

[0077] 1. First, place 100 g of crude arsenic, 5 g of carbon powder, and 10 g of copper powder in an inert atmosphere, fully mix them through a mixer to obtain a mixed arsenic material, and add the mixed arsenic material into a vacuum container.

[0078] 2. Evacuate the vacuum container until the vacuum degree reaches 0.001 Pa, then seal it. Place the sealed vacuum container in a vacuum sublimation furnace with multiple temperature zones for sublimation reaction. The hot end temperature is 700 °C, the cold end temperature is 500 °C, and the sublimation time is 6 h. After the sublimation reaction is completed, cool it to obtain purified arsenic bulk.

[0079] 3. Take out the purified arsenic bulk in an inert atmosphere, crush it through a grinding machine and then screen it. Set the crusher time to 10 minutes and the mesh number of the sieve to 200 meshes, and finally obtain a purified arsenic powder product that meets the requirements.

[0080] In this example, the purity of the purified arsenic powder is 99.95%, the antimony content is 286.5 mg / kg, and the oxygen content is 0.31%.

[0081] Example 2

[0082] Compared with Example 1, only change the dosage of the reducing agent in Step 1:

[0083] 1. First, place 100 g of crude arsenic, 3 g of carbon powder, and 10 g of copper powder in an inert atmosphere, and fully mix them through a mixer to obtain a mixed arsenic material. Then add the mixed arsenic material into a vacuum container.

[0084] 2. Evacuate the vacuum container until the vacuum degree reaches 0.001 Pa, then seal it. Place the sealed vacuum container in a vacuum sublimation furnace with multiple temperature zones for sublimation reaction. The hot end temperature is 700 °C, the cold end temperature is 500 °C, and the sublimation time is 6 h. After the sublimation reaction is completed, cool it to obtain purified arsenic bulk.

[0085] 3. Take out the purified arsenic bulk in an inert atmosphere, crush it through a grinding machine and then screen it. Set the crusher time to 10 minutes and the mesh number of the sieve to 200 meshes, and finally obtain a purified arsenic powder product that meets the requirements.

[0086] In this example, the purity of the purified arsenic powder is 99.95%, the antimony content is 265.2 mg / kg, and the oxygen content is 0.38%.

[0087] Example 3

[0088] Compared with Example 1, only change the dosage of the reducing agent in Step 1:

[0089] 1. First, place 100 g of crude arsenic, 1 g of carbon powder, and 10 g of copper powder in an inert atmosphere, and fully mix them through a mixer to obtain a mixed arsenic material. Then add the mixed arsenic material into a vacuum container.

[0090] 2. Evacuate the vacuum container until the vacuum degree reaches 0.001 Pa, then seal it. Place the sealed vacuum container in a vacuum sublimation furnace with multiple temperature zones for sublimation reaction. The hot end temperature is 700 °C, the cold end temperature is 500 °C, and the sublimation time is 6 h. After the sublimation reaction ends, cool it to obtain purified arsenic bulk.

[0091] 3. Take out the purified arsenic bulk under an inert atmosphere, crush it through a grinding machine and then screen it. Set the crusher time to 10 minutes and the mesh number of the sieve to 200 meshes, and finally obtain a purified arsenic powder product that meets the requirements.

[0092] In this example, the purity of the purified arsenic powder is 99.95%, the antimony content is 234.3 mg / kg, and the oxygen content is 0.47%.

[0093] Example 4

[0094] Compared with Example 1, only change the temperatures of the hot and cold ends in Step 2:

[0095] 1. First, place 100 g of crude arsenic, 5 g of carbon powder, and 10 g of copper powder in an inert atmosphere, and fully mix them through a mixer to obtain a mixed arsenic material. Add the mixed arsenic material into a vacuum container.

[0096] 2. Evacuate the vacuum container until the vacuum degree reaches 0.001 Pa, then seal it. Place the sealed vacuum container in a vacuum sublimation furnace with multiple temperature zones for sublimation reaction. The hot end temperature is 650 °C, the cold end temperature is 450 °C, and the sublimation time is 6 h. After the sublimation reaction ends, cool it to obtain purified arsenic bulk.

[0097] 3. Take out the purified arsenic bulk under an inert atmosphere, crush it through a grinding machine and then screen it. Set the crusher time to 10 minutes and the mesh number of the sieve to 200 meshes, and finally obtain a purified arsenic powder product that meets the requirements.

[0098] In this example, the purity of the purified arsenic powder is 99.99%, the antimony content is 180.7 mg / kg, and the oxygen content is 0.36%.

[0099] Example 5

[0100] Compared with Example 1, only change the vacuum degree in Step 2:

[0101] 1. First, place 100 g of crude arsenic, 5 g of carbon powder, and 10 g of copper powder in an inert atmosphere, and fully mix them through a mixer to obtain a mixed arsenic material. Add the mixed arsenic material into a vacuum container.

[0102] 2. Evacuate the vacuum container until the vacuum degree reaches 0.01 Pa, then seal it. Place the sealed vacuum container in a vacuum sublimation furnace with multiple temperature zones for sublimation reaction. The hot end temperature is 700 °C, the cold end temperature is 500 °C, and the sublimation time is 6 h. After the sublimation reaction ends, cool it to obtain purified arsenic bulk.

[0103] 3. Take out the purified arsenic bulk in an inert atmosphere, crush it through a grinding machine and then screen it. Set the crusher time to 10 minutes and the mesh number of the sieve to 200 mesh, and finally obtain a purified arsenic powder product that meets the requirements.

[0104] In this example, the purity of the purified arsenic powder is 99.95%, the antimony content is 253.2 mg / kg, and the oxygen content is 0.33%.

[0105] Example 6

[0106] Compared with Example 1, only change the vacuum degree in Step 2:

[0107] 1. First, place 100 g of crude arsenic, 5 g of carbon powder, and 10 g of copper powder in an inert atmosphere, fully mix them through a mixer to obtain a mixed arsenic material, and add the mixed arsenic material into a vacuum container.

[0108] 2. Evacuate the vacuum container until the vacuum degree reaches 0.1 Pa, then seal it. Place the sealed vacuum container in a vacuum sublimation furnace with multiple temperature zones for sublimation reaction. The hot end temperature is 700 °C, the cold end temperature is 500 °C, and the sublimation time is 6 h. After the sublimation reaction ends, cool it to obtain purified arsenic bulk.

[0109] 3. Take out the purified arsenic bulk in an inert atmosphere, crush it through a grinding machine and then screen it. Set the crusher time to 10 minutes and the mesh number of the sieve to 200 mesh, and finally obtain a purified arsenic powder product that meets the requirements.

[0110] In this example, the purity of the purified arsenic powder is 99.95%, the antimony content is 223.5 mg / kg, and the oxygen content is 0.39%.

[0111] Example 7

[0112] Compared with Example 1, only change the type of reducing agent in Step 1:

[0113] 1. First, place 100 g of crude arsenic, 5 g of iron powder, and 10 g of copper powder in an inert atmosphere, fully mix them through a mixer to obtain a mixed arsenic material, and add the mixed arsenic material into a vacuum container.

[0114] 2. Evacuate the vacuum container until the vacuum degree reaches 0.001 Pa, then seal it. Place the sealed vacuum container in a vacuum sublimation furnace with multiple temperature zones for sublimation reaction. The hot end temperature is 700 °C, the cold end temperature is 500 °C, and the sublimation time is 6 h. After the sublimation reaction is completed, cool it to obtain purified arsenic bulk.

[0115] 3. Take out the purified arsenic bulk in an inert atmosphere, crush it through a grinding machine and then screen it. Set the crushing time of the crusher to 10 minutes and the mesh number of the sieve to 200 meshes, and finally obtain a purified arsenic powder product that meets the requirements.

[0116] In this example, the purity of the purified arsenic powder is 99.95%, the antimony content is 316.5 mg / kg, and the oxygen content is 0.71%.

[0117] Example 8

[0118] Compared with Example 1, only change the type of purification agent in step 1:

[0119] 1. First, place 100 g of crude arsenic, 5 g of carbon powder, and 10 g of sulfuric acid with a mass concentration of 98% in an inert atmosphere, fully mix them through a mixer to obtain a mixed arsenic material, and add the mixed arsenic material into a vacuum container.

[0120] 2. Evacuate the vacuum container until the vacuum degree reaches 0.001 Pa, then seal it. Place the sealed vacuum container in a vacuum sublimation furnace with multiple temperature zones for sublimation reaction. The hot end temperature is 700 °C, the cold end temperature is 500 °C, and the sublimation time is 6 h. After the sublimation reaction is completed, cool it to obtain purified arsenic bulk.

[0121] 3. Take out the purified arsenic bulk in an inert atmosphere, crush it through a grinding machine and then screen it. Set the crushing time of the crusher to 10 minutes and the mesh number of the sieve to 200 meshes, and finally obtain a purified arsenic powder product that meets the requirements.

[0122] In this example, the purity of the purified arsenic powder is 99.9%, the antimony content is 389.7 mg / kg, and the oxygen content is 0.64%.

[0123] Example 9

[0124] Compared with Example 1, only change the type of reducing agent in step 1:

[0125] 1. First, place 100 g of crude arsenic, 5 g of zinc powder, and 10 g of copper powder in an inert atmosphere, fully mix them through a mixer to obtain a mixed arsenic material, and add the mixed arsenic material into a vacuum container.

[0126] 2. Evacuate the vacuum container with the mixed material until the vacuum degree reaches 0.001 Pa, then seal it. Place the sealed vacuum container in a vacuum sublimation furnace with multiple temperature zones for sublimation reaction. The hot end temperature is 700 °C, the cold end temperature is 500 °C, and the sublimation time is 6 h. After the sublimation reaction is completed, cool it to obtain purified arsenic bulk.

[0127] 3. Take out the purified arsenic bulk in an inert atmosphere, crush it through a grinding machine and then sieve it. Set the crusher time to 10 minutes and the sieve mesh size to 200 meshes to finally obtain the purified arsenic powder product that meets the requirements.

[0128] In this example, the purity of the purified arsenic powder is 99.9%, the antimony content is 564.5 mg / kg, and the oxygen content is 0.87%.

[0129] Comparative Example 1

[0130] Compared with Example 1, only change the type of reducing agent in Step 1:

[0131] 1. First, place 100 g of crude arsenic, 5 g of aluminum powder, and 10 g of copper powder in an inert atmosphere, fully mix them through a mixer to obtain a mixed arsenic material, and add the mixed arsenic material into a vacuum container.

[0132] 2. Evacuate the vacuum container with the mixed material until the vacuum degree reaches 0.001 Pa, then seal it. Place the sealed vacuum container in a vacuum sublimation furnace with multiple temperature zones for sublimation reaction. The hot end temperature is 700 °C, the cold end temperature is 500 °C, and the sublimation time is 6 h. After the sublimation reaction is completed, cool it to obtain purified arsenic bulk.

[0133] 3. Take out the purified arsenic bulk in an inert atmosphere, crush it through a grinding machine and then sieve it. Set the crusher time to 10 minutes and the sieve mesh size to 200 meshes to finally obtain the purified arsenic powder product that meets the requirements.

[0134] In this comparative example, the purity of the purified arsenic powder is 99.6%, the antimony content is 873.8 mg / kg, and the oxygen content is 1.21%. Due to the poor reduction performance of the reducing agent, arsenic oxide and antimony oxide with high saturated vapor pressure are continuously generated and escape to the cold end, resulting in a significant increase in the antimony content concentration in the purified arsenic powder.

[0135] Comparative Example 2

[0136] Compared with Example 1, only change the temperatures of the hot and cold ends in Step 2:

[0137] 1. First, place 100 g of crude arsenic, 5 g of carbon powder, and 10 g of copper powder in an inert atmosphere, fully mix them through a mixer to obtain a mixed arsenic material, and add the mixed arsenic material into a vacuum container.

[0138] 2. Evacuate the vacuum container with the mixed material until the vacuum degree reaches 0.001 Pa, then seal it. Place the sealed vacuum container in a vacuum sublimation furnace with multiple temperature zones for sublimation reaction. The hot end temperature is 450 °C, the cold end temperature is 250 °C, and the sublimation time is 6 h. Since the volatilization temperature is too low, arsenic is not completely volatilized.

[0139] Comparative Example 3

[0140] Compared with Example 1, only the vacuum degree in Step 2 is changed:

[0141] 1. First, place 100 g of crude arsenic, 5 g of carbon powder, and 10 g of copper powder in an inert atmosphere, and fully mix them through a mixer to obtain a mixed arsenic material. Then add the mixed arsenic material into a vacuum container.

[0142] 2. Evacuate the vacuum container with the mixed material until the vacuum degree reaches 100 Pa, then seal it. Place the sealed vacuum container in a vacuum sublimation furnace with multiple temperature zones for sublimation reaction. The hot end temperature is 700 °C, the cold end temperature is 500 °C, and the sublimation time is 6 h. Since the vacuum pressure is too high, arsenic is not completely volatilized.

[0143] Comparative Example 4

[0144] Compared with Example 1, only the vacuum degree in Step 2 is changed:

[0145] 1. First, place 100 g of crude arsenic, 5 g of carbon powder, and 10 g of copper powder in an inert atmosphere, and fully mix them through a mixer to obtain a mixed arsenic material. Then add the mixed arsenic material into a vacuum container.

[0146] 2. Under normal pressure conditions, place the sealed container in a vacuum sublimation furnace with multiple temperature zones for sublimation reaction. The hot end temperature is 700 °C, the cold end temperature is 500 °C, and the sublimation time is 6 h. Since there is no vacuum environment, arsenic is not completely volatilized.

[0147] Comparative Example 5

[0148] Compared with Example 1, only a purification agent is added without adding a reducing agent:

[0149] 1. First, place 100 g of crude arsenic and 10 g of copper powder in an inert atmosphere, and fully mix them through a mixer to obtain a mixed arsenic material. Then add the mixed arsenic material into a vacuum container.

[0150] 2. Evacuate the vacuum container until the vacuum degree reaches 0.001 Pa, then seal it. Place the sealed vacuum container in a vacuum sublimation furnace with multiple temperature zones for sublimation reaction. The hot end temperature is 700 °C, the cold end temperature is 500 °C, and the sublimation time is 6 h. After the sublimation reaction is completed, cool it to obtain a purified arsenic block.

[0151] In this comparative example, the purity of the purified arsenic powder is 99.3%, the antimony content is 853.52 mg / kg, and the oxygen content is 4.56%. Since no reducing agent is added, it is difficult to reduce the oxidized impurities to the lower-valence arsenic that is more easily sublimated. Therefore, the purification effect of arsenic is poor, and most of the remaining oxidized arsenic in the crude arsenic is not reduced.

[0152] Analysis Example 1

[0153] Characterization analysis of the crude arsenic used in Examples 1-9 and Comparative Examples 1-5:

[0154] 1. Elemental quantitative analysis was performed on the crude arsenic, and the analysis results are as Figure 2 shown. According to Figure 2 observations, the Sb content is relatively high at 1326.2 ppm, which is the impurity element with the highest content. Other impurity elements include Si, S, B, etc. The contents of Si, S, and B are 52.3 ppm, 4.6 ppm, and 1.5 ppm respectively. In addition, the oxygen element content is relatively high at 7.4%. It should be noted that the purity of the crude arsenic is 99.1%, which belongs to 2N-grade crude arsenic.

[0155] 2. As Figure 3 shown, a full scan of the elemental content of the crude arsenic was performed, and the purity analysis was carried out using the difference method. The analysis results basically correspond to the elemental quantitative analysis results. Among them, Sb is the main impurity in the crude arsenic, and the impurity content is as high as 0.18%. Other important impurities include Ca, Fe, K, Na, Se, etc. The contents of Ca, Fe, K, Na, and Se are 0.0019%, 0.0053%, 0.0010%, 0.0038%, and 0.0037% respectively.

[0156] 3. XRD phase analysis was performed on the crude arsenic, and the analysis results are as Figure 4 shown. According to Figure 4 observations, the mineral composition of the crude arsenic mainly contains a large amount of arsenic oxide in addition to elemental arsenic.

[0157] Analysis Example 2

[0158] Analysis of the content of antimony and arsenic elements and optimization of the purity in the purified elemental arsenic in Examples 1-9 and Comparative Examples 1-5:

[0159] 1. According to the distribution results of the antimony element content in the purified elemental arsenic prepared in Examples 1-9 and Comparative Examples 1-5, it can be seen that the amount of carbon additive has no obvious effect on the removal of antimony. Compared with the condition of 700 °C, at the lower hot-end temperature of 650 °C, due to the difference between the saturated vapor pressure and the maximum evaporation rate between arsenic and antimony under vacuum conditions, the antimony removal effect is better, and a lower vacuum degree is more conducive to reducing the sublimation temperature, thereby realizing the differential separation between arsenic and antimony.

[0160] 2. Comprehensive optimal embodiment: Under the conditions of a hot-end temperature of 650 °C, a cold-end temperature of 450 °C, a sublimation time of 6 h, adding 5% carbon powder and 10% copper powder, and a vacuum degree of 0.001 Pa, it can obtain better impurity removal performance. As Figure 5 shown, the purity of the pure arsenic prepared in Example 4 was determined for all elements. It was found that after vacuum sublimation, the antimony content decreased significantly by more than 89%, and the purity of the crude arsenic after volatilization increased from 2N to 4N, achieving a good purification effect.

[0161] In the above technical solution of the present invention, the above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural transformation made by using the content of the specification and drawings of the present invention under the technical concept of the present invention, or direct / indirect application in other related technical fields is included in the patent protection scope of the present invention.

Claims

1. A method for purifying crude arsenic, characterized in that: include: Crude arsenic, a reducing agent and a purifying agent are mixed to obtain a mixed arsenic material; the reducing agent includes one or more of zinc powder, iron powder, magnesium powder and carbon powder; the purifying agent includes one or more of copper powder, cadmium powder, lead powder and sulfuric acid; The mixed arsenic material is placed in a sealed high vacuum environment, wherein the high vacuum environment includes a hot end and a cold end, the mixed arsenic material is sublimated at the hot end and condensed at the cold end, and the condensate at the cold end is collected to obtain arsenic element, wherein the vacuum pressure in the high vacuum environment is not greater than 1 Pa; The temperature of the hot end is 600-900°C, and the temperature difference between the hot end and the cold end is not less than 200°C; the temperature of the cold end is 400-700°C.

2. The method for purifying crude arsenic according to claim 1, characterized in that: The vacuum pressure in the high vacuum environment is 0.001~0.1Pa.

3. The method for purifying crude arsenic according to claim 1, characterized in that: The purity of the crude arsenic is 1N to 3N; the impurity elements in the crude arsenic include antimony and sulfur; and the oxygen content of the crude arsenic is >5%.

4. The method for purifying crude arsenic according to claim 1, characterized in that: The amount of the reducing agent added is 1-5% of the mass of the crude arsenic.

5. The method for purifying crude arsenic according to claim 1, characterized in that: The amount of the purifying agent added is 2-10% of the mass of the crude arsenic.

6. The method for purifying crude arsenic according to claim 1, characterized in that: The mixed arsenic material is sublimated at the hot end and condensed at the cold end, and the condensate at the cold end is collected to obtain arsenic element. The sublimation time at the hot end is not less than 2 hours.

7. The method for purifying crude arsenic according to claim 1, characterized in that: The mixed arsenic material is sublimated at the hot end and condensed at the cold end, and the process of collecting the condensate at the cold end to obtain arsenic element also includes transferring the arsenic element to an inert atmosphere, and performing crushing and screening in sequence; wherein the crushing time is 5 to 30 minutes, and the particle size of the screening treatment is 200 to 400 meshes.

8. Use of the crude arsenic purification method according to any one of claims 1 to 7 in the production of elemental arsenic and arsenide.

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