A method for purifying arsenic

Abstract

The present invention provides a method for purifying arsenic, wherein crude arsenic, bismuth powder and an iodine-containing conditioning agent are sealed at the first end of a sealed container, and the sealed container is in a vacuum or inert atmosphere; wherein the sealed container comprises a first end and a second end arranged opposite to each other; the sealed container is heated in the first stage, comprising heating the first end at a first temperature and heating the second end at a second temperature, and the first temperature is greater than the second temperature, and the second temperature is greater than the boiling point of pure arsenic; the sealed container after the first stage heating is heated in the second stage, comprising heating the first end at a third temperature and heating the second end at a fourth temperature to obtain metallic arsenic; the third temperature is greater than the fourth temperature, and the third temperature is less than the boiling point of pure arsenic. The method solves the problems that the raw materials in the prior art are highly toxic substances, which are not conducive to safe production; the process is lengthy; and it is difficult to obtain high-purity metallic arsenic.

Description

Technical Field

[0001] The invention relates to the fields of metallurgical technology and material science and engineering, and in particular to a method for purifying arsenic. Background Art

[0002] Arsenic is a doping material for synthesizing gallium arsenide (GaAs), germanium arsenide (GeAs) and silicon semiconductors, and is widely used in the semiconductor industry. Gallium arsenide can be used in the most advanced high-tech fields such as military equipment data processing, light-emitting devices, etc. At the same time, adding a small amount of metallic arsenic to the alloy can improve the mechanical properties and corrosion resistance of the alloy. Arsenic compounds are also used in the manufacturing industries such as pesticides and dyes, and are also widely used in the medical industries such as leukemia and tumors.

[0003] However, the current production process for arsenic purification faces several major challenges. First, the raw material arsenic oxide (As2O3) and the intermediate arsenic chloride (AsCl3) used in the current chlorination-reduction method for preparing high-purity arsenic are both highly toxic substances, which is not conducive to safe production. Secondly, the overall process is lengthy and requires oxidation before reduction. Depending on the specific process, chlorine, hydrogen and other gases will also be introduced into the process, resulting in a low product qualification rate.

[0004] The purification effect of the sublimation distillation method is limited by the type of impurities, and repeated sublimation and distillation are required to achieve relatively good results. The As(OR)3 thermal decomposition method requires white arsenic to react with an organic solvent to synthesize an organic compound, which is then purified by vacuum distillation, thermal decomposition, condensation, and sublimation. During this process, organic matter will affect the purity of the final metallic arsenic. Arsine (AsH3) thermal decomposition method: Arsine is a highly toxic gas with extremely high requirements for equipment, and its production safety is difficult to ensure. The steam zone refining method and the single crystal method are auxiliary technologies for further purification, and they cannot achieve the desired impurity removal effect when used alone.

[0005] In view of this, it is necessary to provide a method for arsenic purification to solve or at least alleviate the above technical defects. Summary of the invention

[0006] The main purpose of the present invention is to provide a method for purifying arsenic, aiming to solve the problems in the prior art that the raw materials are highly toxic substances, which are not conducive to safe production; the process is lengthy; and it is difficult to obtain high-purity metallic arsenic.

[0007] To achieve the above-mentioned purpose, the present invention provides a method for arsenic purification, comprising the following steps: sealing crude arsenic, bismuth powder and an iodine-containing conditioning agent at the first end of a sealed container, wherein the sealed container is in a vacuum or inert atmosphere; wherein the sealed container comprises a first end and a second end arranged opposite to each other.

[0008] The sealed container is heated in the first stage, including heating the first end at a first temperature and heating the second end at a second temperature, wherein the first temperature is greater than the second temperature, and the second temperature is greater than the boiling point of pure arsenic.

[0009] The sealed container after the first stage heating is subjected to a second stage heating, including heating the first end at a third temperature and heating the second end at a fourth temperature to obtain metallic arsenic; the third temperature is greater than the fourth temperature, and the third temperature is less than the boiling point of pure arsenic.

[0010] Furthermore, the first temperature is 850-900°C; and the third temperature is 500-550°C.

[0011] Furthermore, the temperature difference between the first end and the second end is maintained at 50-60°C.

[0012] Furthermore, the atomic ratio of the crude arsenic to the bismuth powder is 1:3 to 3:1.

[0013] Further, during the first stage heating and the second stage heating, the first end is located above the second end.

[0014] Furthermore, the crude arsenic has an arsenic content of 98% by mass.

[0015] Furthermore, the iodine-containing conditioning agent is elemental iodine.

[0016] Furthermore, after the second stage heating step, a third stage heating is also included, including heating the first end to a temperature of 75-80° C. and heating the second end to a temperature of 15-30° C. to obtain the metallic arsenic.

[0017] Furthermore, the total reaction time of all stages of the reaction is >70h.

[0018] Furthermore, the duration of the first stage heating reaction and the second stage heating reaction are both >20 hours.

[0019] The beneficial effects achieved by the present invention are:

[0020] 1. The process is simple, easy to operate and has high application value.

[0021] 2. Metal arsenic with a purity of >99.9% can be obtained by the purification method of the present invention.

[0022] 3. The raw materials used in the purification method of the present invention are conventional and easy to obtain, which is conducive to application and promotion.

[0023] 4. Under the coordinated action of iodine and bismuth, arsenic can even precipitate on the surface of bismuth melt in the form of single crystals. During the precipitation process, the structure grows in an orderly manner, achieving enhanced impurity removal, so that impurities are directionally enriched in the molten bismuth phase, and at the same time, iodine is driven away from the crystallization area, thereby achieving the purification of metallic arsenic. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0025] Figure 1 For this clear Schematic diagram of the process for arsenic purification;

[0026] Figure 2 This is a physical picture of the metallic arsenic obtained in Example 1;

[0027] Figure 3 This is a scanning electron microscope (SEM) image of metallic arsenic obtained in Example 1;

[0028] Figure 4 is the X-ray diffraction (XRD) pattern of metallic arsenic obtained in Example 1;

[0029] Figure 5 is a scanning electron microscope (SEM) image of 98% crude arsenic in Example 1;

[0030] Figure 6 is the X-ray diffraction (XRD) pattern of 98% crude arsenic in Example 1;

[0031] Figure 7 This is a physical picture of the metallic arsenic obtained in Example 2;

[0032] Figure 8 This is a physical picture of the metallic arsenic obtained in Example 3;

[0033] Fig. 9 This is a physical picture of the metallic arsenic obtained in Example 4;

[0034] Fig.10 This is a physical picture of the metallic arsenic obtained in Example 5;

[0035] Fig.11 This is a physical picture of the product obtained in Comparative Example 1;

[0036] Fig.12 is the X-ray diffraction (XRD) pattern of the product obtained in Comparative Example 1;

[0037] Fig.13 This is a physical picture of the product obtained in Comparative Example 2;

[0038] Fig.14 The X-ray diffraction (XRD) pattern of the product obtained in Comparative Example 2 is shown in FIG.

[0039] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with the implementation methods and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. It should also be understood that the terms used in the embodiments of the present invention are intended to describe specific embodiments rather than to limit the scope of protection of the present invention.

[0042] Unless otherwise defined, all technical and scientific terms used in the present invention are consistent with the prior art mastery of those skilled in the art and the description of the present invention, and any method, device and material of the prior art similar or equivalent to the method, device and material in the embodiments of the present invention can also be used to implement the present invention. It should be known to those skilled in the art that, as an explanation of the present application document, without affecting the actual understanding of the technical solution of the present application, "Intensity (au)" can be expressed as intensity, and "2θ" can be expressed as 2 times the diffraction angle.

[0043] When the embodiments give numerical ranges, it should be understood that unless otherwise specified in the present invention, both endpoints of each numerical range and any value between the two endpoints can be selected. The test methods in the following embodiments without specifying specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturers. The materials or reagents required in the following embodiments are commercially available unless otherwise specified.

[0044] In order to solve the problems of the prior art that the raw materials are highly toxic substances, which are not conducive to safe production; the process is lengthy; and it is difficult to obtain high-purity metallic arsenic, the present invention provides a method for purifying arsenic, comprising the following steps:

[0045] The crude arsenic, bismuth powder and iodine-containing conditioning agent are sealed at the first end of a sealed container, and the sealed container is in a vacuum or inert atmosphere; wherein the sealed container includes a first end and a second end that are arranged oppositely.

[0046] The sealed container is heated in the first stage, including heating the first end at a first temperature and heating the second end at a second temperature, wherein the first temperature is greater than the second temperature, and the second temperature is greater than the boiling point of pure arsenic.

[0047] The sealed container after the first stage heating is heated in the second stage, including heating the first end at a third temperature and heating the second end at a fourth temperature to obtain metallic arsenic; the third temperature is greater than the fourth temperature and less than the boiling point of pure arsenic.

[0048] Specifically, crude arsenic, bismuth powder and iodine-containing conditioning agent can be mixed and placed at the first end of a quartz tube under an inert atmosphere in a glove box, and then sealed with a plug, and then the quartz tube is sealed with a vacuum valve. The quartz tube is then taken out of the glove box, and the quartz tube is evacuated to a vacuum with a duct machine, and then the quartz tube is sealed with a hydrogen and oxygen machine, and placed in a multi-temperature zone tubular furnace, and the temperature of the dual temperature zones is set for reaction. Among them, one temperature zone is a high temperature zone, and the other temperature zone is a low temperature zone. The first end of the closed container, that is, the area where the raw material end is located, is the high temperature zone, and the second end, that is, the area where the product end is located, is the low temperature zone.

[0049] During the reaction process at the raw material end, under the coordinated action of iodine and bismuth, the arsenic in the crude arsenic sublimates, and most of the impurities are directionally enriched in the molten bismuth phase. Most of the arsenic vapor reaches the product end under the transfer action of the iodine-containing conditioning agent and precipitates on the surface of the bismuth melt, and can even grow unidirectionally to obtain single crystal arsenic. During the precipitation of arsenic, the structure grows in an orderly manner, achieving enhanced impurity removal, so that iodine is driven away from the product end at the same time, and the purification of metallic arsenic is achieved.

[0050] The crude arsenic begins to sublime into arsenic vapor when the temperature exceeds 615° C.; the first temperature and the second temperature are both greater than 615° C., and the first temperature is greater than the second temperature.

[0051] The above method has a simple process, is easy to operate, and has high application value; the purity of the obtained metallic arsenic is >99.9%. Moreover, the crude arsenic, bismuth powder, and iodine-containing conditioning agent used are conventionally easy to obtain, which is conducive to application and promotion. After the reaction is completed, precipitated high-purity metallic arsenic can be obtained at both the raw material end and the product end; and high-purity metallic arsenic can be directly obtained at the product end without stripping.

[0052] Furthermore, the first temperature is 850-900°C; the third temperature is 500-550°C. It should be noted that the bismuth powder forms a molten state at 271.5°C. Specifically, when the temperature of the first end is 850-900°C, it can be ensured that the arsenic in the raw material is converted into the form of arsenic vapor. With the assistance of the iodine-containing conditioning agent, the arsenic vapor migrates to the product end. When the temperature of the first end is 500-550°C, most of the impurities in the crude arsenic can be retained in the molten bismuth, and the arsenic vapor begins to grow.

[0053] Furthermore, the temperature difference between the first end and the second end is maintained at 50-60° C. When the temperature difference between the first end and the second end is stabilized at 50-60° C., it is beneficial for arsenic vapor to be transferred from the first end to the second end, and most of the arsenic can also grow into metallic arsenic at the product end.

[0054] Furthermore, the atomic ratio of crude arsenic to bismuth powder is 1:3 to 3:1. When the atomic ratio of crude arsenic to bismuth powder is greater than 3:1, the crystal form of the precipitated arsenic is very unstable; when the atomic ratio of crude arsenic to bismuth powder is less than 1:3, the amount of arsenic precipitated is too small to be precipitated on the surface of bismuth, which is inconvenient for subsequent separation operations.

[0055] Furthermore, during the first stage heating and the second stage heating, the first end is located above the second end. Specifically, the end where the quartz tube mouth is located can be the second end; the sealed quartz tube mouth can be placed tilted toward the product end of the multi-temperature zone tube furnace so that the first end is higher than the second end.

[0056] Furthermore, the crude arsenic has an arsenic content of 98% by mass.

[0057] Furthermore, the iodine-containing conditioning agent is iodine element.

[0058] Furthermore, after the second stage heating step, a third stage heating is also included, including heating the first end to 75-80° C. and heating the second end to 15-30° C. to obtain metallic arsenic. At this time, both the first end and the second end can obtain precipitated high-purity metallic arsenic.

[0059] Furthermore, the total reaction time of all stages of the reaction is greater than 70 hours. Specifically, the total reaction time is greater than 70 hours, which is conducive to single crystal growth and can obtain a large volume of purified metallic arsenic.

[0060] Furthermore, the reaction time of the first stage heating and the reaction time of the second stage heating are both >20h.

[0061] For further understanding of the present invention, examples are given below:

[0062] Example 1

[0063] 1. Soak the quartz tube and the plug in 2% hydrofluoric acid for 10 hours, then rinse with ethanol and deionized water three times in sequence, and place them in a far-infrared drying oven for use; grind the raw material 98% crude arsenic (As) into powder for use.

[0064] Among them, the scanning electron microscope (SEM) image of the raw material 98% crude arsenic is as follows Figure 5 As shown; the X-ray diffraction (XRD) pattern of the raw material 98% crude arsenic is as follows Figure 6 As shown. Figure 5It can be seen that the raw material 98% crude arsenic does not have an obvious crystal structure; Figure 6 It can be seen that 98% of the raw material crude arsenic is in an amorphous state.

[0065] 2. In an inert atmosphere of a glove box, use a 1 / 10,000 electronic balance to weigh 98% crude arsenic (As) and bismuth (Bi) with an atomic ratio of 1:1 as raw materials; among them, weigh 0.134g of 98% crude arsenic and 0.374g of bismuth. And weigh 0.024g of 3wt.% iodine element (I2) as a transfer agent and add it into a quartz tube; seal one end of the quartz tube with a plug, and then seal the quartz tube with a vacuum valve, and then take the quartz tube out of the glove box; use a tube sealing machine to evacuate the quartz tube to a vacuum, and then use a hydrogen-oxygen machine to seal the quartz tube.

[0066] 3. Place the sealed quartz tube with its mouth tilted toward the product end in a multi-temperature zone tubular furnace, set the temperature of the dual temperature zones, and conduct a gas phase synthesis reaction. The reaction procedure is as follows: the temperature of the raw material end (first end) is 900°C, and the temperature of the product end (second end) is 850°C. After maintaining for 20 hours, the raw material end is cooled to 550°C within 10 hours, and the product end is cooled to 500°C. After keeping warm for 20 hours, the raw material end is cooled to 75°C within 20 hours, and the product end is cooled to 25°C. Finally, it is naturally cooled to room temperature to obtain metallic arsenic.

[0067] Among them, the placement of the quartz tube, the setting of each temperature zone, the addition of raw materials and the generation of products, such as Figure 1 The flow diagram of the method for arsenic purification is shown in FIG.

[0068] The actual picture of the obtained metallic arsenic is as follows Figure 2 The scanning electron microscopy (SEM) results are shown in Figure 3 As shown; X-ray diffraction (XRD) diagram as shown Figure 4 shown.

[0069] like Figure 3 As shown, the metal arsenic obtained in this embodiment has an obvious single crystal structure, as shown in Figure 3 As shown on the left, Figure 3 On the right is bismuth. Figure 4 By comparing the XRD standard cards, it can be seen that under the coordinated regulation of bismuth and iodine, the arsenic growth crystal plane structure of the obtained product is mainly (003) (006).

[0070] Example 2

[0071] Compared with Example 1, only the atomic ratio of 98% crude arsenic (As) and bismuth (Bi) is changed, namely:

[0072] In an inert atmosphere of a glove box, 98% crude arsenic (As) and bismuth (Bi) with an atomic ratio of 3:1 were weighed as raw materials using a 1 / 10,000 electronic balance; 0.134 g of 98% crude arsenic and 0.094 g of bismuth were weighed.

[0073] Finally, the physical image of the metal arsenic precipitated on the bismuth surface is as follows: Figure 7 shown.

[0074] Example 3

[0075] Compared with Example 1, only the atomic ratio of 98% crude arsenic (As) and bismuth (Bi) is changed, namely:

[0076] In an inert atmosphere of a glove box, 98% crude arsenic (As) and bismuth (Bi) with an atomic ratio of 2:1 were weighed as raw materials using a 1 / 10,000 electronic balance; 0.134 g of 98% crude arsenic and 0.123 g of bismuth were weighed.

[0077] Finally, the physical image of the metal arsenic precipitated on the bismuth surface is as follows: Figure 8 shown.

[0078] Example 4

[0079] Compared with Example 1, only the atomic ratio of 98% crude arsenic (As) and bismuth (Bi) is changed, namely:

[0080] In an inert atmosphere of a glove box, 98% crude arsenic (As) and bismuth (Bi) with an atomic ratio of 1:2 were weighed as raw materials using a 1 / 10,000th electronic balance; 0.134 g of 98% crude arsenic and 0.748 g of bismuth were weighed.

[0081] Finally, the physical image of the metal arsenic precipitated on the bismuth surface is as follows: Fig. 9 shown.

[0082] Example 5

[0083] Compared with Example 1, only the atomic ratio of 98% crude arsenic (As) and bismuth (Bi) is changed, namely:

[0084] In an inert atmosphere of a glove box, 98% crude arsenic (As) and bismuth (Bi) with an atomic ratio of 1:3 were weighed as raw materials using a 1 / 10,000 electronic balance; 0.134 g of 98% crude arsenic and 1.122 g of bismuth were weighed.

[0085] Finally, the physical image of the metal arsenic precipitated on the bismuth surface is as follows: Fig.10 shown.

[0086] Comparative Example 1

[0087] Compared with Example 1, only iodine is not added, that is:

[0088] In an inert atmosphere of a glove box, 98% crude arsenic (As) and bismuth (Bi) in an atomic ratio of 1:1 were weighed as raw materials using a 1 / 10,000th electronic balance; 0.134 g of 98% crude arsenic and 0.374 g of bismuth were weighed and added into a quartz tube; one end of the quartz tube was sealed with a plug, and then the quartz tube was sealed with a vacuum valve, and then the quartz tube was taken out of the glove box; the quartz tube was evacuated to a vacuum using a tube sealing machine, and then the quartz tube was sealed with a hydrogen-oxygen machine.

[0089] Finally, the physical picture of the obtained product is as follows Fig.11 Its XRD pattern is shown as Fig.12 shown.

[0090] according to Fig.12 It can be observed that in the absence of iodine, arsenic cannot exist in a single crystal form, and a certain impurity removal effect is lost, resulting in a low purity of single crystal arsenic compared to that under bismuth-iodine coordination.

[0091] Comparative Example 2

[0092] Compared with Example 1, only bismuth is not added, that is:

[0093] Under the inert atmosphere of the glove box, 0.134 g of 98% crude arsenic (As) as a raw material is weighed with a 1 / 10,000 electronic balance, and 0.024 g of 3 wt.% elemental iodine (I2) as a transfer agent are weighed and added into a quartz tube; one end of the quartz tube is sealed with a plug, and then the quartz tube is sealed with a vacuum valve, and then the quartz tube is taken out of the glove box; the quartz tube is evacuated to a vacuum with a tube sealing machine, and then the quartz tube is sealed with a hydrogen-oxygen machine.

[0094] Finally, the physical picture of the obtained product is as follows Fig.13 Its XRD pattern is shown as Fig.14 shown.

[0095] according to Fig.13 It can be observed that the obtained product has a single crystal structure; Fig.14 It is shown that it has a (003) crystal structure.

[0096] Analysis example 1

[0097] The metallic arsenic obtained in Example 1, the product obtained in Comparative Example 1, and the product obtained in Comparative Example 2 were subjected to elemental analysis, and the energy spectrum analysis results are shown in Table 1, Table 2, and Table 3, respectively.

[0098] Table 1 Analysis of metallic arsenic elements obtained in Example 1

[0099]

[0100] Table 2 Elemental analysis of products obtained in Comparative Example 1

[0101]

[0102] Table 3 Elemental analysis of products obtained in Comparative Example 2

[0103]

[0104] It can be seen from Table 1 that the arsenic content in the metallic arsenic obtained in Example 1 can be as high as 99.92%, and there is no bismuth residue, and the purification effect is good.

[0105] It can be seen from Tables 2 and 3 that in the product obtained in Comparative Example 1, the purity of arsenic is improved compared with that in Comparative Example 2, which shows that molten bismuth has a good enrichment and retention effect on impurities in crude arsenic, but it is still difficult to achieve an arsenic purification effect of more than 99.9%, and there is still bismuth residue.

[0106] In Table 3, in the product obtained in Comparative Example 2, the purity of arsenic is 99.27%, indicating that under the action of the iodine-containing conditioning agent, the generated single crystal arsenic has a certain impurity removal effect; but there is iodine residue.

[0107] In summary, the effects of both alone are difficult to achieve the arsenic purification effect under the coordination of bismuth and iodine (such as Example 1).

[0108] In summary, the above technical solutions of the present invention are only preferred embodiments of the present invention, and the patent scope of the present invention is not limited thereto. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for purifying arsenic, characterized in that: The following steps are involved: The crude arsenic, bismuth powder and iodine-containing conditioning agent are sealed at the first end of a sealed container, wherein the sealed container is in a vacuum or inert atmosphere; wherein the sealed container comprises a first end and a second end arranged opposite to each other; and the atomic ratio of the crude arsenic to the bismuth powder is 1:3 to 3:1; Heating the sealed container in the first stage, including heating the first end at a first temperature and heating the second end at a second temperature, wherein the first temperature is greater than the second temperature, and the second temperature is greater than the boiling point of pure arsenic; The sealed container after the first stage heating is subjected to a second stage heating, including heating the first end at a third temperature and heating the second end at a fourth temperature to obtain metallic arsenic; the third temperature is greater than the fourth temperature, and the third temperature is less than the boiling point of pure arsenic.

2. The method for purifying arsenic according to claim 1, characterized in that: The first temperature is 850-900°C; the third temperature is 500-550°C.

3. The method for purifying arsenic according to claim 1, characterized in that: The temperature difference between the first end and the second end is maintained at 50-60°C.

4. The method for purifying arsenic according to claim 1, characterized in that: During the first stage heating and the second stage heating, the first end is located above the second end.

5. The method for purifying arsenic according to claim 1, characterized in that: The crude arsenic has an arsenic content of 98% by mass.

6. The method for purifying arsenic according to claim 1, characterized in that: The iodine-containing conditioning agent is iodine element.

7. The method for purifying arsenic according to claim 1, characterized in that: After the second stage heating step, a third stage heating is also included, including heating the first end to a temperature of 75-80° C. and heating the second end to a temperature of 15-30° C. to obtain the metallic arsenic.

8. The method for purifying arsenic according to claim 1 or 7, characterized in that: The total reaction time of all stages of the reaction was >70 h.

9. The method for purifying arsenic according to claim 1, characterized in that: The duration of the first stage heating reaction and the second stage heating reaction are both >20h.

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