A method for purifying arsenic trioxide

Abstract

The application belongs to the technical field of metallurgy, and discloses a purification method of diarsenic trioxide. The purification method comprises the following steps: S1. heating and reacting the crude diarsenic trioxide mixed with nitrate at 250-350 DEG C for 2-4 h; S2. raising the reaction system obtained in step S1 to 550-650 DEG C and maintaining for 3-6 h to sublimate the diarsenic trioxide, so as to obtain roasting slag and arsenic-rich flue gas; and S3. recovering diarsenic trioxide from the arsenic-rich flue gas obtained in step S2. The application uses nitrate as an antimony removal agent, and solves the problem that arsenic and antimony are difficult to separate due to similar physical and chemical properties. The application utilizes the strong oxidizing property of nitrate, and realizes efficient recovery of diarsenic trioxide at a low temperature. The obtained diarsenic trioxide has high purity, and the recovery rates of arsenic and antimony are high.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, specifically relating to a method for purifying arsenic trioxide. Background Technology

[0002] The main source of arsenic trioxide is as a byproduct of gold and non-ferrous metal smelting. In these smelting processes, arsenic-containing ores are smelted at high temperatures, and regardless of whether the environment is oxygen-rich or oxygen-poor, most of the arsenic is oxidized and enters the flue gas system as gaseous oxides. The flue gas is then rapidly cooled using a quenching device, causing the gaseous arsenic oxides to quickly condense into solid particles, which are then effectively captured, forming crude arsenic trioxide. Simultaneously, during the flue gas cooling process, antimony also undergoes similar oxidation and condensation, precipitating from the gas phase as antimony trioxide, which settles together with the arsenic trioxide in the dust collection equipment. Therefore, the final arsenic trioxide product collected from the flue gas usually contains a certain proportion of antimony trioxide as an impurity.

[0003] The most common method for purifying crude arsenic trioxide is the pyrolysis method. However, under high temperature conditions, the As-Sb solid solution formed between antimony trioxide and arsenic trioxide limits the effective removal of antimony trioxide from arsenic trioxide by selective volatilization, resulting in the arsenic trioxide quality failing to meet requirements.

[0004] Currently, in the process of separating arsenic from antimony using solid antimony, metal oxides (such as copper oxide, iron oxide, manganese oxide, nickel oxide, etc.) and their corresponding sulfates are commonly used as reaction media. However, these metal oxides or sulfates have significant limitations in actual reaction processes: at low reaction temperatures, they are difficult to react effectively with antimony trioxide, resulting in poor antimony separation efficiency; while at higher temperatures, these reagents not only react with the target substance antimony trioxide but also with non-target components such as arsenic, causing simultaneous reactions of arsenic and antimony, thus leading to incomplete separation of arsenic and antimony and a low overall recovery rate. Furthermore, the introduction of metallic impurities such as copper, iron, and manganese during the reaction not only affects the selectivity of the reaction but also interferes with subsequent antimony recovery and purification processes, increasing the difficulty and cost of subsequent treatment. Summary of the Invention

[0005] To address the shortcomings of the existing technologies, this invention provides a method for purifying arsenic trioxide, which solves the problem of the difficulty in separating arsenic and antimony due to their similar physicochemical properties. The technical solution of this invention can recover high-purity arsenic trioxide with high arsenic and antimony recovery rates.

[0006] The specific technical solution is as follows:

[0007] This invention provides a method for purifying arsenic trioxide, comprising the following steps:

[0008] S1. Mix crude arsenic trioxide with nitrate and heat at 250-350℃ for 2-4 h;

[0009] S2. Heat the reaction system obtained in step S1 to 550~650℃ and maintain it for 3~6 h to sublimate arsenic trioxide, and obtain roasting residue and arsenic-rich flue gas.

[0010] S3. Recover arsenic trioxide from the arsenic-rich flue gas obtained in step S2.

[0011] The crude arsenic trioxide used as a raw material can be derived from byproducts produced during gold or non-ferrous metal smelting.

[0012] Specifically, the preferred content of the main components in the crude arsenic trioxide includes: As2O3 content of 80wt%~99.5wt% and Sb content of 0.1wt%~13.0wt%.

[0013] The mechanism of this invention is as follows: This invention utilizes the strong oxidizing properties of nitrates (sodium nitrate, potassium nitrate), which readily react with antimony trioxide at low temperatures to generate antimony pentoxide. After the reaction is complete, the temperature is raised, and arsenic trioxide sublimates into a gas. After cooling, the arsenic trioxide is recovered. The obtained arsenic trioxide has high purity, and the recovery rate of arsenic and antimony is high, thus solving the problem of the difficulty in separating arsenic and antimony due to their similar physicochemical properties.

[0014] Furthermore, in step S1, the preferred molar ratio of nitrate to the total amount of antimony in crude arsenic trioxide is (1~2):1.

[0015] Furthermore, in step S1: the nitrate is preferably sodium nitrate or / and potassium nitrate.

[0016] Furthermore, in step S1, the vacuum degree is preferably -0.05~0.00 MPa.

[0017] Specifically, the main reactions that occur in step S1 are as follows:

[0018] Sb2O3+2NaNO3→2NaNO2+Sb2O5.

[0019] Specifically, step S1 is preferably heated in a tubular roasting furnace.

[0020] Specifically, the As content in the roasted residue obtained in step S2 is <1.5wt%.

[0021] Furthermore, in step S2, the vacuum degree is preferably -0.10 to -0.05 MPa.

[0022] Specifically, the main reactions that occur in step S2 are:

[0023] As2O 3(s) →As2O 3(g)

[0024] Specifically, the roasted slag obtained in step S2 is used to recover antimony white through an antimony smelting system.

[0025] Furthermore, in step S3: arsenic trioxide is recovered by a rapid cooling arsenic recovery method. The recovered arsenic trioxide has a purity ≥99.5 wt%.

[0026] The aforementioned rapid cooling arsenic collection involves first rapidly cooling and precipitating arsenic by spraying water mist into the hot flue gas in the rapid cooling tower to promote rapid cooling of the flue gas, while As2O3 crystallizes and precipitates out simultaneously; then collecting arsenic in a baghouse.

[0027] Specifically, the preferred conditions for arsenic recovery by quenching are: the flue gas temperature at the outlet of the quenching tower should be controlled at 180~200℃, and the flue gas temperature at the inlet of the bag filter should be controlled at 160~175℃.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] This invention uses nitrates as an antimony removal agent, solving the problem of difficulty in separating arsenic and antimony due to their similar physicochemical properties. Utilizing the strong oxidizing properties of nitrates, this invention achieves efficient recovery of arsenic trioxide at relatively low temperatures, yielding high-purity arsenic trioxide with high recovery rates of valuable elements arsenic and antimony. The method is simple and convenient, reducing process costs. Attached Figure Description

[0030] Figure 1 This is a process flow diagram of an embodiment of the present invention. Detailed Implementation

[0031] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention. Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0032] In the specific implementation method: crude arsenic trioxide is derived from a byproduct of a complex gold and copper concentrate pyrometallurgical system.

[0033] Example 1

[0034] Arsenic trioxide was purified from crude arsenic trioxide as raw material. The crude arsenic trioxide contained 82.34 wt% As₂O₃ and 12.65 wt% Sb. The method steps are as follows:

[0035] S1. After uniformly mixing crude arsenic trioxide and sodium nitrate, the mixture is added to a tubular calcining furnace and heated at 300℃ for 3 h under a vacuum of -0.05 MPa; wherein the molar ratio of sodium nitrate to the total amount of antimony in crude arsenic trioxide is 1.5:1.

[0036] S2. The reaction system obtained in step S1 is heated to 600℃ and maintained at the temperature for 5 h under a vacuum of -0.10 MPa to obtain calcined residue and arsenic-rich flue gas.

[0037] S3. The roasted residue obtained in step S2 is used to recover antimony white using an antimony smelting system.

[0038] Arsenic-rich flue gas obtained in step S2 is used to recover arsenic trioxide via a rapid cooling method. First, arsenic is rapidly cooled to precipitate it by spraying water mist into the hot flue gas inside the rapid cooling tower to promote rapid cooling. Then, arsenic is collected using a bag filter. The flue gas temperature at the outlet of the rapid cooling tower is controlled at 180℃, and the flue gas temperature at the inlet of the bag filter is controlled at 160℃.

[0039] Example 2

[0040] Arsenic trioxide was purified using crude arsenic trioxide as raw material. The crude arsenic trioxide contained 99.01 wt% As₂O₃ and 0.25 wt% Sb. The method steps are as follows:

[0041] S1. After uniformly mixing crude arsenic trioxide and sodium nitrate, the mixture is added to a tubular calcining furnace and heated at 250°C for 4 h under a vacuum of -0.05 MPa; wherein the molar ratio of sodium nitrate to the total amount of antimony in crude arsenic trioxide is 1:1.

[0042] S2. The reaction system obtained in step S1 is heated to 550℃ and maintained at the temperature for 6 h under a vacuum of -0.10 MPa to obtain calcined residue and arsenic-rich flue gas.

[0043] S3. The roasted residue obtained in step S2 is used to recover antimony white using an antimony smelting system.

[0044] Arsenic-rich flue gas obtained in step S2 is used to recover arsenic trioxide via a rapid cooling method. First, arsenic is rapidly cooled to precipitate it by spraying water mist into the hot flue gas inside the rapid cooling tower to promote rapid cooling. Then, arsenic is collected using a bag filter. The flue gas temperature at the outlet of the rapid cooling tower is controlled at 200℃, and the flue gas temperature at the inlet of the bag filter is controlled at 175℃.

[0045] Example 3

[0046] Arsenic trioxide was purified from crude arsenic trioxide as raw material. The crude arsenic trioxide contained 90.25 wt% As₂O₃ and 6.82 wt% Sb. The method steps are as follows:

[0047] S1. After uniformly mixing crude arsenic trioxide and sodium nitrate, the mixture is added to a tubular calcining furnace and heated at 350°C for 2 h under a vacuum of 0.00 MPa; wherein the molar ratio of sodium nitrate to the total amount of antimony in crude arsenic trioxide is 2:1.

[0048] S2. The reaction system obtained in step S1 is heated to 650℃ and maintained at the temperature for 3 h under a vacuum of -0.05 MPa to obtain calcined residue and arsenic-rich flue gas.

[0049] S3. The roasted residue obtained in step S2 is used to recover antimony white using an antimony smelting system.

[0050] Arsenic-rich flue gas obtained in step S2 is used to recover arsenic trioxide via a rapid cooling method. First, arsenic is rapidly cooled to precipitate it by spraying water mist into the hot flue gas in the rapid cooling tower to promote rapid cooling. Then, arsenic is collected using a bag filter. The flue gas temperature at the outlet of the rapid cooling tower is controlled at 190℃, and the flue gas temperature at the inlet of the bag filter is controlled at 170℃.

[0051] Example 4

[0052] Arsenic trioxide was purified from crude arsenic trioxide as raw material. The crude arsenic trioxide contained 82.34 wt% As₂O₃ and 12.65 wt% Sb. The method steps are as follows:

[0053] S1. After uniformly mixing crude arsenic trioxide and potassium nitrate, the mixture is added to a tube furnace and heated at 300℃ for 3 h under a vacuum of -0.05 MPa; wherein the molar ratio of potassium nitrate to the total amount of antimony in crude arsenic trioxide is 1.5:1.

[0054] S2. The reaction system obtained in step S1 is heated to 600℃ and maintained at the temperature for 5 h under a vacuum of -0.10 MPa to obtain calcined residue and arsenic-rich flue gas.

[0055] S3. The roasted residue obtained in step S2 is used to recover antimony white using an antimony smelting system.

[0056] Arsenic-rich flue gas obtained in step S2 is used to recover arsenic trioxide via a rapid cooling method. First, arsenic is rapidly cooled to precipitate it by spraying water mist into the hot flue gas inside the rapid cooling tower to promote rapid cooling. Then, arsenic is collected using a bag filter. The flue gas temperature at the outlet of the rapid cooling tower is controlled at 180℃, and the flue gas temperature at the inlet of the bag filter is controlled at 160℃.

[0057] Comparative Example 1

[0058] Referring to Example 1, the difference from Example 1 is that sodium nitrate in step S1 is replaced with copper oxide, and the molar ratio of copper oxide to the total amount of antimony in crude arsenic trioxide is 1.5:1. Other technical features are the same as in Example 1.

[0059] Comparative Example 2

[0060] Referring to Example 1, the difference from Example 1 is that sodium nitrate in step S1 is replaced with calcium oxide, and the molar ratio of calcium oxide to the total amount of antimony in crude arsenic trioxide is 1.5:1. Other technical features are the same as in Example 1.

[0061] Comparative Example 3

[0062] Referring to Comparative Example 1, the difference from Comparative Example 1 is that sodium nitrate in step S1 is replaced with calcium oxide and copper sulfate, the molar ratio of calcium oxide to the total amount of antimony in crude arsenic trioxide is 1.5:1, and the molar ratio of copper sulfate to the total amount of antimony in crude arsenic trioxide is 1.5:1. Other technical features are the same as in Example 1.

[0063] test

[0064] The purity of arsenic trioxide obtained in each embodiment and comparative example, as well as the As content in the calcined residue obtained in step S2, were tested, and the results are shown in Table 1. The recovery rates of As and Sb were calculated, and the results are shown in Table 2.

[0065] The purity of arsenic trioxide was determined according to the method in Appendix A of the standard for arsenic trioxide (GB 26721-2011). The As content was determined according to the standard for chemical analysis of copper smelting dust, Part 5: Determination of arsenic content by ferrous ammonium sulfate titration (YS / T 1512.5-2021).

[0066] Table 1. Purity of arsenic trioxide and As content in roasting residue

[0067] <![CDATA[As2O3 purity (%)]]> As content in roasted slag (wt%) Example 1 99.62 1.25 Example 2 99.58 1.34 Example 3 99.64 1.19 Example 4 99.61 1.27 Comparative Example 1 99.52 3.42 Comparative Example 2 99.54 3.04 Comparative Example 3 99.60 3.12

[0068] Table 2 Recovery rates of As and Sb

[0069] As recovery rate (%) Sb recovery rate (%) Example 1 99.01 99.11 Example 2 99.21 99.32 Example 3 99.14 99.14 Example 4 99.13 99.16 Comparative Example 1 97.25 96.24 Comparative Example 2 98.14 96.14 Comparative Example 3 98.07 95.82

[0070] As can be seen from Tables 1 and 2, the purity of arsenic trioxide in both the examples and the comparative examples reached over 99.5%. However, the arsenic content in the roasting residue of the examples was less than 1.5%, while the arsenic content in the roasting residue of the comparative examples was greater than 3.0%. The recovery rates of arsenic and antimony in the examples were both greater than 99%, but the recovery rate of arsenic in the comparative examples was less than 98.5%, and the recovery rate of antimony was less than 96.5%. In summary, this technology has a good purification effect on antimony-containing arsenic trioxide, and the recovery rates of arsenic and antimony are high.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for purifying arsenic trioxide, characterized in that, Includes the following steps: S1. Crude arsenic trioxide is mixed with nitrate and then heated at 250-350℃ for 2-4 h; the nitrate is sodium nitrate and / or potassium nitrate. S2. Heat the reaction system obtained in step S1 to 550~650℃ and maintain it for 3~6 h to sublimate arsenic trioxide, and obtain roasting residue and arsenic-rich flue gas. S3. Recover arsenic trioxide from the arsenic-rich flue gas obtained in step S2.

2. The purification method according to claim 1, characterized in that, In step S1, the molar ratio of nitrate to the total amount of antimony in crude arsenic trioxide is (1~2):

1.

3. The purification method according to claim 1, characterized in that, In step S1: the vacuum degree is -0.05~0.00 MPa.

4. The purification method according to claim 1, characterized in that, In step S2: the vacuum degree is -0.10 to -0.05 MPa.

5. The purification method according to claim 1, characterized in that, The roasted residue obtained in step S2 is used to recover antimony white through an antimony smelting system.

6. The purification method according to claim 1, characterized in that, In step S3: Arsenic trioxide is recovered by quenching.

7. The purification method according to claim 1, characterized in that, The main components of the crude arsenic trioxide include: As2O3 content of 80wt%~99.5wt% and Sb content of 0.1wt%~13.0wt%.

8. The purification method according to claim 1, characterized in that, The crude arsenic trioxide is derived from a byproduct of gold or non-ferrous metal smelting.

Images