Method for efficiently recovering thallium from complex solution

Abstract

The invention relates to the technical field of thallium recovery and treatment, in particular to a method for efficiently recovering thallium from a complex solution. The invention discloses a method for efficiently recovering thallium in a complex solution. The method comprises the following steps: S1, multi-stage replacement; a metal displacer is added into the thallium-containing feed liquid, a multi-stage displacement reaction is carried out, and the pH value during the multi-stage displacement reaction is 3-5; after the reaction is finished, separating to obtain thallium-removed feed liquid and thallium-containing solid; s2, dissolving; dissolving the thallium-containing solid with an inorganic acid to form a thallium-containing solution; s3, oxidizing and precipitating; and adding an oxidizing agent into the thallium-containing solution, adjusting the pH value of the solution to 1-3 after the oxidation is finished, generating a precipitate, and separating to obtain a thallium hydroxide solid. The method disclosed by the invention is wide in application range, can be used for treating thallium-containing wastewater with various concentrations, is simple in process and easy to implement, and meanwhile, thallium and other valuable metals can be recycled, so that efficient recovery and utilization of resources are realized.

Description

Technical Field

[0001] The invention relates to the technical field of recovery and treatment of thallium, and in particular to a method for efficiently recovering thallium in a complex solution. Background Art

[0002] Thallium (Tl) is a highly toxic metal element that is widely found in sulfur ores of lead, zinc, iron, copper and other metals. With the mining and smelting of these metals, thallium inevitably enters industrial wastewater, posing a serious threat to the environment and human health. Thallium pollution is not only spread through water bodies and soil, but also enters crops through irrigation water sources and eventually enters the human body through the food chain. Long-term accumulation may cause a variety of diseases, such as esophageal cancer and liver cancer, which seriously endangers human health.

[0003] At present, the treatment technologies for thallium-containing wastewater mainly include sulfide precipitation, adsorption, electrochemical and comprehensive treatment methods, etc. These methods can control the thallium content in wastewater to a certain extent, but they all have obvious limitations and shortcomings when treating complex thallium-containing liquids.

[0004] 1. Sulfide precipitation method, by adding sulfides such as sodium sulfide, thallium ions are formed into insoluble thallium sulfide precipitation for removal. Although this method has a good effect on the treatment of high-concentration thallium-containing wastewater, it is difficult to meet the standards when treating low-concentration thallium-containing liquid, and requires a large amount of sodium sulfide, which is easy to produce harmful gases such as hydrogen sulfide (H2S), causing secondary pollution.

[0005] 2. Adsorption method, using the adsorption capacity of specific materials for thallium ions to remove them from wastewater. In recent years, some composite adsorption materials composed of low-carbon alcohol-modified organic salts and natural minerals have shown good adsorption effects, but their scope of use is limited, and the regeneration process is complicated, requiring the consumption of strong acids such as sulfuric acid or nitric acid. The thallium removal rate after regeneration decreases, making it difficult to carry out large-scale industrial production.

[0006] 3. Electrochemical method: remove thallium ions from wastewater through electrochemical reaction. Its advantage is high treatment efficiency, but it is easy to remove a large amount of Fe 3+ or Al 3+ The introduction of impurity ions into the solution system requires additional removal, which increases the processing cost and complexity. In addition, electrochemical equipment requires a large investment and high operating and maintenance costs.

[0007] 4. Comprehensive treatment method, combining multiple treatment methods, such as neutralization, sulfide precipitation, oxidation treatment, flocculation sedimentation and physical adsorption, to synergistically treat wastewater. Although this method can achieve a high thallium removal rate, the process is complex, the operation is difficult, and the cost is high. In addition, due to the dispersion of thallium during the treatment process, it is difficult to effectively recover and recycle it.

[0008] To this end, the present application provides a method for efficiently recovering thallium in complex solutions which is efficient, economical, environmentally friendly and easy to industrialize. Summary of the invention

[0009] In order to overcome the shortcomings of the prior art, the present invention provides a method for efficiently recovering thallium in a complex solution. The thallium in the thallium-containing solution is enriched by multi-stage replacement, and then the thallium is recovered by inorganic acid dissolution and oxidation precipitation. The method has a wide range of applications and can be used to treat thallium-containing wastewater of various concentrations. The process is simple and easy to implement. At the same time, thallium and other valuable metals can also be recovered and utilized, thereby achieving efficient recovery and utilization of resources, making up for the problems of substandard thallium removal, complex process, high cost, and waste of resources in the prior art. The method is a preferred method for efficiently recovering thallium from a complex thallium-containing solution.

[0010] The technical solution adopted by this application to solve its technical problem is: A method for efficiently recovering thallium in a complex solution comprises the following steps: S1. Multi-level replacement A metal replacement agent is added to the thallium-containing liquid to carry out a multi-stage replacement reaction, wherein the pH value of the multi-stage replacement reaction is 3-5; after the reaction is completed, separation is carried out to obtain a thallium-removing liquid and a thallium-containing solid; S2. Dissolution dissolving the thallium-containing solid using an inorganic acid to form a thallium-containing solution; S3. Oxidation precipitation An oxidant is added to a solution containing thallium, and after the oxidation is completed, the pH value of the solution is adjusted to 1-3 to generate a precipitate, which is separated to obtain thallium hydroxide solid; In step S1, the multi-stage replacement reaction is to use a metal replacement agent to carry out a replacement reaction on the thallium-containing liquid at least once; after the multi-stage replacement reaction is completed, the liquid after the reaction is collected and separated to obtain a thallium-removed liquid and a thallium-containing solid; The multi-stage replacement reaction takes the thallium ion concentration in the thallium-containing liquid as the reaction end point ≤ 5 μg / L.

[0011] In some embodiments, in step S1, the metal replacement agent is selected from at least one of iron, zinc, and aluminum.

[0012] In some embodiments, in step S1, the temperature during the replacement reaction is 50-70°C, and the time during the replacement reaction is 0.5-1.5h.

[0013] In some embodiments, in step S1, the multi-stage replacement reaction includes a primary replacement reaction, and the amount of the metal replacement agent used in the primary replacement reaction is 5-8 g / L.

[0014] In some embodiments, in step S1, the multi-stage replacement reaction further comprises a secondary replacement reaction, and the amount of the metal replacement agent used in the secondary replacement reaction is 0.5-0.8 g / L.

[0015] In some embodiments, in step S2, the inorganic acid is selected from at least one of sulfuric acid, hydrochloric acid, and nitric acid, and the concentration of the inorganic acid is 2-5 mol / L.

[0016] In some embodiments, in step S2, the liquid-to-solid ratio of the dissolution process is 2-5:1.

[0017] In some embodiments, in step S3, the oxidant is one or more of ferric chloride, hydrogen peroxide, chlorine dioxide, calcium hypochlorite, and liquid chlorine.

[0018] In some embodiments, in step S3, sodium hydroxide or potassium hydroxide is used to adjust the pH of the system to 1-3.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. The method described in the present application is to perform multi-stage replacement of thallium with a metal having a higher activity order than thallium (such as iron powder, zinc powder, zinc wire, aluminum powder, and aluminum foil) to obtain a thallium-removing liquid and a thallium-containing solid; the thallium-containing solid is dissolved with an inorganic acid to obtain a thallium-enriched liquid; an oxidant is added to the thallium-enriched liquid and the pH is adjusted to obtain thallium hydroxide; and efficient recovery of thallium is achieved, with a recovery rate of up to 98-99.9%.

[0020] 2. The method described in this application has a simple process flow, is easy to implement industrial production, and has low operating costs, which helps to improve processing efficiency and reduce production costs.

[0021] 3. The method described in this application does not generate secondary pollution, and the by-products in the recovery process can also be subsequently processed or recycled, reducing pollution to the environment.

[0022] 4. The method described in this application has a wide range of applications and can treat thallium-containing wastewater of various concentrations. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0024] Figure 1 The present invention is a process flow chart of a method for efficiently recovering thallium in a complex solution described in the present application. DETAILED DESCRIPTION

[0025] In order to facilitate the understanding of those skilled in the art, the present invention is further described below in conjunction with embodiments, and the contents mentioned in the implementation modes are not intended to limit the present invention.

[0026] As used herein, "and / or" includes the term of all combinations of any one or more associated listed items. The terms used herein are only used to describe specific embodiments and are not intended to limit the present invention. As used herein, the singular forms "a", "an", "an" and "the" are also intended to include the plural forms, unless the context clearly indicates otherwise. It is further understood that "including", when used in this specification, specifies the stated features, integers, steps, operations, elements and / or compositions, but does not exclude the existence or addition of one or more other features, integers, steps, operations, elements, compositions and / or combinations thereof.

[0027] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. It is further understood that terms, such as defined in commonly used dictionaries, are interpreted in accordance with their meanings in the context of the relevant art and are not idealized or overly formal meanings unless explicitly defined as such herein.

[0028] The exemplary invention described herein may appropriately lack any one or more element limitations that are not specifically disclosed herein. Therefore, the terms "comprise", "include", "contain", etc. should be understood broadly and non-restrictively. In addition, the terminology used herein is used as a description, not a limitation, and it is unintentional to use these terminology expressions that do not include any equivalent characteristics, but only describe some of their characteristics, but various modifications are possible within the scope of the present invention according to the rights. Therefore, although the present invention has been specifically disclosed by preferred embodiments and optional features, the modifications disclosed herein to embody the changes of the present invention may be recorded by those skilled in the art, and such modifications and changes will be considered to be within the scope of the present invention.

[0029] Terminology explanation: Multi-stage replacement, a method of replacing another metal ion in a solution by gradually using a more active metal. In this application, this method is used to replace thallium ions from a complex solution.

[0030] Solid-liquid separation is a physical process used to separate solids from liquids. In this application, this process is used to separate the thallium-containing solids from the solution generated after the replacement reaction.

[0031] Liquid-to-solid ratio, the ratio of liquid volume to solid mass during the dissolution process. In this application, this ratio is used to control the reaction conditions in the sulfuric acid dissolution step.

[0032] In view of the problems of complex operation, low removal rate and high cost in current conventional thallium removal technology, especially the poor treatment effect for complex liquid, this application provides Figure 1As shown, a method for efficiently recovering thallium in a complex solution comprises the following steps: S1. Multi-level replacement A metal replacement agent is added to the thallium-containing liquid to carry out a multi-stage replacement reaction, wherein the pH value during the multi-stage replacement reaction is 3-5; after the reaction is completed, separation is carried out to obtain a thallium-removing liquid and a thallium-containing solid; S2. Dissolution dissolving the thallium-containing solid using an inorganic acid to form a thallium-containing solution; S3. Oxidation precipitation An oxidant is added to a solution containing thallium, and after the oxidation is completed, the pH value of the solution is adjusted to 1-3 to generate a precipitate, which is separated to obtain thallium hydroxide solid; In step S1, the multi-stage replacement reaction is to use a metal replacement agent to carry out a replacement reaction on the thallium-containing liquid at least once; after the multi-stage replacement reaction is completed, the liquid after the reaction is collected and separated to obtain a thallium-removing liquid and a thallium-containing solid; The multi-stage replacement reaction takes the thallium ion concentration in the thallium-containing liquid as the reaction end point ≤ 5 μg / L.

[0033] Specifically, the metal replacement agent is selected from at least one of iron, zinc and aluminum.

[0034] The temperature during the multi-stage replacement reaction is 50-70°C, the time during the multi-stage replacement reaction is 0.5-1.5h, and the pH value during the multi-stage replacement reaction is 3-5. In step S1, the multi-stage replacement reaction includes a primary replacement reaction and a secondary replacement reaction. The amount of the metal replacement agent used in the primary replacement reaction is 5-8g / L (metal replacement agent g: thallium-containing liquid L), and the amount of the metal replacement agent used in the secondary replacement reaction is 0.5-0.8g / L.

[0035] In the present application, multi-stage replacement is achieved based on the difference in the order of metal activity. In the metal activity order table, the metal in the front can replace the metal ion in the back. Therefore, by selecting a metal with stronger activity than thallium as a replacement agent, it can be added to the thallium-containing liquid to undergo a replacement reaction with the thallium ions. As the replacement reaction proceeds, the thallium ions are gradually replaced and insoluble thallium-containing solids are generated and precipitated, and the removal rate and enrichment effect of thallium can be significantly improved by multi-stage replacement.

[0036] Therefore, multi-stage replacement can efficiently remove thallium ions in the solution, so that the thallium ion concentration in the thallium removal solution can be significantly reduced to below the emission standard or meet the requirements of subsequent treatment; the thallium-containing solid generated by multi-stage replacement has a high thallium content, which is convenient for subsequent treatment and recycling, thereby realizing the enrichment and reuse of thallium resources.

[0037] Specifically, the multi-stage replacement process includes: The pH value of the thallium-containing liquid is adjusted to an appropriate range (usually 3-5) using sodium hydroxide solution or potassium hydroxide solution, and then the first-stage replacement agent (such as iron powder, zinc powder, aluminum powder, etc.) is added. The amount of the replacement agent is determined according to the concentration of thallium in the liquid and the required replacement effect.

[0038] In the first stage replacement process, the replacement agent undergoes a replacement reaction with the thallium ions in the solution to generate thallium-containing solids and corresponding metal ions; the reaction is fully carried out by stirring, and after a period of time (usually 0.5-1.5 hours), solid-liquid separation is performed to obtain a first-stage thallium removal liquid and thallium-containing solids.

[0039] If the thallium ion concentration in the solution still does not meet the requirements after the first-stage replacement, the second or third stage replacement can be continued. In the subsequent replacement, the amount of replacement agent is usually reduced (such as the amount of replacement agent is 0.5-0.8g / L) to optimize the cost and maintain a high replacement efficiency; solid-liquid separation is performed after each stage of replacement until the thallium ion concentration in the solution is reduced to ≤5μg / L in the thallium-containing feed solution.

[0040] The solid separated from the solid-liquid separation is collected to obtain a thallium-containing solid.

[0041] In some embodiments, in step S2, the inorganic acid is selected from at least one of sulfuric acid, hydrochloric acid, and nitric acid, the concentration of the inorganic acid is 2-5 mol / L, and the liquid-to-solid ratio of the dissolution process is 2-5:1.

[0042] Specifically, in step S2, a thallium-containing solid is dissolved by using a strong inorganic acid to obtain a soluble thallium salt.

[0043] In some embodiments, in step S3, the oxidant is one or more of ferric chloride, hydrogen peroxide, chlorine dioxide, calcium hypochlorite, and liquid chlorine; sodium hydroxide or potassium hydroxide is used to adjust the pH of the system to 1-3.

[0044] Under the action of the oxidant, the thallium ions in the solution undergo an oxidation reaction and are oxidized from a low-valent state to a high-valent state. In this process, the chemical properties of the thallium ions change, so that they can combine with other ions to form precipitation. The high-valent thallium ions combine with the hydroxide ions or other anions in the solution to form insoluble thallium hydroxide precipitation. Through the oxidation precipitation process, the thallium ions in the solution can be effectively converted into insoluble thallium hydroxide precipitation and removed, thereby achieving the purpose of purifying the solution.

[0045] The following examples further illustrate a method for efficiently recovering thallium in a complex solution described in the present application; In the embodiment, the mass concentration of the sodium hydroxide solution is 30%; the mass concentration of the hydrogen peroxide is 30%. Example 1

[0046] The thallium-containing wastewater of a steel enterprise is shown in Table 1: Table 1 Composition of complex feed liquid containing thallium wastewater

[0047] As shown in Table 1, the thallium-containing solution after sintering dust treatment in steel plants has a complex composition and high content of valuable metals, but the thallium content reaches 147.90 mg / L, which is not conducive to the recovery of valuable metals. Therefore, thallium needs to be removed from the solution, and other impurity ions cannot be introduced to affect the recovery of valuable metals.

[0048] A method for efficiently recovering thallium in a complex solution comprises the following steps: Sodium hydroxide solution was used to adjust the pH of the thallium-containing wastewater to 3, and zinc powder was added to the thallium-containing wastewater for replacement. The addition amount was 5g / L, and the solution was heated to 50°C. After stirring for 0.5h, solid-liquid separation was performed to obtain a primary thallium removal solution and a thallium-containing solid. The content of each element in the primary replacement thallium removal solution is shown in Table 2.

[0049] Table 2 first-stage replacement thallium removal solution composition

[0050] As shown in Table 2, the thallium content in the solution still exceeds the standard, so zinc powder is added to the primary replacement thallium removal solution for secondary replacement, the addition amount is 0.5g / L, the solution temperature is heated to 50°C, stirred for 0.5h, and then solid-liquid separation is performed to obtain a secondary thallium removal solution and a thallium-containing solid. The content of each element in the secondary replacement thallium removal solution is shown in Table 3.

[0051] Table 3 Secondary displacement thallium removal solution composition

[0052] As shown in Table 3, the thallium content in the solution after multi-stage replacement is 0.001 mg / L, and the thallium content meets the emission requirements of GB31573-2015 "Inorganic Chemical Industry Pollutant Emission Standards".

[0053] The thallium-containing solid was dissolved using a 2 mol / L sulfuric acid solution, the liquid-to-solid ratio was controlled to be 2:1 during the dissolution process, and the solution was stirred at room temperature for 1 hour. After the dissolution was completed, a thallium-enriched solution was obtained. The composition of the thallium-enriched solution is shown in Table 4.

[0054] Table 4 Thallium enriched solution composition

[0055] Hydrogen peroxide and ferric chloride were added to the thallium-enriched solution, the amount of hydrogen peroxide added was 0.1% of the volume of the thallium-enriched solution, and the amount of ferric chloride added was 10 g / L (i.e., 10 g of ferric chloride was added to 1 L of thallium-enriched solution). After stirring at room temperature for 1 hour, the pH of the solution was adjusted to 1 using sodium hydroxide solution, and the thallium-removing solution and thallium hydroxide were obtained by filtration. The composition of the thallium-removing solution is shown in Table 5.

[0056] Table 5 Thallium removal solution composition

[0057] As shown in the table, the present invention can efficiently recover thallium in complex liquid, with a recovery rate of 98-99.9%. At the same time, liquid rich in zinc and copper can be obtained, and copper sulfate and zinc sulfate products can be obtained by extraction respectively. Example 2

[0058] The thallium-containing wastewater of a steel enterprise is shown in Table 6: Table 6 Composition of complex feed liquid containing thallium wastewater

[0059] A method for efficiently recovering thallium in a complex solution comprises the following steps: Sodium hydroxide solution was used to adjust the pH of the thallium-containing solution to 4, and zinc powder was added to the thallium-containing wastewater for replacement. The addition amount was 7 g / L, and the solution temperature was heated to 60°C. After stirring for 1 hour, solid-liquid separation was performed to obtain a primary replacement thallium removal solution and a thallium-containing solid. The content of each element in the primary replacement thallium removal solution is shown in Table 7.

[0060] Table 7 First-stage replacement thallium removal solution composition

[0061] Zinc powder was added to the primary thallium removal solution for secondary replacement, the addition amount was 0.7 g / L, the solution temperature was heated to 60°C, and after stirring for 1 hour, solid-liquid separation was performed to obtain a secondary thallium removal solution and thallium-containing solid. The content of each element in the secondary replacement thallium removal solution is shown in Table 8.

[0062] Table 8 Secondary replacement thallium removal solution composition

[0063] As shown in Table 8, the thallium content in the solution after multi-stage replacement is 0.003 mg / L, and the thallium content meets the emission requirements of GB31573-2015 "Inorganic Chemical Industry Pollutant Emission Standards".

[0064] The thallium-containing solid was dissolved using a 4 mol / L sulfuric acid solution, the liquid-to-solid ratio was controlled to be 4:1 during the dissolution process, and the solution was stirred at room temperature for 1.5 hours. After the dissolution was completed, a thallium-enriched solution was obtained. The composition of the thallium-enriched solution is shown in Table 9.

[0065] Table 9 Thallium enriched solution composition

[0066] Hydrogen peroxide and ferric chloride were added to the thallium-enriched solution, the amount of hydrogen peroxide added was 0.3% of the volume of the thallium-enriched solution, and the amount of ferric chloride added was 20 g / L (i.e., 20 g of ferric chloride was added to 1 L of thallium-enriched solution). After stirring at room temperature for 1.5 hours, the pH of the solution was adjusted to 2 using sodium hydroxide solution, and the thallium-removing solution and thallium hydroxide were obtained by filtration. The composition of the thallium-removing solution is shown in Table 10.

[0067] Table 10 Thallium removal solution composition

[0068] As shown in the table, the present invention can efficiently recover thallium in complex liquid, with a recovery rate of 98-99.9%. At the same time, liquid rich in zinc and copper can be obtained, and copper sulfate and zinc sulfate products can be obtained by extraction respectively. Example 3

[0069] The thallium-containing wastewater of a steel enterprise is shown in Table 11: Table 11 Composition of complex liquid wastewater containing thallium

[0070] A method for efficiently recovering thallium in a complex solution comprises the following steps: The pH of the thallium-containing solution was adjusted to 5 using sodium hydroxide solution, and zinc powder was added to the thallium-containing wastewater for replacement, with an addition amount of 8 g / L. The solution temperature was heated to 70°C, and after stirring for 1.5 hours, solid-liquid separation was performed to obtain a primary replacement thallium removal solution and a thallium-containing solid. The content of each element in the primary replacement thallium removal solution is shown in Table 12.

[0071] Table 12 First-stage replacement thallium removal solution composition

[0072] Zinc powder was added to the primary replacement thallium removal solution for secondary replacement, the addition amount was 0.8 g / L, the solution temperature was heated to 70°C, stirred for 1.5 hours, and then solid-liquid separation was performed to obtain a secondary thallium removal solution and a thallium-containing solid. The content of each element in the secondary thallium removal solution is shown in Table 13.

[0073] Table 13 Secondary displacement thallium removal solution composition

[0074] As shown in Table 13, the thallium content in the solution after multi-stage replacement is 0.001 mg / L, and the thallium content meets the emission requirements of GB31573-2015 "Inorganic Chemical Industry Pollutant Emission Standards".

[0075] The thallium-containing solid was dissolved using a 5 mol / L sulfuric acid solution, the liquid-to-solid ratio was controlled to be 5:1 during the dissolution process, and the solution was stirred at room temperature for 2 hours. After the dissolution was completed, a thallium-enriched solution was obtained. The composition of the thallium-enriched solution is shown in Table 14.

[0076] Table 14 Thallium enriched solution composition

[0077] Hydrogen peroxide and ferric chloride were added to the thallium-enriched solution, the amount of hydrogen peroxide added was 0.3% of the volume of the thallium-enriched solution, and the amount of ferric chloride added was 30 g / L (i.e., 30 g of ferric chloride was added to 1 L of thallium-enriched solution). After stirring at room temperature for 2 hours, the pH of the solution was adjusted to 3 using sodium hydroxide solution, and the thallium-removing solution and thallium hydroxide were obtained by filtration. The composition of the thallium-removing solution is shown in Table 15.

[0078] Table 15 Thallium removal solution composition

[0079] As shown in Table 15, the present invention can efficiently recover thallium in complex feed liquid, with a recovery rate of 98-99.9%. At the same time, feed liquid rich in zinc and copper can also be obtained, and copper sulfate and zinc sulfate products can be obtained by extraction respectively.

[0080] The thallium hydroxide obtained in Examples 1, 2 and 3 was tested, and the test results are summarized in Table 16 below.

[0081] Table 16

[0082] It can be found from Table 16 that the prepared thallium hydroxide has high purity and is convenient for commercial use.

[0083] The above embodiments are preferred implementation schemes of the present invention. In addition, the present invention may also be implemented in other ways. Any obvious replacement without departing from the concept of the present invention is within the protection scope of the present invention.

Claims

1. A method for efficiently recovering thallium in a complex solution, characterized in that: The following steps are involved: S1. Multi-level replacement A metal replacement agent is added to the thallium-containing liquid to carry out a multi-stage replacement reaction, wherein the pH value during the multi-stage replacement reaction is 3-5; after the reaction is completed, separation is carried out to obtain a thallium-removing liquid and a thallium-containing solid; S2. Dissolution dissolving the thallium-containing solid using an inorganic acid to form a thallium-containing solution; S3. Oxidation precipitation An oxidant is added to a solution containing thallium, and after the oxidation is completed, the pH value of the solution is adjusted to 1-3 to generate a precipitate, which is separated to obtain thallium hydroxide solid; In step S1, the multi-stage replacement reaction is to use a metal replacement agent to carry out a replacement reaction on the thallium-containing liquid at least once; after the multi-stage replacement reaction is completed, the liquid after the reaction is collected and separated to obtain a thallium-removing liquid and a thallium-containing solid; The multi-stage replacement reaction takes the thallium ion concentration in the thallium-containing liquid as the reaction end point ≤ 5 μg / L.

2. The method according to claim 1, characterized in that In step S1, the metal replacement agent is selected from at least one of iron, zinc and aluminum.

3. The method according to claim 1, characterized in that: In step S1, the temperature during the replacement reaction is 50-70°C, and the time during the replacement reaction is 0.5-1.5h.

4. The method according to claim 1, characterized in that: In step S1, the multi-stage replacement reaction includes a primary replacement reaction, and the amount of the metal replacement agent used in the primary replacement reaction is 5-8 g / L.

5. The method according to claim 4, characterized in that In step S1, the multi-stage replacement reaction also includes a secondary replacement reaction, and the amount of the metal replacement agent used in the secondary replacement reaction is 0.5-0.8 g / L.

6. The method according to claim 1, characterized in that In step S2, the inorganic acid is selected from at least one of sulfuric acid, hydrochloric acid and nitric acid, and the concentration of the inorganic acid is 2-5 mol / L.

7. The method according to claim 1, characterized in that In step S2, the liquid-to-solid ratio during the dissolution process is 2-5:

1.

8. The method according to claim 1, characterized in that In step S3, the oxidant is one or more of ferric chloride, hydrogen peroxide, chlorine dioxide, calcium hypochlorite, and liquid chlorine.

9. The method according to claim 1, characterized in that: In step S3, sodium hydroxide or potassium hydroxide is used to adjust the pH of the system to 1-3.

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