A method for efficiently recovering thallium in a complex solution

Abstract

The present invention relates to the technical field of thallium recovery and treatment, and particularly to a method for efficiently recovering thallium from complex solutions. The present application discloses a method for efficiently recovering thallium from complex solutions, comprising the following steps: S1. Multi-stage replacement; adding a metal replacement agent to the thallium-containing feed liquid for multi-stage replacement reaction, with the pH value during the multi-stage replacement reaction being 3-5; after the reaction is completed, separation is carried out to obtain a thallium-removed feed liquid and a thallium-containing solid; S2. Dissolution; using an inorganic acid to dissolve the thallium-containing solid to form a thallium-containing solution; S3. Oxidation precipitation; adding an oxidizing agent to the thallium-containing solution, after the oxidation is completed, adjusting the pH value of the solution to 1-3 to generate a precipitate, and carrying out separation to obtain thallium hydroxide solid. The method described in the present application has a wide range of applications, can be used to treat thallium-containing wastewater with various concentrations, has a simple process and is easy to implement. At the same time, thallium and other valuable metals can be recovered and utilized, realizing the efficient recovery and utilization of resources.

Description

Technical Field

[0001] The present invention relates to the technical field of thallium recovery and treatment, and particularly to a method for efficiently recovering thallium from complex solutions. Background Art

[0002] Thallium (Tl) is a highly toxic metal element widely present in sulfide ores of metals such as lead, zinc, iron, and copper. 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 not only spreads through water bodies and soil but also enters crops through irrigation water sources and ultimately enters the human body through the food chain. Long-term accumulation may trigger various diseases such as esophageal cancer and liver cancer, seriously endangering human health.

[0003] Currently, the treatment technologies for thallium-containing wastewater mainly include sulfide precipitation method, adsorption method, electrochemistry method, and comprehensive treatment method, etc. These methods can control the thallium content in wastewater to a certain extent, but there are obvious limitations and deficiencies when dealing with complex thallium-containing feed solutions.

[0004] 1. Sulfide precipitation method: By adding sulfides such as sodium sulfide, thallium ions form insoluble thallium sulfide precipitates and are removed. Although this method has a good treatment effect on high-concentration thallium-containing wastewater, it is difficult to meet the standards when treating low-concentration thallium-containing feed solutions, and a large amount of sodium sulfide is required, which is prone to generating harmful gases such as hydrogen sulfide (H 2 S), causing secondary pollution.

[0005] 2. Adsorption method: Utilize the adsorption ability of specific materials for thallium ions to remove them from wastewater. In recent years, some composite adsorption materials formed by assembling low-carbon alcohol-modified organic salts and natural minerals have shown good adsorption effects, but their application scope is limited, and the regeneration process is complex, 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. Electrochemistry method: Remove thallium ions from wastewater through electrochemical reactions. Its advantage is high treatment efficiency, but it is easy to introduce a large number of impurity ions such as Fe 3+ or Al 3+ into the solution system, which needs to be removed additionally, increasing the treatment cost and complexity. In addition, the investment in electrochemical equipment is large, and the operation and maintenance costs are high.

[0007] 4. Comprehensive treatment method: Combine multiple treatment means, such as neutralization, sulfide precipitation, oxidation treatment, flocculation sedimentation, and physical adsorption, etc., to carry out collaborative treatment of wastewater. Although this method can achieve a high thallium removal rate, the process is complex, the operation difficulty is large, and the cost is high. In addition, due to the dispersed presence of thallium during the treatment process, it is difficult to carry out effective recovery and resource utilization.

[0008] Therefore, the present application provides a method for efficiently recovering thallium in a complex solution, which is efficient, economical, environmentally friendly and easy to industrialize, and can efficiently recover thallium in a complex solution. Summary of the Invention

[0009] In order to overcome the deficiencies 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 through multi-stage displacement, and then the thallium is recovered by the methods of inorganic acid dissolution and oxidation precipitation. This method has a wide range of applications, can be used to treat thallium-containing wastewater with various concentrations, has a simple process and is easy to implement. At the same time, thallium and other valuable metals can be recovered and utilized, realizing the efficient recovery and utilization of resources, and making up for the problems of the prior art such as unqualified thallium removal, complex process, high cost and resource waste. It is an optimal method for efficiently recovering thallium from complex thallium-containing solutions.

[0010] The technical solution adopted by the present application to solve its technical problems is as follows:

[0011] A method for efficiently recovering thallium in a complex solution, comprising the following steps:

[0012] S1. Multi-stage displacement

[0013] Add a metal displacement agent to the thallium-containing feed liquid to carry out a multi-stage displacement reaction. The pH value during the multi-stage displacement reaction is 3-5; after the reaction ends, separate to obtain a thallium-removed feed liquid and a thallium-containing solid;

[0014] S2. Dissolution

[0015] Use inorganic acid to dissolve the thallium-containing solid to form a thallium-containing solution;

[0016] S3. Oxidation precipitation

[0017] Add an oxidant to the thallium-containing solution. After the oxidation ends, adjust the pH value of the solution to 1-3 to generate a precipitate, and then separate to obtain thallium hydroxide solid;

[0018] In step S1, the multi-stage displacement reaction is to carry out a displacement reaction on the thallium-containing feed liquid with a metal displacement agent at least once; after the multi-stage displacement reaction ends, collect the reacted feed liquid and separate to obtain a thallium-removed feed liquid and a thallium-containing solid;

[0019] The multi-stage displacement reaction ends when the thallium ion concentration in the thallium-containing feed liquid ≤ 5 μg / L.

[0020] In some embodiments, in step S1, the metal displacement agent is selected from at least one of iron, zinc, and aluminum.

[0021] In some embodiments, in step S1, the temperature during the displacement reaction is 50-70 °C, and the time of the displacement reaction is 0.5-1.5 h.

[0022] In some embodiments, in step S1, the multi-stage displacement reaction includes a primary displacement reaction, and the dosage of the metal displacement agent in the primary displacement reaction is 5-8 g / L.

[0023] In some embodiments, in step S1, the multi-stage displacement reaction further includes a secondary displacement reaction, and the dosage of the metal displacement agent in the secondary displacement reaction is 0.5-0.8 g / L.

[0024] 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.

[0025] In some embodiments, in step S2, the liquid-solid ratio during the dissolution process is 2-5:1.

[0026] In some embodiments, in step S3, the oxidant is one or more of ferric chloride, hydrogen peroxide, chlorine dioxide, calcium hypochlorite, and liquid chlorine.

[0027] In some embodiments, in step S3, sodium hydroxide or potassium hydroxide is used to adjust the pH of the system to 1-3.

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

[0029] 1. In the method described in the present application, thallium is subjected to multi-stage displacement using a metal (such as iron powder, zinc powder, zinc wire, aluminum powder, aluminum foil) with a higher activity order than thallium to obtain a thallium-removed liquid and a thallium-containing solid; the thallium-containing solid is dissolved using an inorganic acid to obtain a thallium-enriched liquid; an oxidant and pH are adjusted in the thallium-enriched liquid to obtain thallium hydroxide; realizing the efficient recovery of thallium, and the recovery rate can reach 98-99.9%.

[0030] 2. The method described in the present application has a simple process flow, is easy to realize industrial production, and has a low operation cost, which helps to improve the treatment efficiency and reduce the production cost.

[0031] 3. The method described in the present application does not produce secondary pollution, and the by-products during the recovery process can also be subjected to subsequent treatment or resource utilization, reducing environmental pollution.

[0032] 4. The method described in the present application has a wide range of applications and can treat thallium-containing wastewater with various concentrations. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will be further described below in conjunction with the drawings and embodiments.

[0034] Figure 1 It is the process flow diagram of a method for efficiently recovering thallium in a complex solution described in the present application. Detailed implementation manners

[0035] For the convenience of those skilled in the art to understand, the present invention will be further described below in conjunction with embodiments. The content mentioned in the implementation manners does not limit the present invention.

[0036] As used herein, the term "and / or" includes all combinations of any one or more of the associated listed items. The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. As used herein, the singular forms "a", "an", "one" and "the" are also intended to include the plural forms unless the context clearly indicates otherwise. Further understanding, when "including" is used in this specification, it specifies the stated features, integers, steps, operations, elements and / or components, but does not exclude the existence or addition of one or more other features, integers, steps, operations, elements, components and / or their combinations.

[0037] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs. Further understanding, terms, such as defined in a common dictionary, are interpreted in accordance with their meanings in the context of the relevant field and are not in an idealized or overly formal sense unless clearly defined as such herein.

[0038] The exemplary inventions described herein may appropriately lack any one or more of the element limitations not specifically disclosed herein. Therefore, terms such as "comprising", "including", "containing", etc. should be understood broadly and non-restrictively. In addition, the terms of expression used herein are used for description without limitation, and it is not intended to use these terms of expression that do not include any equivalent features, but only to describe a part of their features. However, according to the rights, various modifications are possible within the scope of the present invention. Therefore, although the present invention has been specifically disclosed through preferred embodiments and optional features, the modifications to the present invention embodied herein may be recorded by those skilled in the art, and such modifications and variations are considered to be within the scope of the present invention.

[0039] Term explanation:

[0040] Multi-stage replacement, a method of gradually using a more active metal to replace another metal ion in a solution. In this application, this method is used to replace thallium ions from a complex solution.

[0041] Solid-liquid separation, a physical process used to separate solids and liquids. In this application, this process is used to separate the thallium-containing solid generated after the replacement reaction from the solution.

[0042] Liquid-solid ratio, during the dissolution process, is the ratio of the volume of liquid to the mass of solid. In this application, this ratio is used to control the reaction conditions in the sulfuric acid dissolution step.

[0043] Aiming at the problems of the current conventional thallium removal technology, such as complex operation, low removal rate, high cost, especially the poor treatment effect for complex feed solutions, this application provides Figure 1 As shown, a method for efficiently recovering thallium from a complex solution, comprising the following steps:

[0044] S1. Multi-stage replacement

[0045] Add a metal replacement agent to the thallium-containing feed solution for multi-stage replacement reaction. The pH value during the multi-stage replacement reaction is 3-5; after the reaction ends, separation is carried out to obtain a thallium-removed feed solution and thallium-containing solid.

[0046] S2. Dissolution

[0047] Use inorganic acid to dissolve the thallium-containing solid to form a thallium-containing solution.

[0048] S3. Oxidation precipitation

[0049] Add an oxidant to the thallium-containing solution. After the oxidation ends, adjust the pH value of the solution to 1-3 to generate a precipitate, and then carry out separation to obtain thallium hydroxide solid.

[0050] In step S1, the multi-stage replacement reaction is to carry out at least one replacement reaction on the thallium-containing feed solution with a metal replacement agent; after the multi-stage replacement reaction ends, collect the reacted feed solution and carry out separation to obtain a thallium-removed feed solution and thallium-containing solid.

[0051] The multi-stage replacement reaction ends when the thallium ion concentration in the thallium-containing feed solution is ≤5 μg / L.

[0052] Specifically, the metal replacement agent is selected from at least one of iron, zinc, and aluminum.

[0053] The temperature during the multi-stage replacement reaction is 50-70 °C, the time during the multi-stage replacement reaction is 0.5-1.5 h, 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 dosage of the metal replacement agent during the primary replacement reaction is 5-8 g / L (metal replacement agent g: thallium-containing feed solution L), and the dosage of the metal replacement agent during the secondary replacement reaction is 0.5-0.8 g / L.

[0054] In this application, multi-stage replacement is achieved based on the difference in the metal activity series. In the metal activity series table, the metal located in front can displace the metal ions located behind it. Therefore, by selecting a metal with stronger activity than thallium as the replacement agent, it can be added to the thallium-containing feed liquid to undergo a replacement reaction with thallium ions. As the replacement reaction proceeds, thallium ions are gradually displaced and form insoluble thallium-containing solid precipitates. Through multi-stage replacement, the removal rate and enrichment effect of thallium can be significantly improved.

[0055] Therefore, through multi-stage replacement, thallium ions in the solution can be efficiently removed, significantly reducing the thallium ion concentration in the thallium-removing feed liquid to below the discharge standard or meeting the requirements of subsequent treatment; the thallium content in the thallium-containing solid generated through multi-stage replacement is relatively high, facilitating subsequent treatment and recycling, and realizing the enrichment and reuse of thallium resources.

[0056] Specifically, the process of multi-stage replacement includes:

[0057] Use sodium hydroxide solution or potassium hydroxide solution to adjust the pH value of the thallium-containing feed liquid to an appropriate range (usually 3 - 5), and then add the first-stage replacement agent (such as iron powder, zinc powder, aluminum powder, etc.). The dosage of the replacement agent is determined according to the thallium concentration in the feed liquid and the required replacement effect.

[0058] In the first-stage replacement process, the replacement agent reacts with thallium ions in the solution to form thallium-containing solid and corresponding metal ions; through stirring, the reaction proceeds fully. After a period of time (usually 0.5 - 1.5 hours), solid-liquid separation is carried out to obtain the first-stage thallium-removing feed liquid and thallium-containing solid.

[0059] If the thallium ion concentration in the solution after the first-stage replacement still does not meet the requirements, secondary or tertiary replacement can be continued. In subsequent replacements, usually reduce the dosage of the replacement agent (such as the replacement agent dosage is 0.5 - 0.8 g / L) to optimize the cost and maintain a high replacement efficiency; solid-liquid separation is carried out after each stage of replacement until the thallium ion concentration in the solution drops to ≤5 μg / L of the thallium ion concentration in the thallium-containing feed liquid.

[0060] Collect the solid separated by solid-liquid separation to obtain thallium-containing solid.

[0061] 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-solid ratio during the dissolution process is 2 - 5:1.

[0062] Specifically, in step S2, use inorganic strong acid to dissolve the thallium-containing solid to obtain soluble thallium salt.

[0063] 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.

[0064] Under the action of the oxidant, the thallium ions in the solution undergo an oxidation reaction and are oxidized from a low valence state to a high valence state. During this process, the chemical properties of the thallium ions change, enabling them to combine with other ions to form precipitates. The high-valence thallium ions combine with hydroxide ions or other anions in the solution to form insoluble thallium hydroxide precipitates. Through the oxidation precipitation process, the thallium ions in the solution can be effectively converted into insoluble thallium hydroxide precipitates and removed, thereby achieving the purpose of purifying the solution.

[0065] Through the following embodiments, a method for efficiently recovering thallium in a complex solution described in the present application is further elaborated;

[0066] In the embodiments, the mass concentration of the sodium hydroxide solution is 30%; the mass concentration of the hydrogen peroxide is 30%. Example 1

[0067] The thallium-containing wastewater of a certain iron and steel enterprise is shown in Table 1 below:

[0068] Table 1 Composition of thallium-containing wastewater in complex feed liquid

[0069]

[0070] As shown in Table 1, the composition of the thallium-containing solution after treating sintering dust removal ash in the steel plant is complex, with a 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, it is necessary to remove thallium from the solution without introducing other impurity ions that may affect the recovery of valuable metals.

[0071] A method for efficiently recovering thallium in a complex solution includes the following steps:

[0072] Use a sodium hydroxide solution to adjust the pH of the thallium-containing wastewater to 3. Add zinc powder to the thallium-containing wastewater for displacement, with an addition amount of 5 g / L. Heat the solution to 50 °C, stir for 0.5 h, and then perform solid-liquid separation to obtain a primary thallium-removing solution and thallium-containing solid. The element contents of the primary displacement thallium-removing solution are shown in Table 2.

[0073] Table 2 Composition of the primary displacement thallium-removing solution

[0074]

[0075] As shown in Table 2, the thallium content in the solution still exceeds the standard. Therefore, zinc powder is added to the solution for primary thallium replacement for secondary replacement, and the addition amount is 0.5 g / L. The solution temperature is heated to 50 °C, and after stirring for 0.5 h, solid-liquid separation is carried out to obtain a secondary thallium removal solution and a thallium-containing solid. The elemental contents of the secondary thallium removal solution are shown in Table 3.

[0076] Table 3 Composition of the secondary thallium removal solution

[0077]

[0078] As shown in Table 3, after multi-stage replacement, the thallium content in the solution is 0.001 mg / L, and the thallium content meets the discharge requirements of GB31573-2015 "Discharge Standard of Pollutants for Inorganic Chemical Industry".

[0079] The thallium-containing solid is dissolved with a 2 mol / L sulfuric acid solution. During the dissolution process, the liquid-solid ratio is controlled at 2:1, and it is stirred at room temperature for 1 h. After dissolution, a thallium-enriched solution is obtained. The composition of the thallium-enriched solution is shown in Table 4.

[0080] Table 4 Composition of the thallium-enriched solution

[0081]

[0082] Hydrogen peroxide and ferric chloride are added to the thallium-enriched solution. The addition amount of hydrogen peroxide is 0.1% of the volume of the thallium-enriched solution, and the addition amount of ferric chloride is 10 g / L (i.e., 10 g of ferric chloride is added to 1 L of the thallium-enriched solution). After stirring at room temperature for 1 h, the pH of the solution is adjusted to 1 with sodium hydroxide solution, and then filtered to obtain a thallium removal solution and thallium hydroxide. The composition of the thallium removal solution is shown in Table 5.

[0083] Table 5 Composition of the thallium removal solution

[0084]

[0085] As can be seen from the data in the table, the present invention can efficiently recover thallium from complex feed liquid, and the recovery rate can reach 98-99.9%. At the same time, a feed liquid rich in zinc and copper can also be obtained, and copper sulfate and zinc sulfate products can be obtained through extraction respectively. Example 2

[0086] The thallium-containing wastewater of a steel enterprise is as shown in Table 6 below:

[0087] Table 6 Composition of the thallium-containing wastewater of the complex feed liquid

[0088]

[0089] A method for efficiently recovering thallium from a complex solution, comprising the following steps:

[0090] Adjust the pH of the thallium-containing solution to 4 with sodium hydroxide solution, add zinc powder to the thallium-containing wastewater for replacement, with the addition amount being 7 g / L. Heat the solution temperature to 60 °C, stir for 1 h, and then perform solid-liquid separation to obtain the first-stage thallium-removing solution and thallium-containing solid. The element contents of the first-stage thallium-removing solution are shown in Table 7.

[0091] Table 7 Composition of the first-stage thallium-removing solution

[0092]

[0093] Add zinc powder to the first-stage thallium-removing solution for secondary replacement, with the addition amount being 0.7 g / L. Heat the solution temperature to 60 °C, stir for 1 h, and then perform solid-liquid separation to obtain the secondary thallium-removing solution and thallium-containing solid. The element contents of the secondary thallium-removing solution are shown in Table 8.

[0094] Table 8 Composition of the secondary thallium-removing solution

[0095]

[0096] As shown in Table 8, the thallium content in the solution after multiple replacements is 0.003 mg / L, and the thallium content meets the discharge requirements of the "Discharge Standard of Pollutants for Inorganic Chemical Industry" GB31573-2015.

[0097] Dissolve the thallium-containing solid with 4 mol / L sulfuric acid solution, control the liquid-solid ratio at 4:1 during the dissolution process, stir at room temperature for 1.5 h, and obtain the thallium-enriched solution after dissolution. The component composition of the thallium-enriched solution is shown in Table 9.

[0098] Table 9 Composition of the thallium-enriched solution

[0099]

[0100] Add hydrogen peroxide and ferric chloride to the thallium-enriched solution. The addition amount of hydrogen peroxide is 0.3% of the volume of the thallium-enriched solution, and the addition amount of ferric chloride is 20 g / L (i.e., add 20 g of ferric chloride to 1 L of the thallium-enriched solution). After stirring at room temperature for 1.5 h, adjust the pH of the solution to 2 with sodium hydroxide solution, and filter to obtain the thallium-removing solution and thallium hydroxide. The composition of the thallium-removing solution is shown in Table 10.

[0101] Table 10 Composition of the thallium-removing solution

[0102]

[0103] As can be seen from the data in the table, the present invention can efficiently recover thallium from complex feed solutions, and the recovery rate can reach 98 - 99.9%. At the same time, feed solutions rich in zinc and copper can also be obtained, and copper sulfate and zinc sulfate products can be obtained through extraction respectively. Example 3

[0104] The thallium-containing wastewater of a certain iron and steel enterprise is shown in Table 11 below:

[0105] Table 11 Composition of Thallium-Containing Wastewater in Complex Feed Liquid

[0106]

[0107] A method for efficiently recovering thallium from a complex solution, comprising the following steps:

[0108] Adjust the pH of the thallium-containing solution to 5 with sodium hydroxide solution, add zinc powder to the thallium-containing wastewater for displacement, with an addition amount of 8 g / L, heat the solution temperature to 70 °C, stir for 1.5 h, and then perform solid-liquid separation to obtain a first-stage displacement thallium-removing solution and thallium-containing solid. The element contents of the first-stage displacement thallium-removing solution are shown in Table 12.

[0109] Table 12 Composition of the First-Stage Displacement Thallium-removing Solution

[0110]

[0111] Add zinc powder to the first-stage displacement thallium-removing solution for secondary displacement, with an addition amount of 0.8 g / L, heat the solution temperature to 70 °C, stir for 1.5 h, and then perform solid-liquid separation to obtain a secondary thallium-removing solution and thallium-containing solid. The element contents of the secondary thallium-removing solution are shown in Table 13.

[0112] Table 13 Composition of the Secondary Displacement Thallium-removing Solution

[0113]

[0114] As shown in Table 13, the thallium content in the solution after multi-stage displacement is 0.001 mg / L, and the thallium content meets the discharge requirements of GB31573-2015 "Discharge Standards for Pollutants from Inorganic Chemical Industry".

[0115] Dissolve the thallium-containing solid with 5 mol / L sulfuric acid solution, control the liquid-solid ratio at 5:1 during the dissolution process, stir at room temperature for 2 h, and obtain a thallium-enriched solution after dissolution. The composition of the thallium-enriched solution is shown in Table 14.

[0116] Table 14 Composition of the Thallium-enriched Solution

[0117]

[0118] Add hydrogen peroxide and ferric chloride to the thallium-enriched solution. The addition amount of hydrogen peroxide is 0.3% of the volume of the thallium-enriched solution, and the addition amount of ferric chloride is 30 g / L (i.e., add 30 g of ferric chloride to 1 L of the thallium-enriched solution). After stirring at room temperature for 2 h, adjust the pH of the solution to 3 with sodium hydroxide solution, and filter to obtain a thallium-removing solution and thallium hydroxide. The composition of the thallium-removing solution is shown in Table 15.

[0119] Table 15 Composition of the Thallium-removing Solution

[0120]

[0121] As can be seen from the data in Table 15, the present invention can efficiently recover thallium from complex feed liquid, and the recovery rate can reach 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 through extraction respectively.

[0122] The thallium hydroxide obtained in Examples 1, 2, and 3 was detected, and the detection results are summarized in Table 16 below.

[0123] Table 16

[0124]

[0125] It can be found from Table 16 that the prepared thallium hydroxide has high purity and is convenient for commercial use.

[0126] The above embodiments are preferred implementation schemes of the present invention. In addition, the present invention can also be implemented in other ways. Any obvious substitution 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 thallium-containing solution, 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; In step S1, the metal replacement agent is selected from at least one of iron, zinc and aluminum; In step S2, the inorganic acid is selected from at least one of sulfuric acid, hydrochloric acid and nitric acid; In step S3, the oxidant is one or more of ferric chloride, hydrogen peroxide, chlorine dioxide, calcium hypochlorite, and liquid chlorine.

2. 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.

3. 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.

4. The method according to claim 3, 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.

5. The method according to claim 1, characterized in that In step S2, the concentration of the inorganic acid is 2-5 mol / L.

6. 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.

7. 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.

Images