A method for high-concentration thallium solvent extraction in the lithium salt extraction industry

Abstract

This application discloses a high-concentration thallium solvent extraction method for the lithium salt extraction industry, belonging to the field of hydrometallurgical technology. The method provided by this application includes the following steps: Step S1: Adding a pH adjuster to the thallium waste liquid to adjust the pH, then adding an oxidant, and stirring to react and obtain a mixed solution; the pH adjuster is HCl; Step S2: Adding an extractant and a diluent to the mixed solution, stirring to extract and separate, obtaining a thallium-containing organic phase and a first raffinate; the extractant includes N503 extractant and tributyl phosphate; Step S3: Washing the thallium-containing organic phase with hydrochloric acid solution, then adding ammonium acetate solution for back-extraction and separation, obtaining a back-extraction solution and a second raffinate. The method of this application has good selectivity, high extraction rate, low environmental pollution, low cost, and the extractant can be reused.

Description

Technical Field

[0001] This application belongs to the field of hydrometallurgical technology, specifically relating to a high-concentration thallium solvent extraction method for the lithium salt extraction industry. Background Technology

[0002] Thallium is a highly toxic heavy metal trace element. Due to its unique physical and chemical properties, it is widely used in aerospace, defense, electronic communications, chemical engineering, and metallurgy. In nature, thallium mainly exists as Tl. + and Tl 3+ Thallium exists in various forms and is more toxic than lead, mercury, and cadmium. Its content is scarce and highly dispersed; the concentration of thallium in continental and marine crust and rocks is generally below 1 μg / g. Thallium is typically enriched in various sulfide minerals, such as pyrite (5–23 ppm), sphalerite (8–45 ppm), lead-zinc ore (5–23 ppm), and some other minerals. During mineral resource extraction, thallium, as a by-product, is easily leached into wastewater. Through the food chain, it accumulates and can seriously harm liver and kidney function, causing symptoms of poisoning such as hair loss. Therefore, to ensure ecological safety and human health, the concentration of thallium in industrial wastewater must be strictly controlled to ensure it meets relevant national or local environmental protection standards.

[0003] Currently, the main methods for removing thallium from solution include redox methods, adsorption methods, solvent extraction methods, and ion exchange methods, each with its own advantages and limitations. Among these, solvent extraction offers advantages such as ease of operation, speed, high selectivity, flexible selection of extraction systems, and ease of mechanization and automation. However, existing technologies for thallium extraction still face several problems: on the one hand, some organic solvents are highly volatile and toxic, polluting the environment and potentially harming the health of operators; on the other hand, while some green extractants, such as polyethylene glycol, have lower toxicity, they can increase the viscosity of the extraction system, affecting the extraction rate. Furthermore, most existing extraction systems are costly, and the extractants are difficult to recycle and reuse, limiting their large-scale industrial application.

[0004] Therefore, there is an urgent need to develop a thallium extraction method that can achieve high selectivity and high extraction rate, while also being environmentally friendly, low-cost, and having reusable extractant. Summary of the Invention

[0005] In view of this, this application provides a high-concentration thallium solvent extraction method for the lithium salt extraction industry, which has good selectivity, high extraction rate, low environmental pollution, low cost, and reusable extractant.

[0006] In a first aspect, this application provides a method for high-concentration thallium solvent extraction in the lithium salt extraction industry, comprising the following steps:

[0007] Step S1: Add a pH adjuster to the thallium waste liquid to adjust the pH, then add an oxidant, stir to carry out the reaction, and obtain a mixed solution; the pH adjuster is HCl;

[0008] Step S2: Add extractant and diluent to the mixed solution, stir to extract, separate, and obtain thallium-containing organic phase and first raffinate; the extractant includes N503 extractant and tributyl phosphate;

[0009] Step S3: Wash the thallium-containing organic phase with hydrochloric acid solution, then add ammonium acetate solution for back-extraction and separation to obtain back-extraction solution and second raffinate.

[0010] By adopting the above technical solution, the thallium solvent extraction method provided in this application has the advantages of simple operation, high selectivity, high extraction rate, low environmental pollution, low cost, and reusable extractant. It not only solves the problem of volatile organic solvent pollution in traditional extraction methods but also improves the overall economic efficiency of the process, making it suitable for applications involving high-concentration thallium wastewater in the lithium salt extraction industry.

[0011] This application uses HCl as a pH adjuster, which can adjust the solution pH and provide Cl. - Ions, and Tl 3+ Complexation forms [TICl4] - This makes it more conducive to extraction. Step S1 involves adding HCl to the thallium waste liquid to adjust the pH and adding an oxidant, such as Tl. + Oxidized to Tl 3+ It then forms a stable [TICl4] under acidic conditions. - The complexed anions ensured effective capture of thallium during subsequent extraction. Step S2 involves [TICl4] - Adding N503 extractant and tributyl phosphate (TBP) to the mixed solution, the combined effect of both improves the extraction efficiency of [TICl4]. - The selective transfer of thallium from the aqueous phase to the organic phase is achieved, which also reduces the viscosity of the system and enhances the organic phase's ability to react with [TICl4]. - The solubility of N503 extractant improves overall extraction efficiency and enhances the stratification effect. Furthermore, the high selectivity of N503 extractant and tributyl phosphate effectively avoids interference from other coexisting metals such as lithium, rubidium, and cesium, achieving efficient enrichment of thallium and recovery of valuable metals. Step S3 further purifies the thallium-containing organic phase and recovers thallium; ammonium acetate effectively breaks down the interaction between the extractant and [TICl4]. - The combination of these components allows thallium to re-enter the aqueous phase, resulting in a thallium-rich back-extraction solution. Simultaneously, the regenerated organic phase can be recycled, reducing costs.

[0012] This application provides a high-concentration thallium solvent extraction method for the lithium salt extraction industry, which has a high extraction rate and a high thallium back-extraction rate under acidic conditions.

[0013] Optionally, in step S1, the thallium concentration in the thallium waste liquid is 1 mg / L to 10 mg / L.

[0014] By adopting the above technical solution, the thallium waste liquid with a specific thallium concentration in this application can fully utilize the N503 extractant for [TICl4]. - The high selectivity and synergistic effect of TBP significantly improve the extraction efficiency and separation selectivity of thallium.

[0015] Optionally, in step S1, the pH is adjusted to 1-2.

[0016] By adopting the above technical solution, the pH conditions of this application can effectively promote Tl. + To Tl 3+ The oxidation transformation of Tl promotes the oxidation transformation of Tl. 3+ With Cl - Combined to generate stable [TICl4] - The complexation of anions provides a better reaction basis for subsequent extraction. Simultaneously, this pH range also enhances the reaction of the N503 extractant with [TICl4]. - Its selective recognition ability inhibits Li + 、Rb + Cs + Co-extraction with valuable metal ions enabled the efficient enrichment and selective separation of thallium.

[0017] Optionally, in step S1, the oxidant is NaClO; the amount of the oxidant is 0.5 g / L to 5 g / L.

[0018] By adopting the above technical solution, this application uses sodium hypochlorite as an oxidant, which has a high redox potential and can reduce Tl + Fully oxidized to Tl 3+ And the generated Cl - It can also be used with Tl 3+ Complexation. The amount of oxidant used in this application not only ensures Tl + Thorough oxidation can also avoid side reactions caused by excessive use, reduce interference with subsequent extraction and separation operations, and further improve the overall removal rate and resource recovery rate of thallium.

[0019] Optionally, in step S1, a chloride salt is added along with the oxidant; the chloride salt is selected from at least one of sodium chloride, potassium chloride, and lithium chloride.

[0020] By adopting the above technical solution, this application also adds chloride salts to provide sufficient Cl... - Promote Tl 3+ It forms a stable [TICl4] - Complexing anions creates more favorable chemical conditions for subsequent extraction processes, thereby improving extraction efficiency.

[0021] Optionally, in step S1, the stirring speed is 300 r / min to 400 r / min, the stirring time is 20 min to 40 min, and the reaction temperature is 20℃ to 30℃.

[0022] By adopting the above technical solution, the reaction parameters in step S1 of this application can ensure Tl + Efficiently and completely oxidized to Tl 3+ and promote its interaction with Cl - They combine to form a stable [TICl4] - Complexing anions prepares the reactants for subsequent extraction. The stirring speed in this application ensures uniform dispersion, enhances contact efficiency between reactants, and accelerates the oxidation reaction rate. The stirring time ensures the reaction proceeds fully, preventing partial Tl degradation due to incomplete reaction. + Residues can affect the efficiency of subsequent extraction.

[0023] Optionally, in step S2, the extractant accounts for 10% to 50% of the mass concentration of the extraction solution composed of the extractant and diluent; the mass ratio of N503 extractant to tributyl phosphate is 1:1 to 5.

[0024] By adopting the above technical solution, the mass concentration of the extractant in this application ensures sufficient content of active components to achieve efficient thallium enrichment, while avoiding increased costs and operational difficulties caused by excessively high concentrations. The mass ratio of N503 extractant to tributyl phosphate can ensure a high extraction rate while avoiding problems such as excessive viscosity and slow mass transfer caused by an excessively high N503 ratio, or a decrease in extraction capacity caused by an excessively high TBP ratio.

[0025] Optionally, in step S2, the diluent includes at least one of diethylbenzene, xylene, and n-octanol.

[0026] By adopting the above technical solution, the diluent of this application has good solubility and chemical stability, and can effectively dissolve extraction components such as N503 and TBP, while maintaining good physical separation performance between the two phases, which helps to improve the efficiency and stability of the entire extraction process. In addition, these diluents have low toxicity, moderate volatility, low price, and are easy to recycle and reuse.

[0027] Optionally, in step S2, the mass ratio of the extraction solution composed of the extractant and the diluent to the mixed solution is 1:(1~10), the stirring speed is 300r / min~400r / min, and the stirring time is 3min~30min.

[0028] By adopting the above technical solution, the parameter selection in step S2 of this application can optimize the mass transfer efficiency between the two phases, achieving efficient extraction of thallium. The mass ratio of the extraction solution to the aqueous phase can effectively balance extraction efficiency and economy, making [TICl4]... - The thallium is fully transferred to the organic phase, improving the extraction rate. The stirring speed and stirring time in this application ensure that the reaction proceeds fully, preventing incomplete extraction due to too short a time or side reactions caused by too long a time, thus further improving the extraction efficiency and selectivity of thallium.

[0029] Optionally, in step S3, the concentration of the hydrochloric acid solution is 0.1 mol / L to 1 mol / L, and the mass ratio of the hydrochloric acid solution to the thallium-containing organic phase is (1~10):1;

[0030] The concentration of the ammonium acetate solution is 1 mol / L to 5 mol / L, and the mass ratio of the ammonium acetate solution to the thallium-containing organic phase is (1 to 10): 1.

[0031] By adopting the above technical solution, this application uses hydrochloric acid solution washing, which can effectively remove residual metal ions and other impurities in the organic phase, avoiding their interference with the subsequent back-extraction process, while not damaging [TICl4]. - The structure ensures the stability of the organic phase. Using ammonium acetate solution as the stripping agent effectively disrupts the bond between N5O3 and the thallium complex, allowing thallium to re-enter the aqueous phase and achieving efficient stripping recovery.

[0032] In summary, the present invention has at least one of the following beneficial technical effects:

[0033] 1. The thallium solvent extraction method provided in this application has the advantages of simple operation, high selectivity, high extraction rate, low environmental pollution, low cost, and reusable extractant. It not only solves the problem of volatile organic solvent pollution in traditional extraction methods but also improves the overall economic efficiency of the process, making it suitable for applications involving high-concentration thallium wastewater in the lithium salt extraction industry.

[0034] 2. This application provides a high-concentration thallium solvent extraction method for the lithium salt extraction industry, which achieves a high thallium back-extraction rate under acidic conditions.

[0035] 3. The method provided by this invention is simple, operates at normal pressure and temperature, and has low requirements for operating conditions; the solvent used is low in toxicity and inexpensive, and can be recycled, resulting in low processing costs and suitability for industrial applications. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0037] Existing solvent extraction methods for thallium use organic solvents such as benzene, diethyl ether, toluene, isopropyl ether, and methyl isobutyl ketone, which are volatile and toxic, polluting the environment, affecting the health of workers, and are also expensive. To address this, some technologies employ an aqueous two-phase system using polyethylene glycol (PEG) as an extractant to remove and enrich thallium from high-concentration thallium wastewater. However, PEG, being a polymer, can cause excessive viscosity in the extraction system, affecting the extraction rate.

[0038] To address the aforementioned problems, this application proposes a high-concentration thallium solvent extraction method for the lithium salt extraction industry, comprising the following steps:

[0039] Step S1: Add a pH adjuster to the thallium waste liquid to adjust the pH, then add an oxidant, stir to carry out the reaction, and obtain a mixed solution; the pH adjuster is HCl;

[0040] Step S2: Add extractant and diluent to the mixed solution, stir to extract, separate, and obtain thallium-containing organic phase and first raffinate; the extractant includes N503 extractant and tributyl phosphate;

[0041] Step S3: The thallium-containing organic phase is washed with hydrochloric acid solution, then back-extracted with ammonium acetate solution, and separated to obtain the back-extract and the second raffinate. The inventors discovered that this invention uses N503, an amide extractant with high selectivity for thallium, in combination with tributyl phosphate (TBP), to oxidize thallium ions and combine them with chloride ions to form a stable complex anion [TICl4]. - The acidified extractant can react with [TICl4]. - The extraction process achieves rapid binding and extraction. This method is simple to operate, highly selective, has a high extraction rate, minimal environmental pollution, low cost, and the extractant can be reused.

[0042] In some embodiments, in step S1, the thallium concentration in the thallium waste liquid is 1 mg / L to 10 mg / L. The thallium concentration in the thallium waste liquid of this application further improves the extraction efficiency and selectivity of thallium.

[0043] In some embodiments, the thallium waste liquid is preferably a high-concentration thallium-containing leachate or displacement solution from the lithium salt extraction industry.

[0044] In some embodiments, the thallium concentration in the thallium waste liquid is 10 mg / L. The preferred method of controlling the thallium concentration in the thallium waste liquid in this application further improves the extraction efficiency and selectivity of thallium.

[0045] In some embodiments, in step S1, the pH is adjusted to 1-2. This application controls the pH value to further improve the extraction efficiency and selectivity of thallium.

[0046] In some embodiments, the oxidant in step S1 is NaClO. The choice of oxidant in this application further improves the extraction efficiency and selectivity of thallium.

[0047] In some embodiments, the amount of oxidant used is 0.5 g / L to 5 g / L. This application controls the amount of oxidant to further improve the extraction efficiency and selectivity of thallium.

[0048] In some embodiments, in step S1, a chloride salt is added along with the oxidant. This application further improves the extraction efficiency of thallium by adding a chloride salt.

[0049] In some embodiments, the chloride salt is selected from at least one of sodium chloride, potassium chloride, and lithium chloride. The selection of the chloride salt in this application further improves the extraction efficiency of thallium.

[0050] In some embodiments, in step S1, the stirring speed is 300 r / min to 400 r / min, the stirring time is 20 min to 40 min, and the reaction temperature is 20 °C to 30 °C. This application controls the reaction parameters to further improve the extraction efficiency and selectivity of thallium.

[0051] In some embodiments, in step S2, the extractant accounts for 10% to 50% of the mass concentration of the extraction solution composed of the extractant and diluent. This application controls the mass concentration of the extractant, further improving the extraction efficiency of thallium.

[0052] In some embodiments, the mass ratio of N503 extractant to tributyl phosphate is 1:1 to 5. This application controls the mass ratio of N503 extractant to tributyl phosphate, further improving the extraction efficiency of thallium.

[0053] In some embodiments, in step S2, the diluent includes at least one selected from diethylbenzene, xylene, and n-octanol. The choice of diluent in this application further improves the extraction efficiency of thallium.

[0054] In some embodiments, in step S2, the mass ratio of the extraction solution (composed of the extractant and diluent) to the mixed solution is 1:(1~10), the stirring speed is 300 r / min~400 r / min, and the stirring time is 3 min~30 min. This application controls the ratio of the extraction solution to the mixed solution, as well as the reaction parameters, to further improve the extraction efficiency and selectivity of thallium.

[0055] In some embodiments, in step S3, the concentration of the hydrochloric acid solution is 0.1 mol / L to 1 mol / L, and the mass ratio of the hydrochloric acid solution to the thallium-containing organic phase is (1 to 10):1. This application controls the concentration of the hydrochloric acid solution and the mass ratio of the hydrochloric acid solution to the thallium-containing organic phase, thereby further improving the extraction efficiency of thallium.

[0056] In some embodiments, the concentration of the ammonium acetate solution is 1 mol / L to 5 mol / L, and the mass ratio of the ammonium acetate solution to the thallium-containing organic phase is (1 to 10):1. This application controls the concentration of the ammonium acetate solution and the mass ratio of the ammonium acetate solution to the thallium-containing organic phase, thereby further improving the extraction efficiency of thallium.

[0057] The solution of this application will be described below with reference to the following specific embodiments. Unless otherwise specified, the raw materials used in the following embodiments are all from commercially available products, and the devices or equipment used are all purchased from conventional market sales channels. Specific Implementation

[0059] Example 1

[0060] This embodiment provides a high-concentration thallium solvent extraction method for the lithium salt extraction industry, including the following steps:

[0061] Step S1: Add pH adjuster HCl to 1L of thallium waste liquid with a thallium concentration of 5mg / L to adjust the pH to 1.5, then add 2g / L of oxidant NaClO, stir to carry out the reaction at a stirring speed of 350r / min for 30min, and at a reaction temperature of 25℃ to obtain a mixed solution.

[0062] Step S2: Add the extractant and diluent to the mixed solution, stir to extract at a stirring speed of 350 r / min for 3 min, let stand for 10 min, separate, and obtain the thallium-containing organic phase and the first raffinate; the extractant is N503 extractant and tributyl phosphate in a mass ratio of 1:2; the mass concentration of the extractant in the extractant and diluent mixture is 30%; the diluent is diethylbenzene; the mass ratio of the extractant and diluent mixture to the mixed solution is 1:3;

[0063] Step S3: Wash the thallium-containing organic phase with a 0.5 mol / L hydrochloric acid solution, with a mass ratio of hydrochloric acid solution to thallium-containing organic phase of 3:1. Then add a 2 mol / L ammonium acetate solution for back-extraction, with a mass ratio of ammonium acetate solution to thallium-containing organic phase of 3:1. Separate to obtain the back-extraction solution and the second raffinate.

[0064] Example 2

[0065] This embodiment provides a high-concentration thallium solvent extraction method for the lithium salt extraction industry, including the following steps:

[0066] Step S1: Add pH adjuster HCl to 1L of thallium waste liquid with a thallium concentration of 5mg / L to adjust the pH to 1.5, then add 4g / L of oxidant NaClO, stir to carry out the reaction at a stirring speed of 350r / min for 30min, and at a reaction temperature of 25℃ to obtain a mixed solution.

[0067] Step S2: Add the extractant and diluent to the mixed solution, stir to extract at a stirring speed of 350 r / min for 3 min, let stand for 10 min, separate, and obtain the thallium-containing organic phase and the first raffinate; the extractant is N503 extractant and tributyl phosphate in a mass ratio of 1:2; the mass concentration of the extractant in the extractant and diluent mixture is 30%; the diluent is diethylbenzene; the mass ratio of the extractant and diluent mixture to the mixed solution is 1:2;

[0068] Step S3: Wash the thallium-containing organic phase with a 0.5 mol / L hydrochloric acid solution, with a mass ratio of hydrochloric acid solution to thallium-containing organic phase of 2:1. Then add a 2 mol / L ammonium acetate solution for back-extraction, with a mass ratio of ammonium acetate solution to thallium-containing organic phase of 2:1. Separate to obtain the back-extraction solution and the second raffinate.

[0069] Example 3

[0070] This embodiment provides a high-concentration thallium solvent extraction method for the lithium salt extraction industry, including the following steps:

[0071] Step S1: Add pH adjuster HCl to 1L of thallium waste liquid with a thallium concentration of 5mg / L to adjust the pH to 1.5, then add 200ml of oxidant H2O2 with a mass fraction of 10%, stir to carry out the reaction at a stirring speed of 350r / min for 30min, and at a reaction temperature of 25℃ to obtain a mixed solution.

[0072] Step S2: Add the extractant and diluent to the mixed solution, stir to extract at a stirring speed of 350 r / min for 3 min, let stand for 10 min, separate, and obtain the thallium-containing organic phase and the first raffinate; the extractant is N503 extractant and tributyl phosphate in a mass ratio of 1:2; the mass concentration of the extractant in the extractant and diluent mixture is 30%; the diluent is diethylbenzene; the mass ratio of the extractant and diluent mixture to the mixed solution is 1:3;

[0073] Step S3: Wash the thallium-containing organic phase with a 0.5 mol / L hydrochloric acid solution, with a mass ratio of hydrochloric acid solution to thallium-containing organic phase of 3:1. Then add a 2 mol / L ammonium acetate solution for back-extraction, with a mass ratio of ammonium acetate solution to thallium-containing organic phase of 3:1. Separate to obtain the back-extraction solution and the second raffinate.

[0074] Example 4

[0075] This embodiment provides a high-concentration thallium solvent extraction method for the lithium salt extraction industry, including the following steps:

[0076] Step S1: Add pH adjuster HCl to 1L of thallium waste liquid with a thallium concentration of 5mg / L to adjust the pH to 2, then add 5g / L of oxidant NaClO, stir to carry out the reaction at a stirring speed of 300r / min for 40min, and at a reaction temperature of 30℃ to obtain a mixed solution.

[0077] Step S2: Add the extractant and diluent to the mixed solution, stir to extract at a stirring speed of 400 r / min for 15 min, let stand for 10 min, separate, and obtain the thallium-containing organic phase and the first raffinate; the extractant is N503 extractant and tributyl phosphate in a mass ratio of 1:2; the mass concentration of the extractant in the extractant and diluent mixture is 30%; the diluent is xylene; the mass ratio of the extractant and diluent mixture to the mixed solution is 1:5;

[0078] Step S3: Wash the thallium-containing organic phase with a 1 mol / L hydrochloric acid solution, with a mass ratio of hydrochloric acid solution to thallium-containing organic phase of 5:1. Then add a 1 mol / L ammonium acetate solution for back-extraction, with a mass ratio of ammonium acetate solution to thallium-containing organic phase of 5:1. Separate to obtain back-extraction solution and second raffinate.

[0079] Example 5

[0080] This embodiment provides a high-concentration thallium solvent extraction method for the lithium salt extraction industry, including the following steps:

[0081] Step S1: Add pH adjuster HCl to 1L of thallium waste liquid with a thallium concentration of 5mg / L to adjust the pH to 1, then add 0.5g / L of oxidant NaClO, stir to carry out the reaction at a stirring speed of 400r / min for 20min, and at a reaction temperature of 20℃ to obtain a mixed solution.

[0082] Step S2: Add the extractant and diluent to the mixed solution, stir to extract at a stirring speed of 300 r / min for 30 min, let stand for 10 min, separate, and obtain the thallium-containing organic phase and the first raffinate; the extractant is N503 extractant and tributyl phosphate in a mass ratio of 1:2; the mass concentration of the extractant in the extractant and diluent mixture is 30%; the diluent is n-octanol; the mass ratio of the extractant and diluent mixture to the mixed solution is 1:10;

[0083] Step S3: Wash the thallium-containing organic phase with a 0.1 mol / L hydrochloric acid solution, with a mass ratio of hydrochloric acid solution to thallium-containing organic phase of 10:1. Then add a 5 mol / L ammonium acetate solution for back-extraction, with a mass ratio of ammonium acetate solution to thallium-containing organic phase of 10:1. Separate to obtain the back-extraction solution and the second raffinate.

[0084] Comparative Examples 1-2

[0085] Comparative Example 1

[0086] The difference between Comparative Example 1 and Example 1 is that the diluent diethylbenzene in Comparative Example 1 is replaced with sulfonated kerosene, while the rest is the same as in Example 1.

[0087] Comparative Example 2

[0088] The difference between Comparative Example 2 and Example 2 is that Comparative Example 2 replaces N503 extractant with P204 (di(2-ethylhexyl) phosphate), while the rest is the same as Example 2.

[0089] The thallium ion concentration in the thallium waste liquid, back-extraction liquid and second raffinate in Examples 1-5 and Comparative Examples 1-2 was detected by ICP-MS, and the extraction rate and back-extraction rate of thallium were calculated. The detection results are shown in Table 1.

[0090] Table 1

[0091]

[0092] As shown in Table 1, the high-concentration thallium solvent extraction method for the lithium salt extraction industry provided by this invention exhibits good selectivity and high extraction and back-extraction rates of thallium. The methods in Examples 1-5 achieve an extraction rate of 95.6% and a back-extraction rate of 86.7%.

[0093] In Comparative Example 1, replacing the diethylbenzene diluent with sulfonated kerosene resulted in a decrease in both the extraction and back-extraction rates of thallium.

[0094] In Comparative Example 2, replacing N503 extractant with P204 significantly reduced the extraction and back-extraction rates of thallium.

[0095] Examples 6-10

[0096] Example 6

[0097] The difference between Example 6 and Example 1 is that in step S1 of Example 6, the thallium concentration in the thallium waste liquid is 10 mg / L.

[0098] Example 7

[0099] The difference between Example 7 and Example 1 is that in step S1 of Example 7, the thallium concentration in the thallium waste liquid is 1 mg / L.

[0100] Example 8

[0101] The difference between Example 8 and Example 1 is that in step S1 of Example 8, 2 g / L of sodium chloride was added along with the oxidant.

[0102] Example 9

[0103] The difference between Example 9 and Example 1 is that in step S2 of Example 9, the mass concentration of the extractant in the extraction solution composed of the extractant and the diluent is 10%.

[0104] Example 10

[0105] The difference between Example 10 and Example 1 is that in step S2 of Example 10, the mass concentration of the extractant in the extraction solution composed of the extractant and the diluent is 50%.

[0106] The thallium ion concentration in the thallium waste liquid, back-extraction liquid and second raffinate in Examples 6 to 10 was detected by ICP-MS, and the extraction rate and back-extraction rate of thallium were calculated. The detection results are shown in Table 2.

[0107] Table 2

[0108]

[0109] As can be seen from the test results in Table 2, the difference between Example 6, Example 7 and Example 1 is that the thallium concentration in the thallium waste liquid is different. Among them, the extraction rate and back-extraction rate of the method provided in Example 1 are the highest.

[0110] Compared with Example 1, Example 8 also added sodium chloride, and the extraction rate and back-extraction rate of Example 8 were significantly increased.

[0111] The difference between Examples 9 and 10 and Example 1 is that the mass concentration of the extractant is different. Among them, the extraction rate and back-extraction rate of the method provided in Example 1 are the highest.

[0112] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the principles of this application should be included within the protection scope of this application.

Claims

1. A method for solvent extraction of high concentration thallium in lithium salt extraction industry, characterized in that, Includes the following steps: Step S1: Add a pH adjuster to the thallium waste liquid to adjust the pH, then add an oxidant, stir to react, and obtain a mixed solution; the thallium waste liquid is a high-concentration thallium-containing leachate or displacement solution from the lithium salt extraction industry; The pH adjuster is HCl; Step S2: Add extractant and diluent to the mixed solution, stir to extract, separate, and obtain thallium-containing organic phase and first raffinate; the extractant includes N503 extractant and tributyl phosphate; the extractant is used to avoid interference from lithium, rubidium and cesium during the extraction of thallium; Step S3: Wash the thallium-containing organic phase with hydrochloric acid solution, then add ammonium acetate solution for back-extraction and separation to obtain back-extraction solution and second raffinate solution; In step S1, the stirring speed is 300 r / min to 400 r / min.

2. The method of claim 1, wherein, In step S1, the thallium concentration in the thallium waste liquid is 1 mg / L to 10 mg / L.

3. The method of claim 1, wherein, In step S1, the pH is adjusted to 1-2.

4. The method of claim 1, wherein, In step S1, the oxidant is NaClO; the amount of the oxidant used is 0.5 g / L to 5 g / L.

5. The method according to claim 1, characterized in that, In step S1, a chloride salt is added along with the oxidant; the chloride salt is selected from at least one of sodium chloride, potassium chloride, and lithium chloride.

6. The method according to claim 1, characterized in that, In step S1, the stirring time is 20 min to 40 min, and the reaction temperature is 20℃ to 30℃.

7. The method according to claim 1, characterized in that, In step S2, the extractant accounts for 10% to 50% of the mass concentration of the extraction solution composed of the extractant and diluent; the mass ratio of N503 extractant to tributyl phosphate is 1:1 to 5.

8. The method according to claim 1, characterized in that, In step S2, the diluent includes at least one of diethylbenzene, xylene, and n-octanol.

9. The method according to claim 1, characterized in that, In step S2, the mass ratio of the extraction solution composed of the extractant and the diluent to the mixed solution is 1:(1~10), the stirring speed is 300r / min~400r / min, and the stirring time is 3min~30min.

10. The method according to claim 1, characterized in that, In step S3, the concentration of the hydrochloric acid solution is 0.1 mol / L to 1 mol / L, and the mass ratio of the hydrochloric acid solution to the thallium-containing organic phase is (1 to 10):

1. The concentration of the ammonium acetate solution is 1 mol / L to 5 mol / L, and the mass ratio of the ammonium acetate solution to the thallium-containing organic phase is (1 to 10): 1.

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