Leaching agent for removing thallium and beryllium in lithium residue and application thereof

Abstract

The application provides a leaching agent for removing thallium and beryllium in lithium residue and application. The leaching agent comprises a first leaching agent and a second leaching agent. The first leaching agent is an organic acid solution, the organic acid comprises a carboxyl group, and at least one of a hydroxyl group, a sulfhydryl group, a carbonyl group and a sulfonic acid group; the organic acid is a single organic acid or a mixed organic acid; the second leaching agent comprises a cation agent and a reducing agent, the cation agent can form at least one of K + , NH4 + , Mg 2+ , Na + , Fe 3+ in an aqueous solution, and the reducing agent comprises an inorganic reducing agent and / or an organic reducing agent. The organic acid in the first leaching agent can destroy the crystal structure of the lithium residue, and the groups such as the carboxyl group and the hydroxyl group can complex thallium and beryllium ions to make them more easily leached out. On this basis, the cation and the reducing solution in the second leaching agent accelerate the release of thallium and beryllium through ion exchange and reduction. The above leaching agent can remove thallium and beryllium in the lithium residue at the same time, and has a high removal rate of thallium and beryllium.

Description

Technical Field

[0001] This invention relates to the field of metallurgical industrial waste treatment, and particularly to leaching agents for removing thallium and beryllium from lithium slag and their applications. Background Technology

[0002] Lithium, due to its high energy density and long cycle life, is widely used in energy storage devices, such as lithium-ion batteries, and has become an important power source for electric vehicles, portable electronic devices, and other fields. The lithium extraction process from lepidolite mines generates a large amount of waste residue. This waste residue contains highly toxic elements such as thallium and beryllium, as well as other valuable metals besides lithium. If thallium and beryllium in lithium residue are directly stockpiled or discarded in the wild, they will cause significant environmental damage, including polluting soil, water sources, and the atmosphere, thus threatening ecosystems and human health.

[0003] Thallium and beryllium in lithium slag often exist as trace elements within aluminosilicate and iron-containing mineral phases because they lack independent phases, making deep detoxification difficult using conventional methods. Existing technologies include high-temperature roasting and the addition of solidifying agents. High-temperature roasting: This method destroys the mineral phase structure in lithium slag at high temperatures, thereby fixing elements such as thallium and beryllium within the slag and preventing their leaching and water pollution. However, this method does not completely remove thallium and beryllium and suffers from high energy consumption and small processing scale. Adding solidifying agents: This method adds a solidifying agent to combine with thallium to form an inert ceramic material, thus solidifying it. This method also only addresses the leaching problem of thallium, without achieving complete removal of thallium and beryllium.

[0004] Therefore, developing a compound leaching agent that simultaneously and deeply detoxifies thallium and beryllium in lithium slag is crucial for achieving the harmless treatment of lithium slag. This is of great significance for the green and environmentally friendly development of the entire lithium industry. Summary of the Invention

[0005] The main objective of this invention is to provide a leaching agent for removing thallium and beryllium from lithium slag and its application, so as to solve the technical problem that existing leaching agents cannot simultaneously leach and separate thallium and beryllium from lithium slag.

[0006] To achieve the above objectives, the present invention provides a leaching agent for removing thallium and beryllium from lithium slag, comprising a first leaching agent and a second leaching agent, wherein the first leaching agent and the second leaching agent are in a separate state.

[0007] The first leaching agent is an organic acid solution, wherein the organic acid includes a carboxyl group and at least one of a hydroxyl, mercapto, carbonyl, or sulfonic acid group. The organic acid may be a single organic acid or a mixture of organic acids.

[0008] The second leaching agent comprises a cationic agent and a reducing agent, wherein the cationic agent is capable of forming K in an aqueous solution. + NH4+ Mg 2+ Na + Fe 3+ At least one of the following, the reducing agent includes an inorganic reducing agent and / or an organic reducing agent. The inorganic reducing agent is capable of forming Fe in aqueous solution. 2+ or S 2- The organic reducing agent is a thiol compound or a thiourea.

[0009] According to embodiments of this application, the organic acid is at least one selected from formic acid, oxalic acid, acetic acid, lactic acid, malic acid, citric acid, succinic acid, and thiocarboxylic acid.

[0010] According to an embodiment of this application, the organic acid is a mixed organic acid. The mixed organic acid includes a first organic acid and a second organic acid. The first organic acid is formic acid or citric acid, and the second organic acid is acetic acid or malic acid. The concentration of the mixed organic acid is 30–45 g / L. The concentration ratio of the first organic acid to the second organic acid is 5–15:1.

[0011] According to embodiments of this application, the reducing agent includes inorganic reducing agents and organic reducing agents.

[0012] The inorganic reducing agent is ferrous chloride. The organic reducing agent is thiourea. The mass ratio of the inorganic reducing agent to the organic reducing agent is 5–15:1.

[0013] According to an embodiment of this application, the first leaching agent is a mixed organic acid of formic acid and acetic acid, wherein the concentration ratio of formic acid to acetic acid is 5-10:1. The second leaching agent comprises ferrous chloride and thiourea, wherein the mass ratio of ferrous chloride to thiourea is 5-10:1.

[0014] This application also provides the application of the above-mentioned leaching agent for removing thallium and beryllium from lithium slag, including the following steps:

[0015] The lithium slag is mixed with the first leaching agent and subjected to the first leaching to obtain a solid-liquid mixture.

[0016] The solid-liquid mixture is mixed with a second leaching agent and subjected to a second leaching. After solid-liquid separation, detoxified lithium slag is obtained.

[0017] According to an embodiment of this application, in the step of mixing lithium slag with a first leaching agent, the concentration of the first leaching agent is 30–45 g / L. The lithium slag and the first leaching agent are mixed at a liquid-to-solid ratio of (2.5–10):1 mL / g.

[0018] According to an embodiment of this application, the first leaching step includes: leaching for 2 to 3 hours at a temperature of 30 to 60°C and a stirring speed of 200 to 300 rpm in the mixed solution.

[0019] According to an embodiment of this application, in the step of mixing the solid-liquid mixture with the second leaching agent,

[0020] The concentration of the second leaching agent is 10-15 g / L. The solid-liquid mixture is mixed with the second leaching agent at a liquid-solid ratio of (2.5-10):1 mL / g.

[0021] According to an embodiment of this application, the step of performing the second leaching includes: leaching for 2 to 3 hours at a temperature of 30 to 60°C and a stirring speed of 200 to 300 rpm in the mixed solution.

[0022] The aforementioned leaching agents for removing thallium and beryllium from lithium slag utilize the following methods: First, the organic acid in the leaching agent disrupts the crystal structure of the lithium slag, while carboxyl and hydroxyl groups complex thallium and beryllium ions, making them easier to dissolve. Second, the cations and reducing solution in the leaching agent accelerate the release of thallium and beryllium through ion exchange and reduction. Therefore, these leaching agents can simultaneously remove both thallium and beryllium from lithium slag, achieving high removal rates for both. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0024] Figure 1 This is a scanning electron microscope image of lithium slag according to one embodiment of this application.

[0025] Figure 2 This is a scanning electron microscope image of the detoxified lithium slag according to one embodiment of this application.

[0026] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] It should be noted that all directional indicators (such as up, down, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0029] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature.

[0030] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0031] An embodiment of the present invention provides a leaching agent for removing thallium and beryllium from lithium slag, comprising a first leaching agent and a second leaching agent, wherein the first leaching agent and the second leaching agent are in a separate state.

[0032] Studies have found that thallium and beryllium are often difficult to dissolve in the eutectic product lithium slag after high-temperature (700℃) calcination. This is because thallium and beryllium are fixed in the lithium slag during the formation of the eutectic through lattice substitution and mineral phase encapsulation. Therefore, the crystal structure of lepidolite ore waste slag needs to be disrupted before detoxification.

[0033] Based on this, a leaching agent for removing thallium and beryllium from lithium slag was studied. It includes a first leaching agent and a second leaching agent. The first and second leaching agents are stored separately; therefore, the first and second leaching agents are used sequentially to leach the lithium slag.

[0034] The first leaching agent selected is a complex organic acid, which provides H+. + This process can disrupt the structure of lithium slag. Furthermore, the carboxyl and hydroxyl groups in organic acids can complex thallium and beryllium ions, making them easier to dissolve and release. The added second leaching agent works by exchanging thallium and beryllium in the crystalline phase with cations, and also by reducing Tl... 3+For Tl + This further enhances its dissolution and release.

[0035] Specifically, the first leaching agent is an organic acid solution, wherein the organic acid includes a carboxyl group and at least one group selected from hydroxyl, mercapto, carbonyl, and sulfonic acid groups. The organic acid is a single organic acid or a mixture of organic acids.

[0036] For example: the organic acid is a single organic acid, which includes one or more of the following groups in addition to the carboxyl group: hydroxyl, mercapto, carbonyl, and sulfonic acid group.

[0037] For example: the organic acid is a mixture of organic acids, comprising at least two organic acids. The combination of at least two organic acids includes, in addition to a carboxyl group, one or more of a hydroxyl group, a mercapto group, a carbonyl group, and a sulfonic acid group.

[0038] Take the combination of two organic acids as an example. For instance, one organic acid may only contain a carboxyl group, while the other organic acid may contain a carboxyl group, as well as one or more of the following groups: hydroxyl, mercapto, carbonyl, and sulfonic acid groups.

[0039] For example, both organic acids include a carboxyl group, and also include one or more of the following groups: hydroxyl, mercapto, carbonyl, and sulfonic acid groups.

[0040] Returning to the second leaching agent section, this second leaching agent comprises a cationic agent and a reducing agent, wherein the cationic agent is capable of forming K in an aqueous solution. + NH4 + Mg 2+ Na + Fe 3+ At least one of the following, the reducing agent includes an inorganic reducing agent and / or an organic reducing agent; the inorganic reducing agent is capable of forming Fe in aqueous solution. 2+ or S 2- The organic reducing agent is a thiol compound or thiourea.

[0041] The second leaching agent is a composite agent containing both a cationic agent and a reducing agent.

[0042] Cationic agents can hydrolyze in water to form K + NH4 + Mg 2+ Na + Fe 3+ Cationic agents include, but are not limited to, these cations. Correspondingly, cationic agents include NH4Cl, KCl, MgCl2, K2SO4, (NH4)2SO4, Na2SO4, FeCl3, etc.

[0043] Inorganic reducing agents can form Fe in aqueous solution 2+ or S2- Correspondingly, inorganic reducing agents include FeCl2, FeS, and CuS. It should be noted that Fe... 2+ As a reducing agent, it is oxidized to form Fe. 3+ Therefore, this inorganic reducing agent also acts as a cationic agent.

[0044] The first leaching agent simultaneously disrupts the crystal structure of lithium slag and complexes thallium and beryllium ions, while the second leaching agent simultaneously performs ion exchange and reduction. The aforementioned compound leaching agents are widely available in nature and are environmentally friendly and pollution-free.

[0045] The aforementioned leaching agents for removing thallium and beryllium from lithium slag utilize the following methods: First, the organic acid in the leaching agent disrupts the crystal structure of the lithium slag, while carboxyl and hydroxyl groups complex thallium and beryllium ions, making them easier to dissolve. Second, the cations and reducing solution in the leaching agent accelerate the release of thallium and beryllium through ion exchange and reduction. Therefore, these leaching agents can simultaneously remove both thallium and beryllium from lithium slag, achieving high removal rates for both.

[0046] In some embodiments, the organic acid is at least one selected from formic acid, oxalic acid, acetic acid, lactic acid, malic acid, citric acid, succinic acid, and thiocarboxylic acid.

[0047] The mixture of the above-mentioned organic acids includes one or more of the following groups: carboxyl, hydroxyl, mercapto, carbonyl, and sulfonic acid groups. In some specific embodiments, two types of organic acids are used. For example, the organic acid is a mixture of acetic acid and formic acid.

[0048] In some embodiments, the organic acid is a mixed organic acid; the mixed organic acid includes a first organic acid and a second organic acid; the first organic acid is formic acid or citric acid, and the second organic acid is acetic acid or malic acid; the concentration of the mixed organic acid is 30-45 g / L. Too low a concentration will result in a low degree of damage to the crystal structure of lithium slag, thereby affecting the thallium and beryllium leaching rate, while too high a concentration will not improve the leaching rate and will lead to excessive reagent dosage and increased treatment costs; the concentration ratio of the first organic acid to the second organic acid is 5-15:1.

[0049] In some embodiments, the reducing agent includes inorganic reducing agents and organic reducing agents;

[0050] The inorganic reducing agent is ferrous chloride; the organic reducing agent is thiourea; and the mass ratio of the inorganic reducing agent to the organic reducing agent is 5-15:1.

[0051] In some embodiments, the first leaching agent is a mixed organic acid of formic acid and acetic acid, wherein the concentration ratio of formic acid to acetic acid is 5 to 10:1; the second leaching agent includes ferrous chloride and thiourea; wherein the mass ratio of ferrous chloride to thiourea is 5 to 10:1.

[0052] This application also provides the application of the above-mentioned leaching agent for removing thallium and beryllium from lithium slag, including the following steps:

[0053] The lithium slag is mixed with the first leaching agent and subjected to the first leaching to obtain a solid-liquid mixture.

[0054] The solid-liquid mixture is mixed with a second leaching agent and subjected to a second leaching. After solid-liquid separation, detoxified lithium slag is obtained.

[0055] The conditions for the first and second leaching are relatively flexible, such as leaching for 1 to 3 hours at a mixed solution temperature of 30 to 80°C and a stirring speed of 200 to 400 rpm.

[0056] The second leaching agent is added to the solid-liquid mixture in solid form, wherein the cationic agent hydrolyzes in the solid-liquid mixture to form K. + NH4 + Mg 2+ Na + Fe 3+ At least one of the following. The reducing agent includes inorganic reducing agents and / or organic reducing agents; the inorganic reducing agent is capable of forming Fe in the solid-liquid mixture. 2+ or S 2- The organic reducing agent is a mercapto compound or thiourea. In this method, the second leaching agent is not prepared into a solution with additional water, thus reducing the total amount of wastewater generated throughout the application process.

[0057] The aforementioned application of the leaching agent for removing thallium and beryllium from lithium slag utilizes a first leaching agent. By mixing the lithium slag with the first leaching agent, the crystal structure of the lithium slag is disrupted by organic acids. Simultaneously, carboxyl and hydroxyl groups can complex thallium and beryllium ions, making them easier to dissolve. A second leaching agent is then added to this solid-liquid mixture for secondary mixing and leaching, accelerating the release of thallium and beryllium through ion exchange and reduction. In this application, the lithium slag does not require mechanical activation treatment via ball milling, simplifying the process and significantly reducing treatment costs.

[0058] In some embodiments, in the step of mixing lithium slag with a first leaching agent, the concentration of the first leaching agent is 30–45 g / L. The lithium slag and the first leaching agent are mixed at a liquid-solid ratio of (2.5–10):1 mL / g.

[0059] In some specific embodiments, the lithium slag is mixed with the first leaching agent at a liquid-solid ratio of (2.5-10):1 mL / g.

[0060] In some embodiments, the first leaching step includes leaching for 2 to 3 hours at a temperature of 30 to 60°C and a stirring speed of 200 to 300 rpm.

[0061] In some embodiments, during the step of mixing the solid-liquid mixture with the second leaching agent...

[0062] The concentration of the second leaching agent is 10-15 g / L. The solid-liquid mixture is mixed with the second leaching agent at a liquid-solid ratio of (2.5-10):1 mL / g.

[0063] In some embodiments, the second leaching step includes leaching for 2 to 3 hours at a temperature of 30 to 60°C and a stirring speed of 200 to 300 rpm.

[0064] In some embodiments, by optimizing the liquid-to-solid ratio, solute concentration, concentration ratio, reaction time, reaction temperature, stirring rate, and other conditions of the first and second leaching agents with lithium slag, the removal rate of thallium and beryllium in lithium slag can reach up to 80%, and the contents of thallium and beryllium in the toxic leaching solution of the detoxified lithium slag are less than 5 μg / L and 10 μg / L, respectively, which meet the requirements of general industrial solid waste.

[0065] The technical solution of this application will be described below with reference to specific embodiments.

[0066] Example 1

[0067] This embodiment provides a compound leaching agent for the simultaneous removal of thallium and beryllium from lithium slag (i.e., a leaching agent for removing thallium and beryllium from lithium slag) and its application, the application of which includes the following:

[0068] 100g of lithium slag was added to 1000mL of a 30g / L acetic acid-formic acid mixed solution (i.e., the first leaching agent) at a liquid-to-solid ratio of 10:1mL / g. The mixture was reacted at 50℃ and 300rpm for 2 hours to obtain a solid-liquid mixture. In the acetic acid-formic acid mixed solution, water was used as the solvent, and acetic acid and formic acid were used as solutes. The solubility of acetic acid was 25g / L, and the solubility of formic acid was 5g / L.

[0069] Ferrous chloride and thiourea (i.e., the second leaching agent) were added to the solid-liquid mixture to achieve a total ferrous chloride-thiourea concentration of 10 g / L. The mixture was reacted at 50°C and 300 rpm for 2 hours. After solid-liquid separation, the final lepidolite detoxification residue was obtained. (See [link to relevant documentation]). Figure 2 . Figure 2The image shown is a scanning electron microscope image (SEM) magnified 2000x to show the detoxified lithium slag. After detoxification, the lithium slag changed from an agglomerated structure to a petal-like structure, indicating that the crystal structure of the lithium slag was indeed disrupted by the compound leaching agent. The mass ratio of ferrous chloride to thiourea added was 5:1.

[0070] The composition and content of the lithium slag used in this embodiment are shown in Table 1. (See Table 1 for details.) Figure 1 . Figure 1 The image is a scanning electron microscope image of lithium slag magnified 2000 times. The undetoxified lithium slag exhibits a porous agglomerate structure, with thallium and beryllium fixed inside the lithium slag by lattice replacement or encapsulation.

[0071] Table 1

[0072] Calcium (wt%) Aluminum (wt%) Silicon (wt%) Sulfur (wt%) Potassium (wt%) Iron (wt%) content 15.34 9.11 11.97 4.73 3.21 1.82 Manganese (wt%) Rubidium (wt%) Cesium (wt%) Strontium (wt%) Thallium (mg / kg) Beryllium (mg / kg) content 0.27 0.33 0.03 0.03 7.51 60

[0073] Example 2

[0074] This embodiment provides a compound leaching agent for the simultaneous removal of thallium and beryllium from lithium slag and its application, the application of which includes the following:

[0075] 100g of lithium slag was added to 500mL of a 30g / L formic acid solution (i.e., the first leaching agent) at a liquid-to-solid ratio of 5:1mL / g. The temperature of the mixed solution was controlled and the reaction was carried out at 75℃ and 400rpm for 1h to obtain a solid-liquid mixture.

[0076] Ferrous chloride and thiourea (i.e., the second leaching agent) were added to the solid-liquid mixture to achieve a total ferrous chloride-thiourea concentration of 10 g / L. The temperature of the mixed solution was controlled at 75℃ and 400 rpm for 1 hour. After solid-liquid separation, the final lepidolite detoxification residue was obtained. The mass ratio of ferrous chloride to thiourea added was 5:1.

[0077] The lithium slag used in this embodiment is the same as that in Example 1.

[0078] Example 3

[0079] This embodiment provides a compound leaching agent for the simultaneous removal of thallium and beryllium from lithium slag and its application, the application of which includes the following:

[0080] 100g of lithium slag was added to 250mL of a 30g / L acetic acid-formic acid mixed solution (i.e., the first leaching agent) at a liquid-to-solid ratio of 2.5:1mL / g. The mixture was reacted at 50℃ and 300rpm for 2 hours to obtain a solid-liquid mixture. In the acetic acid-formic acid mixed solution, water was used as the solvent, and acetic acid and formic acid were used as solutes. The solubility of acetic acid was 25g / L, and the solubility of formic acid was 5g / L.

[0081] Ferrous chloride and thiourea (i.e., the second leaching agent) were added to the solid-liquid mixture to achieve a total ferrous chloride-thiourea concentration of 10 g / L. The mixture was reacted at 50°C and 300 rpm for 2 hours, followed by solid-liquid separation to obtain the final lepidolite detoxification residue. The mass ratio of ferrous chloride to thiourea added was 5:1.

[0082] The lithium mica ore waste used in this embodiment is the same as that in Embodiment 1.

[0083] Example 4

[0084] This embodiment provides a compound leaching agent for the simultaneous removal of thallium and beryllium from lithium slag and its application, the application of which includes the following:

[0085] 100g of lithium slag was added to 500mL of a 45g / L acetic acid-formic acid mixed solution (i.e., the first leaching agent) at a liquid-to-solid ratio of 5:1 mL / g. The mixture was reacted at 50℃ and 300rpm for 2 hours to obtain a solid-liquid mixture. In the acetic acid-formic acid mixed solution, water was used as the solvent, and acetic acid and formic acid were used as solutes. The solubility of acetic acid was 42g / L, and the solubility of formic acid was 3g / L.

[0086] Ferrous chloride and thiourea (i.e., the second leaching agent) were added to the solid-liquid mixture to achieve a total concentration of ammonium chloride-thiourea of ​​15 g / L. The temperature of the mixed solution was controlled at 50℃ and 300 rpm for 2 hours. After solid-liquid separation, the final lepidolite detoxification residue was obtained. The mass ratio of ferrous chloride to thiourea added was 5:1.

[0087] The lithium mica ore waste used in this embodiment is the same as that in Embodiment 1.

[0088] Comparative Example 1

[0089] This comparative example provides a compound leaching agent for the simultaneous removal of thallium and beryllium from lithium slag and its application, the application of which includes the following:

[0090] 100g of lithium slag was added to 500mL of a 30g / L acetic acid-formic acid mixed solution (i.e., the first leaching agent) at a liquid-to-solid ratio of 5:1 mL / g. The mixture was reacted at 50℃ and 300rpm for 2 hours to obtain a solid-liquid mixture. In the acetic acid-formic acid mixed solution, water was used as the solvent, and acetic acid and formic acid were used as solutes. The solubility of acetic acid was 25g / L, and the solubility of formic acid was 5g / L.

[0091] The lithium mica ore waste used in this comparative example is the same as that in Example 1.

[0092] Comparative Example 2

[0093] This comparative example provides a compound leaching agent for the simultaneous removal of thallium and beryllium from lithium slag and its application, the application of which includes the following:

[0094] 100g of lithium slag was added to 500mL of a 10g / L ammonium chloride-thiourea mixed solution (i.e., the second leaching agent) at a liquid-to-solid ratio of 5:1 mL / g. The temperature of the mixed solution was controlled at 50℃ and 300rpm for 2 hours. After solid-liquid separation, the final lepidolite detoxification residue was obtained. The mass ratio of ferrous chloride to thiourea added was 5:1.

[0095] The lithium mica ore waste used in this comparative example is the same as that in Example 1.

[0096] Example 5

[0097] This embodiment provides a compound leaching agent for the simultaneous removal of thallium and beryllium from lithium slag and its application, the application of which includes the following:

[0098] 100g of lithium slag was added to 500mL of a 30g / L acetic acid-formic acid mixed solution (i.e., the first leaching agent) at a liquid-to-solid ratio of 5:1 mL / g. The temperature of the mixed solution was controlled at 75℃ and 300rpm for 3 hours to obtain a solid-liquid mixture. In the acetic acid-formic acid mixed solution, water was used as the solvent, and acetic acid and formic acid were used as solutes. The solubility of acetic acid was 25g / L, and the solubility of formic acid was 5g / L.

[0099] Ferrous chloride and thiourea (i.e., the second leaching agent) were added to the solid-liquid mixture to achieve a total ferrous chloride-thiourea concentration of 10 g / L. The mixture was reacted at 75°C and 300 rpm for 3 hours, followed by solid-liquid separation to obtain the final lepidolite detoxification residue. The mass ratio of ferrous chloride to thiourea added was 5:1.

[0100] The composition and content of the lithium slag used in this embodiment are shown in Table 2.

[0101] Table 2

[0102] Calcium (wt%) Aluminum (wt%) Silicon (wt%) Sulfur (wt%) Potassium (wt%) Iron (wt%) content 9.11 9.07 12.65 3.41 5.29 1.65 Manganese (wt%) Rubidium (wt%) Cesium (wt%) Strontium (wt%) Thallium (mg / kg) Beryllium (mg / kg) content 0.33 0.46 0.04 0.01 6.92 70

[0103] Example 6

[0104] This embodiment provides a compound leaching agent for the simultaneous removal of thallium and beryllium from lithium slag and its application. Except for the lithium slag used, which is the same as in Example 5, everything else is the same as in Example 2.

[0105] Example 7

[0106] This embodiment provides a compound leaching agent for the simultaneous removal of thallium and beryllium from lithium slag and its application. Except for the lithium slag used, which is the same as in Example 5, everything else is the same as in Example 3.

[0107] Example 8

[0108] This embodiment provides a compound leaching agent for the simultaneous removal of thallium and beryllium from lithium slag and its application. Except for adjusting the concentrations of the acetic acid-formic acid mixed solution and the ferrous chloride-thiourea solution to 50 g / L and 20 g / L respectively, the rest is the same as in Example 1.

[0109] Example 9

[0110] This embodiment provides a compound leaching agent for the simultaneous removal of thallium and beryllium from lithium slag and its application, the application of which includes the following:

[0111] 100g of lithium slag was added to 1000mL of a 30g / L acetic acid-malic acid mixed solution (i.e., the first leaching agent) at a liquid-to-solid ratio of 5:1 mL / g. The mixture was reacted at 50℃ and 300rpm for 2 hours to obtain a solid-liquid mixture. In the acetic acid-malic acid mixed solution, water was used as the solvent, and acetic acid and malic acid were used as solutes. The solubility of acetic acid was 25g / L, and the solubility of malic acid was 5g / L.

[0112] Ferrous chloride and thiourea (i.e., the second leaching agent) were added to the solid-liquid mixture to achieve a total ferrous chloride-thiourea concentration of 10 g / L. The mixture was reacted at 50°C and 300 rpm for 2 hours, followed by solid-liquid separation to obtain the final lepidolite detoxification residue. The mass ratio of ferrous chloride to thiourea added was 5:1.

[0113] In this embodiment, the lithium slag contains thallium and beryllium at concentrations of 8 mg / kg and 40 mg / kg, respectively.

[0114] Example 10

[0115] This embodiment provides a compound leaching agent for the simultaneous removal of thallium and beryllium from lithium slag and its application. The thallium and beryllium contents in the lithium slag used are 10 mg / kg and 50 mg / kg, respectively. All other aspects are the same as in Example 9.

[0116] Example 11

[0117] This embodiment provides a compound leaching agent for the simultaneous removal of thallium and beryllium from lithium slag and its application. The thallium and beryllium contents in the lithium slag are 7 mg / kg and 38 mg / kg, respectively, and the rest are the same as in Example 9.

[0118] Tests and Result Analysis

[0119] The toxicity leaching detection of thallium and beryllium in lithium slag simultaneously and deeply detoxified compound leaching agents and their applications in the above-mentioned embodiments and comparative examples was carried out. The leaching method was in accordance with HJ / T299-2007 "Solid Waste Leaching Toxicity Leaching Method Sulfuric Acid Nitric Acid Method" and the concentration of thallium and beryllium after detoxification was detected in accordance with HJ700-2014 "Determination of 65 Elements in Water Quality by Inductively Coupled Plasma Mass Spectrometry". The results are shown in Table 3.

[0120] Table 3

[0121]

[0122]

[0123] (1) Based on the comprehensive examples 1-11, Comparative Examples 1 and 2, it can be seen that, except for Comparative Examples 1 and 2 which used only a single first leaching agent and a single second leaching agent, resulting in poor detoxification effects, the leaching agents used in this application for removing thallium and beryllium from lithium slag can all detoxify thallium and beryllium in lithium slag. Among them, the liquid-to-solid ratio of Examples 3 and 7 is relatively low, and the beryllium in the treated lithium slag is significantly reduced, meeting the requirements of general solid waste (less than 20 μg / L). The treated lithium slag of the other examples can meet the requirements of Class I solid waste (less than 5 μg / L).

[0124] (2) Based on Examples 1 and 3, and Examples 2 and 4, it can be seen that increasing the liquid-to-solid ratio and increasing the solute concentration of the compound leaching agent (i.e., the leaching agent used to remove thallium and beryllium from lithium slag) helps to improve the detoxification effect of lithium slag. Comparing Examples 1, 2, 8, Comparative Example 1, and Comparative Example 2, it was found that the compound leaching agent is more effective than the single leaching agent (i.e., a single first leaching agent or a single second leaching agent). In addition, although the liquid-to-solid ratio was reduced, increasing the solute concentration of the compound leaching agent did not affect the detoxification effect, and the detoxified lithium slag was still a general solid waste.

[0125] (3) As can be seen from Examples 5-7, increasing the liquid-to-solid ratio and increasing the solute concentration of the compound leaching agent have a significant impact on the detoxification of beryllium in the lithium mica ore waste residue in Example 5. Therefore, it is evident that using a larger liquid-to-solid ratio and a higher concentration of compound leaching agent is beneficial for the detoxification of lithium slag.

[0126] (4) As can be seen from Examples 9 to 11, the optimized conditions for treating lithium slag from different sources all meet the requirements of general industrial solid waste. This is sufficient to prove that the present invention has excellent effects on different lithium slags and also demonstrates the superiority of the invention.

[0127] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. Use of a leaching agent for removing thallium and beryllium from lithium residue, characterized in that, The leaching agent for removing thallium and beryllium in lithium residue comprises a first leaching agent and a second leaching agent, both of which are in a separated state. The first leaching agent is an organic acid solution; the organic acid solution is a mixed organic acid; the mixed organic acid comprises a first organic acid and a second organic acid; the first organic acid is formic acid or citric acid, and the second organic acid is acetic acid or malic acid; the concentration of the mixed organic acid is 30-45 g / L; the concentration ratio of the first organic acid to the second organic acid is 5-15:

1. The second leaching agent comprises a cation agent capable of forming at least one of K + , NH4 + , Mg 2+ , Na + , Fe 3+ in an aqueous solution and a reducing agent comprising an inorganic reducing agent capable of forming Fe 2+ or S 2- in an aqueous solution and / or an organic reducing agent; the organic reducing agent is a mercapto compound or thiourea; The application comprises the following steps: The lithium residue is mixed with the first leaching agent to perform first leaching, and a solid-liquid mixture is obtained; the lithium residue is waste residue generated by a lithium extraction process of lepidolite ore; The solid-liquid mixture is mixed with the second leaching agent to perform second leaching, and detoxified lithium residue is obtained through solid-liquid separation.

2. The use of the leaching agent for removing thallium and beryllium in lithium residue according to claim 1, characterized in that, In the step of mixing the lithium residue with the first leaching agent, the lithium residue is mixed with the first leaching agent at a liquid-solid ratio of (2.5-10):1 mL / g.

3. The use of the leaching agent for removing thallium and beryllium in lithium residue according to claim 1, characterized in that, The step of performing first leaching comprises leaching for 2-3 h under the conditions that the temperature of the mixed solution is 30-60°C and the stirring speed is 200-300 rpm.

4. The use of the leaching agent for removing thallium and beryllium in lithium slag according to any one of claims 1-3, characterized in that, In the step of mixing the solid-liquid mixture with the second leaching agent, The concentration of the second leaching agent is 10-15 g / L; the solid-liquid mixture is mixed with the second leaching agent at a liquid-solid ratio of (2.5-10):1 mL / g.

5. The use of the leaching agent for removing thallium and beryllium in lithium residue according to any one of claims 1-3, characterized in that, The step of performing second leaching comprises leaching for 2-3 h under the conditions that the temperature of the mixed solution is 30-60°C and the stirring speed is 200-300 rpm.

6. The use of the leaching agent for removing thallium and beryllium in lithium residue according to claim 1, characterized in that, The reducing agent comprises an inorganic reducing agent and an organic reducing agent; The inorganic reducing agent is ferrous chloride, and the organic reducing agent is thiourea; the mass ratio of the inorganic reducing agent to the organic reducing agent is 5-15:

1.

7. The use of the leaching agent for removing thallium and beryllium in lithium residue according to claim 1, characterized in that, The first leaching agent is a mixed organic acid of formic acid and acetic acid, and the concentration ratio of the formic acid to the acetic acid is 5-10:1; the second leaching agent comprises ferrous chloride and thiourea; the mass ratio of the ferrous chloride to the thiourea is 5-10:1.

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