Method for removing thallium and beryllium in lithium slag harmless treatment

Abstract

The present application is to provide a harmless treatment method for removing thallium and beryllium from lithium residue, which overcomes the above-mentioned difficulties. The method uses waste lithium residue after lithium extraction from lepidolite as the main raw material, adopts a combination of ball milling machinery and chemical treatment with chemical reagents, further grinds and crushes the waste lithium residue, increases the surface area of the waste lithium residue to make the subsequent stabilization reaction more thorough, releases the soluble salts of potassium, sodium, beryllium and thallium wrapped by the waste lithium residue, and makes them dissolve into water during washing. At the same time, the mechanical ball milling can convert a part of insoluble lithium into soluble lithium to increase the recovery rate of metallic lithium. Through water washing and spray washing, harmful elements such as beryllium and thallium in the waste lithium residue are removed, so that the treated lithium residue meets the standards for beryllium and thallium. The content of beryllium and thallium in the treated lithium residue is as follows: Tl < 0.01 mg / L, Be < 0.02 mg / L. It is beneficial to resource utilization, more environmentally friendly and safer, and realizes the reuse of waste lithium residue.

Description

Technical Field

[0001] The present invention relates to the field of harmless treatment of waste lithium slag, in particular to a method for harmless treatment of waste lithium slag after lithium extraction, namely a method for harmless treatment of lithium slag to remove thallium and beryllium. Background Art

[0002] With lithium becoming a key raw material for new energy lithium batteries, the lithium-ion battery industry has experienced explosive growth. Due to my country's abundant lithium ore reserves, the mining and smelting of lithium ore resources have also seen unprecedented development. However, while lithium extraction meets the demand for lithium-ion battery development, the continued growth and expansion of mining and smelting have led to an increasing impact on the environment and resources. The waste lithium slag generated after lithium mining and smelting, particularly the presence of heavy metals such as beryllium and thallium, has a significant impact on the social environment. If the content of these heavy metals in the waste lithium slag after lithium extraction using lepidolite is too high, it may become a hazardous solid waste, rather than a standard solid waste. This poses significant risks to the storage sites and surrounding environment. Therefore, it is imperative to remove or reduce the content of heavy metals such as beryllium and thallium in the waste lithium slag after lithium extraction.

[0003] Yichun, known as the "Lithium Capital of Asia," boasts a lithium battery industry that is a pillar of the city. With the city's increasing lithium carbonate production, the development and utilization of lepidolite is also expanding. Yichun's lithium carbonate production is projected to reach 500,000 tons by 2025, generating approximately 15 million tons of lithium slag, or waste lithium slag. Testing by relevant departments has revealed that the city's lithium slag contains a variety of elements, including silicon, rubidium, cesium, sodium, and potassium, making it a crucial material for the production of specialty glass, single-crystal silicon, photoelectric tubes, and other products. However, due to the inherent composition of lepidolite ore, lithium slag also contains trace amounts of beryllium and thallium, often exceeding permitted levels. Heavy metals such as beryllium and thallium, and their compounds, are highly polluting and pose a significant risk to human health. Therefore, the high or low levels of beryllium and thallium in waste lithium slag limit its application, necessitating the decontamination of lithium slag containing beryllium and thallium. However, existing technologies for the treatment of waste lithium slag containing beryllium and thallium are relatively limited. Currently, waste lithium slag is only temporarily stored in warehouses, but this method has the disadvantages of large land occupation and potential secondary pollution. Therefore, harmless and environmentally friendly treatment of beryllium and thallium in lithium slag is of great significance to the healthy development of the lithium extraction industry from lepidolite.

[0004] Chinese patent publication number CN118045850A discloses a method for treating heavy metals in lithium ore tailings. The method comprises the following steps: Step a: adding water to a synthesized reagent A to the crushed and screened slag, mixing it uniformly and adsorbing it, followed by curing for three to six hours; Step b: adding reagent B to the previous step to complex the ore slag with the surface of a network polymer, mixing it with the treated material for uniform adsorption, and curing for three to six hours; Step c: after treatment, using a horizontal oscillation method to perform solid-liquid separation and sample water for testing the ore slag ion concentration. In Step a, the slag is first collected and stored in a container, and then the slag in the container is placed in a crusher for pulverization. The method for treating ore slag in the present invention is highly efficient.

[0005] The disclosed technical solution is a method for treating heavy metals in processed lithium ore tailings, specifically treating beryllium and thallium in tailings from lithium concentrate flotation from raw lepidolite ore. The beryllium and thallium content in these tailings is relatively low, rather than harmlessly removing beryllium and thallium from lithium waste residues extracted from lithium ore or lepidolite ore through calcination and leaching. Furthermore, the aforementioned treatment process is relatively complex and expensive.

[0006] Therefore, how to provide a method for harmlessly treating lithium slag to remove thallium and beryllium? Using the waste lithium slag after lithium extraction from lepidolite as the main raw material, ball milling machinery and chemical agent addition methods are used. By further grinding and crushing the waste lithium slag, the surface area of ​​the waste lithium slag is increased, making the subsequent stabilization mixing reaction more thorough, and at the same time releasing the soluble salts of potassium, sodium, beryllium, and thallium wrapped in the waste lithium slag, so that they can be dissolved in water during stirring and washing; at the same time, mechanical ball milling can convert a portion of insoluble lithium into soluble lithium, increasing the recovery rate of metallic lithium, which is beneficial to resource utilization. Then, a chemical precipitation reagent is added to precipitate beryllium and thallium, and after filtration, solid waste slag is formed for hazardous waste treatment. The utilization rate of waste lithium slag is improved, thereby reducing the production cost of lithium extraction and making effective use of resources. Summary of the Invention

[0007] The present invention aims to provide a method for harmlessly treating lithium slag to remove thallium and beryllium, overcoming the above difficulties. The method uses waste lithium slag after lithium extraction from lepidolite as the main raw material, adopts a ball milling machine combined with chemical treatment processes such as adding chemical agents, and further grinds and crushes the waste lithium slag to increase the surface area of ​​the waste lithium slag, making the subsequent stabilization reaction more thorough, and at the same time releases soluble salts of potassium, sodium, beryllium, and thallium wrapped in the waste lithium slag so that they can be dissolved in water during stirring and washing; at the same time, mechanical ball milling can convert a portion of insoluble lithium into soluble lithium to increase the recovery rate of metallic lithium, and water washing and spray washing can remove harmful elements such as beryllium and thallium in the waste lithium slag, which is conducive to resource utilization; more environmentally friendly and safer; and at the same time, the waste lithium slag can be reused.

[0008] The present invention discloses a method for harmlessly treating lithium slag to remove thallium and beryllium, which uses waste lithium slag after lithium extraction as raw material and comprises:

[0009] 1) ball milling, wherein the waste lithium slag and the alkaline agent are first fully mixed to obtain a mixed solution of the waste lithium slag and the alkaline agent; the mixed solution of the waste lithium slag and the alkaline agent is placed in a ball milling device for ball milling to obtain a ball milled mixture of the waste lithium slag and the alkaline agent;

[0010] 2) washing, adding a hot aqueous solution to the mixture of the waste lithium slag and the alkaline agent ball milled in step 1), and fully stirring and washing under alkaline conditions, and filtering to obtain the stirred and washed lithium slag and the stirred and washed liquid;

[0011] 3) multi-stage spray filtration, using a spray device to spray the washed lithium slag in step 2) with spray water to significantly reduce the beryllium and thallium content in the washed lithium slag, thereby obtaining a spray washing liquid and a spray filter residue;

[0012] 4) Stabilization treatment: adding a stabilizing agent to the spray residue from step 3) and performing a mixing reaction while continuously stirring and mixing; after the mixing reaction is completed, washing with hot water and filtering to obtain a filter residue and a filtrate;

[0013] 5) Harmless beryllium and thallium removal treatment: after collecting the stirring washing liquid, the spray washing liquid and the filtrate, a precipitation reagent X is added thereto, and after sufficient stirring and mixing, the beryllium and thallium removal treatment is performed; after the beryllium and thallium enriched in the solution are precipitated, the solid-liquid separation is performed by a filter to obtain a beryllium and thallium-containing filter residue and a filtrate; wherein the separated beryllium and thallium-containing filter residue is collected as hazardous waste and handed over to a company with hazardous waste treatment qualifications for treatment, and the filtrate is recovered and used in the normal production process of lithium carbonate.

[0014] The method for harmlessly treating lithium slag to remove thallium and beryllium, in step 1), the alkaline agent is a mixture of sodium hydroxide and calcium hydroxide; the amount of alkaline agent added is controlled to be 0.5-5.5% of the mass of the waste lithium slag; and the pH of the mixed solution of the waste lithium slag and the alkaline agent is controlled to be 10-11.5.

[0015] The method for harmlessly treating lithium slag to remove thallium and beryllium is preferably as follows: in step 1), the liquid-solid ratio during ball milling is controlled to be 0.5:0.8-1, the ball milling time is controlled to be 1-2 hours, and the particle size of the solid phase waste lithium slag is controlled to be 80-150 mesh.

[0016] Furthermore, in step 2) washing, the temperature of the hot water for washing is controlled to be above 40° C., the stirring and washing time is controlled to be above 10 minutes per time, and the above stirring and washing operation is repeated several times; and each stirring and washing is controlled to be carried out under weak alkaline conditions so that the beryllium and thallium in the waste lithium slag can enter the stirring and washing liquid as much as possible.

[0017] In the method for harmless treatment of lithium slag to remove thallium and beryllium, in step 3), the spray water is condensed hot water and other recycled water, and the stirred and washed lithium slag is sprayed and washed at a fixed distance, and the spray water temperature is controlled at 40-60°C, and the number of spray washing is controlled at 10-15 times.

[0018] The method for harmlessly treating lithium slag to remove thallium and beryllium, wherein in step 4) the stabilizing agent is a mixture of phosphate and silicate; the phosphate is trisodium phosphate and / or disodium phosphate, and the silicate is sodium silicate; the amount of the stabilizing agent added is controlled to be 20-50 kg per 1000 kg of waste lithium slag; and the mixing reaction time is controlled to be 1-4 hours.

[0019] In the method for harmlessly treating lithium slag to remove thallium and beryllium, in step 5), the precipitation reagent X is sodium sulfide or hydrogen sulfide solution.

[0020] Furthermore, the stabilizing agent is a mixture of phosphate and silicate in a mass ratio of 2-5:95-98.

[0021] The present invention discloses a method for harmlessly treating lithium slag to remove thallium and beryllium. The production process is briefly described as follows: mixing waste lithium slag with an alkaline agent → preparing a mixed solution of the waste lithium slag and the alkaline agent → wet ball milling → slurrying → multi-stage stirring and washing of the slurry → filtration and separation → stirring and washing the lithium slag → multi-stage spraying → filtration → stabilization treatment → stirring and washing liquid, spraying washing liquid and precipitation reagent X → treating thallium and beryllium-containing sludge as hazardous waste, and recycling other filtrate for reuse.

[0022] The present invention discloses a method for harmlessly treating lithium slag to remove thallium and beryllium, and explores a new green and innovative path for harmless treatment of beryllium and thallium in lithium slag with dual control of "washing first and stabilizing later". After repeated testing and verification by a third party, the purpose of the present invention of significantly removing harmful metal elements such as beryllium and thallium from waste lithium slag after lithium extraction has been achieved, and at the same time, the metal elements such as lithium in the waste lithium slag can be further recovered. When the waste lithium slag is tested for leaching toxicity, the technical effects include thallium <0.01mg / L, beryllium <0.02mg / L, and fluorine <100mg / L. The content of thallium and beryllium in the above-mentioned treated waste lithium slag is within the above-mentioned range, which meets the requirements of general solid waste.

[0023] The present invention discloses a method for harmlessly treating lithium slag to remove thallium and beryllium. The basic principle of removing beryllium and thallium from waste lithium slag is mainly the process of double salt precipitation and lattice transformation into mineralization. The treated beryllium and thallium elements exist in the natural mineral phase and have long-term ultra-stability. When the treated lithium slag is subjected to toxic leaching, the beryllium and thallium meet the general solid waste standards. The main reaction formula is:

[0024] Tl 3+ +PO4 3- =TlPO4↓

[0025] Be 2+ +2SiO2+Al203+CaO = BeAl2Si2O8+Ca 2+

[0026] BeM+2SiO2+Al203+CaO = BeAl2Si2O8+CaM

[0027] Among them, M is SO4 2- OH - 、F - 、Cl - One or more of the anions.

[0028] Lithium slag washing filtrate precipitation to remove beryllium and thallium: The filtrate (brine) after the solid-liquid separation of lithium slag washing is precipitated to remove beryllium and thallium sludge, which solves the beryllium "export" problem for the harmless treatment cycle of lithium slag. The main reaction formula is:

[0029] Be 2+ +S 2- = BeS↓

[0030] 2Tl 3+ +3S 2- = Tl2S3↓

[0031] The present invention discloses a method for harmlessly treating lithium slag to remove thallium and beryllium. The method uses a water washing + stabilization treatment process to treat lithium slag, also known as waste lithium slag, and can solve the problem of excessive beryllium and beryllium in lithium slag with the effect of dual protection. First, water washing dissolves the soluble beryllium and beryllium in the lithium slag into water, thereby reducing the amount of beryllium and beryllium in the lithium slag. Second, the undissolved and remaining beryllium and beryllium react with an excess of stabilizing agents to produce double salt precipitation, lattice transformation, and mineralization into a natural mineral phase at a temperature that ensures that the beryllium and beryllium content in the treated lithium slag meets the standard. In the leaching toxicity test, the beryllium and beryllium contents in the lithium slag treated by the present invention are as follows: Tl < 0.01 mg / L, Be < 0.02 mg / L.

[0032] The method disclosed in this invention for harmlessly removing thallium and beryllium from lithium slag, also known as waste lithium slag, was used to harmlessly remove thallium and beryllium from lithium slag extracted from lepidolite. The results were tested by a testing team of the Jiangxi Provincial Geological Bureau for specific hazard identification testing, and all met the requirements, namely, they all met general solid waste standards. The specific results are as follows:

[0033] Report number: Environmental Inspection No. 2024-0962,

[0034] Sample name: lithium slag or waste lithium slag,

[0035] Submitting unit for inspection: Inventor's company,

[0036] Sample state: solid

[0037] Standard method and number for testing: Table 1

[0038]

[0039] Note: The test results in the following examples were all carried out according to the above basis, standards and methods.

[0040] The following waste lithium slag after treatment is tested according to GB5085.6-2007, Identification Standard for Hazardous Wastes, Requirements for Identification of Toxic Substance Content and GB5085.3-2007, Identification Standard for Hazardous Wastes, Requirements for Identification of Toxic Substance Content. DETAILED DESCRIPTION

[0041] The specific technical solutions of the present invention are further described in detail below with reference to the examples. The components mentioned in the examples are expressed in parts by mass or mass ratios, and the concentrations mentioned are all expressed in mass concentrations. The lithium slag used in the examples of the present invention is lithium slag or waste lithium slag after lithium extraction from solid lithium-containing raw materials such as lepidolite or spodumene. All raw material components in the following examples can be obtained commercially.

[0042] The present invention discloses a method for harmlessly treating lithium slag to remove thallium and beryllium. The method uses waste lithium slag after lithium extraction as raw material and is carried out as follows: 1) ball milling, wherein the waste lithium slag is first fully mixed with an alkaline agent, wherein the alkaline agent is a mixture of sodium hydroxide and calcium hydroxide; the amount of the alkaline agent added is controlled to be 0.5-5.5% of the mass of the waste lithium slag; and the pH of the mixed solution of the waste lithium slag and the alkaline agent is controlled to be 11.48; the mixed solution of the waste lithium slag and the alkaline agent is placed in a ball milling device for ball milling treatment; at the same time, the liquid-solid ratio during ball milling is controlled to be 0.5:0.8-1, the ball milling time is controlled to be 1-2 hours, and the particle size of the solid phase waste lithium slag is controlled to be 80-150 mesh, thereby obtaining a ball milled mixture of the waste lithium slag and the alkaline agent;

[0043] 2) washing, adding a hot water solution to the ball-milled mixture of the waste lithium slag and the alkaline agent in step 1), and performing sufficient stirring and washing under alkaline conditions, that is, controlling the temperature of the hot water for washing to be above 40° C., controlling the stirring and washing time to be about 10 minutes per time, and repeating the above stirring and washing operation several times; in this embodiment, the stirring and washing is determined to be 10-15 times based on the test results, and each stirring and washing is controlled to be performed under weak alkaline conditions, so that beryllium and thallium in the waste lithium slag enter the stirring and washing solution as much as possible, and filtering to obtain the stirred and washed lithium slag and the stirring and washing solution;

[0044] 3) multi-stage spray filtration, wherein the stirred and washed lithium slag from step 2) is spray-washed using a spray device with spray water to significantly reduce the beryllium and thallium content in the washed lithium slag, or stirred and washed lithium slag. The spray water is condensed hot water and other recycled water. The stirred and washed lithium slag is spray-washed at a fixed distance, and the spray water temperature is controlled at 40-60° C., and the number of spray washings is controlled at 10-15 times to obtain a spray washing liquid and a spray filter residue.

[0045] 4) Stabilization treatment: Add a stabilizing agent to the spray residue from step 3) and perform a mixing reaction while stirring continuously. After the mixing reaction, wash with hot water. The stabilizing agent is a mixture of phosphate and silicate; the phosphate is trisodium phosphate and / or disodium phosphate, and the silicate is sodium silicate. The amount of stabilizing agent added is controlled to be 25 kg per 1000 kg of waste lithium residue. The stabilizing agent is a mixture of phosphate and silicate in a mass ratio of 2-5:98-95. The mixing reaction time is controlled to be 1-4 hours. Filter to obtain the filter residue and filtrate.

[0046] 5) Harmless beryllium and thallium removal treatment: After collecting the stirring and spraying washing liquid and the filtrate, add a precipitating agent X to them, stir and mix thoroughly, and then remove beryllium and thallium. After the beryllium and thallium enriched in the solution are precipitated, pass through a filter to separate the solid and liquid to obtain a beryllium and thallium-containing filter residue and a filtrate. The precipitating agent X is sodium sulfide or hydrogen sulfide solution. The amount of precipitating agent X sodium sulfide or hydrogen sulfide solution added is controlled to ensure that the thallium and beryllium in the mixed solution of the stirring and spraying washing liquid and the filtrate are completely converted into sulfide salts. After precipitation, they are filtered into the filter residue and collected as hazardous waste for treatment. The filtrate obtained by filtration is tested for thallium and beryllium meeting the requirements and is recycled after recovery. The separated beryllium and thallium-containing filter residue is collected as hazardous waste and handed over to a company with hazardous waste treatment qualifications for treatment. The filtrate is recovered and used in the normal lithium carbonate production process. Example

[0047] This embodiment discloses a method for harmlessly treating lithium slag to remove thallium and beryllium, which uses waste lithium slag after lithium extraction as raw material. The contents of thallium and beryllium in the raw material are as shown in the following table:

[0048] It is carried out according to the following method and steps: the raw material used in this embodiment is the waste lithium slag produced by the enterprise after lithium extraction, and its main chemical composition is shown in Table 2 below, and the remainder is others.

[0049] Table 2 takes the waste lithium slag after lithium extraction as raw material, report number: environmental inspection word 2024-0962;

[0050]

[0051] Note: 1. Mass concentration limits of hazardous components in the leachate (mg / L): Be (mg / L): 0.02, fluoride ion: 100 mg / L.

[0052] 2. Detection method and basis The detection method and equipment are as described in Table 1 above.

[0053] The lithium slag raw materials described in Table 2 above are subjected to harmless treatment to remove thallium, beryllium and other harmful substances such as fluorine, etc., according to the following method: 1) ball milling, the waste lithium slag and the alkaline agent are first fully mixed to obtain a mixed solution of the waste lithium slag and the alkaline agent; the mixed solution of the waste lithium slag and the alkaline agent is placed in a ball milling device for ball milling treatment, wherein the alkaline agent is a mixture of sodium hydroxide and calcium hydroxide in a mass ratio of 50% each; the amount of the alkaline agent added is controlled to be 2.5-3.5% of the mass of the waste lithium slag; and the pH of the mixed solution of the waste lithium slag and the alkaline agent is controlled to be 10-11.5; at the same time, the liquid-solid ratio during ball milling is controlled to be 0.5:0.8, the ball milling time is controlled to be 1-2 hours, and the particle size of the solid phase waste lithium slag is controlled to be 80-150 mesh, thereby obtaining a ball milled mixture of the waste lithium slag and the alkaline agent;

[0054] 2) Washing: Add a hot water solution to the ball-milled mixture of the waste lithium slag and the alkaline agent in step 1), and perform sufficient stirring and washing under alkaline conditions. That is, the washing is performed by controlling the temperature of the hot water for washing to be above 40° C., controlling the stirring and washing time to be above 10 minutes per time, and repeating the above stirring and washing operation several times. In this example, the number of washings is 11, and each stirring and washing is performed under weakly alkaline conditions, that is, the pH is between 10 and 11, so that the beryllium and thallium in the waste lithium slag can enter the stirring and washing liquid as much as possible, and filtering to obtain the stirred and washed lithium slag and the stirring and washing liquid.

[0055] 3) multi-stage spray filtration, spray washing the stirred and washed lithium slag from step 2) using a spray device with spray water, so as to significantly reduce the beryllium and thallium content in the stirred and washed lithium slag, wherein the spray water is condensed hot water and other recycled water, and the stirred and washed lithium slag is spray washed at a fixed distance, and the spray water temperature is controlled at about 45° C., and the number of spray washings is controlled at 11 times; thereby obtaining a spray washing liquid and a spray filter residue;

[0056] 4) Stabilization treatment: Add a stabilizing agent to the spray residue from step 3) and allow a mixing reaction to proceed while stirring. After the mixing reaction is complete, wash with hot water. The stabilizing agent is a mixture of phosphate and silicate; the phosphate is trisodium phosphate, and the silicate is sodium silicate. The amount of stabilizing agent added is controlled to be 25 kg per 1000 kg of waste lithium residue; the stabilizing agent is a mixture of phosphate and silicate in a mass ratio of 5:95. The mixing reaction time is controlled to be 1-4 hours. Filter to obtain a filter residue and a filtrate.

[0057] The contents of the main harmful substances thallium and beryllium in the mixed liquid, i.e. the stirring washing liquid, the spray washing liquid and the filtrate, are as shown in Table 3:

[0058]

[0059] 6) Harmless beryllium and thallium removal treatment: After collecting the agitation and spray washing liquid and the filtrate, add a precipitating agent X to them, stir and mix thoroughly, and then remove beryllium and thallium. After precipitating the beryllium and thallium enriched in the solution, pass through a filter to separate the solid and liquid to obtain a beryllium and thallium-containing filter residue and a filtrate. The precipitating agent X is a sodium sulfide solution. The amount of the precipitating agent X sodium sulfide solution added is controlled to ensure that the thallium and beryllium in the mixed solution of the agitation and spray washing liquid and the filtrate are completely converted into sulfide salts, namely thallium sulfide and beryllium sulfide. After precipitation, they are filtered into the filter residue and collected as hazardous waste for treatment. The filtrate obtained by filtration is tested for thallium and beryllium meeting the requirements and is recycled after recovery. The separated beryllium and thallium-containing filter residue is collected as hazardous waste and handed over to a company with hazardous waste treatment qualifications for treatment. The filtrate is recovered and used in the normal lithium carbonate production process.

[0060] Most of the filter residues treated by the above method are harmless lithium residues, while a small part of the filter residues containing beryllium and thallium are treated as hazardous waste. The content of harmful substances thallium and beryllium in the harmless lithium residues is tested by a third-party environmental protection testing agency, as shown in Table 4 below:

[0061] Test results, report number: Environmental Inspection No. 2024-0962, Table 4

[0062]

[0063] Note: 1. In Table 4 above, ND means that it is not detected within the above-mentioned detection value, which means it is below the detection limit. Thallium is also greatly reduced in the lithium slag after harmless treatment, which meets the current national environmental protection conditions and requirements. It will not have an impact on the environment. That is to say, after the waste lithium slag is harmlessly treated to remove thallium and beryllium by the method of the present invention, the thallium and beryllium content in the treated filter residue, i.e., the harmless lithium slag, is greatly reduced. The waste lithium slag implemented in this invention is in accordance with GB5085.6-2007, Hazardous Waste Identification Standard, Toxic Substance Content Identification Requirements and GB5085.3-2007, Hazardous Waste Identification Standard, Toxic Substance Content Identification Requirements. It is tested by relevant third-party agencies. Example

[0064] Except for the following description, the remaining details in the following embodiment 2 are the same as those in the embodiment 1.

[0065] It is carried out according to the following method and steps: the raw material used in this embodiment is the waste lithium slag produced by the enterprise after lithium extraction, and its main chemical composition is shown in Table 5 below, and the remainder is others.

[0066] Table 5 takes the waste lithium slag after lithium extraction as raw material, report number: environmental inspection word 2024-0962;

[0067]

[0068] Note: 1. Mass concentration limits of hazardous components in the leachate (mg / L): Be (mg / L): 0.02, fluoride ion: 100 mg / L.

[0069] 2. Detection method and basis The detection method and equipment are as described in Table 1 above.

[0070] The lithium slag raw materials described in Table 5 above are subjected to harmless treatment to remove thallium, beryllium and other harmful substances such as fluorine, etc., according to the following method: 1) ball milling, the waste lithium slag and the alkaline agent are first fully mixed to obtain a mixed solution of the waste lithium slag and the alkaline agent; the mixed solution of the waste lithium slag and the alkaline agent is placed in a ball milling device for ball milling treatment, wherein the alkaline agent is a mixture of sodium hydroxide and calcium hydroxide at a mass ratio of 50% each; the amount of the alkaline agent added is controlled to be 1.5-2.5% of the mass of the waste lithium slag; and the pH of the mixed solution of the waste lithium slag and the alkaline agent is controlled to be 10-11.5; the waste lithium slag and the alkaline agent are ball milled into a mixture; at the same time, the liquid-solid ratio during ball milling is controlled to be 0.5:1, the ball milling time is controlled to be 1-2 hours, and the particle size of the solid phase waste lithium slag is controlled to be 80-150 mesh.

[0071] 2) washing, adding a hot water solution to the ball-milled mixture of the waste lithium slag and the alkaline agent in step 1), and fully stirring and washing under alkaline conditions, that is, the washing is performed by controlling the temperature of the hot water for washing to be above 48° C., controlling the stirring and washing time to be above 10 minutes per time, and repeating the above stirring and washing operation several times; the number of washing times is 13, and each stirring and washing is controlled to be performed under weak alkaline conditions, so that beryllium and thallium in the waste lithium slag enter the stirring and washing liquid as much as possible, and filtering to obtain the stirred and washed lithium slag and the stirring and washing liquid.

[0072] 3) multi-stage spray filtration, spray washing the stirred and washed lithium slag from step 2) using a spray device with spray water to significantly reduce the beryllium and thallium content in the washed lithium slag, wherein the spray water is condensed hot water and other recycled water, and the stirred and washed lithium slag is spray washed at a fixed distance, and the spray water temperature is controlled at about 48° C., and the number of spray washings is controlled at 13 times; thereby obtaining a spray washing liquid and a spray filter residue;

[0073] 4) Stabilization treatment: Add a stabilizing agent to the spray residue from step 3) and allow a mixing reaction to proceed while stirring. After the mixing reaction is complete, wash the residue with hot water. The stabilizing agent is a mixture of phosphate and silicate; the phosphate is trisodium phosphate, and the silicate is sodium silicate. The amount of stabilizing agent added is controlled to be 35 kg per 1000 kg of waste lithium residue; the stabilizing agent is a mixture of phosphate and silicate in a mass ratio of 2:98. The mixing reaction time is controlled to be 1-4 hours. Filter to obtain the residue and filtrate.

[0074] The contents of the main harmful substances thallium and beryllium in the mixed liquid, i.e. the stirring washing liquid, the spray washing liquid and the filtrate, are as shown in Table 6:

[0075]

[0076] 7) Harmless beryllium and thallium removal treatment: After collecting the agitation and spray washing liquid and the filtrate, add a precipitating agent X to them, stir and mix thoroughly, and then remove beryllium and thallium. After the beryllium and thallium enriched in the solution are precipitated, the solid-liquid separation is carried out through a filter to obtain a beryllium and thallium-containing filter residue and a press filtrate; the precipitating agent X is a sodium sulfide solution; the amount of the precipitating agent X sodium sulfide solution added is controlled to ensure that the thallium and beryllium in the mixed solution of the agitation and spray washing liquid and the filtrate are completely converted into sulfide salts, which are then filtered into the filter residue after precipitation and collected as hazardous waste for treatment. The filtrate obtained by filtration is tested for thallium and beryllium meeting the requirements and is recycled after recovery; the separated beryllium and thallium-containing filter residue is collected as hazardous waste and handed over to a company with hazardous waste treatment qualifications for treatment, and the press filtrate is recovered and used in the normal lithium carbonate production process.

[0077] Most of the filter residues treated by the above method are harmless lithium residues, while a small part of the filter residues containing beryllium and thallium are treated as hazardous waste. The content of harmful substances thallium and beryllium in the harmless lithium residues is tested by a third-party environmental protection testing agency, as shown in Table 7 below:

[0078] Test results, report number: Environmental Inspection No. 2024-0962, Table 7

[0079]

[0080] Note: 1. In Table 7 above, ND means that it is not detected within the above-mentioned detection value, that is, it means that it is below the detection limit. The thallium content in the lithium slag after harmless treatment is also greatly reduced, that is, it meets the current national environmental protection conditions and requirements. It will not have an impact on the environment. That is to say, after the waste lithium slag is harmlessly treated to remove thallium and beryllium by the method of the present invention, the thallium and beryllium content in the treated filter residue, that is, the harmless lithium slag, is greatly reduced. The thallium and beryllium content in the harmless lithium slag after treatment by the present invention is Tl<0.01mg / L, Be<0.02mg / L, which is far lower than the above-mentioned harmless content requirements. Example

[0081] The unspecified parts of this embodiment are the same as those of embodiments 1 and 2, except that 4) stabilization treatment is performed by adding a stabilizing agent to the spray residue in step 3), and performing a mixing reaction under the premise of continuous stirring and mixing; after the mixing reaction is completed, washing is performed with hot water, and the stabilizing agent is a mixture of phosphate and silicate; the phosphate is a mixture of 70% trisodium phosphate and 30% disodium phosphate in percentage by mass, and the silicate is sodium silicate; the amount of the stabilizing agent added is controlled to add 45 kg of the stabilizing agent to every 1000 kg of waste lithium slag; the stabilizing agent is a mixture of phosphate and silicate in a mass ratio of 3:97. The mixing reaction time is controlled to be 3-4 hours. Filter to obtain the filter residue and filtrate. Step 5) is the same as in embodiment 2;

[0082] Most of the filter residues treated by the above method are harmless lithium residues, while a small part of the filter residues containing beryllium and thallium are treated as hazardous waste. The content of harmful substances thallium and beryllium in the harmless lithium residues is tested by a third-party environmental protection testing agency, as shown in Table 8 below:

[0083] Test results, report number: Environmental Inspection No. 2024-0962, Table 8

[0084]

[0085] Note: 1. In Table 8 above, "ND" indicates not detected within the aforementioned detection limits, meaning it is below the detection limit. Thallium levels in the harmlessly treated lithium slag are also significantly reduced, meeting current national environmental protection requirements. This indicates no environmental impact. This means that after the harmless removal of thallium and beryllium from waste lithium slag using the method of the present invention, the thallium and beryllium content in the treated filter residue, i.e., the harmless lithium slag, is significantly reduced.

[0086] The raw materials used in this comparative example are identical to those used in Example 1, but the treatment method employed is merely a mechanized treatment method such as washing and spraying. The thallium and beryllium contents in the treated lithium slag do not meet the harmless treatment requirements of Tl < 0.01 mg / L and Be < 0.02 mg / L.

[0087] Technical features not described in the present invention can be achieved through or by adopting existing technologies and will not be described in detail here.

Claims

1. A method for harmlessly treating lithium slag to remove thallium and beryllium, which uses waste lithium slag after lithium extraction as raw material, and is characterized by: include: 1) ball milling, wherein the waste lithium slag and the alkaline agent are first fully mixed to obtain a mixed solution of the waste lithium slag and the alkaline agent; the mixed solution of the waste lithium slag and the alkaline agent is placed in a ball milling device for ball milling to obtain a ball milled mixture of the waste lithium slag and the alkaline agent; 2) washing, adding a hot aqueous solution to the mixture of the waste lithium slag and the alkaline agent ball milled in step 1), and fully stirring and washing under alkaline conditions, and filtering to obtain the stirred and washed lithium slag and the stirred and washed liquid; 3) multi-stage spray filtration, using a spray device to spray the washed lithium slag in step 2) with spray water to significantly reduce the beryllium and thallium content in the washed lithium slag, thereby obtaining a spray washing liquid and a spray filter residue; 4) Stabilization treatment: adding a stabilizing agent to the spray residue from step 3) and performing a mixing reaction while continuously stirring and mixing; after the mixing reaction is completed, washing with hot water and filtering to obtain a filter residue and a filtrate; 5) Harmless beryllium and thallium removal treatment: after collecting the agitation and washing liquid, the spray washing liquid and the filtrate, a precipitation reagent X is added to the agitation and washing liquid, the spray washing liquid and the filtrate, and the beryllium and thallium removal treatment is performed after sufficient stirring and mixing. After the beryllium and thallium enriched in the solution are precipitated, solid-liquid separation is performed by a filter to obtain a beryllium- and thallium-containing filter residue and a filtrate; and the beryllium- and thallium-containing filter residue obtained by separation is collected as hazardous waste and handed over to a company with hazardous waste treatment qualifications for treatment, and the filtrate is recovered and used in the normal production process of lithium carbonate.

2. The method for harmlessly treating lithium slag to remove thallium and beryllium according to claim 1, wherein: In step 1), the alkaline agent is a mixture of sodium hydroxide and calcium hydroxide; the amount of the alkaline agent added is controlled to be 0.5-5.5% of the mass of the waste lithium slag; and the pH of the mixed solution of the waste lithium slag and the alkaline agent is controlled to be 10-11.

5.

3. The method for harmlessly treating lithium slag to remove thallium and beryllium according to claim 1, wherein: In step 1), the liquid-solid ratio during ball milling is controlled to be 0.5:0.8-1, the ball milling time is controlled to be 1-2 hours, and the ball milling is controlled to control the particle size of the solid phase waste lithium slag to be 80-150 meshes.

4. The method for harmlessly treating lithium slag to remove thallium and beryllium according to claim 1, wherein: In step 2) washing, the temperature of the hot water for washing is controlled to be above 40° C., the stirring and washing time is controlled to be above 10 minutes per time, and the above stirring and washing operation is repeated several times; and each stirring and washing is controlled to be carried out under weak alkaline conditions so that the beryllium and thallium in the waste lithium slag can enter the stirring and washing liquid as much as possible.

5. The method for harmlessly treating lithium slag to remove thallium and beryllium according to claim 1, wherein: Step 3) The spray water is condensed hot water and other recycled water, which is used to spray the stirred and washed lithium slag at a fixed distance, and the spray water temperature is controlled at 40-60°C, and the number of spray washing is controlled at 10-15 times.

6. The method for harmlessly treating lithium slag to remove thallium and beryllium according to claim 1, wherein: Step 4) The stabilizing agent is a mixture of phosphate and silicate; the phosphate is trisodium phosphate and / or disodium phosphate, and the silicate is sodium silicate; the amount of stabilizing agent added is controlled to be 20-50 kg per 1000 kg of waste lithium slag; and the mixing reaction time is controlled to be 1-4 hours.

7. The method for harmlessly treating lithium slag to remove thallium and beryllium according to claim 1, wherein: Step 5) The precipitation reagent X is sodium sulfide or hydrogen sulfide solution.

8. The method for harmlessly treating lithium slag to remove thallium and beryllium according to claim 6, wherein: The stabilizing agent is a mixture of phosphate and silicate in a mass ratio of 2-5:95-98.

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