A novel process for desulfurization of spodumene smelting slag using EDTA

Abstract

A novel process for desulfurizing spodumene smelting slag using EDTA is presented. This process uses the final solid waste obtained from the water leaching lithium extraction process after sulfuric acid roasting of spodumene as raw material. A prepared EDTA solution is added to the smelting slag containing approximately 10% calcium sulfate, allowing the raw material to fully react with the EDTA solution, thus achieving desulfurization of the smelting slag. Finally, the filtrate is subjected to rotary evaporation precipitation, and the EDTA solution is recovered and recycled. This process has high resource utilization, not only achieving 99.9% desulfurization of the smelting slag in a short time but also enabling the recycling of the EDTA solution. The desulfurization method provided by this process is highly efficient, simple, and transforms waste into valuable resources, increasing economic benefits. Furthermore, it effectively addresses the environmental compatibility issues of solid waste in the existing lithium mining industry, which is of great significance for the sustainable and high-quality development of the lithium battery industry.

Description

Technical Field

[0001] This application relates to the field of industrial solid waste recycling technology, and more specifically, to a new process for desulfurization of spodumene smelting slag using EDTA. Background Technology

[0002] Science and technology have always been the driving force for my country's high-quality development. In recent years, with the booming development of the new energy industry, my country's new energy electric vehicle industry has developed rapidly. In 2023, my country's new energy power battery production capacity accounted for 60% of the world's total, and its new energy vehicle production capacity has achieved a leapfrog development. Lithium, as a strategic metal, plays a huge role in the new energy field. Currently, the world's lithium product consumption continues to grow at a rate of 15% to 20% per year. Lithium-rich and economically valuable minerals such as lepidolite and spodumene have become important raw materials for lithium extraction. In 2023, more than 85% of my country's lithium salt products came from lithium ore. If the problem of lithium smelting slag recovery generated from ore lithium extraction is not properly handled, it may seriously restrict the production of lithium chemicals. Currently, in the context of the booming development of the lithium industry, how to deal with lithium smelting slag has become a bottleneck problem for the healthy development of the lithium industry.

[0003] The main chemical composition of lithium smelting slag is the decisive factor in determining its recycling or safe disposal process. Smelting slag produced by the spodumene sulfuric acid roasting method will be hindered from being used in building materials, cement, ceramics, road construction, mine restoration, agricultural silicon fertilizer and other fields due to its excessively high CaSO4·2H2O content.

[0004] EDTA (ethylenediaminetetraacetic acid) is a compound for Ca2+. 2+ It is a strong chelating agent with significant affinity because CaSO4·2H2O can dissolve well in EDTA solution to form a relatively stable EDTA calcium complex and SO4. 2- Finally, the EDTA solution can be recycled after recovery. After desulfurization treatment with EDTA, lithium smelting slag can become a useful resource that can be reused, which is of great significance to spodumene processing enterprises and the new energy vehicle industry, but so far there have been no reports of related industrial applications.

[0005] This invention utilizes the stability difference between EDTA calcium and CaSO4·2H2O to successfully remove CaSO4·2H2O from lithium smelting slag. This method is simple and easy to implement, has high resource utilization, produces no waste, and can turn waste into valuable resources, thus offering significant economic benefits. Summary of the Invention

[0006] This invention provides a novel process for desulfurizing spodumene smelting slag using EDTA. This process achieves 99.9% desulfurization of the smelting slag within a short time through a thorough reaction between the lithium smelting slag and EDTA solution. The filtrate is then recovered by rotary evaporation, resulting in high resource utilization and enabling the recycling of the EDTA solution. This desulfurization method is highly efficient, simple, and achieves high-value utilization of lithium smelting slag, effectively addressing the environmental compatibility issues of solid waste in the existing lithium mining industry. To achieve the above objectives, this invention adopts the following technical solution:

[0007] A novel process for desulfurization of spodumene smelting slag using EDTA includes the following steps:

[0008] I. Mix the dried spodumene smelting slag and EDTA solution at a certain solid-liquid ratio to prepare a slurry;

[0009] II. Stir the mixed slurry from step I at room temperature, and then separate the solid and liquid components of the slurry after a period of reaction to obtain unsaturated filtrate and filter cake after complete desulfurization.

[0010] III. Add a small amount of precipitant to the filtrate obtained in step II. If no white precipitate is formed, repeat steps I to II with the filtrate obtained in step II until a white precipitate is formed after adding a small amount of precipitant. Then stop repeating the experiment. The final solid-liquid separation will yield a saturated filtrate and a filter cake to be processed.

[0011] IV. Place the saturated filtrate from step III into a rotary evaporator for rotary evaporation to obtain CaSO4·2H2O precipitate and a recyclable EDTA solution.

[0012] In the novel process for desulfurization of spodumene smelting slag using EDTA as described above, preferably, the concentration of EDTA in step I is 0.01 mol / L to 0.3 mol / L.

[0013] In the novel process for desulfurization of spodumene smelting slag using EDTA as described above, preferably, the solid-liquid ratio in step I is 1:(5-60), and the slurry pH is 7-11.

[0014] In the novel process for desulfurization of spodumene smelting slag using EDTA as described above, preferably, the content of CaSO4·2H2O in the untreated spodumene smelting slag in step I is greater than 3%.

[0015] In the novel process for desulfurization of spodumene smelting slag using EDTA as described above, preferably, the slurry reaction time in step II is 4–48 h.

[0016] In the novel process for desulfurization of spodumene smelting slag using EDTA as described above, preferably, the precipitant in step III is one or a mixture of two or more of the following: sodium carbonate, potassium carbonate, ammonium carbonate, potassium dihydrogen phosphate, sodium dihydrogen phosphate, sodium monohydrogen phosphate, potassium phosphate, sodium phosphate, ammonium phosphate, trisodium phosphate, sodium trihydrogen phosphate, ammonium fluoride, sodium oxalate, potassium oxalate, ammonium oxalate, sodium silicate, potassium silicate, lithium silicate, ammonium silicate, sodium aluminum silicate, sodium tungstate, cobalt tungstate, ferrous tungstate, ammonium tungstate, zinc tungstate, sodium molybdate, potassium molybdate, sodium aluminate, potassium aluminate, ammonium aluminate, sodium iodide, and potassium iodide. The precipitant is required to be a clear solution within its solubility range.

[0017] In the novel process for desulfurizing spodumene smelting slag using EDTA as described above, preferably, the filter cake obtained in step III is the last filter cake obtained after multiple repeated experiments, which belongs to the smelting slag that has not been completely desulfurized, and steps I to II need to be repeated to obtain the smelting slag that has been completely desulfurized.

[0018] In the novel process for desulfurization of spodumene smelting slag using EDTA as described above, preferably, the rotary evaporation temperature in step IV is 50–100°C, and the reaction time is 0.15–1 h.

[0019] In the novel process for desulfurization of spodumene smelting slag using EDTA as described above, preferably, the EDTA solution obtained in step IV can be recycled in step I.

[0020] The present invention has the following advantages:

[0021] The beneficial effects of this invention are that the method uses EDTA complexation and rotary evaporation separation process to successfully achieve desulfurization of lithium smelting slag, while keeping the economic cost under control. This process is expected to alleviate the current situation of tailings accumulation in lithium mining enterprises, realize the high-value utilization of lithium smelting slag, and promote the sustainable and high-quality development of the lithium salt industry. Attached Figure Description

[0022] Figure 1 A flowchart for desulfurization of spodumene smelting slag using EDTA.

[0023] Figure 2 X-ray powder diffraction pattern of spodumene smelting slag.

[0024] Figure 3 X-ray powder diffraction pattern of desulfurized spodumene smelting slag. Detailed Implementation

[0025] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the invention.

[0026] Example 1

[0027] The spodumene smelting slag used in this embodiment is lithium extraction waste slag from a lithium carbonate processing enterprise in Jiangxi Province. Its chemical composition analysis results are shown in Table 1, and the X-ray powder diffraction pattern analysis is as follows: Figure 2 As shown.

[0028] Table 1. Chemical composition analysis results (wB%) of lithium extraction waste residue

[0029]

[0030] Dry spodumene smelting slag and 0.05 mol / L EDTA solution were mixed at a solid-liquid ratio of 1:20 to prepare a slurry. The pH of the slurry was adjusted to 8, and after stirring at room temperature for 12 hours, it was filtered to obtain a completely desulfurized filter cake and an unsaturated EDTA calcium filtrate. This filtrate and dry spodumene smelting slag were then mixed at a solid-liquid ratio of 1:20, and the pH was adjusted to 8. After stirring at room temperature for 12 hours, it was filtered to obtain a filtrate and a filter cake. At this point, 5 mL of the filtrate was taken, and 2 mL of 1 mol / L sodium carbonate solution was added. When a white precipitate appeared in the filtrate, all the filtrate was placed in a rotary evaporator and evaporated at 80℃ for 20 minutes. CaSO4·2H2O precipitated. The collected rotary evaporation liquid could be used for cyclic desulfurization. The filter cake from the first experiment was collected, indicating successfully desulfurized spodumene smelting slag. By comparing the composition with the original spodumene smelting slag, it was found that most of the CaSO4·2H2O component in the filter cake was effectively removed, as shown in Table 2.

[0031] Table 2. Chemical composition analysis results of the filter cake after impurity removal (wB%)

[0032]

[0033] Example 2

[0034] The spodumene smelting slag used in this embodiment is the same as that in Example 1.

[0035] Dry spodumene smelting slag and 0.15 mol / L EDTA solution were mixed at a solid-liquid ratio of 1:15 to prepare a slurry. The pH of the slurry was adjusted to 9. After stirring at room temperature for 6 hours, the mixture was filtered to obtain a fully desulfurized filter cake and an unsaturated filtrate. The filtrate and dry spodumene smelting slag were then subjected to the same reaction and filtration process at room temperature, with the solid-liquid ratio controlled at 1:15 and pH = 9. The filtrate and spodumene smelting slag were then reacted and filtered twice more at room temperature, yielding two filtrates and filter cakes. 10 mL of the last filtrate was taken and 2 mL of 0.4 mol / L ammonium carbonate solution was added. When a white precipitate appeared in the filtrate, the entire last filtrate was placed in a rotary evaporator and evaporated at 70°C for 15 minutes. CaSO4·2H2O precipitated as a precipitate. The collected rotary evaporation liquid could be used for cyclic desulfurization. The filter cakes from the first and second experiments were collected to determine the successfully desulfurized spodumene smelting slag. By comparing the composition with that of the original spodumene smelting slag, it can be found that most of the CaSO4·2H2O component in the filter cake was effectively removed, as shown in Table 3.

[0036] Table 3. Chemical composition analysis results of the filter cake after impurity removal (wB%)

[0037]

[0038] Example 3

[0039] The spodumene smelting slag used in this embodiment is the same as that in Example 1.

[0040] Dry spodumene smelting slag and 0.1 mol / L EDTA solution were mixed at a solid-liquid ratio of 1:30 to prepare a slurry. The pH of the slurry was adjusted to 10. After stirring at room temperature for 8 hours, the mixture was filtered to obtain a fully desulfurized filter cake and an unsaturated EDTA calcium filtrate. The filtrate and dry spodumene smelting slag were then subjected to the same reaction and filtration process at room temperature for three consecutive times, with filtrates and filter cakes obtained three times in total. At this point, 6 mL of the last filtrate was taken and 3 mL of 0.1 mol / L sodium oxalate solution was added. When a white precipitate appeared in the filtrate, the entire last filtrate was placed in a rotary evaporator and evaporated at 80℃ for 30 minutes. CaSO4·2H2O appeared as a precipitate. The collected rotary evaporation liquid could be used for cyclic desulfurization. The filter cakes collected from the first three experiments were the successfully desulfurized spodumene smelting slag. By comparing the composition with that of the original spodumene smelting slag, it can be found that most of the CaSO4·2H2O component in the filter cake was effectively removed, as shown in Table 4.

[0041] Table 4. Chemical composition analysis results of the filter cake after impurity removal (wB%)

[0042]

[0043] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for desulfurizing spodumene smelting slag using EDTA, characterized in that, The method includes the following steps: I. Mix dried spodumene smelting slag with a CaSO4·2H2O content greater than 1% with EDTA solution with a concentration of 0.001mol / L~0.5mol / L at a solid-liquid ratio of 1:(2~80) to prepare a slurry with a pH of 5~12. II. Stir the mixed slurry from step I at room temperature, and then separate the solid and liquid components of the slurry after a period of reaction to obtain unsaturated filtrate and filter cake after complete desulfurization. III. Repeat steps I to II with the filtrate obtained in step III. When a white precipitate appears after adding a small amount of precipitant to the filtrate, the experiment can be stopped. The final solid-liquid separation will yield a saturated filtrate and a filter cake to be processed. IV. Place the saturated filtrate from step III into a rotary evaporator for rotary evaporation to obtain CaSO4·2H2O precipitate and a recyclable EDTA solution.

2. The method for desulfurization of spodumene smelting slag using EDTA according to claim 1, characterized in that, The reaction time of the slurry in step II is 4~72h.

3. The method for desulfurization of spodumene smelting slag using EDTA according to claim 1, characterized in that, In step III, the precipitant is one or a mixture of two or more of the following: sodium carbonate, potassium carbonate, ammonium carbonate, potassium dihydrogen phosphate, sodium dihydrogen phosphate, potassium monohydrogen phosphate, sodium monohydrogen phosphate, potassium phosphate, sodium phosphate, ammonium phosphate, trisodium phosphate, sodium trihydrogen phosphate, ammonium fluoride, sodium oxalate, potassium oxalate, ammonium oxalate, sodium silicate, potassium silicate, lithium silicate, ammonium silicate, sodium aluminum silicate, sodium tungstate, cobalt tungstate, ferrous tungstate, ammonium tungstate, zinc tungstate, lead tungstate, sodium molybdate, potassium molybdate, sodium aluminate, potassium aluminate, ammonium aluminate, sodium iodide, and potassium iodide. The precipitant must be a clear solution within its solubility range.

4. The method for desulfurization of spodumene smelting slag using EDTA according to claim 1, characterized in that, The filter cake obtained in step III is the final filter cake obtained after multiple repeated experiments. It is a smelting slag that has not been completely desulfurized and needs to be repeated in steps I to II to obtain a completely desulfurized smelting slag.

5. The method for desulfurizing spodumene smelting slag using EDTA according to claim 1, wherein the rotary evaporation temperature in step IV is 50~100℃ and the reaction time is 0.1~2h.

6. The method for desulfurization of spodumene smelting slag using EDTA according to claim 1, characterized in that, The EDTA solution obtained in step IV can be recycled in step I.

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