Lithium slag autoclave leaching method

Abstract

The invention provides a lithium slag autoclaved leaching method. The lithium slag autoclaved leaching method comprises the following steps that S1, lithium slag and an acid solution are subjected to an autoclaved replacement reaction under saturated vapor pressure, and lithium leaching slag is obtained; the lithium slag is not in direct contact with the acid solution; and S2, the lithium leaching residues and water are mixed, pulped and filtered, and lithium-rich brine and leaching residues rich in silicon and aluminum are obtained. The lithium slag autoclave leaching method provided by the invention solves the problem that the high liquid-solid ratio restricts the treatment capacity under the hot pressing condition, and can effectively improve the acid leaching efficiency and reduce the acid and alkali consumption.

Description

Technical Field

[0001] The invention belongs to the field of comprehensive resource utilization of lithium slag, and particularly relates to a lithium slag autoclave leaching method. Background Art

[0002] Lithium slag is mainly leached slag produced by composite sulfate roasting and leaching of spodumene or lithium mica ore. The main components are aluminum sodium potassium silicate, calcium sulfate, cesium rubidium salt, and lithium-containing ore that is not fully sulfated, with a lithium content of 0.1%-0.2%. According to statistics, for every ton of lithium carbonate product produced, 30-40 tons of lithium slag will be produced. Although lithium slag is not acid-base corrosive, it contains soluble thallium, beryllium, etc., which poses a great risk of pollution to the environment. At the same time, the amount of lithium slag produced is huge, occupying a large amount of land resources, and there is an urgent need for stable and reliable bulk resource utilization technology. Therefore, the development of efficient lithium slag leaching technology is a hot spot and difficulty in research. Some studies have proposed a method of multi-step leaching of lithium slag with high liquid-solid specific heat acid, with a pH value controlled at 0-2 and a temperature at 60-65°C. The process is lengthy, the leaching pH value is low, and the acid consumption is large. There are also studies that provide a method for high liquid-solid ratio high-pressure alkaline leaching of mica ore, and then dilute acid leaching to extract lithium after high-pressure alkaline leaching. The parameters of high-pressure alkaline leaching in this process are unclear, but the acid and alkali consumption is large and the process is complicated. A study provides a method for hot-pressing leaching of lithium-containing materials with high liquid-solid ratio carbonate, with a temperature of 140-320°C and a reaction pressure of 0.6-12.5MPa. The process temperature is high and a pressure vessel is used, which is difficult to promote and apply on a large scale. There are also studies that propose a method for high liquid-solid ratio heat acid hot salt high-pressure leaching of lithium mica roasted material, using sodium chloride and hydrochloric acid as leaching agents, pH value controlled at 2-3, reaction temperature of 150-180°C, and reaction time of 4-8h. The leaching pH of this process is low, the temperature is high, the reaction time is too long, and the acid and alkali consumption is large. The above methods all use high liquid-solid ratio hot pressing conditions, or the pH value is too low, or the temperature is high, or the reaction time is long, and there are problems such as limited processing capacity, large acid and alkali consumption, and high energy consumption.

[0003] In summary, there is an urgent need to provide a method for comprehensively recovering calcium and arsenic from calcium arsenic slag with low energy consumption. Summary of the invention

[0004] The present invention aims to solve at least one of the above technical problems existing in the prior art. To this end, the present invention provides a lithium slag autoclave leaching method, which solves the problem that the high liquid-solid ratio under hot pressing conditions restricts the processing volume, can effectively improve the acid leaching efficiency, and reduce the acid and alkali consumption.

[0005] A first aspect of the present invention provides a lithium slag autoclave leaching method, comprising the following steps:

[0006] S1: subjecting lithium slag and acid solution to autoclave replacement reaction under saturated vapor pressure to obtain lithium leaching slag;

[0007] The lithium slag and the acid solution are not in direct contact;

[0008] S2: The lithium leaching residue is mixed with water, slurried, and filtered to obtain lithium-rich brine and silicon-aluminum-rich leaching residue.

[0009] The mechanism of the method is as follows:

[0010] The lithium slag and acid are subjected to autoclave replacement reaction under closed conditions, so that the lithium in the lithium slag is released by the action of concentrated acid, while avoiding the reaction of concentrated acid with lithium slag at room temperature to ensure the effectiveness and safety of the reaction. In the autoclave replacement reaction, the concentrated acid undergoes a replacement reaction with the lithium compounds (such as lithium aluminum minerals or lithium salts) in the lithium slag. The hydrogen ions (H + ) and lithium ions (Li + ) to react to form soluble lithium salts (such as LiCl, Li2SO4, etc.), while releasing other ions (such as sodium, potassium, calcium, etc.) that may also be reacted with anions in concentrated acid (such as chloride ions Cl-, sulfate ions SO4 2- 、Nitrate ion NO3 - etc.) to form other soluble salts. As the steam pressure of the autoclave replacement reaction increases, the reaction is accelerated, and the generation of steam provides sufficient energy to fully react the lithium compound with the acid, while helping to dissolve the generated lithium salt in the liquid phase. After the replacement reaction is completed, water is added and stirred to leach the reaction product. After the reaction is completed, water is added to dilute the reaction product. The addition of water helps to further dissolve and extract the lithium salt to form a lithium-rich brine solution, while the solid residue (such as silicon-aluminum-rich slag) is separated.

[0011] According to the embodiments of the first aspect of the present invention, there are at least the following beneficial effects:

[0012] In the present invention, the lithium slag is not in direct contact with the acid, so that the concentrated acid is prevented from reacting with the lithium slag at room temperature. The minimum amount of water is provided according to the filling degree of the material in the container to achieve the required saturated vapor pressure in the container. Comparative experiments have shown that the leaching effect of the autoclave replacement is more than 10% higher than that of the hydrothermal replacement at the same temperature and pressure. The autoclave leaching method solves the problem of the high liquid-solid ratio restricting the processing volume under hot pressure conditions, can effectively improve the acid leaching efficiency, and reduce the acid and alkali consumption.

[0013] According to some embodiments of the present invention, in step S1, the autoclave replacement reaction is performed under heating conditions.

[0014] According to some embodiments of the present invention, in step S1, the heating method includes at least one of electric heating, oil bath, microwave and electromagnetic heating.

[0015] According to some embodiments of the present invention, in step S1, the acid solution includes at least one of hydrochloric acid, sulfuric acid, and nitric acid.

[0016] According to some embodiments of the present invention, in step S1, when the acid solution is hydrochloric acid, the concentration is 36-38 wt %.

[0017] According to some embodiments of the present invention, in step S1, when the acid solution is sulfuric acid, the concentration is 96-98 wt %.

[0018] According to some embodiments of the present invention, in step S1, when the acid solution is nitric acid, the concentration is 68-70 wt %.

[0019] According to some embodiments of the present invention, in step S1, before the reaction, the step further includes adjusting the water content of the lithium slag to be no higher than 25%.

[0020] The above water content improves the solubility of lithium and other metal ions, promotes effective leaching reaction, maintains the stability of reaction conditions and avoids the occurrence of side reactions.

[0021] According to some embodiments of the present invention, in step S1, the regulated method includes wetting the surface of lithium slag particles with water.

[0022] Wetting the surface of lithium slag particles with water can improve reaction contact, improve fluidity and uniformity, enhance heat conduction and control reaction rate.

[0023] According to some embodiments of the present invention, in step S1, the mass ratio of the lithium slag to the acid solution is 1:002-0.1, based on the dry weight of the lithium slag.

[0024] According to some embodiments of the present invention, in step S1, the temperature of the autoclave replacement reaction is 100-120°C.

[0025] According to some embodiments of the present invention, in step S1, the time of the autoclave replacement reaction is 15-120 min.

[0026] According to some embodiments of the present invention, in step S1, the pH value of the lithium leaching residue is 3-4.

[0027] According to some embodiments of the present invention, in step S1, based on the dry weight of the lithium slag, the solid-to-liquid ratio of the lithium slag to the water is 1:(0.5-2).

[0028] According to some embodiments of the present invention, step S1 further includes adjusting the pH value of the lithium leaching residue to be above 4.

[0029] Under the above conditions, a pH value above 4 can effectively reduce the dissolution of fluorine, aluminum, etc., and ensure the purity of lithium-rich brine.

[0030] According to some embodiments of the present invention, the method further includes removing impurities from the lithium-rich brine.

[0031] According to some embodiments of the present invention, the method of removing impurities includes concentrating, removing impurities and extracting lithium.

[0032] According to some embodiments of the present invention, the step further includes adding silicon-aluminum-rich leached residue to step S1 for autoclaving replacement reaction.

[0033] In step S2, the lithium-rich brine can be further concentrated to remove impurities and extract lithium. After lithium extraction, the residual liquid is circulated for leaching, and the thallium, beryllium, sodium and potassium therein are enriched to a certain extent and then removed by step purification. After ball milling, the silicon-aluminum-rich slag is processed again through steps S1 and S2 to further improve the leaching rate of lithium. The leached slag finally obtained can be used as concrete aggregate, ceramic raw material, cement clinker raw material, etc. DETAILED DESCRIPTION

[0034] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0035] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0036] Unless otherwise specified, "room temperature" in the present invention means 25°C±5°C.

[0037] Unless otherwise specified, "about" in the present invention means that the allowable error is within ±2%.

[0038] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0039] A first aspect of the present invention provides a lithium slag autoclave leaching method, comprising the following steps:

[0040] S1: subjecting lithium slag and acid solution to autoclave replacement reaction under saturated vapor pressure to obtain lithium leaching slag;

[0041] The lithium slag and the acid solution are not in direct contact;

[0042] S2: The lithium leaching residue is mixed with water, slurried, and filtered to obtain lithium-rich brine and silicon-aluminum-rich leaching residue.

[0043] It should be noted that in view of the existing process, the use of high liquid-to-solid ratio hot pressing conditions, or too low pH value, or high temperature, or long reaction time, there are problems such as limited processing capacity, large acid and alkali consumption, and high energy consumption. The present invention conducts an autoclave replacement reaction between lithium slag and acid under closed conditions, so that the lithium in the lithium slag is released through the action of concentrated acid, while avoiding the reaction of concentrated acid with lithium slag at room temperature, thereby ensuring the effectiveness and safety of the reaction. Under the autoclave replacement reaction, the concentrated acid undergoes a replacement reaction with the lithium compound (such as lithium aluminum mineral or lithium salt) in the lithium slag. The hydrogen ions (H + ) and lithium ions (Li + ) to react and form soluble lithium salts (such as LiCl, Li2SO4, etc.), while releasing other ions (such as sodium, potassium, calcium, etc.) that may also be reacted with anions in concentrated acid (such as chloride ions Cl - 、Sulfate ion SO4 2- 、Nitrate ion NO3 - etc.) to form other soluble salts. As the steam pressure of the autoclave replacement reaction increases, the reaction is accelerated, and the generation of steam provides sufficient energy to fully react the lithium compound with the acid, while helping to dissolve the generated lithium salt in the liquid phase. After the replacement reaction is completed, water is added and stirred to leach the reaction product. After the reaction is completed, water is added to dilute the reaction product. The addition of water helps to further dissolve and extract the lithium salt to form a lithium-rich brine solution, while the solid residue (such as silicon-aluminum-rich slag) is separated.

[0044] In combination with the first aspect, in some embodiments of the present invention, in step S1, the autoclave replacement reaction is carried out under heating conditions.

[0045] In combination with the first aspect, in some embodiments of the present invention, in step S1, the heating method includes at least one of electric heating, oil bath, microwave and electromagnetic heating.

[0046] In combination with the first aspect, in some embodiments of the present invention, in step S1, the acid solution includes at least one of hydrochloric acid, sulfuric acid, and nitric acid.

[0047] In combination with the first aspect, in some embodiments of the present invention, in step S1, when the acid solution is hydrochloric acid, the concentration is 36-38 wt %.

[0048] In combination with the first aspect, in some embodiments of the present invention, in step S1, when the acid solution is sulfuric acid, the concentration is 96-98 wt %.

[0049] In combination with the first aspect, in some embodiments of the present invention, in step S1, when the acid solution is nitric acid, the concentration is 68-70 wt %.

[0050] In combination with the first aspect, in some embodiments of the present invention, in step S1, before the reaction, the step further includes adjusting the water content of the lithium slag to be no higher than 25%.

[0051] The above water content improves the solubility of lithium and other metal ions, promotes effective leaching reaction, maintains the stability of reaction conditions and avoids the occurrence of side reactions.

[0052] In combination with the first aspect, in some embodiments of the present invention, in step S1, the regulated method includes wetting the surface of lithium slag particles with water.

[0053] Wetting the surface of lithium slag particles with water can improve reaction contact, improve fluidity and uniformity, enhance heat conduction and control reaction rate.

[0054] In combination with the first aspect, in some embodiments of the present invention, in step S1, the mass ratio of the lithium slag to the acid solution is 1:002-0.1, based on the dry weight of the lithium slag.

[0055] In combination with the first aspect, in some embodiments of the present invention, in step S1, the temperature of the autoclave replacement reaction is 100-120° C.; and / or the time of the autoclave replacement reaction is 15-120 min.

[0056] In combination with the first aspect, in some embodiments of the present invention, in step S1, the pH value of the lithium leaching residue is 3-4.

[0057] In combination with the first aspect, in some embodiments of the present invention, in step S1, based on the dry weight of the lithium slag, the solid-to-liquid ratio of the lithium slag to the water is 1:(0.5-2).

[0058] In combination with the first aspect, in some embodiments of the present invention, step S1 further includes adjusting the pH value of the lithium leaching residue to be above 4.

[0059] Under the above conditions, the purification of silicon and aluminum in lithium-rich brine was achieved. At the same time, under the same conditions, the pH of the leaching slurry produced by the conventional leaching method was lower than the pH of the lithium leaching residue after the autoclave replacement reaction in the present invention, indicating that under the saturated autoclave environment, replacement reactions such as hydrogen and lithium are more effective and thorough.

[0060] In combination with the first aspect, in some embodiments of the present invention, the lithium-rich brine is further removed from the lithium-rich brine.

[0061] In combination with the first aspect, in some embodiments of the present invention, the method of removing impurities includes concentrating, removing impurities and extracting lithium.

[0062] In combination with the first aspect, in some embodiments of the present invention, the method further includes adding silicon-aluminum-rich leached residue to step S1 for autoclaving replacement reaction.

[0063] Combined with the first aspect, in some embodiments of the present invention, in step S2, the lithium-rich brine can be further concentrated to remove impurities and extract lithium, and the residual liquid after lithium extraction is circulated for leaching, and the thallium, beryllium, sodium and potassium therein are enriched to a certain extent and then removed by step purification. After ball milling, the silicon-aluminum-rich slag is processed again through steps S1 and S2 to further improve the leaching rate of lithium, and the leached slag finally obtained can be used as concrete aggregate, ceramic raw material, cement clinker raw material, etc.

[0064] Example 1

[0065] This embodiment provides a lithium slag autoclave leaching method, specifically:

[0066] S1: Weigh 200g of lithium slag from a certain enterprise in Jiangxi, adjust the water content of the lithium slag to 25%, transfer it into a 1L pressure vessel, add 15g of concentrated hydrochloric acid (mass concentration 68%) into the container, the concentrated hydrochloric acid is at the bottom of the lithium slag, and the two are not in direct contact, add 10mL of deionized water to form saturated vapor pressure in the container, cover the container, heat it in an oil bath to 105°C, and keep the temperature and pressure for 15min to carry out the replacement reaction;

[0067] S2: After the reaction, add 750mL of deionized water, stir at 60rpm for 5min, filter to obtain the leachate and leach residue, wash the leach residue, and use the washing liquid to make the leachate volume 800mL, detect the pH value and lithium ion concentration, calculate the leaching rate, and detect the lithium content after washing and drying the leach residue. The test results are shown in Table 1.

[0068] Example 2

[0069] This embodiment provides a lithium slag autoclave leaching method, specifically:

[0070] S1: Weigh 200g of lithium slag from a certain enterprise in Jiangxi, adjust the water content of the lithium slag to 25%, transfer it into a 1L pressure vessel, add 20g of concentrated sulfuric acid (mass concentration 98%) into the container, and the concentrated hydrochloric acid is at the bottom of the lithium slag, and the two are not in direct contact. Add 15mL of deionized water to form saturated vapor pressure in the container, cover the container, heat it in an oil bath to 105℃, and keep it warm and pressurized for 15min to carry out the replacement reaction;

[0071] S2: After the reaction is completed, add 750mL of deionized water, stir at 60rpm for 5min, and filter to obtain the leachate and leach residue. Wash the leach residue, and use the washing liquid to make the leachate volume 800mL, test the pH value and lithium ion concentration, calculate the leaching rate, and test the lithium content after washing and drying the leach residue. The test results are shown in Table 1.

[0072] Comparative Example 1

[0073] The other conditions of this comparative example 1 are the same as those of example 1, except that 10 mL of deionized water is not added.

[0074] The comparison results are shown in Table 1. The results show that without the appropriate amount of water to ensure the corresponding saturated vapor pressure in the container, the lithium, sodium and potassium leaching efficiency is reduced.

[0075] Comparative Example 2

[0076] The other conditions of this comparative example are the same as those of Example 1, except that 750 mL of deionized water and concentrated acid are added simultaneously, and the lithium slag is directly immersed in the acid solution.

[0077] The comparison results are shown in Table 1. The results show that the leaching efficiency of lithium, sodium and potassium decreases when the autoclave leaching is changed to submerged leaching. At the same time, silicon and aluminum are also leached due to the low endpoint pH of the leaching solution.

[0078] Comparative Example 3

[0079] The other conditions of Comparative Example 3 are the same as those of Example 2, except that the pressure state of the container is different. The container seal is opened to maintain a normal pressure environment in the container.

[0080] The comparison results are shown in Table 1. The results show that there is no corresponding saturated vapor pressure in the container, and the lithium, sodium and potassium leaching efficiency is reduced.

[0081] Comparative Example 4

[0082] Comparative Example 4 The other conditions are the same as those of Example 2, except that deionized water is used instead of concentrated sulfuric acid.

[0083] The comparison results are shown in Table 1. The results show that the leaching efficiency of lithium, sodium and potassium is significantly reduced when lithium slag is directly autoclaved and leached with water.

[0084] Test Case

[0085] Table 1. Element content detection of examples and comparative examples

[0086]

[0087] From the test results in Comparative Example 1, it can be seen that without the appropriate amount of water to ensure the corresponding saturated vapor pressure in the container, the lithium, sodium and potassium leaching efficiency is reduced; from the test results in Comparative Example 2, it can be seen that the leaching efficiency of lithium, sodium and potassium is reduced when the autoclave leaching is changed to immersion leaching. At the same time, due to the low pH of the end point of the leaching solution, silicon and aluminum are also leached. From the test results in Comparative Example 3, it can be seen that the results show that there is no corresponding saturated vapor pressure in the container, and the lithium, sodium and potassium leaching efficiency is reduced. From the test results in Comparative Example 4, it can be seen that the results show that the leaching efficiency of lithium, sodium and potassium is significantly reduced when lithium slag is directly autoclaved and leached with water.

Claims

1. A lithium slag autoclave leaching method, characterized in that: The following steps are involved: S1: subjecting lithium slag and acid solution to autoclave replacement reaction under saturated vapor pressure to obtain lithium leaching slag; The lithium slag and the acid solution are not in direct contact; S2: The lithium leaching residue is mixed with water, slurried, and filtered to obtain lithium-rich brine and silicon-aluminum-rich leaching residue.

2. The method according to claim 1, characterized in that In step S1, the acid solution includes at least one of hydrochloric acid, sulfuric acid, and nitric acid.

3. The method according to claim 1, characterized in that In step S1, before the reaction, the water content of the lithium slag is adjusted to be no higher than 25%.

4. The method according to claim 3, characterized in that In step S1, the controlled method includes wetting the surface of lithium slag particles with water.

5. The method according to claim 1, characterized in that In step S1, based on the dry weight of the lithium slag, the mass ratio of the lithium slag to the acid solution is 1:002-0.

1.

6. The method according to claim 1, characterized in that In step S1, the temperature of the autoclave replacement reaction is 100-120° C.; and / or the time of the autoclave replacement reaction is 15-120 min.

7. The method according to claim 1, characterized in that The pH value of the lithium leaching residue is 3-4.

8. The method according to claim 1, characterized in that Based on the dry weight of the lithium slag, the solid-to-liquid ratio of the lithium slag to the water is 1:(0.5-2).

9. The method according to claim 1, characterized in that: It also includes removing impurities from the lithium-rich brine; and / or, the impurity removal method includes concentrating, removing impurities and extracting lithium.

10. The method according to claim 1, characterized in that The step also includes adding the silicon-aluminum-rich leached residue into step S1 to carry out an autoclave replacement reaction.

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