Method for recovering lithium from acid-process intermediate alumina and lithium-containing solution

Abstract

The present invention provides a method for recovering lithium from intermediate alumina by acid method and a lithium-containing solution. The method includes: mixing the intermediate alumina by acid method with a leaching agent, performing leaching under heating conditions, subjecting the mixture obtained after the leaching treatment to solid-liquid separation, and collecting the liquid phase to obtain a crude lithium-containing solution; wherein, the leaching agent is an aqueous solution containing Ca 2+ The use of an aqueous solution containing calcium ions as the leaching agent can significantly improve the leaching rate of lithium and the filterability of the leaching solution. The reason is that the researchers of the present application accidentally discovered that Ca 2+ can prevent Li + from entering the alumina unit cell, enabling Li + to only attach to the surface of the alumina unit cell, thereby improving the lithium leaching rate. Moreover, Ca 2+ can also inhibit the formation of Al(OH)3 colloid, thereby improving the filterability of the leaching solution and greatly enhancing the solid-liquid separation efficiency.

Description

Technical Field

[0001] The present invention relates to hydrometallurgy technology, and more particularly, to a method for recovering lithium from intermediate alumina by acid method and a lithium-containing solution. Background Art

[0002] The "one-step acid leaching method" process technology independently developed by the National Energy Group has been improved and optimized over the years. Currently, it has formed a process technology with alumina extraction as the main line and gallium extraction and preparation of silicon-aluminum-based materials as the secondary lines. The specific process flow chart is shown in Figure 1 . After the fly ash is leached with hydrochloric acid, the acid leaching residue is used to prepare silicon-aluminum-based materials, and the acid leaching solution is used for the extraction of valuable elements, making the fly ash "fully utilized", which fully meets the green and sustainable development goals of our country. The specific process flow of the "one-step acid leaching method" is as follows Figure 1 shown. This process has less waste residue and low energy consumption, and is currently the one with the best application prospect in the comprehensive utilization process of fly ash resource in China.

[0003] Lithium is located in Group IA of the periodic table and belongs to alkali metal elements. It is the metal element with the highest ranking. Lithium is called the energy metal of the 21st century and enjoys the reputation of "metal monosodium glutamate" and "white petroleum". Currently, it has been widely used in many fields such as high-energy storage batteries, nuclear fusion reactors, and aerospace materials. Therefore, lithium has been increasingly valued by countries around the world. Currently, many countries have positioned lithium as a national strategic mineral resource.

[0004] In the above process, it has been detected that the intermediate alumina contains a large amount of lithium. If it is not recovered and utilized, it will cause a great waste of lithium resources.

[0005] The patent application with the application number 201911031937.4 discloses a method for extracting lithium from the alumina production process and preparing battery-grade lithium carbonate: cooling the semen and reacting it with an acidic compound to prepare active seeds of aluminum hydroxide, then mixing the active seeds with sodium aluminate solution to enrich lithium in the sodium aluminate solution to obtain lithium-rich aluminum hydroxide; mixing the lithium-rich aluminum hydroxide with an organic acid for microwave desorption reaction, and after the reaction, performing solid-liquid separation. The solid is lithium-depleted aluminum hydroxide, and the liquid is lithium-rich desorption liquid. This method has a relatively complex process and requires the consumption of organic acids, resulting in a high cost.

[0006] The patent application with the application number 201310046360.0 discloses a method for preparing lithium carbonate from fly ash. This method utilizes the mother liquor separated after evaporation and crystallization of the aluminum chloride refining solution in the process of preparing alumina from fly ash by acid method, and enriches lithium ions by circulating evaporation of the mother liquor for multiple times. This scheme also recovers lithium chloride from the process of preparing alumina from fly ash, but its recovery efficiency of lithium ions is relatively low, the process flow is complex, and the energy consumption is high.

[0007] In summary, it is urgent to develop a method for extracting lithium from the process of producing alumina from fly ash. Efficiently recovering lithium from the process of producing alumina from fly ash is of great strategic significance for the healthy development of China's lithium industry. Summary of the Invention

[0008] The main object of the present invention is to provide a method for recovering lithium from intermediate alumina by acid method and a lithium-containing solution, so as to solve the problems of complex process, low efficiency and high cost in recovering lithium from the process of producing alumina from fly ash in the prior art.

[0009] To achieve the above object, according to one aspect of the present invention, there is provided a method for recovering lithium from intermediate alumina by acid method, the method comprising: mixing intermediate alumina by acid method with a leaching agent, carrying out leaching under heating conditions, separating the solid-liquid of the mixture obtained after leaching treatment, and collecting the liquid phase to obtain a lithium-containing stock solution; wherein, the leaching agent is an aqueous solution containing Ca 2+ .

[0010] Further, the method further comprises: washing the solid phase obtained by solid-liquid separation with water as a washing agent to obtain a lithium-containing washing solution;

[0011] Preferably, the washing agent is deionized water at 80-100 °C;

[0012] Preferably, the liquid-solid ratio of the washing agent to the intermediate alumina by acid method is 4-6 mL / g.

[0013] Further, the leaching agent is process salt-containing wastewater.

[0014] Further, the leaching agent is a lithium-containing washing solution.

[0015] Further, the concentration of Ca 2+ in the leaching agent is 1-2 g / L.

[0016] Further, the liquid-solid ratio of the leaching agent to the intermediate alumina by acid method is 1-8 mL / g.

[0017] Further, the leaching temperature is 120-180 °C.

[0018] Further, the leaching time is 2-6 h.

[0019] Further, mixing the lithium-containing washing solution with the lithium-containing stock solution to obtain a lithium-containing recovery solution.

[0020] To achieve the above object, according to another aspect of the present invention, there is provided a lithium-containing solution, which is the lithium-containing stock solution prepared by any one of the above methods, or the lithium-containing recovery solution prepared by the above method.

[0021] Applying the technical solution of the present invention and using an aqueous solution containing calcium ions as the leaching agent can significantly improve the leaching rate of lithium and the filterability of the leachate. The reason is that the researchers of this application accidentally discovered that Ca 2+ can prevent Li + from entering the alumina unit cell, making Li + only attach to the surface of the alumina unit cell, thereby increasing the lithium leaching rate. Moreover, Ca 2+ can also inhibit the formation of Al(OH) 3 colloid, thus improving the filterability of the leachate and greatly enhancing the solid-liquid separation efficiency. By adopting the above specific leaching agent, this application can efficiently separate lithium from intermediate alumina. The obtained lithium-containing stock solution can be used for lithium extraction, and the separated solid-phase components can be used for alumina production. The process for recovering lithium has a simple process flow, strong operability, short time consumption, high lithium leaching rate, low equipment requirements, and is easy to be popularized industrially. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0023] Figure 1 shows a schematic process flow diagram of the "one-step acid leaching method" in the background art of the present invention;

[0024] Figure 2 shows a process flow diagram of a method for recovering lithium from acid-process intermediate alumina according to an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings in combination with the embodiments.

[0026] As analyzed in the background art of this application, there are problems in the prior art that the process for recovering lithium during the production of alumina from fly ash is relatively complex, inefficient, and costly. To solve this problem, this application provides a method for recovering lithium from acid-process intermediate alumina and a lithium-containing solution.

[0027] According to a typical embodiment of the present application, a method for recovering lithium from acid-process intermediate alumina is provided. The method includes: mixing acid-process intermediate alumina with a leaching agent, performing leaching under heating conditions, separating the solid and liquid of the mixture obtained after the leaching treatment, and collecting the liquid phase to obtain a lithium-containing stock solution; wherein, the leaching agent is an aqueous solution containing Ca 2+ ions.

[0028] In this application, an aqueous solution containing calcium ions is used as the leaching agent, which can significantly improve the leaching rate of lithium and the filterability of the leaching solution. The reason is that the researchers of this application accidentally discovered that Ca 2+ can prevent Li + from entering the alumina unit cell, causing Li + to only attach to the surface of the alumina unit cell, thereby increasing the lithium leaching rate. Moreover, Ca 2+ can also inhibit the formation of Al(OH) 3 colloid, thus improving the filterability of the leaching solution and greatly enhancing the solid-liquid separation efficiency. By using the above specific leaching agent, this application can efficiently separate lithium from intermediate alumina. The obtained lithium-containing stock solution can be used for lithium extraction, and the separated solid-phase components can be used for alumina production. The process for recovering lithium has a simple process flow, strong operability, short time consumption, high lithium leaching rate, low equipment requirements, and is easy to be popularized industrially.

[0029] On the other hand, by the method for recovering lithium from acid-process intermediate alumina of this application, the added value of extracting aluminum from fly ash by the acid method can be increased, and the purity of the intermediate alumina can be further improved, which is convenient for subsequent processing and use.

[0030] The intermediate alumina mentioned in this application is the intermediate product alumina prepared by the acid method. Other metals except aluminum exist mostly in the form of salts, such as chlorides. In some embodiments of this application, for the convenience of testing, the composition of the intermediate alumina is expressed in the form of oxides. By weight percentage, the above intermediate alumina contains 94% - 99% of Al 2 O 3 , 0 - 0.5% of K 2 O, 0 - 1.0% of Na 2 O, 0 - 3.0% of CaO, 0 - 1.0% of MgO, and 0.05% - 1.0% of Li 2 O, as well as other components. For the solid with this composition, the leaching agent containing Ca 2+ has a particularly significant effect on improving the leaching effect of lithium.

[0031] In some typical embodiments of this application, in order to further improve the lithium recovery rate and reduce the lithium content in the solid phase, the method for recovering lithium from acid-process intermediate alumina further includes: washing the solid phase obtained by solid-liquid separation with water as the detergent to obtain a lithium-containing washing solution. Preferably, the above detergent is deionized water at 80 - 100°C, which can quickly dissolve the lithium ions in the solid phase and has a good washing effect. In some embodiments of this application, based on the above raw material acid-process intermediate alumina, the dosage of the detergent is determined. The liquid-solid ratio of the detergent to the acid-process intermediate alumina is 4 - 6 mL / g, which can better balance the water consumption and the washing effect.

[0032] The above aqueous solution containing Ca as the leaching agent 2+ has no special requirements for the source or composition and can be selected according to the actual situation. For example, in some embodiments of the present application, the leaching agent is process salt-containing wastewater, such as the resin calcium-removing wastewater in the production of alumina by the acid method from fly ash.

[0033] In some embodiments of the present application, the leaching agent is the above-mentioned lithium-containing washing liquid, that is, the liquid obtained by washing the solid phase separated from the washing solid-liquid. Since there is a certain content of calcium salt in the intermediate alumina in the acid method, the lithium-containing washing liquid obtained through the above washing step also contains Ca 2+ , used as a leaching agent, can not only make full use of the Ca 2+ therein, but also further enrich lithium to obtain a lithium-containing stock solution with a higher lithium content.

[0034] Using process salt-containing wastewater or lithium-containing washing liquid as the leaching agent, the leaching agent comes from within the alumina production process by the acid method, reducing the investment cost. In some embodiments of the present application, in order to further improve the leaching rate of lithium and the filtration performance of the leaching solution, the concentration of Ca 2+ in the leaching agent is 1-2 g / L.

[0035] In some preferred embodiments of the present application, the liquid-solid ratio of the above leaching agent to the intermediate alumina in the acid method is 1-8 mL / g, and the leaching efficiency is relatively high.

[0036] In some typical embodiments of the present application, the above leaching treatment is carried out at 120-180 °C, which can further improve the leaching efficiency and the recovery rate of lithium. Preferably, the leaching time is 2-6 h.

[0037] The mixture obtained after the leaching treatment is subjected to solid-liquid separation. The specific means of solid-liquid separation can be selected from the prior art, such as suction filtration and pressure filtration. The lithium-containing washing liquid obtained by any of the above methods can be mixed with the lithium-containing stock solution to obtain a lithium-containing recovery solution for lithium extraction.

[0038] In some typical embodiments of the present application, the method for recovering lithium from intermediate alumina in the acid method includes: (1) mixing the intermediate alumina and the leaching agent at a certain liquid-solid ratio, where the leaching agent is process salt-containing wastewater or lithium-containing washing liquid; (2) the mixed material undergoes a leaching reaction in a reaction kettle; (3) suction filtration is used to obtain a lithium-containing stock solution, and hot water is used to wash the filter cake to obtain a lithium-containing washing liquid. The lithium-containing stock solution and the lithium-containing washing liquid are mixed to obtain a lithium-containing solution.

[0039] According to another typical embodiment of the present application, a lithium-containing solution is provided. The lithium-containing solution is the lithium-containing stock solution prepared by any of the above methods, or the lithium-containing recovery solution prepared by the above method.

[0040] In some typical embodiments of the present application, such as Figure 2 shown, the method for leaching lithium from intermediate alumina by the acid method includes: S100, mixing intermediate alumina and a leaching agent to obtain a mixture, wherein the leaching agent is process salt-containing wastewater or lithium-containing washing liquid; S200, performing a leaching reaction on the mixture in a reaction kettle; S300, performing solid-liquid separation to obtain a solid phase and a lithium-containing stock solution; S400, washing the solid phase with hot water to obtain a lithium-containing washing liquid, and combining the lithium-containing washing liquid with the lithium-containing stock solution to obtain a lithium-containing recovery liquid.

[0041] The beneficial effects that can be achieved by the present application will be further described below in conjunction with examples and comparative examples.

[0042] The raw material uses intermediate alumina from the alumina pilot plant of China Energy Group Zhuneng Company, and its chemical composition is shown in Table 1. After XRD analysis, the intermediate alumina is amorphous alumina and contains a small amount of alunite.

[0043] Table 1

[0044]

[0045] Example 1

[0046] A method for leaching lithium from intermediate alumina specifically includes the following steps:

[0047] (1) Take 90 g of intermediate alumina and 360 mL of process salt-containing wastewater solution (resin de-calcium wastewater, with a Ca 2+ concentration of 1.73 g / L), and mix the two in a reaction kettle.

[0048] (2) Place the reaction kettle in a heating furnace, heat it up to 160 °C, keep it at a constant temperature for 4 h, and then naturally cool it down to room temperature.

[0049] (3) Obtain a lithium-containing stock solution by suction filtration, and then wash the filter cake with 450 mL of deionized water at 90 °C to obtain a lithium-containing washing liquid. Mix the lithium-containing stock solution and the lithium-containing washing liquid to obtain a lithium-containing solution.

[0050] After the above step (3) is completed, use ICP-MS to measure the lithium content of the lithium-containing solution, and calculate that the leaching rate of lithium is 91.21%.

[0051] Example 2

[0052] A method for leaching lithium from intermediate alumina specifically includes the following steps:

[0053] (1) Take 90 g of intermediate alumina and 360 mL of lithium-containing washing liquid (with a Ca 2+ concentration of 1.58 g / L), and mix the two in a reaction kettle.

[0054] (2) Place the reaction kettle into the heating furnace, raise the temperature to 160 °C, keep it at a constant temperature for 4 h, and then let it cool down to room temperature naturally.

[0055] (3) Obtain the lithium-containing stock solution by suction filtration, and then wash the filter cake with 450 mL of deionized water at 90 °C to obtain the lithium-containing washing solution. Mix the lithium-containing stock solution and the lithium-containing washing solution to obtain the lithium-containing solution.

[0056] After the above step (3) is completed, measure the lithium content of the lithium-containing solution by ICP-MS, and calculate that the leaching rate of lithium is 92.18%.

[0057] Example 3

[0058] A method for leaching lithium from intermediate alumina specifically includes the following steps:

[0059] (1) Take 90 g of intermediate alumina and 360 mL of the process salt-containing wastewater solution (resin de-calcium wastewater, with the Ca 2+ concentration of 1.73 g / L), and mix the two in the reaction kettle.

[0060] (2) Place the reaction kettle into the heating furnace, raise the temperature to 140 °C, keep it at a constant temperature for 6 h, and then let it cool down to room temperature naturally.

[0061] (3) Obtain the lithium-containing stock solution by suction filtration, and then wash the filter cake with 450 mL of deionized water at 90 °C to obtain the lithium-containing washing solution. Mix the lithium-containing stock solution and the lithium-containing washing solution to obtain the lithium-containing solution.

[0062] After the above step (3) is completed, measure the lithium content of the lithium-containing solution by ICP-MS, and calculate that the leaching rate of lithium is 89.83%.

[0063] Example 4

[0064] A method for leaching lithium from intermediate alumina specifically includes the following steps:

[0065] (1) Take 90 g of intermediate alumina and 360 mL of the lithium-containing washing solution (with the Ca 2+ concentration of 1.58 g / L), and mix the two in the reaction kettle.

[0066] (2) Place the reaction kettle into the heating furnace, raise the temperature to 140 °C, keep it at a constant temperature for 6 h, and then let it cool down to room temperature naturally.

[0067] (3) Obtain the lithium-containing stock solution by suction filtration, and then wash the filter cake with 450 mL of deionized water at 90 °C to obtain the lithium-containing washing solution. Mix the lithium-containing stock solution and the lithium-containing washing solution to obtain the lithium-containing solution.

[0068] After the above step (3) is completed, the lithium content of the lithium-containing solution is determined by ICP-MS, and the calculated leaching rate of lithium is 91.45%.

[0069] Example 5

[0070] A method for leaching lithium from intermediate alumina, specifically including the following steps:

[0071] (1) Take 90 g of intermediate alumina and 360 mL of process salt-containing wastewater solution (resin de-calcium wastewater, with the Ca 2+ concentration of 1.73 g / L), and mix the two in a reaction kettle.

[0072] (2) Place the reaction kettle in a heating furnace, heat it up to 100 °C, keep it at a constant temperature for 4 h, and then naturally cool it down to room temperature.

[0073] (3) Obtain the lithium-containing stock solution by suction filtration, and then wash the filter cake with 450 mL of deionized water at 90 °C to obtain the lithium-containing washing solution. Mix the lithium-containing stock solution and the lithium-containing washing solution to obtain the lithium-containing solution.

[0074] After the above step (3) is completed, the lithium content of the lithium-containing solution is determined by ICP-MS, and the calculated leaching rate of lithium is 81.38%.

[0075] Example 6

[0076] The difference from Example 1 is that in step (2), the temperature is raised to 120 °C.

[0077] After step (3) is completed, the lithium content of the lithium-containing solution is determined by ICP-MS, and the calculated leaching rate of lithium is 85.16%.

[0078] Example 7

[0079] The difference from Example 1 is that in step (2), the temperature is raised to 180 °C.

[0080] After step (3) is completed, the lithium content of the lithium-containing solution is determined by ICP-MS, and the calculated leaching rate of lithium is 91.26%.

[0081] Example 8

[0082] The difference from Example 1 is that in step (2), the constant temperature is maintained for 2 h.

[0083] After step (3) is completed, the lithium content of the lithium-containing solution is determined by ICP-MS, and the calculated leaching rate of lithium is 85.69%.

[0084] Example 9

[0085] The difference from Example 1 is that in step (3), a lithium-containing stock solution was obtained by suction filtration, the filter cake was not washed, and the lithium content of the lithium-containing stock solution was measured by ICP-MS. The calculated lithium leaching rate was 46.37%.

[0086] Example 10

[0087] The difference from Example 1 is that in step (3), the filter cake was washed with the same volume of deionized water at room temperature (25°C).

[0088] After step (3) was completed, the lithium content of the lithium-containing solution was measured by ICP-MS. The calculated lithium leaching rate was 84.64%.

[0089] Example 11

[0090] The difference from Example 2 is that the concentration of Ca in the lithium-containing washing solution 2+ was 1.0 g / L.

[0091] After step (3) was completed, the lithium content of the lithium-containing solution was measured by ICP-MS. The calculated lithium leaching rate was 91.97%.

[0092] Example 12

[0093] The difference from Example 2 is that the concentration of Ca in the lithium-containing washing solution 2+ was 2.0 g / L.

[0094] After step (3) was completed, the lithium content of the lithium-containing solution was measured by ICP-MS. The calculated lithium leaching rate was 92.01%.

[0095] Example 13

[0096] The difference from Example 2 is that the concentration of Ca in the lithium-containing washing solution 2+ was 2.5 g / L.

[0097] After step (3) was completed, the lithium content of the lithium-containing solution was measured by ICP-MS. The calculated lithium leaching rate was 92.01%.

[0098] Comparative Example 1

[0099] A method for leaching lithium from intermediate alumina specifically includes the following steps:

[0100] (1) Take 90 g of intermediate alumina and 360 mL of deionized water, and mix them in a reaction kettle.

[0101] (2) Place the reaction kettle in a heating furnace, heat it to 160°C, keep it at a constant temperature for 4 h, and then naturally cool it to room temperature.

[0102] (3) The lithium-containing stock solution was obtained by suction filtration, and then the filter cake was washed with 450 mL of deionized water at 90 °C to obtain a lithium-containing washing solution. The lithium-containing stock solution and the lithium-containing washing solution were mixed to obtain a lithium-containing solution.

[0103] After the above step (3) was completed, the lithium content of the lithium-containing solution was measured by ICP-MS, and the leaching rate of lithium was calculated to be 79.37%.

[0104] From the above description, it can be seen that the above embodiments of the present invention achieved the following technical effects: Using an aqueous solution containing calcium ions as the leaching agent can significantly improve the leaching rate of lithium and the filterability of the leaching solution. The reason is that the researchers of this application accidentally discovered that Ca 2+ can prevent Li + from entering the alumina unit cell, making Li + only attach to the surface of the alumina unit cell, thereby increasing the lithium leaching rate. Moreover, Ca 2+ can also inhibit the formation of Al(OH) 3 colloid, thereby improving the filterability of the leaching solution and greatly enhancing the solid-liquid separation efficiency. By using the above specific leaching agent, the present application can efficiently separate the lithium in the intermediate alumina. The obtained lithium-containing stock solution can be used for lithium extraction, and the separated solid-phase components can be used for alumina production. The process for recovering lithium has a simple process flow, strong operability, short time consumption, high lithium leaching rate, low equipment requirements, and is easy to be popularized industrially.

[0105] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for recovering lithium from intermediate alumina by acid method, characterized in that, it includes: Mixing the intermediate alumina by acid method with a leaching agent, carrying out leaching under heating conditions, separating the solid-liquid of the mixture obtained after the leaching treatment, and collecting the liquid phase to obtain a lithium-containing stock solution; the intermediate alumina by acid method is the intermediate product alumina prepared by the acid method of fly ash; the temperature of the leaching is 120-180 °C; The leaching agent is an aqueous solution containing Ca 2+ ; the concentration of Ca 2+ in the leaching agent is 1-2 g / L; The liquid-solid ratio of the leaching agent to the intermediate alumina by acid method is 1-8 mL / g; The method further includes: washing the solid phase obtained by the solid-liquid separation with water as a washing agent to obtain a lithium-containing washing solution; The washing agent is deionized water at 80-100 °C; the liquid-solid ratio of the washing agent to the intermediate alumina by acid method is 4-6 mL / g.

2. The method according to claim 1, characterized in that, The leaching agent is process salt-containing wastewater containing Ca 2+ .

3. The method according to claim 1, characterized in that, The liquid obtained by washing the solid phase obtained by the solid-liquid separation is used as the leaching agent.

4. The method according to claim 1, characterized in that, The time of the leaching is 2-6 h.

5. The method according to claim 1 or 2, characterized in that, Mixing the lithium-containing washing solution and the lithium-containing stock solution to obtain a lithium-containing recovery solution.

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