A method for extracting lithium using ion exchange selectivity

Abstract

The invention discloses a method for extracting lithium by utilizing the ion exchange selectivity rule. According to the ion exchange selectivity rule that "in a normal temperature and low-concentration aqueous solution, the ion exchange capacity increases with the increase of the charge number of the ion; the exchange capacity of equivalent ions increases with the increase of the ion radius and", in the alkali solution preparation process, not only high-valent ions such as calcium, magnesium, iron, and aluminum in the leachate are completely removed, but also monovalent potassium ions and anionic sulfate ions are removed, and high-energy-consuming treatments such as freezing and heating are not required; and in the alkali solution preparation process, the same resin is used for cyclic conversion between sodium-type resin, high-valent cation resin, hydrogen-type resin, and monovalent ion resin, and there is no need to arrange multiple levels of resins with different functions, thereby reducing production costs.

Description

Technical Field

[0001] The invention relates to the field of lithium extraction from ores, and in particular to a method for extracting lithium by utilizing the selectivity law of ion exchange. Background Art

[0002] Currently, the main methods for preparing lithium hydroxide from spodumene are the lithium sulfate finished liquid caustic soda conversion method and the lithium carbonate lime milk causticization method. The two methods have the same preliminary process. Spodumene undergoes transformation roasting, cooling fine grinding, acid roasting, leaching filtration, purification, evaporation and other processes to obtain lithium sulfate finished liquid.

[0003] Subsequent preparation processes for lithium hydroxide mainly include caustic soda conversion and lime milk causticizing. In the lithium sulfate finished liquid caustic soda conversion method, the lithium sulfate finished liquid is subjected to a caustic soda conversion-freezing denitrification process to prepare a frozen denitrification mother liquor, which is then evaporated and crystallized to prepare lithium hydroxide monohydrate. It requires a complete set of freezing and denitrification equipment, which continuously consumes electricity, and has relatively high construction and operation and maintenance costs. The lithium carbonate lime milk causticizing method firstly produces lithium carbonate by subjecting the lithium sulfate finished liquid to a lithium precipitation reaction under heating conditions, and uses an automatic centrifuge to separate the lithium precipitation slurry into liquid and solid. To prepare the causticized liquid by the lime milk causticizing method, it is necessary to first add lithium sulfate and soda ash solution to precipitate lithium to obtain lithium carbonate, and then mix the lithium carbonate with lime milk and heat it. After clarification and fine filtration, the causticized finished liquid is prepared, and then the lithium hydroxide monohydrate is prepared by evaporation and crystallization. This method has high energy consumption due to multiple heating, and requires fine filtration operation to filter out impurities, making it difficult to remove impurities.

[0004] Chinese patent CN116212803A discloses a lithium bis(oxalato)borate preparation system and its control system, wherein lithium carbonate and calcium hydroxide are subjected to causticization reaction under strong stirring conditions to obtain lithium hydroxide, which is then filtered to obtain lithium hydroxide. The above patent fails to solve the technical problems of the long process flow and great difficulty in impurity removal of the lime milk causticization method. Summary of the invention

[0005] In order to overcome the deficiencies in the prior art, the present invention provides the following specific technical solutions: A method for extracting lithium using the selectivity rule of ion exchange, comprising the following steps: Step S1. Spodumene is transformed and roasted, cooled and crushed to generate a fine powder roasted material.

[0006] Step S2: Acidification, roasting and cooling of the fine powder roasted material to generate an acidified material.

[0007] Step S3. Leaching and filtering: adding limestone to the acidified material for neutralization to remove residual concentrated sulfuric acid in the acidified material to prevent the concentrated sulfuric acid from causing acid corrosion to subsequent process equipment; then adding water to the acidified material for leaching and filtering to obtain leaching residue and leachate.

[0008] The metal cations in the leachate include aluminum, iron, calcium, magnesium, potassium, sodium, and lithium ions, and the anions include sulfate ions.

[0009] Step S4. Preparation of alkali solution Step S4.1: the leachate is subjected to ion exchange with a sodium type resin: the leachate enters an ion exchange device, in which a sodium type resin is arranged. The leachate passes through the sodium type resin, and according to the ion exchange selectivity rule (the ion exchange capacity increases with the increase of the charge number of the ion, and the exchange capacity of the equivalent ion increases with the increase of the ion radius), the sodium type resin adsorbs the aluminum, iron, calcium, magnesium, and potassium ions in the leachate, and simultaneously precipitates the sodium ions, thereby obtaining a saturated high-valent cationic resin and a finished liquid.

[0010] The cations in the finished solution include sodium and lithium ions; the cations on the high-valent cation resin include aluminum, iron, calcium, magnesium, and potassium ions.

[0011] Step S4.2: Rinse the saturated high-valent cation resin with dilute sulfuric acid: Take out the high-valent cation resin in the ion exchange device, and use excess dilute sulfuric acid solution to rinse the high-valent cation resin. During the flushing process, the aluminum, iron, calcium, magnesium, potassium, and sodium ions on the high-valent cation resin are completely replaced by hydrogen ions to obtain a saturated hydrogen resin and a high-valent ion liquid.

[0012] The cations in the high-valent ionic liquid include aluminum, iron, calcium, magnesium, and potassium ions; the cations on the hydrogen-type resin are hydrogen ions.

[0013] Step S4.3: flushing the hydrogen type resin with the finishing liquid: flushing the hydrogen type resin with the finishing liquid, during which the hydrogen ions on the hydrogen type resin are completely replaced by lithium and sodium to obtain a monovalent ion liquid and a monovalent ion resin; the monovalent ion liquid is stored, and the monovalent ion resin is installed back into the ion exchange device.

[0014] The cations in the monovalent ion liquid include lithium, sodium, and hydrogen ions; the cations in the monovalent ion resin include lithium and sodium ions.

[0015] Step S4.4: Sodium hydroxide and monovalent ion resin are used for ion exchange: Excess sodium hydroxide passes through the monovalent ion resin, which absorbs sodium ions in the sodium hydroxide and simultaneously precipitates lithium ions, thereby obtaining alkali solution and sodium-type resin.

[0016] Alkali solution is a mixture of lithium hydroxide and sodium hydroxide.

[0017] Step S5. preparing lithium hydroxide: evaporating, concentrating, crystallizing, separating and drying the alkali solution to obtain lithium hydroxide.

[0018] Furthermore, in the process of washing the saturated high-valent cation resin with dilute sulfuric acid in step S4.2, in order to prevent the formation of calcium sulfate precipitation in the resin layer, the concentration of dilute sulfuric acid used is 1%~3%, the flow rate is controlled at 5~8m / h, and the resin is washed from top to bottom.

[0019] Furthermore, in order to ensure that the lithium element is not lost, the monovalent ionic liquid stored in step 4.3 is added to the finished liquid produced later, and the hydrogen-type resin is rinsed with a mixture of the finished liquid and the monovalent ionic liquid.

[0020] Furthermore, the sodium type resin obtained in step S4.4 is installed back into the ion exchange device, and the leaching solution is then subjected to ion exchange with the sodium type resin to obtain a high-valent cation resin and a finished solution.

[0021] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a method for extracting lithium by utilizing the law of ion exchange selectivity. According to the law of ion exchange selectivity that "in a normal temperature and low concentration aqueous solution, the ion exchange capacity increases with the increase of the charge number of the ion; the exchange capacity of the equivalent ion increases with the increase of the ion radius and", in the process of preparing the alkali solution, the leachate is first passed through a sodium-type resin, and the aluminum, iron, calcium, magnesium, and potassium ions are replaced on the resin, and the sodium ions are precipitated into the solution to obtain a high-valent cation resin and a finished solution; then the high-valent cation resin is rinsed (equivalent to regeneration) with dilute sulfuric acid to remove the calcium, magnesium, iron, aluminum, and potassium ions, and obtain a hydrogen-type resin; then the hydrogen-type resin is rinsed with the finished solution to form a monovalent ion resin and a monovalent ion liquid containing sodium and potassium ions; further, sodium hydroxide is used to selectively replace the lithium ions on the monovalent ion resin by utilizing ion exchange to obtain an alkali solution including lithium hydroxide and sodium hydroxide. Through the above process, not only the high-valent ions such as calcium, magnesium, iron, and aluminum in the leachate are completely removed, but also the monovalent potassium ions and the anionic sulfate ions are removed, and no high-energy-consuming treatments such as freezing and heating are required.

[0022] 2. The lithium extraction method disclosed in the present invention ensures that lithium ions continue to circulate in the process and reduces the loss of lithium elements by flushing hydrogen-type resin with finished liquid and adding monovalent ion liquid to the finished liquid produced later. In the process of preparing alkali solution, the same resin is used to circulate and switch between sodium-type resin, high-valent cation resin, hydrogen-type resin, and monovalent ion resin, without the need to arrange multiple levels of resins with different functions, thereby reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a flow chart of the lithium extraction method using the ion exchange selectivity rule of the present invention; Figure 2 The flow chart of preparing alkali solution of the present invention; Figure 3 Schematic diagram of resin type conversion of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention clearer, the embodiments of the present invention will be further described below in conjunction with the accompanying drawings. The following is a preferred embodiment of the present invention, which is intended to provide a basic understanding of the present invention, but is not intended to confirm the key or decisive elements of the present invention or to limit the scope of protection.

[0025] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, but the implementation manner of the present invention is not limited thereto.

[0027] Embodiment 1:

[0028] See attached Figure 1 This embodiment provides a method for selectively extracting lithium using ion exchange, comprising the following steps:

[0029] Step S1. Spodumene is transformed and roasted, cooled and crushed to generate a fine powder roasted material.

[0030] Step S2: Acidification, roasting and cooling of the fine powder roasted material to generate an acidified material.

[0031] Step S3. Leaching and filtering: adding limestone to the acidified material for neutralization to remove residual concentrated sulfuric acid in the acidified material to prevent the concentrated sulfuric acid from causing acid corrosion to subsequent process equipment; then adding water to the acidified material for leaching and filtering to obtain leaching residue and leachate.

[0032] The metal cations in the leachate include aluminum, iron, calcium, magnesium, potassium, sodium, and lithium ions, and the anions include sulfate ions.

[0033] Step S4. Preparation of alkali solution Step S4.1: the leachate is subjected to ion exchange with a sodium type resin: the leachate enters an ion exchange device, in which a sodium type resin is arranged. The leachate passes through the sodium type resin, and according to the ion exchange selectivity rule (the ion exchange capacity increases with the increase of the charge number of the ion, and the exchange capacity of the equivalent ion increases with the increase of the ion radius), the sodium type resin adsorbs the aluminum, iron, calcium, magnesium, and potassium ions in the leachate, and simultaneously precipitates the sodium ions, thereby obtaining a saturated high-valent cationic resin and a finished liquid.

[0034] The cations in the finished solution include sodium and lithium ions; the cations on the high-valent cation resin include aluminum, iron, calcium, magnesium, and potassium ions.

[0035] Step S4.2: Rinse the saturated high-valent cation resin with dilute sulfuric acid: Take out the high-valent cation resin in the ion exchange device, and use excess dilute sulfuric acid solution to rinse the high-valent cation resin. During the flushing process, the aluminum, iron, calcium, magnesium, potassium, and sodium ions on the high-valent cation resin are completely replaced by hydrogen ions to obtain a saturated hydrogen resin and a high-valent ion liquid.

[0036] The cations in the high-valent ionic liquid include aluminum, iron, calcium, magnesium, and potassium ions; the cations on the hydrogen-type resin are hydrogen ions.

[0037] Step S4.3: flushing the hydrogen type resin with the finishing liquid: flushing the hydrogen type resin with the finishing liquid, during which the hydrogen ions on the hydrogen type resin are completely replaced by lithium and sodium to obtain a monovalent ion liquid and a monovalent ion resin; the monovalent ion liquid is stored, and the monovalent ion resin is installed back into the ion exchange device.

[0038] The cations in the monovalent ion liquid include lithium, sodium, and hydrogen ions; the cations in the monovalent ion resin include lithium and sodium ions.

[0039] Step S4.4: Sodium hydroxide and monovalent ion resin are used for ion exchange: Excess sodium hydroxide passes through the monovalent ion resin, which absorbs sodium ions in the sodium hydroxide and simultaneously precipitates lithium ions, thereby obtaining alkali solution and sodium-type resin.

[0040] Alkali solution is a mixture of lithium hydroxide and sodium hydroxide.

[0041] Step S5. preparing lithium hydroxide: evaporating, concentrating, crystallizing, separating and drying the alkali solution to obtain lithium hydroxide.

[0042] Embodiment 2: This example is further optimized on the basis of Example 1, and further explains step 4.2 of washing the saturated high-valent cation resin with dilute sulfuric acid.

[0043] In the process of washing the saturated high-valent cation resin with dilute sulfuric acid in step S4.2, in order to prevent the formation of calcium sulfate precipitation in the resin layer, the concentration of dilute sulfuric acid used is 1%~3%, the flow rate is controlled at 5~8m / h, and the resin is washed from top to bottom.

[0044] The other parts of this embodiment are the same as those of Embodiment 1, and thus will not be described in detail.

[0045] Embodiment 3: This embodiment is further optimized on the basis of embodiment 1. In order to ensure that the lithium element is not lost, the monovalent ionic liquid stored in step 4.3 is added to the finished liquid produced later, and the hydrogen-type resin is rinsed with a mixture of the finished liquid and the monovalent ionic liquid.

[0046] The other parts of this embodiment are the same as those of Embodiment 1, and thus will not be described in detail.

[0047] Embodiment 4: This embodiment is further optimized on the basis of Embodiment 1, 2 or 3. The sodium-potassium type resin obtained in step S4.4 is installed back into the ion exchange device, and the subsequent leachate is subjected to ion exchange with the sodium-potassium type resin to obtain a high-valent cation resin and a finished solution.

[0048] In this article, the directional words such as front, back, top, and bottom involved are defined by the positions of the parts in the drawings and the positions of the parts relative to each other, just for the sake of clarity and convenience in expressing the technical solution. It should be understood that they are relative concepts and can change accordingly according to different ways of use and placement, and the use of the directional words should not limit the scope of protection claimed in this application.

[0049] In the absence of conflict, the above embodiments and features in the embodiments may be combined with each other.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for extracting lithium using the selectivity rule of ion exchange, characterized in that: The following steps are involved: Step S1. spodumene is transformed into roasted, cooled and crushed to generate a fine powder roasted material; Step S2: acidifying, roasting and cooling the fine powder roasted material to generate an acidified material; Step S3. Leaching and filtering: adding limestone to the acidified material for neutralization to remove the residual concentrated sulfuric acid in the acidified material to prevent the concentrated sulfuric acid from causing acid corrosion to the subsequent process equipment; then adding water to the acidified material for leaching and filtering to obtain leaching residue and leachate; The metal cations in the leachate include aluminum, iron, calcium, magnesium, potassium, sodium, and lithium ions, and the anions include sulfate ions; Step S4. preparing alkali solution; Step S5. preparing lithium hydroxide: evaporating, concentrating, crystallizing, separating and drying the alkali solution to obtain lithium hydroxide.

2. The method for extracting lithium using the ion exchange selectivity rule according to claim 1, characterized in that: The step S4. preparing alkali solution specifically comprises the following steps: Step S4.1: the leachate is subjected to ion exchange with a sodium resin: the leachate enters an ion exchange device, in which a sodium resin is arranged, and the leachate passes through the sodium resin, which absorbs aluminum, iron, calcium, magnesium, and potassium ions in the leachate and simultaneously precipitates sodium ions, thereby obtaining a saturated high-valent cationic resin and a finished liquid; The cations in the finished solution include sodium and lithium ions; the cations on the high-valent cation resin include aluminum, iron, calcium, magnesium, and potassium ions; Step S4.2: Washing the saturated high-valent cation resin with dilute sulfuric acid: Take out the high-valent cation resin in the ion exchange device, and use an excess of dilute sulfuric acid solution to wash the high-valent cation resin. During the washing process, the aluminum, iron, calcium, magnesium, potassium, and sodium ions on the high-valent cation resin are completely replaced by hydrogen ions to obtain a saturated hydrogen resin and a high-valent ion liquid; The cations in the high-valent ionic liquid include aluminum, iron, calcium, magnesium, and potassium ions; the cations on the hydrogen-type resin are hydrogen ions; Step S4.3: flushing the hydrogen resin with the finishing liquid: flushing the hydrogen resin with the finishing liquid, during which the hydrogen ions on the hydrogen resin are completely replaced by lithium and sodium to obtain a monovalent ion liquid and a monovalent ion resin; storing the monovalent ion liquid, and installing the monovalent ion resin back into the ion exchange device; The cations in the monovalent ion liquid include lithium, sodium, and hydrogen ions; the cations in the monovalent ion resin include lithium and sodium ions; Step S4.4: Sodium hydroxide and monovalent ion resin are subjected to ion exchange: Excess sodium hydroxide passes through the monovalent ion resin, and the monovalent ion resin adsorbs sodium ions in the sodium hydroxide and simultaneously precipitates lithium ions, thereby obtaining alkali solution and sodium type resin; Alkali solution is a mixture of lithium hydroxide and sodium hydroxide.

3. The method for extracting lithium using ion exchange selectivity according to claim 2, characterized in that: In the process of washing the saturated high-valent cation resin with dilute sulfuric acid in step S4.2, the concentration of the dilute sulfuric acid used is 1%~3%, the flow rate is controlled at 5~8m / h, and the resin is washed from top to bottom.

4. The method for extracting lithium using the ion exchange selectivity rule according to any one of claims 1 to 3, characterized in that: The monovalent ionic liquid stored in step 4.3 is added to the finished liquid produced later, and the hydrogen-type resin is rinsed with a mixture of the finished liquid and the monovalent ionic liquid.

5. The method for extracting lithium using ion exchange selectivity according to claim 1 or 2, characterized in that: The sodium type resin obtained in step S4.4 is installed back into the ion exchange device, and the leaching solution is then subjected to ion exchange with the sodium type resin to obtain a high-valent cation resin and a finished solution.

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