A metal-doped lithium ion sieve adsorbent and its preparation method and application

Abstract

The present invention belongs to the technical field of lithium adsorbents, and particularly relates to a metal-doped lithium ion sieve adsorbent, a preparation method thereof, and an application thereof. The preparation method comprises the following steps: lithium hydroxide and aluminum hydroxide are taken, stirred and mixed with a zinc source and / or an iron source and a solvent, reacted under oil bath conditions, and then centrifuged, washed, and dried to obtain a metal-doped lithium ion sieve adsorbent. The metal-doped lithium ion sieve adsorbent prepared by the preparation method of the present invention has the advantages of high adsorption capacity, good cycle stability, and good selectivity. In particular, LiZnFeAl / LDH can achieve unexpected cycle stability effects, and the lithium ion sieve adsorbent LiZnFeAl / LDH has an unexpected air separation effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium adsorbents, and in particular relates to a metal-doped lithium ion sieve adsorbent and a preparation method and application thereof. Background Art

[0002] Against the backdrop of the dual carbon economy, lithium, often called "white oil," has received significant attention worldwide as a key strategic metal. In recent years, with the rapid development of electric vehicles powered by batteries and the gradual transformation of the global energy structure, global demand for lithium has exploded. Over 60% of lithium is naturally found in salt lake brines. From an environmental and economic perspective, salt lake brines offer greater development potential than solid lithium ore.

[0003] So far, there are many methods for extracting lithium from salt lake brine, such as solvent extraction, precipitation, membrane separation, calcination leaching and adsorption, and some of them have been successfully applied in the industrial production of extracting lithium from actual salt lake brine. + It has attracted much attention due to its advantages such as high selectivity, strong applicability, simple process, environmental protection, high efficiency and recyclability. Lithium extraction adsorbents can be divided into three categories: manganese-based, titanium-based and aluminum-based adsorbents. At present, metal-based adsorbents have become the hot spot and focus of lithium adsorbent research. Among them, lithium ion sieves (LISs) are excellent adsorbents based on the "lithium ion memory effect". Lithium aluminum layered double hydroxide (LiAl / LDH) adsorbents have the advantages of high selectivity and eco-friendliness, and have been successfully industrialized, but their corresponding adsorption capacity and cyclic stability are poor. At present, the structural collapse and deactivation problems faced by LiAl / LDH during the adsorption and desorption process have led to low adsorption capacity, slow adsorption rate and poor cyclic stability, which have hindered its development process.

[0004] Therefore, there is an urgent need to provide a new adsorbent to break through the limitations, so that the adsorption capacity and cycle stability of the prepared lithium ion adsorbent can be improved, and the preparation method of the adsorbent can achieve the purpose of being pollution-free and environmentally friendly. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes a metal-doped lithium ion sieve adsorbent and its preparation method and application. The metal-doped lithium ion sieve adsorbent prepared by the preparation method of the present invention has the advantages of high lithium ion adsorption capacity and good cycle stability, and further has the advantage of good selectivity. The lithium ion sieve adsorbent of the present invention does not consume acid and does not produce secondary waste during the lithium ion adsorption-analysis process, and is safe and environmentally friendly. Furthermore, the doped lithium aluminum layered double hydroxide of the present invention also has the advantage of selectively adsorbing oxygen and can be used for air separation.

[0006] A first aspect of the present invention provides a method for preparing a metal-doped lithium ion sieve adsorbent.

[0007] Specifically, a method for preparing a metal-doped lithium ion sieve adsorbent comprises the following steps:

[0008] Lithium hydroxide and aluminum hydroxide are mixed with a zinc source and / or an iron source and a solvent, reacted in an oil bath, and then centrifuged, washed, and dried to obtain the metal-doped lithium ion sieve adsorbent.

[0009] Preferably, the solvent is deionized water.

[0010] Preferably, the zinc source is selected from zinc salts, such as zinc chloride and zinc nitrate, more preferably zinc chloride.

[0011] Preferably, the iron source is selected from iron salts, such as ferric nitrate, ferric chloride or ferric chloride hexahydrate, more preferably ferric chloride hexahydrate.

[0012] Preferably, the molar ratio of the lithium hydroxide to the zinc source is 3:(0.2-0.5), more preferably 3:(0.25-0.4).

[0013] Preferably, the molar ratio of the lithium hydroxide to the iron source is 3:(0.1-0.25), more preferably 3:(0.15-0.2).

[0014] Preferably, the reaction temperature is 80-95°C for 24-48 hours; further preferably, the reaction temperature is 88-90°C for 36-48 hours. The reaction conducted under these relatively low oil bath temperatures results in a lithium ion sieve adsorbent having high adsorption capacity and good cyclic stability.

[0015] Preferably, the drying is carried out in a vacuum chamber at 60-80° C. overnight. Centrifugation and washing are conventional processes in the art.

[0016] A second aspect of the present invention provides a metal-doped lithium ion sieve adsorbent.

[0017] Specifically, a metal-doped lithium ion sieve adsorbent is prepared by the above preparation method.

[0018] Preferably, the abbreviated expression of the lithium ion sieve adsorbent is at least one of LiZnAl / LDH, LiFeAl / LDH, or LiZnFeAl / LDH. LiZnAl / LDH represents zinc-doped lithium aluminum layered double hydroxide, LiFeAl / LDH represents iron-doped lithium aluminum layered double hydroxide, and is a single-metal-doped lithium aluminum layered double hydroxide. LiZnFeAl / LDH represents zinc- and iron-doped lithium aluminum layered double hydroxide, and is a bimetal-doped lithium aluminum layered double hydroxide.

[0019] More preferably, the abbreviated expression of the lithium ion sieve adsorbent is LiZnFeAl / LDH. The LiZnFeAl / LDH can achieve unexpected lithium ion adsorption-desorption cycle stability effect.

[0020] A third aspect of the present invention provides an application of a metal-doped lithium ion sieve adsorbent.

[0021] The application of the above lithium ion sieve adsorbent in lithium extraction.

[0022] Preferably, the above-mentioned lithium ion sieve adsorbent is used in extracting lithium from brine.

[0023] Application of the above lithium ion sieve adsorbent in gas separation.

[0024] Preferably, the application of the lithium ion sieve adsorbent in air separation has the following beneficial effects compared to the prior art:

[0025] (1) The present invention utilizes specific reaction conditions (e.g., oil bath conditions at a relatively low temperature and the use of a zinc source and / or an iron source) to obtain single-metal-doped LiFeAl / LDH or LiZnAl / LDH, or bimetal-doped LiZnFeAl / LDH. The metal-doped lithium ion sieve adsorbent prepared by the preparation method of the present invention has the advantages of high adsorption capacity and good cycling stability. In particular, LiZnFeAl / LDH can achieve unexpected cycling stability.

[0026] (2) The lithium ion sieve adsorbent of the present invention further has the advantage of good selectivity. The lithium ion sieve adsorbent of the present invention does not consume acid and does not generate secondary waste during the adsorption-desorption process, and is safe and environmentally friendly.

[0027] (3) The alkaline hydroxide used in the preparation method of the present invention is a lithium salt and an aluminum source, and a hydrochloric acid solution is used to adjust the pH value of the reaction environment. The present invention adopts a co-precipitation method, washing, centrifugation, and drying to obtain a lithium ion sieve adsorbent. Using a cation control strategy, the metal occupies part of the Al position in the LiAl / LDH main body, thereby improving the performance of the lithium ion sieve adsorbent. The preparation method of the present invention has the characteristics of one-step synthesis, and the aluminum-based lithium adsorbent does not use acidic substances and does not produce secondary waste during the lithium ion adsorption and desorption process, which is beneficial to environmental protection; compared with other existing methods, the lithium ion sieve adsorbent synthesized by the present invention will not collapse and deactivate during the adsorption and desorption process, and has a high adsorption capacity, good cycle stability and selectivity; the lithium ion sieve adsorbent synthesized by the present invention can be used for gas separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Graph showing the cyclic adsorption effects of lithium ions on LiZnAl / LDH, LiFeAl / LDH, LiZnFeAl / LDH, and LiAl / LDH prepared in Examples 1-3 and Comparative Example 1 of the present invention;

[0029] Figure 2 This is a diagram showing the selectivity of LiZnFeAl / LDH prepared in Example 3 of the present invention in simulated high-concentration brine;

[0030] Figure 3 This is the SEM image of LiZnAl / LDH prepared in Example 1;

[0031] Figure 4 This is the SEM image of LiFeAl / LDH prepared in Example 2;

[0032] Figure 5 This is the SEM image of LiZnFeAl / LDH prepared in Example 3. DETAILED DESCRIPTION

[0033] In order to make the technical solution of the present invention more clearly understood by those skilled in the art, the following examples are given for illustration. It should be noted that the following examples do not limit the scope of protection claimed by the present invention.

[0034] Unless otherwise specified, the raw materials, reagents, or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0035] Comparative Example 1: Preparation of Lithium Ion Screen Adsorbent LiAl / LDH

[0036] 0.12 mol of lithium hydroxide, 0.04 mol of aluminum hydroxide, and 40 mL of deionized water were added to a three-necked flask and stirred. Hydrochloric acid was added to adjust the pH to 8. The mixture was reacted in an oil bath at 90° C. for 48 hours. The obtained sample was centrifuged, washed, and dried in a vacuum chamber at 60° C. overnight to obtain LiAl / LDH.

[0037] Example 1: Preparation of Lithium Ion Sieving Adsorbent LiZnAl / LDH

[0038] A method for preparing a metal-doped lithium ion sieve adsorbent comprises the following steps:

[0039] 0.12 mol of lithium hydroxide and 0.04 mol of aluminum hydroxide were added to a three-necked flask, and the mixture was stirred with 0.01 mol of zinc chloride and 60 mL of deionized water. The mixture was reacted in an oil bath at a temperature of 90° C. for 48 hours. The mixture was then centrifuged, washed, and dried to obtain a lithium ion sieve adsorbent (LiZnAl / LDH).

[0040] Example 2: Preparation of LiFeAl / LDH Lithium Ion Sieve Adsorbent

[0041] A method for preparing a metal-doped lithium ion sieve adsorbent comprises the following steps:

[0042] 0.12 mol of lithium hydroxide and 0.04 mol of aluminum hydroxide were added to a three-necked flask, and the mixture was stirred with 0.005 mol of ferric chloride hexahydrate and 60 mL of deionized water. The mixture was reacted in an oil bath at a temperature of 90° C. for 48 hours. The mixture was then centrifuged, washed, and dried to obtain a lithium ion sieve adsorbent (LiFeAl / LDH).

[0043] Example 3: Preparation of Lithium Ion Sieve Adsorbent LiZnFeAl / LDH

[0044] A method for preparing a metal-doped lithium ion sieve adsorbent comprises the following steps:

[0045] 0.12 mol of lithium hydroxide and 0.04 mol of aluminum hydroxide were added to a three-necked flask, and the mixture was stirred with 0.01 mol of zinc chloride, 0.005 mol of ferric chloride hexahydrate, and 60 mL of deionized water. The mixture was reacted in an oil bath at a temperature of 90° C. for 48 hours, and then centrifuged, washed, and dried to obtain a lithium ion sieve adsorbent (LiZnFeAl / LDH).

[0046] Product Effect Test - Direct Lithium Ion Extraction:

[0047] The lithium ion sieve adsorbents LiZnAl / LDH, LiFeAl / LDH, LiZnFeAl / LDH prepared in Examples 1-3 and LiAl / LDH prepared in Comparative Example 1 were tested for their cyclic adsorption effects on lithium ions under the same conditions. The results are as follows: Figure 1 shown.

[0048] The process of testing the cyclic adsorption effect of lithium ions is as follows: a certain amount of lithium adsorbent is weighed, the adsorbent is suspended in a certain volume of 500 mg / L lithium chloride solution, adsorbed at 40-50 ° C for 3-5 hours until adsorption equilibrium is reached, the supernatant is filtered with a 0.1 μm filter membrane, and the lithium ion content is detected by ICP-OES inductively coupled plasma emission spectrometry. Calculate Li + The adsorption amount; where q t is the adsorption capacity at time t, mg / g; C0 is the initial mass concentration of lithium ions in the solution, mg / L; C t is the mass concentration of lithium ions after adsorption, mg / L; m is the mass of the adsorbent, g; V is the volume of the adsorption liquid, L.

[0049] In the desorption experiments, a 0.5% mass concentration of CaCl2 solution was used, and the adsorbent was desorbed at a constant temperature of 40-50 °C for 30-120 min.

[0050] To evaluate the reusability of the adsorbent (lithium ion sieve adsorbent), an adsorption-desorption cycle was tested. The adsorption solution was a 500 mg / L lithium chloride solution, and the desorption solution was a 0.5% CaCl2 solution. The regenerated adsorbent was then placed directly into a lithium-containing solution for the next adsorption-desorption cycle. The cycle was repeated 30 times.

[0051] Figure 1 This is a diagram showing the cyclic adsorption effect of lithium ions on LiZnAl / LDH, LiFeAl / LDH, LiZnFeAl / LDH and LiAl / LDH prepared in Examples 1-3 of the present invention and Comparative Example 1.

[0052] from Figure 1 It can be seen that the initial adsorption capacities of LiZnAl / LDH, LiFeAl / LDH, LiZnFeAl / LDH and LiAl / LDH are 14.0 mg / g, 9.1 mg / g, 12.2 mg / g and 4.4 mg / g, respectively. After 7 cycles, the adsorption capacity corresponding to LiZnFeAl / LDH significantly exceeds that of LiZnAl / LDH and LiFeAl / LDH, achieving an unexpected adsorption effect.

[0053] from Figure 1It can also be seen that the metal-doped lithium ion sieve adsorbent prepared in this embodiment of the present invention, compared with the undoped lithium adsorbent (Comparative Example 1), maintains cyclic stability through 30 adsorption / desorption cycles, and the adsorption capacity remains substantial even after the 30th cycle (for example, the adsorption capacity of LiZnFeAl / LDH remains above 7.7 mg / g after 30 cycles). Cation doping improves the adsorption performance and stability of the lithium adsorbent.

[0054] Figure 2 This is a diagram showing the selectivity of LiZnFeAl / LDH prepared in Example 3 of the present invention in simulated high-concentration brine. Table 1 shows the concentrations of various metal ions in simulated high-concentration brine, as well as Cl - 、SO4 2- concentration.

[0055] Table 1 Simulated brine

[0056] ion <![CDATA[Li + ]]> <![CDATA[Na + ]]> <![CDATA[K + ]]> <![CDATA[Mg 2+ ]]> <![CDATA[Ca 2+ ]]> <![CDATA[Cl - ]]> <![CDATA[SO4 2- ]]> Concentration (mg / L) 210 6930 870 18300 68 16050 1500

[0057] from Figure 2 (The vertical axis represents the selectivity factor) It can be seen that LiZnFeAl / LDH has a high concentration of Li in brine. + / K + 、 Li + / Ca 2+ The selectivity factor exceeds 250, Li + / Mg 2+ 、Li + / Na + The selectivity factor is more than 25, which has a significant separation effect.

[0058] Product effect test-oxygen and nitrogen adsorption:

[0059] A Micromeritics Tristar II 3020 v1.03 gas adsorption and surface area analyzer was used to obtain nitrogen and oxygen adsorption isotherms at 0°C and relative pressures P / P0 between 0 and 1 to evaluate its air separation performance. In all gas adsorption experiments, the powder samples were degassed in a vacuum at 300°C for at least 6 hours before measurement. The maximum adsorption capacity of LiZnFeAl / LDH for oxygen was measured to be 2.8 cm 3 / g, the maximum adsorption capacity of nitrogen is < 0.01 cm 3 / g, with unexpected air separation effect.

[0060] Figure 3 This is the SEM image of LiZnAl / LDH prepared in Example 1; Figure 4 This is the SEM image of LiFeAl / LDH prepared in Example 2; Figure 5This is the SEM image of LiZnFeAl / LDH prepared in Example 3.

[0061] The above content describes some embodiments of the present invention. It should be understood by those skilled in the art that the scope of protection of the present invention is not limited by the above embodiments. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements without paying creative effort, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. Application of lithium ion sieve adsorbent in air separation; The preparation method of the lithium ion sieve adsorbent comprises the following steps: 0.12 mol of lithium hydroxide and 0.04 mol of aluminum hydroxide were added to a three-necked flask, and the mixture was stirred with 0.01 mol of zinc chloride, 0.005 mol of ferric chloride hexahydrate, and 60 mL of deionized water. The mixture was reacted in an oil bath at a temperature of 90° C. for 48 hours, and then centrifuged, washed, and dried to obtain a lithium ion sieve adsorbent. The air separation refers to separating oxygen and nitrogen in the air.

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