Hydrophobic deep eutectic solvents, methods of making and using the same, and methods of extracting lithium ions

Abstract

The application relates to the field of metal lithium ion recovery, and discloses a hydrophobic eutectic solvent, a preparation method and application thereof, and a lithium ion extraction method.The eutectic solvent comprises tributyl phosphate and a phenolic compound, the molar ratio of the tributyl phosphate and the phenolic compound is 2-4:1, and the phenolic compound is selected from at least one of bisphenol A and C8-C 16 alkyl phenol. The hydrophobic eutectic solvent provided by the application can selectively extract and separate metal lithium ions, has a high metal lithium ion extraction efficiency, and can reach more than 89%; in addition, when the hydrophobic eutectic solvent is used as an extractant to extract metal lithium ions in water, the hydrophobic eutectic solvent has the advantages of good stability, simple operation, recyclability, low loss rate, green environmental protection and the like.

Description

Technical Field

[0001] This invention relates to the field of lithium ion recovery, specifically to a hydrophobic eutectic solvent, its preparation method and application, and a method for extracting lithium ions. Background Technology

[0002] Lithium (Li), a "new energy metal" of the 21st century, is the softest and least dense alkali metal in nature. Due to its excellent physicochemical properties, such as extremely high electrochemical activity and high specific heat capacity, it has been regarded as a strategic resource. The future trend will focus on using salt lake brine as the primary source of lithium, comprehensively utilizing it to maximize the role of various elements in production and daily life, reduce environmental problems caused by production, and pursue a green and sustainable development path.

[0003] Lithium extraction from salt lakes has always been a challenge, as the composition of salt lake brine is extremely complex, containing not only Li... + It also contains a large number of other alkali metal and alkaline earth metal ions, and these metal ions with similar properties greatly hinder lithium extraction from the brine. In addition, the complex composition of anions further increases the difficulty of lithium extraction from the brine. Although salt lakes around the world differ in properties and composition, the initial brine treatment processes are very similar. Typically, solar energy is used to evaporate and concentrate the raw brine to enrich lithium, and then a suitable lithium extraction method is selected based on the properties and characteristics of the brine.

[0004] The booming development of the new energy industry has led to a significant increase in global lithium consumption. Precipitation, membrane separation, solvent extraction, and adsorption technologies are important methods for lithium extraction from salt lakes. Among these, solvent extraction is one of the most promising methods. However, traditional extraction systems have many shortcomings, such as severe equipment corrosion and the hazards of volatile organic solvents. Therefore, it is necessary to establish new green extraction systems for lithium extraction from brine. Demodified eutectic solvents (DESs) are considered a "green" solvent that can replace volatile organic solvents due to their low volatility, low toxicity, and high thermal stability.

[0005] CN112226632A discloses a method for selectively extracting lithium from lithium precipitation mother liquor using a hydrophobic eutectic solvent. The hydrophobic eutectic solvent serves as both a co-extractant and a diluent, and tributyl phosphate is used as the extractant to construct the extractive organic phase. The hydrophobic eutectic solvent uses at least one of tetrabutylammonium chloride, tetrahexylammonium chloride, and tetraoctylammonium chloride as the hydrogen bond acceptor and oleic acid as the hydrogen bond donor, with a molar ratio of 1:(1-3). This method utilizes a hydrophobic eutectic solvent to construct the extractive organic phase, which offers advantages such as simple synthesis, convenient operation, and short extraction time. However, it still suffers from a low extraction rate. Summary of the Invention

[0006] The purpose of this invention is to provide a hydrophobic eutectic solvent with high adsorption efficiency and good selectivity for lithium ions.

[0007] To achieve the above objectives, a first aspect of the present invention provides a hydrophobic eutectic solvent comprising tributyl phosphate and a phenolic compound, wherein the molar ratio of the tributyl phosphate to the phenolic compound is 2-4:1.

[0008] The phenolic compound is selected from bisphenol A, C8-C 16 At least one of the alkylphenols.

[0009] Preferably, the phenolic compound is selected from bisphenol A and C. 12 -C 16 At least one of the alkylphenols.

[0010] A second aspect of the present invention provides a method for preparing the hydrophobic eutectic solvent described in the first aspect, the method comprising: contact mixing tributyl phosphate and a phenolic compound to obtain the hydrophobic eutectic solvent.

[0011] Preferably, the contact mixing temperature is 80-100℃.

[0012] Preferably, the method further includes: drying the product obtained by the contact mixing to obtain the hydrophobic eutectic solvent;

[0013] The drying conditions are controlled such that the water content of the hydrophobic eutectic solvent is less than 0.1 wt%.

[0014] A third aspect of the present invention provides the application of the hydrophobic eutectic solvent described in the first aspect in lithium-ion extraction.

[0015] Preferably, the lithium-ion extraction rate of the hydrophobic eutectic solvent is ≥89%.

[0016] A fourth aspect of the present invention provides a method for extracting lithium ions, the method comprising: mixing a hydrophobic eutectic solvent and a lithium-containing solution for extraction treatment;

[0017] The hydrophobic eutectic solvent is the hydrophobic eutectic solvent described in the first aspect.

[0018] Preferably, in the lithium-containing solution, the concentration of lithium ions is 0.08-0.12 g / L, and the concentration of impurity ions is 0.12-0.24 g / L.

[0019] Preferably, the volume ratio of the hydrophobic eutectic solvent to the lithium-containing solution is 0.8-1.2:1.

[0020] Through the above technical solution, the present invention has at least the following advantages:

[0021] (1) The hydrophobic eutectic solvent provided by the present invention can selectively extract and separate lithium ions, with an extraction rate of over 89%, which has good economic benefits.

[0022] (2) The hydrophobic eutectic solvent provided by the present invention is used as an extractant to extract lithium ions in water. It has the advantages of good stability, simple operation, recyclability, low loss rate and green environmental protection.

[0023] (3) The preparation method of the hydrophobic eutectic solvent provided by the present invention is simple to operate and easy to implement. Detailed Implementation

[0024] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0025] As mentioned above, a first aspect of the present invention provides a hydrophobic eutectic solvent comprising tributyl phosphate and a phenolic compound, wherein the molar ratio of the tributyl phosphate to the phenolic compound is 2-4:1.

[0026] The phenolic compound is selected from bisphenol A, C8-C 16 At least one of the alkylphenols.

[0027] Preferably, the phenolic compound is selected from bisphenol A and C. 12 -C 16 At least one of the alkylphenols.

[0028] More preferably, the phenolic compound is dodecylphenol. The inventors of this invention have discovered that, under this preferred condition, the technical solution of this invention can obtain a hydrophobic eutectic solvent with higher lithium-ion adsorption efficiency.

[0029] As previously stated, a second aspect of the present invention provides a method for preparing the hydrophobic eutectic solvent described in the first aspect, the method comprising: contact mixing tributyl phosphate and a phenolic compound to obtain the hydrophobic eutectic solvent.

[0030] Preferably, the contact mixing temperature is 80-100℃.

[0031] This invention does not impose particular limitations on the contact mixing time and rotation speed, as long as a uniform, transparent, liquid-like hydrophobic eutectic solvent can be obtained. For example, the contact mixing time is 100-300 min, and the rotation speed is 200-500 rpm.

[0032] The present invention does not impose any particular limitation on the contact mixing method; for example, the contact mixing can be carried out in an oil bath.

[0033] Preferably, the method further includes: drying the product obtained by the contact mixing to obtain the hydrophobic eutectic solvent;

[0034] The drying conditions are controlled such that the water content of the hydrophobic eutectic solvent is less than 0.1 wt%, for example, it can be 0.02 wt%, 0.04 wt%, 0.06 wt%, or 0.08 wt%.

[0035] As previously stated, a third aspect of the present invention provides the application of the hydrophobic eutectic solvent described in the first aspect in lithium-ion extraction.

[0036] Preferably, the lithium-ion extraction rate of the hydrophobic eutectic solvent is ≥89%, more preferably ≥92%, more preferably ≥94%, and particularly preferably ≥95%.

[0037] As mentioned above, a fourth aspect of the present invention provides a method for extracting lithium ions, the method comprising: mixing a hydrophobic eutectic solvent and a lithium-containing solution for extraction treatment;

[0038] The hydrophobic eutectic solvent is the hydrophobic eutectic solvent described in the first aspect.

[0039] Preferably, in the lithium-containing solution, the concentration of lithium ions is 0.08-0.12 g / L, and the concentration of impurity ions is 0.12-0.24 g / L.

[0040] The impurity ions mentioned in this invention refer to metal ions other than lithium ions. Preferably, the impurity ions include calcium ions and magnesium ions, with the concentration of calcium ions being 0.07-0.11 g / L and the concentration of magnesium ions being 0.05-0.13 g / L. The hydrophobic eutectic solvent provided by this invention exhibits excellent selective adsorption of lithium ions, enabling the extraction of lithium ions from systems containing multiple metal ions.

[0041] Preferably, the volume ratio of the hydrophobic eutectic solvent to the lithium-containing solution is 0.8-1.2:1, for example, it can be 0.8:1, 1.0:1, or 1.2:1.

[0042] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, the raw materials and equipment used are commercially available products.

[0043] Dodecylphenol: CAS number 27193-86-8.

[0044] Hexadecylphenol: CAS No. 2589-78-8.

[0045] Example 1

[0046] Tributyl phosphate and phenolic compound (bisphenol A) were weighed separately using an analytical balance and placed in a flask at a molar ratio of 2:1. The amount of tributyl phosphate was 2 mol. The flask was placed in an oil bath containing silicone oil, and a magnetic stir bar was added. The oil bath was heated to 100°C, and stirring was started (at 400 rpm). When the mixture became a homogeneous and transparent liquid (total time 3 hours), heating was stopped and stirring was turned off.

[0047] The synthesized hydrophobic eutectic solvent was taken out and dried using a rotary evaporator to remove water (the water content was measured to be 0.01 wt% using a Karl Fischer apparatus) to obtain the hydrophobic eutectic solvent.

[0048] Example 2

[0049] The procedure was carried out using a method similar to that in Example 1, except that bisphenol A was replaced with an equal weight of dodecylphenol;

[0050] Everything else is the same, resulting in a hydrophobic eutectic solvent.

[0051] Example 3

[0052] Tributyl phosphate and a phenolic compound (dodecylphenol) were weighed separately using an analytical balance and placed in a flask at a molar ratio of 3:1. The flask was then placed in an oil bath containing silicone oil, and a magnetic stir bar was inserted. The oil bath was heated to 100°C, and stirring was started (at 400 rpm). When the mixture became a homogeneous, transparent liquid (total time 3 hours), heating was stopped, and stirring was turned off.

[0053] The synthesized hydrophobic eutectic solvent was taken out and dried using a rotary evaporator to remove water (the water content was measured to be 0.001 wt% by Karl Fischer apparatus) to obtain the hydrophobic eutectic solvent.

[0054] Example 4

[0055] The procedure was carried out using a method similar to that in Example 3, except that the molar ratio of tributyl phosphate to phenolic compounds was adjusted to 4:1.

[0056] Everything else is the same, resulting in a hydrophobic eutectic solvent.

[0057] Example 5

[0058] The same method as in Example 3 was used, except that the heating temperature was set to 80°C by adjusting the switch.

[0059] Everything else is the same, resulting in a hydrophobic eutectic solvent.

[0060] Example 6

[0061] The same method as in Example 3 was used, except that the heating temperature was set to 90°C by adjusting the switch.

[0062] Everything else is the same, resulting in a hydrophobic eutectic solvent.

[0063] Example 7

[0064] The procedure was carried out using a method similar to that in Example 1, except that bisphenol A was replaced with an equal weight of hexadecylphenol.

[0065] Everything else is the same, resulting in a hydrophobic eutectic solvent.

[0066] Comparative Example 1

[0067] The procedure was carried out using a method similar to that in Example 1, except that bisphenol A was replaced with an equal weight of catechol;

[0068] Everything else is the same, resulting in a hydrophobic eutectic solvent.

[0069] Comparative Example 2

[0070] The procedure was carried out using a method similar to that in Example 1, except that the molar ratio of tributyl phosphate to phenolic compounds was adjusted to 6:1.

[0071] Everything else is the same, resulting in a hydrophobic eutectic solvent.

[0072] Application examples

[0073] The hydrophobic eutectic solvent and the lithium-containing solution (lithium ion concentration 0.1 g / L, calcium ion concentration 0.1 g / L, magnesium ion concentration 0.1 g / L) prepared in the example were mixed at a volume ratio of 1:1 and subjected to extraction under vigorous shaking for 5 hours. After centrifugation to separate the layers, the extract phase and the raffinate phase were obtained. The concentration of metal ions in the extract phase was calculated by measuring the concentration of residual metal ions in the raffinate phase using atomic absorption spectrometry, and the extraction rate of metal ions was calculated using the following formula:

[0074] Extraction rate (%) = (Concentration of metal ions in lithium-containing solution - Concentration of residual metal ions in raffinate phase) / Concentration of metal ions in lithium-containing solution × 100%.

[0075] The calculation results are shown in Table 1.

[0076] Table 1

[0077]

[0078]

[0079] As can be seen from the results in Table 1, the hydrophobic eutectic solvent provided by the present invention can selectively extract and separate lithium metal ions, and the extraction efficiency of lithium metal ions is high, reaching more than 89%.

[0080] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method of extracting lithium ions, characterized by, The method comprises: contacting and mixing tributyl phosphate and a phenolic compound, and then drying the product obtained by the contacting and mixing to obtain a hydrophobic deep eutectic solvent; wherein the phenolic compound is selected from at least one of bisphenol A, C 12 -C 16 alkylphenol; the molar ratio of the use amount of the tributyl phosphate and the phenolic compound is 2-4:1; the temperature of the contact mixing is 80-100℃; the condition of the drying is controlled so that the water content of the hydrophobic deep eutectic solvent is lower than 0.1wt%; mixing the hydrophobic deep eutectic solvent and a lithium-containing solution for extraction treatment.

2. The method of claim 1, wherein, The lithium ion extraction rate of the hydrophobic deep eutectic solvent is greater than or equal to 89%.

3. The method according to claim 1 or 2, characterized in that, In the lithium-containing solution, the concentration of lithium ions is 0.08-0.12 g / L, and the concentration of impurity ions is 0.12-0.24 g / L.

4. The method according to claim 1 or 2, characterized in that, The volume ratio of the hydrophobic deep eutectic solvent to the lithium-containing solution is 0.8-1.2:1.

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