Hydrophobic eutectic solvent, preparation method and application thereof, and method for extracting lithium ions

Abstract

The invention relates to the field of metal lithium ion recovery, and discloses a hydrophobic deep-eutectic solvent, a preparation method and application thereof, and a method for extracting lithium ions. The eutectic solvent comprises tributyl phosphate and a phenolic compound, and the molar ratio of the content of the tributyl phosphate to the content of the phenolic compound is (2-4): 1; the phenolic compound is selected from at least one of bisphenol A and C8-C16 alkyl phenol. The hydrophobic deep-eutectic solvent provided by the invention can selectively extract and separate the metal lithium ions, and the extraction efficiency of the metal lithium ions is relatively high and can reach 89% or above; in addition, the hydrophobic deep-eutectic solvent is used as an extracting agent for extracting metal lithium ions in water, and has the advantages of good stability, simplicity in operation, recyclability, low loss rate, environment friendliness and the like.

Description

Technical Field

[0001] The present invention relates to the field of metal lithium ion recovery, and in particular to a hydrophobic low eutectic solvent, a preparation method and application thereof, and a method for extracting lithium ions. Background Art

[0002] Lithium (Li), as the "new energy metal" of the 21st century, is a silvery white, soft and lightest alkali metal in nature. It has been regarded as a strategic resource due to its excellent physical and chemical properties such as extremely high electrochemical activity and high specific heat capacity. The future trend will be to use salt lake brine as the main source of lithium, make comprehensive use of salt lake brine, maximize the role of various elements in brine in production and life, reduce environmental problems caused by production, and take a green and sustainable development path.

[0003] Lithium extraction from salt lakes has always been a difficult problem. The composition of salt lake brine is very complex. + , and also contains a large number of other alkali metal and alkaline earth metal ions. These metal ions with similar properties greatly hinder the extraction of lithium from brine. In addition, the complex composition of anions further increases the difficulty of extracting lithium from brine. Although the salt lakes in the world are different in properties and composition, the initial brine treatment process is very similar. Usually, solar energy is used to evaporate and concentrate the original brine to enrich lithium, and then a suitable lithium extraction method is selected according to the properties and characteristics of the brine.

[0004] The vigorous development of the new energy industry has led to a significant increase in global lithium consumption. Precipitation, membrane separation, solvent extraction and adsorption are important means of extracting lithium from salt lakes. Among them, solvent extraction is one of the most promising methods for lithium extraction. 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 a new green extraction system for lithium extraction from brine. Deep eutectic solvents (DESs) are considered to be a "green" solvent that can replace volatile organic solvents because of 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 low eutectic solvent, wherein the hydrophobic low eutectic solvent is a co-extractant and a diluent, and tributyl phosphate is an extractant to construct an extraction organic phase. The hydrophobic low eutectic solvent uses at least one of tetrabutylammonium chloride, tetrahexylammonium chloride, and tetraoctylammonium chloride as a hydrogen bond acceptor and oleic acid as a hydrogen bond donor, and the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:(1-3). The extraction organic phase constructed by the hydrophobic low eutectic solvent in this technical solution has the advantages of simple synthesis, convenient operation, and short extraction time, but it still has the defect of low extraction rate. Summary of the invention

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

[0007] In order to achieve the above object, the first aspect of the present invention provides a hydrophobic deep eutectic solvent, the deep eutectic solvent comprises 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, C 12 -C 16 At least one of the alkylphenols.

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

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

[0012] Preferably, the method further comprises: drying the product obtained by the contacting and mixing to obtain the hydrophobic low eutectic solvent;

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

[0014] The third aspect of the present invention provides use of the hydrophobic deep eutectic solvent described in the first aspect in lithium ion extraction.

[0015] Preferably, the lithium ion extraction rate of the hydrophobic deep 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 deep eutectic solvent and a lithium-containing solution to perform an extraction process;

[0017] The hydrophobic deep eutectic solvent is the hydrophobic deep 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 low 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 low eutectic solvent provided by the present invention can selectively extract and separate metallic lithium ions, with an extraction rate of lithium ions exceeding 89%, and has good economic benefits.

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

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

[0024] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0025] As mentioned above, the first aspect of the present invention provides a hydrophobic deep eutectic solvent, the deep 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, C 12 -C 16 At least one of the alkylphenols.

[0028] More preferably, the phenolic compound is dodecylphenol. The inventors of the present invention have found that, in this preferred case, the technical solution of the present invention can obtain a hydrophobic deep eutectic solvent with higher lithium ion adsorption efficiency.

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

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

[0031] The present invention has no particular limitation on the contact mixing time and rotation speed, as long as a uniform, transparent liquid hydrophobic low eutectic solvent can be obtained. Exemplarily, the contact mixing time is 100-300 min and the rotation speed is 200-500 rpm.

[0032] The present invention has no particular limitation on the contact mixing method. For example, the contact mixing can be performed in an oil bath.

[0033] Preferably, the method further comprises: drying the product obtained by the contacting and mixing to obtain the hydrophobic low eutectic solvent;

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

[0035] As mentioned above, the third aspect of the present invention provides the use of the hydrophobic deep eutectic solvent described in the first aspect in lithium ion extraction.

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

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

[0038] The hydrophobic deep eutectic solvent is the hydrophobic deep 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 described in the present invention refer to the remaining metal ions except lithium ions. Preferably, the impurity ions include calcium ions and magnesium ions, the concentration of calcium ions is 0.07-0.11 g / L, and the concentration of magnesium ions is 0.05-0.13 g / L. The hydrophobic deep eutectic solvent provided by the present invention has excellent selective adsorption for lithium ions and can extract lithium ions from a system containing multiple metal ions.

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

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

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

[0044] Hexadecylphenol: CAS number is 2589-78-8.

[0045] Example 1

[0046] Weigh tributyl phosphate and phenolic compound (bisphenol A) respectively using an analytical balance and put them into a flask at a molar ratio of 2:1. The amount of tributyl phosphate is 2 mol. Put the flask into an oil bath filled with silicone oil and put in a magnet. Turn on the oil bath heating, set the heating temperature to 100°C, start stirring (speed is 400 rpm), and stop heating and turn off stirring when stirring until it becomes a uniform, transparent liquid (total time is 3 hours);

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

[0048] Example 2

[0049] The method is similar to that of Example 1, except that an equal weight of dodecylphenol is used to replace bisphenol A;

[0050] The rest are the same, and a hydrophobic deep eutectic solvent is obtained.

[0051] Example 3

[0052] Weigh tributyl phosphate and phenolic compound (dodecylphenol) respectively using an analytical balance and put them into a flask at a molar ratio of 3:1. Put the flask into an oil bath filled with silicone oil and put in a magnet. Turn on the oil bath heating, set the heating temperature to 100°C, start stirring (speed is 400rpm), and stop heating and turn off stirring when stirring until it becomes a uniform, transparent liquid (total time is 3h);

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

[0054] Example 4

[0055] The method is similar to that of Example 3, except that the molar ratio of tributyl phosphate and the phenolic compound is adjusted to 4:1;

[0056] The rest are the same, and a hydrophobic deep eutectic solvent is obtained.

[0057] Example 5

[0058] The method is similar to that of Example 3, except that the switch is adjusted to set the heating temperature to 80°C;

[0059] The rest are the same, and a hydrophobic deep eutectic solvent is obtained.

[0060] Example 6

[0061] The method is similar to that of Example 3, except that the switch is adjusted to set the heating temperature to 90°C;

[0062] The rest are the same, and a hydrophobic deep eutectic solvent is obtained.

[0063] Example 7

[0064] The method is similar to that of Example 1, except that an equal weight of hexadecylphenol is used to replace bisphenol A;

[0065] The rest are the same, and a hydrophobic deep eutectic solvent is obtained.

[0066] Comparative Example 1

[0067] The method is similar to that of Example 1, except that an equal weight of catechol is used to replace bisphenol A;

[0068] The rest are the same, and a hydrophobic deep eutectic solvent is obtained.

[0069] Comparative Example 2

[0070] The method is similar to that of Example 1, except that the molar ratio of tributyl phosphate and the phenolic compound is adjusted to 6:1;

[0071] The rest are the same, and a hydrophobic deep eutectic solvent is obtained.

[0072] Application Examples

[0073] The hydrophobic deep eutectic solvent and the lithium-containing solution (lithium ion concentration is 0.1 g / L, calcium ion concentration is 0.1 g / L, magnesium ion concentration is 0.1 g / L) prepared in the example were mixed in a volume ratio of 1:1, and subjected to extraction treatment under vigorous shaking for 5 hours. The mixture was centrifuged and separated to obtain an extraction phase and a raffinate phase. The concentration of the remaining metal ions in the raffinate phase was measured by an atomic absorption spectrometer to calculate the metal ion concentration in the extraction phase, thereby calculating the extraction rate of the metal ions. The calculation formula is as follows:

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

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

[0076] Table 1

[0077]

[0078]

[0079] It can be seen from the results in Table 1 that the hydrophobic deep eutectic solvent provided by the present invention can selectively extract and separate metallic lithium ions, and the extraction efficiency of metallic lithium ions is relatively high, which can reach more than 89%.

[0080] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A hydrophobic deep eutectic solvent, characterized in that: The low eutectic solvent comprises tributyl phosphate and a phenolic compound, wherein the molar ratio of the tributyl phosphate to the phenolic compound is 2-4:1; The phenolic compound is selected from bisphenol A, C8-C 16 At least one of the alkylphenols.

2. The deep eutectic solvent according to claim 1, characterized in that The phenolic compound is selected from bisphenol A, C 12 -C 16 At least one of the alkylphenols.

3. A method for preparing the hydrophobic deep eutectic solvent according to claim 1 or 2, characterized in that: The method comprises: contacting and mixing tributyl phosphate and a phenolic compound to obtain the hydrophobic low eutectic solvent.

4. The method according to claim 3, characterized in that The temperature of the contact mixing is 80-100°C.

5. The method according to claim 3 or 4, characterized in that: The method further comprises: drying the product obtained by the contacting and mixing to obtain the hydrophobic deep eutectic solvent; The drying conditions are controlled so that the water content of the hydrophobic deep eutectic solvent is less than 0.1 wt %.

6. Use of the hydrophobic deep eutectic solvent according to claim 1 or 2 in lithium ion extraction.

7. The use according to claim 6, characterized in that: The lithium ion extraction rate of the hydrophobic deep eutectic solvent is ≥89%.

8. A method for extracting lithium ions, characterized in that: The method comprises: mixing a hydrophobic deep eutectic solvent and a lithium-containing solution for extraction treatment; The hydrophobic deep eutectic solvent is the hydrophobic deep eutectic solvent according to claim 1 or 2.

9. The method according to claim 8, 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.

10. The method according to claim 8 or 9, characterized in that: The volume ratio of the hydrophobic low eutectic solvent to the lithium-containing solution is 0.8-1.2:1.

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