CN111534690A

CN111534690A - Method for extracting organic phase and separating lithium in lithium-containing brine

Info

Publication number: CN111534690A
Application number: CN202010489586.8A
Authority: CN
Inventors: 姬连敏; 李丽娟; 时东; 彭小五; 张利诚; 宋富根; 宋雪雪; 聂锋; 曾忠民; 张禹泽
Original assignee: Qinghai Institute of Salt Lakes Research of CAS
Current assignee: Qinghai Institute of Salt Lakes Research of CAS
Priority date: 2020-06-02
Filing date: 2020-06-02
Publication date: 2020-08-14

Abstract

The invention discloses a method for extracting an organic phase and separating lithium in lithium-containing brine. The extracted organic phase comprises an amide extractant, and the molecular formula of the amide extractant is as follows: c₁₉H₃₉NO₂The amide extractant can well solve the problems of equipment corrosion, high acid and alkali consumption, three-phase extraction, and the like in the extraction process of an extracted organic phase in the prior art. The organic phase extraction method has excellent extraction efficiency when being used in the field of lithium ion extraction.

Description

Method for extracting organic phase and separating lithium in lithium-containing brine

Technical Field

The invention belongs to the technical field of extraction, and particularly relates to an extraction organic phase and a method for separating lithium in lithium-containing brine.

Background

In recent years, the widespread popularization and wide attention of the Electric Vehicle (EV) industry taking lithium batteries as new energy sources for power make lithium ion batteries one of the most rapidly developing fields at present, and lithium is called as '21 st century energy source new and expensive'. Lithium has become an ideal material for 21 st century energy and light alloy, is a resource with important significance in national economy, and is known as energy metal for promoting world progress.

China is a country with abundant lithium resources, and the total resource reserve of the found lithium ore deposit is 510 million (by Li)₂Calculated as O), is positioned at the fifth place and accounts for 13 percent of the total lithium resources in the world. Meanwhile, China is a major country of salt lake brine lithium resources, the salt lake lithium resources account for 87% of the total amount of lithium resources proven in China, account for 1/3% of the world salt lake lithium resources, and are mainly distributed in Qinghai Sida wood basins (Yili salt lake, Sitai Ginell salt lake and Dongtai Ginell salt lake, the brine lithium reserves account for about 48.5%), Tibet (Zambu salt lake, Zacanka salt lake, Chengdaka salt lake and Longmu staggered salt lake, the salt lake lithium reserves account for 18.8%), and the North lake (underground brine sunken in the Yangtze river, the lithium resource reserves account for 9%).

The method for extracting lithium from the salt lake brine rich in lithium has the characteristics of rich resources, low energy consumption, low cost and the like, and in the process for extracting lithium from the salt lake brine, the original brine is usually further evaporated and concentrated by a brine drying pool, and then the lithium in the concentrated brine is separated and extracted by adopting a proper separation technology. The technological process for extracting lithium salt from concentrated salt lake brine includes evaporating crystallization, precipitation, solvent extraction, membrane separation, ion exchange adsorption, calcination and extraction, and Schw's process.

Solvent extraction is used as a flexible liquid separation method,make full use of lithium (Li)⁺) And magnesium (Mg)²⁺) Different charge and ionic radius, for Li⁺Has high selectivity. Neutral organic phosphorus extraction organic phase tributyl phosphate (TBP) and complex anion FeC1₄]^-Co-extraction of Li⁺The process flow is the most classical industrialized flow reported at home and abroad for recovering lithium chloride (LiCl) from the salt lake old brine with high magnesium-lithium ratio. But the bottleneck restricting the industrialization process is as follows: TBP has large water-soluble loss and is easy to decompose under acidic conditions, and TBP-kerosene composite extraction organic phase has the problems of long process flow, large acid and alkali consumption, serious equipment corrosion and the like. Researchers at Qinghai salt lake research institute of Chinese academy of sciences adopt an amide extractant N523(N, N-di (2-ethylhexyl) acetamide) to completely replace TBP to extract and separate LiCl from Qinghai salt lake brine for detailed research, and concretely refers to research on extracting lithium from salt lake brine with high magnesium-lithium ratio by a new extraction system, Shidong, Qinghai salt lake research institute of Chinese academy of sciences, 2013).

Disclosure of Invention

The invention provides a novel extracted organic phase and further provides a method for separating lithium in lithium-containing brine by using the extracted organic phase.

In order to achieve the above objects, the present invention provides an extracted organic phase comprising an amide extractant having a molecular formula: c₁₉H₃₉NO₂The structural formula of the amide extractant is as follows:

wherein R is₁、R₂、R₃、R₄、R₅And R₆Selected from ethyl and hydrogen atoms.

Preferably, the amide extractant is 2-methoxy acetyl diisooctylamine, and the structural formula is as follows:

further, the extraction organic phase also comprises a diluent and/or a surfactant.

Further, the diluent is selected from at least one of n-heptane, petroleum ether, cyclohexane, n-dodecane, sulfonated kerosene, No. 200 solvent oil or aromatic hydrocarbon diluent; the surfactant is tributyl phosphate, dioctyl phthalate or acetyl tributyl citrate; the volume of the extracted organic phase is calculated by 100 parts, and the volume concentration of the amide extractant is 35-60%.

The invention provides a method for separating lithium in lithium-containing brine based on the extracted organic phase, which comprises the following steps:

mixing the lithium-containing brine with the extracted organic phase, oscillating for extraction, standing for phase separation to obtain an extract phase and raffinate, and transferring all or part of lithium in the original lithium-containing brine to the extract phase.

Preferably, in the lithium-containing brine: the concentration of lithium ions is 0.1-5 g/L; the volume ratio of the extracted organic phase to the lithium-containing brine is more than 1.

Preferably, in the lithium-containing brine: the concentration of chloride ions is more than 5.5mol/L, and the concentration of hydrogen ions is less than 0.9 mol/L.

Preferably, the lithium-containing brine further contains iron ions, and the amount ratio of the lithium iron ions is 1 to 1.5: 1.

Preferably, in the lithium-containing brine: the concentration of lithium ions is 0.1-2 g/L, the concentration of chloride ions is 8-9 mol/L, and the concentration of hydrogen ions is 0.04-0.9 mol/L; the volume ratio of the extracted organic phase to the lithium-containing brine is 2-5: 1.

Further preferably, the extraction organic phase is used to perform a cascade countercurrent extraction with respect to the lithium-containing brine.

Compared with the prior art, the invention has the following beneficial effects:

the extraction organic phase provided by the invention contains the amide extractant with a specific structure, and the amide extractant has weaker alkalinity, so that the acid consumption of the extraction organic phase is lower, and the phase separation effect is better compared with other extractants.

Drawings

Features and advantages of embodiments of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of the electron-withdrawing induction effect in the amide extractant according to the embodiment of the present invention;

FIG. 2 shows an operational diagram and test data of example 11.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the specific embodiments set forth herein. Rather, these embodiments are provided to explain the principles of the invention and its practical application to thereby enable others skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use contemplated.

The invention provides a novel extracted organic phase and further provides a method for separating lithium from lithium-containing brine by using the extracted organic phase based on the problems of corrosion of equipment, high acid and alkali consumption, occurrence of a third phase in two-phase extraction and the like in the extraction process of the extracted organic phase in the prior art.

1. Embodiments of the present invention provide an extracted organic phase comprising an amide extractant having a molecular formula: c₁₉H₃₉NO₂The structural formula of the amide extractant is as follows:

In some embodiments, the amide extractant is 2-methoxyacetyl diisooctylamine having the formula:

it is worth mentioning that the amide extractant is less sterically hindered and more readily interacts with the complex LiFeCl when the ethyl substituent is located further away from the N-C ═ O coordination center than 2-methoxyacetyl diisooctylamine under the same formula and carbon backbone length₄In combination, i.e. with less steric hindrance, amide extractants are more favorable for lithium extraction.

The amide extractant provided by the embodiment of the invention belongs to amide compounds. In the molecules of the amide extractant, pi electrons in carbonyl groups and lone electrons occupying p orbitals on nitrogen atoms form a p-pi electron conjugated system, so that the electron cloud density on the nitrogen atoms is reduced, and the alkalinity of imino groups is weakened. Due to methoxyl (-OCH) in the amide extractant₃) Is a stronger electron-withdrawing group, has electron-withdrawing induction effect (-I) compared with methyl (-CH)₃) The basicity of the imino group can be further weakened, thereby reducing the acid consumption in the extraction process. Therefore, the amide extractant provided by the invention has weaker hydrochloric acid extraction capability and better phase separation effect compared with the existing extractant. The schematic diagram of the electron-withdrawing induction effect is shown in fig. 1.

In some embodiments, the organic phase further comprises a diluent and/or a surfactant.

Diluent agent:

the diluent must be of low viscosity and have a large density difference with the extracted organic phase to improve the density and viscosity of the extracted organic phase and to enlarge the density difference between the extracted organic phase and the lithium-containing brine to facilitate the phase separation process. The diluent may be at least one selected from n-heptane, petroleum ether, cyclohexane, n-dodecane, sulfonated kerosene, No. 200 mineral spirits, and aromatic diluents, and the selection of the diluent is not limited in the present invention. From the phase separation time, the phase separation time of the n-heptane, the petroleum ether and the xylene is equivalent and is less than 50s, and the phase separation time of the sulfonated kerosene is long. But xylene is the most toxic from toxicity analysis. The influence of various diluents on the extraction rate of lithium, the extraction rate of HCl and the separation factor of lithium and magnesium in the lithium-containing brine is small, and a phase interface is clear and no phase interface substance or third phase is generated in the extraction process. Therefore, if the influence of the phase separation time is taken into consideration, n-heptane and petroleum ether are preferable as the diluent. If the influence of the phase separation time is not considered, the sulfonated kerosene which has low toxicity, high safety, low price and most common application is used as the diluent from the consideration of the toxicity and the economic cost of the diluent.

The higher the concentration of the amide extractant, the lower the dilution effect of the diluent, which results in higher viscosity of the extracted organic phase and long extraction phase separation time. Thus, in some preferred embodiments, the volume of the organic phase is controlled to be in the range of (35:65) to (90:10), more preferably (40:60) to (90:10), based on 100 parts by volume of the amide extractant to diluent in the organic phase.

Surface modifier:

the surface modifier is preferably dioctyl phthalate (DOP), tributyl citrate (TBC) or acetyl tributyl citrate (ATBC). Generally, the addition of a surface modifier increases the size of the complex LiFeCl₄Solubility in the extraction organic phase, that is, the addition of a surface modifier, facilitates the extraction of lithium. This is because the addition of the surface modifier causes more iron ions in the extraction system to be carried into the extraction organic phase in the form of a complex, which reduces the probability of hydrolysis of iron ions, and thus can ameliorate the severe phase separation problem that occurs during extraction when an amide extractant is used alone.

However, the inventors of the present invention found through studies that: (1) the increase of the volume concentration of TBP in the extracted organic phase can lead to the sharp increase of the magnesium ion concentration in the extracted phase, and the lithium ion concentration is in a small reduction trend, thus leading to the linear reduction trend of the final lithium extraction rate and the lithium-magnesium separation factor. That is to say that the position of the first electrode,TBP for Mg in lithium-containing brine²⁺The extraction capacity of HCl and the extraction capacity of HCl are both larger than that of 2-methoxy acetyl diisooctylamine, so that negative effects are generated on the extraction and separation effects of lithium; (2) when the volume concentration of DOP in the extracted organic phase is increased, the lithium extraction rate is slightly increased; (3) the Li extraction rate remained essentially unchanged as the volume concentration of ATBC in the extracted organic phase increased. Therefore, although the three surfactants are not suitable as phase modifiers for the extraction system when considering the lithium extraction rate and the phase separation time, the technical scheme of adding the surfactant to the extraction organic phase still falls within the scope of the present invention.

2. The embodiment of the invention provides a method for separating lithium in lithium-containing brine based on the extracted organic phase, which comprises the following steps:

mixing lithium-containing brine with the extracted organic phase, oscillating for extraction, standing for phase separation to obtain an extract phase and raffinate, wherein all or part of lithium in the original lithium-containing brine is transferred to the extract phase, and the rest lithium exists in the raffinate phase.

The lithium-containing brine comprises salt lake brine used in actual production, and the embodiment of the invention uses brine solution artificially prepared to simulate the salt lake brine. In practical salt lake brine, the high-content halogen element is chloride ion, and the chloride ion concentration in saturated magnesium chloride brine is generally higher than 9 mol/L.

(1) Compared with the following steps:

the phase ratio refers to the volume ratio of the extracted organic phase to the lithium-containing brine. Is in some embodiments above 1. When the dosage of the extraction organic phase is excessive, on one hand, the extraction cost is directly increased; on the other hand, a large amount of extract phase is generated during the extraction process, resulting in an increase in the cost of recovering the extract phase. Therefore, in order to avoid the problem of cost increase caused by too high amount of extraction organic phase, in some preferred embodiments, the ratio is 2 to 5:1, and more preferably 2: 1.

(2) Lithium ion concentration:

the substance composition and lithium content of different salt lake brine are different, and the concentration of lithium has great influence on the extraction effect, so in order to balance the problems of extraction efficiency and extraction cost, the optimal lithium ion concentration in the lithium-containing brine is 0.1-5 g/L, and more preferably 0.1-2 g/L.

(3) Chloride ion concentration:

note that the amide extractant and [ FeCl ] are added during the extraction process₄]^-Coordination of anions to combine Li⁺The extract phase is extracted as a complex. Therefore, to achieve a better extraction, higher concentrations of chloride ions are required to ensure more [ FeCl ] formation₄]^-Further more complex LiFeCl is formed₄. Therefore, in some preferred embodiments, the chloride ion concentration is above 5.5mol/L, more preferably 8-9 mol/L. Since the content of magnesium chloride in the salt lake brine is very high and even reaches the saturation concentration of magnesium chloride, the ion content of the brine is expressed by main anions, namely chloride ions, and the concentration of main cations, namely magnesium ions, is not particularly limited in the invention.

(4) The lithium iron ratio:

in addition, since both iron ions and lithium ions participate in the formation of the extraction complex, the ratio of the amount of the substance of iron ions to that of lithium ions affects the extraction rate of lithium as well, and the ratio of the amount of the optimum substance of iron ions to lithium ions is 1 to 1.5:1, more preferably 1.3: 1.

(5) Hydrogen ion concentration:

Li⁺and H⁺In this respect, H is in competition with the binding of the amide extractant⁺The presence of (a) is detrimental to the extraction of the organic phase to lithium; however, due to the presence of Fe in lithium-containing brines³⁺And Mg²⁺The two ions can respectively generate hydrolysis reaction to generate Fe (OH)₃And Mg (OH)₂Precipitation, which affects the phase separation process of extraction. Therefore, the hydrogen ion concentration is preferably below 0.9mol/L, and more preferably 0.04-0.9 mol/L, by comprehensively considering the two factors and performing regulation and control verification through a large amount of implementation data.

In some preferred embodiments, the extraction organic is used to perform a cascade countercurrent extraction on the lithium-containing brine.

In some preferred implementationsIn the example, the lithium-containing brine is subjected to three-stage countercurrent extraction, the lithium extraction rate is higher than 99%, and the lithium-magnesium separation factor is larger than 3.6 × 10⁴. The lithium ion concentration in the raffinate is reduced along with the increase of the cascade row number, and obviously, the cascade experiment performed by adopting the extracted organic phase has a cascade effect.

Compared with the traditional extraction of lithium from the organic phase TBP, the molecular structure and the extraction process thereof have the following advantages.

1. The N atom in the molecular structure of the amide extractant has longer alkyl chain, which is helpful for increasing the solubility of the amide extractant in an organic phase and avoiding the formation of a third phase.

2. The amide extractant of the invention has weaker hydrochloric acid extraction capability, greatly reduces the consumption of hydrochloric acid in the extraction process, and reduces the consumption of alkali in the saponification process in the same proportion, thereby reducing the production cost.

3. The sulfonated kerosene with 60 percent volume fraction of 2-methoxy acetyl diisooctylamine and 40 percent volume fraction of extracted organic phase is subjected to a three-stage countercurrent extraction process, the lithium extraction rate is higher than 99 percent, and the lithium-magnesium separation factor is larger than 3.6 multiplied by 104.

The above-described method for extracting an organic phase and extracting lithium from lithium-containing brine according to the present invention will be described below with reference to specific examples, and it will be understood by those skilled in the art that the following examples are merely specific examples of the above-described method for extracting an organic phase and extracting lithium from lithium-containing brine according to the present invention, and are not intended to limit the entirety thereof.

The calculation formulas involved in the examples are explained below:

(a) compared with R

The ratio of the volume of the extracted organic phase (O) to the volume of the lithium-containing brine (a) is referred to as the phase ratio.

(b) Distribution ratio D

Under certain conditions, when the extraction reaches the equilibrium, the ratio of the concentration of the extracted substance in the extraction phase to the concentration in the lithium-containing brine is represented by D:

(c) separation factor beta

The ratio of the partition ratios of the two substances to be separated in the extraction between the two phases, called the separation factor, is expressed as beta. If A, B represents the two substances to be separated, respectively:

the separation factor quantifies the ease of separation of two species in an extraction system. Wherein, when the separation factor is equal to 1, it means that the two substances cannot be separated; the greater the deviation of 1 of the separation factor pair, the easier it is to separate the two substances, i.e. the higher the separation selectivity of the organic phase of the extraction.

(d) Extraction Rate (E)

The extraction rate is the amount of extracted material transferred from the lithium-containing brine to the extraction phase during extraction as a percentage of the total amount of extracted material in the lithium-containing brine, and represents the degree of extractive separation.

Materials used in examples 1 to 11 of the present invention:

the amide extractant is 2-methoxy acetyl diisooctylamine.

The surfactant is TBP or dioctyl phthalate (DOP), acetyl tributyl citrate (ATBC), and the diluent is n-heptane, petroleum ether, xylene, toluene, cyclohexane, n-dodecane and sulfonated kerosene.

The lithium-containing brine is 2.0g/L Li⁺Brine system, wherein the concentration of magnesium ions is about 115 g/L. Adding certain HCl and FeCl into lithium-containing brine₃·6H₂O, such that wherein: the molar ratio of the lithium iron to the lithium iron is 1.0-1.5: 1,the lithium concentration is 0.1-2.0 g/L, the acid concentration is 0.04-0.9 mol/L, and the chlorine concentration is 8-9 mol/L. Extraction experiments were performed at a certain phase ratio (O/a ═ 2 to 5).

In the following examples, the concentration of the amide extractant means that the volume of the organic phase is 100 parts by volume, and the volume of the amide extractant in the organic phase is 60%, for example, the total volume of the organic phase is 100 parts by volume, wherein the volume of the amide extractant is 60 parts by volume.

Example 1

Firstly, preparing an extraction organic phase: mixing an amide extractant and sulfonated kerosene according to a certain volume ratio to form an extracted organic phase.

Then, preparing lithium-containing brine: preparing saturated magnesium chloride solution, and adding certain amount of HCl, LiCl & H₂O、FeCl₃·6H₂O, such that wherein: the molar ratio of lithium iron to iron is 1.3:1, the molar ratio of magnesium to lithium is 16.9:1, the lithium concentration is 1.973g/L, and the hydrochloric acid concentration is 0.05 mol/L.

And (3) extraction: mixing the extracted organic phase and lithium-containing brine under the condition that the ratio is 2:1, shaking for 10min, and extracting. Wherein, the relationship among the volume concentration of the amide extractant in the extracted organic phase, the extraction phase separation effect, the phase separation time and the extraction rate of lithium and hydrochloric acid (HCl) is shown in Table 1:

TABLE 1 volume concentration of amide extractant and extraction Effect data

As can be seen from table 1, at a 30% by volume concentration of the amide extractant, a third phase appears during the extraction process, and the third phase disappears as its concentration increases.

With the increase of the volume concentration of 2-methoxy acetyl diisooctylamine, Li is added to the lithium-containing brine⁺And the HCl extraction rate increased rapidly, with an inflection point occurring when the extractant volume concentration was 40%, followed by a slow increase. The lithium-magnesium separation factor is in a straight-line rising trend along with the increase of the volume concentration of the extractant. When the volume concentration of the extracting agent is 30-50%,the phase separation time is less than 200s, and the linear descending trend is kept. When the volume concentration of the extractant is more than 50 percent, the phase separation time is greatly prolonged and tends to rise linearly, probably because the viscosity of the organic phase is increased after the volume concentration of the extractant is more than 50 percent, so that the phase separation of the organic phase and the aqueous phase is difficult.

To sum up, in order to obtain a higher Li extraction rate and a better phase separation effect, and simultaneously reduce the amount of the extraction organic phase, the present study determines that the optimal volume concentration of the extractant is 40%.

Under the condition that the acidity of brine is 0.05mol/L, when the volume concentration of the amide extractant is lower than 60%, no phase separation problem occurs between a raffinate phase and an extract phase interface, and when the volume concentration of the amide extractant is as low as 30%, the phase separation problem occurs between the raffinate phase and the extract phase interface.

Example 2

Firstly, preparing an extraction organic phase: mixing 2-methoxy acetyl diisooctylamine (amide extractant), sulfonated kerosene and TBP according to a certain volume ratio to form an extracted organic phase. Wherein, the volume concentration of the amide extractant is 40 percent, the volume concentration of the TBP is 0 to 25 percent, and the volume concentration of the sulfonated kerosene is 60 to 35 percent.

And (3) extraction: mixing the extracted organic phase and lithium-containing brine under the condition that the ratio is 2:1, shaking for 10min, and extracting. Wherein, the relation among the volume concentration of TBP in the extracted organic phase, the phase separation time, the lithium magnesium and the hydrochloric acid extraction is shown in the following table 2:

TABLE 2 volume concentration of surfactant and extraction Effect data

Along with the increase of the volume concentration of TBP, the phase separation time of the extracted organic phase and the lithium-containing brine is prolonged. It is shown that the effect of shortening the phase separation time is not achieved by adding TBP into the 2-methoxy acetyl diisooctylamine-kerosene extraction system.

Along with the increase of the volume concentration of TBP, the concentration of magnesium ions in the extraction phase rises sharply, and the concentration of lithium ions is in a small reduction trend, so that the extraction rate of lithium and the lithium-magnesium separation factor both are in a linear descending trend. The volume concentration of TBP is increased, and the extraction rate of 2-methoxy acetyl diisooctylamine and TBP to lithium-containing brine HCl is increased slowly and then approaches to the equilibrium. It can be seen that TBP is specific to Mg in lithium-containing brine²⁺And the extraction capacity of HCl is larger than that of 2-methoxy acetyl diisooctylamine, so that the lithium extraction and separation effects are negatively influenced. Therefore, TBP is not suitable for selection as a phase modifier for the extraction system.

Example 3

Firstly, preparing an extraction organic phase: mixing 2-methoxy acetyl diisooctylamine (amide extractant), sulfonated kerosene, DOP or ATBC according to a certain volume ratio to form an extracted organic phase. Wherein the volume concentration of the 2-methoxy acetyl diisooctylamine is 40 percent, the volume concentration of DOP or ATBC is changed to be 5 to 40 percent, and the volume concentration of the sulfonated kerosene is 55 to 20 percent.

And (3) extraction: mixing the extracted organic phase and lithium-containing brine under the condition that the ratio is 2:1, shaking for 10min, and extracting. Wherein, the relationship among the volume concentration of DOP or ATBC in the extracted organic phase, the phase separation time, the extraction rate of lithium and the lithium-magnesium separation factor is shown in Table 3:

TABLE 3 volume concentration of surfactant and extraction Effect data

The phase separation time increases with the volume concentration of DOP (ATBC), and the addition of DOP prolongs the phase separation time of the extraction system, so that the phase separation is more difficult.

With the increase of the volume concentration of DOP, the extraction rate of lithium is slightly increased; while the Li extraction rate is basically kept unchanged with the increase of the volume concentration of ATBC. Although the lithium-magnesium separation factor increases with increasing volume concentration of DOP (ATBC), DOP (ATBC) is not suitable as a phase modifier for the extraction system in view of lithium extraction rate and phase separation time. Therefore, the extracted organic phase without any phase modifier, i.e., 40% 2-methoxyacetyl diisooctylamine-60% sulfonated kerosene, was determined to be the optimum extracted organic phase.

Example 4

Firstly, preparing an extraction organic phase: mixing 2-methoxy acetyl diisooctylamine (amide extractant) and diluent according to the volume ratio of 40:60 to form an extracted organic phase.

And (3) extraction: mixing the extracted organic phase and lithium-containing brine under the condition that the ratio is 2:1, shaking for 10min, and extracting. Wherein, the relationship among the type of the diluent, the phase separation time, the extraction rate of lithium and the lithium-magnesium separation factor is shown in Table 4:

TABLE 4 Diluent types and extraction Effect data

The phase separation time of the n-heptane, the petroleum ether and the xylene is equivalent and is less than 50s in all aspects, the phase separation time of the sulfonated kerosene is the longest (201s), but the toxicity of the xylene is the greatest in toxicity analysis.

The 7 diluents have small influence on the extraction rate of lithium, the extraction rate of HCl and the separation factor of lithium and magnesium in the lithium-containing brine, and a phase interface is clear and no phase interface substance or third phase is generated in the extraction process. Therefore, if the influence of the phase separation time is taken into consideration, n-heptane and petroleum ether are preferable as the diluent. If the influence of the phase separation time is not considered, the sulfonated kerosene which has low toxicity, high safety, low price and most common application is used as the diluent from the consideration of the toxicity and the economic cost of the diluent.

Example 5

Then, preparing lithium-containing brine: preparing saturated magnesium chloride solution, and adding certain amount of HCl, LiCl & H₂O、FeCl₃·6H₂O, such that wherein: the molar ratio of lithium iron to lithium iron is 1.3:1, the molar ratio of magnesium to lithium is 16.9:1, the lithium concentration is 1.973g/L, and the hydrochloric acid concentration is 0.04-0.9 mol/L.

And (3) extraction: mixing the extracted organic phase and lithium-containing brine under the condition that the ratio is 2:1, shaking for 10min, and extracting.

After extraction is finished, no third phase appears between the raffinate phase and the extract phase, and the phase splitting effect is good.

Wherein, the relationship among the concentration of hydrochloric acid, the phase separation time, the extraction rate of lithium and hydrochloric acid, the concentration of magnesium hydride ions in the extraction phase and the lithium-magnesium separation factor is shown in Table 5:

TABLE 5 hydrochloric acid concentration and extraction Effect data

As can be seen from table 5, the phase separation time of the extracted organic phase and the lithium-containing brine was shortened as the HCl concentration in the lithium-containing brine increased. Indicating that the increase in HCl concentration in the lithium-containing brine helps to promote phase separation.

With the increase of the concentration of HCl in the lithium-containing brine, the extraction rate of HCl in the lithium-containing brine is in a descending trend along with the increase of the initial concentration, and the concentration of hydrogen ions in the extraction phase is in a straight-line ascending trend. Correspondingly, when the extraction rate of lithium and the concentration of the extraction phase are more than 0.4mol/L, the concentration of magnesium ions in the extraction phase tends to be zero. This is because of the hydrogen ion ratioLithium ions and magnesium ions are easier to form complex HFeCl₄Is extracted, the HCl concentration is increased, and the extraction of lithium ions and magnesium ions is inhibited. The lithium-magnesium separation factor is in an ascending trend, and the increase of the HCl concentration inhibits the extraction of magnesium ions to a greater extent.

Therefore, to ensure the iron ion Fe³⁺Hydrolysis did not occur and the extraction rate of lithium was reduced less, and the lithium-containing brine was selected to have an HCl concentration of 0.05 mol/L.

Under the condition that the volume concentration of the amide extractant is 40 percent, when the acidity of brine is reduced to 0.037mol/L, no phase separation problem still occurs between the raffinate phase and the extract phase interface.

It can be seen from the results of example 1 that the amide extractant of the present invention is less affected by its concentration and acidity of brine than the prior art amide extractant.

Example 6

Then, preparing lithium-containing brine: preparing saturated magnesium chloride solution, and adding certain amount of HCl, LiCl & H₂O、FeCl₃·6H₂O, such that wherein: the molar ratio of magnesium to lithium is 16.6:1, the lithium concentration is 2.004g/L, and the hydrochloric acid concentration is 0.05 mol/L.

And (3) extraction: mixing the extracted organic phase and lithium-containing brine under the condition that the ratio is 2:1, shaking for 10min, and extracting. The relationship between the amount of lithium iron ions (hereinafter referred to as the molar ratio of lithium iron) and the phase separation time, the extraction rate of lithium, the lithium-magnesium separation factor, and the concentration of lithium-magnesium ions in the extraction phase is shown in table 6:

table 6 molar ratio of lithium iron and extraction effect data

As can be seen from table 6, as the molar ratio of lithium iron to lithium containing brine increased, the phase separation time of the organic phase and the lithium containing brine decreased. Indicating lithium-containing brineThe increase of the molar ratio of the lithium iron to water contributes to promotion of phase separation. The reason may be that the molar ratio of lithium iron to iron ion Fe in the lithium-containing brine is increased³⁺The increased concentration increases the density of the lithium-containing brine, thereby increasing the difference in density of the extracted organic phase and the lithium-containing brine to facilitate phase separation.

The reason why the lithium-magnesium separation factor is slowly reduced when the molar ratio of iron to lithium in the lithium-containing brine is increased is that the Li concentration in the extraction phase is increased and then reduced when the molar ratio of iron to lithium in the lithium-containing brine is greater than 1.1. When the molar ratio of the lithium iron is 1.3, the concentration of lithium ions in the extraction phase reaches the highest value. While the concentration of magnesium ions in the extract phase is in a straight-line rising trend. Therefore, in order to maximize the concentration of lithium ions in the extraction phase, the molar ratio Fe/Li of lithium iron was determined to be 1.3, and lithium and magnesium ions in brine can be separated well.

Example 7

Then, preparing lithium-containing brine: preparing saturated magnesium chloride solution, and adding certain amount of HCl, LiCl & H₂O、FeCl₃·6H₂O, such that wherein: the molar ratio of lithium iron to iron is 1.3:1, the molar ratio of magnesium to lithium is 16.6:1, the lithium concentration is 2.004g/L, and the hydrochloric acid concentration is 0.05 mol/L.

And (3) extraction: mixing the extracted organic phase and lithium-containing brine under the condition that the ratio is 2:1, shaking for 10min, and extracting. Wherein the extraction is compared with the phase separation effect, Fe³⁺The relationship between extraction, lithium extraction rate, and lithium distribution ratio is shown in table 7:

TABLE 7 comparison of extraction and Effect data

As can be seen from Table 7, the phase separation time decreased with increasing phase ratio, when the phase ratio (O/A) ≧ 2: after 1, no third phase is produced and Fe³⁺The extraction is complete.

As the ratio (O/a) increases, the extraction rate of lithium increases; when the ratio (O/A) is more than or equal to 2:1, the lithium extraction rate (77.55%) tends to be gentle, which indicates that the lithium ion extraction in the extraction phase and the raffinate phase tends to be balanced. The lithium distribution ratio is increased after being decreased with an increase in the ratio (O/A) of 1/5 to 20/1, and reaches a minimum value when compared with (O/A) of 1/2 and a maximum value when compared with (O/A) of 2/1. Therefore, the optimal phase ratio (O/a) was determined to be 2/1.

Example 8

Then, preparing lithium-containing brine: preparing saturated magnesium chloride solution, and adding certain amount of HCl, LiCl & H₂O、FeCl₃·6H₂O, wherein the molar ratio of the lithium iron to the lithium iron is 1.3:1, and the concentration of the lithium ions is 0.1-8.0 g/L (corresponding to 1.44 × 10)^-2About 1.15mol/L), the concentration of hydrochloric acid is 0.05 mol/L.

And (3) extraction: mixing the extracted organic phase and lithium-containing brine under the condition that the ratio is 2:1, shaking for 10min, and extracting. Wherein, the relationship between the lithium ion concentration and the phase separation effect, the iron ion concentration in the raffinate phase, the lithium concentration in the extract phase, and the extraction rate of lithium and hydrochloric acid is shown in table 8:

TABLE 8 lithium ion concentration and extraction Effect data

As can be seen from Table 8, as the initial lithium ion concentration increases, the phase separation time increases, when the initial lithium ion concentration increasesAfter more than 2.0g/L (0.29mol/L), a third phase is produced; fe after an initial lithium ion concentration of greater than 5.0g/L (0.72mol/L)³⁺Can not be completely extracted, probably because the Fe/Li molar ratio of the lithium-containing brine is fixed to 1.3, the initial lithium ion concentration is continuously increased, and Fe in the lithium-containing brine³⁺The concentration also increased correspondingly, leading to saturation of the 2-methoxyacetodiisooctylamine extraction iron.

Along with the increase of the initial lithium ion concentration of the lithium-containing brine (0.5-5.0 g/L), the lithium concentration in the extraction phase is rapidly increased, and when the initial lithium ion concentration of the lithium-containing brine is more than or equal to 5.0g/L (0.72mol/L), the lithium concentration in the extraction phase is in a higher range. The extraction rates of lithium and HCl both increased and decreased with increasing initial lithium ion concentration, and reached maximum values of 79.5% and 69.4% when the initial lithium ion concentration was 2.0g/L (0.29 mol/L). The subsequent decrease in HCl extraction rate may be due to the tendency of 2-methoxyacetyl diisooctylamine to extract lithium, which is accelerated by the continued increase in initial lithium ion concentration of the lithium-containing brine, thereby reducing the HCl extraction of 2-methoxyacetyl diisooctylamine. Therefore, the extraction organic phase is suitable for extracting and separating lithium from brine with the initial lithium ion concentration of 2.0g/L (0.29 mol/L).

Example 9

Then, preparing lithium-containing brine: preparing saturated magnesium chloride solution, and adding certain amount of HCl, LiCl & H₂O、FeCl₃·6H₂O, such that wherein: the molar ratio of the lithium iron is 1.3:1, and the concentration of the hydrochloric acid is 0.05 mol/L.

And (3) extraction: mixing the extracted organic phase and lithium-containing brine under the condition that the ratio is 2:1, shaking for 10min, and extracting. Wherein, the chloride ion concentration, the extraction rate of lithium and the lithium distribution ratio are shown in table 9:

TABLE 9 chloride ion concentration and extraction data

As is clear from Table 9, the iron extraction rate rapidly increased as the initial chloride ion concentration increased, and when the chloride concentration was higher than 6.0mol/L, the iron extraction rate was close to 100%, and almost completely extracted. The extraction rate of lithium increases along with the initial concentration of chlorine in the lithium-containing brine, and basically shows a straight-line rising trend. This may be because the initial chlorine concentration in the lithium-containing brine is continuously increased, and this contributes to the formation of a complex anion FeCl (tetrachloro iron) by the electrically neutral ferric trichloride and the chloride ion₄ ^-Promoting the formation of the coordination compound of lithium iron tetrachloride LiFeCl₄Thereby increasing the extraction rate of lithium. Therefore, in the solution with high chlorine or saturated chlorine concentration, the lithium can be extracted and separated better.

Example 10

Firstly, preparing lithium-containing brine for simulating salt lake: adding certain amount of HCl to make the acid concentration be 0.05mol/L and adding certain amount of FeCl₃(concentration in Li-containing brine to 0.375mol/L, Fe/Li molar ratio 1.3) as co-extraction agent, and shaking to dissolve. Then a fresh extracted organic phase is prepared: the content of the 2-methoxy acetyl diisooctylamine in the extracted organic phase is 40 percent (V percent) and the content of the sulfonated kerosene is 60 percent.

A plurality of separating funnels are prepared, and are marked as bottles No. 1, No. 2 and No. 3 in sequence, the specific operation method is as follows, wherein 1 part in the embodiment refers to volume part:

(1) to separatory funnel No. 2 was added 1 part lithium-containing brine, 2 parts fresh organic phase of extraction (i.e., compare V)_O/V_A2), shaking for 10min for extraction. After the oscillation is finished, standing and layering to obtain an upper organic phase and a lower aqueous phase.

(2) And (3) respectively feeding the layered lithium-containing brine and the layered extraction organic phase into a No. 1 separating funnel and a No. 3 separating funnel, adding 2 parts of prepared fresh extraction organic phase into the No. 1 separating funnel, respectively adding 1 part of prepared lithium-containing brine into the No. 3 separating funnel, and oscillating for 10min for extraction. After the oscillation is finished, standing and layering are carried out, and an upper organic phase and a lower aqueous phase are obtained again.

(3) The upper layer in No. 1 separating funnel is organicAdding the phases into a No. 2 separating funnel, collecting the lower-layer water phase in the No. 1 separating funnel and detecting the ion concentration in the lower-layer water phase; the lower aqueous phase in separatory funnel No. 3 was added to separatory funnel No. 2, at which time phase ratio V in separatory funnel No. 2_O/V_AThe lower aqueous phase in separatory funnel No. 3 was collected and the ion concentration was measured. And oscillating the No. 2 separating funnel for 10min to extract, and standing and layering after oscillation to obtain an upper organic phase and a lower aqueous phase.

(4) Repeating the steps (2) to (3)15 times.

After 16 cycles in total, Li in the water phase (raffinate phase) and the extracted organic phase (extract phase) at equilibrium were measured separately⁺And Mg²⁺From the concentration, the extraction rate of Li was calculated to be 95.92%, Li⁺、Mg²⁺The distribution ratios were 12.19, 0.00529, respectively. The Li/Mg separation coefficient was 2669.

The "equilibrium" means that the amount of change in the ion content of the two phases is small, and in this embodiment, the extraction equilibrium is substantially reached at the 10 th cycle.

Since the organic phase extracted with 40% 2-methoxyacetyl diisooctylamine-60% sulfonated kerosene was delaminated during the extraction process, and the delamination was not eliminated after the organic phase extracted with lithium in the third stage was left to stand for a while, example 11 was performed to eliminate the delamination of the organic phase.

Example 11

The extraction organic phase was prepared from 60% 2-methoxyacetyl diisooctylamine-40% sulfonated kerosene, and the three-stage countercurrent extraction experiment was carried out for 13 cycles under the same conditions as in example 10.

In the present example, 13 cycles are performed in total, the operation schematic diagram is shown in fig. 1, the lithium ion content (in g/L) measured in the aqueous phase after the separation of the No. 1 separation funnel of each cycle is indicated in the left column of the figure, the lithium ion content measured in the organic phase after the separation of the No. 3 separation funnel of each cycle is indicated in the right column of the figure, and the numbers 1 to 13 on the rightmost side represent the cycle number.

Theoretically, the extraction equilibrium can be reached when the cycle reaches the 10 th time, and in order to make the result more accurate, the cycle number of the three-stage countercurrent extraction process is increased to 13, and the total extraction data of the three-stage countercurrent extraction is calculated by averaging the data of the 10 th to 13 th cycles. Referring to fig. 1 and table 10, the total extraction data of the three-stage countercurrent extraction is calculated by averaging the data of the 10 th to 13 th cycles, and thus, the ion content values shown in table 10 are different from those shown in fig. 1.

TABLE 10 Total extraction data for three-stage countercurrent extraction

As can be seen from Table 10, the Li extraction rate of the three-stage countercurrent extraction process of this example was calculated to be 99.67%, and Li was obtained⁺、Mg²⁺The partition ratios are 142.65 and 0.003998 respectively, and the separation coefficient of Li/Mg is 3.63 × 10⁴. As can be seen from the lithium-magnesium separation factor, the three-stage countercurrent extraction cascade experiment can realize the lithium and the main metal ion Mg²⁺The separation is efficient.

While the invention has been shown and described with reference to certain embodiments, those skilled in the art will understand that: various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.

Claims

1. An extracted organic phase comprising an amide extractant having the formula: c₁₉H₃₉NO₂The structural formula of the amide extractant is as follows:

2. The organic phase of claim 1, wherein the amide extractant is 2-methoxyacetyl diisooctylamine having the formula:

3. the organic extract phase of claim 1, further comprising a diluent and/or a surfactant.

4. The organic extract phase of any of claims 1 to 3, wherein the diluent is at least one selected from n-heptane, petroleum ether, cyclohexane, n-dodecane, sulfonated kerosene, No. 200 mineral spirits, and aromatic diluents; the surfactant is tributyl phosphate, dioctyl phthalate or acetyl tributyl citrate; the volume of the extracted organic phase is calculated by 100 parts, and the volume concentration of the amide extractant is 35-60%.

5. A method for separating lithium from lithium-containing brine, comprising the steps of:

mixing lithium-containing brine with the extracted organic phase of any one of claims 1 to 4, oscillating for extraction, standing for phase separation to obtain an extract phase and raffinate, and transferring all or part of lithium in the original lithium-containing brine to the extract phase.

6. The method of claim 5, wherein in the lithium-containing brine: the concentration of lithium ions is 0.1-5 g/L; the volume ratio of the extracted organic phase to the lithium-containing brine is more than 1.

7. The method of claim 6, wherein in the lithium-containing brine: the concentration of chloride ions is more than 5.5mol/L, and the concentration of hydrogen ions is less than 0.9 mol/L.

8. The method according to claim 6, wherein the lithium-containing brine further contains iron ions and lithium iron ions at a ratio of 1 to 1.5: 1.

9. The method of claim 6, wherein in the lithium-containing brine: the concentration of lithium ions is 0.1-2 g/L, the concentration of chloride ions is 8-9 mol/L, and the concentration of hydrogen ions is 0.04-0.9 mol/L; the volume ratio of the extracted organic phase to the lithium-containing brine is 2-5: 1.

10. The process of any one of claims 5 to 8, wherein the organic phase is subjected to a cascade countercurrent extraction with respect to the lithium-containing brine.