CN109468459B - Lithium extraction agent and method for extracting lithium from salt lake brine - Google Patents

Lithium extraction agent and method for extracting lithium from salt lake brine Download PDF

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CN109468459B
CN109468459B CN201811507854.3A CN201811507854A CN109468459B CN 109468459 B CN109468459 B CN 109468459B CN 201811507854 A CN201811507854 A CN 201811507854A CN 109468459 B CN109468459 B CN 109468459B
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李林艳
李湘兰
李晓宏
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Tsinghua University
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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    • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
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    • C22B3/26—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
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    • C22B26/10—Obtaining alkali metals
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Abstract

The invention discloses a lithium extracting agent and a method for extracting lithium from salt lake brine. The method utilizes N, N-dimethyl alkyl amide as a main extracting agent, and takes ketone as a phase modifier to extract lithium from salt lake brine, and the extracting agent has excellent lithium extraction capacity and selectivity, is not easy to form flocculate influencing the extraction process in use, avoids the use of a phosphorus-containing extracting agent, and is more environment-friendly.

Description

Lithium extraction agent and method for extracting lithium from salt lake brine
Technical Field
The invention relates to the field of extraction chemistry, in particular to a lithium extracting agent and a method for extracting lithium from salt lake brine.
Background
In nature, lithium is mainly present in solid minerals and liquid ore deposits, wherein the lithium resource in salt lake brine accounts for about 90 percent of the globally proven lithium resource, China has rich salt lake brine resource which is mainly distributed in Qinghai, Tibet and other areas, the salt lake lithium resource in Qinghai firewood basin is very rich, and the LiCl storage capacity is about 2.8 × 107t. This type of brine has two significant characteristics: (1) the lithium content is high and reaches 2-3 g/L; (2) the Mg/Li ratio is high, and is usually more than 40 (mass ratio). Because of the chemical similarity of lithium and magnesium, it is difficult to extract lithium from salt lake brine with high magnesium-lithium ratio and separate lithium from magnesium with high concentration by conventional methods.
Solvent extraction is an important means for purification and separation in the chemical process, has the advantages of high separation efficiency, simple process and equipment, continuous operation, easy realization of automatic control and the like, and is considered to be one of the most promising methods for extracting and separating lithium from brine with high magnesium-lithium ratio. Lithium is present in ionic form in salt lake brines. Li+Has small radius, only one electron shell, 2s and 2p as empty orbitals, low polarizability, and sp generation with hard base coordination atoms such as O, N3Hybridization results in a stable tetrahedral structure. In aqueous solution, Li+And H2The O molecule undergoes strong hydration to form Li (H)2O)4 +The extractant molecules have difficulty competing with water molecules for binding to lithium ions, and therefore, no direct extraction of Li has been found to date+The extractant of (1). In thatCl-In high concentration and containing Fe3+In an aqueous solution of (a), the following reaction occurs: mn++FeCl4 -＝M(FeCl4)n。M(FeCl4)nCan be extracted by some neutral extracting agent with specific structure (such as neutral phosphate, amide, etc.). M (FeCl)4)nThe extraction by these extractants is preferably HFeCl4>LiFeCl4>>Mg(FeCl4)2>NaFeCl4>KFeCl4. Based on this principle, scientists developed FeCl3The co-extraction system is used for extracting lithium from salt lake brine and separating lithium from other metal ions, and the principle is as follows: adding FeCl into salt lake brine3Reacting various cations in brine with FeCl3Binding to form M (FeCl)4)nThe HFeCl is preferentially extracted by neutral extractant such as phosphate ester and amide4And LiFeCl4Extracted into an organic phase, and Mg (FeCl)4)2、NaFeCl4、KFeCl4The aqueous phase is left, and the organic phase is back extracted by more concentrated hydrochloric acid to ensure that LiFeCl is obtained4Conversion to HFeCl4And Li+Into the aqueous phase.
However, the existing extraction system and process for extracting lithium from salt lake brine still need to be improved.
Disclosure of Invention
The present invention is based on the discovery by the inventors of the following facts and problems:
patent CN87103431 proposes a process for extracting lithium by a tributyl phosphate (TBP) -kerosene system, and carries out semi-industrial tests. Although the TBP-kerosene system has high extraction capacity and selectivity for lithium, the following problems also exist: (1) TBP has serious swelling corrosion to extraction equipment made of PVC, PP and the like, so that the service life of the equipment is shortened, and swelled macromolecular organic matters enter an extraction system to influence the fluidity and phase splitting of the extraction system; (2) TBP density (0.979g/mL) and molecular polarity are both large, and TBP-LiFeCl is an extract compound4And TBP. HFeCl4The density and the molecular polarity of the crude oil are further increased, the solubility in low-polarity kerosene (diluent) is low, and the crude oil is easy to form in the extraction processThe third phase is not beneficial to the stable operation of the extraction process; (3) in acidic or alkaline aqueous solutions, hydrolysis of TBP occurs, and especially during alkali neutralization to regenerate the organic phase, local alkali excess can greatly accelerate hydrolysis of TBP, and generate water-soluble monobutyl phosphate (MBP) and dibutyl phosphate (DBP). MBP and DBP are not only on LiFeCl4Has no extraction capacity and is easy to be mixed with Fe in the system3+Waxy solids which are difficult to dissolve in kerosene, TBP and water are formed in a combined manner, so that the viscosity of an extraction system is increased until the extraction process cannot be operated; (4) TBP has the solubility of about 0.1 percent in water, but the hydrolysis products MBP and DBP have higher solubility in water, so that more phosphorus-containing organic matters exist in raffinate in the long-term operation process, are difficult to be biochemically degraded or oxidatively degraded into harmless gas or precipitate, and can cause serious damage to the ecology of the salt lake after long-term accumulation. The problems limit the large-scale application of TBP in the lithium extraction industry of salt lake brine.
In order to solve the problems of TBP extractants, a series of amide lithium extractants are proposed by scholars. The amide extractant mainly comprises the following compounds: n, N-di (2-ethylhexyl) propionamide, N-dihexylbenzamide, N-dihexyln-butyramide, N-dihexyl-2-methylpropionamide, N-dihexylpropionamide, N-di (2-ethylhexyl) -2-methoxyacetamide, N-di (2-ethylhexyl) acetamide, N-di (2-ethylhexyl) -2-methylpropionamide and N, N-dihexylp-methylbenzamide. The main structural characteristics of the amide compound are as follows: the nitrogen atom is connected with two long carbon chain alkyl groups (the number of carbon atoms is more than or equal to 6), and the carbonyl group is connected with a short carbon chain alkyl group or an aromatic hydrocarbon group. Wherein, the two long carbon chain alkyl radicals on the nitrogen atom are used for leading the extractant to have lower water solubility and better oil solubility. However, the electron repulsion effect of the two long carbon chain alkyl groups increases the electron cloud density of the lone pair of electrons on the nitrogen atom, so that the amide of the structure has obvious alkalinity. Because the principle of extracting lithium from salt lake brine by the amide compounds is similar to that of TBP, FeCl needs to be added into brine3As a co-extractant. In the extraction process, the amide which is basic can react with H in the aqueous solution+Binding raises the pH of the solution, which in turn leads to Fe3+Hydrolysis and production of Fe (OH)3Floc, which seriously affects the normal operation of the extraction process. Therefore, the extractant has not been industrially applied in the field of lithium extraction in salt lakes. In order to overcome the defects of the amide compounds and TBP, a complex extractant of amide and TBP is proposed, but the problem that the amide with alkalinity causes Fe cannot be solved fundamentally3+Hydrolysis and TBP corrosion of equipment.
In view of the above, the present invention provides a lithium extractant and a method for extracting lithium from salt lake brine. The method utilizes N, N-dimethyl alkyl amide extractant to extract lithium from salt lake brine, and the extractant has excellent lithium extraction capacity and selectivity, is not easy to form flocculate influencing the extraction process in use, avoids the use of phosphorus-containing reagent, and is more environment-friendly.
In one aspect of the invention, the invention provides a method for extracting lithium from salt lake brine by using an extracting agent. According to an embodiment of the invention, the extractant comprises a compound of formula (A),
Figure BDA0001899935050000031
wherein R is1Is C6-20Straight chain alkyl, C6-20Branched alkyl or C6-20A cycloalkyl group.
According to an embodiment of the invention, the compound of formula (A) is a compound in which the two methyl groups are directly attached to the nitrogen atom and R is attached to the carbonyl group1The radical being C6-20Linear, branched or cyclic alkyl. The compound shown in the formula (A) has obvious structural difference with the traditional amide lithium extractants (such as N, N-di (2-ethylhexyl) propionamide, N-dihexylbenzamide, N-di (2-ethylhexyl) acetamide, N-dihexylp-methylbenzamide and the like): attached to the nitrogen atom of the compound of formula (A) are two methyl groups and are linked through a long carbon chain R to a carbonyl group1The groups provide oil solubility, while in conventional amide-based lithium extractants two long carbon chain alkyl groups are attached to the amide nitrogen atom. The electron-repelling effect of alkyl radicals being a function of the number of carbon atomsThe electron repulsion effect of methyl groups relative to long-chain alkyl groups is weaker, so that the electron cloud density of nitrogen atoms in the compound shown in the formula (A) is obviously lower than that of amide nitrogen atoms in a traditional amide lithium extractant, and the alkalinity of the compound shown in the formula (A) is obviously weaker than that of the traditional amide lithium extractant. Therefore, the method for extracting lithium from salt lake brine is carried out by utilizing the extracting agent comprising the compound shown in the formula (A), and Fe is not easily caused by overhigh alkalinity of the extracting agent in the extraction process3+The hydrolysis forms flocculate, thus ensuring the stable operation of the extraction process. In addition, the method avoids the use of phosphorus-containing reagents, is more environment-friendly, and has little swelling corrosion to extraction equipment.
In addition, the method for extracting lithium from salt lake brine by using the extracting agent according to the above embodiment of the present invention may further have the following additional technical features:
in some embodiments of the invention, R1Is C8-14Straight chain alkyl or C8-14A branched alkyl group.
In some embodiments of the invention, the extractant further comprises a compound of formula (B),
Figure BDA0001899935050000032
wherein R is2And R3Are each independently C1-24Straight chain alkyl, C1-24Branched alkyl or C1-24Cycloalkyl radical, and R2And R3Is not less than 5. The compound with the structure has good intermiscibility to the compound shown in the formula (A) and solvent oil, so that the formation of a third phase in the extraction process can be effectively avoided.
In some embodiments of the invention, R2And R3Are each independently C1-12Straight chain alkyl or C1-12A branched alkyl radical, and R2And R3The total number of carbon atoms is 7 to 15.
In some embodiments of the present invention, the volume ratio of the compound represented by the formula (A) to the compound represented by the formula (B) is 1 (0.1-10).
In some embodiments of the invention, the method comprises: (1) mixing the salt lake brine with ferric trichloride to obtain an extraction feed liquid; (2) mixing the extracting agent and a diluent to prepare an extracted organic phase, and mixing the extracted organic phase with the extraction liquid to extract so as to obtain a loaded organic phase and raffinate; (3) washing the loaded organic phase by using a detergent so as to obtain a washed organic phase and a washing residual liquid; (4) and (3) carrying out back extraction on the washed organic phase by using hydrochloric acid so as to obtain a back extraction organic phase and a back extraction raffinate.
In some embodiments of the invention, in the step (1), the concentration of hydrogen ions in the extraction liquid is 0.01-1.0 mol/L, and the molar ratio of iron to lithium is (1-3): 1.
In some embodiments of the present invention, before the step (2), the extractant and the diluent are mixed in advance to obtain an extracted organic phase, and the volume fraction of the extractant in the extracted organic phase is 10-99%.
In some embodiments of the invention, the diluent is selected from mineral spirits having a boiling range of 160-300 degrees Celsius.
In some embodiments of the invention, the diluent is at least one selected from the group consisting of 260# jet fuel, sulfonated kerosene, D70 mineral spirits, and D80 mineral spirits.
In some embodiments of the invention, in the step (2), the volume ratio of the extraction organic phase to the extraction liquid is (4-1): 1-4), the single-stage extraction time is 3-30 min, and the system temperature is 10-50 ℃.
In some embodiments of the invention, in the step (3), the volume ratio of the loaded organic phase to the detergent is (20-50): 1, the contact time is 3-30 min, and the system temperature is 10-50 ℃.
In some embodiments of the invention, in step (3), the detergent is the strip raffinate.
In some embodiments of the invention, in the step (4), the volume ratio of the washed organic phase to the hydrochloric acid is (10-30): 1, the contact time is 2-30 min, and the system temperature is 10-50 ℃; the concentration of the hydrochloric acid is 5.0-9.0 mol/L.
In some embodiments of the invention, the method further comprises: (5) mixing an alkaline liquor with the stripping organic phase to obtain a regenerated stripping organic phase.
In some embodiments of the invention, the alkali liquor is a sodium hydroxide solution, a potassium hydroxide solution, a sodium carbonate solution or a potassium carbonate solution with a concentration of 0.1-1.0 mol/L, and the volume ratio of the stripping organic phase to the alkali liquor is (10-40): 1.
In another aspect of the present invention, the present invention provides a composite extractant. According to the embodiment of the invention, the composite extracting agent comprises a compound shown as a formula (A) and a compound shown as a formula (B),
Figure BDA0001899935050000051
wherein the content of the first and second substances,
R1is C6-20Straight chain alkyl, C6-20Branched alkyl or C6-20A cycloalkyl group;
R2and R3Are each independently C1-24Straight chain alkyl, C1-24Branched alkyl or C1-24Cycloalkyl radical, and R2And R3Is not less than 5.
In the composite extractant according to the embodiment of the present invention, in the compound represented by the formula (A), two methyl groups are directly bonded to the nitrogen atom, and R is bonded to the carbonyl group1The radical being C6-20Linear, branched or cyclic alkyl. The compound shown in the formula (A) has obvious structural difference with the traditional amide lithium extractants (such as N, N-di (2-ethylhexyl) propionamide, N-dihexylbenzamide, N-di (2-ethylhexyl) acetamide, N-dihexylp-methylbenzamide and the like): attached to the nitrogen atom of the compound of formula (A) are two methyl groups, and R is attached through a carbonyl group1The groups provide oil solubility, while in conventional amide-based lithium extractants two long carbon chain alkyl groups are attached to the amide nitrogen atom. The electron-repelling effect of the alkyl radical being associated with a carbon atomThe number is increased and enhanced, and the electron repulsion effect of methyl groups relative to long-carbon chain alkyl groups is weaker, so that the electron cloud density of nitrogen atoms in the compound shown in the formula (A) is obviously lower than that of amide nitrogen atoms in the traditional amide lithium extractant, the alkalinity of the compound shown in the formula (A) is obviously weaker than that of the traditional amide lithium extractant, and Fe is not easy to cause in the extraction process3+Hydrolysis forms flocs. On the other hand, the compound shown in the formula (B) has proper polarity and has better compatibility with an organic phase in an extraction system. Meanwhile, the compound represented by the formula (B) is used for LiFeCl4Also has certain extraction effect and lower viscosity. The compound shown as the formula (B) is used as a compound modifier shown as the formula (A), the formation of a third phase in the extraction process can be effectively avoided, and the LiFeCl of the compound shown as the formula (A) serving as the main extractant is improved4The extraction rate of the extraction process is ensured, and the continuous and stable operation of the extraction process is ensured.
In addition, the composite extracting agent according to the above embodiment of the invention may also have the following additional technical features:
in some embodiments of the invention, R1Is C8-14Straight chain alkyl or C8-14A branched alkyl group; r2And R3Are each independently C1-12Straight chain alkyl or C1-12A branched alkyl radical, and R2And R3The total number of carbon atoms is 7 to 15.
In some embodiments of the present invention, the volume ratio of the compound represented by the formula (A) to the compound represented by the formula (B) is 1 (0.1-10).
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Detailed Description
The following describes embodiments of the present invention in detail. The following examples are illustrative only and are not to be construed as limiting the invention. The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.
In one aspect of the invention, the invention provides a method for extracting lithium from salt lake brine by using an extracting agent. According to an embodiment of the invention, the extractant comprises a compound of formula (A),
Figure BDA0001899935050000061
wherein R is1Is C6-20Straight chain alkyl, C6-20Branched alkyl or C6-20A cycloalkyl group.
According to an embodiment of the invention, the compound of formula (A) is a compound in which the two methyl groups are directly attached to the nitrogen atom and R is attached to the carbonyl group1The radical being C6-20Linear, branched or cyclic alkyl. The compound shown in the formula (A) has obvious structural difference with the traditional amide lithium extractants (such as N, N-di (2-ethylhexyl) propionamide, N-dihexylbenzamide, N-di (2-ethylhexyl) acetamide, N-dihexylp-methylbenzamide and the like): attached to the nitrogen atom of the compound of formula (A) are two methyl groups and are linked through a long carbon chain R to a carbonyl group1The groups provide oil solubility, while in conventional amide-based lithium extractants two long carbon chain alkyl groups are attached to the amide nitrogen atom. The electron repulsion effect of the alkyl is enhanced along with the increase of the number of carbon atoms, and the electron repulsion effect of the methyl is weaker than that of the long-carbon-chain alkyl, so that the electron cloud density of the nitrogen atom in the compound shown in the formula (A) is obviously lower than that of the amide nitrogen atom in the traditional amide lithium extractant, and further, the alkalinity of the compound shown in the formula (A) is obviously weaker than that of the traditional amide lithium extractant. Therefore, the method for extracting lithium from salt lake brine is carried out by utilizing the extracting agent comprising the compound shown in the formula (A), and Fe is not easily caused by overhigh alkalinity of the extracting agent in the extraction process3+The hydrolysis forms flocculate, thus ensuring the stable operation of the extraction process. In addition, the method avoids the use of phosphorus-containing reagents, is more environment-friendly, and has little swelling corrosion to extraction equipment.
Comprehensively considering the oil solubility of the extracting agent,Loss of water solubility, atom economy and availability of raw materials, according to a preferred embodiment of the present invention, in the compound represented by formula (A), R1Is C8-14Straight chain alkyl or C8-14A branched alkyl group. Having the above-mentioned R1The compound shown in the formula (A) of the group has proper oil solubility and lower water solubility, the loss of a water phase in the extraction process is very small, and the raw material has wide source range, is cheap and is easy to obtain.
According to an embodiment of the present invention, the extractant may further comprise a compound represented by formula (B),
Figure BDA0001899935050000062
wherein R is2And R3Are each independently C1-24Straight chain alkyl, C1-24Branched alkyl or C1-24Cycloalkyl radical, and R2And R3The total number of carbon atoms of (a) is not less than 5, in other words, the total number of carbon atoms of the compound represented by the formula (B) is not less than 6. The inventors found in experiments that during extraction with an extractant comprising a compound of formula (a), the compound of formula (a) extracts LiFeCl4The polarity of the molecules of the extraction association complex formed later is increased, and a third phase is easily formed in the system. Although the formation of the third phase has little influence on the technological indexes such as the extraction rate of lithium, the separation coefficient of lithium and magnesium, the separation coefficient of lithium and sodium, the separation coefficient of lithium and potassium and the like, the formation of the third phase has adverse effect on the continuous and stable operation of the extraction process. In view of the above, through a great deal of experimental research, the inventors found that the compound represented by the formula (B) is used as a modifier to form a composite extractant together with the compound represented by the formula (a), so that the formation of a third phase in the extraction process can be effectively avoided.
In particular, according to the embodiment of the present invention, the compound represented by the formula (B) has suitable polarity and better compatibility with the organic phase in the extraction system. Meanwhile, the compound represented by the formula (B) is used for LiFeCl4Also has certain extraction effect and lower viscosity. The compound shown in the formula (B) is used as a compound modifier shown in the formula (A), the formation of a third phase in the extraction process can be effectively avoided, and the compound pair shown in the formula (A) as a main extractant is improvedLiFeCl4The extraction rate of the extraction process is ensured, and the continuous and stable operation of the extraction process is ensured.
Considering the oil solubility, water solubility loss, atom economy and raw material availability of the extractant in combination, according to a preferred embodiment of the invention, R2And R3Are each independently C1-12Straight chain alkyl or C1-12A branched alkyl radical, and R2And R3The total carbon number of (A) is 7 to 15, in other words, the total carbon number of the compound represented by the formula (B) is 8 to 16. Having the above-mentioned R2And R3The compound shown in the formula (B) of the group has proper oil solubility and lower water solubility, the loss of a water phase in the extraction process is very small, and the raw material has wide source range, is cheap and is easy to obtain.
According to the embodiment of the invention, as mentioned above, the compound shown in the formula (A) can be used alone as an extracting agent in the method for extracting lithium from salt lake brine, and the formation of a third phase in an extraction system can be further avoided by forming the compound shown in the formula (A) and the compound shown in the formula (B) into a composite extracting agent. According to the embodiment of the present invention, the ratio of the compound represented by formula (a) to the compound represented by formula (B) in the composite extractant is not particularly limited; preferably, the volume ratio of the compound represented by the formula (A) to the compound represented by the formula (B) is 1 (0.1-10), such as 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.8, 1:1, 1:2, 1:3, 1:5, 1:8, or 1: 10. Therefore, the composite extracting agent can be ensured to have higher extraction capacity and selectivity on lithium.
For convenience of understanding, the method for extracting lithium from salt lake brine by using the extractant described in the above example is further described in detail below. According to an embodiment of the invention, the method comprises:
(1) mixing the salt lake brine with ferric trichloride to obtain an extraction liquid.
According to the embodiment of the invention, the salt lake brine is high magnesium-lithium ratio salt lake brine. The salt lake brine can be untreated salt lake brine, old brine obtained by potassium extraction of the salt lake brine, or old brine obtained by potassium extraction and boron removal. If untreated salt lake brine and old brine obtained by potassium extraction of the salt lake brine are used as a lithium extraction material liquid, a certain amount of hydrochloric acid is added, so that complete dissolution of ferric trichloride is ensured, and the acidity of the material liquid is adjusted to a proper range. Preferably, the old brine after potassium extraction and boron removal is used as a lithium extraction material liquid, because the existence of boron in the brine can interfere the lithium extraction process, hydrochloric acid is required to be added in the boron removal process, the concentration of the hydrochloric acid in the brine after boron removal is 0.05-0.3 mol/L, the acidity requirement of the lithium extraction process is just met, and extra hydrochloric acid is not required. If the acidity of the salt lake brine to be treated is not satisfactory, the acidity can be adjusted by adding HCl or NaOH during this step.
According to the specific example of the invention, a certain amount of ferric trichloride can be added into the old bittern obtained after potassium extraction and boron removal as a co-extraction agent, and the mixture is stirred until the mixed solution is completely dissolved, so that the extraction liquid is obtained.
According to the embodiment of the invention, Li in salt lake brine with high Mg/Li ratio+The concentration range is 0.2-10.0 g/L; the mass ratio of magnesium to lithium, m (Mg)/m (Li), ranges from (30-200): 1, Cl-The content is more than or equal to 5.0 mol/L. The inventor finds out in experiments that if Cl is contained in salt lake brine-Too low a concentration of Fe3+Can not be completely replaced with FeCl4 -Exist in a form of (1), thereby affecting Li+Extraction and phase separation. The acidity (i.e., H) of the extract stream obtained after addition of ferric trichloride+Concentration) is 0.01-1.0 mol/L, and HCl or NaOH can be adopted for adjustment if the acidity is not in the range; the molar ratio n (Fe)/n (Li) of the lithium iron in the extraction liquid is (1-3): 1. The extraction liquid meeting the conditions is prepared from the salt lake brine, so that the extraction process and the extraction of lithium can be further facilitated.
(2) Mixing an extracting agent and a diluting agent to prepare an extracted organic phase, and mixing the extracted organic phase with an extraction liquid to extract so as to obtain a loaded organic phase and raffinate.
In the step, LiFeCl in the extraction liquid is extracted by using an extraction organic phase prepared by mixing an extracting agent and a diluent4Extraction into the loaded organic phase. In some embodiments, the organic phase is loaded in the upper layer of the system and the raffinate in the lower layer of the system by contacting the organic phase with the extract liquor sufficiently, allowing the mixture to stand for stratification. According to the inventionIn the illustrated embodiment, the extractant of the previous embodiment is mixed with a diluent before use in extraction. Wherein the volume fraction of the extractant in the organic phase is 10-99%, such as 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 99%. The extractant is diluted and then used, so that the flowability of the organic phase can be further improved, the density of the organic phase is reduced, the extraction process is easier to carry out, the phase separation effect is good, and the extraction efficiency of the extractant on lithium is improved. According to the embodiment of the invention, the step (2) can adopt single-stage extraction and also can adopt multi-stage countercurrent extraction.
According to an embodiment of the present invention, the diluent may be at least one selected from mineral spirits having a distillation range of 160 to 300 degrees celsius, such as 260# aviation kerosene, sulfonated kerosene, D70 mineral spirits, and D80 mineral spirits. The diluent has stable chemical property, low density and small viscosity, not only plays a good role in diluting the extractant, but also can further improve the fluidity of the organic phase, reduce the density of the organic phase, ensure that the extraction process is easier to carry out and the phase separation effect is good, and is also favorable for improving the extraction efficiency of the extractant on lithium. In addition, the polarity of the compound shown in the formula (B) is between that of the kerosene and the extraction association complex, so that the formation of a third phase in the extraction process can be avoided.
According to the embodiment of the invention, in the step (2), the volume ratio of the extraction organic phase to the extraction liquid is (4-1): 1-4, namely the ratio of O/A is 4: 1-1: 4, the single-stage extraction time is 3-30 min, and the system temperature is 10-50 ℃. By extracting the organic phase from the extraction liquid under the conditions, the extraction capacity and selectivity of the extractant on lithium can be further improved, and the separation of the loaded organic phase from the raffinate is facilitated.
(3) And washing the loaded organic phase by using a washing agent so as to obtain a washed organic phase and a washing residual liquid.
The inventor finds in experiments that although the extractant proposed by the invention has a high selectivity for lithium, a small amount of Mg still remains in the extraction process2+、K+、Na+The plasma impurity ions are inevitably entrained or extracted into the loaded organic phase. Tong (Chinese character of 'tong')The Mg in the loaded organic phase can be effectively removed by washing the loaded organic phase by using a detergent2+、K+、Na+And plasma impurity ions. In some embodiments, the organic phase is in the upper layer of the system after washing, and the washing liquid is in the lower layer of the system. According to the embodiment of the present invention, the step (3) may employ a single-stage washing, and may employ a multi-stage counter-current washing.
According to the embodiment of the invention, in the step (3), the volume ratio of the loaded organic phase to the detergent is (20-50): 1, namely the O/A range is 20-50, the contact time is 3-30 min, and the system temperature is 10-50 ℃. By washing the loaded organic phase with a detergent under the above conditions, Mg can be further increased2+、K+、Na+The removal effect of the impurity ions is good, and the separation of the washed organic phase and the washed residual liquid is facilitated.
According to the embodiment of the present invention, the specific kind of the detergent is not particularly limited as long as Mg in the organic phase can be supported2+、K+、Na+Removing the impurity ions by means of extraction. According to a preferred embodiment of the present invention, the detergent may be the raffinate obtained in step (4) (the first extraction may be formulated as a simulated raffinate). The process of washing the loaded organic phase with the stripping raffinate is also referred to as reflux washing. The back raffinate contains LiCl with higher concentration and hydrochloric acid with certain concentration, and Li is extracted by ferric trichloride co-extraction agent+The binding capacity of the extractant is far greater than that of Mg2+、K+、Na+High concentration of Li in the strip liquor+Mg in the organic phase can be loaded2+、K+、Na+The water is thoroughly extruded out, and other impurities are not introduced in the washing process; at the same time, the Cl in the raffinate is stripped-High concentration of Fe3+Still with FeCl4 -The form remained in the organic phase. According to the embodiment of the invention, the washing residual liquid can be returned to the extraction liquid for recycling.
(4) The washed organic phase is back-extracted with hydrochloric acid to obtain a back-extracted organic phase and a back-extracted raffinate.
In the step, hydrochloric acid is used as a stripping agent to carry out back extraction on the washed loaded organic phase, and Li is added+Back extracting to water phase to obtain Li+The back extraction raffinate and the back extraction organic phase with higher concentration, and the ferric trichloride co-extractant still adopts FeCl4 -The organic phase is retained. In some embodiments, the organic phase is stripped in the upper layer of the system and the strip liquor is in the lower layer of the system by contacting hydrochloric acid with the washed organic phase sufficiently and allowing the mixture to stand for layering. According to the embodiment of the invention, the step (4) can adopt single-stage back extraction and also can adopt multi-stage counter-current back extraction.
According to the embodiment of the invention, the volume ratio of the organic phase to the hydrochloric acid after washing is (10-30): 1, namely, the range of the ratio of O/A is 10-30, the contact time is 2-30 min, and the system temperature is 10-50 ℃; the concentration of the hydrochloric acid is 5.0-9.0 mol/L. If the concentration of the hydrochloric acid is too low or the dosage of the hydrochloric acid is too small, the pH value of the system cannot be ensured to be in a proper range, and Cl in the system can be caused-FeCl in the organic phase at too low a concentration4 -Will be partially converted into Fe3+The lithium enters a water phase, which brings difficulty to the subsequent preparation of lithium products; iron is lost in the organic phase, and iron needs to be supplemented in the extraction liquid in the subsequent extraction process, so that the whole production process is discontinuous.
The inventor finds in experiments that the stripping organic phase obtained by the back extraction not only contains the co-extractant of ferric trichloride, but also contains more hydrochloric acid which exists in an entrained form or an associated form, and a large amount of H+When the back extraction organic phase is continuously contacted with the extraction feed liquid, the Li in the extraction feed liquid+The back extraction organic phase is difficult to enter, so that the back extraction organic phase has the capability of extracting lithium. In view of this, according to an embodiment of the present invention, the method for extracting lithium from salt lake brine of the present invention may further include:
(5) the lye is mixed with the stripping organic phase in order to obtain a regenerated stripping organic phase.
In the step, alkali liquor is used as a regenerant to neutralize the back extraction of the back extraction organic phase, so that the regeneration capacity of the back extraction organic phase is recovered. According to the embodiment of the present invention, the specific kind of the above-mentioned alkali solution is not particularly limited as long as it can be neutralized with hydrochloric acid and easily separated from the regenerated stripping organic phase. According to the preferred embodiment of the invention, the alkali liquor can adopt sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution or potassium carbonate solution with the concentration of 0.1-1.0 mol/L, the alkali liquor is wide in source, cheap and easy to obtain, and impurity ions which are difficult to remove are not introduced into the organic phase.
According to the embodiment of the invention, the volume ratio of the stripping organic phase to the alkali liquor is (10-40): 1, i.e. the ratio of O/A is 10-40. Under the condition of the phase ratio, the back extraction organic phase is neutralized by alkali liquor until the pH value of the water phase is 0.5-3.0.
In another aspect of the present invention, the present invention provides a composite extractant. According to the embodiment of the invention, the composite extracting agent comprises a compound shown as a formula (A) and a compound shown as a formula (B),
Figure BDA0001899935050000101
wherein the content of the first and second substances,
R1is C6-20Straight chain alkyl, C6-20Branched alkyl or C6-20A cycloalkyl group;
R2and R3Are each independently C1-24Straight chain alkyl, C1-24Branched alkyl or C1-24Cycloalkyl radical, and R2And R3Is not less than 5.
In the composite extractant according to the embodiment of the present invention, in the compound represented by the formula (A), two methyl groups are directly bonded to the nitrogen atom, and R is bonded to the carbonyl group1The radical being C6-20Linear, branched or cyclic alkyl. The compound shown in the formula (A) has obvious structural difference with the traditional amide lithium extractants (such as N, N-di (2-ethylhexyl) propionamide, N-dihexylbenzamide, N-di (2-ethylhexyl) acetamide, N-dihexylp-methylbenzamide and the like): attached to the nitrogen atom of the compound of formula (A) are two methyl groups, and R is attached through a carbonyl group1The groups providing oil solubility, while conventional amide-type lithiumThe extractant has two long carbon chain alkyl radicals attached to the amide nitrogen atom. The electron repulsion effect of the alkyl is enhanced along with the increase of the number of carbon atoms, and the electron repulsion effect of the methyl is weaker than that of the long-carbon-chain alkyl, so that the electron cloud density of the nitrogen atom in the compound shown in the formula (A) is obviously lower than that of the amide nitrogen atom in the traditional amide lithium extractant, the alkalinity of the compound shown in the formula (A) is obviously weaker than that of the traditional amide lithium extractant, and Fe is not easy to cause in the extraction process3+Hydrolysis forms flocs. On the other hand, the compound shown in the formula (B) has proper polarity and has better compatibility with an organic phase in an extraction system. Meanwhile, the compound represented by the formula (B) is used for LiFeCl4Also has certain extraction effect and lower viscosity. The compound shown as the formula (B) is used as a compound modifier shown as the formula (A), the formation of a third phase in the extraction process can be effectively avoided, and the LiFeCl of the compound shown as the formula (A) serving as the main extractant is improved4The extraction rate of the extraction process is ensured, and the continuous and stable operation of the extraction process is ensured.
Considering the oil solubility, water solubility loss, atom economy and raw material availability of the extractant in combination, according to a preferred embodiment of the invention, in the compound represented by formula (A), R1Is C8-14Straight chain alkyl or C8-14A branched alkyl group. Having the above-mentioned R1The compound shown in the formula (A) of the group has proper oil solubility and lower water solubility, the loss of a water phase in the extraction process is very small, and the raw material has wide source range, is cheap and is easy to obtain. According to a preferred embodiment of the invention, R2And R3Are each independently C1-12Straight chain alkyl or C1-12A branched alkyl radical, and R2And R3The total carbon number of (A) is 7 to 15, in other words, the total carbon number of the compound represented by the formula (B) is 8 to 16. Having the above-mentioned R2And R3The compound shown in the formula (B) of the group has proper oil solubility and lower water solubility, the loss of a water phase in the extraction process is very small, and the raw material has wide source range, is cheap and is easy to obtain.
According to the embodiment of the present invention, the ratio of the compound represented by formula (a) to the compound represented by formula (B) in the composite extractant is not particularly limited; preferably, the volume ratio of the compound represented by the formula (A) to the compound represented by the formula (B) is 1 (0.1-10), such as 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.8, 1:1, 1:2, 1:3, 1:5, 1:8, or 1: 10. Therefore, the composite extracting agent can be ensured to have higher extracting capacity and selectivity to lithium, and the formation of a third phase in an extraction system is further avoided.
As mentioned above, the composite extractant proposed by the present invention may have at least one advantage selected from the following:
1. compared with the existing widely used salt lake lithium extraction extractant TBP, the compound extractant has extremely low swelling corrosion to equipment, and can greatly prolong the renewal period of the equipment.
2. The hydrolysis stability of the compound shown in the formula (A) and the compound shown in the formula (B) under acidic or alkaline conditions is higher than that of TBP, and the loss of an extracting agent and the emulsification caused by degradation products are both lower than that of TBP.
3. The unique structure of the compound shown in the formula (A) determines that the compound is weak in alkalinity, and the compound is in FeCl3In the co-extraction system, Fe is not easy to react3+Flocs are formed, which is very important for the extraction process.
4. The density of the compound shown in the formula (A) and the density of the compound shown in the formula (B) are both 0.80-0.85 g/cm3Significantly lower than TBP (0.977 g/cm)3) And the density difference with the water phase is large, so that the phase splitting in the processes of extraction, washing, back extraction, regeneration and the like is facilitated.
5. The compound represented by the formula (B) ① has polarity between that of kerosene and extracted associated complex, and good compatibility with both of them, ② it is used for LiFeCl4The method has the advantages that the ① avoids the formation of a third phase in the extraction process, the ② improves the extraction rate of the main extractant, and the ③ extraction process has good circulating fluidity and can continuously and stably run.
6. The composite extracting agent provided by the invention does not contain phosphorus, and the extraction waste water is subjected to biochemical or photocatalytic treatment, wherein dissolved organic matters are degraded into non-toxic and harmless carbon dioxide and nitrogen, so that the composite extracting agent has important significance for ecological protection of salt lakes.
The invention will now be described with reference to specific examples, which are intended to be illustrative only and not to be limiting in any way.
General procedure
Mixing salt lake brine with high magnesium-lithium ratio after potassium extraction and boron removal and ferric trichloride to serve as an extraction material liquid, and extracting lithium in the salt lake brine according to the following steps:
(1) mixing a compound shown in a formula (A), a compound shown in a formula (B) and a diluent to obtain an extracted organic phase;
(2) mixing the extraction organic phase with the extraction liquid and extracting to obtain a loaded organic phase and raffinate;
(3) washing the loaded organic phase by using a detergent so as to obtain a washed organic phase and a washing residual liquid;
(4) carrying out back extraction on the washed organic phase by using hydrochloric acid so as to obtain a back extraction organic phase and a back extraction raffinate;
(5) the lye (regenerant) is mixed with the stripping organic phase to obtain a regenerated stripping organic phase.
The compositions of the salt lake brine with high Mg/Li ratio after extracting potassium and removing boron are shown in Table 1 (the salt lake brine satisfies Cl)-Concentration is more than or equal to 5.0mol/L and H+The concentration is 0.01-1.0 mol/L, so that the composition does not need to be adjusted by adding hydrochloric acid):
TABLE 1 composition of salt lake brine with high Mg/Li ratio after potassium extraction and boron removal
Figure BDA0001899935050000121
Example 1
Treating the salt lake brine with the composition shown in Table 1 according to a general method, wherein the extraction organic phase is a mixture of N, N-dimethyl octanoyl amide and D70 solvent oil, and the volume fractions are respectively 40% and 60%; addition of FeCl to the brine as shown in Table 13Mixing and dissolving the mixture to ensure that Fe/Li is 1.5 (molar ratio) to obtain an extraction solution; extracting the product with O/A being 2.0; washing O/A is 30; stripping agent: 6mol/LHCl, and stripping O/A is 30; a regenerant: 0.5mol/L NaOH solution, regenerated O/A20.
The system is divided into three phases after extraction, the extraction rate of the single-stage lithium is 61.5 percent, and the separation coefficient of the single-stage lithium and magnesium is (β)Li/Mg) Lithium sodium separation coefficient (β)Li/Na) Lithium potassium separation coefficient (β)Li/K) 285.3, 21.5 and 37.7 are respectively achieved. After 6-stage extraction, 5-stage washing and 5-stage back extraction, the recovery rate of lithium reaches 99.5 percent, and Li in the back extraction raffinate+The concentration of (A) is up to 32.1g/L, Mg2+、Na+、K+The concentration of the lithium ion is lower than 1mg/L, and the extraction of lithium and the high-efficiency separation of other impurity elements are realized.
Example 2
Treating the salt lake brine with the composition shown in Table 1 according to a general method, wherein the extraction organic phase is a mixture of N, N-dimethyl octanoyl amide, diisobutyl ketone and D70 solvent oil, and the volume fractions are respectively 40%, 20% and 40%; addition of FeCl to the brine as shown in Table 13Mixing and dissolving the mixture to ensure that Fe/Li is 1.5 (molar ratio) to obtain an extraction solution; extracting the product with O/A being 2.0; washing O/A20; stripping agent: 6mol/L HCl, and stripping O/A is 30; a regenerant: 0.5mol/L NaOH solution, regenerated O/A20.
The system is divided into two clear and transparent phases without intermediate phase (third phase) after extraction, the extraction rate of single-stage lithium is 68.7 percent, and the separation coefficient of single-stage lithium and magnesium is (β)Li/Mg) Lithium sodium separation coefficient (β)Li/Na) Lithium potassium separation coefficient (β)Li/K) Respectively reaching 310.8, 30.4 and 46.5. After 5-stage extraction, 4-stage washing and 5-stage back extraction, the recovery rate of lithium reaches more than 99.5 percent, and Li in the back extraction raffinate+The concentration of (A) is up to 34.2g/L, Mg2+、Na+、K+The concentration of the lithium ion is lower than 1mg/L, and the extraction of lithium and the high-efficiency separation of other impurity elements are realized.
Example 3
Treating the salt lake brine with the composition shown in Table 1 according to a general method, wherein the extraction organic phase is a mixture of N, N-dimethyl octanoyl amide, diisobutyl ketone and 260# aviation kerosene, and the volume fractions are respectively 30%, 30% and 40%; addition of FeCl to the brine as shown in Table 13Mixing and dissolving the mixture to ensure that Fe/Li is 1.3 (molar ratio) to obtain an extraction solution; extracting to obtain 1.0O/A; washing O/A is 30; inverse directionExtracting agent: 6mol/L HCl, and stripping O/A is 30; a regenerant: 0.3mol/L Na2CO3Solution, regenerated O/a ═ 20.
The system is divided into two phases after extraction, the extraction rate of the single-stage lithium is 55.8 percent, and the separation coefficient of the single-stage lithium and magnesium is (β)Li/Mg) Lithium sodium separation coefficient (β)Li/Na) Lithium potassium separation coefficient (β)Li/K) Respectively reaching 280.2, 20.3 and 40.5. After 7-stage extraction, 5-stage washing and 5-stage back extraction, the recovery rate of lithium reaches 99.5 percent, and Li in the back extraction raffinate+The concentration of (A) is up to 32.1g/L, Mg2+、Na+、K+The concentration of the lithium ion is lower than 1mg/L, and the extraction of lithium and the high-efficiency separation of other impurity elements are realized.
Example 4
Treating the salt lake brine with the composition shown in Table 1 according to a general method, wherein the extraction organic phase is a mixture of N, N-dimethyl capramide, 2-decanone and 260# aviation kerosene, and the volume fractions are respectively 30%, 30% and 40%; addition of FeCl to the brine as shown in Table 13Mixing and dissolving the mixture to ensure that Fe/Li is 1.3 (molar ratio) to obtain an extraction solution; extracting the product with O/A being 2.0; washing O/A is 30; stripping agent: 6mol/L HCl, and stripping O/A is 20; a regenerant: 0.6mol/L NaOH solution, regenerated O/A30.
The system is divided into two phases after extraction, the extraction rate of the single-stage lithium is 64.5 percent, and the separation coefficient of the single-stage lithium and magnesium is (β)Li/Mg) Lithium sodium separation coefficient (β)Li/Na) Lithium potassium separation coefficient (β)Li/K) 270.3, 18.5 and 32.6 respectively. After 6-stage extraction, 5-stage washing and 5-stage back extraction, the recovery rate of lithium reaches more than 99.5 percent, and Li in the back extraction raffinate+The concentration of (B) is up to 35.2g/L, Mg2+、Na+、K+The concentration of the lithium ion is lower than 1mg/L, and the extraction of lithium and the high-efficiency separation of other impurity elements are realized.
Example 5
Treating the salt lake brine with the composition shown in Table 1 according to a general method, wherein the extraction organic phase is a mixture of N, N-dimethyl capramide, 2-nonanone and D80 solvent oil, and the volume fractions are respectively 30%, 30% and 40%; addition of FeCl to the brine as shown in Table 13Mixing and dissolving the mixture to make Fe/Li equal to 1.5 (mol ratio) to obtain an extraction solution(ii) a Extracting the product with O/A being 2.0; washing O/A is 30; stripping agent: 6mol/L HCl, and stripping O/A is 20; a regenerant: 0.7mol/L NaOH solution, and regenerated O/A is 30.
The system is divided into two phases after extraction, the extraction rate of the single-stage lithium is 63.8 percent, and the separation coefficient of the single-stage lithium and magnesium is βLi/Mg) Lithium sodium separation coefficient (β)Li/Na) Lithium potassium separation coefficient (β)Li/K) Respectively reaching 290.1, 24.9 and 42.6. After 6-stage extraction, 5-stage washing and 5-stage back extraction, the recovery rate of lithium reaches more than 99.5 percent, and Li in the back extraction raffinate+The concentration of (A) is up to 33.8g/L, Mg2+、Na+、K+The concentration of the lithium ion is lower than 1mg/L, and the extraction of lithium and the high-efficiency separation of other impurity elements are realized.
Example 6
The salt lake brine with the composition shown in table 1 is treated according to a general method, wherein the extraction organic phase is a mixture of N, N-dimethyloctadecylamide (a mixture of N, N-dimethyloctadecylamide and N, N-dimethyldecanoylamide in any proportion), diisobutyl ketone and D80 solvent oil, and the volume fractions are 40%, 30% and 30% respectively; addition of FeCl to the brine as shown in Table 13Mixing and dissolving the mixture to ensure that the Fe/Li ratio is 1.6 (mol ratio) to obtain an extraction solution; extracting to obtain 1.5O/A; washing O/A is 30; stripping agent: 6mol/L HCl, and stripping O/A is 20; a regenerant: 0.6mol/L K2CO3Solution, regenerated O/a 30.
The system is divided into two phases after extraction, the extraction rate of the single-stage lithium is 63.9 percent, and the separation coefficient of the single-stage lithium and magnesium is βLi/Mg) Lithium sodium separation coefficient (β)Li/Na) Lithium potassium separation coefficient (β)Li/K) Respectively reaching 275.6, 28.5 and 32.3. After 6-stage extraction, 4-stage washing and 4-stage back extraction, the recovery rate of lithium reaches more than 99.5 percent, and Li in the back extraction raffinate+The concentration of (A) is up to 33.8g/L, Mg2+、Na+、K+The concentration of the lithium ion is lower than 1mg/L, and the extraction of lithium and the high-efficiency separation of other impurity elements are realized.
Example 7
The salt lake brine with the composition shown in Table 1 was treated according to the general method, wherein the organic phase of extraction was a mixture of N, N-dimethyllauramide, 2-decanone and D70 mineral spirits in volume fractions of40%, 30% and 30%; addition of FeCl to the brine as shown in Table 13Mixing and dissolving the mixture to ensure that the Fe/Li ratio is 1.8 (mol ratio) to obtain an extraction solution; extracting the product with O/A being 2.0; washing O/A is 30; stripping agent: 6mol/L HCl, and stripping O/A is 20; a regenerant: 0.5mol/L NaOH solution, regenerated O/A30.
The system is divided into two phases after extraction, the extraction rate of the single-stage lithium is 69.2 percent, and the separation coefficient of the single-stage lithium and magnesium is βLi/Mg) Lithium sodium separation coefficient (β)Li/Na) Lithium potassium separation coefficient (β)Li/K) Respectively reaching 280.2, 24.4 and 37.8. After 5-stage extraction, 5-stage washing and 5-stage back extraction, the recovery rate of lithium reaches more than 99.5 percent, and Li in the back extraction raffinate+The concentration of (A) is up to 33.1g/L, Mg2+、Na+、K+The concentration of the lithium ion is lower than 1mg/L, and the extraction of lithium and the high-efficiency separation of other impurity elements are realized.
Example 8
Treating the salt lake brine with the composition shown in Table 1 according to a general method, wherein the extraction organic phase is a mixture of N, N-dimethyl lauramide, 2-octanone, 2-decanone and D80 solvent oil, and the volume fractions are respectively 40%, 15% and 30%; addition of FeCl to the brine as shown in Table 13Mixing and dissolving the mixture to ensure that Fe/Li is 1.5 (molar ratio) to obtain an extraction solution; extracting the product with O/A being 2.0; washing O/A is 30; stripping agent: 6mol/L HCl, and stripping O/A is 20; a regenerant: 0.5mol/L Na2CO3Solution, regenerated O/a 30.
The system is divided into two phases after extraction, the extraction rate of the single-stage lithium is 70.4 percent, and the separation coefficient of the single-stage lithium and magnesium is (β)Li/Mg) Lithium sodium separation coefficient (β)Li/Na) Lithium potassium separation coefficient (β)Li/K) Respectively reaching 280.5, 24.1 and 38.0. After 5-stage extraction, 5-stage washing and 5-stage back extraction, the recovery rate of lithium reaches more than 99.5 percent, and Li in the back extraction raffinate+The concentration of (A) is up to 34.2g/L, Mg2+、Na+、K+The concentration of the lithium ion is lower than 1mg/L, and the extraction of lithium and the high-efficiency separation of other impurity elements are realized.
Example 9
The salt lake brine having the composition shown in Table 1 was treated according to a general method, wherein the organic phase for extraction was N, N-dimethyllaurelThe mixture of amide, N-dimethyl octanamide, 2-propyl cyclohexanone, 2-decanone and No. 260 aviation kerosene is 15%, 20%, 15% and 35% in volume fraction respectively; addition of FeCl to the brine as shown in Table 13Mixing and dissolving the mixture to ensure that the Fe/Li ratio is 1.7 (molar ratio) to obtain an extraction solution; extracting the product with O/A being 2.0; washing O/A is 30; stripping agent: 6mol/L HCl, and stripping O/A is 20; a regenerant: 0.5mol/L NaOH solution, regenerated O/A30.
The system is divided into two phases after extraction, the extraction rate of the single-stage lithium is 65.7 percent, and the separation coefficient of the single-stage lithium and magnesium is βLi/Mg) Lithium sodium separation coefficient (β)Li/Na) Lithium potassium separation coefficient (β)Li/K) 293.1, 26.7 and 41.5 are respectively achieved. After 6-stage extraction, 5-stage washing and 5-stage back extraction, the recovery rate of lithium reaches more than 99.5 percent, and Li in the back extraction raffinate+The concentration of (A) is up to 32.3g/L, Mg2+、Na+、K+The concentration of the lithium ion is lower than 1mg/L, and the extraction of lithium and the high-efficiency separation of other impurity elements are realized.
Example 10
During the use process of the extractant, particularly in an acidic or alkaline system, side reactions (collectively referred to as degradation) such as hydrolysis, degradation and oxidation tend to occur gradually, and in addition, the extractant itself has partial dissolution loss. Therefore, fresh extractant needs to be replenished periodically during the extraction process. In addition, if the degradation degree of the extracting agent is serious, the extraction system is often emulsified seriously, so that the extraction process cannot be operated. Therefore, the circulation stability of the extractant is an important index for examining the extractant. In this example, the extraction agent and TBP proposed by the present invention were used to perform a cycle experiment of extracting lithium from salt lake under the same conditions, and their cycle stability was compared.
The experimental conditions are as follows:
the composition of the lithium extraction brine is shown in table 1;
organic phase 1: n, N-dimethyl Decanamide (DMAA) + 2-Nonanone (NK) + D80 solvent oil, the volume fractions are 40%, 20% and 40% respectively;
organic phase 2 (control): TBP + 2-nonanone + D80 solvent oil, the volume fractions are 40%, 20% and 40% respectively;
to the brine shown in Table 1Adding FeCl3Mixing and dissolving to make Fe/Li equal to 1.8 (molar ratio); extracting the product with O/A being 2.0; washing O/A is 30; stripping agent: 6mol/L HCl, and stripping O/A is 20; a regenerant: 0.5mol/L NaOH solution, and regenerated O/A is 20;
the extraction mode is as follows: continuous countercurrent flow; stage number: 6-stage extraction, 5-stage washing, 5-stage back extraction and 1-stage regeneration.
The content of the extractant in the organic phase was determined by gas chromatography. The results are shown in Table 2. As can be seen from Table 2, the extractant proposed by the present invention has higher cycling stability than TBP, and is not easy to emulsify in the extraction process.
TABLE 2 extractant cycling stability comparative experiment
Figure BDA0001899935050000161
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims (16)

1. A method for extracting lithium from salt lake brine by using an extracting agent is characterized in that the extracting agent comprises a compound shown as a formula (A),
Figure FDA0002480296820000011
wherein R is1Is C6-20Straight chain alkyl, C6-20Branched alkyl or C6-20A cycloalkyl group.
2. The method of claim 1, wherein R is1Is C8-14Straight chain alkyl or C8-14A branched alkyl group.
3. The method of claim 1, wherein the extractant further comprises a compound of formula (B),
Figure FDA0002480296820000012
wherein R is2And R3Are each independently C1-24Straight chain alkyl, C1-24Branched alkyl or C1-24Cycloalkyl radical, and R2And R3Is not less than 5.
4. The method of claim 3, wherein R is2And R3Are each independently C1-12Straight chain alkyl or C1-12A branched alkyl radical, and R2And R3The total number of carbon atoms is 7 to 15.
5. The method according to claim 3, wherein the volume ratio of the compound represented by the formula (A) to the compound represented by the formula (B) is 1 (0.1-10).
6. A method according to any one of claims 1 to 5, characterized in that the method comprises:
(1) mixing the salt lake brine with ferric trichloride to obtain an extraction feed liquid;
(2) mixing the extracting agent and a diluent to prepare an extracted organic phase, and mixing the extracted organic phase with the extraction liquid to extract so as to obtain a loaded organic phase and raffinate;
(3) washing the loaded organic phase by using a detergent so as to obtain a washed organic phase and a washing residual liquid;
(4) and (3) carrying out back extraction on the washed organic phase by using hydrochloric acid so as to obtain a back extraction organic phase and a back extraction raffinate.
7. The method according to claim 6, wherein in the step (1), the concentration of the hydrogen ions in the extraction liquid is 0.01-1.0 mol/L, and the molar ratio of iron to lithium is (1-3): 1.
8. The method of claim 6, wherein in step (2), the volume fraction of the extractant in the organic phase is 10-99%.
9. The method according to claim 8, wherein the diluent is selected from mineral spirits having a boiling range of 160-300 degrees Celsius.
10. The method of claim 9, wherein the diluent is at least one selected from the group consisting of 260# jet fuel, sulfonated kerosene, D70 mineral spirits, and D80 mineral spirits.
11. The method as claimed in claim 6, wherein in the step (2), the volume ratio of the extraction organic phase to the extraction liquid is (4-1): 1-4), the single-stage extraction time is 3-30 min, and the system temperature is 10-50 ℃.
12. The method as claimed in claim 6, wherein in the step (3), the volume ratio of the loaded organic phase to the detergent is (20-50): 1, the contact time is 3-30 min, and the system temperature is 10-50 ℃.
13. The process of claim 6, wherein in step (3), the detergent is the strip raffinate.
14. The method according to claim 6, wherein in the step (4), the volume ratio of the washed organic phase to the hydrochloric acid is (10-30): 1, the contact time is 2-30 min, and the system temperature is 10-50 ℃; the concentration of the hydrochloric acid is 5.0-9.0 mol/L.
15. The method of claim 6, further comprising:
(5) mixing an alkaline liquor with the stripping organic phase to obtain a regenerated stripping organic phase.
16. The method of claim 15, wherein the alkali liquor is a sodium hydroxide solution, a potassium hydroxide solution, a sodium carbonate solution or a potassium carbonate solution with a concentration of 0.1-1.0 mol/L, and the volume ratio of the stripping organic phase to the alkali liquor is (10-40): 1.
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