CN108004420B - Centrifugal extractor-based process for extracting lithium from lithium-containing alkaline brine - Google Patents
Centrifugal extractor-based process for extracting lithium from lithium-containing alkaline brine Download PDFInfo
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Abstract
The invention discloses a process for extracting lithium from lithium-containing alkaline brine based on a centrifugal extractor, which comprises the following steps: providing an extraction aqueous phase, providing an extraction organic phase, an extraction step, a washing step, a stripping step and a regeneration step. According to the process, a brand-new extraction system is adopted to extract lithium from a lithium-containing alkaline brine system, and the whole process of extraction-washing-back extraction-regeneration based on a centrifugal extractor is determined for the first time, so that the basic research of extraction sections is stopped, the process parameters such as the stage number, the flow ratio, the concentration of each reagent and the like of each section adapted by the extraction system are finally determined, and an industrial production process route based on the centrifugal extractor is provided; the process for extracting lithium from lithium-containing alkaline brine is particularly suitable for a filtrate system generated in the process of preparing a lithium carbonate product from a lithium chloride solution so as to further extract lithium from the filtrate system, thereby realizing the real comprehensive recycling of salt lake brine and having practical significance.
Description
Technical Field
The invention belongs to the technical field of salt lake chemical industry, and particularly relates to a process for extracting lithium from lithium-containing alkaline brine based on a centrifugal extractor.
Background
Lithium is the lightest metal in nature and has extremely strong electrochemical activity, and the metal and the compound thereof are widely applied to industries and fields of glass, ceramic aluminum smelting, organic chemical industry, aerospace, nuclear fusion and the like as explosives of thermonuclear fusion (hydrogen bomb), high-performance propelling fuels of airplanes, rockets and missiles and shielding materials of nuclear reactors. The lithium battery has 4-30 times higher energy storage than a common battery, has good service performance, and can be used as the driving force of torpedoes, submarines and spacecraft for a long time. The lithium aluminum and lithium magnesium alloy has high strength and light weight, is a good material for aerospace and rocket, and is favored by military industry and aerospace industry. In the 21 st century, with the rising demand for clean energy and the production of low-priced lithium salts, lithium energy will likely deeply affect human lives, and thus lithium is called "energy metal of the 21 st century".
The current effective method for extracting lithium from salt lake brine comprises a solvent extraction method, and FeCl is inevitably adopted in the solvent extraction method3As a co-extractant, the density of an extracted organic phase is increased, the density difference of two phases is reduced, and the requirement on extraction and separation equipment is higher; at the same time, FeCl is introduced3Then, the difficulty is high when the extractant is regenerated by alkali, and very accurate flow control is needed, otherwise, the problems of extraction rate reduction or extractant emulsification failure and the like can be caused. In addition, the organic phase contains FeCl as a synergist3The extraction liquid (brine) is required to be kept weakly acidic, otherwise, Fe hydrolysis is caused, the brine entering an extraction working section is required to be subjected to acidification treatment, lithium and boron in the Qinghai salt lake commonly exist in association, boric acid is inevitably separated out in the acidification process, and filtration treatment is required, so that the method has no applicability to extraction of lithium in an alkaline system. Most of the current extracting agents for lithium can only realize lithium-magnesium separation, and have poor extraction effect on an alkali metal system. In conclusion, FeCl was the synergist3The existing method has the disadvantages of complex process flow, great difficulty in process control and great equipment investment.
Meanwhile, in the extraction equipment used in the solvent extraction industry at present, the centrifugal extractor has the advantages of compact equipment, high mass transfer efficiency and small solute retention, and the extraction process has the following advantages: the extraction process has short balance time, less material retention and rapid phase splitting; the parameter adjustment reaction is rapid, and the automation is easy to realize; the equipment volume is small, the plant area is small, the reagent and material amount is small, and the investment is low; the equipment is closed, and the working environment is good.
Therefore, there is an urgent need to develop a process method based on a centrifugal extractor and suitable for extracting lithium from alkaline brine, so as to provide process guidance for practical industrial production.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a process for extracting lithium from lithium-containing alkaline brine based on a centrifugal extractor, which is different from the traditional extraction system, can extract lithium from the lithium-containing alkaline brine system, determines the whole process of extraction-washing-back extraction-regeneration based on the centrifugal extractor, and provides a process path for practical industrial production.
In order to achieve the purpose of the invention, the invention adopts the following technical scheme:
a centrifugal extractor based process for extracting lithium from lithium-containing alkaline brine comprising the steps of:
providing an extraction aqueous phase: taking lithium-containing alkaline brine as an extraction water phase; wherein the pH value of the lithium-containing alkaline brine is 8-14, and Li is contained in the lithium-containing alkaline brine+Has a mass concentration of 0.05-10 g/L and Na+Has a mass concentration of not more than 80g/L, K+Has a mass concentration of not more than 80g/L and Mg2+Is not more than 1g/L, Ca2+The mass concentration of (A) is not more than 1 g/L;
providing an extracted organic phase: mixing an extracting agent, a co-extracting agent and kerosene to prepare an extracted organic phase; wherein, in the extracted organic phase, the quantity concentration of the extracting agent and the co-extracting agent is 0.05 mol/L-0.6 mol/L, the extracting agent is selected from any one of benzoyl trifluoroacetone, furoyl trifluoroacetone and thenoyl trifluoroacetone, and the co-extracting agent is selected from any one of trioctyl phosphine oxide, tributyl phosphate, trialkyl phosphine oxide and 2-ethylhexyl phosphoric acid;
an extraction step: mixing the extraction organic phase and the extraction water phase in a first centrifugal extractor component according to a flow ratio of 1: 10-10: 1, performing 2-15-stage countercurrent extraction, and performing phase separation to obtain raffinate and a loaded organic phase;
a washing step: taking 0.1-12 mol/L hydrochloric acid solution or lithium-containing solution with the same acidity as washing liquid, mixing the loaded organic phase and the washing liquid in a second centrifugal extractor component according to the flow ratio of 5: 1-80: 1, carrying out 2-15-stage countercurrent washing, and carrying out phase separation to obtain washing residual liquid and washing organic phase;
back extraction: taking 1-12 mol/L hydrochloric acid solution as a stripping solution, mixing the washing organic phase and the stripping solution in a third centrifugal extractor assembly according to a flow ratio of 5: 1-80: 1, performing 2-15-stage counter-current stripping, and performing phase separation to obtain a lithium chloride solution and an empty organic phase;
a regeneration step: carrying out grade 1 regeneration or grade 2-5 countercurrent regeneration on the empty organic phase by taking an alkaline solution as a regeneration solution, and carrying out phase splitting to obtain a regeneration residual liquid and a regeneration organic phase; wherein the flow ratio of the empty organic phase to the regenerated liquid is 1: 5-5: 1.
Further, in the washing step, the concentration of lithium in the washed organic phase is not less than 80% of the concentration of lithium in the loaded organic phase; the total concentration of metals other than lithium in the washed organic phase is no more than 5% of the total concentration of metals other than lithium in the loaded organic phase.
Further, in the regenerating step, the extraction capacity of the regenerated organic phase is not less than 90% of the extraction capacity of the extracted organic phase.
The alkaline solution is any one of a hydroxide solution having a substance concentration of 0.05 to 4mol/L, an ammonia solution having a substance concentration of 0.05 to 4mol/L, or a carbonate solution having a substance concentration of 0.05 to 4 mol/L.
Further, the anion in the lithium-containing alkaline brine is selected from Cl-、SO4 2-、CO3 2-、NO3 -At least one of (1).
Further, in the step of providing an extraction aqueous phase, the lithium-containing alkaline brine is obtained by adding a sodium hydroxide solution, a sodium carbonate solution, or an ammonia solution to the lithium-containing brine.
Furthermore, the mass concentration of the sodium hydroxide solution, the sodium carbonate solution or the ammonia solution is 0.05 mol/L-4 mol/L.
Further, the lithium-containing brine is pretreated to remove solid precipitates and suspended substances before adding a sodium hydroxide solution, a sodium carbonate solution or an ammonia solution into the lithium-containing brine.
Further, the lithium-containing alkaline brine is pretreated to remove solid precipitates and suspended substances before the lithium-containing alkaline brine forms the extraction aqueous phase.
Further, the process also includes the cycling step: returning the regenerated organic phase to the extraction step for use as an extracted organic phase, and repeating the extraction step, the washing step, the stripping step, and the regeneration step.
Further, in the extraction step, the extracted organic phase is pumped through the light phase inlet of the first centrifugal extractor assembly, and the extracted aqueous phase is pumped through the heavy phase inlet of the first centrifugal extractor assembly; in the washing step, the loaded organic phase is pumped in through the light phase inlet of the second centrifugal extractor assembly, and the washing liquid is pumped in through the heavy phase inlet of the second centrifugal extractor assembly; in the back extraction step, the washing organic phase is pumped in from the light phase inlet of the third centrifugal extractor assembly, and the back extraction solution is pumped in from the heavy phase inlet of the third centrifugal extractor assembly.
Further, in the regeneration step, the regeneration equipment is selected from any one of a centrifugal extractor, a mixer-settler and a tubular reactor.
Has the advantages that:
(1) the invention is carried out by using diketone compoundsThe lithium ion extracting agent is an extracting agent and a neutral phosphorus-oxygen compound is used as a co-extracting agent, so that the aim of extracting lithium from the lithium-containing alkaline brine is fulfilled; compared with the method for extracting lithium from salt lake brine by using a TBP-based extraction system in the prior art, the method avoids the co-extraction agent FeCl3The use of the method also avoids the problems of small density difference of two phases, high difficulty in process control and the like in the extraction process.
(2) According to the process, the full-flow process of extraction-washing-back extraction-regeneration is realized, and the process is not only stopped on the basis of basic research of extraction sections, and finally, the process parameters of the extraction system, such as the stage number, the flow ratio of an organic phase to a water phase, the concentration of each reagent and the like, which are adapted to each section of a centrifugal extractor are determined, so that the industrial production is really realized for the first time; the process is particularly suitable for a filtrate system generated in the process of preparing a lithium carbonate product from a lithium chloride solution, so that lithium is further extracted from the alkaline filtrate brine system saturated by the lithium carbonate, and the real comprehensive recycling of the salt lake brine is realized.
(3) According to the process, the water solubility of the extracting agent, the co-extracting agent and the diluent is low, the rest components in the raffinate are basically unchanged, the organic phase can be recycled through the regeneration step, three wastes are not generated, and the lithium recovery rate can reach about 90% or even higher.
(4) The method has the advantages of simple process, easy control, continuous operation, high reliability and high automation degree; the process can effectively separate and recover lithium from the lithium-containing alkaline brine, and the lithium chloride solution obtained by back extraction has high purity of lithium chloride and less impurities, and can be used for preparing a lithium chloride product or a lithium carbonate product.
Drawings
The above and other aspects, 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 process flow diagram of a centrifugal extractor based process for extracting lithium from lithium-containing alkaline brines according to the present invention;
FIG. 2 is a schematic diagram of the extraction principle of the extractant according to the invention;
fig. 3 is a schematic diagram of the extraction principle of the extraction system according to the invention.
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 process for extracting lithium from lithium-containing alkaline brine based on a centrifugal extractor, which provides a full-flow process comprising extraction, washing, back extraction and regeneration based on the centrifugal extractor, and confirms process parameters such as the stage number, the flow ratio of an organic phase to a water phase, the concentration of each reagent and the like of each section so as to form a process method with good extraction efficiency, thereby providing a process route for the industrialized expanded production based on the centrifugal extractor; the process for extracting lithium from lithium-containing alkaline brine is particularly suitable for a filtrate system generated in the process of preparing a lithium carbonate product from a lithium chloride solution, so that lithium is further extracted from the alkaline filtrate brine system saturated by lithium carbonate, thereby realizing the real comprehensive recycling of salt lake brine and having practical significance.
Referring to fig. 1, the process for extracting lithium from lithium-containing alkaline brine based on a centrifugal extractor comprises the following steps:
step S1, providing an extraction water phase.
Specifically, lithium-containing alkaline brine is used as an extraction water phase; wherein the pH of the lithium-containing alkaline brine is 8 to 14, and Li is contained in the lithium-containing alkaline brine+Has a mass concentration of 0.02-10 g/L and Na+Has a mass concentration of not more than 80g/L, K+Has a mass concentration of not more than 80g/L and Mg2+Is not more than 1g/L, Ca2+The mass concentration of (A) is not more than 1 g/L.
The anion in the lithium-containing alkaline brine may be Cl-、SO4 2-、CO3 2-、NO3 -Main anions representing the type of the salt lake brine or the anions introduced in the comprehensive utilization process of the salt lake brine; when lithium carbonate product is prepared by using lithium chloride solution, sodium carbonate is generally added into the system so as to lead Li in the system to be+Precipitating with lithium carbonate precipitate, performing solid-liquid separation to obtain lithium carbonate product, and filtering to obtain filtrate saturated with lithium carbonate and containing Na+And is alkaline, the method of the invention can be used for the filtrate to treat Li therein+Further recovery is carried out to form a lithium chloride solution which can be recycled as a raw material for preparing a lithium carbonate product.
It is worth to be noted that, if the initial pH of the lithium-containing brine cannot meet the above requirements, the lithium-containing alkaline brine with the pH of 8 to 14 can be obtained by adding a sodium hydroxide solution, a sodium carbonate solution or an ammonia solution thereto; the amount concentration of each of the sodium hydroxide solution, sodium carbonate solution, or ammonia solution used for adjusting the pH is preferably 0.05mol/L to 4 mol/L.
Meanwhile, in general, when the lithium-containing alkaline brine requiring no pH adjustment or the lithium-containing brine requiring pH adjustment is used as the actual brine, since impurities are present to some extent, it is preferable to perform a pretreatment to remove solid precipitates, suspended substances, and the like in the lithium-containing alkaline brine before the lithium-containing alkaline brine is used as an extraction aqueous phase or before the lithium-containing brine is subjected to pH adjustment.
Step S2, providing an extracted organic phase.
Specifically, an extraction agent, a synergist and kerosene are mixed to prepare an extraction organic phase.
In the extracted organic phase, the quantity concentration of the extracting agent and the co-extracting agent is controlled to be 0.05 mol/L-0.6 mol/L, the extracting agent is selected from any one of benzoyl trifluoroacetone, furoyl trifluoroacetone and thenoyl trifluoroacetone, and the co-extracting agent is selected from any one of trioctylphosphine oxide, tributyl phosphate, trialkyl phosphine oxide and 2-ethylhexyl phosphoric acid.
In the first of the periodic tableAlkali metals of the main group are very susceptible to losing the outermost s-electron to M+The ions, alkali metal ions, are hard Lewis acids and these cations are generally capable of forming relatively temperature complexes with oxygen-containing coordinating groups (e.g., strong Lewis bases such as carbonyl, phosphono, etc.). The separation of alkali metals from each other is achieved according to the difference in the degree of stability of the formed Lewis acid-base pairs.
Solvent extraction of lithium is not achieved by common extraction systems, and selective extraction of lithium necessitates the search for specific extractants and extraction systems. Depending on the nature of the lithium, the ligand requirements must satisfy the following aspects in order for an effective extraction effect to occur: satisfy Li+The requirement of tetrahedral coordination structure of (a); with energy of reaction with Li+Chelating functional groups that form stronger primary valency bonds, such as-OH or carbonyl compounds that can appear in the enol form during extraction; an O or N ligand having a hard basicity; with Li+Forming a stable chelate ring.
The above-mentioned extractants used in the present invention, benzoyl trifluoroacetone (hereinafter abbreviated as HBTA), furoyl trifluoroacetone (hereinafter abbreviated as HFTA) and thenoyl trifluoroacetone (hereinafter abbreviated as HTTA), all belong to diketone compounds, diketone is an acidic chelate extractant, and the mechanism for extracting lithium mainly utilizes the interconverted hydroxyl group of carbonyl or enol and Li+Combining; specifically, as shown in FIG. 2, in the diketone, there is a tautomeric equilibrium between the keto form (I) and the enol form (II) thereof, and Li is present during extraction+Can form a stable chelate structure (III) with diketone; the diketone is neutral after chelating with the metal ion, and the solubility of the inner complex salt in the organic phase is very small, as shown in fig. 3, if a ligand (S) exists, the diketone can be complexed with the inner complex salt to form an extractable neutral extract, and the ligand is called a synergist, namely trioctylphosphine oxide (hereinafter referred to as TOPO), tributyl phosphate (hereinafter referred to as TRPO), trialkylphosphine oxide and 2-ethylhexyl phosphoric acid used in the present invention. When the diketone is applied to extracting lithium, a synergistic extraction system is usually formed by the diketone and a neutral synergistic extractant for extraction so as to meet the requirement of Li+A four-coordinate structure of (a); furthermore, enolic bis-ketones with Li+After coordination, a stable six-membered chelate ring is formed. At the same time, the above coordinationChelation mode is mainly directed to Li+、Na+、K+Alkali metal and Ca2+、Mg2+Alkaline earth metals, however, the stability of chelates formed by different cations is different, and the stability of chelates formed by diketones and neutral synergists with different structures is also greatly different, so that not every diketone and every neutral synergist can be applied to the process of the present invention.
Specifically, the diketone compounds adopted by the invention as the extracting agents all have trifluoromethyl groups which have strong electron withdrawing effect, so that the enolization degree of the diketone compounds is enhanced, and the diketone compounds and Li are further reacted+Better bonding is possible; while other compounds with diketone structure, such as benzoylacetone, dibenzoylmethane, etc., do not have electron-withdrawing group, and thus have no electron-withdrawing group to Li+The selectivity of (a) is relatively weak and, correspondingly, lithium extraction is less effective. In other words, even though the diketone compound is used as an extractant for lithium ions, the hydroxyl group interconverted by carbonyl group or enol in the diketone structure is utilized with Li+In combination with the formation of cyclics, not every diketone compound can be a good lithium extractant.
More specifically, the synergist adopted by the invention is a neutral phosphine compound containing phosphine-oxygen double bonds, and has stronger synergic effect due to stronger electron-donating capability; other extracting agents containing carbon-oxygen double bonds or nitrogen-oxygen double bonds and sulfur-oxygen double bonds have relatively weak extracting effect due to the weak electron donating capability.
It is noted that, although based on the above extraction principle, the extractant and synergist will also react with Ca2+、Mg2+The alkaline earth metals are complexed for extraction, but the aqueous phase of the extraction according to the invention is alkaline and therefore contains free Ca2+、Mg2+The alkaline earth metal concentration will be very low; that is, the cation in the extract aqueous phase is mainly an alkali metal.
And step S3, extraction.
In particular, the extraction section is based on a centrifugal extractor; specifically, an extraction organic phase and an extraction water phase are mixed according to a flow ratio (hereinafter referred to as extraction flow ratio) of 1: 10-10: 1, 2-15 stages of countercurrent extraction are carried out, and phase splitting is carried out after extraction balance to obtain raffinate and a loaded organic phase.
More specifically, the extraction section of the present invention employs multi-stage counter-current extraction, so that a corresponding number of centrifugal extractors need to be connected to form a first centrifugal extractor assembly; generally, each centrifugal extractor is provided with a light phase inlet, a heavy phase inlet, a light phase outlet and a heavy phase outlet, wherein the extracted organic phase enters from the light phase inlet, the extracted aqueous phase enters from the heavy phase inlet, raffinate generated after extraction is discharged from the heavy phase outlet, and the loaded organic phase is discharged from the light phase outlet.
Preferably, because the present invention is an industrial process based on a centrifugal extractor, the dosage of the process is large, the extraction organic phase and the extraction aqueous phase are added by pumping, and the reagent adding mode of each section is similar.
It should be noted that, after a certain extraction organic phase is determined, the single-stage extraction rate of different extraction organic phases under different extraction flow ratios (corresponding to the extraction phase ratio and extraction time in the basic extraction research) can be determined in advance, then the theoretical extraction stage number corresponding to the predetermined extraction effect can be determined by combining the extraction equilibrium isotherm, and finally, the fluctuation does not exceed two stages on the basis of the theoretical extraction stage number, and the final actual extraction stage number can be determined. It can be seen that, in the multi-stage countercurrent extraction process, the determination of the extraction stages and the extraction flow ratio is not independent process parameters, but is determined by target ion concentrations (specifically referring to Li in the invention) in the extraction organic phase and the extraction aqueous phase+) A unified, mutually influencing parameter combination determined together; in other words, if the concentration of the target ion in the extraction aqueous phase is changed, the finally determined process parameters of the extraction section may also be changed correspondingly, and the composition of the extraction organic phase and the extraction flow ratio are changed in the same way, so as to finally form a short-series, low-cost and short-time preferred process with less extraction organic phase.
And step S4, washing.
Specifically, 0.1-6 mol/L hydrochloric acid solution or lithium-containing solution with the same acidity is used as washing liquid, 2-15 stages of countercurrent washing are carried out on the loaded organic phase, the flow ratio of the loaded organic phase to the washing liquid (hereinafter referred to as washing flow ratio) is controlled to be 5: 1-80: 1, and the washing liquid and the washing organic phase are obtained by phase separation.
More specifically, the washing section of the present invention employs multi-stage counter-current washing, so that a corresponding number of centrifugal extractors need to be connected to form a second centrifugal extractor assembly; the loaded organic phase enters from the light phase inlet, the washing liquid enters from the heavy phase inlet, the washing residual liquid generated after washing is discharged from the heavy phase outlet, and the washing organic phase is discharged from the light phase outlet.
In the extraction of Li+Is inevitably carried out by competitive extraction of other alkali metal ions, so that the part of the alkali metal ions carried in is washed and removed by multi-stage countercurrent washing before back extraction is carried out, but obviously, Li is inevitably caused in the washing process+Therefore, during washing, Li is generally controlled+The loss rate of (a) is less than 20% and the elution rate of the entrained alkali metals other than lithium is not less than 95%; in other words, by the multistage countercurrent washing, the concentration of lithium in the washed organic phase is not less than 80% of the concentration of lithium in the loaded organic phase, and the concentration of alkali metal other than lithium in the washed organic phase is not more than 5% of the concentration of alkali metal other than lithium in the loaded organic phase.
Therefore, in the above-mentioned multistage countercurrent washing process, the concentration of the washing liquid and the washing flow ratio are specifically adjusted depending on the contents of lithium and alkali metals other than lithium in the loaded organic phase, and the above-mentioned washing purpose, so that the cation in the washed organic phase is mainly lithium.
And step S5, back extraction.
Specifically, 1-6 mol/L hydrochloric acid solution is used as stripping solution, 2-15 levels of countercurrent stripping are carried out on the washed organic phase, the flow ratio of the washed organic phase to the stripping solution (hereinafter referred to as stripping flow ratio) is controlled to be 5: 1-80: 1, and after the stripping is balanced, phase separation is carried out to obtain lithium chloride solution and an empty organic phase.
Back extractionThe process is a process of transferring lithium from an organic phase to a water phase, which is equivalent to a reverse reaction of an extraction process, so that the process is similar to an extraction step, after the content of the lithium in the washed organic phase is determined, single-stage back extraction rates of back extraction solutions with different concentrations under different back extraction flow ratios are firstly measured, then a theoretical back extraction stage number corresponding to a preset back extraction effect is determined by combining a back extraction equilibrium isotherm, and finally, the fluctuation does not exceed two stages on the basis of the theoretical back extraction stage number, so that the final actual back extraction stage number is determined. It can be seen from this that, although the stripping process is somewhat simpler than the extraction process, and the process parameters involved are somewhat less, in the process of multistage countercurrent stripping, the solutions defining the stripping stage number and stripping flow ratio are not independent process parameters, but rather the target ion concentration in the organic phase (in the present invention, Li is specifically referred to+) And a uniform parameter combination with mutual influence jointly determined by the stripping solution; in other words, if the concentration of the target ion in the organic phase is changed, the finally determined process parameters of the stripping section may also be changed correspondingly, and the changes of the concentration of the strip liquor and the strip liquor ratio are the same, so as to finally form a preferred process with short series, less strip liquor consumption, low cost and short time consumption.
And step S6, regeneration.
Because the empty organic phase obtained after the back extraction carries or extracts part of back extraction liquid hydrochloric acid, and the part of hydrochloric acid can bring great influence on the recycling of the part of empty organic phase to a subsequent extraction section if the part of hydrochloric acid is not treated, in order to reduce the waste of the extracted organic phase, the empty organic phase should be regenerated to recover the lithium extraction capability, so that the organic phase can be recycled.
Specifically, an alkaline solution is used as a regeneration liquid, an air organic phase is subjected to grade 1 regeneration or grade 2-5 countercurrent regeneration, the flow ratio of the air organic phase to the regeneration liquid (hereinafter referred to as regeneration flow ratio) is controlled to be 1: 5-5: 1, a regeneration residual liquid and a regeneration organic phase are obtained through phase separation, and the regeneration organic phase can be returned to the step S3 to be used as an extraction organic phase for recycling.
More specifically, the alkaline solution may be selected from any one of a hydroxide solution having a substance concentration of 0.05 to 4mol/L, an ammonia solution having a substance concentration of 0.05 to 4mol/L, or a carbonate solution having a substance concentration of 0.05 to 4 mol/L.
It is worth to say that, in the regeneration process, the extraction capacity of the regenerated organic phase is not less than 90% of the extraction capacity of the extracted organic phase as the regeneration target; therefore, during the regeneration, it is necessary to adjust the number of regeneration steps and the type or concentration of the regeneration liquid to meet the above regeneration requirement.
Thus, compared with the extraction system using TBP as the extractant in the prior art, the extraction process does not need to use FeCl as the co-extractant3The problems of small density difference of two phases, high difficulty in process control and the like in the extraction process are avoided; in addition, in the process, the water solubility of the extracting agent, the co-extracting agent and the diluent is low, the rest components in the raffinate are basically unchanged, the organic phase can be recycled through a regeneration step, three wastes are not generated, and the lithium recovery rate is more than 90%; meanwhile, the process is simple, easy to control and high in operation reliability, lithium can be effectively separated and recovered from the lithium-containing alkaline brine, and the lithium chloride solution obtained through back extraction has high purity and few impurities.
In addition, the process is carried out based on a centrifugal extractor, and is an industrial actual production process different from an extraction basic experiment. As understood by those skilled in the art, when the basic extraction experiment is expanded to the practical industrial production based on the centrifugal extractor in the invention, the influence of factors such as operation flow ratio, mixing intensity, phase separation condition, mass transfer efficiency and the like, which are not involved in the basic extraction experiment for the practical production process, needs to be considered; meanwhile, based on the new process parameters brought by the expanded production, other process parameters are also affected, for example, in the process, a very large flow ratio (washing flow ratio and stripping flow ratio) occurs, which is not considered in the basic extraction experiment, on one hand, the flow ratio is a comprehensive consideration of the phase ratio (volume ratio of organic phase to aqueous phase) and time, on the other hand, a too large or too small ratio is almost impossible in the basic extraction experiment, as the flow ratio of 80:1 represents that the volume ratio of the organic phase to the aqueous phase in contact is 80:1, which can not achieve the adverse effect of phase separation in the basic extraction experiment because the volume difference of the two phases is too large and the contact interface is slightly miscible; in other words, only processes that are neither too large nor too small in comparison to the moderate ones can be operated in the extraction basis experiments, and thus the process parameters obtained therefrom have limited process guidance for scaled-up production. Meanwhile, the mass transfer efficiency is also an important factor to be considered in the industrial production process, which affects whether the ion exchange of extraction, back extraction and the like reaches the equilibrium and the time for reaching the equilibrium.
The technical effect of the above-mentioned process for extracting lithium from lithium-containing alkaline brine based on a centrifugal extractor will be shown below by specific examples.
Example 1
The lithium-containing brine is pretreated to remove impurities such as solid, precipitate, suspended matters and the like.
To Li+2mol/L sodium hydroxide solution is added into carbonate type brine with the concentration of 2g/L, and the pH value is adjusted to 11, so as to obtain an extraction water phase.
Mixing HBTA, TOPO and kerosene to obtain an extracted organic phase; wherein, the concentration of HBTA and TOPO substances in the extracted organic phase is 0.3 mol/L.
Pumping the prepared organic phase into a light phase inlet of the first centrifugal extractor assembly, pumping an extraction water phase into a corresponding heavy phase inlet, controlling the extraction flow ratio to be 3:2, performing three-stage countercurrent extraction on the organic phase and the extraction water phase in the first centrifugal extractor assembly, and performing phase separation to obtain raffinate and a loaded organic phase.
And (3) taking a 2mol/L hydrochloric acid solution as a washing solution, pumping the washing solution into a heavy phase inlet of the second centrifugal extractor component, pumping the loaded organic phase into a corresponding light phase inlet, controlling the washing flow ratio to be 20:1, performing three-stage countercurrent washing on the washing solution and the loaded organic phase in the second centrifugal extractor component, and separating the phases to obtain a washing residual solution and a washing organic phase.
And (3) taking a refined hydrochloric acid solution of 6mol/L as a stripping solution, pumping the stripping solution into a heavy phase inlet of the third centrifugal extractor component, pumping a washing organic phase into a corresponding light phase inlet, controlling the stripping flow ratio to be 20:1, performing three-stage counter-current stripping on the refined hydrochloric acid solution and the washing organic phase in the third centrifugal extractor component, and separating the phases to obtain a lithium chloride solution and an empty organic phase.
2mol/L sodium carbonate solution is taken as regeneration liquid, the regeneration liquid is pumped into a heavy phase inlet of a mixer-settler, an empty organic phase is pumped into a light phase inlet of the mixer-settler, the regeneration flow ratio is controlled to be 1:1, the two are subjected to secondary countercurrent regeneration in the mixer-settler, and phase separation is carried out to obtain regeneration residual liquid and regeneration organic phase.
Therefore, the regenerated organic phase obtained in the previous step can be reused as the extraction organic phase in the next period for cyclic utilization, so that the purposes of reducing organic reagent consumption, reducing pollution and reducing extraction cost are achieved.
The detection shows that the extraction rate of lithium in the alkaline lithium-containing brine is 95 percent, the total recovery rate of lithium reaches 90 percent, and the purity of the lithium chloride solution obtained after back extraction is more than 90 percent, so that the lithium chloride solution can be used as a raw material for producing a lithium chloride product and/or a lithium carbonate product.
Example 2
The lithium-containing brine is pretreated to remove impurities such as solid, precipitate, suspended matters and the like.
To Li+2mol/L sodium bicarbonate solution is added into carbonate or sulfate type brine with the concentration of 2g/L, and the pH value is adjusted to 11, so as to obtain an extraction water phase.
Mixing HFTA, TRPO and kerosene to obtain an extracted organic phase; wherein, the mass concentration of HFTA and TRPO in the extracted organic phase is 0.4 mol/L.
Pumping the prepared organic phase into a light phase inlet of the first centrifugal extractor assembly, pumping an extraction water phase into a corresponding heavy phase inlet, controlling the extraction flow ratio to be 1:2, performing six-stage countercurrent extraction on the organic phase and the extraction water phase in the first centrifugal extractor assembly, and separating the phases to obtain raffinate and a loaded organic phase.
And (3) taking a 2mol/L hydrochloric acid solution as a washing solution, pumping the washing solution into a heavy phase inlet of the second centrifugal extractor component, pumping the loaded organic phase into a corresponding light phase inlet, controlling the washing flow ratio to be 10:1, performing four-stage countercurrent washing on the washing solution and the loaded organic phase in the second centrifugal extractor component, and performing phase separation to obtain a washing residual solution and a washing organic phase.
And (3) taking a refined hydrochloric acid solution of 6mol/L as a stripping solution, pumping the stripping solution into a heavy phase inlet of the third centrifugal extractor assembly, pumping a washing organic phase into a corresponding light phase inlet, controlling the stripping flow ratio to be 10:1, performing five-stage counter-current stripping on the refined hydrochloric acid solution and the washing organic phase in the third centrifugal extractor assembly, and separating phases to obtain a lithium chloride solution and an empty organic phase.
2mol/L sodium hydroxide solution is taken as regeneration liquid, the regeneration liquid is pumped into a heavy phase inlet of a mixed clarification tank, an empty organic phase is pumped into a light phase inlet of the mixed clarification tank, the regeneration flow ratio is controlled to be 5:1, the two are subjected to secondary countercurrent regeneration in the mixed clarification tank, and phase separation is carried out to obtain regeneration residual liquid and a regeneration organic phase.
Therefore, the regenerated organic phase obtained in the previous step can be reused as the extraction organic phase in the next period for cyclic utilization, so that the purposes of reducing organic reagent consumption, reducing pollution and reducing extraction cost are achieved.
The detection shows that the extraction rate of lithium in the alkaline lithium-containing brine is 96.5 percent, the total recovery rate of lithium reaches 92 percent, and the purity of the lithium chloride solution obtained after back extraction is more than 90 percent, so that the lithium chloride solution can be used as a raw material for producing a lithium chloride product and/or a lithium carbonate product.
Example 3
The lithium-containing brine is pretreated to remove impurities such as solid, precipitate, suspended matters and the like.
To Li+2mol/L sodium bicarbonate solution was added to 0.5g/L carbonate or chloride brine to adjust the pH to 10.5, thereby obtaining an aqueous extract phase.
Mixing HFTA, TRPO and kerosene to obtain an extracted organic phase; wherein, the mass concentration of HFTA and TRPO in the extracted organic phase is 0.2 mol/L.
Pumping the prepared organic phase into a light phase inlet of the first centrifugal extractor component, pumping an extraction water phase into a corresponding heavy phase inlet, controlling the extraction flow ratio to be 1:3, performing four-stage countercurrent extraction on the organic phase and the extraction water phase in the first centrifugal extractor component, and performing phase separation to obtain raffinate and a loaded organic phase.
And (3) taking 1mol/L hydrochloric acid solution as a washing solution, pumping the washing solution into a heavy phase inlet of the second centrifugal extractor component, pumping the loaded organic phase into a corresponding light phase inlet, controlling the washing flow ratio to be 10:1, performing four-stage countercurrent washing on the washing solution and the loaded organic phase in the second centrifugal extractor component, and performing phase separation to obtain a washing residual solution and a washing organic phase.
And (3) taking a refined hydrochloric acid solution of 3mol/L as a stripping solution, pumping the stripping solution into a heavy phase inlet of the third centrifugal extractor assembly, pumping a washing organic phase into a corresponding light phase inlet, controlling the stripping flow ratio to be 10:1, carrying out five-stage counter-current stripping on the refined hydrochloric acid solution and the washing organic phase in the third centrifugal extractor assembly, and carrying out phase separation to obtain a lithium chloride solution and an empty organic phase.
2mol/L sodium hydroxide solution is taken as regeneration liquid, the regeneration liquid is pumped into a heavy phase inlet of a mixed clarification tank, an empty organic phase is pumped into a light phase inlet of the mixed clarification tank, the regeneration flow ratio is controlled to be 10:1, the heavy phase and the empty organic phase are subjected to primary regeneration in the mixed clarification tank, and phase separation is carried out to obtain regeneration residual liquid and a regeneration organic phase.
Therefore, the regenerated organic phase obtained in the previous step can be reused as the extraction organic phase in the next period for cyclic utilization, so that the purposes of reducing organic reagent consumption, reducing pollution and reducing extraction cost are achieved.
The detection shows that the extraction rate of lithium in the alkaline lithium-containing brine is 95.5 percent, the total recovery rate of lithium reaches 90.2 percent, and the purity of the lithium chloride solution obtained after back extraction reaches 98.6 percent, so that the lithium chloride solution can be used as a raw material for producing lithium chloride products and/or lithium carbonate products.
Example 4
The lithium-containing brine is pretreated to remove impurities such as solid, precipitate, suspended matters and the like.
To Li+2mol/L sodium bicarbonate solution is added into carbonate or sulfate type brine with the concentration of 8g/L, and the pH value is adjusted to 10.5, so as to obtain an extraction water phase.
Mixing HFTA, TRPO and kerosene to obtain an extracted organic phase; wherein, the mass concentration of HFTA and TRPO in the extracted organic phase is 0.5 mol/L.
Pumping the prepared organic phase into a light phase inlet of the first centrifugal extractor assembly, pumping an extraction water phase into a corresponding heavy phase inlet, controlling the extraction flow ratio to be 1:3, performing eight-stage countercurrent extraction on the organic phase and the extraction water phase in the first centrifugal extractor assembly, and separating the phases to obtain raffinate and a loaded organic phase.
And 3mol/L hydrochloric acid solution is taken as a washing solution, the washing solution is pumped into a heavy phase inlet of the second centrifugal extractor component, the loaded organic phase is pumped into a corresponding light phase inlet, the washing flow ratio is controlled to be 10:1, the washing solution and the loaded organic phase are subjected to five-stage countercurrent washing in the second centrifugal extractor component, and the washing raffinate and the washing organic phase are obtained by phase separation.
And (3) taking a refined hydrochloric acid solution of 6mol/L as a stripping solution, pumping the stripping solution into a heavy phase inlet of a third centrifugal extractor assembly, pumping a washing organic phase into a corresponding light phase inlet, controlling the stripping flow ratio to be 30:1, performing six-stage counter-current stripping on the refined hydrochloric acid solution and the washing organic phase in the third centrifugal extractor assembly, and separating phases to obtain a lithium chloride solution and an empty organic phase.
2mol/L sodium carbonate solution is taken as regeneration liquid, the regeneration liquid is pumped into a heavy phase inlet of a mixer-settler, an empty organic phase is pumped into a light phase inlet of the mixer-settler, the regeneration flow ratio is controlled to be 1:1, the two are subjected to secondary countercurrent regeneration in the mixer-settler, and phase separation is carried out to obtain regeneration residual liquid and regeneration organic phase.
Therefore, the regenerated organic phase obtained in the previous step can be reused as the extraction organic phase in the next period for cyclic utilization, so that the purposes of reducing organic reagent consumption, reducing pollution and reducing extraction cost are achieved.
The detection shows that the extraction rate of lithium in the alkaline lithium-containing brine is 90 percent, the total recovery rate of lithium reaches 88.6 percent, and the purity of the lithium chloride solution obtained after back extraction reaches 98.6 percent, so that the lithium chloride solution can be used as a raw material for producing lithium chloride products and/or lithium carbonate products.
It should be noted that the processes adopted in the above embodiments do not represent all the processes of the present invention, but only individual examples thereof, especially for the parameters of flow ratio, number of stages, etc., may be changed by adjusting each other. If in the washing section, the concentration of the washing acid should be adjusted according to the concentration of the metal ion impurities in the loaded organic phase, and when the concentration of the washing acid is higher, the flow ratio of the washing section is properly reduced under the condition of ensuring full mixing, so that a better washing effect can be achieved; it should also be reduced appropriately when the concentration of the washing acid is low; meanwhile, the washing effect of the washing section comes from washing acid, and lithium ions with higher concentration in the washing liquid have certain effect on washing impurity metals, so that the adjustment of the washing section is judged and adjusted according to the complex situation on a loaded organic phase entering the washing section.
Meanwhile, according to the analysis of the principle of extracting lithium by using the diketone and the neutral phosphine oxide substance, the extraction effect of the invention can not be obtained by using each diketone as an extractant and/or each neutral phosphine oxide substance as a synergist, and therefore, the invention carries out the following comparative experiments aiming at other diketones as the extractant and/or other neutral phosphine oxide substances as the synergist.
Comparative example 1
The lithium-containing brine is pretreated to remove impurities such as solid, precipitate, suspended matters and the like.
To Li+2mol/L sodium bicarbonate solution was added to 2g/L carbonate or chloride type brine to adjust the pH to 10.5, thereby obtaining an extract aqueous phase.
Mixing 2, 4-pentanedione, 2-ethylhexyl phosphoric acid and kerosene to obtain an extracted organic phase; wherein the mass concentrations of 2, 4-pentanedione and 2-ethylhexyl phosphoric acid in the extracted organic phase were each 0.3 mol/L.
Pumping the prepared organic phase into a light phase inlet of the first centrifugal extractor assembly, pumping an extraction water phase into a corresponding heavy phase inlet, controlling the extraction flow ratio to be 1:3, performing eight-stage countercurrent extraction on the organic phase and the extraction water phase in the first centrifugal extractor assembly, and separating the phases to obtain raffinate and a loaded organic phase.
And 3mol/L hydrochloric acid solution is taken as a washing solution, the washing solution is pumped into a heavy phase inlet of the second centrifugal extractor component, the loaded organic phase is pumped into a corresponding light phase inlet, the washing flow ratio is controlled to be 10:1, the washing solution and the loaded organic phase are subjected to five-stage countercurrent washing in the second centrifugal extractor component, and the washing raffinate and the washing organic phase are obtained by phase separation.
And (3) taking a refined hydrochloric acid solution of 6mol/L as a stripping solution, pumping the stripping solution into a heavy phase inlet of a third centrifugal extractor assembly, pumping a washing organic phase into a corresponding light phase inlet, controlling the stripping flow ratio to be 30:1, performing six-stage counter-current stripping on the refined hydrochloric acid solution and the washing organic phase in the third centrifugal extractor assembly, and separating phases to obtain a lithium chloride solution and an empty organic phase.
2mol/L sodium carbonate solution is taken as regeneration liquid, the regeneration liquid is pumped into a heavy phase inlet of a mixer-settler, an empty organic phase is pumped into a light phase inlet of the mixer-settler, the regeneration flow ratio is controlled to be 1:1, the two are subjected to secondary countercurrent regeneration in the mixer-settler, and phase separation is carried out to obtain regeneration residual liquid and regeneration organic phase.
Therefore, the regenerated organic phase obtained in the previous step can be reused as the extraction organic phase in the next period for cyclic utilization, so that the purposes of reducing organic reagent consumption, reducing pollution and reducing extraction cost are achieved.
Through detection, the extraction rate of lithium in the alkaline lithium-containing brine is 68%, the total recovery rate of lithium reaches 66.4%, and the purity of the lithium chloride solution obtained after back extraction is about 88.6%.
Comparative example 2
The lithium-containing brine is pretreated to remove impurities such as solid, precipitate, suspended matters and the like.
To Li+2mol/L sodium bicarbonate solution was added to 1g/L carbonate or chloride type brine to adjust the pH to 10.0, thereby obtaining an aqueous extract phase.
Mixing dibenzoyl methane, tributyl phosphine oxide and kerosene to obtain an extracted organic phase; wherein, the mass concentration of dibenzoyl methane and tributyl phosphine oxide in the extracted organic phase is 0.2 mol/L.
Pumping the prepared organic phase into a light phase inlet of the first centrifugal extractor assembly, pumping an extraction water phase into a corresponding heavy phase inlet, controlling the extraction flow ratio to be 1:2, performing eight-stage countercurrent extraction on the organic phase and the extraction water phase in the first centrifugal extractor assembly, and separating the phases to obtain raffinate and a loaded organic phase.
And 3mol/L hydrochloric acid solution is taken as a washing solution, the washing solution is pumped into a heavy phase inlet of the second centrifugal extractor component, the loaded organic phase is pumped into a corresponding light phase inlet, the washing flow ratio is controlled to be 10:1, the washing solution and the loaded organic phase are subjected to five-stage countercurrent washing in the second centrifugal extractor component, and the washing raffinate and the washing organic phase are obtained by phase separation.
And (3) taking a refined hydrochloric acid solution of 6mol/L as a stripping solution, pumping the stripping solution into a heavy phase inlet of a third centrifugal extractor assembly, pumping a washing organic phase into a corresponding light phase inlet, controlling the stripping flow ratio to be 30:1, performing six-stage counter-current stripping on the refined hydrochloric acid solution and the washing organic phase in the third centrifugal extractor assembly, and separating phases to obtain a lithium chloride solution and an empty organic phase.
2mol/L sodium carbonate solution is taken as regeneration liquid, the regeneration liquid is pumped into a heavy phase inlet of a mixed clarification tank, an empty organic phase is pumped into a light phase inlet of the mixed clarification tank, the regeneration flow ratio is controlled to be 1:1, the two are subjected to primary regeneration in the mixed clarification tank, and phase separation is carried out to obtain a regeneration residual liquid and a regeneration organic phase.
Therefore, the regenerated organic phase obtained in the previous step can be reused as the extraction organic phase in the next period for cyclic utilization, so that the purposes of reducing organic reagent consumption, reducing pollution and reducing extraction cost are achieved.
The detection shows that the extraction rate of lithium in the alkaline lithium-containing brine is 72 percent, the total recovery rate of lithium is about 71.3 percent, and the purity of the lithium chloride solution obtained after back extraction is about 85.5 percent.
Comparative example 3
The lithium-containing brine is pretreated to remove impurities such as solid, precipitate, suspended matters and the like.
To Li+2mol/L sodium bicarbonate solution is added into carbonate or sulfate type brine with the concentration of 2g/L, and the pH value is adjusted to 10.8, so as to obtain an extraction water phase.
Mixing thenoylacetone, tributyl phosphate and kerosene to obtain an extracted organic phase; wherein, in the extracted organic phase, the mass concentration of the thiophenecarboxylacetone and the tributyl phosphate are both 0.2 mol/L.
Pumping the prepared organic phase into a light phase inlet of the first centrifugal extractor assembly, pumping an extraction water phase into a corresponding heavy phase inlet, controlling the extraction flow ratio to be 1:4, performing eight-stage countercurrent extraction on the organic phase and the extraction water phase in the first centrifugal extractor assembly, and separating the phases to obtain raffinate and a loaded organic phase.
And 3mol/L hydrochloric acid solution is taken as a washing solution, the washing solution is pumped into a heavy phase inlet of the second centrifugal extractor component, the loaded organic phase is pumped into a corresponding light phase inlet, the washing flow ratio is controlled to be 10:1, the washing solution and the loaded organic phase are subjected to five-stage countercurrent washing in the second centrifugal extractor component, and the washing raffinate and the washing organic phase are obtained by phase separation.
And (3) taking a refined hydrochloric acid solution of 6mol/L as a stripping solution, pumping the stripping solution into a heavy phase inlet of a third centrifugal extractor assembly, pumping a washing organic phase into a corresponding light phase inlet, controlling the stripping flow ratio to be 30:1, performing six-stage counter-current stripping on the refined hydrochloric acid solution and the washing organic phase in the third centrifugal extractor assembly, and separating phases to obtain a lithium chloride solution and an empty organic phase.
2mol/L sodium carbonate solution is taken as regeneration liquid, the regeneration liquid is pumped into a heavy phase inlet of a mixed clarification tank, an empty organic phase is pumped into a light phase inlet of the mixed clarification tank, the regeneration flow ratio is controlled to be 1:1, the two are subjected to primary regeneration in the mixed clarification tank, and phase separation is carried out to obtain a regeneration residual liquid and a regeneration organic phase.
Therefore, the regenerated organic phase obtained in the previous step can be reused as the extraction organic phase in the next period for cyclic utilization, so that the purposes of reducing organic reagent consumption, reducing pollution and reducing extraction cost are achieved.
The detection shows that the extraction rate of lithium in the alkaline lithium-containing brine is 59 percent, the total recovery rate of lithium is about 56.8 percent, and the purity of the lithium chloride solution obtained after back extraction is about 82.6 percent.
Comparative example 4
The lithium-containing brine is pretreated to remove impurities such as solid, precipitate, suspended matters and the like.
To Li+2mol/L sodium bicarbonate solution was added to 2g/L carbonate or chloride type brine to adjust the pH to 10.5, thereby obtaining an extract aqueous phase.
Mixing toluylacetone, tributylphosphine oxide and kerosene to obtain an extracted organic phase; wherein, the mass concentration of the toluoylacetone and the tributyl phosphine oxide in the extracted organic phase is 0.2 mol/L.
Pumping the prepared organic phase into a light phase inlet of the first centrifugal extractor assembly, pumping an extraction water phase into a corresponding heavy phase inlet, controlling the extraction flow ratio to be 1:3, performing eight-stage countercurrent extraction on the organic phase and the extraction water phase in the first centrifugal extractor assembly, and separating the phases to obtain raffinate and a loaded organic phase.
And 3mol/L hydrochloric acid solution is taken as a washing solution, the washing solution is pumped into a heavy phase inlet of the second centrifugal extractor component, the loaded organic phase is pumped into a corresponding light phase inlet, the washing flow ratio is controlled to be 10:1, the washing solution and the loaded organic phase are subjected to five-stage countercurrent washing in the second centrifugal extractor component, and the washing raffinate and the washing organic phase are obtained by phase separation.
And (3) taking a refined hydrochloric acid solution of 6mol/L as a stripping solution, pumping the stripping solution into a heavy phase inlet of a third centrifugal extractor assembly, pumping a washing organic phase into a corresponding light phase inlet, controlling the stripping flow ratio to be 30:1, performing six-stage counter-current stripping on the refined hydrochloric acid solution and the washing organic phase in the third centrifugal extractor assembly, and separating phases to obtain a lithium chloride solution and an empty organic phase.
2mol/L sodium carbonate solution is taken as regeneration liquid, the regeneration liquid is pumped into a heavy phase inlet of a mixer-settler, an empty organic phase is pumped into a light phase inlet of the mixer-settler, the regeneration flow ratio is controlled to be 1:1, the two are subjected to secondary countercurrent regeneration in the mixer-settler, and phase separation is carried out to obtain regeneration residual liquid and regeneration organic phase.
Therefore, the regenerated organic phase obtained in the previous step can be reused as the extraction organic phase in the next period for cyclic utilization, so that the purposes of reducing organic reagent consumption, reducing pollution and reducing extraction cost are achieved.
Through detection, the extraction rate of lithium in the alkaline lithium-containing brine is 68%, the total recovery rate of lithium reaches 66.4%, and the purity of the lithium chloride solution obtained after back extraction is about 88.6%.
It can be seen from the comparison of the examples and the comparative examples that although the same family of diketone extractants or the same family of neutral phosphine oxide synergists, there is still a great difference in the extraction effect between the homologues, so that there is no simple substitution between different extractants and/or different synergists.
Based on the above comparative analysis of different extractants and co-extractants in homologues, it can be seen that a complete extraction process is an integral result of the combined action of multiple factors. In addition, it is worth to be noted that a full-flow process including extraction-washing-stripping-regeneration is more complicated than the process of a general extraction section or extraction-stripping section, and the factors to be considered in the process design are more; this is because the extractant also has a certain extraction effect on the impurity ions contained in the raw material solution (i.e., the extraction aqueous phase) when extracting the target ions, and if the loaded organic phase obtained by extraction is directly subjected to stripping, the impurity ions in the loaded organic phase are also stripped into the stripping product solution (i.e., the lithium chloride solution in the present invention) by the stripping solution, and the purity of the obtained stripping product solution is difficult to ensure. Meanwhile, as the extracted organic phase carries a part of raw material liquid in the extraction process, the part of raw material liquid can enter the counter liquid along with the counter extraction, so that the product purity is reduced and the counter extraction acid liquor is consumed. The washing process provided by the invention not only can maximally elute the impurity ions in the loaded organic phase by adjusting the concentration of the washing acid compared with the washing, but also can separate the extraction section from the back extraction section, thereby maximally reducing the problem of high impurity content of the product caused by entrainment, and further improving the purity and yield of the product. In addition, the regeneration method provided by the invention effectively recovers the extraction capability of the empty organic phase after the back extraction, realizes the recycling of the organic phase, and ensures that the whole extraction flow has a complete flow and has a basic industrial value.
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 (9)
1. A process for extracting lithium from lithium-containing alkaline brine based on a centrifugal extractor is characterized by comprising the following steps:
providing an extraction aqueous phase: to containLithium alkaline brine is used as an extraction water phase; wherein the pH value of the lithium-containing alkaline brine is 8-14, and Li is contained in the lithium-containing alkaline brine+Has a mass concentration of 0.05-10 g/L and Na+Has a mass concentration of not more than 80g/L, K+Has a mass concentration of not more than 80g/L and Mg2+Is not more than 1g/L, Ca2+The mass concentration of (A) is not more than 1 g/L; the anion in the lithium-containing alkaline brine is selected from Cl-、SO4 2-、CO3 2-、NO3 -At least one of;
providing an extracted organic phase: mixing an extracting agent, a co-extracting agent and kerosene to prepare an extracted organic phase; wherein, in the extracted organic phase, the quantity concentration of the substances of the extracting agent and the synergistic agent is 0.05 mol/L-0.6 mol/L, the extracting agent is furyltrifluoroacetone, and the synergistic agent is trialkyl phosphine oxide;
an extraction step: mixing the extraction organic phase and the extraction water phase in a first centrifugal extractor component according to a flow ratio of 1: 10-10: 1, performing 2-15-stage countercurrent extraction, and performing phase separation to obtain raffinate and a loaded organic phase; in the extraction step, the extracted organic phase is pumped in from the light phase inlet of the first centrifugal extractor assembly, and the extracted aqueous phase is pumped in from the heavy phase inlet of the first centrifugal extractor assembly;
a washing step: taking 0.1-12 mol/L hydrochloric acid solution or lithium-containing solution with the same acidity as washing liquid, mixing the loaded organic phase and the washing liquid in a second centrifugal extractor component according to the flow ratio of 5: 1-80: 1, carrying out 2-15-stage countercurrent washing, and carrying out phase separation to obtain washing residual liquid and washing organic phase; in the washing step, the loaded organic phase is pumped in through the light phase inlet of the second centrifugal extractor assembly, and the washing liquid is pumped in through the heavy phase inlet of the second centrifugal extractor assembly;
back extraction: taking 0.1-12 mol/L hydrochloric acid solution as a back extraction solution, mixing the washing organic phase and the back extraction solution in a third centrifugal extractor component according to the flow ratio of 5: 1-80: 1, performing 2-15-stage counter-current back extraction, and performing phase separation to obtain a lithium chloride solution and an empty organic phase; in the back extraction step, the washing organic phase is pumped in from the light phase inlet of the third centrifugal extractor assembly, and the back extraction solution is pumped in from the heavy phase inlet of the third centrifugal extractor assembly;
a regeneration step: carrying out 1-stage regeneration or 2-5-stage countercurrent regeneration on the empty organic phase by taking an ammoniacal solution with the mass concentration of 0.05-4 mol/L or a carbonate solution with the mass concentration of 0.05-4 mol/L as a regeneration liquid, and carrying out phase separation to obtain a regeneration residual liquid and a regeneration organic phase; wherein the flow ratio of the empty organic phase to the regenerated liquid is 1: 10-10: 1.
2. The process of claim 1 wherein, in the washing step, the concentration of lithium in the washed organic phase is no less than 80% of the concentration of lithium in the loaded organic phase; the total concentration of metals other than lithium in the washed organic phase is no more than 5% of the total concentration of metals other than lithium in the loaded organic phase.
3. The process of claim 1, wherein in the regenerating step, the extraction capacity of the regenerated organic phase is no less than 90% of the extraction capacity of the extracted organic phase.
4. The process of claim 1, wherein in the step of providing an aqueous extraction phase, the lithium-containing alkaline brine is obtained by adding a sodium hydroxide solution, a sodium carbonate solution or an ammonia solution to the lithium-containing brine.
5. The process according to claim 4, wherein the sodium hydroxide solution, the sodium carbonate solution or the ammoniacal solution are each in a substance concentration of 0.05 to 4 mol/L.
6. The process of claim 4 or 5, wherein the lithium-containing brine is pretreated to remove solid precipitates and suspended substances before adding a sodium hydroxide solution, a sodium carbonate solution or an ammonia solution to the lithium-containing brine.
7. The process of claim 1, wherein the lithium-containing alkaline brine is pretreated to remove solid precipitates and suspended matter therefrom prior to forming the aqueous extract phase.
8. The process according to any one of claims 1-2, wherein the process further comprises the recycling step of: returning the regenerated organic phase to the extraction step for use as an extracted organic phase, and repeating the extraction step, the washing step, the stripping step, and the regeneration step.
9. The process according to any one of claims 1 to 2, wherein in the regeneration step, the regeneration equipment is selected from any one of a centrifugal extractor, a mixer-settler and a tubular reactor.
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