WO2015096549A1 - Process and apparatus for extracting battery grade lithium from brine - Google Patents

Abstract

Provided are a process and an apparatus for extracting battery grade lithium from brine. The process comprises the following steps: step 1, absorbing the brine with a lithium adsorption agent and then desorbing the lithium adsorption agent with an eluent to obtain a desorption solution; step 2, removing magnesium from the desorption solution to obtain the desorption solution with magnesium removed; step 3, concentrating the desorption solution with magnesium removed, to obtain concentrated brine containing lithium. The apparatus comprises an adsorption desorption device (1), a magnesium-removing device (2), and a concentration device (3), wherein an outlet of the desorption solution of the adsorption desorption device (1) is connected to an inlet of the magnesium-removing device (2), an outlet of the magnesium-removing device (2) is connected to an inlet of the concentration device (3), and an outlet of the concentrated solution of the concentration device (3) is connected to a first precipitation tank (4); the first precipitation tank (4) is also provided with a first sodium carbonate tank (5), and an outlet of the first precipitation tank (4) is also connected to a second solid-liquid separator (6).

Description

Process and device for extracting battery grade lithium from brine Technical field

The invention relates to a process and a device for extracting battery grade lithium from brine, in particular to a method and a device for extracting high-purity lithium in brine by membrane technology, and belongs to the technical field of membrane separation.

Background technique

Lithium is one of the important rare metals related to the national economy and people's lives. It has been widely used in traditional fields such as glass ceramics, petrochemicals, metallurgy, textiles, synthetic rubber, lubricating materials and medical treatment. Lithium carbonate is a basic compound in the lithium chemical industry and has a variety of uses, and can be widely used in medicine, batteries and the like.

The world is rich in lithium resources, mainly distributed in South and North America, Asia, Australia and Africa. The most widely used lithium minerals in the world today are salt lakes such as spodumene, lithium feldspar, lithium mica and lithium phosphite, lithium brine and well water are also important lithium resources. Western countries use salt brine to produce lithium compounds ( Such as lithium carbonate) has accounted for about 30% of the production capacity of lithium products. China is a large country with lithium resources. The proven reserves of lithium resources rank second in the world. The lithium content of brine accounts for 79% of the total reserves, mainly distributed in the salt lakes of Tibet and Qinghai. The reserves of lithium in the Yahui brine in the Qaidam Basin of Qinghai account for about 58% of the national total.

The main methods for extracting lithium from brine include precipitation method, solvent extraction method, ion exchange adsorption method and calcination leaching method. In the prior art, the patent CN102432044A adopts an adsorption method to concentrate lithium chloride in a brine, and then uses a precipitation method to obtain a lithium carbonate product. Patent CN102275956A uses extraction and back extraction to obtain NaCl and LiCl stripping solution and NH4Cl and LiCl stripping solution, and then uses precipitation method to prepare nanometer and micron lithium carbonate products. Patent CN102963914A adopts evaporation concentration, alkali precipitation of impurity ions, filtration and addition of a precipitating agent to prepare lithium carbonate, and after washing and burning, high-purity lithium carbonate is obtained. These methods have problems such as low concentration of lithium chloride in the brine, long time in the precipitation reaction, and high impurity content in the lithium carbonate.

Summary of the invention

The technical problem to be solved by the invention is that the problem of increasing the time for extracting lithium from the brine, the concentration of lithium chloride is not high, the yield is low, the reagent is used in a large amount, and the impurity content in the lithium carbonate product is high, and the problem is raised. A process and apparatus for extracting battery grade lithium from brine.

Technical solutions:

According to an aspect of the invention:

A process for extracting battery grade lithium from brine, comprising the following steps:

In the first step, the brine is adsorbed by a lithium adsorbent, and then the lithium adsorbent is desorbed to obtain a desorption liquid;

Step 2, removing magnesium from the desorbed solution to obtain a desorption solution for removing magnesium;

In the third step, the magnesium-desorbed desorption liquid is concentrated to obtain a lithium-containing concentrated brine.

According to an embodiment of the invention:

The weight ratio of Mg ^{2+ to} Li ⁺ in the brine is preferably 1:1 to 400:1, more preferably 2:1 to 200:1, and most preferably 2:1 to 150:1.

The mass percentage concentration of Li ⁺ is preferably 0.1 to 15.0 g/L, more preferably 0.3 to 10.0 g/L, and most preferably 0.5 to 8.0 g/L.

According to an embodiment of the invention:

The lithium adsorbent refers to a mixture of one or more of an aluminum salt lithium adsorbent, a lithium hydroxide adsorbent, a lithium niobate type adsorbent, and an ion sieve type lithium adsorbent.

According to an embodiment of the invention:

In the first step, the lithium adsorbent is dispersed in the brine to obtain a mixed solution, and the mixed solution is subjected to solid-liquid separation to desorb the separated lithium adsorbent.

The amount of the lithium adsorbent to be added to the brine is preferably 0.05 to 5 g/L, more preferably 0.2 g/L.

After the lithium adsorbent is added to the brine, it is stirred for 30 to 60 minutes, and the brine temperature is 30 to 60 °C.

The step of solid-liquid separation includes a step of concentrating using a separation membrane; the material of the separation membrane is preferably a ceramic membrane; and the separation membrane is preferably a microfiltration membrane.

The step of solid-liquid separation is preferably carried out by using a separation membrane to obtain a concentrate of the adsorbent, and then the adsorbent concentrate is dehydrated by a plate and frame filter.

The separation membrane has an average pore diameter ranging from 50 to 200 nm; a filtration temperature of 30 to 80 ° C, an operating pressure of 0.2 to 0.5 MPa, and a membrane surface flow rate of 1 to 4 m/s.

The separation membrane needs to be periodically backwashed during the concentration process. The backlash interval is 30 to 60 minutes, and the backlash time is 10 to 30 seconds.

According to an embodiment of the invention:

In the first step, the lithium adsorbent is charged into the adsorption column (also referred to as a packed column), and the brine is injected for adsorption, and then the eluent is injected for desorption to obtain a desorption liquid.

After the desorbent is obtained in the first step, after filtering through the filter, the permeate is sent to the magnesium removal step in the second step.

The eluent is water or a phosphoric acid solution, and the pH of the phosphoric acid solution is 1 to 2, and the desorption temperature is 50 to 100 °C.

According to an embodiment of the invention:

The step of removing magnesium in the second step is to remove magnesium ions by nanofiltration membrane filtration or ion exchange resin adsorption.

The nanofiltration membrane has a molecular weight cutoff of 100 to 300 Da, a nanofiltration operating pressure of 1.0 to 3.0 MPa, and an operating temperature of 20 to 45 °C.

When removing magnesium by a nanofiltration membrane, it is filtered through at least two stages of nanofiltration membrane. The concentration ratio of the primary nanofiltration is preferably 3 to 6 times, and the concentration of the secondary nanofiltration is preferably 8 to 12 times.

According to an embodiment of the invention:

After removal of magnesium ions by filtration through a nanofiltration membrane, magnesium removal is carried out using a cation exchange resin.

According to an embodiment of the invention:

The concentration step in the third step employs at least one of reverse osmosis membrane concentration, DTRO membrane concentration, electrodialysis membrane concentration, and evaporation concentration to obtain a lithium-containing concentrated brine.

More preferably, the concentration step is first concentrated with a reverse osmosis membrane, and the reverse osmosis membrane concentrate is concentrated by at least one of DTRO membrane concentration or evaporation concentration to obtain a lithium-containing concentrated brine.

The reverse osmosis concentration process has an operating pressure of 3.0 to 4.0 MPa and a temperature of 30 to 40 °C.

According to an embodiment of the invention:

After obtaining the lithium-containing concentrated brine in the third step, BaCl ₂ , Na ₂ CO ₃ and NaOH solution were added thereto to precipitate SO ₄ ² -, Ca ²⁺ and Mg ²⁺ in the brine, and the precipitate was removed.

The order of addition was to add BaCl ₂ , Na ₂ CO ₃ and NaOH solutions in sequence.

The molar concentration of BaCl ₂ added is 1% to 5% greater than the concentration of SO ₄ ² - in the lithium-containing concentrated brine, and the molar concentration of Na ₂ CO ₃ added is larger than the molar concentration of Ca ²⁺ in the lithium-containing concentrated brine. 1 to 10%, the molar concentration of NaOH added is 1 to 5% larger than twice the molar concentration of Mg ²⁺ in the lithium-containing concentrated brine.

According to an embodiment of the invention:

To the lithium-containing concentrated brine in which the precipitate was removed, a Na ₂ CO ₃ solution was added to precipitate Li ₂ CO ₃ , and the precipitate was separated and dried to obtain lithium carbonate.

According to an embodiment of the invention:

The step of separating the precipitate is separated by a ceramic membrane having a pore diameter of 20 to 200 nm, preferably a membrane pore diameter of 50 nm, a pressure of 0.1 to 0.5 MPa during operation, and a temperature of 10 to 50 °C.

According to another aspect of the invention:

The invention relates to a device for extracting battery grade lithium from brine, comprising an adsorption desorption device, a magnesium removal device, a concentration device, a desorption liquid outlet of the adsorption desorption device and an inlet connection of the magnesium removal device, and an outlet of the magnesium removal device and an inlet connection of the concentration device The concentrate outlet of the concentrating device is connected to the first precipitation tank, and a first sodium carbonate tank is further disposed on the first precipitation tank, and the outlet of the first precipitation tank is further connected to the second solid-liquid separator.

The adsorption desorption device is a sorbent packed column.

A filter is also connected to the outlet of the sorbent packed column, and the outlet of the filter is connected to the magnesium removal device.

The adsorption desorption device comprises an adsorption tank connected in sequence, a first solid-liquid separator and a desorption tank, and an outlet of the desorption tank is connected with the magnesium removal device.

The first solid-liquid separator comprises a ceramic membrane device and a plate and frame filter, the outlet of the ceramic membrane device is connected to the inlet of the plate and frame filter, the inlet of the ceramic membrane device is connected to the adsorption tank, and the frame is filtered. The intercepting side of the device is connected to the desorption tank.

The magnesium removal device refers to a nanofiltration membrane device or an ion exchange resin device.

The magnesium removal device refers to a nanofiltration membrane and an ion exchange resin column connected in sequence, and the inlet of the nanofiltration membrane is connected to the adsorption desorption device, and the permeate side of the nanofiltration membrane is connected to the ion exchange resin column, and the outlet of the ion exchange resin column. Connected to a concentrating device.

The concentrating device is selected from at least one of a reverse osmosis membrane device, a DTRO membrane device, an electrodialysis membrane device, and an evaporation concentration device.

The concentrating device refers to a reverse osmosis membrane and a DTRO membrane connected in series, the inlet of the reverse osmosis membrane is connected to the magnesium removal device, the cut-off side of the reverse osmosis membrane is connected to the inlet of the DTRO membrane, and the outlet of the DTRO membrane is connected to the first precipitate. groove.

The outlet of the concentrating device is sequentially connected to the first precipitation tank through the second precipitation tank and the third solid-liquid separator; the outlet of the concentrating device is connected to the inlet of the second precipitation tank, and the outlet of the second precipitation tank is connected to the first The inlet of the three solid-liquid separation device, the outlet of the third solid-liquid separation device is connected to the first precipitation tank; and the second precipitation tank is respectively provided with a cesium chloride tank, a second sodium carbonate tank, and a sodium hydroxide tank .

The second solid-liquid separator is a ceramic membrane filtration device.

The third solid-liquid separator is a ceramic membrane filtration device.

In the ceramic membrane filtration device, the ceramic membrane has a pore size ranging from 20 to 200 nm, preferably a membrane pore diameter of 50 nm.

In the ceramic membrane device, the ceramic membrane has a pore size ranging from 20 to 200 nm.

Beneficial effect

The invention adopts an adsorbent to adsorb and desorb lithium ions in a brine, and uses a ceramic membrane filter to intercept the adsorbent, and uses a reverse osmosis membrane and a DTRO membrane to deeply concentrate the brine, thereby effectively increasing the concentration ratio of LiCl. Unaffected by weather and salt-salt sites, the product yield and product quality obtained by the lithium carbonate precipitation method are significantly improved.

DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing the structure of an apparatus for extracting battery grade lithium from brine by the present invention.

2 is a schematic view showing the structure of another apparatus for extracting battery grade lithium from brine by the present invention.

Among them, 1, adsorption desorption device; 2, magnesium removal device; 3, concentration device; 4, the first precipitation tank; 5, the first sodium carbonate tank; 6, the second solid-liquid separator; 7, adsorption tank; 8, ceramic membrane device; 9, plate and frame filter; 10, desorption tank; 11, nanofiltration membrane; 12, ion exchange resin column; 13, reverse osmosis membrane; 14, DTRO membrane; Second precipitation tank; 16, cesium chloride tank; 17, second sodium carbonate tank; 18, sodium hydroxide tank; 19, third solid-liquid separator; 20, sorbent packed column; 21, filter; a solid-liquid separator; 23, an adsorbent tank.

detailed description

The invention will now be further described in detail by way of specific embodiments. However, those skilled in the art will understand that the following examples are merely illustrative of the invention and should not be construed as limiting the scope of the invention. In the examples, the specific techniques or conditions are not indicated, according to the techniques or conditions described in the literature in the field (for example, refer to Xu Nanping's "Inorganic Membrane Separation Technology and Application", Chemical Industry Press, 2003) or according to Product manuals are carried out. The reagents or instruments used are not indicated by the manufacturer, and are conventional products that can be obtained commercially.

The Approximations used herein can be used to modify any number of expressions in the entire specification and claims, which can be modified to change without departing from the basic function. Therefore, a value modified by a term such as "about" is not limited to the precise value specified. In at least some cases, the approximation may correspond to the accuracy of the instrument used to measure the value. Range boundaries may be combined and/or interchanged unless otherwise stated in the context or the statement, and such ranges are determined to include and include all sub-ranges included herein. Except in the operating examples or elsewhere, all numbers or expressions indicating quantities of ingredients, reaction conditions, and the like, used in the specification and claims, should be understood in all instances as "The modification."

Values expressed in terms of ranges should be understood in a flexible manner to include not only the numerical values that are explicitly recited as the range limits, but also all individual values or sub-ranges that are within the range, as if each value and sub-range are List it. For example, a concentration range of "about 0.1% to about 5%" should be understood to include not only a concentration of about 0.1% to about 5% that is explicitly listed, but also a single concentration within a range of indications (eg, 1%, 2). %, 3%, and 4%) and subintervals (eg, 0.1% to 0.5%, 1% to 2.2%, 3.3% to 4.4%).

Ordinal words such as "first", "second", "third", etc., used in the claims and the <RTI ID=0.0> </ RTI> </ RTI> <RTIgt; The chronological order before or in the execution of the method steps. However, the elements of the claims are distinguished only by the use of the elements to distinguish between the elements of the claims with the specific names and the elements with the same names (but not for the order).

The main sources of lithium include lithium ore and lithium-containing brines. In the present invention, the term "brine" may mean natural brine (e.g., salt lake brine, underground brine, geothermal brine or brine) or artificially configured brine. In particular, in many cases, the salt lake brine has a high lithium concentration compared to other types of brines and is suitable as a raw material in the present invention. In the present invention, lithium carbonate can be efficiently produced from a high concentration of magnesium and sulfuric acid which are interference components when lithium carbonate is prepared by an ordinary method, and it is difficult to have a Mg/Li ratio and a SO ₄ /Li ratio of more than 10. A lithium-containing brine from which lithium is recovered can be used as a raw material in the present invention. For brine resources, salt lake brine is the most important source. In orogenic belts (such as the Andes), water-soluble components containing sodium chloride (which are dissolved from the surrounding sea-forming rocks) flow into the mountain lake formed by rapid bulging with the flowing water, and are concentrated for a long time to precipitate. Salt and pile up to form a salt lake. It is accumulated in a salt lake inside a saturated brine, which is called a salt lake brine. The salt lake brine contains sodium chloride derived from seawater as a main component, and further contains cationic components (for example, potassium, lithium, magnesium, and calcium) and anionic components (for example, chlorine, bromine, sulfuric acid, and boric acid). In addition to the effects of seawater composition, its composition varies depending on the mineral species and volcanic activity surrounding the salt lake. In the salt lake brine, salt lake brine with high lithium concentration has become the development target of lithium resources. The method of recovering lithium in the brine mainly includes a concentration step by evaporation of the sun, an impurity removal step by adding a chemical, and a carbonation step by adding sodium carbonate. The brine mainly comprising chloride has a high solubility for lithium chloride, and the lithium concentration can be increased to a high concentration of about 60 g/L. However, in the case where the brine contains a large amount of sulfate ions, lithium sulfate (Li ₂ SO ₄ ·H ₂ O) is precipitated during the evaporation concentration. Therefore, the lithium concentration can only be increased to about 6 g/L, and lithium is lost in the form of lithium sulfate. In addition, when the salt lake brine contains the above various ionic components, magnesium is precipitated as magnesium carbonate by a carbonation step, and may be mixed in lithium carbonate as a final product, thereby lowering the purity of the final product, and thus requiring carbonic acid Remove magnesium before the step. Specifically, the brine in Uyuni Salt Lake (Bolivia), Qinghai Salt Lake (China), and the like has a high magnesium content and a concentration ratio of Mg/Li of 19 to 62. Therefore, not only a large amount of chemicals (such as calcium hydroxide and sodium carbonate) are required to remove magnesium, but also a large amount of magnesium hydroxide and magnesium carbonate slurry is formed, and the concentrated brine is wrapped in the mud, which will hinder the lithium-containing Recovery of concentrated brine. Further, the concentration of sulfate ion rich brine is often higher, e.g., in Salt Lake Uyuni (Bolivia), SO ₄ / Li concentration ratio of 24, in Salt Lake Qinghai (China), SO ₄ / Li concentration ratio For 138 (in the Atacama Salt Lake (Chile), the concentration ratio of SO ₄ /Li is 11). In these salt lakes, the current situation is that the lithium concentration can only be raised to 6g / L in the evaporation concentration step. Thus, a concentrated brine suitable for the carbonation step cannot be obtained, wherein the carbonation step is generally applied to a high concentration region having a concentration of about 60 g/L or more. Once the level of impurity ions such as magnesium ions, sulfate ions, strontium ions, etc. is reduced as much as possible, for example to ppm level, such as below 20 ppm, preferably below 0.0005 wt%, or lower such as 0.00001 wt%, lithium-containing The brine can be adapted to carry out a recycling process to recover very pure lithium salts such as lithium chloride and/or lithium carbonate, or lithium metal.

In the brine which can be treated in the present invention, the weight ratio of Mg ^{2+ to} Li ⁺ is preferably from 1:1 to 400:1, more preferably from 2:1 to 200:1, and most preferably from 2:1 to 150:1. The mass percentage concentration of Li ⁺ is preferably 0.1 to 15.0 g/L, more preferably 0.3 to 10.0 g/L, and most preferably 0.5 to 8.0 g/L.

In the present invention, lithium is first adsorbed by a lithium adsorbent, and then lithium is eluted by desorption to obtain a desorbed liquid. The lithium adsorbent described in the present invention may employ a well-known solid adsorbent which selectively adsorbs lithium ions. Generally, such adsorbents are in the form of particles and have a large specific surface area, and the materials generally include organic adsorption. Agent and inorganic adsorbent. The organic adsorbent generally refers to a polymer ion exchange resin, and is basically a strongly acidic adsorption resin such as an IR-120B type cation exchange resin. For the inorganic adsorbent, a conventional lithium salt lithium adsorbent (for example, LiX·2Al(OH) ₃ ·nH ₂ O, wherein X represents an anion, usually Cl, and n represents the number of water of crystallization), Amorphous hydroxide lithium adsorbent (mainly aluminum oxide adsorbent), layered adsorbent (generally arsenate or phosphate lithium adsorbent, or titanate lithium adsorbent), composite tantalum An acid type lithium adsorbent, an ion sieve type lithium adsorbent, and the like. The ion sieve type oxide adsorbent may, for example, be a monoclinic acid silicate type (e.g., Li _1-x H _x SbO ₃ , 0 < x < 1), or a titanate type (such as Li ₂ TiO). ₃ ), manganese oxide system, etc. (such as spinel type manganese oxide, which is composed of a manganese compound such as MnO ₂ , MnCO ₃ or MnOOH and a lithium compound such as LiOH, Li ₂ CO ₃ or a magnesium compound Mg(OH) ₂ reacting to form a precursor, which is obtained by pickling), or may be doped with other metal elements, especially a transition metal element to prepare a doped manganese oxide lithium ion sieve, such as LiMg _0.5 Mn _1.5 O ₄ , LiZn _0.5 Mn _1.5 O ₄ , LiTi _0.5 Mn _1.5 O ₄ , LiFe _0.5 Mn _1.5 O ₄ , Li _1.33-x / ₃ CoxMn _1.67-2x / ₃ O ₄ , LiFeMnO ₄ , LiAlMnO ₄ , LiCu _0.5 Mn _1.5 O ₄ or the like. It may also be a composite adsorbent, for example, a composite adsorbent in which a large amount of LiX·2Al(OH) ₃ ·nH ₂ O is attached to the void of the weakly basic anion exchange resin, wherein X is a halogen. In some embodiments of the invention, an aluminum salt-containing lithium adsorbent is used, and in other embodiments, an iron phosphate ion sieve is used, which is one or more of FeSO ₄ and Me _x Fe _y PO ₄ . mixture. Me is a mixture of one or more of Mg, Al, Ti, Ni, Co, Mn, Mo, Nb. 0<x<1, 0<y<1. The preparation method can be referred to the patent document CN102049237.

For the above adsorption operation, it is possible to use the adsorbent to be packed in the adsorption column to allow the brine to flow through the adsorbent bed in the adsorption column, thereby completing the adsorption of lithium ions on the adsorbent, and then adding the eluent. Thereby, the lithium ions are eluted, and after the desorbed liquid is obtained, preferably filtered through the filter, and then the permeate is sent to the subsequent magnesium removal treatment step, and the filter can be a coarse filter for removing The sorbent particles and the sediment therein are, for example, filter elements such as a conventional sand filter or filter cloth.

Since some magnesium ions and other divalent alkali metal ions are still present in the desorption solution during the adsorption and desorption operations, the magnesium in the desorbed solution can be reduced when the desorbed solution is eluted with magnesium ions. The lithium ratio, the operation for removing magnesium ions herein may be a precipitation method, a nanofiltration or an ion exchange resin for removing magnesium, but in a preferred embodiment of the present invention, a method of removing magnesium by a nanofiltration or ion exchange resin is employed.

When the lithium adsorbent is eluted by feeding the eluent into the adsorption column packed with the adsorbent, the content of Mg ²⁺ in the desorbed solution decreases as the elution process proceeds, and it is found through experiments. Reducing the Mg ²⁺ content in the desorption liquid is beneficial to reducing the process load of the nanofiltration, increasing the nanofiltration concentration ratio, and reducing the Mg ²⁺ content of the nanofiltration permeate, but on the other hand, discovering Mg ²⁺ In the presence of ions, the nanofiltration membrane has a negative entrapment effect on lithium ions, that is, the concentration of Li ^{+ in the} nanofiltration permeate increases, so the content of Mg ²⁺ cannot be too low, otherwise in the nanofiltration process, in the nanofiltration During the process, the negative interception of lithium ions is weakened, and a part of lithium ions are trapped, which affects the product yield. Desorption is stopped when the Mg ²⁺ content in the desorbent is 2 to 3 g/L. Under this preferred condition, the concentration of Li ^{+ in the} permeate of the nanofiltration membrane can be increased by 10 to 20% compared to the raw material liquid. However, this type of operation still has problems of long operation time and low efficiency.

In the process of performing the adsorption operation of the lithium adsorbent, in a modified embodiment of the present invention, the lithium adsorbent is mixed in the brine, stirred and dispersed in the brine, and the operation mode can have a higher work. Efficiency, the time to achieve adsorption saturation is shorter than the method of filling with adsorbent. The operation of mixing the adsorbent in the brine may be carried out in a stirring tank, and then the adsorbent is added to the stirring tank and continuously stirred, and lithium ions are adsorbed onto the adsorbent to obtain a mixture of the adsorbent and the brine; stirring 30~ At 60 min, the brine temperature was 30 to 60 °C. The amount of the lithium adsorbent to be added to the brine is preferably 0.05 to 5 g/L, more preferably 0.2 g/L.

After the above adsorption process is completed, the mixture of the lithium adsorbent and the brine is subjected to solid-liquid separation treatment to separate the adsorbent, so that the desorption operation can be better performed, and the solid-liquid separation described herein. There is no special limit. Specific examples of the solid-liquid separation treatment include a centrifugal separation method, a press separation method, a filtration method, a floating separation method, and a sedimentation separation method. In one preferred embodiment, it is necessary to carry the concentrated liquid into a separation membrane for concentration, and other ions in the salt lake such as Mg ²⁺ , Ca ²⁺ or the like are discharged as a permeate. The separation membrane described herein preferably uses a microfiltration membrane. After the concentrate is obtained, the concentrate is further dehydrated by a conventional dehydration method, for example, evaporation, centrifugation, etc., preferably by means of plate and frame filtration. , to obtain a sorbent filter cake. The microfiltration membrane used in this step is a membrane having an average pore diameter of 0.01 μm to 5 mm. The material of the microfiltration membrane is not particularly limited as long as it can concentrate the adsorbent, and examples thereof include cellulose, cellulose ester, polysulfone, polyethersulfone, polyvinyl chloride, and chlorine. An organic material such as propylene, polyolefin, polyvinyl alcohol, polymethyl methacrylate, polyvinylidene fluoride or polytetrafluoroethylene, or a metal such as stainless steel or an inorganic material such as ceramics. The material of the microfiltration membrane can be appropriately selected in consideration of the properties of the mixed solution or the running cost, and an inorganic material such as ceramic is preferable in view of ease of handling. The ceramic membrane filtration temperature is 30 to 80 ° C, the operating pressure is 0.2 to 0.5 MPa, and the membrane surface flow rate is 1 to 4 m/s. In another embodiment, the yield of the finally obtained lithium can be further increased by controlling the average pore diameter of the microfiltration membrane to be between 50 and 200 nm.

In a modified embodiment, it is preferable to carry out backflushing treatment on the ceramic membrane filter, and the recoil device automatically uses the ceramic membrane permeate to backflush the ceramic membrane filtration device to adsorb the adsorbent filter cake attached to the surface of the membrane passage. Backflushing, effectively reducing membrane fouling, increasing membrane flux, and contributing to long-term stable operation of the system. The recoil interval is too short, which increases the filtration time and increases the cost; the backlash interval is too long, the filter cake on the surface of the membrane is too thick, and the ceramic membrane will operate at a low flux for a long time, which also prolongs the filtration time. The recoil time is too short, the adsorbent on the surface of the membrane can not be completely backflushed, and the filtration flux cannot be recovered effectively; the recoil time is too long, the recoil requires more permeate water, and the ceramic membrane treatment needs to be continued to increase the filtration negative. Amount, so choose the backlash interval 30 ~ 60min, the backlash time is 10 ~ 30s.

After the separation membrane concentrate is further dehydrated to obtain a adsorbent filter cake, in order to further improve the purity of the product, it is also preferred to wash the impurity ions entrained in the filter cake, and then use the desorbent solution. Desorption operation. The detergent is preferably water or an aqueous solution of LiCl, wherein the conductivity of water is preferably 2 to 10 μs/cm, the concentration of LiCl of the aqueous solution of LiCl is preferably 0.02 to 5 g/L; and the lithium ion desorption solution is water (preferably deionized water) or The pH of the phosphoric acid solution and the phosphoric acid solution is preferably controlled to 1 to 2, and the desorption temperature is preferably 50 to 100 °C.

After obtaining the desorption solution, Li ions present therein, will impurity ions Mg ^2+, Ca ²⁺ with an amount such as, Mg ^2+, Ca ²⁺ ions and other impurities Next, require further removed. As described above, the nanofiltration or ion exchange resin can be used to remove the impurity ions. The lithium adsorbent in the previous step functions as a preliminary magnesium removal. This step can lower the magnesium to lithium ratio and, more importantly, the subsequent nanocrystallization. Filtration separation reduces the load, so that the permeability of magnesium in the nanofiltration process is also reduced. More importantly, this step can reduce the intensity of magnesium ions in the filtration system, and increase the concentration factor in the nanofiltration process, so that the nanofiltration In the process, the concentration factor is increased, the extraction yield of lithium is improved, and the automation of the device is easy to realize.

The nanofiltration membrane herein is a membrane defined as "a pressure-driven membrane that blocks particles smaller than 2 nm and dissolved macromolecules". An effective nanofiltration membrane suitable for use in the present invention is preferably a membrane having an electric charge on the surface of the membrane and thus exhibiting by pore separation (particle size separation) and electrostatic separation due to charge on the surface of the membrane. Increased separation efficiency. Therefore, it is necessary to employ a nanofiltration membrane capable of removing a polymer substance by particle size separation while separating an alkali metal ion as a recovery target from other ions having different charge characteristics by a charge. As a material of the nanofiltration membrane used in the present invention, a polymer material such as a cellulose acetate polymer, a polyamide, a sulfonated polysulfone, a polyacrylonitrile, a polyester, a polyimide, or a vinyl polymer can be used. The film is not limited to a film composed of only one material, and may be a film containing a plurality of the materials. Regarding the membrane structure, the membrane may be an asymmetric membrane having a dense layer on at least one side of the membrane and having micropores that gradually become larger from the dense layer to the inside of the membrane or the other surface; or a composite membrane, which is non- The dense layer of the symmetrical membrane has a very thin functional layer formed of other materials.

Advantageously, the nanofiltration membrane can be a primary nanofiltration or a two-stage nanofiltration, preferably a two-stage nanofiltration. The two-stage nanofiltration removal of magnesium can further increase the magnesium removal rate, and can further remove other The divalent ions make the product more pure. This is mainly because multi-stage nanofiltration can increase the rejection rate of divalent salt, but the filtration order of nanofiltration can not be too much, otherwise it will cause some lithium ions in the system to be retained after multi-stage filtration. To the yield. The nanofiltration membrane has a molecular weight cutoff of 100-300, and the nanofiltration operating pressure is 1.0-3.0 MPa. Preferably, the nanofiltration operating pressure can be 2.5 MPa, the operating temperature is 20-45 ° C, and further, the operating temperature can be 25-40. °C. If the temperature is too low, the flux of the nanofiltration membrane will be low, which will directly affect the processing capacity and processing efficiency of the whole process. If the temperature is too high, it will impose a certain burden on the organic nanofiltration membrane components. The filter life is shortened and eventually it is not recyclable. If the pressure is too low, the flux of the nanofiltration membrane will be low, and the retention rate of Mg ²⁺ will be reduced by the nanofiltration membrane element. If the pressure is too high, the energy consumption of the operation will increase directly, and the economic cost will increase. Secondly, it will cause the temperature of the system to rise too fast during the operation, which will affect the life of the membrane element. The concentration ratio of the first-stage nanofiltration is preferably 3-6 times. If the concentration factor is too high, the flux is small, the system energy consumption is too large, and if the concentration is several hours, the permeate cannot be concentrated, so that the subsequent process burden Higher, the concentration ratio of the secondary nanofiltration is preferably 8 to 12 times. In a preferred embodiment, a two-stage nanofiltration is employed. The operating temperature of the primary nanofiltration is 30 ° C, the pressure is 3.0 MPa, the operating temperature of the secondary nanofiltration is 40 ° C, the pressure is 3.0 MPa, and the reverse osmosis operating pressure is 3.5. MPa, the temperature is 35 °C. In a preferred embodiment, the nanofiltration membrane has a rejection of magnesium sulfate of > 98%.

After the ion exchange resin permeate or nanofiltration membrane permeate, the lithium can be precipitated and purified by a carbonate precipitation method, but it is preferable to concentrate the solution to further increase the concentration of lithium ions. It can increase the yield and reduce the consumption of the medicament. According to an embodiment of the present invention, after the ion exchange resin permeate is obtained, it is necessary to concentrate the permeate to increase the concentration thereof. The method of concentration can be concentrated by reverse osmosis membrane, concentrated by evaporation, and the like. It is preferred to use a reverse osmosis membrane to concentrate the ion exchange resin permeate, preferably by concentration through a DTRO membrane (disc type reverse osmosis membrane) or an electrodialysis membrane, so that the concentration of LiCl can be increased by 20 ～30 times, the concentrate was further concentrated by evaporation. The evaporator can be a multi-effect evaporator.

As a material of the reverse osmosis membrane, a polymer material such as a cellulose acetate polymer, a polyamide, a polyester, a polyimide, or a vinyl polymer is generally used. Further, as a configuration thereof, there is a microporous asymmetric membrane having a dense layer on at least one side of the membrane, a pore having a gradually enlarged pore diameter from the dense layer to the inside of the membrane or the other surface, and the asymmetric membrane A composite film having a very thin active layer formed of other materials on the dense layer or the like. Among them, as a form of the reverse osmosis membrane, there are a hollow fiber, a flat membrane, etc. Generally, it is preferable that the film thickness of the hollow fiber and the flat film is 10 μm to 1 mm, and the outer diameter of the hollow fiber is 50μm ~ 4mm. Further, as the flat film, an asymmetric film is preferable, and the composite film is preferably a film supported by a substrate such as a woven fabric, a woven fabric, or a nonwoven fabric. However, the method of the present invention may be independent of the material of the reverse osmosis membrane, the film structure, or Formal use is effective for any situation. The concentrate of the reverse osmosis membrane device generally has pressure energy, and in order to reduce the running cost, it is preferred to recover the energy. As a method of recovering energy, it can be recovered by an energy recovery device mounted on any part of the high pressure pump, preferably by a dedicated turbine type energy recovery pump installed before or after the high pressure pump or between the components.

The reverse osmosis concentration process has an operating pressure of 3.0 to 4.0 MPa and a temperature of 30 to 40 °C. If the temperature is too low, the flux of the reverse osmosis membrane will be low, which will directly affect the processing capacity and processing efficiency of the whole process. If the temperature is too high, it will impose a certain burden on the organic nanofiltration membrane components. The filter life is shortened and eventually it is not recyclable. If the pressure is too low, the flux of the nanofiltration membrane will be low, and the retention rate of Mg ²⁺ will be reduced by the nanofiltration membrane element. If the pressure is too high, the energy consumption of the operation will increase directly, and the economic cost will increase. Compared with the conventional magnesium ion exchange resin, in addition to magnesium, and then concentrated by reverse osmosis, in the method of the invention, the concentration ratio of reverse osmosis can be increased to 5 to 8 times, and the concentration multiple of reverse osmosis of the conventional method. Only 2 to 3 times or even lower.

In one embodiment of the present invention, when the above-described concentration mode can be concentrated by a reverse osmosis membrane, the operation of the magnesium removal step is performed by using a nanofiltration membrane because if the ion exchange resin is used for the magnesium removal operation, Sodium ions are introduced into the system, which greatly increases the sodium ion content in the system, resulting in a low concentration ratio during the reverse osmosis process. The flux during reverse osmosis operation is too low to meet the engineering requirements. Moreover, it also causes a problem of time consuming and high energy consumption when the concentrated solution of reverse osmosis is further concentrated. When the adsorption and nanofiltration separation process is adopted, the magnesium ions are efficiently removed, and sodium ions are not introduced, so that the reverse osmosis process can maintain a high concentration multiple, which is more for subsequent salting, concentration or evaporation. Advantageously, when it is desired to perform precipitation extraction of lithium ions, the amount of agent consumed is also small. In general, when nanofiltration is used to remove magnesium ions, the concentration ratio of the reverse osmosis membrane can be increased from 3 times to more than 6 times with respect to the use of an ion exchange resin for removing magnesium.

The term "concentration factor" in the present invention means the ratio of the volume of the liquid to be filtered to the system of the concentrated liquid after the end of the concentrated filtration.

In an improved embodiment of the present invention, the nanofiltration membrane permeate in the magnesium removal process can also be sent to the ion exchange resin adsorption tower for deep removal of calcium and magnesium ions, preferably using a weak acid type cation exchange resin, and the cation exchange resin is Cation exchange resins which are known to those skilled in the art to be selective for alkaline earth metal cations can be used in the present invention. For example, Lewatit MonoPlus TP208, which is commercially available from Lanxess Europe GmbH, Germany, etc., can be exemplified. The flow rate of the desorbed liquid is preferably 3 to 10 BV/h. The brine after the deep removal of magnesium and calcium is sent to the subsequent concentration step.

According to an embodiment of the present invention, after the concentrated brine enters the evaporator for evaporation, BaCl ₂ , Na ₂ CO ₃ and NaOH solution are added thereto to make SO ₄ ² -, Ca ²⁺ and Mg ²⁺ in the brine. The precipitate is formed, and BaSO ₄ , CaCO ₃ , and Mg(OH) _{2 are formed} , and solid-liquid separation is performed through a ceramic membrane filter to remove impurity ions therein. As an improvement, the molar concentration ratio of BaCl ₂ is added lithium containing brine and concentrated in SO ₄ ² - Large molar concentration of 1% to 5% molar concentration of Na ₂ CO ₃ was added concentrated than the lithium-containing brines of Ca ²⁺ The molar concentration is 1 to 10% larger, and the molar concentration of the added NaOH is 1 to 5% larger than twice the molar concentration of Mg ²⁺ in the lithium-containing concentrated brine. As a modification of the above method, stirring is required in the process of adding BaCl ₂ , Na ₂ CO ₃ and NaOH precipitating agent, the stirring time is 20 to 40 minutes, and the stirring time is preferably 30 minutes.

In the concentrated solution from which the precipitate has been removed, a Na ₂ CO ₃ solution is added to carry out a precipitation reaction, and a Li ₂ CO ₃ precipitate can be formed. The precipitate is washed with a ceramic membrane filter to remove ions therein, and then centrifuged and dried. A finished Li ₂ CO ₃ was obtained. The Na ₂ CO ₃ solution is treated with a membrane filter, a precision filter or the like, and the purity of Na ₂ CO ₃ is more than 99.5%. The Li ₂ CO ₃ washing adopts a "small, multiple" washing method, the concentration ratio is 5-8 times, the water addition amount is 3 to 5 times the volume of the concentrated liquid, and the conductivity of the ceramic membrane permeate is less than 100 μs/cm.

The precipitation of the precipitate (such as BaSO ₄ , CaCO ₃ , Mg(OH) ₂ , Li ₂ CO ₃ described above) by a ceramic membrane, if the pore size range is too small, the filtration flux is low, which cannot meet the engineering requirements. If the pore size is too large, some of the precipitate will not be retained, but will enter the permeate side, which will affect the quality of the product. Too small a pressure will result in a small filtration flux and an excessive pressure, which will cause some smaller particles to be pressed through the membrane and into the permeate side. If the temperature is too low, the filtration flux will be low, and when the temperature is too high, the solubility of the particles will be affected, and a part of the precipitated particles will be redissolved and enter the permeate side. More preferably, the ceramic membrane has a pore size in the range of 20 to 200 nm, preferably a membrane pore diameter of 50 nm, a pressure of 0.1 to 0.5 MPa during operation, and a temperature of 10 to 50 °C.

The ion concentration of the salt lake brine used in the following examples is shown in Table 1:

Table 1

Based on the above method, the extraction separation device that can be used is shown in FIG. 1 and FIG. 2. In FIG. 1, the device is mainly composed of an adsorption desorption device 1, a magnesium removal device 2, a concentration device 3, a first precipitation tank 4, The second solid-liquid separator 6 is connected in order. The adsorption desorption device 1 functions to adsorb and desorb lithium in the brine to obtain a desorption liquid.

The adsorption desorption device 1 may be a structure in which only the structure shown in FIG. 2 is used, or the brine is adsorbed and desorbed by the adsorbent packed column 20, and the adsorbent packed column 20 is filled with a lithium adsorbent, and the brine is first supplied to the adsorption. In the packed column 20, the adsorption operation is performed, the brine is discharged, and then the desorbed liquid is supplied, and the desorbed liquid is supplied to the magnesium removing device 2, and in one embodiment, may be reconnected at the outlet of the adsorbent packed column 20. A filter 21 serves to remove some of the solid impurities in the desorbent.

In another embodiment, the adsorption desorption device 1 is as shown in FIG. 1 and includes a desorption tank 7 for storing brine and adding a lithium adsorbent thereto, thus, in the desorption tank 7 Also attached above is a sorbent tank 23 for adding a lithium sorbent to the desorption tank 7. The outlet of the desorption tank 7 is connected to the first solid-liquid separator 22. Since the desorption tank 7 is mainly a mixture of brine and lithium adsorbent, after it is sent to the first solid-liquid separator 22, it can be saturated. The lithium adsorbent is separated, and the first solid-liquid separator 22 can employ a conventional solid-liquid separation device. In one embodiment, the ceramic membrane device 8 and the plate and frame filter 9 are preferably used, as shown in FIG. Thus, the inlet of the ceramic membrane filter 8 is connected to the outlet of the adsorption tank 7, and the concentrated side of the ceramic membrane filter 8 is connected to the inlet of the plate and frame filter 9, and after the mixture of the lithium adsorbent and the brine is concentrated, Then, the concentrated liquid is sent to the plate and frame filter 9 for pressure filtration to obtain a lithium adsorbent filter cake, and then the outlet side of the cut-off side of the plate-frame filter 9 is connected to the desorption tank 10, and the filter cake can be discharged, and then Further, a desorbing solution is added to the desorption tank 10, and the lithium adsorbent can be desorbed, and after the liquid absorption is known, it is connected to the inlet of the magnesium removing device 2 through the desorption liquid outlet on the desorption tank 10.

The magnesium removal device 2 may be an ion exchange device or a nanofiltration device. In one embodiment, the magnesium removal device 2 includes a nanofiltration membrane 11 and an ion exchange resin column 12 connected in series, and the permeate side of the nanofiltration membrane 11 is connected to the ion. The inlet of the resin column 12 is exchanged, and the outlet of the ion exchange resin column 12 is connected to the concentration device 3.

The concentrating device 3 may be any one of a reverse osmosis membrane device, a DTRO membrane device, an electrodialysis membrane device, and an evaporation concentration device. In one embodiment, a reverse osmosis membrane 13 and a DTRO membrane 14 connected in series as shown in FIG. 1 may be employed, the outlet of the retentate side of the reverse osmosis membrane 13 is connected to the DTRO membrane 14, and the reverse osmosis membrane 13 is subjected to magnesium removal. After the brine was concentrated, it was further concentrated by DTRO membrane 14.

The outlet of the DTRO membrane 14 may be directly connected to the first precipitation tank 4, the first precipitation tank 4 is for precipitating lithium ions in the concentrated liquid to obtain lithium carbonate, and the first precipitation tank 4 is connected with the first sodium carbonate tank. 5, its role is to add sodium carbonate to the sedimentation tank. The outlet of the first precipitation tank 4 is connected to the inlet of the second solid-liquid separator 6, for separating the obtained lithium carbonate precipitate, and the second solid-liquid separator 6 may be a ceramic membrane.

In another embodiment, the outlet of the DTRO membrane 14 may also be first connected to the second precipitation tank 15, and the outlet of the second precipitation tank 15 Connected to the third solid-liquid separator 19, the second precipitation tank 15 is provided with a cesium chloride tank 16, a second sodium carbonate tank 17, and a sodium hydroxide tank 18, respectively for adding a precipitate to the second precipitation tank 15. Agent. The third solid-liquid separator 6 can be a ceramic membrane.

Example 1

100g FeSO ₄ ion sieve lithium adsorbent was charged into the packed column, and the salt lake brine was sent to the adsorbent bed at a rate of 3BV/h. After 2h, the adsorption saturation was reached, the concentration of Li ⁺ was no longer reduced; the desorption was performed with a phosphoric acid solution. The pH of the phosphoric acid solution is controlled to be about 1, the flow rate of the desorbent is 2BV/h, and desorption is completed after about 3 hours. The lithium desorption solution is then passed through the weak acid cation exchange resin D113 to remove a small amount of magnesium in the desorption solution. The flow rate of the desorbent is controlled. 5BV/h, and then use the reverse osmosis membrane to concentrate the lithium ion concentration in the treated desorbed solution to about 20g/L, the reverse osmosis concentration temperature is controlled at 30 ° C, and the operating pressure is 0.15Mpa, that is, by adding sodium carbonate. The lithium ion was converted into lithium carbonate precipitation, and a total of 8.56 g of lithium carbonate was obtained, and the purity was about 93%.

Example 2

The difference from the first embodiment is that the adsorption and desorption processes are carried out by mixing the adsorbent in the brine, and then desorbing the adsorbent by means of ceramic membrane filtration and plate and frame filtration, followed by desorption. The specific steps are:

Add 100g FeSO ₄ ion sieve adsorbent to 50L salt lake brine and heat and stir. Control the solution temperature to 40 ° C and stir for 60 min. Li ⁺ in the brine enters the adsorbent. At this time, the concentration of Li ⁺ in the solution is reduced to 1.07g / L. The FeSO ₄ ion sieve adsorbent adsorbs about 40 mg/g of Li, and then uses a ceramic membrane to concentrate and filter the mixed solution. The average pore diameter of the ceramic membrane is 5, 20, 50, 200, 500 nm, and the filtration pressure is 0.2. MPa, membrane surface flow rate 3m / s, filtration temperature 50 ° C, backlash interval 40min, backlash time is 10s; ceramic membrane filtration concentrate through the plate frame filter to remove most of the impurities and water in the concentrate, get adsorbed Lithium adsorbent filter cake, the adsorbent filter cake obtained by pressure filtration is first washed with water having a conductivity of 6 s/cm to remove the impurity ions such as magnesium, sodium and calcium entrained in the filter cake, and then placed. Stirring in a 1 L phosphoric acid solution, the pH of the phosphoric acid solution is controlled to be about 1, the stirring time is 60 min, the temperature of the control solution is 50 ° C, Li ^{+ is} introduced into the phosphoric acid solution to obtain a lithium desorption solution, and the lithium desorption solution is further subjected to a weak acid cation. Exchange resin D113 removal solution A small amount of magnesium in the liquid, the flow rate of the desorbent is controlled at 5BV/h, and finally concentrated by a reverse osmosis membrane. The reverse osmosis concentration temperature is controlled at 30 ° C, the operating pressure is 0.15 MPa, and the lithium ion concentration in the lithium desorption solution is concentrated to about At about 20 g/L, lithium ions can be converted into lithium carbonate by adding sodium carbonate, and the precipitate is subjected to solid-liquid separation and washing to obtain lithium carbonate. The test results are shown in Table 2.

Table 2

Average pore size nm	5	20	50	200	500
						Ceramic film concentration factor	12	18	26	50	57
Reverse osmosis membrane concentration multiple	3	3	3	3	3
						Lithium carbonate yield g	10.41	13.48	13.95	18.71	15.54
Lithium carbonate purity%	96%	95%	96%	98%	96%

The method of suspending the adsorbent in the brine for adsorption, and then filtering and concentrating the adsorbent by using the ceramic membrane can effectively improve the process efficiency and save the adsorption time of the resin; in addition, it can be seen from the table that due to the microfiltration In the process, the adsorbent is in the double-effect of cross-flow and separation of microfiltration. The colloid and macromolecular impurities in the brine are not easy to be coated and deposited on the surface of the adsorbent, which can prevent the adsorbent from being contaminated, and during the microfiltration process. These macromolecular impurities can enter the permeate side through the microfiltration membrane, and further prevent the impurities from affecting the service life of the adsorbent, so that the adsorbent can adsorb lithium ions as much as possible, thereby increasing the yield of lithium. It also avoids the deposition of impurities on the adsorbent and improves the purity of the product. Compared with Example 1, it can be seen that the lithium carbonate obtained in the present example has high yield and good purity under the same conditions of the amount of adsorbent.

Example 3

The difference from Example 2 is that after the desorption liquid is obtained, magnesium and calcium ions are removed by the primary nanofiltration membrane. The specific steps are:

Add 100g FeSO ₄ ion sieve adsorbent to 50L salt lake brine and heat and stir. Control the solution temperature to 40 ° C and stir for 60 min. Li ⁺ in the brine enters the adsorbent. At this time, the concentration of Li ⁺ in the solution is reduced to 1.07g / L. The FeSO ₄ ion sieve adsorbent adsorbs about 40 mg/g of Li, and then uses a ceramic membrane to concentrate and filter the mixed solution. The average pore diameter of the ceramic membrane is 50 nm, the filtration pressure is 0.2 MPa, and the membrane surface flow rate is 3 m/s. The filtration temperature is 50 ° C, the backlash interval is 40 min, and the recoil time is 10 s. The ceramic membrane filtration concentrate is filtered through the plate frame to remove most of the impurities and water in the concentrate to obtain the adsorbent cake of the adsorbed lithium, which will be pressed. The adsorbent filter cake obtained by filtration is first washed with water having a conductivity of 6 s/cm to remove impurity ions such as magnesium, sodium and calcium entrained in the filter cake, and then stirred in a 1 L phosphoric acid solution for phosphoric acid. The pH of the solution is controlled to be about 1, the stirring time is 60 min, the temperature of the control solution is 50 ° C, Li ⁺ enters the phosphoric acid solution to obtain a lithium desorption solution, and the lithium desorption solution is further removed by a nanofiltration membrane to remove a small amount of magnesium in the desorption liquid. Nanofiltration membrane molecular weight cutoff 300Da The material is polyethersulfone, the operating pressure is 2.0 MPa, the operating temperature is 30 ° C, and the concentration is 5 times. The permeate of the nanofiltration is concentrated by using a reverse osmosis membrane, and the reverse osmosis concentration temperature is controlled at 30 ° C, and the operating pressure is 0.15 MPa. The concentration was 5 times, and the lithium ion was converted into lithium carbonate by adding sodium carbonate. The precipitate was subjected to solid-liquid separation and washing to obtain lithium carbonate, and a total of 14.01 g of lithium carbonate was obtained, and the purity was 96%. It can be seen from Example 2 and Example 3 that when nanofiltration is used as the magnesium removing means, the magnesium removal by the magnesium ion exchange resin can effectively increase the concentration factor in the reverse osmosis concentration step.

Comparative Example 1

The difference between the comparative example 1 and the third embodiment is that the adsorption operation of the brine is not carried out by using the lithium adsorbent, but the brine is pre-filtered through the alumina ceramic membrane having an average pore diameter of 200 nm, and then the permeate of the ceramic membrane is sent to the subsequent Nanofiltration of magnesium, reverse osmosis concentration, sodium carbonate precipitation step. The concentration ratio of the nanofiltration membrane in this comparative example was 3 times, which was less than 5 times that in Example 3. It can be seen that pre-depletion of magnesium by adsorption can significantly increase the concentration factor of the nanofiltration membrane.

Example 4

The difference between the fourth embodiment and the third embodiment is that after the magnesium removal and concentration through the primary nanofiltration membrane, the nanofiltration permeate is subjected to deep magnesium removal using an ion exchange resin, and then the permeate of the ion exchange resin is sent. Into the subsequent reverse osmosis concentration, sodium carbonate precipitation process. The specific steps are:

Add 100g FeSO ₄ ion sieve adsorbent to 50L salt lake brine and heat and stir. Control the solution temperature to 40 ° C and stir for 60 min. Li ⁺ in the brine enters the adsorbent. At this time, the concentration of Li ⁺ in the solution is reduced to 1.07g / L. The FeSO ₄ ion sieve adsorbent adsorbs about 40 mg/g of Li, and then uses a ceramic membrane to concentrate and filter the mixed solution. The average pore diameter of the ceramic membrane is 50 nm, the filtration pressure is 0.2 MPa, and the membrane surface flow rate is 3 m/s. The filtration temperature is 50 ° C, the backlash interval is 40 min, and the recoil time is 10 s. The ceramic membrane filtration concentrate is filtered through the plate frame to remove most of the impurities and water in the concentrate to obtain the adsorbent cake of the adsorbed lithium, which will be pressed. The adsorbent filter cake obtained by filtration is first washed with water having a conductivity of 6 s/cm to remove impurity ions such as magnesium, sodium and calcium entrained in the filter cake, and then stirred in a 1 L phosphoric acid solution for phosphoric acid. The pH of the solution is controlled to be about 1, the stirring time is 60 min, the temperature of the control solution is 50 ° C, Li ⁺ enters the phosphoric acid solution to obtain a lithium desorption solution, and the lithium desorption solution is further removed by a nanofiltration membrane to remove a small amount of magnesium in the desorption liquid. Nanofiltration membrane molecular weight cutoff 300Da The material is polyethersulfone, the operating pressure is 2.0 MPa, the operating temperature is 30 ° C, and the concentration multiple is 5 times. After the nanofiltration permeate is deeply demagnetized by the cation exchange resin Lewatit MonoPlus TP208, the permeate of the ion exchange resin is used. The reverse osmosis membrane is concentrated, the reverse osmosis concentration temperature is controlled at 30 ° C, the operating pressure is 0.15 MPa, the concentration multiple is 5 times, and the lithium ion is converted into lithium carbonate by adding sodium carbonate, and the precipitate is separated by solid-liquid separation and washing. , lithium carbonate was obtained, and a total of 13.95 g of lithium carbonate was obtained, and the purity was 96.5%. It can be seen from Example 3 and Example 4 that further deep removal of magnesium by the cation exchange resin for the sodium filter permeate can be employed, and finally the purity of the lithium carbonate can be improved.

Example 5

The difference from the first embodiment is that the adsorption and desorption processes are carried out by mixing the adsorbent in the brine, and then desorbing the adsorbent by means of ceramic membrane filtration and plate and frame filtration, followed by desorption. The specific steps are:

Add 100g FeSO ₄ ion sieve adsorbent to 50L salt lake brine to heat and stir, control the solution temperature to 50 ° C, stir for 50 min, Li ⁺ in the brine enters the adsorbent, then the concentration of Li ⁺ in the solution is reduced to 1.02g / L The FeSO ₄ ion sieve adsorbent adsorbs about 40 mg/g of Li, and then uses a ceramic membrane to concentrate and filter the mixed solution. The average pore diameter of the ceramic membrane is 200 nm, the filtration pressure is 0.4 MPa, and the membrane surface flow rate is 0.5 m/. s, 1m/s, 2m/s, 3m/s, 4m/s, filtration temperature 60°C, backlash interval 30min, backlash time 30s; ceramic membrane filtration concentrate filtered through plate frame to remove concentrated liquid Most of the impurities and water, get the adsorbent cake of the adsorbed lithium, and the adsorbent filter cake obtained by pressure filtration is first washed with an aqueous solution of LiCl (LiCl concentration: 0.2 g/L) to remove the filter cake. The impurity ions such as magnesium, sodium and calcium entrained in the cake are stirred in a 1 L phosphoric acid solution, the pH of the phosphoric acid solution is controlled at about 1, the stirring time is 50 min, the temperature of the control solution is 45 ° C, and the Li ⁺ solution enters the phosphoric acid solution. In the middle, a lithium desorption solution is obtained, and the lithium desorption solution is further subjected to weak acid type cation separation. The sub-exchange resin D113 removes a small amount of magnesium in the desorption liquid, the flow rate of the desorbed liquid is controlled at 5 BV/h, and finally concentrated by using a reverse osmosis membrane. The reverse osmosis concentration temperature is controlled at 30 ° C, the operating pressure is 0.15 MPa, and the lithium desorption liquid is When the concentration of lithium ions is concentrated to about 20 g/L, lithium ions can be converted into lithium carbonate by adding sodium carbonate, and the precipitate is subjected to solid-liquid separation and washing to obtain lithium carbonate. The test results are shown in Table 3.

table 3

Membrane flow velocity m/s	0	0.5	1	2	3	4	5
								Ceramic film concentration factor	12	14	18	28	35	52	54
Lithium carbonate yield g	14.11	13.44	12.57	14.83	17.25	20.36	18.22
								Lithium carbonate purity%	94%	95%	95%	96%	97%	98%	96%

When the flow velocity of the membrane surface is 0 m/s, that is, the manner of dead-end filtration, it can be seen from the comparison that the concentration mode using the cross-flow filtration is advantageous for not collecting the impurities in the filter cake, compared with the dead-end filtration. The contamination of the adsorbent is effectively avoided, which is advantageous for ultimately increasing the adsorption and elution amount of lithium, and can improve the extraction yield of lithium. In addition, when different membrane surface flow rates are used, different contamination forms of the adsorbent filter cake are caused, and the technical problem of lithium ion extraction yield and purity can be effectively solved when the membrane surface velocity is 4 m/s.

Example 6

In this embodiment, the aluminum salt adsorbent is used to charge the Li ⁺ in the brine in the adsorption column, and the desorbed liquid is concentrated by the second-stage nanofiltration, and the nanofiltration filtrate is subjected to precipitation to remove the impurity alkali metal ions. The specific steps are:

The salt lake brine is adsorbed by Li ⁺ by the aluminum salt adsorbent, and then eluted with deionized water to obtain a desorption liquid. As the desorption process, the content of Mg ²⁺ in the desorbed solution decreases, when desorption is detected. When the content of Mg ²⁺ in the liquid is about 0.5, 2, 3, 4 g/L, respectively, the desorbed liquid is sent to the coarse filter to remove the adsorbent particles and sediment therein, and the permeate enters the primary nanofiltration membrane element. After filtration, the desorbed liquid passes through the primary nanofiltration membrane element to obtain a first-stage nanofiltration permeate. The primary nanofiltration membrane system has an operating temperature of 45 ° C, a pressure of 1.5 MPa, and a concentration multiple of 4 times. The first nanofiltration membrane permeate into the secondary nanofiltration membrane element to obtain a secondary nanofiltration permeate. The secondary nanofiltration membrane system has an operating temperature of 20 ° C, a pressure of 3.5 MPa, and a concentration multiple of 8 times. The secondary nanofiltration membrane permeate into the reverse osmosis system for concentration. The reverse osmosis operating pressure is 3.0 MPa, the temperature is 30 ° C, and after 6 times concentration, the reverse osmosis concentrate is subjected to drying and multi-effect evaporation to obtain multi-effect evaporation. Concentrate. The precipitants BaCl ₂ , Na ₂ CO ₃ and NaOH are sequentially added to the multi-effect evaporated concentrate, and the molar concentration of BaCl ₂ added is 1% larger than the molar concentration of SO ₄ ² - in the brine, and the molar ratio of Na ₂ CO ₃ The concentration is 1% larger than the molar concentration of Ca ²⁺ in the brine, and the molar concentration of NaOH is 1% larger than the molar concentration of Mg ²⁺ in the brine. After each addition of the precipitant, the mixture is stirred for 30 minutes to precipitate. After the reaction, it enters the ceramic membrane filter for filtration and impurity removal. The ceramic membrane has a pore size of 200 nm and a pressure of 0.5 MPa. The recoil device is opened during the filtration process, the backlash interval is 15 min, and the recoil time is 10 s. After filtration through the ceramic membrane, A ceramic membrane permeate is obtained with a turbidity of less than 0.5 NTU. The ion concentration data in each set of tests is shown in the table below.

Table 4

Through the four sets of experiments in this example, it can be seen that when the concentration of Mg ²⁺ ions in the desorbed solution is 0.5 g/L, the final yield of lithium is not high, which is lower than that of the Mg ²⁺ ions in the desorbed solution. It is 2 to 3 g/L. When the Mg ²⁺ ion is at a concentration of 4 g/L, it affects the concentration ratio and separation efficiency of reverse osmosis, resulting in a decrease in the final lithium yield. With the traditional magnesium ion exchange resin-reverse osmosis method, the concentration ratio of the reverse osmosis membrane can only reach about 3 times.

Example 7

The difference between this embodiment and Embodiment 6 is that the relevant process parameters are adjusted. The Li ⁺ content in the ceramic membrane supernatant is further increased, and the content of the impurity alkali metal ions is reduced.

The salt lake brine is adsorbed to the Li ⁺ by the aluminum salt adsorbent, and then eluted with deionized water to obtain a desorption liquid. When the Mg ²⁺ content in the desorbed solution is detected to be about 3 g/L, the desorbed liquid is sent. The coarse filter is used to remove the adsorbent particles and sediment, and the permeate enters the primary nanofiltration membrane element for filtration. The Ca ²⁺ content in the desorbed solution is 48.59 mg/L, and the Mg ²⁺ content is 3 g/L. The Li ⁺ content was 411 mg/L. After the desorbed liquid passed through the primary nanofiltration membrane element, the contents of Ca ²⁺ , Mg ²⁺ and Li ⁺ in the permeate were 29 mg/L, 370 mg/L and 575 mg/L. The primary nanofiltration membrane system has an operating temperature of 25 ° C, a pressure of 3.5 MPa, and a concentration factor of 5 times. The primary nanofiltration membrane permeate into the secondary nanofiltration membrane element, and the contents of Ca ²⁺ , Mg ²⁺ and Li ⁺ in the secondary nanofiltration permeate are 12.54 mg/L, 137.5 mg/L, 680 mg/L. . The secondary nanofiltration membrane system has an operating temperature of 40 ° C, a pressure of 1.5 MPa, and a concentration factor of 10 times. The second nanofiltration membrane permeate into the reverse osmosis system for concentration. The reverse osmosis operating pressure is 4.0 MPa, the temperature is 40 ° C, and the concentration is 6 times. After the reverse osmosis concentrate is subjected to salt drying and multi-effect evaporation, Ca ²⁺ and Mg The contents of ²⁺ and Li ⁺ were 0.17 g/L, 1.21 g/L, and 17.1 g/L. The precipitants BaCl ₂ , Na ₂ CO ₃ and NaOH are sequentially added to the multi-effect evaporated concentrate, and the molar concentration of BaCl ₂ added is 5% larger than the molar concentration of SO ₄ ² - in the brine, and the molar ratio of Na ₂ CO ₃ The concentration is 10% larger than the molar concentration of Ca ²⁺ in the brine, and the molar concentration of NaOH is 5% larger than the molar concentration of Mg ²⁺ in the brine. After each addition of the precipitant, the mixture is stirred for 30 minutes to precipitate. After the reaction, it enters the ceramic membrane filter for filtration and impurity removal. The ceramic membrane has a pore size of 20 nm and a pressure of 0.1 MPa. The recoil device is opened during the filtration process, the recoil interval is 15 min, and the recoil time is 10 s. The ceramic membrane turbidity is less than 0.5 NTU, the Mg ²⁺ + Ca ²⁺ content is 7.5 mg/L, the SO ₄ ² - content is 17 mg/L, and the Li ⁺ content is 18.8 g/L. With the traditional magnesium ion exchange resin-reverse osmosis method, the concentration ratio of the reverse osmosis membrane can only reach about 2.5 times.

Example 8

The difference between this embodiment and Embodiment 7 is that the relevant process parameters are adjusted. The Li ⁺ content in the ceramic membrane supernatant is further increased, and the content of the impurity alkali metal ions is reduced.

The salt lake brine is adsorbed to the Li ⁺ by the aluminum salt adsorbent, and then eluted with deionized water to obtain a desorption liquid. When the Mg ²⁺ content in the desorbed solution is detected to be about 3 g/L, the desorbed liquid is sent. The coarse filter is used to remove the adsorbent particles and sediment, and the permeate enters the primary nanofiltration membrane element for filtration. The Ca ²⁺ content in the desorbed solution is 47.65 mg/L, and the Mg ²⁺ content is 3 g/L. The Li ⁺ content was 421 mg/L. After the desorbed liquid passed through the primary nanofiltration membrane element, the contents of Ca ²⁺ , Mg ²⁺ and Li ⁺ in the permeate were 24 mg/L, 370 mg/L and 615 mg/L. The primary nanofiltration membrane system has an operating temperature of 30 ° C, a pressure of 3.0 MPa, and a concentration factor of 5 times. The primary nanofiltration membrane permeate into the secondary nanofiltration membrane element, and the contents of Ca ²⁺ , Mg ²⁺ and Li ⁺ in the secondary nanofiltration permeate are 12.24 mg/L, 137.5 mg/L, 730 mg/L. . The secondary nanofiltration membrane system has an operating temperature of 40 ° C, a pressure of 3.0 MPa, and a concentration factor of 11 times. The second nanofiltration membrane permeate into the reverse osmosis system for concentration. The reverse osmosis operating pressure is 3.5 MPa, the temperature is 35 ° C, and after 8 times concentration, the reverse osmosis concentrate is subjected to salt drying and multi-effect evaporation, Ca ²⁺ and Mg. The contents of ²⁺ and Li ⁺ were 0.14 g/L, 1.01 g/L, and 19.1 g/L. The precipitants BaCl ₂ , Na ₂ CO ₃ and NaOH are sequentially added to the multi-effect evaporated dope, and the molar concentration of BaCl ₂ added is 2% larger than the molar concentration of SO ₄ ² - in the brine brine, and the molar ratio of Na ₂ CO ₃ The concentration is 2% larger than the molar concentration of Ca ²⁺ in the brine, and the molar concentration of NaOH is 2% larger than the molar concentration of Mg ²⁺ in the brine. After each addition of the precipitant, the mixture is stirred for 30 minutes to precipitate. After the reaction, the ceramic membrane filter was introduced for filtration and impurity removal. The pore size of the ceramic membrane was 50 nm and the pressure was 0.3 MPa. The recoil device was opened during the filtration process, the backlash interval was 15 min, and the recoil time was 10 s. The ceramic membrane turbidity is less than 0.5 NTU, the Mg ²⁺ + Ca ²⁺ content is 7.3 mg/L, the SO ₄ ² - content is 14 mg/L, and the Li ⁺ content is 21.8 g/L. With the traditional magnesium ion exchange resin-reverse osmosis method, the concentration ratio of the reverse osmosis membrane can only reach about 3.5 times.

Example 9

In this embodiment, the adsorbent is first mixed in the brine, and after the adsorption is completed, the mixed solution is filtered through a ceramic membrane to obtain a concentrate containing the adsorbent, and then the concentrate is further dehydrated by a plate and frame filter press. Thereafter, the dehydrated lithium adsorbent filter cake is loaded into the adsorbent, and eluted water is added for desorption to obtain a desorbed liquid. Then, the desorbed solution is subjected to magnesium removal by nanofiltration and ion exchange resin, and then concentrated by a reverse osmosis membrane, and then precipitated agents BaCl ₂ , Na ₂ CO ₃ and NaOH are added to precipitate Ca ²⁺ and Mg ²⁺ impurity ions. After the precipitate was separated, Li ⁺ was precipitated with sodium carbonate to obtain a lithium carbonate precipitate. The specific steps are:

100gFeSO ₄ ion sieve adsorbent was added to 50L salt lake brine to heat and stir. The temperature of the solution was controlled at 40 ° C and stirred for 60 min. Li ⁺ in the brine entered the adsorbent. The adsorption capacity of FeSO ₄ ion sieve adsorbent to Li was about 40 mg. /g, then use the ceramic membrane to concentrate and filter the mixed liquid. The average pore diameter of the ceramic membrane is 50nm, the filtration pressure is 0.2MPa, the membrane surface velocity is 3m/s, the filtration temperature is 50°C, the recoil interval is 40min, and the recoil time is 10s. The ceramic membrane filtration concentrate is subjected to plate and frame filtration to remove most of the impurities and water in the concentrated liquid to obtain a adsorbent cake for adsorbing lithium, and the adsorbent filter cake obtained by pressure filtration is firstly used with a conductivity of 6 s/cm. The sorbent filter cake is washed with water to remove impurity ions such as magnesium, sodium and calcium entrained in the filter cake, and then the adsorbent is filtered and filled in the adsorption column, and deionized water is added for elution. The flow rate of the eluent is 2BV/h, when the Mg ²⁺ content in the desorbed solution is detected to be about 2 g/L, the permeate enters the primary nanofiltration membrane element for filtration, and the Ca ²⁺ content in the desorbed solution is 42.65 mg/L, Mg. ^{The 2+} content was 2 g/L and the Li ⁺ content was 450 mg/L. After the desorbed liquid passed through the primary nanofiltration membrane element, the contents of Ca ²⁺ , Mg ²⁺ and Li ⁺ in the permeate were 20 mg/L, 450 mg/L and 556 mg/L. The primary nanofiltration membrane system has an operating temperature of 45 ° C, a pressure of 1.5 MPa, a concentration factor of 5, and a nanofiltration membrane with a molecular weight cutoff of 300 Da, and the material is polyethersulfone. The first nanofiltration membrane permeate into the ion exchange resin adsorption tower for deep magnesium removal, and the ion exchange resin adsorption tower permeate the liquid, and the contents of Ca ²⁺ , Mg ²⁺ and Li ⁺ are 10 mg/L, 7 mg/L and 750mg/L. The ion exchange resin permeate into the reverse osmosis system for concentration. The reverse osmosis operating pressure is 3.0 MPa, the temperature is 30 ° C, and after concentration 6 times, the precipitants BaCl ₂ , Na ₂ CO ₃ and NaOH are sequentially added to the concentrate, and added. The molar concentration of BaCl ₂ is 2% greater than the molar concentration of SO ₄ ² - in the brine concentrate, and the molar concentration of Na ₂ CO ₃ is 2% greater than the molar concentration of Ca ²⁺ in the brine concentrate, and the molar ratio of NaOH is The molar concentration of Mg ²⁺ in the brine concentrate is twice as large as 2%. After each addition of the precipitant, the mixture is stirred for 30 minutes. After the precipitation reaction, the membrane is filtered into a ceramic membrane filter to remove impurities. The pore diameter of the ceramic membrane is 200 nm. The pressure is 0.5 MPa. The ceramic membrane clear liquid has a turbidity of less than 0.5 NTU, and a purified Na ₂ CO ₃ solution is added thereto, stirred, and then introduced into a ceramic membrane filter for concentration and washing, which is centrifuged and dried to obtain a finished Li ₂ CO ₃ product. After testing, Li ₂ CO _{3 was} obtained at 16.44 g, and the purity was 99.5%, which reached the battery grade Li ₂ CO ₃ standard.

Example 10

The difference from the embodiment 9 is that after the reverse osmosis membrane is concentrated by the reverse osmosis membrane, it is further concentrated by using a DTRO membrane and an MVR evaporator, and then a precipitant BaCl ₂ and Na ₂ CO ₃ are added to the evaporation concentrate. And NaOH precipitates Ca ²⁺ and Mg ²⁺ impurity ions. The specific steps are:

100gFeSO ₄ ion sieve adsorbent was added to 50L salt lake brine to heat and stir. The temperature of the solution was controlled at 40 ° C and stirred for 60 min. Li ⁺ in the brine entered the adsorbent. The adsorption capacity of FeSO ₄ ion sieve adsorbent to Li was about 40 mg. /g, then use the ceramic membrane to concentrate and filter the mixed liquid. The average pore diameter of the ceramic membrane is 50nm, the filtration pressure is 0.2MPa, the membrane surface velocity is 3m/s, the filtration temperature is 50°C, the recoil interval is 40min, and the recoil time is 10s. The ceramic membrane filtration concentrate is subjected to plate and frame filtration to remove most of the impurities and water in the concentrated liquid to obtain a adsorbent cake for adsorbing lithium, and the adsorbent filter cake obtained by pressure filtration is firstly used with a conductivity of 6 s/cm. The sorbent filter cake is washed with water to remove impurity ions such as magnesium, sodium and calcium entrained in the filter cake, and then the adsorbent is filtered and filled in the adsorption column, and deionized water is added for elution. The flow rate of the eluent is 2BV/h, when the Mg ²⁺ content in the desorbed solution is detected to be about 2 g/L, the permeate enters the primary nanofiltration membrane element for filtration, and the Ca ²⁺ content in the desorbed solution is 42.65 mg/L, Mg. ^{The 2+} content was 2 g/L and the Li ⁺ content was 450 mg/L. After the desorbed liquid passed through the primary nanofiltration membrane element, the contents of Ca ²⁺ , Mg ²⁺ and Li ⁺ in the permeate were 20 mg/L, 450 mg/L and 556 mg/L. The primary nanofiltration membrane system has an operating temperature of 45 ° C, a pressure of 1.5 MPa, a concentration factor of 5, and a nanofiltration membrane with a molecular weight cutoff of 300 Da, and the material is polyethersulfone. The first nanofiltration membrane permeate into the ion exchange resin adsorption tower for deep magnesium removal, and the ion exchange resin adsorption tower permeate the liquid, and the contents of Ca ²⁺ , Mg ²⁺ and Li ⁺ are 10 mg/L, 7 mg/L and 750mg/L. The ion exchange resin permeate through the reverse osmosis system. The reverse osmosis pressure is 3.0 MPa, the temperature is 30 ° C, and after 6 times concentration, the reverse osmosis concentrate enters the DTRO membrane for deep concentration, and is concentrated 4 times and then enters the MVR evaporator. After evaporation, the contents of Ca ²⁺ , Mg ²⁺ and Li ⁺ after evaporation were 0.23 g/L, 0.17 g/L, and 18 g/L. The precipitants BaCl ₂ , Na ₂ CO ₃ and NaOH are sequentially added to the multi-effect evaporated concentrate, and the molar concentration of BaCl ₂ added is 2% larger than the molar concentration of SO ₄ ² - in the brine concentrate, Na ₂ CO ₃ The molar concentration is 2% greater than the molar concentration of Ca ²⁺ in the brine concentrate, and the molar concentration of NaOH is 2% greater than the molar concentration of Mg ²⁺ in the brine concentrate. After each addition of the precipitant After stirring for 30 min, the precipitation reaction was carried out, and the ceramic membrane filter was introduced for filtration and impurity removal. The pore diameter of the ceramic membrane was 200 nm, and the pressure was 0.5 MPa. The ceramic membrane clear liquid has a turbidity of less than 0.5 NTU, and a purified Na ₂ CO ₃ solution is added thereto, stirred, and then introduced into a ceramic membrane filter for concentration and washing, which is centrifuged and dried to obtain a finished Li ₂ CO ₃ product. After testing, Li ₂ CO ₃ 21.54 g was obtained, and the purity was 99.8%, which reached the battery grade Li ₂ CO ₃ standard.

Example 11

The difference from the embodiment 9 is that after the multi-effect evaporated concentrated solution is obtained, the order of adding the precipitating agent is to sequentially add NaOH, BaCl ₂ and Na ₂ CO ₃ , and then perform filtration to remove the precipitate, precipitate the lithium carbonate, and precipitate by centrifugation. The operation of drying gave 19.02 g of Li ₂ CO ₃ and a purity of 99.1%.

Example 12

Add 100g FeSO ₄ ion sieve adsorbent to 50L salt lake brine, add activated carbon (concentration about 3g / L), heat and stir, control the solution temperature to 50 ° C, stir for 50min, Li ⁺ in the brine enters the adsorbent, at this time The concentration of Li ⁺ in the solution was reduced to 1.02 g / L, and the adsorption of Li by FeSO ₄ ion sieve adsorbent was about 40 mg / g. The membrane was concentrated by filtration through a ceramic membrane. The average pore diameter of the ceramic membrane was 200 nm, and the filtration pressure was 0.4 MPa. The surface flow rate is 4m/s, the filtration temperature is 60°C, the backlash interval is 40min, the recoil time is 30s, and the concentration multiple is about 52 times. The clear liquid can enter the magnesium extraction process to recover magnesium, and the ceramic membrane filtration concentrate is filtered through the plate frame to remove Most of the impurities and water in the concentrate are used to obtain the adsorbed filter cake of the adsorbed lithium. The filtrate of the plate frame pressure filtration also enters the magnesium extraction process to recover the magnesium, and the adsorbent filter cake obtained by pressure filtration is firstly treated with an aqueous solution of LiCl (LiCl The concentration of the adsorbent filter cake is washed at a concentration of 0.2g/L, and the impurity ions such as magnesium, sodium and calcium entrained in the filter cake are removed, and then stirred in a 1 L phosphoric acid solution, the stirring time is 50 min, and the temperature of the control solution is 45. ℃, Li ⁺ into the phosphoric acid solution, to give Desorbing solution, lithium desorption solution and then removing a small amount of magnesium in the desorption solution through weak acid cation exchange resin D113, the flow rate of desorbent is controlled at 5BV/h, finally concentrated by reverse osmosis membrane, and the reverse osmosis concentration temperature is controlled at 30 °C. When the pressure of 0.15 MPa is concentrated and the concentration of lithium ions in the lithium desorption solution is concentrated to about 20 g/L, lithium ions can be converted into lithium carbonate by adding sodium carbonate, and 22.16 g of lithium carbonate is obtained in total, and the purity is about 99%. It can be seen that by adding activated carbon in the system of the adsorbent, the adsorbent can be effectively dispersed more uniformly, and the activated carbon can adsorb a part of organic impurities, thereby avoiding the influence of these impurities on the service life of the adsorbent, and the obtained lithium carbonate. Yield and purity are better.

Claims (52)

1. A process for extracting battery grade lithium from brine, comprising the steps of: step 1, adsorbing brine with a lithium adsorbent, and desorbing the lithium adsorbent with an eluent to obtain a desorbent; Step, removing the magnesium from the desorbed solution to obtain a desorption solution for removing magnesium; and in the third step, concentrating the desorbed solution containing magnesium to obtain a concentrated lithium-containing brine.
2. The process for extracting battery grade lithium from brine according to claim 1, wherein the weight ratio of Mg ^{2+ to} Li ⁺ in the brine is 1:1 to 400:1.
3. The process for extracting battery grade lithium from brine according to claim 2, wherein the weight ratio of Mg ^{2+ to} Li ⁺ in the brine is from 2:1 to 200:1.
4. The process for extracting battery grade lithium from brine according to claim 3, wherein the weight ratio of Mg ^{2+ to} Li ⁺ in the brine is from 2:1 to 150:1.
5. The process for extracting battery grade lithium from brine according to claim 1, wherein the concentration of Li ⁺ in the brine is from 0.1 to 15.0 g/L.
6. The process for extracting battery grade lithium from brine according to claim 5, wherein the concentration of Li ⁺ in the brine is 0.3 to 10.0 g/L.
7. The process for extracting battery grade lithium from brine according to claim 6, wherein the concentration of Li ⁺ in the brine is from 0.5 to 8.0 g/L.
8. The process for extracting battery grade lithium from brine according to claim 1, wherein the lithium adsorbent is an aluminum salt lithium adsorbent, a lithium hydroxide adsorbent, a lithium acid adsorbent, and an ion sieve type lithium adsorption. a mixture of one or more of the agents.
9. The process for extracting battery grade lithium from brine according to claim 1, wherein in the first step, the lithium adsorbent is dispersed in the brine to obtain a mixed liquid, and then the mixture is subjected to solid-liquid separation and separation. The lithium adsorbent is desorbed.
10. The process for extracting battery grade lithium from brine according to claim 9, wherein the lithium adsorbent is added in the brine in an amount of 0.05 to 5 g/L.
11. The process for extracting battery grade lithium from brine according to claim 1, wherein the lithium adsorbent is added in an amount of 0.2 g/L in the brine.
12. The process for extracting battery grade lithium from brine according to any one of claims 9 to 11, wherein the lithium adsorbent is stirred for 30 to 60 minutes after the brine is added, and the brine temperature is 30 to 60 °C.
13. The process for extracting battery grade lithium from brine according to claim 9, wherein the step of solid-liquid separation comprises the step of concentrating using a separation membrane.
14. The process for extracting battery grade lithium from brine according to claim 1, wherein the step of solid-liquid separation is carried out by using a separation membrane to obtain a concentrate of the adsorbent, and then the adsorbent concentrate is subjected to a plate and frame filter. Dehydration.
15. The process for extracting battery grade lithium from brine according to claim 13 or 14, wherein the material of the separation membrane is preferably a ceramic membrane.
16. The process for extracting battery grade lithium from brine according to claim 15, wherein the separation membrane is a microfiltration membrane.
17. The process for extracting battery grade lithium from brine according to claim 15, wherein the separation membrane has an average pore size ranging from 50 to 200 nm.
18. The process for extracting battery grade lithium from brine according to claim 14, wherein the separation membrane is subjected to a concentration process and a filtration temperature It is 30 to 80 ° C, the operating pressure is 0.2 to 0.5 MPa, and the membrane surface flow rate is 1 to 4 m/s.
19. The process for extracting battery grade lithium from brine according to claim 1, wherein in the first step, the lithium adsorbent is charged into the adsorption column, the brine is injected for adsorption, and the eluent is injected for desorption. Desorption solution.
20. The process for extracting battery grade lithium from brine according to claim 19, wherein after the desorbent is obtained in the first step, after filtering through the filter, the permeate is sent to the magnesium removal in the second step. step.
21. The process for extracting battery grade lithium from brine according to claim 1, wherein the eluent in the first step is water or a phosphoric acid solution.
22. The process for extracting battery grade lithium from brine according to claim 21, wherein the phosphoric acid solution has a pH of 1 to 2 and a desorption temperature of 50 to 100 °C.
23. The process for extracting battery grade lithium from brine according to claim 1, wherein the step of removing magnesium in the second step is to remove magnesium ions by nanofiltration membrane filtration or ion exchange resin adsorption.
24. The process for extracting battery grade lithium from brine according to claim 23, wherein the nanofiltration membrane has a molecular weight cutoff of from 100 to 300 Da.
25. The process for extracting battery grade lithium from brine according to claim 23, wherein the nanofiltration operating pressure is 1.0 to 3.0 MPa.
26. The process for extracting battery grade lithium from brine according to claim 23, wherein the nanofiltration operating temperature is 20 to 45 °C.
27. The process for extracting battery grade lithium from brine according to claim 23, wherein the magnesium removal by the nanofiltration membrane is carried out by at least two stages of nanofiltration membrane.
28. The process for extracting battery grade lithium from brine according to claim 27, wherein the concentration ratio of the primary nanofiltration is 3 to 6 times, and the concentration ratio of the secondary nanofiltration is 8 to 12 times.
29. The process for extracting battery grade lithium from brine according to claim 23, wherein after removing magnesium ions by filtration through a nanofiltration membrane, magnesium removal is carried out using a cation exchange resin.
30. The process for extracting battery grade lithium from brine according to claim 1, wherein the concentration step in the third step is at least one of reverse osmosis membrane concentration, DTRO membrane concentration, electrodialysis membrane concentration, and evaporation concentration. A lithium-containing concentrated brine is obtained.
31. The process for extracting battery grade lithium from brine according to claim 30, wherein the concentration step is first concentrated by a reverse osmosis membrane, and then the reverse osmosis membrane concentrate is subjected to at least one of DTRO membrane concentration or evaporation concentration. Concentration is carried out to obtain a lithium-containing concentrated brine.
32. The process for extracting battery grade lithium from brine according to claim 30 or 31, wherein the reverse osmosis membrane concentration process has an operating pressure of 3.0 to 4.0 MPa and a temperature of 30 to 40 °C.
33. The process for extracting battery grade lithium from brine according to claim 1, wherein after the lithium-containing concentrated brine is obtained in the third step, BaCl ₂ , Na ₂ CO ₃ and NaOH solution are added thereto to make SO in the brine. ₄ ^2- , Ca ²⁺ and Mg ²⁺ form a precipitate and remove the precipitate.
34. The process for extracting battery grade lithium from brine according to claim 33, wherein the BaCl ₂ , Na ₂ CO ₃ and NaOH solutions are added in the order of sequentially adding BaCl ₂ , Na ₂ CO ₃ and NaOH solutions.
35. The process for extracting battery grade lithium from brine according to claim 33, wherein the molar concentration of BaCl ₂ added is 1% to 5% greater than the molar concentration of SO ₄ ^2- in the lithium-containing concentrated brine.
36. The process for extracting battery grade lithium from brine according to claim 33, wherein the molar concentration of Na ₂ CO ₃ added is 1 to 10% greater than the molar concentration of Ca ²⁺ in the lithium-containing concentrated brine.
37. A process for extracting battery grade lithium from brine according to claim 33, wherein the molar concentration of NaOH added is 1 to 5% greater than twice the molar concentration of Mg ²⁺ in the lithium-containing concentrated brine.
38. The process for extracting battery grade lithium from brine according to claim 33, wherein a solution of Li ₂ CO _{3 is} precipitated by adding a Na ₂ CO ₃ solution to the lithium-containing concentrated brine from which the precipitate has been removed, and the precipitate is separated and dried. After that, lithium carbonate was obtained.
39. A process for extracting battery grade lithium from brine according to any one of claims 33 to 38, wherein the step of separating the precipitate is separated by a ceramic membrane.
40. A process for extracting battery grade lithium from brine according to claim 39, wherein the ceramic membrane has a pore size ranging from 20 to 200 nm.
41. The process for extracting battery grade lithium from brine according to claim 40, wherein the ceramic membrane has a membrane pore size of 50 nm.
42. The process for extracting battery grade lithium from brine according to claim 39, wherein the ceramic membrane has a pressure of 0.1 to 0.5 MPa and a temperature of 10 to 50 °C.
43. The invention relates to a device for extracting battery grade lithium from brine, comprising an adsorption desorption device (1), a magnesium removal device (2) and a concentration device (3), characterized in that: the desorption liquid outlet and the magnesium removal of the adsorption desorption device (1) The inlet of the device (2) is connected, the outlet of the magnesium removal device (2) is connected to the inlet of the concentration device (3), and the concentrate outlet of the concentration device (3) is connected to the first precipitation tank (4) in the first precipitation tank. (4) A first sodium carbonate tank (5) is further disposed, and an outlet of the first precipitation tank (5) is further connected to the second solid-liquid separator (6).
44. The apparatus for extracting battery grade lithium from brine according to claim 43, wherein said adsorption desorption device (1) is a sorbent packed column (20); and at the outlet of the sorbent packed column (20) A filter (21) is connected, and the outlet of the filter (21) is connected to the magnesium removal device (2).
45. The apparatus for extracting battery grade lithium from brine according to claim 43, wherein the adsorption desorption device (1) comprises an adsorption tank (7) connected in series, a first solid-liquid separator (22), a desorption tank (10), the outlet of the desorption tank (10) is connected to the magnesium removal device (2); the first solid-liquid separator (22) comprises a ceramic membrane device (8) and a plate and frame filter (9) The outlet of the ceramic membrane device (8) is connected to the inlet of the plate and frame filter (9), and the inlet of the ceramic membrane device (8) is connected to the adsorption tank (10), and the trap side of the plate and frame filter (9) Connected to the desorption tank (10).
46. The apparatus for extracting battery grade lithium from brine according to claim 43, wherein said magnesium removal device (2) means a nanofiltration membrane device or an ion exchange resin device; said magnesium removal device (2) It refers to a nanofiltration membrane (11) and an ion exchange resin column (12) which are sequentially connected. The inlet of the nanofiltration membrane (11) is connected to the adsorption desorption device (1), and the permeate side of the nanofiltration membrane (11) is connected to the ion exchange. The resin column (12) and the outlet of the ion exchange resin column (12) are connected to a concentrating device (3).
47. The apparatus for extracting battery grade lithium from brine according to claim 43, wherein said concentrating means (3) is at least selected from the group consisting of a reverse osmosis membrane device, a DTRO membrane device, an electrodialysis membrane device, and an evaporation concentration device. The concentrating device (3) refers to a reverse osmosis membrane (13) and a DTRO membrane (14) connected in series, and the inlet of the reverse osmosis membrane (13) is connected to the magnesium removal device (2), a reverse osmosis membrane ( The cut-off side of 13) is connected to the inlet of the DTRO membrane (14), and the outlet of the DTRO membrane (14) is connected to the first precipitation tank (4).
48. The apparatus for extracting battery grade lithium from brine according to claim 43, wherein the outlet of said concentrating device (3) passes through the second precipitation tank (15) and the third solid-liquid separator (19) in turn. Connected to the first precipitation tank (4); the outlet of the concentration device (3) is connected to the inlet of the second precipitation tank (15), and the outlet of the second precipitation tank (15) is connected to the third solid-liquid separation device (19) The inlet, the outlet of the third solid-liquid separation device (19) is connected to the first precipitation tank (4); and the second precipitation tank (15) is respectively provided with a cerium chloride tank (16) and a second sodium carbonate. Tank (17), sodium hydroxide tank (18).
49. The apparatus for extracting battery grade lithium from brine according to claim 43, wherein said second solid-liquid separator (6) is ceramic Porcelain membrane filtration device.
50. The apparatus for extracting battery grade lithium from brine according to claim 48, wherein said third solid-liquid separator (19) is a ceramic membrane filtration device.
51. The apparatus for extracting battery-grade lithium from brine according to claim 49 or 50, wherein in the ceramic membrane filtration device, the ceramic membrane has a pore size ranging from 20 to 200 nm.
52. The apparatus for extracting battery-grade lithium from a brine according to claim 43, wherein in the ceramic membrane device (8), the ceramic membrane has a pore size ranging from 20 to 200 nm.

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