Method for purifying lithium-rich brine and collecting lithium

Abstract

The present application belongs to the technical field of lithium extraction from brine, and discloses a method for purifying lithium-rich brine to collect lithium. The method comprises the following steps: heating lithium-rich brine, adding a precipitant to react, and obtaining preliminary impurity-removed brine; mixing the preliminary impurity-removed brine with an acid to obtain a filtrate; mixing the filtrate with an extraction liquid, centrifugal extraction, and obtaining boron-removed brine; sequentially separating the boron-removed brine through first nanofiltration, second nanofiltration, third nanofiltration, and fourth nanofiltration to obtain lithium-rich concentrated water; adding a titanium-based adsorbent to the lithium-rich concentrated water to obtain adsorbed titanium-based adsorbent; desorbing the adsorbed titanium-based adsorbent, and concentrating to obtain a lithium collection mother liquor. The present application adopts the scheme of preliminary impurity removal + boron removal + nanofiltration + adsorption + desorption, reduces the concentration of impurity ions such as magnesium, boron, and sulfur in the final product, and greatly improves the purity and quality of the lithium collection mother liquor. Moreover, the process flow of the present application is simple, which is conducive to industrialization demonstration and large-scale production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium extraction from brine, and particularly relates to a method for purifying lithium-rich brine to collect lithium. BACKGROUND

[0002] As the lightest metal, lithium is known as the key performance energy metal to drive the world forward due to its unique physical and chemical properties. In the context of the increasingly prominent resource and environmental problems in the new century, the development and utilization of lithium energy ushered in a new peak period, and especially due to its environmental protection and sustainability, lithium energy has become the focus of global scientific research and has attracted extensive attention from researchers. Lithium resources mainly include two types, namely, ore type and salt lake type. Among them, salt lake type lithium resources account for 69% of the global reserves. Therefore, efficient extraction of lithium from salt lakes has become an inevitable trend of lithium resource development.

[0003] In the existing lithium extraction process from brine, although the extraction method can effectively extract lithium, the high cost, equipment corrosion problem and serious environmental pollution problem limit the further development of the extraction method; the adsorption method is convenient and fast, but the preparation cost of the adsorbent used is high, the manufacturing process is complex, and the corrosion pollution and adsorbent dissolution loss problems of acid treatment cannot be ignored; the reaction / separation coupling method is easy to cause the decrease of sodium salt purity; the nanofiltration membrane method has high requirements for pretreatment, and may cause membrane pollution and other problems.

[0004] Although researchers have conducted research on lithium extraction from brine for many years, in actual basic research, the difficulties of lithium extraction from brine have not been completely overcome. Therefore, both domestic and international academic circles are actively exploring to find more efficient, environmentally friendly and economical lithium collection processes. SUMMARY

[0005] The purpose of the present application is to provide a method for purifying lithium-rich brine to collect lithium, which solves the problems of low efficiency, low extraction rate and excessive impurities in the final extraction liquid in the existing lithium extraction process from brine.

[0006] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions:

[0007] The present application provides a method for purifying lithium-rich brine to collect lithium, comprising the following steps:

[0008] (1) The lithium-rich brine is heated to 50-80℃, and then a precipitating agent is added for reaction to obtain preliminary impurity-removed brine;

[0009] (2) The preliminary impurity-removed brine is mixed with acid, filtered to obtain a filtrate, and the filtrate is mixed with an extraction liquid, centrifuged and extracted to obtain boron-removed brine;

[0010] (3) sequentially passing the boron-removed brine through a first nanofiltration, a second nanofiltration, a third nanofiltration, and a fourth nanofiltration to separate and obtain a lithium-rich concentrated water;

[0011] (4) adjusting the lithium-rich concentrated water to be alkaline, then adding a titanium-based adsorbent into the lithium-rich concentrated water for continuous dispersion, performing solid-liquid separation after adsorption is completed to obtain the titanium-based adsorbent after adsorption;

[0012] (5) under acidic conditions, desorbing the titanium-based adsorbent after adsorption, then performing solid-liquid separation to obtain a lithium desorption liquid; and concentrating the lithium desorption liquid to obtain a lithium collection mother liquor, thereby completing purification of the lithium-rich brine and lithium collection;

[0013] In the step (3), the pressure of the first nanofiltration is 0.5-1 MPa, the pressure of the second nanofiltration is 1.5-2.5 MPa, the pressure of the third nanofiltration is 3-4 MPa, and the pressure of the fourth nanofiltration is 4.5-5 MPa.

[0014] The titanium-based adsorbent in the step (4) is acid-activated before use.

[0015] Preferably, in the method for purifying and collecting lithium from the lithium-rich brine, the precipitant in the step (1) comprises a mixture of calcium chloride and an alkaline additive, and the alkaline additive comprises one or more of sodium carbonate, sodium oxalate, sodium hydroxide, ammonium bicarbonate, and ammonia water.

[0016] Preferably, in the method for purifying and collecting lithium from the lithium-rich brine, the pH value of the preliminary impurity-removed brine mixed with the acid in the step (2) is 3-5; the extraction liquid in the step (2) is a mixture of sulfonated kerosene and 2-ethyl-1,3-hexanediol, and the volume fraction of 2-ethyl-1,3-hexanediol in the extraction liquid is 20-30%.

[0017] Preferably, in the method for purifying and collecting lithium from the lithium-rich brine, the centrifugal extraction in the step (2) is performed at a speed of 2000-2500 rpm for 3-5 times.

[0018] Preferably, in the method for purifying and collecting lithium from the lithium-rich brine, the nanofiltration membranes used in the first nanofiltration, the second nanofiltration, the third nanofiltration, and the fourth nanofiltration in the step (3) are monovalent ion selective nanofiltration membranes, and the material of the nanofiltration membranes is one or more of cellulose acetate, polyimide, and sulfonated polysulfone.

[0019] Preferably, in the method for purifying and collecting lithium from the lithium-rich brine, the step (3) further comprises repeating the operation of the step (3) for 1-2 times.

[0020] Preferably, in the method for purifying and collecting lithium from lithium-rich brine, the pH value of the lithium-rich concentrated water is adjusted to 9-11 in step (4).

[0021] Preferably, in the method for purifying and collecting lithium from lithium-rich brine, the titanium-based adsorbent is a layered Li2TiO3 ion sieve in step (4).

[0022] Preferably, in the method for purifying and collecting lithium from lithium-rich brine, the pH value of the acid condition is 1-3 in step (5).

[0023] Preferably, in the method for purifying and collecting lithium from lithium-rich brine, the Li + concentration in the lithium collection mother liquor is 50-70 g / L.

[0024] According to the technical solution described above, compared with the prior art, the present application has the following beneficial effects:

[0025] (1) The nanofiltration is set to 4 groups, and the 4 groups of nanofiltration adopt a gradient pressure boosting mode. As the pressure gradually increases, the driving force on both sides of the nanofiltration membrane gradually increases, which helps to remove different sizes of impurities and ions at different stages, thereby improving the overall separation efficiency and filtration efficiency of the nanofiltration membrane. At the same time, compared with the sudden application of high pressure that may cause stress concentration and damage to the membrane material when only one nanofiltration system is set, the gradient pressure boosting of the 4 groups of nanofiltration can gradually adapt and work stably, reducing the risk of membrane wear and damage and prolonging the service life. In addition, since it is a gradient pressure boosting, gradually increasing the pressure helps to slow down the accumulation of solution concentration on the surface of the nanofiltration membrane, reduce the adverse effects of concentration polarization on separation, and make the separation of monovalent ions and other valence ions more complete.

[0026] (2) The titanium-based adsorbent is acid-activated before use, which helps to adsorb lithium ions and has a low dissolution loss rate during lithium removal, so that the titanium-based adsorbent has a longer service life.

[0027] (3) The present application adopts the scheme of precipitant preliminary impurity removal + boron removal + nanofiltration + adsorption + desorption, which reduces the concentration of impurity ions such as magnesium, boron and sulfur in the final product, greatly improves the purity and quality of the lithium collection mother liquor. Moreover, the process flow of the present application is simple, the equipment is easy to operate, the processing efficiency is improved from the aspect of industrial application, which is conducive to industrialization demonstration and large-scale production. DETAILED DESCRIPTION

[0028] The present application provides a method for purifying and collecting lithium from lithium-rich brine, comprising the following steps:

[0029] (1) After the lithium-rich brine is heated, a precipitant is added for reaction to obtain a preliminary impurity-removed brine;

[0030] (2) mixing the preliminary impurity-removed brine with acid, filtering to obtain a filtrate; mixing the filtrate with the extraction liquid, centrifugal extraction to obtain boron-removed brine;

[0031] (3) sequentially separating the boron-removed brine through first nanofiltration, second nanofiltration, third nanofiltration and fourth nanofiltration to obtain lithium-rich concentrated water;

[0032] (4) adjusting the lithium-rich concentrated water to be alkaline, then adding a titanium-based adsorbent to the lithium-rich concentrated water for continuous dispersion, after adsorption, performing solid-liquid separation to obtain the titanium-based adsorbent after adsorption;

[0033] (5) under acidic conditions, desorbing the titanium-based adsorbent after adsorption, then performing solid-liquid separation to obtain lithium desorption liquid; concentrating the lithium desorption liquid to obtain lithium collection mother liquor, i.e. completing purification of lithium-rich brine and lithium collection.

[0034] In the present application, the lithium-rich brine in step (1) preferably contains the following mass concentrations of elements: Na + 4.2~7.5g / L、Li + 5.6~9.7g / L、K + 2.2~4.3g / L、SO4 2- 3.6~4.3g / L、Mg 2+ 3.1~5.3g / L、Ca 2+ 0.05~0.12g / L、B 3+ 2.4~3.6g / L,further preferably contains: Na + 5.1~6.8g / L、Li + 7.9~8.7g / L、K + 2.7~3.5g / L、SO4 2- 3.9~4.0g / L、Mg 2+ 3.4~4.7g / L、Ca 2+ 0.08~0.1g / L、B 3+ 2.8~3.3g / L, more preferably contains: Na + 5.1g / L、Li + 7.9g / L、K + 2.7g / L、SO4 2- 4.0g / L、Mg 2+ 3.4g / L、Ca 2+ 0.1g / L、B 3+ 2.8g / L.

[0035] In the present application, the temperature of heating the lithium-rich brine in step (1) is preferably 50~80℃, further preferably 63~75℃, and more preferably 75℃.

[0036] In the present application, the precipitant in step (1) preferably comprises a mixture of calcium chloride and an alkaline auxiliary.

[0037] In the present application, the alkaline auxiliary preferably comprises one or more of sodium carbonate, sodium oxalate, sodium hydroxide, ammonium bicarbonate and ammonia water, further preferably comprises one or more of sodium carbonate, sodium hydroxide and ammonium bicarbonate, and more preferably comprises two of sodium carbonate, sodium hydroxide.

[0038] When the alkaline auxiliary is preferably multiple, the present application does not limit the ratio between each of the alkaline auxiliaries, which can be adopted by those skilled in the art.

[0039] The present application does not limit the ratio of the amount of calcium chloride to the alkaline auxiliary, which can be adopted by those skilled in the art.

[0040] In the present application, the mass concentration of the precipitant in step (1) in the lithium-rich brine is preferably 24-40 g / L, further preferably 26-38 g / L, and more preferably 32 g / L.

[0041] In the present application, the time for adding the precipitant in step (1) is preferably 60-120 min, further preferably 60-100 min, and more preferably 90 min.

[0042] In the present application, the mode of adding the precipitant in step (1) is preferably: after adding calcium chloride, one or more of sodium carbonate, sodium oxalate, sodium hydroxide, ammonium bicarbonate and ammonia water is added for reaction. The present application does not limit the time for adding calcium chloride, which can be adopted by those skilled in the art.

[0043] In the present application, step (1) after adding the precipitant for reaction preferably further comprises filtration. The present application does not limit the conditions for filtration, which can be adopted by those skilled in the art.

[0044] In the present application, the acid in step (2) is preferably hydrochloric acid or sulfuric acid, and further preferably hydrochloric acid.

[0045] In the present application, the pH value after mixing the primary impurity-removed brine with the acid in step (2) is preferably 3-5, further preferably 3-4, and more preferably 3.

[0046] In the present application, the extraction liquid in step (2) is preferably a mixture of sulfonated kerosene and 2-ethyl-1,3-hexanediol.

[0047] In the present application, the volume fraction of the 2-ethyl-1,3 hexanediol in the extraction liquid in step (2) is preferably 20-30%, further preferably 20-26%, and more preferably 25%.

[0048] In the present application, the volume of the extraction liquid in step (2) is preferably the same as that of the filtrate.

[0049] In the present application, the rotation speed of the centrifugal extraction in step (2) is preferably 2000-2500 rpm, further preferably 2200-2400 rpm, and more preferably 2200 rpm; and the number of centrifugal extractions is preferably 3-5, further preferably 4-5, and more preferably 4.

[0050] In the present application, the nanofiltration membrane used in the first nanofiltration, the second nanofiltration, the third nanofiltration and the fourth nanofiltration in step (3) is preferably a monovalent ion selective nanofiltration membrane.

[0051] In the present application, the material of the nanofiltration membrane is preferably one or more of cellulose acetate, polyimide and sulfonated polysulfone, further preferably one or both of polyimide and sulfonated polysulfone, and more preferably sulfonated polysulfone.

[0052] The manufacturer of the nanofiltration membrane is not limited in the present application, and commercially available products known to those skilled in the art can be used.

[0053] In the present application, the pressure of the first nanofiltration in step (3) is preferably 0.5-1 MPa, further preferably 0.6-0.8 MPa, and more preferably 0.8 MPa.

[0054] In the present application, the pressure of the second nanofiltration in step (3) is preferably 1.5-2.5 MPa, further preferably 1.8-2 MPa, and more preferably 2 MPa.

[0055] In the present application, the pressure of the third nanofiltration in step (3) is preferably 3-4 MPa, further preferably 3.2-3.6 MPa, and more preferably 3.2 MPa.

[0056] In the present application, the pressure of the fourth nanofiltration in step (3) is preferably 4.5-5 MPa, further preferably 4.8-5 MPa, and more preferably 4.8 MPa.

[0057] In the present application, after step (3), the operation of step (3) is preferably repeated 1-2 times, and further preferably 1 time.

[0058] In the present application, the pH value of the adjusted lithium-rich concentrated water in step (4) is preferably 9-11, further preferably 9-10, and more preferably 10.

[0059] In the present application, the titanium-based adsorbent in step (4) is preferably a layered Li2TiO3 ion sieve.

[0060] In the present application, the titanium-based adsorbent in step (4) is preferably subjected to acid activation before use.

[0061] In the present application, the acid activation preferably comprises the following steps:

[0062] The titanium-based adsorbent is mixed with water for ultrasonic dispersion to obtain a titanium-based adsorbent dispersion; an acid solution is added to the titanium-based adsorbent dispersion for activation reaction, and filtration to obtain an activated titanium-based adsorbent.

[0063] In the present application, the power of ultrasonic dispersion is preferably 40-80 W, further preferably 50-60 W, and more preferably 60 W; the frequency is preferably 20-30 kHz, further preferably 20-24 kHz, and more preferably 20 kHz; and the time is preferably 1-2 h, further preferably 1-1.2 h, and more preferably 1 h.

[0064] In the present application, the concentration of the titanium-based adsorbent dispersion is preferably 100-200 g / L, further preferably 140-200 g / L, and more preferably 140 g / L.

[0065] In the present application, the acid solution is preferably sulfuric acid, acetic acid or oxalic acid, further preferably sulfuric acid or oxalic acid, and more preferably sulfuric acid.

[0066] In the present application, the temperature of the activation reaction is preferably 35-65℃, further preferably 40-60℃, and more preferably 50℃; the time is preferably 5-10 h, further preferably 6-10 h, and more preferably 8 h; and the pH value is preferably 1-3, further preferably 1-2, and more preferably 1.

[0067] In the present application, the concentration of the titanium-based adsorbent in step (4) in the lithium-rich concentrated water is preferably 30-40 g / L, further preferably 32-36 g / L, and more preferably 36 g / L.

[0068] In the present application, the rotation speed of the continuous dispersion in step (4) is preferably 1000-4000 rpm, further preferably 1200-3600 rpm, and more preferably 2500 rpm.

[0069] In the present application, the pH value of the acidic condition in step (5) is preferably 1-3, further preferably 1-2, and more preferably 1.

[0070] In the present application, the temperature of the desorption in step (5) is preferably 35-65℃, further preferably 40-50℃, and more preferably 50℃.

[0071] In the present application, the conductivity of the eluate at the end point of the desorption in step (5) is preferably ≤ 500 μS / cm, further preferably ≤ 400 μS / cm, and more preferably ≤ 200 μS / cm.

[0072] The present application does not limit the mode of the solid-liquid separation in step (4) and step (5), and any mode known to those skilled in the art can be used.

[0073] The present application does not limit the mode and conditions of the concentration in step (5), and any mode known to those skilled in the art can be used.

[0074] In the present application, the concentration of Li + in the lithium collecting mother liquor in step (5) is preferably 50-70 g / L, further preferably 60-70 g / L, and more preferably 60 g / L.

[0075] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application. Embodiments

[0076] The present embodiment provides a method for purifying lithium-rich brine and collecting lithium, comprising the following steps:

[0077] (1) The lithium-rich brine contains the following elements with the following mass concentrations: Na + 5.1 g / L, Li + 7.9 g / L, K + 2.7 g / L, SO4 2- 4.0 g / L, Mg 2+ 3.4 g / L, Ca 2+ 0.1 g / L, B 3+ 2.8 g / L; the above lithium-rich brine is heated to 75°C, then calcium chloride is added and reacted for 30 min, then 15.3 g / L of sodium carbonate and 3.2 g / L of sodium hydroxide are added and reacted for 60 min, the concentration of calcium chloride in the lithium-rich brine is 8.6 g / L, the concentration of sodium carbonate in the lithium-rich brine is 15.3 g / L, and the concentration of sodium hydroxide in the lithium-rich brine is 3.2 g / L, and filtration is performed to obtain a preliminary impurity-removed brine;

[0078] (2) The preliminary impurity-removed brine is mixed with hydrochloric acid to make the pH value of the system 3, and filtration is performed to obtain a filtrate; the filtrate is mixed with an extraction liquid composed of an equal volume of sulfonated kerosene and a mixture of 2-ethyl-1,3-hexanediol, and the volume fraction of 2-ethyl-1,3-hexanediol in the extraction liquid is 25%, and centrifugal extraction is performed at a rotation speed of 2200 rpm, and the operation of centrifugal extraction is repeated 4 times, and the inorganic phase is retained, which is the boron-removed brine;

[0079] (3) The boron-removed brine is sequentially separated by first nanofiltration, second nanofiltration, third nanofiltration, and fourth nanofiltration, and the nanofiltration membranes used in the nanofiltration are all monovalent ion-selective sulfonated polysulfone nanofiltration membranes, the pressure of the first nanofiltration is 0.8 MPa, the pressure of the second nanofiltration is 2 MPa, the pressure of the third nanofiltration is 3.2 MPa, and the pressure of the fourth nanofiltration is 4.8 MPa, and the operation of step (3) is repeated once to obtain the lithium-rich concentrated water;

[0080] (4) The layered Li2TiO3 ion sieve is mixed with water, and ultrasonic dispersion is performed at a power of 60 W and a frequency of 20 kHz for 1 h to obtain a layered Li2TiO3 ion sieve dispersion liquid with a concentration of 140 g / L; sulfuric acid is added to the layered Li2TiO3 ion sieve dispersion liquid to make the pH value of the system 1, and an activation reaction is performed at 50°C for 8 h, and filtration is performed to obtain the activated Li2TiO3 ion sieve;

[0081] The pH value of the lithium-rich concentrated water is adjusted to 10, and then the activated Li2TiO3 ion sieve is added to the lithium-rich concentrated water, and the concentration of the activated Li2TiO3 ion sieve in the lithium-rich concentrated water is 36 g / L, and continuous dispersion is performed at a rotation speed of 2500 rpm, and solid-liquid separation is performed after adsorption is completed to obtain the titanium-based adsorbent after adsorption;

[0082] (5) The titanium-based adsorbent after adsorption is desorbed at 50°C under acidic conditions with a pH value of 1, and solid-liquid separation is performed after the conductivity of the washing water is ≤200 μS / cm to obtain the lithium desorption liquid; the lithium desorption liquid is concentrated to obtain Li + with a concentration of 60 g / L, which is the lithium collection mother liquor, and the purification of the lithium-rich brine and the collection of lithium are completed.

[0083] Through testing, the contents of other elements in the lithium collection mother liquor are: Na + 3.5 g / L, K + 1.1 g / L, SO4 2- 0.01 g / L, Mg 2+ 0.2 g / L, Ca 2+ 0 g / L, and B 3+ 0 g / L. Example

[0084] The embodiment provides a method for purifying lithium-rich brine and collecting lithium, which comprises the following steps:

[0085] (1) The lithium-rich brine contains the following elements with the following mass concentrations: Na + 4.2 g / L, Li + 8.7 g / L, K + 4.3 g / L, SO4 2- 3.9 g / L, Mg 2+ 4.7 g / L, Ca 2+ 0.05 g / L, B 3+ 3.6 g / L; the lithium-rich brine is heated to 50°C, calcium chloride is added and reacted for 40 min, and then sodium oxalate is added and reacted for 80 min, the concentration of calcium chloride in the lithium-rich brine is 8.1 g / L, the concentration of sodium oxalate in the lithium-rich brine is 30 g / L, and filtration is performed to obtain a preliminary impurity-removed brine;

[0086] (2) The preliminary impurity-removed brine is mixed with sulfuric acid to make the pH value of the system 5, filtration is performed to obtain a filtrate; the filtrate is mixed with an extraction liquid composed of equal volumes of sulfonated kerosene and a mixture of 2-ethyl-1,3-hexanediol, the volume fraction of 2-ethyl-1,3-hexanediol in the extraction liquid is 26%, centrifugal extraction is performed at a speed of 2000 rpm, the operation of centrifugal extraction is repeated 5 times, and the inorganic phase is retained, which is a boron-removed brine;

[0087] (3) The boron-removed brine is sequentially separated by first nanofiltration, second nanofiltration, third nanofiltration, and fourth nanofiltration, the nanofiltration membranes used in the nanofiltration are all monovalent ion-selective cellulose acetate nanofiltration membranes, the pressure of the first nanofiltration is 0.6 MPa, the pressure of the second nanofiltration is 1.5 MPa, the pressure of the third nanofiltration is 3 MPa, and the pressure of the fourth nanofiltration is 4.5 MPa, and a lithium-rich concentrated water is obtained;

[0088] (4) Layered Li2TiO3 ion sieve is mixed with water, ultrasonic dispersion is performed at a power of 40 W and a frequency of 30 kHz for 1 h to obtain a layered Li2TiO3 ion sieve dispersion liquid with a concentration of 200 g / L; oxalic acid is added to the layered Li2TiO3 ion sieve dispersion liquid to make the pH value of the system 3, and activation reaction is performed at 35°C for 10 h, and filtration is performed to obtain activated Li2TiO3 ion sieve;

[0089] The pH value of the lithium-rich concentrated water is adjusted to 11, and then the activated Li2TiO3 ion sieve is added to the lithium-rich concentrated water, the concentration of the activated Li2TiO3 ion sieve in the lithium-rich concentrated water is 40 g / L, and continuous dispersion is performed at a speed of 1200 rpm, and after adsorption is completed, solid-liquid separation is performed to obtain a titanium-based adsorbent after adsorption;

[0090] (5) under the acid condition of pH value = 2, desorption is carried out on the adsorbed titanium adsorbent at 35℃, and after the conductivity of the eluted water is ≤500 μS / cm, solid-liquid separation is carried out, to obtain lithium desorption liquid; the lithium desorption liquid is concentrated, to obtain Li + The lithium collection mother liquor with a concentration of 70 g / L is collected, and the lithium-rich brine purification is completed.

[0091] Through testing, the content of other elements in the lithium collection mother liquor is: Na + 4.1 g / L, K + 1.8 g / L, SO4 2- 0.06 g / L, Mg 2+ 0.4 g / L, Ca 2+ 0 g / L, B 3+ 0 g / L. Embodiment

[0092] The embodiment provides a method for lithium-rich brine purification and lithium collection, comprising the following steps:

[0093] (1) the lithium-rich brine contains the following mass concentrations of elements: Na + 7.5 g / L, Li + 9.7 g / L, K + 2.2 g / L, SO4 2- 4.3 g / L, Mg 2+ 3.1 g / L, Ca 2+ 0.12 g / L, B 3+ 2.4 g / L; the above lithium-rich brine is heated to 63℃, calcium chloride is added and reacted for 20 min, ammonium bicarbonate is added and reacted for 40 min, the concentration of calcium chloride in the lithium-rich brine is 10 g / L, the concentration of ammonium bicarbonate in the lithium-rich brine is 14 g / L, and filtration is carried out, to obtain preliminary impurity-removed brine;

[0094] (2) the preliminary impurity-removed brine is mixed with hydrochloric acid, so that the pH value of the system is 3, filtration is carried out, to obtain filtrate; the filtrate is mixed with an extraction liquid composed of equal volumes of sulfonated kerosene and 2-ethyl-1,3 hexanediol (the volume fraction of 2-ethyl-1,3 hexanediol in the extraction liquid is 30%), and centrifugal extraction is carried out at a speed of 2500 rpm, the operation of centrifugal extraction is repeated 3 times, and the inorganic phase is reserved, that is, boron-removed brine;

[0095] (3) the boron-removed brine is sequentially separated through first nanofiltration, second nanofiltration, third nanofiltration and fourth nanofiltration, the nanofiltration membranes used in nanofiltration are all monovalent ion selective polyimide nanofiltration membranes, the pressure of the first nanofiltration is 1 MPa, the pressure of the second nanofiltration is 2.5 MPa, the pressure of the third nanofiltration is 4 MPa, and the pressure of the fourth nanofiltration is 4.8 MPa, the operation of step (3) is repeated 2 times, to obtain lithium-rich concentrated water;

[0096] (4) Layered Li2TiO3 ion sieve is mixed with water, ultrasonic dispersion is carried out for 2 h under power of 80 W and frequency of 20 kHz, and a layered Li2TiO3 ion sieve dispersion liquid with a concentration of 100 g / L is obtained; acetic acid is added to the layered Li2TiO3 ion sieve dispersion liquid, so that the pH value of the system is 1, an activation reaction is carried out at 65℃ for 5 h, and filtration is carried out, so that activated Li2TiO3 ion sieve is obtained;

[0097] The pH value of the lithium-rich concentrated water is adjusted to 9, and then the activated Li2TiO3 ion sieve is added to the lithium-rich concentrated water, and the concentration of the activated Li2TiO3 ion sieve in the lithium-rich concentrated water is 30 g / L; continuous dispersion is carried out at a rotation speed of 3600 rpm, solid-liquid separation is carried out after adsorption is completed, and a titanium-based adsorbent after adsorption is obtained;

[0098] (5) The titanium-based adsorbent after adsorption is desorbed at 40℃ under acidic conditions with a pH value of 1, and solid-liquid separation is carried out after the conductivity of the eluate is ≤200 μS / cm, so that a lithium desorption liquid is obtained; the lithium desorption liquid is concentrated, and Li + with a concentration of 65 g / L is obtained, that is, the lithium collection mother liquor is obtained.

[0099] It is tested that the content of other elements in the lithium collection mother liquor is: Na + 5.6 g / L, K + 0.9 g / L, SO4 2- 0.12 g / L, Mg 2+ 0.2 g / L, Ca 2+ 0 g / L, B 3+ 0 g / L. Embodiment

[0100] The embodiment provides a method for purifying lithium-rich brine and collecting lithium, which comprises the following steps:

[0101] (1) The lithium-rich brine contains the following elements with the following mass concentrations: Na + 6.8 g / L, Li + 5.6 g / L, K + 3.5 g / L, SO4 2- 3.6 g / L, Mg 2+ 5.3 g / L, Ca 2+ 0.08 g / L, B 3+3.3g / L; the above lithium-rich brine was heated to 80°C, then calcium chloride was added and reacted for 40 min, then sodium carbonate and ammonia were added and reacted for 60 min, the concentration of calcium chloride in the lithium-rich brine was 9.2 g / L, the concentration of sodium carbonate in the lithium-rich brine was 24.8 g / L, and the concentration of ammonia in the lithium-rich brine was 3.2 g / L, filtration was performed, and a preliminary impurity-removed brine was obtained;

[0102] (2) The preliminary impurity-removed brine was mixed with hydrochloric acid to make the pH value of the system 4, filtration was performed, and a filtrate was obtained; the filtrate was mixed with an extraction liquid composed of equal volumes of sulfonated kerosene and a mixture of 2-ethyl-1,3-hexanediol, centrifugal extraction was performed at a speed of 2400 rpm, the operation of centrifugal extraction was repeated 4 times, and the inorganic phase was retained, which was a boron-removed brine;

[0103] (3) The boron-removed brine was sequentially separated by first nanofiltration, second nanofiltration, third nanofiltration, and fourth nanofiltration, the nanofiltration membranes used in the nanofiltration were monovalent ion selective sulfonated polysulfone nanofiltration membranes, the pressure of the first nanofiltration was 0.5 MPa, the pressure of the second nanofiltration was 1.8 MPa, the pressure of the third nanofiltration was 3.6 MPa, the pressure of the fourth nanofiltration was 5 MPa, the operation of step (3) was repeated once, and a lithium-rich concentrated water was obtained;

[0104] (4) The layered Li2TiO3 ion sieve was mixed with water, ultrasonic dispersion was performed at a power of 50 W and a frequency of 24 kHz for 1.2 h, a layered Li2TiO3 ion sieve dispersion liquid with a concentration of 160 g / L was obtained; sulfuric acid was added to the layered Li2TiO3 ion sieve dispersion liquid to make the pH value of the system 2, an activation reaction was performed at 60°C for 6 h, and filtration was performed, obtaining an activated Li2TiO3 ion sieve;

[0105] The pH value of the lithium-rich concentrated water was adjusted to 10, then the activated Li2TiO3 ion sieve was added to the lithium-rich concentrated water, the concentration of the activated Li2TiO3 ion sieve in the lithium-rich concentrated water was 32 g / L, continuous dispersion was performed at a speed of 2000 rpm, solid-liquid separation was performed after adsorption was completed, and a titanium-based adsorbent after adsorption was obtained;

[0106] (5) Under acidic conditions with a pH value of 3, the titanium-based adsorbent after adsorption was desorbed at 65°C, solid-liquid separation was performed after the conductivity of the washing water was ≤400 μS / cm, and a lithium desorption liquid was obtained; the lithium desorption liquid was concentrated, and Li + concentration of 52 g / L, which was a lithium collection mother liquor, and the purification of the lithium-rich brine and the collection of lithium were completed.

[0107] Through testing, the content of other elements in the lithium collection mother liquor was: Na + 4.7 g / L, K + 1.3 g / L, SO4 2-0.03g / L, Mg 2+ 0.4g / L, Ca 2+ 0g / L, B 3+ 0g / L.

[0108] The comparative example provides a method for purifying lithium-rich brine and collecting lithium, which is different from example 1 in that the first nanofiltration, the second nanofiltration, the third nanofiltration and the fourth nanofiltration in step (3) are modified to be nanofiltration treatment under a constant pressure of 4 MPa, and the Li + concentration of the lithium collection mother liquor in step (5) is 53 g / L, and other parameter conditions are the same as those in example 1.

[0109] It is tested that the content of other elements in the lithium collection mother liquor is: Na + 6.8g / L, K + 1.9g / L, SO4 2- 0.32g / L, Mg 2+ 1.1g / L, Ca 2+ 0.006g / L, B 3+ 0.06g / L.

[0110] The comparative example provides a method for purifying lithium-rich brine and collecting lithium, which is different from example 1 in that the first nanofiltration, the second nanofiltration, the third nanofiltration and the fourth nanofiltration in step (3) are modified to be the first nanofiltration and the second nanofiltration, the pressure of the first nanofiltration is 2 MPa, and the pressure of the second nanofiltration is 4.5 MPa, and the Li + concentration of the lithium collection mother liquor in step (5) is 50 g / L, and other parameter conditions are the same as those in example 1.

[0111] It is tested that the content of other elements in the lithium collection mother liquor is: Na + 4.3g / L, K + 1.5g / L, SO4 2- 0.14g / L, Mg 2+ 0.6g / L, Ca 2+ 0.002g / L, B 3+ 0.014g / L.

[0112] In summary, the nanofiltration in the application is set to 4 groups and the gradient pressure boosting mode is selected, combined with the scheme of preliminary impurity removal + boron removal + nanofiltration + adsorption + desorption, the concentration of magnesium, boron, sulfur and other impurity ions in the final product lithium collection mother liquor is reduced, and the purity and quality of the lithium collection mother liquor are greatly improved; and the process flow of the application is simple, which is conducive to realizing large-scale industrial application.

[0113] The above merely describes the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as falling within the protection scope of the present application.

Claims

1. A method for purifying lithium-rich brine and collecting lithium, characterized in that, The method comprises the following steps: (1) heating the lithium-rich brine to 50-80℃, and then adding a precipitant to obtain a preliminary impurity-removed brine; (2) mixing the preliminary impurity-removed brine with an acid, and filtering to obtain a filtrate; mixing the filtrate with an extraction liquid, and centrifugally extracting to obtain a boron-removed brine; (3) sequentially passing the boron-removed brine through a first nanofiltration, a second nanofiltration, a third nanofiltration, and a fourth nanofiltration to obtain a lithium-rich concentrated water; (4) adjusting the lithium-rich concentrated water to be alkaline, and then continuously dispersing a titanium-based adsorbent into the lithium-rich concentrated water, and after adsorption, performing solid-liquid separation to obtain the titanium-based adsorbent after adsorption; (5) under acidic conditions, desorbing the titanium-based adsorbent after adsorption, and then performing solid-liquid separation to obtain a lithium desorption liquid; concentrating the lithium desorption liquid to obtain a lithium collection mother liquor, i.e., completing purification of the lithium-rich brine and lithium collection; In step (1), the precipitant comprises a mixture of calcium chloride and an alkaline additive, and the alkaline additive comprises one or more of sodium carbonate, sodium oxalate, sodium hydroxide, ammonium bicarbonate, and ammonia water. In step (2), the pH value of the mixture of the preliminary impurity-removed brine and the acid is 3-5; the extraction liquid is a mixture of sulfonated kerosene and 2-ethyl-1,3-hexanediol, and the volume fraction of 2-ethyl-1,3-hexanediol in the extraction liquid is 20-30%. In step (3), the nanofiltration membranes used in the first nanofiltration, the second nanofiltration, the third nanofiltration, and the fourth nanofiltration are monovalent ion-selective nanofiltration membranes, and the nanofiltration membranes are made of one or more of cellulose acetate, polyimide, and sulfonated polysulfone; the pressure of the first nanofiltration is 0.5-1 MPa, the pressure of the second nanofiltration is 1.5-2.5 MPa, the pressure of the third nanofiltration is 3-4 MPa, and the pressure of the fourth nanofiltration is 4.5-5 MPa. In step (4), the titanium-based adsorbent is acid-activated before use.

2. The method for purifying lithium-rich brine and collecting lithium according to claim 1, characterized in that, In step (2), the centrifugal extraction is performed at a speed of 2,000-2,500 rpm for 3-5 times.

3. The method for purifying lithium-rich brine and collecting lithium according to claim 1, characterized in that, After step (3), the operation of step (3) is repeated 1-2 times.

4. The method for purifying lithium-rich brine and collecting lithium according to claim 1, wherein, In step (4), the pH value of the lithium-rich concentrated water adjusted to be alkaline is 9-11.

5. The method for purifying lithium-rich brine and collecting lithium according to claim 1 or 4, characterized in that, In step (4), the titanium-based adsorbent is a layered Li2TiO3 ion sieve.

6. The method for purifying lithium-rich brine and collecting lithium according to claim 5, wherein, In step (5), the pH value of the acidic conditions is 1-3.

7. The method for purifying lithium-rich brine and collecting lithium according to claim 1, wherein, The Li in the lithium collection mother liquor in step (5) + The concentration is 50~70g / L.