CN108946770B - Method for separating lithium and magnesium and enriching lithium - Google Patents
Method for separating lithium and magnesium and enriching lithium Download PDFInfo
- Publication number
- CN108946770B CN108946770B CN201811180004.7A CN201811180004A CN108946770B CN 108946770 B CN108946770 B CN 108946770B CN 201811180004 A CN201811180004 A CN 201811180004A CN 108946770 B CN108946770 B CN 108946770B
- Authority
- CN
- China
- Prior art keywords
- nanofiltration
- lithium
- reverse osmosis
- separation
- concentration
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D15/00—Lithium compounds
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
The invention relates to the technical field of solution separation and purification, in particular to a method for separating lithium and magnesium and enriching lithium, which comprises the steps of diluting and filtering old brine in a salt pan to obtain pretreated brine; separating the pretreated brine through a nanofiltration separation system to obtain nanofiltration fresh water and nanofiltration concentrated water; carrying out primary concentration on the nanofiltration fresh water through a reverse osmosis system to obtain reverse osmosis concentrated solution and reverse osmosis fresh water; performing secondary concentration on the reverse osmosis concentrated solution through an electrodialysis system to obtain electrodialysis concentrated water and electrodialysis fresh water, wherein the electrodialysis concentrated water is a solution enriched with lithium ions; in the separation step, the nanofiltration separation system comprises at least two stages of nanofiltration separation devices, and each stage of nanofiltration separation device is formed by connecting multiple sections of nanofiltration separation units in series; the pretreated brine firstly passes through a multi-section nanofiltration separation unit of a first-stage nanofiltration separation device and then passes through a multi-section nanofiltration separation unit of a next-stage nanofiltration separation device to carry out magnesium-lithium separation. The invention can improve the magnesium-lithium separation efficiency and the lithium enrichment efficiency.
Description
Technical Field
The invention belongs to the technical field of solution separation and purification, and particularly relates to a method for separating lithium and magnesium and enriching lithium.
Background
Lithium is a very important strategic resource, and as the lightest metal element, lithium exists in two forms of solid ore and liquid ore in nature. The reserve of lithium resources in China is rich, the industrial reserve of the proven lithium resources is located in the second place of the world, wherein the lithium brine accounts for 79 percent, and the prospective reserve of the lithium brine in the salt lake in the Qinghai-Tibet plateau area is equivalent to the total reserve which is currently proven in other countries of the world. According to estimation, the reserve (by lithium) of the Qinghai salt lake lithium resources is 150 ten thousand tons, which is the first in China, so the lithium extraction technology of the salt lake brine is the top of the energy strategic high land strived by China, and is the major strategic demand of China. However, in view of the composition characteristics of salt lake brine in China, the difficulty of extracting lithium from salt lake brine is great. This is mainly due to the fact that one of the significant features of salt lake brine is high magnesium and low lithium (i.e. the content of magnesium ions is much higher than that of lithium ions), and the magnesium/lithium mass ratio in most of salt lake brine is higher than 40, for example, the magnesium/lithium mass ratio in the salt lake brine of Kerr sweat is as high as 1800, that in the salt lake of Dachai is 114, and that in the salt lake brine of Qinghai is also very high. Because the chemical properties of magnesium and lithium are similar, the difficulty of separating and extracting lithium is increased due to the existence of a large amount of magnesium, so that a new method for separating and extracting important resources such as magnesium and lithium in salt lake brine is needed to be developed.
The existing magnesium-lithium separation method mainly comprises the following steps: precipitation, adsorption, extraction, etc. The above methods all have a certain degree of limitation in the separation process. Such as: the precipitation method is suitable for brine with low magnesium-lithium ratio, and the problems of excessive consumption of a precipitator and high cost exist when the magnesium-lithium ratio is high; the adsorption method has the problems of low adsorption quantity of the adsorbent and high cost; the extraction method has high requirements on an extracting agent, and easily causes the problems of environmental pollution, equipment corrosion and the like in the extraction process. In addition, although the above method can realize lithium enrichment to a certain extent in the process of reducing the magnesium-lithium ratio of the brine, the lithium ion content in the finally obtained lithium-rich brine does not reach the concentration for preparing high-purity lithium salt, and further enrichment and concentration are required.
Besides the separation method, there are some researches related to separation of magnesium and lithium in salt lake brine by using membrane separation technology. For example, the chinese patent application No. 03108088.X describes a method for separating magnesium and enriching lithium from salt lake brine by using a nanofiltration process. Although the method reduces the magnesium-lithium ratio of the salt lake brine to a certain extent and realizes the enrichment of lithium in the brine, the lithium ion content in the finally obtained lithium-rich brine does not reach the lithium concentration required for preparing high-purity lithium salt, the enrichment and concentration of lithium are required to be continuously carried out, and the lithium ion yield in the separation process is low. Therefore, it is necessary to optimize the existing magnesium-lithium separation technology to solve the problems of lithium ion enrichment efficiency and process cost.
Disclosure of Invention
In order to overcome the defects of the prior art, the inventor conducts diligent research, and finishes the invention after paying a great deal of creative labor and carrying out deep experimental exploration.
The invention provides a method for separating lithium and magnesium and enriching lithium, which comprises the following steps:
pretreatment: diluting and filtering the old brine in the salt pan to obtain pretreated brine;
separation: separating the pretreated brine through a nanofiltration separation system to obtain nanofiltration fresh water and nanofiltration concentrated water;
first concentration: performing primary concentration on the nanofiltration fresh water through a reverse osmosis system to obtain reverse osmosis concentrated solution and reverse osmosis fresh water;
and (3) second concentration: performing secondary concentration on the reverse osmosis concentrated solution through an electrodialysis system to obtain electrodialysis concentrated water and electrodialysis fresh water, wherein the electrodialysis concentrated water is a solution enriched with lithium ions;
in the separation step, the nanofiltration separation system comprises at least two stages of nanofiltration separation devices, and each stage of nanofiltration separation device is formed by connecting multiple stages of nanofiltration separation units in series; the pretreated brine firstly passes through a plurality of sections of the nanofiltration separation unit of the first-stage nanofiltration separation device to carry out magnesium-lithium separation, and then passes through a plurality of sections of the nanofiltration separation unit of the next-stage nanofiltration separation device to carry out magnesium-lithium separation.
Further, in the separation step, the nanofiltration separation system adopts a monovalent ion selective nanofiltration membrane, and the obtained nanofiltration concentrated water is recycled through an energy recovery device.
Furthermore, the nanofiltration separation system comprises two stages of nanofiltration separation devices, each stage of nanofiltration separation device is formed by connecting three sections of nanofiltration separation units in series, and the number ratio of nanofiltration membranes of the three sections of nanofiltration separation units in any stage of nanofiltration separation device is 35-85: 43-70: 25-55; the operating pressure of the nanofiltration separation system is 1.0-5.0 MPa, the concentration of lithium ions in the nanofiltration fresh water is 0.2-2.0 g/L, and the mass ratio of magnesium ions to lithium ions in the nanofiltration fresh water is 0.02-0.5: 1.
Preferably, in any stage of nanofiltration separation device, the number ratio of nanofiltration membranes of three sections of nanofiltration separation units is 55-65: 52-68: 35-45; the operating pressure of the nanofiltration separation system is 3.6-4.0 MPa, the concentration of lithium ions in the nanofiltration fresh water is 0.5-1.2 g/L, and the mass ratio of magnesium ions to lithium ions in the nanofiltration fresh water is 0.05-0.2: 1.
Further, the pretreatment comprises the following steps: and (3) diluting the old brine of the salt pan for the first time, sequentially feeding the diluted old brine of the salt pan into a multi-medium filter for filtering, feeding the diluted old brine into an ultrafiltration system for filtering, and diluting for the second time to obtain the pretreated brine.
Further, in the pretreatment step, the concentration of lithium ions in the salt pan old brine is 0.2-5.0 g/L, and the mass ratio of magnesium ions to lithium ions is 6-180: 1; the multiple of the primary dilution of the old brine in the salt pan is 0.5-4.5 times, and the multiple of the secondary dilution after the filtration by the ultrafiltration system is 3.5-20 times.
Preferably, in the pretreatment step, the concentration of lithium ions in the salt pan old brine is 2.5-4.0 g/L, and the mass ratio of magnesium ions to lithium ions is 6-55: 1; the dilution multiple of the old brine in the salt pan after twice dilution is 5-20 times.
More preferably, the dilution multiple of the salt pan old brine after twice dilution is 14-16 times.
Furthermore, the reverse osmosis system is composed of a plurality of sections of reverse osmosis units which are connected in series, the nanofiltration fresh water sequentially passes through each section of reverse osmosis unit to be concentrated for the first time, so that reverse osmosis concentrated solution and the reverse osmosis fresh water are obtained, and the reverse osmosis fresh water is circulated back to the pretreatment step and is used for diluting the saltern bittern.
Furthermore, the reverse osmosis system is formed by connecting three sections of reverse osmosis units in series, and the quantity ratio of reverse osmosis membranes of all sections of reverse osmosis units is 22-62: 15-45: 5-43; the operating pressure in the first concentration step is 2.0-10.0 MPa, the concentration of lithium ions in the obtained reverse osmosis concentrated solution is 2.0-10 g/L, and the mass ratio of magnesium ions to lithium ions in the reverse osmosis concentrated solution is 0.05-3.0: 1.
Preferably, the number ratio of reverse osmosis membranes of all sections of reverse osmosis units is 38-46: 25-35: 20-28; the operating pressure in the first concentration step is 3.5 MPa-7.0 MPa, the concentration of lithium ions in the obtained reverse osmosis concentrated solution is 3.0 g/L-5.0 g/L, and the mass ratio of magnesium ions to lithium ions in the reverse osmosis concentrated solution is 0.07-0.2: 1.
Further, in the step of electrodialysis, the ion selective membrane used in the electrodialysis system is one of a homogeneous membrane, a semi-homogeneous membrane, or a heterogeneous membrane; the electrodialysis fresh water is recycled to the first concentration step for concentrating lithium ions; the concentration of lithium ions in the electrodialysis concentrated water is 8 g/L-21 g/L, and the mass ratio of magnesium ions to lithium ions in the electrodialysis concentrated water is 0.05-1.0: 1.
Preferably, in the step of electrodialysis, the ion selection membrane used by the electrodialysis system is a homogeneous membrane, the cation selection membrane is a CMX homogeneous membrane, and the anion selection membrane is an AMX homogeneous membrane; the concentration of lithium ions in the electrodialysis concentrated water is 14 g/L-21 g/L, and the mass ratio of magnesium ions to lithium ions in the electrodialysis concentrated water is 0.07-0.2: 1.
The invention has the following beneficial effects:
firstly, the invention utilizes the advantages of different membrane separation technologies to couple a plurality of different membrane separation technologies, so that the salt pan old brine is sequentially treated by an ultrafiltration system, a nanofiltration system, a reverse osmosis system and an electrodialysis system to realize the separation of magnesium and lithium and the enrichment of lithium. The method comprises the following steps: filtering out all mechanical impurities by an ultrafiltration system; the magnesium ions and the lithium ions are fully separated through the nanofiltration system, the concentration of the lithium ions is improved, after nanofiltration, the mass ratio of the magnesium ions to the lithium ions in the nanofiltration fresh water is greatly reduced from 6-180: 1 to 0.02-0.5: 1 in the original salt pan bittern, and therefore the separation step of the invention can efficiently realize magnesium and lithium separation; and finally, further concentrating the lithium-containing concentrated solution by using an electrodialysis system, so that the content of the lithium ions is greatly increased to 8-21 g/L from 0.2-5.0 g/L of the original salt field old brine, the enrichment of the lithium ions is really realized, the enrichment efficiency is improved, and the concentration of the enriched lithium ions can meet the requirement of preparing high-purity lithium salts. In conclusion, through the system research of the inventor of the patent, the coupling sequence of the membrane separation system is provided, so that the process characteristics of different systems can be fully utilized, the magnesium-lithium separation of salt lake brine and the efficient concentration and enrichment of lithium are realized, and the concentration of lithium ions required by the preparation of high-purity lithium salt is reached.
In the separation step, a multistage and multistage nanofiltration separation mode is adopted, and a nanofiltration membrane which is efficient and can work under an ultrahigh pressure condition is also adopted. The pretreated brine is fed into the high-pressure side of the nanofiltration separation system, and the sufficient separation of magnesium and lithium in the brine can be realized by utilizing the pressure difference between two sides of the nanofiltration membrane and the selectivity difference of the nanofiltration membrane on monovalent and divalent ions, so that the mass ratio of magnesium ions to lithium ions in the brine can be effectively reduced, and the improvement of the concentration of the lithium ions in the nanofiltration fresh water is facilitated. Moreover, through the multi-stage nanofiltration separation device, multi-stage nanofiltration can be performed on the pretreated brine, so that the magnesium-lithium separation effect and the membrane flux in the nanofiltration process are improved, the magnesium-lithium ratio of the salt field old brine is greatly reduced, and efficient magnesium-lithium separation is realized.
In the first concentration step, the method adopts a reverse osmosis system formed by connecting multiple sections of reverse osmosis units in series, and effectively improves the lithium ion concentration in the reverse osmosis process through the multiple sections of reverse osmosis operation. Particularly, the invention also researches and limits the quantity and the proportion of each section of reverse osmosis membrane in the multi-section reverse osmosis unit so as to more fully reduce the transmittance of lithium ions in the reverse osmosis carbon water.
Finally, the invention recovers and recycles the nanofiltration concentrated water produced in the nanofiltration process and the reverse osmosis fresh water produced in the reverse osmosis process, thereby effectively reducing the energy consumption of the whole method, reducing the discharge of waste water and saving the process cost.
Drawings
FIG. 1 is a flow chart of a method for separating and enriching lithium according to an embodiment.
Detailed Description
The salt field old brine in the embodiment of the invention is from a sulfate type salt lake in Qinghai regions, the concentration of lithium ions in the salt field old brine is 2.5g/L, the concentration of magnesium ions is 125g/L, and the mass ratio of the magnesium ions to the lithium ions is 50: 1.
Example one
The present embodiment provides a method for separating and enriching lithium, which is a flow chart shown in fig. 1, and the method of the present embodiment includes the following steps:
pretreatment: the salt field old brine is diluted for the first time, the salt field old brine after being diluted for the first time is sent to a multi-medium filter to be filtered to remove partial mechanical impurities such as silt and the like, then is sent to an organic ultrafiltration system to be filtered to be completely purified, then is diluted for the second time, and the dilution multiple after being diluted for the two times is 15 times, so that the brine after pretreatment is obtained.
Separation: and (3) separating the pretreated brine through a nanofiltration separation system to obtain nanofiltration fresh water and nanofiltration concentrated water, wherein the concentration of lithium ions in the nanofiltration fresh water is 1.2g/L, the concentration of magnesium ions is reduced to 0.12g/L, and the mass ratio of the magnesium ions to the lithium ions is 0.10: 1. The method comprises the following steps:
the nanofiltration separation system adopts monovalent ion selective nanofiltration membranes, the nanofiltration separation system comprises two stages of nanofiltration separation devices, and each stage of nanofiltration separation device is formed by connecting three sections of nanofiltration separation units in series. The pretreated brine is subjected to magnesium-lithium separation by a three-section nanofiltration separation unit of a first-stage nanofiltration separation device, is further subjected to magnesium-lithium separation by a three-section nanofiltration separation unit of a second-stage nanofiltration separation device, and is subjected to two-stage nanofiltration separation operation to obtain nanofiltration fresh water and nanofiltration concentrated water, wherein the nanofiltration concentrated water is recycled by an energy recovery device so as to reduce the discharge of wastewater. In the nanofiltration separation device of the embodiment, the number ratio of the nanofiltration membranes of the three sections of nanofiltration separation units is 55-65: 52-68: 35-45 in sequence, the operating pressure of the nanofiltration separation system is 3.6-5.0 MPa, and the nanofiltration membranes can bear the ultrahigh operating pressure of 3.6-5.0 MPa, so that the water flux in the separation process can be greatly increased, the magnesium-lithium separation effect can be improved, and the lithium ion yield in the nanofiltration process can be ensured.
First concentration: and (3) carrying out primary concentration on the nanofiltration fresh water through a reverse osmosis system to obtain reverse osmosis concentrated solution and reverse osmosis fresh water, wherein the concentration of lithium ions in the reverse osmosis concentrated solution is 5.0g/L, and the mass ratio of magnesium ions to lithium ions is 0.102: 1. The method comprises the following steps:
the reverse osmosis system is formed by connecting three sections of reverse osmosis units in series, each section of reverse osmosis unit contains different numbers of reverse osmosis membranes, nanofiltration fresh water is subjected to primary concentration through each section of reverse osmosis unit in sequence to obtain reverse osmosis concentrated solution and reverse osmosis fresh water, and the reverse osmosis fresh water is circulated back to the pretreatment step and is used for diluting bittern in a salt field so as to improve the utilization rate of the reverse osmosis fresh water. In the reverse osmosis system of the embodiment, the number ratio of reverse osmosis membranes of the reverse osmosis units in each section is 38-46: 25-35: 20-28, and the operation pressure of the first concentration is 7.0 MPa. By adopting a mode of multiple sections and different reverse osmosis membrane quantity ratios, the transmittance of lithium in reverse osmosis fresh water can be fully reduced, and the enrichment of lithium in reverse osmosis concentrated solution is facilitated.
And (3) second concentration: and (2) adopting a homogeneous membrane as an ion selection membrane of the electrodialysis system, and performing secondary concentration on the reverse osmosis concentrated solution through the electrodialysis system to obtain electrodialysis concentrated water and electrodialysis fresh water, wherein the concentration of lithium ions in the electrodialysis concentrated water is 20.8g/L, and the mass ratio of magnesium ions to lithium ions is 0.106:1, so that after secondary concentration, the concentration of the lithium ions enriched in the embodiment reaches the concentration of the lithium ions required for preparing high-purity lithium salt, and the lithium ion concentration can be used for the subsequent process step of preparing the lithium salt. In addition, the electrodialysis fresh water is circulated back to the first concentration step and is used for concentrating lithium ions, specifically, the electrodialysis fresh water is mixed with the nanofiltration fresh water obtained from the separation step, and the recovery of residual lithium and the reutilization of the electrodialysis fresh water are realized through a reverse osmosis system of the first concentration.
The compositions of the brine used in this example and the solutions in the respective stages of separation and concentration are shown in table 1 below:
table 1 example one composition of the solution in the stages of brine field brine and separation and concentration
The method of the embodiment realizes magnesium-lithium separation and efficient lithium enrichment of the sulfate type salt lake brine, and the finally obtained electrodialysis concentrated water (namely the second concentrated solution) can be directly used for preparing high-purity lithium salt due to the fact that the electrodialysis concentrated water has high lithium ion concentration. The yield of lithium ions in the whole magnesium-lithium separation process is more than 87%, and the yield of lithium ions in the whole lithium ion concentration process is more than 95%.
Example two
The present embodiment provides a method for separating and enriching lithium, comprising the steps of:
pretreatment: the salt field old brine is diluted for the first time, the salt field old brine after being diluted for the first time is sent to a multi-medium filter to be filtered to remove partial mechanical impurities such as silt and the like, then is sent to an organic ultrafiltration system to be filtered to be completely purified, then is diluted for the second time, and the dilution multiple after being diluted for the two times is 15 times, so that the brine after pretreatment is obtained.
Separation: and (3) separating the pretreated brine through a nanofiltration separation system to obtain nanofiltration fresh water and nanofiltration concentrated water, wherein the concentration of lithium ions in the nanofiltration fresh water is 0.27g/L, the concentration of magnesium ions is reduced to 0.10g/L, and the mass ratio of the magnesium ions to the lithium ions is 0.38: 1. The method comprises the following steps:
the nanofiltration separation system adopts monovalent ion selective nanofiltration membranes, the nanofiltration separation system comprises two stages of nanofiltration separation devices, and each stage of nanofiltration separation device is formed by connecting three sections of nanofiltration separation units in series. The pretreated brine is subjected to magnesium-lithium separation by a three-section nanofiltration separation unit of a first-stage nanofiltration separation device, is further subjected to magnesium-lithium separation by a three-section nanofiltration separation unit of a second-stage nanofiltration separation device, and is subjected to two-stage nanofiltration separation operation to obtain nanofiltration fresh water and nanofiltration concentrated water, wherein the nanofiltration concentrated water is recycled by an energy recovery device so as to reduce the discharge of wastewater. In the nanofiltration separation device of the embodiment, the number ratio of the nanofiltration membranes of the three sections of nanofiltration separation units is 35-42: 45-50: 27-34 in sequence, the operating pressure of the nanofiltration separation system is 3.6-5.0 MPa, and the magnesium-lithium separation can be more effectively realized by adopting the number ratio of the nanofiltration membranes of the sections.
First concentration: and (3) carrying out primary concentration on the nanofiltration fresh water through a reverse osmosis system to obtain reverse osmosis concentrated solution and reverse osmosis fresh water, wherein the concentration of lithium ions in the reverse osmosis concentrated solution is 2.7g/L, and the mass ratio of magnesium ions to lithium ions is 0.37: 1. The method comprises the following steps:
the reverse osmosis system is formed by connecting three sections of reverse osmosis units in series, each section of reverse osmosis unit contains different numbers of reverse osmosis membranes, nanofiltration fresh water is subjected to primary concentration through each section of reverse osmosis unit in sequence to obtain reverse osmosis concentrated solution and reverse osmosis fresh water, and the reverse osmosis fresh water is circulated back to the pretreatment step and is used for diluting bittern in a salt field so as to improve the utilization rate of the reverse osmosis fresh water. In the reverse osmosis system of the embodiment, the number ratio of reverse osmosis membranes of each section of reverse osmosis units is 22-34: 15-22: 32-43, and the operation pressure of the first concentration is 7.0 MPa. By adopting a mode of multiple sections and different reverse osmosis membrane quantity ratios, the transmittance of lithium in reverse osmosis fresh water can be fully reduced, and the enrichment of lithium in reverse osmosis concentrated solution is facilitated.
And (3) second concentration: and (2) adopting a homogeneous membrane as an ion selection membrane of the electrodialysis system, and performing secondary concentration on the reverse osmosis concentrated solution through the electrodialysis system to obtain electrodialysis concentrated water and electrodialysis fresh water, wherein the concentration of lithium ions in the electrodialysis concentrated water is 10g/L, and the mass ratio of magnesium ions to lithium ions is 0.37:1, so that the concentration of the lithium ions enriched in the embodiment reaches the concentration of the lithium ions required for preparing high-purity lithium salt after the secondary concentration. In addition, the electrodialysis fresh water is circulated back to the first concentration step and is used for concentrating lithium ions, specifically, the electrodialysis fresh water is mixed with the nanofiltration fresh water obtained from the separation step, and the recovery of residual lithium and the reutilization of the electrodialysis fresh water are realized through a reverse osmosis system of the first concentration.
The compositions of the brine used in this example and the solutions in the respective stages of separation and concentration are shown in table 2 below:
TABLE 2 composition of the solution in the two stages of brine field brine and separation and concentration in example II
The method of the embodiment realizes magnesium-lithium separation and efficient lithium enrichment of the sulfate type salt lake brine, and the finally obtained electrodialysis concentrated water (namely the second concentrated solution) can be directly used for preparing high-purity lithium salt due to the fact that the electrodialysis concentrated water has high lithium ion concentration. The yield of lithium ions in the whole magnesium-lithium separation process is more than 70%, and the yield of lithium ions in the whole lithium ion concentration process is more than 80%, so that the method of the embodiment can effectively improve the utilization rate of lithium ions in the whole process.
EXAMPLE III
The present embodiment provides a method for separating and enriching lithium, comprising the steps of:
pretreatment: the salt field old brine is diluted for the first time, the salt field old brine after being diluted for the first time is sent to a multi-medium filter to be filtered to remove partial mechanical impurities such as silt and the like, then is sent to an organic ultrafiltration system to be filtered to be completely purified, then is diluted for the second time, and the dilution multiple after being diluted for the two times is 15 times, so that the brine after pretreatment is obtained.
Separation: and (3) separating the pretreated brine through a nanofiltration separation system to obtain nanofiltration fresh water and nanofiltration concentrated water, wherein the concentration of lithium ions in the nanofiltration fresh water is 0.81g/L, the concentration of magnesium ions is reduced to 0.29g/L, and the mass ratio of the magnesium ions to the lithium ions is 0.36: 1. The method comprises the following steps:
the nanofiltration separation system adopts monovalent ion selective nanofiltration membranes, the nanofiltration separation system comprises two stages of nanofiltration separation devices, and each stage of nanofiltration separation device is formed by connecting three sections of nanofiltration separation units in series. The pretreated brine is subjected to magnesium-lithium separation by a three-section nanofiltration separation unit of a first-stage nanofiltration separation device, is further subjected to magnesium-lithium separation by a three-section nanofiltration separation unit of a second-stage nanofiltration separation device, and is subjected to two-stage nanofiltration separation operation to obtain nanofiltration fresh water and nanofiltration concentrated water, wherein the nanofiltration concentrated water is recycled by an energy recovery device so as to reduce the discharge of wastewater. In the nanofiltration separation device of the embodiment, the number ratio of the nanofiltration membranes of the three sections of nanofiltration separation units is 45-60: 30-50 in sequence, the operating pressure of the nanofiltration separation system is 4.0MPa, and the magnesium and lithium separation can be more effectively realized by adopting the number ratio of the nanofiltration membranes, and meanwhile, the nanofiltration separation of the embodiment can be performed under the ultrahigh pressure condition of 4.0MPa, so that the magnesium and lithium separation effect can be further improved, and the lithium ion content in the nanofiltration fresh water can be improved.
First concentration: and (3) carrying out primary concentration on the nanofiltration fresh water through a reverse osmosis system to obtain reverse osmosis concentrated solution and reverse osmosis fresh water, wherein the concentration of lithium ions in the reverse osmosis concentrated solution is 4.2g/L, and the mass ratio of magnesium ions to lithium ions is 0.36: 1. The method comprises the following steps:
the reverse osmosis system is formed by connecting three sections of reverse osmosis units in series, each section of reverse osmosis unit contains different numbers of reverse osmosis membranes, nanofiltration fresh water is subjected to primary concentration through each section of reverse osmosis unit in sequence to obtain reverse osmosis concentrated solution and reverse osmosis fresh water, and the reverse osmosis fresh water is circulated back to the pretreatment step and is used for diluting bittern in a salt field so as to improve the utilization rate of the reverse osmosis fresh water. In the reverse osmosis system of the embodiment, the number ratio of reverse osmosis membranes of the reverse osmosis units in each section is 35-43: 20-30: 20-28, and the operation pressure of the first concentration is 7.0 MPa. By adopting a mode of multiple sections and different reverse osmosis membrane quantity ratios, the transmittance of lithium in reverse osmosis fresh water can be fully reduced, and the enrichment of lithium in reverse osmosis concentrated solution is facilitated.
And (3) second concentration: and (2) adopting a homogeneous membrane as an ion selection membrane of the electrodialysis system, and performing secondary concentration on the reverse osmosis concentrated solution through the electrodialysis system to obtain electrodialysis concentrated water and electrodialysis fresh water, wherein the concentration of lithium ions in the electrodialysis concentrated water is 18g/L, and the mass ratio of magnesium ions to lithium ions is 0.36:1, so that the concentration of the lithium ions enriched in the embodiment reaches the concentration of the lithium ions required for preparing high-purity lithium salt after the secondary concentration. In addition, the electrodialysis fresh water is circulated back to the first concentration step and is used for concentrating lithium ions, specifically, the electrodialysis fresh water is mixed with the nanofiltration fresh water obtained from the separation step, and the recovery of residual lithium and the reutilization of the electrodialysis fresh water are realized through a reverse osmosis system of the first concentration.
The compositions of the brine used in this example and the solutions in the respective stages of separation and concentration are shown in table 3 below:
TABLE 3 composition of the solution in the third stage of brine field brine and separation and concentration
The method of the embodiment realizes magnesium-lithium separation and efficient lithium enrichment of the sulfate type salt lake brine, and the finally obtained electrodialysis concentrated water (namely the second concentrated solution) can be directly used for preparing high-purity lithium salt due to the fact that the electrodialysis concentrated water has high lithium ion concentration.
It should be understood that the above examples are only for illustrating the present invention and are not intended to limit the scope of the present invention. It should also be understood that after reading the technical content of the present invention, those skilled in the art can make appropriate changes to the conditions and steps in the technical solution of the invention to realize the final technical solution without departing from the principle of the present invention, and all the equivalent forms are also within the protection scope defined by the appended claims of the present application.
Claims (6)
1. A method for separating lithium and magnesium and enriching lithium, comprising the steps of:
pretreatment: diluting and filtering the old brine in the salt pan to obtain pretreated brine; after the salt pan old brine is diluted for the first time, sequentially sending the salt pan old brine into a multi-medium filter for filtering, sending the salt pan old brine into an ultrafiltration system for filtering, and then diluting for the second time to obtain the pretreated brine; the concentration of lithium ions in the salt pan old brine is 0.2-5.0 g/L, and the mass ratio of magnesium ions to lithium ions is 6-180: 1; the multiple of the first dilution of the old brine in the salt pan is 0.5-4.5 times, and the multiple of the second dilution after the filtration by the ultrafiltration system is 3.5-20 times;
separation: separating the pretreated brine through a nanofiltration separation system to obtain nanofiltration fresh water and nanofiltration concentrated water;
first concentration: performing primary concentration on the nanofiltration fresh water through a reverse osmosis system to obtain reverse osmosis concentrated solution and reverse osmosis fresh water;
and (3) second concentration: performing secondary concentration on the reverse osmosis concentrated solution through an electrodialysis system to obtain electrodialysis concentrated water and electrodialysis fresh water, wherein the electrodialysis concentrated water is a solution enriched with lithium ions;
in the separation step, the nanofiltration separation system comprises two stages of nanofiltration separation devices, each stage of nanofiltration separation device is formed by connecting three sections of nanofiltration separation units in series, and the number ratio of nanofiltration membranes of the three sections of nanofiltration separation units in any stage of nanofiltration separation device is 55-65: 52-68: 35-45; the pretreated brine firstly passes through a plurality of sections of nanofiltration separation units of a first-stage nanofiltration separation device to carry out magnesium-lithium separation, and then passes through a plurality of sections of nanofiltration separation units of a next-stage nanofiltration separation device to carry out magnesium-lithium separation; the operating pressure of the nanofiltration separation system is 3.6-4.0 MPa, the concentration of lithium ions in the nanofiltration fresh water is 0.5-1.2 g/L, and the mass ratio of magnesium ions to lithium ions in the nanofiltration fresh water is 0.05-0.2: 1.
2. The method of claim 1, wherein in the step of separating, the nanofiltration separation system employs a monovalent ion selective nanofiltration membrane, and the resulting nanofiltration concentrated water is recycled by an energy recovery device.
3. The method of claim 1, wherein the reverse osmosis system comprises a plurality of sections of reverse osmosis units connected in series, the nanofiltration fresh water is subjected to a first concentration by each section of reverse osmosis unit in sequence to obtain the reverse osmosis concentrated solution and the reverse osmosis fresh water, and the reverse osmosis fresh water is recycled to the pretreatment step and is used for diluting the saltern bittern.
4. The method according to claim 3, wherein the reverse osmosis system is composed of three sections of reverse osmosis units connected in series, and the number ratio of reverse osmosis membranes of each section of reverse osmosis unit is 22-62: 15-45: 5-43; the operating pressure in the first concentration step is 2.0-10.0 MPa, the concentration of lithium ions in the obtained reverse osmosis concentrated solution is 2.0-10 g/L, and the mass ratio of magnesium ions to lithium ions in the reverse osmosis concentrated solution is 0.05-3.0: 1.
5. The method of claim 1, wherein in the step of electrodialysis, the ion selective membrane employed by the electrodialysis system is one of a homogeneous membrane, a semi-homogeneous membrane, or a heterogeneous membrane; the electrodialysis fresh water is recycled to the first concentration step for concentrating lithium ions; the concentration of lithium ions in the electrodialysis concentrated water is 8 g/L-21 g/L, and the mass ratio of magnesium ions to lithium ions in the electrodialysis concentrated water is 0.05-1.0: 1.
6. The process of claim 5, wherein, in the step of electrodialysis, the ion-selective membrane used in the electrodialysis system is a homogeneous membrane, and the cation-selective membrane is a CMX homogeneous membrane and the anion-selective membrane is an AMX homogeneous membrane; the concentration of lithium ions in the electrodialysis concentrated water is 14 g/L-21 g/L, and the mass ratio of magnesium ions to lithium ions in the electrodialysis concentrated water is 0.07-0.2: 1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811180004.7A CN108946770B (en) | 2018-10-10 | 2018-10-10 | Method for separating lithium and magnesium and enriching lithium |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201811180004.7A CN108946770B (en) | 2018-10-10 | 2018-10-10 | Method for separating lithium and magnesium and enriching lithium |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN108946770A CN108946770A (en) | 2018-12-07 |
| CN108946770B true CN108946770B (en) | 2020-01-10 |
Family
ID=64480794
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201811180004.7A Active CN108946770B (en) | 2018-10-10 | 2018-10-10 | Method for separating lithium and magnesium and enriching lithium |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN108946770B (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109824065B (en) * | 2019-03-06 | 2020-10-02 | 中国科学院青海盐湖研究所 | Method for separating magnesium and lithium and enriching lithium |
| CN110002476B (en) | 2019-04-12 | 2021-05-25 | 中国科学院青海盐湖研究所 | Preparation method of lithium hydroxide |
| CN112079368A (en) * | 2019-06-12 | 2020-12-15 | 中能实用小微科学科技有限公司 | Method for extracting lithium with low energy consumption and high purity by multi-stage recovery |
| CN114890591A (en) * | 2022-04-02 | 2022-08-12 | 倍杰特集团股份有限公司 | Water treatment system and method without reducing ion content |
| CN114890592A (en) * | 2022-04-02 | 2022-08-12 | 倍杰特集团股份有限公司 | Device and method for recycling lithium-containing wastewater |
| CN114702189A (en) * | 2022-04-02 | 2022-07-05 | 倍杰特集团股份有限公司 | Wastewater filtering treatment system and method |
| CN115385497A (en) * | 2022-09-02 | 2022-11-25 | 碧菲分离膜（大连）有限公司 | Method for extracting lithium from seawater |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101979339A (en) * | 2010-09-29 | 2011-02-23 | 清华大学 | Method and device for removing arsenic and fluorine in water using flocculant combined with nanofiltration membrane system |
| CN102976367B (en) * | 2012-12-20 | 2014-10-22 | 青海锂业有限公司 | Method for preparing battery-level lithium carbonate by using salt lake brine |
| CN106865582B (en) * | 2017-02-17 | 2018-10-09 | 中国科学院青海盐湖研究所 | A kind of method of enriching lithium in salt lake brine containing lithium |
| CN107720785A (en) * | 2017-10-18 | 2018-02-23 | 中国科学院青海盐湖研究所 | A kind of LITHIUM BATTERY lithium hydroxide preparation method based on UF membrane coupled method |
| CN107720786A (en) * | 2017-10-18 | 2018-02-23 | 中国科学院青海盐湖研究所 | A kind of LITHIUM BATTERY lithium hydroxide preparation method based on UF membrane coupled method |
| CN108314064B (en) * | 2018-02-09 | 2020-04-07 | 陕西省膜分离技术研究院有限公司 | Full-membrane separation method for producing lithium extraction mother liquor by multi-stage membrane concentration of salt lake brine |
| CN108264066A (en) * | 2018-03-22 | 2018-07-10 | 何朋飞 | A kind of new process of salt lake bittern production high-purity lithium chloride |
-
2018
- 2018-10-10 CN CN201811180004.7A patent/CN108946770B/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| CN108946770A (en) | 2018-12-07 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN108996527B (en) | Method for separating and enriching lithium | |
| CN109437252B (en) | Method for efficiently separating and enriching lithium | |
| CN108946770B (en) | Method for separating lithium and magnesium and enriching lithium | |
| CN109368670B (en) | Method for separating and enriching lithium | |
| CN109824065B (en) | Method for separating magnesium and lithium and enriching lithium | |
| CN106865582B (en) | A kind of method of enriching lithium in salt lake brine containing lithium | |
| CN107954528B (en) | Method for producing concentrated brine from sea salt | |
| CN112661321B (en) | Salt lake lithium extraction system and method based on membrane separation | |
| CN107399747B (en) | Method and device for extracting lithium from salt lake brine with high magnesium-lithium ratio | |
| CN114105173B (en) | System and process for extracting lithium from salt lake brine | |
| CN108314065B (en) | Full-membrane separation method for producing lithium extraction mother liquor by multi-stage nanofiltration separation of salt lake brine | |
| CN108314064B (en) | Full-membrane separation method for producing lithium extraction mother liquor by multi-stage membrane concentration of salt lake brine | |
| CN105585195A (en) | Coal chemical high-salinity wastewater treatment and recycling system | |
| CN114870633B (en) | Process for enriching lithium in salt lake brine | |
| CN208008625U (en) | A kind of reverse osmosis concentrated water divides salt concentration systems | |
| CN214060200U (en) | Salt lake lithium extraction system based on membrane separation | |
| CN211620231U (en) | Device for efficient desalination and comprehensive utilization of seawater | |
| CN112159005A (en) | Treatment process and treatment system for aluminum processing anode waste liquid | |
| CN218637035U (en) | Concentrated edulcoration device of analytic qualified liquid of salt lake absorption | |
| CN217264876U (en) | Enrichment system of lithium in salt lake brine | |
| CN102728230B (en) | Membrane system and treatment method for resource recovery and zero emission of manganese-containing wastewater and application of membrane system | |
| CN112062222A (en) | High enriched brine decompression concentration system | |
| CN114622103A (en) | A membrane method for lithium extraction from salt lake brine | |
| CN219631035U (en) | Salt lake lithium-titanium adsorbent analysis qualified liquid concentration impurity removal system | |
| CN118084270B (en) | Method for synchronously separating impurity boron and silicon by extracting lithium from carbonate type salt lake |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |