A method for co-producing lithium phosphate and magnesium-based functional materials

Abstract

The present invention discloses a method for co-producing lithium phosphate and magnesium-based functional materials. The method comprises: subjecting salt lake brine to primary adsorption-desorption and secondary adsorption-desorption treatment in sequence to obtain a mixed desorption liquid; subjecting the mixed desorption liquid to a forward osmosis primary concentration treatment to obtain a primary concentrated liquid and forward osmosis fresh water; subjecting the primary concentrated liquid to a high-pressure reverse osmosis secondary concentration treatment to obtain a secondary concentrated liquid and reverse osmosis fresh water; mixing the secondary concentrated liquid with aluminum salt and alkaline solution to a first coprecipitation reaction to obtain a magnesium-based functional material and a filtrate; subjecting the filtrate to a boron removal treatment by an ion exchange method to obtain a boron-removed lithium-rich solution and boric acid; and subjecting the boron-removed lithium-rich solution to a lithium precipitation treatment by an ultrasonic precipitation-ultrasonic coupling method to obtain battery-grade lithium phosphate. The method provided by the present invention realizes the co-production of lithium phosphate and magnesium-based functional materials, and at the same time realizes the comprehensive, green, efficient and high-value development and utilization of salt lake resources.

Description

Technical Field

[0001] The invention belongs to the technical field of comprehensive utilization of salt lake resources, and relates to a method for co-producing lithium phosphate and magnesium-based functional materials, and specifically relates to a method for co-producing lithium phosphate and magnesium-based functional materials by multi-stage adsorption and lithium extraction. Background Art

[0002] Lithium (Li) is the lightest metal element in nature. It is silvery white and has unique physical and chemical properties such as high specific heat, high electrical conductivity and strong chemical activity. It has a wide range of uses. In recent years, with the rapid development of new energy vehicles, the demand for lithium batteries and lithium power batteries has increased, and the demand for lithium has also increased sharply. In nature, lithium resources are mainly found in solid ores and liquid brines. The important position of brine lithium resources in the development of lithium resources in the world has been established for nearly 40 years. It has attracted the attention of the lithium resource development industry in terms of application and extraction of lithium compounds. At present, the main processes for extracting lithium from salt lake brine are precipitation, solvent extraction, adsorption, calcination, electrodialysis, nanofiltration and solar pool. The adsorption method has greater advantages than other methods from the perspective of environment and economy. The adsorption method uses an adsorbent that selectively adsorbs lithium ions to adsorb lithium ions, and then elutes the lithium ions, thereby achieving the purpose of separating lithium ions from other impurity ions. However, the existing process of extracting lithium from salt lakes by adsorption is mostly single-stage multi-column adsorption. The magnesium-lithium ratio in the desorption solution after adsorption is high. The subsequent process requires nanofiltration technology for secondary magnesium-lithium separation to further reduce the magnesium-lithium ratio. The process is complex and costly. The lithium concentration in the desorption is less than 500 mg / L. It needs to be concentrated multiple times before lithium salt can be prepared. The concentration multiple is large, the energy consumption is high, and the cost is high. After the secondary magnesium removal, the lithium-containing solution is concentrated by reverse osmosis, which consumes a lot of energy. Therefore, from the perspective of comprehensive, green, efficient and high-value development of salt lake resources, it is urgent to solve the problems of complex processes and high costs in the existing technology. Summary of the invention

[0003] The main purpose of the present invention is to provide a method for co-producing lithium phosphate and magnesium-based functional materials to overcome the shortcomings of the prior art.

[0004] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes:

[0005] An embodiment of the present invention provides a method for co-producing lithium phosphate and magnesium-based functional materials, which includes:

[0006] The salt lake brine is sequentially subjected to primary adsorption-desorption and secondary adsorption-desorption treatment to obtain a mixed desorption liquid; wherein the mixed desorption liquid comprises a primary desorption liquid and a secondary desorption liquid, the brine after potassium extraction from the salt lake brine, the magnesium-lithium ratio in the brine after potassium extraction is 5-500, and the lithium ion concentration is 0.5-10 g / L; the lithium ion concentration in the mixed desorption liquid is 0.4-1.5 g / L, and the magnesium-lithium ratio is 0.1-0.4;

[0007] Performing forward osmosis primary concentration treatment on the mixed desorption liquid to obtain a primary concentrated liquid and forward osmosis fresh water;

[0008] Performing high-pressure reverse osmosis secondary concentration treatment on the primary concentrated liquid to obtain secondary concentrated liquid and reverse osmosis fresh water;

[0009] The secondary concentrated liquid is mixed with aluminum salt and alkaline solution to carry out a first coprecipitation reaction to obtain a magnesium-based functional material and a filtrate;

[0010] The filtrate is subjected to a boron removal treatment by an ion exchange method to obtain a boron-removed lithium-rich solution and boric acid;

[0011] Furthermore, the boron-removed lithium-rich solution is subjected to lithium precipitation treatment by ultrasonic precipitation-ultrasonic coupling method to obtain battery-grade lithium phosphate.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention develops a multi-stage multi-column adsorption process coupled with titanium, manganese and aluminum adsorbents, which not only reduces the magnesium-lithium ratio in the desorption solution, but also increases the concentration of lithium in the desorption solution. The desorption solution does not need to be separated from magnesium and lithium again, and is directly concentrated by forward osmosis, which shortens the process flow, reduces energy consumption, reduces costs, and improves the recovery rate of lithium resources in salt lakes. At the same time, the present invention comprehensively considers the synergistic extraction of lithium, magnesium and boron resources in salt lakes, prepares battery-grade lithium phosphate in one step, and co-produces magnesium-based functional materials and boric acid, realizing the comprehensive, green, efficient and high-value development and utilization of salt lake resources, and reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0014] Figure 1 It is a schematic diagram of the process of co-producing lithium phosphate and magnesium-based functional materials in a typical implementation scheme of the present invention. DETAILED DESCRIPTION

[0015] In view of the defects of the prior art, the inventors of this case have proposed the technical solution of the present invention after long-term research and extensive practice. The main purpose is to develop a multi-stage multi-column adsorption process coupled with titanium, manganese and aluminum adsorbents, which not only reduces the magnesium-lithium ratio in the desorption solution, but also increases the concentration of lithium in the desorption solution. The desorption solution does not need to be separated from magnesium and lithium again, and forward osmosis is directly used for primary concentration, which shortens the process flow, reduces energy consumption, reduces costs, and improves the recovery rate of lithium resources in salt lakes.

[0016] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] Specifically, as one aspect of the technical solution of the present invention, a method for co-producing lithium phosphate and magnesium-based functional materials includes:

[0018] The salt lake brine is sequentially subjected to primary adsorption-desorption and secondary adsorption-desorption treatment to obtain a mixed desorption liquid; wherein the mixed desorption liquid comprises a primary desorption liquid and a secondary desorption liquid, the brine after potassium extraction from the salt lake brine, the magnesium-lithium ratio in the brine after potassium extraction is 5-500, and the lithium ion concentration is 0.5-10 g / L; the lithium ion concentration in the mixed desorption liquid is 0.4-1.5 g / L, and the magnesium-lithium ratio is 0.1-0.4;

[0019] Performing forward osmosis primary concentration treatment on the mixed desorption liquid to obtain a primary concentrated liquid and forward osmosis fresh water;

[0020] Performing high-pressure reverse osmosis secondary concentration treatment on the primary concentrated liquid to obtain secondary concentrated liquid and reverse osmosis fresh water;

[0021] The secondary concentrated liquid is mixed with aluminum salt and alkaline solution to carry out a first coprecipitation reaction to obtain a magnesium-based functional material and a filtrate;

[0022] The filtrate is subjected to a boron removal treatment by an ion exchange method to obtain a boron-removed lithium-rich solution and boric acid;

[0023] Furthermore, the boron-removed lithium-rich solution is subjected to lithium precipitation treatment by ultrasonic precipitation-ultrasonic coupling method to obtain battery-grade lithium phosphate.

[0024] In some preferred embodiments, the schematic diagram of the process of co-producing lithium phosphate and magnesium-based functional materials from salt lake brine in the present invention is as follows Figure 1 shown.

[0025] Specifically, the method for multi-stage adsorption of lithium to produce lithium phosphate and magnesium-based functional materials comprises:

[0026] (1) After pre-treatment to remove impurities such as silt and organic matter, the salt lake brine enters the primary adsorption system for adsorption. After adsorption, the saturated adsorption column is washed with water. The primary adsorption washing liquid returns to the primary adsorption to recover lithium. After washing, the saturated titanium adsorption column is desorbed with a primary desorbent to obtain a primary desorbent. After desorption, the adsorption column is washed with water and enters the next cycle. The primary washing liquid after desorption is used to wash the saturated adsorption column. After adsorption, the tail liquid enters the secondary adsorption system for secondary adsorption after pH adjustment. The adsorption tail liquid is discharged to the salt field. After the secondary adsorption, the saturated aluminum adsorption column is washed with water and desorbed with a secondary desorbent to obtain a secondary desorbent. The secondary desorbent is mixed with the primary desorbent to obtain a mixed desorbent, which enters the next process.

[0027] (2) Forward osmosis for primary concentration

[0028] The mixed desorption liquid obtained above enters the forward osmosis system for primary concentration to obtain the primary concentrated liquid and forward osmosis fresh water, which enter the next stage process and are returned for primary and secondary adsorption washing water respectively.

[0029] (3) High-pressure reverse osmosis for secondary concentration

[0030] The primary concentrated liquid obtained in the previous step enters the high-pressure reverse osmosis system for secondary concentration to obtain a secondary concentrated lithium-rich solution (i.e., the aforementioned "secondary concentrated liquid") and reverse osmosis fresh water. The secondary concentrated liquid enters the next stage of the process, and the reverse osmosis fresh water is blended with the mixed desorption liquid to achieve the recovery of residual lithium and the reuse of fresh water through the forward osmosis system.

[0031] (4) Deep removal of magnesium to prepare magnesium-based functional materials

[0032] A certain ratio of soluble aluminum salt is added to the secondary concentrated lithium-rich solution to prepare a mixed salt solution, and a mixed alkaline solution of sodium carbonate and sodium hydroxide undergoes a first coprecipitation reaction under certain conditions; after nucleation of the coprecipitation reaction, solid-liquid separation is performed to obtain a filter cake and a filtrate; after solid-liquid separation, the filter cake is washed and dried to obtain a white solid MgAl-LDH product; the filtrate is used for the next process of ion exchange method for boron removal.

[0033] The magnesium-based functional material in this application is a double metal hydroxide with a layered structure. The metal elements are arranged alternately on the layers, and anions can be inserted between the layers, forming a large class of important layered functional materials. It is widely used in the fields of highly dispersed catalysis, selective adsorption, functional additives (flame retardants, UV blockers, thermal stabilizers, etc.), biomedicine, etc.

[0034] (5) Boron removal by ion exchange

[0035] The filtrate is passed through an ion exchange column filled with boron-specific resin to enrich boron in the ion exchange column, so that the boron content in the effluent is below 5 ppm, and a boron-free lithium-rich solution is obtained for the preparation of lithium phosphate for batteries in the next process. The boron-saturated adsorption column is used for the production of boric acid.

[0036] (6) Preparation of battery-grade lithium phosphate by precipitation-ultrasonic coupling

[0037] A sodium carbonate solution is added to the boron-removed lithium-rich solution at a certain flow rate, and a second coprecipitation reaction is carried out under certain pH, ultrasonic and temperature conditions. A solid lithium phosphate product is obtained through the steps of nucleation, aging, filtration, washing and drying.

[0038] In some preferred embodiments, the method specifically comprises:

[0039] The salt lake brine is placed in a primary adsorption system for primary adsorption treatment, and then the saturated adsorption column is washed with water, and then the saturated adsorption column is subjected to primary desorption treatment using a primary desorbent to obtain a primary desorption liquid and a primary tail liquid; wherein the primary adsorption system is an adsorption system filled with a titanium or manganese adsorbent; and the concentration of lithium ions in the primary tail liquid is 0.2-0.4 g / L;

[0040] The pH value of the primary tail liquid is adjusted to 3-6 and placed in a secondary adsorption system for secondary adsorption treatment, after which the saturated adsorption column is washed with water, and then the saturated adsorption column is subjected to secondary desorption treatment using a secondary desorbent to obtain a secondary desorption liquid and a secondary tail liquid; wherein the secondary adsorption system is an adsorption system filled with an aluminum-based adsorbent; and the concentration of lithium ions in the secondary tail liquid is less than 20 ppm

[0041] And, the primary desorption liquid is mixed with the secondary desorption liquid to obtain the mixed desorption liquid; wherein the volume ratio of the primary desorption liquid to the secondary desorption liquid in the mixed desorption liquid is 1:1 to 5:1.

[0042] Furthermore, the primary adsorption treatment uses 3 to 10 multi-column adsorption.

[0043] Furthermore, the first-stage desorption treatment adopts 2 to 5 multi-column desorption.

[0044] Furthermore, the primary desorbent includes hydrochloric acid and / or sulfuric acid.

[0045] Furthermore, the concentration of the primary desorbent is 0.05-2.0 mol / L.

[0046] Furthermore, the secondary adsorption treatment uses 2 to 5 multi-column adsorption.

[0047] Furthermore, the secondary desorption treatment adopts 1 to 3 multi-column desorption.

[0048] Furthermore, the secondary desorption agent includes water; preferably, the temperature of the secondary desorption treatment is 35-70°C.

[0049] In some preferred embodiments, the method specifically comprises: placing the mixed desorption liquid in a forward osmosis system for primary concentration treatment to obtain a primary concentrated liquid and forward osmosis fresh water; wherein the concentration of lithium ions in the primary concentrated liquid is 1.5 to 3.0 g / L; the forward osmosis draw liquid used in the forward osmosis system comprises a saturated magnesium chloride solution or a saturated sodium chloride solution; the concentration of lithium ions in the forward osmosis fresh water is 0.005 to 0.10 g / L; the volume ratio of the mixed desorption liquid to the primary concentrated liquid is 2.0:1 to 4:1; the forward osmosis membrane used in the forward osmosis system comprises a CTA membrane and / or a TFC membrane.

[0050] In some preferred embodiments, the method specifically includes: placing the primary concentrated liquid in a high-pressure reverse osmosis system for secondary concentration treatment to obtain a secondary concentrated liquid and reverse osmosis fresh water; wherein the high-pressure reverse osmosis system adopts a multi-stage reverse osmosis device; the concentration of lithium ions in the secondary concentrated liquid is 5 to 10 g / L; the volume ratio of the secondary concentrated liquid to the primary concentrated liquid is 0.5:1 to 6:1; the concentration of lithium ions in the reverse osmosis fresh water is 0.005 to 0.10 g / L; the mass ratio of Mg to Li in the reverse osmosis fresh water is 0.01-1:1.

[0051] Furthermore, the secondary concentration unit in the high-pressure reverse osmosis system adopts a two-stage series connection.

[0052] Furthermore, the operating pressure of the secondary concentration unit in the high-pressure reverse osmosis system is 1.0-10.0 MPa.

[0053] Furthermore, the reverse osmosis membrane used in the high-pressure reverse osmosis system includes Dow BW membrane and / or SW membrane.

[0054] In some preferred embodiments, the method specifically comprises: adding aluminum salt to the secondary concentrated solution to form a mixed salt solution, then adding an alkaline solution and performing a first coprecipitation reaction under the conditions of pH 8 to 13, a stirring rate of 50 to 200 rpm, and a temperature of 25 to 70° C., followed by aging, separation, washing, and drying to obtain a magnesium-based functional material and a filtrate; wherein the Mg in the mixed salt solution is 2+ With Al 3+ The molar ratio is 2 to 4:1; the aluminum salt includes any one of aluminum nitrate, aluminum sulfate, and aluminum chloride, or a combination of two or more thereof; and the alkaline solution includes a mixed alkaline solution of sodium carbonate and sodium hydroxide.

[0055] Furthermore, the volume of the mixed salt solution is the same as that of the alkaline solution.

[0056] Furthermore, the content of magnesium ions in the filtrate is below 10 ppm.

[0057] In some preferred embodiments, the method specifically comprises: passing the filtrate into an ion exchange column filled with a boron-specific resin to obtain a boron-removed lithium-enriched solution and a boron-saturated adsorption column; wherein the boron content in the boron-removed lithium-enriched solution is below 5 ppm.

[0058] Furthermore, the boron saturated adsorption column is desorbed to obtain a boric acid solution, and the boric acid solution is evaporated and crystallized to prepare boric acid.

[0059] Furthermore, the boron special effect resin includes any one of LSC-800, D403, D564, and XSC-700, or a combination of two or more thereof.

[0060] In some preferred embodiments, the method specifically includes: adding sodium phosphate solution to the deborated lithium-rich solution, and conducting a second coprecipitation reaction under the conditions of an ultrasonic frequency of 10 to 50 kHz, an ultrasonic power of 100 to 1000 W, a pH of 8 to 12, a stirring rate of 50 to 200 rpm, and a temperature of 80 to 110°C, followed by nucleation, aging, filtering, washing, and drying to obtain battery-grade lithium phosphate; wherein the concentration of lithium ions in the deborated lithium-rich solution is 5 to 10 g / L.

[0061] Furthermore, the ultrasonic wave frequency is 20-40 kHz.

[0062] Furthermore, the ultrasonic power is 300-800W.

[0063] Furthermore, the stirring rate is 100-150 rpm.

[0064] Furthermore, the temperature is 90-100°C.

[0065] Furthermore, the ultrasonic time during the second coprecipitation reaction is 10 to 60 minutes.

[0066] Furthermore, the mass concentration of the sodium phosphate solution is 10-30%, preferably 18-25%.

[0067] Furthermore, the washing liquid used in the washing treatment includes water and a dispersant, and the dispersant includes polyethylene glycol and / or ethanol dispersant.

[0068] In some preferred embodiments, the method further comprises: pre-treating the salt lake brine at least to remove silt or organic matter; wherein the turbidity of the solution obtained after the pre-treatment is less than 3NTU.

[0069] Furthermore, the pretreatment is performed by any one of ultrafiltration, ceramic filtration and polyceramic membrane filtration.

[0070] In some preferred embodiments, the purity of the battery-grade lithium phosphate is above 99.5%, and the particle size of the battery-grade lithium phosphate is below 8 μm.

[0071] In some more specific embodiments, the method for multi-stage adsorption of lithium to co-produce lithium phosphate and magnesium-based functional materials comprises:

[0072] (1) After pretreatment, the salt lake brine is subjected to impurities such as silt and organic matter, and then enters the primary adsorption system for adsorption. After adsorption, the saturated adsorption column is washed with water, and the primary adsorption washing liquid is returned to the primary adsorption system to recover lithium. After washing, the saturated titanium or manganese adsorption column is desorbed with a primary desorbent to obtain a primary desorbent. The desorbed adsorption column is washed with water and enters the next cycle. The primary washing liquid after desorption is used to prepare the primary desorbent. After the adsorption, the tail liquid enters the secondary adsorption system for secondary adsorption after the pH is adjusted. The adsorption tail liquid is discharged to the salt field. After the secondary adsorption, the saturated aluminum adsorption column is washed with water, and after washing, it is desorbed with a secondary desorbent to obtain a secondary desorbent. The secondary desorbent is mixed with the primary desorbent to obtain a mixed desorbent and enter the next process. The salt lake brine is brine after potassium extraction, with a magnesium-lithium ratio of 5-500g / L and a lithium concentration of 0.5-10g / L; the pretreatment is one of ultrafiltration, ceramic filtration or polyceramic membrane filtration, and the turbidity in the brine after pretreatment is less than 3NTU; the primary adsorption system is an adsorption system filled with titanium or manganese adsorbents, the adsorption column for primary lithium adsorption is 2-10 multi-column adsorption, and the primary desorption column is 2-5 multi-column desorption; the primary desorbent is hydrochloric acid or sulfuric acid, and the concentration of hydrochloric acid or sulfuric acid is 0.05-2.0mol / L; the tail liquid after adsorption is adjusted to pH 3-6 before entering A two-stage adsorption system, wherein the concentration of lithium in the tail liquid of the first adsorption is 0.2-0.4 g / L; the second adsorption system is an adsorption system filled with an aluminum-based adsorbent, the adsorption column for the second-stage adsorption of lithium is 2-5 multi-column adsorption, and the secondary desorption column is 1-3 multi-column desorption; the secondary desorbent contains pure water, and the secondary desorption temperature is 35-70°C; the mixed volume ratio of the first desorption liquid to the secondary desorption liquid is 1:1-5:1, the lithium concentration in the desorption liquid is 0.4-1.5 g / L, and the magnesium-lithium ratio in the desorption liquid is 0.1-0.4; the lithium concentration in the tail liquid of the secondary adsorption is less than 20 ppm.

[0073] (2) Forward osmosis for primary concentration

[0074] The mixed desorption liquid obtained above enters the forward osmosis system for primary concentration to obtain a primary concentrated liquid and forward osmosis fresh water, which enter the next stage process and are returned for primary and secondary adsorption washing respectively. The lithium concentration in the forward osmosis primary concentrated liquid is 1.5-3.0 g / L, the forward osmosis draw liquid is a saturated magnesium chloride or saturated sodium chloride solution prepared from salt lake magnesium chloride or sodium chloride, the forward osmosis fresh water returns to the secondary adsorption system for secondary washing, the lithium ion content in the forward osmosis fresh water is 0.005-0.10 g / L, the concentration volume ratio (mixed desorption liquid solution volume / primary concentrated liquid) is 2.0:1-4:1, and the forward osmosis membrane is one or both of a CTA membrane or a TFC membrane.

[0075] (3) High-pressure reverse osmosis for secondary concentration

[0076] The primary concentrated lithium-containing solution obtained above enters the high-pressure reverse osmosis system for secondary concentration. The primary concentrated solution obtained through the separation unit is secondary concentrated using a multi-stage reverse osmosis device to further increase the lithium ion concentration and produce fresh water. The reverse osmosis fresh water is blended with the mixed desorption liquid, and the residual lithium is recovered and the fresh water is reused through the forward osmosis system. The high-pressure reverse osmosis concentrated solution enters the deep magnesium removal unit. The secondary concentration unit adopts the form of two sections in series, each section contains a different number of reverse osmosis membranes, and the ratio of reverse osmosis membranes between different sections is 1:1~7:1. After secondary concentration by high-pressure reverse osmosis, the lithium ion content in the reverse osmosis concentrate is 5~10g / L; the lithium ion content in the reverse osmosis fresh water is 0.005~0.10g / L; the Mg / Li mass ratio is 0.01-1 and the concentration volume ratio (volume of the primary concentrated lithium-containing solution / primary concentrated solution) is 0.5:1~6:1; the operating pressure during the secondary concentration unit process is 1.0~10.0MPa; the reverse osmosis membrane is one or both of Dow BW membrane or SW membrane.

[0077] (4) Deep removal of magnesium to prepare magnesium-based functional materials

[0078] A certain proportion of soluble aluminum salt is added to the secondary concentrated lithium-rich solution to prepare a mixed salt solution, and the mixed salt solution is dripped into a mixed alkaline solution of sodium carbonate and sodium hydroxide under certain pH, temperature and flow rate conditions to perform a coprecipitation reaction; after the coprecipitation reaction is nucleated, the solution is aged under stirring and at a certain temperature and then solid-liquid separation is performed to obtain a filter cake and a filtrate; after solid-liquid separation, the filter cake is washed and dried to obtain a white solid MgAl-LDH product; the content of magnesium ions in the magnesium-rich solution does not exceed 10ppm, and the magnesium-rich solution is used for the next step of ion exchange resin boron removal. The mixed salt solution is a solution prepared by adding a certain proportion of soluble aluminum salt to the lithium-rich solution, wherein Mg 2+ With Al 3+The molar ratio of is 2 to 4, the aluminum salt is one of aluminum nitrate, aluminum sulfate, and aluminum chloride; the volume of the mixed alkali solution is the same as the volume of the mixed salt solution, the reaction is a constant pH method, the pH is maintained at 8 to 13, and the reaction temperature is 25°C to 70°C.

[0079] (5) Boron removal by ion exchange

[0080] The filtrate is passed through an ion exchange column filled with a boron-specific resin to enrich boron in the ion exchange column, so that the boron content in the effluent is below 5 ppm, and a boron-free lithium-enriched solution is obtained for the preparation of lithium phosphate for batteries in the next process. The boron-specific resin is one of LSC-800, D403, D564 or XSC-700, and the boron saturated adsorption column is used for boric acid production.

[0081] (6) Preparation of battery-grade lithium phosphate by precipitation-ultrasonic coupling

[0082] Add sodium carbonate solution to the deborated lithium-rich solution at a certain flow rate, and perform a coprecipitation reaction under certain pH, ultrasonic and temperature conditions. After nucleation, aging, filtration, washing, drying and other steps, a solid lithium phosphate product is obtained. Add sodium phosphate solution to the deborated lithium-rich solution at a certain flow rate to perform a coprecipitation reaction to form lithium phosphate nuclei, i.e., lithium phosphate nucleation process. The lithium-rich solution Li--concentration is 5-10g / L; ultrasonic waves are introduced during the reaction stage, and the ultrasonic frequency is 10-50kHZ, preferably 20-40kHZ; ultrasonic power is 100-1000W, preferably 300-800W, and ultrasonic time is 10-60min; the reaction pH value is controlled between 8 and 12; the mass concentration of sodium phosphate is 10-30%, preferably 18-25%; the amount of sodium phosphate is 10-30% in excess, preferably 10-30% in excess. The stirring rate is 50-200 rpm, preferably 100-150 rpm; the reaction temperature is 80-110° C., preferably 90-100° C.; after aging, the slurry is solid-liquid separated, and after solid-liquid separation, the filter cake is washed and dried to obtain a white solid battery-grade lithium phosphate product, wherein the washing is 2 slurry washings, the washing liquid is deionized water, and a small amount of polyethylene glycol or ethanol dispersant is added, and the main content of the prepared lithium phosphate is ≥99.5%, and the particle size is ≤8 μm.

[0083] The invention comprehensively considers the synergistic extraction of lithium, magnesium and boron resources in salt lakes, prepares battery-grade lithium phosphate in one step, and simultaneously co-produces magnesium-based functional materials and boric acid, thereby realizing the comprehensive, green, efficient and high-value development and utilization of salt lake resources and reducing production costs; the invention adopts multi-stage multi-column adsorption-forward osmosis-high-pressure reverse osmosis-co-precipitation to remove magnesium-ion exchange method to remove boron-precipitation-ultrasonic coupling reaction crystallization technology to separate magnesium and lithium, concentrate and enrich lithium, and prepare battery-grade lithium phosphate and co-produce magnesium-based functional materials and boric acid, which has never been reported.

[0084] The technical solution of the present invention is further described in detail below in conjunction with several preferred embodiments and drawings. This embodiment is implemented on the premise of the technical solution of the invention, and a detailed implementation method and specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

[0085] Unless otherwise specified, the experimental materials used in the following examples can be purchased from conventional biochemical reagent companies.

[0086] Example 1

[0087] The salt lake brine used in this embodiment is old brine from a sulfate salt lake in Qinghai, in which the Li+ concentration is 1.5 g / L and the magnesium-lithium ratio is 100.

[0088] The old brine from a sulfate salt lake in Qinghai was ultrafiltrated to reduce the turbidity to below 3 and then entered the primary adsorption system equipped with titanium adsorbent. After 3 columns of adsorption in series, the saturated adsorption column was washed with water. After washing, the saturated lithium saturated adsorption column was desorbed by 2 columns with 0.1 mol / L hydrochloric acid to obtain a primary desorption liquid. The pH of the primary adsorption tail liquid with a lithium concentration of 0.2 g / L was adjusted to 4 and then entered the secondary adsorption system equipped with aluminum adsorbent. After 2 columns of adsorption, the lithium concentration of the secondary adsorption tail liquid was reduced to below 20 ppm and discharged to the salt field. The secondary adsorption saturated aluminum adsorption column was washed with water and then desorbed by 1 column with pure water at 35°C to obtain a secondary desorption liquid. The primary desorption liquid and the secondary desorption liquid were mixed at a ratio of 1:1 to obtain a mixed desorption liquid. The lithium concentration in the mixed desorption liquid was 0.7 g / L and the magnesium-lithium ratio was 0.1. The mixed desorption liquid enters the forward osmosis primary concentration system. The forward osmosis draw liquid is a saturated solution of sodium chloride prepared from salt lakes. The mixed desorption liquid is forward osmosis through a CTA membrane to concentrate the lithium concentration to 1.5g / L to obtain a primary concentrate. The lithium concentration in the fresh water is controlled at 0.005g / L, and the concentration ratio is 2:1. The primary concentrate enters the high-pressure reverse osmosis system for secondary concentration to obtain a secondary concentrate with a lithium ion content of 5g / L and a magnesium-lithium ratio of 0.1; the lithium ion content in the secondary fresh water is 0.10g / L. The reverse osmosis membrane used in the reverse osmosis system is the Dow BW series. The first and second stage membranes are prepared at a ratio of 1:1. The membrane inlet pressure is controlled at 1Mpa and the concentration volume ratio (primary concentrate / secondary concentrate) is 1. The obtained high-pressure reverse osmosis fresh water is directly mixed with the mixed desorption liquid. The secondary concentrated lithium-rich solution uses reaction-separation technology to deeply remove magnesium to prepare magnesium-based functional materials. Aluminum chloride hexahydrate is added to the secondary concentrated lithium-rich solution to prepare Mg 2+ With Al 3+A mixed salt solution with a molar ratio of 2, then a mixed alkali solution of sodium hydroxide and sodium carbonate is prepared, and the mixed salt solution is added dropwise to the mixed alkali solution at a certain speed for co-precipitation reaction, the reaction pH is 8, the reaction temperature is 25°C, and after the reaction is complete, the material is aged and filtered to obtain the MgAl-LDH product; the filtrate is passed through an adsorption column equipped with LSC-800 boron-specific adsorption resin to reduce the boron in the filtrate to less than 5ppm to obtain a lithium-rich boron-removing solution, and the boron-saturated adsorption column is used for the preparation of boric acid by-products; the boron-removing lithium-rich solution is heated to 80°C, wherein the lithium in the lithium-rich solution is 5g / L, and add 10% excess (based on the mass converted into the reaction formula ratio) of 30% sodium phosphate solution, the reaction pH value is 8, the stirring speed is 50rpm for precipitation reaction, and in the feeding nucleation stage, 10kHZ, 100W ultrasonic wave is turned on for 10min; after the reaction, the battery-grade lithium phosphate is obtained by filtering, washing and drying, and the main lithium phosphate content of the battery-grade lithium phosphate prepared by washing twice and adding a small amount of polyethylene glycol dispersant is not less than 99.5%, and the particle size of the battery-grade lithium phosphate is 6μm.

[0089] Example 2

[0090] The salt lake brine used in this example is old brine from a sulfate salt lake in Qinghai, where Li + The concentration is 4g / L and the magnesium to lithium ratio is 12.

[0091] The old brine from a sulfate salt lake in Qinghai was passed through a ceramic membrane to reduce the turbidity to below 3 and then entered a primary adsorption system equipped with a manganese adsorbent. After 10 columns of adsorption in series, the saturated adsorption column was washed with water. After washing, the saturated lithium saturated adsorption column was desorbed for 5 columns with 1 mol / L sulfuric acid to obtain a primary desorption liquid. The pH of the primary adsorption tail liquid with a lithium concentration of 0.4 g / L was adjusted to 5 and then entered a secondary adsorption system equipped with an aluminum adsorbent. After 5 columns of adsorption, the lithium concentration of the secondary adsorption tail liquid was reduced to below 20 ppm and discharged to the salt field. The saturated aluminum adsorption column of the secondary adsorption was washed with water and then desorbed for 2 columns with pure water at 45°C to obtain a secondary desorption liquid. The primary desorption liquid and the secondary desorption liquid were mixed at a ratio of 2:1 to obtain a mixed desorption liquid. The lithium concentration in the mixed desorption liquid was 1.3 g / L and the magnesium-lithium ratio was 0.4. The mixed desorption liquid enters the forward osmosis primary concentration system. The forward osmosis draw liquid is a saturated solution prepared with magnesium chloride from salt lakes. The mixed desorption liquid is forward osmotic through a TFC membrane to concentrate the lithium concentration to 3g / L to obtain a primary concentrate. The lithium concentration in the fresh water is controlled at 0.1g / L, and the concentration ratio is 4:1. The primary concentrate enters the high-pressure reverse osmosis system for secondary concentration, and the lithium ion content in the secondary concentrate is 10g / L, and the magnesium-lithium ratio is 0.4; the lithium ion content in the secondary fresh water is 0.005g / L. The reverse osmosis membrane used in the reverse osmosis system is the Dow SW series. The ratio of the first and second stage membranes is 7:1. The membrane inlet pressure is controlled at 10Mpa and the concentration volume ratio (primary concentrate / secondary concentrate) is 4. The obtained high-pressure reverse osmosis fresh water is directly mixed with the mixed desorption liquid. The secondary concentrated lithium-rich solution uses reaction-separation technology to deeply remove magnesium to prepare magnesium-based functional materials. Aluminum chloride hexahydrate is added to the secondary concentrated lithium-rich solution to prepare Mg 2+ With Al 3+ A mixed salt solution with a molar ratio of 3, then a mixed alkali solution of sodium hydroxide and sodium carbonate is prepared, and the mixed salt solution is added dropwise to the mixed alkali solution at a certain speed for co-precipitation reaction, the reaction pH is 13, the reaction temperature is 70°C, and after the reaction is complete, the material is aged and filtered to obtain the MgAl-LDH product; the filtrate is passed through an adsorption column equipped with D403 boron-specific adsorption resin to reduce the boron in the filtrate to less than 2ppm to obtain a lithium-rich boron-removing solution, and the boron-saturated adsorption column is used for the preparation of boric acid by-products; the boron-removing lithium-rich solution is heated to 110°C, wherein the lithium in the lithium-rich solution is 10g / L , and add 30% excess (based on the mass converted into the reaction formula ratio) of 10% sodium carbonate solution, the reaction pH is 12, the stirring speed is 200rpm for precipitation reaction, and 50kHZ, 1000W ultrasonic wave is turned on in the feeding nucleation stage, and the ultrasonic time is 10min; after the reaction, it is filtered, washed and dried to obtain battery-grade lithium phosphate, the washing adopts 2 pulp washings and adds a small amount of polyethanol dispersant, the main content of lithium phosphate in the prepared battery-grade lithium phosphate is not less than 99.5%, and the particle size of the battery-grade lithium phosphate is 5um.

[0092] Example 3

[0093] The salt lake brine used in this embodiment is old brine from a sulfate salt lake in Qinghai, in which the Li+ concentration is 2 g / L and the magnesium-lithium ratio is 60.

[0094] The old brine from a sulfate salt lake in Qinghai was ultrafiltrated to reduce the turbidity to below 1 and then entered the primary adsorption system equipped with titanium adsorbent. After 5 columns in series adsorption, the saturated adsorption column was washed with water. After washing, the saturated lithium saturated adsorption column was desorbed by 4 columns with 0.5 mol / L hydrochloric acid to obtain a primary desorption liquid. The pH of the primary adsorption tail liquid with a lithium concentration of 0.3 g / L was adjusted to 4.4 and then entered the secondary adsorption system equipped with aluminum adsorbent. After 4 columns of adsorption, the lithium concentration of the secondary adsorption tail liquid was reduced to below 20 ppm and discharged to the salt field. The saturated aluminum adsorption column of the secondary adsorption was washed with water and then desorbed by 3 columns with pure water at 55°C to obtain a secondary desorption liquid. The primary desorption liquid and the secondary desorption liquid were mixed at a ratio of 3:1 to obtain a mixed desorption liquid. The lithium concentration in the mixed desorption liquid was 1.0 g / L and the magnesium-lithium ratio was 0.2. The mixed desorption liquid enters the forward osmosis primary concentration system. The forward osmosis draw liquid is a saturated solution prepared with sodium chloride from a salt lake. The mixed desorption liquid is forward osmotic through a CTA membrane to concentrate the lithium concentration to 2.0 g / L to obtain a primary concentrate. The lithium concentration in the fresh water is controlled at 0.02 g / L, and the concentration ratio is 3:1. The primary concentrate enters the high-pressure reverse osmosis system for secondary concentration, and the lithium ion content in the secondary concentrate is 7 g / L, and the magnesium-lithium ratio is 0.3; the lithium ion content in the secondary fresh water is 0.02 g / L. The reverse osmosis membrane used in the reverse osmosis system is the Dow BW+SW series. The ratio of the first and second stage membranes is 4:1. The membrane pressure is controlled to be 5 MPa, and the concentration volume ratio (lithium-rich solution volume / primary concentrated solution) is 2.0. The obtained high-pressure reverse osmosis fresh water is directly mixed with the mixed desorption liquid. The secondary concentrated lithium-rich solution uses reaction-separation technology to deeply remove magnesium to prepare magnesium-based functional materials. Aluminum chloride hexahydrate is added to the secondary concentrated lithium-rich solution to prepare Mg 2+ With Al 3+A mixed salt solution with a molar ratio of 3, then a mixed alkali solution of sodium hydroxide and sodium carbonate is prepared, and the mixed salt solution is added dropwise to the mixed alkali solution at a certain speed for co-precipitation reaction, the reaction pH is 10, the reaction temperature is 50°C, and after the reaction is complete, the material is aged and filtered to obtain the MgAl-LDH product; the filtrate is passed through an adsorption column equipped with D564 boron-specific adsorption resin to reduce the boron in the filtrate to below 4ppm to obtain a lithium-rich boron-removing solution, and the boron-saturated adsorption column is used for the preparation of boric acid by-products; the boron-removing lithium-rich solution is heated to 90°C, wherein the lithium in the lithium-rich solution is 6g / L , and add thereto an excess of 15% (based on the mass converted into the reaction formula ratio) of a 20% sodium carbonate solution by mass, the reaction pH value is 9, the stirring speed is 100rpm for precipitation reaction 9, and in the feeding nucleation stage, an ultrasonic wave of 20kHZ and a power of 300W is turned on for 10min. After the reaction, the mixture is filtered, washed and dried to obtain battery-grade lithium phosphate. The main content of lithium phosphate in the battery-grade lithium phosphate prepared by washing twice and adding a small amount of polyethylene glycol dispersant is not less than 99.5%, and the particle size of the battery-grade lithium phosphate is 7μm.

[0095] Example 4

[0096] The salt lake brine used in this embodiment is old brine from a sulfate salt lake in Qinghai, in which the Li+ concentration is 3g / L and the magnesium-lithium ratio is 40.

[0097] The old brine from a sulfate salt lake in Qinghai was ultrafiltrated to reduce the turbidity to below 3 and then entered the primary adsorption system equipped with manganese adsorbent. After 8 columns in series adsorption, the saturated adsorption column was washed with water. After washing, the saturated lithium saturated adsorption column was desorbed by 0.2 mol / L sulfuric acid for 3 columns to obtain a primary desorption liquid. The pH of the primary adsorption tail liquid with a lithium concentration of 0.25 g / L was adjusted to 4.8 and entered the secondary adsorption system equipped with aluminum adsorbent. After 3 columns of adsorption, the lithium concentration of the secondary adsorption tail liquid was reduced to below 20 ppm and discharged to the salt field. The secondary adsorption saturated aluminum adsorption column was washed with water and then desorbed by pure water for 1 column at 65°C to obtain a secondary desorption liquid. The primary desorption liquid and the secondary desorption liquid were mixed at a ratio of 5:1 to obtain a mixed desorption liquid. The lithium concentration in the mixed desorption liquid was 0.9 g / L and the magnesium-lithium ratio was 0.3. The mixed desorbent enters the forward osmosis primary concentration system. The forward osmosis draw liquid is a saturated solution prepared with magnesium chloride from salt lakes. The mixed desorbent is forward osmotic through a TFC membrane to concentrate the lithium concentration to 2.5 g / L to obtain a primary concentrate. The lithium concentration in the fresh water is controlled at 0.005 g / L, and the concentration ratio is 2:1. The primary concentrate enters the high-pressure reverse osmosis system for secondary concentration, and the lithium ion content in the secondary concentrate is 8 g / L, and the magnesium-lithium ratio is 0.2; the lithium ion content in the secondary fresh water is 0.08 g / L. The reverse osmosis membrane used in the reverse osmosis system is the Dow BW series. The ratio of the first and second stage membranes is 5:1. The membrane inlet pressure is controlled to be 8 MPa, and the concentration volume ratio (lithium-rich solution volume / primary concentrated solution) is 3.0. The obtained high-pressure reverse osmosis fresh water is directly mixed with the mixed desorbent. The secondary concentrated lithium-rich solution uses reaction-separation technology to deeply remove magnesium to prepare magnesium-based functional materials. Aluminum chloride hexahydrate is added to the secondary concentrated lithium-rich solution to prepare Mg 2+ With Al 3+ A mixed salt solution with a molar ratio of 2 is prepared, and then a mixed alkali solution of sodium hydroxide and sodium carbonate is prepared, and the mixed salt solution is added dropwise to the mixed alkali solution at a certain speed for co-precipitation reaction, the reaction pH is 9, the reaction temperature is 40°C, and after the reaction is complete, the product of MgAl-LDH is obtained by aging and filtering; the filtrate is passed through an adsorption column equipped with XSC-700 boron-specific adsorption resin to reduce the boron in the filtrate to below 5ppm to obtain a lithium-rich boron-removing solution, and the boron-saturated adsorption column is used for the preparation of boric acid by-products. The boron-removed lithium-rich solution is heated to 100° C., wherein the lithium content of the lithium-rich solution is 8 g / L, and an excess of 25% (based on the mass converted into the reaction formula ratio) of a 25% mass fraction of a sodium carbonate solution is added thereto, the reaction pH value is 10, the stirring speed is 150 rpm for precipitation reaction, and an ultrasonic wave of 40 kHz and a power of 800 W is turned on during the feeding nucleation stage, the ultrasonic time is 10 minutes, and after the reaction, the battery-grade lithium phosphate is obtained by filtering, washing and drying. The main lithium phosphate content of the battery-grade lithium phosphate prepared by washing twice and adding a small amount of polyethylene glycol dispersant is not less than 99.5%, and the particle size of the battery-grade lithium phosphate is 8 μm.

[0098] Comparative Example 1

[0099] The salt lake brine used in this comparative example is old brine from a sulfate salt lake in Qinghai, in which the Li+ concentration is 1.5 g / L and the magnesium-lithium ratio is 100.

[0100] The old brine from a sulfate salt lake in Qinghai was ultrafiltrated to reduce the turbidity to below 3 and then entered the primary adsorption system equipped with titanium adsorbent. After 3 columns of adsorption in series, the saturated adsorption column was washed with water. After washing, the saturated lithium saturated adsorption column was desorbed by 2 columns with 0.1 mol / L hydrochloric acid to obtain a primary desorption liquid. The pH of the primary adsorption tail liquid with a lithium concentration of 0.2 g / L was adjusted to 4 and then entered the secondary adsorption system equipped with aluminum adsorbent. After 2 columns of adsorption, the lithium concentration of the secondary adsorption tail liquid was reduced to below 20 ppm and discharged to the salt field. The secondary adsorption saturated aluminum adsorption column was washed with water and then desorbed by 1 column with pure water at 35°C to obtain a secondary desorption liquid. The primary desorption liquid and the secondary desorption liquid were mixed at a ratio of 1:1 to obtain a mixed desorption liquid. The lithium concentration in the mixed desorption liquid was 0.7 g / L and the magnesium-lithium ratio was 0.1. The mixed desorption liquid enters the high-pressure reverse osmosis system for primary concentration, and the lithium ion content in the primary concentrated liquid is 5g / L, and the magnesium-lithium ratio is 0.1; the lithium ion content in the primary fresh water is 0.10g / L. The reverse osmosis system uses the Dow BW series reverse osmosis membrane, and the first and second membranes are configured at 1:1. The membrane inlet pressure is controlled at 1Mpa, and the concentration volume ratio (mixed desorption liquid / primary concentrated liquid) is 4. The obtained high-pressure reverse osmosis fresh water is directly mixed with the mixed desorption liquid. The secondary concentrated lithium-rich solution uses reaction-separation technology to deeply remove magnesium to prepare magnesium-based functional materials. Aluminum trichloride hexahydrate is added to the secondary concentrated lithium-rich solution to prepare Mg 2+ With Al 3+The molar ratio of the molar ratio of the mixed salt solution is 2, and then a mixed alkali solution of sodium hydroxide and sodium carbonate is prepared, and the mixed salt solution is added dropwise to the mixed alkali solution at a certain speed for co-precipitation reaction, the reaction pH is 8, the reaction temperature is 25°C, and after the reaction is complete, the material is aged and filtered to obtain the MgAl-LDH product; the filtrate is passed through an adsorption column equipped with LSC-800 boron-specific adsorption resin to reduce the boron in the filtrate to less than 5ppm to obtain a lithium-rich boron-removing solution, and the boron-saturated adsorption column is used for the preparation of boric acid by-products; the boron-removing lithium-rich solution is heated to 80°C, wherein the lithium in the lithium-rich solution is 5g / L, and an excess of 10% (based on the reaction The mass fraction of sodium phosphate solution is 30% (based on the mass converted from the formula ratio), the reaction pH value is 8, the stirring speed is 50rpm for precipitation reaction, and 10kHZ, 100W power ultrasonic wave is turned on in the feeding nucleation stage, and the ultrasonic time is 10min; after the reaction, it is filtered, washed and dried to obtain battery-grade lithium phosphate. The washing adopts 2 pulp washings and adds a small amount of polyethylene glycol dispersant to prepare the battery-grade lithium phosphate. The main content of lithium phosphate is not less than 99.5%, and the particle size of the battery-grade lithium phosphate is 6μm. In this embodiment, the high-pressure reverse osmosis concentration multiple is increased by 1 times, the energy consumption is increased by 1 times, and the process cost is increased by one quarter.

[0101] Comparative Example 2

[0102] The salt lake brine used in this comparative example is old brine from a sulfate salt lake in Qinghai, in which the Li+ concentration is 1.5 g / L and the magnesium-lithium ratio is 100.

[0103] The old brine from a sulfate salt lake in Qinghai was ultrafiltrated to reduce the turbidity to below 3 and then entered the primary adsorption system equipped with titanium adsorbent. After 3 columns of adsorption in series, the saturated adsorption column was washed with water. After washing, 0.1mol / L hydrochloric acid was used to desorb the saturated lithium saturated adsorption column for 2 columns to obtain a primary desorption liquid; the lithium concentration in the primary desorption liquid was 0.7g / L, and the magnesium-lithium ratio was 0.1. The adsorbed liquid entered the forward osmosis primary concentration system. The forward osmosis draw liquid was a saturated solution prepared with sodium chloride from the salt lake. The mixed desorption liquid was forward osmosis through a CTA membrane to concentrate the lithium concentration to 1.5g / L to obtain a primary concentrate. The lithium concentration in fresh water was controlled at 0.005g / L, and the concentration ratio was 2:1. The primary concentrate enters the high-pressure reverse osmosis system for secondary concentration, and the lithium ion content in the secondary concentrate is 5g / L, and the magnesium-lithium ratio is 0.1; the lithium ion content in the secondary fresh water is 0.10g / L. The reverse osmosis membrane used in the reverse osmosis system is the Dow BW series, and the first and second stage membranes are configured at 1:1. The membrane inlet pressure is controlled to be 1Mpa, and the concentration volume ratio (primary concentrate / secondary concentrate) is 1. The obtained high-pressure reverse osmosis fresh water is directly mixed with the mixed desorption liquid. The secondary concentrated lithium-rich solution uses reaction-separation technology to deeply remove magnesium to prepare magnesium-based functional materials. Aluminum chloride hexahydrate is added to the secondary concentrated lithium-rich solution to prepare Mg 2+ With Al 3+The molar ratio of the molar salt solution is 2, and then a mixed alkali solution of sodium hydroxide and sodium carbonate is prepared, and the mixed salt solution is added dropwise to the mixed alkali solution at a certain speed for co-precipitation reaction, the reaction pH is 8, the reaction temperature is 25°C, and after the reaction is complete, the material is aged and filtered to obtain the MgAl-LDH product; the filtrate is passed through an adsorption column equipped with LSC-800 boron-specific adsorption resin to reduce the boron in the filtrate to less than 5ppm to obtain a lithium-rich boron-removing solution, and the boron-saturated adsorption column is used for the preparation of boric acid by-products; the boron-removing lithium-rich solution is heated to 80°C, wherein the lithium in the lithium-rich solution is 5g / L, and An excess of 10% (based on the mass converted into the reaction formula ratio) of a sodium phosphate solution with a mass fraction of 30% is added, the reaction pH value is 8, the stirring speed is 50 rpm for precipitation reaction, and an ultrasonic wave of 10 kHz and a power of 100 W is turned on during the feeding nucleation stage, and the ultrasonic time is 10 min; after the reaction, the battery-grade lithium phosphate is obtained by filtering, washing and drying. The main lithium phosphate content of the battery-grade lithium phosphate prepared by washing twice and adding a small amount of polyethylene glycol dispersant is not less than 99.5%, the particle size of the battery-grade lithium phosphate is 6 μm, and the lithium yield is only 80.5%.

[0104] Comparative Example 3

[0105] The salt lake brine used in this comparative example is old brine from a sulfate salt lake in Qinghai, in which the Li-- concentration is 1.5 g / L and the magnesium-lithium ratio is 100.

[0106] The old brine from a sulfate salt lake in Qinghai was ultrafiltrated to reduce the turbidity to below 3 and then entered the primary adsorption system equipped with titanium adsorbent. After 3 columns of adsorption in series, the saturated adsorption column was washed with water. After washing, the saturated lithium saturated adsorption column was desorbed by 2 columns with 0.1 mol / L hydrochloric acid to obtain a primary desorption liquid. The pH of the primary adsorption tail liquid with a lithium concentration of 0.2 g / L was adjusted to 4 and then entered the secondary adsorption system equipped with aluminum adsorbent. After 2 columns of adsorption, the lithium concentration of the secondary adsorption tail liquid was reduced to below 20 ppm and discharged to the salt field. The secondary adsorption saturated aluminum adsorption column was washed with water and then desorbed by 1 column with pure water at 35°C to obtain a secondary desorption liquid. The primary desorption liquid and the secondary desorption liquid were mixed at a ratio of 1:1 to obtain a mixed desorption liquid. The lithium concentration in the mixed desorption liquid was 0.7 g / L and the magnesium-lithium ratio was 0.1. The mixed desorption liquid enters the forward osmosis primary concentration system. The forward osmosis draw liquid is a saturated solution prepared with sodium chloride from a salt lake. The mixed desorption liquid is forward osmotic through a CTA membrane to concentrate the lithium concentration to 1.5 g / L to obtain a primary concentrated solution. The lithium concentration in fresh water is controlled at 0.005 g / L, and the concentration ratio is 2:1. Aluminum chloride hexahydrate is added to the primary concentrated lithium-rich solution to prepare Mg 2+ With Al 3+A mixed salt solution with a molar ratio of 2, then a mixed alkali solution of sodium hydroxide and sodium carbonate is prepared, and the mixed salt solution is added dropwise to the mixed alkali solution at a certain speed for co-precipitation reaction, the reaction pH is 8, the reaction temperature is 25°C, and after the reaction is complete, the material is aged and filtered to obtain the MgAl-LDH product; the filtrate is passed through an adsorption column equipped with LSC-800 boron-specific adsorption resin to reduce the boron in the filtrate to less than 5ppm to obtain a lithium-rich boron-removing solution, and the boron-saturated adsorption column is used for the preparation of boric acid by-products; the boron-removing lithium-rich solution is heated to 80°C, wherein the lithium in the lithium-rich solution is 1.5g / L, and An excess of 10% (based on the mass converted into the reaction formula ratio) of a 30% sodium phosphate solution was added thereto, the reaction pH value was 8, the stirring speed was 50 rpm for precipitation reaction, and an ultrasonic wave of 10 kHz and 100 W was turned on during the feeding nucleation stage for 10 min. After the reaction, the battery-grade lithium phosphate was obtained by filtration, washing and drying. The main lithium phosphate content of the battery-grade lithium phosphate prepared by washing twice and adding a small amount of polyethylene glycol dispersant was not less than 99.5%, the particle size of the battery-grade lithium phosphate was 6 μm, and the lithium yield was only 84.2%.

[0107] Comparative Example 4

[0108] The salt lake brine used in this comparative example is old brine from a sulfate salt lake in Qinghai, in which the Li+ concentration is 1.5 g / L and the magnesium-lithium ratio is 100.

[0109] The old brine from a sulfate salt lake in Qinghai was ultrafiltrated to reduce the turbidity to below 3 and then entered the primary adsorption system equipped with titanium adsorbent. After 3 columns of adsorption in series, the saturated adsorption column was washed with water. After washing, the saturated lithium saturated adsorption column was desorbed by 2 columns with 0.1 mol / L hydrochloric acid to obtain a primary desorption liquid. The pH of the primary adsorption tail liquid with a lithium concentration of 0.2 g / L was adjusted to 4 and then entered the secondary adsorption system equipped with aluminum adsorbent. After 2 columns of adsorption, the lithium concentration of the secondary adsorption tail liquid was reduced to below 20 ppm and discharged to the salt field. The secondary adsorption saturated aluminum adsorption column was washed with water and then desorbed by 1 column with pure water at 35°C to obtain a secondary desorption liquid. The primary desorption liquid and the secondary desorption liquid were mixed at a ratio of 1:1 to obtain a mixed desorption liquid. The lithium concentration in the mixed desorption liquid was 0.7 g / L and the magnesium-lithium ratio was 0.1. The mixed desorption liquid enters the forward osmosis primary concentration system. The forward osmosis draw liquid is a saturated solution of sodium chloride prepared from salt lakes. The mixed desorption liquid is forward osmosis through a CTA membrane to concentrate the lithium concentration to 1.5g / L to obtain a primary concentrate. The lithium concentration in the fresh water is controlled at 0.005g / L, and the concentration ratio is 2:1. The primary concentrate enters the high-pressure reverse osmosis system for secondary concentration to obtain a secondary concentrate with a lithium ion content of 5g / L and a magnesium-lithium ratio of 0.1; the lithium ion content in the secondary fresh water is 0.10g / L. The reverse osmosis membrane used in the reverse osmosis system is the Dow BW series. The first and second stage membranes are prepared at a ratio of 1:1. The membrane inlet pressure is controlled at 1Mpa and the concentration volume ratio (primary concentrate / secondary concentrate) is 1. The obtained high-pressure reverse osmosis fresh water is directly mixed with the mixed desorption liquid. The secondary concentrated lithium-rich solution uses reaction-separation technology to deeply remove magnesium to prepare magnesium-based functional materials. Aluminum chloride hexahydrate is added to the secondary concentrated lithium-rich solution to prepare Mg 2+ With Al 3+ A mixed salt solution with a molar ratio of 2, then a mixed alkali solution of sodium hydroxide and sodium carbonate is prepared, and the mixed salt solution is added dropwise to the mixed alkali solution at a certain speed for a co-precipitation reaction, the reaction pH is 8, the reaction temperature is 25°C, and after the reaction is complete, the material is aged and filtered to obtain a MgAl-LDH product; the lithium-rich solution is heated to 80°C, wherein the lithium in the lithium-rich solution is 5g / L, and an excess of 10% (based on the mass converted to the reaction formula ratio) of a sodium phosphate solution with a mass fraction of 30% is added thereto, the reaction pH is 8, the stirring speed is 50rpm for precipitation reaction, and an ultrasonic wave of 10kHZ and a power of 100W is turned on in the feeding nucleation stage, and the ultrasonic time is 10min; after the reaction, it is filtered, washed, and dried to obtain battery-grade lithium phosphate. The main content of lithium phosphate in the battery-grade lithium phosphate prepared by washing twice and adding a small amount of polyethylene glycol dispersant is 99.1%, and the boron content is 1200ppm, which cannot meet the standard of battery-grade lithium phosphate.

[0110] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments with other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0111] It should be understood that the technical solution of the present invention is not limited to the above-mentioned specific implementation cases. Any technical deformation made according to the technical solution of the present invention without departing from the scope of protection of the purpose of the present invention and the claims shall fall within the protection scope of the present invention.

Claims

1. A method for co-producing lithium phosphate and magnesium-based functional materials, characterized in that include: The salt lake brine is placed in a primary adsorption system for primary adsorption treatment, and then the saturated adsorption column is washed with water, and then the saturated adsorption column is subjected to primary desorption treatment using a primary desorbent to obtain a primary desorption liquid and a primary tail liquid; wherein the primary adsorption system is an adsorption system filled with a titanium or manganese adsorbent; wherein the salt lake brine is potassium-extracted brine, the magnesium-lithium ratio in the potassium-extracted brine is 5-500, and the lithium ion concentration is 0.5-10 g / L; 3-10 multi-column adsorption is used in the primary adsorption treatment; The pH value of the primary tail liquid is adjusted to 3-6 and placed in a secondary adsorption system for secondary adsorption treatment, after which the saturated adsorption column is washed with water, and then the saturated adsorption column is subjected to secondary desorption treatment using a secondary desorbent to obtain a secondary desorption liquid and a secondary tail liquid; wherein the secondary adsorption system is an adsorption system filled with an aluminum-based adsorbent; and 2-5 multi-column adsorption is used during the secondary adsorption treatment; The primary desorption liquid is mixed with the secondary desorption liquid to obtain a mixed desorption liquid; wherein the lithium ion concentration in the mixed desorption liquid is 0.4-1.5 g / L, and the magnesium-lithium ratio is 0.1-0.4; Performing forward osmosis primary concentration treatment on the mixed desorption liquid to obtain a primary concentrated liquid and forward osmosis fresh water; Placing the primary concentrated liquid in a high-pressure reverse osmosis system for secondary concentration treatment to obtain secondary concentrated liquid and reverse osmosis fresh water; wherein the operating pressure of the secondary concentration unit in the high-pressure reverse osmosis system is 1.0-10.0 MPa; The secondary concentrated liquid is mixed with aluminum salt and alkaline solution to carry out a first coprecipitation reaction to obtain a magnesium-based functional material and a filtrate; The filtrate is subjected to a boron removal treatment by an ion exchange method to obtain a boron-removed lithium-rich solution and boric acid; Furthermore, the boron-removed lithium-rich solution is subjected to lithium precipitation treatment by ultrasonic precipitation-ultrasonic coupling method to obtain battery-grade lithium phosphate.

2. The method according to claim 1, characterized in that: The concentration of lithium ions in the primary tail liquid is 0.2-0.4 g / L; the concentration of lithium ions in the secondary tail liquid is less than 20 ppm; and the volume ratio of the primary desorption liquid to the secondary desorption liquid in the mixed desorption liquid is 1:1-5:

1.

3. The method according to claim 1, characterized in that: The primary desorption treatment adopts 2 to 5 multi-column desorption; the primary desorbent includes hydrochloric acid and / or sulfuric acid; the concentration of the primary desorbent is 0.05 to 2.0 mol / L.

4. The method according to claim 1, characterized in that: The secondary desorption treatment adopts 1 to 3 multi-column desorption; the secondary desorbent includes water; the temperature of the secondary desorption treatment is 35 to 70°C.

5. The method according to claim 1, characterized in that Specifically include: The mixed desorption liquid is placed in a forward osmosis system for primary concentration treatment to obtain a primary concentrated liquid and forward osmosis fresh water; wherein the concentration of lithium ions in the primary concentrated liquid is 1.5-3.0 g / L; the forward osmosis draw liquid used in the forward osmosis system includes a saturated magnesium chloride solution or a saturated sodium chloride solution; the concentration of lithium ions in the forward osmosis fresh water is 0.005-0.10 g / L; the volume ratio of the mixed desorption liquid to the primary concentrated liquid is 2.0:1-4:1; the forward osmosis membrane used in the forward osmosis system includes a CTA membrane and / or a TFC membrane.

6. The method according to claim 1, characterized in that: The high-pressure reverse osmosis system adopts a multi-stage reverse osmosis device; the concentration of lithium ions in the secondary concentrated solution is 5-10 g / L; the volume ratio of the secondary concentrated solution to the primary concentrated solution is 0.5:1-6:1; the concentration of lithium ions in the reverse osmosis fresh water is 0.005-0.10 g / L; the mass ratio of Mg to Li in the reverse osmosis fresh water is 0.01-1:

1.

7. The method according to claim 6, characterized in that: The secondary concentration unit in the high-pressure reverse osmosis system adopts a two-stage series connection; the reverse osmosis membrane used in the high-pressure reverse osmosis system includes Dow BW membrane and / or SW membrane.

8. The method according to claim 1, characterized in that Specifically include: Aluminum salt is added to the secondary concentrated solution to form a mixed salt solution, and then an alkali solution is added to perform a first coprecipitation reaction under the conditions of pH 8-13, stirring rate 50-200 rpm, and temperature 25-70°C, followed by aging, separation, washing, and drying to obtain a magnesium-based functional material and a filtrate; wherein the Mg in the mixed salt solution is 2+ With Al 3+ The molar ratio is 2 to 4:1; the aluminum salt includes any one of aluminum nitrate, aluminum sulfate, and aluminum chloride, or a combination of two or more thereof; and the alkaline solution includes a mixed alkaline solution of sodium carbonate and sodium hydroxide.

9. The method according to claim 8, characterized in that: The volumes of the mixed salt solution and the alkaline solution are the same.

10. The method according to claim 8, characterized in that: The content of magnesium ions in the filtrate is below 10 ppm.

11. The method according to claim 1, characterized in that: Specifically include: Passing the filtrate into an ion exchange column filled with a boron-specific resin to obtain a boron-removed lithium-enriched solution and a boron-saturated adsorption column; wherein the boron content in the boron-removed lithium-enriched solution is less than 5 ppm; The boron special effect resin includes any one of LSC-800, D403, D564, and XSC-700 or a combination of two or more thereof.

12. The method according to claim 1, characterized in that Specifically include: A sodium phosphate solution is added to the deborated lithium-rich solution, and a second coprecipitation reaction is carried out under the conditions of an ultrasonic frequency of 10-50 kHz, an ultrasonic power of 100-1000 W, a pH of 8-12, a stirring rate of 50-200 rpm, and a temperature of 80-110° C., followed by nucleation, aging, filtering, washing, and drying to obtain battery-grade lithium phosphate; wherein the concentration of lithium ions in the deborated lithium-rich solution is 5-10 g / L.

13. The method according to claim 12, characterized in that: The ultrasonic frequency is 20-40 kHz; the ultrasonic power is 300-800 W; the stirring rate is 100-150 rpm; the temperature is 90-100° C.; and the ultrasonic time during the second coprecipitation reaction is 10-60 min.

14. The method according to claim 12, characterized in that: The mass concentration of the sodium phosphate solution is 10-30%.

15. The method according to claim 12, characterized in that: The washing liquid used in the washing treatment includes water and a dispersant, and the dispersant includes polyethylene glycol and / or ethanol dispersant.

16. The method according to claim 1, characterized in that Also includes: The salt lake brine is first pretreated to at least remove silt or organic matter; wherein the turbidity of the solution obtained after the pretreatment is less than 3NTU; the pretreatment is performed by any one of ultrafiltration, ceramic filtration, and polyceramic membrane filtration.

17. The method according to claim 1, characterized in that: The purity of the battery-grade lithium phosphate is above 99.5%, and the particle size of the battery-grade lithium phosphate is below 8 μm.

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