Method for co-producing lithium carbonate, lithium phosphate and magnesium carbonate by using magnesium sulfate subtype salt lake original brine

Abstract

The invention relates to the technical field of extraction of lithium from salt lake original brine, and discloses a method for co-producing lithium carbonate, lithium phosphate and magnesium carbonate by using magnesium sulfate subtype salt lake original brine. The method comprises the following steps: (1) carrying out adsorption lithium extraction treatment on original brine of the magnesium sulfate subtype salt lake, and then desorbing to obtain qualified lithium liquid and lithium extraction tail liquid; (2) carrying out nanofiltration treatment, reverse osmosis treatment, electrodialysis treatment, ion exchange treatment, MVR (Mechanical Vapor Recompression) concentration and adsorption boron removal treatment on the lithium qualified liquid to obtain boron-removed qualified liquid; (3) carrying out lithium precipitation treatment on the boron-removed qualified liquid to obtain lithium carbonate and lithium precipitation mother liquor; mixing the lithium precipitation mother liquor with the precipitator to obtain lithium phosphate and filtrate; adjusting the pH value of the filtrate to 8-11, then mixing the filtrate with the lithium extraction tail liquid obtained in the step (1), and then separating to obtain magnesium carbonate. According to the technical scheme, the lithium recovery rate is high, the purity of lithium carbonate, lithium phosphate and magnesium carbonate is high, and maximum recovery of lithium is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of lithium extraction from salt lake original brine, and in particular to a method for co-producing lithium carbonate, lithium phosphate and magnesium carbonate by utilizing magnesium sulfate subtype salt lake original brine. Background Art

[0002] There are two main types of terrestrial lithium resources that have been discovered: ore-type lithium resources and salt lake lithium resources. According to statistics, the reserves of salt lake lithium resources account for about 70% to 80% of the total lithium resources. Lithium resources are abundant and mainly distributed in Qinghai, Xinjiang, Tibet and other places, but the lithium resources are generally of low grade, and the content of impurities such as magnesium, sodium, potassium, boron, silicon, and sulfate in the raw brine is also relatively high, which brings certain challenges to the direct use of raw brine for the development of lithium resources. So far, the main methods for extracting lithium from salt lake brine are: precipitation method, membrane method, solvent extraction method, adsorption method, calcination leaching method, electrochemical lithium extraction technology, MOF-based lithium ion channel membrane technology, etc. According to the different storage forms of salt lake brine, the industrially applied brine lithium extraction technologies mainly include: precipitation method, membrane method, extraction method and adsorption method, etc.

[0003] There are still several problems in the process of producing battery-grade lithium carbonate by one-step adsorption of magnesium sulfate subtype salt lake brine: First, the influence of sulfate and boron components in the raw brine of magnesium sulfate subtype salt lake causes the adsorption capacity of the adsorbent to decrease, the adsorption performance to fail, and the separation of magnesium and lithium is difficult. Second, in the pretreatment process, due to the influence of uncontrollable factors such as entrainment and leakage during the brine concentration process, the comprehensive lithium yield is only 30%-35%, and the concentration is affected by the natural environment. The utilization rate of salt lake lithium resources is low, the investment cost is high, and the pressure on ecological and environmental protection of salt field construction is high. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems in the prior art of great difficulty in separating magnesium and lithium from original brine of magnesium sulfate subtype salt lake, low comprehensive lithium yield, low utilization rate of salt lake lithium resource mining, high investment cost and great ecological and environmental protection pressure of salt field construction, and provide a method for co-producing lithium carbonate, lithium phosphate and magnesium carbonate using original brine of magnesium sulfate subtype salt lake. The technical scheme is separated by adsorption method, has universality, high lithium recovery rate, simple process, one-step separation of lithium and other impurities, low cost and good product quality, etc.; moreover, magnesium carbonate and lithium phosphate are prepared by jointly treating lithium precipitation mother liquor and lithium extraction tail liquor, thereby solving the problem of resource loss of lithium precipitation mother liquor, realizing maximum recovery of lithium for brine entering the workshop, and laying a foundation for subsequent development of high-end products of lithium and magnesium resources.

[0005] In order to achieve the above object, the present invention provides a method for co-producing lithium carbonate, lithium phosphate and magnesium carbonate using raw brine of magnesium sulfate subtype salt lake, the method comprising the following steps:

[0006] (1) subjecting the original brine of magnesium sulfate subtype salt lake to adsorption and lithium extraction treatment, followed by desorption, to obtain lithium qualified solution and lithium extraction tail solution;

[0007] (2) The lithium qualified solution is transported to a first nanofiltration device for primary nanofiltration treatment to remove magnesium ions and obtain primary nanofiltration water, and the primary nanofiltration water is subjected to reverse osmosis treatment to obtain reverse osmosis concentrate; the reverse osmosis concentrate is input into an electrodialysis device for electrodialysis treatment to obtain electrodialysis concentrate and fresh water; the electrodialysis concentrate is transported to a second nanofiltration device for secondary nanofiltration treatment to remove magnesium ions and obtain secondary nanofiltration water, and the secondary nanofiltration water is subjected to a first ion exchange to remove magnesium ions and obtain magnesium-removed qualified solution and magnesium-removed desorption solution; the magnesium-removed qualified solution is subjected to MVR concentration to obtain MVR concentrated solution and water; the MVR concentrated solution is subjected to a second ion exchange to remove boron ions and obtain boron-removed qualified solution; wherein the water obtained in the MVR concentration process and the fresh water obtained in the electrodialysis process are returned to the first nanofiltration device to participate in the primary nanofiltration treatment; the magnesium-removed desorption solution is returned to the electrodialysis device to participate in the electrodialysis treatment;

[0008] (3) The qualified boron-removed solution is subjected to lithium precipitation treatment to obtain lithium carbonate and lithium precipitation mother liquor; the lithium precipitation mother liquor is mixed with a precipitant, and then subjected to filter press separation to obtain a crude lithium phosphate product and a filtrate; the hydroxide content in the filtrate is controlled at 1.5-2.5 g / L and the pH value of the filtrate is adjusted to 8-11, and then mixed with the lithium extraction tail liquid obtained in step (1) to obtain a basic magnesium carbonate suspension, and then separated to obtain magnesium carbonate.

[0009] Preferably, in step (1), in the original brine of the magnesium sulfate subtype salt lake, the content of lithium ions is above 150 mg / L, the content of magnesium ions is 15-18 g / L, the content of sodium ions is 75-95 g / L, the content of potassium ions is 9-10 g / L, the content of boron ions is 250-350 mg / L, the content of chloride ions is 170-200 g / L, and the content of sulfate ions is 9-13 g / L.

[0010] Preferably, in step (1), the adsorption process comprises: performing the adsorption through an adsorbent; the adsorbent is at least one of a layered aluminum adsorbent, a layered titanium adsorbent, a spinel structured manganese adsorbent and a spinel structured titanium adsorbent.

[0011] Preferably, the adsorption is carried out in a continuous adsorption lithium extraction device, and the adsorption conditions include: the rotation interval of the adsorption tower is 10-12min, the operating pressure of the device is 2.5-4MPa, the control temperature is 20-50°C, the feed adsorption flow rate is 0.5-3.5BV / h, the top liquid flow rate is 1-3BV / h, and the desorption flow rate is 0.5-4BV / h.

[0012] Preferably, the method further comprises: regenerating the adsorbent by using a regeneration agent.

[0013] Preferably, the regeneration agent is a magnesium chloride solution and / or a hydrochloric acid solution.

[0014] Preferably, the regeneration reagent is the lithium extraction tail liquid obtained in step (1).

[0015] Preferably, the pH value of the regeneration reagent is 7.5-8.5, the content of lithium ions is 10-80 mg / L, and the content of magnesium ions is 15-18 g / L.

[0016] Preferably, in the lithium qualified solution, the content of lithium ions is greater than 400 mg / L, the content of magnesium ions is less than 500 mg / L, the content of sodium ions is less than 300 mg / L, the content of potassium ions is less than 20 mg / L, and the content of boron ions is less than 100 mg / L.

[0017] Preferably, in step (2), the conditions of the primary nanofiltration treatment include: a membrane inlet pressure of 3.5-4 MPa, a feed temperature of 22-25° C., and a feed conductivity of 18-22 ms / cm.

[0018] Preferably, in step (2), the reverse osmosis treatment conditions include: the pH value of the inlet water is 6-7, the membrane inlet pressure is 3.5-4 MPa, the feed temperature is 22-25°C, and the feed conductivity is 12-14 ms / cm.

[0019] Preferably, in the reverse osmosis concentrate, the content of lithium ions is 2.5-3.8 g / L, and the content of magnesium ions is less than 250 mg / L.

[0020] Preferably, in step (2), the conditions of the electrodialysis treatment include: the membrane inlet pressure is above 90 KPa, preferably 90-110 KPa; the conductivity of the polar water is above 80 ms / cm, preferably 80-100 ms / cm; the pH value of the polar water is below 5, preferably 3-5.

[0021] Preferably, in the electrodialysis concentrate, the content of lithium ions is 12-13.5 g / L, and the content of magnesium ions is 500-1000 mg / L.

[0022] Preferably, in step (2), in the qualified magnesium-removal solution, the content of lithium ions is 12-13.5 g / L, and the content of magnesium ions is 0.3-1 mg / L.

[0023] Preferably, in step (2), the second ion exchange process is implemented in a resin ion exchange and boron removal device, which is provided with a resin adsorption column with continuous adsorption regeneration transformation, and the resin ion exchange and boron removal device comprises an adsorption zone, a water washing zone, an acid desorption zone, a water washing acid zone and a qualified liquid top water zone arranged in sequence, and a plurality of resin adsorption columns formed by boron removal ion exchange resins are continuously operated in the adsorption zone, the water washing zone, the acid desorption zone, the water washing acid zone and the qualified liquid top water zone, wherein, in the adsorption zone, the MVR concentrated liquid is fed into the resin adsorption column by an upper feeding method for adsorption to obtain the qualified boron removal liquid.

[0024] Preferably, in the qualified boron removal solution, the content of lithium ions is 19-24 g / L, and the content of boron ions is less than 10 mg / L.

[0025] Preferably, in step (3), the lithium precipitation treatment process comprises: mixing the qualified boron removal solution and a sodium carbonate solution.

[0026] Preferably, in step (3), the precipitant is sodium dihydrogen phosphate solution.

[0027] Preferably, in the lithium precipitation mother solution, the content of lithium ions is 1200-1400 mg / L, and the content of carbonate is 20-25 g / L.

[0028] Preferably, in the lithium extraction tail solution, the content of lithium ions is 10-80 mg / L, and the content of magnesium ions is 15-18 g / L.

[0029] Compared with the prior art, the present invention has the following technical effects:

[0030] (1) Compared with the traditional lithium extraction process, the method described in the present invention uses an adsorption method to directly separate lithium from the raw brine, which is not limited by the endowment characteristics of the raw brine components. It can be carried out even when the lithium content is low. It has good universality and has the advantages of simple process and short process flow. It realizes the separation of lithium and other impurities in one step, improves the lithium recovery rate, reduces costs, improves product quality, and is not limited by natural conditions;

[0031] (2) According to the method of the present invention, in a further preferred case, the lithium extraction tail liquid is used as a regeneration agent to regenerate the adsorbent, which effectively solves the problem of "sulfate poisoning" of the adsorbent and restores a certain performance of the adsorbent;

[0032] (3) The method described in the present invention utilizes lithium extraction tail liquid and lithium precipitation mother liquor to produce lithium phosphate and magnesium carbonate while producing lithium carbonate, thereby solving the problem of resource loss of lithium extraction tail liquid and lithium precipitation mother liquor, and realizing the maximum recovery of lithium for the brine entering the workshop. The process does not require salt pan beach drying, and the brine directly enters the workshop for adsorption and lithium extraction, thereby reducing investment costs and alleviating the ecological and environmental pressure of salt pan construction, and laying a foundation for the subsequent development of high-end products of lithium and magnesium resources. DETAILED DESCRIPTION

[0033] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0034] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0035] The method for co-producing lithium carbonate, lithium phosphate and magnesium carbonate by using the original brine of magnesium sulfate subtype salt lake of the present invention comprises the following steps:

[0036] (1) subjecting the original brine of magnesium sulfate subtype salt lake to adsorption and lithium extraction treatment, followed by desorption, to obtain lithium qualified solution and lithium extraction tail solution;

[0037] (2) The lithium qualified solution is transported to a first nanofiltration device for primary nanofiltration treatment to remove magnesium ions and obtain primary nanofiltration water, and the primary nanofiltration water is subjected to reverse osmosis treatment to obtain reverse osmosis concentrate; the reverse osmosis concentrate is input into an electrodialysis device for electrodialysis treatment to obtain electrodialysis concentrate and fresh water; the electrodialysis concentrate is transported to a second nanofiltration device for secondary nanofiltration treatment to remove magnesium ions and obtain secondary nanofiltration water, and the secondary nanofiltration water is subjected to a first ion exchange to remove magnesium ions and obtain magnesium-removed qualified solution and magnesium-removed desorption solution; the magnesium-removed qualified solution is subjected to MVR concentration to obtain MVR concentrated solution and water; the MVR concentrated solution is subjected to a second ion exchange to remove boron ions and obtain boron-removed qualified solution; wherein the condensed water obtained in the MVR concentration process and the fresh water obtained in the electrodialysis process are returned to the first nanofiltration device to participate in the primary nanofiltration treatment; the magnesium-removed desorption solution is returned to the electrodialysis device to participate in the electrodialysis treatment;

[0038] (3) The qualified boron-removed solution is subjected to lithium precipitation treatment to obtain lithium carbonate and lithium precipitation mother liquor; the lithium precipitation mother liquor is mixed with a precipitant, and then subjected to filter press separation to obtain a crude lithium phosphate product and a filtrate; the hydroxide content in the filtrate is controlled at 1.5-2.5 g / L and the pH value of the filtrate is adjusted to 8-11, and then mixed with the lithium extraction tail liquid obtained in step (1) to obtain a basic magnesium carbonate suspension, and then separated to obtain magnesium carbonate.

[0039] According to the method described in the present invention, the adsorption method is used to directly separate lithium from the raw brine, which is not limited by the endowment characteristics of the raw brine components and can be carried out even when the lithium content is low, and has good universality; while producing lithium carbonate products, the lithium precipitation mother liquor and the lithium extraction tail liquor are jointly treated to jointly produce basic magnesium carbonate and lithium phosphate products, thereby solving the problem of large magnesium and lithium separation, improving the comprehensive lithium yield, fully improving the resource utilization rate of the lithium precipitation mother liquor and the lithium extraction tail liquor, improving the mining and utilization rate of lithium resources in salt lakes, reducing investment costs and alleviating the pressure on ecological and environmental protection of salt field construction.

[0040] In the method of the present invention, in step (1), in the magnesium sulfate subtype salt lake original brine, the content of lithium ions can be above 150 mg / L, preferably 150-300 mg / L; the content of magnesium ions can be 15-18 g / L, preferably 15-17 g / L; the content of sodium ions can be 75-95 g / L, preferably 75-85 g / L; the content of potassium ions can be 9-10 g / L, preferably 9-9.5 g / L; the content of boron ions can be 250-350 mg / L, preferably 250-300 mg / L; the content of chloride ions can be 170-200 g / L, preferably 170-180 g / L; the content of sulfate ions can be 9-13 g / L, preferably 9-11 g / L.

[0041] In the method of the present invention, in step (1), the adsorption process may include: performing the adsorption by an adsorbent. In order to improve lithium selectivity and enhance the ability to resist interference from potassium, sodium, magnesium and other ions, the adsorbent is preferably at least one of a layered aluminum adsorbent, a layered titanium adsorbent, a spinel manganese adsorbent and a spinel titanium adsorbent, preferably a layered aluminum adsorbent.

[0042] In the method described in the present invention, the adsorption is carried out in a continuous adsorption lithium extraction device. The specific process of the adsorption may include: pumping the original brine of the magnesium sulfate subtype salt lake into the continuous adsorption lithium extraction device, and performing the adsorption by an adsorbent. The conditions for the adsorption include: the rotation interval of the adsorption tower can be 10-12min, preferably 10-11min; the operating pressure of the device can be 2.5-4MPa, preferably 2.5-3.8MPa; the control temperature can be 20-50℃, preferably 20-40℃; the feed adsorption flow rate can be 0.5-3.5BV / h, preferably 0.5-2.5BV / h; the top liquid flow rate can be 1-3BV / h, preferably 1-2BV / h; the desorption flow rate can be 0.5-4BV / h, preferably 0.5-2BV / h. The adsorption and lithium extraction treatment according to the method of the present invention solves the problems of low lithium yield, susceptibility of brine concentration to natural environment, high content of impurities such as magnesium, potassium, boron, sodium in raw brine, and difficulty in separating lithium from magnesium, sodium, potassium impurities, and high production and processing costs in the prior art due to the influence of uncontrollable factors such as entrainment and leakage of pre-treated concentrated brine during the salt pan beach drying process. In this article, pressure is gauge pressure.

[0043] In the method of the present invention, in step (1), the desorption process may include: performing the desorption by desorption water. The desorption water may be water with a conductivity of 200-300 us / cm and a pH value of 7-8.

[0044] In the method of the present invention, the method may further include: regenerating the adsorbent by a regeneration agent. The regeneration agent may be a magnesium chloride solution and / or a hydrochloric acid solution. The regeneration agent is preferably the lithium extraction tail solution obtained in step (1). The pH value of the regeneration agent may be 7.5-8.5, preferably 7.5-8; the content of lithium ions may be 10-80 mg / L, preferably 10-50 mg / L; the content of magnesium ions may be 15-18 g / L, preferably 15-17 g / L. In the adsorption process, due to the large ion radius of sulfate ions, a part of sulfate ions enter between the molecular layers of the adsorbent material during the adsorption process, reducing the channel, and a part of them will combine with the lithium ions therein to form lithium sulfate with lower solubility, thereby producing certain crystals and affecting the adsorption performance of the adsorbent, while high concentrations of magnesium chloride solution and hydrochloric acid solution can restore certain performance of the adsorbent. Therefore, using high magnesium solution or hydrochloric acid solution as a regeneration agent for adsorbent regeneration can effectively solve the problem of "sulfate poisoning" of the adsorbent. The magnesium ion concentration in the magnesium chloride solution can be controlled to be 70-85 g / L, preferably 75-80 g / L. The concentration of the hydrochloric acid solution can be 5-12 mol / L, preferably 8-10 mol / L. The dosage ratio of the regeneration agent to the adsorbent can be (0.5-2.2):1, preferably (0.7-2):1.

[0045] In the method of the present invention, in the lithium qualified solution, the content of lithium ions can be more than 400 mg / L, preferably 400-600 mg / L; the content of magnesium ions can be less than 500 mg / L, preferably 300-500 mg / L; the content of sodium ions can be less than 300 mg / L, preferably 200-300 mg / L; the content of potassium ions can be less than 20 mg / L, preferably 10-20 mg / L; the content of boron ions can be less than 100 mg / L, preferably 50-100 mg / L.

[0046] In the method of the present invention, in step (2), the process of the primary nanofiltration treatment may specifically include: pumping the lithium qualified solution into a first nanofiltration device for nanofiltration. The first nanofiltration device is provided with a first nanofiltration membrane. The retention rate of the first nanofiltration membrane may be 80%-95%, preferably 80%-90%. In order to remove calcium ions and magnesium ions, the conditions of the primary nanofiltration treatment include: the membrane inlet pressure is preferably 3.5-4MPa, more preferably 3.5-3.8MPa; the feed temperature is preferably 22-25°C, more preferably 22-24°C; the feed conductivity is preferably 18-22ms / cm, more preferably 18-20ms / cm. The primary nanofiltration treatment is a pure physical process and is a new environmentally friendly process that conforms to the concept of safety and environmental protection. The primary nanofiltration treatment has low requirements for the original brine of the magnesium sulfate subtype salt lake, which correspondingly reduces the loss of lithium resources in the salt field process and increases the comprehensive utilization rate of lithium resources.

[0047] In the method described in the present invention, in step (2), the specific process of the reverse osmosis treatment may include: conveying the primary nanofiltration produced water to a reverse osmosis device for concentration. The conditions of the reverse osmosis treatment include: the pH value of the influent water may be 6-7, preferably 6-6.5; the membrane inlet pressure may be 3.5-4MPa, preferably 3.5-3.8MPa; the feed temperature may be 22-25°C, preferably 22-24°C; the feed conductivity may be 12-14ms / cm, preferably 12-13ms / cm. The reverse osmosis device may be provided with a reverse osmosis membrane. The salt removal rate of the reverse osmosis membrane may be 95%-100%, preferably 97%-99.7%.

[0048] In the method of the present invention, in the reverse osmosis concentrate, the content of lithium ions may be 2.5-3.8 g / L, preferably 3-3.8 g / L; the content of magnesium ions may be less than 250 mg / L, preferably 150-250 mg / L.

[0049] In the method of the present invention, in order to achieve the one-step separation of the difficult-to-separate adjacent elements of lithium and boron and the high-fold concentration of lithium, in step (2), the conditions of the electro-osmosis treatment include: the membrane inlet pressure is preferably above 90KPa, more preferably 90-110KPa; the conductivity of the polar water is preferably above 80ms / cm, more preferably 80-100ms / cm; the pH value of the polar water is preferably below 5, more preferably 3-5. The electrodialysis device can be provided with an electrodialysis membrane. In the process of concentrating lithium ions, the lithium recovery rate of the electrodialysis membrane can be above 99%, preferably 99.5%-99.9%.

[0050] In the method of the present invention, in the electrodialysis concentrate, the content of lithium ions may be 12-13.5 g / L, preferably 12.5-13.5 g / L; the content of magnesium ions may be 500-1000 mg / L, preferably 500-800 mg / L. In the fresh water, the content of lithium ions may be 1000-2000 mg / L, preferably 1500-2000 mg / L; the content of magnesium ions may be 15-55 mg / L, preferably 15-30 mg / L.

[0051] In the method of the present invention, in step (2), the second nanofiltration device is provided with a second nanofiltration membrane. The rejection rate of the second nanofiltration membrane can be 90%-99%, preferably 95%-99%. In order to remove calcium ions and magnesium ions, the conditions of the secondary nanofiltration treatment include: the membrane inlet pressure is preferably 3.5-4MPa, more preferably 3.5-3.8MPa; the feed temperature is preferably 22-25°C, more preferably 22-24°C; the feed conductivity is preferably 18-22ms / cm, more preferably 18-20ms / cm.

[0052] In the method described in the present invention, in step (2), in the secondary nanofiltration produced water, the content of lithium ions can be 12-13.5 g / L, preferably 12.5-13.5 g / L; the content of magnesium ions can be 3-5 mg / L, preferably 3-4 mg / L.

[0053] In the method of the present invention, in step (2), the first ion exchange process is implemented in a resin ion exchange device for removing calcium and magnesium, and the resin ion exchange device for removing calcium and magnesium is provided with a resin adsorption column for continuous adsorption regeneration transformation to achieve deep removal of calcium ions and magnesium ions, so that the magnesium ion content of the qualified magnesium removal solution is less than 1 mg / L. In the resin ion exchange device for removing calcium and magnesium, hydrochloric acid with a mass fraction of 3%-5% and sodium hydroxide solution with a mass fraction of 0.1%-0.2% are used to carry out acid regeneration alkali transformation on the resin adsorption column, respectively. The cycle of the acid regeneration alkali transformation can be 30-40h, preferably 34-38h.

[0054] In the method of the present invention, in step (2), in the magnesium removal qualified solution, the content of lithium ions can be 12-13.5 g / L, preferably 12.5-13.5 g / L; the content of magnesium ions can be 0.3-1 mg / L, preferably 0.3-0.8 mg / L. In the magnesium removal desorption solution, the content of lithium ions can be 5-15 mg / L, preferably 5-10 mg / L; the content of magnesium ions can be 1-5 mg / L, preferably 1-3 mg / L.

[0055] In the method of the present invention, in step (2), the specific process of MVR concentration may include: transporting the magnesium-removed qualified solution to an MVR device for concentration. The content of lithium ions in the MVR concentrated solution may be 19-24 g / L, preferably 21-24 g / L.

[0056] In the method of the present invention, in step (2), the second ion exchange process is implemented in a resin deboronation device, the resin deboronation device is provided with a resin adsorption column for continuous adsorption regeneration transformation, the resin deboronation device comprises an adsorption zone, a water washing zone, an acid desorption zone, a water washing acid zone and a qualified liquid top water zone arranged in sequence, and a plurality of resin adsorption columns formed by deboronation ion exchange resins are continuously operated in the adsorption zone, the water washing zone, the acid desorption zone, the water washing acid zone and the qualified liquid top water zone, wherein, in the adsorption zone, the MVR concentrated liquid is fed into the resin adsorption column by an upper feeding method for adsorption to obtain the deboronation qualified liquid, so as to achieve the purpose of deep removal of boron ions, so that the boron ion content of the deboronation qualified liquid is less than 10 mg / L. In the resin deboronation device, hydrochloric acid with a mass fraction of 3%-5% and sodium hydroxide solution with a mass fraction of 0.1%-0.2% are used to carry out acid regeneration alkali transformation on the resin adsorption column respectively. The cycle of the acid-to-alkali transformation can be 30-40 hours, preferably 34-38 hours.

[0057] In the method described in the present invention, in the qualified boron removal solution, the content of lithium ions can be 19-24 g / L, preferably 21-24 g / L; the content of boron ions can be less than 10 mg / L, preferably 5-10 mg / L.

[0058] In the method of the present invention, in order to obtain a battery-grade lithium carbonate product, in step (3), the lithium precipitation process preferably includes: mixing the qualified deboronation solution and the sodium carbonate solution at a temperature of 80-85°C for 0.5-1h and separating the solid phase by centrifugation at a speed of 800-1000r / min for 15-18min and washing with water 1-2 times, then washing with the reverse osmosis product water obtained by the reverse osmosis treatment in step (2) for 1.5-2min, and then drying in a flash dryer at a temperature of 130-150°C, the flash dryer inlet temperature is controlled to be 250-265°C, and the outlet temperature is controlled to be 110-125°C, to obtain lithium carbonate. The concentration of the sodium carbonate solution can be 170-190g / L, preferably 175-185g / L. The volume ratio of the amount of the qualified deboronation solution and the sodium carbonate solution can be (1.5-2.5):1, preferably (1.5-2):1. In the lithium carbonate, the mass fraction of lithium carbonate is more than 99.65%, the mass fraction of sodium element is less than 0.033%, the mass fraction of potassium element is less than 0.0016%, the mass fraction of magnesium element is less than 0.0012%, the mass fraction of calcium element is less than 0.0014%, the mass fraction of boron element is less than 0.0031%, the mass fraction of iron element is less than 0.0001%, the mass fraction of zinc element is less than 0.0002%, the mass fraction of copper element is less than 0.000017%, the mass fraction of lead element is less than 0.000002%, the mass fraction of silicon element is less than 0.0015%, the mass fraction of aluminum element is less than 0.001%, the mass fraction of manganese element is less than 0.001%, the mass fraction of nickel element is less than 0.001%, the mass fraction of sulfate ion is less than 0.0021%, the mass fraction of chlorine element is less than 0.01%, and the mass fraction of water is less than 0.13%.

[0059] In the method of the present invention, in step (3), the precipitant can be one or two of sodium dihydrogen phosphate solution, trisodium phosphate solution, and disodium hydrogen phosphate solution, preferably sodium dihydrogen phosphate solution. The concentration of the sodium dihydrogen phosphate solution can be 200-220g / L, preferably 210-220g / L. The volume ratio of the lithium precipitation mother solution and the precipitant can be (25-37.5):1, preferably (29-33):1. The conditions for mixing the lithium precipitation mother solution and the precipitant include: the temperature can be 70-85°C, preferably 75-80°C; the time can be 0.5-1h, preferably 0.85-1h.

[0060] In the method of the present invention, in step (3), the method may further include: washing the crude lithium phosphate obtained by the pressure filtration separation with the produced water obtained by the reverse osmosis treatment for 1.5-2 minutes, and then drying it in a flash dryer at a temperature of 175-210°C, the outlet temperature of the dryer is controlled to be 75-85°C, and the feed spiral frequency of the dryer is controlled to be 30-50HZ, to obtain lithium phosphate. In some embodiments, the yield of the finished lithium phosphate is 85%-95%, the mass fraction of lithium phosphate is more than 92%, the mass fraction of calcium element is less than 0.02%, the mass fraction of magnesium element is less than 0.02%, the mass fraction of sulfate ion is less than 0.15%, the mass fraction of boron element is less than 0.02%, the mass fraction of sodium element is less than 2%, the mass fraction of water is less than 0.3%, and the mass fraction of acid insoluble matter is less than 0.015%.

[0061] In the method of the present invention, in the lithium precipitation mother liquor, the content of lithium ions can be 1200-1400 mg / L, preferably 1300-1400 mg / L; the content of carbonate can be 20-25 g / L, preferably 22-25 g / L.

[0062] In the method of the present invention, in the lithium extraction tail liquid, the content of lithium ions can be 10-80 mg / L, preferably 10-50 mg / L; the content of magnesium ions can be 15-18 g / L, preferably 16-18 g / L.

[0063] In the method of the present invention, the hydroxide content in the filtrate can be controlled at 1.5-2.5 g / L, preferably 1.8-2.2 g / L. The pH value of the filtrate can be adjusted to 8-11, preferably 9-11. The carbonate content of the filtrate can be adjusted to 15-22 g / L, preferably 16-20 g / L. The volume ratio of the lithium extraction tail liquid and the solution obtained by acidifying the filtrate can be 2-4:1, preferably 2.5-3.5:1.

[0064] In the method described in the present invention, in step (3), the specific process of separating and obtaining magnesium carbonate may include: separating the solid phase from the basic magnesium carbonate suspension by filter press. In a specific embodiment, the specific process of separating and obtaining magnesium carbonate includes: filtering the basic magnesium carbonate suspension through a filter press to obtain a basic magnesium carbonate filter cake, and controlling the water content of the basic magnesium carbonate filter cake to be below 30%, and then drying the basic magnesium carbonate filter cake through a flash dryer to control the water content of the filter cake to be below 2%, thereby obtaining magnesium carbonate. In some embodiments, in the magnesium carbonate, the mass fraction of chloride is below 0.05%; and the particle size D50 of the magnesium carbonate is below 5 μm.

[0065] In some embodiments, the method of the present invention for co-producing lithium carbonate, lithium phosphate and magnesium carbonate using raw brine of magnesium sulfate subtype salt lake comprises the following steps:

[0066] (1) pumping the magnesium sulfate subtype salt lake original brine into the continuous adsorption lithium extraction device, and performing adsorption lithium extraction treatment by the adsorbent under the conditions of an adsorption tower rotation interval of 10-12min, a device operating pressure of 2.5-4MPa, a control temperature of 20-50°C, a feed adsorption flow rate of 0.5-3.5BV / h, a top liquid flow rate of 1-3BV / h and a desorption flow rate of 0.5-4BV / h, followed by desorption by water with a conductivity of 200-300us / cm and a pH value of 7-8 to obtain a lithium qualified solution and a lithium extraction tail solution, and regenerating the adsorbent by a regeneration reagent, wherein the regeneration reagent is a magnesium chloride solution and / or a hydrochloric acid solution;

[0067] (2) The qualified lithium solution is transported to a first nanofiltration device with a retention rate of 80%-95%, and a first nanofiltration treatment is carried out under the conditions of a membrane inlet pressure of 3.5-4MPa, a feed temperature of 22-25°C, and a feed conductivity of 18-22ms / cm to remove magnesium ions and obtain a first nanofiltration product water; the first nanofiltration product water is transported to a reverse osmosis device with a desalination rate of 95%-100%, and a reverse osmosis treatment is carried out under the conditions of a pH value of 6-7, a membrane inlet pressure of 3.5-4MPa, a feed temperature of 22-25°C, and a feed conductivity of 12-14ms / cm to obtain a reverse osmosis concentrate; the reverse osmosis concentrate is input into an electrodialysis device under the conditions of a membrane inlet pressure of more than 90KPa, a polar water conductivity of more than 80ms / cm, and a reverse osmosis concentrate is obtained. The electrodialysis treatment is carried out under the condition that the pH value of the upper and lower water is below 5 to obtain an electrodialysis concentrate and fresh water; the electrodialysis concentrate is transported to a second nanofiltration device with a retention rate of 90%-99% for secondary nanofiltration treatment under the conditions of a membrane inlet pressure of 3.5-4MPa, a feed temperature of 22-25°C and a feed conductivity of 18-22ms / cm to deeply remove magnesium ions to obtain secondary nanofiltration product water, and the secondary nanofiltration product water is transported to a resin ion exchange device for calcium and magnesium removal to carry out a first ion exchange to remove magnesium ions to obtain a magnesium-removed qualified liquid and a magnesium-removed desorption liquid; and a resin adsorption column in the resin ion exchange device for calcium and magnesium removal is acid-regenerated and alkali-transformed using hydrochloric acid with a mass fraction of 3%-5% and a sodium hydroxide solution with a mass fraction of 0.1%-0.2%. The cycle of the acid regeneration alkali transformation is 30-40h; the qualified magnesium removal liquid is transported to the MVR device for MVR concentration to obtain MVR concentrated liquid and condensed water; the MVR concentrated liquid is transported to the resin ion exchange and boron removal device for a second ion exchange to remove boron ions and obtain a qualified boron removal liquid; the resin adsorption column in the resin ion exchange and boron removal device is transformed into an acid regeneration alkali by using a hydrochloric acid with a mass fraction of 3%-5% and a sodium hydroxide solution with a mass fraction of 0.1%-0.2%, and the cycle of the acid regeneration alkali transformation is 30-40h; wherein, the condensed water obtained in the MVR concentration process and the fresh water obtained in the electrodialysis process are returned to the first nanofiltration device to participate in the primary nanofiltration treatment; the magnesium removal desorption liquid is returned to the electrodialysis device to participate in the electrodialysis treatment;

[0068] (3) mixing the qualified deboronation solution and the sodium carbonate solution at a temperature of 80-85°C for 0.5-1.5h, centrifuging at a speed of 800-1000r / min for 15-18min to separate the solid phase and washing with water 1-2 times, then washing with the reverse osmosis product water obtained by the reverse osmosis treatment in step (2) for 1.5-2min, and then drying with a flash dryer at a temperature of 130-150°C, the inlet air temperature of the flash dryer is controlled at 250-265°C, and the outlet air temperature is controlled at 110-125°C, to obtain lithium carbonate and lithium precipitation mother liquor; mixing the lithium precipitation mother liquor and the precipitant at a temperature of 75-85°C for 0.5-1h, and then performing filter press separation to obtain a crude lithium phosphate product and a filtrate, and separating the crude lithium phosphate obtained by the filter press separation The product is washed with water obtained by the reverse osmosis treatment, and then dried in a flash dryer at a temperature of 175-210° C., the outlet temperature of the dryer is controlled to be about 80° C., and the feed spiral frequency of the dryer is controlled to be 30-50 Hz to obtain lithium phosphate; the pH value of the filtrate is adjusted to 9-11, and then mixed with the lithium extraction tail liquid obtained in step (1) to obtain a basic magnesium carbonate suspension, and the basic magnesium carbonate suspension is subjected to filter press to separate the solid phase to obtain a basic magnesium carbonate filter cake, and the water content of the basic magnesium carbonate filter cake is controlled to be less than 50%, and then washed with water, and the solid phase is separated again by filter press, and the water content of the basic magnesium carbonate filter cake is controlled to be less than 30%, and then the basic magnesium carbonate filter cake is dried in a flash dryer to control the water content of the filter cake to be less than 2%, to obtain magnesium carbonate;

[0069] Among them, in the original brine of the magnesium sulfate subtype salt lake, the content of lithium ions is above 150 mg / L, the content of magnesium ions is 15-18 g / L, the content of sodium ions is 75-95 g / L, the content of potassium ions is 9-10 g / L, the content of boron ions is 250-350 mg / L, the content of chloride ions is 170-200 g / L, and the content of sulfate ions is 9-13 g / L.

[0070] The following examples further illustrate the method for co-producing lithium carbonate, lithium phosphate and magnesium carbonate using the original brine of magnesium sulfate subtype salt lakes of the present invention. The examples are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

[0071] The experimental methods in the following examples, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following examples, unless otherwise specified, are all commercially available.

[0072] Example 1

[0073] (1) The magnesium sulfate subtype salt lake original brine (in the magnesium sulfate subtype salt lake original brine, the lithium ion content is 152 mg / L, the magnesium ion content is 16 g / L, the sodium ion content is 82 g / L, the potassium ion content is 9 g / L, the boron ion content is 304 mg / L, the chloride ion content is 184 g / L, and the sulfate ion content is 11 g / L) is pumped into the continuous adsorption lithium extraction device, and the adsorbent is rotated in the adsorption tower at an interval of 11 min, the device operating pressure is 3.8 MPa, the control temperature is 30° C., the feed adsorption flow rate is 2.5 BV / h, and the top liquid flow rate is 2 BV / h. V / h and a desorption flow rate of 2BV / h, and then desorbing with water having an electrical conductivity of 250us / cm and a pH value of 7.5 to obtain a lithium qualified solution (in the lithium qualified solution, the content of lithium ions is 412mg / L; the content of magnesium ions is 496mg / L; the content of sodium ions is 296mg / L, the content of potassium ions is 18mg / L, and the content of boron ions is 95mg / L) and a lithium extraction tail liquid (the pH value of the lithium extraction tail liquid is 8, the content of lithium ions is 33mg / L, and the content of magnesium ions is 16g / L), and the adsorbent is regenerated by the lithium extraction tail liquid;

[0074] (2) The qualified lithium solution is transported to a first nanofiltration device with a retention rate of 80%, and a first-level nanofiltration treatment is performed under the conditions of a membrane inlet pressure of 3.8 MPa, a feed temperature of 25° C., and a feed conductivity of 20 ms / cm to remove magnesium ions, thereby obtaining a first-level nanofiltration product water. The first-level nanofiltration product water is transported to a reverse osmosis device with a salt removal rate of 97%, and a reverse osmosis treatment is performed under the conditions of a pH value of 6.5, a membrane inlet pressure of 3.8 MPa, a feed temperature of 25° C., and a feed conductivity of 13 ms / cm. The reverse osmosis concentrate was subjected to electrodialysis treatment to obtain a reverse osmosis concentrate (in which the lithium ion content was 3.3 g / L and the magnesium ion content was 250 mg / L); the reverse osmosis concentrate was input into an electrodialysis device for electrodialysis treatment under the conditions of a membrane inlet pressure of 90 KPa, an electric conductivity of the polar water of 80 ms / cm and a pH value of the polar water of 5 to obtain an electrodialysis concentrate (in which the lithium ion content was 12.8 g / L and the magnesium ion content was 765 mg / L) and fresh water (in which the lithium ion content was 1.2 g / L and the magnesium ion content was 1.6 g / L). The electrodialysis concentrate was transported to a second nanofiltration device with a rejection rate of 95% and subjected to secondary nanofiltration treatment under the conditions of a membrane inlet pressure of 3.8 MPa, a feed temperature of 25°C and a feed conductivity of 22 ms / cm to remove magnesium ions and obtain secondary nanofiltration product water (in the secondary nanofiltration product water, the lithium ion content was 12.6 g / L and the magnesium ion content was 4 mg / L), and the secondary nanofiltration product water was transported to a resin A first ion exchange is performed in the ion exchange calcium and magnesium removal device to remove magnesium ions to obtain a qualified magnesium removal solution (in the qualified magnesium removal solution, the lithium ion content is 12.6 g / L, and the magnesium ion content is 0.7 mg / L) and a magnesium removal desorption solution (in the magnesium removal desorption solution, the lithium ion content is 11 mg / L, and the magnesium ion content is 3 mg / L); 4% by mass hydrochloric acid and 0.1% by mass sodium hydroxide solution are used to perform acid regeneration alkali transformation on the resin adsorption column in the resin ion exchange calcium and magnesium removal device.The cycle of the acid-regeneration alkali transformation is 36 hours; the qualified magnesium removal liquid is transported to the MVR device for MVR concentration to obtain MVR concentrated liquid (in the MVR concentrated liquid, the lithium ion content is 22g / L) and water; the MVR concentrated liquid is transported to the resin ion exchange and boron removal device for a second ion exchange to remove boron ions to obtain a qualified boron removal liquid (in the qualified boron removal liquid, the lithium ion content is 22g / L; the boron ion content is 10mg / L); 4% by mass hydrochloric acid and 0.1% by mass sodium hydroxide solution are used to perform acid-regeneration alkali transformation on the resin adsorption column in the resin ion exchange and boron removal device, and the cycle of the acid-regeneration alkali transformation is 36 hours; wherein, the water obtained in the MVR concentration process and the fresh water obtained in the electrodialysis treatment process are returned to the first nanofiltration device to participate in the primary nanofiltration treatment; the magnesium removal desorption liquid is returned to the electrodialysis device to participate in the electrodialysis treatment;.

[0075] (3) The qualified deboronation solution and a sodium carbonate solution with a concentration of 180 g / L were mixed at a temperature of 80° C. for 0.5 h, and the solid phase was separated by centrifugation at a speed of 900 r / min for 16 min, and washed once with water (the volume ratio of the qualified deboronation solution to the sodium carbonate solution was 2.5:1), and then the reverse osmosis product water obtained by the reverse osmosis treatment in step (2) was washed for 1.8 min, and then flashed at a temperature of 130° C. The mixture was dried in a steam dryer, with the air inlet temperature of the flash dryer controlled at 260°C and the air outlet temperature controlled at 115°C, to obtain lithium carbonate and lithium precipitation mother liquor (in the lithium precipitation mother liquor, the lithium ion content was 1373 mg / L and the carbonate content was 23 g / L); the lithium precipitation mother liquor and sodium dihydrogen phosphate solution (the concentration of the sodium dihydrogen phosphate solution was 210 g / L, and the solvent of the sodium dihydrogen phosphate solution was water) were mixed at a temperature of 80°C for 1 h (the amount of the lithium precipitation mother liquor and the sodium dihydrogen phosphate solution was 210 g / L and the solvent of the sodium dihydrogen phosphate solution was 210 g / L and the solvent of the sodium dihydrogen phosphate solution was 210 g / L and the lithium precipitation mother liquor ... sodium dihydrogen phosphate solution was 210 g / L and the solvent of the lithium precipitation mother liquor was 210 g / L and the lithium precipitation mother liquor was 210 g / L and the solvent of the lithium precipitation mother liquor was 210 g / L and the lithium precipitation mother liquor was 210 g / L and the solvent of the lithium precipitation mother liquor was 210 g / L and the lithium precipitation mother liquor was 210 g / L and the solvent of the lithium precipitation mother liquor was 210 g / L and the lithium precipitation mother liquor was 210 g / L and the solvent of The volume ratio of the raw materials is 25:1), followed by filter pressing to obtain a crude lithium phosphate product and a filtrate, the crude lithium phosphate obtained by the filter pressing separation is washed for 1.8 minutes by the produced water obtained by the reverse osmosis treatment, and then dried by a flash dryer at a temperature of 175°C, the outlet temperature of the dryer is controlled to 75°C, and the feed spiral frequency of the dryer is controlled to 40HZ to obtain lithium phosphate; the pH value of the filtrate is adjusted to 9 (in the solution obtained by acidifying the filtrate, the carbonate The content of the filtrate is 15 g / L), and then mixed with the lithium extraction tail liquid obtained in step (1) (the volume ratio of the lithium extraction tail liquid to the solution obtained by acidifying the filtrate is 2:1) to obtain a basic magnesium carbonate suspension, and the basic magnesium carbonate suspension is filtered through a filter press to obtain a basic magnesium carbonate filter cake, and the water content of the basic magnesium carbonate filter cake is controlled to be below 30%, and then the basic magnesium carbonate filter cake is dried by a flash dryer to control the water content of the filter cake to be below 2%, to obtain magnesium carbonate.

[0076] The content of each component in the lithium carbonate, lithium phosphate and magnesium carbonate prepared in Example 1 is tested by national standards or industry standards. The test method refers to the national standard of the People's Republic of China for brine lithium carbonate GB / T23853-2022, the non-ferrous metal industry standard of the People's Republic of China for lithium phosphate YS / T637-202X, and the chemical industry standard of the People's Republic of China for industrial hydrated basic magnesium carbonate HG / T2595-2010. The recovery rate of lithium is calculated as follows: The purity of lithium carbonate, lithium phosphate and magnesium carbonate as well as the recovery rate of lithium are recorded in Table 1.

[0077] In the lithium carbonate prepared in Example 1, the mass fraction of lithium carbonate is 99.65%, the mass fraction of sodium element is 0.033%, the mass fraction of potassium element is 0.0016%, the mass fraction of magnesium element is 0.0012%, the mass fraction of calcium element is 0.0014%, the mass fraction of boron element is 0.0031%, the mass fraction of iron element is 0.0001%, the mass fraction of zinc element is 0.0002%, the mass fraction of copper element is 0.000017%, the mass fraction of lead element is 0.000002%, the mass fraction of silicon element is 0.0015%, the mass fraction of aluminum element is 0.001%, the mass fraction of manganese element is 0.001%, the mass fraction of nickel element is 0.001%, the mass fraction of sulfate ion is 0.0021%, the mass fraction of chlorine element is 0.01%, and the mass fraction of water is 0.13%. The battery-grade lithium carbonate finished product prepared in Example 1 meets the brine battery-grade lithium carbonate standard GB / T23853-2022.

[0078] In the lithium phosphate prepared in Example 1, the mass fraction of lithium phosphate is 92%, the mass fraction of calcium element is 0.02%, the mass fraction of magnesium element is 0.02%, the mass fraction of sulfate ion is 0.15%, the mass fraction of boron element is 0.02%, the mass fraction of sodium element is 2%, the mass fraction of water is 0.3%, and the mass fraction of acid insoluble matter is 0.015%. The yield of the lithium phosphate finished product is 89%.

[0079] In the magnesium carbonate prepared in Example 1, the mass fraction of magnesium carbonate (calculated as MgO) is 44.76%, and the mass fraction of chloride is 0.05%.

[0080] The particle size of the magnesium carbonate prepared in Example 1 was measured by the chemical industry standard. The test method was based on the chemical industry standard of the People's Republic of China, industrial hydrated basic magnesium carbonate HG / T2595-2010. The particle size D50 of the magnesium carbonate was 5 μm.

[0081] Example 2

[0082] (1) The magnesium sulfate subtype salt lake original brine (in the magnesium sulfate subtype salt lake original brine, the lithium ion content is 150 mg / L, the magnesium ion content is 15 g / L, the sodium ion content is 74 g / L, the potassium ion content is 9 g / L, the boron ion content is 251 mg / L, the chloride ion content is 172 g / L, and the sulfate ion content is 9 g / L) is pumped into the continuous adsorption lithium extraction device, and the adsorbent is rotated in the adsorption tower at an interval of 10 min, the device operating pressure is 2.5 MPa, the control temperature is 20° C., the feed adsorption flow rate is 0.5 BV / h, and the top liquid flow rate is 1 BV / h. h and a desorption flow rate of 0.5 BV / h for adsorption and lithium extraction treatment, followed by desorption with water having an electrical conductivity of 210 us / cm and a pH value of 7 to obtain a lithium qualified solution (in the lithium qualified solution, the content of lithium ions is 402 mg / L; the content of magnesium ions is 311 mg / L; the content of sodium ions is 197 mg / L, the content of potassium ions is 11 mg / L, and the content of boron ions is 57 mg / L) and a lithium extraction tail solution (the pH value of the lithium extraction tail solution is 7.5, the content of lithium ions is 11 mg / L, and the content of magnesium ions is 15 g / L), and the adsorbent is regenerated by the lithium extraction tail solution;

[0083] (2) The qualified lithium solution is transported to a first nanofiltration device with a retention rate of 85%, and a first nanofiltration treatment is performed under the conditions of an inlet pressure of 3.5 MPa, a feed temperature of 22° C., and a feed conductivity of 18 ms / cm to remove magnesium ions, thereby obtaining a first nanofiltration product water. The first nanofiltration product water is transported to a reverse osmosis device with a salt removal rate of 98%, and a reverse osmosis treatment is performed under the conditions of an inlet pH value of 6, an inlet pressure of 3.5 MPa, a feed temperature of 22° C., and a feed conductivity of 12 ms / cm. The reverse osmosis concentrate is subjected to an electrodialysis treatment to obtain a reverse osmosis concentrate (in which the lithium ion content is 2.5 g / L and the magnesium ion content is 152 mg / L); the reverse osmosis concentrate is input into an electrodialysis device for electrodialysis treatment under the conditions of a membrane inlet pressure of 110 KPa, an electric conductivity of the polar water of 100 ms / cm and a pH value of the polar water of 3 to obtain an electrodialysis concentrate (in which the lithium ion content is 12 g / L and the magnesium ion content is 515 mg / L) and fresh water (in which the lithium ion content is 2.5 g / L and the magnesium ion content is 152 mg / L). ion content is 1022mg / L, and the magnesium ion content is 14mg / L); the electrodialysis concentrate is transported to a second nanofiltration device with a retention rate of 97%, and a secondary nanofiltration treatment is performed under the conditions of a membrane inlet pressure of 3.5MPa, a feed temperature of 22°C, and a feed conductivity of 18ms / cm to remove magnesium ions to obtain secondary nanofiltration product water (in the secondary nanofiltration product water, the lithium ion content is 12g / L, and the magnesium ion content is 3mg / L), and the secondary nanofiltration product water is transported to a tree The first ion exchange is carried out in the resin ionization and calcium and magnesium removal device to remove magnesium ions, and a qualified magnesium removal solution (in the qualified magnesium removal solution, the lithium ion content is 12g / L, and the magnesium ion content is 0.3mg / L) and a magnesium removal desorption solution (in the magnesium removal desorption solution, the lithium ion content is 5mg / L, and the magnesium ion content is 1mg / L); 3% by mass hydrochloric acid and 0.15% by mass sodium hydroxide solution are used to perform acid regeneration and alkali transformation on the resin adsorption column in the resin ionization and calcium and magnesium removal device.The cycle of the acid-regeneration alkali transformation is 30 hours; the qualified magnesium removal liquid is transported to the MVR device for MVR concentration to obtain MVR concentrated liquid (in the MVR concentrated liquid, the lithium ion content is 19 g / L) and water; the MVR concentrated liquid is transported to the resin ion exchange and boron removal device for a second ion exchange to remove boron ions to obtain a qualified boron removal liquid (in the qualified boron removal liquid, the lithium ion content is 19 g / L; the boron ion content is 5 mg / L); 3% by mass hydrochloric acid and 0.15% by mass sodium hydroxide solution are used to perform acid-regeneration alkali transformation on the resin adsorption column in the resin ion exchange and boron removal device, and the cycle of the acid-regeneration alkali transformation is 30 hours; wherein, the water obtained in the MVR concentration process and the fresh water obtained in the electrodialysis treatment process are returned to the first nanofiltration device to participate in the primary nanofiltration treatment; the magnesium removal desorption liquid is returned to the electrodialysis device to participate in the electrodialysis treatment;.

[0084] (3) The qualified deboronation solution and the sodium carbonate solution with a concentration of 170 g / L were mixed at a temperature of 80° C. for 0.5 h, and the solid phase was separated by centrifugation at a speed of 800 r / min for 15 min, and washed twice with water (the volume ratio of the qualified deboronation solution to the sodium carbonate solution was 2:1), and then washed with the reverse osmosis water obtained by the reverse osmosis treatment in step (2) for 1.5 min, and then flash dried at a temperature of 140° C. The flash dryer is dried, the air inlet temperature of the flash dryer is controlled at 250°C, and the air outlet temperature is controlled at 110°C to obtain lithium carbonate and lithium precipitation mother liquor (in the lithium precipitation mother liquor, the lithium ion content is 1184 mg / L, and the carbonate content is 20 g / L); the lithium precipitation mother liquor and sodium dihydrogen phosphate solution (the concentration of the sodium dihydrogen phosphate solution is 215 g / L, and the solvent of the sodium dihydrogen phosphate solution is water) are mixed at a temperature of 85°C for 0.5 h (the volume of the lithium precipitation mother liquor and the sodium dihydrogen phosphate solution is 20 g / L). The ratio is 33:1), followed by filter pressing to obtain a crude lithium phosphate product and a filtrate, the crude lithium phosphate obtained by the filter pressing separation is washed for 1.5 minutes by the produced water obtained by the reverse osmosis treatment, and then dried by a flash dryer at a temperature of 185°C, the outlet temperature of the dryer is controlled to 80°C, and the feed spiral frequency of the dryer is controlled to 30HZ to obtain lithium phosphate; the pH value of the filtrate is adjusted to 10 (in the solution obtained by adjusting the filtrate to acidity, the content of carbonate ions is The amount is 18g / L), and then mixed with the lithium extraction tail liquid obtained in step (1) (the volume ratio of the lithium extraction tail liquid to the solution obtained by adjusting the filtrate to be acidic is 3:1) to obtain a basic magnesium carbonate suspension. The basic magnesium carbonate suspension is filtered through a filter press to obtain a basic magnesium carbonate filter cake, and the water content of the basic magnesium carbonate filter cake is controlled to be below 30%. The basic magnesium carbonate filter cake is then dried by a flash dryer to control the water content of the filter cake to be below 2%, thereby obtaining magnesium carbonate.

[0085] The content of each component in the lithium carbonate, lithium phosphate and magnesium carbonate prepared in Example 2 is tested by national standards or industry standards. The test method refers to the national standard of the People's Republic of China for brine lithium carbonate GB / T23853-2022, the non-ferrous metal industry standard of the People's Republic of China for lithium phosphate YS / T637-202X, and the chemical industry standard of the People's Republic of China for industrial hydrated basic magnesium carbonate HG / T2595-2010. The recovery rate of lithium is calculated as follows: The purity of lithium carbonate, lithium phosphate and magnesium carbonate as well as the recovery rate of lithium are recorded in Table 1.

[0086] Example 3

[0087] (1) The magnesium sulfate subtype salt lake original brine (in the magnesium sulfate subtype salt lake original brine, the lithium ion content is 317 mg / L, the magnesium ion content is 18 g / L, the sodium ion content is 95 g / L, the potassium ion content is 10 g / L, the boron ion content is 354 mg / L, the chloride ion content is 203 g / L, and the sulfate ion content is 13 g / L) is pumped into the continuous adsorption lithium extraction device, and the adsorbent is rotated in the adsorption tower at an interval of 12 min, the device operating pressure is 4 MPa, the control temperature is 50° C., the feed adsorption flow rate is 3.5 BV / h, and the top liquid flow rate is 2 BV / h. / h and a desorption flow rate of 4BV / h, and then desorbing with water having an electrical conductivity of 310us / cm and a pH value of 8 to obtain a lithium qualified solution (in the lithium qualified solution, the content of lithium ions is 612mg / L; the content of magnesium ions is 487mg / L; the content of sodium ions is 290mg / L, the content of potassium ions is 20mg / L, and the content of boron ions is 99mg / L) and a lithium extraction tail liquid (the pH value of the lithium extraction tail liquid is 8.5, the content of lithium ions is 78mg / L, and the content of magnesium ions is 18g / L), and the adsorbent is regenerated by the lithium extraction tail liquid;

[0088] (2) The qualified lithium solution is transported to a first nanofiltration device with a retention rate of 95%, and a first-level nanofiltration treatment is performed under the conditions of an inlet membrane pressure of 4 MPa, a feed temperature of 25°C, and a feed conductivity of 22 ms / cm to remove magnesium ions, thereby obtaining a first-level nanofiltration product water. The first-level nanofiltration product water is transported to a reverse osmosis device with a salt removal rate of 99%, and a reverse osmosis treatment is performed under the conditions of an inlet water pH value of 7, an inlet membrane pressure of 4 MPa, a feed temperature of 25°C, and a feed conductivity of 14 ms / cm. , obtaining a reverse osmosis concentrate (in which the content of lithium ions is 3.8 g / L and the content of magnesium ions is 245 mg / L); inputting the reverse osmosis concentrate into an electrodialysis device for electrodialysis treatment under the conditions of a membrane inlet pressure of 90 KPa, an electric conductivity of the polar water of 81 ms / cm and a pH value of the polar water of 3, to obtain an electrodialysis concentrate (in which the content of lithium ions is 13.5 g / L and the content of magnesium ions is 997 mg / L) and fresh water (in which the content of lithium ions is 13.5 g / L and the content of magnesium ions is 997 mg / L) The content of lithium ions is 1967 mg / L, and the content of magnesium ions is 54 mg / L); the electrodialysis concentrate is transported to a second nanofiltration device with a retention rate of ≥90%, and a secondary nanofiltration treatment is performed under the conditions of a membrane inlet pressure of 4 MPa, a feed temperature of 25°C, and a feed conductivity of 55 ms / cm to remove magnesium ions to obtain secondary nanofiltration product water (in the secondary nanofiltration product water, the content of lithium ions is 13.5 g / L, and the content of magnesium ions is 5 mg / L), and the secondary nanofiltration product water is transported to a resin A first ion exchange is performed in the ion exchange calcium and magnesium removal device to remove magnesium ions to obtain a qualified magnesium removal solution (in the qualified magnesium removal solution, the content of lithium ions is 13.5 g / L, and the content of magnesium ions is 1 mg / L) and a magnesium removal desorption solution (in the magnesium removal desorption solution, the content of lithium ions is 15 mg / L, and the content of magnesium ions is 5 mg / L); 5% by mass hydrochloric acid and 0.2% by mass sodium hydroxide solution are used to perform acid regeneration alkali transformation on the resin adsorption column in the resin ion exchange calcium and magnesium removal device.The cycle of the acid-regeneration alkali transformation is 40 hours; the qualified magnesium removal liquid is transported to the MVR device for MVR concentration to obtain MVR concentrated liquid (in the MVR concentrated liquid, the lithium ion content is 24g / L) and water; the MVR concentrated liquid is transported to the resin ion exchange and boron removal device for a second ion exchange to remove boron ions and obtain a qualified boron removal liquid (in the qualified boron removal liquid, the lithium ion content is 24g / L; the boron ion content is 10mg / L); 5% by mass hydrochloric acid and 0.2% by mass sodium hydroxide solution are used to perform acid-regeneration alkali transformation on the resin adsorption column in the resin ion exchange and boron removal device, and the cycle of the acid-regeneration alkali transformation is 40 hours; wherein, the water obtained in the MVR concentration process and the fresh water obtained in the electrodialysis treatment process are returned to the first nanofiltration device to participate in the primary nanofiltration treatment; the magnesium removal desorption liquid is returned to the electrodialysis device to participate in the electrodialysis treatment;.

[0089] (3) The qualified deboronation solution and a sodium carbonate solution with a concentration of 190 g / L were mixed at a temperature of 85° C. for 1.5 h, and the solid phase was separated by centrifugation at a speed of 1000 r / min for 18 min, and washed twice with water (the volume ratio of the qualified deboronation solution to the sodium carbonate solution was 1.5:1), and then the reverse osmosis product water obtained by the reverse osmosis treatment in step (2) was washed for 2 min, and then flashed at a temperature of 150° C. The precipitated lithium ion was dried in a flash dryer, and the air inlet temperature of the flash dryer was controlled at 265°C and the air outlet temperature was controlled at 125°C to obtain lithium carbonate and lithium precipitation mother liquor (in the lithium precipitation mother liquor, the lithium ion content was 1405 mg / L and the carbonate content was 25 g / L); the lithium precipitation mother liquor and sodium dihydrogen phosphate solution (the concentration of the sodium dihydrogen phosphate solution was 220 g / L, and the solvent of the sodium dihydrogen phosphate solution was water) were mixed at a temperature of 70°C for 1 hour (the concentration of the lithium precipitation mother liquor and the sodium dihydrogen phosphate solution was 220 g / L). The volume ratio of the amount is 37.5:1), followed by filter pressing to obtain a crude lithium phosphate product and a filtrate, the crude lithium phosphate obtained by the filter pressing separation is washed for 2 minutes with the produced water obtained by the reverse osmosis treatment, and then dried by a flash dryer at a temperature of 210°C, the outlet temperature of the dryer is controlled to 85°C, and the feed spiral frequency of the dryer is controlled to 50HZ to obtain lithium phosphate; the pH value of the filtrate is adjusted to 11 (after the filtrate is adjusted to an acidic solution The content of carbonate ion is 22 g / L), and then mixed with the lithium extraction tail liquid obtained in step (1) (the volume ratio of the lithium extraction tail liquid to the solution obtained by adjusting the filtrate to acidity is 4:1), the basic magnesium carbonate suspension is filtered through a filter press to obtain a basic magnesium carbonate filter cake, and the water content of the basic magnesium carbonate filter cake is controlled to be below 30%, and then the basic magnesium carbonate filter cake is dried by a flash dryer to control the water content of the filter cake to be below 2%, to obtain magnesium carbonate.

[0090] The content of each component in lithium carbonate, lithium phosphate and magnesium carbonate prepared in Example 3 was tested by national standards and industry standards. The test method refers to the national standard of the People's Republic of China for brine lithium carbonate GB / T23853-2022, the non-ferrous metal industry standard of the People's Republic of China for lithium phosphate YS / T637-202X, and the chemical industry standard of the People's Republic of China for industrial hydrated basic magnesium carbonate HG / T2595-2010. The recovery rate of lithium is calculated as follows: The purity of lithium carbonate, lithium phosphate and magnesium carbonate as well as the recovery rate of lithium are recorded in Table 1.

[0091] Comparative Example 1

[0092] The method of Example 1 is implemented, except that the original brine of magnesium sulfate subtype salt lake is subjected to salt pan beach sun-drying to precipitate sodium and potassium to obtain old brine (the composition of the old brine is: lithium ion content 3.43 g / L, magnesium ion content 120.35 g / L, sodium ion content less than 2 g / L, potassium ion content less than 1 g / L, boron ion content 3.51 g / L, chloride ion content 328.64 g / L, sulfate ion content 37.65 g / L), and step (2) is carried out, and the obtained boron-removed qualified solution is subjected to step (1) again, and the lithium qualified solution obtained by step (1) is subjected to lithium precipitation treatment.

[0093] Table 1

[0094]

[0095] It can be seen from the results in Table 1 that although the purities of lithium carbonate, lithium phosphate and magnesium carbonate in the embodiments of the method described in the present invention are not much different, the recovery rate of lithium is significantly better, which fully improves the resource utilization rate of lithium precipitation mother liquor and lithium extraction tail liquor, and improves the utilization rate of salt lake lithium resource mining.

[0096] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for co-producing lithium carbonate, lithium phosphate and magnesium carbonate using raw brine from magnesium sulfate subtype salt lakes, characterized in that: The method comprises the following steps: (1) subjecting the original brine of magnesium sulfate subtype salt lake to adsorption and lithium extraction treatment, followed by desorption, to obtain lithium qualified solution and lithium extraction tail solution; (2) The lithium qualified solution is transported to a first nanofiltration device for primary nanofiltration treatment to remove magnesium ions and obtain primary nanofiltration water, and the primary nanofiltration water is subjected to reverse osmosis treatment to obtain reverse osmosis concentrate; the reverse osmosis concentrate is input into an electrodialysis device for electrodialysis treatment to obtain electrodialysis concentrate and fresh water; the electrodialysis concentrate is transported to a second nanofiltration device for secondary nanofiltration treatment to remove magnesium ions and obtain secondary nanofiltration water, and the secondary nanofiltration water is subjected to a first ion exchange to remove magnesium ions and obtain magnesium-removed qualified solution and magnesium-removed desorption solution; the magnesium-removed qualified solution is subjected to MVR concentration to obtain MVR concentrated solution and water; the MVR concentrated solution is subjected to a second ion exchange to remove boron ions and obtain boron-removed qualified solution; wherein the water obtained in the MVR concentration process and the fresh water obtained in the electrodialysis process are returned to the first nanofiltration device to participate in the primary nanofiltration treatment; the magnesium-removed desorption solution is returned to the electrodialysis device to participate in the electrodialysis treatment; (3) The qualified boron-removed solution is subjected to lithium precipitation treatment to obtain lithium carbonate and lithium precipitation mother liquor; the lithium precipitation mother liquor is mixed with a precipitant, and then subjected to filter press separation to obtain a crude lithium phosphate product and a filtrate; the hydroxide content in the filtrate is controlled at 1.5-2.5 g / L and the pH value of the filtrate is adjusted to 8-11, and then mixed with the lithium extraction tail liquid obtained in step (1) to obtain a basic magnesium carbonate suspension, and then separated to obtain magnesium carbonate.

2. The method according to claim 1, characterized in that In step (1), in the original brine of the magnesium sulfate subtype salt lake, the content of lithium ions is above 150 mg / L, the content of magnesium ions is 15-18 g / L, the content of sodium ions is 75-95 g / L, the content of potassium ions is 9-10 g / L, the content of boron ions is 250-350 mg / L, the content of chloride ions is 170-200 g / L, and the content of sulfate ions is 9-13 g / L.

3. The method according to claim 1 or 2, characterized in that: In step (1), the adsorption process comprises: performing the adsorption by an adsorbent; the adsorbent is at least one of a layered aluminum adsorbent, a layered titanium adsorbent, a spinel structured manganese adsorbent and a spinel structured titanium adsorbent; Preferably, the adsorption is carried out in a continuous adsorption lithium extraction device, and the adsorption conditions include: the rotation interval of the adsorption tower is 10-12min, the operating pressure of the device is 2.5-4MPa, the control temperature is 20-50°C, the feed adsorption flow rate is 0.5-3.5BV / h, the top liquid flow rate is 1-3BV / h, and the desorption flow rate is 0.5-4BV / h; Preferably, the method further comprises: regenerating the adsorbent by a regeneration agent; Preferably, the regeneration agent is a magnesium chloride solution and / or a hydrochloric acid solution; Preferably, the regeneration reagent is the lithium extraction tail liquid obtained in step (1); Preferably, the pH value of the regeneration reagent is 7.5-8.5, the content of lithium ions is 10-80 mg / L, and the content of magnesium ions is 15-18 g / L; Preferably, in the lithium qualified solution, the content of lithium ions is greater than 400 mg / L, the content of magnesium ions is less than 500 mg / L, the content of sodium ions is less than 300 mg / L, the content of potassium ions is less than 20 mg / L, and the content of boron ions is less than 100 mg / L.

4. The method according to any one of claims 1 to 3, characterized in that: In step (2), the conditions of the primary nanofiltration treatment include: a membrane inlet pressure of 3.5-4 MPa, a feed temperature of 22-25° C., and a feed conductivity of 18-22 ms / cm.

5. The method according to any one of claims 1 to 4, characterized in that: In step (2), the reverse osmosis treatment conditions include: the pH value of the inlet water is 6-7, the membrane inlet pressure is 3.5-4 MPa, the feed temperature is 22-25° C., and the feed conductivity is 12-14 ms / cm; Preferably, in the reverse osmosis concentrate, the content of lithium ions is 2.5-3.8 g / L, and the content of magnesium ions is less than 250 mg / L.

6. The method according to any one of claims 1 to 5, characterized in that: In step (2), the conditions of the electrodialysis treatment include: the membrane pressure is above 90 KPa, preferably 90-110 KPa; the conductivity of the polar water is above 80 ms / cm, preferably 80-100 ms / cm; the pH value of the polar water is below 5, preferably 3-5; Preferably, in the electrodialysis concentrate, the content of lithium ions is 12-13.5 g / L, and the content of magnesium ions is 500-1000 mg / L.

7. The method according to any one of claims 1 to 6, characterized in that: In step (2), in the qualified magnesium-removal solution, the content of lithium ions is 12-13.5 g / L, and the content of magnesium ions is 0.3-1 mg / L.

8. The method according to any one of claims 1 to 7, characterized in that: In step (2), the second ion exchange process is implemented in a resin ion exchange and boron removal device, which is provided with a resin adsorption column for continuous adsorption regeneration transformation, and the resin ion exchange and boron removal device comprises an adsorption zone, a water washing zone, an acid desorption zone, a water washing acid zone and a qualified liquid top water zone arranged in sequence, and a plurality of resin adsorption columns formed by boron removal ion exchange resins are continuously operated in the adsorption zone, the water washing zone, the acid desorption zone, the water washing acid zone and the qualified liquid top water zone, wherein: In the adsorption zone, the MVR concentrated solution is fed into the resin adsorption column through an upper feeding method for adsorption to obtain the boron-removed qualified solution; Preferably, in the qualified boron removal solution, the content of lithium ions is 19-24 g / L, and the content of boron ions is less than 10 mg / L.

9. The method according to any one of claims 1 to 8, characterized in that: In step (3), the lithium precipitation treatment process includes: mixing the qualified boron removal solution and a sodium carbonate solution.

10. The method according to any one of claims 1 to 9, characterized in that: In step (3), the precipitant is sodium dihydrogen phosphate solution; Preferably, in the lithium precipitation mother solution, the content of lithium ions is 1200-1400 mg / L, and the content of carbonate is 20-25 g / L; Preferably, in the lithium extraction tail solution, the content of lithium ions is 10-80 mg / L, and the content of magnesium ions is 15-18 g / L.

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