Method for comprehensive exploitation and utilization of magnesium sulfate sub-type salt lake resources

Abstract

The application belongs to the technical field of lithium purification, and relates to a method for comprehensive development and utilization of magnesium sulfate sub-type salt lake resources, which comprises the following steps: adjusting the SO4 2‑ concentration and the molar ratio of Mg 2+ , SO4 2‑ in the composition of brine to be treated to preferentially precipitate K + and realize concentration and enrichment of lithium and boron elements in the salt lake brine. The application can make the brine directly precipitate potassium salt during concentration by controlling the SO4 2‑ concentration and the molar ratio of Mg 2+ , SO4 2‑ , realize separation of potassium element from the brine, and avoid precipitation of lithium element in the form of lithium sulfate by controlling the SO4 2‑ concentration in the composition of the salt lake brine, thereby improving the purity of potassium salt and the subsequent lithium element yield, solving the problem of loss of lithium in the form of lithium sulfate precipitate when the brine with a molar ratio of Mg 2+ , SO4 2‑ <4 is collected in the prior art, and the process does not need to remove magnesium, so that the loss of boron element is small, and effective recovery of boron element is realized.

Description

[0001] This invention patent application is based on the prior patent application filed on November 29, 2024, with application number 202411738809.4 and invention title "A method for comprehensive development and utilization of magnesium sulfate subtype salt lake resources". Technical Field

[0002] This invention relates to the field of lithium purification technology, and in particular to a method for the comprehensive development and utilization of magnesium sulfate subtype salt lake resources. Background Technology

[0003] Magnesium sulfate subtype salt lake brines contain large amounts of sulfate anions and lithium ions, as well as borate anions, magnesium ions, and potassium ions. Lithium carbonate is mostly produced using a method of "salt field evaporation and concentration + reagent removal," with an overall yield of less than 40%, resulting in a significant waste of potassium and boron resources in the brine. In the later stages of natural evaporation, lithium often precipitates as lithium sulfate and mixes with other minerals, further wasting resources. The common practice is to add lime or calcium chloride to the brine to remove sulfate, but this method consumes large amounts of reagents, and the resulting gypsum slurry is difficult to filter. When using lime, borate is also removed as precipitation, wasting boron resources. Furthermore, due to a lack of systematic production technology, potassium is not fully utilized.

[0004] In addition, magnesium sulfate subtype salt lake brines are mostly composed of Mg. 2+ SO4 2- When using brine with a low molar ratio (<4), it is difficult to avoid the formation of Li2SO4 during the traditional evaporation and concentration process to separate lithium and magnesium, resulting in the loss of lithium and a reduction in lithium yield.

[0005] Existing technology for Mg 2+ SO4 2- There is a lack of a comprehensive recovery method for brine with a molar ratio of <4 that can achieve high recovery rates of boron, potassium and lithium ions. Summary of the Invention

[0006] Based on the above analysis, this invention aims to provide a method for the comprehensive development and utilization of magnesium sulfate subtype salt lake resources, in order to solve the problems of the inability to comprehensively recover high-value elements and low recovery rates in the treatment of salt lake brine using existing technologies, as well as the issue of Mg... 2+ SO4 2- At least one of the following problems exists: the brine has a molar ratio of <4 and the lithium element loss is large.

[0007] The objective of this invention is mainly achieved through the following technical solutions:

[0008] A method for the comprehensive development and utilization of magnesium sulfate subtype salt lake resources, comprising:

[0009] Adjusting SO4 content in the brine of the salt lake to be treated2- Concentration and Mg 2+ SO4 2- The molar ratio will preferentially select K + The precipitation process concentrates and enriches lithium and boron in the salt lake brine.

[0010] Preferably, K + With Mg 2+ The salt precipitates as a binary complex salt, preferably K. + With Mg 2+ The aqueous binary complex salt is precipitated, and more preferably, the aqueous binary complex salt is carnallite.

[0011] Preferably, the SO4 content in the brine of the salt lake to be treated is adjusted. 2- Concentration and Mg 2+ SO4 2- The molar ratio satisfies: the Mg content in the brine of the salt lake to be treated after adjustment. 2+ SO4 2- The molar ratio of SO4 is greater than 6. 2- Concentration < 20 g / L.

[0012] Preferably, the SO4 content in the brine of the salt lake to be treated is adjusted. 2- Concentration and Mg 2+ SO4 2- The molar ratios include:

[0013] A first conditioning solution is added to the initial brine to prepare the brine to be treated from the salt lake.

[0014] The first adjustment solution contains Mg 2+ SO4 2- The molar ratio is greater than that of Mg in the initial brine. 2+ SO4 2- molar ratio;

[0015] The first adjusting solution contains SO4 2- Concentration < 20 g / L.

[0016] Preferably, the method for comprehensive development and utilization of salt lake resources further includes:

[0017] K + Potassium was extracted from the precipitate to obtain potassium products and brine B with magnesium chloride as the main solute component;

[0018] Brine B is refluxed as a first conditioning solution or as part of the first conditioning solution, and used with the initial brine to prepare the salt lake brine to be treated.

[0019] Preferably, the method for comprehensive development and utilization of salt lake resources further includes:

[0020] K in the salt lake brine to be treated+ After separation of the precipitated products, the brine obtained is subjected to boron extraction and lithium extraction in sequence to obtain boron products, lithium products, and brine C with magnesium chloride and magnesium sulfate as the main solute components.

[0021] Brine C is refluxed as a first conditioning solution or as part of the first conditioning solution, and used with the initial brine to prepare the salt lake brine to be treated.

[0022] Preferably, the method for comprehensive development and utilization of salt lake resources further includes:

[0023] The first conditioning solution of the brine to be treated, prepared based on the first conditioning solution and the initial brine, contains Mg. 2+ SO4 2- The molar ratio of reagent D to alkaline earth metal salt or alkaline earth metal hydroxide solution is selectively added.

[0024] Preferably, the method for comprehensive development and utilization of magnesium sulfate subtype salt lake resources further includes: adjusting the SO4 content in the brine of the salt lake to be treated. 2- Concentration and Mg 2+ SO4 2- The molar ratio, K + Before precipitation, the brine in the salt lake is evaporated and concentrated to utilize the Ca in the brine. 2+ Removal of some SO4 2- .

[0025] Preferably, the reagent D is a MgCl2 solution or a CaCl2 solution with a mass fraction of 10% or more.

[0026] Preferably, the conditions for adding reagent D are as follows:

[0027] Before adding reagent D, the Mg in the first conditioning solution and the initial brine prepared from the brine of the salt lake to be treated was... 2+ SO4 2- The molar ratio is <6.

[0028] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0029] (1) This invention controls SO4 2- Concentration and Mg 2+ SO4 2- The molar ratio allows potassium salts to precipitate directly from the brine during concentration, achieving the separation of potassium from the brine; simultaneously, by controlling the SO4 content in the salt lake brine... 2- The concentration of potassium salts prevents lithium from precipitating as lithium sulfate, thus improving potassium salt purity and subsequent lithium yield. In addition, K... +The brine precipitates as a hydrous binary complex salt, carnallite, which removes some of the water from the brine, thus concentrating the brine and facilitating subsequent extraction of boron and lithium. This also solves the problem of Mg extraction in existing technologies. 2+ SO4 2- When collecting lithium from brine with a molar ratio < 4, the problem of lithium being lost as lithium sulfate precipitation occurs.

[0030] (2) This invention controls SO4 2- Concentration and Mg 2+ SO4 2- Molar ratio: Compared with the existing two-step magnesium removal method of "lime-sodium carbonate", the process of this invention does not require magnesium removal, so the loss of boron is small, and the boron in solution is conducive to subsequent recovery, thus realizing the effective recovery of boron.

[0031] (3) The magnesium-lithium separation method of the present invention has good compatibility with high magnesium ion concentrations. Compared with the prior art, it does not require magnesium removal, enables magnesium to participate in potassium ion recovery, and realizes the recycling of magnesium to participate in the Mg in the brine of the salt lake to be treated. 2+ SO4 2- The molar ratio can be adjusted, thus greatly reducing the consumption of raw materials such as quicklime and sodium carbonate, resulting in significant economic benefits.

[0032] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained through the embodiments described and the accompanying drawings, which are particularly pointed out. Attached Figure Description

[0033] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0034] Figure 1 This is a process flow diagram of the comprehensive utilization of salt lake brine according to the present invention;

[0035] Figure 2 This is a flow chart of the existing technology for treating salt lake brine. Detailed Implementation

[0036] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0037] Terminology Definition

[0038] Magnesium sulfate type salt lake brine: lithium concentration (as LiCl) ≥ 300 mg / L, boron concentration (as B₂O₅) ≥ 1000 mg / L, K + Mass concentration ≥0.5%~1%, main cation is Na + Mg 2+ The main anion is Cl. - SO4 2- The concentrations of cations and anions are much higher than those of potassium, boron, and lithium.

[0039] The potassium, boron, and lithium content in the above-mentioned magnesium sulfate-type salt lake brine meets the minimum grade requirements for industrial mining as specified in the "Geological Specifications for Salt Lake and Salt Mineral Exploration".

[0040] This invention discloses a method for the comprehensive development and utilization of magnesium sulfate-type salt lake brine resources, comprising:

[0041] Adjusting SO4 content in the brine of the salt lake to be treated 2- Concentration and Mg 2+ SO4 2- The molar ratio will preferentially select K + To precipitate and concentrate lithium and boron elements in salt lake brine.

[0042] In practice, this invention adjusts SO4 2- Concentration and Mg 2+ SO4 2- The molar ratio allows for two main purposes: firstly, it enables the direct precipitation of potassium salts during brine concentration, thus separating potassium from the brine; secondly, it controls the SO4 content in the salt lake brine. 2- The concentration can prevent lithium from precipitating out as lithium sulfate, which would affect the purity of the potassium salt and the subsequent lithium yield.

[0043] Compared with existing technologies, the present invention regulates SO4 2- Concentration and Mg 2+ SO4 2- The molar ratio allows potassium salts to precipitate directly from the brine during concentration, achieving the separation of potassium from the brine; simultaneously, by controlling the SO4 content in the salt lake brine... 2- The concentration of potassium salts prevents lithium from precipitating as lithium sulfate, thus improving potassium salt purity and subsequent lithium yield. In addition, K... + The brine precipitates as a hydrous binary complex salt carnallite, which carries away some of the water from the brine, thus concentrating the brine and facilitating the subsequent extraction of boron and lithium.

[0044] Preferably, K + It is precipitated from potash ore.

[0045] Preferably, K + With Mg 2+It precipitates as a binary complex salt.

[0046] More preferably, K + With Mg 2+ It precipitates as a hydrated binary complex salt.

[0047] Specifically, the hydrated binary complex salt can be carnallite (KCl·MgCl2·6H2O).

[0048] Compared with existing technologies, the present invention controls SO4 2- Concentration and Mg 2+ SO4 2- Molar ratio: Compared with the existing two-step magnesium removal method of "lime-sodium carbonate", the process of this invention does not require magnesium removal, thus the loss of boron is small, and the boron in solution is beneficial for subsequent recovery.

[0049] Specifically, adjusting the SO4 content in the brine of the salt lake to be treated 2- Concentration and Mg 2+ SO4 2- The molar ratio satisfies: the Mg content in the brine of the salt lake to be treated after adjustment. 2+ SO4 2- The molar ratio of SO4 is greater than 6. 2- Concentration < 20 g / L.

[0050] Preferably, the SO4 content in the brine of the salt lake to be treated is adjusted. 2- Concentration and Mg 2+ SO4 2- The molar ratios include:

[0051] A first conditioning solution is added to the initial brine to prepare the brine to be treated from the salt lake.

[0052] The first adjustment solution contains Mg 2+ SO4 2- The molar ratio is greater than that of Mg in the initial brine. 2+ SO4 2- molar ratio;

[0053] The first adjusting solution contains SO4 2- Concentration < 20 g / L.

[0054] During implementation, Mg 2+ SO4 2- The molar ratio of SO4 is much greater than that of the initial brine, and SO4 2- A first conditioning solution with a concentration much lower than that of the initial brine is added to the initial brine to prepare the treated salt lake brine, thereby reducing the Mg content in the brine to be treated. 2+ SO4 2- The molar ratio was increased, and the SO4 content in the solution was reduced by dilution. 2- concentration.

[0055] Preferably, the comprehensive development and utilization method further includes:

[0056] K + Potassium was extracted from the precipitate to obtain potassium products and brine B with magnesium chloride as the main solute component;

[0057] Brine B is refluxed as a first conditioning solution or as part of the first conditioning solution, and used with the initial brine to prepare the salt lake brine to be treated.

[0058] During implementation, Mg in the brine of the salt lake to be treated 2+ With K + The precipitate forms a hydrous binary double salt. After potassium extraction from the binary double salt, brine B containing magnesium chloride is obtained. Brine B is then returned to the brine of the salt lake to be treated, thus achieving the desired magnesium content in the brine. 2+ SO4 2- The molar ratio was adjusted; at the same time, a small amount of lithium ions in brine B were recovered, thereby improving the overall lithium yield.

[0059] Preferably, the comprehensive development and utilization method further includes:

[0060] K in the salt lake brine to be treated + After separation of the precipitated products, the brine obtained is subjected to boron extraction and lithium extraction in sequence to obtain boron products, lithium products, and brine C with magnesium chloride and magnesium sulfate as the main solute components.

[0061] Brine C is refluxed as a first conditioning solution or as part of the first conditioning solution, and used with the initial brine to prepare the salt lake brine to be treated.

[0062] During implementation, K in the brine of the salt lake to be treated + After the double salt precipitation, the binary double salt is subjected to sequential extraction of boron and lithium to obtain brine C containing magnesium chloride and magnesium sulfate. Brine C is then refluxed into the brine of the salt lake to be treated, thus achieving the desired magnesium content in the brine. 2+ SO4 2- The molar ratio was adjusted; at the same time, a small amount of lithium ions in brine C were recovered, thereby improving the overall lithium yield.

[0063] Specifically, the boron extraction method is solvent extraction; the lithium extraction method is any one of solvent extraction lithium extraction, selective electrodialysis lithium extraction, nanofiltration membrane lithium-magnesium separation, and electrochemical deintercalation lithium extraction.

[0064] Preferably, the lithium extraction method is solvent extraction.

[0065] Compared with existing technologies, the magnesium-lithium separation method of the present invention has better compatibility with high magnesium ion concentrations. Unlike existing technologies, it does not require magnesium removal, allows magnesium to participate in potassium ion recovery, and enables the recycling of magnesium to participate in the Mg content of the brine in the salt lake to be treated. 2+ SO4 2- The molar ratio can be adjusted, thus greatly reducing the consumption of raw materials such as quicklime and sodium carbonate, resulting in significant economic benefits.

[0066] Preferably, the comprehensive development and utilization method further includes:

[0067] The first conditioning solution of the brine to be treated, prepared based on the first conditioning solution and the initial brine, contains Mg. 2+ SO4 2- The molar ratio of reagent D to alkaline earth metal salt or alkaline earth metal hydroxide solution is selectively added.

[0068] Preferably, the alkaline earth metal is any one of Mg, Ca, Sr, and Ba.

[0069] Preferably, the reagent D is a MgCl2 solution, CaCl2, SrCl2 or BaCl2 solution with a mass fraction of 10% or more.

[0070] Preferably, the reagent D can be a saturated MgCl2 solution or a saturated CaCl2 solution.

[0071] Specifically, the conditions for adding reagent D are as follows:

[0072] Before adding reagent D, the Mg in the first conditioning solution and the initial brine prepared from the brine of the salt lake to be treated was... 2+ SO4 2- The molar ratio is <6.

[0073] It should be noted that adding MgCl2 solution or saturated CaCl2 solution affects the Mg... 2+ SO4 2- The molar ratio affects the process differently: adding MgCl2 can increase Mg 2+ The addition of CaCl2 can generate CaSO4 precipitate, thus reducing the SO4 content in the solution. 2- Both methods can increase Mg 2+ SO4 2- The molar ratios are different; the difference lies in the fact that when reagent D is a saturated CaCl2 solution, the magnesium in carnallite comes only from brine A; when reagent D is a saturated MgCl2 solution, the magnesium in carnallite can also come from the saturated MgCl2 solution; however, the magnesium content in the brine is much higher than that in potassium, and when reagent D is a saturated CaCl2 solution, the single magnesium source will not affect the formation of carnallite.

[0074] It should be noted that SrCl2 or BaCl2 solution reacts with CaCl2 to remove SO4. 2- The mechanism is the same; adding SrCl2 or BaCl2 can also effectively remove SO4 from the solution. 2- Thus controlling SO4 2- Solution concentration and Mg 2+ SO4 2- The molar ratio.

[0075] Specifically, the amount of reagent D added satisfies the following condition: after adding reagent D, the first conditioning solution and the Mg in the brine to be treated prepared from the initial brine are... 2+ SO4 2- The molar ratio of SO4 is greater than 6. 2- Concentration < 20 g / L.

[0076] It should be noted that Mg 2+ SO4 2- The molar ratio of SO4 is greater than 6. 2- A concentration of <20 g / L is a necessary condition for inhibiting lithium sulfate precipitation.

[0077] Preferably, the method for comprehensive development and utilization of magnesium sulfate subtype salt lake resources further includes: adjusting the SO4 content in the brine of the salt lake to be treated. 2- Concentration and Mg 2+ SO4 2- The molar ratio, K + Before precipitation, the brine in the salt lake is evaporated and concentrated to utilize the Ca in the brine. 2+ Removal of some SO4 2- .

[0078] It is understandable that during the process of evaporating and concentrating the initial salt lake brine into brine A, some of the sulfate ions will be removed due to entrainment and the calcium already present in the salt lake brine, thus reducing the consumption of reagent D.

[0079] Specifically, the comprehensive development and utilization method includes:

[0080] S1: The initial brine is evaporated and concentrated for the first time to precipitate sodium salt and obtain brine A;

[0081] S2: Add the first conditioning solution to brine A to adjust the Mg content of the mixed brine A and the first conditioning solution. 2+ SO4 2- molar ratio;

[0082] S3: The brine A and the first conditioning solution are mixed and evaporated for the second time to concentrate the brine and extract carnallite ore to obtain concentrated brine E. Potassium extraction treatment is performed on the carnallite ore to obtain potassium products.

[0083] S4: The concentrated brine E is sequentially subjected to boron and lithium extraction processes to obtain boron and lithium products.

[0084] Specifically, the precipitation of sodium salt in S1 to obtain brine A includes: the first evaporation and concentration to precipitate sodium salt, until non-sodium salts precipitate, and brine A is at the critical point before the precipitation of non-sodium salts.

[0085] Specifically, the sodium salt can be one or more of sodium chloride and sodium sulfate.

[0086] It should be noted that, taking advantage of the fact that sodium salts are generally less soluble than potassium salts at the same temperature, most sodium ions and some sulfate ions are removed.

[0087] During implementation, the state of brine A can be determined by the following methods: detecting the content of each ion in the initial brine; and calculating the amount of evaporation required for the target precipitated product based on the phase diagram.

[0088] Preferably, Mg in the initial brine 2+ SO4 2- Molar ratio < 4.

[0089] It should be noted that for Mg 2+ SO4 2- When initial brine with a molar ratio <4 is evaporated and concentrated to separate lithium and magnesium, the formation of MgSO4 and MgCl2 inevitably leads to the formation of Li2SO4, resulting in lithium loss and reduced lithium yield. This invention adjusts the Mg content in brine A by adding a first adjusting solution. 2+ SO4 2- The molar ratio of Mg makes 2+ SO4 2- A molar ratio greater than 6 prevents lithium from precipitating as lithium sulfate, thus improving the purity of the potassium salt and the subsequent lithium yield.

[0090] Specifically, S3 includes:

[0091] S301: The brine A and the first conditioning solution are mixed and evaporated for the second time until the mixed brine is saturated with magnesium chloride, and the magnesium chloride is about to precipitate at the critical point.

[0092] S302: Potassium chloride product and brine B are obtained by potassium extraction from carnallite ore.

[0093] Specifically, the potassium extraction process in S302 can be a cold decomposition-positive flotation method.

[0094] It should be noted that there are various processes for producing potassium chloride from carnallite, such as "cold decomposition-positive flotation" and "reverse flotation-cold crystallization". The resulting mother liquor (i.e., brine B) does not differ much in composition and concentration, and is in a magnesium-saturated state with high concentration. Most of the lithium and magnesium are recovered into the mother liquor, while potassium chloride remains mainly in the solid phase. This invention prioritizes the "cold decomposition-positive flotation" method mainly due to overall process considerations: firstly, the mineral has a high sodium content, making positive flotation better; secondly, the core objective of this invention is lithium, and the "cold decomposition-positive flotation" method directly obtains brine B as an auxiliary material. When other potassium extraction processes are used, the process is more complex, with mother liquor generated at multiple stages, which is not conducive to directly obtaining brine B.

[0095] S3 also includes S303: refluxing brine B as a first conditioning solution or part of the first conditioning solution to adjust the Mg content of the mixed brine of brine A and the first conditioning solution. 2+ SO4 2- The molar ratio.

[0096] S3 also includes S304: the first conditioning solution can selectively add reagent D.

[0097] Specifically, S4 includes:

[0098] S401: The concentrated brine E is evaporated and concentrated for the third time to obtain concentrated brine F. The concentrated brine F is saturated with magnesium chloride, and the magnesium chloride is about to precipitate at the critical point.

[0099] S402: The brine after the third evaporation and concentration is subjected to boron extraction treatment to obtain boron products and boron-extracted tail liquid;

[0100] S403: The tail liquid after boron extraction is subjected to lithium extraction treatment to obtain lithium products and brine C.

[0101] Preferably, the concentrated brine E after the third evaporation and concentration in S401 satisfies the following conditions: total sodium and potassium content <3g / L, and magnesium content >110g / L.

[0102] Specifically, the lithium extraction process in S403 can be the existing organic solvent extraction method.

[0103] It should be noted that the extraction method is the best for lithium extraction of the obtained brine F. This is because when using other technologies (such as adsorption, membrane nanofiltration, electrodialysis, etc.), the magnesium in the tail liquid (brine C) is unsaturated, the concentration is not as high as that of the extraction method, and the volume expansion is greater than that of the extraction method, resulting in a large processing volume when adding brine. On the other hand, the above-mentioned lithium extraction processes such as adsorption, membrane nanofiltration, and electrodialysis have poor boron retention capacity, while the "boron extraction + lithium extraction" combination of the present invention can effectively solve the above problems.

[0104] Preferably, S4 further includes S404: refluxing brine C as part of the first conditioning solution to adjust the Mg content of the mixed brine of brine A and the first conditioning solution. 2+ SO4 2- The molar ratio.

[0105] It should be noted that excessively low magnesium concentration has an adverse effect on subsequent boron extraction; excessively high total sodium and potassium content has an adverse effect on subsequent boron-lithium extraction.

[0106] Specifically, the comprehensive development and utilization method further includes S5:

[0107] Mg in the first conditioning solution and the initial brine prepared before adding reagent D in the salt lake brine to be treated 2+ SO4 2- The molar ratio is <6;

[0108] After adding reagent D, the first conditioning solution and the Mg in the brine to be treated salt lake were prepared by mixing the initial brine. 2+ SO4 2- The molar ratio is greater than 6;

[0109] The reagent D contains Mg 2+ Cl - It does not contain SO4 2- , or, satisfying: SO4 2- The concentration is <20 g / L, and the SO4 in reagent D is... 2- The concentration is lower than that of the initial brine, Mg 2+ SO4 2- The molar ratio is greater than that of the initial brine.

[0110] To better illustrate the present invention, the following embodiments and comparative examples are provided:

[0111] Example 1

[0112] This embodiment discloses a method for the comprehensive development and utilization of magnesium sulfate-type salt lake brine resources, including:

[0113] S1: The initial brine is evaporated and concentrated for the first time to precipitate sodium salt and obtain brine A;

[0114] S2: Add the first conditioning solution to brine A to adjust the Mg content of the mixed brine A and the first conditioning solution. 2+ SO4 2- The molar ratio of brine A to the first adjusting solution is 1:0.60.

[0115] S3: The brine A and the first conditioning solution are mixed and evaporated for the second time to concentrate the brine and precipitate carnallite ore to obtain concentrated brine E. Potassium chloride is obtained by potassium extraction from the carnallite ore.

[0116] S301: The mixed brine A and the first conditioning solution are evaporated and concentrated for the second time until the mixed brine is saturated with magnesium chloride, and the magnesium chloride is about to precipitate at the critical point.

[0117] S302: Carnallite ore is subjected to potassium extraction. The potassium extraction process is cold decomposition-positive flotation. Water of 20% of the carnallite ore mass is mixed with the ore, stirred, crushed, and filtered to obtain decomposition mother liquor, i.e. brine B. The remaining solid is crude potassium ore, which is subjected to three stages of flotation to obtain potassium concentrate. After washing and drying, the concentrate yields potassium chloride product with a purity of 58.1%, which meets the standards for agricultural fertilizer.

[0118] S303: Reflux brine B as part of the first conditioning solution to adjust the Mg content of the mixed brine of brine A and the first conditioning solution. 2+ SO4 2- The molar ratio.

[0119] S4: Concentrated brine E is sequentially subjected to boron extraction and lithium extraction processes to obtain boron and lithium products. The boron extraction process is a solvent extraction method, specifically using 2-ethyl-1,3-hexanediol as the core extractant, with 5 stages of extraction and 5 stages of back-extraction to obtain a high-purity boric acid solution. This solution is then evaporated, crystallized, washed, and dried to obtain high-purity boric acid. The lithium extraction process refers to the lithium extraction technology described in Example 1 of the patent "Extraction System, Preparation Method, and Method for Extracting Lithium from Brine, Publication No. CN 113073209 B": Using trialkylphosphine oxyphosphate (TRPO) and di(2-ethylhexyl)phosphoric acid as core extractants, lithium can be extracted from a high-concentration magnesium solution, producing a high-concentration, high-purity lithium chloride solution. This solution is then purified, concentrated, crystallized, and dried to obtain high-purity lithium chloride solid.

[0120] Specifically, the extraction system for lithium extraction from brine in CN 113073209 B includes the following raw materials: extractant, binder, and diluent; the extractant is trialkylphosphine oxide (TRPO) and di(2-ethylhexyl)phosphoric acid; the binder is an aqueous solution of ferric sulfate and sodium chloride, wherein the sodium chloride is saturated; the diluent is kerosene; the extractant and diluent constitute a blank organic phase, and the volume ratio of TRPO, di(2-ethylhexyl)phosphoric acid, and kerosene in the blank organic phase is 1.5:1:4;

[0121] The volume ratio of the blank organic phase to the binder is 1:1.

[0122] The preparation method of the extraction system in CN 113073209 B includes:

[0123] Step 1: Add 19.2 g / L of ferric sulfate to a saturated sodium chloride solution to obtain a binder;

[0124] Step 2: Measure trialkylphosphine oxyphosphate, di(2-ethylhexyl)phosphine and kerosene according to the volume ratio, mix them well, and obtain a blank organic phase;

[0125] Step 3: Chemically extract the blank organic phase prepared in the above steps with the binder. The extraction ratio is O / A = 1:1, and the countercurrent stage is 3 stages. After extraction, an iron-loaded organic phase is obtained.

[0126] Step 4: Wash the iron-loaded organic phase with pure water. The washing ratio is O / A = 3:1, and the countercurrent stage is 5 stages to obtain the lithium extraction system from the brine.

[0127] S401: The concentrated brine E is evaporated and concentrated for the third time to obtain concentrated brine F. The concentrated brine F is saturated with magnesium chloride, and the magnesium chloride is about to precipitate at the critical point.

[0128] S402: The brine after the third evaporation and concentration is subjected to boron extraction treatment to obtain boron products and boron-extracted tail liquid;

[0129] S403: The tail liquid after boron extraction is subjected to lithium extraction treatment to obtain lithium products and brine C.

[0130] S5: Selectively add reagent D as the first conditioning solution;

[0131] Mg in the first conditioning solution and the initial brine prepared before adding reagent D in the salt lake brine to be treated 2+ SO4 2- The molar ratio is <6;

[0132] After adding reagent D, the first conditioning solution and the Mg in the brine to be treated salt lake were prepared by mixing the initial brine. 2+ SO4 2- The molar ratio is greater than 6;

[0133] Reagent D is a saturated magnesium chloride solution.

[0134] The volume ratio of brine B, brine C, and reagent D in the first adjusting solution is 1:4.05:1.01;

[0135] The main ion concentrations of the initial brine, brine B, brine C, and concentrated brine F are shown in Table 1 below.

[0136] Calculations show that in Example 1, the potassium yield was 45.4% and the potassium product purity was 58.1% (potassium product purity is calculated as K2O); the boron yield was 72.04% and the boron product purity was 99.5%; and the lithium yield was 72.9% and the lithium product purity was 99.3%.

[0137] Example 2

[0138] This embodiment discloses a method for the comprehensive development and utilization of magnesium sulfate-type salt lake brine resources. The difference from Embodiment 1 is that the initial brine component content is different, the volume ratio of brine A and the first conditioning solution is different, and the volume ratio of brine B, brine C and reagent D in the first conditioning solution is different.

[0139] The volume ratio of brine A to the first adjusting solution is 1:2.73.

[0140] The volume ratio of brine B, brine C, and reagent D in the first adjusting solution is 1:3.31:2.16.

[0141] The main ion concentrations of the initial brine, brine B, brine C, and concentrated brine F are shown in Table 1 below.

[0142] Calculations show that in Example 2, the potassium yield was 54.46% and the potassium product purity was 57.2%; the boron yield was 67.94% and the boron product purity was 99.5%; and the lithium yield was 68.3% and the lithium product purity was 99.3%.

[0143] Example 3

[0144] This embodiment discloses a method for the comprehensive development and utilization of magnesium sulfate-type salt lake brine resources. The difference from Embodiment 1 is that the initial brine component content is different, the volume ratio of brine A and the first conditioning solution is different, and the volume ratio of brine B, brine C and reagent D in the first conditioning solution is different.

[0145] The volume ratio of brine A to the first adjusting solution is 1:1.09.

[0146] The volume ratio of brine B, brine C, and reagent D in the first adjusting solution is 1:5.01:2.30.

[0147] The main ion concentrations of the initial brine, brine B, brine C, and concentrated brine F are shown in Table 1 below.

[0148] Calculations show that in Example 3, the potassium yield was 44.78% and the potassium product purity was 57.9%; the boron yield was 65.93% and the boron product purity was 99.5%; and the lithium yield was 69.5% and the lithium product purity was 99.3%.

[0149] Example 4

[0150] This embodiment discloses a method for the comprehensive development and utilization of magnesium sulfate-type salt lake brine resources. The difference from Embodiment 3 is that the same raw materials are used as in Embodiment 3, but reagent D is replaced by calcium chloride solution instead of saturated magnesium chloride solution.

[0151] The volume ratios of brine A and the first adjusting solution are different. The volume ratios of brine B, brine C, and reagent D in the first adjusting solution are also different.

[0152] The volume ratio of brine A to the first adjusting solution is 1:0.74.

[0153] The volume ratio of brine B, brine C, and reagent D in the first adjusting solution is 1:4.01:0.90. Reagent D is a 25% calcium chloride solution.

[0154] The main ion concentrations of the initial brine, brine B, brine C, and concentrated brine F are shown in Table 1 below.

[0155] Calculations show that in Example 4, the potassium yield was 55.45% and the potassium product purity was 58.3%; the boron yield was 68.56% and the boron product purity was 99.5%; and the lithium yield was 72.5% and the lithium product purity was 99.3%.

[0156] Comparative Example 1

[0157] This comparative example discloses a method for treating magnesium sulfate-type salt lake brine. The initial brine is the same as in Example 1, and the process flow diagram is as follows: Figure 2 As shown, after the brine is pre-concentrated four times, lime slurry (mainly calcium hydroxide) is added to remove all sulfur and some magnesium and boron elements. The amount of calcium hydroxide used is 103% of the sulfate ions in the brine. Then the brine continues to evaporate, during which potassium halite and carnallite precipitate out, finally yielding concentrated brine F.

[0158] Potassium chloride products can be obtained from halite and carnallite using a similar process to that in Example 1, but since the amount of carnallite is very small, the brine B produced in Comparative Example 1 is negligible.

[0159] Due to the use of lime slurry, most of the boron has been removed, and the boron in the old brine F has lost its extraction value.

[0160] Lithium in concentrated brine F was extracted using the same process as in Example 1 to obtain solid lithium chloride.

[0161] Calculations showed that in Comparative Example 1, the potassium yield was 41.3% and the potassium product purity was 58.1%; the boron yield was 0%; and the lithium yield was 43.3% and the lithium product purity was 99.3%.

[0162] Table 1 Composition of Lithium-Containing Feed Solution

[0163]

[0164] The results showed that the potassium yield in the embodiments of the present invention was 44.78%–55.45%, and the potassium product purity was 57.2%–58.3% (potassium product purity is calculated as K2O); the boron yield was 65.93%–72.04%, and the boron product purity was ≥99.5%; the lithium yield was 68.3%–72.9%, and the lithium product purity was ≥99.3%.

[0165] Comparing Comparative Example 1 and the Example, it can be seen that the yields of potassium, boron, and lithium are significantly reduced by the traditional method.

[0166] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for the comprehensive development and utilization of magnesium sulfate subtype salt lake resources, characterized in that, include: Adjusting the SO4 content in the brine of the salt lake to be treated 2- Concentration and Mg 2+ SO4 2- The molar ratio, preferentially K + The precipitation process concentrates and enriches lithium and boron in the salt lake brine.

2. The method for comprehensive development and utilization of magnesium sulfate subtype salt lake resources according to claim 1, characterized in that, K + With Mg 2+ The salt precipitates as a binary complex salt, preferably K. + With Mg 2+ The aqueous binary complex salt is precipitated, and more preferably, the aqueous binary complex salt is carnallite.

3. The method for comprehensive development and utilization of magnesium sulfate subtype salt lake resources according to claim 2, characterized in that, Adjusting the SO4 content in the brine of the salt lake to be treated 2- Concentration and Mg 2+ SO4 2- The molar ratio satisfies: the Mg content in the brine of the salt lake to be treated after adjustment. 2 + SO4 2- The molar ratio of SO4 is greater than 6. 2- Concentration < 20 g / L.

4. The method for comprehensive development and utilization of magnesium sulfate subtype salt lake resources according to claim 3, characterized in that, Adjusting the SO4 content in the brine of the salt lake to be treated 2- Concentration and Mg 2+ SO4 2- The molar ratios include: A first conditioning solution is added to the initial brine to prepare the brine to be treated from the salt lake. The first adjustment solution contains Mg 2+ SO4 2- The molar ratio is greater than that of Mg in the initial brine. 2+ SO4 2- molar ratio; The first adjusting solution contains SO4 2- Concentration < 20 g / L.

5. The method for comprehensive development and utilization of magnesium sulfate subtype salt lake resources according to claim 4, characterized in that, The method for comprehensive development and utilization of magnesium sulfate subtype salt lake resources also includes: K + Potassium was extracted from the precipitate to obtain potassium products and brine B with magnesium chloride as the main solute component; Brine B is refluxed as a first conditioning solution or as part of the first conditioning solution, and used with the initial brine to prepare the salt lake brine to be treated.

6. The method for comprehensive development and utilization of magnesium sulfate subtype salt lake resources according to claim 5, characterized in that, The method for comprehensive development and utilization of magnesium sulfate subtype salt lake resources also includes: K in the salt lake brine to be treated + After separation of the precipitated products, the brine obtained is subjected to boron extraction and lithium extraction in sequence to obtain boron products, lithium products, and brine C with magnesium chloride and magnesium sulfate as the main solute components. Brine C is refluxed as a first conditioning solution or as part of the first conditioning solution, and used with the initial brine to prepare the salt lake brine to be treated.

7. The method for comprehensive development and utilization of magnesium sulfate subtype salt lake resources according to any one of claims 1-6, characterized in that, The method for comprehensive development and utilization of magnesium sulfate subtype salt lake resources also includes: The first conditioning solution of the brine to be treated, prepared based on the first conditioning solution and the initial brine, contains Mg. 2+ SO4 2- The molar ratio of reagent D to alkaline earth metal salt or alkaline earth metal hydroxide solution is selectively added.

8. The method for comprehensive development and utilization of magnesium sulfate subtype salt lake resources according to claim 7, characterized in that, The method for comprehensive development and utilization of magnesium sulfate subtype salt lake resources also includes: adjusting the SO4 content in the brine of the salt lake to be treated. 2- Concentration and Mg 2+ SO4 2- The molar ratio, K + Before precipitation, the brine in the salt lake is evaporated and concentrated to utilize the Ca in the brine. 2+ Removal of some SO4 2- .

9. The method for comprehensive development and utilization of magnesium sulfate subtype salt lake resources according to claim 8, characterized in that, The reagent D is a MgCl2 solution or CaCl2 solution with a mass fraction of 10% or more.

10. The method for comprehensive development and utilization of magnesium sulfate subtype salt lake resources according to claim 9, characterized in that, The conditions for adding reagent D are as follows: Before adding reagent D, the Mg in the first conditioning solution and the initial brine prepared from the brine of the salt lake to be treated was... 2+ SO4 2- The molar ratio is <6.

Images