阅读说明：本技术 一种高镁锂比卤水提取硫酸锂的方法 (Method for extracting lithium sulfate from brine with high magnesium-lithium ratio ) 是由 周桓 代亚萍 唐晶晶 谷晓龙 白晓琴 于 2019-01-07 设计创作，主要内容包括：本发明涉及一种高镁锂比卤水提取硫酸锂的方法,步骤如下：(1)卤水去除硫酸根；(2)蒸发浓缩析出六水氯化镁和杂盐,得到低镁锂比卤水；(3)低镁锂比卤水中加入硫酸镁,产生一水硫酸锂沉淀；(4)固液分离得到一水硫酸锂和提锂母液；(5)提锂母液返回步骤(1)。本发明实现了镁锂的彻底分离,并获得了一水硫酸锂产品。(The invention relates to a method for extracting lithium sulfate from brine with high magnesium-lithium ratio, which comprises the following steps: (1) removing sulfate radicals from the brine; (2) evaporating and concentrating to separate magnesium chloride hexahydrate and miscellaneous salts to obtain brine with low magnesium-lithium ratio; (3) adding magnesium sulfate into brine with low magnesium-lithium ratio to generate lithium sulfate monohydrate precipitate; (4) solid-liquid separation is carried out to obtain lithium sulfate monohydrate and lithium extraction mother liquor; (5) and (4) returning the lithium extraction mother liquor to the step (1). The invention realizes the complete separation of magnesium and lithium and obtains the lithium sulfate monohydrate product.)

1. A method for extracting lithium sulfate from brine with a high magnesium-lithium ratio comprises the following steps:

(1) removing sulfate radicals from the brine;

(2) evaporating and concentrating to separate magnesium chloride hexahydrate and miscellaneous salts to obtain brine with low magnesium-lithium ratio;

(3) adding magnesium sulfate into brine with low magnesium-lithium ratio to generate lithium sulfate monohydrate precipitate;

(4) solid-liquid separation is carried out to obtain lithium sulfate monohydrate and lithium extraction mother liquor;

(5) and (4) returning the lithium extraction mother liquor to the step (1).

2. The method for extracting lithium sulfate from brine with high magnesium-lithium ratio as claimed in claim 1, wherein the brine with high magnesium-lithium ratio is natural brine or regenerated brine, and the mass ratio of Mg/L i on a dry basis is greater than 10.0.

3. The method for extracting lithium sulfate from brine with high magnesium-lithium ratio as claimed in claim 1 or 2, wherein: the brine with high magnesium-lithium ratio contains sulfate radicals or does not contain sulfate radicals, and the sulfate radicals are removed from the brine with high magnesium-lithium ratio by adopting a freezing method or a method of adding soluble calcium salt.

4. The method for extracting lithium sulfate from brine with high magnesium-lithium ratio as claimed in claim 3, wherein the method comprises the following steps: when dry basis weight SO₄When the/Cl is more than 0.1, removing sulfate radicals and SO by a freezing method or a calcium adding method₄When the/Cl is less than 0.1, sulfate radicals are removed by a method of adding soluble calcium.

5. The method for extracting lithium sulfate from brine with high magnesium-lithium ratio as claimed in claim 4, wherein the method comprises the following steps: the amount of the calcium salt added is 0.9-1.1 in terms of the molar ratio of calcium ions to the total amount of sulfate radicals.

6. The method for extracting lithium sulfate from brine with high magnesium-lithium ratio as claimed in claim 5, wherein the method comprises the following steps: the soluble calcium salt is calcium chloride, calcium hydroxide or lime milk.

7. The method for extracting lithium sulfate from brine with high magnesium-lithium ratio as claimed in claim 1, wherein the brine with low magnesium-lithium ratio in step (2) has a dry-basis mass ratio of Mg/L i in brine of less than 10.0.

8. The method for extracting lithium sulfate from brine with high magnesium-lithium ratio as claimed in claim 1, wherein the method comprises the following steps: the magnesium sulfate added into the brine with low magnesium-lithium ratio in the step (3) refers to magnesium sulfate or a hydrate thereof, or a magnesium sulfate solution, or the mass ratio is as follows: SO (SO)₄A magnesium-containing mixed solution having a/Cl greater than 0.15 and a Mg/L i greater than 2.0.

9. The method for extracting lithium sulfate from brine with high magnesium-lithium ratio as claimed in claim 1, wherein the method comprises the following steps: and (3) the precipitation of the lithium sulfate monohydrate directly generates the precipitation of the lithium sulfate monohydrate, or generates the precipitation of the lithium sulfate monohydrate through evaporation or cooling.

10. The method for extracting lithium sulfate from brine with high magnesium-lithium ratio as claimed in claim 1, wherein the method comprises the following steps: the lithium extraction mother liquor in the step (4) refers to mother liquor obtained by separating a solid phase of lithium sulfate monohydrate, or mother liquor generated in the purification process of lithium sulfate.

Technical Field

The invention belongs to the field of lithium extraction from salt lake brine, and relates to brine with a high magnesium-lithium ratio, in particular to a method for extracting lithium sulfate from brine with a high magnesium-lithium ratio.

Background

The lithium resource is mainly divided into lithium-containing solid ores such as spodumene lepidolite and the like and lithium-containing liquid ores such as salt lake brine, seawater, geothermal water and the like. Wherein the lithium resource reserve of the salt lake brine accounts for about 60-70% of the total amount of the lithium resource, and lithium salt products produced from the brine globally account for more than 85% of the total amount of the lithium products. Wherein, the quantity of the reserve of the Chilean (Atacama) salt lake in the Li-V.Nanmei zone, the Argentina (Olaroz, Rincon, Hombe Muerto, etc.) salt lake and the Bolivian (Uyuni) salt lake accounts for 43.6% of the lithium reserve in the world, the mass ratio of magnesium and lithium in the brine of the salt lakes is usually less than 10, and the mass ratio of magnesium and lithium in the Wells (Searles) lake and the Silver Peak (Silver Peak) lake in the United states is less than 5. The magnesium-lithium ratio of the great salt lake in America is 250. The Zambuya salt lake in China belongs to a carbonate salt lake, has high lithium storage capacity and low magnesium content, the magnesium-lithium ratio of the Kaoer sweat salt lake and the Israel dead sea in China is more than 1000, the east-west Ginell lake, the big chadan and the Yilieng salt lake are magnesium sulfate subtype salt lakes, and the magnesium-lithium ratio is between 50 and 100.

The method for extracting lithium from salt lake brine mainly comprises a precipitation method, an extraction method, an ion exchange adsorption method, a calcination leaching method, an electrodialysis method and the like. The precipitation method is classified into a carbonate precipitation method, an aluminum salt precipitation method and a lithium sulfate hydrate precipitation method. The extraction method, the ion exchange adsorption method, the calcination leaching method, the electrodialysis method and the like are not very relevant to the technology, and are not detailed herein, but only the precipitation method relevant to the technology, in particular the lithium extraction technology from the brine with high magnesium-lithium ratio is detailed herein.

The extraction of lithium from salt lake brine by carbonate precipitation was the first studied and industrially applied method, in which lithium was precipitated as lithium carbonate from industrial soda ash concentrated in salt lake brine, and this method is suitable for extracting lithium from salt lake brine with low magnesium-lithium ratio, and L i was developed from Welsh lake, Yinfeng lithium mine and Chili Alacama salt lake in the United states₂CO₃And (5) producing the product. The method needs to remove sulfate radicals and magnesium ions in brine respectively by using calcium chloride, lime milk, sodium carbonate and the like, and finally, the sodium carbonate is used for precipitating lithium carbonate. The method is not suitable for brine with high magnesium-lithium ratio.

The method comprises the steps of naturally evaporating and concentrating salt lake intercrystalline brine by a solarization evaporation pool, adding a precipitator through fractional crystallization separation to form insoluble salt (magnesium carbonate or magnesium hydroxide) with magnesium ions, performing solid-liquid separation, removing magnesium from a liquid phase, adjusting the pH value of a feed liquid, evaporating and concentrating to separate out NaCI crystals, controlling the concentration of lithium chloride to be above 100 g/L, taking sodium carbonate as a precipitator to precipitate lithium carbonate, separating and drying to obtain a lithium carbonate product, controlling the high-magnesium lithium ratio salt lake brine to reach a supersaturated concentration within the range of 40-100 ℃ by Wang Nigong et al, immediately pumping the high-magnesium lithium ratio salt lake brine into an oscillation separation tower with an agitator in a heat preservation state, adding stoichiometric sodium carbonate, oscillating the agitator and the oscillator for 5-10 min at the same time, standing until lithium magnesium carbonate has an obvious interface, synchronously separating out magnesium carbonate and lithium carbonate, dehydrating the high-magnesium carbonate and refining the lithium carbonate in a centrifuge, and refining the crude lithium carbonate by a conventional lithium carbonate method.

The aluminum salt precipitation method is not very relevant to the research and is not repeated.

Precipitation of lithium sulfate hydrate, a method for salting out lithium sulfate monohydrate using soluble sulfate was first proposed by Garrett et al in 1981 to extract lithium from brine. The method is suitable for the mass content of lithium of at least 0.4 percent and MgCl₂Brine with a concentration of at least 30mol/1000mol water and a boron content of at least 1% (by mass of boric acid) is pre-treated to remove diarrhea salts and used as soluble sulfate for salting out. In 1988 Mehta et al proposed an improved method for extracting lithium from an evaporative concentrated brine based on the above method. The brine is respectively separated out by cooling or evaporating in several steps to obtain potassium chloride, diarrhea salt and carnallite. Adding diarrhea salt into the brine to form slurry with lithium sulfate radical ratio of at least 0.9 and water content less than 60%.

L ukes in 2003 is concentrated by evaporating Atacama salt lake brine to obtain two kinds of brine with different compositions, lithium sulfate in the brine exceeds the solubility of the lithium sulfate after mixing, and L i is precipitated by three stages₂SO₄·H₂And (4) O crystals. The first brine is saturated with potassium chloride, carnallite and lithium sulfate and contains Mg²⁺:4.7～6％，Li⁺:08～1.2％，SO₄ ^2-1.2-4.2 percent of the total amount of the brine, and a second saturated solution of bischofite, carnallite and lithium sulfate monohydrate in the brine, wherein L i⁺2.5-6 percent, the content of magnesium is less than 6 percent, the content of sulfate radical is less than 0.2 percent, and the two kinds of brine are mixed in three forms, wherein firstly, the two kinds of brine are respectively preheated to 30-70 ℃ and are mixed and precipitated in a crystallizer to obtain L i₂SO₄·H₂Directly mixing the two kinds of bittern, firstly precipitating carnallite, after solid-liquid separation, transferring the mother liquor into another crystallizer to precipitate L i₂SO₄·H₂O crystal, and then filtering and washing; thirdly, cooling the saturated brine of potassium chloride, carnallite and lithium sulfate toPrecipitating carnallite at 5-15 ℃, separating mother liquor, preheating to 20-40 ℃, mixing with another bischofite saturated brine, precipitating L i₂SO₄·H₂O crystal, solid-liquid separation, washing, concentrating the residual mother liquid in evaporating pool, and returning to L i₂S0₄·H₂The purity of O can reach 98.97%, and the total recovery rate of lithium can reach 73.3%. The method does not need to add additional chemical raw materials, is suitable for sulfate type salt lake brine with low magnesium-lithium ratio, and has the technical key that the brine with two different compositions is obtained.

Other processes for extracting lithium from brine with high magnesium-lithium ratio.

1994, Wangzhun et al, published a research on a process for separating and extracting lithium sulfate from concentrated bittern, which utilizes a pilot lithium extraction process for extracting boric acid and lithium chloride from DACHADAN bittern to obtain a back-extraction solution according to H₂SO₄-Li₂SO₄-H₂The 97% lithium sulfate can be prepared by technological processes of O system phase diagram analysis, evaporation concentration, concentrated sulfuric acid reaction, separation extraction and the like. The technology is developed on the basis of a back extraction liquid, and is greatly different from the raw materials of the technology.

In 2009, xu hui et al published a paper, a magnesium-lithium separation process of salt lake brine with high magnesium-lithium ratio. The process uses salt lake brine with high magnesium-lithium ratio as raw material, ammonia and ammonium bicarbonate are respectively used for carrying out two-stage magnesium precipitation, 98% of Mg in the brine²⁺The method comprises the steps of precipitating and separating magnesium hydroxide and basic magnesium carbonate, concentrating and crystallizing the solution to separate ammonium chloride, and then deeply removing magnesium by using sodium hydroxide, well realizing the separation of magnesium and lithium, researching the influence of the feeding mode, concentration, feeding speed, end point pH value, reaction temperature and reaction time of NaOH on the magnesium removal effect, wherein the experimental result shows that Mg in mother liquor is removed under the conditions that the concentration of the NaOH solution is 10 mol/L, the feeding speed is 0.3-0.5 m L/min, the pH is 12, the temperature is 25 ℃, and the reaction time is 20-30 min²⁺Can be removed completely, and creates favorable conditions for preparing lithium carbonate in subsequent procedures. The process adopts a method of removing magnesium by carbonate and magnesium hydroxide to reduce the magnesium-lithium ratio, which is different from the method of removing magnesium by evaporation in the technologyAnd (5) sampling.

The patent of Liwu application in 2013 includes the steps of evaporating sulfate type salt lake brine to a sodium chloride saturated state, freezing to separate out mirabilite in winter, performing solid-liquid separation when the content of sulfate ions in the brine is controlled to be 1 g/L-7 g/L, evaporating brine after mirabilite is separated out in spring and summer to separate out sodium chloride, evaporating brine after sodium chloride is separated out to separate out sylvine, carnallite and epsomite, performing solid-liquid separation after the concentration of lithium ions in the brine is controlled to be greater than or equal to 6 g/L, performing solid-liquid separation when the brine after solid-liquid separation is brine with high magnesium chloride content, mixing the brine with the mirabilite to react to separate out sodium salt and magnesium salt, performing solid-liquid separation when the ratio of magnesium to lithium in the solution is controlled to be less than or equal to 8:1 to obtain boron-lithium-rich brine, reacting the boron-lithium-rich brine with water to separate out lithium-rich brine, and introducing the boron-lithium-rich brine into a lithium salt pool to evaporate and separate out lithium-salt ore.

In 2014 li wu application patent: a method for separating and extracting lithium from crude lithium sulfate ores. The method relates to a lithium extraction process, and particularly discloses a method for separating and extracting lithium from lithium sulfate coarse ore, which comprises the steps of removing magnesium, mixing the lithium sulfate coarse ore powder with water, adding calcium oxide, reacting, aging, performing solid-liquid separation, and obtaining a first solution and solid slag; removing sulfate radicals, adding calcium chloride into the first solution, reacting, aging, and carrying out solid-liquid separation to obtain a second solution and solid calcium sulfate; precipitating calcium, adding sodium carbonate into the second solution, reacting, aging, and performing solid-liquid separation to obtain a third solution and solid calcium carbonate; concentrating, namely adjusting the pH of the third solution to 3-8 by using hydrochloric acid, evaporating and concentrating to separate out solids, and performing solid-liquid separation to obtain a first-stage concentrated solution; extracting lithium carbonate, adding sodium carbonate into the primary concentrated solution, reacting, aging, and carrying out solid-liquid separation to obtain solid lithium carbonate. The method has low energy consumption; the used impurity-removing precipitator is cheap and easy to obtain, and the impurity-removing product calcium carbonate can be recycled; simple process, easy operation, high magnesium removal rate and high lithium yield.

A method for separating and extracting lithium from lithium sulfate crude ore is characterized by comprising the following steps: the lithium sulfate crude ore is obtained by a series of salt field separation processes from salt lake brine, and the ore is crushed and uniformly mixedThen extracting lithium, comprising the following steps: s1, removing magnesium, mixing the lithium sulfate coarse ore powder with water, adding calcium oxide to precipitate magnesium, reacting for 1-5 h, aging for 1-3 h, and performing solid-liquid separation to ensure that the magnesium removal rate reaches more than 85 percent to obtain a first solution and solid slag; s₂Removing sulfate radicals, adding calcium chloride into the first solution to remove sulfate radicals, reacting for 30-90 min, aging for 10-60 min, carrying out solid-liquid separation to enable the concentration of the sulfate radicals to be less than 5 g/L to obtain a second solution and solid calcium sulfate, S3 precipitating calcium, adding sodium carbonate into the second solution at 60-90 ℃ to precipitate calcium, reacting for 30-90 min, aging for 10-60 min, carrying out solid-liquid separation to enable the removal rate of the calcium to be more than 85% to obtain a third solution and solid calcium carbonate, S4 concentrating, adjusting the pH of the third solution to 3-8 with hydrochloric acid, evaporating and concentrating the third solution to separate out solids, carrying out solid-liquid separation to obtain a primary concentrated solution, S5 extracting lithium carbonate, adding sodium carbonate into the primary concentrated solution at 60-95 ℃ to precipitate, reacting for 30-90 min, aging for 20-60 min, and carrying out solid-liquid separation to obtain solid lithium carbonate and a filtrate.

In 2013, Mayingxi et al, applied for patent: a process for extracting lithium from brine. The process comprises the following steps: carrying out sulfuric acid acidification on the original halogen, and increasing the sulfate radical concentration in the brine while extracting the boric acid until the sulfate radical is promoted to crystallize; fully neutralizing the excessive acid in the acidified brine after boron extraction; naturally evaporating and crystallizing the brine in a salt pan to crystallize a mixture of lithium sulfate, magnesium sulfate and magnesium chloride; separating lithium salt and magnesium salt by utilizing the physical characteristic that the density of lithium sulfate is larger than that of magnesium sulfate and magnesium chloride and applying the heavy medium gravity separation principle in mineral dressing chemistry to achieve the aim of separating magnesium and lithium; then, caustic soda is adopted to deposit magnesium and soda is adopted to deposit lithium to respectively obtain magnesium hydroxide and lithium carbonate products. The invention completely does not need spray drying and calcining procedures, greatly reduces the energy consumption, can reduce the production cost by 70 percent, has simple process flow, few chemical reactions in the process, does not cause the product quality to be difficult to control due to complex flow, and is environment-friendly and pollution-free.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, and provides a method for extracting lithium sulfate from brine with high magnesium-lithium ratio, so that the magnesium and lithium are completely separated, and a lithium sulfate monohydrate product is obtained.

The technical scheme adopted by the invention for solving the technical problem is as follows:

a method for extracting lithium sulfate from brine with high magnesium-lithium ratio comprises the following steps: (1) removing sulfate radicals from the brine; (2) evaporating and concentrating to separate magnesium chloride hexahydrate and miscellaneous salts to obtain brine with low magnesium-lithium ratio; (3) adding magnesium sulfate into brine with low magnesium-lithium ratio to generate lithium sulfate monohydrate precipitate; (3) solid-liquid separation is carried out to obtain lithium sulfate monohydrate and lithium extraction mother liquor; (4) and (4) returning the lithium extraction mother liquor to the step (1). The above process realizes the complete separation of magnesium and lithium and obtains the lithium sulfate monohydrate product.

The high magnesium-lithium ratio brine is natural brine or regenerated brine, wherein the mass ratio of a dry basis to Mg/L i is more than 10.0, the natural brine is salt lake brine, and the regenerated brine is salt preparation mother liquor, potassium extraction mother liquor, boron extraction mother liquor, lithium extraction mother liquor and the like.

The high magnesium-lithium ratio brine contains sulfate radical or does not contain sulfate radical. If sulfate is contained, it is removed by freezing or adding soluble calcium salt. When dry basis weight SO₄When the/Cl is more than 0.1, the removal is carried out by adopting a freezing method or a calcium adding method, and when the/Cl is less than 0.1, the removal can be carried out by adopting a soluble calcium adding method. The amount of the calcium salt added is 0.9-1.1 in terms of the molar ratio of calcium ions to the total amount of sulfate radicals. The soluble calcium salt is calcium chloride, calcium hydroxide or lime milk.

The evaporation and concentration process refers to any form of natural evaporation (such as sun evaporation), forced evaporation (such as heating evaporation, vacuum evaporation, bubbling forced evaporation and the like).

The solid phase generated by evaporation is mainly magnesium chloride hydrate, and the mixed salt refers to small amount of chloride or sulfate of sodium, potassium, magnesium and calcium, or related double salt, and mixture thereof.

The low magnesium-lithium ratio brine means that the dry basis mass ratio of Mg/L i in the brine is less than 10.0.

The magnesium sulfate added into the brine with medium-low magnesium-lithium ratio refers to magnesium sulfate or hydrate thereof, or magnesium sulfateSolution, or mass ratio: SO (SO)₄A magnesium-containing mixed solution having a/Cl greater than 0.15 and a Mg/L i greater than 2.0.

The formation of the lithium sulfate monohydrate directly produces lithium sulfate monohydrate precipitates, or produces lithium sulfate monohydrate precipitates through evaporation or cooling.

The lithium extraction mother liquor refers to mother liquor obtained by separating a solid phase of lithium sulfate monohydrate, or mother liquor generated in a lithium sulfate purification process, such as a process of washing or recrystallizing lithium sulfate.

The invention has the advantages and positive effects that:

the invention realizes the complete separation of magnesium and lithium and obtains the lithium sulfate monohydrate product.

Detailed Description

The present invention is further illustrated by the following specific examples, which are intended to be illustrative, not limiting and are not intended to limit the scope of the invention.

A method for extracting lithium sulfate from brine with high magnesium-lithium ratio comprises the following steps: (1) removing sulfate radicals from the brine; (2) evaporating and concentrating to separate magnesium chloride hexahydrate and miscellaneous salts to obtain brine with low magnesium-lithium ratio; (3) adding magnesium sulfate into brine with low magnesium-lithium ratio to generate lithium sulfate monohydrate precipitate; (3) solid-liquid separation is carried out to obtain lithium sulfate monohydrate and lithium extraction mother liquor; (4) and (4) returning the lithium extraction mother liquor to the step (1). The above process realizes the complete separation of magnesium and lithium and obtains the lithium sulfate monohydrate product.

The example of removing sulfate from brine in step (1) is as follows: