CN112390266A - Boric acid composite extracting agent and method for recovering boric acid, magnesium and lithium from salt lake old brine - Google Patents

Boric acid composite extracting agent and method for recovering boric acid, magnesium and lithium from salt lake old brine Download PDF

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CN112390266A
CN112390266A CN201910748098.1A CN201910748098A CN112390266A CN 112390266 A CN112390266 A CN 112390266A CN 201910748098 A CN201910748098 A CN 201910748098A CN 112390266 A CN112390266 A CN 112390266A
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magnesium
boric acid
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杨喜云
伍玲龙
徐徽
王园园
王小弟
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Central South University
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B35/00—Boron; Compounds thereof
    • C01B35/08—Compounds containing boron and nitrogen, phosphorus, oxygen, sulfur, selenium or tellurium
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    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D15/00—Lithium compounds
    • C01D15/08—Carbonates; Bicarbonates
    • C—CHEMISTRY; METALLURGY
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    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
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Abstract

The invention belongs to the field of salt lake chemical industry, and particularly relates to a boric acid composite extracting agent which comprises isooctyl alcohol, isoamyl alcohol and 2-ethyl-1, 3-hexanediol. The invention also provides a method for extracting boric acid from the salt lake old brine by using the boric acid composite extracting agent, and a method for extracting boron, magnesium and lithium from the salt lake old brine by step separation. The invention innovatively discovers that isooctyl alcohol, isoamyl alcohol and 2-ethyl-1, 3-hexanediol have unexpected cooperativity in the aspect of extraction of boric acid, and can effectively improve the single-stage extraction rate of the boric acid.

Description

Boric acid composite extracting agent and method for recovering boric acid, magnesium and lithium from salt lake old brine
Technical Field
The invention belongs to the field of salt lake chemical industry, and discloses a method for preparing boric acid, magnesium hydroxide, basic magnesium carbonate and magnesium oxide from salt lake old brine by extracting boron, magnesium and lithium through step separation.
Background
The salt lakes in China are numerous and rich in boron, magnesium, lithium and other resources. The salt lake resources are most abundant in potassium, sodium, magnesium, lithium and boron resources and have large reserves. With the rapid development of economy in China and the rise of new energy automobiles, the demand on potassium, boron, magnesium and lithium, particularly lithium resources, is rapidly increased, and the development of salt lake resources becomes unprecedented and important.
In the development and utilization of salt lake resources, the potassium resources in the salt lake are better solved and have mature technology, the development and utilization of magnesium, lithium and other resources just realize industrial production, and particularly the lithium resource extraction technology is still limited by the market. Therefore, in the present of national science and technology, economy and social development, the research of low-cost comprehensive development and utilization of magnesium, lithium, boron and other resources in salt lakes and the solution of key technical problems are actively developed, and the urgent need is met. It is not only related to the sustainable development of economy in western regions of China, but also has very important significance for improving the ecological environment of salt lakes of China.
At present, the research on the comprehensive utilization of salt lake brine resources is the extraction of single resources, and the combined extraction of various resources is rarely reported. Zhang Chuanfu proposes a method for producing lithium carbonate, boric acid and high-purity magnesium oxide by removing magnesium from salt lake brine through a salting-out method, which comprises three procedures of deep separation of magnesium and lithium, fine magnesium removal and ammonium chloride recovery, qualified lithium carbonate is produced, and magnesium oxide and crude boric acid with higher purity are prepared. Xuli in patent (CN 101024502a) proposes "a method for extracting boron, magnesium and lithium from salt lake brine jointly", which is to prepare boric acid by acidifying brine, precipitate magnesium by the first ammonia process, precipitate magnesium by the second carbonate process, precipitate magnesium mother liquor by the second process, continue to precipitate magnesium by the salt field process or by heating concentration, deeply precipitate magnesium by the third sodium hydroxide solution, and prepare lithium carbonate by the sodium carbonate solution reaction process; the recovery rates of boron, magnesium and lithium reach 87%, 95% and 92% respectively. However, the efficiency of acidification for removing boron is generally not high, and the acidification method and other methods are usually combined for extracting boric acid; the method obtains enriched Li after three times of deep magnesium+The mother liquor has larger process flow and more reagents. Xuli in patent (CN 1618997a) proposes a method for extracting magnesium and lithium from salt lake brine jointly, which uses salt lake brine as raw material and adopts two-stage magnesium precipitation process of ammonia and ammonium bicarbonate, the recovery rate of magnesium is up to above 98%, and the extraction rate of lithium is up to 95%. However, the B content in the actual brine is 2-3 g/L, redundant B is not removed at the early stage, and the purity of the subsequent product is influenced.
At present, researches on boron removal of brine mainly comprise an acidification method, a solvent extraction method, a precipitation method and a fractional crystallization method. Because the salt lake brine has the characteristics of high magnesium and low lithium ratio, the content of boron is low, the efficiency of an acidification method and a precipitation method is not high, and a large amount of chemical reagents are required, the salt lake brine is not popularized in a large amount; the fractional crystallization needs to utilize a forced ammonia distillation method to make different salts in a salt lake undergo step-by-step crystallization separation within an adaptive temperature range, and finally, the boron-containing mother liquor is cooled to obtain the boron-containing mother liquor, and the boron is obtained by cooling, but the method has the problems of extremely high requirements on equipment, high energy consumption and the like.
At present, extraction method is mainly used for extracting a large amount of boron from brine, but the existing extracting agent has poor extraction rate, usually needs multi-stage extraction, has low extraction efficiency, complex treatment process, large medicament consumption and poor industrial practical application prospect.
Disclosure of Invention
In order to solve the problems in the prior art, a first object of the present invention is to provide a boric acid composite extractant, which aims to improve the extraction efficiency and effect of the extractant.
The second purpose of the invention is to provide a method for extracting boric acid from salt lake old brine.
The third purpose of the invention is to provide a method for gradient separation and extraction of boron, magnesium and lithium from the salt lake old brine, aiming at realizing efficient utilization of the salt lake old brine.
The extraction efficiency of the existing boric acid extractant is limited, and multistage extraction is required, therefore, the invention provides a boric acid composite extractant which comprises isooctyl alcohol, isoamyl alcohol and 2-ethyl-1, 3 hexanediol.
The invention innovatively discovers that isooctyl alcohol, isoamyl alcohol and 2-ethyl-1, 3-hexanediol have unexpected cooperativity in the aspect of extraction of boric acid, and can effectively improve the single-stage extraction rate of the boric acid.
Preferably, in the boric acid composite extracting agent, the weight ratio of isooctyl alcohol, isoamyl alcohol and 2-ethyl-1, 3-hexanediol is 0.8-1.2: 0.8-1.2; further preferably 1:1: 1. Researches show that the optimal proportion is helpful for further remarkably improving the synergistic effect of the ternary components, and the single-stage extraction rate can be further improved to more than 99%.
The invention also provides a method for extracting boric acid from the salt lake old brine, which comprises the steps of adjusting the pH value of the salt lake old brine to be 1-3, extracting by using the compound extractant containing the boric acid, collecting an extract phase enriched with the boric acid, and then performing back extraction to collect a back extract phase, namely the boric acid solution.
The research of the invention finds that under the action of the ternary synergistic composite extracting agent, the boric acid in the salt lake old brine can be effectively and selectively extracted, so that the high recycling of resources can be realized, and the high-value recycling of subsequent elements is facilitated.
Preferably, in the method, the boric acid composite extracting agent is diluted by a diluent in advance before extraction; the diluent is preferably sulfonated kerosene.
Preferably, the saponification degree of the sulfonated kerosene is 40-60%; more preferably 50%.
Preferably, the boric acid composite extracting agent and the diluent are mixed according to a volume ratio of 20-50: 50-80 parts; preferably 40-50: 50-60. It can be understood that: in the organic phase for extraction, the boric acid composite extracting agent accounts for 20-50% of the organic phase; preferably 40 to 50%. The research shows that the single-stage extraction effect at the preferred proportion is excellent, and particularly under the preferred condition, the extraction rate can be unexpectedly as high as more than 99%.
Preferably, a first-stage extraction process is adopted, and the O/A ratio in the extraction process is 1:1-1: 4; preferably 1:1 to 2. The O/A is the volume ratio of an organic phase and a water phase in the extraction process, the volume of the organic phase is the volume of the boric acid composite extractant plus the diluent, and the water phase is the salt lake old brine to be extracted. The inventor researches and discovers that the compound extracting agent can further exert the cooperativity at the preferable proportion, and the extraction rate can be further and unexpectedly improved.
In the method, water or alkali liquor is adopted for back extraction treatment.
Preferably, the alkali liquor used in the back extraction process is an aqueous solution of alkali metal hydroxide, and the pH of the alkali liquor is preferably 7-9.
Preferably, the O/A ratio in the back extraction process is 1: 1-2: 1. The O/A is the volume ratio of an organic phase to a water phase in the back extraction process, and the O is an extracted organic phase obtained by extraction; and A is the volume of the back extraction alkali liquor.
The invention also provides a method for gradient separation and extraction of boron, magnesium and lithium from the salt lake old brine, which comprises the following steps:
step (1): extracting and back-extracting the salt lake old brine by adopting the method for extracting the boric acid from the salt lake old brine to obtain the boric acid and extraction raffinate;
step (2): performing magnesium precipitation treatment on the extraction raffinate obtained in the step (1), and recovering to obtain magnesium precipitate and precipitate mother liquor enriched with lithium;
and (3): and (3) recovering lithium from the precipitation mother liquor in the step (2).
The method can efficiently separate the boric acid in the brine by using the composite extracting agent, and is beneficial to subsequently recovering high-quality magnesium and lithium.
Preferably, in the method, in the step (2), the magnesium precipitation treatment includes a primary precipitation for obtaining magnesium hydroxide and a secondary precipitation for recovering basic magnesium carbonate.
Preferably, the primary precipitation process is: adding ammonia water into the extraction raffinate to perform primary precipitation reaction, and controlling the pH value to be 8-9 and the temperature to be 70-90 ℃ in the reaction process; for 1-6h, followed by filtration to obtain mother liquor A and Mg (OH)2。
Preferably, the secondary precipitation process is: adding ammonium bicarbonate into the precipitation mother liquor A, and controlling the pH of the system to be 7-9; the dosage of the ammonium bicarbonate is 1.2-1.5 of the theoretical amount of the magnesium completely converted; carrying out secondary precipitation reaction, and then filtering to obtain precipitation mother liquor and basic magnesium carbonate.
Preferably, in the above method, sodium carbonate is added to the precipitation mother liquor to carry out a lithium precipitation reaction, and lithium carbonate is obtained by solid-liquid separation.
Further preferred is a method comprising evaporating and concentrating the precipitation mother liquor in advance until the concentration of Li reaches 20-30g/L, and separating solid from liquid to obtain NH4And adding sodium carbonate into the crystallization mother liquor to perform precipitation reaction to obtain the lithium carbonate.
The preferred method for extracting boron, magnesium and lithium by the step separation of the salt lake old brine comprises the following steps:
(1) b (extraction of boric acid); acidifying salt lake old brine by hydrochloric acid to adjust the pH value to 1-3, then extracting by using a mixed alcohol extracting agent (mixed alcohol with the mass ratio of isooctyl alcohol, isoamyl alcohol and 2-ethyl-1, 3-hexanediol being 1:1:1), taking 50% sulfonated kerosene as a diluent, controlling the O/A to be 1:1-1:4, performing primary extraction B,
adopting water or 0.1mol/L NaOH solution for back extraction to obtain H3BO3Concentrating and crystallizing to obtain H3BO3And (5) producing the product.
(2)Mg(OH)2Precipitation of (4); precipitating the brine without B by using ammonia water, controlling the reaction temperature to be 70-90 ℃, controlling the reaction pH to be 8-9, reacting for 1-6h, filtering and washing to obtain Mg (OH)2Producing a product;
(3) precipitation of basic magnesium carbonate; adding ammonia water and ammonium bicarbonate into the primary magnesium precipitation mother liquor, carrying out secondary magnesium precipitation reaction, controlling the pH value to be 7.0-9.0, controlling the use amount of the ammonium bicarbonate to be 1.2-1.5 times of the theoretical amount, controlling the reaction temperature to be 60-90 ℃, reacting for 1-4h, and then filtering and washing to obtain a basic magnesium carbonate product;
(4) preparation of high-purity lithium carbonate: the filtrate after the second-stage magnesium precipitation mainly contains NH4 +、Li+、Cl-(ii) a Evaporating the filtrate for concentration, and separatingOut of NH4Cl crystal, adding Na when the concentration of Li reaches 20-30g/L2CO3Carrying out precipitation treatment to obtain Li with higher purity2CO3。
The invention aims to provide a novel method for preparing boric acid, magnesium hydroxide and basic magnesium carbonate by performing step separation extraction on boron, magnesium and lithium from old brine in a salt lake.
Advantageous effects
1. The invention innovatively provides a ternary composite extracting agent containing isooctyl alcohol, isoamyl alcohol and 2-ethyl-1, 3-hexanediol, and innovatively discovers that the ternary components have unexpected cooperativity in the extraction process of boric acid, so that the high-recovery extraction of the boric acid under single-stage extraction can be realized;
2. the single-stage extraction rate of the composite extractant on salt lake brine can reach more than 99 percent, and the composite extractant is obviously superior to the existing extractant;
3. by using the composite extracting agent and further matching with the magnesium and lithium precipitation processes, the high-value recovery of the salt lake brine can be realized.
Drawings
FIG. 1 is a process flow diagram of the present invention;
FIGS. 2 and 3 are an XRD pattern and an SEM image of magnesium hydroxide obtained in example 1;
FIG. 4 is the XRD pattern of basic magnesium carbonate obtained in example 1;
Detailed Description
The technical scheme of the application is explained in detail by combining the following embodiments:
the main element composition (g/L) of the salt lake brine is as follows: mg 111.5, B2.70, Li 3.02
In the following case, the sulfonated kerosene diluent used had a saponification degree of 50% except for the particular life.
According to the chemical industry standard HG/T3607-2007 of industrial magnesium hydroxide, the industrial magnesium hydroxide can be divided into three types:
class I: used mainly as raw material of flame retardant, [ Mg (OH) ]2]Mass fraction/% > is more than or equal to 97.5;
and II: mainly used as raw materials for producing magnesium oxide and magnesium salt; [ Mg (OH)2]Mass fraction/% > or more than 93
Class III: the method is mainly used for flue desulfurization, wastewater treatment, agricultural fertilizers, soil conditioners and the like; [ Mg (OH)2]Mass fraction/% > is more than or equal to 92.
Therefore, the Mg (OH) produced by the process of the invention2The purity requirement of the product meets the I-type standard of the industry.
Example 1
(1) Acidifying salt lake old brine by hydrochloric acid to adjust the pH value to 1.25, extracting by using 20% of mixed alcohol (mixed alcohol of isooctanol, isoamylol and 2-ethyl-1, 3 hexanediol (mass ratio is 1:1:1), using 80% of sulfonated kerosene as a diluent, controlling the O/A to be 1:1, performing primary extraction B, enabling the extraction rate of B to reach 92.01%, performing back extraction by using 0.1mol/L NaOH solution, and enabling the O/A to be 1:1 to obtain H3BO3Concentrating and crystallizing to obtain H3BO3Producing a product;
(2) precipitating the brine without B with ammonia water, controlling reaction temperature at 70 deg.C, reaction pH at 8.0, reacting for 2h, filtering, washing to obtain Mg (OH)2The recovery rate of Mg of the product is 93.6 percent;
(3) adding ammonia water and ammonium bicarbonate into the first-stage magnesium precipitation mother liquor, adjusting the pH value to 9.0, controlling the use amount of the ammonium bicarbonate to be 1.5 times of the theoretical amount, controlling the reaction temperature to be 60 ℃, reacting for 1 hour, and then filtering and washing to obtain a basic magnesium carbonate product;
(4) the mother liquor after the secondary magnesium precipitation mainly contains NH4 +、Li+、Cl-(ii) a Evaporating and concentrating to separate out NH4Cl crystals, and Na is added when the concentration of Li reaches 20g/L2CO3Carrying out precipitation treatment to obtain Li with higher purity2CO3Introduction of Li2CO3Recrystallizing once to obtain the battery grade Li2CO3. The overall recovery of Li was 95%.
Example 2
(1) Acidifying salt lake old brine by hydrochloric acid to adjust the pH value to 1.25, extracting by using 30% mixed alcohol (1:1:1) of isooctanol, isoamylol and 2-ethyl-1, 3 hexanediol), using 70% sulfonated kerosene as a diluent, controlling the O/A ratio to be 1:1, performing primary extraction B, ensuring that the extraction rate of B reaches 98.177%, performing back extraction by using 0.1mol/L NaOH solution, and ensuring that the O/A ratio is 1:1 to obtain H3BO3Concentrating and crystallizing to obtain H3BO3Producing a product;
(2) precipitating the brine without B with ammonia water, controlling reaction temperature at 70 deg.C, reaction pH at 8.0, reacting for 2h, filtering, washing to obtain Mg (OH)2The recovery rate of Mg of the product is 93.6 percent;
(3) adding ammonia water and ammonium bicarbonate into the first-stage magnesium precipitation mother liquor, adjusting the pH value to 9.0, controlling the use amount of the ammonium bicarbonate to be 1.5 times of the theoretical amount, controlling the reaction temperature to be 60 ℃, reacting for 1 hour, filtering and washing to obtain a basic magnesium carbonate product;
(4) the mother liquor after the secondary magnesium precipitation mainly contains NH4 +、Li+、Cl-(ii) a Evaporating and concentrating to separate out NH4Cl crystals, and Na is added when the concentration of Li reaches 20g/L2CO3Carrying out precipitation treatment to obtain Li with higher purity2CO3Introduction of Li2CO3Recrystallizing once to obtain the battery grade Li2CO3. The overall recovery of Li was 95%.
Example 3
(1) Acidifying salt lake old brine by hydrochloric acid to adjust the pH value to 1.25, extracting by using 40% of mixed alcohol (mixed alcohol of isooctanol, isoamylol and 2-ethyl-1, 3 hexanediol (mass ratio is 1:1:1)), using 60% of sulfonated kerosene as a diluent, controlling the O/A to be 1:1, performing primary extraction B, enabling the extraction rate of B to reach 99%, performing back extraction by using 0.1mol/LNaOH solution, and enabling the O/A to be 1:1 to obtain H3BO3Concentrating and crystallizing to obtain H3BO3Producing a product;
(2) precipitating the brine without B with ammonia water at 70 deg.C for 2 hr, controlling reaction pH to 8.0, filtering, and washingTo obtain Mg (OH)2The recovery rate of Mg of the product is 93.6 percent;
(3) adding ammonia water and ammonium bicarbonate into the first-stage magnesium precipitation mother liquor, adjusting the pH value to 9.0, controlling the use amount of the ammonium bicarbonate to be 1.5 times of the theoretical amount, controlling the reaction temperature to be 60 ℃, reacting for 1 hour, filtering and washing to obtain a basic magnesium carbonate product;
(4) the mother liquor after the secondary magnesium precipitation mainly contains NH4 +、Li+、Cl-(ii) a Evaporating and concentrating to separate out NH4Cl crystals, and Na is added when the concentration of Li reaches 20g/L2CO3Carrying out precipitation treatment to obtain Li with higher purity2CO3Introduction of Li2CO3Recrystallizing once to obtain the battery grade Li2CO3. The overall recovery of Li was 95%.
Example 4
(1) Acidifying salt lake old brine by hydrochloric acid to adjust the pH value to 1.25, extracting by adopting 50% of mixed alcohol (mixed alcohol of isooctanol, isoamylol and 2-ethyl-1, 3 hexanediol (the mass ratio is 1:1:1)), taking 50% of sulfonated kerosene as a diluent, controlling the O/A to be 1:1, performing primary extraction B, ensuring the extraction rate of B to reach 99.12%, and performing back extraction by adopting 0.1mol/LNaOH solution, wherein the O/A is 1:1 to obtain H3BO3Concentrating and crystallizing to obtain H3BO3Producing a product;
(2) precipitating the brine without B with ammonia water, controlling reaction temperature at 70 deg.C, reaction pH at 8.0, reacting for 2h, filtering, washing to obtain Mg (OH)2The recovery rate of Mg of the product is 93.6 percent;
(3) adding ammonia water and ammonium bicarbonate into the first-stage magnesium precipitation mother liquor, adjusting the pH value to 9.0, controlling the use amount of the ammonium bicarbonate to be 1.5 times of the theoretical amount, controlling the reaction temperature to be 60 ℃, reacting for 1 hour, filtering and washing to obtain a basic magnesium carbonate product;
(4) the mother liquor after the secondary magnesium precipitation mainly contains NH4 +、Li+、Cl-(ii) a Evaporating and concentrating to separate out NH4Cl crystals, and Na is added when the concentration of Li reaches 20g/L2CO3Performing precipitation treatment to obtainHigh purity Li2CO3Introduction of Li2CO3Recrystallizing once to obtain the battery grade Li2CO3. The overall recovery of Li was 95%.
Example 5
(1) Acidifying salt lake old brine by hydrochloric acid to adjust the pH value to 1.25, extracting by adopting 50% of mixed alcohol (1:1:1) of isooctanol, isoamylol and 2-ethyl-1, 3 hexanediol), taking 50% of sulfonated kerosene as a diluent, controlling the O/A to be 1:2, performing primary extraction B, controlling the extraction rate of B to be 97.88%, performing back extraction by adopting 0.1mol/L NaOH solution, and obtaining H, wherein the O/A is 1:13BO3Concentrating and crystallizing to obtain H3BO3Producing a product;
(2) precipitating the brine without B with ammonia water, controlling reaction temperature at 70 deg.C, reaction pH at 8.0, reacting for 2h, filtering, washing to obtain Mg (OH)2The recovery rate of Mg of the product is 93.6 percent;
(3) adding ammonia water and ammonium bicarbonate into the first-stage magnesium precipitation mother liquor, adjusting the pH value to 9.0, controlling the use amount of the ammonium bicarbonate to be 1.5 times of the theoretical amount, controlling the reaction temperature to be 60 ℃, reacting for 1 hour, filtering and washing to obtain a basic magnesium carbonate product;
(4) the mother liquor after the secondary magnesium precipitation mainly contains NH4 +、Li+、Cl-(ii) a Evaporating and concentrating to separate out NH4Cl crystals, and Na is added when the concentration of Li reaches 20g/L2CO3Carrying out precipitation treatment to obtain Li with higher purity2CO3Introduction of Li2CO3Recrystallizing once to obtain the battery grade Li2CO3. The overall recovery of Li was 95%.
Example 6
(1) Acidifying salt lake old brine by hydrochloric acid to adjust the pH value to 1.25, extracting by adopting 50% of mixed alcohol (mixed alcohol of isooctanol, isoamylol and 2-ethyl-1, 3 hexanediol (mass ratio is 1:1:1)), taking 50% of sulfonated kerosene as a diluent, controlling the O/A to be 1:3, performing primary extraction B, ensuring the extraction rate of B to reach 95.89%, performing back extraction by adopting 0.1mol/LNaOH solution, and ensuring the O/A to be 1:1 to obtain H3BO3By passing through the thick liquidCrystallization to obtain H3BO3Producing a product;
(2) precipitating the brine without B with ammonia water, controlling reaction temperature at 70 deg.C, reaction pH at 8.0, reacting for 2h, filtering, washing to obtain Mg (OH)2The recovery rate of Mg of the product is 93.6 percent;
(3) adding ammonia water and ammonium bicarbonate into the first-stage magnesium precipitation mother liquor, adjusting the pH value to 9.0, controlling the use amount of the ammonium bicarbonate to be 1.5 times of the theoretical amount, controlling the reaction temperature to be 60 ℃, reacting for 1 hour, filtering and washing to obtain a basic magnesium carbonate product;
(4) the mother liquor after the secondary magnesium precipitation mainly contains NH4 +、Li+、Cl-(ii) a Evaporating and concentrating to separate out NH4Cl crystals, and Na is added when the concentration of Li reaches 20g/L2CO3Carrying out precipitation treatment to obtain Li with higher purity2CO3Introduction of Li2CO3Recrystallizing once to obtain the battery grade Li2CO3. The overall recovery of Li was 95%.
Example 7
(1) Acidifying salt lake old brine by hydrochloric acid to adjust the pH value to 1.25, extracting by adopting 50% of mixed alcohol (mixed alcohol of isooctanol, isoamylol and 2-ethyl-1, 3 hexanediol (the mass ratio is 1:1:1)), taking 50% of sulfonated kerosene as a diluent, controlling the O/A to be 1:4, performing primary extraction B, ensuring the extraction rate of B to reach 93.26%, performing back extraction by adopting 0.1mol/LNaOH solution, and ensuring the O/A to be 1:1 to obtain H3BO3Concentrating and crystallizing to obtain H3BO3Producing a product;
(2) precipitating the brine without B with ammonia water, controlling reaction temperature at 70 deg.C, reaction pH at 8.0, reacting for 2h, filtering, washing to obtain Mg (OH)2The recovery rate of Mg of the product is 93.6 percent;
(3) adding ammonia water and ammonium bicarbonate into the first-stage magnesium precipitation mother liquor, adjusting the pH value to 9.0, controlling the use amount of the ammonium bicarbonate to be 1.5 times of the theoretical amount, controlling the reaction temperature to be 60 ℃, reacting for 1 hour, filtering and washing to obtain a basic magnesium carbonate product;
(4) the mother liquor after the secondary magnesium precipitation mainly contains NH4 +、Li+、Cl-(ii) a Evaporating and concentrating to separate out NH4Cl crystals, and Na is added when the concentration of Li reaches 20g/L2CO3Carrying out precipitation treatment to obtain Li with higher purity2CO3Introduction of Li2CO3Recrystallizing once to obtain the battery grade Li2CO3. The overall recovery of Li was 95%.
Comparative example 1
Compared with the embodiment 4, the difference is only that the mixed alcohol of isooctyl alcohol, isoamyl alcohol and 2-ethyl-1, 3-hexanediol is used for replacing the ternary mixed alcohol.
(1) Acidifying salt lake old brine by hydrochloric acid to adjust the pH value to 1.25, extracting by adopting 50% of mixed alcohol (mixed alcohol of isooctanol, isoamylol and 2-ethyl-1, 3 hexanediol (the mass ratio is 1:0:1)), taking 50% of sulfonated kerosene as a diluent, controlling the O/A to be 1:1, performing primary extraction B, ensuring the extraction rate of B to reach 82.54%, performing back extraction by adopting water, and ensuring the O/A to be 1:1 to obtain H3BO3Concentrating and crystallizing to obtain H3BO3Producing a product;
(2) precipitating the brine without B with ammonia water, controlling reaction temperature at 70 deg.C, reaction pH at 8.0, reacting for 2h, filtering, washing to obtain Mg (OH)2The recovery rate of Mg in the product is 85-90%;
(3) adding ammonia water and ammonium bicarbonate into the first-stage magnesium precipitation mother liquor, adjusting the pH value to 9.0, controlling the use amount of the ammonium bicarbonate to be 1.5 times of the theoretical amount, controlling the reaction temperature to be 60 ℃, reacting for 1 hour, filtering and washing to obtain a basic magnesium carbonate product;
(4) the mother liquor after the secondary magnesium precipitation mainly contains NH4 +、Li+、Cl-(ii) a Evaporating and concentrating to separate out NH4Cl crystals, and Na is added when the concentration of Li reaches 20g/L2CO3Carrying out precipitation treatment to obtain Li with higher purity2CO3. The overall recovery of Li was 95%.
Comparative example 2
Compared with example 4, the difference is only that isooctanol single substance is used to replace the ternary mixed alcohol.
The ICP-OES detection result shows that the optimal extraction conditions are as follows: the extracting agent is 50 percent of isooctyl alcohol, the diluting agent is 50 percent of sulfonated kerosene, and the best extracting effect is achieved when the O/A is 1: 1; 200ml of brine is extracted by the first stage, and the extraction rate of B reaches 74.86 percent.
Example 8
The differences from example 1 were that the amount of ammonia water used in step (2) and the theoretical amount of ammonium hydrogencarbonate in step (3) were adjusted, the total yield of the two-stage magnesium precipitate and the precipitation rate of B therein were measured (results are shown in Table 1), the amount of recovered magnesium precipitate and the amount of B remaining in the product were measured (results are shown in Table 2 (D-group purity data in Table 1))
TABLE 1 Mg and B deposition rates for different ammonia concentrations
Figure BDA0002166271850000101
And (3) the total Mg precipitation rate refers to the total magnesium precipitation amount in the steps (2) and (3). The precipitation rate of B refers to the precipitation rate of B in raffinate in the magnesium precipitation process.
TABLE 2Mg (OH)2Basic magnesium carbonate, and B content in MgO
Figure BDA0002166271850000102
In conclusion, the technical scheme of the invention can effectively realize the high-efficiency, high-purity and high-yield recovery of boron, magnesium and lithium in the brine.

Claims (10)

1. The boric acid composite extractant is characterized by comprising isooctyl alcohol, isoamyl alcohol and 2-ethyl-1, 3-hexanediol.
2. The boric acid composite extractant of claim 1, wherein the weight ratio of isooctyl alcohol, isoamyl alcohol and 2-ethyl-1, 3-hexanediol is 0.8-1.2: 0.8-1.2.
3. A method for extracting boric acid from salt lake old brine is characterized in that the pH value of the salt lake old brine is adjusted to be 1-3, then the salt lake old brine is extracted by using a composite extracting agent containing boric acid as defined in any one of claims 1-2, an extract phase enriched with boric acid is collected, and then the extract phase is subjected to back extraction, and a back extraction phase is collected, so that a boric acid solution is obtained.
4. The method for extracting boric acid from the brine of old bittern of salt lake as claimed in claim 3, wherein the boric acid complex extractant is diluted with diluent before extraction; the diluent is preferably sulfonated kerosene;
preferably, the saponification degree of the sulfonated kerosene is 40-60%;
further preferably, the boric acid composite extracting agent and the diluent are mixed according to a volume ratio of 20-50: 50-80 parts; preferably 40-50: 50-60.
5. The method for extracting boric acid from the brine of old brine in salt lake as claimed in claim 3 or 4, wherein the primary extraction process is adopted, and the O/A in the extraction process is 1:1-1: 4; preferably 1:1 to 2.
6. A method for gradient separation extraction of boron, magnesium and lithium from salt lake old brine is characterized by comprising the following steps:
step (1): the method of any one of claims 3 to 5 is adopted to perform extraction and back extraction treatment on the salt lake old brine to obtain boric acid and extraction raffinate;
step (2): performing magnesium precipitation treatment on the extraction raffinate obtained in the step (1), and recovering to obtain magnesium precipitate and precipitate mother liquor enriched with lithium;
and (3): and (3) recovering lithium from the precipitation mother liquor in the step (2).
7. The method for step separation and extraction of boron, magnesium and lithium from the salt lake old brine as claimed in claim 6, wherein in the step (2), the magnesium precipitation treatment comprises a primary precipitation for obtaining magnesium hydroxide and a secondary precipitation for recovering basic magnesium carbonate.
8. The method for step separation and extraction of boron, magnesium and lithium from the salt lake old brine as claimed in claim 7, wherein the primary precipitation process is: adding ammonia water into the extraction raffinate to perform primary precipitation reaction, and controlling the pH value to be 8-9 and the temperature to be 70-90 ℃ in the reaction process; for 1-6h, followed by filtration to obtain mother liquor A and Mg (OH)2。
9. The method for step separation and extraction of boron, magnesium and lithium from the salt lake old brine as claimed in claim 8, wherein the secondary precipitation process is: adding ammonium bicarbonate into the precipitation mother liquor A, and controlling the pH value of the system to be 7-9; the dosage of the ammonium bicarbonate is 1.2-1.5 of the theoretical amount of the magnesium completely converted; carrying out secondary precipitation reaction, and then filtering to obtain precipitation mother liquor and basic magnesium carbonate.
10. The method for step separation and extraction of boron, magnesium and lithium from the salt lake old brine as claimed in any one of claims 6 to 9, wherein sodium carbonate is added into the precipitation mother liquor to carry out lithium precipitation reaction, and lithium carbonate is obtained by solid-liquid separation;
preferably, the precipitation mother liquor is subjected to evaporation concentration treatment in advance, and when the concentration of Li reaches 20-30g/L, NH is obtained by solid-liquid separation4And adding sodium carbonate into the crystallization mother liquor to perform precipitation reaction to obtain the lithium carbonate.
CN201910748098.1A 2019-08-14 2019-08-14 Boric acid composite extracting agent and method for recovering boric acid, magnesium and lithium from salt lake old brine Pending CN112390266A (en)

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