CN110817909A - Lithium-magnesium separation method - Google Patents
Lithium-magnesium separation method Download PDFInfo
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- CN110817909A CN110817909A CN201911134420.8A CN201911134420A CN110817909A CN 110817909 A CN110817909 A CN 110817909A CN 201911134420 A CN201911134420 A CN 201911134420A CN 110817909 A CN110817909 A CN 110817909A
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D15/00—Lithium compounds
- C01D15/08—Carbonates; Bicarbonates
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F5/00—Compounds of magnesium
- C01F5/14—Magnesium hydroxide
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- 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
- C01F5/00—Compounds of magnesium
- C01F5/14—Magnesium hydroxide
- C01F5/145—Purification
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Abstract
The invention provides a lithium-magnesium separation method, which can realize the regulation and control of the lithium-magnesium precipitation separation process by mixing an additive with a solution containing lithium and magnesium and then adding a magnesium precipitation agent into the mixed solution for magnesium precipitation reaction, solves the problem of difficult precipitation and filtration of magnesium hydroxide in the prior art, greatly reduces the adsorption rate of magnesium hydroxide to lithium ions, improves the lithium-magnesium separation efficiency and the lithium ion recovery rate, has the advantages of mild reaction conditions, simple process flow, environmental protection and low consumption, and is suitable for industrial popularization.
Description
Technical Field
The invention relates to the technical field of separation, in particular to a lithium-magnesium separation method.
Background
Lithium is the lightest metal in the world, also known as the "energy metal". With the increasing global demand for lithium, especially the increasing application in the field of new energy, the development and utilization of lithium resources become hot spots for global research and development, and are receiving high attention from people. The lithium resource in China exists in two types of salt lake type and ore type, wherein lithium in salt lake brine is often a trace element and a large amount of alkali metal ions (Mg)2+) Coexisting, their chemical properties are very similar, leading to difficulties in lithium magnesium separation. Thus, high efficiency is achieved andthe economical lithium-magnesium separation and lithium extraction are important technical problems to be solved urgently at present.
The current methods for separating lithium and magnesium mainly comprise: conventional precipitation, extraction, calcination or adsorption methods, etc.
CN105152190B discloses a method for producing lithium carbonate by separating magnesium from low-lithium brine and enriching lithium, which utilizes organic extractants such as trialkyl phosphate to directly extract halogen salt so as to lead Li to be+And Mg2+And (3) separating a large amount of lithium carbonate, performing back extraction by using water to form a lithium-rich solution with a low lithium-magnesium ratio, and concentrating, alkalifying and removing magnesium to obtain the lithium carbonate. The method has the advantages of longer extraction and back extraction process flow, complex equipment, high operation cost and serious corrosion to the equipment.
CN1313373C discloses a method for producing lithium carbonate, magnesium oxide and hydrochloric acid by using high-magnesium lithium-containing brine, which is to evaporate and dry old brine to obtain Li+And Mg2+In solid form, then calcined at high temperature and decomposed to give magnesium oxide, and Li+The water phase exists so as to realize the separation of lithium and magnesium; however, the method has high energy consumption, serious corrosion to equipment and high cost in the drying and calcining processes.
CN108385128B discloses a new process for producing high-purity lithium hydroxide from salt lake brine, which realizes the separation of lithium and magnesium by synthesizing a lithium adsorbent and selectively adsorbing lithium ions; however, the ion sieve adsorbent used in the method has serious adsorption, desorption and dissolution loss in practical application, so that the performances of the adsorption capacity, selectivity and permeability of the ion sieve adsorbent are greatly reduced.
In summary, the precipitation method is most environmentally friendly and has the lowest cost in the lithium-magnesium separation method. However, the magnesium hydroxide precipitate obtained by the traditional precipitation method is very easy to be in a gel state, is difficult to filter and has serious lithium adsorption, so that the lithium adsorption loss is serious.
Therefore, there is a need to develop a lithium magnesium separation method which is simple in operation and equipment, low in energy consumption, and based on a precipitation method, and can effectively reduce the adsorption of lithium by magnesium hydroxide.
Disclosure of Invention
In view of the problems in the prior art, the invention provides a lithium-magnesium separation method which comprises the steps of firstly adding an additive into a solution containing lithium and magnesium and then adding a magnesium precipitation agent, wherein the method improves the filtration rate of magnesium hydroxide and simultaneously reduces the lithium loss, has the advantages of simple process flow, mild conditions, low equipment requirements and low raw material cost, can effectively improve the filtration performance of magnesium hydroxide slurry, can obtain products of magnesium hydroxide, lithium carbonate and crystalline salt, has no waste discharge, and has higher industrial application value.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a lithium-magnesium separation method, comprising the steps of:
(1) adding an additive into a solution containing lithium and magnesium, and stirring and mixing uniformly to obtain a mixed solution, wherein the additive is any one or a combination of at least two of polyethylene glycol, stearic acid, sodium stearate, cationic polyacrylamide, anionic polyacrylamide or nonionic polyacrylamide;
(2) adding a magnesium precipitation agent into the mixed solution, and precipitating magnesium under stirring to obtain magnesium precipitation slurry; filtering the magnesium precipitation slurry to obtain a magnesium precipitation filter cake and a magnesium precipitation filtrate, and washing and drying the magnesium precipitation filter cake to obtain magnesium hydroxide;
(3) adding a lithium precipitation agent into the magnesium precipitation filtrate obtained in the step (2), and precipitating lithium under stirring to obtain lithium precipitation slurry; filtering the lithium precipitation slurry to obtain a lithium precipitation filter cake and a lithium precipitation filtrate, and washing and drying the lithium precipitation filter cake to obtain lithium carbonate;
(4) evaporating and crystallizing the lithium precipitation filtrate to obtain a crystalline salt.
The additive in the invention is any one or combination of at least two of polyethylene glycol, stearic acid, sodium stearate, cationic polyacrylamide, anionic polyacrylamide or nonionic polyacrylamide, wherein typical but non-limiting combinations are as follows: a combination of sodium stearate and cationic polyacrylamide, a combination of polyethylene glycol 10000 and cationic polyacrylamide, a combination of polyethylene glycol 15000 and cationic polyacrylamide, a combination of polyethylene glycol 3000 and anionic polyacrylamide, a combination of cationic polyacrylamide and nonionic polyacrylamide, a combination of anionic polyacrylamide and nonionic polyacrylamide, a combination of polyethylene glycol 3000 and polyethylene glycol 6000, a combination of polyethylene glycol 6000 and sodium stearate, a combination of stearic acid and polyethylene glycol 6000, a combination of stearic acid and cationic polyacrylamide, a combination of stearic acid and anionic polyacrylamide, a combination of sodium stearate and anionic polyacrylamide.
According to the invention, firstly, the additive is added to fully mix with the solution containing lithium and magnesium, and then the magnesium precipitating agent is added to enable magnesium ions to generate precipitation reaction and to be separated from lithium ions; in the second aspect, the additive reduces the adsorption capacity of magnesium hydroxide to lithium ions, improves the lithium-magnesium separation efficiency and reduces the loss rate of the lithium ions; in the third aspect, the additive is added in advance in the method, so that the additive can be uniformly mixed with the solution containing lithium and magnesium and has an effect on the solution, the reaction can be better regulated and controlled, the magnesium hydroxide solid generated by the reaction can be more easily separated, and the adsorption rate of lithium ions is reduced; meanwhile, the method does not need a high-temperature high-pressure reaction environment, is simple in process operation and equipment, mild in reaction conditions and has good popularization value.
Preferably, the mass of the additive in step (1) is 0.1% to 4.0% of the theoretical mass of magnesium hydroxide, and may be, for example, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2.0%, 2.2%, 2.5%, 2.8%, 3.0%, 3.2%, 3.5%, 3.8% or 4.0%, preferably 0.5% to 1.5%.
The theoretical mass of magnesium hydroxide here means the mass of magnesium hydroxide theoretically obtained by calculating the total mass of magnesium ions in the lithium magnesium-containing solution.
The addition mass of the additive is 0.1-4.0% of the theoretical mass of the magnesium hydroxide, so that the regulation and control effect on magnesium deposition reaction can be guaranteed, the addition amount of the additive is less, and the viscosity degree of the solution cannot be further increased.
Preferably, the additive is added directly or prepared into a solution, and is preferably added directly.
The invention preferably adopts a mode of directly adding the additive, so that the operation is simpler, the additive is directly dissolved in the solution containing lithium and magnesium, and the early interaction between the additive and the solution containing lithium and magnesium is better carried out.
Preferably, the additive is any one or a combination of at least two of polyethylene glycol, cationic polyacrylamide or anionic polyacrylamide, preferably cationic polyacrylamide.
The three substances are preferably selected as additives to regulate and control the reaction, because the filtering rate of the magnesium hydroxide can be better improved, the adsorption rate of the magnesium hydroxide to lithium ions is reduced, and the lithium-magnesium separation efficiency is improved.
The invention further prefers cationic polyacrylamide as an additive, because the cationic polyacrylamide has better drag reduction effect on fluid, and can further reduce the adsorption of magnesium hydroxide on lithium ions, so that the lithium ions and the magnesium ions in the solution are separated more efficiently, the filtering speed is higher, and the magnesium precipitation efficiency is higher.
Preferably, the molecular weight of the polyethylene glycol is 2000-20000, for example, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 11000, 12000, 13000, 14000, 15000, 16000, 17000, 18000, 19000 or 20000, preferably 6000-10000.
Preferably, the molecular weight of the cationic polyacrylamide is 1000 to 1400 ten thousand, for example, 1000 ten thousand, 1100 ten thousand, 1200 ten thousand, 1300 ten thousand or 1400 ten thousand, preferably 1000 to 1200 ten thousand.
Preferably, the cationic polyacrylamide has an ionic degree of 5% to 90%, and may be, for example, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85% or 90%, preferably 20% to 60%
According to the invention, the ionic degree of the cationic polyacrylamide is preferably 5-90%, the filtering rate of magnesium hydroxide can be increased better without increasing the viscosity degree of the solution, the adsorption rate of magnesium hydroxide to lithium ions is reduced, and the lithium-magnesium separation efficiency is improved.
Preferably, the molecular weight of the anionic polyacrylamide is 1000 to 2000 ten thousand, for example, 1000 ten thousand, 1100 ten thousand, 1200 ten thousand, 1300 ten thousand, 1400 ten thousand, 1500 ten thousand, 1600 ten thousand, 1700 ten thousand, 1800 ten thousand, 1900 ten thousand or 2000 ten thousand, preferably 1400 to 1800 ten thousand.
According to the invention, the molecular weight of the preferred anionic polyacrylamide is 1000-2000 ten thousand, so that the magnesium precipitation reaction process can be better regulated and controlled, and the magnesium hydroxide filtration rate is accelerated.
Preferably, the stirring speed of the stirring and mixing is 100 to 400r/min, for example, 100r/min, 110r/min, 130r/min, 150r/min, 170r/min, 200r/min, 220r/min, 250r/min, 270r/min, 300r/min, 320r/min, 350r/min, 370r/min or 400r/min, preferably 200 to 300 r/min.
Preferably, lithium in the lithium magnesium containing solution in step (1) is present in the form of lithium sulfate, lithium chloride or lithium nitrate.
Preferably, the magnesium in the lithium magnesium containing solution is present as magnesium sulfate, magnesium chloride or magnesium nitrate.
Preferably, the mass concentration of lithium ions in the lithium magnesium containing solution is 10-30 g/L, for example, 10g/L, 12g/L, 15g/L, 18g/L, 20g/L, 22g/L, 25g/L, 28g/L or 30g/L, preferably 15-25 g/L.
Preferably, the mass concentration of magnesium ions in the lithium magnesium-containing solution is 1-25 g/L, for example, 1g/L, 2g/L, 5g/L, 8g/L, 10g/L, 12g/L, 14g/L, 15g/L, 16g/L, 18g/L, 20g/L, 22g/L or 25g/L, preferably 5-15 g/L.
Preferably, the magnesium precipitating agent in the step (2) is alkali, preferably sodium hydroxide or potassium hydroxide.
Preferably, the addition end point of the alkali is that the pH of the mixed solution is 11 to 13, for example, 11, 11.2, 11.5, 11.6, 11.8, 12.0, 12.2, 12.5, 12.6, 12.8 or 13.0, preferably 11.5 to 12.5.
Preferably, the base is a solid base or a lye base.
Preferably, the alkali concentration of the alkali solution is 15 wt% to 60 wt%, and may be, for example, 15 wt%, 18 wt%, 20 wt%, 22 wt%, 25 wt%, 28 wt%, 30 wt%, 32 wt%, 35 wt%, 38 wt%, 40 wt%, 42 wt%, 45 wt%, 48 wt%, 50 wt%, 52 wt%, 55 wt%, 58 wt% or 60 wt%, preferably 20 wt% to 40 wt%.
Preferably, the magnesium precipitation reaction temperature is 25 ~ 100 ℃, for example can be 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃ or 100 ℃, preferably 35 ~ 65 ℃.
Preferably, the magnesium precipitation reaction time is 0.8-5 h, for example, 0.8h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h, preferably 2-4.5 h.
Preferably, the stirring speed of the magnesium precipitation reaction is 100-500 r/min, such as 100r/min, 110r/min, 130r/min, 150r/min, 170r/min, 200r/min, 220r/min, 250r/min, 270r/min, 300r/min, 320r/min, 350r/min, 370r/min, 400r/min, 420r/min, 450r/min, 470r/min or 500r/min, preferably 200-400 r/min.
Preferably, the temperature for filtering the magnesium precipitation slurry in the step (2) is 40 to 100 ℃, for example, 40 ℃, 42 ℃, 45 ℃, 48 ℃, 50 ℃, 52 ℃, 55 ℃, 58 ℃, 60 ℃, 62 ℃, 65 ℃, 68 ℃, 70 ℃, 72 ℃, 75 ℃, 78 ℃, 80 ℃, 82 ℃, 85 ℃, 88 ℃, 90 ℃, 92 ℃, 95 ℃ or 100 ℃, preferably 70 to 90 ℃.
Preferably, the magnesium precipitation filter cake washing mode is stirring washing or rinsing.
Preferably, the washing liquid for washing the precipitated magnesium filter cake is water.
Preferably, the number of washing times of the precipitated magnesium filter cake is 1 to 4, for example, 1, 2, 3 or 4, preferably 2 to 4.
Preferably, the mass ratio of the volume of the washing liquid to the filter cake in the washing of the precipitated magnesium filter cake is 1.0 to 6.0mL:1g, and may be, for example, 1mL:1g, 1.2mL:1g, 1.5mL:1g, 1.8mL:1g, 2.0mL:1g, 2.2mL:1g, 2.5mL:1g, 2.8mL:1g, 3.0mL:1g, 3.2mL:1g, 3.5mL:1g, 3.8mL:1g, 4.0mL:1g, 4.2mL:1g, 4.5mL:1g, 4.8mL:1g, 5.0mL:1g, 5.2mL:1g, 5.5mL:1g, 5.8mL:1g or 6.0mL:1g, and preferably 3.0 to 5.0mL:1 g.
Preferably, the washing temperature of the precipitated magnesium filter cake is 35 to 95 ℃, for example, 35 ℃, 38 ℃, 40 ℃, 42 ℃, 45 ℃, 48 ℃, 50 ℃, 52 ℃, 55 ℃, 58 ℃, 60 ℃, 62 ℃, 65 ℃, 68 ℃, 70 ℃, 72 ℃, 75 ℃, 78 ℃, 80 ℃, 82 ℃, 85 ℃, 88 ℃, 90 ℃, 92 ℃ or 95 ℃, preferably 55 to 75 ℃.
Preferably, the temperature for drying the precipitated magnesium filter cake is 100 to 200 ℃, for example, 100 ℃, 105 ℃, 110 ℃, 115 ℃, 120 ℃, 125 ℃, 130 ℃, 135 ℃, 140 ℃, 145 ℃, 150 ℃, 155 ℃, 160 ℃, 165 ℃, 170 ℃, 175 ℃, 180 ℃, 185 ℃, 190 ℃, 195 ℃ or 200 ℃, preferably 110 to 130 ℃.
Preferably, the drying time of the precipitated magnesium filter cake is 1-24 h, for example, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h or 24h, preferably 5-15 h.
Preferably, the lithium precipitating agent in the step (3) is carbonate, preferably sodium carbonate or potassium carbonate.
Preferably, the ratio of the amount of the carbonate to the amount of the lithium ion material in the lithium magnesium containing solution is 1 to 1.5:1, and may be, for example, 1:1, 1.02:1, 1.05:1, 1.08:1, 1.10:1, 1.12:1, 1.15:1, 1.18:1, 1.20:1, 1.22:1, 1.25:1, 1.28:1, 1.30:1, 1.32:1, 1.35:1, 1.38:1, 1.40:1, 1.42:1, 1.45:1, 1.48:1, or 1.50:1, preferably 1 to 1.1: 1.
Preferably, the temperature of the lithium precipitation reaction is 70 to 100 ℃, for example, 70 ℃, 72 ℃, 75 ℃, 78 ℃, 80 ℃, 82 ℃, 85 ℃, 88 ℃, 90 ℃, 92 ℃, 95 ℃, 98 ℃ or 100 ℃, preferably 90 to 100 ℃.
Preferably, the time of the lithium precipitation reaction is 0.5 to 4 hours, for example, 0.5 hour, 0.8 hour, 1.0 hour, 1.2 hour, 1.5 hour, 1.8 hour, 2.0 hour, 2.2 hour, 2.5 hour, 2.8 hour, 3.0 hour, 3.2 hour, 3.5 hour, 3.8 hour or 4.0 hour, preferably 2 to 3 hours.
Preferably, the stirring speed of the lithium precipitation reaction is 100-400 r/min, such as 100r/min, 110r/min, 130r/min, 150r/min, 170r/min, 200r/min, 220r/min, 250r/min, 270r/min, 300r/min, 320r/min, 350r/min, 370r/min or 400r/min, preferably 200-300 r/min.
Preferably, the temperature for filtering the lithium deposition slurry in the step (3) is 80-95 ℃, for example, 80 ℃, 81 ℃, 82 ℃, 83 ℃, 84 ℃, 85 ℃, 86 ℃, 87 ℃, 88 ℃, 89 ℃, 90 ℃, 91 ℃, 92 ℃, 93 ℃, 94 ℃ or 95 ℃.
Preferably, the lithium precipitating filter cake washing mode is stirring washing or rinsing.
Preferably, the washing liquid for washing the lithium precipitation filter cake is water.
Preferably, the number of times of washing the lithium precipitation filter cake is 1 to 4, for example, 1, 2, 3 or 4, preferably 2 to 4.
Preferably, the mass ratio of the volume of the washing liquid to the lithium precipitating filter cake in the lithium precipitating filter cake washing is 1.0-4.0 mL:1g, and may be, for example, 1.0mL:1g, 1.2mL:1g, 1.5mL:1g, 1.8mL:1g, 2.0mL:1g, 2.2mL:1g, 2.5mL:1g, 2.8mL:1g, 3.0mL:1g, 3.2mL:1g, 3.5mL:1g, 3.8mL:1g, or 4.0mL:1g, preferably 1.5-3.5 mL:1 g.
Preferably, the temperature for washing the lithium precipitation filter cake is 70-100 ℃, for example, 70 ℃, 72 ℃, 75 ℃, 78 ℃, 80 ℃, 82 ℃, 85 ℃, 88 ℃, 90 ℃, 92 ℃, 95 ℃, 98 ℃ or 100 ℃, preferably 85-95 ℃.
Preferably, the temperature for drying the lithium precipitation filter cake is 100-150 ℃, for example, 100 ℃, 105 ℃, 110 ℃, 115 ℃, 120 ℃, 125 ℃, 130 ℃, 135 ℃, 140 ℃, 145 ℃ or 150 ℃, preferably 120-140 ℃.
Preferably, the time for drying the lithium precipitation filter cake is 1-24 h, for example, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h or 24h, preferably 4-14 h.
Preferably, the crystalline salt obtained by the evaporative crystallization in the step (4) is sodium chloride, potassium chloride, sodium sulfate, potassium nitrate or sodium nitrate.
The method converts other ions in the solution into the crystal salt by evaporating and crystallizing the filtrate and the washing solution together, realizes the full recovery of the resources in the whole process, does not discharge wastes, and has higher industrial application value.
Preferably, the temperature of the evaporative crystallization is 70 to 110 ℃, for example, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃, 100 ℃, 105 ℃ or 110 ℃, preferably 80 to 100 ℃.
As a preferred technical scheme of the invention, the method comprises the following steps:
(1) adding an additive into a lithium-magnesium-containing solution, and uniformly stirring and mixing at 100-400 r/min to obtain a mixed solution, wherein the additive is any one or a combination of at least two of polyethylene glycol, stearic acid, sodium stearate, cationic polyacrylamide, anionic polyacrylamide or nonionic polyacrylamide, the mass of the additive is 0.1-4.0% of the theoretical mass of magnesium hydroxide, the mass concentration of lithium ions in the lithium-magnesium-containing solution is 10-30 g/L, and the mass concentration of magnesium ions is 1-25 g/L;
(2) adding alkali into the mixed solution until the pH value of the mixed solution is 11-13, and precipitating magnesium for reaction for 0.8-5 h at the temperature of 25-100 ℃ under stirring at 100-500 r/min to obtain precipitated magnesium slurry; filtering the magnesium precipitation slurry at 40-100 ℃ to obtain a magnesium precipitation filter cake and a magnesium precipitation filtrate, washing the magnesium precipitation filter cake with 35-95 ℃ water for 1-4 times, and drying at 100-200 ℃ for 1-24 hours to obtain magnesium hydroxide, wherein the mass ratio of the volume of the water used as the magnesium precipitation filter cake washing liquid to the filter cake is 1.0-6.0 mL:1 g;
(3) adding carbonate into the magnesium precipitation filtrate obtained in the step (2), and precipitating lithium for reaction for 0.5-4 h at the temperature of 70-100 ℃ under the stirring of 100-400 r/min to obtain lithium precipitation slurry; filtering the lithium precipitation slurry at 80-95 ℃ to obtain a lithium precipitation filter cake and a lithium precipitation filtrate, washing the lithium precipitation filter cake for 1-4 times by using water at 70-100 ℃, and drying at 100-150 ℃ for 1-24 hours to obtain lithium carbonate, wherein the ratio of the amount of carbonate to the amount of lithium ion substances in a lithium magnesium-containing solution is 1-1.5: 1, and the mass ratio of the volume of water used as a lithium precipitation filter cake washing liquid to the lithium precipitation filter cake is 1.0-4.0 mL:1 g;
(4) evaporating and crystallizing the lithium precipitation filtrate at 70-110 ℃ to obtain crystalline salt.
In a second aspect, the present invention provides a method for treating brine containing lithium and magnesium, wherein the brine containing lithium and magnesium is treated by the method for separating lithium and magnesium as described in the first aspect.
The method for treating the brine containing lithium and magnesium provided by the second aspect of the invention adopts the method for separating lithium and magnesium provided by the first aspect of the invention for treatment, so that the high-efficiency separation of lithium and magnesium can be realized under the operating conditions of low cost and low energy consumption, the operation is simple, the obtained magnesium hydroxide and lithium carbonate products are high in quality, the by-product crystalline salt can be obtained, no waste is discharged, and the industrial application value is high.
Compared with the prior art, the invention has at least the following beneficial effects:
(1) the lithium-magnesium separation method provided by the invention achieves the purpose of regulating and controlling the magnesium hydroxide precipitation reaction by mixing the additive with the solution containing lithium and magnesium, and the filtration rate is more than or equal to 109.56 mL.m-2·s-1The magnesium precipitation efficiency is more than or equal to 97.73 wt%, and the solid-liquid separation rate and the magnesium precipitation efficiency of the slurry are effectively improved;
(2) the lithium-magnesium separation method provided by the invention reduces the adsorption performance of magnesium hydroxide on lithium ions, reduces the loss of lithium ions in the lithium-magnesium separation process, and improves the lithium-magnesium separation efficiency, wherein the adsorption loss rate of the lithium ions is reduced to below 17.56 wt%, and the lithium-magnesium separation method has higher industrial application value;
(3) the lithium-magnesium separation method provided by the invention has the advantages of no need of high temperature and high pressure or electrolysis conditions, simple process operation, low equipment requirement and good popularization value.
Drawings
FIG. 1 is a schematic flow diagram of a lithium-magnesium separation method provided by the present invention.
Detailed Description
The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.
The present invention is described in further detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.
The flow of the lithium-magnesium separation method provided by the invention is shown in fig. 1, and the flow comprises the following steps:
(1) adding an additive into the solution containing lithium and magnesium, and stirring and mixing uniformly to obtain a mixed solution;
(2) adding alkali into the mixed solution, and precipitating magnesium under stirring to obtain precipitated magnesium slurry; filtering the magnesium precipitation slurry to obtain a magnesium precipitation filter cake and a magnesium precipitation filtrate, washing the magnesium precipitation filter cake, and drying to obtain magnesium hydroxide;
(3) adding a lithium precipitation agent into the magnesium precipitation filtrate obtained in the step (2), and precipitating lithium under stirring to obtain lithium precipitation slurry; filtering the lithium precipitation slurry to obtain a lithium precipitation filter cake and a lithium precipitation filtrate, and washing and drying the lithium precipitation filter cake to obtain lithium carbonate;
(4) evaporating and crystallizing the lithium precipitation filtrate to obtain a crystalline salt.
First, an embodiment
Example 1
The embodiment provides a lithium-magnesium separation method, which comprises the following steps:
(1) directly adding a mixture of stearic acid and polyethylene glycol 6000 in a mass ratio of 1:1 into a sulfate solution containing 25g/L lithium ions and 20g/L magnesium ions, and uniformly stirring and mixing at 200r/min to obtain a mixed solution, wherein the mass of the mixture of stearic acid and polyethylene glycol 6000 is 0.1% of the theoretical mass of magnesium hydroxide;
(2) adding a potassium hydroxide solution with the alkali concentration of 20 wt% into the mixed solution until the pH value of the mixed solution is 12.5, and precipitating magnesium for reaction for 1h at the temperature of 50 ℃ under the stirring of 350r/min to obtain magnesium precipitation slurry; filtering the magnesium precipitation slurry at 50 ℃ to obtain a magnesium precipitation filter cake and a magnesium precipitation filtrate, stirring and washing the magnesium precipitation filter cake with water at 40 ℃ for 2 times, and drying at 150 ℃ for 5 hours to obtain magnesium hydroxide, wherein the mass ratio of the volume of the water used as the washing liquid of the magnesium precipitation filter cake to the filter cake is 1mL:1 g;
(3) adding potassium carbonate into the magnesium precipitation filtrate obtained in the step (2), and precipitating lithium for reaction for 0.5h at 70 ℃ under the stirring of 300r/min to obtain lithium precipitation slurry; filtering the lithium precipitation slurry at 85 ℃ to obtain a lithium precipitation filter cake and a lithium precipitation filtrate, stirring and washing the lithium precipitation filter cake with water at 70 ℃ for 2 times, and drying at 120 ℃ for 20 hours to obtain lithium carbonate, wherein the ratio of the substance amount of potassium carbonate to the lithium ion substance amount in the lithium magnesium-containing solution is 1.2:1, and the mass ratio of the volume of water as a lithium precipitation filter cake washing liquid to the lithium precipitation filter cake is 1.0mL:1 g;
(4) evaporating and crystallizing the lithium precipitation filtrate at 85 ℃ to obtain potassium sulfate.
Example 2
The embodiment provides a lithium-magnesium separation method, which comprises the following steps:
(1) adding a mixed solution of polyethylene glycol 15000 and sodium stearate with the mass ratio of 2:1 into a nitrate solution containing 10g/L lithium ions and 15g/L magnesium ions, and uniformly stirring and mixing at 400r/min to obtain a mixed solution, wherein the total mass of the polyethylene glycol 15000 and the sodium stearate in the mixed solution of the polyethylene glycol 15000 and the sodium stearate is 1.0 percent of the theoretical mass of the magnesium hydroxide;
(2) adding a sodium hydroxide solution with the alkali concentration of 10 wt% into the mixed solution until the pH value of the mixed solution is 11, and precipitating magnesium for 2 hours under the stirring of 450r/min at the temperature of 30 ℃ to obtain precipitated magnesium slurry; filtering the magnesium precipitation slurry at 100 ℃ to obtain a magnesium precipitation filter cake and a magnesium precipitation filtrate, stirring and washing the magnesium precipitation filter cake with 50 ℃ water for 1 time, and drying at 200 ℃ for 1h to obtain magnesium hydroxide, wherein the mass ratio of the volume of the water used as the washing liquid of the magnesium precipitation filter cake to the filter cake is 4.0mL:1 g;
(3) adding sodium carbonate into the magnesium precipitation filtrate obtained in the step (2) as a lithium precipitation agent, and precipitating lithium for reaction for 1.5h at 80 ℃ under stirring at 100r/min to obtain lithium precipitation slurry; filtering the lithium precipitation slurry at 80 ℃ to obtain a lithium precipitation filter cake and a lithium precipitation filtrate, stirring and washing the lithium precipitation filter cake with water at 80 ℃ for 4 times, and drying at 150 ℃ for 3 hours to obtain lithium carbonate, wherein the ratio of the mass of the sodium carbonate to the mass of the lithium ion material in the lithium magnesium-containing solution is 1:1, and the mass ratio of the volume of the water used as the lithium precipitation filter cake washing liquid to the lithium precipitation filter cake is 2.0mL:1 g;
(4) evaporating and crystallizing the lithium precipitation filtrate at 110 ℃ to obtain sodium nitrate.
Example 3
The embodiment provides a lithium-magnesium separation method, which comprises the following steps:
(1) directly adding cationic polyacrylamide with the molecular weight of 1400 ten thousand and the ionic degree of 50% into a chloride solution containing 30g/L lithium ions and 25g/L magnesium ions, and uniformly stirring and mixing at 250r/min to obtain a mixed solution, wherein the mass of the cationic polyacrylamide is 1.5% of the theoretical mass of magnesium hydroxide;
(2) adding potassium hydroxide solid into the mixed solution until the pH value of the mixed solution is 12.8, and precipitating magnesium for reaction for 2.5 hours at 40 ℃ under the stirring of 200r/min to obtain precipitated magnesium slurry; filtering the magnesium precipitation slurry at 40 ℃ to obtain a magnesium precipitation filter cake and a magnesium precipitation filtrate, stirring and washing the magnesium precipitation filter cake with water at 60 ℃ for 3 times, and drying at 200 ℃ for 1h to obtain magnesium hydroxide, wherein the mass ratio of the volume of the water used as the washing liquid of the magnesium precipitation filter cake to the filter cake is 6.0mL:1 g;
(3) adding potassium carbonate into the magnesium precipitation filtrate obtained in the step (2) as a lithium precipitation agent, and precipitating lithium for reaction for 2.5 hours at 90 ℃ under the stirring of 300r/min to obtain lithium precipitation slurry; filtering the lithium precipitation slurry at 95 ℃ to obtain a lithium precipitation filter cake and a lithium precipitation filtrate, stirring and washing the lithium precipitation filter cake with water at 90 ℃ for 3 times, and drying at 100 ℃ for 24 hours to obtain lithium carbonate, wherein the ratio of the substance amount of potassium carbonate to the lithium ion substance amount in the lithium magnesium-containing solution is 1.2:1, and the mass ratio of the volume of the water used as the lithium precipitation filter cake washing liquid to the lithium precipitation filter cake is 3.0mL:1 g;
(4) evaporating and crystallizing the lithium precipitation filtrate at 75 ℃ to obtain potassium chloride.
Example 4
The embodiment provides a lithium-magnesium separation method, which comprises the following steps:
(1) directly adding anionic polyacrylamide with the molecular weight of 2000 ten thousand and the ionic degree of 40% into sulfate solution containing 22g/L lithium ions and 22g/L magnesium ions, and uniformly stirring and mixing at 200r/min to obtain mixed solution, wherein the mass of the anionic polyacrylamide is 2.5% of the theoretical mass of magnesium hydroxide;
(2) adding a potassium hydroxide solution with the alkali concentration of 30 wt% into the mixed solution until the pH value of the mixed solution is 11.5, and precipitating magnesium for reaction for 3.5 hours at the temperature of 60 ℃ under the stirring of 500r/min to obtain magnesium precipitation slurry; filtering the magnesium precipitation slurry at 55 ℃ to obtain a magnesium precipitation filter cake and a magnesium precipitation filtrate, leaching the magnesium precipitation filter cake with 70 ℃ water for 4 times, and drying at 180 ℃ for 23 hours to obtain magnesium hydroxide, wherein the mass ratio of the volume of the water used as the washing liquid of the magnesium precipitation filter cake to the filter cake is 5.0mL:1 g;
(3) adding potassium carbonate into the magnesium precipitation filtrate obtained in the step (2) as a lithium precipitation agent, and precipitating lithium for reaction for 0.5h under stirring at 100 ℃ and 350r/min to obtain lithium precipitation slurry; filtering the lithium precipitation slurry at 80 ℃ to obtain a lithium precipitation filter cake and a lithium precipitation filtrate, rinsing the lithium precipitation filter cake with water at 80 ℃ for 4 times, and drying at 105 ℃ for 20 hours to obtain lithium carbonate, wherein the ratio of the substance amount of potassium carbonate to the lithium ion substance amount in the lithium magnesium-containing solution is 1.5:1, and the mass ratio of the volume of water as a lithium precipitation filter cake washing liquid to the lithium precipitation filter cake is 4.0mL:1 g;
(4) evaporating and crystallizing the lithium precipitation filtrate at 105 ℃ to obtain potassium sulfate.
Example 5
The embodiment provides a lithium-magnesium separation method, which comprises the following steps:
(1) adding a mixed solution of stearic acid and polyethylene glycol 3000 in a mass ratio of 1:1 into a nitrate solution containing 28g/L lithium ions and 23g/L magnesium ions, and uniformly stirring and mixing at 150r/min to obtain a mixed solution, wherein the total mass of stearic acid and polyethylene glycol 3000 in the mixed solution of stearic acid and polyethylene glycol 3000 is 3.0% of the theoretical mass of magnesium hydroxide;
(2) adding a sodium hydroxide solution with the alkali concentration of 40 wt% into the mixed solution until the pH value of the mixed solution is 13, and precipitating magnesium for reaction for 4 hours at the temperature of 70 ℃ under the stirring of 150r/min to obtain precipitated magnesium slurry; filtering the magnesium precipitation slurry at 95 ℃ to obtain a magnesium precipitation filter cake and a magnesium precipitation filtrate, stirring and washing the magnesium precipitation filter cake with water at 80 ℃ for 2 times, and drying at 110 ℃ for 12 hours to obtain magnesium hydroxide, wherein the mass ratio of the volume of the water used as the washing liquid of the magnesium precipitation filter cake to the filter cake is 3.0mL:1 g;
(3) adding sodium carbonate into the magnesium precipitation filtrate obtained in the step (2) as a lithium precipitation agent, and precipitating lithium for 4 hours under stirring at 90 ℃ and 350r/min to obtain lithium precipitation slurry; filtering the lithium precipitation slurry at 95 ℃ to obtain a lithium precipitation filter cake and a lithium precipitation filtrate, washing the lithium precipitation filter cake with water at 70 ℃ for 1 time, and drying at 150 ℃ for 4 hours to obtain lithium carbonate, wherein the ratio of the content of sodium carbonate to the content of lithium ion substances in a lithium magnesium-containing solution is 1.3:1, and the mass ratio of the volume of water used as a lithium precipitation filter cake washing liquid to the lithium precipitation filter cake is 2.0mL:1 g;
(4) evaporating and crystallizing the lithium precipitation filtrate at 110 ℃ to obtain sodium nitrate.
Example 6
The embodiment provides a lithium-magnesium separation method, which comprises the following steps:
(1) directly adding anionic polyacrylamide with the molecular weight of 1000 ten thousand and the ionic degree of 80% into a chloride solution containing 16g/L lithium ions and 20g/L magnesium ions, and uniformly stirring and mixing at 120r/min to obtain a mixed solution, wherein the mass of the anionic polyacrylamide is 3.5% of the theoretical mass of magnesium hydroxide;
(2) adding a potassium hydroxide solution with the alkali concentration of 50 wt% into the mixed solution until the pH value of the mixed solution is 11.8, and precipitating magnesium for reaction for 4.5h under the stirring of 500r/min at the temperature of 80 ℃ to obtain magnesium precipitation slurry; filtering the magnesium precipitation slurry at 45 ℃ to obtain a magnesium precipitation filter cake and a magnesium precipitation filtrate, leaching the magnesium precipitation filter cake with water at 90 ℃ for 3 times, and drying at 130 ℃ for 15 hours to obtain magnesium hydroxide, wherein the mass ratio of the volume of the water used as the washing liquid of the magnesium precipitation filter cake to the filter cake is 6.0mL:1 g;
(3) adding potassium carbonate into the magnesium precipitation filtrate obtained in the step (2) as a lithium precipitation agent, and precipitating lithium for 3 hours under the stirring of 250r/min at 80 ℃ to obtain lithium precipitation slurry; filtering the lithium precipitation slurry at 90 ℃ to obtain a lithium precipitation filter cake and a lithium precipitation filtrate, rinsing the lithium precipitation filter cake with water at 80 ℃ for 2 times, and drying at 110 ℃ for 17 hours to obtain lithium carbonate, wherein the ratio of the substance content of potassium carbonate to the lithium ion substance content in the lithium magnesium-containing solution is 1.2:1, and the mass ratio of the volume of water used as a lithium precipitation filter cake washing liquid to the lithium precipitation filter cake is 1.0mL:1 g;
(4) evaporating and crystallizing the lithium precipitation filtrate at 95 ℃ to obtain potassium chloride.
Example 7
The embodiment provides a lithium-magnesium separation method, which comprises the following steps:
(1) directly adding non-ionic polyacrylamide with the molecular weight of 1200 ten thousand into sulfate solution containing 10g/L lithium ions and 16g/L magnesium ions, and uniformly stirring and mixing at 300r/min to obtain mixed solution, wherein the mass of the non-ionic polyacrylamide is 3.7% of the theoretical mass of magnesium hydroxide;
(2) adding sodium hydroxide solid into the mixed solution until the pH value of the mixed solution is 12.0, and precipitating magnesium for 5 hours under the stirring of 150r/min at 90 ℃ to obtain precipitated magnesium slurry; filtering the magnesium precipitation slurry at 95 ℃ to obtain a magnesium precipitation filter cake and a magnesium precipitation filtrate, stirring and washing the magnesium precipitation filter cake with water at 80 ℃ for 2 times, and drying at 190 ℃ for 20 hours to obtain magnesium hydroxide, wherein the mass ratio of the volume of the water used as the washing liquid of the magnesium precipitation filter cake to the filter cake is 5.5mL:1 g;
(3) adding sodium carbonate into the magnesium precipitation filtrate obtained in the step (2) as a lithium precipitation agent, and precipitating lithium for 4 hours under stirring at 90 ℃ and 200r/min to obtain lithium precipitation slurry; filtering the lithium precipitation slurry at 85 ℃ to obtain a lithium precipitation filter cake and a lithium precipitation filtrate, stirring and washing the lithium precipitation filter cake with water at 90 ℃ for 3 times, and drying at 150 ℃ for 1h to obtain lithium carbonate, wherein the ratio of the mass of the sodium carbonate to the mass of the lithium ion material in the lithium magnesium-containing solution is 1:1, and the mass ratio of the volume of the water used as the lithium precipitation filter cake washing liquid to the lithium precipitation filter cake is 3.0mL:1 g;
(4) the lithium precipitation filtrate is evaporated and crystallized at the temperature of 110 ℃, and sodium sulfate is obtained.
Example 8
The embodiment provides a lithium-magnesium separation method, which comprises the following steps:
(1) directly adding cationic polyacrylamide with the molecular weight of 1000 ten thousand and the ionic degree of 55% into sulfate solution containing 20g/L lithium ions and 20g/L magnesium ions, and uniformly stirring and mixing at 250r/min to obtain mixed solution, wherein the mass of the cationic polyacrylamide is 3.5% of the theoretical mass of magnesium hydroxide;
(2) adding sodium hydroxide solid into the mixed solution until the pH value of the mixed solution is 12.2, and precipitating magnesium for reaction for 2 hours at 95 ℃ under the stirring of 300r/min to obtain precipitated magnesium slurry; filtering the magnesium precipitation slurry at 60 ℃ to obtain a magnesium precipitation filter cake and a magnesium precipitation filtrate, leaching the magnesium precipitation filter cake with 50 ℃ water for 3 times, and drying at 150 ℃ for 10 hours to obtain magnesium hydroxide, wherein the mass ratio of the volume of the water used as the washing liquid of the magnesium precipitation filter cake to the filter cake is 4.0mL:1 g;
(3) adding sodium carbonate into the magnesium precipitation filtrate obtained in the step (2) as a lithium precipitation agent, and precipitating lithium for reaction for 2.5 hours at 85 ℃ under the stirring of 250r/min to obtain lithium precipitation slurry; filtering the lithium precipitation slurry at 90 ℃ to obtain a lithium precipitation filter cake and a lithium precipitation filtrate, rinsing the lithium precipitation filter cake with water at 85 ℃ for 3 times, and drying at 120 ℃ for 12 hours to obtain lithium carbonate, wherein the ratio of the content of sodium carbonate to the content of lithium ion substances in a lithium magnesium-containing solution is 1.2:1, and the mass ratio of the volume of water used as a lithium precipitation filter cake washing liquid to the lithium precipitation filter cake is 2.0mL:1 g;
(4) and evaporating and crystallizing the lithium precipitation filtrate at 90 ℃ to obtain sodium sulfate.
Example 9
This example provides a lithium-magnesium separation method that is the same as example 8 except that "cationic polyacrylamide" is replaced with "nonionic polyacrylamide" to maintain its molecular weight at 1000 ten thousand.
Example 10
This example provides a lithium-magnesium separation method, which is the same as example 8 except that "cationic polyacrylamide with 55% ionicity" is replaced with "cationic polyacrylamide with 25% ionicity".
Example 11
This example provides a lithium-magnesium separation method, which is the same as that of example 8 except that "cationic polyacrylamide having an ionic degree of 55%" is replaced with "cationic polyacrylamide having an ionic degree of 15%".
Example 12
This example provides a lithium-magnesium separation method, which is the same as that of example 8 except that "cationic polyacrylamide having an ionicity of 55%" is replaced with "cationic polyacrylamide having an ionicity of 96%".
Example 13
This example provides a lithium-magnesium separation method, which is the same as example 6 except that "anionic polyacrylamide having a molecular weight of 1000 ten thousand" is replaced with "anionic polyacrylamide having a molecular weight of 1400 ten thousand".
Example 14
This example provides a lithium-magnesium separation method, which is the same as example 6 except that "anionic polyacrylamide having a molecular weight of 1000 ten thousand" is replaced with "anionic polyacrylamide having a molecular weight of 1700 ten thousand".
Example 15
This example provides a lithium-magnesium separation method, which is the same as example 6 except that "anionic polyacrylamide having a molecular weight of 1000 ten thousand" is replaced with "anionic polyacrylamide having a molecular weight of 2000 ten thousand".
Second, comparative example
Comparative example 1
This comparative example provides a lithium-magnesium separation process that is the same as example 1 except that step (1) is not performed, i.e., no additives are added.
Comparative example 2
This comparative example provides a lithium-magnesium separation process which is the same as example 2 except that step (1) is not performed, i.e., no additive is added.
Comparative example 3
The comparative example provides a lithium-magnesium separation method, which is the same as that in example 8 except that "cationic polyacrylamide with molecular weight of 1000 ten thousand and ionic degree of 55% in step (1)" and "sodium hydroxide solid" in step (2) are mixed and then added to the solution containing lithium and magnesium in step (1), and specifically comprises the following steps:
(1) mixing cationic polyacrylamide with the molecular weight of 1000 ten thousand and the ionic degree of 55% with a sodium hydroxide solid to obtain a mixed solution, wherein the mass of the cationic polyacrylamide is 3.5% of the theoretical mass of magnesium hydroxide;
(2) adding the mixed solution obtained in the step (1) into sulfate solution containing 20g/L lithium ions and 20g/L magnesium ions, and precipitating magnesium for reaction for 2 hours at the temperature of 95 ℃ under the stirring of 300r/min to obtain precipitated magnesium slurry; filtering the magnesium precipitation slurry at 60 ℃ to obtain a magnesium precipitation filter cake and a magnesium precipitation filtrate, leaching the magnesium precipitation filter cake with 50 ℃ water for 3 times, and drying at 150 ℃ for 10 hours to obtain magnesium hydroxide, wherein the mass ratio of the volume of the water used as the washing liquid of the magnesium precipitation filter cake to the filter cake is 4.0mL:1 g;
(3) adding sodium carbonate into the magnesium precipitation filtrate obtained in the step (2) as a lithium precipitation agent, and precipitating lithium for reaction for 2.5 hours at 85 ℃ under the stirring of 250r/min to obtain lithium precipitation slurry; filtering the lithium precipitation slurry at 90 ℃ to obtain a lithium precipitation filter cake and a lithium precipitation filtrate, rinsing the lithium precipitation filter cake with water at 85 ℃ for 3 times, and drying at 120 ℃ for 12 hours to obtain lithium carbonate, wherein the ratio of the content of sodium carbonate to the content of lithium ion substances in a lithium magnesium-containing solution is 1.2:1, and the mass ratio of the volume of water used as a lithium precipitation filter cake washing liquid to the lithium precipitation filter cake is 2.0mL:1 g;
(4) and evaporating and crystallizing the lithium precipitation filtrate at 90 ℃ to obtain sodium sulfate.
Comparative example 4
This comparative example provides a lithium-magnesium separation method, which is the same as example 8 except that "cationic polyacrylamide having a molecular weight of 1000 ten thousand" is replaced with "polymaleic anhydride having a molecular weight of 800".
Third, test and results
The filtration rate detection method comprises the following steps: carrying out suction filtration separation on the magnesium-precipitated slurry by adopting a vacuum suction filtration mode, and recording the suction drying time, wherein the slurry amount passing through a unit filtration area in unit time is the filtration rate, and the calculation formula is shown as formula (1):
wherein v is the filtration rate mL m-2·s-1(ii) a V is the volume mL of the magnesium precipitation slurry; s is the filter cake area m2(ii) a t is the filtration time s.
The magnesium precipitation efficiency calculation method comprises the following steps: the ratio of the total amount of magnesium ions in the filtrate and the washing liquid after the precipitation, suction filtration and separation to the amount of magnesium ions in the lithium-magnesium-containing solution before the precipitation reaction is magnesium precipitation efficiency, and the specific calculation formula is shown as formula (2):
η＝(1-(C1×V1+C2×V2)/(C0×V0))×100％ (2)
wherein η is the efficiency of magnesium precipitation, C1Performing suction filtration separation on the precipitate to obtain the magnesium ion concentration in the filtrate, wherein the concentration is mol/L; v1Filtering the separated filtrate for precipitation, and obtaining the volume L; c2The concentration of magnesium ions in the washing liquid after precipitation, suction filtration and separation is mol/L; v2The volume of the washing liquid after the precipitation, the suction filtration and the separation is L; c0The concentration of magnesium ions in the solution containing lithium and magnesium before the precipitation reaction is mol/L; v0Is the volume of the solution containing lithium magnesium, L.
The lithium ion adsorption loss rate calculation method comprises the following steps: the ratio of the total mass of lithium elements carried in the magnesium hydroxide solid to the total mass of lithium elements in the initial solution is the lithium ion adsorption loss rate, and the specific calculation formula is shown as formula (3):
δ＝m×ω/(CL×V0)×100％ (3)
wherein, delta is the lithium ion adsorption loss rate; m is the mass of magnesium hydroxide, g; omega is the content of lithium in the magnesium hydroxide,%; cLThe concentration of lithium ions in the initial solution containing lithium and magnesium is g/L; v0Is the volume of the solution containing lithium magnesium, L.
The preparation of magnesium hydroxide was carried out by the methods provided in examples 1 to 15 and comparative examples 1 to 4, and the filtration rate and the efficiency of magnesium precipitation were examined, and the results are shown in table 1.
TABLE 1
From table 1, the following points can be seen:
(1) it can be seen from the comprehensive examples 1 to 15 that the lithium-magnesium separation method provided by the invention improves the lithium-magnesium separation rate and the magnesium precipitation efficiency and reduces the lithium ion adsorption loss rate by adding the additive into the solution containing lithium and magnesium and then adding the magnesium precipitation agent, wherein the filtration rate of the lithium-magnesium separation is not less than 109.56mL · m-2·s-1The magnesium deposition efficiency is more than or equal to 97.73 wt%, and the lithium ion adsorption loss rate is reduced to below 17.56 wt%, so that the method has high industrial application value;
(2) it can be seen from the combination of examples 1-2 and comparative examples 1-2 that in examples 1-2, the additive is added into the lithium magnesium-containing solution, and then the magnesium precipitation reaction is performed, so that compared with the case that the magnesium precipitation reaction is directly performed in comparative examples 1-2, the filtration rates of examples 1 and 2 are 203.344mL m-2·s-1And 245.225mL m-2·s-1The lithium ion adsorption loss rates were only 10.34 wt% and 15.6 wt%, respectively, while the filtration rates of comparative example 1 and comparative example 2 were only 40.67mL · m, respectively-2·s-1And 64.45 mL. m-2·s-1The absorption loss rates of lithium ions are respectively as high as 19.44 wt% and 20.68 wt%, so that the magnesium precipitation reaction is regulated and controlled by adding the additive into the solution containing lithium and magnesium before the magnesium precipitation reaction, the filtration rate of magnesium hydroxide is greatly improved, and the absorption loss rate of lithium ions is reduced;
(3) by combining example 8 with comparative example 3, it can be seen that example 8 was prepared by first adding the additive to a lithium magnesium containing solutionThe additive is mixed with the solution containing lithium and magnesium and then subjected to magnesium precipitation reaction, and compared with the comparative example 3 in which the magnesium precipitation agent and the additive are simultaneously added into the solution containing lithium and magnesium to carry out the magnesium precipitation reaction, the example 8 has the filtering rate as high as 724.85 mL-m under the condition of less reduction of the magnesium precipitation efficiency-2·s-1The lithium ion adsorption loss rate was only 3.24 wt%, while the filtration rate of comparative example 3 was only 60.48mL · m-2·s-1The absorption loss rate of lithium ions is up to 18.90 wt%, so that the additive and the solution containing lithium and magnesium are uniformly mixed before the magnesium deposition reaction, the magnesium deposition reaction is better controlled, the lithium and magnesium separation rate is improved, and the absorption loss rate of lithium ions is reduced;
(4) by combining example 8 with comparative example 4, it can be seen that example 8, by adding cationic polyacrylamide to the lithium magnesium containing solution, compared to comparative example 4, which adds polymaleic anhydride, the filtration rate of example 8 is as high as 724.85mL m-2·s-1The lithium ion adsorption loss rate was only 3.24 wt%, while the filtration rate of comparative example 4 was only 77.89mL · m, respectively-2·s-1The absorption loss rate of lithium ions is up to 19.88 wt%, so that the method can better regulate and control the magnesium precipitation reaction process, accelerate the magnesium hydroxide filtration rate and reduce the absorption loss rate of lithium ions by adding the cationic polyacrylamide before the magnesium precipitation reaction;
(5) combining example 8 with example 9, it can be seen that example 8 has a higher filtration rate of 724.85mL m than example 9 by adding a cationic polyacrylamide to the lithium magnesium containing solution than example 9 with a non-ionic polyacrylamide-2·s-1The lithium ion adsorption loss rate was only 3.24% by weight, and the filtration rate of example 9 was 457.60mL · m-2·s-1The absorption loss rate of lithium ions is 6.60 wt%, thus, the invention preferably adds cationic polyacrylamide before the magnesium precipitation reaction, can further accelerate the filtration rate of magnesium hydroxide, and better reduce the absorption loss rate of lithium ions;
(6) as can be seen from the combination of examples 8 and 10 to 12, examples 8 and 10 were prepared by adding ions to a lithium magnesium-containing solutionCationic polyacrylamide with 55% and 25% of molarity, respectively, cationic polyacrylamide with 15% and 96% of molarity, respectively, is added in comparison with example 11 and example 12, and the filtration rate of example 8 and example 10 is 724.85mL m-2·s-1And 579.45mL m-2·s-1The lithium ion adsorption loss rates were 3.24 wt% and 4.98 wt%, respectively, and the filtration rates of example 11 and example 12 were 385.76mL · m, respectively-2·s-1And 489.68mL m-2·s-1The adsorption loss rate of the lithium ions is 8.48 wt% and 9.65 wt%, so that the invention can better improve the filtration rate during the separation of lithium and magnesium, reduce the adsorption loss rate of the lithium ions and improve the separation efficiency of the lithium and magnesium by controlling the ionic degree of the cationic polyacrylamide within a certain range;
(7) it can be seen from the combination of examples 6 and 13-15 that the filtration rates of examples 13 and 14 are 538.89 mL. m.m.-2·s-1And 510.24mL m-2·s-1The lithium ion adsorption loss rates were 6.94 wt% and 7.55 wt%, respectively, and the filtration rates of example 6 and example 15 were 324.84mL · m, respectively-2·s-1And 255.75mL m-2·s-1The lithium ion adsorption loss rates are 10.95 wt% and 17.56 wt%, which shows that the invention further reduces the lithium ion adsorption loss rate and improves the filtration rate and lithium magnesium separation efficiency during lithium magnesium separation by controlling the molecular weight of the anionic polyacrylamide within a certain range.
In conclusion, the lithium-magnesium separation method provided by the invention is a lithium-magnesium separation method which comprises the steps of uniformly mixing the additive and the solution containing lithium and magnesium, and then adding the magnesium precipitation agent, so that the filtration rate of lithium-magnesium separation is more than or equal to 109.56 mL-m-2·s-1The magnesium deposition efficiency is more than or equal to 97.73 wt%, and the lithium ion adsorption loss rate is reduced to below 17.56 wt%, and the method has mild reaction conditions and high efficiencySimple process flow, environmental protection and low consumption, and is suitable for industrial popularization. The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must be implemented depending on the above detailed structural features. It should be understood by those skilled in the art that any modifications of the present invention, equivalent substitutions of selected components of the present invention, additions of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (10)
1. A lithium-magnesium separation method is characterized by comprising the following steps:
(1) adding an additive into a solution containing lithium and magnesium, and stirring and mixing uniformly to obtain a mixed solution, wherein the additive is any one or a combination of at least two of polyethylene glycol, stearic acid, sodium stearate, cationic polyacrylamide, anionic polyacrylamide or nonionic polyacrylamide;
(2) adding a magnesium precipitation agent into the mixed solution, and precipitating magnesium under stirring to obtain magnesium precipitation slurry; filtering the magnesium precipitation slurry to obtain a magnesium precipitation filter cake and a magnesium precipitation filtrate, and washing and drying the magnesium precipitation filter cake to obtain magnesium hydroxide;
(3) adding a lithium precipitation agent into the magnesium precipitation filtrate obtained in the step (2), and precipitating lithium under stirring to obtain lithium precipitation slurry; filtering the lithium precipitation slurry to obtain a lithium precipitation filter cake and a lithium precipitation filtrate, and washing and drying the lithium precipitation filter cake to obtain lithium carbonate;
(4) evaporating and crystallizing the lithium precipitation filtrate to obtain a crystalline salt.
2. The method according to claim 1, characterized in that the mass of the additive in step (1) is 0.1-4.0%, preferably 0.5-1.5% of the theoretical mass of magnesium hydroxide;
preferably, the addition mode of the additive is direct addition or solution addition prepared, and preferably direct addition;
preferably, the additive is any one or combination of at least two of polyethylene glycol, cationic polyacrylamide or anionic polyacrylamide, preferably cationic polyacrylamide;
preferably, the molecular weight of the polyethylene glycol is 2000-20000, preferably 6000-10000;
preferably, the molecular weight of the cationic polyacrylamide is 1000-1400 ten thousand;
preferably, the ionic degree of the cationic polyacrylamide is 5% -90%, preferably 20% -60%;
preferably, the molecular weight of the anionic polyacrylamide is 1000-2000 ten thousand, preferably 1400-1800 ten thousand;
preferably, the stirring speed of the stirring and mixing is 100-400 r/min, and preferably 200-300 r/min.
3. The method according to claim 1 or 2, wherein lithium in the lithium magnesium containing solution in step (1) is present in the form of lithium sulfate, lithium chloride or lithium nitrate;
preferably, the magnesium in the lithium magnesium containing solution is present as magnesium sulfate, magnesium chloride or magnesium nitrate;
preferably, the mass concentration of lithium ions in the lithium magnesium containing solution is 10-30 g/L, preferably 15-25 g/L;
preferably, the mass concentration of magnesium ions in the lithium magnesium containing solution is 1-25 g/L, preferably 5-15 g/L.
4. The method according to any one of claims 1 to 3, wherein the magnesium precipitating agent in the step (2) is an alkali, preferably sodium hydroxide or potassium hydroxide;
preferably, the addition end point of the alkali is that the pH value of the mixed solution is 11-13, and preferably 11.5-12.5;
preferably, the base is a solid base or an alkali solution;
preferably, the alkali concentration of the alkali liquor is 15 wt% -60 wt%, preferably 20 wt% -40 wt%;
preferably, the temperature of the magnesium precipitation reaction is 25-100 ℃, and preferably 35-65 ℃;
preferably, the magnesium precipitation reaction time is 0.8-5 h, preferably 2-4.5 h;
preferably, the stirring speed of the magnesium precipitation reaction is 100-500 r/min, and preferably 200-400 r/min.
5. The method according to any one of claims 1 to 4, wherein the temperature for filtering the magnesium precipitation slurry in the step (2) is 40 to 100 ℃, preferably 70 to 90 ℃;
preferably, the magnesium precipitation filter cake is washed by stirring or leaching;
preferably, the washing liquid for washing the magnesium precipitation filter cake is water;
preferably, the washing time of the magnesium precipitation filter cake is 1-4 times, preferably 2-4 times;
preferably, the mass ratio of the volume of the washing liquid to the filter cake in the washing of the magnesium precipitation filter cake is 1.0-6.0 mL to 1g, and preferably 3.0-5.0 mL to 1 g;
preferably, the washing temperature of the magnesium precipitation filter cake is 35-95 ℃, and preferably 55-75 ℃;
preferably, the drying temperature of the magnesium precipitation filter cake is 100-200 ℃, and preferably 110-130 ℃;
preferably, the drying time of the magnesium precipitation filter cake is 1-24 hours, and preferably 5-15 hours.
6. The method according to any one of claims 1 to 5, wherein the lithium precipitating agent in the step (3) is a carbonate, preferably sodium carbonate or potassium carbonate;
preferably, the ratio of the amount of the carbonate material to the amount of the lithium ion material in the lithium magnesium containing solution is 1-1.5: 1, preferably 1-1.1: 1;
preferably, the temperature of the lithium precipitation reaction is 70-100 ℃, and preferably 90-100 ℃;
preferably, the time of the lithium precipitation reaction is 0.5-4 h, preferably 2-3 h;
preferably, the stirring speed of the lithium precipitation reaction is 100-400 r/min, and preferably 200-300 r/min.
7. The method according to any one of claims 1 to 6, wherein the temperature of the lithium precipitation slurry filtration in the step (3) is 80 to 95 ℃;
preferably, the lithium precipitating filter cake washing mode is stirring washing or leaching;
preferably, the washing liquid for washing the lithium precipitation filter cake is water;
preferably, the washing time of the lithium precipitation filter cake is 1-4 times, preferably 2-4 times;
preferably, the mass ratio of the volume of the washing liquid to the lithium precipitating filter cake in the lithium precipitating filter cake washing is 1.0-4.0 mL:1g, and preferably 1.5-3.5 mL:1 g;
preferably, the washing temperature of the lithium precipitation filter cake is 70-100 ℃, and preferably 85-95 ℃;
preferably, the drying temperature of the lithium precipitation filter cake is 100-150 ℃, and preferably 120-140 ℃;
preferably, the time for drying the lithium precipitation filter cake is 1-24 hours, and preferably 4-14 hours.
8. The process according to any one of claims 1 to 7, wherein the temperature of the evaporative crystallization in step (4) is 70 to 110 ℃, preferably 80 to 100 ℃.
9. A method according to any one of claims 1 to 8, characterized in that the method comprises the steps of:
(1) adding an additive into a lithium-magnesium-containing solution, and uniformly stirring and mixing at 100-400 r/min to obtain a mixed solution, wherein the additive is any one or a combination of at least two of polyethylene glycol, stearic acid, sodium stearate, cationic polyacrylamide, anionic polyacrylamide or nonionic polyacrylamide, the mass of the additive is 0.1-4.0% of the theoretical mass of magnesium hydroxide, the mass concentration of lithium ions in the lithium-magnesium-containing solution is 10-30 g/L, and the mass concentration of magnesium ions is 1-25 g/L;
(2) adding alkali into the mixed solution until the pH value of the mixed solution is 11-13, and precipitating magnesium for reaction for 0.8-5 h at the temperature of 25-100 ℃ under stirring at 100-500 r/min to obtain precipitated magnesium slurry; filtering the magnesium precipitation slurry at 40-100 ℃ to obtain a magnesium precipitation filter cake and a magnesium precipitation filtrate, washing the magnesium precipitation filter cake with 35-95 ℃ water for 1-4 times, and drying at 100-200 ℃ for 1-24 hours to obtain magnesium hydroxide, wherein the mass ratio of the volume of the water used as the magnesium precipitation filter cake washing liquid to the filter cake is 1.0-6.0 mL:1 g;
(3) adding carbonate into the magnesium precipitation filtrate obtained in the step (2), and precipitating lithium for reaction for 0.5-4 h at the temperature of 70-100 ℃ under the stirring of 100-400 r/min to obtain lithium precipitation slurry; filtering the lithium precipitation slurry at 80-95 ℃ to obtain a lithium precipitation filter cake and a lithium precipitation filtrate, washing the lithium precipitation filter cake for 1-4 times by using water at 70-100 ℃, and drying at 100-150 ℃ for 1-24 hours to obtain lithium carbonate, wherein the ratio of the amount of carbonate to the amount of lithium ion substances in a lithium magnesium-containing solution is 1-1.5: 1, and the mass ratio of the volume of water used as a lithium precipitation filter cake washing liquid to the lithium precipitation filter cake is 1.0-4.0 mL:1 g;
(4) evaporating and crystallizing the lithium precipitation filtrate at 70-110 ℃ to obtain crystalline salt.
10. A method for treating lithium-magnesium-containing brine, which is characterized in that the lithium-magnesium-containing brine is treated by the lithium-magnesium separation method according to any one of claims 1 to 9.
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