Method for co-producing magnesium hydroxide, calcium phosphate and lithium carbonate by using old brine adsorption tail liquid

Abstract

The invention relates to the technical field of comprehensive utilization of magnesium resources, and discloses a method for co-production of magnesium hydroxide, calcium phosphate and lithium carbonate by using old brine adsorption tail liquid. The method comprises the following steps: (1) mixing the old brine adsorption tail liquid with ammonia water to obtain an ammonium chloride solution and a magnesium hydroxide solid; (2) pyrolyzing calcium carbonate to obtain carbon dioxide and calcium oxide; (3) mixing calcium oxide with water, then mixing with an ammonium chloride solution, and evaporating a solid to obtain a calcium chloride solid; (4) mixing the lithium phosphate tail liquid with calcium chloride solid to obtain calcium carbonate solid and a mixed solution, evaporating the mixed solution to obtain calcium phosphate solid and precipitation mother liquor, and recycling the calcium carbonate solid for the step (2); and (5) carrying out carbonization reaction on the factory floor sweeping material and / or the wall bonding material and carbon dioxide, and carrying out impurity removal and hydrothermal decomposition to obtain a lithium carbonate solid. According to the technical scheme, the problems of magnesium harm, excessive discharge of lithium phosphate tail liquid and purification of sweeping materials and wall-bonding materials are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of comprehensive utilization of magnesium resources, and particularly relates to a method for co-producing magnesium hydroxide, calcium phosphate and lithium carbonate by using the tail liquid adsorbed by old brine. Background Art

[0002] With the advancement of the construction of a world-class salt lake industrial base, the diversified development and utilization of salt lake resources is the only way for the salt lake industry. Salt lakes are rich in various elements, and only potassium resources and lithium resources are actually developed on a large scale; the development technologies for boron resources and magnesium resources are also gradually being upgraded and broken through; The Qaidam Basin in Qinghai is known as a "treasure bowl" because it is rich in salt lake resources and has gradually formed an industrial chain for potassium and lithium resources. In recent years, due to the skyrocketing price of lithium, major lithium battery companies have formed a boom in lithium extraction, mostly using new aluminum-based adsorbents for lithium extraction. The tail liquid from lithium extraction by adsorption contains a large amount of magnesium resources. Each company returns it to the salt pan for further solar evaporation of minerals. As time goes by, this will surely cause waste of magnesium resources and form magnesium hazards, and at the same time, it does not conform to the diversified utilization of resources. Summary of the Invention

[0003] The purpose of the present invention is to overcome the problems existing in the prior art that ammonium chloride is generated during the production of magnesium hydroxide by the brine-ammonia precipitation method, calcium chloride solid is generated by the reaction of ammonium chloride and lime milk, and carbon dioxide is generated during the production of lime milk. The emission of by-product carbon dioxide affects air pollution and the greenhouse effect. A method for co-producing magnesium hydroxide, calcium phosphate and lithium carbonate by using the tail liquid adsorbed by old brine is provided. This technical solution uses the old brine adsorption tail liquid and ammonia addition method to produce magnesium hydroxide, and at the same time uses the by-product calcium chloride to produce calcium phosphate to solve the problem of excessive phosphorus emission in the existing lithium phosphate tail liquid. The obtained by-product calcium carbonate can continuously provide calcium oxide and carbon dioxide, so as to purify and preserve the floor sweepings and wall-building materials of the carbon dioxide carbonization plant. It not only solves the problems of magnesium hazards, excessive emission of lithium phosphate tail liquid and purification of lithium carbonate floor sweepings and wall-building materials, but also conforms to the concept of cost reduction, efficiency increase and environmental protection of enterprises, and is a new path for the comprehensive utilization of magnesium resources.

[0004] In order to achieve the above purpose, the present invention provides a method for co-producing magnesium hydroxide, calcium phosphate and lithium carbonate by using the tail liquid adsorbed by old brine. The method comprises the following steps:

[0005] (1) Mix the old brine adsorption tail liquid and ammonia water, and then perform solid-liquid separation to obtain ammonium chloride solution and magnesium hydroxide solid;

[0006] (2) Pyrolyze calcium carbonate to obtain carbon dioxide and calcium oxide;

[0007] (3) Mix the calcium oxide and water obtained in step (2) and stir to form a lime milk suspension. Then, mix the lime milk suspension with the ammonium chloride solution obtained in step (1), and then evaporate to precipitate a solid to obtain calcium chloride solid;

[0008] (4) Mix the lithium phosphate tail liquid with the calcium chloride solid obtained in step (3), then perform solid-liquid separation to obtain calcium carbonate solid and a mixed solution. Then, evaporate the mixed solution to obtain calcium phosphate solid and a precipitation mother liquid, and recycle the calcium carbonate solid to step (2);

[0009] (5) Carry out a carbonization reaction on the factory sweeping materials and / or the wall adhering materials of the lithium precipitation reactor in the lithium carbonate lithium precipitation workshop with the carbon dioxide obtained in step (2), and then carry out impurity removal and hydrothermal decomposition in sequence to obtain lithium carbonate solid;

[0010] Among them, the content of lithium carbonate in the factory sweeping materials is above 90wt%, and the content of lithium carbonate in the wall adhering materials is above 70wt%.

[0011] Preferably, in step (1), in the old brine adsorption tail liquid, the concentration of Mg 2+ is above 75g / L, and the concentration of CI - is above 70g / L.

[0012] Preferably, in step (1), the concentration of the ammonia water is 1 - 2moL / L.

[0013] Preferably, in step (1), the molar ratio of the amount of substance of Mg 2+ in the old brine adsorption tail liquid to the amount of substance of ammonia in the ammonia water is 1:(3 - 5).

[0014] Preferably, in step (2), the conditions for the pyrolysis include: the temperature is above 800°C, preferably 800 - 1200°C; the time is 1 - 1.5h.

[0015] Preferably, in step (3), the solid-liquid ratio of the dosages of the calcium oxide and the water is 1g:(1 - 1.5)mL.

[0016] Preferably, in step (3), the volume ratio of the dosages of the lime milk suspension and the ammonium chloride solution is 1:(2 - 3).

[0017] Preferably, in step (3), the conditions for the stirring and mixing include: the stirring rate is above 400 revolutions per minute, preferably 400 - 800 revolutions per minute; the time is 0.5 - 1.5h.

[0018] Preferably, in step (4), in the lithium phosphate tail liquid, P 5+The concentration of [substance] is 1 - 1.5 g / L, and the concentration of Ca 2+ is 0.5 - 0.8 g / L, and the concentration of CO3 2－ is below 18 g / L.

[0019] Preferably, in step (4), the liquid - solid ratio of the dosage of the lithium phosphate tail liquor and the calcium chloride solid is 1 L:(50 - 100) g.

[0020] Preferably, in step (4), in the precipitation mother liquor, the concentration of P 5+ is below 0.5 mg / L, and the concentration of Ca 2+ is below 0.1 mg / L.

[0021] Preferably, in step (5), the method further includes: before the carbonization, mixing the factory floor sweepings and / or the wall - forming material with water.

[0022] Preferably, in step (5), the solid - liquid ratio of the dosage of the factory floor sweepings or the wall - forming material and water is 1 g:(20 - 40) mL.

[0023] Preferably, in step (5), the conditions of the carbonization reaction include: the flow rate of CO2 is 0.8 - 1.5 L / min, the temperature is 20 - 40 °C, the time is 2 h or more, preferably 2 - 3 h.

[0024] Preferably, in step (5), the conditions of the hydrothermal decomposition include: the temperature is 90 °C or more, preferably 90 - 150 °C; the stirring speed is 400 revolutions per minute or more, preferably 400 - 700 revolutions per minute; the time is 1 - 2 h.

[0025] Compared with the prior art, the technical effects of the present invention are as follows:

[0026] (1) The method for co - producing magnesium hydroxide, calcium phosphate and lithium carbonate by using old brine to adsorb tail liquor of the present invention conforms to the concepts of green environmental protection, cost reduction and efficiency increase, and no waste gas emission;

[0027] (2) The method of the present invention prepares magnesium hydroxide by using old brine to adsorb tail liquor, and at the same time solves the problems of magnesium harm in tail liquor, excessive phosphorus emission of lithium phosphate, low quality of lithium carbonate floor sweepings, etc. At the same time, calcium carbonate and calcium chloride are self - sufficient and do not need to be purchased externally, further reducing production costs;

[0028] (3) The method for co - producing magnesium hydroxide, calcium phosphate and lithium carbonate by using old brine to adsorb tail liquor of the present invention purifies carbon dioxide floor sweepings into lithium carbonate, which belongs to the recycling of waste liquid and conforms to a new - type process technology in new productive forces. Description of the Drawings

[0029] Figure 1 It is the process flow diagram of the method for co-producing magnesium hydroxide, calcium phosphate and lithium carbonate by using old brine to adsorb tail liquid according to the present invention. Specific embodiments

[0030] The following will detail the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only for explaining and illustrating the present invention, and are not used to limit the present invention.

[0031] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range and a single point value, and between single point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0032] The method for co-producing magnesium hydroxide, calcium phosphate and lithium carbonate by using old brine to adsorb tail liquid according to the present invention, as Figure 1 shown, the method comprises the following steps:

[0033] (1) Mix the old brine adsorption tail liquid and ammonia water, and then perform solid-liquid separation to obtain ammonium chloride solution and magnesium hydroxide solid;

[0034] (2) Pyrolyze calcium carbonate to obtain carbon dioxide and calcium oxide;

[0035] (3) Stir and mix the calcium oxide obtained in step (2) with water to form a lime milk suspension, then mix the lime milk suspension with the ammonium chloride solution obtained in step (1), and then evaporate to precipitate solids to obtain calcium chloride solid;

[0036] (4) Mix the lithium phosphate tail liquid with the calcium chloride solid obtained in step (3), then perform solid-liquid separation to obtain calcium carbonate solid and a mixed solution, and then evaporate the mixed solution to obtain calcium phosphate solid and a precipitation mother liquor, and recycle the calcium carbonate solid to step (2);

[0037] (5) Carry out a carbonization reaction on the factory floor sweeping material in the lithium carbonate precipitation workshop and / or the wall adhering material in the lithium precipitation reaction kettle with the carbon dioxide obtained in step (2), and then carry out impurity removal and hydrothermal decomposition in sequence to obtain lithium carbonate solid;

[0038] Wherein, the content of lithium carbonate in the factory floor sweeping material is more than 90wt%, and the content of lithium carbonate in the wall adhering material is more than 70wt%.

[0039] According to the method of the present invention, magnesium hydroxide is produced by using the ammonia addition method with the spent bittern adsorption tail liquid, and at the same time, calcium phosphate is produced by using the by-product calcium chloride to solve the problem of excessive phosphorus discharge in the existing lithium phosphate tail liquid. The by-product calcium carbonate obtained can also continuously provide calcium oxide and carbon dioxide, so as to purify and preserve the carbon dioxide carbonized factory floor sweepings and wall-forming materials, and recycle the waste materials; not only co-produces high-purity magnesium hydroxide, calcium phosphate and lithium carbonate, but also realizes cost reduction, efficiency increase and environmental protection, which is a new path for the comprehensive utilization of magnesium resources.

[0040] In the method of the present invention, in step (1), in the spent bittern adsorption tail liquid, the concentration of Mg 2+ can be 75 g / L or more, preferably 75 - 100 g / L; the concentration of Cl - can be 70 g / L or more, preferably 70 - 100 g / L. The concentration of the ammonia water can be 1 - 2 moL / L, preferably 1.5 - 2 moL / L. The molar ratio of the amount of substance of Mg 2+ in the spent bittern adsorption tail liquid to the amount of substance of ammonia in the ammonia water can be 1:(3 - 5), preferably 1:(3 - 4), specifically, for example, it can be 1:3, 1:3.5, 1:4, 1:4.5 or 1:5. In step (1), the conditions for mixing the spent bittern adsorption tail liquid and the ammonia water include: the temperature can be 40 - 60 °C, preferably 50 - 60 °C; the time can be 1 - 2 h, preferably 1.2 - 2 h. In step (1), the specific process of solid-liquid separation can include: separating the ammonium chloride solution and the magnesium hydroxide solid by filtration. The spent bittern adsorption tail liquid can come from the tail liquid after lithium extraction in the adsorption workshop using spent bittern as the raw material.

[0041] In the method of the present invention, in step (2), the conditions for pyrolysis include: the temperature can be 800 °C or more, preferably 800 - 1200 °C; the time can be 1 - 1.5 h, preferably 1.2 - 1.5 h. The method can also include: recovering the carbon dioxide obtained in step (2).

[0042] In the method of the present invention, in step (3), the solid-liquid ratio of the amounts of the calcium oxide and the water used can be 1 g:(1 - 1.5) mL, preferably 1 g:(1.2 - 1.5) mL. The conditions for stirring and mixing include: the stirring rate can be 400 revolutions per minute or more, preferably 400 - 800 revolutions per minute; the time can be 0.5 - 1.5 h, preferably 0.8 - 1.5 h; the temperature can be 60 - 100 °C, preferably 75 - 100 °C.

[0043] In the method of the present invention, in step (3), the volume ratio of the lime milk suspension to the ammonium chloride solution can be 1:(2 - 3), preferably 1:(2 - 2.5). The conditions for mixing the lime milk suspension with the ammonium chloride solution obtained in step (1) include: the temperature can be 20 - 40°C, preferably 20 - 30°C; the time can be 1 - 2 h, preferably 1 - 1.5 h.

[0044] In the method of the present invention, in step (4), in the lithium phosphate tail liquor, the concentration of P 5+ can be 1 - 1.5 g / L, preferably 1.2 - 1.5 g / L; the concentration of Ca 2+ can be 0.5 - 0.8 g / L, preferably 0.6 - 0.8 g / L; the concentration of CO3 2－ can be 18 g / L or less, preferably 10 - 18 g / L. The lithium phosphate tail liquor can be from the tail liquor of the lithium phosphate workshop. The liquid-solid ratio of the lithium phosphate tail liquor to the calcium chloride solid can be 1 L:(50 - 100) g, preferably 1 L:(70 - 100) g. The conditions for mixing the lithium phosphate tail liquor with the calcium chloride solid obtained in step (3) include: the temperature can be 20 - 30°C, preferably 20 - 25°C; the time can be 1 - 3 h, preferably 2 - 3 h. In step (4), the conditions for evaporation include: the temperature can be 80 - 100°C, preferably 85 - 95°C; the time can be 1 - 2 h, preferably 1 - 1.5 h. The method can further include: in step (4), after evaporation and precipitation of solids, filtering to obtain calcium phosphate solids and drying at a temperature of 100 - 150°C for 1 - 2 h.

[0045] In the method of the present invention, in step (4), in the precipitation mother liquor, the concentration of P 5+ can be 0.5 mg / L or less, preferably 0.1 - 0.3 mg / L; the concentration of Ca 2+ can be 0.1 mg / L or less, preferably 0.05 - 0.1 mg / L. The environmental protection standard for discharging the precipitation mother liquor: the concentration of P 5+ is 0.5 mg / L or less.

[0046] In the method of the present invention, in step (5), the method can further include: before carbonization, mixing the factory floor sweepings and / or the wall scaling material with water at a temperature of 20 - 30°C for 0.1 - 0.5 h. In step (5), the solid-liquid ratio of the factory floor sweepings or the wall scaling material to water can be 1 g:(20 - 40) mL, preferably 1 g:(30 - 40) mL.

[0047] In the method of the present invention, in step (5), the conditions of the carbonization reaction include: the flow rate of CO2 can be 0.8 - 1.5 L / min, preferably 0.8 - 1.2 L / min; the temperature can be 20 - 40 °C, preferably 20 - 30 °C; the time can be more than 2 h, preferably 2 - 3 h. The carbonization reaction makes the obtained solution clear.

[0048] In the method of the present invention, in step (5), the impurity removal can be carried out by chemical method or resin. The specific process of the chemical method can include: reacting the impurities in the solution after the carbonization reaction with chemical reagents to form precipitates and performing solid-liquid separation by filtration. The chemical reagents can be lime milk and / or sodium sulfate. The resin can be a series connection of LS1000 ion exchange resin and D110 resin. In the resin, the flow rate of the solution after the carbonization reaction can be 3 - 5 BV / h, preferably 3 - 4 BV / h. By the impurity removal, magnesium ions and calcium ions in the solution after the carbonization reaction can be removed.

[0049] In the method of the present invention, in step (5), the conditions of the hydrothermal decomposition include: the temperature can be 90 °C or higher, preferably 90 - 150 °C; the stirring speed can be 400 revolutions per minute or higher, preferably 400 - 700 revolutions per minute; the time can be 1 - 2 h, preferably 1.5 - 2 h. The hydrothermal decomposition can be carried out by water bath heating or steam heating.

[0050] In some embodiments, the method for co-producing magnesium hydroxide, calcium phosphate and lithium carbonate by using the old brine adsorption tail liquid of the present invention, as Figure 1 shown, the method comprises the following steps:

[0051] (1) Mix the old brine adsorption tail liquid from the adsorption workshop and ammonia water with a concentration of 1 - 2 moL / L, and then perform solid-liquid separation by filtration to obtain ammonium chloride solution and magnesium hydroxide solid; in the old brine adsorption tail liquid, the concentration of Mg 2+ is 75 g / L or higher, and the concentration of CI - is 70 g / L or higher; the molar ratio of Mg 2+ in the old brine adsorption tail liquid to ammonia in the ammonia water is 1:(3 - 5);

[0052] (2) Pyrolyze calcium carbonate at a temperature of 800 °C or higher for 1 - 1.5 h to obtain carbon dioxide and calcium oxide, and recover the obtained carbon dioxide;

[0053] (3) Mix the calcium oxide and water obtained in step (2) at a solid-liquid ratio of 1 g:(1 - 1.5) mL with a stirring rate of more than 400 revolutions per minute and a temperature of 60 - 100 °C for 0.5 - 1.5 h to form a lime milk suspension. Then, mix the lime milk suspension and the ammonium chloride solution obtained in step (1) at a volume ratio of 1:(2 - 3) at a temperature of 20 - 40 °C for 1 - 2 h to obtain calcium chloride solid;

[0054] (4) Mix the lithium phosphate tail liquid from the lithium phosphate workshop and the calcium chloride solid obtained in step (3) at a liquid-solid ratio of 1 L:(50 - 100) g at a temperature of 20 - 30 °C for 1 - 3 h. Then, perform solid-liquid separation by filtration to obtain calcium carbonate solid and a mixed solution. Then, evaporate the mixed solution at a temperature of 80 - 100 °C for 1 - 2 h to precipitate a solid, and then perform filtration to obtain the solid and dry it at a temperature of 100 - 150 °C for 1 - 2 h to obtain calcium phosphate solid and a mother liquor of the precipitate. The calcium carbonate solid is recycled to step (2); In the lithium phosphate tail liquid, the concentration of P 5+ is 1 - 1.5 g / L, the concentration of Ca 2+ is 0.5 - 0.8 g / L, and the concentration of CO3 2－ is below 18 g / L; In the mother liquor of the precipitate, the concentration of P 5+ is below 0.5 mg / L, and the concentration of Ca 2+ is below 0.1 mg / L;

[0055] (5) Mix the factory floor sweepings from the lithium carbonate precipitation workshop with a lithium carbonate content of more than 90 wt% and / or the wall scale of the precipitation reactor with a lithium carbonate content of more than 70 wt% and water at a solid-liquid ratio of 1 g:(20 - 40) mL at a temperature of 20 - 30 °C for 0.1 - 0.5 h. Then, carry out a carbonization reaction with the carbon dioxide obtained in step (2) at a flow rate of 0.8 - 1.5 L / min at a temperature of 20 - 40 °C for more than 2 h to clarify the resulting solution. Then, perform impurity removal and hydrothermal decomposition at a temperature of more than 90 °C and a stirring speed of more than 400 revolutions per minute for 1 - 2 h to obtain lithium carbonate solid.

[0056] The method for co-producing magnesium hydroxide, calcium phosphate and lithium carbonate by using the waste liquid adsorbed by old brine is further illustrated by the following examples. The examples are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following examples.

[0057] The experimental methods in the following examples are all conventional methods in the art unless otherwise specified. The experimental materials used in the following examples can all be obtained commercially unless otherwise specified.

[0058] Example 1

[0059] (1) Mix the spent brine adsorption tail liquid from the adsorption workshop and ammonia water with a concentration of 1.5 moL / L at 50 °C for 1.2 h, and then perform solid-liquid separation by filtration to obtain ammonium chloride solution and magnesium hydroxide solid; in the spent brine adsorption tail liquid, the concentration of Mg 2+ is 75 g / L, and the concentration of CI - is 75 g / L; the molar ratio of Mg 2+ in the spent brine adsorption tail liquid to ammonia in the ammonia water is 1:3.5;

[0060] (2) Pyrolyze calcium carbonate at 800 °C for 1.5 h to obtain carbon dioxide and calcium oxide, and recover the obtained carbon dioxide;

[0061] (3) Mix the calcium oxide obtained in step (2) and water at a solid-liquid ratio of 1 g:1.2 mL under a stirring rate of 400 revolutions per minute and at a temperature of 85 °C for 0.8 h to form a lime milk suspension, and then mix the lime milk suspension and the ammonium chloride solution obtained in step (1) at a volume ratio of 1:2 at 25 °C for 1 h to obtain calcium chloride solid;

[0062] (4) Mix the lithium phosphate tail liquid from the lithium phosphate workshop and the calcium chloride solid obtained in step (3) at a liquid-solid ratio of 1 L:60 g at 25 °C for 2 h, and then perform solid-liquid separation by filtration to obtain calcium carbonate solid and a mixed solution. Then, evaporate the mixed solution at 85 °C for 1 h to precipitate a solid, and then filter to obtain the solid and dry it at 110 °C for 1 h to obtain calcium phosphate solid and a precipitation mother liquor. The calcium carbonate solid is recycled to step (2), and the precipitation mother liquor is discharged; in the lithium phosphate tail liquid, the concentration of P 5+ is 1.2 g / L, the concentration of Ca 2+ is 0.7 g / L, and the concentration of CO3 2－ is 18 g / L; in the precipitation mother liquor, the concentration of P 5+ is 0.4 mg / L, and the concentration of Ca 2+ is 0.05 mg / L;

[0063] (5) Mix the factory floor sweepings from the lithium precipitation workshop with 91.40 wt% lithium carbonate content (the composition of the factory floor sweepings is shown in Table 4) and water at a solid-liquid ratio of 1 g: 30 mL in a reaction kettle at 25 °C for 0.1 h. Then, introduce the carbon dioxide obtained in step (2) at a flow rate of 1 L / min and carry out a carbonization reaction at 25 °C for 2 h to clarify the resulting solution. Then, pass the resulting solution through a series of LS1000 ion exchange resin and D110 resin at a flow rate of 3 BV / h to remove magnesium ions and calcium ions. Carry out hydrothermal decomposition at 90 °C and a stirring speed of 400 revolutions per minute for 2 h by steam heating to obtain lithium carbonate solid.

[0064] Measure the impurity and physical index content of the product through an inductively coupled plasma emission spectrometer, atomic absorption spectrometer, spectrophotometer, laser particle size analyzer, blue light whiteness meter, and specific surface area analyzer respectively; the purity of lithium carbonate and magnesium hydroxide is determined by the loss on drying method, and the purity of calcium phosphate is analyzed by spectroscopy by measuring the absorption or scattering of light of a specific wavelength by the calcium phosphate solution to determine the purity of calcium phosphate. Among them, the indicators of magnesium hydroxide solid are shown in Table 1, the purity of lithium carbonate is 99.5%, and the purity of calcium phosphate is 96.3%.

[0065] Table 1

[0066]

[0067] Example 2

[0068] (1) Mix the old brine adsorption tail liquid from the adsorption workshop and ammonia water with a concentration of 1 moL / L at 60 °C for 1 h, and then carry out solid-liquid separation by filtration to obtain ammonium chloride solution and magnesium hydroxide solid; in the old brine adsorption tail liquid, the concentration of Mg 2+ is 75 g / L, and the concentration of CI - is 70 g / L; the molar ratio of the amount of substance of Mg 2+ in the old brine adsorption tail liquid to the amount of substance of ammonia in the ammonia water is 1:3;

[0069] (2) Pyrolyze calcium carbonate at 1000 °C for 1 h to obtain carbon dioxide and calcium oxide, and recover the obtained carbon dioxide;

[0070] (3) Mix the calcium oxide obtained in step (2) and water at a solid-liquid ratio of 1 g: 1 mL and stir at a stirring rate of 600 revolutions per minute and a temperature of 100 °C for 0.5 h to form a lime milk suspension. Then, mix the lime milk suspension and the ammonium chloride solution obtained in step (1) at a volume ratio of 1:3 at 40 °C for 1 h to obtain calcium chloride solid;

[0071] (4) Mix the lithium phosphate tail liquid from the lithium phosphate workshop and the calcium chloride solid obtained in step (3) at a liquid-solid ratio of 1 L:50 g at a temperature of 30 °C for 1 h, then perform solid-liquid separation by filtration to obtain calcium carbonate solid and a mixed solution. Then, evaporate the mixed solution at a temperature of 100 °C for 1 h to precipitate solids, then perform filtration to obtain solids and dry them at a temperature of 150 °C for 1 h to obtain calcium phosphate solid and a precipitation mother liquor. The calcium carbonate solid is recycled to step (2), and the precipitation mother liquor is discharged; in the lithium phosphate tail liquid, the concentration of P 5+ is 1 g / L, and the concentration of Ca 2+ is 0.5 g / L, and the concentration of CO3 2－ is 18 g / L; in the precipitation mother liquor, the concentration of P 5+ is 0.3 mg / L, and the concentration of Ca 2+ is 0.04 mg / L;

[0072] (5) Mix the factory sweeping materials from the lithium carbonate precipitation workshop with a lithium carbonate content of 91.40 wt% (the composition of the factory sweeping materials is shown in Table 4) and water at a liquid-solid ratio of 1 g:20 mL in a reaction kettle at a temperature of 20 °C for 0.1 h. Then, introduce the carbon dioxide obtained in step (2) at a flow rate of 0.8 L / min and carry out a carbonization reaction at a temperature of 20 °C for 2.5 h to clarify the resulting solution. Then, pass the resulting solution through a series of LS1000 ion exchange resin and D110 resin at a flow rate of 5 BV / h to remove magnesium ions and calcium ions. Hydrothermal decomposition is carried out by water bath heating at a temperature of 100 °C and a stirring speed of 700 revolutions per minute for 1 h to obtain lithium carbonate solid.

[0073] Measure the impurity and physical index content of the products respectively by inductively coupled plasma emission spectrometer, atomic absorption spectrometer, spectrophotometer, laser particle size analyzer, blue light whiteness meter, and specific surface area analyzer; the purity of lithium carbonate and magnesium hydroxide is determined by the loss on drying method, and the purity of calcium phosphate is analyzed by measuring the absorption or scattering of light of a specific wavelength by a calcium phosphate solution by spectrometry to determine the purity of calcium phosphate. Among them, the indicators of magnesium hydroxide solid are shown in Table 2, the purity of lithium carbonate is 99.5%, and the purity of calcium phosphate is 96.1%.

[0074] Table 2

[0075]

[0076] Example 3

[0077] (1) Mix the old brine adsorption tail liquid from the adsorption workshop and ammonia water with a concentration of 2 moL / L at 40 °C for 2 h, then perform solid-liquid separation by filtration to obtain ammonium chloride solution and magnesium hydroxide solid; in the old brine adsorption tail liquid, the concentration of Mg2+ has a concentration of 100 g / L, CI - has a concentration of 100 g / L; in the adsorbed tail liquor of the old brine, the amount of substance of Mg 2+ and the amount of substance of ammonia in the ammonia water are in a ratio of 1:5;

[0078] (2) Pyrolyze calcium carbonate at 1200 °C for 1.5 h to obtain carbon dioxide and calcium oxide, and recover the obtained carbon dioxide;

[0079] (3) Mix the calcium oxide obtained in step (2) and water at a solid-liquid ratio of 1 g: 1.5 mL, stir and mix at a stirring rate of 800 revolutions per minute and a temperature of 60 °C for 1.5 h to form a lime milk suspension. Then, mix the lime milk suspension and the ammonium chloride solution obtained in step (1) at a volume ratio of 1:2 at a temperature of 20 °C for 2 h to obtain calcium chloride solid;

[0080] (4) Mix the lithium phosphate tail liquor from the lithium phosphate workshop and the calcium chloride solid obtained in step (3) at a liquid-solid ratio of 1 L: 100 g at a temperature of 20 °C for 3 h. Then, perform solid-liquid separation by filtration to obtain calcium carbonate solid and a mixed solution. Then, evaporate the mixed solution at 80 °C for 1.5 h to precipitate solids, and then filter to obtain solids and dry them at 100 °C for 2 h to obtain calcium phosphate solid and a precipitation mother liquor. The calcium carbonate solid is recycled to step (2), and the precipitation mother liquor is discharged; in the lithium phosphate tail liquor, the concentration of P 5+ is 1.5 g / L, the concentration of Ca 2+ is 0.8 g / L, and the concentration of CO3 2－ is 20 g / L; in the precipitation mother liquor, the concentration of P 5+ is 0.5 mg / L, and the concentration of Ca 2+ is 0.07 mg / L;

[0081] (5) Mix the wall - adhering material of the lithium precipitation reactor with 71.18 wt% lithium carbonate content (the composition of the wall - adhering material is shown in Table 4) and water at a solid - liquid ratio of 1 g: 40 mL in the reaction kettle at 30 °C for 0.5 h. Then, introduce the carbon dioxide obtained in step (2) at a flow rate of 1.5 L / min and carry out a carbonization reaction at 40 °C for 2 h to clarify the obtained solution. Then, pass the obtained solution through LS1000 ion - exchange resin and D110 resin in series at a flow rate of 3 BV / h to remove magnesium ions and calcium ions, and carry out hydrothermal decomposition at 100 °C and a stirring speed of 600 revolutions per minute by water - bath heating for 2 h to obtain lithium carbonate solid.

[0082] The impurity and physical index contents of the product are measured by an inductively coupled plasma emission spectrometer, an atomic absorption spectrometer, a spectrophotometer, a laser particle size analyzer, a blue light whiteness meter, and a specific surface area analyzer respectively; the purities of lithium carbonate and magnesium hydroxide are determined by the drying loss method, and the purity of calcium phosphate is analyzed by a spectroscopic method to measure the absorption or scattering of light of a specific wavelength by a calcium phosphate solution to determine the purity of calcium phosphate. Among them, the indexes of solid magnesium hydroxide are shown in Table 3, the purity of lithium carbonate is 99.7%, and the purity of calcium phosphate is 96.7%.

[0083] Table 3

[0084]

[0085] Table 4

[0086] Number Example 1 Example 2 Example 3 Lithium carbonate (%) 91.40 91.40 71.18 Calcium (ppm) 4658.88 4658.88 38.56 Magnesium (ppm) 270.94 270.94 15.02 Sodium (ppm) 1165.55 1165.55 43790.00 Potassium (ppm) 179.35 179.35 633.20 Boron (ppm) 29.13 29.13 62.41 Sulfate radical (ppm) 430.60 430.60 46.71 Iron (ppm) 27.18 27.18 14.82 Chloride ion (ppm) 2042.77 2042.77 88930.00 Moisture content (260°C) (%) 0.23 0.23 6.43 Insoluble in acid (%) 1.45 1.45 0.52 Loss on ignition (500°C) (%) 0.94 0.94 9.85

[0087] From the results in Tables 1 - 3, it can be seen that the examples of the method for co-producing magnesium hydroxide, calcium phosphate, and lithium carbonate by using old brine to adsorb tail liquid described in the present invention can co-produce high-purity magnesium hydroxide, calcium phosphate, and lithium carbonate, and the by-products calcium chloride and calcium carbonate can be recycled as auxiliary materials.

[0088] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the technical concept scope of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for co-producing magnesium hydroxide, calcium phosphate and lithium carbonate by using old brine to adsorb tail liquor, which is characterized in that, The method includes the following steps: (1) Mix the old brine adsorption tail liquid and ammonia water, and then perform solid-liquid separation to obtain ammonium chloride solution and magnesium hydroxide solid; (2) Pyrolyze calcium carbonate to obtain carbon dioxide and calcium oxide; (3) Stir and mix the calcium oxide obtained in step (2) with water to form a lime milk suspension, then mix the lime milk suspension with the ammonium chloride solution obtained in step (1), and then evaporate to precipitate solids to obtain calcium chloride solid; (4) Mix the lithium phosphate tail liquid with the calcium chloride solid obtained in step (3), then perform solid-liquid separation to obtain calcium carbonate solid and a mixed solution, and then evaporate the mixed solution to obtain calcium phosphate solid and a precipitation mother liquor, and recycle the calcium carbonate solid to step (2); (5) Carry out a carbonization reaction on the factory floor sweeping material or the wall scaling material of the lithium carbonate precipitation workshop with the carbon dioxide obtained in step (2), and then carry out impurity removal and hydrothermal decomposition in sequence to obtain lithium carbonate solid; Wherein, the content of lithium carbonate in the factory floor sweeping material is more than 90 wt%, and the content of lithium carbonate in the wall scaling material is more than 70 wt%.

2. The method according to claim 1, wherein In step (1), in the spent brine adsorption tail liquid, the concentration of Mg 2+ is 75 g / L or more, and the concentration of Cl - is 70 g / L or more; Preferably, in step (1), the concentration of the ammonia water is 1-2 moL / L; Preferably, in step (1), the amount of substance of Mg in the old brine adsorption tail liquid 2+ and the amount of substance of ammonia in the ammonia water are in a ratio of 1:(3 - 5).

3. The method according to claim 1 or 2, characterized in that, In step (2), the pyrolysis conditions include: the temperature is above 800 °C, preferably 800-1200 °C; the time is 1-1.5 h.

4. The method according to any one of claims 1 to 3, characterized in that In step (3), the solid-liquid ratio of the amounts of the calcium oxide and the water used is 1 g:(1-1.5) mL; Preferably, in step (3), the volume ratio of the amounts of the lime milk suspension and the ammonium chloride solution used is 1:(2-3); Preferably, in step (3), the stirring and mixing conditions include: the stirring rate is above 400 revolutions per minute, preferably 400-800 revolutions per minute; the time is 0.5-1.5 h.

5. The method according to any one of claims 1-4, characterized in that In step (4), in the lithium phosphate tail liquor, the concentration of P 5+ is 1 - 1.5 g / L, the concentration of Ca 2+ is 0.5 - 0.8 g / L, and the concentration of CO3 2－ is 18 g / L or less.

6. The method according to any one of claims 1-5, characterized in that, In step (4), the liquid-solid ratio of the amounts of the lithium phosphate tail liquid and the calcium chloride solid used is 1 L:(50-100) g.

7. The method according to any one of claims 1-6, characterized in that, In step (4), in the precipitation mother liquor, the concentration of P 5+ is 0.5 mg / L or less, and the concentration of Ca 2+ is 0.1 mg / L or less.

8. The method according to any one of claims 1-7, characterized in that, In step (5), the method further includes: mixing the factory floor sweeping material and / or the wall scaling material with water before carrying out the carbonization; Preferably, in step (5), the solid-liquid ratio of the amounts of the factory floor sweeping material or the wall scaling material and water used is 1 g:(20-40) mL.

9. The method according to any one of claims 1-8, characterized in that, In step (5), the carbonization reaction conditions include: the flow rate of CO2 is 0.8-1.5 L / min, the temperature is 20-40 °C, and the time is above 2 h, preferably 2-3 h.

10. The method according to any one of claims 1-9, characterized in that, In step (5), the hydrothermal decomposition conditions include: the temperature is above 90 °C, preferably 90-150 °C; the stirring speed is above 400 revolutions per minute, preferably 400-700 revolutions per minute; the time is 1-2 h.

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