Alkali carbonate of lanthanum particles and method for preparing the same

Abstract

The application discloses a basic lanthanum carbonate particle and a preparation method thereof. The basic lanthanum carbonate particle has an ellipsoidal appearance, a particle size of 1-4.5 microns, and a particle size distribution alpha satisfying the condition of 1.1<=alpha<=1.5. The preparation method can produce the basic lanthanum carbonate particle on a large scale under mild conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to a basic lanthanum carbonate particle and a preparation method thereof. BACKGROUND

[0002] Basic lanthanum carbonate is a special rare earth compound with good optical and catalytic properties. Basic lanthanum carbonate can be used as a phosphor, a catalyst, a magnetic refrigeration material, a material in the field of nonlinear optics, and a drug. In addition, basic lanthanum carbonate can also be used as a precursor to prepare rare earth sulfides, rare earth oxides, rare earth phosphates, and rare earth fluoride salts. At present, there are few reports on basic lanthanum carbonate. The preparation process of basic lanthanum carbonate is relatively simple, but how to obtain basic lanthanum carbonate with specific appearance and easy to filter under mild conditions still needs to be studied.

[0003] CN103037870B discloses a method for producing a lanthanum carbonate compound. A soluble salt of lanthanum chloride is reacted with ammonium carbonate in a solvent at a reaction temperature of 75-90℃ and a pH of 6.0-7.5 to obtain a precipitated reaction product, wherein the reaction product is basic lanthanum carbonate containing 0.5wt% or less of sodium. The basic lanthanum carbonate obtained by the method has a particle size of 100-200nm and a spherical appearance. Since the particle size of the reaction product is small, gelation is easy to occur, and high-energy-consuming methods such as centrifugation need to be used for filtration, which is not conducive to large-scale production.

[0004] CN102671685A discloses a preparation method of a photocatalyst basic lanthanum carbonate. A carbon source is dissolved in a solvent to obtain a carbon source solution; a lanthanum source compound is dissolved in a solvent to obtain a lanthanum source solution; the carbon source solution is added dropwise into the lanthanum source solution while stirring, and the stirring is continued for 30-180 minutes; the mixture is transferred into a high-pressure reaction kettle and kept at a constant temperature of 90-180℃ for 12-24 hours; the obtained precipitate is washed by centrifugation with water and ethanol until the ion concentration is less than 10ppm; the precipitate is dried at 40-120℃ for 6-24 hours and ground to obtain white basic lanthanum carbonate powder. The particle size of the precipitate obtained by the above method is small, and gelation is easy to occur, so high-energy-consuming methods such as centrifugation need to be used for filtration, which is not conducive to large-scale production.

[0005] CN101279757A discloses a method for preparing lanthanum hydroxycarbonate microcrystals by double hydrolysis, comprising the following steps: (1) using lanthanum oxide and ammonium bicarbonate or glycine as precursors, deionized water as solvent, and placing these substances in a hydrothermal reactor in a proportion of 1:20-1:45 of the molar ratio of lanthanum oxide to glycine or ammonium bicarbonate and 50-80% of the volume of the container; (2) placing the hydrothermal reactor containing the mixture in step (1) in a box-type resistance furnace and heating to 150-200°C, and heating at this temperature for 8-48 h, then taking out the container and naturally cooling to room temperature; (3) washing and centrifugal separation to obtain the desired product. The above method is still carried out at a high temperature, and the energy consumption is high, which is not suitable for large-scale production. In addition, the appearance of the lanthanum hydroxycarbonate microcrystals changes greatly with the reaction conditions, and ellipsoidal lanthanum hydroxycarbonate is not involved. SUMMARY

[0006] Therefore, an object of the present application is to provide a lanthanum hydroxycarbonate particle having an ellipsoidal appearance with uniform particle size, which is easy to filter.

[0007] Another object of the present application is to provide a method for preparing the above-mentioned lanthanum hydroxycarbonate particle, which can produce the lanthanum hydroxycarbonate particle having an ellipsoidal appearance with uniform particle size, which is easy to filter, on a large scale under mild conditions.

[0008] The present application provides a lanthanum hydroxycarbonate particle having an ellipsoidal appearance, a particle size of 1-4.5 μm, and a particle size distribution α satisfying the following condition:

[0009] α = D max / D min ,

[0010] 1.1 ≤ α ≤ 1.5;

[0011] wherein D max represents the maximum size of the lanthanum hydroxycarbonate particle; and D min represents the minimum size of the lanthanum hydroxycarbonate particle.

[0012] According to the lanthanum hydroxycarbonate particle of the present application, preferably, the particle size distribution satisfies the following condition:

[0013] 1.16 ≤ α ≤ 1.2.

[0014] According to the lanthanum hydroxycarbonate particle of the present application, preferably, the particle size is 1-1.2 μm, 3-3.5 μm, or 2.8-4.0 μm.

[0015] According to the lanthanum hydroxycarbonate particle of the present application, preferably, the total amount of rare earths in the particle is greater than 70.2 wt% as REO.

[0016] In another aspect, the present application provides a preparation method of basic lanthanum carbonate particles, comprising the following steps: under stirring at a stirring speed of 170-250 rpm, precipitant solution A containing ammonia and ammonium bicarbonate and lanthanum chloride aqueous solution B are added dropwise into water at a temperature of 45-70℃ in a parallel flow manner to form a mixed solution C with a pH of 6.7-7.5;

[0017] wherein the dropping speed of the precipitant solution A and the lanthanum chloride aqueous solution B is controlled so that the molar ratio of lanthanum in the lanthanum chloride aqueous solution B to NH4+ in the precipitant solution A added dropwise into the water at a temperature of 45-70℃ per minute is 1:2.95-3.05; 4+

[0018] wherein the concentration of NH4+ in the precipitant solution A is 3-7 mol / L. +

[0019] According to the preparation method of the basic lanthanum carbonate particles of the present application, preferably, the amount of the water at a temperature of 45-70℃ is 5-15 vol% of the total volume of the precipitant solution A and the lanthanum chloride aqueous solution B.

[0020] According to the preparation method of the basic lanthanum carbonate particles of the present application, preferably, the precipitant solution A is formed by ammonia and ammonium bicarbonate at a molar ratio of 1.8-2.5:1.

[0021] According to the preparation method of the basic lanthanum carbonate particles of the present application, preferably, the dropping time of the precipitant solution A containing ammonia and ammonium bicarbonate and the lanthanum chloride aqueous solution B is 70-100 min.

[0022] According to the preparation method of the basic lanthanum carbonate particles of the present application, preferably, after the dropping of the precipitant solution A containing ammonia and ammonium bicarbonate and the lanthanum chloride aqueous solution B is completed, the stirring is continued for 25-35 min, and then the aging is performed at room temperature for 2-20 h to obtain an aged slurry; the aged slurry is filtered, washed and dried to obtain the basic lanthanum carbonate particles.

[0023] According to the preparation method of the basic lanthanum carbonate particles of the present application, preferably, the filtration is not performed by centrifugal separation.

[0024] The basic lanthanum carbonate particles of the present application have an ellipsoidal appearance, and are uniform in morphology and particle size, complete in crystal form, good in dispersibility and easy to filter. The total amount of rare earths is greater than 70.2 wt% in terms of REO. The present application can produce the basic lanthanum carbonate particles with an ellipsoidal appearance and uniform particle size under mild conditions on a large scale, and the particles are easy to filter, and the energy consumption is low. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 Scanning electron microscope image of the basic lanthanum carbonate particles of Example 2. ​​

[0026] Figure 2 is a partial enlarged view of Figure 1

[0027] Figure 3 is a scanning electron micrograph of the lanthanum hydroxycarbonate particles of Comparative Example 1.

[0028] Figure 4 is a partial enlarged view of Figure 3

[0029] Figure 5 is a scanning electron micrograph of the lanthanum hydroxycarbonate particles of Comparative Example 2. DETAILED DESCRIPTION

[0030] The present application will be further described in conjunction with specific embodiments, but the scope of protection of the present application is not limited thereto.

[0031] In the present application, REO represents rare earth oxide. Room temperature represents 20-35°C, for example, 25-30°C.

[0032] The present application can not employ centrifugal separation, and can directly employ suction filtration or pressure filtration. For example, the present application employs gravity filtration, pressure filtration or reduced pressure filtration.

[0033] In the present application, the appearance of the lanthanum hydroxycarbonate particles is ellipsoidal, which means that the appearance is ellipsoidal or close to ellipsoidal, for example, can be rugby ball-shaped, etc.

[0034] <lanthanum hydroxycarbonate particles>

[0035] The lanthanum hydroxycarbonate particles of the present application have an ellipsoidal appearance. The chemical structure of lanthanum hydroxycarbonate is known in the art, and will not be described here.

[0036] The appearance of the lanthanum hydroxycarbonate particles of the present application is ellipsoidal or close to ellipsoidal. For example, the appearance of the lanthanum hydroxycarbonate particles of the present application can be rugby ball-shaped, etc.

[0037] The particle size of the lanthanum hydroxycarbonate particles of the present application is 1-4.5 μm. According to one embodiment of the present application, the particle size is 1-1.2 μm. According to another embodiment of the present application, the particle size is 3-3.5 μm. According to still another embodiment of the present application, the particle size is 2.8-4.0 μm. Controlling the particle size of the lanthanum hydroxycarbonate particles in the above range is advantageous for avoiding agglomeration and gelation of the particles, and is advantageous for low energy consumption filtration, for example, separating the precipitate from the supernatant by suction filtration or pressure filtration. It has been found that the lanthanum hydroxycarbonate particles of the present application are more easily separated by filtration when the particle size is 3-3.5 μm.

[0038] The particle size distribution of the lanthanum hydroxycarbonate particles of the present application is α=D​​max D min D max D represents the maximum size of the lanthanum hydroxycarbonate particles; D min D represents the minimum size of the lanthanum hydroxycarbonate particles. Since the lanthanum hydroxycarbonate particles are ellipsoidal, they have a long axis and a short axis. Both the maximum size and the minimum size represent the size of the long axis of the lanthanum hydroxycarbonate particles. The closer α is to 1, the more uniform the particle size distribution.

[0039] In the present application, 1.1 < α < 1.5. Preferably, 1.12 < α < 1.35. More preferably, 1.16 < α < 1.2. The present application finds that controlling the particle size distribution in the above range is advantageous in avoiding agglomeration and gelation of the particles, thus facilitating filtration with low energy consumption.

[0040] The lanthanum hydroxycarbonate particles of the present application have high purity and contain very few impurities. The total amount of rare earths in the lanthanum hydroxycarbonate particles of the present application is greater than 70.2 wt% in terms of REO, for example, 70.2-71.2 wt%.

[0041] In some embodiments, the lanthanum hydroxycarbonate particles of the present application have an ellipsoidal appearance, a particle size of 1-1.2 μm, and a total amount of rare earths in the particles of 70.23 wt% in terms of REO. In other embodiments, the lanthanum hydroxycarbonate particles of the present application have an ellipsoidal appearance, a particle size of 3-3.5 μm, and a total amount of rare earths in the particles of 70.3 wt% in terms of REO. In still other embodiments, the lanthanum hydroxycarbonate particles of the present application have an ellipsoidal appearance, a particle size of 2.8-4.0 μm, and a total amount of rare earths in the particles of 71.2 wt% in terms of REO.

[0042] The lanthanum hydroxycarbonate particles of the present application have an ellipsoidal appearance, a moderate particle size, and a uniform particle size distribution, thus being easy to filter in a low energy consumption manner and facilitating large-scale production.

[0043] PREPARATION OF THE LANTHANUM HYDROXYCARBONATE PARTICLES

[0044] The precipitant solution A and the aqueous lanthanum chloride solution B are added dropwise to water in a concurrent manner under stirring to form a mixed solution C. The pH of the mixed solution C is controlled to form the reaction product lanthanum hydroxycarbonate. The reaction product is aged to obtain an aged slurry. The aged slurry is filtered, washed, and dried to obtain the lanthanum hydroxycarbonate particles of the present application. This is described in detail below.

[0045] Forming the precipitant solution A

[0046] First, the precipitant solution A is prepared. The precipitant solution contains ammonia and ammonium bicarbonate. For example, ammonia and ammonium bicarbonate are mixed to obtain the precipitant solution A. The molar ratio of ammonia to ammonium bicarbonate is 1.8-2.5:1, preferably 1.9-2.3:1, and more preferably 2-2.2:1. The above molar ratio means the molar ratio of NH3 to NH4HCO3. Ammonia is used in the form of a solution. Ammonium bicarbonate can be used in the form of a solid powder or a solution. With the above precipitant, the ellipsoidal appearance of the basic lanthanum carbonate particles can be better controlled, and the particle size distribution is uniform.

[0047] Both ammonia and ammonium bicarbonate can provide NH4 + In the precipitant solution A, the concentration of NH4 + may be 3-7 mol / L, preferably 3.5-6.5 mol / L, and more preferably 4-6 mol / L.

[0048] According to one embodiment of the present application, the precipitant solution A is a mixed solution composed of ammonia and ammonium bicarbonate in a molar ratio of 2-2.2:1, and the concentration of NH4 + in the mixed solution is 4-6 mol / L.

[0049] Forming the aqueous lanthanum chloride solution B

[0050] Second, the lanthanum chloride aqueous solution B is prepared. Lanthanum chloride is dissolved in water to obtain the lanthanum chloride aqueous solution B. In the lanthanum chloride aqueous solution B, the concentration of lanthanum chloride is 1.0-2.2 mol / L, preferably 1.1-2 mol / L, and more preferably 1.2-1.8 mol / L. If the concentration of lanthanum chloride is too low, the concentration of lanthanum ions in the reaction system is too low, and it is difficult to reach the supersaturation state, resulting in a slow reaction rate. If the concentration of lanthanum chloride is too high, the concentration of lanthanum ions in the reaction system is too high, and clustering is likely to occur, resulting in a large amount of impurities doped in the product.

[0051] Forming the mixture C

[0052] The formation steps of the mixed solution C are described below. The precipitant solution A and the lanthanum chloride aqueous solution B are added dropwise to water in a parallel flow manner under stirring to form the mixed solution C.

[0053] The stirring speed can be 170-250 rpm, preferably 170-240 rpm, and more preferably 170-220 rpm. When the stirring speed is lower than 170 rpm, the reaction rate is slow, resulting in agglomeration, and the basic lanthanum carbonate particles do not have an ellipsoidal appearance, and the particle size distribution is not uniform. When the stirring speed is higher than 250 rpm, the shear force is too large, resulting in that the obtained basic lanthanum carbonate particles do not have an ellipsoidal appearance, and the particle size distribution is not uniform.

[0054] The precipitant solution A and the aqueous lanthanum chloride solution B are added in a co-current manner. By co-current, it is meant that both are added simultaneously, the resulting liquid mixing in the vessel. This facilitates precise control of the molar ratio of lanthanum ions to NH4 + , thereby controlling the morphology and particle size distribution of the lanthanum hydroxycarbonate particles.

[0055] The present application uses water as the reaction base. The precipitant solution A and the aqueous lanthanum chloride solution B are added in a co-current manner to the water. The reaction base can be selected from ultra-pure water, pure water, distilled water or deionized water; preferably deionized water.

[0056] As the reaction base, the amount of water is 5-15 vol% of the total volume of the precipitant solution A and the aqueous lanthanum chloride solution B, preferably 5-12 vol%, more preferably 5-10 vol%. If the amount of water is too large, the concentration of lanthanum ions in the reaction system is low, and it takes a long time to reach the supersaturation state, affecting the production efficiency; if the amount of water is too small, the reaction product will locally cluster, and other impurities will be easily mixed in the lanthanum hydroxycarbonate. The temperature of the water can be 45-70°C, preferably 45-65°C, more preferably 45-60°C. When the temperature is lower than 45°C, the reaction is slow, the particle size distribution of the resulting product is not uniform, the product particles are mutually adhered, and it is not easy to form ellipsoidal particles; when the temperature is higher than 70°C, although the reaction rate is too fast, the resulting product particles will also agglomerate, it is not easy to form ellipsoidal particles, and the energy consumption increases.

[0057] The formulations of the precipitant solution A and the aqueous lanthanum chloride solution B are as described above. The molar ratio of lanthanum ions in the aqueous lanthanum chloride solution B to NH4 + in the precipitant solution A added per minute to the water at a temperature of 45-70°C is 1:2.95-3.05, preferably 1:2.97-3.03, more preferably 1:2.99-3.02. When the above molar ratio is less than 1:2.95, lanthanum carbonate can be generated, affecting the purity of the lanthanum hydroxycarbonate; when the above molar ratio is greater than 1:3.05, the morphology of the lanthanum hydroxycarbonate will change to a self-assembled sheet-like aggregate structure. The above molar ratio can be achieved by controlling the relative addition speed of the precipitant solution A and the aqueous lanthanum chloride solution B. According to one embodiment of the present application, the addition speeds of the precipitant solution A and the aqueous lanthanum chloride solution B are controlled so that the molar ratio of lanthanum in the aqueous lanthanum chloride solution B to NH4 + in the precipitant solution A added per minute to the water at a temperature of 45-70°C is 1:2.95-3.05.

[0058] The dropping time of the precipitant solution A and the aqueous lanthanum chloride solution B can be 70-100 min, preferably 75-100 min, and more preferably 80-100 min. If the dropping time is less than 70 min, the ion concentration in the system is too large, the crystal growth rate is too fast, and it is difficult to form ellipsoidal particles, and impurities are easily mixed or generated. If the dropping time is greater than 100 min, the nucleation and crystal growth rate is slow, and it is also difficult to form ellipsoidal particles.

[0059] The precipitant solution A and the aqueous lanthanum chloride solution B react in the water as the reaction bottom solution to form a mixed solution C. The pH of the mixed solution C can be 6.7-7.5, preferably 6.8-7.5, and more preferably 7-7.5. If the pH is less than 6.7, the crystal growth process is slow, and the particle size of the lanthanum hydroxycarbonate formed is too small to be filtered. If the pH is greater than 7.5, the crystal growth is too fast, and it is difficult to form ellipsoidal particles, and impurity ions are easily mixed, resulting in a decrease in the total amount of rare earth in the lanthanum hydroxycarbonate.

[0060] Forming the basic lanthanum carbonate slurry

[0061] After the dropping of the precipitant solution A and the aqueous lanthanum chloride solution B is completed, the stirring is continued for a period of time to obtain a lanthanum hydroxycarbonate slurry. The stirring speed can be 170-250 rpm, preferably 170-240 rpm, and more preferably 170-220 rpm. The stirring time can be 25-35 min, preferably 27-35 min, and more preferably 29-33 min. This is conducive to the further increase of the lanthanum hydroxycarbonate crystals and the formation of ellipsoidal particles with uniform particle size distribution.

[0062] Aging

[0063] The lanthanum hydroxycarbonate slurry is aged to obtain an aged slurry. In some embodiments, the aging can be carried out at room temperature. Room temperature means 20-35°C, preferably 25-30°C. The aging time can be 2-20 h, preferably 2-18 h, and more preferably 4-15 h. If the aging time is too short, it is easy to form lanthanum hydroxycarbonate with very small particle size and high viscosity. If the aging time is too long, the ellipsoidal particles will be deformed, and the particle size distribution will be non-uniform.

[0064] Filtration, washing and drying

[0065] The aged slurry is filtered by a non-centrifugal method to obtain a lanthanum hydroxycarbonate precipitate (or filter cake). This helps to reduce energy consumption and production cost, and facilitates large-scale production. The filtration method can be gravity filtration, pressure filtration or vacuum filtration.

[0066] In the present application, the obtained lanthanum hydroxycarbonate precipitate (or filter cake) is washed. The washing method can be water washing and / or alcohol washing. The amount of washing water can be 2-6 times, preferably 3-5 times, and more preferably 3.5-4.5 times the weight of the lanthanum hydroxycarbonate precipitate.

[0067] The washed lanthanum hydroxycarbonate precipitate (or filter cake) is dried to obtain lanthanum hydroxycarbonate particles. The drying temperature can be 55-70°C, and preferably 55-60°C. The drying time is not particularly limited, as long as the moisture content is sufficiently low to avoid particle agglomeration.

[0068] According to one embodiment of the present application, under stirring at a stirring speed of 170-250 rpm, a precipitant solution A containing ammonia water and ammonium bicarbonate and a lanthanum chloride aqueous solution B are added dropwise in a parallel flow manner into water at a temperature of 45-70°C to form a mixed solution C with a pH of 6.7-7.5; after the dropwise addition is completed, stirring is continued for 25-35 min, and then the slurry is aged at room temperature for 2-20 h to obtain an aged slurry; the aged slurry is filtered, washed and dried to obtain lanthanum hydroxycarbonate particles. In the process, the dropwise addition speed of the precipitant solution A and the lanthanum chloride aqueous solution B is controlled so that the molar ratio of lanthanum in the lanthanum chloride aqueous solution B to NH4+ + in the precipitant solution A added dropwise into the water at a temperature of 45-70°C per minute is 1:2.95-3.05; the concentration of NH4+ + in the precipitant solution A is 3-7 mol / L.

[0069] According to another embodiment of the present application, under stirring at a stirring speed of 170-240 rpm, a precipitant solution A containing ammonia water and ammonium bicarbonate and a lanthanum chloride aqueous solution B are added dropwise in a parallel flow manner into water at a temperature of 45-70°C to form a mixed solution C with a pH of 6.8-7.5; after the dropwise addition is completed, stirring is continued for 25-35 min, and then the slurry is aged at room temperature for 2-20 h to obtain an aged slurry; the aged slurry is filtered, washed and dried to obtain lanthanum hydroxycarbonate particles. In the process, the concentration of NH4+ + in the precipitant solution A is 3.5-7 mol / L; the dropwise addition speed of the precipitant solution A and the lanthanum chloride aqueous solution B is controlled so that the molar ratio of lanthanum in the lanthanum chloride aqueous solution B to NH4+ + in the precipitant solution A added dropwise into the water at a temperature of 45-70°C per minute is 1:2.97-3.03; the amount of water is 5-15 vol% of the total volume of the precipitant solution A and the lanthanum chloride aqueous solution B; the dropwise addition time of the precipitant solution A and the lanthanum chloride aqueous solution B is 70-100 min.

[0070] According to still another embodiment of the present application, under the stirring condition of a stirring speed of 170-220 rpm, the precipitant solution A and the aqueous lanthanum chloride solution B are added dropwise into deionized water at a temperature of 45-70°C in a parallel flow mode to form a mixed solution C with a pH of 7-7.5; after the dropwise addition is completed, the stirring is continued for 29-33 min, and then the aged slurry is obtained by aging at room temperature for 4-15 h; the aged slurry is filtered, washed and dried to obtain the basic lanthanum carbonate particles. In the present application, the precipitant solution A is a solution formed by ammonia water and ammonium bicarbonate in a molar ratio of 1.8-2.5:1, the concentration of NH4 + in the precipitant solution A is 4-7 mol / L; the dropwise addition speed of the precipitant solution A and the aqueous lanthanum chloride solution B is controlled so that the molar ratio of lanthanum in the aqueous lanthanum chloride solution B to NH4 + in the precipitant solution A added dropwise into the water at a temperature of 45-70°C per minute is 1:2.99-3.02; the amount of deionized water added is 5-10 vol% of the total volume of the precipitant solution A and the aqueous lanthanum chloride solution B; and the dropwise addition time of the precipitant solution A and the aqueous lanthanum chloride solution B is 80-100 min.

[0071] The test methods are described as follows:

[0072] (1) Particle size determination: the scanning electron microscope is used to take photos, and the long axis size of the ellipsoidal particles is taken as the particle size of the basic lanthanum carbonate particles. The specific process is as follows: a toothpick is used to dip a small amount of solid powder and stick it on the conductive tape, and then the scanning electron microscope (model: S-3400N) of Hitachi is used for testing.

[0073] (2) Rare earth content determination: the EDTA complexometric titration method is used for rare earth content determination according to the national standard GB / T 14635-2008.

[0074] Example 1

[0075] 1L of a precipitant solution A prepared from ammonia water and ammonium bicarbonate in a molar ratio of 2:1 is provided, and the ionic concentration of NH4 + in the precipitant solution A is 4 mol / L.

[0076] 1L of an aqueous lanthanum chloride solution B is provided, and the concentration of lanthanum chloride is 1.33 mol / L.

[0077] Under the stirring condition of a stirring speed of 170 rpm, the precipitant solution A and the aqueous lanthanum chloride solution B are added dropwise into deionized water at 45°C in a parallel flow mode to form a mixed solution C with a pH of 7; and the amount of deionized water added is 5 vol% of the total volume of the precipitant solution A and the aqueous lanthanum chloride solution B.

[0078] The dropping speed is adjusted so that the molar ratio of La3+ in the aqueous lanthanum chloride solution B to NH4+ in the precipitant solution A added into the deionized water per minute is 1:2.95. The dropping time of the precipitant solution A and the aqueous lanthanum chloride solution B is 80 min, after the dropping is finished, the reaction product is aged for 15 h, then filtered, washed with water, and dried at 60 ℃ to obtain the lanthanum hydroxycarbonate particles. + The dropping speed is adjusted so that the molar ratio of La3+ in the aqueous lanthanum chloride solution B to NH4+ in the precipitant solution A added into the deionized water per minute is 1:2.95. The dropping time of the precipitant solution A and the aqueous lanthanum chloride solution B is 80 min, after the dropping is finished, the reaction product is aged for 15 h, then filtered, washed with water, and dried at 60 ℃ to obtain the lanthanum hydroxycarbonate particles.

[0079] The lanthanum hydroxycarbonate particles prepared by the method of the present application have an ellipsoidal appearance observed by a scanning electron microscope. The detailed properties are shown in Table 1.

[0080] Example 2

[0081] The precipitant solution A is prepared by mixing ammonia water and ammonium bicarbonate in a molar ratio of 2:1, and the ion concentration of NH4+ in the precipitant solution A is 6 mol / L. + The precipitant solution A is prepared by mixing ammonia water and ammonium bicarbonate in a molar ratio of 2:1, and the ion concentration of NH4+ in the precipitant solution A is 6 mol / L.

[0082] The aqueous lanthanum chloride solution B is prepared by mixing lanthanum chloride in a concentration of 1.67 mol / L.

[0083] The precipitant solution A and the aqueous lanthanum chloride solution B are added into the deionized water at a stirring speed of 190 rpm in a concurrent manner to form a mixed solution C with a pH of 7.2, and the amount of the deionized water added is 10 vol% of the total volume of the precipitant solution A and the aqueous lanthanum chloride solution B.

[0084] The dropping speed is adjusted so that the molar ratio of La3+ in the aqueous lanthanum chloride solution B to NH4+ in the precipitant solution A added into the deionized water per minute is 1:2.95. The dropping time of the precipitant solution A and the aqueous lanthanum chloride solution B is 80 min, after the dropping is finished, the reaction product is aged for 15 h, then filtered, washed with water, and dried at 60 ℃ to obtain the lanthanum hydroxycarbonate particles. + The dropping speed is adjusted so that the molar ratio of La3+ in the aqueous lanthanum chloride solution B to NH4+ in the precipitant solution A added into the deionized water per minute is 1:2.95. The dropping time of the precipitant solution A and the aqueous lanthanum chloride solution B is 80 min, after the dropping is finished, the reaction product is aged for 15 h, then filtered, washed with water, and dried at 60 ℃ to obtain the lanthanum hydroxycarbonate particles.

[0085] The lanthanum hydroxycarbonate particles prepared by the method of the present application have an ellipsoidal appearance observed by a scanning electron microscope. The detailed properties are shown in Table 1. Figure 1 , Figure 2 and Table 1. The lanthanum hydroxycarbonate particles prepared by the method of the present application have an ellipsoidal appearance, and the particle size range is 3-3.5 μm with a uniform particle size distribution.

[0086] Example 3

[0087] The precipitant solution A is prepared by mixing ammonia water and ammonium bicarbonate in a molar ratio of 2:1, and the ion concentration of NH4+ in the precipitant solution A is 6 mol / L. + The precipitant solution A is prepared by mixing ammonia water and ammonium bicarbonate in a molar ratio of 2:1, and the ion concentration of NH4+ in the precipitant solution A is 6 mol / L.

[0088] Aqueous lanthanum chloride solution B is provided, and the concentration of the lanthanum chloride is 2.6L 1.8mol / L.

[0089] Under the stirring condition of a stirring speed of 220rpm, the precipitant solution A and the aqueous lanthanum chloride solution B are added to deionized water at 70℃ in a parallel flow mode to form a mixed solution C with a pH of 7.5; the amount of the deionized water added is 10vol% of the total volume of the precipitant solution A and the aqueous lanthanum chloride solution B.

[0090] The dropping speed is adjusted so that the molar ratio of the lanthanum ions in the aqueous lanthanum chloride solution B to the NH4+ ions in the precipitant solution A added to the deionized water per minute is 1:3.05. The dropping time of the precipitant solution A and the aqueous lanthanum chloride solution B is 100min, and after the dropping is completed, the reaction product is left to stand for 2h, and then filtered, washed with water, and dried at 60℃ to obtain lanthanum hydroxycarbonate particles. +

[0091] The lanthanum hydroxycarbonate particles prepared by the method of the present application have an ellipsoidal appearance observed by a scanning electron microscope. The detailed properties are shown in Table 2.

[0092] Comparative Example 1

[0093] A precipitant solution A of 1.1L prepared by mixing ammonia water and ammonium bicarbonate at a molar ratio of 2:1 is provided, and the ionic concentration of the NH4+ ions in the precipitant solution A is 5.13mol / L. +

[0094] An aqueous lanthanum chloride solution B of 1L is provided, and the concentration of the lanthanum chloride is 1.71mol / L.

[0095] Under the stirring condition of a stirring speed of 170rpm, the precipitant solution A and the aqueous lanthanum chloride solution B are added to deionized water at 70℃ in a parallel flow mode to form a mixed solution C with a pH of 7.5; the amount of the deionized water added is 10vol% of the total volume of the precipitant solution A and the aqueous lanthanum chloride solution B.

[0096] The dropping speed is adjusted so that the molar ratio of the lanthanum ions in the aqueous lanthanum chloride solution B to the NH4+ ions in the precipitant solution A added to the deionized water per minute is 1:3.31. The dropping time of the precipitant solution A and the aqueous lanthanum chloride solution B is 90min, and after the dropping is completed, the reaction product is left to stand for 16h, and then filtered, washed with water, and dried at 60℃ to obtain lanthanum hydroxycarbonate particles. +

[0097] The lanthanum hydroxycarbonate prepared in Comparative Example 1 is a multi-ply self-assembled stack structure with different sizes observed by a scanning electron microscope. The detailed properties are shown in Table 2, Figure 3 Figure 4 and Table 2. ​​​​

[0098] Comparative Example 2

[0099] A solution of precipitant A of 1.5 L was prepared by mixing ammonia water and ammonium bicarbonate in a molar ratio of 2:1, and the ion concentration of NH4 + in the solution of precipitant A was 5.34 mol / L.

[0100] A solution of lanthanum chloride B of 1.5 L was prepared by dissolving lanthanum chloride in water, and the concentration of lanthanum chloride was 1.78 mol / L.

[0101] The solution of precipitant A and the solution of lanthanum chloride B were added dropwise to deionized water at 40°C in a concurrent manner under stirring at a stirring speed of 180 rpm to form a mixed solution C with a pH of 7.2, and the amount of deionized water added was 15 vol% of the total volume of the solution of precipitant A and the solution of lanthanum chloride B.

[0102] The dropping speed was adjusted so that the molar ratio of lanthanum ions in the solution of lanthanum chloride B to NH4 + in the solution of precipitant A added dropwise to the deionized water per minute was 1:3. The dropping time of the solution of precipitant A and the solution of lanthanum chloride B was 100 min, and after the dropping was completed, the reaction product was allowed to stand for 16 h, and then was filtered, washed with water, and dried at 60°C to obtain lanthanum hydroxycarbonate particles.

[0103] The lanthanum hydroxycarbonate prepared in Comparative Example 2 was spherical in shape and had a particle size of 0.2-1 μm and a non-uniform particle size distribution. The detailed properties are shown in Table 1 and Table 2. Figure 5

[0104] The lanthanum hydroxycarbonate particles prepared in Examples 1-3 were subjected to powder X-ray diffraction test, and the diffraction pattern thereof was identical to the diffraction pattern of the powder diffraction file with card No. 49-0981. Figure 1

[0105] Table 1

[0106]

[0107] As shown in Table 1-2, the dropping speed of the solution of precipitant A and the solution of lanthanum chloride B was controlled so that the molar ratio of La 3+ in the solution of lanthanum chloride B to NH4 + in the solution of precipitant A added dropwise to water per minute was 1:2.95-3.05, and the reaction temperature was 45-70°C, and the lanthanum hydroxycarbonate particles obtained were ellipsoidal in shape, had a uniform particle size distribution, and were easy to filter.

[0108] The dropping speed of the solution of precipitant A and the solution of lanthanum chloride B was controlled so that the molar ratio of lanthanum ions in the solution of lanthanum chloride B to NH4​​+ The molar ratio of La(NO3)3.6H2O and Na2CO3 is 1:3.31, resulting in the obtained basic lanthanum carbonate particles in a multi-layer self-assembled stacked structure, uneven particle size distribution, and not easy to filter.

[0109] The reaction temperature of Comparative Example 2 is lower, resulting in the obtained basic lanthanum carbonate particles in a spherical shape, uneven particle size distribution, and very difficult to filter by vacuum filtration.

[0110] Table 2

[0111]

[0112] As shown in Table 2, the basic lanthanum carbonate prepared in Examples 1-3 is in an ellipsoidal structure, the particle size is 1-4.5 μm, the particle size distribution α meets 1.1≤α≤1.5, and the REO value is greater than 70.2 wt%. The basic lanthanum carbonate prepared in the present application is easy to filter and has high purity.

[0113] The present application is not limited to the above-described embodiments, and any modification, improvement, or replacement conceived by those skilled in the art without departing from the essential content of the present application falls within the scope of the present application.

Claims

1. A method for producing particles of basic lanthanum carbonate, characterized by, The method comprises the following steps: Under the stirring condition of a stirring speed of 170-250 rpm, precipitant solution A containing ammonia and ammonium bicarbonate and lanthanum chloride aqueous solution B are added dropwise in a parallel flow manner into water at a temperature of 45-70 ℃ to form mixed solution C at a pH of 6.7-7.5; the precipitant solution A is formed from ammonia and ammonium bicarbonate at a molar ratio of 1.8-2.5:1; in the lanthanum chloride aqueous solution B, the concentration of lanthanum chloride is 1.0-2.2 mol / L; and the amount of water at a temperature of 45-70 ℃ is 5-15 vol% of the total volume of the precipitant solution A and the lanthanum chloride aqueous solution B; wherein the dropping speed of the precipitant solution A and the aqueous lanthanum chloride solution B is controlled so that the molar ratio of lanthanum in the aqueous lanthanum chloride solution B to NH4 + in the precipitant solution A dropped into water at a temperature of 45 to 70°C per minute is 1:2.95 to 3.05; the dropping time of the precipitant solution A containing ammonia water and ammonium bicarbonate and the aqueous lanthanum chloride solution B is 70 to 100 minutes; wherein the concentration of NH4 + is 3-7 mol / L; After the dropwise addition of the precipitant solution A containing ammonia and ammonium bicarbonate and the lanthanum chloride aqueous solution B is completed, the stirring is continued for 25-35 min, and then the slurry is aged at room temperature for 2-20 h to obtain an aged slurry; the aged slurry is filtered, washed and dried to obtain the basic lanthanum carbonate particles; The basic lanthanum carbonate particles have an ellipsoidal appearance, a particle size of 1-4.5 μm, and a particle size distribution α that meets the following conditions: a = D max / D min , 1.1≤α≤1.5； wherein D max represents the maximum size of the lanthanum hydroxycarbonate particles; D min represents the minimum size of the lanthanum hydroxycarbonate particles.

2. The production method according to claim 1, characterized by, The particle size distribution meets the following conditions: 1.16≤α≤1.2。 3. The preparation method according to claim 1, characterized in that, The particle size is 1-1.2 μm, 3-3.5 μm or 2.8-4.0 μm.

4. The process according to any one of claims 1 to 3, characterized in that, The total amount of rare earths in the basic lanthanum carbonate particles, as calculated in terms of REO, is greater than 70.2 wt%.

5. The preparation method according to claim 1, characterized in that, The filtration is not performed by centrifugal separation.

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