Method for preparing lanthanum carbonate tetrahydrate based on amorphous lanthanum carbonate precursor aging method

Abstract

The invention relates to a preparation method of lanthanum carbonate tetrahydrate, which comprises the following steps: by taking an ammonium bicarbonate solution as a precipitator and a lanthanum salt solution as a raw material, adding the ammonium bicarbonate solution into the lanthanum salt solution (70-100 DEG C) in a forward precipitation manner, preparing amorphous lanthanum carbonate precursor precipitate after feeding is finished, and aging for 2-8 hours at the temperature of 10-59 DEG C to obtain the lanthanum carbonate tetrahydrate. Filtering, washing and drying the lanthanum carbonate tetrahydrate precipitate to obtain the lanthanum carbonate tetrahydrate compound. The method has the advantages of simple and controllable process, low preparation cost and high product purity, and is suitable for industrial production of pharmaceutical grade phosphate adsorbents.

Description

Technical Field

[0001] This invention belongs to the field of rare earth material preparation technology, specifically relating to a method for preparing lanthanum carbonate tetrahydrate by aging an amorphous lanthanum carbonate precursor, which is applicable to the industrial production of pharmaceutical-grade phosphate adsorbents. Background Technology

[0002] In recent years, metallurgical products containing the highly abundant rare earth element lanthanum have faced a severe market surplus, resulting in prices remaining below cost for an extended period. However, novel lanthanum carbonate salts, due to their unique properties, have shown broad application prospects in several high-value-added fields. For example, lanthanum carbonate tetrahydrate (La2(CO3)3·4H2O) can combine with abnormally high levels of phosphate in patients with renal failure to form insoluble lanthanum phosphate, which exhibits low toxicity, high efficiency, and good tolerability. The US FDA has approved its use for the treatment of hyperphosphatemia.

[0003] Currently, the preparation of La2(CO3)3·4H2O mainly involves drying lanthanum carbonate octahydrate (La2(CO3)3·8H2O) to remove some of its water of crystallization, as described in patent US5968976 by Barry Amurrer et al. of Anor Med Inc. and Chinese patent CN201110287012.3. However, this method is prone to problems such as poor uniformity of the product's water of crystallization. Chinese patent CN202011271874.2 describes obtaining lanthanum carbonate tetrahydrate by refluxing lanthanum carbonate octahydrate in organic solvents such as alcohols (60-100℃). However, the reflux crystallization method requires sophisticated equipment and has limited production efficiency. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing lanthanum carbonate tetrahydrate based on the aging of amorphous lanthanum carbonate precursor, aiming to solve the defects of existing methods such as inconsistent crystal water in the product and high equipment requirements.

[0005] To achieve the above objectives, this invention proposes a method for preparing lanthanum carbonate tetrahydrate based on the aging of an amorphous lanthanum carbonate precursor. The lanthanum carbonate tetrahydrate is used as a pharmaceutical-grade phosphate adsorbent. The method includes the following steps: (1) heating a lanthanum salt solution to 70-100°C and adding an ammonium bicarbonate solution at 30-40°C until the pH is 6.5-7.0 to generate an amorphous lanthanum carbonate precursor; (2) aging the precursor at 10-59°C for 2-8 hours under stirring to obtain a lanthanum carbonate tetrahydrate precipitate; (3) filtering, washing, and vacuum drying the precipitate at 40-60°C to obtain the lanthanum carbonate tetrahydrate compound.

[0006] Preferably, the lanthanum salt in step (1) is lanthanum chloride or lanthanum nitrate.

[0007] Preferably, in step (1), the concentration of the lanthanum salt solution is 0.01-2.0 mol / L and the concentration of the ammonium bicarbonate solution is 0.1-2.0 mol / L.

[0008] Preferably, the stirring conditions in step (2) are 200-1000 rad / min.

[0009] Preferably, the washing method in step (3) is as follows: the filter cake obtained from the initial separation is re-pulped and stirred with purified water to form a slurry suspension, and ultrasonic assistance with a frequency of 100-600Hz is applied for 1 minute, and then the filtration separation is performed again; this process is repeated several times.

[0010] Preferably, drying in step (3) takes 2-6 hours.

[0011] The beneficial effects that this invention can achieve are as follows: This invention, for the first time, uses amorphous lanthanum carbonate prepared by a simple precipitation method under ambient pressure as a precursor. By controlling the aging temperature, it successfully synthesizes pure phases of La2(CO3)3·4H2O with different morphologies. The morphology transforms from a layered structure to nanosheets with increasing aging temperature. This method is simple and controllable, has low preparation cost, and produces high-purity products, making it suitable for the industrial production of pharmaceutical-grade phosphate adsorbents. Attached Figure Description

[0012] Figure 1 The precursor phases after aging at different temperatures are: a) unaged; b) 20℃; c) 40℃; d) 58℃; e) 80℃.

[0013] Figure 2 SEM images of samples aged at different temperatures for 8 hours are shown below: a) Unaged; b) 20℃; c) 40℃; d) 58℃; e) 80℃.

[0014] Figure 3 The thermogravimetric analysis (TGA) diagram of the lanthanum carbonate tetrahydrate compound prepared in Example 1 is shown. Detailed Implementation

[0015] The present invention will be further illustrated by the following examples, but is not limited thereto.

[0016] Example 1: 1. Take 500 mL of 0.1 mol / L LaCl3 solution and keep it at a constant temperature of 80℃ in a water bath; 2. Under magnetic stirring at 1000 rad / min, a 0.5 mol / L NH4HCO3 solution at 40℃ was added dropwise to a LaCl3 solution at a rate of 5 ml / min using a peristaltic pump until the pH reached 7.0. The feed was then stopped, resulting in a white amorphous lanthanum carbonate precipitate. The XRD pattern is shown below. Figure 1As shown in a, the morphology is as follows Figure 2 As shown in a; 3. The solution containing amorphous lanthanum carbonate precipitate was cooled to 20°C and aged at 20°C for 8 hours under magnetic stirring at 1000 rad / min. The mixture was then filtered. The filter cake was re-slurried and stirred with purified water to form a slurry suspension. Ultrasonic stimulation at 200 Hz was applied for 1 minute, followed by another filtration separation. This process was repeated four times to obtain the final filter cake.

[0017] 4. The filter cake was vacuum dried at 60℃ for 4 hours to obtain a white powder of lanthanum carbonate tetrahydrate. The XRD pattern is shown below. Figure 1 As shown in b, the morphology is as follows Figure 2 As shown in b.

[0018] Example 2: The aging temperature was adjusted to 40°C, and the remaining steps were the same as in Example 1. The XRD pattern is shown below. Figure 1 As shown in c, the morphology is as follows Figure 2 As shown in c.

[0019] Example 3: The aging temperature was adjusted to 58°C, and the remaining steps were the same as in Example 1. The XRD pattern is shown below. Figure 1 As shown in d, the morphology is as follows Figure 2 As shown in d.

[0020] Comparative Example 1: The aging temperature was adjusted to 80°C, and the remaining steps were the same as in Example 1. The final product obtained was LaCO3OH.

[0021] Comparative Example 2 1. Take 500 mL of 0.1 mol / L LaCl3 solution and keep it at a constant temperature of 40℃ in a water bath; 2. Under magnetic stirring conditions of 1000 rad / min, a 0.5 mol / L NH4HCO3 solution at 40℃ was added dropwise to a LaCl3 solution at a rate of 5 ml / min using a peristaltic pump until the pH reached 7.0. The feed was then stopped, and a white crystalline lanthanum carbonate precipitate was formed, with the phase being La2(CO3)3·8H2O. 3. The solution containing La2(CO3)3·8H2O precipitate was aged at 20℃ for 8 hours under magnetic stirring at 1000 rad / min, then filtered. The filter cake was re-slurried and stirred with purified water to form a slurry suspension. Ultrasonic stimulation at 200 Hz was applied for 1 minute, followed by filtration again. This process was repeated 4 times. The filter cake was then vacuum dried at 60℃ for 4 hours to obtain a La2(CO3)3 product containing x ions of water of crystallization. Since the number of ions of water of crystallization was not exactly four, it did not meet the requirements for pharmaceutical-grade phosphate adsorbents.

[0022] Figure 1a represents the XRD pattern of the amorphous lanthanum carbonate precipitate formed at the end of the feeding process. Figure 1 b, 1c, and 1d are XRD patterns of solutions containing amorphous lanthanum carbonate precursor aged at 20, 40, and 58 °C for 8 h, respectively. The peak positions of these three XRD patterns are consistent. The XRD patterns show obvious characteristic peaks at diffraction angles of 2θ, namely 13.5°, 18.4°, 19.7°, 22.9°, 24.0°, 27.1°, 28.0°, 30.3°, 39.3°, and 42.5°, with the strongest characteristic peak at 2θ=13.5°. By comparing with patent US 20230227322A1, the phase is determined to be the pure phase La2(CO3)3·4H2O. Figure 1 e is the XRD spectrum of a solution containing an amorphous lanthanum carbonate precursor aged at 80°C for 8 hours, with the phase being LaCO3OH.

[0023] Figure 2 a shows the SEM morphology of the amorphous lanthanum carbonate precursor, which is a hard aggregated state formed by the aggregation of nano-spherical particles; Figure 2 b, 2c, and 2d are SEM images of La2(CO3)3·4H2O obtained by aging a solution containing amorphous lanthanum carbonate precursor at 20, 40, and 58 °C for 8 h, respectively. Its morphology changes from a layered structure to nanosheets as the aging temperature increases. Figure 2 e is a SEM image of LaCO3OH obtained by aging a solution containing amorphous lanthanum carbonate precursor at 80℃ for 8h, showing the aggregated state formed by nanoparticles.

[0024] To further determine the water of crystallization content in the product obtained in Example 1, the decomposition process of the prepared La2(CO3)3·4H2O was analyzed using thermogravimetric analysis (TG). The thermogravimetric analysis results are shown below. Figure 3 As shown, in the first stage from 30 ℃ to 350 ℃, La2(CO3)3·4H2O loses 4 water molecules of crystallization, and the measured weight decreases by 13.6%, which is consistent with the theoretical calculation value, indicating that the sample is indeed the pure phase of La2(CO3)3·4H2O.

[0025] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing lanthanum carbonate tetrahydrate based on the aging of amorphous lanthanum carbonate precursor, characterized in that, The lanthanum carbonate tetrahydrate is used in pharmaceutical-grade phosphate adsorbents. The method includes the following steps: (1) heating the lanthanum salt solution to 70-100℃ and adding ammonium bicarbonate solution at 30-40℃ until the pH is 6.5-7.0 to generate an amorphous lanthanum carbonate precursor; (2) aging the precursor at 10-59℃ for 2-8 hours under stirring to obtain lanthanum carbonate tetrahydrate precipitate; (3) filtering, washing and vacuum drying the precipitate at 40-60℃ to obtain lanthanum carbonate tetrahydrate compound.

2. The method according to claim 1, characterized in that, In step (1), the lanthanum salt is either lanthanum chloride or lanthanum nitrate.

3. The method according to claim 1, characterized in that, In step (1), the concentration of the lanthanum salt solution is 0.01-2.0 mol / L, and the concentration of the ammonium bicarbonate solution is 0.1-2.0 mol / L.

4. The method according to claim 1, characterized in that, The stirring conditions in step (2) are 200-1000 rad / min.

5. The method according to claim 1, characterized in that, The washing method in step (3) is as follows: the filter cake obtained from the initial separation is re-pulped and stirred with purified water to form a slurry suspension, and ultrasonic assistance with a frequency of 100-600Hz is applied for 1 minute, and then the filtration separation is performed again; this process is repeated several times.

6. The method according to claim 1, characterized in that, Dry for 2-6 hours in step (3).

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