CN102442692B - Preparation method of lanthanum carbonate hydrate - Google Patents

Abstract

The invention relates to a preparation method of lanthanum carbonate hydrate, comprising the following steps: 1) adding sodium bicarbonate solution into lanthanum chloride solution to prepare lanthanum carbonate octahydrate; Stable lanthanum carbonate containing 1 to 4 waters can be prepared by dehydration under certain conditions. The present invention also relates to octahydrated lanthanum carbonate La ₂ (CO ₃ ) ₃ ·8H ₂ O and lanthanum carbonate La ₂ (CO ₃ ) ₃ ·xH ₂ O containing 1 to 4 waters (where x is in 1-4), and the application of the lanthanum carbonate hydrate in the preparation of a medicament for treating hyperphosphatemia. The invention also relates to a judging method for detecting whether basic lanthanum carbonate is included in the lanthanum carbonate by calculating the carbon-lanthanum molar ratio of the lanthanum carbonate sample.

Description

The preparation method of lanthanum carbonate hydrate

technical field

The present invention relates to a preparation method of lanthanum carbonate hydrate, and lanthanum carbonate octahydrate La ₂ (CO ₃ ) ₃ 8H ₂ O obtained by the preparation method, lanthanum carbonate La ₂ (CO ₃ ) containing 1 to 4 water ) ₃ ·xH ₂ O (wherein x is between 1-4), the present invention also relates to a method for judging whether lanthanum carbonate is mixed with basic lanthanum carbonate.

Background technique

Chronic kidney disease is a common public health problem all over the world. One of its main complications is hyperphosphatemia caused by the inability of the kidneys to excrete phosphate in the body, resulting in elevated phosphate levels in the blood. The symptoms of hyperphosphatemia are mainly blood phosphate levels that exceed normal levels, and may be related to secondary hyperparathyroidism, metabolic bone disease, soft tissue calcification, and cardiovascular calcification. the

At present, the treatment of hyperphosphatemia mainly includes dietary control of phosphorus intake, phosphorus removal by dialysis, application of phosphorus binders, and removal of parathyroid glands when necessary. However, 90% to 95% of patients with end-stage renal disease treat hyperphosphatemia by taking phosphorus binders to reduce intestinal absorption of phosphorus. Phosphorus binders are mainly divided into two types: traditional aluminum or calcium-containing phosphorus binders and non-aluminum, non-calcium phosphorus binders. Aluminum-containing phosphorus binders such as aluminum hydroxide, aluminum carbonate, etc., if taken for a long time, will cause aluminum poisoning, causing microcytic anemia, osteomalacia, Alzheimer's disease, etc. And calcium-containing phosphorus binders such as calcium carbonate, calcium acetate, etc., if used for a long time, will increase the absorption of calcium in the intestine and cause hypercalcemia, causing heart and blood vessel calcification. Therefore, the ideal binder for the treatment of hyperphosphatemia should be non-aluminum and non-calcium. Lanthanum carbonate is one of them. the

Lanthanum is a rare earth element with a strong affinity for oxygen donor atoms. Lanthanum salts can combine with phosphate in food to form a lanthanum phosphate complex, which can reduce the level of phosphate in the blood by hindering the absorption of phosphate. Lanthanum carbonate (LC) is currently one of the relatively mature non-aluminum and non-calcium phosphate binders. It has little absorption in the gastrointestinal tract and little accumulation in tissues in the body. It will not cause vascular calcification and other side effects. The tolerance is also good, and it will surely become a new drug for the treatment of hyperphosphatemia. The US FDA approved lanthanum carbonate for clinical use in October 2004. So far, there have been many reports on the treatment of hyperphosphatemia with lanthanum carbonate. However, lanthanum ion is a hard Lewis acid, which has a strong ability to combine with hydroxide. If you do not pay attention to the conditions when preparing lanthanum carbonate, it is easy to generate basic lanthanum carbonate. So far, basic carbonate has not been approved by the US FDA to treat hyperphosphatemia, and its safety in humans has not been confirmed. For the health and safety of patients with hyperphosphatemia, it is necessary to develop a reliable method for avoiding the generation of lanthanum carbonate in the process of preparing lanthanum carbonate. the

The preparation method about lanthanum carbonate in the prior art generally all uses sodium carbonate as raw material to prepare. For example, someone reported in a patent the method of preparing lanthanum carbonate by reacting Na ₂ CO ₃ with LaCl ₃ , but repeating this method found that a certain amount of La(OH)CO ₃ was mixed in the generated lanthanum carbonate precipitate. In addition, the lanthanum carbonate sample produced by the existing method has relatively large particles, most of which are 3-4 μm. Large particles will result in a relatively small surface area, and the effect of absorbing and adsorbing phosphate is not good. Therefore, the existing lanthanum carbonate preparation method cannot guarantee that the prepared lanthanum carbonate does not contain basic lanthanum carbonate.

Contents of the invention

The purpose of the present invention mainly provides a kind of method that can avoid the preparation lanthanum carbonate hydrate that basic lanthanum carbonate generates. the

The inventor noticed that the Na ₂ CO ₃ aqueous solution is alkaline, and the pH value of the solution would easily increase if not controlled during the reaction process, resulting in inclusion of La(OH)CO ₃ in the formed precipitate. The inventor has found through research that if _NaHCO3 and _LaCl3 are used as raw materials to prepare lanthanum carbonate, in the preparation process, the following two parallel reactions will take place:

(1) NaHCO ₃ reacts with LaCl ₃ to release H ⁺ ,

(2) H ⁺ will react with HCO ₃ ^- to generate water and CO ₂ .

These two reactions are in dynamic equilibrium during the preparation of lanthanum carbonate, and the reaction can be carried out at a lower pH, thereby avoiding the generation of basic lanthanum carbonate while preparing lanthanum carbonate. the

The invention provides a kind of preparation method of lanthanum carbonate hydrate, comprises the following steps:

Step 1), adding sodium bicarbonate solution into lanthanum chloride solution to prepare lanthanum carbonate octahydrate, La ₂ (CO ₃ ) ₃ 8H ₂ O, the characteristic peaks of its infrared spectrum are mainly at 850.3cm ^-1 and 746.6cm ^-1 and 678.6cm ^-1 , and there are also characteristic peaks at 1477.9cm ^-1 and 1377.7cm ^-1 ; the La ³⁺ concentration of the lanthanum chloride solution is 0.5-5mol/L; and

Step 2), then dehydration at normal pressure, 40-120°C, preferably 50-100°C, more preferably 60-80°C, to prepare stable lanthanum carbonate containing 1-4 water, La ₂ (CO ₃ ) ₃ ·xH ₂ O, where x is between 1-4, the characteristic peaks of its infrared spectrum are mainly at 849.6cm ^-1 , 747.4cm ^-1 and 681.0cm ^-1 ; in addition at 1483.4cm ^-1 and 1394.9cm ^-1 There are also characteristic peaks.

Wherein, in step 1), the equation that generates lanthanum carbonate octahydrate is as follows:

H ⁺ +HCO ^- ＝H ₂ O+CO ₂ ↑

2La ³⁺ +3HCO ₃ ^- ＝La ₂ (CO ₃ ) ₃ ↓+3H ⁺

2La ³⁺ +6HCO ₃ ^- ＝La ₂ (CO ₃ ) ₃ ↓+3H ₂ O+3CO ₂ ↑

It can be seen from the equation that there are two reactions in the solution, one is the reaction of La ³⁺ and HCO ₃ ^- to form La ₂ (CO ₃ ) ₃ precipitation, and the other is the acid-base neutralization of HCO ₃ ^- and H ⁺ in the solution reaction. One of the above two parallel reactions is an acid-base neutralization reaction, and the reaction speed is very fast; the other is a precipitation formation reaction, and the reaction hardly proceeds under the condition that there is no lanthanum carbonate crystal nucleus in the reaction system. When the speed of adding sodium bicarbonate is slow, because there is no lanthanum carbonate crystal nucleus to generate, the precipitation reaction does not proceed, so the added sodium bicarbonate only participates in the acid-base neutralization reaction, so that the pH of the solution can rise in the initial stage of the reaction. To about 5.5 without the formation of lanthanum carbonate precipitate (see Figure 1).

In this case, due to the higher pH value of the system, the risk of inclusion of basic lanthanum carbonate in the prepared lanthanum carbonate product is greater. In order to avoid the above risks, we take the following measures:

According to the present invention, in step 1), first add lanthanum chloride aqueous solution in the reactor, its La concentration is ^0.5-5mol /L, preferably 1-3mol/L, more preferably 2mol/L, pH is 0-3 .

Wherein, in step 1), the addition of aqueous sodium bicarbonate solution is divided into two stages:

In the initial stage, first quickly add a small amount of sodium bicarbonate aqueous solution to the aqueous lanthanum chloride solution at a time, the concentration of which is 0.2-4mol/L, preferably 0.3-3mol/L, more preferably 1mol/L, and the aqueous sodium bicarbonate solution accounts for The volume of the aqueous solution is 0.05-0.4, preferably 0.1-0.3, more preferably 0.15-0.25, most preferably 0.2. the

In this case, when a small amount of sodium bicarbonate solution was quickly added at one time, the pH value of the solution rose to about 3, and flocculent La ₂ (CO ₃ ) ₃ precipitates appeared at the same time. This is because a part of NaHCO ₃ neutralizes the H ⁺ in the system, which increases the pH value of the solution. On the other hand, the addition of pulsed NaHCO ₃ will cause a higher local concentration of NaHCO ₃ in the reaction system, which will promote HCO ₃ ^- and La ^{3 +} reaction to generate lanthanum carbonate nuclei.

Then, with 0.01mL/s-10mL/s, preferably 0.05mL/s-5mL/s, more preferably 0.08mL/s-2mL/s, most preferably 0.1mL/s-1mL/s speed to lanthanum chloride Sodium bicarbonate solution was added dropwise in the solution until the reaction stopped when the inflection point appeared in the pH value. the

During this process, the pH value of the reaction system decreased after further adding HCO ₃ ^- , which was mainly due to the reaction of HCO ₃ ^- and La ³⁺ to generate La ₂ (CO ₃ ) ₃ and release a large amount of H ⁺ . With the further addition of sodium bicarbonate, the amount of La ₂ (CO ₃ ) ₃ produced in the solution reaction system increases continuously, but the pH value of the system remains basically unchanged, which is due to the acid-base neutralization reaction and precipitation reaction reaching a Due to dynamic equilibrium, the entire La ₂ (CO ₃ ) ₃ generation reaction is carried out at a lower pH (such as around 4). When the La ³⁺ in the system is completely converted into La ₂ (CO ₃ ) ₃ precipitates, with the further addition of NaHCO ₃ , the pH of the system rises abruptly, so the end of the reaction can be judged by the last jump .

According to the present invention, in step 1), after the reaction stops, the filtrate is sucked and washed three times with distilled water, and the octahydrate lanthanum carbonate filter cake is placed in a ventilated place to dry naturally. According to infrared spectrum identification, the infrared spectrum characteristic peaks of the octahydrate lanthanum carbonate are mainly at 850.3cm ^-1 , 746.6cm ^-1 and 678.6cm ^-1 , and there are also characteristic peaks at 1477.9cm ^-1 and 1377.7cm ^-1 .

In step 2), in order to dehydrate the eight-hydrated lanthanum carbonate formed in step 1), according to the present invention, octahydrated lanthanum carbonate is placed in an oven under normal pressure at a temperature of 40 to 120° C., preferably 50 to 100 °C, more preferably 60-80 °C for 18-24 hours, you can get a more stable lanthanum carbonate containing 1-4 water, La ₂ (CO ₃ ) ₃ ·xH ₂ O, where x is between 1-4 , preferably x is 1.5-3.5, more preferably x is 2.5-3.4, most preferably x is 3.3.

According to infrared spectrum identification, the ^infrared spectrum characteristic peaks of lanthanum carbonate containing 1 ^to 4 waters are mainly at 849.6cm ^-1 , 747.4cm ^-1 and 681.0cm ^-1 ; Characteristic peaks.

The lanthanum carbonate hydrate obtained in the present invention, especially the lanthanum carbonate containing 1 to 4 hydrates, can be used for preparing medicine for treating hyperphosphatemia. The inventor's research also found that the lanthanum carbonate can be better used to treat hyperphosphatemia after further treatment, specifically, for the larger lanthanum carbonate sample prepared by the direct method, if the method of ball milling is adopted for the treatment of hyperphosphatemia. Grinding the sample can make the sample particles smaller, even reaching the nanometer level, and its surface area is significantly increased, so that it can better absorb and adsorb phosphate, so it has good performance in drugs for the treatment of hyperphosphatemia treatment effect. the

Therefore, in order to prepare nanoscale lanthanum carbonate, according to the present invention, the lanthanum carbonate obtained by step 2) containing 1 to 4 waters is placed in a ball mill for ball milling for 1-5 hours, preferably 1.5-3 hours, most preferably 2 hours, to obtain Lanthanum carbonate particles with a particle size of 100-400 nm, preferably 200-300 nm. The lanthanum carbonate nanoparticle can be used to prepare medicine for treating hyperphosphatemia. the

In addition, the molar ratio of carbon to lanthanum in the prepared product can be determined by elemental analysis and EDTA titration. In theory, if the prepared sample is octahydrate lanthanum carbonate, the molecular formula is La ₂ (CO ₃ ) ₃ ·8H ₂ O, so the carbon lanthanum in the molecule The molar ratio should be 3/2=1.5, and if the prepared sample is basic lanthanum carbonate (molecular formula is La(OH)CO ₃ ) or doped with basic lanthanum carbonate, the carbon lanthanum mol ratio in the sample will be less than 1.5, Specifically, when the molar ratio of carbon to lanthanum is 1.0, the sample is lanthanum subcarbonate; when the molar ratio of carbon to lanthanum is between 1.0 and 1.5, the lanthanum carbonate is doped with lanthanum subcarbonate.

Therefore the present invention also provides a kind of judging method of whether inclusion basic lanthanum carbonate is detected in lanthanum carbonate, it is characterized in that, calculate the carbon lanthanum mol ratio of lanthanum carbonate, when carbon lanthanum mol ratio is 1.5, then do not mix basic lanthanum carbonate, When the molar ratio of carbon to lanthanum is less than 1.5, basic lanthanum carbonate is mixed. the

The present invention uses the carbon-lanthanum molar ratio of the sample as a criterion to detect, for example, whether lanthanum carbonate raw material is mixed with basic lanthanum carbonate, and has the characteristics of simple operation and accurate and reliable results. the

The innovation of the present invention is mainly reflected in the following aspects:

1. To avoid the formation of basic lanthanum carbonate, we use NaHCO ₃ instead of Na ₂ CO ₃ , so two parallel reactions occur during the preparation process: (1) H ⁺ is released in the reaction of NaHCO ₃ and LaCl ₃ , (2) H ⁺ reacts with HCO ₃ ^2- to generate water and CO ₂ . These two reactions are in dynamic equilibrium during the preparation of lanthanum carbonate, which can make the reaction proceed at a lower pH, thereby avoiding the generation of basic lanthanum carbonate.

2. One of the above two parallel reactions is an acid-base neutralization reaction, and the reaction speed is very fast; the other is a precipitation formation reaction, and the reaction is hardly carried out under the condition that there is no lanthanum carbonate crystal nucleus in the reaction system. In order to promote the normal carrying out of the second reaction, at the beginning of the reaction, a certain amount of _NaHCO was added quickly once in the _LaCl solution at the beginning of the reaction. Add NaHCO ₃ aqueous solution drop by drop to the LaCl ₃ solution to make the newly formed lanthanum carbonate precipitate epitaxially grow on the initial crystal nucleus. Only like this, two parallel reactions in the system are carried out synchronously, thereby the pH value of reaction system is realized dynamic balance, thereby prepares lanthanum carbonate under lower pH environment.

3. The pH value of the solution is monitored throughout the process, and the pH-reaction time curve of the entire reaction process is drawn. When the lanthanum ions in the system are completely converted into lanthanum carbonate, the pH of the system will suddenly jump. This jump can be used as a criterion to stop the reaction. the

4. Using the pH-reaction time curve of the reaction process, the production automation of lanthanum carbonate can be realized. the

5. After the product prepared by the direct method is sucked and filtered, lanthanum carbonate octahydrate (La ₂ (CO ₃ ) ₃ 8H ₂ O) can be obtained, and lanthanum carbonate octahydrate is placed at normal pressure, 40-120°C, preferably 50-100°C, More preferably, dehydration at 60-80°C can produce more stable and medicinally valuable La ₂ (CO ₃ ) ₃ ·xH ₂ O, wherein x is between 1-4, preferably x is 1.5-3.5, more preferably x is 2.5-3.4, most preferably x is 3.3.

Description of drawings

Figure 1: Add volume-pH change curve in the process of slowly adding NaHCO ₃ ;

Fig. 2: The time-pH change curve of direct method preparation octahydrate lanthanum carbonate;

Fig. 3: Direct method synthesis octahydrate lanthanum carbonate compares with standard card (25-1400);

Figure 4: Infrared spectrum of lanthanum carbonate octahydrate;

Figure 5: Infrared spectrum of lanthanum subcarbonate;

Figure 6: Infrared spectrum of lanthanum carbonate containing 1 to 4 water; the lanthanum carbonate in this figure contains 3.3 water, and its characteristic wavenumber is in the low band;

Figure 7: SEM image of hydrous lanthanum carbonate;

Figure 8: SEM image of nanoparticle lanthanum carbonate obtained after ball milling;

Figure 9: The thermogravimetric curve of lanthanum carbonate octahydrate;

Fig. 10: The thermogravimetric curve of the lanthanum carbonate containing 1～4 water;

Figure 11: standard curve of phosphate;

Figure 12: Phosphate adsorption curve at pH 3.0;

Figure 13: Phosphate adsorption curve at pH5.4;

Figure 14: XRD pattern of nanoparticles. the

Detailed ways

The present invention is further described by the following examples, but the present invention is not limited to these embodiments. the

1. Characterization experiment of lanthanum carbonate

1. XRD

X-ray polycrystal diffractometer (XRD, Rigaku Dmax-2000): CuK Monochromatic radiation source, accelerating voltage 40KV, current 150mV, used to determine the crystal form and its change, crystallinity and crystallization perfection of the sample. Scanning range: 5~60°, using continuous scanning mode. And compared with La ₂ (CO ₃ ) ₃ ·8H ₂ O standard card 25-1400.

2. Titration and elemental analysis

2.1 The experiment uses EDTA to titrate the sample to obtain the content of lanthanum element

Prepare 250mL 0.02mol/L zinc standard solution:

The standard zinc oxide was dried in a muffle furnace at 1000°C for 5 hours, cooled to 120°C, placed in a desiccator, and cooled to room temperature. Weigh 0.8118g of zinc oxide, add hydrochloric acid to dissolve it, dilute to 250mL, and prepare a zinc solution with a concentration of 1.995×10 ^-2 M

Prepare EDTA solution:

Weigh 7.4464g of EDTA and dissolve it in 1000mL of water. the

EDTA calibration:

Use a pipette to draw 20.00mL Zn ²⁺ standard solution into the conical flask, add 2 drops of xylenol orange indicator, add 200g/L hexamethylenetetramine dropwise until the solution becomes stable purple, then add 5mL Methylenetetramine. Titrate with EDTA, when the solution changes from purple to yellow, it is the end point. Measured three times in parallel.

Determination of La ³⁺ content:

Weigh a certain amount of sample, add hydrochloric acid to dissolve it completely, set the volume to 100.00mL, draw 15.00mL with a pipette, and titrate with EDTA. Measured three times in parallel. the

2.2 Elemental analysis

Use the vario EL elemental analyzer (Elementar Analysensysteme GmbH) to analyze the elements of samples C and H to obtain the carbon content and hydrogen content of the sample, and at the same time, the amount of water in the sample can be calculated through the H content. the

3. Infrared spectroscopy

NICOLET iN10 MX micro-infrared spectrometer from Thermo Scientific Company was used; detector: MCT/A; beam splitter: KBr/Ge; number of scans: 64; resolution: 4cm ^-1 .

4. SEM (scanning electron microscope) to observe the particle size

JSM-6700F Field Emission Scanning Electron Microscope produced by JEOL Company was used, and the accelerating voltage was 5kV. the

5. Thermogravimetric Characterization

The Q600SDT TGA-DTA-DSC synchronous analyzer from Thermal Analysis Company of the United States was used, the scanning range was 10°C--1000°C, and the heating rate was 10°C/min. the

Two, preparation embodiment

Example 1:

First add 50 mL of lanthanum chloride aqueous solution into the flask, its La ³⁺ concentration is 2 mol/L, and its pH is 0-2. At the beginning, first quickly add 10 mL of sodium bicarbonate aqueous solution to the lanthanum chloride aqueous solution at one time, and its concentration is 1mol/L. At this time, the pH value of the solution has a sudden rise to about 3, and flocculent La ₂ ( CO ₃ ) ₃ precipitates. Then add sodium bicarbonate solution to the lanthanum chloride solution at a speed of 0.08mL/s until the pH value shows an inflection point, and the reaction stops when the pH value rises abruptly, and a total of 320mL of sodium bicarbonate solution is added. Figure 2 shows the time-pH curve for the preparation of lanthanum carbonate octahydrate by the direct method.

The filtrate was suction filtered, washed three times with distilled water, and the filter cake was placed in a ventilated place to dry naturally. the

Figure 3 shows the obtained lanthanum carbonate octahydrate (labeled 03-25) compared with the standard card (25-1400). It can be seen that the peak positions are basically the same, and the matching degree with the standard card is about 920 (the value is 1000 for 100% matching). the

Table 1 shows the results of EDTA titration of La content in La ₂ (CO ₃ ) ₃ ·8H ₂ O.

Table 1

Table 3 shows the elemental analysis results of lanthanum carbonate octahydrate before and after drying and dehydration. the

table 3

Put the obtained lanthanum carbonate octahydrate in an oven, keep it at a certain temperature under normal pressure for 18 hours, and obtain lanthanum carbonate containing 1 to 4 water, specifically, when the temperature is 55°C, you can get lanthanum carbonate containing 3. The lanthanum carbonate of 3 waters, when this temperature is 75 ℃, obtains the lanthanum carbonate that contains 2.5 waters, and when this temperature is 120 ℃, obtains the lanthanum carbonate that contains 1 water. the

Table 4 shows the changes in C and La content of the samples before and after drying. the

Table 4

It can be seen that there is basically no lanthanum carbonate subsistence. the

Fig. 4 is the infrared spectrum of octahydrate lanthanum carbonate,

Fig. 5 is the infrared spectrum of basic lanthanum carbonate,

Fig. 6 is the infrared spectrum of lanthanum carbonate containing 1 to 4 waters. the

It can be seen that, at lower wavenumbers, the characteristic peaks of lanthanum carbonate octahydrate are respectively at 850, 746, and 678cm ^-1 , while the characteristic peaks of lanthanum carbonate basic are at 858,724, and 696cm ^-1 ; The product obtained was lanthanum carbonate rather than lanthanum hydroxycarbonate.

Figure 7 is an SEM image of hydrous lanthanum carbonate. It can be seen from Figure 7 that the sample has a sheet-like structure with a particle size of 3-4 μm. the

The prepared lanthanum carbonate containing 1 to 4 water is placed in a ball mill and ball milled for 2 hours to obtain lanthanum carbonate particles with a size of 200 to 300 nm. the

Figure 8 is the SEM of the nanoparticle lanthanum carbonate obtained after ball milling. It can be seen from Fig. 8 that nanoscale particles are obtained after ball milling, and the sample particles become 200-300 nm. the

Fig. 9 is the thermogravimetric curve of octahydrate lanthanum carbonate;

Fig. 10 is the thermogravimetric curve of lanthanum carbonate containing 1 to 4 waters. the

Example 2:

First add 50 mL of lanthanum chloride aqueous solution to the flask, the La ³⁺ concentration is 2.5 mol/L, and the pH is 1.5. At the beginning, add 15mL sodium bicarbonate aqueous solution to the lanthanum chloride aqueous solution at one time quickly, and its concentration is 0.81mol/L _. (CO ₃ ) ₃ precipitates. Then add sodium bicarbonate solution to the lanthanum chloride solution at a rate of 2 mL/s until the pH value shows an inflection point, and the reaction stops when the pH value rises abruptly, and a total of 380 mL of sodium bicarbonate solution is added. The filtrate was suction filtered, washed three times with distilled water, and the filter cake was placed in a ventilated place to dry naturally.

Figure 3 shows the obtained lanthanum carbonate octahydrate (labeled 02-23) compared with the standard card (25-1400). It can be seen that the peak positions are basically the same, and the matching degree with the standard card is about 920. the

Put the obtained lanthanum carbonate octahydrate in an oven, keep it at a certain temperature under normal pressure for 24 hours, and obtain lanthanum carbonate with 1 to 4 hydrates. Specifically, when the temperature is 60°C, you can get The lanthanum carbonate of water, when this temperature is 75 ℃, obtains the lanthanum carbonate that contains 2.4 waters, and when this temperature is 110 ℃, obtains the lanthanum carbonate that contains 1.5 waters. the

The prepared lanthanum carbonate of 1-4 water is placed in a ball mill and ball-milled for 3 hours to obtain lanthanum carbonate particles of 200-300 nm. the

Table 2 EDTA titration results of La content in La ₂ (CO ₃ ) ₃ ·8H ₂ O

Table 2

Example 3:

First add 50 mL of lanthanum chloride aqueous solution to the flask, its La ³⁺ concentration is 1.5 mol/L, and its pH is 1.0. At the beginning, add 8 mL of sodium bicarbonate solution to the aqueous solution of lanthanum chloride quickly at one time, and its concentration is 1.51 mol/L _. (CO ₃ ) ₃ precipitates. Then add sodium bicarbonate solution to the lanthanum chloride solution at a rate of 1.5 mL/s until the pH value shows an inflection point, and the reaction stops when the pH value rises abruptly, and 260 mL of sodium bicarbonate solution is added in total. The filtrate was suction filtered, washed three times with distilled water, and the filter cake was placed in a ventilated place to dry naturally.

Put the obtained lanthanum carbonate octahydrate in an oven, keep it at a certain temperature under normal pressure for 20 hours, and obtain lanthanum carbonate with 3 to 4 water, specifically, when the temperature is 50°C, you can get The lanthanum carbonate of water, when this temperature is 80 ℃, obtain the lanthanum carbonate that contains 2.0 water, when this temperature is 120 ℃, obtain the lanthanum carbonate that contains 1 water. the

The prepared lanthanum carbonate with 1 to 4 water is placed in a ball mill and ball milled for 1.5 hours to obtain lanthanum carbonate particles with a size of 200 to 300 nm. the

3. Application Examples

Phosphate Adsorption Experiment: Determination of Phosphate Content by Molybdenum Antimony Antimolybdenum Blue Photometric Method

Drawing of phosphate standard curve

Take 7 50mL colorimetric tubes, add 1mL ascorbic acid solution to the phosphoric acid standard operating solution 0mL, 0.50mL, 1.00mL, 3.00mL, 5.00mL, 10.00mL, 15.00mL respectively, and mix well. After 30s, add 2mL molybdate solution and mix well. Stand for 15 minutes, measure the absorbance at a wavelength of 700nm with the reagent blank solution as a reference, and draw a standard curve. the

Figure 11 is a phosphate standard curve. the

Phosphate adsorption curve at pH3.0

Prepare acetic acid-lithium hydroxide as 3.0 buffer solution, use molybdenum antimony antimolybdenum blue ultraviolet photometry to measure the phosphate content in the solution, and determine the binding rate of lanthanum carbonate. the

Figure 12 is the pH 3.0 phosphate adsorption curve. the

It can be seen from Figure 12 that an inflection point appeared in the reaction at 10 minutes, 55% of PO ₄ ^3- was converted into LaPO ₄ , and then the reaction speed slowed down, and almost 100% of PO ₄ ^3- in the solution was converted into LaPO ₄ after 4 hours.

Phosphate adsorption curve at pH5.4

Prepare hexamethylenetetramine-HCl as pH5.4 buffer solution, use molybdenum antimony antimolybdenum blue ultraviolet photometry to measure the phosphate content in the solution, and determine the binding rate of lanthanum carbonate. the

Figure 13 is the pH 5.4 phosphate adsorption curve. the

It can be seen from Fig. 13 that under the condition of pH 5.4, the adsorption curve does not have an obvious inflection point, and after 4 hours, the phosphate in the solution has basically been completely adsorbed. the

Claims (6)

1. a preparation method for lanthanum carbonate hydrates, comprises the following steps:

Step 1), sodium bicarbonate solution is added in lanthanum chloride solution to preparation eight artificial lanthanites, La ₂(CO ₃) ₃8H ₂o, its diffuse reflectance infrared spectroscopy peak is mainly at 850.3cm ^-1, 746.6cm ^-1and 678.6cm ^-1, the La of described lanthanum chloride solution ³⁺concentration is 1-3mol/L, and pH is 0-3,

Adding point two stages of sodium bicarbonate aqueous solution:

In the incipient stage, first once in lanthanum chloride solution, add a small amount of sodium bicarbonate aqueous solution fast, its concentration is 0.3-3mol/L, sodium bicarbonate aqueous solution accounts for the 0.15-0.25 of lanthanum chloride solution volume,

Then, then in lanthanum chloride solution, add sodium bicarbonate solution with the speed of 0.08mL/s-2mL/s, until flex point appears in pH value, time reaction stops; With

Step 2), then at normal pressure, under the condition of 60～80 DEG C of temperature, Dehydration is for La ₂(CO ₃) ₃xH ₂o, wherein x is 1.5-3.5, its diffuse reflectance infrared spectroscopy peak is mainly at 849.6cm ^-1, 747.4cm ^-1and 681.0cm ^-1.

2. according to the preparation method of claim 1, it is characterized in that,

Step 1) in, first in reactor, add lanthanum chloride solution, its La ³⁺concentration is 2mol/L, and pH is 0-3;

Adding point two stages of sodium bicarbonate aqueous solution:

In the incipient stage, first once in lanthanum chloride solution, add a small amount of sodium bicarbonate aqueous solution fast, its concentration is 1mol/L, sodium bicarbonate aqueous solution accounts for 0.2 of lanthanum chloride solution volume,

Then, then in lanthanum chloride solution, add sodium bicarbonate solution with the speed of 0.1mL/s-1mL/s, until flex point appears in pH value, time reaction stops.

3. according to the preparation method of claim 1 or 2, it is characterized in that,

Step 1) in, after reaction stops, by filtrate suction filtration, and with distilled water washing three times, eight artificial lanthanite filter cakes are placed on to ventilation and naturally dry.

4. according to the preparation method of claim 1, it is characterized in that,

Step 2) in, eight artificial lanthanites are placed in baking oven, under normal pressure, be to keep 18～24h at 60～80 DEG C in temperature.

5. according to the preparation method of claim 1, it is characterized in that, wherein x is 2.5-3.4.

6. according to the preparation method of claim 1, it is characterized in that, wherein x is 3.3.