A method for preparing low-chlorine precipitated lanthanum carbonate

Abstract

The application belongs to the field of rare earth smelting, and particularly discloses a preparation method of low-chlorine precipitated lanthanum carbonate, which comprises the following steps: preparing a precipitant, a mixed solution of sodium bicarbonate and sodium carbonate and an additive A; adding bottom water and crystal seeds into a reaction tank; preparing a material solution, adding an additive B into the lanthanum chloride material solution; under heating, the precipitant and the material solution are added into the reaction tank in a parallel flow mode; after the reaction is completed, the precipitate is filtered out and washed with clean water for more than five times, and the obtained product is placed into an oven for drying. The obtained product is the low-chlorine precipitated lanthanum carbonate with REO of 52-56%, chlorine ions of 0.005%-0.015% and calcium ions less than 0.015%. The preparation method has the advantages of simple process and convenient operation, and can prepare the low-chlorine and low-calcium lanthanum carbonate from the high-concentration and high-calcium-content lanthanum chloride material solution used in industrial production; and the precipitated lanthanum carbonate has very low contents of chlorine ions and calcium ions, and can meet the requirements of the La2O3-4N grade in the national standard GB / T 4154-2015 after calcination.

Description

Technical Field

[0001] This invention relates to the field of rare earth smelting and separation, and particularly to a method for preparing low-chlorine precipitated lanthanum carbonate from light rare earths. Background Technology

[0002] Rare earth elements possess unique optical, electrical, and magnetic properties, and are widely used in materials, catalysts, metallurgy, and pharmaceutical chemistry. Lanthanum, in particular, is widely used in optical glass, catalysts, phosphors, and pharmaceuticals. Currently, industrially, lanthanum chloride is mainly precipitated by extraction to obtain rare earth salt solids, which are then calcined at high temperatures to obtain lanthanum oxide. The quality of the precursor, lanthanum carbonate, is closely related to the final lanthanum oxide product. Common precipitation methods for preparing lanthanum carbonate industrially include oxalic acid precipitation and carbonate precipitation. While oxalic acid precipitation offers better crystallization and lower impurity content, it is unsuitable for inexpensive rare earth elements due to the high cost of raw materials, complex post-processing, high overall cost, and significant environmental impact. Carbonate precipitation is currently the mainstream process for precipitating lanthanum chloride, and commonly used precipitants include ammonium bicarbonate, sodium bicarbonate, magnesium bicarbonate, and sodium carbonate. The ammonium bicarbonate precipitation method results in high nitrogen content in industrial wastewater. To meet environmental protection requirements, additional nitrogen-containing wastewater treatment equipment is needed, which is costly and requires a large area. Sodium bicarbonate and magnesium bicarbonate precipitants produce lanthanum carbonate crystals with larger grains, but require large quantities and are costly. Furthermore, magnesium bicarbonate is unstable and its preparation process is complex, thus limiting the industrial application of this technology. Sodium carbonate precipitant is inexpensive and requires less reagent, but it easily forms amorphous flocculent precipitates and has poor crystallization, making product filtration difficult and resulting in low purity. Moreover, high-concentration, high-impurity lanthanum chloride solutions are commonly used industrially as raw materials, typically yielding lanthanum carbonate products with high chloride and calcium ion content. With societal development, the market demand for low-chloride lanthanum carbonate products is increasing daily. Therefore, there is an urgent need for a simple method to precipitate high-concentration, high-impurity lanthanum chloride solutions to obtain low-chloride lanthanum carbonate precipitate. Summary of the Invention

[0003] This invention discloses a method for preparing low-chlorine precipitated lanthanum carbonate to solve any of the above-mentioned and other potential problems in the prior art.

[0004] To achieve the above objectives, the technical solution of the present invention is: a method for preparing low-chlorine precipitated lanthanum carbonate, the preparation method comprising the following steps:

[0005] S1) Prepare a mixed precipitant;

[0006] S2) Add seed crystals and bottom water to the reaction vessel;

[0007] S3) Lanthanum chloride solution and additive B are mixed in a certain proportion to obtain a mixed solution;

[0008] S4) The precipitant obtained in S1) and the mixed liquid obtained in S3) are added to the reaction vessel of S2) in a parallel flow, and heated to a certain temperature at the same time to obtain precipitate residue and supernatant.

[0009] S5) Wash the precipitate obtained in S4) with water several times, dry the product, and collect the product to obtain precipitated lanthanum carbonate.

[0010] Furthermore, the yield of precipitated lanthanum carbonate in the preparation method is 95-99%, and the REO content in the precipitated lanthanum carbonate is 52-56%.

[0011] Further, the mixed precipitant in S1) includes a mixed solution of sodium bicarbonate and sodium carbonate, and additive A, wherein the total concentration of sodium carbonate and sodium bicarbonate in the mixed solution is 80-200 g / L, and the content of additive A is 0.1-20% mol of the total amount of lanthanum chloride to be precipitated.

[0012] Furthermore, the additive A is one or more of sodium acetate, sodium hydroxide, sodium nitrate, sodium sulfate, sodium dodecyl sulfonate, sodium benzenesulfonate, potassium sulfate, sodium ethoxide, and sodium citrate.

[0013] Furthermore, the seed crystal added in S2) is lanthanum carbonate, and the amount added is 5-20% of the theoretical product mass;

[0014] The bottom water consists of lanthanum chloride solution and clean water; the lanthanum chloride solution accounts for 1%-30% of the bottom water volume.

[0015] Furthermore, the lanthanum chloride solution in S3) is an industrially produced lanthanum chloride solution with a concentration of 1-2 mol / L, and the calcium ion content in the solution does not exceed 4 g / L;

[0016] The content of additive B is 0.005-1% of the concentration of lanthanum chloride.

[0017] Furthermore, the additive B is one or more of polyvinyl alcohol, ethanol, polyvinylpyrrolidone, dodecyl alcohol, and hexamethylphosphoric triamine.

[0018] Furthermore, in step S4), the volume ratio of the mixed precipitant to the mixed liquid is within V. 沉淀剂 V 料液 =1:1 to 3:1;

[0019] The reaction temperature is 30-60℃, and the concurrent flow rate ratio is V. 沉淀剂 V 料液 =1:1 to 2:1.

[0020] A low-chlorine precipitated lanthanum carbonate, wherein the precipitated lanthanum carbonate is prepared by the above-described preparation method.

[0021] The chloride ion content in the precipitated lanthanum carbonate is between 0.005% and 0.015%, and the calcium ion content is less than 0.015%.

[0022] Compared with the prior art, the advantages of the present invention are: the high concentration and high calcium content of lanthanum chloride solution produced in the present invention is used to prepare lanthanum carbonate with low chlorine and low calcium content.

[0023] The additives A and B used in this invention can be directly added to the precipitant and the liquid, making the preparation simple, the operation convenient, the price low, and significantly reducing the chloride and calcium ion content.

[0024] The method used in this invention can precipitate up to all of the lanthanum chloride, and the wastewater can be discharged after simple treatment;

[0025] The precipitated lanthanum carbonate obtained by this invention has extremely low chloride and calcium ion content, and after calcination, it can meet the requirements of the national standard GB / T4154-2015 for the La2O3-4N grade. Attached Figure Description

[0026] Figure 1 This is a flowchart of a method for preparing low-chlorine precipitated lanthanum carbonate according to the present invention. Detailed Implementation

[0027] The technical solution of the present invention will be further described below with reference to specific embodiments, but the scope of protection is not limited to the description.

[0028] like Figure 1 As shown, this invention discloses a method for preparing low-chlorine precipitated lanthanum carbonate, which includes the following steps:

[0029] S1) Prepare a mixed precipitant;

[0030] Specifically, the process involves preparing a mixed solution of sodium carbonate and sodium bicarbonate with a total concentration of 80-200 g / L. Then, 0.1-20% mol of additive A (based on the total amount of lanthanum chloride to be precipitated) is added to the mixed solution to obtain a mixed precipitant. The addition of additive A reduces the inclusion of lanthanum carbonate during the precipitation and crystallization process through complexation with lanthanum ions, thereby lowering the chloride and calcium ion content in the precipitated lanthanum carbonate.

[0031] S2) Add seed crystals and bottom water to the reaction vessel; wherein, the amount of seed crystals added is 5-20% of the theoretical product mass; the lanthanum chloride solution occupies 1%-30% of the bottom water volume, and is ready for use;

[0032] S3) Select a lanthanum chloride solution with a concentration of 1-2 mol / L and a calcium ion content of no more than 4 g / L. Add additive B to the lanthanum chloride solution so that the content of additive B is 0.005-1% of the concentration of lanthanum chloride. After mixing, a mixed solution is obtained. The addition of additive B reduces the surface tension of the lanthanum chloride solution, which is more conducive to the precipitation and crystallization process.

[0033] S4) Mix the precipitant and the mixture liquid at a volume ratio of V 沉淀剂 V 料液 The mixture is prepared in a ratio of 1:1 to 3:1, and at a reaction temperature of 30-60℃, with a co-current flow rate ratio of V. 沉淀剂 V 料液 =1:1 to 2:1, after being added to the reaction vessel, precipitate residue and supernatant are obtained; by controlling the concentration and rate of addition of precipitant and lanthanum chloride solution, the concentration of precipitant and lanthanum chloride solution and the reaction pH during the lanthanum carbonate precipitation and crystallization process are controlled, so that the reaction is carried out within the optimal pH range;

[0034] S5) The precipitate residue is washed with clean water more than five times, the product is dried and collected to obtain precipitated lanthanum carbonate. After multiple washings, further impurities are removed from the precipitate residue.

[0035] The yield of precipitated lanthanum carbonate in the preparation method is 95-99%, and the REO content in the precipitated lanthanum carbonate is 52-56%.

[0036] Additive A is one or more of sodium acetate, sodium hydroxide, sodium nitrate, sodium sulfate, sodium dodecyl sulfonate, sodium benzenesulfonate, potassium sulfate, sodium ethoxide, and sodium citrate.

[0037] Additive B is one or more of polyvinyl alcohol, ethanol, polyvinylpyrrolidone, dodecyl alcohol, and hexamethylphosphoric triamine.

[0038] A low-chlorine precipitated lanthanum carbonate, wherein the precipitated lanthanum carbonate is prepared by the above-described preparation method.

[0039] The chloride ion content in the precipitated lanthanum carbonate is between 0.005% and 0.015%, and the calcium ion content is less than 0.015%.

[0040] Example 1: Take 30 L of 1.4 M LaCl3 solution (CaO content 4 g / L) and add 0.01% HMPA (hexamethylphosphoric triamine) additive. Prepare 60 L of 77 g / L sodium carbonate and 33 g / L sodium bicarbonate solution, and add 5% sodium sulfate. Add 3 L LaCl3 solution, 40 L water, and 1 kg lanthanum carbonate seed crystals to the bottom water and heat to 45-50 °C. Add the LaCl3 solution and precipitant in parallel using a peristaltic pump at a flow rate ratio of 150 ml / min:180 ml / min. After the precipitant is added, continue stirring for 30-60 min, followed by aging for at least 2 h. Filter using a centrifuge, wash with hot water at 50-60 °C, repeat 5-6 times, and collect the product and dry it in a 50 °C forced-air dryer for 6 h. The obtained lanthanum carbonate product has REO 53.68%, Cl- 0.0062%, and CaO 0.01%.

[0041] Example 2: Take 30 L of 1.6 M LaCl3 solution (CaO content 4 g / L) and add 0.05% polyvinylpyrrolidone as an additive. Prepare 90 L of 72 g / L sodium carbonate and 31 g / L sodium bicarbonate solution. Add 3 L of LaCl3 solution, 40 L of water, and 1 kg of lanthanum carbonate seed crystals to the bottom water and heat to 45-50 °C. Add the LaCl3 solution and precipitant in parallel using a peristaltic pump at a flow rate ratio of 150 ml / min:250 ml / min. After the precipitant is added, continue stirring for 30-60 min, followed by aging for at least 2 h. Filter using a centrifuge, wash with hot water at 50-60 °C, repeat 5-6 times, and collect the product and dry it in a 50 °C forced-air dryer for 6 h. The obtained lanthanum carbonate product has REO 55.24% and Cl - 0.0054%, CaO 0.01%.

[0042] Example 3: Take 30 L of 1.48 M LaCl3 solution (CaO content 4 g / L) and add 2% ethanol. Prepare 50 L of 77 g / L sodium carbonate and 33 g / L sodium bicarbonate solution. Add 3 L of LaCl3 solution, 40 L of water, and 1 kg of lanthanum carbonate seed crystals to the bottom water and heat to 45-50 °C. Add the LaCl3 solution and precipitant in parallel using a peristaltic pump at a flow rate ratio of 150 ml / min:180 ml / min. After the precipitant is added, continue stirring for 30-60 min, followed by aging for at least 2 h. Filter using a centrifuge, wash with hot water at 50-60 °C, repeat 5-6 times, and collect the product and dry it in a 50 °C forced-air dryer for 6 h. The obtained lanthanum carbonate product has REO 51.98%, Cl- 0.0061%, and CaO 0.012%.

[0043] Example 4: Take 30 L of 1.45 M LaCl3 solution (CaO content 4 g / L) and add 1% ethanol as an additive. Prepare 60 L of 77 g / L sodium carbonate and 33 g / L sodium bicarbonate solution and add 2% sodium nitrate. Add 3 L of LaCl3 solution, 40 L of water, and 1 kg of lanthanum carbonate seed crystals to the bottom water and heat to 45-50 °C. Add the LaCl3 solution and precipitant in parallel using a peristaltic pump at a flow rate ratio of 150 ml / min:180 ml / min. After the precipitant is added, continue stirring for 30-60 min, followed by aging for at least 2 h. Filter using a centrifuge, wash with hot water at 50-60 °C, repeat 5-6 times, and collect the product and dry it in a 50 °C forced-air dryer for 6 h. The obtained lanthanum carbonate product has REO 53.98%, Cl- 0.0058%, and CaO 0.011%.

[0044] Example 5: Take 30 L of 1.45 M LaCl3 solution (CaO content 4 g / L) and add 1% polyvinyl alcohol as an additive. Prepare 60 L of 77 g / L sodium carbonate and 33 g / L sodium bicarbonate solution and add it. Add 3 L of LaCl3 solution, 40 L of water, and 1 kg of lanthanum carbonate seed crystals to the bottom water and heat to 45-50 °C. Add the LaCl3 solution and precipitant in parallel using a peristaltic pump at a flow rate ratio of 120 ml / min:150 ml / min. After the precipitant is added, continue stirring for 30-60 min, followed by aging for at least 2 hours. Filter using a centrifuge, wash with hot water at 50-60 °C, repeat 5-6 times, and collect the product and dry it in a 50 °C forced-air dryer for 6 hours. The obtained lanthanum carbonate product has REO 53.98% and Cl - 0.0057%, CaO 0.011%.

[0045] Comparative Example 6: Take 30 L of 1.56 M LaCl3 solution (CaO content 4 g / L). Prepare 50 L of 130 g / L sodium carbonate and 56 g / L sodium bicarbonate solution. Add 3 L of LaCl3 solution, 40 L of water, and 1 kg of lanthanum carbonate seed crystals to the bottom water and heat to 45-50 °C. Add the LaCl3 solution and precipitant in parallel using a peristaltic pump at a flow rate ratio of 150 ml / min:210 ml / min. After the precipitant is added, continue stirring for 30-60 min, followed by aging for at least 2 h. Filter using a centrifuge, wash with hot water at 50-60 °C, repeat 5-6 times, and collect the product. Dry in a 50 °C forced-air dryer for 6 h. The obtained lanthanum carbonate product has REO 53.81%, Cl- 0.036%, and CaO 0.024%.

[0046] Example 7: Take 30 L of 1.56 M LaCl3 solution (CaO content 4 g / L), add 0.05% HMPA (hexamethylphosphoric triamine) and 1% ethanol as additives. Prepare 50 L of 130 g / L sodium carbonate and 56 g / L sodium bicarbonate solution, add 5% sodium sulfate as additive. Add 3 L of LaCl3 solution, 40 L of water, and 1 kg of lanthanum carbonate seed crystals to the bottom water, and heat to 45-50 °C. Add the LaCl3 solution and precipitant in parallel using a peristaltic pump, with a flow rate ratio of 150 ml / min:210 ml / min. After the precipitant is added, continue stirring for 30-60 min, followed by aging for at least 2 h. Filter using a centrifuge, wash with hot water at 50-60 °C, repeat 5-6 times, and collect the product and dry it in a 50 °C forced-air dryer for 6 h. The obtained lanthanum carbonate product has REO 54.01% and Cl - 0.013%, CaO 0.012%.

[0047] Table 1 compares the effects of additives on impurities such as chloride ions in precipitated lanthanum carbonate products:

[0048]

[0049]

[0050] The preparation method of low-chlorine precipitated lanthanum carbonate provided in the embodiments of this application has been described in detail above. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​this application; at the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​this application. Therefore, the content of this specification should not be construed as a limitation of this application.

[0051] Certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The terms "comprising" and "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising / including but not limited to". "Approximately" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect within a certain margin of error. The following descriptions in the specification are preferred embodiments for carrying out this application; however, these descriptions are for the purpose of illustrating the general principles of this application and are not intended to limit the scope of this application. The scope of protection of this application shall be determined by the appended claims.

[0052] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the product or system that includes said element.

[0053] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0054] The foregoing description illustrates and describes several preferred embodiments of this application. However, as previously stated, it should be understood that this application is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the application concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of this application should be within the protection scope of the appended claims.

Claims

1. A method for preparing low-chlorine precipitated lanthanum carbonate, characterized by, The method comprises the following steps: S1) preparing a mixed precipitant; The mixed precipitant comprises a mixed solution of sodium bicarbonate and sodium carbonate, and an additive A, wherein the total concentration of sodium carbonate and sodium bicarbonate in the mixed solution is 80-200 g / L, and the content of the additive A is 0.1-20 mol% of the total amount of the precipitated lanthanum chloride required; The additive A is one or more of sodium acetate, sodium hydroxide, sodium nitrate, sodium sulfate, sodium dodecyl sulfonate, sodium benzenesulfonate, potassium sulfate, sodium ethoxide, and sodium citrate; S2) adding seed crystals and bottom water into a reaction tank; S3) mixing lanthanum chloride feed liquid with an additive B in a certain proportion to obtain a mixed feed liquid; The additive B is one or more of polyvinyl alcohol, ethanol, polyvinylpyrrolidone, dodecanol, and hexamethylphosphorus triamide; S4) adding the mixed precipitant obtained in S1) and the mixed feed liquid obtained in S3) into the reaction tank in a co-current manner, and heating to a certain temperature to obtain a precipitate and a supernatant; S5) filtering the precipitate obtained in S4) and washing it with clean water for multiple times, drying the obtained product, and collecting the product to obtain low-chlorine precipitated lanthanum carbonate.

2. The production method according to claim 1, characterized by, The yield of the low-chlorine precipitated lanthanum carbonate in the preparation method is 95-99%, and the REO in the precipitated lanthanum carbonate is 52-56%.

3. The preparation method according to claim 1, characterized in that, The seed crystals added in S2) are lanthanum carbonate, and the amount added is 5-20% of the theoretical mass; The bottom water is lanthanum chloride feed liquid and clean water; the volume of the lanthanum chloride feed liquid accounts for 1-30% of the volume of the bottom water.

4. The preparation method according to claim 1, characterized in that, The lanthanum chloride feed liquid in S3) is an industrially produced lanthanum chloride feed liquid, and the concentration thereof is 1-2 mol / L, and the calcium ion content in the feed liquid is not more than 4 g / L; The content of the additive B is 0.005-1% of the concentration of the lanthanum chloride.

5. The preparation method according to claim 1, characterized in that, The volume ratio of the mixed precipitant and the mixed solution in S4) is V 沉淀剂 : V 料液 = 1:1 ~ 3:1; The reaction temperature is 30-60 o C, and the concurrent flow rate ratio is V 沉淀剂 : V 料液 = 1:1 ~ 2:1.

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