Micron-sized lanthanum hydroxide particles and preparation method thereof

Abstract

The invention discloses micron-sized lanthanum hydroxide particles and a preparation method thereof. The preparation method comprises the following steps: 1) dropwise adding a lanthanum salt aqueous solution and ammonia water into water for reaction at a reaction temperature of 30-90 DEG C under a stirring condition, and obtaining a suspension after dropwise adding is finished; wherein in the parallel flow dropwise adding process, the relative dropwise adding speed of the lanthanum salt aqueous solution and the ammonia water is controlled so that the molar ratio of NH3 in the ammonia water to lanthanum ions in the lanthanum salt aqueous solution is larger than 3.0, and the pH value of the reaction system is controlled to be larger than or equal to 7.5 and smaller than or equal to 9.5; 2) directly carrying out solid-liquid separation on the suspension obtained in the step 1) without aging to obtain a solid; and washing and drying the obtained solid to obtain the micron-sized lanthanum hydroxide particles. According to the invention, micron-sized lanthanum hydroxide crystal particles can be obtained.

Description

Technical Field

[0001] The invention relates to micron-sized lanthanum hydroxide particles and a preparation method thereof. Background Art

[0002] Rare earth hydroxide can be used to prepare rare earth oxides. Compared with the use of rare earth carbonate as a precursor to prepare rare earth oxides, rare earth hydroxide has the advantages of less crystal water, higher total rare earth content, lower calcination temperature, and only water as a byproduct without carbon dioxide release.

[0003] However, it is difficult to control the microstructure of rare earth hydroxide. It is easy to form flocculent precipitation or colloid during precipitation, and the particles cannot grow and have poor filtration performance. At present, there are many processes for preparing rare earth hydroxide powder at home and abroad, and the main preparation methods are: chemical precipitation method, hydrothermal method, sol-gel method, microemulsion method, alcohol salt hydrolysis method, electrochemical method, etc. However, they are basically focused on the research and preparation of nano-scale materials.

[0004] CN112811458A discloses a method for preparing a mesoporous rare earth hydroxide nanomaterial, which is to react in a water-cyclohexane system, use hexadecyltrimethylammonium bromide and citric acid as structure directing agents, sodium salicylate as pore expanding agent, rare earth chloride as rare earth source, hexamethylenetetramine or urea as catalyst, and carry out synthesis reaction under heating conditions; the specific steps are as follows: (1) dissolving hexadecyltrimethylammonium bromide, rare earth chloride, citric acid, sodium salicylate, hexamethylenetetramine or urea in water in sequence to obtain a clear solution; (2) adding cyclohexane and stirring and mixing evenly; (3) controlling the temperature to 50-70°C and reacting for 6-7 hours; (4) after the reaction is completed, taking the aqueous phase in the reaction system, centrifuging and washing. The obtained rare earth hydroxide is a spherical nanoparticle with an adjustable size of 100-600nm.

[0005] Lanthanum hydroxide is a very important rare earth hydroxide.

[0006] CN103145167A discloses a controllable synthesis of lanthanum hydroxide nanoparticles, comprising: adding a dispersant to a lanthanum chloride solution under magnetic stirring, stirring until the dispersant is completely dissolved, and slowly dropping a certain concentration of ammonia solution to react for 1 to 3 hours. After cooling, centrifugation is performed to obtain a white precipitate, which is washed with ethanol and water for 3 to 5 times each, and then dried in an oven to obtain dry lanthanum hydroxide nanoparticles with a particle size of about 100 nm.

[0007] CN106219588A discloses a method for preparing rod-shaped lanthanum hydroxide nanomaterials by uniform precipitation oil bath method, comprising the following steps: 1) dissolving La(NO3)3·2H2O in water to prepare a transparent solution A with a concentration of 0.05-1 mol / L; 2) adding diethylenetriamine to the transparent solution A so that the concentration of diethylenetriamine in the solution is 0.005-0.1 mol / L, stirring well to obtain suspension B; 3) placing suspension B in an oil bath pot, reacting at 60-100°C for 2-5 hours, cooling to room temperature after the reaction is completed, centrifuging the reaction product, washing and drying, and obtaining a rod-shaped La(OH)3 nanomaterial. The diameter of the nanomaterial is about 15-40nm.

[0008] CN110563018A discloses a method for preparing highly dispersed nano lanthanum hydroxide, which includes the following steps: 1) dissolving lanthanum salt in water, organic solvent or a mixture of water and organic solvent to obtain lanthanum salt solution; dissolving alkali in water, organic solvent or a mixture of water and organic solvent to obtain alkali solution; 2) adding lanthanum salt solution and alkali solution to a common reactor or a supergravity rotating packed bed for precipitation and crystallization reaction to obtain lanthanum hydroxide suspension; 3) placing lanthanum hydroxide suspension in a constant temperature box for aging treatment; 4) adding a modifier to the slurry after aging treatment for modification; 5) cooling the modified slurry to room temperature, ultrafiltration or centrifugal washing to obtain a filter cake; 6) dispersing the filter cake in a liquid medium to obtain a highly dispersed nano lanthanum hydroxide dispersion; or drying the filter cake to obtain a highly dispersed nano lanthanum hydroxide powder. The one-dimensional size of the lanthanum hydroxide particles obtained by this method is 15 to 250 nm.

[0009] CN111235624A discloses a method for preparing lanthanum hydroxide nano whiskers, comprising the following steps: (1) adding alkali solution dropwise to an ethanol-water solution containing lanthanum salt under stirring conditions to obtain a mixed solution; wherein the alkali solution is a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution, and the pH value of the mixed solution is not less than 7.5; (2) placing the mixed solution in a closed reaction device and heating it to a reaction temperature to react to obtain a reaction mixture; (3) post-treating the reaction mixture to obtain lanthanum hydroxide nano whiskers. The diameter of the obtained lanthanum hydroxide nano whiskers is 30 to 50 nm.

[0010] CN117756161A discloses a method for synthesizing a lanthanum hydroxide nanomaterial, comprising: uniformly mixing a lanthanum salt and a surfactant in water to obtain a mixed solution; adding a precipitant to the mixed solution, adjusting the pH value of the mixed solution to alkaline, and performing a heat-insulating reaction under stirring to obtain a lanthanum hydroxide nanomaterial. The size of the obtained lanthanum hydroxide nanomaterial is 100 to 200 nm.

[0011] So far, there is no report on the preparation of micron-sized lanthanum hydroxide. Summary of the invention

[0012] In view of this, an object of the present invention is to provide a method for preparing micron-sized lanthanum hydroxide particles, wherein the preparation method can obtain micron-sized lanthanum hydroxide particles. 50 Another object of the present invention is to provide a micron-sized lanthanum hydroxide particle prepared according to the preparation method as described above. The present invention adopts the following technical scheme to achieve the above object.

[0013] In one aspect, the present invention provides a method for preparing micron-sized lanthanum hydroxide particles, comprising the following steps:

[0014] 1) adding a lanthanum salt aqueous solution and ammonia water to water in parallel under stirring at a reaction temperature of 30 to 90° C. to react, and obtaining a suspension after the addition is completed;

[0015] wherein water is used as the base liquid; during the co-current dripping process, the relative dripping speeds of the lanthanum salt aqueous solution and the ammonia water are controlled so that the molar ratio of NH3 in the ammonia water to the lanthanum ions in the lanthanum salt aqueous solution is greater than 3.0, and the pH value of the reaction system is controlled to be greater than or equal to 7.5 and less than or equal to 9.5;

[0016] 2) directly subjecting the suspension obtained in step 1) to solid-liquid separation without aging to obtain a solid; washing and drying the obtained solid to obtain micron-sized lanthanum hydroxide particles.

[0017] According to the preparation method of the present invention, preferably, in step 1), the lanthanum salt in the lanthanum salt aqueous solution is selected from one of lanthanum chloride, lanthanum nitrate and lanthanum sulfate.

[0018] According to the preparation method of the present invention, preferably, in step 1), the lanthanum salt aqueous solution is a lanthanum chloride aqueous solution, and the REO concentration in the lanthanum salt aqueous solution is 20-120 g / L.

[0019] According to the preparation method of the present invention, preferably, in step 1), the concentration of ammonia water is 2-6 mol / L.

[0020] According to the preparation method of the present invention, preferably, in step 1), the stirring speed is 150-350 rpm.

[0021] According to the preparation method of the present invention, preferably, in step 1), the pH value of the reaction system is controlled to be greater than or equal to 8.0 and less than or equal to 9.0.

[0022] According to the preparation method of the present invention, preferably, during the co-current dropwise addition process of step 1), the relative dropwise addition speeds of the lanthanum salt aqueous solution and the ammonia water are controlled so that the molar ratio of NH3 in the ammonia water to the lanthanum ions in the lanthanum salt aqueous solution is greater than 3.0 and less than or equal to 5.0.

[0023] According to the preparation method of the present invention, preferably, in step 1), the volume of the bottom liquid water is 3-15% of the volume of the reaction container.

[0024] According to the preparation method of the present invention, preferably, in step 2), the solid is washed with water until the pH of the washing liquid is 7.0; and the drying temperature is 60-120°C.

[0025] On the other hand, the present invention also provides a micron-sized lanthanum hydroxide particle, which is prepared according to the preparation method as described above, and the D of the micron-sized lanthanum hydroxide particle is 50 3~20μm.

[0026] The preparation method of the present invention can obtain micron-sized lanthanum hydroxide crystal particles, and the product particle size distribution is uniform and easy to filter. The preparation method of the present invention does not need to add crystal seeds or perform aging. The preparation method of the present invention is simple, has mild conditions, is easy to control, has low cost, and has industrial promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The particle size distribution diagram of the lanthanum hydroxide products prepared in Examples 1 to 3 and Comparative Example 1.

[0028] Figure 2 The XRD diagram of the lanthanum hydroxide products prepared in Examples 4 to 6.

[0029] Figure 3 This is the XRD diagram of the lanthanum hydroxide product prepared in Comparative Example 2.

[0030] Figure 4 This is a scanning electron microscope image of the lanthanum hydroxide product prepared in Example 2.

[0031] Figure 5 This is a scanning electron microscope image of the lanthanum hydroxide product prepared in Comparative Example 1. DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0033] The present invention provides a method for preparing micron-sized lanthanum hydroxide particles, comprising the following steps: (1) a co-current dripping step; and (2) a post-treatment step. In certain embodiments, the method further comprises a preparation step of a lanthanum salt aqueous solution.

[0034] <Parallel flow dropping step>

[0035] Under the condition of reaction temperature of 30-90°C and stirring, the lanthanum salt aqueous solution and ammonia water are added dropwise to water in parallel for reaction, and a suspension is obtained after the addition is completed. This is conducive to obtaining micron-sized lanthanum hydroxide.

[0036] The present invention drips the lanthanum salt aqueous solution and ammonia water into the bottom liquid water in parallel. The parallel dripping method is very important. The present invention believes that this can ensure that the rare earth ions and the precipitant (ammonia water) react chemically in time and keep the supersaturation of the precipitation reaction crystallization system unchanged, so that the nucleation and growth environment of the lanthanum hydroxide crystals are always maintained stable, which is conducive to the generation of micron-level products with uniform particle size distribution.

[0037] In the present invention, the lanthanum salt aqueous solution can be formed by dissolving a water-soluble lanthanum salt in water and mixing until it is clarified. The lanthanum salt in the lanthanum salt aqueous solution is selected from one of lanthanum chloride, lanthanum nitrate, and lanthanum sulfate, preferably lanthanum chloride. The REO concentration (i.e., in terms of lanthanum oxide concentration) in the lanthanum salt aqueous solution is 20 to 120 g / L, preferably 40 to 110 g / L, more preferably 60 to 110 g / L, and further preferably 80 to 100 g / L.

[0038] According to one embodiment of the present invention, the lanthanum salt aqueous solution is a lanthanum chloride aqueous solution, and its REO concentration is 20-120 g / L.

[0039] In the present invention, the concentration of aqueous ammonia may be 2 to 6 mol / L, preferably 3 to 5 mol / L, and more preferably 3.5 to 4 mol / L.

[0040] In the present invention, water is used as the base liquid. The volume of the base liquid water is 3-15%, preferably 5-10% of the volume of the reaction container. The water can be preferably deionized water, distilled water, or purified water.

[0041] In the process of co-current dripping, the relative dripping speed of the lanthanum salt solution and the ammonia water is controlled so that the molar ratio of NH3 in the ammonia water and the lanthanum ions in the lanthanum salt solution is greater than 3.0, and the pH value of the reaction system is controlled to be greater than or equal to 7.5 and less than or equal to 9.5. The present invention finds that during the dripping process, if the pH value of the reaction system is less than 7.5, basically no precipitation reaction occurs; if the pH value of the reaction system is greater than 9.5, the supersaturation of the reaction system will increase exponentially with the increase of alkalinity, and the supersaturation increases. The product particle size will be reduced to the nanometer level, and it is not easy to filter, and serious hard agglomeration will occur in the drying process, affecting the activity of the product. The present invention also finds that if the molar ratio is too low, lanthanum hydroxide cannot be completely generated. When the lanthanum salt is lanthanum chloride, the molar ratio is too low to easily form La-OH-Cl; if the molar ratio is too high, the lanthanum hydroxide particles formed are too fine.

[0042] In the present invention, preferably, the pH value of the reaction system is controlled to be greater than or equal to 7.5 and less than or equal to 9.0, and more preferably, the pH value of the reaction system is controlled to be greater than or equal to 8.0 and less than or equal to 8.5.

[0043] In the present invention, preferably, during the co-current dropwise addition process, the relative dropwise addition speed of the lanthanum salt aqueous solution and the ammonia water is controlled so that the molar ratio of NH3 in the ammonia water to the lanthanum ions in the lanthanum salt aqueous solution is greater than 3.0 and less than or equal to 5.0. More preferably, the relative dropwise addition speed of the lanthanum salt aqueous solution and the ammonia water is controlled so that the molar ratio of NH3 in the ammonia water to the lanthanum ions in the lanthanum salt aqueous solution is 3.5 to 5.0, and further preferably 4.0 to 5.0.

[0044] The reaction temperature of the present invention can be 30 to 90°C, preferably 40 to 80°C, and more preferably 40 to 60°C. The present invention finds that it is important to control the reaction temperature within the scope of the present invention. If the temperature is too low, the energy provided is not conducive to crystal growth, and if the temperature is too high, the energy provided will cause side reactions. In the present invention, the reaction temperature refers to the temperature of the reaction system during dropwise addition, and when the co-current dropwise addition is started, the temperature of the bottom liquid water is also controlled at 30 to 90°C.

[0045] In the present invention, the stirring speed may be 150 to 350 rpm, preferably 200 to 350 rpm, more preferably 230 to 300 rpm, and further preferably 230 to 250 rpm. This is conducive to obtaining micron-sized lanthanum hydroxide.

[0046] In the present invention, the lanthanum salt aqueous solution and the ammonia water can be controlled to start and end dropping at the same time, which is beneficial to ensure that the environment for generating crystals by precipitation reaction remains unchanged and is also beneficial to realize continuous production.

[0047] In the present invention, the co-current dripping time can be 30 to 280 min, preferably 80 to 250 min, and more preferably 150 to 200 min. Basically, solid-liquid separation is performed after the dripping is completed.

[0048] <Post-processing steps>

[0049] The obtained suspension is directly separated from the solid and liquid without aging to obtain a solid; the obtained solid is washed and dried to obtain micron-sized lanthanum hydroxide particles. The present invention does not require aging and directly separates the solid and liquid. This is conducive to obtaining micron-sized lanthanum hydroxide.

[0050] In the present invention, the solid-liquid separation can be centrifugation or filtration, preferably filtration. The lanthanum hydroxide particles of the present invention are relatively large and easy to filter.

[0051] The obtained solid is washed with water to remove other impurity ions adsorbed or contained in the solid product. The washing is performed until the pH value of the washing liquid is 7.0, that is, washed to neutrality.

[0052] The drying temperature can be 60 to 120° C., preferably 70 to 110° C., more preferably 70 to 100° C., and further preferably 70 to 90° C. Within the drying temperature range of the present invention, both efficient removal of water can be ensured and the agglomeration of lanthanum hydroxide crystal particles can be reduced, thereby improving the uniformity of particle size distribution.

[0053] According to a specific embodiment of the present invention, under the condition of a reaction temperature of 30 to 90° C. and stirring, an aqueous solution of lanthanum chloride and aqueous ammonia are added dropwise to water in parallel for reaction, and a suspension is obtained after the addition is completed;

[0054] wherein water is used as the base liquid; during the cocurrent dropwise addition process, the relative dropwise addition speeds of the lanthanum chloride aqueous solution and the ammonia water are controlled so that the molar ratio of NH3 in the ammonia water to the lanthanum ions in the lanthanum chloride aqueous solution is greater than 3.0, and the pH value of the reaction system is controlled to be greater than or equal to 7.5 and less than or equal to 9.5;

[0055] 2) directly subjecting the suspension obtained in step 1) to solid-liquid separation without aging to obtain a solid; washing and drying the obtained solid to obtain micron-sized lanthanum hydroxide particles.

[0056] In this way, chloride ions do not participate in the coordination chemical reaction to generate La-OH-Cl chemical bonds during the formation of rare earth hydroxide, and exist in an adsorbed or included state. Chloride ions can be removed directly by washing with water, and high-quality, low-impurity micron-sized lanthanum hydroxide crystals can be obtained.

[0057] The median particle size D of the micron-sized lanthanum hydroxide particles obtained by the present invention is 50 In the range of 3 to 20 μm, it is basically a pure La(OH)3 close-packed hexagonal crystal structure with good dispersion performance and complete crystal morphology.

[0058] The test methods used in the following examples and comparative examples are described as follows:

[0059] XRD: The phase structure of the samples was analyzed using an X-ray diffractometer (X'Pert Power, PIXcel1D receiver) from Philips of the Netherlands, using a Cu target.

[0060] SEM: The microstructure and agglomeration of the samples were observed using a field emission scanning electron microscope (ZEISS Sigma500) from Zeiss, Germany.

[0061] PSA: The particle size distribution of the sample was measured by a British Malvern laser particle size analyzer (Mastersizer 3000), with wet sampling and deionized water as the dispersion medium.

[0062] In the following examples, the amount of base liquid water used is: the volume of water is 10% of the volume of the reaction container.

[0063] Example 1

[0064] Under the stirring conditions of a reaction temperature of 50° C. and a stirring speed of 230 rpm, a 100 g / L lanthanum chloride aqueous solution (the concentration of the lanthanum chloride aqueous solution is calculated as lanthanum oxide) and a 4 mol / L ammonia aqueous solution are co-currently added dropwise to water (as a base liquid) for reaction. During the co-current addition, the relative dropping speeds of the lanthanum chloride aqueous solution and the ammonia aqueous solution are controlled so that the molar ratio of NH3 in the ammonia aqueous solution to the lanthanum ion in the lanthanum chloride aqueous solution is 3.2:1, the pH value of the reaction system is controlled to be 7.5, and the dropping is completed for 180 min to obtain a suspension.

[0065] The suspension is directly filtered without aging, and the solid is easily filtered. The solid is washed with water until the pH value of the washing liquid is 7.0. The washed solid is dried at 75° C. to obtain micron-sized lanthanum hydroxide particles.

[0066] The total rare earth content of the obtained micron-sized lanthanum hydroxide particles (referring to the REO content, the same as in Example 1 below) is 80.18 wt %, and the median particle size D 50 The particle size distribution of the obtained product is shown in Figure 1 .

[0067] Example 2

[0068] Under the stirring conditions of a reaction temperature of 50° C. and a stirring speed of 230 rpm, a 100 g / L lanthanum chloride aqueous solution (the concentration of the lanthanum chloride aqueous solution is calculated as lanthanum oxide) and a 4 mol / L ammonia aqueous solution are co-currently added dropwise to water (as a base liquid) for reaction. During the co-current dropping process, the relative dropping speeds of the lanthanum chloride aqueous solution and the ammonia aqueous solution are controlled so that the molar ratio of NH3 in the ammonia aqueous solution to the lanthanum ion in the lanthanum chloride aqueous solution is 4.0:1, the pH value of the reaction system is controlled to be 8.0, and the dropping is completed for 180 min to obtain a suspension.

[0069] The suspension is directly filtered without aging, and the solid is easily filtered. The solid is washed with water until the pH value of the washing liquid is 7.0. The washed solid is dried at 75° C. to obtain micron-sized lanthanum hydroxide particles.

[0070] The total amount of rare earth in the obtained micron-sized lanthanum hydroxide particles is 82.07 wt %, and the median particle size D 50 The particle size distribution of the obtained product is shown in Figure 1 The scanning electron microscopy results of the obtained products are shown in Figure 4 .

[0071] Example 3

[0072] Under the stirring conditions of a reaction temperature of 50° C. and a stirring speed of 230 rpm, a 100 g / L lanthanum chloride aqueous solution (the concentration of the lanthanum chloride aqueous solution is calculated as lanthanum oxide) and a 4 mol / L ammonia aqueous solution are co-currently added dropwise to water (as a base liquid) for reaction. During the co-current addition, the relative dropping speeds of the lanthanum chloride aqueous solution and the ammonia aqueous solution are controlled so that the molar ratio of NH3 in the ammonia aqueous solution to the lanthanum ion in the lanthanum chloride aqueous solution is 4.5:1, the pH value of the reaction system is controlled to be 8.5, and the dropping is completed for 180 min to obtain a suspension.

[0073] The suspension is directly filtered without aging, and the solid is easily filtered. The solid is washed with water until the pH value of the washing liquid is 7.0. The washed solid is dried at 75° C. to obtain micron-sized lanthanum hydroxide particles.

[0074] The total amount of rare earth in the obtained micron-sized lanthanum hydroxide particles is 82.47 wt % and the median particle size D 50 The particle size distribution of the obtained product is shown in Figure 1 .

[0075] Example 4

[0076] Under the stirring conditions of a reaction temperature of 50° C. and a stirring speed of 230 rpm, a 100 g / L lanthanum chloride aqueous solution (the concentration of the lanthanum chloride aqueous solution is calculated as lanthanum oxide) and a 4 mol / L ammonia aqueous solution are co-currently added dropwise to water (as a base liquid) for reaction. During the co-current dropping process, the relative dropping speeds of the lanthanum chloride aqueous solution and the ammonia aqueous solution are controlled so that the molar ratio of NH3 in the ammonia aqueous solution to the lanthanum ion in the lanthanum chloride aqueous solution is 5.0:1, the pH value of the reaction system is controlled to be 9.0, and the dropping is completed for 180 min to obtain a suspension.

[0077] The suspension is directly filtered without aging, and the solid is easily filtered. The solid is washed with water until the pH value of the washing liquid is 7.0. The washed solid is dried at 75° C. to obtain micron-sized lanthanum hydroxide particles.

[0078] The total amount of rare earth in the obtained micron-sized lanthanum hydroxide particles is 83.27 wt % and the median particle size D 50 The XRD results of the obtained product are shown in Figure 2 .

[0079] Example 5

[0080] Under the stirring conditions of a reaction temperature of 60° C. and a stirring speed of 230 rpm, a 100 g / L lanthanum chloride aqueous solution (the concentration of the lanthanum chloride aqueous solution is calculated as lanthanum oxide) and a 4 mol / L ammonia aqueous solution are co-currently added dropwise to water (as a base liquid) for reaction. During the co-current addition, the relative dropping speeds of the lanthanum chloride aqueous solution and the ammonia aqueous solution are controlled so that the molar ratio of NH3 in the ammonia aqueous solution to the lanthanum ion in the lanthanum chloride aqueous solution is 5.0:1, the pH value of the reaction system is controlled to be 9.0, and the dropping is completed for 180 min to obtain a suspension.

[0081] The suspension is directly filtered without aging, and the solid is easily filtered. The solid is washed with water until the pH value of the washing liquid is 7.0. The washed solid is dried at 75° C. to obtain micron-sized lanthanum hydroxide particles.

[0082] The total amount of rare earth in the obtained micron-sized lanthanum hydroxide particles is 83.21wt%, and the median particle size D 50 The XRD results of the obtained product are shown in Figure 2 .

[0083] Example 6

[0084] Under the stirring conditions of a reaction temperature of 70° C. and a stirring speed of 230 rpm, a 100 g / L lanthanum chloride aqueous solution (the concentration of the lanthanum chloride aqueous solution is calculated as lanthanum oxide) and a 4 mol / L ammonia aqueous solution are co-currently added dropwise to water (as a base liquid) for reaction. During the co-current addition, the relative dropping speeds of the lanthanum chloride aqueous solution and the ammonia aqueous solution are controlled so that the molar ratio of NH3 in the ammonia aqueous solution to the lanthanum ion in the lanthanum chloride aqueous solution is 5.0:1, the pH value of the reaction system is controlled to be 9.0, and the dropping is completed for 180 min to obtain a suspension.

[0085] The suspension is directly filtered without aging, and the solid is easily filtered. The solid is washed with water until the pH value of the washing liquid is 7.0. The washed solid is dried at 75° C. to obtain micron-sized lanthanum hydroxide particles.

[0086] The total amount of rare earth in the obtained micron-sized lanthanum hydroxide particles is 82.07 wt %, and the median particle size D 50 The XRD results of the obtained product are shown in Figure 2 .

[0087] Example 7

[0088] The difference from Example 4 is only that the concentration of the lanthanum chloride aqueous solution is 80g / L, and the concentration of ammoniacal liquor is 2mol / L.

[0089] The total amount of rare earth in the obtained lanthanum hydroxide particles is 83.68wt%, and the median particle size D 50It is 9.86μm.

[0090] Comparative Example 1

[0091] The only difference from Example 1 is that during the co-current dropwise addition, the pH value of the reaction system is controlled to be 10.0.

[0092] The total amount of rare earth in the obtained lanthanum hydroxide product is 82.68wt%, and the median particle size D 50 =0.995 μm. The particle size distribution diagram of the obtained product is shown in Figure 1 The SEM results of the obtained products are shown in Figure 5 .

[0093] Comparative Example 2

[0094] The only difference from Example 4 is that the reaction temperature is 95°C.

[0095] The total amount of rare earth in the obtained lanthanum hydroxide product is 76.18wt%, and the median particle size D 50 =18.3μm. XRD results are shown in Figure 3 .Depend on Figure 3 It can be seen that the crystal structure of basic lanthanum chloride appears in the product obtained in this comparative example.

[0096] Table 1

[0097]

[0098] Note: The lanthanum hydroxide product of Comparative Example 2 contains basic lanthanum chloride.

[0099] The present invention is not limited to the above-mentioned embodiments. Without departing from the essential content of the present invention, any deformation, improvement and substitution that can be conceived by those skilled in the art shall fall within the scope of the present invention.

Claims

1. A method for preparing micron-sized lanthanum hydroxide particles, It is characterized in that The steps include: 1) adding a lanthanum salt aqueous solution and ammonia water to water in parallel under stirring at a reaction temperature of 30 to 90° C. to react, and obtaining a suspension after the addition is completed; In which, water is used as the base liquid; during the co-current dripping process, the relative dripping speed of the lanthanum salt aqueous solution and the ammonia water is controlled so that the NH 3 The molar ratio of the lanthanum ions in the aqueous solution of the lanthanum salt is greater than 3.0, and the pH value of the reaction system is controlled to be greater than or equal to 7.5 and less than or equal to 9.5; 2) directly subjecting the suspension obtained in step 1) to solid-liquid separation without aging to obtain a solid; washing and drying the obtained solid to obtain micron-sized lanthanum hydroxide particles.

2. The preparation method according to claim 1, It is characterized in that In step 1), the lanthanum salt in the lanthanum salt aqueous solution is selected from one of lanthanum chloride, lanthanum nitrate and lanthanum sulfate.

3. The preparation method according to claim 1, It is characterized in that In step 1), the lanthanum salt aqueous solution is a lanthanum chloride aqueous solution, and the REO concentration in the lanthanum salt aqueous solution is 20 to 120 g / L.

4. The preparation method according to claim 1, It is characterized in that In step 1), the concentration of aqueous ammonia is 2-6 mol / L.

5. The preparation method according to claim 1, It is characterized in that In step 1), the stirring speed is 150-350 rpm.

6. The preparation method according to claim 1, It is characterized in that In step 1), the pH value of the reaction system is controlled to be greater than or equal to 8.0 and less than or equal to 9.

0.

7. The preparation method according to claim 1, It is characterized in that During the co-current addition process of step 1), the relative dropping speed of the lanthanum salt aqueous solution and the ammonia water is controlled so that the NH 3 The molar ratio of the lanthanum ions to the lanthanum salt aqueous solution is greater than 3.0 and less than or equal to 5.

0.

8. The preparation method according to claim 1, It is characterized in that In step 1), the volume of the bottom liquid water is 3-15% of the volume of the reaction container.

9. The preparation method according to claim 1, It is characterized in that In step 2), the solid is washed with water until the pH of the washing liquid is 7.0; the drying temperature is 60-120°C.

10. A micron-sized lanthanum hydroxide particle, It is characterized in that It is prepared by the preparation method according to any one of claims 1 to 9, and the D of the micron-sized lanthanum hydroxide particles is 50 3~20μm.

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