CN116675242A - Method for preparing hexagonal system lanthanum hydroxycarbonate by adopting hydrothermal synthesis - Google Patents
Method for preparing hexagonal system lanthanum hydroxycarbonate by adopting hydrothermal synthesis Download PDFInfo
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- 229910052746 lanthanum Inorganic materials 0.000 title claims abstract description 34
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 title claims abstract description 34
- NKCVNYJQLIWBHK-UHFFFAOYSA-N carbonodiperoxoic acid Chemical compound OOC(=O)OO NKCVNYJQLIWBHK-UHFFFAOYSA-N 0.000 title claims abstract description 33
- 238000000034 method Methods 0.000 title claims abstract description 30
- 238000001027 hydrothermal synthesis Methods 0.000 title claims abstract description 27
- 238000001556 precipitation Methods 0.000 claims abstract description 62
- 238000006243 chemical reaction Methods 0.000 claims abstract description 53
- NZPIUJUFIFZSPW-UHFFFAOYSA-H lanthanum carbonate Chemical compound [La+3].[La+3].[O-]C([O-])=O.[O-]C([O-])=O.[O-]C([O-])=O NZPIUJUFIFZSPW-UHFFFAOYSA-H 0.000 claims abstract description 40
- 229910017569 La2(CO3)3 Inorganic materials 0.000 claims abstract description 39
- 229960001633 lanthanum carbonate Drugs 0.000 claims abstract description 39
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 33
- 239000008367 deionised water Substances 0.000 claims abstract description 30
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 30
- ICAKDTKJOYSXGC-UHFFFAOYSA-K lanthanum(iii) chloride Chemical compound Cl[La](Cl)Cl ICAKDTKJOYSXGC-UHFFFAOYSA-K 0.000 claims abstract description 23
- 239000007788 liquid Substances 0.000 claims abstract description 21
- 239000013078 crystal Substances 0.000 claims abstract description 20
- 239000002243 precursor Substances 0.000 claims abstract description 11
- 238000001035 drying Methods 0.000 claims abstract description 9
- 238000005406 washing Methods 0.000 claims abstract description 9
- 238000001914 filtration Methods 0.000 claims abstract description 8
- 239000007787 solid Substances 0.000 claims abstract description 8
- 238000005119 centrifugation Methods 0.000 claims abstract description 4
- 238000007865 diluting Methods 0.000 claims abstract description 4
- 239000012467 final product Substances 0.000 claims abstract description 4
- VYGHOXHBHAWHDO-UHFFFAOYSA-K lanthanum(3+);carbonate;hydroxide Chemical compound [OH-].[La+3].[O-]C([O-])=O VYGHOXHBHAWHDO-UHFFFAOYSA-K 0.000 claims abstract description 4
- 238000000967 suction filtration Methods 0.000 claims abstract description 4
- 239000000243 solution Substances 0.000 claims description 55
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 claims description 21
- 239000001099 ammonium carbonate Substances 0.000 claims description 21
- 229910000013 Ammonium bicarbonate Inorganic materials 0.000 claims description 20
- 235000012538 ammonium bicarbonate Nutrition 0.000 claims description 20
- 239000000203 mixture Substances 0.000 claims description 15
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 11
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 11
- 238000003756 stirring Methods 0.000 claims description 10
- 239000011259 mixed solution Substances 0.000 claims description 9
- 229910001404 rare earth metal oxide Inorganic materials 0.000 claims description 8
- 238000010438 heat treatment Methods 0.000 claims description 5
- 239000006228 supernatant Substances 0.000 claims description 4
- 238000002156 mixing Methods 0.000 claims description 3
- 238000004321 preservation Methods 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 abstract description 7
- 239000000047 product Substances 0.000 description 18
- 239000002585 base Substances 0.000 description 16
- 229910052761 rare earth metal Inorganic materials 0.000 description 12
- 239000000463 material Substances 0.000 description 11
- 230000001276 controlling effect Effects 0.000 description 10
- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 description 10
- 238000002360 preparation method Methods 0.000 description 9
- 150000002910 rare earth metals Chemical class 0.000 description 8
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 7
- 239000002994 raw material Substances 0.000 description 7
- DHMQDGOQFOQNFH-UHFFFAOYSA-N Glycine Chemical compound NCC(O)=O DHMQDGOQFOQNFH-UHFFFAOYSA-N 0.000 description 6
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- 239000007864 aqueous solution Substances 0.000 description 6
- UMGDCJDMYOKAJW-UHFFFAOYSA-N thiourea Chemical compound NC(N)=S UMGDCJDMYOKAJW-UHFFFAOYSA-N 0.000 description 6
- 239000012065 filter cake Substances 0.000 description 5
- 238000005086 pumping Methods 0.000 description 5
- 238000002441 X-ray diffraction Methods 0.000 description 4
- -1 rare earth nitrate Chemical class 0.000 description 4
- CDBYLPFSWZWCQE-UHFFFAOYSA-L sodium carbonate Substances [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 4
- 239000000758 substrate Substances 0.000 description 4
- 239000004471 Glycine Substances 0.000 description 3
- 229910002651 NO3 Inorganic materials 0.000 description 3
- 238000002386 leaching Methods 0.000 description 3
- 239000000843 powder Substances 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 230000035484 reaction time Effects 0.000 description 3
- 238000001228 spectrum Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000004202 carbamide Substances 0.000 description 2
- 238000002425 crystallisation Methods 0.000 description 2
- 230000008025 crystallization Effects 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 238000009854 hydrometallurgy Methods 0.000 description 2
- JLRJWBUSTKIQQH-UHFFFAOYSA-K lanthanum(3+);triacetate Chemical compound [La+3].CC([O-])=O.CC([O-])=O.CC([O-])=O JLRJWBUSTKIQQH-UHFFFAOYSA-K 0.000 description 2
- FYDKNKUEBJQCCN-UHFFFAOYSA-N lanthanum(3+);trinitrate Chemical compound [La+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O FYDKNKUEBJQCCN-UHFFFAOYSA-N 0.000 description 2
- 238000001000 micrograph Methods 0.000 description 2
- 230000001376 precipitating effect Effects 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 229910000029 sodium carbonate Inorganic materials 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 235000012501 ammonium carbonate Nutrition 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000012527 feed solution Substances 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 229910052736 halogen Inorganic materials 0.000 description 1
- 150000002367 halogens Chemical class 0.000 description 1
- 238000005286 illumination Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 239000011941 photocatalyst Substances 0.000 description 1
- 238000004886 process control Methods 0.000 description 1
- 238000011112 process operation Methods 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000005185 salting out Methods 0.000 description 1
- 238000004062 sedimentation Methods 0.000 description 1
- 238000003746 solid phase reaction Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 235000012431 wafers Nutrition 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F17/00—Compounds of rare earth metals
- C01F17/20—Compounds containing only rare earth metals as the metal element
- C01F17/247—Carbonates
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F17/00—Compounds of rare earth metals
- C01F17/10—Preparation or treatment, e.g. separation or purification
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/77—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by unit-cell parameters, atom positions or structure diagrams
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/03—Particle morphology depicted by an image obtained by SEM
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/30—Particle morphology extending in three dimensions
- C01P2004/32—Spheres
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/50—Agglomerated particles
Abstract
The invention discloses a method for preparing hexagonal hydroxy lanthanum carbonate by hydrothermal synthesis, which comprises the following steps: diluting lanthanum chloride solution with deionized water in a precipitation reaction kettle to serve as base solution, and adding lanthanum carbonate to serve as seed crystal; adding feed liquid and a precipitant into a precipitation reaction kettle in a parallel flow precipitation mode, generating lanthanum carbonate after precipitation reaction, controlling the time of the precipitation reaction and adjusting the pH value by controlling the input speed of the feed liquid and the precipitant; taking out precipitated lanthanum carbonate in the precipitation reaction kettle, filtering and drying to obtain lanthanum carbonate serving as a precursor; adding lanthanum carbonate and deionized water into a reactor for hydrothermal synthesis reaction, washing the obtained final product with deionized water, and then carrying out suction filtration or centrifugation to obtain a white solid, placing the white solid into an oven, and drying to obtain hexagonal-system lanthanum hydroxycarbonate. The invention has simple production process and is suitable for industrialized mass production of hexagonal hydroxy lanthanum carbonate.
Description
This patent application is application number: 202110525397.6, filing date: 2021, 05, 12, name: a method for preparing hexagonal hydroxy lanthanum carbonate by hydrothermal synthesis.
Technical Field
The invention belongs to the field of hydrometallurgy, and particularly relates to a method for preparing hexagonal system lanthanum hydroxycarbonate by adopting hydrothermal synthesis.
Background
The rare earth luminescent material is mainly applied to rare earth energy-saving lamps and white light LED lamp lighting devices. The rare earth energy-saving lamp is a high-quality and high-efficiency green lighting product, and has the advantages of high light efficiency, energy saving, low light attenuation, long service life and the like compared with fluorescent powder prepared from incandescent lamps and halogen powder. At present, the export quantity of the three-primary-color energy-saving lamp produced in China reaches about 80%, the three-primary-color energy-saving lamp is a global energy-saving light source maximum manufacturing base, and along with the gradual popularization of green illumination, the market demand of the three-primary-color fluorescent powder for the energy-saving lamp in the future is larger.
There are many factors that affect the luminous efficiency of phosphors, and it is particularly important to select a good luminescent matrix. Lanthanum hydroxycarbonate in hexagonal system has a superior crystal structure and is often used as a luminescent substrate for phosphor production.
The literature 'photocatalyst basic lanthanum carbonate and its preparation method and application' is that adding aqueous solution of carbon source (urea or mixture of sodium hydroxide and sodium carbonate) into aqueous solution of lanthanum source (lanthanum oxide, lanthanum nitrate and lanthanum acetate), stirring to react for 30-180 min, then placing the mixed solution into a high-pressure reaction kettle with 90-180 ℃ to keep temperature for 12-24 h, centrifugally washing the obtained precipitate with water and ethanol, drying at 40-120 ℃ for 6-24 h, grinding to obtain basic lanthanum carbonate powder. The precipitant adopts urea or a mixture of sodium hydroxide and sodium carbonate, the feed liquid adopts aqueous solution of lanthanum oxide, lanthanum nitrate and lanthanum acetate, and the hydrothermal reaction is carried out in high-pressure reaction, so that the prepared lanthanum hydroxycarbonate has a non-hexagonal structure.
Chinese publication No. CN101279757a discloses that lanthanum oxide and ammonium bicarbonate or glycine are used as precursors, deionized water is used as a solvent, and the precursors are put into a sealed hydrothermal reaction kettle according to a proportion, wherein the molar ratio of lanthanum oxide to ammonium bicarbonate or glycine is 1: 20-1: 45, placing the hydrothermal reaction kettle of the mixture into a box-type resistance furnace, heating to 150-220 ℃, heating for 8-48 h at the temperature, taking out, and naturally cooling to room temperature to obtain the lanthanum hydroxycarbonate. However, the precursor of lanthanum hydroxycarbonate prepared by the process is lanthanum oxide, so that the process reaction steps and consumption of materials and energy sources are increased, and the product lanthanum hydroxycarbonate has a non-hexagonal crystal structure.
Chinese publication No. CN1369578A discloses that an aqueous solution of rare earth nitrate and thiourea, or an aqueous solution of thiourea and rare earth oxide after being dissolved with nitric acid, is injected into a closed pressure-resistant reactor in which a substrate is placed in advance, and reacts at 150-200 ℃ for not less than 3 hours; and taking out the substrate, washing with water and drying to obtain the rare earth basic carbonate crystal film deposited on the substrate. However, the auxiliary materials required by the equipment and the process are special, and the preparation difficulty and the cost are increased.
At present, in the rare earth hydrometallurgy industry, a hexagonal system lanthanum hydroxycarbonate prepared by normal-pressure hydrothermal synthesis has no description.
Disclosure of Invention
The invention aims to provide a method for preparing hexagonal lanthanum hydroxycarbonate by adopting hydrothermal synthesis, which has the advantages of low cost and easy acquisition of raw materials and auxiliary materials in the production process, simple process control and suitability for industrialized mass production of hexagonal lanthanum hydroxycarbonate.
In order to achieve the above purpose, the technical solution adopted by the invention is as follows:
the method for preparing hexagonal system lanthanum hydroxycarbonate by adopting hydrothermal synthesis comprises the following steps:
diluting lanthanum chloride solution with deionized water in a precipitation reaction kettle to obtain a base solution, wherein the concentration of the base solution is 0.177-0.89 mol/L, adding lanthanum carbonate with the base solution accounting for 10-50wt% as seed crystal, heating to the set temperature of 30-55 ℃, preserving heat at the set temperature, and uniformly stirring;
adding feed liquid and a precipitant into a precipitation reaction kettle in a parallel flow precipitation mode, keeping the temperature at a set temperature, and generating lanthanum carbonate after precipitation reaction; the feed liquid adopts lanthanum chloride solution with the concentration of 1.42-1.84 mol/L, and the precipitant adopts ammonium bicarbonate solution with the concentration of 1.0-5.72 mol/L or mixed solution of ammonium bicarbonate and ammonia water; controlling the time of precipitation reaction and adjusting the pH value by controlling the input speed of feed liquid and precipitant, wherein the time of the precipitation reaction is 4-18 hours, and the pH value of the precipitation end point is=6.5-7;
taking out precipitated lanthanum carbonate in the precipitation reaction kettle, filtering and drying to obtain lanthanum carbonate serving as a precursor; lanthanum carbonate and deionized water are mixed according to a mass ratio of 1: 2-1: 6, adding the mixture into a reactor, stirring the mixture at the temperature of between 110 and 160 ℃ and carrying out hydrothermal synthesis reaction, wherein the heat preservation time is between 6 and 20 hours;
washing the obtained final product with deionized water, performing suction filtration or centrifugation to obtain a white solid, and placing the white solid in an oven to be dried for 3-12 hours at 150-200 ℃ to obtain hexagonal lanthanum hydroxycarbonate with the rare earth oxide accounting for 66-73 wt%.
Further, lanthanum chloride solution with the concentration of 1.42-1.84 mol/L is adopted as an original solution, the original solution is diluted by deionized water to form a base solution, and the supernatant of the previous batch is diluted by the subsequent batch to form the base solution.
Further, the precipitant adopts ammonium bicarbonate solution or mixed solution prepared by mixing ammonium bicarbonate and ammonia water, the concentration of the solution is 1.0-5.72 mol/L, wherein the mol ratio of the ammonium bicarbonate to the ammonia water is 7:3.
further, during parallel flow precipitation, adding a precipitant into the precipitation reaction kettle while adding the feed liquid; lanthanum chloride solution with the concentration of 1.42-1.84 mol/L is input into a feed liquid input port of the precipitation reaction kettle, and the precipitant with the concentration of 1.0-5.72 mol/L is input into a precipitant input port of the precipitation reaction kettle.
Further, the precipitation reaction kettle and the reactor work under normal pressure.
And further, taking out precipitate lanthanum carbonate in the precipitation reaction kettle, filtering, eluting a filter cake with deionized water, and vacuum-pumping to obtain the precursor lanthanum carbonate.
The technical effects of the invention include:
1. in the preparation method provided by the invention, raw materials and auxiliary materials are common materials in industrial production in the hydrometallurgical industry, and the raw materials and the auxiliary materials are low in price and easy to obtain; the raw materials used in the precipitation process are lanthanum chloride solution obtained by an extraction separation process, and precursor lanthanum carbonate of hexagonal lanthanum hydroxycarbonate can be directly prepared by precipitation, so that the preparation of lanthanum hydroxycarbonate after the precursor lanthanum carbonate is processed into oxide or nitrate is not needed, the process steps are greatly shortened, the energy consumption in the preparation process is reduced, and the preparation of other additives is avoided, so that the auxiliary material cost is increased.
2. The hydrothermal synthesis reaction is carried out under normal pressure, and the process flow can be realized without special pressurizing equipment.
3. The method has the advantages of simple process operation, good repeatability, stable product quality and easy realization of industrialized and automatic continuous operation.
Drawings
FIG. 1 is an XRD (X-ray diffraction analysis) pattern of hexagonal lanthanum hydroxycarbonate prepared in the present invention;
FIG. 2 is a scanning electron microscope image of hexagonal lanthanum hydroxycarbonate prepared in example 1 of the present invention.
Detailed Description
The following description fully illustrates the specific embodiments of the invention to enable those skilled in the art to practice and reproduce it.
The method for preparing hexagonal system lanthanum hydroxycarbonate by adopting hydrothermal synthesis comprises the following specific steps:
step 1: diluting lanthanum chloride solution with deionized water in a precipitation reaction kettle to obtain a base solution, wherein the concentration of the base solution is 0.177-0.89 mol/L, adding lanthanum carbonate with the base solution accounting for 10-50wt% as seed crystal, heating to the set temperature of 30-55 ℃, preserving heat at the set temperature, and uniformly stirring;
rare earth carbonates have little solubility in water, but have significantly increased solubility in alkali metal or ammonium carbonate solutions.
In the process of precipitating rare earth carbonate, a stable crystal growth environment is provided for obtaining a good crystal form by a base solution, a buffer environment with a moderate pH value is a key factor for determining the difficulty of crystallization in a crystallization induction period, and if the instantaneous pH value is too high, a salt is formed, but a mixture of a plurality of salts is formed, and the crystal is of an amorphous structure.
The invention adopts lanthanum chloride solution with the concentration of 1.42-1.84 mol/L as the raw solution, the raw solution is diluted by deionized water to form base solution, and the second batch and the subsequent batches are diluted by supernatant fluid of the previous batch to form reaction base solution.
Step 2: adding feed liquid and a precipitant into a precipitation reaction kettle in a parallel flow precipitation mode, keeping the temperature at a set temperature, and generating lanthanum carbonate after precipitation reaction; the feed liquid is lanthanum chloride solution with the concentration of 1.42-1.84 mol/L;
the raw materials used in the precipitation process are lanthanum chloride solution, the lanthanum chloride solution obtained by an extraction separation process can be directly subjected to precipitation preparation, the increase of auxiliary material cost and energy consumption cost caused by other processes of thiourea and glycine or oxide and nitrate preparation is avoided, and the preparation can be realized from the front-end raw material.
In the invention, the precipitant adopts ammonium bicarbonate solution with the concentration of 1.0-5.72 mol/L; or the precipitant adopts a mixed solution prepared by mixing ammonium bicarbonate and ammonia water, the concentration of the mixed solution is 1.0-5.72 mol/L, wherein the molar ratio of the ammonium bicarbonate to the ammonia water is 7:3. the precipitant of the invention adopts ammonium bicarbonate or the mixture of ammonium bicarbonate and ammonia water, and the raw materials are widely supplied and have low cost.
In the invention, the parallel flow sedimentation mode is as follows: adding a precipitant into the precipitation reaction kettle while adding the feed liquid. Lanthanum chloride solution with the concentration of 1.42-1.84 mol/L is input into a feed liquid input port of the precipitation reaction kettle, and the precipitant with the concentration of 1.0-5.72 mol/L is input into a precipitant input port of the precipitation reaction kettle.
In the whole process of parallel flow precipitation, the concentration of each ion in the base solution is maintained in a stable range, the pH value favorable for crystal growth can be well controlled, and the precipitation environment is relatively stable. In the invention, the time of precipitation reaction and the pH value are controlled and regulated by controlling the input speed of lanthanum chloride solution and precipitant. The input speed is controlled by the input port, the mixture is slowly added into the reaction kettle during parallel flow precipitation, the precipitation reaction time is controlled to be 4-18 hours, and the precipitation endpoint pH=6.5-7. The pH value is a key factor of the rare earth carbonate precipitation crystallization process and the crystal morphology, the accurate pH value is controlled in the reaction process, the phenomenon of unstable precipitation environment caused by overlarge addition of one party is avoided, the production speed of crystal nucleus is affected, and amorphous flocculent precipitation and non-rare earth impurities are prevented from being mixed in the product. In order to achieve the balance of rare earth yield, crystal growth and product purity, the precipitation is preferably controlled to be at a pH value of between 6.5 and 7.
Step 3: taking out precipitate lanthanum carbonate in the precipitation reaction kettle, filtering, eluting a filter cake with deionized water, and vacuum-pumping to obtain lanthanum carbonate serving as a precursor;
step 4: lanthanum carbonate and deionized water are mixed according to a mass ratio of 1: 2-1: 6, adding the mixture into a reactor, stirring the mixture at the temperature of between 110 and 160 ℃ and carrying out hydrothermal synthesis reaction; the heat preservation time is 6 to 20 hours;
principle of hydrothermal synthesis: the synthesis is carried out by chemical reaction of substances in aqueous solution under the conditions of 100-1000 ℃ and 1 MPa-1 GPa. The hydrothermal method has a trend towards low temperature and low pressure, namely, hydrothermal conditions that the temperature is lower than 100 ℃ and the pressure is close to 1 standard atmosphere. Under such subcritical and supercritical hydrothermal conditions, since the reaction is at a molecular level, the reactivity is improved, and thus the hydrothermal reaction can replace some of the high-temperature solid-phase reaction. The use of hydrothermal technology to dissolve insoluble or poorly soluble substances is an effective method for recrystallization, inorganic synthesis and material treatment.
In the present invention, the holding time is preferably 8 to 16 hours. The precipitation reaction kettle and the reactor work under normal pressure, lanthanum hydroxycarbonate can be obtained by adopting a hydrothermal synthesis process under normal pressure, the rare earth of the product has high total quantity and high purity, the product is in a hexagonal system, the whole process is simple to operate, no new equipment is added, and the product can be prepared by using the existing equipment and raw and auxiliary materials; the labor cost and the labor intensity are not increased, and the method is suitable for realizing industrialization and automatic continuous operation.
Step 5: washing the obtained final product with deionized water, performing suction filtration or centrifugation to obtain a white solid, and placing the white solid in an oven to be dried for 3-12 hours at 150-200 ℃ to obtain hexagonal lanthanum hydroxycarbonate with the Rare Earth Oxide (REO) accounting for 66-73 wt%.
Lanthanum hydroxycarbonate, also known as lanthanum hydroxycarbonate, has the chemical formula La (OH) CO 3 Belongs to a hexagonal system, is a P-6 space group, and has the following unit cell parameters: a=12.616, b=12.616, c=10.022.
As shown in FIG. 1, XRD (X-ray diffraction analysis) patterns of hexagonal lanthanum hydroxycarbonate prepared in the present invention are shown.
The spectrum of the lanthanum hydroxycarbonate represented in the spectrum is completely consistent with the peak value numbered 26-0815 in the diffraction spectrum, the diffraction intensity is high, the peak type is complete, the peak position is clear, and the crystallinity of the product is good. The unit cell parameters of 26-0815 are structural parameters of the hexagonal system.
Example 1
Preparing lanthanum chloride solution into base solution with the concentration of 0.7mol/L by deionized water in a precipitation reaction kettle, adding 30% of lanthanum carbonate as seed crystal, uniformly stirring, and simultaneously controlling the flow rates of the added lanthanum chloride feed solution and precipitant (ammonium bicarbonate solution) by adopting a parallel flow precipitation mode; the concentration of the feed liquid is 1.5mol/L, the concentration of the precipitant is 3mol/L, the reaction temperature is controlled to be 32 ℃, the reaction time is 6 hours, and the pH of the precipitation end point is=6.7.
And after filtration, leaching the filter cake by deionized water and vacuum-pumping to obtain lanthanum carbonate. Lanthanum carbonate and deionized water are mixed according to a mass ratio of 1:4, adding the mixture into a reactor, controlling the reaction temperature to be 110 ℃, preserving heat for 20 hours, washing the obtained product with deionized water, then placing the washed product into an oven, and drying the dried product at 150 ℃ for 12 hours to obtain hexagonal basic lanthanum carbonate, wherein the total REO=65%.
FIG. 2 is a scanning electron microscope image of hexagonal lanthanum hydroxycarbonate prepared in example 1 of the present invention.
The crystal structure of the hexagonal system lanthanum hydroxycarbonate obtained by firing is clear, spherical crystals are formed by regular flaky wafers, and the crystal size is uniform.
Example 2
Preparing lanthanum chloride solution into base solution with concentration of 0.5mol/L by deionized water, adding 20% lanthanum carbonate as seed crystal, uniformly stirring, adopting a parallel flow precipitation mode to simultaneously control the addition of lanthanum chloride feed liquid and precipitant (mixed solution of ammonium bicarbonate and ammonia water) and flow rate, controlling the concentration of precipitant to 2mol/L, controlling the reaction temperature to 48 ℃, reacting for 8 hours, and precipitating end-point pH=6.5.
And after filtration, leaching the filter cake by deionized water and vacuum-pumping to obtain lanthanum carbonate. Lanthanum carbonate and deionized water are mixed according to a mass ratio of 1:3, adding the mixture into a reactor, controlling the reaction temperature to be 150 ℃, preserving heat for 10 hours, washing the obtained product with deionized water, then placing the washed product into an oven, and drying the dried product at 180 ℃ for 8 hours to obtain hexagonal basic lanthanum carbonate, wherein the total REO=68%.
Example 3
Preparing lanthanum chloride solution into base solution with concentration of 0.3mol/L by using supernatant of the previous batch, adding 40% lanthanum carbonate as seed crystal, uniformly stirring, and simultaneously controlling flow rate of adding lanthanum chloride feed liquid and precipitant (mixed solution of ammonium bicarbonate and ammonia water) by adopting a parallel flow precipitation mode; the concentration of the feed liquid is 1.8mol/L, the concentration of the precipitant is 4mol/L, the reaction temperature is controlled to be 40 ℃, the reaction time is 12 hours, and the pH of the precipitation end point is=6.7.
And after filtration, leaching the filter cake by deionized water and vacuum-pumping to obtain lanthanum carbonate. Lanthanum carbonate and deionized water are mixed according to the mass/volume ratio of 1:6, adding the mixture into a reactor, controlling the reaction temperature to be 130 ℃, preserving heat for 11 hours, washing the obtained product with deionized water, and then placing the washed product into an oven, and drying the dried product at 190 ℃ for 5 hours to obtain hexagonal basic lanthanum carbonate, wherein the total REO=70%.
The terminology used herein is for the purpose of description and illustration only and is not intended to be limiting. As the present invention may be embodied in several forms without departing from the spirit or essential attributes thereof, it should be understood that the above-described embodiments are not limited by any of the details of the foregoing description, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalences of such metes and bounds are therefore intended to be embraced by the appended claims.
Claims (6)
1. A method for preparing hexagonal system lanthanum hydroxycarbonate by hydrothermal synthesis, comprising:
diluting lanthanum chloride solution with deionized water in a precipitation reaction kettle to obtain a base solution, wherein the concentration of the base solution is 0.177-0.89 mol/L, adding lanthanum carbonate with the base solution accounting for 10-50wt% as seed crystal, heating to the set temperature of 30-55 ℃, preserving heat at the set temperature, and uniformly stirring;
adding feed liquid and a precipitant into a precipitation reaction kettle in a parallel flow precipitation mode, keeping the temperature at a set temperature, and generating lanthanum carbonate after precipitation reaction; the feed liquid adopts lanthanum chloride solution with the concentration of 1.42-1.84 mol/L, and the precipitant adopts ammonium bicarbonate solution with the concentration of 1.0-5.72 mol/L or mixed solution of ammonium bicarbonate and ammonia water; controlling the time of precipitation reaction and adjusting the pH value by controlling the input speed of feed liquid and precipitant, wherein the time of the precipitation reaction is 4-18 hours, and the pH value of the precipitation end point is=6.5-7;
taking out precipitated lanthanum carbonate in the precipitation reaction kettle, filtering and drying to obtain lanthanum carbonate serving as a precursor; lanthanum carbonate and deionized water are mixed according to a mass ratio of 1: 2-1: 6, adding the mixture into a reactor, stirring the mixture at the temperature of between 110 and 160 ℃ and carrying out hydrothermal synthesis reaction, wherein the heat preservation time is between 6 and 20 hours;
washing the obtained final product with deionized water, performing suction filtration or centrifugation to obtain a white solid, and placing the white solid in an oven to be dried for 3-12 hours at 150-200 ℃ to obtain hexagonal lanthanum hydroxycarbonate with the rare earth oxide accounting for 66-73 wt%.
2. The method for preparing hexagonal lanthanum hydroxycarbonate by hydrothermal synthesis according to claim 1, wherein a lanthanum chloride solution having a concentration of 1.42 to 1.84mol/L is used as a raw solution, the raw solution is diluted with deionized water to form a base solution, and the subsequent batch is diluted with the supernatant of the previous batch to form the base solution.
3. The method for preparing hexagonal hydroxy lanthanum carbonate by hydrothermal synthesis according to claim 1, wherein the precipitant is ammonium bicarbonate solution or a mixed solution prepared by mixing ammonium bicarbonate and ammonia water, the concentration of the solution is 1.0-5.72 mol/L, and the molar ratio of ammonium bicarbonate to ammonia water is 7:3.
4. the method for preparing hexagonal lanthanum hydroxycarbonate by hydrothermal synthesis according to claim 1, wherein a precipitant is added to the precipitation reactor while the feed liquid is added during the parallel-flow precipitation; lanthanum chloride solution with the concentration of 1.42-1.84 mol/L is input into a feed liquid input port of the precipitation reaction kettle, and the precipitant with the concentration of 1.0-5.72 mol/L is input into a precipitant input port of the precipitation reaction kettle.
5. The method for preparing hexagonal lanthanum hydroxycarbonate by hydrothermal synthesis according to claim 1, wherein the precipitation reactor and the reactor are operated at normal pressure.
6. The method for preparing hexagonal lanthanum hydroxycarbonate by hydrothermal synthesis according to claim 1, wherein the precipitated lanthanum carbonate in the precipitation reactor is taken out, filtered, rinsed with deionized water, and vacuum-pumped to obtain lanthanum carbonate as a precursor.
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