CN110282651B - Method for preparing high-purity rare earth oxide by using composite precipitator - Google Patents

Method for preparing high-purity rare earth oxide by using composite precipitator Download PDF

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CN110282651B
CN110282651B CN201910734227.1A CN201910734227A CN110282651B CN 110282651 B CN110282651 B CN 110282651B CN 201910734227 A CN201910734227 A CN 201910734227A CN 110282651 B CN110282651 B CN 110282651B
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rare earth
feed liquid
carbonate
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chloride feed
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CN110282651A (en
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张积锴
陈东英
周洁英
赖兰萍
陈后兴
洪侃
王明
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Ganzhou Nonferrous Metallurgy Research Institute Co ltd
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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
    • C01F17/206—Compounds containing only rare earth metals as the metal element oxide or hydroxide being the only anion
    • 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
    • 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
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/80—Compositional purity

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Abstract

The invention relates to the technical field of rare earth hydrometallurgy, and provides a method for preparing high-purity rare earth oxide by using a composite precipitator. Adding seed crystal into a reactor, adding rare earth chloride feed liquid and a composite precipitator solution for precipitation reaction, then sequentially performing aging, liquid-solid separation and washing, and firing the obtained rare earth carbonate to obtain high-purity rare earth oxide; the composite precipitator used in the invention comprises sodium bicarbonate and sodium carbonate, wherein the mass ratio of the sodium bicarbonate to the sodium carbonate is 0.2-10: 1. The invention adopts the composite precipitator to precipitate the rare earth chloride, can comprehensively exert the advantages of sodium bicarbonate and sodium carbonate, reduce the generation of carbon dioxide during the precipitation of the sodium bicarbonate, reduce the risk of bubbles from overflowing a groove, prevent the generation of slurry-like product rare earth hydroxide caused by over-strong alkalinity of the sodium carbonate, prepare the rare earth carbonate with good crystallinity, stable crystal form, narrow particle size distribution and low impurity content, and obtain the high-purity rare earth oxide with various indexes superior to the national standard requirements after the firing.

Description

Method for preparing high-purity rare earth oxide by using composite precipitator
Technical Field
The invention relates to the technical field of rare earth hydrometallurgy, in particular to a method for preparing high-purity rare earth oxide by using a composite precipitator.
Background
The rare earth elements are widely applied in the fields of petroleum, chemical industry, metallurgy, textile, ceramics, glass, permanent magnet materials and the like, and the value of the rare earth oxide is increased along with the improvement of science and technology. The preparation method of rare earth oxide generally comprises the steps of adding a precipitant into a rare earth solution, and then firing the precipitated rare earth compound to obtain the rare earth oxide. In order to prepare the rare earth oxide with higher purity, a rare earth compound with good crystallinity, stable crystal form, narrow particle size distribution and low impurity content needs to be precipitated in the rare earth precipitation process. At present, the rare earth precipitation is usually performed by an oxalic acid precipitation method, the method has obvious advantages in the aspect of ensuring the product quality, the product purity is high, the content of non-rare earth impurities in the product can be effectively controlled, but the production cost is high, the oxalic acid toxicity is strong, and the applied environmental benefit and the economic benefit are not ideal.
In addition, ammonium bicarbonate is mostly adopted as a precipitator in the traditional rare earth precipitation, and the method has the advantages that the obtained rare earth carbonate particles are large and thick, the washing is easy, the cost is low, but a large amount of ammonia nitrogen wastewater can be generated by the ammonium bicarbonate precipitation, ammonia nitrogen is a main oxygen-consuming pollutant in a water body, high-content ammonia nitrogen can cause eutrophication of surface water, the excessive consumption of dissolved oxygen in water can seriously affect the water quality. In order to protect the ecological environment and reduce the water pollution, the discharge standard of the rare earth industrial pollutants (GB 26451-2011) clearly stipulates that the ammonia nitrogen direct discharge limit value of the rare earth industry is reduced from 25mg/L to 15mg/L from 1 month and 1 day 2014, and the influence of ammonia nitrogen wastewater on the environment has attracted attention in the environmental protection field and the global scope. The ammonia nitrogen wastewater has serious influence on the environment, so that the ammonium bicarbonate precipitation process faces the problem of standard discharge after severe water treatment.
At present, sodium bicarbonate and sodium carbonate are used as rare earth precipitating agents instead of ammonium bicarbonate, which is a hot spot of common attention in the industry. The precipitant required for producing rare earth carbonate is cheap, wide in source, friendly to environment and human body, and most potential to replace rare earth oxalate for industrial production of rare earth, so that it is an ideal method to use sodium carbonate or sodium bicarbonate as precipitant to replace oxalic acid and ammonium bicarbonate to precipitate rare earth. However, the use of sodium carbonate or sodium bicarbonate as a precipitant is liable to form amorphous precipitate, contains a large amount of water and impurities, is difficult to filter and wash, and has low product purity; especially, sodium carbonate is difficult to control when precipitating, is easy to generate rare earth hydroxide by local over-alkalization to form a pasty product, has poor crystallinity, long crystallization conversion time and longer ageing time, and Na is used for washing+、Cl-Is not easy to be washed and easily causes oxideThe content of impurities exceeds the standard; sodium bicarbonate as a precipitating agent will produce a large amount of CO2The consumption of gas and precipitator is large, the utilization rate is low, and the gas and the precipitator easily overflow from the tank, so that the production efficiency is influenced.
Disclosure of Invention
The invention aims to provide a method for preparing high-purity rare earth oxide by using a composite precipitator. The invention utilizes the composite precipitator to precipitate the rare earth ions, the obtained precipitated product has good crystallinity, stable crystal form, narrow particle size distribution, low impurity content and high purity of the obtained rare earth oxide.
In order to achieve the above object, the present invention provides the following technical solutions:
a method for preparing high-purity rare earth oxide by using a composite precipitator comprises the following steps:
adding seed crystals into a reactor, then adding rare earth chloride feed liquid and a composite precipitator solution into the reactor for precipitation reaction, and then sequentially performing aging, liquid-solid separation and washing to obtain rare earth carbonate;
firing the rare earth carbonate to obtain high-purity rare earth oxide;
wherein the precipitant in the composite precipitant solution comprises sodium bicarbonate and sodium carbonate; the mass ratio of the sodium bicarbonate to the sodium carbonate is 0.2-10: 1;
the REO mass content in the high-purity rare earth oxide is more than or equal to 99 percent.
Preferably, the total concentration of the sodium bicarbonate and the sodium carbonate in the composite precipitator solution is 50-200 g/L.
Preferably, the concentration of REO in the rare earth chloride feed liquid is 0.2-1.5 mol/L; the pH value of the rare earth chloride feed liquid is 0.5-2.5.
Preferably, the seed crystal comprises rare earth carbonate and/or rare earth oxalate.
Preferably, the addition amount of the seed crystal is 2-20% of the total rare earth mass; the total rare earth mass is calculated by the REO content in the rare earth chloride feed liquid.
Preferably, in the process of adding the rare earth chloride feed liquid and the composite precipitator solution, the pH value of the mixed feed liquid in the reactor is controlled to be 4-5.5.
Preferably, the pH value of the end point of the precipitation reaction is 6.5-7.5.
Preferably, the aging time is 2-24 h.
Preferably, the firing temperature is 850-1000 ℃, and the time is 1.5-3 h.
The invention provides a method for preparing high-purity rare earth oxide by using a composite precipitator, which comprises the steps of adding seed crystals into a reactor, then adding rare earth chloride feed liquid and a composite precipitator solution into the reactor for precipitation reaction, then sequentially aging, carrying out liquid-solid separation and washing, and firing the obtained rare earth carbonate to obtain high-purity rare earth oxide; the precipitator used in the invention comprises sodium bicarbonate and sodium carbonate, and the mass ratio of the sodium bicarbonate to the sodium carbonate is 0.2-10: 1. Compared with a precipitator which is singly composed of sodium bicarbonate, sodium carbonate, ammonium bicarbonate and the like, the composite precipitator can comprehensively exert the advantages of the sodium bicarbonate and the sodium carbonate, reduces the generation of carbon dioxide during the precipitation of the sodium bicarbonate, reduces the risk of bubbles overflowing, increases the effective utilization rate of the precipitator in unit mass, prevents the generation of a pasty product rare earth hydroxide due to too strong alkalinity of the sodium carbonate, improves the production efficiency, reduces the washing pressure, improves the washing effect, and prepares the rare earth carbonate with good crystallinity, stable crystal form, narrow particle size distribution and low impurity content; meanwhile, the method realizes low-cost, clean and environment-friendly production, and provides effective guarantee for development and development of rare earth materials; in addition, the method has wide applicability, can be realized on the basis of not changing the existing process equipment in industrial scale production, and has strong operability, low cost and obvious economic benefit. The embodiment result shows that the content of chlorine in the prepared rare earth oxide is less than or equal to 0.03 percent, the REO is more than or equal to 99.00 percent, and the yield of the REO in the precipitation process is more than or equal to 98.00 percent.
Drawings
FIG. 1 is a process flow diagram of an embodiment of the invention;
FIG. 2 is an SEM photograph of rare earth carbonate obtained in example 4;
FIG. 3 is a particle size distribution diagram of rare earth carbonate obtained in example 4;
FIG. 4 is an XRD pattern of rare earth carbonate obtained in examples 1 to 3.
Detailed Description
The invention provides a method for preparing high-purity rare earth oxide by using a composite precipitator, which comprises the following steps:
adding seed crystals into a reactor, then adding rare earth chloride feed liquid and a composite precipitator solution into the reactor for precipitation reaction, and then sequentially performing aging, liquid-solid separation and washing to obtain rare earth carbonate;
firing the rare earth carbonate to obtain high-purity rare earth oxide; the mass content of REO (rare earth oxide) in the high-purity rare earth oxide is more than or equal to 99 percent.
In the present invention, the precipitant in the composite precipitant solution includes sodium bicarbonate and sodium carbonate; the mass ratio of the sodium bicarbonate to the sodium carbonate is 0.2-10: 1, preferably 0.5-8: 1, and more preferably 1-5: 1; the total concentration of sodium bicarbonate and sodium carbonate in the composite precipitator solution is preferably 50-200 g/L, and more preferably 100-150 g/L; the solvent of the composite precipitant solution is preferably water. According to the invention, the sodium bicarbonate and the sodium carbonate are used as the composite precipitator to precipitate the rare earth chloride feed liquid, and the advantages of the sodium bicarbonate and the sodium carbonate can be comprehensively exerted to the greatest extent by controlling the ratio of the sodium bicarbonate to the sodium carbonate, so that the defects of the sodium bicarbonate and the sodium carbonate are avoided, and the effective utilization rate of the precipitator is increased.
In the invention, the REO concentration in the rare earth chloride feed liquid is preferably 0.2-1.5 mol/L, and more preferably 0.5-1 mol/L; the pH value of the rare earth chloride feed liquid is preferably 0.5-2.5, and more preferably 1-2. The invention has no special requirement on the source of the rare earth chloride, and in the specific embodiment of the invention, the rare earth chloride feed liquid with the impurity content reaching the standard obtained by extraction and separation is preferably directly used; in the specific embodiment of the invention, the pH value of the rare earth chloride feed liquid discharged from the extraction tank after extraction and separation is generally in the range of 0.5-2.5, and the rare earth chloride feed liquid can be directly used without further adjustment, if the REO concentration in the rare earth chloride feed liquid discharged from the extraction tank is too high, the rare earth chloride feed liquid is preferably diluted by water or low-concentration feed liquid, and if the REO concentration is too low, a proper amount of high-concentration feed liquid is added to obtain the rare earth chloride feed liquid with the REO concentration meeting the requirements of the invention. The rare earth chloride feed liquid has too high concentration, the phenomena of serious agglomeration and serious impurity wrapping can occur during precipitation, and the precipitated product is difficult to wash; the rare earth chloride feed liquid has too low concentration, amorphous precipitation can be generated, crystallization is not facilitated, and the required aging time is long; the method controls the concentration of REO in the rare earth chloride feed liquid within the range, can reduce the impurity content in the precipitated product, ensures the granularity and the particle morphology of the rare earth carbonate, and is favorable for obtaining the rare earth carbonate with good crystallinity.
The rare earth chloride feed liquid has no special requirements on the types of rare earth chloride in the rare earth chloride feed liquid, and can be single rare earth chloride or mixed rare earth chloride, and specifically can be lanthanum chloride, praseodymium neodymium chloride and the like.
In the present invention, the seed crystal is preferably rare earth carbonate and/or rare earth oxalate; the addition amount of the seed crystal is preferably 2-20% of the total rare earth mass, and more preferably 5-15%; the total rare earth mass is calculated by the content of REO in the rare earth chloride feed liquid; the invention can effectively shorten the crystallization conversion time in the precipitation process, increase the granularity of the crystal form rare earth carbonate, improve the crystal form and the granularity distribution, reduce fine particles, make the granularity distribution more uniform, further improve the physical index of the product, and reduce the impurities (such as Cl) in the product by pre-adding the seed crystal-、Na+) The content has obvious effect.
The invention has no special requirements on the reactor, and can be a beaker, a sedimentation barrel and the like.
The present invention preferably performs the charging and precipitation reactions under stirring conditions; according to the invention, preferably, before the seed crystal is added, part of water is added into the reactor to facilitate stirring, and the method has no special requirement on the amount of added water, can submerge a stirring paddle and is convenient to stir; after adding seed crystal, adding rare earth chloride feed liquid and composite precipitator solution into a reactor to carry out precipitation reaction; in the invention, in the process of adding the rare earth chloride feed liquid and the composite precipitator solution, the pH value of the mixed feed liquid in the reactor is preferably controlled to be 4-5.5. In the invention, the rare earth chloride feed liquid and the composite precipitator solution are preferably added into the reactor at a certain flow rate, the pH value range of the feed liquid in the reactor in the feeding process is controlled by controlling the flow rate of the rare earth chloride feed liquid and the composite precipitator solution, and the specific flow rate is controlled according to the size of the reactor, so that the pH value in the precipitation process can meet the requirement. In the charging process, the fluctuation of the pH value of the feed liquid in the reactor is reduced as much as possible, the smaller the fluctuation of the pH value is, the narrower the particle size distribution of the obtained rare earth carbonate is, the more stable the crystal form is, and the less the impurity content is.
In the embodiment of the invention, preferably, a part of rare earth chloride feed liquid is added to the reactor until the pH value of the feed liquid in the reactor is less than 4, and then the rest rare earth chloride feed liquid and the composite precipitator solution are added into the reactor together to ensure the smooth operation of the precipitation process and avoid the generation of rare earth hydroxide due to local over-alkali after the precipitator is added.
In the invention, the rare earth chloride feed liquid is slightly added before the composite precipitator solution is added, the composite precipitator solution is continuously added, the precipitation reaction in the reactor is continuously carried out, and the addition of the composite precipitator solution is stopped after the feed liquid in the reactor reaches the end point pH value; in the invention, the pH value of the end point of the precipitation reaction is preferably 6.5-7.5, and more preferably 7; after the pH value reaches the end point, the stirring is preferably stopped, and the aging is started; in the invention, the aging time is preferably 2-24 h, and more preferably 2 h.
After the aging is finished, carrying out liquid-solid separation on the aging feed liquid to obtain rare earth carbonate; the method for liquid-solid separation is preferably suction filtration; after the suction filtration is finished, the obtained solid product is preferably washed by deionized water so as to remove water-soluble impurity ions on the surface of the solid product; the rare earth carbonate obtained by precipitation by using the composite precipitator has good crystallization, less impurities in the precipitate, easy liquid-solid separation and Na in the precipitate+And Cl-Easily removed by washing. In the invention, the filtrate obtained by liquid-solid separation and the washing liquid generated by washing are preferably returned to the step of preparing the composite precipitator solution for reuse or discharged into a waste water station for treatment.
After rare earth carbonate is obtained, the invention burns the rare earth carbonate to obtain high-purity rare earth oxide. In the invention, the burning temperature is preferably 850-1000 ℃, and the time is preferably 1.5-3 h. The invention has no special requirements on equipment used in the burning process, the heating rate and the like, and the burning is carried out according to the method well known by the technical personnel in the field.
The embodiments of the present invention will be described in detail with reference to the following examples, but they should not be construed as limiting the scope of the present invention.
The process flow diagram of an embodiment of the invention is shown in fig. 1.
Example 1
Firstly, 200mL of deionized water is added into a 15L keg, 100g of lanthanum carbonate seed crystal is added, 3728mL of lanthanum chloride feed liquid is prepared, the concentration of REO is 100g/L, and 5950mL of composite precipitator solution (195g of sodium bicarbonate +485g of sodium carbonate, mNaHCO)3:mNa2CO30.4:1), the concentration is 114.3g/L, the temperature is 20 ℃, under the condition of proper stirring, lanthanum chloride feed liquid is firstly added until the pH value of the feed liquid in a container is less than 4, then the ratio of the flow speed of the lanthanum chloride feed liquid to the flow speed of a precipitator is controlled to be about 1:2, the flow between the lanthanum chloride feed liquid and the precipitator is properly adjusted, the pH value range in the precipitation process is controlled to be 4-5.5 until the solution is added, the end point pH value is 6.5-7.5, then the stirring is stopped, the aging is carried out for 2h, the suction filtration is carried out, the precipitation is washed by deionized water, rare earth carbonate is obtained, and finally the rare earth oxide is obtained by burning for 2h at 850 ℃.
Example 2
200mL of deionized water is added into a 15L keg, 100g of lanthanum carbonate seed crystal is added, 3728mL of lanthanum chloride feed liquid is prepared, the concentration of REO is 100g/L, and 5950mL of composite precipitator solution (108g of sodium bicarbonate +540g of sodium carbonate, mNaHCO)3:mNa2CO30.2:1), the concentration is 108.9g/L, the temperature is 20 ℃, under the condition of proper stirring, lanthanum chloride feed liquid is firstly added until the pH value of the feed liquid in a container is less than 4, then the ratio of the flow speed of the lanthanum chloride feed liquid to the flow speed of a precipitator is controlled to be about 1:2, the flow between the lanthanum chloride feed liquid and the precipitator is properly adjusted, the pH value range in the precipitation process is controlled to be 4-5.5 until the solution is added, the end point pH value is 6.5-7.5, the stirring is stopped, the solution is aged for 2h, the suction filtration is carried out, deionized water is used for washing and precipitation, and the lanthanum chloride solution is obtainedFinally burning for 2h at 850 ℃ to obtain the rare earth oxide.
Example 3
8.4kg of sodium bicarbonate and 41.9kg of sodium carbonate (mNaHCO) were taken3:mNa2CO30.2:1) is dissolved in a 1000L liquid preparation barrel, 370L of water is added to prepare a composite precipitator with the concentration of 135g/L, the composite precipitator is thrown into a high-level storage barrel for standby, 350L of lanthanum chloride feed liquid is prepared, the REO concentration is 131.9g/L, and the initial pH value is 1.8. Adding deionized water into a precipitation barrel in advance to submerge a stirring paddle, adding 10kg of lanthanum carbonate seed crystal, starting stirring, adding lanthanum chloride feed liquid until the pH value of the feed liquid in the precipitation barrel is less than 4, then adding the lanthanum chloride feed liquid and a composite precipitator solution, properly adjusting the flow between the lanthanum chloride feed liquid and the composite precipitator solution, controlling the pH value range in the precipitation process to be 4-5.5, stopping stirring until the feed liquid is added, stopping stirring, aging for 2 hours, performing suction filtration, washing and precipitating with deionized water to obtain rare earth carbonate, and finally firing to obtain rare earth oxide.
Example 4
12kg of sodium bicarbonate and 39.7kg of sodium carbonate (mNaHCO) are taken3:mNa2CO30.3:1) is dissolved in a 1000L liquid preparation barrel, 370L of water is added to prepare a composite precipitator with the concentration of 139.7g/L, the composite precipitator is thrown into a high-level storage barrel for standby, 350L of lanthanum chloride feed liquid is prepared, the concentration is 131.9g/L, and the initial pH value is 1.8. Adding deionized water into a precipitation barrel in advance to cover a stirring paddle, adding 10kg of lanthanum carbonate seed crystal, starting stirring, adding lanthanum chloride feed liquid until the pH value of the feed liquid in the precipitation barrel is less than 4, then adding the lanthanum chloride feed liquid and a composite precipitator solution, controlling the pH value range to be 4-5.5 by controlling the flow of the lanthanum chloride feed liquid and the composite precipitator solution in the precipitation process until the feed liquid is added completely, controlling the end pH value to be 6.5-7.5, stopping stirring, measuring the rare earth concentration in a supernatant after aging for 2 hours, performing suction filtration, washing and precipitating with deionized water to obtain rare earth carbonate, and finally firing for 2 hours at 850 ℃ to obtain rare earth oxide.
Example 5
15.2kg of sodium bicarbonate and 37.6kg of sodium carbonate (mNaHCO) were taken3:mNa2CO30.4:1) is dissolved in a 1000L liquid preparation barrel, 370L water is added to prepare a composite precipitator with the concentration of 142.7g/L, and the mixture is thrown into a high-level storage barrelPreparing 350L of lanthanum chloride feed liquid for later use, and measuring the concentration of the lanthanum chloride feed liquid to be 131.9g/L and the initial pH value to be 1.8. Adding deionized water into a precipitation barrel in advance to submerge a stirring paddle, adding 10kg of lanthanum carbonate seed crystal, starting stirring, adding lanthanum chloride feed liquid until the pH value of the feed liquid in the precipitation barrel is less than 4, then adding the lanthanum chloride feed liquid and a composite precipitator solution, controlling the pH value range to be 4-5.5 by controlling the flow of the lanthanum chloride feed liquid and the composite precipitator solution in the precipitation process until the solution is added, and controlling the end-point pH value to be 6.5-7.5; stopping stirring, aging for 2h, measuring the rare earth concentration in the supernatant to be less than 10mg/L, performing suction filtration, washing and precipitating with deionized water to obtain rare earth carbonate, and finally firing at 850 ℃ for 2h to obtain rare earth oxide.
Example 6
500L of deionized water was added to a 1000L compounding barrel, and 20.5kg of sodium bicarbonate and 50.8kg of sodium carbonate (mNaHCO) were weighed3:mNa2CO30.4:1), preparing a compound precipitator with the concentration of 142.7g/L, and throwing the compound precipitator into a high-level storage bucket for later use; 350L of feed liquid of 20-80 praseodymium neodymium chloride (namely, the feed liquid contains 20 percent and 80 percent of praseodymium oxide and neodymium oxide by mass respectively) of a rare earth separation plant is taken, the REO concentration is measured to be 150g/L, and the initial pH value is measured to be 1.8. Adding deionized water into a precipitation barrel in advance to cover a stirring paddle, adding 10kg of praseodymium neodymium carbonate crystal seeds, starting stirring, adding lanthanum chloride feed liquid until the pH value of the feed liquid in the precipitation barrel is less than 4, then adding praseodymium neodymium chloride feed liquid and a composite precipitator solution, controlling the pH value range to be 4-5.5 by controlling the flow of the lanthanum chloride feed liquid and the composite precipitator solution in the precipitation process until the praseodymium neodymium chloride feed liquid is added completely, controlling the end-point pH value to be 6.5-7.5, stopping stirring, measuring the rare earth concentration in a supernatant after aging for 2 hours, performing suction filtration, washing with deionized water to obtain qualified rare earth carbonate, and finally firing for 2 hours at 850 ℃ to obtain rare earth oxide.
And (3) quality analysis:
(1) particle size and chemical composition analysis
Particle size testing is carried out on the rare earth carbonate obtained in the embodiments 1-6, and chemical analysis is carried out on the rare earth oxide obtained after firing, and the obtained results are shown in table 1;
TABLE 1 particle size of rare earth carbonate, Span, and total amount of chlorine, REO, Na in rare earth oxide+Content and REO yield phaseData sheet
Figure BDA0002161619730000081
The percentages in table 1 are mass percentages.
The results in table 1 show that in embodiments 1 to 6 of the present invention, sodium bicarbonate and sodium carbonate are used as a composite precipitant, the prepared rare earth carbonate has stable particle size and uniform distribution, the content of chlorine and sodium ion impurities in the burned rare earth oxide is low, the total content of rare earth is high, and the related indexes are all superior to the national standard requirements.
FIG. 2 is an SEM image of the rare earth carbonate prepared in example 4, and it can be seen from FIG. 2 that the rare earth carbonate prepared in example 4 has a uniform particle size; SEM test of the rare earth carbonates obtained in examples 1-3 and examples 5-6 is similar to that in FIG. 2.
FIG. 3 is a particle size distribution diagram of rare earth carbonate obtained in example 4; table 2 shows the particle size distribution data of the rare earth carbonate obtained in example 4;
TABLE 2 data of particle size distribution of rare earth carbonate obtained in example 4
D10/μm D25/μm D50/μm D75/μm D90/μm
8.693 12.622 17.16 22.122 27.638
D97/μm D(3,2)/μm D(4,3)/μm Span Specific surface area by weight/m2/kg
34.774 14.867 17.927 1.104 149.473
As can be seen from FIG. 3 and Table 2, the particle size distribution of the rare earth carbonate obtained in example 4 is narrow.
(2) XRD detection
The crystallization characteristics of the rare earth carbonate precipitates of the embodiments 1 to 3 are characterized by X-ray diffraction, and the obtained results are shown in FIG. 4, as can be seen from FIG. 4, the rare earth carbonate obtained in the embodiments 1 to 3 has strong, sharp and symmetrical diffraction peaks, each characteristic peak can be well matched with the characteristic peak of the PDF card corresponding to the standard substance, and the peak shape is good, which indicates that the rare earth carbonate is a crystal form precipitate with good crystallization, is a substance corresponding to the PDF card, and has no obvious other impurities.
XRD detection is carried out on the rare earth carbonate obtained in the embodiments 4-6, and the obtained result is similar to that in figure 4.
The embodiment shows that the method provided by the invention utilizes the composite precipitator consisting of the sodium bicarbonate and the sodium carbonate to prepare the high-purity rare earth oxide, can integrate the advantages of the sodium bicarbonate and the sodium carbonate, avoids the defects of the sodium bicarbonate and the sodium carbonate, has good crystallinity, stable crystal form, narrow particle size distribution, low impurity content and high purity of the rare earth oxide obtained after burning, and has various indexes superior to the requirements of national standards.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (7)

1. A method for preparing high-purity rare earth oxide by using a composite precipitator is characterized by comprising the following steps:
adding seed crystals into a reactor, then adding rare earth chloride feed liquid and a composite precipitator solution into the reactor for precipitation reaction, and then sequentially performing aging, liquid-solid separation and washing to obtain rare earth carbonate; in the process of adding the rare earth chloride feed liquid and the composite precipitator solution, the pH value of the mixed feed liquid in the reactor is controlled to be 4-5.5; the pH value of the end point of the precipitation reaction is 7-7.5; the method for adding the rare earth chloride feed liquid and the composite precipitator solution into the reactor comprises the following steps: firstly, adding a part of rare earth chloride feed liquid until the pH value of the feed liquid in the reactor is less than 4, then adding the rest rare earth chloride feed liquid and the composite precipitator solution into the reactor together, wherein the rare earth chloride feed liquid is added before the composite precipitator solution is added, the composite precipitator solution is continuously added, and after the pH value of the feed liquid in the reactor reaches the end point, the composite precipitator solution is stopped to be added;
firing the rare earth carbonate to obtain high-purity rare earth oxide;
wherein the precipitant in the composite precipitant solution comprises sodium bicarbonate and sodium carbonate; the mass ratio of the sodium bicarbonate to the sodium carbonate is 0.2-10: 1;
the REO mass content in the high-purity rare earth oxide is more than or equal to 99 percent.
2. The method according to claim 1, wherein the total concentration of sodium bicarbonate and sodium carbonate in the composite precipitant solution is 50-200 g/L.
3. The method according to claim 1, wherein the REO concentration in the rare earth chloride feed liquid is 0.2-1.5 mol/L; the pH value of the rare earth chloride feed liquid is 0.5-2.5.
4. The method of claim 1, wherein the seed crystal comprises rare earth carbonate and/or rare earth oxalate.
5. The method according to claim 1 or 4, characterized in that the seed crystal is added in an amount of 2-20% of the total rare earth mass; the total rare earth mass is calculated by the REO content in the rare earth chloride feed liquid.
6. The method according to claim 1, wherein the aging time is 2 to 24 hours.
7. The method of claim 1, wherein the burning temperature is 850-1000 ℃ and the time is 1.5-3 h.
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