Method for preparing rare earth fluoride by carbon cycle

Abstract

The present invention discloses a method for preparing rare earth fluorides by carbon cycle in the field of rare earth fluoride preparation, comprising the following steps: (1) mixing rare earth carbonate and water to form a slurry; (2) adding a rare earth chloride solution, a fluorinating agent and an anionic co-precipitant, heating and stirring to produce a precipitate; (3) filtering, washing with ethanol and water respectively, drying and pulverizing to obtain rare earth fluorides; (4) absorbing carbon dioxide with ammonia water to obtain an ammonium bicarbonate solution; (5) reacting the ammonium bicarbonate solution with rare earth chloride to obtain rare earth carbonate, and repeating the above steps. The present invention uses a fluorine ion-containing organic solution to replace the traditional fluorinating agent, with mild reaction conditions and a green and environmentally friendly process; using rare earth chloride as an initiator to participate in the fluorination reaction together with rare earth carbonate, the reaction process is easy to control; the product has a small particle size, can settle rapidly, is easy to filter and has a higher purity; the present invention realizes the recycling of carbon elements and avoids the pollution caused by carbon dioxide emissions.

Description

Technical Field

[0001] The present invention belongs to the field of rare earth fluoride preparation, and particularly relates to a method for preparing rare earth fluoride by carbon cycle. Background Art

[0002] Rare earth fluoride nanomaterials exhibit unique optical, electrical, magnetic and other properties due to the rich 4f energy levels, low phonon energy and nanoscale size effects of rare earth elements, which have attracted extensive attention from scientists around the world. These materials can emit light through the inner layer 4f electron transition of rare earth elements. Since the inner layer electrons are less affected by the chemical environment and the 4f electron transition is a forbidden transition, the emission spectrum of rare earth elements presents a linear shape and has a long fluorescence lifetime. Due to the strong ionic bond characteristics, the light transmission range of rare earth fluorides extends from near ultraviolet to mid-infrared bands, making them ideal substrates for laser crystals and upconversion luminescent materials. These properties enable rare earth fluoride nanomaterials to have broad application prospects in the fields of fluoride optical fibers, infrared antireflection film materials, luminescent crystal materials, lubricants and optical anti-counterfeiting.

[0003] At present, the preparation processes of rare earth fluorides are mainly divided into two types, wet fluorination process and dry fluorination process. The former mainly uses rare earth carbonates, chlorides, nitrates, etc. and hydrofluoric acid or ammonium fluoride as raw materials to obtain rare earth fluorides, but there are problems such as long process, low production efficiency, many introduced impurities, and low recovery rate. The latter mainly uses rare earth oxides or carbonates and hydrogen fluoride gas or ammonium bifluoride as raw materials to obtain rare earth fluorides. Due to the simplicity and low cost of the wet process, it has been widely used. However, the traditional wet process has problems such as low fluorine conversion rate, high fluorine content in wastewater, small rare earth fluoride particles, difficult filtration, and inability to recycle carbon elements. Therefore, in the production process, it is necessary to improve the existing wet fluorination process. Summary of the Invention

[0004] In view of the above situation, to overcome the defects of the existing technology, the present invention provides a method for preparing rare earth fluoride by carbon cycle. The present invention does not use highly corrosive fluorinating agents, avoids corrosion of the reaction device, has mild reaction conditions, a green and environmentally friendly process, the reaction process is easy to control, the prepared product has small particle size, can quickly settle, is easy to filter, and has higher purity. It realizes the recycling of carbon elements and avoids environmental pollution caused by carbon dioxide emissions.

[0005] To achieve the above object, the following technical solution is adopted: The present invention provides a method for preparing rare earth fluoride by carbon cycle, and the method for preparing rare earth fluoride by carbon cycle includes the following steps:

[0006] (1) Add rare earth carbonate and water to the reaction kettle according to a solid-liquid volume ratio of 1:8, stir at a speed of 800 - 1000 rpm to form a slurry;

[0007] (2) Prepare a rare earth chloride solution and add it to the slurry. Then add a fluorinating agent and an anionic co-precipitant, heat it, maintain the stirring speed for 1 h, and let it stand for 2 h to obtain a precipitate.

[0008] (3) Filter out the precipitate, wash it once with ethanol and once with water, dry it at 90 °C for 8 h, and pulverize it to obtain rare earth fluoride.

[0009] (4) During the reaction in step (2), use a bubbler to bubble, and absorb the evolved carbon dioxide with ammonia water to obtain an ammonium bicarbonate solution.

[0010] (5) React the ammonium bicarbonate solution with the rare earth chloride to obtain rare earth carbonate, and repeat steps (1)-(4) to prepare rare earth fluoride.

[0011] Further, the rare earth carbonate is one of lanthanum carbonate, cerium carbonate, praseodymium carbonate, neodymium carbonate, samarium carbonate, gadolinium carbonate, erbium carbonate, dysprosium carbonate, europium carbonate, yttrium carbonate, lanthanum cerium carbonate, and praseodymium neodymium carbonate.

[0012] Further, the rare earth chloride is one of lanthanum chloride, cerium chloride, praseodymium chloride, neodymium chloride, samarium chloride, gadolinium chloride, erbium chloride, dysprosium chloride, europium chloride, yttrium chloride, lanthanum cerium chloride, and praseodymium neodymium chloride.

[0013] Further, in step (2), the molar ratio of the rare earth chloride to the rare earth carbonate is 1:8 - 1:10; the concentration of the rare earth chloride in step (2) is 0.08 - 0.16 mol / L.

[0014] Further, the fluorinating agent is one of 1-octyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium hexafluoroantimonate, 1-ethyl-3-methylimidazolium tetrafluoroborate, and 1-butyl-3-methylimidazolium trifluoromethanesulfonate.

[0015] Further, the anionic co-precipitant is one of sodium dodecyl alcohol ether sulfate, trimethyloctadecylammonium bromide, and sodium dodecylbenzenesulfonate.

[0016] Further, the molar ratio of the rare earth ions in the rare earth carbonate to the fluoride ions in the fluorinating agent is 1:3.1 - 1:3.3.

[0017] Further, the molar ratio of the anionic co-precipitant to the rare earth carbonate is 1:100 - 1:200.

[0018] Further, the reaction temperature in step (2) is 75 - 95 °C.

[0019] Further, the mass fraction of the ammonia water is 18% - 25%.

[0020] Further, in the step (5), the molar ratio of rare earth ions in the rare earth chloride to ammonium ions in the ammonium bicarbonate solution is 1:1.5 - 1:2.

[0021] The beneficial effects of the present invention are as follows:

[0022] (1) Using the fluoride ion-containing organic solution to replace traditional hydrogen fluoride and ammonium bifluoride fluorinating agents, no toxic and harmful hydrogen fluoride gas is generated, effectively avoiding the corrosion of the reaction device, the reaction conditions are milder, and the process is more environmentally friendly and green;

[0023] (2) The reaction between rare earth carbonate and the fluorinating agent is slow. Rare earth chloride can initiate the fluorination of rare earth carbonate and participate in the fluorination reaction together. At the same time, the reaction process can be controlled according to the addition amount and addition rate of rare earth chloride;

[0024] (3) In the traditional wet fluorination process, there is a large amount of hydrofluoric acid. Fluoride ions will produce a complexing effect with rare earth fluorides. In this precipitation process, the nucleation rate is greater than the growth rate, and rare earth fluorides are in the form of colloidal precipitates, which are difficult to filter and have a low conversion rate. In the present invention, the fluoride ion-containing organic solution is used as the fluorinating agent, weakening the complexing effect between fluoride ions and rare earth fluorides. When the anionic co-precipitating agent hydrolyzes, anions are generated, which have a competitive effect with fluoride ions, further weakening the complexing effect between fluoride ions and rare earth fluorides. At the same time, the anionic co-precipitating agent can produce a "bridging effect" with rare earth fluorides, making the growth rate in the precipitation process greater than the nucleation rate, promoting the rapid agglomeration and precipitation of fluorides, avoiding the formation of colloids of rare earth fluorides, and the prepared product has small particle size, fast sedimentation, easy filtration, higher purity and fluorine conversion rate;

[0025] (4) In the traditional wet fluorination process, due to the presence of hydrogen fluoride, a large amount of hydrogen ions produce an acid effect on the rare earth fluoride precipitate, increasing the solubility of the precipitate. However, the hydrogen ion concentration of the fluoride ion-containing organic solution is low, and the anionic co-precipitating agent hydrolyzes to be weakly alkaline. The combined action of the two weakens the acid effect of hydrogen ions, reduces the dissolution loss of the precipitate, and has a higher fluorine conversion rate;

[0026] (5) The present invention also realizes the recycling of carbon elements, avoiding environmental pollution caused by carbon dioxide emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 XRD pattern of lanthanum fluoride prepared in Example 1;

[0028] Figure 2 XRD pattern of neodymium fluoride prepared in Example 2;

[0029] Figure 3 Line graph of fluorine conversion rates of Examples 1 - 6 and Comparative Examples 1 - 2;

[0030] Figure 4Line graph of carbon resource utilization rates for Examples 1-6 and Comparative Examples 1-2;

[0031] Figure 5 Graph of particle size detection results for Example 1;

[0032] Figure 6 Graph of particle size detection results for Comparative Example 1;

[0033] Figure 7 Graph of particle size detection results for Comparative Example 2.

[0034] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation to the present invention. Detailed Embodiments

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0036] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to the described content can be applied to the present invention. The preferred implementation methods and materials described herein are only for illustrative purposes and do not limit the content of this application.

[0037] The experimental methods in the following embodiments are all conventional methods unless otherwise specified. The test materials used in the following embodiments are all obtained from commercial channels unless otherwise specified.

[0038] Example 1

[0039] Method for preparing rare earth fluoride by carbon cycle

[0040] The rare earth fluoride prepared in this example is lanthanum fluoride. The method for preparing rare earth fluoride by carbon cycle includes the following steps:

[0041] (1) Add rare earth carbonate and water to the reaction kettle at a solid-liquid volume ratio of 1:8, and stir at a speed of 800 - 1000 rpm to form a slurry;

[0042] (2) Prepare a rare earth chloride solution, add it to the slurry, add a fluorinating agent and an anionic co-precipitant, heat, maintain the stirring speed for 1 h, and let it stand for 2 h to obtain a precipitate;

[0043] (3) Filter out the precipitate, wash it once with ethanol and once with water, dry it at 90 °C for 8 h, and pulverize it to obtain rare earth fluoride;

[0044] (4) When reacting in step (2), use a bubbler to bubble, and absorb the evolved carbon dioxide with ammonia water to obtain ammonium bicarbonate solution;

[0045] (5) React the ammonium bicarbonate solution with rare earth chloride to obtain rare earth carbonate, and repeat steps (1)-(4) to prepare rare earth fluoride.

[0046] Further, the rare earth carbonate is lanthanum carbonate; the rare earth chloride is lanthanum chloride; the molar ratio of rare earth chloride to rare earth carbonate in step (2) is 1:8.5; the concentration of rare earth chloride in step (2) is 0.10 mol / L; the fluorinating agent is 1-octyl-3-methylimidazolium hexafluorophosphate; the anionic co-precipitant is sodium dodecyl alcohol ether sulfate; the molar ratio of the rare earth ions of the rare earth carbonate to the fluoride ions of the fluorinating agent is 1:3.1; the molar ratio of the anionic co-precipitant to the rare earth carbonate is 1:120; the reaction temperature in step (2) is 75 °C; the mass fraction of ammonia water is 20%; the molar ratio of the rare earth ions of the rare earth chloride to the ammonium ions of the ammonium bicarbonate solution in step (5) is 1:1.6.

[0047] Example 2

[0048] Method for preparing rare earth fluoride by carbon cycle

[0049] The rare earth fluoride prepared in this example is neodymium fluoride, and the steps included in the method for preparing rare earth fluoride by carbon cycle are the same as those in Example 1.

[0050] Further, the rare earth carbonate is neodymium carbonate; the rare earth chloride is neodymium chloride; the molar ratio of rare earth chloride to rare earth carbonate in step (2) is 1:8; the concentration of rare earth chloride in step (2) is 0.10 mol / L; the fluorinating agent is 1-octyl-3-methylimidazolium hexafluorophosphate; the anionic co-precipitant is sodium dodecyl alcohol ether sulfate; the molar ratio of the rare earth ions of the rare earth carbonate to the fluoride ions of the fluorinating agent is 1:3.2; the molar ratio of the anionic co-precipitant to the rare earth carbonate is 1:150; the reaction temperature in step (2) is 85 °C; the mass fraction of ammonia water is 25%; the molar ratio of the rare earth ions of the rare earth chloride to the ammonium ions of the ammonium bicarbonate solution in step (5) is 1:1.8.

[0051] Example 3

[0052] Method for preparing rare earth fluoride by carbon cycle

[0053] The rare earth fluoride prepared in this example is yttrium fluoride, and the steps included in the method for preparing rare earth fluoride by carbon cycle are the same as those in Example 1.

[0054] Furthermore, the rare earth carbonate is lanthanum cerium carbonate; the rare earth chloride is lanthanum cerium chloride; the molar ratio of rare earth chloride to rare earth carbonate in step (2) is 1:9; the concentration of rare earth chloride in step (2) is 0.12 mol / L; the fluorinating agent is 1-octyl-3-methylimidazolium hexafluorophosphate; the anionic co-precipitant is sodium dodecyl alcohol ether sulfate; the molar ratio of rare earth ions in the rare earth carbonate to fluoride ions in the fluorinating agent is 1:3.3; the molar ratio of the anionic co-precipitant to the rare earth carbonate is 1:180; the reaction temperature in step (2) is 90 °C; the mass fraction of ammonia water is 25%; the molar ratio of rare earth ions in the rare earth chloride to ammonium ions in the ammonium bicarbonate solution in step (5) is 1:1.8.

[0055] Example 4

[0056] Method for preparing rare earth fluoride by carbon cycle

[0057] The rare earth fluoride prepared in this example is lanthanum cerium fluoride, and the steps included in the method for preparing rare earth fluoride by carbon cycle are the same as those in Example 1.

[0058] Furthermore, the rare earth carbonate is lanthanum cerium carbonate; the rare earth chloride is lanthanum cerium chloride; the molar ratio of rare earth chloride to rare earth carbonate in step (2) is 1:8.5; the concentration of rare earth chloride in step (2) is 0.15 mol / L; the fluorinating agent is 1-octyl-3-methylimidazolium hexafluorophosphate; the anionic co-precipitant is sodium dodecyl alcohol ether sulfate; the molar ratio of rare earth ions in the rare earth carbonate to fluoride ions in the fluorinating agent is 1:3.2; the molar ratio of the anionic co-precipitant to the rare earth carbonate is 1:180; the reaction temperature in step (2) is 90 °C; the mass fraction of ammonia water is 20%; the molar ratio of rare earth ions in the rare earth chloride to ammonium ions in the ammonium bicarbonate solution in step (5) is 1:1.8.

[0059] Example 5

[0060] Method for preparing rare earth fluoride by carbon cycle

[0061] The rare earth fluoride prepared in this example is praseodymium neodymium fluoride, and the steps included in the method for preparing rare earth fluoride by carbon cycle are the same as those in Example 1.

[0062] Further, the rare earth carbonate is praseodymium-neodymium carbonate; the rare earth chloride is praseodymium-neodymium chloride; the molar ratio of rare earth chloride to rare earth carbonate in step (2) is 1:9; the concentration of rare earth chloride in step (2) is 0.15 mol / L; the fluorinating agent is 1-octyl-3-methylimidazolium hexafluorophosphate; the anionic co-precipitant is trimethyloctadecylammonium bromide; the molar ratio of rare earth ions of the rare earth carbonate to fluoride ions of the fluorinating agent is 1:3.2; the molar ratio of the anionic co-precipitant to the rare earth carbonate is 1:180; the reaction temperature in step (2) is 90 °C; the mass fraction of ammonia water is 20%; the molar ratio of rare earth ions of the rare earth chloride to ammonium ions of the ammonium bicarbonate solution in step (5) is 1:2.

[0063] Example 6

[0064] Method for preparing rare earth fluoride by carbon cycle

[0065] The rare earth fluoride prepared in this example is erbium fluoride, and the steps included in the method for preparing rare earth fluoride by carbon cycle are the same as those in Example 1.

[0066] Further, the rare earth carbonate is erbium carbonate; the rare earth chloride is erbium chloride; the molar ratio of rare earth chloride to rare earth carbonate in step (2) is 1:9; the concentration of rare earth chloride in step (2) is 0.15 mol / L; the fluorinating agent is 1-butyl-3-methylimidazolium trifluoromethanesulfonate; the anionic co-precipitant is trimethyloctadecylammonium bromide; the molar ratio of rare earth ions of the rare earth carbonate to fluoride ions of the fluorinating agent is 1:3.2; the molar ratio of the anionic co-precipitant to the rare earth carbonate is 1:180; the reaction temperature in step (2) is 90 °C; the mass fraction of ammonia water is 20%; the molar ratio of rare earth ions of the rare earth chloride to ammonium ions of the ammonium bicarbonate solution in step (5) is 1:2.

[0067] Comparative Example 1

[0068] This comparative example provides a method for preparing rare earth fluoride, which is different from Comparative Example 1 in that the fluorinating agent is hydrofluoric acid with a volume fraction of 20%, and the other components, component contents, and preparation methods are the same as those in Example 1.

[0069] Comparative Example 2

[0070] This comparative example provides a method for preparing rare earth fluoride, which is different from Comparative Example 1 in that no anionic co-precipitant is added in step (2), and an equal weight of water is used instead, and the other components, component contents, and preparation methods are the same as those in Example 1.

[0071] Result analysis

[0072] The rare earth fluorides prepared in Example 1 and Example 2 were detected using an X-ray diffractometer, and the results are shown respectively as Figure 1 and Figure 2 shown.

[0073] From Figure 1 and Figure 2 it can be seen that the peaks in the XRD patterns of the rare earth fluorides prepared in the present invention coincide with the heights and positions of the characteristic peaks in the standard pattern, and no obvious impurity peaks are detected, indicating that the rare earth fluorides prepared in the present invention have a high purity.

[0074] The fluorine conversion rates and carbon resource utilization rates of Examples 1-6 and Comparative Examples 1-2 were calculated respectively, and the results are shown respectively as Figure 3 and Figure 4 shown. The fluorine conversion rate = weight of fluorine in rare earth fluoride / weight of fluorine in fluorinating agent × 100%; the carbon resource utilization rate = (weight of rare earth carbonate calculated as carbon dioxide - weight of carbon dioxide emitted) / weight of rare earth carbonate calculated as carbon dioxide × 100%.

[0075] From Figure 3 and Figure 4 it can be seen that in the present invention, an organic solution containing fluoride ions is used to replace the traditional fluorinating agent, and an anionic co-precipitant is added, reducing the complexation and acid effect of hydrogen fluoride. The fluorine conversion rate is higher, and the recycling of carbon elements is also realized, reducing the environmental pollution caused by carbon dioxide emissions.

[0076] The particle sizes of the lanthanum fluorides prepared in Example 1 and Comparative Examples 1-2 were detected using a laser scattering particle size distribution analyzer, and the results are shown respectively as Figures 5 - 7 shown.

[0077] From Figures 5 - 7 it can be seen that the rare earth fluorides prepared in the present invention have smaller particle sizes, can settle rapidly, are easy to filter, and the particle sizes are mainly concentrated in the medium range.

[0078] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

[0079] The above describes the present invention and its embodiments. Such a description is not restrictive. What is shown in the drawings is only one of the embodiments of the present invention, and the actual application is not limited thereto. Generally speaking, if those of ordinary skill in the art are inspired by it and, without departing from the purpose of the present invention, design similar ways and embodiments to this technical solution without creative efforts, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing rare earth fluorides by carbon cycle, characterized in that: The method for preparing rare earth fluoride by carbon cycle comprises the following steps: (1) Add rare earth carbonate and water into a reaction kettle at a solid-liquid volume ratio of 1:8, stir at a speed of 800-1000 rpm to form a slurry; (2) Prepare a rare earth chloride solution, add it to the slurry, add a fluorinating agent and an anionic co-precipitant, heat, maintain the stirring speed for 1 h, and let it stand for 2 h to obtain a precipitate; (3) Filter out the precipitate, wash it once with ethanol and once with water, dry it at 90 °C for 8 h, and pulverize it to obtain rare earth fluoride; (4) When reacting in step (2), use a bubbler to bubble, and absorb the escaped carbon dioxide with ammonia water to obtain an ammonium bicarbonate solution; (5) React the ammonium bicarbonate solution with rare earth chloride to obtain rare earth carbonate, and repeat steps (1)-(4) to prepare rare earth fluoride; The rare earth chloride is one of lanthanum chloride, cerium chloride, praseodymium chloride, neodymium chloride, samarium chloride, gadolinium chloride, erbium chloride, dysprosium chloride, europium chloride, and yttrium chloride; The fluorinating agent is one of 1-octyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium hexafluoroantimonate, 1-ethyl-3-methylimidazolium tetrafluoroborate, and 1-butyl-3-methylimidazolium trifluoromethanesulfonate; The anionic co-precipitant is one of sodium dodecyl alcohol ether sulfate, trimethyloctadecylammonium bromide, and sodium dodecylbenzenesulfonate.

2. The method for preparing rare earth fluoride by carbon cycle according to claim 1, wherein: The rare earth carbonate is one of lanthanum carbonate, cerium carbonate, praseodymium carbonate, neodymium carbonate, samarium carbonate, gadolinium carbonate, erbium carbonate, dysprosium carbonate, europium carbonate, and yttrium carbonate.

3. The method for preparing rare earth fluoride by carbon cycle according to claim 2, characterized in that: In step (2), the molar ratio of rare earth chloride to rare earth carbonate is 1:8-1:10; the concentration of rare earth chloride in step (2) is 0.08-0.16 mol / L.

4. The method for preparing rare earth fluoride by carbon cycle according to claim 3, wherein: The molar ratio of the rare earth ions of the rare earth carbonate to the fluoride ions of the fluorinating agent is 1:3.1-1:3.

3.

5. The method for preparing rare earth fluoride by carbon cycle according to claim 4, characterized in that: The molar ratio of the anionic co-precipitant to the rare earth carbonate is 1:100-1:

200.

6. The method for preparing rare earth fluoride by carbon cycle according to claim 5, wherein: The reaction temperature in step (2) is 75-95 °C.

7. The method for preparing rare earth fluoride by carbon cycle according to claim 6, characterized in that: The mass fraction of the ammonia water is 18%-25%; in step (5), the molar ratio of the rare earth ions of the rare earth chloride to the ammonium ions of the ammonium bicarbonate solution is 1:1.5-1:2.

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