Method for removing fluorine in rare earth chloride solution

Abstract

The invention relates to a method for removing fluorine in a rare earth chloride solution, which comprises the following steps: (1) carrying out first mixing on the rare earth chloride solution and a rare earth oxide to obtain a mixed material A; and (2) the mixed material A and rare earth carbonate are subjected to second mixing, stirring and leaching are conducted to remove fluorine, and a fluorine-removed rare earth chloride solution is obtained. According to the method, the rare earth oxide and the rare earth carbonate are sequentially used for reacting with the fluorine element in the rare earth chloride solution, the fluorine element in the rare earth chloride solution can be well removed, the rare earth chloride solution with the high fluorine element content can be directly treated, and the rare earth chloride solution does not need to be diluted.

Description

Technical Field

[0001] This invention relates to the field of rare earth processing technology, and in particular to a method for removing fluoride from rare earth chloride solutions. Background Technology

[0002] In the rare earth preparation process, various single rare earth chloride solutions are separated through an extraction separation process using a mixed rare earth chloride solution. During this extraction separation process, fluoride ions in the rare earth chloride solution can form chelates or insoluble precipitates with other ions under certain acidity and concentration conditions, ultimately forming an intercalated third phase, which seriously affects the extraction and separation effect of rare earths. Existing technologies do not easily recover the extracted organic phase and rare earth materials when dealing with the third phase, thus placing higher demands on the fluoride content in the rare earth chloride solution during production. Simultaneously, fluoride can enter rare earth oxide products during the rare earth production process, ultimately affecting product quality. To eliminate the adverse effects of fluoride on the rare earth production process and rare earth products, it is necessary to remove fluoride from the rare earth chloride solution and reduce its fluoride content.

[0003] CN111636002A discloses a method for removing fluoride from a mixed solution of rare earth chlorides using a combined acid-base method, comprising the following steps: S1, in the process of treating bastnaesite using a combined acid-base method, the washing liquid of the secondary acid leaching residue is treated with soluble carbonate for carbon precipitation to obtain carbon precipitate, which is set aside; S2, the carbon precipitate is added to the mixed solution of rare earth chlorides, and the pH value of the solution system is controlled to be no greater than 2.5; S3, when the pH value of the solution system reaches 3.0±0.5, the addition of carbon precipitate is stopped, and then the solution is heated to above 80°C, and soluble carbonate is added to the solution while stirring; S4, when the pH value of the solution system reaches 4.5±0.5, the addition of soluble carbonate is stopped, the solution is filtered, and the filtrate is the defluorinated mixed solution of rare earth chlorides. This method requires multiple steps to remove fluoride from the rare earth chloride solution.

[0004] CN119506618A discloses a green and efficient process for removing fluoride from rare earth chloride solutions in carbonate ore. The steps are as follows: Step 1: Alumina modification; Step 2: Acid dissolution; Step 3: Adsorption defluorination; Step 4: Filter column defluorination; Step 5: Washing; Step 6: Regeneration. This process requires multiple steps to remove fluoride from the rare earth chloride solution.

[0005] In summary, there is a need to develop a simple and effective method for removing fluoride from solutions containing high levels of rare earth chloride. Summary of the Invention

[0006] To solve the above-mentioned technical problems, the present invention provides a method for removing fluoride from a rare earth chloride solution. The method involves mixing the rare earth chloride solution with rare earth oxides and rare earth carbonates, respectively. The rare earth oxides and rare earth carbonates undergo a chemical adsorption reaction with fluoride ions in the rare earth chloride solution, allowing fluoride ions to enter the rare earth oxides and rare earth carbonates from the rare earth solution, thereby removing fluoride from the rare earth chloride solution.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for removing fluoride from a rare earth chloride solution, the method comprising the following steps:

[0009] (1) The rare earth chloride solution and rare earth oxide are mixed in the first step to obtain mixture A;

[0010] (2) Mix the mixture A and rare earth carbonate for a second time, and stir and leach to remove fluorine to obtain a defluorinated rare earth chloride solution.

[0011] The rare earth chloride solution in this invention is an acidic solution. First, the rare earth chloride solution and rare earth oxides are mixed to obtain mixture A. Then, mixture A and rare earth carbonate are mixed to obtain a second mixture. Both rare earth oxides and rare earth carbonates undergo chemical adsorption reactions with fluoride ions in the rare earth chloride solution to remove fluoride ions from the solution, resulting in a defluorinated rare earth chloride solution.

[0012] As a preferred embodiment of the present invention, the rare earth chloride solution includes rare earth chloride, fluoride ions, aluminum ions and silicon ions.

[0013] Preferably, the concentration of rare earth chloride in the rare earth chloride solution is 0.5 to 3 mol / L, for example, it can be 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L or 3 mol / L, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0014] Preferably, the pH value of the rare earth chloride solution is 0.5 to 3, for example, it can be 0.5, 1, 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.8 or 3, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0015] This invention allows for the direct addition of rare earth oxide concentrate to a rare earth chloride solution with a pH of 0.5–3. This is because the added rare earth oxide reacts with hydrogen ions in the rare earth solution, consuming the hydrogen ions and increasing the rare earth concentration in the solution. This ensures that the pH of the solution after the reaction meets the requirements of the next step, eliminating the need to adjust the pH of the rare earth chloride solution with an alkaline solution.

[0016] As a preferred technical solution of the present invention, the content of fluoride ions in the rare earth chloride solution is 0.1 to 20 g / L, for example, it can be 0.1 g / L, 1 g / L, 2 g / L, 5 g / L, 8 g / L, 10 g / L, 15 g / L or 20 g / L, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0017] This invention removes fluoride by sequentially reacting rare earth oxides and rare earth carbonates with rare earth chloride solutions. It can directly treat rare earth chloride solutions with fluoride content as high as 20 g / L without diluting the rare earth chloride solution to reduce the fluoride concentration before treatment, making the treatment method simpler.

[0018] Preferably, the rare earth elements in the rare earth chloride solution include any one or at least two combinations of lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, or yttrium. Typical but non-limiting combinations include: combinations of lanthanum and cerium, lanthanum and praseodymium, lanthanum and neodymium, lanthanum and europium, lanthanum and gadolinium, lanthanum and erbium, lanthanum, cerium, and praseodymium, lanthanum, cerium, and neodymium, lanthanum, cerium, and samarium, lanthanum, cerium, and gadolinium, lanthanum, cerium, and erbium, and lanthanum, cerium, praseodymium, and neodymium.

[0019] As a preferred technical solution of the present invention, the method further includes premixing the rare earth chloride solution and the alkaline solution before step (1).

[0020] In this invention, the alkaline solution can be premixed with the rare earth chloride solution to adjust the pH of the rare earth chloride solution and promote the reaction between the rare earth chloride solution and rare earth oxides.

[0021] Preferably, the volume ratio of the alkaline solution to the rare earth chloride solution is (0.01 to 0.1):1, for example, it can be 0.01:1, 0.02:1, 0.04:1, 0.06:1, 0.08:1 or 0.1:1, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0022] Preferably, the alkaline solution comprises any one or a combination of at least two of sodium hydroxide solution, sodium carbonate solution, sodium bicarbonate solution, ammonium carbonate solution, or ammonium bicarbonate solution. Typical but non-limiting combinations include: combinations of sodium hydroxide solution and sodium carbonate solution, combinations of sodium hydroxide solution and sodium bicarbonate solution, combinations of sodium hydroxide solution and ammonium carbonate solution, combinations of sodium hydroxide solution and ammonium bicarbonate solution, combinations of sodium hydroxide solution, sodium carbonate solution and sodium bicarbonate solution, combinations of sodium hydroxide solution, sodium carbonate solution and ammonium carbonate solution, combinations of sodium hydroxide solution, sodium carbonate solution and sodium bicarbonate solution and ammonium carbonate solution, combinations of sodium hydroxide solution, sodium carbonate solution, sodium bicarbonate solution and ammonium bicarbonate solution, combinations of sodium hydroxide solution, sodium carbonate solution, ammonium carbonate solution and ammonium bicarbonate solution, combinations of sodium carbonate solution, sodium bicarbonate solution and ammonium carbonate solution, combinations of sodium carbonate solution, sodium bicarbonate solution and ammonium carbonate solution, combinations of sodium hydroxide solution, sodium carbonate solution, sodium bicarbonate solution, ammonium carbonate solution and ammonium bicarbonate solution, combinations of sodium hydroxide solution, sodium carbonate solution, sodium bicarbonate solution, ammonium carbonate solution and ammonium bicarbonate solution.

[0023] Preferably, the molar concentration of the alkaline solution is 0.5 to 10 mol / L, for example, it can be 0.5 mol / L, 1 mol / L, 2 mol / L, 5 mol / L, 8 mol / L or 10 mol / L, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0024] As a preferred technical solution of the present invention, the liquid-solid ratio of the rare earth chloride solution and the rare earth oxide is 1:(0.01 to 0.08), for example, it can be 1:0.01, 1:0.02, 1:0.04, 1:0.06 or 1:0.08, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0025] Preferably, the purity of the rare earth oxide is ≥99.5%, for example, it can be 99.5%, 99.6%, 99.7%, 99.8%, 99.9% or 99.99%, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0026] Preferably, the rare earth oxide includes rare earth oxide concentrate.

[0027] This invention uses rare earth oxide concentrate to remove fluorine from rare earth chloride solution. It removes fluoride ions from the solution by utilizing only the components of rare earth itself through chemical adsorption and precipitation reaction, without the need to introduce other metal ions. This maintains the purity of the rare earth chloride solution. At the same time, the rare earth enrichment slag enriched with fluorine impurities can be further washed with water and filtered with alkali. Calcium oxide is added to the solution to recover fluorine, thus realizing the recycling of fluorine resources.

[0028] Preferably, the rare earth oxide concentrate includes rare earth oxide concentrate produced by the calcination and decomposition of rare earth carbonate and / or rare earth oxide concentrate produced by the calcination and decomposition of rare earth oxalate.

[0029] As a preferred technical solution of the present invention, the particle size of the rare earth oxide concentrate is <0.15mm, for example, it can be 0.02mm, 0.05mm, 0.1mm, 0.12mm or 0.14mm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0030] Preferably, the fluorine content in the rare earth oxide concentrate is less than 100 ppm, for example, it can be 10 ppm, 20 ppm, 40 ppm, 50 ppm, 60 ppm, 70 ppm, 80 ppm or 90 ppm, but is not limited to the listed values, other unlisted values ​​within the above range are also applicable.

[0031] Preferably, the aluminum content in the rare earth oxide concentrate is less than 500 ppm, for example, it can be 100 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm, 350 ppm, 400 ppm or 450 ppm, but is not limited to the listed values, other unlisted values ​​within the above range are also applicable.

[0032] As a preferred technical solution of the present invention, the mass ratio of the mixture A and the rare earth carbonate in step (2) is 1:(0.03~0.1), for example, it can be 1:0.03, 1:0.05, 1:0.07, 1:0.09 or 1:0.1, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0033] Preferably, the rare earth carbonate includes any one or a combination of at least two of cerium carbonate, neodymium carbonate, praseodymium carbonate, lanthanum carbonate, or mixed rare earth carbonates. Typical but non-limiting combinations include: combinations of cerium carbonate and neodymium carbonate, combinations of cerium carbonate and praseodymium carbonate, combinations of cerium carbonate and lanthanum carbonate, combinations of neodymium carbonate and lanthanum carbonate, combinations of praseodymium carbonate and lanthanum carbonate, combinations of cerium carbonate, neodymium carbonate, and praseodymium carbonate, combinations of cerium carbonate, neodymium carbonate, and lanthanum carbonate, combinations of cerium carbonate, praseodymium carbonate, and lanthanum carbonate, combinations of neodymium carbonate, praseodymium carbonate, and lanthanum carbonate, and preferably a combination of lanthanum carbonate and cerium carbonate.

[0034] Preferably, the mass ratio of lanthanum carbonate to cerium carbonate is (0.4 to 1):1, for example, it can be 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1 or 1:1, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0035] In this invention, when the rare earth carbonate is a combination of lanthanum carbonate and cerium carbonate, and the mass ratio of the two is (0.4~1):1, the removal rate of fluorine can be significantly increased. This is because lanthanum and cerium have larger atomic radii and will adsorb more fluoride ions, resulting in a better fluorine removal effect.

[0036] Preferably, the fluorine content in the rare earth carbonate is less than 100 ppm, for example, it can be 10 ppm, 20 ppm, 40 ppm, 60 ppm or 90 ppm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0037] Preferably, the aluminum content in the rare earth carbonate is less than 500 ppm, for example, it can be 100 ppm, 200 ppm, 300 ppm, 400 ppm or 450 ppm, but is not limited to the listed values, other unlisted values ​​within the above range are also applicable.

[0038] As a preferred technical solution of the present invention, the first mixing in step (1) and the second mixing in step (2) are carried out independently under heating and stirring.

[0039] Preferably, the heating temperature for heating and stirring is 20 to 100°C, for example, it can be 20°C, 40°C, 60°C, 80°C or 100°C, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0040] Preferably, the heating and stirring time is 0.2 to 10 hours, for example, 0.2 hours, 1 hour, 2 hours, 5 hours or 10 hours, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0041] Preferably, the stirring speed of the heating and stirring is 60 to 1000 r / min, for example, it can be 60 r / min, 100 r / min, 200 r / min, 500 r / min or 1000 r / min, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0042] As a preferred technical solution of the present invention, the fluorine content in the rare earth chloride solution after defluorination is 40 to 500 ppm, for example, it can be 40 ppm, 100 ppm, 200 ppm, 300 ppm, 400 ppm or 500 ppm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0043] As a preferred technical solution of the present invention, the method includes the following steps:

[0044] (1) A rare earth chloride solution with a fluoride ion content of 0.1-20 g / L and an alkaline solution are premixed to obtain a mixed solution with a pH value of 3-4;

[0045] (2) Under the conditions of temperature of 20-100℃ and stirring speed of 60-1000r / min, the mixed solution obtained in step (1) and rare earth oxide concentrate with particle size <0.15mm, fluorine content less than 100ppm and aluminum content less than 500ppm are first mixed for 0.2-10h to obtain mixture A;

[0046] (3) Mixture A and rare earth carbonate are mixed for 0.2 to 10 hours at a temperature of 20 to 100°C and a stirring speed of 60 to 1000 r / min, and then stirred and leached to remove fluorine, so as to obtain a rare earth chloride solution with a fluorine content of 40 to 500 ppm.

[0047] Compared with the prior art, the present invention has at least the following beneficial effects:

[0048] (1) The present invention uses rare earth oxides and rare earth carbonates in sequence to remove fluorine from rare earth chloride solution. It uses only the rare earth components to precipitate fluorine without introducing other ions, thus maintaining the purity of rare earth chloride solution.

[0049] (2) The defluorination method provided by the present invention has the advantages of simple process and low cost. It can directly treat rare earth chloride solution with high fluorine content without diluting the rare earth chloride solution. At the same time, the fluorine content in the rare earth chloride solution after defluorination can be controlled below 500 ppm, and the fluorine removal rate can reach more than 95%. Attached Figure Description

[0050] Figure 1This is a process flow diagram of defluorination in rare earth chloride solution provided in Embodiment 1 of the present invention. Detailed Implementation

[0051] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0052] Example 1

[0053] This embodiment provides a method for removing fluoride from a rare earth chloride solution. (See [link to previous document]) Figure 1 The method includes the following steps:

[0054] (1) A rare earth chloride solution and a sodium hydroxide solution are premixed to obtain a mixed solution; wherein the volume ratio of the sodium hydroxide solution to the rare earth chloride solution is 0.02:1, the rare earth chloride solution includes 1.5 mol / L rare earth chloride, 10 g / L fluoride ions, 10 g / L aluminum ions and 0.1 g / L silicon ions; and the rare earth chloride includes a mixed rare earth chloride of lanthanum chloride, cerium chloride, praseodymium chloride, neodymium chloride, samarium chloride and dysprosium chloride; the molar concentration of sodium hydroxide in the sodium hydroxide solution is 5 mol / L; the pH value of the rare earth chloride solution is 2, and the pH value of the mixed solution is 3;

[0055] (2) The mixed solution and the oxide concentrate produced by the calcination and decomposition of rare earth oxalate were first mixed at a heating temperature of 60℃ and a stirring speed of 200r / min for 3 hours to obtain mixture A; wherein, the oxide concentrate produced by calcination and decomposition included 23.22% yttrium oxide, 18.58% lanthanum oxide, 18.13% cerium oxide, 4.59% praseodymium oxide, 16.38% neodymium oxide, 3.96% samarium oxide, and 0.25% [unclear text - possibly related to yttrium oxide]. The oxide concentrate contains europium oxide, 4.02% gadolinium oxide, 0.75% terbium oxide, 4.14% dysprosium oxide, 0.83% holmium oxide, 2.46% erbium oxide, 0.31% thulium oxide, 2.01% ytterbium oxide, and 0.33% lutetium oxide. The purity of the oxide concentrate is 99.6%. The liquid-solid ratio of the rare earth chloride solution to the oxide concentrate is 1:0.05. The oxide concentrate has a particle size of 0.1 mm, a fluorine content of 60 ppm, and an aluminum content of 300 ppm.

[0056] (3) Mixture A and rare earth carbonate are mixed again at a mass ratio of 1:0.05 under the conditions of heating temperature of 50℃ and stirring speed of 500r / min, and the stirring time is 5h. The rare earth carbonate is a mixture of lanthanum carbonate and cerium carbonate at a mass ratio of 0.6:1. The mixture is stirred and leached for 2h at a temperature of 90℃ and a speed of 200r / min to remove fluorine, and a rare earth chloride solution after fluorine removal is obtained. The fluorine content of lanthanum carbonate is 50ppm and the aluminum content is 100ppm, and the fluorine content of cerium carbonate is 60ppm and the aluminum content is 200ppm.

[0057] In this embodiment, the fluoride content in the defluorinated rare earth chloride solution is 100 ppm.

[0058] Example 2

[0059] This embodiment provides a method for removing fluoride from a rare earth chloride solution, the method comprising the following steps:

[0060] (1) Under the conditions of heating temperature of 100℃ and stirring speed of 1000r / min, rare earth chloride solution and oxide concentrate produced by calcination and decomposition of rare earth oxalate are first mixed for 0.2h to obtain mixture A; wherein, the rare earth chloride solution includes 0.5mol / L rare earth chloride, 10g / L fluoride ions, 20g / L aluminum ions and 0.2g / L silicon ions; and the rare earth chloride includes a mixture of rare earth chlorides of lanthanum chloride, cerium chloride, praseodymium chloride, neodymium chloride, samarium chloride, dysprosium chloride, gadolinium chloride and holmium chloride; the pH value of the rare earth chloride solution is 3; the oxide concentrate produced by calcination and decomposition includes 22.72% yttrium oxide, The oxide concentrate contains 19.88% lanthanum oxide, 16.80% cerium oxide, 4.75% praseodymium oxide, 16.33% neodymium oxide, 4.11% samarium oxide, 0.23% europium oxide, 4.19% gadolinium oxide, 0.75% terbium oxide, 4.24% dysprosium oxide, 0.82% holmium oxide, 2.33% erbium oxide, 0.31% thulium oxide, 2.01% ytterbium oxide, and 0.33% lutetium oxide. The purity of the oxide concentrate is 99.8%. The liquid-solid ratio of the rare earth chloride solution to the oxide concentrate is 1:0.08. The particle size of the oxide concentrate is 0.14 mm, the fluorine content is 10 ppm, and the aluminum content is 100 ppm.

[0061] (2) Mixture A and cerium carbonate were mixed again at a mass ratio of 1:0.03 under the conditions of heating temperature of 20℃ and stirring speed of 60r / min. The stirring time was 10h, and the mixture was stirred and leached for 1.5h at a temperature of 90℃ and a speed of 600r / min to remove fluorine, so as to obtain a rare earth chloride solution after fluorine removal, wherein the fluorine content of cerium carbonate was 20ppm and the aluminum content was 300ppm.

[0062] In this embodiment, the fluoride content in the defluorinated rare earth chloride solution is 150 ppm.

[0063] Example 3

[0064] This embodiment provides a method for removing fluoride from a rare earth chloride solution, the method comprising the following steps:

[0065] (1) A rare earth chloride solution and a sodium hydroxide solution are premixed to obtain a mixed solution; wherein the volume ratio of the sodium hydroxide solution to the rare earth chloride solution is 0.01:1, the rare earth chloride solution includes 3 mol / L rare earth chloride, 1 g / L fluoride ions, 5 g / L aluminum ions and 0.2 g / L silicon ions; and the rare earth chloride includes a mixture of rare earth chlorides of lanthanum chloride, cerium chloride, praseodymium chloride, neodymium chloride, samarium chloride, dysprosium chloride, gadolinium chloride and holmium chloride; the molar concentration of sodium hydroxide in the sodium hydroxide solution is 10 mol / L; the pH value of the rare earth chloride solution is 0.5, and the pH value of the mixed solution is 2.5;

[0066] (2) The mixed solution and the oxide concentrate produced by the calcination and decomposition of rare earth carbonate were first mixed at a heating temperature of 20℃ and a stirring speed of 60 r / min for 10 h to obtain mixture A; wherein, the oxide concentrate produced by calcination and decomposition included 25.38% yttrium oxide, 18.64% lanthanum oxide, 12.31% cerium oxide, 4.18% praseodymium oxide, 17.34% neodymium oxide, 4.06% samarium oxide, and 2.49% [unclear - possibly referring to a specific component or component]. The oxide concentrate contains europium oxide, 4.49% gadolinium oxide, 0.73% terbium oxide, 4.78% dysprosium oxide, 0.51% holmium oxide, 2.76% erbium oxide, 0.31% thulium oxide, 2.81% ytterbium oxide, and 0.33% lutetium oxide. The purity of the oxide concentrate is 99.5%. The liquid-solid ratio of the rare earth chloride solution to the oxide concentrate is 1:0.01. The particle size of the oxide concentrate is 0.02 mm, the fluorine content is 90 ppm, and the aluminum content is 450 ppm.

[0067] (3) Mixture A and lanthanum carbonate were mixed at a mass ratio of 1:0.1 under the conditions of heating temperature of 100℃ and stirring speed of 1000r / min for a second time. The stirring time was 0.5h, and the mixture was stirred and leached for 2h at a temperature of 90℃ and a speed of 300r / min to remove fluorine, so as to obtain a rare earth chloride solution after fluorine removal, wherein the fluorine content of lanthanum carbonate was 90ppm and the aluminum content was 200ppm.

[0068] In this embodiment, the fluoride content in the defluorinated rare earth chloride solution is 40 ppm.

[0069] Example 4

[0070] This embodiment provides a method for removing fluoride from a rare earth chloride solution. The only difference from Embodiment 1 is that the fluoride ion content in the rare earth chloride solution is 20 g / L, while the rest is the same as in Embodiment 1.

[0071] In this embodiment, the fluoride content in the defluorinated rare earth chloride solution is 500 ppm.

[0072] Example 5

[0073] This embodiment provides a method for removing fluoride from a rare earth chloride solution. The only difference from Embodiment 1 is that the liquid-solid ratio of the rare earth chloride solution and the oxide concentrate is adjusted from 1:0.05 to 1:0.005. All other aspects are the same as in Embodiment 1.

[0074] In this embodiment, the fluoride content in the rare earth chloride solution after defluorination is 480 ppm.

[0075] Example 6

[0076] This embodiment provides a method for removing fluoride from a rare earth chloride solution. The only difference from Embodiment 1 is that the mass ratio of mixture A and rare earth carbonate is adjusted from 1:0.05 to 1:0.01. All other aspects are the same as in Embodiment 1.

[0077] In this embodiment, the fluoride content in the defluorinated rare earth chloride solution is 450 ppm.

[0078] Comparative Example 1

[0079] This comparative example provides a method for removing fluoride from a rare earth chloride solution. The only difference from Example 1 is that, except for directly stirring and leaching the mixture A to obtain a defluorinated rare earth chloride solution, i.e., the method does not include step (3), the rest is the same as Example 1.

[0080] The fluoride content in the defluorinated rare earth chloride solution described in this comparative example is 3000 ppm.

[0081] Comparative Example 2

[0082] This comparative example provides a method for removing fluoride from a rare earth chloride solution. The only difference from Example 1 is that, except that the mixed solution is first mixed with rare earth carbonate for a second time, and then the resulting mixture is first mixed with the oxide concentrate produced by the calcination and decomposition of rare earth oxalate, i.e., the method performs step (3) first and then step (2), the rest is the same as Example 1.

[0083] The fluoride content in the defluorinated rare earth chloride solution described in this comparative example is 2000 ppm.

[0084] Comparative Example 3

[0085] This comparative example provides a method for removing fluoride from a rare earth chloride solution. The difference between this method and Example 1 is that the method includes the following steps:

[0086] (1) After adjusting the pH of the rare earth chloride solution to 3 using ammonia water, the rare earth hydroxide with the same rare earth element as the rare earth chloride solution was mixed with the pH-adjusted rare earth chloride solution at a mass-volume ratio of 20 g / L. The mixture was stirred at 500 rpm at 60 °C for 3 hours to carry out a one-step reaction.

[0087] (2) The material obtained from the first step reaction in step (1) is subjected to a one-step solid-liquid separation process to obtain impurity slag and rare earth chloride purification liquid. 5g of the impurity slag is mixed with a sodium hydroxide solution with a mass concentration of 20g / L and stirred at 200rpm at 80℃ for a two-step reaction for 5h. The material obtained from the two-step reaction is subjected to a two-step solid-liquid separation process to obtain a rare earth chloride solution after fluorination and a fluorine-containing waste liquid.

[0088] The fluoride content in the defluorinated rare earth chloride solution described in this comparative example is 3500 ppm.

[0089] Comparative Example 4

[0090] This comparative example provides a method for removing fluoride from a rare earth chloride solution. The only difference from Example 1 is that, except for directly mixing the mixed solution obtained in step (1) with rare earth carbonate, i.e., the method does not include step (2), the rest is the same as Example 1.

[0091] The fluoride content in the defluorinated rare earth chloride solution described in this comparative example is 1500 ppm.

[0092] Comparative Example 5

[0093] This comparative example provides a method for removing fluoride from a rare earth chloride solution. The only difference from Example 1 is that the oxide concentrate produced by the calcination and decomposition of rare earth oxalate in step (2) is replaced with yttrium hydroxide with a fluorine content of 60 ppm and an aluminum content of 300 ppm. All other aspects are the same as in Example 1.

[0094] The fluoride content in the defluorinated rare earth chloride solution described in this comparative example is 7000 ppm.

[0095] Comparative Example 6

[0096] This comparative example provides a method for removing fluoride from a rare earth chloride solution. The only difference from Example 1 is that, except that in step (3), rare earth carbonate is replaced with cerium hydroxide with a fluorine content of 50 ppm and an aluminum content of 100 ppm, the rest is the same as in Example 1.

[0097] The fluoride content in the defluorinated rare earth chloride solution described in this comparative example is 6000 ppm.

[0098] The fluoride content of the defluorinated rare earth chloride solutions obtained in Examples 1-6 and Comparative Examples 1-6 was detected by ion chromatography. The fluoride removal rate was calculated according to the formula: Removal rate (%) = (fluoride ion content in rare earth chloride solution - fluoride ion content in defluorinated rare earth chloride solution) / fluoride ion content in rare earth chloride solution × 100%. The detection results are shown in Table 1.

[0099] Table 1

[0100]

[0101]

[0102] The test results show that:

[0103] (1) As can be seen from Examples 1 to 3, the present invention can effectively remove fluorine from rare earth chloride solution by reacting rare earth oxides and rare earth carbonates with fluorine in rare earth chloride solution in sequence, so that the removal rate of fluorine in rare earth chloride solution can reach more than 96%.

[0104] (2) As can be seen from Examples 1 and 4, the rare earth chloride solution in Example 1 contains fluoride ions of 10 g / L, and the fluoride removal rate after treatment can reach 99%; while the rare earth chloride solution in Example 4 contains fluoride ions of 20 g / L, and the fluoride removal rate after treatment is 97.5%. It can be seen that the present invention has a better removal effect on high fluoride impurities in rare earth chloride solution, and can directly treat high fluoride solution of 20 g / L without diluting the rare earth chloride solution to reduce the concentration of fluoride before treatment. Moreover, when the same defluorinating agent is added, the removal rate can still be as high as 97.5%.

[0105] (3) As can be seen from Examples 1 and 5, in Example 1, the liquid-solid ratio of rare earth chloride solution and oxide concentrate is 1:0.05, and the fluorine removal rate after treatment can reach 99%; while in Example 5, the liquid-solid ratio of rare earth chloride solution and oxide concentrate is 1:0.005, and the fluorine removal rate after treatment is 95.2%. It can be seen that by changing the liquid-solid ratio of rare earth chloride solution and oxide concentrate, the present invention found that the defluorination effect is significantly worse when the amount of oxide concentrate added is reduced. Appropriately increasing the amount of oxide concentrate added can achieve a better defluorination effect.

[0106] (4) As can be seen from Examples 1 and 6, in Example 1, the mass ratio of mixture A to rare earth carbonate is 1:0.05, and the fluorine removal rate after treatment can reach 99%; while in Example 6, the mass ratio of mixture A to rare earth carbonate is 1:0.01, and the fluorine removal rate after treatment is 95.5%. It can be seen that by changing the mass ratio of mixture A to rare earth carbonate, the present invention found that the fluorine removal effect is significantly worse when the amount of rare earth carbonate added is reduced, and a better defluorination effect can be achieved by appropriately increasing the mass ratio of mixture A to rare earth carbonate.

[0107] (5) As can be seen from Example 1 and Comparative Examples 1-6, the present invention can effectively remove fluorine from rare earth chloride solution by reacting rare earth oxides and rare earth carbonates with fluorine in rare earth chloride solution in sequence.

[0108] In summary, this invention removes fluoride from rare earth chloride solutions by using rare earth oxides and rare earth carbonates. It utilizes only the chemical precipitation of rare earth components to adsorb fluoride without introducing other metal ions, thus maintaining the purity of the rare earth chloride solution. At the same time, the fluoride content in the rare earth chloride solution after fluoride removal can be controlled below 500 ppm, and the fluoride removal rate can reach over 95%.

[0109] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for removing fluoride from a rare earth chloride solution, characterized in that, The method includes the following steps: (1) The rare earth chloride solution and rare earth oxide are mixed in the first step to obtain mixture A; (2) Mix the mixture A and rare earth carbonate for a second time, and stir and leach to remove fluorine to obtain a defluorinated rare earth chloride solution.

2. The method according to claim 1, characterized in that, The rare earth chloride solution includes rare earth chloride, fluoride ions, aluminum ions, and silicon ions. Preferably, the concentration of rare earth chloride in the rare earth chloride solution is 0.5–3 mol / L; Preferably, the pH value of the rare earth chloride solution is 0.5 to 3.

3. The method according to claim 2, characterized in that, The fluoride ion content in the rare earth chloride solution is 0.1–20 g / L; Preferably, the rare earth elements in the rare earth chloride solution include any one or a combination of at least two of lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, or yttrium.

4. The method according to any one of claims 1-3, characterized in that, The method further includes premixing the rare earth chloride solution and the alkaline solution before step (1); Preferably, the volume ratio of the alkaline solution to the rare earth chloride solution is (0.01-0.1):1; Preferably, the alkaline solution includes any one or a combination of at least two of sodium hydroxide solution, sodium carbonate solution, sodium bicarbonate solution, ammonium carbonate solution, or ammonium bicarbonate solution; Preferably, the molar concentration of the alkaline solution is 0.5 to 10 mol / L.

5. The method according to any one of claims 1-4, characterized in that, The liquid-to-solid ratio of the rare earth chloride solution and the rare earth oxide is 1:(0.01~0.08); Preferably, the purity of the rare earth oxide is ≥99.5%; Preferably, the rare earth oxide comprises rare earth oxide concentrate; Preferably, the rare earth oxide concentrate includes rare earth oxide concentrate produced by the calcination and decomposition of rare earth carbonate and / or rare earth oxide concentrate produced by the calcination and decomposition of rare earth oxalate.

6. The method according to claim 5, characterized in that, The particle size of the rare earth oxide concentrate is <0.15 mm; Preferably, the fluorine content in the rare earth oxide concentrate is less than 100 ppm; Preferably, the aluminum content in the rare earth oxide concentrate is less than 500 ppm.

7. The method according to any one of claims 1-6, characterized in that, In step (2), the mass ratio of the mixture A and the rare earth carbonate is 1:(0.03~0.1); Preferably, the rare earth carbonate includes any one or a combination of at least two of cerium carbonate, neodymium carbonate, praseodymium carbonate, lanthanum carbonate, or mixed rare earth carbonates, and is preferably a combination of lanthanum carbonate and cerium carbonate. Preferably, the mass ratio of lanthanum carbonate to cerium carbonate is (0.4–1):1; Preferably, the fluorine content in the rare earth carbonate is less than 100 ppm; Preferably, the aluminum content in the rare earth carbonate is less than 500 ppm.

8. The method according to any one of claims 1-7, characterized in that, Step (1) the first mixing and step (2) the second mixing are each carried out independently under heating and stirring; Preferably, the heating temperature for the heating and stirring is 20–100°C; Preferably, the heating and stirring time is 0.2 to 10 hours; Preferably, the stirring speed for heating and stirring is 60 to 1000 r / min.

9. The method according to any one of claims 1-8, characterized in that, The fluorine content in the defluorinated rare earth chloride solution is 40-500 ppm.

10. The method according to any one of claims 1-9, characterized in that, The method includes the following steps: (1) A rare earth chloride solution with a fluoride ion content of 0.1-20 g / L and an alkaline solution are premixed to obtain a mixed solution with a pH value of 3-4; (2) Under the conditions of temperature of 20-100℃ and stirring speed of 60-1000r / min, the mixed solution obtained in step (1) and rare earth oxide concentrate with particle size <0.15mm, fluorine content less than 100ppm and aluminum content less than 500ppm are first mixed for 0.2-10h to obtain mixture A; (3) Mixture A and rare earth carbonate are mixed for 0.2 to 10 hours at a temperature of 20 to 100°C and a stirring speed of 60 to 1000 r / min, and then stirred and leached to remove fluorine, so as to obtain a rare earth chloride solution with a fluorine content of 40 to 500 ppm.

Images