Method for removing fluorine ions in rare earth feed liquid by utilizing rare earth fluoride seed crystal induced crystallization

Abstract

The invention relates to the technical field of rare earth smelting and separation, in particular to a method for removing fluorine ions in rare earth feed liquid by utilizing rare earth fluoride seed crystal induced crystallization, which comprises the following steps: adjusting the pH value of fluorine-containing rare earth feed liquid to 0.5-4.0, and controlling the temperature to 20-60 DEG C to obtain pretreated feed liquid; the pretreatment feed liquid is fed into a crystallizing tank containing rare earth fluoride seed crystals, induced crystallization reaction is conducted for 0.5-10 hours under the stirring condition, and the solid-to-liquid ratio of the rare earth fluoride seed crystals in the crystallizing tank is maintained to be 5%-15%; after the reaction, carrying out solid-liquid separation to obtain supernate as fluorine-removed rare earth feed liquid; and the rare earth fluoride crystals are discharged and recovered. According to the method, the fluorine ion removal rate reaches 80% or above, the method can be suitable for fluorine removal of fluorine ion feed liquid with the initial concentration of 50-5000 micrograms / mL, and rare earth feed liquid with the lower fluorine ion concentration can be obtained through repeated fluorine removal for multiple times. Interference of fluorine on a subsequent extraction process is effectively avoided, and the purity of a rare earth product is improved.

Description

Technical Field

[0001] This invention relates to the field of rare earth smelting and separation technology, and in particular to a method for removing fluoride ions from rare earth feedstock by inducing crystallization using rare earth fluoride seed crystals. Background Technology

[0002] In rare earth solvent extraction and separation processes, the raw materials often contain a certain amount of fluoride ions. High concentrations of fluoride ions not only reduce the performance of the extractant and cause "poisoning" of the organic phase, but may also generate insoluble crystals, clogging equipment, hindering the flow of the two phases, and seriously affecting the extraction efficiency and product quality. Traditional defluorination methods, such as chemical precipitation, adsorption, or ion exchange, generally suffer from low defluorination efficiency, high cost, secondary pollution, or difficulty in resource recovery.

[0003] Therefore, there is an urgent need to develop a new defluorination process that is efficient, economical, environmentally friendly, and allows for resource recycling. Summary of the Invention

[0004] The purpose of this invention is to provide a method for removing fluoride ions from rare earth feed solutions by inducing crystallization using rare earth fluoride seeds. The fluoride ion removal rate reaches over 80%, and the method is applicable to defluorination of feed solutions with initial concentrations of 50–5000 μg / mL of fluoride ions. This effectively avoids interference from fluoride in subsequent extraction processes and improves the purity of rare earth products.

[0005] To achieve the above objectives, the present invention provides a method for removing fluoride ions from rare earth feed solution by inducing crystallization using rare earth fluoride seeds, comprising adjusting the pH of the rare earth fluoride feed solution to 0.5–4.0 and controlling the temperature to 20–60°C to obtain a pretreated feed solution; The pretreated solution is fed into a crystallization tank containing rare earth fluoride seed crystals, and an induced crystallization reaction is carried out under stirring conditions for 0.5–10 hours. The solid-liquid ratio of the rare earth fluoride seed crystals is maintained at 5%–15% in the crystallization tank. After the reaction, solid-liquid separation is performed to obtain the supernatant as the rare earth fluoride removal solution; and the rare earth fluoride crystals are discharged and recycled.

[0006] The rare earth fluoride seed crystals are one or more of LaF3, CeF3, PrF3, NdF3, SmF3, and YF3.

[0007] The crystallization tank is equipped with a heat preservation device, a bottom stirrer, and an upper clarification zone; The heat preservation device is used to maintain the reaction temperature consistent with the pretreated liquid. The bottom stirrer is used to keep the rare earth fluoride seed crystals in a suspended state to ensure full contact and reaction with the liquid. The upper clarification zone is used for solid-liquid separation and collection of the supernatant.

[0008] The specific method for discharging and recovering rare earth fluoride crystals is as follows: when using continuous operation mode, a portion of the crystal slurry is periodically discharged and fresh liquid is added to maintain a stable solid-liquid ratio in the system; after solid-liquid separation, the discharged crystal slurry is partially reused as seed crystals, and the remainder is used to recover rare earth and fluorine resources.

[0009] The specific method for discharging and recovering rare earth fluoride crystals is as follows: when using intermittent operation mode, after the reaction is completed, the entire material is discharged and filtered, and the filter residue is partially returned to the crystallization tank as seed crystals as needed, while the remainder is sent to the resource recovery process.

[0010] The fluoride ion removal rate is over 80%.

[0011] This invention discloses a method for removing fluoride ions from rare earth feed solutions using fluoride rare earth seed crystals. The method includes: adjusting the pH of the fluoride-containing rare earth feed solution to 0.5–4.0 and controlling the temperature to 20–60°C to obtain a pretreated feed solution; feeding the pretreated feed solution into a crystallization tank containing fluoride rare earth seed crystals, and conducting an induced crystallization reaction for 0.5–10 hours under stirring conditions, maintaining a solid-liquid ratio of 5%–15% for the fluoride rare earth seed crystals in the crystallization tank; performing solid-liquid separation after the reaction to obtain the supernatant as the defluorinated rare earth feed solution; and discharging and recovering the fluoride rare earth crystals. This invention achieves a fluoride ion removal rate of over 80%, applicable to defluorination of fluoride ion feed solutions with an initial concentration of 50–5000 μg / mL, and can obtain rare earth feed solutions with even lower fluoride ion concentrations through repeated defluorination. It effectively avoids interference from fluoride in subsequent extraction processes, improving the purity of rare earth products. The precipitated fluoride rare earth precipitate can be used to recover rare earth and fluorine resources, achieving green production. It is suitable for different types of rare earth solutions and fluoride ion concentration ranges, supports intermittent or continuous operation, and is easy to scale up industrially. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a flowchart of the method for reducing fluoride ions in rare earth feed solution by inducing crystallization using rare earth fluoride seed crystals according to the present invention.

[0014] Figure 2 This is a diagram of the preparation system used in this invention. Detailed Implementation

[0015] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0016] First Embodiment This invention provides a method for removing fluoride ions from rare earth solutions by inducing crystallization using rare earth fluoride seeds. The method includes adjusting the pH of the rare earth fluoride solution to 0.5–4.0 and controlling the temperature to 20–60°C to obtain a pretreated solution; feeding the pretreated solution into a crystallization tank containing rare earth fluoride seeds, and inducing crystallization for 0.5–10 hours under stirring conditions, maintaining a solid-liquid ratio of 5%–15% for the rare earth fluoride seeds in the crystallization tank; performing solid-liquid separation after the reaction to obtain the supernatant as the rare earth fluoride removal solution; and discharging and recovering the rare earth fluoride crystals. The rare earth fluoride seeds are one or more mixtures selected from LaF3, CeF3, PrF3, NdF3, SmF3, and YF3.

[0017] Please see Figures 1-2 This invention provides a method for removing fluoride ions from rare earth feed solutions by inducing crystallization using rare earth fluoride seeds, comprising: S101 The pH of the fluorine-containing rare earth solution is adjusted to 1.0 and the temperature is controlled to 50℃ to obtain the pretreated solution; S102 The pretreated liquid is fed into a crystallization tank containing rare earth fluoride seeds, and an induced crystallization reaction is carried out under stirring conditions for 6 hours. The solid-liquid ratio of rare earth fluoride seeds is maintained at 10% (wt.%) in the crystallization tank. The main reaction principle and reaction equation are as follows: After the S103 reaction, solid-liquid separation is performed to obtain the supernatant as the rare earth defluorination solution; and the rare earth fluoride crystals are discharged for recycling.

[0018] The rare earth fluoride seed crystals are one or more of LaF3, CeF3, PrF3, NdF3, SmF3, and YF3.

[0019] The crystallization tank is equipped with a heat preservation device, a bottom stirrer, and an upper clarification zone; The heat preservation device is used to maintain the same reaction temperature (50°C) as the pretreated liquid. The bottom stirrer is used to keep the rare earth fluoride seed crystals in a suspended state to ensure full contact and reaction with the liquid. The upper clarification zone is used for solid-liquid separation and collection of the supernatant.

[0020] The specific method for discharging and recovering rare earth fluoride crystals is as follows: when using continuous operation mode, a portion of the crystal slurry is periodically discharged and fresh liquid is added to maintain a stable solid-liquid ratio in the system; after solid-liquid separation, part of the discharged crystal slurry is reused as seed crystals, and the remainder is used to recover rare earth and fluorine resources.

[0021] The concentration of fluoride ions in the treated rare earth feed solution decreased from the initial 600 μg / mL to 80 μg / mL, with a fluoride ion removal rate of 86.7%, meeting the target of a fluoride removal rate greater than 80%.

[0022] Second Embodiment This invention provides a method for removing fluoride ions from rare earth feed solutions by inducing crystallization using rare earth fluoride seeds, comprising: One-time defluorination process: S101 The pH of the fluorine-containing rare earth solution is adjusted to 2.0 and the temperature is controlled to 40℃ to obtain the pretreated solution; S102 The pretreated liquid is fed into a crystallization tank containing rare earth fluoride seeds, and an induced crystallization reaction is carried out under stirring conditions for 2 hours. The solid-liquid ratio of rare earth fluoride seeds is maintained at 6% (wt.%) in the crystallization tank. After the S103 reaction, solid-liquid separation is performed to obtain the supernatant as the rare earth defluorination solution; and the rare earth fluoride crystals are discharged for recycling.

[0023] The rare earth fluoride seed crystals are one or more of LaF3, CeF3, PrF3, NdF3, SmF3, and YF3.

[0024] The crystallization tank is equipped with a heat preservation device, a bottom stirrer, and an upper clarification zone; The heat preservation device is used to maintain the same reaction temperature (40°C) as the pretreated liquid. The bottom stirrer is used to keep the rare earth fluoride seed crystals in a suspended state to ensure full contact and reaction with the liquid. The upper clarification zone is used for solid-liquid separation and collection of the supernatant.

[0025] The specific method for discharging and recovering rare earth fluoride crystals is as follows: when using intermittent operation mode, after the reaction is completed, the entire material is discharged and filtered, and the filter residue is partially returned to the crystallization tank as seed crystals as needed, while the remainder is sent to the resource recovery process.

[0026] The concentration of fluoride ions in the treated rare earth solution decreased from the initial 1500 μg / mL to 300 μg / mL, with a fluoride ion removal rate of 80% in one treatment.

[0027] Secondary defluorination process: S101 adjusts the pH of the primary rare earth defluorination solution to 3.5 and controls the temperature to 55℃ to obtain the pretreated solution; S102 The pretreated liquid is fed into a crystallization tank containing rare earth fluoride seeds, and an induced crystallization reaction is carried out under stirring conditions for 4 hours. The solid-liquid ratio of rare earth fluoride seeds is maintained at 15% (wt.%) in the crystallization tank. After the S103 reaction, solid-liquid separation is performed to obtain the supernatant as a secondary rare earth defluorination solution; and the rare earth fluoride crystals are discharged and recycled.

[0028] The rare earth fluoride seed crystals are a mixture of LaF3, CeF3, and PrF3.

[0029] The remaining operating conditions are the same as those for a single defluorination process.

[0030] The concentration of fluoride ions in the treated rare earth solution decreased from the initial 300 μg / mL to 20 μg / mL, with a secondary fluoride ion removal rate of 93.3%.

[0031] The two defluorination processes achieved a cumulative fluoride ion removal rate of 98.7%, meeting the target of a defluorination rate greater than 80%.

[0032] The above description discloses only one preferred embodiment of the present invention, and should not be construed as limiting the scope of the present invention. Those skilled in the art will understand that all or part of the processes of the above embodiments can be implemented, and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for removing fluoride ions from rare earth feed solution by inducing crystallization using rare earth fluoride seeds, characterized in that, include: The pH of the fluorine-containing rare earth solution was adjusted to 0.5–4.0, and the temperature was controlled to 20–60℃ to obtain the pretreated solution. The pretreated solution is fed into a crystallization tank containing rare earth fluoride seed crystals, and an induced crystallization reaction is carried out under stirring conditions for 0.5–10 hours. The solid-liquid ratio of the rare earth fluoride seed crystals is maintained at 5%–15% in the crystallization tank. After the reaction, solid-liquid separation is performed to obtain the supernatant as the rare earth fluoride removal solution; and the rare earth fluoride crystals are discharged and recycled.

2. The method for reducing fluoride ions in rare earth feed solution by inducing crystallization using rare earth fluoride seeds as described in claim 1, characterized in that, The rare earth fluoride seed crystals are one or more of LaF3, CeF3, PrF3, NdF3, SmF3, and YF3.

3. The method for reducing fluoride ions in rare earth feed solution by inducing crystallization using rare earth fluoride seeds as described in claim 1, characterized in that... The crystallization tank is equipped with a heat preservation device, a bottom stirrer, and an upper clarification zone; The heat preservation device is used to maintain the reaction temperature consistent with the pretreated liquid. The bottom stirrer is used to keep the rare earth fluoride seed crystals in a suspended state to ensure full contact and reaction with the liquid. The upper clarification zone is used for solid-liquid separation and collection of the supernatant.

4. The method for reducing fluoride ions in rare earth feed solution by inducing crystallization using rare earth fluoride seeds as described in claim 1, characterized in that, The specific method for discharging and recovering rare earth fluoride crystals is as follows: when using continuous operation mode, a portion of the crystal slurry is periodically discharged and fresh liquid is added to maintain a stable solid-liquid ratio in the system; after solid-liquid separation, part of the discharged crystal slurry is reused as seed crystals, and the remainder is used to recover rare earth and fluorine resources.

5. The method for reducing fluoride ions in rare earth feed solution by inducing crystallization using rare earth fluoride seeds as described in claim 1, characterized in that, The specific method for discharging and recovering rare earth fluoride crystals is as follows: when using intermittent operation mode, after the reaction is completed, the entire material is discharged and filtered, and the filter residue is partially returned to the crystallization tank as seed crystals as needed, while the remainder is sent to the resource recovery process.

6. The method for reducing fluoride ions in rare earth feed solution by inducing crystallization using rare earth fluoride seeds as described in claim 1, characterized in that, The fluoride ion removal rate reaches over 80%, and it is suitable for defluorination of fluoride ion solutions with an initial concentration of 50–5000 μg / mL. Furthermore, rare earth solutions with even lower fluoride ion concentrations can be obtained through repeated defluorination processes.

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