Treatment method of fluorine-containing rare earth material

Abstract

The invention discloses a treatment method of a fluorine-containing rare earth material. The treatment method comprises the following steps: reacting a fluorine-containing rare earth material with an alkali carbonate solution to obtain an alkali decomposition product; carrying out solid-liquid separation on the alkali decomposition product to obtain a solid product and a liquid product; washing the solid product with water to obtain a washed solid product and an alkali wash solution; and separating out the alkali metal fluoride in the alkali wash solution to obtain an alkali metal fluoride solid and residual alkali liquor. According to the method, the fluorine element and the rare earth element in the fluorine-containing rare earth material can be recycled respectively.

Description

Technical Field

[0001] The invention relates to a method for treating fluorine-containing rare earth materials. Background Art

[0002] Fluorine-containing rare earth materials primarily include bastnaesite, mixed rare earth ores containing bastnaesite, waste rare earth polishing powder, and fluorine-containing waste generated during rare earth metal smelting. Separately recovering the fluorine and rare earth elements from these fluorine-containing rare earth materials has become a pressing issue.

[0003] CN109517974A discloses a smelting method for comprehensively recovering rare earth and fluorine from bastnaesite, comprising the following steps: (1) calcining the bastnaesite by passing water vapor to obtain a calcined ore and a fluorine-containing gas; dissolving the calcined ore for the first time with hydrochloric acid to obtain a first leaching residue and a first leachate containing rare earth chloride, the first leachate being a rare earth solution; (2) saponifying the extractant with a calcium ion agent, saponifying the rare earth solution with the saponified extractant, and discharging calcium-containing extraction wastewater; then stripping the rare earth solution in hydrochloric acid to obtain a rare earth chloride solution; reacting the calcium-containing extraction wastewater with a fluorine-containing gas to prepare a calcium fluoride product; precipitating the rare earth chloride solution with sodium carbonate to obtain rare earth carbonate after precipitation, and calcining the carbonate at high temperature to obtain rare earth oxides. This method decomposes the bastnaesite by passing water vapor, and the reaction temperature is relatively high.

[0004] CN113564343A discloses a green chemical alkali defluorination method for roasting fluorine-containing rare earth ore and solid slag, comprising the following steps: adding the fluorine-containing rare earth ore and slag into a corundum crucible, then adding sodium hydroxide and mixing evenly, so that the fluorine and rare earth in the fluorine-containing rare earth ore and slag are completely converted into NaF and RE x O y The alkali-converted slag is ground and added to deionized water. The slag is heated at 40-80°C and stirred for 6-20 minutes to obtain a leachate. The resulting leachate is separated into solid and liquid using a high-speed centrifuge to obtain a leachate containing NaF and a slag containing RE(OH)3. The RE(OH)3-containing slag is mixed with 3 mol / L hydrochloric acid, and the rare earth elements in the slag are leached with RECl3. This method has high reaction temperatures and complex steps.

[0005] CN106191454A discloses a method for extracting rare earths from calcium-thermal reduction rare earth smelting slag, comprising the following steps: uniformly mixing the calcium-thermal reduction rare earth smelting slag with sodium carbonate to obtain a mixture; roasting the mixture in a high-temperature furnace to obtain a roasted product; finely grinding the roasted product and then leaching it in water, filtering, washing it with water, and drying it; collecting the above-mentioned water leaching liquid and washing liquid, and recovering the sodium carbonate by steam crystallization; leaching the solid product after washing and drying with hydrochloric acid to finally obtain a feed solution containing rare earths, thereby completing the extraction of rare earths. This method has a high reaction temperature and cannot recover fluorine. Summary of the Invention

[0006] In view of this, the present invention aims to provide a method for treating fluorine-containing rare earth materials. The method of the present invention can separately recover fluorine and rare earth elements from the fluorine-containing rare earth materials. Furthermore, the method of the present invention has a high fluorine recovery rate. Furthermore, the alkali metal fluoride obtained by the method of the present invention has a high purity.

[0007] The present invention achieves the above-mentioned purpose through the following technical solutions.

[0008] The present invention provides a method for treating fluorine-containing rare earth materials, comprising the following steps:

[0009] The fluorine-containing rare earth material is reacted with an alkali metal carbonate solution to obtain an alkali decomposition product; the alkali decomposition product is separated into solid and liquid to obtain a solid product and a liquid product; the solid product is washed with water to obtain a washed solid product and an alkali washing liquid; and the alkali metal fluoride in the alkali washing liquid is precipitated to obtain an alkali metal fluoride solid and a residual alkali liquid.

[0010] According to the treatment method of the present invention, preferably, the fluorine-containing rare earth material reacts with the alkali metal carbonate solution at a pressure of 0.1-1 MPa and a temperature of 100-200°C.

[0011] According to the treatment method of the present invention, preferably, the reaction time of the fluorine-containing rare earth material and the alkali metal carbonate solution is 0.2 to 5 hours.

[0012] According to the treatment method of the present invention, preferably, the concentration of the alkali metal carbonate solution is 10-35 wt %, and the mass volume ratio of the fluorine-containing rare earth material to the alkali metal carbonate solution is 1 kg: (0.7-6) L;

[0013] The alkali metal carbonate is selected from one or more of sodium carbonate and potassium carbonate.

[0014] According to the treatment method of the present invention, preferably, the content of rare earth elements in the fluorine-containing rare earth material is ≥40 wt %, and the content of fluorine elements is ≥3.5 wt %.

[0015] According to the treatment method of the present invention, preferably, the alkali metal fluoride in the alkaline washing solution is precipitated by concentration crystallization or salting out.

[0016] The processing method according to the present invention preferably further comprises the following steps:

[0017] The washed solid product is reacted with an aqueous solution containing hydrogen chloride, and then the solid and liquid are separated to obtain acid slag and rare earth chloride solution.

[0018] According to the treatment method of the present invention, preferably, the fluorine-containing rare earth material is selected from one or more of rare earth polishing powder waste and rare earth metal furnace bottom slag.

[0019] The processing method according to the present invention preferably further comprises the following steps:

[0020] reacting the rare earth concentrate with hydrochloric acid to obtain an acid leaching product; separating the acid leaching product into solid and liquid to obtain a fluorine-containing rare earth material and a rare earth chloride acid solution;

[0021] The rare earth concentrate is selected from bastnaesite concentrate or a mixed rare earth concentrate containing bastnaesite.

[0022] According to the treatment method of the present invention, preferably, the concentration of hydrochloric acid is 6 to 12 mol / L, and the mass volume ratio of rare earth concentrate to hydrochloric acid is 1 kg: (0.8 to 4) L;

[0023] The reaction temperature of the rare earth concentrate and hydrochloric acid is 70-120° C., and the reaction time is 0.3-5 h.

[0024] The method of the present invention can separately recover fluorine and rare earth elements from fluorine-containing rare earth materials. Furthermore, the method of the present invention has a high fluorine recovery rate. Furthermore, the alkali metal fluoride obtained by the method of the present invention has a high purity. The method of the present invention has a low reaction temperature, low energy consumption, and simple reaction steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a flow chart of a method for treating fluorine-containing rare earth materials. DETAILED DESCRIPTION

[0026] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0027] The treatment method of the fluorine-containing rare earth material of the present invention comprises the following steps: reacting the fluorine-containing rare earth material with an alkali metal carbonate solution to obtain an alkali decomposition product; separating the alkali decomposition product into solid and liquid to obtain a solid product and a liquid product; washing the solid product with water to obtain a washed solid product and an alkali washing liquid; and precipitating the alkali metal fluoride in the alkali washing liquid to obtain an alkali metal fluoride solid and residual alkali liquid.

[0028] The reaction pressure of the fluorine-containing rare earth material and the alkali metal carbonate solution is 0.1 to 1 MPa. In certain embodiments, the reaction pressure of the fluorine-containing rare earth material and the alkali metal carbonate solution is 0.5 to 0.6 MPa. In other embodiments, the reaction pressure of the fluorine-containing rare earth material and the alkali metal carbonate solution is 0.8 to 0.9 MPa. The present invention has found that when the reaction pressure is controlled within the above range, the alkaline decomposition reaction can be promoted to proceed in the forward direction, thereby improving the decomposition rate.

[0029] The reaction temperature of the fluorine-containing rare earth material and the alkali metal carbonate solution is 100-200°C, preferably 120-180°C. In certain embodiments, the reaction temperature of the fluorine-containing rare earth material and the alkali metal carbonate solution is 150-160°C. The present invention has discovered that when the reaction temperature is controlled within the above range, the alkaline decomposition reaction can be promoted in the forward direction, thereby increasing the decomposition rate.

[0030] The reaction time of the fluorine-containing rare earth material and the alkali metal carbonate solution can be 0.2 to 5 hours, preferably 0.5 to 4 hours. In certain embodiments, the reaction time of the fluorine-containing rare earth material and the alkali metal carbonate solution is 1.5 to 2 hours. This helps the alkaline decomposition reaction to proceed fully.

[0031] The alkali metal carbonate can be selected from one or more of sodium carbonate and potassium carbonate. According to one embodiment of the present invention, the alkali metal carbonate is sodium carbonate. Although sodium carbonate is a conventional alkali metal carbonate, it is unconventional to use it in the present invention to improve the fluorine recovery rate and the purity of the alkali metal fluoride.

[0032] The alkali metal carbonate solution in the present invention refers to an aqueous solution of alkali metal carbonate.

[0033] The concentration of the alkali metal carbonate solution can be 10-35 wt %, preferably 15-33 wt %. In certain embodiments, the concentration of the alkali metal carbonate solution is 25-30 wt %. This helps to separate the rare earth-containing material and the fluorine-containing material obtained by decomposition.

[0034] The mass-to-volume ratio of the fluorine-containing rare earth material to the alkali metal carbonate solution can be 1 kg: (0.7-6) L, preferably 1 kg: (1-5) L. In certain embodiments, the mass-to-volume ratio of the fluorine-containing rare earth material to the alkali metal carbonate solution is 1 kg: (2-4) L. This helps to fully decompose the rare earth fluorides in the fluorine-containing rare earth material.

[0035] The content of rare earth elements in the fluorine-containing rare earth material may be ≥40 wt %. In some embodiments, the content of rare earth elements is 57-73 wt %. In other embodiments, the content of rare earth elements is 62-63 wt %.

[0036] The fluorine content of the fluorine-containing rare earth material may be ≥3.5 wt %. In some embodiments, the fluorine content is 7-30 wt %. In other embodiments, the fluorine content is 20-27 wt %.

[0037] Preferably, at least a portion of the rare earth elements and fluorine elements in the fluorine-containing rare earth material are present in the form of rare earth fluorides. Preferably, the fluorine-containing rare earth material is a fluorinated rare earth material. This facilitates the alkaline decomposition reaction.

[0038] The alkali metal fluoride in the alkaline washing solution can be precipitated by concentration crystallization or salting out. According to one embodiment of the present invention, the alkali metal fluoride in the alkaline washing solution is precipitated by concentration crystallization.

[0039] According to one embodiment of the present invention, a fluorine-containing rare earth material (fluorine content of 22-28 wt % and rare earth content of 62-63 wt %) is reacted with a 28-31 wt % alkali metal carbonate solution at a pressure of 0.7-0.9 MPa and a temperature of 170-190°C for 1.2-1.7 hours to obtain an alkali decomposition product; the alkali decomposition product is subjected to solid-liquid separation to obtain a solid product and a liquid product; the solid product is washed with water to obtain a washed solid product and an alkali wash solution; and the alkali metal fluoride in the alkali wash solution is precipitated to obtain an alkali metal fluoride solid and a residual alkali solution. The mass volume ratio of the fluorine-containing rare earth material to the alkali metal carbonate solution is 1 kg: 2.5-3.5 L.

[0040] The residual alkali solution and liquid product obtained in the present invention can be used as raw materials for preparing alkali metal carbonate solution.

[0041] In certain embodiments, the process further comprises reacting the washed solid product with an aqueous solution containing hydrogen chloride, followed by solid-liquid separation to produce an acid-soluble residue and a rare earth chloride solution. Specifically, the solid acid-hydrolyzed product obtained by the solid-liquid separation is washed with water to produce a water wash and an acid-soluble residue; and the liquid acid-hydrolyzed product obtained by the solid-liquid separation and the water wash are combined to produce a rare earth chloride solution. The aqueous solution containing hydrogen chloride can be hydrochloric acid or a rare earth chloride acid solution.

[0042] The fluorine-containing rare earth material of the present invention can be selected from one or more of rare earth polishing powder waste and rare earth metal furnace bottom slag. The fluorine-containing rare earth material can also be obtained by reacting materials containing rare earth fluorocarbonate or rare earth oxyfluoride.

[0043] In certain embodiments, the method further comprises the following steps: reacting the rare earth concentrate with hydrochloric acid to obtain an acid leaching product; and separating the acid leaching product into a solid-liquid state to obtain a fluorine-containing rare earth material and a rare earth chloride acid solution.

[0044] The rare earth concentrate of the present invention is selected from bastnaesite concentrate or mixed rare earth concentrate containing bastnaesite.

[0045] The concentration of hydrochloric acid can be 6 to 12 mol / L, preferably 8 to 11 mol / L. In certain embodiments, the concentration of hydrochloric acid is 8 to 10 mol / L.

[0046] The mass volume ratio of the rare earth concentrate to the hydrochloric acid may be 1 kg: (0.8-4) L, preferably 1 kg: (1-3) L. In certain embodiments, the mass volume ratio of the rare earth concentrate to the hydrochloric acid is 1 kg: (1-1.5) L.

[0047] The reaction temperature of the rare earth concentrate and hydrochloric acid can be 70-120° C., preferably 80-100° C. In certain embodiments, the reaction temperature of the rare earth concentrate and hydrochloric acid is 80-90° C.

[0048] The reaction time of the rare earth concentrate and hydrochloric acid can be 0.3 to 5 hours, preferably 0.5 to 4 hours. In certain embodiments, the reaction time of the rare earth concentrate and hydrochloric acid is 0.5 to 2 hours.

[0049] During the reaction, tail gas can be absorbed by spraying to obtain a mixed acid of hydrochloric acid and hydrofluoric acid.

[0050] The rare earth acid chloride solution obtained by the reaction can be used as an aqueous solution containing hydrogen chloride to react with the solid product after washing.

[0051] The following describes the test method:

[0052] Fluorine recovery rate: The fluorine content is analyzed by distillation. The fluorine recovery rate is calculated using the following formula:

[0053] The recovery rate of fluorine element=(the weight of fluorine element contained in sodium fluoride / the weight of fluorine contained in the fluorine-containing rare earth material)×100%.

[0054] Recovery of rare earth elements: REO content was analyzed by gravimetric method.

[0055] The recovery of rare earth elements was calculated using the following formula in Examples 1 and 2:

[0056] Recovery rate of rare earth elements = (weight of rare earth elements contained in rare earth chloride solution / weight of rare earth elements contained in fluorine-containing rare earth concentrate) × 100%;

[0057] Examples 3 and 4 use the following formula to calculate the recovery of rare earth elements:

[0058] Recovery rate of rare earth elements = (weight of rare earth elements contained in rare earth chloride solution / weight of rare earth elements contained in fluorine-containing rare earth material) × 100%.

[0059] Purity of sodium fluoride: tested using the method specified in YS / T 517-2024.

[0060] Example 1

[0061] Bastnaesium concentrate was mixed with 8 mol / L hydrochloric acid at a mass-to-volume ratio of 1 kg:3 L and reacted at 100°C for 0.5 h to produce an acid leaching product. During the reaction, exhaust gas was sprayed and absorbed to produce a mixed acid of hydrochloric acid and hydrofluoric acid. The acid leaching product was then separated into a fluorine-containing rare earth material (fluorine content of 9.3 wt% and rare earth content of 63.2 wt%) and a rare earth chloride acid solution.

[0062] A fluorine-containing rare earth material is mixed with a 15 wt% sodium carbonate solution at a mass-to-volume ratio of 1 kg:5 L. The mixture is then reacted at a pressure of 0.1 MPa and a temperature of 100°C for 4 hours to produce an alkaline decomposition product. The alkaline decomposition product is subjected to solid-liquid separation to produce a solid product and a liquid product. The solid product is washed with water to produce a washed solid product and an alkali wash solution. The alkali wash solution is concentrated and crystallized to precipitate sodium fluoride, producing sodium fluoride solid and residual alkali solution. The residual alkali solution and liquid product are used to prepare a sodium carbonate solution.

[0063] The washed solid product is reacted with a rare earth chloride acid solution, followed by solid-liquid separation to obtain an acid hydrolysis solid product and an acid hydrolysis liquid product. The acid hydrolysis solid product is washed with water to obtain a water wash and an acid-soluble residue. The water wash and the acid hydrolysis liquid product are combined to obtain a rare earth chloride solution.

[0064] The recovery rates of fluorine and rare earth elements and the purity of sodium fluoride are shown in Table 1.

[0065] Example 2

[0066] A mixed rare earth concentrate containing fluorine-containing bastnaesite was mixed with 12 mol / L hydrochloric acid at a mass-to-volume ratio of 1 kg:1 L and reacted at 80°C for 4 hours to produce an acid leaching product. During the reaction, exhaust gas was sprayed and absorbed to produce a mixed acid of hydrochloric acid and hydrofluoric acid. The acid leaching product was then separated into a fluorine-containing rare earth material (fluorine content of 8.9 wt% and rare earth content of 69.4 wt%) and a rare earth chloride acid solution.

[0067] A fluorine-containing rare earth material is mixed with a 25wt% sodium carbonate solution at a mass-to-volume ratio of 1kg:3L. The mixture is then reacted at a pressure of 0.6MPa and a temperature of 160°C for 2 hours to produce an alkaline decomposition product. The alkaline decomposition product is subjected to solid-liquid separation to produce a solid product and a liquid product. The solid product is washed with water to produce a washed solid product and an alkali wash solution. The alkali wash solution is concentrated and crystallized to precipitate sodium fluoride, producing sodium fluoride solid and residual alkali solution. The residual alkali solution and liquid product are used to prepare a sodium carbonate solution.

[0068] The washed solid product is reacted with a rare earth chloride acid solution, followed by solid-liquid separation to obtain an acid hydrolysis solid product and an acid hydrolysis liquid product. The acid hydrolysis solid product is washed with water to obtain a water wash and an acid-soluble residue. The water wash and the acid hydrolysis liquid product are combined to obtain a rare earth chloride solution.

[0069] The recovery rates of fluorine and rare earth elements and the purity of sodium fluoride are shown in Table 1.

[0070] Example 3

[0071] Rare earth metal bottom ash (fluorine content of 25.5wt%, rare earth element content of 62.5wt%) is mixed with a 30wt% sodium carbonate solution at a mass-to-volume ratio of 1kg:3L. The mixture is then reacted at a pressure of 0.8MPa and a temperature of 180°C for 1.5 hours to produce an alkali decomposition product. The alkali decomposition product is subjected to solid-liquid separation to produce a solid product and a liquid product. The solid product is washed with water to produce a washed solid product and an alkali wash solution. The alkali wash solution is concentrated and crystallized to precipitate sodium fluoride, producing sodium fluoride solid and residual alkali solution. The residual alkali solution and liquid product are used to prepare the sodium carbonate solution.

[0072] The washed solid product is reacted with hydrochloric acid, followed by solid-liquid separation to obtain an acid hydrolysis solid product and an acid hydrolysis liquid product. The acid hydrolysis solid product is washed with water to obtain a water wash and an acid-soluble residue. The water wash and the acid hydrolysis liquid product are combined to obtain a rare earth chloride solution.

[0073] The recovery rates of fluorine and rare earth elements and the purity of sodium fluoride are shown in Table 1.

[0074] Example 4

[0075] Rare earth polishing powder waste (fluorine content of 3.52wt%, rare earth element content of 64.58wt%) is mixed with a 33wt% sodium carbonate solution at a mass-to-volume ratio of 1kg:1L, and then reacted at a pressure of 1MPa and a temperature of 200°C for 0.5h to produce an alkali decomposition product. The alkali decomposition product is subjected to solid-liquid separation to produce a solid product and a liquid product. The solid product is washed with water to produce a washed solid product and an alkali wash solution. The alkali wash solution is concentrated and crystallized to precipitate sodium fluoride, producing sodium fluoride solid and residual alkali solution. The residual alkali solution and liquid product are used to prepare the sodium carbonate solution.

[0076] The washed solid product is reacted with hydrochloric acid, followed by solid-liquid separation to obtain an acid hydrolysis solid product and an acid hydrolysis liquid product. The acid hydrolysis solid product is washed with water to obtain a water wash and an acid-soluble residue. The water wash and the acid hydrolysis liquid product are combined to obtain a rare earth chloride solution.

[0077] The recovery rates of fluorine and rare earth elements and the purity of sodium fluoride are shown in Table 1.

[0078] Table 1

[0079] Example 1 Example 2 Example 3 Example 4 Recovery rate of fluorine element (wt%) 91.4 92.5 94.8 92.3 Recovery rate of rare earth elements (wt%) 93.6 64.5 97.4 95.2 Purity of sodium fluoride (wt%) 94.2 94.6 94.9 94.7

[0080] As shown in Table 1, the method of the present invention can recover fluorine and rare earth elements from the fluorine-containing rare earth material separately. By controlling the above process parameters, the recovery rate of fluorine and the purity of alkali metal fluoride can be improved.

[0081] The present invention is not limited to the above-mentioned embodiments. Any modification, improvement, or substitution that can be conceived by those skilled in the art without departing from the essential content of the present invention shall fall within the scope of the present invention.

Claims

1. A method for treating fluorine-containing rare earth materials, characterized in that: The steps include: The fluorine-containing rare earth material is reacted with an alkali metal carbonate solution to obtain an alkali decomposition product; the alkali decomposition product is separated into solid and liquid to obtain a solid product and a liquid product; the solid product is washed with water to obtain a washed solid product and an alkali washing liquid; and the alkali metal fluoride in the alkali washing liquid is precipitated to obtain an alkali metal fluoride solid and a residual alkali liquid.

2. The processing method according to claim 1, characterized in that The fluorine-containing rare earth material reacts with an alkali metal carbonate solution at a pressure of 0.1-1 MPa and a temperature of 100-200°C.

3. The processing method according to claim 1, characterized in that The reaction time of the fluorine-containing rare earth material and the alkali metal carbonate solution is 0.2 to 5 hours.

4. The processing method according to claim 1, characterized in that The concentration of the alkali metal carbonate solution is 10-35 wt %, and the mass volume ratio of the fluorine-containing rare earth material to the alkali metal carbonate solution is 1 kg: (0.7-6) L; The alkali metal carbonate is selected from one or more of sodium carbonate and potassium carbonate.

5. The processing method according to claim 1, characterized in that The content of rare earth elements in the fluorine-containing rare earth material is ≥40wt%, and the content of fluorine elements is ≥3.5wt%.

6. The processing method according to claim 1, characterized in that The alkali metal fluoride in the alkaline washing solution is precipitated by concentration crystallization or salting out.

7. The processing method according to claim 1, characterized in that The following steps are also included: The washed solid product is reacted with an aqueous solution containing hydrogen chloride, and then the solid and liquid are separated to obtain acid slag and rare earth chloride solution.

8. The processing method according to claim 1, characterized in that The fluorine-containing rare earth material is selected from one or more of rare earth polishing powder waste and rare earth metal furnace bottom slag.

9. The processing method according to claim 1, characterized in that: The following steps are also included: reacting the rare earth concentrate with hydrochloric acid to obtain an acid leaching product; separating the acid leaching product into solid and liquid to obtain a fluorine-containing rare earth material and a rare earth chloride acid solution; The rare earth concentrate is selected from bastnaesite concentrate or a mixed rare earth concentrate containing bastnaesite.

10. The processing method according to claim 9, characterized in that: The concentration of hydrochloric acid is 6-12 mol / L, and the mass volume ratio of rare earth concentrate to hydrochloric acid is 1 kg: (0.8-4) L; The reaction temperature of the rare earth concentrate and hydrochloric acid is 70-120° C., and the reaction time is 0.3-5 h.

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