A method for recovering rare earths from fine-grained sedimentary clay rock type rare earth ore

Abstract

The present invention provides a method for recovering rare earths from fine-particle sedimentary claystone-type rare earth ore, belonging to the field of rare earth processing technology. The method comprises the following steps: first, crushing and grinding the fine-particle sedimentary claystone-type rare earth ore, mixing it with a calcining agent, and calcining it to obtain a calcined rare earth ore; then, leaching the rare earths from the calcined rare earth ore with a lixiviant to obtain a rare earth-rich mother liquor; then, precipitating and removing impurities from the rare earth-rich mother liquor to obtain an aluminum-rich precipitate and a decontaminated rare earth-rich mother liquor; finally, precipitating rare earths from the decontaminated rare earth-rich mother liquor to obtain a rare earth-rich precipitate, which is then calcined to obtain mixed rare earth oxides. This method provides a complete process flow from raw rare earth ore to rare earth oxide products, resulting in high-purity rare earth oxide products.

Description

Technical Field

[0001] The invention belongs to the technical field of rare earth processing, and in particular relates to a method for recovering rare earth from fine-particle sedimentary clay rock type rare earth ore. Background Art

[0002] Sedimentary claystone-type rare earth deposits are widely distributed in the adjacent areas of Sichuan, Yunnan, and Guizhou. The average rare earth oxide grade is 0.39%, exceeding the industrial grade of ion-adsorption rare earth deposits of 500 μg / g. This widespread rare earth resource offers enormous development potential. The primary mineral composition of these deposits is kaolinite (over 89%), with minor minerals including ceriumite, anatase, mica, illite, chlorite, hematite, sericite, and muscovite. Rare earths occur primarily as ultramicroscopic inclusions in ceriumite and as standalone minerals; smaller amounts occur as isomorphous elements within the kaolinite. These rare earth deposits are a weathering product of Emeishan basalt. Minerals are relatively fine, mostly in the micron range, with rare earth minerals typically below 1 μm. Reports on the comprehensive utilization of this rare earth resource are limited.

[0003] Publication No. CN109266839A reports a method for selectively leaching sedimentary rare earth ores. The method involves roasting sedimentary rare earth ore powder with sulfuric acid at high temperature and then acid leaching it to obtain a rare earth-rich liquid. However, the method lacks a subsequent process flow.

[0004] Publication No. CN114134348A discloses a method for recovering sedimentary rare earths using a hot high-acid direct leaching process. The rare earth-rich leachate is crystallized into ammonium aluminum sulfate using ammonium sulfate, and then the rare earths are recovered by extraction and back-extraction. The process is complex and the cost is high.

[0005] Publication No. CN104711424A discloses a method for recovering rare earths from the residue removed from the leachate of weathering crust-eluvial rare earth ore. The method uses alkaline solution precipitation to obtain an aluminum product, which is then precipitated with an alkaline solution to obtain a rare earth product. This process requires a long aging time and is suitable for solutions with high rare earth and aluminum content.

[0006] Publication No. CN115058609A discloses a method for leaching rare earths from basalt weathering crusts. The method has a long roasting time and is suitable for basalt weathering crusts with a relatively high degree of weathering.

[0007] Publication No. CN113621837A discloses a rare earth extraction method for low-grade fine-grained rare earth ores, which is mainly aimed at rare earth ores with a rare earth REEO content of no more than 0.113%. It completes the rare earth roasting and leaching process and finally obtains rare earth leachate and leaching residue.

[0008] At present, there are few reports on the complete process flow of sedimentary rare earth ores from raw ore to rare earth oxides. Summary of the Invention

[0009] In order to solve the defects of low rare earth leaching rate and high impurity content in existing sedimentary clay rock type rare earth ores, the present invention provides a method for recovering rare earths from fine particle-grade sedimentary clay rock type rare earth ores, thereby realizing the green and efficient comprehensive utilization of rare earths and other valuable elements.

[0010] The technical solutions of the present invention are as follows:

[0011] The present invention provides a method for recovering rare earths from fine-particle sedimentary clay rock type rare earth ore, comprising the following steps:

[0012] (1) Calcination: crushing and grinding fine-particle sedimentary clay rock type rare earth ore, mixing with a calcining agent, and calcining to obtain a calcined rare earth ore;

[0013] (2) Leaching: Leaching rare earths from the roasted rare earth ore using a leaching agent to obtain a rare earth-rich mother liquor;

[0014] (3) precipitation and impurity removal: the rare earth-rich mother liquor is subjected to impurity removal using an impurity remover to obtain an aluminum-rich precipitate and a rare earth-rich mother liquor after impurity removal;

[0015] (4) Precipitating rare earths: using a precipitant to precipitate rare earths from the impurity-removed rare earth-rich mother liquor to obtain a rare earth-rich precipitate;

[0016] (5) Calcination: Calcinate the rare earth-rich precipitate to obtain mixed rare earth oxides.

[0017] In a specific embodiment, the rare earth content in the fine-particle sedimentary clay rock type rare earth ore is 0.05% to 2.50%.

[0018] The present invention is also applicable to fine-particle sedimentary clay rock type rare earth ores with a rare earth content greater than 2.5% or less than 0.05%.

[0019] In one embodiment, in step (1), the particle size after crushing and grinding is -160 μm to -75 μm.

[0020] In a specific embodiment, when the iron content in the fine-particle sedimentary clay rock type rare earth ore is higher than 1.5%, an acidic reagent is required to remove iron before mixing with the roasting reagent; the acidic reagent is at least one of hydrochloric acid, nitric acid and sulfuric acid; the concentration of the acidic reagent is 0.5 to 4 mol / L; during the process of removing iron with the acidic reagent, the acidification temperature is 40 to 90°C, the acidification time is 0.5 to 2 hours, and the ratio of the acidic reagent to the ore sample is 10 to 40 mL / g.

[0021] Removing iron before roasting can not only effectively reduce the consumption of roasting reagents and the aluminum-iron separation process, but also reduce the impact of iron impurity ions on the product quality of rare earth precipitation crystallization and improve the recovery rate of rare earth.

[0022] In one specific embodiment, in step (1), the roasting agent is at least one of sulfuric acid, ammonium sulfate, sodium sulfate, sodium oxalate, ammonium chloride, magnesium chloride, sodium chloride and ammonium citrate. Preferably, the roasting agent is sulfuric acid or ammonium sulfate with a volume concentration of 60-98%; the ratio of the roasting agent sulfuric acid to the rare earth ore is 0.4-2 mL / g, and the mass ratio of the remaining roasting agents to the rare earth ore is 3:1-1:3; the roasting temperature is 300-800°C, and the roasting time is 5-55 min.

[0023] In one embodiment, in step (2), the leaching agent is an aqueous solution of at least one of sodium chloride, sodium citrate and ammonium chloride; the mass concentration of the leaching agent is 1 to 20%; the leaching temperature is 50 to 90° C., the leaching time is 3 to 6 hours; and the ratio of the leaching agent to the rare earth ore is 10 to 30 mL / g.

[0024] In one embodiment, in step (3), the impurity remover is at least one of sodium carbonate, sodium bicarbonate, sodium hydroxide, ammonia water and sodium sulfide; the mass concentration of the impurity remover is 7.8-49.7%; the temperature during the impurity removal process is 5-40° C., the pH value is 4.5-5.5, the impurity removal process is continuously stirred, and filtration is completed 0-30 minutes after the precipitation is completed.

[0025] In a specific embodiment, the aluminum-rich precipitate in step (3) is calcined to obtain rich aluminum oxide; the calcination temperature is 700-900° C., and the calcination time is 0.5-2 h.

[0026] In one embodiment, in step (4), the precipitant is at least one of oxalic acid, ammonium oxalate and sodium oxalate, and the mass concentration of the precipitant solution is 6 to 12.5%.

[0027] In one embodiment, in step (5), the calcination temperature is 500-900° C., and the calcination time is 0.5-1 h.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The present invention aims at the comprehensive utilization of rare earths in fine-particle sedimentary clay rock-type rare earth ores. In view of the fact that the rare earths mainly exist in the form of ultramicroscopic inclusions of cerium phosphate and independent minerals of cerium phosphate, a process flow of pre-iron removal - roasting - leaching - rare earth mother liquor impurity removal - precipitation - calcination is proposed to realize the process flow from rare earth ore to rare earth oxide products, and the obtained rare earth oxide products have high purity.

[0030] 2. The present invention relates to a process for the development and utilization of potential rare earth resources. The invention has simple equipment, easy operation, good product stability and high added value. It provides a new approach for the comprehensive utilization of fine-particle sedimentary clay rock-type rare earth ores and has good economic benefits and strategic significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the process flow of the present invention;

[0032] Figure 2 This is the XRD pattern of the rare earth oxide of Example 3. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] The process flow chart of the embodiment is shown in Figure 1 shown.

[0035] In the embodiment, the fine-particle sedimentary clay rock type rare earth ore was obtained from a basalt weathering crust in northwest Guizhou, wherein the rare earth (REE) content was between 0.05% and 2.50%. Based on the rare earth content and the lithology of the ore, the rare earth ore was divided into rare earth ore with high iron content (a mixture of rare earth ore samples with an iron oxide content greater than 1.50%, with a rare earth content of 0.247% and an iron oxide content of 13.8%) and rare earth ore with low iron content (a mixture of rare earth ore samples with an iron oxide content less than 1.50%, with a representative mixed sample having a rare earth content of 2.20% and an iron oxide content of 1.2%).

[0036] Example 1

[0037] Sampling was performed based on a particle size of -124 μm. 30 g of a rare earth ore with a low iron content (1.2% iron oxide content) was directly mixed with 90% sulfuric acid by volume. The ratio of roasting agent to mixed rare earth ore was 1.35 mL / g. The roasting temperature was 700°C and the roasting time was 15 minutes to obtain the roasted rare earth ore. The roasted rare earth ore was mixed with a 5% sodium citrate solution by mass for leaching at 90°C for 4 hours. The ratio of leaching agent to ore sample was 10 mL / g to obtain a rare earth-rich mother liquor, achieving a rare earth leaching rate of 89.30%. A 49.7% sodium carbonate solution was used as a precipitant to remove impurities at a precipitation temperature of 30°C and a pH of 5.0. After precipitation, the pure rare earth-rich mother liquor was directly filtered. Rare earths were then precipitated with a 12.5% ​​sodium oxalate solution to obtain a rare earth oxalate precipitate. This precipitate was calcined at 500°C for 1 hour to obtain a mixed rare earth oxide with a purity of 97.59%. The overall recovery rate of rare earths was 79.03%.

[0038] Example 2

[0039] Sampling was performed based on a particle size of -75μm. 30g of a rare earth ore with a high iron content (13.8% iron oxide content) was sampled using 1mol / L hydrochloric acid at an acidification temperature of 90°C, with a ratio of 30mL / g of the acidic reagent to the ore sample, and the acidification time was 2h to obtain a rare earth ore with iron removed. The rare earth ore with iron removed and a rare earth ore with a low iron content (1.2% iron oxide content) were sampled in a 1:1 mass ratio to obtain 30g of a mixed rare earth ore. This was directly mixed with sulfuric acid having a volume concentration of 98%, and the ratio of the roasting agent to the mixed rare earth ore was 1.35mL / g. The roasting temperature was 700°C, and the roasting time was 20min to obtain the roasted rare earth ore. The calcined rare earth ore was mixed with a 5% sodium chloride solution for leaching at 90°C for 4 hours, with a leaching agent to ore sample ratio of 20 mL / g, yielding a rare earth-rich mother liquor with a rare earth recovery rate of 89.09%. A 49.7% sodium carbonate solution was used as a precipitant to remove impurities at 30°C and a pH of 5.0. After precipitation, the purified rare earth-rich mother liquor was directly filtered. Rare earths were then precipitated with a 12.5% ​​sodium oxalate solution to yield a rare earth oxalate precipitate. This precipitate was calcined at 500°C for 1 hour to yield mixed rare earth oxides with a purity of 97.90%. The overall recovery rate of rare earths was 76.13%.

[0040] Example 3

[0041] Sampling was performed according to the particle size of the ore sample of -124μm. 30g of rare earth ore with a high iron content (iron oxide content of 13.8%) was taken, and 3mol / L hydrochloric acid was used, the acidification temperature was 90℃, the ratio of the acidic reagent to the ore sample was 30mL / g, and the acidification time was 1h to obtain the iron-removed rare earth ore. The iron-removed rare earth ore and the rare earth ore with a low iron content (iron oxide content of 1.2%) were sampled at a mass ratio of 2.5:1 to obtain 28g of mixed rare earth ore, which was directly mixed with sulfuric acid with a volume concentration of 80%. The mixed roasting agent sulfuric acid and rare earth ore were mixed at a ratio of 1.35mL / g, the roasting temperature was 700℃, and the roasting time was 15min to obtain the roasted rare earth ore. The calcined rare earth ore was mixed with a 5% ammonium chloride solution and leached at 90°C for 4.5 hours, with a leaching agent to ore sample ratio of 20 mL / g. This produced a rare earth-rich mother liquor, achieving a rare earth recovery rate of 88.02%. A 49.7% sodium carbonate solution was used as a precipitant to remove impurities at 30°C and a pH of 5.0. After precipitation, the purified rare earth-rich mother liquor was directly filtered. Rare earths were then precipitated with a 12.5% ​​sodium oxalate solution to obtain a rare earth oxalate precipitate. This was then calcined at 500°C for 1 hour to produce mixed rare earth oxides with a product purity of 98.51%. This completes the process from raw rare earth ore to rare earth oxide products, achieving a comprehensive rare earth recovery rate of 75.22%.

[0042] The mixed rare earth oxide prepared in this example was subjected to X-ray diffraction analysis, and the XRD pattern was shown in FIG. Figure 2 As shown, mixed rare earth oxides are mainly light rare earth oxides, such as NdO2 and Ce 0.5 Nd 0.5 O 1.75 .

[0043] Comparative Example 1

[0044] Sampling was performed based on a particle size of -124 μm. 30 g of a rare earth ore with a high iron content (13.8% iron oxide content) was directly mixed with 90% sulfuric acid by volume. The ratio of roasting agent to mixed rare earth ore was 0.8 mL / g. The roasting temperature was 700°C and the roasting time was 45 minutes to obtain the roasted rare earth ore. The roasted rare earth ore was mixed with a 5% sodium citrate solution by mass for leaching at 90°C for 3 hours. The ratio of leaching agent to ore sample was 20 mL / g to obtain a rare earth-rich mother liquor, achieving a rare earth leaching rate of 81.66%. The method uses 49.7% sodium carbonate as a precipitant to remove impurities at a precipitation temperature of 30°C and a pH of 5.0. After precipitation, the purified rare earth-rich mother liquor is directly filtered. Rare earths are then precipitated with a 12.5% ​​sodium oxalate solution to obtain a rare earth oxalate precipitate. This precipitate is then calcined at 500°C for 1 hour to obtain a mixed rare earth oxide with a purity of 80.41%. The overall recovery rate of rare earths is 50.59%.

[0045] Comparative Example 2

[0046] Sampling was performed based on a particle size of -124 μm. 30 g of a rare earth ore with a low iron content (1.2% iron oxide content) was directly mixed with 90% sulfuric acid by volume. The ratio of roasting agent to mixed rare earth ore was 0.8 mL / g. The roasting temperature was 700°C and the roasting time was 30 minutes to obtain the roasted rare earth ore. The roasted rare earth ore was mixed with distilled water for leaching at 90°C for 4 hours. The ratio of leaching agent to ore sample was 50 mL / g to obtain a rare earth-rich mother liquor, achieving a rare earth leaching rate of 75.11%.

[0047] Comparative Example 3

[0048] Samples were taken at a particle size of -124μm. 30g of a rare earth ore with a high iron content (13.8% iron oxide content) was directly mixed with ammonium sulfate, sodium sulfate, sodium oxalate, ammonium chloride, magnesium chloride, sodium chloride, or ammonium citrate, with a 1:1 ratio of roasting agent to mixed rare earth ore. The roasting temperature was 700°C, and the roasting time was 30 minutes to obtain the roasted rare earth ore. The roasted rare earth ore was then mixed with a 5% sodium citrate solution for leaching at 90°C for 3 hours, with a leaching agent to ore sample ratio of 20mL / g, to obtain a rare earth-rich mother liquor. The rare earth leaching rate for ammonium sulfate roasting was approximately 50%, while the rare earth leaching rates for the other reagents were all less than 30%.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for recovering rare earths from fine-grained sedimentary clay rock type rare earth ores, characterized in that: The rare earth in the sedimentary clay rock type rare earth ore mainly exists in the form of ultramicroscopic cerium phosphate inclusions and independent mineral forms of cerium phosphate; a small amount of rare earth exists in kaolinite in an isomorphous form. The method comprises the following steps: (1) Calcination: crush and grind the fine-grained sedimentary clay rock type rare earth ore, mix it with a calcining agent, and calcine it to obtain the calcined rare earth ore; wherein, when the iron content in the fine-grained sedimentary clay rock type rare earth ore is higher than 1.5%, the iron is removed by an acidic agent before mixing it with the calcining agent; the acidic agent is hydrochloric acid with a concentration of 0.5 to 4 mol / L; during the process of removing iron with the acidic agent, the acidification temperature is 40 to 90°C, the acidification time is 0.5 to 2 h, and the ratio of the acidic agent to the ore sample is 10 to 40 mL / g; the calcining agent volume concentration is 60 to 98% sulfuric acid or ammonium sulfate; the ratio of the calcining agent sulfuric acid to the rare earth ore is 0.4 to 2 mL / g, and the mass ratio of the remaining calcining agents to the rare earth ore is 3:1 to 1:3; the calcining temperature is 300 to 800°C, and the calcining time is 5 to 55 min; (2) Leaching: Leaching rare earths from the roasted rare earth ore with a leaching agent to obtain a rare earth-rich mother liquor; wherein the leaching agent is an aqueous solution of at least one of sodium chloride, sodium citrate and ammonium chloride; the mass concentration of the leaching agent is 1-20%; the leaching temperature is 50-90°C, the leaching time is 3-6 h; the ratio of the leaching agent to the rare earth ore is 10-30 mL / g; (3) Precipitation and impurity removal: The rare earth-rich mother liquor is removed with an impurity remover to obtain an aluminum-rich precipitate and a rare earth-rich mother liquor after impurity removal; wherein the impurity remover is at least one of sodium carbonate, sodium bicarbonate, sodium hydroxide, ammonia water and sodium sulfide; the mass concentration of the impurity remover is 7.8-49.7%; the temperature during the impurity removal process is 5-40°C, the pH value is 4.5-5.5, the impurity removal process is continuously stirred, and filtration is completed 0-30 minutes after the precipitation is completed; (4) Precipitating rare earths: using a precipitant to precipitate rare earths from the impurity-removed rare earth-rich mother liquor to obtain a rare earth-rich precipitate; (5) Calcination: Calcinate the rare earth-rich precipitate to obtain mixed rare earth oxides.

2. The method for recovering rare earths from fine-particle sedimentary clay rock type rare earth ore according to claim 1, characterized in that: The rare earth content in the fine-particle sedimentary clay rock type rare earth ore is 0.05% to 2.50%.

3. The method for recovering rare earths from fine-particle sedimentary clay rock type rare earth ore according to claim 1, characterized in that: In step (1), the particle size of the rare earth ore after crushing and grinding is -160 μm to -75 μm.

4. The method for recovering rare earths from fine-particle sedimentary clay rock type rare earth ore according to claim 1, characterized in that: The aluminum-rich precipitate of step (3) is calcined to obtain rich aluminum oxide; the calcination temperature is 700-900° C., and the calcination time is 0.5-2 h.

5. The method for recovering rare earths from fine-particle sedimentary clay rock type rare earth ore according to claim 1, characterized in that: In step (4), the precipitant is at least one of oxalic acid, ammonium oxalate and sodium oxalate, and the mass concentration of the precipitant is 6-12.5%.

6. The method for recovering rare earths from fine-particle sedimentary clay rock type rare earth ore according to claim 1, characterized in that: In step (5), the calcination temperature is 500-900°C, and the calcination time is 0.5-1 h.

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