A method for separating, enriching and extracting rare earth elements from coal gangue

Abstract

The present invention discloses a method for separating, enriching and extracting rare earth elements from coal gangue, which relates to the technical field of comprehensive utilization of mineral resources. The method mainly comprises the following steps: (1) performing optoelectronic separation on the coal gangue raw material to separate the rare earth-rich coal gangue and the low-grade coal product; (2) performing crushing, grinding and pulp adjustment on the rare earth-rich coal gangue; (3) performing one-stage flotation on the pulp to remove sulfide minerals and residual easily floatable coal quality; (4) performing two-stage flotation on the pulp to remove carbonate minerals and residual oxidized coal quality. When applied in conjugation, the flotation tailings obtained in (4) are concentrated and then subjected to acid leaching strengthening treatment, and then filtered to separate the leaching residue, and a rare earth leaching solution is obtained. The method of the present invention realizes the efficient extraction of rare earth elements, especially heavy rare earths, in coal gangue, efficiently separates rare earth-rich minerals from other minerals, reduces the ore treatment volume, drug consumption and energy consumption, realizes the high-value utilization of coal gangue, and has both economic and environmental benefits.

Description

Technical Field

[0001] The present invention discloses a method for separating, enriching and extracting rare earth elements from coal gangue, which relates to the technical field of comprehensive utilization of mineral resources. Background Art

[0002] Rare earth elements include 17 elements such as lanthanide series elements, scandium and yttrium, and are widely used in emerging industries such as new energy, new materials, energy conservation and environmental protection, and high-end equipment manufacturing due to their unique physical and chemical properties.

[0003] Among alternative resources, coal resources have a relatively high content of rare earth elements, and the rare earth elements are mainly hosted in the inorganic mineral components of coal. And such inorganic minerals are all solid wastes in coal washing and processing, and most of them are concentrated in coal gangue.

[0004] Coal gangue has complex mineral components, and the content of rare earth elements in some mineral components is extremely low. If it is directly subjected to hydrometallurgical treatment, it will not only increase the consumption of reagents and leaching solutions, but also restrict the recovery efficiency of rare earth elements. In addition, some coal gangue has characteristics such as poor wettability and low leaching activity, resulting in problems such as high production costs and low leaching efficiency. At the same time, in the existing technology, there are few reports on increasing the enrichment ratio of medium and heavy rare earths while enriching rare earths in coal gangue.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art, and provide a method for separating, enriching and extracting rare earth elements from coal gangue, so as to effectively separate the rare earth-rich mineral components in coal gangue from other components, gradually reduce the amount of ore entering the grinding, flotation and leaching processes, save costs such as flotation reagents, leaching solutions and equipment energy consumption, improve the leaching activity of coal gangue, and at the same time improve the extraction efficiency of rare earth elements and increase the enrichment ratio of medium and heavy rare earths.

[0007] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0008] The present invention provides a method for separating, enriching and extracting rare earth elements from coal gangue, comprising the following steps:

[0009] (1) Optoelectronically separating the coal gangue raw material, and removing the low-grade coal products in the raw material according to the different reflectivities of coal and coal gangue surfaces to X-rays, so as to obtain rare earth-rich coal gangue; the R of the rare earth-rich coal gangue is < 1.30;

[0010] (2) Crushing, screening and grinding the rare earth-rich coal gangue, and then performing pulp conditioning to obtain a flotation pulp;

[0011] (3) Subject the floated ore pulp to first-stage flotation to remove sulfide minerals and residual easily floatable coal, obtaining first-stage flotation tailings;

[0012] (4) Subject the first-stage flotation tailings to second-stage flotation to remove carbonate minerals and residual oxidized coal, obtaining second-stage flotation tailings.

[0013] After drying the obtained second-stage flotation tailings, the mass percentage of rare earth (calculated as oxide) is 3 - 8 times or more of the rare earth content in the coal gangue raw material.

[0014] Concentrate the second-stage flotation tailings obtained in step (4), then perform acid leaching treatment, followed by solid-liquid separation to obtain a rare earth leaching solution. After drying the rare earth leaching solution, the mass ratio of heavy rare earth to light rare earth is (2.5 - 6.5) : 1.

[0015] Preferably, the content of rare earth elements in the coal gangue raw material is 104 - 1347 μg / g.

[0016] Preferably, the ore feeding speed of the optoelectronic separation is 0.5 - 1.2 m / s. The ore feeding speed should not be too fast, as it is likely to cause inaccurate mineral identification or incorrect injection by the high-pressure air gun; while if the ore feeding speed is too slow, the processing efficiency will decrease.

[0017] In some specific embodiments, the ore feeding speed of the optoelectronic separation can be, but is not limited to, 0.5 m / s, 0.6 m / s, 0.8 m / s, 1.0 m / s or 1.2 m / s.

[0018] Preferably, the discrimination criterion for the optoelectronic separation is as follows: the mineral attribute R value (reflectivity R of the mineral) of the X-ray reflectivity is analyzed by the computer terminal. The R value of the material attribute of coal is 1.30 - 1.35, and the R value of the material attribute of gangue is less than 1.20. Minerals with R > 1.30 are discriminated as coal, and minerals with R < 1.30 are discriminated as coal gangue. In the optoelectronic separation of coal gangue, the mineral attribute R value and its discrimination criterion are relatively important. If the setting is too high, some low-grade coal cannot be removed; if the setting is too low, some rare earth-rich coal gangue will be removed.

[0019] In some specific embodiments, the discrimination criterion for the optoelectronic separation can be, but is not limited to, minerals with R < 1.30, R < 1.28, R < 1.26, R < 1.24, R < 1.22 or R < 1.20 are discriminated as coal gangue.

[0020] Preferably, grind the rare earth-rich coal gangue to a fineness of less than 0.074 mm. More preferably, the fineness is 0.038 - 0.074 mm. In this fineness range, the minerals are fully dissociated. Over-grinding not only increases the ineffective grinding time, throughput and energy consumption, but also easily causes a decrease in the subsequent flotation efficiency, concentration efficiency, leaching efficiency and solid-liquid separation efficiency.

[0021] Preferably, the mass fraction of the floated ore pulp after pulp preparation is 25-40%.

[0022] In some specific embodiments, the mass fraction of the floated ore pulp after pulp preparation can be, but is not limited to, 25%, 30%, 35% or 40%.

[0023] Preferably, the flotation reagents used in the first-stage flotation include: butyl xanthate collector and no. 2 oil frother. Further preferably, the dosage of butyl xanthate collector is 20-500 g / t, preferably 20-200 g / t, and further preferably 30-100 g / t; the dosage of no. 2 oil frother is 5-80 g / t, preferably 10-60 g / t, and further preferably 20-50 g / t.

[0024] Preferably, the flotation reagents used in the second-stage flotation include: hydroxamic acid collectors or / and short-chain fatty acid collectors, and no. 2 oil frother. Further preferably, the dosage of hydroxamic acid collectors or / and short-chain fatty acid collectors is 20-1000 g / t, preferably 30-500 g / t, and further preferably 40-200 g / t; the dosage of no. 2 oil frother is 5-80 g / t, preferably 10-50 g / t, and further preferably 15-40 g / t.

[0025] The hydroxamic acid collectors are selected from at least one of benzohydroxamic acid, octyl hydroxamic acid, and alkyl hydroxamic acid.

[0026] The short-chain fatty acid collectors are selected from at least one of oleic acid, linoleic acid, and palmitic acid.

[0027] Preferably, during the second-stage flotation, the collector used is composed of hydroxamic acid and fatty acid in a mass ratio of hydroxamic acid:fatty acid = 5-8:1.

[0028] In the present invention, 20-500 g / t of butyl xanthate collector and 5-80 g / t of no. 2 oil frother are used in the first-stage flotation. The purpose is to enrich rare earth elements while removing acid-consuming impurity minerals in coal gangue. Combined with the second-stage flotation and enhanced leaching with appropriate subsequent parameters, it can further enrich heavy rare earths while ensuring a relatively high leaching rate of rare earths.

[0029] Preferably, the mass fraction of the flotation tailings after concentration treatment is 45-65%. Maximizing the mass fraction of the flotation tailings concentration treatment can not only improve the recycling of water, but also reduce the pollution and cyclic addition amount of the leaching solution in the subsequent leaching process.

[0030] Preferably, the acid solution for acid leaching includes sulfuric acid and / or hydrochloric acid; the concentration of the acid solution for acid leaching is 1.2 - 5.0 mol / L, and more preferably 2.0 - 4.0 mol / L.

[0031] In some specific embodiments, the concentration of the acid solution for acid leaching can be, but is not limited to, 1.2 mol / L, 2.0 mol / L, 3.0 mol / L, 4.0 mol / L or 5.0 mol / L.

[0032] Preferably, the leaching intensifying agent added to the acid solution includes: sodium dodecyl sulfonate surfactant. More preferably, the mass fraction of sodium dodecyl sulfonate surfactant added to the acid solution is 0.001 - 0.006%. In the present invention, adding an appropriate amount of sodium dodecyl sulfonate surfactant is to improve the wettability and leaching activity of rare earth-rich coal gangue, thereby increasing the contact area between the acid solution and mineral particles, and improving the leaching ratio of medium and heavy rare earths and the total rare earth leaching rate.

[0033] Preferably, the liquid-solid ratio of the acid leaching is 8:1 - 12:1; the temperature of the acid leaching is 65 - 85 °C; the time of the acid leaching is 2 - 4 h.

[0034] In some specific embodiments, the liquid-solid ratio of the acid leaching can be, but is not limited to, 8:1, 9:1, 10:1, 11:1 or 12:1; the temperature of the acid leaching can be, but is not limited to, 65 °C, 70 °C, 75 °C, 80 °C or 85 °C; the time of the acid leaching can be, but is not limited to, 2 h, 3 h or 4 h.

[0035] Beneficial effects

[0036] In the traditional method for extracting rare earth elements from coal gangue by hydrometallurgy, since the rare earth-rich coal gangue is not pre-concentrated, the processing volume and production cost are increased. At the same time, due to the strong hydrophobicity and low leaching activity of some rare earth-rich coal gangue, the extraction efficiency of rare earth elements is restricted. The present invention uses rare earth-rich coal gangue as the raw material, and through the combined process of beneficiation and metallurgy for multi-point impurity removal and leaching intensification, the purpose of efficiently extracting rare earth elements from coal gangue is achieved. The advantages are as follows:

[0037] (1) The present invention uses the optoelectronic sorting method to effectively separate the rare earth-rich coal gangue from the low-grade coal products in the raw material, reduce the amount of ore entering the crushing and grinding and subsequent processes, and the effective reduction amount is greater than or equal to 10%;

[0038] (2) The present invention adopts a flotation-based separation method to specifically remove oxidant-consuming and acid-consuming substances such as sulfide minerals, carbonate minerals, and residual coal quality in coal gangue, reducing production costs such as acid consumption and reagent consumption in the metallurgical process; after flotation-based separation, the ore volume is effectively reduced by no less than 5%, with the sulfide rejection rate being greater than 80% and the carbonate mineral rejection rate being greater than 50%.

[0039] (3) The present invention adopts a method of surfactant-enhanced leaching to enhance the wettability and leaching activity of rare earth-rich coal gangue, increase the contact area between the acid solution and mineral particles, promote the leaching reaction rate of medium and heavy rare earths, and at the same time improve the leaching recovery rate of rare earth elements in coal gangue. Additionally, the present invention also realizes the efficient enrichment of heavy rare earths for the first time.

[0040] The method provided by the present invention can effectively extract rare earth elements from coal gangue, especially medium and heavy rare earths. While efficiently separating rare earth-rich minerals from other minerals, it reduces the ore volume entering the grinding, flotation, and leaching processes, saves process reagent consumption and energy consumption, and realizes the high-value utilization of coal gangue, having good social and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a simplified process flow diagram of the method for selective leaching of rare earth elements from coal gangue by quality and grade provided by the present invention;

[0042] Figure 2 It is the specific process flow diagram of Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] The technical solutions of the present invention will be clearly and elaborately described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments only represent a part of the present invention, not all of it. According to the embodiments of the present invention, other embodiments obtained by those of ordinary skill in the art without creative efforts are protected by the present invention.

[0044] Example 1

[0045] The method for selective leaching of rare earth elements from coal gangue by quality and grade provided in this example includes the following steps:

[0046] Using Inner Mongolia coal gangue as the raw material, with the total rare earth element content being 177 μg / g (the content of heavy rare earth elements being 20.38 μg / g), the specific process flow diagram is shown in Figure 2 .

[0047] (1) Feed the coal gangue raw material into the coal gangue photoelectric separator through the feeder belt at a feeding speed of 0.8 m / s. In the coal gangue photoelectric separator, the computer terminal analyzes the mineral attribute R value according to the different X-ray reflectivities of the surfaces of coal and coal gangue. Minerals with R > 1.28 are identified as coal, and minerals with R < 1.28 are identified as coal gangue. After the computer terminal discriminates the minerals, they are sprayed by a high-pressure air gun, so that the rare earth-rich coal gangue and low-grade coal products fall into different tanks respectively.

[0048] (2) Crush the rare earth-rich coal gangue obtained in step (1) by a jaw crusher and let it fall into a high-frequency vibrating screen with a screen hole of 5.0 mm. The products on the screen (+5.0 mm) are returned to the jaw crusher for further processing, and the products under the screen (-5.0 mm) enter a vertical stirring mill for fine crushing. Then, through an ultra-fine classification hydrocyclone, the slurry of the +0.074 mm particle size is returned to the vertical stirring mill for further processing, while the slurry of the -0.074 mm particle size is subjected to pulp adjustment treatment to obtain a flotation pulp with a mass fraction of 30% and is transported to a flotation machine.

[0049] (3) Conduct one-stage flotation on the flotation pulp obtained in step (2) to remove sulfide minerals and residual easily floatable coal quality (foam products), and obtain the tailings of the first-stage flotation of coal gangue (bottom products in the tank). The flotation reagents used are 60 g / t of butyl xanthate collector and 20 g / t of No. 2 oil frother, and the flotation time is 5 min.

[0050] (4) Conduct two-stage flotation on the tailings of the first-stage flotation of coal gangue obtained in step (3) to remove carbonate minerals and residual oxidized coal quality (foam products), and obtain the tailings of the second-stage flotation of coal gangue (bottom products in the tank). The flotation reagents used in the second-stage flotation are 70 g / t of benzohydroxamic acid collector, 30 g / t of modified oleic acid auxiliary collector, and 20 g / t of No. 2 oil frother, and the flotation time is 5 min. Then, sediment and concentrate the tailings of the second-stage flotation of coal gangue. The mass fraction of the concentrated flotation tailings after the concentration treatment is 47.5%.

[0051] (5) Feed the concentrated flotation tailings obtained in step (4) into a leaching tank for acid leaching treatment. The acid solution for acid leaching is a mixed acid with a molar ratio of sulfuric acid to hydrochloric acid of 1:1, and the acid solution concentration is 3.0 mol / L. A surfactant of sodium dodecyl sulfonate with a mass fraction of 0.004% is added to the acid solution as a leaching intensifying reagent. The liquid-solid ratio (mass ratio) of the acid leaching is 10:1, the acid leaching temperature is 80 °C, and the acid leaching time is 3 h. After the acid leaching is completed, remove the slag through a filtering device to obtain a rare earth leaching solution.

[0052] In this embodiment, 20.04% of impurities are removed by mineral separation. After the rare earth element leaching solution is dried, the recovery rate of heavy rare earths is 39.46%, the recovery rate of light rare earths is 17.88%, and the ratio of heavy rare earths to light rare earths (mass ratio) is 3.49.

[0053] Example 2

[0054] The method for selectively leaching rare earth elements from coal gangue by quality and grade separation provided in this example includes the following steps:

[0055] (1)-(3) are the same as those in Example 1;

[0056] (4) Subject the first-stage flotation tailings of coal gangue obtained in step (3) to second-stage flotation to remove carbonate minerals and residual oxidized coal quality (foam products), and obtain second-stage flotation tailings of coal gangue (bottom products in the cell); the flotation reagents used in the second-stage flotation are 70 g / t of octyl hydroxamic acid collector, 30 g / t of palmitic acid auxiliary collector, and 20 g / t of No. 2 oil foaming agent, and the flotation time is 5 min; then settle and concentrate the second-stage flotation tailings of coal gangue; the mass fraction of the flotation tailings after concentration treatment is 45.3%;

[0057] (5) is the same as that in Example 1;

[0058] In this example, 19.83% of impurities are removed by mineral separation. After drying the rare earth element leaching solution, the recovery rate of heavy rare earths is 37.59%, the recovery rate of light rare earths is 17.11%, and the ratio of heavy rare earths to light rare earths is 3.51.

[0059] Example 3

[0060] The method for selectively leaching rare earth elements from coal gangue by quality and grade separation provided in this example includes the following steps:

[0061] (1)-(3) are the same as those in Example 1;

[0062] (4) Subject the first-stage flotation tailings of coal gangue obtained in step (3) to second-stage flotation to remove carbonate minerals and residual oxidized coal quality (foam products), and obtain second-stage flotation tailings of coal gangue (bottom products in the cell); the flotation reagents used in the second-stage flotation are 100 g / t of benzohydroxamic acid collector and 20 g / t of No. 2 oil foaming agent, and the flotation time is 5 min; then settle and concentrate the second-stage flotation tailings of coal gangue; the mass fraction of the flotation tailings after concentration treatment is 43.8%;

[0063] (5) is the same as that in Example 1;

[0064] In this example, 19.66% of impurities are removed by mineral separation. After drying the rare earth element leaching solution, the recovery rate of heavy rare earths is 36.80%, the recovery rate of light rare earths is 20.86%, and the ratio of heavy rare earths to light rare earths is 3.76.

[0065] Example 4

[0066] The method for selectively leaching rare earth elements from coal gangue by quality and grade separation provided in this example includes the following steps:

[0067] (1) to (4) are the same as in Example 1;

[0068] (5) Feed the concentrated flotation tailings obtained in step (4) into a leaching tank for acid leaching. The acid solution for acid leaching is sulfuric acid, and the acid concentration is 3.0 mol / L; a surfactant of sodium dodecyl sulfonate with a mass fraction of 0.004% is added to the acid solution as a leaching intensifying agent; the liquid-solid ratio for acid leaching is 10:1, the acid leaching temperature is 80 °C; the acid leaching time is 3 h; after the acid leaching is completed, the slag is removed through a filtering device to obtain a rare earth leaching solution.

[0069] In this example, 19.98% of impurities are removed by mineral separation. After the rare earth element leaching solution is dried, the recovery rate of heavy rare earths is 37.12%, the recovery rate of light rare earths is 17.64%, and the ratio of heavy rare earths to light rare earths is 3.65.

[0070] Example 5

[0071] The method for selective leaching of rare earth elements by coal gangue quality grading provided in this example includes the following steps:

[0072] (1) to (4) are the same as in Example 1;

[0073] (5) Feed the concentrated flotation tailings obtained in step (4) into a leaching tank for acid leaching. The acid solution for acid leaching is a mixed acid with a molar ratio of sulfuric acid to hydrochloric acid of 1:1, and the acid concentration is 2.0 mol / L; a surfactant of sodium dodecyl sulfonate with a mass fraction of 0.004% is added to the acid solution as a leaching intensifying agent; the liquid-solid ratio for acid leaching is 11:1, the acid leaching temperature is 65 °C; the acid leaching time is 4 h; after the acid leaching is completed, the slag is removed through a filtering device to obtain a rare earth leaching solution.

[0074] In this example, 20.01% of impurities are removed by mineral separation. After the rare earth element leaching solution is dried, the recovery rate of heavy rare earths is 33.51%, the recovery rate of light rare earths is 16.79%, and the ratio of heavy rare earths to light rare earths is 3.86.

[0075] Example 6

[0076] The method for selective leaching of rare earth elements by coal gangue quality grading provided in this example includes the following steps:

[0077] (1) to (4) are the same as in Example 1;

[0078] (5) Feed the concentrated flotation tailings obtained in step (4) into a leaching tank for acid leaching treatment. The acid solution for acid leaching is a mixed acid with a molar ratio of sulfuric acid to hydrochloric acid of 1:1, and the acid solution concentration is 3.0 mol / L; a surfactant of sodium dodecyl sulfonate with a mass fraction of 0.002% is added to the acid solution as a leaching intensifying agent; the liquid-solid ratio of acid leaching is 10:1, the acid leaching temperature is 80 °C; the acid leaching time is 3 h; after the acid leaching is completed, the slag is removed through a filtering device to obtain a rare earth leaching solution.

[0079] In this example, 19.88% of impurities are removed by mineral separation. After the rare earth element leaching solution is dried, the recovery rate of heavy rare earths is 31.47%, the recovery rate of light rare earths is 17.63%, and the ratio of heavy rare earths to light rare earths is 4.28.

[0080] Comparative Example 1

[0081] The method for selective leaching of rare earth elements by coal gangue fractional classification provided in this comparative example is different from that in Example 1 in that the coal gangue raw material does not undergo the coal gangue optoelectronic separation in step (1), and the coal gangue raw material directly enters the crushing, screening, and grinding processes in step (2).

[0082] In this comparative example, 9.28% of impurities are removed by mineral separation. After the rare earth element leaching solution is dried, the recovery rate of heavy rare earths is 17.39%, the recovery rate of light rare earths is 11.13%, and the ratio of heavy rare earths to light rare earths is 4.93.

[0083] Comparative Example 2

[0084] The method for selective leaching of rare earth elements by coal gangue fractional classification provided in this comparative example is different from that in Example 1 in that after the coal gangue raw material undergoes the coal gangue optoelectronic separation and crushing and grinding processes in steps (1) to (2), the rare earth-rich coal gangue does not undergo the flotation impurity removal process in steps (3) to (4), and the pulp with a mass fraction of 65% after crushing and grinding is fed into a leaching tank for acid leaching treatment.

[0085] In this comparative example, 10.19% of impurities are removed by mineral separation. After the rare earth element leaching solution is dried, the recovery rate of heavy rare earths is 17.54%, the recovery rate of light rare earths is 13.29%, and the ratio of heavy rare earths to light rare earths is 5.87.

[0086] Comparative Example 3

[0087] The method for selective leaching of rare earth elements by coal gangue fractional classification provided in this comparative example is different from that in Example 1 in that after the coal gangue raw material undergoes the coal gangue optoelectronic separation and crushing and grinding processes in steps (1) to (2), the rare earth-rich coal gangue does not undergo the flotation impurity removal process in step (3), and the pulp with a mass fraction of 65% after crushing and grinding is fed into a leaching tank for acid leaching treatment.

[0088] In this comparative example, 14.76% of impurities were removed by mineral separation. After the rare earth element leaching solution was dried, the recovery rate of heavy rare earths was 25.10%, the recovery rate of light rare earths was 13.93%, and the ratio of heavy rare earths to light rare earths was 4.25.

[0089] Comparative Example 4

[0090] The method for selective leaching of rare earth elements by coal gangue quality grading provided in this comparative example is different from that in Example 1 in that after the coal gangue raw material undergoes the coal gangue optoelectronic separation and grinding process in steps (1)-(2), the rare earth-rich coal gangue does not undergo the flotation impurity removal process in step (4), and the pulp with a mass fraction of 65% after grinding is sent to the leaching tank for acid leaching treatment.

[0091] In this comparative example, 14.29% of impurities were removed by mineral separation. After the rare earth element leaching solution was dried, the recovery rate of heavy rare earths was 21.13%, the recovery rate of light rare earths was 12.72%, and the ratio of heavy rare earths to light rare earths was 4.64.

[0092] Comparative Example 5

[0093] The method for selective leaching of rare earth elements by coal gangue quality grading provided in this comparative example is different from that in Example 1 in that no leaching strengthening agent, that is, sodium dodecyl sulfonate surfactant, was added to the acid solution in step (5).

[0094] In this comparative example, 19.07% of impurities were removed by mineral separation. After the rare earth element leaching solution was dried, the recovery rate of heavy rare earths was 16.93%, the recovery rate of light rare earths was 15.02%, and the ratio of heavy rare earths to light rare earths was 6.81.

[0095] Comparative Example 6

[0096] The method for selective leaching of rare earth elements by coal gangue quality grading provided in this comparative example is different from that in Example 1 in that the surfactant added to the acid solution in step (5) is cetyltrimethylammonium bromide (CTAB) with a mass fraction of 0.004%.

[0097] In this comparative example, 19.11% of impurities were removed by mineral separation. The leaching rate of rare earth elements was 52.13%. After the rare earth element leaching solution was dried, the recovery rate of heavy rare earths was 18.20%, the recovery rate of light rare earths was 15.92%, and the ratio of heavy rare earths to light rare earths was 6.72.

[0098] As mentioned above, the above are only the preferred specific embodiments of the present invention and some cases in the technical exploration process of the present invention. However, the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A method for separating, enriching and extracting rare earth elements from coal gangue, characterized in that It includes the following steps: (1) Optoelectronically separate the coal gangue raw material, and remove the low-grade coal products in the raw material according to the different reflectivities R of X-rays on the surfaces of coal and coal gangue, to obtain rare-earth-rich coal gangue; the R of the rare-earth-rich coal gangue < 1.30; (2) Crush, screen, and grind the rare-earth-rich coal gangue, and then perform pulp conditioning to obtain a flotation pulp; (3) Perform first-stage flotation on the flotation pulp to remove sulfide minerals and residual easily flotable coal quality, to obtain first-stage flotation tailings; (4) Perform second-stage flotation on the first-stage flotation tailings to remove carbonate minerals and residual oxidized coal quality, to obtain second-stage flotation tailings; After concentrating the second-stage flotation tailings obtained in step (4), perform acid leaching treatment, and then perform solid-liquid separation to obtain a rare-earth leaching solution; after drying the rare-earth leaching solution, the mass ratio of heavy rare earths to light rare earths is (2.5 - 6.5) : 1; The acid solution for the acid leaching includes sulfuric acid or / and hydrochloric acid; the concentration of the acid solution for the acid leaching is 1.2 - 5.0 mol / L, the liquid-solid ratio for the acid leaching is 8:1 - 12:1; the temperature for the acid leaching is 65 - 85°C; the time for the acid leaching is 2 - 4 h; The leaching intensifying agent added to the acid solution includes: sodium dodecyl sulfonate surfactant; the mass fraction of sodium dodecyl sulfonate surfactant added to the acid solution is 0.001 - 0.006%; 2. The method for separating, enriching and extracting rare earth elements from coal gangue according to claim 1, wherein: The content of rare-earth elements in the coal gangue raw material is 104 - 1347 μg / g.

3. A method for separating, enriching and extracting rare earth elements from coal gangue according to claim 1, characterized in that: The feeding speed for the optoelectronic separation is 0.5 - 1.2 m / s.

4. A method for separating, enriching and extracting rare earth elements from coal gangue according to claim 1, characterized in that: The rare-earth-rich coal gangue is ground to a fineness of less than 0.074 mm; the mass fraction of the flotation pulp after the pulp conditioning is 25 - 40%.

5. A method for separating, enriching and extracting rare earth elements from coal gangue according to claim 1, characterized in that: The flotation reagents used for the first-stage flotation include: butyl xanthate collector and no. 2 oil frother; The flotation reagents used for the second-stage flotation include: hydroxamic acid collector or / and short-chain fatty acid collector, and no. 2 oil frother; the dosage of the hydroxamic acid collector or / and short-chain fatty acid collector is 20 - 1000 g / t, and the dosage of the no. 2 oil frother is 5 - 80 g / t.

6. The method for separating, enriching and extracting rare earth elements from coal gangue according to claim 5, characterized in that: The hydroxamic acid collector is selected from at least one of benzohydroxamic acid, octyl hydroxamic acid, and alkyl hydroxamic acid; The short-chain fatty acid collector is selected from at least one of oleic acid, linoleic acid, and palmitic acid.

7. A method for separating, enriching and extracting rare earth elements from coal gangue according to claim 5, characterized in that: In the first-stage flotation, 20 - 500 g / t of butyl xanthate collector and 5 - 80 g / t of no. 2 oil frother are used.

8. A method for separating, enriching and extracting rare earth elements from coal gangue according to claim 1, characterized in that: The concentration of the acid solution for the acid leaching is 2.0 - 4.0 mol / L.

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