Method for synergistically recycling rare earth-containing coal mine acid wastewater and coal gangue

Abstract

The invention discloses a method for synergistically recycling rare earth-containing coal mine acid wastewater and coal gangue, and relates to the technical field of comprehensive utilization of mineral resources, the method mainly comprises the following steps: S1, arranging a rare earth-rich coal gangue dump leaching field and building a heap; s2, spraying the rare earth-containing coal mine acid wastewater and collecting leachate; s3, separation and enrichment of rare earth elements; and S4, carrying out high-valued treatment on resources such as iron and aluminum in the residual solution. According to the method, valuable resources such as rare earth in the rare-earth-containing coal mine acid wastewater and the rare-earth-rich coal gangue are synergistically recycled, meanwhile, treatment of the coal mine acid wastewater and preparation of the polymeric ferric aluminum sulfate are achieved, the concept of maximum value of comprehensive utilization of resources is achieved, and the treatment process is low in cost and little in environmental pollution.

Description

Technical Field

[0001] The invention discloses a method for cooperatively recycling rare earth-containing coal mine acid wastewater and coal gangue, and relates to the technical field of comprehensive utilization of mineral resources. Background Art

[0002] Rare earth elements have key functions and roles in advanced technology, emerging clean energy, national defense and military industry, aerospace and other fields. With the continuous innovation of technology, the demand for rare earths continues to grow. In order to expand the reserves of rare earth resources and solve the supply risks of rare earths, it has gradually become a trend to seek to recover rare earth elements from alternative resources. Studies have shown that coal waste is rich in rare earth elements, such as coal gangue, fly ash and acid mine drainage. Coal gangue is a solid waste generated in the process of mining and mineral processing, and the comprehensive utilization rate of resources is extremely low. Acid mine drainage is acidic drainage generated in the mining process, containing high concentrations of heavy metal ions, which has become a serious hidden danger to the ecological environment around mines. Since these wastes contain a variety of key metal elements including rare earth elements, how to achieve the extraction and recovery of key metal elements and comprehensive waste management has become an important topic in the field of mining engineering.

[0003] In recent years, researchers have conducted a lot of research on the extraction and recovery of rare earth elements from coal gangue and acid mine wastewater. In the process of extracting rare earth elements from coal gangue, the method of oxidative roasting of coal gangue and then acid leaching / alkaline leaching is often used. The crushing and roasting steps in the process consume a lot of energy, and the leaching step consumes a lot of acid / alkaline solution, and the production cost is relatively high; in the process of extracting rare earth elements from acid mine wastewater, the neutralization precipitation method is often used to treat acidic wastewater. This method consumes a lot of neutralizers, and the residues produced will also cause secondary pollution, and the recovery efficiency of rare earth elements is relatively low. Other recovery technologies such as solvent extraction, ion exchange and membrane filtration also have problems such as complex processes, high production costs, and low recovery efficiency, which make it impossible to achieve widespread application. Therefore, it is urgent to develop methods for extracting rare earth elements and other key metal elements from coal waste that have both economic benefits and environmental protection.

[0004] The method for synergistically recovering rare earth-containing acidic coal mine wastewater and coal gangue provided by the present invention utilizes acidic coal mine wastewater to replace acid solution used in acid leaching of coal gangue. At the same time, the reaction between acidic wastewater and coal gangue also plays a neutralizing role. On the one hand, the consumption of a large amount of acid / alkali solution in the process of separate treatment of coal gangue and acidic coal mine wastewater is greatly reduced, and at the same time, the enrichment and recovery efficiency of rare earth elements is improved. The method is a comprehensive utilization method of coal waste with both economic benefits and environmental protection. Summary of the invention

[0005] The purpose of the present invention is to provide a method for the coordinated recycling of rare earth-containing acidic coal mine wastewater and coal gangue. In view of the problems of complex process, high production cost, low recovery efficiency, etc. when extracting rare earth elements from acidic mine wastewater or coal gangue, the present invention proposes to utilize the strong acidity of coal mine wastewater and the rare earth-rich properties of solid waste coal gangue, and apply the heap leaching method to comprehensively extract the rare earth elements in the raw materials. At the same time, the acidic characteristics of the iron-aluminum raffinate are utilized to save process steps and directly prepare polyaluminum ferrous sulfate products. The method of the present invention can effectively reduce production costs and environmental pollution, and at the same time realize the high-value utilization of coal mine waste.

[0006] The present invention provides a method for synergistically recycling rare earth-containing coal mine acid wastewater and coal gangue, comprising the following steps:

[0007] S1: Layout and construction of rare earth-rich coal gangue leaching site

[0008] Construct a heap leaching site, which is divided into at least two working areas; arrange leachate collection pipes, ventilation pipes and spraying devices in each working area; pile up the rare earth-containing coal gangue from bottom to top in the heap leaching site in each production cycle, and loosen it by sledding on the ore pile; mix the rare earth-containing coal mine acid wastewater and leaching agent to a target pH value and then use it for spraying; the target pH value is selected in the range of 0.5 to 1.5; the leaching agent includes an inorganic acid;

[0009] S2: Spraying of acidic wastewater from rare earth-containing coal mines and collection of leachate

[0010] At the beginning of heap leaching, the ore pile is sprayed with high intensity. In the middle of heap leaching, the ore pile is sprayed with low intensity because of the acid production by the ore pile. At the end of heap leaching, the ore pile is sprayed with medium intensity to enhance the leaching of rare earths. The leachate seeps into the rich liquid pool through the collection pipes of each partition, and is pumped to the extraction workshop after reaching a certain volume and concentration.

[0011] In step S2, the intensity of the high-intensity spray is greater than 8 L / m 2 ‧h, medium intensity spraying: the spraying intensity is 5~8 L / m 2 ‧h, low intensity spraying: the spraying intensity is 3~5 L / m 2 ‧h; and the spraying intensity of medium-intensity spraying is greater than that of low-intensity spraying;

[0012] In step S2, the initial heap leaching period is 10 to 20 days, the middle heap leaching period is 50 to 70 days, the final heap leaching period is 30 to 60 days, and each heap leaching production cycle is 90 to 150 days;

[0013] S3: Separation and enrichment of rare earth elements

[0014] The rare earth elements in the leaching solution are extracted and separated by using an extractant, and rare earth enriched solution with a high proportion of medium and heavy rare earths and iron-aluminum-containing raffinate are obtained after extraction, stripping and other processes;

[0015] S4: High value of resources such as iron and aluminum in residual solution

[0016] The iron-aluminum raffinate is first concentrated, and then a combined oxidant is added, and the molar ratio of iron to aluminum and the pH value of the solution are adjusted; then the solution is heated and continuously stirred to carry out a polymerization reaction, and the obtained polymerization solution is left to stand and mature to prepare a polyaluminum ferric sulfate product.

[0017] When used in industry, heap leaching sites are usually built on gentle slopes around coal mines.

[0018] Preferably, in step S1, the rare earth content in the rare earth-containing coal gangue is not less than 200 μg / g, and the rare earth content in the rare earth-containing coal mine acidic wastewater is not less than 35 mg / L.

[0019] Preferably, in step S1, the ground inclination angle of the heap leaching site is preferably 3-8°; after the heap leaching site is built, the slope inclination angle is preferably 15-25°.

[0020] Preferably, in step S1, the diameter of the leachate collection pipe is 50-200 mm, and it is arranged in the entire heap leaching field at a spacing of 1-2 m. The dense arrangement can improve the recovery efficiency of the rare earth leachate.

[0021] Preferably, in step S1, the amount of ore piled in the heap leaching field in each production cycle is 300-1000 t. The production cycle of heap leaching refers to the entire process from ore preparation, heap building, spraying, leaching, collection of leachate to subsequent treatment.

[0022] Preferably, in step S1, the height of the pile is 3-9 m, and the area of ​​a single pile is 50-500 m 2 ; Further preferably, the pile height is 3~6 m as the best, which not only ensures the sufficient leaching of coal gangue, but also makes full use of the heap leaching area.

[0023] Preferably, in step S1, the spraying device is arranged above the ore pile.

[0024] Preferably, in step S1, after the rare earth-containing coal mine acid wastewater is mixed with the leaching agent sulfuric acid, the pH value of the qualified acid solution should be set in the range of 0.5~1.5; further preferably, under the condition that the pH value of the acid solution is 0.5~1.0, the rare earth leaching rate is basically the same, the pH value of the acid solution continues to increase from 1.0, and the rare earth leaching rate gradually decreases. Therefore, it is best to adjust the pH of the acid solution to about 1.0 (such as a pH of 0.8~1.0). If the pH value is too low, a large amount of leaching agent will be consumed, and if it is too high, the rare earth leaching rate will be affected.

[0025] Preferably, in step S2, the spray intensity is divided into three types: low, medium and high, and the low intensity is 3-4 L / m 2 ‧h, medium intensity is 6~8 L / m 2 ‧h, high intensity is 9~10 L / m 2 ‧h. In step S2, the ore pile is sprayed with high intensity at the initial stage of heap leaching to allow the gangue to fully contact and react with the acid solution; in the middle stage of heap leaching, the sulfide contained in the gangue can be oxidized into sulfate ions, while releasing hydrogen ions to generate sulfuric acid by itself, so only low intensity spraying is required; in the final stage of heap leaching, the rare earth element content in the gangue is reduced, so the ore pile needs to be sprayed with medium intensity to enhance the extraction rate of rare earth elements.

[0026] Preferably, in step S2, the time of the initial heap leaching is 10-20 days, preferably 14-16 days, the time of the middle heap leaching is 50-70 days, preferably 55-65 days, the time of the final heap leaching is 30-60 days, preferably 40-55 days, and each heap leaching production cycle is 90-150 days, preferably 109-136 days. The time control of the entire heap leaching cycle is to achieve the best extraction efficiency and economic benefits. The time control of the initial heap leaching is to make the solution evenly distributed. Too long time will lead to excessive acid consumption, and too short time will make the acid unable to fully contact with the coal gangue; the time of the middle heap leaching should be sufficient to allow the coal gangue to produce acid stably. Too long time may lead to acid exhaustion, and too short time will lead to insufficient self-production of acid; the time control of the final heap leaching period needs to ensure that the extraction of the remaining rare earth is as complete as possible. Too long time will increase acid consumption and operating costs, and too short time may lead to incomplete extraction.

[0027] Preferably, in step S3, the main extracting agent in the extraction process of the rare earth elements is P204 or / and P507, the diluent is sulfonated kerosene, and the stripping agent is sulfuric acid.

[0028] Preferably, the concentration of the extractant in the extraction process is 0.5-2.0 mol / L, more preferably 1.0-1.5 mol / L, the extractant and the diluent sulfonated kerosene are mixed in a volume ratio of 1:(1-10), more preferably 1:(2-8), the concentration of the stripping agent sulfuric acid is 2.0-8.0 mol / L, more preferably 3-6 mol / L, and the solution should maintain a pH of ≥2.0, more preferably pH ≥3.0 during the extraction process.

[0029] In S4, the iron-aluminum raffinate is first concentrated by natural airing.

[0030] Preferably, in step S4, the oxidant is any one of hydrogen peroxide, sodium percarbonate and sodium persulfate, and ferrous sulfate in the system is oxidized to ferric sulfate; in the present invention, the amount of the oxidant is: oxidizing the ferrous iron in the system to 1.0 to 1.05 times the theoretical amount of trivalent iron.

[0031] Preferably, in step S4, the raw materials for adjusting the molar ratio of iron and aluminum elements in the enriched solution are aluminum sulfate and iron sulfate, and the molar ratio of iron and aluminum elements after adjustment is (5~9): (1~3).

[0032] Preferably, in step S4, the pH of the solution is adjusted by NaOH, and the pH of the solution after adjustment is 1.5-3.0.

[0033] Preferably, in step S4, the polymerization reaction temperature is 60-85° C., and the reaction time is 1-4 h.

[0034] Preferably, in step S4, the polymerization solution is allowed to stand and mature for 8 to 24 hours; further preferably, the aging time is controlled at 12 to 18 hours to help the polyaluminum ferric sulfate product have optimal performance.

[0035] In the present invention, the light rare earth is selected from at least one of lanthanum, cerium, praseodymium, neodymium and promethium; the medium rare earth is selected from at least one of samarium, europium, gadolinium, terbium and dysprosium; and the heavy rare earth is selected from at least one of holmium, europium, erbium, thulium, ytterbium, lutetium, yttrium and scandium.

[0036] Principles and advantages of the present invention:

[0037] (1) Coal gangue is rich in rare earth elements, which require a large amount of acid for leaching and extraction. Coal mine acid wastewater not only contains rare earth elements, but also has natural strong acidity. It can replace the acid used for acid leaching of coal gangue, greatly reducing the acid consumption in the process of recovering rare earth elements and saving production costs.

[0038] (2) The treatment of acid mine wastewater or the recovery of rare earth elements usually adopts the neutralization precipitation method, which consumes a large amount of alkali solution. The acid mine wastewater reacts with coal gangue to neutralize the wastewater, which can greatly reduce the consumption of alkali. While effectively treating acid mine wastewater, it can also improve the enrichment and recovery efficiency of rare earth elements, thus achieving waste treatment with waste;

[0039] (3) The present invention adopts a heap leaching method to extract rare earth elements from coal mine waste, utilizing the chemical properties of the sulfides in the coal gangue. During the heap leaching process, the sulfides are oxidized into sulfate ions and hydrogen ions are released, thereby realizing the self-generation of sulfuric acid, saving the cost and energy consumption of adding sulfuric acid externally, and improving the leaching efficiency of the heap leaching process;

[0040] (4) The present invention utilizes the iron-aluminum enriched solution obtained by the leaching-extraction process as a resource, giving full play to the characteristics of iron-aluminum enrichment and strong acidity in the solution, directly preparing the polyaluminum ferric sulfate product, eliminating the early stages of the traditional preparation process of the product, effectively reducing production costs, and realizing the comprehensive resource utilization of coal mine waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The figure is a process flow diagram of a method for synergistically recovering rare earth-containing coal mine acid wastewater and coal gangue of the present invention; DETAILED DESCRIPTION

[0042] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

[0043] In the embodiments and comparative examples, the source of rare earth-containing coal mine acidic wastewater is the output of rare earth-rich coal mines.

[0044] Example 1

[0045] The raw materials are rare earth-rich coal gangue from Inner Mongolia and local rare earth-containing coal mine acidic wastewater. The rare earth element content in the coal gangue is 218 μg / g, the pH value of the coal mine acidic wastewater is 1.8, and the rare earth element content is 48.8 mg / L. The process flow diagram is shown in Figure 1 .

[0046] A heap leaching site was built on the gentle slope around the coal mine. The slope angle of the heap leaching site was 19° and the site was divided into 12 working areas. Leachate collection pipes, ventilation pipes and spray devices were laid out in each working area. The diameter of the leachate collection pipes was 100 mm and the spacing was 2 m. A set of spray devices was set up for every three working areas and arranged along the top of the ore pile. 1000 t of coal gangue was piled up in the heap leaching site from bottom to top with a pile height of 9 m and loosened on the ore pile by climbing a sled. The acidic wastewater from the coal mine was mixed with the leaching agent sulfuric acid to form a spray acid solution with a pH value of 1.0. In the initial 15 days of heap leaching, 10 L / m 2 ‧h high-intensity spraying (i.e. 10 L / m from the first to the 15th day of spraying) 2 ‧h high-intensity spraying, where L represents the volume unit of the sprayed acid, m 2 represents unit area, h represents time unit). During the 60 days in the middle of heap leaching, 4 L / m 2 ‧h low-intensity spraying (i.e. 4 L / m 2 ‧h low intensity spraying), and 8 L / m 2 ‧h of medium intensity spraying (i.e. 8 L / m 2 ‧h medium-intensity spraying); during this process, the leachate seeps into the rich liquid pool through the collection pipes of each partition. The total rare earth element recovery rate is 31.47%, and the recovery ratio of medium and heavy rare earths is 43.73%.

[0047] A 1.5 mol / L mixed extractant (the volume ratio of P204 to P507 is 3:7) is mixed with a diluent sulfonated kerosene in a volume ratio of 1:8, and 6.0 mol / L sulfuric acid is used as a stripping agent to extract and separate the rare earth elements in the leachate to obtain a rare earth enriched solution and an iron-aluminum raffinate. The iron-aluminum raffinate is first naturally dried and concentrated, and then a combined oxidant hydrogen peroxide and sodium percarbonate are added, and the molar ratio of iron and aluminum elements is adjusted to 4:1 by ferric sulfate and aluminum sulfate, and the pH of the solution is adjusted to 2.5 by NaOH. After completion, the enriched solution is transferred to a reactor, heated to 70°C and stirred for 3 hours to carry out a polymerization reaction. After the reaction is completed, the heating and stirring are stopped, and the solution is left to mature for 16 hours to obtain a polyferric aluminum sulfate liquid product with a total iron content of 5.96%, an alumina content of 1.03%, and a basicity of 24.81%.

[0048] Example 1-1

[0049] The other conditions are exactly the same as those in Example 1, except that:

[0050] In the first 12 days of heap leaching, 10 L / m 2‧h high-intensity spraying (i.e. 10 L / m from the first to the 12th day of spraying) 2 ‧h high-intensity spraying, where L represents the volume unit of the sprayed acid, m 2 represents unit area, h represents time unit), and 4 L / m 2 ‧h low-intensity spraying (i.e. 4 L / m 2 ‧h low intensity spraying), and 8 L / m 2 ‧h of medium intensity spraying (i.e. 8 L / m 2 ‧h medium-intensity spraying); during this process, the leachate seeps into the rich liquid pool through the collection pipes of each partition. The total rare earth element recovery rate is 25.54%, and the recovery rate of medium and heavy rare earths is 39.85%.

[0051] After the leachate is extracted and separated, the iron-aluminum raffinate obtained is processed under the same conditions to prepare a polyaluminum ferric sulfate liquid product, which has a total iron content of 5.21%, an alumina content of 0.92% and a basicity of 26.17%.

[0052] Example 1-2

[0053] The other conditions are exactly the same as those in Example 1, except that:

[0054] The iron-aluminum extract was first naturally dried and concentrated, and then a combined oxidant of hydrogen peroxide and sodium percarbonate was added, the molar ratio of iron and aluminum elements was adjusted to 4:1 by ferric sulfate and aluminum sulfate, and the pH of the solution was adjusted to 2.5 by NaOH; after completion, the enriched liquid was transferred to a reactor, heated to 80°C and continuously stirred for 2 h for polymerization reaction; after the reaction was completed, heating and stirring were stopped, and the solution was allowed to stand and mature for 16 h to obtain a polyferric aluminum sulfate liquid product with a total iron content of 5.04%, an alumina content of 0.87%, and a basicity of 26.70%.

[0055] During the exploration of the present invention, the following solutions were tried based on Example 1:

[0056] The iron-aluminum extract was first naturally dried and concentrated, and then a single oxidant hydrogen peroxide was added, the molar ratio of iron and aluminum elements was adjusted to 4:1 by ferric sulfate and aluminum sulfate, and the pH of the solution was adjusted to 2.5 by NaOH; after completion, the enriched liquid was transferred to the reactor, heated to 70°C and continuously stirred for 3 hours for polymerization reaction; after the reaction, heating and stirring were stopped, and the solution was allowed to stand and mature for 16 hours to obtain a polyferric aluminum sulfate liquid product with a total iron content of 4.85%, an alumina content of 0.79%, and a basicity of 28.63%.

[0057] Example 2

[0058] The raw materials were rare earth-rich coal gangue from Ningxia and local rare earth-containing coal mine acidic wastewater. The rare earth element content in the coal gangue was 271 μg / g, the pH value of the coal mine acidic wastewater was 1.6, and the rare earth element content was 65.6 mg / L.

[0059] A heap leaching site was built on the gentle slope around the coal mine. The slope angle of the heap leaching site was 21° and the site was divided into 6 working areas. Leachate collection pipes, ventilation pipes and spray devices were laid out in each working area. The diameter of the leachate collection pipes was 100 mm and the spacing was 1 m. A set of spray devices was set up for every two working areas and arranged along the top of the ore pile. 300 t of coal gangue was piled up from bottom to top in the heap leaching site with a pile height of 3 m and loosened on the ore pile by climbing a sled. Acidic wastewater was mixed with leaching agent sulfuric acid to form a spray acid solution with a pH value of 1.0. 9 L / m 2 ‧h high-intensity spraying (i.e. 9 L / m from the first to the 15th day of spraying) 2 ‧h high-intensity spraying, where L represents the volume unit of the sprayed acid, m 2 represents unit area, h represents time unit). During the 60 days in the middle of heap leaching, 3 L / m 2 ‧h low-intensity spraying (i.e. 3 L / m 2 ‧h low intensity spraying), and 6 L / m 2 ‧h of moderate intensity spraying (i.e. 6 L / m 2 ‧h medium-intensity spraying); during this process, the leachate seeps into the rich liquid pool through the collection pipes of each partition. The total rare earth element recovery rate is 34.86%, and the recovery ratio of medium and heavy rare earths is 46.51%.

[0060] A 1.5 mol / L mixed extractant (the volume ratio of P204 to P507 is 3:7) is mixed with a diluent sulfonated kerosene at a volume ratio of 1:8, and 6.0 mol / L sulfuric acid is used as a stripping agent to extract and separate the rare earth elements in the leachate to obtain a rare earth enriched solution and an iron-aluminum raffinate; the iron-aluminum raffinate is first naturally dried and concentrated, and then a combined oxidant hydrogen peroxide and sodium persulfate are added, and the molar ratio of iron and aluminum elements is adjusted to 8:1 by ferric sulfate and aluminum sulfate, and the pH of the solution is adjusted to 3.0 by NaOH; after completion, the enriched solution is transferred to a reactor, heated to 80°C and stirred for 3 h to carry out a polymerization reaction; after the reaction is completed, the heating and stirring are stopped, and the solution is left to mature for 18 h to obtain a polyferric aluminum sulfate liquid product with a total iron content of 8.31%, an alumina content of 1.19%, and a basicity of 20.24%.

[0061] Example 2-1

[0062] The other conditions are exactly the same as those in Example 2, except that:

[0063] In the first 15 days of heap leaching, 10 L / m 2 ‧h high-intensity spraying (i.e. 10 L / m from the first to the 15th day of spraying) 2 ‧h high-intensity spraying, where L represents the volume unit of the sprayed acid, m 2 represents unit area, h represents time unit). During the 55th day of the middle stage of heap leaching, 4 L / m 2 ‧h low-intensity spraying (i.e. 4 L / m 2 ‧h low intensity spraying), and 7 L / m 2 ‧h of medium intensity spraying (i.e. 7 L / m 2 ‧h medium-intensity spraying); during this process, the leachate seeps into the rich liquid pool through the collection pipes of each partition. The total rare earth element recovery rate is 35.44%, and the recovery ratio of medium and heavy rare earths is 46.79%.

[0064] After the leachate is extracted and separated, the iron-aluminum raffinate obtained is processed under the same conditions to prepare a polyaluminum ferric sulfate liquid product, which has a total iron content of 8.67%, an alumina content of 1.32% and a basicity of 19.88%.

[0065] Example 2-2

[0066] The other conditions are exactly the same as those in Example 2, except that:

[0067] The iron-aluminum extract was first naturally dried and concentrated, and then a combined oxidant of hydrogen peroxide and sodium percarbonate was added, the molar ratio of iron and aluminum elements was adjusted to 6:1 by ferric sulfate and aluminum sulfate, and the pH of the solution was adjusted to 2.5 by NaOH; after completion, the enriched liquid was transferred to a reactor, heated to 80°C and continuously stirred for 3 hours for polymerization reaction; after the reaction was completed, heating and stirring were stopped, and the solution was allowed to stand and mature for 16 hours to obtain a polyferric aluminum sulfate liquid product with a total iron content of 7.38%, an alumina content of 1.49%, and a basicity of 23.06%.

[0068] During the exploration process, the following solutions were tried based on Example 2:

[0069] The spray acid solution does not contain additional leaching agent sulfuric acid, that is, only coal mine acid wastewater with a pH value of 1.6 is used as the spray acid solution for the heap leaching field. After heap leaching through the same spray system, the total rare earth element recovery rate in the leachate is 24.33%, and the recovery rate of medium and heavy rare earths is 35.17%.

[0070] After the leachate is extracted and separated, the iron-aluminum raffinate obtained is processed under the same conditions to prepare a polyaluminum ferric sulfate liquid product, which has a total iron content of 5.39%, an alumina content of 0.89% and a basicity of 27.43%.

[0071] Compared with the existing heap leaching technology, the rare earth leaching rate of the present invention is much higher than that of the existing technology.

[0072] The above are only some of the preferred specific embodiments of the present invention and some of the cases in the process of technical exploration of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for the coordinated recovery and utilization of rare earth-containing coal mine acidic wastewater and coal gangue, characterized in that: The steps include: S1: Layout and construction of rare earth-rich coal gangue leaching site Construct a heap leaching site, which is divided into at least two working areas; arrange leachate collection pipes, ventilation pipes and spraying devices in each working area; pile up the rare earth-containing coal gangue from bottom to top in the heap leaching site in each production cycle, and loosen it by sledding on the ore pile; mix the rare earth-containing coal mine acid wastewater and leaching agent to a target pH value and then use it for spraying; the target pH value is selected in the range of 0.5 to 1.5; the leaching agent includes an inorganic acid; S2: Spraying of acidic wastewater from rare earth-containing coal mines and collection of leachate At the beginning of heap leaching, the ore pile is sprayed with high intensity. In the middle of heap leaching, the ore pile is sprayed with low intensity because of the acid production by the ore pile. At the end of heap leaching, the ore pile is sprayed with medium intensity to enhance the leaching of rare earths. The leachate seeps into the rich liquid pool through the collection pipes of each partition, and is pumped to the extraction workshop after reaching a certain volume and concentration. In step S2, the intensity of the high-intensity spray is greater than 8 L / m 2 ‧h, medium intensity spraying: the spraying intensity is 5~8 L / m 2 ‧h, low intensity spraying: the spraying intensity is 3~5 L / m 2 ‧h; and the spraying intensity of medium-intensity spraying is greater than that of low-intensity spraying; In step S2, the initial heap leaching period is 10 to 20 days, the middle heap leaching period is 50 to 70 days, the final heap leaching period is 30 to 60 days, and each heap leaching production cycle is 90 to 150 days; S3: Separation and enrichment of rare earth elements The rare earth elements in the leaching solution are extracted and separated by using an extractant, and rare earth enriched solution with a high proportion of medium and heavy rare earths and iron-aluminum-containing raffinate are obtained after extraction, stripping and other processes; S4: High value of resources such as iron and aluminum in residual solution The iron-aluminum extract is first concentrated, and then an oxidant is added, and the molar ratio of iron and aluminum and the pH value of the solution are adjusted; then the polymerization reaction is carried out by heating and continuous stirring, and the obtained polymerization solution is left to stand and mature to prepare a polyaluminum ferric sulfate product.

2. The method for synergistically recycling rare earth-containing coal mine acid wastewater and coal gangue according to claim 1, characterized in that: In step S1, the rare earth content in the rare earth-containing coal gangue is not less than 200 μg / g, and the rare earth content in the rare earth-containing coal mine acidic wastewater is not less than 35 mg / L.

3. The method for synergistically recycling rare earth-containing coal mine acid wastewater and coal gangue according to claim 1, characterized in that: In step S1, the bottom surface of the heap leaching site is inclined at 3-8°. After the heap leaching site is built, the slope angle is 15-25°. The diameter of the leachate collecting pipe is 50-200 mm, and the spacing between the leachate collecting pipes is 1-2 m. The height of the heap is 3-9 m. The spray device is arranged above the ore heap.

4. The method for synergistically recycling rare earth-containing coal mine acid wastewater and coal gangue according to claim 1, characterized in that: In step S1, the rare earth-containing coal mine acid wastewater is mixed with leaching agent sulfuric acid to a target pH value and then used for spraying; the target pH value is selected in the range of 0.5-1.

0.

5. The method for synergistically recycling rare earth-containing coal mine acid wastewater and coal gangue according to claim 1, characterized in that: In step S1, the amount of ore piled in the heap leaching field in each production cycle is 300~1000t.

6. The method for synergistically recovering rare earth-containing coal mine acidic wastewater and coal gangue according to claim 1, characterized in that: In step S2, the intensity of low-intensity spraying is 3~4 L / m 2 ‧h, the intensity of medium-intensity spray is 6~8 L / m 2 ‧h, the intensity of high-intensity spray is 9~10 L / m 2 ‧h.

7. The method for synergistically recovering rare earth-containing coal mine acid wastewater and coal gangue according to claim 6, characterized in that: In step S2, the time of the initial heap leaching is 14 to 16 days, the time of the middle heap leaching is 55 to 65 days, the time of the final heap leaching is 40 to 55 days, and each heap leaching production cycle is 109 to 136 days.

8. The method for synergistically recovering rare earth-containing coal mine acidic wastewater and coal gangue according to claim 1, characterized in that: In step S3, the extractant of the rare earth element extraction process is P204 or / and P507, the diluent is sulfonated kerosene, and the stripping agent is sulfuric acid.

9. The method for synergistically recovering rare earth-containing coal mine acid wastewater and coal gangue according to claim 1, characterized in that: In step S4, the oxidant is hydrogen peroxide, sodium percarbonate or sodium persulfate; the molar ratio of iron to aluminum after adjustment is (5-9): (1-3); the pH of the solution is adjusted to 1.5-3.0; the temperature of the polymerization reaction is 60-85°, and the reaction time is 1-4 h; the polymerization solution is allowed to stand for 8-24 h.

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