Ionic type rare earth ore in-situ leaching mining and impurity removal precipitation method

Abstract

The invention discloses an ion-type rare earth ore in-situ leaching and impurity-removing precipitation method which comprises the following steps: adding water into magnesium oxide for fully dissolving, slowly adding concentrated sulfuric acid to adjust the pH value to 2.5-3.5 to obtain an ore leaching agent, quantitatively injecting the ore leaching agent into a rare earth ore area, and carrying out rare earth ore in-situ leaching to obtain a leaching solution; adding water into sodium bicarbonate to fully dissolve the sodium bicarbonate to obtain a sodium bicarbonate solution with the mass percent concentration of 2-5%, spraying the sodium bicarbonate solution into the leachate, and performing stirring treatment, so that impurities are precipitated and separated; adding water into sodium bicarbonate, fully dissolving the sodium bicarbonate to obtain a sodium bicarbonate solution with the mass percent concentration of 8-15%, spraying the sodium bicarbonate solution into the upper-layer clear liquid from which the impurity precipitates are separated, stirring to separate the rare earth precipitates, and drying and roasting the rare earth precipitates to obtain a rare earth oxide product. The magnesium oxide type mineral leaching agent and the sodium bicarbonate type impurity removal precipitator are adopted, and the problem that ammonia nitrogen in surface water exceeds the standard due to the fact that ammonium sulfate, ammonium bicarbonate and other agents are used in an existing process is solved.

Description

Technical Field

[0001] This invention belongs to the field of rare earth production technology, specifically relating to an in-situ leaching and impurity removal precipitation method for ion-type rare earth ores. Background Technology

[0002] Rare earth elements, due to their unique physicochemical properties (such as catalytic activity, magnetism, and luminescence), are widely used in new energy (such as wind turbines and electric vehicle batteries), electronics (smartphones and displays), and defense (missile guidance and stealth coatings). Rare earth elements are divided into light rare earth elements (cerium group) and heavy rare earth elements (yttrium group), with heavy rare earth elements being more valuable due to their scarcity. Ion-adsorption rare earth deposits (also known as weathering crust leaching rare earth deposits), mainly distributed in Jiangxi, Guangdong, Guangxi, Fujian, and Hunan provinces, are characterized by wide distribution, abundant reserves, low radioactivity, complete rare earth element composition, and high content of medium and heavy rare earth elements. In this type of rare earth deposit, rare earth elements are adsorbed onto clay minerals as hydrated ions or hydroxyl hydrated ions, making it impossible to enrich rare earth elements using conventional beneficiation methods. Currently, ion-adsorption rare earth mines commonly use ammonium sulfate leaching, ammonium bicarbonate impurity removal, and precipitation processes to produce mixed rare earth carbonates. However, this process easily causes problems such as excessive ammonia nitrogen in surface water, putting enormous environmental pressure on ion-adsorption rare earth mining companies. Developing suitable environmentally friendly leaching agents and impurity removal and precipitation agents remains one of the key research focuses in rare earth production. Summary of the Invention

[0003] To address the aforementioned shortcomings, this invention discloses an in-situ leaching and impurity removal precipitation method for ion-adsorption rare earth ores. It develops a suitable environmentally friendly leaching agent based on magnesium oxide and a highly efficient and environmentally friendly agent for impurity removal and precipitation based on sodium bicarbonate, thus solving the problem of excessive ammonia nitrogen in surface water caused by the use of ammonium sulfate, ammonium bicarbonate, and other agents in existing processes.

[0004] This invention is achieved using the following technical solution: A method for in-situ leaching and impurity removal precipitation of ion-adsorption rare earth minerals, comprising the following steps: (1) After dissolving magnesium oxide in water, concentrated sulfuric acid is slowly added to adjust the pH value to 2.5-3.5 to obtain the leaching agent; the mass ratio of magnesium oxide to water is (1.0-3.5):100; (2) Construction of tunnels and diversion holes in the rare earth mining area for collecting leachate, and simultaneous construction of injection holes for injecting the leaching agent obtained in step (1), with each injection hole injecting 0.5–0.8 m³ of leaching agent per day. 3 ; (3) Dissolve sodium bicarbonate in water to obtain a sodium bicarbonate solution with a mass percentage concentration of 2-5%, and use it as a precipitant for removing impurities; when the REO concentration in the leachate collected in step (2) reaches 0.1 g / L or more, place the collected leachate in the impurity removal tank and stir it, and add the precipitant to the leachate by spraying to adjust the pH value to 5-5.5, then stop adding the precipitant, continue stirring for 5-30 min and let it stand for 1-4 h, and take the clear solution from the upper layer of the impurity removal sedimentation tank to the sedimentation tank for treatment; (4) Dissolve sodium bicarbonate in water to obtain a sodium bicarbonate solution with a mass percentage concentration of 8-15%, and use it as a precipitant. Take the upper clear liquid obtained in step (3) and place it in a sedimentation tank for stirring. Add the precipitant to the upper clear liquid by spraying to adjust the pH value to 6.5-7. Then stop adding the precipitant, continue stirring for 5-30 minutes and let it stand for 1-4 hours. After the upper clear liquid in the sedimentation tank is discharged, the precipitate is obtained. Then the precipitate is dried and roasted to obtain rare earth oxide products.

[0005] Furthermore, in step (2), when the leaching agent is first injected, the daily volume of leaching agent injected into each injection hole is 0.7–0.8 m³. 3 The leaching agent used is obtained by uniformly mixing magnesium oxide and water at a mass ratio of (3.0-3.5):100; when water is flowing out of the tunnel and diversion holes, the volume of leaching agent injected into each injection hole per day is 0.4-0.6 m³. 3 Furthermore, the leaching agent used was obtained by uniformly mixing magnesium oxide and water at a mass ratio of (2.0 to 2.5): 100.

[0006] Furthermore, in step (2), when the REO concentration in the collected leachate decreases, concentrated sulfuric acid is added to the upper clarified liquid from the sedimentation tank described in step (6) to adjust the pH to 3.5 before use as a leaching agent. The volume of leaching agent injected into each injection hole per day is 0.6–0.7 m³. 3 When the REO concentration in the collected leachate is below 0.1 g / L, the collection and injection of the leachate shall be stopped.

[0007] Further, in step (1), the leaching agent contains an additive with a molar concentration of 0.05 to 0.1 mol / L. The additive is prepared by uniformly mixing fumaric acid and water, heating to 80 to 85°C and maintaining the temperature, then adding ammonium persulfate and acrylic acid monomer and stirring for 15 to 30 minutes, then adding sodium hydroxide solution to adjust the pH to 7, and then filtering to obtain acrylic acid and fumaric acid graft copolymer as the additive. In step (3), the collected leachate is placed in a purification tank and stirred. First, calcium chloride solution is added and stirred for 3 to 5 minutes. Then, a purification precipitant is added to the leachate by spraying to adjust the pH to 5 to 5.5.

[0008] Furthermore, the grafting rate of the acrylic acid and fumaric acid graft copolymer is 10-30%.

[0009] Furthermore, the molar concentration of the calcium chloride solution is 2 to 2.5 mol / L, and the volume ratio of the calcium chloride solution to the leachate is 1:(20 to 50).

[0010] Compared with existing technologies, this technical solution has the following advantages: 1. This invention dissolves magnesium oxide in water and adds concentrated sulfuric acid to adjust the pH to obtain a leaching agent for the leaching of ion-adsorption rare earth ores. Simultaneously, sodium bicarbonate solutions of different concentrations are prepared for impurity removal and rare earth precipitation recovery in the leaching solution. This not only achieves a good rare earth recovery rate but also avoids environmental problems such as excessive ammonia nitrogen in surface water caused by the use of ammonium sulfate, ammonium bicarbonate, and other reagents. Furthermore, this invention further studies and analyzes the rare earth leaching process, rationally adjusting the concentration of magnesium oxide and the injection volume of the leaching agent according to different leaching stages. This effectively leaches rare earths from the minerals while controlling the consumption cost of the leaching agent. In particular, the clarified liquid generated during the rare earth precipitation process is adjusted to pH with concentrated sulfuric acid and reused in later leaching stages, achieving efficient resource utilization.

[0011] 2. This invention uses a copolymer obtained from the grafting reaction of acrylic acid and fumaric acid as an additive added to the leaching agent. During the leaching process, it can electrostatically attract rare earth ions, weakening the binding force between rare earth ions and minerals and promoting rare earth leaching. Furthermore, it expands the mineral pores, promoting the penetration of the leaching agent and further improving the leaching efficiency. Before the impurity removal and precipitation process in the leaching solution, calcium chloride solution is added for treatment. Calcium ions replace the rare earth elements adsorbed on the acrylic acid and fumaric acid graft copolymer, releasing rare earth ions and ensuring the recovery rate of rare earths. Moreover, as the pH increases, the copolymer after replacement easily forms flocs and adsorbs impurity metals for co-precipitation, thereby improving the impurity removal effect. Detailed Implementation

[0012] The present invention is further illustrated by the following examples, but these are not intended to limit the invention. Specific experimental conditions and methods not specified in the following examples are generally conventional methods well known to those skilled in the art.

[0013] In an ion-adsorption rare earth mine (granite porphyry) in Guangxi, an in-situ rare earth leaching experiment was conducted according to the method of this invention. The mining area was 18,679 m². 2 The ore body has an average thickness of 12.5m, the overburden has an average thickness of 7.3m, and the average REO grade is 0.46‰. Based on supplementary production exploration, the calculated REO reserves are 171.85t. Production construction included 8 roadways with a main roadway depth of 70–110m; 1023 diversion holes with depths of 27–52m; and 6500 injection wells with depths of 8–12m.

[0014] Example 1: A method for in-situ leaching and impurity removal precipitation of ion-adsorption rare earth ores, comprising the following steps: (1) After dissolving magnesium oxide in water, concentrated sulfuric acid is slowly added to adjust the pH value to 3.2 to obtain the leaching agent; the mass ratio of magnesium oxide to water is (1.0~3.5):100; (2) Construction of tunnels and diversion holes in the rare earth mining area for collecting leachate, and simultaneous construction of injection holes for injecting the leaching agent obtained in step (1), with each injection hole injecting 0.5–0.8 m³ of leaching agent per day. 3 ; When the leaching agent injection begins, the daily volume of leaching agent injected into each injection hole is 0.75 m³. 3 Furthermore, the leaching agent used was obtained by uniformly mixing magnesium oxide and water at a mass ratio of 3.0:100. When water is present in the tunnels and diversion holes, the volume of leaching agent injected into each injection hole per day is 0.5 m³. 3 Furthermore, the leaching agent used was obtained by uniformly mixing magnesium oxide and water at a mass ratio of 2.0:100. When the REO concentration in the collected leachate decreases, concentrated sulfuric acid is added to the upper clarified liquid from the sedimentation tank described in step (6) to adjust the pH to 3.5 before use as a leaching agent. The daily volume of leaching agent injected into each injection hole is 0.60 m³. 3 ; When the REO concentration in the collected leachate is below 0.1 g / L, the collection and injection of the leachate should be stopped. (3) Dissolve sodium bicarbonate in water to obtain a sodium bicarbonate solution with a mass percentage concentration of 3%, and use it as a precipitant for removing impurities. When the REO concentration in the leachate collected in step (2) reaches 0.1 g / L or more, place the collected leachate in the impurity removal tank and stir it. Add the precipitant to the leachate by spraying to adjust the pH value to 5.4. Then stop adding the precipitant, continue stirring for 30 min and let it stand for 4 h. Take the clear solution from the upper layer of the impurity removal sedimentation tank and send it to the sedimentation tank for treatment. (4) Sodium bicarbonate is dissolved in water to obtain a sodium bicarbonate solution with a mass percentage concentration of 10%, which is used as a precipitant. The upper clear liquid obtained in step (3) is placed in a sedimentation tank and stirred. The precipitant is added to the upper clear liquid by spraying to adjust the pH value to 6.7. Then the addition of precipitant is stopped, and stirring is continued for 30 minutes. After standing for 4 hours, the upper clear liquid in the sedimentation tank is discharged to obtain the precipitate. The precipitate is then dried and roasted to obtain rare earth oxide products. The rare earth recovery rate of the leaching method described in this embodiment is 92.48%.

[0015] Example 2: A method for in-situ leaching and impurity removal precipitation of ion-adsorption rare earth ores, comprising the following steps: (1) After dissolving magnesium oxide in water, concentrated sulfuric acid is slowly added to adjust the pH value to 2.5 to obtain the leaching agent; the mass ratio of magnesium oxide to water is (1.0~3.5):100; (2) Construction of tunnels and diversion holes in the rare earth mining area for collecting leachate, and simultaneous construction of injection holes for injecting the leaching agent obtained in step (1), with each injection hole injecting 0.5–0.8 m³ of leaching agent per day. 3 ; When the leaching agent injection begins, the daily volume of leaching agent injected into each injection hole is 0.8 m³. 3 Furthermore, the leaching agent used was obtained by uniformly mixing magnesium oxide and water at a mass ratio of 3.2:100. When water is present in the tunnels and diversion holes, the volume of leaching agent injected into each injection hole per day is 0.6 m³. 3 Furthermore, the leaching agent used was obtained by uniformly mixing magnesium oxide and water at a mass ratio of 2.2:100. When the REO concentration in the collected leachate decreases, concentrated sulfuric acid is added to the upper clarified liquid from the sedimentation tank described in step (6) to adjust the pH to 3.5 before use as a leaching agent. The volume of leaching agent injected into each injection hole per day is 0.7 m³. 3 ; When the REO concentration in the collected leachate is below 0.1 g / L, the collection and injection of the leachate should be stopped. (3) Dissolve sodium bicarbonate in water to obtain a sodium bicarbonate solution with a mass percentage concentration of 5%, and use it as a precipitant for removing impurities. When the REO concentration in the leachate collected in step (2) reaches 0.1 g / L or more, place the collected leachate in the impurity removal tank and stir it. Add the precipitant to the leachate by spraying to adjust the pH value to 5.5. Then stop adding the precipitant, continue stirring for 5 min and let it stand for 1 h. Take the clear solution from the upper layer of the impurity removal sedimentation tank and send it to the sedimentation tank for treatment. (4) Sodium bicarbonate is dissolved in water to obtain a sodium bicarbonate solution with a mass percentage concentration of 15%, which is used as a precipitant. The upper clear liquid obtained in step (3) is placed in a sedimentation tank and stirred. The precipitant is added to the upper clear liquid by spraying to adjust the pH value to 7. Then the addition of precipitant is stopped, and stirring is continued for 5 minutes. After standing for 1 hour, the upper clear liquid in the sedimentation tank is discharged to obtain the precipitate. The precipitate is then dried and roasted to obtain rare earth oxide products. The rare earth recovery rate of the leaching method described in this embodiment is 91.88%.

[0016] Example 3: A method for in-situ leaching and impurity removal precipitation of ion-adsorption rare earth minerals, comprising the following steps: (1) After dissolving magnesium oxide in water, concentrated sulfuric acid is slowly added to adjust the pH value to 3.5 to obtain the leaching agent; the mass ratio of magnesium oxide to water is (1.0~3.5):100; (2) Construction of tunnels and diversion holes in the rare earth mining area for collecting leachate, and simultaneous construction of injection holes for injecting the leaching agent obtained in step (1), with each injection hole injecting 0.5–0.8 m³ of leaching agent per day. 3 ; When the leaching agent injection begins, the daily volume of leaching agent injected into each injection hole is 0.7 m³. 3 Furthermore, the leaching agent used was obtained by uniformly mixing magnesium oxide and water at a mass ratio of 3.5:100. When water is present in the tunnels and diversion holes, the daily volume of leaching agent injected into each injection hole is 0.4 m³. 3 Furthermore, the leaching agent used was obtained by uniformly mixing magnesium oxide and water at a mass ratio of 2.5:100. When the REO concentration in the collected leachate decreases, concentrated sulfuric acid is added to the upper clarified liquid from the sedimentation tank described in step (6) to adjust the pH to 3.5 before use as a leaching agent. The volume of leaching agent injected into each injection hole per day is 0.6 m³. 3 ; When the REO concentration in the collected leachate is below 0.1 g / L, the collection and injection of the leachate should be stopped. (3) Dissolve sodium bicarbonate in water to obtain a sodium bicarbonate solution with a mass percentage concentration of 2%, and use it as a precipitant for removing impurities. When the REO concentration in the leachate collected in step (2) reaches 0.1 g / L or more, place the collected leachate in the impurity removal tank and stir it. Add the precipitant to the leachate by spraying to adjust the pH value to 5. Then stop adding the precipitant, continue stirring for 20 min and let it stand for 2 h. Take the clear solution from the upper layer of the impurity removal sedimentation tank and send it to the sedimentation tank for treatment. (4) Dissolve sodium bicarbonate in water to obtain a sodium bicarbonate solution with a mass percentage concentration of 8%, and use it as a precipitant; take the upper clear liquid obtained in step (3) and place it in a sedimentation tank for stirring, and add the precipitant to the upper clear liquid by spraying to adjust the pH value to 6.5, then stop adding the precipitant, continue stirring for 20 minutes and let it stand for 2 hours, then discharge the upper clear liquid from the sedimentation tank to obtain the precipitate, and then dry and roast the precipitate to obtain rare earth oxide products. The rare earth recovery rate of the leaching method described in this embodiment is 92.56%.

[0017] Example 4: A method for in-situ leaching and impurity removal precipitation of ion-adsorption rare earth ores, comprising the following steps: (1) After dissolving magnesium oxide in water, concentrated sulfuric acid is slowly added to adjust the pH to 3.2 to obtain the leaching agent; the mass ratio of magnesium oxide to water is (1.0~3.5):100; the leaching agent contains an auxiliary agent with a molar concentration of 0.08 mol / L. The auxiliary agent is prepared by mixing fumaric acid and water evenly, heating to 82°C and maintaining the temperature, then adding ammonium persulfate and acrylic acid monomer and stirring for 20 min, then adding sodium hydroxide solution to adjust the pH to 7, and then filtering to obtain an acrylic acid and fumaric acid graft copolymer as an auxiliary agent. The grafting rate of the acrylic acid and fumaric acid graft copolymer is 22%. (2) Construction of tunnels and diversion holes in the rare earth mining area for collecting leachate, and simultaneous construction of injection holes for injecting the leaching agent obtained in step (1), with each injection hole injecting 0.5–0.8 m³ of leaching agent per day. 3 ; When the leaching agent injection begins, the daily volume of leaching agent injected into each injection hole is 0.75 m³. 3 Furthermore, the leaching agent used was obtained by uniformly mixing magnesium oxide and water at a mass ratio of 3.0:100. When water is present in the tunnels and diversion holes, the daily volume of leaching agent injected into each injection hole is 0.45 m³. 3 Furthermore, the leaching agent used was obtained by uniformly mixing magnesium oxide and water at a mass ratio of 2.2:100. When the REO concentration in the collected leachate decreases, concentrated sulfuric acid is added to the upper clarified liquid from the sedimentation tank described in step (6) to adjust the pH to 3.5 before use as a leaching agent. The daily volume of leaching agent injected into each injection hole is 0.65 m³. 3 ; When the REO concentration in the collected leachate is below 0.1 g / L, the collection and injection of the leachate should be stopped. (3) Dissolve sodium bicarbonate in water to obtain a sodium bicarbonate solution with a mass percentage concentration of 3%, and use it as a precipitant for removing impurities; when the REO concentration in the leachate collected in step (2) reaches 0.1 g / L or more, place the collected leachate in a purification tank and stir. First, add calcium chloride solution and stir for 4 min. Then, add the precipitant for removing impurities to the leachate by spraying to adjust the pH value to 5.2. Then, stop adding the precipitant for removing impurities, continue stirring for 15 min, and let it stand for 2 h. Take the clear solution from the upper layer of the purification sedimentation tank and send it to the sedimentation tank for treatment; the molar concentration of the calcium chloride solution is 2 mol / L, and the volume ratio of calcium chloride solution to leachate is 1:25; (4) Dissolve sodium bicarbonate in water to obtain a sodium bicarbonate solution with a mass percentage concentration of 12%, and use it as a precipitant; take the upper clear liquid obtained in step (3) and place it in a sedimentation tank for stirring, and add the precipitant to the upper clear liquid by spraying to adjust the pH value to 6.7, then stop adding the precipitant, continue stirring for 15 minutes and let it stand for 2 hours, discharge the upper clear liquid from the sedimentation tank to obtain the precipitate, and then dry and roast the precipitate to obtain rare earth oxide products. The rare earth recovery rate of the leaching method described in this embodiment is 93.11%.

[0018] Example 5: A method for in-situ leaching and impurity removal precipitation of ion-adsorption rare earth ores, comprising the following steps: (1) After dissolving magnesium oxide in water, concentrated sulfuric acid is slowly added to adjust the pH to 3.0 to obtain the leaching agent; the mass ratio of magnesium oxide to water is (1.0~3.5):100; the leaching agent contains an auxiliary agent with a molar concentration of 0.05mol / L. The auxiliary agent is prepared by mixing fumaric acid and water evenly, heating to 80℃ and maintaining the temperature, then adding ammonium persulfate and acrylic acid monomer and stirring for 30 minutes, then adding sodium hydroxide solution to adjust the pH to 7, and then filtering to obtain an acrylic acid and fumaric acid graft copolymer as an auxiliary agent. The grafting rate of the acrylic acid and fumaric acid graft copolymer is 30%. (2) Construction of tunnels and diversion holes in the rare earth mining area for collecting leachate, and simultaneous construction of injection holes for injecting the leaching agent obtained in step (1), with each injection hole injecting 0.5–0.8 m³ of leaching agent per day. 3 ; When the leaching agent injection begins, the daily volume of leaching agent injected into each injection hole is 0.75 m³. 3 Furthermore, the leaching agent used was obtained by uniformly mixing magnesium oxide and water at a mass ratio of 3.5:100. When water is present in the tunnels and diversion holes, the volume of leaching agent injected into each injection hole per day is 0.5 m³. 3 Furthermore, the leaching agent used was obtained by uniformly mixing magnesium oxide and water at a mass ratio of 2.5:100. When the REO concentration in the collected leachate decreases, concentrated sulfuric acid is added to the upper clarified liquid from the sedimentation tank described in step (6) to adjust the pH to 3.5 before use as a leaching agent. The daily volume of leaching agent injected into each injection hole is 0.65 m³. 3 ; When the REO concentration in the collected leachate is below 0.1 g / L, the collection and injection of the leachate should be stopped. (3) Dissolve sodium bicarbonate in water to obtain a sodium bicarbonate solution with a mass percentage concentration of 4%, and use it as a precipitant for removing impurities; when the REO concentration in the leachate collected in step (2) reaches 0.1 g / L or more, place the collected leachate in a purification tank and stir. First, add calcium chloride solution and stir for 5 min. Then, add the precipitant for removing impurities to the leachate by spraying to adjust the pH value to 5. Then, stop adding the precipitant for removing impurities, continue stirring for 20 min, and let it stand for 3 h. Take the clear solution from the upper layer of the purification tank and send it to the sedimentation tank for treatment. The molar concentration of the calcium chloride solution is 2.5 mol / L, and the volume ratio of the calcium chloride solution to the leachate is 1:50. (4) Dissolve sodium bicarbonate in water to obtain a sodium bicarbonate solution with a mass percentage concentration of 10%, and use it as a precipitant; take the upper clear liquid obtained in step (3) and place it in a sedimentation tank for stirring, and add the precipitant to the upper clear liquid by spraying to adjust the pH value to 6.8, then stop adding the precipitant, continue stirring for 20 minutes and let it stand for 3 hours, discharge the upper clear liquid from the sedimentation tank to obtain the precipitate, and then dry and calcine the precipitate to obtain rare earth oxide products. The rare earth recovery rate of the leaching method described in this embodiment is 92.94%.

[0019] Example 6: A method for in-situ leaching and impurity removal precipitation of ion-adsorption rare earth ores, comprising the following steps: (1) After dissolving magnesium oxide in water, concentrated sulfuric acid is slowly added to adjust the pH to 2.8 to obtain the leaching agent; the mass ratio of magnesium oxide to water is (1.0~3.5):100; the leaching agent contains an auxiliary agent with a molar concentration of 0.1 mol / L. The auxiliary agent is prepared by mixing fumaric acid and water evenly, heating to 85°C and maintaining the temperature, then adding ammonium persulfate and acrylic acid monomer and stirring for 15 min, then adding sodium hydroxide solution to adjust the pH to 7, and then filtering to obtain an acrylic acid and fumaric acid graft copolymer as an auxiliary agent. The grafting rate of the acrylic acid and fumaric acid graft copolymer is 10%. (2) Construction of tunnels and diversion holes in the rare earth mining area for collecting leachate, and simultaneous construction of injection holes for injecting the leaching agent obtained in step (1), with each injection hole injecting 0.5–0.8 m³ of leaching agent per day. 3 ; When the leaching agent injection begins, the daily volume of leaching agent injected into each injection hole is 0.7 m³. 3 Furthermore, the leaching agent used was obtained by uniformly mixing magnesium oxide and water at a mass ratio of 3.5:100. When water is present in the tunnels and diversion holes, the volume of leaching agent injected into each injection hole per day is 0.6 m³. 3 Furthermore, the leaching agent used was obtained by uniformly mixing magnesium oxide and water at a mass ratio of 2.0:100. When the REO concentration in the collected leachate decreases, concentrated sulfuric acid is added to the upper clarified liquid from the sedimentation tank described in step (6) to adjust the pH to 3.5 before use as a leaching agent. The volume of leaching agent injected into each injection hole per day is 0.7 m³. 3 ; When the REO concentration in the collected leachate is below 0.1 g / L, the collection and injection of the leachate should be stopped. (3) Dissolve sodium bicarbonate in water to obtain a sodium bicarbonate solution with a mass percentage concentration of 2%, and use it as a precipitant for removing impurities; when the REO concentration in the leachate collected in step (2) reaches 0.1 g / L or more, place the collected leachate in a purification tank and stir. First, add calcium chloride solution and stir for 3 min. Then, add the precipitant for removing impurities to the leachate by spraying to adjust the pH value to 5. Then, stop adding the precipitant for removing impurities, continue stirring for 20 min, and let it stand for 2 h. Take the clear solution from the upper layer of the purification tank and send it to the sedimentation tank for treatment. The molar concentration of the calcium chloride solution is 2.5 mol / L, and the volume ratio of calcium chloride solution to leachate is 1:20. (4) Sodium bicarbonate is dissolved in water to obtain a sodium bicarbonate solution with a mass percentage concentration of 10%, which is used as a precipitant. The upper clear liquid obtained in step (3) is placed in a sedimentation tank and stirred. The precipitant is added to the upper clear liquid by spraying to adjust the pH value to 6.5. Then the addition of precipitant is stopped, and stirring is continued for 20 minutes. After standing for 2 hours, the upper clear liquid in the sedimentation tank is discharged to obtain the precipitate. The precipitate is then dried and roasted to obtain rare earth oxide products. The rare earth recovery rate of the leaching method described in this embodiment is 93.02%.

[0020] Experimental Example: Based on the method described in Example 1, different types of ion-adsorption rare earth ores were selected for testing. The specific process is as follows: S1. For ion-adsorption rare earth ores of different origins, take 10.00 kg of ore samples (dry weight) and place them in a self-made leaching simulation test column. S2. Take analytical grade magnesium oxide and add it to pure water at a mass ratio of 3:100 to obtain a solution by stirring. Then add analytical grade concentrated sulfuric acid (98%) to adjust the pH value to obtain leaching solutions with different pH values. S3. Add the prepared leaching solution into the leaching simulation test column continuously for 24 hours at a rate of 4.5L / d. S4. Take samples of the leachate three times a day, in the morning, noon and evening, and analyze them, focusing on pH value and REO concentration; S5. Take sodium bicarbonate of analytical purity and add it to pure water at a mass ratio of 3:100 to obtain a purified solution by stirring and dissolving. S6. Take 500 mL of the leachate after analysis in step S4, add it by spraying with the impurity removal solution, while stirring and observing the change in pH value. When the pH value reaches 5.4, stop adding the impurity removal solution, continue stirring for 5 minutes and let it stand for 1 hour. S7. Sodium bicarbonate of analytical purity was added to pure water at a mass ratio of 10:100 to sodium bicarbonate and stirred to dissolve, thus obtaining a precipitate solution. S8. After removing impurities in step S6, take 300 mL of the clear upper layer that has been allowed to stand, and add it by spraying with the precipitating solution. At the same time, stir and observe the change in pH value of the solution. When the pH value reaches 6.7, stop adding the precipitating solution, continue stirring for 5 minutes, and then let it stand for 1 hour. S9. Take the clear liquid from the precipitation step and the supernatant from the impurity removal step for analysis, focusing on the REO concentration and calculating the impurity removal and precipitation loss rates. S10. The experiment was conducted continuously for 7 days until the REO concentration in the leachate was <0.1 g / L. The experiment was then terminated, and the ore samples after leaching were analyzed to determine the remaining REO content and calculate the leaching efficiency. The optimal leaching pH was calculated by adjusting magnesium oxide leaching solutions at different pH values.

[0021] Table 1. Statistical table of optimal leaching pH in laboratory column leaching tests

[0022] During the experimental period, leaching simulation tests were conducted on ion-adsorption rare earth ores with different lithologies. After sampling and analysis, it was found that under the optimal pH leaching conditions, the leaching effect of magnesium oxide was comparable to that of ammonium sulfate.

[0023] Table 2. Statistical table of leaching rates in laboratory column leaching tests

[0024] During the experimental period, sodium bicarbonate was used as a purification and precipitation agent. The clear liquid above the purification and precipitation layer was sampled and analyzed. Under correct operating conditions, sodium bicarbonate was as effective as ammonium bicarbonate as a purification and precipitation agent.

[0025] Table 3. Statistical Table of Precipitation Loss Rate in Laboratory Purification

[0026] Laboratory experiments have shown that using magnesium oxide as a leaching agent and sodium bicarbonate as a precipitant is economical and feasible.

[0027] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for in-situ leaching and impurity removal and precipitation of ion-type rare earth ore, characterized in that: The method comprises the following steps: (1) taking magnesium oxide, adding water to dissolve it, slowly adding concentrated sulfuric acid to adjust the pH value to 2.5-3.5 to obtain a leaching agent; the mass ratio of the magnesium oxide to water is (1.0-3.5):100; (2) constructing a roadway and a diversion hole in the rare earth ore area for collecting the leaching solution, and constructing a liquid injection hole for injecting the ore leaching agent obtained in step (1), and the volume of the ore leaching agent injected into each liquid injection hole per day is 0.5-0.8 m 3 ; (3) taking sodium bicarbonate, adding water to dissolve it to obtain a sodium bicarbonate solution with a mass percentage concentration of 2-5%, which is used as a removal impurity precipitant; when the REO concentration of the leaching solution collected in step (2) reaches 0.1 g / L or more, the collected leaching solution is placed in a removal impurity tank for stirring, and the removal impurity precipitant is added to the leaching solution in a spraying manner to adjust the pH value to 5-5.5, then the addition of the removal impurity precipitant is stopped, the stirring is continued for 5-30 min, and then the solution is left to stand for 1-4 h, and the upper clear solution of the removal impurity tank is taken out and sent to a precipitation tank for treatment; (4) taking sodium bicarbonate, adding water to dissolve it to obtain a sodium bicarbonate solution with a mass percentage concentration of 8-15%, which is used as a precipitant; the upper clear solution obtained in step (3) is placed in a precipitation tank for stirring, and the precipitant is added to the upper clear solution in a spraying manner to adjust the pH value to 6.5-7, then the addition of the precipitant is stopped, the stirring is continued for 5-30 min, and then the solution is left to stand for 1-4 h, the upper clear solution of the precipitation tank is discharged to obtain a precipitate, and then the precipitate is dried and calcined to obtain a rare earth oxide product.

2. The in-situ leaching and impurity removal and precipitation method of ion-type rare earth ore according to claim 1, characterized in that: In step (2), the volume of the leaching agent injected by each injection hole per day is 0.7-0.8m 3 when the leaching agent used is obtained by uniformly mixing magnesium oxide and water in a mass ratio of (3.0-3.5):100; and when there is water in the roadway and the flow guide hole, the volume of the leaching agent injected by each injection hole per day is 0.4-0.6m 3 when the leaching agent used is obtained by uniformly mixing magnesium oxide and water in a mass ratio of (2.0-2.5):

100.

3. The in-situ leaching and impurity removal and precipitation method of ion-type rare earth ore according to claim 1, characterized in that: In step (2), when the REO concentration in the collected leaching solution is reduced, the supernatant in the precipitation tank in step (6) is taken and adjusted to a pH value of 3.5 by concentrated sulfuric acid, and then used as a leaching agent. The volume of the leaching agent injected into each injection hole per day is 0.6-0.7 m 3 When the REO concentration in the collected leaching solution is less than 0.1 g / L, the liquid collection and injection production is stopped.

4. The in-situ leaching and impurity removal and precipitation method of ion-type rare earth ore according to claim 1, characterized in that: In step (1), the leaching agent contains an auxiliary agent with a molar concentration of 0.05-0.1 mol / L; the auxiliary agent is prepared by uniformly mixing fumaric acid and water, heating to 80-85 ℃, and then adding ammonium persulfate and acrylic acid monomer for stirring and reaction for 15-30 min, and then adding sodium hydroxide solution to adjust the pH value to 7, and then filtering to obtain an acrylic acid and fumaric acid graft copolymer as the auxiliary agent; in step (3), the collected leaching solution is placed in a removal impurity tank for stirring, calcium chloride solution is first added and stirred for 3-5 min, and then the removal impurity precipitant is added to the leaching solution in a spraying manner to adjust the pH value to 5-5.

5.

5. The in-situ leaching and impurity removal and precipitation method of ion-type rare earth ore according to claim 1, characterized in that: The grafting rate of the acrylic acid and fumaric acid graft copolymer is 10-30%.

6. The in-situ leaching and impurity removal and precipitation method of ion-type rare earth ore according to claim 1, characterized in that: The molar concentration of the calcium chloride solution is 2-2.5 mol / L, and the volume ratio of the calcium chloride solution to the leaching solution is 1: (20-50).

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