Method for controlling contamination in ion-type rare earth ore bodies or ore residues

Abstract

The application provides a pollution control method for ion type rare earth ore body or slag. The pollution control method comprises the following steps: S1, performing nitrogen fixation treatment on the rare earth ore by using a first treatment liquid, wherein the first treatment liquid comprises a magnesium salt and a phosphate; S2, performing washing on the rare earth ore after the nitrogen fixation treatment by using a second treatment liquid, wherein the second treatment liquid comprises water; the mass concentration of magnesium ions in the first treatment liquid is 40-1615 mg / L, and the mass concentration of phosphate ions in the first treatment liquid is 30-1900 mg / L. Through the above nitrogen fixation treatment and washing process, the water-soluble ammonia nitrogen in the rare earth ore body or slag is fixed in the water-insoluble magnesium ammonium phosphate, so that the generation of pollutants is reduced from the source.

Description

Technical Field

[0001] This invention relates to the field of rare earth mineral pollution control technology, and more specifically, to a method for controlling pollution in ion-type rare earth mineral bodies or slag. Background Technology

[0002] Currently, the main method for mining rare earth minerals is in-situ leaching. This involves injecting an ammonium-containing leaching solution (usually ammonium sulfate solution) into the mine, causing an ion exchange between the ammonium ions in the leaching solution and the rare earth ions adsorbed in the soil. The exchanged ammonium ions remain in the soil, while the desorbed rare earth ions enter the leaching solution. Due to the displacement and adsorption of rare earth ions by ammonium ions in the leaching solution, as well as the seepage and leakage of the ammonium sulfate solution, a large amount of ammonia nitrogen remains in the rare earth ore treated with ammonium sulfate or other ammonia-containing leaching solutions. This ammonia nitrogen accumulates continuously, causing serious ammonia nitrogen pollution to the surrounding surface and groundwater systems.

[0003] The ammonium salt mining process for rare earth mines in southern my country, due to the large amount of ammonium salt used, easily causes ammonia nitrogen pollution in surface water and groundwater. Existing technologies for addressing ammonia nitrogen pollution focus on end-of-pipe treatment, i.e., treating the contaminated water after ammonia nitrogen has seeped out from tailings / soil with groundwater and surface water. Commonly used methods include precipitation, membrane methods, ion exchange, and evaporation crystallization. Chinese patent application CN101190809A discloses a precipitation method that divides water into two parts: one part is treated with magnesium salts, and the other with phosphates. The two parts are then combined to form magnesium ammonium phosphate precipitate, thereby removing ammonia nitrogen from the wastewater. Chinese patent application CN109354229A discloses a method for treating low-concentration ammonia nitrogen wastewater using nanofiltration membranes to further purify the ammonia-containing wastewater; Chinese patent application CN106630009A discloses a method for treating high-concentration ammonia nitrogen wastewater using ion exchangers to adsorb ammonia nitrogen from the water, achieving ammonia nitrogen removal through further treatment; and Chinese patent application CN109455862A discloses a method for passing high-concentration ammonia nitrogen wastewater into an evaporator to separate ammonia from water, obtaining ammonia water and treated liquid.

[0004] The existing technology has the following disadvantages: (1) Existing methods are all aimed at treating nitrogen flowing into water bodies, and have failed to reduce the generation of pollutants from the source (nitrogen-rich soil); (2) Existing technology can only treat the collected polluted water. Although this part of the water accounts for the majority of the total water volume, some polluted water is still discharged into the surrounding water bodies without being collected, causing pollution; (3) Due to the characteristics of the in-situ leaching process, the existing ammonia nitrogen treatment model requires long-term monitoring and treatment of surface water and groundwater.

[0005] Therefore, it is of great significance to research and develop a method that can solve the problem of pollution of mine water bodies caused by in-situ leaching of rare earth minerals at the source. Summary of the Invention

[0006] The main objective of this invention is to provide a method for controlling pollution in ion-type rare earth ore bodies or slag, so as to solve the problem of ammonia nitrogen pollution in mine water caused by in-situ leaching processes of rare earth ore, which cannot be solved from the source in the existing technology.

[0007] To achieve the above objectives, according to one aspect of the present invention, this application provides a method for controlling pollution in ion-type rare earth ore bodies or slag. The method includes: step S1, performing nitrogen fixation treatment on the rare earth ore body or slag using a first treatment solution, the first treatment solution containing magnesium salts and phosphates; the mass concentration of magnesium ions in the first treatment solution is 40–1615 mg / L, and the mass concentration of phosphate ions in the first treatment solution is 30–1900 mg / L; step S2, washing the nitrogen-fixed rare earth ore body or slag using a second treatment solution, the second treatment solution containing water.

[0008] Further, in step S1, the rare earth ore is subjected to a first leaching treatment using a first treatment solution, and in step S2, the rare earth ore body or slag after nitrogen fixation treatment is subjected to a second leaching treatment using a second treatment solution.

[0009] Furthermore, for each cubic meter of rare earth ore body or slag, the injection rate of the first treatment liquid is 0.1 to 5 t / d per cubic meter of ore body, and the duration of the first leaching treatment is 10 to 30 days. Preferably, the injection rate of the second treatment liquid is 0.1 to 5 t / d per cubic meter of ore body, and the duration of the second leaching treatment is 20 to 90 days.

[0010] Furthermore, the magnesium salt is selected from one or more of magnesium sulfate, magnesium chloride, and magnesium nitrate, and the phosphate salt is preferably selected from one or more of disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, potassium phosphate, and calcium dihydrogen phosphate.

[0011] Furthermore, when step S1 uses the first treatment solution to perform the first leaching treatment on the rare earth ore body or slag, the mass concentration of magnesium ions and the mass concentration of phosphate ions in the first treatment solution gradually decrease with the duration of the first leaching treatment.

[0012] Furthermore, the solvent in the first treatment solution is water.

[0013] Furthermore, when using the second treatment solution for washing, step S2 also includes a step of pre-washing the nitrogen-fixed rare earth ore body or slag with an alkaline treatment solution, preferably with a pH value of 7 to 10.

[0014] Further, the second rinsing treatment is carried out in n stages, where 1 < n ≤ 6. Step S2 includes: Step S21, during the first to m stages of the second rinsing treatment, an alkaline second treatment solution is used to pre-rinse the nitrogen-fixed rare earth ore body or slag to obtain a pre-rinsed ore body, where 1 ≤ m ≤ 3, and preferably the pH value of the alkaline second treatment solution is 7 to 10; Step S22, during the m+1 to n stages of the second rinsing treatment, water is used as the second treatment solution to rinse the pre-rinsed ore body.

[0015] Furthermore, the first and second treatment solutions are injected into the rare earth ore body through injection wells, preferably with the bottom of the injection well located at the top of the weathered layer of the rare earth ore body.

[0016] Furthermore, the pollution control method also includes: step A1, after the first leaching treatment, collecting the first treatment liquid that has passed through the rare earth ore body or slag to obtain the first recovery liquid; step A2, adjusting the molar ratio of ammonium ions, phosphate ions and magnesium ions in the first recovery liquid to 1:(1~5):(1~5), and performing solid-liquid separation on the first recovery liquid to obtain magnesium ammonium phosphate and the first recovery treatment liquid, and returning the first recovery treatment liquid to step S1 for reuse.

[0017] Furthermore, the method for controlling pollution in ion-adsorption rare earth ore bodies or slag also includes: step B1, after the second leaching treatment, collecting the second treatment liquid that has passed through the rare earth ore body or slag to obtain a second recovery liquid; step B2, adjusting the molar ratio of ammonium ions, phosphate ions and magnesium ions in the recovered second recovery liquid to 1:1:(1~5), and performing solid-liquid separation on the second recovery liquid to obtain magnesium ammonium phosphate and a second recovery treatment liquid, the second recovery treatment liquid being returned to step S2 for reuse.

[0018] Applying the technical solution of this invention, the pollution control method of this application utilizes a first treatment solution containing magnesium salts and phosphates to treat rare earth ore bodies or slag. After treatment with the first treatment solution, a large amount of residual ammonia nitrogen in the rare earth ore body or slag reacts with magnesium ions and phosphate ions in the first treatment solution to generate magnesium ammonium phosphate. Magnesium ammonium phosphate has very low water solubility; therefore, the above treatment method can effectively fix nitrogen, fixing the ammonia nitrogen in the rare earth ore body or slag within the water-insoluble rare earth ore body or slag, effectively reducing the amount of ammonia nitrogen leached into the water from the rare earth ore body or slag. Furthermore, after treating the rare earth ore body or slag with the first treatment solution, a second treatment solution is used to wash the rare earth ore body or slag, washing away a small amount of unfixed ammonia nitrogen and unreacted phosphates from the ore body, allowing the ammonia nitrogen, magnesium salts, and phosphates to fully contact and further react to generate magnesium ammonium phosphate. This application employs the aforementioned nitrogen fixation treatment and washing process to fix water-soluble ammonia nitrogen in rare earth ore bodies or slag into water-insoluble magnesium ammonium phosphate, thereby reducing the generation of pollutants from the source.

[0019] When treating the collected slag from pool leaching and heap leaching processes, the above control method can mix the slag with the first treatment solution to achieve nitrogen fixation. For example, the slag can be soaked in the first treatment solution for nitrogen fixation, and then the nitrogen-fixed slag can be placed in the second treatment solution for soaking. Fresh second treatment solution can be replaced or added regularly for washing. Detailed Implementation

[0020] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0021] As described in the background section of this application, existing technologies only treat nitrogen flowing into water bodies, failing to reduce pollutant generation at the source. To address this problem, this application provides a method for controlling pollution from rare earth ore bodies or slag. This pollution control method includes: step S1, treating rare earth ore with a first treatment solution containing magnesium salts and phosphates for nitrogen fixation; step S2, washing the nitrogen-fixed rare earth ore with a second treatment solution containing water; the mass concentration of magnesium ions in the first treatment solution is 40–1615 mg / L, and the mass concentration of phosphate ions in the first treatment solution is 30–1900 mg / L.

[0022] Existing technologies utilize phosphate ions and magnesium salts in wastewater treatment processes, such as as wastewater treatment agents. However, the application of phosphate ions and magnesium salts in the rare earth mining field is currently undocumented, especially regarding in-situ treatment methods for rare earth mine pollution. Furthermore, the inventors, through extensive research, discovered that applying a first treatment solution with specific magnesium and phosphate ion concentrations to rare earth mines for nitrogen fixation, followed by washing the nitrogen-fixed rare earth mines with a second treatment solution, can fix water-soluble ammonia nitrogen in the ore body into water-insoluble magnesium ammonium phosphate, thereby reducing pollutant generation at the source.

[0023] The pollution control method of this application utilizes a first treatment solution containing magnesium salts and phosphates to treat rare earth ore bodies or slag. After treatment with the first treatment solution, the large amount of residual ammonia nitrogen in the rare earth ore body or slag reacts with magnesium ions and phosphate ions in the first treatment solution to generate magnesium ammonium phosphate. Magnesium ammonium phosphate has very low water solubility; therefore, the above treatment method can effectively fix nitrogen, fixing the ammonia nitrogen in the rare earth ore body or slag in the water-insoluble magnesium ammonium phosphate, effectively reducing the amount of ammonia nitrogen leached into the water from the rare earth ore body or slag. The above process involves the following chemical reaction: PO4 3- +NH4 + +Mg 2+→MgNH4PO4 (magnesium ammonium phosphate, also known as struvite); and after treating the rare earth ore body or slag with the first treatment solution, the rare earth ore body or slag is washed with the second treatment solution to wash out a small amount of unfixed ammonia nitrogen and unreacted phosphate from the ore body, so that ammonia nitrogen, magnesium salt and phosphate can come into full contact and further react to generate magnesium ammonium phosphate.

[0024] The concentrations of magnesium ions and phosphate ions in the first treatment solution include, but are not limited to, the ranges mentioned above. Limiting them to these ranges is beneficial for improving the ammonia nitrogen fixation efficiency, thereby helping to reduce the generation of pollutants.

[0025] In summary, by employing the aforementioned nitrogen fixation treatment and washing process, this application enables the water-soluble ammonia nitrogen in rare earth ore bodies or slag to be fixed in water-insoluble magnesium ammonium phosphate, thereby reducing the generation of pollutants from the source.

[0026] When treating the collected slag from pool leaching and heap leaching processes, the above control method can mix the slag with the first treatment solution to achieve nitrogen fixation. For example, the slag can be soaked in the first treatment solution for nitrogen fixation, and then the nitrogen-fixed slag can be placed in the second treatment solution for soaking. Fresh second treatment solution can be replaced or added regularly for washing.

[0027] In some preferred embodiments, for rare earth ore bodies or slag located within a mine, step S1 involves using a first treatment solution via an injection system to perform a first leaching treatment on the rare earth ore body or slag, and step S2 involves using a second treatment solution to perform a second leaching treatment on the nitrogen-fixed rare earth ore body or slag. This leaching method is easy to operate, has low labor costs, and allows the first and second treatment solutions to come into more thorough contact with the rare earth ore body or slag, improving the efficiency and effectiveness of nitrogen fixation and washing. Those skilled in the art can refer to commonly used leaching processes in the prior art to perform the leaching treatment described in this application for in-situ leaching. For example, a new treatment solution injection system can be constructed to inject the solution from the top of the mine into the mine, allowing the treatment solution to leach the ore body in the mine during in-situ leaching. Alternatively, an existing in-situ leaching injection system can be used.

[0028] During the leaching process, the daily dosage of the first and second treatment solutions, as well as the duration of the first and second leaching processes, can be selected by those skilled in the art based on the size of the mine, the amount of ammonium salt used in the treatment process, and other conditions in practical applications. In a preferred embodiment, for each cubic meter of rare earth ore body or slag, the injection rate of the first treatment solution is 0.1–5 t / d per cubic meter of ore body, and the duration of the first leaching treatment is 10–30 days. Preferably, the injection rate of the second treatment solution is 0.1–5 t / d per cubic meter of ore body, and the duration of the second leaching treatment is 20–90 days. The injection rate of the first treatment solution, the duration of the first leaching treatment, the injection rate of the second treatment solution, and the duration of the second leaching treatment are not limited to the above ranges. Limiting them to these ranges is beneficial for more effective treatment of ammonia nitrogen while reducing the waste of reagents and the problem of excessively long treatment cycles.

[0029] The magnesium salts and phosphates used in this application can be water-soluble. To avoid introducing other polluting substances into the rare earth ore body or slag, preferably, the magnesium salts include, but are not limited to, one or more of magnesium sulfate, magnesium chloride, and magnesium nitrate; the phosphates include, but are not limited to, one or more of disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, potassium phosphate, and calcium dihydrogen phosphate. Compared to other types, the above-mentioned magnesium salts and phosphates are common, low-cost reagents, which helps to reduce the cost of the ammonia nitrogen control method of this application and expand its applicability.

[0030] To reduce reagent waste and further enhance nitrogen fixation, preferably, during step S1 when the rare earth ore body or slag is subjected to a first leaching treatment using the first treatment solution, the mass concentrations of magnesium ions and phosphate ions in the first treatment solution gradually decrease with the duration of the first leaching treatment. By gradually reducing the concentrations of magnesium salts and phosphates in the first treatment solution over time, it is beneficial to reduce the amount of reagents used in the first treatment solution while ensuring effectiveness. Simultaneously, reducing the amount of the second treatment solution can improve the pollution control effect.

[0031] In a preferred embodiment, water is preferably used as the solvent in the first treatment solution. To conserve water resources, the water used in the first and second treatment solutions of this application is preferably surface water or groundwater that meets the Class III standard of the "Surface Water Environmental Quality Standard GB3838-2002", or surface water or reclaimed water that has been treated to meet the Class III standard of the "Surface Water Environmental Quality Standard GB3838-2002". By using the aforementioned water, ammonia nitrogen in rare earth ore bodies or slag can be treated simultaneously while avoiding secondary pollution of the ore body, thus further enhancing the effectiveness of pollution prevention and control.

[0032] The inventors discovered in experiments that pre-treating the rare earth ore body or slag with an alkaline treatment solution before washing it with the second treatment solution further enhances the effectiveness of the pollution control method of this application. Preferably, before washing with the second treatment solution, step S2 includes a step of pre-washing the nitrogen-fixed rare earth ore body or slag with an alkaline treatment solution, preferably with a pH value of 7-10; step S22 uses the second treatment solution to wash the pre-washed rare earth ore body or slag.

[0033] When using a second treatment solution to leach rare earth ore bodies or slag, it is preferable that the second leaching process is carried out in n stages, where 1 < n ≤ 6. Step S2 includes: Step S21, during the first to m stages of the second leaching process, an alkaline second treatment solution is used to pre-leach the nitrogen-fixed rare earth ore body or slag to obtain a pre-leached ore body, where 1 ≤ m ≤ 3, and the pH value of the alkaline second treatment solution is preferably 7 to 10; Step S22, during the (m+1)th to nth stages of the second leaching process, water is used as the second treatment solution to leach the pre-leached ore body. Using the above-mentioned alkaline treatment solution helps to reduce the concentration of ammonium ions in groundwater. The alkaline treatment solution mentioned in this application can use commonly used alkaline reagents, such as sodium hydroxide solution or potassium hydroxide solution, or lime suspension or aqueous solution.

[0034] When leaching rare earth ore bodies or slag, the first and second treatment solutions of this application can be injected into the rare earth ore bodies or slag using techniques commonly used in the art. Preferably, the first and second treatment solutions are injected into the rare earth ore bodies or slag through injection wells. For example, existing injection wells used for injecting ammonium sulfate can be used to inject the treatment solutions into the mine to leach the rare earth ore bodies or slag. Preferably, the bottom of the injection well is located in the weathered layer of the rare earth ore body or slag. Because the soil in the weathered layer is relatively loose, the treatment solutions are more easily injected into the in-situ leaching ore body, thereby enabling faster and more effective solidification of ammonia nitrogen in the ore body.

[0035] When using a leaching process to treat rare earth ore bodies or slag, the amount of treatment liquid used is relatively large. In order to make the treatment liquid reusable, the above-mentioned pollution control methods also include the recovery process of the first treatment liquid and the second treatment liquid.

[0036] The recovery process of the first treatment liquid includes: Step A1, after the first leaching treatment, the first treatment liquid that has passed through the rare earth ore body or slag is collected to obtain the first recovery liquid; Step A2, the molar ratio of ammonium ions, phosphate ions and magnesium ions in the first recovery liquid is adjusted to 1:(1~5):(1~5), and the first recovery liquid is subjected to solid-liquid separation to obtain magnesium ammonium phosphate and the first recovery treatment liquid. The first recovery treatment liquid is returned to step S1 for reuse.

[0037] The recovery process of the second treatment liquid includes: Step B1, after the second leaching treatment, collecting the second treatment liquid that has passed through the rare earth ore body or slag to obtain the second recovery liquid; Step B2, adjusting the molar ratio of ammonium ions, phosphate ions and magnesium ions in the recovered second recovery liquid to 1:1:(1~5), and performing solid-liquid separation on the second recovery liquid to obtain magnesium ammonium phosphate and the second recovery treatment liquid, which is returned to step S2 for reuse.

[0038] Through the above steps, the first and second treatment solutions can be effectively reused, thereby effectively saving the amount of treatment solution used and reducing water waste.

[0039] The beneficial effects of this application will be further illustrated below with reference to embodiments and comparative examples.

[0040] It should be noted that in Examples 1 to 6, southern rare earth ore slag was used as the ore sample for the soil column experiment. In this case, 300g of southern rare earth ore slag was first placed in an organosilicon glass container, and then a pipeline for circulating water was introduced to allow the circulating water to rinse all the slag from top to bottom. 50mL of 0.2mol / L ammonium chloride was added, and the mixture was allowed to stand at 25℃ for 24h to obtain rare earth ore slag with an ammonia nitrogen concentration of 600mg / kg.

[0041] Example 1

[0042] Use a 50 mL aqueous solution containing 0.02 mol / L magnesium sulfate and 0.02 mol / L disodium hydrogen phosphate (i.e., the first treatment solution, which contains 480 mg / L Mg). 2+ Contains 1900 mg / L PO4 3- The first treatment solution contained Mg from the leaching of the mineral sample column. 2+ With PO4 3- The mass concentration gradually decreased with the duration of the first leaching treatment, and nitrogen fixation was completed after standing for 24 hours. The soil column was then leached with water at pH 7, using 50 mL of water each time, for 5 leaches. The ammonia nitrogen concentration in the leaching water after the last leaching was measured. The test showed that the ammonia nitrogen concentration in the last leaching water was 25.12 mg / L, which was a decrease of 34.29%.

[0043] Example 2

[0044] The mineral sample column was leached with a 50 mL aqueous solution (same as the first treatment solution in Example 1) containing 0.02 mol / L magnesium sulfate and 0.01 mol / L disodium hydrogen phosphate, and nitrogen fixation was completed after standing for 24 hours. The column was then leached with 50 mL of water at pH 7 for 5 leaches, and the ammonia nitrogen concentration in the last leaching water was measured. The test showed that the ammonia nitrogen concentration in the last leaching water was 20.68 mg / L, which was a reduction of 45.90%.

[0045] Example 3

[0046] The mineral sample column was leached with 50 mL of an aqueous solution containing 0.02 mol / L magnesium sulfate and 0.02 mol / L disodium hydrogen phosphate (the same as the first treatment solution in Example 1), and allowed to stand for 24 h to complete the nitrogen fixation treatment. The column was then leached twice with 50 mL of water adjusted to pH 10 with NaOH. The column was then leached three times with 50 mL of water at pH 7. The ammonia nitrogen concentration in the final leaching water was measured. The test showed that the ammonia nitrogen concentration in the final leaching water was 14.26 mg / L, a reduction of 62.69%.

[0047] Example 4

[0048] The mineral sample column was leached with a 50 mL aqueous solution (same as the first treatment solution in Example 1) containing 0.02 mol / L magnesium sulfate and 0.02 mol / L disodium hydrogen phosphate, and nitrogen fixation treatment was completed after standing for 48 h. The column was then leached with 50 mL of water at pH 7 for 5 leaches, and the ammonia nitrogen concentration in the last leaching water was measured. The test showed that the ammonia nitrogen concentration in the last leaching water was 16.17 mg / L, which was a reduction of 57.70%.

[0049] Example 5

[0050] The mineral sample column was leached with a 25 mL aqueous solution (same as the first treatment solution in Example 1) containing 0.04 mol / L magnesium sulfate and 0.04 mol / L disodium hydrogen phosphate, and allowed to stand for 24 h to complete the nitrogen fixation treatment. The column was then leached with water at pH 7, with 25 mL of water used initially and allowed to stand for 24 h. Subsequent leachings were performed with 50 mL of water each time, for a total of 6 leachings. The ammonia nitrogen concentration in the leaching water after the last leaching was measured. The test results showed that the ammonia nitrogen concentration in the last leaching water was 23.59 mg / L, a reduction of 38.29%.

[0051] Example 6

[0052] First, the mineral sample column was rinsed with 25 mL of an aqueous solution containing 0.08 mol / L magnesium sulfate and 0.04 mol / L disodium hydrogen phosphate (the same as the first treatment solution in Example 1), followed by rinsing with 25 mL of water. After standing for 48 hours, nitrogen fixation treatment was completed. Then, the column was rinsed twice with 50 mL of water adjusted to pH 10 with NaOH. Finally, the column was rinsed three times with 50 mL of water at pH 7. The ammonia nitrogen concentration in the final rinsing water was measured. The test showed that the ammonia nitrogen concentration in the final rinsing water was 24.33 mg / L, a reduction of 76.57%.

[0053] Example 7

[0054] The difference from Example 1 is that: at the rare earth mine site, the same first treatment liquid as in Example 1 is injected into the rare earth ore body, the injection volume of the first treatment liquid is 0.1t / d per cubic meter of ore body, and the duration of the first leaching treatment is 30d; the injection volume of the second treatment liquid is 0.1t / d per cubic meter of ore body, and the duration of the second leaching treatment is 90d.

[0055] Tests revealed that the ammonia nitrogen concentration in the final rinse water was 32.56 mg / L, a reduction of 14.83%.

[0056] Example 8

[0057] The difference from Example 1 is that: at the rare earth mine site, the same first treatment liquid as in Example 1 is injected into the rare earth ore body, the injection volume of the first treatment liquid is 5t / d per cubic meter of ore body, and the duration of the first leaching treatment is 10d; the injection volume of the second treatment liquid is 5t / d per cubic meter of ore body, and the duration of the second leaching treatment is 20d.

[0058] Tests revealed that the ammonia nitrogen concentration in the final rinse water was 25.33 mg / L, a reduction of 33.74%.

[0059] Comparative Example 1

[0060] The mineral sample column was rinsed with 50 mL of water at pH 7 and allowed to stand for 24 hours to complete nitrogen fixation. The column was then rinsed again with 50 mL of water at pH 7, 50 mL each time, for a total of 5 rinsing cycles. The ammonia nitrogen concentration in the final rinsing water was measured. The test results showed that the ammonia nitrogen concentration in the final rinsing water was 38.23 mg / L.

[0061] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0062] Comparing Examples 1 and 2, it can be seen that increasing the mass concentration of magnesium sulfate in the first treatment solution is beneficial to reducing the concentration of ammonia nitrogen in the second recovery solution.

[0063] Comparative Examples 1 to 8 and Comparative Example 1 show that after treatment with the first treatment solution, the large amount of ammonia nitrogen remaining in the rare earth ore body or slag reacts with magnesium ions and phosphate ions in the first treatment solution to generate magnesium ammonium phosphate. Magnesium ammonium phosphate has very low water solubility; therefore, the above treatment method can effectively fix nitrogen, fixing the ammonia nitrogen in the rare earth ore body or slag in the water-insoluble magnesium ammonium phosphate, effectively reducing the amount of ammonia nitrogen leached into the water from the rare earth ore body or slag.

[0064] Comparing Examples 1 and 5, it can be seen that increasing the settling time after the first treatment solution is beneficial to reducing the concentration of ammonia nitrogen in the second recovery solution.

[0065] Comparing Examples 7 and 8, it can be seen that the injection volume of the first treatment liquid, the duration of the first rinsing treatment, the injection volume of the second treatment liquid, and the duration of the second rinsing treatment are not limited to the above ranges. Limiting them to the above ranges is beneficial for treating ammonia nitrogen more effectively while reducing the waste of reagents and the problem of excessively long treatment cycles.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for controlling pollution in ion-adsorption rare earth ore bodies or slag, characterized in that, The pollution control methods include: Step S1 involves using a first treatment solution to perform nitrogen fixation treatment on the rare earth ore body or slag. The first treatment solution contains magnesium salts and phosphates. The mass concentration of magnesium ions in the first treatment solution is 40–1615 mg / L, and the mass concentration of phosphate ions in the first treatment solution is 30–1900 mg / L. In step S1, the first treatment solution is used to perform a first leaching treatment on the rare earth ore body or slag. The mass concentrations of magnesium ions and phosphate ions in the first treatment solution gradually decrease with the duration of the first leaching treatment. Step S2: The rare earth ore body or slag after nitrogen fixation treatment is washed with a second treatment solution containing water. When using the second treatment solution for washing, step S2 further includes a step of pre-washing the nitrogen-fixed rare earth ore body or slag with an alkaline treatment solution, wherein the pH value of the alkaline treatment solution is 7 to 10.

2. The method for controlling pollution in ion-adsorption rare earth ore bodies or slag according to claim 1, characterized in that, In step S2, the nitrogen-fixed rare earth ore body or slag is subjected to a second rinsing treatment using the second treatment liquid.

3. The method for controlling pollution in ion-adsorption rare earth ore bodies or slag according to claim 2, characterized in that, For each cubic meter of rare earth ore body or slag, the injection rate of the first treatment liquid is 0.1 to 5 t / d per cubic meter of ore body, and the duration of the first leaching treatment is 10 to 30 days. The injection rate of the second treatment liquid is 0.1 to 5 t / d per cubic meter of ore body, and the duration of the second leaching treatment is 20 to 90 days.

4. The method for controlling pollution in ion-adsorption rare earth ore bodies or slag according to any one of claims 1 to 3, characterized in that, The magnesium salt is selected from one or more of magnesium sulfate, magnesium chloride, and magnesium nitrate, and the phosphate is selected from one or more of disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, potassium phosphate, and calcium dihydrogen phosphate.

5. The method for controlling pollution in ion-adsorption rare earth ore bodies or slag according to any one of claims 1 to 3, characterized in that, The solvent in the first treatment solution is water.

6. The method for controlling pollution in ion-adsorption rare earth ore bodies or slag according to claim 2, characterized in that, The second rinsing treatment is performed in n stages, where 1 < n ≤ 6. Step S2 includes: Step S21, during the first to m times of the second rinsing treatment, an alkaline second treatment solution is used to pre-rinse the nitrogen-fixed rare earth ore body or slag to obtain a pre-rinsed ore body, where 1≤m≤3, and the pH value of the alkaline second treatment solution is 7~10. In step S22, during the second rinsing process from m+1 to n, water is used as the second treatment liquid to rinse the pre-rinsed ore body.

7. The method for controlling pollution in ion-adsorption rare earth ore bodies or slag according to claim 2, characterized in that, The first treatment liquid and the second treatment liquid are injected into the rare earth ore body through injection wells, the bottom of which is located at the top of the weathered layer of the rare earth ore body.

8. The method for controlling pollution in ion-adsorption rare earth ore bodies or slag according to claim 2, characterized in that, The pollution control method also includes: Step A1: After the first rinsing treatment, the first treatment liquid that has passed through the rare earth ore body or slag is collected to obtain the first recovery liquid; Step A2: Adjust the molar ratio of ammonium ions, phosphate ions and magnesium ions in the first recovered liquid to 1:(1~5):(1~5), and perform solid-liquid separation on the first recovered liquid to obtain magnesium ammonium phosphate and the first recovered liquid. The first recovered liquid is returned to step S1 for reuse.

9. The method for controlling pollution in ion-adsorption rare earth ore bodies or slag according to claim 2, characterized in that, The method for controlling pollution in ion-adsorption rare earth ore bodies or slag also includes: Step B1: After the second leaching treatment, the second treatment liquid that has passed through the rare earth ore body or slag is collected to obtain the second recovery liquid; Step B2: Adjust the molar ratio of ammonium ions, phosphate ions and magnesium ions in the second recovered liquid to 1:1:(1-5), and perform solid-liquid separation on the second recovered liquid to obtain magnesium ammonium phosphate and a second recovered treatment liquid. The second recovered treatment liquid is returned to step S2 for reuse.