Ionic type rare earth ore in-situ ammonium-magnesium relay leaching and ammonia nitrogen recycling method

Abstract

The invention relates to an ion type rare earth ore in-situ ammonium-magnesium relay leaching and ammonia nitrogen recycling method which comprises the following steps: (1) sequentially leaching an ion type rare earth ore body by using a first ore leaching agent and a second ore leaching agent, leaching, and collecting from the bottom of the ore body to obtain a rare earth mother solution; (2) adding an alkaline compound into the rare earth mother liquor obtained in the step (1) to carry out a first precipitation reaction, and carrying out first solid-liquid separation to obtain a rare earth precipitate and a precipitate mother liquor; (3) adding phosphate into the precipitation mother liquor obtained in the step (2) to carry out second precipitation reaction, and carrying out second solid-liquid separation to obtain magnesium ammonium phosphate precipitate and supernatant liquid; the first mineral leaching agent comprises an ammonium sulfate solution, and the second mineral leaching agent comprises a magnesium sulfate solution. Different ion exchange capacities and selectivity of the first ore leaching agent and the second ore leaching agent are utilized, the consumption of the ore leaching agents is reduced, the rare earth leaching efficiency is improved, and ammonia nitrogen resource utilization is achieved.

Description

Technical Field

[0001] This invention relates to the field of efficient mining technology for ion-adsorption rare earth mines, and in particular to a method for in-situ ammonium-magnesium relay leaching and ammonia nitrogen resource utilization of ion-adsorption rare earth mines. Background Technology

[0002] Rare earth elements are not only widely used in traditional industries such as metallurgy, chemicals, and ceramics, but also occupy an important strategic position in modern technological fields such as new energy, electronics, information, superconductivity, and aerospace, serving as key raw materials for driving technological innovation and industrial upgrading. my country possesses abundant rare earth resources and is a major producer of rare earth raw materials, providing over 80% of the global supply. In particular, ion-adsorption rare earth mines in southern China account for 90% of the global demand for medium and heavy rare earth elements. In ion-adsorption rare earth mines, rare earth elements are mainly adsorbed on the surface of clay minerals in the form of hydroxyl or hydrated hydroxyl groups, and can be extracted through ion exchange. The leaching agents used have evolved from sodium chloride to ammonium sulfate and magnesium sulfate.

[0003] Traditional ammonium sulfate solution leaching, NH4 + Ammonium sulfate can rapidly exchange rare earth ions adsorbed on mineral surfaces, and the solution seepage rate is relatively fast during the leaching process. Generally, the consumption of ammonium sulfate during leaching is 7.5-8.0 t / t of rare earth product, while the consumption of ammonium bicarbonate during rare earth enrichment is 3.0-3.5 t / t of rare earth product. Clearly, a large amount of ammonia nitrogen is generated during the entire rare earth resource recovery process, and ammonia nitrogen pollution has become a bottleneck in the application of ammonium sulfate solution in rare earth leaching. If ammonia nitrogen cannot be effectively treated, it will not only pollute water and soil but may also affect the stability of the surrounding ecosystem.

[0004] Existing technology CN114318019A discloses a method for separating rare earth elements and aluminum from ion-type rare earth mine leachate. This method involves precipitating the mine leachate obtained from in-situ ammonium sulfate leaching by adding excess carbonate; the resulting precipitate is then mixed with alkali and roasted to convert aluminum-containing impurities into sodium aluminate; the roasted slag is washed with hot water, dissolving the sodium aluminate in the water and entering the solution, leaving the remaining slag phase as rare earth oxides. This patent still uses ammonium sulfate for leaching, which still results in ammonia nitrogen pollution.

[0005] Therefore, effectively addressing ammonia nitrogen pollution has become a significant technical challenge in current ammonium sulfate leaching technology. Magnesium sulfate, as a widely used leaching agent, has the advantage of not generating ammonia nitrogen pollution during the leaching process. However, its leaching efficiency is relatively slow, the leaching process has a long tailing time, and its usage is typically much higher than that of ammonium sulfate. Generally, the consumption of magnesium sulfate heptahydrate during leaching is 30-50 t / t of rare earth product. Excessive magnesium sulfate may lead to Mg contamination in the rare earth ore body and surrounding soil and water. 2+ Concentration exceeded the standard, soil acidification, and Mg2+ It cannot be biodegraded naturally, and if the leachate is naturally discharged into surface water, it will pose a potential threat to the ecological environment, which is a major technical problem that limits its application.

[0006] In summary, given the problems of low rare earth recovery rate, long production cycle, high leaching agent consumption, and water and soil pollution in the mining area caused by the current in-situ leaching process for ion-adsorption rare earth ores, improving the mining efficiency and greening level of ion-adsorption rare earth ores has always been the key to the successful promotion of in-situ leaching technology. How to provide a method for in-situ ammonium-magnesium relay leaching and ammonia nitrogen resource utilization of ion-adsorption rare earth ores has become an urgent problem to be solved. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a method for in-situ ammonium-magnesium relay leaching and ammonia nitrogen resource utilization of ion-adsorption rare earth ores. This invention fully utilizes NH4 + Strong exchange capacity and Mg 2+ Its green and highly selective characteristics, combined with the synergistic optimization of the overall performance of the leaching agent, reduce the amount of ammonium sulfate used, enable faster and more effective exchange of adsorbed rare earth ions, significantly improve the leaching rate and final recovery rate of rare earth, and convert ammonia nitrogen into high-quality slow-release fertilizer magnesium ammonium phosphate, thus realizing the resource utilization of ammonia nitrogen.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a method for in-situ ammonium-magnesium relay leaching and ammonia nitrogen resource utilization of ion-adsorption rare earth ores, the method comprising the following steps:

[0010] (1) The ion-adsorption rare earth ore body is leached sequentially with the first leaching agent and the second leaching agent, and the rare earth mother liquor is collected from the bottom of the ore body.

[0011] (2) Add an alkaline compound to the rare earth mother liquor described in step (1) to carry out the first precipitation reaction, and obtain rare earth precipitate and precipitate mother liquor by the first solid-liquid separation;

[0012] (3) Add phosphate to the mother liquor of the precipitate in step (2) to carry out a second precipitation reaction, and obtain magnesium ammonium phosphate precipitate and supernatant after a second solid-liquid separation;

[0013] The first leaching agent comprises an ammonium sulfate solution, and the second leaching agent comprises a magnesium sulfate solution.

[0014] This invention first uses an ammonium sulfate solution as a leaching agent to leach the ion-adsorption rare earth ore body. The leaching agent solution enters the ore body along the pores and fissures of the weathered ore body. Under the action of gravity and pressure, the ore body containing NH4+ is leached. + The solution permeates and diffuses within the pores and fissures, displacing the pore water. Simultaneously, during the flow, NH4+ in the solution...+ RE adsorbed on mineral surface 3+ An exchange occurs, RE 3+ Diffusion enters the solution, creating pores and fractures to leach tailings; subsequently, magnesium sulfate solution is used to leach the ore body, where, under the same conditions of gravity and pressure, Mg is present. 2+ The solution permeates and diffuses within the pores and fissures, displacing the pore water, due to Mg 2+ It has a strong exchange capacity and can effectively replace NH4 adsorbed on the surface of mineral soil. + During the flow process, Mg in the solution 2+ NH4 adsorbed on mineral surface + An exchange occurs, and Mg 2+ The ore body surface can be replaced again if it is not exposed to NH4 + Exchanged RE 3+ NH4 + and RE 3+ The rare earth nitrogen diffuses into the solution, and the rare earth mother liquor is collected. Then, an alkaline compound is added to the rare earth mother liquor to carry out the first precipitation reaction. After the first solid-liquid separation, rare earth precipitate and precipitate mother liquor are obtained. Phosphate is added to the precipitate mother liquor to carry out the second precipitation reaction. After the second solid-liquid separation, magnesium ammonium phosphate precipitate and supernatant are obtained, thus realizing the resource utilization of ammonia nitrogen.

[0015] In this invention, the in-situ leaching process for ion-adsorption rare earth minerals involves injecting leaching agents into the ore body by excavating injection holes on the surface of the ore body. The cations in the leaching agent exchange ions with the rare earth ions on the surface of the ore body. After entering the solution, the rare earth ions are collected in the collection ditch through the guide holes at the bottom of the ore body and then gathered into the mother liquor pool.

[0016] In this invention, the equipment for solid-liquid separation includes plate and frame filter presses, membrane separation equipment, or centrifugal sedimentation equipment.

[0017] As a preferred technical solution of the present invention, the method further includes the following steps: when the concentration of the rare earth mother liquor in step (1) is <40g / L, it is returned to step (1) for recycling.

[0018] In this invention, low-concentration rare earth mother liquor and upper clear liquor are mixed, replenished and adjusted, and can be used as leaching agent or recycled in subsequent cleaning or lime water rinsing stages, realizing a closed-loop cycle of mine rinsing and tailings treatment.

[0019] In this invention, the reaction mechanism involved in leaching minerals with ammonium sulfate solution is as follows: [Al2(Si2O5)(OH)4] m ·RE 3+ (s)+3NH4 + (aq)→[Al2(Si2O5)(OH)4] m ·3NH4 + (s)+RE3+ (aq), NH4 in the solution + RE adsorbed on mineral surface 3+ An exchange occurs, RE 3+ Diffusion into the solution; the reaction mechanism involved in leaching with magnesium sulfate solution is as follows: [Al2(Si2O5)(OH)4] m ·RE 3+ (s)+3Mg 2+ (aq)→[Al2(Si2O5)(OH)4] m ·3Mg 2+ (s)+RE 3+ (aq), [Al2(Si2O5)(OH)4] m ·3NH4 + (s)+3Mg 2+ (aq) → [Al2(Si2O5)(OH)4] m ·3Mg 2+ (s)+3NH4 + (aq), Mg in the solution 2+ NH4 adsorbed on the surface of the ore body + An exchange will be conducted, and those not previously targeted by NH4 will also be exchanged. + Exchanged RE 3+ The reaction mechanism involved in the first precipitation by adding basic oxides is as follows: MgO(s) + H₂O(l) → Mg(OH)₂(s), 2RE 3+ (aq)+3Mg(OH)2(s)→2RE(OH)3(s)+3Mg 2+ (aq), 2Al 3+ (aq)+3Mg(OH)2(s)→2Al(OH)3(s)+3Mg 2+ (aq), Ca 2+ (aq)+Mg(OH)2(s)→Ca(OH)2(s)+Mg 2+ (aq), 2Fe 3+ (aq)+3Mg(OH)2(s)=2Fe(OH)3(s)+3Mg 2+ (aq) The precipitate in the sedimentation tank is a mixture of rare earth hydroxide, magnesium hydroxide, iron hydroxide, aluminum hydroxide, and a small amount of calcium hydroxide; the reaction mechanism involved in the second precipitation by adding phosphate is as follows: Na3PO4(s)→3Na + (aq)+PO4 3- (aq), Mg 2+ (aq)+NH4 + (aq)+PO4 3-(aq)+H2O(l)→MgNH4PO4·6H2O(s).

[0020] As a preferred technical solution of the present invention, in step (1), the volume ratio of the first leaching agent to the second leaching agent is (0.5-0.6):1, for example, it can be 0.5:1, 0.52:1, 0.54:1, 0.56:1, 0.58:1 or 0.6:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0021] This invention, by further limiting the volume ratio of the first leaching agent (ammonium sulfate solution) and the second leaching agent (magnesium sulfate solution), fully utilizes NH4+. + Strong exchange capacity and Mg 2+ Its green and highly selective characteristics synergistically optimize the overall performance of the leaching agent, enabling rapid and effective exchange of adsorbed rare earth ions and reducing the amount of ammonium sulfate required. When the volume ratio of ammonium sulfate solution to magnesium sulfate solution is too low, i.e., when the amount of ammonium sulfate is insufficient, the NH4+ in the leaching agent... + The concentration is insufficient to provide enough driving force to remove all RE adsorbed on the ore body. 3+ The exchange reaction is incomplete, leading to a decrease in rare earth leaching rate. When the volume ratio of ammonium sulfate solution to magnesium sulfate solution is too high, i.e., when the amount of ammonium sulfate used is excessive, the excess NH4+ is not fully utilized. + It will remain in the leached ore body and leachate, forming high-concentration ammonia nitrogen wastewater, causing environmental pollution.

[0022] Preferably, the ratio of the total volume of the first leaching agent and the second leaching agent to the volume of the ion-adsorption rare earth ore body is 1:(1.1-1.3), for example, it can be 1:1.1, 1:1.15, 1:1.2, 1:1.25 or 1:1.3, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0023] As a preferred embodiment of the present invention, the mass fraction of the ammonium sulfate solution is 1-5 wt%, for example, it can be 1 wt%, 2 wt%, 3 wt%, 4 wt% or 5 wt%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] Preferably, the pH value of the ammonium sulfate solution is 5-5.5, for example, it can be 5, 5.1, 5.2, 5.3, 5.4 or 5.5, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] Preferably, the magnesium sulfate solution has a mass fraction of 1-5 wt%, for example, it can be 1 wt%, 2 wt%, 3 wt%, 4 wt% or 5 wt%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0026] Preferably, the pH value of the magnesium sulfate solution is 5-5.5, for example, it can be 5, 5.1, 5.2, 5.3, 5.4 or 5.5, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] As a preferred technical solution of the present invention, after leaching in step (1), the method further includes: sequentially using top water and tailings solution to rinse the leached ion-type rare earth ore body.

[0028] Preferably, the rare earth mother liquor in step (1) contains SO4 2- When the concentration is <800mg / L, stop injecting top water.

[0029] Preferably, the top water comprises deionized water.

[0030] In this invention, clean water is used to recover residual leaching agent from the ore body and to wash away residual SO4 from the ore body. 2- .

[0031] As a preferred embodiment of the present invention, the tail-protecting liquid comprises a calcium hydroxide solution.

[0032] Preferably, the mass fraction of the calcium hydroxide solution is 1-2 wt%, for example, it can be 1 wt%, 1.2 wt%, 1.4 wt%, 1.6 wt%, 1.8 wt% or 2 wt%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0033] Preferably, the volume ratio of the tailing fluid to the volume of the ion-adsorption rare earth ore body is (0.1-0.2):1, for example, it can be 0.1:1, 0.12:1, 0.14:1, 0.16:1, 0.18:1 or 0.2:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] In this invention, soil acidification is addressed by leaching with a certain amount of lime water solution.

[0035] As a preferred technical solution of the present invention, the endpoint of the first precipitation reaction in step (2) is a pH of 7-7.5, for example, it can be 7, 7.1, 7.2, 7.3, 7.4 or 7.5, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0036] In this invention, rare earth ions form hydroxide precipitates within this range, and aluminum ions, calcium ions, iron ions, etc. contained in the rare earth mother liquor are also precipitated together.

[0037] Preferably, step (2) the first solid-liquid separation includes any one or a combination of at least two of the following: first settling treatment, centrifugation treatment, pressure filtration treatment or atmospheric pressure filtration, wherein typical but non-limiting combinations include: first settling treatment and centrifugation treatment, first settling treatment and pressure filtration treatment, first settling treatment and atmospheric pressure filtration, etc.

[0038] Preferably, the first settling time is 5-10 hours, for example, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours, but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0039] In this invention, the supernatant (precipitate mother liquor) after the first settling treatment enters the ammonia precipitation tank for precipitation. The remaining solid-liquid mixture is separated into solid and liquid, and the filtrate is reused. The final solid obtained is rare earth enrichment precipitate.

[0040] Preferably, the alkaline compound in step (2) includes magnesium oxide slurry.

[0041] As a preferred technical solution of the present invention, the method for preparing the magnesium oxide slurry includes: mixing magnesium oxide and water at a mass ratio of 1:(8-12), for example, 1:8, 1:9, 1:10, 1:11 or 1:12, but not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0042] Preferably, the mixing time is 30-60 minutes, for example, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes or 60 minutes, but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0043] In this invention, thorough mixing ensures complete dispersion of magnesium oxide.

[0044] Preferably, the magnesium oxide has a particle size of 200-400 mesh, such as 200 mesh, 250 mesh, 300 mesh, 350 mesh or 400 mesh, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0045] Preferably, the purity of the magnesium oxide is ≥95%, for example, it can be 95%, 96%, 97%, 98%, 99% or 100%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0046] As a preferred technical solution of the present invention, the phosphate in step (3) includes a trisodium phosphate solution.

[0047] Preferably, the trisodium phosphate solution has a mass fraction of 8-13 wt%, for example, it can be 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt% or 13 wt%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0048] In this invention, the addition of phosphate precipitates NH4 in the mother liquor. + Mg 2+ and PO4 3- The ions react to form magnesium ammonium phosphate precipitate, which is a high-quality slow-release fertilizer, realizing the resource utilization of ammonia nitrogen.

[0049] Preferably, the conditions for the second precipitation reaction in step (3) are NH4. + With PO4 3- The molar ratio is 1:(1-1.1), for example, it can be 1:1, 1:1.02, 1:1.04, 1:1.06, 1:1.08 or 1:1.1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0050] Preferably, the endpoint of the second precipitation reaction in step (3) is a pH of 9-9.5, for example, it can be 9, 9.1, 9.2, 9.3, 9.4 or 9.5, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0051] Preferably, step (3) the second solid-liquid separation includes any one or a combination of at least two of the following: second settling treatment, centrifugation treatment, pressure filtration treatment or atmospheric pressure filtration, wherein typical but non-limiting combinations include: second settling treatment and centrifugation treatment, second settling treatment and pressure filtration treatment, second settling treatment and atmospheric pressure filtration, etc.

[0052] In this invention, the supernatant after the second settling treatment is returned to step (1) for recycling. The remaining solid-liquid mixture is separated into solid and liquid, and the filtrate is reused. The final solid obtained is slow-release fertilizer magnesium ammonium phosphate.

[0053] Preferably, the second settling time is 5-7 hours, for example, 5 hours, 5.5 hours, 6 hours, 6.5 hours, or 7 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0054] Preferably, the supernatant from step (3) is returned to step (1) for recycling.

[0055] As a preferred technical solution of the present invention, the method specifically includes the following steps:

[0056] (1) The ion-adsorption rare earth ore body is leached sequentially with a first leaching agent and a second leaching agent for leaching. Then, top water and tailings solution are used for leaching sequentially, and rare earth mother liquor is collected at the bottom of the ore body. The volume ratio of the first leaching agent to the second leaching agent is (0.5-0.6):1; the total volume ratio of the first and second leaching agents to the volume of the ion-adsorption rare earth ore body is 1:(1.1-1.3). The first leaching agent includes ammonium sulfate solution, and the second leaching agent includes magnesium sulfate solution. The mass fraction of the ammonium sulfate solution is 1-5 wt%, and the pH value of the ammonium sulfate solution is 5-5.5. The mass fraction of the magnesium sulfate solution is 1-5 wt%, and the pH value of the magnesium sulfate solution is 5-5.5. The rare earth mother liquor contains SO42-200 mg / L. 2- When the concentration of the top water is less than 800 mg / L, the injection of top water shall be stopped. The top water includes deionized water. The tailing solution includes calcium hydroxide solution with a mass fraction of 1-2 wt%. The volume ratio of the tailing solution to the volume of the ion-adsorption rare earth ore body is (0.1-0.2):1.

[0057] (2) Add an alkaline compound to the rare earth mother liquor in step (1) to carry out a first precipitation reaction, and obtain rare earth precipitate and precipitate mother liquor by first solid-liquid separation; wherein, the endpoint of the first precipitation reaction is pH 7-7.5, the first solid-liquid separation includes any one or a combination of at least two of the following: first settling treatment, centrifugation treatment, pressure filtration treatment or atmospheric pressure filtration, the first settling treatment time is 5-10h, the alkaline compound in step (2) includes magnesium oxide slurry; the preparation method of the magnesium oxide slurry includes: mixing magnesium oxide and water at a mass ratio of 1:(8-12), the mixing time is 30-60min, the particle size of the magnesium oxide is 200-400 mesh, and the purity of the magnesium oxide is ≥95%;

[0058] (3) Add phosphate to the mother liquor from step (2) to carry out a second precipitation reaction. After a second solid-liquid separation, magnesium ammonium phosphate precipitate and supernatant are obtained. The supernatant is returned to step (1) for recycling. The phosphate includes trisodium phosphate solution with a mass fraction of 8-13 wt%. The conditions for the second precipitation reaction are NH4+. + With PO4 3- The molar ratio is 1:(1-1.1), the endpoint of the second precipitation reaction is pH 9-9.5, the second solid-liquid separation includes any one or a combination of at least two of the following: second settling treatment, centrifugation treatment, pressure filtration treatment or atmospheric pressure filtration, and the time of the second settling treatment is 5-7h.

[0059] (4) When the concentration of the rare earth mother liquor in step (1) is <40g / L, it is returned to step (1) for recycling.

[0060] Compared with the prior art, the present invention has at least the following beneficial effects:

[0061] (1) This invention utilizes the ammonium-magnesium relay leaching strategy to fully leverage NH4 + Strong exchange capacity and Mg 2+ Its green and highly selective characteristics synergistically optimize the overall performance of the leaching agent, reduce the amount of ammonium sulfate used, and can exchange adsorbed rare earth ions more quickly and effectively, thereby significantly improving the leaching rate and final recovery rate of rare earths, which is superior to single leaching agent systems.

[0062] (2) This invention utilizes the cation exchange of magnesium sulfate solution with residual NH4 on the surface of the mineral soil. + To prevent ammonia nitrogen from accumulating in the soil and polluting groundwater during the rainy season, the solution is added to control ammonia nitrogen pollution at its source, providing environmental protection for sustainable development, simplifying the rare earth recycling process and improving recycling efficiency.

[0063] (3) This invention converts ammonia nitrogen into high-quality slow-release fertilizer magnesium ammonium phosphate by adding phosphate to the supernatant after rare earth precipitation, thereby realizing the resource utilization of ammonia nitrogen, eliminating pollution risks, turning waste into treasure, reducing the overall operating cost of mining and environmental governance investment, and improving economic benefits. Attached Figure Description

[0064] Figure 1 This is the ammonium-magnesium relay leaching and ammonia nitrogen resource utilization process provided in Example 1 of the present invention. Detailed Implementation

[0065] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0066] Example 1

[0067] This embodiment provides a method for in-situ ammonium-magnesium relay leaching and ammonia nitrogen resource utilization of ion-adsorption rare earth ores, such as... Figure 1 As shown, the method includes the following steps:

[0068] (1) The volume of the ion-adsorption rare earth ore body is 1000 m³. 3 First use 300m 3 The ion-adsorption rare earth ore body, with a pH of 5.5 and a mass fraction of 1 wt%, was leached with an ammonium sulfate solution. The volume of the ion-adsorption rare earth ore body was 1000 m³. 3 Then use 500m 3 The solution was rinsed and leached with a 1 wt% magnesium sulfate solution at pH 5.5, followed by sequential use of 600 m...3 clean water and 100m 3 A 1 wt% calcium hydroxide solution was used to leach the ion-adsorption rare earth ore body after leaching, removing residual leaching agent and addressing soil acidification issues. The resulting rare earth mother liquor was collected from the bottom of the ore body. The rare earth mother liquor contained SO4. 2- When the concentration is <800 mg / L, stop injecting top water;

[0069] (2) Add magnesium oxide slurry to the rare earth mother liquor described in step (1) to carry out the first precipitation reaction. The endpoint of the first precipitation reaction is pH 7.5. After standing for 8 hours, the resulting supernatant (precipitate mother liquor) is sent to the ammonia precipitation tank for precipitation. The remaining solid-liquid mixture is centrifuged and the filtrate is reused. The final solid obtained is rare earth precipitate. The preparation method of magnesium oxide slurry includes: mixing magnesium oxide and water at a mass ratio of 1:10 for 45 minutes. The average particle size of magnesium oxide is 200 mesh and the purity of magnesium oxide is 95%.

[0070] (3) Add NH4 to the precipitate mother liquor obtained in step (2). + With PO4 3- The molar ratio is 1:1. A 10wt% trisodium phosphate solution is added to carry out the second precipitation reaction. The endpoint of the second precipitation reaction is pH 9. After standing for 6 hours, the supernatant is returned to step (1) for recycling. The remaining solid-liquid mixture is centrifuged and the filtrate is reused. The solid is magnesium ammonium phosphate precipitate.

[0071] (4) When the concentration of the rare earth mother liquor in step (1) is lower than 40 g / L, it is returned to step (1) for recycling.

[0072] Comparative Example 1

[0073] This comparative example provides a method for in-situ ammonium-magnesium relay leaching of ionic rare earth minerals and ammonia nitrogen resource utilization. The difference from Example 1 is that only ammonium sulfate solution, the first leaching agent, is added in step (1) for leaching.

[0074] Comparative Example 2

[0075] This comparative example provides a method for in-situ ammonium-magnesium relay leaching of ionic rare earth minerals and ammonia nitrogen resource utilization. The difference from Example 1 is that only magnesium sulfate solution, the second leaching agent, is added in step (1) for leaching.

[0076] Test methods: Inductively coupled plasma atomic absorption spectrometry (ICP-AES) was used to detect the rare earth ion content in the rare earth mother liquor obtained in Example 1 and Comparative Examples 1-2. X-ray fluorescence spectrometry was used to detect the rare earth ion content in ion-adsorption rare earth ore, rare earth ion content in rare earth precipitate, ammonium and magnesium ion content in magnesium ammonium phosphate precipitate, and residual ammonium ion content in tailings. The results were obtained according to the following formulas: Rare earth leaching rate (%) = Rare earth ion content in rare earth mother liquor / Rare earth ion content in ion-adsorption rare earth ore × 100%; Rare earth recovery rate (%) = Rare earth ion content in recovered rare earth precipitate / Rare earth ion content in rare earth mother liquor × 100%; Ammonium recovery rate (%) = Ammonium ion content in magnesium ammonium phosphate precipitate / Ammonium ion content in ammonium sulfate solution × 100%; Magnesium recovery rate (%) = Magnesium ion content in magnesium ammonium phosphate precipitate / Magnesium ion content in magnesium sulfate solution × 100%; Residual ammonium ion rate in tailings (%) = Residual ammonium ion content in tailings / Injected ammonium ion content × 100%.

[0077] The test results are shown in Table 1.

[0078] Table 1

[0079]

[0080] The test results show that:

[0081] (1) As can be seen from Example 1, the present invention can improve the leaching efficiency of rare earth by ammonium-magnesium relay leaching, ammonia nitrogen resource utilization and solution recycling, and can also transform ammonia nitrogen pollution into useful resources, while reducing the consumption of leaching agent, thus realizing the green and efficient mining of ion-type rare earth minerals.

[0082] (2) As can be seen from Example 1 and Comparative Examples 1 and 2, the present invention can improve the leaching efficiency of rare earth by ammonium-magnesium relay leaching and can convert ammonia nitrogen pollution into useful resources. However, when only ammonium sulfate solution is used, it will cause serious ammonia nitrogen pollution. When only magnesium sulfate solution is used, its rare earth leaching efficiency will be significantly reduced.

[0083] In summary, this invention, through ammonium-magnesium relay leaching, ammonia nitrogen resource utilization, and solution recycling, can not only improve the leaching efficiency of rare earths, achieving a leaching rate of over 92%, but also transform ammonia nitrogen pollution into useful resources, while reducing the consumption of leaching agents, thus realizing the green and efficient mining of ion-adsorption rare earth ores.

[0084] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for in-situ ammonium-magnesium relay leaching and ammonia nitrogen resource utilization of ion-adsorption rare earth ores, characterized in that, The method includes the following steps: (1) The ion-adsorption rare earth ore body is leached sequentially with the first leaching agent and the second leaching agent, and the rare earth mother liquor is collected from the bottom of the ore body. (2) Add an alkaline compound to the rare earth mother liquor described in step (1) to carry out the first precipitation reaction, and obtain rare earth precipitate and precipitate mother liquor by the first solid-liquid separation; (3) Add phosphate to the mother liquor of the precipitate in step (2) to carry out a second precipitation reaction, and obtain magnesium ammonium phosphate precipitate and supernatant after a second solid-liquid separation; The first leaching agent comprises an ammonium sulfate solution, and the second leaching agent comprises a magnesium sulfate solution.

2. The method according to claim 1, characterized in that, The method further includes the following steps: when the concentration of the rare earth mother liquor in step (1) is <40g / L, it is returned to step (1) for recycling.

3. The method according to claim 1 or 2, characterized in that, Step (1) The volume ratio of the first leaching agent to the second leaching agent is (0.5-0.6):1; Preferably, the total volume ratio of the first leaching agent and the second leaching agent to the volume ratio of the ion-type rare earth ore body is 1:(1.1-1.3).

4. The method according to any one of claims 1-3, characterized in that, The ammonium sulfate solution has a mass fraction of 1-5 wt%. Preferably, the pH value of the ammonium sulfate solution is 5-5.5; Preferably, the magnesium sulfate solution has a mass fraction of 1-5 wt%. Preferably, the pH value of the magnesium sulfate solution is 5-5.

5.

5. The method according to any one of claims 1-4, characterized in that, Step (1) after leaching also includes: sequentially using top water and tailings solution to rinse the leached ion-type rare earth ore body; Preferably, the rare earth mother liquor in step (1) contains SO4 2- When the concentration is <800 mg / L, stop injecting top water; Preferably, the top water comprises deionized water.

6. The method according to claim 5, characterized in that, The tail-protecting liquid includes a calcium hydroxide solution; Preferably, the calcium hydroxide solution has a mass fraction of 1-2 wt%. Preferably, the volume ratio of the tailing fluid to the volume of the ion-type rare earth ore body is (0.1-0.2):

1.

7. The method according to any one of claims 1-6, characterized in that, Step (2) The endpoint of the first precipitation reaction is a pH of 7-7.5; Preferably, step (2) the first solid-liquid separation includes any one or a combination of at least two of the following: first settling treatment, centrifugation treatment, pressure filtration treatment, or atmospheric pressure filtration; Preferably, the first settling time is 5-10 hours; Preferably, the alkaline compound in step (2) includes magnesium oxide slurry.

8. The method according to claim 7, characterized in that, The method for preparing the magnesium oxide slurry includes: mixing magnesium oxide and water at a mass ratio of 1:(8-12); Preferably, the mixing time is 30-60 minutes; Preferably, the magnesium oxide has a particle size of 200-400 mesh; Preferably, the purity of the magnesium oxide is ≥95%.

9. The method according to any one of claims 1-8, characterized in that, The phosphate in step (3) includes a trisodium phosphate solution; Preferably, the trisodium phosphate solution has a mass fraction of 8-13 wt%. Preferably, the conditions for the second precipitation reaction in step (3) are NH4. + With PO4 3- The molar ratio is 1:(1-1.1); Preferably, the endpoint of the second precipitation reaction in step (3) is a pH of 9-9.5; Preferably, step (3) the second solid-liquid separation includes any one or a combination of at least two of the following: second settling treatment, centrifugation treatment, pressure filtration treatment, or atmospheric pressure filtration; Preferably, the second settling time is 5-7 hours; Preferably, the supernatant from step (3) is returned to step (1) for recycling.

10. The method according to any one of claims 1-9, characterized in that, The method specifically includes the following steps: (1) The ion-adsorption rare earth ore body is leached sequentially with a first leaching agent and a second leaching agent for leaching. Then, top water and tailings solution are used for leaching sequentially, and rare earth mother liquor is collected at the bottom of the ore body. The volume ratio of the first leaching agent to the second leaching agent is (0.5-0.6):1; the total volume ratio of the first and second leaching agents to the volume of the ion-adsorption rare earth ore body is 1:(1.1-1.3). The first leaching agent includes ammonium sulfate solution, and the second leaching agent includes magnesium sulfate solution. The mass fraction of the ammonium sulfate solution is 1-5 wt%, and the pH value of the ammonium sulfate solution is 5-5.

5. The mass fraction of the magnesium sulfate solution is 1-5 wt%, and the pH value of the magnesium sulfate solution is 5-5.

5. The rare earth mother liquor contains SO42-200 mg / L. 2- When the concentration of the top water is less than 800 mg / L, the injection of top water shall be stopped. The top water includes deionized water. The tailing solution includes calcium hydroxide solution with a mass fraction of 1-2 wt%. The volume ratio of the tailing solution to the volume of the ion-adsorption rare earth ore body is (0.1-0.2):

1. (2) Add an alkaline compound to the rare earth mother liquor in step (1) to carry out a first precipitation reaction, and obtain rare earth precipitate and precipitate mother liquor by first solid-liquid separation; wherein, the endpoint of the first precipitation reaction is pH 7-7.5, the first solid-liquid separation includes any one or a combination of at least two of the following: first settling treatment, centrifugation treatment, pressure filtration treatment or atmospheric pressure filtration, the first settling treatment time is 5-10h, the alkaline compound in step (2) includes magnesium oxide slurry; the preparation method of the magnesium oxide slurry includes: mixing magnesium oxide and water at a mass ratio of 1:(8-12), the mixing time is 30-60min, the particle size of the magnesium oxide is 200-400 mesh, and the purity of the magnesium oxide is ≥95%; (3) Add phosphate to the mother liquor from step (2) to carry out a second precipitation reaction. After a second solid-liquid separation, magnesium ammonium phosphate precipitate and supernatant are obtained. The supernatant is returned to step (1) for recycling. The phosphate includes trisodium phosphate solution with a mass fraction of 8-13 wt%. The conditions for the second precipitation reaction are NH4+. + With PO4 3- The molar ratio is 1:(1-1.1), the endpoint of the second precipitation reaction is pH 9-9.5, the second solid-liquid separation includes any one or a combination of at least two of the following: second settling treatment, centrifugation treatment, pressure filtration treatment or atmospheric pressure filtration, and the time of the second settling treatment is 5-7h. (4) When the concentration of the rare earth mother liquor in step (1) is <40g / L, it is recycled back to step (1).

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