A method for enriching rare earth from rare earth ore leaching solution

Abstract

The present invention relates to a method for enriching rare earth from rare earth ore leachate, the method comprising the following steps: (1) subjecting the rare earth ore leachate obtained by magnesium salt leaching to microfiltration membrane impurity removal treatment to obtain impurity-removed leachate; (2) uniformly mixing a complexing agent with the impurity-removed leachate obtained in step (1), and then subjecting the mixture to ultrafiltration membrane separation treatment to obtain an intercepted rare earth solution and a permeated magnesium salt solution; (3) mixing a precipitant with the rare earth solution obtained in step (2), and obtaining a rare earth hydroxide precipitate and a precipitate mother liquor after solid-liquid separation; the obtained precipitate mother liquor is combined with the magnesium salt solution obtained in step (2) and reused in the magnesium salt leaching in step (1). The present invention adopts a rare earth purification and enrichment process integrating microfiltration-complexation ultrafiltration-precipitation, which reduces the amount of precipitant used and improves the precipitation rate and rare earth purity. The method is simple and clean, and the cost is low.

Description

Technical Field

[0001] The invention relates to the technical field of rare earth ore mining and separation, and in particular to a method for enriching rare earth from rare earth ore leaching solution. Background Art

[0002] The leaching process of ionic rare earth ores has gone through three generations of development, namely, pool leaching, heap leaching and in-situ leaching. In order to reduce ammonia nitrogen pollution, the in-situ leaching process currently uses magnesium salts instead of ammonium sulfate as a leaching agent. The rare earth concentration in the ionic rare earth ore leachate obtained is low, while the magnesium concentration is high. Rare earth ore leachate needs to be extracted and separated before rare earth products can be recovered. In order to achieve the goal of green recycling, magnesium oxide is currently used as a precipitant for rare earth ore leachate mined from magnesium salts.

[0003] CN 101037219A discloses a production process of magnesium oxide for rare earth solution precipitant, wherein the prepared magnesium oxide slurry and the prepared rare earth liquid are added to a precipitation reaction tank in equivalent amounts for precipitation reaction, the precipitated slurry is dehydrated to produce a filter cake, and the filter cake is washed and dehydrated to obtain a rare earth hydroxide product. However, due to the slow hydrolysis rate of magnesium oxide, the time for complete precipitation of rare earth is prolonged, and since the magnesium ion concentration is much higher than the rare earth ion concentration, as the hydrolysis of magnesium oxide proceeds, the balance will proceed in the reverse reaction direction, thereby inhibiting the precipitation of rare earth. In order to ensure complete enrichment of rare earth, it is necessary to add excessive magnesium oxide for precipitation, which results in a significant reduction in the purity of rare earth in the precipitation product.

[0004] Membrane separation technology is a new separation technology with the advantages of high efficiency, low energy consumption, no phase change, simple process, and continuous operation. Membrane separation technology includes microfiltration, ultrafiltration, nanofiltration, reverse osmosis, etc. Among them, microfiltration and ultrafiltration are mainly screened and concentrated by pore size. In addition to pore size screening, nanofiltration membranes can also separate different ions according to the different charges carried by different ions through the Donan effect. However, the hydration radius of rare earth ions and magnesium ions is less than At the same time, according to ze / (4πr 2 ) It can be seen that the charge strength of the two is not much different, so it is difficult to separate rare earth ions and magnesium ions only through pore size screening and Donan effect of membrane technology.

[0005] CN 105018754A discloses an extraction process for ionic rare earth ore, which is to filter the rare earth leaching solution into a nanofiltration membrane system after preliminary filtration, then introduce the nanofiltration membrane concentrate into a decontamination tank or decontamination tank, add saturated ammonium bicarbonate solution or ammonia water for sedimentation, add a rare earth precipitant into the clear liquid, and obtain a precipitate as a mixed rare earth product. The precipitant is a saturated ammonium bicarbonate solution or a saturated oxalic acid solution. The invention uses ammonium bicarbonate precipitation method or oxalic acid precipitation method to enrich rare earth to obtain mixed ammonium bicarbonate rare earth or mixed oxalate rare earth. The former has a high content of non-rare earth impurities, which is not conducive to subsequent processing; the latter produces wastewater with high oxalate ion and hydrogen ion content, which needs to be neutralized, and produces ammonia nitrogen or COD, which has an adverse impact on the environment.

[0006] CN 113737030A discloses a method for separating rare earths using a water-soluble polymer complexing agent, wherein phospho-chitosan (PCS) is used as a complexing agent, and the difference in shear stability of macromolecular complexes generated by complexing PCS with different rare earth ions is utilized to separate a mixed rare earth ion solution by shear decomplexation coupled ultrafiltration. However, this method only involves the separation of different rare earth ions, and it is difficult to separate rare earth ions and magnesium ions in a complex system of mine leachate.

[0007] In view of the shortcomings of the existing technology, it is necessary to provide a method with low precipitation agent dosage, fast precipitation speed, high rare earth recovery rate and high purity. Summary of the invention

[0008] The object of the present invention is to provide a method for enriching rare earths from rare earth ore leachate, by adopting a rare earth purification and enrichment process integrating microfiltration-complexation ultrafiltration-precipitation, to enrich rare earths from ionic rare earth ore leachate obtained by in-situ leaching of magnesium salts, the method having the advantages of small amount of precipitant, fast precipitation rate, high rare earth recovery rate and purity.

[0009] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0010] The present invention provides a method for enriching rare earth from rare earth ore leaching solution, the method comprising the following steps:

[0011] (1) subjecting the rare earth ore leachate obtained by magnesium salt leaching to a microfiltration membrane for impurity removal to obtain an impurity-removed leachate;

[0012] (2) uniformly mixing the complexing agent with the impurity-removed leaching solution obtained in step (1), and then separating and treating the mixture with an ultrafiltration membrane to obtain a retained rare earth solution and a permeated magnesium salt solution;

[0013] (3) mixing the precipitant with the rare earth solution obtained in step (2), and obtaining rare earth hydroxide precipitate and precipitate mother liquor after solid-liquid separation; the obtained precipitate mother liquor is combined with the magnesium salt solution obtained in step (2) and reused in the magnesium salt leaching in step (1).

[0014] The method for enriching rare earths from rare earth ore leachate provided by the present invention adopts a rare earth purification and enrichment process integrated with microfiltration-complexation ultrafiltration-precipitation to enrich and purify rare earths from ionic rare earth ore leachate obtained by in-situ leaching of magnesium salts. First, the rare earth ore leachate is impurity-removed by a microfiltration membrane, and then a complexing agent is used to complex with rare earth ions instead of magnesium ions, so that the sizes of rare earth ions and magnesium ions are significantly different, and the separation of the two is further achieved by membrane technology, and rare earth ions are concentrated and precipitated. The method of the present invention combines the precipitation rare earth process with the means of ultrafiltration membrane concentration and separation, reduces the amount of precipitant, increases the precipitation rate, and improves the purity of rare earths while ensuring a high rare earth recovery rate; in addition, the permeate and precipitation mother liquor produced in the method can be recycled, which increases the circulation of magnesium and improves resource utilization.

[0015] Preferably, the magnesium salt in step (1) comprises magnesium sulfate.

[0016] Preferably, the rare earth ion content in the rare earth ore leaching solution of step (1) is 0.15-1 g / L, and the magnesium ion content is 0.6-10 g / L.

[0017] The content of rare earth ions in the rare earth ore leachate is 0.15-1 g / L, for example, it can be 0.15 g / L, 0.184 g / L, 0.203 g / L, 0.214 g / L, 0.257 g / L, 0.5 g / L, 0.8 g / L or 1 g / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0018] The content of magnesium ions in the rare earth ore leachate is 0.6-10 g / L, for example, it can be 0.6 g / L, 0.66 g / L, 0.85 g / L, 0.9 g / L, 0.94 g / L, 5 g / L, 8 g / L or 10 g / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0019] Preferably, the pH value of the rare earth ore leaching solution in step (1) is 4-7, for example, 4, 5, 6 or 7, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0020] Preferably, the pore size of the microfiltration membrane in step (1) is 30-500 nm, for example, 30 nm, 200 nm, 300 nm, 400 nm, 450 nm or 500 nm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0021] Preferably, the microfiltration membrane in step (1) comprises any one of a ceramic membrane, an organic tubular membrane or an organic hollow fiber membrane.

[0022] Preferably, the temperature of the impurity removal treatment in step (1) is 25-50°C, for example, 25°C, 35°C, 40°C, 45°C or 50°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0023] Preferably, the membrane flux of the impurity removal treatment in step (1) is 300-1000 L / (m 2 h), for example, it can be 300L / (m 2 ·h)、600L / (m 2 ·h)、800L / (m 2 ·h)、900L / (m 2 h) or 1000L / (m 2 h), but not limited to the listed values, other values ​​not listed within the numerical range are also applicable.

[0024] Preferably, the operating pressure of the impurity removal treatment in step (1) is 0.1-1 MPa, for example, 0.1 MPa, 0.2 MPa, 0.5 MPa, 0.8 MPa or 1 MPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0025] Preferably, the impurity removal treatment in step (1) is performed until the rare earth ore leaching solution becomes clear and transparent.

[0026] Preferably, the molar ratio of the complexing agent in step (2) to the rare earth in the impurity-removing leaching solution is (1-15):1, for example, it can be 1:1, 3:1, 5:1, 10:1 or 15:1, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0027] Preferably, the complexing agent in step (2) comprises any one of glycine, citric acid, diglycolic acid, maleic acid or ethylenediaminetetraacetic acid, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of glycine and citric acid, a combination of diglycolic acid, maleic acid and ethylenediaminetetraacetic acid, a combination of glycine, citric acid, diglycolic acid and maleic acid, or a combination of glycine, citric acid, diglycolic acid, maleic acid and ethylenediaminetetraacetic acid.

[0028] Preferably, the glycine comprises N-(phosphomethyl)glycine and / or N,N-bis(phosphonomethyl)glycine.

[0029] Preferably, the complexing agent in step (2) is a combination of two reagents, and the molar ratio of the two reagents is 5:(1-2), for example, it can be 5:1, 5:1.2, 5:1.5, 5:1.8 or 5:2, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] The complexing agent is a small molecule complexing agent that forms complex macromolecules with rare earth ions, which then have a significant size difference with magnesium ions, and the separation of the two is achieved through an ultrafiltration membrane.

[0031] Preferably, the uniform mixing in step (2) is carried out at a pH value of 4-6.5, for example, 4, 4.5, 5, 5.5 or 6.5, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0032] The complexation of the complexing agent with the rare earth ion needs to be carried out at a limited pH value. In an unrestricted range, the complexing agent and the rare earth cannot form a macromolecule.

[0033] Preferably, the ultrafiltration membrane component used in step (2) includes any one of a roll component, a tubular component, a hollow fiber component or a flat-plate component.

[0034] Preferably, the molecular weight cutoff of the separation treatment in step (2) is 3000-12000Da, for example, 3000Da, 4000Da, 6000Da, 8000Da or 12000Da, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0035] Preferably, the ultrafiltration concentration multiple of the separation treatment in step (2) is 20-100 times, for example, 20 times, 30 times, 50 times, 80 times or 100 times, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0036] Preferably, the molar ratio of the precipitant in step (3) to the rare earth in the rare earth solution is (1.15-11.5):1, for example, it can be 1.15:1, 3.45:1, 5.75:1, 9.2:1 or 11.5:1, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0037] Preferably, the precipitant in step (3) comprises magnesium oxide.

[0038] Preferably, the magnesium oxide is mixed with the rare earth solution in the state of magnesium oxide hydrolyzate.

[0039] The magnesium oxide is hydrolyzed before being mixed with the rare earth solution so that the pH value can reach the condition required for rare earth precipitation and the precipitation time can be reduced.

[0040] Preferably, the magnesium oxide hydrolyzate is obtained by hydrolyzing magnesium oxide at 45-75° C. for 30-120 min.

[0041] The hydrolysis temperature of the magnesium oxide is 45-75°C, for example, 45°C, 50°C, 60°C, 70°C or 75°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0042] The hydrolysis time of the magnesium oxide is 30-120 min, for example, 30 min, 50 min, 80 min, 100 min or 120 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0043] Preferably, the mixing time in step (3) is 5-30 min, for example, 5 min, 12 min, 18 min, 25 min or 30 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0044] Preferably, the solid-liquid separation in step (3) comprises any one of centrifugal separation, plate and frame filtration separation, vibrating screen filtration or belt filtration, or a combination of at least two of them. Typical but non-limiting combinations include a combination of centrifugal separation and plate and frame filtration separation, a combination of plate and frame filtration separation, vibrating screen filtration and belt filtration, or a combination of centrifugal separation, plate and frame filtration separation, vibrating screen filtration and belt filtration.

[0045] As a preferred technical solution of the method of the present invention, the method comprises the following steps:

[0046] (1) The rare earth ore leaching solution with a pH value of 4-7 obtained by magnesium salt leaching is heated at 25-50°C, 0.1-1MPa and a membrane flux of 300-1000L / (m 2 h) under the conditions of removing impurities through a microfiltration membrane until it is clear and transparent to obtain a cleaned leachate;

[0047] The rare earth ion content in the rare earth ore leachate is 0.15-1 g / L, and the magnesium ion content is 0.6-10 g / L; the pore size of the microfiltration membrane is 30-500 nm;

[0048] (2) uniformly mixing the complexing agent with the impurity-removed leaching solution obtained in step (1) at a pH value of 4-6.5, and then separating and treating the mixture with an ultrafiltration membrane to obtain a retained rare earth solution and a permeated magnesium salt solution;

[0049] The molar ratio of the complexing agent to the rare earth in the impurity-removing leaching solution is (1-15):1; the molecular weight cut-off of the separation treatment is 3000-12000Da, and the ultrafiltration concentration multiple is 20-100 times;

[0050] (3) mixing the precipitant with the rare earth solution obtained in step (2) for 5-30 minutes, and obtaining rare earth hydroxide precipitate and precipitate mother liquor after solid-liquid separation; combining the obtained precipitate mother liquor with the magnesium salt solution obtained in step (2) and returning them to the magnesium salt leaching in step (1);

[0051] The molar ratio of the precipitant to the rare earth in the rare earth solution is (1.15-11.5):1; the precipitant includes magnesium oxide; the magnesium oxide is mixed with the rare earth solution in the state of magnesium oxide hydrolyzate; the magnesium oxide hydrolyzate is obtained by hydrolyzing magnesium oxide at 45-75° C. for 30-120 minutes.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] The method for enriching rare earth from rare earth ore leachate provided by the present invention adopts a rare earth purification and enrichment process integrating microfiltration-complexation ultrafiltration-precipitation to enrich and purify rare earth from ionic rare earth ore leachate obtained by in-situ leaching of magnesium salts. By utilizing ultrafiltration membrane concentration and separation technology, the rare earth ion retention rate can reach 97.5%, the magnesium ion retention rate is 1.9%, and the separation coefficient between the two can reach 51.3. At the same time, the precipitant is pre-hydrolyzed, which further reduces the amount of the precipitant and improves the precipitation rate. The rare earth extraction rate can reach 100%, and the rare earth purity can reach 65.4%. In addition, the permeate and the precipitation mother liquor generated in the method can be recycled, which increases the circulation of magnesium and improves the resource utilization rate. DETAILED DESCRIPTION

[0054] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0055] Example 1

[0056] This embodiment provides a method for enriching rare earth from a rare earth ore leachate, the method comprising the following steps:

[0057] (1) The rare earth ore leaching solution with a pH value of 5 obtained by magnesium sulfate leaching was heated at 40°C, 0.5 MPa and a membrane flux of 800 L / (m 2 h) under the conditions of removing impurities through an organic tubular microfiltration membrane until it is clear and transparent to obtain a purified leachate; the rare earth ion content in the rare earth ore leachate is 0.203 g / L, and the magnesium ion content is 0.85 g / L; the pore size of the organic tubular microfiltration membrane is 400 nm;

[0058] (2) uniformly mixing N,N-bis(phosphonomethyl)glycine and the impurity-removed leaching solution obtained in step (1) at a pH value of 5, and then separating and treating with a spiral ultrafiltration membrane to obtain a retained rare earth solution and a permeated magnesium sulfate solution; the molar ratio of the N,N-bis(phosphonomethyl)glycine to the rare earth in the impurity-removed leaching solution is 5:1; the molecular weight cutoff of the separation treatment is 6000Da, and the ultrafiltration concentration multiple is 50 times;

[0059] (3) mixing the magnesium oxide hydrolyzate with the rare earth solution obtained in step (2) for 18 minutes, and obtaining a rare earth hydroxide precipitate and a precipitate mother liquor after centrifugal separation; combining the obtained precipitate mother liquor with the magnesium sulfate solution obtained in step (2) and returning them to the magnesium salt leaching in step (1); the molar ratio of the magnesium oxide to the rare earth in the rare earth solution is 5.75:1; and the magnesium oxide hydrolyzate is obtained by hydrolyzing magnesium oxide at 60° C. for 80 minutes.

[0060] Example 2

[0061] This embodiment provides a method for enriching rare earth from a rare earth ore leachate, the method comprising the following steps:

[0062] (1) The rare earth ore leaching solution with a pH value of 5 obtained by magnesium sulfate leaching was heated at 45°C, 0.2 MPa and a membrane flux of 900 L / (m 2 h) under the conditions of removing impurities through an organic tubular microfiltration membrane until it is clear and transparent to obtain a de-impurity leaching solution; the rare earth ion content in the rare earth ore leaching solution is 0.184 g / L, and the magnesium ion content is 0.9 g / L; the pore size of the organic tubular microfiltration membrane is 450 nm;

[0063] (2) uniformly mixing N,N-bis(phosphonomethyl)glycine and the impurity-removed leaching solution obtained in step (1) at a pH value of 4.5, and then separating and treating with a spiral ultrafiltration membrane to obtain a retained rare earth solution and a permeated magnesium sulfate solution; the molar ratio of the N,N-bis(phosphonomethyl)glycine to the rare earth in the impurity-removed leaching solution is 3:1; the molecular weight cutoff of the separation treatment is 8000Da, and the ultrafiltration concentration multiple is 80 times;

[0064] (3) mixing the magnesium oxide hydrolyzate with the rare earth solution obtained in step (2) for 12 minutes, and centrifuging to obtain a rare earth hydroxide precipitate and a precipitate mother liquor; combining the obtained precipitate mother liquor with the magnesium sulfate solution obtained in step (2) and returning them to the magnesium salt leaching in step (1); the molar ratio of the magnesium oxide to the rare earth in the rare earth solution is 3.45:1; and the magnesium oxide hydrolyzate is obtained by hydrolyzing magnesium oxide at 50° C. for 100 minutes.

[0065] Example 3

[0066] This embodiment provides a method for enriching rare earth from a rare earth ore leachate, the method comprising the following steps:

[0067] (1) The rare earth ore leaching solution with a pH value of 4 obtained by magnesium sulfate leaching was heated at 50°C, 0.1 MPa and a membrane flux of 1000 L / (m 2 h) under the conditions of removing impurities through an organic tubular microfiltration membrane until it is clear and transparent to obtain a removed impurity leaching solution; the rare earth ion content in the rare earth ore leaching solution is 0.214 g / L, and the magnesium ion content is 0.66 g / L; the pore size of the organic tubular microfiltration membrane is 500 nm;

[0068] (2) uniformly mixing the complexing agent and the impurity-removed leaching solution obtained in step (1) at a pH value of 4, and then separating and treating with a tubular ultrafiltration membrane to obtain a retained rare earth solution and a permeated magnesium sulfate solution; the molar ratio of the complexing agent to the rare earth in the impurity-removed leaching solution is 1:1; the complexing agent comprises N,N-bis(phosphonomethyl)glycine and N-(phosphomethyl)glycine in a molar ratio of 5:2; the molecular weight cutoff of the separation treatment is 12000Da, and the ultrafiltration concentration multiple is 100 times;

[0069] (3) mixing the magnesium oxide hydrolyzate with the rare earth solution obtained in step (2) for 5 minutes, and centrifuging to obtain a rare earth hydroxide precipitate and a precipitate mother liquor; combining the obtained precipitate mother liquor with the magnesium sulfate solution obtained in step (2) and returning to the magnesium salt leaching in step (1); the molar ratio of the magnesium oxide to the rare earth in the rare earth solution is 1.15:1; and the magnesium oxide hydrolyzate is obtained by hydrolyzing magnesium oxide at 45° C. for 120 minutes.

[0070] Example 4

[0071] This embodiment provides a method for enriching rare earth from a rare earth ore leachate, the method comprising the following steps:

[0072] (1) The rare earth ore leaching solution with a pH value of 7 obtained by magnesium sulfate leaching was heated at 25°C, 1 MPa and a membrane flux of 300 L / (m 2 h) under the conditions of removing impurities through an organic tubular microfiltration membrane until it is clear and transparent to obtain a purified leachate; the rare earth ion content in the rare earth ore leachate is 0.184 g / L, and the magnesium ion content is 0.9 g / L; the pore size of the organic tubular microfiltration membrane is 30 nm;

[0073] (2) uniformly mixing the complexing agent and the impurity-removed leaching solution obtained in step (1) at a pH value of 6, and then separating and treating the mixture through a hollow fiber ultrafiltration membrane to obtain a retained rare earth solution and a permeated magnesium sulfate solution; the molar ratio of the complexing agent to the rare earth in the impurity-removed leaching solution is 15:1; the complexing agent comprises N,N-bis(phosphonomethyl)glycine and citric acid in a molar ratio of 5:1; the molecular weight cutoff of the separation treatment is 3000Da, and the ultrafiltration concentration multiple is 20 times;

[0074] (3) mixing the magnesium oxide hydrolyzate with the rare earth solution obtained in step (2) for 30 minutes, and obtaining a rare earth hydroxide precipitate and a precipitate mother liquor after centrifugal separation; combining the obtained precipitate mother liquor with the magnesium sulfate solution obtained in step (2) and returning it to the magnesium salt leaching in step (1); the molar ratio of the magnesium oxide to the rare earth in the rare earth solution is 11.5:1; and the magnesium oxide hydrolyzate is obtained by hydrolyzing magnesium oxide at 75° C. for 30 minutes.

[0075] Example 5

[0076] This embodiment provides a method for enriching rare earth from a rare earth ore leachate, the method comprising the following steps:

[0077] (1) The rare earth ore leaching solution with a pH value of 7 obtained by magnesium sulfate leaching was heated at 35°C, 0.8 MPa and a membrane flux of 600 L / (m 2 h) under the conditions of removing impurities through an organic tubular microfiltration membrane until it is clear and transparent to obtain a purified leachate; the rare earth ion content in the rare earth ore leachate is 0.257 g / L, and the magnesium ion content is 0.94 g / L; the pore size of the organic tubular microfiltration membrane is 200 nm;

[0078] (2) uniformly mixing N-(phosphomethyl)glycine and the impurity-removed leaching solution obtained in step (1) at a pH value of 5.5, and then separating and treating with a tubular ultrafiltration membrane to obtain a retained rare earth solution and a permeated magnesium sulfate solution; the molar ratio of the N-(phosphomethyl)glycine to the rare earth in the impurity-removed leaching solution is 10:1; the molecular weight cutoff of the separation treatment is 4000Da, and the ultrafiltration concentration multiple is 30 times;

[0079] (3) mixing the magnesium oxide hydrolyzate with the rare earth solution obtained in step (2) for 25 minutes, and obtaining a rare earth hydroxide precipitate and a precipitate mother liquor after centrifugal separation; combining the obtained precipitate mother liquor with the magnesium sulfate solution obtained in step (2) and returning it to the magnesium salt leaching in step (1); the molar ratio of the magnesium oxide to the rare earth in the rare earth solution is 9.2:1; and the magnesium oxide hydrolyzate is obtained by hydrolyzing magnesium oxide at 70° C. for 50 minutes.

[0080] Example 6

[0081] This embodiment provides a method for enriching rare earths from a rare earth ore leachate, which is different from Embodiment 1 in that, except that the molar ratio of N,N-bis(phosphonomethyl)glycine to the rare earth in the impurity-free leachate in step (2) is adjusted to 0.5:1, the rest is the same as Embodiment 1.

[0082] Example 7

[0083] This embodiment provides a method for enriching rare earths from a rare earth ore leachate, which is different from Embodiment 1 in that, except that the molar ratio of N,N-bis(phosphonomethyl)glycine to the rare earth in the impurity-free leachate in step (2) is adjusted to 16:1, the rest is the same as Embodiment 1.

[0084] Example 8

[0085] This embodiment provides a method for enriching rare earths from a rare earth ore leachate. The difference from Embodiment 1 is that, except for adjusting the molar ratio of magnesium oxide to rare earth in the rare earth solution in step (3) to 0.575:1, the rest is the same as Embodiment 1.

[0086] Example 9

[0087] This embodiment provides a method for enriching rare earths from a rare earth ore leachate. The difference from Embodiment 1 is that, except for adjusting the molar ratio of magnesium oxide to rare earth in the rare earth solution in step (3) to 12.65:1, the rest is the same as Embodiment 1.

[0088] Example 10

[0089] This embodiment provides a method for enriching rare earths from a rare earth ore leachate. The difference from Embodiment 1 is that in step (3), the precipitant is mixed with the rare earth solution in the form of magnesium oxide without undergoing hydrolysis treatment. The rest is the same as Embodiment 1.

[0090] Embodiment 11

[0091] This embodiment provides a method for enriching rare earths from a rare earth ore leachate. The difference from Embodiment 1 is that the magnesium oxide hydrolyzate in step (3) is replaced by an equimolar amount of sodium bicarbonate solution, and the rest is the same as Embodiment 1.

[0092] Comparative Example 1

[0093] This comparative example provides a method for enriching rare earths from a rare earth ore leachate. The difference from Example 1 is that step (1) does not involve microfiltration membrane impurity removal treatment, and lauryl glucoside impurity remover is uniformly mixed with the rare earth ore leachate to a pH value of 5. The rest is the same as Example 1.

[0094] Comparative Example 2

[0095] This comparative example provides a method for enriching rare earth from rare earth ore leachate, which differs from Example 1 in that no complexing agent is added in step (2), and the rest is the same as Example 1.

[0096] Comparative Example 3

[0097] This comparative example provides a method for enriching rare earths from rare earth ore leachate, which differs from Example 1 in that the microfiltration membrane impurity removal treatment and ultrafiltration membrane separation treatment described in step (2) are omitted, and the rest are the same as Example 1.

[0098] Separation effect: The methods provided in Examples 1-11 and Comparative Examples 1-3 were used to enrich rare earth from the rare earth ore leachate, and the contents of rare earth ions and magnesium ions in the retained rare earth solution were determined using an inductively coupled plasma spectrometer, and the retention rate and separation coefficient were calculated. The results are shown in Table 1.

[0099] Rare earth extraction rate and purity: The precipitated product was dissolved in hydrochloric acid, and the rare earth content in the acid solution was determined by inductively coupled plasma spectrometer. The rare earth extraction rate and purity were calculated. The results are shown in Table 2.

[0100] Table 1

[0101] Rare earth ion retention rate (%) Magnesium ion retention rate (%) Separation factor Example 1 97.5 1.9 51.3 Example 2 94.2 2.8 33.6 Example 3 95.2 4.2 22.6 Example 4 97.1 3.4 28.5 Example 5 93.2 7.5 12.4 Example 6 45.2 3.8 11.9 Example 7 97.0 5.4 17.9 Example 8 96.2 2.7 35.6 Example 9 97.3 2.0 48.7 Example 10 96.0 2.2 43.6 Embodiment 11 96.2 2.0 48.1 Comparative Example 1 94.0 3.0 31.3 Comparative Example 2 12.4 10.0 1.24 Comparative Example 3 / / /

[0102] Table 2

[0103]

[0104]

[0105] It can be seen from Table 1 and Table 2 that the method for enriching rare earth from rare earth ore leachate provided by the present invention adopts a rare earth purification and enrichment process integrating microfiltration-complexation ultrafiltration-precipitation, and the obtained retained rare earth solution has a higher rare earth ion retention rate and a lower magnesium ion retention rate, thereby achieving effective separation of rare earth ions and magnesium ions; the rare earth extraction rate obtained by the precipitation method can reach 100%, and the rare earth purity is relatively high;

[0106] By comparing Example 1 with Examples 6 and 7, it can be seen that the dosage of the complexing agent is too low, the rare earth ions cannot be completely complexed, resulting in a decrease in the rare earth retention rate; the dosage of the complexing agent is too high, more magnesium ions are complexed, the separation coefficient is reduced, and the complexing agent is wasted; by comparing Example 1 with Examples 8 and 9, it can be seen that the dosage of the magnesium oxide precipitant is too small, the rare earth extraction rate is reduced, and the dosage is too large, the rare earth purity in the precipitated product is significantly reduced; by comparing Example 1 with Example 10, it can be seen that magnesium oxide is not pre-hydrolyzed, and the rare earth extraction rate and purity are significantly reduced; by comparing Example 1 with Example 11, it can be seen that sodium bicarbonate solution is used as a precipitant, and the obtained rare earth precipitation product is an amorphous flocculent colloidal precipitate, and there will be rare earth loss during the solid-liquid separation process, resulting in a decrease in the rare earth extraction rate;

[0107] By comparing Example 1 with Comparative Example 1, it can be seen that when a microfiltration membrane is not used for impurity removal, but an impurity remover is used for impurity removal treatment, the impurity removal effect will be significantly reduced and other impurities will be introduced, resulting in lower rare earth purity; by comparing Example 1 with Comparative Example 2, it can be seen that without using a complexing agent, the ultrafiltration membrane cannot separate rare earth ions and magnesium ions, resulting in a significant decrease in the final rare earth purity; by comparing Example 1 with Comparative Example 3, it can be seen that without microfiltration impurity removal and ultrafiltration concentration separation treatment, the rare earth extraction rate is significantly reduced and the purity of the precipitated product is low.

[0108] In summary, the method for enriching rare earths from rare earth ore leachate provided by the present invention adopts a rare earth purification and enrichment process integrating microfiltration-complex ultrafiltration-precipitation to enrich and purify rare earths from an ionic rare earth ore leachate obtained by in-situ leaching of magnesium salts. By utilizing ultrafiltration membrane concentration and separation technology, the rare earth ion retention rate can reach 97.5%, the magnesium ion retention rate is 1.9%, and the separation coefficient between the two can reach 51.3. At the same time, the precipitant is pre-hydrolyzed, which further reduces the amount of the precipitant and increases the precipitation rate. The rare earth extraction rate can reach 100%, and the rare earth purity can reach 65.4%. In addition, the permeate and the precipitation mother liquor generated in the method can be recycled, which increases the circulation of magnesium and improves the resource utilization rate.

[0109] The above description is only a specific implementation mode 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 thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for enriching rare earth from rare earth ore leachate, characterized in that: The method comprises the following steps: (1) subjecting the rare earth ore leachate obtained by magnesium salt leaching to a microfiltration membrane for impurity removal to obtain an impurity-removed leachate; (2) uniformly mixing the complexing agent with the impurity-removed leaching solution obtained in step (1), and then separating and treating the mixture with an ultrafiltration membrane to obtain a retained rare earth solution and a permeated magnesium salt solution; The uniform mixing is carried out under the condition of pH value of 4-6.5; the molar ratio of the complexing agent to the rare earth in the impurity removal leaching solution is (1-15):1; the complexing agent includes any one of glycine, citric acid, diglycolic acid, maleic acid or ethylenediaminetetraacetic acid or a combination of at least two thereof; the glycine includes N-(phosphomethyl)glycine and / or N,N-bis(phosphonomethyl)glycine; (3) mixing a precipitant with the rare earth solution obtained in step (2), and obtaining a rare earth hydroxide precipitate and a precipitate mother liquor after solid-liquid separation; combining the obtained precipitate mother liquor with the magnesium salt solution obtained in step (2) and returning them to the magnesium salt leaching in step (1); The molar ratio of the precipitant to the rare earth in the rare earth solution is (1.15-11.5):1, and the precipitant includes magnesium oxide, which is mixed with the rare earth solution in the state of magnesium oxide hydrolyzate.

2. The method according to claim 1, characterized in that The magnesium salt in step (1) includes magnesium sulfate.

3. The method according to claim 1, characterized in that The rare earth ion content in the rare earth ore leaching solution of step (1) is 0.15-1 g / L, and the magnesium ion content is 0.6-10 g / L.

4. The method according to claim 1, characterized in that: The pH value of the rare earth ore leaching solution in step (1) is 4-7.

5. The method according to claim 1, characterized in that: The pore size of the microfiltration membrane in step (1) is 30-500 nm.

6. The method according to claim 5, characterized in that The microfiltration membrane in step (1) comprises any one of a ceramic membrane, an organic tubular membrane or an organic hollow fiber membrane.

7. The method according to claim 1, characterized in that The temperature of the impurity removal treatment in step (1) is 25-50°C.

8. The method according to claim 1, characterized in that The membrane flux of the impurity removal treatment in step (1) is 300-1000L / (m 2 h).

9. The method according to claim 1, characterized in that: The operating pressure of the impurity removal treatment in step (1) is 0.1-1 MPa.

10. The method according to claim 1, characterized in that The ultrafiltration membrane components used in step (2) include any one of a roll component, a tubular component, a hollow fiber component or a flat-plate component.

11. The method according to claim 1, characterized in that: The molecular weight cutoff of the separation treatment in step (2) is 3000-12000Da.

12. The method according to claim 1, characterized in that The ultrafiltration concentration multiple of the separation treatment in step (2) is 20-100 times.

13. The method according to claim 1, characterized in that The magnesium oxide hydrolyzate is obtained by hydrolyzing magnesium oxide at 45-75° C. for 30-120 min.

14. The method according to claim 1, characterized in that The mixing time in step (3) is 5-30 minutes.

15. The method according to claim 1, characterized in that The solid-liquid separation in step (3) includes any one of centrifugal separation, plate and frame filtration separation, vibrating screen filtration or belt filtration, or a combination of at least two of them.

16. The method according to claim 1, characterized in that The method comprises the following steps: (1) The rare earth ore leaching solution with a pH value of 4-7 obtained by magnesium salt leaching is heated at 25-50°C, 0.1-1MPa and a membrane flux of 300-1000L / (m 2 h) performing a microfiltration membrane impurity removal treatment to obtain an impurity-removed leaching solution; The rare earth ion content in the rare earth ore leachate is 0.15-1 g / L, and the magnesium ion content is 0.6-10 g / L; the pore size of the microfiltration membrane is 30-500 nm; (2) uniformly mixing the complexing agent with the impurity-removed leaching solution obtained in step (1) at a pH value of 4-6.5, and then separating and treating the mixture with an ultrafiltration membrane to obtain a retained rare earth solution and a permeated magnesium salt solution; The molar ratio of the complexing agent to the rare earth in the impurity-removing leaching solution is (1-15):1; the molecular weight cut-off of the separation treatment is 3000-12000Da, and the ultrafiltration concentration multiple is 20-100 times; (3) mixing the precipitant with the rare earth solution obtained in step (2) for 5-30 minutes, and obtaining rare earth hydroxide precipitate and precipitate mother liquor after solid-liquid separation; combining the obtained precipitate mother liquor with the magnesium salt solution obtained in step (2) and returning them to the magnesium salt leaching in step (1); The molar ratio of the precipitant to the rare earth in the rare earth solution is (1.15-11.5):1; the precipitant includes magnesium oxide; the magnesium oxide is mixed with the rare earth solution in the state of magnesium oxide hydrolyzate; the magnesium oxide hydrolyzate is obtained by hydrolyzing magnesium oxide at 45-75° C. for 30-120 minutes.

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