A method for enriching and recovering high-purity rare earth elements using a microemulsion method

Abstract

The present invention specifically relates to a method for enriching and recovering high-purity rare earth elements using a microemulsion method, belonging to the field of rare earth hydrometallurgy. This method uses an acidic, low-concentration rare earth ion aqueous solution as the rare earth feed solution, and uses a microemulsion system to enrich the rare earth ions. After centrifugation, a rare earth ion-loaded microemulsion system and a raffinate are obtained. The rare earth ion-loaded microemulsion system is reacted with a precipitant to obtain a rare earth precursor, which is then washed and dried to obtain a high-purity rare earth material. As a novel separation technology, this method offers many advantages over traditional methods, such as high mass transfer rates and high enrichment ratios. It provides a highly efficient enrichment and separation technology for low-concentration rare earths and can produce nano-rare earth compounds with a purity greater than 99%. Compared with conventional technologies, the purity of the rare earth compounds is higher, and it has important theoretical significance for the preparation, development and application of rare earth materials.

Description

Technical Field

[0001] The invention belongs to the technical field of rare earth hydrometallurgy, and particularly relates to a method for enriching and recovering high-purity rare earth elements by adopting a microemulsion method. Background Art

[0002] Rare earth elements (REEs) are a collective term for 17 elements in the periodic table, including the lanthanides with atomic numbers 57 to 71, scandium, and yttrium. Rare earth elements possess excellent physical and chemical properties and are widely used in various fields of industrial production. Among them, medium and heavy rare earth elements are unique to my country, primarily sourced from ionic rare earth deposits in southern China. In recent years, they have made progress in the development and research of high-tech materials and are considered by many countries to be irreplaceable strategic resources crucial to national security and development. Consequently, the mining of rare earth elements is attracting increasing attention.

[0003] The continuous development and utilization of rare earth resources has led to a decline in their availability. The content of medium and heavy rare earth elements in the Earth's crust is only 0.02-1%. The mining and processing of ionic rare earth minerals, ionic rare earth tailings, and rare earth ores with coexisting elements produces large quantities of low-concentration rare earth solutions, containing only 1-5 g / L, which seriously impacts the sustainable development of rare earth smelting. Therefore, it is necessary to extract the dispersed rare earth ions with extremely low recovery rates from these low-concentration solutions. Developing separation technologies that improve extraction and enrichment efficiency and resource utilization is an effective approach to this problem.

[0004] Currently, rare earth element enrichment and separation methods primarily include precipitation separation, reverse osmosis, adsorption, and solvent extraction. Precipitation separation is the most widely used method, requiring the use of precipitants such as oxalic acid, ammonium bicarbonate, and sodium carbonate. While this method is simple and convenient, the precipitants often have poor selectivity for rare earth elements, leading to the co-precipitation of non-rare earth impurities (such as silicon, iron, calcium, and zirconium), which can lead to a large influx of non-rare earth impurities into the enrichment solution, negatively impacting subsequent separation processes and the final product quality. Furthermore, precipitation is suitable for the enrichment of high-concentration rare earth solutions, but the precipitation rate is low for low-concentration solutions, resulting in fine, viscous precipitates that are difficult to recover. Reverse osmosis, which enriches rare earth elements by promoting ion migration through external pressure, offers simple equipment, high ion selectivity, and high product purity. However, its drawbacks include significant susceptibility to impurity ions, membrane damage, and high costs. Adsorption is also an effective method for rare earth recovery. While simple and easy to implement, the saturated adsorption capacity of the adsorbent is generally low, and further research is needed to address the reproducibility and reuse of the adsorbent. Extraction is an effective method for rare earth element enrichment and recovery. It features simple steps, mature methodology, easy automation, and high product purity and ion selectivity. However, traditional solvent extraction processes suffer from low enrichment efficiency and are unsuitable for low-concentration rare earth solutions. Furthermore, the high solubility of the extractant in aqueous solution results in resource waste, and the extraction process is prone to emulsification. The stripping solution obtained after extraction undergoes a stripping step, which is then further processed through precipitation to obtain the rare earth product, increasing process steps and costs. Summary of the Invention

[0005] In response to the problems of low enrichment efficiency and low product purity in the existing technology for the enrichment and separation of rare earths in low-concentration rare earth solutions, the present invention proposes a method for enriching and recovering high-purity rare earth elements using a microemulsion method, providing a high-efficiency enrichment and separation technology with a simple process and a large enrichment ratio for low-concentration rare earths, and providing a rich technical theoretical basis for the efficient and high-value utilization of rare earth ores.

[0006] The present invention provides a method for enriching and recovering high-purity rare earth elements using a microemulsion method, comprising the following steps:

[0007] 1. Rare earth feed liquid: A low-concentration acidic rare earth ion aqueous solution is used as the rare earth feed liquid;

[0008] 2. Rare earth enrichment: The microemulsion system is mixed with the rare earth feed solution for reaction; after the reaction is completed, the mixed system is centrifuged to obtain a microemulsion system loaded with rare earth ions and a raffinate.

[0009] 3. Rare earth recovery: The microemulsion system loaded with rare earth ions and the precipitant are mixed and reacted to obtain a suspension containing rare earth precipitates; the suspension containing rare earth precipitates is centrifuged to obtain a rare earth precursor; the precursor is washed and dried to obtain a high-purity rare earth material.

[0010] In step 1, the rare earth ions include La 3+ 、Ce 3+ 、Pr 3+ 、Nd 3+ 、Pm 3+ 、Sm 3+ 、Eu 3+ 、Gd 3+ , Tb 3+ 、Dy 3+ 、Ho 3+ 、Er 3+ 、Tm 3+ 、Yb 3+ 、Lu 3+ Sc 3+ and Y 3+ One or more of

[0011] In step 1, the rare earth ion concentration is 0.01 to 0.1 mol / L, preferably 0.01 to 0.05 mol / L; the pH of the rare earth solution is 1 to 6;

[0012] In step 2, the microemulsion system is formed by mixing a surfactant, a cosurfactant, an organic solvent, and an aqueous phase; the mass fraction of the surfactant is 15-25%, the mass fraction of the cosurfactant is 25-45%, and the mass fraction of the organic solvent is 35-55%; and the aqueous phase is hydrochloric acid;

[0013] The surfactant is one of sodium 2-ethylhexyl sulfosuccinate (AOT), sodium dodecylbenzenesulfonate (SDBS) or sodium dodecyl sulfate (SDS);

[0014] The cosurfactant is one of n-butanol, n-pentanol or benzyl alcohol;

[0015] The organic solvent is one of n-heptane, n-octane or cyclohexane;

[0016] The hydrochloric acid concentration is 1 to 6 mol / L, and the volume fraction of the microemulsion system is 1 to 10%;

[0017] In step 2, the volume ratio of the microemulsion system to the rare earth liquid is 1:1 to 1:10, more preferably 1:1 to 1:5;

[0018] In step 2, the reaction speed of the microemulsion system and the rare earth liquid is 100-400 r / min, the time is 2-20 min, and the temperature is 25-55° C.; the centrifugal separation speed is 1000-4000 r / min, and the centrifugal time is 2-10 min;

[0019] In step 3, the precipitant is one of NH4OH, NaOH, (NH4)2CO3, NH4HCO3 or H2C2O4, and the concentration of the precipitant is 1 to 3 mol / L;

[0020] In step 3, the volume ratio of the rare earth ion-loaded microemulsion system to the precipitant is 1:1 to 1:5;

[0021] In step 3, the reaction temperature of the mixed reaction is 25 to 55° C., and the reaction time is 2 to 24 hours;

[0022] In step 3, the centrifugal separation is performed at a speed of 1000 to 4000 r / min and a centrifugal time of 2 to 10 min;

[0023] In step 3, the precursor is washed, specifically using water and ethanol, alternately washing 5 to 6 times;

[0024] In step 3, the drying temperature is 50-90° C. and the drying time is 12-48 hours;

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. Based on the high enrichment ratio characteristics of liquid membrane separation, the present invention uses the microemulsion method to achieve the enrichment and separation of rare earth elements in low-concentration rare earth solutions. As a new separation technology, it has many advantages over traditional methods, such as high mass transfer rate and large enrichment ratio, and provides an efficient and green enrichment and separation technology for low-concentration rare earths.

[0027] 2. The present invention can recycle and obtain nano rare earth compounds with a purity greater than 99%. Compared with conventional technologies, the purity of rare earth compounds is higher, which has important theoretical significance for the preparation, development and application of rare earth materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The relationship curve between the enrichment ratio of some medium and heavy rare earths and the concentration of rare earth solution obtained by the method of the present invention is shown;

[0029] Figure 2 The following is an SEM image of the high-purity rare earth material obtained by the method of the present invention. DETAILED DESCRIPTION

[0030] The following non-limiting embodiments may enable those skilled in the art to more fully understand the present invention, but the present invention is not limited to these embodiments.

[0031] In the present invention, the rare earth ion concentration is determined by the EDTA titration method in accordance with the national standard GB / T 14635-2008, and the rare earth concentration in the rare earth ion-loaded microemulsion system is obtained by subtraction.

[0032] The enrichment ratio of rare earth is calculated as follows:

[0033]

[0034] Where: C o is the rare earth ion concentration in the rare earth solution before enrichment, C t is the rare earth ion concentration in the aqueous phase of the microemulsion after enrichment, mol / L.

[0035] Example 1:

[0036] 1. A microemulsion system: AOT is used as a surfactant, n-butanol is used as a cosurfactant, n-heptane is used as an organic solvent, wt% AOT:wt% n-butanol:wt% n-heptane is 15:30:55, the volume fraction of hydrochloric acid is 2%, and the concentration of hydrochloric acid is 2 mol / L.

[0037] 2. Rare earth liquid; prepare low concentration Sm 3+ Aqueous solution is used as rare earth material solution, Sm 3+ The concentration is 0.01 mol / L and the pH is 2;

[0038] 3. Rare earth enrichment: The above-mentioned microemulsion system and rare earth liquid were mixed in a volume ratio of 1:1, with a speed of 200 r / min, a time of 5 minutes, and a temperature of 25°C. After the reaction was completed, the mixed system was centrifuged at a speed of 2000 r / min and a centrifugal time of 5 minutes. After the centrifugation was completed, a microemulsion system loaded with rare earth ions and a raffinate were obtained.

[0039] 4. Rare earth recovery: The microemulsion system loaded with rare earth ions and NH4OH are mixed in a volume ratio of 1:1, the reaction temperature is 25°C, and the reaction time is 4 hours to obtain a suspension containing rare earth precipitates; the suspension is centrifuged to separate the solid and liquid at a centrifugal speed of 2000 r / min and a centrifugal time of 5 minutes to obtain a rare earth precursor; the precursor is washed and dried at a drying temperature of 60°C and a drying time of 12 hours to obtain a high-purity rare earth material.

[0040] The relationship curve between the enrichment ratio of some medium and heavy rare earths and the concentration of rare earth solution is as follows: Figure 1 As shown, the SEM image of the obtained high-purity rare earth material is as follows Figure 2 shown.

[0041] After calculation, in this embodiment, Sm 3+ The enrichment ratio is 42.73, the purity of the obtained rare earth compound is 99.2%, and the particle size is about 20 nm.

[0042] Example 2:

[0043] 1. A microemulsion system: AOT is used as a surfactant, n-butanol is used as a cosurfactant, n-heptane is used as an organic solvent, wt% AOT:wt% n-butanol:wt% n-heptane is 15:30:55, the volume fraction of hydrochloric acid is 2%, and the concentration of hydrochloric acid is 3 mol / L.

[0044] 2. Rare earth liquid; prepare low concentration Gd 3+ Aqueous solution is used as rare earth material solution, Gd 3+ The concentration is 0.01 mol / L and the pH is 2;

[0045] 3. Rare earth enrichment: The above-mentioned microemulsion system and rare earth liquid were mixed in a volume ratio of 1:2 for reaction at a speed of 200 r / min, a time of 5 min, and a temperature of 25°C. After the reaction was completed, the mixed system was centrifuged at a speed of 2000 r / min and a centrifugal time of 5 min. After the centrifugation was completed, a microemulsion system loaded with rare earth ions and a raffinate were obtained.

[0046] 4. Rare earth recovery: The microemulsion system loaded with rare earth ions and NH4OH are mixed in a volume ratio of 1:1, the reaction temperature is 25°C, and the reaction time is 4 hours to obtain a suspension containing rare earth precipitates; the suspension is centrifuged to separate the solid and liquid at a centrifugal speed of 2000 r / min and a centrifugal time of 5 minutes to obtain a rare earth precursor; the precursor is washed and dried at a drying temperature of 90°C and a drying time of 24 hours to obtain a high-purity rare earth material.

[0047] After calculation, in this embodiment, Gd 3+ The enrichment ratio is 34.56, the purity of the obtained rare earth compound is 99.3%, and the particle size is about 20 nm.

[0048] Example 3:

[0049] 1. A microemulsion system: AOT is used as a surfactant, benzyl alcohol is used as a cosurfactant, cyclohexane is used as an organic solvent, wt% AOT:wt% benzyl alcohol:wt% cyclohexane is 16:34:50, the volume fraction of hydrochloric acid is 4%, and the concentration of hydrochloric acid is 2 mol / L.

[0050] 2. Rare earth liquid; prepare low concentration Tb 3+ Aqueous solution as rare earth material solution, Tb 3+ The concentration is 0.02 mol / L and the pH is 3;

[0051] 3. Rare earth enrichment: The above-mentioned microemulsion system and rare earth liquid were mixed in a volume ratio of 1:3, with a speed of 300 r / min, a time of 10 min, and a temperature of 35°C. After the reaction was completed, the mixed system was centrifuged at a speed of 3000 r / min and a centrifugal time of 10 min. After the centrifugation was completed, a microemulsion system loaded with rare earth ions and a raffinate were obtained.

[0052] 4. Rare earth recovery: The microemulsion system loaded with rare earth ions and NaOH are mixed in a volume ratio of 1:1, the reaction temperature is 25°C, and the reaction time is 8 hours to obtain a suspension containing rare earth precipitates; the suspension is centrifuged to separate the solid and liquid at a centrifugal speed of 3000 r / min and a centrifugal time of 10 minutes to obtain a rare earth precursor; the precursor is washed and dried at a drying temperature of 80°C and a drying time of 24 hours to obtain a high-purity rare earth material.

[0053] After calculation, in this embodiment, Tb 3+ The enrichment ratio is 29.27, the purity of the obtained rare earth compound is 99.5%, and the particle size is about 20 nm.

[0054] Example 4:

[0055] 1. A microemulsion system: SDBS is used as a surfactant, n-butanol is used as a cosurfactant, n-heptane is used as an organic solvent, the wt% SDBS:wt% n-butanol:wt% n-heptane is 15:30:55, the volume fraction of hydrochloric acid is 2%, and the concentration of hydrochloric acid is 3 mol / L.

[0056] 2. Rare earth liquid; prepare low concentration Ho 3+ Aqueous solution as rare earth feed solution, Ho 3+ The concentration is 0.01 mol / L and the pH is 3;

[0057] 3. Rare earth enrichment: The above-mentioned microemulsion system and rare earth liquid were mixed in a volume ratio of 1:1, with a speed of 400 r / min, a time of 10 min, and a temperature of 25°C. After the reaction was completed, the mixed system was centrifuged at a speed of 2000 r / min and a centrifugal time of 10 min. After the centrifugation was completed, a microemulsion system loaded with rare earth ions and a raffinate were obtained.

[0058] 4. Rare earth recovery: The microemulsion system loaded with rare earth ions and NH4OH are mixed in a volume ratio of 1:1, the reaction temperature is 35°C, and the reaction time is 24 hours to obtain a suspension containing rare earth precipitates; the suspension is centrifuged to separate the solid and liquid at a centrifugal speed of 2000 r / min and a centrifugal time of 10 minutes to obtain a rare earth precursor; the precursor is washed and dried at a drying temperature of 80°C and a drying time of 48 hours to obtain a high-purity rare earth material.

[0059] After calculation, in this embodiment, Ho 3+ The enrichment ratio is 36.75, the purity of the obtained rare earth compound is 99.7%, and the particle size is about 40 nm.

[0060] Example 5:

[0061] 1. A microemulsion system: SDS is used as a surfactant, n-pentanol is used as a co-surfactant, n-octane is used as an organic solvent, the wt% SDS:wt% n-pentanol:wt% n-octane is 15:30:55, the volume fraction of hydrochloric acid is 6%, and the concentration of hydrochloric acid is 2 mol / L.

[0062] 2. Rare earth liquid; prepare low concentration Er 3+ Aqueous solution is used as rare earth feed solution, Er 3+ The concentration is 0.01 mol / L and the pH is 3;

[0063] 3. Rare earth enrichment: The above-mentioned microemulsion system and rare earth liquid were mixed in a volume ratio of 1:1 for reaction at a speed of 400 r / min, a time of 20 min, and a temperature of 35°C. After the reaction was completed, the mixed system was centrifuged at a speed of 4000 r / min and a centrifugal time of 5 min. After the centrifugation was completed, a microemulsion system loaded with rare earth ions and a raffinate were obtained.

[0064] 4. Rare earth recovery: The microemulsion system loaded with rare earth ions and (NH4)2CO3 are mixed in a volume ratio of 1:1, the reaction temperature is 35°C, and the reaction time is 24 hours to obtain a suspension containing rare earth precipitates; the suspension is centrifuged to separate the solid and liquid at a centrifugal speed of 3000 r / min and a centrifugal time of 10 minutes to obtain a rare earth precursor; the precursor is washed and dried at a drying temperature of 90°C and a drying time of 48 hours to obtain a high-purity rare earth material.

[0065] After calculation, in this embodiment, Er 3+ The enrichment ratio is 35.83, the purity of the obtained rare earth compound is 99.5%, and the particle size is 40 nm.

Claims

1. A method for enriching and recovering high-purity rare earth elements using a microemulsion method, characterized in that: The following steps are involved: (1) Rare earth solution: Acidic rare earth ion aqueous solution is used as rare earth solution, and rare earth ions include La 3+ 、Ce 3+ 、Pr 3+ 、Nd 3+ 、Pm 3+ 、Sm 3+ 、Eu 3+ 、Gd 3+ 、Tb 3+ 、Dy 3+ 、Ho 3+ 、Er 3+ 、Tm 3+ 、Yb 3+ 、Lu 3+ Sc 3+ and Y 3+ One or more; rare earth ion concentration is 0.01-0.05 mol / L; the pH of the rare earth liquid is 1-6; (2) Rare earth enrichment: mixing the microemulsion system with the rare earth liquid; After the reaction is completed, the mixed system is centrifuged to obtain a microemulsion system loaded with rare earth ions and a raffinate; the volume ratio of the microemulsion system to the rare earth feed liquid is 1:1 to 1:10; the microemulsion system is formed by mixing a surfactant, a cosurfactant, an organic solvent, and an aqueous phase; the mass fraction of the surfactant is 15 to 25%, the mass fraction of the cosurfactant is 25 to 45%, and the mass fraction of the organic solvent is 35 to 55%; the aqueous phase is hydrochloric acid; the surfactant is 2-ethylhexylsuccinic acid One of sodium ester sulfonate (AOT), sodium dodecylbenzenesulfonate (SDBS) or sodium dodecyl sulfate (SDS); the cosurfactant is one of n-butanol, n-pentanol or benzyl alcohol; the organic solvent is one of n-heptane, n-octane or cyclohexane; the rotation speed of the microemulsion system and the rare earth liquid for mixing reaction is 100-400 r / min, the reaction time is 2-20 min, and the reaction temperature is 25-55° C.; the volume ratio of the microemulsion system to the rare earth liquid is 1:1-1:10; (3) Rare earth recovery: a microemulsion system loaded with rare earth ions and a precipitant are mixed and reacted to obtain a suspension containing rare earth precipitates; the suspension containing rare earth precipitates is centrifuged to obtain a rare earth precursor; the precursor is washed and dried to obtain a high-purity rare earth material; the temperature of the mixed reaction is 25 to 55°C, and the reaction time is 2 to 24 hours; the precursor is washed, specifically with water and ethanol, alternately washed 5 to 6 times; the drying temperature is 50 to 90°C, and the drying time is 12 to 48 hours.

2. The method for enriching and recovering high-purity rare earth elements using a microemulsion method according to claim 1, characterized in that: The hydrochloric acid concentration is 1-6 mol / L, and the volume fraction of the hydrochloric acid in the microemulsion system is 1-10%.

3. The method for enriching and recovering high-purity rare earth elements using a microemulsion method according to claim 1, characterized in that: The volume ratio of the microemulsion system to the rare earth liquid in step (2) is preferably 1:1 to 1:

5.

4. The method for enriching and recovering high-purity rare earth elements using a microemulsion method according to claim 1, characterized in that: In the step (3), the precipitant includes one of NH4OH, NaOH, (NH4)2CO3, NH4HCO3 or H2C2O4, and the concentration of the precipitant is 1 to 3 mol / L; the volume ratio of the rare earth ion-loaded microemulsion system to the precipitant is 1:1 to 1:5.

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