Method for multi-stage classified recovery of rare earth elements

Abstract

The invention provides a rare earth element multi-stage classification recovery method, which mainly utilizes humic acid, iron (hydrogen) oxide and inorganic phosphate to carry out multi-stage classification recovery on a fully-distributed rare earth element solution so as to respectively obtain solutions which are relatively rich in light rare earth, medium rare earth and heavy rare earth. The method can effectively separate and purify fully-distributed rare earth ions into a solution rich in light rare earth, a solution rich in medium rare earth and a solution rich in heavy rare earth.

Description

Technical Field

[0001] The invention relates to the separation and purification of rare earth elements in an ionic rare earth smelting process, and belongs to the technical field of rare earth ion separation and recovery. Background Art

[0002] Rare earth elements are known as "industrial vitamins" and are irreplaceable in many fields such as aerospace, special materials, and high-energy technologies. Rare earth elements refer to the lanthanide elements in the periodic table, including: lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and yttrium (Y) and scandium (Sc) with similar chemical properties to lanthanide elements, a total of 17 elements.

[0003] Rare earth elements are classified into three categories according to the size of atomic number and extraction and separation: light, medium and heavy rare earth elements. Among them, light rare earth elements are (La, Ce, Pr, Nd), medium rare earth elements are (Sm, Eu, Gd, Tb, Dy), and heavy rare earth elements are (Ho, Er, Tm, Yb, Lu). Although they are all rare earth elements, the economic value of each element varies greatly. Generally speaking, the economic value of medium and heavy rare earths is usually much higher than that of light rare earth elements. For example, in March 2023, the market price of medium rare earth Tb element was 13,670 yuan / kg, the market price of heavy rare earth Lu element was 5,000 yuan / kg, and the market price of light rare earth La element was only 26 yuan / kg. Therefore, the technology of separating and purifying light, medium and heavy rare earth elements has great economic value. However, rare earth elements have similar electronic structures, physical and chemical properties, and similar geochemical behaviors. Therefore, they always appear together in the natural environment and are difficult to separate.

[0004] my country is a major rare earth country with two major types of rare earth deposits, namely, Bayan Obo and South China ion adsorption type. Among them, the ionic rare earth deposits unique to South China have the characteristics of simple mining process, complete rare earth distribution and relatively high content of medium and heavy rare earths, and have become an important source of medium and heavy rare earths in the world. In ionic rare earth ores, rare earth elements are mainly adsorbed on the surface of clay minerals such as kaolinite by electrostatic force. This unstable physical adsorption is easily desorbed by leaching agents such as ammonium sulfate, thereby obtaining a rare earth mother liquor with full distribution (containing 15 kinds of rare earth ions). However, although ionic rare earth deposits are famous for their rich production of medium and heavy rare earths, the content of light rare earths is still significantly higher than that of medium and heavy rare earths. It is just that the content of medium and heavy rare earths is higher than that of light rare earth deposits in Bayan Obo. Therefore, no matter which type of deposit, the rare earth leaching solution contains more light rare earths with lower economic value, which will lead to a significant increase in the purification and separation workload of medium and heavy rare earths with higher economic value but very low content.

[0005] Most of the existing extraction and separation technologies are ion exchange resins and solvent extraction, while the industrial method mostly uses solvent extraction: multi-stage extraction using different organic solvents (such as amines, esters, ethers, organic phosphides, etc.). Generally speaking, these extractants are flammable, toxic, expensive, and prone to environmental pollution. Therefore, in order to effectively separate light rare earths, medium rare earths, and heavy rare earths, it is very important to develop a cheap, pollution-free process method for enriching and separating the three types of rare earths, in order to improve the recovery rate of rare earth ions and simplify the rare earth extraction process. Summary of the invention

[0006] The purpose of the present invention is to solve the defects of the above-mentioned prior art and provide a method for multi-stage classification and recovery of rare earth elements. Only cheap, environmentally friendly, pollution-free and recyclable humic acid, iron (hydroxide) oxide and inorganic phosphate are used to grade and classify the fully distributed rare earth elements (15 kinds) in the solution, and solutions relatively rich in light rare earth, medium rare earth and heavy rare earth can be obtained respectively.

[0007] The present invention can realize the classified recovery in the mining and smelting process, or the specific and efficient recovery of trace elements in natural water bodies.

[0008] The present invention adopts the following technical solution:

[0009] A method for multi-level classification and recovery of rare earth elements, comprising:

[0010] Step (1). In the rare earth separation tank, iron oxide I is added, and its mass concentration is 0.1-5g / L, and then an inorganic phosphate with a concentration of 20-100μmol / L is added, and a certain amount of inorganic acid is used to adjust the pH of the suspension to 4-6, and stirred for more than 8 hours. After the iron oxide I and the phosphate are fully reacted, the fully distributed rare earth leaching solution is introduced into the rare earth separation tank, stirred for more than 24 hours, and solid-liquid separation is performed by suction filtration, wherein the phosphated iron oxide I is recovered for secondary recovery of the rare earth elements, and the filtrate A is collected for standby use;

[0011] Step (2). Adding iron oxide II to the heavy rare earth element separation tank, the mass concentration of which is 0.1-5 g / L; adjusting the pH to 7-8 using an inorganic alkaline solution, introducing the filtrate A in step (1) into the heavy rare earth separation tank, stirring for more than 24 hours, and performing solid-liquid separation by suction filtration on the mixed filtrate, wherein the iron oxide II is recovered for secondary recovery of heavy rare earth elements, and the filtrate B is collected for standby use;

[0012] Step (3). In the light rare earth separation tank, humic acid is first added to a mass concentration of 0.1-5 g / L, and the pH of the solution is adjusted to 7-8 using an inorganic acid. The filtrate B in step (2) is introduced into the light rare earth separation tank, and stirred for more than 24 hours before solid-liquid separation, wherein the humic acid is recovered for secondary recovery of light rare earth elements, and the filtrate C flows into the heavy rare earth separation tank to achieve recovery of heavy rare earth elements;

[0013] Step (4). Secondary recovery of medium rare earth elements: The recovered iron oxide I is placed in a medium rare earth collection pool, and an inorganic acid is added to adjust the pH of the suspension to 3-5, and the suspension is fully stirred for more than 24 hours. After the rare earth ions adsorbed on the iron oxide I are fully desorbed into the solution, the suspension is subjected to solid-liquid separation, and the solution rich in medium rare earth elements is collected and dried to obtain purified medium rare earth. The iron oxide I is recycled, and the number of cycles is 1-3 times.

[0014] Step (5). Secondary recovery of heavy rare earth elements: Place iron oxide II in a heavy rare earth recovery pool, add inorganic acid to adjust the pH to 3-5, stir thoroughly for more than 24 hours, wait for the rare earth ions in the filtrate C and adsorbed on the iron oxide II to be fully desorbed into the solution, separate the suspension into solid and liquid, collect the filtrate rich in heavy rare earth elements, and obtain purified heavy rare earth after drying. The iron oxide II is recycled for 1-3 times.

[0015] Step (6). Secondary recovery of light rare earth elements: The recovered humic acid is placed in a light rare earth collection pool I, and an inorganic acid is added to adjust the pH to 3-5. The mixture is stirred for more than 24 hours. After the rare earth ions adsorbed on the humic acid are completely desorbed into the solution, the suspension is subjected to solid-liquid separation, and the solution rich in light rare earth elements is collected and dried to obtain purified and separated light rare earth. The humic acid is recycled for 1-3 times.

[0016] Preferably, the iron oxide I is ferrihydrite, and its synthesis method is: slowly adding a 1 mol / L potassium hydroxide (KOH) solution to a 0.5 mol / L iron nitrate (Fe(NO3)3) solution, stirring fully, until the pH of the solution reaches 7-8, and then centrifuging rapidly, and the obtained solid material is repeatedly rinsed with deionized water until the conductivity is less than 20S cm -1 After that, pure phase ferrihydrite was obtained after freeze drying. The synthetic ferrihydrite has a specific surface area of ​​about 300m 2 / g, pH zpc =8.

[0017] Preferably, iron oxide II is goethite, and its synthesis method is as follows: Slowly add a 2.5 mol / L potassium hydroxide (KOH) solution to a 0.2 mol / L iron nitrate (Fe(NO3)3) solution while stirring vigorously until the solution pH reaches 12. Then, age the well-stirred suspension in a 60 °C water bath for 72 hours and then centrifuge at high speed. Wash the solid repeatedly with deionized water until the conductivity is lower than 20 S cm -1 After that, freeze-dry to obtain pure-phase goethite. The specific surface area of the synthesized goethite is about 60 m 2 / g, pH zpc = 9.

[0018] Preferably, in step (1), adjust the pH of the suspension to 5 - 5.5. The weakly acidic pH condition is conducive to the adsorption of ferrihydrite on inorganic phosphate, thereby enhancing the ternary complexation of rare earth ions and phosphate radicals, which is the key to the selective adsorption of medium rare earth ions. When pH < 3, ferrihydrite may dissolve to a certain extent, resulting in adverse effects. When 3 < pH < 5, the surface of ferrihydrite carries too much positive charge, generating a strong repulsive effect with rare earth cations, which is not conducive to the adsorption of rare earth ions. When pH > 5.5, the adsorption of ferrihydrite on phosphate radicals weakens, while the direct adsorption of rare earth ions increases, which is not conducive to the formation of ternary complexation of phosphate radicals and rare earth ions, reducing the selectivity for medium rare earth ions and resulting in adverse effects.

[0019] Preferably, in step (2), adjust the pH of the suspension to 7 - 7.5. Under the medium alkaline pH condition, the surface of goethite is negatively charged, which is conducive to the adsorption of positively charged rare earth cations. However, when pH > 7.5, rare earth ions are prone to form REE(OH)3 precipitates, which is not conducive to the selective adsorption of goethite on heavy rare earth ions and cannot desorb and recover rare earth ions anymore.

[0020] Preferably, in step (3), adjust the solution pH to 7 - 7.5. Under the medium alkaline pH condition, it is conducive to the adsorption of humic acid on rare earth cations. However, when pH > 7.5, rare earth ions are prone to form REE(OH)3 precipitates, which is not conducive to the selective adsorption of humic acid on light rare earth ions and cannot desorb and recover rare earth ions anymore.

[0021] Preferably, in step (4), adjust the pH of the suspension to 3 - 3.5. Under the acidic pH condition, it is conducive to the desorption of rare earth ions from the surface of ferrihydrite, realizing the recovery of rare earth ions. When pH < 3, ferrihydrite may dissolve to a certain extent, thereby generating free Fe 3+ , forming impurities and reducing the purity of rare earth ions.

[0022] Preferably, in step (5), the pH of the suspension is adjusted to 3-3.5. Acidic pH conditions are conducive to the desorption of rare earth ions from the surface of goethite, thereby realizing the recovery of rare earth ions. When pH < 3, ferrihydrite may dissolve to a certain extent, thereby generating free Fe 3+ , forming impurities and reducing the purity of rare earth ions.

[0023] Preferably, in step (6), the pH of the suspension is adjusted to 3-4. Acidic pH conditions are conducive to the desorption of rare earth ions from the surface of goethite, thereby realizing the recovery of rare earth ions. When the pH is less than 3, humic acid may partially dissociate or precipitate, resulting in the inability to recycle humic acid.

[0024] Beneficial effects of the present invention:

[0025] 1. The present invention can effectively separate and purify fully distributed rare earth ions into light rare earth-rich, medium rare earth-rich and heavy rare earth-rich solutions.

[0026] 2. It can avoid the use of organic solvent extractants and reduce environmental pollution. It can also reduce the workload of subsequent single element purification process engineering.

[0027] 3. The adsorption and desorption fillers used, including iron oxide I and humus, can be recycled to reduce costs. The extractant of the present invention is green, environmentally friendly and pollution-free. It is a natural mineral and natural humus and is inexpensive. Note: Adsorption reaction refers to the fixation of metal ions or acid ions on the surface of the adsorption material through electrostatic attraction (physical adsorption) or through complexation reaction (chemical adsorption). It is a common, cheap and economical recovery and classification method that does not require additional energy. Different adsorption materials combined with different solution environment factors (such as pH, ionic strength, etc.) can be used to efficiently and selectively separate target ions.

[0028] 4. Microscopic mechanism: (1) Under acidic conditions, the iron hydroxyl groups on the surface of ferrihydrite (including isolated iron hydroxyl groups FeOH, geminal iron hydroxyl groups Fe2OH, and tricoordinate iron hydroxyl groups Fe3OH) will undergo protonation to form positively charged FeOH2 surface groups, which are helpful for the adsorption of free phosphate (H2PO4 - It is the main form of inorganic phosphate under acidic conditions. At this time, the phosphate undergoes inner circle adsorption on the surface of ferrihydrite to form a protonated bidentate binuclear configuration (Fe2O2PO2H). When rare earth ions are added to the solution, they interact with the phosphate adsorbed on the surface of ferrihydrite to form a stable ternary complex with phosphate as the bridge. Under acidic conditions, the ternary complex generally presents a monodentate ternary complex configuration (Fe2O2POOREE + ), while under neutral conditions, it transforms into a bidentate ternary complex configuration (Fe2O2PO2REE +). This ternary complexation mechanism not only significantly enhances the adsorption capacity of rare earth ions, but also exhibits selectivity for middle rare earth ions in the macroscopic adsorption process due to the lower adsorption energy of the monodentate ternary complex configuration with middle rare earth elements (MREEs).

[0029] (2) Goethite has a needle-like morphology, with the main exposed crystal faces being (101) and (210), of which the (210) face exhibits higher reactivity. Both of these crystal faces are rich in isolated iron hydroxyl groups (FeOH), which are easy to form bidentate adsorption configurations (Fe2O2REE) with rare earth ions. Since heavy rare earth ions (HREE) have a smaller ionic radius, they are more susceptible to hydrolysis and thus more likely to complex with isolated iron hydroxyl groups. Therefore, goethite exhibits significant selective adsorption for heavy rare earth ions.

[0030] (3) The surface of humic acid is usually rich in various functional groups such as carboxyl (-COOH), hydroxyl (-OH) and phenolic hydroxyl. The complex structure and diverse functional groups can provide multiple adsorption sites for rare earth ions and form various coordination configurations. The radius of light rare earth ions is relatively large, and the steric hindrance of the complex formed is small. It can form a stable multi-dentate complex with multiple coordination groups of humic acid. Therefore, humic acid has selective adsorption for light rare earth ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a flow chart for separation and collection of light, medium and heavy rare earth elements of the present invention.

[0032] Figure 2 This is the preferential selective adsorption diagram of humus on light rare earths.

[0033] Figure 3 This is the selective adsorption diagram of rare earth ions by phosphate-loaded ferrihydrite.

[0034] Figure 4 This is the selective adsorption diagram of goethite for heavy rare earth ions.

[0035] Figure 5 This is a diagram showing the separation effect of light, medium and heavy rare earth ions after the implementation of the plan. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] In the present invention, the preferential adsorption behavior of humus (HA) on light rare earth ions, the preferential adsorption behavior of goethite on heavy rare earth ions, and the preferential adsorption behavior of phosphated ferrihydrite (ferrihydrite loaded with phosphate) on medium rare earth ions are discovered and fully utilized, and a suitable adsorption sequence is constructed to achieve an economical, environmentally friendly, and efficient separation and purification scheme for light rare earth, medium rare earth, and heavy rare earth. The adsorption rates of the three adsorption systems are shown below:

[0038] (1) Figure 2 As shown in the figure, under neutral pH conditions (pH = 7), humus has a higher adsorption rate (80%-100%) for light rare earth, while the adsorption rate of heavy rare earth is very low (less than 20%), so humus can separate light rare earth ions from medium and heavy rare earth ions. Only through a simple filtration operation, the humus adsorbing light rare earth ions can desorb the light rare earth ions by adjusting the pH (acidic, such as pH = 3), and finally a large amount of light rare earth ions can be released into the light rare earth collection pool.

[0039] (2) Figure 3 As shown, ferrihydrite loaded with phosphate has a strong selective adsorption effect on medium rare earths. The adsorption rate of medium rare earths reaches 60%, while the adsorption rate of light rare earth ions is only 20%-40%, and the adsorption rate of heavy rare earths is about 30%.

[0040] (3) Figure 4 As shown in the figure, from light rare earth to heavy rare earth, the adsorption rate of goethite increases almost linearly, and the heavy rare earth ions are more enriched. Therefore, after the separation of medium rare earth and light rare earth ions, the selective enrichment of heavy rare earth by goethite will be more obvious.

[0041] Example 1

[0042] The laboratory simulated the purification and separation operation of a fully distributed rare earth ion standard solution, the commercial brand of which is Accustandard (the content of each rare earth ion is 100 ppb).

[0043] like Figure 1 , Figure 5As shown, step (1). In the medium rare earth separation tank, first add water ferrihydrite with a water and soil mass concentration of 1g / L. Of course, the mass concentration is also suitable at 0.1-5g / L, and then add sodium dihydrogen phosphate with a concentration of 60μmol / L. Of course, the concentration is also suitable at 20-100μmol / L. Use hydrochloric acid or nitric acid with a concentration of 0.1mol / L to adjust the suspension pH to 5, of course, pH = 4-6 is also suitable, and stir thoroughly for 8 hours or more. The rare earth full distribution solution (the concentration of each adsorbed ion is 100ppb) is introduced into the medium rare earth separation tank, and stirred thoroughly for 24h. The mixed liquid is separated into solid and liquid by suction filtration, wherein the phosphated iron oxide I (surface adsorbed rare earth ions) is recovered for secondary recovery of medium rare earth elements, and the filtrate A is collected for standby use. The rare earth ion concentration is determined by ICP-MS.

[0044] Step (2). Add iron oxide II to the heavy rare earth element separation tank at a mass concentration of 1 g / L, and of course a mass concentration of 0.1-5 g / L is also suitable. Use a concentration of 0.1-1 mol / L sodium hydroxide to adjust the solution pH to 7.5, and of course pH = 7-8 is also suitable. Introduce the filtrate A of step (1) into the heavy rare earth separation tank and stir it thoroughly for 24 hours; the mixed filtrate is separated into solid and liquid by suction filtration, wherein the iron oxide II is recovered for secondary recovery of heavy rare earth elements, and the filtrate B is collected for standby use.

[0045] Step (3). In the light rare earth separation tank, first add 1g / L humus (HA), of course, the mass concentration of 0.1-5g / L is also suitable, and use hydrochloric acid or nitric acid with a concentration of 0.1-1mol / L to adjust the suspension pH to 7-8. The filtrate B in step (2) is introduced into the light rare earth separation tank, fully stirred for 24 hours, and then solid-liquid separation is performed by suction filtration, wherein the humus (containing rare earth) is recovered for secondary recovery of light rare earth elements, and the filtrate C flows into the heavy rare earth element recovery tank to achieve the recovery of heavy rare earth elements. The rare earth ion concentration table of the adsorbent and the filtrate is shown in Table 1:

[0046] Table 1 Rare earth ion concentrations in the adsorbent and filtrate during each stage of separation:

[0047]

[0048]

[0049] Step (4). Secondary recovery of medium rare earth elements: Place the recovered iron oxide I in a medium rare earth collection pool, add hydrochloric acid or nitric acid with a concentration of 0.1-1 mol / L to adjust the suspension pH to 3, of course pH = 3-5 is also suitable, stir thoroughly for 24 hours, after the rare earth ions are completely desorbed into the solution, the suspension is filtered for solid-liquid separation, and the solution rich in medium rare earth elements is collected, and the purified medium rare earth is obtained after simple evaporation and drying. Iron oxide I is recycled for 1-3 times. The measured concentrations of adsorbed medium rare earth ions and recovered medium rare earth ion concentrations are shown in Table 2 as follows:

[0050] Table 2 Concentration of adsorbed medium rare earth ions and recovered medium rare earth ions in ppb (rich medium rare earth pool)

[0051]

[0052] Step (5). Secondary recovery of heavy rare earth elements: Place iron oxide II in a heavy rare earth recovery pool, add hydrochloric acid or nitric acid at a concentration of 0.1 mol / L to adjust the suspension pH to 3, of course pH = 3-5 is also suitable, stir thoroughly for 24 hours, and after the rare earth ions adsorbed on iron oxide II and in filtrate C are desorbed into the solution, the suspension is filtered for solid-liquid separation, and the filtrate rich in heavy rare earth elements is collected. After simple evaporation and drying, purified heavy rare earth is obtained. Iron oxide II is recycled for 1-3 times. The concentrations of adsorbed heavy rare earth ions and recovered heavy rare earth ions are shown in Table 3:

[0053] Table 3 Adsorbed heavy rare earth ions and co-recovered heavy rare earth ion concentrations ppb (rich heavy rare earth pool)

[0054]

[0055] Step (6). Secondary recovery of light rare earth elements: Place the recovered humus in the light rare earth collection pool I, add hydrochloric acid or nitric acid with a concentration of 0.1 mol / L to adjust the suspension pH to 3, of course pH = 3-5 is also suitable, stir thoroughly for 24 hours, after the rare earth ions are completely desorbed into the solution, the suspension is filtered for solid-liquid separation, the solution rich in light rare earth elements is collected, and simply evaporated and dried to obtain purified and separated light rare earth. The humus is recycled for 1-3 times. The concentrations of adsorbed light rare earth ions and recovered light rare earth ions are shown in Table 4:

[0056] Table 4 Adsorbed light rare earth ions and recovered light rare earth ion concentrations ppb (light rare earth rich pool)

[0057]

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for multi-level classification and recovery of rare earth elements, characterized in that: The steps include: Step (1). In the medium rare earth separation tank, an iron oxide I solution having a mass concentration of 0.1-5 g / L is added, and then an inorganic phosphate having a concentration of 20-100 μmol / L is added, and a certain amount of inorganic acid is used to adjust the pH of the suspension to 4-6, and stirred for more than 8 hours. After the iron oxide I solution and the inorganic phosphate are fully reacted, the fully distributed rare earth leaching solution is introduced into the medium rare earth separation tank, stirred for more than 24 hours, and solid-liquid separation is performed by suction filtration, wherein the phosphated iron oxide I is recovered for secondary recovery of the medium rare earth elements, and the filtrate A is collected for standby use; Step (2). Adding an iron oxide II solution having a mass concentration of 0.1-5 g / L into a heavy rare earth element separation tank; adjusting the pH to 7-8 using an inorganic alkaline solution, introducing the filtrate A in step (1) into the heavy rare earth separation tank, stirring for more than 24 hours, and performing solid-liquid separation by suction filtration on the mixed filtrate, wherein the iron oxide II is recovered for secondary recovery of heavy rare earth elements, and the filtrate B is collected for standby use; Step (3). In the light rare earth separation tank, a humic acid solution is first added, the mass concentration of which is 0.1-5 g / L, and the pH of the solution is adjusted to 7-8 using an inorganic acid. The filtrate B in step (2) is introduced into the light rare earth separation tank, and stirred for more than 24 hours and then filtered for solid-liquid separation, wherein the humic acid is recovered for secondary recovery of light rare earth elements, and the filtrate C flows into the heavy rare earth separation tank to achieve recovery of heavy rare earth elements; Step (4). Secondary recovery of medium rare earth elements: The recovered iron oxide I is placed in a medium rare earth collection pool, an inorganic acid is added to adjust the pH of the suspension to 3-5, and the suspension is stirred for more than 24 hours. After the rare earth ions attached to the iron oxide I are fully desorbed into the solution, the suspension is filtered for solid-liquid separation, and a solution rich in medium rare earth elements is collected. After evaporation and drying, the purified medium rare earth is obtained, and the iron oxide I is returned to step (1) for use again; Step (5). Secondary recovery of heavy rare earth elements: Place iron oxide II in a heavy rare earth recovery pool, add inorganic acid to adjust the pH to 3-5, and stir thoroughly for more than 24 hours. After the rare earth ions attached to iron oxide II and in filtrate C are fully desorbed into the solution, the suspension is filtered for solid-liquid separation, and the filtrate rich in heavy rare earth elements is collected. After evaporation and drying, purified heavy rare earths are obtained, and iron oxide II is returned to step (2) for utilization again; Step (6). Secondary recovery of light rare earth elements: The recovered humic acid is placed in a light rare earth collection pool I, and an inorganic acid is added to adjust the pH to 3-5. The mixture is stirred for more than 24 hours. After the rare earth ions adsorbed on the humic acid are completely desorbed into the solution, the suspension is filtered for solid-liquid separation, and the solution rich in light rare earth elements is collected. The solution is simply evaporated and dried to obtain purified and separated light rare earths. The humus is returned to step (3) for utilization again.

2. The method according to claim 1, characterized in that: In step (1), the iron oxide I is ferrihydrite; and in step (2), the iron oxide II is goethite.

3. The method according to claim 3, wherein the inorganic phosphate in step (1) is sodium dihydrogen phosphate.

4. The method according to claim 1, characterized in that In step (4), the iron oxide I is cycled 1-3 times; in step (5), the iron oxide II is cycled 1-3 times; and in step (6), the humic acid is cycled 1-3 times.

5. The method according to claim 1, characterized in that Step (1) adjusting the pH of the suspension to 5-5.

5.

6. The method according to claim 1, characterized in that Step (2) adjusting the pH of the suspension to 7-7.

5.

7. The method according to claim 1, characterized in that Step (3) adjusts the solution pH to 7-7.

5.

8. The method according to claim 1, characterized in that Step (4) adjusting the suspension to pH=3-3.

5.

9. The method according to claim 1, characterized in that: Step (5) adjusting the pH of the suspension to 3-3.

5.

10. The method according to claim 1, characterized in that Step (6) adjusting the pH of the suspension to 3-4.

Images