Use and method of mixed extractant of aminophosphonic compound and phosphonohydroxyacetic compound for the extraction separation of rare earths and aluminum

Abstract

The present application relates to the use and method of mixed extractant of aminophosphonic acid compound and phosphono glycolic acid compound for extracting and separating rare earth and aluminum. The aminophosphonic acid compound and phosphono glycolic acid compound are respectively shown as formula I and II. The mixed extractant of the present application has good extraction capacity for rare earth when extracting and separating rare earth and aluminum, effectively overcomes the limitation of single aminophosphonic acid extractant for poor extraction efficiency of light and medium rare earth, has good extraction capacity for overall rare earth, greatly improves the extraction efficiency of rare earth, has good selectivity for rare earth ions, can selectively extract rare earth preferentially, has weak extraction performance for aluminum, and almost does not extract aluminum in part of the mixed system, effectively reduces the aluminum entrainment generated when extracting rare earth, so as to keep aluminum ions in the aqueous phase, realizes the separation of rare earth and aluminum. Therefore, the present application has obvious advantages in the separation of rare earth and aluminum. (I) (II)

Description

Technical Field

[0001] This invention relates to the field of rare earth and aluminum extraction and separation technology, specifically to the use and method of a mixed extractant of aminophosphonic acid compound and phosphonohydroxyacetic acid compound for the extraction and separation of rare earth and aluminum. Background Technology

[0002] The leaching solution of southern ionic rare earth ores contains a large number of aluminum ions, which can easily cause emulsification of the extraction system during the subsequent extraction and separation process, affecting the normal operation of rare earth extraction and separation.

[0003] To address the aforementioned issues, CN112063861A discloses a technique for separating rare earth elements and aluminum using bifunctional diamide ether extractants. These extractants exhibit good extraction performance for rare earth elements even at low pH conditions, but their extraction efficiency for aluminum is low. However, the synthesis route for these extractants is cumbersome, time-consuming, and costly. CN113373304B discloses a method for separating rare earth elements and aluminum using complexation-cloud point extraction. This method achieves a single-shot extraction efficiency of 70% for aluminum, but only 6% for rare earth elements. However, it requires strict control over the acidity of the feed solution and the extraction temperature, and the amount of complexing agent used is large, making the operation process complex. CN120924818A discloses a method for extracting and separating rare earth elements and aluminum from acetic acid solution using kinetic differences. This method improves the separation coefficient between rare earth elements and aluminum, but it requires precise control of reaction time and feed solution acidity, and the subsequent recovery method is complex. CN101979680A discloses a method for removing aluminum using a naphthenic acid-alcohol-kerosene system. This method is simple to operate, has few steps, and is low in cost. However, the extraction process is prone to emulsification and requires a large amount of acid and alkali, which is highly corrosive to the equipment.

[0004] Current solvent extraction technologies for separating rare earth elements from aluminum suffer from problems such as complex processes, high costs, and poor separation efficiency. Therefore, developing an extraction system with a high separation coefficient for rare earth elements and aluminum, good extraction phenomena, and preferential extraction of rare earth elements is crucial for the efficient separation and recovery of rare earth elements from aluminum-containing feed solutions. Summary of the Invention

[0005] To address the problems encountered in the solvent extraction techniques for separating rare earth elements and aluminum, the inventors attempted to develop a new method for extracting and separating rare earth elements and aluminum. The inventors first tried using aminophosphonic acid compounds as extractants to separate rare earth elements and aluminum. The results showed that single aminophosphonic acid extractants had poor extraction efficiency for light and medium rare earth elements, leading to low overall extraction efficiency for all rare earth elements. Furthermore, some single aminophosphonic acid extractants were prone to co-extraction of aluminum, resulting in aluminum entrainment during rare earth extraction.

[0006] To overcome the aforementioned problems, the inventors attempted to compensate for the deficiencies of single aminophosphonic acid extractants by using a mixed extraction system. They unexpectedly discovered that adding phosphonoglycolic acid compounds to aminophosphonic acid compounds to form a mixed extraction system effectively separates rare earth elements from aluminum. Compared to single aminophosphonic acid extractants, the mixed extraction system of aminophosphonic acid compounds and phosphonoglycolic acid effectively overcomes the limitation of poor extraction efficiency of light and medium rare earth elements, demonstrating good extraction capability for overall rare earth elements and significantly improving extraction efficiency. Furthermore, it exhibits good selectivity for rare earth ions, preferentially extracting rare earth elements while showing weaker extraction performance for aluminum; some mixed systems extract almost no aluminum, effectively reducing aluminum entrainment during rare earth extraction and thus retaining aluminum ions in the aqueous phase, achieving separation of rare earth elements and aluminum. Therefore, this invention has significant advantages in the separation of rare earth elements and aluminum.

[0007] This invention provides, in one aspect, the use of a mixed extractant comprising an aminophosphonic acid compound of Formula I or a salt thereof and a phosphonohydroxyacetic acid compound of Formula II or a salt thereof for the extraction and separation of rare earth elements from an aluminum-containing rare earth feed solution: (I) (II) in, R1 is selected from C 1-14 alkyl; R2 and R3 are each independently selected from C 1-10 Alkyl and hydrogen; R4 and R5 are each independently selected from C 1-16 Alkyl and hydrogen; R6 and R7 are each independently selected from C 1-14 Alkyl or alkoxy groups, and the total number of carbon atoms in R6 and R7 is 10 or greater; R8 is selected from C 1-8 Alkyl, C 3-10 Alicyclic alkyl groups and C 6-10 Aryl.

[0008] Compounds of formula I and II are described in detail below.

[0009] (1) Aminophosphonic acid compounds In Equation I, R1 is selected from C 2-14 Alkyl, preferably C 4-10 Alkyl, more preferably C 5-9 alkyl.

[0010] R2 and R3 may be the same or different; preferably, R2 and R3 are selected from C. 1-8 Alkyl and hydrogen, preferably C 1-5 Alkyl and hydrogen, more preferably C 1-3 Alkyl groups and hydrogen.

[0011] R4 and R5 may be the same or different; preferably, R4 and R5 are selected from C. 1-10 Alkyl, preferably C 1-8 Alkyl group. Preferably, the total number of carbon atoms in R4 and R5 is an integer between 8 and 20, more preferably an integer between 12 and 17, such as 13, 14, 15, 16, etc.

[0012] Preferably, the total number of carbon atoms in R1, R2, R3, R4 and R5 is 2 to 40, more preferably 10 to 26, such as 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, etc.

[0013] Preferably, the aminophosphonic acid compound represented by Formula I is selected from one or more of the following compounds:

[0014] The aminophosphonic acid compounds of Formula I can be synthesized similarly to, but not limited to, the method disclosed in CN109097570B.

[0015] In this invention, the salt of the aminophosphonic acid compound of Formula I is not particularly limited, as long as its cation does not adversely affect the extraction of rare earth elements. For example, it can be an ammonium salt, an alkali metal salt (e.g., lithium salt, sodium salt, potassium salt) or an alkaline earth metal salt (e.g., magnesium salt, calcium salt), preferably a sodium salt. However, this invention is not limited thereto.

[0016] (2) Phosphonohydroxyacetic acid compounds In Equation II, R6 and R7 may be the same or different, and R6 and R7 are each independently selected from C. 2-14 Alkyl or alkoxy, more preferably C 4-12 Alkyl or alkoxy.

[0017] Preferably, R6 and R7 are the same and are selected from C. 5-12 Alkyl or alkoxy. Preferably, the total number of carbon atoms in R6 and R7 is an integer between 10 and 24, more preferably an integer between 12 and 20, such as 13, 14, 15, 16, 17, 18, 19, etc.

[0018] Preferably, R8 is selected from C 1-6 Alkyl, C 3-8 Alicyclic alkyl groups and C 6-10 Aryl group, preferably selected from C 1-4 Alkyl, C 3-6 Alicyclic alkyl groups, C 6-8 Aryl.

[0019] Preferably, the total number of carbon atoms in R6, R7, and R8 is 10 to 38, more preferably 11 to 34, and even more preferably 14 to 30, for example, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, etc.

[0020] Preferably, the phosphonohydroxyacetic acid compound of formula II is selected from one or more of the following compounds:

[0021] The phosphonoglycolic acid compound of Formula II can be synthesized similarly to the method disclosed in CN115369267A, but is not limited thereto. In this invention, the salt of the phosphonoglycolic acid compound of Formula II is not particularly limited, as long as its cation does not adversely affect the extraction of rare earth elements. For example, it can be an ammonium salt, an alkali metal salt (e.g., lithium salt, sodium salt, potassium salt), or an alkaline earth metal salt (e.g., magnesium salt, calcium salt), preferably a sodium salt. However, this invention is not limited thereto.

[0022] In the mixed extractant of the present invention, the molar ratio of the aminophosphonic acid compound or its salt represented by Formula I to the phosphonohydroxyacetic acid compound or its salt represented by Formula II can be 1:9 to 9:1, preferably 2:8 to 8:2, for example 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, etc., but is not limited thereto.

[0023] In this invention, the mixed extractant has different extraction rates and distribution ratios for aluminum and rare earth elements when extracting and separating rare earth elements and aluminum. In particular, the extraction rate and distribution ratio for rare earth elements are significantly greater than those for aluminum, so that rare earth elements and aluminum elements can be separated by extraction.

[0024] The mixed extractant can be prepared as an extraction system to extract aluminum-containing rare earth solutions to separate rare earth elements from aluminum through extraction. In other words, the present invention provides the use of the above-mentioned mixed extractant in the preparation of an extraction system for the extraction and separation of rare earth elements and aluminum. Alternatively, the present invention provides the use of the above-mentioned extraction system for the separation of rare earth elements and aluminum. A detailed description of the extraction system is set forth below.

[0025] Another aspect of the present invention provides a method for extracting and separating rare earth elements from a rare earth feed solution containing rare earth elements and aluminum. The method includes contacting the rare earth feed solution with a mixed extractant comprising an aminophosphonic acid compound of Formula I or a salt thereof and a phosphonohydroxyacetic acid compound of Formula II or a salt thereof to extract the rare earth elements, thereby separating the rare earth elements and aluminum.

[0026] The method of extracting and separating rare earth elements from a rare earth feed solution containing rare earth elements and aluminum according to the present invention can first extract most or all of the rare earth elements from the rare earth feed solution containing rare earth elements and aluminum, while retaining most or all of the aluminum in the feed solution, thereby separating the rare earth elements and aluminum.

[0027] In some embodiments, the method of the present invention for extracting and separating rare earths from a rare earth feed solution containing rare earths and aluminum can be carried out by solvent extraction. The method includes: contacting a liquid phase extraction system containing the above-mentioned mixed extractant with a rare earth feed solution containing rare earths and aluminum to extract and obtain an extract containing rare earths and an aluminum-containing extract residue.

[0028] After the liquid-phase extraction system (organic phase) comes into contact with the rare earth elements in the feed liquid, the rare earth elements can form extraction complexes with the extractant, thereby selectively separating most or all of the rare earth elements from the feed liquid and entering the organic phase, while most or all of the aluminum remains in the extraction residue.

[0029] The liquid-phase extraction system comprises: the above-described mixed extractant and a diluent. Preferably, the liquid-phase extraction system is substantially composed of the above-described components.

[0030] In this invention, the liquid-phase extraction system is mainly composed of organic matter, and is therefore sometimes referred to as the organic phase during the extraction process. The aluminum-containing rare earth feed solution is an aqueous solution, and is therefore sometimes referred to as the aqueous phase during the extraction process. Both the rare earth elements and aluminum in the feed solution are in trivalent ionic form. Preferably, the aluminum-containing rare earth feed solution contains one or more rare earth ions selected from lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and yttrium. Specifically, the total concentration of rare earth elements in the feed solution can be approximately 0.0001~2 mol / L, and the acidity of the feed solution, expressed as pH, is pH=0.5~3.5. However, it is not limited to these specifications.

[0031] In addition, the concentration of aluminum in aluminum-containing rare earth solutions can be 0.0001~2 mol / L.

[0032] In some embodiments, the diluent may be selected from: C5~C 16 Alkanes, such as pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, etc.; aviation kerosene; sulfonated kerosene; liquid paraffin, such as light lubricating oil fractions at 250~400℃; C5~C 16 Alicyclic alkanes, such as cyclopentane, C1-C4 alkyl-substituted cyclopentane, cyclohexane, C1-C4 alkyl-substituted cyclohexane, decahydronaphthalene, etc.; C6-C 10Aromatic hydrocarbons, such as benzene, toluene, xylene (including ortho-, meta-, para-xylenes and mixed xylenes), etc. Preferably, the diluent can be one or more selected from aviation kerosene, sulfonated kerosene, heptane, and xylene. However, the invention is not limited thereto.

[0033] In the extraction system, based on the volume of the liquid-phase extraction system (i.e., the organic phase), the concentration of the mixed extractant (i.e., the total concentration of the aminophosphonic acid compound represented by Formula I and the phosphonohydroxyacetic acid compound represented by Formula II) can be 0.0001~1.0 mol / L, preferably 0.01~0.5 mol / L, for example 0.16, 0.32, 0.2, 0.4 mol / L. However, the present invention is not limited thereto.

[0034] In some embodiments, the liquid-phase extraction system may further include an auxiliary extractant and / or a phase modifier. That is, the auxiliary extractant and phase modifier may or may not be present in the liquid-phase extraction system.

[0035] The auxiliary extractant mainly plays an auxiliary extraction role, which can enhance the extraction performance of the above mixed extractant for rare earth elements.

[0036] The auxiliary extractant may be selected from neutral phosphorus or phosphine extractants, carboxylic acid extractants or their salts, acidic phosphorus or phosphine extractants, neutral phosphoramide extractants, and mixed extractants of the above extractants in any proportion.

[0037] The neutral phosphorus or phosphine extractant can be an alkylphosphine oxide, an alkyl phosphonate, or an alkyl phosphate ester. Specifically, the neutral phosphorus or phosphine extractant can be as shown in Formula III: (III) Among them, R 31 R 32 and R 33 Each is independently selected from C 1-12 Alkyl and C 1-12 alkoxy, and R 31 R 32 and R 33 The total number of carbon atoms is more than 10.

[0038] More specifically, the neutral phosphorus or phosphine extractant may be selected from linear trialkylphosphine oxide (Cyanex 923), branched trialkylphosphine oxide (Cyanex 925), trioctylphosphine oxide, dimethylheptyl methylphosphonate, di(-2-ethylhexyl) 2-ethylhexylphosphonate, tributyl phosphate, and any combination thereof, but is not limited thereto.

[0039] The carboxylic acid extractant or its salt may be selected from, but is not limited to, sec-octylphenoxy-substituted acetic acid (CA-12), sec-nonylphenoxy-substituted acetic acid (CA-100), etc.

[0040] The acidic phosphorus or phosphine extractant may be an acidic phospho(phosphine) ester of formula IV or a salt thereof, but is not limited thereto: (IV) in, Z is either O or S; R 43 and R 44 Each is selected independently from C 1-12 Alkyl, C 1-12 Alkoxy; Suitable acidic phosphonates of formula VI may be selected from: bis(2,4,4-trimethylpentyl)thiophosphonic acid (Cyanex 302), bis(2-ethylhexyl)phosphonic acid (P204), 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (P507), bis(2,4,4-trimethylpentyl)phosphonic acid (Cyanex 272), bis(2-ethylhexyl)phosphonic acid (P227 or P229), and any combination thereof, but not limited thereto.

[0041] In this invention, the salts of the acidic phosphonate of formula IV are not particularly limited, as long as their cations do not adversely affect the extraction of rare earth elements. For example, they can be ammonium salts, alkali metal salts (e.g., lithium salts, sodium salts, potassium salts) or alkaline earth metal salts (e.g., magnesium salts, calcium salts), preferably sodium salts. However, this invention is not limited thereto.

[0042] The neutral phosphoramide extractant may be a neutral phosphoramide extractant of formula V, but is not limited thereto: (V) in, R 51 C 1-18 alkyl; R 52 and R 53 Each is independently selected from: C 1-18 Alkyl, C 1-18 Alkylamino and C 1-18 Alkoxy; Among them, R 51 R 52 and R 53 The total number of carbon atoms is 14 to 36, preferably 16 to 30, such as 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, etc.

[0043] The neutral phosphoramide extractant of Formula V may be selected from: triisooctylphosphamide, diisooctyl-isooctyloxyphosphamide, isooctyl-diisooctyloxyphosphamide, tri(diisobutyl)phosphamide, di(diisobutyl)-isooctyloxyphosphamide, tridecylphosphamide and dihexyl-decyloxyphosphamide and any combination thereof, but not limited thereto.

[0044] In the liquid-phase extraction system, based on the total volume of the liquid-phase extraction system (i.e., the organic phase), the concentration of the auxiliary extractant can be 0 to 1.0 mol / L, preferably 0 to 0.5 mol / L, such as 0.01 mol / L, 0.05 mol / L, 0.10 mol / L, 0.15 mol / L, 0.20 mol / L, 0.25 mol / L, 0.30 mol / L, 0.35 mol / L, 0.40 mol / L, 0.45 mol / L, 0.50 mol / L, etc., but is not limited thereto.

[0045] The phase modifier mainly functions to improve the physical phenomena of extraction, and it can be selected from C4~C6. 12 The alcohol is selected from one or more of the following: alkanol and tributyl phosphate, di(2-ethylhexyl)phosphonate, and di(2-ethylhexyl)[(2-ethylhexyl)amino]methylenephosphonate; preferably one or more of the following: n-octanol, isooctol, 2-methylheptanol, a mixture of the above three alcohols in any proportion, and tributyl phosphate; more preferably isooctol or 2-methylheptanol, but not limited thereto.

[0046] In the liquid-phase extraction system, based on the total volume of the liquid-phase extraction system (organic phase), the concentration of the phase modifier can be 0 ~ 1.0 mol / L, preferably 0 ~ 0.5 mol / L, such as 0.01 mol / L, 0.05 mol / L, 0.10 mol / L, 0.15 mol / L, 0.20 mol / L, 0.25 mol / L, 0.30 mol / L, 0.35 mol / L, 0.40 mol / L, 0.45 mol / L, 0.50 mol / L, etc., but is not limited thereto.

[0047] Furthermore, some compounds can function as both auxiliary extractants and phase modifiers, such as the aforementioned tributyl phosphate, di(2-ethylhexyl)phosphonate, and di(2-ethylhexyl)[(2-ethylhexyl)amino]methylenephosphonate. In these cases, they can be used according to the desired purpose. For example, they can be used as auxiliary extractants with or without additional phase modifiers; or they can be used as phase modifiers with or without additional auxiliary extractants.

[0048] The liquid-phase extraction system can be prepared using conventional mixing methods, as long as the components are mixed evenly. In some embodiments, the liquid-phase extraction system is prepared as follows: an aminophosphonic acid compound of formula I and a phosphonohydroxyacetic acid compound of formula II are mixed with a diluent, and, optionally, the degree of saponification is adjusted to obtain the liquid-phase extraction system.

[0049] The degree of saponification refers to the salt-forming degree of the acidic extractant (including aminophosphonic acid compounds of formula I, phosphonoglycolic acid compounds of formula II, and non-essential acidic auxiliary extractants) in the liquid-phase extraction system, which can be calculated as follows: Saponification degree % = (molar amount of acidic extractant used for salt formation) / (molar amount of total acidic extractant) × 100%.

[0050] The degree of saponification in the liquid-phase extraction system can be 10-90%, preferably 20-70%, and more preferably 25-35%, such as 25%, 30%, 35%, etc. Since the extraction reaction mechanism is a cation exchange mechanism, if a saponification process is not performed, rare earth ions will be extracted into the organic phase during the extraction reaction, and hydrogen ions will be displaced into the aqueous phase, thereby increasing the acidity of the aqueous phase and affecting the subsequent extraction reaction. Therefore, it is preferable to adjust the acidic extractant extraction system to a suitable degree of saponification before extraction.

[0051] There are no particular limitations on the method for adjusting the degree of saponification. Saponification can be achieved by adding a saponifying agent to the liquid-phase extraction system. The saponifying agent can be selected from ammonia, ammonium carbonate, ammonium bicarbonate, soluble carbonates, bicarbonates, and hydroxides of alkali metals or alkaline earth metals, such as sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, magnesium bicarbonate, calcium bicarbonate, sodium hydroxide, and potassium hydroxide, preferably ammonia or sodium hydroxide. In some embodiments, the saponifying agent can be prepared as an aqueous solution for use.

[0052] Based on the mixed extractant of the present invention, those skilled in the art can determine the appropriate amount of diluent, select a suitable saponifying agent, and determine the appropriate degree of saponification through experiments. Therefore, the scope of the present invention is not limited to the above description of diluent, saponifying agent, and degree of saponification.

[0053] In some implementations, the number of extraction stages can be 1 to 50, for example 5 to 40, or 8 to 35, or 10 to 30, for example 12, 15, 18, 20, 25, etc. Too many extraction stages will increase the amount of separation equipment and extractant required.

[0054] In some embodiments, the flow ratio of the liquid extraction system to the feed liquid can be about 0.1 to 20:1, preferably about 0.2 to 10:1, such as 0.5:1, 1:1, 2:1, 3:1, 5:1, 8:1, 10:1, etc. The variation in the flow ratio mainly depends on the concentration of rare earth elements in the feed liquid. When the concentration of rare earth elements in the feed liquid is high, the flow rate of the liquid extraction system is appropriately increased to ensure that the rare earth elements are fully extracted into the liquid extraction system.

[0055] In some embodiments, the extraction is performed using countercurrent extraction, and the aluminum-containing extraction residue is collected.

[0056] The rare earth elements contained in the extract (i.e., the liquid phase extraction system containing the extracted rare earth elements) can be further recovered.

[0057] Therefore, the solvent extraction method for extracting and separating rare earth elements from a rare earth feed solution containing rare earth elements and aluminum according to the present invention may further include the step of treating the extract to recover the rare earth elements therein, including the following process: If not necessary, wash the extract with a washing solution; The rare earth elements in the extract were back-extracted using the back-extraction solution to obtain a back-extraction product containing rare earth elements.

[0058] In this invention, the washing solution can also be referred to as washing liquid, washing acid, or detergent. The above washing process can further reduce the aluminum content in the extract, thereby helping to improve the purity of the final rare earth product.

[0059] The washing solution can be a mixture of nitric acid, hydrochloric acid, or any proportion of the above acids. The acidity of the washing solution, expressed as the molar concentration of hydrogen ions, is approximately 0.2–2.5 mol / L.

[0060] The number of washing stages can range from 0 to 30, preferably 0 to 15. The number of washing stages can be adjusted based on the amount of aluminum entrained in the extract. If the aluminum content is high, the number of washing stages can be increased appropriately; if the aluminum content is extremely low or even nonexistent, the number of washing stages can be zero. Excessive washing stages will affect the rare earth yield and waste energy and extractant.

[0061] The washing flow rate ratio can be approximately 1:0.1 to 5, preferably approximately 1:0.1 to 1. Increasing the washing flow rate can improve the purity of rare earth products, but it will also reduce the yield of rare earths and consume more washing acid and alkali needed to neutralize it, thus increasing production costs.

[0062] The washing liquid obtained from washing contains a small amount of aluminum, which can be incorporated into the aluminum-containing extraction residue (of the extraction section) or used to prepare feed solutions for further recovery.

[0063] After back-extracting the rare earth elements from the extract using the back-extraction solution, the back-extracted extract can be recycled as a liquid-phase extraction system and used again to extract and separate rare earths from rare earth feed containing rare earths and aluminum.

[0064] The back-extraction solution can be an inorganic acid solution, such as hydrochloric acid solution, nitric acid solution, sulfuric acid solution, or a mixed acid solution of the above acids in any proportion. The H+ concentration of the acid solution is 0.5–10 mol / L; preferably 1–3 mol / L.

[0065] In some embodiments, the number of back-extraction stages is 1 to 20, preferably 2 to 10. In some embodiments, the flow rate ratio is extractant:extraction liquid = 1:0.1 to 5, preferably 1:0.1 to 2. In some embodiments, the back-extraction is performed in a countercurrent back-extraction manner.

[0066] In the solvent extraction method according to the present invention, extraction, washing and back-extraction can be carried out using a separatory apparatus known in the art, preferably in a series of separatory funnels, a mixing and clarifying extraction tank or a centrifugal extractor, more preferably in a mixing and clarifying extraction tank or a centrifugal extractor.

[0067] In the solvent extraction method according to the present invention, the extraction, washing and back-extraction described above can be carried out intermittently or continuously, preferably continuously.

[0068] Based on the mixed extractant of the present invention, those skilled in the art can determine the appropriate washing liquid, back-extraction liquid, extraction stage, washing stage, and back-extraction stage through experiments according to the concentration of rare earth and aluminum in the feed solution, and select appropriate extraction equipment and operating mode. Therefore, the scope of the present invention is not limited to the above description of the washing liquid, back-extraction liquid, extraction stage, washing stage, extraction equipment, and operating mode.

[0069] In some embodiments, the method of the present invention for extracting and separating rare earths from a rare earth feed solution containing rare earths and aluminum can be carried out by solid-liquid extraction. The method includes: contacting a solid-phase extraction system containing the above-mentioned mixed extractant with a rare earth feed solution containing rare earths and aluminum to extract and obtain a solid-phase extraction system containing rare earths and an aluminum-containing extraction residue.

[0070] The solid-phase extraction system can be a resin, porous silica spheres, diatomaceous earth, etc., loaded with the mixed extractant of the present invention. The solid-phase extraction system can be prepared using conventional methods in the art, such as the method disclosed in CN201910842104.X, for example, by impregnation, in-situ polymerization, chemical bonding, etc. (preferably by impregnation, in-situ polymerization, etc.) to load the mixed extractant of the present invention onto resin, porous silica spheres, or diatomaceous earth. However, the present invention is not limited thereto.

[0071] The solid-phase extraction system may also be loaded with an auxiliary extractant. The description of the auxiliary extractant is the same as that above, so it will not be repeated here.

[0072] The description of saponification degree in liquid phase extraction systems also applies to solid phase extraction systems, so it will not be repeated here.

[0073] When the solid-phase extraction system comes into contact with rare earth elements in a feed solution containing rare earth and aluminum, the rare earth elements can preferentially form extraction complexes with the extractant in the solid-phase extraction system. This allows most or all of the rare earth elements to be selectively extracted from the feed solution and enter the solid phase, while most or all of the aluminum remains in the extraction residue, thus separating the aluminum from the rare earth elements.

[0074] In some embodiments, the solid-liquid extraction method is carried out in a column, wherein a solid extraction system is added to the column, and then a feed solution containing rare earth elements and aluminum is added to bring the solid extraction system into contact with the feed solution containing rare earth elements and aluminum to perform solid-liquid extraction.

[0075] The description of feed solutions containing rare earth elements and aluminum in solvent extraction methods also applies to solid-liquid extraction methods, so it will not be repeated here.

[0076] The rare earth elements contained in the solid-state extraction system obtained after the above extraction steps can be further recovered. Therefore, the solid-liquid extraction method for extracting and separating rare earths from a rare earth feed solution containing rare earths and aluminum according to the present invention can further include the step of treating the solid-phase extraction system containing rare earths to recover the rare earth elements therein, including the following process: If not necessary, wash the solid extraction system with a washing solution; Rare earth elements were back-extracted from a solid-state extraction system using a back-extraction agent to obtain a back-extraction product containing rare earth elements.

[0077] The washing process can further reduce the content of impurity elements in the solid-state extraction system, thereby helping to improve the purity of the final rare earth product.

[0078] The description of the washing solution in solvent extraction methods also applies to solid-liquid extraction methods, so it will not be repeated here.

[0079] During the back-extraction process, the back-extraction solution is collected. Adding the back-extraction solution can be stopped when the rare earth element content in the solution falls below 0.01 g / L. The solid-state extraction system after back-extraction can be recycled and reused to extract and separate rare earth elements from rare earth feed solutions containing rare earth elements and aluminum.

[0080] The description of the back-extraction solution in solvent extraction methods also applies to solid-liquid extraction methods, so it will not be repeated here.

[0081] the term In this invention, "separation of rare earth and aluminum" refers to separating rare earth elements from aluminum elements through extraction.

[0082] In this invention, rare earth elements refer to lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and yttrium, of which heavy rare earth elements refer to holmium, erbium, thulium, ytterbium, and lutetium.

[0083] The term C used in this invention 1-18 Alkyl or alkoxy refers to a straight-chain or branched alkyl or alkoxy group having 1 to 18 carbon atoms, such as straight-chain or branched alkyl groups having 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 carbon atoms. It includes, without limitation, methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, isobutyl, n-pentyl, neopentyl, isopentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, etc. 1-14 Alkyl, C 1-12 Alkyl, C 1-10 Alkyl, C 1-6 Alkyl, C 1-4 Alkyl, C 2-9 Alkyl, C 2-8 Alkyl, C 4-12 Alkyl, C 6-10 Alkyl, C 6-9 The meanings of alkyl groups, etc., follow the same logic.

[0084] In this invention, "alkylamino" refers to an R-NH- group, where R is an alkyl group as described above.

[0085] In this invention, "alkoxy" refers to an RO- group, where R is an alkyl group as described above. This invention is not limited in scope to the specific embodiments described herein, which are merely illustrative. Functionally equivalent methods are clearly within the scope of the disclosure herein.

[0086] Unless otherwise stated, numerical values ​​in this invention represent approximate measures or limitations on the range of embodiments including minute deviations from a given value and having approximately the mentioned value as well as having the mentioned precise value. Except in the detailed description of the final embodiments, all numerical values ​​of parameters (e.g., quantities or conditions) in this application (including the appended claims) should in all cases be understood to be modified by the term "approximately," regardless of whether "approximately" actually appears before the numerical value. "Approximately" indicates that the stated numerical value allows for slight inaccuracies (some close to precision at that value; approximately or reasonably close to the value; approximate). If the inaccuracy provided by "approximately" is not understood in this general sense in the art, then "approximately" as used herein at least indicates a variation that can be produced by common methods of measuring and using these parameters. For example, "approximately" can include variations of less than or equal to 15%, less than or equal to 10%, less than or equal to 5%, less than or equal to 4%, less than or equal to 3%, less than or equal to 2%, less than or equal to 1%, less than or equal to 0.5%, less than or equal to 0.1%, and in some respects, less than or equal to 0.01%.

[0087] The present invention has been described in detail above, but the present invention is not limited to the above content.

[0088] Beneficial effects The mixed extractant used in this invention can selectively extract rare earth elements from acidic rare earth solutions containing aluminum, leaving aluminum in the raffinate, thus achieving the separation of rare earth elements and aluminum. Based on aminophosphonic acid compounds, the mixed extractant of this invention improves the extraction effect on light and medium rare earth elements, achieving rare earth enrichment. The liquid-phase extraction system of this invention is simple to prepare and requires no addition of phase modifiers / auxiliaries such as fatty alcohols or TBP before use. The mixed extractant of this invention is suitable for solutions with different aluminum concentrations, exhibits no emulsification, demonstrates good extraction, and has a clear phase interface. Therefore, the mixed extractant of this invention has high industrial application value in the separation of rare earth elements and aluminum. Detailed Implementation

[0089] To further illustrate the present invention, specific embodiments are provided to help those skilled in the art understand and implement the invention; however, the invention is not limited to these embodiments.

[0090] Reagents and sources: (1) The aminophosphonic acid compounds and phosphonohydroxyacetic acid compounds were prepared according to the methods in CN109097570B and ZL202110535569.8.

[0091] (2) The reagents such as n-heptane and sulfonated kerosene were purchased from Aladdin Reagent Co., Ltd.

[0092] (3) The aluminum-containing rare earth solution is prepared as follows: Lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium and aluminum hydrochloride salts are prepared into a mixed aqueous solution with a concentration of 0.001 mol / L for each metal ion and a total concentration of 0.016 mol / L. The pH is adjusted to 2 with hydrochloric acid and sodium hydroxide.

[0093] (4) Other reagents (such as acids, bases, etc.) are all commercially available analytical grade reagents.

[0094] The concentrations of rare earth ions were determined using ICP-OES (instrument model: Optical-8000, manufacturer: Perkin Elmer).

[0095] The structures of the extractants used in the examples and comparative examples are shown in Table 1.

[0096] Table 1

[0097] Extraction rate E % and the separation factor between rare earth elements (RE) and aluminum (Al) β RE / Al The calculation formula is as follows:

[0098]

[0099]

[0100] Among them, [M] (a, ini) Represents the initial concentration of rare earth ions in the feed solution before extraction, in mg / L; [M] (a) and [M] (o) These represent the rare earth ion concentrations in the equilibrium aqueous phase and the equilibrium organic phase, respectively, in mg / L.

[0101] Examples 1-4 and Comparative Examples 1-4 Organic phase: Following the extractant composition in Table 2 and controlling the total concentration of the extractant based on the total volume of the extraction system to be 0.08 mol / L, extractants HA1, HA2, HA3, HA4, and HB1 were mixed with n-heptane as a diluent to prepare a series of extraction systems as the organic phase. The molar fraction of HB1 (X...) HB1 () refers to the fraction of the total number of moles of extractant HB1 out of the total number of moles of extractant.

[0102] The organic phase and the feed liquid were mixed at a volume ratio of 1:1, and single-stage extraction was carried out at room temperature for 15 minutes.

[0103] After extraction, the extraction rates E% and separation coefficients β of rare earth ions (RE) and aluminum ions (Al) were calculated. RE / Al The results of Examples 1-4 are shown in Tables 3-6. The results of Comparative Examples 1-5 are shown in Table 7. In all examples and comparative examples, phase separation was rapid and the phase interfaces were clear during the extraction process.

[0104] Table 2. Composition of extractants and HB1 mole fraction used in Examples 1-4 and Comparative Examples 1-5

[0105] Table 3. Extraction and separation results of rare earth elements and aluminum in Example 1

[0106] Table 4. Extraction and separation results of rare earth elements and aluminum in Example 2.

[0107] Table 5. Extraction and separation results of rare earth elements and aluminum in Example 3.

[0108] Table 6. Extraction and separation results of rare earth elements and aluminum in Example 4.

[0109] Table 7 shows the extraction and separation results of rare earth elements and aluminum in Comparative Examples 1-5.

[0110] As shown in Table 7, the single aminophosphonic acid extractants HA1 to HA4 have slightly weaker extraction capabilities for light and medium rare earth elements such as La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Dy, resulting in low overall extraction efficiency for all rare earth elements. Furthermore, some single aminophosphonic acid extractants are prone to aluminum co-extraction, leading to aluminum entrainment during rare earth extraction. Tables 3-6 show that in Examples 1-4, which used a mixed extractant of aminophosphonic acid compound and phosphonoglycolic acid HB1, the extraction efficiency for light and medium rare earth elements was significantly improved, and the overall extraction efficiency for all rare earth elements was significantly enhanced. This was especially true when the molar fraction of phosphonoglycolic acid was high, where the improvement in overall rare earth extraction efficiency was more pronounced, effectively overcoming the limitation of poor extraction efficiency for light and medium rare earth elements by single aminophosphonic acid compound extractants. Moreover, the mixed extractant has weaker aluminum extraction performance, with some mixed extractants almost not extracting aluminum, effectively reducing aluminum entrainment during rare earth extraction. Overall, the mixed extractant composed of aminophosphonic acid compound and phosphonohydroxyacetic acid compound of the present invention has a better average separation coefficient for rare earth and aluminum than the single aminophosphonic acid extractant system, and is also better than the sum of the extraction effects of the two extractants used alone, showing a synergistic effect.

[0111] Examples 5-8 and Comparative Examples 6-10 Organic phase: Following the extractant composition in Table 8 and controlling the total concentration of the extractant based on the total volume of the extraction system to be 0.135 mol / L, extractants HA1, HA2, HA3, HA4, and HB2 were mixed with sulfonated kerosene as a diluent to prepare a series of extraction systems as the organic phase. The molar fraction of HB2 (X...) HB2 This refers to the fraction of the total number of moles of extractant HB2 out of the total number of moles of extractant. The extraction process and data calculations are the same as in Example 1.

[0112] The results of Examples 5-8 are shown in Tables 9-12. The results of Comparative Examples 6-10 are shown in Table 13. In all examples and comparative examples, phase separation was rapid and the phase interfaces were clear during the extraction process.

[0113] Table 8. Composition of extractants and HB2 mole fraction used in Examples 5-8 and Comparative Examples 6-10

[0114] Table 9. Extraction and separation results of rare earth elements and aluminum in Example 5

[0115] Table 10. Extraction and separation results of rare earth elements and aluminum in Example 6

[0116] Table 11 Results of extraction and separation of rare earth elements and aluminum in Example 7

[0117] Table 12 Results of extraction and separation of rare earth elements and aluminum in Example 8

[0118] Table 13 shows the extraction and separation results of rare earth elements and aluminum in Comparative Examples 6-10.

[0119] The results in Table 13 show that single aminophosphonic acid extractants HA1 to HA4 have slightly weaker extraction capabilities for light and medium rare earth elements such as La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Dy, resulting in low overall extraction efficiency for all rare earth elements. Furthermore, some single aminophosphonic acid extractants are prone to aluminum co-extraction, leading to aluminum entrainment during rare earth extraction. The results in Tables 9-12 show that in Examples 5-8, which used a mixed extractant of aminophosphonic acid compound and phosphonoglycolic acid HB2, the extraction efficiency for light and medium rare earth elements was significantly improved, and the overall extraction efficiency for all rare earth elements was significantly enhanced. This was especially true when the molar fraction of phosphonoglycolic acid was high, where the improvement in overall rare earth extraction efficiency was more pronounced, effectively overcoming the limitation of poor extraction efficiency for light and medium rare earth elements by single aminophosphonic acid compound extractants. Moreover, the mixed extractant has weaker aluminum extraction performance, with some mixed extractants almost not extracting aluminum, effectively reducing aluminum entrainment during rare earth extraction. Overall, the mixed extractant composed of aminophosphonic acid compound and phosphonohydroxyacetic acid compound of the present invention has a better average separation coefficient for rare earth and aluminum than the single aminophosphonic acid extractant system, and is also better than the sum of the extraction effects of the two extractants used alone, showing a synergistic effect.

[0120] In summary, the binary mixed extractant of the present invention has the dual advantages of improving the overall extraction efficiency of rare earth and enhancing the rare earth / aluminum separation effect, providing a practical and feasible technical path for the efficient extraction and separation of rare earth in ion adsorption type rare earth ore leachate.

[0121] The above description is a detailed description of the preferred embodiments of the present invention. However, the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modifications made under the technical spirit of the present invention should fall within the patent scope covered by the present invention.

Claims

1. The use of a mixed extractant comprising an aminophosphonic acid compound of Formula I or a salt thereof and a phosphonohydroxyacetic acid compound of Formula II or a salt thereof for the extraction and separation of rare earth elements from aluminum-containing rare earth feed solutions: (AND) (II) in, R1 is selected from C 1-14 alkyl; R2 and R3 are each independently selected from C 1-10 Alkyl and hydrogen; R4 and R5 are each independently selected from C 1-16 Alkyl and hydrogen; R6 and R7 are each independently selected from C 1-14 Alkyl or alkoxy groups, and the total number of carbon atoms in R6 and R7 is 10 or greater; R8 is selected from C 1-8 Alkyl, C 3-10 Alicyclic alkyl groups and C 6-10 Aryl.

2. The use according to claim 1, wherein, In formula I, R1 is selected from C 2-14 Alkyl, preferably C 4-10 Alkyl, more preferably C 5-9 Alkyl groups; and / or R2 and R3 are selected from C 1-8 Alkyl and hydrogen, preferably C 1-5 Alkyl and hydrogen, more preferably C 1-3 Alkyl and hydrogen; and / or R4 and R5 are selected from C 1-10 Alkyl, preferably C 1-8 Alkyl group; preferably, the total number of carbon atoms in R4 and R5 is an integer between 8 and 20, more preferably an integer between 12 and 17; and / or The total number of carbon atoms in R1, R2, R3, R4, and R5 is 2 to 40, preferably 10 to 26. Preferably, the aminophosphonic acid compound represented by Formula I is selected from one or more of the following compounds:

3. The use according to claim 1, wherein, In formula II, R6 and R7 are each independently selected from C 2-14 Alkyl or alkoxy, more preferably C 4-12 Alkyl or alkoxy; preferably, R6 and R7 are the same and selected from C 5-12 Alkyl or alkoxy; preferably, the total number of carbon atoms in R6 and R7 is an integer between 10 and 24, more preferably an integer between 12 and 20; and / or R8 is selected from C 1-6 Alkyl, C 3-8 Alicyclic alkyl groups and C 6-10 Aryl group, preferably selected from C 1-4 Alkyl, C 3-6 Alicyclic alkyl groups, C 6-8 aryl; and / or The total number of carbon atoms in R6, R7, and R8 is 10 to 38, preferably 11 to 34, and more preferably 14 to 30. Preferably, the phosphonohydroxyacetic acid compound of formula II is selected from one or more of the following compounds:

4. The use according to claim 1, wherein, In the mixed extractant, the molar ratio of the aminophosphonic acid compound or its salt represented by Formula I to the phosphonohydroxyacetic acid compound or its salt represented by Formula II is 1:9 to 9:1, preferably 2:8 to 8:

2.

5. Use of the mixed extractant according to any one of claims 1-4 in the preparation of an extraction system for the extraction and separation of rare earth elements and aluminum.

6. A method for extracting and separating rare earth elements from a rare earth feed solution containing rare earth elements and aluminum, the method comprising the step of contacting the rare earth feed solution with a mixed extractant as described in any one of claims 1-4 to extract the rare earth elements, thereby separating the rare earth elements and aluminum.

7. The method according to claim 6, wherein, The method employs solvent extraction, comprising: contacting a liquid-phase extraction system containing the mixed extractant with a rare-earth feed liquid containing rare earth elements and aluminum to obtain an extract containing rare earth elements and an aluminum-containing extract residue; or The method employs a solid-liquid extraction approach, comprising: contacting a solid-phase extraction system containing the mixed extractant with a rare earth liquid containing rare earth and aluminum to extract a solid-phase extraction system containing rare earth and an aluminum-containing extraction residue.

8. The method according to claim 7, wherein, The liquid phase extraction system comprises: the mixed extractant and the diluent; The solid-phase extraction system is a resin, porous silica spheres, or diatomaceous earth loaded with the mixed extractant.

9. The method according to claim 7, wherein, In the liquid-phase extraction system, based on the volume of the liquid-phase extraction system, the concentration of the mixed extractant system is 0.0001~1.0 mol / L, preferably 0.01~0.5 mol / L; and / or The degree of saponification of the liquid phase extraction system is 10-90%, preferably 20-70%, and more preferably 25-35%.

10. The method of claim 6, wherein, In the aluminum-containing rare earth solution, the total concentration of rare earth elements is 0.0001~2 mol / L, the acidity of the solution, expressed as pH, is pH=0.5~3.5, and the concentration of aluminum is 0.0001~2 mol / L.

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