Mixed extraction agent based on phosphonoglycolic acid and application of mixed extraction agent

Abstract

The invention relates to a mixed extraction agent based on phosphonoglycolic acid and application thereof, in particular to a mixed extraction agent based on phosphonoglycolic acid, an extraction system containing the mixed extraction agent and a method for separating yttrium from heavy rare earth. The mixed extraction agent is composed of a first extraction agent of phosphonoglycolic acid as shown in a formula I and a second extraction agent selected from an acidic phosphine compound as shown in a formula II and an amino acid-containing phosphine compound as shown in a formula III. When the mixed extraction agent is used for extracting and separating yttrium and non-yttrium heavy rare earth ions, a good separation effect is achieved, and the mixed extraction agent has remarkable advantages in the aspect of separation of yttrium and non-yttrium heavy rare earth ions.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of separation of rare earth element yttrium, and particularly relates to a mixed extractant based on phosphonohydroxyacetic acid and its use, an extraction system comprising the same, and a method for separating yttrium from heavy rare earths. BACKGROUND

[0002] Ion-adsorbed rare earth ore is a unique resource of medium and heavy rare earths in China, wherein the average content of yttrium is about 35%, and the highest content is up to 70%. Therefore, the preferential separation of yttrium is an important link for efficient and economic smelting of ion-type rare earths.

[0003] Initially, rare earth separation plants mainly used naphthenic acid extractants to separate yttrium, but naphthenic acid has the defects of limited source, easy esterification, emulsification, and small separation coefficient of yttrium and light rare earths.

[0004] In view of the above problems, CN93112500.6 discloses an alkylphenoxyacetic acid extractant, which significantly improves the separation coefficient of yttrium and light rare earths, but still has the problems of easy esterification and emulsification, and a low separation coefficient of yttrium and heavy rare earths. CN99118261.8 discloses the use of a mixed system of secondary octylphenoxy-substituted acetic acid (CA12), monobasic phosphonic acid, and fatty alcohol to separate yttrium, which improves the separation coefficient of yttrium and heavy rare earths, but still requires the addition of fatty alcohol as a modifier, which causes esterification reactions, resulting in a decrease in the effective concentration of the extractant and a decrease in the extraction capacity. CN200410010737.8 uses TBP as an additive, which solves the esterification problem, but TBP has high water solubility and needs to be supplemented regularly, and has strong corrosiveness to PVC tanks. CN201710087507.9 develops an alkylphenoxy carboxylic acid extractant, but still does not solve the problems of a small separation coefficient of yttrium and heavy rare earths and poor extraction performance. CN202110535569.8 discloses a phosphonohydroxyacetic acid and its use and method for separating yttrium, which has a single component, a clear structure, does not require the addition of a phase modifier, has a high extraction equilibrium acidity, and does not cause esterification and emulsification, but has a small separation coefficient of yttrium and heavy rare earths.

[0005] The main components of the ion-type rare earth concentrate after grouping are heavy rare earths (holmium, erbium, thulium, ytterbium, lutetium, and yttrium), and the content of yttrium is 80-90%. Therefore, it is of great significance to develop an extraction system with a large separation coefficient of yttrium and heavy rare earths, without the addition of a phase modifier, and good extraction performance for the efficient, preferential, and sustainable separation of yttrium from ion-type rare earth concentrates. SUMMARY

[0006] The inventors of the present application have developed a method for separating yttrium from non-yttrium rare earth elements using phosphonohydroxycarboxylic acid or a salt thereof, and have successively filed invention patent applications CN202110535569.8 and CN202210393441.7 thereon. Although it is mentioned in the applications that an auxiliary extractant such as an acidic phospho(phosphonic) acid ester or a salt thereof can be added to the phosphonohydroxyacetic acid extraction system to enhance the extraction performance of the phosphonohydroxyacetic acid extractant for non-yttrium rare earth elements, no examples are given, so it is difficult to confirm whether the auxiliary extractant can enhance the extraction performance of the phosphonohydroxyacetic acid extractant for non-yttrium rare earth elements and for which non-yttrium rare earth elements the separation performance from yttrium can be enhanced.

[0007] In recent experiments, the inventors used a binary mixed system composed of phosphonohydroxyacetic acid extractant and a partially acidic phosphonic extractant or an amino-containing acidic phosphonic extractant to extract and separate yttrium from non-yttrium heavy rare earth ions such as holmium, erbium, thulium, ytterbium, and lutetium, and achieved good separation results, thereby completing the present application.

[0008] A significant feature of the present application is that the binary mixed system composed of phosphonohydroxyacetic acid extractant and a partially acidic phosphonic extractant or an amino-containing acidic phosphonic extractant significantly improves the separation effect of yttrium from non-yttrium heavy rare earth elements, is superior to the phosphonohydroxyacetic acid extractant single system, and greatly improves the separation coefficient of yttrium from non-yttrium heavy rare earth elements. Compared with P507, Cyanex272, and other extractants, the mixed extraction system of the present application has the weakest extraction ability for yttrium, can preferentially extract non-yttrium elements in heavy rare earth elements, and thereby separates yttrium from non-yttrium heavy rare earth elements. Therefore, the present application has a significant advantage in the separation of yttrium from non-yttrium heavy rare earth elements.

[0009] An object of the present application is to provide a mixed extractant based on phosphonohydroxyacetic acid extractant.

[0010] Another object of the present application is to provide an extraction system comprising the above-mentioned mixed extractant.

[0011] Another object of the present application is to provide the use of the above-mentioned mixed extractant for separating yttrium from non-yttrium heavy rare earth elements.

[0012] Still another object of the present application is to provide a method for separating yttrium from non-yttrium heavy rare earth elements using the above-mentioned mixed extractant.

[0013] (I) Mixed extractant

[0014] In a first aspect, the present application provides a mixed extractant composed of a first extractant and a second extractant, wherein,

[0015] The first extractant is selected from phosphonohydroxyacetic acid represented by formula I:

[0016]

[0017] wherein,

[0018] R1and R2are each independently selected from C 1-14 alkyl or alkoxy, and the total number of carbon atoms of R1and R2is 10 or more;

[0019] R3is selected from H, C 1-8 alkyl, C 3-10 cycloalkyl, and C 6-10 aryl;

[0020] the second extractant is selected from an acidic phosphine compound represented by Formula II and an amino-containing acidic phosphine compound represented by Formula III,

[0021]

[0022] wherein,

[0023] R4and R5are each independently selected from C 1-14 alkyl or alkoxy, and the total number of carbon atoms of R1and R2is 10 or more;

[0024] R6is selected from C 1-12 alkyl;

[0025] R7and R8are independently selected from hydrogen, C 1-10 alkyl, C 3-10 cycloalkyl, and C 6-12 aryl;

[0026] R9and R 10 are independently selected from hydrogen, C 1-12 alkyl.

[0027] The compounds of Formulae I, II and III are described in detail below, respectively.

[0028] (1) a phosphinyl hydroxy acetic acid represented by Formula I

[0029] In embodiments, R1and R2are each independently selected from C 2-14 alkyl or alkoxy, more preferably C 4-12 alkyl or alkoxy.

[0030] Preferably, R1and R2are the same and selected from C 5-12 alkyl or alkoxy, preferably C 6-10 alkyl or alkoxy.

[0031] Preferably, the total number of carbon atoms of R1and R2is an integer between 10 and 24, preferably an integer between 12 and 20, such as 13, 14, 15, 16, 17, 18, 19, etc.

[0032] In embodiments, R3is selected from H, C1-6 alkyl, C 3-8 cycloalkyl and C 6-10 aryl, preferably selected from H, C 1-4 alkyl, C3 -6 cycloalkyl, C 6-8 aryl, more preferably methyl or ethyl.

[0033] Preferably, the total number of carbon atoms of R1, R2, R3 is an integer between 10 and 38, preferably an integer between 11 and 34, more preferably an integer between 14 and 30, for example 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, etc.

[0034] Preferably, the phosphonooxyacetic acid of formula I is selected from di(2- ethylhexyloxy)phosphonooxyacetic acid, 2-(di(2-ethylhexyloxy)phosphono)-2- hydroxypropanoic acid and mixtures of the above extractants in any proportion.

[0035] The phosphonooxyacetic acid of formula I can be commercially available or synthesized according to the methods disclosed in CN202110535569.8 and CN202210393441.7.

[0036] (2) acidic phosphine compound of formula II

[0037] In embodiments, R4 and R5 are each independently selected from C 4-14 alkyl or alkoxy, more preferably each independently selected from C 6-12 alkyl or alkoxy, more preferably each independently selected from C 6-10 alkyl or alkoxy.

[0038] Preferably, R4 and R5 are the same and selected from C 6-12 alkyl or alkoxy, preferably C 6-10 alkyl or alkoxy.

[0039] Preferably, the total number of carbon atoms of R4 and R5 is an integer between 10 and 24, preferably an integer between 12 and 20, for example 13, 14, 15, 16, 17, 18, 19, etc.

[0040] Preferably, the acidic phosphine compound of formula II can be selected from di(2- ethylhexyl)phosphoric acid (P204), 2-ethylhexylphosphonic acid mono-2- ethylhexyl ester (P507), di(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272), di(2- ethylhexyl)phosphinic acid (P227) and mixtures of the above extractants in any proportion.

[0041]

[0042] The acidic phosphine compound shown in formula II can be commercially available or synthesized according to the method disclosed in reference (Xu Guangxian, Yuan Chengye. Solvent extraction of rare earth. Beijing: Science Press, 1987.) and CN102690286A.

[0043] (3) The amino-containing acidic phosphine compound shown in formula III

[0044] In embodiments, R6 is selected from C 4-12 alkyl, more preferably C 5-10 alkyl, most preferably C 6-9 alkyl.

[0045] R7 and R8 are independently selected from hydrogen, C 1-4 alkyl, C 5-7 cycloalkyl and C 6-10 aryl; more preferably selected from hydrogen, methyl, ethyl;

[0046] R9 and R 10 are independently selected from hydrogen, C 4-12 alkyl, preferably selected from hydrogen, C 5-10 alkyl, more preferably selected from hydrogen, C 6-10 alkyl.

[0047] The amino-containing acidic phosphine compound shown in formula III can be selected from 2-ethylhexylaminomethylphosphonic acid mono 2-ethylhexyl ester (HEHAMP), bis(2-ethylhexyl) aminomethylphosphonic acid mono-2-ethylhexyl ester (HEDEAP) and a mixture of the above extractants mixed in any proportion.

[0048] The amino-containing acidic phosphine compound shown in formula III can be commercially available or synthesized according to the method disclosed in CN201811119533.6.

[0049] In embodiments, in the mixed extractant according to the present application, the molar fraction of the first extractant is 0.5-0.9, preferably 0.6-0.8, for example 0.60, 0.65, 0.70, 0.75, 0.80, etc., based on 1 mol of the total amount of the first extractant and the second extractant. Within the above range of proportions, the technical effect of more efficiently separating yttrium from heavy rare earth elements can be achieved. If the molar fraction of the first extractant is too small, the mixed system cannot preferentially extract non-yttrium elements in heavy rare earth elements; if it is too large, the separation coefficient of non-yttrium elements and yttrium will not be significantly improved.

[0050] (ii) Use

[0051] It can be known through experiments that the average separation coefficient of non-yttrium heavy rare earth elements and yttrium of the extraction system prepared using the mixed extractant according to the present application is better than that of a single phosphonooxyacetic acid extractant system, and the separation coefficient of heavy rare earth elements such as thulium, ytterbium and lutetium from yttrium is greatly improved.

[0052] Accordingly, the second aspect of the present application provides the use of the mixed extractant according to the present application as an extractant for separating yttrium from non-yttrium heavy rare earths, in particular for extractive separation of yttrium from non-yttrium heavy rare earths selected from the group consisting of thulium, ytterbium, lutetium. In other words, the present application provides the use of the mixed extractant according to the present application as an extractant in the preparation of an extractive system for extractive separation of yttrium from non-yttrium heavy rare earths, in particular for extractive separation of yttrium from non-yttrium heavy rare earths selected from the group consisting of thulium, ytterbium, lutetium.

[0053] (III) Extractive system

[0054] In a third aspect, the present application provides an extractive system comprising the mixed extractant according to the present application as an extractant. The extractive system can also be referred to as an extractive composition.

[0055] The extractive system can be a liquid phase or a solid phase extractive system. The liquid phase extractive system can be prepared by mixing the mixed extractant according to the present application with a diluent and, optionally, a phase modifier; while the solid phase extractive system can be prepared by loading the mixed extractant according to the present application on a suitable solid support such as a liquid ion exchange resin, a zeolite, an alumina, etc., but not limited thereto.

[0056] In some embodiments, the extractive system according to the present application is a liquid phase extractive system, comprising, or consisting essentially of, the following components:

[0057] (1) the mixed extractant according to the present application as an extractant, and

[0058] (2) a diluent.

[0059] In some embodiments, the diluent can be selected from the group consisting of: C 5-16 alkanes such as pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, etc.; aviation kerosene; sulfonated kerosene, liquid paraffin such as 250-400 °C light lubricating oil fraction, etc.; C 5-16 cycloalkanes such as cyclopentane, C 1-4 alkyl-substituted cyclopentane, cyclohexane, C 1-4 alkyl-substituted cyclohexane, decalin, etc.; C 6-10 aromatic hydrocarbons such as benzene, toluene, xylene (including o-, m-, p-xylene and mixed xylene), etc. Preferably, the diluent can be one or more selected from the group consisting of aviation kerosene, sulfonated kerosene, heptane and xylene. However, the present application is not limited thereto.

[0060] In the extraction system, the concentration of the extractant (i.e., the total concentration of the first and second extractants) can be 0.0001 to 1.0 mol / L, preferably 0.01 to 0.5 mol / L, for example, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45 mol / L, based on the total volume of the liquid phase extraction system.

[0061] A phase modifier can also be contained in the liquid phase extraction system. The phase modifier mainly functions to improve the extraction physical phenomenon, and can be one or more selected from the group consisting of C 4-12 alkyl alcohols and tributyl phosphate, di(2-ethylhexyl) (2-ethylhexyl) phosphonate, di(2-ethylhexyl) [(2-ethylhexyl) amino] methylene phosphonate, preferably one or more selected from the group consisting of n-octanol, iso-octanol, 2-methylheptanol, a mixed alcohol of the above three alcohols in any ratio, and tributyl phosphate. However, the present application is not limited thereto.

[0062] In some embodiments, the liquid phase extraction system is prepared by mixing the first extractant with the second extractant and the diluent, but the present application is not limited thereto.

[0063] (iv) Extraction method

[0064] The fourth aspect of the present application relates to a method for extracting and separating yttrium from non-yttrium heavy rare earth elements, the method comprising:

[0065] (1) adjusting the saponification degree of the extraction system according to the present application to 10 to 90%;

[0066] (2) contacting a feed solution containing yttrium and non-yttrium heavy rare earth elements with the saponified extraction system to obtain an extraction system containing non-yttrium heavy rare earth elements and a raffinate containing yttrium.

[0067] In the method according to the present application, the extraction system according to the present application has different extraction rates and distribution ratios for yttrium and non-yttrium heavy rare earth elements when extracting the heavy rare earth elements, and in particular, the extraction rate and distribution ratio for non-yttrium heavy rare earth elements are significantly greater than the extraction rate and distribution ratio for yttrium, so that non-yttrium heavy rare earth elements are preferably extracted and yttrium is left in the raffinate during extraction, thereby allowing the separation of yttrium from non-yttrium heavy rare earth elements by extraction.

[0068] In the method of the present application, the extraction system is preferably a liquid phase extraction system. Since the liquid phase extraction system is mainly composed of organic substances, it is sometimes referred to as an organic phase during extraction, and the feed solution containing yttrium and non-yttrium heavy rare earth elements is an aqueous solution, so it is sometimes referred to as an aqueous phase during extraction.

[0069] The saponification degree represents the degree of salt formation of the extractant (including phosphonoyl glycolic acid of formula I, acidic phosphine compound of formula II, amino-containing acidic phosphine compound of formula III) in the liquid phase extraction system, expressed in mole percentage, refers to the amount of salted acidic extractant accounting for the total extractant can be calculated as follows:

[0070] Saponification degree % = molar amount of salted acidic extractant / molar amount of total acidic extractant x 100%.

[0071] The saponification degree of the extraction system is preferably 20-85%, more preferably 40-75%, for example 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, etc. Within the above saponification degree range, the technical effect of more efficiently separating yttrium from heavy rare earth elements can be achieved. If the saponification degree is too low, the extraction rate of rare earth ions is low and separation cannot be achieved; if the saponification degree is too high, the extraction rates of yttrium and non-yttrium heavy rare earth elements are both too high, and separation cannot be achieved. Since the extraction reaction mechanism is cation exchange mechanism, if the saponification process is not carried out, during the extraction reaction process, the rare earth ions are extracted into the organic phase, and the hydrogen ions are replaced into the aqueous phase, thereby increasing the acidity of the aqueous phase and affecting the subsequent extraction reaction. Therefore, it is preferred to adjust the acidic extractant extraction system to a suitable saponification degree before extraction.

[0072] There is no special limitation to the method for adjusting the saponification degree. For example, the saponification treatment can be carried out by adding a saponification agent to the extraction system. The saponification agent can be selected from ammonia, ammonium carbonate, ammonium bicarbonate, soluble carbonates, bicarbonates and hydroxides of alkali metals or alkaline earth metals, etc., such as sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, magnesium bicarbonate, calcium bicarbonate, sodium hydroxide, potassium hydroxide, etc., preferably ammonia or sodium hydroxide. In some embodiments, the saponification agent can be formulated in the form of an aqueous solution for use. The extractant can be reacted with the saponification agent as needed to obtain a suitable saponification degree.

[0073] The non-yttrium heavy rare earth is one or more or all selected from holmium, erbium, thulium, ytterbium, lutetium, in particular one or more or all selected from thulium, ytterbium, lutetium. That is, the yttrium-containing and non-yttrium heavy rare earth-containing feed liquid comprises yttrium and one or more or all selected from holmium, erbium, thulium, ytterbium, lutetium.

[0074] In embodiments, the yttrium-containing and non-yttrium heavy rare earth-containing feed solution does not contain other rare earth elements other than heavy rare earth elements. Here, "does not contain" means substantially does not contain, i.e., does not contain other rare earth elements other than impurity content. For example, the yttrium-containing and non-yttrium heavy rare earth-containing feed solution can be obtained by first separating light, medium, and heavy rare earth elements from a rare earth feed solution to obtain a feed solution containing mainly heavy rare earth elements, wherein only residual amounts of light and medium rare earth elements are contained. The method for separating light, medium, and heavy rare earth elements from the rare earth feed solution can use any suitable method, such as the methods disclosed in CN103122410A, CN107922997B, J. Rare Earths. 27, 830-833; Chem. Eng. J. 119 (2006) 167-174; Sep. Purif. Technol. 75, 295-302; J Chem Technol Biotechnol 81:755-760 (2006); Sep. Sci. Technol. 47 (2012) 1-7; Chin Rare Earths 23:69-70 (2002); Sep Sci Technol 42:2315-2325 (2007); Anal Chim Acta 533:83-88 (2005), etc., as long as a feed solution containing mainly heavy rare earth elements can be obtained.

[0075] In the yttrium-containing and non-yttrium heavy rare earth-containing feed solution, both yttrium and non-yttrium heavy rare earth elements are in the form of trivalent ions.

[0076] Preferably, in the yttrium-containing and non-yttrium heavy rare earth-containing feed solution, the total concentration of rare earth ions is 0.05-1.5 mol / L, such as 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4 mol / L.

[0077] Preferably, the initial pH value of the feed solution is 0.5-4, preferably 1.5-3.0, such as 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, etc. Within the above pH range, a technical effect of more efficiently separating yttrium from heavy rare earth elements can be achieved. If the pH is too low, the extraction rate of rare earth ions is low and separation cannot be achieved; if the pH is too high, precipitation may occur during extraction, resulting in poor phase separation and high extraction rates of both yttrium and non-yttrium heavy rare earth elements, which also cannot achieve separation.

[0078] Beneficial effects

[0079] The beneficial effects achieved by one or more technical solutions of the present application can be one or more of the following:

[0080] (1) The mixed extractant system of the present application has obvious synergistic effect on non-yttrium heavy rare earth, effectively improving the separation coefficient of phosphono hydroxyacetic acid extractant for non-yttrium heavy rare earth and yttrium.

[0081] (2) Compared with non-yttrium heavy rare earth elements, the mixed extractant system of the present application has the weakest extraction ability for yttrium, can preferentially extract non-yttrium elements in heavy rare earth elements, thereby effectively realizing the separation of non-yttrium heavy rare earth elements and yttrium.

[0082] (3) The mixed extractant system of the present application has simple preparation process, and even does not need to add fatty alcohols or TBP and the like phase modifiers / auxiliaries.

[0083] (4) The mixed extractant system of the present application has high extraction equilibrium acidity, no emulsification phenomenon, good extraction phenomenon, and clear phase interface.

[0084] Therefore, the mixed extractant system of the present application has high industrial application value in the separation of yttrium and heavy rare earth.

[0085] Terms

[0086] In the present application, "separation of yttrium and non-yttrium heavy rare earth" refers to separating yttrium (i.e. trivalent yttrium (III) or trivalent yttrium ion Y 3+ ) from non-yttrium heavy rare earth ions (trivalent non-yttrium heavy rare earth ions (Ln 3+ )) by extraction.

[0087] In the present application, non-yttrium heavy rare earth elements refer to holmium, erbium, thulium, ytterbium and lutetium, in particular thulium, ytterbium and lutetium.

[0088] The term "C 1-14 alkyl or alkoxy" used in the present application refers to a straight-chain or branched-chain alkyl or alkoxy group having 1 to 14 carbon atoms, for example a straight-chain or branched-chain alkyl group having 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14 carbon atoms. C 1-12 alkyl, C 1-10 alkyl, C 1-8 alkyl, C 2-14 alkyl or alkoxy, C 4-14 alkyl or alkoxy, C 4-12 alkyl or alkoxy, C 5-12 alkyl or alkoxy, C 5-10 alkyl, C 6-12 alkyl or alkoxy, C 6-10 alkyl or alkoxy, C 6-9 alkyl, C 1-6The meanings of alkyl and the like are analogous. The alkyl group is, for example, propyl (including n-propyl, isopropyl), butyl (for example, n-butyl, sec-butyl, t-butyl), pentyl (for example, n-pentyl, sec-pentyl, t-pentyl, neopentyl, and the like), hexyl (for example, n-hexyl, isohexyl, sec-hexyl, and the like), heptyl (for example, n-heptyl, isoheptyl, sec-heptyl, and the like), octyl (for example, n-octyl, sec-octyl, iso-octyl, 2-ethylhexyl, and the like), nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, and the like. The alkoxy group is, for example, propoxy (including n-propoxy, isopropoxy), butoxy (for example, n-butoxy, sec-butoxy, t-butoxy), pentoxy (for example, n-pentoxy, sec-pentoxy, t-pentoxy, neopentoxy, and the like), hexyloxy (for example, n-hexyloxy, isohexyloxy, sec-hexyloxy, and the like), heptyloxy (for example, n-heptyloxy, isoheptyloxy, sec-heptyloxy, and the like), octyloxy (for example, n-octyloxy, sec-octyloxy, iso-octyloxy, 2-ethylhexyloxy, and the like), nonyloxy, decyloxy, undecyloxy, dodecyloxy, tridecyloxy, tetradecyloxy, and the like.

[0089] The term C 3-10 Cycloalkyl refers to a saturated cyclic alkyl group having 3 to 10 carbon atoms, including the number of carbon atoms of the substituents, which can be monocyclic or bicyclic, such as cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, decalin, and the like, which can be substituted with a substituent selected from the group consisting of C 1-4 Cycloalkyl, C3 3-8 Cycloalkyl, C3 -6 Cycloalkyl, C 5-7 The meanings of cycloalkyl are analogous.

[0090] The term C 6-12 Aryl refers to an aromatic group having 6 to 12 carbon atoms, including the number of carbon atoms of the substituents, such as phenyl, naphthyl, and the like, which can be substituted with one or more substituents selected from the group consisting of C 1-4 Phenyl substituted with one or more substituents selected from the group consisting of C 6-10 Aryl, C 6-8 The meanings of aryl are analogous.

[0091] The term C 5-16 Alkane refers to a straight-chain or branched alkane having 5 to 16 carbon atoms, i.e., a straight-chain or branched alkane having 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 carbon atoms, such as pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, and the like.

[0092] The term C 5-16Cycloalkane refers to a saturated cyclic alkane containing 5 to 16 carbon atoms including the number of carbon atoms in the substituents, which can be monocyclic or bicyclic, for example, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, decalin, and the like, which can be substituted with one or more substituents selected from C 1-4 one or more substituents of alkyl.

[0093] The term C 6-10 Aryl refers to an aromatic hydrocarbon containing 6 to 10 carbon atoms including the number of carbon atoms in the substituents, for example, benzene and benzene substituted with one or more substituents of alkyl, for example, benzene, toluene, xylene, and the like. 1-4 Aryl refers to an aromatic hydrocarbon containing 6 to 10 carbon atoms including the number of carbon atoms in the substituents, for example, benzene and benzene substituted with one or more substituents of alkyl, for example, benzene, toluene, xylene, and the like.

[0094] The term "C 6-10 Aryl refers to an aromatic hydrocarbon containing 6 to 10 carbon atoms including the number of carbon atoms in the substituents, for example, benzene and benzene substituted with one or more substituents of alkyl, for example, benzene, toluene, xylene, and the like. 1-4 Aryl refers to an aromatic hydrocarbon containing 6 to 10 carbon atoms including the number of carbon atoms in the substituents, for example, benzene and benzene substituted with one or more substituents of alkyl, for example, benzene, toluene, xylene, and the like.

[0095] The term C 4-12 Alkanol refers to a straight chain or branched chain alkanol containing 4 to 12 carbon atoms, for example, a straight chain or branched chain alkanol having 4, 5, 6, 7, 8, 9, 10, or 11 carbon atoms, including, without limitation, n-butanol, t-butanol, isobutanol, n-pentanol, neopentyl alcohol, isoamyl alcohol, hexanol, heptanol, octanol, nonanol, decanol, and the like.

[0096] Unless otherwise indicated, the numerical values in the present application are approximate which means that the numerical values set forth herein are intended to consist of the number recited plus or minus a variance to account for slight experimental error, to account for about the value recited, and to account for the value recited with the precision indicated. Except in the last example of the detailed description, all numerical values of parameters (e.g., of quantities or conditions) in this application file (including the claims) are to be construed as approximately recited, even if an exact numerical value is stated. Approximately means that the stated numerical value allows for slight inaccuracy (some approximation to the value; about or reasonably close to the value; approximate). If the inaccuracy provided by "about" is not understood in the art to have this ordinary meaning, then "about" as used herein means at least the variation that can be produced by the ordinary methods of measurement and use of the parameters. For example, "about" can include a variation 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 certain aspects, less than or equal to 0.01%.

[0097] The application has been described in detail above, but the above-described embodiments are merely illustrative in nature and are not intended to limit the application. Furthermore, the present disclosure is not limited by any theory of the prior art or the summary or the description of the following examples. DETAILED DESCRIPTION

[0098] The technical solutions of the present application will be described clearly and completely below in conjunction with the embodiments of the present application. The specific embodiments of the present application are provided to help those skilled in the art to understand and implement the present application, but the described embodiments are only a part of the embodiments of the present application, not all the embodiments, so the present application is not limited to these embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0099] Embodiments

[0100] Reagents and sources

[0101] Di(2-ethylhexyloxy)phosphinyl hydroxyacetic acid and 2-(di-(2-ethylhexyloxy)phosphinyl)-2-hydroxypropanoic acid were prepared according to the methods in CN202110535569.8 and CN202210393441.7, respectively.

[0102] P507, Cyanex272, sulfonated kerosene and aviation kerosene were purchased from Shanghai Liayishihua Chemical Co., Ltd.

[0103] 2-Ethylhexylaminomethylphosphonic acid mono-2-ethylhexyl ester (HEHAMP) and di(2-ethylhexyl) aminomethylphosphonic acid mono-2-ethylhexyl ester (HEDEAP) were prepared according to the method in CN201811119533.6.

[0104] Other reagents (such as acids, bases, etc.) are commercially available analytical reagents.

[0105] The metal ion concentration in the aqueous phase before and after extraction was determined by ICP-OES (Analytik Jena PQ9000).

[0106] The structures of the extractants in the examples are shown in Table 1.

[0107] Table 1 Structure of each extractant in the examples

[0108]

[0109]

[0110] The distribution ratio D and the separation coefficient β of heavy rare earth (Ln) and yttrium of each example Ln / Y The calculation formula is as follows:

[0111]

[0112] wherein [M] org and [M] aq represent the content of the extracted metal in the organic phase and in the aqueous phase at the extraction equilibrium, respectively.

[0113] The preliminary experimental results confirm that the optimal extraction conditions for the extraction and separation of yttrium from the above rare earth feed solution are different for the extraction systems prepared with different extractants, i.e. the initial feed solution pH and the saponification degree of the organic phase for achieving the optimal extraction and separation effect are different. Therefore, in order to more clearly show the advantages of the extraction system according to the present application over the existing extraction systems, the following examples are based on the better or optimal extraction conditions of each extraction system for the separation of yttrium from the rare earth feed solution.

[0114] Examples 1-8

[0115] Preparation of the rare earth feed solution:

[0116] A rare earth chloride solution containing trivalent ions of holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu) or yttrium (Y) was mixed, diluted with distilled water, and adjusted to the initial pH shown in Table 2 with dilute hydrochloric acid and sodium hydroxide to prepare a yttrium-containing rare earth feed solution with a concentration of 0.001 mol / L for each rare earth.

[0117] Preparation of the organic phase:

[0118] HA or HB as the first extractant and P507, Cyanex 272, HEHAMP or HEDEAP as the second extractant were mixed according to the predetermined molar fraction (based on the total moles of the first extractant and the second extractant) in Table 2, and then an appropriate amount of 5 mol / L sodium hydroxide was added according to the predetermined saponification degree in Table 2, and saponification was carried out at 25°C for 5 min with stirring to obtain the organic phase, wherein the total concentration of the first extractant and the second extractant was 0.05 mol / L based on the total volume of the organic phase.

[0119] Extraction:

[0120] The organic phase 5 mL and the rare earth feed solution 5 mL were mixed at room temperature, and single-stage extraction was carried out for 15 min. The concentration of rare earth ions in the aqueous phase before and after extraction was tested, and the separation coefficient β Ho / Y of non-yttrium heavy rare earth ions holmium (Ho) and yttrium ions (Y) was calculated.

[0121] The extractant composition, saponification degree, initial pH of the rare earth feed solution and test results are shown in Table 2.

[0122] Table 2: Extractant composition, molar fraction of HA or HB, degree of saponification, initial pH of the feed solution and test results in Examples 1-8

[0123]

[0124] The test results in Table 2 demonstrate that in the extraction system according to the present application, when the molar fraction of the first extractant (e.g. HA or HB) (the percentage of the molar fraction of the first extractant based on the total molar amount of the first extractant and the second extractant) is low (e.g. less than 0.5, specifically 0.4 or 0.2), the separation factor β Ho / Y is about 1.0 or less, so that when the rare earth feed solution containing holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu) and yttrium (Y) trivalent ions is subjected to extraction separation, holmium is separated first or holmium and yttrium are separated simultaneously, i.e. Ho, Y is subjected to positive order extraction or simultaneous extraction, and the preferential separation of yttrium cannot be achieved.

[0125] Further experiments demonstrate that when the molar fraction of the first extractant is in the range of 0.5-0.9, when the rare earth feed solution containing holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu) and yttrium (Y) trivalent ions is subjected to extraction separation, the separation factor β Ho / Y is significantly greater than 1.0, and the extraction rate of yttrium is the lowest among the entire heavy rare earth, so that the preferential separation of yttrium can be achieved. Therefore, the present application preferably, the percentage of the molar fraction of the first extractant based on the total molar amount of the first extractant and the second extractant is 0.5-0.9.

[0126] Examples 9-12

[0127] In addition to adjusting the extractant composition, the initial pH of the rare earth feed solution and the degree of saponification according to Table 3 below, the method of Example 1 is followed, and the separation factor β Ln / Y of each non-yttrium heavy rare earth ion (Ln) and yttrium ion (Y) is calculated, and the results are shown in Tables 4-5.

[0128] Comparative Example 1

[0129] In addition to adjusting the extractant composition, the initial pH of the rare earth feed solution and the degree of saponification according to Table 3 below, the method of Example 1 is followed, and the results are shown in Table 5.

[0130] Table 3: Extractant, molar fraction of HA, degree of saponification and initial pH of the feed solution in Examples 9-12 and Comparative Example 1

[0131]

[0132] Table 4: Optimal extraction separation effect when the molar fraction of extractant HA is 0.6

[0133] β Ln / Y ]]> Example 9 Example 10 Example 11 Example 12 Ho / Y 1.19 1.80 1.91 1.72 Er / Y 1.60 1.73 1.81 1.64 Tm / Y 3.58 2.74 2.12 1.78 Yb / Y 10.04 5.69 2.89 2.74 Lu / Y 16.23 7.63 3.34 3.42 Mean 6.53 3.92 2.41 2.26

[0134] Table 5 Optimum extraction separation effect when the molar fraction of the extractant HA is 0.8

[0135] β Ln / Y ]]> Example 9 Example 10 Example 11 Example 12 Comparative Example 1 Ho / Y 1.49 1.71 1.89 1.85 1.88 Er / Y 1.60 1.66 1.80 1.80 1.65 Tm / Y 2.72 2.24 1.92 1.96 1.72 Yb / Y 6.62 4.26 2.33 2.34 2.16 Lu / Y 9.92 5.69 2.49 2.50 2.52 Mean 4.47 3.11 2.09 2.09 1.99

[0136] In addition, referring to the prior art (Qiang Shengting, Synthesis of different steric hindrance aminophosphine extractants and their extraction of rare earths [D], University of Science and Technology of China; Qizhao Zhao, Study on extraction of rare earths by nitrogen-containing organic phosphine acids [D], Northeastern University; Luyan Chen, N,N'-Di(-ethylhexyl) aminomethyl phosphonic acid mono-2-ethylhexyl ester and its synergistic system for extraction of heavy rare earths [D], University of Science and Technology of China), the separation coefficients of P507, Cyanex272, HEHAMP or HEDEAP for non-yttrium heavy rare earths and yttrium are summarized in Table 6 below.

[0137] Table 6 Optimum separation coefficients of different second extractants used as extractants alone for non-yttrium heavy rare earths and yttrium

[0138] β Ln / Y ]]> P507 Cyanex 272 HEHAMP HEDEAP Ho / Y 0.58-0.67 0.62 0.88 0.92 Er / Y 1.3-1.5 1.2 1.58 1.34 Tm / Y 3.25-4.5 2.71 3.06 4.68 Yb / Y 6.5-15.3 6.5 4.17 16.46 Lu / Y 9.1-27.54 8.59 5.15 27.32

[0139] From the above separation results, it can be seen that the average separation coefficients of the phosphonohydroxyacetic acid-containing extractant HA mixed extraction system and P507, Cyanex272, HEHAMP or HEDEAP for non-yttrium heavy rare earths and yttrium are all better than those of the single phosphonohydroxyacetic acid extractant system. In particular, compared with the use of HA alone, the mixed extraction system greatly improves the separation coefficients of heavy rare earth elements such as thulium, ytterbium and lutetium from yttrium. Therefore, the mixed extraction system of the present application has good application prospects in the extraction and separation of yttrium and non-yttrium heavy rare earths, especially in the extraction and separation of heavy rare earth elements such as thulium, ytterbium and lutetium from yttrium.

[0140] Examples 13-16

[0141] In addition to adjusting the extractant composition, the initial pH of the rare earth feed solution and the saponification degree according to Table 7 below, the method of Example 1 was followed.

[0142] The extractant composition, saponification degree and initial pH of the rare earth feed solution are shown in Table 7, and the test results are shown in Tables 8-9.

[0143] Comparative Example 2

[0144] In addition to adjusting the extractant composition, the initial pH of the rare earth feed solution and the saponification degree according to Table 7 below, the method of Example 1 was followed, and the results are shown in Table 9.

[0145] Table 7 Molar fraction of extractant HB, initial pH of the feed solution and saponification degree in Examples 13-16 and Comparative Example 2

[0146]

[0147] Table 8 Optimum separation effect when the molar fraction of extractant HB is 0.6

[0148] β Ln / Y ]]> Example 13 Example 14 Example 15 Ho / Y 1.83 1.76 1.77 Er / Y 2.03 1.80 1.92 Tm / Y 6.05 2.32 2.59 Yb / Y 16.75 3.40 4.31 Lu / Y 26.60 4.33 5.52 Mean 10.65 2.72 3.22

[0149] Table 9 Optimum extraction separation effect when the molar fraction of extractant HB is 0.8

[0150] β Ln / Y ]]> Example 13 Example 14 Example 15 Example 16 Comparative Example 2 Ho / Y 1.42 1.59 1.83 1.86 2.03 Er / Y 1.61 1.78 1.93 1.96 1.83 Tm / Y 3.35 3.97 2.33 2.65 2.01 Yb / Y 8.96 10.67 3.23 4.18 2.76 Lu / Y 14.1 16.64 3.96 5.56 3.54 Mean 5.89 6.93 2.66 3.24 2.43

[0151] From the above separation results, it can be seen that the mixed extraction system containing the phosphono hydroxy acetic acid extractant of the present application has a better average separation coefficient of non-yttrium heavy rare earth and yttrium than the single phosphono hydroxy acetic acid extractant system. In particular, compared with the single phosphono hydroxy acetic acid extractant system, the mixed extraction system greatly improves the separation coefficient of thulium, ytterbium, lutetium and other heavy rare earth elements and yttrium. Compared with P507, Cyanex272, HEHAMP, HEDEAP and other extractants, the mixed extractant system of the present application has the weakest extraction ability for yttrium, and can more effectively extract non-yttrium heavy rare earth elements from the heavy rare earth element solution first, thereby separating non-yttrium heavy rare earth elements from yttrium. Therefore, the mixed extraction system containing the phosphono hydroxy acetic acid extractant in the present application has a good application prospect in the separation of yttrium from heavy rare earth, especially in the extraction and separation of thulium, ytterbium, lutetium and other heavy rare earth elements and yttrium.

[0152] The above description is a detailed description of the preferred embodiments of the present application, but the embodiments are not intended to limit the scope of the patent application of the present application. Any equivalent changes or modifications made under the technical spirit of the present application should be included in the scope of the patent.

Claims

1. A mixed extractant consisting of a first extractant and a second extractant, wherein, the first extractant is selected from the group consisting of phosphonooxy acetic acid represented by Formula I: wherein, R1and R2are each independently selected from C 1-14 alkyl or alkoxy, and the total number of carbon atoms of R1and R2is 10 or more; R3is selected from H, C 1-8 alkyl, C 3-10 cycloalkyl and C 6-10 aryl; the second extractant is selected from the group consisting of acidic phosphine compounds represented by Formula II and amino-containing acidic phosphine compounds represented by Formula III, wherein, R4and R5are each independently selected from C 1-14 alkyl or alkoxy, and the total number of carbon atoms in R1and R2is 10 or more; R6is selected from C 1-12 alkyl; R7and R8are independently selected from hydrogen, C 1-10 alkyl, C 3-10 cycloalkyl and C 6-12 aryl; R9and R 10 are independently selected from hydrogen, C 1-12 alkyl.

2. The mixed extractant according to claim 1, wherein, in Formula I, R1and R2are each independently selected from C 2-14 alkyl or alkoxy, more preferably C 4-12 alkyl or alkoxy; preferably, R1and R2are identical and selected from C 5-12 alkyl or alkoxy, preferably C 6-10 alkyl or alkoxy; preferably, the total number of carbon atoms of R1and R2is an integer between 10 and 24, preferably an integer between 12 and 20; R3is selected from H, C 1-6 alkyl, C 3-8 cycloalkyl and C 6-10 aryl, preferably selected from H, C 1-4 alkyl, C 3-6 cycloalkyl, C 6-8 aryl, more preferably methyl or ethyl; preferably the total number of carbon atoms of R1, R2, R3is from 10 to 38, preferably from 11 to 34, more preferably from 14 to 30; in Formula II, R4and R5are each independently selected from C 4-14 alkyl or alkoxy, more preferably each independently selected from C 6-12 alkyl or alkoxy, more preferably each independently selected from C 6-10 alkyl or alkoxy; R4and R5are identical and selected from C 6-12 alkyl or alkoxy, preferably C 6-10 alkyl or alkoxy; preferably the total number of carbon atoms of R4and R5is an integer between 10 and 24, preferably an integer between 12 and 20; in Formula III, R6is selected from C 4-12 alkyl, more preferably C 5-10 alkyl, most preferably C 6-9 alkyl; R7and R8are independently selected from the group consisting of hydrogen, C 1-4 alkyl, C 5-7 cycloalkyl and C 6-10 aryl; more preferably from the group consisting of hydrogen, methyl, ethyl; R9and R 10 are independently selected from hydrogen, C 4-12 alkyl, preferably from hydrogen, C 5-10 alkyl, more preferably from hydrogen, C 6-10 alkyl.

3. The mixed extractant according to claim 1, wherein, the phosphonooxy acetic acid represented by Formula I is selected from the group consisting of bis(2-ethylhexyloxy)phosphonooxy acetic acid, 2-(bis(2-ethylhexyloxy)phosphono)-2-hydroxypropanoic acid and a mixture of the above extractants in any ratio; the acidic phosphine compound represented by Formula II is selected from the group consisting of bis(2-ethylhexyl)phosphoric acid, 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester, bis(2,4,4-trimethylpentyl)phosphinic acid, bis(2-ethylhexyl)phosphinic acid and a mixture of the above extractants in any ratio; the amino-containing acidic phosphine compound represented by Formula III is selected from the group consisting of 2-ethylhexylaminomethylphosphonic acid mono 2-ethylhexyl ester, bis(2-ethylhexyl)aminomethylphosphonic acid mono-2-ethylhexyl ester and a mixture of the above extractants in any ratio.

4. The hybrid extractive agent of claim 1, wherein, The molar fraction of the first extractant is 0.5-0.9, preferably 0.6-0.8, based on the total amount of 1 mol of the first extractant and the second extractant.

5. Use of the mixed extractant according to any one of claims 1-4 as an extractant for separating yttrium from non-yttrium heavy rare earths, in particular for extractive separation of yttrium from non-yttrium heavy rare earths selected from the group consisting of thulium, ytterbium and lutetium.

6. An extraction system comprising the mixed extractant according to any one of claims 1-4 as an extractant.

7. The extraction system according to claim 6, which is a liquid phase extraction system comprising, or consisting essentially of: (1) the mixed extractant according to the present application as an extractant, and (2) a diluent, wherein the diluent is selected from the group consisting of: C 5-16 alkanes, such as pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane; aviation kerosene; sulfonated kerosene, liquid paraffin, such as 250-400 °C light lubricating oil fraction; C 5-16 cycloalkanes, such as cyclopentane, C 1-4 alkyl-substituted cyclopentane, cyclohexane, C 1-4 alkyl-substituted cyclohexane, decalin; C 6-10 arenes, such as benzene, toluene, xylene; preferably, the diluent is one or more selected from the group consisting of aviation kerosene, sulfonated kerosene, heptane and xylene.

8. The extraction system of claim 7, wherein, The concentration of the extractant is 0.0001-1.0 mol / L, preferably 0.01-0.5 mol / L, based on the total volume of the liquid phase extraction system.

9. A method for extractive separation of yttrium from non-yttrium heavy rare earths, the method comprising: (1) adjusting the saponification degree of the extraction system according to any one of claims 6-8 to 10-90%; (2) contacting a feed solution containing yttrium and non-yttrium heavy rare earths with the saponified extraction system to obtain an extraction system containing non-yttrium heavy rare earths and a yttrium-containing raffinate; wherein the saponification degree is calculated as follows: Saponification degree % = molar amount of salified acidic extractant / molar amount of total acidic extractant x 100% the non-yttrium heavy rare earths are one or more or all selected from the group consisting of holmium, erbium, thulium, ytterbium and lutetium, in particular one or more or all selected from the group consisting of thulium, ytterbium and lutetium; in the feed solution containing yttrium and non-yttrium heavy rare earths, both yttrium and non-yttrium heavy rare earth elements are in the form of trivalent ions.

10. The method according to claim 9, wherein, the saponification degree of the extraction system is 20-85%, preferably 40-75%. The total concentration of rare earth ions in the yttrium-containing and non-yttrium-containing heavy rare earth solution is 0.05-1.5 mol / L. The initial pH value of the solution is 0.5-4, preferably 1.5-3.0.

Images