A carboxylic acid extractant and a method for separating impurity aluminum ions from rare earth liquid using the same

Abstract

The present invention provides a carboxylic acid extractant and a method for separating impure aluminum ions from a rare earth solution using the carboxylic acid extractant. The carboxylic acid extractant is used to remove aluminum ions from a rare earth solution containing impure aluminum, and comprises a carboxylic acid and a diluent; the pKa value of the extractant is 2 to 10. The carboxylic acid extractant used in the present invention has good selectivity for impure aluminum ions in the rare earth solution, and can better achieve the separation of aluminum ions and rare earth ions.

Description

Technical Field

[0001] The present invention belongs to the technical field of rare earth separation and extraction, and specifically relates to a carboxylic acid extractant and a method for separating impurity aluminum ions (Al2O3) from rare earth liquid by using the carboxylic acid extractant. 3+ ) method. Background Art

[0002] Among natural resources, rare earth elements are very precious. They are widely used in defense, industry, optics, catalysis, metallurgy, medicine and other fields. They are important raw materials for manufacturing new materials, so they are called "industrial gold". With the increasing global demand for rare earth elements, more and more methods for separating and purifying rare earth elements have been studied. If rare earths are to be well applied in high-tech fields, the purity of rare earth elements must be guaranteed. Therefore, the removal of impurities is very important in the separation of rare earth production.

[0003] Ion adsorption rare earth ores, also known as weathering crust leaching ores, are mainly produced in southern China, especially in southern Jiangxi. Ion adsorption rare earth ores contain high contents of medium and heavy rare earth elements (Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) and have extremely high mining value. (NH4)2SO4 is usually used as a leaching agent to obtain rare earths from ion adsorption rare earth ores, but Al 3+ As an impurity, aluminum ions enter the leachate together with rare earth ions. Due to the similar properties of aluminum ions and rare earth ions, their separation is an industrial challenge. The presence of aluminum ions has a negative impact on the subsequent extraction and separation of rare earths. Therefore, it is particularly important to find an effective method to remove aluminum ions in the production and processing of rare earth minerals.

[0004] There have been many studies on the separation and recovery of aluminum and rare earths. There are also reports on the removal of impurity aluminum ions from ion-adsorbed ores, such as the removal of aluminum from rare earth leachate by composite precipitation. In order to reduce the content of aluminum ions, aluminum inhibitors are added to the leachate to inhibit the leaching of aluminum. There are related reports. The inhibitory effect of sulfosalicylic acid on aluminum in ion-adsorbed rare earth ore leachate has been reported. In the waste residue of FCC catalyst production, the step-by-step leaching-selective precipitation method has also been studied to recover rare earths and aluminum. The total recovery rates of rare earths and aluminum are as high as 97% and 98.4%, respectively. In addition, there are also reports on the use of D290 resin to adsorb aluminum ions in the leachate to achieve the separation of aluminum and rare earths.

[0005] Compared with other separation technologies, solvent extraction has a higher extraction and separation efficiency and is also an important means and basic method for the separation and purification of rare earth elements. Cyclohexane acid is an effective acidic extractant that can effectively remove impurity aluminum ions from rare earth ions. So far, there have been few studies on the extraction and separation of aluminum and rare earths, and relatively few studies on extractants for separation of aluminum and rare earths. Therefore, it is of great significance to study the extractant for dealumination from rare earths. Summary of the invention

[0006] The present invention is directed to the use of (NH4)2SO4 in-situ leaching of ion adsorption type rare earth ores. 3+ The problem of impurity ions remaining in the rare earth leaching solution was solved. A method for separating impurity aluminum ions (Al2O3) from rare earth leaching solution using a carboxylic acid extractant was invented. 3+ ) method.

[0007] The invention provides a carboxylic acid extractant, which comprises carboxylic acid and a diluent; the pKa value of the extractant is 2-10.

[0008] According to an embodiment of the present invention, the pKa value of the extractant is 3-10, for example, 2, 2.5, 3, 4, 4.2, 4.4, 4.42, 4.44, 4.46, 4.48, 4.5, 4.6, 4.8, 5, 6, 7, 8, 9 or 10.

[0009] According to an embodiment of the present invention, the carboxylic acid extractant includes saponified carboxylic acid, and the mass percentage of the saponified carboxylic acid is not less than 80% based on the total weight of the carboxylic acid and the saponified carboxylic acid.

[0010] According to an embodiment of the present invention, the carboxylic acid is selected from at least one of the compounds represented by the following formula 1:

[0011]

[0012] In Formula 1, R is selected from an alkoxy group.

[0013] According to an embodiment of the present invention, in Formula 1, the R is selected from C 4-10 For example, the C 4-10 The alkyl group is selected from n-butyl or its isomers, n-pentyl or its isomers, n-hexyl or its isomers, n-heptyl or its isomers, n-octyl or its isomers, n-nonyl or its isomers, and n-decyl or its isomers.

[0014] According to an embodiment of the present invention, in Formula 1, the R is located at the 2nd, 3rd or 4th position; illustratively, at the 4th position.

[0015] According to an embodiment of the present invention, the carboxylic acid is selected from at least one of 4-n-pentyloxybenzoic acid (PPOA), 4-n-hexyloxybenzoic acid (PHOA), 4-n-heptyloxybenzoic acid (PNOA) and 4-n-octyloxybenzoic acid (POOA). Exemplarily, the carboxylic acid is selected from 4-n-octyloxybenzoic acid.

[0016] According to an embodiment of the present invention, the diluent is selected from at least one of kerosene, toluene, pentane, hexane, octane and n-heptane.

[0017] According to an embodiment of the present invention, the carboxylic acid extractant is used to remove aluminum ions from a rare earth feed solution containing aluminum impurities.

[0018] According to an embodiment of the present invention, in the carboxylic acid extractant, the concentration of carboxylic acid is 0.1-0.2 mol / L; if a saponified carboxylic acid is contained, the concentration of the sum of the carboxylic acid and the saponified carboxylic acid is 0.1-0.2 mol / L, exemplarily 0.1 mol / L, 0.11 mol / L, 0.12 mol / L, 0.13 mol / L, 0.14 mol / L, 0.16 mol / L, 0.18 mol / L or 0.2 mol / L.

[0019] According to an embodiment of the present invention, the carboxylic acid extractant further comprises a phase modifier. Exemplarily, the phase modifier can be a phase modifier known in the art, specifically isooctyl alcohol.

[0020] According to an embodiment of the present invention, the volume ratio of the phase modifier to the diluent is (1-3):(2-10), for example, 2:(2-10), and specifically 2:(3-5).

[0021] The present invention also provides an extraction method, specifically a method for extracting impurity aluminum ions from a rare earth feed solution, the extraction method comprising the following steps:

[0022] (1) preparing an aqueous solution of rare earth containing impurity aluminum ions as an aqueous phase feed liquid;

[0023] (2) preparing the above-mentioned carboxylic acid extractant as an organic phase extractant;

[0024] (3) The aqueous phase feed liquid and the organic phase extractant are mixed and extracted, and the mixed solution after extraction is subjected to phase separation to obtain an organic phase extraction layer loaded with aluminum ions and an aqueous phase extraction layer containing rare earth ions, thereby completing the extraction.

[0025] According to an embodiment of the present invention, in the step (1), the concentration of rare earth ions in the aqueous phase is greater than or equal to 0.3 mol / L, Al 3+ The concentration of rare earth ions in the aqueous phase is less than or equal to 0.04 mol / L. For example, the concentration of rare earth ions in the aqueous phase is 0.3 mol / L, Al 3+ The concentration is 0.04mol / L.

[0026] In the step (1), the pH value of the aqueous phase liquid is 1 to 4, illustratively 2.5 to 3.0.

[0027] According to an embodiment of the present invention, in step (2), the carboxylic acid is dissolved in a diluent, with or without a phase modifier, and subjected to saponification treatment to obtain the carboxylic acid extractant.

[0028] According to an embodiment of the present invention, the saponification refers to a saponification reaction commonly used in the art, such as a reaction between a base (usually a strong base) and an acid to produce alcohol and a carboxylate. Exemplarily, the base is selected from NaOH, for example, and its concentration is 0.1 to 1.0 mol / L.

[0029] According to an embodiment of the present invention, in step (2), the saponification degree of the carboxylic acid extractant is greater than or equal to 80%. In the present invention, the saponification degree is the mass percentage of the saponified carboxylic acid based on the total weight of the carboxylic acid and the saponified carboxylic acid.

[0030] According to an embodiment of the present invention, in step (3), the mixed extraction comprises: mixing the aqueous phase feed liquid and the organic phase extractant, shaking, and separating the phases after centrifugation. Specifically, the shaking time is 30 min to 60 min, for example, 40 min to 50 min.

[0031] According to an embodiment of the present invention, the volume ratio of the aqueous phase feed liquid to the organic phase extractant is 1:3 to 3:1, for example, 1:3, 1:2, 1:1, 2:1 or 3:1.

[0032] According to an embodiment of the present invention, the temperature of the mixed extraction is 20-60°C, for example 25-50°C, illustratively 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C or 60°C.

[0033] According to an embodiment of the present invention, in the step (3), the concentration ratio of aluminum ions in the organic phase extraction layer and the aqueous phase extraction layer is greater than or equal to 3:1, for example, 3:1 to 5:1, and for example, 3:1 to 4:1.

[0034] According to an embodiment of the present invention, the step (3) is loaded with Al 3+ The organic phase extract layer is stripped with stripping solution to remove Al 3+ Remove from the organic phase.

[0035] According to an embodiment of the present invention, the back extraction comprises: back extracting the organic phase extraction layer using a back extraction solution, and optionally, the back extraction is performed 1 to 2 times.

[0036] According to an embodiment of the present invention, the stripping solution is a low-concentration inorganic acid, such as dilute hydrochloric acid. + The concentration is 0.4-0.8 mol / L, for example 0.6 mol / L.

[0037] According to an embodiment of the present invention, the back extraction time is 10 min to 60 min, for example, 20 min.

[0038] According to an embodiment of the present invention, after the organic phase extraction layer is stripped, a recovered carboxylic acid extractant is obtained, and the recovered carboxylic acid extractant can be recycled and reused.

[0039] Beneficial effects of the present invention:

[0040] (1) The carboxylic acid extractant used in the present invention is found to be effective for the extraction of impurity aluminum ions (Al 3+ ) has good selectivity and can better realize Al 3+ and separation of rare earth ions.

[0041] (2) The water solubility of the extractant used in the present invention is very low, so the loss during extraction is small.

[0042] (3) The extractant used in the present invention does not emulsify during the extraction process, and the interface between the two phases is obvious.

[0043] (4) The acid concentration used in the stripping of the present invention is low and environmentally friendly.

[0044] (5) The carboxylic acid extractant of the present invention can be recycled and reused after recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 is the chemical structural formula of 4-n-octyloxybenzoic acid of Example 1;

[0046] Figure 2 The infrared spectrum analysis of the carboxylic acid extractant of Example 1 during the extraction process;

[0047] Figure 3 is the extraction rate (E) of the organic extraction layer of Comparative Example 1;

[0048] Figure 4 This is a graph showing the variation of the extraction rate (E) of the organic extraction layer with temperature. DETAILED DESCRIPTION

[0049] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0050] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0051] In the present invention, the extraction rate (E) can intuitively show the extraction ability of the extractant, and E is the change in the concentration of metal ions in the aqueous phase extraction layer before and after extraction, that is, the extraction rate E = (metal ion concentration before extraction - metal ion concentration after extraction) / metal ion concentration before extraction); the separation coefficient (β) is an important basis for indicating the separation effect. The concentrations of all metal ions in the present invention are determined by ICP.

[0052] Example 1

[0053] 1. Preparation of carboxylic acid extractant: Take 0.1502 g of 4-n-octyloxybenzoic acid (see Figure 1 The structure shown in FIG. 1 has a pKa value of 4.48), which is dissolved in 3 mL of n-heptane, and 2 mL of a phase modifier, isooctyl alcohol, is added to obtain POOA, and a NaOH solution (with a concentration of 0.1 mol / L) is added to carry out a saponification reaction to obtain a carboxylic acid extractant with a saponification degree of 80%;

[0054] 2. Extraction: The carboxylic acid extractant and feed liquid (the feed liquid is an aqueous solution, pH=3, containing Al 3+ and RE 3+ , using [Al 3+ ] and [RE 3+ ] represent Al 3+ and RE 3+ The molar concentration of [Al 3+ ]=0.04mol / L, [RE 3+ ]=0.3mol / L) with a volume ratio of 1:1, put it into an oscillation box and oscillate at an extraction temperature of 50°C for 40 minutes, then put it into a centrifuge for centrifugation and phase separation to obtain an aqueous phase extraction layer and an organic phase extraction layer.

[0055] 3. Back extraction: The organic phase extraction layer of step 2 was back extracted with 0.60 mol / L HCl for 20 min to obtain an organic phase layer and an aqueous phase layer;

[0056] 4. The organic phase layer of step 3 is used again in steps 2-3, and the cycle is repeated 6 times.

[0057] After taking the aqueous phase extraction layer of step 2 for ICP test, it can be seen that the rare earth metal RE 3+ The extraction rate of Al 3+ The extraction rate reached 89.41% and the separation coefficient (β) was 75.

[0058] The POOA in the extractant before saponification is recorded as sample a, the POOA in the extractant after saponification is recorded as sample b, the aluminum-loaded POOA in the organic phase extraction layer is recorded as sample c, and the POOA obtained by steam stripping after back extraction is recorded as sample d; wherein, the POOA in the extractant after saponification (sample b) refers to: taking the carboxylic acid extractant of step 1, evaporating the solvent, and completely drying under vacuum conditions; the aluminum-loaded POOA in the organic phase extraction layer (sample c) refers to: taking the organic phase extraction layer of step 2, evaporating the solvent, and completely drying under vacuum conditions; the POOA obtained by steam stripping after back extraction (sample d) refers to: taking the aqueous phase layer of step 3, evaporating the solvent, and completely drying under vacuum conditions.

[0059] Figure 2 The infrared spectrum of the extractant of Example 1 during the extraction process (i.e., the above-mentioned samples ad) is shown in Figure 1, wherein the test conditions are 2500-800 cm -1 Infrared spectrum in the range of Figure 2 As shown in the infrared spectrum of sample a, the stretching vibration of C=O in the -COOH functional group is 1688 cm -1 After saponification, the stretching vibration of C=O in sample b changes from 1688cm -1 Move to 1695cm -1 After extraction, the C=O stretching vibration of -COOH in sample c changed from 1688 cm -1 Transformed to 1692cm -1 After stripping, the infrared spectrum of sample d shows that the stretching vibration of C=O in the functional group COOH has recovered to 1688 cm -1 .pass Figure 2 The results show that the carboxyl functional group in the carboxylic acid POOA participates in the extraction process. The above test results show that the carboxylic acid extractant of the present invention can effectively remove the impurity Al in the rare earth solution. 3+ .

[0060] Embodiment 2-4

[0061] 1. Preparation of carboxylic acid extractant: The carboxylic acid extractants of Examples 2-4 were prepared using the following organic solvents: n-hexane, kerosene and toluene, respectively. The rest was the same as in Example 1.

[0062] 2. The steps of extraction and back extraction are the same as in Example 1.

[0063] Among them, the extraction rate of n-hexane is 86%, the extraction rate of kerosene is 84%, and the extraction rate of toluene is 86%.

[0064] By comparing Example 1 with Examples 2-4, it can be seen that when n-heptane is used as the diluent of the carboxylic acid extractant, the extraction effect of POOA is significantly better than that of the extractants whose diluents are n-hexane, kerosene and toluene.

[0065] Embodiment 5-7

[0066] 1. The carboxylic acid extractants of Examples 5-7 are the same as those of Example 1.

[0067] 2. During extraction, the extraction temperature is 25°C and the pH value of the feed solution is adjusted to 1, 2 and 3 respectively.

[0068] 3. The step of stripping is the same as in Example 1.

[0069] When pH=1, the extraction rate is 80%; when pH=2, the extraction rate is 86%; when pH=3, the extraction rate is 87%.

[0070] Comparing Example 1 with Examples 5-7, it can be seen that Al 3+ The extraction rate increases with the increase of pH value during extraction, and the extraction rate is highest when the pH value is 3.

[0071] Example 8

[0072] 1. The carboxylic acid extractant in Example 8 is the same as that in Example 1.

[0073] 2. During extraction, adjust the extraction temperature to 25℃, 30℃, 35℃, 40℃ and 45℃ respectively.

[0074] 3. The step of stripping is the same as in Example 1.

[0075] Figure 4 The extraction rate (E) of the organic extraction layer varies with the extraction temperature. The separation coefficients at extraction temperatures of 25°C, 30°C, 35°C, 40°C, 45°C and 50°C are 32, 42, 44, 61, 63 and 75 respectively. By comparing the extraction results of Example 1 and Example 8, it can be seen that the extraction temperature also has an effect on the extraction rate. When the extraction temperature is 50°C, the separation coefficients of Al 3+ and RE 3+ The separation factor reaches the highest.

[0076] Comparative Example 1

[0077] 1. Preparation of extractant: The extractant of this comparative example uses cyclohexane acid instead of 4-n-octyloxybenzoic acid, and the remaining steps are the same as those of Example 1.

[0078] 2. The steps of extraction and back extraction are the same as in Example 1.

[0079] 3. After back extraction, the organic phase layer is turbid and cannot be used for extraction and back extraction in step 2.

[0080] Figure 3 is the extraction rate (E) of the organic extraction layer of Example 1 and Comparative Example 1, wherein the Al in the organic phase extraction layer of Example 1 is 3+ and RE3+ The extraction rates E were 89.41% and 9% respectively; the Al in the organic phase extraction layer of Comparative Example 1 3+ and RE 3+ The extraction rates E are 80% and 20% respectively. Figure 3 The results show that the present invention uses 4-octyloxybenzoic acid to better remove Al from the rare earth liquid. 3+ Moreover, after the carboxylic acid extractant of Example 1 was recycled for 6 times, its extraction capacity remained almost unchanged, proving that the extractant can be recycled and reused.

[0081] Moreover, when the carboxylic acid extractant of 4-octyloxybenzoic acid was used for extraction in Example 1, the interface between the aqueous phase and the organic phase was obvious. After 24 hours of standing, the interface was still obvious, and the two phases were clear and transparent. However, after the extractant of Comparative Example 1 was back-extracted, the organic phase layer was turbid and could not be used any more. It can be seen that under the same conditions, the carboxylic acid extractant of Example 1 can better separate Al 3+ and RE 3+ , with good extraction and separation phenomenon.

[0082] The above is a description of the exemplary embodiments of the present invention. However, the protection scope of the present application is not limited to the above embodiments. Any modification, equivalent substitution, improvement, etc. made by those skilled in the art within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A carboxylic acid extractant for removing aluminum ions from a rare earth feed solution containing aluminum impurities, characterized in that: The carboxylic acid extractant comprises a carboxylic acid and a diluent; the pKa value of the carboxylic acid extractant is 2 to 10; The carboxylic acid extractant includes a saponified product of carboxylic acid, and the mass percentage of the saponified product of carboxylic acid is not less than 80% based on the total weight of the carboxylic acid and the saponified product of carboxylic acid; the carboxylic acid is selected from at least one of 4-n-pentyloxybenzoic acid, 4-n-hexyloxybenzoic acid, 4-n-heptyloxybenzoic acid and 4-n-octyloxybenzoic acid.

2. The carboxylic acid extractant according to claim 1, characterized in that The pKa value of the carboxylic acid extractant is 3-10.

3. The carboxylic acid extractant according to claim 1, characterized in that In the carboxylic acid extractant, the concentration of the sum of the carboxylic acid and the saponified product of the carboxylic acid is 0.1-0.2 mol / L.

4. The carboxylic acid extractant according to claim 1, characterized in that The diluent is selected from at least one of kerosene, toluene, pentane, hexane, octane and n-heptane.

5. The carboxylic acid extractant according to claim 1, characterized in that The carboxylic acid extractant also includes a phase modifier; The volume ratio of the phase modifier to the diluent is (1-3):(2-10).

6. A method for extracting impurity aluminum ions from rare earth liquid, characterized in that: The extraction method comprises the following steps: (1) preparing an aqueous solution of rare earth containing impurity aluminum ions as an aqueous phase feed liquid; (2) preparing the carboxylic acid extractant according to any one of claims 1 to 5 as an organic phase extractant; (3) The aqueous phase feed liquid and the organic phase extractant are mixed and extracted, and the mixed solution after extraction is subjected to phase separation to obtain an organic phase extraction layer loaded with aluminum ions and an aqueous phase extraction layer containing rare earth ions, thereby completing the extraction.

7. The extraction method according to claim 6, characterized in that In the step (1), the concentration of rare earth ions in the aqueous phase liquid is greater than or equal to 0.3 mol / L, Al 3+ The concentration is less than or equal to 0.04 mol / L.

8. The extraction method according to claim 6, characterized in that In the step (3), the mixed extraction comprises: mixing the aqueous phase feed liquid and the organic phase extractant, shaking, and separating the phases after centrifugation; In the step (3), the concentration ratio of aluminum ions in the organic phase extraction layer and the aqueous phase extraction layer is greater than or equal to 3:

1.

9. The extraction method according to claim 8, characterized in that The concentration ratio of aluminum ions in the organic phase extraction layer and the aqueous phase extraction layer is 3:1~5:

1.

10. The extraction method according to any one of claims 6 to 9, characterized in that: Load Al in step (3) 3+ The organic phase extract layer is stripped with stripping solution to remove Al 3+ Remove from the organic phase extraction layer; The stripping solution is a low concentration inorganic acid; The back extraction time is 10min to 60min.

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