A high-efficiency aluminum solvent extraction system

Abstract

The present invention discloses an aluminum solvent extraction system, comprising a modified carboxylic acid extractant, a cosolvent, and a diluent, wherein the modified carboxylic acid extractant has a structure of formula I, wherein R is a linear or branched alkyl chain; n represents the number of CH2 units connected to the carboxyl functional group, which is an integer of 0-2, and #imgabs0#

Description

Technical Field

[0001] The present invention belongs to the field of metal extraction and relates to an aluminum solvent extraction system, in particular to a high-efficiency aluminum solvent extraction system based on a modified carboxylic acid extractant. Background Art

[0002] Aluminum separation is a key link in many production processes. For example, in the recycling of retired batteries and the mining of rare earth ores, aluminum is often leached along with other metals, forming a solution containing aluminum mixed with alkali metals (such as lithium, sodium, potassium, etc.), alkaline earth metals (such as magnesium, calcium, etc.), transition metals (such as cobalt, nickel, iron, manganese, etc.) or rare earth metals (such as praseodymium, neodymium, etc.). In order to obtain high-purity, high-value metals such as rare earths, cobalt, nickel, lithium, etc., it is of great significance to highly selectively separate aluminum from mixed solutions. In actual production, solvent extraction is a more commonly used method for separating aluminum from solutions. Compared with other methods, such as precipitation, it has the advantages of low energy consumption, simple equipment operation and high selectivity.

[0003] Currently, the most common aluminum extractant is the cyclohexane acid extraction system (e.g., disclosed in CN101979680A, CN103146921B, and CN103966441A). However, due to the high viscosity and easy emulsification of cyclohexane acid, the organic and aqueous phases undergo a long separation process during the extraction process, resulting in an unclear interface and a high risk of loss of both the extractant and the metal in actual use.

[0004] CN111944998A discloses an aluminum isodecanoate extractant that enables multi-stage continuous aluminum extraction. The extraction system has low viscosity, resists emulsification, and shortens the separation time between the organic and aqueous phases. However, isodecanoic acid has poor selectivity for aluminum. In the presence of other metals, aluminum ions are easily extracted together with other metals, such as manganese, cobalt, and nickel.

[0005] CN112921176B discloses an aluminum phenoxycarboxylate extractant with high selectivity and extraction efficiency for aluminum ions. However, phenoxycarboxylic acid extractants have low solubility in alkane solvents such as kerosene. After enriching aluminum ions, they tend to emulsify, making separation of the aqueous and organic phases more difficult. While phenoxycarboxylic acid has good solubility in aromatic solvents such as toluene, the toxicity of these solvents limits their practical application.

[0006] In response to the problems existing in the prior art, the present invention provides a low-toxic, low-cost extraction system with high selectivity and high extraction rate for aluminum ions and easy solubility in alkanes. It is suitable for a variety of production scenarios, can solve the problem of separating aluminum ions from solutions containing multiple metal ions, avoid the waste of other metals, and has important application value. Summary of the Invention

[0007] The present invention aims to provide a modified carboxylic acid-based efficient aluminum solvent extraction system which has strong selectivity for aluminum ions, high extraction rate, and is suitable for alkane solvents.

[0008] The present invention relates to an efficient aluminum solvent extraction system comprising a modified carboxylic acid extractant, a cosolvent, and a diluent. The modified carboxylic acid extractant comprises 0.5% to 95% by volume, preferably 10% to 50% by volume, the cosolvent comprises 1% to 30% by volume, preferably 10% to 30% by volume, and the remainder is the diluent, based on the total volume of the extraction system.

[0009] The modified carboxylic acid extractant is a compound containing a carboxyl functional group and an alkoxy chain functional group connected to the carboxyl functional group, and has the structural formula (I):

[0010]

[0011] Wherein R is a C4-C18 straight-chain or branched alkyl group, and n represents the number of CH2 units connected to the carboxyl functional group, which is an integer of 0-2.

[0012] The cosolvent is one or a mixture of phosphate esters and alkyl alcohols. The phosphate esters are C4-C8 phosphate esters, such as tributyl phosphate, tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, and trioctyl phosphate. The alkyl alcohols are C8-C12 alkyl alcohols, such as n-octanol, isooctyl alcohol, n-nonanol, 2-nonanol, undecanol, and dodecanol.

[0013] The diluent is selected from one or a mixture of C6-C16 alkanes, such as kerosene, n-heptane, octane, preferably kerosene.

[0014] The present invention further relates to a method for extracting aluminum from a mixed metal ion solution, wherein the modified carboxylic acid-based high-efficiency aluminum solvent extraction system according to the present invention is used, comprising the following steps:

[0015] (1) mixing a modified carboxylic acid extractant, a cosolvent, and a diluent to form a high-efficiency aluminum solvent extraction system of the present invention;

[0016] (2) contacting the solvent extraction system prepared in step (1) with a certain amount of base to saponify the modified carboxylic acid extractant therein to obtain a saponified solvent extraction system;

[0017] (3) introducing the saponified solvent extraction system obtained in step (2) and the solution to be extracted into an extraction device for mixing, performing a single-stage extraction or a multi-stage countercurrent extraction reaction to obtain an aluminum-loaded organic phase, wherein the pH value at the equilibrium of the extraction reaction is in the range of 2.5-4.5;

[0018] (4) performing single-stage washing or multi-stage countercurrent washing on the aluminum-loaded organic phase obtained in step (3) with a washing liquid to remove co-extracted impurity ions, thereby obtaining a washed aluminum-loaded organic phase;

[0019] (5) subjecting the washed organic phase obtained in step (4) to single-stage back-extraction or multi-stage countercurrent back-extraction with a back-extraction liquid to obtain a back-extracted organic phase and a high-purity aluminum salt solution;

[0020] (6) returning the organic phase after stripping obtained in step (5) to the organic phase storage tank, saponifying it again, and recycling it for extracting aluminum.

[0021] In step (1), the cosolvent is one or more of a phosphate ester and an alkyl alcohol, wherein the phosphate ester is a C4-C8 phosphate ester, such as tributyl phosphate, tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, and trioctyl phosphate; and the alkyl alcohol is a C8-C12 alkyl alcohol, such as n-octanol, isooctyl alcohol, n-nonanol, 2-nonanol, 1-undecanol, and dodecanol. The volume ratio of the modified carboxylic acid extractant is 0.5%-95%, and the volume ratio of the cosolvent is 1-30%, based on the total volume of the extraction system. The diluent is selected from a mixture of one or more C6-C16 alkanes, such as kerosene, n-heptane, and octane, preferably kerosene.

[0022] In step (2), the concentration of the carboxylic acid extractant in the solvent extraction system is determined based on the molar concentration of aluminum in the solution to be extracted. Furthermore, a certain amount of base is added to achieve a saponification rate of the extractant in the range of 5% to 100%. The base can be sodium hydroxide, potassium hydroxide, ammonia water, or any mixture thereof, preferably sodium hydroxide.

[0023] In step (3), the extraction equipment may use an extraction clarification tank, an extraction tower or a centrifugal extractor, and the number of extraction stages is 1-20. The volume ratio of the saponified solvent extraction system to the liquid to be extracted is 1:50-50:1.

[0024] In step (4), the washing liquid is water, dilute hydrochloric acid or dilute sulfuric acid, and the concentration of the hydrochloric acid or sulfuric acid solution is 0.01-3.0 mol / L; the volume ratio of the organic phase to the washing liquid is 1:50-50:1, and the washing stage is 0-20.

[0025] In step (5), the stripping solution is a hydrochloric acid solution or a sulfuric acid solution with a concentration of 0.1-12.0 mol / L; the volume ratio of the organic phase to the stripping solution is 1:50-50:1, and the stripping stage is 1-20.

[0026] The solvent extraction system of the present invention has strong selectivity for aluminum ions, and the single-stage extraction rate can reach more than 90%. For aqueous solutions containing complex metal ions, only one-stage reaction is needed to efficiently extract aluminum ions, and other metal ions are hardly extracted.

[0027] The solvent extraction system of the present invention is suitable for extracting and separating aluminum from mixed solutions of alkali metal, alkaline earth metal, transition metal, and rare earth metal ions. Examples of such alkali metals include lithium, sodium, and potassium; alkaline earth metals include magnesium and calcium; transition metals include cobalt, nickel, iron, and manganese; and rare earth metals include praseodymium and neodymium. Furthermore, the cosolvent in the system helps increase the solubility of the complex generated by the extraction reaction in the diluent, reducing the viscosity of the organic phase and thereby enhancing the separation efficiency between the organic and aqueous phases.

[0028] Therefore, the present invention further relates to the use of the solvent extraction system according to the present invention for extracting and separating aluminum ions from a mixed solution of metal ions, which is suitable for a variety of production scenarios, such as aluminum removal from rare earth separation raw material liquid, aluminum recovery from retired battery leachate, aluminum-magnesium-lithium separation from coal slag leachate, and aluminum separation from laterite nickel ore.

[0029] Beneficial effects

[0030] The solvent extraction system of the present invention can solve the problem of separating aluminum ions from solutions containing multiple metal ions, avoid the waste of other metals, and has low cost, low toxicity, and is suitable for industrial production. Compared with the existing technology, the advantages are:

[0031] (1) It has higher selectivity and higher extraction efficiency for aluminum ions, and does not extract or extracts very little other metals in the mixed metal ion solution.

[0032] (2) In the present invention, by adding alkali to adjust the pH value after extraction equilibrium, or first saponifying the organic phase with alkali, aluminum ion extraction is achieved at a lower pH value, avoiding the loss of other metal ions caused by precipitation at high pH values.

[0033] (3) The solvent extraction system of the present invention uses alkanes as diluents, avoiding or reducing the use of aromatic solvents such as toluene and S150. It has low toxicity to the production environment, low solvent cost, and is suitable for large-scale production.

[0034] (4) The cosolvent in the system can increase the solubility of the extractant loaded with aluminum ions in the alkane diluent, improve the fluidity of the organic phase after loading aluminum ions, and the separation effect from the aqueous phase.

[0035] (5) After the organic phase of the solvent extraction system of the present invention is loaded with aluminum ions, it can be back-extracted with hydrochloric acid or sulfuric acid solution, thereby realizing the recycling of the organic phase or continuous multi-stage extraction. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The figures are the metal ion extraction results at different reaction equilibrium pH values in Example 1. DETAILED DESCRIPTION

[0037] The present invention is further described below with reference to specific examples, but the present invention is not limited to these embodiments. Within the technical concept of the present invention, those skilled in the art can make various modifications.

[0038] Example 1:

[0039] Single-stage extraction and separation of aluminum from lithium battery leachate. The metal types and concentrations in the leachate were: aluminum 8.1 g / L, manganese 13.8 g / L, cobalt 9.1 g / L, magnesium 2.2 g / L, nickel 23.2 g / L, and lithium 4.2 g / L. The extraction agent was 2-(decyloxy)acetic acid, the cosolvent was TBP, and the diluent was kerosene.

[0040] Add 24mL of 2-(decyloxy)acetic acid (95% purity, about 0.1mol) to a 100mL volumetric flask, add 20mL of TBP (20% volume ratio), add kerosene to 100mL to make up the volume, and prepare the organic phase with an extractant concentration of about 1mol / L aluminum extraction. Take 3mL of the organic phase, add 120μL of 10mol / L NaOH solution, and mix thoroughly for 30min to saponify the extractant (saponification rate 40%). The saponified organic phase is mixed with 3mL of the solution to be extracted and stirred for 30min. After standing and separating the phases, the lower layer of the raffinate aqueous phase is taken for analysis. At this time, the pH value after the extraction reaction is balanced is about 4.3. Take 2mL of the upper organic phase, add 2mL of 1.5mol / L HCl aqueous solution, and mix thoroughly for 30min for back extraction. Stand and separate the phases. The organic phase after back extraction can be reused. Take the lower layer of aqueous phase for analysis, and the aluminum extraction rate is calculated to be about 92%, while the extraction rates of other metals are <2% (see Figure 1 , extraction results at different reaction equilibrium pH values).

[0041] Example 2:

[0042] Multi-stage extraction and separation of aluminum from lithium battery leachate. The metal types and concentrations in the leachate were: aluminum 8.1 g / L, manganese 13.8 g / L, cobalt 9.1 g / L, magnesium 2.2 g / L, nickel 23.2 g / L, and lithium 4.2 g / L. The extractant was 2-(decyloxy)acetic acid, the cosolvent was TBP, and the diluent was kerosene.

[0043] An aluminum extraction organic phase was prepared by mixing 24 vol% 2-(decyloxy)acetic acid, 20 vol% TBP, and 56 vol% kerosene. A 4 vol% 10 mol / L NaOH solution was added to the organic phase and mixed thoroughly for 30 minutes to saponify the extractant (saponification rate 40%). The saponified organic phase was subjected to four continuous countercurrent extractions with an aqueous phase at a 1:1 volume ratio in an extraction clarifier to obtain an aluminum-loaded organic phase. The aluminum extraction rate was measured to be >98%, and the pH after equilibrium was approximately 4.3. The aluminum-loaded organic phase was then further washed with 1 mol / L hydrochloric acid at a 10:1 volume ratio in the extraction clarifier for three steps to remove co-extracted manganese, cobalt, and nickel ions. The wash solution was then returned to the aqueous phase inlet. The washed organic phase was then stripped with 10 mol / L hydrochloric acid at a 10:1 volume ratio in the extraction clarifier for three steps to obtain an aluminum chloride solution with an aluminum purity >99% and an aluminum concentration of 48-81 g / L. The organic phase after stripping is returned to the extraction section for recycling.

[0044] Example 3:

[0045] The system of the present invention is used to separate aluminum and magnesium from coal slag leachate. The metal types and contents in the leachate are: aluminum 1.5g / L, magnesium 0.5g / L. The extractant is 2-(decyloxy)acetic acid, the cosolvent is TBP, and the diluent is kerosene.

[0046] Take 4vol% 2-(decyloxy)acetic acid, 4vol% TBP and 92vol% kerosene to form the aluminum extraction organic phase. Add 2vol% 4mol / L NaOH solution to the organic phase and mix thoroughly for 30 minutes to saponify the extractant (saponification rate 48%). The saponified organic phase and the aqueous phase are subjected to four-stage continuous countercurrent extraction in an extraction clarification tank at a volume ratio of 1:1 to obtain an aluminum-loaded organic phase. The aluminum extraction rate is measured to be >99% and the magnesium extraction rate is 0 (no washing step is required). The organic phase is further stripped with 3mol / L hydrochloric acid at a volume ratio of 10:1 in the extraction clarification tank, and stripped for 3 stages to obtain an aluminum chloride solution with an aluminum purity of >99.5% and an aluminum concentration of 9-15g / L. The organic phase after stripping is returned to the extraction section for recycling.

[0047] Example 4:

[0048] The system of the present invention is used to extract and separate aluminum from rare earth ore leachate. The metal types and contents in the leachate are: 8.1 g / L aluminum, 14.4 g / L neodymium, and 14 g / L praseodymium. The extractant is 2-(decyloxy)acetic acid, the cosolvent is TBP, and the diluent is kerosene.

[0049] An aluminum extraction organic phase was prepared by mixing 24 vol% 2-(decyloxy)acetic acid, 20 vol% TBP, and 56 vol% kerosene. A 2 vol% 10 mol / L NaOH solution was added to the organic phase and mixed thoroughly for 30 minutes to saponify the extractant (saponification rate 20%). The saponified organic phase was subjected to four continuous countercurrent extractions with an aqueous phase at a 1:1 volume ratio in an extraction clarifier to obtain an aluminum-loaded organic phase. The aluminum extraction rate was measured to be >99%, and the pH after equilibrium was approximately 3.6. The aluminum-loaded organic phase was then washed with 1 mol / L hydrochloric acid at a 10:1 volume ratio in the extraction clarifier for three washes to remove co-extracted neodymium and praseodymium ions. The wash solution was then returned to the aqueous phase inlet. The organic phase was then stripped with 10 mol / L hydrochloric acid at a 10:1 volume ratio in the extraction clarifier for three strips to obtain an aluminum chloride solution with an aluminum purity >99% and an aluminum concentration of 48-81 g / L. The organic phase after stripping is returned to the extraction section for recycling.

[0050] Example 5:

[0051] The system of the present invention is used to extract and separate aluminum from laterite nickel ore leachate. The metal types and contents in the leachate are: 5.4 g / L aluminum, 2.7 g / L manganese, 3.0 g / L cobalt, 2.4 g / L magnesium, and 5.9 g / L nickel. The extractant is 2-(octyloxy)acetic acid, the cosolvent is n-octanol, and the diluent is kerosene.

[0052] The aluminum extraction organic phase was prepared by combining 16.8 vol% 2-(octyloxy)acetic acid (95% purity), 20 vol% n-octanol, and 63.2 vol% kerosene. A 2 vol% 10 mol / L NaOH solution was added to the organic phase and mixed thoroughly for 30 minutes to saponify the extractant (saponification rate 25%). The saponified organic phase was subjected to four continuous countercurrent extractions with the aqueous phase in a 1:1 volume ratio in an extraction clarifier to obtain an aluminum-loaded organic phase. The aluminum extraction rate was measured to be >98%, and the pH value after the extraction reaction equilibrium was approximately 4.2. The aluminum-loaded organic phase was then further washed with 1 mol / L hydrochloric acid in a 10:1 volume ratio in the extraction clarifier for three washes, with the wash solution returned to the aqueous phase inlet. The washed organic phase is then stripped in the extraction and clarification tank using 10 mol / L hydrochloric acid at a volume ratio of 10:1 for three stages, yielding an aluminum chloride solution with an aluminum purity of >99% and an aluminum concentration of 32-54 g / L. The stripped organic phase is then returned to the extraction section for recycling.

Claims

1. An aluminum solvent extraction system comprising a modified carboxylic acid extractant, a cosolvent, and a diluent, wherein the modified carboxylic acid extractant has a structure of Formula I, wherein R is a C4-C18 linear or branched alkyl group; n represents the number of CH2 units connected to the carboxyl functional group and is an integer from 0 to 2; 2. The aluminum solvent extraction system according to claim 1, characterized in that: The volume ratio of the modified carboxylic acid extractant is 0.5%-95%, the volume ratio of the co-solvent is 1-30%, and the balance is the diluent, based on the total volume of the extraction system.

3. The aluminum solvent extraction system according to claim 1, characterized in that: The cosolvent is one or a mixture of phosphate ester and alkyl alcohol; the diluent is one or a mixture of C6-C16 alkanes.

4. A method for extracting aluminum from a mixed metal ion solution, using the aluminum solvent extraction system according to any one of claims 1 to 3, comprising the following steps: (1) mixing a modified carboxylic acid extractant, a cosolvent, and a diluent to prepare an aluminum solvent extraction system; (2) contacting the solvent extraction system prepared in step (1) with a certain amount of base to saponify the modified carboxylic acid extractant therein to obtain a saponified solvent extraction system; (3) introducing the saponified solvent extraction system obtained in step (2) and the solution to be extracted into an extraction device for mixing, performing a single-stage extraction or a multi-stage countercurrent extraction reaction to obtain an aluminum-loaded organic phase, wherein the pH value at the equilibrium of the extraction reaction is in the range of 2.5-4.5; (4) performing single-stage washing or multi-stage countercurrent washing on the aluminum-loaded organic phase obtained in step (3) with a washing liquid to remove co-extracted impurity ions, thereby obtaining a washed aluminum-loaded organic phase; (5) subjecting the washed organic phase obtained in step (4) to single-stage back-extraction or multi-stage countercurrent back-extraction with a back-extraction liquid to obtain a back-extracted organic phase and a high-purity aluminum salt solution; (6) The organic phase after stripping obtained in step (5) is returned to the organic phase storage tank, saponified again, and recycled for aluminum extraction.

5. The method according to claim 4, characterized in that: In step (2), based on the molar concentration of aluminum in the solution to be extracted, the concentration of the carboxylic acid extractant in the solvent extraction system is determined, and the amount of the base added is determined so that the saponification rate of the extractant is in the range of 5% to 100%. The base is sodium hydroxide, potassium hydroxide, ammonia water or any mixture thereof.

6. The method according to claim 4, characterized in that: In step (3), the volume ratio of the saponified solvent extraction system to the liquid to be extracted is 1:50-50:

1.

7. The method according to claim 4, characterized in that: In step (4), the washing liquid is water, dilute hydrochloric acid or dilute sulfuric acid, and the concentration of the hydrochloric acid or sulfuric acid solution is 0.01-3.0 mol / L; the volume ratio of the organic phase to the washing liquid is 1:50-50:

1.

8. The method according to claim 4, wherein: In step (5), the stripping solution is a hydrochloric acid or sulfuric acid solution with a concentration of 0.1-12.0 mol / L; the volume ratio of the organic phase to the stripping solution is 1:50-50:

1.

9. Use of the aluminum solvent extraction system according to any one of claims 1 to 3 for extracting aluminum ions from a mixed metal ion solution.

10. The use according to claim 9, wherein the extraction of aluminum ions from a mixed metal ion solution comprises aluminum removal from a rare earth separation raw material solution, aluminum recovery from a retired battery leachate, aluminum-magnesium-lithium separation from a coal slag leachate, and aluminum separation from laterite-nickel ore.

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