A temperature-controlled homogeneous phase separation gold (III) hydrophobic extractant and its preparation and extraction method

Abstract

The application belongs to the technical field of noble metal separation, and relates to a temperature control type hydrophobic extractant for separating gold (III) in a homogeneous phase and a preparation and extraction method thereof. The extractant is a piperidine ethyl acetate type ionic liquid. The ionic liquid has excellent high selectivity, only has high extraction efficiency on gold (III) in a multi-metal mixed solution, and the extraction efficiency can be as high as 98% and above. The ionic liquid extracted into an organic phase is back-extracted by potassium oxalate to obtain high-purity gold single element, so that the separation and collection of gold are realized. After back-extraction, the ionic liquid can have good cycle efficiency, so that efficient cyclic utilization of the ionic liquid is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of noble metal separation, and relates to a hydrophobic extractant for temperature-controlled homogeneous separation of gold (III) and a preparation and extraction method thereof. BACKGROUND

[0002] Ionic liquids (ILs) are a class of organic salt compounds with unique properties. Their main characteristics include a wide electrochemical window, low vapor pressure, good thermal stability, adjustable solubility, and relatively low toxicity. These characteristics make ionic liquids have wide application potential in many fields, including chemical engineering, chemical analysis, electrochemistry, biochemistry, etc. Among them, ionic liquids show excellent performance in the separation and extraction of metal ions, thus attracting widespread attention. Traditional metal extraction methods include cyanide method, solvent extraction method and ammonia leaching method, etc. However, these methods have some significant problems, such as adverse effects on the environment, difficulties in waste disposal, poor safety, etc. Therefore, finding a more environmentally friendly and efficient metal extraction method has always been one of the focuses of research.

[0003] Ionic liquid temperature-controlled homogeneous extraction of gold is a new type of metal extraction method that has emerged in this field. Its basic principle is to use ionic liquids as extraction, and at appropriate temperatures, form a homogeneous system with lower polarity, to efficiently separate gold from other impurities. Because ionic liquids have adjustable properties, the extraction process can be designed and optimized according to the type of gold and the characteristics of the system, achieving highly selective and efficient separation. In addition, ionic liquids are easy to recover and regenerate after extraction, reducing waste generation and thus reducing adverse effects on the environment.

[0004] The ionic liquid temperature-controlled homogeneous extraction of gold technology has wide application prospects in various fields, including gold ore processing, precious metal recovery from waste electronic devices, and environmental remediation. In recent years, with the development of electronic information technology, more and more electronic waste has been generated. Precious metal recovery from waste electronic devices is an important activity in the field of resource recycling and environmental protection. With the widespread use of electronic devices and the acceleration of the replacement rate, waste electronic devices contain a large amount of precious metals, including gold, silver, platinum, palladium, etc. These precious metals are widely used in electronic circuits, connectors, semiconductors, and other components, so recovering them has multiple benefits. First, the content of precious metals in waste electronic devices is relatively high, and these metals are limited resources, whose mining and refining have adverse effects on the environment. Therefore, recovering these precious metals from waste electronic devices can reduce dependence on natural resources and reduce the environmental damage caused by mining activities. Second, waste electronic devices often contain toxic substances such as heavy metals, halides, and organic pollutants. By effectively recovering and processing these devices, the adverse effects on the environment and human health can be reduced, and the pollution of soil, water, and air by waste electronic devices can be reduced. The recovery of precious metals from waste electronic devices can also create economic benefits. These metals have high value in the market, and after recovery, they can be reused to manufacture new electronic devices or other industrial applications. Therefore, it not only helps resource conservation but also provides business opportunities for recycling companies. In summary, the recovery of precious metals from waste electronic devices is an important activity with environmental and economic benefits. By adopting innovative technologies such as ionic liquid temperature-controlled homogeneous extraction of gold, these valuable resources can be more effectively recovered, environmental damage can be reduced, and sustainable resource management can be promoted.

[0005] In summary, the ionic liquid temperature-controlled homogeneous extraction of gold(III) technology, as a new metal extraction method, has potential important application value in improving extraction efficiency and reducing environmental pollution. Therefore, further research and development work will help promote the application and development of this technology. SUMMARY

[0006] In view of the shortcomings of the prior art, the present application provides a hydrophobic ionic liquid for temperature-controlled homogeneous separation of gold(III), a preparation method and an extraction method. Based on the advantages of ionic liquids as ideal extractants with high selectivity, the present application provides a hydrophobic ionic liquid that can efficiently separate and extract gold(III) at room temperature and pressure without using diluents. The preparation method of the ionic liquid and the method for extracting and separating gold(III) using the extractant are also provided.

[0007] To achieve the above-mentioned purposes, the present application is realized by adopting the following technical solutions:

[0008] The first object of the present application is to provide a temperature-controlled homogeneous phase separation of gold (III) hydrophobic extractant, which is a piperidine ethyl acetate type ionic liquid, and its structural formula is as follows:

[0009] .

[0010] The second object of the present application is to provide a preparation method of a temperature-controlled homogeneous phase separation of gold (III) hydrophobic extractant, comprising the following steps:

[0011] Step S1, 10ml of acetonitrile is used as a solvent in a three-necked flask, and 0.3mol of 1-methylpiperidine and 0.3mol of 2-bromoethyl acetate are mixed, and then stirred at 80℃ for 8h, and then the reaction intermediate is washed and dried with ethyl acetate;

[0012] Step S2, the dried sample 5g and 5.5g of LiNTf2 are dissolved in 50ml of ultrapure water, and then stirred and mixed, and then centrifuged by a 10000 (rpm) centrifuge, and then washed with ultrapure water for 3 times, so as to remove lithium bromide and unreacted LiNTf2; then the supernatant is detected by silver nitrate solution, and no bromide ion is detected, that is, the washing is clean, and finally dried in a vacuum drying box for 48h for standby.

[0013] The third object of the present application is to provide a method for extracting gold by using the temperature-controlled homogeneous hydrophobic extractant, comprising the following steps:

[0014] (1) The gold mother liquor with a concentration of 5mmol / L and an acidity of 0.1mol / L is prepared, and the specific operation is as follows: 1g of chloroauric acid is dissolved in 12mol / L of concentrated hydrochloric acid to prepare a gold mother liquor with a concentration of 48.56 mol / L and an acidity of 0.1mol / L, and then 10.397ml of the gold mother liquor is taken and 747ul of concentrated hydrochloric acid is added, and then water is added to 100ml to obtain a gold solution with a concentration of 5mmol / L and an acidity of 0.1mol / L;

[0015] (2) The ionic liquid is directly used as an organic phase without using a diluent; 10.6mg of the organic ionic liquid is mixed with 1ml of the gold mother liquor in a constant temperature oscillator for 30 minutes, so that the gold (III) is extracted into the organic phase;

[0016] (3) The gold loaded in the ionic liquid organic phase is reduced and stripped by 0.1mol / L of potassium oxalate.

[0017] On the basis of the above scheme, further, the optimal extraction temperature in step (2) is 45℃.

[0018] Compared with the prior art, the present application has the beneficial technical effects that:

[0019] 1.The ionic liquid of the present application has simple structure, cheap and easy-to-obtain raw materials, simple synthesis method, and good thermal stability and acid resistance.

[0020] 2.The ionic liquid prepared by the present application is a green organic solvent, which overcomes the need for chloroform, organic alcohol and other organic reagents in traditional extraction of noble metals, and does not need to add volatile or toxic diluents, is more friendly to the environment, and meets the environmental protection concept of green chemistry.

[0021] 3.The ionic liquid prepared by the present application has excellent high selectivity, and in a mixed solution of multiple metals (palladium, platinum, rhodium, copper, iron, zinc, etc.), only gold (III) has very high extraction efficiency, the extraction efficiency can be as high as 98% or more, and the ionic liquid extracted into the organic phase is back-extracted with potassium oxalate to obtain high-purity gold element, realizing the separation and collection of gold. The ionic liquid after back-extraction can have good recycling efficiency, realizing efficient recycling of the ionic liquid. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is the UCST phase diagram of the ionic liquid [EOMP][NTf2];

[0023] Figure 2 is the nuclear magnetic hydrogen spectrum diagram of the ionic liquid. DETAILED DESCRIPTION

[0024] In order to more clearly define the purpose, features and advantages of the present application, the present application will be further described below in conjunction with specific examples, and in the following implementation scheme, if not specially stated, all are conventional methods.

[0025] After the extraction and separation process is completed, the metal ion concentration in the supernatant of the extraction solution before and after extraction is determined by colorimetry, and the formula for the extraction rate used is as follows:

[0026]

[0027] C in and C eq are the concentration of metal ions in the initial original solution and the concentration of residual metal ions in the equilibrium aqueous solution after extraction, respectively.

[0028] The reagents and materials used in the following examples can be obtained from commercial channels if not specially stated.

[0029] Example 1

[0030] (1) Preparation of ionic liquid [EOMP][NTf2]

[0031] In a three-necked flask, acetonitrile was used as solvent and 0.3 mol of 1-methylpiperidine was mixed with 0.3 mol of ethyl 2-bromoacetate, and then stirred magnetically at 80°C for 8 h. The reaction intermediate was washed with ethyl acetate and dried. The dried sample (5 g) and 5.5 g of LiNTf2 were dissolved in 50 ml of ultrapure water, stirred and mixed, and then centrifuged by a 10000 (rpm) centrifuge and washed with ultrapure water three times to remove lithium bromide and unreacted LiNTf2. The supernatant was then tested with silver nitrate solution and no bromide ions were detected, indicating that the washing was complete. Finally, the sample was dried in a vacuum drying oven for 48 h for standby use. The prepared ionic liquid was characterized by nuclear magnetic resonance hydrogen spectrum as shown in Figure 2 .

[0032] (2) Phase diagram drawing

[0033] A series of ionic liquids with different masses were weighed, and then 2 ml of water was added. After heating and cooling, the temperature at which the cloud point appeared was measured using a thermometer. The obtained phase diagram is shown in Figure 1 .

[0034] Table 1 UCST of [EOMP][NTf2] with different masses

[0035]

[0036] (2) Gold (III) extraction process

[0037] Ionic liquid phase: different masses of ionic liquid [EOMP][NTf2] were used as the ionic liquid organic phase;

[0038] Preparation of aqueous phase: 1 g of chloroauric acid was dissolved in 12 mol / L concentrated hydrochloric acid to prepare a 48.56 mol / L gold stock solution with an acidity of 0.1 mol / L. Then, 10.397 ml of the gold stock solution was taken and 747 ul of concentrated hydrochloric acid was added, and the volume was made up to 100 ml with water to obtain a gold solution with a concentration of 5 mmol / L and an acidity of 0.1 mol / L;

[0039] Eight 1 ml volumes of 5 mmol / L gold (III) solution with an acidity of 0.1 mol / L were taken in 7 ml centrifuge tubes, and different masses of ionic liquid (as shown in Table 2 below) were added to the above gold (III) solution and mixed. The centrifuge tubes were placed in a room temperature mechanical shaker for 30 minutes to allow the ionic liquid organic phase to fully mix with the aqueous phase. Then, the supernatant was taken after centrifugation for two minutes, and the gold (III) ion concentration of the supernatant was detected.

[0040] In the above extraction and separation process, the extraction rates of gold (III) by ionic liquids with different masses are shown in Table 2.

[0041] Table 2 Extraction efficiency of [EOMP][NTf2] for gold (III) at different quality

[0042]

[0043] Example 2

[0044] The synthesis method of the ionic liquid in this example is specifically referred to Example 1. 10.6 mg of the ionic liquid is directly used as the organic phase without using diluents;

[0045] The organic ionic liquid 10.6 mg and the gold mother liquor 1 ml prepared in Example 1 are placed in a constant temperature oscillator and shaken for 30 minutes, and the shaking temperature is 25-50°C

[0046] Table 3 Extraction efficiency of [EOMP][NTf2] for gold (III) at different temperatures for 15 minutes

[0047]

[0048] With the increase of temperature, the extraction efficiency gradually increases, and when the temperature is 45°C, the extraction efficiency basically remains unchanged. This is mainly because with the increase of temperature, the UCST temperature of the ionic liquid and the aqueous phase is reached, and the mass transfer rate between the ionic liquid and the aqueous phase is accelerated, so that the extraction efficiency can be increased.

[0049] Example 3

[0050] (1) Preparation of ionic liquid [EOMP][NTf2]

[0051] The synthesis method of the ionic liquid in this example is specifically referred to Example 1.

[0052] (2) Extraction process of gold (III) ionic liquid phase: 10.6 mg of ionic liquid is used as the ionic liquid phase.

[0053] (3) Preparation of aqueous phase: a certain volume of gold (III) mother liquor prepared in Example 1 is taken, the chloride ion concentration is unchanged, then different volumes of concentrated HCl are added, and water is added to 100 ml to prepare gold solutions with different hydrochloric acid concentrations (5 mmol / L), which are added to 7 ml centrifuge tubes to mix with the ionic liquid. Then put it into a constant temperature mechanical shaker and shake for 30 minutes to make the ionic liquid and the aqueous phase fully mixed. Then use the centrifuge to centrifuge for two minutes, and then take out the supernatant extraction liquid.

[0054] In the above extraction and separation process, the extraction efficiency of different hydrochloric acid concentrations is as shown in Table 4.

[0055] Table 4 Extraction efficiency of [EOMP][NTf2] for gold (III) at different hydrochloric acid concentrations

[0056]

[0057] With the addition of hydrochloric acid, the extraction rate of ionic liquid to gold decreased, which was mainly due to the competition between hydrogen ions in hydrochloric acid and ionic liquid cations for gold tetrachloride anions, which reduced the combination of ionic liquid cations and gold tetrachloride anions, thereby leading to a decrease in extraction efficiency.

[0058] Example 4

[0059] (1) Preparation of ionic liquid [EOMP][NTf2]

[0060] The synthesis method of the ionic liquid in this example is specifically referred to Example 1.

[0061] (2) Extraction process of gold (III)

[0062] Ionic liquid phase: 10.6 mg of ionic liquid was taken as the ionic liquid phase.

[0063] (3) Preparation of aqueous phase: 5 parts of gold mother liquor were taken, and by adding concentrated hydrochloric acid and sodium chloride, a mixed solution with a gold (III) concentration of 5 mmol / L and a fixed chloride ion concentration of 4 mol / L was prepared. The volume of the final mixed solution was the same, so that the hydrogen ion concentration in each part of the mixed solution was different. The ionic liquid and gold mother liquor were mixed in a 7 ml centrifuge tube, then put into a room temperature shaker for 30 minutes, so that the ionic liquid phase and the aqueous phase were fully mixed, then put into a centrifuge for two minutes to separate the supernatant raffinate, and detect the residual gold (III) ion concentration of the raffinate.

[0064] The extraction efficiency under different hydrogen ion concentrations in the above extraction process is shown in Table 5.

[0065] Table 5 Extraction rate of [EOMP][NTf2] to gold (III) under different hydrogen ion concentrations

[0066]

[0067] In order to further prove that it is the influence of hydrogen ion concentration in hydrochloric acid, here the chloride ion concentration is fixed at 4 mol / L, it can be found that with the increase of hydrogen ion concentration, the extraction efficiency decreases.

[0068] Example 5

[0069] (1) Preparation of ionic liquid [EOMP][NTf2]

[0070] The synthesis method of the ionic liquid in this example is specifically referred to Example 1.

[0071] (2) Extraction process of gold (III)

[0072] The water phase was prepared by taking the mother liquor of gold, fixing the hydrogen ion concentration at 0.1 mol / L, adding sodium chloride solution to prepare a series of different chloride ion concentrations as shown in the table below, and then taking 1 ml of the solution and mixing it with the ionic liquid in a 7 ml centrifuge tube, and placing it in a room temperature mechanical shaker for 30 minutes. After the shaking was completed, it was placed in a centrifuge for two minutes, and the supernatant extract was taken, and the gold (III) ion concentration of the supernatant raffinate was detected.

[0073] The extraction efficiency of the above extraction process under different hydrogen ion concentrations is shown in Table 6.

[0074] Table 6 [EOMP][NTf2] extraction rate of gold (III) under different chloride ion concentrations

[0075]

[0076] As can be seen from the table, as the chloride ion concentration increases, the extraction rate remains essentially unchanged, which indicates that the main factor affecting the extraction of gold by ionic liquid is the hydrogen ion concentration.

[0077] Example 6

[0078] In this example, the extraction rate of the extractant for other metals was studied and counted.

[0079] (1) Preparation of ionic liquid [EOMP][NTf2]

[0080] The synthesis method of the ionic liquid in this example is specifically referred to in Example 1.

[0081] (2) Extraction process of gold (III)

[0082] Ionic liquid phase: 10.6 mg of ionic liquid was taken as the ionic liquid phase.

[0083] Preparation of water phase: take the mother liquor containing gold and other metal ions (Pd(II), Pt(IV), Ru(III), Rh(II), Ir(II)), add hydrochloric acid and dilute with ultrapure water to prepare a 5 mmol / L mixed metal solution, and the hydrochloric acid concentration of the water phase is 0.1 mol / L. The water phase was mixed with the ionic liquid in a 7 ml centrifuge tube, and placed in a room temperature mechanical shaker for 30 minutes. After the shaking was completed, it was placed in a centrifuge for two minutes, and the supernatant extract was taken, and the gold (III) ion concentration of the supernatant raffinate was detected.

[0084] The extraction rate of each metal in the above extraction and separation process is shown in Table 7. This ionic liquid has high selectivity for gold (III), and has poor extraction selectivity for other metal ions.

[0085] Table 7 [EOMP][NTf2] extraction rate of each metal extraction agent

[0086]

[0087] Example 7

[0088] This embodiment is to strip separation of gold (III) in ionic liquid

[0089] (1) Gold (III) loaded ionic liquid phase: take the gold (III) loaded ionic liquid phase after extraction in Example 2.

[0090] (2) Stripping separation process of gold

[0091] Take the gold loaded ionic liquid phase after extraction in Example 2 and put it into a 7ml centrifuge tube, then add 1ml of 1mol / L potassium oxalate as stripping agent, mechanically shake for 30 minutes at room temperature, so that the gold loaded organic phase and oxalic acid aqueous phase fully react, and the gold originally loaded in the organic phase can be clearly seen to gradually separate from the organic phase and adhere to the wall of the test tube during the shaking process. After a certain amount of stripping solution is taken, the stripping rate of gold (III) is analyzed after detection, and the stripping efficiency can reach more than 99%.

[0092] The present application relates to a kind of high-efficiency separation gold (III) extractant and extraction means, to provide a kind of efficient, environmental protection, sustainable metal extraction method.Extractant based on piperidine ethyl acetate type ionic liquid, the extractant of the present application is simple in structure, raw material is cheap, preparation method is simple and easy to obtain, and the prepared ionic liquid has good thermal stability and acid resistance.The method provided by the present application realizes the highly selective extraction of gold (III) by forming a homogeneous system under appropriate temperature operation.This method not only improves the recovery rate of gold, but also helps to reduce the adverse effects on the environment.In addition, ionic liquid is easy to recover and regenerate, reduces waste generation, thereby improving resource utilization efficiency.The present application describes in detail the operation steps of ionic liquid temperature control homogeneous extraction of gold (III) and the selection of related parameters, as well as the synthesis and regeneration method of ionic liquid.The extractant has high selectivity and realizes the separation of gold from other types of metal ions in a multi-metal mixed solution.The extraction method provided by the present application directly uses ionic liquid for direct extraction, without the help of any diluent to directly contact with gold in aqueous phase, and is not affected by the concentration of chloride ions in the extraction process, has high salt resistance, conforms to the concept of environmental green and efficient chemistry, and finally, the present application provides an innovative metal extraction method, which is expected to realize efficient gold extraction and resource management in multiple fields, while reducing the adverse effects on the environment.

[0093] The above merely describes preferred embodiments of the present application, but is not intended to limit the present application to other forms, any person skilled in the art can make changes or modifications to the above disclosed technical contents into equivalent embodiments with equivalent changes, and apply to other fields, but any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application without departing from the technical solution content of the present application still belongs to the protection scope of the present application technical solution.

Claims

1. A temperature dependent homogenous phase separation hydrophobic extractant for trivalent gold, characterized in that: The extractant is piperidine ethyl acetate type ionic liquid, and its structural formula is as follows: 。 2. A process for the preparation of a temperature dependent homogeneous phase separation trivalent gold hydrophobic extractant as claimed in claim 1, characterized in that: The method comprises the following steps: Step S1, 10ml acetonitrile is used as a solvent in a three-necked flask, and 0.3mol 1-methylpiperidine and 0.3mol 2-bromoethyl acetate are added and mixed, and then stirred at 80℃ for 8h, and then the reaction intermediate is washed and dried with ethyl acetate; Step S2, the dried sample 5g and 5.5g of LiNTf2 are dissolved in 50ml ultrapure water, and then stirred and mixed, and then centrifuged by a 10000rpm centrifuge, and then washed with ultrapure water for 3 times, so as to remove lithium bromide and unreacted LiNTf2; then the supernatant is taken and detected by silver nitrate solution, and no bromide ion is detected, that is, the washing is clean, and finally dried in a vacuum drying box for 48h for standby.

3. A method of extracting gold using the temperature dependent homogeneous liquid-liquid extraction of trivalent gold with the hydrophobic extractant of claim 1, characterized in that: The method comprises the following steps: (1) chloroauric acid is dissolved in 12mol / L concentrated hydrochloric acid, and water is added to constant volume, and a gold mother liquor with a concentration of 5mmol / L and an acidity of 0.1mol / L is prepared; (2) the ionic liquid is directly used as an organic phase without using a diluent; 10.6mg of the organic ionic liquid is shaken with 1ml of the gold mother liquor in a constant temperature oscillator for 30min, so that the trivalent gold is extracted into the organic phase; (3) the gold loaded in the ionic liquid organic phase is reduced and back-extracted by using 0.1mol / L potassium oxalate.

4. The method of claim 3, wherein the temperature-dependent homogeneous liquid-liquid separation of trivalent gold using a hydrophobic gold extractant is characterized by: The optimal extraction temperature in the step (2) is 45℃.

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