A deep eutectic solvent and a preparation method and application thereof

Abstract

The application discloses a kind of eutectic solvent and its preparation method and application, will thymol and DL-lactic acid according to molar ratio 1:3 mixed, heating stirring, obtain eutectic solvent.Sodium nitrate and eutectic solvent are added to environmental water, vortex, stratify after standing, i.e. organic phase containing silver ion is obtained, the organic phase is eutectic solvent.The eutectic solvent liquid-liquid extraction technology overcomes the traditional liquid-liquid distribution cumbersome, time-consuming, needs to consume a large amount of toxic and harmful solvent, easy to pollute environment and other shortcomings, make sample more environmentally friendly in the pretreatment process, and reduce the amount of organic reagent, compared with existing solid phase extraction adsorbent, without preparing solid phase extraction adsorbent, preparation method is simple, the obtained eutectic solvent is applied to the extraction of silver ion in environmental water, with high accuracy, high precision, good reproducibility, high sensitivity, simple operation, fast and other advantages, show wide application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of heavy metal detection, and particularly relates to a deep eutectic solvent and a preparation method and application thereof. BACKGROUND

[0002] Liquid-liquid extraction (LLE) refers to a process that after two completely immiscible or partially miscible liquid phases are contacted, a solute in one liquid phase is subjected to physical or chemical action on the other liquid phase, or is redistributed in the two phases, and has the characteristics of large processing capacity, good separation effect, high recovery rate, continuous operation, etc.

[0003] Deep eutectic solvent (DESs) is a homogeneous mixture composed of two or more substances in a certain molar ratio. Common DESs are mainly composed of organic salts such as quaternary ammonium salt and quaternary phosphonium salt, and organic compounds such as carboxylic acid, polyol and urea. The former is a hydrogen bond acceptor (HBA), and the latter is a hydrogen bond donor (HBD). According to the different types of cations of the constituent ionic liquid, the ionic liquid can be divided into imidazole, pyridine, quaternary ammonium salt, etc. In recent years, natural deep eutectic solvent (NADES) has also appeared.

[0004] Compared with ordinary organic reagents, deep eutectic solvents have many unique properties, such as a wide variety of deep eutectic solvents with high designability, simple preparation and low technical requirements, good solubility for various biological organic matter and metal inorganic matter, basic green reagents for composition components, low toxicity or non-toxicity of the solvent, and almost negligible vapor pressure, so the volatility is extremely small, and it is more safe. With the above advantages, deep eutectic solvents are often considered as an environmentally friendly green solvent, especially the more green natural deep eutectic solvent.

[0005] The development trend of modern analysis methods is to reduce the use of toxic and harmful solvents, reduce experimental costs, and at the same time improve the sensitivity and selectivity of detection, and as much as possible realize the integration of enrichment, extraction and detection. Deep eutectic solvents inherit the advantages of ionic liquids and have good solubility for many natural ingredients. At the same time, compared with other ionic liquids, the price of deep eutectic solvents is low, and they also have low toxicity, showing good environmental friendliness. In the extraction experiment, deep eutectic solvents begin to replace traditional solvents, and their green and efficient characteristics provide help for the development of the field of analytical chemistry, especially in the field of sample pretreatment.

[0006] Silver is a non-essential trace metal element in human body and also exists in nature. As an excellent antibacterial material, nano-silver and silver ions have been widely used in medicine, environment and other fields. Most people still stay on the antibacterial property of silver, ignoring the potential adverse effects on the growth of animals and plants. Excessive intake of silver from the outside world will cause silver deposition in the human body, causing harm to the immune system, digestive and nervous systems.

[0007] Silver is a noble metal, which is widely used in material industry, electronic industry and aerospace department. At the same time, silver is also an important environmental element, and its content in water is low. Silver or silver salt will deposit in the skin, eyes and mucous membranes after entering the human body, causing pathological changes and chronic poisoning. Therefore, it is necessary to determine trace silver. Inductively coupled plasma atomic emission spectrometry is the most common atomic emission spectrometer at present, which can determine most elements in the periodic table. It has the characteristics of high sensitivity, small interference, wide linear range and simultaneous (or sequential) determination of multiple elements. Although ICP-AES has high sensitivity, it is still difficult to directly determine trace silver in environmental water, which is mainly caused by low silver ion concentration and matrix interference.

[0008] Patent CN102225247A discloses a method for treating a solution containing trace silver ions and a solid phase extraction adsorbent used in the method. The method comprises the following steps: ① preparing a solid phase extraction adsorbent; ② adsorbing silver ions in the solution containing trace silver ions with the solid phase extraction adsorbent; ③ eluting the silver ions adsorbed on the solid phase extraction adsorbent with a nitric acid solution, so that the nitric acid solution becomes an eluent containing silver ions. The solid phase extraction adsorbent is obtained by activating nano-silicon dioxide with concentrated hydrochloric acid, then silanizing the activated nano-silicon dioxide with a silane coupling agent, and then modifying the silanized nano-silicon dioxide with ammonium pyrrolidine dithiocarbamate. The method needs to prepare the solid phase extraction adsorbent before extracting silver ions in water. After the silver ions are adsorbed on the solid phase extraction adsorbent, the silver ions need to be eluted and determined. The operation method is complicated and not suitable for large-scale promotion.

[0009] Therefore, how to provide a eutectic solvent for extracting silver ions from environmental water, which is safe for the environment and the operator, and has a simple preparation method, has become a problem that a person skilled in the art needs to solve urgently. SUMMARY

[0010] The purpose of the present application is to provide a eutectic solvent, a preparation method and application thereof, to solve the problems existing in the prior art.

[0011] The present application provides a eutectic solvent, which is composed of musk amphenol and DL-lactic acid with a molar ratio of 1:3.

[0012] Beneficial effects: the eutectic solvent containing carboxyl group is easy to chelate with metal cations to form a complex, the hydrogen bond donor of the eutectic solvent is lactic acid (scientific name 2-hydroxypropanoic acid), which can be used as a hydroxyl carboxylic acid chelating agent, the pH value of the eutectic solvent obtained by mixing lactic acid and thymol according to a molar ratio of 1:3 is 3-4, at the pH value, the chelating ability of the eutectic solvent provided by the application to other metal ions except silver ions is weak, and the chelating effect of silver ions attached to the eutectic solvent by forming a coordination bond with lactic acid does not produce precipitation, realizing separation from the aqueous phase.

[0013] The application further provides a preparation method of the eutectic solvent: mixing thymol and DL-lactic acid, heating and stirring to obtain the eutectic solvent.

[0014] Further, the mixing time is 5-10 min; the heating temperature is 40-50 DEG C, and the time is 10-20 min.

[0015] The application further provides an application of the eutectic solvent in extracting silver ions from environmental water.

[0016] Further, sodium nitrate and the eutectic solvent are added to the environmental water, vortexed, and then allowed to stand and separate, and the silver ions are extracted into the organic phase, i.e. the eutectic solvent.

[0017] Further, the adding amount ratio of the environmental water, the eutectic solvent and sodium nitrate is 5.0 mL:10 mL:5 mg; the vortexing time is 4 min; and the standing time is 6 h.

[0018] Beneficial effects: when the silver ions are extracted from the environmental water, an appropriate amount of sodium nitrate is first added, and then the eutectic solvent is added, the added sodium nitrate promotes the reaction of the silver ions and the eutectic solvent through salting-out effect, so that the extraction purpose is achieved, the viscosity of the eutectic solvent itself is greater than that of water, and the addition of excessive salt will affect the viscosity of the eutectic solvent, the viscosity of the organic phase solution will increase, the rate of the target into the eutectic solvent will be reduced, and the extraction of the silver ions is not conducive.

[0019] Beneficial effects of the application:

[0020] (1) The present application obtains a natural eutectic solvent by mixing thymol and DL-lactic acid, stirring and heating, the natural eutectic solvent overcomes the defects of traditional liquid-liquid distribution operation, such as complicated operation, time-consuming, consumption of a large amount of toxic and harmful solvents, easy to pollute the environment, etc., so that the sample is more environmentally friendly in the pretreatment process, and the use amount of organic reagent is reduced, compared with the existing solid phase extraction adsorbent, the solid phase extraction adsorbent does not need to be prepared, the preparation method is simple, the obtained eutectic solvent is applied to the extraction of silver ions in environmental water, and the eutectic solvent has the advantages of high accuracy, high precision, good reproducibility, high sensitivity, simple operation, rapidness and the like, and shows a broad application prospect;

[0021] (2) When detecting silver ions in drinking water, the silver ions in the drinking water are extracted into an organic phase by the eutectic solvent, then the organic matter is removed by microwave digestion, and after being diluted with 2% nitric acid solution, a silver ion analysis solution is obtained. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description only constitute some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without any creative labor.

[0023] Figure 1 The experimental flow chart for detecting silver ion concentration in water in the present embodiment 1;

[0024] Figure 2 The standard curve obtained in embodiment 1, with the spectral line intensity (A) as the ordinate and the concentration (C) as the abscissa. DETAILED DESCRIPTION

[0025] Now, various exemplary embodiments of the present application will be described in detail, which should not be considered as limitations of the present application, but should be understood as a more detailed description of some aspects, characteristics and embodiments of the present application.

[0026] It should be understood that the terms described in the present application are only for describing the specific embodiments, and are not used to limit the present application. In addition, for the numerical range in the present application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or intermediate value in the stated range and any other stated value or intermediate value in the stated range is also included in the present application. The upper limit and the lower limit of these smaller ranges can be independently included or excluded from the range.

[0027] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as those of ordinary skill in the art to which the application relates. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, preferred methods and materials are described. All publications mentioned in the specification are incorporated by reference to disclose and describe the methods and / or materials in connection with which the publications are cited. In case of conflict between the content of the specification and that of any document incorporated by reference, the content of the specification prevails.

[0028] Many modifications and variations of the present application described in the specification are possible without departing from the scope or spirit of the application. Other implementations of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples given are exemplary only.

[0029] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having" or the like are open-ended terms that are intended to mean including, but not limited to.

[0030] The room temperature of the present application refers to 25±2℃.

[0031] The DL-lactic acid used in the present application refers to racemic lactic acid, which is obtained by purchase.

[0032] The present embodiment provides a eutectic solvent, which is composed of thymol and DL-lactic acid in a molar ratio of 1:3.

[0033] The preparation method of the eutectic solvent is to mix thymol and DL-lactic acid, heat and stir to obtain the eutectic solvent.

[0034] Further, the mixing time is 5-10 min; the heating temperature is 40-50℃, and the time is 10-20 min.

[0035] The present embodiment also provides the application of the eutectic solvent in extracting silver ions from environmental water.

[0036] Sodium nitrate and eutectic solvent are added to environmental water, vortexed, and allowed to stand and separate into layers, to obtain an organic phase containing silver ions, which is the eutectic solvent.

[0037] Further, the ratio of the amount of environmental water, eutectic solvent and sodium nitrate added is 5.0 mL:10 mL:5 mg; the vortexing time is 4 min; and the standing time is 6 h.

[0038] The inductively coupled plasma emission spectroscopy conditions in this embodiment are as follows: sample lift: 1 mL; plasma gas flow rate: 15.0 L / min; auxiliary flow rate: 0.2 L / min; nebulizer gas flow rate: 0.55 L / min; radio frequency power: 1300 W; detection wavelength: Ag 328.068 nm.

[0039] In the following examples and comparative examples, inductively coupled plasma optical emission spectrometry (ICP-OES) was used to detect the sample analysis solution. The model of the inductively coupled plasma optical emission spectrometer was Optima8000, the automatic AC voltage regulator was TND1-10, the oil-free air compressor was W120D, and the refrigerator was POLYSCIENCE WHISPERCOOL.

[0040] The experimental consumables included: high-purity argon, vortex mixer, stirrer heater, 0.22μm organic phase microporous filter membrane, 10mL pipette and 5mL syringe; all reagents were of analytical grade and the water used in the entire experiment was ultrapure water.

[0041] Example 1

[0042] Methodological validation for the determination of silver ions in water by inductively coupled plasma atomic emission spectrometry

[0043] Inductively coupled plasma emission spectroscopy conditions: sample lift: 1 mL; plasma gas flow rate: 15.0 L / min; auxiliary flow rate: 0.2 L / min; nebulizer gas flow rate: 0.55 L / min; RF power: 1300 W; detection wavelength: Ag (328.068 nm);

[0044] Construction of standard curves: Take five 50 mL volumetric flasks and add 0.05 mL, 0.25 mL, 0.50 mL, 1.00 mL, 2.50 mL, and 5.00 mL of 10 mg / L silver standard stock solution, respectively. Then, add 5% (mass concentration) nitric acid solution to make up to the volume to obtain silver standard solutions with concentrations of 0.01 mg / L, 0.05 mg / L, 0.10 mg / L, 0.20 mg / L, 0.50 mg / L, and 1.00 mg / L.

[0045] Under the above spectral detection conditions of the inductively coupled plasma atomic emission spectrometer, the above concentrations of silver standard solutions were tested on the instrument, and each concentration was measured in parallel three times. A standard curve was plotted with spectral line intensity (A) as the ordinate and concentration (C) as the abscissa. The linear equation, correlation coefficient and linear range are shown in Table 1. The instrument detection limit is 1.8 μg / L and the quantitation limit is 6.0 μg / L.

[0046] Table 1

[0047] Name Linear equation Linear range / (mg / L) Correlation coefficient r 2 ]] Silver ion A = 348617C + 2567.2 0.01～1.00 0.9998

[0048] Example 2

[0049] A method for preparing a eutectic solvent

[0050] Thymol and DL-lactic acid were mixed at a molar ratio of 1:3 for 5 min, and then heated in a water bath at 50°C for 10 min under magnetic stirring of a constant temperature magnetic stirrer to obtain a eutectic solvent.

[0051] Example 3

[0052] A method for preparing a eutectic solvent

[0053] Thymol and DL-lactic acid were mixed at a molar ratio of 1:3 for 8 min, and then heated in a water bath at 45°C for 15 min with magnetic stirring to obtain a eutectic solvent.

[0054] Example 4

[0055] A method for preparing a eutectic solvent

[0056] Thymol and DL-lactic acid were mixed at a molar ratio of 1:3 for 10 min, and then heated in a water bath at 40 °C for 20 min with magnetic stirring to obtain a eutectic solvent.

[0057] Example 5

[0058] 1. Determination of the recovery rate of silver ions extracted from water using eutectic solvents

[0059] 1) Preparation of spiked silver solutions: Prepare silver standard solutions with concentrations of 0.05 mg / L, 0.10 mg / L, and 0.15 mg / L as spiked silver solutions;

[0060] 2) Preparation of sample analysis solution; Take three 20mL transparent volumetric flasks, add 5.00mL of the spiked silver solution from step 1) to each flask, then add 5mg of sodium nitrate to each flask, and then add 10mL of the eutectic solvent obtained in Example 2. Vortex for 4min, let stand at room temperature for 6h, and wait for the aqueous phase and organic phase to separate into layers. Use a 5mL syringe to aspirate the lower aqueous phase solution, and filter the aspirated aqueous phase through a 0.22μm organic phase microporous filter membrane to obtain the sample analysis solution.

[0061] 3) Determination of recovery rate: The sample analysis solution obtained in step 2) was measured 5 times using the determination method provided in Example 1, and the recovery rate was calculated. See Table 2.

[0062] Figure 1 This is a flowchart of the experiment for extracting silver ions from a water sample in Example 4.

[0063] 2. Determination of the precision of silver ion extraction from water using eutectic solvents

[0064] 2.1 Determination of intra-day precision

[0065] Within one day, the spiked silver solutions of various concentrations in step 1) of Example 4 were treated in parallel five times using step 2) of Example 4, and the results were determined by the determination method provided in Example 1. The RSD of the obtained recovery rate is expressed as shown in Table 2.

[0066] 2.2 Determination of intraday precision

[0067] The sample was processed five times daily using the silver spiking solution of various concentrations in step 1) of Example 4, with each sample being processed in parallel for three days. The resulting sample was analyzed using the determination method provided in Example 1. The results were expressed as the RSD of the recovery rate, as shown in Table 2.

[0068] 3. Determination of the linear range for the extraction of silver ions from water using eutectic solvents

[0069] 1) Preparation of spiked silver solutions: Prepare silver standard solutions with concentrations of 0.05 mg / L, 0.15 mg / L, 0.6 mg / L, 2.5 mg / L, and 10 mg / L as spiked silver solutions;

[0070] 2) Preparation of sample analysis solution; Take five 20mL transparent volumetric flasks, add 5.00mL of the spiked silver solution from step 1) to each flask, then add 5mg of sodium nitrate to each flask, and then add 10mL of the eutectic solvent obtained in Example 2. Vortex for 4min, let stand at room temperature for 6h, and wait for the aqueous phase and organic phase to separate into layers. Use a 5mL syringe to aspirate the lower aqueous phase solution, and filter the aspirated aqueous phase through a 0.22μm organic phase microporous filter membrane to obtain the sample analysis solution.

[0071] 3) Determination of linear range: The sample analysis solution obtained in step 2) was measured 6 times using the determination method provided in Example 1. The correlation coefficient, linear equation and linear range are shown in Table 3.

[0072] 4. Determination of the detection limit and quantitation limit of silver ions extracted from water using eutectic solvents.

[0073] 1) Preparation of spiked silver solutions: Prepare silver standard solutions with concentrations of 0.001 mg / L and 0.005 mg / L as spiked silver solutions;

[0074] 2) Preparation of sample analysis solution; Take two 20mL transparent volumetric flasks, add 5.00mL of the spiked silver solution from step 1) to each flask, then add 5mg of sodium nitrate to each flask, and then add 10mL of the eutectic solvent obtained in Example 2. Vortex for 4min, let stand at room temperature for 6h, and wait for the aqueous phase and organic phase to separate into layers. Use a 5mL syringe to aspirate the lower aqueous phase solution, and filter the aspirated aqueous phase through a 0.22μm organic phase microporous filter membrane to obtain the sample analysis solution.

[0075] 3) Determination of detection limit and quantitation limit: The sample analysis solution obtained in step 2) was measured 6 times using the determination method provided in Example 1. The detection limit and quantitation limit were calculated and are shown in Table 4.

[0076] 5. Interference test of silver ion extraction from water by eutectic solvents

[0077] A mixed standard solution of seven metal ions (Ag, Zn, Cu, Ba, Mn, Ni, Cr) with a concentration of 1000 μg / mL was prepared using a 5% (mass concentration) nitric acid solution.

[0078] Take 10 mL of the above metal ion mixed standard solution, place it in a 100 mL volumetric flask, add 5% (mass concentration) nitric acid solution to make up to volume, and then serially dilute to 10 μg / mL to obtain the interference test solution.

[0079] Take a 20mL transparent volumetric flask, add 5.00mL of the above interference test solution, then add 5mg of sodium nitrate, and then add 10mL of the eutectic solvent obtained in Example 2. Vortex for 4min, let stand at room temperature for 6h, and wait for the aqueous phase and organic phase to separate into layers. Use a 5mL syringe to draw up the lower aqueous phase solution, and filter the drawn aqueous phase through a 0.22μm organic phase microporous membrane to obtain the interference test sample analysis solution.

[0080] The measurement wavelengths provided in Example 1 were adjusted to Ag (328.068 nm), Zn (206.200 nm), Cu (327.393 nm), Ba (233.527 nm), Mn (257.610 nm), Ni (231.604 nm), and Cr (267.716 nm), respectively, while keeping other conditions unchanged. The analytical solutions of the resulting interference test samples were measured, and the recovery rates of the above seven metals were calculated, as shown in Table 5.

[0081] Comparative Example 1

[0082] Similar to Examples 2 and 5, except that the molar ratio of thymol to DL-lactic acid is 1:2. The recovery rate and precision test results of silver ions extracted from water are shown in Table 2, the linearity test results are shown in Table 3, the detection limit and quantitative phase results are shown in Table 4, and the interference test results are shown in Table 5.

[0083] Comparative Example 2

[0084] Similar to Examples 2 and 5, except that the molar ratio of thymol to DL-lactic acid is 1:4. The recovery rate and precision test results of silver ions extracted from water are shown in Table 2, the linearity test results are shown in Table 3, the detection limit and quantitative phase results are shown in Table 4, and the interference test results are shown in Table 5.

[0085] Comparative Example 3

[0086] Same as Example 5, except that the amounts of spiked silver solution, eutectic solvent and sodium nitrate added are 5 mL: 10 mL: 0 mg, and the concentration of sodium nitrate is 0 mg / mL. The recovery rate and precision test results of silver ions extracted from water are shown in Table 2, the linearity test results are shown in Table 3, the detection limit and quantitative phase results are shown in Table 4, and the interference test results are shown in Table 5.

[0087] Comparative Example 4

[0088] Same as Example 5, except that the amounts of spiked silver solution, eutectic solvent and sodium nitrate added are 5 mL: 10 mL: 50 mg, and the concentration of sodium nitrate is 10 mg / mL. The recovery rate and precision test results of silver ions extracted from water are shown in Table 2, the linearity test results are shown in Table 3, the detection limit and quantitative phase results are shown in Table 4, and the interference test results are shown in Table 5.

[0089] Comparative Example 5

[0090] Same as Example 5, except that the vortex oscillation time is 1 min. The recovery rate and precision test results of silver ions extracted from water are shown in Table 2, the linearity test results are shown in Table 3, the detection limit and quantitative phase results are shown in Table 4, and the interference test results are shown in Table 5.

[0091] Table 2

[0092]

[0093]

[0094] As shown in Table 2, when silver ions in water samples are extracted using the eutectic solvent provided by this invention, the addition amounts of water sample, eutectic solvent, and sodium nitrate are limited to 5 mL: 10 mL: 5 mg, and the recovery rate and precision are better than those of comparative examples 1-5.

[0095] Table 3

[0096] Name Linear equation Linear range / (mg / L) Correlation coefficient r 2 ]] Example 5 y = 395744x + 18.2 0.05～10 0.9990 Comparative Example 1 y = 254185x + 486.2. 0.05～10 0.9840 Comparative Example 2 y = 336382x + 102.7 0.05～10 0.9972 Comparative Example 3 y = 387433x + 47.4 0.05～10 0.9973 Comparative Example 4 y = 379310x + 80.1 0.05～10 0.9952 Comparative Example 5 y = 387829x + 21.8 0.05～10 0.9989

[0097] As shown in Table 3, under the extraction method provided by the present invention, by setting the molar ratio of thymol and DL-lactic acid to 1:3, and limiting the amount of water sample, eutectic solvent and sodium nitrate to 5 mL: 10 mL: 5 mg, the correlation linearity obtained in the linear range of 0.05 to 10 mg / L is better than that of comparative examples 1-5.

[0098] Table 4

[0099] Limit of detection (pg / L) Limit of quantification (pg / L) Example 5 2.0 6.6 Comparative Example 1 4.4 14.5 Comparative Example 2 2.8 9.2 Comparative Example 3 2.1 6.9 Comparative Example 4 3.5 11.6 Comparative Example 5 2.0 6.6

[0100] As shown in Table 4, when silver ions in water samples were extracted using the eutectic solvent provided by this invention, the addition amounts of water sample, eutectic solvent, and sodium nitrate were limited to 5 mL: 10 mL: 5 mg. The detection limit and quantitation limit were both lower than those of comparative examples 1-4. This demonstrates that the eutectic solvent provided by this invention exhibits good sensitivity when applied to the extraction of mercury ions in the environment.

[0101] Table 5

[0102]

[0103] As shown in Table 5, when silver ions in water samples are extracted using the eutectic solvent provided by this invention, the addition amounts of water sample, eutectic solvent, and sodium nitrate are limited to 5 mL: 10 mL: 5 mg, resulting in low interference from the extraction of silver ions by the remaining metal ions in the water sample.

[0104] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. The application of a eutectic solvent in the extraction of silver ions from ambient water; characterized in that, Sodium nitrate and a eutectic solvent were added sequentially to the ambient water, vortexed, and allowed to stand to separate into layers. Silver ions were extracted into the organic phase. The ratio of the amount of environmental water, eutectic solvent and sodium nitrate added is 5.0 mL: 10 mL: 5 mg; The vortex duration is 4 minutes; The eutectic solvent is composed of thymol and DL-lactic acid in a molar ratio of 1:

3. The resulting eutectic solvent has a pH value of 3-4. The eutectic solvent has a weak chelating ability for metal ions other than silver ions. Silver ions adhere to the eutectic solvent through the chelation effect of forming a coordinate bond with lactic acid without precipitation, thus achieving separation from the aqueous phase.

2. The application according to claim 1, characterized in that, Thymol and DL-lactic acid were mixed and heated with stirring to obtain a eutectic solvent.

3. The application according to claim 2, characterized in that, The mixing time is 5-10 minutes.

4. The application according to claim 2, characterized in that, The heating temperature is 40-50℃, and the time is 10-20 minutes.

5. The application according to claim 1, characterized in that, The settling period is at room temperature for 6 hours.

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