A deep eutectic solvent and preparation thereof, a metal leaching agent and a metal leaching method

Abstract

This invention discloses a eutectic solvent and its preparation, a metal leaching agent, and a metal leaching method. The eutectic solvent is prepared by mixing choline chloride and a sulfonamide compound in a specific ratio; the sulfonamide compound is sulfonamide, 4-amino-N-(aminoiminomethyl)benzenesulfonic acid, or p-aminobenzenesulfonamide. This invention provides a metal leaching agent containing the aforementioned eutectic solvent, which is a transparent liquid prepared from the eutectic solvent and an auxiliary agent. The auxiliary agent is at least one selected from 1,3-dibromo-5,5-dimethylhydantoin, 1,3-dichloro-5,5-dimethylhydantoin, N-chlorosuccinimide, N-bromosuccinimide, chloramine T, and sodium hypochlorite. The eutectic solvent of this invention is an environmentally friendly compound, and the metal leaching agent system containing this eutectic solvent possesses both good oxidizing and coordinating abilities, enabling the leaching of gold and palladium with rapid leaching speed and high extraction rate.

Description

Technical Field

[0001] This invention relates to a eutectic solvent and its preparation method, a metal leaching agent containing the eutectic solvent, and a metal leaching method based on the metal leaching agent. Background Technology

[0002] In 2003, Abbott et al. defined a new type of solvent, the so-called eutectic solvent (DESs). Eutectic solvents (DESs) are a new class of ionic liquid analogs, but unlike ionic liquids, they are not entirely composed of ionic substances. As a novel type of green solvent, DESs are inexpensive, biodegradable, and structurally more diverse. By changing the molar ratio of hydrogen bond acceptors (HBAs) and hydrogen bond donors (HBDs) or selecting appropriate ratios of HBAs and HBDs, their physicochemical properties can be customized to meet specific requirements, replacing traditional hazardous chemical solvents. They are now widely used in research. The preparation of DESs does not require environmentally polluting hazardous chemical solvents. Through the establishment of hydrogen bonds, these solvents exhibit melting points much lower than those of their constituent compounds.

[0003] Hydrogen bond acceptors (DESs) are mixtures of hydrogen bond acceptors (HBAs) such as quaternary ammonium, phosphonium, metal, or sulfonium halide salts and hydrogen bond donors (HBDs) such as amides, amines, alcohols, or carboxylic acids. DESs are synthesized by mixing HBAs and HBDs together in a specific molar ratio at low temperatures to obtain a homogeneous liquid without the formation of any additional solvents or byproducts. Generally, these mixtures have low vapor pressures, resulting in low volatility, non-flammability, and water compatibility, theoretically making them environmentally friendly. DESs have attracted scientific attention due to their potential applications. These mixtures can be used in organic synthesis, electrochemistry, extraction media, biotechnology, or biodiesel synthesis and separation processes, as solvents in bioanalytical or enzymatic reactions, biocatalysis, or biomedical applications. Furthermore, they are used in the pharmaceutical industry as excipients to increase the solubility of hydrophobic drugs or in drug delivery formulations.

[0004] Precious metals are widely used in various industrial sectors, including modern electronics, medicine, and chemical catalysis. The high value and depletion of precious metal reserves make the recovery of these metals from secondary resources highly desirable. For millennia, gold and silver, as representative precious metals, have played a vital role in national monetary systems. With economic development, the monetary function of precious metals has gradually weakened, but their unique properties have been effectively utilized in industry. Currently, the most widely used precious metals include platinum group metals (such as palladium, gold, platinum, rhodium, iridium, and ruthenium), which are rare and possess high economic value. Materials made from precious metals are widely used in electronics, petroleum, chemicals, aerospace, military, medicine, and pharmaceuticals. They have provided guidance for the energy and environmental revolution, but overuse has also caused a severe global resource crisis. With rapid product upgrades, the demand for precious metals continues to expand, but supply is already insufficient.

[0005] Currently, the recovery of platinum group metals is typically carried out, in most cases, through selective precipitation with ammonium salts or solvent extraction using organic ligands (such as dialkyl sulfides, β-hydroxyoximes, and tributyl phosphate) in extraction stages such as kerosene. Industrial recovery of gold from ores currently relies almost entirely on the so-called cyanidation process, which requires cyanide ions and causes environmental and health problems. Given the finite nature of these metals, finding green and efficient methods for extracting precious metals is of great significance for the sustainable development of precious metal utilization and recovery.

[0006] Processing ores via hydrometallurgy or pyrometallurgy typically requires significant energy input and involves the release of carbon dioxide. Furthermore, thermal treatment methods are energy-intensive, emit pollutants, and suffer metal loss due to scrap steel during combustion. The use of lime and coke during processing and testing can also negatively impact the climate, thus limiting their application. While hydrometallurgical technology is far superior to other methods, it still generates wastewater requiring further treatment. Therefore, there is a need to develop more energy-efficient and environmentally compatible methods for recovering precious metals to replace the organic solvents used in recovering contaminated or precious metals.

[0007] In recent decades, significant efforts have been made to find new solvents that are safe, inexpensive, environmentally and health-friendly, and also possess good performance for industrial applications. Several groups of solvents, including ionic liquids, supercritical solvents, and biomass solvents, have been investigated to find competitive, safer, and more environmentally friendly alternatives to traditional solvents. Compared to traditional solvents, ionic liquids and DESs are considered greener options. Compared to ionic liquids, DESs have advantages such as lower cost of raw materials, lower production costs, ease of synthesis through simple mixing of components via gentle heating, and no need for further purification.

[0008] Although ionic liquids have been extensively studied and widely used in the extraction of metal ions, there has been little research on their analogues, eutectic solvents, for the extraction of elemental precious metals. Summary of the Invention

[0009] The primary objective of this invention is to provide a novel type of eutectic solvent—choline chloride / sulfonamide compounds DES and its preparation method. This type of eutectic solvent is characterized by its low cost, non-toxicity to the environment, and biodegradability.

[0010] The secondary objective of this invention is to provide a metal leaching agent containing the aforementioned eutectic solvent and a metal leaching method based on the metal leaching agent. The metal leaching agent can leach precious metals such as palladium and gold, with a fast leaching speed and high extraction rate. The metal leaching method is characterized by being green, environmentally friendly, and highly efficient.

[0011] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0012] In a first aspect, the present invention provides a type of eutectic solvent, which is prepared by mixing choline chloride with a sulfonamide compound in a certain proportion; wherein the sulfonamide compound is sulfonamide (I), 4-amino-N-(aminoiminomethyl)benzenesulfonic acid (II) or p-aminobenzenesulfonamide (III); wherein the molar ratio of choline chloride to sulfonamide (I) is 1:1-3, and the molar ratio of choline chloride to 4-amino-N-(aminoiminomethyl)benzenesulfonic acid (II) or p-aminobenzenesulfonamide (III) is 1:1;

[0013]

[0014]

[0015] Preferably, the eutectic solvent is prepared by mixing choline chloride and sulfonamide in a molar ratio of 1:2.

[0016] Secondly, the present invention provides a method for preparing a eutectic solvent, the method comprising:

[0017] 1) Vacuum dry the raw materials, choline chloride and sulfonamide compounds, to remove water;

[0018] 2) Add choline chloride and sulfonamide compounds to the reactor in a certain proportion, heat and stir the mixture until it becomes a uniform and transparent liquid to obtain a eutectic solvent;

[0019] The sulfonamide compounds are sulfonamide (I), 4-amino-N-(aminoiminomethyl)benzenesulfonic acid (II), or p-aminobenzenesulfonamide (III).

[0020] Preferably, in step 2), the sulfonamide compound is a sulfonamide, the reaction temperature is ≥60℃, the eutectic solvent cannot be synthesized at a temperature below 60℃, and the higher the reaction temperature, the faster the reaction rate.

[0021] Preferably, in step 2), the sulfonamide compound is 4-amino-N-(aminoiminomethyl)benzenesulfonic acid, and the reaction temperature is ≥70℃. The eutectic solvent cannot be synthesized at temperatures below 70℃, and the reaction rate is faster at higher reaction temperatures.

[0022] Preferably, in step 2), the sulfonamide compound is p-aminobenzenesulfonamide, the reaction temperature is ≥80℃, the eutectic solvent cannot be synthesized at a temperature below 80℃, and the higher the reaction temperature, the faster the reaction rate.

[0023] Thirdly, the present invention provides a metal leaching agent containing the aforementioned eutectic solvent, the metal leaching agent being a transparent liquid made from the eutectic solvent and an auxiliary agent, wherein the auxiliary agent is at least one selected from 1,3-dibromo-5,5-dimethylhydantoin, 1,3-dichloro-5,5-dimethylhydantoin, N-chlorosuccinimide, N-bromosuccinimide, chloramine T, and sodium hypochlorite; wherein the feeding ratio of the eutectic solvent and the auxiliary agent is 4-5 mL: 0.2-0.4 g.

[0024] The metal leaching agent is simple to prepare. A certain amount of auxiliary agent can be added to a eutectic solvent, and the mixture is heated and stirred until a transparent liquid is obtained. Preferably, the mixture is heated to ≥60℃ and stirred until a transparent liquid is obtained.

[0025] Preferably, the auxiliary agent is 1,3-dibromo-5,5-dimethylhydantoin.

[0026] Preferably, the ratio of eutectic solvent to auxiliary agent is 4-5 mL: 0.23-0.30 g.

[0027] Fourthly, the present invention further provides a metal leaching method based on the metal leaching agent, the leaching method comprising: weighing a sample containing a precious metal and adding it to the metal leaching agent, controlling the leaching temperature above the melting point temperature of the metal leaching agent, and stirring thoroughly to leach the precious metal.

[0028] Preferably, the precious metal is at least one of gold and palladium.

[0029] Preferably, the sample containing precious metals is precious metal powder or gold ore particles.

[0030] Preferably, the mass ratio of metal leaching agent to precious metal is controlled to be 3000-4000:1.

[0031] Preferably, the stirring rate is controlled at 600 r / min.

[0032] Preferably, the leaching temperature is controlled at 60-80℃. Within this temperature range, the palladium-gold leaching system exhibits excellent palladium leaching efficiency, with the most preferred leaching temperature being 80℃.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] 1. The eutectic solvent system used in the metal leaching agent of the present invention is an environmentally friendly compound that poses almost no harm to the environment and people during the production process. It meets the requirements of building an environmentally friendly society and is a sustainable development system.

[0035] 2. The metal leaching agent system of the present invention has both good oxidizing and coordination capabilities, and can leach gold and palladium with fast leaching speed and high extraction rate.

[0036] 3. The metal leaching agent of the present invention can perform palladium dissolution treatment at room temperature, with high palladium leaching efficiency, mild conditions, and low overall energy consumption. Attached Figure Description

[0037] Figure 1 Infrared spectrum of the eutectic solvent of choline chloride / sulfonamide with a molar ratio of 1:1 prepared in Example 1;

[0038] Figure 2 Infrared spectrum of the eutectic solvent with a molar ratio of 1:2 choline chloride / sulfonamide prepared in Example 1;

[0039] Figure 3 Infrared spectrum of the eutectic solvent of choline chloride / sulfonamide with a molar ratio of 1:3 prepared in Example 1;

[0040] Figure 4 Infrared spectrum of the eutectic solvent of choline chloride / 4-amino-N-(aminoiminomethyl)benzenesulfonic acid with a molar ratio of 1:1 prepared in Example 1;

[0041] Figure 5 Infrared spectrum of the eutectic solvent of choline chloride / p-aminobenzenesulfonamide with a molar ratio of 1:1 prepared in Example 1. Detailed Implementation

[0042] The present invention will be illustrated below with specific examples. It should be noted that the embodiments are only for further illustrative purposes and should not be construed as limiting the scope of protection of the present invention. The present invention is not limited thereto in any way. Those skilled in the art can make some non-essential improvements and adjustments based on the above-described invention.

[0043] Example 1

[0044] 1. Before use, the raw materials choline chloride and sulfonamide should be vacuum dried. Weigh 8.3778 g of choline chloride and 5.7666 g of sulfonamide (molar ratio 1:1) and add them separately to a 100 ml round-bottom flask equipped with a magnetic stir bar. Stir the mixture at 60 °C until a homogeneous, transparent liquid is obtained to yield the choline chloride / sulfonamide eutectic solvent. The infrared spectrum of this substance is shown below. Figure 1 .

[0045] 2. The raw materials, choline chloride and sulfonamide, were vacuum dried before use. 16.7556 g of choline chloride and 23.0664 g of sulfonamide (molar ratio 1:2) were weighed and added separately to 100 ml round-bottom flasks equipped with magnetic stirrups. The mixture was stirred at 60 °C until a homogeneous, transparent liquid was obtained, yielding the choline chloride / sulfonamide eutectic solvent. The infrared spectrum of this substance is shown below. Figure 2 .

[0046] 3. The raw materials, choline chloride and sulfonamide, were vacuum dried before use. 11.1704 g of choline chloride and 23.0664 g of sulfonamide (molar ratio 1:3) were added separately to 100 ml round-bottom flasks equipped with magnetic stirrups. The mixture was stirred at 60 °C until a homogeneous, transparent liquid was obtained, yielding the choline chloride / sulfonamide eutectic solvent. The infrared spectrum of this substance is shown below. Figure 3 .

[0047] 4. Before use, the raw materials choline chloride and 4-amino-N-(aminoiminomethyl)benzenesulfonic acid should be vacuum dried. Weigh 6.9815 g of choline chloride and 10.712 g of 4-amino-N-(aminoiminomethyl)benzenesulfonic acid (molar ratio 1:1) and add them separately to a 50 ml round-bottom flask equipped with a magnetic stir bar. Stir the mixture at 70 °C until a homogeneous, transparent liquid is obtained to yield the eutectic solvent of choline chloride / 4-amino-N-(aminoiminomethyl)benzenesulfonic acid. The infrared spectrum of this substance is shown below. Figure 4 .

[0048] 5. Before use, the raw materials choline chloride and p-aminobenzenesulfonamide should be vacuum dried. Weigh 6.9815 g of choline chloride and 8.61 g of p-aminobenzenesulfonamide (molar ratio 1:1) and add them separately to a 50 ml round-bottom flask equipped with a magnetic stir bar. Stir the mixture at 80 °C until a homogeneous, transparent liquid is obtained to yield the choline chloride / p-aminobenzenesulfonamide eutectic solvent. The infrared spectrum of this substance is shown below. Figure 5 .

[0049] 6. The synthesized eutectic solvent needs to be vacuum dried overnight at 80°C before forming a metal leaching agent.

[0050] Example 2

[0051] Use a pipette to take 4 ml of the synthesized choline chloride / sulfonamide DES (molar ratio 1:1) into a 30 ml sample vial containing a magnetic swab. Add 0.2860 g of the auxiliary agent 1,3-dibromo-5,5-dimethylhydantoin. Heat and stir the mixture at 60 °C until it becomes an orange transparent liquid to obtain the metal leaching agent. Weigh 0.0024 g of palladium powder and heat and stir at 60 °C (stirring rate 600 r / min) to leach the metal. The palladium powder is completely dissolved in 12 min.

[0052] 50 μL of the leachate was diluted 200 times with deionized water, and the Pd concentration in the solution was determined to be 2.945 ug / ml using atomic absorption spectrometry. The solubility rate was calculated to be 98.17%.

[0053] Example 3

[0054] Use a pipette to take 4 ml of the synthesized choline chloride / sulfonamide DES (molar ratio 1:2) into a 30 ml sample vial containing a magnetic swab. Add 0.2861 g of the auxiliary agent 1,3-dibromo-5,5-dimethylhydantoin. Heat and stir the mixture at 60°C until it becomes an orange transparent liquid to obtain the metal leaching agent. Weigh 0.0024 g of palladium powder and heat and stir at 60°C (stirring rate 600 r / min) to leach the metal. The palladium powder is completely dissolved in 8 min.

[0055] 50 μL of the leachate was diluted 200 times with deionized water, and the Pd concentration in the solution was determined to be 2.976 ug / ml using atomic absorption spectrometry. The solubility rate was calculated to be 99.20%.

[0056] Example 4

[0057] Use a pipette to take 4 ml of the synthesized choline chloride / sulfonamide DES (molar ratio 1:3) into a 30 ml sample vial containing a magnetic swab. Add 0.2863 g of the auxiliary agent 1,3-dibromo-5,5-dimethylhydantoin. Heat and stir the mixture at 60°C until it becomes an orange transparent liquid to obtain the metal leaching agent. Weigh 0.0024 g of palladium powder and heat and stir at 60°C (stirring rate 600 r / min) to leach the metal. The palladium powder is completely dissolved in 6 min.

[0058] 50 μL of the leachate was diluted 200 times with deionized water, and the Pd concentration in the solution was determined to be 2.943 ug / ml using atomic absorption spectrometry. The solubility rate was calculated to be 98.10%.

[0059] Example 5

[0060] Using a pipette, take 4 ml of the synthesized choline chloride / 4-amino-N-(aminoiminomethyl)benzenesulfonic acid DES (molar ratio 1:1) into a 30 ml sample vial containing a magnetic swab. Add 0.2862 g of the auxiliary agent 1,3-dibromo-5,5-dimethylhydantoin. Heat and stir the mixture at 70°C until it becomes an orange transparent liquid to obtain the metal leaching agent. Weigh 0.0023 g of palladium powder and heat and stir at 70°C (stirring rate 600 r / min) to leach the metal. The palladium powder is completely dissolved in 10 min.

[0061] 50 μL of the leachate was diluted 200 times with deionized water, and the Pd concentration in the solution was determined to be 2.603 ug / ml using atomic absorption spectrometry. The solubility rate was calculated to be 90.54%.

[0062] Example 6

[0063] Use a pipette to take 4 ml of the synthesized choline chloride / p-aminobenzenesulfonamide DES (molar ratio 1:1) into a 30 ml sample vial containing a magnetic swab. Add 0.2864 g of the auxiliary agent 1,3-dibromo-5,5-dimethylhydantoin. Heat the mixture at 80°C and stir until it becomes an orange transparent liquid to obtain the metal leaching agent. Weigh 0.0024 g of palladium powder and heat and stir at 80°C (stirring rate 600 r / min) to leach the metal. The palladium powder is completely dissolved in 8 min.

[0064] 50 μL of the leachate was diluted 200 times with deionized water, and the Pd concentration in the solution was determined to be 2.738 ug / ml using atomic absorption spectrometry. The solubility rate was calculated to be 91.27%.

[0065] Example 7

[0066] Use a pipette to take 4 ml of the synthesized choline chloride / sulfonamide DES (molar ratio 1:2) into a 30 ml sample vial containing a magnetic swab. Add 0.2863 g of the auxiliary agent 1,3-dibromo-5,5-dimethylhydantoin. Heat the mixture at 60 °C and stir until it becomes an orange transparent liquid to obtain the metal leaching agent. Weigh 0.0025 g of palladium powder and heat and stir at 80 °C (stirring rate 600 r / min) to leach the metal. The palladium powder is completely dissolved in 5 min.

[0067] 50 μL of the leachate was diluted 200 times with deionized water, and the Pd concentration in the solution was determined to be 3.109 ug / ml using atomic absorption spectrometry. The solubility rate was calculated to be 99.49%.

[0068] Example 8

[0069] Use a pipette to take 4 ml of the synthesized choline chloride / sulfonamide DES (molar ratio 1:2) into a 30 ml sample vial containing a magnetic swab. Add 0.2863 g of the auxiliary agent 1,3-dibromo-5,5-dimethylhydantoin. Heat and stir the mixture at 60 °C until it becomes an orange transparent liquid to obtain the metal leaching agent. Weigh 0.0021 g of palladium powder and heat and stir at 25 °C (stirring rate 600 r / min) to leach the metal. The palladium powder is completely dissolved in 60 min.

[0070] 50 μL of the leachate was diluted 200 times with deionized water, and the Pd concentration in the solution was determined to be 2.524 ug / ml using atomic absorption spectrometry. The solubility rate was calculated to be 96.15%.

[0071] Example 9

[0072] Use a pipette to take 4 ml of the synthesized choline chloride / sulfonamide DES (molar ratio 1:2) into a 30 ml sample vial containing a magnetic swab. Add 0.2862 g of the auxiliary agent 1,3-dibromo-5,5-dimethylhydantoin. Heat and stir the mixture at 60 °C until it becomes an orange transparent liquid to obtain the metal leaching agent. Weigh 0.0024 g of palladium powder and heat and stir at 40 °C (stirring rate 600 r / min) to leach the metal. The palladium powder is completely dissolved in 40 min.

[0073] 50 μL of the leachate was diluted 200 times with deionized water, and the Pd concentration in the solution was determined to be 2.910 ug / ml using atomic absorption spectrometry. The solubility rate was calculated to be 97.00%.

[0074] Example 10

[0075] Use a pipette to take 5 ml of the synthesized choline chloride / sulfonamide DES (molar ratio 1:2) into a 30 ml sample vial containing a magnetic swab. Add 0.2868 g of the auxiliary agent 1,3-dibromo-5,5-dimethylhydantoin. Heat and stir the mixture at 60 °C until it becomes an orange transparent liquid to obtain the metal leaching agent. Weigh 0.0037 g of gold powder and heat and stir at 25 °C (stirring rate 600 r / min) for 5 h.

[0076] 50 μL of the leachate was diluted 200 times with deionized water, and the Au concentration in the solution was determined to be 3.290 ug / ml using an atomic absorption spectrometer. The solubility rate was calculated to be 88.92%.

[0077] Example 11

[0078] Use a pipette to take 5 ml of the synthesized choline chloride / sulfonamide DES (molar ratio 1:2) into a 30 ml sample vial containing a magnetic swab. Add 0.2870 g of the auxiliary agent 1,3-dibromo-5,5-dimethylhydantoin. Heat and stir the mixture at 60 °C until it becomes an orange transparent liquid to obtain the metal leaching agent. Weigh 0.0034 g of gold powder and heat and stir at 40 °C (stirring rate 600 r / min) for 4 h.

[0079] 50 μL of the leachate was diluted 200 times with deionized water, and the Au concentration in the solution was determined to be 3.260 ug / ml using atomic absorption spectrometry. The solubility rate was calculated to be 95.88%.

[0080] Example 12

[0081] Use a pipette to take 5 ml of the synthesized choline chloride / sulfonamide DES (molar ratio 1:2) into a 30 ml sample vial containing a magnetic swab. Add 0.2869 g of the auxiliary agent 1,3-dibromo-5,5-dimethylhydantoin. Heat the mixture at 60 °C and stir until it becomes an orange transparent liquid to obtain the metal leaching agent. Weigh 0.0034 g of gold powder and heat and stir at 60 °C (stirring rate 600 r / min) for 3 h.

[0082] 50 μL of the leachate was diluted 200 times with deionized water, and the Au concentration in the solution was determined to be 3.370 ug / ml using atomic absorption spectrometry. The solubility rate was calculated to be 99.12%.

[0083] Example 13

[0084] Use a pipette to take 5 ml of the synthesized choline chloride / sulfonamide DES (molar ratio 1:2) into a 30 ml sample vial containing a magnetic swab. Add 0.2870 g of the auxiliary agent 1,3-dibromo-5,5-dimethylhydantoin. Heat the mixture at 60 °C and stir until it becomes an orange transparent liquid to obtain the metal leaching agent. Weigh 0.0035 g of gold powder and heat and stir at 80 °C (stirring rate 600 r / min) for 1 h.

[0085] 50 μL of the leachate was diluted 200 times with deionized water, and the Au concentration in the solution was determined to be 3.471 ug / ml using atomic absorption spectrometry. The solubility rate was calculated to be 99.17%.

[0086] Example 14

[0087] Use a pipette to take 4 ml of the synthesized choline chloride / sulfonamide DES (molar ratio 1:2) into a 30 ml sample vial containing a magnetic swab. Add 0.2875 g of the auxiliary agent 1,3-dichloro-5,5-dimethylhydantoin. Heat and stir the mixture at 60 °C until it becomes an orange transparent liquid to obtain the metal leaching agent. Weigh 0.0026 g of palladium powder and heat and stir at 60 °C (stirring rate 600 r / min) for 5 min.

[0088] 50 μL of the leachate was diluted 200 times with deionized water, and the Pd concentration in the solution was determined to be 3.012 ug / ml using atomic absorption spectrometry. The solubility rate was calculated to be 92.68%.

[0089] Example 15

[0090] Use a pipette to take 4 ml of the synthesized choline chloride / sulfonamide DES (molar ratio 1:2) into a 30 ml sample vial containing a magnetic swab. Add 0.2873 g of the auxiliary agent N-chlorosuccinimide. Heat and stir the mixture at 60 °C until it becomes a colorless and transparent liquid to obtain the metal leaching agent. Weigh 0.0029 g of palladium powder and heat and stir at 60 °C (stirring rate 600 r / min) for 5 min.

[0091] 50 μL of the leachate was diluted 200 times with deionized water, and the Pd concentration in the solution was determined to be 3.285 ug / ml using atomic absorption spectrometry. The solubility rate was calculated to be 90.62%.

[0092] Example 16

[0093] Use a pipette to take 4 ml of the synthesized choline chloride / sulfonamide DES (molar ratio 1:2) into a 30 ml sample vial containing a magnetic swab. Add 0.2872 g of the auxiliary agent N-bromosuccinimide. Heat the mixture at 60 °C and stir until it becomes an orange transparent liquid to obtain the metal leaching agent. Weigh 0.0027 g of palladium powder and heat and stir at 60 °C (stirring rate 600 r / min) for 5 min.

[0094] 50 μL of the leachate was diluted 200 times with deionized water, and the Pd concentration in the solution was determined to be 3.134 ug / ml using atomic absorption spectrometry. The solubility rate was calculated to be 92.86%.

[0095] Example 17

[0096] Use a pipette to take 4 ml of the synthesized choline chloride / sulfonamide DES (molar ratio 1:2) into a 30 ml sample bottle containing a magnetic swab. Add 0.2875 g of chloramine T as an auxiliary agent. Heat and stir the mixture at 60 °C until it becomes a colorless and transparent liquid to obtain the metal leaching agent. Weigh 0.0027 g of palladium powder and heat and stir at 60 °C (stirring rate 600 r / min) for 5 min.

[0097] 50 μL of the leachate was diluted 200 times with deionized water, and the Pd concentration in the solution was determined to be 3.163 ug / ml using atomic absorption spectrometry. The solubility rate was calculated to be 93.72%.

[0098] Example 18

[0099] Use a pipette to take 4 ml of the synthesized choline chloride / sulfonamide DES (molar ratio 1:2) into a 30 ml sample vial containing a magnetic swab. Add 1 ml of sodium hypochlorite as an auxiliary agent. Heat and stir the mixture at 60°C until it becomes a colorless and transparent liquid to obtain the metal leaching agent. Weigh 0.0029 g of palladium powder and heat and stir at 60°C (stirring rate 600 r / min) for 5 min.

[0100] 50 μL of the leachate was diluted 200 times with deionized water, and the Pd concentration in the solution was determined to be 3.274 ug / ml using atomic absorption spectrometry. The solubility rate was calculated to be 90.32%.

[0101] Comparative Example 1

[0102] Weigh 2.7926 g of choline chloride and 2.4024 g of urea (molar ratio 1:2) and add them to a 30 ml sample vial equipped with a magnetic stir bar. Heat the mixture at 60 °C and stir until homogeneous, turning it into a transparent liquid to obtain choline chloride / urea DES. Use a pipette to take 4 ml of the synthesized choline chloride / urea DES into a 30 ml sample vial equipped with a magnetic stir bar, add 0.2859 g of the auxiliary agent 1,3-dibromo-5,5-dimethylhydantoin, and heat the mixture at 60 °C until it becomes an orange transparent liquid to obtain the metal leaching agent. Weigh 0.0023 g of palladium powder and heat and stir at 60 °C (stirring speed 600 r / min) for 8 min.

[0103] 50 μL of the leachate was diluted 200 times with deionized water, and the Pd concentration in the solution was determined to be 0.938 ug / ml using atomic absorption spectrometry. The solubility rate was calculated to be 32.63%.

[0104] Comparative Example 2

[0105] Weigh 2.0944 g of choline chloride and 1.88 ml of ethylene glycol (molar ratio 1:2) and add them to a 30 ml sample vial equipped with a magnetic stir bar. Stir and mix at 60 °C until a clear liquid is formed to obtain choline chloride / ethylene glycol DES. Pipette 4 ml of the synthesized choline chloride / ethylene glycol DES into a 30 ml sample vial equipped with a magnetic stir bar, add 0.2859 g of the auxiliary agent 1,3-dibromo-5,5-dimethylhydantoin, and heat and stir the mixture at 60 °C until a colorless and transparent liquid is obtained to obtain the metal leaching agent. Weigh 0.0024 g of palladium powder and heat and stir at 60 °C (stirring speed 600 r / min) for 8 min.

[0106] 50 μL of the leachate was diluted 200 times with deionized water, and the Pd concentration in the solution was determined to be 0.455 ug / ml using atomic absorption spectrometry. The solubility rate was calculated to be 15.17%.

[0107] Comparative Example 3

[0108] Weigh 2.0944 g of choline chloride and 2.79 ml of glycerol (molar ratio 1:2) and add them to a 30 ml sample vial equipped with a magnetic stir bar. Stir and mix at 60 °C until a clear liquid is formed to obtain choline chloride / glycerol DES. Pipette 4 ml of the synthesized choline chloride / glycerol DES into a 30 ml sample vial equipped with a magnetic stir bar, add 0.2859 g of the auxiliary agent 1,3-dibromo-5,5-dimethylhydantoin, and heat and stir the mixture at 60 °C until an orange transparent liquid is obtained to obtain the metal leaching agent. Weigh 0.0024 g of palladium powder and heat and stir at 60 °C (stirring speed 600 r / min) for 8 min.

[0109] 50 μL of the leachate was diluted 200 times with deionized water, and the Pd concentration in the solution was determined to be 0.663 ug / ml using atomic absorption spectrometry. The solubility rate was calculated to be 22.10%.

[0110] Comparative Example 4

[0111] Weigh 2.3441 g of DL-menthol and 3.07 ml of lactic acid (molar ratio 1:2) and add them to a 30 ml sample vial equipped with a magnetic stir bar. Stir and mix at 60 °C until a transparent liquid is formed to obtain DL-menthol / lactic acid DES. Use a pipette to transfer 4 ml of the synthesized DL-menthol / lactic acid DES to a 30 ml sample vial equipped with a magnetic stir bar, add 0.2860 g of the auxiliary agent 1,3-dibromo-5,5-dimethylhydantoin, and heat and stir the mixture at 60 °C until an orange transparent liquid is obtained to obtain the metal leaching agent. Weigh 0.0023 g of palladium powder and heat and stir at 60 °C (stirring rate 600 r / min) for 8 min.

[0112] Take 50 μL of the leachate and dilute it 200 times with deionized water. The concentration of Pd in ​​the solution was determined to be 0.00 ug / ml using an atomic absorption spectrometer, and the solubility rate was calculated to be 0.00%.

[0113] Comparative Example 5

[0114] Weigh 1.3816 g of L-proline and 4.5650 g of p-toluenesulfonic acid hydrate (molar ratio 1:2) and add them to a 30 ml sample vial equipped with a magnetic stir bar. Stir and mix at 60 °C until a clear liquid is formed to obtain L-proline / p-toluenesulfonic acid hydrate DES. Pipette 4 ml of L-proline / p-toluenesulfonic acid hydrate DES into a 30 ml sample vial equipped with a magnetic stir bar, add 0.2862 g of 1,3-dibromo-5,5-dimethylhydantoin auxiliary agent, and heat and stir the mixture at 60 °C until a colorless and transparent liquid is obtained to obtain the metal leaching agent. Weigh 0.0024 g of palladium powder and heat and stir at 60 °C (stirring rate 600 r / min) for 8 min.

[0115] Take 50 μL of the leachate and dilute it 200 times with deionized water. The concentration of Pd in ​​the solution was determined to be 0.00 ug / ml using an atomic absorption spectrometer, and the solubility rate was calculated to be 0.00%.

[0116] Comparative Example 6

[0117] Weigh 2.7926 g of choline chloride and 2.0812 g of malonic acid (molar ratio 1:1) and add them to a 30 ml sample vial containing a magnetic chalcanthus. Stir and mix at 60 °C until a clear liquid is obtained, yielding choline chloride / malonic acid DES. Pipette 5 ml of choline chloride / malonic acid DES into a 30 ml sample vial containing a magnetic chalcanthus, add 0.2864 g of the auxiliary agent 1,3-dibromo-5,5-dimethylhydantoin, and heat and stir the mixture at 60 °C until a colorless and transparent liquid is obtained, yielding the metal leaching agent. Weigh 0.0035 g of gold powder and heat and stir at 60 °C (stirring rate 600 r / min) for 3 h.

[0118] Take 50 μL of the leachate and dilute it 200 times with deionized water. The Au concentration in the solution was measured to be 0.00 ug / ml using an atomic absorption spectrometer, and the solubility was calculated to be 0.00%.

[0119] Comparative Example 7

[0120] Weigh 1.8617 g of choline chloride and 3.39 ml of hexafluoroisopropanol (molar ratio 2:3) and add them to a 30 ml sample vial equipped with a magnetic chalcopyrite. Stir and mix at 60°C until a clear liquid is obtained, yielding choline chloride / hexafluoroisopropanol DES. Pipette 5 ml of choline chloride / hexafluoroisopropanol DES into a 30 ml sample vial equipped with a magnetic chalcopyrite, add 0.2865 g of the auxiliary agent 1,3-dibromo-5,5-dimethylhydantoin, and heat and stir the mixture at 60°C until an orange transparent liquid is obtained, yielding the metal leaching agent. Weigh 0.0034 g of gold powder and heat and stir at 60°C (stirring rate 600 r / min) for 3 hours.

[0121] 50 μL of the leachate was diluted 200 times with deionized water, and the Au concentration in the solution was determined to be 0.783 ug / ml using atomic absorption spectrometry. The solubility rate was calculated to be 23.03%.

Claims

1. A metal lixiviant comprising a deep eutectic solvent, characterized in that: The metal is a precious metal, specifically at least one of gold and palladium; the metal leaching agent is a transparent liquid made from a eutectic solvent and an auxiliary agent, wherein the auxiliary agent is at least one of 1,3-dibromo-5,5-dimethylhydantoin, 1,3-dichloro-5,5-dimethylhydantoin, N-chlorosuccinimide, N-bromosuccinimide, chloramine T, and sodium hypochlorite; wherein the feeding ratio of the eutectic solvent to the auxiliary agent is 4-5 mL: 0.2-0.4 g; The eutectic solvent is prepared by mixing choline chloride with a sulfonamide compound in a specific ratio; the sulfonamide compound is sulfonamide (I), 4-amino-N-(aminoiminomethyl)benzenesulfonic acid (II), or p-aminobenzenesulfonamide (III); the molar ratio of choline chloride to sulfonamide (I) is 1:1-3, and the molar ratio of choline chloride to 4-amino-N-(aminoiminomethyl)benzenesulfonic acid (II) or p-aminobenzenesulfonamide (III) is 1:1; (I) (II) (III).

2. The metal leaching agent containing a eutectic solvent as described in claim 1, characterized in that: The feeding ratio of the eutectic solvent and the auxiliary agent is 4-5 mL: 0.23-0.30 g.

3. The metal leaching agent containing a eutectic solvent as described in claim 1 or 2, characterized in that: The eutectic solvent is prepared by mixing choline chloride and sulfonamide in a molar ratio of 1:

2.

4. A metal leaching method based on the metal leaching agent according to any one of claims 1-3, characterized in that: The leaching method includes: weighing a sample containing precious metal and adding it to a metal leaching agent, controlling the leaching temperature above the melting point of the metal leaching agent, and stirring thoroughly to leach the precious metal; the precious metal is at least one of gold and palladium.

5. The metal leaching method as described in claim 4, characterized in that: The sample containing precious metals is either precious metal powder or gold ore particles.

6. The metal leaching method as described in claim 4, characterized in that: The leaching temperature should be controlled at 60-80℃.

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