A hydrophobic deep eutectic solvent, a method for extracting Au (III) from waste liquid, and a method for converting Au (III) into Au (0)

Abstract

The present invention provides a method for preparing a hydrophobic low eutectic solvent, which specifically comprises the following steps: step 1, mixing one or more of diammonium hydrogen phosphate, tetrabutylammonium hydrogen sulfate, ammonium dihydrogen phosphate, octyltrimethylammonium chloride and one or more of capric acid, n-butanol, thymol, and menthol in a certain molar ratio; step 2, heating the mixture in step 1 in a water bath for a period of time until a transparent and uniform liquid is formed, which is the hydrophobic low eutectic solvent; in the low eutectic solvent, one or more of diammonium hydrogen phosphate, tetrabutylammonium hydrogen sulfate, ammonium dihydrogen phosphate, octyltrimethylammonium chloride and one or more of capric acid, n-butanol, thymol, and menthol interact with each other through hydrogen bonds.

Description

Technical Field

[0001] The invention belongs to the field of precious metal recovery and relates to a hydrophobic low eutectic solvent, a method for extracting Au(III) in waste liquid and a method for converting Au(III) into Au(0). Background Art

[0002] Precious metals not only have good physical properties (such as ductility and conductivity), but also have high chemical stability and strong corrosion resistance. In recent years, precious metals have been increasingly used in electronic devices and modern industrial catalysis. In addition, the consumption of platinum group metals is increasing due to the continuous development of the automotive industry. Electronic waste containing precious metals, including discarded computers, mobile phones and household electronic devices, can become a major sustainable source of precious metals once appropriate technologies are developed. Liquid-liquid extraction-based methods are of great significance in hydrometallurgical processes, including the refining of precious metals and the analysis of various process media. Due to the small volume of the extractant, these methods have the advantages of fast kinetics and high enrichment factors, while allowing the treatment of solutions with complex salt compositions and high concentrations of matrix components. Many extractants have been proposed for the selective separation and recovery of precious metals. However, in actual industrial environments, most extractants have limitations such as large reagent consumption, third phase formation, emulsification, flammability, toxicity, and low stability of the extractant in strong acid solutions. In recent years, ionic liquids have become increasingly popular as an extractant with high chemical stability and the ability to interact with ion exchange and complex formation. The extraction of precious metals is still under extensive research, with phosphorus-based and imidazolyl-based ionic liquids as examples. These types of ionic liquids ensure efficient and selective recovery of Pt(IV), Pd(II) and Au(III) from hydrochloric acid leachates. Despite their advantages, ionic liquids have the main disadvantages of complex synthesis, high cost and potential toxicity.

[0003] Currently, there is a growing interest in replacing ionic liquids with more environmentally friendly and cheaper reagents, especially deep eutectic solvents (DES). DES are composed of two or more compounds that are able to form hydrogen bonds with each other. The formation of these chemical bonds leads to a significant decrease in the melting points of the component substances. Therefore, most DESs exist in a liquid state at temperatures close to room temperature and can be used as solvents and extractants. Hydrophobic deep eutectic solvents have been widely studied for the separation of organic and inorganic analytes from various matrices. Summary of the invention

[0004] The object of the present invention is to provide a hydrophobic low eutectic solvent, a method for extracting Au(III) in waste liquid and a method for converting Au(III) into Au(0), and to use DES solvent for the recovery of Au(III).

[0005] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0006] A method for preparing a hydrophobic deep eutectic solvent comprises the following steps:

[0007] Step 1, mixing one or more of diammonium hydrogen phosphate, tetrabutylammonium hydrogen sulfate, ammonium dihydrogen phosphate, octyltrimethylammonium chloride and one or more of capric acid, n-butanol, thymol, and menthol in a certain molar ratio;

[0008] Step 2, heating the mixture in step 1 in a water bath for a period of time until a transparent and uniform liquid is formed, which is a hydrophobic deep eutectic solvent;

[0009] In the deep eutectic solvent, one or more of diammonium hydrogen phosphate, tetrabutylammonium hydrogen sulfate, ammonium dihydrogen phosphate, and octyltrimethylammonium chloride interact with one or more of decanoic acid, n-butanol, thymol, and menthol through hydrogen bonds.

[0010] The present invention also provides a hydrophobic low eutectic solvent, which is prepared by the above preparation method.

[0011] The present invention also provides a method for extracting Au(III) from wastewater using a hydrophobic low eutectic solvent.

[0012] Step 3, taking a certain amount of a hydrophobic deep eutectic solvent and mixing it with an aqueous solution containing Au(III), wherein the hydrophobic deep eutectic solvent is prepared by the above-mentioned preparation method;

[0013] Step 4: Place a magnetic particle in the mixed solution. After the magnetic particle rotates for a period of time, the extraction is completed when the Au(III) aqueous solution changes from golden yellow to colorless and transparent, and the hydrophobic deep eutectic solvent changes from colorless and transparent to golden yellow.

[0014] Step 5: After the extraction is completed, the extracted liquid is centrifuged to separate the water phase and the oil phase, and Au (III) is in the oil phase.

[0015] The present invention also provides a method for converting Au(III) into Au(0), wherein the Au(III) is the oil phase in step five, and specifically comprises the following steps:

[0016] Step 6: Add a certain amount of TiO2 to the oil phase obtained in step 5 and mix well;

[0017] Step 7: Irradiate with light of a certain wavelength for a period of time until the oil phase turns dark red and no more precipitate appears at the bottom, and separate the precipitate at the bottom, which is Au(0).

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention creatively develops a hydrophobic low eutectic solvent for extracting Au(III) from wastewater, and the extraction efficiency can reach 99.9%. Au(III) can be reduced to Au(0) in one step by using TiO2 photocatalysis. The intermediate process does not involve any toxic organic reagents and strong acids and bases. The whole process is non-toxic, environmentally friendly and low-cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Effect of solution acidity on DES extraction efficiency

[0021] Figure 2 The XRD spectrum of the reduced Au(0) is compared with the standard material card of Au

[0022] Figure 3 The effect of DES extraction times on extraction efficiency DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0024] Example 1

[0025] This embodiment provides a method for extracting Au(III) from wastewater using a hydrophobic deep eutectic solvent, which specifically comprises the following steps:

[0026] Step 1, adding one or more of diammonium hydrogen phosphate / tetrabutylammonium hydrogen sulfate / diammonium phosphate / octyltrimethylammonium chloride and one or more of decanoic acid / n-butanol / thymol / menthol into a reactor at a molar ratio of 1:1-1:10, heating in a water bath at 80° C. for 60 minutes until a transparent and uniform liquid is formed in the reactor; diammonium hydrogen phosphate / tetrabutylammonium hydrogen sulfate / diammonium phosphate / octyltrimethylammonium chloride and decanoic acid / n-butanol / thymol / menthol interact with each other through hydrogen bonds;

[0027] Step 2: Control Cl in aqueous solution - The concentration of H was kept constant and then different + concentration, 0.5-4 mol / L, to obtain DES solution;

[0028] Step 3, take 0.1g of DES and 5ml of aqueous solution containing Au(III) and place them in a centrifuge tube;

[0029] Step 4: Place a magnetic particle in the centrifuge tube at a speed of 700 rpm for 30 minutes. When the Au(III) aqueous solution changes from golden yellow to colorless and transparent, and the DES changes from colorless and transparent to golden yellow, the extraction is complete.

[0030] Step 5: After extraction, centrifuge at a speed of 12000 r / min for 7 min to separate the water and oil phases, collect the water phase, and use ICP-OES to test the concentration of residual Au (III) in the aqueous solution. The extraction efficiency is calculated according to the following formula:

[0031]

[0032] C 金 --initial aqueous gold ion concentration,

[0033] C 萃余液 --Gold ion concentration in aqueous phase after extraction.

[0034] Effect of solution acidity on DES extraction efficiency, such as Figure 1 Shown

[0035] Example 2

[0036] This embodiment provides a method for photocatalytically reducing Au(III) in the oil phase in Embodiment 1 to Au(0) using TiO2, and the steps are as follows:

[0037] Step a, adding 1-10 mg TiO2 to the oil phase obtained in step 5 and mixing evenly;

[0038] Step b, irradiating with 300-800 nm light for 1-6 hours until the oil phase turns dark red and no more precipitate appears at the bottom, separating the bottom precipitate, which is Au(0);

[0039] The precipitate was tested by XRD, and the test results were as follows: Figure 2 As shown, the peak of the precipitate completely corresponds to the standard card and can be identified as Au(0).

[0040] Experimental Example 3

[0041] The oil phase of step b in Example 2 was taken as the low eutectic solvent, and the operations of Example 1 and Example 2 were repeated 8 times, and the low eutectic solvent used each time was the oil phase separated in the previous Example 2. The effect of the number of extractions on the extraction efficiency is shown in Figure 3 As shown, the extraction efficiency of the first five times can still reach more than 85%, indicating that the DES has the characteristics of reusability.

[0042] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection claimed by the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for converting Au (III) in wastewater into Au (0), characterized in that: The specific steps include: Step 1: extracting Au (III) from wastewater using a hydrophobic low eutectic solvent, specifically comprising the following steps: Step 11, taking a certain amount of a hydrophobic deep eutectic solvent and mixing it with an aqueous solution containing Au (III); Step 12, placing a magnetic particle in the mixed solution, and rotating the magnetic particle for a period of time, until the Au (III) aqueous solution changes from golden yellow to colorless and transparent, and the hydrophobic deep eutectic solvent changes from colorless and transparent to golden yellow, the extraction is completed; Step 13: After the extraction is completed, the extracted liquid is centrifuged to separate the water phase and the oil phase, and Au (III) is in the oil phase; The hydrophobic deep eutectic solvent is prepared by the following method, which specifically comprises the following steps: Step 14, mixing one or more of diammonium hydrogen phosphate, tetrabutylammonium hydrogen sulfate, ammonium dihydrogen phosphate, and octyltrimethylammonium chloride with one or more of capric acid, n-butanol, thymol, and menthol in a certain molar ratio, wherein any one of diammonium hydrogen phosphate, tetrabutylammonium hydrogen sulfate, ammonium dihydrogen phosphate, and octyltrimethylammonium chloride can interact with any one of capric acid, n-butanol, thymol, and menthol through hydrogen bonds; Step 15, heating the mixture in step 14 in a water bath for a period of time until a transparent and uniform liquid is formed, which is a hydrophobic deep eutectic solvent; Step 2: converting Au(III) in the oil phase in step 13 into Au(0), specifically comprising the following steps: Step 21, adding a certain amount of TiO2 to the oil phase obtained in step 13 and mixing evenly; Step 22: Irradiate with light of a certain wavelength for a period of time until the oil phase turns dark red and no more precipitate appears at the bottom, and separate the precipitate at the bottom, which is Au (0).

2. A method for converting Au(III) in wastewater into Au(0) according to claim 1, characterized in that: The oil phase in step 13 can be repeatedly used as a hydrophobic deep eutectic solvent.

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