Triphenylphosphine ionic liquid, preparation method and application thereof, and method for liquid-liquid extraction of Au (III)

Abstract

The invention belongs to the technical field of gold recovery, and particularly relates to a triphenylphosphine ionic liquid, a preparation method and application thereof, and a method for liquid-liquid extraction of Au (III). The invention provides a triphenylphosphine ionic liquid. The chemical formula of the triphenylphosphine ionic liquid is as shown in formula 1. Compared with other metal ions, in actual and simulated multi-metal ion solutions, the ionic liquid [EtPh3P] [PF6] provided by the invention has higher selectivity to Au (III), and the extraction capacity of the ionic liquid is as high as 550mg / g. In conclusion, the invention provides a series of economic, good-selectivity and environment-friendly triphenylphosphine ionic liquid extraction agents, and the triphenylphosphine ionic liquid extraction agents can be applied to extraction and recovery of gold (III) from actual electronic waste and can be further amplified and used in an industrial actual system.

Description

Technical Field

[0001] The invention belongs to the technical field of gold recovery, and specifically relates to a triphenylphosphine ionic liquid and a preparation method and application thereof, and a liquid-liquid extraction method for Au (III). Background Art

[0002] As one of the most representative precious metals, gold plays an irreplaceable role in human life and modern process systems due to its unique physical and chemical properties, such as excellent conductivity and corrosion resistance. The main supply of gold comes from gold ore, but the amount of gold obtained from each ton of gold ore can only meet the needs of 40 mobile phones. Moreover, with the vigorous development of industry, the demand for gold has gradually increased, leading to over-exploitation of gold mines. As a gradually depleted natural resource, gold is in serious shortage of supply. At the same time, with the rapid development of information technology and the communications industry, human demand for electronic equipment is huge. According to statistics, as of 2019, about 17.4% of the electronic waste (e-waste) generated worldwide has not been properly handled or recycled, while the remaining 82.6% has not been recorded. Electronic waste components, especially printed circuit boards (PCBs), contain a large amount of precious metals. PCBs are an important component of almost all electronic products, accounting for about 3-6% of global electronic waste, and the gold content is about 25-250 times that of typical gold mines. Although the weight percentage of gold in PCBs is less than 1%, its monetary value accounts for more than 70% of all metals, and the economic value after recycling is very objective.

[0003] At present, gold recovery mostly adopts precipitation method or solvent extraction method. Traditional extractants include propylene carbonate, di-n-hexyl sulfide and tributyl phosphate. Although solvent extraction has advantages over traditional precipitation method, it still has disadvantages such as slow kinetics and poor selectivity for precious metal purification. At present, there are some literature reports on the extraction and recovery of Au(III) by solvent extraction. However, most extractants have disadvantages such as high price, unfriendly to the environment and low extraction capacity.

[0004] In recent years, ionic liquids (ILs) have attracted widespread attention. Compared with traditional extractants, ionic liquids have the advantages of high extraction efficiency, adjustable performance, good chemical stability and thermal stability. The ionic liquids commonly used in the literature for precious metal extraction include quaternary phosphonium ionic liquids and quaternary ammonium ionic liquids. Phosphonium ionic liquids have the characteristics of high thermal stability, high hydrophobicity, unique miscibility behavior and fast extraction kinetics. As an emerging precious metal extractant, they have received widespread attention and have also been used to extract gold from hydrochloric acid media.

[0005] However, in actual electronic waste, the content of each metal is inconsistent, and other substances and high acidity may be contained, which has a stronger interference with the selective extraction of gold. Therefore, the above-mentioned ionic liquid extractant solution currently disclosed cannot achieve effective selective separation of Au (III) in actual electronic waste. Summary of the invention

[0006] The purpose of the present invention is to provide a triphenylphosphine ionic liquid and a preparation method and application thereof, and a liquid-liquid extraction method for Au(III). The triphenylphosphine ionic liquid provided by the present invention has the characteristics of high extraction capacity, good selectivity and low economic cost for Au(III) in actual electronic waste, and is suitable for the recycling of secondary resources such as electronic waste.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a triphenylphosphine ionic liquid, the chemical formula of the triphenylphosphine ionic liquid is shown in Formula 1:

[0009] [RPh3P][PF6] Formula 1;

[0010] In Formula 1, R is a C1-10 alkyl group.

[0011] Preferably, the triphenylphosphine ionic liquid includes one or more of ethyltriphenylphosphine hexafluorophosphonic acid ionic liquid, propyltriphenylphosphine bromide hexafluorophosphonic acid ionic liquid, n-butyltriphenylphosphine hexafluorophosphonic acid ionic liquid and n-pentyltriphenylphosphine hexafluorophosphonic acid ionic liquid.

[0012] The present invention provides a method for preparing the triphenylphosphine ionic liquid described in the above technical scheme, comprising the following steps:

[0013] The triphenylphosphonium bromide substituted with a C1-10 alkyl group, an alkali metal hexafluorophosphate, water and an organic solvent are mixed to carry out an anion exchange reaction to obtain an organic phase product;

[0014] The organic phase product is sequentially washed with water, the organic solvent is removed and dried to obtain the triphenylphosphine ionic liquid.

[0015] Preferably, the mass ratio of the C1-10 alkyl-substituted triphenylphosphonium bromide to the alkali metal hexafluorophosphate is (1-4):(1-2); the organic solvent is a chlorinated alkane, and the volume ratio of the water to the organic solvent is 1:1-2.

[0016] The present invention provides the use of the triphenylphosphine ionic liquid described in the above technical solution or the triphenylphosphine ionic liquid prepared by the preparation method described in the above technical solution in liquid-liquid extraction of Au (III).

[0017] The present invention provides a method for liquid-liquid extraction of Au(III), comprising the following steps:

[0018] An extractant organic phase solution and an aqueous phase solution containing Au(III) are mixed for extraction to obtain an extracted organic phase enriched in Au(III) and a raffinate aqueous phase; the extractant organic phase solution comprises an extractant and an organic diluent, and the extractant is the triphenylphosphine ionic liquid described in the above technical solution or the triphenylphosphine ionic liquid prepared by the preparation method described in the above technical solution; the aqueous phase solution containing Au(III) is an acidic solution.

[0019] Preferably, the organic diluent is a chlorinated alkane;

[0020] The molar concentration of the extractant in the extractant organic phase solution is 1-5 mmol / L.

[0021] Preferably, the aqueous solution containing Au(III) comprises Au(III), water and a strong inorganic acid; in the aqueous solution containing Au(III): the molar concentration of Au(III) is 1 to 2 mmol / L, and the molar concentration of the strong inorganic acid is 0.1 to 3 mol / L.

[0022] Preferably, the volume ratio of the organic phase solution of the extractant to the aqueous phase solution containing Au(III) is 1:9 to 9:1; and the extraction temperature is room temperature.

[0023] Preferably, after obtaining the Au(III)-enriched extracted organic phase, the method further comprises: mixing the Au(III)-enriched extracted organic phase and a stripping agent aqueous phase solution for stripping to obtain an Au(III)-enriched extracted aqueous phase and a raffinate organic phase; the stripping agent aqueous phase solution comprises a stripping agent and water, and the stripping agent is thiourea and HCl.

[0024] The present invention provides a triphenylphosphine ionic liquid, the chemical formula of which is shown in Formula 1: [RPh3P][PF6] Formula 1; R in Formula 1 is a C1-10 alkyl group. Four phosphine-containing ionic liquids [EtPh3P][PF6], [PrPh3P][PF6], [BuPh3P][PF6], and [PentylPh3P][PF6] are provided in the embodiment of the present invention, and a homogeneous extraction system composed of an ionic liquid-water system is studied for one-time separation and recovery of Au(III) from secondary resources. Experimental results show that compared with other metal ions, in actual and simulated multi-metal ion solutions, the ionic liquid [EtPh3P][PF6] has a higher selectivity for Au(III), and its extraction capacity can be as high as 550 mg / g. In addition, it has ultra-fast extraction kinetics and can reach extraction equilibrium within 1 minute. According to the Job method and the concentration of the extractant, the ionic liquids [EtPh3P][PF6], [PrPh3P][PF6], [BuPh3P][PF6], [PentylPh3P][PF6] and AuCl4 - The stoichiometric ratio is 1:1. Combined with UV-visible, infrared and nuclear magnetic resonance studies, the extraction mechanism of ionic liquid and Au(III) was determined to be anion exchange. The mechanism of the influence of carbon chain length on the extraction performance was systematically explored using ESP. [EtPh3P][PF6] has the best extraction effect on Au(III), which can be attributed to the gradual increase in the electron-withdrawing ability of the four substituents as the alkyl chain of the triphenylphosphine cation grows. In a complex environment where a variety of high-content other metal ions coexist, the extraction rate of gold by the ionic liquid [EtPh3P][PF6] can still reach 99.57%. Finally, using a mixed aqueous solution containing CS(NH2)2 and HCl as a stripping agent, a good stripping effect can be achieved, and [EtPh3P][PF6] also shows a good extraction efficiency (98.73%) after 5 cycles. In general, the present invention not only overcomes the disadvantage of slow kinetics of solvent extraction methods, but also has the characteristics of high extraction capacity, good selectivity and low economic cost, and can provide theoretical support for the recycling of secondary resources such as electronic waste.

[0025] In summary, the present invention provides a series of economical, selective and environmentally friendly triphenylphosphine ionic liquid extractants, which can be applied to extract and recover gold (III) from actual electronic waste and can be further scaled up for use in actual industrial systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The synthetic routes of four ionic liquids in the examples are as follows ( Figure 1 a) and physicochemical properties ( Figure 1 b and c);

[0027] Figure 2 The experimental results of optimizing the conditions for extracting Au(Ⅲ) with four ionic liquids are shown in Figure 2. Figure 2 a in the graph is the effect of ionic liquid concentration on Au(III) extraction ([ionic liquid] = 0.2 mmol / L to 10 mmol / L, aqueous solution = 1 mmol / L Au(III), [HCl] = 0.1 mol / L, T = 25°C, t = 5 h), Figure 2 b in the figure is the distribution ratio of Au(III) content in the four ionic liquid extraction systems (the extraction conditions are the same as a). Figure 2 c in the figure is the effect of hydrochloric acid concentration on Au(Ⅲ) extraction ([ionic liquid] = 1 mmol / L, aqueous solution = 1 mmol / L Au(Ⅲ), T = 25°C), Figure 2 The d in the figure is the effect of hydrogen ion concentration on the extraction of Au(III) (the extraction conditions are the same as those in c). Figure 2 e in the figure is the effect of chloride ion concentration on Au(III) extraction (extraction conditions are the same as c). Figure 2 f in the figure is the effect of pH on Au(III) extraction (extraction conditions are the same as c);

[0028] Figure 3 The kinetic and thermodynamic experimental results of the extraction of Au(Ⅲ) by four ionic liquids are shown in Figure 2. Figure 3 a in the figure is the effect of extraction temperature on Au(III) extraction ([ionic liquid] = 1 mmol / L; aqueous solution = 1 mmol / L Au(III), [HCl] = 0.1 mol / L; t = 5 h), Figure 3 b in the figure is the effect of extraction time on Au(Ⅲ) extraction. Figure 3 where c is the pseudo-first-order kinetic model and Figure 3 The d in the figure is a pseudo-second-order kinetic model ([ionic liquid] = 1 mmol / L, aqueous solution = 1 mmol / LAu(III), [HCl] = 0.1 mol / L, T = 25 °C;

[0029] Figure 4 The extraction capacity, recyclability and economy of Au(III) extracted by four ionic liquids are shown in Table 1. Figure 4 a in the equation is the effect of the initial concentration of Au(III) on the extraction capacity (mg / g). Figure 4 b in the figure is the comparison result of the maximum extraction capacity of [EtPh3P][PF6] and other materials. Figure 4 c in the figure is the effect of the initial concentration of Au(Ⅲ) on the extraction capacity (mol / mol). Figure 4 d in the figure is a schematic diagram of the extraction and stripping of Au(III) by ionic liquid. Figure 4where e is the reusability of Au(Ⅲ) extracted by ionic liquid [EtPh3P][PF6] ([ionic liquid] = 5 mmol / L, aqueous solution = 1 mmol / L Au(Ⅲ), T = 25 °C, 0.1 mol / L HCl, t E =30min, t s =2h, T = 25°C) Figure 4 Where f is the economic cost comparison result of [EtPh3P][PF6] and other materials;

[0030] Figure 5 for [EtPh3P] + , [PrPh3P] + , [BuPh3P] + and [PentylPh3P] + Electrostatic potential (ESP) diagram of [EtPh3P] + , [PrPh3P] + , [BuPh3P] + and [PentylPh3P] + The surface area within each ESP range on the vdW surface;

[0031] Figure 6 To explore the mechanism of Au(Ⅲ) extraction by four ionic liquids. Figure 6 a in the figure is the Job's diagram of the extraction of Au(III) by ionic liquid ([ionic liquid] = 4.8-1.5 mmol / L, aqueous solution = 1.2-4.5 mmol / L Au(III), T = 25°C, 0.1 mol / L HCl, t = 5 h), Figure 6 b in the figure is the UV-vis spectrum of [EtPh3P][PF6], Au(III), and [EtPh3P]AuCl4 complex. Figure 6 c in the figure is the FT-IR spectrum of the [EtPh3P][PF6] and [EtPh3P]AuCl4 extracts. Figure 6 The d in the equation is the extract of [EtPh3P][PF6] and [EtPh3P]AuCl4 31 P NMR spectrum;

[0032] Figure 7 Schematic diagram of the anion exchange mechanism of Au(III) extraction using triphenylphosphine ionic liquid;

[0033] Figure 8 The selective extraction of Au(Ⅲ) by ionic liquid [EtPh3P][PF6] and the actual application experimental results of electronic waste are shown in the figure. Figure 8 a in the equation is the selective extraction result of Au(Ⅲ) by [EtPh3P][PF6], Figure 8b in the figure is the experimental result of extracting Au(Ⅲ) from actual electronic waste by [EtPh3P][PF6], Figure 8 Figure c is a schematic diagram of the selective extraction of Au(III) by [EtPh3P][PF6]. DETAILED DESCRIPTION

[0034] The present invention provides a triphenylphosphine ionic liquid, the chemical formula of the triphenylphosphine ionic liquid is shown in Formula 1:

[0035] [RPh3P][PF6] Formula 1;

[0036] In Formula 1, R is a C1-10 alkyl group.

[0037] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well known to those skilled in the art.

[0038] In the present invention, the triphenylphosphine ionic liquid preferably includes one or more of ethyltriphenylphosphine hexafluorophosphonate ionic liquid ([EtPh3P][PF6]), propyltriphenylphosphine bromide hexafluorophosphonate ionic liquid ([PrPh3P][PF6]), n-butyltriphenylphosphine hexafluorophosphonate ionic liquid ([BuPh3P][PF6]) and n-pentyltriphenylphosphine hexafluorophosphonate ionic liquid ([PentylPh3P][PF6]), and the most preferred is [EtPh3P][PF6].

[0039] The present invention provides a method for preparing the triphenylphosphine ionic liquid described in the above technical scheme, comprising the following steps:

[0040] The triphenylphosphonium bromide substituted with a C1-10 alkyl group, an alkali metal hexafluorophosphate, water and an organic solvent are mixed to carry out an anion exchange reaction to obtain an organic phase product;

[0041] The organic phase product is sequentially washed with water, the organic solvent is removed and dried to obtain the triphenylphosphine ionic liquid.

[0042] The present invention mixes C1-10 alkyl-substituted triphenylphosphonium bromide, alkali metal hexafluorophosphate, water and an organic solvent to carry out anion exchange reaction to obtain an organic phase product. In the present invention, the C1-10 alkyl-substituted triphenylphosphonium bromide is preferably ethyl triphenylphosphonium bromide, propyl triphenylphosphonium bromide, n-butyl triphenylphosphonium bromide or n-pentyl triphenylphosphonium bromide. The alkali metal hexafluorophosphate is preferably lithium hexafluorophosphate. The organic solvent is preferably a chloroalkane, and is preferably dichloromethane. The mass ratio of the C1-10 alkyl-substituted triphenylphosphonium bromide to the alkali metal hexafluorophosphate is preferably (1-4): (1-2), more preferably (3-4): (1.2-1.6), and is preferably 3.71:1.51. The volume ratio of the water to the organic solvent is preferably 1:1-2, and is preferably 1:2. The mixing preferably comprises the following steps: dissolving the C1-10 alkyl-substituted triphenylphosphine bromide and the alkali metal hexafluorophosphate in water, and then adding the organic solvent. The temperature of the anion exchange reaction is preferably room temperature, and the time is preferably 12-24 hours. The anion exchange reaction is preferably carried out under stirring.

[0043] After obtaining the organic phase product, the present invention sequentially washes the organic phase product with water, removes the organic solvent and dries it to obtain the triphenylphosphine ionic liquid. The number of times of washing with water is preferably 1 to 5 times. The specific implementation of removing the organic solvent is preferably rotary evaporation. The drying is preferably vacuum drying, and the vacuum drying time is preferably 3 hours.

[0044] The present invention provides the use of the triphenylphosphine ionic liquid described in the above technical solution or the triphenylphosphine ionic liquid prepared by the preparation method described in the above technical solution in liquid-liquid extraction of Au (III).

[0045] In the present invention, the Au(III) is preferably Au(III) in the electronic waste leachate.

[0046] The present invention provides a method for liquid-liquid extraction of Au(III), comprising the following steps:

[0047] An extractant organic phase solution and an aqueous phase solution containing Au(III) are mixed for extraction to obtain an extracted organic phase enriched in Au(III) and a raffinate aqueous phase; the extractant organic phase solution comprises an extractant and an organic diluent, and the extractant is the triphenylphosphine ionic liquid described in the above technical solution or the triphenylphosphine ionic liquid prepared by the preparation method described in the above technical solution; the aqueous phase solution containing Au(III) is an acidic solution.

[0048] In the present invention, the organic diluent is preferably a chlorinated alkane, and more preferably dichloromethane. The molar concentration of the extractant in the organic phase solution of the extractant is preferably 1 to 5 mmol / L.

[0049] In the present invention, the aqueous solution containing Au(III) comprises Au(III), water and a strong inorganic acid. The strong inorganic acid is preferably HCl. In the aqueous solution containing Au(III): the molar concentration of Au(III) is preferably 1 to 2 mmol / L, more preferably 1 mmol / L. The molar concentration of HCl in the aqueous solution containing Au(III) is preferably 0.1 to 3 mol / L. The pH value of the aqueous solution containing Au(III) is preferably 1 to 5, more preferably 1 to 4.

[0050] In the present invention, the volume ratio of the organic phase solution of the extractant to the aqueous phase solution containing Au(III) is preferably 1:9 to 9:1, more preferably 1:5 to 5:1, and most preferably 1:1.

[0051] In the present invention, the extraction temperature is preferably room temperature, specifically preferably 25° C., and the extraction time is preferably ≥0.1 min.

[0052] In the present invention, after the extraction is completed, an extracted organic phase enriched in Au(III) is obtained, and the extracted organic phase enriched in Au(III) contains Au(III), [RPh3P][PF6] and an organic diluent.

[0053] In the present invention, after obtaining the Au(III)-enriched extracted organic phase, the present invention preferably further comprises: mixing the Au(III)-enriched extracted organic phase and a stripping agent aqueous phase solution for stripping to obtain an Au(III)-enriched extracted aqueous phase and a raffinate organic phase; the stripping agent aqueous phase solution comprises a stripping agent and water, and the stripping agent is thiourea and HCl.

[0054] In the present invention, in the aqueous solution of the stripping agent: the molar concentration of thiourea (CS(NH2)2) is preferably 0.2 mol / L. The molar concentration of the HCl is preferably 0.1 mol / L. The stripping agent acts as both a stripping agent and a reducing agent for Au(III) during the stripping process, reducing Au(III) to Au(Ι). During the stripping process, [RPh3P][PF6] in the Au(III)-enriched extraction organic phase is also converted into [RPh3P]·Cl by the stripping agent. Therefore, the substance contained in the obtained raffinate organic phase is [RPh3P]·Cl, which cannot be directly recycled. The present invention preferably mixes the raffinate organic phase obtained by stripping with an alkali metal hexafluorophosphate to carry out anion exchange reaction to obtain [RPh3P][PF6] for recycling. The alkali metal hexafluorophosphate is specifically preferably lithium hexafluorophosphate.

[0055] In the present invention, the volume ratio of the Au(III)-enriched extraction organic phase to the stripping agent aqueous phase solution is preferably 1:1.

[0056] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0057] The reagents, materials and analytical instruments used in the following embodiments and test examples are as follows:

[0058] The reagents and materials used in this example include:

[0059] Ethyltriphenylphosphonium bromide (98%), propyltriphenylphosphonium bromide (98%), (1-butyl)triphenylphosphonium bromide (98%), amyltriphenylphosphonium bromide (98%), lithium hexafluorophosphate (99.9%), dichloromethane (≥99.9%), MnCl2·4H2O (≥99.9%), SnCl2·5H2O (98%), CoCl2·6H2O (>99%), MgCl2·6H2O (98%), CuCl2·2H2O (≥99.9%), NiCl2·6H2O (98%), FeCl3·6H2O (99%), PbCl2 (≥99.9%), and AuCl3 (99.9%) were purchased from Shanghai Titan Technology Co., Ltd., China. Other chemical reagents were of analytical grade. Electronic waste powder was provided by Chenzhou Lvmei Solid Waste Treatment Co., Ltd., China. All reagents were used as received without further purification.

[0060] The analytical instruments used in this embodiment include:

[0061] The concentration of metal ions in aqueous solution was analyzed by flame atomic absorption spectrometry (AA-6880, Shimadzu, Japan) and ICP-MS (ICAP-7850, Agilent, USA). The functional groups in ionic liquids (ILs) were determined by Nicolet iS50 Fourier transform infrared spectrometer (Nicolet, USA) and analyzed by UV-visible spectroscopy (UV-2600, Shimadzu, Japan). 1 H NMR, 13 C NMR and 10 The P NMR spectra were measured using a Bruker AV400 nuclear magnetic resonance spectrometer from Bruker Scientific Instruments, Germany. The thermal stability of the ionic liquids was determined using a thermogravimetric analyzer (TGA55, TAINSTRUMENTS, USA).

[0062] Example 1

[0063] Ethyl triphenylphosphine bromide (3.71 g) and lithium hexafluorophosphate (1.51 g) were dissolved in 10 mL of water, and 20 mL of dichloromethane was added, and the mixture was stirred for anion exchange reaction for 12 h. After the reaction was completed, the mixture was washed with water 5 times, dichloromethane was removed by rotary evaporation, and vacuum dried for 3 h to obtain ethyl triphenylphosphine hexafluorophosphonic acid ionic liquid [EtPh3P][PF6].

[0064] The preparation steps of propyltriphenylphosphonium bromide hexafluorophosphonate ionic liquid [PrPh3P][PF6], n-butyltriphenylphosphonium hexafluorophosphonate ionic liquid [BuPh3P][PF6], and n-pentyltriphenylphosphonium hexafluorophosphonate ionic liquid [PentylPh3P][PF6] are the same as above, except that the raw materials are replaced by propyltriphenylphosphonium bromide, n-butyltriphenylphosphonium bromide, and n-pentyltriphenylphosphonium bromide, respectively.

[0065] Example 2: Extraction experiment

[0066] The extraction efficiency of Au(Ⅲ) by [EtPh3P][PF6], [PrPh3P][PF6], [BuPh3P][PF6], [PentylPh3P]][PF6] ionic liquids prepared in Example 1 was investigated by liquid-liquid extraction experiment. First, AuCl3 was dissolved in acidic deionized water (pH value was 1) to obtain a stock solution of 2000mg / L, and the stock solution was diluted with 0.1mol / L HCl deionized water solution to prepare Au(Ⅲ) solution at the corresponding concentration. The four ionic liquids [EtPh3P][PF6], [PrPh3P][PF6], [BuPh3P][PF6], [PentylPh3P][PF6] were dissolved in dichloromethane (organic diluent) to obtain an ionic liquid phase (concentration was 1mmol / L or 5mmol / L, different concentrations were selected according to different experiments). Subsequently, a liquid-liquid extraction experiment was carried out in a two-phase system in which both the ionic liquid phase and the aqueous phase were 5mL. The experiment was carried out at room temperature and the two phases were separated by shaking in a shaker at 230 r / min for 5 hours. In order to minimize the impact of the loss of diluent volatilization on the extraction process, the entire extraction process was carried out in a well-sealed reactor. Finally, the concentration of Au(III) in the aqueous phase before and after extraction was determined by atomic absorption spectroscopy. All experiments were repeated 3 times under the above conditions, and the average value and standard deviation were calculated. The present invention systematically investigated the concentration of HCl, Cl - Concentration, H + Effects of extraction conditions such as concentration, pH value, extractant concentration, temperature, and extraction time on the extraction performance of [EtPh3P][PF6], [PrPh3P][PF6], [BuPh3P][PF6], and [PentylPh3P][PF6]. The extraction rate E (%) and the distribution ratio D were calculated by formula (1) and formula (2):

[0067]

[0068] In formula (1) and formula (2), C in and C eq are the initial concentration and equilibrium concentration of metal ions in the aqueous phase, respectively. IL and C aq are the gold concentrations in the ionic liquid phase and the aqueous phase after extraction, respectively.

[0069] Example 3: Stripping Experiment

[0070] The reverse extraction experiment of [EtPh3P][PF6] extractant was carried out using CS(NH2)2 with a concentration of 0.2 mol / L. The experimental conditions were set as follows: hydrochloric acid concentration: 0.1 mol / L, temperature: 25°C, time: 2 h. Au(Ⅲ) enters the thiourea phase from the organic phase, and the reverse extraction rate S (%) is calculated according to formula (3). After the reverse extraction is completed, the raffinate is mixed with [PF6] - The regenerated [EtPh3P][PF6] was washed three times with deionized water to remove a small amount of CS(NH2)2 and HCl contained in the ionic liquid phase, and then the ionic liquid phase was recycled.

[0071]

[0072] In formula (3), n aq represents the molar mass of metal ions in the aqueous phase after back extraction, n IL It represents the molar mass of metal ions in the ionic liquid phase after back extraction.

[0073] Calculation details in Example 2 and Example 3:

[0074] Using B3LYP / 6-311++G(d,p) as the basis set, density functional theory (DFT) was used to investigate the relationship between [EtPh3P] + , [PrPh3P] + , [BuPh3P] + , and [PentylPh3P] + The geometry was optimized with Gaussian 09, and the general solvation model (SMD) was used to account for solvation effects in water. Electrostatic potential (ESP) maps were generated with Multiwfn-3.8 and rendered with VMD-1.9.3. Following Bader et al., the present analysis of ESP on van der Waals (vdW) surfaces was referenced to ρ = 0.001 e / bohr 3 isosurface of .

[0075] Example 4: Recovery of [EtPh3P][PF6] gold from electronic waste leachate

[0076] Dissolve 1g of electronic waste powder in freshly prepared aqua regia solution, sonicate to fully dissolve it, filter out impurities, and dilute ten times to obtain electronic waste leaching solution. Then take 5mL of the above solution as the aqueous phase and shake it with 5mL of the ionic liquid phase in a shaker for 5h. Finally, determine the concentration of metal ions in the aqueous phase and study the extraction performance of [EtPh3P][PF6] extractant for gold in electronic waste.

[0077] Results and Discussion of Examples 1 to 4:

[0078] (1) Synthesis and properties of triphenylphosphine ionic liquid

[0079] The present invention successfully prepares four phosphine-containing ionic liquids with different carbon chain lengths by using ethyl triphenylphosphonium bromide, propyl triphenylphosphonium bromide, n-butyl triphenylphosphonium bromide, n-pentyl triphenylphosphonium bromide and lithium hexafluorophosphate. The synthesis route is as follows: Figure 1 As shown in a. All four ionic liquids have strong stability and high hydrophobicity. Thermogravimetric analysis was performed on the ionic liquids [EtPh3P][PF6], [PrPh3P][PF6], [BuPh3P][PF6], and [PentylPh3P][PF6]. The test results are shown in Figure 1 As shown in b. From the above thermogravimetric diagrams of ionic liquids, it can be seen that the four ionic liquids have good thermal stability, that is, they can be used in a wide temperature range. Figure 1 From b, we can see that the ionic liquid [EtPh3P][PF6] has better thermal stability than the ionic liquids [PrPh3P][PF6], [BuPh3P][PF6], and [PentylPh3P][PF6]. When the temperature exceeds 550°C, all four ionic liquids have been completely degraded. 1 H NMR characterization of the water solubility of the four ionic liquids showed Figure 1 As shown in c. As shown in Table 1, the water solubility of the four ionic liquids is relatively small, and the water solubility is [EtPh3P][PF6](0.3036g / L)>[PrPh3P][PF6](0.2709g / L)>[BuPh3P][PF6](0.2648g / L)>[PentylPh3P][PF6](0.2626g / L). This may be related to the length of its carbon chain. The shorter the carbon chain, the greater the water solubility. In summary, the four ionic liquids prepared in the embodiments of the present invention have good thermal stability and low water solubility, and are suitable for the selective separation of gold.

[0080] Table 1 Four ionic liquids 1 H NMR characterization results

[0081]

[0082] (2) Optimization of extraction conditions

[0083] The present invention first investigated the effect of the concentration of [EtPh3P][PF6], [PrPh3P][PF6], [BuPh3P][PF6], and [PentylPh3P][PF6] ionic liquids on the extraction efficiency of Au(III). Figure 2 As shown in a in the figure. It can be observed that the extraction efficiency of Au(Ⅲ) increases with the increase of the ionic liquid concentration in the organic phase, and finally remains unchanged and tends to be stable when the concentration of the ionic liquids of [EtPh3P][PF6], [PrPh3P][PF6], [BuPh3P][PF6], and [PentylPh3P][PF6] are all 1mmol / L. Correspondingly, the distribution ratio of [EtPh3P][PF6] also increases from 0.7 to 237.0, the distribution ratio of [PrPh3P][PF6] increases from 0.7 to 204.9, the distribution ratio of [BuPh3P][PF6] increases from 0.4 to 98.7, and the distribution ratio of [PentylPh3P][PF6] increases from 0.5 to 36.4 ( Figure 2 b). With the increase of ionic liquid concentration, the number of Au(Ⅲ) extraction active sites increases, resulting in more Au(Ⅲ) migrating to the ionic liquid phase, and then the extraction rate increases. Compared with [EtPh3P][PF6], the long carbon chain [PentylPh3P][PF6] is difficult to exchange anions with Au(Ⅲ) due to obvious steric hindrance, resulting in its low extraction rate. Considering this aspect, the shorter the carbon chain of the extractant, the better the extraction efficiency of Au(Ⅲ). Therefore, [EtPh3P][PF6] has the best extraction performance, and [PentylPh3P][PF6] has the worst extraction performance. The results show that every 1mmol / L [EtPh3P][PF6], [PrPh3P][PF6], [BuPh3P][PF6], [PentylPh3P][PF6] ionic liquid can extract 1mmol / LAu(Ⅲ), that is, the molar ratio of ionic liquid to Au(Ⅲ) is 1:1. Subsequent molar ratio experiments can also prove this conclusion.

[0084] The concentration of hydrochloric acid may affect the ionic form of Au(III) in the acidic solution and therefore plays a vital role in the extraction of Au(III). Therefore, the present invention investigates the effect of hydrochloric acid concentration on the extraction efficiency of Au(III). Figure 2As shown in c. It shows that when the HCl concentration is 0.1-3.0 mol / L, the extraction effect of [EtPh3P][PF6], [PrPh3P][PF6], [BuPh3P][PF6], [PentylPh3P][PF6] ionic liquids on Au(Ⅲ) does not show obvious changes, and the extraction rate has been stable. Combining the extraction efficiency and the stable existence form of gold and considering the economic benefits, 0.1 mol / L HCl was selected in the subsequent experiments.

[0085] In order to further explore the effect of hydrochloric acid concentration on extraction, the present invention explored the effects of hydrogen ion concentration and chloride ion concentration on Au(III) extraction efficiency. When investigating the effect of hydrogen ion concentration on Au(III) extraction efficiency, the chloride ion concentration was fixed at 3.0 mol / L and the hydrogen ion concentration was changed from 0.1 mol / L to 3.0 mol / L. Figure 2 From the d in the figure, we can see that with the increase of hydrogen ion concentration, the extraction rate of Au(Ⅲ) by the four ionic liquids [EtPh3P][PF6], [PrPh3P][PF6], [BuPh3P][PF6], and [PentylPh3P][PF6] remains almost unchanged. The effect of chloride ion concentration on the extraction of Au(Ⅲ) was investigated. The hydrogen ion concentration was fixed at 0.1 mol / L, and the chloride ion concentration was changed from 0.1 mol / L to 3.0 mol / L. Figure 2 It can be seen from the graph that when the chloride ion concentration is 0.1-3.0 mol / L, the extraction rates of Au(Ⅲ) by the four ionic liquids [EtPh3P][PF6], [PrPh3P][PF6], [BuPh3P][PF6], and [PentylPh3P][PF6] remain almost unchanged. Therefore, the hydrogen ion concentration and the chloride ion concentration have almost no effect on the extraction effect of Au(Ⅲ).

[0086] Figure 2 The experimental results of optimizing the conditions for extracting Au(Ⅲ) with four ionic liquids are shown in Figure 2. Figure 2 a in the graph is the effect of ionic liquid concentration on Au(III) extraction ([ionic liquid] = 0.2 mmol / L to 10 mmol / L, aqueous solution = 1 mmol / L Au(III), [HCl] = 0.1 mol / L, T = 25°C, t = 5 h), Figure 2 b is the distribution ratio of Au(Ⅲ) content in the four ionic liquid extraction systems (the extraction conditions are the same as Figure 2 a) in the above formula, Figure 2 c in the figure is the effect of hydrochloric acid concentration on Au(Ⅲ) extraction ([ionic liquid] = 1 mmol / L, aqueous solution = 1 mmol / L Au(Ⅲ), T = 25°C), Figure 2 The d in the figure is the effect of hydrogen ion concentration on Au(Ⅲ) extraction (the extraction conditions are the same as Figure 2c) in the above, Figure 2 e in the figure is the effect of chloride ion concentration on Au(Ⅲ) extraction (the extraction conditions are the same as Figure 2 c) in the above, Figure 2 f in the figure is the effect of pH on Au(Ⅲ) extraction (the extraction conditions are the same as Figure 2 c) in.

[0087] In order to further explore the experimental conditions that affect the extraction efficiency of Au(III), the present invention further investigated the effect of the pH of the Au(III) aqueous solution on the extraction efficiency. Since the existence form of gold ions is affected by the pH value, the results are as follows Figure 2 As shown in f. At pH values ​​of 1 to 4, the gold extraction rate remains stable. When the pH value increases from 4 to 5, the extraction rate drops sharply. As the pH value increases further, the extraction rate continues to drop. When the pH is less than 5, gold is mainly in the form of AuCl4 - It exists in the form of anions; when the pH value is between 5 and 8, gold exists in the form of AuCl4 - , AuCl3(OH)-, AuCl2(OH)2 - , AuCl(OH)3 - Therefore, when the pH is less than 5, AuCl4 - Possibly with anions in [EtPh3P][PF6], [PrPh3P][PF6], [BuPh3P][PF6], [PentylPh3P][PF6] ionic liquids [PF6] - Anion exchange occurs, and the specific extraction mechanism will be verified and described in detail later. When the pH is 5 to 6, AuCl4 in the acidic gold solution - The content of anions decreases, resulting in anions [PF6] - The number of anion exchanges decreased, resulting in a downward trend in the extraction rates of Au(Ⅲ) by the four ionic liquids [EtPh3P][PF6], [PrPh3P][PF6], [BuPh3P][PF6], and [PentylPh3P][PF6].

[0088] In summary, in the above extraction process, the concentration of gold that can be extracted by 1mmol / L [EtPh3P][PF6], [PrPh3P][PF6], [BuPh3P][PF6], [PentylPh3P][PF6] ionic liquid is 200ppm, and the concentration of HCl, H + and Cl - The concentration has almost no effect on the extraction of ionic liquids. Considering the extraction efficiency, the stable existence form of gold and economic benefits, 0.1 mol / L HCl was selected in subsequent experiments.

[0089] (3) Thermodynamics and kinetics

[0090] In order to explore the relationship between the extraction system and temperature, the present invention conducts a detailed study on the extraction thermodynamics. The extraction behavior of 1mmol / LAu(Ⅲ) was studied when the temperature range was 278-318K and the concentration of four ionic liquids, [EtPh3P][PF6], [PrPh3P][PF6], [BuPh3P][PF6], and [PentylPh3P][PF6], was 1mmol / L. Figure 3 As shown in a, as the temperature changes, the extraction efficiency of the four ionic liquids [EtPh3P][PF6], [PrPh3P][PF6], [BuPh3P][PF6], and [PentylPh3P][PF6] is almost unchanged. Therefore, it can be concluded that the process of extracting gold with the four ionic liquids [EtPh3P][PF6], [PrPh3P][PF6], [BuPh3P][PF6], and [PentylPh3P][PF6] is almost unaffected by temperature. The experimental temperature selected by the subsequent present invention is 298K.

[0091] In order to gain a deeper understanding of the main factors that determine the extraction rate, the present invention also conducted a detailed study on the extraction kinetics. The extraction equilibrium time was determined by changing the oscillation time within the range of 5 s and 5 min. Figure 3 The results in b show that the four ionic liquids can reach equilibrium in the extraction of gold within 1 minute. The ionic liquid [EtPh3P][PF6] can reach 94.2%, [PrPh3P][PF6] can reach 95.5%, [BuPh3P][PF6] and [PentylPh3P][PF6] can reach 89.7%, indicating that the extraction kinetics is rapid. In order to further clarify the kinetic process, the present invention combines formula (4) and formula (5) to fit the pseudo-first-order kinetic model and pseudo-second-order kinetic model of the extraction capacity changing with time. The results are shown in Figure 3 As shown in c and d. Figure 3 From c and d in the figure, we can see that the correlation coefficient R of the pseudo first-order kinetic model 2 The correlation coefficient of the pseudo-second-order kinetic model is 0.4732-0.7495, while the correlation coefficient R 2 The extraction reaction is more consistent with the pseudo second-order kinetic model, and the present invention believes that the main extraction mechanism is a chemical process.

[0092] ln(q e -q t )=lnq e -k1t(4);

[0093]

[0094] In formula (4) and formula (5), qe and q t They represent the extraction capacity at equilibrium time t and time t respectively. k1(min -1 ) and k2(mol·min -1 ) represents the constants of the pseudo first-order equation and the pseudo second-order equation.

[0095] 3 shows the kinetic and thermodynamic experimental results of the extraction of Au(Ⅲ) by four ionic liquids. Figure 3 a in the figure is the effect of extraction temperature on Au(III) extraction ([ionic liquid] = 1 mmol / L; aqueous solution = 1 mmol / LAu(III), [HCl] = 0.1 mol / L; t = 5 h). Figure 3 b in the figure is the effect of extraction time on Au(Ⅲ) extraction. Figure 3 where c is the pseudo-first-order kinetic model and Figure 3 The d in the equation is a pseudo-second-order kinetic model ([ionic liquid] = 1 mmol / L, aqueous solution = 1 mmol / LAu(III), [HCl] = 0.1 mol / L. T = 25°C.

[0096] (4) Maximum extraction capacity and economy

[0097] The extraction capacity of the extractant is the most direct indicator of the performance of the extractant. The present invention examines the extraction capacity of the extractant by examining the initial metal ion concentrations of different concentrations and continuously increasing the concentration of Au(III) to obtain the maximum extraction amount (q e ).q e The value of (mg / g) is as shown in formula (6):

[0098]

[0099] In formula (6), C in (mmol / L) and C ep are the initial and equilibrium metal ion concentrations, m (g) is the mass of the ionic liquid, V (L) is the volume of the aqueous phase, and the relative atomic mass of Au is 196.97 mg / mmol.

[0100] like Figure 4As shown in a, with the increase of the initial concentration of Au(III) solution, the extraction capacity of ionic liquid for Au(III) continues to increase and eventually tends to equilibrium, indicating that the ionic liquid has achieved saturated extraction. The maximum extraction capacity of the four ionic liquids for Au(III) is in the following order: [EtPh3P][PF6]>[PrPh3P][PF6]>[BuPh3P][PF6]>[PentylPh3P][PF6]. In particular, the maximum extraction capacity of the ionic liquid [EtPh3P][PF6] reaches 550 mg / g, which indicates that the ionic liquid [EtPh3P][PF6] has better extraction capacity and is an effective extractant for Au(III) extraction. Figure 4 As shown in b, compared with the reported ionic liquids (CyIL102, CyIL101, [C6-EfTMEDAPLP][Tf2N], [Pyr-C2OC2][Tf2N], [Suc][Tf2N]2, [diPTMG][Tf2N], [diPTMG][Tf2N], [EtbetmMor][Tf2N], [Pyr-Bu][Tf2N], [diMTMG][Tf2N],), [EtPh3P][PF6] has a larger extraction capacity, indicating that it is very efficient in extracting Au(III). In the subsequent characterization, reuse and actual application of electronic waste, the present invention selects [EtPh3P][PF6] for related experiments.

[0101] Table 2 Performance comparison of various ionic liquid gold recovery methods

[0102]

[0103]

[0104] in:

[0105] [1]Q.Liu,L.Zeng,W.Wang,K.Tang,Efficient extraction of gold from model and real leach solutions using guanidinium ionic liquids,J.Environ.Chem.Eng.12(2024)112810, http: / / dx.doi.org / 10.1016 / j.jece.2024.112810 .

[0106] [2]X.Liu,Y.Wang,R.Liu,P.Lv,W.Xue,J.Guo,H.Wei,Y.Yang,Selective andEfficient Gold Extraction from E-Waste by Pyrrolidinium-Based Ionic Liquidswith Various N-Substituents,ACS Sustainable Chem.Eng.11(2023)638-648, http: / / dx.doi.org / 10.1021 / acssuschemeng.2c05455 。

[0107] [3]Y.Wang,X.Liu,A.Yang,P.Lv,L.Zhang,Y.Li,Y.Yang,Extraction andseparation onAu(III)and Pt(IV)from HCl media using novel piperazine-basedionic liquid as an ionic exchanger,J.Mol.Liq.353(2022)118846, http: / / dx.doi.org / 10.1016 / j.molliq.2022.118846 。

[0108] [4]N.Wang,Q.Wang,Y.Geng,X.Sun,D.Wu,Y.Yang,Recovery ofAu(III)fromAcidic Chloride Media by Homogenous Liquid-Liquid Extraction with UCST-TypeIonic Liquids,ACS Sustainable Chem.Eng.7(2019)19975-19983, http: / / dx.doi.org / 10.1021 / acssuschemeng.9b05602 。

[0109] [5]M.Wang,Q.Wang,J.Wang,R.Liu,G.Zhang,Y.Yang,Homogenous Liquid-LiquidExtraction of Au(III)from Acidic Medium by Ionic Liquid ThermomorphicSystems,ACS Sustainable Chem.Eng.9(2021)4894-4902, http: / / dx.doi.org / 10.1021 / acssuschemeng.1c00497 。

[0110] [6]H.Mahandra,F.Faraji,A.Ghahreman,Novel Extraction Process for GoldRecovery from Thiosulfate Solution Using Phosphonium Ionic Liquids,ACSSustainable Chem.Eng.9(2021)8179-8185, http: / / dx.doi.org / 10.1021 / acssuschemeng.1c01705 .

[0111] Figure 4 The extraction capacity, recyclability and economy of Au(III) extracted by four ionic liquids. Figure 4 a in the equation is the effect of the initial concentration of Au(III) on the extraction capacity (mg / g). Figure 4 b in the figure is the comparison result of the maximum extraction capacity of [EtPh3P][PF6] and other materials. Figure 4 c in the figure is the effect of the initial concentration of Au(Ⅲ) on the extraction capacity (mol / mol). Figure 4 d in the figure is a schematic diagram of the extraction and stripping of Au(III) by ionic liquid. Figure 4 where e is the reusability of Au(Ⅲ) extracted by ionic liquid [EtPh3P][PF6] ([ionic liquid] = 5 mmol / L, aqueous solution = 1 mmol / L Au(Ⅲ), T = 25 °C, 0.1 mol / L HCl, t E =30min, t s =2h, T = 25°C) Figure 4 Where f is the economic cost comparison result of [EtPh3P][PF6] and other materials.

[0112] In practical applications, the recycling of ionic liquids can save energy and reduce costs. Therefore, the present invention conducted a series of extraction-stripping tests to evaluate the [EtPh3P][PF6] cycle performance. When a mixture of 0.1mol / L HCl and 0.2mol / L CS(NH2)2 was used as the stripping agent and reducing agent, Au(III) was reduced to Au(I), and the stripping efficiency could reach 100%, thereby achieving further separation from the ionic liquid phase.

[0113] It is worth noting that [EtPh3P][PF6] is converted into [EtPh3P]Cl after stripping in a mixture of HCl and CS(NH2)2, and therefore cannot be used directly in the next cycle. - The regenerated [EtPh3P][PF6] was washed three times with deionized water to remove residual CS(NH2)2 and HCl. Figure 4 As shown in c, due to the low water solubility of [EtPh3P][PF6], after 5 cycles, the extraction efficiency can still be maintained at 98.73%, indicating that the extraction performance of the regenerated ionic liquid is basically the same as that of the fresh ionic liquid, and has a good reuse value.

[0114] In order to verify whether the regenerated ionic liquid has the same structure as the fresh ionic liquid, the present invention uses UV-vis, FT-IR and 31 P NMR was used to characterize [EtPh3P][PF6] after five extraction cycles. Figure 6 As shown in b, the fresh ionic liquid has obvious double peaks, and the maximum absorption peaks appear at 205 and 225nm. After extraction, the maximum absorption peak of the extractant [EtPh3P]AuCl4 changes, while the corresponding change of the regenerated ionic liquid disappears, and the maximum absorption peak position of the regenerated ionic liquid is close to that of the fresh ionic liquid. Figure 6 As shown in c, after extraction, the vibration band of the functional group of the extractant [EtPh3P]AuCl4 changed, and the anion [PF6] - PF stretch belt 840.77cm -1 The signal peak of the regenerated ionic liquid disappeared, while the signal peak of 840.77 cm -1 According to the signal peak. Figure 6 As shown in d, after extraction, the signal peak of the extractant [EtPh3P]AuCl4 at -150ppm disappears, the peak at -150ppm is attributed to P in [PF6]-, and the regenerated ionic liquid has a signal peak at -150ppm. In summary, UV-vis, FT-IR and 31 P NMR confirmed that the ionic liquid after five extraction cycles had the same chemical structure as the fresh ionic liquid, thus achieving the regeneration of the ionic liquid.

[0115] Finally, the present invention estimates the economic feasibility of extracting and recovering Au(III) using the ionic liquid [EtPh3P][PF6]. Figure 4 As shown in f, the cost of synthesizing 1g of [EtPh3P][PF6] is about $0.24. Compared with other extractants, the cost of extracting gold with ionic liquid [EtPh3P][PF6] is low and can be recycled 5 times. Therefore, the economic value of extracting gold with ionic liquid [EtPh3P][PF6] is considerable. In view of the reusability and economic cost of ionic liquid [EtPh3P][PF6], the use of ionic liquid [EtPh3P][PF6] to recover gold from secondary resources such as electronic waste has great application prospects.

[0116] (5) Extraction mechanism of Au(III) by triphenylphosphine ionic liquid

[0117] To further investigate the effect of alkyl substituents on the electronic environment of the four phenyl compounds, the [EtPh3P] + , [PrPh3P] + , [BuPh3P] + and [PentylPh3P] + ESP value. Figure 5 Medium [EtPh3P] + , [PrPh3P] + , [BuPh3P] + and [PentylPh3P] + As shown in the electrostatic potential (ESP) diagram, the most electron-deficient area is mainly near the P atom, indicating that the P atom is + The site of interaction. Figure 5 Medium [EtPh3P] + , [PrPh3P] + , [BuPh3P] + and [PentylPh3P] + The vdW surface area within each ESP range shows that the decreasing order of average ESP values ​​is: [EtPh3P] + (70.15kcal / moL)>[PrPh3P] + (68.98kcal / moL)>[BuPh3P] + (67.63kcal / moL)>[PentylPh3P] + (66.16 kcal / moL), from which we can infer the ability of the four ionic liquids to form stable extraction complexes. This is because as the alkyl chain grows, the electron-withdrawing ability of the four substituents gradually increases, resulting in a decrease in the electron density of the P atoms in the four ionic liquids. In other words, the ESP value of the triphenylphosphine cation increases with the increase of positive charge. It can be inferred that the extraction performance roughly follows the order of the ESP value, and this conclusion can also be confirmed by relevant literature. The calculated results are consistent with the above experimental results. [EtPh3P][PF6] has the largest ESP value and the highest extraction efficiency.

[0118] Job's method is widely used to explore the mechanism analysis of extraction complexes. In the present invention, the present invention uses Job's method to study the reaction between ionic liquid and AuCl4 - The stoichiometric ratio was determined by varying the gold mole fraction from 0 to 3 while keeping the total moles of metal and ionic liquid constant at 6 mmol. Figure 6As shown in a, the four ionic liquids [EtPh3P][PF6], [PrPh3P][PF6], [BuPh3P][PF6], and [pentylPh3P][PF6] exhibit similar behaviors. When the extraction of Au(Ⅲ) is pushed out to the maximum value, the molar fractions are close to 1. The above results clearly show that AuCl4 - It is combined with ionic liquids [EtPh3P][PF6], [PrPh3P][PF6], [BuPh3P][PF6], and [PentylPh3P][PF6] in a 1:1 ratio.

[0119] Figure 6 To explore the mechanism of Au(Ⅲ) extraction by four ionic liquids. Figure 6 a in the figure is the Job's diagram of the extraction of Au(III) by ionic liquid ([ionic liquid] = 4.8-1.5 mmol / L, aqueous solution = 1.2-4.5 mmol / L Au(III), T = 25°C, 0.1 mol / L HCl, t = 5 h), Figure 6 b in the figure is the UV-vis spectrum of [EtPh3P][PF6], Au(III), and [EtPh3P]AuCl4 complex. Figure 6 c in the figure is the FT-IR spectrum of the [EtPh3P][PF6] and [EtPh3P]AuCl4 extracts. Figure 6 The d in the equation is the extract of [EtPh3P][PF6] and [EtPh3P]AuCl4 31 P NMR spectrum.

[0120] Secondly, taking the ionic liquid [EtPh3P][PF6] as an example, the ionic liquid [EtPh3P][PF6], Au(Ⅲ), and the complex of the ionic liquid [EtPh3P][PF6] and Au(Ⅲ) were characterized by UV-visible spectroscopy.

[0121] Depend on Figure 6 In b, we can see that AuCl4 - It is a double peak, with maximum absorption peaks at 227 and 313nm; the ionic liquid [EtPh3P][PF6] also has obvious double peaks, with maximum absorption peaks at 205 and 225nm; the maximum absorption peaks of the extractant [EtPh3P]AuCl4 are 202, 225 and 318nm. - The maximum absorption peak position of the extractant [EtPh3P]AuCl4 is close, indicating that AuCl4 - The morphology remains unchanged before and after extraction, AuCl4 - The ultraviolet peaks of the extractant [EtPh3P]AuCl4 (318nm) showed a lower blue shift, which may be due to the presence of AuCl4- With the cation P in the ionic liquid [EtPh3P][PF6] + Therefore, AuCl4 - It combines with the ionic liquid [EtPh3P][PF6] through electrostatic interaction, and its extraction mechanism is anion exchange.

[0122] In order to further understand the extraction process and determine its mechanism, the present invention conducted FT-IR spectroscopy analysis. Figure 6 As can be seen from the c in the figure, 1442.56cm -1 The signal peak is the characteristic peak of Ph-P. There is no obvious shift in the absorption peak of Ph-P before and after extraction. The PF stretching band in LiPF6 is between 800 and 900 cm -1 Between, before extraction 840.77cm -1 For anion [PF6] - PF stretching band in; 840.77cm after extraction -1 The signal peak disappears, indicating that the anion [PF6 - disappeared after extraction. This indicates that the anion [PF6] - The transfer from the ionic liquid phase to the aqueous phase further proved that the extraction mechanism was anion exchange.

[0123] Finally, the ionic liquid [EtPh3P][PF6] and the extractant [EtPh3P]AuCl4 were 31 P NMR characterization further verified its extraction mechanism. Figure 6 As shown in d, after extraction, it belongs to [PF6] - The signal peak at -150ppm of P in the medium disappears, which is attributed to [EtPh3P] + The signal peak at 25ppm of P in the solution remains unchanged. [1] During the extraction process, the anion [PF6] of the ionic liquid [EtPh3P] [PF6] - When transferred to the aqueous phase, its characteristic peak disappeared, indicating the formation of an ionic liquid [EtPh3P][PF6] and Au(Ⅲ) extractant, further proving the anion exchange mechanism.

[0124] In summary, the ionic liquids [EtPh3P][PF6], [PrPh3P][PF6], [BuPh3P][PF6], [PentylPh3P][PF6] and AuCl4 - The stoichiometric ratio is 1:1, and the combined UV-vis, FT-IR and 31 The results of P NMR confirm that the extraction mechanism of these four ionic liquids follows the anion exchange mechanism. Figure 7 shown.

[0125] (7) Practical application of gold recovery from electronic waste

[0126] In actual production, Au(III) often coexists with various metals in electronic waste. The high selectivity of ionic liquids in multi-metal ion solutions is one of the important indicators for evaluating their applicability in secondary resources. Therefore, the selective extraction of Au(III) from multi-metal mixed solutions is of great significance. The present invention prepares a multi-metal mixed solution that simulates secondary resources, examines the selectivity of the synthesized ionic liquid, and further explores the extraction behavior of the ionic liquid. Therefore, the present invention studies the selectivity of the ionic liquid [EtPh3P][PF6] for Au(III) in various metal ion solutions. Various metal chlorides were dissolved in 0.1 mol / L, 1 mol / L and 2 mol / L HCl, respectively, to obtain various metal ion solutions, all of which had an initial concentration of 1 mmol / L. The metal ions examined included precious metal ions (AuCl4 - 、PdCl4 2- ) and base metal ions (Al 3+ Mg 2+ , Fe 3 + , Cu 2+ 、Co 2+ 、Cd 2+ 、Zn 2+ ).from Figure 8 It can be seen from a in that the ionic liquid [EtPh3P][PF6] exhibits good selective extraction ability for Au(Ⅲ) in both base metal ion solutions and noble metal ion solutions. In the presence of multiple metal ions in different hydrochloric acid concentrations, the extraction rate of Au(Ⅲ) by the ionic liquid [EtPh3P][PF6] remains above 5%, and the extraction rates of other metal ions are also less than 10%. The main reasons are as follows: (1) PdCl4 2- The charge number is AuCl4 - twice as much, substances with low charge numbers are more easily extracted. In other words, the ionic liquid [EtPh3P][PF6] extracts AuCl4 - The stoichiometric ratio is 1:1, and the ionic liquid [EtPh3P][PF6] extracts PdCl4 2- The stoichiometric ratio is 1:2. The smaller the charge number of the metal chloride anion, the easier it is to exchange ions or the less anions are needed. - PdCl4 2- It is more easily extracted by the ionic liquid [EtPh3P][PF6]. (2) Since the solution needs to maintain electrical neutrality, the cation [EtPh3P] + Easier to anion AuCl4 -contact with cation Al 3+ Mg 2+ , Fe 3+ , Cu 2+ 、Co 2+ 、Cd 2+ 、Zn 2+ Contact, maintaining electrical neutrality and extraction through ion exchange are required, so the extraction rate of Au(Ⅲ) by ionic liquid [EtPh3P][PF6] is greater than that of other cations Al 3+ Mg 2+ , Fe 3+ , Cu 2+ 、Co 2 + 、Cd 2+ 、Zn 2+ [1] In summary, the ionic liquid [EtPh3P][PF6] has good selective extraction and separation ability for Au(Ⅲ).

[0127] Figure 8 The selective extraction of Au(Ⅲ) by ionic liquid [EtPh3P][PF6] and the actual application experimental results of electronic waste are shown in the figure. Figure 8 a in the equation is the experimental result of the selective extraction of Au(Ⅲ) by [EtPh3P][PF6], Figure 8 b in the figure is the experimental result of extracting Au(Ⅲ) from actual electronic waste by [EtPh3P][PF6], Figure 8 Figure c is a schematic diagram of the selective extraction of Au(III) by [EtPh3P][PF6].

[0128] In order to verify the practical application value of the synthesized ionic liquid, it was applied to the extraction and recovery of gold in actual electronic waste. Aqua regia was used as the leaching solution, and [EtPh3P][PF6] was used as the extractant to extract Au(III) in actual electronic waste. The results showed that there were many types of metal elements in electronic waste, mainly Cu, Mg, Fe, Zn, Mn and Au. The original electronic waste contained 847.2mg / LCu, 7.2mg / LAu, 4.88mg / L Mg, 3.61mg / LFe, 0.31mg / LZn, and 0.19mg / LMn. Figure 8 As shown in b, in a complex environment where a variety of high-content other metal ions coexist, the ionic liquid [EtPh3P][PF6] can still achieve an extraction rate of 99.57% for gold, while almost no other metal ions are extracted. The results once again prove that [EtPh3P][PF6] has good selectivity for Au(III) and has great application value.

[0129] From the above examples, it can be seen that the present invention provides a series of triphenylphosphine ionic liquids. By changing the chain length of the quaternary phosphine cation, the performance of the ionic liquid can be improved and the separation efficiency of Au(III) can be increased. At the same time, the present invention further explores the relationship between the structure and performance of the ionic liquid. The present invention synthesized four phosphine-containing ionic liquids with different carbon chain lengths for extracting Au(III) from HCl medium. The four ionic liquids have fast extraction kinetics and can reach extraction equilibrium within 1 minute. The effect of carbon chain length on extraction performance was studied using electrostatic potential (ESP). Among them, [EtPh3P][PF6] has the largest ESP value and the highest extraction efficiency. In particular, the ionic liquid [EtPh3P][PF6] can selectively and efficiently extract Au(III) in actual and simulated multi-metal ion solutions, and its extraction capacity can be as high as 550 mg / g. [EtPh3P][PF6] has obvious reusability and can still maintain an extraction efficiency of 98.73% after 5 cycles. These excellent properties, together with low cost ($0.24 / g[EtPh3P][PF6]), confirm that [EtPh3P][PF6] has good practical application prospects in the sustainable recovery of gold from electronic waste.

[0130] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A triphenylphosphine ionic liquid, characterized in that The chemical formula of the triphenylphosphine ionic liquid is shown in Formula 1: [RPh3P][PF6] Formula 1; In Formula 1, R is a C1-10 alkyl group.

2. The triphenylphosphine ionic liquid according to claim 1, characterized in that The ionic liquid comprises one or more of ethyltriphenylphosphine hexafluorophosphonic acid ionic liquid, propyltriphenylphosphine bromide hexafluorophosphonic acid ionic liquid, n-butyltriphenylphosphine hexafluorophosphonic acid ionic liquid and n-pentyltriphenylphosphine hexafluorophosphonic acid ionic liquid.

3. The method for preparing the triphenylphosphine ionic liquid according to claim 1 or 2, characterized in that: The following steps are involved: The triphenylphosphonium bromide substituted with a C1-10 alkyl group, an alkali metal hexafluorophosphate, water and an organic solvent are mixed to carry out an anion exchange reaction to obtain an organic phase product; The organic phase product is sequentially washed with water, the organic solvent is removed and dried to obtain the triphenylphosphine ionic liquid.

4. The preparation method according to claim 3, characterized in that: The mass ratio of the C1-10 alkyl-substituted triphenylphosphonium bromide to the alkali metal hexafluorophosphate is (1-4):(1-2); the organic solvent is a chloroalkane, and the volume ratio of the water to the organic solvent is 1:(1-2).

5. Use of the triphenylphosphine ionic liquid according to claim 1 or 2 or the triphenylphosphine ionic liquid prepared by the preparation method according to claim 3 or 4 in liquid-liquid extraction of Au(III).

6. A method for liquid-liquid extraction of Au(III), characterized in that: The following steps are involved: An extractant organic phase solution and an aqueous phase solution containing Au (III) are mixed for extraction to obtain an extracted organic phase enriched in Au (III) and a raffinate aqueous phase; the extractant organic phase solution comprises an extractant and an organic diluent, and the extractant is the triphenylphosphine ionic liquid described in claim 1 or 2 or the triphenylphosphine ionic liquid prepared by the preparation method described in claim 3 or 4; the aqueous phase solution containing Au (III) is an acidic solution.

7. The method according to claim 6, characterized in that The organic diluent is a chlorinated alkane; The molar concentration of the extractant in the extractant organic phase solution is 1-5 mmol / L.

8. The method according to claim 6, characterized in that The aqueous solution containing Au(III) comprises Au(III), water and inorganic strong acid; in the aqueous solution containing Au(III): the molar concentration of Au(III) is 1-2 mmol / L, and the molar concentration of the inorganic strong acid is 0.1-3 mol / L.

9. The method according to any one of claims 6 to 8, characterized in that: The volume ratio of the extractant organic phase solution to the water phase solution containing Au (III) is (1-9): (1-9); the extraction temperature is room temperature.

10. The method according to claim 6, characterized in that After obtaining the Au(III)-enriched extracted organic phase, the method further comprises: mixing the Au(III)-enriched extracted organic phase and a stripping agent aqueous phase solution for stripping to obtain an Au(III)-enriched extracted aqueous phase and a raffinate organic phase; the stripping agent aqueous phase solution comprises a stripping agent and water, and the stripping agent is thiourea and HCl.

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