Pincerlike diphenyl sulfide compound as well as preparation method and application thereof

Abstract

The invention provides a diphenyl sulfide compound with a symmetrical structure as well as a preparation method and application thereof, and belongs to the technical field of resource recovery. The invention provides a diphenyl sulfide compound (ES and EO) with a symmetrical (pincerlike) structure and a paired complexing strategy taking the diphenyl sulfide compound as an extracting agent for example, and the diphenyl sulfide compound is used for effectively and selectively recovering Au (III) and Pd (II) from secondary resources. The main active sites of the pincer-like extractant are located on the two sides of the structure of the diphenyl sulfide compound and can form a pairing structure with Au (III) and Pd (II) in PMs, the middle S atom only has an extraction effect on Pd, and Au (III) and Pd (II) can be effectively and selectively recycled from secondary resources.

Description

Technical Field

[0001] The present invention belongs to the technical field of resource recovery, and particularly relates to a pincer-type diphenyl sulfide compound, a preparation method thereof, and an application thereof. Background Art

[0002] Precious metals (PMs), such as gold (Au) and palladium (Pd), have good physical and chemical properties, including excellent ductility, electrical conductivity, and excellent catalytic performance. In recent years, their applications in the electronics and catalytic industries have increased significantly. Based on this upsurge, there is an urgent need to recover precious metals from secondary resources such as electronic waste and spent catalysts to meet the growing demand for non-renewable precious metal resources.

[0003] Generally, hydrometallurgical processes (such as extraction, precipitation, adsorption, ion exchange) have been used to recover precious metals from secondary resources, which involves precisely recovering precious metal ions from leachate. Among these methods, liquid-liquid extraction has the advantages of large capacity, low cost, and simple operation, and has the prospect of large-scale application. The strong coordination between the functional atoms of the extractant and precious metal ions in different states is the main reason for the successful extraction of precious metals from the aqueous phase by the extractant. On this basis, the development and synthesis of innovative extractants focus on introducing multiple active sites and optimizing the molecular structure. For example, atoms with strong interactions with Au(III) and Pd(II), such as elements of amino groups (i.e., N and P) and oxygen-containing groups (i.e., O and S), are modified into extractants for the recovery of PMs. Compared with amino extractants with toxicity and solubility problems, oxygen-containing extractants offer greater hope in effectively extracting Au(III) and Pd(II). Their advantage lies in their affinity for Au(III) and Pd(II), and they are more likely to coordinate with target precious metal ions during the extraction process. This is represented by sulfide extractants. According to the hard-soft acid-base (HSAB) theory, the "S" atom of sulfide extractants acts as a "soft acid" when recognizing the "soft base" of Au(III) and Pd(II).

[0004] However, due to the complex hydrochemical conditions of the leachate (such as extremely low PM concentration and coexistence of multiple metal ions), the selectivity of extractants that only consider the functional atoms of active sites for coexisting metal ions is not ideal. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a symmetric diphenyl sulfide compound, a preparation method thereof, and an application thereof. The symmetric diphenyl sulfide compound provided by the present invention can selectively recover Au(III) and Pd(II) from secondary resources as an extractant, and has a high extraction rate.

[0006] The present invention provides a symmetric diphenyl sulfide compound having formula I (denoted as E S) or formula II (denoted as E O ) the structure shown:

[0007]

[0008] In formula I, R1 is an alkyl group with 4 to 8 carbon atoms; in formula II, R2 is an alkyl group with 4 to 8 carbon atoms. The present invention provides a structurally symmetric (pincer-shaped) diphenyl sulfide compound (E S and E O ), using it as an extractant, adopting a paired complexation strategy (that is, two extractant molecules sandwich two metal ions, paired extraction, as shown in Figure 14 the right figure), for the effective and selective recovery of Au(III) and Pd(II) from secondary resources. The main active sites of the pincer-shaped extractant are located on both sides of the diphenyl sulfide compound structure, and can form a paired structure with Au(III) and Pd(II) in PMs, while the middle S atom only has an extraction effect on Pd. Specifically, the S atoms on both sides of E S have an extraction effect on both Au and Pd, while the middle S only has an extraction effect on Pd. When extracting precious metals with E O , Au is coordinated through the O atoms on both sides of E O , while the middle S atom only has an extraction effect on Pd, and can effectively and selectively recover Au(III) and Pd(II) from secondary resources.

[0009] In addition, by extending the length of the alkyl groups on both sides of the extractant, the present invention can increase the hydrophobicity, reduce the loss of the extractant dissolved in the acidic leaching solution, make the extractant more stable, and thus better realize the reuse of the extractant. In addition, for E O , when the length of the alkyl group is extended, the electronegativity of the oxygen atom can be increased, further increasing the extraction activity. For E S , the shorter the length of the alkyl group, the smaller the steric hindrance and the smaller the influence on the sulfur atom, thus increasing the extraction activity; by introducing a benzene ring into the thioether, the present invention can eliminate the pungent odor.

[0010] By adjusting the functional atoms (S or O) at the ends of the alkyl groups and the carbon chain length (alkyl groups with 4 to 8 carbon atoms), the present invention prepares diphenyl sulfide compounds with optimized active sites and structures. The extraction capacities of E S for Au and Pd are 818.15 mg / g and 522.12 mg / g respectively. The results of the examples show that the diphenyl sulfide compounds provided by the present invention can accurately recover (~100%) gold and palladium from actual electronic waste and waste catalysts, while the extraction rates of various base metal ions are extremely low (~<1.7%). In addition, after the extractant is reused 10 times, the extraction rates of gold and palladium still remain at 90.7 - 94.5%. Description of the Drawings

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0012] Figure 1 is the synthesis route of diphenyl sulfide extractant;

[0013] Figure 2 is E S -1's (a) 1 HNMR and (b) 13 C NMR;

[0014] Figure 3 is E S -2's (a) 1 HNMR and (b) 13 C NMR;

[0015] Figure 4 is E S -3's (a) 1 HNMR and (b) 13 C NMR;

[0016] Figure 5 is E O -1's (a) 1 HNMR and (b) 13 C NMR;

[0017] Figure 6 is E O -2's (a) 1 HNMR and (b) 13 C NMR;

[0018] Figure 7 is E O -3's (a) 1 HNMR and (b) 13 C NMR;

[0019] Figure 8 is the pseudo-first-order kinetic model of Au(III) and Pd(II) on (a) E S -1 and (b) E O -1, and the pseudo-second-order kinetic model of Au(III) and Pd(II) on (c) E S -1 and (d) E O -1;

[0020] Figure 9is the saturation extraction capacity (mol / mol) of the extractant (a - b) for Au(III) and Pd(II), and the saturation extraction capacity (mg / g) of the extractant (c - d) for Au(III) and Pd(II);

[0021] Figure 10 is the extraction of Au(III) and Pd(II) from the simulated mixed metal ion solution by (a - b);

[0022] Figure 11 is the metal concentration in the PCB leachate (a - b), and the metal concentration in the CPU leachate (c - d);

[0023] Figure 12 is the FT - IR spectrum of E S -1 after the stripping of Au(III) and Pd(II);

[0024] Figure 13 is E S -1's quantitative NMR of solubility in water;

[0025] Figure 14 (Left figure) Schematic diagram of the synthesized diphenyl sulfide extractants with different carbon chain lengths and (right figure) the corresponding extraction process;

[0026] Figure 15 is the influence of the diluent of the extractant on the extraction effect of Au(III) and Pd(II);

[0027] Figure 16 is the phase separation photo of the extraction of Au(III) and Pd(II) by E S -1 when using dichloromethane and n - hexane as diluents;

[0028] Figure 17 is the influence of HCl concentration on the extraction effect of Au(III) and Pd(II);

[0029] Figure 18 is the influence of extractant concentration on the extraction effect of Au(III) and Pd(II);

[0030] Figure 19 is the extraction kinetics during the extraction of Au(III) and Pd(II);

[0031] Figure 20 E S and E O 's maximum extraction capacity in the extraction of Au(III) and Pd(II);

[0032] Figure 21 is the comparison of the extraction capacity of E S -1 with relevant literature;

[0033] Figure 22 (Left figure) FTIR spectra of the extractant before and after coordination with Au(III) and Pd(II) in the present invention; (right figure) E S -1 and E S -1-Pd XPS deconvolution results of the S2p spectrum;

[0034] Figure 23 For E S and E O Schematic diagrams of the binding sites with Au and Pd;

[0035] Figure 24 (Left figure) E S and (right figure) E O electrostatic potential (ESP) maps;

[0036] Figure 25 (Upper row of figures) [E S [AuCl4 - and (lower row of figures) [E O [AuCl4 - IRI isosurfaces;

[0037] Figure 26 Standard coloring method and chemical interpretation of sign(λ2) on the IRI isosurface;

[0038] Figure 27 (Upper figure) Adsorption energy of the interaction between E S and AuCl4 - and the Δ Eels and ΔE xrep terms in the sobEDA method; (lower figure) Structure of E S -16C;

[0039] Figure 28 For E S -1 and E S -16C extraction effect comparison;

[0040] Figure 29 For H + and Cl - concentration effects on the extraction performance of Au(III) and Pd(II);

[0041] Figure 30 For E S -1-Au(III) and E S -1-Pd(II) complex Job plots;

[0042] Figure 31 For the plot of lg[D] vs. lg[Cl - ;

[0043] Figure 32 For E S UV-Vis spectra before and after Au(III) extraction;

[0044] Figure 33 For E S Double descriptor of -1;

[0045] Figure 34 (a) Formation of E S -1-Au and E S -1-Pd complex Gibbs free energy, and (b) corresponding optimized structures;

[0046] Figure 35 SEM images of the actual PCB board and the leaching solution;

[0047] Figure 36 SEM images of the actual CPU and the leaching solution;

[0048] Figure 37 At H + Under the conditions of 0.1 M and 0.5 M concentration, using 2 mM of E S -1 to recover Au (the inset is a digital image of the gold (46.4 mg) extracted from the PCB leaching solution);

[0049] Figure 38 (a) Initial ion concentrations of the leaching solution of the waste catalyst dissolved in HNO3; (b) E S -1 extraction performance of the waste catalyst leaching solution;

[0050] Figure 39 (Left figure) Recycling extraction - stripping test of Au and (right figure) Pd;

[0051] Figure 40 For E S -1 overall performance schematic diagram. Detailed implementation mode

[0052] The present invention provides a diphenyl sulfide compound with a symmetric structure, having the structures shown in Formula I or Formula II:

[0053]

[0054] In Formula I, R1 is an alkyl group with 4 to 8 carbon atoms; in Formula II, R2 is an alkyl group with 4 to 8 carbon atoms.

[0055] The present invention provides two diphenyl sulfide compounds with the structures of Formula I and Formula II, with "sulfur" or "oxygen" placed on both sides, and they are respectively labeled as E S or E O .

[0056] In the present invention, R1 and R2 are -C4H9, -C6H 13 or -C8H 17 .

[0057] In the present invention, the diphenyl sulfide compound has a structure shown in any one of Formulas 1 to 6:

[0058]

[0059] The present invention provides a structurally symmetric (pincer-shaped) diphenyl sulfide compound (E S and E O ), which is used as an extractant and adopts a paired complexation strategy (that is, two extractant molecules sandwich two metal ions and extract them in pairs, as shown in Figure 14 the right figure) for effectively and selectively recovering Au(III) and Pd(II) from secondary resources. The main active sites of the pincer-shaped extractant are located on both sides of the diphenyl sulfide compound structure and can form a paired structure with Au(III) and Pd(II) in PMs, while the middle S atom only has an extraction effect on Pd. Specifically, the S atoms on both sides of E S have an extraction effect on both Au and Pd, while the middle S only has an extraction effect on Pd. When E O extracts precious metals, Au is coordinated through the O atoms on both sides of E O , while the middle S atom only has an extraction effect on Pd, and it can effectively and selectively recover Au(III) and Pd(II) from secondary resources.

[0060] In addition, by extending the length of the alkyl groups on both sides of the extractant, the present invention can increase the hydrophobicity, reduce the loss of the extractant dissolved in the acidic leaching solution, make the extractant more stable, and thus better realize the reuse of the extractant. In addition, for E O , extending the length of the alkyl group can increase the electronegativity of the oxygen atom and further increase the extraction activity. For E S , the shorter the length of the alkyl group, the smaller the steric hindrance and the smaller the influence on the sulfur atom, thereby increasing the extraction activity; by introducing a benzene ring into the thioether, the present invention can eliminate the pungent odor.

[0061] The present invention provides a preparation method of the diphenyl sulfide compound described in the above solution, including the following steps:

[0062] Mix mercapto diphenyl sulfide or hydroxy diphenyl sulfide, haloalkane, organic solvent, acid-binding agent and organic ammonium salt catalyst, and carry out a substitution reaction to obtain the diphenyl sulfide compound; the alkane in the haloalkane is an alkane with 4 to 8 carbon atoms; the mercapto diphenyl sulfide includes 4,4'-dimercapto diphenyl sulfide; the hydroxy diphenyl sulfide includes 4,4'-dihydroxy diphenyl sulfide.

[0063] In the present invention, the haloalkane preferably includes halogenated butyl, halogenated hexyl or halogenated octyl; the organic solvent preferably includes one or more of acetonitrile, acetone and N,N-dimethylformamide; the acid-binding agent preferably includes carbonate and / or sodium hydroxide; the carbonate preferably includes potassium carbonate and / or cesium carbonate; the organic ammonium salt catalyst preferably includes tetrabutylammonium bromide.

[0064] In the present invention, the mercapto diphenyl sulfide preferably has the structure shown in Formula III, and the hydroxy diphenyl sulfide preferably has the structure shown in Formula IV;

[0065]

[0066] In the present invention, the molar ratio of the mercapto diphenyl sulfide or hydroxy diphenyl sulfide to the haloalkane is preferably 1:2.2; the molar ratio of the mercapto diphenyl sulfide or hydroxy diphenyl sulfide to the acid-binding agent is preferably 1:2; the mass ratio of the molar amount of the mercapto diphenyl sulfide or hydroxy diphenyl sulfide to the organic ammonium salt catalyst is preferably 1 mmol: 2 mg; the volume ratio of the molar amount of the mercapto diphenyl sulfide or hydroxy diphenyl sulfide to the organic solvent is preferably 10 mmol: 15 mL. In the present invention, the temperature of the substitution reaction is preferably 70-90 °C, and in the examples of the present invention, it can specifically be 70 °C, 75 °C, 80 °C, 85 °C or 90 °C; the time of the substitution reaction is preferably 24-60 h, and in the examples of the present invention, it can specifically be 24 h, 30 h, 40 h, 50 h, 55 h or 60 h.

[0067] After completing the substitution reaction, the present invention preferably performs post-treatment on the obtained reaction solution; the post-treatment preferably includes: removing the solvent, then adding an aqueous solvent acid-binding agent, and extracting the obtained aqueous solution with an organic solvent (such as dichloromethane), washing the organic phase with water, drying the organic phase with anhydrous sodium sulfate, and removing the organic solvent to obtain an extractant.

[0068] The present invention provides the use of the diphenyl sulfide compound described in the above scheme or the diphenyl sulfide compound prepared by the preparation method described in the above scheme as an extractant in the extraction of Au 3+ and / or Pd 2+ therein.

[0069] In the present invention, the extraction preferably includes: mixing an acidic leaching solution containing Au 3+ and / or Pd 2+ with a diluted extractant for extraction.

[0070] In the present invention, it is preferred to mix a waste material containing Au and / or Pd with an acidic reagent for leaching to obtain an acidic leaching solution containing Au 3+ and Pd2+ The acidic leaching solution. In the present invention, the waste material containing Au and / or Pd preferably includes PCB boards, CPU boards or waste palladium catalysts.

[0071] In the present invention, the hydrogen ion concentration in the acidic leaching solution is preferably 0.1 - 18 mol / L. In the examples of the present invention, specifically, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 1 mol / L, 5 mol / L, 10 mol / L, 15 mol / L, 16 mol / L, 17 mol / L or 18 mol / L; the concentration of Au in the acidic leaching solution 3+ is preferably 0 - 80 mg / L. In the examples of the present invention, specifically, it can be 0 mg / L, 2 mg / L, 5 mg / L, 10 mg / L, 20 mg / L, 30 mg / L, 40 mg / L, 50 mg / L, 60 mg / L, 70 mg / L or 80 mg / L; the concentration of Pd 2+ is preferably 0 - 15 mg / L. In the examples of the present invention, specifically, it can be 0 mg / L, 3 mg / L, 4 mg / L, 5 mg / L, 6 mg / L, 8 mg / L or 10 mg / L. In the present invention, the concentrations of Au 3+ and Pd 2+ in the acidic leaching solution are preferably not both 0 at the same time.

[0072] In the present invention, the diluent in the extractant diluent preferably includes one or more of dichloromethane, dichloroethane, toluene, n - hexane, petroleum ether and kerosene; the concentration of the extractant in the extractant diluent is preferably 1 - 10 mmol / L. In the examples of the present invention, specifically, it can be 1 mmol / L, 2 mmol / L, 4 mmol / L, 5 mmol / L, 6 mmol / L, 8 mmol / L or 10 mmol / L. In the present invention, the volume ratio of the acidic leaching solution to the extractant diluent is preferably (1 - 9):(1 - 9). In the examples of the present invention, specifically, it can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 3:4, 5:6, 9:1, 9:2, 9:3, 9:4, 9:5, 9:6, 9:7 or 9:8. In the present invention, the extraction time is preferably 4 h - 15 h. In the examples of the present invention, specifically, it can be 4 h, 5 h, 6 h, 8 h, 10 h, 12 h, 14 h or 15 h.

[0073] The present invention prepares diphenyl sulfide compounds with optimized active sites and structures by adjusting the functional atoms (S or O) of the terminal alkyl group and the carbon chain length (alkane groups with C4 - C8), E SThe extraction capacities for Au and Pd are 818.15 mg / g and 522.12 mg / g, respectively. The results of the examples show that the diphenyl sulfide compounds provided by the present invention can accurately recover (∼100%) gold and palladium from actual electronic waste and waste catalysts, while the extraction rates of various base metal ions are extremely low (∼<1.7%). In addition, after the extractant is reused 10 times, the extraction rates for gold and palladium still remain at 90.7 - 94.5%.

[0074] To further illustrate the present invention, a symmetric diphenyl sulfide compound provided by the present invention, its preparation method and application will be described in detail below in conjunction with the drawings and examples, but they should not be construed as limiting the protection scope of the present invention.

[0075] Example 1

[0076] E S The synthesis process of -1 is as follows: 4,4'-dimercapto diphenyl sulfide (2.5 g, 10 mmol), n-butyl bromide (22 mmol), acetonitrile (15 mL), potassium carbonate (K2CO3, 20 mmol, 2.76 g) and tetrabutylammonium bromide (20 mg) are mixed and stirred at 80 °C for a substitution reaction; after 48 h of substitution reaction, the solvent is removed by rotary evaporation, then water is added to dissolve K2CO3, and the product formed by the reaction is extracted with dichloromethane. After washing the organic phase three times with water, the organic phase is dried with anhydrous sodium sulfate, and the solvent is removed by evaporation using a rotary evaporator to obtain the extractant, denoted as E S -1. The compound is a light green liquid, and the specific synthesis route is as Figure 1 shown.

[0077] Figure 2 For E S -1 (a) 1 HNMR and (b) 13 C NMR. The structure characterization data are: ( 1 HNMR (400 MHz, CDCl3) δ 7.23 (s, 8H), 2.90 (dd, J = 7.9, 6.8 Hz, 4H), 1.68 - 1.59 (m, 4H), 1.50 - 1.39 (m, 4H), 0.92 (t, J = 7.3 Hz, 6H). 13 C NMR (101 MHz, CDCl3) δ 136.51, 132.72, 131.42, 129.23, 33.14, 31.12, 21.99, 13.67.

[0078] Example 2

[0079] E S The synthesis of -2 is the same as that of E SThe synthesis process of -1 is the same, with the only difference being that 4,4'-dimercaptodiphenyl sulfide (2.5 g, 10 mmol), bromohexane (22 mmol), acetonitrile (15 mL), potassium carbonate (K2CO3, 20 mmol, 2.76 g), and tetrabutylammonium bromide (20 mg) are mixed. Designated as E S -2, the compound appears as a white solid, and the specific synthesis route is as Figure 1 shown.

[0080] Figure 3 for E S -2's (a) 1 HNMR and (b) 13 C NMR. The structure characterization data are: (1HNMR(400MHz,CDCl3)δ7.22(d,J=1.7Hz,8H),2.89(td,J=7.4,1.6Hz,4H),1.68-1.59(m,4H),1.46-1.37(m,4H),1.34-1.23(m,8H),0.88(td,J=7.0,1.7Hz,6H). 13 C NMR(101MHz,CDCl3)δ136.52,132.72,131.42,129.23,33.47,31.37,29.03,28.54,22.56,14.05.

[0081] Example 3

[0082] E S The synthesis of E S -3 is the same as that of E S -1, with the only difference being that 4,4'-dimercaptodiphenyl sulfide (2.5 g, 10 mmol), bromooctane (22 mmol), acetonitrile (15 mL), potassium carbonate (K2CO3, 20 mmol, 2.76 g), and tetrabutylammonium bromide (20 mg) are mixed. Designated as E Figure 1 shown.

[0083] Figure 4 for E S -3's (a) 1 HNMR and (b) 13 CNMR. The structure characterization data are:( 1 HNMR(400MHz,CDCl3)δ7.23(s,8H),2.90(td,J=7.4,1.3Hz,4H),1.69-1.60(m,4H),1.41(h,J=6.7Hz,4H),1.28(q,J=5.9Hz,16H),0.92-0.84(m,6H).13 13C NMR (101 MHz, CDCl3) δ 136.51, 132.71, 131.41, 129.23, 33.47, 31.80, 29.18 - 28.86, 22.66, 14.12.

[0084] Example 4

[0085] E O The synthesis of E - 1 is the same as that of E - 1, except that: 4,4'-dihydroxydiphenyl sulfide (2.18 g, 10 mmol), n - butyl bromide (22 mmol), acetonitrile (15 mL), potassium carbonate (K2CO3, 20 mmol, 2.76 g) and tetrabutylammonium bromide (20 mg) are mixed. Denote it as E - 1 S Compound E - 1 is a pale yellow solid. The specific synthesis route is as O shown. Figure 1 shown.

[0086] Figure 5 For E - 1 O (a) 1H NMR and (b) 1 13C NMR. The structure characterization data are:( 13 (1H NMR (400 MHz, CDCl3) δ 7.27 - 7.24 (m, 4H), 6.86 - 6.74 (m, 4H), 3.93 (t, J = 6.5 Hz, 4H), 1.76 (dd, J = 15.3, 6.1 Hz, 4H), 1.49 (dt, J = 14.9, 7.4 Hz, 4H), 0.96 (t, J = 7.4 Hz, 6H). 1 13C NMR (101 MHz, CDCl3) δ 158.55, 132.71, 127.19, 115.30, 67.82, 31.28, 19.24, 13.86 13

[0087] Example 5

[0088] Figure 1 E O The synthesis of E - 2 is the same as that of E - 1, except that: 4,4'-dihydroxydiphenyl sulfide (2.18 g, 10 mmol), n - hexyl bromide (22 mmol), acetonitrile (15 mL), potassium carbonate (K2CO3, 20 mmol, 2.76 g) and tetrabutylammonium bromide (20 mg) are mixed. Denote it as E - 2 S Compound E - 2 is a white solid. The specific synthesis route is as O shown. Figure 1 shown.

[0089] Figure 6 For E - 2 O (a) 1H NMR of E - 21 1H NMR and (b) 13 13C NMR. The structure characterization data are as follows: 1H NMR (400 MHz, CDCl3) δ 7.27 - 7.24 (m, 4H), 6.86 - 6.78 (m, 4H), 3.92 (t, J = 6.6 Hz, 4H), 1.76 (p, J = 6.7 Hz, 4H), 1.49 - 1.40 (m, 4H), 1.37 - 1.28 (m, 8H), 0.90 (td, J = 5.7, 2.9 Hz, 6H). 13 13C NMR (101 MHz, CDCl3) δ 158.54, 132.71, 127.18, 115.30, 68.14, 31.59, 29.20, 25.72, 22.62, 14.06.

[0090] Example 6

[0091] E O The synthesis of E - 3 is the same as that of E - 1, except that: 4,4'-dihydroxydiphenyl sulfide (2.18 g, 10 mmol), octyl bromide (22 mmol), acetonitrile (15 mL), potassium carbonate (K2CO3, 20 mmol, 2.76 g) and tetrabutylammonium bromide (20 mg) were mixed. It is denoted as E - 3. The compound presented as a white solid, and the specific synthesis route is as S shown. O For the (a) 1H NMR and (b) 13C NMR of E - 3. The structure characterization data are as follows: (1H NMR (400 MHz, CDCl3) δ 7.27 - 7.24 (m, 4H), 6.86 - 6.77 (m, 4H), 3.92 (t, J = 6.6 Hz, 4H), 1.81 - 1.71 (m, 4H), 1.48 - 1.39 (m, 4H), 1.37 - 1.24 (m, 16H), 0.92 - 0.84 (m, 6H). Figure 1 13C NMR (101 MHz, CDCl3) δ 158.54, 132.70, 127.17, 115.30, 68.14, 31.82, 29.36, 29.25, 29.23, 26.04, 22.67, 14.12.

[0092] Figure 7 For E O -3's (a) 1 1H NMR and (b) 13 13C NMR. The structure characterization data are as follows: ( 1 1H NMR (400 MHz, CDCl3) δ 7.27 - 7.24 (m, 4H), 6.86 - 6.77 (m, 4H), 3.92 (t, J = 6.6 Hz, 4H), 1.81 - 1.71 (m, 4H), 1.48 - 1.39 (m, 4H), 1.37 - 1.24 (m, 16H), 0.92 - 0.84 (m, 6H). 13 13C NMR (101 MHz, CDCl3) δ 158.54, 132.70, 127.17, 115.30, 68.14, 31.82, 29.36, 29.25, 29.23, 26.04, 22.67, 14.12.

[0093] Comparative Example 1

[0094] E S The synthesis of E - 16C is the same as that of E SThe synthesis process of -1 is the same, except that octyl bromide is replaced by Br-(CH2) 15 -CH3, denoted as E S -16C.

[0095] Halogenated alkanes with less than C4 have relatively low boiling points, and the synthesis temperature for preparing the extractant in the present invention is relatively high. Halogenated alkanes with less than C4 will volatilize, so the preparation of the extractant cannot be completed.

[0096] Application Examples 1 - 3

[0097] PCB (WeAct Studio, China) and CPU (Intel, USA) are both from discarded computers and circuit boards, while the waste catalyst is collected after being used in the hydrogenation reaction.

[0098] The actual leachate feed solution was prepared according to previous reports. Specifically, a 12*12 cm PCB board was immersed in 80 mL of aqua regia for two days, then filtered. 32 g of solid NaOH was added to the obtained extract, and the H + concentration was adjusted to 0.1 M and 0.5 M with 1 mol / L NaOH aqueous solution.

[0099] The leaching process of the CPU board is the same as that of the PCB board, except that a CPU board was immersed in 100 mL of aqua regia for two days, then filtered. 40.5 g of NaOH was added to the obtained extract, and then the H + concentration was adjusted to 0.1 M and 0.5 M with 5 mol / L NaOH solution.

[0100] Leaching of waste palladium catalyst: Take 5 g of waste palladium catalyst, wash it three times with ethanol, then dry it thoroughly, dissolve it with 100 mL of HNO3 (concentration 15.2 mol / L), and leach it at 25 °C for 48 h to obtain an acidic leachate. The Pd concentration in the acidic leachate is 13.92 ppm, the Fe concentration is 4.11 ppm, and the Cu concentration is 2.06 ppm.

[0101] Extract gold and palladium from the above leachate (5 mL) respectively, using a 2 mM E S -1 dichloromethane solution with a volume of 5 mL and an extraction time of 4 h.

[0102] Subsequently, the concentration of metal ions in the leachate was measured by atomic absorption spectrometry (AAS), and the error was ensured to be within an acceptable range. The metal composition of the original leachate is as Figure 11 shown.

[0103] Performance Test

[0104] The present invention provides two kinds of diphenyl sulfide compounds, with "sulfur" or "oxygen" placed on both sides respectively, and they are respectively labeled as E S or E O . During the synthesis process, halogenated hydrocarbons with different carbon chain lengths were used to replace 4,4'-dimercapto diphenyl sulfide and 4,4'-dihydroxy diphenyl sulfide (see Figures 1 - 7 ). The number of terminal carbon atoms in the extractant is 4, 6, and 8 respectively, and they are respectively named E S -1, E S -2, E S -3 and E O -1, E O -2, E O -3 (see Figure 14 left figure).

[0105] Figure 14 (Left figure) Schematic diagram of diphenyl sulfide extractants with different carbon chain lengths synthesized and their (right figure) corresponding extraction processes; Figure 15 Shows the influence of the diluent of the extractant on the extraction effects of Au(III) and Pd(II). Test conditions: [E S and E O = 5 mM, [Au(III)] = [Pd(II)] = 1 mM, [HCl] = 0.1 M, reaction time is 12 hours; Figure 16 Shows the phase separation photos of the extraction of Au(III) and Pd(II) by E S -1 when using dichloromethane and n-hexane as diluents; Figure 17 Shows the influence of HCl concentration on the extraction effects of Au(III) and Pd(II). Test conditions: [E S = 1 mM, [E O = 5 mM, [Au(III)] = [Pd(II)] = 1 mM, reaction time is 12 hours; Figure 18 Shows the influence of extractant concentration on the extraction effects of Au(III) and Pd(II); Figure 19 Shows the extraction kinetics during the extraction of Au(III) and Pd(II). Figures 14 - 19 The specific extraction steps are as follows: First, weigh the extractant and dissolve it in dichloromethane as the organic phase (prepared according to the corresponding above test conditions); the aqueous phase consists of 0.1 M HCl and 1 mM precious metal ions (Au(III) or Pd(II)); then, a mixture of 5 mL each of the organic phase and the aqueous phase (O / A = 1) is mechanically shaken at 230 rpm at 25 °C for the required stirring time (i.e., the reaction time in the above test conditions). After separation, the concentration of metal ions in the aqueous phase is measured using an atomic absorption spectrometer (AAS). The extraction efficiency (E%) is calculated according to the following formula:

[0106]

[0107] Among them, C in and C eq (mM) refer to the metal ion concentration in the aqueous phase before extraction and the metal ion concentration in the aqueous phase after extraction, respectively.

[0108] During the liquid-liquid extraction process, AuCl4 - or PdCl4 2 - in the aqueous phase is successfully separated from different leachates for precious metals Au and Pd by coordinating with the extractant in the organic phase (see Figure 14 the right figure). Therefore, the choice of diluent has an important impact on the extraction performance, because the polarity, viscosity of the diluent and the solubility of the extractant in the solvent will directly affect the extraction effect. For this reason, the present invention selects six solvents as diluents for precious metal extraction, specifically including dichloromethane, dichloroethane, toluene, n-hexane, petroleum ether and kerosene, and at the same time fixes the concentration of the extractant at 5 mM.

[0109] From Figure 15 it can be clearly seen that there are certain differences in the extraction results of various diluents. The extraction effects of the first three diluents are better than those of the last three, which may be related to the polarity differences of the diluents. Dichloromethane, dichloroethane and toluene, these diluents with stronger polarity, provide satisfactory extraction effects for E S of Au (99.3 - 100%) and Pd (100%), and the two phases are still transparent after extraction (see Figure 16 ). In contrast, the extraction effects of Au in n-hexane, petroleum ether and kerosene are only 16.4 - 24.7%. Taking n-hexane as an example, after Pd extraction, we found that insoluble substances appeared in the organic phase (see Figure 14 e in). These results indicate that the polarity of the solvent (diluent) is crucial in the extraction process, because it affects the solubility of the complex. In addition, the poor extraction effect of E O also indicates that the functional atoms play an important role in the extraction process. Given that dichloromethane shows the best performance among the six diluents, the present invention selects dichloromethane as the diluent for subsequent experiments.

[0110] Since the precious metals in secondary resources are generally leached with strong acids, the present invention studied the influence of HCl concentration on the extraction performance of different extractants for Au(III) and Pd(II), and the HCl concentration range was from 0.1 M to 4 M. Figure 17 It shows that as the HCl concentration in the aqueous phase increases, the performance of all studied extractants in precious metal extraction decreases. This phenomenon is more obvious in the extraction of Pd, E S and E OThe extraction performance in 2M HCl drops sharply to 16.3% and 14.4%. This indicates that high concentrations of H + or Cl - have an adverse effect on the coordination reaction between the extractant and metal ions. Research shows that Au(III) exists in the form of AuCl4 - at low acidity, while the coexistence of HAuCl4 at high acidity hinders the binding of AuCl4 - to the extractant. In addition, the increase in Cl - in the aqueous phase has a negative impact on extraction, especially for Pd(II). Cl - is a product in the coordination reaction. When it is present in large amounts at high acidity, it causes the reverse reaction of the coordination reaction, and the specific details are as follows.

[0111] In addition, different carbon chain lengths in diphenyl sulfide extractants have different effects on the extraction of Au(III) and Pd(II). Specifically, as can be seen from the left figures in Figure 17 and Figure 18 , the extractant E S -1 with the shortest carbon chain length exhibits the best Au(III) extraction performance. For E O , the Au(III) extraction performance shows the order of E O -3 > E O -2 > E O -1. This opposite trend indicates that functional atoms play a decisive role in Au(III) extraction, especially in extractants with active sites of different carbon chain lengths. In the extraction of Pd(II), the situation is different (right figures in Figure 17 and Figure 18 ). With the increase in the length of the terminal alkyl carbon chain, the extraction effect of E S slightly decreases, while the extraction effect of E O remains consistent among E O -1, E O -2, and E O -3. This indicates that the participating functional atoms and the extraction mechanisms of Au(III) and Pd(II) are different.

[0112] Extraction kinetics is of great significance in the extraction of precious metals because they directly affect the efficiency of the overall extraction process. Using 0.1M HCl as the aqueous phase medium and dichloromethane as the diluent, we detected the extraction equilibrium time of 1 mM Au(III) and Pd(II), and the concentrations of E S and E O were fixed at 2 mM and 10 mM respectively. As shown in Figure 19As shown, Au(III) and Pd(II) were effectively extracted within 2 - 3 hours by E S , demonstrating the high efficiency of the selected extractant in removing PM ions. Within the same time period, the extraction of E O also reached equilibrium, although its extraction efficiency for Au(III) and Pd(II) was only 77.0 - 92.0% and approximately 82.0% respectively. To more comprehensively explain the extraction kinetic mechanism, we conducted data fitting analysis and used the pseudo-first-order kinetic model (Equation 1) and the pseudo-second-order kinetic model (Equation 2) to evaluate the extraction process.

[0113] ln(q e - q t ) = lnq e - k1t Equation 1;

[0114] where q e and q t represent the extraction capacity at equilibrium and the extraction capacity at different time points respectively, k1 and k2 represent the constants of the pseudo-first-order equation and the pseudo-second-order equation respectively, and t represents the extraction equilibrium time.

[0115] As Figure 8 ( Figure 8 shows the pseudo-first-order kinetic models of Au(III) and Pd(II) on (a) E S - 1 and (b) E O - 1, and the pseudo-second-order kinetic models of Au(III) and Pd(II) on (c) E S - 1 and (d) E O - 1), the extraction reactions of E S - 1 and E O - 3 are more in line with the pseudo-second-order kinetic model, indicating that the chemical reaction between E S / E O and AuCl4 - / PdCl4 2- is the key rate-controlling step.

[0116] Verifying the role of functional atoms in modulating the structure-selectivity relationship through carbon chain length

[0117] The extraction capacity (q e ) is very important in industry and is a key indicator for evaluating the performance of extractants. In this context, the mass ratio (mg / g) can accurately reflect the efficiency and economy of extractants. In this invention, the concentration of the extractant was set to 1 mM, and then the concentration of metal ions was gradually increased to determine the saturated extraction capacity. The value of the extraction capacity q e (mg / g) was calculated by Equation 3,

[0118]

[0119] Among them, C in and C eq (mM) represent the concentration of metal ions in the aqueous phase before extraction and the concentration after reaching equilibrium, respectively. m E is the mass of the extractant used, V aq (L) is the volume of the aqueous phase, and M M is the relative atomic mass of Au (196.97 g / mol) and Pd (106.42 g / mol).

[0120] Figures 20 - 23 It is the study of the role of functional atoms in the extraction capacity. Among them, Figure 20 E S and E O The maximum extraction capacity in the extraction of Au(III) and Pd(II); Figure 21 is the comparison of the extraction capacity of E S -1 with relevant literature; Figure 22 (Left figure) FTIR spectra of the extractant before and after coordination with Au(III) and Pd(II) in the present invention; (Right figure) XPS deconvolution results of the S2p spectra of E S -1 and E S -1-Au; Figure 23 is the schematic diagram of the binding sites of E S and E O with Au and Pd.

[0121] From Figure 9 a and Figure 9 b in Figure 9 ((a - b) The saturated extraction capacity of the extractant for Au(III) and Pd(II) (mol / mol), (c - d) The saturated extraction capacity of the extractant for Au(III) and Pd(II) (mg / g) Test conditions: [E S and E O = 1 mM, [Au(III)] = 0.25 - 3 mM, [Pd(II)] = 0.5 - 5 mM, [HCl] = 0.1 M), it can be seen that as the number of metal ions increases, the extraction capacity of the extractant also increases and finally reaches an equilibrium point. The saturated state of these extractants is achieved when the ion concentration of Au(III) is 2.0 mM and the ion concentration of Pd(II) is 3.0 mM. In the extraction of Au(III) and Pd(II), the order of the maximum extraction capacity is E S -1 > E S -2 > E S -3 > E O -3 > E O -2 > EO -1 (see Figure 20 ). These results indicate that E S is superior to E O in terms of extraction capacity. As mentioned earlier, the S atom, as a stronger soft base, is more likely to bind to Au(III) compared to the O atom, thus enhancing the extraction performance for Au. In particular, diphenyl sulfide E S -1 with the shortest carbon chain exhibits the highest extraction capacity, which is similar to the results in Figure 18 . It is worth noting that the extraction capacities of E S -1 for Au(III) and Pd(II) are 818.15 mg / g and 522.12 mg / g respectively (see c in Figure 9 and d in Figure 9 ), which are much higher than those of most reported extractants (see Figure 21 ), highlighting its potential for efficient recovery of Au and Pd from secondary resources.

[0122] As can be seen from the above results, the carbon chain length in diphenyl sulfide compounds has different effects on the extraction behaviors of E S and E O . The elongation of the carbon chain brings about both an increase in steric hindrance and an enhancement in the electron cloud density of the functional atom. Although steric hindrance may inhibit the binding with metal ions, the increase in electron cloud density strengthens the interaction between the extractant and Au(III). Therefore, in diphenyl sulfide extractants, the type of functional atom (S or O) leads to a fundamentally opposite structural selectivity relationship when the carbon chain length changes.

[0123] The extraction of metal ions by the extractant is mainly achieved through the binding of the functional atom to the metal ion. Therefore, we characterized the extractant before and after the extraction of Au(III) and Pd(II) using a Fourier transform infrared spectrometer (FTIR) to explore the specific interactions between them. As shown in the left figure of Figure 22 , the original E S -1 shows two C-S absorption peaks: one at 745 cm -1 , representing the Ar-S-Ar connection formed by two benzene rings; the other at 1435 cm -1 , related to the alkyl chains at both ends of the benzene ring. After the extraction of Au(III), the C-S peak at 745 cm -1 remains unchanged, while the peak at 1435 cm -1 shifts to 1462 cm -1 , and the peak shape changes significantly. This indicates that the binding occurs on the two S atoms on both sides, and the central S atom between the benzene rings does not participate in the extraction process, probably because steric hindrance blocks AuCl4- Combination. Similarly, the C-O absorption peak shifts from 1048 cm -1 to 1072 cm -1 , while the C-S peak at 725 cm -1 remains unchanged, indicating that the main active binding sites of E O during the extraction of Au(III) are the O atoms located on both sides of the diphenyl sulfide structure. In the extraction of Pd(II), both C-S peaks in the spectrum of E S -1-Au shift significantly, indicating that all three S atoms in E S interact with Pd(II). This is also verified in the results of X-ray photoelectron spectroscopy (XPS) ( Figure 22 right figure), and the S2p1 / 2 and S2p3 / 2 peaks of E S -1 originally located at 164.3 eV and 163.2 eV shift to 163.9 eV and 162.7 eV respectively after binding to Pd. After the extraction of Pd(II), different phenomena appear in the spectrum of E O , the C-S peak shifts from 740 cm -1 to 755 cm -1 , however, the C-O peak at 1025 cm -1 remains unchanged. This observation indicates that only the central S atom participates in the extraction of Pd(II), which has been reported in detail by a large number of studies. The side O atoms of E O have little effect on the coordination of Pd, which also explains the slight difference in the maximum capacity among E O -1, E O -2 and E O -3. Based on the above results, it can be summarized that the S atoms on both sides of E S have extraction effects on both Au and Pd ( Figure 23 ), while the central S only has an extraction effect on Pd. In the case of using E O to extract precious metals, Au is coordinated through the O atoms on both sides of E O , while the middle S atom only has an extraction effect on Pd.

[0124] To deeply explore the role of functional atoms in revealing the structure-selectivity relationship by adjusting the carbon chain length, we used DFT (density functional theory) calculations to analyze the electrostatic potential (ESP) of the extractant. As Figure 24 shown, with the increase of the carbon chain length, the ESP of the functional atoms (O or S) on both sides of the diphenyl sulfide structure decreases by 1.1 - 1.4% for E S respectively, while it decreases by 34.4 - 34.5% for E O . This indicates that extending the terminal carbon chain significantly enhances E Othe electronegativity of the O atom in the middle has less influence on the S atom in E S As reported in previous studies, atoms with higher electronegativity are more conducive to the binding of the extractant to AuCl4 - . Therefore, using AuCl4 - as the model ion, we calculated the energy when different extractants attracted each other with AuCl4 - , which is called the adsorption energy. As shown in Table 1, E O -3 with a longer carbon chain has the lowest adsorption energy for [E O [AuCl4 - , which is -131.12 kJ / mol, indicating that its Au extraction ability is significantly better than that of E O -1 and E O -2. Surprisingly, although the ESP of the S atom in E S -1 is relatively high, its adsorption energy with AuCl4 - is calculated to be -148.94 kJ / mol, significantly lower than the adsorption energies of E S -2 and E S -3 with AuCl4 - (Table 2). This is contrary to the corresponding ESP results, indicating that the ESP of the functional atom is not the main factor for the improvement of the extraction performance of E S .

[0125] Table 1 Adsorption energies of E O and AuCl4 -

[0126] Structure Energy (kJ / mol) Adsorption Energy (kJ / mol) Adsorption Energy (kcal / mol) <![CDATA[AuCl4 - > -5190373.134 / / <![CDATA[E O -1]]> -3483770.87 / / <![CDATA[E O -2]]> -3896844.504 / / <![CDATA[E O -3]]> -4308771.291 / / <![CDATA[[E O -1][AuCl4 - > -8674232.349 -88.34 -21.1006 <![CDATA[[E O -2][AuCl4 - > -9087331.364 -113.73 -27.163 <![CDATA[[E O -3][AuCl4 - > -9499275.549 -131.12 -31.3185

[0127] Table 2 Adsorption energies of E S and AuCl4 -

[0128] Structure Energy (kJ / mol) Adsorption Energy (kJ / mol) Adsorption Energy (kcal / mol) <![CDATA[AuCl4 - > -5190373.134 / / <![CDATA[E S -1]]> -5179726.39 / / <![CDATA[E S -2]]> -5592799.96 / / <![CDATA[E S -3]]> -6005873.22 / / <![CDATA[[E S -1][AuCl4 - > -10370248.46 -148.94 -35.5734 <![CDATA[[E S -2][AuCl4 - > -10783294.25 -121.16 -28.9377 <![CDATA[[E S -3][AuCl4 - > -11196352.03 -105.68 -25.2408

[0129] Therefore, the present invention performed energy decomposition and interaction region indicator function (IRI) analysis to quantitatively and visually display the interaction between E S and AuCl4 - ( Figure 25 ). The green isosurface represents the region mainly affected by van der Waals forces or dispersion forces, while the darker color indicates a greater steric hindrance ( Figure 26 ). The transition from green to brown indicates an increase in steric hindrance, reflecting an enhancement of repulsive forces. It was found that the structure with a longer side chain exhibited stronger steric hindrance (more brown regions) and less van der Waals interaction in the E S and E O extractants ( Figure 25 ​​)。To quantitatively analyze the effects of steric hindrance and enhanced electrostatic effects (caused by carbon chain elongation) on AuCl4 - attracting E S on the extractant surface, the present invention employs sobEDA. This method can perform energy decomposition analysis on the adsorption energies between different extractants and AuCl4 - to quantitatively evaluate the reasons for the changes in interactions from an energy perspective.

[0130] The adsorption energy decomposition formula obtained through sobEDA is as follows:

[0131] ΔE int =ΔE els +ΔE x +ΔE rep +ΔE orb +ΔE DFTc +ΔE dc Formula 4;

[0132] Among them, ΔE x is the exchange interaction energy, ΔE DFTc is the DFT correlation energy, reflecting the contribution of the Coulomb correlation effect to the interaction energy between fragments, ΔE rep is the Pauli repulsion energy, ΔE orb is the orbital interaction energy, ΔE dc is the dispersion correction energy.

[0133] Figures 24 - 28 For the theoretical calculation of mechanism research. Among them, Figure 24 (Left figure) E S and (right figure) E O electrostatic potential (ESP) maps. Figure 25 (Upper row of figures) [E S [AuCl4 - and (lower row of figures) [E O [AuCl4 - IRI isosurfaces. Figure 26 For the standard coloring method and chemical interpretation of sign(λ2) on the IRI isosurface. Figure 27 (Upper figure) The adsorption energy of the interaction between E S and AuCl4 - as well as the Δ Eels and ΔE xrep terms in the sobEDA method, in units of kcal / mol; (lower figure) The structure of E S -16C. Figure 28 For the comparison of the extraction effects of E S -1 and E S -16C. Test conditions: [E S]=1mM, [Au(III)]=[Pd(II)]=1mM, [HCl]=0.1M, 4h.

[0134] Steric hindrance is caused by the antisymmetry of electron exchange, ΔE x and ΔE rep Together, it reflects the specific size of the steric hindrance (defined as ΔE xrep =ΔE x +ΔE rep ). As the carbon chain increases, E S ΔE xrep It gradually increased from 40.38 kcal / mol to 45.07 and 54.78 kcal / mol ( Figure 27 Figure 3). This increase significantly exceeds the ΔE associated with electrostatic interactions. els Based on these results, it can be inferred that the electronegativity of O atoms varies with E O It plays a dominant role in the extraction of Au(III). S In the case of , although the electronegativity of the S atom is improved to a certain extent with the increase of the carbon chain length, the resulting steric hindrance has a more significant impact on the extraction performance.

[0135] Table 3E S and AuCl4 - Various sobEDA items between

[0136] Energy (kcal / mol) <![CDATA[E S -1]]> <![CDATA[E S -2]]> <![CDATA[E S -3 <!-- 11 -->]]> <![CDATA[ΔE els > -18.79 -20.61 -22.89 <![CDATA[ΔE x > -14.53 -15.94 -18.04 <![CDATA[ΔE rep > 54.91 61.01 72.82 <![CDATA[ΔE orb > -10.24 -12.41 -12.94 <![CDATA[ΔE DFTc > -18.91 -17.49 -17.46 <![CDATA[ΔE dc > -24.53 -24.98 -24.87 <![CDATA[ΔE xrep > 40.38 45.07 54.78

[0137] In order to verify the effect of carbon chain length on the extraction performance, E S The side carbon chain length is extended to 16 (i.e. E S -16C)( Figure 27 The Au and Pd recovery tests were performed ( Figure 28 ). Under the same test conditions, the extraction performance of Au(III) and Pd(II) decreased by 73.3% and 68.2%, respectively, which further confirmed the important influence of steric hindrance on the extraction effect.

[0138] Study on the Extraction Mechanism of Au(III) and Pd(II)

[0139] Figures 29 - 24 is the extraction mechanism. Figure 29 H + and Cl - Effect of concentration on the extraction performance of Au(III) and Pd(II). Test conditions: [E S -1]=2mM, [Au(III)]=[Pd(II)]=1mM; Figure 30 For ES -1-Au(III) and E S -1-Job plots of Pd(II) complexes; Figure 31 For the relationship diagram of lg[D] and lg[Cl - . Test conditions: [E S -1]=2 mM, [Au(III)] = [Pd(II)] = 1 mM; Figure 32 For E S UV-Vis spectra before and after Au(III) extraction; Figure 33 For E S -1 dual descriptor. Figure 34 (a) Formation of E S -1-Au and E S -1-Gibbs free energy of Pd complexes (obtained by DFT calculations), and (b) corresponding optimized structures. Figures 29 - 34 Test method: The specific extraction steps are as follows: First, weigh the extractant and dissolve it in dichloromethane as the organic phase; the aqueous phase consists of HCl and precious metal ions (Au(III) or Pd(II)); then, the mixture of the organic phase and the aqueous phase is mechanically shaken at 25 °C at a speed of 230 rpm (prepared according to the corresponding test conditions).

[0140] Note that when this patent studies the influence of different test conditions on test results, the test methods are the same as those described above, and corresponding settings can be made according to different parameters to be studied.

[0141] The present invention studies the mechanism of E S -1 extraction of Au(III) and Pd(II). Since the extraction of metals is carried out in hydrochloric acid medium, the influence of H + and Cl - concentrations on extraction performance was first studied. By adding a certain amount of NaCl to 0.1 M HCl solution, the concentration of Cl - was varied in the range of 0.1 - 4 M. Similarly, to control the concentration of Cl - , hydrochloric acid was added to keep the concentration of H + at 0.1 - 4 M, and then a certain amount of NaCl was added to ensure that the concentration of Cl - was maintained at 4 M. As Figure 29 shown, an increase in the concentration of either H + or Cl - results in a decrease in Au(III) extraction performance. On the one hand, as mentioned above, an increase in the concentration of H + hinders the hydrolysis of HAuCl4, thus inhibiting AuCl4 -Binding with the extractant. On the other hand, it is speculated that Cl will be generated during the extraction process - ions, which hinder the progress of the extraction reaction and reduce the extraction efficiency. For the extraction of Pd(II), the change in H + concentration has little effect on the hydrolysis of H2PdCl4. Only the increase in Cl - concentration has an adverse effect on the extraction performance of Pd(II), indicating that Cl is generated during the extraction process - .

[0142] To further understand the binding of the extractant with PM ions, the Job's continuous variation method was used to analyze their stoichiometry. Briefly, the total volume was kept at 10 mL, and the contact volume ratio of the organic phase to the aqueous phase was adjusted from 1:9 to 9:1, while ensuring that the concentrations of E S -1 and the metal ions were maintained at 1 mM. The metal ion concentrations in the aqueous and organic phases were measured and calculated based on the principle of mass conservation. Subsequently, linear regression analysis was performed to determine the coordination stoichiometric relationship. As Figure 30 shown, when the mole fractions of E S -1 reached 0.47 and 0.38 respectively, the concentrations of Au(III) and Pd(II) in the organic phase reached the highest points, indicating that the complex ratios formed by E S -1 with Au(III) and Pd(II) were 1:1.1 and 1:1.6 respectively. In other words, one molecule of E S -1 binds to one molecule of Au(III), while three Pd(II) are bound together by two molecules of E S -1.

[0143] To determine the state of Au(III) and Pd(II) existing as complexes after extraction, the stoichiometry of the complex was determined by plotting the relationship between lg[D] (distribution ratio) and lg[Cl - . Briefly, the concentrations of H + , PM ions and the extractant were fixed at 0.1 M, 1 mM and 2 mM respectively. The concentration of Cl - was changed by adding NaCl to study the effect of Cl- on lg[D] when Au(III) and Pd(II) were extracted using E S -1. After plotting the relationship between lg[D] and lg[Cl-], the absolute value (k) of the slope of the obtained straight line was regarded as the stoichiometric coefficient of Cl- in the chemical equation. As can be seen from Figure 31 , the slope of the straight line involving the extraction of Au(III) is -0.81, indicating that each AuCl4 - participating in the reaction generates one Cl -Ions. This was further confirmed by UV-Vis characterization ( Figure 32 ), and after binding with E S -1, the absorption peak of Au(III) at 313 nm disappeared, indicating that the state of Au changed during the extraction process. In the reaction involving the extraction of Pd(II), the slope of the fitting line was -1.91, so it was deduced that two Cl - ions were generated. These results suggest that the extraction of Au(III) and Pd(II) by E S proceeds through a coordination substitution mechanism.

[0144] Combining the results of the Job method, stoichiometric studies, and various characterizations, the extraction mechanisms of Au(III) and Pd(II) with E S are described as follows:

[0145]

[0146] The Gibbs free energies (ΔG) generated during the extraction of Au(III) and Pd(II) were calculated to be -1581.69 kJ / mol and -654.93 kJ / mol, respectively (see Figure 33 and Table 4). This indicates that the reaction is spontaneous thermodynamically and the assumed extraction mechanism is feasible. To better understand the structure of the complex and explore the extraction mechanism in depth, we further confirmed the active sites of E S -1 through the dual descriptor. It was noted that the electro-nucleophilic reaction easily occurs in the blue region. In E S -1, the region near the S atom and parallel to the benzene ring plane was identified as the site for the electro-nucleophilic reaction of nucleophilic ions (such as AuCl4 - and PdCl4 2- ) (see a) in Figure 34 ). Based on the deduced mechanism and the dual descriptor of E S -1, the structure of the complex is shown in b of Figure 34 . The paired structure of the extractant highlights the excellent extraction performance of E S , emphasizing its great potential for recovering precious metals from secondary resources.

[0147] Table 4 Binding energies of E S -1 and PMs

[0148] Structure Energy / kJ / mol Binding Energy / kJ / mol <![CDATA[E S -1]]> -5179809.76 / <![CDATA[Cl - > -1208809.28 / <![CDATA[AuCl4 - > -5189884.51 / <![CDATA[E S -1-Au]]> -18323351.68 -1581.69 <![CDATA[PdCl4 2- > -5170505.854 / <![CDATA[E S -1-Pd]]> -18618936.34 -654.93

[0149] Selective recovery of Au(III) and Pd(II) from secondary resources

[0150] Figure 10To extract Au(III) and Pd(II) from a simulated mixed metal ion solution with (a - b), test conditions: [E S -1] = 2 mM, [metal ion] = 1 mM, [HCl] = 0.1 M, O / A = 1, 25 °C, 4 h.

[0151] Specific experimental procedure: The prepared solution is 50 mL with a metal ion concentration of 1 mM. Weigh the amounts of various metal salts required for 50 mL of the solution and make up to the mark with a 50 mL volumetric flask. The specific experiments carried out are the same as before. The organic phase is E S -1 dissolved in dichloromethane, and the aqueous phase is the above - prepared mixed metal solution. The organic phase and the aqueous phase are each 5 mL, and after mixing, they are shaken.

[0152] Selectively extracting precious metal ions from complex multi - metal solutions is an important ability for efficient resource recovery. In this study, we first prepared a simulated mixed metal solution containing 1 mM of Pd(II), Au(III), and metal nitrates and chlorides of Fe(III), Cu(II), Ni(II), Co(II), Mn(II), Zn(II), Cd(II), and Pb(II) to examine the selectivity of E S . As shown in Figure 10 a, the extraction rates of Au(III) and Pd(II) by E S -1 in nitrates are as high as 87.3% and 99.8% respectively, while the extraction of bulk metals is very low, with a level below 2%. In chlorides, the extraction rates of Au(III) and Pd(II) also reach 91.11% and 82.52%. The extraction rate of Pd(II) in chlorides is significantly lower, mainly because the presence of Cl - affects the extraction of Pd(II). The specific situation can be referred to in Figure 10 b. These results highlight the potential ability of E S to selectively extract Au(III) and Pd(II) in complex multi - metal systems.

[0153] Figures 35 - 40 For the performance of recovering Au(III) and Pd(II) from secondary resources. It includes SEM images, elemental imaging, and the corresponding leaching solutions. Among them, Figure 35 is the SEM image of the actual PCB board and the leaching solution. Figure 36 is the SEM image of the actual CPU and the leaching solution; Figure 37 At H + concentrations of 0.1 M and 0.5 M, using 2 mM of E S -1 to recover Au (the inset is a digital image of the gold (46.4 mg) extracted from the PCB leaching solution).Figure 38 (a) Initial ion concentrations of the leaching solution of waste catalysts dissolved in HNO3. (b) E S -1's extraction performance for the leaching solution of waste catalysts. Figure 39 (Left figure) Cyclic extraction - stripping tests for Au and (right figure) Pd. The test conditions are as follows: [E S -1] = 2 mM, [Au(III)] = [Pd(II)] = 1 mM, [HCl] = 0.1 M, elution was carried out using 1 M thiourea in 0.5 M HCl, temperature 25 °C, for 4 hours. Figure 40 For E S -1's overall performance schematic diagram. The specific test method is as described in Application Examples 1 - 3.

[0154] Next, we evaluated the feasibility of E S -1 in recovering precious metals from the leaching solutions of actual PCBs, CPUs, and waste Pd catalysts. Here, PCB and CPU boards were selected as typical representatives of gold - containing electronic waste ( Figures 35 - 36 ). In leaching solutions with different H + concentrations, E S achieved almost complete Au(III) recovery (i.e., extraction rate 94.8% - 100%), with the lowest concentration used being 2 mM, and no co - existing metal ions were extracted ( Figure 37 , where the percentage represents the extraction rate). It is worth mentioning that E S failed to extract the main component Cu in the CPU leaching solution under various media and concentrations, even when its concentration was as high as 1.87×10 5 mg / L (see Figure 11 , Figure 11 for the metal concentrations in (a - b) PCB leaching solution and (c - d) CPU leaching solution). In addition, waste Pd catalysts containing Pd, Fe, and Cu metal ions were selected as Pd - based secondary resources for actual Pd recovery ( Figure 38 a). Excitingly, E S -1 successfully achieved effective and precise recovery of Pd (extraction rate exceeding 99.99%), while no co - existing metal ions were extracted (see Figure 38 b). These results demonstrate the practical feasibility and excellent performance of E S in precious metal recovery, which is mainly due to its coordination mechanism and the stable complexation maintained in the paired structure (see Figure 34 a). In addition, E S -1 can also recover precious metals from E S -1 - Au and E S -1 - Pd by following the established stripping method using stripping agents (thiourea and HCl), thus enabling reuse. AsFigure 39 As shown, with the increase in the number of extraction-stripping cycles, the extraction rate of E S -1 decreased by 6.5% (for Au) and approximately 2.6% (for Pd), respectively. After ten cycles, its extraction performance for Au and Pd still remained at a high level, which confirmed its excellent reusability. In addition, we conducted FTIR tests on E S -1 after multiple elution cycles, and the results showed that its main functional group peaks were maintained quite well (see Figure 12 , Figure 12 for the FT-IR spectra of E S -1 after stripping of Au(III) and Pd(II)). In addition, we also evaluated this important physicochemical property of water solubility through quantitative nuclear magnetic resonance (qNMR) tests to judge the hydrophilicity of the extractant towards water and to study the stability of the extractant during use. As Figure 13 ( Figure 13 for the quantitative NMR of the solubility of E S -1 in water) and Table 5 show, the solubility of E S -1 in water was calculated to be 0.987 g / L, indicating its good water stability. Combining its performance in terms of high capacity, excellent selectivity, low solubility, and remarkable reusability (see Figure 40 ), we believe that E S -1 is a strong candidate for the efficient recovery of precious metals from secondary resources.

[0155] Table 5 qNMR parameters of E S -1

[0156]

[0157] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, rather than all embodiments. People can also obtain other embodiments based on these embodiments without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A diphenyl sulfide compound with a symmetrical structure, characterized in that, Having the structure shown in Formula I or Formula II: In Formula I, R1 is an alkyl group with 4 to 8 carbon atoms; in Formula II, R2 is an alkyl group with 4 to 8 carbon atoms.

2. The diphenyl sulfide compound according to claim 1, characterized in that, The R1 and R2 are -C4H9, -C6H 13 or -C8H 17 .

3. The preparation method of the diphenyl sulfide compound according to claim 1 or 2, characterized in that, Including the following steps: Mix mercapto diphenyl sulfide or hydroxy diphenyl sulfide, haloalkane, organic solvent, acid-binding agent and organic ammonium salt catalyst, and carry out a substitution reaction to obtain the diphenyl sulfide compound; the alkane in the haloalkane is an alkane with 4 to 8 carbon atoms; the mercapto diphenyl sulfide includes 4,4'-dimercapto diphenyl sulfide; the hydroxy diphenyl sulfide includes 4,4'-dihydroxy diphenyl sulfide.

4. The preparation method according to claim 3, characterized in that, The haloalkane includes halobutyl, halohexyl or halooctyl.

5. The preparation method according to claim 3, characterized in that, The temperature of the substitution reaction is 70 to 90 °C, and the time is 24 to 60 h.

6. The use of the diphenyl sulfide compound according to claim 1 or 2 or the diphenyl sulfide compound prepared by the preparation method according to any one of claims 3 to 5 as an extractant in extracting Au 3+ and / or Pd 2+ therefrom.

7. The application according to claim 6, wherein The extraction includes: Mix an acidic leaching solution containing Au 3+ and / or Pd 2+ with a diluent of an extractant for extraction.

8. The application according to claim 6 or 7, characterized in that, The hydrogen ion concentration in the acidic leaching solution is 0.1 to 18 mol / L.

9. The application according to claim 6 or 7, characterized in that, The diluent in the extractant diluent includes one or more of dichloromethane, dichloroethane, toluene, n-hexane, petroleum ether and kerosene; the concentration of the extractant in the extractant diluent is 1 to 10 mmol / L.

10. The application according to claim 6 or 7, characterized in that The Au in the acidic leaching solution 3+ has a concentration of 0 - 80 mg / L, and the Pd 2+ has a concentration of 0 - 15 mg / L, and the concentrations of Au 3+ and Pd 2+ are not both 0 at the same time.

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