Sulfide-containing bisphosphonium cation ionic liquid, preparation method thereof, and extraction method for heavy metals in aqueous solution

Abstract

The present invention relates to a sulfur - ether - containing bis - phosphonium cationic ionic liquid, a preparation method thereof, and an extraction method for heavy metals in an aqueous solution; the bis - cationic ionic liquid is composed of a bis - phosphonium - type cation and a sulfur - ether - containing anion; (1) using bis - quaternary phosphonium salts as bis - cations, the introduction of bis - cations increases the number of anions per unit mass, thereby increasing the number of sulfur - ether or mercapto groups and increasing the adsorption sites for metal ions, improving the extraction capacity and rate; the leaching rate of the ionic liquid is relatively low, avoiding the leaching of the ionic liquid into water after extracting metal ions and reducing the risk of secondary pollution; the ionic liquid has the highest extraction efficiency for Cd 2+ and Pb 2+ reaching 94.02% and 53.74% respectively. The regeneration of the ionic liquid is achieved by sequentially rinsing with HNO3 and NaHCO3 to extract Cd 2+ and Pb 2+ realizing the recycling of the ionic liquid.

Description

Technical Field

[0001] The present invention belongs to the technical field of heavy metal separation and purification, and more specifically, relates to a sulfur ether-containing bisphosphonium cationic ionic liquid, a preparation method thereof, and a method for extracting heavy metals in an aqueous solution. Background Art

[0002] With the rapid development of industries such as metal mining and smelting, chemical engineering, papermaking, electroplating, leather making, batteries, and pesticides, a large amount of wastewater containing heavy metals is directly or indirectly discharged into the environment. Different from organic pollutants, heavy metal elements (such as cadmium and lead) in wastewater are non-biodegradable, and will only transform from one valence state to another, or migrate from one place to another, and gradually accumulate in organisms, ultimately endangering human health. Therefore, it is crucial to explore a method for green and efficient separation of heavy metal elements from the environment.

[0003] Common heavy metal wastewater treatment methods include precipitation, ion exchange, electrolysis, adsorption, etc. These technologies are limited by selectivity or high operating costs, and the treatment effect on wastewater containing heavy metal ions is not ideal, and intermediate pollutants may also be generated. With the continuous development of water treatment technology, wastewater treatment not only needs to purify water quality but also recover valuable components in wastewater as much as possible to achieve resource recycling and follow the path of sustainable and clean development. Therefore, it is imperative to develop a new type of efficient extractant for treating heavy metal ions in water.

[0004] As a new type of green environmental purification material, ionic liquids can, to a certain extent, replace traditional volatile organic solvents for extracting and enriching heavy metal ions due to their unique physical and chemical properties, such as low vapor pressure, good solubility, strong extraction ability, and good stability. In addition, the cation and anion structures of ionic liquids can be designed more strongly, and ionic liquids with different functional characteristics can be prepared for the removal or enrichment of heavy metal ions in wastewater. Quaternary phosphonium salts are an important subclass of ionic liquids, which are in a solid or viscous state at room temperature, and the phosphonium-containing cations can endow the ionic liquids with hydrophobicity. It can be seen from the literature published in recent years that there are generally problems in the current domestic and foreign research, such as poor selectivity of ionic liquids for heavy metals, insignificant removal effect on low-concentration heavy metal ions, and difficulty in separating the extractant from heavy metals. Moreover, due to the number limitation of cations and anions in ionic liquids, the extraction time is too long. Therefore, it is necessary to fully design ionic liquids to develop a new type of bisphosphonium cationic ionic liquid with both physical and quasi-chemical absorption effects, which can not only maintain a high absorption capacity and a fast adsorption rate for low-concentration heavy metal ions (such as cadmium and lead), but also be convenient for subsequent separation and recovery from heavy metal ions. Summary of the Invention

[0005] The object of the present invention is to provide a bisphosphonium cation ionic liquid containing thioether, a preparation method thereof, and a method for extracting heavy metals in an aqueous solution, so as to overcome the defects existing in the prior art. The present invention can obtain a novel bisphosphonium cationic ionic liquid with high extraction capacity and fast extraction speed, and the novel bisphosphonium cationic ionic liquid can be recycled and reused, which is green and environmentally friendly.

[0006] The technical object of the present invention is achieved by the following technical solutions.

[0007] A novel dicationic ionic liquid containing thioether, which is composed of a bisphosphonium cation and a thioether-containing anion; wherein the bisphosphonium cation (abbreviated as PPh3PrPPh3, molecular formula C9H 36 P2 2+ ) has the following structural formula

[0008]

[0009] The thioether-containing anion is one of 2-mercaptobenzoate (TS), S-benzyl-benzoate (BTB), S-methyl-benzoate (MTBA), 2,2'-dithiobisbenzoate (DTSA), 2,3-dimercaptosuccinate (DMSA), 5,5'-dithiobis(2-nitrobenzoate) (DTNB) or 3,3'-dithiobispropionate (DA), as shown in Table 1 specifically.

[0010] Table 1 Types of anions involved in the present invention

[0011]

[0012]

[0013] The preparation method of the thioether-containing bisphosphonium cation ionic liquid is an indirect synthesis method, including the following steps:

[0014] (1) React a halide salt containing the target cation, i.e., propane-1,3-diylbis(triphenylphosphine) bromide (abbreviated as [PPhr3PrP Ph3][Br]2), a thioether-containing acid, and sodium methoxide by stirring in anhydrous methanol;

[0015] (2) Put the mixed solution obtained in step (1) into a rotary evaporator, and rotary evaporate until anhydrous methanol completely escapes to obtain a solid precipitate;

[0016] (3) Extract and wash the solid precipitate three times with dichloromethane or chloroform and water;

[0017] (4) Put the liquid washed in step (3) into a rotary evaporator, and rotary evaporate until dichloromethane or chloroform completely overflows to obtain a crude product;

[0018] (5) The crude product was placed in a vacuum drying oven containing phosphorus pentoxide for vacuum drying to obtain the ionic liquid.

[0019] The synthesis equation is as follows:

[0020]

[0021] In the above technical solution, in step (1), the molar ratio of propane-1,3-diylbis(triphenylphosphine) bromide ([PPhr3PrPPh3][Br]2) to the sulfur ether-containing acid R1-H is 1:(2 - 2.5), and the sulfur ether-containing acid R1-H includes 2-mercaptobenzoic acid, S-benzyl-benzoic acid, or S-methyl-benzoic acid; the molar ratio of propane-1,3-diylbis(triphenylphosphine) bromide ([PPhr3PrPPh3][Br]2) to the sulfur ether-containing acid H-R2-H is 1:(1 - 1.5), and the sulfur ether-containing acid H-R2-H includes (2,2'-dithiobisbenzoic acid, 2,3-dimercaptosuccinic acid, 5,5'-dithiobis(2-nitrobenzoic acid), or 3,3'-dithiobispropionic acid;

[0022] The stirring reaction temperature in step (1) is 10 - 60 °C, preferably 40 - 60 °C, and the reaction time is 6 - 24 h, preferably 12 - 20 h;

[0023] The rotary evaporation temperature in step (2) is 70 - 90 °C;

[0024] In step (3), the volume ratio of dichloromethane or chloroform to water is 5:3;

[0025] The rotary evaporation temperature in step (4) is 40 - 90 °C.

[0026] In the above technical solution, the halide salt containing the target bisphosphonium cation (molecular formula C9H 36 P2Br2) has the following structural formula:

[0027]

[0028] The halide of the bisphosphonium cation has two bromide ions, and its name is [1,10-(propane-1,4-diyl)-bis(triphenylphosphine)] dibromide, abbreviated as [PPh3PrPPh3][Br]2.

[0029] The application of the sulfur ether-containing bisphosphonium cation ionic liquid of the present invention in heavy metal wastewater treatment is applicable to the efficient and reversible extraction of heavy metal ions in different states. The method for using the sulfur ether-containing bisphosphonium cation ionic liquid of the present invention for heavy metal extraction includes the following steps:

[0030] (1) Place the heavy metal aqueous solution in a container, add a sulfur ether-containing bisphosphonium cation ionic liquid to the container, and use the ionic liquid to extract heavy metals from the heavy metal solution.

[0031] (2) After the extraction is completed, filter the ionic liquid.

[0032] In the above technical solution, the heavy metal ions in the heavy metal solution are Cd 2+ and Pb 2+ .

[0033] In the above technical solution, the extraction temperature is room temperature.

[0034] In the above technical solution, all solutions are prepared using ultrapure water, and the extraction pH value is controlled in the range of 3.5 - 13.5 by HNO3 or NaOH, preferably 5.5 - 13.5.

[0035] In the above technical solution, the container is oscillated at a speed of 300 rpm for 1 - 120 min during the extraction process, and the oscillation time is the extraction time of the ionic liquid for metal ions in water, preferably 5 - 60 min.

[0036] In the above technical solution, the bisphosphonium cation ionic liquid after filtration and separation is regenerated by rinsing, and after vacuum drying, it is returned to step (1) for secondary use.

[0037] In the above technical solution, the bisphosphonium cation ionic liquid after filtration and separation is regenerated by rinsing successively with HNO3 and NaHCO3.

[0038] In the above technical solution, the concentration of the HNO3 solution used is controlled in the range of 0.1 - 0.5 mol / L, preferably 0.5 mol / L; NaHCO3 is a saturated solution.

[0039] Compared with the prior art, the novel sulfur ether-containing bisphosphonium cation ionic liquid of the present invention has the following beneficial technical effects: (1) Using bisquaternary phosphonium salts as the dication has good thermal stability and is a solid under normal temperature and pressure, which is conducive to the rapid separation of the extraction phase and the raffinate phase after extraction; (2) The introduction of the dication increases the number of anions per unit mass, thus increasing the number of sulfur ethers or mercapto groups and increasing the adsorption sites for metal ions, improving the extraction capacity and rate; (3) The leaching rate of the ionic liquid is relatively low, avoiding the leaching of the ionic liquid into water after extracting metal ions and reducing the risk of secondary pollution; (4) When the concentration of the ionic liquid in Cd 2+ and Pb 2+ is relatively low, the extraction efficiency still remains at a relatively high level. Under the conditions of 25 °C, an extraction rotation speed of 300 rpm / min, an extraction concentration of 5 mg / L, and an extraction time of 1 min, the ionic liquid for Cd 2+ and Pb2+ The highest extraction efficiency reached 94.02% and 53.74% respectively, which is the highest level at present; (5) The strong interaction between the electronegative S atoms in the sulfide group and the metal ions makes the ionic liquid have a strong affinity for Cd 2+ and Pb 2+ The extraction capacity of the product was 0.52 mg / g·min at 25°C and 300 rpm / min. -1 and 0.51mg / g·min -1 , which is at the highest level at present; (6) Cd is stripped by washing with HNO3 and NaHCO3 in sequence 2+ and Pb 2+ The regeneration of the ionic liquid is realized, and the regeneration and utilization of the ionic liquid is realized. DETAILED DESCRIPTION

[0040] The present invention is described in detail through the following embodiments, but is not limited to the following embodiments. All technologies realized based on the above contents of the present invention belong to the technical scope of the present invention.

[0041] Example 1

[0042] This embodiment relates to the preparation process of a sulfide-containing bisphosphine-based cationic ionic liquid propane-1,3-diylbis(triphenylphosphine) 2,2'-dithiodibenzoate ([PPh3PrPPh3][DTSA]). The specific preparation method is as follows:

[0043] (1) Dissolve 0.01 mol of [1,10-(propane-1,4-diyl)-bis(triphenylphosphine)] dibromide, 0.01 mol of 2,2'-dithiodibenzoic acid and 4 mL of sodium methoxide in 150 mL of anhydrous methanol and stir at 60°C for 6 h;

[0044] (2) The mixed solution obtained in step (1) is placed in a rotary evaporator, and the liquid after the reaction is rotary evaporated at 90° C. for a sufficient time to remove anhydrous methanol to obtain a solid precipitate.

[0045] (3) Add 50 mL of chloroform and 30 mL of ultrapure water to the flask for extraction. The liquid in the flask is separated into two layers, the upper layer is the aqueous phase, and the lower layer is the organic phase. The liquid in the lower layer is separated and washed three times with ultrapure water.

[0046] (4) using a rotary evaporator to evaporate the washed liquid at 70° C. for a sufficient time to remove chloroform to obtain a crude product;

[0047] (5) After placing the crude product in a vacuum drying oven equipped with phosphorus pentoxide and drying it under vacuum at room temperature, propane-1,3-diylbis(triphenylphosphine) 2,2'-dithiobenzoate is obtained. Its structural formula is as follows:

[0048]

[0049] The proton nuclear magnetic resonance spectrum data of it are as follows: 1 H NMR(400MHz,MeOD)δ7.88–7.81(m,3H,H arom ),7.81–7.75(m,3H,H arom ),7.74(d,J=1.4Hz,1H,H arom ),7.69(dt,J=10.9,5.4Hz,5H,H arom ),7.56(ddd,J=7.7,5.4,2.4Hz,1H,H arom ),7.20–7.02(m,1H,H arom ),3.83(td,J=12.4,6.7Hz,2H,-CH2-),2.19–1.79(m,1H,-CH2-). 1313C NMR (101 MHz, MeOD) δ 172.29, 137.99, 135.16, 135.14, 135.13, 135.04, 133.53, 133.47, 133.45, 133.42, 133.40, 133.37, 133.35, 133.32, 132.38, 131.73, 131.63, 130.41, 130.37, 130.33, 130.30, 130.27, 130.24, 130.19, 130.12, 130.08, 128.64, 128.52, 125.14, 124.87, 124.70, 124.39, 118.01, 117.64, 117.14, 48.25, 48.23, 48.11, 48.03, 48.00, 47.99, 47.97, 47.96, 47.94, 47.93, 47.91, 47.90, 47.89, 47.87, 47.82, 47.80, 47.78, 47.76, 47.75, 47.73, 47.72, 47.70, 47.69, 47.61, 47.56, 47.55, 47.53, 47.52, 47.50, 47.49, 47.47, 47.46, 47.40, 47.36, 47.35, 47.33, 47.32, 47.31, 47.29, 47.28, 47.26, 47.25, 47.23, 47.22, 47.18, 46.97, 22.53, 22.36, 21.98, 21.81, 16.61. Its infrared data are as follows: (4000 - 400 cm -1 ) 3746, 3417, 3056, 3018, 2902, 2871, 2798, 2362, 2335, 2217, 1705, 1590, 1484, 1437, 1398, 1365, 1251, 1112, 1031, 995, 969, 828, 747, 691, 573, 537.

[0050] Example 2

[0051] This example relates to the preparation process of a sulfur - ether - containing bis - phosphonium - based cationic ionic liquid propane - 1,3 - diylbis(triphenylphosphonium) 2,3 - dimercaptosuccinate ([PPh3PrPPh3][DMSA]), and the specific preparation method is as follows:

[0052] (1) Dissolve 0.01 mol of [1,10 - (propane - 1,4 - diyl) - bis(triphenylphosphonium)] dibromide, 0.01 mol of 2,3 - dimercaptosuccinic acid and 4 mL of sodium methoxide in 150 mL of anhydrous methanol, and stir at 50 °C for 8 h;

[0053] (2) Put the mixed solution obtained in step (1) into a rotary evaporator, and use the rotary evaporator to rotary evaporate the reacted liquid at 80 °C for a sufficient time to remove anhydrous methanol, obtaining a solid precipitate.

[0054] (3) Add 50 mL of dichloromethane and 30 mL of ultrapure water to a flask for extraction. The liquid in the flask is divided into two layers, the upper layer is the aqueous phase and the lower layer is the organic phase. Separate the lower layer of the liquid and wash it three times with ultrapure water;

[0055] (4) Use a rotary evaporator to rotary evaporate the washed liquid at 50 °C for a sufficient time to remove dichloromethane, obtaining a crude product;

[0056] (5) Put the crude product into a vacuum drying oven equipped with phosphorus pentoxide and dry it under vacuum at room temperature, then propane-1,3-diylbis(triphenylphosphine) 2,3-dimercaptosuccinate is obtained. Its structural formula is as follows:

[0057]

[0058] Its nuclear magnetic resonance hydrogen spectrum data are as follows: 1 H NMR(400MHz,MeOD)δ7.88(td,J=8.3,2.4Hz,4H,H arom ),7.85–7.68(m,17H,H arom ),3.83(td,J=12.9,7.8Hz,3H,-SH),2.07–1.77(m,2H,-CH). 13 C NMR(101MHz,MeOD)δ135.19,133.51,133.45,133.40,133.35,130.41,130.37,130.30,130.28,130.24,130.19,118.01,117.14,48.24,48.02,47.81,47.78,47.76,47.75,47.73,47.72,47.70,47.69,47.67,47.66,47.64,47.60,47.55,47.53,47.52,47.51,47.49,47.48,47.46,47.45,47.43,47.42,47.38,47.35,47.34,47.32,47.31,47.29,47.28,47.26,47.25,47.23,47.22,47.20,47.17,47.12,46.96,16.56. Its infrared data are: (4000-400cm -1)3898,3861,3744,3621,3422,3182,3013,2906,2870,2362,1724,1586,1484,1437,1402,1334,1191,1161,1112,995,827,728,691,537,509。

[0059] Example 3

[0060] This example relates to the preparation process of a sulfur - ether - containing bis - phosphonium - based cationic ionic liquid propane - 1,3 - diylbis(triphenylphosphonium) 2-(benzylthio)benzoate ([PPh3PrPPh3][BTB]2). The specific preparation method is as follows:

[0061] (1) Dissolve 0.01 mol of [1,10-(propane - 1,4 - diyl)-bis(triphenylphosphonium)] dibromide, 0.02 mol of S - benzyl - benzoic acid, and 4 mL of sodium methoxide in 150 mL of anhydrous methanol, and stir at 40 °C for 12 h;

[0062] (2) Put the mixed solution obtained in step (1) into a rotary evaporator, and use the rotary evaporator to rotary evaporate the reacted liquid at 70 °C for sufficient time to remove anhydrous methanol, obtaining a solid precipitate.

[0063] (3) Add 50 mL of dichloromethane and 30 mL of ultrapure water to a flask for extraction. The liquid in the flask is divided into two layers, the upper layer is the aqueous phase, and the lower layer is the organic phase. Separate the lower - layer liquid and wash it three times with ultrapure water;

[0064] (4) Use the rotary evaporator to rotary evaporate the washed liquid at 40 °C for sufficient time to remove dichloromethane, obtaining a crude product;

[0065] (5) Put the crude product into a vacuum drying oven equipped with phosphorus pentoxide and conduct vacuum drying at room temperature, then propane - 1,3 - diylbis(triphenylphosphonium) 2-(benzylthio)benzoate is obtained. Its structural formula is as follows:

[0066]

[0067] Its infrared data is: (4000 - 400 cm -1 )3883,3744,3649,3410,3052,3013,2870,2804,1724,1585,1488,1437,1279,1234,1194,1147,1111,1021,972,744,692,572,508。

[0068] Example 4

[0069] This example relates to the preparation process of a sulfur - ether - containing bis - phosphine - based cationic ionic liquid propane - 1,3 - diylbis(triphenylphosphine) 2-(methylthio)benzoate ([PPh3PrPPh3][MTBA]2). The specific preparation method is as follows:

[0070] (1) Dissolve 0.01 mol of [1,10-(propane - 1,4 - diyl)-bis(triphenylphosphine)] dibromide, 0.02 mol of S - methyl - benzoic acid, and 4 mL of sodium methoxide in 150 mL of anhydrous methanol, and stir at 30 °C for 20 h;

[0071] (2) Put the mixed solution obtained in step (1) into a rotary evaporator, and use the rotary evaporator to rotary - evaporate the reacted liquid at 90 °C for a sufficient time to remove anhydrous methanol, obtaining a solid precipitate.

[0072] (3) Add 50 mL of dichloromethane and 30 mL of ultrapure water to a flask for extraction. The liquid in the flask is divided into two layers, the upper layer is the aqueous phase, and the lower layer is the organic phase. Separate the lower - layer liquid and wash it three times with ultrapure water;

[0073] (4) Use the rotary evaporator to rotary - evaporate the washed liquid at 60 °C for a sufficient time to remove dichloromethane, obtaining a crude product;

[0074] (5) Put the crude product into a vacuum drying oven equipped with phosphorus pentoxide and dry it under vacuum at room temperature to obtain propane - 1,3 - diylbis(triphenylphosphine) 2-(methylthio)benzoate. Its structural formula is as follows:

[0075]

[0076] Its infrared data is: (4000 - 400 cm -1 ) 3977, 3895, 3741, 3414, 3170, 3058, 2907, 2469, 2356, 1591, 1552, 1485, 1438, 1397, 1254, 1193, 1113, 1036, 996, 795, 748, 692, 650, 537, 508.

[0077] Example 5

[0078] This example relates to the preparation process of a sulfur - ether - containing bis - phosphine - based cationic ionic liquid propane - 1,3 - diylbis(triphenylphosphine) thiosalicylate ([PPh3PrPPh3][TS]2). The specific preparation method is as follows:

[0079] (1) Dissolve 0.01 mol of [1,10-(propane-1,4-diyl)-bis(triphenylphosphine)] dibromide, 0.02 mol of thiosalicylic acid and 4 mL of sodium methoxide in 150 mL of anhydrous methanol, and stir at 20 °C for 24 h;

[0080] (2) Put the mixed solution obtained in step (1) into a rotary evaporator, and use the rotary evaporator to rotary evaporate the reacted liquid at 90 °C for sufficient time to remove anhydrous methanol, obtaining a solid precipitate.

[0081] (3) Add 50 mL of chloroform and 30 mL of ultrapure water to a flask for extraction. The liquid in the flask is divided into upper and lower layers. The upper layer is the aqueous phase and the lower layer is the organic phase. Separate the lower layer of liquid and wash it three times with ultrapure water;

[0082] (4) Use a rotary evaporator to rotary evaporate the washed liquid at 90 °C for sufficient time to remove chloroform, obtaining a crude product;

[0083] (5) Put the crude product into a vacuum drying oven equipped with phosphorus pentoxide and dry it under vacuum at room temperature, then propane-1,3-diylbis(triphenylphosphine) thiosalicylate is obtained. Its structural formula is as follows:

[0084]

[0085] Its infrared data are: (4000 - 400 cm -1 ) 3984, 3906, 3744, 3649, 3416, 3119, 2793, 2620, 2469, 2405, 2362, 2335, 2222, 2109, 1951, 1799, 1645, 1582, 1436, 1400, 1262, 1193, 1113, 1037, 992, 828, 796, 745, 691, 535, 506.

[0086] Example 6

[0087] This example relates to the preparation process of a sulfur ether-containing bisphosphonium-based cationic ionic liquid propane-1,3-diylbis(triphenylphosphine) 5,5'-dithiobis(2-nitrobenzoate) ([PPh3PrPPh3][DTNB]), and the specific preparation method is as follows:

[0088] (1) Dissolve 0.01 mol of [1,10-(propane-1,4-diyl)-bis(triphenylphosphine)] dibromide, 0.01 mol of 5,5'-dithiobis(2-nitrobenzoic acid) and 4 mL of sodium methoxide in 150 mL of anhydrous methanol, and stir at 10 °C for 24 h;

[0089] (2) Put the mixed solution obtained in step (1) into a rotary evaporator, and use the rotary evaporator to rotary evaporate the reacted liquid at 90 °C for a sufficient time to remove anhydrous methanol, obtaining a solid precipitate.

[0090] (3) Add 50 mL of chloroform and 30 mL of ultrapure water to a flask for extraction. The liquid in the flask is divided into two layers, the upper layer is the aqueous phase and the lower layer is the organic phase. Separate the lower layer of the liquid and wash it three times with ultrapure water;

[0091] (4) Use a rotary evaporator to rotary evaporate the washed liquid at 80 °C for a sufficient time to remove chloroform, obtaining a crude product;

[0092] (5) Put the crude product into a vacuum drying oven equipped with phosphorus pentoxide and dry it under vacuum at room temperature, then propane-1,3-diylbis(triphenylphosphine) 5,5'-dithiobis(2-nitrobenzoate) is obtained. Its structural formula is as follows:

[0093]

[0094] Its infrared data are: (4000 - 400 cm -1 ) 3896, 3736, 3650, 3414, 3056, 3013, 2873, 2466, 1732, 1616, 1563, 1525, 1437, 1344, 1271, 1191, 1111, 996, 835, 731, 692, 582, 537, 508.

[0095] Example 7

[0096] This example relates to the preparation process of a sulfur ether-containing bisphosphonium-based cationic ionic liquid propane-1,3-diylbis(triphenylphosphine) 3,3'-dithiobis(propionate) ([PPh3PrPPh3][DA]), and the specific preparation method is as follows:

[0097] (1) Dissolve 0.01 mol of [1,10-(propane-1,4-diyl)-bis(triphenylphosphine)] dibromide, 0.01 mol of 3,3'-dithiobis(propionic acid) and 4 mL of sodium methoxide in 150 mL of anhydrous methanol, and stir at 50 °C for 24 h;

[0098] (2) Put the mixed solution obtained in step (1) into a rotary evaporator, and use the rotary evaporator to rotary evaporate the reacted liquid at 90 °C for a sufficient time to remove anhydrous methanol, obtaining a solid precipitate.

[0099] (3) Add 50 mL of chloroform and 30 mL of ultrapure water to a flask for extraction. The liquid in the flask is divided into two layers, the upper layer is the aqueous phase and the lower layer is the organic phase. Separate the lower layer of the liquid and wash it three times with ultrapure water;

[0100] (4) Use a rotary evaporator to rotary evaporate the washed liquid at 80 °C for a sufficient time to remove chloroform, obtaining a crude product;

[0101] (5) Put the crude product into a vacuum drying oven equipped with phosphorus pentoxide and dry it under vacuum at room temperature, then propane-1,3-diylbis(triphenylphosphine) 3,3'-dithiobispropionate is obtained. Its structural formula is as follows:

[0102]

[0103] Its infrared data are: (4000 - 400 cm -1 ) 3863, 3745, 3425, 3111, 3013, 2906, 2870, 2804, 1836, 1727, 1616, 1584, 1484, 1436, 1402, 1333, 1190, 1112, 995, 828, 728, 691, 537, 508.

[0104] Example 8

[0105] This example relates to the preparation process of a sulfur ether-containing bisphosphonium-based cationic ionic liquid propane-1,3-diylbis(triphenylphosphine) 2-(benzylthio)benzoate ([PPh3PrPPh3][BTB]2), and the specific preparation method is as follows:

[0106] (1) Dissolve 0.01 mol of [1,10-(propane-1,4-diyl)-bis(triphenylphosphine)] dibromide, 0.022 mol of S-benzyl-benzoic acid and 4 mL of sodium methoxide in 150 mL of anhydrous methanol, and stir at 40 °C for 12 h;

[0107] (2) Put the mixed solution obtained in step (1) into a rotary evaporator, and use the rotary evaporator to rotary evaporate the reacted liquid at 70 °C for a sufficient time to remove anhydrous methanol, obtaining a solid precipitate.

[0108] (3) Add 50 mL of dichloromethane and 30 mL of ultrapure water to a flask for extraction. The liquid in the flask is divided into upper and lower layers. The upper layer is the aqueous phase and the lower layer is the organic phase. Separate the lower layer liquid and wash it three times with ultrapure water;

[0109] (4) Use a rotary evaporator to rotary evaporate the washed liquid at 40 °C for a sufficient time to remove dichloromethane, obtaining a crude product;

[0110] (5) Put the crude product into a vacuum drying oven equipped with phosphorus pentoxide and dry it under vacuum at room temperature, then propane-1,3-diylbis(triphenylphosphine) 2-(benzylthio)benzoate is obtained. Its structural formula is as follows:

[0111]

[0112] Its infrared data are: (4000 - 400 cm -1 ) 3883, 3744, 3649, 3410, 3052, 3013, 2870, 2804, 1724, 1585, 1488, 1437, 1279, 1234, 1194, 1147, 1111, 1021, 972, 744, 692, 572, 508.

[0113] Example 9

[0114] This example relates to the preparation process of a sulfur - ether - containing bis - phosphonium - based cationic ionic liquid propane - 1,3 - diylbis(triphenylphosphonium) thiosalicylate ([PPh3PrPPh3][TS]2). The specific preparation method is as follows:

[0115] (1) Dissolve 0.01 mol of [1,10-(propane - 1,4 - diyl)-bis(triphenylphosphonium)] dibromide, 0.025 mol of thiosalicylic acid, and 4 mL of sodium methoxide in 150 mL of anhydrous methanol, and stir at 20 °C for 24 h;

[0116] (2) Put the mixed solution obtained in step (1) into a rotary evaporator, and use the rotary evaporator to rotary evaporate the reacted liquid at 90 °C for a sufficient time to remove anhydrous methanol, obtaining a solid precipitate.

[0117] (3) Add 50 mL of chloroform and 30 mL of ultrapure water to a flask for extraction. The liquid in the flask is divided into two layers, the upper layer is the aqueous phase, and the lower layer is the organic phase. Separate the lower - layer liquid and wash it three times with ultrapure water;

[0118] (4) Use the rotary evaporator to rotary evaporate the washed liquid at 90 °C for a sufficient time to remove chloroform, obtaining a crude product;

[0119] (5) Put the crude product into a vacuum drying oven equipped with phosphorus pentoxide and dry it under vacuum at room temperature to obtain propane - 1,3 - diylbis(triphenylphosphonium) thiosalicylate. Its structural formula is as follows:

[0120]

[0121] Its infrared data are: (4000 - 400 cm -1)3984,3906,3744,3649,3416,3119,2793,2620,2469,2405,2362,2335,2222,2109,1951,1799,1645,1582,1436,1400,1262,1193,1113,1037,992,828,796,745,691,535,506。

[0122] Example 10

[0123] This example relates to the preparation process of a sulfur - containing ether - based bis - phosphonium cationic ionic liquid propane - 1,3 - diylbis(triphenylphosphine) 5,5'-dithiobis(2 - nitrobenzoate) ([PPh3PrPPh3][DTNB]). The specific preparation method is as follows:

[0124] (1) Dissolve 0.01 mol of [1,10-(propane - 1,4 - diyl)-bis(triphenylphosphine)] dibromide, 0.012 mol of 5,5'-dithiobis(2 - nitrobenzoic acid) and 4 mL of sodium methoxide in 150 mL of anhydrous methanol, and stir at 10 °C for 24 h;

[0125] (2) Put the mixed solution obtained in step (1) into a rotary evaporator, and use the rotary evaporator to rotary - evaporate the reacted liquid at 90 °C for sufficient time to remove anhydrous methanol, obtaining a solid precipitate.

[0126] (3) Add 50 mL of chloroform and 30 mL of ultrapure water to a flask for extraction. The liquid in the flask is divided into two layers, the upper layer is the aqueous phase, and the lower layer is the organic phase. Separate the lower - layer liquid and wash it three times with ultrapure water;

[0127] (4) Use the rotary evaporator to rotary - evaporate the washed liquid at 80 °C for sufficient time to remove chloroform, obtaining a crude product;

[0128] (5) After placing the crude product in a vacuum drying oven equipped with phosphorus pentoxide and drying it under vacuum at room temperature, propane - 1,3 - diylbis(triphenylphosphine) 5,5'-dithiobis(2 - nitrobenzoate) is obtained. Its structural formula is as follows:

[0129]

[0130] Its infrared data is: (4000 - 400 cm -1 )3896,3736,3650,3414,3056,3013,2873,2466,1732,1616,1563,1525,1437,1344,1271,1191,1111,996,835,731,692,582,537,508。

[0131] Example 11

[0132] This example relates to the preparation process of a sulfur - ether - containing bis - phosphonium - based cationic ionic liquid propane - 1,3 - diylbis(triphenylphosphonium) 2,3 - dimercaptosuccinate ([PPh3PrPPh3][DMSA]). The specific preparation method is as follows:

[0133] (1) Dissolve 0.01 mol of [1,10-(propane - 1,4 - diyl)-bis(triphenylphosphonium)] dibromide, 0.015 mol of 2,3 - dimercaptosuccinic acid and 4 mL of sodium methoxide in 150 mL of anhydrous methanol, and stir at 50 °C for 8 h;

[0134] (2) Put the mixed solution obtained in step (1) into a rotary evaporator, and use the rotary evaporator to rotary evaporate the reacted liquid at 80 °C for sufficient time to remove anhydrous methanol, obtaining a solid precipitate.

[0135] (3) Add 50 mL of dichloromethane and 30 mL of ultrapure water to a flask for extraction. The liquid in the flask is divided into upper and lower layers. The upper layer is the aqueous phase, and the lower layer is the organic phase. Separate the lower - layer liquid and wash it three times with ultrapure water;

[0136] (4) Use the rotary evaporator to rotary evaporate the washed liquid at 50 °C for sufficient time to remove dichloromethane, obtaining a crude product;

[0137] (5) Put the crude product into a vacuum drying oven equipped with phosphorus pentoxide and dry it under vacuum at room temperature to obtain propane - 1,3 - diylbis(triphenylphosphonium) 2,3 - dimercaptosuccinate. Its structural formula is as follows:

[0138]

[0139] Its infrared data are: (4000 - 400 cm -1 ) 3898, 3861, 3744, 3621, 3422, 3182, 3013, 2906, 2870, 2362, 1724, 1586, 1484, 1437, 1402, 1334, 1191, 1161, 1112, 995, 827, 728, 691, 537, 509.

[0140] Example 12

[0141] This example relates to the removal of Cd 2+ and Pb 2+The extraction process is as follows:

[0142] (1) Place 5 mL of a heavy metal solution containing Cd 2+ or Pb 2+ (Cd 2+ or Pb 2 concentration is 5.00 mg / L) in a container. Add 100 mg of the ionic liquid in Example 1, i.e., propane-1,3-diylbis(triphenylphosphine) 2,2'-dithiobisbenzoate ([PPh3PrPPh3][DTSA]), to the container. Adjust the pH value of the aqueous solution to 7.5 and place it in a shaker to shake and extract at a speed of 300 rpm for 1, 5, 15, 30, 60, and 120 min respectively.

[0143] (2) Filter the ionic liquid after the extraction is completed.

[0144] The extraction efficiency of this ionic liquid for Cd 2+ and Pb 2+ in the heavy metal solution at different times is shown in Table 2.

[0145] Table 2 Extraction efficiency of [PPh3PrPPh3][DTSA] for Cd 2+ and Pb 2+ in the heavy metal solution

[0146]

[0147]

[0148] Examples 13 - 18

[0149] Similar to Example 8, Examples 13 - 18 relate to the extraction process of the remaining sulfide-containing bisphosphine-based cationic ionic liquids in the present invention for Cd 2+ and Pb 2+ in the heavy metal aqueous solution. The specific steps are as follows:

[0150] (1) Place 5 mL of a heavy metal solution containing Cd 2+ or Pb 2+ (Cd 2+ or Pb 2 concentration is 5.00 mg / L) in a container. Replace the ionic liquid added to the container, that is, replace it with 100 mg of the ionic liquids in Examples 2 - 7 respectively. Adjust the pH value of the aqueous solution to 7.5 and place it in a shaker to shake and extract at a speed of 300 rpm for 1, 5, 15, 30, 60, and 120 min respectively.

[0151] (2) Filter the ionic liquid after the extraction is completed.

[0152] The extraction efficiencies of these ionic liquids for Cd in heavy metal solutions at different times were measured. 2+ and Pb 2+ are shown in Table 3.

[0153] Table 3 Extraction effects of thioether bisphosphine-based cationic ionic liquids on Cd 2+ and Pb 2+ at different times

[0154]

[0155]

[0156] Example 19

[0157] This example involves the extraction process of propane-1,3-diylbis(triphenylphosphine) 2,3-dimercaptosuccinate ([PPh3PrPPh3][DMSA]), a thioether-containing bisphosphine-based cationic ionic liquid, for Cd 2+ and Pb 2+ in heavy metal aqueous solutions with different pH values. The specific steps are as follows:

[0158] (1) Place 5 mL of a heavy metal solution containing Cd 2+ or Pb 2+ (the concentration of Cd 2+ or Pb 2 is 5.00 mg / L) in a container. Add 100 mg of propane-1,3-diylbis(triphenylphosphine) 2,3-dimercaptosuccinate ([PPh3PrPPh3][DMSA]) to the container. Control the extraction pH to pH = 3.5 - 13.5 with HNO3 and NaOH solutions, and place it in a shaker to shake and extract at a speed of 300 rpm for 60 min.

[0159] (2) After the extraction is completed, filter the ionic liquid.

[0160] The extraction efficiencies of this ionic liquid for Cd 2+ and Pb 2+ in heavy metal solutions at different pH values are shown in Table 4.

[0161] Table 4 Extraction efficiencies of [PPh3PrPPh3][DMSA] for Cd 2+ and Pb 2+ in heavy metal solutions at different pH values

[0162]

[0163] Example 20

[0164] This example involves the extraction process of propane-1,3-diylbis(triphenylphosphonium) 2,3-dimercaptosuccinate ([PPh3PrPPh3][DMSA]), a sulfur ether-containing bisphosphonium-based cationic ionic liquid, for Cd in heavy metal aqueous solutions with different initial volumes 2+ and Pb 2+ The specific steps are as follows:

[0165] (1) Respectively place 2.5, 5, 7.5, 10, 12.5 mL of heavy metal solutions containing Cd 2+ or Pb 2+ (the concentration of Cd 2+ or Pb 2 is 5.00 mg / L) in a container, add 100 mg of propane-1,3-diylbis(triphenylphosphonium) 2,3-dimercaptosuccinate ([PPh3PrPPh3][DMSA]) to the container, adjust the pH of the aqueous solution to 7.5, and place it in a shaker to shake and extract at a speed of 300 rpm for 60 min.

[0166] (2) After the extraction, filter the ionic liquid.

[0167] Measure the extraction efficiency of this ionic liquid for Cd 2+ and Pb 2+ in the heavy metal solution at different initial solution volumes as shown in Table 5.

[0168] Table 5 Extraction efficiency of [PPh3PrPPh3][DMSA] for Cd 2+ and Pb 2+ in the heavy metal solution at different initial solution volumes

[0169]

[0170] Example 21

[0171] This example involves the extraction process and secondary utilization of propane-1,3-diylbis(triphenylphosphonium) 2,3-dimercaptosuccinate ([PPh3PrPPh3][DMSA]), a sulfur ether-containing bisphosphonium-based cationic ionic liquid, for Cd 2+ and Pb 2+ in heavy metal aqueous solutions. The specific steps are as follows:

[0172] (1) Place 5 mL of heavy metal solution containing Cd 2+ or Pb 2+ (the concentration of Cd 2+ or Pb 2Put it (with a concentration of 5.00 mg / L) in a container, add 100 mg of propane-1,3-diylbis(triphenylphosphine) 2,3-dimercaptosuccinate ([PPh3PrPPh3][DMSA]) to the container, adjust the pH value of the aqueous solution to 7.5, and place it in a shaker to shake and extract at a speed of 300 rpm for 60 min.

[0173] (2) After the extraction, filter the ionic liquid.

[0174] The [PPh3PrPPh3][DMSA] after filtration and separation is rinsed successively with 0.1 - 0.5 mol / L HNO3 solution and saturated NaHCO3 solution and then returned to step (1) for secondary utilization. When the ionic liquid is used for secondary utilization, the extraction efficiency of Cd 2+ and Pb 2+ in the heavy metal solution is shown in Table 6.

[0175] Table 6 Extraction efficiency of Cd 2+ and Pb 2+ in the heavy metal solution by [PPh3PrPPh3][DMSA] during secondary utilization

[0176]

[0177]

[0178] Example 22

[0179] Analyze the structure of propane-1,3-diylbis(triphenylphosphine) 2,3-dimercaptosuccinate ([PPh3PrPPh3][DMSA]) after extracting Cd 2+ by Multiwfn software. It can be seen that the mechanism of extracting heavy metal Cd 2+ has both physical and quasi-chemical absorption effects, as shown in Table 7.

[0180] Table 7 Topological parameters (unit: a.u.) at the BCP of M - O and M - S bonds of [PPh3PrPPh3][DMSA]

[0181]

[0182] According to the content of the present invention for parameter adjustment, the preparation of the ionic liquid in the present invention can be achieved, and it shows basically the same performance as the present invention, that is, it shows high-efficiency reversible extraction performance for heavy metals Cd 2+ and Pb 2+ . The above is an exemplary description of the present invention. It should be noted that without departing from the core of the present invention, any simple deformation, modification or equivalent substitution that can be made by those skilled in the art without creative labor falls within the protection scope of the present invention.

Claims

1. Sulfur-containing bisphosphonium cation ionic liquid, characterized in that, It consists of a phosphine-based dication and a sulfur-containing anion, and the structural formula is as follows: The sulfur-containing anion has the following structure or or or or or 2. Preparation method of the sulfur-containing bisphosphonium cation ionic liquid of claim 1, characterized in that, It includes the following steps: (1) Stir and react a halide salt containing the target cation, namely propane-1,3-diylbis(triphenylphosphine) bromide ([PPhr3PrPPh3][Br]2), a sulfur-containing acid, and sodium methoxide in anhydrous methanol; (2) Put the mixed solution obtained in step (1) into a rotary evaporator and rotate and evaporate until all the anhydrous methanol escapes to obtain a solid precipitate; (3) Extract and wash the solid precipitate with dichloromethane or chloroform and water; (4) Put the liquid washed in step (3) into a rotary evaporator and rotate and evaporate until all the dichloromethane or chloroform overflows to obtain a crude product; (5) Put the crude product into a vacuum drying oven equipped with phosphorus pentoxide for vacuum drying to obtain an ionic liquid; The synthesis equation is as follows:

3. The preparation method of the sulfur-containing bisphosphonium cation ionic liquid according to claim 2, characterized in that, In step (1), the molar ratio of propane-1,3-diylbis(triphenylphosphine) bromide ([PPhr3PrPPh3][Br]2) to the sulfur-containing acid R1-H is 1:(2-2.5), and the sulfur-containing acid R1-H is 2-mercaptobenzoic acid, S-benzyl-benzoic acid or S-methyl-benzoic acid; the molar ratio of propane-1,3-diylbis(triphenylphosphine) bromide ([PPhr3PrPPh3][Br]2) to the sulfur-containing acid H-R2-H is 1:(1-1.5), and the sulfur-containing acid H-R2-H is 2,2'-dithiobisbenzoic acid, 2,3-dimercaptosuccinic acid, 5,5'-dithiobis(2-nitrobenzoic acid) or 3,3'-dithiobispropionic acid; the stirring reaction temperature in step (1) is 10-60 °C, and the reaction time is 6-24 h; the rotary evaporation temperature in step (2) is 70-90 °C; the ratio of dichloromethane or chloroform to water in step (3) is 5:3; the rotary evaporation temperature in step (4) is 40-90 °C.

4. The sulfur-containing bisphosphonium cation ionic liquid according to claim 1, characterized in that, For extracting Cd 2+ and Pb 2+ ions from an aqueous solution.

5. Application of the sulfur-containing bisphosphonium cation ionic liquid according to claim 4 in the extraction of Cd 2+ and Pb 2+ ions, characterized in that, It includes the following steps: (1) Place an aqueous solution containing Cd 2+ and Pb 2+ ions in a container, add a sulfur-containing bisphosphonium cation ionic liquid to the container, and use the ionic liquid to extract Cd 2+ and Pb 2+ ions from the aqueous solution; (2) Filter the ionic liquid after the extraction ends.

6. Application of the sulfur-containing bisphosphonium cation ionic liquid according to claim 5 in the extraction of Cd 2+ and Pb 2+ ions, characterized in that, The bisphosphonium cation ionic liquid after filtration and separation can be rinsed successively with 0.1-0.5 mol / L HNO3 solution and saturated NaHCO3 solution and then returned to step (1) for secondary utilization.

7. Application of the sulfur-containing bisphosphonium cation ionic liquid according to claim 5 in the extraction of heavy metals, characterized in that, The heavy metal ions in the heavy metal solution are Cd 2+ and Pb 2+ .

8. Application of the sulfur-containing bisphosphonium cation ionic liquid according to claim 5 in the extraction of Cd 2+ and Pb 2+ ions, characterized in that, The mass M of the ionic liquid used for extraction IL is in g, and the ratio M 2+ to the volume V 2+ of the ionic simulated wastewater containing Cd 水 and Pb IL is M 水 :V = 8 - 40:

1.

9. Application of the sulfur-containing bisphosphonium cation ionic liquid according to claim 5 in the extraction of Cd 2+ and Pb 2+ ions, characterized in that,The extraction temperature is room temperature, the extraction pH is controlled to be pH = 3.5-13.5 by HNO3 and NaOH solutions, and the container is oscillated at a speed of 300 rpm for 1-120 min during the extraction process. The oscillation time is the extraction time of the ionic liquid for metal ions in water.

10. Use of the sulfur-containing bisphosphonium cation ionic liquid as described in claim 5 in the extraction of Cd 2+ and Pb 2+ ions, characterized in that The mechanism of extracting heavy metals combines physical and quasi-chemical absorption effects.

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