Nitrogen-containing polyion liquid as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of precious metal recovery materials, and relates to a nitrogen-containing polyion liquid and a preparation method and application thereof. The polyion liquid adsorbs noble metal ions through electrostatic attraction and oxidation reduction, the adsorption efficiency is higher than 99.99%, and the polyion liquid has good acid resistance and chemical stability. And step-by-step reverse extraction is realized by selecting a proper reverse extraction agent, so that cyclic recycling of the polyion liquid is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of materials for the recovery of precious metals, and relates to a nitrogen-containing polyionic liquid and a preparation method and application thereof. Background Art

[0002] In industrial production and daily life, the discharge of wastewater, waste residue and waste gas containing precious metals and other heavy metals has become an important source of environmental pollution. Once these heavy metals enter the environment, they will accumulate in aquatic organisms and crops, enter the human body through drinking water and the food chain, and seriously threaten human health. Therefore, how to remove heavy metal ions in water efficiently and at low cost, especially precious metal ions, has become an important issue in the current field of environmental protection. Traditional heavy metal ion removal technologies include chemical precipitation, membrane separation, ion exchange, etc., but these methods often have problems such as high cost, complex operation and secondary pollution. Adsorption technology has become a research hotspot for heavy metal wastewater treatment due to its advantages of high efficiency, simplicity, low cost and easy handling. Currently, commonly used adsorbents include minerals, activated carbon and its fibers, liquid extracts, ion exchangers, lactic acid bacteria and chelates. Among them, activated carbon fiber has a good adsorption effect, but its preparation cost is high, and it is mainly based on physical adsorption, with problems such as insufficient adsorption and difficulty in recycling. Therefore, it is particularly important to develop new, low-cost and efficient adsorption materials. As a new type of functional material, polyionic liquids have attracted widespread attention due to their unique structure and excellent adsorption properties. Polyionic liquids have good chemical and thermal stability, high ionic conductivity and adjustable structural characteristics, especially nitrogen-containing polyionic liquids, which have strong affinity with noble metal ions and show excellent adsorption properties. However, there is a lack of relevant research on polyionic liquid materials for efficient adsorption of noble metal ions.

[0003] The invention provides a nitrogen-containing polyionic liquid, which can efficiently adsorb noble metal ions such as chloroaurate ions, chloroplatinate ions and chloropalladate ions, solves the problems of insufficient adsorption, high preparation cost and difficulty in recycling in the prior art, and has broad application prospects. Summary of the invention

[0004] In response to the above technical problems, the present invention provides a nitrogen-containing polyionic liquid and a preparation method and application thereof. The nitrogen-containing polyionic liquid adsorbs precious metal ions through electrostatic attraction and redox effects, only a trace amount of polyionic liquid is used, the adsorption recovery efficiency is high, the chemical stability is good and the cycle performance is good.

[0005] The present invention provides a nitrogen-containing polyionic liquid and a preparation method and application thereof. The polyionic liquid adsorbs noble metal ions through electrostatic attraction and redox reaction, and the adsorption efficiency is higher than 99.99%. The polyionic liquid has good acid resistance and chemical stability. By selecting a suitable stripping agent to achieve step-by-step stripping, the polyionic liquid can be recycled.

[0006] The present invention is achieved through the following technical solutions: A nitrogen-containing polyionic liquid, the structural formula is as follows: .

[0007] The second object of the present invention is to provide a method for preparing the nitrogen-containing polyionic liquid, comprising the following steps: (1) Synthesis of nitrogen-containing ionic liquid monomers; In the acetonitrile solution, N,N,N'-tetramethyl-1,6-hexanediamine and 4-vinylbenzylchlorobenzene were added to react to generate a white solid, which was subsequently washed with ethyl acetate and dried for later use; The reaction equation is as follows: (2) Preparation of polyionic liquids In a mixed solution of ethyl acetate, ethanol and water, add the product 1-(4-vinylbenzyl)-N,N,N',N'-tetramethylhexanediammonium chloride obtained in step (1), then add an initiator azobisisobutyronitrile, and react. After the reaction, wash with ethanol and then with deionized water, and lyophilize to obtain the target product; The reaction equation is as follows: .

[0008] Furthermore, in step (1), the molar ratio of N,N,N,N'-tetramethyl-1,6-hexanediamine to 4-vinylbenzyl chloride is 1:1.

[0009] Furthermore, the reaction conditions of step (1) are heating to 70-85° C. under the condition of introducing nitrogen, and controlling the reaction time to be 5-10 h.

[0010] Furthermore, in the mixed solution of step (2), the volume ratio of ethyl acetate, ethanol and water is 5:1:1.

[0011] Furthermore, in the mixed solution of step (2), the mass ratio of 1-(4-vinylbenzyl)-N,N,N',N'-tetramethylhexanediammonium chloride to azobisisobutyronitrile is 20:1.

[0012] Furthermore, the reaction conditions of step (2) are: firstly pass nitrogen for 15 minutes without heating, then adjust the temperature to 70-80°C, and control the heating time to 6-18 h.

[0013] The invention also provides application of the nitrogen-containing ionic liquid in adsorption of noble metal ions.

[0014] Furthermore, the nitrogen-containing ionic liquid selectively adsorbs Au(III), Pd(II), and Pt(IV), and can be recycled.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: the present invention first synthesizes nitrogen-containing ionic liquid monomers, and then uses azobisisobutyronitrile (AIBN) to achieve free radical polymerization of the ionic liquid monomers in a nitrogen environment, and finally forms a nitrogen-containing polyionic liquid with a carbon skeleton single-chain polymer structure.

[0016] The nitrogen-containing polyionic liquid contains a nitrogen positive ion center, which adsorbs precious metal ions through electrostatic attraction and redox reaction, and the adsorption rate is greater than 99.99%. Through this feature, the precious metal ions in the nickel-containing anode mud wastewater can be significantly recovered. The concentration of residual gold after adsorption is less than 0.01 mg / L, the content of palladium is less than 0.01 mg / L, and the content of platinum is also less than 0.01 mg / L. In addition, the polyionic liquid is a non-toxic and odorless molecular polymer that will not harm the natural environment. At the same time, compared with the fluorine-containing ionic liquid, the precious metal adsorbent has a more obvious advantage.

[0017] By adopting the technical solution of the present invention, this new type of nitrogen-containing polymer material exhibits excellent adsorption capacity for precious metals and has significant economic and technical advantages in the field of wastewater treatment. As a high-efficiency adsorbent separation technology, it has the characteristics of high efficiency and low energy consumption. This not only provides an effective purification method for solving the current problem of wastewater in secondary resources in anode mud, but also opens up a new way for the recycling of precious metals, achieving the goal of turning waste into treasure. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the H-NMR spectrum of the polyionic liquid monomer; Figure 2 is the nitrogen adsorption-desorption isotherm; Figure 3 This is the pore size distribution diagram of the BET test material; Figure 4 This is the infrared characterization of the acid and salt resistance test results of polyionic liquids; Figure 5 Scanning electron microscopy images of untreated polyionic liquid (a, b) and polyionic liquid treated with 6 mol / L HCl (c, d); Figure 6 is the selective extraction diagram; Figure 7 The figure is a recycling flow chart. DETAILED DESCRIPTION

[0019] The present invention will be further described below in conjunction with examples, but the present invention is not limited to the following examples.

[0020] Example 1 S1. Add N,N,N,N'-tetramethyl-1,6-hexanediamine (0.01 mol) and 4-vinylbenzyl chloride (0.01 mol) dropwise into a three-necked flask containing 30 ml of acetonitrile solution, and then heat to 78°C under the condition of passing nitrogen. Control the reaction time to 8 h to generate a white precipitate, which is then washed three times with ethyl acetate and placed in a vacuum drying oven for use.

[0021] S2. Weigh 2.0 g of 1-(4-vinylbenzyl)-N, N, N', N'-tetramethylhexanediammonium chloride into a mixed solution (ethyl acetate: ethanol: water volume ratio of 5:1:1), and then weigh azobisisobutyronitrile (0.1 g) and add it to a three-necked flask. First, pass nitrogen for 15 minutes without heating to blow out the oxygen in the three-necked flask and eliminate the effect of oxygen in the three-necked flask on free radical polymerization. Then adjust the temperature to 75°C and control the heating time to 12 h. After the reaction is completed, wash it with ethanol 3 times and then with deionized water 3 times, and then freeze-dry it for use.

[0022] Example 2 S1. Add N,N,N,N'-tetramethyl-1,6-hexanediamine (0.01 mol) and 4-vinylbenzyl chloride (0.01 mol) dropwise into a three-necked flask containing 30 ml of acetonitrile solution, and then heat to 70°C under the condition of passing nitrogen. Control the reaction time to 10 h to generate a white precipitate, which is then washed three times with ethyl acetate and placed in a vacuum drying oven for use.

[0023] S2. Weigh 2.0 g of 1-(4-vinylbenzyl)-N, N, N', N'-tetramethylhexanediammonium chloride into a mixed solution (ethyl acetate: ethanol: water volume ratio of 5:1:1), and then weigh azobisisobutyronitrile (0.1 g) and add it to a three-necked flask. First, pass nitrogen for 15 minutes without heating to blow out the oxygen in the three-necked flask and eliminate the effect of oxygen in the three-necked flask on free radical polymerization. Then adjust the temperature to 70°C and control the heating time to 18 h. After the reaction is completed, wash it with ethanol 3 times and then with deionized water 3 times, and then freeze-dry it for use.

[0024] Example 3 S1. Add N,N,N,N'-tetramethyl-1,6-hexanediamine (0.01 mol) and 4-vinylbenzyl chloride (0.01 mol) dropwise into a three-necked flask containing 30 ml of acetonitrile solution, and then heat to 85°C under the condition of passing nitrogen. Control the reaction time to 5h to generate a white precipitate, which is then washed three times with ethyl acetate and placed in a vacuum drying oven for use.

[0025] S2. Weigh 2.0 g of 1-(4-vinylbenzyl)-N, N, N', N'-tetramethylhexanediammonium chloride into a mixed solution (ethyl acetate: ethanol: water volume ratio of 5:1:1), and then weigh azobisisobutyronitrile (0.1 g) and add it to the three-necked flask. First, pass nitrogen for 15 minutes without heating to blow out the oxygen in the three-necked flask and eliminate the effect of oxygen in the three-necked flask on free radical polymerization. Then adjust the temperature to 80°C and control the heating time to 6 hours. After the reaction is completed, wash it with ethanol 3 times and then with deionized water 3 times, and then freeze-dry it for use.

[0026] The 1-(4-vinylbenzyl)-N,N,N',N'-tetramethylhexanediammonium chloride obtained in step S1 of Example 1 was characterized by nuclear magnetic resonance. Figure 1 As shown, by nuclear magnetic resonance spectroscopy, it can be found that there are peaks at the following positions1H NMR: (400 MHz, CD3OD, δ / ppm): 1.52 (m, 4H, 2CH2), 2.00 (m, 4H, 2 CH2), 3.08 (m, 12H, 4 CH3), 3.40 (m, 4H, 2 CH2) 4.59 (s, 4H, 4 CH2) 5.38 (q, 2H, 2 CH) 5.93 (q, 2H, 2 CH), 6.84 (q, 2H, 4 CH), 7.61 (m, 8H, 4 CH), which proves the synthesis of the dicationic central ionic liquid.

[0027] The nitrogen-containing polyionic liquid obtained in Example 1 was characterized by nitrogen adsorption, and the nitrogen adsorption isotherm of the nitrogen-containing polyionic liquid under the conditions of P / P0=1 and 150 K was tested. Figure 2 It can be seen that the maximum nitrogen adsorption capacity of the ionic liquid is 26.755m 2 / g, and the specific surface area calculated based on nitrogen adsorption data is 26.755 m 2 / g, the pore size distribution is mainly 2.77nm (see Figure 3 ).

[0028] In order to study the stability of the polyionic liquid structure, 10 mg of polyionic liquid was weighed in a 7 ml centrifuge tube, and then 1 ml of 6 mol / L HCl, 12 mol / L HCl, and 5 mol / L NaCl solution were added, respectively. The mixture was shaken at room temperature for 1 h, centrifuged, washed with deionized water, and dried in a vacuum drying oven. The polyionic liquid was then detected using a Fourier transform infrared spectrometer. Figure 4 As shown in Figure 2, the characteristic functional groups of the polyionic liquids treated with various solutions did not change. The untreated polyionic liquids and the polyionic liquids treated with 6 mol / L HCl were characterized by scanning electron microscopy. The results are shown in Figure 2. Figure 5 As shown, it was found that the morphology of the polyionic liquid treated with acid did not change compared with the untreated polyionic liquid, that is, it has good acid resistance and its morphology will not be destroyed by hydrochloric acid.

[0029] Example 4 The extraction experiment was carried out in a 7 ml plastic centrifuge tube. First, 3 ml of 5 mmol / L Au(III) solution was added to the centrifuge tube, and then 3 mg, 4 mg, 5 mg, 6 mg, 7 mg, and 8 mg of the polyionic liquid prepared in Example 1 were added respectively. Then, the centrifuge tube was placed in a room temperature oscillator for half an hour. Then, the supernatant was taken out, and the content of Au(III) in the solution was determined using an inductively coupled plasma spectrometer ICP-OES.

[0030] The calculation formulas for the extraction efficiency (E%) and stripping efficiency (S%) used are as follows: in, c in and c eq Represent the concentrations of Au(Ⅲ), Pd(Ⅱ), and Pt(Ⅳ) in the solution before and after extraction, respectively. c a represents the concentration of Au(Ⅲ), Pd(Ⅱ), Pt(Ⅳ) in the solution after stripping equilibrium, v a represents the volume of stripping agent added, v in Represents the volume of Au(Ⅲ), Pd(Ⅱ), and Pt(Ⅳ) solutions added.

[0031] Table 1 Extraction rate of Au(III) by ionic liquids of different masses.

[0032] Example 5 The extraction of palladium (II) and Pt (IV) was carried out in a 7 ml plastic centrifuge tube. First, 2 ml of 5 mmol / L palladium (IV) and platinum (IV) solution was added, and then 4 mg, 6 mg, 8 mg, 10 mg, 12 mg, and 14 mg of the polyionic liquid prepared in Example 1 were added respectively, and then the centrifuge tube was placed in a room temperature oscillator for half an hour. Then the supernatant was taken out and the content of the remaining Pd (II) and Pt (IV) in the solution was determined using an inductively coupled plasma spectrometer ICP-OES.

[0033] Table 2 Extraction rates of Pd(Ⅱ) and Pt(Ⅳ) by ionic liquids of different masses As shown in Tables 1 and 2, by fixing the volume of the precious metal solution and increasing the mass of the polyionic liquid, it was determined that when the volume of the gold solution was 3 ml, the optimal extraction dosage of 6 mg could achieve an extraction rate of 98%; when the volume of the palladium and platinum solutions was 2 ml, the optimal extraction agent dosage was 8 mg and the extraction efficiency was also above 98%.

[0034] Example 6 1. Effect of acidic conditions on gold extraction with polyionic liquids The extraction was carried out in a 7 ml plastic centrifuge tube. The design configuration fixed the concentration of Au (III) to 5 mmol / L, and the hydrochloric acid concentration gradient was designed to be 0.1-1.6 mol / L. In order to further explore the effects of hydrogen ion concentration and chloride ion concentration in hydrochloric acid, the hydrogen ion concentration was fixed at 0.1 mol / L and the chloride ion concentration was increased to 0.1-1.6 mol / L; and the chloride ion concentration was fixed at 1.6 mol / L and the hydrogen ion concentration was increased to 0.1-1.6 mol / L. Then, 6 mg of polyionic liquid was added, and the volume of different series of hydrochloric acid concentrations, hydrogen ion concentrations, and chloride ion concentrations was 3 ml in a 7 ml centrifuge tube, placed in a room temperature oscillator for half an hour, and the supernatant was extracted after centrifugation. The concentration of the remaining Au (III) ions in the solution was determined using an inductively coupled plasma spectrometer ICP-OES. It can be seen from Tables 3, 4, and 5 that the polyionic liquid maintained a high extraction efficiency in different chemical environments. In general, the extraction efficiency can reach 98% or more.

[0035] Table 3 Extraction rate of Au(Ⅲ) by ionic liquids with different hydrochloric acid concentrations Table 4 Extraction rate of Au(Ⅲ) by ionic liquids with different hydrogen ion concentrations Table 5 Extraction rate of Au(Ⅲ) by ionic liquids with different chloride ion concentrations 2. Effect of acidic conditions on the extraction of Pd(Ⅱ) and Pt(Ⅳ) by polyionic liquids The extraction was carried out in a 7 ml plastic centrifuge tube. The concentration of Pd(Ⅱ) and Pt(Ⅳ) was designed to be 5 mmol / L, and the hydrochloric acid concentration gradient was designed to be 0.1-1.6 mol / L. In order to further explore the effects of hydrogen ion concentration and chloride ion concentration in hydrochloric acid, the hydrogen ion concentration was fixed at 0.1 mol / L and the chloride ion concentration was increased to 0.1-1.6 mol / L; and the chloride ion concentration was fixed at 1.6 mol / L and the hydrogen ion concentration was increased to 0.1-1.6 mol / L. Then, 8 mg of polyionic liquid was added, and the volume of the solution with different series of hydrochloric acid concentration, hydrogen ion concentration, and chloride ion concentration was adjusted to 2 ml in a 7 ml centrifuge tube. After being placed in a room temperature oscillator for half an hour, the supernatant was extracted after centrifugation to determine the concentration of the remaining Pd(Ⅱ) and Pt(Ⅳ) ions that were not extracted.

[0036] Table 6 Extraction rate of Pd(Ⅱ) and Pt(Ⅳ) by ionic liquids with different hydrochloric acid concentrations Table 7 Extraction rate of Pd(Ⅱ) and Pt(Ⅳ) by ionic liquids with different hydrogen ion concentrations Table 8 Extraction rates of ionic liquids Pd(Ⅱ) and Pt(Ⅳ) at different chloride ion concentrations Example 7 Selective adsorption of various metal ions in nickel-containing anode mud leachate wastewater by polyionic liquid Take industrial wastewater, adsorb it in a 7 ml plastic centrifuge tube, adjust the pH of the solution to 0.1 mol / L with sodium hydroxide solution, take 1 ml of wastewater and add 8 mg of polyionic liquid, place it in a room temperature oscillator and shake it for half an hour, extract the supernatant after centrifugation, and use ICP to measure the metal ion concentration of the supernatant. In the presence of metal ions such as copper, nickel, lead, and arsenic, the polyionic liquid has a good adsorption effect only on the three metal ions of gold, palladium, and platinum, and the adsorption efficiency is 99.99%.

[0037] Experimental Example 8: Recycling of the Nitrogen-Containing Polyionic Liquid by Stepwise Stripping The nitrogen-containing polyionic liquid prepared in Example 1 can remove precious metal ions from water by adsorption, and then remove them by step-by-step stripping. Figure 7The flow chart separates the adsorbed precious metal ions. Use 0.1mol / L Na2S2O3 solution to extract gold from the metal-loaded polyionic liquid, then use NH4Cl / H2O2 solution to extract palladium, and then use 0.1mol / L CS(NH2)2 / HCl mixed solution to extract platinum, where the HCl concentration is 0.1mol / L, and repeat this process to calculate the extraction rate of each round. In the first step of the stripping process, when gold is extracted, due to the different redox potentials of gold, palladium and platinum, different chemical reagents are used to recover gold, palladium and platinum respectively. First, a certain concentration of sodium sulfite solution can be used to treat the polyionic liquid adsorbed with gold, so that the adsorbed trivalent gold is converted into monovalent gold, and returned to the solution to achieve the purpose of desorbing gold. For the targeted desorption of palladium, NH4Cl / H2O2 can be used to form a black precipitate of (NH4)2PdCl6, which is then heated to decompose and released into the solution. The palladium is then stripped out, and finally acidic thiourea is added to strip out divalent platinum, achieving effective elution of platinum.

[0038] Table 9 Cycle efficiency of nitrogen-containing polyionic liquids

Claims

1. A nitrogen-containing polyionic liquid, characterized in that: The structural formula is as follows: 。 2. A method for preparing a nitrogen-containing polyionic liquid, characterized in that: The steps include: (1) Synthesis of nitrogen-containing ionic liquid monomers; In the acetonitrile solution, N,N,N'-tetramethyl-1,6-hexanediamine and 4-vinylbenzylchlorobenzene were added to react to generate a white solid, which was subsequently washed with ethyl acetate and dried for later use; The reaction equation is as follows: (2) Preparation of polyionic liquids In a mixed solution of ethyl acetate, ethanol and water, add the product 1-(4-vinylbenzyl)-N,N,N',N'-tetramethylhexanediammonium chloride obtained in step (1), then add an initiator azobisisobutyronitrile, and react. After the reaction, wash with ethanol and then with deionized water, and lyophilize to obtain the target product; The reaction equation is as follows: 。 3. The method for preparing the nitrogen-containing polyionic liquid according to claim 2, characterized in that: In step (1), the molar ratio of N,N,N,N'-tetramethyl-1,6-hexanediamine to 4-vinylbenzyl chloride is 1:

1.

4. The method for preparing the nitrogen-containing polyionic liquid according to claim 2, characterized in that: The reaction conditions of step (1) are heating to 70-85° C. under nitrogen flow, and controlling the reaction time to 5-10 h.

5. The method for preparing the nitrogen-containing polyionic liquid according to claim 2, characterized in that: In the mixed solution of step (2), the volume ratio of ethyl acetate, ethanol and water is 5:1:

1.

6. The method for preparing the nitrogen-containing polyionic liquid according to claim 2, characterized in that: In the mixed solution of step (2), the mass ratio of 1-(4-vinylbenzyl)-N,N,N',N'-tetramethylhexanediammonium chloride to azobisisobutyronitrile is 20:

1.

7. The method for preparing the nitrogen-containing polyionic liquid according to claim 2, characterized in that: The reaction conditions of step (2) are as follows: firstly, nitrogen is passed for 15 minutes without heating, then the temperature is adjusted to 70-80° C., and the heating time is controlled to be 6-18 h.

8. Use of the nitrogen-containing ionic liquid as claimed in claim 1 for selective adsorption of noble metal ions.

9. The use of the nitrogen-containing ionic liquid according to claim 8 for selective adsorption of noble metal ions, characterized in that: The noble metal ions are Au(III), Pd(II), and Pt(IV), and the nitrogen-containing ionic liquid can be recycled.

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