CN108912269B - A kind of polyimidazole ionic liquid-based copolymer and its preparation method and application - Google Patents

Abstract

The invention relates to a polyimidazole ionic liquid-based copolymer and a preparation method and application thereof. It belongs to the field of adsorbent synthesis. Take N-vinylimidazole and dichloroalkane and add them to the reactor, then add acetonitrile, mix evenly, react at 70-80 ° C for 8-12 h, remove acetonitrile by vacuum distillation, wash and purify to obtain imidazole ionic liquid [C _x Vmir][Cl]; the imidazole ionic liquid [C _x Vmir][Cl], N,N-methylenebisacrylamide MBA, divinylbenzene DVB and acetonitrile were stirred uniformly by ultrasonic, and potassium persulfate was added to the React at 70-80°C for 18-24h, after cooling, suction filtration, washing, purification, and vacuum drying to obtain the target product polyimidazole ionic liquid-based copolymer DVB-p[C _x Vmir][Cl]. The preparation method of the invention is simple and safe, has high adsorption efficiency for rhenium, energy saving and environmental protection, large adsorption capacity and practical applicability.

Description

A kind of polyimidazole ionic liquid-based copolymer and its preparation method and application

technical field

The invention relates to a preparation method of a polyionic liquid-based copolymer and its application in the environmental and chemical fields, in particular to a polyimidazole-based ionic liquid-based copolymer adsorbent for selectively adsorbing rhenium, and a preparation method and application thereof.

Background technique

Rare scattered metals (abbreviated RSE) can also be called rare scattered metals, of which rhenium is a precious rare metal. It is the rarest metal on earth with high strength, high melting point and excellent ductility, mechanical stability and formability. It is an important emerging metal material today and is widely used in petroleum industry, aerospace industry, automobile industry, electronics Industry and other modern industrial sectors.

At present, the methods of extracting rhenium mainly include: extraction separation method, ion exchange method, liquid membrane method, redox method, precipitation method and electrodialysis method. The most prominent shortcomings of these methods are that the operation is cumbersome, the operation cost is high, the energy consumption is high, and secondary pollution is easily caused when dealing with low-concentration metal wastewater. The advantages of adsorption separation are that it will not pollute the environment and has strong adsorption capacity.

As a new type of green solvent, ionic liquids have the advantages of low vapor pressure, high ionic conductivity, good thermal stability and chemical stability. As a good adsorption functional group, ionic liquid can not only improve the physical and chemical properties of the adsorption material after curing, but also overcome the problem of easy loss in liquid-liquid extraction and improve the adsorption capacity and adsorption selectivity of the adsorption material. Solid phase extraction is also very useful. Polymeric ionic liquids not only have the advantages of ionic liquids, but also can form special shapes and structures that ionic liquids do not have. At the same time, they have introduced effective functional groups as adsorbent materials. Therefore, in recent years, polymeric ionic liquids have been widely used in solid phase extraction. Research.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a polyimidazole ionic liquid-based copolymer, which uses the polyionic liquid as an adsorption functional group to synthesize a copolymer adsorbent. The adsorbent has a simple preparation method, strong regeneration ability, high adsorption capacity for Re(VII), and can well selectively adsorb rhenium from a rhenium-containing solution. The invention is safe, energy-saving and environment-friendly, and has practical applicability.

The object of the present invention is achieved through the following technical solutions: a polyimidazole-based ionic liquid-based copolymer, wherein the polyimidazole-based ionic liquid-based copolymer is DVB-p[C _x Vmir][Cl], wherein x=2 , 4, 6; using imidazole ionic liquid as the monomer, N,N-methylenebisacrylamide MBA as the crosslinking agent, and divinylbenzene DVB as the basic skeleton, it is synthesized by free radical polymerization.

A preparation method of polyimidazole ionic liquid-based copolymer, comprising the following steps:

1) Synthesis of imidazole ionic liquid: take N-vinylimidazole and dichloroalkane into the reactor, then add acetonitrile, mix well, react at 70-80 ° C for 8-12 h, remove acetonitrile by vacuum distillation, wash, Purification to obtain imidazole ionic liquid [C _x Vmir][Cl];

2) Synthesis of polyimidazole-based ionic liquid-based copolymer: The imidazole-based ionic liquid [C _x Vmir][Cl], N,N-methylenebisacrylamide MBA, divinylbenzene DVB and acetonitrile were stirred uniformly by ultrasonic wave, Add potassium persulfate, react at 70-80 ℃ for 18-24h, after cooling, suction filter, wash, purify, and vacuum dry to obtain the target product polyimidazole ionic liquid-based copolymer DVB-p[C _x Vmir][Cl ], where x=2, 4, 6.

Preferably, in the above-mentioned preparation method of a polyimidazole ionic liquid-based copolymer, the molar ratio of N-vinylimidazole:dichloroalkane is 0.33-4.00:1.

Preferably, in the above-mentioned preparation method of a polyimidazole ionic liquid-based copolymer, the dichloroalkane is 1,2-dichloroethane, 1,4-dichlorobutane, or 1,6-dichlorobutane Chlorohexane.

Preferably, the above-mentioned preparation method of a polyimidazole ionic liquid-based copolymer comprises imidazole ionic liquids [C _x Vmir][Cl], N,N-methylenebisacrylamide MBA, divinylbenzene DVB and The mass ratio between potassium persulfates is 1:2.42×10 ⁻³ −7.25×10 ⁻³ :0.07-0.86:0.04-0.05.

The application of the above-mentioned polyimidazole ionic liquid-based copolymer as an adsorbent in recovering scattered metal rhenium. The method is as follows: in a solution containing rhenium, adjust the pH of the solution to 1-7, add the above-mentioned polyimidazole ionic liquid-based copolymer DVB-p[C _x Vmir][Cl], and after oscillating and adsorbing for 8-10 hours, use eluent to elute.

Preferably, the pH of the adjusted solution is 3.

Preferably, the eluent is hydrochloric acid. More preferably, the eluent is hydrochloric acid with a volume percent concentration of 1-10%.

Compared with the prior art, the present invention has the following advantages and positive effects:

(1) The polyimidazole ionic liquid-based copolymer prepared by the present invention has high separation efficiency as an adsorbent, can adsorb rhenium with high selectivity from mixed ionic solutions, has large adsorption capacity and multiple recycling performance, has a wide range of applications, and has practical applicability.

(2) The synthesis process conditions of the present invention are easy to control, the energy consumption is low, and the operation is simple, which belongs to the clean production process and is easy to be industrialized.

(3) The invention has fast adsorption speed, good desorption performance and high selectivity, and the maximum adsorption amount of Re(VII) can reach 517.61 mg·g ^-1 .

(4) In the present invention, polyionic liquid is used as functional group, MBA is used as crosslinking agent, and DVB is used as basic skeleton to indirectly synthesize polymer adsorbent through radical polymerization reaction, which is used for the adsorption of Re(VII) in water. The preparation method of the adsorbent is simple, safe, low in cost and high in separation and enrichment efficiency, and can be obtained from coexisting ionic solutions such as Cu(II), Fe(II), Zn(II), Mn(II), Mo(VI), etc. Selective adsorption of Re(VII).

Description of drawings

FIG. 1a is the FT-IR image of DVB-p[C ₂ Vmir][Cl] prepared in Example 1. FIG.

FIG. 1b is the FT-IR image of DVB-p[C ₄ Vmir][Cl] prepared in Example 1. FIG.

FIG. 1 c is the FT-IR image of DVB-p[C ₆ Vmir][Cl] prepared in Example 1. FIG.

Fig. 2 is the SEM image of polyimidazole ionic liquid-based copolymer;

Wherein, a: DVB-p[C ₂ Vmir][Cl]; b: DVB-p[C ₄ Vmir][Cl]; c: DVB-p[C ₆ Vmir][Cl].

Figure 3 shows the effects of DVB-p[C ₂ Vmir][Cl], DVB-p[C ₄ Vmir][Cl], DVB-p[C ₆ Vmir][Cl] on the adsorption of Re(VII) at different acidities .

Figure 4 is an adsorption isotherm of DVB-p[C ₄ Vmir][Cl] adsorbing Re(VII).

Figure 5 is the selectivity of DVB-p[C ₄ Vmir][Cl] for Re(VII) at different acidities.

Figure ₆ is the selectivity of DVB-p[C6Vmir][Cl] for Re(VII) at different acidity.

Detailed ways

In order to better understand the technical solutions of the present invention, specific embodiments are used for further detailed description, but the solutions are not limited thereto.

Embodiment 1 A kind of polyimidazole ionic liquid-based copolymer

(1) Polyimidazole ionic liquid-based copolymer DVB-p[C ₂ Vmir][Cl]

The preparation method is as follows:

1) Synthesis of imidazole ionic liquid: take 4.706g of N-vinylimidazole and 9.896g of 1,2-dichloroethane into a 100mL single-neck flask, then add 40mL of acetonitrile to mix evenly, and react at 80°C for 9h to obtain a brown viscous The acetonitrile was removed by distillation under reduced pressure, washed and purified to obtain the intermediate product imidazole ionic liquid [C ₂ Vmir][Cl].

2) Add 4 mL of the obtained [C ₂ Vmir][Cl] into the three-necked flask, and then add 0.02 g of N,N-methylenebisacrylamide (MBA), 0.3 mL of divinylbenzene (DVB), and 40 mL of acetonitrile, Ultrasonic for 20min, then add 0.2g potassium persulfate, react at 80℃ for 24h, after cooling, suction filter, wash, purify, and vacuum dry to obtain polyimidazole ionic liquid-based copolymer DVB-p[C ₂ Vmir][Cl] .

(2) Polyimidazole ionic liquid-based copolymer DVB-p[C ₄ Vmir][Cl]

The preparation method is as follows:

1) Synthesis of imidazole ionic liquid, take 4.706g of N-vinylimidazole and 12.701g of 1,4-dichlorobutane into a 100mL single-neck flask, then add 40mL of acetonitrile to mix evenly, and react at 80°C for 9h to obtain a brown viscous The acetonitrile was removed by distillation under reduced pressure, washed and purified to obtain the intermediate product imidazole ionic liquid [C ₄ Vmir][Cl].

2) Add 4 mL of the obtained [C ₄ Vmir][Cl] into the three-necked flask, and then add 0.02 g of N,N-methylenebisacrylamide (MBA), 0.3 mL of divinylbenzene (DVB), and 40 mL of acetonitrile, Sonicate for 20 min, then add 0.2 g of potassium persulfate and react at 80°C for 24 h. After cooling, suction filtration, washing, purification, and vacuum drying to obtain polyimidazole ionic liquid-based copolymer DVB-p[C ₄ Vmir][Cl].

(3) Polyimidazole ionic liquid-based copolymer DVB-p[C ₆ Vmir][Cl]

The preparation method is as follows:

1) Synthesis of imidazole ionic liquid, take 4.706g of N-vinylimidazole and 15.506g of 1,6-dichlorohexane into a 250mL single-neck flask, then add 40mL of acetonitrile to mix evenly, and react at 80°C for 9h to obtain a brown viscous The solvent was removed by distillation under reduced pressure, washed and purified to obtain the intermediate product imidazole ionic liquid [C ₆ Vmir][Cl].

2) Add 4 mL of the obtained [C ₆ Vmir][Cl] into the three-necked flask, then add 0.02 g of N,N-methylenebisacrylamide (MBA), 0.3 mL of divinylbenzene (DVB), 40 mL of acetonitrile, Sonicate for 20 min, then add 0.2 g of potassium persulfate and react at 80°C for 24 h. After cooling, suction filtration, washing, purification, and vacuum drying to obtain polyimidazole ionic liquid-based copolymer DVB-p[C ₆ Vmir][Cl].

(4) Characterization:

1) IR analysis: the results are shown in Figure 1a, Figure 1b and Figure 1c, it can be seen from Figure 1b that [C ₄ Vmir][Cl] at 1638 cm ^-1 is the C=C of the vinyl group on N-vinylimidazole and The stretching vibration peaks of C=C and C=N in the imidazole ring, the stretching vibration peaks of CH in C=C and the stretching vibration peaks of CH on the imidazole ring appear at 3108 and 3065 cm ^-1 , which can prove that [C ₄ Successful synthesis of Vmir][Cl]. [C ₂ Vmir][Cl] and [C ₆ Vmir][Cl] were successfully synthesized from Fig. 1a and Fig. 1c.

Comparing the infrared images of DVB-p[C ₄ Vmir][Cl] and [C ₄ Vmir][Cl] in Fig. 1b, it can be seen that the absorption peak at 1638 cm ^-1 in DVB-p[C ₄ Vmir][Cl] changes. Weak, because the stretching vibration peak of C=C of vinyl group on N-vinylimidazole participates in the reaction, the stretching vibration peak of C=N in N ^- vinylimidazole still exists; The stretching vibration peak of CH disappears; it can also be found that there is an obvious stretching vibration peak of NH at 3500 cm ^-1 , which indicates that free radical polymerization occurs in the synthesis process. In addition, in DVB-p[C ₄ Vmir][Cl], the stretching vibration peak of C=O of secondary amide also appeared at ^{1655cm -1} , which indicated that MBA also participated in the polymerization; The flexural vibration peaks of , show that the absorption peak of the benzene ring overlaps with the characteristic absorption peak of the imidazole ring, which can indicate that DVB participates in the radical polymerization reaction. In conclusion, the successful synthesis of DVB-p[C ₄ Vmir][Cl] is demonstrated. The successful synthesis of DVB-p[C ₂ Vmir][Cl] and DVB-p[C ₆ Vmir][Cl] is similarly proved from Figure 1a and Figure 1c.

2) SEM and particle size analysis: average particle size of three polymers DVB-p[C ₂ Vmir][Cl], DVB-p[C ₄ Vmir][Cl] and DVB-p[C ₆ Vmir][Cl] The diameters increased with the increase of the alkyl chain of the ionic liquid, which were 6.21, 8.24, and 8.38 μm, respectively. The SEM results are shown in Figure 2. It can be clearly seen from Figure 2 that the microscopic morphologies of the three polymers are different. Figure 2 (a) is the microscopic morphology of DVB-p[C ₂ Vmir][Cl]. In Figure 2, the aggregated sponge sheet structure can be clearly seen; the microscopic morphology of DVB-p[C ₄ Vmir][Cl] in Figure 2 (b) is a clear and relatively dispersed sheet structure. The boundary between them is more obvious; Fig. 2(c) is the microstructure of DVB-p[C ₆ Vmir][Cl] showing many spherical structures. This is because polyionic liquids with different carbon chain lengths have changed during the synthesis process, and polyionic liquid-based copolymers with longer carbon chains will undergo bending changes, making them spherical structures, which also lead to changes in the particle size of the polymer. In addition, the "thermodynamic effect" between the copolymer and the solvent will also promote the bending of its molecular chain to make the aggregate form a spherical structure, which can reduce the contact between the aggregate and the solvent. Therefore, the particle size increases with the increase of the carbon chain length, and the microscopically presents a spherical structure.

Example 2 Recovery of rhenium by polyimidazole ionic liquid-based copolymer as adsorbent

(1) Adsorption effect of polyimidazole ionic liquid-based copolymer adsorbents with different carbon chain lengths on Re(VII)

Method: Take 10 mg of polymers DVB-p[C ₂ Vmir][Cl], DVB-p[C ₄ Vmir][Cl], DVB-p[C ₆ Vmir][Cl] prepared in Example 1, respectively, add Different pH (pH=1, 2, 3, 4, 5, 6, 7) 5 mL, 20 mg·L ^-1 Re(VII) solutions were shaken in a shaking box for 8 h, and the results are shown in Figure 3 .

As can be seen from Figure 3, it can be seen that the adsorption capacity of the three adsorbents for Re(VII) is relatively low under high acid conditions, which may be because the Cl ^- concentration in the solution is higher at higher acidity, which is not conducive to adsorption. The Cl ^- on the material undergoes anion exchange with ReO ₄ ^- ; at lower acidity, the electrostatic attraction between ReO ₄ ^- and the imidazole ring is enhanced, thereby improving the adsorption capacity, DVB-p[C ₄ Vmir][Cl] and DVB- The variation trend of the adsorption capacity of p[C ₆ Vmir][Cl] is similar, with the increase of pH, the adsorption capacity increases rapidly, reaching the maximum adsorption capacity of 97.00% and 98.20% at pH 3, and then the adsorption capacity decreases slightly , reaching a minimum of 91.06% and 92.70% at pH 6, respectively, while the adsorption capacity of DVB-p[ _C2Vmir ][Cl] also reached a maximum of 92.58% at pH 3, but as the pH continued to increase, the adsorption capacity The decrease is more obvious, and it has dropped to 73.65% at pH 6; the adsorption capacity of DVB-p[C ₄ Vmir][Cl] and DVB-p[C ₆ Vmir][Cl] for Re(VII) under different acidity conditions are higher than DVB-p[C ₂ Vmir][Cl], which may be due to the short carbon chain of DVB-p[C ₂ Vmir][Cl], in which the electrostatic force between Cl ^- and imidazole ring is large, which is not conducive to the interaction with the imidazole ring. ReO ₄ ^- in the solution undergoes ion exchange, so it is not conducive to the adsorption of Re(VII).

(2) The effect of different Re(VII) concentrations on adsorption

Method: Take 10 mg of the polymer DVB-p[C ₄ Vmir][Cl] prepared in Example 1, add 5 mL of pH=3 respectively, and the concentrations of Re(VII) are 20 mg·L ^-1 , 50 mg·L ^-1 , 100 mg· L ^-1 , 200mg·L ^-1 , 300mg·L ^-1 , 400mg·L ^-1 , 500mg·L ^-1 , 800mg·L ^-1 containing rhenium solution, shake it in a shaking box for 8h, the results are as follows shown in Figure 4.

It can be seen from Fig. 4 that at low concentration, the adsorption amount increases with the increase of Re(VII) concentration, and the adsorption amount q _e of DVB-p[C ₄ Vmir][Cl] for rhenium reaches 517.61 mg·g ^{− 1} o'clock tends to balance. From the correlation coefficients fitted by different types of adsorption isotherms, it can be concluded that the adsorption conforms to the Langmuir adsorption isotherm model.

(3) Separation effect of DVB-p[C ₄ Vmir][Cl] adsorbent on Re(VII) in mixed metal solution under different acidity

Take 10 mL of each solution containing 20 mg·L ^-1 of Re(VII), Cu(II), Zn(II), Mn(II), Fe(III), and Mo(VI), respectively, and adjust the pH of the solution to 1, 2 , 3, 4 and 5, then add 10 mg of the DVB-p[C ₄ Vmir][Cl] adsorbent prepared in Example 1, shake for 8 hours, and measure the concentration of each ion in the solution. The results are shown in Figure 5 .

It can be seen from Figure 5 that at pH 3, the adsorption of DVB-p[C ₄ Vmir][Cl] for Re(VII) can reach more than 90%, while for other metals except Mo(VI) The ions were hardly adsorbed, indicating that DVB-p[C ₄ Vmir][Cl] has high selectivity for Re(VII), while the interference of other coexisting metal ions is small.

(4) Separation effect of DVB-p[C ₆ Vmir][Cl] adsorbent on Re(VII) in mixed metal solution under different acidity

Take 10 mL of each solution containing 20 mg·L ^-1 of Re(VII), Cu(II), Zn(II), Mn(II), Fe(III), and Mo(VI), respectively, and adjust the pH of the solution to 1, 2 , 3, 4 and 5, then add 10 mg of the DVB-p[C ₆ Vmir][Cl] adsorbent prepared in Example 1, shake for 8 hours, and measure the concentration of each ion in the solution, the results are shown in Figure 6 .

It can be seen from Fig. 6 that at pH=1, the adsorption rate of DVB-p[C ₆ Vmir][Cl] to rhenium can reach more than 90%, while the adsorption of molybdenum is almost not, indicating that DVB-p[C ₆ Vmir][Cl] has better separation selectivity for Re(VII), which can realize the separation of molybdenum and rhenium in the mixed feed liquid.

(5) Elution effect of different eluents on Re(VII)

Method: 100 mg of DVB-p[C ₄ Vmir][Cl] adsorbent prepared in Example 1 was placed in 100 mL of Re(VII) solution with pH=3 concentration of 400 mg·L ^-1 , and shaken for 8 h at room temperature to reach adsorption saturation. Filter and dry. Weigh 10 mg of the dried adsorbent, put it into a vial containing different eluents, shake at room temperature for 8 h and filter, and measure the concentration of rhenium in the filtrate. The results are shown in Table 1.

Table 1 Elution rate of DVB-p[C ₄ Vmir][Cl] adsorbent prepared in Example 1 under different eluents

As shown in Table 1, hydrochloric acid as an eluent has a remarkable effect, and the hydrochloric acid with a concentration of 10% by volume has the best analytical effect on Re(VII), and the elution rate can reach 96.79%.

(6) Recycling performance of adsorbent

Method: Weigh 100 mg of adsorbent and place it in 100 mL of Re(VII) solution with pH=3 and concentration of 50 mg·L ^-1 , shake at room temperature for 8 h after adsorption saturation, filter, and then elute with 4% hydrochloric acid solution, After 4 adsorption-elution cycles, the results are shown in Table 2.

Table 2 Cycle experiment of DVB-p[C ₄ Vmir][Cl] adsorbent prepared in Example 1

It can be seen from Table 2 that after 4 adsorption-elution cycles, the adsorption capacity of the adsorbent DVB-p[C ₄ Vmir][Cl] to Re(VII) can still reach 48.80 mg·g ^-1 , and the recovery rate can reach 48.80 mg·g -1 . 95.59%, which proves that the adsorbent DVB-p[C ₄ Vmir][Cl] has good stability and reproducibility.

Claims (6)

1. The application of the polyimidazole ionic liquid-based copolymer as an adsorbent in the recovery of scattered metal rhenium is characterized in that the pH of a solution containing rhenium is adjusted to be 3, and the polyimidazole ionic liquid-based copolymer DVB-p [ C ] is added₄Vmir][Cl]After oscillating and adsorbing for 8h, eluting by using an eluant; or in solution containing rhenium, adjusting the pH value of the solution to be 1-3, adding the polyimidazole ionic liquid-based copolymer DVB-p [ C ]₆Vmir][Cl]After oscillating and adsorbing for 8h, eluting by using an eluant;

the polyimidazoles ionic liquid based copolymer is DVB-p [ C ]_xVmir][Cl]Wherein x =4, 6; the preparation method is characterized in that the preparation method is synthesized by taking imidazole ionic liquid as a monomer, N, N-Methylene Bisacrylamide (MBA) as a cross-linking agent and divinylbenzene DVB as a basic skeleton through free radical polymerization;

said [ C ]₄Vmir][Cl]The structural formula is shown as (I), the [ C ] is₆Vmir][Cl]The structural formula of (II):

（Ⅰ）

（Ⅱ）。

2. the use according to claim 1, characterized in that the preparation method of the polyimidazolium ionic liquid based copolymer comprises the following steps:

synthesizing imidazole ionic liquid: adding N-vinylimidazole and 1, 4-dichlorobutane or 1, 4-dichlorohexane into a reactor, adding acetonitrile, mixing uniformly, reacting at 70-80 ℃ for 8-12h, distilling under reduced pressure to remove acetonitrile, washing, and purifying to obtain imidazole ionic liquid [ C₄Vmir][Cl]Or [ C₆Vmir][Cl]；

Synthesizing a polyimidazole ionic liquid-based copolymer: imidazole ionic liquid [ C₄Vmir][Cl]Or [ C₆Vmir][Cl]Uniformly stirring N, N-methylene bisacrylamide MBA, divinylbenzene DVB and acetonitrile by ultrasonic wave, adding potassium persulfate, reacting at 70-80 ℃ for 18-24h, cooling, performing suction filtration, washing, purifying, and performing vacuum drying to obtain a target product, namely the polyimidazole ionic liquid based copolymer DVB-p [ C ] C_xVmir][Cl]Where x =4, 6.

3. The use as claimed in claim 2, wherein the molar ratio of N-vinylimidazole: 1, 4-dichlorobutane or 1, 4-dichlorohexane =1: 2.

4. Use according to claim 3, characterised in that imidazole-based ionic liquids [ C₄Vmir][Cl]Or [ C₆Vmir][Cl]The mass ratio of the N, N-methylene bisacrylamide MBA to the divinylbenzene DVB to the potassium persulfate is 1: 2.42X 10^-3-7.25×10^-3：0.07-0.86：0.04-0.05。

5. The use as claimed in claim 1, wherein the eluent is hydrochloric acid.

6. The use according to claim 1, wherein the eluent is hydrochloric acid with a concentration of 1-10% by volume.

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