Composite resin for removing metal ions as well as preparation method and application of composite resin

Abstract

The invention discloses composite resin for removing metal ions as well as a preparation method and application of the composite resin, and belongs to the technical field of resin materials. In order to solve the problem that the traditional cation exchange resin has poor removal rate on heavy metals in a solution containing alkali metals and heavy metals at the same time, the invention provides the composite resin with a weak acid cation functional group and a nitrogen-containing chelating functional group at the same time. The composite resin contains a nitrogen-oxygen-containing chelating functional group and a weakly acidic cation functional group, the nitrogen-oxygen-containing chelating functional group can selectively remove heavy metal ions such as chromium, and the weakly acidic cation functional group can effectively remove alkali metal ions such as calcium. Therefore, the composite resin has the advantages of cation exchange resin and chelating resin, heavy metal ions and alkali metal ions in an ethanolamine stock solution can be effectively removed, and the concentration of the metal ions in the ethanolamine solution treated by the composite resin is lower than 30 ppb.

Description

Technical Field

[0001] The invention belongs to the technical field of resin materials, and in particular relates to a composite resin for removing metal ions and a preparation method and application thereof. Background Art

[0002] Ethanolamine and its downstream products are widely used in many industrial fields, such as cosmetics, detergents, electroplating solutions, etc. The presence of metal ions may affect the quality and performance of these products, such as affecting product stability, safety, pH value, cleaning and electroplating effects, etc. Therefore, removing metal ions from ethanolamine is crucial to improving product quality. The ion exchange method can efficiently remove metal ions from ethanolamine to a very low concentration level. At the same time, it is easy to operate, can regenerate ion exchange resins, has good economic efficiency, and is a commonly used method for removing metal ions.

[0003] Ion exchange resin is a polymer material with ion exchange function. Its working principle is that the ions on the resin are exchanged with the ions in the solution, so as to achieve the purpose of removing specific ions in the solution. Cation exchange resin contains functional groups such as sulfonic acid group, carboxyl group, etc., which can attract and bind ions with positive charge, such as metal ions, organic cations, etc. This resin realizes the adsorption of cations through electrostatic action, and releases the original cations on the resin (such as hydrogen ions, sodium ions), thereby realizing the ion exchange process. Among them, the exchange capacity of weak acid cation exchange resin is usually large, which enables the resin to adsorb and exchange more cations when treating a large amount of solution, improves the treatment efficiency, and its acid consumption is relatively low, reducing the cost and environmental burden in the regeneration process. Ion exchange resin has outstanding advantages in purification and desalination, but the presence of a large amount of salt or alkali (earth) metal salt in the solution will directly compete with heavy metal ions for adsorption sites and significantly reduce the exchange capacity of the resin for the target heavy metal, which seriously limits its selective removal of heavy metal ions. Chelating resin is a kind of cross-linked functional polymer material that can form multi-coordinated complexes with metal ions. It can use its lone pair electron atoms to combine with the empty orbitals of metal ions to form coordination bonds. Chelating resin has advantages that ion exchange resins do not have, such as strong selectivity for metals, fast adsorption rate and strong binding force. In addition, chelating resin can also quickly capture metal ions and easily release captured metal ions in a specific environment, so chelating resin has become an excellent material for adsorbing heavy metal ions. Using chelating resin to complex with heavy metals for selective adsorption and separation can effectively avoid the negative effects caused by coexisting inorganic salts. Summary of the invention

[0004] In view of the above-mentioned prior art, the present invention provides a composite resin for removing metal ions and a preparation method and application thereof, so as to solve the technical problem that it is difficult to remove metal ions from existing resin materials.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is to provide a method for preparing a composite resin for removing metal ions, comprising the following steps: S1: adding chloromethylated polystyrene resin to N,N-dimethylformamide, swelling for 10-15 h, then dissolving the swollen chloromethylated polystyrene resin, diethyl malonate and anhydrous potassium carbonate in a first solvent, and reacting at 60-70 °C for 6-10 h; then filtering, washing and drying to obtain a first intermediate product; S2: adding the first intermediate product to N,N-dimethylformamide and swelling it for 10-15 hours, then dissolving the swollen first intermediate product, diethyl iminodiacetate and anhydrous potassium carbonate in a second solvent, and reacting it at 75-85°C for 4-8 hours; then filtering, washing and drying to obtain a second intermediate product; S3: Add the second intermediate product to N,N-dimethylformamide and swell for 10-15 h, then dissolve the swelled second intermediate product and sodium hydroxide in a mixed solvent, and heat to reflux for 8-10 h; then filter and wash, then add the washed product to a 1 M hydrochloric acid solution, stir for 8 h, filter, wash, and dry to obtain; the mixed solvent is obtained by mixing N,N-dimethylformamide and water.

[0006] Based on the above technical solution, the present invention can also be improved as follows.

[0007] Furthermore, the swelling time in S1, S2, and S3 was 12 h.

[0008] Furthermore, the mass ratio of diethyl malonate and anhydrous potassium carbonate to chloromethylated polystyrene resin in S1 is 4-5:7-8:10.

[0009] Furthermore, the first solvent in S1 is N,N-dimethylformamide; the reaction temperature is 65° C., and the reaction time is 8 h.

[0010] Furthermore, the mass ratio of diethyl iminodiacetate and anhydrous potassium carbonate to the first intermediate product in S2 is 41~42:7~8:11~12.

[0011] Furthermore, the second solvent in S2 is N,N-dimethylformamide; the reaction temperature is 80° C., and the reaction time is 6 h.

[0012] Furthermore, in S3, the ratio of sodium hydroxide to the second intermediate product is 17~18:13~14.

[0013] Furthermore, the mixed solvent in S3 is prepared by mixing equal volumes of N,N-dimethylformamide and water; the heating reflux time is 9 h.

[0014] The invention also discloses a composite resin for removing metal ions, which is prepared by adopting the preparation method.

[0015] The invention also discloses an application of a composite resin for removing metal ions, specifically using the composite resin for removing metal ions to remove metal ions in ethanolamine.

[0016] The beneficial effects of the present invention are: The present invention provides a composite resin having both weakly acidic cation functional groups and nitrogen-containing chelating functional groups in order to overcome the problem that conventional cation exchange resins have a poor heavy metal removal rate in solutions containing both alkali metals and heavy metals. The composite resin in the present invention contains nitrogen-containing oxygen chelating functional groups and weakly acidic cation functional groups. The nitrogen-containing oxygen chelating functional groups can selectively remove heavy metal ions such as chromium, while the weakly acidic cation functional groups can effectively remove alkali metal ions such as calcium. Thus, the composite resin in the present invention has the advantages of both cation exchange resins and chelating resins, and can effectively remove heavy metal ions and alkali metal ions in ethanolamine stock solution. The metal ion concentration in the ethanolamine solution treated with the composite resin in the present invention is lower than 30 ppb. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A process roadmap for preparing composite resins for removing metal ions; Figure 2 is the infrared spectrum of the composite resin used to remove metal ions; Figure 3 Thermogravimetric curves of different resins; Figure 4 Schematic diagram of the device for treating ethanolamine solution using composite resin. DETAILED DESCRIPTION

[0018] The specific implementation modes of the present invention are described in detail below with reference to the embodiments.

[0019] Example 1 A composite resin (PCR) for removing metal ions, the preparation process route is as follows Figure 1 As shown, the preparation process specifically includes the following steps: (1) With chloromethylated polystyrene resin ( Figure 1Compound 1 in the mixture; purchased from Adamas, CAS: 55844-94-5) was used as a raw material, 10.0 g of chloromethylated polystyrene resin was added to 20 mL of N,N-dimethylformamide and swelled at room temperature for 12 h; then the swollen chloromethylated polystyrene resin, 4.4 g of diethyl malonate and 7.6 g of anhydrous potassium carbonate were added to a round-bottom flask, and N,N-dimethylformamide was added as a solvent. After complete dissolution, the mixture was reacted at 65 °C for 8 h; after the reaction was completed, the reaction solution was filtered, the filter cake was collected and washed with deionized water and ethanol for 3 times respectively, and then placed in a vacuum drying oven and dried to obtain compound 2.

[0020] (2) 11.8 g of compound 2 was added to 20 mL of N,N-dimethylformamide and swelled at room temperature for 12 h. The swollen compound 2, 41.4 g of diethyl iminodiacetate and 7.6 g of anhydrous potassium carbonate were then added to a round-bottom flask, and N,N-dimethylformamide was added as a solvent. After complete dissolution, the mixture was reacted at 80 °C for 6 h. After the reaction was completed, the reaction solution was filtered, and the filter cake was collected and washed three times with deionized water and ethanol respectively, and then placed in a vacuum drying oven and dried to obtain compound 3.

[0021] (3) 13.6 g of compound 3 was added to 20 mL of N,N-dimethylformamide and swelled at room temperature for 12 h. The swollen compound 3 and 17.5 g of sodium hydroxide were then added to a round-bottom flask, and a mixed solution of N,N-dimethylformamide and water in a volume ratio of 1:1 was added as a solvent, and the mixture was heated under reflux for 9 h. After the reaction, the obtained reaction solution was filtered, and the filter cake was collected and washed with deionized water and ethanol for 3 times respectively. The washed product was then added to a 1 M hydrochloric acid solution and stirred for 8 h, filtered, washed with deionized water and ethanol for 3 times respectively, and then placed in a vacuum drying oven. After drying, a composite resin PCR for removing metal ions was obtained.

[0022] Example 2 A composite resin (PCR) for removing metal ions, the preparation process route is as follows Figure 1 As shown, the preparation process specifically includes the following steps: (1) With chloromethylated polystyrene resin ( Figure 1Compound 1 in the mixture; purchased from Adamas, CAS: 55844-94-5) was used as a raw material, 10.0 g of chloromethylated polystyrene resin was added to 20 mL of N,N-dimethylformamide and swelled at room temperature for 10 h; then the swollen chloromethylated polystyrene resin, 4 g of diethyl malonate and 7 g of anhydrous potassium carbonate were added to a round-bottom flask, and N,N-dimethylformamide was added as a solvent. After complete dissolution, the mixture was reacted at 60 °C for 10 h; after the reaction was completed, the reaction solution was filtered, the filter cake was collected and washed with deionized water and ethanol for 3 times respectively, and then placed in a vacuum drying oven and dried to obtain compound 2.

[0023] (2) 11 g of compound 2 was added to 20 mL of N,N-dimethylformamide and swelled at room temperature for 10 h. Then, the swollen compound 2, 41 g of diethyl iminodiacetate and 7 g of anhydrous potassium carbonate were added to a round-bottom flask, and N,N-dimethylformamide was added as a solvent. After complete dissolution, the mixture was reacted at 75 °C for 8 h. After the reaction was completed, the reaction solution was filtered, and the filter cake was collected and washed three times with deionized water and ethanol respectively, and then placed in a vacuum drying oven and dried to obtain compound 3.

[0024] (3) 13 g of compound 3 was added to 20 mL of N,N-dimethylformamide and swelled at room temperature for 10 h. The swollen compound 3 and 17 g of sodium hydroxide were then added to a round-bottom flask, and a mixed solution of N,N-dimethylformamide and water in a volume ratio of 1:1 was added as a solvent, and the mixture was heated under reflux for 8 h. After the reaction, the obtained reaction solution was filtered, and the filter cake was collected and washed with deionized water and ethanol for 3 times respectively. The washed product was then added to a 1 M hydrochloric acid solution and stirred for 8 h, filtered, washed with deionized water and ethanol for 3 times respectively, and then placed in a vacuum drying oven. After drying, a composite resin PCR for removing metal ions was obtained.

[0025] Example 3 A composite resin (PCR) for removing metal ions, the preparation process route is as follows Figure 1 As shown, the preparation process specifically includes the following steps: (1) With chloromethylated polystyrene resin ( Figure 1Compound 1 in the mixture; purchased from Adamas, CAS: 55844-94-5) was used as a raw material, 10.0 g of chloromethylated polystyrene resin was added to 20 mL of N,N-dimethylformamide and swelled at room temperature for 15 h; then the swollen chloromethylated polystyrene resin, 5 g of diethyl malonate and 8 g of anhydrous potassium carbonate were added to a round-bottom flask, and N,N-dimethylformamide was added as a solvent. After complete dissolution, the mixture was reacted at 70 °C for 6 h; after the reaction was completed, the reaction solution was filtered, the filter cake was collected and washed with deionized water and ethanol for 3 times respectively, and then placed in a vacuum drying oven and dried to obtain compound 2.

[0026] (2) 12 g of compound 2 was added to 20 mL of N,N-dimethylformamide and swelled at room temperature for 15 h. The swollen compound 2, 42 g of diethyl iminodiacetate and 8 g of anhydrous potassium carbonate were then added to a round-bottom flask, and N,N-dimethylformamide was added as a solvent. After complete dissolution, the mixture was reacted at 85 °C for 4 h. After the reaction was completed, the reaction solution was filtered, and the filter cake was collected and washed three times with deionized water and ethanol respectively, and then placed in a vacuum drying oven and dried to obtain compound 3.

[0027] (3) 14 g of compound 3 was added to 20 mL of N,N-dimethylformamide and swelled at room temperature for 15 h. The swollen compound 3 and 18 g of sodium hydroxide were then added to a round-bottom flask, and a mixed solution of N,N-dimethylformamide and water in a volume ratio of 1:1 was added as a solvent, and the mixture was heated under reflux for 10 h. After the reaction, the obtained reaction solution was filtered, and the filter cake was collected and washed with deionized water and ethanol for 3 times respectively. The washed product was then added to a 1 M hydrochloric acid solution and stirred for 8 h, filtered, washed with deionized water and ethanol for 3 times respectively, and then placed in a vacuum drying oven. After drying, a composite resin PCR for removing metal ions was obtained.

[0028] Results Analysis The composite resins for removing metal ions prepared in Examples 1 to 3 have similar performances. The composite resin for removing metal ions prepared in Example 1 is taken as an example to illustrate the performance of the composite resin for removing metal ions.

[0029] 1. Characterization of composite resins for metal ion removal (1) Infrared spectrum test The molecular structure of the composite resin was determined using a Spectrum Two Fourier infrared spectrometer. Potassium bromide tablets were used to prepare the sample. The composite resin PCR and potassium bromide were dried in a vacuum oven before testing. The test results are shown in Figure 2 As shown. Figure 2It can be seen that 1729 cm -1 The C=O stretching vibration peak appeared at 2500~3600 cm -1 The -OH stretching vibration peak of the carboxyl group appeared at 1020~1360 cm -1 The CN stretching vibration peak of the tertiary amine appeared at the 50°C, indicating that the chelating functional group containing nitrogen elements was successfully grafted.

[0030] (2) Elemental analysis test The element content of the composite resin was determined using Elementar Unicube elemental analyzer. The chelating functional group content of the composite resin can be inferred based on the nitrogen content of the composite resin. The elemental analysis results are shown in Table 1.

[0031] Table 1 Elemental analysis results

[0032] The elemental analysis results also proved that the two functional groups were successfully grafted onto the chloromethylated polystyrene. By calculation, it was found that x=0.44 and y=0.56 in the composite resin, thereby determining that the molecular formula of the composite resin PCR is as shown in Formula I.

[0033]

[0034] (3) Thermogravimetric analysis The thermal stability of the composite resin was analyzed and tested using a NETZSCH TG209F1 thermogravimetric analyzer, with nitrogen as the protective atmosphere and a heating rate of 10 °C / min. The composite resin was compared with the corresponding cation exchange resin (compound shown in Formula II) and chelating resin (compound shown in Formula III). The thermogravimetric curves of the three are shown in Figure 2. Figure 3 As shown. Figure 3 It can be seen that the temperatures at which the composite resin PCR, chelating resin and cation exchange resin lose 5% of their weight are 223°C, 201°C and 229°C respectively, with little difference among the three. At 320°C, the composite resin PCR only loses 21% of its weight, which is significantly better than the corresponding chelating resin (36%) and cation exchange resin (34%).

[0035]

[0036] Thermogravimetric analysis results show that the composite resin PCR prepared by the grafting reaction of the present invention has good thermal stability, and the introduction of two functional groups will not affect the heat resistance of the resin itself.

[0037] 2. Performance test of composite resin for removing metal ions First, rinse the glass column with deionized water several times, fill the prepared composite resin PCR into the glass column (filling height is 20 cm), then add monoethanolamine and diethanolamine stock solutions from the top, pressurize with a pressure pump at a constant pressure, and collect the treated monoethanolamine and diethanolamine solutions from the bottom of the glass column. The schematic diagram of the experimental device is shown in Figure 4 The metal ion concentrations of monoethanolamine and diethanolamine stock solutions are shown in Table 2.

[0038] Table 2 Metal ion concentrations in monoethanolamine and diethanolamine stock solutions

[0039] As can be seen from Table 2, the ethanolamine stock solution mainly contains excessive iron, calcium, chromium and other elements. The treated liquid after the composite resin column treatment was subjected to ICP-MS test to determine the metal ion concentration, and the test results are shown in Table 3.

[0040] Table 3 Metal ion concentrations in monoethanolamine and diethanolamine after composite resin treatment

[0041] As can be seen from Table 3, after the composite resin treatment, the average content of chromium / iron in monoethanolamine and diethanolamine decreased from 0.1540 / 0.2574 ppm and 0.2549 / 0.2332 ppm to 0.0077 / 6.6076 ppb and 0.0058 / 5.0226 ppb, respectively, indicating that the introduction of chelating functional groups containing nitrogen and oxygen elements enables the composite resin to have a good selective removal effect on heavy metal elements such as chromium and iron. At the same time, the average content of alkali metal element calcium with a high content decreased from 0.2604 / 0.6606 ppm to 25.7737 / 20.8245 ppb, which was effectively removed due to the introduction of cationic functional groups.

[0042] The experimental results show that the composite resin PCR in the present invention has a good removal effect on alkali metal ions and heavy metal ions in the ethanolamine stock solution, and the concentrations of various metal ions are all within 30 ppb.

[0043] Although the specific implementation of the present invention is described in detail in conjunction with the embodiments, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A method for preparing a composite resin for removing metal ions, characterized in that: The following steps are involved: S1: adding chloromethylated polystyrene resin to N,N-dimethylformamide, swelling for 10-15 hours, then dissolving the swollen chloromethylated polystyrene resin, diethyl malonate and anhydrous potassium carbonate in a first solvent, and reacting at 60-70° C. for 6-10 hours; then filtering, washing and drying to obtain a first intermediate product; S2: adding the first intermediate product to N,N-dimethylformamide and swelling it for 10-15 hours, then dissolving the swollen first intermediate product, diethyl iminodiacetate and anhydrous potassium carbonate in a second solvent, and reacting it at 75-85°C for 4-8 hours; then filtering, washing and drying to obtain a second intermediate product; S3: Add the second intermediate product to N,N-dimethylformamide and swell for 10 to 15 hours, then dissolve the swelled second intermediate product and sodium hydroxide in a mixed solvent, and heat to reflux for 8 to 10 hours; then filter and wash, and then add the washed product to a 1 M hydrochloric acid solution, stir for 8 hours, filter, wash, and dry to obtain; the mixed solvent is obtained by mixing N,N-dimethylformamide and water.

2. The preparation method according to claim 1, characterized in that: The swelling time in S1, S2 and S3 was 12 h.

3. The preparation method according to claim 1, characterized in that: The mass ratio of diethyl malonate and anhydrous potassium carbonate to chloromethylated polystyrene resin in S1 is 4-5:7-8:

10.

4. The preparation method according to claim 3, characterized in that: The first solvent in S1 is N,N-dimethylformamide; the reaction temperature is 65°C, and the reaction time is 8 h.

5. The preparation method according to claim 1, characterized in that: The mass ratio of diethyl iminodiacetate and anhydrous potassium carbonate to the first intermediate product in S2 is 41~42:7~8:11~12.

6. The preparation method according to claim 5, characterized in that: The second solvent in S2 is N,N-dimethylformamide; the reaction temperature is 80°C and the reaction time is 6 h.

7. The preparation method according to claim 1, characterized in that: The ratio of sodium hydroxide to the second intermediate product in S3 is 17~18:13~14.

8. The preparation method according to claim 7, characterized in that: The mixed solvent in S3 is a mixture of equal volumes of N,N-dimethylformamide and water; the heating reflux time is 9 h.

9. A composite resin for removing metal ions prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the composite resin for removing metal ions according to claim 9 in removing metal ions from ethanolamine.

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