Modified polyethyleneimine as well as preparation method and application thereof
By introducing thiol groups into polyethyleneimine to prepare modified polyethyleneimine, the problem of poor Pd(II) binding selectivity in low pH and high salinity water samples was solved, and efficient removal and recovery of Pd(II) was achieved, reaching a removal rate of 90% and a recovery rate of 91.5%.
Patent Information
- Application Number
- CN202510921603.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-04
- Publication Date
- 2025-10-10
AI Technical Summary
In existing technologies, polyethyleneimine has poor binding selectivity for the specific metal ion Pd(II) in complex water samples with low pH and high salinity, making it difficult to achieve efficient removal and recovery.
Modified polyethyleneimine (TPEI) was prepared by introducing thiol groups into polyethyleneimine, and chelated with Pd(II) under low pH and high salinity conditions, and concentrated by combining tangential flow ultrafiltration or dialysis process, followed by electrolytic recovery of Pd metal.
Under low pH and high salinity conditions, a highly selective removal rate of Pd(II) of over 90% was achieved, and the recovery rate of Pd metal reached 91.5%, solving the problem of poor selectivity in the prior art and reducing treatment costs.
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Figure CN120757776A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a modified polyethyleneimine, and also relates to a preparation method of the modified polyethyleneimine and application of the modified polyethyleneimine in recovering Pd(II) from industrial wastewater. Background Art
[0002] Currently, treatment methods for palladium-containing wastewater primarily focus on harmless treatment. Based on their reaction principles, these methods can be categorized as chemical precipitation, electrochemical methods, extraction methods, adsorption methods, biological treatment methods, and membrane treatment methods. Chemical precipitation is simple to operate and relatively low-cost. Using a suitable precipitant, it can achieve high precipitation efficiencies (over 95%). However, it presents challenges such as difficulty in solid-liquid separation, large volumes of sludge with complex composition, and the potential for secondary pollution. Further treatment is required for metal extraction, and chemical precipitation is only suitable for wastewaters with high palladium content. Electrochemical methods offer the advantages of high removal efficiency and no secondary pollution, but they require high currents for low-conductivity wastewater, resulting in increased energy consumption. Furthermore, electrode material corrosion during operation may necessitate frequent replacement, further increasing operating costs. Extraction methods can effectively enrich palladium from wastewater, resulting in high-purity products and achieving a total recovery rate of over 95% for Pd(II). However, the extractant preparation is complex, expensive, and difficult to reuse. Furthermore, they are not suitable for wastewaters with high palladium content or large water volumes. The adsorption method has significant environmental benefits. Currently, there are many commercial ion exchange resins used to separate palladium. Although the resin material has a high adsorption capacity and good desorption performance, it has problems such as high cost and slow solid-liquid ion exchange rate. The organisms used in the biological treatment method have high affinity and selectivity for heavy metals, but this method is still in the theoretical research stage and has not entered into actual engineering applications. In addition, some organisms have long growth and repair cycles and high requirements for the growth environment, making it difficult to meet the treatment needs of large amounts of palladium-containing wastewater. Membrane treatment has the advantages of good separation performance and no secondary pollution, but it generally has problems such as severe membrane pollution, high operating costs, and poor selectivity in complex water environments.
[0003] Polyethyleneimine (PEI), a polyelectrolyte material, can form complexes with various metal ions in water, allowing for the removal of heavy metals from wastewater through membrane filtration or the addition of surfactants. However, PEI's amino groups are easily protonated at low pH, significantly reducing its ability to bind metal ions. Furthermore, PEI exhibits poor selectivity for specific metal ions, making it difficult to selectively remove specific metal ions in complex, high-salinity water samples. Summary of the Invention
[0004] Invention purposes: The purpose of the present application is to provide a modified polyethyleneimine with good binding selectivity for specific metal ions (Pd(II)) in low pH and high salinity complex water samples, and another purpose of the present application is to provide a preparation method of the modified polyethyleneimine and its application in recovering Pd(II) in industrial wastewater.
[0005] Technical solutions: The modified polyethyleneimine (TPEI) provided by the present application has the following structural formula:
[0006]
[0007] The molecular weight of the TPEI is 210,000 or more, which is easily intercepted by an ultrafiltration membrane.
[0008] The preparation method of the modified polyethyleneimine comprises the following steps:
[0009] (1) Mix mercaptoacetic acid (TGA), 1-ethyl-(3-dimethylaminopropyl) carbonyldiimidazole (EDC) and N-hydroxysuccinimide (NHS), and fully stir the mixture at room temperature, then add a PEI aqueous solution to the mixture;
[0010] (2) Fully react the reaction solution of step (1) at room temperature, then add the reaction solution to a dialysis bag for dialysis to obtain a TPEI aqueous solution.
[0011] In step (1), the PEI has a branched chain structure and a molecular weight of 70,000 or more; and the molar ratio of TGA to PEI (calculated by monomer) is 1-1.5:1.
[0012] In step (2), the reaction time is not less than 6 hours; the molecular weight of the dialysis bag is 7 kDa, the dialysis time is not less than 6 hours, and 1-ethyl-(3-dimethylaminopropyl) carbonyldiimidazole (EDC) and N-hydroxysuccinimide (NHS) and unreacted reactants are filtered out through the dialysis bag. The sample is loaded into the dialysis bag and placed in a large enough beaker containing deionized water, the deionized water in the beaker is replaced every 1 h, the internal liquid of the dialysis bag is taken out after 6 h of dialysis, and the purification of TPEI is completed.
[0013] The application of the modified polyethyleneimine in the recovery of Pd(II) from industrial wastewater comprises the following specific application process: adding TPEI to palladium-containing industrial wastewater at a molar ratio of TPEI to Pd(II) of not less than 2:1; after sufficient reaction, TPEI selectively chelates Pd(II) in the wastewater; concentrating the fully reacted solution by ultrafiltration (ultrafiltration using a tangential flow ultrafiltration facility), dialysis, or a polyelectrolyte-surfactant aggregate (PSAs) process to obtain a concentrated solution enriched in a TPEI-Pd complex and wastewater after palladium removal; and placing the concentrated solution in an electrolytic cell for electrolysis to achieve decomplexation of the TPEI-Pd complex, thereby achieving recovery of the Pd metal.
[0014] During the electrolysis process, the pH of the concentrated solution is adjusted to 1-3 and the electrolysis current is 0.05-0.1A.
[0015] During application, the Pd(II) concentration in the wastewater must be measured first. TPEI is then added based on the amount of Pd(II) at a molar ratio of 2:1 to achieve efficient chelation. When the TPEI:Pd molar ratio is lower than 2:1, Pd cannot be fully complexed. When the TPEI:Pd molar ratio is higher than 2:1, the excess TPEI binds other metal ions, resulting in a decrease in Pd selectivity.
[0016] TPEI is a process in which the carbonyl group in the TGA molecule undergoes an amidation reaction with the amino group in the PEI molecule, thereby introducing a thiol group into the PEI molecule. The introduction of this group increases TPEI's selectivity for Pd(II), enabling specific and efficient chelation of Pd(II) at low pH and high salinity. Furthermore, at a TPEI:Pd(II) molar ratio of 2:1, combined with tangential flow ultrafiltration, dialysis, or PSAs, the removal rate of Pd(II) in wastewater can reach over 90%. Finally, Pd(II) is recovered through electrolysis of the concentrate, with a Pd metal recovery rate of up to 91.5%.
[0017] PEI contains only amino groups, while TPEI contains amide and thiol groups. At low pH, the amide groups have a weaker protonation ability. At pH 6, 50% of the amino groups on PEI are protonated. When the pH is further reduced to 3, the protonation degree of the amino groups is close to 100%. However, at pH 3, the protonation degree of the amide groups on TPEI is less than 50%. Due to the weak protonation ability of the amide groups, the protonation degree of TPEI is much lower than that of PEI at low pH, because TPEI does not lose its ability to bind metal ions at low pH. At the same time, under high salinity conditions, the thiol groups in TPEI have a strong affinity and selectivity for Pd.
[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The thioglycolic acid-modified polyethyleneimine (TPEI) of the present invention can specifically chelate with Pd(II) in complex water samples with low pH and high salinity, thereby overcoming the problem that the existing polyelectrolyte material (PEI) has poor binding ability with metal ions in low pH and high salinity water; (2) The method of the present invention achieves high selective removal of Pd(II) in industrial wastewater with low pH and high salinity or complex water bodies containing palladium through a polyelectrolyte material with a specific structure and a polyelectrolyte material with a specific molar ratio to Pd(II), with a removal rate of more than 90%; (3) The method of the present invention can achieve low-cost treatment of industrial wastewater, which can not only remove Pd(II) in the wastewater to meet the wastewater discharge standard, but also achieve selective capture and recovery of Pd(II), with a recovery rate of up to 91.5%. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 The reaction equation for preparing TPEI in Example 1;
[0020] Figure 2 : The Fourier transform infrared spectra of TPEI, PEI and TGA in Example 1;
[0021] Figure 3 The removal results of Pd(II) at different pH and different polyelectrolyte materials (TPEI and PEI);
[0022] Figure 4 The removal results of Pd(II) by different salinities and different polyelectrolyte materials (TPEI and PEI);
[0023] Figure 5 The results of TPEI removal of Pd(II) in complex water samples are shown;
[0024] Figure 6 The results of Pd(II) removal by TPEI under high coexisting ion concentration conditions are shown;
[0025] Figure 7 The results of Pd(II) removal by PEI in complex water samples. DETAILED DESCRIPTION
[0026] Example 1
[0027] like Figure 1 As shown, the preparation method of TPEI of the present invention specifically comprises the following steps:
[0028] (1) Weigh 2.71 g of 85 wt.% TGA (0.025 mol), 0.5 mL of EDC, and 0.5 mL of NHS stock solution and mix them in a sample tube. Stir the mixture at room temperature for 30 min to activate the carboxyl groups on the TGA.
[0029] (2) Weigh 2.15 g of a 50 wt.% PEI (0.025 mol) aqueous solution and add it to the mixture in step (1). The molar ratio of PEI (based on monomer) to TGA is 1:1.
[0030] (3) The reaction solution of step (2) was stirred at room temperature, the rotor speed was set to 1000 rpm, and the initial preparation of TPEI was completed after stirring for 6 hours; at this time, the liquid viscosity may be high and the rotor may not rotate. A small amount of distilled water can be added to dilute the solution to reduce the solution viscosity;
[0031] (4) Add the TPEI prepared in step (3) to a dialysis bag with a molecular weight of 7 kDa, place the dialysis bag in a sufficiently large beaker filled with deionized water, replace the deionized water in the beaker every 1 hour, and dialyze for 6 hours to remove the catalyst and unreacted TGA;
[0032] (5) The dialyzed TPEI was prepared into a 0.5 M stock solution (TPEI aqueous solution) for later use. In the above steps, the container and dialysis bag must be washed with distilled water during the sample transfer process to ensure that the TPEI sample is completely transferred.
[0033] Figure 2 The Fourier transform infrared spectroscopy (FTIR) characterization results of PEI, TGA, and TPEI are shown in Figure 2. The FTIR spectrum of PEI shows typical characteristic peaks, namely the NH stretching vibration peaks of primary and secondary amines at approximately 3300-3500 cm -1 , the NH bending vibration peak is about 1600-1650cm -1 , the CN stretching vibration peak is about 1050cm -1 In addition, CH in NCH can be observed at 2808 cm -1 The FTIR spectrum of TGA contains two obvious characteristic peaks, namely, at 2563cm -1 The stretching vibration peak caused by SH and 1701cm -1 After the reaction, the FTIR spectrum of the synthesized product TPEI can observe characteristic peaks similar to those of PEI and TGA, including 2835cm -1 The characteristic peaks caused by CH and 2540 cm -1In addition, at 1560 cm -1 There is an additional coupled vibration peak generated by the in-plane bending vibration of NH and the stretching vibration of CN, which suggests that there are amide groups in the TPEI molecule that are generated by the amidation reaction between the -COOH in the TGA molecule and the -NH2 in the PEI molecule.
[0034] Example 2
[0035] Based on the TPEI prepared in Example 1, Pd(II) was removed from palladium-containing wastewater with high selectivity. The initial Pd(II) concentration in the palladium-containing wastewater was 0.2 mM. Three parallel experiments were set up. In the three experiments, the pH of the wastewater was 1, 3, and 5, respectively. The specific steps were as follows:
[0036] (1) According to the molar ratio of TPEI to Pd(II) of 2:1, 0.2 mL of 0.5 M TPEI aqueous solution was added to 250 mL of palladium-containing wastewater to make the concentration of TPEI 0.4 mM. After sufficient stirring, TPEI selectively chelated Pd(II) in the wastewater.
[0037] (2) The fully reacted solution was concentrated and filtered by ultrafiltration to obtain a palladium-containing concentrated solution and wastewater with Pd(II) removed; the removal rates of Pd(II) in the three groups of experimental wastewater were detected. The Pd(II) removal rates corresponding to the wastewater with pH values of 1, 3, and 5 were 90.88%, 97.45%, and 98.33%, respectively. Figure 3 shown.
[0038] Under the same conditions as above, PEI was added, and the Pd(II) removal rates of wastewater with pH values of 1, 3, and 5 were 16.5%, 22.7%, and 36.9%, respectively. Figure 3 shown.
[0039] Take equal volumes (250 mL) of filtered palladium-containing concentrated solutions (containing TPEI-Pd complex) with pH values of 1 and 3 respectively and place them in an electrolytic cell for electrolysis. The cathode and anode electrode plates are both graphite electrodes with an electrode area of 25 cm 2 ; The current was controlled to be constant at 0.05A, the electrolysis time was 6 hours, and electrolyte samples were taken every 1 hour to determine the concentration of Pd(II) in the solution; within 2 hours after the start of electrolysis, the recovery rate of Pd(II) in electrolytes of different pH values was about 30%; after 6 hours of electrolysis, the recovery rate of Pd(II) in the electrolyte with a final pH of 3 was only about 50%, while the recovery rate of Pd(II) in the electrolyte with a pH of 1 was 85.8%.
[0040] Two equal amounts (250 mL) of the filtered palladium-containing concentrated solution (containing TPEI-Pd complex) corresponding to a pH value of 1 were placed in an electrolytic cell for electrolysis. The cathode and anode electrode plates were both graphite electrodes with an electrode area of 25 cm. 2 ; The electrolysis current values were set to 0.05A and 0.1A respectively, the electrolysis time was 6 hours, and electrolyte samples were taken every hour to determine the concentration of Pd(II) in the solution; after 6 hours of electrolysis, the recovery rate of Pd(II) in the electrolyte with a final current value of 0.05A was 85.8%, while the recovery rate of Pd(II) in the electrolyte with a current value of 0.1A was 91.5%.
[0041] Example 3
[0042] Based on the TPEI prepared in Example 1, Pd(II) was removed from palladium-containing wastewater with high selectivity. In the palladium-containing wastewater, the initial Pd(II) concentration was 0.2 mM, and the pH of the palladium-containing wastewater was controlled to 3. Five parallel experiments were set up. In the five experiments, NaCl at concentrations of 0, 0.1 M, 0.25 M, 0.5 M, and 1 M were added to the wastewater, respectively.
[0043] The specific steps of the removal process are as follows:
[0044] (1) According to the molar ratio of TPEI to Pd(II) of 2:1, 0.2 mL of 0.5 M TPEI aqueous solution was added to 250 mL of palladium-containing wastewater to make the concentration of TPEI 0.4 mM. After sufficient stirring, TPEI selectively chelated Pd(II) in the wastewater.
[0045] (2) The fully reacted solution was concentrated and filtered by ultrafiltration to obtain a concentrated solution containing palladium and wastewater with Pd(II) removed; the removal rates of Pd(II) in the five groups of experiments were tested. Figure 4 It can be seen that the removal of Pd(II) by TPEI is almost unaffected by the high salt environment. When the NaCl concentration is 0 M, the Pd(II) removal rate is 97.45%. When the NaCl concentration is 1 M, the Pd(II) removal rate is 98.7%. After adding salt, the removal rate increases slightly. It may be that the salinity affects the detection of ICP, but overall, TPEI is more stable than PEI in terms of fluctuations in salinity.
[0046] Example 4
[0047] The process of Example 4 is basically the same as that of Example 2, except that the pH of the palladium-containing wastewater is controlled to be 3; the wastewater also contains Fe 3+ Cr 3+ , Pb 2+ 、Pd 2+ 、Sn 4+ 、Zn 2+ 、Cu2+ 、Ni 2+ A total of 8 heavy metal ions were tested, and the concentration of all heavy metal ions was 0.2 mM. Six parallel experiments were set up, and the concentrations of TPEI added in the six parallel experiments were 0, 0.4 mM, 0.8 mM, 1.2 mM, 1.6 mM, and 3.2 mM, respectively. Finally, when the molar ratio of TPEI to Pd(II) was 2:1, the removal rate of Pd(II) was 91.9%, while the removal rates of other heavy metal ions did not exceed 30%, such as Figure 5 shown.
[0048] The pH of palladium-containing wastewater is controlled at 3; the wastewater also contains Fe 3+ Cr 3+ , Pb 2+ 、Pd 2+ 、Sn 4+ 、Zn 2+ 、Cu 2+ 、Ni 2+ There are a total of 8 heavy metal ions, and the concentration of all heavy metal ions is 0.2mM. Six parallel experiments were set up, and the concentrations of PEI added in the six parallel experiments were 0, 0.8mM, 1.6mM, 3.2mM, 4.8mM, and 8mM respectively. Finally, when the molar ratio of PEI to Pd(II) was 4:1, the removal rate of Pd(II) was 75.9%, while the removal rate of Sn was 1. 4+ The removal rate of can also reach 70.8%, which is close to that of Figure 7 shown.
[0049] Example 5
[0050] The process of Example 5 is basically the same as that of Example 4, except that: Fe 3+ Cr 3+ , Pb 2+ 、Sn 4+ 、Zn 2+ 、Cu 2+ 、Ni 2+ The total concentration of 7 heavy metal ions was set in two gradients of 1mM and 2mM, and Pd 2+ The concentrations of all heavy metal ions were 0.2 mM. Finally, when the molar ratio of TPEI to Pd(II) was 2:1, the removal rate of Pd(II) was 89.3% when the concentrations of the other seven heavy metal ions were 1 mM, and 87.0% when the concentrations of the other seven heavy metal ions were 2 mM. Figure 6 shown.
[0051] Examples 4 and 5 demonstrate that TPEI exhibits superior selective adsorption and removal efficiency for Pd(II) compared to PEI in complex water systems. Furthermore, even in the presence of high concentrations of coexisting ions, TPEI maintains a high Pd(II) removal rate, showing no significant decrease. This demonstrates the significant application advantages of TPEI in treating complex water environments.
Claims
1. A modified polyethyleneimine, characterized in that Its structural formula is:
2. The modified polyethyleneimine according to claim 1, wherein: The molecular weight of the modified polyethyleneimine is 210,000 or above.
3. The method for preparing the modified polyethyleneimine according to claim 1, wherein The steps include: (1) mercaptoacetic acid, 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide were mixed, stirred and mixed at room temperature, and then a PEI aqueous solution was added thereto; (2) The reaction solution of step (1) is fully reacted at room temperature. After the reaction, the reaction solution is added to a dialysis bag for dialysis to obtain a TPEI aqueous solution.
4. The preparation method according to claim 3, wherein: In step (1), the PEI is a branched chain structure with a molecular weight of 70,000 or above.
5. The preparation method according to claim 3, wherein: In step (1), the molar ratio of TGA to PEI is 1 to 1.5:1 based on PEI monomer.
6. The preparation method according to claim 3, wherein: In step (2), the reaction time is not less than 6 hours.
7. The preparation method according to claim 3, wherein: In step (2), the molecular weight of the dialysis bag is 7 kDa, and the dialysis time is not less than 6 hours.
8. Use of the modified polyethyleneimine according to claim 1 in recovering Pd(II) from industrial wastewater.
9. The use according to claim 8, characterized in that The specific application process is: TPEI is added to palladium-containing industrial wastewater at a molar ratio of TPEI to Pd(II) of not less than 2:
1. After sufficient reaction, the solution is concentrated by ultrafiltration, dialysis, or polyelectrolyte-surfactant aggregate process to obtain a concentrated solution enriched in TPEI-Pd complex and wastewater after palladium removal; the concentrated solution is placed in an electrolytic cell for electrolysis to obtain decomplexed TPEI and Pd.
10. The use according to claim 9, characterized in that: During the electrolysis process, the pH of the concentrated solution is adjusted to 1-3 and the electrolysis current is 0.05-0.1A.