A synthesis method of an adsorbent for quickly removing methylene blue in water by using waste plastic as raw material

Abstract

This invention discloses a method for synthesizing an adsorbent for the rapid removal of methylene blue from water using waste plastics as raw materials, belonging to the field of pollutant treatment technology. The method for synthesizing the methylene blue adsorbent using PET as raw material includes the following steps: mixing PET material, sodium chloride, and zinc chloride, carbonizing to obtain a PET-based carbon material, mixing with a polyoxometalate solution, and reacting to obtain the methylene blue adsorbent. The adsorbent synthesized by this invention has advantages such as high removal rate and short adsorption equilibrium time. It facilitates the resource utilization of PET material while overcoming the shortcomings of existing adsorbents, such as low removal rate and long adsorption equilibrium time. This invention converts PET material into an adsorbent through carbonization, not only promoting the upgrading and recycling of PET materials but also providing another possibility for methylene blue adsorption.

Description

Technical Field

[0001] This invention relates to the field of pollutant treatment technology, and in particular to a method for synthesizing an adsorbent that rapidly removes methylene blue from water using waste plastics as raw materials. Background Technology

[0002] Methylene blue is an industrial dye with wide applications in printing, textiles, pharmaceuticals, and papermaking. However, it also poses a serious threat to humans and the environment. Wastewater containing methylene blue, once discharged into the natural world, severely damages the surrounding ecosystem and poses carcinogenic risks to humans. Currently, the treatment methods for methylene blue wastewater mainly include traditional sedimentation, adsorption, activated sludge processes, and membrane technology. Among these, adsorption is popular due to its high selectivity and ease of operation. However, current methylene blue adsorbents still suffer from low removal rates and long adsorption equilibrium times, requiring further improvement. For example, the activated carbon complex nFeOOH@AC synthesized in patent CN 117228776 A only achieved a maximum removal rate of 73.4% within 24 hours when the initial methylene blue concentration in the wastewater ranged from 1 to 150 mg / L and the pH value was between 2 and 13. Patent CN 107335402 A describes the use of mangosteen shell activated carbon to adsorb methylene blue, which can adsorb 99.5% of the methylene blue in 1 hour. Summary of the Invention

[0003] The purpose of this invention is to provide a method for synthesizing an adsorbent for the rapid removal of methylene blue from water using waste plastics as raw materials. The main component of waste plastics is PET material. The adsorbent synthesized in this invention has advantages such as high removal rate and short adsorption equilibrium time. It facilitates the resource utilization of PET material while overcoming the shortcomings of existing adsorbents, such as low removal rate and long adsorption equilibrium time.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] One of the technical solutions of this invention is to provide a method for synthesizing methylene blue adsorbent using PET as raw material, comprising the following steps:

[0006] PET material, sodium chloride, and zinc chloride are mixed and carbonized to obtain PET-based carbon material, which is then mixed with a polyoxometalate solution and reacted to obtain the methylene blue adsorbent.

[0007] Preferably, the PET material is waste plastic.

[0008] Preferably, the mass ratio of the PET-based carbon material to the polyoxometalate is 0.2:0.023-0.20; the polyoxometalate solution is a PMoV heteropolyacid solution with a concentration of 0.2875 g / L.

[0009] More preferably, the method for preparing the PMoV heteropolyacid includes the following steps:

[0010] Dissolve 0.71 g of disodium hydrogen phosphate dodecahydrate and 2.44 g of sodium metavanadate in 20 mL of water, stir for 5 min, add 0.5 mL of concentrated sulfuric acid to obtain solution M; dissolve 12.10 g of sodium molybdate dihydrate in 20 mL of water, mix with solution M, add 8.5 mL of concentrated sulfuric acid, and then extract with 50 mL of diethyl ether to obtain the PMoV heteropolyacid.

[0011] Preferably, the mass ratio of the PET material, sodium chloride, and zinc chloride is 2:1:0.9.

[0012] Preferably, the carbonization includes the following steps: heating to 280°C at 10°C / min and holding for 8 min, then heating to 550°C at 10°C / min and holding for 10 min.

[0013] In the preparation method defined in this invention, since sodium chloride lowers the melting point of zinc chloride (283°C), zinc chloride can be melted at 280°C. Furthermore, by maintaining the temperature at 280°C for 8 minutes, this invention allows zinc chloride to completely fuse with the carbon material, facilitating pore formation during carbonization and fully utilizing its role as a pore-forming agent.

[0014] Preferably, the reaction is carried out at a temperature of 180°C for 24 hours.

[0015] The second technical solution of the present invention provides a methylene blue adsorbent obtained according to the above preparation method.

[0016] The third technical solution of the present invention provides an application of the above-mentioned methylene blue adsorbent in the field of methylene blue adsorption.

[0017] The third technical solution of the present invention provides a method for adsorbing methylene blue, comprising the following steps:

[0018] The above-mentioned methylene blue adsorbent is added to a solution containing methylene blue, an adsorption reaction occurs, and then the methylene blue adsorbent is recovered by vacuum filtration.

[0019] Preferably, the mass ratio of methylene blue to methylene blue adsorbent is 0.4:5-25; the adsorption reaction temperature is 5-40℃ and the time is 0.5-5 min.

[0020] More preferably, the concentration of methylene blue in the methylene blue-containing solution is 10 mg / L.

[0021] The beneficial technical effects of the present invention are as follows:

[0022] The adsorbent synthesized in this invention has advantages such as high removal rate and short adsorption equilibrium time. It helps to utilize PET materials as resources while overcoming the disadvantages of existing adsorbents such as low removal rate and long adsorption equilibrium time.

[0023] This adsorbent is produced by first carbonizing PET material (waste plastic) to obtain PET-based carbon material, then adding the PET-based carbon material to a polyoxometalate solution, stirring evenly, and then carrying out a hydrothermal reaction. The final product is an adsorbent with a very high removal rate, which can remove methylene blue from water within 5 minutes (with a removal rate of up to 100%). Furthermore, the adsorbent can be recovered through simple vacuum filtration, making it easy to operate.

[0024] In the methylene blue adsorbent of the present invention, since the negatively charged PMoV is immobilized on C-PET, PMoV@C-PET has strong electronegativity. As a cationic dye, when the adsorbent is dispersed in water, the positive and negative charges attract each other, so that MB is adsorbed on PMoV@C-PET.

[0025] This invention transforms PET material into an adsorbent through carbonization, which not only promotes the upgrading and recycling of PET material, but also provides another possibility for the adsorption scheme of methylene blue. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 The infrared spectra of PMoV and C-PET synthesized in Example 1, and PMoV@C-PET (10%), PMoV@C-PET (20%), PMoV@C-PET (30%), PMoV@C-PET (40%), and PMoV@C-PET (50%) synthesized in Examples 1-5, respectively.

[0028] Figure 2 The images show the adsorption effect of methylene blue on PMoV and C-PET synthesized in Example 1, as well as PMoV@C-PET (10%), PMoV@C-PET (20%), PMoV@C-PET (30%), PMoV@C-PET (40%), and PMoV@C-PET (50%) synthesized in Examples 1-5, and the comparative example synthesized in Comparative Example 1.

[0029] Figure 3The image shows the adsorption effect of PMoV@C-PET (30%) synthesized in Example 3 on methylene blue at different dosages.

[0030] Figure 4 The image shows the adsorption effect of PMoV@C-PET (30%) synthesized in Example 3 on methylene blue at different adsorption temperatures.

[0031] Figure 5 The image shows the adsorption effect of PMoV@C-PET (30%) synthesized in Example 3 on methylene blue at different adsorption times.

[0032] Figure 6 The image shows the adsorption effect of PMoV@C-PET (30%) synthesized in Example 3 on methylene blue at different adsorption pH.

[0033] Figure 7 This is a physical image of the PET-based carbon material in Example 1. Detailed Implementation

[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0035] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0036] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0037] The terms “comprising,” “including,” “having,” “containing,” etc., used in this invention are all open-ended terms, meaning that they include but are not limited to.

[0038] All raw materials used in the following embodiments and comparative examples of the present invention are commercially available products.

[0039] Example 1

[0040] Preparation of methylene blue adsorbent:

[0041] (1) Synthesis of PMoV heteropoly acid: Dissolve 0.71g of Na2HPO4·12H2O in 10mL of deionized water, and fully dissolve 2.44g of sodium metavanadate in 10mL of boiling water. Then mix the two solutions and stir for 5min. Let it cool to 25℃ and add 0.5mL of concentrated sulfuric acid to generate a red solution M.

[0042] Dissolve 12.10 g of Na₂MoO₄·2H₂O in 20 mL of water to obtain solution L. Add solution L to solution M and mix thoroughly. Then add 8.5 mL of concentrated sulfuric acid and cool to 25 °C. Extract the solution with 50 mL of diethyl ether and transfer it to a beaker. Add 5 mL of distilled water and heat in a water bath at 45 °C until a large amount of red crystals precipitate. Then dry the red crystals to obtain PMoV heteropoly acid (denoted as PMoV).

[0043] (2) Synthesis of PET-based carbon material: The PET material used in this embodiment is a Nongfu Spring mineral water bottle. It was cut into 0.5cm x 0.5cm square plastic sheets, rinsed three times with deionized water, and then allowed to air dry. 2.0g of the plastic sheets, 1g of sodium chloride, and 0.9g of zinc chloride were mixed evenly and then placed in a tube furnace for heat treatment. The tube furnace program was set as follows: atmospheric atmosphere, first heating at 10℃ / min to 280℃, holding for 8min, second heating at 10℃ / min to 550℃, holding for 10min, and ending at 550℃. After natural cooling, it was ground into powder using a ceramic mortar, then washed three times with 1M hydrochloric acid, followed by three washes with deionized water, and then dried at 60℃ for 12h to obtain the sample PET-based carbon material (denoted as C-PET, its physical image is shown below). Figure 7 (As shown).

[0044] (3) Synthesis of methylene blue adsorbent: Dissolve 0.023 g of PMoV heteropoly acid in 80.0 mL of deionized water, then add 0.2 g of C-PET, stir evenly and then sonicate for 30 min. Transfer the solution to a stainless steel reactor lined with polytetrafluoroethylene and react at 180 °C for 24 h. After the reaction is completed, allow it to cool naturally to 25 °C, then wash it 5 times with deionized water, and finally dry it in a vacuum drying oven at 60 °C for 12 h to obtain methylene blue adsorbent, denoted as PMoV@C-PET (10%).

[0045] Example 2

[0046] The only difference from Example 1 is that the content of PMoV heteropoly acid in step (3) is increased to 0.050 g to obtain adsorbent PMoV@C-PET (20%).

[0047] Example 3

[0048] The only difference from Example 1 is that the content of PMoV heteropoly acid in step (3) is increased to 0.086g to obtain adsorbent PMoV@C-PET (30%).

[0049] Example 4

[0050] The only difference from Example 1 is that the content of PMoV heteropoly acid in step (3) is increased to 0.132g to obtain adsorbent PMoV@C-PET (40%).

[0051] Example 5

[0052] The only difference from Example 1 is that the content of PMoV heteropoly acid in step (3) is increased to 0.200g to obtain adsorbent PMoV@C-PET (50%).

[0053] Figure 1 Infrared spectra of PMoV and C-PET synthesized in Example 1, and PMoV@C-PET (10%), PMoV@C-PET (20%), PMoV@C-PET (30%), PMoV@C-PET (40%), and PMoV@C-PET (50%) synthesized in Examples 1-5, respectively. Figure 1 It can be seen that, compared with C-PET without PMoV loading, a characteristic peak belonging to PMoV can be observed on PMoV@C-PET(X) (X=20%, 30%, 40%, 50%), namely at 1058 cm⁻¹. -1 The presence of PO bonds indicates successful loading of PMoV onto C-PET. Furthermore, a peak representing the (C=O)-C stretching vibration (1246 cm⁻¹) was observed on PMoV@C-PET (30%). -1 It can form a π-π bond with the aromatic ring of MB through electron-pair interactions, thereby adsorbing MB.

[0054] Comparative Example 1

[0055] The only difference from Example 3 is that sodium chloride and zinc chloride were not added; instead, the plastic sheet was simply placed in a tube furnace for heat treatment. The resulting adsorbent was named the Comparative Example.

[0056] Effect verification

[0057] (1) Methylene blue adsorption experiment: The steps are as follows: Prepare eight clean 50mL beakers, add 40mL of 10mg / L methylene blue solution to each, and then add 20mg of PMoV@C-PET (10%), PMoV@C-PET (20%), PMoV@C-PET (30%), PMoV@C-PET (40%), PMoV@C-PET (50%) synthesized in Examples 1, C-PET (20mg) and PMoV (6.0mg) synthesized in Example 1, and the comparative example (20mg) synthesized in Comparative Example 1. Label the beakers for differentiation and to facilitate recording of corresponding experimental data. Adsorb for 5min at 30℃ and pH=5.9. Finally, measure the absorbance of the solution using UV-Vis spectrophotometry and record the data. The experimental results are as follows: Figure 2 As shown.

[0058] Figure 2 The graphs show the adsorption effects of PMoV and C-PET synthesized in Example 1, as well as PMoV@C-PET (10%), PMoV@C-PET (20%), PMoV@C-PET (30%), PMoV@C-PET (40%), and PMoV@C-PET (50%) synthesized in Examples 1-5, and the comparative example synthesized in Comparative Example 1, on methylene blue adsorption. Figure 2 The product of Example 3 showed a higher removal rate of methylene blue than other adsorbents in the first 0-5 minutes, achieving complete removal at 5 minutes. Although PMoV@C-PET (40%) also achieved complete removal at 5 minutes, considering both adsorption efficiency and cost, PMoV@C-PET (30%) was the preferred adsorbent. Therefore, PMoV@C-PET (30%) was selected for testing other optimal reaction conditions.

[0059] Combination Figure 1-2 It can also be seen that although no characteristic peaks attributable to PMoV were clearly observed in C-PET (Example 1) loaded with 10% PMoV, the adsorption capacity of PMoV@C-PET (10%) for methylene blue was improved compared with C-PET without PMoV loading, which can indirectly prove that PMoV loading was successful. In summary, PMoV@C-PET (X) was successfully prepared.

[0060] (2) The addition amount test experiment was conducted as follows: Five clean 50mL beakers were prepared, and 40mL of 10mg / L methylene blue solution was added to each. Then, 5mg, 10mg, 15mg, 20mg, and 25mg of PMoV@C-PET (30%) were added respectively. Adsorption was carried out at 30℃ and pH=5.9 for 5min. Finally, the absorbance of the solution was measured using the UV-Vis method, and the data were recorded. The experimental results are shown in Table 3 and... Figure 3 .

[0061] Table 3 Adsorption results at different PMoV@C-PET (30%) dosages

[0062]

[0063] Figure 3 The image shows the adsorption effect of PMoV@C-PET (30%) synthesized in Example 3 on methylene blue at different dosages.

[0064] From observation table 3 and Figure 3 It was found that when the adsorption temperature was 30℃, the time was 5min, and the amount of PMoV@C-PET (30%) was 20mg, the methylene blue in the solution was completely removed. Therefore, 20mg was taken as the amount of PMoV@C-PET (30%) for subsequent adsorption experiments.

[0065] (3) Adsorption temperature test experiment, the steps are as follows: Prepare 8 clean 50mL beakers, add 40mL of 10mg / L methylene blue solution to each, and then adjust the solution temperature to 5℃, 10℃, 15℃, 20℃, 25℃, 30℃, 35℃ and 40℃ respectively. Then add 20mg PMoV@C-PET (30%) to each beaker and adsorb for 5min at pH=5.9. Measure the absorbance of the solution using UV-Vis method and record the data. The experimental results are shown in Table 4 and Figure 4 .

[0066] Table 4. Adsorption results of PMoV@C-PET (30%) at different adsorption temperatures.

[0067]

[0068] Figure 4 The image shows the adsorption effect of PMoV@C-PET (30%) synthesized in Example 3 on methylene blue at different adsorption temperatures.

[0069] From observation table 4 and Figure 4 It was found that when the adsorption temperature was 30℃, 35℃, and 40℃, and the adsorption time was 5min, the methylene blue was completely removed. However, considering the cost of heating and the actual situation, the optimal temperature was finally determined to be 30℃.

[0070] (4) Adsorption time test experiment, the steps are as follows: Prepare a 50mL beaker, add 40mL of 10mg / L methylene blue solution, and then add 20mg of PMoV@C-PET (30%). Adsorb for 0.5min, 1min, 2min, 3min, 4min and 5min respectively under the conditions of 30℃ and pH=5.9. Measure the absorbance of the solution at different adsorption times using the UV-Vis method. The experimental results are shown in Table 5 and Figure 5 .

[0071] Table 5 Adsorption results of PMoV@C-PET (30%) at different adsorption times

[0072]

[0073] Figure 5 The image shows the adsorption effect of PMoV@C-PET (30%) synthesized in Example 3 on methylene blue at different adsorption times.

[0074] From Table 5 and Figure 5 As can be seen from the data, PMoV@C-PET (30%) showed the best adsorbent effect at 5 minutes, achieving complete adsorption. Therefore, the optimal adsorption time is 5 minutes.

[0075] (5) Adsorption pH test experiment, the steps are as follows: Prepare 6 clean 50mL beakers, add 40mL of 10mg / L methylene blue solution to each, and adjust the pH to 1, 3, 5, 7, 9 and 11 respectively. Then add 20.0mg of PMoV@C-PET (30%) to each beaker, and adsorb at 30℃ for 5min. Measure the absorbance of the solution using the UV-Vis method. The experimental results are shown in Table 6 and... Figure 6 .

[0076] Table 6 Adsorption results of PMoV@C-PET (30%) at different adsorption pH values

[0077]

[0078] Figure 6 The image shows the adsorption effect of PMoV@C-PET (30%) synthesized in Example 3 on methylene blue at different adsorption pH.

[0079] From Table 6 and Figure 6 As can be seen, the adsorbent works best when the pH is 7-9, achieving complete adsorption, thus concluding that a pH of 7-9 is beneficial for adsorption experiments.

[0080] (6) The specific surface area of ​​C-PET in Example 1, as well as PMoV@C-PET (10%) and PMoV@C-PET (30%) in Examples 1 and 3, was tested. The results showed that the specific surface area of ​​C-PET was 65.6 g / cm³ when loaded with 0% PMoV. 2 The specific surface area increased to 135.6 g / cm³ after loading with 10.0% PMoV. 2 When the PMoV content was further increased to 30.0%, the specific surface area of ​​PMoV@C-PET (30%) also climbed to 155.7 g / cm³. 2 .

[0081] (7) The removal efficiency of PMoV@C-PET (30%) in Example 3 for Sudan I (SD) was tested. 40 mL of SD solution (concentration 10 mg / L, pH 5.25) was added to a clean 50 mL beaker, followed by the addition of 20.0 mg of PMoV@C-PET (30%). Adsorption was carried out at 30 °C for 5 min, and the absorbance of the solution was measured using the UV-Vis method. The test results showed that the SD removal rate was 34.2%.

[0082] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. An application of a methylene blue adsorbent in the field of methylene blue adsorption, characterized in that, The preparation method of the methylene blue adsorbent includes the following steps: PET material, sodium chloride, and zinc chloride are mixed and carbonized to obtain PET-based carbon material, which is then mixed with a polyoxometalate solution and reacted to obtain the methylene blue adsorbent. The polyoxometalate solution is a PMoV heteropolyacid solution.

2. The application according to claim 1, characterized in that, The mass ratio of the PET-based carbon material to the polyoxometalate is 0.2:0.023-0.20; the polyoxometalate solution is a PMoV heteropolyacid solution with a concentration of 0.2875 g / L.

3. The application according to claim 2, characterized in that, The preparation method of the PMoV heteropoly acid Includes the following steps: Dissolve 0.71 g of disodium hydrogen phosphate dodecahydrate and 2.44 g of sodium metavanadate in 20 mL of water, stir for 5 min, add 0.5 mL of concentrated sulfuric acid to obtain solution M; dissolve 12.10 g of sodium molybdate dihydrate in 20 mL of water, mix with solution M, add 8.5 mL of concentrated sulfuric acid, and then extract with 50 mL of diethyl ether to obtain the PMoV heteropoly acid.

4. The application according to claim 1, characterized in that, The mass ratio of the PET material, sodium chloride, and zinc chloride is 2:1:0.

9.

5. The application according to claim 1, characterized in that, The carbonization process includes the following steps: heating to 280°C at 10°C / min and holding for 8 min, then heating to 550°C at 10°C / min and holding for 10 min.

6. The application according to claim 1, characterized in that, The reaction was carried out at a temperature of 180 °C for 24 h.

7. A method for adsorbing methylene blue, characterized in that, Includes the following steps: Add the methylene blue adsorbent as described in any one of claims 1-6 to a solution containing methylene blue, allow the adsorption reaction to occur, and then recover the methylene blue adsorbent by vacuum filtration.

8. The adsorption method according to claim 7, characterized in that, The mass ratio of methylene blue to methylene blue adsorbent is 0.4:5-25; the adsorption reaction temperature is 5-40 ℃.

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