Modified polyvinyl alcohol-sodium carboxymethyl cellulose hydrogel as well as preparation method and application thereof

Abstract

The invention discloses a modified polyvinyl alcohol-sodium carboxymethyl cellulose hydrogel as well as a preparation method and application thereof. The hydrogel comprises matrix gel formed by polyvinyl alcohol and sodium carboxymethyl cellulose, and a pomegranate peel source component combined in the matrix gel. The hydrogel takes environment-friendly polyvinyl alcohol, degradable sodium carboxymethyl cellulose and pomegranate rind as raw materials, and has the characteristics of being green and environment-friendly, and matrix gel formed by the polyvinyl alcohol and the sodium carboxymethyl cellulose interacts with a pomegranate rind source component, so that the hydrogel has good biocompatibility. The pore size of the hydrogel is increased, and meanwhile, the adsorption sites of the cationic dye are increased, so that the efficient removal of the cationic dye in water can be realized.

Description

Technical Field

[0001] This invention belongs to the field of adsorption materials technology, and particularly relates to a modified polyvinyl alcohol-sodium carboxymethyl cellulose hydrogel, its preparation method and application. Background Technology

[0002] As we all know, water resources are essential for human survival and development. However, with rapid industrial development, water pollution has increased alarmingly, becoming an increasingly serious environmental and public problem. Heavy metal ions and dyes have been proven to be toxic and carcinogenic, and are common pollutants in wastewater. Existing technologies for removing pollutants from wastewater include adsorption, membrane processes, biological treatment, flocculation, and advanced oxidation processes. Among these, adsorption is widely used in the treatment of dyes and wastewater, possessing advantages such as environmental friendliness, directness, high efficiency, and low cost. It is considered the most promising and widely applied adsorption technology, and various adsorbents such as carbon nanotubes, activated carbon, graphene, and metal oxides have been used in water treatment. However, existing hydrogel adsorbents suffer from problems such as complex operation, high cost, insufficient removal rate, difficulty in recycling some materials, poor biocompatibility and degradability, and a tendency to cause secondary environmental pollution. Therefore, there is an urgent need to develop an adsorbent with high removal rate, simple preparation method, and easy recovery to overcome the limitations of existing adsorbents.

[0003] Pomegranate is a widely consumed fruit globally. Research has confirmed that pomegranate peel contains abundant polyphenols, flavonoids, and other compounds. It is rich in aromatic ring structures, phenolic hydroxyl functional groups, and a small amount of carboxyl groups, allowing it to bind with various substances through chemical bonding, hydrogen bonding, hydrophobic interactions, π-π interactions, and cation-π interactions. In the process of consuming and industrializing pomegranates, the peel, which accounts for approximately 40% of the fruit's total weight, is often discarded in large quantities, resulting in a waste of polyphenolic active substances and causing solid waste pollution. Therefore, combining pomegranate peel with hydrogels holds promise for the simple manufacture of hydrogels and their application in water treatment. Summary of the Invention

[0004] To address the shortcomings of the existing technology, a modified polyvinyl alcohol-sodium carboxymethyl cellulose hydrogel, its preparation method, and its application are provided. This hydrogel uses environmentally friendly polyvinyl alcohol, biodegradable sodium carboxymethyl cellulose, and pomegranate peel as raw materials, exhibiting green and environmentally friendly characteristics. Furthermore, the matrix gel formed by polyvinyl alcohol and sodium carboxymethyl cellulose interacts with the pomegranate peel-derived components, increasing the pore size of the hydrogel and also increasing the adsorption sites for cationic dyes, thereby achieving efficient removal of cationic dyes from water.

[0005] The first objective of this invention is to provide a modified polyvinyl alcohol-sodium carboxymethyl cellulose hydrogel (PVA / CMC / PPP), comprising a matrix gel formed of polyvinyl alcohol (PVA) and sodium carboxymethyl cellulose (CMC), and a pomegranate peel-derived component (PPP) incorporated in the matrix gel.

[0006] In some embodiments of the present invention, the preparation method of the modified polyvinyl alcohol-carboxymethyl cellulose sodium hydrogel includes the following steps: immersing the matrix gel in a pomegranate peel powder aqueous dispersion to obtain the modified polyvinyl alcohol-carboxymethyl cellulose sodium hydrogel.

[0007] The pomegranate peel powder includes components derived from pomegranate peel, such as pomegranate polyphenols.

[0008] In some embodiments of the present invention, the pomegranate peel powder in the aqueous dispersion has a mass concentration of 1-30 wt%, preferably 5-15 wt%.

[0009] In some embodiments of the present invention, the pomegranate peel powder is obtained by washing pomegranate peel with ethanol and water, drying, and crushing it into powder.

[0010] In some embodiments of the present invention, in the raw materials for preparing the matrix gel, the mass ratio of polyvinyl alcohol to sodium carboxymethyl cellulose is 4~12:1, preferably 8:1.

[0011] A second objective of this invention is to provide a method for preparing the above-mentioned modified polyvinyl alcohol-sodium carboxymethyl cellulose hydrogel, comprising the following steps:

[0012] S1. The polyvinyl alcohol and the sodium carboxymethyl cellulose form a matrix gel;

[0013] S2. The matrix gel is immersed in a pomegranate peel powder aqueous dispersion to obtain the modified polyvinyl alcohol-carboxymethyl cellulose sodium hydrogel.

[0014] In some embodiments of the present invention, step S1 includes the following steps:

[0015] S11. Mix the polyvinyl alcohol with water and stir until completely dissolved to obtain a polyvinyl alcohol solution;

[0016] S12. Add the sodium carboxymethyl cellulose to the polyvinyl alcohol solution and stir until completely dissolved to obtain a matrix solution;

[0017] S13. The matrix solution is processed by a freeze-thaw process to obtain the matrix gel.

[0018] In some embodiments of the present invention, in S11, the water is deionized water.

[0019] In some embodiments of the present invention, in S12, the mass percentage of the solute (i.e., the polyvinyl alcohol and the sodium carboxymethyl cellulose) in the matrix solution is 2 to 20 wt%, preferably 8 to 12 wt%, and more preferably 10 wt%.

[0020] In some embodiments of the present invention, in S13, the freezing-thawing process is repeated 2 to 5 times, preferably 3 times.

[0021] In some embodiments of the present invention, in S13, the freezing temperature is -30~0℃.

[0022] In some embodiments of the present invention, in S13, the thawing temperature is 10~40°C.

[0023] In some embodiments of the present invention, in step S2, the soaking temperature is 25~45°C, preferably 35~40°C.

[0024] In some embodiments of the present invention, in S2, the soaking time is 12-36 hours.

[0025] In some embodiments of the present invention, in step S2, after the soaking step, a washing step with water is further included.

[0026] A third objective of this invention is to provide the application of the modified polyvinyl alcohol-sodium carboxymethyl cellulose hydrogel or the modified polyvinyl alcohol-sodium carboxymethyl cellulose hydrogel obtained by the above preparation method in the adsorption of cationic dyes in water.

[0027] In some embodiments of the present invention, the cationic dye includes methylene blue.

[0028] In some embodiments of the present invention, the concentration of the cationic dye in the water is 0.1~200 mg / L, preferably 10~100 mg / L.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The polymers used in this invention are environmentally friendly polyvinyl alcohol, biodegradable sodium carboxymethyl cellulose, and pomegranate peel as raw materials. The preparation process only uses a simple freeze-thaw process and soaking method. No chemical crosslinking agent is used, and no complicated extraction process is required. It has the characteristics of green and environmentally friendly raw material source, simple preparation method and environmental friendliness.

[0031] (2) The hydrogel obtained by the present invention has a large pore size and a large number of adsorption sites for cationic dyes, which can achieve efficient removal of cationic dyes in water. Attached Figure Description

[0032] Figure 1The FTIR spectra of the hydrogel obtained in Comparative Example 1 and the hydrogel obtained in Example 1 before and after MB adsorption are shown.

[0033] Figure 2 TGA images of the hydrogels obtained in Examples 1-3 and Comparative Example 1;

[0034] Figure 3 SEM images of the hydrogels obtained in Examples 1-3 and Comparative Example 1;

[0035] Figure 4 XPS analysis curves of the hydrogels obtained in Examples 1-3 and Comparative Example 1, and the hydrogel obtained in Example 1 after adsorbing MB;

[0036] Figure 5 The adsorption kinetics diagrams are shown for the adsorption time versus removal rate of the hydrogels obtained in Examples 1-3 and Comparative Example 1 when they adsorb MB.

[0037] Figure 6 The graph shows the initial concentration of MB versus the adsorption capacity of MB when the hydrogels obtained in Examples 1-3 and Comparative Example 1 adsorb MB.

[0038] Figure 7 The graph shows the initial concentration of MB and the removal rate when the hydrogels obtained in Examples 1-3 and Comparative Example 1 adsorb MB. Detailed Implementation

[0039] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0040] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0041] Polyvinyl alcohol: Provided by Anhui Wanwei Group Co., Ltd.;

[0042] Sodium carboxymethyl cellulose: Provided by Shanghai Aladdin Biochemical Technology Co., Ltd.

[0043] Methylene blue: Provided by Tianjin Guangfu Fine Chemical Research Institute.

[0044] Example 1

[0045] This embodiment provides a modified polyvinyl alcohol-sodium carboxymethyl cellulose hydrogel, the preparation method of which includes the following steps:

[0046] S1. Formation of matrix gel:

[0047] S11. Weigh 4.0 parts by weight of polyvinyl alcohol (PVA) and 45.5 parts by weight of distilled water and add them to a round-bottom flask. Add a stir bar and stir until completely dissolved to obtain a polyvinyl alcohol solution.

[0048] S12. Add 0.5 parts of sodium carboxymethyl cellulose (CMC) to the polyvinyl alcohol solution, stir until completely dissolved, and remove air bubbles by sonication to obtain the matrix solution;

[0049] S13. Pour the matrix solution into a mold, freeze it at -18°C for 20 h, then thaw it for 4 h, repeat 3 times to obtain the matrix gel PVA / CMC;

[0050] S2. Formation of modified polyvinyl alcohol-sodium carboxymethyl cellulose hydrogel:

[0051] S21. The waste pomegranate peels are washed with ethanol and water, dried in an oven at 50°C, and then ground into powder using a mechanical pulverizer to obtain pomegranate peel powder.

[0052] S22. The matrix gel obtained in S1 was immersed in a 5 wt% pomegranate peel powder aqueous dispersion at 37°C for 24 h. The hydrogel was then removed and washed several times with distilled water to obtain the modified polyvinyl alcohol-carboxymethyl cellulose sodium hydrogel PVA / CMC / PPP5.

[0053] Example 2

[0054] This embodiment provides a modified polyvinyl alcohol-carboxymethyl cellulose sodium hydrogel, which differs from Example 1 only in that the mass concentration of pomegranate peel powder in water dispersion in step S22 is 10 wt%, resulting in a modified polyvinyl alcohol-carboxymethyl cellulose sodium hydrogel PVA / CMC / PPP. 10 Everything else remains the same as in Example 1.

[0055] Example 3

[0056] This embodiment provides a modified polyvinyl alcohol-carboxymethyl cellulose sodium hydrogel, which differs from Example 1 only in that the mass concentration of pomegranate peel powder in water dispersion in step S22 is 15wt%, resulting in a modified polyvinyl alcohol-carboxymethyl cellulose sodium hydrogel PVA / CMC / PPP. 15 Everything else remains the same as in Example 1.

[0057] Comparative Example 1

[0058] This comparative example provides a polyvinyl alcohol-sodium carboxymethyl cellulose hydrogel, which differs from Example 1 only in that step S2 is omitted, resulting in a polyvinyl alcohol-sodium carboxymethyl cellulose hydrogel (PVA / CMC). Everything else remains the same as in Example 1.

[0059] Application Example 1

[0060] This application example provides an application of hydrogel in adsorbing cationic dyes in water. The specific application method is as follows: Weigh 0.25g of the hydrogel PVA / CMC / PPP5 obtained in Example 1 and put it into 25 mL of methylene blue (MB) solution with a concentration of 50 mg / L. Adsorption is carried out at room temperature using a water bath constant temperature shaker. The adsorbed hydrogel is PVA / CMC / PPP5-MB.

[0061] Application Examples 2-3 and Comparative Application Example 1

[0062] This application example provides an application of hydrogels in the adsorption of cationic dyes in water. The only difference between this example and Application Example 1 is that the hydrogels PVA / CMC / PPP obtained in Example 2 are used respectively. 10 The hydrogel PVA / CMC / PPP obtained in Example 3 15 The PVA / CMC hydrogel obtained in Comparative Example 1 was used to replace the PVA / CMC / PPP5 hydrogel obtained in Example 1. The resulting hydrogels were PVA / CMC / PPP5 respectively. 10 -MB, PVA / CMC / PPP 15 -MB, PVA / CMC-MB. Everything else remains the same as in Application Example 1.

[0063] Performance testing:

[0064] (1) FTIR analysis

[0065] Infrared analysis was performed on the PVA / CMC / PPP5 hydrogel obtained in Example 1, the PVA / CMC hydrogel obtained in Comparative Example 1, and the PVA / CMC / PPP5-MB hydrogel after adsorption obtained in Application Example 1. The results are as follows: Figure 1 As shown.

[0066] For the PVA / CMC hydrogel obtained in Comparative Example 1, the infrared spectrum was observed in the range of 3050–3650 cm⁻¹. -1 There is a broadband peak at 2830-2980 cm⁻¹, which originates from the stretching vibration of the OH bond. -1 There is a broadband peak at 1045 cm⁻¹ originating from the C-H bond stretching vibration. -1 The peak at 1601 cm⁻¹ is related to the stretching vibration of the CO bond. -1 The strong absorption peak at 1430 cm⁻¹ is attributed to the symmetric stretching vibration of the carboxyl group. -1 This is due to the COC stretching vibration of polyvinyl alcohol and the asymmetric stretching vibration of the carboxyl group.

[0067] After joining PPP, at 1701 cm -1The characteristic peak of C=O stretching vibration appears at 1608 cm⁻¹; in addition, at 1608 cm⁻¹... -1 and 1508cm -1 Characteristic peaks were observed, which are caused by the C=C skeletal vibration of the benzene ring. These unique peaks indicate the successful preparation of the PVA / CMC / PPP hydrogel.

[0068] After the hydrogel adsorbed MB, it was at 1384 cm⁻¹ -1 A peak was observed at 3050–3650 cm⁻¹, corresponding to the symmetric deformation vibration of the methyl group; this specific peak is a characteristic peak of methylene blue. -1 The peak enhancement at [location] indicates that hydrogen bonding interactions occurred during adsorption. The peak of the C=O stretching vibration increased from 1701 cm⁻¹. -1 Moved to 1698cm -1 The increased intensity of the peak highlights the involvement of the carboxyl group in the adsorption of methylene blue. Furthermore, the vibrational peak of the benzene ring shifts from 1608 cm⁻¹. -1 Moved to 1597 cm -1 The presence of these characteristic peaks and their variations indicate that methylene blue is successfully adsorbed onto the hydrogel.

[0069] (2) TGA analysis

[0070] The hydrogels PVA / CMC / PPP5 and PVA / CMC / PPP obtained in Examples 1-3 and Comparative Example 1 10 PVA / CMC / PPP 15 TGA analysis was performed on PVA / CMC, and the results are as follows: Figure 2 As shown.

[0071] Depend on Figure 2 It can be seen that the hydrogel exhibits three weight loss plateaus: the first is due to the evaporation of the water of crystallization contained in the hydrogel, the second is due to the breakage of the (OH) side chains of PVA and CMC, and the third is due to the breakage of the CC backbone of PVA and CMC. The PVA / CMC / PPP hydrogel experiences a fourth weight loss, caused by the decomposition of benzene rings on components derived from pomegranate peel, such as pomegranate polyphenols. After soaking in PPP, the weight loss in the first and second stages of the hydrogel significantly decreased, while the temperature at which the third stage of weight loss occurred increased from 250℃ to 330℃, indicating that PPP can enhance the thermal stability of the hydrogel.

[0072] (3) SEM analysis

[0073] The hydrogels PVA / CMC / PPP5 and PVA / CMC / PPP obtained in Examples 1-3 and Comparative Example 1 10PVA / CMC / PPP 15 SEM analysis was performed on PVA / CMC, and the results are as follows: Figure 3 As shown.

[0074] Depend on Figure 3 It is evident that, compared to PVA / CMC, PVA / CMC / PPP hydrogel has a more complex pore structure. Furthermore, the higher the concentration of PPP in the soaking solution, the larger the pores become, indicating that soaking PPP has a positive effect on the pore structure of this hydrogel.

[0075] (4) XPS analysis

[0076] The hydrogels PVA / CMC / PPP5 and PVA / CMC / PPP obtained in Examples 1-3 and Comparative Example 1 10 PVA / CMC / PPP 15 XPS analysis was performed on PVA / CMC and the adsorbed hydrogel PVA / CMC / PPP5-MB obtained in Example 1. The C1s curve fitting results and O1s curve fitting results are as follows: Figure 4 As shown.

[0077] The C1s spectrum of PVA / CMC can be decomposed into three peaks: 287.47, 285.49, and 283.97 eV, corresponding to OC=O, CO, and CC / CC bonds, respectively. After soaking in PPP, the OC=O peak is enhanced, which is due to the presence of carboxyl groups in the pomegranate peel-derived component. After adsorption, the binding energy of the C=O bond decreases by 288.0 eV. In addition, due to the overlap between CN in the adsorbed MB and CO in PVA, the CO peak shifts towards the direction of decreasing binding energy (284.15 eV) and its intensity increases.

[0078] The O1s spectrum of PVA / CMC shows a single peak with a binding energy of 531.63 eV, corresponding to the OC=O peak. After soaking PPP, the O1s spectrum peak decomposes into three peaks: 531.56, 532.1, and 532.89 eV, representing the CO and C-OH peaks in the polyphenol structure, indicating that PPP has successfully incorporated into the hydrogel. After adsorption, all three peaks shift towards lower binding energies (531.39, 532.0, and 532.61 eV), indicating their participation in the methylene blue adsorption process.

[0079] (5) Adsorption kinetics analysis

[0080] Adsorption solutions from Application Examples 1-3 and Comparative Application Example 1 were taken at regular intervals within 0-24 hours. The absorbance of the solutions was measured using ultraviolet-visible spectrophotometry, and kinetic curves were plotted. The results are as follows: Figure 5 As shown.

[0081] The results showed that the hydrogels of Examples 1-3 and Comparative Example 1 could almost reach adsorption saturation within 750 min. It was also evident that the removal rate of methylene blue by the hydrogels obtained after soaking pomegranate peel powder in water significantly increased.

[0082] (6) Analysis of the effect of initial MB concentration on adsorption capacity and removal rate

[0083] Accurately weigh multiple 0.25 g samples of hydrogel from Examples 1-3 and Comparative Example 1, and place them in 25 mL of methylene blue solutions with initial concentrations of 10, 30, 50, 70, and 100 mg / L, respectively. Adsorption was carried out in a constant-temperature water bath at room temperature with shaking for 24 hours. The absorbance of the solutions before and after adsorption was measured using UV-Vis spectrophotometry. The adsorption capacity and removal rate were calculated based on the data. The adsorption capacity represents the mass of methylene blue that can be adsorbed per g of hydrogel sample, expressed in mg / g. The adsorption capacity results are shown below. Figure 6 As shown, the removal rate results Figure 7 As shown.

[0084] according to Figure 6 It can be seen that after soaking in PPP, the adsorption capacity of the hydrogel for methylene blue increases significantly with the increase of the initial concentration of methylene blue. However, for the PVA / CMC hydrogel that has not been soaked in PPP, the increase in adsorption capacity slows down when the initial concentration of methylene blue exceeds 50 mg / L.

[0085] according to Figure 7 It can be seen that after soaking in PPP, the removal rate of methylene blue by the hydrogel does not change significantly with the increase of the initial concentration of methylene blue, and remains above 80%. However, the removal rate of the PVA / CMC hydrogel without PPP soaking decreases with the increase of the initial concentration of methylene blue. This indicates that after soaking in PPP, the number of sites on the hydrogel available for adsorbing methylene blue increases significantly, and the adsorption performance is significantly improved.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading this application specification, they can still modify or make equivalent substitutions to the specific implementation of the present invention, but these modifications or changes do not depart from the protection scope of the pending claims of the present invention.

Claims

1. A modified polyvinyl alcohol-sodium carboxymethyl cellulose hydrogel, characterized by, A matrix gel formed by polyvinyl alcohol and sodium carboxymethyl cellulose, and a Punica granatum L. derived component incorporated into the matrix gel.

2. The modified polyvinyl alcohol-sodium carboxymethyl cellulose hydrogel according to claim 1, characterized in that, The preparation method of the modified polyvinyl alcohol-sodium carboxymethyl cellulose hydrogel comprises the following steps: soaking the matrix gel in an aqueous dispersion of Punica granatum L. powder to obtain the modified polyvinyl alcohol-sodium carboxymethyl cellulose hydrogel.

3. The non-modified polyvinyl alcohol-sodium carboxymethyl cellulose hydrogel according to claim 2, characterized in that, The mass concentration of the Punica granatum L. powder in the aqueous dispersion is 1-30 wt%.

4. The modified polyvinyl alcohol-sodium carboxymethyl cellulose hydrogel according to claim 1, wherein, The mass ratio of the polyvinyl alcohol to the sodium carboxymethyl cellulose in the raw materials for forming the matrix gel is 4-12:

1.

5. The method for preparing the modified polyvinyl alcohol-sodium carboxymethyl cellulose hydrogel according to any one of claims 1 to 4, characterized in that, The preparation method comprises the following steps: S1. The polyvinyl alcohol and the sodium carboxymethyl cellulose form a matrix gel; S2. The matrix gel is soaked in an aqueous dispersion of Punica granatum L. powder to obtain the modified polyvinyl alcohol-sodium carboxymethyl cellulose hydrogel.

6. The preparation method according to claim 5, characterized in that, The S1 comprises the following steps: S11. The polyvinyl alcohol is mixed with water and stirred until completely dissolved to obtain a polyvinyl alcohol solution; S12. The sodium carboxymethyl cellulose is added to the polyvinyl alcohol solution and stirred until completely dissolved to obtain a matrix solution; S13. The matrix solution is treated by a freeze-thaw process to obtain the matrix gel.

7. The preparation method according to claim 6, characterized in that, In S13, the freeze-thaw process treatment step is repeated 2-5 times; And / or, the freezing temperature is -30-0℃; And / or, the thawing temperature is 10-40℃.

8. The preparation method according to claim 5, characterized in that, In S2, the soaking temperature is 25-45℃; And / or, the soaking time is 12-36 h; And / or, after the soaking step, a step of washing with water is further included.

9. The modified polyvinyl alcohol-sodium carboxymethyl cellulose hydrogel according to any one of claims 1-4 or the modified polyvinyl alcohol-sodium carboxymethyl cellulose hydrogel obtained by the preparation method according to any one of claims 5-8, for use in adsorbing cationic dyes in water.

10. Use according to claim 9, characterized in that, The cationic dyes include methylene blue; and / or, the concentration of the cationic dyes in the water is 0.1-200 mg / L.

Images