Preparation method and application of modified carboxymethyl cellulose
By using melamine-modified carboxymethyl cellulose in aqueous solution, the problem of poor cellulose modification effect in soil remediation was solved, achieving efficient reduction of mercury flux at the soil-air interface and environmentally friendly mercury ion adsorption effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GUIZHOU NORMAL UNIVERSITY
- Filing Date
- 2023-11-10
- Publication Date
- 2026-06-23
Smart Images
Figure CN117417460B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of environmental remediation and fixation technology. Background Technology
[0002] In the current field of soil heavy metal pollution remediation, the most widely used and mature remediation technologies include thermal desorption, leaching, and electrokinetic remediation. However, thermal desorption requires soil excavation and transportation, disrupts soil structure, is costly, and is unsuitable for treating large areas of contaminated soil. Leaching also disrupts soil structure, has high requirements for contaminated soil, and is not suitable for soils with high clay content. While various remediation technologies can achieve different treatment effects, they all have drawbacks such as producing byproducts and high costs; therefore, there is a need to find better remediation methods.
[0003] In recent years, biosorbents have gained favor in sustainable development due to their low toxicity, wide availability, and low carbon footprint, and are widely used in environmental remediation. Cellulose is the most abundant, renewable, and environmentally friendly biopolymer in nature. Its main structural unit is β-D-glucopyranosyl, a linear polymer formed by β-1,4 glycosidic bonds between units. Due to its excellent mechanical properties, ease of surface modification, ease of assembly and composite, and ease of device fabrication, it has become one of the most promising sustainable adsorbent materials.
[0004] Cellulose exhibits relatively strong hydrogen bonding interactions between the hydroxyl groups of adjacent molecules. This supramolecular structure endows cellulose with properties such as hydrophilicity, chirality, and durability. However, cellulose itself has limited stability, surface area, and active sites, and can only perform coordination adsorption via its surface hydroxyl groups, making it unsuitable for adsorbing heavy metal ions, thus limiting its adsorption capacity and efficiency. Therefore, cellulose can be modified to obtain sufficient structure and properties to improve its ability to remove heavy metal ion pollutants.
[0005] Modified cellulose has demonstrated excellent performance in effectively controlling and treating pollution. However, existing modified cellulose applications are mostly focused on the removal of heavy metal pollutants from aquatic environments, with very few applications in soil remediation research, and the removal effects in soil remediation are unsatisfactory. If it could be adapted to more complex soil remediation, its market application potential would be enormous. Furthermore, current cellulose modification methods mainly include esterification, acetylation, and silane methods. However, these chemical modification methods mostly involve reactions in non-aqueous organic solvent systems, which are time-consuming and therefore have certain limitations. Summary of the Invention
[0006] The present invention aims to address the problems of poor removal efficiency of existing modified cellulose in soil remediation and the long reaction time of existing cellulose modification methods carried out in non-aqueous organic solvent systems, and thus provides a method for preparing modified carboxymethyl cellulose and its application.
[0007] A method for preparing modified carboxymethyl cellulose, comprising the following steps:
[0008] Carboxymethyl cellulose was dissolved in pure water, and then N-hydroxysuccinimide and melamine were added sequentially to dissolve the cellulose. The pH was adjusted to 7.5-8, and then EDC·HCl aqueous solution was added. The mixture was stirred at room temperature, and finally washed and freeze-dried to obtain modified carboxymethyl cellulose.
[0009] The mass ratio of carboxymethyl cellulose to N-hydroxysuccinimide is 1:(1.3-1.6); the mass ratio of carboxymethyl cellulose to melamine is 1:(0.3-0.6); the mass ratio of carboxymethyl cellulose to 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride in EDC·HCl aqueous solution is 1:(1.3-1.6).
[0010] Application: It is used to control mercury release from soil.
[0011] The beneficial effects of this invention are:
[0012] This invention uses melamine, an environmentally friendly modifier, to modify carboxymethyl cellulose in order to improve its resistance to Hg. 2+ It has excellent adsorption capacity, and the generated CMC-M is environmentally friendly. In Hg 2+ In the presence of certain conditions, the -NH2 and other groups on the surface of CMC-M can react with Hg. 2+ This process combines with melamine, thereby reducing the concentration of mercury ions. Melamine modification of carboxymethyl cellulose (CMC) using a solution stirring method avoids the drawbacks of conventional modification methods, such as the time-consuming and solvent-dependent processes of esterification and acetylation. Furthermore, when the synthesized CMC-M was added to soil to simulate a greenhouse environment, it was found to significantly reduce the mercury flux at the soil-air interface compared to the blank control group, without causing secondary pollution to the environment. The modification not only increases the number of groups on the surface of CMC that can adsorb mercury ions but also alters the hydrophobicity of CMC, making it more readily adsorbable of mercury ions. Attached Figure Description
[0013] Figure 1 The synthetic route for the modified carboxymethyl cellulose of this invention is as follows;
[0014] Figure 2 The images show the infrared spectra of carboxymethyl cellulose before and after modification. 1 represents the modified carboxymethyl cellulose prepared in Example 1, and 2 represents the unmodified carboxymethyl cellulose.
[0015] Figure 3 The XPS spectra of unmodified carboxymethyl cellulose are shown in (a) for the full spectrum, (b) for the C spectrum, and (c) for the O spectrum.
[0016] Figure 4 The XPS spectra of the modified carboxymethyl cellulose prepared in Example 1 are shown in (a) as the full spectrum, (b) as the C spectrum, (c) as the O spectrum, and (d) as the N spectrum.
[0017] Figure 5 SEM-EDC spectra of unmodified carboxymethyl cellulose: (a) SEM, (b) EDC.
[0018] Figure 6 The images show the SEM-EDC spectra of the modified carboxymethyl cellulose prepared in Example 1: (a) SEM, (b) EDC.
[0019] Figure 7 Images of unmodified carboxymethyl cellulose and modified carboxymethyl cellulose prepared in Example 1 in water. Detailed Implementation
[0020] Specific implementation method one: Combining Figure 1 Specifically, this embodiment describes a method for preparing modified carboxymethyl cellulose, which is carried out according to the following steps:
[0021] Carboxymethyl cellulose was dissolved in pure water, and then N-hydroxysuccinimide and melamine were added sequentially to dissolve the cellulose. The pH was adjusted to 7.5-8, and then EDC·HCl aqueous solution was added. The mixture was stirred at room temperature, and finally washed and freeze-dried to obtain modified carboxymethyl cellulose.
[0022] The mass ratio of carboxymethyl cellulose to N-hydroxysuccinimide is 1:(1.3-1.6); the mass ratio of carboxymethyl cellulose to melamine is 1:(0.3-0.6); the mass ratio of carboxymethyl cellulose to 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride in EDC·HCl aqueous solution is 1:(1.3-1.6).
[0023] In this specific embodiment, stirring is carried out at room temperature to ensure that melamine has been grafted into the carboxymethyl cellulose molecular chain structure. If the time is too short, the melamine grafting will be incomplete, and if the time is too long, resources will be wasted.
[0024] In this specific embodiment, washing with anhydrous ethanol is used to remove excess melamine.
[0025] In this specific embodiment, the modified carboxymethyl cellulose (CMC-M) is stored in a sealed bag: CMC-M has a certain degree of water absorption and needs to be stored in a sealed bag.
[0026] The beneficial effects of this embodiment are:
[0027] This embodiment uses melamine, an environmentally friendly modifier, to modify carboxymethyl cellulose in order to improve its resistance to Hg.2+ It has excellent adsorption capacity, and the generated CMC-M is environmentally friendly. In Hg 2+ In the presence of certain conditions, the -NH2 and other groups on the surface of CMC-M can react with Hg. 2+ This process combines with melamine, thereby reducing the concentration of mercury ions. Melamine modification of carboxymethyl cellulose (CMC) using a solution stirring method avoids the drawbacks of conventional modification methods, such as the time-consuming and solvent-dependent processes of esterification and acetylation. Furthermore, when the synthesized CMC-M was added to soil to simulate a greenhouse environment, it was found to significantly reduce the mercury flux at the soil-air interface compared to the blank control group, without causing secondary pollution to the environment. The modification not only increases the number of groups on the surface of CMC that can adsorb mercury ions but also alters the hydrophobicity of CMC, making it more readily adsorbable of mercury ions.
[0028] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the concentration of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride in the EDC·HCl aqueous solution is 48 mg / mL to 52 mg / mL. Everything else is the same as in Specific Implementation Method One.
[0029] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the mass ratio of carboxymethyl cellulose to pure water is 1g:(135-150)mL. Everything else is the same as in Specific Implementation Method One or Two.
[0030] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the pH is adjusted to 7.5 to 8 using HCl with a concentration of 0.7 mol / L to 1.3 mol / L and NaOH with a concentration of 0.7 mol / L to 1.3 mol / L. Everything else is the same as in Specific Implementation Methods One to Three.
[0031] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the stirring at room temperature specifically refers to stirring at room temperature and a rotation speed of 180 r / min to 500 r / min for 12 h to 24 h. Everything else is the same as in Specific Implementation Methods One to Four.
[0032] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the freeze-drying is specifically carried out at a temperature of -60℃ to -70℃ for 12 to 24 hours. Everything else is the same as Specific Implementation Methods One to Five.
[0033] Specific implementation method seven: The application of modified carboxymethyl cellulose in this implementation method is used to control mercury release from soil.
[0034] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Method Seven in that modified carboxymethyl cellulose is used to control mercury release from the soil, specifically by following these steps:
[0035] Modified carboxymethyl cellulose was mixed with water to obtain a modified carboxymethyl cellulose solution. This solution was then mixed with mercury-containing soil and treated for 5 to 60 days at a temperature of 20°C–30°C and a humidity of 50%–70%. Other procedures were the same as in Specific Implementation Method Seven.
[0036] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Method Seven or Eight in that the mass ratio of modified carboxymethyl cellulose to mercury-containing soil in the modified carboxymethyl cellulose solution is (0.5-1.2):100. Everything else is the same as in Specific Implementation Method Seven or Eight.
[0037] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods Seven to Nine in that the concentration of the modified carboxymethyl cellulose solution is 20 g / L to 30 g / L; and the mercury content in the mercury-containing soil is 45 mg / kg to 55 mg / kg. Everything else is the same as in Specific Implementation Methods Seven to Nine.
[0038] The beneficial effects of the present invention are verified using the following embodiments:
[0039] Example 1:
[0040] A method for preparing modified carboxymethyl cellulose, comprising the following steps:
[0041] 70 mg of carboxymethyl cellulose (CMC) was dissolved in 10 mL of pure water, and then 100 mg of N-hydroxysuccinimide (NHS) and 30 mg of melamine were added sequentially to dissolve the cellulose. The pH was adjusted to 7.55 using 1 mol / L HCl and 1 mol / L NaOH. Then, 2 mL of EDC·HCl aqueous solution was added, and the mixture was stirred for 12 h at room temperature and 240 r / min. Finally, the mixture was washed with anhydrous ethanol and freeze-dried to obtain modified carboxymethyl cellulose (CMC-M).
[0042] The concentration of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride in the EDC·HCl aqueous solution is 50 mg / mL;
[0043] The freeze-drying process specifically involves freeze-drying at a temperature of -65°C for 12 hours.
[0044] In this embodiment, the modified carboxymethyl cellulose is stored in a sealed bag.
[0045] All aqueous solutions used in the synthesis process of this embodiment are pure water.
[0046] Figure 2 The figures show the infrared spectra of carboxymethyl cellulose (CMC) before and after modification. 1 represents the modified CMC prepared in Example 1, and 2 represents the unmodified CMC. As shown in the figure, the wavenumber of CMC in the infrared spectrum is 1602 cm⁻¹. -1 1417cm -1 These represent the antisymmetric and symmetric stretching vibration peaks of the -COO- group in the carboxymethyl cellulose structure, respectively. The wavenumber in the CMC-M infrared spectrum is 1630 cm⁻¹. -1 The absorption peak at [value] corresponds to the carbonyl stretching vibration peak of the amide. The wavenumber is 1556 cm⁻¹. -1 1436cm -1 815cm -1 The absorption peak at this point is attributed to the characteristic peak of the triazine ring in melamine. The wavenumber is 1021 cm⁻¹. -1 The absorption peak at this location corresponds to the -CO- stretching vibration peak of the pyranose ring in carboxymethyl cellulose. The change in the infrared spectrum indicates that the modification was successful.
[0047] Figure 3 The XPS spectra of unmodified carboxymethyl cellulose are shown in (a) for the full spectrum, (b) for the C spectrum, and (c) for the O spectrum. Figure 4 The XPS spectra of the modified carboxymethyl cellulose prepared in Example 1 are shown in (a) as the full spectrum, (b) as the C spectrum, (c) as the O spectrum, and (d) as the N spectrum. The full spectrum and elemental composition analysis show that the N content of the modified CMC-M increased from 0% to 14.65%, which is due to the contribution of melamine, indicating that the material composite was successfully completed. Figure 4 The high-resolution XPS spectra showed three peaks at C1s, corresponding to the sp1 (CC, 284.8 eV), carbon-oxygen bond (CO, 287.29 eV), and amide bond (C=ON, 288.32 eV). The O1s peaks corresponded to the carbonyl group (C=O, 530.98 eV) and hydroxyl group (-OH, 532.65 eV) of the amide. The N1s peaks corresponded to the amide group (CONH, 398.89 eV) and imine bond (C=N, 401.36 eV), indicating that melamine was successfully grafted onto the surface of CMC.
[0048] According to SEM-EDS testing, Figure 5 SEM-EDC spectra of unmodified carboxymethyl cellulose: (a) SEM, (b) EDC. Figure 6The images show the SEM-EDC spectra of the modified carboxymethyl cellulose prepared in Example 1: (a) SEM, (b) EDC. Before modification, the weight percentages of CMC elements were C: 49.62%, N: 1.08%, and O: 49.3%; after modification, the weight percentages of CMC-M were C: 39.25%, N: 34.21%, and O: 26.54%. It can be seen that the N content of the modified carboxymethyl cellulose increased from 1.08% to 34.2%, and Hg... 2+ The nitrogen content mainly binds to the -NH2 functional groups in melamine, and the increase in nitrogen content is primarily a result of melamine grafting. This indicates that the modification can improve the adsorption capacity of carboxymethyl cellulose (CMC), thereby enhancing its removal efficiency of Hg in water and its fixation capacity of Hg in soil. SEM analysis revealed significant changes in the surface morphology of the CMC sample before and after modification, with an increased specific surface area. A larger specific surface area corresponds to higher surface energy, resulting in not only stronger physical adsorption capacity but also an increase in adsorption sites, thus enhancing adsorption capacity.
[0049] Compared to carboxymethyl cellulose, modified carboxymethyl cellulose exhibits increased hydrophobicity, as shown in Figure 7. Figure 7 Physical images of unmodified carboxymethyl cellulose and modified carboxymethyl cellulose prepared in Example 1 in water: 0.005g of modified carboxymethyl cellulose or unmodified carboxymethyl cellulose prepared in Example 1 was added to 20mL of water. The modified carboxymethyl cellulose prepared in Example 1 showed sedimentation in water, while the unmodified carboxymethyl cellulose formed a stable suspension in water.
[0050] The modified carboxymethyl cellulose prepared in Example 1 has potential applications in areas such as soil pollutant immobilization and heavy metal removal from water.
[0051] ① Fixing soil pollutants: Experimental group: The modified carboxymethyl cellulose prepared in Example 1 was mixed with water to obtain a modified carboxymethyl cellulose solution. 8 kg of mercury-containing soil was placed in a greenhouse, and then 80 g of the modified carboxymethyl cellulose solution was mixed with 8 kg of mercury-containing soil. The mixture was treated for 60 days at a temperature of 20℃~30℃ and a humidity of 50%~70%. The mass ratio of modified carboxymethyl cellulose to mercury-containing soil in the modified carboxymethyl cellulose solution was 1:100. The concentration of the modified carboxymethyl cellulose solution was 25 g / L. The mercury content in the mercury-containing soil was 50 mg / kg.
[0052] Blank control group: 8 kg (50 mg / kg) of mercury-contaminated soil.
[0053] Experimental results showed that the addition of CMC-M reduced the mercury release flux at the soil-air interface, compared to 35.140 ng·m⁻² in the control group. 2 ·h-1 In comparison, CMC-M decreased to 12.309 ng·m 2 ·h -1 The above experiments demonstrate that CMC-M can be used in mercury-contaminated soil to reduce the mercury flux released from the soil-air interface.
[0054] ② The adsorption experiment of the water-soil mixture system showed that: In the experimental group, 0.005g of the modified carboxymethyl cellulose prepared in Example 1 was mixed with 0.005g of soil to obtain soil containing modified carboxymethyl cellulose. 0.01g of the soil containing modified carboxymethyl cellulose was added to 20mL of mercury-containing water. The adsorption was carried out for 2h under the conditions of room temperature, shaking frequency of 60r / min and pH=6. The initial concentration of mercury in the mercury-containing water was 200mg / L.
[0055] Control group: 0.01g of soil without CMC-M was added to 20mL of mercury-containing water and adsorbed for 2h under the conditions of room temperature, shaking frequency of 60r / min and pH=6; the initial concentration of mercury in the mercury-containing water was 200mg / L.
[0056] Compared to soil with the same amount of CMC-M added, the adsorption capacity of soil without CMC-M was 142.650 mg / g. -1 Increased to 248.630 mg / g -1 The adsorption capacity increased by 1.74 times, indicating that the addition of CMC-M can improve the soil's adsorption performance for mercury ions.
Claims
1. A method for preparing modified carboxymethyl cellulose, characterized in that... It is done in the following steps: 70 mg of carboxymethyl cellulose was dissolved in 10 mL of pure water, and then 100 mg of N-hydroxysuccinimide and 30 mg of melamine were added sequentially to dissolve them. The pH was adjusted to 7.55 using 1 mol / L HCl and 1 mol / L NaOH. Then, 2 mL of EDC•HCl aqueous solution was added, and the mixture was stirred for 12 h at room temperature and 240 r / min. Finally, the mixture was washed with anhydrous ethanol and freeze-dried to obtain modified carboxymethyl cellulose. The concentration of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride in the EDC•HCl aqueous solution is 50 mg / mL; The freeze-drying process specifically involves freeze-drying at a temperature of -65°C for 12 hours. The addition of the modified carboxymethyl cellulose reduced the mercury release flux at the soil-air interface to 12.309 ng·m 2 ·h -1 ; In a water-soil mixture system with added modified carboxymethyl cellulose, the adsorption capacity was 248.630 mg.g. -1 .