A porous material of epoxidized cellulose for preparing an adsorbent

Abstract

The application provides an epoxidized cellulose porous material for preparing an adsorbent, belongs to the field of environment and chemical materials, and particularly relates to a multifunctional platform material preparation method and application for promoting the preparation of the adsorbent. The epoxidized cellulose porous material is prepared by an epoxy chain growth method, modified microcrystalline cellulose with bromoisobutyryl bromide is selected as an epoxy chain growth site, and glycidyl methacrylate is selected as an epoxy chain, and an atom transfer radical polymerization method is adopted. The epoxidized cellulose porous material has rich epoxy groups and a porous structure, and can be applied to the preparation platform of the adsorbent to promote the treatment of polluted wastewater.

Description

Technical Field

[0001] This invention relates to a process for preparing epoxidized cellulose porous materials and adsorbents, and more particularly to a method and product for preparing adsorbents by grafting epoxy chains onto cellulose as a new platform, belonging to the field of environmental and chemical technology. Background Technology

[0002] Due to its complex composition and environmental durability and biotoxicity, the direct discharge of dyeing and printing wastewater into the natural environment poses a significant threat to human health and severely impacts ecosystems. Among various technologies for treating dyeing and printing wastewater, dye degradation and adsorption are commonly used. However, with the development of dyeing and printing technology, organic synthetic dyes are becoming increasingly difficult to completely degrade through biodegradation, photodegradation, and oxidative degradation. Incompletely degraded organic synthetic dyes may release more harmful substances, leading to secondary pollution. Adsorption, due to its renewability, simplicity, flexibility, low cost, high flow rate, applicability to the removal of all types of organic compounds, and excellent removal of various stable organic synthetic dyes, is considered one of the most efficient technologies for dye removal. However, developing low-cost, environmentally friendly adsorbents has become a new challenge.

[0003] Natural, renewable, biodegradable, chemically stable, and reusable biomaterials have enormous application potential in the treatment of dyeing and printing wastewater. Natural cellulose is the most abundant, renewable, non-toxic, and biodegradable polysaccharide in nature. Its abundant hydroxyl groups allow for the enhancement of its overall performance through various chemical modification methods and the introduction of functional groups with different characteristics, thus holding great potential in the design and manufacture of adsorbents. However, single-stage modification increases the application cost of cellulose adsorbents. Grafting high-density side chains with multifunctional functional groups onto the cellulose backbone allows for the simultaneous preparation of multiple adsorbents with a single modification. The high reactivity of epoxy groups enables them to interact with most functional groups, facilitating the preparation of adsorbents.

[0004] Therefore, this invention utilizes atom transfer radical polymerization to prepare epoxidized cellulose porous materials, specifically glycidyl methacrylate with epoxy groups on the cellulose main chain, to achieve the preparation of an adsorbent platform. Modification of cellulose with bromoisobutyryl bromide breaks the hydrogen bonds of cellulose, forming a porous structure and simultaneously providing reaction sites for the growth of epoxy chains. The growth of glycidyl methacrylate on cellulose further enhances the porous structure and endows the cellulose with abundant epoxy groups. Two adsorbents were prepared, and adsorption experiments were conducted. Summary of the Invention

[0005] In view of the above-mentioned technical problems, the purpose of this invention is to provide a method for preparing an epoxidized porous material. This material possesses excellent porous structure and epoxy chains, which is beneficial for the rapid preparation of adsorbents. The method includes the following steps:

[0006] (1) Preparation of MCC-BiBB: Microcrystalline cellulose was dissolved in a binary dissolution system of 1-butyl-3-methylimidazolium chloride and N,N-dimethylformamide;

[0007] (2) The reaction system in (1) was placed under an ice-water bath. Bromoisobutyryl bromide was added to the system by titration and reacted at room temperature for 10 hours and 16 hours. Excess impurities were removed by dialysis. The resulting solution was freeze-dried to obtain the modified cellulose, named MCC-BiBB.

[0008] (3) Preparation of MCC-g-PGMA: The MCC-BiBB described in step (2) was dissolved in N,N-dimethylformamide as an initiator, and glycidyl methacrylate and cuprous bromide catalyst were added simultaneously for three freeze-thaw cycles. Then, N,N,N′,N″,N″-pentamethyldiethylenetriamine was added for another three freeze-thaw cycles. Unreacted monomers and impurities were removed by dialysis to obtain the target product, named MCC-g. - PGMA;

[0009] (4) MCC-g - Preparation of PGMA-TA: MCC-g-PGMA and dimethyl sulfoxide were added to a reaction tube, followed by tannic acid and the catalyst triphenylphosphine. After three freeze-thaw cycles to remove air, the mixture was dialyzed to remove unreacted substances and dimethyl sulfoxide. Finally, the product was freeze-dried.

[0010] (5) Preparation of MCC-g-PGMA-Lys: MCC-g-PGMA, dimethyl sulfoxide, and 1-butyl-3-methylimidazolium chloride were added to a round-bottom flask. The reaction mixture was stirred at 50°C for 1 h to completely dissolve the reactants. Then, L-lysine was added to the flask. Finally, the reaction mixture was transferred to room temperature and reacted for 24 h. After the reaction was completed, the mixture was dialyzed for 48 h to remove unreacted lysine and dimethyl sulfoxide solvent. Finally, the product was freeze-dried for 48 h.

[0011] In step (1), the reaction dissolution temperature is 90-100℃, and the mass ratio of the microcrystalline cellulose, 1-butyl-3-methylimidazolium chloride and N,N-dimethylformamide is 1:20:9.44.

[0012] In step (2), the molar ratio of cellulose to bromoisobutyryl bromide is 1:3, 1:5, and 1:7, and the reaction time is 10 hours and 16 hours, respectively. Preferably, the molar ratio is 1:7 and the reaction time is 16 hours.

[0013] In step (3), the feed ratios of glycidyl methacrylate, MCC-BiBB, and cuprous bromide are 100:1:1, 200:1:1, and 300:1:1. The solvent is 15 mL of N,N-dimethylformamide, and 0.21 mmol of N,N,N′,N″N″-pentamethyldiethylenetriamine. The reaction environment is an N2 atmosphere, and the reaction temperature is 70°C. Preferably, the feed ratio is 300:1:1.

[0014] In step (4), the mass ratio of MCC-g-PGMA to tannic acid is 1:1, 1:2, and 1:4, and the mass of the catalyst is 7.5 mg. Preferably, the ratio is 1:2.

[0015] In step (5), the mass ratio of MCC-g-PGMA to L-lysine is 10:1, 10:2.5, and 10:4. Preferably, the ratio is 10:2.5.

[0016] In this invention, the epoxidized cellulose porous material can be used to prepare a variety of adsorbents through the interaction between epoxy and adsorption groups. MCC-g-PGMA-TA and MCC-g-PGMA-Lys prepared based on the epoxidized cellulose porous material of this invention can be used to treat anionic dyes and cations in dyeing and printing wastewater, and promote water purification.

[0017] The epoxidized porous material prepared in this invention is produced by homogeneous modification of microcrystalline cellulose with bromoisobutyryl bromine, providing more reaction sites compared to conventional graft modification. Atom transfer radical polymerization is used to grow epoxy chains at these reaction sites as an epoxy platform. The high reactivity of epoxy is utilized to prepare various adsorbents, effectively reducing adsorbent preparation costs and simplifying the preparation process. Adsorbents prepared from epoxidized cellulose porous materials can effectively adsorb dyes, achieving the purification of dyeing and printing wastewater. Attached Figure Description

[0018] Figure 1 The preparation process of epoxidized cellulose porous materials can be used as an abstract figure.

[0019] Figure 2 A shows the SEM images of the porous material and the adsorbent. Figure 2 B is the aperture distribution diagram. Figure 2 C represents the N2 adsorption-desorption diagram. This demonstrates that the epoxidized cellulose material possesses a rich porous structure.

[0020] Figure 3 A-3B represent the adsorption of methylene blue and methyl orange by MCC-g-PGMA-Lys at different pH values ​​and their zeta potentials, respectively. Figure 3C-3D represent the adsorption and zeta potential of MCC-g-PGMA-TA for methylene blue, methyl orange, and rhodamine B at different pH values.

[0021] Figure 4 A-4C-4E-4G represents the adsorption kinetics of MCC-g-PGMA-Lys. Figure 4 B-4D-4F-4H represents the adsorption kinetics of MCC-g-PGMA-TA.

[0022] Figure 5 A-5B is the adsorption cycle diagram of MCC-g-PGMA-Lys. Figure 5 C-5D is the adsorption cycle diagram of MCC-g-PGMA-TA. Detailed Implementation

[0023] To clearly illustrate the technical features of this solution, the present invention will be further described in detail below with reference to the specific embodiments and accompanying drawings.

[0024] Example 1:

[0025] Preparation method of MCC-BiBB:

[0026] Step 1: Weigh 1.0 g of microcrystalline cellulose and 20.0 g of 1-butyl-3-methylimidazolium chloride into a round-bottom flask, then add 10.0 mL of N,N-dimethylformamide solution. Stir the mixture at 90 °C until completely dissolved. Then transfer the reaction mixture to an ice-water bath and stir for 20 min. Subsequently, add 2.3 mL of bromoisobutyryl bromide to the flask using a constant-pressure dropping method. Finally, stir the mixture below 0 °C for 30 min, and then continue the reaction at room temperature for 16 h. After the reaction is complete, precipitate with deionized water and wash several times to obtain a white flocculent product. Freeze-dry the product for 24 h to obtain the reaction product, which is named MCC-BiBB.

[0027] Step 2: The preparation method is the same as in Step 1, except that the volume of bromoisobutyryl bromide added is 3.24 mL;

[0028] Step 3: The preparation method is the same as in Step 1, except that the volume of bromoisobutyryl bromide added is 5.3 mL;

[0029] Example 2:

[0030] Preparation method of MCC-g-PGMA:

[0031] Step 1: Under a nitrogen atmosphere, 63.8 mg of MCC-BiBB as the initiator, 30.4 mg of CuBr as the catalyst, and 2.6 mL of glycidyl methacrylate were simultaneously dissolved in 15.0 mL of N,N-dimethylformamide. The solution was then added to a 50 mL Schlenk reaction tube. After three freeze-thaw cycles, 44.20 μL of N,N,N′,N″,N″-pentamethyldiethylenetriamine dissolved in 0.8 mL of N,N-dimethylformamide was injected into the reaction tube. After three freeze-thaw cycles, the solution was stirred at 70 °C for 1 h, and then exposed to air to terminate the reaction. The reaction mixture was then poured into a large amount of deionized water to precipitate the product, and the precipitate was soaked in sufficient acetone for 12 h to remove unreacted monomers. Finally, the precipitate was dialyzed in deionized water for 24 h, and the dialysate was freeze-dried to obtain the target product.

[0032] Step 2: The preparation method is similar to Step 1, but the volume of glycidyl methacrylate added is 5.2 mL;

[0033] Step 3: The preparation method is similar to Step 2, with 7.8 mL of glycidyl methacrylate added.

[0034] Example 3:

[0035] Preparation method of MCC-g-PGMA-TA:

[0036] Step 1: Add 0.5 g of MCC-g-PGMA and 15.0 mL of dimethyl sulfoxide to a 50 mL Schlenk reaction tube, then add 0.5 g of tannic acid and 7.5 mg of triphenylphosphine catalyst to the reaction tube. After three freeze-thaw cycles to remove air, stir the solution at 80 °C for 12 h, then expose it to air to terminate the reaction. Dialyze the solution in deionized water for 48 h using a dialysis bag to remove unreacted substances and dimethyl sulfoxide solvent. Finally, freeze-dry the product for 48 h and name it MCC-g-PGMA-TA.

[0037] Example 4:

[0038] Preparation method of MCC-g-PGMA-Lys:

[0039] Step 1: Add 1.0 g of MCC-g-PGMA, 15.0 mL of dimethyl sulfoxide, and 10.0 g of 1-butyl-3-methylimidazolium chloride to a 50 mL round-bottom flask. Stir the reaction mixture at 50 °C for 1 h to completely dissolve the reactants. Then add 0.1 g of L-lysine to the flask. Finally, transfer the reaction mixture to room temperature and react for 24 h. After the reaction is complete, dialyze the reaction solution in deionized water for 48 h using a dialysis bag to remove unreacted Lys and dimethyl sulfoxide solvent. Finally, freeze-dry the product for 48 h and name it MCC-g-PGMA-Lys.

[0040] Example 5:

[0041] Microstructure and pore size distribution testing, adsorption testing at different pH values, adsorption kinetics studies, and adsorption cycle studies:

[0042] (1) SEM and BET testing

[0043] The microstructure of the samples was observed using scanning electron microscopy (SEM). The SEM test voltage was 10 kV, and the sample was uniformly dispersed in powder form on a conductive adhesive. Gold was sputtered onto the sample stage for 1 min using an ion sputtering instrument. The specific surface area and pore size of the prepared samples were measured using an automated physicochemical adsorption analyzer (Autosorb-iQ-C), with N2 as the adsorption / desorption gas. The specific surface area was determined according to the standard Brunauer-Emmett-Teller (BET) method, and the average pore size was determined directly from the adsorption isotherm using the Barrett-Joyner-Halenda (BJH) method.

[0044] Figure 2 Image A shows the microstructure of the porous material and two adsorbents. Microcrystalline cellulose exhibits a relatively smooth and dense structure, without any observed porous structure. After epoxidation grafting, a porous structure appears; the higher the grafting ratio, the more pronounced the porous structure. The adsorbent prepared from the porous material also possesses a porous structure. The pore size distribution of the porous material is consistent with the SEM scan results.

[0045] (2) Adsorption test at different pH values

[0046] The effects of pH on the adsorption of MB, RhB, and MO dyes by MCC-g-PGMA-TA were investigated within a pH range of 2-12. The effects of pH on the adsorption of MB and MO dyes by MCC-g-PGMA-Lys were also investigated. The initial concentrations of MB and MO were 200 mg / L, and RhB was 150 mg / L.

[0047] Figure 3A indicates that the optimal pH for MCC-g-PGMA-Lys adsorption of MB is 12, with an adsorption capacity of 425.83 mg / g. The optimal pH for MO is 3.5, with an adsorption capacity of 480.70 mg / g and an isoelectric point potential of 7.05. The optimal pH for MCC-g-PGMA-TA adsorption of cationic dyes MB and Rh B is 10, with adsorption capacities of 191.30 mg / g and 123.70 mg / g, respectively. The zeta potential decreases with increasing pH.

[0048] (3) Adsorption kinetics study

[0049] The equilibrium time and adsorption type of the adsorbent were studied using adsorption kinetics.

[0050] Figure 4 The adsorption equilibrium time, pseudo-first-order, pseudo-second-order, and intraparticle diffusion models for dye adsorption were presented. The results showed that the equilibrium time for MCC-g-PGMA-Lys was 450 min, and for MCC-g-PGMA-TA it was 500 min. Both adsorption processes conformed to the pseudo-second-order kinetic model, indicating chemisorption, with electrostatic interactions as the primary driving force. The intraparticle diffusion fitting indicated that the adsorption process was controlled by a multi-step mechanism.

[0051] (4) Adsorption cycle test

[0052] 20 mg of MCC-g-PGMA-Lys was placed in 50 mL of MB and MO dye solution, and 10 mg of MCC-g-PGMA-TA was placed in 10 mL of MB and Rh B dye solution. The adsorption system was shaken uniformly at 25 °C and 110 rpm for 24 h, then centrifuged and filtered. The adsorbed dye was removed by shaking in 25 mL of 0.05 M HCl and NaOH solution. The adsorption-desorption process was repeated 8 times.

[0053] Figure 5 The cyclic performance of the adsorbents was demonstrated. After eight adsorption-desorption cycles, the adsorption capacity of MCC-g-PGMA-Lys for MB and MO decreased slightly, but the adsorption capacity still reached 73.43% and 72.81% of the initial adsorption capacity, respectively. The adsorption capacity of MCC-g-PGMA-TA for MB and RhB still reached 88.54% and 89.64% of the initial adsorption capacity, respectively. The tests show that the adsorbents possess excellent regenerability.

[0054] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. An epoxidized cellulose porous material for preparing adsorbents, characterized in that, The epoxidized cellulose is synthesized from microcrystalline cellulose, bromoisobutyryl bromide, and glycidyl methacrylate via atom transfer radical polymerization.

2. The method for preparing the epoxidized cellulose porous material as described in claim 1, characterized in that, The epoxidized cellulose porous material is prepared by the following method: (1) Dissolve microcrystalline cellulose in a binary dissolution system of 1-butyl-3-methylimidazolium chloride and N,N-dimethylformamide; (2) Place the reaction system in step (1) under an ice-water bath, add bromoisobutyroxyl bromide to the system by titration and react at room temperature for 10 hours and 16 hours, remove excess impurities by dialysis, and freeze-dry the resulting solution to obtain the modified cellulose, named MCC-BiBB. (3) Dissolve the MCC-BiBB described in step (2) in DMF as an initiator, and simultaneously add glycidyl methacrylate and cuprous bromide catalyst for three freeze-thaw cycles. Then add N,N,N′,N″,N″-pentamethyldiethylenetriamine for three more freeze-thaw cycles. Dialyze to remove unreacted monomers and impurities to obtain the target product named MCC-g-PGMA.

3. The method as described in claim 2, characterized in that, In step (1), the dissolution temperature is 90-100℃, and the mass ratio of microcrystalline cellulose, 1-butyl-3-methylimidazolium chloride and N,N-dimethylformamide is 1:20:9.

44.

4. The method as described in claim 2, characterized in that, In step (2), the molar ratio of cellulose to bromoisobutyryl bromide is 1:3, 1:5 and 1:7, and the reaction time is 10 hours and 16 hours, respectively.

5. The method as described in claim 2, characterized in that, In step (3), the feeding ratios of glycidyl methacrylate, MCC-BiBB and cuprous bromide are 100:1:1, 200:1:1 and 300:1:

1.

6. The method as described in claim 2, characterized in that, In step (3), the reaction conditions are as follows: the solvent is 15 mL of N,N-dimethylformamide, and the concentrations of N,N,N′,N″,N″-pentamethyldiethylenetriamine are all 0.21 mmol. The reaction environment is N2 atmosphere, and the reaction temperature is 70℃.

7. The method as described in claim 1, characterized in that, The epoxidized cellulose is used to build the platform through the growth of epoxy chains.

8. The method as described in claim 1, characterized in that, The prepared epoxidized cellulose porous material has a high epoxy content and a porous structure.

9. An epoxidized cellulose porous material for preparing adsorbents as described in claim 1, wherein the epoxidized cellulose porous material can be used to prepare a variety of adsorbents for the adsorption of dye wastewater by utilizing the high reactivity of epoxidation.

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