A PHMB-modified sodium carboxymethyl cellulose oxidized hydrogel adsorbent, its preparation method and application

Abstract

This invention relates to the field of polymer adsorption materials technology, providing a PHMB-modified sodium carboxymethyl cellulose (CCM)-based hydrogel adsorbent, its preparation method, and its applications. First, sodium CCM is prepared; then, the sodium CCM is reacted with polyhexamethylene biguanide (PHMB) to form a pregel via a Schiff base reaction; a crosslinking agent is added, followed by an initiator to initiate polymerization; finally, after washing, purification, and freeze-drying, the PHMB-modified sodium CCM-based hydrogel adsorbent is obtained. The PHMB-modified sodium CCM-based hydrogel adsorbent is used for dye wastewater treatment, improving upon the limitations of traditional cellulose-based hydrogels such as limited adsorption capacity and general structural stability. The preparation process is simple, the raw materials are readily available, and recovery can be achieved through simple filtration, with a simple regeneration method and low energy consumption.

Description

Technical Field

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

[0002] With the development of industries such as textiles and dyeing, the discharge of dye wastewater has a certain impact on the water environment, making its efficient treatment a key focus of environmental protection. Among dye wastewater treatment technologies, adsorption is one of the most widely used methods due to its significant advantages, including simple operation, high treatment efficiency, economic cost, and no secondary pollution. Sodium carboxymethyl cellulose, as a water-soluble derivative of natural cellulose, is widely available, inexpensive, and has excellent biocompatibility. Hydrogel adsorbents prepared from sodium carboxymethyl cellulose possess good swelling properties and a porous structure, enabling effective adsorption of dye molecules through physical and chemical adsorption. Therefore, it has great application potential in the field of dye wastewater treatment.

[0003] However, traditional hydrogel adsorbents prepared from sodium carboxymethyl cellulose in existing technologies still have many insurmountable technical defects, failing to meet the requirements of high efficiency and stability for adsorbents in actual industrial dye wastewater treatment. Specifically, these defects include: limited number of functional groups, low adsorption capacity; poor structural stability, short service life; poor adsorption selectivity, and weak anti-interference ability. Therefore, this invention provides a PHMB-modified sodium carboxymethyl cellulose oxidized hydrogel adsorbent. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a PHMB-modified sodium carboxymethyl cellulose oxidized hydrogel adsorbent, its preparation method, and its application, aiming to solve the problems mentioned in the background art.

[0005] In a first aspect, the present invention provides a method for preparing a PHMB-modified sodium carboxymethyl cellulose oxidized hydrogel adsorbent, comprising the following steps: Step (a): Dissolve sodium carboxymethyl cellulose (CMC-Na) in an aqueous acetic acid solution, add sodium periodate for oxidation reaction in the dark, quench with ethylene glycol, dialyze and dry to obtain oxidized sodium carboxymethyl cellulose (OCMC-Na). Step (b): Dissolve sodium carboxymethyl cellulose oxide in deionized water, add polyhexamethylene biguanide (PHMB), and form a pregel at room temperature via a Schiff base reaction; Step (c): Add crosslinking agent to the pregel, stir until clear and transparent, then add initiator, and carry out free radical polymerization reaction under closed conditions at 60-70℃ to obtain crude hydrogel; Step (d): After washing, purifying and freeze-drying the crude hydrogel, PHMB-modified sodium carboxymethyl cellulose oxidized hydrogel adsorbent is obtained.

[0006] Further, in step (a), the mass ratio of sodium periodate to sodium carboxymethyl cellulose is 1-1.5:1; the oxidation reaction time is 2-4 h; and oxidized sodium carboxymethyl cellulose with an oxidation degree of 15-60% is obtained, preferably 50-55%.

[0007] Furthermore, in step (b), the mass ratio of sodium carboxymethyl cellulose oxide to polyhexamethylene biguanide is 1:0.1-2; the Schiff base reaction time is 1-3 h.

[0008] Further, in step (c), the crosslinking agent is N,N-methylenebisacrylamide; the initiator is potassium persulfate or ammonium persulfate.

[0009] Furthermore, the amount of crosslinking agent is 0.1-0.2% of the total mass of sodium carboxymethyl cellulose oxide and polyhexamethylene biguanide, preferably 0.15%; the amount of initiator is 0.5-1.5% of the total mass of sodium carboxymethyl cellulose oxide and polyhexamethylene biguanide, preferably 1%.

[0010] Furthermore, in step (c), the free radical polymerization reaction time is 2-6 hours.

[0011] Secondly, the present invention provides a PHMB-modified sodium carboxymethyl cellulose oxidized hydrogel adsorbent, which is prepared by a method for preparing a PHMB-modified sodium carboxymethyl cellulose oxidized hydrogel adsorbent.

[0012] Thirdly, the present invention provides an application of PHMB-modified sodium carboxymethyl cellulose hydrogel adsorbent in dye wastewater treatment.

[0013] Further, the specific operating steps are as follows: add the PHMB-modified sodium carboxymethyl cellulose hydrogel adsorbent to the wastewater containing methyl orange, adjust the pH of the wastewater to 1-5, and adsorb to equilibrium under the conditions of 20-45℃ and 100-200rpm shaking; wherein, the amount of PHMB-modified sodium carboxymethyl cellulose hydrogel adsorbent is 0.1-1g / L, and the initial concentration of methyl orange is 50-200mg / L.

[0014] Furthermore, the PHMB-modified sodium carboxymethyl cellulose hydrogel adsorbent, which is saturated with adsorption, is regenerated by desorption with 0.05-0.2M NaOH solution for 10-14 hours, and can be reused after desorption.

[0015] The present invention has the following effects: (1) The modification method is mild and feasible: polyhexamethylene biguanide is grafted onto the sodium carboxymethyl cellulose molecular chain through Schiff base reaction. The reaction conditions are mild and no complicated equipment is required, which can effectively introduce amino active sites into the hydrogel.

[0016] (2) Improved structure and adsorption performance: The synergistic effect of polyhexamethylene biguanide modification and free radical crosslinking can optimize the network structure of hydrogel, increase adsorption sites, and play a positive role in improving the dye adsorption capacity.

[0017] (3) The process is simple and green: the raw materials are mainly natural polymer derivatives, which are relatively abundant. No toxic organic solvents are involved in the preparation process. The post-processing is simple. The hydrogel adsorbent obtained can be desorbed and reused, and has the potential for large-scale preparation.

[0018] (4) The scope of application is relatively clear: the obtained hydrogel adsorbent has an adsorption effect on common dyes and can be used as an adsorbent material for dye wastewater treatment. Attached Figure Description

[0019] Exemplary embodiments of the present invention can be more fully understood by referring to the following figures: Figure 1 This is a scanning electron microscope (SEM) image of the PHMB-modified sodium oxidized carboxymethyl cellulose hydrogel adsorbent (PHMB / OCMC-Na) prepared in Example 1 of the present invention.

[0020] Figure 2 The compression stress-strain curve of the PHMB-modified sodium carboxymethyl cellulose hydrogel adsorbent prepared in Example 1 of this invention is shown.

[0021] Figure 3 The diagram shows the cyclic regeneration performance of the PHMB-modified sodium carboxymethyl cellulose hydrogel adsorbent prepared in Example 1 of this invention. Detailed Implementation

[0022] To make the technical problems, solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific embodiments described herein are merely illustrative and are not intended to limit the scope of the invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0024] Example 1: (1) Preparation of oxidized sodium carboxymethyl cellulose: 1 g of sodium carboxymethyl cellulose (CMC-Na) was dissolved in 50 mL of 0.01 M acetic acid solution and stirred until completely dissolved; 1.2 g of sodium periodate was added and stirred at room temperature in the dark for 3 h; 1 mL of ethylene glycol was added and stirred for 2 h to quench unreacted sodium periodate; the reaction solution was transferred to a dialysis bag (molecular weight cutoff 8000-14000 Da) and dialyzed with deionized water for 3 days, changing the water every 8 h; after dialysis, the solution was freeze-dried to obtain oxidized sodium carboxymethyl cellulose (OCMC-Na) with an oxidation degree of 55%; (2) Preparation of PHMB-OCMC-Na pregel: Weigh 0.5g of sodium carboxymethyl cellulose oxide, add 50mL of deionized water, stir at room temperature until completely dissolved to obtain sodium carboxymethyl cellulose oxide solution; add 0.15g of polyhexamethylene biguanide (PHMB) to sodium carboxymethyl cellulose oxide solution, stir at room temperature for 2h to form a uniform pregel by reacting polyhexamethylene biguanide with sodium carboxymethyl cellulose oxide through Schiff base reaction; (3) Preparation of hydrogel: Add 0.001g of crosslinking agent: N,N-methylenebisacrylamide (MBA) and 0.005g of initiator: potassium persulfate (KPS) to the pregel. After stirring evenly, transfer the mixture to a sealed container and keep it at 60℃ for 3h to complete the free radical polymerization and obtain the crude hydrogel. (4) Purification and drying: Take out the crude hydrogel, wash it three times with anhydrous ethanol and 0.1M NaOH solution, soak and wash it with deionized water for 48h (change the water once every 12h) to remove unreacted substances, and freeze dry to obtain PHMB modified sodium carboxymethyl cellulose oxidized hydrogel adsorbent (PHMB / OCMC-Na).

[0025] Scanning electron microscopy image of PHMB-modified sodium carboxymethyl cellulose hydrogel adsorbent as shown below Figure 1 As shown, the results indicate that the PHMB-modified sodium carboxymethyl cellulose oxidized hydrogel adsorbent possesses a uniform, continuous three-dimensional network structure with high porosity and thin pore walls. It is speculated that the formation of intramolecular and intermolecular cross-linking networks endows the material with a more compact gel structure, ultimately resulting in this dense gel network. This structural feature increases the surface area for interaction between the hydrogel and pollutants, exposing more active sites and thus effectively enhancing its adsorption capacity.

[0026] The compressive stress-strain curve of the PHMB-modified sodium carboxymethyl cellulose hydrogel adsorbent is shown below. Figure 2As shown in the results, the PHMB-modified sodium carboxymethyl cellulose oxidized hydrogel adsorbent has a compressive modulus of 61.91 kPa and a compressive strength of 103.81 kPa. The compressive strength is higher than that of most pure bio-based hydrogels, indicating that it can maintain sufficient mechanical integrity under high swelling conditions, without structural collapse, meeting the mechanical requirements for recycling and possessing practical application potential.

[0027] Example 2: (1) Preparation of oxidized sodium carboxymethyl cellulose: 1 g of sodium carboxymethyl cellulose (CMC-Na) was dissolved in 50 mL of 0.01 M acetic acid solution and stirred until completely dissolved; 1.0 g of sodium periodate was added and stirred at room temperature in the dark for 2 h; 1 mL of ethylene glycol was added and stirred for 2 h to quench the reaction; the reaction solution was transferred to a dialysis bag (molecular weight cutoff 8000-14000 Da) and dialyzed with deionized water for 3 days, with the water changed every 8 h; after dialysis, the solution was freeze-dried to obtain oxidized sodium carboxymethyl cellulose with an oxidation degree of 48%.

[0028] (2) Preparation of PHMB-OCMC-Na pregel: Weigh 0.5g sodium carboxymethyl cellulose oxide, add 50mL of deionized water, and stir at room temperature until completely dissolved; add 0.05g polyhexamethylene biguanide, stir at room temperature for 1h to form a uniform pregel.

[0029] (3) Preparation of hydrogel: Add 0.0006 g of crosslinking agent N,N-methylenebisacrylamide to the pregel; add 0.0027 g of initiator potassium persulfate; after stirring evenly, transfer the mixture to a sealed container and keep it at 60°C for 2 h to obtain crude hydrogel.

[0030] (4) Purification and drying: Take out the crude hydrogel, wash it three times with anhydrous ethanol and 0.1M NaOH solution, soak and wash it with deionized water for 48h (change the water once every 12h) to remove unreacted substances, and freeze dry to obtain PHMB modified sodium carboxymethyl cellulose oxidized hydrogel adsorbent.

[0031] Example 3: (1) Preparation of oxidized sodium carboxymethyl cellulose: 1 g of sodium carboxymethyl cellulose (CMC-Na) was dissolved in 50 mL of 0.01 M acetic acid solution and stirred until completely dissolved; 1.5 g of sodium periodate was added and stirred at room temperature in the dark for 4 h; 1 mL of ethylene glycol was added and stirred for 2 h to quench the reaction; the reaction solution was transferred to a dialysis bag (molecular weight cutoff 8000-14000 Da) and dialyzed with deionized water for 3 days, with the water changed every 8 h; after dialysis, the solution was freeze-dried to obtain oxidized sodium carboxymethyl cellulose with an oxidation degree of 60%.

[0032] (2) Preparation of PHMB-OCMC-Na pregel: Weigh 0.5g sodium carboxymethyl cellulose oxide, add 50mL of deionized water, and stir at room temperature until completely dissolved; add 1.0g polyhexamethylene biguanide, stir at room temperature for 3h to form a uniform pregel.

[0033] (3) Preparation of hydrogel: Add MBA to the pregel at a rate of 0.2% of the total monomer mass (1.5g), i.e. 0.003g; add ammonium persulfate (APS) as an initiator at a rate of 1.5% of the total monomer mass, i.e. 0.0225g; stir evenly and transfer to a sealed container, keep warm at 70℃ for 6h to obtain crude hydrogel.

[0034] (4) Purification and drying: Take out the crude hydrogel, wash it three times with anhydrous ethanol and 0.1M NaOH solution, soak and wash it with deionized water for 48h (change the water once every 12h) to remove unreacted substances, and freeze dry to obtain PHMB modified sodium carboxymethyl cellulose oxidized hydrogel adsorbent.

[0035] Application Example 1: (1) Adsorption performance test: Weigh 5 mg of the dry-state PHMB-modified sodium carboxymethyl cellulose hydrogel adsorbent prepared in Example 1 and add it to 50 mL of a 100 mg / L methyl orange (MO) dye solution. Adjust the pH to 3 with 0.1 M HCl or NaOH solution and allow it to adsorb under light-protected conditions at 25 °C and 150 rpm. Take samples at regular intervals and determine the residual MO concentration at 464 nm using a UV-Vis spectrophotometer to calculate the adsorption capacity.

[0036] The results showed that at adsorption equilibrium, the adsorption capacity of the PHMB-modified sodium carboxymethyl cellulose hydrogel adsorbent prepared in Example 1 was 118.48 mg / g.

[0037] (2) Cyclic regeneration performance test: The PHMB-modified sodium carboxymethyl cellulose hydrogel adsorbent prepared in Example 1, saturated with MO, was placed in 50 mL of 0.1 M NaOH solution and desorbed by shaking at room temperature for 12 h. After desorption, the gel was washed with deionized water until neutral, freeze-dried, and reused for adsorption experiments. The above adsorption-desorption operation was repeated 5 times, and the adsorption capacity retention rate after each cycle was calculated.

[0038] The recycling performance of PHMB-modified sodium carboxymethyl cellulose hydrogel adsorbent is as follows: Figure 3As shown, the results indicate that the PHMB-modified sodium carboxymethyl cellulose hydrogel adsorbent retained 79.17% of its adsorption capacity after 4 cycles; after the 5th cycle, some adsorption sites were encapsulated, and the adsorption capacity retention rate was 62.77%.

[0039] Comparative Example 1: The preparation method is the same as in Example 1, except that: instead of adding polyhexamethylene biguanide, sodium carboxymethyl cellulose oxidized solution is directly mixed with N,N-methylenebisacrylamide and potassium persulfate for polymerization to obtain unmodified hydrogel.

[0040] Referring to Application Example 1, the adsorption capacity of the unmodified hydrogel was tested. The results showed that the adsorption capacity of the unmodified hydrogel for methyl orange was 61.53 mg / g, which was much lower than that of the PHMB-modified sodium carboxymethyl cellulose hydrogel adsorbent prepared in Example 1.

[0041] Comparative Example 2: The preparation method was the same as in Example 3, except that: MBA was added to the pregel at 0.05% of the total monomer mass, i.e., 0.0005 g; 0.01 g (1.0%) of KPS was added, and after stirring evenly, the mixture was transferred to a sealed container and reacted at 65°C for 4 h. The resulting product could not form a complete hydrogel, exhibiting a viscous, flowing consistency with extremely poor mechanical strength, making subsequent washing and purification impossible. This indicates that when the amount of crosslinking agent is too low (0.05%), free radical polymerization cannot form an effective three-dimensional network structure.

[0042] The above description is merely an embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a PHMB-modified sodium carboxymethyl cellulose oxidized hydrogel adsorbent, characterized in that, Includes the following steps: Step (a): Dissolve sodium carboxymethyl cellulose in an aqueous acetic acid solution, add sodium periodate to oxidize in the dark, quench with ethylene glycol, dialyze, and dry to obtain oxidized sodium carboxymethyl cellulose; Step (b): Dissolve sodium carboxymethyl cellulose oxide in deionized water, add polyhexamethylene biguanide, and form a pregel at room temperature via a Schiff base reaction; Step (c): Add crosslinking agent to the pregel, stir until clear and transparent, then add initiator, and carry out free radical polymerization reaction under closed conditions at 60-70℃ to obtain crude hydrogel; Step (d): After washing, purifying and freeze-drying the crude hydrogel, PHMB-modified sodium carboxymethyl cellulose oxidized hydrogel adsorbent is obtained.

2. The preparation method according to claim 1, characterized in that, In step (a), the mass ratio of sodium periodate to sodium carboxymethyl cellulose is 1-1.5:1; the oxidation reaction time is 2-4 h; and sodium carboxymethyl cellulose oxide with an oxidation degree of 15-60% is obtained.

3. The preparation method according to claim 1, characterized in that, In step (b), the mass ratio of sodium carboxymethyl cellulose oxide to polyhexamethylene biguanide is 1:0.1-2; the Schiff base reaction time is 1-3 h.

4. The preparation method according to claim 1, characterized in that, In step (c), the crosslinking agent is N,N-methylenebisacrylamide; the initiator is potassium persulfate or ammonium persulfate.

5. The preparation method according to claim 4, characterized in that, The amount of crosslinking agent is 0.1-0.2% of the total mass of monomers; the amount of initiator is 0.5-1.5% of the total mass of monomers.

6. The preparation method according to claim 1, characterized in that, In step (c), the free radical polymerization reaction time is 2-6 hours.

7. A PHMB-modified sodium carboxymethyl cellulose hydroxyl hydrogel adsorbent, characterized in that, It is prepared by the method for preparing a PHMB-modified sodium carboxymethyl cellulose hydrogel adsorbent according to any one of claims 1-6.

8. Application of a PHMB-modified sodium carboxymethyl cellulose oxidized hydrogel adsorbent in dye wastewater treatment.

9. The application as described in claim 8, characterized in that, The specific operating steps are as follows: Add the PHMB-modified sodium carboxymethyl cellulose hydrogel adsorbent to the wastewater containing methyl orange, adjust the pH of the wastewater to 1-5, and adsorb until equilibrium is reached under the conditions of 20-45℃ and 100-200rpm shaking; wherein, the amount of PHMB-modified sodium carboxymethyl cellulose hydrogel adsorbent is 0.1-1g / L, and the initial concentration of methyl orange is 50-200mg / L.

10. The application as described in claim 9, characterized in that, The PHMB-modified sodium carboxymethyl cellulose hydrogel adsorbent, which is saturated with adsorption, is regenerated by desorption with 0.05-0.2M NaOH solution for 10-14 hours, and can be reused after desorption.

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