Carboxylated titanium dioxide modified hydrogel nanofiltration membrane as well as preparation method and application thereof

Abstract

The invention belongs to the field of nanofiltration membrane preparation, and particularly relates to a carboxylated titanium dioxide modified hydrogel nanofiltration membrane as well as a preparation method and application thereof. The hydrogel nanofiltration membrane comprises a base membrane and carboxylated titanium dioxide dispersed in the base membrane. According to the technical scheme, the titanium dioxide with the photocatalysis effect is added into the base membrane, the membrane surface photocatalysis anti-pollution effect can be achieved, preferably, carboxymethyl cellulose, polyethylene glycol and sodium alginate of a full-biomass material substrate are selected for preparing the base membrane, the good biodegradation effect is achieved, and the anti-pollution effect is achieved. The problem that subsequent waste films are difficult to treat can be effectively solved, and environmental friendliness is truly achieved. Meanwhile, the technical scheme of the invention has a good filtering effect.

Description

Technical Field

[0001] This invention belongs to the field of nanofiltration membrane preparation, specifically relating to a carboxylated titanium dioxide modified hydrogel nanofiltration membrane, its preparation method, and its application. Background Technology

[0002] In the fields of material separation and wastewater treatment, membrane filtration technology has become an indispensable core technology due to its advantages such as high separation efficiency, low energy consumption, and ease of operation. However, existing membrane separation technologies are consistently limited by membrane fouling in practical industrial applications. In wastewater treatment, especially in the separation of dyeing and printing wastewater, organic dyes are easily adsorbed and deposited on the membrane surface and pores, leading to a rapid decline in membrane flux. Conventional membranes lack self-cleaning capabilities and require chemical cleaning methods, which significantly shorten membrane lifespan and increase operating costs. Therefore, achieving efficient cleaning of membrane surface contaminants has become a key breakthrough in solving the membrane fouling problem.

[0003] Furthermore, traditional membrane materials are mostly petroleum-based materials such as polysulfone and polyethersulfone, which are difficult to biodegrade. Large quantities of discarded membranes easily become difficult-to-manage solid waste, and some are even classified as hazardous waste due to residual chemical pollutants, significantly increasing the difficulty and burden of subsequent environmental remediation. In summary, the two major problems of membrane fouling and environmental pollution from discarded membranes have seriously restricted the sustainable development of membrane filtration technology. Therefore, developing a new type of filter membrane that combines high-efficiency self-cleaning performance with environmentally friendly characteristics is of significant practical importance. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a carboxylated titanium dioxide modified hydrogel nanofiltration membrane, its preparation method and application.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A hydrogel nanofiltration membrane based on carboxylated titanium dioxide modification includes a base membrane and titanium dioxide dispersed in the base membrane.

[0006] The base membrane is prepared from carboxymethyl cellulose, polyethylene glycol and sodium alginate; preferably, the polyethylene glycol has a relative molecular weight of 3000-5000.

[0007] The present invention also includes a method for preparing a hydrogel nanofiltration membrane based on carboxylated titanium dioxide modification, comprising the following steps: 1) preparing carboxylated titanium dioxide; 2) adding carboxylated titanium dioxide to a base membrane solution to form a uniform casting solution; 3) casting a film and adding a crosslinking agent to crosslink and obtain a hydrogel nanofiltration membrane.

[0008] The base film solution includes carboxymethyl cellulose, polyethylene glycol, and sodium alginate.

[0009] Preferably, the mass ratio of carboxylated titanium dioxide, carboxymethyl cellulose, polyethylene glycol, and sodium alginate is 3-5:3-5:40-50:20; preferably, the mass ratio of carboxylated titanium dioxide, carboxymethyl cellulose, polyethylene glycol, and sodium alginate is 3-5:3-5:40:20.

[0010] Preferably, the amount of carboxylated titanium dioxide added to the base film solution is 0.2-0.5 wt%; more preferably 0.3 wt%.

[0011] Preferably, step 1) involves adding titanium dioxide nanoparticles to an alkaline solution to obtain a TiO2 suspension; adding sodium chloroacetate to the TiO2 suspension and heating to 100-120°C for a hydrothermal reaction to obtain carboxylated TiO2; preferably, the mass ratio of titanium dioxide to sodium chloroacetate is (1.5-3.5):(2-4); more preferably, it is 2.3:2.92.

[0012] The crosslinking agent is BaCl2, and the amount of the crosslinking agent added is 1-5 wt% of the base film solution; preferably 2.5 wt%.

[0013] The present invention also includes an application of the carboxylated titanium dioxide modified hydrogel nanofiltration membrane. Preferably, it is used for filtration separation.

[0014] Compared with the prior art, the beneficial effects of the present invention are: The technical solution of this application achieves photocatalytic antifouling of the membrane surface by adding titanium dioxide, which has photocatalytic activity, to the base membrane. Preferably, the base membrane is prepared using a fully biomass substrate of carboxymethyl cellulose, polyethylene glycol, and sodium alginate, which exhibits good biodegradability and effectively solves the problem of difficult disposal of subsequent waste membranes, truly achieving environmental friendliness. Simultaneously, the technical solution of this application also demonstrates excellent filtration performance. Attached Figure Description

[0015] Figure 1 A schematic diagram of the preparation process for carboxylated titanium dioxide modified hydrogel nanofiltration membrane; Figure 2 Infrared comparison of carboxylated cellulose, sodium alginate, carboxylated titanium dioxide modified hydrogel nanofiltration membrane (self-cleaning membrane) and ordinary nanofiltration membrane; Figure 3 A comparison chart of flux and rejection rate of a titanium dioxide-modified hydrogel nanofiltration membrane (self-cleaning membrane) and a conventional nanofiltration membrane; Figure 4 Comparison of dyes on the surface of a titanium dioxide-modified hydrogel nanofiltration membrane (self-cleaning membrane) and a regular nanofiltration membrane before and after photocatalysis at different times. Detailed Implementation

[0016] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments.

[0017] Example 1 A method for preparing a hydrogel nanofiltration membrane based on carboxylated titanium dioxide modification includes the following steps: (1) Preparation of carboxylated titanium dioxide (TiO2-COOH): 2.3 g of titanium dioxide nanoparticles and 30 mL of 1 mol / L NaOH solution were added to 300 mL of deionized water and stirred at room temperature for 1 hour, followed by sonication for 30 minutes. Then, 2.92 g of sodium chloroacetate was added to the TiO2 suspension, and the mixture was stirred at 110 °C for 4 hours. After cooling, the solution was repeatedly washed with deionized water until the pH value was neutral. Finally, the carboxylated TiO2 particles were centrifuged at 4000 r / min for 30 minutes and dried in a vacuum oven at 80 °C for 12 hours to further remove impurities.

[0018] (2) Preparation of hydrogel nanofiltration membranes ( Figure 1 A schematic diagram of the preparation process for carboxylated titanium dioxide-modified hydrogel nanofiltration membrane: TiO2-COOH (0.3 wt% concentration of TiO2-COOH in the base membrane solution) is added to a carboxymethyl cellulose dispersion. After stirring at room temperature for 30 minutes, the mixture is ultrasonically treated for 1 hour to obtain a uniformly dispersed solution. Subsequently, polyethylene glycol-4000 and sodium alginate are added in a certain mass ratio, wherein the mass ratio of TiO2-COOH, carboxymethyl cellulose, polyethylene glycol-4000, and sodium alginate is 3:3:40:20. The mixed solution is stirred at room temperature for 6 hours until a uniform casting solution is formed. After casting and degassing, the membrane is dried in a 60°C oven for about 12 hours until there is no obvious water on the surface. Then, an excess of BaCl2 solution (2.5 wt% of the base membrane solution) is poured in, and complete crosslinking is carried out for 24 hours to obtain a carboxylated titanium dioxide-modified hydrogel nanofiltration membrane. Figure 2 Infrared comparison images of carboxymethyl cellulose, sodium alginate, and hydrogel nanofiltration membrane (self-cleaning membrane) show that the concentrations in carboxymethyl cellulose and sodium alginate are located at 3434 cm⁻¹, respectively. -1 3438 cm -1 The peak exhibits a hydroxyl peak, which is also observed on the self-cleaning membrane, but shifted to the right (3277 cm⁻¹). -1 Therefore, it can be inferred that the connection between the components of the self-cleaning membrane is mainly achieved through hydrogen bonding via ionic cross-linking.

[0019] Example 2 The only difference between Example 3 and Example 1 is that in step 2), the mass ratio of TiO2-COOH, carboxymethyl cellulose, polyethylene glycol-4000 and sodium alginate is 5:3:30:20.

[0020] Example 3 The only difference between Example 2 and Example 1 is that in step 2), the mass ratio of TiO2-COOH, carboxymethyl cellulose, polyethylene glycol-4000 and sodium alginate is 3:5:40:20.

[0021] Example 4 The only difference between Example 3 and Example 1 is that in step 2), the mass ratio of TiO2-COOH, carboxymethyl cellulose, polyethylene glycol-4000 and sodium alginate is 3:3:50:20.

[0022] Example 5 The only difference between Example 3 and Example 1 is that in step 2), the mass ratio of TiO2-COOH, carboxymethyl cellulose, polyethylene glycol-4000 and sodium alginate is 3:3:40:30.

[0023] Comparative Example 1: Meanwhile, to examine the differences between photocatalytic membranes and traditional nanofiltration, a traditional nanofiltration membrane was also fabricated. The specific fabrication process is as follows: First, a polyethersulfone (PES) base membrane was immersed in a piperazine solution (1% by volume, 20±1℃) for 2 minutes; then, a 1,3,5-benzenetricarboxyl chloride / cyclohexane solution (0.1% by volume) was dropped onto the membrane surface, and the reaction was allowed to proceed for 1 minute; finally, the membrane was cured at 60℃ for 5 minutes to obtain a traditional NF-PIP nanofiltration membrane. The prepared nanofiltration membrane was thoroughly cleaned with deionized water to remove residual chemical reagents, and then stored in deionized water.

[0024] Performance tests were conducted on different embodiments and comparative examples, including 1. Mechanical strength: The tensile strength of the membrane was measured using a universal tensile testing machine (GRS-DZSC001-500, China).

[0025] 2. Membrane pore size was determined using a Quantachrome Autosorb-iQ fully automated surface area and porosity analyzer employing the BET method. Samples underwent freeze-drying before pore size analysis.

[0026] 3. The contact angle of the membrane surface was measured using a contact angle meter (OCA50, Germany). Specifically, a 2μL water droplet was used for measurement. To obtain accurate values, more than 5 contact angle samples were collected at different locations on each surface at room temperature, and the average value was taken.

[0027] 4. The membrane rejection rate was continuously measured using a 60 mg / L Congo red solution as the filtration solution. During the filtration process, the parameters were set to continuously permeate at 3 bar for 4 hours, and the rejection rate of Congo red in the solution by the nanofiltration membrane was recorded.

[0028] Table 1 shows the separation membrane parameters at different addition ratios in different embodiments. Table 1

[0029] The results show that within the scope defined by this patent, the photocatalytic membranes all exhibit good retention rates. Examples 1, 2, and 5 all have retention rates close to 100%, with Example 2 showing the highest retention rate, further demonstrating that the overall performance is optimal under this ratio. In contrast, Examples 3 and 4 show significant decreases in retention rates. This is because Example 3 increased the content of carboxymethyl cellulose, which, while increasing the membrane's mechanical strength, resulted in a decrease in retention performance due to the larger pore size of cellulose compared to sodium alginate. The significant decrease in retention rate in Example 4 is mainly due to the large amount of pore-forming agent added, which weakens the membrane's surface retention performance.

[0030] Meanwhile, comparing Example 2 (the optimal embodiment) with traditional nanofiltration membranes, its retention capacity, mechanical properties, and hydrophilic properties are all superior to those of traditional nanofiltration membranes. Figure 3 A comparison chart of flux and rejection rate of a titanium dioxide-modified hydrogel nanofiltration membrane (self-cleaning membrane, Example 2) and a conventional nanofiltration membrane (Comparative Example 1); Figure 4 The images show a comparison of the dye content on the membrane surfaces of a titanium dioxide-modified hydrogel nanofiltration membrane (self-cleaning membrane, Example 2) and a conventional nanofiltration membrane (Comparative Example 1) before and after photocatalysis at different times. The left half represents the membrane surface before photocatalysis, and the accompanying half represents the membrane surface after photocatalysis. This further demonstrates the superiority of the novel photocatalytic filter membrane proposed in this patent.

[0031] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A hydrogel nanofiltration membrane based on carboxylated titanium dioxide modification, characterized in that, This includes the base film and carboxylated titanium dioxide dispersed in the base film.

2. The hydrogel nanofiltration membrane based on carboxylated titanium dioxide modification according to claim 1, characterized in that, The base film comprises carboxymethyl cellulose, polyethylene glycol, and sodium alginate; the mass ratio of carboxymethyl cellulose, polyethylene glycol, and sodium alginate is (3-5):(40-50):

20.

3. The hydrogel nanofiltration membrane based on carboxylated titanium dioxide modification according to claim 1, characterized in that, The mass ratio of carboxymethyl cellulose, polyethylene glycol, and sodium alginate is 3-5:40:20; preferably, the relative molecular weight of polyethylene glycol is 3000-5000.

4. The hydrogel nanofiltration membrane based on carboxylated titanium dioxide modification according to claim 1, characterized in that, Carboxylated titanium dioxide is prepared by adding titanium dioxide nanoparticles to an alkaline solution to obtain a TiO2 suspension; adding sodium chloroacetate to the TiO2 suspension and heating to 100-120℃ for a hydrothermal reaction to obtain carboxylated TiO2; preferably, the mass ratio of titanium dioxide to sodium chloroacetate is (1.5-3.5):(2-4).

5. The hydrogel nanofiltration membrane based on carboxylated titanium dioxide modification according to claim 1, characterized in that, The amount of carboxylated titanium dioxide added to the base film solution is 0.2-0.5 wt%; preferably 0.3 wt%.

6. A method for preparing a hydrogel nanofiltration membrane based on carboxylated titanium dioxide modification as described in any one of claims 1-5, characterized in that, The process includes the following steps: adding carboxylated titanium dioxide to a base membrane solution to form a homogeneous casting solution; casting the membrane and adding a crosslinking agent to crosslink it to obtain a hydrogel nanofiltration membrane; Preferably, the base film solution comprises carboxymethyl cellulose, polyethylene glycol, and sodium alginate; preferably, the mass ratio of carboxylated titanium dioxide, carboxymethyl cellulose, polyethylene glycol, and sodium alginate is 3-5:3-5:40-50:20; preferably, the mass ratio of carboxylated titanium dioxide, carboxymethyl cellulose, polyethylene glycol, and sodium alginate is 3-5:3-5:40:20, more preferably 5:3:40:

20.

7. The method for preparing a hydrogel nanofiltration membrane based on carboxylated titanium dioxide modification according to claim 6, characterized in that, The crosslinking agent is BaCl2, and the amount of the crosslinking agent added is 1-5 wt% of the base film solution; preferably 2.5 wt%.

8. The method for preparing a hydrogel nanofiltration membrane based on carboxylated titanium dioxide modification according to claim 6, characterized in that, The crosslinking agent is BaCl2, and the amount of the crosslinking agent added is 1-5 wt% of the base film solution; preferably 2.5 wt%.

9. The application of a carboxylated titanium dioxide modified hydrogel nanofiltration membrane according to any one of claims 1-5.

10. The application according to claim 9, characterized in that, It is used for filtration and separation.

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