Preparation method and application of foam cellulose loaded sulfur-doped carbon nitride photocatalyst

Abstract

The invention discloses a preparation method and application of a foam cellulose loaded sulfur-doped carbon nitride photocatalyst, and the preparation method comprises the following steps: S1, grinding thiourea and urea according to a mass ratio of 1: (45-55), mixing, then gradually heating to 500-520 DEG C, continuously heating, and calcining the mixture to obtain an SCN material; s2, dispersing the SCN material, polylactic acid and sodium dodecyl hexanesulfonate in water, and stirring and mixing to obtain an additive; s3, after the bamboo pulp and the additive are mixed, fiber separation / dispersion is carried out, beating is formed, and a product is obtained; and S4, pouring the product into a mold, and putting the mold into a drying oven for drying and shaping to obtain the foam cellulose loaded sulfur-doped carbon nitride catalyst. The porous composite material loaded sulfur-doped graphite phase carbon nitride photocatalyst is synthesized, the adsorption-photocatalysis effect is enhanced, the mechanical stability of the catalyst is improved, and the service life of the catalyst is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of environmental functional materials and water treatment technology, specifically relating to a method for preparing and applying a sulfur-doped carbon nitride photocatalyst supported on foamed cellulose. Background Technology

[0002] With rapid industrialization, water pollution has become increasingly serious, especially persistent organic pollutants (such as dyes, antibiotics, and pesticides), which pose a severe threat to the ecological environment and human health. Traditional water treatment methods (such as adsorption, flocculation, and biodegradation) suffer from low efficiency, secondary pollution, or high energy consumption. Therefore, developing efficient, economical, and environmentally friendly water treatment technologies has become a research hotspot.

[0003] Photocatalysis utilizes semiconductor materials to generate reactive oxygen species (such as ·OH and ·O2-) under light irradiation, which can efficiently degrade organic pollutants and even mineralize them into CO2 and H2O, offering advantages such as being green, low-energy, and free of secondary pollution. Among these, graphitic carbon nitride (g-C3N4) has become one of the most promising photocatalytic materials due to its good chemical stability, visible light responsiveness, and low cost. However, pure g-C3N4 suffers from problems such as high photogenerated carrier recombination rate, small specific surface area, and insufficient visible light utilization, which limits its practical application.

[0004] Chinese patent publication CN118751297B discloses a method for preparing and using a supported photocatalyst. In this patent, 3,4-dihydroxybenzoic acid-modified nano-titanium dioxide is added to xylene, stirred and dispersed, then a self-polymerizing monomer, p-toluenesulfonic acid, is added. The mixture is heated to the reaction temperature and stirred to carry out a graft polymerization reaction. During the reaction, the mixture is refluxed, cooled, and centrifuged. The nano-titanium dioxide is then washed successively with xylene and ethanol, dried, and polyimide-modified. The polyimide-modified nano-titanium dioxide is placed in a resistance furnace for calcination and carbonization. The carbonized product is then mixed with potassium hydroxide and placed back into the resistance furnace for activation and pore formation, followed by cooling, washing with water, and drying to obtain the supported photocatalyst. However, this catalyst is complex to prepare, has poor mechanical stability, and is environmentally unfriendly. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing and applying a sulfur-doped carbon nitride photocatalyst supported on foamed cellulose, thereby solving the aforementioned technical problems in the prior art.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for preparing a sulfur-doped carbon nitride photocatalyst supported on foamed cellulose includes the following steps:

[0008] S1. Thiourea and urea are ground and mixed at a mass ratio of 1:45-55, and then the mixture is gradually heated to 500-520℃ and continuously heated to obtain SCN material.

[0009] S2. Disperse SCN material, polylactic acid and sodium dodecyl hexasulfonate in water and stir to obtain the additive;

[0010] S3. After mixing bamboo pulp and additives, fiber separation / dispersion is performed to form pulp and obtain the product;

[0011] S4. Pour the product into a mold and place it in an oven to dry and shape it, thereby obtaining a foamed cellulose-supported sulfur-doped carbon nitride catalyst.

[0012] Furthermore, in S1, thiourea and urea are mixed at a mass ratio of 1:50.

[0013] Furthermore, the temperature rise in S1 is controlled at 2-3℃ / min; after the temperature rises to the specified temperature, the holding time is 2-3h.

[0014] Further, in S2, SCN material, polylactic acid, sodium dodecyl hexasulfonate, and water are mixed in a mass ratio of 7.5:15:1:750.

[0015] Furthermore, in step S2, the water used is deionized water.

[0016] Furthermore, in step S3, the dry weight of bamboo pulp and polylactic acid are mixed at a mass ratio of 1:1.

[0017] Furthermore, in step S4, after drying at 60°C for 6 hours, the temperature is raised again to 160°C for 1 hour.

[0018] The method for preparing the foamed cellulose supported sulfur-doped carbon nitride catalyst, and the application of the foamed cellulose supported sulfur-doped carbon nitride catalyst in the photocatalytic degradation of organic dyes and antibiotics.

[0019] The beneficial effects of this invention are:

[0020] 1. The catalyst involved in this invention modifies carbon nitride materials with sulfur, significantly broadening the material's photoresponse range and thus enhancing its photocatalytic activity. Simultaneously, the foamed cellulose support not only provides a stable three-dimensional framework structure for the catalyst but also effectively prevents the loss of catalytic components. This composite catalyst combines excellent photocatalytic performance with structural stability.

[0021] 2. This invention achieves sulfur doping through the co-calcination of thiourea and urea, thereby regulating the electronic structure of g-C3N4 and enhancing its visible light absorption and redox capabilities. Sulfur atoms replace nitrogen atoms to form defect sites, increasing the number of reactive sites and improving photocatalytic efficiency.

[0022] The porous structure of cellulose foam provides a high specific surface area, which can adsorb and enrich pollutants (such as organic dyes and antibiotics), increase the local reaction concentration, and achieve "adsorption-catalysis" synergistic degradation.

[0023] 3. In terms of process, thiourea and urea are mixed at a mass ratio of 1:50 and calcined at 2℃ / min slowly to 520℃ to ensure the integrity of SCN crystallization and uniformity of doping. Polylactic acid and sodium dodecyl hexasulfonate are used as binders and dispersants to uniformly load SCN nanosheets onto bamboo pulp fibers. The drying process (60℃, 6h + 160℃, 1h) balances the mechanical strength and porous structure of the foam.

[0024] 4. This invention utilizes the porous properties of cellulose foam to achieve efficient enrichment of organic pollutants. Its three-dimensional network structure adsorbs and immobilizes dye molecules near the catalytically active sites. This adsorption-photocatalysis synergistic mechanism significantly increases the pollutant concentration at the reaction interface, thereby enhancing the photocatalytic degradation efficiency. The synergistic effect of the porous support and catalytic components enables the simultaneous rapid capture and efficient degradation of pollutants on the material surface.

[0025] 5. The cellulose-based support material used in this invention has excellent biodegradability. After photocatalysis, it can be decomposed by microorganisms in the natural environment without causing secondary pollution. This characteristic fully complies with the concept of sustainable development, making the entire catalytic system environmentally friendly from preparation to disposal, and realizing a truly green chemical process. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a synthetic route diagram of the preparation method of the present invention;

[0028] Figure 2 These are the XRD diffraction patterns of the materials prepared in Examples 1, 2, 1, and 2 of the present invention, and the infrared spectra of Examples 1, 2, 1, and 2 of the present invention, and Comparative Examples 1 and 2.

[0029] Figure 3These are scanning electron microscope images and micro-CT images of various materials from embodiments of the present invention;

[0030] Figure 4 This is a series of images illustrating the photocatalytic degradation of tetracycline hydrochloride in Example 3 of the present invention;

[0031] Figure 5 These are a series of images illustrating the photocatalytic degradation of Rhodamine B in Example 4 of this invention;

[0032] Figure 6 These are a series of images illustrating the outdoor photodegradation of Rhodamine B according to Embodiment 2 of the present invention;

[0033] Figure 7 This is a comparison chart of the degradation changes in the natural environment during the burial experiment of Example 2 of the present invention;

[0034] Figure 8 This is an experimental diagram of the photocatalytic degradation of tetracycline hydrochloride free radical capture in Example 2 of the present invention;

[0035] Figure 9 This is a diagram of the photocatalytic degradation mechanism in Example 2 of the present invention. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] like Figure 1 The image shows an embodiment of this application of a method for preparing a sulfur-doped carbon nitride catalyst supported on foamed cellulose, comprising the following steps:

[0038] S1. Thiourea and urea are ground and mixed at a mass ratio of 1:45-55 (preferably 1:50). The mixture is then gradually heated to 500-520℃ and calcined. The temperature is controlled at 2-3℃ / min and the holding time is 2-3h to obtain SCN material.

[0039] S2. Disperse SCN material, polylactic acid and sodium dodecyl hexasulfonate in deionized water and stir to mix to obtain the additive;

[0040] At this time, the mass ratio of SCN material to polylactic acid is 1:2; the mass ratio of sodium dodecyl hexasulfonate to SCN material is 1:7.5; and the mass ratio of water to SCN material is 100:1.

[0041] S3. Place 15g of dry bamboo pulp and additives into a fiber standard descrambler and beat at 3000×10 revolutions to obtain the product.

[0042] S4. Pour the product into a mold and place it in an oven to dry and shape it to obtain a foamed cellulose supported sulfur-doped carbon nitride catalyst.

[0043] At this point, the oven drying temperature is set to 60℃ for 6 hours; then it is dried at 160℃ for 1 hour.

[0044] Sulfur-doped carbon nitride photocatalysts supported on foamed cellulose are used in the photocatalytic degradation of organic dyes and antibiotics.

[0045] In this application, S-doped g-C3N4 exhibits stronger photocatalytic activity, more favorable redox performance, and improved visible light absorption efficiency. It also broadens the response range. Since the ionic radius and electronegativity of element S are comparable to those of element N, the defective structures formed by S replacing N in g-C3N4 during doping can regulate the interlayer order of g-C3N4, increasing reaction sites and thus enhancing photocatalytic activity. Simultaneously, a series of porous composite matrix materials, such as foam cellulose, are selected as the support. Foam cellulose itself possesses good adsorption properties and degradability, while also exhibiting a certain degree of mechanical stability, which can reduce catalyst loss.

[0046] Therefore, loading it with S-doped g-C3N4 onto cellulose foam can achieve the following: 1. Photocatalysis-adsorption synergy: the porous structure of cellulose foam can adsorb organic dyes in water, enriching them on the catalyst surface, thereby improving the local concentration and efficiency of the photocatalytic reaction; 2. Green and environmentally friendly: during the photocatalytic process, cellulose foam itself can also be partially degraded, further demonstrating its environmental protection characteristics.

[0047] Example 1:

[0048] S1: Place 5g of urea and 0.1g of thiourea into a mortar and grind them thoroughly to obtain the ground material;

[0049] S2: The ground material obtained in S1 is placed in a ceramic boat and heated in a tube furnace at 520°C, with a gradual heating rate of 2°C / min and a holding time of 2 hours.

[0050] S3: SCN nanosheets were obtained by grinding the sample obtained in S2.

[0051] Example 2:

[0052] S1, Disperse 7.5g SCN material, 15g polylactic acid and 1g sodium dodecyl hexasulfonate in 750mL deionized water and stir to mix to obtain the additive;

[0053] S2, pour 15g dry weight bamboo pulp and the additive obtained in S1 into the fiber standard desorber and carry out the pulping process at 3000×10 revolutions;

[0054] The slurries obtained from S3 and S2 are poured into a mold and placed in an oven to dry at 60°C for 6 hours, and then dried at 160°C for 1 hour to obtain the product.

[0055] Example 3:

[0056] S1, place the sulfur-doped carbon nitride photocatalyst supported on foam cellulose cut into 5*5cm size into 500mL of tetracycline hydrochloride solution with a concentration of 10mg / L, and separate it from the stirring magnet through a perforated quartz.

[0057] S2, place the suspension obtained in S1 under a 300W xenon lamp (λ>420nm) for illumination, and take 3mL of liquid every 30 minutes;

[0058] S3. Detect the liquid obtained in step S2 using a UV-Vis spectrophotometer to evaluate its photocatalytic performance.

[0059] Example 4:

[0060] S1, place the sulfur-doped carbon nitride photocatalyst supported on foam cellulose cut into 5*5cm size into 500mL of tetracycline hydrochloride solution with a concentration of 10mg / L, and separate it from the stirring magnet through a perforated quartz.

[0061] S2, place the suspension obtained in S1 under a 300W xenon lamp (λ>420nm) for illumination, and take 3mL of liquid every 20 minutes;

[0062] S3. The liquid obtained in S2 is detected in a UV-Vis spectrophotometer to evaluate its photocatalytic performance.

[0063] Comparative Example 1:

[0064] S1, disperse 15g of polylactic acid and 1g of sodium dodecyl hexasulfonate in 750mL of deionized water and stir to obtain the additive;

[0065] S2, pour 15g dry weight bamboo pulp and the additive obtained in S1 into the fiber standard desorber and carry out the pulping process at 3000×10 revolutions;

[0066] The slurries obtained from S3 and S2 were poured into a mold and dried in an oven at 60°C for 6 hours, and then dried at 160°C for 1 hour to obtain product C-SCN0.

[0067] Comparative Example 2:

[0068] S1, Disperse 15g SCN material, 15g polylactic acid and 1g sodium dodecyl hexasulfonate in 750mL deionized water and stir to obtain the additive;

[0069] S2, pour 15g dry weight bamboo pulp and the additive obtained in S1 into the fiber standard desorber and carry out the pulping process at 3000×10 revolutions;

[0070] The slurries obtained from S3 and S2 are poured into a mold and placed in an oven to dry at 60°C for 6 hours, then dried at 160°C for 1 hour to obtain product C-SCN15.

[0071] like Figure 2 The XRD diffraction patterns and infrared spectra of the materials prepared in Examples 1, 2, Comparative Example 1, and 2 are shown. X-ray diffraction analysis showed that the composite material exhibited obvious diffraction characteristics at 2θ = 14.5°, 15.6°, and 22.5°, which are consistent with the type I crystal structure of cellulose, confirming that bamboo pulp cellulose retained its original crystal form. Meanwhile, the diffraction peaks at 2θ = 13.1° and 27.5° corresponded to the (100) crystal plane triazine ring structure and the (002) crystal plane layered stacking characteristics of g-C3N4, respectively. The coexistence of characteristic diffraction peaks of the two substances indicates that a composite system was successfully constructed and that each crystal form was completely preserved. Infrared spectroscopy analysis showed that in the 1150-1750 cm⁻¹ range... -1 The absorption bands appearing in the wavenumber range originate from the vibrations of CN and C=N bonds; 808 cm⁻¹ -1 The characteristic peak at 3000-3400 cm⁻¹ corresponds to the skeletal vibration of the triazine ring; -1 The broad absorption band is due to the stretching vibration of the NH bond. Furthermore, at 3320 cm⁻¹... -1 The hydroxyl stretching vibration peak at 1631 cm⁻¹ -1 The hydroxyl bending vibration peak and 1367 cm⁻¹ -1 The CH bending vibration peaks all confirmed the existence of the cellulose structure.

[0072] Figure 3 (a) and (b) are scanning electron microscope images of the C-SCN0 material prepared in Comparative Example 1, (c) and (d) are scanning electron microscope images of the C-SCN7.5 material prepared in Example 1, (e) and (f) are scanning electron microscope images of the C-SCN15 material prepared in Example 2, (g) is a cross-sectional micro-CT image of the C-SCN0 material prepared in Comparative Example 1, and (h) is a cross-sectional micro-CT image of the C-SCN7.5 material of the vegetation in Example 1. It can be observed that the cellulose tissue structure becomes coarser after the addition of SCN, which is attributed to the adsorption and bonding between polylactic acid and carbon nitride nanosheets and bamboo pulp fibers, which is beneficial to enhancing the mechanical stability of cellulose foam. (i) is a micro-CT reconstruction image of the C-SCN7.5 material of the vegetation in Example 1.

[0073] Figure 4Figures (a) and (b) show the tetracycline (TC) degradation tests conducted using four different foam carrier sizes ranging from 3×3 cm to 6×6 cm in Example 2 and Comparative Study 2. When the SCN loading was 7.5 g, the 5×5 cm C-SCN7.5 exhibited the best catalytic activity, achieving a degradation rate of 57.8% within 180 min. Subsequent photocatalytic degradation experiments all used foams of the 5×5 cm size. Figure (c) shows the foam degradation fitting curve for Example 2, where the 5×5 cm foam carrier exhibited the highest reaction rate constant (k = 0.0054 min). -1 Furthermore, Figures (d) and (e) show the effect of adding 5 mg of potassium chloride, sodium chloride, magnesium chloride, sodium sulfate, and sodium nitrate during catalysis on the results of Example 3. The results indicate that the introduction of anions and cations has a limited impact on the catalytic process, which may be attributed to the interference effect of the abundant active sites in cellulose foam reducing the concentration of ions in the solution. To test the catalyst stability, a cyclic degradation experiment was conducted on the catalyst. Specifically, the catalyst was collected in S3 of Example 3, dried, and then added to the next degradation experiment. Figure (f) shows the results of the cyclic experiment. After 5 cycles, the catalyst still maintained 92% degradation effect, and the foam mass decreased by only 11%. This demonstrates that the cellulose foam-supported SCN catalyst has strong mechanical stability.

[0074] Figure 5 (a) and (b) show the degradation effect of Rhodamine B in Example 4. C-SCN7.5 showed the best degradation effect. The remaining steps (c), (d), and (e) are the same as those in Example 4, except that the sampling interval is 20 min. Figure 4 The test was the same. In Figure (f), 5 mg of Rhodamine B was added to the solution every 120 min. After running continuously for 12 h, the catalytic effect was still maintained at 84%.

[0075] Figure 6 (a) shows the apparatus for degrading Rhodamine B solution under natural light conditions in Example 2. The light intensity and temperature were recorded by a digital optical power and energy meter, and the degradation effect of the solution was evaluated by an ultraviolet spectrophotometer. The results are shown in Figures (b) and (c). C-SCN7.5 has good catalytic performance, and the degradation rate of 10 mg / L RhB reached 95.5% within 4 hours and 87% within 1 hour.

[0076] Figure 7 For the self-degradation experiment of burial;

[0077] The experimental steps are as follows: Select a piece of prepared foam (C-SCN7.5), bury it in the soil, and dig up the soil every week to take photos and samples for continuous observation. The results of the soil burial method self-degradation experiment are as follows: Figure 5-7As shown, the foam body was quickly degraded by bacteria and microorganisms in the soil within a week, and almost completely degraded within four weeks, indicating that the synthesized material has self-degradable properties, which is in line with the concept of green and environmentally friendly development.

[0078] Figure 8 This is a diagram of the photocatalytic degradation of tetracycline hydrochloride free radical capture experiment in Example 2 of the invention after trimming;

[0079] The experimental steps are as follows: In Example 4, 5 mg of ammonium formate, isopropanol, and silver nitrate were added to S2, and nitrogen gas was passed through for half an hour before the photocatalytic degradation step was carried out. Sampling was performed every 20 minutes. The results are as follows: Figure 8 As shown, the degradation effect of TC was almost unaffected by the addition of isopropanol, indicating that masking ·OH had little effect on the photocatalytic effect. Subsequent introduction of ammonium formate, silver nitrate, and nitrogen also weakened the degradation effect, with the introduction of nitrogen and the addition of ammonium formate having the greatest impact on degradation, indicating that ·O2... - and h + It mainly participates in the photocatalytic degradation process. The addition of silver nitrate also weakens the degradation effect, indicating that e - It also promotes the degradation process, mainly due to O2. - This originates from the reaction of e- with dissolved oxygen in water. In summary, in the SCN-supported bamboo pulp fiber composite catalytic system, the combined effect of ·O2-, h+, and e- enhances the photocatalytic efficiency, while ·OH has a relatively small promoting effect. The catalytic mechanism is as follows: Figure 9 As shown.

[0080] This application provides a method for preparing efficient, stable, and environmentally friendly photocatalytic materials, applicable to: industrial wastewater treatment (degrading recalcitrant organic pollutants such as dyes and antibiotics); environmental remediation (photocatalytic purification of organic pollutants in rivers and lakes); and sustainable materials development (promoting the application of biodegradable catalysts in green chemistry). This technology can further enhance catalytic performance and promote its industrial application by optimizing the cellulose support structure (e.g., 3D printing to customize pores) and expanding the doping elements of SCN (e.g., co-doping with S and P).

[0081] In summary, by loading the SCN catalyst onto porous cellulose foam, a suitable support is provided, ensuring the catalyst's stability during operation. The foam maintained good stability during cyclic experiments, with minimal catalyst loss during catalytic cycling. As a green and biodegradable material, the support can rapidly degrade in the natural environment, meeting the environmental requirements of sustainable development. Furthermore, the material is widely available and its preparation process is simple, making its industrial-scale application feasible.

[0082] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for preparing a sulfur-doped carbon nitride photocatalyst supported on foamed cellulose, characterized in that, Includes the following steps: S1. Thiourea and urea are ground and mixed at a mass ratio of 1:45-55, and then the mixture is gradually heated to 500-520℃ and continuously heated to obtain SCN material. S2. Disperse SCN material, polylactic acid and sodium dodecyl hexasulfonate in water and stir to obtain the additive; S3. After mixing bamboo pulp and additives, fiber separation / dispersion is performed to form pulp and obtain the product; S4. Pour the product into a mold and place it in an oven to dry and shape it, thereby obtaining a foamed cellulose-supported sulfur-doped carbon nitride catalyst.

2. The method for preparing the foamed cellulose-supported sulfur-doped carbon nitride catalyst according to claim 1, characterized in that, In S1, thiourea and urea are mixed at a mass ratio of 1:

50.

3. The method for preparing the sulfur-doped carbon nitride catalyst supported on foamed cellulose according to claim 2, characterized in that, The temperature rise in S1 is controlled at 2-3℃ / min; after the temperature rises to the specified temperature, the holding time is 2-3h.

4. The method for preparing the foamed cellulose-supported sulfur-doped carbon nitride catalyst according to claim 1, characterized in that, In S2, SCN material, polylactic acid, sodium dodecyl hexasulfonate, and water are mixed in a mass ratio of 7.5:15:1:

750.

5. The method for preparing the sulfur-doped carbon nitride catalyst supported on foamed cellulose according to claim 4, characterized in that, In S2, the water used is deionized water.

6. The method for preparing the foamed cellulose-supported sulfur-doped carbon nitride catalyst according to claim 1, characterized in that, In step S3, the dry weight of bamboo pulp and polylactic acid are mixed at a mass ratio of 1:

1.

7. The method for preparing the sulfur-doped carbon nitride catalyst supported on foamed cellulose according to claim 1, characterized in that, In step S4, after drying at 60°C for 6 hours, the temperature is raised to 160°C and dried for another hour.

8. The method for preparing the foamed cellulose supported sulfur-doped carbon nitride catalyst according to any one of claims 1 to 7, characterized in that, The foamed cellulose supported sulfur-doped carbon nitride catalyst is used in the photocatalytic degradation of organic dyes and antibiotics.

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