Visible light-Fenton-like synergistic catalyst as well as preparation method and application thereof

Abstract

According to the technical scheme, the visible light-Fenton-like synergistic catalyst and the preparation method and application thereof are provided, rGH / TiO2-g-C3N4-RM aerogel is obtained through the steps that dicyandiamide, TiO2 and RM powder are added into deionized water for a reaction, drying, nitrogen atmosphere constant-temperature calcination and grinding are conducted, then the rGH / TiO2-g-C3N4-RM aerogel, graphene oxide, ascorbic acid and polyethylene glycol are mixed and subjected to ball milling, a hydrothermal reaction and vacuum freeze drying are conducted, and the visible light-Fenton-like synergistic catalyst is obtained. The preparation method is simple, raw materials are easy to obtain, and the method is suitable for large-scale amplification. The visible light-fenton-like synergistic catalyst provided by the invention has excellent catalytic efficiency, and under the synergistic effect of visible light-fenton-like, the COD removal rate of high-salinity wastewater can reach 95% or above; according to the catalyst, through multi-level innovation of heterojunction design-active site regulation and control-three-dimensional structure construction, the key technical bottlenecks that a visible light-Fenton-like system is high in electron recombination rate, iron mud is generated, the catalyst is difficult to recycle and the like are successfully solved, and an efficient and stable solution is provided for treatment of high-salt degradation-resistant organic wastewater.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation and application, specifically relating to a visible light-Fenton-like synergistic catalyst, its preparation method, and its application. Background Technology

[0002] In recent years, with the rapid development of the chemical industry, the environmental governance of recalcitrant organic pollutants (such as polycyclic aromatic hydrocarbons and heterocyclic compounds) in high-salinity wastewater has become increasingly prominent. These pollutants, due to their complex aromatic ring structures and chemical stability, pose a serious threat to the ecological environment and human health, and traditional physical, chemical, and biological treatment methods often fail to achieve ideal removal results.

[0003] Advanced oxidation technologies (AOPs) exhibit unique advantages in the treatment of recalcitrant organic wastewater due to their ability to generate highly oxidizing hydroxyl radicals (·OH). Among them, Fenton oxidation technology is widely used due to its rapid reaction and ease of operation; however, its practical application still faces technical bottlenecks such as a narrow pH range, abundant iron sludge byproducts, and low hydrogen peroxide utilization. Meanwhile, although photocatalytic oxidation technology can achieve deep mineralization of pollutants, traditional TiO2-based photocatalysts suffer from inherent defects such as a large band gap (3.2 eV), poor visible light response, and easy recombination of photogenerated electron-hole pairs, severely restricting their industrial application.

[0004] To address the aforementioned issues, in 2009, Wang Xinchen's team developed a graphitic carbon nitride (g-C3N4) photocatalyst. Due to its suitable bandgap of 2.7 eV, excellent chemical stability, and environmentally friendly properties, it brought a new breakthrough to visible light photocatalysis technology. This material forms a highly delocalized conjugated system through sp2 hybridization of C and N atoms, exhibiting excellent performance in visible light degradation of organic matter and photocatalytic water splitting for hydrogen production. However, single g-C3N4 still suffers from drawbacks such as small specific surface area and low photogenerated carrier separation efficiency.

[0005] Red mud (RM) is a major industrial solid waste in my country, generated during the alumina production process from bauxite ore. Its main components are SiO2, Al2O3, CaO, and Fe2O3. my country's red mud stockpile has exceeded 1×10⁻⁶ tons. 9 t, with 1×10 8With increasing t / a utilization rate, the utilization rate is only about 4%. Currently, the main use of red mud is in the preparation of building materials. Developing multiple utilization pathways is crucial for its resource utilization. Many scholars have used red mud as a raw material, modifying it for the removal of pollutants in wastewater. For example, Ma Hongfei et al. used red mud modified with sodium dodecylbenzene sulfonate for the adsorption of methylene blue in wastewater, achieving an adsorption capacity of 16.37 mg / g. AN et al. used red mud as a raw material, added pore-forming agents and binders to synthesize porous granular materials, and loaded active zinc on its surface for the adsorption of Congo red in wastewater, achieving an adsorption capacity of 6.5 mg / g. Qian Yi et al. used a calcination-reduction-reconstruction method to synthesize red mud-based base metal oxide materials and used them for the adsorption of reactive brilliant blue dyes in water, achieving a removal rate as high as 97%.

[0006] In recent years, graphene-based composite materials have shown great potential in the field of photocatalysis due to their unique π-π conjugated structure and excellent electron transport properties. Studies have shown that heterojunction systems such as TiO2 / GO constructed by Zhang et al. and WO3 / graphene constructed by Zeng et al. can significantly improve the separation efficiency of photogenerated carriers. In particular, Chen et al. successfully synthesized three-dimensional graphene gel materials (such as rGO-Ag@Ag3PO4), which not only have a larger specific surface area and abundant active sites, but their three-dimensional conductive network can also effectively promote charge transport. However, these materials generally suffer from problems such as complex preparation processes, high costs, and insufficient stability, and their actual treatment effect in complex high-salt wastewater systems still needs to be improved. Summary of the Invention

[0007] The purpose of this invention is to develop a novel visible-light-Fenton-like synergistic catalyst, aiming to systematically address key shortcomings in existing technologies: First, it addresses the inherent defects of traditional TiO2-based catalysts, such as narrow visible light response range (only utilizing ultraviolet light) and high recombination rate of photogenerated carriers; second, it overcomes the bottlenecks in engineering applications, such as the difficulty in separation and recovery of powdered catalysts; third, it effectively suppresses the formation of iron sludge byproducts during Fenton catalysis; ultimately achieving a significant improvement in the treatment efficiency of high-salt, recalcitrant organic wastewater. By constructing a multiphase synergistic catalytic system, this invention achieves technological breakthroughs at both the material design and process optimization levels, providing a more efficient and stable solution for the treatment of high-salt chemical wastewater.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a visible light-Fenton-like synergistic catalyst includes the following steps: S1: Add dicyandiamide, TiO2 and RM powder to deionized water, stir and react at 80°C, and dry in an oven after the reaction is complete; S2: Place the dried sample obtained in S1 in a tube furnace, program the temperature to the calcination temperature under a nitrogen atmosphere, calcine at a constant temperature, and cool naturally after calcination. Grind to obtain TiO2-g-C3N4-RM powder. S3: The TiO2-g-C3N4-RM powder obtained in S2 is mixed with graphene oxide, ascorbic acid and polyethylene glycol, and ball milling is performed by adding ball milling media. The mixture after ball milling is taken out and placed in a container for hydrothermal reaction to obtain rGH / TiO2-g-C3N4-RM hydrogel. S4: The rGH / TiO2-g-C3N4-RM hydrogel was freeze-dried under vacuum at -50℃ to obtain the rGH / TiO2-g-C3N4-RM aerogel, which is a visible light-like Fenton synergistic catalyst.

[0009] Furthermore, in S1, the mass ratio of dicyandiamide, TiO2, and RM is 20:(2~4):1.

[0010] Furthermore, in S2, the programmed heating rate is 2℃ / min, the calcination temperature is 400~600℃, and the isothermal calcination time is 3~6h.

[0011] Furthermore, the mass ratio of TiO2-g-C3N4-RM powder to graphene oxide, ascorbic acid, and polyethylene glycol in S3 is 1:(10~20):(0.3~0.5):(0.3~0.5).

[0012] Furthermore, the hydrothermal reaction conditions in S3 are a reaction temperature of 90~100℃ and a reaction time of 1~3h.

[0013] The present invention also provides a visible light-Fenton-like synergistic catalyst, which is prepared using the above method.

[0014] The present invention also provides an application of a visible light-Fenton-like synergistic catalyst, wherein the above-mentioned visible light-Fenton-like synergistic catalyst is added to high-salt wastewater at a dosage of 0.02% of the mass of the high-salt wastewater, 27.5% hydrogen peroxide is added at a dosage of 5% of the mass of the high-salt wastewater, the pH of the high-salt wastewater is adjusted to 4.5, the light intensity is 2kW, and the reaction is carried out at room temperature for 1 hour.

[0015] The beneficial effects of this invention are: This invention provides a method for preparing a visible light-Fenton-like synergistic catalyst. The method involves adding dicyandiamide, TiO2, and RM powder to deionized water, stirring the mixture at 80°C, and then drying it in an oven after the reaction. The dried sample is then placed in a tube furnace and heated to the calcination temperature under a nitrogen atmosphere using a programmed heating method. The sample is then calcined at a constant temperature, allowed to cool naturally after calcination, and ground to obtain TiO2-g-C3N4-RM powder. TiO2-g-C3N4-RM powder was mixed with graphene oxide, ascorbic acid, and polyethylene glycol, and then ball-milled using ball milling media. The resulting mixture was then placed in a container for hydrothermal reaction to obtain rGH / TiO2-g-C3N4-RM hydrogel. The rGH / TiO2-g-C3N4-RM hydrogel was then freeze-dried under vacuum at -50°C to obtain rGH / TiO2-g-C3N4-RM aerogel, which is a visible-light-based Fenton-like synergistic catalyst. The preparation method of this invention is simple, the raw materials are readily available, and it is suitable for large-scale production.

[0016] This invention provides a visible light-Fenton-like synergistic catalyst with the following advantages: (1) Novel structural design: By using the Z-type heterojunction design of g-C3N4 and TiO2, while maintaining the strong oxidation-reduction ability of the material, the active sites for H2O2 oxidation are precisely introduced; Fe2O3 in red mud is used to significantly promote the Fenton-like oxidation process, effectively avoiding the iron mud by-products of the traditional Fenton reaction. At the same time, the porous structure of red mud increases the exposure of active sites, increasing the utilization rate of hydrogen peroxide to more than 85%. (2) Optimization of electron transport system: Introducing graphene as an electron transport medium: Utilizing its sp² carbon-based structure to achieve rapid transfer of photogenerated electrons, reducing the electron-hole recombination rate by more than 60%, and simultaneously promoting the decomposition of H2O2 to generate ·OH free radicals; (3) Three-dimensional structure optimization: By converting two-dimensional graphene into a three-dimensional gel network, the specific surface area is increased by 3 to 5 times (reaching 500 to 800 m² / g), the number of pollutant contact sites is increased by more than 80%, and a stable multi-level porous loading framework is provided for TiO2-g-C3N4-RM.

[0017] This invention provides an application of a visible light-Fenton-like synergistic catalyst. The visible light-Fenton-like synergistic catalyst provided by this invention has excellent catalytic efficiency. Under the synergistic effect of visible light and Fenton-like catalyst, the COD removal rate of high-salt wastewater can reach more than 95%, the mineralization rate is increased by 2-3 times compared with the single system, the catalytic activity retention rate is >95%, the catalyst filtration recovery efficiency is more than 95%, the iron dissolution is <0.5 mg / L, and the structural integrity is well maintained.

[0018] This catalytic system, through multi-level innovation of "heterojunction design - active site regulation - three-dimensional structure construction", has successfully solved the key technical bottlenecks of visible light-Fenton-like systems, such as high electron recombination rate, iron sludge generation, and difficulty in catalyst recovery, providing an efficient and stable solution for the treatment of high-salt and recalcitrant organic wastewater. Attached Figure Description

[0019] Figure 1 SEM images of TiO2 powder; Figure 2 SEM images of TiO2-g-C3N4 / RM powder; Figure 3 TEM image of rGH / TiO2-g-C3N4-RM aerogel. Detailed Implementation

[0020] To make the technical means, features and effects of the present invention easier to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0021] 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.

[0022] Example 1 A method for preparing a visible light-Fenton-like synergistic catalyst includes the following steps: S1: Add 2.0g of dicyandiamide, 0.3g of TiO2 and 0.1g of RM powder to 100g of deionized water, stir and react at 80℃ for 2h, and dry in an oven after the reaction is completed; S2: The dried sample obtained in S1 was placed in a tube furnace and heated to 500℃ at 2℃ / min under a nitrogen atmosphere. It was then calcined at a constant temperature for 4 hours. After calcination, it was naturally cooled and ground to obtain TiO2-g-C3N4-RM powder. S3: 2.0g of TiO2-g-C3N4-RM powder obtained in S2 was mixed with 20.0g of graphene oxide, 0.6g of ascorbic acid and 0.6g of polyethylene glycol. The mixture was placed in an agate jar, agate beads were added, and the mixture was ball-milled at 420r / min. The ball-milled mixture was then placed in a beaker and subjected to hydrothermal reaction in a 95℃ water bath to obtain rGH / TiO2-g-C3N4-RM hydrogel. S4: The rGH / TiO2-g-C3N4-RM hydrogel was freeze-dried under vacuum at -50℃ to obtain the rGH / TiO2-g-C3N4-RM aerogel, which is a visible light-like Fenton synergistic catalyst.

[0023] The catalyst sample obtained in Example 1 is denoted as Ex1.

[0024] like Figure 1 As shown in the SEM image, TiO2 powder consists of spherical particles, but the agglomeration of these particles leads to a decrease in catalytic activity. like Figure 2As shown in the SEM image of TiO2-g-C3N4 / RM powder, the doping of g-C3N4 and RM disperses the TiO2 surface structure, increases the exposure of active sites and specific surface area. like Figure 3 As shown in the TEM image of rGH / TiO2-g-C3N4-RM aerogel, the powder catalyst is uniformly loaded into the three-dimensional framework of the graphene gel through the action of graphene, which increases the specific surface area of ​​the catalyst. This composite method of sheet structure increases the contact area of ​​the material, which is beneficial to the transfer of photogenerated charge.

[0025] Examples 2-3 Unlike Example 1, the amount of TiO2 used in Example 2 S1 is 0.2g; In Example 3, the amount of TiO2 used in S1 was 0.4g; The catalyst sample obtained in Example 2 is designated as Ex2; The catalyst sample obtained in Example 3 is designated as Ex3.

[0026] Examples 4-5 Unlike Example 1, the calcination temperature in Example 4 S2 was 400°C; Unlike Example 1, the calcination temperature in Example 5 S2 was 600°C; The catalyst sample obtained in Example 4 is designated as Ex4; The catalyst sample obtained in Example 5 is designated as Ex5.

[0027] Examples 6-8 Unlike Example 1, the calcination time in Example 6 S2 was 3 hours; Unlike Example 1, the calcination time in Example 7 S2 was 5 hours; Unlike Example 1, the calcination time in Example 8 S2 was 6 hours; The catalyst sample obtained in Example 6 is designated as Ex6; The catalyst sample obtained in Example 7 is designated as Ex7; The catalyst sample obtained in Example 8 is designated as Ex8.

[0028] Example 10 Unlike Example 1, the amount of ascorbic acid used in Example 10 S3 was 1.0g; The catalyst sample obtained in Example 10 is designated as Ex10.

[0029] Example 11 Unlike Example 1, in Example 11 S3, the amount of ascorbic acid used was 1.0g and the amount of polyethylene glycol used was 1.0g; The catalyst sample obtained in Example 11 is designated as Ex11.

[0030] Comparative Example 1 A method for preparing TiO2-g-C3N4-RM powder includes the following steps: S1: Add 5.0g of dicyandiamide, 0.5g of TiO2 and 0.1g of RM powder to 100g of deionized water, stir and react at 80℃ for 1h, and dry in an oven after the reaction is completed; S2: The dried sample obtained in S1 was placed in a tube furnace and heated to a calcination temperature of 550℃ at a rate of 2℃ / min under a nitrogen atmosphere. The sample was calcined at a constant temperature for 4 hours. After calcination, the sample was naturally cooled and ground to obtain TiO2-g-C3N4-RM powder, which was denoted as CEx1.

[0031] Comparative Example 2 A method for preparing nano-TiO2 powder includes the following steps: S1: Tetrabutyl titanate and anhydrous ethanol are mixed at a ratio of 1:10 to 1:20 (volume ratio), stirred until transparent, and the stabilizer acetylacetone is added. The molar ratio of tetrabutyl titanate to acetylacetone is controlled at 1:1 to inhibit violent hydrolysis, and a titanium precursor solution is obtained. S2: Add acidic aqueous solution (volume ratio H2O: anhydrous ethanol = 1:5, HNO3 concentration 0.5mol / L) dropwise to titanium precursor solution (volume ratio acidic aqueous solution: tetrabutyl titanate ≈ 4), control the dropping rate at 1.5 mL / min, and stir continuously at 750 rpm at 80℃ for 2 h to obtain titanium gel. S3: The titanium gel was left to stand for 24 hours, and then the solvent was evaporated in a fume hood (2 days) to obtain a dry gel. The dry gel was ground and placed in a muffle furnace and heated to 550°C at 4°C / min and kept at that temperature for 4 hours to obtain white nano TiO2 powder, which was denoted as CEx2.

[0032] Comparative Example 3 A method for preparing TiO2-RM powder: S1: Place 0.5g of TiO2 and 0.1g of RM in 50ml of deionized water, sonicate for 30min, and then dry in an oven at 80℃; S2: The dried sample obtained in S1 was placed in a tube furnace and heated to a calcination temperature of 550℃ at a rate of 2℃ / min under a nitrogen atmosphere. The sample was calcined at a constant temperature for 4 hours. After calcination, the sample was naturally cooled and ground to obtain TiO2-RM powder, which was denoted as CEx3.

[0033] Comparative Example 4 A method for preparing TiO2-g-C3N4 powder: S1: Place 5g of dicyandiamide and 0.5g of TiO2 in 50ml of deionized water, ultrasonically disperse for 30min, and then dry in an oven at 80℃; S2: The dried sample obtained in S1 was placed in a tube furnace and heated to a calcination temperature of 550℃ at a rate of 2℃ / min under a nitrogen atmosphere. The sample was calcined at a constant temperature for 4 hours. After calcination, the sample was naturally cooled and ground to obtain TiO2-g-C3N4 powder, which was denoted as CeX4.

[0034] Example 12 The experimental water sample came from high-salt wastewater (COD: 12320ppm, phenol: 233ppm) produced by a chemical company in the production of phenol and acetone.

[0035] The catalysts (Ex1~11, CEx1~4) were added to 1L of high-salt wastewater at a dosage of 0.02% of the mass of the high-salt wastewater. 27.5% hydrogen peroxide was added at a dosage of 5% of the mass of the high-salt wastewater. The pH of the high-salt wastewater was adjusted to 4.5. The light intensity was 2kW, and the reaction was carried out at room temperature for 1 hour.

[0036] After the reaction was completed, the COD and phenol content of the high-salt wastewater treated by visible light-Fenton-like synergistic catalysis with different catalysts were analyzed. The data are shown in Table 1.

[0037] Table 1. Data on the synergistic catalytic treatment of 1 L of high-salinity wastewater by different catalysts under visible light and Fenton-like light. The data in Table 1 show that, after the reaction, the COD removal rate of high-salt wastewater treated by Ex1~Ex11 catalysts all reached over 97%. In particular, for the optimal Ex1 catalyst, the COD can be reduced to 165 ppm and phenol can be reduced to 0.01 ppm, with a COD removal rate of 98.66% and a phenol removal rate of 99.99%. The treated wastewater meets the requirements for receiving the wastewater. At the same time, the catalyst has a high removal efficiency of organic matter in high-salt chemical wastewater under visible light-Fenton-like synergistic catalytic system.

[0038] The COD values ​​of the high-salinity wastewater treated by catalysts Cex1, Cex2, Cex3, and Cex4 decreased from an initial 12,320 ppm to 928, 2,312, 1,543, and 1,686 ppm, respectively, with removal rates of 92.47%, 81.23%, 87.48%, and 86.31%. The phenol content decreased from an initial 233 ppm to 5.78, 32.45, 15.67, and 17.34 ppm, respectively, with removal rates of 97.52%, 86.07%, 93.27%, and 92.56%. The treatment effect was poor, and the treated wastewater could not meet the requirements for receiving the wastewater.

[0039] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the substantive protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a visible light-Fenton-like synergistic catalyst, characterized in that, Includes the following steps: S1: Add dicyandiamide, TiO2 and RM powder to deionized water, stir and react at 80°C, and dry in an oven after the reaction is complete; S2: Place the dried sample obtained in S1 in a tube furnace, program the temperature to the calcination temperature under a nitrogen atmosphere, calcine at a constant temperature, and cool naturally after calcination. Grind to obtain TiO2-g-C3N4-RM powder. S3: The TiO2-g-C3N4-RM powder obtained in S2 is mixed with graphene oxide, ascorbic acid and polyethylene glycol, and ball milling is performed by adding ball milling media. The mixture after ball milling is taken out and placed in a container for hydrothermal reaction to obtain rGH / TiO2-g-C3N4-RM hydrogel. S4: The rGH / TiO2-g-C3N4-RM hydrogel was freeze-dried under vacuum at -50℃ to obtain the rGH / TiO2-g-C3N4-RM aerogel, which is a visible light-like Fenton synergistic catalyst.

2. The preparation method of the visible light-Fenton-like synergistic catalyst as described in claim 1, characterized in that, In S1, the mass ratio of dicyandiamide, TiO2, and RM is 20:(2~4):

1.

3. The preparation method of the visible light-Fenton-like synergistic catalyst as described in claim 1, characterized in that, In S2, the programmed heating rate is 2℃ / min, the calcination temperature is 400~600℃, and the isothermal calcination time is 3~6h.

4. The preparation method of the visible light-Fenton-like synergistic catalyst as described in claim 1, characterized in that, In S3, the mass ratio of TiO2-g-C3N4-RM powder to graphene oxide, ascorbic acid, and polyethylene glycol is 1:(10~20):(0.3~0.5):(0.3~0.5).

5. The preparation method of the visible light-Fenton-like synergistic catalyst as described in claim 1, characterized in that, The hydrothermal reaction conditions in S3 are a reaction temperature of 90~100℃ and a reaction time of 1~3h.

6. A visible light-Fenton-like synergistic catalyst, characterized in that, It is prepared using the method described in any one of claims 1 to 5.

7. An application of a visible light-Fenton-like synergistic catalyst, characterized in that, The visible light-Fenton-like synergistic catalyst of claim 6 was added to high-salt wastewater at a dosage of 0.02% of the mass of the high-salt wastewater. 27.5% hydrogen peroxide was added at a dosage of 5% of the mass of the high-salt wastewater. The pH of the high-salt wastewater was adjusted to 4.

5. The light intensity was 2kW, and the reaction was carried out at room temperature for 1 hour.

Images