Integrated catalyst capable of efficiently degrading toxic organic substances in low-temperature water and application thereof
By combining a carbon-based diatomic catalyst with an aerogel framework, an integral catalyst was prepared, which solved the problems of low catalyst efficiency at low temperatures and easy aggregation of nanocatalysts. This enabled the efficient degradation of toxic organic matter in low-temperature water and is suitable for low-temperature wastewater treatment.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NANJING INST OF ENVIRONMENTAL SCI MINIST OF ECOLOGY & ENVIRONMENT OF THE PEOPLES REPUBLIC OF CHINA
- Filing Date
- 2024-02-29
- Publication Date
- 2026-05-29
AI Technical Summary
Existing catalysts have low catalytic efficiency at low temperatures, making it difficult to effectively degrade toxic organic matter in low-temperature water. Furthermore, nanocatalysts are prone to aggregation and are difficult to recover, resulting in low reaction efficiency and potential pollution.
A monolithic catalyst was prepared by combining a carbon-based diatomic catalyst with an aerogel framework. Axial microchannels were formed by directional freeze-drying technology to inhibit the aggregation of nanocatalysts, and the catalyst was degraded by oxidant in a fixed-bed reactor.
It improves the activation efficiency of catalysts at low temperatures, overcomes mass transfer resistance, and achieves efficient degradation of toxic organic matter in low-temperature water. It is suitable for wastewater treatment in low-temperature climates, and the catalyst is not easily lost, thus avoiding secondary pollution.
Smart Images
Figure CN118162213B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of new environmental materials technology, specifically to an integral catalyst capable of efficiently degrading toxic organic matter in low-temperature water and its application. Background Technology
[0002] Biological methods are the most economical technology for treating organic wastewater, but they are prone to large-scale microbial death and biochemical system collapse when faced with the toxic impact of harmful organic matter. Advanced oxidation technologies, through the activation of oxidants such as hydrogen peroxide, persulfate, and ozone by catalysts, generate highly reactive oxygen species with strong oxidizing properties, which can rapidly decompose and mineralize toxic organic matter, effectively reducing the biological toxicity of organic wastewater, and are widely used as pretreatment technologies for biological methods.
[0003] However, my country spans latitudes from 4° to 53° north, and most areas, especially high-latitude and high-altitude regions, experience low temperatures (<5°C) every winter. For advanced oxidation technologies, cooling reduces the proportion of activated molecules that can overcome the activation energy barrier and react, while significantly increasing water viscosity, thus slowing mass transfer (water viscosity increases by 87.18% when the temperature drops from 25°C to 2°C). This inhibits the catalytic reaction from both thermodynamic and mass transfer kinetic perspectives. Although various types of metal-based and carbon-based catalysts have been developed for advanced oxidation technologies, the performance of almost all catalysts shows a significant decreasing trend with decreasing temperature. Currently, maintaining catalytic efficiency at low temperatures relies on increasing reagent dosage or heating wastewater, but this significantly increases the cost and carbon emissions of toxic organic wastewater oxidation pretreatment. Therefore, there is an urgent need to develop highly efficient catalysts suitable for low-temperature environments.
[0004] Carbon-based single-atom catalysts, which anchor metals in an atomically dispersed state on a carbon nanofiber matrix, possess 100% atomic utilization and unsaturated metal coordination structures, exhibiting reaction efficiencies far exceeding those of nanocatalysts in activating oxidants, and are thus hailed as "next-generation catalysts." Recent studies have found that loading two metals in the form of atomic pairs onto a carbon nanofiber matrix can optimize the adsorption state of active intermediates through intermetallic electronic interactions, thereby further reducing the activation energy and significantly increasing the proportion of activated molecules. Simultaneously, the coordination strength of diatomic sites for oxidants is higher than that of single-atom sites, and the carbon matrix can also adsorb organic pollutants through hydrophobic or π-π interactions. Therefore, it can overcome the high mass transfer resistance caused by increased water viscosity at low temperatures, promote the enrichment of reactants into the catalyst, and increase the effective collision frequency between reactive oxygen species and pollutants on the catalyst surface. However, after entering water, nanoscale carbon-based diatomic catalysts are prone to aggregation due to their high surface energy, reducing the exposure of active sites and hindering the shortening of solid-liquid mass transfer distances from oxidants and pollutants to the catalytic center. Furthermore, nanocatalysts are difficult to recover after the reaction, easily lost with water, and can cause potential secondary pollution.
[0005] For example, some scholars have studied the preparation of Co-Cu bimetallic oxide to activate persulfate for the removal of sulfamethoxazole from water. However, the metal in this catalyst exists in the form of nanoparticles rather than atomically dispersed. At the same time, it cannot solve the above-mentioned application problems faced by nanocatalysts in wastewater treatment, and the effect of the catalyst on degrading organic matter in low-temperature water has not been investigated. Summary of the Invention
[0006] To address the aforementioned problems, this invention provides an integral catalyst capable of efficiently degrading toxic organic matter in low-temperature water and its applications.
[0007] The technical solution of this invention is:
[0008] This monolithic catalyst, capable of efficiently degrading toxic organic matter in low-temperature water, is prepared from a carbon-based diatomic catalyst and an aerogel framework. The preparation method is as follows:
[0009] A carbon-based diatomic catalyst was dispersed in ultrapure water, and the mass concentration of the carbon-based diatomic catalyst was controlled at 0.1-1 g / L. An aerogel framework was added, and the mass concentration ratio of the carbon-based diatomic catalyst to the aerogel framework was controlled at 1:5-20. The mixture was stirred to form a suspension. The suspension was poured into a mold, and the bottom of the mold was directionally frozen using an iron block cooled with liquid nitrogen until the upper surface of the suspension was frozen. The frozen suspension was then placed in a vacuum freeze dryer for drying to obtain an integral catalyst.
[0010] The aerogel framework is composed of cellulose nanofibers.
[0011] Furthermore, the preparation method of the carbon-based diatomic catalyst is as follows:
[0012] S1. Bimetallic Ion Adsorption: Two inorganic salts of heavy metals are dissolved in ultrapure water to form a mixed metal solution. The heavy metal inorganic salts are nitrates, chlorides, or sulfates of iron, manganese, nickel, cobalt, or copper. Pyrrole and an oxidant are added sequentially to the mixed metal solution to initiate a polymerization reaction. The molar concentration ratio of the two heavy metal ions to the pyrrole to be added in the mixed metal solution is 1:1:50-500. The molar concentration of each heavy metal ion is controlled at 0.01-0.1 mmol / L. The molar concentration ratio of pyrrole to oxidant is 1:0.5-1. The polymerization reaction temperature is 5-80℃, and the polymerization reaction time is 1-6 h. The two heavy metal ions are fixed in the polypyrrole framework through the coordination of nitrogen atoms in pyrrole to obtain a polypyrrole-based solution. The polypyrrole-based solution is then filtered, washed with water, and dried to obtain polypyrrole adsorbing bimetallic ions.
[0013] S2. Preparation of carbon-based diatomic catalyst by pyrolysis: The polypyrrole with adsorbed bimetallic ions obtained in step S1 is pyrolyzed under inert gas protection at a temperature of 500-1000℃ for 1-12 hours to obtain a carbon-based diatomic catalyst.
[0014] Furthermore, in step S1, the two heavy metal salts are preferably Fe(NO3)3·9H2O and Co(NO3)2·6H2O, and the oxidant is one of sodium persulfate, ammonium persulfate, and potassium persulfate.
[0015] Note: Iron and cobalt were preferred as heavy metal sources for the carbon-based diatomic catalyst. The resulting monolithic catalyst showed good treatment effect on sulfamethoxazole, an organic pollutant in low-temperature water.
[0016] Furthermore, in step S1, the drying temperature is 40–80°C.
[0017] Furthermore, in step S2, the inert gas is one of nitrogen, argon, or helium, and the heating rate of the pyrolysis is 1–10 °C / min.
[0018] Furthermore, in step S3, the diameter of the cellulose nanofibers is 5-25 nm, and the mold material is one of plastic, rubber, or glass.
[0019] Note: By optimizing the diameter of cellulose nanofibers to use aerogel carriers as solid dispersion media, the aggregation of nano-carbon-based diatomic catalysts can be suppressed, and the solid-liquid mass transfer distance can be shortened.
[0020] Furthermore, in step S3, the specific method of directional freezing is as follows: first, the iron block is placed in liquid nitrogen at -196℃ for cooling for 0.5 to 1 hour and then taken out. Then, the mold containing the suspension is placed on the iron block. At this time, the ice crystals inside the suspension grow directionally from bottom to top until the upper surface of the suspension is frozen.
[0021] Note: The directional freeze-drying method causes ice crystals to grow upward, forming axial micron channels, which helps to reduce water permeability resistance and increase water flux.
[0022] Furthermore, in step S3, the freeze-drying time is 12–48 hours.
[0023] The application of the monolithic catalyst described above, which can efficiently degrade toxic organic matter in low-temperature water, involves applying the monolithic catalyst to the degradation of toxic organic matter in low-temperature water by an activated oxidant.
[0024] Preferably, the specific method for applying the monolithic catalyst to the degradation of toxic organic matter in low-temperature water by an activated oxidant is as follows: a fixed-bed catalytic reactor is constructed using the monolithic catalyst as packing material; low-temperature aqueous solutions containing oxidant and organic pollutants are pumped separately into the upper part of the fixed-bed catalytic reactor for mixing; the resulting mixture permeates into the packing material, initiating the degradation of organic pollutants; the mass concentration ratio of the oxidant to the organic pollutants is 2.5–10:1; the flow rate of the mixture is 0.01–0.1 bed volume / min; the oxidant is any one of sodium persulfate, potassium persulfate, potassium peroxymonosulfate complex salt, hydrogen peroxide, etc.; and the temperature of the low-temperature aqueous solution is <5°C.
[0025] The beneficial effects of this invention are:
[0026] (1) The monolithic catalyst of the present invention, which can efficiently degrade toxic organic matter in low-temperature water, has a multi-scale hierarchical structure of "atomic-level sites - nanoscale matrix - centimeter-level carrier", integrating multiple functions into one. It can solve the problem of low catalytic efficiency at low temperatures from the perspective of thermodynamics and mass transfer kinetics. Among them, the diatomic sites optimize the adsorption state of intermediates based on intermetallic synergistic effects, thereby significantly reducing the reaction activation energy and increasing the proportion of activated molecules. The diatomic sites and nano-carbon matrix can respectively apply coordination and hydrophobic, π-π and other strong forces to oxidant molecules and organic pollutants in water, overcome the mass transfer resistance caused by the increase in water viscosity at low temperatures, and increase the effective collision frequency of active oxygen species and pollutants on the catalyst surface. The aerogel carrier, as a solid dispersion medium, can inhibit the aggregation of nano-carbon-based diatomic catalysts and shorten the solid-liquid mass transfer distance, thereby further improving the mass transfer kinetic efficiency. Based on the above multi-component synergistic effects, the monolithic catalyst can efficiently activate oxidants to rapidly degrade recalcitrant organic matter in low-temperature water (<5℃), and is suitable for efficient oxidation pretreatment of toxic organic wastewater in low-temperature climates.
[0027] (2) The monolithic catalyst of the present invention, which can efficiently degrade toxic organic matter in low-temperature water, stably disperses nano-sized carbon-based diatomic catalysts in an aerogel cross-linked grid, so that the catalysts will not be lost with water and thus avoid potential ecological hazards caused by nano-catalysts entering the water body.
[0028] (3) The monolithic catalyst of this invention, which can efficiently degrade toxic organic matter in low-temperature water, has excellent hydrophilicity due to its aerogel framework composed of cellulose nanofibers. Simultaneously, the directional freeze-drying method forms axial micron channels, which helps reduce water permeation resistance and increase water flux. Therefore, this monolithic catalyst can be used as a packing material to build a fixed-bed catalytic reactor. Furthermore, the mold can be adjusted according to the reactor size, thereby controlling the shape and size of the catalyst, making it suitable for batch, large-scale, and customized production, and possessing broad practical application prospects. Attached Figure Description
[0029] Figure 1 This is a photograph of the monolithic catalyst prepared in the experimental example of this invention;
[0030] Figure 2 This is a dynamic contact angle test diagram of the monolithic catalyst prepared in the experimental example of this invention;
[0031] Figure 3 This is a photograph of a small fixed-bed catalytic reactor constructed with an integral catalyst, as shown in the experimental examples of this invention.
[0032] Figure 4 This is the invention Figure 3 A schematic diagram of a local structure in the image;
[0033] Figure 5 This is a diagram showing the effect of treating low-temperature sulfamethoxazole (SMZ) wastewater in an experimental example of the present invention. Detailed Implementation
[0034] Example 1
[0035] This monolithic catalyst, capable of efficiently degrading toxic organic matter in low-temperature water, is prepared from a carbon-based diatomic catalyst and an aerogel framework. The preparation method is as follows:
[0036] S1. Bimetallic Ion Adsorption: Two inorganic salts of heavy metals are dissolved in ultrapure water to form a mixed metal solution. The preferred heavy metal salts are Fe(NO3)3·9H2O and Co(NO3)2·6H2O. The oxidant is ammonium persulfate. Pyrrole and the oxidant are added sequentially to the mixed metal solution to initiate a polymerization reaction. The molar concentration ratio of the two heavy metal ions to the pyrrole to be added in the mixed metal solution is 1:1:300. The molar concentration of each heavy metal ion is controlled at 0.05 mmol / L. The molar concentration ratio of pyrrole to oxidant is 1:0.75. The polymerization reaction temperature is 60℃ and the polymerization reaction time is 2h. The two heavy metal ions are fixed in the polypyrrole framework through the coordination of nitrogen atoms in pyrrole to obtain a polypyrrole-based solution. The polypyrrole-based solution is then filtered, washed with water, and dried to obtain polypyrrole adsorbing bimetallic ions. The drying temperature is 60℃.
[0037] S2. Preparation of carbon-based diatomic catalyst by pyrolysis: The polypyrrole with adsorbed bimetallic ions obtained in step S1 is pyrolyzed under inert gas protection. The inert gas is nitrogen. The pyrolysis heating rate is 2℃ / min, the pyrolysis temperature is 800℃, and the pyrolysis time is 2h to obtain a carbon-based diatomic catalyst.
[0038] The carbon-based diatomic catalyst obtained in step S2 was dispersed in ultrapure water, and the mass concentration of the carbon-based diatomic catalyst was controlled at 0.5 g / L. Cellulose nanofibers with a diameter of 25 nm were added as an aerogel framework, and the mass concentration ratio of carbon-based diatomic catalyst to cellulose nanofibers was controlled at 1:10. The mixture was stirred to form a suspension, which was then poured into a mold made of plastic. The bottom of the mold was directionally frozen using an iron block cooled with liquid nitrogen. The specific method of directional freezing was as follows: the iron block was first placed in liquid nitrogen at -196℃ for 0.75 h and then removed. The mold containing the suspension was then placed on the iron block. At this time, the ice crystals inside the suspension grew directionally from bottom to top until the upper surface of the suspension was frozen. The frozen suspension was then placed in a vacuum freeze dryer for 24 h to obtain the monolithic catalyst.
[0039] Example 2
[0040] The difference between this embodiment and Embodiment 1 is that the two heavy metal salts are selected differently.
[0041] The preferred heavy metal salts are Fe(NO3)3·9H2O and CuCl2·2H2O.
[0042] Example 3
[0043] The difference between this embodiment and Embodiment 1 is that the two heavy metal salts are selected differently.
[0044] The preferred heavy metal salts are Fe(NO3)3·9H2O and MnCl2.
[0045] Example 4
[0046] The difference between this embodiment and Embodiment 1 is that the two heavy metal salts are selected differently.
[0047] The preferred heavy metal salts are Ni(NO3)2·6H2O and CuCl2·2H2O.
[0048] Example 5
[0049] The difference between this embodiment and Embodiment 1 is that the two heavy metal salts are selected differently.
[0050] The preferred heavy metal salts are MnCl2 and CoCl2·6H2O.
[0051] Example 6
[0052] The difference between this embodiment and Embodiment 1 is that the specific preparation parameters are different.
[0053] S1. Bimetallic Ion Adsorption: Two inorganic salts of heavy metals are dissolved in ultrapure water to form a mixed metal solution. The preferred heavy metal salts are Fe(NO3)3·9H2O and Co(NO3)2·6H2O. The oxidant is sodium persulfate. Pyrrole and the oxidant are added sequentially to the mixed metal solution to initiate a polymerization reaction. The molar concentration ratio of the two heavy metal ions to the pyrrole to be added in the mixed metal solution is 1:1:50. The molar concentration of each heavy metal ion is controlled at 0.01 mmol / L. The molar concentration ratio of pyrrole to oxidant is 1:0.5. The polymerization reaction temperature is 5℃ and the polymerization reaction time is 1h. The two heavy metal ions are fixed in the polypyrrole framework through the coordination of nitrogen atoms in pyrrole to obtain a polypyrrole-based solution. The polypyrrole-based solution is filtered, washed with water, and dried sequentially to obtain polypyrrole adsorbing bimetallic ions. The drying temperature is 40℃.
[0054] S2. Preparation of carbon-based diatomic catalyst by pyrolysis: The polypyrrole with adsorbed bimetallic ions obtained in step S1 is pyrolyzed under inert gas protection. The inert gas is argon. The heating rate of pyrolysis is 1℃ / min, the pyrolysis temperature is 500℃, and the pyrolysis time is 1h to obtain a carbon-based diatomic catalyst.
[0055] The carbon-based diatomic catalyst obtained in step S2 was dispersed in ultrapure water, and the mass concentration of the carbon-based diatomic catalyst was controlled at 0.1 g / L. Cellulose nanofibers with a diameter of 5 nm were added as an aerogel framework, and the mass concentration ratio of carbon-based diatomic catalyst to cellulose nanofibers was controlled at 1:5. The mixture was stirred to form a suspension, which was then poured into a mold made of rubber. The bottom of the mold was directionally frozen using an iron block cooled by liquid nitrogen. The specific method of directional freezing was as follows: first, the iron block was placed in liquid nitrogen at -196℃ for 0.5 h and then removed. Then, the mold containing the suspension was placed on the iron block. At this time, the ice crystals inside the suspension grew directionally from bottom to top until the upper surface of the suspension was frozen. Subsequently, the frozen suspension was placed in a vacuum freeze dryer for 12 h to obtain the monolithic catalyst.
[0056] Example 7
[0057] The difference between this embodiment and Embodiment 1 is that the specific preparation parameters are different.
[0058] S1. Bimetallic Ion Adsorption: Two inorganic salts of heavy metals are dissolved in ultrapure water to form a mixed metal solution. The preferred heavy metal salts are Fe(NO3)3·9H2O and Co(NO3)2·6H2O. The oxidant is potassium persulfate. Pyrrole and the oxidant are added sequentially to the mixed metal solution to initiate a polymerization reaction. The molar concentration ratio of the two heavy metal ions to the pyrrole to be added in the mixed metal solution is 1:1:500. The molar concentration of each heavy metal ion is controlled at 0.1 mmol / L. The molar concentration ratio of pyrrole to oxidant is 1:1. The polymerization reaction temperature is 80℃ and the polymerization reaction time is 6h. The two heavy metal ions are fixed in the polypyrrole framework through the coordination of nitrogen atoms in pyrrole to obtain a polypyrrole-based solution. The polypyrrole-based solution is sequentially filtered, washed with water, and dried to obtain polypyrrole adsorbing bimetallic ions. The drying temperature is 80℃.
[0059] S2. Preparation of carbon-based diatomic catalyst by pyrolysis: The polypyrrole with adsorbed bimetallic ions obtained in step S1 is pyrolyzed under the protection of an inert gas, helium, the heating rate of the pyrolysis is 10℃ / min, the pyrolysis temperature is 1000℃, and the pyrolysis time is 12h to obtain a carbon-based diatomic catalyst.
[0060] The carbon-based diatomic catalyst obtained in step S2 was dispersed in ultrapure water, and the mass concentration of the carbon-based diatomic catalyst was controlled at 1 g / L. Cellulose nanofibers with a diameter of 20 nm were added as an aerogel framework, and the mass concentration ratio of carbon-based diatomic catalyst to cellulose nanofibers was controlled at 1:20. The mixture was stirred to form a suspension, which was then poured into a glass mold. The bottom of the mold was directionally frozen using an iron block cooled with liquid nitrogen. The specific method of directional freezing was as follows: the iron block was first placed in liquid nitrogen at -196℃ for 1 hour and then removed. The mold containing the suspension was then placed on the iron block. At this time, the ice crystals inside the suspension grew directionally from bottom to top until the upper surface of the suspension was frozen. The frozen suspension was then placed in a vacuum freeze dryer for 48 hours to obtain the monolithic catalyst.
[0061] Example 8
[0062] This embodiment is an application of the monolithic catalyst in Example 1 that can efficiently degrade toxic organic matter in low-temperature water. The monolithic catalyst is applied to the degradation of toxic organic matter in low-temperature water by activating oxidants. The specific method is as follows: a fixed-bed catalytic reactor is built with the monolithic catalyst as the packing material. Low-temperature aqueous solutions containing oxidants and organic pollutants are pumped into the upper part of the fixed-bed catalytic reactor for mixing. The resulting mixture permeates into the packing material, initiating the degradation of organic pollutants. The mass concentration ratio of oxidant to organic pollutants is 6:1, the flow rate of the mixture is 0.05 bed volume / min, the oxidant is sodium persulfate, and the temperature of the low-temperature aqueous solution is 2°C.
[0063] Example 9
[0064] The difference between this embodiment and Embodiment 8 is that the specific parameters are different.
[0065] The mass concentration ratio of oxidant to organic pollutant is 2.5:1, the flow rate of the mixed solution is 0.01 bed volume / min, the oxidant is potassium persulfate, and the temperature of the low-temperature aqueous solution is 3℃.
[0066] Example 10
[0067] The difference between this embodiment and Embodiment 8 is that the specific parameters are different.
[0068] The mass concentration ratio of oxidant to organic pollutant is 10:1, the flow rate of the mixed liquid is 0.1 bed volume / min, the oxidant is potassium persulfate complex salt or hydrogen peroxide, and the temperature of the low-temperature aqueous solution is 4℃.
[0069] Experimental Example 1
[0070] The preparation results and usage effects of the monolithic catalyst for efficiently degrading toxic organic matter in low-temperature water of the present invention are tested below. Taking the main parameters in Example 1 as an example, in step S1, 20.20 mg of Fe(NO3)3·9H2O and 14.55 mg of Co(NO3)2·6H2O are dissolved in 1 L of ultrapure water to form a mixed metal solution, the dosage of pyrrole is 1006.5 mg, and the dosage of oxidant is 2567.25 mg.
[0071] 10 mg of carbon-based diatomic catalyst was dispersed in 20 mL of ultrapure water, and 100 mg of cellulose nanofibers were taken.
[0072] like Figure 1 As shown, the monolithic catalyst exhibits a cylindrical aerogel shape;
[0073] like Figure 2 As shown, this monolithic catalyst is superhydrophilic, and water droplets can penetrate into its interior in just 330 ms with extremely low permeation resistance.
[0074] Sulfamethoxazole (SMZ) is a commonly used broad-spectrum antibiotic that has been widely detected in water bodies in recent years. We used the aforementioned monolithic catalyst as packing material to construct a small fixed-bed catalytic reactor. A reactor photograph is shown below. Figure 3 and Figure 4 As shown, the treatment effect of low-temperature sulfamethoxazole (SMZ) wastewater is as follows: Figure 5As shown. Experimental conditions: During reactor operation, to maintain a low temperature, ice packs were immersed below the liquid level in the beaker at the inlet and tied around the syringe, and replaced periodically. Packing volume = 45 mL, hydraulic retention time = 20 min, [potassium persulfate compound salt (PMS)] = 0.05 g / L, [SMZ] = 5 mg / L, T = 2 or 25℃. From Figure 5 It can be seen that at 2℃, SMZ was only detected in the effluent after processing 295 bed volumes (BV), which was only 3.28% lower than the 305 BV at 25℃.
[0075] Meanwhile, set up Comparative Example 1:
[0076] To demonstrate the synergistic effect between metal atoms in carbon-based diatomic catalysts, carbon-based single-atom catalysts were prepared, and their performance was compared with that of the catalyst obtained in Experimental Example 1 when operating a fixed-bed catalytic reactor. The preparation method was the same as in Experimental Example 1, except that the dosages of Fe(NO3)3·9H2O and Co(NO3)2·6H2O were changed to 40.40 mg and 0 mg, or 0 mg and 29.10 mg, respectively, to prepare carbon-based iron single-atom catalysts and carbon-based cobalt single-atom catalysts, which were then used for subsequent monolithic catalyst preparation. Under the same experimental conditions as in Experimental Example 1, after treatment at 2°C for 205 BV and 230 BV, respectively, the obtained monolithic catalysts showed detectable SMZ in the effluent. Figure 5 As shown, this demonstrates that diatomic sites exhibit superior catalytic activity compared to monoatomic sites.
[0077] The above results demonstrate that the monolithic catalyst has high permeability and can be used as a packing material to build a fixed-bed reactor for the oxidation pretreatment of low-temperature toxic organic wastewater.
Claims
1. A monolithic catalyst capable of efficiently degrading toxic organic matter in low-temperature water, characterized in that, It is prepared from a carbon-based diatomic catalyst and an aerogel framework. The preparation method is as follows: A carbon-based diatomic catalyst was dispersed in ultrapure water, and the mass concentration of the carbon-based diatomic catalyst was controlled at 0.1~1 g / L. An aerogel framework was added, and the mass concentration ratio of the carbon-based diatomic catalyst to the aerogel framework was controlled at 1:5~20. The mixture was stirred to form a suspension. The suspension was poured into a mold, and the bottom of the mold was directionally frozen using an iron block cooled with liquid nitrogen until the upper surface of the suspension was frozen. The frozen suspension was then placed in a vacuum freeze dryer for drying to obtain an integral catalyst. The aerogel framework is composed of cellulose nanofibers; The preparation method of the carbon-based diatomic catalyst is as follows: S1. Bimetallic Ion Adsorption: Two inorganic salts of heavy metals are dissolved in ultrapure water to form a mixed metal solution. The heavy metal inorganic salts are nitrates, chlorides, or sulfates of iron, manganese, nickel, cobalt, or copper. Pyrrole and an oxidant are added sequentially to the mixed metal solution to initiate a polymerization reaction. The molar concentration ratio of the two heavy metal ions to the pyrrole to be added in the mixed metal solution is 1:1:50~500. The molar concentration of each heavy metal ion is controlled at 0.01~0.1 mmol / L. The molar concentration ratio of pyrrole to oxidant is 1:0.5~1. The polymerization reaction temperature is 5~80℃, and the polymerization reaction time is 1~6h. The two heavy metal ions are fixed in the polypyrrole framework through the coordination of nitrogen atoms in pyrrole to obtain a polypyrrole-based solution. The polypyrrole-based solution is then filtered, washed with water, and dried to obtain polypyrrole adsorbing bimetallic ions. S2. Preparation of carbon-based diatomic catalyst by pyrolysis: The polypyrrole with adsorbed bimetallic ions obtained in step S1 is pyrolyzed under inert gas protection at a temperature of 500~1000℃ for 1~12h to obtain a carbon-based diatomic catalyst.
2. The monolithic catalyst for efficiently degrading toxic organic matter in low-temperature water according to claim 1, characterized in that, In step S1, the two heavy metal salts are preferably Fe(NO3)3∙9H2O and Co(NO3)2∙6H2O, and the oxidant is one of sodium persulfate, ammonium persulfate, and potassium persulfate.
3. The monolithic catalyst for efficiently degrading toxic organic matter in low-temperature water according to claim 1, characterized in that, In step S1, the drying temperature is 40~80℃.
4. The monolithic catalyst for efficiently degrading toxic organic matter in low-temperature water according to claim 1, characterized in that, In step S2, the inert gas is one of nitrogen, argon, or helium, and the heating rate of pyrolysis is 1~10℃ / min.
5. The monolithic catalyst for efficiently degrading toxic organic matter in low-temperature water according to claim 1, characterized in that, The cellulose nanofibers have a diameter of 5-25 nm, and the mold material is one of plastic, rubber, or glass.
6. The monolithic catalyst for efficiently degrading toxic organic matter in low-temperature water according to claim 1, characterized in that, The specific method of directional freezing is as follows: First, the iron block is placed in liquid nitrogen at -196℃ for cooling for 0.5~1h and then taken out. Then, the mold containing the suspension is placed on the iron block. At this time, the ice crystals inside the suspension grow directionally from bottom to top until the upper surface of the suspension is frozen.
7. The monolithic catalyst for efficiently degrading toxic organic matter in low-temperature water according to claim 1, characterized in that, The freeze-drying time is 12~48h.
8. The application of the monolithic catalyst for efficiently degrading toxic organic matter in low-temperature water according to any one of claims 1 to 7, characterized in that, The monolithic catalyst was applied to the degradation of toxic organic matter in low-temperature water by an activated oxidant.
9. The application of the monolithic catalyst for efficiently degrading toxic organic matter in low-temperature water according to claim 8, characterized in that, The specific method for applying the monolithic catalyst to the degradation of toxic organic matter in low-temperature water by activated oxidant is as follows: a fixed-bed catalytic reactor is constructed using the monolithic catalyst as packing material. Low-temperature aqueous solutions containing oxidant and organic pollutants are pumped separately into the upper part of the fixed-bed catalytic reactor for mixing. The resulting mixture permeates into the packing material, initiating the degradation of organic pollutants. The mass concentration ratio of the oxidant to the organic pollutants is 2.5~10:1, the flow rate of the mixture is 0.01~0.1 bed volume / min, and the oxidant is any one of sodium persulfate, potassium persulfate, potassium peroxymonosulfate complex salt, and hydrogen peroxide. The temperature of the low-temperature aqueous solution is <5℃.