Multiphase CoxAlO4 catalyst for photocatalytic degradation of anionic dye

Abstract

The invention relates to a multiphase CoxAlO4 catalyst for photocatalytic degradation of an anionic dye. The heterogeneous cobalt aluminum oxide catalyst is prepared from the following raw materials: Co (NO3) 3.6 H2O, Al (NO3) 3.9 H2O, NH4F and urea. The preparation method comprises the following steps: dissolving raw materials with distilled water and pouring into a reaction kettle; heating until the reaction is complete; and collecting the precipitate, cleaning and dehydrating to obtain the multiphase cobalt-aluminum oxide catalyst. Examples prove that the prepared multiphase cobalt aluminum oxide catalyst has very high photocatalytic activity and good stability when being used for decomposing various anionic dyes; good recoverability is also shown under ultraviolet light, and the practical application in water treatment is shown. The invention provides a new thought for developing efficient and environment-friendly photocatalytic substances, and provides a feasible choice for repairing dye-polluted wastewater.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts containing metal oxides, and in particular to a multiphase Co catalyst for photocatalytic degradation of anionic dyes. x AlO4 catalyst. Background Art

[0002] As the problem of industrial dye wastewater discharge becomes increasingly serious, the persistence and toxicity of refractory dye molecules pose a major threat to the ecological environment and human health. Dyes and pigments are widely used in industries such as textiles and leather, and are difficult to degrade during conventional biological treatment processes, resulting in their accumulation in water bodies. Traditional physical and chemical techniques such as adsorption and advanced oxidation can achieve high removal efficiencies, but their cost-effectiveness is usually low and may cause secondary pollution.

[0003] Among the emerging methods, photocatalysis can use light energy to decompose harmful pollutants and has gradually become one of the most promising technologies. In particular, the photocatalytic degradation of dyes widely used in industries such as textiles, leather, and food has become a major research area. Domestic and foreign scholars have studied and developed a wide variety of catalysts for the degradation of organic pollutants, among which titanium dioxide (TiO2) is one of the most widely studied photocatalysts. In order to obtain higher light utilization efficiency and pollutant degradation rate, recent research has begun to focus on the development of more efficient and economical alternatives. Among these materials, catalysts based on metal oxides, especially heterogeneous cobalt aluminum oxide (Co2O3), are the most promising technologies for the degradation of organic pollutants. x AlO y ), which has attracted attention due to its unique electronic properties, high stability and excellent catalytic efficiency.

[0004] Compared with traditional TiO2, multiphase Co x AlO y The catalyst has obvious advantages: it can absorb a wider spectrum, improve energy utilization efficiency, and has unique redox properties and higher electron transfer ability, thus achieving higher catalytic efficiency. x AlO y The catalysts are more stable, durable, less susceptible to photocorrosion, and cost-effective for large-scale applications. More importantly, they can decompose a variety of organic pollutants under mild reaction conditions, making them particularly attractive for practical environmental applications.

[0005] Nano-CoAl2-xLa prepared by lemon sol-gel method x The photocatalytic degradation mechanism of rhodamine B by O4 catalyst under visible light showed that hydroxyl and superoxide anion radicals were the main active species. The photodegradation of Congo red (CR) by heterogeneous CoAl2O4 / ZnO showed that the free radical O 2-is the cause of CR photooxidation. Solar photocatalysis improves the degradation performance of CR by activating ZnO through UVA sunlight. In addition, CoAlO4 catalysts have also been widely studied in oxidation reactions, combustion, CO2 methanation reactions, etc. However, there are few studies on it as a photocatalyst for the photodegradation of anionic dyes. Despite the above advantages, multiphase cobalt aluminum oxides still face challenges such as limited light absorption range, aggregation, and potential environmental hazards due to the dissolution of cobalt ions. Summary of the invention

[0006] The present invention aims to disclose a multiphase Co photocatalytic degradation of anionic dyes. x AlO4 catalyst can solve one or more technical problems existing in the prior art and provide at least one beneficial option or create conditions.

[0007] The first aspect of the present invention is to provide a heterogeneous cobalt aluminum oxide catalyst.

[0008] The second aspect of the present invention is to provide a method for preparing the multiphase cobalt aluminum oxide catalyst described in the first aspect of the present invention.

[0009] The third aspect of the present invention is to provide application directions of the multi-phase cobalt aluminum oxide catalyst described in the first aspect of the present invention.

[0010] The raw materials of the heterogeneous cobalt aluminum oxide catalyst in the first aspect of the present invention include Co(NO3)3·6H2O, Al(NO3)3·9H2O, NH4F and urea. The chemical formula of the heterogeneous cobalt aluminum oxide catalyst is Co x AlO4, where x is 1.2~1.8. Co x AlO4 is a multiphase physical mixture with the highest adsorption intensity, which is attributed to its flower-like hierarchical structure and band gap energy (Eg) of 3.77 eV, with high scattering and electron transfer efficiency. Among them, Co3O4 acts as a relay center for electron transfer, while Al2O3 acts as a supporting system to improve stability. The immobilization of Co3O4 and Al2O3 can improve the activity of photocatalysts for pollutant degradation, reduce the recombination of electron-hole pairs, and the degradation process of dyes follows a pseudo-first-order reaction mechanism, which promotes the significant mineralization of dye molecules. It has been verified that Co3O4 x The AlO4 nanocomposite can effectively utilize UV ​​energy for dye decolorization and maintain a high level of photocatalytic activity over multiple cycles, highlighting its practicality and sustainability.

[0011] The preparation method described in the second aspect of the present invention comprises the following steps: (1) Dissolve Co(NO3)3·6H2O, Al(NO3)3·9H2O, NH4F and urea in distilled water and pour the solution into the reactor; (2) heating the reactor to completely react the raw materials in the reactor by hydrothermal method; (3) collecting the precipitate in the reaction kettle, washing it and then dehydrating it to obtain the heterogeneous cobalt aluminum oxide catalyst.

[0012] The above preparation method can produce nanoscale Co x AlO4, the nano-scale multiphase cobalt aluminum oxide catalyst has the advantages of high specific surface area, size effect, localized electronic effect, etc., which enables it to show higher activity, selectivity and efficiency in chemical reactions.

[0013] In a further application embodiment, the inner lining of the reactor is selected from polytetrafluoroethylene (PTFE), polyphenylene sulfide resin (PPS), polyetheretherketone resin (PEEK), polyimide (PI) or phenyl silicone rubber. The inner lining is selected from materials with chemical stability, high temperature resistance, non-stick properties, certain mechanical strength and non-toxicity, so as to ensure that the container does not participate in the reaction during the material synthesis process, and facilitate the separation of the synthetic material from the container.

[0014] In a further application embodiment, the total volume of the raw materials is not greater than 70% of the volume of the reactor. Since a hydrothermal reaction is used, 30% of the space is reserved to prevent safety problems caused by hydrothermal boiling.

[0015] In a further application embodiment, the temperature of the heating reaction is 100±1° C. A stainless steel reactor is selected, and the reaction temperature is controlled by an electric furnace to ensure stable synthesis of the material and form a relatively uniform microstructure.

[0016] In a further application embodiment, the duration of the heating reaction is not less than 24 hours to ensure that the synthesis reaction is fully carried out.

[0017] In a further application embodiment, the cleaning is to use ethanol and distilled water to wash the reaction product respectively to remove the synthesis by-products and fully release the adsorption sites on the surface of the material.

[0018] In a further application embodiment, the temperature of the dehydration treatment is 60±1° C. Within this temperature range, the properties of the product can be controlled while accelerating the dehydration, avoiding the possibility that too high a temperature may affect the properties of the material, and also avoiding too low a temperature for too long a dehydration time.

[0019] The application described in the second aspect of the present invention means that the multiphase cobalt aluminum oxide catalyst can be used for photocatalytic degradation of anionic dyes, and further for purifying industrial dye wastewater.

[0020] Compared with the prior art, the beneficial effects provided by the present invention include: the multiphase cobalt aluminum oxide catalyst is prepared by a hydrothermal method, and the prepared multiphase cobalt aluminum oxide catalyst uses Co3O4 as a relay center for electron transfer and Al2O3 as a supporting system. The SEM microstructure image shows that the original Co3O4 has an aggregated rod-like structure with a small surface area, which reduces the catalytic efficiency; while the multiphase cobalt aluminum oxide catalyst has an increased surface area due to its petal-like nanostructure, thereby improving the reactivity and making it more suitable for surface interaction applications. The difference in microstructure determines the performance and applicability of the material in a specific application. Steady-state fluorescence verifies that the optimal combination of the multiphase cobalt aluminum oxide catalyst provides a new pathway for the transmission of photogenerated electrons, and compared with pure Co3O4, the recombination rate of photogenerated electron-hole pairs is reduced, and the effective differentiation of charge carriers improves the photocatalytic efficiency. The multiphase cobalt aluminum oxide catalyst has high photocatalytic activity and good stability when decomposing various anionic dyes. The multiphase cobalt aluminum oxide catalyst exhibits good recyclability under ultraviolet light, indicating its feasibility in actual water treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a process schematic diagram of a method for preparing the heterogeneous cobalt aluminum oxide catalyst; Figure 2 is the XPS spectrum of the heterogeneous cobalt aluminum oxide catalyst; Figure 3 are the SEM and TEM test results of the heterogeneous cobalt aluminum oxide catalyst; Figure 4 is a graph showing the photocatalytic degradation effect of the heterogeneous cobalt aluminum oxide catalyst on methyl orange; Figure 5 It is a bar graph showing the effect of the multiphase cobalt aluminum oxide catalyst in actual printing and dyeing wastewater treatment. DETAILED DESCRIPTION

[0022] The following examples further illustrate the content of the present invention, but should not be construed as limiting the present invention. Without departing from the spirit and essence of the present invention, modifications and substitutions made to the methods, steps or conditions of the present invention all belong to the scope of the present invention.

[0023] Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.

[0024] Among them can Example 1: Co 1.4 Preparation of AlO4.

[0025] Use distilled water to dissolve 2 mmol Co(NO3)3·6H2O, 1.38 mmol Al(NO3)3·9H2O, 8 mmol NH4F and 10 mmol urea, and make up to 70 mL. Pour the final solution into a 100 mL tetrafluoroethylene-lined stainless steel autoclave. Then, place the autoclave in an electric oven at 100°C for 24 hours. Collect the precipitate, wash it thoroughly with ethanol and distilled water, and then dehydrate it at 60°C to obtain Co 1.4 AlO4.

[0026] The preparation process of the heterogeneous cobalt aluminum oxide catalyst is as follows Figure 1 By changing the ratio of Co(NO3)3·6H2O and Al(NO3)3·9H2O in the raw materials, the Co / Al / O ratio in the heterogeneous cobalt aluminum oxide catalyst can be changed accordingly, as shown in Examples 2 and 3.

[0027] Example 2: Co 1.27 Preparation of AlO4.

[0028] Dissolve 2 mmol Co(NO3)3·6H2O, 0.5 mmol Al(NO3)3·9H2O, 8 mmol NH4F and 10 mmol urea in distilled water and make up to 70 mL. Pour the final solution into a 100 mL tetrafluoroethylene-lined stainless steel autoclave. Then, place the autoclave in an electric oven at 100°C for 24 hours. Collect the precipitate, wash it thoroughly with ethanol and distilled water, and then dehydrate it at 60°C to obtain Co 1.27 AlO4.

[0029] Example 3: Co 1.75 Preparation of AlO4.

[0030] Dissolve 2 mmol Co(NO3)3·6H2O, 1.5 mmol Al(NO3)3·9H2O, 8 mmol NH4F and 10 mmol urea in distilled water and make up to 70 mL. Pour the final solution into a 100 mL tetrafluoroethylene-lined stainless steel autoclave. Then, place the autoclave in an electric oven at 100°C for 24 hours. Collect the precipitate, wash it thoroughly with ethanol and distilled water, and then dehydrate it at 60°C to obtain Co 1.75 AlO4.

[0031] Example 4: Characterization of heterogeneous cobalt aluminum oxide catalysts.

[0032] The multiphase cobalt aluminum oxide catalysts prepared in Examples 1 to 3 were respectively subjected to XPS spectrum detection to achieve elemental quantitative analysis.

[0033] Data such as Figure 2 As shown in the figure, it is proved that adding raw materials in different proportions can obtain Co with corresponding Co / Al / O ratios. x AlO4 nanocomposite materials.

[0034] Take the Co prepared in Example 1 1.4 The SEM and TEM microstructures of AlO4 and original Co3O4 were compared. Figure 3 As shown, the original Co3O4 has a typical aggregated rod-like microstructure with a diameter of about 3 to 5 μm (e.g. Figure 3 In contrast, Co 1.4 AlO4 nanostructures are aggregated and petal-shaped (e.g. Figure 3 As shown in b in the figure). Since the original Co3O4 has an aggregated rod-like structure, its surface area is small, which reduces the catalytic efficiency. 1.4 The petal-like nanostructure of AlO4 increases the surface area, thereby improving reactivity and making it more suitable for surface interaction applications. The difference in microstructure determines the performance and suitability of the material in a specific application. TEM analysis shows that the original Co3O4 is composed of extremely thin nanosheets stacked in monolayers, about 100 nm in length, with a characteristic layered structure (see Figure 3 The layered configuration observed in TEM is consistent with the rod-like appearance noted in SEM, explaining its enhanced surface interaction properties. 1.4 AlO4 shows a layered stacking of about 0.53 nm. At the same time, 220 Co 1.4 The typical spacing between AlO4 planes is 0.28 nm (see Figure 3 (at point d in the middle).

[0035] Example 5: Detection of the photocatalytic degradation effect of heterogeneous cobalt aluminum oxide catalyst on methyl orange.

[0036] Taking methyl orange as a representative anionic dye, the photocatalytic degradation effects of heterogeneous cobalt aluminum oxide catalysts under different Co / Al / O ratios under ultraviolet light were evaluated. 1.4 AlO4、Co 1.27 AlO4、Co 1.75 AlO4 was added to 10 mg / L methyl orange solution with a solid-liquid ratio of 5 mg / 10 mL. The blank group did not add the heterogeneous cobalt aluminum oxide catalyst. The solution was left to stand for 24 hours under ultraviolet light for full reaction, and the absorbance changes at wavelengths of 200-800 nm were scanned. The change in the characteristic peak of methyl orange at 464 nm was used to characterize the photocatalytic degradation effect of the heterogeneous cobalt aluminum oxide catalyst. Figure 4 As shown, compared with the blank group, Co 1.4AlO4 group, Co 1.27 AlO4 group and Co 1.75 The AlO4 treatment can reduce the concentration of methyl orange by 53.69%, 45.59% and 38.35% respectively. The experiment shows that the heterogeneous cobalt aluminum oxide catalyst has a significant degradation effect on methyl orange under different Co / Al / O ratios.

[0037] Example 6: Testing of the treatment effect of the multiphase cobalt aluminum oxide catalyst on actual printing and dyeing wastewater.

[0038] In order to explore the feasibility of using the multiphase cobalt aluminum oxide catalyst for actual printing and dyeing wastewater treatment, catalytic experiments were carried out using the raw water of a printing and dyeing wastewater treatment plant in Shantou City and the tail water of a printing and dyeing wastewater treatment plant. 1.4 Add AlO4 to 10 mL of printing and dyeing wastewater raw water / printing and dyeing wastewater treatment plant tail water solution, let it stand for 24 hours to fully react, and measure the color change of the printing and dyeing wastewater before and after the reaction. Figure 5 As shown, the heterogeneous cobalt aluminum oxide catalyst Co x AlO4 nanocomposite materials can catalytically degrade 82.5% of the color in the raw water of printing and dyeing wastewater, and 50.8% of the color in the tail water of printing and dyeing wastewater treatment plants. x AlO4 nanocomposites can be used in actual printing and dyeing wastewater treatment. From an economic point of view, it is recommended to be used for deep treatment of tail water from printing and dyeing wastewater treatment plants.

[0039] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

Claims

1. A heterogeneous cobalt aluminum oxide catalyst, characterized in that: The raw materials include Co(NO3)3·6H2O, Al(NO3)3·9H2O, NH4F and urea.

2. The method for preparing the heterogeneous cobalt aluminum oxide catalyst according to claim 1, characterized in that: Includes steps: The raw materials are dissolved in distilled water and poured into a reaction kettle; the mixture is heated until the reaction is complete; and the precipitate is collected, washed and dehydrated to obtain the multiphase cobalt aluminum oxide catalyst.

3. The preparation method according to claim 2, characterized in that: The inner lining of the reaction kettle is selected from polytetrafluoroethylene, polyphenylene sulfide resin, polyetheretherketone resin, polyimide or phenyl silicone rubber.

4. The preparation method according to claim 2, characterized in that: The total volume of the raw materials is not more than 70% of the volume of the reactor.

5. The preparation method according to claim 2, characterized in that: The temperature of the heating reaction is 100±1°C.

6. The preparation method according to claim 5, characterized in that: The duration of the heating reaction is not less than 24 hours.

7. The preparation method according to claim 2, characterized in that: The cleaning is to use ethanol and distilled water to wash the reaction product respectively.

8. The preparation method according to claim 2, characterized in that: The temperature of the dehydration treatment is 60±1°C.

9. Use of the heterogeneous cobalt aluminum oxide catalyst according to claim 1 in wastewater purification.

10. Use of the heterogeneous cobalt aluminum oxide catalyst according to claim 1 in photocatalytic degradation of anionic dyes.

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