Preparation method and application of cobalt prussian blue / carbon nitride sphere composite photocatalyst

Abstract

The application provides a preparation method of a cobalt Prussian blue / carbon nitride ball composite photocatalyst, which comprises the following steps: (1) dissolving melamine and cyanuric acid in dimethyl sulfoxide solutions respectively, mixing the two solutions, stirring, and then centrifuging to obtain white solids; and after centrifugal separation, calcination and drying, carbon nitride nanoballs are obtained; (2) dispersing the carbon nitride nanoballs obtained in step (1) in a mixed solution of water and methanol, and ultrasonically dispersing to obtain a mixed solution A; (3) adding potassium hexacyanocobaltate into the dispersed mixed solution of step (2) and stirring to obtain a mixed solution B; (4) dissolving cobalt acetate in a mixed solution of water and methanol, and adding into the mixed solution of step (3) drop by drop, and continuing to stir for 1 h to obtain a mixed solution C; and (5) standing the mixed solution C of step (4) for 12 h, centrifugally separating, washing with ultrapure water, and drying in a vacuum oven to obtain the cobalt Prussian blue / carbon nitride ball composite photocatalyst.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysis technology, and relates to a method for preparing a cobalt Prussian blue / carbon nitride sphere composite photocatalyst and its application. Background Technology

[0002] Organic dye wastewater is characterized by large discharge volumes, high levels of organic pollutants, and complex compositions. Untreated wastewater entering the environment will cause significant harm to human health and the ecological environment. Currently, the most commonly used methods for treating organic wastewater include microbial degradation, physical sedimentation, electrochemical degradation, and oxidation, all of which consume large amounts of energy and are prone to secondary pollution. Photocatalysis offers advantages such as simple operation, readily available energy sources, and low energy consumption. However, traditional photocatalytic methods still require the addition of oxidants such as hydrogen peroxide and oxygen, which can easily cause secondary water pollution. Limited by factors such as catalyst solubility and water stability, most photocatalytic degradation of organic pollutants still requires systems doped with organic solvents. The design and synthesis of photocatalysts for pollutant degradation in pure water systems remains a significant challenge. Existing photocatalysts for the degradation of organic dyes are mostly still developed under experimental conditions, requiring high light intensity and temperature. Therefore, developing efficient, additive-free photocatalysts that can be driven by natural light to achieve the degradation of organic dyes is a key technology for water pollution treatment, possessing significant academic and practical value.

[0003] Carbon nitride materials possess advantages such as good visible light absorption, high photoelectron transport efficiency, simple preparation, and stable photochemical performance, and are widely used as catalyst supports. Cobalt Prussian blue has advantages such as simple preparation, low raw material cost, multiple active sites, and low toxicity, and has great potential in the field of organic matter degradation. Combining photosensitive carbon nitride materials with cobalt Prussian blue through a mild technical means can combine the photocatalytic properties of carbon nitride materials with the catalytic sites of nano-Prussian blue, and further suppress photoelectron recombination during the photocatalytic process, enabling rapid degradation of organic pollutants in pure aqueous solutions under sunlight.

[0004] A search revealed two patent documents related to this patent. Chinese patent CN106622383A discloses a PB / WO3 composite photocatalyst, composed of iron-based Prussian blue and a WO3 matrix. The PB / WO3 composite in this invention not only broadens the visible light absorption range of WO3 but also effectively suppresses photogenerated carrier recombination in semiconductors. With the synergistic effect of hydrogen peroxide, it can rapidly degrade methyl orange organic dye. Patent CN106966459A discloses a method for using a magnetic nanocatalyst CoFe-PBAs@rGO to catalyze the degradation of organic dye wastewater by Oxone. This material, in a 0.9 mL solution of 0.01 M Oxone co-catalyst, utilizes an oxidation system composed of the CoFe-PBAs@rGO catalyst to degrade Rhodamine B with 100% efficiency. The magnetic nanocatalyst CoFe-PBAs@rGO in this invention can be separated and recycled, exhibiting good stability under neutral and alkaline conditions. Comparative analysis revealed that although the two patents mentioned above are similar to this case in their basic applications, the degradation of organic pollutants in both of them requires the addition of auxiliary oxidants, which can easily cause secondary pollution, and they have not achieved practical application under sunlight.

[0005] This invention provides a simple method for preparing a composite photocatalyst of cobalt Prussian blue and carbon nitride spheres (PB-Co / CN). In an aqueous solution system, without the addition of any oxidant, it enables the photocatalytic degradation of organic dyes under sunlight, and is applicable to the degradation of various organic dyes such as Rhodamine B, methylene blue, methyl orange, eosin, rose red, and BODIPY. This PB-Co / CN catalyst exhibits high photocatalytic efficiency, achieving a degradation rate of 228.1 mg / h under sunlight. -1 gcat -1 This catalyst exhibits a significantly higher photodegradation rate for organic dyes than other photocatalysts. It addresses the limitations of existing photocatalysts, such as stringent preparation conditions, relatively weak performance in degrading organic dyes, the need for oxidants and co-catalysts, and severe restrictions on practical applications. This provides a new approach for the clean and efficient treatment of water pollution. Summary of the Invention

[0006] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention provides a method for preparing a cobalt Prussian blue / carbon nitride sphere composite photocatalyst. This composite photocatalyst achieves the photocatalytic degradation of organic pollutants in a pure aqueous solution system without any auxiliary catalysts.

[0007] The specific technical solution is as follows:

[0008] A method for preparing a cobalt Prussian blue / carbon nitride sphere composite photocatalyst, comprising the following steps:

[0009] (1) Melamine and cyanuric acid were dissolved in dimethyl sulfoxide solution, and after sonication, the two solutions were mixed evenly and stirred for 10 min. After centrifugation, a white solid was obtained. After centrifugation and calcination, carbon nitride nanospheres were obtained.

[0010] (2) Disperse the carbon nitride nanospheres described in step (1) in a mixed solution of water and methanol, and sonicate to fully disperse them to obtain mixture A;

[0011] (3) Add potassium hexacyanocobaltate to the dispersed mixture from step (2) and stir for 1.5 h to obtain mixture B;

[0012] (4) Dissolve cobalt acetate in a mixture of water and methanol, add it dropwise to the mixture in step (3), and continue stirring for 1 hour to obtain mixture C;

[0013] (5) Let the mixture C from step (4) stand for 12 hours, centrifuge, wash with ultrapure water, and dry in a vacuum oven at 60°C for 12 hours to obtain a cobalt Prussian blue / carbon nitride sphere composite photocatalyst.

[0014] Moreover, in step (1), the calcination is carried out by heating to 550°C at a rate of 2.3 to 5°C / min for 4 hours.

[0015] Moreover, in step (1), the ratio of melamine to dimethyl sulfoxide solution is 25:1, w / v.

[0016] Moreover, in step (1), the ratio of cyanuric acid to dimethyl sulfoxide solution is 51:1, w / v.

[0017] Moreover, in step (2), the ratio of carbon nitride nanospheres, water, and ethanol is 25:4:1, w / v / v.

[0018] Moreover, in steps (2) and (3), the weight ratio of potassium hexacyanocobalaminate to carbon nitride nanospheres is 11:50.

[0019] Moreover, in steps (4) and (3), the weight ratio of cobalt acetate to carbon nitride nanospheres is 1:4.

[0020] Moreover, in step (4), the ratio of cobalt acetate, water, and ethanol is 25:16:4, w / v / v.

[0021] This invention also provides an application of a cobalt Prussian blue / carbon nitride sphere composite photocatalyst in the photocatalytic degradation of organic dyes. The method is as follows: the cobalt Prussian blue / carbon nitride sphere composite photocatalyst is placed in a pure aqueous solution system under natural light conditions to achieve the photocatalytic degradation of high-concentration organic dyes.

[0022] Furthermore, the cobalt Prussian blue / carbon nitride sphere composite photocatalyst was dispersed in an organic dye containing 0.4 g / L, and sonicated for 5 min at room temperature to obtain a uniformly dispersed mixture. The mixture was then irradiated with sunlight for 2 h. During the irradiation process, the reaction solution was continuously sampled to monitor the catalytic progress. A standard curve was established using an ultraviolet spectrophotometer to quantify the catalytic process. The final measured dye degradation rate of Rhodamine B was 228.1 mg h⁻¹ gcat⁻¹.

[0023] Moreover, the photocatalytic reaction is a solid-liquid reaction, the reaction temperature is at room temperature, and the light irradiation is full-spectrum sunlight.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) In this invention, cobalt Prussian blue is grown in situ on carbon nitride nanospheres, and then heated under mild conditions to obtain a PB-Co / CN composite material. The spherical carbon nitride material in this patent has a large number of wrinkles, and the increased specific surface area helps to load a large amount of cobalt Prussian blue and achieve a large amount of adsorption of organic dyes. The carbon nitride material can not only serve as a carrier for cobalt Prussian blue, but also absorb visible light to achieve rapid photogenerated electron transfer. At the same time, the catalytic sites exposed by cobalt Prussian blue can achieve rapid degradation of organic dyes under the drive of photoelectrons and holes. The prepared PB-Co / CN can significantly promote the photodegradation rate of organic dyes, and its photocatalytic effect is significantly better than most catalysts.

[0026] (2) This invention develops a convenient and simple method for synthesizing photocatalyst composite materials. The product can be obtained through in-situ synthesis and mild calcination. This invention can achieve large-scale synthesis of catalysts without damaging the catalytic efficiency of the catalyst itself. The composite nanomaterials of this invention are free of heavy metals, have high stability, and are highly safe.

[0027] (3) The catalytic application of this invention can be carried out in a pure water system without any co-catalysts or oxidants. The catalytic process is highly efficient and environmentally friendly. This invention uses sunlight as the driving force, has a wide range of energy sources, and is highly operable. The photocatalytic efficiency of this invention is high, reaching 228.1 mg / h. -1 g cat -1 . Attached Figure Description

[0028] Figure 1 X-ray powder diffraction patterns of simulated PB-Co, experimentally obtained PB-Co / CN, and CN.

[0029] Figure 2 This is a high-magnification transmission electron microscope image of PB-Co / CN. Detailed Implementation

[0030] The technical solution of the present invention will be further illustrated below with reference to specific embodiments.

[0031] Example 1

[0032] This invention provides a photocatalytic material composed of cobalt Prussian blue and carbon nitride nanospheres, the preparation method of which includes the following steps:

[0033] (1) Dissolve 500 mg of melamine and 510 mg of cyanuric acid in 20 mL and 10 mL of dimethyl sulfoxide, respectively. After sonication, mix the two solutions evenly and stir for 10 min. Centrifuge to obtain a white solid. Then heat to 550 °C at a rate of 2.3 °C / min and calcine for 4 h to obtain carbon nitride nanospheres.

[0034] (2) Disperse 50 mg of carbon nitride nanospheres in a mixed solution of 8 mL of water and 2 mL of methanol, and sonicate to fully disperse them to obtain mixture A;

[0035] (3) Add 11 mg of potassium hexacyanocobalamin to the mixture in step (2) and stir for 1.5 h to obtain mixture B;

[0036] (4) Dissolve 12.5 mg cobalt acetate in a mixture of 8 mL water and 2 mL methanol, add it dropwise to the mixture in step (3), and continue stirring for 1 h to obtain mixture C;

[0037] (5) Let the mixture C from step (4) stand for 12 hours, centrifuge, wash with ultrapure water, and dry in a vacuum oven at 60°C for 12 hours to obtain a cobalt Prussian blue / carbon nitride sphere composite photocatalyst.

[0038] Example 2

[0039] The structure of the prepared PB-Co / CN photocatalyst was characterized by powder X-ray powder diffraction (PXRD) and high-magnification transmission electron microscopy (HRTEM), and the results are as follows:

[0040] 1) PB-Co / CN composite material

[0041] The XRD pattern of PB-Co / CN is shown below. Figure 1 As shown. By Figure 1 It can be seen that PB-Co / CN exhibits diffraction peaks for both carbon nitride nanospheres and cobalt Prussian blue, confirming the successful synthesis of the PB-Co / CN composite material.

[0042] 2) PB-Co / CN composite material

[0043] HRTEM image of PB-Co / CN as shown Figure 2 As shown. By Figure 2As can be seen from a, the PB-Co / CN composite material exhibits a uniform spherical structure with PB-Co dispersed on it. From Figure 2 As can be seen from the magnified image of b, PB-Co nanoparticles are uniformly dispersed on the surface of carbon nitride nanospheres.

[0044] In summary, PB-Co nanomaterials can be successfully loaded onto carbon nitride nanospheres to synthesize PB-Co / CN.

[0045] Example 3

[0046] This invention prepares a cobalt Prussian blue / carbon nitride sphere composite photocatalyst for the photocatalytic degradation of organic dyes. The specific method is as follows:

[0047] Take 2 mg of the cobalt Prussian blue / carbon nitride sphere composite photocatalyst prepared in Example 1 and disperse it in a solution containing 0.4 g L -1 A homogeneous dispersion of Rhodamine B was obtained by sonication for 5 minutes in an aqueous solution. The solution was then irradiated with sunlight from 9:00 AM to 11:00 AM Beijing time for 2 hours. During the irradiation process, samples were taken continuously to monitor the catalytic progress. A standard curve was established using a UV spectrophotometer to quantify the catalytic process. The final dye degradation rate of Rhodamine B was 228.1 mg / h. -1 g cat -1 .

[0048] The above embodiments are representative implementations of the present invention. Currently, this method has been successfully used to degrade many organic dyes, including Rhodamine B, methylene blue, methyl orange, eosin, and rose red. However, the implementation of the present invention is not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are included within the scope of protection of the present invention.

Claims

1. An application of a cobalt Prussian blue / carbon nitride sphere composite photocatalyst in the photocatalytic degradation of organic dyes by sunlight, characterized in that: The method involves using a cobalt Prussian blue / carbon nitride sphere composite photocatalyst in a pure aqueous solution under natural light conditions, without the addition of any oxidant, to achieve the photocatalytic degradation of high-concentration organic dyes through a solid-liquid reaction. The preparation steps of the cobalt Prussian blue / carbon nitride sphere composite photocatalyst are as follows: (1) Melamine and cyanuric acid were dissolved in dimethyl sulfoxide solution, and after sonication, the two solutions were mixed evenly and stirred for 10 min. After centrifugation, a white solid was obtained. After centrifugation and calcination, carbon nitride nanospheres were obtained. (2) Disperse the carbon nitride nanospheres described in step (1) in a mixed solution of water and methanol, and then sonicate them thoroughly to obtain mixture A; (3) Add potassium hexacyanocobaltate to the dispersed mixture from step (2) and stir for 1.5 h to obtain mixture B; (4) Dissolve cobalt acetate in a mixture of water and methanol, add it dropwise to the mixture in step (3), and continue stirring for 1 h to obtain mixture C; The mixture C from step (4) was allowed to stand for 12 h, centrifuged, washed with ultrapure water, and dried in a vacuum oven at 60°C for 12 h to obtain a cobalt Prussian blue / carbon nitride sphere composite photocatalyst.

2. The application of the cobalt Prussian blue / carbon nitride sphere composite photocatalyst according to claim 1 in the photocatalytic degradation of organic dyes by sunlight, characterized in that: In step (1), the calcination is carried out by heating the temperature to 550 ℃ at a rate of 2.3~5 ℃ / min for 4 h.

3. The application of the cobalt Prussian blue / carbon nitride sphere composite photocatalyst according to claim 1 in the photocatalytic degradation of organic dyes by sunlight, characterized in that: In step (1), the ratio of melamine to dimethyl sulfoxide solution is 25:1, w / v.

4. The application of the cobalt Prussian blue / carbon nitride sphere composite photocatalyst according to claim 1 in the photocatalytic degradation of organic dyes by sunlight, characterized in that: In step (1), the ratio of cyanuric acid to dimethyl sulfoxide solution is 51:1, w / v.

5. The application of the cobalt Prussian blue / carbon nitride sphere composite photocatalyst according to claim 1 in the photocatalytic degradation of organic dyes by sunlight, characterized in that: In step (2), the ratio of carbon nitride nanospheres, water, and ethanol is 25:4:1, w / v / v.

6. The application of the cobalt Prussian blue / carbon nitride sphere composite photocatalyst according to claim 1 in the photocatalytic degradation of organic dyes by sunlight, characterized in that: In steps (2) and (3), the weight ratio of potassium hexacyanocobalaminate to carbon nitride nanospheres is 11:

50.

7. The application of the cobalt Prussian blue / carbon nitride sphere composite photocatalyst according to claim 1 in the photocatalytic degradation of organic dyes by sunlight, characterized in that: In steps (4) and (3), the weight ratio of cobalt acetate to carbon nitride nanospheres is 1:

4.

8. The application of the cobalt Prussian blue / carbon nitride sphere composite photocatalyst according to claim 1 in the photocatalytic degradation of organic dyes by sunlight, characterized in that: In step (4), the ratio of cobalt acetate, water, and ethanol is 25:16:4, w / v / v.

9. The application of the cobalt Prussian blue / carbon nitride sphere composite photocatalyst according to claim 1 in the photocatalytic degradation of organic dyes by sunlight, characterized in that: The cobalt Prussian blue / carbon nitride sphere composite photocatalyst was dispersed in an organic dye containing 0.4 g / L. The mixture was sonicated for 5 min at room temperature to obtain a uniformly dispersed solution, which was then irradiated with sunlight for 2 h. During the irradiation process, the reaction solution was continuously sampled to monitor the catalytic progress. A standard curve was established using a UV spectrophotometer to quantify the catalytic process. The final measured degradation rate of Rhodamine B was 228.1 mg / h. -1 g cat -1 .

Images