Preparation method and application of DCN / Ni-FeOCl composite catalyst

Abstract

The invention discloses a preparation method of a DCN / Ni-FeOCl composite catalyst and application of the DCN / Ni-FeOCl composite catalyst. The catalyst is formed by taking a two-dimensional graphite phase carbon nitride nanosheet (DCN) as a carrier and loading nickel-doped oxyferric chloride (Ni-FeOCl). Performing thermal polycondensation reaction on the precursor by using microwave heating to obtain two-dimensional graphite phase carbon nitride; two-dimensional graphite phase carbon nitride, ferric chloride hexahydrate (FeCl3. 6H2O) and nickel chloride hexahydrate (NiCl2. 6H2O) are calcined in proportion to prepare DCN / Ni-FeOCl, and the DCN / Ni-FeOCl composite catalyst is formed. Ni-FeOCl and DCN form a Z-type heterojunction, the Z-type heterojunction has good electronic conductivity, generation of photon-generated carriers is promoted, the dynamic characteristic of catalytic reaction is improved, and organic pollutants in water can be efficiently degraded.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalysis, and particularly relates to a preparation method and application of a DCN / Ni-FeOCl composite catalyst. Background Art

[0002] With the abuse of antibiotics and the development of the textile industry, the concentrations of antibiotics and organic dyes in natural water bodies have been continuously rising, posing a threat to the ecosystem and human health. Photocatalysis technology is a green and efficient environmental purification method, which has shown great potential in the fields of degrading organic pollutants and antibiotics in recent years. Photocatalysis utilizes light to excite semiconductors to generate electron-hole pairs, and then generates highly oxidative free radicals, which can effectively degrade these refractory small-molecule organic substances, providing a new direction for solving environmental pollution problems.

[0003] Graphitic carbon nitride (CN) has become a research focus in the field of photocatalysis due to its high photocatalytic activity and chemical stability. Graphitic carbon nitride can absorb light energy in the visible and ultraviolet regions. However, due to the restriction of the low electron conductivity of g-C3N4, the photogenerated carriers generated inside it cannot be effectively separated and migrated. Therefore, studying how to improve the electron conductivity of graphitic carbon nitride to enhance its photocatalytic efficiency has become a research hotspot and frontier in this field. Summary of the Invention

[0004] Aiming at the above problems, the purpose of the present invention is to provide a preparation method of a DCN / Ni-FeOCl composite catalyst, which enables graphitic carbon nitride to have good electron conductivity, is conducive to the generation and migration of photogenerated carriers, improves the catalytic reaction rate, and can achieve efficient degradation of organic pollutants in water.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is: a preparation method of a DCN / Ni-FeOCl composite catalyst, comprising the following steps:

[0006] 1) Put the nitrogen-rich organic matter into a crucible, use silicon carbide as a wave absorber, heat the nitrogen-rich organic matter by microwave method, and obtain DCN through thermal polycondensation;

[0007] 2) Mix DCN, FeCl3·6H2O and NiCl2·6H2O and calcine them into DCN / Ni-FeOCl, collect the brownish-red product, grind it into powder, rinse it with deionized water and dry it.

[0008] As a possible implementation manner, further, in step 1), the nitrogen-rich organic matter is selected from any one or more of melamine, cyanuric acid, dicyandiamide, monocyanamide, thiourea, and urea.

[0009] As a possible implementation, further, step 1) specifically includes the following steps:

[0010] 1.1) Place nitrogen-rich organic matter as a precursor into a ceramic crucible, and place a silicon carbide crucible buckle on top of the ceramic crucible as a wave absorbing device;

[0011] 1.2) Place the crucible assembly in a microwave oven cavity, evacuate to vacuum, set the microwave irradiation power to 3 kW, and the microwave frequency to 2-3 GHz, heat the raw material to 500-550° C. by microwave irradiation, and heat and maintain for a total of 10-20 minutes to obtain two-dimensional graphite phase carbon nitride DCN.

[0012] As a possible implementation manner, further, in step 1.2), the microwave oven is evacuated to 5 kPa.

[0013] As a possible implementation, further, step 2) specifically includes the following steps:

[0014] 2.1) Take 1g DCN, 2.7g FeCl3·6H2O and 0.47g NiCl2·6H2O and mix them thoroughly in anhydrous ethanol;

[0015] 2.2) After removing the anhydrous ethanol, the mixture is dried, and the dried mixture is placed in a ceramic crucible and calcined in a muffle furnace to obtain a DCN / Ni-FeOCl heterojunction;

[0016] 2.3) The obtained brown-red product was ground into powder, washed with deionized water 2-3 times, collected, and vacuum dried.

[0017] As a possible implementation mode, further, after removing the anhydrous ethanol and drying in step 2.2), the mixture is heated to 220° C. at a rate of 5° C. / min in a muffle furnace and calcined for 2 hours to obtain a DCN / Ni-FeOCl heterojunction.

[0018] The present invention also provides a photocatalyst, which is prepared by the above method and can be used to catalyze the degradation of organic pollutants in water.

[0019] As a possible implementation, further, in the photocatalytic degradation reaction of organic pollutants in water, the reaction temperature is 25-30°C, the reaction time is 1-2h, and the light source is a 300w xenon lamp.

[0020] As a possible implementation manner, further, the pollutant is rhodamine b, ceftiofur sodium, etc.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1) The present invention uses DCN (two-dimensional graphitic carbon nitride) as a substrate, and heats ferric chloride and nickel chloride to directly generate nickel-modified iron oxy chloride on DCN. Usually, the carbon nitride prepared by thermal polycondensation is bulk carbon nitride, i.e., three-dimensional carbon nitride. There is generally a serious interlayer stacking phenomenon in bulk g-C3N4, resulting in the disadvantages of small specific surface area and low porosity of the catalyst. In contrast, the two-dimensional graphitic carbon nitride (DCN) prepared by thermal polycondensation in the present invention reduces interlayer stacking compared with three-dimensional carbon nitride, exposes more surface active sites, increases the specific surface area, and thus significantly improves the mass transfer efficiency and the exposure of active sites in the catalytic reaction.

[0023] 2) In the DCN / Ni-FeOCl catalyst prepared by the present invention, the loading of Ni-FeOCl forms a Z-type heterojunction with DCN, which has good electronic conductivity, is beneficial to promoting the generation of photo-generated carriers, improves the kinetic characteristics of the catalytic reaction, and can efficiently degrade organic pollutants in water.

[0024] 3) The preparation method provided by the present invention has the advantages of fast catalyst preparation, low cost, and simple operation. The obtained product is basically non-toxic or has low toxicity and will not cause harm to the environment. The obtained catalyst has a fast photocatalytic degradation rate and can be carried out at room temperature. Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 It is the photocatalytic mechanism diagram of the DCN / Ni-FeOCl heterojunction;

[0027] Figure 2 It is the XRD image of DCN;

[0028] Figure 3 It is the XRD image of the DCN / Ni-FeOCl heterojunction;

[0029] Figure 4 It is the SEM image of the DCN / Ni-FeOCl heterojunction;

[0030] Figure 5 It is the degradation curve of rhodamine b degraded by the DCN / Ni-FeOCl heterojunction;

[0031] Figure 6 It is the degradation curve of cefotaxime sodium degraded by the DCN / Ni-FeOCl heterojunction. Detailed Embodiments

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0033] Example 1

[0034] The preparation method of the DCN / Ni-FeOCl composite catalyst in this example is as follows:

[0035] (1) Put 5 g of melamine into a ceramic crucible, and invert a silicon carbide crucible over the ceramic crucible as a microwave absorption device. Place it at the center of an industrial high-energy microwave cavity, and evacuate to 5 kPa. Turn on the microwave, with a microwave irradiation power of 3 kW. After the temperature reaches 500 °C, keep it warm. After a total of 20 min for heating and holding, turn off the microwave oven. After cooling to room temperature, take out the light yellow sample, wash it 2 - 3 times with deionized water and then dry it to collect the sample to obtain DCN;

[0036] (2) Dissolve 0.1 g of DCN, 2.7 g of FeCl3·6H2O, and 0.47 g of NiCl2·6H2O in 20 ml of absolute ethanol and ultrasonicate for 30 min. After removing the absolute ethanol, dry it. Place the dried medicine in a ceramic crucible and put it into a muffle furnace for calcination: heat it at a heating rate of 5 °C / min to 220 °C and calcine for 2 hours. After cooling, obtain a brownish-red product, grind it, rinse it 2 - 3 times with deionized water, and vacuum dry it for 12 h.

[0037] Photocatalytic degradation test: Use the DCN / Ni-FeOCl sample prepared in Example 1 as a photocatalyst to test the degradation performance of rhodamine b. Specifically: Use a 300 W xenon lamp as the light source, with a dosage of 10 mg of the DCN / Ni-FeOCl heterojunction photocatalyst, a concentration of 20 mg / L of the rhodamine b solution, and a dosage of 50 mL of the rhodamine b solution.

[0038] After adding the photocatalyst to the rhodamine b solution, conduct a dark reaction for 1 h. After the dark reaction ends, perform light irradiation. Starting from 0 min to 60 min, take 1 mL of samples every 10 min, for a total of 7 samples; the taken samples are filtered through a 0.45 μm filter membrane to remove the photocatalyst in the solution.

[0039] Use an enzyme-labeled instrument to measure the absorbance of the obtained filtrate, and calculate the degradation curve of rhodamine b according to the relationship between the absorbance and the concentration (as Figure 5As shown, the removal rate of Rhodamine B reached 98.7% within 60 min.

[0040] Example 2

[0041] In this example, the preparation method of the DCN / Ni-FeOCl composite catalyst is as follows:

[0042] (1) Put 10 g of urea into a ceramic crucible, invert a silicon carbide crucible over the ceramic crucible as a microwave absorption device. Place it in the center of an industrial high-energy microwave cavity, evacuate to 5 kPa. Turn on the microwave, with a microwave irradiation power of 3 kW. After the temperature reaches 500 °C, start heat preservation. After a total heating and heat preservation time of 20 min, turn off the microwave oven. Let the reaction system cool to room temperature with the furnace and then take out the pale yellow sample. Wash it with deionized water, dry it, and collect the sample to obtain DCN;

[0043] (2) The preparation method of DCN / Ni-FeOCl is the same as that in Example 1.

[0044] Photocatalytic degradation test: Use the DCN / Ni-FeOCl sample prepared in this Example 2 as a photocatalyst to test the removal performance of cefotaxime sodium. Specifically: Use a 300 W xenon lamp as the light source, the dosage of the DCN / Ni-FeOCl heterojunction photocatalyst is 10 mg, the concentration of the cefotaxime sodium solution is 20 mg / L, and the dosage of the cefotaxime sodium solution is 50 mL.

[0045] After adding the photocatalyst to the cefotaxime sodium solution, carry out a dark reaction for 1 h. After the dark reaction ends, carry out illumination. Take 1 mL of samples at 1 min, 2 min, 4 min, 6 min, 8 min, 10 min, and 20 min respectively, for a total of 7 samples; The samples taken are filtered through a 0.45 μm filter membrane to remove the photocatalyst in the solution.

[0046] Use an enzyme-labeled instrument to measure the absorbance of the obtained filtrate, and calculate the degradation curve of cefotaxime sodium according to the relationship between the absorbance and the concentration (as shown in the appendix Figure 6 As shown). After calculation, the removal rate of cefotaxime sodium within 20 min is 96.1%.

[0047] Comparative Example 1

[0048] In this comparative example, the preparation method of the composite catalyst is as follows:

[0049] (1) Put 5 g of melamine into a ceramic crucible, heat it in a muffle furnace at a heating rate of 5 °C / min to 550 °C, keep it warm for 2 h, cool to room temperature, take out the pale yellow sample, wash it with deionized water 2 - 3 times, and then dry it and collect the sample, denoted as CN;

[0050] (2) 2.7 g of FeCl3·6H2O and 0.47 g of NiCl2·6H2O were thoroughly ground and placed in a ceramic crucible, then put into a muffle furnace for air calcination: heated to 220 °C at a heating rate of 5 °C / min and calcined for 2 hours. After cooling, brownish-red Ni-FeOCl was obtained, ground and rinsed 2 - 3 times with deionized water, and dried in vacuum for 12 h.

[0051] (3) 0.8 g of CN and 0.2 g of Ni-FeOCl were ground and mixed, and heat-treated at 200 °C for 2 h in a muffle furnace to obtain the CN / Ni-FeOCl composite catalyst.

[0052] The results showed that: after being treated with the photocatalyst with graphitic carbon nitride as the carrier and Ni-FeOCl loaded in this comparative example, the degradation rate of rhodamine b was 89.4%. While for the photocatalyst with graphitic carbon nitride nanosheets as the carrier and Ni-FeOCl loaded in Example 1 in the same wastewater, the degradation rate of rhodamine b was 98.7%.

[0053] Comparative Example 2

[0054] The preparation method of the composite catalyst in this comparative example is as follows:

[0055] (1) 10 g of urea was put into a ceramic crucible, heated to 550 °C at a heating rate of 5 °C / min in a muffle furnace and kept warm for 2 h. After cooling to room temperature, the pale yellow sample was taken out, washed 2 - 3 times with deionized water and dried to collect the sample, denoted as CN;

[0056] (2) 2.7 g of FeCl3·6H2O and 0.47 g of NiCl2·6H2O were thoroughly ground and placed in a ceramic crucible, then put into a muffle furnace for air calcination: heated to 220 °C at a heating rate of 5 °C / min and calcined for 2 hours. After cooling, brownish-red Ni-FeOCl was obtained, ground and rinsed 2 - 3 times with ethanol and deionized water, and dried in vacuum for 12 h;

[0057] (3) 0.8 g of CN and 0.2 g of Ni-FeOCl were ground and mixed, and heat-treated at 200 °C for 2 h in a muffle furnace to obtain the CN / Ni-FeOCl composite catalyst.

[0058] The results showed that: after being treated with the photocatalyst with graphitic carbon nitride as the carrier and Ni-FeOCl loaded in this comparative example, the degradation rate of cefotaxime sodium was 84.7%. While for the photocatalyst with graphitic carbon nitride nanosheets as the carrier and Ni-FeOCl loaded in Example 2 in the same wastewater, the degradation rate of cefotaxime sodium was 96.1%.

[0059] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing a DCN / Ni-FeOCl composite catalyst, characterized in that: The steps include: 1) Putting nitrogen-rich organic matter into a crucible, using silicon carbide as a microwave absorber, heating the nitrogen-rich organic matter by microwave method, and obtaining DCN by thermal polycondensation; 2) DCN, FeCl3·6H2O and NiCl2·6H2O were mixed and calcined to obtain DCN / Ni-FeOCl. The brown-red product was collected, ground into powder, rinsed with deionized water and dried.

2. The method for preparing the DCN / Ni-FeOCl composite catalyst according to claim 1, characterized in that: The nitrogen-rich organic matter in step 1) is selected from any one or more of melamine, cyanuric acid, melamine, cyanamide, thiourea and urea.

3. The method for preparing the DCN / Ni-FeOCl composite catalyst according to claim 1, characterized in that: Step 1) specifically includes the following steps: 1.1) Place nitrogen-rich organic matter as a precursor into a ceramic crucible, and place a silicon carbide crucible buckle on top of the ceramic crucible as a wave absorbing device; 1.2) Place the crucible assembly in a microwave oven cavity, evacuate to vacuum, set the microwave irradiation power to 3 kW, and the microwave frequency to 2-3 GHz, heat the raw material to 500-550° C. by microwave irradiation, and heat and maintain for a total of 10-20 minutes to obtain two-dimensional graphite phase carbon nitride DCN.

4. The method for preparing the DCN / Ni-FeOCl composite catalyst according to claim 1, characterized in that: In step 1.2), the microwave oven is evacuated to 5 kPa.

5. The method for preparing the DCN / Ni-FeOCl composite catalyst according to claim 1, characterized in that: Step 2) specifically includes the following steps: 2.1) Take 1g DCN, 2.7g FeCl3·6H2O and 0.47g NiCl2·6H2O and mix them thoroughly in anhydrous ethanol; 2.2) After removing the anhydrous ethanol, the mixture is dried, and the dried mixture is placed in a ceramic crucible and calcined in a muffle furnace to obtain a DCN / Ni-FeOCl heterojunction; 2.3) The obtained brown-red product was ground into powder, washed with deionized water 2-3 times, collected, and vacuum dried.

6. The method for preparing the DCN / Ni-FeOCl composite catalyst according to claim 5, characterized in that: After removing the anhydrous ethanol and drying in step 2.2), the mixture was heated to 220° C. at a rate of 5° C. / min in a muffle furnace and calcined for 2 hours to obtain a DCN / Ni-FeOCl heterojunction.

7. A photocatalyst, characterized in that: The method is prepared by the method according to any one of claims 1 to 6.

8. Use of the photocatalyst as claimed in claim 7 in catalyzing the degradation of organic pollutants in water.

9. The use according to claim 8, characterized in that: In the photocatalytic degradation of organic pollutants in water, the reaction temperature is 25-30°C, the reaction time is 1-2h, and the light source is a 300w xenon lamp.

10. The use according to claim 8, characterized in that: The pollutants are rhodamine b and ceftiofur sodium.

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