A light-free carbon nitride photocatalyst, its preparation method, and its application in the degradation of pollutants in water by activated persulfate.

Abstract

This invention discloses a light-free carbon nitride photocatalyst, its preparation method, and its application in the degradation of pollutants in water using activated persulfate. It belongs to the field of environmental pollution removal technology. This invention obtains a light-free carbon nitride photocatalyst by high-temperature calcination of 2,5-thiophene-dicarboxylic acid, nickel acetate tetrahydrate, and cobalt acetate tetrahydrate with urea. Its activated persulfate can efficiently degrade various high-concentration pollutants without light exposure. 15 mg of this catalyst can degrade 50 mg of persulfate. ‑1 The degradation rates of methyl orange, methylene blue, rhodamine B, tetracycline, ciprofloxacin, and metronidazole reached 100% (1 min), 100% (2 min), 99% (5 min), 97% (30 s), 97% (20 min), and 88% (30 min), respectively; after five consecutive cycles, 50 mg L of the product was degraded. ‑1 Tetracycline, degradation rate >96%; 10 mg of this catalyst degrades 50 mg L in different water sources. ‑1 Tetracycline degradation rate >95%. High degradation efficiency, high stability and versatility indicate that this catalyst has great potential for application in the field of water pollution control.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of environmental pollution removal, and particularly relates to a carbon nitride photocatalyst capable of being used without light, a preparation method thereof and application of the photocatalyst in activating persulfate to degrade pollutants in water. BACKGROUND

[0002] With the rapid development of industrialization / urbanization and the exponential growth of population, water pollution is becoming more and more serious. Developing water pollution remediation technology with environmental and economic benefits has become the focus of work of environmental protection departments and researchers. Photocatalytic solar conversion technology has the advantages of high efficiency, greenness and economy, and is considered as one of the most effective strategies to solve global environmental crisis. Carbon nitride (g-C3N4 or CN) is an emerging all-organic semiconductor photocatalytic material, which has great application potential in the field of water pollution remediation due to its simple synthesis, cheap and common raw materials, suitable band gap and easy to control. Photocatalysts can only work under light conditions, which limits the range and efficiency of the practical application of photocatalytic technology. If a full-time photocatalyst capable of maintaining photocatalytic activity under light and non-light conditions can be developed, the sewage treatment capacity of photocatalytic technology will be improved, and the application scope of photocatalytic field will be broadened. In recent years, the advanced oxidation process (PS-AOP) based on persulfate (PS) has attracted much attention and is considered as a promising, fast and efficient purification technology for removing high-concentration and refractory pollutants in water. At present, there are very few reports on carbon nitride photocatalysts capable of activating persulfate under non-light conditions. In addition, photocatalysts with simple preparation method, free from light dependence, high efficiency in degrading various high-concentration pollutants, high stability and strong universality have not been reported. SUMMARY

[0003] The purpose of the present application is to fill the defects of the prior art, and to provide a simple method for preparing a carbon nitride photocatalyst capable of being used without light, which is free from light dependence, has high efficiency in degrading various high-concentration pollutants, high stability and strong universality, improves the sewage treatment capacity of photocatalytic technology, and broadens the application scope of photocatalytic field. The catalyst and preparation technology have not been reported so far.

[0004] The specific technical solutions of the present application are as follows:

[0005] A preparation method of a carbon nitride photocatalyst capable of being used without light, comprising the following steps:

[0006] (1) Preparation of a mixture of 2,5-thiophene dicarboxylic acid, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and urea:

[0007] The 2,5-thiophene dicarboxylic acid, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and urea are placed in a mixed solvent in a certain mass ratio and stirred, and then dried and ground thoroughly;

[0008] (2) Preparation of a carbon nitride photocatalyst that can be used without light:

[0009] The mixture of 2,5-thiophene dicarboxylic acid, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and urea obtained in step (1) was placed in a heater and heated at a fixed heating rate for a period of time. After naturally cooling to room temperature, the product was ground into powder to obtain a carbon nitride photocatalyst that is not used for light.

[0010] Preferably, the mixed solvent in step (1) is a mixture of 10-90% methanol-water or 10-90% ethanol-water.

[0011] Preferably, the drying method in step (1) is one of freeze drying, ordinary drying, air drying or vacuum drying.

[0012] Preferably, the mass ratio of 2,5-thiophene dicarboxylic acid to urea in step (1) is 2-15 mg: 1 g.

[0013] Preferably, the mass ratio of nickel acetate tetrahydrate to urea in step (1) is 13.69 mg: 1 g.

[0014] Preferably, the mass ratio of cobalt acetate tetrahydrate to urea in step (1) is 54.8 mg: 1 g.

[0015] Preferably, the heater in step (2) is a muffle furnace or a tubular furnace.

[0016] Preferably, in step (2), the heating rate of the mixture of 2,5-thiophene dicarboxylic acid, nickel acetate tetrahydrate, cobalt acetate tetrahydrate, and urea in the heater is 4–6 °C / min. -1 .

[0017] Preferably, in step (2), the mixture of 2,5-thiophene dicarboxylic acid, nickel acetate tetrahydrate, cobalt acetate tetrahydrate, and urea is kept at a temperature of 580–620°C in the heater.

[0018] Preferably, in step (2), the mixture of 2,5-thiophene dicarboxylic acid, nickel acetate tetrahydrate, cobalt acetate tetrahydrate, and urea is held in the heater for 2.5 to 3.5 hours.

[0019] Another objective of this invention is to provide an application of carbon nitride photocatalyst that can be used without light in activating persulfate degradation of organic matter, specifically including the following steps: mixing and stirring a certain mass of catalyst and an aqueous solution of organic pollutants of a certain concentration, centrifuging the mixed liquid at intervals, and analyzing the change in absorbance value (concentration) of the supernatant at a certain wavelength using a UV-Vis spectrophotometer.

[0020] Preferably, the catalyst mass to tetracycline concentration ratio is 1 mg: 1–5 mg / L.-1 The volume of the organic solution is 30–60 mL; the organic substance is one of tetracycline, rhodamine B, methylene blue, metronidazole, methyl orange, and ciprofloxacin; the sampling time interval is 0.05–10 min; the amount of each sample is 2 mL; the wavelength of the UV-Vis spectrophotometer is 355–358 nm, 551–554 nm, 660–662 nm, 276–278 nm, 463–465 nm, and 276–278 nm.

[0021] Compared with the prior art, the advantages of the present invention are as follows:

[0022] 1. The raw materials are inexpensive and readily available, and the synthesis method is simple and easy to operate;

[0023] 2. The product is pure. No surfactants, templates, or substrates are introduced during the synthesis, which greatly reduces the content of impurities and reduces the impact of impurity components on the structure and properties of the target product. The integrated structure makes the physical and chemical properties of the product stable.

[0024] 3. The raw materials are only low-cost urea and 2,5-thiophene dicarboxylic acid, nickel acetate tetrahydrate, and cobalt acetate tetrahydrate. No expensive or environmentally harmful reagents such as organic solvents or protective gases are used, so there are basically no risk factors.

[0025] 4. The product can be used for the efficient degradation of many types of high-concentration organic pollutants, and has strong versatility;

[0026] 5. Different water systems have very little impact on degradation efficiency and have strong anti-interference ability.

[0027] 6. High cycle stability. Attached Figure Description

[0028] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. The elements or parts in the drawings are not necessarily drawn to scale.

[0029] Figure 1 FT-IR images of Co,Ni-xTACN, 100TACN, Co,Ni-CN and pure CN prepared in Examples 1-7;

[0030] Figure 2 Scanning electron microscope (SEM) images of Co,Ni-CN (a) and Co,Ni-100TACN prepared in Examples 3 and 6 (b);

[0031] Figure 3Nitrogen adsorption-desorption diagrams of Co,Ni-CN and Co,Ni-100TACN prepared in Examples 3 and 6 are shown.

[0032] Figure 4 The catalytic degradation of TC by Co,Ni-xTACN, 100TACN, Co,Ni-CN and pure CN prepared in Examples 1-7, and the degradation of metronidazole MDZ, ciprofloxacin CIP and rhodamine B RhB, methylene blue MB and methyl orange MO by Co,Ni-100TACN prepared in Example 3.

[0033] Figure 5 The effect of different water sources on the catalytic degradation of TC by Co,Ni-100TACN prepared in Example 3;

[0034] Figure 6 The graph shows the cyclic degradation performance of Co,Ni-100TACN prepared in Example 3. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings and examples:

[0036] Example 1

[0037] 20 mg of 2,5-thiophene dicarboxylic acid, 0.1369 g of nickel acetate tetrahydrate, 0.5480 g of cobalt acetate tetrahydrate, and 10 g of urea were placed in a solution of 10 mL of water and 10 mL of ethanol and stirred for 12 h. The mixture was then freeze-dried for 24 h, thoroughly ground, and placed in a muffle furnace at a heating rate of 5 °C / min. -1 Heat to 600℃ and hold for 3 hours. After naturally cooling to room temperature, grind the product into powder and label it as Co,Ni-20TACN.

[0038] Example 2

[0039] 50 mg of 2,5-thiophene dicarboxylic acid, 0.1369 g of nickel acetate tetrahydrate, 0.5480 g of cobalt acetate tetrahydrate, and 10 g of urea were placed in a solution of 10 mL of water and 10 mL of ethanol and stirred for 12 h. The mixture was then freeze-dried for 24 h, thoroughly ground, and placed in a muffle furnace at a heating rate of 5 °C / min. -1 Heat to 600℃ and hold for 3 hours. After naturally cooling to room temperature, grind the product into powder and label it as Co,Ni-50TACN.

[0040] Example 3

[0041] 100 mg of 2,5-thiophene dicarboxylic acid, 0.1369 g of nickel acetate tetrahydrate, 0.5480 g of cobalt acetate tetrahydrate, and 10 g of urea were placed in a solution of 10 mL of water and 10 mL of ethanol and stirred for 12 h. The mixture was then freeze-dried for 24 h, thoroughly ground, and placed in a muffle furnace at a heating rate of 5 °C / min. -1 Heat to 600℃ and hold for 3 hours. After naturally cooling to room temperature, grind the product into powder and label it as Co,Ni-100TACN.

[0042] Example 4

[0043] 150 mg of 2,5-thiophene dicarboxylic acid, 0.1369 g of nickel acetate tetrahydrate, 0.5480 g of cobalt acetate tetrahydrate, and 10 g of urea were placed in a solution of 10 mL of water and 10 mL of ethanol and stirred for 12 h. The mixture was then freeze-dried for 24 h, thoroughly ground, and placed in a muffle furnace at a heating rate of 5 °C / min. -1 Heat to 600℃ and hold for 3 hours. After naturally cooling to room temperature, grind the product into powder and label it as Co,Ni-150TACN.

[0044] Example 5 (Comparative Example)

[0045] 100 mg of 2,5-thiophene dicarboxylic acid and 10 g of urea were placed in 10 mL of water and 10 mL of ethanol solution and stirred for 12 h. The mixture was then freeze-dried for 24 h and thoroughly ground. The mixture was then placed in a muffle furnace and heated at a rate of 5 °C / min. -1 Heat to 600°C and hold for 3 hours. After naturally cooling to room temperature, grind the product into powder and label it as 100TACN.

[0046] Example 6 (Comparative Example)

[0047] 0.1369 g of nickel acetate tetrahydrate, 0.5480 g of cobalt acetate tetrahydrate, and 10 g of urea were placed in a solution of 10 mL of water and 10 mL of ethanol and stirred for 12 h. The mixture was then freeze-dried for 24 h and thoroughly ground. The mixture was then placed in a muffle furnace and heated at a rate of 5 °C / min. -1 Heat to 600℃ and hold for 3 hours. After naturally cooling to room temperature, grind the product into powder and label it as Co,Ni-CN.

[0048] Example 7 (Comparative Example)

[0049] 10g of urea was placed in 10mL of water and 10mL of ethanol solution and stirred for 12 hours. The mixture was then freeze-dried for 24 hours and thoroughly ground. The mixture was then placed in a muffle furnace and heated at a rate of 5℃ / min. -1 Heat to 600℃ and maintain for 3 hours. After naturally cooling to room temperature, grind the product into powder and label it as CN.

[0050] Example 8

[0051] An application of a light-free carbon nitride photocatalyst for activating persulfate degradation of total chloride (TC) is described below: The degradation effects of a series of prepared catalysts targeting TC were investigated. 15 mg of catalyst, 10 mg of PMS, and 50 mg / L of TC were mixed. -1 Mix 50 mL of the aqueous solution and stir. Every so often, take 2 mL of the liquid, centrifuge and collect the supernatant. Use a UV-Vis spectrophotometer at 358 nm to analyze the change in TC absorbance (concentration).

[0052] Example 9

[0053] An application of a light-free carbon nitride photocatalyst for activating persulfate degradation of RhB is described below: The degradation effects of a series of prepared catalysts targeting RhB were investigated. 15 mg of catalyst, 10 mg of PMS, and 50 mg of RhB (L...) were mixed. -1 Mix the 50 mL aqueous solution with stirring. Every so often, take 2 mL of the liquid, centrifuge and collect the supernatant. Use a UV-Vis spectrophotometer at 554 nm to analyze the change in RhB absorbance (concentration).

[0054] Example 10

[0055] An application of a light-free carbon nitride photocatalyst for activating persulfate degradation of bromine (MB) is described below: The degradation effects of a series of prepared catalysts were investigated using MB as the target pollutant. 15 mg of catalyst, 10 mg of PMS, and 50 mg of MB (L...) were... -1 Mix the 50 mL aqueous solution with stirring. Every so often, take 2 mL of the liquid, centrifuge and collect the supernatant. Use a UV-Vis spectrophotometer to analyze the change in MB absorbance (concentration) at 662 nm.

[0056] Example 11

[0057] An application of a light-free carbon nitride photocatalyst for activating persulfate degradation of MDZ is described below: The degradation effects of a series of prepared catalysts were investigated using MDZ as the target pollutant. 15 mg of catalyst, 10 mg of PMS, and 50 mg of MDZ (L...) were mixed. -1 Mix the MDZ absorbance (concentration) with an aqueous solution of 50 mL and stir. Every so often, take 2 mL of the liquid, centrifuge and collect the supernatant. Use a UV-Vis spectrophotometer at 277 nm to analyze the changes in MDZ absorbance (concentration).

[0058] Example 12

[0059] An application of a light-free carbon nitride photocatalyst for activating persulfate degradation of MO is described below: The degradation effects of a series of prepared catalysts were investigated using MO as the target pollutant. 15 mg of catalyst, 10 mg of PMS, and 50 mg of MO (L...) were... -1 Mix 50 mL of the aqueous solution and stir. Every so often, take 2 mL of the liquid, centrifuge and collect the supernatant. Use a UV-Vis spectrophotometer to analyze the change in MO absorbance (concentration) at 464 nm.

[0060] Example 13

[0061] An application of a light-free carbon nitride photocatalyst for activating persulfate degradation of CIP is described below: The degradation effects of a series of prepared catalysts were investigated using CIP as the target pollutant. 15 mg of catalyst, 10 mg of PMS, and 50 mg of CIP (L...) were... -1 Mix the 50 mL aqueous solution with stirring. Every so often, take 2 mL of the liquid, centrifuge and collect the supernatant. Use a UV-Vis spectrophotometer at 277 nm to analyze the change in CIP absorbance (concentration).

[0062] Figure 1 The following are the FTIR spectra of all catalysts, 810 cm⁻¹. -1 The signal corresponds to the vibration of the heptaazine ring, 1200-1600 cm. -1 The series of characteristic peaks are typical of triazine ring tensile vibrations, 3100-3500 cm⁻¹. -1 The broad peaks originate from unreacted terminal hydroxyl and amino groups. These peaks are observed at 563.1 and 650.4 cm⁻¹. -1 The peak values ​​correspond to the Co-O and Ni-O groups of NiCo2O4, respectively.

[0063] Figure 2 SEM images show that Co,Ni-CN (a) has a dense, lamellar structure, while Co,Ni-100TACN (b) exhibits a distinctly rough, porous structure. Furthermore, Figure 3 It was confirmed that the specific surface area was 34.6543 m². 2 g -1 (Co,Ni-CN) increased to 43.6026m 2 g -1 (Co,Ni-100TACN). The porous structure and increased specific surface area of ​​Co,Ni-100TACN facilitate the exposure of more active sites, thereby improving degradation efficiency.

[0064] like Figure 4 Figure ac shows the effect of CN and Co,Ni-xTACN catalytic activation on the degradation of pollutants in PMS. As can be seen from the figure, 15 mg of catalyst significantly reduced the degradation of pollutants by 50 mg L...-1 The degradation rates of methyl orange, methylene blue, rhodamine B, tetracycline, ciprofloxacin, and metronidazole reached 100% (1 min), 100% (2 min), 99% (5 min), 97% (30 s), 97% (20 min), and 88% (30 min), respectively.

[0065] Figure 5 The effects of different water sources (tap water, Yitong River water, Jingyuetan Lake water, and Songhua River water) on the degradation rate were explored. 15 mg of this catalyst degraded 50 mg of L from different water sources (tap water, river water, lake water, and river water). -1 The degradation rate of tetracycline is still above 95%.

[0066] Figure 6 The results show that after five consecutive catalytic cycle degradation experiments, the degradation rate of TC by Co,Ni-100TACN can still be maintained above 96%, indicating that the catalyst has good cycle stability.

[0067] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0068] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0069] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A photocatalyst activated persulfate for the degradation of pollutants in water that can be used without light, characterized by that, The preparation method of the applied catalyst comprises the following steps: (1) Preparation of a mixture of 2,5-thiophene dicarboxylic acid, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and urea: Put 2,5-thiophene dicarboxylic acid, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and urea in a certain mass ratio into a mixed solvent and stir, then dry and grind thoroughly; (2) Preparation of a carbon nitride photocatalyst that can be used without light: Put the mixture of 2,5-thiophene dicarboxylic acid, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and urea prepared in step (1) into a heater, heat at a constant heating rate and keep for a period of time; after natural cooling to room temperature, grind the product into powder to obtain a carbon nitride photocatalyst that can be used without light; Mix a certain mass of the catalyst prepared in step (2) and a certain concentration of an aqueous organic pollutant solution, stir, centrifuge the mixed liquid every certain time interval, and analyze the change in absorbance value at a certain wavelength using a UV-visible spectrophotometer for the supernatant.

2. A photocatalyst activated persulfate for the degradation of pollutants in water that can be used without light according to claim 1, characterized by, The mixed solvent in step (1) is a mixture of 10-90% methanol water or 10-90% ethanol water.

3. A non-light application of a carbon nitride photocatalyst activated persulfate for degrading pollutants in water according to claim 1, characterized in that, The drying method in step (1) is one of freeze-drying, air drying or vacuum drying.

4. A non-light application of a carbon nitride photocatalyst activated persulfate for degrading pollutants in water according to claim 1, characterized in that, The mass ratio of 2,5-thiophene dicarboxylic acid to urea in step (1) is 2-15 mg: 1 g; the mass ratio of nickel acetate tetrahydrate to urea in step (1) is 13.69 mg: 1 g.

5. A non-light application of a carbon nitride photocatalyst activated persulfate for degrading pollutants in water according to claim 1, characterized in that, The mass ratio of cobalt acetate tetrahydrate to urea in step (1) is 54.8 mg: 1 g.

6. A non-light application of a carbon nitride photocatalyst activated persulfate for degrading pollutants in water according to claim 1, characterized in that, The heater in step (2) is one of a muffle furnace or a tube furnace.

7. A non-light application of a carbon nitride photocatalyst activated persulfate for degrading pollutants in water according to claim 1, characterized in that, The heating rate of the mixture of 2,5-thiophenedicarboxylic acid, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and urea in the heater in step (2) is 4-6 ℃·min -1 The holding temperature of the mixture of 2,5-thiophenedicarboxylic acid, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and urea in the heater in step (2) is 580-620 ℃; and the holding time of the mixture of 2,5-thiophenedicarboxylic acid, nickel acetate tetrahydrate, cobalt acetate tetrahydrate and urea in the heater in step (2) is 2.5-3.5 h.

8. A non-light application of a carbon nitride photocatalyst activated persulfate for degrading pollutants in water according to claim 1, characterized in that, The volume of the organic pollutant solution is 30-60 mL; the organic pollutant is one of tetracycline, rhodamine B, methylene blue, metronidazole, methyl orange and ciprofloxacin; the sampling time interval is 0.05-10 min; the amount of each sampling is 2 mL; and the wavelength of the UV-visible spectrophotometer corresponding to the organic pollutant is 355-358 nm, 551-554 nm, 660-662 nm, 276-278 nm, 463-465 nm and 276-278 nm, respectively.

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