An S-doped graphitic carbon nitride material with N defects, its preparation method and applications

Abstract

A sulfur-doped graphitic carbon nitride material with N defects, its preparation method and application. The present invention discloses a sulfur-doped graphitic carbon nitride material with N defects, which has bifunctionality. This bifunctionality enables it to both perform organic synthesis of green energy in a photocatalytic system and treat antibiotic pollution in water environment, showing great application potential in both environmental governance and clean energy fields. Melamine is calcined in air to form pristine graphitic carbon nitride CN-E, and then CN-E is heated with sublimed sulfur powder under water bath conditions, washed, dried, and then calcined in nitrogen to obtain a light yellow powder material SCN-E polymer, that is, the sulfur-doped graphitic carbon nitride material with N defects.

Description

Technical Field

[0001] The present invention relates to the field of photocatalysis, and particularly to an S-doped graphitic carbon nitride material with N defects, a preparation method thereof, and an application thereof. Background Art

[0002] In terms of energy, hydrogen peroxide (H2O2) is a multifunctional green oxidant and is widely used in many fields such as medicine, chemical industry, and environmental remediation. In terms of environmental pollution, the water pollution problem caused by antibiotics poses a serious threat to humans and the ecosystem. In particular, the water pollution caused by tetracycline antibiotics will produce drug-resistant bacteria and drug-resistant genes in the water body, and the harm caused cannot be underestimated.

[0003] The photocatalysis technology replaces the anthraquinone process that has pollution and explosion risks, utilizes clean and renewable solar energy, induces the separation of electron-hole pairs on the surface of the photocatalyst, and thus performs redox reactions. Only water and oxygen (O2) are required to produce H2O2 under sunlight irradiation. In the presence of a photocatalyst, the photocatalysis technology can effectively utilize solar energy to remove tetracycline antibiotics in the water body, and has good degradation effects in different water matrices. Graphitic carbon nitride (g-C3N4) is regarded as an excellent semiconductor photocatalyst due to its stable physical and chemical properties and suitable energy band structure. However, the original graphitic carbon nitride still needs to improve its light absorption rate, increase reactive sites, and reduce the recombination of photo-generated carriers through modification strategies. Summary of the Invention

[0004] In order to overcome the problems existing in the prior art, the present invention prepares an S-doped g-C3N4 photocatalyst with N defects, which can produce up to 1183.54 μmol·L -1 of H2O2 within 60 min of photocatalysis, and the degradation rates of 5 mg·L -1 tetracycline hydrochloride (TC) solution, 10 mg·L -1 oxytetracycline (OTC) solution, and 10 mg·L -1 chlortetracycline (CTC) solution reach 100%, 92.2%, and 93.8% respectively within 30 min, and can perform multiple cycles of efficient H2O2 production and efficient degradation of tetracycline antibiotics solution.

[0005] The S-doped graphitic carbon nitride material with N defects of the present invention has dual functionality. On the one hand, it can photocatalytically degrade tetracycline antibiotics solution, and on the other hand, it can photocatalytically produce H2O2. The dual functionality of this invention enables it to not only carry out the green synthesis of energy in the photocatalytic system but also treat the antibiotic pollution in the water environment, showing great application potential in both the field of environmental governance and clean energy.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A kind of S-doped graphitic carbon nitride material with N defects, the graphitic carbon nitride material can photocatalytically degrade tetracycline antibiotics solution on the one hand and photocatalytically produce H2O2 on the other hand. The graphitic carbon nitride material produces 1183.54 μmol·L -1 of H2O2 within 60 min of photocatalysis, and the degradation rates of 5 mg·L -1 of tetracycline hydrochloride solution, 10 mg·L -1 of oxytetracycline solution and 10 mg·L -1 of chlortetracycline solution reach 100%, 92.2% and 93.8% respectively within 30 min, and it can efficiently produce H2O2 and efficiently degrade tetracycline antibiotics solution through multiple cycles.

[0008] The present invention provides a preparation method of the above-mentioned S-doped graphitic carbon nitride material with N defects. Melamine is calcined at high temperature in the air to prepare the original graphitic carbon nitride. Sublimed sulfur powder is added to the original graphitic carbon nitride and mixed, and then the above-mentioned S-doped graphitic carbon nitride material with N defects is prepared through a hydrothermal method and a secondary calcination method.

[0009] Furthermore, it includes the following steps:

[0010] (1) Preparation of CN-E: Take 15 g of melamine and calcine it at 520 °C in the air for 4 h at a heating rate of 10 °C / min, and then perform secondary calcination at 580 °C in the air for 4 h at the same heating rate to form the original graphitic carbon nitride CN-E.

[0011] (2) Preparation of SCN-E: 0.4 g of CN-E and 3.5 g of sublimated sulfur powder were added to 50 ml of deionized water, and the mixture was stirred continuously for 1 h in a water bath at 60 °C. After stirring, the mixture was mixed evenly, and then heated at 180 °C for 12 h to obtain a yellow solid material. The yellow solid material was then washed alternately with ethanol and water for 3 times, and dried to obtain a light yellow block material. The light yellow block material was calcined at 520 °C in nitrogen at a heating rate of 10 °C / min for 2 h to obtain a light yellow powder material SCN-E polymer, i.e., the S-doped graphite carbon nitride material with N defects.

[0012] The present invention also provides a bifunctional photocatalyst prepared by the above method. In the photocatalytic system, a certain amount of the S-doped graphite carbon nitride material with N defects is taken and placed in 50 ml of tetracycline antibiotic aqueous solution and 50 ml of methanol aqueous solution respectively to achieve photocatalytic degradation of tetracycline antibiotics and photocatalytic production of H2O2.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] (1) Compared with other S-doped graphitic carbon nitride photocatalytic systems, the present invention has the dual functions of efficiently degrading tetracycline antibiotics and producing H2O2, providing a new idea for combining the degradation of antibiotics in water with the generation of value-added clean energy using solar energy.

[0015] (2) The S-doped graphitic carbon nitride material (SCN-E) with N defects prepared in the present invention can be recycled to achieve the effect of stable and efficient photocatalytic degradation of tetracycline antibiotics and production of H2O2.

[0016] (3) The S-doped graphite carbon nitride material (SCN-E) with N defects prepared in the present invention can still have a high degradation rate for tetracycline antibiotics in a variety of water matrices. The impurities in different water matrices have little effect on the degradation effect. The SCN-E polymer has good anti-interference ability to impurities in different water matrices during photocatalytic degradation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a comparison of the degradation effects of the prepared SCN-E polymer and the original graphite phase carbon nitride (CN-E) on tetracycline hydrochloride (TC) under simulated sunlight;

[0018] Figure 2 This is a comparison of the degradation effects of the prepared SCN-E polymer and the original graphite phase carbon nitride (CN-E) on oxytetracycline (OTC) under simulated sunlight;

[0019] Figure 3 It is a comparison chart of the degradation effects of the prepared SCN-E polymer and the original graphitic carbon nitride (CN-E) on chlortetracycline (CTC) under simulated sunlight irradiation;

[0020] Figure 4 It is a cyclic degradation chart of the prepared SCN-E polymer on tetracycline hydrochloride (TC) under simulated sunlight irradiation;

[0021] Figure 5 It is a cyclic degradation chart of the prepared SCN-E polymer on oxytetracycline (OTC) under simulated sunlight irradiation;

[0022] Figure 6 It is a cyclic degradation chart of the prepared SCN-E polymer on chlortetracycline (CTC) under simulated sunlight irradiation;

[0023] Figure 7 It is a comparison chart of the degradation effects of the prepared SCN-E polymer on tetracycline hydrochloride (TC) in different water matrices under simulated sunlight irradiation;

[0024] Figure 8 It is a comparison chart of the degradation effects of the prepared SCN-E polymer on oxytetracycline (OTC) in different water matrices under simulated sunlight irradiation;

[0025] Figure 9 It is a comparison chart of the degradation effects of the prepared SCN-E polymer on chlortetracycline (CTC) in different water matrices under simulated sunlight irradiation;

[0026] Figure 10 It is a chart of the H₂O₂ production of the prepared CN-E and SCN-E polymers under simulated sunlight irradiation;

[0027] Figure 11 It is a cyclic degradation chart of the H₂O₂ production of the prepared SCN-E polymer under simulated sunlight irradiation;

[0028] Figure 12 It is the XRD pattern of the CN-E and SCN-E polymers in Example 1;

[0029] Figure 13 It is the electron paramagnetic resonance diagram of the CN-E and SCN-E polymers in Example 1. Detailed implementation mode

[0030] The present invention will be described in detail below with reference to specific embodiments. Example 1

[0031] Preparation of an S-doped graphitic carbon nitride material with N defects (SCN-E polymer)

[0032] (1) Preparation of CN-E: 15 g of melamine was calcined at 520 °C in air at a heating rate of 10 °C / min for 4 h, and then calcined again at 580 °C in air at the same heating rate for 4 h to form the original graphite phase carbon nitride CN-E.

[0033] (2) Preparation of SCN-E: 0.4 g of CN-E and 3.5 g of sublimated sulfur powder were added to 50 ml of deionized water, and the mixture was stirred continuously for 1 h in a water bath at 60 °C. After stirring, the mixture was mixed evenly, and then heated at 180 °C for 12 h to obtain a yellow solid material. The yellow solid material was then washed alternately with ethanol and water for 3 times, and dried to obtain a light yellow block material. The light yellow block material was calcined at 520 °C in nitrogen at a heating rate of 10 °C / min for 2 h to obtain a light yellow powder material SCN-E polymer, i.e., the S-doped graphite carbon nitride material with N defects.

[0034] Example 2: Photocatalytic degradation of tetracycline antibiotics

[0035] Take 20 mg of SCN-E polymer from Example 1 and add it to 50 ml of 5 mg·L -1 A 3W LED lamp was used to simulate visible light, and the reaction should be dark for 30 min before illumination to achieve adsorption and desorption equilibrium. The degradation of tetracycline hydrochloride (TC) was analyzed by high performance liquid chromatography. Furthermore, the SCN-E polymer in the system after the first run was saved, and the above operation was repeated in the second run to continue to observe the cyclic degradation activity of the reused SCN-E polymer on the tetracycline hydrochloride solution. 5 mg·L -1 The tetracycline hydrochloride solution was replaced with 10 mg·L -1 Oxytetracycline (OTC) solution and 10 mg·L -1 The photocatalytic degradation and photocatalytic cyclic degradation of oxytetracycline and chlortetracycline by SCN-E polymer were investigated with chlortetracycline (CTC) solution, while other conditions and operations remained unchanged.

[0036] Figure 1 This is a comparison chart of the degradation effects of tetracycline hydrochloride on the best performing SCN-E polymer and pristine graphite phase carbon nitride (CN-E) under simulated sunlight. It can be seen from the figure that in the presence of CN-E, the degradation rate of tetracycline hydrochloride after 30 minutes of illumination is only 65%, while the degradation rate of tetracycline hydrochloride by SCN-E polymer reaches nearly 100%.

[0037] Figure 2It is a comparison chart of the degradation effects of the best-performing SCN-E polymer and the original graphitic carbon nitride (CN-E) on oxytetracycline under simulated sunlight irradiation. As can be seen from the chart, in the presence of CN-E, the degradation rate of oxytetracycline after 30 minutes of light irradiation is only 41.9%, while the degradation rate of the SCN-E polymer for oxytetracycline reaches 92.2%.

[0038] Figure 3 It is a comparison chart of the degradation effects of the best-performing SCN-E polymer and the original graphitic carbon nitride (CN-E) on chlortetracycline under simulated sunlight irradiation. As can be seen from the chart, in the presence of CN-E, the degradation rate of chlortetracycline after 30 minutes of light irradiation is only 44.9%, while the degradation rate of the SCN-E polymer for chlortetracycline reaches nearly 93.8%.

[0039] Figure 4 It is a cyclic degradation experiment of the SCN-E polymer on tetracycline hydrochloride under simulated sunlight irradiation. In 5 cyclic degradation experiments, the degradation rates of tetracycline hydrochloride are 100%, 98.52%, 97.36%, 96.57% and 95.59% respectively. It can be seen from this that the SCN-E polymer has excellent cyclic degradation stability for tetracycline hydrochloride.

[0040] Figure 5 It is a cyclic degradation experiment of the SCN-E polymer on oxytetracycline under simulated sunlight irradiation. In 5 cyclic degradation experiments, the degradation rates of oxytetracycline are 93.8%, 92.1%, 91.5%, 90.8% and 90.1% respectively. It can be seen from this that the SCN-E polymer has excellent cyclic degradation stability for oxytetracycline.

[0041] Figure 6 It is a cyclic degradation experiment of the SCN-E polymer on chlortetracycline under simulated sunlight irradiation. In 5 cyclic degradation experiments, the degradation rates of chlortetracycline are 93.9%, 93%, 92.5%, 92% and 91.5% respectively. It can be seen from this that the SCN-E polymer has excellent cyclic degradation stability for chlortetracycline.

[0042] Example 3: Photocatalytic degradation of tetracycline antibiotics in different water matrices

[0043] Take 20 mg of the SCN-E polymer in Example 1 and add it to 50 ml of 5 mg·L -1 of tetracycline hydrochloride aqueous solution, tap water solution, Yellow River water solution and seawater solution. Use a 3W LED lamp to simulate visible light. Dark reaction should be carried out for 30 minutes before light irradiation to achieve adsorption and desorption equilibrium. Use high performance liquid chromatography to analyze and test the photocatalytic degradation activity of the SCN-E polymer on tetracycline hydrochloride solution in different water matrices. For 5 mg·L-1 Replace tetracycline hydrochloride with 10 mg·L -1 of oxytetracycline and 10 mg·L -1 of chlortetracycline, with other conditions and operations unchanged, to investigate the photocatalytic degradation activity of SCN-E polymer towards oxytetracycline and chlortetracycline in different water matrices.

[0044] Figure 7 It is a comparison chart of the degradation effect of SCN-E polymer on tetracycline hydrochloride in different water matrices under simulated sunlight irradiation. As can be seen from the chart, in deionized water matrix, tap water matrix, Yellow River water matrix and seawater matrix, the degradation rates of tetracycline hydrochloride after 30 min of illumination are 100%, 97.2%, 95.6% and 92.5% respectively, proving that the SCN-E polymer has excellent photocatalytic degradation ability towards tetracycline hydrochloride in different water matrices and has good anti-interference ability against impurities in different water matrices.

[0045] Figure 8 It is a comparison chart of the degradation effect of SCN-E polymer on oxytetracycline in different water matrices under simulated sunlight irradiation. As can be seen from the chart, in deionized water matrix, tap water matrix, Yellow River water matrix and seawater matrix, the degradation rates of oxytetracycline after 30 min of illumination are 92.2%, 90.1%, 87.5% and 84.2% respectively, proving that the SCN-E polymer has excellent photocatalytic degradation ability towards oxytetracycline in different water matrices and has good anti-interference ability against impurities in different water matrices.

[0046] Figure 9 It is a comparison chart of the degradation effect of SCN-E polymer on chlortetracycline in different water matrices under simulated sunlight irradiation. As can be seen from the chart, in deionized water matrix, tap water matrix, Yellow River water matrix and seawater matrix, the degradation rates of chlortetracycline after 30 min of illumination are 93.8%, 90.2%, 87.7% and 83.3% respectively, proving that the SCN-E polymer has excellent photocatalytic degradation ability towards chlortetracycline in different water matrices and has good anti-interference ability against impurities in different water matrices.

[0047] Example 4: Photocatalytic production of H2O2

[0048] 50 mg of the SCN-E polymer in Example 1 was added to 50 ml of deionized aqueous solution containing 5% methanol. A 3W LED lamp was used to simulate visible light. Before illumination, a dark reaction should be carried out for 30 min to achieve adsorption-desorption equilibrium. The common titanium salt spectrophotometry was used to analyze and test the concentration of H2O2. Further, the SCN-E polymer in the system after the first run was preserved and the above operations were repeated in the second run, and the photocatalytic cycle activity of the reused SCN-E polymer for the production of H2O2 was continuously observed.

[0049] Figure 10 shows the production of H2O2 by CN-E and SCN-E polymers under simulated sunlight irradiation. Under illumination, the H2O2 production rate of CN-E was 275.16 μmol·L -1 , while the H2O2 production rate of the SCN-E polymer was 1183.54 μmol·L -1 . The H2O2 production rate of the SCN-E polymer was 3 times that of CN-E, proving that the photocatalytic H2O2 production performance of the modified SCN-E polymer was better than that of CN-E.

[0050] Figure 11 shows the cyclic degradation experiment of H2O2 production by the SCN-E polymer under simulated sunlight irradiation. In the 5 cyclic H2O2 production experiments, the H2O2 production rates for the 5 times were 1183.54 μmol·L -1 , 1106.83 μmol·L -1 , 1081.83 μmol·L -1 , 1025.17 μmol·L -1 %, and 996.83 μmol·L -1 . Thus, it can be seen that the SCN-E polymer has excellent cyclic stability for photocatalytic H2O2 production.

[0051] Figure 12It is the XRD pattern of the CN-E and SCN-E polymers in Example 1. The peak pattern of CN-E corresponds to that in the PDF card (JCPDS-87-1526). The 12.8° and 27.8° peaks belong to the (100) and (002) planes in g-C3N4, corresponding to the in-plane and interlayer stacking modes of the conjugated aryl groups respectively. The peak pattern of the SCN-E polymer corresponds to that in the PDF card (JCPDS-01-83-2285). Compared with CN-E, the diffraction peak of the SCN-E polymer at 12.7° almost disappears, indicating that the doping of S reduces the degree of order of its skeleton. Moreover, the intensity of the diffraction peak of the SCN-E polymer at 12.8° is significantly weakened, which may be caused by the thinning of the SCN-E polymer size during high-temperature treatment. The diffraction peak of S8 can be seen in the XRD pattern of the SCN-E polymer, indicating that the surface of the SCN-E polymer is wrapped by sulfur species.

[0052] Figure 13 It is the electron paramagnetic resonance diagram of the CN-E and SCN-E polymers in Example 1. The existence of N defects is proved by electron paramagnetic resonance. The existence of N defects accelerates the interfacial electron transfer rate of the SCN-E polymer, which is beneficial to capturing delocalized electrons, forming local states and improving the separation ability of electron-hole pairs, thus improving the photocatalytic ability of the SCN-E polymer.

Claims

1. A preparation method of an S-doped graphitic carbon nitride material with N defects, characterized in that, Melamine is calcined at high temperature in air to prepare pristine graphitic carbon nitride. Sublimed sulfur powder is added to the pristine graphitic carbon nitride and mixed, and then the described S-doped graphitic carbon nitride material with N defects is prepared by a hydrothermal method and a secondary calcination method. On the one hand, the graphitic carbon nitride material can photocatalytically degrade tetracycline antibiotics solution. The degradation rates of 5 mg·L -1 tetracycline hydrochloride solution, 10 mg·L -1 oxytetracycline solution and 10 mg·L -1 chlortetracycline solution reach 100%, 92.2% and 93.8% respectively within 30 min. On the other hand, it can photocatalytically produce H2O2. The graphitic carbon nitride material produces 1183.54 μmol·L -1 of H2O2 within 60 min of photocatalysis, and can efficiently produce H2O2 and efficiently degrade tetracycline antibiotics in multiple cycles. The specific steps are as follows: (1) Preparation of CN-E: 15 g of melamine was calcined at 520 °C in air at a heating rate of 10 °C / min for 4 h, and then calcined again at 580 °C in air at the same heating rate for 4 h to form the original graphite phase carbon nitride CN-E; (2) Preparation of SCN-E: 0.4 g of CN-E and 3.5 g of sublimated sulfur powder were added to 50 ml of deionized water, and the mixture was stirred continuously for 1 h in a water bath at 60 °C. After stirring, the mixture was mixed evenly, and then heated at 180 °C for 12 h to obtain a yellow solid material. The yellow solid material was then washed alternately with ethanol and water for 3 times, and dried to obtain a light yellow block material. The light yellow block material was calcined at 520 °C in nitrogen at a heating rate of 10 °C / min for 2 h to obtain a light yellow powder material SCN-E polymer, i.e., the S-doped graphite carbon nitride material with N defects.

2. A bifunctional photocatalyst prepared by the method of claim 1, wherein a certain amount of the S-doped graphite carbon nitride material having N defects is placed in 50 ml of a tetracycline antibiotic aqueous solution and 50 ml of a methanol aqueous solution, respectively, to achieve photocatalytic degradation of tetracycline antibiotics and photocatalytic production of H2O2.

Images