Preparation method and application of co-copper co-doped carbon nitride-based composite material

Abstract

The application discloses a preparation method and application of a Co and Cu co-doped CN-based composite material, and relates to the following steps: after urea is calcined in a muffle furnace, the urea is treated in a constant-temperature oil bath together with a mixed solution containing 1,10-phenanthroline, copper acetate and cobalt acetate; after the solvent is evaporated by heating, pyrolysis is further carried out under N2 atmosphere, so that the Co and Cu co-doped CN-based composite material is obtained. The composite material can be used for activating peroxymonosulfate (PMS) to degrade BPA in wastewater, and the removal effect is excellent, and the removal rate of BPA can reach 97.07% within 15 min.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of wastewater pollutant treatment by advanced oxidation technology, and particularly relates to a preparation method of a double-metal doped carbon-based material and application thereof in advanced oxidation technology. BACKGROUND

[0002] Bisphenol A (BPA) is an important raw material for manufacturing polycarbonate plastics and epoxy resins, and is also considered as a typical pollutant in tailings wastewater associated with mining. In addition, BPA is an endocrine disruptor, which can destroy the balance of the endocrine system in the human body, cause metabolic disorders and cancer, and have adverse effects on human health. In order to remove organic pollutants in natural water bodies and wastewater, researchers have made great efforts in this field, and have proposed a large number of methods in the past few decades, such as adsorption, ozonation, biodegradation, catalytic oxidation and advanced oxidation.

[0003] Based on the advanced oxidation technology (AOP) of persulfate (PMS) activation, a large amount of active oxygen can be generated in a wide pH range, and it has attracted more and more attention in purifying refractory organic pollutants in water. Common methods for activating PMS include ultraviolet radiation, ultrasonic wave, heat and transition metal ion catalysis, among which transition metal ions (Fe 2+ , Co 2+ and Cu 2+ ) are of great concern due to their high activation efficiency. Transition metal ions can catalyze PMS to generate SO4 ·- , which has a stronger oxidation-reduction potential and a longer half-life (30-40 μs) than ·OH, and thus has higher reaction activity. However, the homogeneous reaction of transition metal ions has the disadvantages of secondary pollution and inability to be recycled, so researchers have begun to focus on the use of transition metal doped CN materials for PMS activation.

[0004] Compared with other transition metals, Co-doped CN materials are of great concern due to their high catalytic efficiency, such as the use of CoO x , CoMO x (M = Cu, Fe or Mn) and some supported Co-based catalysts (Co@NC). However, most single-metal Co-based catalysts are faced with the problem of serious leaching of metal ions during the catalytic process, which leads to the loss of Co 2+Secondary pollution, so need to develop a method to reduce the ion leaching of Co-based catalyst. Compared with single metal-doped CN materials, double metal-doped catalysts exhibit significantly improved stability, activity and multifunctionality. Copper-based catalysts are attracting more and more attention due to their cost-effectiveness, low toxicity and environmental friendliness. In particular, it has been reported in the literature that electron transfer can occur between Cu(I) and Co(III), changing the Co(II) / Co(III) redox cycle and increasing the likelihood of ROS production. Therefore, the synergistic effect of Co and Cu active sites is attempted to accelerate the redox cycle to improve the catalytic activity of the material while reducing secondary pollution to the environment. However, the aggregation of nanoparticles may inhibit the active site, so an ideal carrier is needed to realize the environmental remediation application of Co and Cu bimetallic catalysts for PMS. SUMMARY

[0005] The present application provides a preparation method of Co and Cu co-doped CN-based composite material, aiming to meet the efficient activation of PMS, study the synergistic effect of Co and Cu bimetallic sites on PMS activation, and expand the preparation method and synergistic mechanism of Co and Cu co-doped CN-based composite material.

[0006] To solve the technical problems, the application adopts the following technical scheme:

[0007] A preparation method of Co and Cu co-doped CN-based composite material, comprising the following steps:

[0008] Step 1, placing urea in a crucible, calcining in a muffle furnace under air atmosphere to obtain solid powder g-C3N4;

[0009] Step 2, weighing Co(CH3COO)2·4H2O, Cu(CH3COO)2·H2O and C 12 H8N2·H2O, dissolving them in ethanol to obtain a mixed solution; placing the solid powder g-C3N4 obtained in step 1 in the mixed solution, oil bath stirring and oven drying to obtain a precursor;

[0010] Step 3, placing the precursor obtained in step 2 in a porcelain boat, pyrolyzing and calcining in a tube furnace under N2 atmosphere, and then grinding to obtain a Co and Cu co-doped CN-based composite material.

[0011] Preferably, in step 1, the calcination conditions of urea are as follows: heating to 500℃ at a heating rate of 5℃ / min, holding for 2h, and then naturally cooling to room temperature.

[0012] Preferably, in step 2, the Co(CH3COO)2·4H2O, Cu(CH3COO)2·H2O and C 12The molar ratio of H8N2·H2O to H2O to g-C3N4 is 1:2.95-3.05:23.95-24.05.

[0013] Preferably, in step 2, the C 12 The mass ratio of H8N2·H2O to g-C3N4 is 1:2.2-2.3.

[0014] Preferably, in step 2, the oil bath stirring is set as follows: first constant temperature stirring at 60℃ oil bath for 4h, then heating to 80℃ to evaporate the solvent, and the obtained product is placed in a 60℃ oven for drying.

[0015] Preferably, in step 3, the pyrolysis calcination is set as follows: heating to 600℃ at a heating rate of 10℃ / min under a N2 flow rate of 60mL / min, holding for 2h, and then naturally cooling to room temperature.

[0016] The Co and Cu co-doped CN-based composite material obtained by the method can be used for activating peroxymonosulfate (PMS) to improve the removal efficiency of organic pollutants BPA in wastewater. Based on this, the application provides a method for efficiently activating PMS for BPA degradation in wastewater, which comprises the following steps:

[0017] The Co and Cu co-doped CN-based composite material is added to the bisphenol A wastewater to be treated, and stirred in the dark for a period of time to reach adsorption-desorption equilibrium; after the adsorption is completed, the oxidant PMS is added for oxidative degradation.

[0018] Preferably, the mass ratio of the Co and Cu co-doped CN composite material to bisphenol A is 2.5:1, and the mass ratio of the amount of PMS to bisphenol A is 10:1.

[0019] The beneficial effects of the application are as follows:

[0020] The application provides a preparation method of a Co and Cu co-doped CN-based composite material, which is used for activating PMS to efficiently degrade organic pollutants BPA in wastewater. 12 The pyridine type N in the added 1,10-phenanthroline (C 2+ H8N2·H2O) can be coordinated with metal ions to obtain a uniform and stable metal complex, which is beneficial to forming stable Co-Nx and Cu-Nx structures in the further calcination process, improves the dispersion of metal particles, and firmly anchors the metal on the CN substrate, effectively inhibits the aggregation of Co 2+The leaching ensures the stability of the material, and the introduced N source can improve the electronic structure of adjacent carbon atoms, realize efficient activation and utilization of PMS. Meanwhile, the g-C3N4 introduced by the application as a carbon-based carrier and an electron transport medium can not only further prevent the agglomeration of metal nanoparticles, but also accelerate the electron transfer process, further improve the catalytic activity of the material. In addition, electron transfer can occur between Cu(I) and Co(III), changing the redox cycle of Co(II) / Co(III), thereby increasing the possibility of active species generation. This further illustrates the synergistic effect of the Co and Cu bimetallic active site, which can realize efficient activation of PMS and greatly improve the degradation rate of BPA. Therefore, the application provides a novel preparation method of a bimetallic doped CN-based composite material, and the obtained material has high and stable catalytic activity, and the application provides a reference idea for the preparation of a bimetallic doped CN-based material with high efficiency and low cost. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The SEM image of the Co and Cu co-doped CN-based composite material obtained in Example 1 of the application.

[0022] Figure 2 The XPS image of the Co and Cu co-doped CN-based composite material obtained in Example 1 of the application.

[0023] Figure 3 The BPA degradation experiment graph of the CN-based composite material obtained in Examples 1-3 of the application.

[0024] Figure 4 The BPA degradation experiment graph of the CN-based composite material obtained in Example 1 and Comparative Examples 1-3 of the application. DETAILED DESCRIPTION

[0025] The application will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the application, but do not limit the application in any form. It should be pointed out that, for those skilled in the art, without departing from the concept of the application, a number of modifications and improvements can be made, which all belong to the protection scope of the application.

[0026] I. Preparation of CN-based composite material

[0027] Example 1

[0028] In this embodiment, the Co and Cu co-doped CN-based composite material is prepared by the following steps:

[0029] 20 g of urea was placed in a crucible, heated to 500℃ at a heating rate of 5℃ / min in a muffle furnace under air atmosphere, and kept for 2 h, and then naturally cooled to room temperature to obtain a light yellow fluffy solid powder, i.e. g-C3N4.

[0030] Metal salts (0.15 mmol in total) with a molar ratio of Cu(Ac)2-H2O:Co(Ac)2-4H2O = 3:1 and 198 mg of C 12 H8N2-H2O (0.9 mmol) was mixed in 25 mL of ethanol, 438 mg of g-C3N4 was added, stirred at 60°C in an oil bath for 4 h, then the temperature was raised to 80°C to evaporate the solvent, and the resulting product was placed in an oven at 60°C overnight to dry, to obtain the precursor.

[0031] The precursor obtained in step 2 was placed in a porcelain boat and put into a tube furnace, heated to 600°C at a temperature rising rate of 10°C / min under a N2 flow rate of 60 mL / min for 2 h, then naturally cooled to room temperature, and ground with an agate mortar to obtain the Co and Cu co-doped CN-based composite material (Cu3Co1-CN).

[0032] The SEM image of Cu3Co1-CN prepared in this example is shown in Figure 1 It can be seen from Figure 1 that the sample is folded by ultra-thin and compact nanosheets, and no obvious metal nanoparticles are found on the surface, indicating that the particle size of the metal nanoparticles may be small and difficult to observe.

[0033] The XPS image of Cu3Co1-CN prepared in this example is shown in Figure 2 It can be seen from Figure 2 that C, N, O, Co and Cu elements exist on the surface of the sample, proving the successful doping of Co and Cu.

[0034] Example 2

[0035] This example prepared a Co and Cu co-doped CN-based composite material according to the following steps:

[0036] 20 g of urea was placed in a crucible, heated to 500°C at a temperature rising rate of 5°C / min in a muffle furnace under air atmosphere, and kept for 2 h, then naturally cooled to room temperature to obtain a light yellow fluffy solid powder, i.e. g-C3N4.

[0037] Metal salts (0.15 mmol in total) with a molar ratio of Cu(Ac)2-H2O:Co(Ac)2-4H2O = 3:1 and 198 mg of C 12 H8N2-H2O (0.9 mmol) was mixed in 25 mL of ethanol, 438 mg of g-C3N4 was added, stirred at 60°C in an oil bath for 4 h, then the temperature was raised to 80°C to evaporate the solvent, and the resulting product was placed in an oven at 60°C overnight to dry, to obtain the precursor.

[0038] The precursor obtained in step 2 was placed in a ceramic boat and placed in a tube furnace. It was heated to 650°C at a heating rate of 10°C / min under a N2 flow rate of 60 mL / min and held for 2 hours. Then it was naturally cooled to room temperature and ground with an agate mortar to obtain the CN-based composite material co-doped with Co and Cu (Cu3Co1-CN-650).

[0039] Example 3

[0040] In this embodiment, the CN-based composite material co-doped with Co and Cu was prepared according to the following steps:

[0041] 20g of urea was placed in a crucible and heated to 500℃ in an air atmosphere in a muffle furnace at a heating rate of 5℃ / min. The temperature was held for 2 hours and then naturally cooled to room temperature to obtain a light yellow fluffy solid powder, namely g-C3N4.

[0042] A metal salt with a molar ratio of Cu(Ac)₂·H₂O:Co(Ac)₂·4H₂O = 3:1 (total 0.15 mmol) and 198 mg of C 12 H8N2·H2O (0.9 mmol) was mixed in 25 mL of ethanol, and 438 mg of g-C3N4 was added to it. The mixture was stirred in an oil bath at 60 °C for 4 h, and then the solvent was evaporated at 80 °C. The resulting product was dried in an oven at 60 °C overnight to obtain the precursor.

[0043] The precursor obtained in step 2 was placed in a ceramic boat and placed in a tube furnace. It was heated to 550°C at a heating rate of 10°C / min under a N2 flow rate of 60 mL / min and held for 2 hours. Then it was naturally cooled to room temperature and ground with an agate mortar to obtain the CN-based composite material co-doped with Co and Cu (Cu3Co1-CN-550).

[0044] Comparative Example 1

[0045] In this comparative example, Cu-doped CN-based composite materials were prepared according to the following steps:

[0046] 20g of urea was placed in a crucible and heated to 500℃ in an air atmosphere in a muffle furnace at a heating rate of 5℃ / min. The temperature was held for 2 hours and then naturally cooled to room temperature to obtain a light yellow fluffy solid powder, namely g-C3N4.

[0047] 0.15 mmol Cu(Ac)₂·H₂O and 198 mg C 12 H8N2·H2O (0.9 mmol) was mixed in 25 mL of ethanol, and 438 mg of g-C3N4 was added to it. The mixture was stirred in an oil bath at 60 °C for 4 h, and then the solvent was evaporated at 80 °C. The resulting product was dried in an oven at 60 °C overnight to obtain the precursor.

[0048] The precursor obtained in step 2 was placed in a porcelain boat and put into a tube furnace, heated to 600°C at a temperature rising rate of 10°C / min under a N2flow rate of 60 mL / min for 2 h, and then naturally cooled to room temperature. The product was ground with an agate mortar to obtain a Cu-doped CN-based composite material (Cu-CN).

[0049] Comparative Example 2

[0050] The Co-doped CN-based composite material was prepared according to the following steps:

[0051] 20 g of urea was placed in a crucible and heated to 500°C at a temperature rising rate of 5°C / min under an air atmosphere in a muffle furnace for 2 h, and then naturally cooled to room temperature to obtain a light yellow fluffy solid powder, i.e., g-C3N4.

[0052] 0.15 mmol of Co(Ac)2·4H2O and 198 mg of C 12 H8N2·H2O (0.9 mmol) were mixed in 25 mL of ethanol, and 438 mg of g-C3N4was added thereto. The mixture was stirred at 60°C in an oil bath for 4 h, and then the temperature was raised to 80°C to evaporate the solvent. The obtained product was placed in an oven and dried at 60°C overnight to obtain a precursor.

[0053] The precursor obtained in step 2 was placed in a porcelain boat and put into a tube furnace, heated to 600°C at a temperature rising rate of 10°C / min under a N2flow rate of 60 mL / min for 2 h, and then naturally cooled to room temperature. The product was ground with an agate mortar to obtain a Co-doped CN-based composite material (Co-CN).

[0054] Comparative Example 3

[0055] The Co and Cu co-doped CN-based composite material was prepared according to the following steps:

[0056] 20 g of urea was placed in a crucible and heated to 500°C at a temperature rising rate of 5°C / min under an air atmosphere in a muffle furnace for 2 h, and then naturally cooled to room temperature to obtain a light yellow fluffy solid powder, i.e., g-C3N4.

[0057] Metallic salts (0.15 mmol in total) with a molar ratio of Cu(Ac)2·H2O:Co(Ac)2·4H2O = 3:1 were mixed in 25 mL of ethanol, and 438 mg of g-C3N4was added thereto. The mixture was stirred at 60°C in an oil bath for 4 h, and then the temperature was raised to 80°C to evaporate the solvent. The obtained product was placed in an oven and dried at 60°C overnight to obtain a precursor.

[0058] The precursor obtained in step 2 was placed in a porcelain boat and put into a tube furnace, heated to 600℃ at a temperature rising rate of 10℃ / min under a N2 flow rate of 60 mL / min for 2h, and then naturally cooled to room temperature, and ground with a corundum mortar to obtain a Co and Cu co-doped CN-based composite material (Cu3Co1-gC3N4).

[0059] II. Oxidative degradation of BPA:

[0060] 2.5 mg of the CN-based composite material prepared in each of the examples and the comparative examples was added to 50 mL of a BPA solution with a concentration of 20 mg / L, stirred in the dark for 30 min to reach adsorption-desorption equilibrium, 1 mL of a PMS solution with a concentration of 10 g / L was added, and timing was started, 2.5 mL of the solution was removed at the specified reaction time points of 0, 1, 3, 5, 10, and 15 min, filtered through a water-based filter membrane with a pore size of 0.45 μm to remove the catalyst, and immediately detected by a UV spectrophotometer with a test wavelength λ = 276 nm.

[0061] The BPA degradation effect of the materials prepared in examples 1-3 is shown in Figure 3 From Figure 3 It can be seen that the removal rates of BPA by the samples of examples 1-3 within 15 min through activation of PMS are 97.07%, 90%, and 20% respectively, and the effect of example 1 (Cu3Co1-CN) is the best, which shows that the material obtained under the calcination condition of 600℃ has the best performance.

[0062] The BPA degradation effect of the materials prepared in examples 1 and comparative examples 1-3 for activating PMS is shown in Figure 4 From Figure 4 It can be seen that the removal rates of BPA by the samples of comparative examples 1-3 within 15 min through activation of PMS are 22.71%, 56.02%, and 11.23% respectively, which are far lower than the removal rate of example 1 (97.07%), which shows that the Co and Cu co-doped CN-based composite material (example 1) has a much better effect on activation of PMS than the Cu-doped material (comparative example 1), the Co-doped material (comparative example 2), and the material without doping Co and Cu (comparative example 3). 12 This further proves that the Co and Cu bimetallic sites exhibit a synergistic effect in catalytic activation, and also shows the key role of C 12 H8N2·H2O in the preparation process.

[0063] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered within the protection scope of the present application.

Claims

1. A method for preparing Co and Cu co-doped CN-based composite material, characterized in that, The method comprises the following steps: Step 1, calcining urea to obtain solid powder g-C3N4; Step 2, Co(CH3COO)2-4H2O, Cu(CH3COO)2-H2O and C 12 H8N2-H2O were weighed and dissolved in ethanol to obtain a mixed solution; the solid powder g-C3N4 obtained in step 1 was placed in the mixed solution, and stirred in an oil bath and dried in an oven to obtain a precursor; Step 3, pyrolysis calcination of the precursor obtained in step 2 under N2 atmosphere, and then grinding, to obtain a Co and Cu co-doped CN-based composite material.

2. The method for preparing a CN-based composite material co-doped with Co and Cu according to claim 1, characterized in that: In step 1, the calcination conditions of urea are as follows: heating to 500 DEG C at a heating rate of 5 DEG C / min, keeping for 2 h, and then naturally cooling to room temperature.

3. The method for preparing a CN-based composite material co-doped with Co and Cu according to claim 1, characterized in that: In Step 2, the Co(CH3COO)2-4H2O, Cu(CH3COO)2-H2O and C 12 The molar ratio of H8N2-H2O to Co(CH3COO)2-4H2O to Cu(CH3COO)2-H2O to C 4. The method for preparing a Co- and Cu co-doped CN-based composite material according to claim 1, characterized in that: In Step 2, the C 12 The mass ratio of H8N2-H2O and g-C3N4 is 1:2.2-2.

3.

5. The method for preparing a CN-based composite material co-doped with Co and Cu according to claim 1, characterized in that: In step 2, the oil bath stirring conditions are set as follows: first constant temperature stirring at 60 DEG C oil bath for 4 h, and then heating to 80 DEG C to evaporate the solvent, and then putting the obtained product into a 60 DEG C oven for drying.

6. The method for preparing a CN-based composite material co-doped with Co and Cu according to claim 1, characterized in that: In step 3, the pyrolysis calcination conditions are as follows: heating to 600 DEG C at a heating rate of 10 DEG C / min under a N2 flow rate of 60 mL / min, keeping for 2 h, and then naturally cooling to room temperature.

7. A Co and Cu co-doped CN-based composite material prepared by the preparation method in any one of claims 1-6.

8. Use of the Co and Cu co-doped CN-based composite material according to claim 7, characterized in that: The Co and Cu co-doped CN-based composite material is used for activating peroxymonosulfate to efficiently remove organic pollutants in wastewater.

9. Use according to claim 8, characterized in that: The Co and Cu co-doped CN-based composite material is added into the organic pollutant wastewater to be treated, and stirring is carried out in dark conditions until adsorption and desorption equilibrium is reached; after adsorption is completed, an oxidant peroxymonosulfate is added to carry out oxidative degradation.

10. Use according to claim 8 or 9, characterized in that: The organic pollutant is bisphenol A. The Co and Cu co-doped CN-based composite material is used for activating peroxymonosulfate to efficiently remove organic pollutants in wastewater. The Co and Cu co-doped CN-based composite material is added into the organic pollutant wastewater to be treated, and stirring is carried out in dark conditions until adsorption and desorption equilibrium is reached; after adsorption is completed, an oxidant peroxymonosulfate is added to carry out oxidative degradation. The organic pollutant is bisphenol A.

Images