Material doped on g-C3N4 based on Fe and application of material in removal of emerging micropollutants in wastewater

Abstract

The invention relates to the field of environmental engineering and sewage treatment, in particular to a material based on doping of Fe on g-C3N4 and application of the material to removal of emerging micropollutants in wastewater. The preparation method of the material is simpler, the preparation process is simpler, and multiple sites in contact with pollutants can be provided for active sites. The material does not have the adsorption effect of a traditional carbon material, and the pollutant removal effect is caused by chemical reaction. Compared with a traditional advanced oxidation process which is mostly used for treating micro-polluted wastewater, the Fe-doped carbon nitride material disclosed by the invention is wider in pollutant application range. Compared with a traditional advanced oxidation process which is easily influenced by inorganic anions and HA in water, the method for removing micro-pollutants in water based on Fe-doped carbon nitride material activated PAA disclosed by the invention has the advantage that the inorganic anions and HA in water do not influence the method.

Description

Technical Field

[0001] This invention relates to the fields of environmental engineering and wastewater treatment, specifically to a material based on Fe doping on g-C3N4 and its application in removing emerging micropollutants from wastewater. Background Technology

[0002] In recent years, a variety of complex and recalcitrant micropollutants have been frequently detected in various water bodies and wastewaters, posing significant challenges to water pollution remediation and water resource recycling. Therefore, developing efficient and affordable water purification technologies is crucial, among which advanced oxidation processes (AOPs) aimed at completely destroying various harmful pollutants are essential. S Therefore, increasing public health and environmental concerns necessitate the development of new technologies to treat wastewater containing micropollutants (MPs) and reduce emerging micropollutants in the water. Advanced oxidation processes (AOPs) utilizing oxidants such as persulfate, hydrogen peroxide (H₂O₂), and chlorine have previously proven effective in pollutant degradation. In recent years, peracetic acid (PAA), as an emerging oxidant in advanced oxidation processes, has attracted widespread attention due to its advantages such as good stability, strong activation ability, and high decontamination efficiency. Peracetic acid-based advanced oxidation technologies (PAA-AOPs) are also increasingly gaining attention in water pollution treatment.

[0003] Conventional advanced oxidation technologies typically use PDS, PMS, etc., as oxidants, which introduce sulfate ions during use, causing secondary pollution to the environment. Furthermore, traditional advanced oxidant technologies generally rely on carbon materials, resulting in very high adsorption rates and necessitating secondary treatment to remove micro-pollutants primarily through adsorption. Based on this, an advanced oxidation technology using PAA as an oxidant has been proposed. PAA, as a commonly used disinfectant, does not cause secondary pollution to the environment. Moreover, the addition of Fe element to carbon nitride does not adsorb micro-pollutants; instead, it primarily degrades them by disrupting their structure.

[0004] Traditionally, loading metal elements onto carbon nitride involves first preparing the carbon nitride and then loading the metal, which significantly increases preparation costs and yields relatively small quantities of material. To produce larger quantities of material, more carbon nitride needs to be prepared first, further increasing costs and time. Therefore, this paper proposes simultaneously loading metal elements onto carbon nitride and preparing the carbon nitride. This approach increases the amount of material produced, improves efficiency, and significantly reduces costs. Summary of the Invention

[0005] To address the shortcomings of the prior art, this invention discloses a material preparation method based on simultaneously loading metal elements onto carbon nitride and preparing the carbon nitride, and its application using PAA as an oxidant to treat micro-pollutants. The material is prepared using liquid-phase glacial acetic acid, melamine, and FeCl3. A catalyst with Fe supported on carbon nitride is prepared, exhibiting uniform Fe dispersion, increased specific surface area, and a porous structure within the material that provides abundant pathways for contacting pollutants with active sites, demonstrating excellent degradation properties. This optimizes the degradation effect of advanced oxidation technology systems on wastewater containing extremely low concentrations of micro-pollutants, and avoids adsorption to degrade the pollutant structure.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: a Fe-doped carbon nitride material is prepared by reacting melamine, glacial acetic acid and ferric chloride hexahydrate in an aqueous solution to obtain a precursor material, which is then dried, calcined, cleaned and dried to obtain the Fe-doped carbon nitride material.

[0007] In the aforementioned Fe-doped carbon nitride material, the drying process involves drying at 90°C for 12 hours.

[0008] The aforementioned Fe-doped carbon nitride material is calcined at 500°C for 2 hours, with a heating rate of 5°C / min.

[0009] An advanced oxidation system for removing micro-pollutants includes a degradation tank, a foam cotton loaded with the aforementioned Fe-doped carbon nitride material, a peristaltic pump, and an outlet container. The degradation tank and the outlet container are connected by the peristaltic pump and a connecting pipe. The foam cotton loaded with Fe-doped carbon nitride material is located inside the connecting pipe.

[0010] The aforementioned advanced oxidation system for removing micro-pollutants uses PU foam.

[0011] An application of Fe-doped carbon nitride material in the removal of emerging pollutants from wastewater is characterized by the following method: the above-mentioned Fe-doped carbon nitride material is loaded onto foam cotton, placed in wastewater containing pollutants, and PAA solution is added to the wastewater to degrade the pollutants in the wastewater.

[0012] In the above application, the PAA solution is obtained by reacting CH3COOH and H2O2. CH3COOH and H2O2 are mixed at a volume ratio of 3:2, aged for 24 h, and then refrigerated to obtain the PAA solution.

[0013] In the above applications, the emerging pollutant is one or more of the following: Dimethicone A, 4-p-chlorophenol, tetracycline, rhodamine-B, and naproxen.

[0014] The beneficial effects of this invention are as follows: 1. This invention discloses an application of Fe-doped carbon nitride material-activated PAA in the removal of micro-pollutants in water. Compared with traditional materials, this material has a simpler preparation method and a simpler preparation process, and can provide more contact sites for pollutants for the active sites.

[0015] 2. Unlike traditional activated carbon, it does not have adsorption properties. The removal of pollutants is achieved through a chemical reaction that destroys their structure, rather than simply through adsorption.

[0016] 3. Compared to traditional materials that rely on a large amount of metal as active sites to remove pollutants, but are prone to metal leaching problems that cause secondary environmental pollution, the Fe-doped carbon nitride material disclosed in this invention uses less metal than traditional materials, and the leaching is far below the national standard. The Fe element used is also environmentally friendly.

[0017] 4. Compared to traditional advanced oxidation processes, which are mostly used to treat wastewater containing only one type of micro-pollutant, the application method for removing micro-pollutants in water based on Fe-doped carbon nitride material-activated PAA disclosed in this invention has a wider range of applicable pollutants and can be applied to wastewater with different pH values.

[0018] 5. Compared to traditional advanced oxidation processes, which are easily affected by inorganic anions and HA in water, resulting in reduced degradation efficiency, the present invention discloses an application method for the removal of micro-pollutants in water based on Fe-doped carbon nitride material-activated PAA, which is not affected by inorganic anions and HA in water. Attached Figure Description

[0019] Figure 1 XRD pattern of Fe-doped carbon nitride material; Figure 2 Degradation diagram of PAA activation to remove contaminants using Fe-doped carbon nitride materials; Figure 3 The graph shows the degradation of pollutants after the material undergoes eight consecutive cycles.

[0020] Figure 4 A schematic diagram of an advanced oxidation system for removing micro-pollutants.

[0021] The following are marked in the figure: (1) iron frame, (2) connecting pipe, (3) degradation tank, (4) peristaltic pump, and (5) outlet container. Detailed Implementation

[0022] Example 1

[0023] Preparation of Fe-doped carbon nitride materials

[0024] 6.3 g of melamine and 1.08 g of ferric chloride hexahydrate were placed in an aqueous solution, and then 1 mL of glacial acetic acid was added. The mixture was stirred at 90-95 °C for 15-18 minutes to prepare the precursor material, which was then dried in a vacuum oven at 90 °C for 12 h. Afterward, it was calcined in a tube furnace at 500 °C under a nitrogen atmosphere for 2 h at a heating rate of 5 °C / min. The obtained product was ground and repeatedly washed several times with deionized water and methanol, then vacuum dried in a vacuum oven at 40 °C for 10 h. Finally, it was ground again to obtain Fe-doped carbon nitride material. The obtained material was characterized, and the XRD pattern is shown below. Figure 1 In the XRD patterns, two distinct characteristic peaks appear at 2θ of 12.96° and 27.51°, corresponding to the (100) and (002) crystal planes of g-C3N4, respectively.

[0025] Example 2

[0026] The advanced oxidation system for removing micro-pollutants consists of a degradation tank 3 and an outlet container 5 connected by a peristaltic pump 4 and a connecting pipe 2. PU foam cotton loaded with Fe-doped carbon nitride material is located inside the connecting pipe 2. Figure 4 As shown; among them, the degradation tank 3, the outlet container 5, and the PU foam cotton all need to be thoroughly cleaned with deionized water before use. The connecting pipe 2 should be cleaned with an ultrasonic cleaner for 30 minutes and then thoroughly cleaned with deionized water.

[0027] Before activating PAA to remove contaminants, the Fe-doped carbon nitride material was washed twice or more with deionized water and methanol, and then dried in a vacuum oven at 40°C for 10 hours. Finally, 1g of Fe-doped carbon nitride material was added to an appropriate amount of water and loaded onto a 0.5cm×3cm×8cm PU foam and dried in a vacuum oven for 12 hours. The PU foam loaded with Fe-doped carbon nitride material was placed in a connecting tube, with the cross-section of the PU foam being larger than that of the connecting tube, to ensure that the wastewater containing contaminants could fully contact the Fe-doped carbon nitride material.

[0028] The application of PAA activation based on Fe-doped carbon nitride material for removing micro-contaminants is carried out according to the following steps: 1) Prepare 100 mg / L of bisphenol A (BPA) wastewater with 1000 ml of deionized water one day in advance. Dilute the 100 mg / L BPA wastewater to 10 mg / L as the wastewater to be treated. Use a magnetic stirrer that is always kept at 520 rpm. 2) Prepare the PAA stock solution one day in advance. The PAA stock solution is obtained by reacting CH3COOH with H2O2. First, mix 60 mL of CH3COOH and 40 mL of H2O2 into a 250 mL beaker, age the resulting solution for 24 h, and place it in a refrigerator at 4°C.

[0029] 3) Add 1000mL of 10mg / L BPA wastewater and 0.75mL of the above-mentioned PAA stock solution to the degradation tank 3, and place the connecting pipe 2 with built-in PU foam cotton on the iron frame 1. 4) Connect one end of the pump pipe of the degradation tank 3 to the pump pipe of the peristaltic pump 4, and connect the other end of the peristaltic pump 4 to the outlet container of the connecting pipe 2 which is filled with PU foam cotton. Turn on the peristaltic pump 4 so that the wastewater to be treated in the degradation tank 3 passes through the PU foam cotton loaded with Fe-doped carbon nitride material. During this process, the water flow rate is always kept at 5 ml / min. 5) Measure the pH value of the wastewater to be treated using pH test paper before degradation; 6) Take a water sample of 1 mL every five minutes from the outlet container, add 40 μL of sodium thiosulfate, shake well to stop the reaction; 7) The BPA content in the wastewater was measured every 5 minutes using a high-performance liquid chromatograph (HPLC). The BPA degradation effect is shown in the figure below. Figure 2 As shown; 8) The BPA removal rate calculation results are shown in Table 1.

[0030] 9) After 30 minutes, the leached iron ions in the reaction solution were measured using inductively coupled plasma mass spectrometry (ICP-MS) to determine the leaching of iron ions during the catalytic process. The measured iron ion concentration was 0.039 mg L⁻¹. 1 It is far below the surface water environmental quality standard (GB3838-2002, China) and will not cause secondary pollution to the environment.

[0031] Example 3

[0032] Following the method in Example 2, the pollutant BPA in the wastewater was replaced with 4-p-chlorophenol (PCP), and the removal rate of pollutant PCP was calculated. The results are detailed in Table 1 and... Figure 2 .

[0033] Example 4

[0034] Following the method in Example 2, the pollutant BPA in the wastewater was replaced with tetracycline (TC), and the removal rate of pollutant TC was calculated. The results are detailed in Table 1. Figure 2 .

[0035] Example 5

[0036] Following the method in Example 2, the BPA pollutant in the wastewater was replaced with Rhodamine-B (RhB), and the removal rate of pollutant RhB was calculated. The results are detailed in Table 1 and... Figure 2 .

[0037] Comparative Example 1

[0038] Following the method of Example 2, without placing PU foam cotton loaded with Fe-doped carbon nitride material into the connecting tube 2, BPA, PCP, TC, RhB, and NAP pollutants were degraded respectively.

[0039] Example 6

[0040] Based on Example 1, the pollutant BPA in the wastewater was replaced with naproxen (NAP), and the removal rate of pollutant NAP was calculated. The results are detailed in Table 1. Figure 2 .

[0041] Table 1. Removal rates of micropollutants BPA, PCP, TC, RhB, and NAP by PAA activated with Fe-doped carbon nitride materials.

[0042] Table 2. Removal rates of micropollutants BPA, PCP, TC, RhB, and NAP by the advanced oxidation system.

[0043] As shown in Table 1, the removal rates of micropollutants BPA, PCP, TC, RhB, and NAP by PAA activated with Fe-doped carbon nitride material are all above 90%, demonstrating excellent degradation effects and wide applicability. Meanwhile, without using Fe-doped carbon nitride material, using only this system (without loading Fe-doped carbon nitride material onto PU cotton) results in removal rates of less than 8% for micropollutants BPA, PCP, TC, RhB, and NAP, as shown in Table 2.

[0044] Example 7

[0045] Based on Example 1, a degradation process was performed in 30-minute intervals. After completion, the catalyst was recovered, washed several times with methanol and deionized water, and then dried in an oven at 40°C. After drying, the catalyst was reused for BPA degradation. This process was repeated seven times to test the catalyst's stability. The cycle effect diagram is shown below. Figure 3 As shown, it can still maintain a BPA removal rate of over 85% after 8 cycles; the removal rates from the beginning to the end of the cycle experiment were 98.3%, 97.8%, 97.1%, 91.6%, 89.8%, 91.3%, 91.1%, and 88.1%, respectively. This indicates its strong stability.

Claims

1. A Fe-doped carbon nitride material, characterized in that, The preparation method is as follows: melamine, glacial acetic acid and ferric chloride hexahydrate are reacted in an aqueous solution to obtain a precursor substance, which is dried, calcined, washed and dried to obtain the Fe-doped carbon nitride material. 2.The Fe-doped carbon nitride material according to claim 1, characterized in that, The drying is drying at 90℃ for 12h. 3.The Fe-doped carbon nitride material according to claim 1, characterized in that, The calcination is calcination at 500℃ for 2h, and the temperature rising rate is 5℃ / min.

4. An advanced oxidation system for removing micropollutants, characterized in that, The device comprises a degradation tank, a foam cotton loaded with the Fe-doped carbon nitride material according to any one of claims 1-3, a peristaltic pump and a water outlet container, the degradation tank is connected with the water outlet container through the peristaltic pump and a connecting pipe, and the foam cotton loaded with the Fe-doped carbon nitride material is located in the connecting pipe.

5. The advanced oxidation system for removing micropollutants of claim 4, wherein, The foam cotton is PU foam cotton.

6. Application of Fe-doped carbon nitride material in removing emerging pollutants in wastewater, characterized in that, The method is as follows: the Fe-doped carbon nitride material according to any one of claims 1-3 is loaded on the foam cotton, and then the foam cotton is placed in wastewater containing pollutants, PAA solution is added to the wastewater, and the pollutants in the wastewater are degraded.

7. Use according to claim 6, characterized in that, The PAA solution is obtained by reacting CH3COOH with H2O2, mixing CH3COOH and H2O2 according to a volume ratio of 3:2, aging for 24h and cold storage.

8. Use according to claim 6, characterized in that, The emerging pollutants are one or more of Bisphenol A, 4-PC, tetracycline, rhodamine-B and naproxen.

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