Co (at) g-C3N4 / CeO2 catalyst for photo-thermal degradation of coal chemical wastewater and application
Through the photothermal degradation technology of Co@g-C3N4/CeO2 catalyst, the problem of efficient degradation in coal chemical wastewater treatment is solved, rapid degradation effect and environmental protection are achieved, and treatment costs are reduced.
Patent Information
- Application Number
- CN202410007389.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-01-03
- Publication Date
- 2025-07-22
AI Technical Summary
The existing coal chemical wastewater treatment methods are difficult to effectively degrade high-concentration organic pollutants, and the water quality of traditional methods is difficult to meet the standards, and there is a risk of secondary pollution.
The Co@g-C3N4/CeO2 catalyst is used, which uses CeO2 modified g-C3N4 as a support and supports the active component Co., which degrades coal chemical wastewater by photothermal to improve the migration efficiency of photogenerated carriers and electron-hole pairs.
It achieves rapid and efficient degradation of coal chemical wastewater, reduces treatment costs, does not require pretreatment, has a wide range of applicable concentrations, and does not have secondary pollution, and the catalyst can be reused.
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Figure CN120346822A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of coal chemical wastewater treatment, and particularly relates to a Co@g-C3N4 / CeO2 catalyst for photothermal degradation of coal chemical wastewater and a method for degrading coal chemical wastewater with this catalyst. Background Art
[0002] Coal chemical industry uses coal as raw material, and through chemical processing, coal is converted into gaseous, liquid and solid products or semi-products, and then further processed into chemical and energy products. Among various chemical processing methods of coal, there are high-temperature carbonization, low-temperature carbonization, gasification, liquefaction, coal-based chemical production and other coal processing products. Coking is the earliest and still the most important method, and its main purpose is to produce metallurgical coke and semi-coke. The wastewater discharged by coal chemical enterprises is generated during the coal processing process, including coking wastewater, gasification wastewater, liquefaction wastewater, mainly high-concentration gas washing wastewater. At the same time, by-products such as gas and aromatics such as benzene, toluene, xylene, and naphthalene are produced.
[0003] Coal chemical enterprises have a large water consumption, and the discharged wastewater mainly comes from processes such as coal coking, gas purification, and chemical product recovery and refining. This kind of wastewater has a large volume and complex quality, containing a large amount of organic pollutants, phenols, sulfur, ammonia, etc., and also containing a large amount of phenolic, polycyclic aromatic compounds and heterocyclic compounds containing nitrogen, oxygen, sulfur, as well as toxic and harmful substances such as cyanide, oil, and ammonia nitrogen, with extremely high toxicity. The traditional wastewater treatment methods have poor biodegradability, and it is difficult to meet the biochemical treatment standard after photodegradation. Summary of the Invention
[0004] Aiming at the problems of poor effluent water quality, high phenol and heterocyclic ring content in the existing front-end treatment process of coal chemical wastewater, the present invention provides a composite catalyst for rapidly and efficiently degrading coal chemical wastewater; as well as a preparation method of this composite catalyst and a method for treating coal chemical wastewater by irradiating with this composite catalyst.
[0005] For the above purpose, the composite catalyst for degrading coal chemical wastewater adopted by the present invention is Co@g-C3N4 / CeO2, which uses CeO2-modified g-C3N4 as the carrier and loads the active component Co. Based on the mass of g-C3N4 being 100%, the content of CeO2 is 0.1% - 2.5%, and the content of Co is 0.5% - 2.5%.
[0006] Furthermore, in the Co@g-C3N4 / CeO2 catalyst of the present invention, based on the mass of g-C3N4 being 100%, preferably the content of CeO2 is 1% - 2%, and the content of Co is 0.5% - 2.5%.
[0007] The preparation method of the Co@g-C3N4 / CeO2 catalyst of the present invention is as follows:
[0008] Step 1: Preparation of g-C3N4 / CeO2
[0009] Add cerium nitrate hexahydrate and urea to deionized water, stir at 15-30°C for 0.5-1h, transfer the resulting mixture into a corundum crucible, first dry it at 60-120°C in a blast drying oven for 4-10h, then calcine it at 350-450°C in a muffle furnace for 1-2h, then heat it to 550-600°C for 1-3h, cool it naturally after calcination, and grind it to obtain g-C3N4 / CeO2;
[0010] Step 2: Preparation of Co@g-C3N4 / CeO2
[0011] Cobalt nitrate hexahydrate and g-C3N4 / CeO2 are added to a mixed aqueous solution containing hexadecyltrimethylammonium bromide and mannitol, and after stirring evenly, cobalt carbonyl is added, and the pH is adjusted to 11-13 with sodium hydroxide aqueous solution, and then water and hydrazine are added. After stirring evenly, the solution is transferred into a polytetrafluoroethylene liner and reacted at 180-220°C for 60-80h; after the reaction is completed, the solution is centrifuged, washed, and dried, and calcined at 550-650°C for 6-10h in a nitrogen atmosphere, and Co@g-C3N4 / CeO2 is obtained after cooling.
[0012] Furthermore, in the above step 1, preferably, the mass ratio of the cerium nitrate hexahydrate to urea is 1:4-6, and the mass ratio of urea to deionized water is 1:1-1.5.
[0013] Furthermore, in the above step 2, the mass ratio of the cobalt carbonyl to cobalt nitrate hexahydrate is preferably 1:1-3, the amount of cetyltrimethylammonium bromide added is 1%-2% of the mass of g-C3N4 / CeO2, the mass ratio of g-C3N4 / CeO2 to mannitol is 1:1-2, the mass concentration of hydrazine hydrate is 80%, and the mass ratio of g-C3N4 / CeO2 to hydrazine hydrate is 1:5-10.
[0014] Furthermore, in the above step 2, the heating rate of the calcination is preferably 4 to 10° C. / min.
[0015] The Co@g-C3N4 / CeO2 catalyst of the present invention can be used for photothermal degradation of coal chemical wastewater.
[0016] The beneficial effects of the present invention are as follows:
[0017] 1. The catalyst of the present invention uses CeO2-modified g-C3N4 as a carrier to increase the photogenerated carriers and electron-hole pairs of the catalyst, and the Co element is used to improve the electron migration efficiency of the catalyst to achieve a better catalytic effect;
[0018] 2. The catalyst of the present invention has a simple preparation process, short duration, abundant and easily available raw materials, can be reused, degrades wastewater efficiently and rapidly, and greatly reduces the treatment cost of coal chemical wastewater;
[0019] 3. When applying the catalyst of the present invention to treat coal chemical wastewater, the applicable wastewater concentration range is wide, the concentrations of pollutants and COD in the wastewater can be reduced in a short time, and the environmental requirements are low;
[0020] 4. During the process of applying the catalyst of the present invention to treat coal chemical wastewater, it is not necessary to pre-treat the wastewater, no sludge is generated, and no secondary pollution is produced during the reaction. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 are the XRD patterns of g-C3N4 and g-C3N4 / CeO2, Co@g-C3N4 / CeO2 prepared in Example 1.
[0022] Figure 2 is the FT-IR pattern of Co@g-C3N4 / CeO2 prepared in Example 1.
[0023] Figure 3 is the SEM image of Co@g-C3N4 / CeO2 prepared in Example 1.
[0024] Figure 4 is the TEM image of Co@g-C3N4 / CeO2 prepared in Example 1.
[0025] Figure 5 is the EDS spectrum of Co@g-C3N4 / CeO2 prepared in Example 1.
[0026] Figure 6 is the degradation rate of coal chemical wastewater by Co@g-C3N4 / CeO2 prepared in Example 1 with temperature change.
[0027] Figure 7 is the degradation rate of coal chemical wastewater by Co@g-C3N4 / CeO2 prepared in Example 1 with pH change.
[0028] Figure 8 is the degradation rate of furan by Co@g-C3N4 / CeO2 with different Co contents.
[0029] Figure 9 is the degradation rate of thiophene by Co@g-C3N4 / CeO2 with different Co contents.
[0030] Figure 10 is the degradation rate of pyridine by Co@g-C3N4 / CeO2 with different Co contents.
[0031] Figure 11Degradation rates of Co@g-C3N4 / CeO2 with different Co contents for quinoline.
[0032] Figure 12 Degradation rates of Co@g-C3N4 / CeO2 with different Co contents for phenol.
[0033] Figure 13 Degradation rate of the Co@g-C3N4 / CeO2 prepared in Example 1 for coal chemical industry wastewater with the change of the number of recycling uses. Detailed implementation manners
[0034] The present invention will be further described in detail below with reference to the accompanying drawings and examples, but the protection scope of the present invention is not limited to these examples only.
[0035] Example 1
[0036] Step 1: Preparation of g-C3N4 / CeO2
[0037] 3.000 g of cerium nitrate hexahydrate and 15.000 g of urea were added to 20 mL of deionized water, and magnetically stirred at 400 r / min at 20 °C for 1 h. The obtained mixed solution was transferred into a 100 mL corundum crucible, first dried at 100 °C for 5 h in a blast drying oven, then calcined at 400 °C for 1 h in a muffle furnace, and then the temperature was raised to 575 °C at a heating rate of 5 °C / min and calcined for 2 h. After calcination, it was naturally cooled and ground to obtain g-C3N4 / CeO2.
[0038] Step 2: Preparation of Co@g-C3N4 / CeO2
[0039] 0.375 g of cobalt nitrate hexahydrate and 1.520 g of g-C3N4 / CeO2 were added to 20 mL of a mixed aqueous solution containing 20 mg of cetyltrimethylammonium bromide and 2 g of mannitol. After stirring evenly, 0.1550 g of cobalt carbonyl was added, and the pH was adjusted to 12.5 with 2 mol / L sodium hydroxide aqueous solution, then 10 g of 80% by mass hydrazine hydrate was added. After stirring evenly, it was transferred into a polytetrafluoroethylene inner liner and reacted at 200 °C for 72 h. After centrifugation, washing and drying, it was calcined at 600 °C for 8 h in a nitrogen atmosphere. After cooling, the final product Co@g-C3N4 / CeO2 was obtained. Based on the mass of g-C3N4 being 100%, the content of CeO2 was 1.25% and the content of Co was 1%.
[0040] The obtained product was subjected to structural characterization, and the results are shown in Figures 1 - 5 . From Figure 1 it can be seen that g-C3N4 has two peaks, and the peak at 13.12° corresponds to the (100) crystal plane of g-C3N4. The calculation method of this distance is d 1 / 40.671 nm. The peak at 27.50° corresponds to the interlayer stacking of the aromatic segments, with a distance of 0.324 nm, which is denoted as the (002) peak of the conjugated aromatic system stacking. Figure 2 In, 810.2 cm -1 corresponds to the bending vibration peak of the pyrazine ring unit, and the peaks between 1200 and 1600 cm -1 (1234.2, 1315.4, 1406.3, 1572.1) correspond to the stretching vibration peaks of C-N and C=N on the nitrogen-carbon ring, and these values further prove that the synthesized material is graphitic carbon nitride. Figures 3 - 5 It can be clearly seen that Co@g-C3N4 / CeO2 is an ultrathin layered structure with good Co loading on the surface.
[0041] Example 2
[0042] In step 2 of this example, 0.250 g of cobalt nitrate hexahydrate and 1.520 g of g-C3N4 / CeO2 were added to 20 mL of a mixed aqueous solution containing 20 mg of cetyltrimethylammonium bromide and 2 g of mannitol. After stirring evenly, 0.1050 g of cobalt carbonyl was added. The other steps were the same as those in Example 1, and Co@g-C3N4 / CeO2 was obtained. Based on the mass of g-C3N4 being 100%, the CeO2 content was 1.25% and the Co content was 1.5%.
[0043] Example 3
[0044] In step 2 of this example, 0.400 g of cobalt nitrate hexahydrate and 1.520 g of g-C3N4 / CeO2 were added to 20 mL of a mixed aqueous solution containing 20 mg of cetyltrimethylammonium bromide and 2 g of mannitol. After stirring evenly, 0.1900 g of cobalt carbonyl was added. The other steps were the same as those in Example 1, and Co@g-C3N4 / CeO2 was obtained. Based on the mass of g-C3N4 being 100%, the CeO2 content was 1.25% and the Co content was 2%.
[0045] Example 4
[0046] In step 2 of this example, 0.205 g of cobalt nitrate hexahydrate and 1.520 g of g-C3N4 / CeO2 were added to 20 mL of a mixed aqueous solution containing 20 mg of cetyltrimethylammonium bromide and 2 g of mannitol. After stirring evenly, 0.095 g of cobalt carbonyl was added. The other steps were the same as those in Example 1, and Co@g-C3N4 / CeO2 was obtained. Based on the mass of g-C3N4 being 100%, the CeO2 content was 1.25% and the Co content was 0.5%.
[0047] Example 5
[0048] Application of Co@g-C3N4 / CeO2 in Photothermal Degradation of Coal Chemical Industry Wastewater
[0049] (1) Influence of Temperature on the Degradation of Coal Chemical Industry Wastewater by Co@g-C3N4 / CeO2
[0050] Furan, thiophene, pyridine, quinoline and phenol were dispersed in cyclohexane according to the volume ratio of 1:1:1:1:1 to obtain a mixed solution. This mixed solution was used to simulate the coal chemical industry wastewater. 0.100 g of Co@g-C3N4 / CeO2 prepared in Example 1 and 50 mL of the coal chemical industry wastewater were transferred into a colorimetric tube, and photothermal degradation reaction was carried out at 20 °C, 35 °C, 50 °C, 65 °C and 80 °C with a stirring speed of 300 r / min for 120 min and dark reaction for 20 min. The absorbance was measured every 20 min during the reaction and the values were recorded. The results are shown in Figure 6 . From Figure 6 it can be seen that Co@g-C3N4 / CeO2 has the best photothermal degradation effect at 65 °C, and the degradation rate reaches 79.7%.
[0051] (2) Influence of pH on the Degradation of Coal Chemical Industry Wastewater by Co@g-C3N4 / CeO2
[0052] 0.100 g of Co@g-C3N4 / CeO2 prepared in Example 1 and 50 mL of the coal chemical industry wastewater were transferred into a colorimetric tube. At 65 °C, the pH value of the coal chemical industry wastewater was adjusted to 3, 5, 7, 9 and 11 with 3 mol / L NaOH aqueous solution and 10% (mass concentration) HCl aqueous solution respectively, and photothermal degradation reaction was carried out at a stirring speed of 300 r / min for 120 min and dark reaction for 20 min. The absorbance was measured every 20 min during the reaction and the values were recorded. The results are shown in Figure 7 . From Figure 7 it can be seen that Co@g-C3N4 / CeO2 has the best photothermal degradation effect at 65 °C and pH value of 9, and the degradation rate reaches 83.2%.
[0053] (3) Influence of Cobalt Content on the Degradation of Each Component by Co@g-C3N4 / CeO2
[0054] 0.100 g of Co@g-C3N4 / CeO2 prepared in Examples 1 to 4 were taken respectively, and 50 mL of an anhydrous ethanol solution of furan with a mass fraction of 10% was transferred into a colorimetric tube. At 65 °C, the pH was adjusted to 9 with 2 mol / L sodium hydroxide aqueous solution, and photothermal degradation reaction was carried out at a stirring speed of 300 r / min for 120 min and dark reaction for 20 min. The absorbance was measured every 20 min during the reaction and the values were recorded. The results are shown in Figure 8 . From Figure 8It can be seen that 1.5 wt% Co@g-C3N4 / CeO2 has the best photothermal degradation effect at 65 °C and pH 9, and the degradation rate reaches 97.2%.
[0055] Replace the above-mentioned anhydrous ethanol solution of furan with a mass fraction of 10% with 50 mL of anhydrous ethanol solution of thiophene with a mass fraction of 10%. The results are shown in Figure 9 . From Figure 9 It can be seen that 1.5 wt% Co@g-C3N4 / CeO2 has the best photothermal degradation effect at 65 °C and pH 9, and the degradation rate reaches 92.1%.
[0056] Replace the above-mentioned anhydrous ethanol solution of furan with a mass fraction of 10% with 50 mL of anhydrous ethanol solution of pyridine with a mass fraction of 10%. The results are shown in Figure 10 . From Figure 10 It can be seen that 1.5 wt% Co@g-C3N4 / CeO2 has the best photothermal degradation effect at 65 °C and pH 9, and the degradation rate reaches 96.8%.
[0057] Replace the above-mentioned anhydrous ethanol solution of furan with a mass fraction of 10% with 50 mL of anhydrous ethanol solution of quinoline with a mass fraction of 10%. The results are shown in Figure 12 . From Figure 12 It can be seen that 1.5 wt% Co@g-C3N4 / CeO2 has the best photothermal degradation effect at 65 °C and pH 9, and the degradation rate reaches 93.9%.
[0058] This proves that the Co@g-C3N4 / CeO2 with different cobalt contents above has an effect on degrading each component of coal chemical wastewater, and it is not limited to this content.
[0059] (4) Influence of the number of recycling times on the degradation of coal chemical wastewater by Co@g-C3N4 / CeO2
[0060] Take 0.100 g of Co@g-C3N4 / CeO2 prepared in Example 1 and 50 mL of coal chemical wastewater, transfer them into a colorimetric tube, adjust the pH value of the coal chemical wastewater to 9 with 3 mol / L NaOH aqueous solution at 65 °C, and carry out photothermal degradation reaction at a rotation speed of 300 r / min for 120 min and dark reaction for 20 min; then centrifuge and separate Co@g-C3N4 / CeO2, wash it with anhydrous ethanol and deionized water and then dry it, and reuse it for photocatalytic degradation of coal chemical wastewater. It can be seen from Figure 13 that after 6 times of recycling of Co@g-C3N4 / CeO2, the degradation effect decreases by about 12% compared with the first time, with an average decrease of 2.4% each time, and the degradation rate of the last time can still be higher than 70%. Thus, it can be seen that the Co@g-C3N4 / CeO2 of the present invention has relatively stable performance and can be used for multiple recycling.
Claims
1. A Co@g-C3N4 / CeO2 catalyst for the photothermal degradation of coal chemical industry wastewater, characterized in that: The catalyst uses g-C3N4 modified by CeO2 as a carrier and loads the active component Co. Taking the mass of g-C3N4 as 100%, the content of CeO2 is 0.1% - 2.5%, and the content of Co is 0.5% - 2.5%. This catalyst is prepared by the following method: Step 1: Prepare g-C3N4 / CeO2 Add cerium nitrate hexahydrate and urea into deionized water, stir at 15 - 30 °C for 0.5 - 1 h. Transfer the obtained mixed solution into a corundum crucible, first dry it in a blast drying oven at 60 - 120 °C for 4 - 10 h, then calcine it in a muffle furnace at 350 - 450 °C for 1 - 2 h while keeping the temperature, and then raise the temperature to 550 - 600 °C and calcine for 1 - 3 h. After calcination, cool it naturally and grind it to obtain g-C3N4 / CeO2; Step 2: Prepare Co@g-C3N4 / CeO2 Add cobalt nitrate hexahydrate and g-C3N4 / CeO2 into a mixed aqueous solution containing cetyltrimethylammonium bromide and mannitol. After stirring evenly, add cobalt carbonyl. Adjust the pH to 11 - 13 with an aqueous sodium hydroxide solution, then add water and hydrazine hydrate. After stirring evenly, transfer it into a polytetrafluoroethylene inner liner and react at 180 - 220 °C for 60 - 80 h; After the reaction, centrifuge, wash, and dry, and calcine it in a nitrogen atmosphere at 550 - 650 °C for 6 - 10 h, and cool to obtain Co@g-C3N4 / CeO2.
2. The Co@g-C3N4 / CeO2 catalyst for photothermal degradation of coal chemical wastewater according to claim 1, wherein: In the said catalyst, taking the mass of g-C3N4 as 100%, the content of CeO2 is 1% - 2%, and the content of Co is 0.5% - 2.5%.
3. The Co@g-C3N4 / CeO2 catalyst for photocatalytic degradation of coal chemical wastewater according to claim 1 or 2, characterized in that: In Step 1, the mass ratio of cerium nitrate hexahydrate to urea is 1:4 - 6, and the mass ratio of urea to deionized water is 1:1 - 1.
5.
4. The Co@g-C3N4 / CeO2 catalyst for photocatalytic degradation of coal chemical wastewater according to claim 1 or 2, characterized in that: In Step 2, the mass ratio of cobalt carbonyl to cobalt nitrate hexahydrate is 1:1 - 3.
5. The Co@g-C3N4 / CeO2 catalyst for photothermal degradation of coal chemical industry wastewater according to claim 1 or 2, characterized in that: In Step 2, the addition amount of cetyltrimethylammonium bromide is 1% - 2% of the mass of g-C3N4 / CeO2.
6. The Co@g-C3N4 / CeO2 catalyst for photocatalytic degradation of coal chemical wastewater according to claim 1 or 2, characterized in that: In Step 2, the mass ratio of g-C3N4 / CeO2 to mannitol is 1:1 - 2.
7. The Co@g-C3N4 / CeO2 catalyst for photocatalytic degradation of coal chemical industry wastewater according to claim 1 or 2, characterized in that: In Step 2, the mass concentration of hydrazine hydrate is 80%, and the mass ratio of g-C3N4 / CeO2 to hydrazine hydrate is 1:5 - 10.
8. The Co@g-C3N4 / CeO2 catalyst for photocatalytic degradation of coal chemical wastewater according to claim 1 or 2, characterized in that: In Step 2, the heating rate of the calcination is 4 - 10 °C / min.
9. Use of the Co@g-C3N4 / CeO2 catalyst as claimed in claim 1 for photocatalytic thermal degradation of coal chemical industry wastewater.