Method for removing organic pollutants in water body by activating persulfate with alkali-modified copper-iron bimetallic catalyst

Abstract

The invention discloses a method for removing organic pollutants in a water body by activating persulfate with an alkali-modified copper-iron bimetallic catalyst, which is characterized in that the alkali-modified copper-iron bimetallic catalyst is used as a catalyst for activating the persulfate and degrading the organic pollutants in the water body. Wherein the alkali modified copper-iron bimetallic catalyst comprises a copper-iron metal compound (CuFeO2) and oxygen vacancies loaded on the copper-iron metal compound. The catalyst disclosed by the invention has the advantages of large specific surface area, large number of active sites, high catalytic activity, good structural stability and the like, can construct a core mechanism degradation system based on a non-free radical pathway when being used for activating persulfate, can more quickly and thoroughly remove organic pollutants in water when being used for degrading the organic pollutants in the water, and has a good application prospect. The method has the advantages of simple process, convenience in operation, low cost, high practicability, wide application range, high treatment efficiency, good degradation effect, environment friendliness and the like, and is high in use value and good in application prospect.

Description

Technical Field

[0001] The present invention belongs to the field of advanced oxidation treatment of organic pollutants, and relates to a method for activating persulfate by using an alkali-modified copper-iron bimetallic catalyst to remove organic pollutants in water bodies. Background Art

[0002] In traditional advanced oxidation reaction systems, the free radical pathway, as the core mechanism for degrading organic pollutants, the differences in its characteristics directly affect the applicability and efficiency of the technology. At the same time, the free radical pathway attacks pollutants indiscriminately through chain reactions, showing extremely strong oxidation ability and fast reaction rate, especially suitable for the treatment of high-concentration dye wastewater or pesticide wastewater, but its limitations are obvious. On the one hand, background components such as natural organic matter (NOM) and chloride ions (Cl - -) in water bodies are prone to competing reactions with free radicals, significantly reducing the degradation efficiency of target pollutants; on the other hand, its strong pH dependence (such as ·OH having the highest activity under neutral conditions, while the Fenton system requires pH≈3) increases the complexity of process regulation; in addition, the characteristic of the free radical attacking indiscriminately may lead to an increase in the toxicity of intermediate products, such as the formation of chlorinated organic compounds or bromate, and even bring the risk of secondary pollution.

[0003] In contrast, the non-free radical pathway shows more precise selectivity and environmental adaptability through mechanisms such as surface-mediated electron transfer, singlet oxygen ( 1 1O2), or high-valent metal species. Moreover, it directly transfers electrons through the surface functional groups of the catalyst to destroy pollutant molecules, or generates 1 1O2 to selectively oxidize organic compounds containing electron-rich groups (such as phenols and antibiotics). This selectivity not only reduces the sensitivity to background components (such as Cl - , HCO3 - -), but also greatly reduces the risk of generating toxic by-products. At the same time, non-free radical reactions often occur on the surface of heterogeneous catalysts (such as porous carbon and metal oxides), and their broad pH adaptability (such as pH 3-9) makes them more advantageous in complex water qualities (such as seawater and landfill leachate). Therefore, obtaining a suitable catalyst for activating persulfate and forming a non-free radical pathway degradation mechanism is of great significance for efficiently degrading organic pollutants in water bodies.

[0004] Copper ferrite (CuFeO2), as a copper-iron bimetallic catalyst, can be used as a catalyst for activating persulfate. However, existing copper-iron bimetallic catalysts still have deficiencies such as small specific surface area, small number of active sites, poor catalytic activity, and poor structural stability. Therefore, when using them to activate persulfate, there are still defects such as poor activation effect on persulfate, difficulty in efficiently activating persulfate with a small amount of catalyst, poor degradation effect, and risk of secondary pollution. In particular, the degradation system established when existing copper-iron bimetallic catalysts are used to activate persulfate is still based on a free radical pathway degradation mechanism, making it difficult to achieve selective degradation of organic pollutants in water bodies and being easily interfered by external factors. Therefore, obtaining a copper-iron bimetallic catalyst with a large specific surface area, a large number of active sites, high catalytic activity, good structural stability, and capable of constructing a degradation mechanism based on a non-free radical pathway is of great significance for promoting the efficient degradation of organic pollutants in water bodies. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for removing organic pollutants in water bodies by activating persulfate with an alkali-modified copper-iron bimetallic catalyst, which has the advantages of simple process, convenient operation, low cost, strong practicability, wide adaptability, high treatment efficiency, good degradation effect, and environmental friendliness.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions: A method for removing organic pollutants in water bodies by activating persulfate with an alkali-modified copper-iron bimetallic catalyst, wherein the method uses the alkali-modified copper-iron bimetallic catalyst as a catalyst to activate persulfate and degrade the organic pollutants in the water body; the alkali-modified copper-iron bimetallic catalyst includes a copper-iron metal compound, and oxygen vacancies are loaded on the copper-iron metal compound; the copper-iron metal compound is CuFeO2.

[0007] In the above method, further improved, the valence state of copper in the alkali-modified copper-iron bimetallic catalyst is monovalent, and the valence state of iron is divalent; the copper-iron metal compound has a cubic structure.

[0008] In the above method, further improved, the alkali-modified copper-iron bimetallic catalyst is prepared by etching a copper-iron metal compound with an alkaline solution; the concentration of the alkaline solution ≥ 1 mol / L.

[0009] In the above method, further improved, the concentration of the alkaline solution is 1.5 mol / L to 4 mol / L.

[0010] In the above method, further improved, the concentration of the alkaline solution is 1.5 mol / L to 2.5 mol / L; the alkaline solution is at least one of sodium hydroxide solution and potassium hydroxide solution.

[0011] For the above method, further improved, the preparation method of the alkali-modified copper-iron bimetallic catalyst comprises the following steps: S1. Obtain copper-iron metal compounds; S2. Mix the copper-iron metal compounds with an alkaline solution for etching to obtain an alkali-modified copper-iron bimetallic catalyst.

[0012] For the above method, further improved, the preparation conditions of the alkali-modified copper-iron bimetallic catalyst include at least one of (1.1) to (1.3): (1.1) In step S1, the copper-iron metal compounds are prepared by hydrothermal reaction using copper salt and iron salt as raw materials; the molar ratio of the copper salt to the iron salt is 1:1; the copper salt is copper nitrate trihydrate; the iron salt is ferric nitrate nonahydrate; the hydrothermal reaction is carried out at a temperature of 180 °C, and the time of the hydrothermal reaction is 48 h; (1.2) In step S2, the ratio of the copper-iron metal compounds to the alkaline solution is 1 g:100 mL; (1.3) In step S2, the etching is carried out under stirring conditions; the rotation speed of the stirring is 500 rpm; the time of the stirring is 60 min.

[0013] For the above method, further improved, using the alkali-modified copper-iron bimetallic catalyst as a catalyst to activate persulfate and degrade organic pollutants in water, it comprises the following steps: Mix the alkali-modified copper-iron bimetallic catalyst, persulfate and the water body containing organic pollutants for a degradation reaction to complete the degradation of organic pollutants in the water body; the initial concentration of the alkali-modified copper-iron bimetallic catalyst in the degradation reaction system is ≥0.1 g / L, and the initial concentration of persulfate is ≥0.2 g / L.

[0014] For the above method, further improved, the initial concentration of the alkali-modified copper-iron bimetallic catalyst in the degradation reaction system is 0.1 g / L to 0.5 g / L, and the initial concentration of persulfate is 0.2 g / L to 0.8 g / L; the initial pH value in the degradation reaction system is 3 to 11.

[0015] For the above method, further improved, the persulfate is monopersulfate; the monopersulfate is at least one of sodium monopersulfate and potassium monopersulfate; the initial concentration of organic pollutants in the water body containing organic pollutants is ≤30 mg / L; the organic pollutants in the water body containing organic pollutants are antibiotics; the antibiotic is at least one of oxytetracycline; the degradation reaction is carried out under shaking conditions; the rotation speed of the shaking is 700 rpm; the temperature of the degradation reaction is 25 °C to 30 °C; the time of the degradation reaction is 0.5 min to 60 min.

[0016] Compared with the prior art, the advantages of the present invention are as follows: (1) Aiming at the deficiencies of the existing copper-iron bimetallic catalyst, such as small specific surface area, small number of active sites, poor catalytic activity, poor structural stability, etc., and the resulting defects such as poor activation effect on persulfate, difficulty in efficiently activating persulfate with a small amount of catalyst, poor degradation effect, and risk of secondary pollution, the present invention creatively proposes a method for activating persulfate with an alkali-modified copper-iron bimetallic catalyst to remove organic pollutants in water. The alkali-modified copper-iron bimetallic catalyst is used as a catalyst to activate persulfate and degrade the organic pollutants in water. The alkali-modified copper-iron bimetallic catalyst includes a copper-iron metal compound, and oxygen vacancies are loaded on the copper-iron metal compound. The copper-iron metal compound is CuFeO2. In the present invention, by loading oxygen vacancies (Ov) on the copper-iron metal compound and using the oxygen vacancies (Ov) to improve the inherent activity of the catalyst, the electronic structure of the copper-iron metal compound can be effectively adjusted and electron transfer can be promoted. At the same time, these oxygen vacancies (Ov) can be used as active sites, which can significantly improve the catalytic performance of the catalyst. Therefore, when it is used as a catalyst to activate persulfate, a large amount of singlet oxygen ( 1 O2) and other active substances can be rapidly and continuously generated, and a core mechanism based on a non-radical pathway can be constructed. Finally, under this mechanism, these active substances are used to efficiently degrade the organic pollutants in water. Taking tetracycline as an example, the involved degradation mechanism is shown in formulas (1) to (9). In particular, in the degradation system constructed in the present invention, on the one hand, tetracycline can be efficiently degraded under the condition of a very low catalyst dosage. For example, when the catalyst dosage is 0.02 g / L, the degradation rate of tetracycline is as high as 96%, and the degradation effect is very good. On the other hand, oxytetracycline can be degraded into non-toxic or low-toxic small-molecule substances, realizing the harmless treatment of oxytetracycline. Compared with the conventional copper-iron bimetallic catalyst (CuFeO2), the alkali-modified copper-iron bimetallic catalyst adopted in the present invention has the following advantages: (a) excellent catalytic performance. By introducing a large number of oxygen vacancies, the catalytic activity and catalytic rate of the catalyst can be significantly improved, so that the catalyst exhibits very excellent catalytic performance. When used to activate persulfate and degrade organic pollutants, it shows a very fast degradation rate, and the degradation rate can reach 0.0539 min -1, almost reaching four times that of CuFeO2; (b) The surface morphology of the alkali-modified copper-iron bimetallic catalyst is a complete cubic structure, which is not easy to break, can effectively provide attachment sites, is not easy to be missing, and has better structural stability. On the one hand, it still exhibits very excellent catalytic activity after multiple uses and has good reusability. On the other hand, it can effectively prevent the leaching of metal ions. The leaching amount of iron is only 0.1876 mg / L, and its leaching amount is lower than the standard limit of surface water for domestic drinking water (0.3 mg / L), meeting the specifications of domestic drinking water. The method for activating persulfate by the alkali-modified copper-iron bimetallic catalyst to remove organic pollutants in water has the advantages of simple process, convenient operation, low cost, strong practicability, wide adaptability, high treatment efficiency, good degradation effect, environmental friendliness, etc. It can effectively degrade high-concentration organic pollutants in water, especially has a better removal effect on organic pollutants with a concentration ≤ 30 mg / L, has high use value and good application prospects.

[0017] .

[0018] (2) In the present invention, the copper-iron metal compound adopted has a cubic structure, which can not only provide more attachment sites, but also better prevent metal leaching.

[0019] (3) In the present invention, the alkali-modified copper-iron bimetallic catalyst is prepared by etching a copper-iron metal compound with an alkaline solution. The concentration of the alkaline solution ≥ 1 mol / L. By performing alkali etching treatment on the copper-iron metal compound in the alkaline solution, a large number of oxygen vacancies can be introduced on the copper-iron metal compound, and at the same time, more copper-iron sites can be exposed. While increasing the specific surface area, the number of active sites on the catalyst surface can be significantly increased. In particular, by optimizing the concentration of the alkaline solution to 1.5 mol / L - 4 mol / L, over-etching can be prevented while increasing the specific surface area and the number of active sites, thereby avoiding structural collapse and enabling the catalyst to have better structural stability. Finally, an alkali-modified copper-iron bimetallic catalyst with a large specific surface area, a large number of active sites, high catalytic activity, and good structural stability can be prepared. At the same time, when the catalyst is used to activate persulfate and degrade organic pollutants in water, the organic pollutants in water can be removed more quickly and thoroughly.

[0020] (4) In the present invention, the alkali-modified copper-iron bimetallic catalyst used exhibits very good pH adaptability and can efficiently activate persulfate in acidic, neutral, and alkaline solutions. Therefore, it can efficiently remove organic pollutants under different pH conditions. When the initial pH value in the degradation reaction system is ≥3, especially when the initial pH value is 3-9, the removal rate of organic pollutants does not show an obvious decrease, and the removal rate is above 90%. Further, due to the very good pH adaptability of the alkali-modified copper-iron bimetallic catalyst used, there is no need to adjust the pH value during the actual treatment process, which is also beneficial to reducing the treatment cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0022] Figure 1 Comparative diagram of the removal effects of different alkali-modified copper-iron bimetallic catalysts (CuFeO2, CuFeO2-AT0.5, CuFeO2-AT1, CuFeO2-AT2, CuFeO2-AT3, CuFeO2-AT4) on oxytetracycline in Example 1 of the present invention.

[0023] Figure 2 Comparative diagram of the degradation rates of different alkali-modified copper-iron bimetallic catalysts (CuFeO2, CuFeO2-AT0.5, CuFeO2-AT1, CuFeO2-AT2, CuFeO2-AT3, CuFeO2-AT4) on oxytetracycline in Example 1 of the present invention.

[0024] Figure 3 Comparative diagram of the removal effects of different dosages of alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) on oxytetracycline in Example 2 of the present invention.

[0025] Figure 4 Comparative diagram of the removal effects of alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) on oxytetracycline under different dosages of potassium monopersulfate in Example 3 of the present invention.

[0026] Figure 5 Comparative diagram of the removal effect diagrams of alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) on different concentrations of oxytetracycline when activating monopersulfate in Example 4 of the present invention.

[0027] Figure 6 Comparative diagram of the removal effect diagrams of alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) on oxytetracycline under different pH conditions when activating monopersulfate in Example 5 of the present invention.

[0028] Figure 7 This is a comparison chart of the removal effect of oxytetracycline under different radical scavenger conditions when the alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) activates peroxymonosulfate in Example 6 of the present invention.

[0029] Figure 8 This is the EPR chart of the alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) in Example 7 of the present invention.

[0030] Figure 9 This is the cyclic degradation effect chart of the alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) on oxytetracycline in water in Example 8 of the present invention.

[0031] Figure 10 This is the SEM chart of the alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) and copper-iron metal compound (CuFeO2) prepared in Example 9 of the present invention. Detailed implementation manners

[0032] The present invention will be further described below in conjunction with the accompanying drawings of the specification and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

[0033] In the following embodiments of the present invention, unless otherwise specified, the materials and instruments used are commercially available, the equipment used is conventional equipment, and the data obtained are the averages of more than three repeated experiments.

[0034] Example 1: A method for removing organic pollutants in water by activating persulfate with an alkali-modified copper-iron bimetallic catalyst, specifically using the alkali-modified copper-iron bimetallic catalyst as a catalyst to activate persulfate and degrade oxytetracycline (OTC) in water, including the following steps: (1) Prepare 5 groups of 100 mL of oxytetracycline aqueous solutions with a concentration of 20 mg / L (the original pH value of this aqueous solution is 6.54), and set two parallel samples for each group.

[0035] (2) Add the alkali-modified copper-iron bimetallic catalysts (CuFeO2, CuFeO2-AT0.5, CuFeO2-AT1, CuFeO2-AT2, CuFeO2-AT3, CuFeO2-AT4) obtained by etching with different concentrations of sodium hydroxide solution into each group of solutions. The catalyst content added to the solution is 30 mg, and then add potassium monopersulfate to make the concentration of potassium monopersulfate in the solution 0.2 g / L. Carry out the degradation reaction at 25 °C and 700 rpm for 60 min to complete the removal of oxytetracycline in water.

[0036] In this example, 2 mL of the sample solution was taken at 0 min, 2 min, 5 min, 10 min, 15 min, 30 min, 45 min, and 60 min during the degradation reaction, filtered through a 0.45 μm filter head, and the filtered solution was added to a sample bottle containing an excessive amount of Na2S2O3 solution to terminate the reaction. The concentration of Na2S2O3 was 5 mM. The concentration of oxytetracycline was measured using a uv2600 ultraviolet spectrophotometer at an absorption wavelength of 357 nm to obtain the corresponding concentration of oxytetracycline, and the removal effect of the base-modified copper-iron bimetallic catalyst (CuFeO2, CuFeO2-AT0.5, CuFeO2-AT1, CuFeO2-AT2, CuFeO2-AT3, CuFeO2-AT4) obtained by etching with sodium hydroxide solutions at different concentrations was plotted. The results are as Figure 1 shown.

[0037] Figure 1 This is a comparison chart of the removal effects of different base-modified copper-iron bimetallic catalysts (CuFeO2, CuFeO2-AT0.5, CuFeO2-AT1, CuFeO2-AT2, CuFeO2-AT3, CuFeO2-AT4) in Example 1 of the present invention on oxytetracycline. As Figure 1 can be seen, the degradation rate of oxytetracycline by the copper-iron bimetallic catalyst (CuFeO2) after etching with sodium hydroxide solution has been significantly improved. When the concentration of sodium hydroxide solution is 2 mol / L to 4 mol / L, the degradation rate of the corresponding base-modified copper-iron bimetallic catalyst on oxytetracycline almost reaches 100%.

[0038] Figure 2 This is a comparison chart of the degradation rates of different base-modified copper-iron bimetallic catalysts (CuFeO2, CuFeO2-AT0.5, CuFeO2-AT1, CuFeO2-AT2, CuFeO2-AT3, CuFeO2-AT4) in Example 1 of the present invention on oxytetracycline.

[0039] As Figure 2 can be seen, the degradation rate of oxytetracycline by the copper-iron bimetallic catalyst (CuFeO2) after etching with sodium hydroxide solution has been significantly improved. When the concentration of sodium hydroxide solution is 2 mol / L to 4 mol / L, the degradation rate of the base-modified copper-iron bimetallic catalyst is as high as 0.0489 min -1 , and when the concentration of sodium hydroxide solution is 2 mol / L, the degradation rate of the corresponding CuFeO2-AT2 is 0.0539 min -1 , both higher than the catalysts etched with other sodium hydroxide concentrations, and almost four times that of the copper-iron metal compound (CuFeO2).

[0040] AsFigure 1 and Figure 2 The results show that the etching treatment (alkali modification) of sodium hydroxide solution is an effective strategy to improve the catalytic activity of the CuFeO2-ATx / PMS system, significantly enhancing the degradation efficiency of oxytetracycline. In particular, when etching copper-iron metal compounds with sodium hydroxide solution, when the concentration of the sodium hydroxide solution used is 2 mol / L, an alkali-modified copper-iron bimetallic catalyst with the best effect can be prepared.

[0041] Example 2: A method for removing organic pollutants in water by activating persulfate with an alkali-modified copper-iron bimetallic catalyst, specifically using an alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) as a catalyst to activate persulfate and degrade oxytetracycline (OTC) in water, including the following steps: (1) Prepare 4 groups of 100 mL of oxytetracycline aqueous solution with a concentration of 20 mg / L (the original pH value of this aqueous solution is 6.54), and set two parallel samples for each group.

[0042] (2) Add different amounts of alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) to each group of solutions so that the concentration of CuFeO2-AT2 in the solution is 0.01 g / L, 0.02 g / L, 0.03 g / L, 0.05 g / L, and then add potassium monopersulfate so that the concentration of potassium monopersulfate in the solution is 0.2 g / L; carry out the degradation reaction at 25 °C and 700 rpm for 60 min to complete the removal of oxytetracycline in water.

[0043] Control group: Do not add CuFeO2-AT2, and other conditions are the same.

[0044] In this example, 2 mL of sample solution was taken at 0 min, 2 min, 5 min, 10 min, 15 min, 30 min, 45 min, and 60 min of the degradation reaction, filtered with a 0.45 μm filter head, and the filtered solution was added to a sample bottle containing an excessive amount of Na2S2O3 solution to terminate the reaction, and the concentration of Na2S2O3 was 5 mM. The concentration of oxytetracycline was measured with a uv2600 ultraviolet spectrophotometer at an absorption wavelength of 357 nm to obtain the corresponding concentration of oxytetracycline, and the degradation effect of the alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) with different dosages on oxytetracycline was plotted. The results are as Figure 3 shown.

[0045] Figure 3 This is a comparison chart of the removal effects of the alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) with different dosages on oxytetracycline in Example 2 of the present invention. From Figure 3It can be seen that when different dosages of CuFeO2-AT2 are added, the removal rate of oxytetracycline can remain above 90%. In particular, when the concentration of CuFeO2-AT2 reaches 0.02 g / L or more, the degradation rate remains at 0.05 min -1 , indicating that CuFeO2-AT2 has strong catalytic activity. Even with a small dosage, it can efficiently and thoroughly remove oxytetracycline in water, showing good economic applicability.

[0046] Example 3: A method for removing organic pollutants in water by activating persulfate with an alkali-modified copper-iron bimetallic catalyst specifically uses an alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) as a catalyst to activate persulfate and degrade oxytetracycline (OTC) in water, including the following steps: (1) Prepare 4 groups of 100 mL of oxytetracycline aqueous solution with a concentration of 20 mg / L (the original pH value of this aqueous solution is 6.54), and set two parallel samples for each group.

[0047] (2) Add an alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) to each group of solutions so that the concentration of CuFeO2-AT2 in the solution is 0.02 g / L; then add different dosages of potassium monopersulfate, and the dosages are 0.2 g / L, 0.4 g / L, 0.6 g / L, and 0.8 g / L respectively; carry out a degradation reaction at 25°C and 700 rpm for 60 min to complete the removal of oxytetracycline in water.

[0048] Control group: Without adding potassium monopersulfate, with other conditions being the same.

[0049] In this example, 2 mL of sample solution is taken at 0 min, 2 min, 5 min, 10 min, 15 min, 30 min, 45 min, and 60 min of the degradation reaction, filtered with a 0.45 μm filter head, and the filtered solution is added to a sample bottle containing an excessive amount of Na2S2O3 solution to terminate the reaction, and the concentration of Na2S2O3 is 5 mM. The concentration of oxytetracycline is measured with a uv2600 ultraviolet spectrophotometer at an absorption wavelength of 357 nm to obtain the corresponding concentration of oxytetracycline, and the degradation effect of the alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) on oxytetracycline under different dosages of potassium monopersulfate is plotted, and the results are as Figure 4 shown.

[0050] Figure 4 This is a comparison chart of the removal effect of the alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) on oxytetracycline under different dosages of potassium monopersulfate in Example 3 of the present invention. From Figure 4It can be seen that as the dosage of PMS increases gradually from 0.2 g / L to 0.8 g / L, the degradation rate of oxytetracycline decreases from 97% to 85% instead. At the same time, kobs decreases from 0.048 min of 0.2 g / L PMS -1 to 0.0269 min of 0.8 g / L -1 , and the dosage of 0.2 g / L PMS is almost twice that of 0.8 g / L PMS. The reasons for the decrease in the degradation rate and the slowdown of the reaction rate may be as follows: A large number of PMS molecules collide with the catalytic active sites, which instead affects the generation of singlet oxygen therein, thereby slowing down the progress of the reaction, resulting in a decrease in the degradation rate. Therefore, when the initial concentration of potassium monopersulfate in the degradation reaction system of the present invention is 0.2 g / L to 0.8 g / L, it can be conducive to the efficient and thorough removal of oxytetracycline in water, and has high economic benefits. In particular, when the concentration of potassium monopersulfate in the degradation reaction system is 0.2 g / L, the best removal effect and economic benefits can be obtained.

[0051] Example 4: A method for removing organic pollutants in water by activating persulfate with an alkali-modified copper-iron bimetallic catalyst, specifically using an alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) as a catalyst to activate persulfate and degrade oxytetracycline (OTC) in water, including the following steps: (1) Prepare 4 groups of 100 mL oxytetracycline aqueous solutions (the original pH value of this aqueous solution is 6.54), and the concentrations of oxytetracycline are 20 mg / L, 50 mg / L, 80 mg / L, and 100 mg / L respectively. Each group has two parallel samples.

[0052] (2) Add an alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) to each group of solutions respectively, so that the concentration of CuFeO2-AT2 in the solution is 0.02 g / L; then add potassium monopersulfate, so that the concentration of potassium monopersulfate in the solution is 0.2 g / L; carry out a degradation reaction at 25 °C and 700 rpm for 60 min to complete the removal of oxytetracycline in water.

[0053] In this example, 2 mL of sample solution was taken at 0 min, 2 min, 5 min, 10 min, 15 min, 30 min, 45 min, and 60 min during the degradation reaction, filtered with a 0.45 μm filter head, and the filtered solution was added to a sample bottle containing an excessive amount of Na2S2O3 solution to terminate the reaction. The concentration of Na2S2O3 was 5 mM. The concentration of oxytetracycline was measured with a uv2600 ultraviolet spectrophotometer at an absorption wavelength of 357 nm to obtain the corresponding concentration of oxytetracycline, and the degradation effect of the base-modified copper-iron bimetallic catalyst (CuFeO2-AT2) on different concentrations of oxytetracycline was plotted. The results are as Figure 5 shown.

[0054] Figure 5 This is a comparative chart of the removal effect diagrams of different concentrations of oxytetracycline when the base-modified copper-iron bimetallic catalyst (CuFeO2-AT2) activates peroxymonosulfate in Example 4 of the present invention. From Figure 5 it can be seen that as the initial concentration of OTC increases, the degradation effect of the CuFeO2-AT2 / PMS system on OTC decreases significantly. This is because: at a fixed dosage of potassium peroxymonosulfate, the amount of reactive species generated is certain. When the initial concentration of OTC increases, it is difficult to generate more reactive species in the system, so only part of the OTC can be degraded, resulting in a significant decrease in the removal rate. Therefore, when treating high-concentration organic pollutant wastewater, the dosage of peroxymonosulfate and CuFeO2-AT2 can be increased to achieve efficient removal of organic pollutants in high-concentration wastewater.

[0055] Example 5: A method for removing organic pollutants in water by activating persulfate with a base-modified copper-iron bimetallic catalyst, specifically using the base-modified copper-iron bimetallic catalyst (CuFeO2-AT2) as a catalyst to activate persulfate and degrade oxytetracycline (OTC) in water, including the following steps: (1) Prepare 5 groups of 100 mL of oxytetracycline aqueous solution with a concentration of 20 mg / L, and use 0.1 mol / L HCl or 0.1 mol / L NaOH to adjust the pH values of 4 groups of solutions to 3, 5, 6.54, 9, and 11. Each group has two parallel samples.

[0056] (2) Add the base-modified copper-iron bimetallic catalyst (CuFeO2-AT2) to each group of solutions so that the concentration of CuFeO2-AT2 in the solution is 0.02 g / L; then add potassium monopersulfate so that the concentration of potassium monopersulfate in the solution is 0.2 g / L; carry out the degradation reaction at 25 °C and 700 rpm for 60 min to complete the removal of oxytetracycline in the water.

[0057] In this example, 2 mL of sample solution was taken at 0 min, 2 min, 5 min, 10 min, 15 min, 30 min, 45 min, and 60 min during the degradation reaction, filtered through a 0.45 μm filter head, and the filtered solution was added to a sample bottle containing an excessive amount of Na2S2O3 solution to terminate the reaction. The concentration of Na2S2O3 was 5 mM. The concentration of oxytetracycline was measured with a uv2600 ultraviolet spectrophotometer at an absorption wavelength of 357 nm to obtain the corresponding concentration of oxytetracycline, and the degradation effect of the base-modified copper-iron bimetallic catalyst (CuFeO2-AT2) on oxytetracycline under different pH conditions was plotted. The results are as Figure 6 shown.

[0058] Figure 6 This is a comparative diagram of the removal effect of oxytetracycline by the base-modified copper-iron bimetallic catalyst (CuFeO2-AT2) when activating peroxymonosulfate under different pH conditions in Example 5 of the present invention.

[0059] It can be Figure 6 seen that under the condition that the initial pH value is 3 - 9, the removal rate of OTC did not show a significant decrease, and the removal rate was about 90%. Even when the pH value was 11, the degradation rate could reach about 80%. This shows that whether in acidic, neutral, or alkaline solutions, the CuFeO2-AT2 / PMS system is not affected by it, further indicating that the working pH value range of the system is relatively wide, and it has strong resistance to pH value during the degradation process. Therefore, there is no need to adjust the pH value during the actual treatment process, which is beneficial to reducing the treatment cost.

[0060] Example 6: A method for removing organic pollutants in water by activating persulfate with a base-modified copper-iron bimetallic catalyst, specifically using the base-modified copper-iron bimetallic catalyst (CuFeO2-AT2) as a catalyst to activate persulfate and degrade oxytetracycline (OTC) in water, including the following steps: (1) Prepare 5 groups of 100 mL of oxytetracycline aqueous solution with a concentration of 20 mg / L (the original pH value of this aqueous solution is 6.54). Among them, four groups were added with tert-butanol (TBA), absolute ethanol (AE), sugar alcohol (FFA), and p-benzoquinone (p-BQ) as radical scavengers, respectively, so that the concentration of each radical scavenger in the solution was 20 mM, and the other group was used as a control. Each group had two parallel samples.

[0061] (2) Add the alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) to each group of solutions respectively, so that the concentration of CuFeO2-AT2 in the solution is 0.02 g / L; then add potassium monopersulfate, so that the concentration of potassium monopersulfate in the solution is 0.2 g / L; carry out the degradation reaction at 25 °C and 700 rpm for 60 min to complete the removal of oxytetracycline in the water body.

[0062] In this example, 1 mL of sample solution was taken at 0 min, 2 min, 5 min, 10 min, 15 min, 30 min, and 60 min of the degradation reaction respectively, filtered with a 0.22 μm filter head, and the filtered solution was added to a liquid-phase injection bottle containing 20 μL of sodium thiosulfate quenching agent solution (1 mol / L), and then the concentration of oxytetracycline after the reaction was measured using a high-performance liquid chromatograph to obtain the corresponding concentration of oxytetracycline, and the change curve of the removal rate of oxytetracycline under different radical scavenger conditions was plotted. The results are as Figure 7 shown.

[0063] Figure 7 It is a comparative diagram of the removal effect of oxytetracycline under different radical scavenger conditions when the alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) activates peroxymonosulfate in Example 6 of the present invention. From Figure 7 it can be seen that tert-butanol (TBA) is a typical hydroxyl radical scavenger. After adding tert-butanol, the oxidation activity in the CuFeO2-AT2 / PMS system shows a slight decrease, indicating that a small amount of hydroxyl radicals play a partial role in the degradation mechanism in the degradation system. Anhydrous ethanol (AE) is usually used as a scavenger for hydroxyl radicals and sulfate radicals. When anhydrous ethanol is added, it can be observed that the degradation rate of oxytetracycline decreases significantly, confirming that hydroxyl radicals and sulfate radicals are generated and act together during the degradation reaction. It should be noted that when furfuryl alcohol (FFA) and p-benzoquinone (p-BQ) are added, the degradation rates are only 19% and 30% respectively, and kobs decreases from 0.048 min -1 to 0.002 min -1 and 0.005 min -1 respectively. This indicates that in the reaction 1 O2, ·O2 - may play a major role, and the reason for the influence of ·O2 - on the degradation rate may be that as an intermediate product for generating 1 O2, the addition of p-benzoquinone scavenges superoxide radicals, thus affecting the generation of singlet oxygen, thereby affecting the decrease in the degradation rate and the slowdown of the degradation rate. The above results show that in the present invention, when the alkali-modified copper-iron bimetallic catalyst activates peroxymonosulfate, a core mechanism based on a non-radical pathway can be constructed.

[0064] Example 7: To explore the contribution of reactive species in the CuFeO2-AT2 / PMS system, EPR experiments were conducted in this invention to determine the reactive oxygen species and the possible reaction mechanisms. DMPO was used as a spin trap for free radicals (·OH, ·O2 - and SO4 ·- ) to detect the EPR signals of free radicals in the CuFeO2-AT2 / PMS system.

[0065] Figure 8 This is the EPR spectrum of the base-modified copper-iron bimetallic catalyst (CuFeO2-AT2) in Example 7 of this invention. Figure 8 Among them, (a) are the signals of hydroxyl radicals and sulfate radicals measured in the EPR characterization, (b) is the signal of superoxide radicals measured in the EPR characterization, and (c) is the signal of singlet oxygen measured in the EPR characterization. As can be Figure 8 seen, the characteristic peaks of the adducts of ·OH and SO4 ·- reacting with DMPO did not appear in the reaction system. This phenomenon proves that ·OH and SO4 ·- are not the main oxidation reactive species, but seven characteristic peaks with an intensity ratio of 1∶2∶1∶2∶1∶2∶1 (α N = 7.3 ± 0.1 G, α H = 3.9 ± 0.1 G) appeared. This may be due to the hyperfine cleavage of (DMPOX). The appearance of this characteristic peak indicates that DMPO can be rapidly oxidized, which also proves from another aspect that there are strong oxidizing substances in this system. In Figure 8 , the signal of ·O2 - appeared, as well as 1 the typical triplet peak of 1∶1∶1 for O2. The reason for this phenomenon may be that the generated ·O2 - is only an intermediate product for the generation of 1 O2, that is, ·O 2- recombines to generate 1 O2, which further proves that the main reactive species in the CuFeO2-AT2 / PMS system is singlet oxygen and the core mechanism is a non-radical pathway.

[0066] Example 8: To investigate the stability and repeated applicability of the base-modified copper-iron bimetallic catalyst (CuFeO2-AT2), the following steps were included: (1) Prepare 1 group of 1000 mL of oxytetracycline aqueous solution with a concentration of 20 mg / L (the original pH value of this aqueous solution is 6.54), and set two parallel samples for each group.

[0067] (2) Add the alkali-modified copper-iron bimetallic catalyst (CuFeO₂-AT₂) to each group of solutions respectively, so that the concentration of CuFeO₂-AT₂ in the solution is 0.02 g / L; then add potassium monopersulfate so that the concentration of potassium monopersulfate in the solution is 0.2 g / L; carry out the degradation reaction at 25 °C and 700 rpm for 60 min to complete the removal of oxytetracycline in the water body.

[0068] After each reaction, filter the remaining mixture by suction, dry the remaining solid material, keep it at 60 °C in the oven and dry for 12 h, then take out the obtained solid material for the next experiment. Repeat steps (1)-(2) three times.

[0069] Figure 9 It is the cyclic degradation effect diagram of the alkali-modified copper-iron bimetallic catalyst (CuFeO₂-AT₂) on oxytetracycline in the water body in Example 8 of the present invention. From Figure 9 the results, it can be seen that after three cycles, the removal rate of OTC can still be maintained at about 80%. In addition, the leaching of metal ions of CuFeO₂-AT₂ after the reaction was detected by ICP-MS. The leaching amount of iron was only 0.1876 mg / L, and its leaching amount was lower than the standard limit value of surface water for domestic drinking water (0.3 mg / L), meeting the domestic drinking water specification.

[0070] Example 9: The preparation method of the alkali-modified copper-iron bimetallic catalyst (CuFeO₂-AT₂) used in the above examples is specifically to first prepare a copper-iron metal compound by hydrothermal reaction using copper salt and iron salt as raw materials, and then prepare an alkali-modified copper-iron bimetallic catalyst by etching the copper-iron metal compound with an alkaline solution, including the following steps: S1. Dissolve 8 mmol of copper nitrate trihydrate and 8 mmol of iron nitrate nonahydrate in 15 mL of pure water to make a copper-iron solution, add 60 mL of sodium hydroxide solution with a concentration of 1 mol / L, stir at a rotation speed of 300 rpm for 10 min, and ultrasonicate for 10 min to obtain a precipitate suspension.

[0071] S2. According to the ratio of propionaldehyde to copper salt of 1 ml∶10 mmol, mix propionaldehyde with the precipitate suspension obtained in step S1 and transfer it to a high-pressure reaction kettle for hydrothermal reaction. The temperature of the hydrothermal reaction is 180 °C and the time is 48 h. After the reaction, filter the solid-liquid mixture after the reaction, wash the filtered solid with pure water for 3 times, and dry the washed solid product at 60 °C for 12 h to obtain a copper-iron oxide precursor (copper-iron metal compound), denoted as CuFeO₂.

[0072] S3. According to the ratio of copper-iron metal compound to alkaline solution being 1 g∶100 mL, the copper-iron oxide precursor was added to a sodium hydroxide solution with a concentration of 2 mol / L for etching. During the etching process, continuous stirring was carried out, where the stirring speed was 500 rpm and the time was 60 min. After the stirring ended, the stirred product was filtered, and the filtered solid was washed with pure water for 3 times. The washed solid product was dried at a temperature of 60 °C for 12 h to obtain an alkali-modified copper-iron bimetallic catalyst, denoted as CuFeO2-AT2.

[0073] In this example, the prepared alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) includes a copper-iron metal compound, and oxygen vacancies are loaded on the copper-iron metal compound. The copper-iron metal compound is CuFeO2 and has a cubic structure.

[0074] In this example, the valence state of copper in the prepared alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) is monovalent, and the valence state of iron is divalent.

[0075] In this example, alkali-modified copper-iron bimetallic catalysts (CuFeO2-AT0.5, CuFeO2-AT1, CuFeO2-AT3, CuFeO2-AT4) etched under different concentrations of sodium hydroxide solution were also prepared. Their preparation methods are basically the same as that of the alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2), with the only difference being that in the preparation methods of the alkali-modified copper-iron bimetallic catalysts (CuFeO2-AT0.5, CuFeO2-AT1, CuFeO2-AT3, CuFeO2-AT4), the concentrations of the sodium hydroxide solution used for etching the copper-iron metal compound are 0.5 mol / L, 1 mol / L, 3 mol / L, and 4 mol / L in sequence. That is, when the concentrations of the sodium hydroxide solution used for etching the copper-iron metal compound are 0.5 mol / L, 1 mol / L, 3 mol / L, and 4 mol / L in sequence, the corresponding alkali-modified copper-iron bimetallic catalysts are denoted as CuFeO2-AT0.5, CuFeO2-AT1, CuFeO2-AT3, and CuFeO2-AT4 in sequence.

[0076] The surface morphologies of CuFeO2-AT2 and CuFeO2 were observed using a scanning electron microscope (SEM). The specific results are as follows: Figure 10 This is the SEM image of the alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) and the copper-iron metal compound (CuFeO2) prepared in Example 9 of the present invention. Figure 10Among them, (a) is the SEM image of CuFeO2 at the scale of 500 nm, and (b) and (c) are the SEM images of CuFeO2-AT2 at the scales of 200 nm and 500 nm, respectively. As shown by Figure 10 the results in, the CuFeO2-AT2 catalyst material has a more compact cubic structure to provide more attachment sites and can better prevent metal leaching.

[0077] Based on the above results, compared with the conventional copper-iron bimetallic catalyst (CuFeO2), the alkali-modified copper-iron bimetallic catalyst used in the present invention has the following advantages: (a) excellent catalytic performance. By introducing a large number of oxygen vacancies, the catalytic activity and catalytic rate of the catalyst can be significantly improved, making the catalyst exhibit very excellent catalytic performance. When used to activate persulfate and degrade organic pollutants, it shows a very fast degradation rate, and the degradation rate can reach 0.0539 min -1 , almost four times that of CuFeO2; (b) better structural stability. On the one hand, it still exhibits very excellent catalytic activity after multiple uses and has good reusability. On the other hand, it can effectively prevent metal ion leaching. The leaching amount of iron is only 0.1876 mg / L, which is lower than the standard limit of surface water for domestic drinking water (0.3 mg / L) and meets the domestic drinking water specification. The method for removing organic pollutants in water by activating persulfate with the alkali-modified copper-iron bimetallic catalyst of the present invention has the advantages of simple process, convenient operation, low cost, strong practicability, wide adaptability, high treatment efficiency, good degradation effect, environmental friendliness, etc. It can effectively degrade high-concentration organic pollutants in water, especially has a better removal effect on organic pollutants with a concentration ≤ 30 mg / L, has high use value and good application prospects.

[0078] The above embodiments are only the preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, improvements and refinements should also be regarded as within the protection scope of the present invention.

Claims

1. A method for activating persulfate by using an alkali-modified copper-iron bimetallic catalyst to remove organic pollutants in water, which is characterized in that The method uses an alkali-modified copper-iron bimetallic catalyst to activate persulfate and degrade organic pollutants in water; the alkali-modified copper-iron bimetallic catalyst includes a copper-iron metal compound, and oxygen vacancies are loaded on the copper-iron metal compound; the copper-iron metal compound is CuFeO2.

2. The method according to claim 1, wherein In the alkali-modified copper-iron bimetallic catalyst, the valence state of copper is monovalent and the valence state of iron is divalent; the copper-iron metal compound has a cubic structure.

3. The method according to claim 2, wherein The alkali-modified copper-iron bimetallic catalyst is prepared by etching a copper-iron metal compound with an alkaline solution; the concentration of the alkaline solution ≥ 1 mol / L.

4. The method according to claim 3, wherein The concentration of the alkaline solution is 1.5 mol / L to 4 mol / L.

5. The method according to claim 4, characterized in that The concentration of the alkaline solution is 1.5 mol / L to 2.5 mol / L; the alkaline solution is at least one of sodium hydroxide solution and potassium hydroxide solution.

6. The method according to claim 5, wherein The preparation method of the alkali-modified copper-iron bimetallic catalyst includes the following steps: S1. Obtain a copper-iron metal compound; S2. Mix the copper-iron metal compound with an alkaline solution for etching to obtain an alkali-modified copper-iron bimetallic catalyst.

7. The method according to claim 6, wherein The preparation conditions of the alkali-modified copper-iron bimetallic catalyst include at least one of (1.1) to (1.3): (1.1) In step S1, the copper-iron metal compound is prepared by a hydrothermal reaction using a copper salt and an iron salt as raw materials; the molar ratio of the copper salt to the iron salt is 1:1; the copper salt is copper nitrate trihydrate; the iron salt is iron nitrate nonahydrate; the hydrothermal reaction is carried out at a temperature of 180 °C, and the time of the hydrothermal reaction is 48 h; (1.2) In step S2, the ratio of the copper-iron metal compound to the alkaline solution is 1 g:100 mL; (1.3) In step S2, the etching is carried out under stirring conditions; the rotation speed of the stirring is 500 rpm; the time of the stirring is 60 min.

8. The method according to any one of claims 1 to 7, characterized in that Using the alkali-modified copper-iron bimetallic catalyst to activate persulfate and degrade organic pollutants in water includes the following steps: Mix the alkali-modified copper-iron bimetallic catalyst, persulfate and the water containing organic pollutants for a degradation reaction to complete the degradation of the organic pollutants in the water; the initial concentration of the alkali-modified copper-iron bimetallic catalyst in the degradation reaction system ≥ 0.01 g / L, and the initial concentration of persulfate ≥ 0.2 g / L.

9. The method according to claim 8, characterized in that, The initial concentration of the alkali-modified copper-iron bimetallic catalyst in the degradation reaction system is 0.01 g / L to 0.05 g / L, and the initial concentration of persulfate is 0.2 g / L to 0.8 g / L; the initial pH value in the degradation reaction system is 3 to 11.

10. The method according to claim 9, wherein The persulfate is peroxymonosulfate; the peroxymonosulfate is at least one of sodium peroxymonosulfate and potassium peroxymonosulfate; the initial concentration of the organic pollutants in the water body containing organic pollutants ≤ 30 mg / L; the organic pollutants in the water body containing organic pollutants are antibiotics; the antibiotic is at least one of oxytetracycline; the degradation reaction is carried out under shaking conditions; the rotation speed of the shaking is 700 rpm; the temperature of the degradation reaction is 25°C to 30°C; the time of the degradation reaction is 0.5 min to 60 min.

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