Method for removing organic pollutants from water using alkali-modified copper-iron bimetallic catalyst to activate persulfate

Abstract

The present invention discloses a method for removing organic pollutants from water bodies by activating persulfate with an alkali-modified copper-iron bimetallic catalyst. The method utilizes the alkali-modified copper-iron bimetallic catalyst as a catalyst for activating persulfate and degrading organic pollutants in water bodies. The alkali-modified copper-iron bimetallic catalyst comprises a copper-iron metal compound (CuFeO2) and oxygen vacancies supported thereon. The catalyst of the present invention has advantages such as a large specific surface area, a large number of active sites, high catalytic activity, and good structural stability. When used to activate persulfate, it can establish a core mechanism degradation system based on a non-free radical pathway. When used to degrade organic pollutants in water bodies, it can more quickly and thoroughly remove organic pollutants. The method has the advantages of simple process, convenient operation, low cost, strong practicality, wide adaptability, high treatment efficiency, good degradation effect, and environmental friendliness. It has high practical value and promising application prospects.

Description

Technical Field

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

[0002] In traditional advanced oxidation reaction systems, free radical pathways are the core mechanism for degrading organic pollutants. The differences in their characteristics directly affect the applicability and efficiency of the technology. At the same time, free radical pathways indiscriminately attack pollutants through chain reactions, showing strong oxidation ability and fast reaction rate. They are particularly suitable for the treatment of high-concentration dye wastewater or pesticide wastewater, but their limitations are obvious. On the one hand, natural organic matter (NOM) and chloride ions (Cl - ) and other background components are prone to competitive reactions with free radicals, significantly reducing the degradation efficiency of target pollutants; on the other hand, their strong pH dependence (for example, ·OH is most active under neutral conditions, while the Fenton system requires pH ≈ 3) increases the complexity of process regulation; in addition, the indiscriminate attack of free radicals may lead to increased toxicity of intermediates, such as the formation of chlorinated organic matter or bromate, and even bring the risk of secondary pollution.

[0003] In contrast, non-radical pathways involve surface-mediated electron transfer, singlet oxygen ( 1 O2) or high-valent metal species, etc., showing more precise selectivity and environmental adaptability, and directly transferring electrons through the functional groups on the catalyst surface to destroy pollutant molecules, or generate 1 O2 selectively oxidizes organic compounds containing electron-rich groups (such as phenols and antibiotics). This selectivity not only reduces the impact on background components (such as Cl - 、HCO3 - ) and significantly reduces the risk of toxic byproducts. Furthermore, non-radical reactions often occur on the surfaces of heterogeneous catalysts (such as porous carbon and metal oxides), and their wide pH adaptability (e.g., pH 3-9) makes them particularly advantageous in complex waters (such as seawater and landfill leachate). Therefore, obtaining a suitable catalyst to activate persulfate and initiate a non-radical degradation mechanism is crucial for the efficient degradation of organic pollutants in water.

[0004] Copper ferrite (CuFeO2), a copper-iron bimetallic catalyst, can be used to activate persulfate. However, existing copper-iron bimetallic catalysts still suffer from shortcomings such as small specific surface area, a small number of active sites, poor catalytic activity, and poor structural stability. Consequently, when used to activate persulfate, these catalysts still suffer from poor persulfate activation, difficulty in efficiently activating persulfate with low catalyst dosage, poor degradation, and the risk of secondary pollution. In particular, the degradation mechanism established by existing copper-iron bimetallic catalysts for persulfate activation is still based on a free radical pathway, making it difficult to achieve selective degradation of organic pollutants in water and susceptible to interference from external factors. Therefore, developing a copper-iron bimetallic catalyst with a large specific surface area, a large number of active sites, high catalytic activity, excellent structural stability, and the ability to construct a non-free radical degradation mechanism is of great significance for promoting the efficient degradation of organic pollutants in water. Summary of the Invention

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

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A method for removing organic pollutants from water by activating persulfate with an alkali-modified copper-iron bimetallic catalyst. The method uses the alkali-modified copper-iron bimetallic catalyst as a catalyst to activate persulfate and degrade the organic pollutants in the water. The alkali-modified copper-iron bimetallic catalyst comprises a copper-iron metal compound loaded with oxygen vacancies. The copper-iron metal compound is CuFeO2.

[0008] The above method is further improved in that the valence of copper in the alkali-modified copper-iron bimetallic catalyst is monovalent and the valence of iron is divalent; and the copper-iron metal compound has a cubic structure.

[0009] The above method is further improved in that the alkali-modified copper-iron bimetallic catalyst is prepared by etching a copper-iron metal compound as a raw material with an alkaline solution; the concentration of the alkaline solution is ≥1 mol / L.

[0010] The above method is further improved in that the concentration of the alkaline solution is 1.5 mol / L to 4 mol / L.

[0011] The above method is further improved 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 a sodium hydroxide solution and a potassium hydroxide solution.

[0012] The above method is further improved, and the preparation method of the alkali-modified copper-iron bimetallic catalyst comprises the following steps:

[0013] S1. Obtaining copper-iron metal compounds;

[0014] S2. Mixing the copper-iron metal compound with an alkaline solution and etching the mixture to obtain an alkali-modified copper-iron bimetallic catalyst.

[0015] The above method is further improved, wherein the preparation conditions of the base-modified copper-iron bimetallic catalyst include at least one of (1.1) to (1.3):

[0016] (1.1) In step S1, the copper-iron metal compound is 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 iron nitrate nonahydrate; the hydrothermal reaction is carried out at a temperature of 180° C. and for a time of 48 hours;

[0017] (1.2) In step S2, the ratio of the copper-iron metal compound to the alkaline solution is 1 g: 100 mL;

[0018] (1.3) In step S2, the etching is performed under stirring conditions; the stirring speed is 500 rpm; and the stirring time is 60 minutes.

[0019] The above method is further improved, using an alkali-modified copper-iron bimetallic catalyst as a catalyst to activate persulfate and degrade organic pollutants in water, comprising the following steps: mixing the alkali-modified copper-iron bimetallic catalyst, persulfate and water containing organic pollutants to carry out a degradation reaction to complete the degradation of organic pollutants in the water; 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.

[0020] The above method is further improved in that 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 the persulfate is 0.2 g / L to 0.8 g / L; the initial pH value in the degradation reaction system is 3 to 11.

[0021] The above method is further improved, wherein the persulfate is peroxymonosulfate; the peroxymonosulfate is at least one of sodium peroxymonosulfate and potassium peroxymonosulfate; 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 antibiotics are at least one of oxytetracycline; the degradation reaction is carried out under shaking conditions; the shaking speed is 700 rpm; the temperature of the degradation reaction is 25°C to 30°C; and the time of the degradation reaction is 0.5 min to 60 min.

[0022] Compared with the prior art, the advantages of the present invention are:

[0023] (1) In view of the shortcomings of existing copper-iron bimetallic catalysts, such as small specific surface area, small number of active sites, poor catalytic activity, and poor structural stability, as well as 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 the risk of secondary pollution, the present invention creatively proposes a method for removing organic pollutants in water by activating persulfate using an alkali-modified copper-iron bimetallic catalyst, wherein the alkali-modified copper-iron bimetallic catalyst is used as a catalyst to activate persulfate and degrade organic pollutants in water, wherein the alkali-modified copper-iron bimetallic catalyst includes a copper-iron metal compound, and the copper-iron metal compound is loaded with oxygen vacancies, and the copper-iron metal compound is CuFeO2. In the present invention, oxygen vacancies (Ov) are loaded on the copper-iron metal compound, and the oxygen vacancies (Ov) are used to improve the intrinsic activity of the catalyst, which can effectively adjust the electronic structure of the copper-iron metal compound and promote electron transfer. At the same time, the oxygen vacancies (Ov) can be used as active sites to significantly improve the catalytic performance of the catalyst. When it is used as a catalyst for activating persulfate, it can quickly and continuously generate a large amount of singlet oxygen ( 1O2) and other active substances, and construct a core mechanism based on the non-free radical pathway, and finally use these active substances to efficiently degrade organic pollutants in water under this mechanism. Taking tetracycline as an example, the degradation mechanism involved is shown in formulas (1) to (9). In particular, in the degradation system constructed by the present invention, on the one hand, tetracycline can be efficiently degraded under the condition of very low catalyst dosage. For example, when the catalyst dosage is 0.02g / 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 molecules, realizing the harmless treatment of oxytetracycline. 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, so that the catalyst exhibits very excellent catalytic performance. When used to activate persulfate and degrade organic pollutants, it exhibits a very fast degradation rate, wherein the degradation rate can reach 0.0539min -1 , almost 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 lose, and has better structural stability. On the one hand, it still shows very excellent catalytic activity after multiple uses and has good reusability. On the other hand, it can effectively prevent metal ion leaching, of which the amount of iron leached is only 0.1876 mg / L, which is lower than the standard limit of surface water for drinking water (0.3 mg / L) and meets the standards for drinking water. The method of the present invention using alkali-modified copper-iron bimetallic catalyst to activate persulfate to remove organic pollutants in water has the advantages of simple process, convenient operation, low cost, strong practicality, wide adaptability, high treatment efficiency, good degradation effect, and green environmental protection. It can effectively degrade high-concentration organic pollutants in water, especially for organic pollutants with a concentration of ≤30 mg / L, with better removal effect, high use value and good application prospects.

[0024] .

[0025] (2) In the present invention, the copper-iron metal compound used has a cubic structure, which can not only provide more attachment sites but also better prevent metal leaching.

[0026] (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, wherein the concentration of the alkaline solution is ≥1 mol / L. The copper-iron metal compound is subjected to alkali etching in the alkaline solution, which can introduce a large number of oxygen vacancies on the copper-iron metal compound and expose more copper-iron sites, thereby significantly increasing the number of active sites on the catalyst surface while increasing the specific surface area. In particular, by optimizing the concentration of the alkaline solution to 1.5 mol / L to 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 making the catalyst 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, it can remove organic pollutants in water more quickly and thoroughly.

[0027] (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, thereby being able to efficiently remove organic pollutants under different pH conditions. When the initial pH value in the degradation reaction system is ≥3, in particular, when the initial pH value is 3-9, the removal rate of organic pollutants does not show a significant decrease, and the removal rate is above 90%. Furthermore, based on the excellent 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 conducive to reducing treatment costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to make the purpose, 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.

[0029] 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) on oxytetracycline in Example 1 of the present invention.

[0030] Figure 2 This is a comparison chart of the degradation rates of oxytetracycline by 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.

[0031] Figure 3This is a comparison chart of the removal effects of oxytetracycline using different amounts of alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) in Example 2 of the present invention.

[0032] Figure 4 This is a comparison chart of the removal effect of oxytetracycline by the alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) under different dosages of potassium monopersulfate in Example 3 of the present invention.

[0033] Figure 5 This is a comparison chart of the removal effects of oxytetracycline at different concentrations when activating peroxymonosulfate using the alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) in Example 4 of the present invention.

[0034] Figure 6 This is a comparison diagram of the removal effect of oxytetracycline under different pH conditions when the alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) activates peroxymonosulfate in Example 5 of the present invention.

[0035] Figure 7 This is a comparison chart of the removal effects of oxytetracycline on peroxymonosulfate under different free radical scavenger conditions when the base-modified copper-iron bimetallic catalyst (CuFeO2-AT2) in Example 6 of the present invention is activated.

[0036] Figure 8 This is the EPR diagram of the alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) in Example 7 of the present invention.

[0037] Figure 9 This is a diagram showing the cyclic degradation effect of oxytetracycline in water by the alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) in Example 8 of the present invention.

[0038] Figure 10 2 is an 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. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the scope of protection of the present invention is not limited thereby.

[0040] In the following examples 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 average values ​​of more than three repeated experiments.

[0041] Example 1:

[0042] A method for removing organic pollutants from 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 the water, comprising the following steps:

[0043] (1) Prepare five groups of 100 mL of a 20 mg / L oxytetracycline aqueous solution (the original pH value of the aqueous solution is 6.54), with two replicates in each group.

[0044] (2) Different concentrations of sodium hydroxide solution were added to each group of solutions for etching to obtain alkali-modified copper-iron bimetallic catalysts (CuFeO2, CuFeO2-AT0.5, CuFeO2-AT1, CuFeO2-AT2, CuFeO2-AT3, CuFeO2-AT4). The catalyst content added to the solution was 30 mg. Potassium monopersulfate was then added to make the concentration of potassium monopersulfate in the solution 0.2 g / L. The degradation reaction was carried out at 25°C and 700 rpm for 60 min to complete the removal of oxytetracycline in the water.

[0045] 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, respectively. The sample solution was filtered with a 0.45 μm filter, and the filtered solution was added to a sample bottle containing an excess of Na2S2O3 solution to terminate the reaction. The concentration of Na2S2O3 was 5 mM. The concentration of oxytetracycline was measured using a UV2600 spectrophotometer at an absorption wavelength of 357 nm to obtain the corresponding concentration of oxytetracycline. The removal effect of oxytetracycline on the alkali-modified copper-iron bimetallic catalyst (CuFeO2, CuFeO2-AT0.5, CuFeO2-AT1, CuFeO2-AT2, CuFeO2-AT3, and CuFeO2-AT4) obtained after etching with different concentrations of sodium hydroxide solution was plotted. The results are shown in Figure 2. Figure 1 shown.

[0046] Figure 1 This is a comparison chart of the removal effects of different alkali-modified copper-iron bimetallic catalysts (CuFeO2, CuFeO2-AT0.5, CuFeO2-AT1, CuFeO2-AT2, CuFeO2-AT3, and CuFeO2-AT4) on oxytetracycline in Example 1 of the present invention. Figure 1 It can be seen that the copper-iron bimetallic catalyst (CuFeO2) after etching with sodium hydroxide solution has a significantly improved degradation rate of oxytetracycline. When the concentration of the sodium hydroxide solution is 2 mol / L~4 mol / L, the degradation rate of oxytetracycline by the corresponding alkali-modified copper-iron bimetallic catalyst is almost 100%.

[0047] Figure 2 This is a comparison chart of the degradation rates of oxytetracycline by 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.

[0048] Depend on Figure 2 It can be seen that the copper-iron bimetallic catalyst (CuFeO2) after etching with sodium hydroxide solution significantly improves the degradation rate of oxytetracycline. When the concentration of sodium hydroxide solution is 2 mol / L~4 mol / L, the degradation rate of the alkali-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 corresponding degradation rate of CuFeO2-AT2 is 0.0539 min -1 , which is higher than other catalysts etched by sodium hydroxide concentration, and is almost four times that of copper-iron metal compound (CuFeO2).

[0049] Depend on Figure 1 and Figure 2 The results showed that etching with sodium hydroxide (alkali modification) is an effective strategy for enhancing the catalytic activity of the CuFeO2-ATx / PMS system, significantly improving the degradation efficiency of oxytetracycline. Specifically, when etching the copper-iron metal compound with sodium hydroxide solution, a 2 mol / L sodium hydroxide solution concentration resulted in the production of the most effective alkaline-modified copper-iron bimetallic catalyst.

[0050] Example 2:

[0051] A method for removing organic pollutants from 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 the water, comprising the following steps:

[0052] (1) Prepare four groups of 100 mL of a 20 mg / L oxytetracycline aqueous solution (the original pH value of the aqueous solution is 6.54), with two replicates in each group.

[0053] (2) Different amounts of alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) were added to each group of solutions, so that the concentration of CuFeO2-AT2 in the solution was 0.01 g / L, 0.02 g / L, 0.03 g / L, and 0.05 g / L. Potassium monopersulfate was then added to make the concentration of potassium monopersulfate in the solution 0.2 g / L. The degradation reaction was carried out at 25°C and 700 rpm for 60 min to complete the removal of oxytetracycline in the water.

[0054] Control group: no CuFeO2-AT2 was added, and other conditions were the same.

[0055] 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, respectively. The sample solution was filtered with a 0.45 μm filter. The filtered solution was added to a sample bottle containing an excess of Na2S2O3 solution to terminate the reaction. The concentration of Na2S2O3 was 5 mM. The concentration of oxytetracycline was measured at an absorption wavelength of 357 nm using a UV2600 spectrophotometer to obtain the corresponding concentration of oxytetracycline. The degradation effect of different amounts of base-modified copper-iron bimetallic catalyst (CuFeO2-AT2) on oxytetracycline was plotted. The results are shown in Figure 2. Figure 3 shown.

[0056] Figure 3 The figure is a comparison of the removal effects of oxytetracycline by different amounts of alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) in Example 2 of the present invention. Figure 3 It can be seen that the removal rate of oxytetracycline can be maintained above 90% when different amounts of CuFeO2-AT2 are added. In particular, when the concentration of CuFeO2-AT2 reaches above 0.02 g / L, the degradation rate is maintained at 0.05 min. -1 This shows that CuFeO2-AT2 has strong catalytic activity and can effectively and thoroughly remove oxytetracycline in water even with a small dosage, and has good economic applicability.

[0057] Example 3:

[0058] A method for removing organic pollutants from 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 the water, comprising the following steps:

[0059] (1) Prepare four groups of 100 mL of a 20 mg / L oxytetracycline aqueous solution (the original pH value of the aqueous solution is 6.54), with two replicates in each group.

[0060] (2) Alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) was added to each group of solutions to make the concentration of CuFeO2-AT2 in the solution 0.02 g / L; then different amounts of potassium monopersulfate were added, and the amounts were 0.2 g / L, 0.4 g / L, 0.6 g / L, and 0.8 g / L, respectively; the degradation reaction was carried out at 25 °C and 700 rpm for 60 min to complete the removal of oxytetracycline in the water.

[0061] Control group: no potassium monopersulfate was added, and other conditions were the same.

[0062] 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, respectively. The sample solution was filtered through a 0.45 μm filter, and the filtered solution was added to a sample bottle containing an excess of Na2S2O3 solution to terminate the reaction. The concentration of Na2S2O3 was 5 mM. The concentration of oxytetracycline was measured using a UV2600 spectrophotometer at an absorption wavelength of 357 nm to obtain the corresponding concentration of oxytetracycline. The degradation effect of the base-modified copper-iron bimetallic catalyst (CuFeO2-AT2) on oxytetracycline under different dosages of potassium monopersulfate was plotted. The results are shown in Figure 2. Figure 4 shown.

[0063] Figure 4 This is a comparison chart of the removal effect of oxytetracycline by the alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) under different dosages of potassium monopersulfate in Example 3 of the present invention. Figure 4 It can be seen that as the PMS dosage gradually increased from 0.2 g / L to 0.8 g / L, the degradation rate of oxytetracycline decreased from 97% to 85%. At the same time, kobs decreased from 0.048 min at 0.2 g / L PMS. -1 0.0269 min down to 0.8 g / L -1 , the dosage of 0.2 g / L PMS is almost twice that of 0.8 g / L PMS. The reason for the reduced degradation rate and slowed reaction rate may be that a large number of PMS molecules collide with the catalytic active sites, which in turn affects the production of singlet oxygen, thereby slowing down the reaction and resulting in a reduced 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 the economic benefit is high. In particular, when the concentration of potassium monopersulfate in the degradation reaction system is 0.2 g / L, the best removal effect and economic benefit can be achieved.

[0064] Example 4:

[0065] A method for removing organic pollutants from 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 the water, comprising the following steps:

[0066] (1) Prepare four groups of 100 mL of oxytetracycline aqueous solution (the original pH value of the aqueous solution is 6.54), with the concentrations of oxytetracycline being 20 mg / L, 50 mg / L, 80 mg / L, and 100 mg / L, respectively. Set up two parallel samples in each group.

[0067] (2) Alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) was added to each solution to make the concentration of CuFeO2-AT2 in the solution 0.02 g / L; potassium monopersulfate was then added to make the concentration of potassium monopersulfate in the solution 0.2 g / L; the degradation reaction was carried out at 25°C and 700 rpm for 60 min to complete the removal of oxytetracycline in the water.

[0068] 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, respectively. The sample solution was filtered through a 0.45 μm filter. The filtered solution was added to a sample bottle containing an excess of Na2S2O3 solution to terminate the reaction. The concentration of Na2S2O3 was 5 mM. The concentration of oxytetracycline was measured using a UV2600 spectrophotometer at an absorption wavelength of 357 nm to obtain the corresponding concentration of oxytetracycline. The degradation effect of the base-modified copper-iron bimetallic catalyst (CuFeO2-AT2) on different concentrations of oxytetracycline was plotted. The results are shown in Figure 2. Figure 5 shown.

[0069] Figure 5 This is a comparison of the removal effects of oxytetracycline at different concentrations when the base-modified copper-iron bimetallic catalyst (CuFeO2-AT2) activates peroxymonosulfate in Example 4 of the present invention. Figure 5 It can be seen that as the initial OTC concentration increases, the degradation effect of the CuFeO2-AT2 / PMS system on OTC decreases significantly. This is because: at a fixed dosage of potassium permonosulfate, the active species produced are fixed, making it difficult for the system to produce more active species when the initial OTC concentration increases. As a result, only a portion of the OTC can be degraded, resulting in a significant decrease in the removal rate. Therefore, when treating wastewater with high concentrations of organic pollutants, increasing the dosage of permonosulfate and CuFeO2-AT2 can achieve efficient removal of organic pollutants in high-concentration wastewater.

[0070] Example 5:

[0071] A method for removing organic pollutants from 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 the water, comprising the following steps:

[0072] (1) Prepare five groups of 100 mL oxytetracycline aqueous solutions with a concentration of 20 mg / L. Use 0.1 mol / L HCl or 0.1 mol / L NaOH to adjust the pH values ​​of the four groups of solutions to 3, 5, 6.54, 9, and 11. Set up two parallel samples for each group.

[0073] (2) Alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) was added to each solution to make the concentration of CuFeO2-AT2 in the solution 0.02 g / L; potassium monopersulfate was then added to make the concentration of potassium monopersulfate in the solution 0.2 g / L; the degradation reaction was carried out at 25°C and 700 rpm for 60 min to complete the removal of oxytetracycline in the water.

[0074] 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, respectively. The sample solution was filtered with a 0.45 μm filter. The filtered solution was added to a sample bottle containing an excess of Na2S2O3 solution to terminate the reaction. The concentration of Na2S2O3 was 5 mM. The concentration of oxytetracycline was measured using a UV2600 spectrophotometer at an absorption wavelength of 357 nm to obtain the corresponding concentration of oxytetracycline. The degradation effect of the base-modified copper-iron bimetallic catalyst (CuFeO2-AT2) on oxytetracycline under different pH conditions was plotted. The results are shown in Figure 2. Figure 6 shown.

[0075] Figure 6 This is a comparison diagram of the removal effect of oxytetracycline under different pH conditions when the alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) activates peroxymonosulfate in Example 5 of the present invention.

[0076] Depend on Figure 6 It can be seen that under the condition of initial pH value of 3-9, the OTC removal rate did not show a significant decrease, and the removal rate was around 90%. Even when the pH value was 11, the degradation rate could reach about 80%. This shows that the CuFeO2-AT2 / PMS system is not affected by acidic, neutral and alkaline solutions. It further shows that the working pH range of the system is wide and the resistance to pH value during the degradation process is strong. Therefore, there is no need to adjust the pH value during the actual treatment process, which is conducive to reducing treatment costs.

[0077] Example 6:

[0078] A method for removing organic pollutants from 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 the water, comprising the following steps:

[0079] (1) Prepare five groups of 100 mL oxytetracycline aqueous solutions with a concentration of 20 mg / L (the original pH value of the aqueous solution is 6.54). Four of the groups were added with tert-butyl alcohol (TBA), anhydrous ethanol (AE), a sugar alcohol (FFA), and p-benzoquinone (p-BQ) as free radical scavengers, respectively, so that the concentration of each free radical scavenger in the solution was 20 mM. The other group was used as a control. Two parallel samples were set up for each group.

[0080] (2) Alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) was added to each solution to make the concentration of CuFeO2-AT2 in the solution 0.02 g / L; potassium monopersulfate was then added to make the concentration of potassium monopersulfate in the solution 0.2 g / L; the degradation reaction was carried out at 25°C and 700 rpm for 60 min to complete the removal of oxytetracycline in the water.

[0081] In this embodiment, 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, and filtered with a 0.22 μm filter head. The filtered solution was added to a liquid injection bottle containing 20 μL of sodium thiosulfate quencher solution (1 mol / L), and the concentration of oxytetracycline after the reaction was measured using a high performance liquid chromatograph to obtain the corresponding concentration of oxytetracycline. The change curve of the oxytetracycline removal rate under different free radical scavenger conditions was drawn, and the results are shown as follows. Figure 7 shown.

[0082] Figure 7 This is a comparison chart of the removal effects of oxytetracycline on peroxymonosulfate by the base-modified copper-iron bimetallic catalyst (CuFeO2-AT2) under different free radical scavenger conditions in Example 6 of the present invention. Figure 7It can be seen that tert-butanol (TBA) is a typical hydroxyl radical scavenger. After the addition of tert-butanol, the oxidation activity in the CuFeO2-AT2 / PMS system showed a slight decrease, indicating that a small amount of hydroxyl radicals in the degradation system played a partial role in the degradation mechanism. Anhydrous ethanol (AE) is usually used as a scavenger of hydroxyl radicals and sulfate radicals. When anhydrous ethanol was added, it was observed that the degradation rate of oxytetracycline decreased significantly, confirming that the hydroxyl radicals and sulfate radicals produced during the degradation reaction acted together. It is worth noting that when furfuryl alcohol (FFA) and p-benzoquinone (p-BQ) were added, the degradation rates were only 19% and 30%, and kobs decreased from 0.048min -1 respectively decreased to 0.002 min -1 and 0.005 min -1 , which indicates that in the reaction 1 O2, O2 - may play a major role, while O2 - The reason for affecting the degradation rate may be that 1 The addition of p-benzoquinone, an intermediate product of O2, scavenges superoxide radicals, thereby affecting the generation of singlet oxygen, thereby affecting the decrease in degradation rate and slowing down the degradation rate. The above results show that in the present invention, when using a base-modified copper-iron bimetallic catalyst to activate peroxymonosulfate, a core mechanism based on a non-radical pathway can be constructed.

[0083] Example 7:

[0084] In order to explore the contribution of active species in the CuFeO2-AT2 / PMS system, the present invention uses EPR experiments to determine its active oxygen and possible reaction mechanism. DMPO as a free radical (·OH, ·O2 - and SO4 ·- ) spin trapping agent was used to detect the EPR signal of free radicals in the CuFeO2-AT2 / PMS system.

[0085] Figure 8 This is the EPR diagram of the alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) in Example 7 of the present invention. Figure 8 In the figure, (a) is the hydroxyl radical and sulfate radical signal measured in the EPR characterization, (b) is the superoxide radical signal measured in the EPR characterization, and (c) is the singlet oxygen signal measured in the EPR characterization. Figure 8 It can be seen that OH and SO4 do not appear in the reaction system. ·- The characteristic peaks of the adducts reacting with DMPO prove that OH and SO4 ·- It is not the main oxidative active species, but there are 7 species with an intensity ratio of 1:2:1:2:1:2:1 (α N=7.3±0.1G,α H =3.9±0.1G), which may be due to the ultrafine cracking of (DMPOX). The appearance of this characteristic peak indicates that DMPO can be rapidly oxidized, which can also prove the presence of strong oxidizing substances in the system. Figure 8 O2 appeared in - The signal and 1 O2 typically has a triplet peak with an intensity ratio of 1:1:1. This phenomenon may be caused by the generation of O2 - Just as a generation 1 The intermediate product of O2, namely O 2- Generated by recombination 1 O2, further proving that the main active species of the CuFeO2-AT2 / PMS system is singlet oxygen and the core mechanism is a non-radical pathway.

[0086] Example 8:

[0087] The stability and reproducibility of the base-modified copper-iron bimetallic catalyst (CuFeO2-AT2) were investigated, including the following steps:

[0088] (1) Prepare 1000 mL of a 20 mg / L oxytetracycline aqueous solution (the original pH value of the aqueous solution is 6.54), with two parallel samples in each group.

[0089] (2) Alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) was added to each solution to make the concentration of CuFeO2-AT2 in the solution 0.02 g / L; potassium monopersulfate was then added to make the concentration of potassium monopersulfate in the solution 0.2 g / L; the degradation reaction was carried out at 25°C and 700 rpm for 60 min to complete the removal of oxytetracycline in the water.

[0090] After each reaction, the remaining mixture was filtered and the remaining solid material was dried in an oven at 60°C for 12 hours. The resulting solid material was then removed and used in the next experiment. Steps (1) to (2) were repeated three times.

[0091] Figure 9 This is a graph showing the effect of alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) on the cyclic degradation of oxytetracycline in water in Example 8 of the present invention. Figure 9 The results show that after three cycles, the OTC removal rate can still be maintained at around 80%. In addition, the metal ion leaching of CuFeO2-AT2 after the reaction was detected by ICP-MS, and the iron ion leaching amount was only 0.1876 mg / L. Its leaching amount is lower than the standard limit of drinking water surface water (0.3 mg / L) and meets the drinking water standard.

[0092] Example 9:

[0093] The preparation method of the alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) used in the above embodiment specifically comprises first preparing a copper-iron metal compound by hydrothermal reaction using copper salt and iron salt as raw materials, and then preparing an alkali-modified copper-iron bimetallic catalyst by etching the copper-iron metal compound with an alkaline solution, comprising the following steps:

[0094] S1. Dissolve 8 mmol of copper nitrate trihydrate and 8 mmol of ferric nitrate nonahydrate in 15 mL of pure water to prepare a copper-iron solution. Add 60 mL of 1 mol / L sodium hydroxide solution, stir at 300 rpm for 10 min, and ultrasonicate for 10 min to obtain a precipitate suspension.

[0095] S2. According to the ratio of propionaldehyde to copper salt of 1 ml: 10 mmol, propionaldehyde is mixed with the precipitate suspension obtained in step S1, and the mixture is transferred to a high-pressure reactor for hydrothermal reaction, wherein the temperature of the hydrothermal reaction is 180° C. and the reaction time is 48 h. After the reaction is completed, the solid-liquid mixture after the reaction is filtered, and the filtered solid is washed with pure water for 3 times. The washed solid product is dried at a temperature of 60° C. for 12 h to obtain a copper iron oxide precursor (copper-iron metal compound), which is recorded as CuFeO2.

[0096] S3. According to the ratio of copper-iron metal compound to alkaline solution of 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. The etching was continuously stirred at a speed of 500 rpm for 60 min. After the stirring was completed, 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, which was recorded as CuFeO2-AT2.

[0097] In this embodiment, the prepared alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) includes a copper-iron metal compound on which oxygen vacancies are loaded. The copper-iron metal compound is CuFeO2 and has a cubic structure.

[0098] In this embodiment, the valence of copper in the prepared alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2) is monovalent, and the valence of iron is divalent.

[0099] In this embodiment, alkali-modified copper-iron bimetallic catalysts (CuFeO2-AT0.5, CuFeO2-AT1, CuFeO2-AT3, and CuFeO2-AT4) obtained by etching under conditions of different concentrations of sodium hydroxide solution were also prepared. The preparation method was basically the same as that of the alkali-modified copper-iron bimetallic catalyst (CuFeO2-AT2), with the only difference being that in the preparation method of the alkali-modified copper-iron bimetallic catalysts (CuFeO2-AT0.5, CuFeO2-AT1, CuFeO2-AT3, and CuFeO2-AT4), the concentrations of the sodium hydroxide solution used when etching the copper-iron metal compound were 0.5 mol / L, 1 mol / L, 3 mol / L, and 4 mol / L, respectively. That is, when the concentrations of the sodium hydroxide solution used in etching the copper-iron metal compound are 0.5 mol / L, 1 mol / L, 3 mol / L, and 4 mol / L, respectively, the corresponding alkali-modified copper-iron bimetallic catalysts are recorded as CuFeO2-AT0.5, CuFeO2-AT1, CuFeO2-AT3, and CuFeO2-AT4, respectively.

[0100] The surface morphology of CuFeO2-AT2 and CuFeO2 was observed using a scanning electron microscope (SEM). The specific results are as follows:

[0101] Figure 10 2 is an 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 10 In the figure, (a) is the SEM image of CuFeO2 at a scale of 500nm, (b) and (c) are the SEM images of CuFeO2-AT2 at a scale of 200nm and 500nm respectively. Figure 10 The results in

[15] show that the CuFeO2-AT2 catalyst material has a more compact cubic structure to provide more attachment sites and better prevent metal leaching.

[0102] Based on the above results, it can be seen that 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 exhibits a very fast degradation rate, where the degradation rate can reach 0.0539min -1, almost four times that of CuFeO2; (b) better structural stability. On the one hand, it still shows very excellent catalytic activity after multiple uses and has good reusability. On the other hand, it can effectively prevent metal ion leaching, of which the amount of iron leached is only 0.1876 mg / L, which is lower than the standard limit of surface water for drinking water (0.3 mg / L) and meets the standards for drinking water. The method of the present invention using an alkali-modified copper-iron bimetallic catalyst to activate persulfate to remove organic pollutants in water has the advantages of simple process, convenient operation, low cost, strong practicality, wide adaptability, high treatment efficiency, good degradation effect, and environmental protection. It can effectively degrade high-concentration organic pollutants in water, especially for organic pollutants with a concentration of ≤30 mg / L, with better removal effect, high use value and good application prospects.

[0103] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions that fall within the scope of protection of the present invention are within the scope of protection of the present invention. It should be noted that improvements and modifications that can be made by a person skilled in the art without departing from the principles of the present invention are also considered to be within the scope of protection of the present invention.

Claims

1. A method for removing organic pollutants from water by activating persulfate with an alkali-modified copper-iron bimetallic catalyst, characterized in that: The method uses an alkali-modified copper-iron bimetallic catalyst as a catalyst to activate persulfate and degrade organic pollutants in water. The alkali-modified copper-iron bimetallic catalyst includes CuFeO2 loaded with oxygen vacancies. The alkali-modified copper-iron bimetallic catalyst is prepared by etching a copper-iron metal compound as a raw material with an alkaline solution. The concentration of the alkaline solution is 1.5 mol / L to 4 mol / L. The copper-iron metal compound is prepared by a hydrothermal reaction using copper salt and iron salt as raw materials.

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

3. The method according to claim 2, 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 a sodium hydroxide solution and a potassium hydroxide solution.

4. The method according to claim 3, characterized in that The preparation method of the alkali-modified copper-iron bimetallic catalyst comprises the following steps: S1. Obtaining copper-iron metal compounds; S2. Mixing the copper-iron metal compound with an alkaline solution and etching the mixture to obtain an alkali-modified copper-iron bimetallic catalyst.

5. The method according to claim 4, characterized in that 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 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. for 48 hours; (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 performed under stirring conditions; the stirring speed is 500 rpm; and the stirring time is 60 minutes.

6. The method according to any one of claims 1 to 5, characterized in that An alkali-modified copper-iron bimetallic catalyst is used as a catalyst to activate persulfate and degrade organic pollutants in water, comprising the following steps: mixing the alkali-modified copper-iron bimetallic catalyst, persulfate and water containing organic pollutants to carry out a degradation reaction to complete the degradation of the organic pollutants in the water; in the degradation reaction system, the initial concentration of the alkali-modified copper-iron bimetallic catalyst is ≥0.01 g / L, and the initial concentration of the persulfate is ≥0.2 g / L.

7. The method according to claim 6, 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 the persulfate is 0.2 g / L to 0.8 g / L; the initial pH value in the degradation reaction system is 3 to 11.

8. The method according to claim 7, characterized in that The persulfate is peroxymonosulfate; the peroxymonosulfate is at least one of sodium peroxymonosulfate and potassium peroxymonosulfate; 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 antibiotics are at least one of oxytetracycline; the degradation reaction is carried out under shaking conditions; the shaking speed 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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