A method for removing imidacloprid from wastewater using a nitrogen-doped carbon-based zinc-iron diatomic catalyst

Abstract

The present invention discloses a method for removing imidacloprid from wastewater using a nitrogen-doped carbon-based zinc-iron diatomic catalyst, comprising the following steps: a first step: preparing a chitosan / zinc-iron dimetallic ion chelate; a second step: preparing a nitrogen-doped carbon-based zinc-iron dimetallic nanocatalyst; a third step: preparing a nitrogen-doped carbon-based zinc-iron diatomic catalyst; and a fourth step: removing imidacloprid using a nitrogen-doped carbon-based zinc-iron diatomic catalyst / PMS system. The method of the present invention has mild reaction conditions, environmentally friendly materials, and high atomic utilization. The catalyst not only has a wide range of applications but also exhibits excellent removal efficiency for various organic pollutants in other wastewaters. Under optimal conditions, the nitrogen-doped carbon-based zinc-iron diatomic catalyst can remove more than 90% of imidacloprid within 10 minutes. Furthermore, the method of the present invention has simple steps, readily available raw materials, and is environmentally friendly, making it suitable for wastewater treatment.

Description

Technical Field

[0001] The invention relates to the technical field of removing imidacloprid from wastewater using a catalyst, and in particular to a method for removing imidacloprid from wastewater using a nitrogen-doped carbon-based zinc-iron diatomic catalyst. Background Art

[0002] With the withdrawal of highly toxic pesticides from the global market, neonicotinoid insecticides have become one of the most widely used insecticides in the world due to their low toxicity, high efficiency, and broad spectrum. Imidacloprid is the most widely used neonicotinoid insecticide in the world. In the industrial production process, the problem of three wastes is imminent. The production wastewater is highly toxic, has complex components, and is difficult to treat. Direct discharge will seriously pollute the environment. Traditional water treatment technologies are difficult to effectively remove such organic pollutants. In the advanced oxidation process (AOPs) based on persulfate (PS), transition metal ions such as Co 2+ 、Fe 2+ 、Cu 2+ and Mn 2+ Heterogeneous catalysts can activate the asymmetric structure of peroxymonosulfate (PMS), effectively removing pollutants from wastewater. While conventional metal nanoparticle catalysts have demonstrated some effectiveness, they are plagued by challenges such as low atomic utilization efficiency and susceptibility to agglomeration and deactivation. These factors limit the practical application of persulfate-advanced oxidation processes in water treatment.

[0003] Therefore, there is an urgent need to develop single-atom catalysts (SACs) with atomically dispersed metals in this field. These catalysts can efficiently remove the organic pollutant imidacloprid from water bodies in a shorter time by improving atom utilization and increasing specific surface area. Summary of the Invention

[0004] In view of this, the present invention provides a method for removing imidacloprid from wastewater using a nitrogen-doped carbon-based zinc-iron diatomic catalyst.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A method for removing imidacloprid from wastewater using a nitrogen-doped carbon-based zinc-iron diatomic catalyst comprises the following steps:

[0007] Step 1: Preparation of chitosan / zinc-iron double metal ion chelate

[0008] Dispersing chitosan in deionized water and stirring at room temperature to obtain a chitosan suspension; then adding zinc chloride solution and continuing to stir; then adding ferric chloride hexahydrate solution; continuing to stir until dry to obtain a chitosan / zinc-iron bimetallic ion chelate;

[0009] Step 2: Preparation of nitrogen-doped carbon-based zinc-iron bimetallic nanocatalysts

[0010] The chitosan / zinc-iron bimetallic ion chelate is heated under an argon atmosphere, and the product cooled to room temperature is ground into powder to obtain a nitrogen-doped carbon-based zinc-iron bimetallic nanocatalyst;

[0011] Step 3: Preparation of nitrogen-doped carbon-based zinc-iron diatomic catalyst

[0012] The nitrogen-doped carbon-based zinc-iron bimetallic nanocatalyst is acid-washed with a nitric acid solution under high temperature conditions, and then the precipitate collected by filtration is rinsed with deionized water until it is neutral, dried in a vacuum drying oven, heated under the protection of an inert gas, and then naturally cooled to obtain a nitrogen-doped carbon-based zinc-iron diatomic catalyst;

[0013] Step 4: Removal of Imidacloprid by Nitrogen-doped Carbon-based Zinc-Iron Diatomic Catalyst / PMS System

[0014] An aqueous solution of imidacloprid was added to a photoprotective catalytic reactor, and a heterogeneous reaction was initiated by adding 0.2 g / L nitrogen-doped carbon-based zinc-iron diatomic catalyst and 0.25 g / L PMS. The pH value of the initial solution was precisely controlled using H2SO4 and NaOH. 1 mL of sample was extracted at specified time intervals, filtered through a filter, and methanol was added. Before HPLC detection, methanol was used as a reaction terminator to remove residual free radicals.

[0015] Preferably, in the first step, the weight portion of chitosan is 1-10 parts, the weight portion of deionized water is 100 parts; the weight portion of zinc chloride solution is 40 parts, and the concentration is 0.1-1 mol / L; the weight portion of ferric chloride hexahydrate is 40 parts, and the concentration is 0.1-1 mol / L.

[0016] Preferably, in the first step, the first stirring time is 2-4 hours, the second stirring time is continued for 2-4 hours, and the third stirring time is continued for 12 hours.

[0017] Preferably, in the first step, the fourth stirring is carried out at 80°C.

[0018] Preferably, in the second step, the temperature is raised to 400-800° C. at a rate of 5° C. / min under an argon atmosphere and maintained at this temperature for 2-4 hours, and then the product that has naturally cooled to room temperature is ground into powder.

[0019] Preferably, in the third step, the high temperature condition is 80°C.

[0020] Preferably, in the third step, the concentration of the nitric acid solution is 1 mol / L, and the pickling time with the nitric acid solution is 4-8 hours.

[0021] Preferably, in the third step, the drying temperature of the vacuum drying oven is 60°C, the drying time is 12 hours, and under the protection of inert gas, it is heated from room temperature to 450-850°C at a heating rate of 5°C / min, and maintained at this temperature for 2-4 hours, and then naturally cooled.

[0022] Preferably, in the fourth step, the concentration of the imidacloprid aqueous solution is 20 mg / L, the amount added is 100 mL, the concentrations of H2SO4 and NaOH used are 0.1 M, and the amount of methanol added is 0.1 mL.

[0023] Preferably, in the fourth step, the pore size of the filter is 0.22 μm.

[0024] Compared with the prior art, the present invention has achieved the following technical effects:

[0025] (1) Chitosan serves as a carbon and nitrogen source for the catalyst. Because of its abundant hydroxyl and amino groups and high specific surface area, it can chelate with metal ions and disperse metal ions well, facilitating the preparation of single-atom catalysts.

[0026] (2) The nitrogen-doped carbon-based zinc-iron dual-atom catalyst has high metal active site utilization, specific surface area, and catalytic activity. Under optimal conditions, the nitrogen-doped carbon-based zinc-iron dual-atom catalyst can remove more than 90% of imidacloprid within 10 minutes;

[0027] (3) The synthetic raw materials used are all environmentally friendly green materials, which are friendly to the environment and avoid secondary pollution;

[0028] (4) The catalyst of the present invention not only has a wide range of applications, but also exhibits excellent removal efficiency for a variety of organic pollutants in other wastewaters (such as rhodamine B, sulfamethoxazole, tetracycline, bisphenol A, etc.);

[0029] (5) The method provided by the present invention has simple steps, easily obtainable raw materials, does not pollute the environment, and is applicable to the field of wastewater treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a SEM image of the nitrogen-doped carbon-based zinc-iron diatomic catalyst of the present invention;

[0031] Figure 2 This is a performance diagram of the nitrogen-doped carbon-based zinc-iron diatomic catalyst / PMS reaction system in the present invention for removing various organic pollutants from water;

[0032] Figure 3 The main active oxygen species produced during the PMS reaction catalyzed by nitrogen-doped carbon-based zinc-iron diatoms were obtained by EPR spectrum testing in the present invention. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] Example 1

[0035] Step 1: Preparation of chitosan / zinc-iron double metal ion chelate

[0036] Disperse 1 part chitosan in 100 parts deionized water and stir at room temperature for 2 hours to obtain a chitosan suspension. Add 40 parts of a 0.1 mol / L zinc chloride solution and continue stirring for 2 hours. Then, add 40 parts of a 0.1 mol / L ferric chloride hexahydrate solution. Continue stirring the suspension for 12 hours and then stir at 80°C until dry. This yields a chitosan / zinc-iron bimetallic ion chelate, which is ready for use.

[0037] Step 2: Preparation of nitrogen-doped carbon-based zinc-iron bimetallic nanocatalysts

[0038] The chitosan / zinc-iron bimetallic ion chelate prepared in the first step was heated to 400°C at a heating rate of 5°C / min under argon atmosphere and maintained at this temperature for 2 hours. After the heating was completed, the product was naturally cooled to room temperature and ground into powder to obtain a nitrogen-doped carbon-based zinc-iron bimetallic nanocatalyst for later use.

[0039] Step 3: Preparation of nitrogen-doped carbon-based zinc-iron diatomic catalyst

[0040] The nitrogen-doped carbon-based zinc-iron bimetallic nanocatalyst prepared in the second step was acid-washed with a 1 mol / L nitric acid solution at 80°C for 4 h, and then the precipitate collected by filtration was rinsed with deionized water until the pH was neutral. After drying in a vacuum drying oven at 60°C for 12 h, it was heated from room temperature to 450°C at a heating rate of 5°C / min under inert gas protection and maintained at this temperature for 2 h. After heating was completed and naturally cooled, a nitrogen-doped carbon-based zinc-iron diatomic catalyst was obtained.

[0041] Step 4: Removal of Imidacloprid by Nitrogen-doped Carbon-based Zinc-Iron Diatomic Catalyst / PMS System

[0042] A 100 mL solution of 20 mg / L imidacloprid in water was added to a photoprotected catalytic reactor. A heterogeneous reaction was initiated by adding 0.2 g / L of a nitrogen-doped carbon-based zinc-iron diatomic catalyst and 0.25 g / L of PMS. The initial solution pH was precisely controlled using 0.1 M H₂SO₄ and NaOH. At selected time intervals, 1 mL of sample was extracted, filtered through a 0.22 μm filter, and 0.5 mL of methanol was added. Methanol was used as a reaction terminator to remove residual free radicals before HPLC analysis.

[0043] To enhance the reliability of the experimental results, each set of experiments was performed three times to control the standard deviation. After each set of experiments, the solid-liquid separation was performed by filtration, and the used solid catalyst was collected. The residual concentration of imidacloprid was analyzed using ultra-high performance liquid chromatography (UHPLC) using a C18 column (5 μm, 4.6 mm × 250 mm) and a UV absorbance detector.

[0044] Example 2

[0045] Step 1: Preparation of chitosan / zinc-iron double metal ion chelate

[0046] Disperse 5 parts of chitosan in 100 parts of deionized water and stir at room temperature for 3 hours to obtain a chitosan suspension. Add 40 parts of a 0.5 mol / L zinc chloride solution and continue stirring for 3 hours. Then, add 40 parts of a 0.5 mol / L ferric chloride hexahydrate solution. Continue stirring the suspension for 12 hours and then stir at 80°C until dry. This yields a chitosan / zinc-iron bimetallic ion chelate, which is then set aside.

[0047] Step 2: Preparation of nitrogen-doped carbon-based zinc-iron bimetallic nanocatalysts

[0048] The chitosan / zinc-iron bimetallic ion chelate prepared in the first step was heated to 600°C at a heating rate of 5°C / min under argon atmosphere and maintained at this temperature for 3 hours. After the heating was completed, the product was naturally cooled to room temperature and ground into powder to obtain a nitrogen-doped carbon-based zinc-iron bimetallic nanocatalyst for later use.

[0049] Step 3: Preparation of nitrogen-doped carbon-based zinc-iron diatomic catalyst

[0050] The nitrogen-doped carbon-based zinc-iron bimetallic nanocatalyst prepared in the second step was acid-washed with a 1 mol / L nitric acid solution at 80°C for 6 h, and then the precipitate collected by filtration was rinsed with deionized water until the pH was neutral. After drying in a vacuum drying oven at 60°C for 12 h, it was heated from room temperature to 650°C at a heating rate of 5°C / min under inert gas protection and maintained at this temperature for 3 h. After heating was completed and naturally cooled, a nitrogen-doped carbon-based zinc-iron diatomic catalyst was obtained.

[0051] Step 4: Removal of Imidacloprid by Nitrogen-doped Carbon-based Zinc-Iron Diatomic Catalyst / PMS System

[0052] A 100 mL solution of 20 mg / L imidacloprid in water was added to a photoprotected catalytic reactor. A heterogeneous reaction was initiated by adding 0.2 g / L of a nitrogen-doped carbon-based zinc-iron diatomic catalyst and 0.25 g / L of PMS. The initial solution pH was precisely controlled using 0.1 M H₂SO₄ and NaOH. At selected time intervals, 1 mL of sample was extracted, filtered through a 0.22 μm filter, and 0.5 mL of methanol was added. Methanol was used as a reaction terminator to remove residual free radicals before HPLC analysis.

[0053] To enhance the reliability of the experimental results, each set of experiments was performed three times to control the standard deviation. After each set of experiments, the solid-liquid separation was performed by filtration, and the used solid catalyst was collected. The residual concentration of imidacloprid was analyzed using ultra-high performance liquid chromatography (UHPLC) using a C18 column (5 μm, 4.6 mm × 250 mm) and a UV absorbance detector.

[0054] Example 3

[0055] Step 1: Preparation of chitosan / zinc-iron double metal ion chelate

[0056] Disperse 10 parts of chitosan in 100 parts of deionized water and stir at room temperature for 4 hours to obtain a chitosan suspension. Add 40 parts of a 1 mol / L zinc chloride solution and continue stirring for 4 hours. Then, add 40 parts of a 1 mol / L ferric chloride hexahydrate solution. Continue stirring the suspension for 12 hours and then stir at 80°C until dry. This yields a chitosan / zinc-iron bimetallic ion chelate, which is then set aside.

[0057] Step 2: Preparation of nitrogen-doped carbon-based zinc-iron bimetallic nanocatalysts

[0058] The chitosan / zinc-iron bimetallic ion chelate prepared in the first step was heated to 800°C at a heating rate of 5°C / min under argon atmosphere and maintained at this temperature for 4 hours. After the heating was completed, the product was naturally cooled to room temperature and ground into powder to obtain a nitrogen-doped carbon-based zinc-iron bimetallic nanocatalyst for later use.

[0059] Step 3: Preparation of nitrogen-doped carbon-based zinc-iron diatomic catalyst

[0060] The nitrogen-doped carbon-based zinc-iron bimetallic nanocatalyst prepared in the second step was acid-washed with a 1 mol / L nitric acid solution at 80°C for 8 h, and then the precipitate collected by filtration was rinsed with deionized water until the pH was neutral. After drying in a vacuum drying oven at 60°C for 12 h, it was heated from room temperature to 850°C at a heating rate of 5°C / min under inert gas protection and maintained at this temperature for 4 h. After heating was completed and naturally cooled, a nitrogen-doped carbon-based zinc-iron diatomic catalyst was obtained.

[0061] Step 4: Removal of Imidacloprid by Nitrogen-doped Carbon-based Zinc-Iron Diatomic Catalyst / PMS System

[0062] A 100 mL solution of 20 mg / L imidacloprid in water was added to a photoprotected catalytic reactor. A heterogeneous reaction was initiated by adding 0.2 g / L of a nitrogen-doped carbon-based zinc-iron diatomic catalyst and 0.25 g / L of PMS. The initial solution pH was precisely controlled using 0.1 M H₂SO₄ and NaOH. At selected time intervals, 1 mL of sample was extracted, filtered through a 0.22 μm filter, and 0.5 mL of methanol was added. Methanol was used as a reaction terminator to remove residual free radicals before HPLC analysis.

[0063] To enhance the reliability of the experimental results, each set of experiments was performed three times to control the standard deviation. After each set of experiments, the solid-liquid separation was performed by filtration, and the used solid catalyst was collected. The residual concentration of imidacloprid was analyzed using ultra-high performance liquid chromatography (UHPLC) using a C18 column (5 μm, 4.6 mm × 250 mm) and a UV absorbance detector.

[0064] The above description is merely a preferred embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any minor modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for removing imidacloprid from wastewater using a nitrogen-doped carbon-based zinc-iron diatomic catalyst, characterized in that: The following steps are involved: Step 1: Preparation of chitosan / zinc-iron double metal ion chelate Dispersing chitosan in deionized water and stirring at room temperature to obtain a chitosan suspension; then adding zinc chloride solution and continuing to stir; then adding ferric chloride hexahydrate solution; continuing to stir until dry to obtain a chitosan / zinc-iron bimetallic ion chelate; Step 2: Preparation of nitrogen-doped carbon-based zinc-iron bimetallic nanocatalysts The chitosan / zinc-iron bimetallic ion chelate is heated under an argon atmosphere, and the product cooled to room temperature is ground into powder to obtain a nitrogen-doped carbon-based zinc-iron bimetallic nanocatalyst; Step 3: Preparation of nitrogen-doped carbon-based zinc-iron diatomic catalyst The nitrogen-doped carbon-based zinc-iron bimetallic nanocatalyst is acid-washed with a nitric acid solution under high temperature conditions, and then the precipitate collected by filtration is rinsed with deionized water until it is neutral, dried in a vacuum drying oven, heated under the protection of an inert gas, and then naturally cooled to obtain a nitrogen-doped carbon-based zinc-iron diatomic catalyst; Step 4: Removal of Imidacloprid by Nitrogen-doped Carbon-based Zinc-Iron Diatomic Catalyst / PMS System An imidacloprid aqueous solution was added to a photoprotected catalytic reactor, and a heterogeneous reaction was initiated by adding 0.2 g / L nitrogen-doped carbon-based zinc-iron diatomic catalyst and 0.25 g / L PMS. The pH value of the initial solution was precisely controlled using H2SO4 and NaOH. 1 mL of sample was extracted at specified time intervals, filtered, and methanol was added. Before HPLC detection, methanol was used as a reaction terminator to remove residual free radicals.

2. The method for removing imidacloprid from wastewater using a nitrogen-doped carbon-based zinc-iron diatomic catalyst according to claim 1, characterized in that: In the first step, the weight portion of chitosan is 1-10 parts, the weight portion of deionized water is 100 parts; the weight portion of zinc chloride solution is 40 parts, and the concentration is 0.1-1 mol / L; the weight portion of ferric chloride hexahydrate is 40 parts, and the concentration is 0.1-1 mol / L.

3. The method for removing imidacloprid from wastewater using a nitrogen-doped carbon-based zinc-iron diatomic catalyst according to claim 1, characterized in that: In the first step, the first stirring time is 2-4 hours, the second stirring time is continued for 2-4 hours, and the third stirring time is continued for 12 hours.

4. The method for removing imidacloprid from wastewater using a nitrogen-doped carbon-based zinc-iron diatomic catalyst according to claim 1, characterized in that: In the first step, the fourth stirring is carried out at 80°C.

5. The method for removing imidacloprid from wastewater using a nitrogen-doped carbon-based zinc-iron diatomic catalyst according to claim 1, characterized in that: In the second step, the temperature is raised to 400-800° C. at a rate of 5° C. / min under an argon atmosphere and maintained at this temperature for 2-4 hours, and then the product that has naturally cooled to room temperature is ground into powder.

6. The method for removing imidacloprid from wastewater using a nitrogen-doped carbon-based zinc-iron diatomic catalyst according to claim 1, characterized in that: In the third step, the high temperature condition is 80°C.

7. The method for removing imidacloprid from wastewater using a nitrogen-doped carbon-based zinc-iron diatomic catalyst according to claim 1, characterized in that: In the third step, the concentration of the nitric acid solution is 1 mol / L, and the pickling time with the nitric acid solution is 4-8 hours.

8. The method for removing imidacloprid from wastewater using a nitrogen-doped carbon-based zinc-iron diatomic catalyst according to claim 1, characterized in that: In the third step, the drying temperature of the vacuum drying oven is 60°C, the drying time is 12 hours, and under the protection of inert gas, it is heated from room temperature to 450-850°C at a heating rate of 5°C / min, and maintained at this temperature for 2-4 hours, and then naturally cooled.

9. The method for removing imidacloprid from wastewater using a nitrogen-doped carbon-based zinc-iron diatomic catalyst according to claim 1, characterized in that: In the fourth step, the concentration of the imidacloprid aqueous solution is 20 mg / L, the amount added is 100 mL, the concentrations of H2SO4 and NaOH used are 0.1 M, and the amount of methanol added is 0.1 mL.

10. The method for removing imidacloprid from wastewater using a nitrogen-doped carbon-based zinc-iron diatomic catalyst according to claim 1, characterized in that: In the fourth step, the pore size of the filter is 0.22 μm.

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