Method for removing imidacloprid in wastewater by using nitrogen-doped carbon-based zinc-iron diatomic catalyst

Abstract

The invention discloses a method for removing imidacloprid in wastewater by using a nitrogen-doped carbon-based zinc-iron double-atom catalyst. The method comprises the following steps: 1, preparing a chitosan / zinc-iron double-metal ion chelate; step 2, preparing a nitrogen-doped carbon-based zinc-iron bimetallic nano-catalyst; 3, preparing a nitrogen-doped carbon-based zinc-iron diatomic catalyst; and 4, removing imidacloprid by using a nitrogen-doped carbon-based zinc-iron diatomic catalyst / PMS system. The method is mild in reaction condition, green and environment-friendly in material and high in atom utilization rate, the catalyst is wide in application range and shows excellent removal efficiency on various organic pollutants in other wastewater, under the optimal condition, the nitrogen-doped carbon-based zinc-iron diatomic catalyst can remove more than 90% of imidacloprid within 10 min, and the nitrogen-doped carbon-based zinc-iron diatomic catalyst can be used for preparing the nitrogen-doped carbon-based zinc-iron diatomic catalyst. The method has the advantages of simple steps, easily available raw materials and no environmental pollution, and is suitable for the field of 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, complex in composition, and 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 processes (AOPs) based on persulfate (PS), transition metal ions such as Co 2+ , Fe 2+ , Cu 2+ and Mn 2+ The heterogeneous catalyst can activate the asymmetric structure of peroxymonosulfate (PMS), thereby efficiently removing pollutants from wastewater. Although traditional metal nanoparticle catalysts have certain effects, they are plagued by challenges such as low atomic utilization efficiency and easy agglomeration and deactivation. These factors limit the application of persulfate-advanced oxidation process in actual water treatment processes.

[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 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 in 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 bimetallic ion chelate

[0008] Dispersing chitosan in deionized water, stirring at room temperature to obtain a chitosan suspension; then adding a zinc chloride solution, continuing to stir, and then adding a ferric chloride hexahydrate solution; continuing to stir until dry, thereby obtaining 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 then 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 catalysts

[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 washed 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] The imidacloprid aqueous solution was added into a photoprotective catalytic reactor, and the 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, and 1 mL of the sample was extracted at specified time intervals, filtered with 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 2-4 hours, and the third stirring time is 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 increased 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 12h, 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 2-4h, and then cooled naturally.

[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 is used as a carbon and nitrogen source for the catalyst. Because it has abundant hydroxyl and amino groups and a high specific surface area, it can chelate with metal ions and disperse metal ions well, making it easy to prepare single-atom catalysts.

[0026] (2) The nitrogen-doped carbon-based zinc-iron diatomic catalyst has high metal active site utilization, specific surface area and catalytic activity. Under the optimal conditions, the nitrogen-doped carbon-based zinc-iron diatomic 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 environmentally friendly 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 available raw materials, does not pollute the environment, and is suitable for 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 in the process of nitrogen-doped carbon-based zinc-iron diatomic catalysis PMS reaction are obtained by EPR spectrum test in the present invention. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0034] Example 1

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

[0036] Disperse 1 part of chitosan in 100 parts of deionized water, stir at room temperature for 2 hours to obtain a chitosan suspension. Add 40 parts of 0.1 mol / L zinc chloride solution, continue stirring for 2 hours, then add 40 parts of 0.1 mol / L ferric chloride hexahydrate solution; continue stirring the suspension for 12 hours, and stir at 80°C until dry to obtain chitosan / zinc-iron bimetallic ion chelate 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, the product was naturally cooled to room temperature and ground into powder to obtain a nitrogen-doped carbon-based zinc-iron bimetallic nanocatalyst for use.

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

[0040] The nitrogen-doped carbon-based zinc-iron bimetallic nanocatalyst prepared in the second step was acid-washed with 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] 100 mL of 20 mg / L imidacloprid aqueous solution was added to a photoprotected catalytic reactor, and a heterogeneous reaction was initiated by adding 0.2 g / L of nitrogen-doped carbon-based zinc-iron diatomic catalyst and 0.25 g / L of PMS. The pH value of the initial solution was precisely controlled using 0.1 M H2SO4 and NaOH, and 1 mL of the sample was extracted at selected time intervals, filtered with 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 detection.

[0043] To improve the reliability of the experimental results, each group of experiments was conducted three times to control the standard deviation. After each group of experiments, the solid and liquid were separated by filtration and the used solid catalyst was collected. The residual concentration of imidacloprid was analyzed by ultra-high performance liquid chromatography (UHPLC) using a C18 chromatographic column (5um, 4.6mm×250mm) and an ultraviolet absorbance detector.

[0044] Example 2

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

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

[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, the product was naturally cooled to room temperature and ground into powder to obtain a nitrogen-doped carbon-based zinc-iron bimetallic nanocatalyst for use.

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

[0050] The nitrogen-doped carbon-based zinc-iron bimetallic nanocatalyst prepared in the second step was acid-washed with 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] 100 mL of 20 mg / L imidacloprid aqueous solution was added to a photoprotected catalytic reactor, and a heterogeneous reaction was initiated by adding 0.2 g / L of nitrogen-doped carbon-based zinc-iron diatomic catalyst and 0.25 g / L of PMS. The pH value of the initial solution was precisely controlled using 0.1 M H2SO4 and NaOH, and 1 mL of the sample was extracted at selected time intervals, filtered with 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 detection.

[0053] To improve the reliability of the experimental results, each group of experiments was conducted three times to control the standard deviation. After each group of experiments, the solid and liquid were separated by filtration and the used solid catalyst was collected. The residual concentration of imidacloprid was analyzed by ultra-high performance liquid chromatography (UHPLC) using a C18 chromatographic column (5um, 4.6mm×250mm) and an ultraviolet absorbance detector.

[0054] Example 3

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

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

[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, the product was naturally cooled to room temperature and ground into powder to obtain a nitrogen-doped carbon-based zinc-iron bimetallic nanocatalyst for use.

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

[0060] The nitrogen-doped carbon-based zinc-iron bimetallic nanocatalyst prepared in the second step was acid-washed with 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] 100 mL of 20 mg / L imidacloprid aqueous solution was added to a photoprotected catalytic reactor, and a heterogeneous reaction was initiated by adding 0.2 g / L of nitrogen-doped carbon-based zinc-iron diatomic catalyst and 0.25 g / L of PMS. The pH value of the initial solution was precisely controlled using 0.1 M H2SO4 and NaOH, and 1 mL of the sample was extracted at selected time intervals, filtered with 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 detection.

[0063] To improve the reliability of the experimental results, each group of experiments was conducted three times to control the standard deviation. After each group of experiments, the solid and liquid were separated by filtration and the used solid catalyst was collected. The residual concentration of imidacloprid was analyzed by ultra-high performance liquid chromatography (UHPLC) using a C18 chromatographic column (5um, 4.6mm×250mm) and an ultraviolet absorbance detector.

[0064] The above description is only a preferred embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any slight 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 bimetallic ion chelate Dispersing chitosan in deionized water, stirring at room temperature to obtain a chitosan suspension; then adding a zinc chloride solution, continuing to stir, and then adding a ferric chloride hexahydrate solution; continuing to stir until dry, thereby obtaining 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 then 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 catalysts 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 washed 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 The imidacloprid aqueous solution 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, and 1 mL of sample was extracted at specified time intervals, filtered with a filter, 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 of chitosan is 1-10 parts, the weight of deionized water is 100 parts; the weight of zinc chloride solution is 40 parts, and the concentration is 0.1-1 mol / L; the weight 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 2-4 hours, and the third stirring time is 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 12h, 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 2-4h, and then cooled naturally.

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 concentration of H2SO4 and NaOH used is 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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