Preparation of cobalt diatomic catalyst and application of cobalt diatomic catalyst in catalytic ozonation removal of organic pollutants in wastewater

Abstract

The invention discloses preparation of a cobalt diatom catalyst and application of the cobalt diatom catalyst to removal of organic pollutants in wastewater through catalytic ozonation, and belongs to the technical field of industrial wastewater treatment. The method is characterized in that a cobalt diatom catalyst is synthesized by a simple and controllable process, and the catalyst can catalyze ozone to generate high-selectivity Co (IV) active species, so that efficient removal of organic pollutants in a complex high-salt environment is realized. Compared with a traditional method, the technology has the advantages of being easy and convenient to operate, high in anti-interference capacity and environmentally friendly, is especially suitable for high-salinity wastewater treatment in the chemical industry, the pharmacy industry, the printing and dyeing industry and the like, and provides an innovative solution for solving the problem of removing organic pollutants in the high-salinity wastewater.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial wastewater treatment, and in particular to the preparation of a cobalt diatomic catalyst and the application of the catalyst in catalyzing ozone oxidation to remove organic pollutants in wastewater. The catalyst significantly improves the ozone decomposition efficiency through the synergistic effect of diatomic sites, directionally generates Co(IV) as an active species, and realizes efficient and selective removal of organic pollutants. The catalyst is suitable for wastewater treatment in the chemical, pharmaceutical, printing and dyeing industries. Background Art

[0002] With the rapid development of industries such as petroleum processing, coal chemical industry, printing and dyeing, papermaking and coking, the discharge of high-salt wastewater continues to rise. High-salt wastewater has the characteristics of high salt components (total dissolved solids>1.0 wt%, mainly composed of chlorides (such as NaCl) and sulfates (such as Na2SO4)) and high chemical oxygen demand (COD can reach up to 200,000 mg / L). If it is discharged directly without effective treatment, it will not only pose a serious threat to the environment and human health, but also cause a waste of more than one million tons of salt resources each year. The deep removal of organic pollutants in high-salt wastewater is an important prerequisite for subsequent salt recovery and water resource reuse. At present, the chemical oxidation technologies commonly used in the treatment of high-salt wastewater include Fenton technology, wet catalytic oxidation technology and heterogeneous catalytic ozone oxidation technology. Among them, although Fenton technology is simple to operate and reagents are easily available, it has limitations such as a narrow pH range and easy production of iron mud; although wet catalytic oxidation technology has no secondary pollution, the reaction conditions are harsh (high temperature and high pressure), and the equipment investment cost is high. In comparison, heterogeneous catalytic oxidation technology has mild conditions (normal temperature and pressure), is easy to operate, and has no secondary pollution. It is considered to be an ideal choice for removing organic pollutants in high-salinity wastewater. However, traditional heterogeneous catalytic ozone oxidation technology mainly relies on the generated HO• as an active oxidizing species. The non-selective oxidation characteristics of this species make it susceptible to strong interference from various competing substances (such as chloride ions and carbonate ions) in actual wastewater, making it difficult to achieve efficient removal of organic matter in the treatment of high-salinity wastewater. Therefore, the development of a new type of anti-interference heterogeneous catalytic ozone oxidation technology to achieve efficient and selective removal of organic matter in high-salinity wastewater has important scientific significance and practical value in the field of environmental pollution control. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the above-mentioned traditional technologies and provide a method for efficiently and selectively removing organic pollutants in high-salt wastewater by using a cobalt diatomic catalyst to catalyze ozone to produce highly active Co(IV), thereby solving a difficult problem in the current field of industrial wastewater treatment.

[0004] The objective of the present invention is achieved through the following technical solutions: A method for preparing a cobalt diatomic catalyst, the method comprising the following steps: Step 1, dissolving 2-methylimidazole in methanol to obtain a 2-methylimidazole methanol solution with a concentration of 100-200 g / L, dissolving zinc nitrate hexahydrate and dicobalt octacarbonyl in methanol to obtain a mixed methanol solution; the concentration of zinc nitrate hexahydrate in the mixed methanol solution is 50-100 g / L, and the concentration of dicobalt octacarbonyl is 1-5 g / L; Step 2: Mix the 2-methylimidazole methanol solution obtained in step 1 with the mixed methanol solution in a volume ratio of 1:1.5, and perform ultrasonic treatment to make them evenly mixed; Step 3, stirring the mixture obtained in step 2 and standing until a light pink solid product is obtained; the stirring time is 30 minutes and the standing time is 1 to 24 hours; Step 4, separating the solid product obtained in step 3 from the solvent by high-speed centrifugation, and washing the obtained solid product with methanol; Step 5, drying the solid obtained in step 4; Step six, transferring the solid obtained in step five to an argon atmosphere for calcination and heating to obtain the cobalt diatomic catalyst; the calcination and heating time is 1 to 4 hours; the calcination temperature is 600 to 1000°C.

[0005] A cobalt diatomic catalyst prepared based on the method.

[0006] An application of the cobalt diatomic catalyst in treating wastewater containing organic pollutants is to add the cobalt diatomic catalyst and ozone into the wastewater and react for a period of time to achieve efficient removal of organic pollutants in the wastewater; wherein the catalyst dosage is 0.02-10 g / 100 mL of wastewater; the ozone dosage is 0.1-50 g / 100 mL of wastewater; and the reaction time is 15-60 minutes.

[0007] The above-mentioned cobalt diatomic catalyst is used to treat wastewater containing organic pollutants.

[0008] Specifically, the organic matter in the organic pollutant wastewater includes small molecule organic acids, phenolic organic matter, antibiotics, and organic dyes.

[0009] Furthermore, the organic pollutants include any one or more of oxalic acid, phenol, aniline, sulfamethoxazole, rhodamine B, and methyl orange.

[0010] The method for treating organic pollutant wastewater using a cobalt diatomic catalyst comprises adding the cobalt diatomic catalyst and ozone to the organic pollutant wastewater to be treated, wherein the amount of the cobalt diatomic catalyst is 0.02-10 g / 100 mL of wastewater, the amount of ozone is 0.1-50 g / 100 mL of wastewater, and after reacting for 15-60 minutes, wastewater treated with degradation of organic pollutants is obtained.

[0011] Compared with other prior arts, the present invention has the following advantages: The present invention provides a method for selectively removing organic pollutants from high-salinity wastewater by using a cobalt diatomic catalyst to catalyze ozone to produce highly active Co(IV). First, the Co(IV) produced by the present method has better selectivity, longer half-life (Co(IV): 7–10–1 seconds > HO•: 10–6–10–9 seconds) and higher steady-state concentration (Co(IV): 10–8 mol / L > HO•: 10–12–10–15 mol / L) than HO• produced in the traditional method, and can achieve efficient and selective removal of organic pollutants in complex environmental matrices. Secondly, the synergistic effect of the diatomic catalytic sites on the catalyst effectively enhances the catalyst's ability to activate ozone, thereby increasing the degradation rate of organic pollutants by the entire system. In addition, the method is simple to operate, and the metal dissolution rate of the catalyst during the treatment process is low, and there is no secondary pollution. The present invention not only greatly accelerates the treatment speed of organic polluted wastewater, significantly improves the water quality of discharged wastewater, but also greatly reduces the post-treatment cost and the cost of the entire wastewater treatment system, and has significant economic benefits and application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG1 is a spherical aberration transmission electron micrograph of the cobalt diatomic catalyst prepared in Example 1; Figure 2 This is a spherical aberration transmission electron microscopy image of the cobalt diatomic catalyst prepared in Example 2; Figure 3 This is a spherical aberration transmission electron microscopy image of the cobalt diatomic catalyst prepared in Example 3; Figure 4 This is a schematic diagram of the test results of the removal effect of the cobalt diatomic catalyst prepared in Example 1 on oxalic acid under different pH conditions; Figure 5 This is a schematic diagram of the test results of the removal effect of the cobalt diatomic catalyst prepared in Example 1 on oxalic acid under different inorganic salt interference environments; Figure 6 This is a schematic diagram of the activation rate test of the cobalt diatomic catalyst prepared in Example 1 to ozone; Figure 7 Schematic diagram of the test results of the removal effect of the cobalt diatomic catalyst prepared in Example 1 on different types of pollutants. DETAILED DESCRIPTION

[0013] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments and drawings. Example 1

[0014] As an experiment to realize and verify the above preparation method and product in the laboratory, a cobalt diatomic catalyst, the preparation method of which includes the following steps: Step 1, dissolving 2-methylimidazole in methanol to obtain a 2-methylimidazole methanol solution, and dissolving zinc nitrate hexahydrate and dicobalt octacarbonyl in methanol to obtain a mixed methanol solution; The concentration of the obtained 2-methylimidazole methanol solution is 131 g / L; the concentration of zinc nitrate hexahydrate in the obtained mixed methanol solution is 75 g / L, and the concentration of dicobalt octacarbonyl is 1.86 g / L.

[0015] Step 2: Mix the 2-methylimidazole methanol solution obtained in step 1 with the mixed methanol solution in a volume ratio of 1:1.5, and perform ultrasonic treatment to make them evenly mixed; Step 3, stirring the mixture obtained in step 2 and standing until a light pink solid product is obtained; Step 4, separating the solid product obtained in step 3 from the solvent by high-speed centrifugation, and washing the obtained solid product with methanol; Step 5, drying the solid obtained in step 4.

[0016] The drying time is 12 hours and the drying temperature is 60°C.

[0017] Step six, transferring the solid obtained in step five to an argon atmosphere for calcination and heating to obtain the catalyst.

[0018] The solid product was heated for 3 hours and the calcination temperature was 1000°C.

[0019] Figure 1 This is a spherical aberration transmission electron microscope image of the cobalt diatomic catalyst prepared in Example 1. The bright spots in the image indicate that the metallic cobalt is present on the catalyst in the form of diatoms. Example 2

[0020] As an experiment to realize and verify the above preparation method and product in the laboratory, a cobalt diatomic catalyst, the preparation method of which includes the following steps: Step 1, dissolving 2-methylimidazole in methanol to obtain a 2-methylimidazole methanol solution, and dissolving zinc nitrate hexahydrate and dicobalt octacarbonyl in methanol to obtain a mixed methanol solution; The concentration of the obtained 2-methylimidazole methanol solution is 100 g / L; the concentration of zinc nitrate hexahydrate in the obtained mixed methanol solution is 50 g / L, and the concentration of dicobalt octacarbonyl is 1 g / L.

[0021] Step 2: Mix the 2-methylimidazole methanol solution obtained in step 1 with the mixed methanol solution in a volume ratio of 1:1.5, and perform ultrasonic treatment to make them uniformly mixed. Step 3, stirring the mixture obtained in step 2 and standing until a light pink solid product is obtained; Step 4, separating the solid product obtained in step 3 from the solvent by high-speed centrifugation, and washing the obtained solid product with methanol; Step 5, drying the solid obtained in step 4.

[0022] The drying time is 12 hours and the drying temperature is 60°C.

[0023] Step six, transferring the solid obtained in step five to an argon atmosphere for calcination and heating to obtain the catalyst.

[0024] The solid product was heated for 2 hours and the calcination temperature was 900°C.

[0025] Figure 2 This is a spherical aberration transmission electron microscope image of the cobalt diatomic catalyst prepared in Example 2. The bright spots in the image indicate that the metallic cobalt is present on the catalyst in the form of diatoms. Example 3

[0026] As an experiment to realize and verify the above preparation method and product in the laboratory, a cobalt diatomic catalyst, the preparation method of which includes the following steps: Step 1, dissolving 2-methylimidazole in methanol to obtain a 2-methylimidazole methanol solution, and dissolving zinc nitrate hexahydrate and dicobalt octacarbonyl in methanol to obtain a mixed methanol solution; The concentration of the obtained 2-methylimidazole methanol solution is 200 g / L; the concentration of zinc nitrate hexahydrate in the obtained mixed methanol solution is 100 g / L, and the concentration of dicobalt octacarbonyl is 5 g / L.

[0027] Step 2: Mix the 2-methylimidazole methanol solution obtained in step 1 with the mixed methanol solution in a volume ratio of 1:1.5, and perform ultrasonic treatment to make them uniformly mixed. Step 3, stirring the mixture obtained in step 2 and standing until a light pink solid product is obtained; Step 4, separating the solid product obtained in step 3 from the solvent by high-speed centrifugation, and washing the obtained solid product with methanol; Step 5, drying the solid obtained in step 4.

[0028] The drying time is 12 hours and the drying temperature is 60°C.

[0029] Step six, transferring the solid obtained in step five to an argon atmosphere for calcination and heating to obtain the catalyst.

[0030] The solid product was heated for 3.5 hours and the calcination temperature was 950°C.

[0031] Figure 3 This is a spherical aberration transmission electron microscope image of the cobalt diatomic catalyst prepared in Example 3. The bright spots in the image indicate that the metallic cobalt is present on the catalyst in the form of diatoms. Example 4

[0032] The method for treating wastewater with organic pollutants using the cobalt diatomic catalyst obtained in Example 1 is to add the cobalt diatomic catalyst and ozone into the wastewater and react for a period of time to achieve efficient removal of organic pollutants in the wastewater.

[0033] Specifically, the effectiveness of this method is tested through the following experiments.

[0034] Experiment 1: Test of the removal effect of oxalic acid under different pH conditions.

[0035] In this case, oxalic acid is selected as a model compound for catalytic ozone oxidation. Oxalic acid is produced in the ozone oxidation products of most organic matter, and ozone itself has a poor removal effect on it. Therefore, using oxalic acid as the target pollutant can better measure the ability of the catalyst-catalyzed ozone system to mineralize organic matter in wastewater. In order to test the performance of the cobalt diatomic catalyst under different pH conditions, oxalic acid solutions with different initial pH values ​​were configured in the experiment. The removal effect of the cobalt diatomic catalyst prepared in Example 1 on oxalic acid was tested, and the following groups of conditions were set for comparative experiments: (1) Add 20 mg of cobalt diatomic catalyst to 100 mL of 90 mg / L oxalic acid solution, stir evenly, and adjust the pH to 3.0. The ozone inlet concentration is 30 mg / L, the inlet rate is 125 mL / min, and the reaction time is 30 minutes (the total ozone dosage is 0.1125 g / 100 mL of wastewater); (2) Add 20 mg of cobalt diatomic catalyst to 100 mL of 90 mg / L oxalic acid solution, stir evenly, and adjust the pH to 5.0. The ozone inlet concentration is 30 mg / L, the inlet rate is 125 mL / min, and the reaction time is 30 min. (3) Add 20 mg of cobalt diatomic catalyst to 100 mL of 90 mg / L oxalic acid solution, stir evenly, and adjust the pH to 7.0. The ozone inlet concentration is 30 mg / L, the inlet rate is 125 mL / min, and the reaction time is 30 min. (4) Add 20 mg of cobalt diatomic catalyst to 100 mL of 90 mg / L oxalic acid solution, stir evenly, and adjust the pH to 9.0. The ozone inlet concentration is 30 mg / L, the inlet rate is 125 mL / min, and the reaction time is 30 min.

[0036] The experimental results are as follows Figure 4 As shown, the experiment shows that the prepared cobalt diatomic catalyst has low dependence on pH, and achieves efficient degradation of oxalic acid in the range of pH = 3.0 ~ 9.00, with a degradation rate of 90~100% within 30 minutes.

[0037] Experiment 2: Test of the removal effect of phenol under different inorganic salt interference environments.

[0038] In order to test the performance of the cobalt diatomic catalyst under different inorganic salt interference environments, the experiment was configured with oxalic acid solutions containing different types of inorganic salts. The removal effect of the cobalt diatomic catalyst prepared in Example 1 on oxalic acid was tested, and the following groups of conditions were set for comparative experiments: (1) Add 20 mg of cobalt diatomic catalyst and 10 g / L of sodium chloride to 100 mL of 90 mg / L oxalic acid solution, and add ozone inlet concentration of 30 mg / L at an inlet rate of 125 mL / min. Stir evenly and the reaction time is 30 minutes. (2) Add 20 mg of cobalt diatomic catalyst and 10 g / L sodium sulfate to 100 mL of 90 mg / L oxalic acid solution, and set the ozone inlet concentration to 30 mg / L at an inlet rate of 125 mL / min. Stir evenly and the reaction time is 30 minutes. (3) Add 20 mg of cobalt diatomic catalyst and 10 g / L sodium bicarbonate to 100 mL of 90 mg / L oxalic acid solution, set the ozone inlet concentration to 30 mg / L, and the inlet rate to 125 mL / min. Stir evenly and the reaction time is 30 minutes. (4) Add 20 mg of cobalt diatomic catalyst and 10 g / L sodium nitrate to 100 mL of 90 mg / L oxalic acid solution. The ozone inlet concentration is 30 mg / L and the inlet rate is 125 mL / min. Stir evenly and the reaction time is 30 min.

[0039] The experimental results are as follows Figure 5 As shown, the experiment shows that the prepared cobalt diatomic catalyst has a strong anti-interference ability to different types of inorganic salts, overcoming the disadvantage of traditional catalytic ozone reaction that is easily affected by inorganic salts in the solution. The degradation rate reaches 90~100% within 30 minutes.

[0040] Experiment 3: Test of ozone activation rate by cobalt diatomic catalyst.

[0041] In order to test the activation rate of cobalt diatomic catalyst to ozone, an ozone solution containing a certain concentration was configured in the experiment. The activation rate of cobalt diatomic catalyst prepared in Example 1 and cobalt chloride with 20 times the cobalt element equivalent to ozone was tested, and the following groups of conditions were set for comparative experiments: (1) Add 20 mg of cobalt diatomic catalyst to 100 mL of 3 mg / L ozone and stir evenly. (2) Add 20 times the cobalt equivalent of cobalt chloride to 100 mL of 3 mg / L ozone and stir evenly; (3) Stir 100 mL of 3 mg / L ozone evenly.

[0042] The experimental results are as follows Figure 6 As shown, the experiment shows that the activation rate of ozone by the prepared cobalt diatomic catalyst is much higher than that of cobalt chloride with 20 times the cobalt element equivalent. Therefore, the activation effect of cobalt diatomic catalyst on ozone is better than that of homogeneous cobalt ions.

[0043] Experiment 4: Test of the degradation efficiency of cobalt diatomic catalyst on different organic pollutants.

[0044] In order to test the degradation efficiency of the cobalt diatomic catalyst on different organic pollutants, the experiment prepared solutions containing different model pollutants at certain concentrations. The degradation efficiency of the cobalt diatomic catalyst prepared in Example 1 on different organic pollutants was tested: (1) Add 20 mg of cobalt diatomic catalyst to 100 mL of 90 mg / L phenol solution, set the ozone inlet concentration to 30 mg / L, and the inlet rate to 125 mL / min. Stir evenly and the reaction time is 30 min. (2) Add 20 mg of cobalt diatomic catalyst to 100 mL of 90 mg / L aniline solution, and set the ozone concentration to 30 mg / L at an intake rate of 125 mL / min. Stir evenly and the reaction time is 30 minutes. (3) Add 20 mg of cobalt diatomic catalyst to 100 mL of 90 mg / L sulfamethoxazole solution, set the ozone inlet concentration to 30 mg / L, and the inlet rate to 125 mL / min. Stir evenly and the reaction time is 30 min. (4) Add 20 mg of cobalt diatomic catalyst to 100 mL of 90 mg / L rhodamine B solution, set the ozone inlet concentration to 30 mg / L, and the inlet rate to 125 mL / min. Stir evenly and the reaction time is 30 min. (5) Add 20 mg of cobalt diatomic catalyst to 100 mL of 90 mg / L methyl orange solution, set the ozone inlet concentration to 30 mg / L, and the inlet rate to 125 mL / min. Stir evenly and the reaction time is 30 min. The experimental results are as follows Figure 7 As shown in the figure, the experiment shows that the prepared cobalt diatomic catalyst can effectively activate ozone and has a good degradation effect on the six model organic pollutants, namely oxalic acid, phenol, aniline, sulfamethoxazole, rhodamine B, and methyl orange. Therefore, the prepared cobalt diatomic catalyst can be actually used in the treatment of organic pollutant wastewater.

[0045] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing a cobalt diatomic catalyst, characterized in that: The method comprises the following steps: Step 1, dissolving 2-methylimidazole in methanol to obtain a 2-methylimidazole methanol solution with a concentration of 100-200 g / L, dissolving zinc nitrate hexahydrate and dicobalt octacarbonyl in methanol to obtain a mixed methanol solution; the concentration of zinc nitrate hexahydrate in the mixed methanol solution is 50-100 g / L, and the concentration of dicobalt octacarbonyl is 1-5 g / L; Step 2: Mix the 2-methylimidazole methanol solution obtained in step 1 with the mixed methanol solution in a volume ratio of 1:1.5, and perform ultrasonic treatment to make them evenly mixed; Step 3, stirring the mixture obtained in step 2 and standing until a light pink solid product is obtained; the stirring time is 30 minutes and the standing time is 1 to 24 hours; Step 4, separating the solid product obtained in step 3 from the solvent by high-speed centrifugation, and washing the obtained solid product with methanol; Step 5, drying the solid obtained in step 4; Step six, transferring the solid obtained in step five to an argon atmosphere for calcination and heating to obtain the cobalt diatomic catalyst; the calcination and heating time is 1 to 4 hours; the calcination temperature is 600 to 1000°C.

2. A cobalt diatomic catalyst prepared by the method according to claim 1.

3. Use of the cobalt diatomic catalyst according to claim 2 in treating wastewater containing organic pollutants.

4. The use according to claim 3, characterized in that: The cobalt diatomic catalyst and ozone are added into wastewater and reacted for 15 to 60 minutes to achieve efficient removal of organic pollutants in the wastewater; wherein the catalyst dosage is 0.02 to 10 g / 100 mL of wastewater; and the ozone dosage is 0.1 to 50 g / 100 mL of wastewater.

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