A method of polymerization removal of benzohydroxamic acid using a cobalt monatomic catalyst

Abstract

This invention belongs to the field of water treatment and discloses a method for removing benzohydroxyxamic acid by polymerization using a cobalt single-atom catalyst. The method includes the following steps: mixing a potassium persulfate solution and an aqueous solution containing benzohydroxyxamic acid, then adding a cobalt single-atom catalyst; the mixture reacts to polymerize and remove benzohydroxyxamic acid. The cobalt single-atom catalyst has a Co-N4 atomic coordination structure; the loading of cobalt single atoms is 2%–3%. The method disclosed in this invention has a high benzohydroxyxamic acid removal rate, low oxidant consumption, is suitable for a wide pH range, is recyclable, and maintains a high removal rate even after multiple uses. It can achieve efficient removal of benzohydroxyxamic acid and targeted carbon resource recovery in actual mineral processing wastewater treatment, and has very high economic benefits.

Description

Technical Field

[0001] This invention belongs to the field of water treatment, and specifically relates to a method for removing benzohydroxyxamic acid by polymerization using a cobalt single-atom catalyst. Background Technology

[0002] In recent years, the need for efficient treatment of mine wastewater and water environment protection has become increasingly urgent, and improving the recycling rate of wastewater is an ideal way to solve this problem. Currently, one of the main challenges limiting the reuse of mine wastewater is the presence of recalcitrant mineral processing reagents remaining in the recycled water. These reagents are difficult to effectively degrade during the natural purification process in tailings ponds, leading to a significant impact on mineral flotation in the mineral processing flow. Benzyl hydroxamic acid, as an organic flotation reagent, is widely used in the flotation process of sulfide or oxide minerals. It develops benzene ring structures and oxime groups, resulting in stable chemical properties and toxicity. Its residue in wastewater leads to an increase in the chemical oxygen demand (COD) of the water body, and the accumulation of nitrogen can easily cause eutrophication, which is detrimental to the survival of aquatic plants, ultimately damaging water quality and affecting the ecological balance. Therefore, the treatment of benzoyl hydroxamic acid in mineral processing wastewater is urgently needed.

[0003] Currently, the main methods for treating benzyl oxime-containing mineral processing wastewater fall into three categories: flocculation sedimentation, biological methods, and advanced oxidation methods. Flocculation sedimentation removes benzyl oxime-containing wastewater by adding metal ions, precipitants, chelating agents, and flocculants. However, its treatment effect is limited, the treatment time is long, and the sludge settles slowly and is difficult to dewater. Biological methods introduce microorganisms capable of decomposing benzyl oxime into the wastewater, removing it through biodegradation. However, this method has a long treatment cycle and requires harsh conditions, making it difficult to apply widely. Advanced oxidation methods primarily rely on generating free radicals with high redox potentials to attack benzyl oxime molecules, causing ring-opening and bond breaking, ultimately producing carbon dioxide and water for removal. This method has advantages such as rapid decomposition and strong wastewater purification capacity, making it a promising approach for treating recalcitrant benzyl oxime-containing mineral processing wastewater.

[0004] However, the current advanced oxidation method for treating mineral processing wastewater containing benzohydroxyxamic acid still has obvious shortcomings: (1) The selectivity of active free radicals for benzohydroxyxamic acid is low, and the oxidation capacity is greatly affected by the quality conditions of the mineral processing wastewater; (2) Existing technologies generally decompose benzohydroxyxamic acid in mineral processing wastewater to generate carbon dioxide, nitrogen oxides and water. The energy consumption is huge, which is determined by the stoichiometric ratio of the chemical reaction. Taking potassium persulfate (KHSO5·0.5KHSO4·0.5K2SO4) as an oxidant as an example, 18 mol (5526 g) of potassium persulfate is required to treat 1 mol of benzohydroxyxamic acid (137 g); (3) After being attacked by free radicals, benzohydroxyxamic acid may form stronger dicarboxylic acid intermediates and nitrogen oxides, which pose a risk of secondary pollution.

[0005] Therefore, there is an urgent need for a treatment method for benzyl hydroxamic acid beneficiation wastewater that has high selectivity, low oxidant consumption, and does not rely on active free radicals as the main oxidation mode, in order to overcome the above-mentioned shortcomings. Summary of the Invention

[0006] In order to overcome the shortcomings and deficiencies of the prior art, the primary objective of this invention is to provide an application of a cobalt single-atom catalyst in the polymerization removal of benzo[a]oxime acid.

[0007] Another objective of this invention is to provide a method for removing benzohydroxyxamic acid by polymerization using a cobalt single-atom catalyst.

[0008] The objective of this invention is achieved through the following solution:

[0009] Application of a cobalt single-atom catalyst in the polymerization removal of benzo(hydroxyoxime) acid.

[0010] The cobalt single-atom catalyst has a Co-N4 atomic coordination structure; the loading of cobalt single atoms is 2% to 3%; and it features high catalytic activity and low metal component dissolution.

[0011] The cobalt single-atom catalyst was prepared according to the following steps:

[0012] S1. In the presence of a solvent, 2-methylimidazole and zinc nitrate hexahydrate are dissolved by ultrasonication to obtain a white suspension, denoted as solution A.

[0013] S2. Cobalt nitrate hexahydrate is dissolved by ultrasonication in the presence of a solvent, and this solution is referred to as solution B.

[0014] S3. Mix and stir liquid A and liquid B to undergo a complexation substitution reaction, and obtain a purple suspension containing a cobalt single-atom catalyst precursor.

[0015] S4. The cobalt single-atom catalyst precursor suspension is centrifuged, washed and dried to obtain a purple cobalt single-atom catalyst precursor.

[0016] S5. The cobalt single-atom catalyst precursor is subjected to high-temperature treatment to obtain the cobalt single-atom catalyst;

[0017] The solvent used in steps S1 and S2 is the same, and the solvent is selected from at least one of water, ethanol and methanol, preferably methanol;

[0018] The mass ratio of 2-methylimidazole, zinc nitrate hexahydrate, and cobalt nitrate hexahydrate is (5.5–6.5):(3.5–4.5):(0.1–0.5).

[0019] The volume ratio of liquid A to liquid B in step S3 is (100-200):(50-100);

[0020] The complexation substitution reaction conditions described in step S3 are: stirring temperature of 20-60℃, stirring speed of 200-800 r / min, and stirring time of 10-24 h;

[0021] The cleaning described in step S4 is preferably performed using at least one of water, ethanol, and methanol.

[0022] The high-temperature treatment conditions described in step S5 are as follows: under an inert gas atmosphere, the temperature is 900-1100℃, the heating rate is 2-5℃ / min, and the time is 1-3h.

[0023] A method for removing benzyl hydroxamic acid via cobalt single-atom catalyst polymerization includes the following steps:

[0024] A potassium persulfate solution and an aqueous solution containing benzoyl hydroxamic acid are mixed, and a cobalt single-atom catalyst is added. The mixture reacts to polymerize and remove benzoyl hydroxamic acid.

[0025] Before mixing potassium hydrogen sulfate solution and aqueous solution containing benzoyl hydroxamic acid, it is preferable to adjust the two solutions to the same pH, with the pH range being 3.00 to 11.00; the pH adjuster is sulfuric acid solution or sodium hydroxide solution with a concentration of 0.1 to 1 mol / L.

[0026] Before adding a cobalt single-atom catalyst, the concentration of potassium persulfate solution in the mixed solution is 0.5–6 mmol / L and the concentration of benzohydroxyxamic acid solution is 0.1–3 mmol / L.

[0027] After adding the cobalt single-atom catalyst, the concentration of the cobalt single-atom catalyst is 0.1-0.5 g / L.

[0028] Preferably, before adding the cobalt single-atom catalyst, the concentration of potassium persulfate solution is 1-3 mmol / L and the concentration of benzohydroxyxamic acid solution is 0.5-1.5 mmol / L. After adding the cobalt single-atom catalyst, the concentration of the cobalt single-atom catalyst is 0.3 g / L, which can make the benzohydroxyxamic acid removal rate >99.5%.

[0029] The reaction refers to a stirred reaction at room temperature, with a stirring rate of 200–600 r / min and a time of 10–30 min. After the reaction, the system is separated to obtain a solid phase, which is then extracted with an organic solvent to obtain a polymerization product solution. The solid-phase polymerization product can be recovered by solvent evaporation. The organic solvent is one of tetrahydrofuran, toluene, or methanol, preferably tetrahydrofuran.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] The method disclosed in this invention has a high removal rate of benzohydroxyxamic acid, low oxidant consumption, is applicable to a wide range of pH conditions, can be recycled, and can maintain a high removal rate even after multiple uses. It can achieve efficient removal of benzohydroxyxamic acid and targeted recovery of carbon resources in actual mineral processing wastewater treatment, and has very high economic benefits. Attached Figure Description

[0032] Figure 1 for Figure 1 This is a molecular weight determination graph of the polymerization product after the reaction in Example 3 of the present invention.

[0033] Figure 2 Aberration-corrected high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) image of the cobalt single-atom catalyst prepared in Example 1 of this invention.

[0034] Figure 3 This is a surface scan distribution map of the cobalt single-atom catalyst prepared in Example 1 of the present invention.

[0035] Figure 4 The image shows the K-side EXAFS Fourier transform spectrum of Co in the cobalt single-atom catalyst prepared in Example 1 of this invention.

[0036] Figure 5 The figures show the removal effects of benzohydroxyxamic acid under different concentrations of potassium persulfate in Examples 2, 4-7.

[0037] Figure 6 The figures show the removal effect of benzohydroxyxamic acid under different pH conditions in Examples 2, 8-11.

[0038] Figure 7 The images show the removal effect of benzohydroxyxamic acid in repeated experiments of Examples 12-16.

[0039] Figure 8 The images show the benzohydroxyxamic acid removal effect of Example 2 and Test Examples 1-2. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0041] Unless otherwise specified, all reagents used in the examples are commercially available.

[0042] Example 1

[0043] 1) Dissolve 5.994g of 2-methylimidazole and 4.044g of zinc nitrate hexahydrate in 150mL of methanol by sonication for 25min to obtain a white suspension, which is denoted as solution A.

[0044] 2) Dissolve 0.132g of cobalt nitrate hexahydrate in 50mL of methanol by sonication for 15min, and record this as solution B.

[0045] 3) Mix solution A and solution B, stir at room temperature at a speed of 600 r / min for 18 h to induce a complexation substitution reaction and obtain a purple suspension containing a cobalt single-atom catalyst precursor.

[0046] 4) Centrifuge the cobalt single-atom catalyst precursor at 7000 r / min for 6 min, wash the cobalt single-atom catalyst precursor with methanol, and dry the cobalt single-atom catalyst precursor at 60℃ for 4 h.

[0047] 5) Under argon protection, the cobalt single-atom catalyst precursor was heated to 900℃ at a rate of 5℃ / min, held for 2h, and then cooled naturally to obtain the cobalt single-atom catalyst with a loading of 2.5wt%.

[0048] Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) image of the obtained cobalt single-atom catalyst, as shown below. Figure 2 As shown, this proves that cobalt exists in single-atom form.

[0049] The surface scan distribution of the obtained cobalt single-atom catalyst is shown in the figure below. Figure 3 As shown, this demonstrates that cobalt is uniformly distributed in the catalyst material. The catalyst's specific surface area is measured to be 280 m². 2 / g, pore volume is 0.13cm³ 3 / g.

[0050] The K-side Fourier transform spectrum of Co in the obtained cobalt single-atom catalyst is shown in the figure below. Figure 4 As shown, this demonstrates that cobalt has a Co-N4 coordination structure.

[0051] Example 2

[0052] 1) Using sodium hydroxide reagent (1 mol / L), adjust the pH of a 2 mmol / L potassium persulfate solution to 7.00, and denote it as solution a; adjust the pH of a 1 mmol / L benzohydroxyxamic acid solution to 7.00, and denote it as solution b.

[0053] 2) Mix solutions a and b obtained in step 1) at a volume ratio of 1:1 (the concentration of potassium persulfate in the mixed system is 1 mmol / L; the concentration of benzohydroxyxamic acid is 0.5 mmol / L), add cobalt single-atom catalyst (catalyst concentration is 0.3 g / L), and react for 15 min at room temperature and stirring at 400 r / min. Then, separate the solid and liquid phases, and perform quantitative analysis by liquid chromatography. The removal rate of benzohydroxyxamic acid was found to be 99.5%.

[0054] Example 3

[0055] 1) The other steps are the same as in Example 2, except that the concentration of potassium persulfate solution in step 1 is changed to 6 mmol / L and the concentration of benzoyl hydroxamic acid solution is changed to 3 mmol / L. After the experiment, the polymerization product in the solid phase after solid-liquid separation is extracted with tetrahydrofuran, the extraction solution is evaporated by solvent, and the molecular weight of the solid-phase polymerization product is tested.

[0056] 2) After quantitative analysis of the liquid phase product, the removal rate of benzohydroxyxamic acid was calculated to be 99.8%.

[0057] Figure 1 The graph shows the molecular weight of the solid-phase polymerization product after the reaction. As can be seen from the graph, the mass-to-charge ratio of the solid-phase polymerization product is between 450 and 1200. This indicates that benzyl hydroxyxamic acid underwent a polymerization reaction during the conversion process, thereby generating a high molecular weight water-insoluble polymer product.

[0058] Example 4

[0059] The other steps were the same as in Example 2, except that the concentration of potassium persulfate solution in step 1 was 3 mmol / L (the concentration of potassium persulfate in the mixed system was 1.5 mmol / L). After quantitative analysis, the removal rate of benzohydroxyxamic acid was calculated to be 100%.

[0060] Example 5

[0061] The other steps were the same as in Example 2, except that the concentration of potassium persulfate solution in step 1 was 1 mmol / L (the concentration of potassium persulfate in the mixed system was 0.5 mmol / L). After quantitative analysis, the removal rate of benzohydroxyxamic acid was calculated to be 71.8%.

[0062] Example 6

[0063] The other steps are the same as in Example 2, except that the concentration of potassium persulfate solution in step 1 is 0.5 mmol / L (the concentration of potassium persulfate in the mixed system is 0.25 mmol / L). After quantitative analysis, the removal rate of benzohydroxyxamic acid was calculated to be 60%.

[0064] Example 7

[0065] The other steps are the same as in Example 2, except that the concentration of potassium persulfate solution in step 1 is 0.25 mmol / L (the concentration of potassium persulfate in the mixed system is 0.125 mmol / L). After quantitative analysis, the removal rate of benzohydroxyxamic acid was calculated to be 41.5%.

[0066] Figure 5 The figures show the removal effects of benzohydroxyxamic acid under different potassium persulfate concentrations in Examples 2, 4-7. As can be seen from the figures, the reaction rate and final removal rate of benzohydroxyxamic acid gradually increase with the increase of potassium persulfate concentration. At low potassium persulfate concentrations, due to insufficient potassium persulfate, a high residual amount of benzohydroxyxamic acid remains after its consumption. At high potassium persulfate concentrations, benzohydroxyxamic acid can be rapidly and completely removed.

[0067] Example 8

[0068] The other steps were the same as in Example 2, except that the pH of both the potassium persulfate solution and the benzohydroxyxamic acid solution was adjusted to 3.00. Quantitative analysis showed that the benzohydroxyxamic acid removal rate was 96.8%.

[0069] Example 9

[0070] The other steps were the same as in Example 2, except that the pH of both the potassium persulfate solution and the benzohydroxyxamic acid solution was adjusted to 5.00. Quantitative analysis showed that the benzohydroxyxamic acid removal rate was 97.8%.

[0071] Example 10

[0072] The other steps were the same as in Example 2, except that the pH of both the potassium persulfate solution and the benzohydroxyxamic acid solution was adjusted to 9.00. Quantitative analysis showed that the benzohydroxyxamic acid removal rate was 99.8%.

[0073] Example 11

[0074] The other steps were the same as in Example 2, except that the pH values ​​of both the potassium persulfate solution and the benzohydroxyxamic acid solution were adjusted to 11.00. After quantitative analysis, the benzohydroxyxamic acid removal rate was calculated to be 100%.

[0075] Figure 6 The figures show the removal efficiency of benzohydroxyxamic acid at different pH values ​​in Examples 2, 8-11. As can be seen from the figures, the removal rate of benzohydroxyxamic acid is greater than 96% under different pH conditions, which proves that the cobalt single-atom catalyst of the present invention is applicable to a wide range of pH conditions.

[0076] Example 12

[0077] After following the procedure in Example 2, a first repetition was performed.

[0078] First repetition: All other steps were the same as in Example 2, except that the solid phase obtained in Example 2 was washed three times with water and then added to a mixed solution of a and b. Quantitative analysis showed that the removal rate of benzohydroxyxamic acid was 99.7%.

[0079] Example 13

[0080] After following the procedure in Example 12, a second repetition was performed.

[0081] Second repetition: All other steps were the same as in Example 2, except that the solid phase obtained in Example 12 was washed three times with water and then added to a mixed solution of a and b. Quantitative analysis showed that the removal rate of benzohydroxyxamic acid was 97.0%.

[0082] Example 14

[0083] After following the procedure in Example 13, a third repetition was performed.

[0084] Third repetition: All other steps were the same as in Example 2, except that the solid phase obtained in Example 13 was washed three times with water and then added to a mixed solution of a and b. Quantitative analysis showed that the removal rate of benzohydroxyxamic acid was 93.1%.

[0085] Example 15

[0086] After following the procedure in Example 14, a fourth repetition was performed.

[0087] Fourth repetition: All other steps were the same as in Example 2, except that the solid phase obtained in Example 14 was washed three times with water and then added to a mixed solution of a and b. Quantitative analysis showed that the removal rate of benzohydroxyxamic acid was 90.1%.

[0088] Example 16

[0089] After following the procedure in Example 15, a fifth repetition was performed.

[0090] Fifth repetition: All other steps were the same as in Example 2, except that the solid phase obtained in Example 15 was washed three times with water and then added to a mixed solution of a and b. Quantitative analysis showed that the removal rate of benzohydroxyxamic acid was 88.0%.

[0091] Figure 7 The figures show the removal efficiency of benzo[a]hydroxyxamic acid in repeated experiments of Examples 12-16. As can be seen from the figures, the removal rate of benzo[a]hydroxyxamic acid in Example 16 was only 11.7% lower than that in Example 12, demonstrating the good repeatability and high economic efficiency of the cobalt single-atom catalyst of the present invention.

[0092] Test Example 1

[0093] The other steps were the same as in Example 2, except that tert-butanol (at a concentration of 500 mmol / L) was added to the mixed solution of a and b before the addition of the cobalt single-atom catalyst. Quantitative analysis showed that the removal rate of benzohydroxyxamic acid was 96.7%.

[0094] Test Example 2

[0095] The other steps were the same as in Example 2, except that methanol (at a concentration of 500 mmol / L) was added to the mixed solution of a and b before the addition of the cobalt single-atom catalyst. Quantitative analysis showed that the removal rate of benzohydroxyxamic acid was 98.7%.

[0096] Figure 8 Example 2 (i.e.) Figure 8 The figures show the removal effects of benzohydroxyxamic acid in the control group and test examples 1-2. As can be seen from the figures, since tert-butanol is a strong binder of hydroxyl radicals and methanol is a strong binder of hydroxyl radicals and sulfate radicals, the addition of these two substances only had a small impact on the removal of benzohydroxyxamic acid (<5%). This indicates that the hydroxyl radicals and sulfate radicals commonly found in the potassium persulfate oxidation system are not the main intermediate species in the reaction process of this invention.

[0097] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for removing benzyl hydroxamic acid via cobalt single-atom catalyst polymerization, characterized in that... Includes the following steps: A potassium persulfate solution and an aqueous solution containing benzoyl hydroxamic acid are mixed, and then a cobalt single-atom catalyst is added. The mixture reacts to polymerize and remove benzoyl hydroxamic acid. The cobalt single-atom catalyst has a Co-N4 atomic coordination structure. The cobalt single-atom catalyst was prepared according to the following steps: S1. In the presence of a solvent, 2-methylimidazole and zinc nitrate hexahydrate are dissolved by ultrasonication to obtain a white suspension, denoted as solution A. S2. Cobalt nitrate hexahydrate is dissolved by ultrasonication in the presence of a solvent, and this solution is referred to as solution B. S3. Mix and stir liquid A and liquid B to undergo a complexation substitution reaction, and obtain a purple suspension containing a cobalt single-atom catalyst precursor. S4. The purple suspension of the cobalt single-atom catalyst precursor is centrifuged, washed and dried to obtain the purple cobalt single-atom catalyst precursor. S5. The purple cobalt single-atom catalyst precursor is subjected to high-temperature treatment to obtain the cobalt single-atom catalyst.

2. The method for removing benzyl hydroxamic acid by polymerization using a cobalt single-atom catalyst according to claim 1, characterized in that: The loading of cobalt single atoms in the cobalt single-atom catalyst is 2wt% to 3wt%.

3. The method for removing benzyl hydroxamic acid by polymerization using a cobalt single-atom catalyst according to claim 1, characterized in that: The solvent used in steps S1 and S2 is the same, and the solvent is selected from at least one of water, ethanol and methanol; The mass ratio of 2-methylimidazole, zinc nitrate hexahydrate, and cobalt nitrate hexahydrate is (5.5–6.5): (3.5–4.5): (0.1–0.5). The volume ratio of liquid A to liquid B in step S3 is (100-200):(50-100). The complexation substitution reaction conditions described in step S3 are: stirring temperature of 20–60 °C and stirring time of 10–24 h.

4. The method for removing benzyl hydroxamic acid by polymerization using a cobalt single-atom catalyst according to claim 1, characterized in that: The high-temperature treatment conditions described in step S5 are as follows: under an inert gas atmosphere, the temperature is 900-1100 °C, the heating rate is 2-5 °C / min, and the time is 1-3 h.

5. The method for removing benzyl hydroxamic acid by polymerization using a cobalt single-atom catalyst according to claim 1, characterized in that: Before mixing potassium hydrogen sulfate solution and aqueous solution containing benzoyl hydroxamic acid, adjust both solutions to the same pH, with the pH range being 3.00 to 11.

00.

6. The method for removing benzyl hydroxamic acid by polymerization using a cobalt single-atom catalyst according to claim 1, characterized in that: Before adding a cobalt single-atom catalyst, the concentration of potassium persulfate solution in the mixed solution is 0.5–6 mmol / L and the concentration of benzohydroxyxamic acid solution is 0.1–3 mmol / L. After adding the cobalt single-atom catalyst, the concentration of the cobalt single-atom catalyst is 0.1–0.5 g / L.

7. The method for removing benzyl hydroxamic acid by polymerization using a cobalt single-atom catalyst according to claim 1, characterized in that: Before adding a cobalt single-atom catalyst, the concentration of potassium persulfate solution in the mixed solution was 1–3 mmol / L and the concentration of benzohydroxyxamic acid solution was 0.5–1.5 mmol / L. After adding the cobalt single-atom catalyst, the concentration of the cobalt single-atom catalyst is 0.1–0.5 g / L.

8. The method for removing benzyl hydroxamic acid by polymerization using a cobalt single-atom catalyst according to claim 1, characterized in that: The aforementioned mixing reaction refers to a stirring reaction at room temperature for 10–30 minutes.

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