Method for removing chlorophenol by catalyzing permanganate based on silver oxide with polymerization regulation

Abstract

The application discloses a method for removing chlorophenol by using silver oxide catalyzed permanganate based on polymerization regulation, which comprises the following steps: (1) dissolving Ag2O in a solvent to obtain Ag2O suspension; (2) dissolving permanganate in a solvent to obtain a permanganate stock solution; (3) adding the Ag2O suspension into a solution containing chlorophenol, mixing and adjusting pH to obtain a mixed solution; and (4) adding the permanganate stock solution into the mixed solution to start a polymerization reaction, and removing the obtained precipitate by a phase separation method after the reaction is completed. The method can improve the ability of the existing permanganate single oxidation system to oxidize and degrade pollutants by adding silver oxide, and can also promote the polymerization of chlorophenol into easily-separated hydrophobic oligomers, thereby significantly improving the degradation rate of chlorophenol.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of pollutant removal, and particularly relates to a method for removing chlorophenols by using silver oxide catalyzed permanganate based on polymerization regulation. BACKGROUND

[0002] With the advancement of modern industrialization, various pollutants generated in agricultural and industrial activities are released into the natural environment, causing great ecological disturbance to aquatic organisms and human health. In particular, chlorophenols (CPs), as important intermediates and raw materials for synthetic pesticides, pharmaceuticals, dyes, plastics, wood preservatives and other industries, are a class of harmful organic compounds to the environment. DNA oxidative damage, red blood cell morphological changes and hemolysis, and the development of cancer are significantly related to the contact with chlorophenols. However, due to the stable aromatic ring structure and the passivation effect of halogen groups, they exhibit high persistence in the natural environment. Therefore, they can persist in water bodies for a long time and enter the atmosphere for long-distance transport due to their semi-volatility. In the past few decades, CPs have been mainly deposited in the environment through human means, especially through direct discharge of industrial waste. Generally, the environmental concentration of total CPs in surface water ranges from 0.005 to 20 μg / L, and up to 1000 μg / L in contaminated river basins.

[0003] Various chemical oxidation technologies have been studied to remove CPs in aqueous phase, such as ferrate oxidation, chlorination, ozonation and advanced oxidation processes (AOPs). Compared with other oxidants, permanganate (Mn(VII)) is a promising selective oxidant that can effectively treat organic compounds containing electron-rich functional groups, and has the advantages of low cost, convenient storage and transportation. However, there are some defects in its application, such as insufficient oxidation capacity at low concentrations, and relative to the technology of advanced oxidation process based on free radical reaction, the COD removal effect of water body is relatively poor. The application of carbon-based materials, colloidal manganese dioxide and other heterogeneous catalysts can significantly improve the oxidation capacity of Mn(VII) oxidation process to environmental pollutants through various mechanisms, such as strengthening the generation of intermediate reaction substances and enhancing electron transfer. However, the related catalytic technology usually only focuses on the removal of micro-pollutants themselves, lacks attention to reducing the COD in the solution, and the aquatic toxicity of part of the soluble oxidation products after Mn(VII) treatment may increase, affecting the treatment effect of polluted water bodies. SUMMARY

[0004] The present application aims to provide a method for removing chlorophenol pollutants by using silver oxide catalyzed permanganate based on polymerization regulation, which has high degradation efficiency, is green and environmentally friendly, and has low toxicity.

[0005] Technical solution: The method for removing chlorophenol by using silver oxide catalyzed permanganate based on polymerization control provided by the application comprises the following steps:

[0006] (1) dissolving Ag2O in a solvent to obtain Ag2O suspension;

[0007] (2) dissolving permanganate in a solvent to obtain a permanganate stock solution;

[0008] (3) adding the Ag2O suspension into a solution containing chlorophenol, mixing thoroughly, and adjusting the pH to obtain a mixed solution;

[0009] (4) adding the permanganate stock solution into the mixed solution to start the polymerization reaction, and the chlorophenol is converted into easily separable hydrophobic oligomers, and the hydrophobic oligomers are precipitated and removed by phase separation after the reaction is completed.

[0010] Further, in step (1), the concentration of Ag2O in the Ag2O suspension is 10-20 g / L, preferably 16 g / L.

[0011] Further, in step (2), the permanganate is one or more of potassium permanganate, sodium permanganate, calcium permanganate or ammonium permanganate, preferably potassium permanganate; and the molar concentration of the permanganate in the permanganate stock solution is 10-50 mmol / L, preferably 25 mmol / L.

[0012] Further, in steps (1)-(2), the solvent is water.

[0013] Further, in step (3), the chlorophenol includes one or more of 4-chlorophenol, 2,4-dichlorophenol, 2,5-dichlorophenol, 2,6-dichlorophenol, 3,5-dichlorophenol, 2,4,6-trichlorophenol or 2,3,4,6-tetrachlorophenol, preferably 2,4-dichlorophenol (2,4-DCP).

[0014] Further, in step (3), the concentration of chlorophenol in the solution containing chlorophenol is 10-1000 μmol / L.

[0015] Further, in step (3), the concentration of Ag2O in the mixed solution is 5-80 mg / L, preferably 20 mg / L.

[0016] Further, in step (3), the pH value of the mixed solution is 5.0-9.0, preferably 9.0.

[0017] Further, in step (4), after the permanganate stock solution is added into the mixed solution, the molar concentration of the permanganate in the mixed solution formed is 1-4 times, preferably 3-4 times, the molar concentration of the chlorophenol.

[0018] Further, in step (4), the conditions of the polymerization reaction are: a reaction temperature of 15-30℃, and a reaction time of 20-40 min.

[0019] Further, in step (4), the phase separation method comprises filtration or coagulation.

[0020] Further, step (5) is further included, wherein Ag2O in the filtrate obtained after phase separation is precipitated by adjusting the pH value, and Ag2O that can be recycled is obtained after centrifugation; the pH value is adjusted to a range of 11±0.2.

[0021] Principle: In the present application, Ag2O is used to improve the oxidation potential of the Mn(VII) oxidation system, and its catalytic effect strengthens the free radical attack path of the destruction of the C-Cl bond in chlorophenol compounds, so that most of the chlorophenol pollutants form phenol oxygen free radicals in the Mn(VII) oxidation process, and then mediate the chain polymerization of free radicals; the content of the chlorophenol oxidation product with high polymerization degree is significantly increased under the catalysis of Ag2O, which indicates that Ag2O regulates the development of CPs to a deep polymerization direction, and due to the increased molecular size and hydrophobicity, the obtained polymer obviously shows a visual flocculation body in an aqueous solution, and a precipitate appears, so that the polymer can be removed from the aquatic environment by a simple phase separation method such as filtration or coagulation, and then the content of organic matter in the solution is reduced.

[0022] In addition, Mn(VII) can generate an insoluble and environmentally friendly reduction product MnO2(s), which can assist in enhancing the coagulation effect and adsorbing trace metals, and then the trace metals are removed by precipitation / filtration. Therefore, the Mn(VII)-Ag2O system in the present application is a high-efficiency and green method for removing chlorophenol pollutants, Ag2O can effectively improve the oxidation ability of Mn(VII), and has excellent recycling performance and good COD removal effect, and provides a new idea for other organic pollutants that can be treated by Mn(VII), including antibiotics, estrogens and other organic pollutants, cyanide, ammonia, hydroxylamine, hydrogen sulfide and other inorganic pollutants and sterilization.

[0023] Advantages: Compared with the prior art, the present application has the following obvious advantages: (1) in the process of removing chlorophenol pollutants by using silver oxide to catalyze permanganate, Ag2O increases the potential of the Mn(VII) oxidation system, thereby strengthening the degradation of pollutants, and the oxidation ability is improved compared with the Mn(VII) system alone; (2) Ag2O regulates the deep polymerization of chlorophenol through a free radical pathway, and the polymer can be separated from the water body by methods such as filtration or coagulation precipitation, which significantly reduces the COD of the solution and provides additional advantages for low-carbon treatment of wastewater; (3) Ag2O particles mediate the rapid degradation of chlorophenol pollutants by Mn(VII), and have good recycling catalytic properties, which solves the problem of deactivation after multiple uses of ordinary reductive activators. Attached Figure Description

[0024] Figure 1 The graph shows the combination of removal efficiency and reaction rate of 2,4-DCP in Examples 1-4 and Comparative Examples 1-4.

[0025] Figure 2 The graph shows the reaction rate combinations at different pH values ​​in Examples 3, 5, 6, Comparative Examples 3, 5, and 6.

[0026] Figure 3 The graph shows the change in 2,4-DCP removal efficiency during the cyclic experiment measured in Example 7.

[0027] Figure 4 A comparison diagram of the peak area and intensity of the polymerization products measured by liquid chromatography-mass spectrometry in Example 3 and Comparative Example 3;

[0028] Figure 5 The reaction diagram is for permanganate, Ag2O and 2,4-DCP. Detailed Implementation

[0029] The present invention will now be further described in conjunction with specific embodiments and accompanying drawings.

[0030] Example 1: The method for removing chlorophenols using polymer-controlled silver oxide-catalyzed permanganate based on polymerization includes the following steps:

[0031] (1) At room temperature, dissolve 32 mg of silver oxide particles in 2 mL of deionized water and sonicate for 10 s to disperse the silver oxide evenly, and prepare an Ag2O suspension.

[0032] (2) At room temperature, dissolve 0.988 g of potassium permanganate solid in 250 mL of deionized water to prepare a stock solution of Mn(VII) with a concentration of 25 mmol / L.

[0033] (3) Take 50 μL of silver oxide suspension from step (1) and add it to 40 mL of solution containing 10 μmol / L 2,4-DCP. Stir continuously with magnetic force and adjust the pH value to 7.0 to obtain a mixed solution.

[0034] (4) Take 16 μL of Mn(VII) stock solution from step (2) and quickly inject it into the above mixture to start the polymerization reaction, and run the reaction at 20°C for 40 min.

[0035] Example 2: The difference from Example 1 is that in step (4), the amount of Mn(VII) stock solution used is 32 μL.

[0036] Example 3: The difference from Example 1 is that in step (4), the amount of Mn(VII) stock solution used is 48 μL.

[0037] Example 4: The difference from Example 1 is that in step (4), the amount of Mn(VII) stock solution used is 64 μL.

[0038] Example 5: The difference from Example 3 is that in step (3), the pH value is 5.0.

[0039] Example 6: The difference from Example 3 is that in step (3), the pH value is 9.0.

[0040] Example 7: The catalyst recycling performance test includes the following steps:

[0041] (1) At room temperature, 32 mg of silver oxide particles is dissolved in 2 mL of deionized water and ultrasonically dispersed for 10 s to prepare a Ag2O suspension;

[0042] (2) At room temperature, 0.988 g of potassium permanganate solid is dissolved in 250 mL of deionized water to prepare a Mn(VII) stock solution with a concentration of 25 mmol / L;

[0043] (3) 50 μL of the silver oxide suspension in step (1) is added to 40 mL of a solution containing 10 μmol / L 2,4-DCP, and continuously magnetically stirred to adjust the pH value to 7.0 to obtain a mixture;

[0044] (4) 48 μL of the Mn(VII) stock solution in step (2) is quickly injected into the above mixture to start the polymerization reaction, and the reaction is run at 20°C for 40 min;

[0045] (5) The solution after the reaction in the above step is added with 0.5 mol / L NaOH to adjust the pH to 11 to precipitate Ag2O, and after centrifugation, the Ag2O can be recycled;

[0046] (6) The recycled Ag2O in the above step is added to 40 mL of a solution containing 10 μmol / L 2,4-DCP, and continuously magnetically stirred to adjust the pH value to 7.0 to obtain a mixture;

[0047] (7) 48 μL of the Mn(VII) stock solution in step (2) is quickly injected into the above mixture to start the polymerization reaction, and the polymerization reaction is run at 20°C for 40 min.

[0048] (8) The operations of steps (5)-(7) are repeated three times to complete five cycles of Ag2O recycling.

[0049] Comparative Example 1: The method for removing chlorophenol using permanganate provided in this comparative example includes the following steps:

[0050] (1) At room temperature, 0.988 g of potassium permanganate solid was dissolved in 250 mL of deionized water to prepare a Mn(VII) stock solution with a concentration of 25 mmol / L;

[0051] (2) 16 μL of the Mn(VII) stock solution was quickly injected into a solution containing 40 mL of 10 μmol / L 2,4-DCP, the pH value was adjusted to 7.0, and the polymerization reaction was started. The reaction was run at 20°C for 40 min.

[0052] Comparative Example 2: The difference from Comparative Example 1 is that in step (2), the amount of Mn(VII) stock solution used is 32 μL.

[0053] Comparative Example 3: The difference from Comparative Example 1 is that in step (2), the amount of Mn(VII) stock solution used is 48 μL.

[0054] Comparative Example 4: The difference from Comparative Example 1 is that in step (2), the amount of Mn(VII) stock solution used is 64 μL.

[0055] Comparative Example 5: The difference from Comparative Example 3 is that in step (2), the pH value is 5.0.

[0056] Comparative Example 6: The difference from Comparative Example 3 is that in step (2), the pH value is 9.0.

[0057] The combination of removal efficiency and reaction rate measured in Examples 1-4 and Comparative Examples 1-4 is shown in Figure 1 When the molar concentration of potassium permanganate is three times that of the pollutant chlorophenol, the removal efficiency can reach more than 90%; in addition, the oxidation reaction rate (k obs ) of 2,4-DCP can be increased by about 2-4 times through the catalytic action of Ag2O.

[0058] The combination of reaction rates at different pH values in Example 3, Example 5, Example 6, Comparative Example 3, Comparative Example 5, and Comparative Example 6 is shown in Figure 2 Under neutral conditions, Mn(VII) alone has the best degradation effect on 2,4-DCP (k -1 ). In the Mn(VII)-Ag2O system, when the pH value is increased from 5.0 or 7.0 to 9.0, k obs is sharply increased from 0.07 min -1 to 0.14 min -1, which proves that the oxidation ability of the Ag2O assisted Mn(VII) system is further improved under alkaline conditions. The silver oxide catalyzed permanganate oxidation system adopted in the application is suitable for a wide pH condition of weak acidity, neutrality and weak alkalinity, and all of them show obvious promotion.

[0059] The Ag2O cycle performance results measured in Example 7 are shown in Figure 3 As shown in the table, after 5 cycles of use, the removal efficiency of the catalyst after 40 min treatment is all above 90%, and the catalytic performance is stable.

[0060] The peak area intensity contrast chart of the polymerization products measured by liquid chromatography-mass spectrometry technology in Example 3 and Comparative Example 3 is shown in Figure 4 , Figure 4 The peak area intensity chart of the polymerization products measured by liquid chromatography-mass spectrometry technology in Example 3 and Comparative Example 1 is shown in the figure, and it can be seen from the figure that the silver oxide and permanganate catalytic oxidation system adopted in the application breaks through to increase the content of pentamer and hexamer of 2,4-DCP by one order of magnitude, which indicates that the system significantly strengthens the production of large molecular polymers that can be separated.

[0061] The reaction formula of permanganate, Ag2O and 2,4-DCP is shown in Figure 5 Under the catalysis of Ag2O, 2,4-DCP is oxidized by permanganate to lose one single electron to form active phenoxy radicals, a large number of phenoxy radicals attack 2,4-DCP monomers to occur polymerization to form dimers, and the above radical polymerization reaction continuously occurs, then forming trimers, tetramers, and even hexamers of high molecular weight polymers, until they are separated from the aqueous phase.

Claims

1. A method for the removal of chlorophenols by catalytic permanganate based on polymeric regulated silver oxide, characterized by, The method comprises the following steps: (1) dissolving Ag2O in a solvent to obtain a Ag2O suspension; (2) dissolving permanganate in a solvent to obtain a permanganate stock solution; (3) adding the Ag2O suspension into a solution containing chlorophenol, mixing thoroughly, and adjusting the pH to obtain a mixed solution; (4) adding the permanganate stock solution into the mixed solution to start the polymerization reaction, and the chlorophenol is converted into easily separable hydrophobic oligomers by polymerization, and the hydrophobic oligomers are precipitated and removed by phase separation after the reaction is completed.

2. The method of claim 1, wherein, In step (1), the mass concentration of Ag2O in the Ag2O suspension is 10-20 g / L.

3. The method of claim 1, wherein, In step (2), the permanganate is one or more of potassium permanganate, sodium permanganate, calcium permanganate, or ammonium permanganate.

4. The method of claim 1, wherein, In step (3), the chlorophenol includes one or more of 4-chlorophenol, 2,4-dichlorophenol, 2,5-dichlorophenol, 2,6-dichlorophenol, 3,5-dichlorophenol, 2,4,6-trichlorophenol, or 2,3,4,6-tetrachlorophenol.

5. The method of claim 1, wherein, In step (3), the concentration of chlorophenol in the solution containing chlorophenol pollutants is 10-1000 μmol / L.

6. The method of claim 1, wherein, In step (3), the mass concentration of Ag2O in the mixed solution is 5-80 mg / L.

7. The method of claim 1, wherein, In step (3), the pH of the mixed solution is 5.0-9.

0.

8. The method of claim 1, wherein, In step (4), the molar concentration of permanganate in the mixed solution formed after adding the permanganate stock solution into the mixed solution is 1-4 times the molar concentration of chlorophenol.

9. The method of claim 1, wherein, In step (4), the polymerization reaction conditions are as follows: the reaction temperature is 15-30℃, and the reaction time is 20-40 min.

10. The method of claim 1, wherein, Further comprising step (5) that Ag2O in the filtrate obtained after phase separation is precipitated by adjusting the pH, and the recycled Ag2O is obtained after centrifugation.

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