A method for treating polyphenol coal chemical wastewater using modified zero-valent iron activated persulfate.

Abstract

This invention belongs to the field of wastewater treatment technology, specifically disclosing a method for treating polyphenol coal chemical wastewater using modified zero-valent iron activated persulfate. The method involves adding modified zero-valent iron and persulfate to the polyphenol coal chemical wastewater, followed by thorough shaking to achieve the degradation of phenolic compounds in the water. This invention combines nano-zero-valent iron with a sulfiding reagent and adds ethanol during the modification process to prepare modified nano-zero-valent iron, improving the defects of zero-valent iron such as easy aggregation and oxidation. This modified nano-zero-valent iron is used to activate persulfate, expanding the applicable pH range and effectively degrading polyphenols, while showing relatively poor degradation effect on monophenols. Furthermore, the reaction conditions of this invention can be carried out under normal pressure, making the operation convenient and the reaction conditions simple, and it is environmentally friendly. Therefore, it has good application prospects in the field of coal chemical wastewater treatment.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a method for treating polyphenol coal chemical wastewater using modified zero-valent iron activated persulfate. Background Technology

[0002] The processing of low-quality coal easily generates high-concentration coal chemical wastewater containing phenols. For example, Lurgi gasification wastewater has a COD as high as 20,000 to 30,000, a total phenol content of 5,000 to 6,000, and a polyphenol content of 2,000. Semi-coke wastewater has a COD of 40,000 to 50,000 or even higher, a total phenol content of 12,000 to 20,000, and a polyphenol content of 8,000 or higher. Currently, the main method to reduce COD is through phenol recovery processes to recover ammonia, acidic gases, phenols, or other organic pollutants from the wastewater. After phenol recovery, the total phenol content in semi-coke wastewater is often as high as 550 to 700 ppm, the vast majority of which is polyphenols. The total phenol content in the bottom effluent of Lurgi gasification wastewater after phenol recovery, after using different extractants, can reach as high as 1200 ppm, again mostly polyphenols. High polyphenol content affects the activity of microorganisms in subsequent biochemical processes, and sometimes makes it difficult to degrade in anaerobic treatment. Phenol is an easily degradable organic matter in coal pyrolysis wastewater and is also the main carbon source in the microbial degradation process. When the phenol content is low, glucose or other substances need to be added in subsequent biochemical treatment to increase the carbon source. The content of monophenols in the wastewater after the phenol recovery process is already low enough, while the content of polyphenols is higher than that of ordinary biological treatment. Therefore, minimizing the content of polyphenols and slightly reducing the content of phenols is the key task in connecting phenol recovery and biological treatment.

[0003] Chinese patent application CN105110448A discloses a method for simultaneously removing heavy metal-organic compound pollutants from water using zero-valent iron and persulfate. This method removes hexavalent chromium ions and phenol from the water. The phenol concentration in the water is 10 ppm, the dosage of bentonite-supported nano-zero-valent iron is 0.25-0.50 g / L, and the concentration of persulfate ions is 0.33-1.67 mmol / L. This patent achieves a phenol removal rate of 40.50-73.10%. CN105110448A aims to remove phenol, while the treatment of polyphenol coal chemical wastewater after phenol recovery aims to retain phenol as much as possible while removing unknown polyphenols. Summary of the Invention

[0004] The purpose of this invention is to provide a wastewater treatment method for coal chemical wastewater containing polyphenols based on modified zero-valent iron activated persulfate, so as to minimize the high polyphenol content caused by extraction efficiency and facilitate subsequent biochemical treatment.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for treating polyphenol coal chemical wastewater using modified zero-valent iron activated persulfate includes the following steps: adding modified zero-valent iron and persulfate to the polyphenol coal chemical wastewater and allowing it to fully vibrate and react, thereby achieving the degradation of phenolic compounds in the water.

[0007] The above method can degrade high concentrations of phenolic compounds in water, and the degradation efficiency of polyphenols is better than that of monophenols.

[0008] Preferably, the polyphenol coal chemical wastewater is coal chemical wastewater after phenol removal from high-concentration coal chemical phenol and ammonia wastewater.

[0009] Preferably, the polyphenol coal chemical wastewater contains monophenols (such as phenol) and polyphenols (such as hydroquinone, catechol, resorcinol).

[0010] More preferably, the concentration range of the monophenol in the water is 20-150 mg / L, and the concentration range of the polyphenol in the water is 150-1200 mg / L.

[0011] Preferably, the persulfate includes at least one of perdisulfate and permonsulfate.

[0012] Preferably, the amount of persulfate added to the reaction system is 20–40 mmol / L, and more preferably 30 mmol / L.

[0013] Preferably, the concentration of modified zero-valent iron in the reaction system is 0.025–0.25 g / L, and more preferably 0.125 g / L.

[0014] Preferably, the reaction temperature is 30–70°C and the reaction time is 10–60 min.

[0015] Preferably, the pH value of the polyphenol coal chemical wastewater is 3 to 9.

[0016] Preferably, the modified zero-valent iron is prepared by adding ethanol and a sulfiding agent during the preparation of zero-valent iron.

[0017] More preferably, the method for preparing the modified zero-valent iron includes the following steps: (1) preparing a mixed solution of sodium borohydride and sulfide reagent in ethanol and water, and preparing a mixed solution of ferrous sulfate in ethanol and water; (2) transferring the ferrous sulfate solution to a reaction vessel, stirring and adding the mixed solution of sodium borohydride and sulfide reagent in ethanol and water dropwise, continuously introducing nitrogen gas during the reaction, and continuing the reaction after the addition is completed (preferably 30 min); (3) using a magnet to separate the obtained black particles from the reaction solution, washing them with deionized water and anhydrous ethanol, and drying the washed modified zero-valent iron under vacuum for later use.

[0018] More preferably, the molar ratio of sodium borohydride to ferrous sulfate is 3:1; the molar ratio of the sulfiding agent to ferrous sulfate is 0.1 to 0.4:1, preferably 0.3:1.

[0019] More preferably, the volume ratio of ethanol to water in the ethanol-water mixed solution is 1:1.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] (1) This invention adopts a reverse thinking approach, and the treatment method provided aims to retain phenol as much as possible while removing polyphenols. The method used is to modify zero-valent iron by adding ethanol and a sulfiding agent during the preparation process. The strong polar hydroxyl groups in ethanol make the prepared zero-valent iron more dispersible and reduce the reaction between zero-valent iron and water and oxygen, thus reducing the degree of oxidation. The sulfiding agent causes the ferrous sulfate on the surface of zero-valent iron to replace the oxide layer, reducing the particle size of zero-valent iron, increasing its surface area, and increasing the number of reactive sites. The modification reduces the required persulfate concentration, thereby achieving sufficient degradation of polyphenols in water and slowing down the degradation efficiency of phenol.

[0022] (2) The reaction conditions of the present invention can be carried out under normal pressure, which is convenient to operate, simple to react, has good degradation effect, and is environmentally friendly. Attached Figure Description

[0023] Figure 1 This is a scanning electron microscope (SEM) image of S-nZVI with an S / Fe molar ratio of 0.3.

[0024] Figure 2 This is the X-ray diffraction (XRD) pattern of S-nZVI with an S / Fe molar ratio of 0.3. Detailed Implementation

[0025] 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. All raw materials involved in the present invention can be purchased directly from the market. For process parameters not specifically specified, conventional techniques can be referred to.

[0026] Example 1:

[0027] (1) The specific steps for zero-valent iron modification are as follows: Dissolve 2.02g of sodium borohydride solid and 1.285g of sodium sulfide nonahydrate in 100mL of a 1:1 mixture of ethanol and water; dissolve 4.96g of ferrous sulfate heptahydrate in 100mL of a 1:1 mixture of ethanol and water, and transfer the solution to a 250mL three-necked flask. Stir the flask in a magnetic stirrer. Turn on the stirrer and aerate the solution with high-purity nitrogen (99.999% purity) for 10min to remove dissolved oxygen. Continuously purge the solution with high-purity nitrogen (99.999% purity) during the reaction to maintain an oxygen-free state. Add the sodium borohydride solution dropwise using a constant-pressure dropping funnel. After the addition is complete, continue the reaction for 30min to ensure complete reaction. Stop stirring, remove the three-necked flask, and transfer the reaction solution to a beaker. Use a strong magnet to separate the solid and liquid, separating the resulting black particles. Wash the particles three times with deionized water and anhydrous ethanol, respectively. Place the washed S-nZVI in a vacuum drying oven and dry it under vacuum at 60°C for 6 hours to obtain S-nZVI powder (S / Fe molar ratio of 0.3).

[0028] The S-nZVI prepared in the examples was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), and the results are as follows: Figure 1 and Figure 2 As shown, the modified zero-valent iron S-nZVI particles exhibit an irregular spherical structure with a particle size between 50-100 nm, showing plate-like or needle-like forms. This indicates that the introduction of sulfur can increase the specific surface area of ​​zero-valent iron and increase the number of active reaction sites. All the prepared samples showed obvious diffraction peaks at a diffraction angle of 2θ = 44.672°, corresponding to Fe... 0 The (110) crystal plane also showed relatively obvious diffraction peaks at diffraction angles of 2θ = 65.021° and 2θ = 82.332°, corresponding to Fe 0 The (200) and (211) crystal planes indicate that the introduction of sulfur can promote the growth of Fe. 0 Crystal formation.

[0029] (2) A phenol solution with a concentration of 100 mg / L and a catechol solution with a concentration of 150 mg / L was used as a model. Sodium persulfate and modified zero-valent iron with an S / Fe molar ratio of 0.3 were added to the solution. The concentration of sodium persulfate in the system was 30 mmol / L, and the concentration of modified zero-valent iron was 0.25 g / L. The experiment was conducted in an electrically heated constant-temperature shaking water bath, with the pH adjusted to 9 and the temperature maintained at 30℃. After 60 min of reaction, 5 ml of water sample was taken and placed in a test tube. 1 mL of methanol was added to quench the reaction and terminate it. The solution was filtered using a 0.22 μm organic filter membrane, and the filtrate was collected. The concentrations of phenol and catechol were determined by high-performance liquid chromatography. Test results: The degradation rate of phenol was 20.1%, and the degradation rate of catechol was 93.2%.

[0030] Example 2:

[0031] (1) Following the steps of Example 1, the amount of sodium sulfide nonahydrate sulfide reagent was changed to prepare modified zero-valent iron with an S / Fe molar ratio of 0.4.

[0032] (2) A phenol solution with a concentration of 20 mg / L and a hydroquinone solution with a concentration of 300 mg / L was used as a model. Sodium persulfate and modified zero-valent iron with an S / Fe molar ratio of 0.4 were added to the solution. The concentration of sodium persulfate in the system was 20 mmol / L, and the concentration of modified zero-valent iron was 0.05 g / L. The experiment was conducted in an electrically heated constant-temperature shaking water bath, with the pH adjusted to 3 and the temperature maintained at 70℃. After 10 min of reaction, 5 ml of water sample was taken and placed in a test tube. 1 mL of methanol was added to quench the reaction and terminate it. The solution was filtered using a 0.22 μm organic filter membrane, and the filtrate was collected. The concentrations of phenol and hydroquinone were determined by high-performance liquid chromatography. Test results: The degradation rate of phenol was 35.8%, and the degradation rate of hydroquinone was 87.6%.

[0033] Example 3:

[0034] (1) Following the steps in Example 1, modified zero-valent iron with an S / Fe molar ratio of 0.3 was prepared.

[0035] (2) A phenol solution with a concentration of 20 mg / L and a hydroquinone solution with a concentration of 1200 mg / L was used as a model. Sodium persulfate and modified zero-valent iron with an S / Fe molar ratio of 0.3 were added to the solution. The concentration of sodium persulfate in the system was 40 mmol / L, and the concentration of modified zero-valent iron was 0.125 g / L. The experiment was conducted in an electrically heated constant-temperature shaking water bath, with the pH adjusted to 7 and the temperature maintained at 70℃. After 60 min of reaction, 5 ml of water sample was taken and placed in a test tube. 1 mL of methanol was added to quench the reaction and terminate it. The solution was filtered using a 0.22 μm organic filter membrane, and the filtrate was collected. The concentrations of phenol and hydroquinone were determined by high-performance liquid chromatography. Test results: The degradation rate of phenol was 34.3%, and the degradation rate of hydroquinone was 62.1%.

[0036] Example 4:

[0037] (1) Following the steps in Example 1, modified zero-valent iron with an S / Fe molar ratio of 0.3 was prepared.

[0038] (2) A phenol and hydroquinone solution with concentrations of 150 mg / L and 150 mg / L respectively was used as a model. Sodium persulfate and modified zero-valent iron with an S / Fe molar ratio of 0.3 were added to the solution. The concentration of sodium persulfate in the system was 30 mmol / L, and the concentration of modified zero-valent iron was 0.125 g / L. The experiment was conducted in an electrically heated constant-temperature shaking water bath, with the pH adjusted to 7 and the temperature maintained at 40℃. After 30 min of reaction, 5 ml of water sample was taken and placed in a test tube. 1 mL of methanol was added to quench the reaction and terminate it. The solution was filtered using a 0.22 μm organic filter membrane, and the filtrate was collected. The concentrations of phenol and hydroquinone were determined by high-performance liquid chromatography. Test results: The degradation rate of phenol was 18.7%, and the degradation rate of hydroquinone was 96.4%.

[0039] Example 5:

[0040] (1) Following the steps in Example 1, modified zero-valent iron with an S / Fe molar ratio of 0.3 was prepared.

[0041] (2) A phenol solution with a concentration of 100 mg / L and a hydroquinone solution with a concentration of 600 mg / L was used as a model. Sodium persulfate and modified zero-valent iron with an S / Fe molar ratio of 0.3 were added to the solution. The concentration of sodium persulfate in the system was 40 mmol / L, and the concentration of modified zero-valent iron was 0.025 g / L. The experiment was conducted in an electrically heated constant-temperature shaking water bath, with the pH adjusted to 5 and the temperature maintained at 40℃. After 30 min of reaction, 5 ml of water sample was taken and placed in a test tube. 1 mL of methanol was added to quench the reaction and terminate it. The solution was filtered using a 0.22 μm organic filter membrane, and the filtrate was collected. The concentrations of phenol and hydroquinone were determined by high-performance liquid chromatography. Test results: The degradation rate of phenol was 22.3%, and the degradation rate of hydroquinone was 72.7%.

[0042] Example 6:

[0043] (1) Following the steps of Example 1, the amount of sodium sulfide nonahydrate sulfide reagent was changed to prepare modified zero-valent iron with an S / Fe molar ratio of 0.1.

[0044] (2) A phenol solution with a concentration of 100 mg / L and a resorcinol solution with a concentration of 300 mg / L was used as a model. Sodium persulfate and modified zero-valent iron with an S / Fe molar ratio of 0.1 were added to the solution. The concentration of sodium persulfate in the system was 30 mmol / L, and the concentration of modified zero-valent iron was 0.025 g / L. The experiment was conducted in an electrically heated constant-temperature shaking water bath, with the pH adjusted to 7 and the temperature maintained at 50℃. After 60 min of reaction, 5 ml of water sample was taken and placed in a test tube. 1 mL of methanol was added to quench the reaction and terminate it. The solution was filtered using a 0.22 μm organic filter membrane, and the filtrate was collected. The concentrations of phenol and resorcinol were determined by high-performance liquid chromatography. Test results: The degradation rate of phenol was 19.5%, and the degradation rate of resorcinol was 89.7%.

[0045] Example 7:

[0046] (1) Following the steps in Example 1, modified zero-valent iron with an S / Fe molar ratio of 0.3 was prepared.

[0047] (2) A phenol solution with a concentration of 100 mg / L and a catechol solution with a concentration of 150 mg / L was used as a model. Sodium persulfate and modified zero-valent iron with an S / Fe molar ratio of 0.3 were added to the solution. The concentration of sodium persulfate in the system was 20 mmol / L, and the concentration of modified zero-valent iron was 0.125 g / L. The experiment was conducted in an electrically heated constant-temperature shaking water bath, with the pH adjusted to 3 and the temperature maintained at 40℃. After 60 min of reaction, 5 ml of water sample was taken and placed in a test tube. 1 mL of methanol was added to quench the reaction and terminate it. The solution was filtered using a 0.22 μm organic filter membrane, and the filtrate was collected. The concentrations of phenol and catechol were determined by high-performance liquid chromatography. Test results: The degradation rate of phenol was 17.6%, and the degradation rate of catechol was 92.5%.

[0048] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for treating polyphenol coal chemical wastewater using modified zero-valent iron activated persulfate, characterized in that, Includes the following steps: Modified zero-valent iron and persulfate are added to polyphenol coal chemical wastewater, and the reaction is carried out with full shaking to achieve the degradation of phenolic compounds in the water; the polyphenol coal chemical wastewater contains monophenols and polyphenols, and the pH value of the polyphenol coal chemical wastewater is 3-9; The dosage of persulfate in the reaction system is 20–40 mmol / L, and the concentration of modified zero-valent iron in the reaction system is 0.025–0.25 g / L; the reaction temperature is 30–70 °C, and the reaction time is 10–60 min. The preparation of the modified zero-valent iron includes the following steps: (1) preparing a mixed solution of sodium borohydride and sulfiding reagent in ethanol and water, and preparing a mixed solution of ferrous sulfate in ethanol and water; (2) Transfer the ferrous sulfate solution to the reaction vessel, stir and add the ethanol-water mixture of sodium borohydride and sulfide reagent dropwise. Nitrogen gas is continuously introduced during the reaction. After the addition is completed, continue the reaction. (3) Use a magnet to separate the obtained black particles from the reaction solution and wash them with deionized water and anhydrous ethanol. Dry the washed modified zero-valent iron in a vacuum for later use. The molar ratio of sodium borohydride to ferrous sulfate is 3:1, and the molar ratio of sulfiding reagent to ferrous sulfate is 0.1 to 0.4:1; the volume ratio of ethanol to water in the ethanol-water mixed solution is 1:

1.

2. The method according to claim 1, characterized in that, The polyphenol coal chemical wastewater refers to the coal chemical wastewater after phenol recovery from high-concentration coal chemical phenol and ammonia wastewater.

3. The method according to claim 2, characterized in that, The concentration range of the monophenols in water is 20–150 mg / L, and the concentration range of the polyphenols in water is 150–1200 mg / L.

4. The method according to claim 1, characterized in that, The persulfate includes at least one of perdisulfate and permonsulfate.

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