Wastewater treatment method

Abstract

The invention provides a wastewater treatment method. The wastewater treatment method comprises the following steps: S1, acidifying wastewater, and mixing the acidified wastewater with activated carbon and persulfate for reaction to obtain acidified wastewater; and S2, inserting a cathode plate and an anode plate into the acidified wastewater, and then carrying out electrocatalytic reaction. According to the wastewater treatment method provided by the invention, organic pollutants in wastewater are degraded by coupling three-dimensional electrocatalytic oxidation with persulfate activation until the wastewater reaches the standard and is discharged.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and in particular relates to a wastewater treatment method. Background Art

[0002] The discharge of wastewater has become one of the important sources of environmental pollution. Existing wastewater treatment methods mainly include physical, chemical and biological methods. Physical methods remove suspended matter and particulate pollutants by means of precipitation, filtration and adsorption, but have limited removal effects on soluble pollutants. Chemical methods use chemical reactions such as neutralization, redox and precipitation to remove pollutants in wastewater, which may introduce secondary pollution, require high reaction conditions, and have high use costs for certain chemical agents, which restricts their widespread application. Biological methods degrade organic pollutants through the metabolism of microorganisms, such as activated sludge and biofilm methods, which perform well in treating conventional organic wastewater, but have poor treatment effects on difficult-to-degrade organic matter, and are affected by environmental conditions such as temperature, pH and oxygen concentration, and often require a longer residence time. Therefore, although the existing technologies have achieved certain results in wastewater treatment, their respective defects limit the efficiency and economy in complex wastewater treatment. It is urgent to explore new wastewater treatment technologies to meet increasingly stringent environmental protection requirements. Summary of the invention

[0003] The present invention aims to solve at least one of the above technical problems existing in the prior art. To this end, the present invention provides a wastewater treatment method, which degrades organic pollutants in wastewater by three-dimensional electrocatalytic oxidation coupled with persulfate activation until the wastewater meets the discharge standards.

[0004] A first aspect of the present invention provides a wastewater treatment method, comprising the following steps:

[0005] S1: acidifying the wastewater and mixing it with activated carbon and persulfate to obtain acidified wastewater;

[0006] S2: inserting cathode plates and anode plates into the acidified wastewater for electrocatalytic reaction.

[0007] Ordinary activated carbon has a low activation efficiency for persulfate, and needs to be loaded, doped, and modified to improve the activation efficiency. In the electrocatalytic technology of the present invention, activated carbon can be used as a particle electrode for electrocatalysis in the electrocatalytic reaction to improve the reaction efficiency of electrocatalytic degradation of organic pollutants, and can also activate persulfate to degrade organic pollutants. The two are coupled to treat organic wastewater. Persulfate can increase the conductivity of activated carbon and improve the electrocatalytic efficiency. At the same time, the passage of current will also increase the activation efficiency of persulfate, greatly improving the reaction efficiency and reducing costs. Activated carbon is used as a particle electrode, and current is applied to polarize it. Under the action of the electric field, each particle can be regarded as an electrolysis unit, with opposite charges at both ends, thereby forming a third electrode, reducing the mass transfer distance of pollutants, improving current efficiency, and reducing reaction energy consumption. Activated carbon has the characteristics of low density, high specific surface area, and high conductivity, and is a relatively common particle electrode. Persulfate can be activated to produce sulfate radicals with strong oxidizing properties to degrade organic pollutants. Persulfate is easy to store, highly soluble and stable. It can be activated to produce SO4 with stronger oxidizing power than OH (standard redox potential is 2.7V). - (standard redox potential is 2.5~3.1V), and SO4 - It has a longer half-life and acts on the target for a longer time, thus being able to better oxidize and degrade most organic pollutants.

[0008] The present invention simultaneously utilizes three technologies of activated carbon adsorption, electrocatalytic oxidation and persulfate activation to treat organic wastewater, thereby greatly improving the degradation efficiency; persulfate can increase the conductivity of activated carbon and improve the efficiency of three-dimensional electrocatalysis; the current generated by electrocatalysis can play a role in electroactivating persulfate, thereby improving the efficiency of activated carbon in activating persulfate; through coupled synergistic effects, the degradation efficiency of organic matter is further improved.

[0009] According to some embodiments of the present invention, in step S1, the preparation raw material further includes carbon nanotubes modified with phenolic hydroxyl groups.

[0010] According to some embodiments of the present invention, the following steps are included:

[0011] S1: acidifying the wastewater and reacting it with activated carbon, carbon nanotubes modified with phenolic hydroxyl groups, and persulfate to obtain acidified wastewater;

[0012] S2: inserting cathode plates and anode plates into the acidified wastewater for electrocatalytic reaction.

[0013] According to some embodiments of the present invention, the raw materials for preparing the carbon nanotubes modified with phenolic hydroxyl groups include carbon nanotubes and catecholamines.

[0014] According to some embodiments of the present invention, the method for preparing carbon nanotubes modified with phenolic hydroxyl groups comprises dispersing carbon nanotubes, adding p-hydroxyphenol, and stirring to react to obtain a dispersion of carbon nanotubes modified with phenolic hydroxyl groups.

[0015] The synergistic effect of phenolic hydroxyl-modified carbon nanotubes and activated carbon is manifested as an enhanced adsorption effect, providing more "reaction sites" for subsequent electrocatalytic degradation reactions, thereby improving the degradation efficiency of pollutants. On the other hand, the chemical structure of phenolic hydroxyl has a strong electron supply capacity, which enables it to promote the decomposition of persulfate. Specifically, phenolic hydroxyl can activate the S–O bond in persulfate through an electron transfer process to generate highly oxidizing free radicals, such as SO4· and ·OH. These free radicals can efficiently oxidize and degrade organic pollutants in water during the electrocatalytic process, especially in the face of difficult-to-degrade organic substances. Phenolic hydroxyl-modified carbon nanotubes significantly enhance the generation and activity of free radicals by providing additional reaction sites and electron conduction channels, thereby improving the electrocatalytic degradation efficiency.

[0016] According to some embodiments of the present invention, in step S1, the mass ratio of the persulfate dosage to the COD in the wastewater is 1 to 2:1.

[0017] According to some embodiments of the present invention, in step S1, the mass ratio of the activated carbon to the persulfate is 1:1 to 1:5.

[0018] According to some embodiments of the present invention, in step S1, the pH of the acidified wastewater is 2-6.

[0019] According to some embodiments of the present invention, in step S1, the pH of the acidified wastewater is 4-6.

[0020] According to some embodiments of the present invention, in step S1, the reaction time is 0.5 to 1 h.

[0021] According to some embodiments of the present invention, the distance between the cathode plate and the anode plate is 0.5 to 10 cm.

[0022] According to some embodiments of the present invention, the current density in the electrocatalytic reaction is 100 to 1000 A / m 2 .

[0023] According to some embodiments of the present invention, the material of the cathode plate includes at least one of a titanium electrode, a silver electrode and a copper electrode.

[0024] According to some embodiments of the present invention, the material of the anode plate includes at least one of a boron-doped diamond electrode and a platinum electrode.

[0025] The above-mentioned electrode has a higher electrocatalytic efficiency, especially in the oxygen evolution reaction (OER). Its good electrocatalytic performance not only improves the efficiency of electrocatalytic degradation of organic pollutants, but also plays an important role in the activation process of persulfate. The activated carbon electrode can effectively accelerate the decomposition of persulfate and generate sulfate radicals (SO4· - ), thereby further improving the degradation rate of organic pollutants. In addition, the electrode structure helps to improve current transfer and reaction kinetics, enhances the overall efficiency of the reaction process, and fully realizes its potential in environmental pollution control. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0027] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0028] Unless otherwise specified, "room temperature" in the present invention means 25°C±5°C.

[0029] Unless otherwise specified, "about" in the present invention means that the allowable error is within ±2%.

[0030] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0031] A first aspect of the present invention provides a lithium slag autoclave leaching method, comprising the following steps:

[0032] S1: acidifying the wastewater and mixing it with activated carbon and persulfate to obtain acidified wastewater;

[0033] S2: inserting cathode plates and anode plates into the acidified wastewater for electrocatalytic reaction.

[0034] It should be noted that the activation efficiency of ordinary activated carbon for persulfate is low, and it needs to be loaded, doped and modified to improve the activation efficiency. In the electrocatalytic technology of the present invention, activated carbon can be used as a particle electrode for electrocatalysis in the electrocatalytic reaction to improve the reaction efficiency of electrocatalytic degradation of organic pollutants, and can also activate persulfate to degrade organic pollutants. The two are coupled to treat organic wastewater. Persulfate can increase the conductivity of activated carbon and improve the electrocatalytic efficiency. At the same time, the activation efficiency of persulfate can also be increased by passing current, which greatly improves the reaction efficiency and reduces the cost. Activated carbon is used as a particle electrode, and current is applied to polarize it. Under the action of the electric field, each particle can be regarded as an electrolysis unit, with opposite charges at both ends, thereby forming a third electrode, reducing the mass transfer distance of pollutants, improving current efficiency, and reducing reaction energy consumption. Activated carbon has the characteristics of low density, high specific surface area and high conductivity, and is a relatively common particle electrode. Persulfate can be activated to produce sulfate radicals with strong oxidizing properties to degrade organic pollutants. Persulfate is easy to store, highly soluble and stable. It can be activated to produce SO4 with stronger oxidizing power than OH (standard redox potential is 2.7V). - (standard redox potential is 2.5~3.1V), and SO4 - It has a longer half-life and acts on the target for a longer time, thus being able to better oxidize and degrade most organic pollutants.

[0035] In combination with the first aspect, in some embodiments of the present invention, in step S1, the mass ratio of the amount of persulfate added to the COD in the wastewater is 1:1.

[0036] In combination with the first aspect, in some embodiments of the present invention, in step S1, the mass ratio of the activated carbon to the persulfate is 1:1 to 1:5.

[0037] In combination with the first aspect, in some embodiments of the present invention, in step S1, the pH of the acidified wastewater is 2-6.

[0038] In combination with the first aspect, in some embodiments of the present invention, the pH of the acidified wastewater is 4-6.

[0039] In combination with the first aspect, in some embodiments of the present invention, the reaction time is 0.5 to 1 hour.

[0040] In combination with the first aspect, in some embodiments of the present invention, the raw materials for preparing the carbon nanotubes modified with phenolic hydroxyl groups include carbon nanotubes and catecholamines.

[0041] In combination with the first aspect, in some embodiments of the present invention, the method for preparing carbon nanotubes modified with phenolic hydroxyl groups comprises dispersing carbon nanotubes, adding p-hydroxyphenol, and stirring to react to obtain a dispersion of carbon nanotubes modified with phenolic hydroxyl groups.

[0042] The synergistic effect of phenolic hydroxyl-modified carbon nanotubes and activated carbon is manifested as an enhanced adsorption effect, providing more "reaction sites" for subsequent electrocatalytic degradation reactions, thereby improving the degradation efficiency of pollutants. On the other hand, the chemical structure of phenolic hydroxyl has a strong electron supply capacity, which enables it to promote the decomposition of persulfate. Specifically, phenolic hydroxyl can activate the S–O bond in persulfate through an electron transfer process to generate highly oxidizing free radicals, such as SO4· and ·OH. These free radicals can efficiently oxidize and degrade organic pollutants in water during the electrocatalytic process, especially in the face of difficult-to-degrade organic substances. Phenolic hydroxyl-modified carbon nanotubes significantly enhance the generation and activity of free radicals by providing additional reaction sites and electron conduction channels, thereby improving the electrocatalytic degradation efficiency.

[0043] In combination with the first aspect, in some embodiments of the present invention, the distance between the cathode plate and the anode plate is 0.5 to 10 cm.

[0044] In combination with the first aspect, in some embodiments of the present invention, the current density in the electrocatalytic reaction is 100-1000 A / m 2 .

[0045] In combination with the first aspect, in some embodiments of the present invention, the material of the cathode plate includes at least one of a titanium electrode, a silver electrode and a copper electrode.

[0046] In combination with the first aspect, in some embodiments of the present invention, the material of the anode plate includes at least one of a boron-doped diamond electrode and a platinum electrode.

[0047] Example 1

[0048] This embodiment provides a wastewater treatment method, wherein the water quality indicators of aniline simulated wastewater are shown in Table 1, specifically:

[0049] S1. Add 1L of simulated aniline wastewater of properties in Table 1 to the reaction vessel, then add sulfuric acid to adjust the pH of the wastewater to 4, then add 1g of sodium persulfate, stir to dissolve, then add 0.5g of activated carbon, and react for 1h;

[0050] S2. Insert electrode plates into the solution, where the cathode is a titanium electrode and the anode is a boron-doped diamond electrode. The distance between the plates is 5 cm and the current density is set to 200 A / m 2 , turn on the power, and after 1 hour of reaction, the COD removal rate of the wastewater was measured to be 91.36%.

[0051] Table 1 Water quality indicators of a certain aniline simulated wastewater

[0052]

[0053] Example 2

[0054] This embodiment provides a wastewater treatment method, wherein the water quality index of a certain chemical wastewater is shown in Table 2, specifically:

[0055] S1. Add 1L of chemical wastewater of the properties in Table 2 to the reaction vessel, then add sulfuric acid to adjust the pH of the wastewater to 5, then add 4.5g of sodium persulfate, stir to dissolve, add 1.5g of activated carbon, and react for 1h;

[0056] S2. Insert electrode plates into the solution, where the cathode is a titanium electrode and the anode is a boron-doped diamond electrode. The distance between the plates is 2 cm and the current density is set to 550 A / m 2 , turn on the power, and after 1 hour of reaction, the COD removal rate of the wastewater was measured to be 95.28%.

[0057] In Example 2, activated carbon not only serves as an electrocatalytic particle electrode in the electrocatalytic reaction, improving the reaction efficiency of electrocatalytic degradation of organic pollutants, but also can effectively activate persulfate, thereby further promoting the degradation of organic pollutants. By coupling the treatment method of activated carbon and persulfate, the activation of persulfate can not only increase the conductivity of activated carbon, thereby improving the electrocatalytic efficiency, but also the application of current can help improve the activation efficiency of persulfate, significantly enhance the reaction performance, and reduce the operating cost of the system. As a particle electrode, activated carbon can achieve a polarization effect under the action of applied current, so that it appears as a uniformly distributed electrolytic unit in the electric field. Each activated carbon particle carries opposite charges at both ends, forming a "third electrode" effect, shortening the distance that pollutants need to diffuse during the electrolysis process, thereby significantly improving the utilization efficiency of current and reducing energy consumption. Activated carbon has become a commonly used particle electrode material due to its low density, high specific surface area and excellent conductivity. By activating persulfate, sulfate radicals (SO4· - ) to effectively degrade organic pollutants. Persulfate has high solubility and stability and is easy to store. Under activation conditions, the generated sulfate radical (SO4· - , whose standard redox potential is 2.5-3.1V) has stronger oxidizing ability than hydroxyl radicals (·OH, with a standard redox potential of 2.7V), and sulfate radicals have a longer half-life, so they can continue to act on target pollutants for a longer time, thereby significantly improving the degradation efficiency of organic pollutants.

[0058] Table 2 Water quality indicators of a chemical wastewater

[0059]

[0060] Example 3

[0061] This embodiment provides a wastewater treatment method, wherein the water quality index of a certain landfill leachate is shown in Table 3, specifically:

[0062] S1. Add 1L of chemical wastewater of the properties in Table 3 to the reaction vessel, then add sulfuric acid to adjust the pH of the wastewater to 3, then add 6g of sodium persulfate, stir to dissolve, add 2g of activated carbon, and react for 1h;

[0063] S2. Insert electrode plates into the solution, where the cathode is a titanium electrode and the anode is a boron-doped diamond electrode. The distance between the plates is 1 cm and the current density is set to 800 A / m 2 , turn on the power, and after 1 hour of reaction, the COD removal rate of the wastewater was measured to be 99.78%.

[0064] Table 3 Water quality index of a certain landfill leachate

[0065]

[0066] Example 4

[0067] This embodiment provides a wastewater treatment method, wherein the water quality index of a certain landfill leachate is shown in Table 1, specifically:

[0068] S1. Add 1L of simulated aniline wastewater of the properties in Table 1 to the reaction vessel, then add sulfuric acid to adjust the pH of the wastewater to 4, 3g of carbon nanotubes modified with phenolic hydroxyl groups, and then add 1g of sodium persulfate, stir to dissolve, then add 0.5g of activated carbon, and react for 1h;

[0069] S2. Insert electrode plates into the solution, where the cathode is a titanium electrode and the anode is a boron-doped diamond electrode. The distance between the plates is 5 cm and the current density is set to 200 A / m 2 , turn on the power, and after 1 hour of reaction, the COD removal rate of the wastewater was measured to be 95.22%.

[0070] The preparation method of carbon nanotubes (CNTs) modified with phenolic hydroxyl groups is as follows: 1 g of multi-walled carbon nanotubes is added to 100 mL of deionized water, and ultrasonic treatment is used (ultrasonic time is 30 minutes, ultrasonic power is 100 W) to ensure that the carbon nanotubes are completely dispersed to form a uniform suspension, then 5 g of p-hydroxyphenol is taken and added to the dispersed carbon nanotube suspension, reacted at 80° C. for 4 hours, and then separated and impurities are removed to obtain the obtained CNTs.

[0071] This wastewater treatment method combines the synergistic effect of carbon nanotubes modified with phenolic hydroxyl groups and persulfate by optimizing the electrocatalytic degradation technology. The use of carbon nanotubes (CNTs) modified with phenolic hydroxyl groups not only enhances the electrocatalytic performance, but also effectively promotes the activation of sodium persulfate, generates strong oxidizing free radicals, and further improves the degradation efficiency of organic pollutants in wastewater. The combination of boron-doped diamond electrode and titanium electrode provides a stable electric field, effectively improving the efficiency of oxygen evolution reaction (OER), while achieving a higher COD removal rate (95.22%) through current density control. This method demonstrates high efficiency and economy in complex water treatment.

[0072] Comparative Example 1

[0073] This comparative example provides a wastewater treatment method, wherein the water quality indicators of aniline simulated wastewater are shown in Table 1, specifically:

[0074] S1. Add 1L of simulated aniline wastewater of properties in Table 1 to the reaction vessel, then add 1g of sodium persulfate, stir to dissolve, then add 0.5g of activated carbon, and react for 1h;

[0075] S2. Insert electrode plates into the solution, where the cathode is a titanium electrode and the anode is a boron-doped diamond electrode. The distance between the plates is 5 cm and the current density is set to 200 A / m 2 , turn on the power, and after 1 hour of reaction, the COD removal rate of the wastewater was measured to be 79.36%.

[0076] Comparative Example 2

[0077] This embodiment provides a wastewater treatment method, wherein the water quality index of a certain chemical wastewater is shown in Table 2, specifically:

[0078] S1. Add 1L of chemical wastewater of the properties in Table 2 to the reaction vessel, then add sulfuric acid to adjust the pH of the wastewater to 5, then add 4.5g of sodium persulfate, stir to dissolve, add 9g of activated carbon, and react for 1h;

[0079] S2. Insert electrode plates into the solution, where the cathode is a titanium electrode and the anode is a boron-doped diamond electrode. The distance between the plates is 2 cm and the current density is set to 550 A / m 2 , turn on the power, and after 1 hour of reaction, the COD removal rate of the wastewater was measured to be 68.28%.

[0080] Comparative Example 3

[0081] This comparative example provides a wastewater treatment method, wherein the water quality index of a certain landfill leachate is shown in Table 3, specifically:

[0082] S1. Add 1L of chemical wastewater of the properties in Table 3 to the reaction vessel, then add sulfuric acid to adjust the pH of the wastewater to 3, then add 6g of sodium persulfate, stir to dissolve, add 2g of activated carbon, and react for 1h;

[0083] S2. Insert electrode plates into the solution, where the cathode is a titanium electrode and the anode is a boron-doped diamond electrode. The distance between the plates is 1 cm and the current density is set to 80 A / m 2 , turn on the power, and after 1 hour of reaction, the COD removal rate of the wastewater was measured to be 49.78%.

[0084] Ordinary activated carbon has a low activation efficiency for persulfate, and needs to be modified by loading, doping, etc. to improve the activation efficiency. In the electrocatalytic technology of the present invention, activated carbon can be used as a particle electrode for electrocatalysis in the electrocatalytic reaction to improve the reaction efficiency of electrocatalytic degradation of organic pollutants, and can also activate persulfate to degrade organic pollutants. The two are coupled to treat organic wastewater. Persulfate can increase the conductivity of activated carbon and improve the electrocatalytic efficiency. At the same time, the passage of electric current will also increase the activation efficiency of persulfate, greatly improving the reaction efficiency while reducing costs.

[0085] In Comparative Example 1, the pH value is not adjusted. Especially under alkaline conditions, the decomposition efficiency of sodium persulfate is reduced, the oxidizing property of the electrochemical oxidation reaction is weakened, and the degradation efficiency of aniline is reduced, thereby causing a significant decrease in the COD removal rate.

[0086] The excess activated carbon in Comparative Example 2 will adsorb other substances in the water (such as inorganic salts, suspended matter, other pollutants, etc.). These substances may compete for the limited adsorption sites on the surface of the activated carbon, thereby reducing the adsorption efficiency of organic pollutants. Excessive addition of activated carbon will cause the particles to accumulate with each other, resulting in physical shielding between the particles, reducing the effective contact area on the surface of the particles, and reducing the contact opportunity between the pollutants in the wastewater and the activated carbon, thereby affecting the adsorption efficiency of the pollutants.

[0087] In Comparative Example 3, too low current density will lead to a decrease in the rate of the electrochemical oxidation reaction, thereby affecting the degradation effect of organic pollutants and causing a decrease in COD removal rate.

[0088] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A wastewater treatment method, characterized in that: The following steps are involved: S1: acidifying the wastewater and mixing it with activated carbon and persulfate to obtain acidified wastewater; S2: inserting cathode plates and anode plates into the acidified wastewater for electrocatalytic reaction.

2. The method according to claim 1, characterized in that In step S1, the mass ratio of the persulfate dosage to the COD in the wastewater is 1 to 2:

1.

3. The method according to claim 1, characterized in that: In step S1, the mass ratio of the activated carbon to the persulfate is 1:1 to 1:

5.

4. The method according to claim 1, characterized in that: In step S1, the pH of the acidified wastewater is 2-6.

5. The method according to claim 1, characterized in that In step S1, the pH of the acidified wastewater is 4-6.

6. The method according to claim 1, characterized in that In step S1, the reaction time is 0.5 to 1 h.

7. The method according to claim 1, characterized in that The distance between the cathode plate and the anode plate is 0.5-10 cm.

8. The method according to claim 1, characterized in that The current density in the electrocatalytic reaction is 100 to 1000 A / m 2 .

9. The method according to claim 1, characterized in that: The material of the cathode plate includes at least one of a titanium electrode, a silver electrode and a copper electrode.

10. The method according to claim 1, characterized in that The material of the anode plate includes at least one of a boron-doped diamond electrode, a platinum electrode, a ruthenium-iridium electrode and a lead dioxide electrode.

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