Wastewater treatment agent and preparation method thereof

Abstract

The invention provides a wastewater treatment agent and a preparation method thereof. The wastewater treatment agent is prepared from the following raw materials: modified carbon nanotubes, persulfate and activated carbon, the modified carbon nanotube is prepared from the following raw materials: a carbon nanotube, phenol and borate. The modified carbon nanotubes are combined with the activated carbon to enhance the specific surface area and the pore structure, so that the wastewater treatment efficiency is improved, the phenolic hydroxyl group can induce persulfate to generate active sulfate free radicals (SO4 <->) and improve the oxidation reaction, meanwhile, boron ions and the phenolic hydroxyl group form a compound, the reactivity is improved, an intermediate is stabilized, and the pH value is optimized to improve the overall reaction efficiency. And finally, the pollutant removal rate is improved.

Description

Technical Field

[0001] The invention belongs to the field of wastewater treatment materials, and particularly relates to an organic wastewater treatment agent and a wastewater treatment method. Background Art

[0002] In industrial wastewater discharge, organic wastewater has become one of the environmental pollution problems that need to be solved urgently due to its complex composition, strong toxicity, high chemical oxygen demand (COD) and poor biodegradability. Traditional wastewater treatment methods, such as biodegradation, physical adsorption and chemical precipitation, often show the disadvantages of low efficiency or inapplicability when facing organic wastewater, especially wastewater with high concentration and complex composition. Therefore, seeking an efficient, economical and sustainable organic wastewater treatment technology has become a research hotspot in the current field of environmental engineering. In recent years, chemical oxidation technology, especially ozone catalytic oxidation, has been widely regarded as an effective organic wastewater treatment process. Ozone has strong oxidizing properties and can quickly degrade organic matter, especially toxic and harmful substances that are difficult to degrade. Therefore, the application of ozone treatment technology in water treatment has made significant progress. However, when ozone is used alone for wastewater treatment, due to its poor stability, slow reaction rate, and easy reaction with impurities in wastewater, ozone consumption is large and the reaction efficiency is low. Therefore, combining ozone with a catalyst and using the action of the catalyst to promote the activation of ozone is an important strategy to improve the efficiency of ozone catalytic oxidation reactions.

[0003] According to the phase state of the catalyst, ozone catalytic oxidation reactions can be divided into two categories: homogeneous catalysis and heterogeneous catalysis. In a homogeneous catalytic system, the catalyst and the reactant are in the same phase (usually the liquid phase), the catalyst activity is high, and the reaction efficiency is high. However, homogeneous catalysts often need to be separated and recovered after the catalytic reaction, which not only increases the difficulty of operation, but also may introduce secondary pollution problems. In contrast, heterogeneous catalytic systems have advantages in practical applications because the catalyst and the reactant are in different phases (usually solid-phase catalysts react with liquid-phase wastewater). The catalyst can be separated and recovered more easily. Heterogeneous catalytic oxidation technology avoids the difficulty of catalyst recovery and secondary pollution problems in homogeneous catalysis, and shows higher application potential. Among the heterogeneous catalysts for ozone catalytic oxidation, transition metal catalysts (such as manganese (Mn), iron (Fe), copper (Cu), etc.) and rare earth metal catalysts (such as cerium (Ce)) are the focus of current research. These metals and their oxides can effectively promote the decomposition of ozone to generate highly active oxides (such as nitrogen oxide free radicals, hydroxyl free radicals, etc.), thereby enhancing the oxidative degradation ability of organic pollutants. In particular, transition metal catalysts can react with ozone molecules to form active species with high oxidation ability during the activation process of ozone, such as oxygen atoms (O·) or hydroxyl radicals (·OH) produced by ozone decomposition. These active species can quickly degrade organic pollutants in water and achieve high treatment efficiency. However, current heterogeneous catalysts still face some challenges. Many catalysts are mainly composed of a single transition metal or its oxide. Although they have certain catalytic activity, they often show low stability and poor catalytic efficiency during the catalytic reaction. In addition, many transition metal catalysts have a short service life and are easily deactivated by factors such as acids and alkalis in the reaction environment. In order to overcome these problems, researchers have begun to explore the combination of transition metal catalysts with rare earth metals (such as cerium, yttrium, lanthanum, etc.) in order to improve the stability, corrosion resistance and catalytic efficiency of the catalyst. Rare earth metals, especially cerium (Ce), have been widely used in the design and optimization of catalysts due to their excellent redox properties and good chemical stability. The redox properties of cerium enable it to effectively promote the activation of ozone in catalytic reactions, while enhancing the stability of the catalyst and reducing the deactivation of the catalyst. In order to further improve the efficiency and stability of ozone catalytic oxidation reaction, the design of modern catalysts is developing in the direction of multifunctionalization, nano-ization and composite. For example, catalysts prepared by nanotechnology have a larger specific surface area and more active sites, which helps to improve the efficiency of catalytic reactions. By compounding transition metals with rare earth metals or carbon materials (such as graphene, carbon nanotubes, etc.), however, existing heterogeneous catalysts mostly use a single transition metal and its oxide as the main active ingredient, and often face the problem of low catalytic efficiency. Summary of the invention

[0004] 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 agent for degrading organic pollutants in water.

[0005] The principle of the present invention is:

[0006] Concentrated sulfuric acid and concentrated nitric acid are used as mixed acid solutions, which have strong oxidizing properties and can effectively oxidize the surface of carbon nanotubes to form carboxylated carbon nanotubes. Sodium borate and phenol are added for modification. The modified carbon nanotube surface can provide more adsorption sites, thereby increasing the specific surface area of ​​the overall composite material and improving its adsorption performance. Phenol (especially its phenolic hydroxyl group) can induce persulfate (PS) to generate sulfate radicals (SO4·) with high oxidizing ability. These sulfate radicals are strong oxidants that can attack organic pollutants in wastewater and destroy their chemical structure, thereby accelerating the degradation process. The presence of phenol increases the reactivity between persulfate and pollutants, making the oxidation process faster and more efficient. When phenol molecules react with persulfate, they can not only increase the decomposition rate of persulfate, but also reduce the time required for pollutant degradation. Boron ions can combine with phenolic hydroxyl groups in phenol to form a stable complex. Not only does it enhance the reactivity of phenol, but it can also promote the decomposition process of persulfate. Boron ions can effectively increase the interaction between phenol and persulfate during the reaction process, thereby improving the overall oxidation efficiency. During the oxidation process, boron ions can stabilize the intermediate reaction products and prevent them from premature degradation or conversion, thereby improving the efficiency of the final reaction.

[0007] The first aspect of the present invention provides a wastewater treatment agent, wherein the raw materials for preparing the wastewater treatment agent include: modified carbon nanotubes, persulfate and activated carbon;

[0008] The raw materials for preparing the modified carbon nanotubes include: carbon nanotubes, phenol and borate.

[0009] According to the implementation of the first aspect of the present invention, there are at least the following beneficial effects:

[0010] The combination of modified carbon nanotubes and activated carbon has unique structure and properties. The introduction of modified carbon nanotubes increases the specific surface area of ​​activated carbon, strengthens its pore structure, and realizes the rapid aggregation of target pollutants, making the wastewater treatment process more efficient and significantly improving the removal effect.

[0011] The phenolic hydroxyl group of phenol can effectively induce persulfate to produce sulfate radicals (SO4 - ), thereby enhancing the efficiency of the oxidation reaction.

[0012] Boron ions can form complexes with phenolic hydroxyl groups, increasing the reactivity of phenolic compounds while promoting reactions with persulfate, thus improving the oxidation effect. During the oxidation process, boron ions help stabilize reaction intermediates, prevent premature degradation, and increase the removal rate of the final product. The pH value of the system under the regulation of borate is conducive to improving the activation efficiency of persulfate and the generation of hydroxyl radicals.

[0013] According to some embodiments of the present invention, the modified carbon nanotubes, the persulfate and the activated carbon are in a ratio of 1:0.1-0.5:2-5 in parts by weight.

[0014] According to some embodiments of the present invention, the modified carbon nanotubes, the persulfate and the activated carbon are in a ratio of 1:0.1-0.2:2-5 in parts by weight.

[0015] The above ratio can effectively achieve the synergistic effect of each component, enhance the oxidation and adsorption effects, and achieve better treatment effects. Persulfate generates active free radicals to strongly oxidize and decompose organic pollutants. The appropriate persulfate concentration can maintain the oxidation effect while avoiding the increase in treatment costs or side reactions caused by excessive oxidation. The combination of persulfate and modified carbon nanotubes can improve the efficiency of releasing free radicals, thereby enhancing the degradation rate of organic matter in wastewater. Activated carbon further enhances the overall oxidation reaction effect by adsorbing and decomposing harmful substances, while preventing the accumulation of harmful intermediates produced in the reaction.

[0016] Modified carbon nanotubes improve their adsorption capacity for pollutants and promote oxidation reactions through their surface hydrophilicity and efficient conductivity.

[0017] According to a second aspect of the present invention, a method for preparing a wastewater treatment agent is provided, comprising: mixing the modified carbon nanotubes and persulfate and dispersing them with activated carbon to obtain the wastewater treatment agent.

[0018] According to some embodiments of the present invention, the method for preparing the modified carbon nanotubes comprises:

[0019] The carbon nanotubes are dispersed after carboxylation, mixed with borate and phenol under heating conditions for reaction, and then impurities are removed to obtain modified carbon nanotubes.

[0020] According to some embodiments of the present invention, the reaction temperature is 60-80°C.

[0021] The above reaction temperature helps to control the reaction products, has a higher reaction efficiency, and avoids the occurrence of side reactions.

[0022] According to some embodiments of the present invention, the carboxylation step includes: mixing concentrated sulfuric acid and concentrated nitric acid, adding carbon nanotubes and potassium permanganate, and then removing impurities to obtain carboxylated carbon nanotubes.

[0023] According to some embodiments of the present invention, a weight ratio of the carbon nanotubes, the borate and the phenol is 1:0.2-0.5:0.1-0.3.

[0024] At the above ratio, the nanotubes serve as the main substrate for the reaction and carry the introduction of functional groups in the reaction. The above ratio helps to provide an appropriate amount of boron source to form boroxy groups on the surface of the carbon nanotubes, increase their hydrophilicity or other chemical reactivity, and avoid excessive reactions or unnecessary by-products caused by excessive borates. Phenol molecules can undergo esterification reactions with oxidized groups (such as carboxyl or hydroxyl) on the surface of carbon nanotubes to form aromatic functional groups, which help to improve the dispersibility, compatibility and chemical reactivity of carbon nanotubes. The lower ratio of phenol avoids unnecessary side reactions or multifunctionalization caused by excessive use.

[0025] According to some embodiments of the present invention, the mixing reaction is performed under ultrasonic conditions.

[0026] According to some embodiments of the present invention, the ultrasonic treatment conditions are: 100-300W ultrasonic treatment for 10-20min. DETAILED DESCRIPTION

[0027] 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.

[0028] 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.

[0029] Unless otherwise specified, "room temperature" in the present invention means 25°C±5°C.

[0030] Unless otherwise specified, "about" in the present invention means that the allowable error is within ±2%.

[0031] 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.

[0032] The first aspect of the present invention provides a wastewater treatment agent, wherein the raw materials for preparing the wastewater treatment agent include: modified carbon nanotubes, persulfate and activated carbon;

[0033] The raw materials for preparing the modified carbon nanotubes include: carbon nanotubes, phenol and borate.

[0034] The combination of modified carbon nanotubes and activated carbon has unique structure and properties. The introduction of modified carbon nanotubes increases the specific surface area of ​​activated carbon, strengthens its pore structure, and realizes the rapid aggregation of target pollutants, making the wastewater treatment process more efficient and significantly improving the removal effect.

[0035] The phenolic hydroxyl group of phenol can effectively induce persulfate to produce sulfate radicals (SO4 - ), thereby enhancing the efficiency of the oxidation reaction.

[0036] Boron ions can form complexes with phenolic hydroxyl groups, increasing the reactivity of phenolic compounds while promoting reactions with persulfate, thus improving the oxidation effect. During the oxidation process, boron ions help stabilize reaction intermediates, prevent premature degradation, and increase the removal rate of the final product. The pH value of the system under the regulation of borate is conducive to improving the activation efficiency of persulfate and the generation of hydroxyl radicals.

[0037] In combination with the first aspect, in some embodiments of the present invention, the modified carbon nanotubes, the persulfate and the activated carbon are in a ratio of 1:0.2-0.5:2-5 in parts by weight.

[0038] At the above ratio, the nanotubes serve as the main substrate for the reaction and carry the introduction of functional groups in the reaction. The above ratio helps to provide an appropriate amount of boron source to form boroxy groups on the surface of the carbon nanotubes, increase their hydrophilicity or other chemical reactivity, and avoid excessive reactions or unnecessary by-products caused by excessive borates. Phenol molecules can undergo esterification reactions with oxidized groups (such as carboxyl or hydroxyl) on the surface of carbon nanotubes to form aromatic functional groups, which help to improve the dispersibility, compatibility and chemical reactivity of carbon nanotubes. The lower ratio of phenol avoids unnecessary side reactions or multifunctionalization caused by excessive use.

[0039] In combination with the second aspect, in some embodiments of the present invention, a method for preparing a wastewater treatment agent is provided, comprising: mixing the modified carbon nanotubes and persulfate and dispersing them with activated carbon.

[0040] In combination with the second aspect, in some embodiments of the present invention, the method for preparing the modified carbon nanotubes comprises:

[0041] The carbon nanotubes are dispersed after carboxylation, mixed with borate and phenol under heating conditions for reaction, and then impurities are removed to obtain modified carbon nanotubes.

[0042] In combination with the second aspect, in some embodiments of the present invention, the reaction temperature is 60-80°C.

[0043] In combination with the second aspect, in some embodiments of the present invention, the carboxylation step includes: mixing concentrated sulfuric acid and concentrated nitric acid, adding carbon nanotubes and potassium permanganate, reacting, and removing impurities to obtain carboxylated carbon nanotubes.

[0044] In combination with the second aspect, in some embodiments of the present invention, the weight ratio of the carbon nanotubes, the borate and the phenol is 1:0.2-0.5:0.1-0.3.

[0045] In combination with the second aspect, in some embodiments of the present invention, the mixing reaction is carried out under ultrasonic conditions.

[0046] In combination with the second aspect, in some embodiments of the present invention, the ultrasonic treatment conditions are: 100-300W ultrasonic treatment for 10-20min.

[0047] Example 1

[0048] This embodiment provides a wastewater treatment agent, specifically:

[0049] A1. Add 10 g of carbon nanotubes and 6.5 g of potassium permanganate (KMnO4) to a mixed acid solution (500 mL of 98% concentrated sulfuric acid and 100 mL of 65% concentrated nitric acid), stir and react at 40°C for 2 h, filter, wash the solid product with deionized water until neutral, and vacuum dry at 75°C for 8 h to obtain carboxylated carbon nanotubes;

[0050] A2. Add 5 g of carboxylated carbon nanotubes to 200 mL of deionized water, and ultrasonically disperse for 20 min to obtain a CNT dispersion. Use an ammonia solution to adjust the pH of the reaction system to 9, add 2 g of sodium borate, stir and react at 60°C for 2 h, then add 1.5 g of phenol and stir and react for 20 h to ensure that phenol can be effectively adsorbed onto the CNT surface to form modified carbon nanotubes;

[0051] A3. Take 1g of sodium persulfate, dissolve it in 50ml of deionized water, stir thoroughly until completely dissolved, add it to the dispersion of carbon nanotubes dried in step A2, mix well, add 20g of activated carbon powder, and add 5g of polyvinyl alcohol, continue stirring, and ultrasonically treat at 100W for 20min.

[0052] Example 2

[0053] This embodiment provides a wastewater treatment agent, specifically:

[0054] A1. Add 10 g of carbon nanotubes and 6.5 g of potassium permanganate (KMnO4) to a mixed acid solution (500 mL of 98% concentrated sulfuric acid and 100 mL of 65% concentrated nitric acid), stir and react at 40°C for 2 h, filter, wash the solid product with deionized water until neutral, and vacuum dry at 75°C for 8 h to obtain carboxylated carbon nanotubes;

[0055] A2. Add 5 g of carboxylated carbon nanotubes to 200 mL of deionized water, and ultrasonically disperse for 20 min to obtain a CNT dispersion. Use an ammonia solution to adjust the pH of the reaction system to 9, add 2 g of sodium borate, stir and react at 60°C for 2 h, then add a phenol solution and stir and react for 20 h to ensure that phenol can be effectively adsorbed onto the CNT surface to form modified carbon nanotubes;

[0056] A3. Take 1g of sodium persulfate, dissolve it in 50ml of deionized water, stir thoroughly until completely dissolved, add it to the dispersion of modified carbon nanotubes in step A2, mix well, add 20g of activated carbon powder, and add 5g of polyvinyl alcohol, continue stirring, and ultrasonically treat at 100W for 20min.

[0057] Comparative Example 1

[0058] This comparative example provides a wastewater treatment agent. The difference between this comparative example and Example 1 is that phenol is not added, specifically:

[0059] A1. Add 10 g of carbon nanotubes and 6.5 g of potassium permanganate (KMnO4) to a mixed acid solution (500 mL of 98% concentrated sulfuric acid and 100 mL of 65% concentrated nitric acid), stir and react at 40°C for 2 h, filter, wash the solid product with deionized water until neutral, and vacuum dry at 75°C for 8 h to obtain carboxylated carbon nanotubes;

[0060] A2. 5 g of carboxylated carbon nanotubes were added to 200 mL of deionized water and ultrasonically dispersed for 20 min to obtain a CNT dispersion. The pH of the reaction system was adjusted to 9 with an aqueous ammonia solution. 2 g of sodium borate was added and stirred at 60 ° C for 2 h. The reaction was stirred for 20 h to form modified carbon nanotubes.

[0061] A3. Take 1g of sodium persulfate, dissolve it in 50ml of deionized water, stir thoroughly until completely dissolved, add it to the dispersion of carbon nanotubes dried in step A2, mix well, add 20g of activated carbon powder, and add 5g of polyvinyl alcohol, continue stirring, and ultrasonically treat at 100W for 20min.

[0062] Comparative Example 2

[0063] This comparative example provides a wastewater treatment agent. The difference between this comparative example and Example 1 is that no borate is added, specifically:

[0064] A1. Add 10 g of carbon nanotubes and 6.5 g of potassium permanganate (KMnO4) to a mixed acid solution (500 mL of 98% concentrated sulfuric acid and 100 mL of 65% concentrated nitric acid), stir and react at 40°C for 2 h, filter, wash the solid product with deionized water until neutral, and vacuum dry at 75°C for 8 h to obtain carboxylated carbon nanotubes;

[0065] A2. 5 g of carboxylated carbon nanotubes were added to 200 mL of deionized water and ultrasonically dispersed for 20 min to obtain a CNT dispersion. The pH of the reaction system was adjusted to 9 using an aqueous ammonia solution and the reaction was stirred to form modified carbon nanotubes.

[0066] A3. Take 1g of sodium persulfate, dissolve it in 50ml of deionized water, stir thoroughly until completely dissolved, add it to the dispersion of carbon nanotubes dried in step A2, mix well, add 20g of activated carbon powder, and add 5g of polyvinyl alcohol, continue stirring, and ultrasonically treat at 100W for 20min.

[0067] Comparative Example 3

[0068] This comparative example provides a wastewater treatment agent. The difference between this comparative example and Example 1 is that the carbon nanotubes are modified with amino groups instead of phenolic hydroxyl groups.

[0069] Test Case

[0070] The test results are shown in Table 1 below. The wastewater treatment agents prepared in the embodiments and comparative examples were analyzed using simulated wastewater: the wastewater was divided into several portions, and the wastewater treatment agents prepared in the embodiments and comparative examples were added respectively. Under natural light and a temperature of 25°C, the dosage of the wastewater treatment agent was 6 g / L. Sampling was performed every 10 minutes, and the COD removal rate of the wastewater was measured as shown in Table 2.

[0071] Table 1 Table 1 Water quality indicators of a chemical wastewater

[0072]

[0073] Table 2. Wastewater COD removal rate

[0074] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 98.1 96.7 97.1 80.1 78.2 77.5

[0075] The combination of modified carbon nanotubes and activated carbon has unique structure and properties. The introduction of modified carbon nanotubes increases the specific surface area of ​​activated carbon and strengthens its pore structure, thus achieving rapid aggregation of target pollutants, making the wastewater treatment process more efficient and significantly improving the COD removal effect. The phenolic hydroxyl group of phenol can effectively induce persulfate to produce sulfate radicals (SO4 - ), thereby enhancing the efficiency of the oxidation reaction. Comparative Example 1 lacks phenolic hydroxyl groups, and the reactivity is reduced, and the removal effect of organic matter (such as COD) in wastewater may be significantly weakened. Comparative Example 2 lacks borate and cannot form a complex with phenolic hydroxyl groups, and cannot promote the reaction with persulfate, resulting in a decrease in oxidation effect. During the oxidation process, boron ions help stabilize the reaction intermediates, prevent their premature degradation, and increase the removal rate of the final product. In Comparative Example 3, the amino group will not directly induce persulfate to produce sulfate radicals (SO4 - ) thus reducing the efficiency of the oxidation reaction.

Claims

1. A wastewater treatment agent, characterized in that: The raw materials for preparing the wastewater treatment agent include: modified carbon nanotubes, persulfate and activated carbon; The raw materials for preparing the modified carbon nanotubes include: carbon nanotubes, phenol and borate.

2. The wastewater treatment agent according to claim 1, characterized in that In parts by weight, the modified carbon nanotubes, the persulfate and the activated carbon are in a ratio of 1:0.01-0.5:2-5.

3. The wastewater treatment agent according to claim 1, characterized in that The borate includes at least one of calcium borate and sodium borate.

4. A method for preparing a wastewater treatment agent as claimed in any one of claims 1 to 3, characterized in that: include: The modified carbon nanotubes and persulfate are mixed and dispersed with activated carbon to obtain the product.

5. The method for preparing a wastewater treatment agent according to claim 4, characterized in that: The preparation method of the modified carbon nanotubes comprises: dispersing the carbon nanotubes after carboxylation, mixing with borate and phenol under heating conditions, and removing impurities to obtain the modified carbon nanotubes.

6. The method for preparing a wastewater treatment agent according to claim 5, characterized in that: The reaction temperature is 60-80°C.

7. The method for preparing a wastewater treatment agent according to claim 5, characterized in that: The carboxylation step comprises: mixing concentrated sulfuric acid and concentrated nitric acid, adding carbon nanotubes and potassium permanganate, reacting, removing impurities, and obtaining carboxylated carbon nanotubes.

8. The method for preparing a wastewater treatment agent according to claim 4, characterized in that: The weight ratio of the carbon nanotubes, the borate and the phenol is 1:0.01-0.5:0.1-0.

3.

9. The method for preparing a wastewater treatment agent according to claim 4, characterized in that: The mixing is performed under ultrasonic conditions.

10. The method for preparing a wastewater treatment agent according to claim 9, characterized in that: In step S2, the ultrasonic treatment conditions are: 100-300W ultrasonic treatment for 10-20min.

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