Preparation method of modified activated carbon and method for treating wastewater by using modified activated carbon

Abstract

The invention provides a preparation method of modified activated carbon and a method for treating wastewater with the modified activated carbon, and belongs to the technical field of wastewater treatment.The preparation method of the modified activated carbon comprises the steps that activated carbon is taken and activated, a cerous nitrate solution and a copper nitrate solution are added into the activated activated carbon, and the modified activated carbon is prepared through stirring, filtering and microwave irradiation; the method for treating the wastewater by using the modified activated carbon comprises the following steps: taking the wastewater, adjusting the initial pH value, adding the modified activated carbon, FeSO4. 7H2O and hydrogen peroxide, carrying out microwave irradiation, cooling, adjusting the pH value to be neutral, and standing to finish wastewater treatment. The modified activated carbon prepared by the method can well cooperate with a microwave Fenton method to promote rapid adsorption and oxidative degradation of organic matters, so that phenolic substances in wastewater are removed, and COD (Chemical Oxygen Demand) is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a method for preparing modified activated carbon and a method for treating wastewater using the modified activated carbon. Background Art

[0002] With the rapid economic development, the increasing science and technology and comprehensive strength, environmental problems have become increasingly prominent. Phenolic wastewater is wastewater mainly containing volatile phenol and non-volatile phenol in the industrial production process. Phenolic wastewater mainly comes from the chemical, petroleum, pharmaceutical and other industries. Among them, phenolic compounds such as phenol are highly toxic, difficult to be biodegraded, and easily accumulated in water bodies, posing a serious threat to aquatic organisms and human health. The increase of phenol content in phenolic wastewater will lead to an increase in COD. Therefore, it is very important to effectively treat phenolic wastewater and reduce COD.

[0003] At present, the methods for treating phenol-containing wastewater and reducing COD mainly include three categories: physical method, biological method and chemical method. Physical methods include adsorption method, extraction method, flocculation precipitation method and membrane separation method. However, the adsorption method for treating phenol-containing wastewater only completes the migration of organic matter from liquid phase to solid phase, and there are still problems such as poor adsorption capacity and secondary pollution caused by abandoned adsorbents; the extraction method is only suitable for wastewater treatment processes with single pollutants and high concentrations; using the extraction method to treat phenol-containing wastewater, it is easy to leave the extractant in the wastewater, and the extractant is an organic solvent. The extractant remaining in the wastewater still needs to be treated twice to meet the discharge requirements, affecting the subsequent treatment process; the flocculation precipitation method has the problem of large dosage, narrow pH application range and sediment removal when treating wastewater; the membrane separation method has the problem of membrane pollution in treating phenol-containing wastewater, and it is easy to cause membrane pore blockage during the use of the membrane, affecting the filtration effect of the membrane and even destroying the membrane structure, resulting in membrane failure. In the process of biological wastewater treatment, there are problems such as high pollutant concentration causing microbial death and organic pollutants inhibiting degradation efficiency due to their toxicity. Chemical methods generally refer to ozone oxidation and photocatalytic oxidation. The ozone oxidation method has the problem of expensive large ozone generators and high costs. The photocatalytic oxidation method has the problem of low light energy utilization.

[0004] Therefore, it is necessary to further develop treatment methods for phenolic wastewater in order to better reduce the COD in the wastewater while improving efficiency. Summary of the invention

[0005] In view of the above problems, the present invention provides a method for preparing modified activated carbon and a method for treating wastewater using modified activated carbon.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is:

[0007] A method for preparing modified activated carbon comprises the following steps: activating activated carbon, adding cerium nitrate solution and copper nitrate solution to the activated carbon, stirring, filtering and microwave irradiating to obtain the modified activated carbon.

[0008] Furthermore, the concentration of the cerium nitrate solution is 0.4-0.5 mol / L; the concentration of the copper nitrate solution is 0.5-0.6 mol / L.

[0009] Furthermore, the mass volume ratio of the activated activated carbon to the cerium nitrate solution and the copper nitrate solution is 1:4.5-5.5:4.5-5.5.

[0010] Furthermore, the power of microwave irradiation is above 700W.

[0011] Furthermore, the stirring time is more than 12 hours, and the microwave irradiation time is more than 5 minutes.

[0012] Furthermore, the activated carbon activation is to soak the activated carbon in a 5-8% dilute hydrochloric acid aqueous solution for 5-6 hours, then oscillate at room temperature for 10-12 hours, then boil for 30-40 minutes, wash with distilled water until the pH value is neutral, then heat until the activated carbon is in a nearly dry state, and finally dry at 105-110°C for 24-48 hours to obtain the activated activated carbon.

[0013] A method for treating wastewater using modified activated carbon prepared by the above preparation method, wherein the method comprises taking wastewater and adjusting the initial pH value, adding modified activated carbon, FeSO 4 7H 2 O and hydrogen peroxide, microwave irradiation, cooling, adjusting the pH to neutral, and standing to complete the wastewater treatment.

[0014] Furthermore, the initial pH value after adjustment is 4.0-5.0.

[0015] Furthermore, the power of microwave irradiation is above 500W.

[0016] Furthermore, the volume-to-weight ratio of wastewater to activated carbon is 100 mL: 0.15-0.3 g;

[0017] Wastewater and FeSO 4 7H 2 The volume-to-weight ratio of O is 100 mL: 60-80 mg;

[0018] The volume ratio of wastewater to hydrogen peroxide is 100:1.2-1.5;

[0019] The microwave irradiation time is more than 15 minutes;

[0020] The standing time is more than 30 minutes.

[0021] The beneficial effects of the method for preparing modified activated carbon and the method for treating wastewater with modified activated carbon of the present invention are:

[0022] The present invention adopts the microwave Fenton method. Through the action of microwaves, the reaction system can effectively increase the temperature, reduce the reaction activation energy, accelerate the reaction speed, and synergistically oxidize on the basis of the generation of hydroxyl radicals OH by the Fenton reagent, thereby increasing the speed and efficiency of generating hydroxyl radicals.

[0023] The present invention adds modified activated carbon to the wastewater treatment system, utilizes the heterogeneity of the modified activated carbon structure, forms more "hot spots" on its surface through microwave heating, and further promotes the Fenton reaction by combining the catalytic performance of the modified activated carbon surface, thereby effectively completing the adsorption and oxidative degradation of organic matter, and achieving the purpose of effectively removing COD in wastewater;

[0024] The modified activated carbon prepared by the present invention can cooperate well with the microwave Fenton method, promote the rapid adsorption and oxidative degradation of organic matter, remove phenolic substances in wastewater, and reduce COD. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a result diagram of the investigation of the concentration of the cerium nitrate solution in Example 6 of the present invention;

[0026] Figure 2 This is a graph showing the results of the investigation of the concentration of the copper nitrate solution in Example 6 of the present invention;

[0027] Figure 3 This is a result diagram of the investigation of the power of microwave irradiation during the preparation of modified activated carbon in Example 6 of the present invention;

[0028] Figure 4 This is a result diagram of the investigation of the amount of modified activated carbon used and the microwave irradiation time in the wastewater treatment process in Example 7 of the present invention;

[0029] Figure 5 This is a result diagram of the initial pH value investigation during the wastewater treatment process in Example 7 of the present invention;

[0030] Figure 6 This is a graph showing the results of a power study of microwave irradiation during wastewater treatment in Example 7 of the present invention. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention are described clearly and completely below. In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0032] Example 1 A method for preparing modified activated carbon and a method for treating wastewater using modified activated carbon

[0033] This embodiment is a method for preparing modified activated carbon and a method for treating wastewater using modified activated carbon, which are specifically as follows:

[0034] 1. Preparation method of modified activated carbon

[0035] S1. Take activated carbon and soak it in a 5wt% dilute hydrochloric acid aqueous solution for 5 hours, then put it in a constant temperature shaking incubator, shake it at room temperature for 10 hours, take it out and boil it on an electric stove for 30 minutes, wash it with distilled water until the pH value is neutral, and then heat it on an electric stove until the activated carbon is nearly dry. Finally, put it in an oven and dry it at 105°C for 24 hours, cool it, and obtain the activated carbon for use.

[0036] S2. Weigh 10 g of activated activated carbon, add 50 mL of 0.45 mol / L cerium nitrate solution and 50 mL of 0.55 mol / L copper nitrate solution, stir for 12 h, filter, place in a microwave reactor, irradiate with 800 W microwaves for 5 min, cool, and obtain modified activated carbon.

[0037] 2. Method for treating wastewater using the modified activated carbon

[0038] Take 100 mL of the secondary sedimentation water after biochemical treatment (COD value is 715 mg / L), adjust the pH value to 4.5 with HCl (i.e. the initial pH value is 4.5), add 0.2 g of modified activated carbon, 70 mg of FeSO 4 7H 2 O and 1.2mL of 30% hydrogen peroxide, shake well, put it in a microwave reactor, irradiate it with 600W microwave for 15min, cool it to room temperature, adjust the pH to neutral, let it stand for 30min, separate the supernatant, and the wastewater treatment is completed. The COD value of the supernatant is 33mg / L, and the removal rate is 95.38%.

[0039] Embodiments 2 to 5 Method for preparing modified activated carbon and method for treating wastewater using modified activated carbon

[0040] Examples 2 to 5 are respectively a method for preparing modified activated carbon and a method for treating wastewater using modified activated carbon, which are basically the same as Example 1, except that some process parameters are different, as shown in Table 1:

[0041] Table 1 List of process parameters in Examples 2 to 5

[0042]

[0043]

[0044] The contents and results of other parts of Examples 2 to 5 are the same as those of Example 1 and will not be repeated here.

[0045] Example 6 Investigation of process parameters in the preparation of modified activated carbon

[0046] In this example, various process conditions in the preparation process of modified activated carbon in Example 1 are investigated. During the investigation, the preparation method of modified activated carbon is basically the same as the preparation method in Example 1, and the method for treating wastewater using the above-mentioned modified activated carbon is the same as the method in Example 1.

[0047] 1. Investigation of the concentration of cerium nitrate solution

[0048] After the same batch of activated carbon was activated, it was modified with cerium nitrate solutions of concentrations of 0 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, and 0.8 mol / L, respectively (i.e., only the concentration of the cerium nitrate solution in Example 1 was changed, and other conditions remained unchanged) to prepare modified activated carbons corresponding to cerium nitrate solutions of different concentrations. The modified activated carbons corresponding to cerium nitrate solutions of different concentrations were then used to treat the same batch of biochemical secondary sedimentation effluents, and the treatment results are shown in Tables 2 and 3. Figure 1 .

[0049] Table 2 Summary of the results of the investigation on the concentration of cerium nitrate solution

[0050]

[0051]

[0052] From Table 2 and Figure 1 It can be seen that with the increase in the concentration of the cerium nitrate solution for preparing the modified activated carbon, the removal rate of COD in the wastewater by the modified activated carbon prepared therefrom is significantly improved, but when a certain concentration is exceeded, the removal rate of COD in the wastewater will decrease instead. This may be because when the concentration of the cerium nitrate solution is too low, the cerium nitrate attached to the surface of the activated carbon is low, resulting in a decrease in the catalytic effect of the modified activated carbon, while when the concentration of the cerium nitrate solution is too high, the amount of cerium nitrate attached to the surface of the activated carbon increases, but the content of copper nitrate attached is reduced in disguise, thereby resulting in a decrease in the catalytic effect of the modified activated carbon. Therefore, the present invention selects a 0.4-0.5 mol / L cerium nitrate solution with a better effect to prepare the modified activated carbon.

[0053] 2. Investigation of copper nitrate solution concentration

[0054] After the same batch of activated carbon was activated, it was modified with copper nitrate solutions of concentrations of 0 mol / L, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, and 0.8 mol / L, respectively (i.e., only the concentration of the copper nitrate solution in Example 1 was changed, and other conditions remained unchanged) to prepare modified activated carbons corresponding to copper nitrate solutions of different concentrations. The modified activated carbons corresponding to copper nitrate solutions of different concentrations were then used to treat the same batch of biochemical secondary sedimentation effluents, and the treatment results are shown in Tables 3 and 4. Figure 2 .

[0055] Table 3. Results of investigation on copper nitrate solution concentration

[0056]

[0057]

[0058] From Table 3 and Figure 2 It can be seen that as the concentration of the copper nitrate solution for preparing the modified activated carbon increases, the removal rate of COD in the wastewater by the modified activated carbon prepared therefrom is significantly improved, but when a certain concentration is exceeded, the removal rate of COD in the wastewater will decrease instead. This may be because when the concentration of the copper nitrate solution is too low, the copper nitrate attached to the surface of the activated carbon is low, resulting in a decrease in the catalytic effect of the modified activated carbon, and when the concentration of the copper nitrate solution is too high, although the amount of copper nitrate attached to the surface of the activated carbon increases, it will cause the content of the attached cerium nitrate to decrease in disguise, thereby resulting in a decrease in the catalytic effect of the modified activated carbon. Therefore, the present invention selects a copper nitrate solution of 0.5 to 0.6 mol / L with a better effect to prepare the modified activated carbon.

[0059] 3. Investigation of microwave irradiation power during the preparation of modified activated carbon

[0060] After activation, the same batch of activated carbon was modified at powers of 0 W, 100 W, 200 W, 300 W, 400 W, 500 W, 600 W, 700 W, 800 W, 900 W, and 1000 W (i.e., only the power of microwave irradiation in the preparation process of modified activated carbon in Example 1 was changed, and other conditions remained unchanged) to prepare modified activated carbons corresponding to different powers. The modified activated carbons corresponding to different powers were then used to treat the same batch of biochemical secondary sedimentation effluents. The treatment results are shown in Tables 4 and Figure 3 .

[0061] Table 4 Summary of the results of microwave irradiation power investigation during the preparation of modified activated carbon

[0062]

[0063] From Table 4 and Figure 3It can be seen that in the process of preparing modified activated carbon, the power of microwave irradiation has a great influence on the COD removal effect of modified activated carbon. In order to save energy consumption, the present invention preferably uses a power of 700-800W for microwave irradiation to prepare modified activated carbon, so that COD in the secondary sedimentation effluent after biochemical treatment can be well removed.

[0064] Example 7 Investigation of process parameters in wastewater treatment using modified activated carbon

[0065] This example investigates various process conditions in the process of treating wastewater with modified activated carbon in Example 1. During the investigation, wastewater is treated with the modified activated carbon prepared in Example 1, wherein the method for treating wastewater is basically the same as the method in Example 1.

[0066] 1. Investigation of the amount of modified activated carbon and microwave irradiation time in wastewater treatment

[0067] The same batch of biochemical secondary sedimentation effluent was taken, and the modified activated carbon prepared in Example 1 was used to investigate the effect of different modified activated carbon addition amounts on the wastewater treatment effect after microwave irradiation for 5, 10, 15, 20, and 30 minutes (that is, only the amount of modified activated carbon and the microwave irradiation time in the wastewater treatment process of Example 1 were changed, and other conditions remained unchanged). The addition amounts of different modified activated carbon were 0g, 0.05g, 0.1g, 0.15g, 0.2g, 0.25g and 0.3g, respectively. The treatment results are shown in Tables 5 and Figure 4 .

[0068] Table 5 Results of investigation on dosage of modified activated carbon and microwave irradiation time

[0069]

[0070] From Table 5 and Figure 4 It can be seen that the amount of modified activated carbon has a great influence on the reaction rate, and the appropriate amount of modified activated carbon is explored to maximize the efficiency of modified activated carbon. When the amount of modified activated carbon is different, under the same reaction conditions, the COD removal rate increases with the increase of the amount of modified activated carbon. When the amount of modified activated carbon exceeds 0.2g, the COD removal rate no longer increases significantly and reaches a balance. During the reaction process, the amount of modified activated carbon has a great influence on the reaction rate. The larger the amount, the faster the reaction rate. It can provide more "hot spots" combined with the catalytic properties of the surface of modified activated carbon to promote the rapid oxidation and decomposition of wastewater, but when the amount reaches a certain amount, the reaction rate no longer changes significantly with the increase of the amount of modified activated carbon. Therefore, the present invention selects 0.15-0.2g of modified activated carbon and 15min of microwave irradiation time for wastewater treatment.

[0071] 2. Initial pH value investigation

[0072] The same batch of biochemical secondary sedimentation effluent was taken, and the modified activated carbon prepared in Example 1 was used to investigate the effect of different initial pH values ​​on the wastewater treatment effect (that is, only the initial pH value in the wastewater treatment process of Example 1 was changed, and other conditions remained unchanged). The different initial pH values ​​were 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, and 10.0. The treatment results are shown in Tables 6 and Figure 5 .

[0073] Table 6 Summary of initial pH value investigation results

[0074]

[0075] From Table 6 and Figure 5 It can be seen that the initial pH value affects the surface properties of modified activated carbon and the generation of free radicals, and is an important factor in the wastewater treatment process. In the wastewater treatment process, when the initial pH value is 4.0-5.0, the COD removal effect is significantly better than the COD removal effect of other initial pH values. This may be because in the wastewater treatment process, the initial pH value is reduced to a certain range, the acidity of the solution is enhanced, and the H + The concentration is too high, which hinders the catalytic reaction during the reaction process and the treatment effect is poor. When the initial pH value is 4.0-5.0, the COD removal rate of the wastewater reaches a better removal effect. The addition of modified activated carbon changes the pH range of the traditional Fenton reaction. Within a certain pH range, H 2 O 2 In Fe 2+ In the presence of hydroxyl radicals ·OH with strong oxidizing ability, more other active oxygen species are generated to achieve COD degradation in wastewater. When the initial pH value is too high, the surface properties of the modified activated carbon will be changed, resulting in a decrease in the catalytic performance of the modified activated carbon. Therefore, the present invention selects an initial pH value of 4.0 to 5.0 for wastewater treatment.

[0076] 3. Investigation of microwave irradiation power in wastewater treatment

[0077] The same batch of biochemical secondary sedimentation effluent was taken, and the modified activated carbon prepared in Example 1 was used to investigate the effects of different microwave irradiation powers on the wastewater treatment effect during the wastewater treatment process (i.e., only the microwave irradiation power in the wastewater treatment process of Example 1 was changed, and other conditions remained unchanged). The different microwave irradiation powers were 0W, 100W, 200W, 300W, 400W, 500W, 600W, 700W, and 800W. The treatment results are shown in Tables 7 and Figure 6 .

[0078] Table 7 Summary of the results of microwave irradiation power investigation during wastewater treatment

[0079]

[0080] From Table 7 and Figure 6 It can be seen that the power of microwave irradiation affects the activation energy of the reaction and is a relatively important factor in the process of treating wastewater. In the process of wastewater treatment, as the microwave irradiation power increases, the treatment effect of wastewater increases significantly. This is because microwaves heat up quickly in a relatively short period of time at the beginning. The higher the irradiation power, the faster the temperature rises, and the pollutants are more easily degraded. However, the greater the microwave irradiation power, the higher the energy consumption, and microwave irradiation at a power of 500W can achieve a better COD removal rate. Therefore, the present invention uses 500-600W power for microwave irradiation, which can effectively remove COD in the secondary sedimentation effluent after biochemical treatment.

[0081] Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A method for preparing modified activated carbon, characterized in that: The preparation method comprises the following steps: activating the activated carbon, adding a cerium nitrate solution and a copper nitrate solution to the activated carbon, stirring, filtering and microwave irradiating the activated carbon to obtain the modified activated carbon.

2. The method for preparing modified activated carbon according to claim 1, characterized in that: The concentration of the cerium nitrate solution is 0.4-0.5 mol / L; the concentration of the copper nitrate solution is 0.5-0.6 mol / L.

3. The method for preparing modified activated carbon according to claim 1 or 2, characterized in that: The mass volume ratio of the activated activated carbon to the cerium nitrate solution and the copper nitrate solution is 1:4.5-5.5:4.5-5.

5.

4. The method for preparing modified activated carbon according to claim 1 or 2, characterized in that: The power of microwave irradiation is above 700W.

5. The method for preparing modified activated carbon according to claim 1 or 2, characterized in that: The stirring time is more than 12 hours, and the microwave irradiation time is more than 5 minutes.

6. The method for preparing modified activated carbon according to claim 1 or 2, characterized in that: The activated carbon activation is to soak the activated carbon in a 5-8% dilute hydrochloric acid aqueous solution for 5-6 hours, then oscillate at room temperature for 10-12 hours, then boil for 30-40 minutes, wash with distilled water until the pH value is neutral, then heat until the activated carbon is nearly dry, and finally dry at 105-110° C. for 24-48 hours to obtain the activated carbon.

7. A method for treating wastewater using modified activated carbon prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: adjusting the initial pH value of wastewater, adding modified activated carbon, FeSO4·7H2O and hydrogen peroxide, irradiating with microwaves, cooling, adjusting the pH value to neutral, and standing to complete the wastewater treatment.

8. The method for treating wastewater with modified activated carbon according to claim 7, characterized in that: The initial pH value after adjustment is 4.0-5.

0.

9. The method for treating wastewater with modified activated carbon according to claim 7 or 8, characterized in that: The power of microwave irradiation is above 500W.

10. The method for treating wastewater with modified activated carbon according to claim 7 or 8, characterized in that: The volume-to-weight ratio of wastewater to activated carbon is 100 mL: 0.15-0.3 g; The volume-to-weight ratio of wastewater to FeSO4·7H2O is 100mL: 60-80mg; The volume ratio of wastewater to hydrogen peroxide is 100:1.2-1.5; The microwave irradiation time is more than 15 minutes; The standing time is more than 30 minutes.

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