A method for preparing activated carbon to improve COD removal efficiency

Abstract

This invention provides a method for preparing activated carbon to improve COD removal efficiency, belonging to the field of activated carbon preparation technology. The method mainly involves the following steps: crushing coconut shells, soaking them in a saturated sodium chloride solution, evaporating and freeze-drying, carbonizing by heating, further activating by spraying with a saturated sodium chloride solution, soaking in a ferric nitrate solution, and then filtering and drying. This invention overcomes the shortcomings of existing technologies, and the activated carbon prepared can achieve high COD removal efficiency with a low dosage, comprehensively reducing the cost of wastewater treatment and making the activated carbon have a wider range of applications.

Description

Technical Field

[0001] This invention relates to the field of activated carbon preparation technology, and specifically to a method for preparing activated carbon to improve COD removal efficiency. Background Technology

[0002] Chemical Oxygen Demand (COD) is an important indicator of the content of organic matter and reducing inorganic matter in water bodies, reflecting the degree of organic pollution. COD is an indicator of the amount of reducing substances in water, which includes various organic substances, nitrites, sulfides, ferrous salts, etc., but mainly organic matter. Wastewater rich in organic matter is usually called organic wastewater. Organic wastewater easily causes eutrophication, which is quite harmful. This wastewater contains a large amount of organic matter such as carbohydrates, fats, proteins, and cellulose. If discharged directly, it will cause serious pollution. Some organic wastewater contains aromatic compounds and heterocyclic compounds, as well as sulfides, nitrogen compounds, heavy metals, and toxic organic matter. The wastewater has poor biodegradability and is toxic to microorganisms, making it difficult to treat with general biological methods.

[0003] Activated carbon is a substance that can effectively adsorb pollutants in water, especially organic or inorganic pollutants in sewage. Therefore, activated carbon is commonly used for sewage treatment at present. However, conventional activated carbon has poor adsorption effect and requires a large amount of activated carbon, which is relatively expensive for water purification. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for preparing activated carbon that improves COD removal efficiency. A higher COD removal efficiency can be achieved with a lower amount of activated carbon, thereby reducing the overall cost of wastewater treatment and enabling activated carbon to have a wider range of applications.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for preparing activated carbon to improve COD removal efficiency, the method comprising the following steps:

[0007] S1. Raw material pretreatment: Select coconut shells as raw materials, clean them and crush them, then soak them in sodium chloride solution, steam them and freeze dry them to obtain pretreated raw materials for later use.

[0008] S2. Preliminary carbonization: Place the above pretreated raw materials in a rotary kiln, heat to 400-500℃, and carbonize for 1-3 hours to obtain raw char for later use.

[0009] S3. Preliminary modification treatment: Place the above raw carbon material in a rotary kiln and heat it to 600-650℃. Then spray a saturated sodium chloride solution onto the surface of the raw carbon material. After heat treatment for 2-3 minutes, cool it down to 300-350℃ and spray a saturated sodium chloride solution once more. Then heat it for 10-20 minutes to obtain the preliminary modified carbon.

[0010] S4. Secondary modification: The pre-modified carbon is directly taken out and placed in an 80-100℃ ferric nitrate solution, stirred and treated, then allowed to cool naturally to room temperature, filtered and dried to obtain the finished activated carbon for later use.

[0011] Preferably, the size of the crushed coconut shell in step S1 is 0.1-1cm.

[0012] Preferably, in step S1, the sodium chloride solution is a saturated sodium chloride solution, and the soaking time is 4-6 hours.

[0013] Preferably, the steaming method in step S1 is to use hot steam at 102-120℃ for 20-30 minutes.

[0014] Preferably, in step S2, the heating method is to heat at a rate of 3-5℃ / min, and nitrogen is used to replace air in the entire rotary kiln for carbonization treatment.

[0015] Preferably, in step S3, the amount of saturated sodium chloride solution sprayed in a single application is 2-3 times the total volume of the original charcoal.

[0016] Preferably, the heating and cooling rates in step S3 are both 5-10℃ / min, and the entire preliminary modification process is carried out under nitrogen protection.

[0017] Preferably, the concentration of the ferric nitrate solution in step S4 is 2-4 mol / L.

[0018] Preferably, the drying method in step S4 is to dry to constant weight at a temperature of 100-120°C.

[0019] This invention provides a method for preparing activated carbon to improve COD removal efficiency, which has the following advantages compared with the prior art:

[0020] This invention uses coconut shells as raw materials for activated carbon production. Early soaking of coconut shells in brine followed by steaming and freeze-drying creates pores in the shell material. Subsequent carbonization yields biochar with uniform pores. Activation of the biochar with a saturated sodium chloride solution at high temperature further enriches the pores and enhances the adsorption effect. Finally, mixing with ferric nitrate solution, allowing it to stand, and then drying effectively improves the static adsorption efficiency of the activated carbon, thereby further enhancing its efficiency in removing COD from wastewater. Attached Figure Description

[0021] Figure 1 The images shown are electron microscope images of activated carbon prepared in the embodiments and comparative examples of the present invention, where a is the activated carbon prepared in Example 1; b is the activated carbon prepared in Comparative Example 1; c is the activated carbon prepared in Comparative Example 2; and d is the activated carbon prepared in Comparative Example 3. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1:

[0024] Preparation of activated carbon-1:

[0025] (1) Select coconut shell as raw material, clean it and crush it to a particle size of 0.1-1cm, then add sodium chloride saturated solution and soak at room temperature for 5 hours, then take it out and steam it under 110℃ hot steam for 25 minutes, then freeze dry to obtain pretreated raw material for use.

[0026] (2) Place the above pretreated raw materials in a rotary kiln, replace the air in the kiln with nitrogen, raise the temperature to 450°C at a rate of 3-5°C / min, and carbonize for 2 hours to obtain raw carbon material for later use.

[0027] (3) The above raw carbon material is kept in a rotary kiln (nitrogen atmosphere) and heated to 600°C at a rate of 5-10°C / min. Then, a sodium chloride saturated solution with a volume of 3 times the total volume of the raw carbon material is sprayed onto the surface of the raw carbon material and kept at the temperature for 3 min. Then, the temperature is lowered to 350°C at a rate of 5-10°C / min and a sodium chloride saturated solution with a volume of 2 times the total volume of the raw carbon material is sprayed onto the surface of the raw carbon material and kept at the temperature for 15 min to obtain the preliminary modified carbon.

[0028] (4) The above-mentioned pre-modified carbon was taken out while hot and placed in a 3 mol / L ferric nitrate solution at 100℃. After stirring and cooling naturally to room temperature, it was filtered and dried at 120℃ to constant weight to obtain activated carbon-1.

[0029] Comparative Example 1:

[0030] Preparation of activated carbon-2:

[0031] (1) Select coconut shells as raw materials, clean them and crush them to a particle size of 0.1-1cm. Then soak them in clean water at room temperature for 5 hours, take them out and steam them under 110℃ hot steam for 25 minutes, and then freeze dry them to obtain pre-treated raw materials for later use.

[0032] (2) Place the above pretreated raw materials in a rotary kiln, replace the air in the kiln with nitrogen, raise the temperature to 450°C at a rate of 3-5°C / min, and carbonize for 2 hours to obtain raw carbon material for later use.

[0033] (3) The above raw carbon material is kept in a rotary kiln (nitrogen atmosphere) and heated to 600°C at a rate of 5-10°C / min. Then, a sodium chloride saturated solution with a volume of 3 times the total volume of the raw carbon material is sprayed onto the surface of the raw carbon material and kept at the temperature for 3 min. Then, the temperature is lowered to 350°C at a rate of 5-10°C / min and a sodium chloride saturated solution with a volume of 2 times the total volume of the raw carbon material is sprayed onto the surface of the raw carbon material and kept at the temperature for 15 min to obtain the preliminary modified carbon.

[0034] (4) The above-mentioned pre-modified carbon was taken out while hot and placed in a 3 mol / L ferric nitrate solution at 100℃. After stirring and cooling naturally to room temperature, it was filtered and dried at 120℃ to constant weight to obtain activated carbon-2.

[0035] Comparative Example 2:

[0036] Preparation of activated carbon-3:

[0037] (1) Select coconut shells as raw materials, clean them and crush them to a particle size of 0.1-1cm to obtain pre-treated raw materials for later use;

[0038] (2) Place the above pretreated raw materials in a rotary kiln, replace the air in the kiln with nitrogen, raise the temperature to 450°C at a rate of 3-5°C / min, and carbonize for 2 hours to obtain raw carbon material for later use.

[0039] (3) The above raw carbon material is kept in a rotary kiln (nitrogen atmosphere) and heated to 600°C at a rate of 5-10°C / min. Then, a sodium chloride saturated solution with a volume of 3 times the total volume of the raw carbon material is sprayed onto the surface of the raw carbon material and kept at the temperature for 3 min. Then, the temperature is lowered to 350°C at a rate of 5-10°C / min and a sodium chloride saturated solution with a volume of 2 times the total volume of the raw carbon material is sprayed onto the surface of the raw carbon material and kept at the temperature for 15 min to obtain the preliminary modified carbon.

[0040] (4) The above-mentioned pre-modified carbon was taken out while hot and placed in a 3 mol / L ferric nitrate solution at 100℃. After stirring and cooling naturally to room temperature, it was filtered and dried at 120℃ to constant weight to obtain activated carbon-3.

[0041] Comparative Example 3:

[0042] Preparation of activated carbon-4:

[0043] (1) Select coconut shell as raw material, clean it and crush it to a particle size of 0.1-1cm, then add sodium chloride saturated solution and soak at room temperature for 5 hours, then take it out and steam it under 110℃ hot steam for 25 minutes, then freeze dry to obtain pretreated raw material for use.

[0044] (2) Place the above pretreated raw materials in a rotary kiln, replace the air in the kiln with nitrogen, raise the temperature to 450°C at a rate of 3-5°C / min, and carbonize for 2 hours to obtain raw carbon material for later use.

[0045] (3) The above raw carbon material is kept in a rotary kiln (nitrogen atmosphere) and heated to 600°C at a rate of 5-10°C / min. Then, 3 times the total volume of the raw carbon material is sprayed onto the surface of the raw carbon material with clean water and kept at the temperature for 3 min. Then, the temperature is lowered to 350°C at a rate of 5-10°C / min and 2 times the total volume of the raw carbon material is sprayed onto the surface of the raw carbon material with clean water and kept at the temperature for 15 min to obtain the preliminary modified carbon.

[0046] (4) The above-mentioned pre-modified carbon was taken out while hot and placed in a 3 mol / L ferric nitrate solution at 100℃. After stirring and cooling naturally to room temperature, it was filtered and dried at 120℃ to constant weight to obtain activated carbon-4.

[0047] Detection:

[0048] 1. The apparent morphology of activated carbon-1, activated carbon-2, activated carbon-3, and activated carbon-4 prepared above was analyzed, and the specific results are as follows: Figure 1 As shown, activated carbon-1 and activated carbon-4 ( Figure 1 a and Figure 1 d) It has more pores and a larger surface area, but the surface of activated carbon-4 has a plate-like structure that is somewhat different from that of activated carbon-1.

[0049] 2. Detection of COD removal efficiency of each group of activated carbon in wastewater:

[0050] Using the same batch of wastewater as experimental material, the COD content in the wastewater was measured to be 1132 mg / L. Different types of activated carbon were added to the wastewater at a dosage of 0.5 g / L, stirred evenly, and allowed to stand at room temperature. Samples were then taken at different times to detect the COD content in the wastewater, and the removal rate was calculated. The details are shown in Table 1 below.

[0051] Table 1

[0052]

[0053] As shown in the table above, the activated carbon prepared in Example 1 reached adsorption saturation in about 30 minutes, and the overall COD removal rate was over 92%. The final COD removal rate of Comparative Example 1 was about 90%, which was not much different from that of Example 1, but Comparative Example 1 only reached a certain saturation state after 60 minutes. The overall adsorption capacity and adsorption rate of Comparative Example 2 were also significantly lower than those of Example 1. In addition, the adsorption rate of Comparative Example 3 was slightly higher than that of Example 1 in the early stage, but the total adsorption capacity was lower than that of Example 1. In summary, the activated carbon in Example 1 has a better COD adsorption effect.

[0054] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing activated carbon to improve COD removal efficiency, characterized in that, The activated carbon preparation method includes the following steps: S1. Raw material pretreatment: Select coconut shells as raw materials, clean them and crush them, then soak them in sodium chloride solution, steam them and freeze dry them to obtain pretreated raw materials for later use. S2. Preliminary carbonization: Place the above pretreated raw materials in a rotary kiln, heat to 400-500℃, and carbonize for 1-3 hours to obtain raw char for later use. S3. Preliminary modification treatment: Place the above raw carbon material in a rotary kiln and heat it to 600-650℃. Then spray a saturated sodium chloride solution onto the surface of the raw carbon material. After heat treatment for 2-3 minutes, cool it down to 300-350℃ and spray a saturated sodium chloride solution once more. Then heat it for 10-20 minutes to obtain the preliminary modified carbon. S4. Secondary modification: The pre-modified carbon is directly taken out and placed in an 80-100℃ ferric nitrate solution, stirred and treated, then allowed to cool naturally to room temperature, filtered and dried to obtain the finished activated carbon for later use.

2. The preparation method according to claim 1, characterized in that: The size of the crushed coconut shell in step S1 is 0.1-1cm.

3. The preparation method according to claim 1, characterized in that: In step S1, the sodium chloride solution is a saturated sodium chloride solution, and the soaking time is 4-6 hours.

4. The preparation method according to claim 1, characterized in that: In step S1, the steaming method is to use hot steam at 102-120℃ for 20-30 minutes.

5. The preparation method according to claim 1, characterized in that: In step S2, the temperature is increased at a rate of 3-5℃ / min, and nitrogen is used to replace air in the entire rotary kiln for carbonization.

6. The preparation method according to claim 1, characterized in that: In step S3, the amount of saturated sodium chloride solution sprayed in a single application is 2-3 times the total volume of the original charcoal.

7. The preparation method according to claim 1, characterized in that: In step S3, the heating and cooling rates are both 5-10℃ / min, and the entire preliminary modification process is carried out under nitrogen protection.

8. The preparation method according to claim 1, characterized in that: The concentration of the ferric nitrate solution in step S4 is 2-4 mol / L.

9. The preparation method according to claim 1, characterized in that: In step S4, the drying method is to dry the product to a constant weight at a temperature of 100-120°C.

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