A method for regenerating hazardous waste activated carbon
Through the combination of high-temperature pyrolysis, chemical complexing and microwave irradiation, the problem of poor regeneration effect of hazardous waste activated carbon was successfully solved, and an efficient and simple regeneration process was achieved, which improved the regeneration efficiency and reduced the operational complexity.
Patent Information
- Application Number
- CN202410344819.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-25
- Publication Date
- 2025-01-03
- Estimated Expiration
- 2044-03-25
AI Technical Summary
In the prior art, the regeneration method of hazardous waste activated carbon varies greatly and requires selective treatment. There is a lack of a method with simple operation and excellent treatment effect to alleviate the pressure of hazardous waste treatment.
Using a combination of high-temperature pyrolysis, chemical complex degradation and microwave irradiation, high-temperature pyrolysis is performed through ball milled hazardous waste activated carbon, and then mixed with a composite treatment solution composed of citric acid, tartaric acid, etc., to remove heavy metal elements by microwave irradiation. , and roast at high temperature in a low oxygen environment to meet the standards of reactive carbon.
The rapid regeneration of hazardous waste activated carbon is achieved, with the initial regeneration efficiency of up to 89%, and the regeneration efficiency of over 60% is still maintained after 10 regenerations, which simplifies operation and significantly improves the treatment effect.
Smart Images
Figure CN118162120B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of hazardous waste treatment, and specifically discloses a method for regenerating hazardous waste activated carbon. Background Art
[0002] Activated carbon is a porous material made from carbon-rich materials. It has the advantages of high mechanical strength, large specific surface area, and excellent pore structure. Activated carbon is widely used in industrial pollution treatment, waste disposal, and environmental remediation, especially in air purification, wastewater treatment, and heavy metal adsorption. However, the pore structure of activated carbon that has adsorbed pollutants is blocked, resulting in a significant decrease or complete loss of adsorption capacity. It no longer meets the original process conditions and requirements and is discarded, forming solid hazardous waste over time. In particular, hazardous activated carbon that has treated industrial wastewater has adsorbed a variety of impurities such as organic matter and heavy metals, and must be regenerated before it can be used as a resource. If improperly disposed, it is very easy to cause pollutants to desorb and cause secondary pollution. Therefore, the treatment of hazardous activated carbon has become a problem that scientists need to solve urgently.
[0003] In the prior art, the regeneration methods for hazardous waste activated carbon include pyrolysis treatment, chemical treatment, biological treatment, oxidation treatment, catalytic treatment and microwave treatment, but each has its own advantages and disadvantages. Pyrolysis treatment is only applicable to the treatment of waste activated carbon that adsorbs a single volatile organic or easily decomposable organic matter, and its application scope is limited. The selection range of chemical treatment is narrow, and there will be problems of incomplete treatment. Biological treatment can only degrade soluble organic matter with good biodegradability, the degradation process is slow and inefficient, and the metabolic products of microorganisms are easy to block the pore channels of activated carbon, so the application of biological treatment is extremely limited. Catalytic treatment requires catalytic treatment under specific conditions, and the treatment time is long, and the treatment effect is poor. As a new treatment method, microwave treatment lacks research on the mechanism of microwave treatment of hazardous waste activated carbon. Therefore, the development of a regeneration method for hazardous waste activated carbon that is simple and effective to operate and has excellent treatment effect is of great practical significance for alleviating the pressure of hazardous waste treatment. Summary of the invention
[0004] In view of the problem that the treatment effects of methods for treating hazardous waste activated carbon in the prior art vary greatly and that the hazardous waste activated carbon needs to be selectively treated, the present invention provides a method for regenerating hazardous waste activated carbon.
[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:
[0006] The first aspect of the present invention provides a method for regenerating hazardous waste activated carbon, the treatment method comprising the following steps:
[0007] Step 1: ball-mill the hazardous waste activated carbon, heat it to 930-950°C for high-temperature pyrolysis, and obtain primary activated carbon;
[0008] Step 2, the primary activated carbon and the composite treatment liquid are mixed evenly, microwave irradiated at a microwave power of 1000W-5000W, solid-liquid separation, and drying to obtain intermediate activated carbon;
[0009] Step 3: immerse the intermediate activated carbon in a strong alkaline solution at 70-90°C, screen it, and calcine the sieved material at a high temperature of 250-350°C in a low oxygen environment to obtain the treated regenerated activated carbon.
[0010] The composite treatment solution comprises the following raw material components in percentage by mass: 1%-5% of citric acid, 1%-5% of tartaric acid, 5%-10% of persulfate, 5%-10% of hydrogen peroxide and the balance of water.
[0011] Preferably, the hazardous waste activated carbon is any one or more of activated carbon used to treat dye wastewater, activated carbon used to treat mining wastewater, or activated carbon used to treat laboratory wastewater.
[0012] Further preferably, the COD value of the dye wastewater, mining wastewater or laboratory wastewater is ≥3000 mg / L.
[0013] Compared with the prior art, the present invention firstly performs high-temperature pyrolysis treatment on the hazardous waste activated carbon after ball milling, and preliminarily degrades the organic matter adsorbed in the pores of the activated carbon. The obtained primary activated carbon still contains a large amount of heavy metal elements and some residual organic matter; then, the present invention mixes the primary activated carbon with an acidic composite treatment liquid, and uses citric acid and tartaric acid as complexing agents to complex the heavy metal elements to obtain a heavy metal complex; under microwave irradiation, the persulfate and hydrogen peroxide in the composite treatment liquid will break the heavy metal complex and then transform and remove it, thereby achieving the purpose of removing heavy metal elements in the activated carbon. In addition, the microwave energy generated by microwave irradiation further promotes the degradation ability of persulfate, so that it can achieve efficient removal of heavy metal elements in a shorter time. At the same time, the hydroxyl radicals and persulfate radicals generated by the persulfate itself have strong oxidizing properties, and can degrade the organic matter that is not completely removed while removing the heavy metal elements; finally, the activated carbon from which the organic matter and heavy metal elements have been removed is activated to meet the standards of regenerated activated carbon.
[0014] The present invention utilizes high temperature pyrolysis, chemical complexation degradation and microwave irradiation to successfully achieve the purpose of treating and regenerating hazardous waste activated carbon containing a large amount of toxic and harmful organic matter and heavy metal elements. The present invention provides a method for regenerating hazardous waste activated carbon, which can quickly activate and regenerate hazardous waste activated carbon in a short time, is easy to operate and has excellent treatment effect, and provides a practical idea for the regeneration of hazardous waste activated carbon.
[0015] Preferably, in step one, the temperature is raised in stages, wherein the temperature is raised to 230-260°C and kept warm for 20-50 minutes in the first stage; the temperature is raised to 560-590°C and kept warm for 30-100 minutes in the second stage; and the temperature is raised to 930-950°C in the third stage.
[0016] Preferably, in step 1, the high temperature pyrolysis time is 30-50 min.
[0017] Further preferably, the staged heating is performed by programmed heating, wherein the heating rate of the first stage is 5-10°C / min; the heating rate of the second stage is 10-15°C / min; and the heating rate of the third stage is 20-25°C / min.
[0018] The present invention adopts a staged heating method to perform high-temperature pyrolysis, uses a specific heating rate to heat to a specific temperature and then keeps the temperature, uses different temperatures to harmlessly treat organic matter of different components in hazardous waste activated carbon, and degrades the organic matter to the greatest extent. Different heating rates cause the pore structure of hazardous waste activated carbon to expand slowly, which is more conducive to degrading impurities and organic matter adsorbed in the pores.
[0019] Preferably, in step 1, the rotation speed of the ball mill is 250-400 rpm, and the ball milling time is 140-180 min.
[0020] Preferably, in step 2, the mass volume ratio of the primary activated carbon to the composite treatment liquid is 1g:2mL-3mL.
[0021] Preferably, in step 2, the microwave irradiation time is 40-70 min.
[0022] Microwave irradiation will generate a certain amount of microwave energy, which will prompt the persulfate in the composite treatment solution to release more oxidative free radicals, thereby achieving the purpose of completely degrading heavy metal elements and residual organic matter.
[0023] Preferably, in step 2, the persulfate is any one or more of ammonium persulfate, sodium persulfate or potassium persulfate.
[0024] Preferably, in step 2, the drying temperature is 80-100° C., and the drying time is 3-6 hours.
[0025] Preferably, in step three, the strong alkaline solution is any one or both of a 0.5-1 mol / L sodium hydroxide solution or a 0.5-1 mol / L potassium hydroxide solution.
[0026] Further preferably, in step three, the mass volume ratio of the intermediate activated carbon to the alkaline solution is 1g:3mL-5mL.
[0027] Preferably, in step three, the oxygen content of the hypoxic environment is 5%-8%.
[0028] Preferably, in step three, the high temperature calcination time is 1.5-3h.
[0029] High temperature roasting in a low oxygen environment can reduce equipment requirements and save operating costs.
[0030] A second aspect of the present invention provides a regenerated activated carbon, which is obtained by treating hazardous waste activated carbon using the hazardous waste activated carbon regeneration method.
[0031] In summary, in view of the large differences in treatment effects of hazardous waste activated carbon treatment methods in the prior art and the need to selectively treat hazardous waste activated carbon, the present invention proposes a new method for regenerating hazardous waste activated carbon. The present invention combines high-temperature pyrolysis, chemical complex degradation and microwave irradiation methods to regenerate hazardous waste activated carbon that has adsorbed a large amount of organic matter and heavy metal elements in wastewater in a short period of time. The resulting regenerated activated carbon can be regenerated repeatedly, and the initial regeneration efficiency is as high as 89% or more. After 10 regenerations, the regeneration efficiency of the resulting regenerated activated carbon is still as high as 60% or more. BRIEF DESCRIPTION OF THE DRAWINGS
[0032] Figure 1 This is a relationship diagram between the regeneration times and regeneration efficiency of the regenerated activated carbon obtained in Examples 1-3 and Comparative Examples 1-2. DETAILED DESCRIPTION
[0033] The technical solutions in the embodiments of the present invention are described clearly and completely below. 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, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0034] Example 1
[0035] This embodiment provides a method for regenerating hazardous waste activated carbon, which specifically includes the following contents.
[0036] Step 1: 500 g of hazardous waste activated carbon was heated to 940 ° C for high-temperature pyrolysis at a ball mill speed of 350 rpm for 150 min in a staged heating manner, wherein the first stage was heated to 250 ° C at a heating rate of 10 ° C / min and kept warm for 35 min; then heated to 580 ° C at a heating rate of 15 ° C / min and kept warm for 80 min; finally, heated to 940 ° C at a heating rate of 24 ° C / min, kept warm for 40 min, and cooled to room temperature to obtain 442 g of primary activated carbon;
[0037] Step 2: Evenly mix the primary activated carbon with 1100 mL of the composite treatment liquid, irradiate the mixture at a microwave power of 3500 W for 55 min, separate the solid and liquid, and dry the mixture at 90° C. for 3 h to obtain 401 g of intermediate activated carbon; wherein the composite treatment liquid comprises the following raw material components in percentage by weight: 3% citric acid, 4% tartaric acid, 8% ammonium persulfate, 6% hydrogen peroxide and 79% water.
[0038] Step 3: Immerse the intermediate activated carbon in 1400 mL of 0.5 mol / L sodium hydroxide solution at 85°C, sieve, and calcine the sieve material at 8% oxygen content and 320°C for 2.5 hours to obtain treated regenerated activated carbon.
[0039] Example 2
[0040] This embodiment provides a method for regenerating hazardous waste activated carbon, which specifically includes the following contents.
[0041] Step 1, 500g of hazardous waste activated carbon was heated to 930°C for high-temperature pyrolysis at a ball mill speed of 300rpm for 150min in a staged heating manner, wherein the first stage was heated to 230°C at a heating rate of 5°C / min and kept warm for 50min; then heated to 550°C at a heating rate of 10°C / min and kept warm for 100min; finally heated to 930°C at a heating rate of 20°C / min, kept warm for 35min, and cooled to room temperature to obtain 435g of primary activated carbon;
[0042] Step 2: Evenly mix the primary activated carbon with 1000 mL of the composite treatment liquid, irradiate the mixture at a microwave power of 4000 W for 60 min, separate the solid and liquid, and dry the mixture at 85° C. for 4 h to obtain 386 g of intermediate activated carbon; wherein the composite treatment liquid comprises the following raw material components in percentage by weight: 4% citric acid, 5% tartaric acid, 6% sodium persulfate, 7% hydrogen peroxide and 68% water.
[0043] Step 3: Immerse the intermediate activated carbon in 1500 mL of a 0.8 mol / L sodium hydroxide solution at 90° C., sieve, and calcine the sieved material at a high temperature of 300° C. for 3 h at an oxygen content of 5% to obtain the treated regenerated activated carbon.
[0044] Example 3
[0045] This embodiment provides a method for regenerating hazardous waste activated carbon, which specifically includes the following contents.
[0046] Step 1: 500 g of hazardous waste activated carbon was heated to 950 ° C for high-temperature pyrolysis at a ball mill speed of 400 rpm for 140 min in a staged heating manner, wherein the first stage was heated to 240 ° C at a heating rate of 8 ° C / min and kept warm for 50 min; then heated to 560 ° C at a heating rate of 10 ° C / min and kept warm for 75 min; finally, heated to 940 ° C at a heating rate of 20 ° C / min, kept warm for 50 min, and cooled to room temperature to obtain 428 g of primary activated carbon;
[0047] Step 2: Evenly mix the primary activated carbon with 1050 mL of the composite treatment liquid, irradiate the mixture at a microwave power of 4500 W for 55 min, separate the solid and liquid, and dry the mixture at 90° C. for 3 h to obtain 394 g of intermediate activated carbon; wherein the composite treatment liquid comprises the following raw material components in percentage by weight: 2% of citric acid, 5% of tartaric acid, 7% of potassium persulfate, 8% of hydrogen peroxide and 78% of water.
[0048] Step 3: Immerse the intermediate activated carbon in 1800 mL of 0.5 mol / L sodium hydroxide solution at 85°C, sieve, and calcine the sieve material at 300°C for 2 hours at an oxygen content of 6% to obtain the treated regenerated activated carbon.
[0049] Comparative Example 1
[0050] This comparative example provides a method for regenerating hazardous waste activated carbon, which differs from Example 1 in that the composite treatment liquid is replaced with an ammonium persulfate solution, and specifically includes the following contents.
[0051] Step 1: 500 g of hazardous waste activated carbon was heated to 940 ° C for high-temperature pyrolysis at a ball mill speed of 350 rpm for 150 min in a staged heating manner, wherein the first stage was heated to 250 ° C at a heating rate of 10 ° C / min and kept warm for 35 min; then heated to 580 ° C at a heating rate of 15 ° C / min and kept warm for 80 min; finally, heated to 940 ° C at a heating rate of 24 ° C / min, kept warm for 40 min, and cooled to room temperature to obtain 442 g of primary activated carbon;
[0052] Step 2: Evenly mix the primary activated carbon with 1100 mL of ammonium persulfate solution, irradiate with microwaves at a microwave power of 3500 W for 55 min, separate the solid from the liquid, and dry at 90° C. for 3 h to obtain 386 g of intermediate activated carbon;
[0053] Step 3: Immerse the intermediate activated carbon in 1400 mL of 0.5 mol / L sodium hydroxide solution at 85°C, sieve, and calcine the sieve material at 8% oxygen content and 320°C for 2.5 hours to obtain treated regenerated activated carbon.
[0054] Comparative Example 2
[0055] This comparative example provides a method for regenerating hazardous waste activated carbon, which is different from Example 1 in that the hazardous waste activated carbon is not subjected to high-temperature pyrolysis treatment, and specifically includes the following contents.
[0056] Step 1: Evenly mix 442 g of hazardous waste activated carbon and 1100 mL of composite treatment liquid, irradiate with microwaves at a microwave power of 3500 W for 55 min, separate the solid and liquid, and dry at 90° C. for 3 h to obtain 394 g of intermediate activated carbon; wherein the composite treatment liquid includes the following raw material components in percentage by weight: 3% of citric acid, 4% of tartaric acid, 8% of ammonium persulfate, 6% of hydrogen peroxide and 79% of water.
[0057] Step 3: Immerse the intermediate activated carbon in 1400 mL of 0.5 mol / L sodium hydroxide solution at 85°C, sieve, and calcine the sieve material at 8% oxygen content and 320°C for 2.5 hours to obtain treated regenerated activated carbon.
[0058] Comparative Example 3
[0059] This comparative example provides a kind of fresh activated carbon before treating the wastewater in Example 1.
[0060] Comparative Example 4
[0061] This comparative example provides an untreated hazardous waste activated carbon obtained after wastewater treatment in Example 1.
[0062] In order to further demonstrate the technical effect of the present invention, the present invention conducted performance tests on the regenerated activated carbon obtained in Examples 1-3 and Comparative Examples 1-2, and conducted iodine adsorption value tests on the obtained regenerated activated carbon according to the method described in the national standard GB / T12496.22-1999. The test results are shown in Table 1.
[0063] Table 1 Test results 1
[0064] project Iodine adsorption value (mg / g) Example 1 1346.1 Example 2 1279.3 Example 3 1245.7 Comparative Example 1 987.8 Comparative Example 2 906.4 Comparative Example 3 1499.2 Comparative Example 4 462.7
[0065] The present invention also conducts a regeneration efficiency test on the regenerated activated carbon obtained in Examples 1-3 and Comparative Examples 1-2, with Comparative Example 3 as the control group. The specific testing method is as follows: 2 g of the regenerated activated carbon obtained in Examples 1-3 and Comparative Examples 1-2 or the activated carbon in the control group is placed in a 500 mL conical flask, 250 mL of dye wastewater with a measured COD value is added, and the two are mixed evenly at a speed of 150 rpm, and kept for 3 hours, the COD value of the dye wastewater after treatment is measured, and the removal rate is calculated. The regeneration efficiency of the regenerated activated carbon is calculated according to the removal rate. The calculation formula of the regeneration efficiency is as follows, and the calculation results are shown in Table 2.
[0066] Regeneration efficiency = (removal efficiency of regenerated activated carbon / removal efficiency of fresh activated carbon) × 100%
[0067] Table 2 Test results 2
[0068] project Regeneration efficiency (%) Example 1 89.79 Example 2 85.33 Example 3 83.09 Comparative Example 1 65.89 Comparative Example 2 60.46 Comparative Example 3 /
[0069] For regenerated activated carbon, whether it can be repeatedly regenerated and used is an important indicator. Based on this, the present invention tests the number of regeneration times of the regenerated activated carbon obtained in Examples 1-3 and Comparative Examples 1-2. The specific operation is as follows: 500g of the regenerated activated carbon obtained in Examples 1-3 and Comparative Examples 1-2 is placed in an activated carbon adsorption tower to adsorb dye biochemical wastewater continuously until the activated carbon is fully saturated (the COD value in the wastewater remains unchanged for one month as a fully saturated state), and after regeneration according to the treatment method recorded in each embodiment or each comparative example, it is repeatedly operated until it is fully saturated, and the measurement is repeated 10 times. The regeneration efficiency that can be achieved by each regeneration of the activated carbon is calculated by measuring the COD value of the wastewater according to the formula of regeneration efficiency = (removal efficiency of regenerated activated carbon / removal efficiency of fresh activated carbon) × 100%. The specific test results are shown in Table 3.
[0070] Table 3 Test results 3
[0071]
[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims
1. A method for regenerating hazardous waste activated carbon, characterized in that: The steps include: Step 1: ball-mill the hazardous waste activated carbon, heat it to 930-950°C for high-temperature pyrolysis, and obtain primary activated carbon; Step 2, the primary activated carbon and the composite treatment liquid are mixed evenly, microwave irradiated at a microwave power of 1000W-5000W, solid-liquid separation, and drying to obtain intermediate activated carbon; Step 3, immersing the intermediate activated carbon in a strong alkaline solution at 70-90°C, sieving, and calcining the sieved material at a high temperature of 250-350°C in a low oxygen environment to obtain treated regenerated activated carbon; The composite treatment solution comprises the following raw material components in percentage by weight: 1%-5% citric acid, 1%-5% tartaric acid, 5%-10% persulfate, 5%-10% hydrogen peroxide and the balance water; In step 1, the temperature is raised in stages, wherein the temperature is raised to 230-260°C and kept warm for 20-50 minutes in the first stage; the temperature is raised to 560-590°C and kept warm for 30-100 minutes in the second stage; and the temperature is raised to 930-950°C in the third stage.
2. The method for regenerating hazardous waste activated carbon according to claim 1, characterized in that: In step 1, the high temperature pyrolysis time is 30-50 minutes.
3. The method for regenerating hazardous waste activated carbon according to claim 2, characterized in that: The staged heating is performed by programmed heating, wherein the heating rate of the first stage is 5-10°C / min; the heating rate of the second stage is 10-15°C / min; and the heating rate of the third stage is 20-25°C / min.
4. The method for regenerating hazardous waste activated carbon according to claim 1, characterized in that: In step 1, the rotation speed of the ball mill is 250-400 rpm, and the ball milling time is 140-180 min.
5. The method for regenerating hazardous waste activated carbon according to claim 1, characterized in that: In step 2, the mass volume ratio of the primary activated carbon to the composite treatment liquid is 1g:2mL-3mL; and / or In step 2, the microwave irradiation time is 40-70 min; and / or In step 2, the persulfate is any one or more of ammonium persulfate, sodium persulfate or potassium persulfate.
6. The method for regenerating hazardous waste activated carbon according to claim 1, characterized in that: In step 3, the strong alkaline solution is any one or both of a 0.5-1 mol / L sodium hydroxide solution or a 0.5-1 mol / L potassium hydroxide solution.
7. The method for regenerating hazardous waste activated carbon according to claim 6, characterized in that: In step three, the mass volume ratio of the intermediate activated carbon to the strong alkaline solution is 1g:3mL-5mL.
8. The method for regenerating hazardous waste activated carbon according to claim 1, characterized in that: In step three, the oxygen content of the hypoxic environment is 5%-8%.
9. The method for regenerating hazardous waste activated carbon according to claim 1, characterized in that: In step three, the high temperature calcination time is 1.5-3h.