A method for removing heavy metal elements from fly ash

Abstract

This invention provides a method for removing heavy metal elements from fly ash. The removal method includes the following steps: (1) sieving fly ash to obtain unburned carbon and sieved fly ash; (2) ultrasonically mixing adsorbent carbon, solvent, and the sieved fly ash obtained in step (1) to obtain a mixed slurry; (3) sequentially performing adsorbent carbon separation and solid-liquid separation on the mixed slurry obtained in step (2) to obtain fly ash with heavy metal elements removed; the adsorbent carbon in step (2) is obtained by alkali treatment of the unburned carbon obtained in step (1). This invention utilizes the unburned carbon contained in fly ash itself, which is used as an adsorbent for heavy metal elements after alkali treatment, and combines it with ultrasonic means to remove heavy metal elements. At the same time, it realizes the secondary utilization of unburned carbon in fly ash, which is of great significance for the comprehensive utilization of fly ash.

Description

Technical Field

[0001] This invention relates to the field of ecological environment improvement and restoration technology, specifically to a method for removing heavy metal elements from fly ash. Background Technology

[0002] Fly ash is a type of fine ash collected from the flue gas of coal-fired power plant boilers, and is a major industrial solid waste. The chemical composition of fly ash is similar to that of soil, and it is rich in micronutrients essential for plant growth, making it promising for soil improvement and ecological restoration. However, the presence of heavy metals such as Hg, Cd, As, Cr, and Pb in fly ash significantly restricts its application and promotion in agriculture and ecology. Therefore, there is an urgent need to develop methods for separating heavy metals from fly ash.

[0003] CN 113846218A discloses a method for removing heavy metals from fly ash and purifying heavy metal-containing tailings. This method first mixes fly ash with acid for reaction, then washes the resulting leaching residue. The washed leaching residue is the fly ash from which heavy metals have been removed. This method has a high heavy metal removal rate, but it generates a large amount of acid wastewater, resulting in high costs for subsequent wastewater treatment.

[0004] CN 111264113A discloses a modified fly ash material, a composite material, and a modification method for desertified land reclamation. The modified fly ash material involves neutralizing fly ash with sulfuric acid solution, dissolving and removing heavy metals such as arsenic, cadmium, and lead from the fly ash in an acidic environment, resulting in a significant reduction in the heavy metal pollutant content. This allows for safe and large-scale application in desertified land reclamation. However, this method still suffers from complex acid wastewater treatment operations and high costs.

[0005] CN 108607501A discloses a method and system for mercury removal from fly ash. The method includes weighing fly ash and bromide solids after boiler combustion; placing the fly ash and bromide solids in a beaker, adding water for dissolution and stirring to obtain a first fly ash modifier; drying the first fly ash modifier and grinding it in a ball mill to obtain a second fly ash modifier; and placing the second fly ash modifier in a fixed bed for mercury adsorption. However, this method involves complex mercury removal processes from fly ash, and the desorption process employs heating separation, resulting in high energy consumption.

[0006] To address the shortcomings of existing technologies, there is a need for a method that is highly efficient, simple to operate, and low in cost for removing heavy metals from fly ash. Summary of the Invention

[0007] The purpose of this invention is to provide a method for removing heavy metal elements from fly ash. By modifying the unburned carbon contained in fly ash as a heavy metal adsorbent and combining it with ultrasonic means, the heavy metal elements are removed. The method is simple to operate and low in cost. The treated fly ash can be used for high-value applications in agriculture, ecological restoration and environmental protection.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] This invention provides a method for removing heavy metal elements from fly ash, the method comprising the following steps:

[0010] (1) The fly ash is screened to obtain unburned carbon and sieved fly ash;

[0011] (2) Ultrasonic mixing of adsorbed carbon, solvent and sieved fly ash obtained in step (1) yields a mixed slurry;

[0012] (3) The mixed slurry obtained in step (2) is subjected to adsorption carbon separation and solid-liquid separation in sequence to obtain fly ash with heavy metal elements removed;

[0013] The adsorbed carbon in step (2) is obtained by treating the unburned carbon obtained in step (1) with alkali.

[0014] The unburned carbon has a large specific surface area, but few surface active sites, resulting in weak adsorption capacity. This invention obtains adsorbed carbon by treating unburned carbon with alkali. This increases both the specific surface area and pore size of the unburned carbon, as well as the number of active sites, thereby significantly improving its ability to adsorb heavy metals. Combined with ultrasonic conditions, the adsorbed carbon can adsorb heavy metals dissolved and detached from the surface of fly ash particles, achieving the purpose of removing heavy metals from fly ash, while simultaneously realizing the secondary utilization of unburned carbon in fly ash.

[0015] Preferably, the sieve aperture size of the sieving process in step (1) is 50-200 mesh, for example, it can be 50 mesh, 60 mesh, 100 mesh, 120 mesh, 150 mesh or 200 mesh, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 60-120 mesh.

[0016] If the sieve aperture is too large, the unburned carbon contained in the fly ash cannot be effectively separated and collected; if the sieve aperture is too small, more fly ash will be trapped. During the subsequent alkali treatment of the unburned carbon, the fly ash will react with the alkali, causing the loss of the effective components of the fly ash and increasing the consumption of alkali.

[0017] Preferably, the mass-volume ratio of the sieved fly ash to the solvent in step (2) is 1g:(3-30)mL, for example, it can be 1g:3mL, 1g:5mL, 1g:10mL, 1g:15mL, 1g:20mL, 1g:25mL or 1g:30mL, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 1g:(5-15)mL.

[0018] If the mass-volume ratio of the sieved fly ash to the solvent is too high, it will result in excessive solvent consumption and increased economic costs. If it is too low, it will affect the stirring and mass transfer efficiency and reduce the heavy metal removal effect.

[0019] Preferably, the mass ratio of adsorbed carbon to sieved fly ash in step (2) is 1:(20-200), for example, it can be 1:20, 1:30, 1:50, 1:100, 1:150 or 1:200, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 1:(30-150).

[0020] Preferably, the solvent in step (2) includes water.

[0021] Preferably, the alkali used for the alkali treatment includes any one or a combination of at least two of sodium hydroxide, potassium hydroxide, calcium hydroxide, or ammonia. Typical but non-limiting combinations include a combination of sodium hydroxide and potassium hydroxide, a combination of calcium hydroxide and ammonia, a combination of sodium hydroxide, potassium hydroxide, and calcium hydroxide, or a combination of sodium hydroxide, potassium hydroxide, calcium hydroxide, and ammonia.

[0022] This invention treats unburned carbon with alkali, which alters the surface characteristics and structural sites of the unburned carbon. The alkali solution reacts with the acidic functional groups on the surface of the unburned carbon, reducing the number of oxygen-containing acidic functional groups and significantly increasing the number of basic functional groups. At the same time, it can open the pores blocked by aluminosilicates, increasing the specific surface area and thus improving the adsorption capacity for heavy metals.

[0023] Preferably, the concentration of alkali in the alkali treatment is 0.5-5 mol / L, for example, it can be 0.5 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L or 5 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 1-3 mol / L.

[0024] Preferably, the temperature of the alkali treatment is 40-100℃, for example, it can be 40℃, 50℃, 60℃, 70℃, 75℃, 80℃, 90℃, 95℃ or 100℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 75-95℃.

[0025] Preferably, the alkali treatment time is 0.5-10h, for example, it can be 0.5h, 0.8h, 1h, 3h, 5h, 8h or 10h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 0.8-3h.

[0026] Preferably, the frequency of the ultrasonic mixing in step (2) is 25-80KHz, for example, it can be 25KHz, 30KHz, 33KHz, 40KHz, 50KHz, 60KHz, 70KHz or 80KHz, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 33-50KHz.

[0027] The ultrasonic frequency has a significant impact on the removal of heavy metals. Because fly ash and adsorbent carbon have significantly different adsorption capacities for heavy metals, the binding force between heavy metals and fly ash / adsorbent carbon also differs significantly; that is, the binding force of heavy metals to adsorbent carbon is much greater than that to fly ash. When the ultrasonic frequency is too low, the resulting cavitation is weak, making it difficult to break the adsorption between heavy metals and fly ash particles, thus failing to effectively remove heavy metals. When the ultrasonic frequency is too high, the resulting cavitation is too strong, preventing heavy metals separated from fly ash from being re-adsorbed onto adsorbent carbon particles, also affecting the removal efficiency. Only within the specific frequency range provided by this invention can heavy metals be separated from the surface of fly ash particles and transferred to the surface of adsorbent carbon particles, improving the heavy metal removal efficiency.

[0028] Preferably, the ultrasonic mixing time in step (2) is 0.2-5h, for example, it can be 0.2h, 1h, 1.5h, 2h, 3h, 4h or 5h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 0.5-1.5h.

[0029] Most heavy metal elements in fly ash are adsorbed and enriched on the particle surface. Ultrasonic waves, with their strong directionality, high energy, and strong penetrability, exhibit a powerful cavitation effect. Using ultrasonic cavitation as a driving force, bubbles are formed in the solution. The high-temperature, high-pressure shock waves generated when these bubbles collapse under pressure can disrupt the adsorption between fly ash and surface heavy metals, thus separating the surface heavy metals from the fly ash particles. Simultaneously, the bubbles can also enter the gaps between the fly ash and surface heavy metal particles, causing the heavy metals to detach through energy-generated vibrations.

[0030] Preferably, the method for separating the adsorbed carbon in step (3) includes sieving and / or centrifugation.

[0031] Preferably, the solid-liquid separation method in step (3) includes any one or a combination of at least two of filtration, centrifugation or sedimentation. Typical but non-limiting combinations include a combination of filtration and centrifugation, a combination of centrifugation and sedimentation, or a combination of filtration, centrifugation and sedimentation.

[0032] As a preferred embodiment of the removal method of the present invention, the removal method includes the following steps:

[0033] (1) The fly ash is sieved through a 50-200 mesh sieve to obtain unburned carbon and sieved fly ash;

[0034] (2) The adsorbed carbon, solvent and sieved fly ash obtained in step (1) are ultrasonically mixed at a frequency of 25-80KHz for 0.2-5h to obtain a mixed slurry;

[0035] The mass-to-volume ratio of the sieved fly ash to the solvent is 1 g:(3-30) mL; the mass ratio of the adsorbed carbon to the sieved fly ash is 1:(20-200); the adsorbed carbon is obtained by treating the unburned carbon obtained in step (1) with alkali at 40-100℃ for 0.5-10 h; the concentration of alkali in the alkali treatment is 0.5-5 mol / L;

[0036] (3) The mixed slurry obtained in step (2) is subjected to adsorption carbon separation and solid-liquid separation in sequence to obtain fly ash with heavy metal elements removed.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) This invention makes full use of the unburned carbon contained in fly ash itself, which is used as an adsorbent for heavy metal elements after alkali treatment, and combined with ultrasonic means to remove heavy metal elements. The removal rate of heavy metal elements Hg, As, Cd, Cr and Pb can reach 31-84%. At the same time, it realizes the secondary utilization of unburned carbon in fly ash, which is of great significance to the comprehensive utilization of fly ash.

[0039] (2) The removal method described in this invention does not introduce other impurities and will not cause pollution to fly ash; at the same time, the heavy metal removal process has no adverse effect on the composition and phase of fly ash, which is conducive to the high-value utilization of subsequent farmland, saline-alkali land, grassland improvement and ecological restoration. Detailed Implementation

[0040] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0041] Example 1

[0042] This embodiment provides a method for removing heavy metal elements from fly ash, the method comprising the following steps:

[0043] (1) The fly ash was sieved through an 80-mesh sieve to obtain unburned carbon and sieved fly ash;

[0044] (2) Ultrasonic mixing of adsorbed carbon, water and sieved fly ash obtained in step (1) was performed at a frequency of 40KHz for 1 hour to obtain a mixed slurry.

[0045] The mass-to-volume ratio of the sieved fly ash to water is 1g:10mL; the mass ratio of the adsorbed carbon to the sieved fly ash is 1:80; the adsorbed carbon is obtained by treating the unburned carbon obtained in step (1) with sodium hydroxide at 85℃ for 1.5h; the concentration of the sodium hydroxide is 2.5mol / L.

[0046] (3) The mixed slurry obtained in step (2) is centrifuged and filtered in sequence, and the resulting solid phase is fly ash with heavy metal elements removed.

[0047] Example 2

[0048] This embodiment provides a method for removing heavy metal elements from fly ash, the method comprising the following steps:

[0049] (1) The fly ash was sieved through a 120-mesh sieve to obtain unburned carbon and sieved fly ash;

[0050] (2) The adsorbed carbon, water and the sieved fly ash obtained in step (1) were ultrasonically mixed at a frequency of 50KHz for 0.5h to obtain a mixed slurry.

[0051] The mass-to-volume ratio of the sieved fly ash to water is 1g:15mL; the mass ratio of the adsorbed carbon to the sieved fly ash is 1:150; the adsorbed carbon is obtained by treating the unburned carbon obtained in step (1) with sodium hydroxide at 75℃ for 3h; the concentration of the sodium hydroxide is 3mol / L.

[0052] (3) The mixed slurry obtained in step (2) is screened and filtered in sequence, and the resulting solid phase is fly ash with heavy metal elements removed.

[0053] Example 3

[0054] This embodiment provides a method for removing heavy metal elements from fly ash, the method comprising the following steps:

[0055] (1) The fly ash was sieved through a 60-mesh sieve to obtain unburned carbon and sieved fly ash;

[0056] (2) The adsorbed carbon, water and the sieved fly ash obtained in step (1) were ultrasonically mixed at a frequency of 33KHz for 1.5h to obtain a mixed slurry.

[0057] The mass-to-volume ratio of the sieved fly ash to water is 1 g: 5 mL; the mass ratio of the adsorbed carbon to the sieved fly ash is 1:30; the adsorbed carbon is obtained by treating the unburned carbon obtained in step (1) with sodium hydroxide at 95°C for 0.8 h; the concentration of the sodium hydroxide is 1 mol / L.

[0058] (3) The mixed slurry obtained in step (2) is screened and centrifuged in sequence, and the resulting solid phase is fly ash with heavy metal elements removed.

[0059] Example 4

[0060] This embodiment provides a method for removing heavy metal elements from fly ash, the method comprising the following steps:

[0061] (1) The fly ash was sieved through a 200-mesh sieve to obtain unburned carbon and sieved fly ash;

[0062] (2) The adsorbed carbon, water and the sieved fly ash obtained in step (1) were ultrasonically mixed at a frequency of 80KHz for 0.2h to obtain a mixed slurry;

[0063] The mass-to-volume ratio of the sieved fly ash to water is 1g:30mL; the mass ratio of the adsorbed carbon to the sieved fly ash is 1:200; the adsorbed carbon is obtained by treating the unburned carbon obtained in step (1) with calcium hydroxide at 100℃ for 0.5h; the concentration of the calcium hydroxide is 0.5mol / L.

[0064] (3) The mixed slurry obtained in step (2) is screened and sedimented in sequence, and the resulting solid phase is fly ash with heavy metal elements removed.

[0065] Example 5

[0066] This embodiment provides a method for removing heavy metal elements from fly ash, the method comprising the following steps:

[0067] (1) The fly ash was sieved through a 50-mesh sieve to obtain unburned carbon and sieved fly ash;

[0068] (2) Ultrasonic mixing of adsorbed carbon, water and sieved fly ash obtained in step (1) was performed at a frequency of 25KHz for 5 hours to obtain a mixed slurry.

[0069] The mass-to-volume ratio of the sieved fly ash to water is 1g:3mL; the mass ratio of the adsorbed carbon to the sieved fly ash is 1:20; the adsorbed carbon is obtained by treating the unburned carbon obtained in step (1) with potassium hydroxide at 40℃ for 10h; the concentration of the potassium hydroxide is 5mol / L.

[0070] (3) The mixed slurry obtained in step (2) is centrifuged and filtered in sequence, and the resulting solid phase is fly ash with heavy metal elements removed.

[0071] Example 6

[0072] This embodiment provides a method for removing heavy metal elements from fly ash. The difference from Embodiment 1 is that, except for adjusting the mass-volume ratio of sieved fly ash to water in step (2) to 1g:1mL, the rest is the same as in Embodiment 1.

[0073] Example 7

[0074] This embodiment provides a method for removing heavy metal elements from fly ash. The difference from Embodiment 1 is that, except for adjusting the mass-volume ratio of sieved fly ash to water in step (2) to 1g:50mL, the rest is the same as in Embodiment 1.

[0075] Example 8

[0076] This embodiment provides a method for removing heavy metal elements from fly ash. The difference from Embodiment 1 is that, except for adjusting the mass ratio of adsorbent carbon to sieved fly ash in step (2) to 1:10, everything else is the same as in Embodiment 1.

[0077] Example 9

[0078] This embodiment provides a method for removing heavy metal elements from fly ash. The difference from Embodiment 1 is that, except for adjusting the mass ratio of adsorbent carbon to sieved fly ash in step (2) to 1:220, the rest is the same as in Embodiment 1.

[0079] Example 10

[0080] This embodiment provides a method for removing heavy metal elements from fly ash. The difference from Embodiment 1 is that, except for adjusting the frequency of the ultrasound in step (2) to 15KHz, the rest is the same as in Embodiment 1.

[0081] Example 11

[0082] This embodiment provides a method for removing heavy metal elements from fly ash. The difference between this embodiment and Embodiment 1 is that, except for adjusting the frequency of the ultrasound in step (2) to 90KHz, the rest is the same as in Embodiment 1.

[0083] Example 12

[0084] This embodiment provides a method for removing heavy metal elements from fly ash. The difference from Embodiment 1 is that, except for replacing sodium hydroxide in step (2) with ammonia, the rest is the same as in Embodiment 1.

[0085] Comparative Example 1

[0086] This comparative example provides a method for removing heavy metal elements from fly ash. The difference between this method and Example 1 is that, except for replacing sodium hydroxide in step (2) with hydrochloric acid, the method is the same as Example 1.

[0087] Comparative Example 2

[0088] This comparative example provides a method for removing heavy metal elements from fly ash. The difference from Example 1 is that the unburned carbon is not treated with sodium hydroxide, and the adsorbed carbon in step (2) is directly replaced with unburned carbon. The method is the same as in Example 1.

[0089] Comparative Example 3

[0090] This comparative example provides a method for removing heavy metal elements from fly ash. The difference from Example 1 is that step (2) does not involve ultrasonic mixing, but the steps are the same as in Example 1.

[0091] The removal methods provided in Examples 1-12 and Comparative Examples 1-3 were used to remove heavy metals from fly ash. The removal rate of heavy metals in fly ash was determined by microwave digestion-ICP-MS method, and the results are shown in Table 1.

[0092] Table 1

[0093]

[0094]

[0095] As can be seen from Table 1, by comparing Example 1 with Examples 2-5, it can be seen that the method for removing heavy metal elements from fly ash described in this invention can efficiently remove heavy metal elements, and the treated fly ash can be utilized in the fields of agriculture and ecology for high value.

[0096] A comparison of Examples 1, 6, and 7 shows that if the ratio of sieved activated carbon to solvent is too low, the unburned carbon cannot be completely modified, thus reducing performance; if the ratio is too high, it will damage part of the structure and generate too much waste liquid. A comparison of Examples 1, 8, and 9 shows that if the ratio of adsorbed carbon to sieved fly ash is too low, optimal adsorption cannot be achieved, reducing the heavy metal removal rate; if the ratio is too high, some fine fly ash particles adhere to the surface of the adsorbed carbon, resulting in a lower result. A comparison of Examples 1, 10, and 11 shows that if the ultrasonic frequency is too low, it is difficult to break the adsorption between heavy metals and fly ash particles, and heavy metals cannot be effectively removed; if the ultrasonic frequency is too high, the heavy metals separated from the fly ash cannot be re-adsorbed onto the adsorbed carbon particles, thus affecting the heavy metal removal effect. A comparison of Examples 1 and 12 shows that treating the unburned carbon with ammonia water reduces the heavy metal removal effect of the resulting adsorbed carbon.

[0097] A comparison of Example 1 and Comparative Example 1 shows that using hydrochloric acid instead of alkaline reagents to treat unburned carbon results in the neutralization of some alkaline functional groups on the surface of activated carbon, generating new acidic functional groups on the activated carbon surface, which is not conducive to the adsorption of heavy metals. At the same time, the acidic solution is not conducive to opening the pores blocked by aluminosilicates. A comparison of Example 1 and Comparative Example 2 shows that directly using unburned carbon to remove heavy metals from sieved fly ash significantly reduces the removal efficiency. A comparison of Example 1 and Comparative Example 3 shows that the absence of ultrasonic mixing significantly reduces the degree of separation of heavy metal elements on the surface of sieved fly ash, thereby reducing the removal rate of heavy metals.

[0098] In summary, this invention fully utilizes the unburned carbon contained in fly ash, which is then treated with alkali and used as an adsorbent for heavy metal elements. Combined with ultrasonic methods, it achieves the removal of heavy metal elements. The removal rate of heavy metal elements Hg, As, Cd, Cr and Pb can reach 31-84%. At the same time, it realizes the secondary utilization of unburned carbon in fly ash, which is of great significance for the comprehensive utilization of fly ash.

[0099] The removal method described in this invention does not introduce other impurities and will not pollute fly ash. At the same time, the heavy metal removal process has no adverse effect on the composition and phase of fly ash, which is conducive to its high-value utilization in subsequent fields such as farmland, saline-alkali land, grassland improvement and ecological restoration.

[0100] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for removing heavy metal elements from fly ash, characterized in that, The removal method includes the following steps: (1) The fly ash is sieved through a 50-200 mesh sieve to obtain unburned carbon and sieved fly ash; (2) The adsorbed carbon, solvent and sieved fly ash obtained in step (1) are ultrasonically mixed at a frequency of 25-80KHz for 0.2-5h to obtain a mixed slurry; The mass-to-volume ratio of the sieved fly ash to the solvent is 1 g:(3-30) mL; the mass ratio of the adsorbed carbon to the sieved fly ash is 1:(20-200); the adsorbed carbon is obtained by treating the unburned carbon obtained in step (1) with alkali at 40-100℃ for 0.5-10 h; the concentration of alkali in the alkali treatment is 0.5-5 mol / L; (3) The mixed slurry obtained in step (2) is subjected to adsorption carbon separation and solid-liquid separation in sequence to obtain fly ash with heavy metal elements removed.

2. The removal method according to claim 1, characterized in that, The sieve size for the sieving process in step (1) is 60-120 mesh.

3. The removal method according to claim 1, characterized in that, The mass-volume ratio of the sieved fly ash to the solvent in step (2) is 1g:(5-15)mL.

4. The removal method according to claim 1, characterized in that, The mass ratio of the adsorbed carbon to the sieved fly ash in step (2) is 1:(30-150).

5. The removal method according to claim 1, characterized in that, The solvent in step (2) includes water.

6. The removal method according to claim 1, characterized in that, The alkali used in the alkaline treatment includes any one or a combination of at least two of sodium hydroxide, potassium hydroxide, calcium hydroxide, or ammonia water.

7. The removal method according to claim 1, characterized in that, The concentration of alkali in the alkali treatment is 1-3 mol / L.

8. The removal method according to claim 1, characterized in that, The temperature for the alkali treatment is 75-95℃.

9. The removal method according to claim 1, characterized in that, The alkali treatment time is 0.8-3 hours.

10. The removal method according to claim 1, characterized in that, The frequency of the ultrasonic mixing in step (2) is 33-50KHz.

11. The removal method according to claim 1, characterized in that, The ultrasonic mixing time in step (2) is 0.5-1.5h.

12. The removal method according to claim 1, characterized in that, The method for separating adsorbed carbon in step (3) includes sieving and / or centrifugation.

13. The removal method according to claim 1, characterized in that, The solid-liquid separation method described in step (3) includes any one or a combination of at least two of filtration, centrifugation, or sedimentation.

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