Method for preparing industrial activated carbon from residual sludge of printing and dyeing wastewater

Abstract

The invention provides a method for preparing industrial activated carbon from residual sludge of printing and dyeing wastewater. The method comprises the following steps: collecting sludge, rinsing, and activating the rinsed sludge by adopting an activating agent; after activation is completed, dewatering is conducted, then flash evaporation is conducted on the dewatered sludge, and the water content is further reduced; calcining the flashed sludge for 2-4 hours at 550-600 DEG C in a nitrogen atmosphere to obtain an activated carbon crude product; washing the activated carbon crude product with diluted hydrochloric acid, washing with deionized water, and drying to obtain the activated carbon. The activating agent is one or more of zinc chloride, ferric sulfate, sulfuric acid, hydrogen peroxide or sodium hydroxide; preferably, the activating agent is hydrogen peroxide; preferably, the concentration of the hydrogen peroxide is 0.5 mol / L to 1.5 mol / L. According to the preparation method provided by the invention, the residual sludge of the printing and dyeing wastewater is taken as a raw material, so that the activated carbon with strong adsorption performance is prepared, and the preparation process is simple, low in cost and pollution-free.

Description

Technical Field

[0001] The invention belongs to the technical field of industrial wastewater excess sludge treatment, and in particular to a method for preparing industrial activated carbon by using printing and dyeing wastewater excess sludge. Background Art

[0002] As a high-water-consuming and highly polluting industry, the printing and dyeing industry produces a large amount of wastewater containing dyes, auxiliaries and heavy metals every year. After biochemical treatment, 30-50% of the pollutants in the wastewater are converted into sludge. The sludge has a high organic matter content, a high heavy metal risk and high treatment cost. Most existing technologies treat sludge by preparing the sludge into activated carbon. However, there are many bottlenecks in the current printing and dyeing sludge disposal technology. For example, the traditional activated carbon preparation method uses zinc chloride or phosphoric acid for activation. Although high specific surface area activated carbon can be obtained through zinc chloride or phosphoric acid activation, the residual activator limits its application field, and subsequent wastewater treatment requires additional heavy metal removal steps. Although direct pyrolysis can also achieve the purpose of preparing activated carbon from sludge, oxygen-free calcination at 400-600°C can solidify heavy metals, but the pore structure is poor and the iodine adsorption value is low.

[0003] Therefore, there is an urgent need to develop a green, efficient, economical and environmentally friendly method for preparing industrial activated carbon with high iodine adsorption value and good pore structure from residual sludge from printing and dyeing wastewater.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The first purpose of the present invention is to provide a method for preparing industrial activated carbon from excess sludge from printing and dyeing wastewater. The method uses excess sludge from printing and dyeing wastewater as raw material and prepares high-performance industrial activated carbon through a three-step process of "green activation-flash dehydration-temperature controlled calcination".

[0006] A second object of the present invention is to provide an industrial activated carbon having a strong adsorption capacity and a high iodine value.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted: A method for preparing industrial activated carbon from residual sludge from printing and dyeing wastewater comprises the following steps: collecting the sludge, washing it, and activating the washed sludge with an activator; After activation, dehydration is performed, and then the dehydrated sludge is flashed to further reduce the water content; The flashed sludge is calcined at 550-600°C for 2-4 hours under a nitrogen atmosphere to obtain crude activated carbon; The crude activated carbon was then washed with dilute hydrochloric acid, rinsed with deionized water, and dried. The activator is one or more of zinc chloride, ferric sulfate, sulfuric acid, hydrogen peroxide or sodium hydroxide; Preferably, the activator is hydrogen peroxide; Preferably, the concentration of hydrogen peroxide is 0.5-1.5 mol / L.

[0008] In the present invention, one or more of zinc chloride, ferric sulfate, sulfuric acid, hydrogen peroxide or sodium hydroxide is used as an activator to replace the traditional activator to activate the sludge. Since traditional printing and dyeing sludge contains a large amount of difficult-to-degrade organic matter, when the traditional direct calcination method is used to prepare activated carbon, the pore structure of the prepared activated carbon will be underdeveloped and its adsorption performance will be poor. Therefore, the sludge is pretreated by using an activator, so that the sludge is "etched" by chemical or physical means during the carbonization process, thereby forming a rich void structure. Therefore, the choice of activator is very important for the present invention. Among them, the preferred activator for the present invention is hydrogen peroxide, which oxidizes and decomposes the macromolecular organic matter contained in the sludge through the free radicals it contains. The -OH ions contained in the sludge can attack the benzene rings, azo bonds and other difficult-to-degrade structures, thereby forming oxygen-containing functional groups, thereby providing active sites for subsequent carbonization, and at the same time avoiding the introduction of heavy metals. Compared with zinc chloride, it does not introduce heavy metal ions. Sulfuric acid is a strong acid. Although it can improve the porosity, the pH of the product is low, which requires subsequent neutralization treatment, increasing the cost. Hydrogen peroxide, as a green oxidant, only produces water and oxygen during the decomposition process, leaving no residual pollution. The hydroxyl radicals it produces can efficiently oxidize the macromolecular organic matter in the sludge, thereby forming oxygen-containing functional groups, thereby providing active sites for subsequent carbonization. After a series of creative work, the inventors found that when hydrogen peroxide is at a concentration of 0.5-1.5 mol / L concentration range, hydrogen peroxide can more effectively decompose the dye molecules in the sludge, thereby forming a better microporous precursor and making the specific surface area higher; then, after the present invention uses an activator to activate the sludge, it also flashes the activated sludge to further reduce the water content in the sludge. Compared with the traditional hot air drying method in the traditional technology, the flash evaporation method adopted by the present invention can achieve sludge dehydration in a short time and make the water content in the sludge lower. The flash evaporation method can instantly penetrate the sludge particles, vaporize the water and destroy the sludge colloidal structure, thereby releasing more organic matter to participate in subsequent reactions; at the same time, the present invention also performs temperature-controlled calcination under nitrogen addition. This method achieves better carbonization of the sludge. The nitrogen protection effectively prevents the oxidation loss of organic matter in the sludge and ensures the orderly contraction of the carbon skeleton. Therefore, the calcination temperature and heating rate directly affect the void distribution of the activated carbon. In this invention, excellent results can be achieved when the calcination temperature is between 550-600°C. This is because when the temperature is too low, the sludge is not completely carbonized, resulting in a low specific surface area of ​​the prepared activated carbon. However, if the temperature is too high, the micropores of the prepared activated carbon will merge, the voids will collapse, and the adsorption capacity will decrease. After obtaining the crude activated carbon, the present invention uses dilute hydrochloric acid to wash it to remove ash, thereby increasing the porosity of the prepared industrial activated carbon and enhancing its adsorption capacity for pollutants.

[0009] Preferably, as a further feasible solution, the concentration of hydrogen peroxide is 1 mol / L.

[0010] In the present invention, the concentration of hydrogen peroxide directly affects the oxidation efficiency and pore structure of the sludge. When the concentration of hydrogen peroxide is 0.5-1.5 mol / L, the effect achieved is excellent. When the concentration of hydrogen peroxide is too low, the oxidation ability of the sludge is insufficient, resulting in incomplete decomposition of organic matter in the sludge and a decrease in specific surface area. If the concentration of hydrogen peroxide is too high, the sludge will be over-oxidized, thereby destroying the carbon skeleton, collapsing the pores, and reducing the specific surface area.

[0011] Preferably, as a further feasible solution, the flash evaporation step is: flash evaporating the dewatered sludge using saturated steam at a pressure of 0.8-1.2 MPa.

[0012] Preferably, as a further feasible solution, the pressure of the saturated steam is 1 MPa, and the flash time is 30-60 min.

[0013] In the present invention, the flash evaporation pressure and time determine the dehydration efficiency and energy consumption of the sludge to a certain extent. When the flash evaporation pressure in the present invention is 0.8-1.2MPa and the flash evaporation time is 30-60min, the effect that can be achieved is excellent. This is because if the flash evaporation pressure is too low, the steam penetration will be insufficient, resulting in poor sludge dehydration effect. If the flash evaporation pressure is too high, it will cause a surge in energy consumption and destroy the carbon skeleton to a certain extent. If the flash evaporation time is too short, too much water will remain in the sludge, affecting the subsequent calcination efficiency. If the flash evaporation time is too long, it will cause excessive decomposition of organic matter, resulting in a decrease in porosity.

[0014] Preferably, as a further feasible solution, the concentration of the dilute hydrochloric acid is 0.1-0.5 mol / L, and the washing time is 1-2 h.

[0015] Preferably, as a further feasible solution, the concentration of the dilute hydrochloric acid is 0.3 mol / L, and the washing time is 1 h.

[0016] In the present invention, the concentration of dilute hydrochloric acid and the washing time are very important for the present invention. This is because the present invention mainly removes the ash on the surface of the crude activated carbon and modifies the surface chemical properties by washing the crude activated carbon with dilute hydrochloric acid. For the present invention, when the concentration of dilute hydrochloric acid is 0.1-0.5 mol / L and the washing time is 1-2 h, preferably, the concentration of dilute hydrochloric acid is 0.3 mol / L and the washing time is 1 h, the effect that can be achieved is excellent. If the concentration of dilute hydrochloric acid is too low, the ash removal rate will be reduced. If the concentration of dilute hydrochloric acid is too high, the crude carbon skeleton prepared will be corroded and its specific surface area will be lost. The washing time is to ensure that the ash is fully dissolved while avoiding excessive erosion.

[0017] Preferably, as a further feasible solution, the organic matter content of the residual sludge from printing and dyeing wastewater is ≥60%, and the heavy metal content is ≤100 mg / kg.

[0018] Preferably, as a further feasible solution, the calcination is performed at a heating rate of 5-10°C / min.

[0019] Preferably, as a further feasible solution, the calcination temperature is 580° C. and the calcination time is 3 hours.

[0020] The present invention also provides the industrial activated carbon, wherein the surface hydroxyl content of the industrial activated carbon is ≥0.8 mmol / g, and the phenolic hydroxyl content is ≥0.5 mmol / g.

[0021] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention provides a method for preparing industrial activated carbon from excess sludge from printing and dyeing wastewater. The method uses excess sludge from printing and dyeing wastewater as raw material and prepares high-performance industrial activated carbon through a three-step process of "green activation-flash dehydration-temperature controlled calcination".

[0022] (2) The present invention provides an industrial activated carbon having strong adsorption capacity and high iodine value. DETAILED DESCRIPTION

[0023] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0024] Example 1 The specific steps of the method for preparing industrial activated carbon from excess sludge from printing and dyeing wastewater of the present invention are as follows: The residual sludge from the sewage treatment facility of a printing and dyeing plant was used as raw material to prepare sludge activated carbon. Soaking: After collecting the sludge, soak it in distilled water for 2 hours to clean the residual color preservatives, pH regulators and other inorganic salt components in the remaining sludge.

[0025] Activation stage: Use zinc chloride with a concentration of 1 mol / L as an activator to soak the sludge for 8 hours, in order to decompose and strip the macromolecular organic matter in the activated carbon to generate pores.

[0026] Flash evaporation stage: the sludge is flash-evaporated and dehydrated. High-pressure saturated steam with a pressure of 0.8 MPa is used to flash-evaporate the dehydrated residual sludge for 30 minutes to dry it and reduce the moisture content to below 40%; Calcination stage: The residual sludge was calcined in an oxygen-free manner for 2 h in a muffle furnace at a heating rate of 5°C / min to 550°C under a nitrogen atmosphere to prepare crude activated carbon; The crude activated carbon was then washed with dilute hydrochloric acid at a concentration of 0.1 mol / L for 1 hour, rinsed with deionized water, and dried.

[0027] Example 2 The specific steps of the method for preparing industrial activated carbon from excess sludge from printing and dyeing wastewater of the present invention are as follows: The residual sludge from the sewage treatment facility of a printing and dyeing plant was used as raw material to prepare sludge activated carbon. Soaking: After collecting the sludge, soak it in distilled water for 2 hours to clean the residual color preservatives, pH regulators and other inorganic salt components in the remaining sludge.

[0028] Activation stage: Use zinc chloride with a concentration of 1 mol / L as an activator to soak the sludge for 8 hours, in order to decompose and strip the macromolecular organic matter in the activated carbon to generate pores.

[0029] Flash evaporation stage: The sludge is flash-evaporated and dehydrated. High-pressure saturated steam at a pressure of 1.2 MPa is used to flash-evaporate the dehydrated residual sludge for 60 minutes to dry it and reduce the moisture content to below 40%; Calcination stage: The residual sludge was calcined in an oxygen-free state for 4 h in a muffle furnace at a heating rate of 10°C / min to 600°C under a nitrogen atmosphere to prepare crude activated carbon; The crude activated carbon was then washed with dilute hydrochloric acid at a concentration of 0.5 mol / L for 1 hour, rinsed with deionized water, and dried.

[0030] Example 3 The specific steps of the method for preparing industrial activated carbon from excess sludge from printing and dyeing wastewater of the present invention are as follows: The residual sludge from the sewage treatment facility of a printing and dyeing plant was used as raw material to prepare sludge activated carbon. Soaking: After collecting the sludge, soak it in distilled water for 2 hours to clean the residual color preservatives, pH regulators and other inorganic salt components in the remaining sludge.

[0031] Activation stage: Use zinc chloride with a concentration of 1 mol / L as an activator to soak the sludge for 8 hours, in order to decompose and strip the macromolecular organic matter in the activated carbon to generate pores.

[0032] Flash evaporation stage: the sludge is flash-evaporated and dehydrated. High-pressure saturated steam with a pressure of 1 MPa is used to flash-evaporate the dehydrated residual sludge for 40 minutes to dry it and reduce the moisture content to below 40%; Calcination stage: The residual sludge was calcined in an oxygen-free manner for 3 h in a muffle furnace at a heating rate of 10°C / min to 580°C under a nitrogen atmosphere to prepare crude activated carbon; The crude activated carbon was then washed with dilute hydrochloric acid at a concentration of 0.5 mol / L for 1 hour, rinsed with deionized water, and dried.

[0033] Example 4 The specific steps of the method for preparing industrial activated carbon from excess sludge from printing and dyeing wastewater of the present invention are as follows: The residual sludge from the sewage treatment facility of a printing and dyeing plant was used as raw material to prepare sludge activated carbon. Soaking: After collecting the sludge, soak it in distilled water for 2 hours to clean the residual color preservatives, pH regulators and other inorganic salt components in the remaining sludge.

[0034] Activation stage: Use hydrogen peroxide with a concentration of 0.5 mol / L as an activator to soak the sludge for 8 hours, in order to decompose and peel off the macromolecular organic matter in the activated carbon to generate pores.

[0035] Flash evaporation stage: the sludge is flash-evaporated and dehydrated. High-pressure saturated steam with a pressure of 1 MPa is used to flash-evaporate the dehydrated residual sludge for 40 minutes to dry it and reduce the moisture content to below 40%; Calcination stage: The residual sludge was calcined in an oxygen-free manner for 3 h in a muffle furnace at a heating rate of 10°C / min to 580°C under a nitrogen atmosphere to prepare crude activated carbon; The crude activated carbon was then washed with dilute hydrochloric acid at a concentration of 0.5 mol / L for 1 hour, rinsed with deionized water, and dried.

[0036] Example 6 The specific steps of the method for preparing industrial activated carbon from excess sludge from printing and dyeing wastewater of the present invention are as follows: The residual sludge from the sewage treatment facility of a printing and dyeing plant was used as raw material to prepare sludge activated carbon. Soaking: After collecting the sludge, soak it in distilled water for 2 hours to clean the residual color preservatives, pH regulators and other inorganic salt components in the remaining sludge.

[0037] Activation stage: Use hydrogen peroxide with a concentration of 1.5 mol / L as an activator to soak the sludge for 8 hours, in order to decompose and peel off the macromolecular organic matter in the activated carbon to generate pores.

[0038] Flash evaporation stage: the sludge is flash-evaporated and dehydrated. High-pressure saturated steam with a pressure of 1 MPa is used to flash-evaporate the dehydrated residual sludge for 40 minutes to dry it and reduce the moisture content to below 40%; Calcination stage: The residual sludge was calcined in an oxygen-free manner for 3 h in a muffle furnace at a heating rate of 10°C / min to 580°C under a nitrogen atmosphere to prepare crude activated carbon; The crude activated carbon was then washed with dilute hydrochloric acid at a concentration of 0.5 mol / L for 1 hour, rinsed with deionized water, and dried.

[0039] Example 7 The specific steps of the method for preparing industrial activated carbon from excess sludge from printing and dyeing wastewater of the present invention are as follows: The residual sludge from the sewage treatment facility of a printing and dyeing plant was used as raw material to prepare sludge activated carbon. Soaking: After collecting the sludge, soak it in distilled water for 2 hours to clean the residual color preservatives, pH regulators and other inorganic salt components in the remaining sludge.

[0040] Activation stage: Use hydrogen peroxide with a concentration of 1 mol / L as an activator to soak the sludge for 8 hours, in order to decompose and peel off the macromolecular organic matter in the activated carbon to generate pores.

[0041] Flash evaporation stage: the sludge is flash-evaporated and dehydrated. High-pressure saturated steam with a pressure of 1 MPa is used to flash-evaporate the dehydrated residual sludge for 40 minutes to dry it and reduce the moisture content to below 40%; Calcination stage: The residual sludge was calcined in an oxygen-free manner for 3 h in a muffle furnace at a heating rate of 10°C / min to 580°C under a nitrogen atmosphere to prepare crude activated carbon; The crude activated carbon was then washed with dilute hydrochloric acid at a concentration of 0.5 mol / L for 1 hour, rinsed with deionized water, and dried.

[0042] Example 8 The specific implementation steps are the same as those in Example 7, except that the hydrogen peroxide concentration is adjusted to 0.1 mol / L.

[0043] Example 9 The specific implementation steps are the same as those in Example 7, except that the hydrogen peroxide concentration is adjusted to 4 mol / L.

[0044] Example 10 The specific implementation steps are the same as those in Example 7, except that the pressure of the saturated steam is adjusted to 0.1 MPa.

[0045] Example 11 The specific implementation steps are the same as those in Example 7, except that the pressure of the saturated steam is adjusted to 5 MPa.

[0046] Example 12 The specific implementation steps are the same as those in Example 7, except that the flash evaporation time is adjusted to 10 minutes.

[0047] Example 13 The specific implementation steps are consistent with those in Example 7, except that the flash evaporation time is adjusted to 2 h.

[0048] Example 14 The specific implementation steps are the same as those in Example 7, except that the concentration of dilute hydrochloric acid is adjusted to 0.01 mol / L.

[0049] Example 15 The specific implementation steps are the same as those in Example 7, except that the concentration of dilute hydrochloric acid is adjusted to 1 mol / L.

[0050] Experimental Example 1 Performance Test of Industrial Activated Carbon Prepared from Excess Sludge in Printing and Dyeing Wastewater The industrial activated carbon obtained in Examples 1-15 was tested for iodine adsorption value, specific surface area, heavy metal residue, and hydroxyl content; The iodine adsorption value test is determined according to GB / T 12496.8-2015; The specific surface area was determined using the BET method; Heavy metal residues were detected using ICP-MS detection method; The hydroxyl content was determined by acid-base titration; The specific test results are shown in Table 1 below:

[0051] From the above data, it can be seen from the comparison of Examples 1-7 that the selection of the type of activator and the optimization of its concentration are very important for the present invention. Examples 1-7 examine the effects of different activators and their concentrations on the performance of activated carbon. The data show that Examples 4-7 using hydrogen peroxide as an activator are significantly better than Examples 1-3 using traditional zinc chloride activation in terms of iodine adsorption value, specific surface area and heavy metal residue in the prepared industrial activated carbon. This is because hydrogen peroxide is a green activator, and its decomposition products are only water and oxygen. Therefore, when it is used as an activator, no heavy metal residue will be generated, and its hydroxyl radicals can specifically oxidize the benzene ring and azo bond in the sludge, thereby forming oxygen-containing functional groups and improving its surface activity. At the same time, when the concentration of hydrogen peroxide is 0.5-1.5 mol / L, the effect that can be achieved is excellent. This is because if the hydrogen peroxide concentration is too low, the oxidation will not be complete, so that the iodine adsorption value of the prepared industrial activated carbon is low, and if the hydrogen peroxide concentration is too high, it will lead to excessive oxidation, thereby reducing the specific surface area. When the hydrogen peroxide concentration is selected as 1 mol / L in Example 7, it can well balance the oxidation efficiency and carbon skeleton protection, so that the iodine adsorption value and specific surface area are excellent.

[0052] By comparing Examples 8-9, it can be seen that the concentration of hydrogen peroxide is very important for the present invention. When the concentration of hydrogen peroxide in Example 8 is too low, the oxidizing ability of hydrogen peroxide is insufficient, resulting in the failure to fully decompose the single-molecule organic matter in the sludge, resulting in a small specific surface area of ​​the prepared industrial activated carbon and a high heavy metal residue. This is because the low concentration of hydrogen peroxide fails to form sufficient oxygen-containing functional groups to fix metal ions; and when the concentration of hydrogen peroxide in Example 9 is too high, the excessively high concentration of hydrogen peroxide will destroy the carbon skeleton, causing the micropores to merge into mesopores, resulting in a decrease in specific surface area. By comparing Examples 10 and 11, it can be seen that the flash evaporation pressure is very important for the preparation method of the present invention. When the steam pressure is too low in Example 10, the steam penetration is weak, resulting in a high water content during the flash evaporation of the sludge, which affects the subsequent calcination. In addition, when the flash evaporation pressure is too low, the pore structure is not fully opened, resulting in a low specific surface area and iodine adsorption value. When the steam pressure in Example 11 is too high, the steam impact force is too strong, resulting in the collapse of part of the carbon skeleton, and the high pressure promotes the dissolution of heavy metals. By comparing Examples 12 and 13, it can be seen that the flash time is also very important for the present invention. When the flash time in Example 12 is too short, more water remains in the sludge, which requires higher energy consumption during subsequent calcination. At the same time, insufficient flash time leads to incomplete pore development, resulting in a low iodine adsorption value and specific surface area of ​​the prepared activated carbon. When the flash time in Example 13 is too long, the organic matter in the sludge is excessively decomposed, resulting in a reduction in micropores. By comparing Examples 14-15, it can be seen that the concentration of dilute hydrochloric acid is also very important for the present invention. When the concentration of dilute hydrochloric acid in Example 14 is too low, the ash removal rate in the crude activated carbon is reduced, thereby clogging the pores, and the heavy metal residue is high; when the concentration of dilute hydrochloric acid in Example 15 is too high, the hydrochloric acid corrodes the carbon skeleton, resulting in a loss of specific surface area.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing industrial activated carbon from excess sludge from printing and dyeing wastewater, characterized in that: The following steps are involved: After collecting the sludge and washing it, an activator is used to activate the washed sludge; After activation, dehydration is performed, and then the dehydrated sludge is flashed to further reduce the water content; The flashed sludge is calcined at 550-600°C for 2-4 hours under a nitrogen atmosphere to obtain crude activated carbon; The crude activated carbon was then washed with dilute hydrochloric acid, rinsed with deionized water, and dried. The activator is one or more of zinc chloride, ferric sulfate, sulfuric acid, hydrogen peroxide or sodium hydroxide; Preferably, the activator is hydrogen peroxide; Preferably, the concentration of hydrogen peroxide is 0.5-1.5 mol / L.

2. The method according to claim 1, characterized in that The concentration of the hydrogen peroxide is 1 mol / L.

3. The method according to claim 1, characterized in that The flash evaporation step is: flash evaporating the dewatered sludge with saturated steam at a pressure of 0.8-1.2 MPa.

4. The method according to claim 3, characterized in that The pressure of the saturated steam is 1 MPa, and the flash time is 30-60 min.

5. The method according to claim 1, wherein The concentration of the dilute hydrochloric acid is 0.1-0.5 mol / L, and the washing time is 1-2 hours.

6. The method according to claim 5, characterized in that The concentration of the dilute hydrochloric acid is 0.3 mol / L, and the washing time is 1 h.

7. The method according to claim 1, characterized in that The organic matter content of the residual sludge from the printing and dyeing wastewater is ≥60%, and the heavy metal content is ≤100 mg / kg.

8. The method according to claim 1, wherein: During the calcination, the temperature is increased at a heating rate of 5-10°C / min.

9. The method according to claim 1, characterized in that The calcination temperature is 580° C. and the calcination time is 3 hours.

10. An industrial activated carbon prepared by the method according to any one of claims 1 to 9, characterized in that The surface hydroxyl content of the industrial activated carbon is ≥0.8 mmol / g, and the phenolic hydroxyl content is ≥0.5 mmol / g.

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