One-step preparation method of sulfur-modified heavy metal adsorption regenerated carbon

Abstract

This application discloses a one-step preparation method for sulfur-modified heavy metal adsorption regenerated carbon, belonging to the field of environmental remediation materials technology. Using hazardous waste powdered activated carbon as raw material, the process involves nitrogen purging and mixed acid washing pretreatment to remove heavy metals and impurities. A mixed gas consisting of water vapor, nitrogen, and a sulfur modification agent is introduced into a rotary activation furnace. Activation, pore building, and sulfur grafting modification are simultaneously completed through gradient heating. The product is then rapidly cooled and passivated with nitrogen to obtain the regenerated carbon. This application achieves pore construction and surface sulfur modification in one step, with a simple process and low energy consumption. The resulting regenerated carbon has a high specific surface area and excellent adsorption capacity and selectivity for heavy metals such as lead, cadmium, copper, and nickel. It can be widely used in the deep treatment of wastewater and waste gas containing heavy metals, possessing both hazardous waste resource utilization value and environmental remediation benefits.

Description

Technical Field

[0001] This application relates to the field of environmental remediation materials technology, specifically to a one-step preparation method of sulfide-modified heavy metal adsorption and regeneration carbon. Background Technology

[0002] Heavy metal pollutants are characterized by high toxicity, easy accumulation, and non-degradability, making it difficult for conventional treatment processes to achieve deep compliance with emission standards. Powdered activated carbon, due to its large specific surface area and excellent adsorption performance, is widely used in wastewater treatment and waste gas treatment. However, after use, powdered activated carbon adsorbs large amounts of heavy metal ions and organic pollutants, becoming hazardous waste (hazardous waste powdered activated carbon). Direct landfilling or incineration not only wastes resources but also leads to secondary heavy metal pollution, harming the ecological environment and human health. Therefore, the regeneration of hazardous waste powdered activated carbon to achieve resource utilization is a current research focus in the field of hazardous waste treatment. Currently, the main regeneration methods for hazardous waste powdered activated carbon include thermal regeneration, chemical regeneration, and biological regeneration. Among these, thermal regeneration is the most widely used method due to its high regeneration efficiency and good recovery of activated carbon performance after regeneration. Chinese invention patent application CN112569916A discloses a method for regenerating waste activated carbon. The method involves vacuum thermal desorption of the waste activated carbon until the desorption rate of VOCs in the waste activated carbon reaches more than 90%. The waste activated carbon is then washed to obtain wet activated carbon. After drying, the wet activated carbon is first calcined under a protective atmosphere, then carbonized in an atmosphere with an oxygen content of ≤1%, and then activated in a mixed atmosphere of water vapor and carbon dioxide. After cooling, the regenerated activated carbon is obtained. However, existing thermal regeneration technology has the following drawbacks: First, the regeneration process can only restore the pore structure of activated carbon and cannot modify it for heavy metal adsorption. The regenerated activated carbon has low selectivity and adsorption capacity for heavy metals, which is difficult to meet the needs of special treatment for heavy metals. Second, traditional modification processes are mostly two-step methods of activation and regeneration followed by modification treatment. The process is cumbersome, energy-intensive, and has a long processing cycle. Moreover, the modification process can easily damage the pore structure of activated carbon, reducing the adsorption performance of the regenerated carbon. Third, the regeneration process can easily generate pollutants such as dioxins and sulfur-containing waste gas, posing a risk of secondary pollution. In addition, the removal of heavy metals is incomplete, affecting the safety of the regenerated carbon.

[0003] Therefore, developing a simple, low-energy-consumption method for regenerating hazardous waste powdered activated carbon with excellent heavy metal adsorption performance is of great practical significance and application value. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the primary objective of this application is to provide a one-step preparation method for sulfur-modified heavy metal adsorption and regeneration carbon. The method involves purging hazardous waste powdered activated carbon with nitrogen to remove loose impurities and volatile gaseous impurities, followed by pretreatment with hydrochloric acid and sulfuric acid to desorb heavy metal ions adsorbed in the activated carbon. The pretreated activated carbon is then placed in a continuous rotary activation furnace, and an activation and modification mixed gas is introduced to perform activation and modification treatments in one step. Finally, passivation treatment is performed to obtain sulfur-modified heavy metal adsorption and regeneration carbon.

[0005] To achieve the above objectives, this application provides the following technical solution:

[0006] This application provides a one-step preparation method for sulfide-modified heavy metal adsorption and regeneration carbon, comprising the following steps:

[0007] Hazardous waste powdered activated carbon was placed in a closed pretreatment unit, purged with nitrogen, and pretreatment liquid was added. The mixture was stirred and pretreated, and then filtered to obtain activated carbon residue and pretreatment waste liquid. The activated carbon residue was washed with deionized water until neutral and dried until the moisture content was ≤5% to obtain pretreated activated carbon. The pretreatment waste liquid was sent to the waste liquid treatment unit, sodium hydroxide was added to adjust the pH, sodium sulfide was added to precipitate the residue, and the mixture was filtered to obtain precipitated residue and filtrate. The precipitated residue was recycled and treated, and the filtrate was concentrated by membrane and reused in the pretreatment step.

[0008] Pretreated activated carbon is fed into a continuous rotary activation furnace through a sealed conveying unit. Activation and modification mixed gas is introduced into the furnace, and the temperature is gradually increased to carry out activation and modification treatment to obtain primary recycled carbon. The tail gas of activation and modification treatment is sent to the tail gas treatment unit and discharged after treatment to meet the standards.

[0009] The primary recycled carbon is fed into a closed cooling device through a sealed conveying unit. Nitrogen gas is first introduced for rapid cooling, followed by the introduction of a passivation mixed gas. After passivation treatment, the carbon is cooled to room temperature to obtain sulfide-modified heavy metal adsorption recycled carbon, which is then sent to a finished product storage tank for later use.

[0010] Preferably, the nitrogen purging time is 30-60 minutes, and the nitrogen flow rate is 0.5-1.5 m³ / min. 3 / h.

[0011] It should be noted that nitrogen purging can prevent activated carbon from oxidizing when it comes into contact with air during the pretreatment process, while also removing volatile organic compounds and reducing the generation of pollutants during subsequent regeneration.

[0012] Preferably, the pretreatment solution is obtained by mixing dilute hydrochloric acid with a concentration of 5-10wt% and dilute sulfuric acid with a concentration of 2-5wt% at a volume ratio of 1:1-2; the mass ratio of the hazardous waste powdered activated carbon to the pretreatment solution is 1:3-5.

[0013] Preferably, the stirring rate in the stirring pretreatment step is 100-200 rpm, and the treatment time is 2-4 hours.

[0014] It should be noted that the mixed pretreatment solution of dilute hydrochloric acid and dilute sulfuric acid can effectively remove some of the heavy metal ions (such as lead, cadmium, copper, nickel, etc.) adsorbed in the hazardous waste powder activated carbon, while dissolving inorganic impurities on the surface of the activated carbon and clearing some of the blocked pores, laying the foundation for subsequent activation and modification.

[0015] Preferably, the drying step is vacuum drying, with a drying temperature of 105-120℃ and a vacuum degree of -0.08~-0.1MPa.

[0016] Preferably, the pH value of the added sodium hydroxide is adjusted to 8-9; the amount of sodium sulfide added is 0.1-0.8% of the mass of the pretreated waste liquid.

[0017] Preferably, the continuous rotary activation furnace rotates at 1-3 rpm; the activation-modifying mixed gas consists of water vapor, nitrogen, and a sulfurizing modifier; and the water vapor flow rate is 0.8-1.2 m³ / h. 3 / h, nitrogen flow rate is 0.3-0.8m 3 / h, the amount of sulfidation modifier added is 2-8% of the mass of the pretreated activated carbon.

[0018] Preferably, the sulfidation modifier is any one or more of hydrogen sulfide, carbon disulfide, or sodium thiosulfate vapor.

[0019] Preferably, the sulfur modification agent is a mixed vapor of hydrogen sulfide and carbon disulfide, with a mixing volume ratio of 1:1-3. This mixed modification agent can introduce more types of sulfur-containing functional groups onto the surface of activated carbon, further improving the adsorption performance of regenerated carbon for heavy metals.

[0020] It should be noted that the activation and modification process is carried out simultaneously with the sulfidation modification process, eliminating the need for a separate modification step, thus simplifying the process flow and reducing energy consumption. Water vapor, acting as an activator, reacts with the carbon on the activated carbon surface to generate new pores or expand existing pores, restoring the specific surface area of ​​the activated carbon. Nitrogen, acting as a protective gas, prevents the activated carbon from oxidizing and burning at high temperatures, while also inhibiting the formation of harmful gases such as dioxins. During the high-temperature activation process, the sulfidation modifier binds to the active sites on the activated carbon surface, introducing sulfur-containing functional groups such as thiol groups (-SH) and thioether groups (-S-). These functional groups can form stable complexes with heavy metal ions, significantly improving the adsorption selectivity and adsorption capacity of the regenerated carbon for heavy metals.

[0021] Preferably, the specific steps of the gradient heating are as follows: heating to 200-300℃ at a rate of 5-10℃ / min and holding for 30-45min; heating to 500-600℃ at a rate of 8-15℃ / min and holding for 60-90min; and heating to 700-850℃ at a rate of 10-20℃ / min and holding for 90-120min.

[0022] It should be noted that gradient heating can achieve the gradual removal of organic pollutants and the gradual restoration of the pore structure in activated carbon, avoiding the destruction of the pore structure of activated carbon due to excessively rapid heating, while ensuring that the sulfurization modifier and activated carbon are fully combined, thereby improving the modification effect.

[0023] Preferably, the specific parameters for the rapid cooling are: cooling to 100-150℃ at a rate of 15-25℃ / min; the passivation mixed gas is a mixture of nitrogen and oxygen, with an oxygen volume fraction of 5-10% and a flow rate of 0.5-1.5 m³ / min. 3 / h; the passivation treatment time is 30-60min.

[0024] It should be noted that rapid nitrogen cooling can prevent the primary recycled carbon from spontaneously combusting due to high temperature contact with air, while maintaining the stability of the pore structure and sulfur-containing functional groups on the surface of the activated carbon; passivation treatment can form a thin oxide film on the surface of the recycled carbon, further improving the storage stability of the recycled carbon, preventing it from oxidizing or adsorbing impurities during storage and transportation, while not affecting its adsorption performance for heavy metals.

[0025] The beneficial effects of this application are:

[0026] This application employs a one-step method to simultaneously activate and sulfide-modify activated carbon, simplifying the process, shortening the processing cycle, and reducing energy consumption and processing costs. Simultaneously, it introduces a large number of sulfur-containing functional groups such as thiol and thioether groups onto the surface of the regenerated carbon, restoring the pore structure of the activated carbon and significantly improving the adsorption selectivity and capacity for heavy metal ions. The preparation method of this application utilizes nitrogen protection throughout the process, effectively suppressing the generation of harmful gases such as dioxins and hydrogen sulfide, and achieving harmless treatment and resource utilization of treated waste liquid and tail gas, meeting environmental protection requirements. The process is simple to operate, can achieve continuous production, and is suitable for large-scale industrial applications, demonstrating good economic and environmental benefits. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 A flowchart illustrating a one-step preparation method for sulfide-modified heavy metal adsorption and regeneration carbon provided in this application.

[0029] Figure 2 This is a schematic diagram of an apparatus for a one-step preparation method of sulfide-modified heavy metal adsorption and regeneration carbon provided in this application.

[0030] Figure descriptions: 1. Pretreatment unit; 2. Conveying unit; 3. Continuous rotary activation furnace; 4. Sealed cooling device; 5. Finished product storage tank; 6. Tail gas treatment unit; 7. Waste liquid treatment unit. Detailed Implementation

[0031] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0032] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0033] The hazardous waste powdered activated carbon used in the embodiments of this application was taken from the wastewater treatment process of an electroplating plant and adsorbed heavy metals such as lead, cadmium, copper, and nickel. All embodiments of this application employ the following... Figure 2 The apparatus shown is used for the preparation of recycled carbon.

[0034] The following specific embodiments further illustrate this point:

[0035] Example 1

[0036] like Figure 1 As shown in the figure, this embodiment provides a one-step preparation method for sulfide-modified heavy metal adsorption and regeneration carbon:

[0037] 1. Place 100 kg of hazardous waste powdered activated carbon in a sealed pretreatment unit 1, and spray it at a rate of 1 m... 3 Purging with nitrogen gas at a flow rate of / h for 45 min, adding 300 kg of pretreatment solution obtained by mixing 8 wt% dilute hydrochloric acid and 3 wt% dilute sulfuric acid at a volume ratio of 1:1.5, stirring at 150 rpm for 3 h, filtering to obtain activated carbon residue and pretreatment waste liquid, washing the activated carbon residue with deionized water until neutral, and drying at 110℃ and -0.09 MPa vacuum until the moisture content is 4% to obtain pretreated activated carbon.

[0038] 2. The pretreated waste liquid is sent to the waste liquid treatment unit 7, sodium hydroxide is added to adjust the pH value to 8.5, and sodium sulfide of 0.5% by weight of the pretreated waste liquid is added for precipitation. After filtration, precipitated filter residue and filtrate are obtained. The precipitated filter residue is recycled and treated, and the filtrate is concentrated by membrane and reused in the pretreatment step.

[0039] 3. The pretreated activated carbon is fed into a continuous rotary activation furnace 3 with a rotation speed of 2 rpm through a sealed conveying unit 2. An activation-modified mixed gas is introduced into the furnace, and the temperature is simultaneously increased to 250℃ at a rate of 8℃ / min and held for 40 min, then increased to 550℃ at a rate of 12℃ / min and held for 75 min, and finally increased to 800℃ at a rate of 15℃ / min and held for 105 min, yielding primary regenerated carbon. The activation-modified exhaust gas is sent to an exhaust gas treatment unit 6 and discharged after treatment to meet standards. The water vapor flow rate in the activation-modified mixed gas is 1.0 m³ / min. 3 / h, nitrogen flow rate is 0.5m 3 / h, the sulfurization modifier is a mixture of hydrogen sulfide and carbon disulfide in a volume ratio of 1:2, and the amount added is 5% of the mass of the pretreated activated carbon.

[0040] 4. The primary recycled charcoal is fed into the sealed cooling device 4 through the sealed conveying unit 2. Nitrogen gas is first introduced, and the temperature is lowered to 120°C at a rate of 20°C / min. Then, the temperature is lowered at a rate of 1m... 3 A mixture of nitrogen and oxygen is introduced at a flow rate of / h, with an oxygen volume fraction of 8%. The mixture is passivated for 45 minutes and then cooled to room temperature to obtain the sulfide-modified heavy metal adsorption regenerated carbon prepared by the method described in Example 1. The carbon is then sent to the finished product storage tank 5 for later use.

[0041] Example 2

[0042] like Figure 1 As shown in the figure, this embodiment provides a one-step preparation method for sulfide-modified heavy metal adsorption and regeneration carbon:

[0043] 1. Place 100 kg of hazardous waste powdered activated carbon in a sealed pretreatment unit 1, and heat it at a pressure of 0.5 m³ / h. 3 Purging with nitrogen gas at a flow rate of / h for 30 min, adding 400 kg of pretreatment solution obtained by mixing 5 wt% dilute hydrochloric acid and 2 wt% dilute sulfuric acid in a volume ratio of 1:1, stirring at 100 rpm for 2 h, filtering to obtain activated carbon residue and pretreatment waste liquid, washing the activated carbon residue with deionized water until neutral, and drying it at a temperature of 105℃ and a vacuum degree of -0.08 MPa until the moisture content is 3% to obtain pretreated activated carbon.

[0044] 2. The pretreated waste liquid is sent to the waste liquid treatment unit 7, sodium hydroxide is added to adjust the pH value to 8, and 0.1% sodium sulfide by mass of the pretreated waste liquid is added for precipitation. After filtration, precipitated filter residue and filtrate are obtained. The precipitated filter residue is recycled and treated, and the filtrate is concentrated by membrane and reused in the pretreatment step.

[0045] 3. The pretreated activated carbon is fed into a continuous rotary activation furnace 3 with a rotation speed of 1 rpm through a sealed conveying unit 2. An activation-modified mixed gas is introduced into the furnace, and the temperature is simultaneously increased to 200℃ at a rate of 5℃ / min and held for 30 min, then increased to 500℃ at a rate of 8℃ / min and held for 60 min, and finally increased to 700℃ at a rate of 10℃ / min and held for 90 min, yielding primary regenerated carbon. The activation-modified exhaust gas is sent to an exhaust gas treatment unit 6 and discharged after treatment to meet standards. The water vapor flow rate in the activation-modified mixed gas is 0.8 m³ / min. 3 / h, nitrogen flow rate is 0.3m 3 / h, the sulfurization modifier is sodium thiosulfate vapor, and the addition amount is 2% of the mass of the pretreated activated carbon.

[0046] 4. The primary recycled charcoal is fed into the sealed cooling device 4 through the sealed conveying unit 2. Nitrogen gas is first introduced, and the temperature is lowered to 100°C at a rate of 15°C / min. Then, the temperature is lowered at a rate of 0.5m... 3 A mixture of nitrogen and oxygen is introduced at a flow rate of / h, with an oxygen volume fraction of 5%. The mixture is passivated for 30 minutes and then cooled to room temperature to obtain the sulfide-modified heavy metal adsorption regenerated carbon prepared by the method described in Example 2. The carbon is then sent to the finished product storage tank 5 for later use.

[0047] Example 3

[0048] like Figure 1 As shown in the figure, this embodiment provides a one-step preparation method for sulfide-modified heavy metal adsorption and regeneration carbon:

[0049] 1. Place 100 kg of hazardous waste powdered activated carbon in a sealed pretreatment unit 1, and heat it at a pressure of 1.5 m. 3 Purging with nitrogen gas at a flow rate of / h for 60 min, adding 500 kg of pretreatment solution obtained by mixing 10 wt% dilute hydrochloric acid and 5 wt% dilute sulfuric acid at a volume ratio of 1:2, stirring at 200 rpm for 4 h, filtering to obtain activated carbon residue and pretreatment waste liquid, washing the activated carbon residue with deionized water until neutral, and drying it at 120℃ and a vacuum of -0.1 MPa until the moisture content is 5% to obtain pretreated activated carbon.

[0050] 2. The pretreated waste liquid is sent to the waste liquid treatment unit 7, sodium hydroxide is added to adjust the pH value to 9, and sodium sulfide of 0.8% by mass of the pretreated waste liquid is added for precipitation. After filtration, precipitated filter residue and filtrate are obtained. The precipitated filter residue is recycled and treated, and the filtrate is concentrated by membrane and reused in the pretreatment step.

[0051] 3. The pretreated activated carbon is fed into a continuous rotary activation furnace 3 at a rotation speed of 3 rpm via a sealed conveying unit 2. An activation-modified mixed gas is introduced into the furnace, and the temperature is simultaneously increased to 300℃ at a rate of 10℃ / min and held for 45 min, then increased to 600℃ at a rate of 15℃ / min and held for 90 min, and finally increased to 850℃ at a rate of 20℃ / min and held for 120 min, yielding primary regenerated carbon. The activation-modified exhaust gas is sent to an exhaust gas treatment unit 6 and discharged after treatment to meet standards. The water vapor flow rate in the activation-modified mixed gas is 1.2 m³ / min. 3 / h, nitrogen flow rate is 0.8m 3 / h, the sulfidation modifier is hydrogen sulfide vapor, and the addition amount is 8% of the mass of the pretreated activated carbon.

[0052] 4. The primary recycled charcoal is fed into the sealed cooling device 4 through the sealed conveying unit 2. Nitrogen gas is first introduced, and the temperature is lowered to 150°C at a rate of 25°C / min. Then, the temperature is lowered at a rate of 1.5m... 3 A mixture of nitrogen and oxygen is introduced at a flow rate of / h, with an oxygen volume fraction of 10%. The mixture is passivated for 60 minutes and then cooled to room temperature to obtain the sulfide-modified heavy metal adsorption regenerated carbon prepared by the method described in Example 3. The carbon is then sent to the finished product storage tank 5 for later use.

[0053] Comparative Example 1

[0054] This comparative example provides a one-step preparation method for sulfurized modified heavy metal adsorption regenerated carbon. The difference from Example 1 is that no sulfurizing agent is added to the activated modified mixed gas. The remaining steps are the same as in Example 1 and will not be repeated here.

[0055] Comparative Example 2

[0056] This comparative example provides a one-step preparation method for sulfide-modified heavy metal adsorption regenerated carbon. Compared with Example 1, the difference is that gradient heating is not performed, but activation modification is carried out by direct heating. The remaining steps are the same as in Example 1, and will not be repeated here.

[0057] To demonstrate the beneficial effects of the proposed solution, the following performance tests were conducted on Examples 1-3 and Comparative Examples 1-2:

[0058] Specific surface area determination: The activated carbon sample was ground to below 200 mesh, and 0.2~0.3g was weighed and placed in a sample tube. The sample was degassed for 6 hours at 120℃ and a vacuum degree ≤10Pa to completely remove adsorbed water and impurities from the sample surface. During the test, high-purity nitrogen (99.999%) was used as the adsorbate, and adsorption-desorption tests were conducted in a constant temperature environment of liquid nitrogen at 77K. The relative pressure P / P0 test range was 0.005~0.995. After the test, the specific surface area of ​​the sample was calculated by the testing instrument. The test results are shown in Table 1.

[0059] Iodine adsorption value determination: Weigh 0.5g of dried activated carbon sample and place it in a 250mL iodine flask. Add 10.0mL of 1mol / L hydrochloric acid and gently shake to completely wet the sample. Add 50.0mL of 0.1000mol / L iodine standard solution, immediately stopper the flask, and place it in a constant temperature shaker. Control the temperature at 25℃ and the shaking frequency at 150r / min. Shake and adsorb for 15min. After standing and separating the layers, accurately transfer 10.0mL of the supernatant and titrate with sodium thiosulfate standard solution until light yellow. Add starch indicator and continue titrating until the blue color disappears. Record the volume consumed. Calculate the equilibrium iodine concentration based on the titration results. Obtain the iodine adsorption value by referring to the standard curve. The test results are shown in Table 1.

[0060] Determination of methylene blue adsorption value: Weigh 0.1g of activated carbon sample and place it in a 250mL Erlenmeyer flask. Add 50mL of phosphate buffer solution with pH=7.0, and then add a quantitative concentration of 1.5g / L methylene blue standard solution. After sealing, place the flask in a constant temperature shaker at 25℃ and 150r / min for 30min of shaking adsorption. Centrifuge the mixture at 4000r / min for 5min. Filter the supernatant through a 0.45μm filter membrane and measure the absorbance at 665nm wavelength. Calculate the remaining concentration of methylene blue in the equilibrium solution according to the standard curve. Calculate the methylene blue adsorption value by mass difference. The test results are shown in Table 1.

[0061] Determination of heavy metal ion adsorption capacity: The activated carbon sample was ground to 100-200 mesh, dried at 105℃ for 2 hours, and then cooled to room temperature in a desiccator. 0.05 g of the sample was accurately weighed into a 100 mL stoppered conical flask, and 50 mL of a 200 mg / L single heavy metal solution was added. The pH was adjusted to 5.0, the flask was sealed, and the mixture was placed in a constant temperature shaking incubator for 24 hours for adsorption. After adsorption, the mixture was centrifuged at 4000 r / min for 10 min. The supernatant was filtered through a 0.22 μm filter membrane, and the concentration of the remaining heavy metal in the filtrate was determined using an atomic absorption spectrophotometer. The adsorption capacity was calculated using the formula: Adsorption capacity = (Initial concentration of heavy metal ions - Concentration of heavy metal ions after adsorption) × Solution volume ÷ Mass of activated carbon sample; Pb was tested sequentially. 2+ Cd 2+Cu 2+ Ni 2+ The adsorption capacity was measured, and the test results are shown in Table 1.

[0062] Table 1. Test results of activated carbon samples from Examples 1-3 and Comparative Examples 1-2

[0063]

[0064] As can be seen from the test results in Table 1, the specific surface area, iodine adsorption value, and methylene blue adsorption value of Examples 1-3 are all at a high level, proving that the regenerated carbon prepared by the method of this application meets the mass transfer and physical adsorption requirements of adsorption materials. In contrast, in the scheme of Comparative Example 1, no sulfur modification agent was added, and its specific surface area, iodine adsorption value, and methylene blue adsorption value are similar to those of Examples 1-3. This indicates that the addition of sulfur modification agent does not destroy the pore structure of activated carbon. However, the adsorption capacity of the regenerated carbon prepared in Comparative Example 1 for heavy metal ions is significantly reduced. This is because the lack of sulfur modification agent treatment results in the absence of sulfur-containing functional groups such as mercapto (-SH) and thioether (-S-) groups on the surface of the regenerated carbon, which cannot complex with heavy metal ions, thereby reducing its adsorption capacity for heavy metal ions. In Comparative Example 2, instead of using a gradient heating activation modification method, the activation modification was performed by directly heating. This caused the organic pollutants on the surface of the activated carbon to escape too quickly, which easily led to pore collapse and carbon skeleton burn-off, ultimately affecting the repair and regeneration of pores. As a result, its basic adsorption properties, such as specific surface area and iodine adsorption value, decreased. This also led to a decrease in the amount of functional group grafting during the sulfidation modification process, thus reducing its adsorption capacity for heavy metal ions.

[0065] In summary, the proposed solution effectively improves the adsorption effect of the regenerated activated carbon on heavy metal ions by simultaneously activating, regenerating, and modifying the powdered activated carbon in hazardous waste. It also shortens the regeneration process, saves costs, and is suitable for the deep treatment of wastewater and exhaust gas containing heavy metals in the electroplating, chemical, and metallurgical industries.

[0066] It should be noted that the above description is only a preferred embodiment of this application, and the protection scope of this application is not limited to the above embodiments. All technical solutions within the scope of this application's concept are within the protection scope of this application. It should be pointed out that for those skilled in the art, any improvements and modifications made without departing from the principles of this application should also be considered within the protection scope of this application.

Claims

1. A one-step preparation method for sulfide-modified heavy metal adsorption and regeneration carbon, characterized in that, Includes the following steps: Hazardous waste powdered activated carbon is placed in a closed pretreatment unit (1), nitrogen is purged, pretreatment liquid is added, stirring is performed, activated carbon filter residue and pretreatment waste liquid are obtained by filtration, activated carbon filter residue is washed with deionized water until neutral and dried until the moisture content is ≤5% to obtain pretreated activated carbon. The pretreated waste liquid is sent to the waste liquid treatment unit (7), sodium hydroxide is added to adjust the pH, sodium sulfide is added to precipitate, and the mixture is filtered to obtain precipitated residue and filtrate. The precipitated residue is recycled and the filtrate is concentrated by membrane and then reused in the pretreatment step. The pretreated activated carbon is fed into the continuous rotary activation furnace (3) through the sealed conveying unit (2), and the activation and modification mixed gas is introduced into the furnace. At the same time, the temperature is increased in a gradient to carry out the activation and modification treatment to obtain the primary recycled carbon. The tail gas of the activation and modification treatment is sent to the tail gas treatment unit (6) and discharged after being treated to meet the standards. The primary recycled carbon is fed into a closed cooling device (4) through a sealed conveying unit (2). Nitrogen gas is first introduced for rapid cooling, and then passivation mixed gas is introduced. After passivation treatment, it is cooled to room temperature to obtain sulfide-modified heavy metal adsorption recycled carbon, which is then sent to the finished product storage tank (5) for later use.

2. The one-step preparation method of sulfide-modified heavy metal adsorption regenerated carbon according to claim 1, characterized in that, The nitrogen purging time is 30-60 minutes, and the nitrogen flow rate is 0.5-1.5 m³ / min. 3 / h.

3. The one-step preparation method of sulfide-modified heavy metal adsorption regenerated carbon according to claim 1, characterized in that, The pretreatment solution is obtained by mixing 5-10wt% dilute hydrochloric acid and 2-5wt% dilute sulfuric acid at a volume ratio of 1:1-2; the mass ratio of hazardous waste powdered activated carbon to the pretreatment solution is 1:3-5.

4. The one-step preparation method of sulfide-modified heavy metal adsorption regenerated carbon according to claim 1, characterized in that, The stirring rate of the pretreatment step is 100-200 rpm, and the treatment time is 2-4 hours.

5. A one-step preparation method for sulfide-modified heavy metal adsorption and regeneration carbon according to claim 1, characterized in that, The drying step employs vacuum drying at a temperature of 105-120℃ and a vacuum degree of -0.08 to -0.1 MPa.

6. A one-step preparation method for sulfide-modified heavy metal adsorption regenerated carbon according to claim 1, characterized in that, The pH value of the added sodium hydroxide is adjusted to 8-9; the amount of added sodium sulfide is 0.1-0.8% of the mass of the pretreated waste liquid.

7. A one-step preparation method for sulfide-modified heavy metal adsorption and regeneration carbon according to claim 1, characterized in that, The continuous rotary activation furnace (3) operates at a speed of 1-3 rpm; the activation-modifying mixed gas consists of water vapor, nitrogen, and a sulfurizing modifier; the water vapor flow rate is 0.8-1.2 m³ / h. 3 / h, nitrogen flow rate is 0.3-0.8m 3 / h, the amount of sulfidation modifier added is 2-8% of the mass of the pretreated activated carbon.

8. A one-step preparation method for sulfide-modified heavy metal adsorption and regeneration carbon according to claim 1, characterized in that, The sulfidation modifier is any one or more of hydrogen sulfide, carbon disulfide, or sodium thiosulfate vapor.

9. A one-step preparation method for sulfide-modified heavy metal adsorption and regeneration carbon according to claim 1, characterized in that, The specific steps of the gradient heating are as follows: heat to 200-300℃ at a rate of 5-10℃ / min, hold for 30-45min, heat to 500-600℃ at a rate of 8-15℃ / min, hold for 60-90min, heat to 700-850℃ at a rate of 10-20℃ / min, and hold for 90-120min.

10. A one-step preparation method for sulfide-modified heavy metal adsorption and regeneration carbon according to claim 1, characterized in that, The specific parameters for the rapid cooling are: cooling to 100-150℃ at a rate of 15-25℃ / min; the passivation mixed gas is a mixture of nitrogen and oxygen, with an oxygen volume fraction of 5-10% and a flow rate of 0.5-1.5 m³ / min. 3 / h; the passivation treatment time is 30-60min.

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