Method for removing methanethiol from kitchen waste using KOH-modified biochar activation persulfate.

Abstract

This invention discloses a method for removing methanethiol from kitchen waste during disposal using KOH-modified biochar activated with persulfate. The method first prepares KOH-modified biochar using walnut shell powder and KOH. Then, the KOH-modified biochar, persulfate, and water are added to a reaction apparatus. Methanethiol from the kitchen waste disposal process is introduced into the reaction apparatus, where a bubble generator produces bubbles, ensuring sufficient contact between the methanethiol and the KOH-modified biochar and persulfate. Through adsorption and catalytic oxidation, the methanethiol is removed. This method can continuously and efficiently remove methanethiol under conventional conditions, maintaining a removal rate of approximately 91% per hour. It has advantages such as high removal efficiency, simple operation, and low cost.

Description

Technical Field

[0001] This invention belongs to the field of advanced oxidation technology, specifically relating to a method for removing methanethiol from kitchen waste during the process of using KOH-modified biochar to activate persulfate. Background Technology

[0002] Kitchen waste generally includes vegetable and fruit scraps, fruit peels, leftover food, and spoiled food. It is characterized by high water content, high salt content, high oil content, and easy decomposition. It typically contains abundant organic matter such as protein, fat, and starch. If not treated promptly and harmlessly, it easily produces foul-smelling gases and breeds pathogenic microorganisms. During composting, under aerobic or anaerobic conditions, kitchen waste easily produces irritating gases such as ammonia, hydrogen sulfide, and thiols, as well as nitrogen-containing compounds such as amines and amides through metabolism. Furthermore, due to differences in the source and composition of kitchen waste, as well as different treatment methods, different waste components and treatment conditions have a significant impact on the amount of odorous substances generated. Among the odorous substances generated during kitchen waste disposal, methanethiol (CH3SH) is a ubiquitous sulfur-containing volatile organic compound (S-VOC) with an extremely low odor threshold and high toxicity, posing a significant threat to the ecological environment and human health. Currently, many methods have been developed for the pollution management of methanethiol, including adsorption, spraying, and biological treatment. However, these methods have problems such as high cost, low treatment efficiency, complex operation, and harsh treatment conditions. Therefore, it is necessary to develop a simple, low-cost method with high degradation capabilities to remove methanethiol.

[0003] Sulfate advanced oxidation processes (PS-AOPs) are widely used for the degradation of various organic pollutants due to their low cost and high efficiency. In the PS-AOPs process, the peroxy bonds of persulfate (PS) are easily broken by the catalyst, generating various reactive oxygen species (ROS), which have strong oxidizing power. Many catalysts are available, including activated carbon, carbon nanotubes, and biochar, all considered effective catalysts for activating PS. Among them, biochar is widely used in PS-AOPs for pollutant removal due to its strong adsorption capacity, good catalytic effect, and simple preparation. Biochar is generally prepared from biomass materials such as straw, nut shells, and sludge through thermochemical processes such as pyrolysis and hydrothermal carbonization. Biochar has a large specific surface area and abundant oxygen-containing functional groups, which enable it to efficiently activate PS. However, traditional biochar is limited by its specific surface area and lacks defect sites, usually requiring modification to improve its ability to activate PS and degrade organic pollutants. Therefore, various methods have been applied to modify biochar in order to enhance its role in environmental remediation, including nitrogen doping, metal oxide loading, acid modification, and alkali modification. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for removing methanethiol from kitchen waste by KOH-modified biochar-activated persulfate, which is simple to operate, low in cost, and can efficiently and continuously degrade methanethiol under mild conditions.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0006] A method for removing methanethiol from kitchen waste during the disposal process using KOH-modified biochar activated persulfate, comprising the following steps:

[0007] Preparation of S1 and KOH modified biochar:

[0008] S1.1 Add walnut shell powder and KOH to water, stir until completely cooled, and then dry to obtain a biochar precursor; wherein the mass ratio of the walnut shell powder to the KOH is 1:2 to 3.

[0009] S1.2 The precursor obtained above is calcined at 600℃~800℃ for 1h~2h, then acid is added and stirred, and then washed alternately with ethanol and water. After filtration and drying, KOH modified biochar is obtained.

[0010] S2. Add the obtained KOH-modified biochar, persulfate, and water to a reaction device. Introduce methanethiol from the kitchen waste disposal process into the reaction device. The reaction device is equipped with a bubble generator. The bubbles generated by the bubble generator allow the methanethiol to come into full contact with the KOH-modified biochar and persulfate. Through adsorption and catalytic oxidation reactions, the methanethiol is removed.

[0011] In the above-mentioned method for removing methanethiol from kitchen waste by activating persulfate with KOH-modified biochar, preferably, in step S2, the ratio of the mass of the KOH-modified biochar, the mass of the persulfate, the volume of the water, and the volume of the reaction device is 0.1g~0.15g∶1.0g~1.5g∶1L∶1L, and the mass flow rate of the methanethiol-containing mixed gas is 1L / min~2L / min.

[0012] In the above-mentioned method for removing methanethiol from kitchen waste by KOH-modified biochar activation of persulfate, preferably, in step S2, the methanethiol from the kitchen waste disposal process is introduced into the reaction device in the form of a methanethiol-containing mixed gas, and the methanethiol-containing mixed gas is generated from the kitchen waste disposal process.

[0013] In the above-mentioned method for removing methanethiol from kitchen waste by KOH-modified biochar-activated persulfate, preferably, in step S2, the bubble generator is located at the bottom of the reaction device, the inlet of the reaction device is connected to a gas cylinder via a pipeline, the gas cylinder contains the methanethiol-containing mixed gas, a mass flow controller is provided on the pipeline, a first methanethiol detector for detecting the inlet methanethiol concentration is provided on the pipeline near the inlet of the reaction device, and a second methanethiol detector for detecting the outlet methanethiol concentration is provided at the outlet of the reaction device.

[0014] In the above-mentioned method for removing methanethiol from kitchen waste by activating persulfate with KOH-modified biochar, preferably, in step S1.1, the stirring time is 3h to 5h and the drying temperature is 105℃ to 120℃.

[0015] In the above-mentioned method for removing methanethiol from kitchen waste by KOH-modified biochar activation of persulfate, preferably, in step S1.2, the acid used is 5% to 15% dilute nitric acid by mass fraction, the stirring time is 3 to 5 hours, and the drying temperature is 60°C to 105°C.

[0016] In this invention, the preferred method for removing methanethiol from kitchen waste using KOH-modified biochar-activated persulfate is implemented in conjunction with the following system, but is not limited thereto:

[0017] (1) Add KOH-modified biochar, persulfate and water to the reaction apparatus;

[0018] (2) Continuously pass the gas mixture containing methanethiol from the gas cylinder into the reaction apparatus;

[0019] (3) Turn on the bubble generator at the bottom of the reaction device. The generated bubbles allow methanethiol to come into full contact with KOH-modified biochar and persulfate. Through adsorption and catalytic oxidation reactions, methanethiol is removed. The inlet concentration and outlet concentration of methanethiol are detected by the first methanethiol detector at the inlet of the reaction device and the second methanethiol detector at the outlet of the reaction device, respectively.

[0020] Compared with the prior art, the advantages of the present invention are as follows:

[0021] 1. This invention provides a method for the continuous removal of methanethiol from kitchen waste during the disposal process using KOH-modified biochar to activate persulfate. In this method, methanethiol can react with KOH-modified biochar (BC) KOH The process involves thorough contact between the methanethiol (BTM) and persulfate (PS), resulting in adsorption and catalytic oxidation reactions, which can continuously and efficiently degrade methanethiol. The method of this invention is simple to operate and [BC is missing from the original text]. KOHIt requires less dosage and has a lower cost, and can continuously and efficiently degrade methanethiol under mild conditions.

[0022] 2. The method of this invention provides KOH-modified biochar, which has the advantages of strong adsorption capacity and high PS activation efficiency. The applicant discovered that alkali modification can give biochar a more porous structure and stronger adsorption capacity. KOH modification not only makes the microporous structure of the biochar highly developed and significantly increases the number of micropores, but also makes the biochar structure thinner and increases the specific surface area. This not only facilitates the adsorption of organic matter by the biochar, but also creates favorable conditions for PS activation by exposing more active sites. The KOH-modified biochar provided by this invention is simple to synthesize, the material is derived from walnut shell powder, and it has the advantages of low cost, good effect, and environmental friendliness. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the system structure for removing methanethiol from kitchen waste using KOH-modified biochar activated persulfate in Example 1 of the present invention.

[0024] Figure 2 The unmodified biochar BC in Comparative Example 1 and the KOH-modified biochar BC in Example 1 of this invention. KOH The SEM images are shown, where (a) is Comparative Example 1 and (b) is Example 1.

[0025] Figure 3 The KOH-modified biochar BC in Example 1 of this invention KOH Nitrogen adsorption-desorption isotherms of unmodified biochar BC in Comparative Example 1.

[0026] Figure 4 The KOH-modified biochar BC in Example 1 of this invention KOH The removal efficiency of methanethiol by unmodified biochar BC-activated PS in Comparative Example 1.

[0027] Legend:

[0028] 1. Reaction apparatus; 2. Bubble generator; 3. Gas cylinder; 4. Mass flow controller; 5. First methanethiol detector; 6. Second methanethiol detector. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention. The materials and instruments used in the following embodiments are all commercially available. The first and second methanethiol detectors are Cornuom MOT500-CH4S methanethiol detectors, which can directly record the concentration of methanethiol.

[0030] Example 1

[0031] A method for removing methanethiol from kitchen waste during the disposal process using KOH-modified biochar activated persulfate, according to the present invention, includes the following steps:

[0032] Preparation of S1 and KOH modified biochar:

[0033] S1.1 Add walnut shell powder and KOH to water at a mass ratio of 1:3, stir for 5 hours until the heat is completely dissipated, and then dry in an oven at 105℃ to obtain biochar precursor.

[0034] S1.2. The biochar precursor was placed in a tube furnace and calcined at 600℃ for 1 hour. After calcination, 150 mL of 5 wt% dilute nitric acid was added, and the mixture was stirred for 5 hours. The biochar was then washed three times alternately with ethanol and ultrapure water. After washing, the mixture was filtered and dried at 105℃ to obtain KOH-modified biochar, denoted as BC. KOH .

[0035] S2. Add the obtained KOH-modified biochar, persulfate (PS) (potassium persulfate is used in this embodiment, but it is not limited to this), and water to the reaction device 1. Continuously introduce the methanethiol generated during the kitchen waste disposal process into the reaction device 1. The reaction device 1 is equipped with a bubble generator 2 (i.e., a bubbling device). The bubble generator 2 generates bubbles, which allow the methanethiol to come into full contact with the KOH-modified biochar and persulfate. Through adsorption and catalytic oxidation reactions, the methanethiol is removed.

[0036] In step S2 of this embodiment, as follows Figure 1 As shown, bubble generator 2 is located at the bottom of reaction device 1. The inlet of reaction device 1 is connected to gas cylinder 3 via a pipeline. Gas cylinder 3 contains a mixture of methanethiol-containing gas, which is generated during the disposal of kitchen waste (mainly malodorous gas). This mixture is collected into gas cylinder 3 under negative pressure. A mass flow controller 4 is installed on the pipeline to control the flow rate of the methanethiol-containing gas mixture. A first methanethiol detector 5 is installed on the pipeline near reaction device 1 to detect the methanethiol concentration at the inlet of reaction device 1, and a second methanethiol detector 6 is installed at the outlet of reaction device 1 to detect the methanethiol concentration at the outlet of reaction device 1. This system is a system for removing methanethiol from kitchen waste during the disposal process using KOH-modified biochar activated persulfate. Based on this system, the specific process flow of step S2 is as follows:

[0037] (1) Add 0.1g of BC to a 1L reaction apparatus 1. KOH 1.0g PS and 1L water;

[0038] (2) The mixed gas containing methanethiol in gas cylinder 3 is continuously introduced into reaction apparatus 1 at a mass flow rate of 1 L / min;

[0039] (3) Turn on the bubble generator 2 at the bottom of the reaction device 1. The generated bubbles cause methanethiol to react with BC. KOH With full contact with PS, BC KOH Methanethiol is adsorbed into the pores of the device, and reactive oxygen species (ROS) are generated by the activation of PS by oxygen-containing functional groups on the PS surface. These ROS react with the Methanethiol, thus removing it. The inlet and outlet concentrations of Methanethiol are detected by a first Methanethiol detector 5 at the inlet of the reaction device 1 and a second Methanethiol detector 6 at the outlet of the reaction device 1, respectively.

[0040] The removal efficiency E of methanethiol is calculated using the formula E = (Cin - Cout) / Cin × 100%. Where Cin is the inlet concentration of methanethiol and Cout is the outlet concentration of methanethiol.

[0041] Comparative Example 1

[0042] The process is basically the same as in Example 1, except that in step S1, KOH is not added, and unmodified biochar (BC) is prepared.

[0043] The unmodified biochar BC prepared in Comparative Example 1 and the KOH-modified biochar BC prepared in Example 1 were compared. KOH The physicochemical properties and the ability of activated PS to remove methanethiol were characterized. For example... Figure 2 As shown, (a) is the SEM image of BC, and (b) is the SEM image of BC. KOH The SEM images show that, compared to BC, KOH modification makes the biochar structure thinner and increases the number of micropores.

[0044] The KOH-modified biochar BC prepared in Example 1 KOH BET analysis was performed on the unmodified biochar BC prepared in Comparative Example 1, and the nitrogen adsorption-desorption isotherms of the two were obtained, as follows: Figure 3 As shown. Calculations show that BC KOH Compared with BC, the specific surface area of ​​the biochar increased by 51.73%, the pore volume increased by 50.99%, and the number of micropores increased significantly. This not only facilitates the adsorption of organic matter by biochar, but also creates favorable conditions for the activation of PS by exposing more active sites.

[0045] Figure 4 KOH-modified biochar BC prepared in Example 1 KOH The graph shows the removal efficiency of methanethiol by unmodified biochar (BC) activated PS prepared in Comparative Example 1, which also includes control PS, water, BC, and BC. KOH .like Figure 4 As shown, in the presence of only BC, the removal efficiency of methanethiol decreased from 69.44% to 27.85% within 1 hour, while in the presence of only BC... KOHWithin 1 hour, the removal efficiency of methanethiol also decreased significantly (from 75.12% to 38.44%). This indicates that KOH modification can improve the adsorption performance of biochar; however, due to the limited contact time and the limited adsorption performance of biochar, simple adsorption is insufficient for efficient removal of methanethiol. Methanethiol has very poor water solubility, with a solubility close to 0 within 1 hour, so the effect of water solubility on this experiment can be largely ignored. The removal efficiency of PS alone for methanethiol decreased from 10.34% to 1.69% within 1 hour, indicating that PS itself has a very low oxidation efficiency for methanethiol. When biochar and PS were added simultaneously, the removal efficiency of methanethiol was significantly improved. Specifically, after BC activated PS, the removal efficiency of methanethiol decreased from 77.51% to 51.58% within 1 hour, while BC… KOH The removal efficiency after PS activation is not only as high as 91%, but can also be maintained at around 91%. Therefore, the method for removing methanethiol using KOH-modified biochar activated persulfate according to Example 1 of this invention can achieve continuous and efficient removal of methanethiol.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for removing methanethiol from kitchen waste during the disposal process using KOH-modified biochar activated persulfate, characterized in that, Includes the following steps: Preparation of S1 and KOH modified biochar: S1.1 Add walnut shell powder and KOH to water, stir until completely cooled, and then dry to obtain a biochar precursor; wherein the mass ratio of the walnut shell powder to the KOH is 1:2 to 3. S1.2 The precursor obtained above is calcined at 600℃~800℃ for 1h~2h, then acid is added and stirred, and then washed alternately with ethanol and water. After filtration and drying, KOH modified biochar is obtained. S2. Add the obtained KOH modified biochar, persulfate and water to a reaction device (1). Introduce methanethiol from the kitchen waste disposal process into the reaction device (1). The reaction device (1) is equipped with a bubble generator (2). The bubbles generated by the bubble generator (2) allow methanethiol to come into full contact with KOH modified biochar and persulfate. Through adsorption and catalytic oxidation reaction, the methanethiol is removed.

2. The method for removing methanethiol from kitchen waste during the disposal process using KOH-modified biochar activated persulfate according to claim 1, characterized in that, In step S2, the methanethiol from the kitchen waste disposal process is introduced into the reaction device (1) in the form of a methanethiol-containing mixed gas, which is generated from the kitchen waste disposal process; the ratio of the mass of the KOH-modified biochar, the mass of the persulfate, the volume of the water, and the volume of the reaction device (1) is 0.1g~0.15g∶1.0g~1.5g∶1L∶1L, and the mass flow rate of the methanethiol-containing mixed gas is 1L / min~2L / min.

3. The method for removing methanethiol from kitchen waste during the disposal process using KOH-modified biochar activated persulfate according to claim 2, characterized in that, In step S2, the bubble generator (2) is located at the bottom of the reaction device (1). The inlet of the reaction device (1) is connected to a gas cylinder (3) through a pipe. The gas cylinder (3) contains the mixed gas containing methanethiol. A mass flow controller (4) is provided on the pipe. A first methanethiol detector (5) for detecting the concentration of methanethiol at the inlet is provided on the pipe near the inlet of the reaction device (1). A second methanethiol detector (6) for detecting the concentration of methanethiol at the outlet is provided at the outlet of the reaction device (1).

4. The method for removing methanethiol from kitchen waste using KOH-modified biochar activated persulfate according to any one of claims 1 to 3, characterized in that, In step S1.1, the stirring time is 3h to 5h, and the drying temperature is 105℃ to 120℃.

5. The method for removing methanethiol from kitchen waste during the disposal process using KOH-modified biochar activated persulfate according to any one of claims 1 to 3, characterized in that, In step S1.2, the acid used is dilute nitric acid with a mass fraction of 5% to 15%, the stirring time is 3 to 5 hours, and the drying temperature is 60°C to 105°C.

Images