A cobalt-modified sludge biochar, its preparation method and application

Abstract

The present invention discloses a cobalt-modified sludge biochar and its preparation method and application, belonging to the field of biomass recycling technology. Kitchen sludge is used as raw material, and biochar is obtained by high-temperature slow pyrolysis. A high concentration of divalent cobalt ions is loaded on the biochar to achieve modification. The modification with high-concentration divalent cobalt ions effectively increases the specific surface area and total pore volume of the biochar, which can significantly improve the production capacity of the anaerobic effect process. The optimal dosage is 4 to 6 g / L. Under the same dosage, compared with unmodified biochar, the cobalt-modified sludge biochar can increase the cumulative methane production by 195.09%. The present invention uses kitchen sludge to prepare biochar and modify it to form biochar for improving the system performance in the anaerobic digestion of kitchen waste, forming a unique closed-loop treatment for kitchen waste, which is of great significance for achieving the reduction, harmlessness and resource utilization of kitchen waste.

Description

Technical Field

[0001] The present invention belongs to the technical field of biomass recycling, and in particular relates to a cobalt-modified sludge biochar and a preparation method and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] With the global population growth and accelerated urbanization, the amount of food waste generated by the catering industry and households has surged, placing a significant burden on the environment and resources. According to reports, over 1.3 billion tons of food waste are generated globally annually, and this amount is projected to reach approximately 2.2 billion tons by 2025. Large quantities of leftovers, fruit peels, eggshells, and expired food are discarded, occupying a significant portion of landfills. Therefore, developing technologies for the harmless treatment and resource utilization of food waste is crucial for sustainable development.

[0004] Anaerobic digestion (AD) technology, as a cost-effective and efficient treatment technology, has been used for renewable energy production and waste treatment. This process is of great significance for reducing the environmental impact of organic waste and realizing waste resource utilization. However, traditional anaerobic digestion processes have several limitations, such as slow reaction rates, poor system stability, and susceptibility to acidification and ammonia nitrogen inhibition. These issues restrict the widespread application and efficiency of anaerobic digestion technology and increase the risks of anaerobic fermentation systems. To effectively address these issues, many researchers have found in recent years that the addition of conductive biochar can effectively improve the efficiency of anaerobic digestion.

[0005] Biochar has properties such as high specific surface area, porous structure, abundant surface functional groups, and good electrical conductivity, which make it an effective material for improving anaerobic digestion processes. In recent years, it has been considered feasible to enhance the stability of AD systems by adding biochar. Metal Co is required for coenzyme M methyltransferase. The combination of biochar and metal ions can improve its performance by introducing functional groups and increasing porosity. However, metal loading may also reduce the pore size of biochar, thereby reducing the attachment of functional microorganisms. Therefore, the use of different concentrations of metal ion modifiers will result in different properties of the modified biochar. Liu Yutong et al. (Liu Yutong, Peng Ziyu, Zhang Yang et al. Co-modified hydrothermal biochar enhances anaerobic digestion of chicken manure under high concentration of sulfamethazine [J]. Contemporary Chemical Research, 2023, (24): 39-41.) used low concentrations of divalent cobalt ions to modify Enteromorpha-based hydrothermal biochar and found that compared with hydrothermal biochar, Co-modified hydrothermal biochar can enhance the anaerobic digestion of chicken manure under high concentration of sulfamethazine. In the AD system, the optimized concentration of Co-hydrothermal biochar modification was 1.5 mmol / L, and the maximum cumulative methane production increased by 1.25 times. However, its enhanced anaerobic digestion effect is still not ideal and needs to be further improved. At present, there is no report on high concentration of divalent cobalt ion modified biochar for harmless treatment and resource utilization of food waste. Therefore, studying high concentration of divalent cobalt ion modified biochar to improve its enhanced anaerobic digestion effect is of great significance in the harmless treatment and resource utilization of food waste and enriching the performance of different divalent cobalt ion loading concentrations. Summary of the Invention

[0006] In order to address the deficiencies of the prior art, the present invention aims to provide a cobalt-modified sludge biochar, a preparation method, and an application thereof. The present invention utilizes food sludge to prepare sludge biochar, and uses a high-concentration cobalt salt to modify the food sludge biochar, significantly increasing the specific surface area and total void volume of the biochar. By controlling the dosage of the cobalt salt, the anaerobic digestion process of food waste is promoted and the anaerobic digestion effect is enhanced.

[0007] In order to achieve the above object, the technical solution of the present invention is:

[0008] The first aspect of the present invention provides a method for preparing cobalt-modified sludge biochar, comprising the following steps:

[0009] The kitchen sludge is dried, ground and sieved to obtain sludge particles;

[0010] The sludge particles are carbonized and pyrolyzed by a high-temperature slow pyrolysis method to obtain biochar;

[0011] The obtained biochar is modified with a cobalt salt solution having a concentration of 0.08-0.17 mol / L, and the cobalt-modified sludge biochar is obtained after solid-liquid separation, washing, and freeze-drying.

[0012] In some embodiments of the present invention, the kitchen sludge is dried at a temperature of 100-110° C. and a drying time of 10-30 hours.

[0013] In some embodiments of the present invention, the particle size of the sludge particles is less than 150 mesh.

[0014] In some embodiments of the present invention, the high-temperature slow pyrolysis is: under anaerobic conditions, heating to 400-600°C at a heating rate of 4-6°C / min, keeping the temperature constant for 1.5-2.5 hours, then stopping heating and cooling to room temperature.

[0015] In some embodiments of the present invention, anaerobic conditions are ensured by introducing protective gas; the flow rate of the protective gas is 0.2-0.5 L / min.

[0016] Preferably, the protective gas comprises nitrogen or helium.

[0017] In some embodiments of the present invention, the biochar obtained after carbonization and pyrolysis is washed, solid-liquid separated, and dried, and then modified with a cobalt salt solution.

[0018] Preferably, the washing is performed multiple times using ethanol and deionized water.

[0019] Preferably, the solid-liquid separation is achieved by using a 0.45 μm membrane filtration to separate the biochar from the solution.

[0020] Preferably, the drying is carried out at 100-110° C. for 10-15 hours.

[0021] In some embodiments of the present invention, the modification process comprises the following steps:

[0022] The obtained biochar is placed in a cobalt salt solution with a concentration of 0.08-0.17 mol / L and shaken at 25-35° C. for 20-30 hours to complete the modification.

[0023] The present invention uses a high-concentration cobalt salt solution to modify the sludge biochar, thereby changing the surface morphology of the biochar. A flocculent structure is formed on the surface of the biochar, which increases the specific surface area and extends the pore structure, providing certain conditions for the attachment of microorganisms.

[0024] Preferably, the cobalt salt includes one of cobalt chloride, cobalt sulfate or cobalt nitrate.

[0025] Preferably, the ratio of biochar to cobalt salt solution is 1 g:8-12 mL.

[0026] In some embodiments of the present invention, the solid-liquid separation is achieved by using a 0.45 μm membrane filtration to separate the cobalt-modified biochar from the solution.

[0027] In some embodiments of the present invention, the washing is performed with deionized water.

[0028] In some embodiments of the present invention, the drying is freeze drying, which is performed after freezing at -85 to -75° C. The purpose of freezing is to match the temperature of the cobalt-modified biochar with the temperature of the freeze drying equipment.

[0029] The second aspect of the present invention provides a cobalt-modified sludge biochar, which is prepared by the preparation method described in the first aspect.

[0030] The cobalt-modified sludge biochar provided by the present invention has a high specific surface area and total pore volume. After testing, the specific surface area of the biochar is 98.6842 m 2 / g, micropore specific surface area is 37.9010m 2 / g; total pore and micropore volumes were 114.3 and 17.9 μL / g, respectively; and the average pore diameter was 8.1045 nm. Compared to unmodified biochar, the sludge biochar loaded with divalent cobalt ions increased its total specific surface area by 37.4%, its micropore specific surface area by 13.1%, its micropore volume by 12.6%, and its total pore volume by 30.6%, providing an ideal habitat for subsequent microbial growth.

[0031] The third aspect of the present invention provides a use of the cobalt-modified sludge biochar described in the second aspect in enhancing anaerobic digestion of food waste.

[0032] A fourth aspect of the present invention provides a method for enhancing anaerobic digestion of food waste, comprising the following steps: adding the cobalt-modified sludge biochar described in the second aspect to the food waste; the cobalt-modified sludge biochar is used at a concentration of 4 g / L to 6 g / L.

[0033] Through experiments and tests, the present invention found that adding 4g / L and 6g / L of cobalt-modified sludge biochar can increase the cumulative biogas production by 81.0% and 16.0%; adding 8g / L of cobalt-modified sludge biochar inhibited the anaerobic digestion process. It can be seen that the performance of cobalt-modified biochar on the anaerobic digestion system can be summarized as "low promotion and high inhibition", and its optimal addition amount is determined to be 4-6g / L.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The present invention provides a method for preparing cobalt-modified sludge biochar, wherein the biochar is obtained by carbonizing and pyrolyzing the food sludge through high-temperature slow pyrolysis, and the modification is achieved by loading a high concentration of divalent cobalt ions on the biochar. The preparation method of the present invention is simple and can effectively increase the specific surface area and total pore volume of the biochar, providing a good habitat for subsequent microorganisms. Secondly, the present invention uses high-carbon food sludge as an excellent raw material for preparing biochar, utilizes the food sludge produced by anaerobic digestion of food waste to prepare biochar and modifies it, forming biochar for improving the system performance in anaerobic digestion of food waste, forming a unique closed-loop treatment for food waste, which is of great significance for achieving food waste reduction, harmlessness, and resource utilization.

[0036] This method modifies sludge biochar by loading it with a high concentration of divalent cobalt ions, resulting in a functional biochar with excellent performance. Compared to unmodified biochar, the biochar loaded with high-concentration divalent cobalt ions has a 37.4% increase in total specific surface area, a 13.1% increase in micropore specific surface area, a 12.6% increase in micropore volume, and a 30.6% increase in total pore volume, providing an ideal habitat for subsequent microbial growth.

[0037] The cobalt-modified sludge biochar provided by the present invention can significantly improve the production capacity effect of the anaerobic effect process. Compared with the blank group, the addition of 4g / L and 6g / L of cobalt-modified sludge biochar can increase the cumulative biogas production by 81.0% and 16.0%; the addition of 8g / L of cobalt-modified sludge biochar inhibited the anaerobic digestion process. The performance of cobalt-modified sludge biochar on the anaerobic digestion system can be summarized as "low promotion and high inhibition", and its optimal dosage is 4-6g / L. Under the same dosage (4g / L), compared with unmodified biochar, cobalt-modified sludge biochar can increase the cumulative methane production by 202.6%. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0039] Figure 1 Schematic diagram of the process of enhancing anaerobic digestion by using cobalt-modified biochar in Example 1 of the present invention;

[0040] Figure 2 Schematic diagrams of scanning electron micrographs of primary sludge biochar and cobalt-modified sludge biochar in Example 1. (a) is a scanning electron micrograph of the primary sludge biochar prepared in Example 1, at a magnification of 20,000 times; (b) is a scanning electron micrograph of the cobalt-modified sludge biochar prepared in Example 1, at a magnification of 20,000 times;

[0041] Figure 3are the basic characterization parameters of the primary sludge biochar and cobalt-modified sludge biochar in Example 1, including specific surface area, total pore volume, micropore volume, and average pore diameter;

[0042] FIG4( a ) is a graph of daily gas production in Experimental Example 1 of the present invention;

[0043] FIG4( b ) is a graph showing the cumulative gas production in Experimental Example 1 of the present invention;

[0044] Figure 5 is a graph showing changes in the total volatile fatty acid content in Experimental Example 1 of the present invention;

[0045] FIG6( a ) is a graph of daily gas production in Experimental Example 2 of the present invention;

[0046] FIG6( b ) is a graph showing the cumulative gas production in Experimental Example 2 of the present invention. DETAILED DESCRIPTION

[0047] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0048] The raw materials used in the examples of the present invention can be obtained commercially. The kitchen sludge used in the examples and comparative examples was taken from Qingdao Shifang Bioenergy Co., Ltd.; the inoculum sludge (i.e., inoculum) was from the Nibuwan Sewage Treatment Plant in Huangdao District, Qingdao City.

[0049] The anaerobic digestion system described in this invention is a mesophilic anaerobic digestion system using self-prepared food waste as the substrate. The anaerobic fermentation tank volume is 500 mL, the actual working volume is 400 mL, the operating temperature is 30±1°C, and the stirring speed is 140 rpm. Sludge from the anaerobic biological tank of a sewage treatment plant is used as the inoculum, and the volume ratio of food waste to inoculum is controlled at 3:1. The anaerobic digestion operation is carried out for 45 days until the biogas production of the entire system is almost zero.

[0050] Analytical indicators: Total solid content (TS) refers to the content measured after the sample is dried at 105°C for 24 hours; volatile solid content (VS) refers to the content of solid matter that evaporates when the suspended solids in the water sample are dried to constant weight by heating under certain conditions; methane production is obtained by daily manual extraction and gas chromatography detection; volatile fatty acid (VFA) content is obtained by liquid chromatography detection.

[0051] Example 1

[0052] A method for preparing cobalt-modified sludge biochar comprises the following steps:

[0053] Fresh kitchen sludge (water content 80.7%-81.61%) was taken, impurities were removed, and it was placed in an oven and dried at 105°C for 24 hours. It was then ground in a mortar and pestle, and particles with a size less than 150 mesh were collected and stored.

[0054] Prior to pyrolysis, the air in the tube furnace was vigorously purged with a 0.2 L / min N2 flow for 30 minutes. The ground sludge was then placed in a quartz boat and fed into the tube furnace. The pyrolysis temperature was raised to 550°C at a heating rate of 5°C / min from room temperature at 30°C and maintained at this temperature for 2 hours. Furthermore, throughout the pyrolysis process, a 0.2 L / min N2 flow was introduced to ensure oxygen-free conditions until the temperature of the tube furnace naturally cooled to room temperature. Upon cooling to ambient temperature, the product was removed from the furnace. The resulting biochar was washed several times with ethanol and deionized water and filtered. The cleaned biochar was dried at 105°C for 12 hours and ultimately passed through a 150-mesh sieve. Biochar with a particle size less than 150 mesh was collected and placed in sealed bags to obtain primary sludge biochar, designated as BRB.

[0055] Modification was performed with a 0.1 mol / L CoCl2·6H2O solution (cobalt chloride solution was prepared in advance). 10 g of primary sludge biochar was soaked in 100 mL of 0.1 mol / L cobalt chloride solution. After wrapping the container mouth with tin foil, the conical flask was placed in a constant temperature oscillator with a temperature and speed of 30°C and 140 rpm, and oscillated for 24 hours. The treated biochar and the solution were separated by a suction filter with a 0.45 μm membrane, and then thoroughly washed repeatedly with deionized water. Freeze in a -80°C refrigerator for several hours, and then freeze-dry using a freeze dryer to obtain cobalt-modified sludge biochar, which was recorded as BRB-CoCl2.

[0056] Scanning electron microscope images of primary sludge biochar and cobalt-modified sludge biochar are shown in Figure 2. Figure 2 It can be clearly seen that the modified biochar presents a flocculent structure with larger pores and longer pores, which will undoubtedly increase the specific surface area of the biochar and provide conditions for the subsequent attachment of microorganisms.

[0057] Figure 3 The basic physical properties of primary sludge biochar and cobalt-modified sludge biochar are shown. It can be seen that the specific surface area of primary sludge biochar is 71.8106m 2 / g, and the specific surface area of cobalt-modified sludge biochar is 98.6842m 2 / g, a 37.4% increase over primary sludge biochar; the total pore volume of primary sludge biochar was 87.5 μL / g, while the total pore volume of cobalt-modified sludge biochar was 114.3 μL / g, a 30.6% increase over primary sludge biochar. The increase in specific surface area and total pore volume, on the one hand, provides more attachment points and growth space for microorganisms, facilitating the establishment and reproduction of microbial communities, thereby promoting the decomposition of organic matter during anaerobic digestion; on the other hand, the increased specific surface area and pore volume give the modified biochar a stronger adsorption capacity, improving buffering capacity, adsorbing and fixing inhibitory substances such as volatile fatty acids, alleviating the inhibitory effect of adverse factors on anaerobic digestion, and improving system stability. The reason why the micropore volume and average pore size of cobalt-modified sludge biochar are lower than those of primary sludge biochar may be that the cobalt ion load blocks and occupies the pores.

[0058] Example 2

[0059] A method for preparing cobalt-modified sludge biochar is provided, which differs from Example 1 in that a 0.15 mol / L CoCl2·6H2O solution is used for modification, and the remaining steps are the same as those of Example 1. The cobalt-modified sludge biochar obtained in this example is designated BRB-0.15CoCl2.

[0060] Comparative Example 1

[0061] A method for preparing cobalt-modified sludge biochar is provided, which differs from Example 1 in that a 1 mol / L CoCl2·6H2O solution is used for modification, and the remaining steps are the same as those of Example 1. The cobalt-modified sludge biochar obtained in this comparative example is designated BRB-1CoCl2.

[0062] Comparative Example 2

[0063] A method for preparing cobalt-modified sludge biochar is provided, which differs from Example 1 in that a 1.5 mol / L CoCl2·6H2O solution is used for modification, and the remaining steps are the same as those of Example 1. The cobalt-modified sludge biochar obtained in this comparative example is designated BRB-1.5CoCl2.

[0064] Experimental Example 1

[0065] Application of cobalt-modified sludge biochar prepared in Example 1 in enhanced anaerobic digestion

[0066] The following experiment used synthetic food waste as the fermentation substrate. The synthesis process involved adding a total of 2,000 g of material to a blender in four separate batches: 35% rice, 15% meat, 21% vegetables, 21% pasta, 7% eggs, and 1% oil. 450 mL of water was added with each addition.

[0067] The anaerobic digestion reaction apparatus consisted of an aluminum foil double-valve gas collection bag, a digestion bottle (500 mL) with a working volume of 400 mL, and a constant temperature shaking incubator. The gas collection bag (collecting biogas) and the upper end of the digestion bottle were connected by silicone tubing to form an anaerobic reactor. Each digestion bottle was placed with 300 mL of food waste and 100 mL of inoculum to control the mixing ratio of the reactor at 3:1, and then the initial pH of each reactor was adjusted to neutral. Subsequently, 0 g / L BRB, 4 g / L BRB, 4 g / L BRB-CoCl2, 6 g / L BRB-CoCl2, and 8 g / L BRB-CoCl2 were added to the five digestion bottles respectively. After all materials were added, each bottle was purged with nitrogen for approximately 2 minutes to ensure anaerobic conditions. During the subsequent 45-day anaerobic digestion process, all bottles were incubated in a constant temperature shaking incubator at 30±1°C and 140 rpm.

[0068] In the above method, the blank group (CK) was used without adding additional substances, the unmodified group was used with 4 g / L primary sludge biochar, the modified group was used with 4 g / L BRB-CoCl2, the modified group was used with 6 g / L BRB-CoCl2, and the modified group was used with 8 g / L BRB-CoCl2.

[0069] Final results: The final cumulative biogas production with the addition of 4g / L BRB-CoCl2 was 205.33mL / g VS, the final cumulative biogas production with the addition of 6g / L BRB-CoCl2 was 131.68mL / gVS, the final cumulative biogas production with the addition of 8g / L BRB-CoCl2 was 78.68mL / g VS, the final cumulative biogas production of the blank group was 113.47mL / g VS, and the final cumulative biogas production with the addition of 4g / L primary sludge biochar was 67.86mL / g VS.

[0070] Compared to the blank group, modified groups 1 and 2 increased their cumulative biogas production by 81.0% and 16.0%, respectively. In this example, low-concentration unmodified biochar exhibited an inhibitory effect. This may be due to the relatively low amount of biochar, which was insufficient to absorb all inhibitory substances. This led to the accumulation of these substances within the biochar, thereby inhibiting the activity of methanogenic microorganisms.

[0071] Figure 4(a) shows the daily biogas production of Experimental Example 1, and Figure 4(b) shows the cumulative biogas production of Experimental Example 1. The blank CK group produced relatively high biogas in the first five days, reaching its maximum daily production on the fourth day. Within the 10-20 day timeframe, Modified Groups 1 and 2 produced the most biogas, reaching their maximum daily production on the 13th and 14th days, respectively. Overall, the cumulative methane production of Modified Groups 1 and 2 increased by 81.0% and 16.0%, respectively, compared to the blank group.

[0072] Figure 5 The figure shows the changes in volatile short-chain fatty acid content over the entire experimental period of Experiment 1. The overall trend shows an initial increase followed by a decrease, then an increase and then a decrease. It can be seen that the volatile short-chain fatty acid content in Modification Groups 1 and 2 was almost entirely lower than that in the blank group. This suggests that the low-concentration cobalt-modified biochar loading effectively alleviated system acidification and accelerated its conversion rate, which is consistent with the gas production results.

[0073] Based on the above explanations, we can conclude that low concentrations of cobalt-modified biochar can effectively promote the anaerobic digestion of food waste, while high concentrations of cobalt-modified biochar inhibit the anaerobic digestion process. The concentration range of cobalt-modified biochar obtained by the present invention that can promote the anaerobic digestion of food waste is 4g / L to 6g / L.

[0074] Experimental Example 2

[0075] The anaerobic reactor described in Experimental Example 1 was used to test the performance of biochar prepared in the examples and comparative examples for enhanced anaerobic digestion.

[0076] The experiment was carried out in three groups of anaerobic reactors, each group of reactors including five digestion bottles. Each digestion bottle was placed with 300mL of food waste and 100mL of inoculum to control the mixing ratio of the reactor at 3:1, and then the initial pH of each reactor was adjusted to neutral. Subsequently, 0g / L BRB, 4g / L BRB-CoCl2, 4g / LBRB-0.15CoCl2, 4g / L BRB-1CoCl2, and 4g / L BRB-1.5CoCl2 were added to the five digestion bottles respectively. After all materials were added, each bottle was purged with nitrogen for about 2 minutes to ensure anaerobic conditions. During the subsequent 45-day anaerobic digestion process, all bottles were incubated in a constant temperature shaking box at 30±1℃ and 140rpm. In the above method, the blank group (CK) was the one without adding additional substances, the modified group 1 was the one with 4 g / L BRB-CoCl2 added, the modified group 4 was the one with 4 g / L BRB-0.15CoCl2 added, the modified group 5 was the one with 4 g / L BRB-1CoCl2 added, and the modified group 6 was the one with 4 g / L BRB-1.5CoCl2 added.

[0077] Final results: The final cumulative biogas production of the sample with 4g / L BRB-CoCl2 was 205.33mL / g VS, the sample with 4g / L BRB-0.15CoCl2 was 134.69mL / g VS, the sample with 4g / L BRB-1CoCl2 was 66.12mL / g VS, and the sample with 4g / L BRB-1.5CoCl2 was 28.69mL / g VS. The final cumulative biogas production of the blank group was 113.47mL / g VS.

[0078] Compared with the blank group, the cumulative biogas production of modified groups 1 and 4 increased by 81.0% and 18.7%, respectively. Modified groups 5 and 6 showed inhibition, which may be due to the inhibitory or toxic effects of high cobalt concentration on the microbial community, resulting in the inhibition of microbial growth and even the death of microorganisms.

[0079] Figure 6(a) shows the daily biogas production of Experimental Example 2, and Figure 6(b) shows the cumulative biogas production of Experimental Example 2. It can be seen that Modifications 1 and 4 increased the system's biogas production, with Modification 1 showing the most significant increase. For Modification 4, biogas production was lower than that of the blank control for the first 14 days, but then began to increase. Modifications 5 and 6 both showed inhibition.

[0080] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A cobalt-modified sludge biochar, characterized in that: The preparation method of the cobalt-modified sludge biochar comprises the following steps: The kitchen sludge is dried, ground and sieved to obtain sludge particles; The sludge particles are carbonized and pyrolyzed by a high-temperature slow pyrolysis method to obtain biochar; The obtained biochar was modified with a cobalt salt solution having a concentration of 0.08-0.17 mol / L, and solid-liquid separation, washing, and freeze-drying were performed to obtain cobalt-modified sludge biochar. The modification process comprises the following steps: The obtained biochar was placed in a cobalt salt solution with a concentration of 0.08-0.17 mol / L and shaken at 25-35°C for 20-30 hours to complete the modification; The cobalt salt includes one of cobalt chloride, cobalt sulfate or cobalt nitrate; The ratio of biochar to cobalt salt solution is 1 g:8-12 mL.

2. The cobalt-modified sludge biochar according to claim 1, characterized in that The kitchen sludge is dried at a temperature of 100-110° C. and a drying time of 10-30 h; The particle size of the sludge particles is less than 150 meshes.

3. The cobalt-modified sludge biochar according to claim 1, wherein The high-temperature slow pyrolysis comprises: heating to 400-600° C. at a heating rate of 4-6° C. / min under anaerobic conditions, maintaining the temperature for 1.5-2.5 hours, then stopping heating and cooling to room temperature.

4. The cobalt-modified sludge biochar according to claim 3, wherein Anaerobic conditions were ensured by passing protective gas; the flow rate of the protective gas was 0.2-0.5 L / min.

5. The cobalt-modified sludge biochar according to claim 4, characterized in that The protective gas includes nitrogen or helium.

6. The cobalt-modified sludge biochar according to claim 1, wherein The biochar obtained after carbonization and pyrolysis is washed, solid-liquid separated and dried, and then modified with a cobalt salt solution.

7. The cobalt-modified sludge biochar according to claim 6, wherein: The washing is performed by using ethanol and deionized water for multiple times.

8. The cobalt-modified sludge biochar according to claim 6, characterized in that: The solid-liquid separation is achieved by using a 0.45 μm membrane filtration to separate the biochar and the solution.

9. The cobalt-modified sludge biochar according to claim 6, characterized in that: The drying is carried out at 100-110° C. for 10-15 h.

10. The cobalt-modified sludge biochar according to claim 1, wherein The solid-liquid separation is achieved by using a 0.45 μm membrane filtration to separate the cobalt-modified biochar from the solution; Or, the washing is performed with deionized water; Alternatively, the drying is freeze drying, which is performed after freezing at -85 to -75°C.

11. Use of the cobalt-modified sludge biochar according to any one of claims 1 to 10 in enhancing anaerobic digestion of food waste.

12. A method for enhancing anaerobic digestion of food waste, characterized in that: The method comprises the following steps: adding the cobalt-modified sludge biochar according to claim 1 to food waste; and the concentration of the cobalt-modified sludge biochar is 4 g / L to 6 g / L.

Images