CN112938929B - Method for efficiently preparing magnetic biochar from straws and application - Google Patents
Method for efficiently preparing magnetic biochar from straws and application Download PDFInfo
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/02—Biological treatment
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E50/00—Technologies for the production of fuel of non-fossil origin
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
Abstract
The invention provides a method for efficiently preparing magnetic biochar by using straws and application, and belongs to the technical field of organic waste resource utilization. Detailed description of the inventionThe preparation method comprises the following steps: firstly, carrying out pretreatment on straws through water washing, drying, crushing and screening; then it is mixed with FeCl 3 ·6H 2 Mixing the O in a certain proportion, and performing ball milling to obtain the iron-containing straw-based biomass; and finally, putting the magnetic charcoal into a tubular furnace, and calcining the magnetic charcoal for 2 hours at 850 ℃ in a nitrogen environment to obtain the magnetic charcoal. The prepared magnetic biochar is added into a sludge anaerobic digestion system, so that the organic matter degradation rate and the methane yield can be effectively improved. The invention strengthens the process of producing methane by anaerobic digestion of sludge promoted based on the conductive material under the conditions of simplifying the preparation process, reducing the raw material input and the raw material cost, and realizes high-efficiency energy utilization of organic wastes.
Description
Technical Field
The invention relates to the field of environment-friendly functional materials and the technical field of organic waste resource utilization, in particular to a method for efficiently preparing magnetic biochar from straws and application of the method.
Background
Excess sludge containing a large amount of organic matter produced in the sewage treatment process is considered as an energy resource. Anaerobic digestion technology can convert organic matters in sludge into CH-rich sludge under the condition of no oxygen 4 The biogas becomes one of the most popular sludge reduction and resource treatment technologies in the world at present. In the traditional anaerobic digestion process, the extracellular electron transfer rate of microorganisms is slow, so that the methane yield is low and the anaerobic digestion efficiency is low.
At present, the addition of conductive materials into an anaerobic system is proved to be one of important ways for improving the methane production efficiency of anaerobic digestion of sludge, because the conductive materials can replace some biological accessory structures (such as fimbriae and cytochrome c) to realize the direct electron transfer process among microorganisms, and H is avoided 2 When the organic matter oxidation catalyst is used as an electron carrier, the energy consumption in the electron transfer process is reduced, and electrons generated in the organic matter oxidation process are transferred to methanogens in time, so that the organic matter oxidation and the methane generation are accelerated at the same time. Currently, commonly used conductive materials include carbon-based materials and iron-based materials.
Straw is one of the most abundant global biomasses, can form biochar with higher graphitization degree under the condition of oxygen-free high-temperature carbonization, and is an ideal raw material for preparing low-cost carbon-based conductive materials. But the high-temperature carbonization condition can greatly reduce the content of functional groups with charge-discharge capacity on the surface of the straw biochar, so that the electron capture capacity of the straw biochar has certain defects. Compared with single biochar, the iron-based substance in the magnetic biochar can be used as a catalyst to provide sufficient electroactive sites for the biochar, and the electron capture capacity of the biochar is enhanced. Meanwhile, compared with a single iron-based material, the biochar can be used as a physical carrier of iron-based substances, and the loss and agglomeration of small-size iron-based substances in the anaerobic digestion process are prevented. More notably, the biochar with magnetism can realize the recycling of the conductive material in an anaerobic system. Therefore, the straw magnetic biochar composite conductive material with high conductive capability and electron capture capability is prepared and used for strengthening electron transfer in the anaerobic digestion process, and the preparation method is a promising technology.
Patent CN111408349A discloses a preparation method of straw-based magnetic porous biochar, which comprises the steps of straw pretreatment, straw powder soaking, high-temperature carbonization treatment and preparation of straw-based magnetic porous biochar by a hydrothermal method. Patent CN105536700A discloses a method for preparing magnetic biochar from straws, which comprises cleaning and pretreating straws, sequentially immersing with ferric salt solution, vacuum filtering, drying filter cake, and carbonizing under inert gas to obtain the final product.
However, in the preparation of common magnetic biochar, a large amount of chemical reagents (such as sodium borohydride, sodium nitrate, ammonium hydroxide) and magnetic iron precursors (such as FeCl) are generally required 3 And FeCl 2 ) The reaction is carried out to load the magnetic substance into the biochar, and a large amount of dangerous chemical reagents are required in the process, so that the threshold of preparing the magnetic biochar is greatly increased. Another common preparation method of magnetic biochar is to soak biochar raw materials in an iron-containing precursor solution, treat the biochar raw materials through multiple steps of stirring, solid-liquid separation, drying and the like, and then carbonize the biochar raw materials in one step to obtain the magnetic biocharThe preparation efficiency of the magnetic activated carbon is improved.
Patent CN112007608A discloses a ball-milled zero-valent iron biochar composite material, and a preparation method and application thereof, wherein corn stalks are treated under an oxygen-limited environment to obtain biochar, then the biochar is mixed with iron powder, and ball milling is performed under a nitrogen or inert gas environment to obtain the ball-milled zero-valent iron biochar composite material, however, expensive iron powder is directly used as an iron source in the process, and the economic cost for preparing the material is increased. In addition, because the process uses a mode of firstly carbonizing and then ball milling, in order to ensure the formation of the biochar in the carbonization process and the maintenance of the zero-valent iron state in the ball milling process, the oxygen-limited environment needs to be maintained in the two stages by wrapping the tinfoil paper and introducing inert gas respectively. In addition, the ball milling stage of the preparation process is too long, so that the time cost for preparing the material is further improved, and the feasibility of the practical application of the material is reduced.
Therefore, a low-cost method for efficiently preparing magnetic biochar by using straws needs to be found.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a method for efficiently preparing magnetic biochar by using straws aiming at the defects in the prior art, and the prepared magnetic biochar is applied to the anaerobic digestion process of sludge, so that the magnetic biochar can be used as a good conductive medium among microorganisms, and the degradation of organic matters and the generation of methane in the anaerobic digestion process of sludge are enhanced.
The purpose of the invention can be realized by the following technical scheme:
a method for efficiently preparing magnetic biochar by using straws comprises the following steps:
1) Cleaning, drying and grinding the straws, and sieving the straws by a standard sieve of 30-60 meshes to obtain a pretreated straw sample;
2) Mixing the straw sample with FeCl 3 ·6H 2 Placing the O in a ball mill according to a certain weight proportion, mixing and ball-milling, and repeating for many times to obtain the iron-containing straw-based biomass;
3) And (3) putting the obtained iron-containing straw-based biomass into a tubular furnace filled with nitrogen for carbonization, and naturally cooling the temperature of the tubular furnace to room temperature to obtain the straw magnetic biochar.
Preferably, in step 1), the straw comprises rice straw, wheat straw and corn straw.
Preferably, in step 1), drying is carried out in an oven at 100-110 ℃ for 20-28h, and further preferably drying is carried out in an oven at 105 ℃ for 24h.
Preferably, in step 2), the straw sample and FeCl are 3 ·6H 2 The weight ratio of O is 2.
Preferably, in the step 2), the ball milling is carried out in the ball mill for 1-3min, then the ball milling is suspended for 5-15min, and the repeating is carried out for 4-8 times, and further preferably, the ball milling is carried out in the ball mill for 2min, then the ball milling is suspended for 10min, and the repeating is carried out for 6 times.
Preferably, in the step 3), the temperature in the tube furnace is increased to 800-900 ℃ at the speed of 4-6 ℃/min and maintained at the temperature for 1-3h for carbonization, and further preferably, the temperature in the tube furnace is increased to 850 ℃ at the speed of 5 ℃/min and maintained at the temperature for 2h for carbonization.
A method for producing methane by anaerobic digestion with sludge as a substrate is characterized in that digested sludge which stably runs in an anaerobic digestion reactor is used as an inoculum, municipal sludge is used as a substrate, magnetic biochar is used as a conductive medium, and methane is produced by anaerobic digestion under the conditions of pH =6.8-7.2 and temperature of 35-37 ℃, wherein the magnetic biochar is prepared by the method.
Preferably, the inoculum in the anaerobic system has a total solids content of 2.1% to 4.8% and a mass ratio of volatile solids to total solids of 46.2% to 57.1%.
Preferably, the mass ratio of volatile solids in the inoculum to volatile solids in the matrix is 1.
Preferably, the mass ratio of the magnetic biochar to the total solids in the matrix in the anaerobic system is 1.
Compared with the prior art, the invention has the following advantages:
(1) The method is different from the traditional preparation method of the magnetic biochar, the straw magnetic biochar conductive material is obtained by direct carbonization through a solvent-free ball milling-carbonization method, a large amount of chemical reagents are not needed to be added, the process is simple, the preparation efficiency of the conductive material is greatly improved, and the feasibility of applying the conductive material to an actual anaerobic digestion process is improved;
(2) The method is different from the existing preparation method of the ball-milling zero-valent iron biochar composite material, expensive zero-valent iron powder is not directly adopted, and rather, iron salt (FeCl) with lower cost is adopted 3 ·6H 2 O) is used as an iron source for material preparation, so that the preparation cost of the magnetic biochar is reduced while the efficient preparation process is ensured.
(3) The method is different from the existing zero-valent iron biochar preparation method with the steps of firstly carbonizing and then ball milling, adopts the preparation concept of firstly ball milling and then carbonizing reaction, utilizes the catalytic capacity of ferric salt loaded on biomass and the oxidation process of C-O in the biomass in the carbonization stage, realizes the simultaneous formation of an oxidized graphite structure and zero-valent iron, fully utilizes the advantages of the ferric salt and the biomass in the carbonization process, avoids the requirement of an oxygen-free environment in the ball milling stage, and further optimizes the efficient preparation process of the magnetic biochar.
(4) The invention adopts the straws as the preparation raw material of the carbon-based material in the magnetic carbon, applies the straws to the anaerobic digestion of the sludge to produce methane, treats waste with waste, and realizes the purpose of the synergistic efficient resource utilization of the organic waste.
Drawings
FIG. 1 is a schematic diagram of a process for preparing magnetic biochar from straws according to the invention;
FIG. 2 is an X-ray diffraction (XRD) spectrum of the straw magnetic biochar prepared in example 1;
FIG. 3 is a Raman spectrum (Raman) chart of the straw magnetic biochar prepared in example 1 and the single straw biochar prepared in comparative example 1;
fig. 4 is an X-ray diffraction spectrum (XRD) pattern of the straw magnetic biochar prepared in example 2, example 3 and example 4.
Detailed Description
The invention is further illustrated with reference to the following figures and examples:
example 1
The embodiment aims to prepare the low-cost straw magnetic biochar, and the single straw biochar and the straw magnetic biochar are applied to the low-solid-content sludge anaerobic digestion system, so that the influence of the modification of iron substances on the performance of the straw biochar in promoting anaerobic digestion is researched.
A method for efficiently preparing magnetic biochar by using straws comprises the following steps: (1) Cleaning and filtering rice straws by using distilled water, drying the rice straws in a drying oven at 105 ℃ for 24 hours, grinding the dried samples, and sieving the ground samples by using a standard sieve of 30-60 meshes to obtain pretreated straw samples; (2) Mixing the straw sample with FeCl 3 ·6H 2 Placing O in a ball mill according to the dry weight proportion of 1; (3) And (3) placing the obtained iron-containing straw-based biomass in a tubular furnace filled with nitrogen, heating to 850 ℃ at the speed of 5 ℃/min, maintaining the temperature for 2 hours for carbonization, and naturally cooling the temperature of the tubular furnace to room temperature to obtain the straw magnetic biochar.
The straw magnetic biochar obtained in the embodiment is characterized by X-ray diffraction, and the result is shown in fig. 2, and the comparison of a standard substance card shows that the phase of the iron-based substance in the straw magnetic biochar is mainly Fe (0).
Comparative example 1
The difference from the embodiment 1 is that single rice straw is adopted for anaerobic high-temperature carbonization, and the step (2) in the preparation method is omitted, so that the single straw biochar is prepared.
Performing Raman spectrum characterization on the straw magnetic biochar obtained in example 1 and the single straw biochar obtained in comparative example 1, and utilizing the intensity ratio (I) of a G band and a D band in a spectrogram G /I D ) The degree of order of the carbon-based material can be characterized, and as a result, as shown in fig. 3, it can be seen that the introduction of the iron-based substance does not reduce the order of the carbon-based material, and thus does not reduce the ability of the carbon-based material to transport electrons inside.
And carrying out a batch methane production experiment on the obtained product by anaerobic digestion of the low-solid sludge. The specific experimental operation is as follows: the method comprises the steps of adopting excess sludge of a secondary sedimentation tank as a substrate (TS =2.5% -3.6%, VS/TS =42.3% -58.4%), adopting digested sludge which stably runs in an anaerobic digestion reactor as an inoculum (TS =2.1% -4.8%, VS/TS =46.2% -57.1%), and starting three serum bottles with a working volume of 500mL to perform batch experiments of sludge anaerobic digestion and methane production under the conditions of pH =6.8-7.2, temperature of 35-37 ℃ and stirring speed of 120r/min. Adding glass beads (blank groups) into three serum bottles respectively, wherein the mass ratio of the added materials to the residual sludge VS of the secondary sedimentation tank is 1; and then adding the inoculation sludge and the secondary sedimentation tank excess sludge in sequence, wherein the VS ratio of the inoculation sludge to the secondary sedimentation tank excess sludge is 1. During the experiment, the yield and composition of the gas in the anaerobic system were monitored, and the TS and VS contents before and after anaerobic digestion were determined.
Compared with a blank group added with glass beads, the maximum daily methane generation rates of the anaerobic sludge digestion systems corresponding to the example 1 and the comparative example 1 are respectively increased by 31.88 percent and 49.26 percent, and the electric conductivity of the anaerobic sludge digestion system is respectively increased by 15.20 percent and 23.11 percent; the single straw biochar and the straw magnetic biochar can both strengthen anaerobic digestion of sludge to produce methane, but compared with the single straw biochar, the straw magnetic biochar has a more obvious effect of strengthening electron transfer in an anaerobic digestion system, so that the anaerobic digestion and methane production performance of the sludge is further improved.
Comparative example 2
The difference from the embodiment 1 is that in the step 2) of preparing the magnetic biochar efficiently by using straws, the ball milling of the ball mill is suspended for 15min after 3min, and the process is repeated for 8 times.
Comparative example 3
The difference from the embodiment 1 is that in the step 2) of preparing the magnetic biochar efficiently by using straws, the ball milling of the ball mill is suspended for 5min after 1min, and the process is repeated for 4 times.
And carrying out a batch methane production experiment on the obtained product by anaerobic digestion of the low-solid sludge. The specific experimental operation is as follows: the method comprises the steps of adopting excess sludge of a secondary sedimentation tank as a substrate (TS =2.5% -3.6%, VS/TS =42.3% -58.4%), adopting digested sludge which stably runs in an anaerobic digestion reactor as an inoculum (TS =2.1% -4.8%, VS/TS =46.2% -57.1%), and starting three serum bottles with a working volume of 500mL to perform batch experiments of sludge anaerobic digestion and methane production under the conditions of pH =6.8-7.2, temperature of 35-37 ℃ and stirring speed of 120r/min. Adding glass beads (blank groups) into three serum bottles respectively, wherein the mass ratio of the added materials to the residual sludge VS of the secondary sedimentation tank is 1; and then adding the inoculation sludge and the secondary sedimentation tank excess sludge into the sewage treatment tank in sequence, wherein the VS ratio of the inoculation sludge to the secondary sedimentation tank excess sludge is 1. During the experiment, the gas yield and composition in the anaerobic system were monitored, and the TS and VS contents before and after anaerobic digestion were determined.
Compared with example 1, the maximum daily methane production rate of the anaerobic sludge digestion system corresponding to comparative example 2 and comparative example 3 is respectively reduced by 18.32% and 10.76%, which shows that in the ball milling process of preparing the material, when the ball milling time is 2min and the pause time is 10 and the repetition time is 6 times, the prepared straw-based magnetic biochar promotes the anaerobic sludge digestion to produce methane, and the performance is optimal.
Example 2
The embodiment aims to prepare the straw magnetic biochar by adopting different types of straw biomass, apply the straw magnetic biochar to a high solid content sludge anaerobic digestion system, explore the performance of the magnetic biochar for promoting the anaerobic digestion of the high solid content sludge, and simultaneously explore the influence of preparation raw materials of different magnetic biochar on the performance of the magnetic biochar for promoting the anaerobic digestion.
A method for efficiently preparing magnetic biochar by using straws comprises the following steps: (1) Cleaning and filtering corn straws by using distilled water, drying the corn straws in a drying oven at 105 ℃ for 24 hours, grinding the dried samples, and sieving the ground samples by using a standard sieve of 30-60 meshes to obtain pretreated straw samples; (2) Mixing the straw sample with FeCl 3 ·6H 2 Placing O in a ball mill according to the dry weight ratio of 2; (3) Placing the obtained iron-containing straw-based biomass in a tubular furnace filled with nitrogen, heating to 850 ℃ at the speed of 5 ℃/min, maintaining the temperature for 2h for carbonization, and naturally cooling to room temperature to obtain the cornStraw magnetic biochar.
Example 3
The difference from the example 2 is that the magnetic biochar is prepared by replacing the corn stalks with rice stalks as raw materials.
Example 4
The difference from the example 2 is that the magnetic biochar is prepared by replacing the corn straws with the wheat straws as the raw material.
The straw magnetic biochar obtained in the embodiment 2, the embodiment 3 and the embodiment 4 is subjected to X-ray diffraction characterization, and the result is shown in FIG. 4, and it can be seen that the type of the straw has no significant influence on the crystal structure of the straw magnetic biochar.
And carrying out a batch methane production experiment on the obtained product by high solid-containing sludge anaerobic digestion. The specific experimental operation is as follows: sludge after gravity concentration and dehydration is used as a substrate (TS =6.3% -8.5%, VS/TS =45.6% -59.1%), digested sludge which stably runs in an anaerobic digestion reactor is used as an inoculum (TS =2.1% -4.8%, VS/TS =46.2% -57.1%), and four serum bottles with the working volume of 500mL are started to carry out batch experiments of sludge anaerobic digestion and methane production under the conditions of pH =6.8-7.2, the temperature of 35-37 ℃ and the stirring speed of 120r/min. Adding glass beads (blank groups) into four serum bottles respectively, wherein the mass ratio of the added materials to the sludge VS after gravity concentration and dehydration is 1; and then sequentially adding the inoculation sludge and the sludge subjected to gravity concentration dehydration, wherein the VS ratio of the inoculation sludge to the sludge subjected to gravity concentration dehydration is 1. The yield and composition of the gas in the anaerobic system, as well as the Volatile Fatty Acid (VFAs) content, were monitored during the experiment.
Compared with a blank group added with glass beads, the maximum daily methane production rate of the anaerobic digestion system with high solid content sludge corresponding to the embodiment 2-4 is respectively increased by 49.36%,55.46% and 53.31%, and meanwhile, the VFAs content is not accumulated, which shows that the straw magnetic biochar can effectively promote the anaerobic digestion methane production performance of the high solid content sludge and can maintain the stable operation of the anaerobic system.
Example 5
The embodiment aims to efficiently prepare magnetic biochar from straws, apply the magnetic biochar to an anaerobic digestion system with high solid-containing sludge semi-continuous operation and explore the process feasibility of promoting the anaerobic digestion of the sludge by the magnetic biochar.
A method for efficiently preparing magnetic biochar by using straws comprises the following steps: (1) Cleaning and filtering rice straws by distilled water, drying the rice straws in a drying oven at 105 ℃ for 24 hours, grinding the dried sample, and sieving the ground sample by a standard sieve of 30-60 meshes to obtain a pretreated straw sample; (2) Mixing the straw sample with FeCl 3 ·6H 2 Placing O in a ball mill according to the dry weight proportion of 1; (3) And (3) placing the obtained iron-containing straw-based biomass in a tubular furnace filled with nitrogen, heating to 850 ℃ at the speed of 5 ℃/min, maintaining the temperature for 2 hours for carbonization, and naturally cooling the temperature of the tubular furnace to room temperature to obtain the straw magnetic biochar.
The obtained product is subjected to anaerobic digestion semi-continuous methane production experiment. The specific experimental operation is as follows: sludge after gravity concentration and dehydration is used as a substrate (TS =6.3% -8.5%, VS/TS =45.6% -59.1%), digested sludge which stably runs in an anaerobic digestion reactor is used as an inoculum (TS =2.1% -4.8%, VS/TS =46.2% -57.1%), and two reactors with the working volume of 2L are started to carry out a sludge anaerobic digestion methane production semi-continuous flow experiment under the conditions of pH =6.8-7.2 and the temperature of 35-37 ℃. 2L of inoculation mud is added into a semicontinuous reactor, 200mL of inoculation mud is fed every day, 200mL of discharge material is discharged, SRT (srt) =15d is fed every day, 1 minute is stopped when the mixture is stirred for 1 minute, and the stirring speed is 120r/min. Adding glass beads (blank group) and the materials prepared in the example 5 into the two reactors respectively, wherein the mass ratio of the added materials to the sludge VS after gravity concentration and dehydration is 1; the VS ratio of the inoculation sludge to the sludge after gravity concentration and dehydration is 1; and (3) measuring the gas yield and proportion in the experimental process, and monitoring the contents of TS, VS and VFAs of the fed and discharged materials.
Compared with a blank group added with glass beads, the starting time of the semi-continuous reactor corresponding to the embodiment 5 is shortened, the methane proportion in the methane is increased from 75.10% of the blank group to 83.76%, meanwhile, the VFAs content is not accumulated, and the semi-continuous flow anaerobic digestion system keeps stable operation.
Claims (7)
1. A method for efficiently preparing magnetic biochar by using straws is characterized by comprising the following steps:
1) Cleaning, drying and grinding the straws, and screening the straws through a standard sieve of 30-60 meshes to obtain a pretreated straw sample;
2) Mixing the straw sample with FeCl 3 ·6H 2 Placing the O in a ball mill according to a certain weight proportion, mixing and ball-milling, and repeating for many times to obtain the iron-containing straw-based biomass;
3) Placing the obtained iron-containing straw-based biomass in a tubular furnace filled with nitrogen for carbonization, and naturally cooling the temperature of the tubular furnace to room temperature to obtain straw magnetic biochar;
in the step 2), suspending for 5-15min after ball milling for 1-3min in a ball mill, and repeating for 4-8 times;
in step 2), the straw sample and FeCl 3 ·6H 2 The weight ratio of O is 2;
in the step 3), the temperature is raised to 800-900 ℃ in the tube furnace at the speed of 4-6 ℃/min, and the carbonization is carried out for 1-3h under the temperature.
2. The method for efficiently preparing magnetic biochar by using straws as claimed in claim 1, wherein in the step 1), the straws comprise rice straws, wheat straws and corn straws.
3. The method for efficiently preparing magnetic biochar by using straws as claimed in claim 1, wherein in the step 1), the straws are washed and filtered by distilled water and then are placed in a range of 100-110 o And C, drying in an oven for 20-28 h.
4. A method for producing methane by anaerobic digestion with sludge as a substrate is characterized in that the method uses the stabilization in an anaerobic digestion reactorThe running digested sludge is used as an inoculum, municipal sludge is used as a matrix, magnetic biochar is used as a conductive medium, and the pH is =6.8-7.2, and the temperature is 35-37 o And C, under the condition of anaerobic digestion, producing methane, wherein the magnetic biochar is prepared by the method for efficiently preparing the magnetic biochar by utilizing the straws according to any one of claims 1-3.
5. The method for producing methane by anaerobic digestion of sludge as claimed in claim 4, wherein the inoculum in the anaerobic system has a total solids content of 2.1% to 4.8%, and the mass ratio of volatile solids to total solids is 46.2% to 57.1%.
6. The method of claim 4, wherein the mass ratio of volatile solids in the inoculum to volatile solids in the substrate is 1.
7. The method for producing methane by anaerobic digestion of sludge as claimed in claim 4, wherein the mass ratio of the magnetic biochar to the total solids in the substrate in the anaerobic system is 1.
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| CN113816497B (en) * | 2021-10-28 | 2022-04-15 | 徐州工程学院 | Ecological floating bed for restoring aquaculture environment |
| CN113856683B (en) * | 2021-10-29 | 2024-01-23 | 陕西科技大学 | Fenton-like catalyst of carbon-supported iron ions and preparation method and application thereof |
| CN114230005A (en) * | 2021-12-30 | 2022-03-25 | 中建安装集团有限公司 | Preparation method and application of magnetic biochar |
| CN114477683B (en) * | 2022-01-25 | 2023-08-18 | 安徽工程大学 | Pigment sludge treatment method |
| CN115231680A (en) * | 2022-06-28 | 2022-10-25 | 同济大学 | Preparation method and application of biochar loaded nano zero-valent iron material |
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