CN116425156A - Method for preparing modified biochar by activating wood vinegar - Google Patents
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/30—Active carbon
- C01B32/312—Preparation
- C01B32/342—Preparation characterised by non-gaseous activating agents
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
- B01J20/20—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising free carbon; comprising carbon obtained by carbonising processes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
- B01J20/28054—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their surface properties or porosity
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/28—Treatment of water, waste water, or sewage by sorption
- C02F1/283—Treatment of water, waste water, or sewage by sorption using coal, charred products, or inorganic mixtures containing them
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal compounds
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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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- 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
- Y02E50/10—Biofuels, e.g. bio-diesel
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Abstract
The invention discloses a method for preparing modified biochar by activating wood vinegar. The method comprises the steps of pretreating biomass raw materials by taking wood vinegar as an activating agent, and pyrolyzing the pretreated material to prepare the modified biochar. The invention avoids using inorganic acid such as hydrochloric acid, sulfuric acid, phosphoric acid and the like and alkali such as sodium hydroxide, potassium hydroxide and the like adopted in the traditional activation process, not only utilizes byproducts in the biochar production process, but also avoids environmental pollution, reduces the production cost and has high resource utilization rate. Compared with the biological carbon directly produced without modification, the modified biological carbon prepared by wood vinegar activation has the advantages of high specific surface area and pore volume, high porosity, increased surface acid functional groups and enhanced adsorption capacity for heavy metal ions in aqueous solution.
Description
Technical Field
The invention relates to the technical field of preparation and application of modified biochar, in particular to a method for preparing modified biochar by pretreatment of wood vinegar.
Background
The yield of organic waste in agriculture and forestry in China is huge. For example, the comprehensive utilization degree of straw in China is still low so far, and a large amount of straw resources are abandoned or burnt, so that serious waste and environmental pollution are caused. The preparation of biochar with wide application by processing biomass agricultural wastes such as straw is a way of utilizing biomass resources efficiently and with high value, and is a novel carbon fixation technology, and is receiving wide attention in recent years. The biochar is a carbon-rich solid product prepared by carrying out high-temperature pyrolysis on wood, straw and other agricultural and forestry wastes under the anaerobic or anoxic condition. In the biomass pyrolysis process, raw biomass can be simultaneously converted into products such as combustible gas, pyroligneous liquor and pyrolysis oil. The biochar has the advantages of remarkably improved carbon content, larger specific surface area, abundant micropore structures, smaller self specific gravity and higher aromaticity. Meanwhile, the surface of the biochar has rich oxygen-containing functional groups such as hydroxyl, carboxyl, carbonyl and the like. The biomass-derived carbon material generally has excellent adsorptivity, thermal stability and mechanical strength, and has great application prospects in the aspects of carbon fixation, emission reduction, pollution control, agricultural production, ecological environment restoration, clean biomass energy utilization and the like.
The physicochemical properties of biochar significantly affect its use in various fields. For example, the adsorption capacity of biochar is mainly affected by specific surface area, pore structure and surface chemistry. A great deal of research shows that the specific surface area, the pore diameter structure, the surface functional group amount and the like of the biochar produced by directly pyrolyzing biomass at high temperature can be improved through modification, so that the adsorption capacity of the biochar on various organic and inorganic pollutants such as organic pollutants, heavy metal ions and the like is enhanced. Therefore, modifying the biochar to prepare modified biochar or activated biochar has become one of the hot spots and important development directions of the biochar industry, and has important significance for meeting the increasingly strict application requirements. Common chemical modification methods include metal salt/metal oxide modification, organic modification, surface grafting modification, metal ion loading, acid-base modification, and the like. Among them, modification by acid and base is one of the most common chemical methods for producing modified biochar. At present, most of the chemical modification methods of the biochar are solution methods, and a large amount of dangerous chemicals such as strong acid, strong alkali, organic solvent and the like are needed, so that environmental pollution is easy to cause, production steps are increased, production cost is increased, and large-scale popularization and application are difficult.
The main components of biomass include cellulose, hemicellulose, lignin and small amounts of inorganic salts. Wherein, cellulose and hemicellulose belong to polysaccharide organic polymers, and the structure contains a large number of more active hydroxyl groups. Lignin is a natural aromatic polymer compound and has more and more stable annular crosslinking structures. Lignin is therefore more thermally stable than cellulose and hemicellulose. The reaction path of biomass pyrolysis processes is often complex involving a variety of radical reactions. Specifically, in the biomass pyrolysis process, covalent bonds in the polysaccharide polymer compound cellulose and hemicellulose structures in biomass are firstly broken to generate free radical fragments, and along with the rise of temperature, the free radicals are further broken and undergo a large amount of polycondensation reaction to form a large amount of volatile matters and biochar in the form of smoke. The separated flue gas is subjected to multistage condensation and filtration to obtain pyroligneous liquor, biomass pyrolysis oil and noncondensable gas (refer to figure 1). Typically, pyroligneous liquor is produced before the biomass pyrolysis temperature reaches 320 ℃. Wood vinegar is generally a tan liquid and contains mainly moisture and various organic acids including formic acid, acetic acid, propionic acid, glycolic acid, acetone, methanol, etc., phenols, alcohols, ketones and small amounts of metal elements. Among them, organic acids such as formic acid, acetic acid and propionic acid are mainly derived from thermal cracking reaction of cellulose and hemicellulose in biomass raw materials, and are also a main source of acidity of wood vinegar. By further refining, the conversion of liquid products such as pyroligneous liquor, pyrolysis oil, etc. into high value-added chemicals having higher value is an important way to make high value use of these products. However, the chemical components of pyroligneous liquor and pyrolysis oil are generally complex, and the pyroligneous liquor and pyrolysis oil have high yield, low heat value, high oxygen content, strong acidity and poor stability, so that the application of pyroligneous liquor and pyrolysis oil in the aspect of preparing high-added-value chemicals through separation and purification is restricted.
In conclusion, the research and production of the modified biochar are very important to improve the performance and application value of the biochar. However, the existing chemical modification and activation methods all involve the use of a large number of dangerous chemicals such as strong acids, strong bases, organic solvents, and the like. The methods not only cause the rising of production cost, but also cause environmental pollution or secondary pollution, and limit industrial production and application. Meanwhile, a large amount of acidic liquid products including pyroligneous liquor are generated in the production process of the biochar, and the high-valued and harmless utilization of the acidic liquid products is one of the important bottlenecks facing related industries at present.
Disclosure of Invention
The invention aims to provide a modified activated carbon produced by using wood vinegar as an activating agent, aiming at the defects existing in the existing biological carbon modification and activation technology. The biomass raw material is pretreated by adopting wood vinegar rich in organic acid generated in the biomass pyrolysis process as an activating agent, and the specific surface area, pore volume and adsorption capacity of heavy metal ions in aqueous solution of the obtained biochar are increased. The method disclosed by the invention fully utilizes the acid liquid product pyroligneous liquor generated in the biomass pyrolysis process, avoids the use of dangerous chemicals such as strong acid, strong alkali, organic solvents and the like used in the traditional acid-base activation process, prepares the modified biochar with better adsorption performance under the condition of not increasing the process cost by the developed process, overcomes the defects of the prior art in the background art, and has the characteristics of low cost, easiness in realizing large-scale popularization and application, environmental friendliness, comprehensive utilization of biomass pyrolysis products and the like.
In order to achieve the above purpose, the invention is realized by the following technical scheme:
a method for preparing modified biochar by wood vinegar activation comprises the following steps: pretreating biomass raw materials by taking wood vinegar as an activating agent, and pyrolyzing the obtained pretreated material to obtain the modified biochar.
Wherein the pyroligneous liquor is pyroligneous liquor generated in the biomass pyrolysis process.
Specifically, the method for preparing the modified biochar comprises the following steps:
1) Pulverizing biomass raw materials, drying, sieving, adding wood vinegar, stirring at 30-60deg.C, soaking, filtering, and drying to obtain pretreated material;
2) Carrying out high-temperature pyrolysis reaction on the pretreated material to obtain modified biochar,
in the step 1), the biomass raw material is lignocellulose biomass, and can be at least one of corn straw, wheat straw, rice straw, bamboo wood, wood dust, peanut shell, wheat shell, rice hull, leaf and weed;
sieving with 10-100 mesh sieve;
the pyroligneous liquor is pyroligneous liquor generated in the biomass pyrolysis process or is derived from pyroligneous liquor generated in other lignocellulose biomass pyrolysis processes;
the moisture content of the wood vinegar is 30-90%, and can be 60% -90%;
the wood vinegar is prepared by the following steps: pyrolyzing biomass raw materials in inert atmosphere at 300-900 ℃ for 1-4h, collecting flue gas, and condensing to obtain a tan liquid.
The wood vinegar is also subjected to pretreatment before being added into a reaction system, and the pretreatment operation sequentially comprises the following steps: standing, filtering, removing impurities, collecting filtrate, and concentrating;
the ratio of the biomass raw material to the wood vinegar is 1:2-1:8 (w/w), and can be specifically 1:2-1:5;
the time of the impregnation may be 12-48 hours;
in the method step 2), the pyrolysis reaction is carried out in an inert atmosphere or in vacuum;
the operation of the high-temperature pyrolysis reaction is as follows: heating to 300-900 deg.c (500-800 deg.c), maintaining for 1-4 hr, cooling to room temperature, washing with deionized water to neutrality, and drying to obtain modified biochar.
Wherein the temperature rise is continuous temperature rise or stage temperature rise,
the continuous heating rate is 5-20 ℃/min, the temperature is raised to 300-900 ℃ (specifically 500-800 ℃), and the temperature is kept for 1-4 hours;
the temperature is raised at a rate of 5-20 ℃/min, the reaction temperature is kept at 100 ℃ for 0.5 hours every time, the temperature is raised to 300-900 ℃ (particularly 500-800 ℃), and the temperature is kept for 1-4 hours.
The method further comprises the step of collecting pyroligneous liquor in the pyrolysis reaction process, wherein the pyroligneous liquor is pretreated and then used as an activating agent to activate the biomass raw material in the step 1).
The modified biochar prepared by the method also belongs to the protection scope of the invention.
Compared with the biochar directly produced without modification, the modified biochar has high specific surface area, pore volume and porosity, the surface acid functional group is increased, and the adsorption capacity of heavy metal ions in aqueous solution is also increased.
The application of the modified biochar in the adsorption of heavy metal ions in aqueous solution also belongs to the protection scope of the invention.
The heavy metal ions include, but are not limited to, copper ions and lead ions.
The invention utilizes the acidity of acidic organic active substances in wood vinegar to promote the formation of biochar and pore structures thereof. In the pretreatment process, acidic active substances in the wood vinegar enter a pore structure of the biomass raw material by fully mixing and soaking. In the high-temperature pyrolysis process, along with the increase of temperature, on one hand, the acidity of the acidic substances can promote the rupture of chemical bonds in biomass, and formed small molecules overflow a reaction system, so that the formation of pore structures in the biochar structure is facilitated. On the other hand, at high temperature, the organic active substances in the wood vinegar can react with the active hydroxyl groups in the biomass, and are removed from the surface of the biochar after being treated at high temperature and repeatedly washed, so that the formation of pore channel structures in the biochar and the enrichment of functional groups on the surface of the biochar are facilitated.
Referring to fig. 2 and 3, the organic acid-rich acidic wood vinegar used as the acidic activator may be derived from the same raw material and pyrolysis process as the biochar, or may be derived from other different biomass raw materials and pyrolysis processes. Because of acidic substances in the wood vinegar, such as organic acids including formic acid, acetic acid, propionic acid, glycolic acid, and the like, and mainly pyrolysis products of cellulose and hemicellulose, the biomass raw material for producing the wood vinegar rich in the organic acids should be rich in cellulose and hemicellulose, such as straw biomass, wood biomass, and the like. Wood vinegar prepared by pyrolysis of biomass raw materials rich in cellulose and hemicellulose generally contains a large amount of acidic active molecules, and can better play a role of an acidic activator.
Compared with the prior art, the invention has the following beneficial effects:
the method for preparing the modified biochar by using the wood vinegar rich in organic acid as the activating agent avoids the use of inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid and the like and strong bases such as sodium hydroxide, potassium hydroxide and the like used in the traditional activating process. Not only utilizes byproducts in the biochar production process, but also avoids environmental pollution, reduces the production cost and has high resource utilization rate. Compared with the charcoal directly produced without modification, the modified charcoal prepared by wood vinegar activation has the advantages of high specific surface area and pore volume, high porosity and increased surface acid functional groups. The method is simple, environment-friendly and low in cost, realizes high-value harmless comprehensive utilization of byproducts in the biomass pyrolysis process, and the prepared modified biochar product can be widely applied to the aspects of pollutant adsorption, sewage air purification and the like.
Drawings
Fig. 1 shows a schematic diagram of biomass pyrolysis and the formation of primary products.
Fig. 2 shows a schematic flow chart of a preparation method for preparing modified biochar by activating wood vinegar.
Fig. 3 shows a schematic flow chart of a preparation method for preparing modified biochar by using acid wood vinegar with different sources as an activating agent.
Fig. 4 shows a scanning electron microscope image of the fir wood charcoal prepared in comparative example 1 provided by the present invention.
Fig. 5 shows a scanning electron microscope image of the modified fir charcoal prepared in example 2 provided by the present invention.
Detailed Description
The following detailed description of the invention is provided in connection with the accompanying drawings that are presented to illustrate the invention and not to limit the scope thereof. The examples provided below are intended as guidelines for further modifications by one of ordinary skill in the art and are not to be construed as limiting the invention in any way.
The experimental methods in the following examples, unless otherwise specified, are conventional methods, and are carried out according to techniques or conditions described in the literature in the field or according to the product specifications. Materials, reagents and the like used in the examples described below are commercially available unless otherwise specified.
Example 1 preparation of modified corn straw biochar
The method comprises the following steps: crushing corn stalk, drying and sieving to 30 mesh. And (3) standing, filtering, removing impurities, collecting filtrate and concentrating acid wood vinegar generated in the corn straw pyrolysis process (crushing corn straw to 30 meshes, heating to a pyrolysis temperature of 650 ℃ at a heating rate of 20 ℃/min in nitrogen atmosphere, preserving heat for 1h, collecting flue gas, and condensing to obtain the acid wood vinegar), so that the water content of the acid wood vinegar is about 75%. Mixing the obtained acidic wood vinegar with corn straw raw materials according to a ratio of 3:1 (w/w), stirring and mixing uniformly at 45 ℃, soaking for 48 hours, filtering, and drying at 105 ℃ to obtain the corn straw pretreatment material. And then heating the obtained corn stalk pretreatment material to 650 ℃ at a heating rate of 20 ℃/min in nitrogen atmosphere, maintaining the temperature for 1 hour for high-temperature pyrolysis reaction, cooling the reaction system to room temperature after the reaction is finished, repeatedly washing the obtained crude product to neutrality by deionized water, and drying at 105 ℃ to obtain the modified corn stalk biochar. The specific surface area of the obtained modified corn stalk biochar is 302m 2 /g。
Example 2 preparation of modified fir biochar
The method comprises the following steps: pulverizing fir wood chip, drying, and sieving to 30 mesh. And (3) standing, filtering, removing impurities, collecting filtrate and concentrating acid wood vinegar generated in the pyrolysis process of the fir wood chips (the fir wood chips are crushed to 30 meshes, the temperature is increased to 800 ℃ at the heating rate of 20 ℃/min in a nitrogen atmosphere, the temperature is kept for 1h, and the flue gas is collected and condensed to obtain the acid wood vinegar), so that the water content of the acid wood vinegar is about 75%. Mixing the obtained acidic wood vinegar with fir wood chip raw materials according to a ratio of 3:1 (w/w), stirring and mixing uniformly at 45 ℃, soaking for 48 hours, filtering, and drying at 105 ℃ to obtain the fir wood chip pretreatment material. And then heating the obtained fir wood chip pretreatment material to 800 ℃ at a heating rate of 20 ℃/min in nitrogen atmosphere, maintaining the temperature for 1 hour for high-temperature pyrolysis reaction, cooling the reaction system to room temperature after the reaction is finished, repeatedly washing the obtained crude product to be neutral by deionized water, and drying at 105 ℃ to obtain the modified fir wood biochar. The specific surface area of the obtained modified fir biochar is 523m 2 /g。
Example 3 preparation of modified wheat straw biochar
The method comprises the following steps: the wheat straw is crushed, dried and sieved to 30 meshes. And (3) standing, filtering, removing impurities, collecting filtrate and concentrating acid pyroligneous liquor generated in the pyrolysis process of the wheat straw (the wheat straw is crushed to 30 meshes, the temperature is increased to 700 ℃ at the heating rate of 20 ℃/min in nitrogen atmosphere, the temperature is kept for 1h, and the flue gas is collected and condensed, so that the water content of the acid pyroligneous liquor is about 75%). Mixing the obtained acidic wood vinegar with wheat straw raw materials according to a ratio of 3:1 (w/w), stirring and mixing uniformly at 45 ℃, soaking for 48 hours, filtering, and drying at 105 ℃ to obtain the wheat straw pretreatment material. And then heating the obtained wheat straw pretreatment material to 700 ℃ at a heating rate of 20 ℃/min in nitrogen atmosphere, keeping the temperature for 1 hour for high-temperature pyrolysis reaction, cooling the reaction system to room temperature after the reaction is finished, repeatedly washing the obtained crude product to be neutral by deionized water, and drying at 105 ℃ to obtain the modified wheat straw biochar. Warp yarnThe specific surface area of the obtained modified wheat straw biochar is 413m 2 /g。
Example 4 preparation of modified Rice husk biochar
The method comprises the following steps: pulverizing rice hull, drying, and sieving to 30 mesh. And (3) crushing rice hulls to 30 meshes, heating to a pyrolysis temperature of 800 ℃ at a heating rate of 20 ℃/min in a nitrogen atmosphere, preserving heat for 1h, collecting flue gas, condensing to obtain the acidic wood vinegar, standing, filtering, removing impurities, collecting filtrate, and concentrating to obtain the acidic wood vinegar with the water content of about 75%. Mixing the obtained acidic wood vinegar with rice hull raw materials according to a ratio of 3:1 (w/w), stirring and mixing uniformly at 45 ℃, soaking for 48 hours, filtering, and drying at 105 ℃ to obtain the rice hull pretreatment material. And then heating the rice hull pretreatment material to 800 ℃ at a heating rate of 20 ℃/min in a nitrogen atmosphere, keeping the temperature for 1 hour for high-temperature pyrolysis reaction, cooling the reaction system to room temperature after the reaction is finished, repeatedly washing the obtained crude product with deionized water to be neutral, and drying at 105 ℃ to obtain the modified rice hull biochar. The specific surface area of the obtained modified rice hull biochar is 310m 2 /g。
Example 5 preparation of modified peanut Shell biochar
The method comprises the following steps: pulverizing peanut shell, drying, and sieving to 30 mesh. And (3) crushing the peanut shells to 30 meshes, heating to the pyrolysis temperature of 700 ℃ at a heating rate of 10 ℃/min in a nitrogen atmosphere, preserving heat for 1h, collecting flue gas, condensing to obtain the acid wood vinegar generated in the pyrolysis process of the peanut shells, standing, filtering, removing impurities, collecting filtrate, and concentrating to ensure that the water content of the acid wood vinegar is about 75%. Mixing the obtained acidic wood vinegar with peanut shell raw materials according to a ratio of 3:1 (w/w), stirring and mixing uniformly at 45 ℃, soaking for 48 hours, filtering, and drying at 105 ℃ to obtain the rice hull pretreatment material. Then heating the rice hull pretreatment material to 700 ℃ at a heating rate of 10 ℃/min in nitrogen atmosphere, maintaining the temperature for 1 hour for high-temperature pyrolysis reaction, cooling the reaction system to room temperature after the reaction is finished, repeatedly washing the obtained crude product with deionized water to neutrality, and drying at 105 ℃ to obtain the modified rice hullA sexual peanut shell biochar. The specific surface area of the obtained modified peanut shell biochar is 295m 2 /g。
Example 6 preparation of modified fir biochar
The method comprises the following steps: pulverizing fir wood chip, drying, and sieving to 30 mesh. The acidic wood vinegar generated in the process of preparing the modified corn stalk biochar in the embodiment 1 is subjected to standing, filtering, impurity removal, filtrate collection and concentration, so that the water content of the acidic wood vinegar is about 70%. Mixing the obtained acidic wood vinegar produced by pyrolysis of corn straw with fir wood chip raw materials according to a ratio of 2:1 (w/w), stirring and mixing uniformly at 45 ℃, soaking for 48 hours, filtering, and drying at 105 ℃ to obtain the fir wood chip pretreatment material. And then heating the obtained fir wood chip pretreatment material to 800 ℃ at a heating rate of 15 ℃/min in nitrogen atmosphere, maintaining the temperature for 1 hour for high-temperature pyrolysis reaction, cooling the reaction system to room temperature after the reaction is finished, repeatedly washing the obtained crude product to be neutral by deionized water, and drying at 105 ℃ to obtain the modified fir wood biochar. The specific surface area of the obtained modified fir biochar is 509m 2 /g。
Example 7 preparation of modified corn straw biochar
The method comprises the following steps: crushing corn stalk, drying and sieving to 50 mesh. The acidic wood vinegar produced in the process of preparing the modified fir charcoal in example 2 is left to stand, filtered, purified, and the filtrate is collected and concentrated so that the water content of the acidic wood vinegar is about 60%. Mixing the obtained acid wood vinegar produced by pyrolysis of fir wood chips with corn straw raw materials according to a ratio of 2:1 (w/w), stirring and mixing uniformly at 45 ℃, soaking for 48 hours, filtering, and drying at 105 ℃ to obtain the corn straw pretreatment material. And then heating the obtained corn stalk pretreatment material to 700 ℃ at a heating rate of 10 ℃/min in a nitrogen atmosphere, keeping the temperature at 100 ℃ for 0.5 hour every time, keeping the temperature at 700 ℃ for 1 hour, carrying out high-temperature pyrolysis reaction, cooling the reaction system to room temperature after the reaction is finished, repeatedly washing the obtained crude product to be neutral by deionized water, and drying at 105 ℃ to obtain the modified corn stalk biochar. The biological matter of the modified corn stalk is obtained through measurementThe specific surface area of the carbon was 313m 2 /g。
Example 8 preparation of modified corn straw biochar
The method comprises the following steps: crushing corn stalk, drying and sieving to 50 mesh. The acidic wood vinegar generated in the process of preparing the modified wheat straw biochar in example 3 is subjected to standing, filtering, impurity removal, filtrate collection and concentration, so that the water content of the acidic wood vinegar is about 60%. Mixing the obtained acidic wood vinegar produced by pyrolysis of the wheat straw with corn straw raw materials according to a ratio of 3:1 (w/w), stirring and mixing uniformly at 45 ℃, soaking for 48 hours, filtering, and drying at 105 ℃ to obtain the corn straw pretreatment material. And then heating the obtained corn stalk pretreatment material in nitrogen atmosphere at a heating rate of 10 ℃/min, keeping the temperature at 100 ℃ for 0.5 hour every time, keeping the temperature at 700 ℃ for 1 hour, carrying out high-temperature pyrolysis reaction, cooling the reaction system to room temperature after the reaction is finished, repeatedly washing the obtained crude product to be neutral by deionized water, and drying at 105 ℃ to obtain the modified corn stalk biochar. The specific surface area of the obtained modified corn stalk biochar is 365m 2 /g。
Example 9 preparation of modified fir biochar
The method comprises the following steps: pulverizing fir wood chip, drying, and sieving to 50 mesh. The acidic wood vinegar generated in the process of preparing the modified wheat straw biochar in example 3 is subjected to standing, filtering, impurity removal, filtrate collection and concentration, so that the water content of the acidic wood vinegar is about 65%. Mixing the obtained acid wood vinegar produced by pyrolysis of the wheat straw with fir wood chip raw materials according to a ratio of 2:1 (w/w), stirring and mixing uniformly at 45 ℃, soaking for 48 hours, filtering, and drying at 105 ℃ to obtain the fir wood chip pretreatment material. And then heating the obtained fir wood chip pretreatment material in nitrogen atmosphere at a heating rate of 10 ℃/min, keeping the temperature at 100 ℃ for 0.5 hour every time, heating to 800 ℃ and keeping the temperature for 1 hour for high-temperature pyrolysis reaction, cooling the reaction system to room temperature after the reaction is finished, repeatedly washing the obtained crude product to be neutral by deionized water, and drying at 105 ℃ to obtain the modified fir wood biochar. The specific surface area of the obtained modified fir charcoal is 413m 2 /g。
Example 10 preparation of modified Rice husk biochar
The method comprises the following steps: pulverizing rice hull, drying, and sieving to 30 mesh. The acidic wood vinegar generated in the process of preparing the modified corn stalk biochar in the embodiment 1 is subjected to standing, filtering, impurity removal, filtrate collection and concentration, so that the water content of the acidic wood vinegar is about 70%. Mixing the obtained acidic wood vinegar produced by pyrolysis of corn straw with rice hull raw materials according to a ratio of 2:1 (w/w), stirring and mixing uniformly at 45 ℃, soaking for 48 hours, filtering, and drying at 105 ℃ to obtain the rice hull pretreatment material. And then heating the rice hull pretreatment material in nitrogen atmosphere at a heating rate of 10 ℃/min, keeping the temperature at 100 ℃ for 0.5 hour every time, keeping the temperature at 800 ℃ for 1 hour, carrying out high-temperature pyrolysis reaction, cooling the reaction system to room temperature after the reaction is finished, repeatedly washing the obtained crude product with deionized water to be neutral, and drying at 105 ℃ to obtain the modified rice hull biochar. The specific surface area of the obtained modified rice hull biochar is 356m 2 /g。
Example 11 preparation of modified wheat straw biochar
The method comprises the following steps: the wheat straw is crushed, dried and sieved to 50 meshes. The acidic wood vinegar generated in the process of preparing the modified wheat straw biochar in example 3 is subjected to standing, filtering, impurity removal, filtrate collection and concentration, so that the water content of the acidic wood vinegar is about 70%. Mixing the obtained acidic wood vinegar with wheat straw raw materials according to a ratio of 2:1 (w/w), stirring and mixing uniformly at 45 ℃, soaking for 48 hours, filtering, and drying at 105 ℃ to obtain the wheat straw pretreatment material. And then heating the obtained wheat straw pretreatment material in nitrogen atmosphere at a heating rate of 20 ℃/min, keeping the temperature at 100 ℃ for 0.5 hour every time, keeping the temperature at 800 ℃ for 1 hour, carrying out high-temperature pyrolysis reaction, cooling the reaction system to room temperature after the reaction is finished, repeatedly washing the obtained crude product to be neutral by deionized water, and drying at 105 ℃ to obtain the modified wheat straw biochar. The specific surface area of the obtained modified wheat straw biochar is 496m 2 /g。
Example 12 preparation of modified corn straw biochar
The method comprises the following steps: crushing corn stalk, drying and sieving to 50 mesh. The acidic wood vinegar generated in the process of preparing the modified corn stalk biochar in the embodiment 1 is subjected to standing, filtering, impurity removal, filtrate collection and concentration, so that the water content of the acidic wood vinegar is about 70%. Mixing the obtained acidic wood vinegar with corn straw raw materials according to a ratio of 2:1 (w/w), stirring and mixing uniformly at 45 ℃, soaking for 48 hours, filtering, and drying at 105 ℃ to obtain the wheat straw pretreatment material. And then heating the obtained wheat straw pretreatment material in nitrogen atmosphere at a heating rate of 10 ℃/min, keeping the temperature at 100 ℃ for 0.5 hour every time, keeping the temperature at 600 ℃ for 1 hour, carrying out high-temperature pyrolysis reaction, cooling the reaction system to room temperature after the reaction is finished, repeatedly washing the obtained crude product to be neutral by deionized water, and drying at 105 ℃ to obtain the modified corn straw biochar. The specific surface area of the obtained modified corn stalk biochar is 318m 2 /g。
Example 13 preparation of modified fir biochar
The method comprises the following steps: pulverizing fir wood chip, drying, and sieving to 50 mesh. The acidic wood vinegar produced in the process of preparing the modified fir charcoal in example 2 was allowed to stand, filtered, purified, and the filtrate was collected and concentrated so that the water content of the acidic wood vinegar was about 80%. Mixing the obtained acidic wood vinegar with fir wood chip raw materials according to a ratio of 2:1 (w/w), stirring and mixing uniformly at 45 ℃, soaking for 48 hours, filtering, and drying at 105 ℃ to obtain the fir wood chip pretreatment material. And then heating the obtained fir wood chip pretreatment material in nitrogen atmosphere at a heating rate of 10 ℃/min, keeping the temperature at 100 ℃ for 0.5 hour every time, keeping the temperature at 700 ℃ for 2 hours, carrying out high-temperature pyrolysis reaction, cooling the reaction system to room temperature after the reaction is finished, repeatedly washing the obtained crude product with deionized water to be neutral, and drying at 105 ℃ to obtain the modified fir wood charcoal. The specific surface area of the obtained modified fir charcoal is 493m 2 /g。
Comparative example 1
The comparative example differs from example 2 only in that no wood was usedThe vinegar liquid is used for preprocessing the fir wood chip raw material, and the rest materials are the same. Pulverizing fir wood chip, drying, and sieving to 30 mesh. And then heating the raw materials to 800 ℃ at a heating rate of 20 ℃/min in a nitrogen atmosphere, maintaining the temperature for 1 hour for high-temperature pyrolysis reaction, cooling the reaction system to room temperature after the reaction is finished, repeatedly washing the obtained crude product with deionized water to be neutral, and drying the crude product at 105 ℃ to obtain the fir biochar. The specific surface area of the obtained unmodified fir biochar is 186m 2 /g。
Comparative example 2
This comparative example is different from example 3 only in that no pretreatment of the wheat straw raw material with any pyroligneous liquor was performed, and the rest were the same. Namely, the wheat straw is crushed, dried and sieved to 30 meshes. And then heating the raw materials to 700 ℃ at a heating rate of 20 ℃/min in a nitrogen atmosphere, maintaining the temperature for 1 hour for high-temperature pyrolysis reaction, cooling the reaction system to room temperature after the reaction is finished, repeatedly washing the obtained crude product to be neutral by deionized water, and drying the crude product at 105 ℃ to obtain the wheat straw biochar. The specific surface area of the obtained unmodified wheat straw biochar is 89m 2 /g。
From the experimental data of the examples, it can be seen that the specific surface area of the obtained modified biochar can be increased by pretreating the biomass raw material with the acid wood vinegar rich in the organic acid and then performing the pyrolysis reaction, and the specific surface area of the modified biochar in examples 1 to 13 is increased as compared with that of the unmodified biochar. The source of the acid wood vinegar has no obvious influence on the modification effect, namely, wood vinegar generated in the pyrolysis process of biomass rich in lignocellulose or acid wood vinegar which is a byproduct in the preparation process of the modified biochar is adopted to pretreat biomass raw materials, so that the specific surface area of the modified biochar can be improved.
As can be seen from the scanning electron microscope, the modified fir charcoal prepared in example 2 has more pore structure in the structure compared with the fir charcoal prepared in comparative example 1.
Test examples
The modified or unmodified fir biochar prepared in example 2 and comparative example 1 was added to a contaminated water body containing 200mg/L of copper ions and lead ions at 3.0g/L, and vibration-adsorbed at room temperature for 6 hours, and the concentrations of copper ions and lead ions in the aqueous solution at the adsorption equilibrium were measured using an atomic absorption spectrometer, and the saturated adsorption amount and removal rate were calculated. Under the acidic condition (the pH of the sewage water body containing copper ions and lead ions is about 6.0), the removal rate of the modified fir wood biochar on the copper ions is 99.8%, and the removal rate of the modified fir wood biochar on the lead ions is 98.9%. Under the same conditions, the removal rate of the unmodified fir biochar on copper ions is 83.9%, and the removal rate of the unmodified fir biochar on lead ions is 75.6%.
The present invention is described in detail above. It will be apparent to those skilled in the art that the present invention can be practiced in a wide range of equivalent parameters, concentrations, and conditions without departing from the spirit and scope of the invention and without undue experimentation. While the invention has been described with respect to specific embodiments, it will be appreciated that the invention may be further modified. In general, this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains.
Claims (10)
1. A method for preparing modified biochar, which comprises the following steps: pretreating biomass raw materials by taking wood vinegar as an activating agent, and pyrolyzing the obtained pretreated material to obtain the modified biochar.
2. The method according to claim 1, characterized in that: the pyroligneous liquor is pyroligneous liquor generated in the biomass pyrolysis process.
3. The method according to claim 1 or 2, characterized in that: the method for preparing the modified biochar comprises the following steps:
1) Pulverizing biomass raw materials, drying, sieving, adding wood vinegar, stirring at 30-60deg.C, soaking, filtering, and drying to obtain pretreated material;
2) And (3) carrying out high-temperature pyrolysis reaction on the pretreated material to obtain the modified biochar.
4. A method according to claim 3, characterized in that: in the step 1), the biomass raw material is lignocellulose biomass, and can be specifically at least one of corn straw, wheat straw, rice straw, bamboo wood, wood dust, peanut shell, wheat shell, rice hull, leaf and weed;
sieving with 10-100 mesh sieve;
the pyroligneous liquor is pyroligneous liquor generated in the biomass pyrolysis process or is derived from pyroligneous liquor generated in other lignocellulose biomass pyrolysis processes.
5. A method according to claim 3, characterized in that: the water content of the wood vinegar is 30-90%, and the wood vinegar is prepared by the following method: pyrolyzing biomass raw materials in inert atmosphere at 300-900 ℃ for 1-4 hours, collecting flue gas, and condensing to obtain a tan liquid;
the wood vinegar is also subjected to pretreatment before being added into a reaction system, and the pretreatment operation sequentially comprises the following steps: standing, filtering, removing impurities, collecting filtrate, and concentrating.
6. A method according to claim 3, characterized in that: the mass ratio of the biomass raw material to the wood vinegar is 1:2-1:8;
the time of the soaking is 12-48 hours.
7. A method according to claim 3, characterized in that: in the step 2), the pyrolysis reaction is carried out in an inert atmosphere or in vacuum;
the operation of the high-temperature pyrolysis reaction is as follows: heating to 300-900 ℃, preserving heat for 1-4 hours, cooling to room temperature after the reaction is completed, washing to neutrality by deionized water, and drying to obtain the modified biochar.
8. The method according to claim 7, wherein:
the temperature rise is continuous temperature rise or stage temperature rise,
the continuous heating rate is 5-20 ℃/min, the temperature is raised to 300-900 ℃, and the temperature is kept for 1-4 hours;
the temperature is raised at a speed of 5-20 ℃/min, the reaction temperature is kept at 100 ℃ for 0.5 hours every time, and the temperature is raised to 300-900 ℃ and kept for 1-4 hours.
9. A modified biochar produced by the method of any one of claims 1-8.
10. The use of the modified biochar according to claim 9 for the adsorption of heavy metal ions in aqueous solutions.
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