CN115477302A - Biochar and preparation method and application thereof - Google Patents

Biochar and preparation method and application thereof Download PDF

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CN115477302A
CN115477302A CN202211197592.1A CN202211197592A CN115477302A CN 115477302 A CN115477302 A CN 115477302A CN 202211197592 A CN202211197592 A CN 202211197592A CN 115477302 A CN115477302 A CN 115477302A
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biochar
algae
potassium hydroxide
pyrolysis
prepared
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李文魁
张雅丽
陈智琴
罗珊珊
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Jiangxi Science and Technology Normal University
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Jiangxi Science and Technology Normal University
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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
    • C01B32/318—Preparation characterised by the starting materials
    • C01B32/324—Preparation characterised by the starting materials from waste materials, e.g. tyres or spent sulfite pulp liquor
    • 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
    • C01B32/348—Metallic compounds
    • 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
    • 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
    • C02F2101/30—Organic compounds
    • C02F2101/308—Dyes; Colorants; Fluorescent agents
    • 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
    • C02F2101/30—Organic compounds
    • C02F2101/34—Organic compounds containing oxygen
    • 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
    • C02F2101/30—Organic compounds
    • C02F2101/36—Organic compounds containing halogen
    • 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
    • C02F2101/30—Organic compounds
    • C02F2101/38—Organic compounds containing nitrogen
    • 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
    • C02F2101/30—Organic compounds
    • C02F2101/40—Organic compounds containing sulfur
    • 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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  • Organic Chemistry (AREA)
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  • Water Supply & Treatment (AREA)
  • Preparation Of Compounds By Using Micro-Organisms (AREA)

Abstract

The invention belongs to the technical field of new material preparation, and particularly relates to a biochar as well as a preparation method and application thereof. According to the invention, the algae residues and the potassium hydroxide are pyrolyzed in one step to prepare the biochar, the potassium hydroxide and the algae residues are mixed to promote the release of organic components in the algae residues, so that the potassium hydroxide and the algae residues are in full contact in the subsequent pyrolysis stage, and the potassium hydroxide is used as a support body during pyrolysis to promote the biochar to form a rich pore structure, so that the prepared biochar is more fluffy in structure, the lamellar structure in the microstructure is obviously increased, the particles are uniformly dispersed, the specific surface area is greatly increased, and the adsorption performance is further improved. The biochar prepared by the method has large adsorption capacity on organic pollutants in simulated wastewater, has good effect on different pollutants, and has the adsorption capacity on anionic dye methyl orange of 244.63mg/g and the adsorption capacity on cationic dye methylene blue of 485.43mg/g.

Description

Biochar and preparation method and application thereof
Technical Field
The invention belongs to the technical field of new material preparation, and particularly relates to a biochar as well as a preparation method and application thereof.
Background
With the increase of social production and human living demands and the rapid development of the printing and dyeing industry, people have higher requirements on the richness, the tinctorial strength and the degradation resistance of the dye, so that a large amount of high-load wastewater can be generated in the processes of dye preparation and printing and dyeing operation. The dye wastewater has complex components, has the characteristics of high solubility, deep chromaticity, difficult biodegradation, high content of toxic and harmful substances and the like, and has great harm to discharge of peripheral aquatic organisms and ecological environment. Therefore, the method has positive significance for effectively relieving the water pollution by properly treating the waste dye in the water body. The adsorption method is a physical method commonly used in a method for treating dye wastewater, and adsorbs organic and inorganic pollutants such as dye by utilizing the properties of abundant pore structures, surface functional groups, large specific surface area and the like of an adsorbent.
Microalgae are a type of photosynthetic based unicellular autotrophic organism widely distributed in freshwater, marine and land water environments, do not require fertile land, can be propagated on a large scale in wastewater and grow rapidly. The chlorella is rich in oil and is a promising candidate for producing biodiesel, the chlorella residue after the oil extraction contains polar organic solvents, the direct stacking treatment is not safe and proper enough, and the environmental pollution is possibly caused, and the chlorella residue waste still contains abundant carbohydrate or protein and other substances, so that the resource waste is caused when the chlorella residue is not effectively utilized. Chinese patent CN108373146A discloses algae residue biochar for catalyzing persulfate or monopersulfate to degrade organic pollutants, and Chinese patent CN 111004053A discloses chlorella hydrothermal carbon for recycling phosphorus from sewage to farmland, promoting utilization efficiency of wheat to phosphorus and achieving the purposes of reducing phosphorus and improving efficiency. However, the biochar material prepared by utilizing microalgae in the prior art has the problem of poor adsorption performance.
Disclosure of Invention
In view of the above, the present invention aims to provide a biochar, and a preparation method and application thereof. The biochar prepared by the method has large specific surface area and good adsorption performance.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of biochar, which comprises the following steps:
crushing algae powder, removing grease and performing primary drying in sequence to obtain algae residues;
mixing the algae residue, potassium hydroxide and water, and then sequentially carrying out secondary drying and grinding to obtain mixed powder;
pyrolyzing the mixed powder to obtain carbide of algae residue;
and sequentially carrying out acid washing, water washing and third drying on the carbide of the algae residues to obtain the biochar.
Preferably, the mass ratio of the algae residue to the potassium hydroxide is 1:1-5.
Preferably, the temperature of the pyrolysis is 300 to 900 ℃.
Preferably, the pyrolysis time is 1 to 5 hours.
Preferably, the pyrolysis atmosphere is nitrogen.
Preferably, the mixed powder has a particle size of 1 to 10 μm.
Preferably, the algae powder is chlorella algae powder.
The invention also provides the biochar prepared by the preparation method in the technical scheme, and the specific surface area of the biochar is 40-1500 m 2 /g。
The invention also provides application of the biochar obtained by the preparation method in the technical scheme in adsorption of wastewater pollutants.
Compared with the prior art, the invention has the following beneficial effects:
according to the invention, the algae residue and the potassium hydroxide are pyrolyzed in one step to prepare the biochar, the release of organic components in the algae residue is promoted in the mixing process of the potassium hydroxide and the algae residue, the potassium hydroxide and the algae residue are in full contact in the subsequent pyrolysis stage, the potassium hydroxide is used as a support body during pyrolysis to promote the biochar to form a rich pore structure, so that the prepared biochar is more fluffy in structure, the lamellar structure in the microstructure is obviously increased, the particles are uniformly dispersed, the specific surface area is greatly increased, and the embodiment result shows that the biochar is 40-1500 m 2 And/g, thereby improving the adsorption performance. The data of the examples show that the biochar prepared by the invention has large adsorption capacity on organic pollutants in simulated wastewater and good effect on different pollutants, and the adsorption capacity on the anionic dye methyl orange is 244.63mg/g, and the adsorption capacity on the cationic dye methylene blue is 485.43mg/g.
Furthermore, the method takes the chlorella algae residues after grease removal as raw materials to prepare the biochar, solves the problems that the structure of algae raw materials is seriously damaged, pore structures are easy to block and cake and pores are few in the pyrolysis process, has little grease content and relatively high carbohydrate content in the chlorella algae residues after grease removal, and has a better porous structure, the specific surface area is further increased, and the adsorption performance of the biochar is further improved.
Furthermore, the preparation method is simple and easy to implement, has higher efficiency compared with the traditional method for preparing the biological carbon by step firing, has less types and dosage of chemical reagents and lower cost, and the prepared biological carbon material has good adsorption performance.
The invention also provides the biological carbon obtained by the preparation method of the technical scheme and the application of the biological carbon in adsorbing wastewater pollutants, and the specific surface area of the biological carbon is large and is 40-1500 m 2 Per g, good adsorption performance and good adsorption effect on the dye in the wastewater.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a flow chart of biochar production in the examples;
FIG. 2 shows the results of the amounts of methyl orange and methylene blue adsorbed by biochar obtained in examples 1 to 3;
FIG. 3 is an SEM scanning electron micrograph of a biochar material prepared in example 4 at a low magnification;
FIG. 4 is an SEM scanning electron micrograph of a biochar material prepared in example 4 at high magnification;
FIG. 5 shows the results of the amount of biochar adsorbed to Methyl Orange (MO) and Methylene Blue (MB) obtained in example 8;
FIG. 6 is a diagram showing the results of removing methyl orange (concentration: 100 mg/L) from wastewater containing biochar obtained in example 8 (pyrolysis time: 150 min);
FIG. 7 is a real object diagram of the wastewater from example 8 (pyrolysis time: 120 min) before and after the removal of methylene blue (concentration: 150 mg/L).
Detailed Description
The invention provides a preparation method of biochar, which comprises the following steps:
crushing algae powder, removing grease and performing primary drying in sequence to obtain algae residues;
mixing the algae residue, potassium hydroxide and water, and then sequentially carrying out secondary drying and grinding to obtain mixed powder;
pyrolyzing the mixed powder to obtain carbide of algae residue;
and sequentially carrying out acid washing, water washing and third drying on the algae residue carbide to obtain the biochar.
In the present invention, materials and equipment used are commercially available in the art unless otherwise specified.
The method comprises the steps of crushing algae powder, removing grease and carrying out primary drying to obtain algae residues.
In the present invention, the algal powder is preferably chlorella algal powder.
The method comprises the steps of sequentially crushing chlorella powder, removing grease and carrying out primary drying to obtain chlorella residue.
In the invention, before crushing, the method preferably further comprises the step of mixing chlorella powder with water, wherein the dosage ratio of the chlorella powder to the water is preferably 10-50g.
In the present invention, the particle size of the chlorella powder is preferably less than 10 μm.
In the present invention, the disruption preferably comprises ultrasonication, and the conditions of the ultrasonication preferably comprise: the frequency is 15-25 KHz, the time is 10-30 min, the interval is 1-10 s, the ultrasonic crushing is repeated for 1-3 times, and the algae cells can be crushed more uniformly by the ultrasonic crushing, so that more oil in the algae cells can be removed in the subsequent oil removing process.
In the present invention, the method for removing oil and fat is preferably a Floch method, the solvent used in the Floch method is preferably a mixed solution of methanol, chloroform and water, the dosage ratio of the mixed solution to chlorella algae powder is preferably from 400 to 800ml.
In the present invention, it is preferable that the method further includes water washing after the removal of the oil and fat, the water washing is performed to remove soluble organic substances, the water is preferably deionized water, and the soluble organic substances preferably include a pigment.
According to the invention, the solution obtained by washing with water is preferably centrifuged, and the solid precipitate obtained by centrifugation is subjected to first drying, wherein the rotation speed of centrifugation is preferably 5000-10000 r/min, and the time is preferably 5-20 min.
In the invention, the first drying is preferably freeze drying, and the method also comprises prefreezing before the freeze drying, wherein the prefreezing temperature is preferably-20 to-80 ℃, and the time is preferably 5 to 12 hours; the temperature of the freeze drying is preferably-60 to-90 ℃, and the time is preferably 12 to 48 hours.
In the present invention, it is preferable that the chlorella algal pomace is obtained by performing first grinding after the first drying.
In the present invention, the preparation method of the algal residues other than chlorella is preferably the same as that of chlorella, and thus the detailed description thereof is omitted.
In the present invention, the particle size of the algal residue is preferably less than 10 μm.
The biomass of the raw material of the small-ball algae has rich grease content, the original structure of the biomass can be seriously damaged in the pyrolysis process, the pore structure is easy to block and agglomerate, and the pores are few. The algae residue after the oil extraction is adopted for activation, the oil content in the algae residue after the oil extraction is low, the carbohydrate content is relatively high, and the prepared biological carbon has a larger porous structure and can obtain a more ideal adsorption effect.
After the algae residue is obtained, the algae residue, potassium hydroxide and water are mixed, and then secondary drying and grinding are sequentially carried out to obtain mixed powder.
In the invention, the dosage ratio of the algal residue, the potassium hydroxide and the water is preferably 2-10g, and is more preferably 1 g.
In the present invention, the mass ratio of the algal residue to potassium hydroxide is preferably 1:1 to 5, more preferably 1:3. In the mixing process, the release of organic components in the algae residues can be promoted, the full contact of potassium hydroxide and the algae residues in the subsequent pyrolysis stage is facilitated, and the potassium hydroxide is used as a support body during pyrolysis, so that the formation of rich pore structures by biological carbon can be promoted.
In the present invention, the mixing is preferably performed by stirring, and the stirring time is preferably 12 to 20 hours, more preferably 16 hours, and in the specific embodiment of the present invention, the stirring is performed overnight.
In the present invention, the temperature of the second drying is preferably 80 to 120 ℃, more preferably 110 ℃, and the time is preferably 12 to 48 hours, more preferably 24 hours.
In the present invention, the particle diameter of the mixed powder is preferably 1 to 10 μm.
After the mixed powder is obtained, the algae residue carbide is obtained by pyrolyzing the mixed powder.
In the present invention, the temperature of the pyrolysis is preferably 300 to 900 ℃, more preferably 500 to 700 ℃, most preferably 650 ℃, and the time is preferably 1 to 5 hours, more preferably 2 to 4 hours, most preferably 2 to 2.5 hours.
In the present invention, the rate of temperature increase from room temperature to the temperature for pyrolysis is preferably 5 to 15 ℃/min, more preferably 10 ℃/min.
In the present invention, the atmosphere for pyrolysis is preferably nitrogen. In a specific embodiment of the invention, the pyrolysis is carried out in a corundum tube furnace, and the specific process comprises the following steps: transferring the mixed powder into a corundum boat, and putting the corundum boat into a corundum tube furnace; sealing the corundum tube furnace, introducing nitrogen for 30min, placing the tail end of an air outlet pipe of the corundum tube furnace in water to ensure that the furnace is in an oxygen-deficient atmosphere, heating to 300-900 ℃ at the speed of 5-15 ℃/min, keeping for 1-5 h, and introducing nitrogen in the whole process.
In the present invention, the pyrolysis carbonizes the algal residue.
In the present invention, the pyrolysis preferably further comprises cooling, the final temperature of the cooling is preferably room temperature, and the cooling is preferably furnace cooling.
After the algae residue carbide is obtained, the algae residue carbide is sequentially subjected to acid washing, water washing and third drying to obtain the biochar.
In the invention, the acid washing reagent is preferably hydrochloric acid solution, the concentration of the hydrochloric acid solution is preferably 1mol/L, the dosage of the hydrochloric acid solution is not specially required, and the algae residue carbide is washed to be neutral. In the specific embodiment of the present invention, the acid washing is performed in a manner of stirring while dropping.
In the present invention, the reagent for washing with water is preferably distilled water, the number of washing with water is preferably two, and the washing with water is preferably accompanied with suction filtration.
In the invention, the algae residue carbide is neutral by acid washing and water washing.
In the present invention, the temperature of the third drying is preferably 80 to 120 ℃, more preferably 110 ℃; the time for the third drying is preferably 1 to 12 hours, and more preferably 2 hours.
In the present invention, it is preferable that the third drying further comprises cooling to obtain the biochar, and the cooling method is not particularly required in the present invention.
The invention also provides the biochar prepared by the preparation method in the technical scheme, and the specific surface area of the biochar is 40-1500 m 2 /g。
In the present invention, the specific area of the biochar is preferably 500 to 1500m 2 Per g, more preferably 524.47 to 1438.7m 2 /g。
In the present invention, the particle size of the biochar is preferably 1 to 4 μm.
The invention also provides application of the biochar obtained by the preparation method in the technical scheme in adsorption of wastewater pollutants.
In the present invention, the kind of the wastewater contaminant preferably includes an anionic dye and/or a cationic dye, more preferably methyl orange and/or methylene blue; the concentration of the wastewater pollutants is preferably 10-500 mg/L, and more preferably 100-200 mg/L.
In the present invention, the amount of the biochar added to the wastewater is preferably 2 to 6mg/10mL, and more preferably 4mg/10mL.
In the present invention, the adsorption time is preferably 40 to 90min, and more preferably 60min.
The biochar prepared by the invention has good adsorption effect on dye, wherein the adsorption capacity on the anionic dye methyl orange can reach 244.63mg/g which is far higher than the adsorption capacity of 100-150 mg/g of the biochar of the same type; the adsorption capacity to the cationic dye methylene blue can reach 485.43mg/g, which is higher than the adsorption capacity of 454.2mg/g of the active carbon.
In order to further illustrate the present invention, the biochar provided by the present invention, the preparation method and the application thereof are described in detail below with reference to the accompanying drawings and examples, but they should not be construed as limiting the scope of the present invention.
FIG. 1 is a flow chart of the preparation of biochar in the example: first step, removing oil from algae powder to obtain algae residue, and second step: mixing and stirring the algae residue with KOH and water, and activating, wherein the third step is as follows: carbonizing the activated algae residue by high-temperature pyrolysis; the fourth step: acid washing to obtain neutral biological carbon; the fifth step: and drying and cooling the target biochar for later use.
Example 1
1) Dissolving 20g of chlorella powder in 150mL of deionized water, and performing ultrasonic treatment at a frequency of 20KHz for 13min at an interval of 3s; then, 160mL of methanol: chloroform: the volume ratio of water is 1; and then placing the mixture in a vacuum freeze dryer with the working temperature of 70 ℃ below zero, taking out the mixture after 24 hours, and grinding the mixture into powder with the average grain diameter of less than 10 mu m, thus obtaining the algae residue.
2) Weighing 5g of dried algae residue, 15g of potassium hydroxide (namely the mass ratio of the algae residue to the potassium hydroxide is 1:3) and 25mL of deionized water, adding the three into a small beaker, stirring overnight, then placing the beaker in an oven for drying for 24h at 110 ℃, and grinding the beaker into mixed powder with the particle size of less than 10 mu m.
3) Transferring the mixed powder into a corundum boat, putting the corundum boat into a corundum tube furnace, sealing the tube furnace, introducing nitrogen for 30min, placing the tail end of an air outlet pipe into water to ensure that the furnace is in an oxygen-deficient atmosphere, introducing nitrogen in the whole heating process, heating to 600 ℃ (pyrolysis temperature) at a speed of 10 ℃/min, keeping the temperature for 90min (pyrolysis time), and then naturally cooling to room temperature.
4) Pouring the materials in the corundum boat into a small beaker, dropwise adding 1mol/L hydrochloric acid solution while stirring until the mixed liquid is neutral, performing suction filtration, and then cleaning twice by using distilled water.
5) Drying the material obtained in the step 4) in an oven at 110 ℃ for 1h, and then taking out and cooling to obtain the biochar.
Example 2
The only difference between this example and example 1 is that the mass of potassium hydroxide in step 2) is 5g (i.e., the mass ratio of algal residue to potassium hydroxide is 1:1).
Example 3
The difference between this example and example 1 is only that the mass of potassium hydroxide in step 2) is 10g (i.e. the mass ratio of algal residue to potassium hydroxide is 1:2).
Application example 1
The biochar prepared in examples 1-3 was used to remove organic pollutants from simulated wastewater:
respectively taking 10mL of methyl orange solution (MO) with the concentration of 100mg/L and methylene blue solution (MB) with the concentration of 150mg/L to obtain a wastewater sample and marking;
adding the biochar prepared in the embodiments 1-3 into a wastewater sample respectively, wherein the addition amount is 4mg/10mL, then placing the biochar on a magnetic stirrer to adsorb at the rotating speed of 300rpm, and sampling after adsorbing for 1 h; the concentration of methyl orange in the wastewater sample is measured by an ultraviolet-visible spectrophotometer at the wavelength of 446nm, the concentration of methylene blue in the wastewater sample is measured at the wavelength of 664nm, and the adsorption capacity is calculated and obtained as shown in figure 2, wherein 1:1, 1:2 and 1:3 in figure 2 refer to the mass ratio of algae residue to potassium hydroxide.
When the concentration of methyl orange is 100mg/L and the concentration of methylene blue is 150mg/L, the adsorption capacity of the biochar prepared in example 1 on the methyl orange and the methylene blue is 70.1mg/g and 160.36mg/g respectively; the adsorption amounts of the biochar prepared in example 2 on methyl orange and methylene blue are 28.33mg/g and 86.62mg/g respectively; the adsorption amounts of the biochar prepared in example 3 to methyl orange and methylene blue are 50.68mg/g and 131.05mg/g respectively. As can be seen from the adsorption data of the biological carbon material on methyl orange and methylene blue, when the mass ratio of the algae residue to the potassium hydroxide is 1:3, the prepared biological carbon has the best adsorption effect.
Example 4
This example differs from example 1 only in the pyrolysis temperature, which is 650 ℃.
Fig. 3 and 4 are SEM scanning electron micrographs of the biocarbon material prepared in example 4 at different magnifications, and it can be seen that the biocarbon material prepared in the present invention exhibits fluffy black uneven particulates, and a large number of lamella and particulate structures can be observed under the scanning electron microscope, which is advantageous for the occurrence of adsorption.
Example 5
This example differs from example 1 only in the pyrolysis temperature, which is 700 ℃.
Example 6
The difference between this example and example 1 is only the pyrolysis temperature, which is 750 ℃.
Example 7
The difference between this example and example 1 is only the pyrolysis temperature, which is 500 deg.C
Table 1 shows BET results of the biochar materials obtained in examples 1, 4 and 7.
TABLE 1 BET results for biochar materials produced at different temperatures
Example 1 Example 4 Example 5 Example 6 Example 7
Different temperatures (. Degree. C.) 600 650 700 750 500
Specific surface area (m) 2 /g) 1345.64 1438.7 562.47 46.24 524.47
As can be seen from the data in Table 1, the prepared biological carbon material has large specific surface area, is favorable for achieving good adsorption effect, and the maximum specific surface area reaches 1438.7m at the pyrolysis temperature of 650 DEG C 2 The specific surface area of the biochar prepared by the method is 4-6 times higher than that of the biochar prepared by the prior art at the same temperature.
Example 8
This example differs from example 4 only in that the pyrolysis time in step 3) is different, and the example sets the pyrolysis time separately: 60. 90, 120, 150, 180, 210, 240 and 270min, preparing biochar.
Application example 2
The biochar prepared in example 8 was used to remove organic pollutants from simulated wastewater according to the method of application example 1, and the results of adsorption amounts of Methyl Orange (MO) and Methylene Blue (MB) are shown in fig. 5.
When the concentration of methyl orange is 100mg/L, the adsorption capacity of the prepared biochar for pyrolysis time of 150min to methyl orange is 244.63mg/g, and a real object diagram before and after the removal of the methyl orange (with the concentration of 100 mg/L) in the wastewater is shown in FIG. 6; the adsorption capacity of the biochar prepared by pyrolysis for 180min to methyl orange is 240.86mg/g.
When the concentration of methylene blue is 150mg/L, the adsorption capacity of the prepared biological carbon for pyrolysis for 120min is 375mg/g, and the real object graphs before and after the methylene blue (with the concentration of 150 mg/L) in the wastewater is removed are shown in FIG. 7; the adsorption amount of the biochar prepared by pyrolysis for 180min to methylene blue is 375mg/g, because the methylene blue is completely adsorbed, the concentration of the methylene blue is increased to 200mg/L, and the adsorption amount of the biochar prepared by pyrolysis for 120min reaches 485.43mg/g.
As can be seen from FIG. 5, the biochar prepared when the pyrolysis time is 120-210 min has basically consistent adsorption amounts of methyl orange and methylene blue in the wastewater, and the summary result of the maximum adsorption amounts is shown in Table 2.
TABLE 2 results on the adsorption amounts of methyl orange and methylene blue
Contaminants and concentrations Methyl orange (100 mg/L) Methylene blue (150 mg/L) Methylene blue 200 (mg/L)
Adsorption Capacity (mg/g) 244.63 375 485.43
Removal Rate (%) 97.85 100 97.08
As can be seen from the data in Table 2, the biological carbon has the advantages of large adsorption capacity for removing organic pollutants in simulated wastewater, high removal rate and good effect on various pollutants, and the adsorption capacity for the anionic dye methyl orange reaches 244.63mg/g and the adsorption capacity for the cationic dye methylene blue reaches 485.43mg/g.
Comparative example 1
1) Dissolving 20g of chlorella powder in 150mL of deionized water, and performing ultrasonic treatment at a frequency of 20KHz for 13min at an interval of 3s; then, 160mL of methanol: chloroform: the volume ratio of water is 1; and then placing the mixture in a vacuum freeze dryer with the working temperature of 70 ℃ below zero, taking out the mixture after 24 hours, and grinding the mixture into powder with the average grain diameter of less than 10 mu m, thus obtaining the algae residue.
2) Transferring the algae residue powder into a corundum boat, putting the corundum boat into a corundum tube furnace, sealing the tube furnace, introducing nitrogen for 30min, placing the tail end of an air outlet pipe into water to ensure that the furnace is in an anoxic atmosphere, introducing nitrogen in the whole heating process, heating to 600 ℃ (pyrolysis temperature) at a speed of 10 ℃/min, keeping the temperature for 90min (pyrolysis time), and then naturally cooling to room temperature to obtain the biochar.
No potassium hydroxide activator is added in the preparation process, so that the steps of acid washing, water washing and drying are omitted, and the biochar prepared by the comparative example has the specific surface area of 0.338m 2 /g。
Comparative example 2
The comparative example differs from comparative example 1 only in the pyrolysis process in step 2), and step 2) of the comparative example is: transferring the algae residue powder into a corundum boat, putting the corundum boat into a corundum tube furnace, sealing the tube furnace, introducing nitrogen for 30min, placing the tail end of an air outlet pipe into water to ensure that the furnace is in an oxygen-deficient atmosphere, introducing nitrogen in the whole heating process, heating to 400 ℃ at the speed of 10 ℃/min, keeping for 30min, heating to 600 ℃ at the speed of 10 ℃/min, keeping for 90min, and then naturally cooling to room temperature to obtain the biochar.
The biochar prepared by the comparative example has the specific surface area of 3.9969m 2 (ii) in terms of/g. The specific surface area of the biological carbon prepared in the embodiment 4 of the invention is 1438.7m 2 The specific surface area increased 359 times compared with comparative example 2.
Comparative example 3
Zone of this comparative example and example 1Except that the oil and fat are not removed, namely, the chlorella algae powder is directly used for replacing the algae residue to carry out the step 2), the biochar prepared by the comparative example has the specific surface area of 1.261m 2 /g。
According to the invention, the algae residue and potassium hydroxide are pyrolyzed in one step to prepare the biochar, the prepared biochar is more fluffy in structure, the lamellar structure in the microstructure is obviously increased, the particles are uniformly dispersed, the specific surface area is greatly increased, the adsorption performance of the biochar can be further improved, the adsorption capacity to the anionic dye methyl orange is 244.63mg/g, and the adsorption capacity to the cationic dye methylene blue is 485.43mg/g.
Although the present invention has been described in detail with reference to the above embodiments, it is only a part of the embodiments of the present invention, not all of the embodiments, and other embodiments can be obtained without inventive work according to the embodiments of the present invention, and the embodiments are within the scope of the present invention.

Claims (9)

1. A method for preparing biochar is characterized by comprising the following steps:
crushing algae powder, removing grease and performing primary drying in sequence to obtain algae residues;
mixing the algae residue, potassium hydroxide and water, and then sequentially carrying out secondary drying and grinding to obtain mixed powder;
pyrolyzing the mixed powder to obtain carbide of algae residues;
and sequentially carrying out acid washing, water washing and third drying on the algae residue carbide to obtain the biochar.
2. The preparation method according to claim 1, wherein the mass ratio of the algae residue to the potassium hydroxide is 1:1-5.
3. The method of claim 1, wherein the pyrolysis temperature is 300 to 900 ℃.
4. The method of claim 1, wherein the pyrolysis time is 1 to 5 hours.
5. The method according to claim 1, 3 or 4, wherein the atmosphere for pyrolysis is nitrogen.
6. The method according to claim 1, wherein the mixed powder has a particle size of 1 to 10 μm.
7. The method according to claim 1, wherein the algal powder is chlorella algal powder.
8. The biochar obtained by the production method according to any one of claims 1 to 7, wherein the specific surface area of the biochar is 40 to 1500m 2 /g。
9. Use of the biochar of claim 8 for adsorbing wastewater contaminants.
CN202211197592.1A 2022-09-29 2022-09-29 Biochar and preparation method and application thereof Pending CN115477302A (en)

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