CN115092904A - Method for improving proportion of persistent functional groups on surface of biochar, prepared biochar and application of biochar - Google Patents
Method for improving proportion of persistent functional groups on surface of biochar, prepared biochar and application of biochar Download PDFInfo
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- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
- B01J21/18—Carbon
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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
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
- C02F1/725—Treatment of water, waste water, or sewage by oxidation by catalytic oxidation
-
- 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
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Abstract
The invention discloses a method for improving the proportion of persistent functional groups on the surface of biochar, the prepared biochar and application thereof, wherein crop straws are crushed and subjected to ball milling to enable straw powder to be sieved to obtain straw powder; cellulose and hemicellulose components of the straw powder are degraded into various monosaccharides through cellulase treatment; collecting straw powder, cleaning and drying to obtain dried straw powder; then placing the straw powder into heating equipment, and treating for at least 2 hours at the temperature of 500-700 ℃ in an oxygen-free environment to obtain the biochar with high-proportion durable functional groups on the surface. The biochar with high-proportion of persistent functional groups on the surface is used as an activating agent in the advanced oxidation method. According to the invention, the lignin content is increased, the proportion of the persistent functional groups on the surface of the biochar is improved, the group loss is reduced, and the method can be applied to an advanced oxidation technology to stably, continuously and efficiently repair organic pollutants, so that the effect of treating wastes with processes of wastes against one another is achieved.
Description
Technical Field
The invention belongs to the field of comprehensive utilization of waste crops and advanced oxidation treatment of organic pollutants, and particularly relates to a preparation method for improving the proportion of a persistent functional group on the surface of biochar and application of the preparation method in an advanced oxidation technology.
Background
As a big agricultural country, the yield of main food crops and other agricultural and sideline products keeps the leading level all the year round in China, and the quantity of the crop wastes is kept at a higher level, for example, the quantity of straws generated each year reaches about 8 hundred million tons. Direct incineration of crop straw can produce large amounts of carbon dioxide and other pollutants. The country aims to improve the comprehensive utilization rate of the national straw all the time, and the aim is to achieve 97 percent of the comprehensive utilization rate of the straw in 2025. The effective utilization of straw resources can realize carbon emission reduction, pollutant emission reduction (such as PM2.5) and production of products with economic value.
The biochar is a straw product which is researched more at present. The straw is mainly composed of cellulose, hemicellulose and lignin. After the crop straws with high cellulose and hemicellulose contents are prepared into the biochar, the surface groups of the finished carbon are easy to lose. The pyrolysis characteristic of the lignin is the most stable, the temperature span of the lignin in the pyrolysis process is large, and the lignin is easy to carbonize in the pyrolysis process to form a stable carbon skeleton. Therefore, if biochar is prepared from raw materials with high lignin content, the properties of the biochar should be more stable without causing radical loss.
The persulfate advanced oxidation technology becomes an organic pollution remediation technology which is highly concerned at home and abroad due to the advantages of short period, quick response, low cost, high treatment efficiency and the like. The charcoal serving as an economic, green and environment-friendly carbon-based material activator has the activation performance which is not transferred to a metal material, so that the charcoal can replace a metal activator to activate persulfate so as to degrade organic pollutant. Biochar is reported to contain certain amounts of soluble and insoluble components, with the soluble component containing a large number of groups. In actual in-situ advanced oxidation repair, after the biochar is input into an in-situ system, soluble components of the biochar can be separated from large biochar particles due to hydraulic scouring, so that a large amount of biochar groups can be lost, and the repair efficiency is reduced. And the lost groups can cooperate with heavy metals and organic pollutants to be co-transferred to a non-pollution area in underground water, so that secondary pollution is caused.
Disclosure of Invention
In order to solve the problems in the prior art, the invention aims to overcome the defects in the prior art and provide a method for improving the proportion of persistent functional groups on the surface of biochar, the prepared biochar and application thereof.
In order to achieve the purpose of the invention, the invention adopts the following technical scheme:
a method for improving the proportion of the persistent functional groups on the surface of the biochar comprises the following steps:
(1) crushing crop straws, and further ball-milling the crushed crop straws by a ball mill to ensure that the straw powder can be sieved by a screen with the size of a sieve hole not larger than 100 meshes to obtain the sieved and collected straw powder for later use; the crop straw is gramineous crop straw or leguminous straw;
(2) treating the straw powder obtained in the step (1) by cellulase, and degrading cellulose and hemicellulose components of the straw powder into various monosaccharides so as to improve the lignin content of the straw powder, wherein the total amount of lignin in the treated straw powder is not less than 50% by mass percent;
(3) collecting the straw powder obtained in the step (2), washing with water at least twice, and drying at 60-80 ℃ for at least 24 hours to obtain dried straw powder;
(4) and (4) taking the straw powder obtained in the step (3) as a raw material for preparing the biochar, placing the straw powder in heating equipment, and treating at 500-700 ℃ for at least 2 hours in an oxygen-free environment, thereby obtaining the biochar with high-proportion durable functional groups on the surface.
Preferably, in the step (1), the crop straw is at least one of barley straw, wheat straw and rice straw.
Preferably, in the step (1), the crop straws are dried and then crushed. Further preferably, the temperature of the drying is not lower than 60 ℃.
Preferably, in the step (2), when the straw powder is treated by cellulase, the reaction is carried out in a shaker of not less than 200 r/min at a temperature of not less than 45 ℃ for at least 48 hours to obtain the enzyme-treated straw powder.
Preferably, in the step (2), the total amount of lignin in the treated straw powder is 50-80% by mass.
Preferably, in the step (4), the heating device is a tube furnace.
The invention relates to biochar with a high-proportion of persistent functional groups on the surface, which is prepared by adopting the method for improving the proportion of the persistent functional groups on the surface of the biochar.
Preferably, the biochar provided by the invention has a high proportion of permanent functional groups on the surface, wherein the mass percentage content of lignin is not lower than 50.66%, and the concentration of water-soluble release substances is not higher than 24.22 mg/L.
Preferably, the biochar provided by the invention has a high proportion of persistent functional groups on the surface, wherein the carboxyl content, the lactone group content and the phenolic hydroxyl content in the persistent functional groups are respectively not less than 0.10mmol/g, not less than 0.12mmol/g, not less than 0.14mmol/g and not less than 1.19 multiplied by 10 carbonyl content 9 groups/cm 2 。
Preferably, after the biochar with the high-proportion permanent functional groups on the surface is stirred in water for 1 hour in a vortex mode at normal temperature and normal pressure, the loss rate of the permanent functional groups is not higher than 12%.
The invention relates to application of biochar with a high proportion of persistent functional groups on the surface, which is characterized in that: biochar having a high proportion of persistent functional groups on its surface is used as an activator in advanced oxidation processes.
Compared with the prior art, the invention has the following obvious substantive characteristics and remarkable advantages:
1. the invention takes the crop straws as the raw material to prepare the biochar, so as to achieve the purpose of recycling agricultural wastes, reduce the environmental pollution generated during incineration treatment and realize changing waste into valuables;
2. according to the invention, the content proportion of lignin is increased through cellulase hydrolysis, the pyrolysis characteristic of the lignin is the most stable, and the proportion of the persistent functional groups on the surface of the biochar can be obviously improved. The permanent functional groups can not cause group loss along with hydraulic flushing, can durably activate peroxide, and provide theoretical basis and guidance for the application of actual advanced oxidation remediation of organic pollution;
3. the biochar has high stability, the content of water-soluble release substances is extremely low, and a large amount of organic components cannot be lost, so that the risk of secondary pollution is reduced in practical application.
Drawings
FIG. 1 is a diagram showing the recycling effect of charcoal activated peroxyacetic acid of example 3 of the present invention in degrading triclosan.
Detailed Description
The above-described scheme is further illustrated below with reference to specific embodiments, which are detailed below:
example 1
In the embodiment, the treatment target is barley straws, and the method for improving the proportion of the persistent functional groups on the surface of the biochar comprises the following steps:
(1) barley straws come from Jiangsu province salt cities, are dried at 60 ℃, are subjected to coarse grinding and crushing by a crusher, and are further subjected to fine grinding by a ball mill, so that the straw powder can pass through a 100-mesh sieve, and the sieved and collected straw powder is obtained for later use;
(2) adding cellulase, treating the straw powder obtained in the step (1) by the cellulase, reacting for 48 hours in a shaking table at the temperature of 45 ℃ and at 200 revolutions per minute, and collecting the straw powder after enzyme treatment; degrading cellulose and hemicellulose components of the straw powder into various monosaccharides through enzyme treatment, so that the lignin content of the straw powder is improved;
(3) collecting the straw powder obtained in the step (2), washing with water at least twice, and drying at 60 ℃ for 24 hours to obtain dried straw powder;
(4) and (4) taking the straw powder obtained in the step (3) as a raw material for preparing the biochar, placing the straw powder in heating equipment, and treating for 2 hours at 500 ℃ in an oxygen-free environment to obtain the biochar with high-proportion durable functional groups on the surface.
Experimental test analysis:
1. detecting the lignin content after enzyme treatment:
the method comprises the steps of taking barley straws which are not treated by enzyme as comparison samples, taking comparison under the same condition, and detecting the lignin content of each sample through biomass component analysis.
The experimental results are as follows: the lignin content of the biochar sample prepared in the embodiment is improved from 37% of the comparative sample to 58%, and the concentration of the water-soluble release substance is reduced from 71.26mg/L of the comparative sample to 24.22 mg/L.
Therefore, the biochar prepared by the embodiment has better stability and high lignin content.
Biochar prepared from barley straws which are not treated by enzyme under the same condition is used as a comparison, and the content of the surface groups of the biochar is measured by a Boehm titration method and a fluorescence labeling method.
2. The content of each group on the surface of the biochar is as follows:
biochar prepared from straws which are not treated by enzyme under the same condition is used as a comparison, and the content of the surface groups of the biochar is measured by a Boehm titration method and a fluorescence labeling method.
The experimental results are as follows: the biochar of this example had a carboxyl content of 0.37mmol/g, a lactone group content of 0.12mmol/g, a phenolic hydroxyl group content of 0.19mmol/g, and a carbonyl content of 1.34X 10 9 groups/cm 2 . And under normal temperature and pressure, after vortex stirring the comparative sample and the biochar with high-proportion of persistent functional groups on the surface prepared in the embodiment in water for 1 hour, measuring the groups again, and finding that the group loss rate of the comparative sample as common biochar reaches over 34 percent, while the group loss rate of the biochar in the embodiment is 9 percent, and the group loss rate is reduced by 25 percent. In the embodiment, the content of lignin is increased, the proportion of the persistent functional groups on the surface of the biochar is increased, and the content of the lignin is reducedThe radicals are lost.
3. The test of the effect and the recycling times of the activator is as follows:
the method of the embodiment takes barley straws as raw materials to prepare the biochar at 500 ℃. The finished carbon is used for activating peroxyacetic acid to degrade triclosan:
the experiment was performed in a wide-mouth flask with a capacity of 100mL and a total liquid volume of 50 mL; the using amount of the biochar is 2.9g/L, the using amount of the peracetic acid is 1.3mM, the concentration of the pollutant triclosan is 10mg/L, and the reaction is carried out for 2 hours on a magnetic stirrer at normal temperature and normal pressure and at 200 revolutions per minute; sampling was performed at regular time intervals using a pipette gun, after which 1mL of the reaction solution was filtered through a 0.22 μm filter; anhydrous ethanol was used as a radical scavenger.
And detecting the concentration of the pollutants in the sample by using a high performance liquid chromatograph. And (4) filtering, washing, drying, collecting and recycling the biochar after the reaction. And repeating the operation steps to research the recycling effect.
The experimental results are as follows: the biochar has lasting, stable and efficient activation capacity. When the triclosan is used for the first time, the degradation rate of the triclosan can reach 94.6% after reacting for 2 hours, and can reach 81.3% after being repeatedly used for ten times. This is because the biochar has a high proportion of persistent functional groups, and can durably and efficiently activate peroxyacetic acid to generate active oxygen species (CH) 3 COO·、CH 3 COOO.,. OH and 1 O 2 ) And the high-efficiency removal effect is kept.
Example 2
This embodiment is substantially the same as embodiment 1, and is characterized in that:
in the embodiment, the treatment target is wheat straw, and the method for improving the proportion of the durable functional groups on the surface of the biochar comprises the following steps:
(1) the wheat straw is from Jiangsu province salt cities, is dried at 60 ℃, is subjected to coarse grinding and crushing by a crusher, and is further subjected to fine grinding by a ball mill, so that the straw powder can pass through a 100-mesh sieve, and the sieved and collected straw powder is obtained for later use;
(2) adding cellulase, treating the straw powder obtained in the step (1) by the cellulase, reacting for 48 hours in a shaking table at the temperature of 45 ℃ and at 200 revolutions per minute, and collecting the straw powder after enzyme treatment; degrading cellulose and hemicellulose components of the straw powder into various monosaccharides through enzyme treatment, so that the lignin content of the straw powder is improved;
(3) collecting the straw powder obtained in the step (2), washing with water at least twice, and drying at 60 ℃ for 24 hours to obtain dried straw powder;
(4) and (4) taking the straw powder obtained in the step (3) as a raw material for preparing the biochar, placing the straw powder in heating equipment, and treating for 2 hours at 500 ℃ in an oxygen-free environment to obtain the biochar with high-proportion durable functional groups on the surface.
Experimental test analysis:
1. detecting the lignin content after enzyme treatment:
the method comprises the steps of taking wheat straws which are not treated by enzyme as comparison samples, taking comparison under the same conditions, and detecting the lignin content of each sample through biomass component analysis.
The experimental results are as follows: the lignin content of the biochar sample prepared in the embodiment is increased from 38.29% of the comparative sample to 50.66%, and the concentration of the water-soluble release substance is reduced from 45.83mg/L of the comparative sample to 12.02 mg/L.
Therefore, the biochar prepared by the embodiment has better stability and high lignin content.
Biochar prepared from wheat straws which are not treated by enzyme under the same condition is used as a comparison, and the content of the surface groups of the biochar is measured by a Boehm titration method and a fluorescence labeling method.
2. The content of each group on the surface of the biochar is as follows:
biochar prepared from straws which are not treated by enzyme under the same condition is used as a comparison, and the content of the surface groups of the biochar is measured by a Boehm titration method and a fluorescence labeling method.
The experimental results are as follows: in this example, the content of carboxyl groups, lactone groups and carbonyl groups in the charcoal was 0.22mmol/g, 0.20mmol/g, 0.14mmol/g and 1.19X 10 9 groups/cm 2 . And under normal temperature and pressure, after vortex stirring the comparative sample and the biochar with high-proportion of persistent functional groups on the surface prepared in the embodiment in water for 1 hour, measuring the groups again, and finding that the group loss rate of the comparative sample as common biochar reaches over 33 percent, while the group loss rate of the biochar in the embodiment is 12 percent, and the group loss rate is reduced by 21 percent. In the embodiment, the ratio of the durable functional groups on the surface of the biochar is improved and the loss of the groups is reduced by increasing the content of lignin.
3. The test of the effect and the recycling times of the activator is as follows:
the method takes wheat straws as raw materials to prepare the biochar at 500 ℃. The finished carbon is used for activating peroxyacetic acid to degrade triclosan:
the experiment was performed in a wide-mouth flask with a capacity of 100mL, and the total liquid volume was 50 mL; the using amount of the biochar is 2.9g/L, the using amount of the peroxyacetic acid is 1.3mM, the concentration of a pollutant triclosan is 10mg/L, and the reaction is placed on a magnetic stirrer at normal temperature and normal pressure and at 200 revolutions per minute for 2 hours; sampling was performed at regular time intervals using a pipette gun, after which 1mL of the reaction solution was filtered through a 0.22 μm filter; anhydrous ethanol was used as a radical scavenger.
And detecting the concentration of the pollutants in the sample by using a high performance liquid chromatograph. And (4) filtering, washing, drying, collecting and recycling the biochar after the reaction. And repeating the operation steps to research the recycling effect.
The experimental results are as follows: the biochar has lasting, stable and efficient activation capacity. When the triclosan is used for the first time, the degradation rate of the triclosan can reach 92.2% after reacting for 2 hours, and can reach 78.1% after being repeatedly used for ten times. This is because the biochar has a high proportion of persistent functional groups, and can durably and efficiently activate peroxyacetic acid to generate active oxygen species (CH) 3 COO·、CH 3 COOO.,. OH and 1 O 2 ) And the high-efficiency removal effect is maintained.
Example 3
This embodiment is substantially the same as the above embodiment, and is characterized in that:
in the embodiment, the treatment target is rice straw, and the method for improving the proportion of the persistent functional groups on the surface of the biochar comprises the following steps:
(1) the rice straw is from Jiangsu province salt cities, is dried at 60 ℃, is subjected to coarse grinding and crushing by a crusher, and is further subjected to fine grinding by a ball mill, so that the straw powder can pass through a 100-mesh sieve, and the sieved and collected straw powder is obtained for later use;
(2) adding cellulase, treating the straw powder obtained in the step (1) by the cellulase, reacting for 48 hours at the temperature of 45 ℃ in a shaker at 200 revolutions per minute, and collecting the straw powder after enzyme treatment; degrading cellulose and hemicellulose components of the straw powder into various monosaccharides through enzyme treatment, so that the lignin content of the straw powder is improved;
(3) collecting the straw powder obtained in the step (2), washing with water at least twice, and drying at 80 ℃ for 24 hours to obtain dried straw powder;
(4) and (4) taking the straw powder obtained in the step (3) as a raw material for preparing the biochar, placing the straw powder in heating equipment, and treating for 2 hours at 700 ℃ in an oxygen-free environment to obtain the biochar with high-proportion durable functional groups on the surface.
Experimental test analysis:
1. detecting the lignin content after enzyme treatment:
the method comprises the steps of taking rice straws which are not treated by enzyme as comparison samples, taking comparison under the same condition, and detecting the lignin content of each sample through biomass component analysis.
The experimental results are as follows: the lignin content of the biochar sample prepared in the embodiment is improved to 51 percent from 39 percent of the comparative sample, and the concentration of the water-soluble release material is reduced to 11.81mg/L from 34.44mg/L of the comparative sample.
Therefore, the biochar prepared by the embodiment has better stability and high lignin content.
Biochar prepared from rice straws which are not treated by enzyme under the same condition is used as a comparison, and the content of the surface groups of the biochar is measured by a Boehm titration method and a fluorescence labeling method.
2. The content of each group on the surface of the biochar is as follows:
biochar prepared from straws which are not treated by enzyme under the same condition is used as a comparison, and the content of the surface groups of the biochar is measured by a Boehm titration method and a fluorescence labeling method.
The experimental results are as follows: in this example, the content of carboxyl groups, lactone groups and carbonyl groups in the charcoal was 0.10mmol/g, 0.22mmol/g, 0.24mmol/g and 1.58X 10 9 groups/cm 2 . On the other hand, under normal temperature and pressure, after swirling the biochar with high-proportion of persistent functional groups on the surface in water for 1 hour, the groups are measured again, and it is found that the group loss rate of the comparison sample as common biochar reaches over 29%, while the group loss rate of the biochar in the embodiment is 10%, and the group loss rate is reduced by 19%. In the embodiment, the ratio of the durable functional groups on the surface of the biochar is improved and the loss of the groups is reduced by increasing the content of lignin.
3. The test of the effect and the recycling times of the activator is as follows:
according to the method, rice straws are used as raw materials, and the biochar is prepared at 500 ℃. The finished carbon is used for activating peroxyacetic acid to degrade triclosan:
the experiment was performed in a wide-mouth flask with a capacity of 100mL and a total liquid volume of 50 mL; the using amount of the biochar is 2.9g/L, the using amount of the peracetic acid is 1.3mM, the concentration of the pollutant triclosan is 10mg/L, and the reaction is carried out for 2 hours on a magnetic stirrer at normal temperature and normal pressure and at 200 revolutions per minute; sampling was performed at regular time intervals using a pipette gun, after which 1mL of the reaction solution was filtered through a 0.22 μm filter; anhydrous ethanol was used as a radical scavenger.
And detecting the concentration of the pollutants in the sample by using a high performance liquid chromatograph. And (4) filtering, washing, drying, collecting and recycling the biochar after the reaction. And repeating the operation steps to research the recycling effect.
The experimental results are as follows: the biochar has lasting, stable and efficient activation capacity. As shown in figure 1, when the triclosan is used for the first time, the degradation rate of the triclosan can reach 99 percent after reacting for 2 hours,after ten times of repeated use, the content can reach 77 percent. This is because the biochar has a high proportion of persistent functional groups, and can durably and efficiently activate peroxyacetic acid to generate active oxygen species (CH) 3 COO·、CH 3 COOO.,. OH and 1 O 2 ) And the high-efficiency removal effect is kept.
According to the embodiment, the lignin content is increased, the proportion of the persistent functional groups on the surface of the biochar is improved, the loss of the groups is reduced, and the method can be applied to an advanced oxidation technology to stably, continuously and efficiently repair organic pollutants, so that the effect of treating wastes with processes of wastes against one another is achieved.
The embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made according to the purpose of the invention, and all changes, modifications, substitutions, combinations or simplifications made according to the spirit and principle of the technical solution of the present invention shall be made in the form of equivalent substitution, so long as the invention is in accordance with the purpose of the invention, and the invention shall fall within the protection scope of the present invention as long as the technical principle and the inventive concept of the present invention are not departed from the present invention.
Claims (10)
1. A method for improving the proportion of the persistent functional groups on the surface of the biochar is characterized by comprising the following steps:
(1) crushing crop straws, and further ball-milling the crushed crop straws by a ball mill to ensure that the straw powder can be sieved by a screen with the size of a sieve hole not larger than 100 meshes to obtain the sieved and collected straw powder for later use; the crop straw is gramineous crop straw or leguminous straw;
(2) treating the straw powder obtained in the step (1) by cellulase, and degrading cellulose and hemicellulose components of the straw powder into various monosaccharides so as to improve the lignin content, wherein the total amount of lignin in the treated straw powder is not less than 50% by mass percent;
(3) collecting the straw powder obtained in the step (2), washing with water at least twice, and drying at 60-80 ℃ for at least 24 hours to obtain dried straw powder;
(4) and (4) taking the straw powder obtained in the step (3) as a raw material for preparing the biochar, placing the straw powder in heating equipment, and treating at 500-700 ℃ for at least 2 hours in an oxygen-free environment, thereby obtaining the biochar with high-proportion durable functional groups on the surface.
2. The method for increasing the proportion of the permanent functional groups on the surface of the biochar as claimed in claim 1, wherein the method comprises the following steps: in the step (1), the crop straw is at least one of barley straw, wheat straw and rice straw.
3. The method for increasing the proportion of the permanent functional groups on the surface of the biochar as claimed in claim 1, wherein the method comprises the following steps: in the step (2), when the straw powder is treated by cellulase, the reaction is carried out in a shaking table with the speed of not less than 200 revolutions per minute for at least 48 hours at the temperature of not less than 45 ℃ to obtain the straw powder after enzyme treatment.
4. The method for increasing the proportion of the permanent functional groups on the surface of the biochar as claimed in claim 1, wherein: in the step (2), the total amount of lignin in the treated straw powder is 50-80% by mass.
5. The method for increasing the proportion of the permanent functional groups on the surface of the biochar as claimed in claim 1, wherein: in the step (4), the heating device is a tube furnace.
6. A biochar with a high proportion of persistent functional groups on the surface is characterized in that: the biochar is prepared by the method for improving the proportion of the persistent functional groups on the biochar surface according to claim 1.
7. Biochar having a high proportion of persistent functional groups on its surface according to claim 6, characterized in that: wherein the mass percent content of the lignin is not less than 50.66 percent, and the concentration of the water-soluble release substance is not more than 24.22 mg/L.
8. Biochar having a high proportion of persistent functional groups on its surface according to claim 6, characterized in that: the content of carboxyl group in the persistent functional group is not less than 0.10mmol/g, the content of lactone group is not less than 0.12mmol/g, the content of phenolic hydroxyl group is not less than 0.14mmol/g, and the content of carbonyl group is not less than 1.19 multiplied by 10 9 groups/cm 2 。
9. Biochar having a high proportion of persistent functional groups on its surface according to claim 6, characterized in that: and (3) stirring the biochar with the high-proportion permanent functional groups on the surface in water at normal temperature and normal pressure for 1 hour in a vortex manner, wherein the loss rate of the permanent functional groups is not higher than 12%.
10. Use of biochar according to claim 6 having a high proportion of permanent functional groups on its surface, characterized in that: biochar having a high proportion of persistent functional groups on its surface is used as an activator in advanced oxidation processes.
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