CN113426408B - Hydrophobically modified biochar by utilizing natural organic acid as well as preparation method and application of biochar - Google Patents

Hydrophobically modified biochar by utilizing natural organic acid as well as preparation method and application of biochar Download PDF

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CN113426408B
CN113426408B CN202011642245.6A CN202011642245A CN113426408B CN 113426408 B CN113426408 B CN 113426408B CN 202011642245 A CN202011642245 A CN 202011642245A CN 113426408 B CN113426408 B CN 113426408B
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biochar
organic acid
stirring
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filtering
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CN113426408A (en
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王小红
黄皓旻
成海荣
叶光政
焦裕均
朱文富
姚帆
王钰钦
叶代启
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South China University of Technology SCUT
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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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
    • 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
    • B01J20/30—Processes for preparing, regenerating, or reactivating
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
    • B01D2253/10—Inorganic adsorbents
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
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    • B01D2257/708—Volatile organic compounds V.O.C.'s
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    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
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    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

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Abstract

The invention discloses a hydrophobic modified biochar by utilizing natural organic acid and a preparation method and application thereof. The preparation method comprises the following steps: (1) mixing biochar with a hydrogen peroxide solution, softening, stirring and filtering to obtain hydroxylated biochar; (2) mixing hydroxylated biochar, sodium borohydride and absolute ethyl alcohol, stirring, filtering, and drying at 50-100 ℃ in an inert gas atmosphere to obtain dried biochar; (3) adding dried biochar into a solution in which natural macromolecular organic acid, absolute ethyl alcohol and a dehydrating agent are dissolved, heating and stirring to obtain a mixed solution; (4) filtering the mixed solution, washing with ethanol and deionized water, and drying at 50-100 deg.C in inert gas atmosphere to obtain modified charcoal. The method has the advantages of simple operation, low price, environmental protection, less influence on the pore diameter structure of the carbon material and good adsorption performance on volatile organic compounds in a high-humidity environment.

Description

Hydrophobic modified biochar by utilizing natural organic acid as well as preparation method and application thereof
Technical Field
The invention belongs to the field of porous carbon materials, and particularly relates to a hydrophobic modified biochar prepared by using natural organic acid, and a preparation method and application thereof.
Background
The adsorption technology and the adsorption-catalytic combustion technology are the main technologies for effectively treating the medium-low concentration organic waste gas at present. Among them, the adsorbent becomes one of the key materials, and the carbon-based hierarchical porous material is widely used as the adsorbent for the VOCs due to its wide source, such as activated carbon, biochar fiber, etc., low price, excellent performance, etc. However, engineering experience has shown that common carbon-based adsorbents face the challenge of competing adsorption with water vapor in engineering applications, such as in the painting process of automotive manufacturing, where wet spraying is often used to remove excess paint, thereby increasing the humidity of the VOCs exhaust. In addition, the gradual popularization of the water-based raw and auxiliary materials for replacing solvent-based raw and auxiliary materials has more and more outstanding contradictions of the carbon-based adsorbent in the selective adsorption of VOCs and water vapor. The adsorption capacity of the carbon-based adsorbent VOCs can be greatly reduced under high humidity conditions, and the carbon-based adsorbent VOCs can easily reach a saturated state and is not beneficial to the purification of organic waste gas.
For the aspect of material hydrophobicity, the document reports that stable superhydrophobicity can be effectively realized by using the functional coating, and the functional coating can be applied to aspects such as building environment control, hydrodynamic drag reduction and the like. In addition, some coatings such as organosilanes and perfluorinated compounds tend to be toxic, flammable, corrosive, difficult to handle, and environmentally damaging. However, the application of the natural macromolecular organic acid modified hydrophobic carbon material in the adsorption of VOCs in a high-humidity environment is rarely reported. Therefore, the preparation of the hierarchical porous carbon material with high hydrophobic property as the efficient VOCs adsorbent is expected to overcome the defects of low adsorption capacity, poor competitive adsorption performance with water vapor and the like of the existing carbon material, and the preparation method has a good application prospect.
Disclosure of Invention
Aiming at the problems, the invention provides a hydrophobic modified biochar by utilizing natural organic acid as well as a preparation method and application thereof.
The object of the present invention is achieved by at least one of the following aspects.
A preparation method of hydrophobically modified biochar by utilizing natural organic acid comprises the following steps:
(1) mixing the biochar with a hydrogen peroxide solution, stirring and filtering to obtain hydroxylated biochar;
(2) mixing the hydroxylated biochar in the step (1), sodium borohydride and absolute ethyl alcohol, stirring, filtering, and drying at 50-100 ℃ in an inert gas atmosphere to obtain dried biochar;
(3) adding the dried biochar in the step (2) into a solution dissolved with natural macromolecular organic acid, absolute ethyl alcohol and a dehydrating agent, heating and stirring to obtain a mixed solution;
(4) and (4) filtering the mixed solution obtained in the step (3), washing the precipitate with ethanol and deionized water, and drying at 50-100 ℃ in an inert gas atmosphere to obtain the modified biochar.
Further, in the step (1), the biochar is one or more of coconut shell biochar, bagasse biochar and walnut shell biochar; the mass fraction of the hydrogen peroxide solution is 5-30%.
Further, in the step (1), the stirring time is 1-6 h.
Further, in the step (2), the mass ratio of the hydroxylated biochar to the sodium borohydride is 10: 1-0.1: 1; the ratio of the volume of the absolute ethyl alcohol to the mass of the hydroxylated biochar is 1:1-1: 50L/g; the stirring time is 1-6 h.
Further, in the step (3), the natural macromolecular organic acid is one or more of cinnamic acid, caffeic acid, myristic acid or lauric acid.
Further, in the step (3), the volume ratio of the mass of the natural macromolecular organic acid to the absolute ethyl alcohol is (1-20: 1) g/L; the dosage of the dehydrating agent is 10-50wt% of the dosage of the natural macromolecular organic acid.
Further, in the step (3), the stirring time is 6-24 h.
The biochar prepared by the preparation method utilizes natural organic acid to hydrophobically modify.
The application of the hydrophobic modified biochar by utilizing the natural organic acid in the aspect of adsorbing VOCs is disclosed.
Further, the relative humidity of the environment in which the VOCs are adsorbed is greater than 70%.
The basic principle of the invention is as follows: the natural macromolecular organic acid has a large amount of carboxyl, the organic acid and hydroxyl functional groups on the surface of the biochar are subjected to esterification reaction by an ethanol chemical deposition method to generate chemical bonds, and the dehydrating agent in the reaction process can promote the formation of covalent bonds between the carboxyl and the hydroxyl groups without being adsorbed on the surface, so that the biochar forms a stable hydrophobic structure.
Compared with the prior art, the invention has the following advantages:
(1) the preparation method disclosed by the invention is simple to operate, low in price, green, environment-friendly and hydrophobic, and has small influence on the pore diameter structure of the carbon material;
(2) the hydrophobic modified biochar prepared by utilizing natural organic acid has good adsorption performance on Volatile Organic Compounds (VOCs) in a high-humidity environment.
Drawings
FIG. 1 is a flow chart of the preparation method of the biochar hydrophobically modified by natural organic acid provided by the invention;
FIG. 2 is an infrared spectrum before and after modification of biochar in example;
FIG. 3 is a graph showing the breakthrough curves of VOCs adsorption in a dry environment before and after biochar modification in the examples;
FIG. 4 is a graph showing the breakthrough curves of VOCs adsorbed at 70% relative humidity before and after biochar modification in the examples.
Detailed Description
Specific embodiments of the present invention will be described in further detail below with reference to specific examples and drawings, but the present invention is not limited thereto.
The following examples the method of preparing hydrophobically modified bio-char using natural organic acids refer to the preparation steps shown in fig. 1.
The application comprises the following steps: the biochar prepared in example 1 before and after modification is applied to adsorption of volatile organic compounds in dry environments and at a relative humidity of 70% respectively, and a VOCs adsorption performance test experiment is carried out;
(1) adsorption of dry environment volatile organic compounds: firstly, measuring the concentration of VOCs in mixed gas of VOCs and air by using GC, stabilizing the concentration of VOCs at 100ppm, filling 0.05g of adsorbing material (biochar) into an adsorption evaluation device, introducing the mixed gas of VOCs and air into the adsorbing material, finally measuring the concentration of outlet VOCs by using Gas Chromatography (GC), wherein each chromatogram analysis time is 8.5min, and measuring the adsorption capacity of the material on VOCs.
(2) Adsorption of environmental volatile organic compounds with a relative humidity of 70%: firstly, measuring the concentration and humidity of VOCs and the VOCs of the mixed gas of water vapor and air by using a GC and a hygrometer to ensure that the concentration and humidity are stabilized at 100ppm and 70 percent relative humidity, finally, measuring the concentration of the outlet VOCs by using Gas Chromatography (GC), wherein the analysis time of each chromatogram is 8.5min, and measuring the adsorption capacity of the material on the VOCs.
Example 1
(1) Adding 1.5g of biochar (marked as BC) into a beaker, then adding 50mL of hydrogen peroxide solution with the mass fraction of 10%, mixing and softening, stirring for 2h, and filtering to obtain hydroxylated biochar.
(2) And then mixing the hydroxylated biochar with sodium borohydride in a mass ratio of 1:1 and 50mL of absolute ethanol, stirring for 2 hours, filtering, and drying for 60 minutes at 80 ℃ in a nitrogen atmosphere to obtain the dried biochar.
(3) 0.5g of the biochar dried in step (2), 1g of myristic acid, 0.4g of a dehydrating agent, and 100mL of anhydrous ethanol were added to a round-bottomed flask, and heated and stirred at 75 ℃ for 24 hours to obtain a mixture.
(4) And (4) finally, washing the precipitate obtained after filtering the mixed solution obtained in the step (3) with ethanol and deionized water, and drying the precipitate for 60min at 80 ℃ in a nitrogen atmosphere to obtain modified biochar (marked as BC-E).
The evaluation results of the change of the functional group after the hydrophobic modification and the adsorption performance of the VOCs under the dry and wet conditions obtained in the above examples are respectively as follows:
FIG. 2 utilizes infrared spectroscopy (FTIR) to study the difference of the functional groups on the BC and BC-E surfaces of the biochar before and after modification, and explore the chemical reaction on the surface of the hydrophobically modified activated carbon. The results show-CH in organic acids 3 And the signals of the functional groups of the aliphatic compounds are only shown in the modified material BC-E, and the natural hydrophobic substances are preliminarily proved to be capable of being effectively modified to the carbon material so as to change the surface groups of the carbon material.
Adsorption performance of VOCs of BC and BC-E biochar materials under different relative humidity:
table 1 shows the adsorption performance of VOCs before and after the modification of biochar under the conditions of drying and 70% relative humidity, respectively;
TABLE 1
Figure GDA0003207580450000041
FIG. 3 is a graph showing the breakthrough curves of VOCs adsorption in a dry environment before and after biochar modification in the examples;
FIG. 4 is a graph showing the breakthrough curves of VOCs adsorbed before and after the modification of biochar in the example under an environment of 70% relative humidity;
in combination with fig. 3, fig. 4 and the breakthrough curves of table 1, it can be found that in a dry VOCs environment (RH ═ 0%), the adsorption capacity of BC to VOCs is greater than BC-E. When the relative humidity is increased from 0% to 70%, the adsorption capacity of the unmodified biochar BC is reduced by 44% from 380 to 212mg/g, and the adsorption performance of the biochar BC on VOCs in a humid environment is greatly reduced. While the adsorption capacity of the biochar BC-E modified by organic acid is reduced by only 20 percent from 308 to 245 mg/g. Compared with BC, the BC-E has smaller influence on the adsorption of VOCs by the water, and the selectivity of the hydrophobically modified biochar on the VOCs is enhanced. The results show that the active carbon obtained by the invention after hydrophobic modification has good adsorption performance on VOCs in a high-humidity environment, and the treatment cost of VOCs in the high-humidity environment is greatly reduced.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way. Any equivalent changes, modifications or alterations made by the person skilled in the art on the basis of the technical solutions of the present invention to the above-described embodiments are still within the scope of the technical solutions of the present invention.

Claims (1)

1. The application of the hydrophobically modified biochar utilizing natural organic acid in the aspect of adsorbing VOCs is characterized in that the relative humidity of the environment for adsorbing VOCs is more than 70%;
the preparation method of the biochar hydrophobically modified by utilizing the natural organic acid comprises the following steps:
(1) mixing the biochar with a hydrogen peroxide solution, stirring and filtering to obtain hydroxylated biochar; the biochar is one or more of coconut shell biochar, bagasse biochar and walnut shell biochar; the mass fraction of the hydrogen peroxide solution is 5-30%; the stirring time is 1-6 h;
(2) mixing the hydroxylated biochar in the step (1), sodium borohydride and absolute ethyl alcohol, stirring, filtering, and drying at 50-100 ℃ in an inert gas atmosphere to obtain dried biochar; the mass ratio of the hydroxylated biochar to the sodium borohydride is (10: 1) - (0.1: 1); the ratio of the volume of the absolute ethyl alcohol to the mass of the hydroxylated biochar is (1: 1) - (1: 50) L/g; the stirring time is 1-6 h;
(3) adding the dried biochar in the step (2) into a solution in which natural organic acid, absolute ethyl alcohol and a dehydrating agent are dissolved, heating and stirring to obtain a mixed solution; the natural organic acid is one or more of myristic acid or lauric acid; the volume ratio of the mass of the natural organic acid to the absolute ethyl alcohol is (1-20): 1 g/L; the dosage of the dehydrating agent is 10-50wt% of the dosage of the natural organic acid; the stirring time is 6-24 h;
(4) and (4) filtering the mixed solution obtained in the step (3), washing the precipitate with ethanol and deionized water, and drying at 50-100 ℃ in an inert gas atmosphere to obtain modified biochar.
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