CN111589414A - Preparation method of activated carbon material surface hydrophobic protective layer - Google Patents
Preparation method of activated carbon material surface hydrophobic protective layer Download PDFInfo
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- CN111589414A CN111589414A CN202010275754.3A CN202010275754A CN111589414A CN 111589414 A CN111589414 A CN 111589414A CN 202010275754 A CN202010275754 A CN 202010275754A CN 111589414 A CN111589414 A CN 111589414A
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- chain alkyl
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- trimethoxy silane
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- 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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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- 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
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01D2257/70—Organic compounds not provided for in groups B01D2257/00 - B01D2257/602
- B01D2257/708—Volatile organic compounds V.O.C.'s
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Abstract
A preparation method of a hydrophobic protective layer on the surface of an activated carbon material comprises the steps of cleaning and drying activated carbon; dipping the dried activated carbon by using short-chain alkyl trimethoxy silane and long-chain alkyl trimethoxy silane as mixed precursors and absolute ethyl alcohol as a solvent, and reacting at the temperature of 100-160 ℃ after dipping to obtain the activated carbon with the hydrophobic protective layer; the lower alkyl is selected from C3‑C8A chain alkyl group of (1); the long-chain alkyl is selected from C9‑C18A chain alkyl group of (1). The preparation method has the advantages of simple operation process, low cost, environmental friendliness, wide application range, effect on most of activated carbon in the market and suitability for industrial practical application. The prepared protective layer shows better hydrophobicity and stability. For using activated carbon under high humidity conditionThe problem that the active carbon absorbs moisture and mildews is solved and made possible.
Description
Technical Field
The invention belongs to the technology of active carbon material modification, and particularly relates to a preparation method of a hydrophobic protective layer on the surface of an active carbon material.
Background
Volatile organic pollutants (VOCs) are one of the main atmospheric pollutants in the global scope, and the control of pollution sources of the VOCs is a problem to be solved urgently in the field of the environment at present. High-concentration single-component VOC in the industries of packaging, printing and the like has higher recycling value, and the activated carbon material is widely applied due to the excellent adsorption performance. However, the conventional activated carbon has a super-hydrophilic property due to the fact that the surface of the conventional activated carbon contains a large number of oxygen-containing functional groups, and water molecules competitively occupy a large number of adsorption sites in a humid environment, so that the adsorption capacity and the adsorption selectivity of the activated carbon on target pollutants are severely limited. Meanwhile, long-term moisture absorption easily enables the activated carbon to grow fungi and mildew, and the service life of the activated carbon is shortened. A hydrophobic protective layer is constructed on the surface of the activated carbon, so that the problem caused by water adsorption can be effectively solved. At present, two methods are commonly used for constructing a hydrophobic protective layer, one is to modify a low-surface-energy substance on the surface, and the other is to construct a rough structure on the surface to increase the surface roughness. However, the compactness of the hydrophobic protective layer prepared by the above two methods is to be improved.
Disclosure of Invention
The invention aims to provide a method for preparing a hydrophobic protective layer for an activated carbon material, which has the advantages of simple process, low cost and environmental friendliness. The obtained protective layer has alternate long-chain and short-chain alkyl groups, has better hydrophobicity, can stably exist in a humid environment for a long time, and provides possibility for the use of the activated carbon in a high-humidity environment.
The invention combines two strategies described in the background technology, selects short-chain alkyl trimethoxy silane and long-chain alkyl trimethoxy silane as mixed precursors, not only introduces hydrophobic alkyl chains with low surface energy on the surface of the activated carbon, but also takes the best role when the surface roughness is increased by the combination of alkyl chains with different lengths, the short-chain silane can make up pore passages which cannot be entered by the long-chain silane, and a tighter protective layer is formed on the surface of the activated carbon.
The technical scheme of the invention is as follows:
in one aspect, the invention provides a preparation method of an activated carbon surface hydrophobic protective layer, which comprises the following steps: cleaning and drying the activated carbon; dipping the dried activated carbon by using short-chain alkyl trimethoxy silane and long-chain alkyl trimethoxy silane as mixed precursors and absolute ethyl alcohol as a solvent, and reacting at the temperature of 100-160 ℃ after dipping to obtain the activated carbon with the hydrophobic protective layer;
the lower alkyl is selected from C3-C8A chain alkyl group of (1); the long-chain alkyl is selected from C9-C18A chain alkyl group of (1).
Based on the above scheme, preferably, the method comprises the following steps:
1) sequentially stirring and cleaning activated carbon with water and ethanol at room temperature for 10min, filtering, and drying in a drying oven at 80-100 deg.C for 5-10 h;
2) adding the short-chain alkyl trimethoxy silane and the long-chain alkyl trimethoxy silane into absolute ethyl alcohol to obtain an ethanol solution of mixed silane with different chain lengths, soaking the dried activated carbon into the ethanol solution of the mixed silane with different chain lengths, adding deionized water, stirring at room temperature for 0.1-1h, standing, soaking for 24h, and performing suction filtration;
3) placing the activated carbon obtained after suction filtration in an oven, reacting for 5-10h at 160 ℃, performing polymerization reaction on silane adsorbed on the surface of the activated carbon at the temperature, grafting the silane on the surface of the activated carbon through hydrogen bond action to obtain the activated carbon with the hydrophobic protective layer, washing unreacted silane by using ethanol, drying and storing.
Based on the scheme, the concentration of the deionized water in the impregnation process is preferably 0.5-5 wt%.
Based on the above scheme, preferably, the concentration of the short-chain alkyl trimethoxy silane and the long-chain alkyl trimethoxy silane in the ethanol solution is 0.1 to 10 wt%.
Based on the scheme, the mass ratio of the short-chain alkyl trimethoxy silane to the long-chain alkyl trimethoxy silane is preferably 1:3-3: 1.
In another aspect, the present invention provides an activated carbon having a surface covered with a hydrophobic protective layer, the activated carbon having a surface covered with a hydrophobic protective layer being prepared according to the above-mentioned method.
The preparation principle of the hydrophobic protective layer is as follows: the method comprises the following steps that alkyl trimethoxy silane is hydrolyzed in water to form alkyl trihydroxy silane, hydroxyl adsorbed to the surface of active carbon forms hydrogen bonds with oxygen-containing functional groups on the surface of the active carbon, meanwhile, two silane hydroxyl groups are subjected to dehydration condensation to form a polymer, chain alkyl groups are exposed outside, and a compact hydrophobic protective layer is formed on the surface of the active carbon.
Advantageous effects
1) The method has simple operation process and lower cost, is suitable for industrial practical application, provides possibility for the use of the activated carbon under the condition of high humidity, and solves the problem that the activated carbon absorbs moisture and mildews.
2) Due to the mixed use of the long-chain silane and the short-chain silane, the compactness of the hydrophobic protective layer is better, and better hydrophobicity and stability are further shown.
3) The method is wide in application range as long as the hydroxyl after silane hydrolysis is combined with the oxygen-containing functional group on the surface of the activated carbon through hydrogen bonding, and has an effect on most of activated carbon in the market.
4) The method has no toxic and harmful reagent in the preparation process, so the preparation process is environment-friendly and the product has good environmental compatibility.
Drawings
FIG. 1 is a photograph of the water contact angle of the raw activated carbon of example 1;
fig. 2 is a water contact angle picture of the activated carbon loaded with a hydrophobic protective layer prepared in example 1;
fig. 3 is a photograph of water contact angle of the activated carbon loaded with the hydrophobic protective layer prepared in example 1 after being washed with ethanol and dried at 90 c for 24 hours for recovery.
Detailed Description
Example 1
A method for preparing a surface hydrophobic protective layer of an activated carbon material adopts columnar coconut shell activated carbon as original activated carbon, and the activated carbon is cleaned and dried; the method is characterized in that octa-alkyl trimethoxy silane and octadecyl trimethoxy silane are used as mixed modifiers, absolute ethyl alcohol is used as a solvent, dried active carbon is soaked and grafted to prepare the hydrophobic protective layer, and the specific modification steps are as follows:
1) sequentially stirring and cleaning 10g of activated carbon with 20mL of deionized water and ethanol at room temperature for 10min, filtering, and drying in a drying oven at 80 ℃ for 10 h;
2) soaking the dried activated carbon in 50mL of ethanol solution of octaalkyltrimethoxysilane and octadecyltrimethoxysilane, wherein the concentration of the octaalkyltrimethoxysilane and the octadecyltrimethoxysilane is 1 wt%, adding 0.5mL of deionized water, stirring at room temperature for 0.5h, standing, soaking for 24h, and filtering;
3) and placing the activated carbon obtained after suction filtration in an oven, reacting for 10 hours at 150 ℃ to form a hydrophobic protective layer, washing off the unreacted silane by using 20mL of ethanol, and drying and storing.
As can be seen from fig. 1, the water contact angle of the original activated carbon is 28 °, and as can be seen from fig. 2, after the hydrophobic protective layer is prepared, the water contact angle of the activated carbon is increased to 83 °, and the hydrophobicity is greatly improved.
After the VOC adsorption test of the activated carbon with the hydrophobic protective layer, the activated carbon is washed by ethanol and dried and recovered at 80-100 ℃, and then the water contact angle test is carried out, as can be seen from figure 3, the hydrophobic property is well maintained, which indicates that the hydrophobic coating has good stability.
TABLE 1 comparison of original activated carbon and activated carbon loaded with hydrophobic protective layer
As can be seen from Table 1, the specific surface area of the original activated carbon was 1400m2The comparative area of the activated carbon loaded with the hydrophobic protective layer is still 1253m2The/g shows that the preparation method of the hydrophobic coating has small influence on the specific surface area of the activated carbon.
The above embodiments are merely exemplary embodiments of the present invention, and not intended to limit the present invention, and any modifications, substitutions, etc. within the scope of the present invention should be included.
Claims (6)
1. A preparation method of an active carbon surface hydrophobic protective layer is characterized by comprising the following steps: cleaning and drying the activated carbon; dipping the dried activated carbon by using short-chain alkyl trimethoxy silane and long-chain alkyl trimethoxy silane as mixed precursors and absolute ethyl alcohol as a solvent, and reacting at the temperature of 100-160 ℃ after dipping to obtain the activated carbon with the hydrophobic protective layer;
the lower alkyl is selected from C3-C8A chain alkyl group of (1); the long-chain alkyl is selected from C9-C18A chain alkyl group of (1).
2. The method for preparing the activated carbon hydrophobic protective layer according to claim 1, wherein the method comprises the following steps:
1) sequentially washing activated carbon with water and ethanol at room temperature under stirring for 10min, filtering, and drying at 80-100 deg.C for 5-10 h;
2) adding the short-chain alkyl trimethoxy silane and the long-chain alkyl trimethoxy silane into absolute ethyl alcohol to obtain an ethanol solution of mixed silane with different chain lengths, soaking the dried activated carbon into the ethanol solution of the mixed silane with different chain lengths, adding deionized water, stirring at room temperature for 0.1-1h, standing, soaking for 24h, and performing suction filtration;
3) and reacting the activated carbon obtained after suction filtration for 5-10h to obtain the activated carbon with the hydrophobic protective layer, washing off unreacted silane by using ethanol, and drying and storing.
3. The method for preparing the hydrophobic protective layer on the activated carbon as claimed in claim 2, wherein the concentration of the deionized water in the impregnation process is 0.5-5 wt%.
4. The method for preparing an activated carbon hydrophobic protective layer according to claim 2, wherein the concentration of the short-chain alkyl trimethoxy silane and the concentration of the long-chain alkyl trimethoxy silane in the ethanol solution are both 0.1 to 10 wt%.
5. The method for preparing the activated carbon hydrophobic protective layer according to claim 4, wherein the mass ratio of the short-chain alkyl trimethoxy silane to the long-chain alkyl trimethoxy silane is 1:3-3: 1.
6. An activated carbon with a surface covered with a hydrophobic protective layer, characterized in that the activated carbon with the surface covered with the hydrophobic protective layer is prepared according to the method of claims 1-5.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112371083A (en) * | 2020-09-11 | 2021-02-19 | 浙江大学 | Method for compounding hydrophobic coating on surface of activated carbon |
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| US20030032681A1 (en) * | 2001-05-18 | 2003-02-13 | The Regents Of The University Of Clifornia | Super-hydrophobic fluorine containing aerogels |
| GB2391224A (en) * | 2002-07-26 | 2004-02-04 | Sutcliffe Speakman Carbons Ltd | Activated carbon treated with silicon-containing compounds |
| CN107321304A (en) * | 2017-06-19 | 2017-11-07 | 东南大学 | A kind of preparation method of moistureproof super-hydrophobic activated carbon of breathing freely |
| CN110512428A (en) * | 2019-08-12 | 2019-11-29 | 江苏理工学院 | A kind of method of durable floride-free super-hydrophobic fabric finishing liquor and its finish fabric |
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- 2020-04-09 CN CN202010275754.3A patent/CN111589414A/en active Pending
Patent Citations (4)
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| US20030032681A1 (en) * | 2001-05-18 | 2003-02-13 | The Regents Of The University Of Clifornia | Super-hydrophobic fluorine containing aerogels |
| GB2391224A (en) * | 2002-07-26 | 2004-02-04 | Sutcliffe Speakman Carbons Ltd | Activated carbon treated with silicon-containing compounds |
| CN107321304A (en) * | 2017-06-19 | 2017-11-07 | 东南大学 | A kind of preparation method of moistureproof super-hydrophobic activated carbon of breathing freely |
| CN110512428A (en) * | 2019-08-12 | 2019-11-29 | 江苏理工学院 | A kind of method of durable floride-free super-hydrophobic fabric finishing liquor and its finish fabric |
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Cited By (1)
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| CN112371083A (en) * | 2020-09-11 | 2021-02-19 | 浙江大学 | Method for compounding hydrophobic coating on surface of activated carbon |
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Application publication date: 20200828 |