A hydrophobic modification method for pore structure parameters of non-destructive activated carbon

Abstract

The present invention relates to a hydrophobic modification method for non-destructive activated carbon pore structure parameters. The method includes: first, subjecting the activated carbon to alkali washing, acid washing, water washing, and drying, then subjecting it to hydrothermal treatment, and then loading myristic acid. The contact angle of the obtained activated carbon can reach 110-155°, greatly exceeding the contact angle of the activated carbon before modification; in addition, the specific surface area and total pore volume of the modified activated carbon can reach 0.92-1.34 times the corresponding indexes before modification. The invention can greatly improve the hydrophobicity of activated carbon without damaging the pore structure parameters of activated carbon, and does not require the use of toxic chemicals, having industrial application value.

Description

Technical Field

[0001] The present invention relates to a method for modifying activated carbon, belonging to the technical field of activated carbon; specifically, it relates to a hydrophobic modification method that does not damage the pore structure parameters of activated carbon. Background Art

[0002] Using activated carbon adsorption is an effective method for treating volatile organic compounds (VOCs) and has been widely used in many industrial sectors. However, the VOCs gas stream emitted in the actual industrial process usually contains water vapor, and the humidity can even exceed 80%. Water vapor can compete with VOCs for adsorption, so the presence of water vapor will reduce the adsorption performance of activated carbon for VOCs. This reduction effect is particularly obvious under high humidity conditions.

[0003] To overcome the above problems, the activated carbon can be hydrophobically modified. Hydrophobic modification can improve the affinity of activated carbon for VOCs and reduce its affinity for water vapor. To obtain the hydrophobic modification effect, the activated carbon can be reacted with a silane coupling agent, a compound containing a Si-halogen bond, or a compound containing an acyl chloride (such as patent CN110773127B), or hydrophobic organic compounds such as stearic acid and perfluorooctanol can be loaded on the activated carbon (such as patent CN111330543A), or the activated carbon can be coated with a hydrophobic resin (such as patent CN110354807A). These methods can all obtain hydrophobic effects.

[0004] However, the above modification methods still have some deficiencies: ① It is difficult for the contact angle of the obtained modified activated carbon to exceed 150°, that is, it is difficult to have superhydrophobicity. ② During the hydrophobic modification, it is easy to block some pore channels of the activated carbon, resulting in a significant decrease in pore structure parameters such as specific surface area and pore volume compared with before modification, and then leading to a decrease in the VOCs adsorption performance. Summary of the Invention

[0005] The purpose of the present invention is to provide a method to hydrophobically modify activated carbon without damaging the pore structure parameters, and the static water contact angle of the obtained activated carbon can exceed 150°, showing superhydrophobicity.

[0006] The technical solution of the present invention is as follows: Wash and dry the activated carbon, then perform hydrothermal treatment under hydrogen, and then load myristic acid, so as to obtain strongly hydrophobic activated carbon without damaging the pore structure parameters of the activated carbon;

[0007] The above washing treatment refers to washing successively with a 0.2 - 2 mol / L NaOH solution, a 0.2 - 2 mol / L acid solution, and deionized water;

[0008] The above-mentioned hydrothermal treatment refers to heating the washed activated carbon in a gas stream containing 1-4.8 vol% H2 (the remaining gas is N2, Ar or He) at ≥850 °C for ≥2 h;

[0009] The above-mentioned loading of myristic acid means placing the hydrothermally treated activated carbon in an alcohol solution of myristic acid, so that the activated carbon is loaded with 1 wt% - 6 wt% of myristic acid;

[0010] The above-mentioned non-destructive activated carbon pore structure parameters mean that the ratio of the specific surface area, total pore volume of the activated carbon after hydrophobic modification to the corresponding indicators before modification is 0.92 - 1.34:1;

[0011] The above-mentioned strongly hydrophobic activated carbon refers to being pretreated by sanding with 10,000-mesh sandpaper, and then the measured static water contact angle is 110 - 155°;

[0012] The above-mentioned acid washing refers to using hydrochloric acid or acetic acid;

[0013] The above-mentioned drying means heating the washed activated carbon in a blast at 50 - 150 °C until constant weight;

[0014] The above-mentioned myristic acid alcohol solution refers to a methanol or ethanol solution of myristic acid, and the concentration of myristic acid therein is 0.01 - 0.1 mol / L;

[0015] The above-mentioned specific surface area and total pore volume are obtained by N2 adsorption - desorption technology.

[0016] Compared with the existing hydrophobic modification methods of activated carbon, the advantages of the present invention are: 1) Hydrophobic modification can be achieved without damaging the pore structure parameters of activated carbon; 2) The activated carbon can have strong hydrophobicity, and its contact angle can exceed 150°; 3) The modification process is simple, without using toxic chemicals, and is easy to control and apply. Detailed implementation mode

[0017] Figure 1 is the hydrophobic modification method of the present invention.

[0018] The following further illustrates the present invention with examples, but does not limit the present invention. Examples

[0019] The following process is used for the hydrophobic modification of granular activated carbon:

[0020] (1) Mix and stir activated carbon with a static water contact angle of 65°, specific surface area of 876 m 2 / g and pore volume of 0.7 ml / g with 1 mol / L, 80 °C NaOH solution, filter by suction after 2 h, wash the carbon sample with 0.2 mol / L hydrochloric acid, then repeatedly wash the carbon sample with deionized water until the washing liquid is nearly neutral, and then dry it to constant weight at 110 °C;

[0021] (2) Heat the dried activated carbon to 850 °C in a 4.0 vol% H2 stream, hold the temperature constant for 2 h, and then cool it to near room temperature under N2 conditions;

[0022] (3) Mix the activated carbon treated with H2 with a 0.05 mol / L methanol myristate solution, stir for 1 h, then filter and dry to obtain modified activated carbon loaded with 3 wt% myristic acid.

[0023] Tests show that the static water contact angle of the modified activated carbon is 130°, much higher than 65° before modification; the specific surface area and pore volume are 990 m 2 / g and 0.78 mL / g, which are 1.13 and 1.11 times the corresponding index values before modification, respectively. Example

[0024] The modification process adopted is basically the same as that in Example 1, but the H2 heat treatment time is extended. The detailed modification process is as follows:

[0025] (1) Mix activated carbon with a static water contact angle of 65°, a specific surface area of 876 m 2 / g, and a pore volume of 0.7 mL / g with a 1 mol / L NaOH solution at 80 °C, stir, filter after 2 h, wash the carbon sample with 0.2 mol / L hydrochloric acid, then wash the carbon sample repeatedly with deionized water until the washing solution is nearly neutral, and then dry it to constant weight at 110 °C;

[0026] (2) Heat the dried activated carbon to 850 °C in a 4.0 vol% H2 stream, hold the temperature constant for 4 h, and then cool it to near room temperature under N2 conditions;

[0027] (3) Mix the activated carbon treated with H2 with a 0.05 mol / L methanol myristate solution, stir for 1 h, then filter and dry to obtain modified activated carbon loaded with 3 wt% myristic acid.

[0028] Tests show that the static water contact angle of the modified activated carbon is 144°, much higher than 65° before modification; the specific surface area and pore volume are 1080 m 2 / g and 0.84 mL / g, which are 1.23 and 1.20 times the corresponding index values before modification, respectively. In addition, the contact angle after modification > the contact angle of the modified sample in Example 1, indicating that extending the H2 heat treatment time has a positive effect on improving hydrophobicity. Example

[0029] The modification process adopted is basically the same as that in Example 2, but the loading amount of myristic acid is increased. The detailed modification process is as follows:

[0030] (1) Mix activated carbon with a static water contact angle of 65°, a specific surface area of 876 m2 Activated carbon with a specific surface area of 970 m² / g and a pore volume of 0.7 ml / g was mixed and stirred with 1 mol / L NaOH solution at 80 °C. After 2 h, filtration was carried out, and the carbon sample was washed with 0.2 mol / L hydrochloric acid, and then repeatedly washed with deionized water until the washing solution was nearly neutral, and then dried to constant weight at 110 °C;

[0031] (2) The dried activated carbon was heated to 850 °C in a 4.0 vol% H₂ stream and held at a constant temperature for 4 h, and then cooled to near room temperature under N₂ conditions;

[0032] (3) The activated carbon treated with H₂ was mixed with 0.067 mol / L myristic acid methanol solution, stirred for 1 h, then filtered and dried to obtain modified activated carbon loaded with 4 wt% myristic acid.

[0033] Tests showed that the static water contact angle of the modified activated carbon was 153°, much higher than 65° before modification; the specific surface area and pore volume were 970 m² / g and 0.72 mL / g respectively, which were 1.11 and 1.03 times the corresponding index values before modification. In addition, the contact angle after modification > the contact angle of the modified sample in Example 2, indicating that increasing the loading amount of myristic acid has a positive effect on improving hydrophobicity. 2 / g, 0.72 mL / g, which were 1.11 and 1.03 times the corresponding index values before modification respectively. In addition, the contact angle after modification > the contact angle of the modified sample in Example 2, indicating that increasing the loading amount of myristic acid has a positive effect on improving hydrophobicity. Example

[0034] A commercial columnar activated carbon was not polished with sandpaper. The static water contact angle of this sample was measured five times, and the results were 32°, 45°, 57°, 62°, 71°, with large fluctuations; after the columnar activated carbon was polished with 10,000-mesh sandpaper, the contact angle was measured five times, and the results were 60°, 62°, 61°, 60°, 62°, and the results were relatively stable, which could reflect the true hydrophobicity.

[0035] Comparative Example 1

[0036] The following process was used for the hydrophobic modification of activated carbon:

[0037] (1) Activated carbon with a static water contact angle of 65°, a specific surface area of 876 m² / g, and a pore volume of 0.7 ml / g was mixed and stirred with 1 mol / L NaOH solution at 80 °C. After 2 h, filtration was carried out, and the carbon sample was washed with 0.2 mol / L hydrochloric acid, and then repeatedly washed with deionized water until the washing solution was nearly neutral, and then dried to constant weight at 110 °C; 2 / g, and a pore volume of 0.7 ml / g was mixed and stirred with 1 mol / L NaOH solution at 80 °C. After 2 h, filtration was carried out, and the carbon sample was washed with 0.2 mol / L hydrochloric acid, and then repeatedly washed with deionized water until the washing solution was nearly neutral, and then dried to constant weight at 110 °C;

[0038] (2) No hydrothermal treatment was carried out;

[0039] (3) Myristic acid was not loaded.

[0040] The activated carbon was polished with 10,000 - mesh sandpaper, and then the contact angle was measured. The results showed that the static water contact angle of the modified activated carbon was 74°, slightly higher than 65° before modification; the specific surface area and pore volume were 920 m 2 / g and 0.73 mL / g respectively, which were 1.05 and 1.04 times the corresponding index values before modification. It can be seen from this that the washing treatment has a certain effect on the hydrophobic modification and pore volume increase of activated carbon.

[0041] Comparative Example 2

[0042] The following process was used for the hydrophobic modification of activated carbon:

[0043] (1) The activated carbon was not subjected to washing treatment;

[0044] (2) The activated carbon was heated to 850 °C in a 4.0 vol% H2 stream, held at a constant temperature for 2 h, and then cooled to near room temperature under N2 conditions;

[0045] (3) Myristic acid was not loaded.

[0046] The test showed that the static water contact angle of the modified activated carbon was 110°, higher than 65° before modification; the specific surface area and pore volume were 930 m 2 / g and 0.86 mL / g respectively, which were 1.06 and 1.23 times the corresponding index values before modification. It can be seen from this that the hydrothermal treatment has a certain effect on the hydrophobic modification and pore volume increase of activated carbon.

[0047] Comparative Example 3

[0048] The following process was used for the hydrophobic modification of activated carbon:

[0049] (1) The activated carbon was not subjected to washing treatment;

[0050] (2) The activated carbon was not subjected to hydrothermal treatment;

[0051] (3) The activated carbon was mixed with 0.05 mol / L myristic acid methanol solution, stirred for 1 h, then filtered and dried to obtain modified activated carbon loaded with 3 wt% myristic acid.

[0052] The test showed that the static water contact angle of the modified activated carbon was 100°, higher than 65° before modification; the specific surface area and pore volume were 812 m 2 / g and 0.66 mL / g respectively, which were 0.93 and 0.94 times the corresponding index values before modification. It can be seen from this that loading myristic acid has a significant effect on the hydrophobic modification of activated carbon, but has a certain reducing effect on the pore structure parameters.

[0053] Comparative Example 4

[0054] The hydrophobic modification of activated carbon is carried out by the following process:

[0055] (1) Mix activated carbon with a static water contact angle of 65°, a specific surface area of 876 m 2 / g, and a pore volume of 0.7 ml / g with 1 mol / L NaOH solution at 80 °C, stir, filter after 2 h, wash the carbon sample with 0.2 mol / L hydrochloric acid, then wash the carbon sample repeatedly with deionized water until the washing liquid is nearly neutral, and then dry at 110 °C to constant weight;

[0056] (2) Heat the dried activated carbon to 850 °C in a 4.0 vol% H2 stream, keep it at a constant temperature for 2 h, and then cool it to near room temperature under N2 conditions;

[0057] (3) Do not load myristic acid.

[0058] Tests show that the static water contact angle of the modified activated carbon is 118°, greatly exceeding 65° before modification; the specific surface area and pore volume are 960 m 2 / g and 0.91 mL / g respectively, which are 1.1 times and 1.3 times the corresponding index values before modification.

[0059] Comparative Example 5

[0060] The hydrophobic modification of activated carbon is carried out by the following process:

[0061] (1) Mix activated carbon with a static water contact angle of 65°, a specific surface area of 876 m 2 / g, and a pore volume of 0.7 ml / g with 1 mol / L NaOH solution at 80 °C, stir, filter after 2 h, wash the carbon sample with 0.2 mol / L hydrochloric acid, then wash the carbon sample repeatedly with deionized water until the washing liquid is nearly neutral, and then dry at 110 °C to constant weight;

[0062] (2) Do not carry out hydrothermal treatment;

[0063] (3) Mix the activated carbon with 0.05 mol / L myristic acid methanol solution, stir for 1 h, then filter and dry to obtain modified activated carbon loaded with 3 wt% myristic acid.

[0064] Tests show that the static water contact angle of the modified activated carbon is 98°, greatly exceeding 65° before modification; the specific surface area and pore volume are 815 m 2 / g and 0.65 mL / g respectively, which are 0.93 times and 0.93 times the corresponding index values before modification.

[0065] Comparative Example 6

[0066] The hydrophobic modification of activated carbon is carried out by the following process:

[0067] (1) Activated carbon with a static water contact angle of 65°, a specific surface area of 876 m 2 / g, and a pore volume of 0.7 ml / g was obtained without washing treatment;

[0068] (2) The activated carbon was heated to 850 °C in a 4.0 vol% H2 stream and held at a constant temperature for 2 h, and then cooled to near room temperature under N2 conditions;

[0069] (3) The H2-treated activated carbon was mixed with a 0.05 mol / L methanol myristate solution, stirred for 1 h, filtered by suction, and dried to obtain modified activated carbon loaded with 3 wt% myristic acid.

[0070] Tests showed that the static water contact angle of the modified activated carbon was 121°, greatly exceeding the 65° before modification; the specific surface area and pore volume were 905 m 2 / g and 0.74 mL / g, which were 1.03 and 1.16 times the corresponding index values before modification, respectively.

[0071] Table 1 Effects of hydrophobic modification of activated carbon with a static water contact angle of 65°, a specific surface area of 876 m 2 / g, and a pore volume of 0.7 ml / g by different methods

[0072]

Claims

1. A hydrophobic modification method for the pore structure parameters of non-destructive activated carbon, characterized in that: First, wash and dry the activated carbon, then conduct hydrothermal treatment in the presence of hydrogen, and then load myristic acid, so as to obtain highly hydrophobic activated carbon without damaging the pore structure parameters of the activated carbon; The washing treatment mentioned above refers to washing successively with a NaOH solution of 0.2 - 2 mol / L, an acid of 0.2 - 2 mol / L, and deionized water; The hydrothermal treatment in the presence of hydrogen mentioned above refers to placing the washed activated carbon in a gas stream containing 4.0 vol% - 4.8 vol% H2, with the remaining gas being N2, Ar, or He, and heating at ≥850 °C for ≥2 h; The loading of myristic acid mentioned above refers to placing the hydrothermally treated activated carbon in an alcohol solution of myristic acid, so that the activated carbon loads 4 wt% - 6 wt% of myristic acid; The non - damage of the activated carbon pore structure parameters mentioned above means that the ratios of the specific surface area and total pore volume of the activated carbon after hydrophobic modification to the corresponding indexes before modification are all 0.92 - 1.34:1; The highly hydrophobic activated carbon mentioned above means that first, the activated carbon is polished with 10,000 - mesh sandpaper, and then the measured static water contact angle can reach 153 - 155°, which can meet the static water contact angle required for super - hydrophobicity.

2. The hydrophobic modification method for non-destructive activated carbon pore structure parameters according to claim 1, characterized in that The acid washing mentioned above refers to using hydrochloric acid or acetic acid.

3. A hydrophobic modification method for non-destructive activated carbon pore structure parameters according to claim 1, characterized in that, The drying mentioned above refers to blowing and heating the washed activated carbon at 50 - 150 °C until constant weight.

4. A hydrophobic modification method for the pore structure parameters of non-destructive activated carbon, characterized in that, The alcohol solution of myristic acid mentioned above refers to a methanol or ethanol solution of myristic acid, and the concentration of myristic acid is 0.01 - 0.1 mol / L.

5. A hydrophobic modification method for non-destructive activated carbon pore structure parameters according to claim 1, characterized in that, The specific surface area and total pore volume mentioned above refer to those measured by the N2 adsorption - desorption technique.

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