CN107512722B - Method for adjusting expansibility of black cotton soil - Google Patents
Method for adjusting expansibility of black cotton soil Download PDFInfo
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- CN107512722B CN107512722B CN201710557269.3A CN201710557269A CN107512722B CN 107512722 B CN107512722 B CN 107512722B CN 201710557269 A CN201710557269 A CN 201710557269A CN 107512722 B CN107512722 B CN 107512722B
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Abstract
The invention provides a method for adjusting expansibility of black cotton soil, which comprises the following steps: pretreating black cotton soil to obtain a black cotton soil sample, wherein the pretreatment comprises acidification treatment or sodium pillared treatment; hydrolyzing silane to obtain silane hydrolysis solution; and performing silane grafting on the pretreated black cotton by using the silane hydrolysis solution to obtain a silane-grafted black cotton sample. According to the method provided by the embodiment of the invention, the black cotton soil with certain activity is obtained mainly by carrying out acidification or sodium treatment on the black cotton soil, then silane with different concentrations is used for grafting, and the silane and hydroxyl of a black cotton soil lamella are subjected to condensation reaction to change the hydrophilicity of the black cotton soil into hydrophobicity, so that the water absorption expansion characteristic of the black cotton soil is changed.
Description
Technical Field
The invention relates to the field of building materials, in particular to a method for adjusting expansibility of black cotton soil.
Background
The black cotton soil is hydrated high-expansibility clay, has dark brown appearance and is widely distributed all over the world. The main mineral component of the black cotton soil is montmorillonite which is high-plasticity clay, and the clay expands when meeting water and shrinks after losing water, when the soil body is soaked in water, a combined water film on the surface of soil particles is thickened, and the distance between the particles is enlarged, so that the volume is expanded. When the soil body loses water, the distance between particles is reduced by combining with the thinning of the water film, so that the volume is reduced. The mechanical properties are greatly reduced while the water absorption expansion and the water loss shrinkage are carried out. For example: is in the middle and east regions of Africa and belongs to tropical monsoon climate with alternate dry season and rainy season. In dry seasons, the precipitation is little, the black cotton soil is in a cementing state, the strength is high, but a lot of cracks appear. In rainy season, the black cotton soil can be in a plastic-soft plastic state and has lower strength. For this reason, the black cotton soil is not suitable for the direct construction of foundation facilities such as foundations and road beds because it has a serious influence on the construction of buildings and roads on the ground surface.
To solve this problem, many attempts have been made: maneli et al in the text of "underfluid of flash ash, ground-grained blast furnace slag and lime on unconfined compressive strip of black cotton soil" utilize industrial waste to treat black cotton soil in order to improve its engineering mechanical property, wherein the industrial waste is mainly fly ash, blast furnace slag and lime, the industrial waste is regarded as the curing agent of black cotton soil, can improve the stability of black cotton soil effectively, the maximum unconfined compression resistance can reach 2MPa, meet the use requirement of road surface material; in Study of Black cotton engineering with concrete dust and lime, Oza et al treated black cotton soil with waste cement and lime, the plasticity index and compressive strength of the treated black cotton soil are changed to a large extent, the plasticity index is about 10%, the compressive strength can reach 15MPa to the maximum, and the grade standard of MU15 in GB5101-2003 is reached. For black cotton soil as a roadbed material, great-Germany construction and other people refer to a treatment scheme for bentonite in highway construction in ' research on engineering characteristics and roadbed treatment technology of Escherisia black cotton soil and ' treatment of black cotton soil foundation in African region ' of Wangbai, namely, a method of changing and filling is adopted to solve the problems caused by bentonite, and different changing and filling treatment schemes are provided according to different expansion potentials aiming at black cotton soil regions; and different filling modes are adopted according to different roadbed forms. Although the replacement can solve the road construction problem to a certain extent, the soil after the replacement is stored in a designated place as industrial waste, which causes a series of problems: the excavated soil needs a large area for storage, and becomes a solid waste.
Nowadays, a commonly used method for improving expansive soil at home and abroad is chemical curing, and a common method is to mix a curing agent into the expansive soil to react with particles in the expansive soil, so that the expansibility of the expansive soil and the water absorbability of the expansive soil can be reduced, and the engineering performance of the expansive soil can be improved, thereby meeting the conditions required by construction. At present, the main methods for chemical solidification are lime, cement, fly ash and the like, wherein the lime and the cement are used as solidifying agents to be the most common and practical methods for improving the expansive soil. Tests show that lime and the like have little influence on the engineering mechanical property of the black cotton soil, and the processed sample can not reach the engineering mechanical standard.
Disclosure of Invention
The present invention provides a method of adjusting the expandability of black cotton to overcome the above problems or to at least partially solve the above problems.
According to one aspect of the present invention, there is provided a method of adjusting the expandability of black cotton comprising:
pretreating black cotton soil to obtain a black cotton soil sample, wherein the pretreatment comprises acidification treatment or sodium pillared treatment;
hydrolyzing silane to obtain silane hydrolysis solution;
and performing silane grafting on the black cotton by using the silane hydrolysis solution to obtain a silane-grafted black cotton sample.
Optionally, the acidification treatment comprises:
adding the black cotton soil into H2SO4Obtaining a first prepared solution in the solution, and magnetically stirring the solution in a water bath at the temperature of 70 ℃ for 3 hours;
washing the stirred first preparation solution by using deionized water until the pH value is neutral;
drying the first prepared solution washed by the deionized water at 105 ℃ for 12 hours to obtain a first black cotton soil sample crude product;
and grinding the first black cotton soil sample crude product to obtain a first black cotton soil sample.
Alternatively, the H2SO4The volume fraction of the solution was 7.5%.
Optionally, the sodium pillared processing comprises:
adding black cotton soil into Na2CO3Obtaining a second prepared solution in the solution, and magnetically stirring for 3 hours at normal temperature;
adding an HCl solution into the stirred second preparation solution;
washing the second preparation solution added with the HCl solution by using deionized water until Cl ions are removed;
drying the second prepared solution washed by the deionized water at 105 ℃ for 12 hours to obtain a second black cotton soil sample crude product;
and grinding the second black cotton soil sample crude product to obtain a second black cotton soil sample.
Alternatively, the Na2CO3The mass fraction of the solution was 8%.
Optionally, the hydrolyzing silane to obtain a silane hydrolyzed solution comprises:
preparing a first mixed solution of ethanol and water in a volume ratio of 9: 1;
adding a silane coupling agent into the first mixed solution, adjusting the pH value of the first mixed solution added with the silane coupling agent to a preset pH range by using glacial acetic acid, and stirring to obtain a silane hydrolysis solution.
Optionally, the agitating comprises: magnetically stirring at room temperature for 1 hour.
Optionally, the preset pH value range is 4-5.
Optionally, the silane grafting of the black cotton soil using the silane hydrolysis solution comprises:
preparing a second mixed solution of ethanol and water in a volume ratio of 9: 1;
placing the black cotton soil sample in the second mixed solution for stirring to form stable suspension;
dripping the silane hydrolysis solution into the suspension, and heating in water bath at 70 ℃ for a preset time;
washing the suspension liquid which is heated in the water bath and is dripped with the silane hydrolysis solution to be neutral and drying to obtain a silane grafted black cotton soil crude product;
and grinding the crude product of the silane grafted black cotton to obtain a silane grafted black cotton sample.
Optionally, the preset time includes: 2 hours, 4 hours, 8 hours, or 12 hours.
The invention provides a method for adjusting expansibility of black cotton soil, which comprises the steps of firstly carrying out acidification treatment or sodium pillared treatment on the black cotton soil to obtain the black cotton soil with certain activity, then hydrolyzing silane to obtain silane hydrolysate, grafting silane with different concentrations, carrying out condensation reaction on the silane and hydroxyl of a black cotton soil lamella to change the hydrophilicity of the black cotton soil into hydrophobicity, and further changing the water absorption expansibility of the black cotton soil. Due to the particularity of the silane molecular structure, namely that the silane molecules are in a chain structure, groups at two ends of the silane molecular structure have different hydrophilicity and hydrophobicity, when the silane molecular structure reacts with black cotton, one end of a hydrophilic group can be subjected to condensation reaction with hydroxyl between the black cotton piece layers, and the hydrophobic end is exposed on the surface of the piece layer, so that the purpose of hydrophobic is achieved, and the expansibility of the black cotton is reduced. The modified black cotton soil not only realizes the recovery problem of the waste black cotton soil, but also solves the problem of occupation of land by a large amount of black cotton soil.
The foregoing description is only an overview of the technical solutions of the present invention, and the embodiments of the present invention are described below in order to make the technical means of the present invention more clearly understood and to make the above and other objects, features, and advantages of the present invention more clearly understandable.
The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments thereof, taken in conjunction with the accompanying drawings.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:
FIG. 1 is a schematic flow diagram of a method of adjusting the expandability of black cotton in accordance with an embodiment of the present invention;
figure 2 is an XRD pattern of a black cotton sample treated in a different manner according to an example of the present invention.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
Fig. 1 is a schematic flow chart of a method for adjusting black cotton expansibility according to an embodiment of the invention, as shown in fig. 1, the method for adjusting black cotton expansibility according to an embodiment of the invention comprises:
step S102, preprocessing black cotton soil to obtain a black cotton soil sample, wherein the preprocessing comprises acidification or sodium pillared processing;
step S104, hydrolyzing silane to obtain silane hydrolysis solution;
and step S106, performing silane grafting on the surface of the pretreated black cotton by using a silane hydrolysis solution to obtain a silane-grafted black cotton sample.
The embodiment of the invention provides a method for adjusting expansibility of black cotton soil. Due to the particularity of the silane molecular structure, namely that the silane molecules are in a chain structure, groups at two ends of the silane molecular structure have different hydrophilicity and hydrophobicity, when the silane molecular structure reacts with black cotton, one end of a hydrophilic group can be subjected to condensation reaction with hydroxyl between the black cotton piece layers, and the hydrophobic end is exposed on the surface of the piece layer, so that the purpose of hydrophobic is achieved, and the expansibility of the black cotton is reduced. The modified black cotton soil not only realizes the recovery problem of the waste black cotton soil, but also solves the problem of occupation of land by a large amount of black cotton soil.
The black cotton soil is a tropical soil widely distributed all over the world, has strong hydration expansibility, and is not suitable for roadbed construction directly. The black cotton soil used in the invention is soil at the south loop road of Neurobi Kenya, and is analyzed as follows: the black cotton soil mainly contains mineral phases such as montmorillonite, feldspar and quartz, the black cotton soil is high-hydration-expansibility soil, a lamellar structure is observed through SEM, a large number of hydroxyl groups are contained among the black cotton soil lamellar layers, and the black cotton soil lamellar layers are negatively charged and are easy to adsorb hydrated cations in water to form an electric double layer structure.
When the black cotton soil is acidized, the black cotton soil can be added with H firstly2SO4Obtaining a first prepared solution in (sulfuric acid) solution, and magnetically stirring in a water bath at 70 ℃ for 3 hours, wherein H with 7.5% volume fraction is preferred2SO4A solution; secondly, washing the stirred first prepared solution by deionized water until the pH value is neutral; drying the first prepared solution washed by deionized water at 105 ℃ for 12 hours to obtain a first black cotton soil sample crude product; and finally, grinding the first black cotton soil sample crude product to obtain a first black cotton soil sample.
When the black cotton soil is subjected to sodium pillared treatment, the black cotton soil can be added into Na firstly2CO3Obtaining a second prepared solution from the (sodium carbonate) solution, and magnetically stirring for 3 hours at normal temperature, wherein the preferable mass fraction is 8 percent of Na2CO3The solution of (1); secondly, adding HCl solution into the stirred second preparation solution; washing the second prepared solution added with the HCl solution by using deionized water until Cl ions are removed; drying the second prepared solution washed by the deionized water at 105 ℃ for 12 hours to obtain a second black cotton soil sample crude product; and finally, grinding the second black cotton soil sample crude product to obtain a second black cotton soil sample.
Preferably, when the silane is hydrolyzed to obtain the silane hydrolyzed solution, the following steps may be performed:
preparing a first mixed solution of ethanol and water in a volume ratio of 9: 1; adding a silane coupling agent into the first mixed solution, adjusting the pH value of the first mixed solution added with the silane coupling agent to a preset pH range by using glacial acetic acid, and stirring to obtain a silane hydrolysis solution.
Wherein the preset pH range is preferably 4-5, and the hydrolysis of the silane coupling agent is facilitated within the range. While, in the case of stirring, magnetic stirring may be carried out at normal temperature for 1 hour.
In the above-described processes for treating black cotton soil and silane hydrolysate, respectively, in the embodiment of the present invention, the structural specificity of the silane molecule in a chain structure is mainly utilized, and the silane coupling agent is utilized to reduce the expansibility of black cotton soil. Therefore, it is important to perform silane grafting on the pretreated black cotton by using a silane hydrolysis solution.
In an embodiment of the present invention, surface grafting of black cotton soil using a silane hydrolysis solution may include:
preparing a second mixed solution of ethanol and water in a volume ratio of 9: 1;
placing the pretreated black cotton soil sample in a second mixed solution for stirring to form a stable suspension;
dripping the silane hydrolysis solution into the suspension, and heating in water bath at 70 ℃ for a preset time;
washing the suspension liquid which is heated in a water bath and is dripped with the silane hydrolysis solution to be neutral and drying to obtain a silane grafted black cotton soil crude product;
and grinding the crude product of the silane grafted black cotton to obtain a silane grafted black cotton sample.
Alternatively, the heating time of the water bath at 70 ℃ after dropping the silane hydrolysis solution into the suspension may be 2 hours, 4 hours, 8 hours, or 12 hours.
The method for adjusting the expansibility of the black cotton soil mainly comprises the steps of carrying out acidification or sodium treatment on the black cotton soil to obtain the black cotton soil with certain activity, carrying out surface modification on the black cotton soil by adopting a silane coupling agent, namely 3-aminopropyltrimethoxysilane, grafting by using silanes with different concentrations, carrying out condensation reaction on the silanes and hydroxyl groups of a black cotton soil sheet layer to change the hydrophilicity of the black cotton soil into the hydrophobicity, and further changing the water absorption expansibility of the black cotton soil. Due to the particularity of the silane molecular structure, the silane molecules are in a chain structure, the groups at two ends have different hydrophilicity and hydrophobicity, when the silane molecules react with the black cotton soil, one end of a hydrophilic group can be subjected to condensation reaction with hydroxyl groups between the black cotton soil lamella layers, and the hydrophobic end is exposed on the surface of the lamella layer, so that the hydrophobic purpose is achieved, and the expansibility of the black cotton soil is reduced. The modified black cotton soil not only realizes the recovery problem of the waste black cotton soil, but also solves the problem of occupation of land by a large amount of black cotton soil.
Based on the technical scheme provided by the embodiment, the invention also provides a plurality of embodiments for carrying out surface silane grafting on the black cotton soil, and the expansibility test is carried out.
For comparison, the pristine black cotton soil may be directly silane grafted without pretreatment, as in examples 1-3 below.
Example 1
Silane grafting of original black cotton soil
1. Hydrolysis of silane: adding 0.5% silane coupling agent into 100mL ethanol/water (volume ratio of 9:1), adjusting pH to 4-5 with glacial acetic acid to promote hydrolysis, and magnetically stirring at room temperature for 1 hr.
2. Surface grafting of black cotton soil: 15g of black cotton soil is dispersed in 100ml of mixed solution of ethanol/water (volume ratio is 9:1), placed in a beaker and stirred until the mixture is uniformly dispersed to form stable suspension, and the silane solution is slowly dropped into the suspension. Water bath at 70 ℃ for 4 hours. After the reaction is finished, performing suction filtration and washing to be neutral, and drying in an oven at 80 ℃ for 12 hours; and grinding in a mortar for later use to obtain the silane grafted black cotton sample.
The free swell was determined to be 120%.
Example 2
Silane grafting of original black cotton soil
1. Hydrolysis of silane: adding 1% silane coupling agent into 100mL ethanol/water (volume ratio of 9:1), adjusting pH to 4-5 with glacial acetic acid to promote hydrolysis, and magnetically stirring at room temperature for 1 hr.
2. Surface grafting of black cotton soil: dispersing 15g of black cotton soil in 100mL of ethanol/water (volume ratio of 9:1) mixed solution, placing the mixed solution in a beaker for magnetic stirring, slowly dropping a silane solution into the suspension liquid after uniform dispersion to obtain a stable suspension liquid, and carrying out water bath at 70 ℃ for 4 hours; after the reaction is finished, performing suction filtration and washing to be neutral, drying in an oven at 80 ℃ for 12 hours, and grinding a mortar for later use to obtain the silane-grafted black cotton soil sample.
The free swell was determined to be 61%.
Example 3
Silane grafting of original black cotton soil
1. Hydrolysis of silane: adding 2% silane coupling agent into 100mL ethanol/water (volume ratio of 9:1), adjusting pH to 4-5 with glacial acetic acid to promote hydrolysis, and magnetically stirring at room temperature for 1 hr.
2. Surface grafting of black cotton soil: dispersing 15g of black cotton soil in 100mL of ethanol/water (volume ratio of 9:1) mixed solution, placing the mixed solution in a beaker for magnetic stirring, slowly dropping a silane solution into the suspension liquid after uniform dispersion to obtain a stable suspension liquid, and carrying out water bath at 70 ℃ for 4 hours; after the reaction is finished, performing suction filtration and washing to be neutral, drying in an oven at 80 ℃ for 12 hours, and grinding a mortar for later use to obtain the silane-grafted black cotton soil sample.
The free swell was determined to be 41%.
The following examples will pretreat the black cotton soil prior to silane grafting.
Example 4
1. Acidifying black cotton soil, adding H with volume fraction of 7.5% into 15g of black cotton soil2SO4In the solution, the prepared solution is placed in a water bath with the temperature of 70 ℃ for magnetic stirring for 3 hours; then, carrying out suction filtration and washing by using deionized water until the pH value of the filtrate is neutral, and drying for 12 hours in an oven at 105 ℃; grinding a mortar for later use;
2. hydrolysis of silane: adding 0.5% silane coupling agent into 100mL ethanol/water (volume ratio of 9:1), adjusting pH to 4-5 with glacial acetic acid, promoting hydrolysis, and magnetically stirring at room temperature for 1 hr.
3. Surface grafting of black cotton soil: 15g of black cotton soil is dispersed in 100mL of mixed solution of ethanol/water (volume ratio is 9:1), placed in a beaker for magnetic stirring, and after uniform dispersion, stable suspension is formed, and silane solution is slowly dripped into the suspension, and water bath is carried out at 70 ℃ for 4 hours. After the reaction is finished, performing suction filtration and washing until the solution is neutral, putting the solution into an oven to dry for 12 hours at the temperature of 80 ℃, and grinding a mortar for later use to obtain the silane grafted black cotton sample.
The free swell was determined to be 17%.
Example 5
1. Acidifying black cotton soil, adding H with volume fraction of 7.5% into 15g of black cotton soil2SO4In the solution, the prepared solution is placed in a water bath with the temperature of 70 ℃ for magnetic stirring for 3 hours; washing the stirred solution with deionized water until the pH value is neutral, and drying the solution in an oven at 105 ℃ for 12 hours; grinding a mortar for later use;
2. hydrolysis of silane: adding 1% silane coupling agent into 100mL ethanol/water (volume ratio of 9:1), adjusting pH to 4-5 with glacial acetic acid, promoting hydrolysis, and magnetically stirring at room temperature for 1 hr.
3. Surface grafting of black cotton soil: 15g of black cotton soil is dispersed in 100mL of mixed solution of ethanol and water (volume ratio is 9:1), placed in a beaker for magnetic stirring, and when the mixture is uniformly dispersed, stable suspension is formed, and silane solution is slowly dripped into the suspension. Water bath at 70 ℃ for 4 hours. After the reaction is finished, performing suction filtration and washing to be neutral, putting the mixture into an oven to dry for 12 hours at the temperature of 80 ℃, and grinding a mortar for later use to obtain the silane grafted black cotton sample.
The free swell was determined to be 10%.
Example 6
1. Acidifying black cotton soil, adding H with volume fraction of 7.5% into 15g of black cotton soil2SO4In the solution, the prepared solution is placed in a water bath with the temperature of 70 ℃ for magnetic stirring for 3 hours; the stirred solution was usedWashing with ionized water until the pH value is neutral, and drying in an oven at 105 ℃ for 12 hours; grinding a mortar for later use;
2. hydrolysis of silane: adding 2% silane coupling agent into 100mL ethanol/water (volume ratio of 9:1), adjusting pH to 4-5 with glacial acetic acid, promoting hydrolysis, and magnetically stirring at room temperature for 1 hr.
3. Surface grafting of black cotton soil: 15g of black cotton soil is dispersed in 100mL of mixed solution of ethanol and water (volume ratio is 9:1), placed in a beaker for magnetic stirring, and when the mixture is uniformly dispersed, stable suspension is formed, and silane solution is slowly dripped into the suspension. Water bath at 70 ℃ for 4 hours. After the reaction is finished, performing suction filtration and washing to be neutral, putting the mixture into an oven to dry for 12 hours at the temperature of 80 ℃, and grinding a mortar for later use to obtain the silane grafted black cotton sample.
The free swell was determined to be 13%.
Example 7
1. Acidifying black cotton soil, adding H with volume fraction of 7.5% into 15g of black cotton soil2SO4In the solution, the prepared solution is placed in a water bath with the temperature of 70 ℃ for magnetic stirring for 3 hours; washing the stirred solution with deionized water until the pH value is neutral, and drying the solution in an oven at 105 ℃ for 12 hours; grinding a mortar for later use;
2. hydrolysis of silane: adding 1% silane coupling agent into 100mL ethanol/water (volume ratio of 9:1), adjusting pH to 4-5 with glacial acetic acid, promoting hydrolysis, and magnetically stirring at room temperature for 1 hr.
3. Surface grafting of black cotton soil: 15g of black cotton soil is dispersed in 100mL of mixed solution of ethanol and water (volume ratio is 9:1), placed in a beaker for magnetic stirring, and when the mixture is uniformly dispersed, stable suspension is formed, and silane solution is slowly dripped into the suspension. Water bath at 70 ℃ for 2 hours. After the reaction is finished, performing suction filtration and washing to be neutral, putting the mixture into an oven to dry for 12 hours at the temperature of 80 ℃, and grinding a mortar for later use to obtain the silane grafted black cotton sample.
The free swell was determined to be 30%.
Example 8
1. For black cottonAcidifying soil, adding 7.5 vol% H into 15g of black cotton soil2SO4In the solution, the prepared solution is placed in a water bath with the temperature of 70 ℃ for magnetic stirring for 3 hours; washing the stirred solution with deionized water until the pH value is neutral, and drying the solution in an oven at 105 ℃ for 12 hours; grinding a mortar for later use;
2. hydrolysis of silane: adding 1% silane coupling agent into 100mL ethanol/water (volume ratio of 9:1), adjusting pH to 4-5 with glacial acetic acid, promoting hydrolysis, and magnetically stirring at room temperature for 1 hr.
3. Surface grafting of black cotton soil: 15g of black cotton soil is dispersed in 100mL of mixed solution of ethanol and water (volume ratio is 9:1), placed in a beaker for magnetic stirring, and when the mixture is uniformly dispersed, stable suspension is formed, and silane solution is slowly dripped into the suspension. Water bath at 70 ℃ for 8 hours. After the reaction is finished, performing suction filtration and washing to be neutral, putting the mixture into an oven to dry for 12 hours at the temperature of 80 ℃, and grinding a mortar for later use to obtain the silane grafted black cotton sample.
The free expansion rate is 13 percent by measurement
Example 9
1. Carrying out sodium pillaring on the black cotton soil: adding black cotton soil into a sodium carbonate solution with the mass fraction of 8%, and magnetically stirring for 3 hours at normal temperature; adding HCl solution to remove excessive CO3 2-. The suspension is filtered and washed with deionized water until Cl is removed-(ii) a Drying for 12 hours in an oven at 105 ℃, and grinding the sample for later use;
2. hydrolysis of silane: adding 0.5% by volume of silane coupling agent into 100mL of ethanol/water (volume ratio of 9:1) mixed solution, adjusting pH to 4-5 with glacial acetic acid, and magnetically stirring at room temperature for 1 hour.
3. Surface grafting of black cotton soil: 15g of black cotton soil is dispersed in 100mL of mixed solution of ethanol/water (volume ratio is 9:1), placed in a beaker and stirred until the mixture is uniformly dispersed to form stable suspension, and the silane solution is slowly dropped into the suspension. Water bath at 70 ℃ for 4 hours. After the reaction is finished, performing suction filtration and washing to be neutral, drying for 12 hours at 80 ℃, and grinding to obtain the silane grafted black cotton soil sample.
The free swell was determined to be 60%.
Example 10
1. Carrying out sodium pillaring on the black cotton soil: adding black cotton soil into a sodium carbonate solution with the mass fraction of 8%, and magnetically stirring for 3 hours at normal temperature; adding HCl solution to remove excessive CO3 2-. The suspension is filtered and washed with deionized water until Cl is removed-(ii) a Drying for 12 hours in an oven at 105 ℃, and grinding the sample for later use;
2. hydrolysis of silane: adding 1% silane coupling agent by volume into 100mL ethanol/water (volume ratio of 9:1) mixed solution, adjusting pH to 4-5 with glacial acetic acid, and magnetically stirring at room temperature for 1 hr.
3. Surface grafting of black cotton soil: 15g of black cotton soil is dispersed in 100mL of mixed solution of ethanol/water (volume ratio is 9:1), placed in a beaker and stirred until the mixture is uniformly dispersed to form stable suspension, and the silane solution is slowly dropped into the suspension. Water bath at 70 ℃ for 4 hours. After the reaction is finished, performing suction filtration and washing to be neutral, drying for 12 hours at 80 ℃, and grinding to obtain the silane grafted black cotton soil sample.
The free swell was determined to be 38%.
Example 11
1. Carrying out sodium pillaring on the black cotton soil: adding black cotton soil into a sodium carbonate solution with the mass fraction of 8%, and magnetically stirring for 3 hours at normal temperature; adding HCl solution to remove excessive CO3 2-. The suspension is filtered and washed with deionized water until Cl is removed-(ii) a Drying for 12 hours in an oven at 105 ℃, and grinding the sample for later use;
2. hydrolysis of silane: adding 2% by volume of silane coupling agent into 100mL of ethanol/water (volume ratio of 9:1) mixed solution, adjusting pH to 4-5 with glacial acetic acid, and magnetically stirring at room temperature for 1 hour.
3. Surface grafting of black cotton soil: 15g of black cotton soil is dispersed in 100mL of mixed solution of ethanol/water (volume ratio is 9:1), placed in a beaker and stirred until the mixture is uniformly dispersed to form stable suspension, and the silane solution is slowly dropped into the suspension. Water bath at 70 ℃ for 4 hours. After the reaction is finished, performing suction filtration and washing to be neutral, drying for 12 hours at 80 ℃, and grinding to obtain the silane grafted black cotton soil sample.
The free swell was determined to be 40%.
It can be seen from the comparison of the above examples that in examples 1-3, when the silane grafting was directly performed on the raw black cotton without performing the pretreatment, the swelling ratio of the black cotton was still high after the silane grafting was performed on the surface of the black cotton based on the silane hydrolysis solutions prepared under different conditions. And after the black cotton soil is subjected to acidification treatment or sodium pillared treatment, the treated black cotton soil is subjected to silane grafting, so that the expansion rate of the black cotton soil is obviously reduced.
FIG. 2 is an XRD (X-ray diffraction) pattern of a differently treated black cotton sample according to an embodiment of the present invention, as shown in FIG. 2, wherein a represents the XRD pattern of untreated black cotton; b represents a sample of black cotton grafted with 1% by volume of Silanes; c is a warp volume fraction of 7.5% H2SO4Acidizing the solution, and grafting a black cotton soil sample by using a silane coupling agent with the volume fraction of 1%; d represents that the black cotton soil sample is subjected to sodium pillared treatment by 8 percent by mass of sodium carbonate solution and is grafted by 1 percent by volume of silane coupling agent. Wherein 1.50nm, 1.64nm, 1.74nm and 1.66nm are interplanar spacings corresponding to the first-order diffraction peak of montmorillonite in the sample.
As can be seen from the figure, the first-order diffraction peak of XRD of the modified black cotton soil is shifted, indicating that silane molecules enter clay layers.
Table 1 shows the FS (free swelling ratio) of the modified black cotton soil as a function of modification conditions.
TABLE 1
| FS(％) | BCS+ |
8％Na2CO3+Silanes | 7.5％H2SO4+Silanes |
| 0.5％Silanes | 120 | 60 | 17 |
| 1％Silanes | 61 | 38 | 10 |
| 2％Silanes | 41 | 40 | 13 |
FS stands for free swell ratio; silanes represent Silanes; BCS stands for Black Cotton Soil; wherein the water bath time for treating the black cotton soil with silane was 4 hours.
The original BCS free expansion rate was determined to be 160%.
From table 1 it can be observed that: the expansion rate of the black cotton soil after acidification treatment or sodium pillared treatment is reduced.
Further, via H2SO4The expansibility of the pretreated black cotton is obviously reduced, and the free expansion rate is reduced from the original 160% to 10%. By using Na2CO3Carrying out sodium pillared treatment on the black cotton soil, wherein only Na is used+Ca in the black cotton soil sheet layer2+The plasma is replaced, and the sulfuric acid treatment can remove organic matters distributed in the black cotton soil; h+Will also be octahedralAl in the body3+The plasma is dissolved out, so that the clay particles carry more negative charges; acid washing also produces a large amount of broken bonds; the reaction activity of the black cotton soil is increased, and silane is easier to adsorb. Thus, compare with H2SO4Pretreating the black cotton soil with Na2CO3The expansibility of the pretreated black cotton is obviously reduced.
In the description provided herein, numerous specific details are set forth. It is understood, however, that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.
Similarly, it should be appreciated that in the foregoing description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. However, the disclosed method should not be interpreted as reflecting an intention that: that the invention as claimed requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.
Furthermore, those skilled in the art will appreciate that while some embodiments described herein include some features included in other embodiments, rather than other features, combinations of features of different embodiments are meant to be within the scope of the invention and form different embodiments. For example, in the claims, any of the claimed embodiments may be used in any combination.
Thus, it should be appreciated by those skilled in the art that while a number of exemplary embodiments of the invention have been illustrated and described in detail herein, many other variations or modifications consistent with the principles of the invention may be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be understood and interpreted to cover all such other variations or modifications.
Claims (9)
1. A method of adjusting the expandability of a black cotton soil, comprising:
pretreating black cotton soil to obtain a black cotton soil sample, wherein the pretreatment comprises acidification treatment or sodium pillared treatment;
hydrolyzing silane to obtain silane hydrolysis solution;
performing silane grafting on the pretreated black cotton by using the silane hydrolysis solution to obtain a silane-grafted black cotton sample;
wherein the acidification treatment comprises: adding the black cotton soil into H2SO4Obtaining a first prepared solution in the solution, and magnetically stirring the solution in a water bath at the temperature of 70 ℃ for 3 hours;
washing the stirred first preparation solution by using deionized water until the pH value is neutral;
drying the first prepared solution washed by the deionized water at 105 ℃ for 12 hours to obtain a first black cotton soil sample crude product;
and grinding the first black cotton soil sample crude product to obtain a first black cotton soil sample.
2. The method of claim 1, wherein the H2SO4The volume fraction of the solution was 7.5%.
3. The method of claim 1, wherein the sodium pillared processing comprises:
adding black cotton soil into Na2CO3Obtaining a second prepared solution in the solution, and magnetically stirring for 3 hours at normal temperature;
adding an HCl solution into the stirred second preparation solution;
washing the second preparation solution added with the HCl solution by using deionized water until Cl ions are removed;
drying the second prepared solution washed by the deionized water at 105 ℃ for 12 hours to obtain a second black cotton soil sample crude product;
and grinding the second black cotton soil sample crude product to obtain a second black cotton soil sample.
4. The method of claim 3, wherein the Na2CO3The mass fraction of the solution was 8%.
5. The method of claim 1, wherein the hydrolyzing silane to obtain a silane hydrolyzed solution comprises:
preparing a first mixed solution of ethanol and water in a volume ratio of 9: 1;
adding a silane coupling agent into the first mixed solution, adjusting the pH value of the first mixed solution added with the silane coupling agent to a preset pH range by using glacial acetic acid, and stirring to obtain a silane hydrolysis solution.
6. The method according to claim 5, wherein the predetermined pH value is in the range of 4 to 5.
7. The method of claim 5, wherein the agitating comprises: magnetically stirring at room temperature for 1 hour.
8. The method of claim 1, wherein the silane grafting of black cotton using the silane hydrolysis solution comprises:
preparing a second mixed solution of ethanol and water in a volume ratio of 9: 1;
placing the black cotton soil sample in the second mixed solution for stirring to form stable suspension;
dripping the silane hydrolysis solution into the suspension, and heating in water bath at 70 ℃ for a preset time;
washing the suspension liquid which is heated in the water bath and is dripped with the silane hydrolysis solution to be neutral and drying to obtain a silane grafted black cotton soil crude product;
and grinding the crude product of the silane grafted black cotton to obtain a silane grafted black cotton sample.
9. The method of claim 8, wherein the preset time comprises: 2 hours, 4 hours, 8 hours, or 12 hours.
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| CN103896294A (en) * | 2014-03-26 | 2014-07-02 | 芜湖恒杰膨润土科技有限公司 | Artificial sodium bentonite |
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| CN101254924A (en) * | 2008-04-09 | 2008-09-03 | 中国科学院化学研究所 | Silicane coupling agent surface grafted modified clay as well as preparation method and use thereof |
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