Preparation method of carbon sequestration cement-based material and carbon sequestration cement-based material thereof

Abstract

The application discloses a preparation method of a carbon sequestration cement-based material and the carbon sequestration cement-based material, and steps of the method comprise the following: obtaining original biochar by pyrolyzing pretreated biomass raw materials, and modifying the original biochar by using a modified solution to obtain modified biochar, wherein the modified solution is prepared by mixing citric acid, anhydrous ethanol, distilled water, ammonia water, tetraethyl silicate and calcium chloride, and the modified biochar is added into a cement-based material to obtain the carbon sequestration cement-based material. Thus, the original biochar is optimized by selecting citric acid and a tetraethyl silicate solution as influencing factors, so that the best modified biochar is obtained to enhance the cement-based material, and the carbon sequestration rate and the compressive strength are simultaneously improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of cement production, in particular to a carbon fixation cement-based material. BACKGROUND

[0002] Due to the porosity of the cement-based material itself, it can become an adsorption carrier of CO2 in the environment, but the adsorption carrier has limited capacity, and it is necessary to dope porous materials with more physical and chemical properties to enhance the material transport capacity of the entire cement-based material microsystem and expand the adsorption capacity of the cement-based material to CO2. However, if the traditional cement-based material contains too much porous material, the overall mechanical properties will be reduced.

[0003] Biochar is produced under anaerobic or partially anaerobic conditions through high-temperature pyrolysis. At this time, carbon is fixed in biochar as an unsaturated carbon element in biomass. Therefore, biochar material itself is carbon negative. At the same time, biochar material is widely used in agriculture, environment, construction and energy due to its high specific surface area, rich functional groups, developed pore structure and good thermal stability. Internationally, biochar is called "black gold", which is the third generation of materials after stone and steel.

[0004] Due to the unique physicochemical properties of biomass charcoal, adding biochar to cement can easily meet the carbon emission reduction index. However, due to the characteristics of the raw materials and the pyrolysis method, the original biochar added to cement has limited benefits, especially when biochar is directly replaced by cement. It has a negative effect on strength, resulting in low hardness and reduced strength of cement-based composite materials. SUMMARY

[0005] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application proposes a preparation method of a carbon fixation cement-based material, which uses straw as raw material and selects citric acid and tetraethyl silicate solution as influencing factors to optimize the original biochar and obtain the best modified biochar to enhance the cement-based material.

[0006] The present application further proposes a carbon fixation cement-based material.

[0007] According to the preparation method of the carbon fixation cement-based material according to the first aspect of the present application, the method comprises the following steps:

[0008] The biomass raw material is pretreated and pyrolyzed to obtain original biochar;

[0009] The original biochar is modified by a modification solution to obtain modified biochar, wherein the modification solution is a mixture of citric acid, anhydrous ethanol, distilled water, ammonia, tetraethyl silicate and calcium chloride.

[0010] adding the modified biochar into a cement-based material to obtain a carbon sequestration cement-based material.

[0011] Specifically, by modifying the biochar with the modification solution, firstly, more carboxyl groups can be introduced without changing the hydroxyl groups by citric acid modification, the carboxyl groups belong to hydrophilic functional groups, which can enhance the water retention performance of the biochar particles, and further enhance the secondary hydration of the cement-based composite material, and meanwhile, the higher concentration of hydroxyl and carboxyl groups can promote the chemical adsorption of CO2.

[0012] Secondly, more nano-silica can be introduced to the surface of the biochar by tetraethyl orthosilicate, anhydrous ethanol and other reagents, which not only increases the specific surface area of the biochar, enhances the physical adsorption and hardness of CO2, but also introduces the substances required for hydration (calcium and silicon), thereby increasing the nucleation sites of cement hydration products, and meanwhile, the introduction of calcium ions also enhances the negative charge of the biochar, thereby increasing the adsorption of CO2.

[0013] The ammonia water is added to adjust the acidity and alkalinity of the solution to provide a suitable alkaline environment for the generation of nano-silica.

[0014] In addition, the higher concentration of carboxyl groups also plays a positive role in the introduction of calcium ions in the modifier into the cement-based composite material.

[0015] According to some embodiments of the present application, the biomass raw material is agricultural solid waste and / or forest waste, wherein the agricultural solid waste includes corn stalks, rice husks, soybean stalks, peanut shells, and coconut shells; and the forest waste includes bamboo, birch, and sycamore wood.

[0016] Preferably, the biomass raw material is corn stalks, and the corn stalk biochar has high carbon content and high degree of aromatization, large specific surface area, and thus excellent stability and CO2 adsorption performance, and is rich in SiO2 which is beneficial to cement.

[0017] According to some embodiments of the present application, the step of pyrolyzing the pretreated biomass raw material to obtain the original biochar specifically includes: sequentially rinsing, drying and crushing the biomass raw material, and then grinding and sieving the pyrolyzed product in an inert gas atmosphere to obtain the original biochar, wherein the heating rate of pyrolysis is 5-20℃ / min, the pyrolysis temperature is 400-600℃, and the pyrolysis time is 1-2 hours.

[0018] According to some embodiments of the present application, the step of modifying the original biochar with the modification solution to obtain the modified biochar specifically includes:

[0019] After mixing and stirring the original biochar with the citric acid solution, drying is performed;

[0020] The above dried biochar is mixed with anhydrous ethanol, distilled water and ammonia water, and then tetraethyl silicate and calcium chloride are added for stirring, and then filtration, drying and grinding are sequentially performed to obtain the modified biochar.

[0021] According to some embodiments of the present application, when the dried biochar is mixed with anhydrous ethanol, distilled water and ammonia water, and then tetraethyl silicate and calcium chloride are added for stirring, the following steps are required:

[0022] The dried biochar is mixed with anhydrous ethanol, distilled water and ammonia water, and then tetraethyl silicate is added to obtain solution A;

[0023] Distilled water, ammonia water and anhydrous ethanol are mixed to obtain solution B;

[0024] Solution A and solution B are mixed, and then tetraethyl silicate and calcium chloride are added for stirring, and then filtration, drying and grinding are sequentially performed to obtain the modified biochar;

[0025] Specifically, the two solutions A and B are prepared separately in this step to avoid unwanted reactions before mixing, that is, in order to obtain sufficient nanosilica, if the solutions are not separated, calcium ions will compete with calcium silicate ions, resulting in a decrease in the amount of silicon dioxide. Therefore, separate mixing can better control the reaction process of each solution.

[0026] According to some embodiments of the present application, anhydrous ethanol is further added and ultrasonic dispersion is performed before the dried biochar is mixed with anhydrous ethanol, distilled water and ammonia water. Through this step, the biochar can be dispersed and suspended in the solvent, so that it is more easily reacted with the subsequent added reagents.

[0027] According to some embodiments of the present application, the mass of the modified biochar added into the cement-based material is 1% to 5% of the mass of the cement-based material.

[0028] According to some embodiments of the present application, the mass of the modified biochar added into the cement-based material is 3% of the mass of the cement-based material.

[0029] According to the second aspect of the embodiment of the present application, the carbon sequestration cement-based material is prepared by any of the above preparation methods.

[0030] Beneficial effects:

[0031] The carbon sequestration cement-based material prepared by the present application can not only sequester carbon, but also improve the compressive performance of cement. The original biochar properties are improved and calcium ions are introduced into the cement to enhance the carbon sequestration and emission reduction mode of the cement-based material, thereby enhancing the carbon dioxide capture capacity of the biochar, and further increasing the process of the increased carbon dioxide reacting with cement clinker particles and calcium hydroxide to generate carbonate. BRIEF DESCRIPTION OF DRAWINGS

[0032] The above and / or additional aspects and advantages of the present application will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings in which:

[0033] Figure 1 is a schematic diagram of compressive strength and carbon sequestration growth rate of a carbon sequestration cement-based material according to an embodiment of the present application;

[0034] Figure 2 is a schematic diagram of nano-silica attached biochar according to an embodiment of the present application. DETAILED DESCRIPTION

[0035] Embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0036] Reference is made below to Figures 1-2 A method for preparing a carbon sequestration cement-based material according to an embodiment of the present application is described.

[0037] The method for preparing a carbon sequestration cement-based material according to an embodiment of the present application includes the following steps:

[0038] S1, preparing original biochar by pyrolysis;

[0039] Corn straw biomass is rinsed, dried and crushed, nitrogen is introduced into a pyrolysis device to make the pyrolysis environment anoxic or hypoxic, then the corn straw is placed in a tube furnace, the heating rate is set to 5-20℃ / min, and the temperature is maintained at 400-600℃ for 1-2 hours, then it is removed and cooled to room temperature, ground using a ball mill, and sieved, thereby obtaining original biochar.

[0040] S2, preparing modified biochar;

[0041] S21, a citric acid solution is prepared, preferably a 0.5-1.5 mol / l citric acid solution, the original biochar is stirred in the citric acid solution for 2h, dried in a 60℃ oven for 24h, then dried at 120℃ for 2h, washed and dried;

[0042] S22, 5-25g of biochar is added to a beaker with 400mL of anhydrous ethanol, ultrasonically dispersed for 30min, then 200mL of anhydrous ethanol, 100mL of distilled water and 30mL of ammonia water are added, and stirred at room temperature for 6h;

[0043] S23, 25mL of tetraethyl silicate (TEOS) is added to the solution, the resulting solution is solution A, at the same time, 20mL of distilled water, 5mL of ammonia water and 300ml of anhydrous ethanol are all added to the beaker and mixed, the resulting solution is solution B,

[0044] S24, mixing solution A and solution B at room temperature, first add 50 mL TEOS, then add 200 ml of 1 mol / l calcium chloride and stir for 6h.

[0045] S25, filter the solution, wash with anhydrous ethanol and distilled water alternately, dry at 80℃ for 12h, grind, and finally obtain the modified biochar, grind and reserve.

[0046] S3, preparing carbon sequestration cement-based material;

[0047] The modified biochar is added into the Portland cement in proportion, and finally the carbon sequestration cement-based material is obtained.

[0048] Example 1

[0049] The net paste ratio is: cement 570.24g, water 230.4g, modified corn straw biochar 5.76g, standard curing, and the 7d compressive strength of the net paste test piece is 44.2Mpa after testing.

[0050] Take the same ingredients, mix them and place the mixture in a carbon dioxide gas environment with a concentration of 99.99% at a temperature of 25℃ for 7d of mineralization.

[0051] The mineralized mixture is crushed into powder, which is the mineralized biochar cement. The carbon sequestration amount of the modified biochar is calculated by data calculation, sample mass m1, weight m2 from room temperature to 1000℃, calculation method is (m1-m2) / m1, after subtracting the carbon sequestration amount of the original cement, the carbon sequestration growth rate is 0.81%.

[0052] Example 2

[0053] The net paste ratio is: cement 564.48g, water 230.4g, modified corn straw biochar 11.52g, standard curing, and the 7d compressive strength of the net paste test piece is 47.7Mpa after testing.

[0054] The carbon sequestration growth rate is 1.03% calculated by the example one-step method.

[0055] Example 3

[0056] The net paste ratio is: cement 558.72g, water 230.4g, modified corn straw biochar 17.28g, standard curing, and the 7d compressive strength of the net paste test piece is 49.9Mpa after testing.

[0057] The carbon sequestration growth rate is 1.14% calculated by the example one-step method.

[0058] Example 4

[0059] The net paste ratio is: cement 547.2g, water 230.4g, modified corn straw biochar 28.8g, standard curing, after testing, the 3d compressive strength of the net paste test piece is 40.5Mpa.

[0060] The carbon sequestration growth rate calculated by the step of the example is 1.05%.

[0061] Comparative Example 1

[0062] The net paste ratio is: cement 570.24g, water 230.4g, original corn straw biochar 5.76g, standard curing, after testing, the 3d compressive strength of the net paste test piece is 39Mpa.

[0063] The carbon sequestration growth rate calculated by the step of Example 1 is 0.7%.

[0064] Comparative Example 2

[0065] The net paste ratio is: cement 564.48g, water 230.4g, original corn straw biochar 11.52g, standard curing, after testing, the 7d compressive strength of the net paste test piece is 42.5Mpa.

[0066] The carbon sequestration growth rate calculated by the step of the example is 0.88%.

[0067] Comparative Example 3

[0068] The net paste ratio is: cement 558.72g, water 230.4g, original corn straw biochar 17.28g, standard curing, after testing, the 7d compressive strength of the net paste test piece is 43.7Mpa.

[0069] The carbon sequestration growth rate calculated by the step of the example is 0.98%.

[0070] Comparative Example 4

[0071] The net paste ratio is: cement 547.2g, water 230.4g, original corn straw biochar 28.8g, standard curing, after testing, the 7d compressive strength of the net paste test piece is 31.6Mpa.

[0072] The carbon sequestration growth rate calculated by the step of the example is 0.9%.

[0073] Comparative Example 5

[0074] The net paste ratio is: cement 576g, water 230.4g, original / modified corn straw biochar 0g, standard curing, after testing, the 7d compressive strength of the net paste test piece is 40.4Mpa.

[0075] In summary, the parameter data of the experimental examples and comparative examples can be summarized as follows Figure 1The compressive strength and carbon sequestration growth rate of the cement with 1% corn stalk biochar are compared with the original cement, and it can be seen that the compressive strength of the cement with unmodified corn stalk biochar is lower than that of the original cement, while the compressive strength of the cement with modified corn stalk biochar is higher than that of the original cement.

[0076] Similarly, the compressive strength and carbon sequestration growth rate of the cement with 2% or 3% corn stalk biochar are compared with the original cement, and it can be seen that in this range, the cement with unmodified corn stalk biochar can slightly improve the compressive strength, but more intuitively, the compressive strength of the cement with modified corn stalk biochar is significantly higher than that of the original cement, and also higher than that of the cement with unmodified corn stalk biochar.

[0077] Especially when the proportion of modified corn stalk biochar is 3%, the compressive strength and carbon sequestration growth rate of the cement are improved.

[0078] However, the difference is that when the proportion of unmodified corn stalk biochar reaches 5%, the compressive strength decreases significantly, and the carbon sequestration growth rate also decreases, while when the proportion of modified corn stalk biochar reaches 5%, the compressive strength also decreases to a certain extent, but it can at least ensure that the compressive strength is the same as that of the original cement.

[0079] Therefore, it is also proved that the cement with modified corn stalk biochar can improve the carbon sequestration rate and the compressive strength at the same time, achieving both goals.

[0080] According to the carbon sequestration cement-based material of the embodiment of the present application, the carbon sequestration cement-based material prepared by the preparation method of the above embodiment has better carbon sequestration rate and compressive strength.

[0081] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0082] In the description of the specification, reference to "one embodiment", "some embodiments", "an exemplary embodiment", "an example", "a specific example", or "some examples" means that a particular feature, structure, material, or characteristic being described is included in at least one embodiment or example of the application. The appearances of the phrases "in one embodiment", "in some embodiments", "in an exemplary embodiment", "an example", "a specific example", or "some examples" in various places in the specification are not necessarily referring to the same embodiment or example.

[0083] While embodiments of the application have been shown and described, it is to be understood that the application is not limited to these embodiments. Rather, it is the intention that modifications, changes, substitutions, and variations be made to the embodiments disclosed herein without departing from the spirit and scope of the application, which is defined solely by the claims and their equivalents.

Claims

1. A method for preparing a carbon-fixed cement-based material, characterized in that, The method includes the following steps: S1. Pre-treat biomass raw materials and then pyrolyze them to obtain raw biochar; S2, Preparation of modified biochar; among which, S21. Prepare a 0.5-1.5 mol / L citric acid solution, stir the raw biochar in the citric acid solution for 2 hours, dry it in a 60°C oven for 24 hours, then heat it to 120°C and dry it for 2 hours, wash it, and dry it. S22. Add 5-25g of treated biochar to a beaker, add 400mL of anhydrous ethanol, and sonicate for 30min. Then add 200mL of anhydrous ethanol, 100mL of distilled water and 30mL of ammonia water, stir at room temperature for 6h, and add 25mL of tetraethyl silicate. The resulting solution is solution A. S23. Add 20 mL of distilled water, 5 mL of ammonia water and 300 mL of anhydrous ethanol to a beaker and mix them. The resulting solution is solution B. S24. Mix solution A and solution B at room temperature, first add 50 mL of tetraethyl orthosilicate (TEOS), then add 200 mL of 1 mol / L calcium chloride and stir for 6 hours. S25. Filter the solution, wash it alternately with anhydrous ethanol and distilled water, dry it at 80℃ for 12 hours, grind it, and the final product is the modified biochar. Grind it and set it aside. S3. Add modified biochar to cement-based materials and mix to obtain carbon-fixed cement-based materials.

2. The method for preparing a carbon-fixed cement-based material according to claim 1, characterized in that, The biomass raw materials are agricultural solid waste and / or forestry waste, wherein the agricultural solid waste includes corn stalks, rice husks, soybean stalks, peanut shells, and coconut shells; and the forestry waste includes bamboo, birch, and paulownia wood.

3. The method for preparing a carbon-fixed cement-based material according to claim 2, characterized in that, The biomass raw material is corn stalks.

4. The method for preparing a carbon-fixed cement-based material according to claim 1, characterized in that, The steps for obtaining raw biochar by pyrolysis after pretreatment of biomass raw materials specifically include: washing, drying and pulverizing the biomass raw materials in sequence, pyrolyzing them in an inert gas atmosphere, grinding and sieving them to obtain raw biochar, wherein the pyrolysis heating rate is 5-20℃ / min, the pyrolysis temperature is 400℃-600℃, and the pyrolysis time is 1-2 hours.

5. The method for preparing a carbon-fixed cement-based material according to claim 1, characterized in that, The modified biochar added to the cement-based material is 1% to 5% of the mass of the cement-based material.

6. The method for preparing a carbon-fixed cement-based material according to claim 5, characterized in that, The modified biochar added to the cement-based material accounts for 3% of the mass of the cement-based material.

7. A carbon-fixed cement-based material, characterized in that: The carbon-fixed cement-based material prepared by any one of the preparation methods of carbon-fixed cement-based materials according to claims 1-6.

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