Application of cement-modified activated carbon composite cementitious material in adsorbing chloride ion in seawater

Abstract

This invention relates to a cement-modified activated carbon composite cementitious material, its preparation method, and concrete. The cement-modified activated carbon composite cementitious material includes cement and modified activated carbon; by mass fraction, the cement-modified activated carbon composite cementitious material includes 40-60% modified activated carbon. The modified activated carbon is prepared by carbonizing coffee husks, mixing with an activating agent, and then heating and activating. The modified activated carbon in the composite cementitious material of this invention uses coffee husks as raw material, making full use of waste biological resources, resulting in low cost, economic efficiency, and environmental friendliness, realizing the utilization of solid waste. This invention partially replaces cement with modified activated carbon, and the resulting composite cementitious material, when used in building materials, exhibits good corrosion resistance in seawater environments with high chloride ion concentrations, solving the problems of concrete cracking and steel corrosion caused by seawater infiltration in marine environments.

Description

Technical Field

[0001] This invention relates to the field of industrial building materials technology, specifically to the application of a cement-modified activated carbon composite cementitious material in the adsorption of chloride ions in seawater. Background Technology

[0002] Seawater has a high chloride ion content, and over time, these ions can actively penetrate into the reinforced concrete of buildings, causing the internal steel bars to rust and corrode. Steel corrosion is one of the main factors affecting the structural durability of buildings, and the durability of buildings in marine environments has received widespread attention.

[0003] Calcium hydroxide, a hydration product of concrete, provides an alkaline environment and forms a passivating protective film on the surface of reinforcing steel, effectively blocking chloride ion penetration and preventing steel corrosion. However, due to the continuous penetration of chloride ions, the pH of the environment decreases, and the protective film on the surface of the reinforcing steel is gradually destroyed, leading to a significant reduction in the service life of reinforced concrete structures.

[0004] Compared to steel corrosion caused by carbonation of the concrete cover, steel corrosion caused by chloride ions in seawater is far greater, resulting in countless losses. For example, seawater with high chloride ion content can cause steel reinforcement in concrete to rust, reducing the strength and durability of both the concrete and the reinforcement, thus damaging the building. Furthermore, chloride ions can also affect the internal chemical reactions and microstructure of concrete, leading to cracking and spalling.

[0005] In existing technologies, anti-corrosion coatings are generally applied to the surface of steel bars to prevent them from being corroded by chloride ions. However, the durability of the anti-corrosion coating is low, and it is easy to fall off under the continuous scouring of seawater, causing environmental pollution.

[0006] Therefore, it is necessary to reduce chloride ion corrosion and improve the durability of buildings in marine environments. Summary of the Invention

[0007] (a) Technical problems to be solved

[0008] In view of the above-mentioned technical problems, in order to solve the problem that existing methods of reducing steel corrosion by coating the steel surface with anti-corrosion coatings are not durable, steel reinforcement is easily damaged by chloride ions in seawater. This invention provides an application of cement-modified activated carbon composite cementitious material in the adsorption of chloride ions in seawater.

[0009] (II) Technical Solution

[0010] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0011] In a first aspect, the present invention provides a cement-modified activated carbon composite cementitious material, comprising cement and modified activated carbon; the cement-modified activated carbon composite cementitious material comprises 40-60% modified activated carbon by mass fraction.

[0012] The modified activated carbon is prepared by carbonizing coffee husks, mixing them with an activating agent, and then heating and activating them.

[0013] The cement-modified activated carbon composite cementitious material described above preferably contains 50-60% activated carbon by mass fraction.

[0014] Secondly, the present invention provides a method for preparing the above-mentioned cement-modified activated carbon composite cementitious material, comprising the following steps:

[0015] S1: The coffee skins are carbonized under anaerobic conditions to obtain activated carbon; in this step, the coffee skins are converted into activated carbon after carbonization.

[0016] S2: Activated carbon is mixed with an activating agent, and then the mixture is heated and activated under anaerobic conditions to obtain modified activated carbon. Since the performance of the activated carbon is insufficient, this step further modifies the activated carbon using a modifier and heating. This modification process enriches the pore structure and functional groups on the surface of the activated carbon.

[0017] S3: Grind the modified activated carbon to obtain modified activated carbon powder;

[0018] S4: The modified activated carbon powder is mixed with cement to obtain a cement-modified activated carbon composite cementitious material; wherein, by mass fraction, the modified activated carbon powder accounts for 40-60% of the cement-modified activated carbon composite cementitious material. More preferably, the modified activated carbon powder accounts for 50-60% of the composite cementitious material. In this step, the proportion of modified activated carbon powder in the composite cementitious material directly affects the adsorption and binding capacity of the composite cementitious material for chloride ions. When the modified activated carbon powder accounts for less than 40% of the total amount of the composite cementitious material, the adsorption and binding capacity of the composite cementitious material for chloride ions will be significantly reduced. In addition, maintaining the modified activated carbon powder at 40-60% of the composite cementitious material can also enable the composite cementitious material to have better mechanical properties. If the proportion of modified activated carbon powder exceeds 60%, the composite cementitious material will be difficult to maintain its shape.

[0019] In the preparation method described above, preferably, in step S1, the temperature is increased to 400-450 ℃ at a rate of 5-10 ℃ / min under anaerobic conditions, held at that temperature for 30-40 min, and then cooled to room temperature.

[0020] In the preparation method described above, preferably, in step S2, the activator is potassium hydroxide or sodium hydroxide; the mass ratio of the activator to activated carbon is 2:1-4:1, preferably 3:1.

[0021] In the preparation method described above, preferably, in step S2, the temperature is increased to 450-550 ℃ at a heating rate of 5-10 ℃ / min under anaerobic conditions, and held for 50-60 min.

[0022] In the preparation method described above, preferably, in step S2, after mixing the activator and activated carbon, deionized water is added and stirred evenly; the solid-liquid ratio of the activator and activated carbon to the deionized water is 1:2-1:3, preferably 1:2.

[0023] In the preparation method described above, preferably, in step S3, the modified activated carbon is ground and passed through a 50-200 mesh sieve to obtain modified activated carbon powder, which can be sealed in a desiccator for later use.

[0024] In the preparation method described above, preferably, before step S1, the coffee skins are washed with deionized water to remove dust and other impurities from their surface, and then dried at 85-105 °C; after step S2 and before step S3, the modified activated carbon is also washed with deionized water, specifically until the pH is 6-7, and then dried at 85-105 °C.

[0025] Thirdly, the present invention also provides a corrosion-resistant concrete, comprising the above-mentioned cement-modified activated carbon composite cementitious material or the cement-modified activated carbon composite cementitious material prepared by the above-mentioned preparation method.

[0026] Coffee is one of the world's three major non-alcoholic beverages and holds an important position in the market. In recent years, coffee consumption has grown rapidly, with consumption increasing year by year. During coffee production, coffee husks are typically disposed of through incineration or landfill, without effective recycling. This method not only increases manpower and material resources and wastes resources but also causes environmental pollution. This invention uses coffee husks as raw material to prepare modified activated carbon, making full use of waste biological resources. Compared with non-renewable materials such as commercial activated carbon, this invention uses coffee husks as raw material, which is inexpensive, readily available, economical, and environmentally friendly, achieving solid waste utilization.

[0027] This invention partially replaces cement with modified activated carbon to obtain a composite cementitious material used in building materials. It exhibits good and sustained corrosion resistance in seawater environments with high chloride ion concentrations, effectively addressing problems such as concrete cracking and steel reinforcement corrosion caused by seawater infiltration in marine environments. When this cement-modified activated carbon composite cementitious material is added to concrete, it achieves both physical and chemical adsorption of chloride ions from seawater, maintaining the strength and durability of the concrete and thus reducing the corrosion of steel reinforcement by chloride ions in seawater. The principles of physical and chemical adsorption of chloride ions by the cement-modified activated carbon composite cementitious material in this invention are as follows:

[0028] First, after modification, the surface of the modified activated carbon of this invention is loose and porous, possessing a rich pore structure and numerous functional groups, such as hydroxyl groups, amino groups, and acidic oxides. Chloride ions in seawater can combine with the functional groups in the pores and on the pore walls of the modified activated carbon to form hydrogen bonds or ionic bonds, thereby being effectively adsorbed.

[0029] Secondly, in this invention, the modified activated carbon can store free water through its rich pore structure. After the initial cement hydration is completed, the free water stored in the pore structure can flow out in small amounts continuously, further promoting the cement hydration reaction, and continuously producing monosulfide sulfoaluminate and hydrated calcium silicate during the hydration reaction.

[0030] Monosulfoaluminates are layered dioxin compounds with positive charges between the layers. Additionally, OH groups generated during cement hydration exist between the two layers of monosulfoaluminates. - and SO4 2- and / or CO3 2- Chloride ions in seawater, as anions, can combine between two positively charged layers and also react with OH groups in the interlayer. - and SO4 2- and / or CO3 2- Anions are exchanged.

[0031] Calcium silicate hydrate is a medium with numerous capillary and mesopore structures. Chloride ions in seawater can be partially blocked by calcium silicate hydrate, preventing them from penetrating into the concrete and contacting the reinforcing steel. In addition to its blocking effect, calcium silicate hydrate can also adsorb chloride ions through chemical adsorption, interlayer adsorption, and the tight bonding of its crystal lattice.

[0032] Through the combined effect of the above factors, the composite cementitious material of the present invention can continuously adsorb water through the rich pore structure of modified activated carbon, promote the continuous hydration of cement, and continuously and stably combine or adsorb monosulfide sulfoaluminate and hydrated calcium silicate produced by cement hydration with chloride ions, so that the concrete has high strength and good durability, effectively reduces the corrosion of steel bars by chloride ions in seawater, and ensures that the corrosion resistance effect is effective and stable for a long time.

[0033] (III) Beneficial Effects

[0034] The modified activated carbon in the composite cementitious material of this invention uses coffee husks as raw material, making full use of waste biological resources, which is low-cost, economical and environmentally friendly, and realizes the utilization of solid waste.

[0035] This invention uses modified activated carbon to partially replace cement, resulting in a composite cementitious material that exhibits good corrosion resistance in seawater environments with high chloride ion concentrations. This material can solve the problems of concrete cracking and steel corrosion caused by seawater infiltration in marine environments.

[0036] The modified activated carbon of this invention has a loose and porous surface with abundant pore structure and a large number of functional groups, such as hydroxyl groups, amino groups, and acidic oxides. Chloride ions in seawater can combine with the functional groups in the pores and on the pore walls of the modified activated carbon to form hydrogen bonds or ionic bonds, thereby being effectively adsorbed.

[0037] In this invention, the modified activated carbon mixed with cement can store free water through its abundant pore structure. After the initial hydration is completed, the free water stored in the pore structure can continuously flow out in small amounts, further promoting the hydration reaction of cement, and continuously producing monosulfide sulfoaluminate and hydrated calcium silicate during the hydration reaction. Monosulfide sulfoaluminate is a layered dioxin compound with a positive charge between the layers. In addition, OH groups generated during cement hydration also exist between the two layers of monosulfide sulfoaluminate. - and SO4 2- and / or CO3 2- Chloride ions in seawater, as anions, can combine between two positively charged layers and also react with OH groups in the interlayer. - and SO4 2- and / or CO3 2-Anion exchange occurs. Calcium silicate hydrate is a medium with numerous capillary and mesopores. Chloride ions in seawater can be partially blocked by calcium silicate hydrate, preventing them from penetrating into the concrete and contacting the reinforcing steel. Furthermore, calcium silicate hydrate can also adsorb chloride ions through chemical adsorption, interlayer adsorption, and the tight bonding of the crystal lattice. Therefore, the composite cementitious material of this invention can continuously adsorb water through the rich pore structure of modified activated carbon, promoting continuous cement hydration. The monosulfide sulfoaluminate and calcium silicate hydrate produced during cement hydration continuously and stably bind to or adsorb chloride ions. Attached Figure Description

[0038] Figure 1 This is a flowchart illustrating the preparation process of the cement-modified activated carbon composite cementitious material in this invention.

[0039] Figure 2 The adsorption-desorption curves are shown for the coffee skins and the modified activated carbon prepared in Example 1.

[0040] Figure 3 The image shows the TG-DTG curve obtained from the combustion of coffee skins under a nitrogen atmosphere.

[0041] Figure 4 The images show the FTIR spectra of the cement-modified activated carbon composite cementitious materials prepared in Example 1 and Comparative Example 1 before and after chloride ion adsorption. Detailed Implementation

[0042] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to specific embodiments.

[0043] Example 1

[0044] This embodiment provides a method for preparing a cement-modified activated carbon composite cementitious material, comprising the following steps:

[0045] S1: Rinse the coffee skins (coffee shells) with deionized water, and then dry them in a drying oven at 105 ℃ for 12 hours.

[0046] S2: Place the dried coffee skins into a muffle furnace and heat them to 400 ℃ in an anaerobic environment at a heating rate of 10 ℃ / min. Carbonize for 30 min to obtain activated carbon.

[0047] S3: Potassium hydroxide and activated carbon were mixed at a mass ratio of 3:1, and then deionized water was added at a solid-liquid ratio of 1:2. After stirring evenly, the mixture was heated to 450 °C at a heating rate of 10 °C / min under anaerobic conditions for 60 min to obtain modified activated carbon. The modified activated carbon was then washed by vacuum filtration with water until the pH of the washing solution reached 6, and then dried in an oven.

[0048] S4: After drying, the modified activated carbon is crushed in a pulverizer and then passed through a 200-mesh sieve. The resulting modified activated carbon powder (MAC) is collected in a sealed container.

[0049] S5: Weigh the sieved modified activated carbon powder and pour it into a mixing pot for later use. Then weigh the cement and pour it into the mixing pot for dry mixing to obtain cement-modified activated carbon composite cementitious material. The mass ratio of modified activated carbon powder in the cement-modified activated carbon composite cementitious material is 60%.

[0050] Example 2

[0051] This embodiment provides a method for preparing a cement-modified activated carbon composite cementitious material, comprising the following steps:

[0052] S1: Rinse the coffee skins with deionized water, then dry them in a 90°C oven for 12 hours.

[0053] S2: Place the dried coffee skins into a muffle oven and heat them to 450 ℃ in an anaerobic environment at a heating rate of 5 ℃ / min. Carbonize for 40 min to obtain activated carbon.

[0054] S3: Potassium hydroxide and activated carbon were mixed at a mass ratio of 4:1, and then deionized water was added at a solid-liquid ratio of 1:3. After stirring evenly, the mixture was heated to 550 °C at a heating rate of 8 °C / min under anaerobic conditions for 50 min to obtain modified activated carbon. The modified activated carbon was then washed by vacuum filtration with water until the pH of the washing solution reached 7, and then dried in an oven.

[0055] S4: After drying, the modified activated carbon is crushed in a pulverizer and then passed through a 150-mesh sieve. The resulting modified activated carbon powder (MAC) is collected in a sealed container.

[0056] S5: Weigh the sieved modified activated carbon powder and pour it into a mixing pot for later use. Then weigh the cement and pour it into the mixing pot for dry mixing to obtain cement-modified activated carbon composite cementitious material. The mass ratio of modified activated carbon powder in the cement-modified activated carbon composite cementitious material is 40%.

[0057] Example 3

[0058] This embodiment provides a method for preparing a cement-modified activated carbon composite cementitious material, comprising the following steps:

[0059] S1: Rinse the coffee skins with deionized water, then dry them in an 85°C oven for 12 hours.

[0060] S2: Place the dried coffee skins into a muffle furnace and heat them to 420 ℃ in an anaerobic environment at a heating rate of 8 ℃ / min. Carbonize for 35 min to obtain activated carbon.

[0061] S3: Mix potassium hydroxide and activated carbon at a mass ratio of 2:1, then add deionized water at a solid-liquid ratio of 1:2.5. After stirring evenly, heat the mixture to 500 °C at a heating rate of 5 °C / min under anaerobic conditions for 55 min to obtain modified activated carbon. Wash the modified activated carbon with water using a circulating vacuum pump until the pH of the washing solution reaches 6.5, then dry it in an oven.

[0062] S4: After drying, the modified activated carbon is crushed in a pulverizer and then passed through a 50-mesh sieve. The resulting modified activated carbon powder (MAC) is collected in a sealed container.

[0063] S5: Weigh the sieved modified activated carbon powder and pour it into a mixing pot for later use. Then weigh the cement and pour it into the mixing pot for dry mixing to obtain cement-modified activated carbon composite cementitious material. The mass ratio of modified activated carbon powder in the cement-modified activated carbon composite cementitious material is 50%.

[0064] Example 4

[0065] This embodiment provides a method for preparing a cement-modified activated carbon composite cementitious material, a method for preparing a composite cementitious material. The difference from Embodiment 1 is that the mass ratio of thermally modified activated carbon powder in the cement-modified activated carbon composite cementitious material is 55%.

[0066] Comparative Example 1

[0067] The difference between Comparative Example 1 and Example 1 is that the mass ratio of modified activated carbon powder in the composite cementitious material is 0%.

[0068] Comparative Example 2

[0069] The difference between this comparative example and Example 1 is that the mass ratio of modified activated carbon powder in the cement-modified activated carbon composite cementitious material is 20%.

[0070] Performance testing:

[0071] Sodium chloride was added to the cement-modified activated carbon composite cementitious materials prepared in Examples 1-4 and Comparative Examples 1-2, respectively. After thorough mixing, deionized water was added to the mixed powder. The mixture was stirred slowly for 2 minutes, then quickly for 2 minutes. After thorough mixing, specimens measuring 25 mm × 25 mm × 25 mm were prepared. The specimens were demolded the next day and cured in a standard curing room for 28 days. In the raw materials of the above specimens, the mass ratio of deionized water to cement-modified activated carbon composite cementitious material was w / c = 0.5 (water-cement ratio). For every 100 ml of deionized water added, the corresponding mass of sodium chloride added was 32.12 g. Chloride ions were incorporated into the specimens through the above operation. The concentration of added sodium chloride was approximately 321200 mg / L, which is much higher than the chloride ion concentration in seawater.

[0072] Using deionized water as the extractant, this study simulates the immersion of a building in water under specific conditions, where unfixed chloride ions may leach out and enter the deionized water. Specifically, the cured specimen was immersed entirely in deionized water, and after standing for 72 hours, the immersion solution was collected and the chloride ion concentration in the solution was measured.

[0073] Specifically, take 100 ml of the soaking solution sample and place it in an Erlenmeyer flask. Add 5 drops of potassium chromate indicator and titrate with silver nitrate standard solution until a brick-red potassium chromate precipitate is formed in the solution. Record the volume consumed. (Note: To avoid the chloride ion content being too high and affecting the experimental results, the soaking solution sample can be diluted to a certain extent during the detection process.)

[0074] The adsorption effect of the composite cementitious materials in each embodiment and comparative example on chloride ions, that is, the concentration of chloride ions adsorbed on the composite cementitious materials, is calculated by subtracting the chloride ion concentration detected in the soaking solution sample from the initial chloride ion concentration.

[0075] Following the steps described above, deionized water and soaking solution were used as samples for testing. The deionized water group served as the blank control group, and the soaking solution group served as the experimental group. The volumes of reagents consumed in the blank control group and the experimental group were recorded.

[0076] The formulas for calculating the chloride ion content in each experimental group are as follows:

[0077]

[0078] η

[0079] In the formula C clC1 is the chloride ion content in the soaking solution, in mg / L; C2 is the concentration of silver nitrate standard solution (0.03 mol / L), in mol / L; V1 is the volume of silver nitrate standard solution consumed in the blank experiment, in mL; V2 is the volume of silver nitrate standard solution consumed in the experimental group, in mL; V is the volume of the soaking solution, in mL; 35.45 is the molar mass of chloride ions, in g / mol; C0 is the initial concentration of chloride ions in the solution, in mg / L; C e The equilibrium mass concentration of chloride ions in the solution is given in mg / L. The adsorption rates of chloride ions are shown in Table 1.

[0080] Table 1. Statistical table of adsorption rates of internally doped chloride ions for specimens in each embodiment and comparative example.

[0081]

[0082] As shown in Table 1, the cement-modified activated carbon composite cementitious materials of Examples 1-4 have a good adsorption effect on chloride ions, and can fix more than 96% of the chloride ions in the specimens. This indicates that the addition of modified activated carbon and the proportion of modified activated carbon in the composite cementitious material directly affect the adsorption effect of chloride ions.

[0083] In reality, the chloride ion concentration in seawater exhibits a stepped distribution, making it impossible to simulate. Furthermore, if a specimen without chloride ions is placed in a sodium chloride solution to adsorb chloride ions, it becomes difficult to determine when the specimen reaches adsorption equilibrium, hindering performance testing. Therefore, during testing, a high concentration of sodium chloride is incorporated into the specimen, which is then immersed in deionized water. The degree of chloride ion leaching is then examined to determine the specimen's chloride ion fixation capacity.

[0084] In addition, the specimens prepared by adding chloride ions to the composite cementitious materials of each embodiment and comparative example were further placed in sodium chloride solution and soaked for 72 h. The concentration of chloride ions remaining in the sodium chloride solution was detected, and the adsorption rate of chloride ions in the solution by each specimen was calculated. The specific data are shown in Table 2.

[0085] The concentration of the sodium chloride solution was 321200 mg / L (i.e., 32.12 g of sodium chloride was added to 100 g of water). In addition, the mass ratio of the composite cementitious material to the sodium chloride in the sodium chloride solution in the specimen was 200:32.12.

[0086] Table 2. Statistical table of adsorption rates of chloride ion solutions on specimens of each embodiment and comparative example.

[0087]

[0088] As shown in Table 2, the specimens of Examples 1-4 can not only fix more than 96% of the internally incorporated chloride ions, but also further adsorb chloride ions in the sodium chloride solution. Moreover, the adsorption capacity is much higher than that of Comparative Example 1 and Comparative Example 2. This indicates that the cement-modified activated carbon composite cementitious material of Examples 1-4 has good and continuous corrosion resistance to chloride ions, and can prevent chloride ions from causing concrete cracking and prevent steel corrosion.

[0089] Figure 2 The adsorption-desorption curves of the coffee bark used in Example 1 and the modified activated carbon prepared therefrom are shown below. Figure 2 It can be seen that the adsorption curve and desorption curve of coffee skin are significantly different, and the fluctuations of the adsorption and desorption curves are large. The adsorption curve and desorption curve of modified activated carbon are closer. Compared with coffee skin, the adsorption performance of the modified activated carbon prepared is more stable.

[0090] In addition, the appropriate carbon ratio was determined using a PerKinELmer STA 8000 synchronous thermal analyzer from the United States, and the surface functional groups of the composite cementitious materials obtained in Example 1 and Comparative Example 1 were tested using a Nicolet iS 10 Fourier transform infrared spectrometer.

[0091] TG-DTG Analysis:

[0092] In a nitrogen atmosphere, at 15 °C·min -1 The heating rate burns the coffee skins to obtain Figure 3 The TG-DTG curves shown are illustrated, where the TG curve represents the relationship between coffee skin weight and temperature, and the DTG curve is obtained by differentiating the TG curve with respect to time. Figure 3 It can be seen that the combustion of coffee skin can be divided into three stages: the first stage (<200 ℃) is the moisture evaporation stage, the second stage (200 ℃-400 ℃) is the combustion stage, and the third stage (>400 ℃) is the burnout and stabilization stage. The third stage is the burning of residual ash.

[0093] In the DTG curve, there is one weight loss peak representing moisture evaporation in stage I, three weight loss peaks in stage II, and a stable state in stage III. Therefore, activated carbon obtained by roasting coffee skins at 400℃-450℃ exhibits the best performance.

[0094] Fourier transform infrared spectroscopy (FTIR) analysis:

[0095] The surface functional groups of the composite cementitious materials obtained in Example 1 and Comparative Example 1 were tested using a Nicolet iS 10 Fourier transform infrared spectroscopy analyzer. Additionally, the surface functional groups of the composite cementitious materials obtained in Example 1 and Comparative Example 1 after adsorbing chloride ions were also tested. Figure 4.

[0096] pass Figure 4 It can be seen that the composite cementitious materials are all within 3432 cm. -1 An absorption peak for the -OH stretching vibration appeared nearby; at 1420 cm⁻¹ -1 An in-plane bending vibration absorption peak appeared at 1619 cm⁻¹; -1 The presence of a C=O stretching vibration absorption peak indicates that the composite cementitious materials all possess oxygen-containing functional groups such as carboxylic acid, carbonyl, and hydroxyl groups, and are capable of chemically reacting with chloride ions. For example, the hydroxyl groups on the surface of activated carbon react with chloride ions to form chlorides. The aforementioned peak is enhanced in the composite cementitious material with 60% modified activated carbon content, due to the abundance of functional groups in the modified activated carbon itself. However, after chloride ion adsorption, the absorption peak weakens again, as shown in the MAC (60%)-Cl curve, because the functional groups react with chloride ions to form chlorides.

[0097] As can be seen from the above, the abundant functional groups contained in modified activated carbon can combine with chloride ions and thus be effectively adsorbed.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. The application of a cement-modified activated carbon composite cementitious material in the adsorption of chloride ions in seawater, characterized in that, The cement-modified activated carbon composite cementitious material includes cement and modified activated carbon; by mass fraction, the cement-modified activated carbon composite cementitious material includes 40-60% modified activated carbon; The modified activated carbon is prepared by carbonizing coffee husks, mixing them with an activating agent, and then heating and activating them. The cement-modified activated carbon composite cementitious material is prepared by the following steps: S1: Activated carbon is obtained by carbonizing coffee skins under anaerobic conditions; S2: Activated carbon and activator are mixed, and then the mixture is heated and activated under anaerobic conditions to obtain modified activated carbon; the mass ratio of activator to activated carbon is 2:1-4:

1. S3: Grind the modified activated carbon to obtain modified activated carbon powder; S4: Modified activated carbon powder is mixed with cement to obtain cement-modified activated carbon composite cementitious material; wherein, by mass fraction, modified activated carbon powder accounts for 40-60% of the cement-modified activated carbon composite cementitious material; In step S1, the temperature is increased to 400-450 ℃ at a rate of 5-10 ℃ / min under anaerobic conditions, and held for 30-40 min. The activator is potassium hydroxide or sodium hydroxide; In step S2, the temperature is increased to 450-550 ℃ at a heating rate of 5-10 ℃ / min under anaerobic conditions, and held for 50-60 min. The cement-modified activated carbon composite cementitious material is used in coastal building materials. It is used to adsorb chloride ions in seawater to reduce the corrosion of steel bars by chloride ions in seawater.

2. The application according to claim 1, characterized in that, Based on mass fraction, cement-modified activated carbon composite gel materials contain 50-60% modified activated carbon.

3. The application according to claim 1, characterized in that, In step S2, after mixing the activator and activated carbon, deionized water is added and stirred evenly; the solid-liquid ratio of the activator and activated carbon to the deionized water is 1:2-1:

3.

4. The application according to claim 1, characterized in that, In step S3, the modified activated carbon is ground and passed through a 50-200 mesh sieve to obtain modified activated carbon powder.

5. The application according to claim 1, characterized in that, Before step S1, the coffee husks are washed and dried; after step S2 and before step S3, the modified activated carbon is also washed and then dried.

6. The application of corrosion-resistant concrete in adsorbing chloride ions from seawater, characterized in that, The corrosion-resistant concrete includes the cement-modified activated carbon composite cementitious material as described in any one of claims 1-5.

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