A chelating carbonation method for improving the cementitious activity and stability of steel slag

Abstract

The application discloses a chelation carbonation method for improving cementitious activity and stability of steel slag, and relates to the cross technical field of solid waste resource utilization and CO2 capture, utilization and storage. The method comprises the following steps: mixing organic amine with water to obtain an organic amine absorption solution; introducing CO2 gas into the organic amine absorption solution, and then adding a dispersing agent to obtain a carbon-loaded organic amine solution; adding steel slag to be treated into the carbon-loaded organic amine solution to perform a chelation carbonation reaction, and obtaining a chelation carbonation modified steel slag slurry. The application is based on the double mechanism of chelation of organic amine and calcium, magnesium and other metal ions, which promotes the dissolution of steel slag and the precipitation of carbonation induced products, and significantly improves the cementitious activity and stability of the steel slag. The steel slag treated by the chelation carbonation method can be used as an auxiliary cementitious material, realizes the resource utilization of the steel slag, and promotes the low-carbon and sustainable development of building materials.

Description

Technical Field

[0001] This invention relates to the field of cross-technical technology of solid waste resource utilization and CO2 capture, utilization and storage, and in particular to a chelation carbonation method for improving the cementitious activity and stability of steel slag. Background Technology

[0002] Steel slag is a major industrial byproduct generated during the iron and steel smelting process. However, due to the high proportion of free calcium oxide (f-CaO) and free magnesium oxide (f-MgO) in steel slag, it suffers from poor volume stability, poor grindability, and low hydration activity, resulting in a comprehensive utilization rate of less than 30%. The accumulation of large amounts of steel slag not only occupies land resources but also poses a potential threat to the ecological environment.

[0003] Using steel slag powder as an auxiliary cementitious material to partially replace cement is currently the main resource utilization approach. However, the hydration expansion problem of f-CaO and f-MgO severely restricts their dosage in cement. On the other hand, the abundant calcium and magnesium components in steel slag give it good CO2 mineralization potential. Carbonation treatment can fix CO2 while consuming f-CaO and f-MgO to generate carbonate products, thereby improving the volume stability and cementitious activity of steel slag. However, existing wet carbonation technologies suffer from problems such as low steel slag reactivity, slow calcium and magnesium ion leaching rates, and excessive deposition of carbonate products on the steel slag surface forming a passivation layer that leads to reaction stagnation. Therefore, it is essential to develop new carbonation methods that can efficiently improve the cementitious activity and stability of steel slag. Summary of the Invention

[0004] The purpose of this invention is to provide a chelation carbonation method for improving the cementitious activity and stability of steel slag, thereby solving problems such as slow ion leaching rate, easy surface passivation, and insufficient activation of cementitious activity in the existing steel slag carbonation process. The method of this invention is a steel slag activation and modification method based on the synergistic effect of organic amine chelation and carbonation, utilizing organic amines with specific structures to chelate and carbonate Ca... 2+ Mg 2+ The cyclic chelation effect promotes the dissolution of active components in steel slag and regulates the carbonation reaction process, thereby significantly improving the cementitious activity and volume stability of steel slag while achieving efficient CO2 fixation.

[0005] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of the present invention: a chelation carbonation method for improving the cementitious activity and stability of steel slag, comprising the following steps: Organic amines are mixed with water to obtain an organic amine absorbent; CO2 gas is introduced into the organic amine absorbent, and then a dispersant is added to obtain a carbon-supported organic amine solution. The steel slag to be treated is added to the carbon-supported organic amine solution to carry out a chelation and carbonation reaction, thereby obtaining a chelated and carbonated modified steel slag slurry.

[0006] The technical principle of this invention is as follows: This invention is based on the principle of coordination chemistry, coupling the chelation of organic amines with the carbonation process of steel slag: the selected organic amine (specifically a polynitrogen organic amine) reacts with the Ca released from the dissolution of steel slag through the lone pair electrons of its nitrogen atom. 2+ Mg 2+ The formation of five- or six-membered cyclic chelates lowers the activation energy for ion dissolution, significantly increasing the leaching rate of calcium and magnesium ions and providing a sufficient ion source for the carbonation reaction. Furthermore, when chelated ions react with CO2, organic amines act as ligands to regulate carbonate nucleation and growth, preventing the formation of a dense passivation layer on the steel slag surface. They also alter charge properties through surface adsorption, inhibiting excessive product deposition and maintaining the activity of the reaction interface. Simultaneously, the added dispersant improves the dispersibility of the steel slag, increases the reaction contact area, and synergistically promotes the dissolution of calcium and magnesium ions and the carbonation reaction with the organic amines. Through this multi-effect synergy of chelation, carbonation, and dispersion, this invention achieves efficient CO2 fixation while significantly consuming f-CaO and f-MgO in the steel slag, effectively stimulating their gelling activity and laying the foundation for the high-volume application of steel slag in cement-based materials.

[0007] Furthermore, the organic amine includes one or more of N-(2-hydroxyethyl)ethylenediamine (AEEA), N,N'-bis(2-hydroxyethyl)ethylenediamine (BHEEA), and diethylenetriaminepentaacetic acid (DTPA).

[0008] The aforementioned organic amines contain polyamino or hydroxyamino groups in their molecular structure, enabling them to react with metal ions (Ca). 2+ Mg 2+ Compounds that form five-membered or six-membered ring chelate structures.

[0009] Preferably, the organic amine is N-(2-hydroxyethyl)ethylenediamine (AEEA) or N,N'-bis(2-hydroxyethyl)ethylenediamine (BHEEA), in which the nitrogen atom in its molecular structure can coordinate with the metal ion to form a stable five-membered chelate ring.

[0010] Further, the mass of the organic amine (i.e., the mass of the organic amine used to prepare the carbon-supported organic amine solution) is 0.01-0.05% of the mass of the steel slag to be treated, preferably 0.02%.

[0011] Further, introducing CO2 gas into the organic amine absorbent includes: introducing CO2 gas into the organic amine absorbent until the CO2 absorption amount is 0.1-2.0% of the mass of the steel slag to be treated, preferably 0.88%.

[0012] Furthermore, the process of introducing CO2 gas into the organic amine absorption liquid is carried out under stirring conditions of 20-60 ℃ and 100-500 rpm, that is, the temperature of the absorption reaction is 20-60 ℃ and the rotation speed is 100-500 rpm.

[0013] Preferably, the process of introducing CO2 gas into the organic amine absorption liquid is carried out under stirring conditions of 40 °C and 300 rpm.

[0014] Furthermore, the dispersant includes one or more of polycarboxylate superplasticizers, naphthalene sulfonate superplasticizers, lignin sulfonate, and polyethylene glycol.

[0015] Further, the mass of the dispersant is 0.05-0.3% of the mass of the steel slag to be treated, preferably 0.1%.

[0016] Furthermore, the ratio of the mass of the water (i.e. the mass of the water used to prepare the organic amine absorbent) to the mass of the steel slag to be treated is 0.8-2:1.

[0017] Furthermore, the conditions for the chelation carbonation reaction include: a reaction temperature of 15-50 °C, a stirring rate of 100-400 rpm, and a reaction time of 0.5-3.0 h.

[0018] Preferably, the conditions for the chelation carbonation reaction include: a reaction temperature of 30 °C, a stirring rate of 200 rpm, and a reaction time of 1.0 h.

[0019] The second technical solution of the present invention: a chelated carbonation modified steel slag slurry prepared by the chelation carbonation method described above for improving the cementitious activity and stability of steel slag.

[0020] The third technical solution of the present invention: the application of the above-mentioned chelated carbonic acid modified steel slag slurry in the preparation of cement-based materials.

[0021] Furthermore, the steel slag contained in the chelated carbonated modified steel slag slurry serves as an auxiliary cementitious material, replacing 10-40 wt% of cement in the cement-based material.

[0022] Preferably, the steel slag contained in the chelated carbonated modified steel slag slurry is used as an auxiliary cementitious material to replace 30 wt% of cement in the cement-based material.

[0023] Furthermore, the water-cement ratio of the cement-based material (i.e., the sum of the mass of steel slag and the mass of cement contained in the chelated carbonic acid modified steel slag slurry: the mass of water) is 0.3-0.6, preferably 0.5.

[0024] This invention significantly enhances the cementitious activity and stability of steel slag through a dual mechanism: the chelation of organic amines with metal ions such as calcium and magnesium promotes steel slag dissolution, while carbonation induces product precipitation. The chelated and carbonated steel slag can then be used as an auxiliary cementitious material, realizing the resource utilization of steel slag and promoting the low-carbon and sustainable development of building materials.

[0025] Moreover, this invention uses the carbon-loaded organic amine solution after absorbing CO2 to modify steel slag, which also solves the problem of high energy consumption in the thermal desorption and regeneration process of traditional organic amine CO2 capture technology, and expands the industrial application of organic amine CO2 capture technology.

[0026] The present invention discloses the following technical effects: This invention promotes the dissolution of calcium and magnesium ions through the cyclic chelation of organic amines, significantly improving the carbonation reaction rate and carbon fixation efficiency of steel slag, thus achieving efficient carbon fixation. The cementitious activity of steel slag treated by this invention is significantly enhanced, and when used as an auxiliary cementitious material to replace cement, the early strength of cement mortar is significantly improved. The chelation carbonation treatment effectively consumes f-CaO and f-MgO in steel slag, significantly improving volume stability and greatly reducing expansion value. Detailed Implementation

[0027] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0028] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0029] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0030] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0031] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0032] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0033] In the following embodiments, comparative examples and test examples of the present invention, if room temperature is involved, it specifically refers to 20-30°C.

[0034] Unless otherwise specified, all raw materials used in the following embodiments, comparative examples and test examples of this invention are commercially available products. Among them, the content of f-CaO in the steel slag to be treated is 2.75wt%, and the content of f-MgO is 3.8wt%; the polycarboxylate superplasticizer is model HZ-P1 with a solid content of 40wt%; and the cement is P·O 42.5 ordinary Portland cement.

[0035] Example 1 A chelation carbonation method for improving the cementitious activity and stability of steel slag includes the following steps: Preparation of carbon-supported organic amine solution: N-(2-hydroxyethyl)ethylenediamine (AEEA) at 0.02% of the mass of the steel slag to be treated was added to deionized water (the mass ratio of deionized water to the steel slag to be treated was 1:1) to prepare an organic amine absorbent. CO2 gas was introduced into the organic amine absorbent at 40 °C and 300 rpm, controlling the CO2 absorption rate to be 0.88% of the mass of the steel slag to be treated. Then, polycarboxylate superplasticizer at 0.10% of the mass of the steel slag to be treated was added to the organic amine absorbent, and the mixture was stirred until homogeneous to obtain a carbon-supported organic amine solution.

[0036] Chelating and carbonation modification of steel slag: The steel slag to be treated, after passing through a 200-mesh sieve, was added to the carbon-supported organic amine solution prepared above. The mixture was placed in a reaction vessel and subjected to a chelation-carbonation reaction for 1.0 h under stirring conditions of 30 ℃ and 200 rpm. After the reaction was completed, a chelated-carbonated modified steel slag slurry was obtained.

[0037] Application of chelated carbonic acid modified steel slag slurry in cement-based materials: The chelated carbonic acid modified steel slag slurry prepared above was mixed with cement and standard sand. The mass ratio of steel slag to cement in the chelated carbonic acid modified steel slag slurry was 3:7, and the mass of standard sand was three times the sum of the mass of steel slag and cement in the chelated carbonic acid modified steel slag slurry. Water was then added to control the water-cement ratio at 0.5, and the mixture was stirred evenly to obtain mortar. The mortar was then molded and cured according to the requirements of standard GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)" to obtain test mortar specimens, which were denoted as S1 (both the mortar obtained after stirring and the mortar specimens obtained after molding and curing were denoted as S1).

[0038] Example 2 Same as Example 1, except that AEEA is replaced with N,N'-bis(2-hydroxyethyl)ethylenediamine (BHEEA). The test mortar specimen obtained in this example is designated as S2.

[0039] Example 3 Same as Example 1, except that AEEA is replaced by diethylenetriaminepentaacetic acid (DTPA) at the same mass. The test mortar specimen obtained in this example is designated as S3.

[0040] Example 4 Same as Example 1, except that the CO2 absorption is controlled at 1.32% of the mass of the steel slag to be treated. The test mortar specimen obtained in this example is designated as S4.

[0041] Example 5 Same as Example 1, except that the CO2 absorption is controlled at 1.32% of the mass of the steel slag to be treated, and the amount of polycarboxylate superplasticizer added is adjusted to 0.15% of the mass of the steel slag to be treated. The test mortar specimen obtained in this example is designated as S5.

[0042] Comparative Example 1 Chelating and carbonation modification of steel slag: The steel slag to be treated, which has passed through a 200-mesh sieve, 0.02% (by weight) of AEEA (by weight of the steel slag to be treated), and 0.10% (by weight) of polycarboxylate superplasticizer (by weight of the steel slag to be treated) were added to deionized water (the mass ratio of deionized water to steel slag to be treated was 1:1). CO2 gas was introduced into the mixture under stirring conditions of 30 ℃ and 200 rpm, controlling the CO2 absorption to be 0.88% of the mass of the steel slag to be treated, and the chelation carbonation reaction was carried out for 1.0 h (the chelation carbonation reaction was carried out simultaneously with the introduction of CO2, i.e., the CO2 absorption was controlled to be 0.88% during the 1 h chelation carbonation reaction). After the reaction was completed, a chelated carbonation modified steel slag slurry was obtained.

[0043] Application of chelated carbonic acid modified steel slag slurry in cement-based materials: The chelated carbonic acid modified steel slag slurry prepared above was mixed with cement and standard sand. The mass ratio of steel slag to cement in the chelated carbonic acid modified steel slag slurry was 3:7, and the mass of standard sand was three times the sum of the mass of steel slag and cement in the chelated carbonic acid modified steel slag slurry. Water was then added to control the water-cement ratio at 0.5, and the mixture was stirred evenly to obtain mortar. The mortar was then molded and cured according to the requirements of standard GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)" to obtain test mortar specimens, denoted as C1.

[0044] Comparative Example 2 Same as Example 1, except that no polycarboxylate superplasticizer was added to the carbon-supported organic amine solution. The test mortar specimen obtained in this comparative example is designated as C2.

[0045] Comparative Example 3 Preparation of carbon-supported organic amine solution: AEEA (0.02% by mass of the steel slag to be treated) was added to deionized water (the mass ratio of deionized water to the steel slag to be treated was 1:1) to prepare an organic amine absorbent. CO2 gas was introduced into the organic amine absorbent under stirring conditions of 40 ℃ and 300 rpm, controlling the CO2 absorption rate to be 0.88% of the mass of the steel slag to be treated, thus obtaining a carbon-loaded organic amine solution.

[0046] Chelating and carbonation modification of steel slag: The steel slag to be treated, after passing through a 200-mesh sieve, was added to the carbon-supported organic amine solution prepared above. The mixture was placed in a reaction vessel and subjected to a chelation-carbonation reaction for 1.0 h under stirring conditions of 30 ℃ and 200 rpm. After the reaction was completed, a chelated-carbonated modified steel slag slurry was obtained.

[0047] Application of chelated carbonic acid modified steel slag slurry in cement-based materials: The chelated carbonic acid modified steel slag slurry prepared above was mixed with cement, polycarboxylate superplasticizer (0.10% by weight of the steel slag in the chelated carbonic acid modified steel slag slurry), and standard sand. The mass ratio of steel slag to cement in the chelated carbonic acid modified steel slag slurry was 3:7, and the mass of standard sand was three times the sum of the mass of steel slag and cement in the chelated carbonic acid modified steel slag slurry. Water was then added to control the water-cement ratio at 0.5, and the mixture was stirred evenly to obtain mortar. The mortar was then molded and cured according to the requirements of standard GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)" to obtain test mortar specimens, which were denoted as C3.

[0048] Comparative Example 4 Same as Example 1, except that AEEA was replaced by monoethanolamine (MEA) at the same mass. The test mortar specimen obtained in this comparative example is designated as C4.

[0049] Comparative Example 5 Steel slag that has passed through a 200-mesh sieve is mixed with deionized water (the mass ratio of steel slag to deionized water is 1:1). The mixture is placed in a reactor and stirred for 1.0 h at 30 ℃ and 200 rpm to obtain steel slag slurry.

[0050] The steel slag slurry prepared above was mixed with cement and standard sand, wherein the mass ratio of steel slag to cement in the slurry was 3:7, and the mass of standard sand was three times the sum of the mass of steel slag and cement in the slurry. Water was then added to control the water-cement ratio at 0.5, and the mixture was stirred evenly to obtain mortar. The mortar was then molded and cured according to the requirements of standard GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)" to obtain test mortar specimens, which were designated as C5 (untreated steel slag control group).

[0051] Test Example 1 The soundness of steel slag was tested using the boiling method, and the test method was carried out in accordance with the provisions of standard GB / T 1346 "Test Method for Standard Consistency Water Requirement, Setting Time and Soundness of Cement". The mortar obtained after uniform mixing in each example and comparative example was used as the raw material to be tested. The test results are shown in Table 1.

[0052] The 3-day compressive strength of mortar specimens obtained in each example and comparative example was tested according to standard GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)". The test results are shown in Table 2.

[0053] Table 1 As shown in Table 1, compared with the untreated steel slag control group (C5), the expansion values ​​of all steel slags modified by chelation and carbonation according to the method of this invention (Examples 1-5) were significantly reduced after being added to cement. This indicates that after treatment with the carbon-supported organic amine solution, the components in the steel slag that cause poor volume stability, such as f-CaO and f-MgO, were consumed, and the volume stability of the steel slag was effectively improved. Moreover, the expansion value of group S1, which adopted the process of "absorbing CO2 first and then reacting with steel slag", decreased by 3.10 mm, which was better than that of group C1, which adopted the process of "simultaneously introducing CO2 and reacting with steel slag". This shows that the "absorption first and then reaction" sequence in this invention is more conducive to the consumption of unstable components in steel slag.

[0054] Table 2 Table 2 shows that compared with the addition of untreated steel slag (C5), the 3-day compressive strength of the mortar was significantly improved after using chelated carbonation modified steel slag. Among them, group S1 performed the best, with a 3-day compressive strength increase of 7.48 MPa compared with group C5, verifying the positive effect of chelated carbonation steel slag in improving cement performance. Comparing S1 and C1, it can be seen that the 3-day strength of group S1 (21.86 MPa), which adopts the process of "absorbing CO2 first and then reacting with steel slag", is significantly higher than that of group C1 (18.76 MPa), which adopts the process of "simultaneously introducing CO2 and reacting with steel slag", further confirming the effectiveness of the process sequence of the present invention.

[0055] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A chelation carbonation method for improving the cementitious activity and stability of steel slag, characterized in that, Includes the following steps: Organic amines are mixed with water to obtain an organic amine absorbent; CO2 gas is introduced into the organic amine absorbent, and then a dispersant is added to obtain a carbon-supported organic amine solution. The steel slag to be treated is added to the carbon-supported organic amine solution to carry out a chelation and carbonation reaction, thereby obtaining a chelated and carbonated modified steel slag slurry.

2. The chelation carbonation method for improving the cementitious activity and stability of steel slag as described in claim 1, characterized in that, The organic amine includes one or more of N-(2-hydroxyethyl)ethylenediamine, N,N'-bis(2-hydroxyethyl)ethylenediamine, and diethylenetriaminepentaacetic acid.

3. The chelation carbonation method for improving the cementitious activity and stability of steel slag as described in claim 1, characterized in that, The mass of the organic amine is 0.01-0.05% of the mass of the steel slag to be treated.

4. The chelation carbonation method for improving the cementitious activity and stability of steel slag as described in claim 1, characterized in that, Introducing CO2 gas into the organic amine absorption liquid includes: introducing CO2 gas into the organic amine absorption liquid until the CO2 absorption amount is 0.1-2.0% of the mass of the steel slag to be treated.

5. The chelation carbonation method for improving the cementitious activity and stability of steel slag as described in claim 1, characterized in that, The dispersant includes one or more of polycarboxylate superplasticizers, naphthalene sulfonate superplasticizers, lignin sulfonate, and polyethylene glycol.

6. The chelation carbonation method for improving the cementitious activity and stability of steel slag as described in claim 1, characterized in that, The mass of the dispersant is 0.05-0.3% of the mass of the steel slag to be treated.

7. The chelation carbonation method for improving the cementitious activity and stability of steel slag as described in claim 1, characterized in that, The ratio of the mass of the water to the mass of the steel slag to be treated is 0.8-2:

1.

8. The chelation carbonation method for improving the cementitious activity and stability of steel slag as described in claim 1, characterized in that, The conditions for the chelation carbonation reaction include: a reaction temperature of 15-50 °C, a stirring rate of 100-400 rpm, and a reaction time of 0.5-3.0 h.

9. A chelated carbonation modified steel slag slurry prepared by the chelation carbonation method for improving the cementitious activity and stability of steel slag as described in any one of claims 1-8.

10. The application of the chelated carbonation modified steel slag slurry as described in claim 9 in the preparation of cement-based materials.

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