CN114644477B - Cement hexavalent chromium reducing agent and preparation method thereof - Google Patents
Cement hexavalent chromium reducing agent and preparation method thereof Download PDFInfo
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- CN114644477B CN114644477B CN202210469872.7A CN202210469872A CN114644477B CN 114644477 B CN114644477 B CN 114644477B CN 202210469872 A CN202210469872 A CN 202210469872A CN 114644477 B CN114644477 B CN 114644477B
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- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
- C04B40/0028—Aspects relating to the mixing step of the mortar preparation
- C04B40/0039—Premixtures of ingredients
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Abstract
The invention discloses a cement hexavalent chromium reducing agent and a preparation method thereof, and the cement hexavalent chromium is alsoThe raw materials comprise the following raw materials in percentage by mass: 30-99% of dispersant containing hydroxyl and 1-70% of ferrous sulfate solution. The cement hexavalent chromium reducing agent has the advantages of simple preparation method and low cost, and the dispersant is used for forming the dispersant coated ferrous sulfate hydrophilic microsphere, so that Fe under the high-temperature condition can be avoided 2+ The chromium-free cement has excellent reducibility and stability in high-temperature environment after being contacted with oxygen, can stably reduce hexavalent chromium in cement into trivalent chromium, and is favorable for practical popularization and application.
Description
Technical Field
The invention belongs to the technical field of building material additives, and particularly relates to a cement hexavalent chromium reducing agent and a preparation method thereof.
Background
Cement is used as a basic material of modern buildings, and the quality safety of the cement directly affects the health and ecological environment of human beings. With the continuous construction of the infrastructure in China, the huge cement usage amount leads to the cement yield which is the first in the world for many years. In the production process of cement, due to raw materials, production process and the like, a small amount of toxic and harmful substances such as lead, cadmium, chromium and the like are often contained in cement and products thereof, wherein the harm of hexavalent chromium is the most serious. Hexavalent chromium ions have a harmful effect on human bodies, and are light in weight, causing skin ulcers, dermatitis and the like, and heavy in weight, causing skin or organ canceration. Secondly, the cement product contacted with soil or rainwater can release soluble hexavalent chromium, and after entering surface water or underground, the cement product can pollute a water system and finally endanger the surrounding ecological environment.
The European Union promulgates 2003/53/EC bans on month 6 and 18 of 2003, specifying that soluble hexavalent chromium in cement be below 2ppm. On 9 months and 11 days of 2015, china issues mandatory standard GB 31893-2015 for limiting hexavalent chromium content in cement, namely a method for limiting and measuring water-soluble hexavalent chromium (VI) in cement, wherein the standard prescribes that the content of the soluble hexavalent chromium in the cement is not more than 10ppm. According to the difference of the areas where the raw materials belong and the production process equipment, the hexavalent chromium content in the cement clinker or the cement is 5-20ppm, and in actual use, a reducing agent is required to be added into the cement, so that the hexavalent chromium is reduced into insoluble trivalent chromium.
At present, the method for adding hexavalent chromium reducing agent into cement is not uniform. The reducer is added before the cement ball milling, and the reducer needs to bear the high temperature of more than 150-200 ℃ in the cement mill, so that certain requirements are placed on the stability of the reducer; some reducing agents are added to the homogenization silo with the cement after cement production and also need to withstand temperatures of 60-80 ℃. Hexavalent chromium reducing agents are various in variety, but ferrous sulfate is the main source of application in a wider range, because the hexavalent chromium reducing agents are low in price and remarkable in reducing effect, and do not negatively affect the performance of cement. However, due to the influence of factors such as unstable crystallization water, poor chemical stability and the like, the ferrous sulfate can cause the removal of the crystallization water when being exposed to high-temperature environment or air, and Fe is lost after the protection of the crystallization water 2+ Is easily oxidized into Fe by air 3+ Reducing the reducibility of the cement in the using process of the cement, reducing hexavalent chromium in the cement disadvantageously, and greatly influencing the environment and ecology.
Disclosure of Invention
The invention aims to provide a cement hexavalent chromium reducing agent and a preparation method thereof, wherein the reducing agent forms dispersant coated ferrous sulfate hydrophilic microspheres by virtue of a dispersant, so that high-temperature Fe can be avoided 2+ The protective effect of the disperse component on the reducing component by contacting with oxygen can improve the stability of ferrous sulfate in the high-temperature environment inside a cement mill and a cement warehouse, so that the reducing agent has stronger high-temperature stability and reducibility, and hexavalent chromium in cement can be effectively reduced.
The invention provides a cement hexavalent chromium reducing agent, which comprises the following raw materials in percentage by mass: 30-99% of a hydroxyl-containing dispersing agent and 1-70% of ferrous sulfate solution, wherein the hydroxyl-containing dispersing agent is micro-scale or nano-scale particles or slurry with a hydroxyl-rich surface.
Further, the ferrous sulfate solution is a ferrous sulfate heptahydrate solution and/or a ferrous sulfate monohydrate solution, and the mixing ratio of the ferrous sulfate heptahydrate solution and the ferrous sulfate monohydrate solution is any ratio.
Further, the particles are at least one of silicon micropowder, nano silicon oxide, glass microsphere, floating bead and nano aluminum oxide.
Further, the slurry is a mixture of water and at least one of silica micropowder, nano-silica, glass microsphere, floating bead and nano-alumina.
Further, the invention also provides a preparation method of the cement hexavalent chromium reducing agent, which comprises the following steps: spraying ferrous sulfate solution on the surface of the hydroxyl-containing dispersing agent, and stirring to obtain the product.
Further, when the hydroxyl-containing dispersing agent is slurry, the stirred material is evaporated, concentrated, cooled, crystallized, filtered, dried in vacuum and ground to prepare the cement hexavalent chromium reducing agent;
wherein the temperature of the cooling crystallization is 0-15 ℃, and the temperature of the vacuum drying is 40-80 ℃.
Further, the particle size of the polishing was 200 mesh or more.
Further, when the hydroxyl-containing dispersant is a particle, the cement hexavalent chromium reducing agent can be prepared by stirring and granulating.
In summary, the invention has the following advantages:
the reducing agent of the invention forms hydrophilic microspheres of the dispersing agent coated ferrous sulfate by the dispersing agent, and can avoid high temperature Fe 2+ The protective effect of the disperse component on the reducing component by contacting with oxygen can improve the stability of ferrous sulfate in the high-temperature environment inside a cement mill and a cement warehouse, so that the reducing agent has stronger high-temperature stability and reducibility, and hexavalent chromium in cement can be effectively reduced.
Detailed Description
In the invention, the hydrated ferrous sulfate is prepared from SO 4 2- ，Fe(H 2 O) 6 2+ H and H 2 O composition. The coordinated oxygen atom of each S is derived from the water of crystallization H 2 Acceptors for three hydrogen bonds of O. Free H 2 O is not only H in octahedra 2 The donor of the O group is also the acceptor. Thus, there are 14 hydrogen bonds distributed in total inside the molecule. The hydrated ferrous sulfate can remove three crystal water at about 60 ℃, and becomes after the temperature reaches 80-90 DEG CFerrous sulfate monohydrate changes to basic ferric sulfate when the temperature rises above 156 ℃. In the invention, the surface of the dispersing agent particle is rich in hydroxyl groups, and according to the theory of hard agglomeration chemical bond, the hydroxyl groups on the surface can bridge with crystal water to form hydrogen bonds. Therefore, the micro-nano particles can be coated on the surface of ferrous sulfate to form a shell in the agglomeration process. The particles of the outer layer are not hydrogen bonded to ferrous sulfate and are in an unstable state and, under surface energy actuation, spontaneously come close to the particles on the first shell, thereby forming a second shell.
It should be noted that although the shell is tightly wrapped on the surface of the ferrous sulfate, the solubility and dissolution rate of the ferrous sulfate are not affected. A large number of hydroxyl groups on the surface layer of the shell are polar hydrophilic functional groups, and can be rapidly dissolved to release ferrous sulfate inside when the shell is contacted with water. Therefore, in the mixing process of cement, the shell can be quickly disintegrated to release the ferrous sulfate in the shell so as to achieve the purpose of reducing hexavalent chromium.
The ferrous sulfate in the invention is one or two of ferrous sulfate heptahydrate or ferrous sulfate monohydrate, which are mixed according to any proportion to obtain a mixture or ferrous sulfate solution.
In the present invention, the dispersant is a micro-or nano-sized particle or slurry having a hydroxyl-rich surface. Are all conventional commercial products, but the hydroxyl-rich surface product must be selected. For example, nano silicon dioxide of Beijing Kodak island gold technology Co., ltd, which has the characteristics of small particle size, multiple micropores, large specific surface area, high surface hydroxyl content, strong ultraviolet, visible and infrared reflection capability and the like. Physical parameters: silicon oxide formula: siO (SiO) 2 The components are as follows: 60.084, density: 2.2g/cm 3 Melting point: 1723 degrees, boiling point: 2230 degree, hardness: 4.5, thermal conductivity 4W/(m.K).
For example, nano alumina of Beijing Kodak gold technology Co., ltd, the main component is nano alumina r-a-alumina. For example, silica fume (i.e. silica micropowder) of Luoyang silicon-collecting silica micropowder company, the silica fume is easy to form-Si-OH groups in water, has stronger hydrophilicity and activity, can enhance the agglomeration of refractory materials, simultaneously has larger improvement on high-temperature performance, and can prolong the service life of refractory products.
For example, yan Tai cloud commercial high-performance hollow glass beads (GS 20, GS25, GS32, GS38Hs, GS40, GS46 and GS 60) have good hydrophilicity, and are suitable for fields of oil fields, composite materials, coating materials and the like.
For example, the floating beads of Jiahui floating beads are all conventional products with hydroxyl groups on the market.
The particle size enters micro-nano level, so that the micro-nano composite material has quantum size effect, small size effect, surface effect and macroscopic quantum size effect, and the micro-nano particles have a series of excellent physical, chemical, surface and interface properties, and can obtain extraordinary effects when being used in concrete. Meanwhile, the micro-nano particles have high surface energy and high surface activity, and are in an unstable state when in a single particle form. In order to reduce the surface energy and achieve a stable state, particles are mutually close to each other to cause agglomeration of micro-nano particles, so that agglomerated pellets with different sizes are obtained.
The dispersing agent can be in the form of powder particles or slurry; when the dispersing agent is particles, the particles can be one or a mixture of a plurality of silicon micropowder, nano silicon oxide, glass microsphere, floating bead and nano aluminum oxide according to any proportion.
When the dispersing agent is slurry, one or more of silicon micropowder, nano silicon oxide, glass microsphere, floating bead and nano aluminum oxide can be selected and mixed with water according to any proportion to obtain the slurry. Particles in the dispersing agent slurry are formed into a multi-element body by silicon oxygen tetrahedron and aluminum oxygen octahedron by Si-O-Si and Al-O-Al, a large number of broken bonds and hydrogen bonds exist on the surface, when ferrous sulfate is dissolved in the slurry, part of ferrous ions and micro-nano particles form an electric double layer, and part of hydrogen bonds exist in a dispersion distribution in a gel liquid phase. After vacuum low-temperature drying, ferrous sulfate starts to slowly crystallize as the liquid phase is evaporated, and finally ferrous sulfate crystals are uniformly distributed in a framework bridged by the dispersing agent particles. During the grinding process, a large number of hydroxyl groups are distributed on the surface of the particles, so that hydrogen bonds can be formed between the particles and crystal water of ferrous sulfate. Therefore, the particles are coated on the surface of the ferrous sulfate crystal to form a protective shell.
At high temperatures, the surface hydroxyl-rich shell formed is protected against the internal reducing components. The shell isolates the ferrous sulfate from direct contact with the outside, and reduces the oxidation of the air to the reducing component. In addition, the shell can slow down the heating rate of the ferrous sulfate in the shell. On the one hand, the shell has an inhibiting effect on heat transfer from outside to inside; on the other hand, as the shell is heated first, the temperature excites Si-OH on the shell to generate dehydration condensation reaction so as to form Si-O-Si, and the reaction can absorb a part of heat so as to protect the internal reduction component. In addition, hydrogen bonds formed between the shell and the water of crystallization of ferrous sulfate can increase the energy required for the ferrous sulfate to lose the water of crystallization, and increase the critical temperature for invalidation of ferrous sulfate.
The application method of the cement hexavalent chromium reducing agent provided by the invention comprises the following steps: after cement clinker, gypsum and blending balls are ground, the ground cement is added into a homogenization silo together with the ground cement. The cement hexavalent chromium reducing agent has low mixing amount, simple process and higher hexavalent chromium reducing efficiency, and has no negative influence on the relevant performance of the cement.
The principles and features of the present invention are described below in connection with the following examples, which are set forth to illustrate, but are not to be construed as limiting the scope of the invention. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
Example 1
The embodiment provides a cement hexavalent chromium reducing agent, which comprises the following raw materials in percentage by mass: 80% of silicon micropowder with rich hydroxyl surface and 20% of ferrous sulfate monohydrate.
The preparation method of the cement hexavalent chromium reducing agent in the embodiment comprises the following steps: preparing ferrous sulfate into saturated solution, then spraying the saturated solution on the surface of the silicon micro powder, and granulating after high-speed stirring to obtain the cement hexavalent chromium reducing agent.
Example 2
The embodiment provides a cement hexavalent chromium reducing agent, which comprises the following raw materials in percentage by mass: 70% of nano silicon oxide with a hydroxyl-rich surface, 20% of ferrous sulfate monohydrate and 10% of ferrous sulfate heptahydrate.
The preparation method of the cement hexavalent chromium reducing agent in the embodiment comprises the following steps: preparing ferrous sulfate into saturated solution, then spraying the saturated solution on the surface of nano silicon oxide, and granulating after high-speed stirring to obtain the cement hexavalent chromium reducing agent.
Example 3
The embodiment provides a cement hexavalent chromium reducing agent, which comprises the following raw materials in percentage by mass: 30% of nano silicon oxide with a hydroxyl-rich surface, 40% of glass beads with a hydroxyl-rich surface, 20% of ferrous sulfate monohydrate and 10% of ferrous sulfate heptahydrate.
The preparation method of the cement hexavalent chromium reducing agent in the embodiment comprises the following steps: preparing ferrous sulfate into saturated solution, then spraying the saturated solution on the surfaces of the uniformly mixed nano silicon oxide and glass beads, and granulating after high-speed stirring to obtain the cement hexavalent chromium reducing agent.
Example 4
The embodiment provides a cement hexavalent chromium reducing agent, which comprises the following raw materials in percentage by mass: 10% of floating beads with a hydroxyl-enriched surface, 20% of nano alumina with a hydroxyl-enriched surface, 30% of silicon micropowder with a hydroxyl-enriched surface, 20% of ferrous sulfate monohydrate and 20% of ferrous sulfate heptahydrate.
The preparation method of the cement hexavalent chromium reducing agent in the embodiment comprises the following steps: preparing ferrous sulfate into saturated solution, then spraying the saturated solution on the surfaces of the uniformly mixed floating beads, nano alumina and silicon micro powder, and granulating after high-speed stirring to obtain the cement hexavalent chromium reducer.
Example 5
The embodiment provides a cement hexavalent chromium reducing agent, which comprises the following raw materials in percentage by mass: 10% of floating beads on the surface rich in hydroxyl groups, 30% of nano silicon oxide on the surface rich in hydroxyl groups, 10% of silicon micro powder on the surface rich in hydroxyl groups, 10% of glass micro beads on the surface rich in hydroxyl groups, 20% of ferrous sulfate monohydrate and 20% of ferrous sulfate heptahydrate.
The preparation method of the cement hexavalent chromium reducing agent in the embodiment comprises the following steps: preparing ferrous sulfate into saturated solution, then spraying the saturated solution on the surfaces of the uniformly mixed floating beads, nano silicon oxide, silicon micro powder and glass micro beads, and granulating after high-speed stirring to obtain the cement hexavalent chromium reducing agent.
Example 6
The embodiment provides a cement hexavalent chromium reducing agent, which comprises the following raw materials in percentage by mass: 10% of floating beads on the surface rich in hydroxyl groups, 10% of nano silicon oxide on the surface rich in hydroxyl groups, 10% of silicon micro powder on the surface rich in hydroxyl groups, 10% of glass micro beads on the surface rich in hydroxyl groups and 60% of ferrous sulfate heptahydrate.
The preparation method of the cement hexavalent chromium reducing agent in the embodiment comprises the following steps: preparing ferrous sulfate into saturated solution, then spraying the saturated solution on the surfaces of the uniformly mixed floating beads, nano silicon oxide, silicon micro powder and glass micro beads, and granulating after high-speed stirring to obtain the cement hexavalent chromium reducing agent.
Example 7
The embodiment provides a cement hexavalent chromium reducing agent, which comprises the following raw materials in percentage by mass: 10% of floating beads with rich hydroxyl surfaces, 5% of nano alumina with rich hydroxyl surfaces, 25% of silicon micro powder with rich hydroxyl surfaces, 10% of glass micro beads with rich hydroxyl surfaces and 50% of ferrous sulfate heptahydrate.
The preparation method of the cement hexavalent chromium reducing agent in the embodiment comprises the following steps: preparing ferrous sulfate into saturated solution, then spraying the saturated solution on the surfaces of the uniformly mixed floating beads, nano alumina, silicon micro powder and glass micro beads, and granulating after high-speed stirring to obtain the cement hexavalent chromium reducing agent.
Example 8
The embodiment provides a cement hexavalent chromium reducing agent, which comprises the following raw materials in percentage by mass: 40% of silicon micropowder with rich hydroxyl surface and 60% of ferrous sulfate monohydrate.
The preparation method of the cement hexavalent chromium reducing agent in the embodiment comprises the following steps: mixing silicon micropowder with water according to the following powder materials: water = 1:2, mixing and stirring the materials according to the mass ratio to prepare the slurry dispersing agent. And then uniformly mixing the slurry dispersing agent with ferrous sulfate, evaporating and concentrating, cooling and crystallizing at 0 ℃, filtering, vacuum drying at 40 ℃, and grinding to 200 meshes to obtain the cement hexavalent chromium reducing agent.
Example 9
The embodiment provides a cement hexavalent chromium reducing agent, which comprises the following raw materials in percentage by mass: 70% of nano silicon oxide with a hydroxyl-rich surface and 30% of ferrous sulfate heptahydrate.
The preparation method of the cement hexavalent chromium reducing agent in the embodiment comprises the following steps: mixing nano silicon oxide with water according to powder: water = 1: mixing and stirring the materials according to the mass ratio of 1.5 to prepare the slurry dispersing agent. And then uniformly mixing the slurry dispersing agent with ferrous sulfate, evaporating and concentrating, cooling and crystallizing at 5 ℃, filtering, vacuum drying at 50 ℃, and grinding to 200 meshes to obtain the cement hexavalent chromium reducing agent.
Example 10
The embodiment provides a cement hexavalent chromium reducing agent, which comprises the following raw materials in percentage by mass:
30% of nano silicon oxide with a hydroxyl-rich surface, 50% of silicon micropowder with a hydroxyl-rich surface, 10% of ferrous sulfate heptahydrate and 10% of ferrous sulfate monohydrate.
The preparation method of the cement hexavalent chromium reducing agent in the embodiment comprises the following steps: mixing nano silicon oxide, silicon micropowder and water according to the following powder materials: water = 1: mixing and stirring the materials according to the mass ratio of 1.5 to prepare the slurry dispersing agent. And then uniformly mixing the slurry dispersing agent with ferrous sulfate, evaporating and concentrating, cooling and crystallizing at 10 ℃, filtering, vacuum drying at 60 ℃, and grinding to 200 meshes to obtain the cement hexavalent chromium reducing agent.
Example 11
The embodiment provides a cement hexavalent chromium reducing agent, which comprises the following raw materials in percentage by mass: 40% of glass beads with hydroxyl-enriched surfaces, 20% of silicon micropowder with hydroxyl-enriched surfaces, 20% of ferrous sulfate heptahydrate and 20% of ferrous sulfate monohydrate.
The preparation method of the cement hexavalent chromium reducing agent in the embodiment comprises the following steps: mixing glass beads, silicon micropowder and water according to the following powder materials: water = 1:2, mixing and stirring the materials according to the mass ratio to prepare the slurry dispersing agent. And then uniformly mixing the slurry dispersing agent with ferrous sulfate, evaporating and concentrating, cooling and crystallizing at 15 ℃, filtering, vacuum drying at 70 ℃, and grinding to 200 meshes to obtain the cement hexavalent chromium reducing agent.
Example 12
The embodiment provides a cement hexavalent chromium reducing agent, which comprises the following raw materials in percentage by mass: 10% of floating beads with a hydroxyl-enriched surface, 20% of nano alumina with a hydroxyl-enriched surface, 30% of silicon micropowder with a hydroxyl-enriched surface, 20% of ferrous sulfate monohydrate and 20% of ferrous sulfate heptahydrate.
The preparation method of the cement hexavalent chromium reducing agent in the embodiment comprises the following steps: mixing floating beads, nano alumina, silicon micropowder and water according to the powder materials: water = 1:2, mixing and stirring the materials according to the mass ratio to prepare the slurry dispersing agent. And then uniformly mixing the slurry dispersing agent with ferrous sulfate, evaporating and concentrating, cooling and crystallizing at 15 ℃, filtering, vacuum drying at 80 ℃, and grinding to 200 meshes to obtain the cement hexavalent chromium reducing agent.
Example 13
The embodiment provides a cement hexavalent chromium reducing agent, which comprises the following raw materials in percentage by mass: 10% of floating beads on the surface rich in hydroxyl groups, 30% of nano silicon oxide on the surface rich in hydroxyl groups, 10% of silicon micro powder on the surface rich in hydroxyl groups, 10% of glass micro beads on the surface rich in hydroxyl groups and 40% of ferrous sulfate heptahydrate.
The preparation method of the cement hexavalent chromium reducing agent in the embodiment comprises the following steps: mixing floating beads, nano silicon oxide, silicon micropowder, glass beads and water according to powder: water = 1:2, mixing and stirring the materials according to the mass ratio to prepare the slurry dispersing agent. And then uniformly mixing the slurry dispersing agent with ferrous sulfate, evaporating and concentrating, cooling and crystallizing at 0 ℃, filtering, vacuum drying at 80 ℃, and grinding to 200 meshes to obtain the cement hexavalent chromium reducing agent.
Example 14
The embodiment provides a cement hexavalent chromium reducing agent, which comprises the following raw materials in percentage by mass: 10% of floating beads on the surface rich in hydroxyl groups, 30% of nano alumina on the surface rich in hydroxyl groups, 10% of silicon micro powder on the surface rich in hydroxyl groups, 10% of glass micro beads on the surface rich in hydroxyl groups, 20% of ferrous sulfate monohydrate and 20% of ferrous sulfate heptahydrate.
The preparation method of the cement hexavalent chromium reducing agent in the embodiment comprises the following steps: mixing floating beads, nano alumina, silica micropowder, glass beads and water according to powder: water = 1:2, mixing and stirring the materials according to the mass ratio to prepare the slurry dispersing agent. And then uniformly mixing the slurry dispersing agent with ferrous sulfate, evaporating and concentrating, cooling and crystallizing at 15 ℃, filtering, vacuum drying at 40 ℃, and grinding to 200 meshes to obtain the cement hexavalent chromium reducing agent.
Test example 1
According to the conventional 42.5-grade cement production process flow, the cement hexavalent chromium reducing agent of the examples 1-14, cement clinker, gypsum, mixed materials and the like are ball-milled in a cement mill of a cement plant according to the addition amount of 100 g/ton to obtain cement.
Comparative example 1
According to the conventional 42.5-grade cement production process, no reducing agent is added, and cement clinker, gypsum, mixed materials and the like are ball-milled together to obtain cement.
Comparative example 2
According to the conventional 42.5 grade cement production process flow, ferrous sulfate monohydrate, cement clinker, gypsum, mixed materials and the like are ball-milled together according to the addition amount of 100 g/ton to obtain cement.
Comparative example 3
According to the conventional 42.5 grade cement production process flow, the ferrous sulfate heptahydrate, cement clinker, gypsum, mixed materials and the like are ball-milled together according to the addition amount of 100 g/ton to obtain cement.
Wherein, the cement clinker is silicate cement clinker meeting GB175, the mixture is granulated blast furnace slag meeting GB175, a pozzolanic mixture material and a fly ash mixture, and the cement clinker: gypsum: blast furnace slag: pozzolanic blend material: fly ash=82:4.5:3:6.5:4.
The hexavalent chromium content of test example 1 and comparative examples 1 to 3 at different times was measured using GB 31893-2015 "limit and measurement method of Water-soluble hexavalent chromium (VI) in Cement", and the results are shown in Table 1:
table 1: water-soluble hexavalent chromium content in cement
While specific embodiments of the invention have been described in detail, it should not be construed as limiting the scope of the patent. Various modifications and variations which may be made by those skilled in the art without the creative effort are within the scope of the patent described in the claims.
Claims (2)
1. The cement hexavalent chromium reducing agent is characterized by comprising the following raw materials in percentage by mass: 30-99% of a hydroxyl-containing dispersing agent and 1-70% of a ferrous sulfate solution, wherein the hydroxyl-containing dispersing agent is micro-scale or nano-scale slurry with a hydroxyl-rich surface;
wherein the ferrous sulfate solution is a ferrous sulfate heptahydrate solution and/or a ferrous sulfate monohydrate solution, and the mixing ratio of the ferrous sulfate heptahydrate solution and the ferrous sulfate monohydrate solution is any proportion;
the slurry is a mixture of water and at least one of silica micropowder, nano silicon oxide, glass microsphere, floating bead and nano aluminum oxide;
the cement hexavalent chromium reducing agent is prepared by the following method:
mixing and stirring at least one of silicon micropowder, nano silicon oxide, glass beads, floating beads and nano aluminum oxide with water according to a proportion, preparing a slurry dispersing agent, uniformly mixing with a ferrous sulfate solution, evaporating, concentrating, cooling, crystallizing, filtering, vacuum drying and grinding to obtain the cement hexavalent chromium reducing agent;
the temperature of the cooling crystallization is 0-15 ℃, and the temperature of the vacuum drying is 40-80 ℃.
2. The cement hexavalent chromium reducing agent of claim 1, wherein said milled particle size is 200 mesh and above.
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| CN103978229A (en) * | 2013-12-06 | 2014-08-13 | 南昌大学 | Preparation method of aluminum oxide loaded nanoscale zero-valent iron nanorod |
| TWI666172B (en) * | 2018-03-12 | 2019-07-21 | 國立高雄科技大學 | Nano iron-alumina composite material, and preparation method and application thereof |
| CN111807749A (en) * | 2020-06-11 | 2020-10-23 | 内蒙古同佳技术发展有限公司 | Hexavalent chromium reducing agent and preparation method thereof |
| CN114213056A (en) * | 2022-01-17 | 2022-03-22 | 安徽精公检测检验中心有限公司 | Ferrous sulfate-antimony trisulfide composite liquid chromium remover and preparation method and application thereof |
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