Cement chromium removal agent using industrial solid waste as well as preparation method and application of cement chromium removal agent

Abstract

The invention discloses a cement chromium removal agent using industrial solid waste as well as a preparation method and application of the cement chromium removal agent. The cement chromium removal agent comprises the following components in percentage by mass: 49%-63% of fly ash, 31%-39% of ferrous sulfate, 2%-4% of soluble metaaluminate, 3%-5% of soluble silicate and 1%-3% of polycarboxylic acid. The effect of removing chromium in the cement is achieved through the synergistic effect of the reducibility of the ferrous sulfate and the adsorbability of the fly ash in the chromium removal agent, meanwhile, the soluble silicate and the soluble meta-aluminate react with water to generate hydrated aluminosilicate of a frame-shaped structure, and the hydrated aluminosilicate of the frame-shaped structure has high selective adsorbability; chromium ions in the cement can be selectively adsorbed, and the removal effect of chromium in the cement is further improved. And the addition of polycarboxylic acid provides a weak acid environment, and ensures the reducibility of ferrous sulfate, so that the cement chromium removal agent can be stored for a long time, and the polycarboxylic acid also improves the performance of cement.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, and in particular to a cement chromium removal agent and a preparation method and application thereof. Background Art

[0002] Chromium in nature mainly exists in the form of hexavalent chromium, the most common of which is chromate and dichromate. Hexavalent chromium is soluble in water, has strong oxidizing properties and high permeability to the skin, and short-term skin contact can cause chrome dermatitis and eczema. Due to its extremely strong solubility and migration, humans or animals can absorb hexavalent chromium through the skin, mucous membranes, respiratory tract and digestive tract. The absorbed hexavalent chromium quickly enters the cells through nonspecific anion channels on the cell membrane and is transferred between cells, causing liver and kidney damage. Hexavalent chromium absorbed through the respiratory tract can cause nasal septum ulcers, nosebleeds, and even lung cancer when it enters the human body. After being ingested into the human body through the digestive tract, due to the irritation and corrosion of the digestive tract by hexavalent chromium, trace amounts can cause nausea, gastrointestinal spasms, gastrointestinal lesions and other reactions, and excessive amounts can even lead to death. After contact with the conjunctiva and lips, irritation and corrosion occur, causing local inflammation and ulcers. In the environment, it can also migrate and transfer through the atmosphere, water and food chains, and be enriched in organisms through the food chain.

[0003] Cement, as a common building material, is closely related to people's lives. People are very likely to come into contact with cement in their daily lives and work. In the process of cement production, water-soluble chromium (VI) will be introduced into the raw materials and process flow. The raw materials of cement are often limestone, clay and iron ore, etc. These raw materials usually contain chromium substances in nature. In the production process of cement, chromium slag is often used as a raw material in the process of calcining clinker, which leads to a significant increase in the content of water-soluble hexavalent chromium (VI) in the clinker; chromium-containing grinding bodies and liners are usually used in the process of cement grinding, which will cause the incorporation of water-soluble chromium; and refractory materials used in cement production, such as chromium-containing refractories, will also become a source of chromium.

[0004] Chromium in cement usually exists in the form of hexavalent chromium. Workers who produce cement and people in daily life will be more or less exposed to cement, so the hexavalent chromium in cement will cause varying degrees of damage to the human body. On October 1, 2016, the country implemented the GB31893-2015 "Limits and Determination Methods of Water-soluble Chromium (VI) in Cement" standard, which stipulates that cement with a water-soluble chromium (VI) content exceeding 10 mg / kg is prohibited from use and sale. In the GB175-2023 "General Portland Cement" standard implemented on June 1, 2024, water-soluble chromium (VI) in cement is officially included in the technical requirements.

[0005] In the prior art, reducing agents are mainly used to reduce the water-soluble hexavalent chromium in cement to trivalent chromium with lower toxicity, so as to reduce the content and toxicity of water-soluble hexavalent chromium in cement. Ferrous sulfate is often used as a reducing agent for cement chromium removers due to its excellent reducing performance and low price. However, ferrous sulfate is unstable and easily oxidized to ferrous sulfate by oxygen in the air, which reduces its reducing property. At the same time, this type of cement chromium remover is not easy to store and has a short service life. Therefore, the use of ferrous sulfate as a reducing agent in cement chromium removers is limited. Other reducing agents also have various defects, such as high iron powder price and low safety performance; sodium sulfite and sodium thiosulfate are highly corrosive and harmful to the human body; stannous sulfate is expensive and toxic, etc. Therefore, it is urgent to invent a chromium remover that can effectively protect the reducing property of ferrous sulfate and further significantly improve the removal effect of water-soluble hexavalent chromium in cement, which is a problem that urgently needs to be solved in cement production. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a cement chromium removal agent using industrial solid waste, a preparation method and application thereof, which realizes efficient removal of water-soluble hexavalent chromium in cement.

[0007] The first aspect of the present invention provides a cement chromium remover using industrial solid waste. The cement chromium remover is composed of the following components by mass percentage: 49%-63% fly ash, 31%-39% ferrous sulfate, 2%-4% soluble aluminate, 3%-5% soluble silicate and 1%-3% polycarboxylic acid.

[0008] Preferably, the soluble aluminate is sodium aluminate or potassium aluminate.

[0009] Preferably, the soluble silicate is sodium silicate or potassium silicate.

[0010] Preferably, the ferrous sulfate is obtained by grinding and removing impurities from ferrous sulfate waste residue. The ferrous sulfate waste residue in the present invention comes from solid waste generated in the industrial production process. It mainly includes by-products in the production process of titanium dioxide produced by sulfuric acid method. For every ton of titanium dioxide produced, about 1 ton of ferrous sulfate waste residue will be generated; ferrous sulfate is generated in the pickling process of steel pipe production. The secondary utilization of these industrial solid wastes not only reduces the cost of producing cement chromium removal agent, but also has a good protective effect on the environment.

[0011] Preferably, the cement chromium remover consists of 54%-58% fly ash, 34%-36% ferrous sulfate, 2.5%-3.5% soluble aluminate, 3.5%-4.5% soluble silicate and 1.5%-2.5% polycarboxylic acid in percentage by mass.

[0012] Preferably, in terms of mass percentage, the cement chromium removal agent consists of 56% fly ash, 35% ferrous sulfate, 3% soluble metaaluminate, 4% soluble silicate, and 2% polycarboxylic acid.

[0013] Preferably, in terms of mass percentage, the cement chromium removal agent consists of 55.5% fly ash, 35% ferrous sulfate, 3% soluble metaaluminate, 4% soluble silicate, and 2.5% polycarboxylic acid.

[0014] Preferably, in terms of mass percentage, the cement chromium removal agent consists of 57% fly ash, 35.5% ferrous sulfate, 2.5% soluble metaaluminate, 3.5% soluble silicate, and 1.5% polycarboxylic acid.

[0015] Preferably, in terms of mass percentage, the cement chromium remover consists of 54% fly ash, 36% ferrous sulfate, 3.5% soluble metaaluminate, 4.5% soluble silicate, and 2% polycarboxylic acid.

[0016] Preferably, the cement chromium removal agent is composed of 58% fly ash, 34% ferrous sulfate, 2.5% soluble metaaluminate, 3.5% soluble silicate and 2% polycarboxylic acid in percentage by mass.

[0017] Preferably, the polycarboxylic acid comprises one or more of polyacrylic acid, polymethacrylic acid, hydrolyzed polymaleic anhydride or phosphine-based polymaleic anhydride.

[0018] Specifically, the ferrous sulfate is used as a reducing agent to reduce Cr 6+ Reduction to Cr 3+ Cr 6+ It is a toxic water-soluble substance, through Cr2O7 2- +6Fe 2+ +14H + = =2Cr 3+ +6Fe 3+ +7H2O reaction, becoming Cr with low toxicity 3+ .

[0019] More specifically, the mass percentage of the fly ash is one of 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63% or a range value composed of any two thereof.

[0020] The mass percentage of the ferrous sulfate is one of 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39% or a range value formed between any two of them.

[0021] The mass percentage of the soluble aluminate is one of 2%, 2.5%, 3%, 3.5%, 4%, or a range of any two of them.

[0022] The mass percentage of the soluble silicate is one of 3%, 3.5%, 3%, 4%, 4.5%, 5%, or a range of any two of them.

[0023] The mass percentage of the polycarboxylic acid is one of 1%, 1.5%, 2%, 2.5%, 3%, or a range of any two of them.

[0024] The fly ash is used as a carrier. Since the fly ash particles have a special micro-bead structure, the rich glass particles in the microstructure make the interior present a porous honeycomb structure, which has a large specific surface area and strong adsorption performance. Due to its porous honeycomb structure, ferrous sulfate can be evenly dispersed in its pores, thereby reacting with water-soluble Cr 6+ The reaction is fully contacted, which improves the reaction efficiency. At the same time, the excellent adsorption performance of fly ash makes the Cr produced by the reaction 3+ Firmly adsorbed in the carrier; the synergistic effect of fly ash and ferrous sulfate greatly improves the chromium removal effect of the chromium removal agent. Moreover, fly ash is easy to obtain as waste residue often produced in various industrial processes, and can be reused as waste, which greatly reduces the cost of cement chromium removal agent.

[0025] Preferably, the particle size of the soluble aluminate is ≤38 microns.

[0026] Preferably, the soluble silicate is powdered fast-dissolving metasilicate, and the particle size of the powdered fast-dissolving metasilicate is ≤38 microns.

[0027] The powder particle size of the soluble metaaluminate and the soluble silicate are both ≤38 microns, and the two can be fully mixed. When the cement is used, they can react quickly with water to generate hydrated aluminosilicate, generating 2SiO3 2- +2AlO2 - +2H2O═Al2Si2O8 2- ↓+4OH - Reaction: soluble aluminate will hydrolyze in water to form aluminum oxide tetrahedron, and react with silicon oxide tetrahedron generated by hydrolysis of soluble silicate in water to form hydrated aluminum silicate with a three-dimensional network structure or a layered porous structure. At the same time, the alkaline substance generated by the reaction can decompose the active components in the fly ash, thereby increasing the porous honeycomb structure in the fly ash. This synergistic effect further improves the excellent selective adsorption performance for water-soluble hexavalent chromium, so that the amount of chromium removal agent used to achieve the same chromium removal effect is greatly reduced.

[0028] The chromium removal agent of the present invention is added with polycarboxylic acid, which provides a weakly acidic environment to ensure that the Fe in ferrous sulfate is 2+ It is not oxidized, ensuring the reducing property of ferrous sulfate and extending the service life of the chromium remover. On the other hand, polycarboxylic acid is a water retaining agent in cement, which can ensure that the cement does not dry out for a long time, improves the working performance of cement, and can be used in various types of cement, so that the chromium remover of the present invention has a wider application range.

[0029] At the same time, under the reduction effect of ferrous sulfate and the dual adsorption effect of fly ash and hydrated aluminum silicate, the Cr content in cement can be effectively reduced. 6+ The content.

[0030] The second aspect of the present invention provides a method for preparing a cement chromium removal agent using industrial solid waste, wherein the preparation method produces the cement chromium removal agent described in any one of the above items, and the method comprises the following steps:

[0031] 1) dissolving the polycarboxylic acid liquid in water and heating it to 40° C.-50° C.;

[0032] 2) Modification of ferrous sulfate: grinding the ferrous sulfate waste residue to remove impurities to obtain ferrous sulfate; adding the ferrous sulfate to the polycarboxylic acid liquid, and continuously stirring to make the two mixed evenly to obtain a mixed solution A;

[0033] 3) Add the fly ash into the mixed solution A, stir, heat and dry, grind and sieve to obtain a mixed powder with a moisture content of less than 1% and a particle size of ≤8.47 microns.

[0034] 4) adding soluble silicate and soluble metaaluminate into the mixed powder, stirring and mixing them evenly to obtain the cement chromium remover.

[0035] The third aspect of the present invention provides an application of a cement chromium remover using industrial solid waste, wherein the cement chromium remover described in any one of the above items is used to remove water-soluble hexavalent chromium in cement, and the cement is general-purpose cement, special-purpose cement or characteristic cement.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1) Wide applicability: The cement chromium removal agent prepared by the present invention using industrial solid waste can be added to cements of various grades to remove water-soluble hexavalent chromium therein, so that the chromium content in the cement reaches the national standard GB30485-2013 "Regulations on Limitation of Pollutants in Cement".

[0038] 2) High chromium removal rate: Due to the reasonable ratio of fly ash, ferrous sulfate, water-soluble metasilicate, water-soluble silicate and polycarboxylic acid, the adsorption of fly ash, the reduction of ferrous sulfate, and the selective adsorption of the generated three-dimensional framework or layered structure, the effective combination of the three greatly improves the chromium removal efficiency of the cement chromium removal agent of the present invention, reduces the amount of addition for the same chromium removal effect, and significantly improves the chromium removal efficiency.

[0039] 3) Low cost: the ferrous sulfate and fly ash in the raw materials of the cement chromium removal agent of the present invention are from industrial solid waste, which are secondary utilization, easy to mine and obtain, low in cost and widely available. DETAILED DESCRIPTION

[0040] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0041] The embodiment of the present invention solves the technical problems of instability of ferrous sulfate in the chromium removal agent and poor chromium removal effect in the prior art by providing a cement chromium removal agent using industrial solid waste and a preparation method and application thereof.

[0042] Example 1

[0043] A cement chromium removal agent prepared by utilizing industrial solid wastes comprises the following components by mass: 49% fly ash, 39% ferrous sulfate, 4% sodium metaaluminate, 5% sodium silicate, and 3% polycarboxylic acid.

[0044] The preparation method of the above-mentioned cement chromium removal agent comprises the following steps:

[0045] (1) dissolving 3 g of polycarboxylic acid in water and heating to 40° C.

[0046] (2) Ferrous sulfate modification: Grind the collected ferrous sulfate waste residue to remove impurities to obtain ferrous sulfate; take 39 g of the ferrous sulfate, add it to the above polycarboxylic acid solution, and continue stirring to make the two fully mixed to obtain a mixed solution A;

[0047] (3) adding 49 g of fly ash to the mixed solution A, stirring, heating and drying, grinding and sieving to prepare a powder with a moisture content of less than 1% and a particle size of ≤8.47 μm;

[0048] (4) 5 g of sodium silicate and 4 g of sodium aluminate were added to the mixed powder in sequence and mixed evenly to prepare cement chromium removal agent 1.

[0049] Example 2

[0050] A cement chromium removal agent prepared by utilizing industrial solid wastes comprises the following components by mass: 63% fly ash, 31% ferrous sulfate, 2% sodium metaaluminate, 3% sodium silicate, and 1% polycarboxylic acid.

[0051] The preparation method of the above-mentioned cement chromium removal agent comprises the following steps:

[0052] (1) Dissolve 1 g of polycarboxylic acid in water and heat to 45° C.

[0053] (2) Ferrous sulfate modification: Grind the collected ferrous sulfate waste residue to remove impurities to obtain ferrous sulfate; add 31 g of the ferrous sulfate to the polycarboxylic acid solution, and continue stirring to fully mix the two to obtain a mixed solution A;

[0054] (3) adding 63 g of fly ash to the mixed solution A, stirring, heating and drying, grinding and sieving to prepare a powder with a moisture content of less than 1% and a particle size of ≤8.47 μm;

[0055] (4) Add 3 g of sodium silicate and 2 g of sodium aluminate to the mixed powder and mix them evenly to prepare cement chromium remover 2.

[0056] Example 3

[0057] A cement chromium removal agent prepared by utilizing industrial solid wastes comprises the following components by mass: 56% fly ash, 35% ferrous sulfate, 3% sodium metaaluminate, 4% sodium silicate, and 2% polycarboxylic acid.

[0058] The preparation method of the above-mentioned cement chromium removal agent comprises the following steps:

[0059] (1) Dissolve 2 g of polycarboxylic acid in water and heat to 50°C;

[0060] (2) Ferrous sulfate modification: Grind the collected ferrous sulfate waste residue to remove impurities to obtain ferrous sulfate; take 35 g of the above ferrous sulfate, add it to the polycarboxylic acid solution, and continue stirring to make the two fully mixed to obtain a mixed solution A;

[0061] (3) adding 56 g of fly ash to the mixed solution A, stirring, heating and drying, grinding and sieving, and preparing a powder with a moisture content of less than 1% and a particle size of ≤8.47 μm;

[0062] (4) Add 4 g of sodium silicate and 3 g of sodium aluminate to the mixed powder and mix them evenly to prepare cement chromium remover 3.

[0063] Example 4

[0064] A cement chromium removal agent prepared by utilizing industrial solid wastes comprises the following components by mass: 54% fly ash, 36% ferrous sulfate, 3.5% sodium aluminate, 4.5% sodium silicate and 2% polycarboxylic acid.

[0065] The preparation method of the cement chromium removal agent comprises the following steps:

[0066] (1) Dissolve 2 g of polycarboxylic acid in water and heat to 50°C;

[0067] (2) Ferrous sulfate modification: Grind the collected ferrous sulfate waste residue to remove impurities to obtain ferrous sulfate; take 36 g of the ferrous sulfate, add it to the polycarboxylic acid solution, and continue stirring to make the two fully mixed to obtain a mixed solution A;

[0068] (3) adding 54 g of fly ash to the mixed solution A, stirring, heating and drying, grinding and sieving, and preparing a powder with a moisture content of less than 1% and a particle size of ≤8.47 μm;

[0069] (4) Add 4.5 g of sodium silicate and 3.5 g of sodium aluminate to the mixed powder and mix well to prepare cement chromium remover 4.

[0070] Example 5

[0071] A cement chromium removal agent prepared by utilizing industrial solid wastes comprises the following components by mass: 58% fly ash, 34% ferrous sulfate, 2.5% sodium aluminate, 3.5% sodium silicate and 2% polycarboxylic acid.

[0072] The preparation method of the above-mentioned cement chromium removal agent comprises the following steps:

[0073] (1) Dissolve 2 g of polycarboxylic acid in water and heat to 50°C;

[0074] (2) Ferrous sulfate modification: Grind the collected ferrous sulfate waste residue to remove impurities to obtain ferrous sulfate; take 34 g of the ferrous sulfate, add it to the polycarboxylic acid liquid, and continue stirring to make the two fully mixed to obtain a mixed solution A;

[0075] (3) adding 58 g of fly ash to the mixed solution A, stirring, heating and drying, grinding and sieving, and preparing a powder with a moisture content of less than 1% and a particle size of ≤8.47 μm;

[0076] (4) Add 3.5 g of sodium silicate and 2.5 g of sodium aluminate to the mixed powder and mix them evenly to prepare cement chromium removal agent 5.

[0077] Example 6

[0078] A cement chromium removal agent prepared by utilizing industrial solid wastes comprises the following components by mass: 55.5% fly ash, 35% ferrous sulfate, 3% sodium aluminate, 4% sodium silicate and 2.5% polycarboxylic acid.

[0079] The preparation method of the above-mentioned cement chromium removal agent comprises the following steps:

[0080] (1) Dissolve 2.5 g of polycarboxylic acid in water and heat to 50°C;

[0081] (2) Ferrous sulfate modification: Grind the collected ferrous sulfate waste residue to remove impurities to obtain ferrous sulfate; take 35 g of the ferrous sulfate, add it to the polycarboxylic acid liquid, and continue stirring to make the two fully mixed to obtain a mixed solution A;

[0082] (3) adding 55.5 g of fly ash to the mixed solution A, stirring, heating and drying, grinding and sieving, and preparing a powder with a moisture content of less than 1% and a particle size of ≤8.47 μm;

[0083] (4) Add 4 g of sodium silicate and 3 g of sodium aluminate to the mixed powder and mix them evenly to prepare cement chromium removal agent 6.

[0084] Example 7

[0085] A cement chromium removal agent prepared by utilizing industrial solid wastes comprises the following components by mass: 57% fly ash, 35.5% ferrous sulfate, 2.5% sodium aluminate, 3.5% sodium silicate and 1.5% polycarboxylic acid.

[0086] The preparation method of the above-mentioned cement chromium removal agent comprises the following steps:

[0087] (1) Dissolve 1.5 g of polycarboxylic acid in water and heat to 50°C;

[0088] (2) Ferrous sulfate modification: Grind the collected ferrous sulfate waste residue to remove impurities to obtain ferrous sulfate; take 35.5 g of the ferrous sulfate, add it to the polycarboxylic acid solution, and continue stirring to make the two fully mixed to obtain a mixed solution A;

[0089] (3) adding 57 g of fly ash to the mixed solution A, stirring, heating and drying, grinding and sieving, and preparing a powder with a moisture content of less than 1% and a particle size of ≤8.47 μm;

[0090] (4) Add 3.5 g of sodium silicate and 2.5 g of sodium aluminate to the mixed powder and mix well to prepare cement chromium remover 7.

[0091] Example 8

[0092] A cement chromium removal agent prepared by utilizing industrial solid wastes comprises the following components by mass: 62% fly ash, 30% ferrous sulfate, 2% sodium aluminate, 3% sodium silicate and 3% polycarboxylic acid.

[0093] The preparation method of the above-mentioned cement chromium removal agent comprises the following steps:

[0094] (1) Dissolve 3 g of polycarboxylic acid in water and heat to 50°C;

[0095] (2) Ferrous sulfate modification: Grind the collected ferrous sulfate waste residue to remove impurities to obtain ferrous sulfate; take 30 g of ferrous sulfate, add it to the polycarboxylic acid solution, and continue stirring to make the two fully mixed to obtain a mixed solution A;

[0096] (3) adding 62 g of fly ash to the mixed solution A, stirring, heating and drying, grinding and sieving, and preparing a powder with a moisture content of less than 1% and a particle size of ≤8.47 μm;

[0097] (4) Add 3 g of sodium silicate and 3 g of sodium aluminate to the mixed powder and mix them evenly to prepare cement chromium removal agent 8.

[0098] Example 9

[0099] A cement chromium removal agent prepared by utilizing industrial solid wastes comprises the following components by mass: 50.6% fly ash, 38% ferrous sulfate, 3.8% sodium aluminate, 4.8% sodium silicate, and 2.8% polycarboxylic acid.

[0100] The preparation method of the above-mentioned cement chromium removal agent comprises the following steps:

[0101] (1) Dissolve 2.8 g of polycarboxylic acid in water and heat to 50°C;

[0102] (2) Ferrous sulfate modification: Grind the collected ferrous sulfate waste residue to remove impurities to obtain ferrous sulfate; take 38 g of the ferrous sulfate, add it to the polycarboxylic acid solution, and continue stirring to make the two fully mixed to obtain a mixed solution A;

[0103] (3) adding 50.6 g of fly ash to the mixed solution A, stirring, heating and drying, grinding and sieving, and preparing a powder with a moisture content of less than 1% and a particle size of ≤8.47 μm;

[0104] (4) Add 4.8 g of sodium silicate and 3.8 g of sodium aluminate to the mixed powder and mix well to prepare cement chromium remover 9.

[0105] Comparative Example 1

[0106] A cement chromium removal agent (containing ferrous sulfate) in the prior art has the following components in percentage: 40% ferrous sulfate, 10% ferrous citrate, 8% nitrilotriacetic acid, 5% sodium oxalate, 2% (low) polydextrose, 4.0% sodium sulfate, and 31.0% fly ash.

[0107] Comparative Example 2

[0108] A cement chromium removal agent comprises the following components by mass: 52% fly ash, 39% ferrous sulfate, 4% sodium metaaluminate and 5% sodium silicate.

[0109] The preparation method of the above-mentioned cement chromium removal agent comprises the following steps:

[0110] (1) 52 g of fly ash and 39 g of ferrous sulfate were mixed, stirred, heated and dried, and ground and sieved to prepare a powder having a moisture content of less than 1% and a particle size of ≤8.47 μm;

[0111] (2) Add 5 g of sodium silicate and 4 g of sodium aluminate to the mixed powder and mix them evenly to prepare a chromium removal agent.

[0112] Comparative Example 3

[0113] A cement chromium removal agent comprises the following components by mass: 49% fly ash, 39% ferrous sulfate, 4% sodium metaaluminate, 5% sodium silicate and 3% citric acid.

[0114] The preparation method of the above-mentioned cement chromium removal agent comprises the following steps:

[0115] (1) Dissolve 3 g of citric acid in water and heat to 50°C;

[0116] (2) adding 39 g of the ferrous sulfate to the citric acid solution, and continuously stirring to make the two thoroughly mixed, to obtain a mixed solution A;

[0117] (3) adding 49 g of fly ash to the mixed solution A, stirring, heating and drying, grinding and sieving to prepare a powder with a moisture content of less than 1% and a particle size of ≤8.47 μm;

[0118] (4) Add 5 g of sodium silicate and 4 g of sodium aluminate to the mixed powder and mix them evenly to prepare a chromium removal agent.

[0119] Comparative Example 4

[0120] A cement chromium removal agent comprises the following components by mass: 60% fly ash, 37% ferrous sulfate and 3% polycarboxylic acid.

[0121] The preparation method of the above-mentioned cement chromium removal agent comprises the following steps:

[0122] (1) Dissolve 3 g of polycarboxylic acid in water and heat to 50°C;

[0123] (2) Ferrous sulfate modification: 37 g of the ferrous sulfate was added to the polycarboxylic acid solution, and the mixture was stirred continuously to make the two mixtures fully mixed to obtain a mixed solution A;

[0124] (3) Add 60 g of fly ash to the mixed solution A, stir, heat and dry, grind and sieve to prepare a powder with a moisture content of less than 1% and a particle size of ≤8.47 μm.

[0125] Comparative Example 5

[0126] A cement chromium removal agent comprises the following components by mass: 45% fly ash, 44% ferrous sulfate, 5% sodium metaaluminate, 2% sodium silicate and 4% polycarboxylic acid.

[0127] The preparation method of the above-mentioned cement chromium removal agent comprises the following steps:

[0128] (1) Dissolve 4 g of polycarboxylic acid in water and heat to 50°C;

[0129] (2) Ferrous sulfate modification: 44 g of the ferrous sulfate was added to the polycarboxylic acid solution, and the mixture was stirred continuously to make the two mixtures fully mixed to obtain a mixed solution A;

[0130] (3) adding 45 g of fly ash to the mixed solution A, stirring, heating and drying, grinding and sieving to prepare a powder with a moisture content of less than 1% and a particle size of ≤8.47 μm;

[0131] (4) Add 2 g of sodium silicate and 5 g of sodium aluminate to the mixed powder and mix them evenly to prepare a cement chromium remover.

[0132] Comparative Example 6

[0133] A cement chromium removal agent comprises the following components by mass: 54% fly ash, 39% ferrous sulfate, 4% sodium metaaluminate and 3% polycarboxylic acid.

[0134] The preparation method of the above-mentioned cement chromium removal agent comprises the following steps:

[0135] (1) Dissolve 3 g of polycarboxylic acid in water and heat to 50°C;

[0136] (2) Ferrous sulfate modification: 39 g of the ferrous sulfate was added to the polycarboxylic acid solution, and the mixture was stirred continuously to make the two mixtures fully mixed to obtain a mixed solution A;

[0137] (3) adding 54 g of fly ash to the mixed solution A, stirring, heating and drying, grinding and sieving, and preparing a powder with a moisture content of less than 1% and a particle size of ≤8.47 μm;

[0138] (4) Add 4 g of sodium aluminate to the mixed powder and mix well to prepare a cement chromium remover.

[0139] Comparative Example 7

[0140] A cement chromium removal agent comprises the following components by mass: 53% fly ash, 39% ferrous sulfate, 5% sodium silicate and 3% polycarboxylic acid.

[0141] The preparation method of the above-mentioned cement chromium removal agent comprises the following steps:

[0142] (1) Dissolve 3 g of polycarboxylic acid in water and heat to 50°C;

[0143] (2) Ferrous sulfate modification: 39 g of the ferrous sulfate was added to the polycarboxylic acid solution, and the mixture was stirred continuously to make the two mixtures fully mixed to obtain a mixed solution A;

[0144] (3) adding 53 g of fly ash to the mixed solution A, stirring, heating and drying, grinding and sieving, and preparing a powder with a moisture content of less than 1% and a particle size of ≤8.47 μm;

[0145] (4) Add 5 g of sodium silicate to the mixed powder and mix well to prepare a cement chromium remover.

[0146] Comparative Example 8

[0147] A cement chromium removal agent comprises the following components by mass: 49% fly ash, 38% ferrous sulfate, 5% sodium metaaluminate, 5% sodium silicate and 3% polycarboxylic acid.

[0148] The preparation method of the above-mentioned cement chromium removal agent comprises the following steps:

[0149] (1) Dissolve 3 g of polycarboxylic acid in water and heat to 50°C;

[0150] (2) Ferrous sulfate modification: 38 g of the ferrous sulfate was added to the polycarboxylic acid solution, and the mixture was stirred continuously to make the two mixtures fully mixed to obtain a mixed solution A;

[0151] (3) adding 49 g of fly ash to the mixed solution A, stirring, heating and drying, grinding and sieving to prepare a powder with a moisture content of less than 1% and a particle size of ≤8.47 μm;

[0152] (4) Add 5 g of sodium silicate and 5 g of sodium aluminate to the mixed powder and mix them evenly to prepare a cement chromium remover.

[0153] Comparative Example 9

[0154] A cement chromium removal agent comprises the following components by mass: 50% fly ash, 37% ferrous sulfate, 4% sodium metaaluminate, 6% sodium silicate and 3% polycarboxylic acid.

[0155] The preparation method of the above-mentioned cement chromium removal agent comprises the following steps:

[0156] (1) Dissolve 3 g of polycarboxylic acid in water and heat to 50°C;

[0157] (2) Ferrous sulfate modification: 37 g of the ferrous sulfate was added to the polycarboxylic acid solution, and the mixture was stirred continuously to make the two mixtures fully mixed to obtain a mixed solution A;

[0158] (3) adding 50 g of fly ash to the mixed solution A, stirring, heating and drying, grinding and sieving, and preparing a powder with a moisture content of less than 1% and a particle size of ≤8.47 μm;

[0159] (4) Add 6 g of sodium silicate and 4 g of sodium aluminate to the mixed powder and mix them evenly to prepare a cement chromium remover.

[0160] Comparative Example 10

[0161] A cement chromium removal agent comprises the following components by mass: 49% fly ash, 37% ferrous sulfate, 5% sodium metaaluminate, 6% sodium silicate and 3% polycarboxylic acid.

[0162] The preparation method of the above-mentioned cement chromium removal agent comprises the following steps:

[0163] (1) Dissolve 3 g of polycarboxylic acid liquid in water and heat to 50°C;

[0164] (2) Ferrous sulfate modification: 37 g of ferrous sulfate was added to the polycarboxylic acid solution, and the mixture was stirred continuously to make the two mixtures fully mixed to obtain a mixed solution A;

[0165] (3) adding 49 g of fly ash to the mixed solution A, stirring, heating and drying, grinding and sieving to prepare a powder with a moisture content of less than 1% and a particle size of ≤8.47 μm;

[0166] (4) Add 6 g of sodium silicate and 5 g of sodium aluminate to the mixed powder and mix them evenly to prepare a cement chromium remover.

[0167] 0.3 g of the cement chromium remover prepared in Examples 1-9 and Comparative Examples 1-10 was added to 100 g of cement, and according to the relevant methods in the national standard GB 31893-2015 "Limits and determination methods of water-soluble chromium (VI) in cement", such as the diphenylphthalocyanine diphosphine spectrophotometry, the content of water-soluble hexavalent chromium after being placed at room temperature, 80°C, and 120°C for 12 hours was detected, respectively. The test results are shown in Table 1.

[0168] Table 1

[0169]

[0170] As can be seen from Table 1, the chromium removal agents of Examples 1-9 are very effective in reducing the water-soluble chromium (VI) in cement, all of which are reduced to less than 10 mg / kg, so that the content of hexavalent chromium in cement meets the standard requirements. Moreover, the effect of chromium removal is less affected by temperature. This is because in addition to providing the reducibility of ferrous sulfate in a weak acid environment to protect the ferrous sulfate, polycarboxylic acid is also wrapped on the surface of ferrous sulfate particles during the modification process of ferrous sulfate, which reduces the area of ​​contact with oxygen and slows down the oxidation process of ferrous sulfate, thereby extending the effective period of the chromium removal agent; at the same time, sodium aluminate will hydrolyze in water to form aluminum oxide tetrahedrons, which react with silicon oxide tetrahedrons hydrolyzed by sodium silicate in water to form hydrated aluminum silicate with a three-dimensional network structure or a layered porous structure. At the same time, the alkaline substances generated by the reaction can decompose the active components in the fly ash, thereby further increasing the porous honeycomb structure in the fly ash. This mutual synergistic effect increases the excellent selective adsorption performance for water-soluble hexavalent chromium; especially in Examples 3-7, the effect of chromium removal is particularly obvious. By comparison, it is found that although Comparative Example 1 also has a certain chromium removal effect, the chromium removal effect is significantly reduced as the temperature increases. The poor chromium removal effect of Comparative Example 2 is because the ferrous sulfate in the comparative example lacks the protection of polycarboxylic acid, and the ferrous sulfate is easily oxidized under high temperature conditions, which reduces its reduction and chromium removal effect. Although citric acid is added in Comparative Example 3, it is unable to form a protective film on the surface of ferrous sulfate due to its short molecular chain, resulting in a significant reduction in the chromium removal effect of the chromium removal agent as the temperature increases. In Comparative Example 4, the chromium removal effect is significantly inferior to that of Examples 1-9, which is caused by the lack of the synergistic adsorption of hydrated aluminosilicate minerals; it can be seen from Comparative Example 5 that the chromium removal effect exceeding the range of Examples 1-9 will be reduced; Comparative Examples 6 and 7, respectively, did not add sodium aluminate and sodium silicate, resulting in the failure to generate hydrated aluminosilicate, and could not produce a synergistic adsorption effect with fly ash, resulting in a reduction in the chromium removal effect.

[0171] Examples 1-9 and Comparative Examples 1-10 were added to cement at a dosage of 0.3%, and the content of water-soluble chromium (VI) after 1d, 30d, 60d, and 90d was detected according to the relevant methods in standard GB31893-2015 "Limits and determination methods of water-soluble chromium (VI) in cement". The test results are shown in Table 2.

[0172] Table 2

[0173]

[0174]

[0175] As can be seen from Table 2, as time goes on, the chromium removal effects of Examples 1-9 and Comparative Examples 1-10 show a similar pattern to that of Table 1, and the chromium removal effect of Examples 1-9 does not decrease significantly as time goes on; especially in Examples 3-7, the chromium removal effect is particularly obvious; but by comparison, it is found that although Comparative Example 1 also has a chromium removal effect, the chromium removal effect decreases as time goes on; the chromium removal effect of Comparative Example 2 is not good because the ferrous sulfate in the comparative example lacks the protection of polycarboxylic acid, and is gradually oxidized in the air as time goes on, reducing its reduction chromium removal effect; although citric acid is added in Comparative Example 3, it cannot form a protective film on the surface of ferrous sulfate due to its short molecular chain, resulting in a decrease in the effect of the chromium removal agent as time goes on; in Comparative Example 4, the chromium removal effect is obviously not as good as that of Examples 1-9, which is caused by the lack of the synergistic adsorption effect of hydrated aluminum silicate minerals; it can be seen from Comparative Example 5 that the chromium removal effect will decrease if the proportion exceeds the range of Examples 1-9.

[0176] Examples 1-9 and Comparative Examples 1-10 were added to cement at a dosage of 0.3%, and the setting time, flexural and compressive strength were tested according to the test method for water consumption and setting time of cement standard consistency in GB / T 1346-2011 and the relevant methods in GB / T 17671-2021 "Test method for strength of cement mortar", and the test results are shown in Table 3.

[0177] Table 3

[0178]

[0179]

[0180] As can be seen from Table 3, Examples 1-9 have improved the compressive strength of cement, especially Examples 3-7, which have a more obvious improvement effect. This is because polycarboxylic acid can reduce the surface energy of cement particles, so that cement particles can fully contact with water, so that hydration is more thorough, more hydration products are produced, and the strength is improved; at the same time, the hydrated aluminum silicate generated by sodium silicate and sodium metaaluminate can fill the gaps of cement hydration products, increase the density of hydration products, and thus improve its strength. However, the excessive sodium metaaluminate in Comparative Examples 5, 6, and 8 shortens the setting time of cement; while the excessive sodium silicate in Comparative Examples 7 and 9 leads to a slight decrease in the strength of cement 28; Comparative Example 10 shows a trend of shortened setting time and decreased strength.

[0181] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A cement chromium removal agent using industrial solid waste, characterized in that: Calculated by mass percentage, the cement chromium remover consists of 49%-63% fly ash, 31%-39% ferrous sulfate, 2%-4% soluble metaaluminate, 3%-5% soluble silicate and 1%-3% polycarboxylic acid.

2. The cement chromium removal agent using industrial solid waste according to claim 1, characterized in that: The soluble aluminate is sodium aluminate or potassium aluminate.

3. The cement chromium removal agent using industrial solid waste according to claim 1, characterized in that: The soluble silicate is sodium silicate or potassium silicate.

4. The cement chromium removal agent using industrial solid waste according to claim 1, characterized in that: The ferrous sulfate is prepared by grinding and removing impurities from ferrous sulfate waste residue.

5. The cement chromium removal agent using industrial solid waste according to claim 1, characterized in that: The polycarboxylic acid includes one or more of polyacrylic acid, polymethacrylic acid, hydrolyzed polymaleic anhydride or phosphine-based polymaleic anhydride.

6. The cement chromium removal agent using industrial solid waste according to claim 1, characterized in that: Calculated by mass percentage, the cement chromium remover consists of 54%-58% fly ash, 34%-36% ferrous sulfate, 2.5%-3.5% soluble aluminate, 3.5%-4.5% soluble silicate and 1.5%-2.5% polycarboxylic acid.

7. The cement chromium removal agent using industrial solid waste according to claim 1, characterized in that: The particle size of the soluble aluminate is ≤38 microns.

8. The cement chromium removal agent using industrial solid waste according to claim 1, characterized in that: The soluble silicate is a powdery fast-dissolving silicate, and the particle size of the powdery fast-dissolving silicate is ≤38 microns.

9. The method for preparing a cement chromium removal agent using industrial solid waste according to any one of claims 1 to 8, characterized in that: (1) dissolving the polycarboxylic acid liquid in water and heating it to 40° C.-50° C.; (2) Modification of ferrous sulfate: Grind the ferrous sulfate waste residue to remove impurities to obtain ferrous sulfate, add the ferrous sulfate to the polycarboxylic acid liquid, and continue stirring to mix the two evenly to obtain a mixed solution A; (3) Add the fly ash to the mixed solution A, stir, heat and dry, grind and sieve to obtain a mixed powder with a moisture content of less than 1% and a particle size of ≤8.47 μm. (4) adding soluble silicate and soluble aluminate to the mixed powder, stirring and mixing them evenly to obtain the cement chromium remover.

10. The use of a cement chromium removal agent using industrial solid waste according to any one of claims 1 to 8, characterized in that: The cement chromium remover is used for removing water-soluble hexavalent chromium in cement, and the cement is general-purpose cement, special-purpose cement or characteristic cement.

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