Water-soluble hexavalent chromium reduction type powder cement chromium reducing agent and preparation method thereof

Abstract

The invention relates to a water-soluble hexavalent chromium reduction type powder cement chromium reducing agent. The powder cement chromium reducing agent is prepared from the following raw materials in percentage by mass: 20-25% of a reducing agent, 1% of an antioxidant, 2-4% of a microcapsule shell coating material and the balance of water, the reducing agent is one or two of ferrous sulfate heptahydrate and stannous chloride. Meanwhile, the invention further discloses a preparation method of the powder cement chromium reducing agent. In a high-temperature environment, the problem that the reduction efficiency of FeSO4. 7H2O and / or SnCl2 is reduced along with temperature rise can be effectively inhibited, the reduction efficiency of the cement chromium reducing agent can reach 90%, and meanwhile, the cement chromium reducing agent almost has no influence on the physical performance of cement.

Description

Technical Field

[0001] The invention relates to the technical field of building material additives, and in particular to a water-soluble hexavalent chromium reducing powder cement chromium reducing agent and a preparation method thereof. Background Art

[0002] Cement is a basic material for current economic construction. Due to the raw materials and production process, cement and its products often contain a small amount of toxic and harmful substances such as cadmium, chromium, and lead. Among them, hexavalent chromium (Cr 6+ ) is the most serious: the harm of chromium is highly dependent on the form of existence. Chromium exists in several chemical forms with different oxidation states from zero to six, but in the natural environment, only Cr(III) and Cr(VI) are stable. Cr(III) in alkaline environment has low solubility and low reactivity, and is easily precipitated by OH-, so it has the least impact on the environment and health. On June 18, 2003, the European Union issued the 2003 / 53 / EC ban, stipulating that the soluble hexavalent chromium in cement should be less than 2ppm. On September 11, 2015, my country issued the mandatory standard GB 31893-2015 "Limits and determination methods of water-soluble hexavalent chromium (VI) in cement" to limit the content of hexavalent chromium in cement. The standard stipulates that the content of soluble hexavalent chromium in cement shall not exceed 10ppm.

[0003] At present, hexavalent chromium reducing agents can be divided into liquid reducing agents and solid reducing agents according to their state; they can be divided into inorganic reducing agents and organic reducing agents according to the type of reducing groups or ions. At present, the most studied and applied reducing agents are ferrous salts, stannous salts, divalent manganese salts, sulfides, aldehydes and slag. However, these traditional reducing agents generally have various disadvantages such as poor reducing performance, poor stability, easy failure at high temperature, affecting cement performance, and endangering human health. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a water-soluble hexavalent chromium reducing powder cement chromium reducing agent which can effectively improve the reduction efficiency.

[0005] Another technical problem to be solved by the present invention is to provide a method for preparing the water-soluble hexavalent chromium reducing powder cement chromium reducing agent.

[0006] In order to solve the above problems, the present invention discloses a water-soluble hexavalent chromium reducing powder cement chromium reducing agent, which is characterized in that the powder cement chromium reducing agent is made of the following raw materials by mass percentage: 20% to 25% of reducing agent, 1% of antioxidant, 2% to 4% of microcapsule shell coating material, and the balance is water; the reducing agent is one or both of ferrous sulfate heptahydrate and stannous chloride.

[0007] The antioxidant is one or both of vitamin C and sodium dioctyl sulfosuccinate.

[0008] The microcapsule shell coating material is one or more of polysaccharide substances and protein substances; the polysaccharide substance is gum arabic or shell ribose; and the protein substance is gelatin.

[0009] The preparation method of a water-soluble hexavalent chromium reducing powder cement chromium reducing agent as described above is characterized in that: the method refers to first weighing according to the ratio; then mixing the capsule shell coating material and water evenly to obtain a mixed solution A; adding an antioxidant to the mixed solution A, stirring for 3 to 5 minutes, then adding a reducing agent, stirring at room temperature for 30 to 40 minutes, and stopping stirring after the solution is uniform, to obtain a mixed solution B; finally, the mixed solution B is spray-dried to obtain a dry powder cement chromium reducing agent.

[0010] The spray drying conditions are as follows: the inlet air temperature is 180°C and the feed flow rate is 4-6 mL / min.

[0011] Compared with the prior art, the present invention has the following advantages: 1. Vitamin C and / or sodium dioctyl sulfosuccinate are used as antioxidants in the present invention, which can effectively reduce the oxidation rate of FeSO4·7H2O and / or SnCl2 in the microcapsule structure. At the same time, sodium dioctyl sulfosuccinate is an anionic surfactant, has high penetration, fast and uniform penetration, and good lubricity.

[0012] 2. Generally, FeSO4·7H2O almost completely loses its reducing ability at 80-100°C, while the cement chromium reducing agent of the present invention is a dry powder coated with a microcapsule structure, which can effectively inhibit the problem of decreased reduction efficiency of FeSO4·7H2O and / or SnCl2 as the temperature rises under high temperature environment.

[0013] 3. According to tests, the cement chromium reduction agent prepared by the present invention has a reduction efficiency of up to 90%, and has almost no effect on the physical properties of cement. DETAILED DESCRIPTION

[0014] A water-soluble hexavalent chromium reducing powder cement chromium reducing agent is prepared from the following raw materials by mass percentage (g / g): 20%-25% of a reducing agent, 1% of an antioxidant, 2%-4% of a microcapsule shell coating material, and the remainder is water; the reducing agent is one or both of ferrous sulfate heptahydrate and stannous chloride.

[0015] Wherein: the antioxidant is one or two of vitamin C and sodium dioctyl sulfosuccinate.

[0016] The microcapsule shell coating material is one or more of polysaccharide substances and protein substances; the polysaccharide substance is gum arabic or shell ribose; and the protein substance is gelatin.

[0017] The preparation method of the water-soluble hexavalent chromium reduction type powder cement chromium reducing agent: First, weigh according to the ratio; then mix the capsule shell coating material and water evenly to obtain a mixed solution A; add an antioxidant to the mixed solution A, stir for 3 to 5 minutes, then add a reducing agent, stir at room temperature for 30 to 40 minutes, and stop stirring after the solution is uniform to obtain a mixed solution B; finally, spray dry the mixed solution B with an inlet air temperature of 180°C and a feed flow rate of 4 to 6 mL / min until the spray drying of the mixed solution B is completed to obtain a dry powder cement chromium reducing agent.

[0018] The materials used in the following examples 1 to 4 are described as follows: Ferrous sulfate heptahydrate and stannous chloride were both commercially available and of analytical grade, vitamin C was of Shijiazhuang Pharmaceutical Group food grade, and sodium dioctyl sulfosuccinate, gelatin, ribose, and gum arabic were all commercially available.

[0019] Example 1 A water-soluble hexavalent chromium reducing powder cement chromium reducing agent is prepared from the following raw materials: 21 g of reducing agent, 1 g of antioxidant, 2 g of microcapsule shell coating material, and 76 g of water.

[0020] The reducing agent is stannous chloride, the antioxidant is sodium dioctyl sulfosuccinate, and the microcapsule shell coating material is gum arabic.

[0021] The preparation method of the water-soluble hexavalent chromium reduction type powder cement chromium reducing agent: First, weigh according to the ratio; then mix the capsule shell coating material and water evenly to obtain a mixed solution A; add an antioxidant to the mixed solution A, stir for 3 minutes, then add a reducing agent, stir at room temperature for 30 minutes, stop stirring after the solution is uniform, and obtain a mixed solution B; finally, spray dry the mixed solution B, with an inlet air temperature of 180°C and a feed flow rate of 6mL / min, until the spray drying of the mixed solution B is completed, and a dry powder cement chromium reducing agent is obtained.

[0022] Example 2 A water-soluble hexavalent chromium reducing powder cement chromium reducing agent is prepared from the following raw materials: 23 g of reducing agent, 1 g of antioxidant, 3 g of microcapsule shell coating material, and 73 g of water.

[0023] The reducing agent is stannous chloride, the antioxidant is sodium dioctyl sulfosuccinate, and the microcapsule shell coating material is shell ribose.

[0024] The preparation method of the water-soluble hexavalent chromium reduction type powder cement chromium reducing agent: First, weigh according to the ratio; then mix the capsule shell coating material and water evenly to obtain mixed solution A; add antioxidant to mixed solution A, stir for 4 minutes, then add reducing agent, stir at room temperature for 40 minutes, stop stirring after the solution is uniform, and obtain mixed solution B; finally, spray dry the mixed solution B with an inlet air temperature of 180°C and a feed flow rate of 4mL / min until the spray drying of the mixed solution B is completed, and obtain a dry powder cement chromium reducing agent.

[0025] Example 3 A water-soluble hexavalent chromium reducing powder cement chromium reducing agent is prepared from the following raw materials: 20 g of reducing agent, 1 g of antioxidant, 2 g of microcapsule shell coating material, and 77 g of water.

[0026] The reducing agent is ferrous sulfate heptahydrate, the antioxidant is sodium dioctyl sulfosuccinate, and the microcapsule shell coating material is gum arabic.

[0027] The preparation method of the water-soluble hexavalent chromium reduction type powder cement chromium reducing agent: First, weigh according to the ratio; then mix the capsule shell coating material and water evenly to obtain a mixed solution A; add an antioxidant to the mixed solution A, stir for 5 minutes, then add a reducing agent, stir at room temperature for 30 minutes, stop stirring after the solution is uniform, and obtain a mixed solution B; finally, spray dry the mixed solution B, with an inlet air temperature of 180°C and a feed flow rate of 4mL / min, until the spray drying of the mixed solution B is completed, and a dry powder cement chromium reducing agent is obtained.

[0028] Example 4 A water-soluble hexavalent chromium reducing powder cement chromium reducing agent is prepared from the following raw materials: 20 g of reducing agent, 1 g of antioxidant, 3 g of microcapsule shell coating material, and 76 g of water.

[0029] The reducing agent is 10 g of ferrous sulfate heptahydrate and 10 g of stannous chloride, the antioxidant is 0.5 g of vitamin C and 0.5 g of sodium dioctyl sulfosuccinate, and the microcapsule shell coating material is gelatin.

[0030] The preparation method of the water-soluble hexavalent chromium reduction type powder cement chromium reducing agent: First, weigh according to the ratio; then mix the capsule shell coating material and water evenly to obtain a mixed solution A; add an antioxidant to the mixed solution A, stir for 3 minutes, then add a reducing agent, stir at room temperature for 30 minutes, stop stirring after the solution is uniform, and obtain a mixed solution B; finally, spray dry the mixed solution B, with an inlet air temperature of 180°C and a feed flow rate of 6mL / min, until the spray drying of the mixed solution B is completed, and a dry powder cement chromium reducing agent is obtained.

[0031] The powder cement chromium reducing agent obtained in the above Examples 1 to 4 was tested, and its performance is shown in Table 1.

[0032] Table 1 Performance of powder cement chromium reducing agent in: ⑴The embedding rate is calculated as follows: The mass of reducing agent embedded in the microcapsules / the mass of total reducing agent × 100%.

[0033] (2) The hexavalent chromium reduction efficiency is tested according to the national standard GB31893-2015 "Limits and determination methods of water-soluble hexavalent chromium (VI) in cement" and calculated according to the following formula: (Water-soluble hexavalent chromium content in cement before reduction - hexavalent chromium content in cement after reduction) / water-soluble hexavalent chromium content in cement before reduction × 100%.

Claims

1. A water-soluble hexavalent chromium reduction powder cement chromium reducing agent, characterized in that: The powder cement chromium reducing agent is prepared from the following raw materials by mass percentage: 20%-25% of a reducing agent, 1% of an antioxidant, 2%-4% of a microcapsule shell coating material, and the balance is water; the reducing agent is one or both of ferrous sulfate heptahydrate and stannous chloride.

2. A water-soluble hexavalent chromium reduction type powder cement chromium reducing agent as claimed in claim 1, characterized in that: The antioxidant is one or both of vitamin C and sodium dioctyl sulfosuccinate.

3. A water-soluble hexavalent chromium reducing powder cement chromium reducing agent as claimed in claim 1, characterized in that: The microcapsule shell coating material is one or more of polysaccharide substances and protein substances; the polysaccharide substance is gum arabic or shell ribose; and the protein substance is gelatin.

4. A method for preparing a water-soluble hexavalent chromium reducing powder cement chromium reducing agent according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: firstly weighing the mixture according to the proportion; then uniformly mixing the capsule shell coating material and water to obtain a mixed solution A; adding an antioxidant to the mixed solution A, stirring for 3 to 5 minutes, then adding a reducing agent, stirring at room temperature for 30 to 40 minutes, and stopping stirring after the solution is uniform to obtain a mixed solution B; finally, spray drying the mixed solution B to obtain a dry powder cement chromium reducing agent.

5. The method for preparing a water-soluble hexavalent chromium reducing powder cement chromium reducing agent according to claim 4, characterized in that: The spray drying conditions are as follows: the inlet air temperature is 180°C and the feed flow rate is 4-6 mL / min.

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