Alkali-activated gel geopolymer as well as preparation method and application thereof

Abstract

The invention discloses an alkali-activated gel geopolymer and a preparation method and application thereof.The alkali-activated gel geopolymer is prepared from, by 100 parts, 10-70 parts of municipal solid waste incineration fly ash, 10-70 parts of silicon powder materials, 5-30 parts of an alkali activator, 10-50 parts of water and 1-5 parts of NaOH; wherein the alkaline activator comprises sodium silicate and sodium hydroxide; the alkali-activated gel geopolymer is prepared by steam curing. The material in a steam curing mode has low free Cu and Cr with high leaching property, the total Pb with low leaching property has a small difference from samples in other curing schemes, the environment influence is low in risk when the material is used as an engineering material or directly buried, the Na distribution of the geopolymer sample shows a good polymerization degree, and the geopolymer sample has high leaching property. The compressive strength is very excellent, and the application prospect is good.

Description

Technical Field

[0001] The present invention relates to the technical field of geopolymer preparation, and in particular to an alkali-activated gel geopolymer and a preparation method and application thereof. Background Art

[0002] With the development and progress of society, the treatment of the increasing amount of industrial solid waste is an urgent environmental problem. Landfilling solid waste is considered a short-term, unsustainable, land-resource-consuming measure that cannot realize their resource utilization. The use of solid waste to synthesize geopolymers is considered to be a way to achieve both the treatment and resource utilization of solid waste. Especially for the treatment of solid waste containing heavy metals, the synthesized geopolymer has a three-dimensional network structure that can effectively encapsulate heavy metal ions. At the same time, geopolymers, an inorganic adhesive, have good fire resistance, high chemical resistance, good mechanical strength, and low greenhouse gas emissions during the production process. Solid waste synthetic geopolymers are considered to be a more sustainable building material than ordinary Portland cement.

[0003] Geopolymer is a new type of cementitious material, which has the characteristics of organic matter, ceramics and cement. Compared with conventional silicate cement, it has the advantages of high strength, fast hardening and acid and alkali corrosion resistance. At present, geopolymer composite materials are mainly prepared by using metakaolin, slag and fly ash activated in alkaline solution as aluminum-silicon mineral materials. The performance of geopolymer depends largely on the type of aluminum-silicate material and alkaline solution used, which can significantly affect the setting time and compressive strength of the geopolymer composite.

[0004] At present, fly ash is commonly used in the preparation of geopolymers. In addition, fly ash is activated by an alkaline activator to carry out a chemical reaction. One of the most commonly used alkaline activators is water glass. At present, most literature reports that the appropriate modulus (SiO2 / Na2O) of water glass is in the range of 0.8 to 2.0.

[0005] Municipal solid waste incineration fly ash (MSWIFA) is a byproduct of the municipal solid waste incineration (MSWI) industry. The presence of heavy metals and dioxins makes it classified as hazardous solid waste. MSWIFA is used in the synthesis of geopolymers, which has attracted widespread attention because it can fix the heavy metals in it and realize its resource utilization. Exploring better material properties and heavy metal solidification efficiency has positive significance for the larger-scale resource utilization of materials containing heavy metals such as MSWIFA geopolymers.

[0006] Therefore, there is an urgent need for a method that can effectively combine municipal solid waste incineration fly ash with an alkaline activator to effectively solve the problem of treating municipal solid waste incineration fly ash. Summary of the invention

[0007] The technical problem to be solved by this application is to overcome the defects in the prior art such as the lack of effective treatment means for municipal solid waste incineration fly ash and the lack of an oxidation method for combining municipal solid waste incineration fly ash with an alkaline activator, and to provide an alkali-activated gel geopolymers and its preparation method and application. This application uses steam curing to make the free heavy metals relatively low, with lower heavy metal leaching potential.

[0008] This application adopts the following technical solutions to solve the above technical problems:

[0009] This application provides an alkali-activated gel geopolymers. Calculated on a basis of 100 parts, the raw materials include:

[0010] 10 - 70 parts of municipal solid waste incineration fly ash, 10 - 70 parts of silicon powder material, 5 - 30 parts of alkaline activator, 10 - 50 parts of water, 1 - 5 parts of NaOH;

[0011] Among them, the alkaline activator includes sodium silicate and sodium hydroxide; the alkali-activated gel geopolymers is prepared by steam curing.

[0012] Preferably, calculated on a basis of 100 parts, the raw materials include:

[0013] 22 parts of municipal solid waste incineration fly ash, 35 parts of silicon powder material, 25 parts of alkaline activator, 18 parts of water, 2 parts of Na2O.

[0014] Preferably, the elemental ratio in the municipal solid waste incineration fly ash includes: the mass fraction of CaO is 40 - 50%, the mass fraction of SiO2 is 2 - 4%, the mass fraction of Al2O3 is 0.5 - 1%, the mass fraction of Na2O is 8 - 10%, the mass fraction of Fe2O3 is 0.5 - 1%, the mass fraction of K2O is 4 - 6%, the mass fraction of MgO is 1 - 2%, the mass fraction of P2O5 is 0.2 - 0.5%, and the mass fraction of Cl - is 18 - 25%.

[0015] Preferably, the elemental ratio in the municipal solid waste incineration fly ash includes: the mass fraction of CaO is 47.04%, the mass fraction of SiO2 is 3.45%, the mass fraction of Al2O3 is 0.91%, the mass fraction of Na2O is 9.48%, the mass fraction of Fe2O3 is 0.98%, the mass fraction of K2O is 4.52%, the mass fraction of MgO is 1.30%, the mass fraction of P2O5 is 0.37%, and the mass fraction of Cl is 21.4%.

[0016] Preferably, the silicon powder material includes one of fly ash, metakaolin, kaolin, blast furnace slag, steel slag, clay, red mud.

[0017] Preferably, the proportions of the powdery silicon material are as follows: the mass fraction of CaO is 4-5%, the mass fraction of SiO2 is 9-12%, the mass fraction of Al2O3 is 18-22%, the mass fraction of Na2O is 5-7%, the mass fraction of Fe2O3 is 48-60%, the mass fraction of K2O is 0.1-0.3%, the mass fraction of MgO is 0.15-0.3%, the mass fraction of P2O5 is 0.15-0.3%, and the mass fraction of Cl is 0.08-0.15%.

[0018] Preferably, the proportions of the powdery silicon material are as follows: the mass fraction of CaO is 4.5%, the mass fraction of SiO2 is 10.37%, the mass fraction of Al2O3 is 19.37%, the mass fraction of Na2O is 5.69%, the mass fraction of Fe2O3 is 52.61%, the mass fraction of K2O is 0.18%, the mass fraction of MgO is 0.22%, the mass fraction of P2O5 is 0.28%, and the mass fraction of Cl is 0.1%.

[0019] The present application also provides a preparation method of an alkali-activated gel geopolymers, which is characterized in that after the municipal solid waste incineration fly ash, the powdery silicon material, the alkaline activator, and the additive are fully stirred in a cement paste mixer to obtain a paste, it is vibrated and compacted to complete pouring, and then steam curing is carried out.

[0020] On the basis of conforming to the common knowledge in the art, the above preferred conditions can be combined arbitrarily to obtain various preferred examples of the present application.

[0021] The reagents and raw materials used in the present application are all commercially available.

[0022] The positive and progressive effects of the present application are as follows: the materials under the steam curing method in the present application have low free and highly leachable Cu and Cr, the total low leachable Pb has a small difference from the samples under other curing schemes, and it is of low risk to the environmental impact when used as an engineering material or directly landfilled, with good environmental friendliness. The Na distribution of the geopolymer samples shows good polymerization degree, and the compressive strength is very excellent, having good application prospects. Specific Embodiments

[0023] The present application will be further illustrated below by way of examples, but the present application is not limited to the scope of the described examples. For the experimental methods without specific conditions in the following examples, they are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0024] The experimental methods used in the following examples are all conventional methods unless otherwise specified.

[0025] The red mud in the following examples is a by-product of the aluminum processing industry.

[0026] Example 1

[0027] This application provides a preparation method of an alkali-activated gel geopolymers. After taking various raw materials in Table 2 in a cement paste mixer and fully stirring to obtain a paste, pour it into a 20mm×20mm×20mm mold, vibrate it densely to complete the pouring. The slurry is sealed and cured with a plastic film in the mold for 24h, then demolded, and the prepared FRGM specimens are placed in steam curing.

[0028] Among them, the compound compositions of municipal solid waste incineration fly ash and red mud are shown in Table 1.

[0029] Table 1 Main compound compositions (wt%) of municipal solid waste incineration fly ash (MSW) and red mud (RM)

[0030]

[0031] The mix proportion of the alkali-activated gel geopolymers is shown in Table 2.

[0032] Table 2 Mix proportion design

[0033]

[0034] Na2O% refers to the equivalent Na2O% of the total mass of the precursors, reflecting the alkali addition amount, which is provided by NaOH and sodium silicate solution.

[0035] Comparative Example 1

[0036] The difference from Example 1 is that standard curing is carried out.

[0037] Effect Example 1.

[0038] After 28d of curing, the heavy metal leaching concentrations of all FGM samples were obtained through leaching tests. Fig.8 compares the heavy metal leaching concentrations of all samples with the regulatory limits, and the detailed data are shown in Table 4. After S / S, the heavy metal leaching concentrations of all samples were significantly reduced. Although the leaching concentrations of all 6 elements meet the requirements of the USEPA limit, the leaching risks of some elements still exceed the acceptable limits of Chinese standards, such as Cd and Ni in F60R40N6 and Ni in F80R20N6. Among the samples in Group A, compare F20R80N6 and F40R60N6. Although the MFA content of the two samples differs by 20%, the leaching concentrations of the six heavy metal elements in F40R60N6 are always lower than or similar to those in F20R80N6. Combining the discussion in Section 3.6, it is proved that the reduction of the heavy metal leaching concentration in F40R60N6 is not related to the dilution effect caused by the change of MFA content. The S / S of F40R60N6 for toxic elements is attributed to the low permeability of the matrix and the physical encapsulation and chemical bonding of the target elements by the aluminosilicate gel network.

[0039] Effect Example 2

[0040] Heavy metal leaching

[0041] Table 4

[0042]

[0043] After 28 days of curing, the heavy metal leaching concentrations of all FGM samples were obtained through leaching tests. Fig. 8 compares the heavy metal leaching concentrations of all samples with the regulatory limits, and the detailed data are shown in Table 4. After S / S, the heavy metal leaching concentrations of all samples were significantly reduced. Although the leaching concentrations of all six elements met the requirements of the USEPA limit, the leaching risks of some elements still exceeded the acceptable limits of the Chinese standard, such as Cd and Ni in F60R40N6 and Ni in F80R20N6. Among the samples in Group A, compare F20R80N6 and F40R60N6. Although the MFA content of the two samples differed by 20%, the leaching concentrations of the six heavy metal elements in F40R60N6 were always lower than or similar to those in F20R80N6. Combining the discussion in Section 3.6, it was demonstrated that the reduction in the heavy metal leaching concentration in F40R60N6 was not related to the dilution effect caused by the change in MFA content. The S / S of F40R60N6 for toxic elements was attributed to the low permeability of the matrix and the physical encapsulation and chemical bonding of the target elements by the aluminosilicate gel network.

[0044] Finally, it should also be noted that in this application, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device.

[0045] Although the present application has been disclosed above through the description of specific embodiments of the present application, it should be understood that those skilled in the art can design various modifications, improvements or equivalents to the present application within the spirit and scope of the appended claims. These modifications, improvements or equivalents should also be considered to be included within the scope claimed by the present application.

Claims

1. An alkali-activated gel geopolymers, characterized in that, Based on 100 parts, the raw materials include: 10 - 70 parts of municipal solid waste incineration fly ash, 10 - 70 parts of silicon powder material, 5 - 30 parts of alkaline activator, 10 - 50 parts of water, 1 - 5 parts of NaOH; Among them, the alkaline activator includes sodium silicate and sodium hydroxide; the alkali-activated gel geopolymers are prepared by steam curing.

2. The alkali-activated gel geopolymers according to claim 1, characterized in that, Based on 100 parts, the raw materials include: 22 parts of municipal solid waste incineration fly ash, 35 parts of silicon powder material, 25 parts of alkaline activator, 18 parts of water, 2 parts of Na2O.

3. The alkali-activated gel geopolymers according to claim 1 or 2, characterized in that, The elemental proportions in the municipal solid waste incineration fly ash include: the mass fraction of CaO is 40-50%, the mass fraction of SiO2 is 2-4%, the mass fraction of Al2O3 is 0.5-1%, the mass fraction of Na2O is 8-10%, the mass fraction of Fe2O3 is 0.5-1%, the mass fraction of K2O is 4-6%, the mass fraction of MgO is 1-2%, the mass fraction of P2O5 is 0.2-0.5%, and Cl - The mass fraction is 18-25%.

4. The alkali-activated gel geopolymers according to claim 3, characterized in that, The elemental ratios in the municipal solid waste incineration fly ash include: mass fraction of CaO is 47.04%, mass fraction of SiO2 is 3.45%, mass fraction of Al2O3 is 0.91%, mass fraction of Na2O is 9.48%, mass fraction of Fe2O3 is 0.98%, mass fraction of K2O is 4.52%, mass fraction of MgO is 1.30%, mass fraction of P2O5 is 0.37%, mass fraction of Cl is 21.4%.

5. The alkali-activated gel geopolymers according to claim 1 or 2, characterized in that, The silicon powder material includes one of fly ash, metakaolin, kaolin, blast furnace slag, steel slag, clay, red mud.

6. The alkali-activated gel geopolymers according to claim 1 or 2, characterized in that, The ratios of the silicon powder material include: mass fraction of CaO is 4 - 5%, mass fraction of SiO2 is 9 - 12%, mass fraction of Al2O3 is 18 - 22%, mass fraction of Na2O is 5 - 7%, mass fraction of Fe2O3 is 48 - 60%, mass fraction of K2O is 0.1 - 0.3%, mass fraction of MgO is 0.15 - 0.3%, mass fraction of P2O5 is 0.15 - 0.3%, mass fraction of Cl is 0.08 - 0.15%.

7. The alkali-activated gel geopolymers according to claim 6, characterized in that, The ratios of the silicon powder material include: mass fraction of CaO is 4.5%, mass fraction of SiO2 is 10.37%, mass fraction of Al2O3 is 19.37%, mass fraction of Na2O is 5.69%, mass fraction of Fe2O3 is 52.61%, mass fraction of K2O is 0.18%, mass fraction of MgO is 0.22%, mass fraction of P2O5 is 0.28%, mass fraction of Cl is 0.1%.

8. A preparation method of an alkali-activated gel geopolymers, characterized in that, After fully stirring the municipal solid waste incineration fly ash, the silicon powder material, the alkaline activator, and the additive in a cement paste mixer to obtain a paste, vibrate it densely to complete pouring, and perform steam curing.

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