Acid-excited metakaolin-ferrotitanium tailing-based lead ion fixing and sealing geopolymer material and preparation method of acid-excited metakaolin-ferrotitanium tailing-based lead ion fixing and sealing geopolymer material

Abstract

The invention relates to the technical field of acid-activated cementing materials, and particularly discloses an acid-activated metakaolin-ferrotitanium tailing-based lead ion fixing and sealing geopolymer material and a preparation method thereof in order to solve the problems that an existing acid-activated geopolymer material is poor in stability and reduced in mechanical property. The geopolymer material is prepared from the following components in parts by mass: 20 to 35 parts of ferrotitanium tailings, 30 to 45 parts of metakaolin, 5 to 10 parts of nano silicon dioxide, 15 to 25 parts of phosphoric acid composite exciting agent and 0.5 to 2.5 parts of solid sealing auxiliary agent, the phosphoric acid composite exciting agent comprises phosphoric acid and ammonium dihydrogen phosphate, and the sealing auxiliary agent comprises modified attapulgite and sodium polyacrylate. Through compounding of multiple components, multiple synergistic effects of physical encapsulation, ion exchange, chemical bonding and interface adsorption enhancement are realized, the lead ion encapsulation efficiency and mechanical properties are improved, the maintenance energy consumption is reduced, and the problems of insufficient long-term stability, low low-temperature curing efficiency and the like of the existing acid-activated geopolymer material can be effectively solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of acid-activated cementitious materials, in particular, relates to an acid-activated metakaolin-titanium-iron tailings-based solidified lead ion geological polymer material and a preparation method thereof. BACKGROUND

[0002] Geopolymers are a kind of inorganic cementitious materials generated by chemical reaction of aluminosilicate mineral raw materials such as fly ash, slag, metakaolin, etc., and activators such as sodium hydroxide and sodium silicate solution. They have high strength, high durability, high temperature resistance, corrosion resistance, and other characteristics, and have low energy consumption, low carbon emissions, strong raw material compatibility, and excellent durability in the production process. They are considered as green alternative materials to traditional cement and are widely used in building structures, solid waste treatment, wear-resistant and corrosion-resistant engineering, etc. Therefore, using geopolymers as cement for the building industry can effectively alleviate the ecological degradation and environmental pollution caused by sand and limestone mining and cement production, etc.

[0003] In addition, the accumulation scale of industrial solid waste such as titanium-iron tailings continues to expand, and its low activity greatly hinders resource utilization. At the same time, heavy metal pollution problems such as lead ions are particularly prominent, and Pb 2+ Such heavy metal ions pose a long-term threat to soil and water due to their high toxicity and bioaccumulation.

[0004] Based on the above situation, it has been proposed to use titanium-iron tailings as raw material components to prepare geological polymer materials and replace cement in the building industry. For example, the patent with publication number CN108640547A provides an iron tailings / metakaolin-based geological polymer and a preparation method thereof. The components are prepared as follows: iron tailings: 40.8-52.5wt%, metakaolin: 29.2-37.5wt%, alkali slag: 10-30wt%, and the mass of the alkali activator solution is 25-35wt% of the total mass of the solid powder. First, mix the iron tailings, metakaolin, and alkali slag in proportion, then add the alkali activator solution prepared from sodium hydroxide, water, and liquid water glass to the well-mixed raw materials, stir, then press into shape, and after demolding, place the sample in a curing box at 80℃ for a certain period of time, then in a standard constant temperature and humidity curing box for a specified period of time to obtain an iron tailings / metakaolin / alkali slag geological polymer.

[0005] Compared with traditional alkali-activated systems, acid-activated geopolymers can form a stable heavy metal solidification matrix by adjusting P / Si, P / Al, Al / Si, Fe / Si, etc., so acid-activated geopolymers have become an important development direction. However, the stability of composite geopolymer materials under acidic conditions is poor, and the acid resistance is insufficient; and the acid activation to improve the Pb 2+The curing rate of the acid-activated geopolymer material is reduced, and the mechanical properties of the material are obviously decreased with the increase of the heavy metal content. Therefore, there is an urgent need for a geopolymer material system and a production process thereof, which has high utilization rate of solid waste, is stable, has good mechanical properties and high environmental safety, so as to realize the efficient solidification of Pb 2+ and the resource utilization of tailings, so as to solve the problems of resource waste and environmental pollution caused by the accumulation of titanium-iron tailings. 2+ SUMMARY

[0006] The present application aims to solve the problems of poor stability and decreased mechanical properties of the existing acid-activated geopolymer material.

[0007] The present application is achieved by the following technical solutions: The acid-activated metakaolin-titanium-iron tailings-based solidification lead ion geopolymer material provided by the present application comprises, by mass fraction, 20-35 parts of titanium-iron tailings, 30-45 parts of metakaolin, 5-10 parts of nano-silicon dioxide, 15-25 parts of a phosphoric acid composite activator and 0.5-2.5 parts of a solidification aid. The phosphoric acid composite activator comprises phosphoric acid and ammonium dihydrogen phosphate, and the solidification aid comprises modified attapulgite and sodium polyacrylate.

[0008] Preferably, the content of Pb 2+ in the geopolymer material is 0.5-2.5%, the Fe / Si ratio is 0.06-0.15, the P / Al ratio is 0.65-0.85, and the Si / Al ratio is 1.2-1.8.

[0009] Preferably, the titanium-iron tailings contain 28-35wt% SiO2, 22-20wt% Fe2O3 and 3-5wt% CaO by mass fraction, and the specific surface area of the titanium-iron tailings is 2500-2600m 2 / kg, and the particle size is ≤20μm.

[0010] Preferably, the metakaolin contains 52-60wt% SiO2 and 42-50wt% Al2O3, and the specific surface area of the metakaolin is 2000-2200m 2 / kg, and the particle size is ≤20μm.

[0011] Preferably, the specific surface area of the nano-silicon dioxide is 500-800m 2 / kg, and the particle size is 10-20μm.

[0012] Preferably, the phosphoric acid composite activator comprises 80-90% phosphoric acid by mass fraction, 5-8% ammonium dihydrogen phosphate by mass fraction and distilled water, and the solute concentration of the phosphoric acid composite activator is controlled to be 8-12mol / L.

[0013] ​Preferably, the modified palygorskite is obtained by modifying palygorskite clay with 3-aminopropyl triethoxysilane, and the modified palygorskite accounts for 0.5-2% of the total mass of the geopolymer material.

[0014] Preferably, the molecular weight of the sodium polyacrylate is controlled at 8-10 million, and the sodium polyacrylate accounts for 0.1-0.5% of the total mass of the geopolymer material.

[0015] The application further provides a preparation method of the acid-activated metakaolin-titanium-iron tailings-based geopolymer material for sealing lead ions. S1 pretreatment: The titanium-iron tailings industrial solid waste containing lead is calcined at 600-650 DEG C for 1-3 h, and then cooled to obtain titanium-iron tailings as a raw material for standby use; The titanium-iron tailings, metakaolin and nano-silicon dioxide are stirred at 1500-2000 r / min for 20 min to obtain a mixed base material; S2 preparation of a phosphoric acid composite activator: The phosphoric acid, ammonium dihydrogen phosphate and distilled water are placed in a 40-50 DEG C constant-temperature water bath, stirred for 30 min, and then cooled to obtain a phosphoric acid composite activator for standby use; S3 material recombination: The mixed base material is added with modified palygorskite and sodium polyacrylate, and stirred at 500-800 r / min for 5-15 min, then the phosphoric acid composite activator is added and continuously stirred for 5-10 min, and then stirred at 2000-2500 r / min for 5-8 min to form a uniform slurry; S4 curing and shaping: The slurry is placed in a mold, subjected to vibration degassing, and then sequentially cured at 35-45 DEG C for 10-20 h, cured at 60-80 DEG C for 3-8 h, and finally cured at room temperature under a humidity of 60-70% for 8-10 h to be solidified and shaped to obtain the geopolymer material.

[0016] Preferably, in step S4, the vibration degassing is performed in a vacuum environment of -0.09 to -0.08 MPa, and the vibration frequency is controlled at 50-60 Hz for 10 min.

[0017] The technical scheme of the application has the following beneficial effects: The acid-activated metakaolin-titanium-iron tailings-based geopolymer material for sealing lead ions and the preparation method thereof can improve the sealing effect and stability of lead and other heavy metal ions through four synergistic mechanisms of physical encapsulation, ion exchange, chemical bonding and interface adsorption.

[0018] Specifically, the nanosilica and the ilmenite tailings synergize to form dense nanopores with a pore size of 1-3 nm, the dense and small pores can enhance the confinement effect, and the Pb is fixed through the double effects of pore interception and network wrapping 2+ , to realize physical encapsulation; then, through the synergy of the modified attapulgite surface amino groups and AlPO4, the adsorption capacity is improved through the double ion exchange effects of Al 3+ -Pb 2+ and NH2-Pb 2+ , to realize ion exchange; secondly, the NH 4+ in the phosphoric acid solution promotes the reaction of Pb 2+ with HPO4 2- and PO4 3- to generate double precipitates of PbHPO4 and Pb3(PO4)2, and form Si-O-Pb and P-O-Pb covalent bonds with the silicon-oxygen tetrahedron, to realize strong chemical bonding); in addition, the sodium polyacrylate forms an adsorption film at the material interface, forms a coordination compound with Pb 2+ through the carboxyl group, and the layered structure of the modified attapulgite provides additional adsorption sites, which can significantly strengthen the interface adsorption effect.

[0019] Through the synergistic effect of the above-mentioned multiple components, the problems of insufficient long-term stability and low curing efficiency at low temperature of the existing acid-activated geopolymer material can be effectively solved, the sealing rate of lead ions and the mechanical properties are improved at the same time through component synergy and process optimization, the maintenance energy consumption is reduced; the preparation method uses widely available materials, uses industrial solid waste ilmenite tailings as raw materials to realize resource utilization, and the preparation process is simple and controllable, which is suitable for lead-containing solid waste treatment and soil remediation in different temperature environments, and has a wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 The scanning electron microscope-energy spectrum analysis diagram of the geopolymer material in test example A1.

[0021] DETAILED DESCRIPTION To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below. Wherein, the specific conditions in the embodiments are not specified, which are carried out according to conventional conditions or manufacturer's recommended conditions; the instruments, devices or reagents, raw materials, etc. not specified by the manufacturer are all conventional products that can be obtained by market purchase.

[0022] The present application provides an acid-activated metakaolin-ilmenite tailings-based lead ion sealing geopolymer material, which comprises 20-35 parts by mass of ilmenite tailings, 30-45 parts by mass of metakaolin, 5-10 parts by mass of nanosilica, 15-25 parts by mass of phosphoric acid composite activator and 0.5-2.5 parts by mass of sealing aid.

[0023] In the application, the Pb content in the geopolymer material 2+ is 0.5-2.5%, the solid-liquid ratio is 0.7-0.8, the Fe / Si ratio is 0.06-0.15, the P / Al ratio is 0.65-0.85, and the Si / Al ratio is 1.2-1.8.

[0024] The titanium-iron tailings contain 28-35wt% SiO2, 22-20wt% Fe2O3 and 3-5wt% CaO, the specific surface area of the titanium-iron tailings is 2500-2600m 2 / kg, and the particle size is ≤20μm; the metakaolin contains 52-60wt% SiO2 and 42-50wt% Al2O3, the specific surface area of the metakaolin is 2000-2200m 2 / kg, and the particle size is ≤20μm; and the specific surface area of the nanosilica is 500-800m 2 / kg, and the particle size is 10-20μm.

[0025] The phosphoric acid composite activator comprises 80-90% of phosphoric acid, 5-8% of ammonium dihydrogen phosphate and distilled water, and the solute concentration of the phosphoric acid composite activator is controlled to be 8-12mol / L.

[0026] The solidification aid comprises modified attapulgite and sodium polyacrylate, the modified attapulgite accounts for 0.5-2% of the total mass of the geopolymer material, the sodium polyacrylate accounts for 0.1-0.5% of the total mass of the geopolymer material, and the molecular weight of the sodium polyacrylate is controlled to be 8-10 million.

[0027] The modified attapulgite is obtained by modifying attapulgite clay with 3-aminopropyl triethoxysilane, and the specific surface area of the modified attapulgite is 300-400m 2 / kg.

[0028] In the application, the introduction of the titanium-iron tailings can promote the conversion of the Si-O-Al layered structure to the Si-O-P-O-Fe three-dimensional network structure, and the Pb 2+ is solidified through the triple mechanisms of physical encapsulation, ion exchange and chemical bonding, i.e., Fe 3+ replaces Al 3+ to form the Si-O-P-O-Fe network, the physical encapsulation of Pb 2+ through the nanopore channel confinement effect with a pore size of about 2-5nm; Al 3+ reacts with PO4 3+ to generate high-specific-surface-area AlPO4, the ion exchange of Al 3+ -Pb 2+ enhances the ion exchange of adsorption; and Pb 2+ reacts with HPO42+ It forms a PbHPO4 precipitate, and X-ray diffraction (XRD) analysis shows that its quantitative proportion can reach 69.7%, and it forms a Si-O-Pb covalent bond with silicon-oxygen tetrahedra.

[0029] The acid-activated metakaolin-ilmenite tailings-based geopolymer material for sealing lead ions provided by this invention is prepared by the following steps: (1) Pre-processing Lead-containing ilmenite tailings industrial solid waste is taken and calcined at 600~650℃ for 1~3 hours to remove impurities and activate active sites. After cooling to room temperature, ilmenite tailings are obtained and used as raw materials.

[0030] Mix the following raw materials in the specified amounts: ilmenite tailings, metamorphic terre, and nano-silica. Add them to a high-speed mixer and stir at 1500~2000 r / min for 20 min to obtain a mixed substrate.

[0031] (2) Preparation of phosphoric acid composite activator Phosphoric acid (80-90% by mass), ammonium dihydrogen phosphate (5-8% by mass), and distilled water are mixed in the correct proportions and placed in a constant temperature water bath at 40-50°C. The mixture is stirred for 30 minutes and then cooled to room temperature to obtain a phosphoric acid composite activator for later use.

[0032] (3) Material compounding Take the mixed substrate, add the modified attapulgite and sodium polyacrylate according to the specified amount, and stir at a low speed of 500~800r / min for 5~15min; then slowly add the phosphate composite activator, stir at the same low speed for 5~10min to avoid local overheating, and then stir at a high speed of 2000~2500r / min for 5~8min to form a uniform slurry.

[0033] (4) Curing and shaping The slurry is injected into the mold and degassed using vacuum vibration, with the pressure controlled at -0.09 to -0.08 MPa and the vibration frequency at 50 to 60 Hz for 10 minutes. Then, it is cured sequentially at 35 to 45℃ for 10 to 20 hours, at 60 to 80℃ for 3 to 8 hours, and finally at room temperature with 60 to 70% humidity for 8 to 10 hours to solidify and form the geopolymer material.

[0034] Example 1 Step 1: Take lead-containing ilmenite tailings industrial solid waste, place it at 625℃ and calcine for 2 hours, then cool to room temperature to obtain ilmenite tailings, which will be used as raw material. Mix the following raw materials in the following proportions: 28 parts by mass of ilmenite tailings, 38 parts by mass of meta-terrestrial oxide, and 7 parts by mass of nano-silica, add them to a high-speed mixer, and stir at 1800 r / min for 20 min to obtain a mixed matrix.

[0035] Step 2: Mix 85% phosphoric acid, 6.5% ammonium dihydrogen phosphate and distilled water in the correct proportions, place in a 45℃ constant temperature water bath, stir for 30 minutes, cool to room temperature, and prepare a 10 mol / L phosphoric acid composite activator.

[0036] Step 3: Take the mixed substrate, add 1.5 parts by weight of modified attapulgite and 0.25 parts by weight of sodium polyacrylate, and stir at a low speed of 500~800 r / min for 5~15 min; then slowly add 20 L of phosphoric acid composite activator, stir at the same low speed for 5~10 min to avoid local overheating, and then stir at a high speed of 2000~2500 r / min for 5~8 min to form a uniform slurry.

[0037] Step 4: Inject the slurry into the mold, degas it using vacuum vibration, control the pressure at -0.085MPa and the vibration frequency at 55Hz, and process it for 10 minutes; then cure it sequentially at 35℃ for 16 hours, at 70℃ for 4 hours, and finally at room temperature with 65% humidity for 8.5 hours to solidify and form the geopolymer material.

[0038] Test case Based on the preparation process of Example 1, the contents of different raw material components were adjusted to form different experimental groups A1 to A7. The specific contents of the raw material components are shown in Table 1 below: Table 1. Raw material components and their contents in different experimental groups (unit: parts by mass)

[0039] The performance of geopolymer material samples prepared from the different experimental groups was tested, and their compressive strength and Pb content under leaching conditions at pH=0.6 were determined. 2+ The curing properties are shown in Table 2 below: Table 2. Material property test results of samples from different test groups

[0040] Based on the experimental results in Tables 1 and 2 above, and in conjunction with the appendix... Figure 1 The scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) analysis of the geopolymer material in Experimental Example A1 is shown. It can be observed that the proposed method enables the geopolymer material to maintain good mechanical properties. After curing treatment, it can achieve higher mechanical strength properties more quickly, and after acid leaching treatment, Pb... 2+ The leaching concentration can be kept below 0.1 mg / L, and the solidification rate can reach 98.76% or higher. It has a significant lead ion solidification effect and long-term stability, which can solve the problems of poor stability and decreased mechanical properties of existing acid-activated geopolymer materials.

[0041] The preferred embodiments of the present application have been described above with the intent to enable those skilled in the art to make and use it. Various modifications to the preferred embodiments will be obvious to those skilled in the art and the principles and applications disclosed can be used together with other applications and as components in undreamed of applications. The present application should not be limited to the embodiments described above, but can be practiced with modification and alteration within the scope and spirit of the present application. Accordingly, the disclosure of the preferred embodiments of the present application are intended to be illustrative only and not limiting of the scope of the present application, which is set forth in the following claims.

Claims

1. A geopolymer material for encapsulating lead ions based on acid-activated metakaolinite-ilmenite tailings, characterized in that, By weight, it includes 20-35 parts ilmenite tailings, 30-45 parts metakaolin, 5-10 parts nano silica, 15-25 parts phosphoric acid composite activator and 0.5-2.5 parts solidification agent; The phosphoric acid composite activator includes phosphoric acid and ammonium dihydrogen phosphate, and the solidification agent includes modified attapulgite and sodium polyacrylate.

2. The acid-activated metakaolin-ilmenite tailings-based geopolymer material for sealing lead ions according to claim 1, characterized in that, Pb in geopolymer materials 2+ The content is 0.5~2.5%, and the Fe / Si ratio is 0.06~0.15, the P / Al ratio is 0.65~0.85, and the Si / Al ratio is 1.2~1.

8.

3. The acid-activated metakaolin-ilmenite tailings-based geopolymer material for sealing lead ions according to claim 1, characterized in that, By mass fraction, ilmenite tailings contain 28–35 wt% SiO2, 22–20 wt% Fe2O3, and 3–5 wt% CaO, and the specific surface area of ​​ilmenite tailings is 2500–2600 m². 2 / kg, and particle size ≤20μm.

4. The acid-activated metakaolin-ilmenite tailings-based geopolymer material for sealing lead ions according to claim 1, characterized in that, Metakaolin contains 52-60 wt% SiO2 and 42-50 wt% Al2O3, and its specific surface area is 2000-2200 m². 2 / kg, particle size ≤20μm.

5. The acid-activated metakaolin-ilmenite tailings-based geopolymer material for sealing lead ions according to claim 1, characterized in that, The specific surface area of ​​nano-silica is 500~800 m². 2 / kg, particle size 10~20μm.

6. The acid-activated metakaolin-ilmenite tailings-based geopolymer material for sealing lead ions according to claim 1, characterized in that, The phosphoric acid composite activator consists of 80-90% phosphoric acid, 5-8% ammonium dihydrogen phosphate, and distilled water, and the solute concentration of the phosphoric acid composite activator is controlled at 8-12 mol / L.

7. The acid-activated metakaolin-ilmenite tailings-based geopolymer material for sealing lead ions according to claim 1, characterized in that, Modified attapulgite is obtained by modifying attapulgite clay with 3-aminopropyltriethoxysilane, and the modified attapulgite accounts for 0.5-2% of the total mass of the geological polymer material.

8. The acid-activated metakaolin-ilmenite tailings-based geopolymer material for sealing lead ions according to claim 1, characterized in that, Sodium polyacrylate has a molecular weight controlled between 8 million and 10 million, and it accounts for 0.1% to 0.5% of the total mass of the geological polymer material.

9. A method for preparing an acid-activated metakaolin-ilmenite tailings-based geopolymer material for sealing lead ions as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1 Preprocessing: Take lead-containing ilmenite tailings industrial solid waste, place it at 600~650℃, calcine for 1~3 hours, cool it to obtain ilmenite tailings, which can be used as raw materials for later use. Take ilmenite tailings, meta-high terrestrial material, and nano-silica, and stir at 1500~2000 r / min for 20 min to obtain a mixed substrate; S2 is used to prepare a phosphoric acid complex activator: Take phosphoric acid, ammonium dihydrogen phosphate and distilled water, place them in a constant temperature water bath at 40~50℃, stir for 30 minutes, cool, and obtain the phosphoric acid complex activator for later use; S3 Material Combination: Take the mixed substrate, add modified attapulgite and sodium polyacrylate, stir at a low speed of 500~800 r / min for 5~15 min, then add phosphoric acid composite activator and continue stirring for 5~10 min, then stir at a high speed of 2000~2500 r / min for 5~8 min to form a uniform slurry; S4 curing and shaping: The slurry is placed in a mold and vibrated to degas it. Then it is cured sequentially at 35-45℃ for 10-20 hours, at 60-80℃ for 3-8 hours, and finally at room temperature with 60-70% humidity for 8-10 hours to solidify and form the geopolymer material.

10. The method for preparing the acid-activated metakaolin-ilmenite tailings-based geopolymer material for sealing lead ions according to claim 9, characterized in that, In step S4, the vibration degassing is carried out in a vacuum environment of -0.09 to -0.08 MPa, and the vibration frequency is controlled at 50 to 60 Hz for 10 min.

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