Method for regulating and controlling dissolution activity of industrial solid waste-based composite material in alkaline sulfate coupling environment

Abstract

The invention relates to the technical field of geotechnical engineering, and discloses a method for regulating the dissolution activity of an industrial solid waste-based composite material in an alkaline sulfate coupling environment, which comprises the following steps: respectively crushing and drying red mud, steel slag and fly ash to obtain three solid wastes for later use; mixing a NaOH solution and a NaSOsolution to serve as a dissolution agent, mixing one or more of the three prepared solid wastes with the dissolution agent according to a solid-to-liquid ratio, stirring in a constant-temperature water bath, and adding the dissolution agent in the reaction process to supplement evaporation loss so as to keep the volume of the solution constant; in the reaction process, sampling, determining the ion concentration of silicon, aluminum and calcium by adopting ICP-OES (Inductively Coupled Plasma-Optical Emission Spectrometer), and drawing a dissolution curve; and carrying out vacuum filtration to separate residual solids and filtrate, washing with deionized water until the pH is neutral, washing with ethanol for three times, and drying in a vacuum oven at 60 DEG C for later use.

Description

Technical Field

[0001] The present invention belongs to the field of geotechnical engineering, and particularly relates to resource utilization of industrial solid waste, and specifically provides a method for regulating the dissolution activity of industrial solid waste-based composite materials in an alkaline sulfate coupling environment. Background Art

[0002] As a vital component of modern construction and infrastructure, cement is used worldwide to drive urbanization. However, cement production is associated with high energy consumption and emissions, leading to an increasingly serious negative impact on climate change.

[0003] The recycling of industrial solid waste is increasingly being considered an ideal alternative due to its high efficiency and sustainability. Using industrial solid waste (such as red mud, steel slag, and fly ash) to replace traditional cement has become a research hotspot. Red mud, an alkaline byproduct of bauxite extraction, has a complex composition, is rich in Si, Al, and Fe, and has high alkalinity. Steel slag, a byproduct of steelmaking, contains large amounts of Ca and has potential hydraulic properties. Fly ash, a fine particulate matter emitted by coal-fired power plants, is rich in active Si and Al and exhibits excellent pozzolanic activity.

[0004] Although these solid waste materials have unique advantages in physical, chemical and mineralogical properties, their insufficient reactivity and low dissolution rate still limit their application in geotechnical engineering, especially their potential in soil improvement, land remediation and underground engineering.

[0005] Existing technologies use alkaline solutions or alkali-sulfate mixed solutions to activate these materials, which helps enhance their pozzolanic activity and, in turn, improve their overall performance. However, the resulting industrial solid waste-based composite materials (red mud, steel slag, and fly ash, used as soil improvement materials or underground engineering materials) primarily focus on macroscopic performance evaluation, lacking systematic research on dissolution mechanisms and micro-control, resulting in low solid waste utilization.

[0006] In order to solve the above problems, the present invention proposes a method for regulating the dissolution activity of industrial solid waste-based composite materials in an alkaline sulfate coupling environment. Summary of the Invention

[0007] In order to solve the problems in the prior art of using alkaline solutions or alkali-sulfate mixed solutions to activate these materials to improve the overall performance, but the industrial solid waste-based composite materials obtained focus on the evaluation of their macroscopic performance, lack research and directional control on the dissolution mechanism and micro-regulation, resulting in low solid waste utilization, the present invention provides a method for regulating the dissolution activity of industrial solid waste-based composite materials in an alkaline sulfate coupling environment.

[0008] The present invention is implemented by the following technologies: The present invention provides a method for regulating the dissolution activity of an industrial solid waste-based composite material in an alkaline sulfate coupling environment, comprising the following steps: a. Raw material pretreatment Red mud, steel slag and fly ash were crushed to particle sizes of 0.15-0.25 mm, respectively, and dried in an electric constant temperature oven to prepare three types of solid wastes for use.

[0009] b. Prepare dissolution agent A mixture of NaOH solution (sodium hydroxide solution) and Na2SO4 solution (sodium sulfate solution) is used as a dissolution agent, wherein the concentration of NaOH is 1~5 mol / L and the concentration of Na2SO4 is 0.005~0.025 mol / L.

[0010] c. Dissolution reaction One or more of the three solid wastes obtained in step a are mixed with a dissolving agent at a solid-liquid ratio of 1: (5-100) g / mL, stirred in a constant temperature water bath at 15-60°C at a stirring rate of 180 rpm, and a reaction time of 40-200 min; during the reaction, the dissolving agent is added to supplement the evaporation loss to keep the solution volume constant.

[0011] d. Product post-processing The residual solid and the filtrate were separated by vacuum filtration, and then washed with deionized water until the pH was neutral to remove the alkaline substances remaining on the solid surface. Subsequently, the solid was washed three times with ethanol to remove the water-soluble impurities on the solid surface, and dried in a vacuum oven at 60°C for later use to obtain a dry product, which is convenient for long-term storage and subsequent analysis and use, while preventing the product from being oxidized by oxygen in the air during the drying process.

[0012] Each set of experiments was repeated three times to ensure the reliability of the data.

[0013] Preferably, when the product requires high Si and Al activity, the solid-liquid ratio is adjusted to 1:5 g / mL, the NaOH concentration is 4-5 mol / L, and the constant temperature water bath temperature is 60°C. When the product requires high Si activity, in steps b and c, the NaOH concentration is 4-5 mol / L, the Na2SO4 concentration is 0.005-0.01 mol / L, red mud, steel slag and fly ash are mixed in a mass ratio of 1:1:1, and mixed with the dissolving agent in a solid-liquid ratio of 1:5 g / mL, stirred in a constant temperature water bath at 60°C, and the reaction time is 120 min; When the product requires high Al activity, in steps b and c, the NaOH concentration is 4-5 mol / L, the Na2SO4 concentration is 0.015-0.020 mol / L, red mud, steel slag and fly ash are mixed in a mass ratio of 1:2:1, and mixed with the dissolving agent in a solid-liquid ratio of 1:5 g / mL, stirred in a constant temperature water bath at 60°C, and the reaction time is 80 min.

[0014] When the product requires high Ca activity, the Na2SO4 concentration is adjusted to 0.005~0.015 mol / L and the NaOH concentration is adjusted to 1~3 mol / L.

[0015] Among them, when the product requires high Ca activity, in steps b and c, the NaOH concentration is 1~3 mol / L, the Na2SO4 concentration is 0.01~0.025 mol / L, red mud, steel slag and fly ash are mixed in a mass ratio of 2:1:1, and mixed with the dissolving agent in a solid-liquid ratio of 1:20 g / mL, stirred in a constant temperature water bath at 45°C, and the reaction time is 80 min.

[0016] When using red mud as a single raw material, adjusting the Na₂SO₄ concentration positively regulated the dissolution concentrations of Si, Al, and Ca ions. Adjusting the solid-to-liquid ratio assisted in positively regulating the dissolution concentrations of Si and Al ions, while adjusting the solid-to-liquid ratio assisted in negatively regulating the dissolution concentration of Ca ions. The dissolution concentration of Si ions showed a significant positive correlation with the solid-to-liquid ratio (correlation coefficient of 0.61) and a moderate positive correlation with the concentration of NaOH solution (correlation coefficient of 0.49). The dissolution concentration of Al ions showed a strong positive correlation with the solid-to-liquid ratio (correlation coefficient of 0.7) and a moderate positive correlation with the water bath temperature (correlation coefficient of 0.43). The dissolution concentration of Ca ions showed a strong positive correlation with the sodium sulfate concentration (correlation coefficient of 0.72).

[0017] When using steel slag as raw material, the dissolution concentrations of Si and Al ions were positively regulated by adjusting the solid-liquid ratio, and the dissolution concentrations of Si and Al ions were assisted by adjusting the Na2SO4 concentration. The dissolution concentration of Ca ions was positively regulated by adjusting the Na2SO4 concentration. The dissolution concentrations of Si and Al ions were significantly correlated with the solid-liquid ratio (correlation coefficients were 0.83 and 0.92, respectively), and the dissolution concentration of Ca ions maintained a strong positive correlation with the sodium sulfate concentration (correlation coefficient was 0.73).

[0018] Using fly ash as the raw material, the dissolution concentrations of Si and Al ions were positively regulated by adjusting the Na₂SO₄ concentration and the solid-to-liquid ratio. The dissolution concentration of Ca ions was also positively regulated by adjusting the Na₂SO₄ concentration. The dissolution concentrations of Si and Al ions were significantly positively correlated with the solid-to-liquid ratio (correlation coefficients of 0.79 and 0.59, respectively), and there was a strong positive correlation between the two (correlation coefficient of 0.87). The dissolution concentration of Ca ions was strongly positively correlated with the sodium sulfate concentration (correlation coefficient of 0.68) but negatively correlated with the NaOH solution concentration (correlation coefficient of -0.44).

[0019] Taking NaOH solution concentration (X1), water bath temperature (X2), solid-liquid ratio of solid waste to dissolving agent (X3), reaction time (X4) and Na2SO4 concentration (X5) as key influencing factors, the dissolution amount of Si ions (Y1), Al ions (Y2) and Ca ions (Y3) conforms to the equation: Using red mud as raw material, Y1=20.16X1+2.39X2+767.97X3+0.094X4+1573.80X5, Y2=12.90X1+2.27X2+699.01X3+0.111X4+1873.20X5, Y3=-0.92X1+0.09X2-49.92X3-0.029X4+1382.92X5, Using steel slag as raw material, Y1=13.3X1+1.74X2+1160.08X3+0.27X4+333.45X5, Y2=5.58X1-0.63X2+1368.12X3+0.22X4+834.1X5, Y3=-5.15X1+0.59X2+5.44X3-0.1X4+2125.5X5, Using fly ash as raw material, Y1=27.56X1+3.94X2+1986.55X3+1.41X4+1344.43X5, Y2=7.81X1+2.04X2+472.31X3+0.19X4+1779.93X5, Y3=-16.09X1+0.28X2-12.6X3+0.09X4+3181.28X5.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The present application provides a method for regulating the dissolution activity of industrial solid waste-based composite materials in an alkaline sulfate coupling environment. Alkaline solution and alkali-sulfate composite solution are used as dissolution agents. Based on the dissolution kinetics of silicon, aluminum, and calcium elements in red mud, steel slag, and fly ash under different solution conditions, the dissolution rate, activation energy, and kinetic parameters are measured. Through the synergistic effect of the alkaline sulfate coupling environment, the dissolution rate and ratio of silicon (Si), aluminum (Al), and calcium (Ca) in red mud, steel slag, and fly ash are directionally regulated to form a highly active gel product, thereby improving its applicability in geotechnical engineering. This provides a scientific basis for the synergistic utilization strategy based on alkaline substances, sulfates, and silicon-aluminum solid wastes, especially for the application potential and feasibility analysis in geotechnical engineering fields such as soil improvement, underground engineering, and infrastructure construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the chemical composition analysis diagram of the raw materials.

[0022] Figure 2 BSE images of red mud, steel slag and fly ash before and after dissolution.

[0023] Figure 3 This is the EDS spectrum of mineral phases at different points in red mud before and after dissolution.

[0024] Figure 4 This is the EDS spectrum of mineral phases at different points in steel slag before and after dissolution.

[0025] Figure 5 This is the EDS spectrum of mineral phases at different points in fly ash before and after dissolution.

[0026] Figure 6 This is the SEM-EDS spectrum of red mud after leaching.

[0027] Figure 7 This is the SEM-EDS spectrum of the slag after leaching.

[0028] Figure 8 This is the SEM-EDS spectrum of fly ash after leaching.

[0029] Figure 9 Figure 2 shows the XRD patterns of red mud, steel slag and fly ash before and after dissolution.

[0030] Figure 10 The dissolution kinetics of silicon, aluminum and calcium in red mud.

[0031] Figure 11 The dissolution kinetics of silicon, aluminum and calcium in steel slag.

[0032] Figure 12 The dissolution kinetics of silicon, aluminum and calcium in fly ash. DETAILED DESCRIPTION

[0033] The specific embodiments of the present invention are described in detail below. Example 1

[0034] A method for regulating the dissolution activity of industrial solid waste-based composite materials in an alkaline sulfate coupling environment, when the Si dissolution activity requirement is high, comprises the following steps: a. Raw material pretreatment Bauxite red mud samples were obtained from Xiaoyi Aluminum Factory, Shanxi Province, China, and steel slag and fly ash were purchased from Yuanheng Qingshui Material Factory, Gongyi City, Henan Province.

[0035] The red mud or steel slag is crushed to a particle size of 0.15-0.25 mm, placed in an electric constant temperature oven for drying, and solid waste is prepared for use.

[0036] Chemical composition analysis uses X-ray fluorescence spectroscopy (XRF) to analyze the main components of the raw materials. The results are as follows Figure 1 As shown in the figure, by weight percentage (wt%): Red mud is primarily composed of SiO2 and Al2O3, with a relatively low Fe2O3 content; Steel slag is rich in CaO, with a Fe2O3 content close to that of red mud, and also contains a certain amount of SiO2; Fly ash is primarily composed of SiO2, followed by Al2O3 and CaO. MgO is primarily present in steel slag, with lower levels in other samples; Na2O is a trace element.

[0037] b. Prepare dissolution agent A mixture of NaOH solution and Na2SO4 solution was used as a dissolution agent. When the NaOH concentration was 4 mol / L, the Si dissolution rate was close to saturation. Excessive alkali concentration caused a sodium silicate gel coating to form on the mineral surface, inhibiting further dissolution. When red mud was used as the raw material, the Na2SO4 concentration was 0.005 mol / L. The dissolution rate was high at low concentrations, but decreased at high concentrations. This was because sodium sulfate inhibited the dissolution of silicon source minerals. When steel slag was used as the raw material, the Na2SO4 concentration was 0.02 mol / L. The amount of silicon ions dissolved increased with the increase of sodium sulfate concentration. Sodium sulfate promoted the dissolution of silicon, which is speculated to be related to the sulfate reducing the Ca content in the system. 2+ activity and inhibition of the formation of Ca-Si secondary precipitation.

[0038] c. Dissolution reaction The red mud or steel slag prepared in step a is mixed with a dissolving agent at a solid-liquid ratio of 1:5 g / mL. A higher solid-liquid ratio helps promote the dissolution of silicon source minerals in these materials. The mixture is stirred in a constant temperature water bath at 60°C at a stirring rate of 180 rpm for a reaction time of 120 min. The high temperature accelerates the dissolution of silicon minerals. Initial silicates dissolve rapidly, then reach saturation or form secondary silicates. The Si ion concentration in the steel slag shows complex changes, reflecting the alternating process of silicate dissolution and precipitation. The dissolving agent is added during the reaction to compensate for evaporation losses to maintain a constant solution volume. d. Product post-processing The residual solid and the filtrate were separated by vacuum filtration, and then washed with deionized water until the pH was neutral to remove the alkaline substances remaining on the solid surface. Subsequently, the solid was washed three times with ethanol to remove the water-soluble impurities on the solid surface, and dried in a vacuum oven at 60°C for later use to obtain a dry product, which is convenient for long-term storage and subsequent analysis and use, while preventing the product from being oxidized by oxygen in the air during the drying process.

[0039] Each set of experiments was repeated three times to ensure the reliability of the data. Example 2

[0040] A method for regulating the dissolution activity of industrial solid waste-based composite materials in an alkaline sulfate coupling environment, when the Al dissolution activity requirement is high, comprises the following steps: a. Raw material pretreatment The fly ash is crushed into particle sizes of 0.15-0.25 mm, placed in an electric constant temperature oven for drying, and solid waste is prepared for use.

[0041] b. Prepare dissolution agent A mixture of NaOH solution and Na2SO4 solution was used as the dissolution agent, with a NaOH concentration of 4 mol / L. Under this condition, the amount of aluminum ions dissolved was high, but excessively high alkali concentrations may cause aluminate precipitation or a gel layer to form on the surface, inhibiting continued dissolution. The Na2SO4 concentration was 0.02 mol / L. The amount of aluminum ions decreased at low concentrations and rebounded at higher concentrations. c. Dissolution reaction The fly ash prepared in step a was mixed with a dissolving agent at a solid-liquid ratio of 1:5 g / mL. The high temperature accelerated the dissolution of aluminum minerals and effectively promoted the dissolution of aluminum. The mixture was stirred in a constant temperature water bath at 60°C at a stirring rate of 180 rpm for a reaction time of 200 min. The Al ion concentration initially increased rapidly, and then the dissolution rate gradually slowed down, showing a nonlinear change. This is presumably related to the gradual dissolution of aluminate and a possible secondary precipitation process. The dissolving agent was added during the reaction to compensate for evaporation losses to maintain a constant solution volume. The remaining steps are exactly the same as those in Example 1. Example 3

[0042] A method for regulating the dissolution activity of industrial solid waste-based composite materials in an alkaline sulfate coupling environment, when the Al dissolution activity requirement is high, comprises the following steps: a. Raw material pretreatment The red mud, steel slag and fly ash were crushed to particle sizes of 0.15-0.25 mm, respectively, and dried in an electric constant temperature oven to prepare solid waste for use.

[0043] b. Prepare dissolution agent Take NaOH solution and Na2SO4 solution mixed as dissolution agent, where the concentration of NaOH is 5 mol / L and the concentration of Na2SO4 is 0.025 mol / L. c. Dissolution reaction The three solid wastes obtained in step a were mixed with a dissolving agent at a solid-liquid ratio of 1:100 g / mL, stirred in a constant temperature water bath at 45°C at a stirring rate of 180 rpm and a reaction time of 80 min; during the reaction, the dissolving agent was added to compensate for evaporation losses to maintain a constant solution volume; The remaining steps are exactly the same as those in Example 1. Example 4

[0044] A method for controlling a high-Si activity composite system comprises crushing red mud, steel slag, and fly ash to 0.15-0.25 mm, mixing them in a mass ratio of 1:1:1, and preparing a dissolving agent with a NaOH concentration of 4 mol / L and a Na2SO4 concentration of 0.01 mol / L. The mixed solid waste and dissolving agent are mixed in a ratio of 1:5 g / mL and stirred in a 60°C constant temperature water bath for 120 minutes. The remaining steps are identical to those in Example 1.

[0045] After dissolution, the ion concentration was measured by ICP-OES.

[0046] The results showed that the Si ion concentration increased by 22.7% compared with the single red mud system (except for the raw materials, the rest were the same as in this example), indicating that the composite system significantly enhanced the Si dissolution efficiency. Example 5

[0047] A method for controlling a high-Al activity composite system comprises red mud, steel slag, and fly ash in a mass ratio of 1:2:1. A NaOH concentration of 4 mol / L and a Na2SO4 concentration of 0.02 mol / L are used as dissolution agents. The solid-liquid ratio is 1:5 g / mL, the reaction temperature is 60°C, and the reaction time is 80 min. The remaining steps and tests are identical to those in Example 4.

[0048] The results show that the amount of Al ion dissolution increased by about 28% compared with the fly ash alone system (except for the raw materials, the rest is the same as this example), indicating that the multi-component compounding reduces the precipitation risk of Al to a certain extent and improves its stable release ability. Example 6

[0049] A method for regulating a high-Ca active composite system comprises the following steps: red mud, steel slag, and fly ash are mixed and post-treated in a ratio of 2:1:1; the NaOH concentration is set to 2 mol / L; the Na2SO4 concentration is set to 0.015 mol / L; the reaction temperature is 45°C; the reaction time is 80 min; and the remaining steps and tests are identical to those in Example 4.

[0050] The results show that the Ca ion concentration after dissolution is 35% higher than that of the single steel slag system (except for the raw materials, the rest are the same as in this example). At the same time, the pH of the solution remains stable, and no obvious CaSO4 precipitation is observed, verifying the sustained release effect of the multi-component system on Ca release.

[0051] Combined with Examples 4 to 6, it can be seen that compared with the traditional alkali-activated system of a single solid waste material, the present invention introduces a synergistic ratio design of three materials: red mud, steel slag, and fly ash, so that the respective advantageous components complement each other synergistically. The experimental results show that in terms of regulating the dissolution activity of the target elements, the dissolution efficiency of the ternary composite system for Si, Al, and Ca is superior to that of the single or two-component system. In particular, after controlling parameters such as the dissolution agent ratio and temperature, it is possible to achieve precise regulation of the ion release rate and product composition, providing a basis for directional design in geotechnical engineering applications. This system can be widely used in the fields of soft soil foundation reinforcement, heavy metal contaminated soil remediation, tailings and red mud dump ecological management, deep treatment of industrial wastewater, and preparation of green cementitious materials, and has good engineering adaptability and promotion value.

[0052] Dynamic monitoring of the dissolution process During the reaction, samples were taken and the ion concentrations of silicon, aluminum, and calcium were determined using ICP-OES (inductively coupled plasma spectroscopy), and a dissolution curve was drawn. XRD technology was used to evaluate the changes in mineral composition before and after dissolution, and BSE-IA-EDS was used to analyze the distribution of elements in the mineral phase. SEM-EDS technology was used to observe and analyze the microstructure and elemental composition of the material before and after dissolution. The details are as follows: The energy spectrum before and after dissolution was tested. According to the principle of backscattered electron imaging, the brightness of the mineral phase is proportional to its average atomic number. By analyzing the brightness of the mineral phase and combining it with the average atomic number (in the order of Fe, Ca, Si, Al, Na), the mineral can be qualitatively analyzed. Figure 2As shown in the figure, the white dots are high atomic number mineral phases mainly composed of iron (Fe). The area ratio of each mineral phase was quantitatively analyzed using the BSE-IA method. The results are shown in Table 1. In order to further study the elemental composition of the mineral phase, a point energy spectrum test was performed. The results are shown in Table 1. Figures 3-5 shown.

[0053]

[0054] In the analysis of red mud, three main mineral phases were identified: mineral phase 1 is the Ca-Si-Al phase, which is mainly composed of light elements Ca, Si and Al, including tricalcium silicate (Ca3SiO5·CaSO4) and hydrogarnet (Ca3Al2(SiO4)(OH)8); mineral phase 2 is the Ca-Al-Na-Si phase, which is mainly composed of Ca, Al, Na, Si, and cancrinite (Na6Ca2Al6Si6O 24 (CO3)2); Mineral phase 3 is Fe phase with a high iron content, mainly composed of hematite (Fe2O3) and a small amount of magnetite (Fe3O4). In the steel slag sample, mineral phase 4 (Ca-Si phase), mineral phase 5 (Fe-Mg phase) and mineral phase 6 (Ca-Fe phase) were identified. Mineral phase 4 is mainly composed of Ca and Si, and contains calcium silicate minerals; mineral phase 5 is composed of Mg and Fe, mainly brucite (Mg(OH)2) and wurtzite (FeO); mineral phase 6 is mainly composed of Ca and Fe, and contains calcium silicate and wurtzite. In the fly ash sample, mineral phase 7 (Si-Al phase), mineral phase 8 (Ca-Si-Al phase) and mineral phase 9 (Fe phase) were identified. Mineral phase 7 is mainly composed of Si and Al, and contains sillimanite (Al2SiO5) and mullite (Al6Si2O 13 ); Mineral phase 8 is composed of Ca, Si and Al, mainly anorthite (CaAl2Si2O8); Mineral phase 9 is mainly composed of Fe, mainly magnetite (Fe3O4).

[0055] Analysis of red mud residues revealed the presence of two main mineral phases (labeled 10 and 11). Phase 10 contained high levels of calcium but low levels of silicon and aluminum, indicating that silicon and aluminum have high solubility in alkaline and sulfate environments; Phase 11 was primarily composed of iron and had low solubility. Analysis of steel slag residues revealed that the silicon content in the calcium-silicon phase (phase 12) decreased, indicating that silicon was more soluble; the magnesium content in the ferromagnesian phase (phase 13) decreased, while the iron remained stable, possibly due to Fe2(SO4)3 precipitation; in the calcium-iron phase (phase 14), calcium partially dissolved to form CaSO4, while iron was stabilized by sulfate precipitation. Analysis of fly ash residues revealed three main mineral phases (labeled 15, 16, and 17). Phase 15 contained primarily silicon and aluminum, Phase 16 consisted primarily of calcium and silicon, and Phase 17 was rich in iron. Although quartz (SiO2) and mullite (Al6Si2O13 ) are somewhat soluble under certain conditions, but they are relatively stable; the iron mineral phase 17 also shows good stability.

[0056] like Figures 6-8 As shown in the figure, SEM and EDS analysis of red mud, steel slag and fly ash showed that after the solution eroded the surface, silicon and aluminum elements were significantly dissolved, and the Ca(N)-ASH, CSH and CAH gel layers formed by the reaction covered the undissolved particles. With the increase of reaction time and temperature, the gel layer gradually thickened, further inhibiting the dissolution of the particles.

[0057] like Figure 9 As shown in Figure 2, the crystal structures of red mud, steel slag and fly ash have changed.

[0058] The diffraction peaks of hematite (Fe2O3) and calcium aluminum silicate minerals weakened, indicating that these minerals were partially dissolved in a strong alkaline and sulfate-rich environment, and the iron element may exist in the form of iron sulfate (Fe2(SO4)3). At the same time, the weakening of the peaks of calcium aluminum silicate minerals further indicates the dissolution of aluminum and silicon, and the reaction with calcium to form a hydrated gel. The XRD spectrum of steel slag shows that the diffraction peaks of calcium silicate (CaSiO3) and magnesite (MgCO3) weakened, indicating the dissolution of silicon and a decrease in magnesium content, while the diffraction peak of iron remained stable, which may be related to the formation of iron sulfate. The XRD analysis results of fly ash show that quartz (SiO2), mullite (Al6Si2O 13 ) and sillimanite (Al2SiO5) and other minerals weakened, reflecting the dissolution process of silicon and aluminum elements; at the same time, the diffraction peak of calcium hydroxide appeared, indicating that calcium element re-precipitated under alkaline conditions.

[0059] The dissolution process kinetics analysis is as follows: The reaction rate is influenced by both the cation diffusion rate and the chemical reaction rate. Given the lack of clarity regarding the mechanism of ion diffusion, a model fitting approach was employed to investigate the dissolution kinetics in alkaline and sulfate solutions. This model employed a first-order reaction model for mineral dissolution, a reaction-controlled model, and an internal diffusion model of the shrinking core model. The results are shown in the table below.

[0060]

[0061] According to the fitting results, the internal diffusion model has the best fitting effect among the shrinking core models, so this model is selected as the kinetic model of the dissolution process of red mud, steel slag and fly ash.

[0062] According to the Arrhenius formula, we can get the following formula: , , .

[0063] Where, T is temperature (K), T1 is the initial temperature, and T2 is the temperature at a specific moment; k is the reaction rate constant at temperature T, k1 represents the reaction rate constant at T1, and k2 represents the reaction rate constant at T2; E a ——Activation energy (J / mol), which reflects the energy required for the system to transform from the normal state to the reactive state; R——ideal gas constant (J / (mol·K)); A——Pre-exponential factor.

[0064] The magnitude of activation energy directly affects the sensitivity of a reaction to temperature changes and the difficulty of the reaction. The lower the activation energy, the easier the reaction is to proceed and the faster the reaction rate is; conversely, the higher the activation energy, the slower the reaction rate is. Using the exponential form of the Arrhenius equation, the slope −E a / R can be used to obtain the activation energy of the reaction, thereby revealing the energy barrier characteristics of the reaction.

[0065] according to Figures 10-12 The Arrhenius plot shown shows the slopes of the linear fitting for the dissolution kinetics of Si, Al, and Ca from red mud, steel slag, and fly ash, respectively: red mud (Si, Al, Ca) are −4785.95, −5171.60, and −6556.39; steel slag (Si, Al, Ca) are −5310.35, −5598.35, and −7066.61; and fly ash (Si, Al, Ca) are −4175.56, −4024.66, and −6644.41. The corresponding linear correlation coefficients R 2 The activation energies calculated from these slopes show that the activation energies of Si, Al, and Ca in red mud are 39.790 kJ / mol, 42.997 kJ / mol, and 54.510 kJ / mol, respectively; in steel slag, they are 44.150 kJ / mol, 46.545 kJ / mol, and 58.752 kJ / mol; and in fly ash, they are 34.716 kJ / mol, 33.461 kJ / mol, and 55.241 kJ / mol, respectively.

[0066] The results show that Si is most easily dissolved in red mud and steel slag, followed by Al, while Ca is relatively difficult to dissolve; Al is most easily dissolved in fly ash, followed by Si, while Ca is still difficult to dissolve.

[0067] Aluminosilicates in red mud and steel slag are more soluble under alkaline conditions, while fly ash has a high aluminate content and is prone to reacting with hydroxyl groups in the solvent. On the other hand, calcium exhibits a high activation energy in all materials because calcium silicates or calcium aluminates are difficult to dissolve under conventional dissolution conditions, especially in the presence of sulfate, where they may form more stable complexes such as calcium sulfate, further reducing their dissolution rate.

[0068] The scope of protection claimed by the present invention is not limited to the above specific embodiments. For those skilled in the art, the present invention may have various variations and modifications. Any modifications, improvements and equivalent substitutions made within the concept and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for regulating the dissolution activity of industrial solid waste-based composite materials in an alkaline sulfate coupling environment, characterized in that: The following steps are involved: a. Raw material pretreatment Red mud, steel slag and fly ash were crushed to particle sizes of 0.15-0.25 mm, dried and prepared into three solid wastes for use; b. Prepare dissolution agent A mixture of NaOH solution and Na2SO4 solution is used as the dissolution agent, wherein the concentration of NaOH is 1-5 mol / L and the concentration of Na2SO4 is 0.005-0.025 mol / L; c. Dissolution reaction One or more of the three solid wastes prepared in step a are mixed with a dissolving agent at a solid-liquid ratio of 1: (5-100) g / mL, and stirred in a constant temperature water bath at 15-60°C at a stirring rate of 180 rpm for a reaction time of 40-200 min; during the reaction, the dissolving agent is added to compensate for evaporation losses to maintain a constant solution volume; d. Product post-processing The residual solid and the filtrate were separated by vacuum filtration, washed with deionized water until the pH was neutral, then washed three times with ethanol, and dried in a vacuum oven at 60°C for use.

2. The method for controlling the dissolution activity of an industrial solid waste-based composite material in an alkaline sulfate coupling environment according to claim 1, characterized in that: When the product requires high Si and Al activity, the solid-liquid ratio is adjusted to 1:5 g / mL, the NaOH concentration is 4-5 mol / L, and the constant temperature water bath temperature is 60°C. When the product requires high Ca activity, the Na2SO4 concentration is adjusted to 0.005~0.015 mol / L and the NaOH concentration is adjusted to 1~3 mol / L.

3. The method for controlling the dissolution activity of an industrial solid waste-based composite material in an alkaline sulfate coupling environment according to claim 1, characterized in that: When the product requires high Si activity, in steps b and c, use a NaOH concentration of 4-5 mol / L and a Na2SO4 concentration of 0.005-0.01 mol / L, mix red mud, steel slag, and fly ash in a mass ratio of 1:1:1, and mix with a dissolving agent in a solid-liquid ratio of 1:5 g / mL, stir in a constant temperature water bath at 60°C, and the reaction time is 120 min; When the product requires high Al activity, in steps b and c, use a NaOH concentration of 4-5 mol / L and a Na2SO4 concentration of 0.015-0.020 mol / L, mix red mud, steel slag, and fly ash in a mass ratio of 1:2:1, and mix with a dissolving agent in a solid-liquid ratio of 1:5 g / mL, stir in a constant temperature water bath at 60°C, and the reaction time is 80 min; When the product requires high Ca activity, in steps b and c, the NaOH concentration is 1-3 mol / L and the Na2SO4 concentration is 0.01-0.025 mol / L. Red mud, steel slag and fly ash are mixed in a mass ratio of 2:1:1, and mixed with the dissolving agent in a solid-liquid ratio of 1:20 g / mL. The mixture is stirred in a constant temperature water bath at 45°C, and the reaction time is 80 min.

4. The method for controlling the dissolution activity of an industrial solid waste-based composite material in an alkaline sulfate coupling environment according to claim 1, characterized in that: Using red mud as raw material, the dissolution concentrations of Si, Al and Ca ions are positively regulated by adjusting the concentration of Na2SO4, and the dissolution concentrations of Si and Al ions are positively regulated by adjusting the solid-liquid ratio; the dissolution concentration of Ca ions is negatively regulated by adjusting the solid-liquid ratio. When steel slag is used as raw material, the dissolution concentration of Si and Al ions is positively regulated by adjusting the solid-liquid ratio, and the dissolution concentration of Si and Al ions is assisted by adjusting the concentration of Na2SO4. The dissolution concentration of Ca ions is positively regulated by adjusting the concentration of Na2SO4. When fly ash is used as raw material, the dissolution concentrations of Si and Al ions are positively regulated by adjusting the Na2SO4 concentration and the solid-liquid ratio; the dissolution concentration of Ca ions is positively regulated by adjusting the Na2SO4 concentration.

5. The method for controlling the dissolution activity of an industrial solid waste-based composite material in an alkaline sulfate coupling environment according to claim 4, characterized in that: Taking NaOH solution concentration (X1), water bath temperature (X2), solid-liquid ratio of solid waste to dissolving agent (X3), reaction time (X4) and Na2SO4 concentration (X5) as key influencing factors, the dissolution amount of Si ions (Y1), Al ions (Y2) and Ca ions (Y3) conforms to the equation: Using red mud as raw material, Y1=20.16X1+2.39X2+767.97X3+0.094X4+1573.80X5, Y2=12.90X1+2.27X2+699.01X3+0.111X4+1873.20X5, Y3=-0.92X1+0.09X2-49.92X3-0.029X4+1382.92X5, Using steel slag as raw material, Y1=13.3X1+1.74X2+1160.08X3+0.27X4+333.45X5, Y2=5.58X1-0.63X2+1368.12X3+0.22X4+834.1X5, Y3=-5.15X1+0.59X2+5.44X3-0.1X4+2125.5X5, Using fly ash as raw material, Y1=27.56X1+3.94X2+1986.55X3+1.41X4+1344.43X5, Y2=7.81X1+2.04X2+472.31X3+0.19X4+1779.93X5, <h2 style=";text-align:left;direction:ltr">Y3=-16.09X1+0.28X2-12.6X3+0.09X4+3181.28X<h2 style=";text-align:left;direction:ltr"> 5。 6. The method for controlling the dissolution activity of an industrial solid waste-based composite material in an alkaline sulfate coupling environment according to claim 1, characterized in that: In red mud or steel slag, When the Si dissolution activity requirement is high, in step b, the NaOH concentration is 4 mol / L, the Na2SO4 concentration in the red mud is 0.005 mol / L, and the Na2SO4 concentration in the steel slag is 0.02 mol / L; In step c, red mud or steel slag is mixed with a dissolving agent at a solid-liquid ratio of 1:5 g / mL, stirred in a constant temperature water bath at 60° C., and the reaction time is 120 min.

7. The method for controlling the dissolution activity of an industrial solid waste-based composite material in an alkaline sulfate coupling environment according to claim 1, characterized in that: In fly ash, When the Al dissolution activity requirement is high, in step b, the NaOH concentration is 4 mol / L and the Na2SO4 concentration is 0.02 mol / L. In step c, red mud or steel slag is mixed with a dissolving agent at a solid-liquid ratio of 1:5 g / mL and stirred in a constant temperature water bath at 60°C.

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