Compound reagent for neutralization and passivation remediation of antimony mine acid soil and application thereof

Abstract

The present application relates to the technical field of contaminated soil remediation, and discloses a composite reagent for neutralization and passivation remediation of antimony mine acid soil and application thereof, which comprises finely ground blast furnace slag powder, ferrous sulfate heptahydrate and carbide slag. The present application utilizes the solid phase micro-interface acid etching mechanism among the components to pre-activate the alumina tetrahedral site on the surface of the slag, eliminate the hydration induction period, and solve the kinetic mismatch problem caused by the difference in dissolution rate of the easily soluble iron salt and the insoluble slag in the soil remediation process. The present application builds a crystalline environment of poor sulfur calcium aluminate, makes the antimony acid root ions in the soil enter the mineral lattice as a structural replacement component, realizes atomic-level chemical solidification of the antimony pollutants, reduces the antimony leaching concentration of the remediated soil under the condition of acid rain leaching, and utilizes the trace reducing components of the carbide slag to synergistically inhibit the generation of highly toxic pentavalent antimony, thereby realizing long-term and safe remediation of the acid soil.

Description

Technical Field

[0001] This invention relates to a composite agent for neutralizing and passivating acidic soil in antimony mines and its application, belonging to the field of contaminated soil remediation technology. Background Technology

[0002] Currently, for soils with high acidity and heavy metal contamination in antimony mines, in-situ chemical stabilization technology is commonly used. The industry-standard approach involves adding alkaline substances to the soil to neutralize the active acidity, using iron salt chemical amendments to reduce the migration of antimony heavy metals, utilizing carbide slag to provide alkalinity, using ferrous sulfate to provide iron and sulfate sources, and supplementing with finely ground blast furnace slag powder as a cementing skeleton material. The hydration reaction constructs a mineral structure to solidify pollutants, achieving resource utilization of bulk solid waste and low-cost soil remediation.

[0003] When treating antimony, a metalloid pollutant with amphoteric characteristics and sensitivity to environmental pH, conventional methods of simple physical mixing of components face limitations imposed by the physicochemical properties of the materials. Finely ground blast furnace slag powder, with its dense, glassy structure, exhibits a slow release rate of aluminum-oxygen tetrahedra in ambient soil environments, requiring a reaction induction period. Ferrous sulfate heptahydrate, a lattice inducer, is readily soluble, rapidly dissolving and hydrolyzing upon contact with soil pore water. Differences in dissolution and reaction rates between components lead to asynchronous microscopic reaction kinetics within the remediation system. Existing technologies focus on the simple superposition of modifiers, lacking microscopic kinetic control of multiphase reaction systems, making them ineffective against the complex chemical behavior of antimony pollution. For example, publicly available... Chinese invention patent CN118616472A discloses a method for remediating cadmium-contaminated acidic soil with biochar and wood ash, and a special composite remediation agent thereof. Although the scheme improves acidic soil and passivates cationic heavy metal cadmium through the physical coupling of biochar and wood ash, it is essentially still based on the physicochemical regulation of surface adsorption and alkaline neutralization. For antimony pollutants that exist in the form of anionic antimony ions and have strong migration, such physical mixed remediation agents are difficult to construct a stable lattice solidification structure. The problem of reaction sequence mismatch caused by the difference in dissolution rate between components is not solved. Under acid rain leaching or environmental pH fluctuations, physically adsorbed antimony is easy to desorb, causing secondary pollution.

[0004] Therefore, the technical problem to be solved by this invention is how to overcome the difference in reaction kinetic rates among multi-component remediation materials, eliminate the mismatch between the hysteresis of slag hydration and the instantaneous hydrolysis of iron salts, and achieve in-situ lattice locking of antimony pollutants rather than simple adsorption during the neutralization process of acidic soil. Summary of the Invention

[0005] To address the problems mentioned in the background art, the technical solution of this invention is as follows: A composite agent for neutralizing and passivating acidic soil in antimony mines, wherein the composite agent is a surface-modified dry powder mixture prepared from finely ground blast furnace slag powder, ferrous sulfate heptahydrate, and carbide slag. The content of finely ground blast furnace slag powder is 40 to 60 parts by weight, the content of ferrous sulfate heptahydrate is 5 to 15 parts by weight, and the content of calcium carbide slag is 30 to 50 parts by weight; the mass ratio of finely ground blast furnace slag powder to ferrous sulfate heptahydrate is 4:1 to 8:1. The composite agent contains activated slag particles with surface etching characteristics. These activated slag particles are prepared by an acid etching modification step. The acid etching modification step is as follows: under conditions without added free water, finely ground blast furnace slag powder is mixed with ferrous sulfate heptahydrate. The water of crystallization released by ferrous sulfate heptahydrate forms an acidic liquid film at the contact interface, which etches the surface of the finely ground blast furnace slag powder to form a modified premix. Carbide slag, in dry powder form, coats the surface of the modified premix particles, forming a physical barrier layer to delay the release of alkalinity; the composite agent is used when in contact with water-containing acidic soils. The aluminum ions released by the activated slag particles react with dissolved iron ions and antimony ions in the soil to form antimony-containing calcite mineral crystals.

[0006] Preferably, the specific surface area of ​​the finely ground blast furnace slag powder is greater than or equal to 420 square meters per kilogram, and the glass content is greater than 85%; the moisture content of the finely ground blast furnace slag powder before entering the acid etching modification step is less than 1%, so as to control the acid etching reaction to be limited to the particle surface; the composite agent does not contain artificially added phosphates or sulfides, and relies solely on the mineral structure generated by the hydration of the finely ground blast furnace slag powder to fix the antimony contaminants.

[0007] Preferably, the process parameters for the acid etching modification step are as follows: finely ground blast furnace slag powder and ferrous sulfate heptahydrate are added to a mixing device and mixed for 15 to 30 minutes at a linear velocity of 15 to 25 meters per second until the material is uniformly mixed and free of lumps; during this process, the material temperature is controlled below 45°C to prevent ferrous sulfate heptahydrate from losing its water of crystallization too early, and the pH value of the particle contact surface is maintained between 3.0 and 4.0.

[0008] Preferably, the carbide slag is a powder that has been ground and hydrophobically treated, with a particle size D90 of less than 0.075 mm and a calcium oxide content of more than 60%. The physical isolation layer is used to slow down the rise of the pH value of the system in the initial stage after the compound agent is applied to the soil, so that the soil environment is kept in a weakly acidic to neutral range within 10 minutes after the reaction begins, and to release aluminate ions in conjunction with the activation of slag particles.

[0009] Preferably, the reaction process is a crystallization process controlled by sulfate content; the mass ratio of 4:1 to 8:1 is used to limit the sulfate content in the reaction system, so that antimony ions in the soil solution can enter the ettringite crystal structure; the formation rate of antimony-containing ettringite mineral crystals depends on the dissolution rate of aluminum components in the activated slag particles.

[0010] Preferably, the component ratios of the compound agent satisfy the following matching index. Relationship: in, The matching index ranges from 2.5 to 4.0. This refers to the mass fraction of finely ground blast furnace slag powder; The specific surface area of ​​finely ground blast furnace slag powder is expressed in square meters per gram. The mass fractions of ferrous sulfate heptahydrate; This is the acidity coefficient, with a value of 0.0005; This is a correction factor, with a value of [value missing]. grams per square meter; the index This is used to measure the matching relationship between the surface area of ​​finely ground blast furnace slag powder and the acid content in the system, so as to ensure that the material agglomerates while destroying the surface structure of the particles.

[0011] Preferably, the amount of the compound agent added to the soil is 2% to 5% of the dry weight of the soil; the antimony-containing calcite mineral crystals generated by the reaction have a columnar structure and are covered with a gel layer with a thickness of 5 nanometers to 20 nanometers. This gel layer is formed by the oxidation of residual ferrous ions and is used to prevent external acidic liquids from contacting the internal minerals. The compound agent utilizes the reducing substances remaining in the carbide slag to form a reducing environment on the particle surface, preventing the oxidation of pentavalent antimony in the soil and allowing trivalent antimony to be adsorbed and fixed in the hydration products of the activated slag particles.

[0012] Preferably, the preparation method of the compound agent further includes a coating step: after the modified premix is ​​prepared, the mixture is kept in a stirring state and carbide slag powder is sprayed in and mixed for 5 to 10 minutes so that the carbide slag powder adheres to the surface of the modified premix.

[0013] Preferably, the compound agent is used to remediate acidic soil with a pH of 2.0 to 5.0 and an antimony content of no more than 5000 mg / kg; after treatment with the compound agent and maintenance for 28 days, the soil exhibits an antimony leaching concentration of less than 0.005 mg / L in a leaching toxicity test conducted according to the sulfuric acid-nitric acid method, and the soil pH increases to 6.5 to 8.0.

[0014] Application of a composite agent for neutralizing and passivating the remediation of acidic soil in antimony mines, wherein the composite agent is applied to acidic soil or antimony-containing waste rock in antimony mines.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. In the acidic soil of antimony mines and in the composite agent for passivation remediation, the solid-phase micro-interface coupling mechanism between components is utilized to overcome the reaction timing mismatch caused by the much faster dissolution rate of iron salts than that of slag hydration in the traditional slag-iron salt system. Finely ground blast furnace slag powder and ferrous sulfate heptahydrate are in solid-phase contact at a specific mass ratio. The micro-acidic liquid film on the surface of the ferrous salt crystal is used to etch the dense glassy network of slag in situ, so that the aluminum-oxygen tetrahedral sites on the slag surface are exposed in advance and are in a high-energy metastable state. When the composite agent is applied to the water-bearing soil, the acid etching activates the slag, eliminates the hydration induction period of conventional silicate materials, and rapidly releases the aluminum source. It is synchronized with the instantaneously dissolved iron ions and antimonate ions in the soil on the reaction time scale. The kinetic matching ensures that in the early stage of mineral phase formation and nucleation, free antimonate ions directly participate in the construction of ettringite mineral lattice and occupy structural sites.

[0016] 2. Utilizing the principle of ion competition and substitution during crystal lattice assembly, this method addresses the challenge of desorption and reactivation of anionic pollutants during pH neutralization and remediation of antimony-contaminated soils. By limiting the ratio of slag to ferrous sulfate, a stoichiometric window of sulfate deficiency is constructed in the soil microenvironment. This allows amphoteric antimony ions to act as structural substitute anions, competitively replacing sulfate ions and entering the interior of the newly formed ettringite columnar lattice channels. This forms a chemically stable antimony-containing solid solution. Based on an atomic-level chemical bonding and solidification mode, the pollutants maintain the thermodynamic stability of the crystal structure even under conditions of increased soil pH or drastic pH fluctuations caused by acid rain erosion. This reduces the leaching toxicity and environmental migration risks of heavy metal pollutants in the remediated soil.

[0017] 3. By leveraging the complementary physicochemical properties of carbide slag components and acid-etched slag system, an adaptive soil regeneration reaction system is constructed. The carbonated film or hydrophobic impurity layer on the surface of carbide slag particles acts as a microencapsulation for physical slow release in the early stage of the reaction, moderately delaying the instantaneous formation of a strongly alkaline environment. This provides a necessary kinetic time window for the release of aluminum sources from the acid-etched slag and the orderly nucleation and growth of antimony-containing crystals, avoiding premature termination of the gelation reaction due to excessively high local alkalinity. In the later stage of the reaction, residual ferrous ions in the system are oxidized in situ to form a dense iron-based cementitious layer, which performs secondary physical coating and cementation on the already formed antimony-containing mineral microcrystals. This dual barrier mechanism, from internal lattice chemical solidification to external microscopic physical encapsulation, blocks the erosion path of oxidants and acidic seepage in soil pore water on the solidified products, enabling low-cost and high-durability application of bulk industrial solid waste in in-situ soil remediation projects. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the preparation process and lattice solidification mechanism of solid-phase micro-interface acid etching according to the present invention. Figure 2 This is a reaction kinetic matching curve of aluminum source release and antimonate consumption in this invention; Figure 3This is a schematic diagram of the microstructure of the reagent and the hierarchical solidification model of antimony contaminants in this invention. Detailed Implementation

[0019] This specific embodiment aims to clearly and completely describe the technical solution of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] This invention provides a composite agent for neutralizing and passivating acidic soils in antimony mines and its application. Prepared via a solid-phase micro-interface acid etching premixing process, the components are in a specific interfacial coupling state, solving the kinetic mismatch problem caused by the difference in dissolution rates between readily soluble iron salts and sparingly soluble slag during soil remediation. In antimony mine acidic soil remediation projects, the conventionally used slag-calcium-based-iron salt system suffers from asynchronous reaction rates due to physical barriers. Ferrous sulfate heptahydrate, as a readily soluble salt, typically dissolves and hydrolyzes within less than 10 minutes after contact with soil moisture, rapidly consuming sulfate ions and producing precipitation. Meanwhile, finely ground blast furnace slag has a dense glassy structure, and its hydrolysis and alumina tetrahedral release under ambient soil conditions are typically delayed by several hours. This time difference results in insufficient aluminum framework in the initial nucleation stage of the reaction to construct antimony-containing ettringite crystals, thus hindering the formation of antimony. Physical adsorption can easily lead to the failure of repair effects under acid rain leaching. To address this issue, the composite agent of this invention employs a pre-treatment strategy involving solid-phase micro-interface acid etching. Under conditions without added free water, the slightly acidic liquid film on the surface of ferrous sulfate heptahydrate crystals is used to perform in-situ etching on the surface of finely ground blast furnace slag powder particles. This process disrupts the calcium-oxygen and silicon-oxygen-silicon bonds on the slag surface, exposing high-energy aluminum-oxygen tetrahedral sites in advance, placing them in a metastable state with acid-induced vacancies. When the agent is applied to water-containing soil, the metastable slag eliminates the conventional hydration induction period, and the rate of aluminum source release is synchronized with the iron salt dissolution rate on a time scale. In the initial stage of the reaction, sufficient calcium ions, aluminate ions, and controlled concentrations of sulfate ions are simultaneously present in the system, allowing free antimonate ions to participate in the construction of the ettringite lattice as structural substitutes, achieving a transformation from surface adsorption to lattice solidification.

[0021] The composite reagent of this invention comprises the following components in a solid-phase coupled state: finely ground blast furnace slag powder, ferrous sulfate heptahydrate, and carbide slag; the finely ground blast furnace slag powder serves as a supplier of alumina tetrahedra. The carrier of the skeleton, used in an amount of 40 to 60 parts by weight, has a specific surface area greater than or equal to 420 to ensure acid etching response activity. Furthermore, the glass content is greater than 85%. If the dosage is less than 40 parts by weight, the aluminum framework of the system is insufficient, and a sufficient amount of mineral-encapsulated antimony cannot be generated; if it is greater than 60 parts by weight, unreacted slag can easily lead to soil compaction. Ferrous sulfate heptahydrate provides a crystal nucleation inducing agent. The acid source required for etching is used in an amount of 5 to 15 parts by weight. The mass ratio of finely ground blast furnace slag powder to ferrous sulfate heptahydrate is controlled between 4:1 and 8:1. This ratio range defines the effective micro-interface etching window: when the ratio is lower than 4:1, i.e., when iron salt is excessive, the excessive acidic liquid film leads to excessive corrosion of the slag structure and material agglomeration, and the excessively high concentration of sulfate ions hinders antimonate ions from entering the crystal lattice; when the ratio is higher than 8:1, i.e., when iron salt is insufficient, the density of etching sites on the particle contact surface is insufficient, which cannot effectively destroy the slag glass network, resulting in a delayed release of aluminum source. Calcium carbide slag is used as a delayed alkali activator, in an amount of 30 to 50 parts by weight. This calcium carbide slag is dried and ground, with a particle size D90 of less than 0.075. With a calcium oxide content greater than 60%, carbide slag provides the alkalinity needed to neutralize acidic soil. and calcium source The trace carbonation film on the surface of the particles acts as a physical barrier, delaying the instantaneous release of alkalinity and preventing the formation of amorphous precipitates due to excessively high local pH before the release of aluminum source. In addition, trace reducing organic impurities in the carbide slag, originating from the acetylene preparation process, construct a weak reducing environment at the microscopic interface, inhibiting the formation of pentavalent antimony.

[0022] The preparation of this composite agent follows the following solid-phase micro-interface acid etching premixing process: First, solid-phase acid etching activation: finely ground blast furnace slag powder and ferrous sulfate heptahydrate are added to a mixing device in a specific ratio. Under conditions without added free water, the linear velocity of the mixing device is set to 15 to 25. The mixing time is 15 to 30 minutes, and the material temperature is controlled below 45°C. To prevent premature loss of crystal water from ferrous sulfate heptahydrate, high-speed shearing force is used to increase the frequency of particle collisions. The crystal water film on the surface of ferrous sulfate heptahydrate forms a localized acidic environment with a pH of 3.0 to 4.0 at the contact interface, etching the slag surface. The mixing endpoint is determined by the uniform color of the material and the absence of visible lumps. In the second step, an inert coating is applied while the mixing equipment is running. Calcium carbide slag powder is added to the acid-etched and activated premix and mixed at low speed for 5 to 10 minutes. The calcium carbide slag powder adheres to the surface of the activated particles, forming a physical isolation layer to prevent moisture absorption and failure during storage, thus producing a composite agent. The reaction process of this composite agent after being applied to water-containing acidic soil is as follows: Within 10 minutes of contact with water, the surface calcium carbide slag slowly dissolves, while the acid-etched slag inside rapidly hydrolyzes due to surface lattice defects, releasing aluminate ions. Within 10 to 60 minutes, due to the controlled relative deficit of sulfate concentration, antimonate ions... Competitive substitution of sulfate sites allows for the assembly of antimony-containing calcite crystals with calcium and aluminum. After 60 minutes, residual ferrous ions oxidize on the crystal surface to form a ferrite gel layer, completing the secondary encapsulation.

[0023] To optimize component matching, this invention limits the component ratios of the composite agent to meet a matching index. Relationship: ,in, This refers to the mass fraction of finely ground blast furnace slag powder; The specific surface area of ​​finely ground blast furnace slag powder is given in units of... ; The mass fractions of ferrous sulfate heptahydrate; This is the acidity coefficient, with a value of 0.0005; This is a correction factor, with a value of [value missing]. Matching index The numerical range is controlled between 2.5 and 4.0. This index is used to quantify the balance between the slag surface area and the total acidity of the system: if A value below 2.5 indicates that the acid content is too large relative to the slag surface area, requiring adjustment of the proportion to prevent agglomeration; a value above 4.0 indicates insufficient acid etching intensity, requiring an increase in the acid source or a reduction in the amount of slag. Before production starts, the nitrogen adsorption specific surface area of ​​the batch of finely ground blast furnace slag powder is measured. The measured data is used as the sole variable input into the preset matching index calculation logic to lock the precise feeding amount of ferrous sulfate heptahydrate. When fluctuations in the specific surface area of ​​the slag raw material between different batches are detected, the batching system reverses the mass fraction of ferrous sulfate heptahydrate based on the constant matching index target value, maintaining the acid etching medium based on the dynamic metering compensation mechanism of the microscopic surface area. The total mass and the number of reactive sites in the slag are stoichiometrically balanced to avoid insufficient acid etching or excessive agglomeration due to changes in raw material fineness, ensuring that the exposure density of alumina tetrahedral sites in each batch of premixed material is within the preset reactive window. During the mixing process, the real-time load power curve of the stirring motor and the temperature change of the material bed are monitored to determine the endpoint of the solid-phase micro-interface acid etching reaction. During the stage of ferrous sulfate heptahydrate crystal water release and liquid film formation on the slag surface, the rheological properties of the material system undergo a sudden change due to the establishment of interparticle liquid bridge forces, manifested as a sharp increase in the stirring motor load current and a stable plateau period, accompanied by an exothermic acid-base reaction causing the material temperature to rise 3°C above the ambient temperature. Up to 5 The control system locks the moment when the load power curve changes from fluctuating to flat and the temperature gradient reaches the set threshold as the cut-off point of the acid etching modification process, and starts the carbide slag powder feeding and coating program to eliminate the deviation in reaction degree caused by controlling the mixing time.

[0024] Example 1: This example describes the specific application and practical simulation of the composite agent prepared based on the solid-phase micro-interface acid etching premixing process in a typical high-acidity, strongly oxidizing, and alternating wet and dry waste rock dump environment in an antimony mine. In a typical antimony mine waste rock dump scenario in a rainy southern region, the soil pH value is maintained between 2.0 and 3.0 for a long period of time, and the antimony content is as high as 4500. The area is frequently subjected to acid rain erosion with a pH value of less than 4.5, and the surface runoff is intense. These extreme conditions pose a challenge: although conventional alkaline neutralizers can temporarily raise the soil pH value, the soil pH value drops rapidly under continuous acid rain leaching, causing a large amount of temporarily adsorbed antimony pollutants to desorb and migrate with the runoff, resulting in secondary pollution. At the same time, conventional iron salt passivating agents have poor stability in such high acid and strong oxidizing environments, and the ferric hydroxide colloids produced by hydrolysis are prone to aging and crystallization, thus losing their ability to adsorb antimony.

[0025] To address this challenge, the composite agent of this invention was applied to the surface soil of the waste rock dump at a dosage of 4% of the soil dry weight. Within the first 10 minutes after application, the finely ground blast furnace slag powder in the agent, which had been activated by micro-interface acid etching, rapidly responded to soil moisture and released a high concentration of aluminate ions instantaneously using the pre-exposed alumina tetrahedral sites on its surface. Simultaneously, sulfate ions are generated from the dissolution of ferrous sulfate heptahydrate. The concentration was limited to a low-sulfur level, while the calcium carbide slag began to slowly release calcium ions. and hydroxide ions At this point, a stoichiometric environment is established within the system, characterized by aluminum and calcium enrichment but relative sulfate deficiency. Under this specific microenvironment, free antimonate ions in the soil... As a structural substitute component, it competes with calcium and aluminum ions for crystallization. Due to the controlled sulfate concentration, antimonate ions occupy sulfate sites in the ettringite lattice and self-assemble in situ to form an antimony-containing ettringite solid solution. This lattice solidification mechanism transforms antimony pollutants from an unstable surface adsorption state to a stable mineral structure state, enabling them to resist subsequent acid rain erosion and environmental pH fluctuations.

[0026] After 60 minutes of reaction, the alkalinity continuously released by the carbide slag gradually stabilized the soil pH between 6.5 and 8.0. At this point, the residual ferrous ions in the agent... In-situ oxidation of antimony-containing calcite crystals forms a dense ferrite gel layer, which provides secondary physical encapsulation of the solidified antimony-containing microcrystals. Furthermore, the surface hydroxyl groups further adsorb residual trace antimony ions. In addition, the weakly reducing environment created by trace reducing organic impurities in the carbide slag at the particle interface effectively inhibits the conversion of trivalent antimony to highly toxic pentavalent antimony in the soil. After the above treatment and 28 days of curing, the antimony leaching concentration in the soil of this area remained at 0.005% under simulated acid rain continuous leaching conditions with a pH of 3.0. The following values ​​are far below the national standard limits. This invention avoids the kinetic mismatch problem of traditional repair materials in extreme acidic environments by using solid-phase micro-interface acid etching coupling between components, thereby achieving long-term and stable curing of antimony contaminants.

[0027] Example 2: This example describes a rigorous controlled experiment designed to objectively verify the practical effectiveness of the composite agent of this invention in the remediation of acidic soil in antimony mines, and to quantitatively analyze the scientific laws governing the synergistic effect of its components and the matching of reaction kinetics. All data from this experiment were obtained based on a standardized laboratory simulation platform, directly reflecting the engineering performance of the technical solution. The experiment used heavy metal-contaminated soil collected from a typical antimony mine waste rock dump, with an initial pH of 2.5 and a total antimony content of 4800 mg / L. Furthermore, antimony exhibits strong oxidizing properties. To simulate real-world environmental erosion, a soil column test system with dynamic acid rain leaching function was established. This system consists of an acrylic column, a constant-flow peristaltic pump, a leachate collection device, and a data monitoring terminal. The constant-flow peristaltic pump drips artificial acid rain with a pH of 3.0 onto the top of the soil column at a constant flow rate to simulate continuous erosion under extreme climatic conditions. The leachate collection device automatically collects the effluent at preset time intervals and immediately sends it to an inductively coupled plasma mass spectrometer (ICP-MS) for antimony concentration determination. The detection limit of the ICP-MS was set to 0.01. .

[0028] To comprehensively evaluate the technical effects of this invention and the non-obvious synergistic relationships between its components, six parallel treatment groups were set up in the experiment. The sample group of this invention: used the composite reagent of this invention, wherein finely ground blast furnace slag powder (specific surface area 450...) 50 parts ferrous sulfate heptahydrate, 10 parts calcium carbide slag, and 40 parts ferrous sulfate were prepared using a solid-phase micro-interface acid etching premixing process, with the slag to ferrous sulfate mass ratio being 5:1. Control group A (mixed and used immediately): The component types and amounts were completely consistent with the sample group of this invention, but no acid etching pretreatment was performed before application; instead, the three dry powders were simply physically mixed and directly applied to the soil. Control group B (excess iron salt): The ratio was changed, with the slag to ferrous sulfate mass ratio adjusted to 2:1 (i.e., 25 parts ferrous sulfate, 50 parts slag, and 25 parts calcium carbide slag), while other conditions remained unchanged. This group aimed to verify the effect of deviating from the sulfur-depleted window on lattice solidification. Control group C (insufficient iron salt): The ratio was changed, with the slag to ferrous sulfate mass ratio being 5:1. The ferrous sulfate mass ratio was adjusted to 10:1 (i.e., 5 parts ferrous sulfate, 50 parts slag, and 45 parts carbide slag), with other conditions remaining unchanged. This group aimed to verify the effect of insufficient acid etching on reaction kinetics. Control group D (traditional lime + iron salt): The industry-standard lime neutralization and ferrous sulfate adsorption scheme was used, without the addition of slag. Blank control group: Only an equal amount of deionized water was applied, without the addition of any remediation agents. The amount of agent added to all treatment groups was uniformly 4% of the dry weight of the soil. The experimental period was set at 28 days, during which continuous acid rain leaching was maintained. Key monitoring indicators included the trend of antimony concentration change in the leaching solution and the stability of soil pH. The experimental results showed a pattern of differences. Specific data are shown in Table 1.

[0029] Table 1: Monitoring data of antimony concentration in leachate and soil pH value for each treatment group A thorough analysis of the data in Table 1 reveals the underlying mechanisms of action of each component and process. Throughout the entire 28-day leaching cycle, the antimony leaching concentration in the sample group of this invention remained stable at 0.005%. The pH value remained around 7.2, confirming that acid etching activation synchronized the release of aluminum source with the dissolution of iron salts, constructing an antimony-containing calcite lattice. This resulted in antimony pollutants exhibiting extremely high inertness to acid rain erosion. Furthermore, the control group A (prepared and used immediately) initially had a low antimony concentration, which rapidly rebounded to 0.550 over time. The results indicate that the lack of acid etching pretreatment led to a mismatch in reaction kinetics. Initially, unstable surface adsorption was formed, and later, as the adsorption sites became saturated and pH fluctuated, a large amount of adsorbed antimony was desorbed. This comparison strongly proves that solid-phase micro-interface acid etching is a key prerequisite for achieving lattice solidification, rather than a simple superposition of components. Furthermore, although the antimony concentration in control group B (excessive iron salt) was relatively well controlled, the pH value dropped rapidly to 5.8, and soil column compaction was observed. This indicates that excessive acidic iron salt disrupted the acid-base balance of the system, and the excessively high sulfate concentration competed for ettringite lattice sites, inhibiting the entry of antimony and also bringing the side effect of deteriorating soil physical properties. Finally, the antimony leaching concentrations in control groups C (insufficient iron salt) and D (traditional scheme) were much higher than those in the sample group of this invention, and they showed a clear pH-migration inversion phenomenon, that is, the decrease in pH was accompanied by a surge in antimony concentration. In particular, in control group D, when the pH value dropped below 7.0 in the later stage, the antimony concentration was released explosively.

[0030] Example 3: This example combines Figures 1 to 3 Instructions for the application of compound agents for neutralizing and passivating acidic soils in antimony mines, such as... Figure 1 As shown, the process begins with ferrous sulfate heptahydrate providing the acid source for crystallization and finely ground blast furnace slag powder providing aluminum-oxygen tetrahedral sites. Through a solid-phase micro-interface acid etching mechanism, the water of crystallization forms an acidic liquid film to activate the slag surface and eliminate the hydration induction period, thereby producing modified premixed activated slag particles with exposed high-energy aluminum-oxygen tetrahedral sites. After physical encapsulation, a physical isolation layer is formed using carbide slag dry powder to delay the release of alkaline substances, resulting in a composite agent dry powder possessing both surface etching characteristics and a physical isolation layer. The agent is applied to the acidic soil of antimony mines containing antimony ions and in a highly acidic environment. With the physical isolation layer provided by carbide slag and the cooperation of trace reducing components, the synchronous release of aluminum and iron ions is achieved through kinetic matching to create a sulfur-poor calcite crystallization environment. Antimony ions enter the crystal lattice as structural substitutes, generating atomically solidified products, namely antimony-containing calcite mineral crystals. At the same time, the trace reducing components are used to synergistically inhibit the formation of highly toxic pentavalent antimony, ultimately reducing the antimony leaching concentration and achieving long-term safe remediation of acidic soil.

[0031] like Figure 2 As shown in the kinetic curve of ion concentration change over time in the reaction system, the horizontal axis represents the reaction time, ranging from 0 to 60 minutes, and the vertical axis represents the relative percentage of ion concentration, ranging from 0 to 100. The graph shows that the aluminum ion concentration rises rapidly from 0 in the initial stage of the reaction, reaches a peak of 55% at about 5 minutes, and then slowly decreases, indicating that the aluminum source is rapidly released. Simultaneously, the sulfate ion concentration shows a continuous decreasing trend from the initial 100%, dropping to about 30% by 60 minutes. The antimonate ion concentration also starts from 100% and shows a similar decreasing trend as the reaction progresses. Figure 3As shown, the microstructure of the composite agent consists of exposed aluminum-oxygen tetrahedral sites of activated slag particles as the core, and a physical isolation layer of carbide slag coating layer encapsulating them. Furthermore, a ferrite gel encapsulation layer is formed in the later stages of the reaction. The reaction process of this system after contact with acidic soil is divided into three regions in space and time: the surface reaction zone from 0 to 10 minutes, during which the carbide slag coating layer releases... , and The second phase is a lattice solidification zone lasting 10 to 60 minutes, during which time... The material migrates and is assembled into the antimony-containing ettringite crystal as a structural component to achieve lattice solidification. Finally, after 60 minutes, a secondary encapsulation zone is formed on the outside of the generated antimony-containing ettringite crystal, forming a ferrite gel layer with a thickness of 5nm to 20nm, which completes the shielding and protection of the solidified product.

[0032] Example 4: This example addresses the issue of unstable reagent performance caused by fluctuations in the specific surface area of ​​finely ground blast furnace slag powder raw materials in industrial continuous production scenarios. It provides a set of reagents based on a matching index. The dynamic batching and process quality control procedures aim to eliminate the black box regarding the degree of acid etching and the aluminum source release rate, ensuring that each batch of composite reagents can accurately achieve the expected solid-phase micro-interface acid etching effect, when treating a batch with a specific surface area fluctuation range of 420. Up to 480 In the process of grinding blast furnace slag into fine powder, to ensure a constant acid etching effect, the production system does not use a fixed component mass ratio. Instead, it executes an adaptive batching logic based on microscopic surface area matching to measure the specific surface area of ​​the incoming finely ground blast furnace slag powder. Real-time detection, assuming the current batch of slag is detected. 460 That is, 0.46 The system is based on the preset target value of the matching index. (This value is within the optimal working window of 2.5 to 4.0). Use the following formula to calculate the required mass fractions of ferrous sulfate heptahydrate. : ,in, Set the baseline value to 50 copies. Take 0.0005, Pick Substituting the measured values ​​into the calculation, the required amount of ferrous sulfate heptahydrate for this batch was obtained. It should be precisely adjusted to 14.375 parts, rather than the fixed value in the general formula. This step ensures that the total acidity in the system and the total microscopic surface area of ​​the slag always maintain a constant stoichiometric relationship.

[0033] After determining the proportions, the solid-phase micro-interface acid etching and activation step is initiated. To address the engineering black box issue of determining the mixing endpoint, this embodiment introduces a mixing power-temperature coupled monitoring procedure. The metered slag and ferrous sulfate heptahydrate are added to the mixer, and the linear velocity is set to 20. During the mixing process, the load power of the mixing motor and the material temperature are monitored in real time. When the water of crystallization on the surface of ferrous sulfate heptahydrate is released under mechanical force and forms a liquid film on the slag surface, the fluidity of the material will change characteristically, causing fluctuations in the mixing power. At the same time, the acid etching reaction is accompanied by a weak exothermic reaction. The procedure is set to: when the material temperature rises by 3 degrees Celsius from the initial temperature... Up to 5 When the mixing power curve changes from fluctuation to a stable straight line for more than 3 minutes, it is determined that the micro-interface acid etching has reached thermodynamic equilibrium, that is, the aluminum-oxygen tetrahedral sites have been fully exposed and no excessive reaction has occurred. At this time, intermediate product quality verification is performed: a small amount of premix is ​​taken for a 5-minute rapid dissolution test. If the aluminum ion concentration in the solution exceeds the preset threshold, such as 50%, the test is considered successful. If the acid etching activation is successful, then 40 parts of carbide slag powder are added under stirring for inert coating, and the final product is obtained. The composite agent produced according to this procedure, when added to simulated acidic soil with a moisture content of 30% (pH=2.5), exhibits a high degree of synchronicity between the aluminum source release kinetics curve and the iron salt dissolution curve. Specifically, within 5 minutes of the reaction starting, the dissolved aluminum concentration in the system rapidly reaches its peak, matching the decay rate of the sulfate concentration, confirming the construction of an acid-induced metastable structure. The remediated soil prepared in this way, after undergoing 10 consecutive cycles of acid rain leaching (pH=3.0), consistently shows a cumulative antimony dissolution of less than 0.02%. Furthermore, no performance deviations were observed due to fluctuations in raw materials between batches.

[0034] Example 5: This example describes a standardized on-site calibration procedure for adaptability verification and parameter optimization of the solid-phase micro-interface acid etching premixing process before actual engineering deployment. This ensures that the composite agent of this invention can stably construct acid-induced metastable structures under different batches of slag powder raw materials, soils with different moisture contents, and different environmental temperature and humidity conditions. In a specific antimony mine acidic soil remediation project, because the slag raw materials originated from different blast furnace batches, their glassy microstructure and alkalinity coefficient fluctuated, and the soil moisture content varied significantly due to seasonal rainfall. To eliminate these... To investigate the impact of uncontrollable variables on the solid-phase acid etching effect, the following preliminary calibration steps were performed: Soil samples to be treated and the batch of finely ground blast furnace slag powder raw materials were collected from the site. Under the average temperature conditions simulating the site in the laboratory, a series of premixed samples with different slag to ferrous sulfate mass ratios (from 4:1 to 8:1, with a gradient of 0.5) were prepared. For each group of premixed samples, samples were taken at 5 minutes, 15 minutes and 30 minutes after mixing for rapid detection of micro-acid etching degree. This was achieved by measuring the instantaneous (within 30 seconds) aluminum ion dissolution amount per unit mass of premix in deionized water.

[0035] Furthermore, the instantaneous aluminum ion dissolution rate was used as a direct indicator of acid etching activation efficiency. Data analysis showed that as the amount of ferrous sulfate increased, the aluminum ion dissolution rate first increased and then decreased. When the dissolution rate reached its peak and remained stable thereafter, the corresponding ratio was the acid etching window of the batch of raw materials under the current environment. Based on this calibration result, the on-site engineering team locked the batching parameters on the production line to the mass ratio corresponding to the acid etching window, such as 4.8:1, and adjusted the mixing time of the mixer accordingly to ensure that each batch of composite reagent leaving the factory was in the best activation state.

[0036] Example 6: This example describes an adaptive pre-calibration and formulation fine-tuning procedure for introducing a new batch of finely ground blast furnace slag powder raw materials. This procedure addresses the uncertainty of acid etching effects caused by fluctuations in the specific surface area of ​​the raw materials, ensuring consistent product performance in large-scale continuous production. When introducing a new batch of finely ground blast furnace slag powder raw materials, the production system performs a pre-calibration procedure, taking a representative sample of the batch and measuring its specific surface area under standard laboratory conditions. If the actual measured value is 450 The system is based on the preset target value of the matching index. Substitute into the formula Calculate the required mass fractions of ferrous sulfate heptahydrate in reverse order. ,in, Set the baseline value to 50 copies. Take 0.0005, Pick Calculations show that the required amount of ferrous sulfate heptahydrate for this batch is... The number of locked copies is 14.06.

[0037] Based on this calculation result, a small-scale experiment was conducted. The calculated amount of ferrous sulfate heptahydrate was mixed with 50 parts of slag powder. The mixture was stirred at a standard linear velocity, and the mixing power and material temperature were monitored in real time. When the mixing power curve changed from fluctuation to stability and the material temperature rose to 3... Up to 5 When the characteristic range is reached, it is determined that the acid etching of the solid micro-interface has reached equilibrium. At this time, a sample is taken to detect the aluminum ion dissolution concentration in water after 5 minutes. If the dissolution concentration reaches the preset 50%, If the threshold is met, the calculated ratio is confirmed to be valid, and this parameter matrix (slag: ferrous sulfate = 50: 14.06) is solidified as the control benchmark for the production operation of this batch of raw materials; if the leaching concentration does not meet the standard, the amount of ferrous sulfate is finely adjusted in a gradient of 0.5 parts and the verification is repeated until the leaching index is met.

[0038] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A composite agent for neutralizing and passivating acidic soil in antimony mines, characterized in that, The composite agent is a surface-modified dry powder mixture, prepared from finely ground blast furnace slag powder, ferrous sulfate heptahydrate, and carbide slag. The content of finely ground blast furnace slag powder is 40 to 60 parts by weight, the content of ferrous sulfate heptahydrate is 5 to 15 parts by weight, and the content of calcium carbide slag is 30 to 50 parts by weight; the mass ratio of finely ground blast furnace slag powder to ferrous sulfate heptahydrate is 4:1 to 8:

1. The composite agent contains activated slag particles with surface etching characteristics. These activated slag particles are prepared by an acid etching modification step. The acid etching modification step is as follows: under conditions without added free water, finely ground blast furnace slag powder is mixed with ferrous sulfate heptahydrate. The water of crystallization released by ferrous sulfate heptahydrate forms an acidic liquid film at the contact interface, which etches the surface of the finely ground blast furnace slag powder to form a modified premix. Carbide slag, in dry powder form, coats the surface of the modified premix particles, forming a physical barrier layer to delay the release of alkalinity; the composite agent is used when in contact with water-containing acidic soils. The aluminum ions released by the activated slag particles react with dissolved iron ions and antimony ions in the soil to form antimony-containing calcite mineral crystals.

2. The composite agent for neutralizing and passivating acidic soil in antimony mines according to claim 1, characterized in that, The specific surface area of ​​the finely ground blast furnace slag powder is greater than or equal to 420 square meters per kilogram, and the glass content is greater than 85%. The moisture content of the finely ground blast furnace slag powder before entering the acid etching modification step is less than 1% to control the acid etching reaction to be limited to the particle surface. The composite agent does not contain artificially added phosphates or sulfides, and relies solely on the mineral structure generated by the hydration of the finely ground blast furnace slag powder to fix antimony contaminants.

3. The composite agent for neutralizing and passivating acidic soil in antimony mines according to claim 1, characterized in that, The process parameters for the acid etching modification step are as follows: finely ground blast furnace slag powder and ferrous sulfate heptahydrate are added to a mixing device and mixed for 15 to 30 minutes at a linear velocity of 15 to 25 meters per second until the material is uniformly mixed and free of lumps. During this process, the material temperature is controlled below 45°C to prevent ferrous sulfate heptahydrate from losing its water of crystallization too early, and the pH value of the particle contact surface is maintained between 3.0 and 4.

0.

4. The composite agent for neutralizing and passivating acidic soil in antimony mines according to claim 1, characterized in that, The carbide slag is a powder that has been ground and hydrophobically treated, with a particle size D90 of less than 0.075 mm and a calcium oxide content of more than 60%. The physical isolation layer is used to slow down the rise of the pH value of the system in the initial stage after the compound agent is applied to the soil, so that the soil environment is kept in a weakly acidic to neutral range within 10 minutes after the reaction begins, and to release aluminate ions in conjunction with the activation of slag particles.

5. The composite agent for neutralizing and passivating acidic soil in antimony mines according to claim 1, characterized in that, The reaction process is a crystallization process controlled by sulfate content; a mass ratio of 4:1 to 8:1 is used to limit the sulfate content in the reaction system, allowing antimonate ions in the soil solution to enter the ettringite crystal lattice structure; The formation rate of antimony-containing calcite mineral crystals depends on the dissolution rate of the aluminum component in the activated slag particles.

6. The composite agent for neutralizing and passivating acidic soil in antimony mines according to claim 1, characterized in that, The component ratios of the compound agent satisfy the following matching index. Relationship: ,in, The matching index ranges from 2.5 to 4.

0. This refers to the mass fraction of finely ground blast furnace slag powder; The specific surface area of ​​finely ground blast furnace slag powder is expressed in square meters per gram. The mass fractions of ferrous sulfate heptahydrate; This is the acidity coefficient, with a value of 0.0005; This is a correction factor, with a value of [value missing]. grams per square meter; the index This is used to measure the matching relationship between the surface area of ​​finely ground blast furnace slag powder and the acid content in the system, so as to ensure that the material agglomerates while destroying the surface structure of the particles.

7. The composite agent for neutralizing and passivating acidic soil in antimony mines according to claim 1, characterized in that, The compound agent is added to the soil at a rate of 2% to 5% of the soil dry weight. The antimony-containing calcite mineral crystals generated by the reaction have a columnar structure and are covered with a gel layer with a thickness of 5 to 20 nanometers. This gel layer is formed by the oxidation of residual ferrous ions and is used to prevent external acidic liquids from contacting the internal minerals. The compound agent utilizes the reducing substances remaining in the carbide slag to form a reducing environment on the particle surface and allows trivalent antimony to be adsorbed and fixed in the hydration products of the activated slag particles.

8. The composite agent for neutralizing and passivating acidic soil in antimony mines according to claim 1, characterized in that, The preparation method of the compound agent also includes a coating step: after the modified premix is ​​prepared, the mixture is kept in a stirring state and carbide slag powder is sprayed in and mixed for 5 to 10 minutes so that the carbide slag powder adheres to the surface of the modified premix.

9. The composite agent for neutralizing and passivating acidic soil in antimony mines according to claim 1, characterized in that, The compound agent is used to remediate acidic soils with a pH of 2.0 to 5.0 and an antimony content of no more than 5000 mg / kg. After treatment with compound agents and maintenance for 28 days, the leaching concentration of antimony in the soil was less than 0.005 mg / L in the leaching toxicity test conducted according to the sulfuric acid-nitric acid method, and the soil pH value increased to 6.5 to 8.

0.

10. The application of a composite agent for neutralizing and passivating acidic soil in antimony mines, characterized in that, The composite agent described in claim 1 is applied to acidic soil or antimony-containing waste rock in antimony mines.

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