Ferrous sulfide particles with shells as well as preparation method and application of ferrous sulfide particles

Abstract

The invention relates to the technical field of land pollution treatment, solves the problem that in the prior art, when a large-area medium polluted by hexavalent chromium is treated, the addition amount of ferrous sulfide is prone to being inaccurate, and consequently the remediation effect is not ideal, and provides ferrous sulfide particles with shells and a preparation method and application of the ferrous sulfide particles. The prepared ferrous sulfide particles with the shells can keep efficient removal of chromium within the pH value range of 5-9, the problem that the adsorption behavior of a traditional model in a low-chromium-concentration area is difficult to predict is effectively solved by means of a correction adsorption model with higher fitting precision, and therefore the actual demand quantity of target repairing liquid can be accurately predicted, and the application prospect is wide. The target repairing liquid can be injected more accurately, and excessive or insufficient injection is avoided. After hexavalent chromium is reduced into trivalent chromium by ferrous sulfide, the trivalent chromium and carboxymethyl cellulose can form a stable chelate, and zero-valent sulfur can also form a compact passivation layer on the surface of a polluted medium, so that the trivalent chromium is prevented from being reoxidized, and long-term stable repair of hexavalent chromium is realized.

Description

Technical Field

[0001] This invention relates to the field of chromium pollution control, and more particularly to a ferrous sulfide particle with a shell, its preparation method, and its application. Background Technology

[0002] Hexavalent chromium, a highly toxic and mobile heavy metal pollutant, is widely derived from industrial activities such as metallurgy, electroplating, and leather tanning. In the environment, it exists primarily as CrO4. 2- HCrO4 - It exists in anionic form, has strong water solubility and biopermeability, and can accumulate through the food chain, causing carcinogenic and teratogenic risks, posing a serious threat to the ecological environment and human health.

[0003] Traditional hexavalent chromium remediation technologies mainly include chemical reduction and electrochemical methods, but they have many limitations: chemical reduction uses reducing agents such as sulfites and ferrous sulfate, which are difficult to diffuse evenly in the soil and cannot remediate evenly. Moreover, under acidic conditions, the iron dissolution rate is as high as 44.3 mg / L, which can easily cause secondary pollution; electrochemical methods are expensive and can damage the soil structure, making them unsuitable for large-scale pollution remediation.

[0004] Ferrous sulfide possesses Fe 2+ / S 2- Dual-reduction active sites are present in existing technologies, such as the use of ferrous sulfide for the remediation of hexavalent chromium. For example, Chinese patent CN105460979A discloses a method for preparing and using FeS particles for remediating hexavalent chromium-contaminated soil. However, the actual dosage of FeS particles used for soil remediation of hexavalent chromium is still based on theoretical calculations. While existing technologies assume that iron reduction dominates the removal process of hexavalent chromium, they lack density functional theory support, and the atomic-level mechanism of sulfide sites in electron transfer remains unclear. This results in a deviation of more than 20% between the theoretically calculated dosage and the actual required dosage, leading to either too few or too many FeS particles, which is detrimental to the remediation of hexavalent chromium pollution. Furthermore, the remediation solution containing FeS particles is prone to pore blockage due to the filter cake effect, making existing technologies unsuitable for the remediation of large-area media contaminated with hexavalent chromium. Summary of the Invention

[0005] In view of this, embodiments of the present invention provide ferrous sulfide particles with a shell, a method for preparing the same, and their applications, to solve the problem that in the prior art, when treating media contaminated with hexavalent chromium over a large area, the dosage of ferrous sulfide is often inaccurate, leading to unsatisfactory remediation results.

[0006] In a first aspect, embodiments of the present invention provide ferrous sulfide particles with a shell, comprising: ferrous sulfide particles and a stabilizer shell covering the surface of the ferrous sulfide particles; wherein the molar ratio of the stabilizer shell to the ferrous sulfide particles is in the range of 0.0006-0.002, and the stabilizer shell comprises carboxymethyl cellulose.

[0007] As an optional implementation, the zeta potential of the ferrous sulfide particles with the shell ranges from -35mV to -42mV, the particle size of the ferrous sulfide particles with the shell ranges from 130nm to 200nm, and the thickness of the stabilizer shell ranges from 0.8nm to 2nm.

[0008] In a second aspect, embodiments of the present invention provide a method for preparing ferrous sulfide particles with a shell as described in the first aspect, comprising: mixing a ferrous salt solution and a sulfide solution according to a first molar ratio to prepare a suspension containing ferrous sulfide particles; adding a stabilizer solution to the suspension according to a second molar ratio to obtain a target reaction solution, wherein the target reaction solution contains the ferrous sulfide particles with a shell, and the stabilizer solution comprises an aqueous solution of carboxymethyl cellulose; and concentrating the ferrous sulfide particles with a shell in the target reaction solution to obtain solid ferrous sulfide particles with a shell.

[0009] As an optional implementation, the step of mixing the ferrous salt solution and the sulfide solution based on a first molar ratio to prepare a suspension containing ferrous sulfide particles includes: preparing a ferrous salt solution with a concentration range of 0.05 mol to 0.2 mol / L and a sulfide solution with a concentration range of 0.05 mol to 0.2 mol / L in an environment filled with inert gas; using the molar ratio of ferrous sulfide ions to sulfur ions as the first molar ratio, and adding the sulfide solution dropwise to the ferrous salt solution based on the first molar ratio to prepare the suspension, controlling the stirring speed range to be 250 to 550 r / min, controlling the dropping rate of the sulfide solution to be 0.8 to 2.5 ml / min, and the first molar ratio range to be 1 to 1.1.

[0010] As an optional implementation, the step of adding a stabilizer solution to the suspension based on a second molar ratio to obtain the target reaction solution includes: using the molar ratio of carboxymethyl cellulose to ferrous sulfide particles as the second molar ratio, adding the stabilizer solution to the suspension based on the second molar ratio, controlling the stirring time to be in the range of 25 min to 45 min, and the second molar ratio to be in the range of 0.0006 to 0.002.

[0011] As an optional implementation, the concentration of the shelled ferrous sulfide particles in the target reaction solution to obtain solid shelled ferrous sulfide particles includes: centrifuging the target reaction solution to obtain a concentrated solution, controlling the centrifugation time to be within the range of 8 to 20 minutes and the centrifugation speed to be within the range of 7000 to 12000 r / min; and vacuum freeze-drying the concentrated solution to obtain solid shelled ferrous sulfide particles, controlling the vacuum freezing temperature to be within the range of -60℃ to -30℃ and controlling the vacuum degree of the vacuum freezing to be less than or equal to 20 Pa.

[0012] Thirdly, embodiments of the present invention provide an application of ferrous sulfide particles with a shell as described in the first aspect, comprising: mixing the ferrous sulfide particles with a shell with a buffer solution to prepare a target remediation solution; injecting the target remediation solution into a medium to be treated based on initial remediation parameters, and continuously monitoring real-time remediation index parameters in the medium to be treated; determining dynamic remediation parameters based on a preset modified adsorption model and the real-time remediation index parameters, and using the dynamic remediation parameters to remediate the medium to be treated.

[0013] As an optional implementation, the step of mixing the shelled ferrous sulfide particles with a buffer solution to obtain the target repair solution includes: mixing the shelled ferrous sulfide particles with a mass concentration range of 0.08~0.12 g / L with the buffer solution with a molar concentration range of 8~12 mM / L to obtain the target repair solution with a pH range of 6.5~7.8.

[0014] As an optional implementation, the step of injecting the target remediation solution into the medium to be treated based on initial remediation parameters and continuously monitoring the real-time remediation index parameters in the medium to be treated includes: determining the injection method of the target remediation solution according to the type of the medium to be treated, and injecting the target remediation solution into the medium to be treated based on the initial remediation parameters, wherein the initial remediation parameters include initial injection pressure, single-pulse injection volume, and initial pulse period; and monitoring at least one point in the medium to be treated to obtain the real-time remediation index parameters, wherein the real-time remediation index parameters include hexavalent chromium concentration and pH value.

[0015] As an optional implementation, the step of determining dynamic remediation parameters based on a preset modified adsorption model and the real-time remediation index parameters, and using the dynamic remediation parameters to remediate the medium to be treated, includes: establishing the modified adsorption model based on the linear partition coefficient, the reciprocal of cadmium concentration, and the Langmuir equation; determining the dynamic remediation parameters of the target remediation solution using the modified adsorption model and the real-time remediation index parameters; and using the dynamic remediation parameters to remediate the medium to be treated, wherein the dynamic remediation parameters include the replenishment volume of the buffer solution, the injection flow rate of the target remediation solution, and the injection concentration.

[0016] In summary, the beneficial effects of the present invention are as follows: This invention provides a shelled ferrous sulfide particle, its preparation method, and its application. The prepared shelled ferrous sulfide particles exhibit excellent dispersibility, high reactivity, and large adsorption capacity. When applied to the remediation of hexavalent chromium pollution, firstly, it maintains efficient chromium removal within a pH range of 5-9, demonstrating strong environmental adaptability; secondly, by utilizing a more accurate modified adsorption model, it effectively solves the problem of unpredictable adsorption behavior in traditional low-chromium concentration areas, thereby dynamically adjusting the injection parameters of the target remediation solution based on real-time remediation index parameters, effectively improving the utilization rate of the remediation material; thirdly, after hexavalent chromium is reduced to trivalent chromium by ferrous sulfide, it forms stable Cr(III)-O-Fe(III) and Cr(III)-O-CMC chelates with carboxymethyl cellulose, forming a dense passivation layer containing zero-valent sulfur on the surface of the polluted medium, completely inhibiting the re-oxidation of trivalent chromium and achieving long-term stable remediation of hexavalent chromium. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, and these are all within the protection scope of the present invention.

[0018] Figure 1 This is a flowchart of a method for preparing ferrous sulfide particles with a shell according to an embodiment of the present invention; Figure 2 This is a flowchart illustrating the application of ferrous sulfide particles with a shell according to an embodiment of the present invention. Detailed Implementation

[0019] The features and exemplary embodiments of various aspects of the present invention will now be described in detail. To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present invention and are not configured to limit the present invention. For those skilled in the art, the present invention can be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the invention.

[0020] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0021] In a first aspect, embodiments of the present invention provide ferrous sulfide particles with a shell, the particles comprising: ferrous sulfide particles and a stabilizer shell covering the surface of the ferrous sulfide particles; wherein the molar ratio of the stabilizer shell to the ferrous sulfide particles is in the range of 0.0006-0.002, and the stabilizer shell comprises carboxymethyl cellulose (CMC).

[0022] Specifically, carboxymethyl cellulose includes at least one of sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, and ammonium carboxymethyl cellulose; ferrous sulfide includes at least one of natural ferrous sulfide, chemically synthesized ferrous sulfide, and biosynthesized ferrous sulfide. The zeta potential of the shelled ferrous sulfide particles ranges from -35 mV to -42 mV, the particle size ranges from 130 nm to 200 nm, the thickness of the stabilizer shell ranges from 0.8 to 2 nm, and the sulfur vacancy density of the shelled ferrous sulfide particles is ≥1.5 × 10⁻⁶. 14 sites / cm 2 The adsorption capacity for hexavalent chromium is ≥300mg / g.

[0023] In one optional embodiment, the molar ratio of the stabilizer shell to the ferrous sulfide particles can be 0.001. Carboxymethyl cellulose molecules chelate with ferrous ions through their carboxyl groups to form a monolayer stabilizer shell with a thickness of approximately 1.2 nm, reducing the particle size of the ferrous sulfide particles from the conventional unmodified 253 nm to 166 nm, achieving a Zeta potential of -38.5 mV, and completely suppressing the aggregation between ferrous sulfide particles due to electrostatic repulsion.

[0024] The prepared ferrous sulfide particles with a shell have a sulfur vacancy density of 1.8 × 10⁻⁶. 14 sites / cm 2 The sulfur vacancy density of the modified ferrous sulfide particles is three times higher than that of unmodified ferrous sulfide particles, providing a structural basis for the high adsorption capacity of hexavalent chromium. The ferrous sulfide particles with a shell provided in this embodiment of the invention can achieve an adsorption capacity of 327.9 mg / g for hexavalent chromium, which is 17.3% higher than that of unmodified ferrous sulfide particles.

[0025] Secondly, embodiments of the present invention provide a method for preparing ferrous sulfide particles with a shell as described in the first aspect, please refer to... Figure 1 As shown, the preparation method includes the following steps S101~S103: Step S101: Mix the ferrous salt solution and the sulfide solution according to the first molar ratio to prepare a suspension containing ferrous sulfide particles.

[0026] Specifically, a ferrous salt solution with a concentration range of 0.05 mol to 0.2 mol / L and a sulfide solution with a concentration range of 0.05 mol to 0.2 mol / L can be prepared in an inert gas atmosphere. In practice, the 0.05-0.2 mol / L ferrous salt solution and the 0.05-0.2 mol / L sulfide solution can be prepared first and placed in a low-temperature environment of 0-8°C under the protection of an inert gas atmosphere to prevent the oxidation of ferrous ions. The ferrous salt can include at least one of ferrous sulfate, ferrous chloride, and ferrous nitrate; the sulfide can include at least one of sodium sulfide, potassium sulfide, ammonium sulfide, and hydrogen sulfide; and the inert gas can include at least one of nitrogen and argon.

[0027] The molar ratio of ferrous sulfide ions to sulfide ions is used as the first molar ratio. Based on this first molar ratio, the sulfide solution is added dropwise to the ferrous salt solution to prepare a suspension. The stirring speed is controlled within the range of 250~550 r / min, the dropping rate of the sulfide solution is controlled within the range of 0.8~2.5 ml / min, and the first molar ratio is controlled within the range of 1~1.1. In specific implementation, the first molar ratio can be set to 1:1.05. Sodium sulfide solution is added dropwise to the ferrous sulfate solution, and the magnetic stirring speed is controlled within the range of 300-500 r / min. The dropping rate of sodium sulfide solution can be 1-2 mL / min. After reacting for 15-20 min, a suspension containing ferrous sulfide particles is generated.

[0028] Step S102: Add a stabilizer solution to the suspension based on the second molar ratio to obtain the target reaction solution.

[0029] The target reaction solution contains ferrous sulfide particles with a shell, and the stabilizer solution includes an aqueous solution of carboxymethyl cellulose. Specifically, the molar ratio of carboxymethyl cellulose to ferrous sulfide particles can be used as the second molar ratio, and the stabilizer solution is added to the suspension based on the second molar ratio. The stirring time is controlled within the range of 25 min to 45 min, and the second molar ratio ranges from 0.0006 to 0.002.

[0030] In specific implementation, the second molar ratio can be set to 0.0010, and carboxymethyl cellulose solution can be added to the suspension obtained in step S101. Stirring can be continued for 30-40 minutes to form nanoparticles of ferrous sulfide coated with a carboxymethyl cellulose monolayer, i.e. ferrous sulfide particles with a shell.

[0031] Step S103: Concentrate the shelled ferrous sulfide particles in the target reaction solution to obtain solid shelled ferrous sulfide particles.

[0032] Finally, the target reaction solution is centrifuged to obtain a concentrated solution, and the centrifugation time is controlled within the range of 8 to 20 minutes, and the centrifugation speed is controlled within the range of 7000 to 12000 r / min. The concentrated solution is then subjected to vacuum freeze-drying to obtain solid ferrous sulfide particles with a shell, and the vacuum freezing temperature is controlled within the range of -60℃ to -30℃, and the vacuum degree is controlled to be less than or equal to 20 Pa.

[0033] In practice, the centrifugal separation speed can be set to 8000-10000 r / min, and the centrifugal separation duration can be 10-15 min. After washing the concentrated liquid after centrifugation, it is freeze-dried under vacuum at -50~-40℃ and a vacuum degree ≤10Pa to obtain powder of ferrous sulfide particles with a shell.

[0034] In addition to centrifugal separation for concentrating the target reaction solution, filtration or membrane separation can also be used for concentration. Furthermore, in addition to vacuum freeze drying, spray drying or vacuum drying can also be used to obtain powder of ferrous sulfide particles with a shell.

[0035] Thirdly, embodiments of the present invention provide an application of ferrous sulfide particles with a shell, as described in the first aspect, capable of treating large areas of media contaminated with hexavalent chromium. The media may include any one or more of soil, groundwater, sediment, and deposits. Specifically, it can remediate at least one of the following: industrial contaminated sites, contaminated farmland soil, groundwater contaminated areas, riverbed sediment contaminated areas, and mining contaminated areas, wherein the concentration of hexavalent chromium contamination in the soil or sediment ranges from 5.7 to 1000 mg / kg, and the concentration of hexavalent chromium contamination in the groundwater ranges from 0.05 to 50 mg / L. Figure 2 As shown, the application process includes the following steps: Step S201: Mix the ferrous sulfide particles with the shell with the buffer solution to prepare the target repair solution.

[0036] Specifically, ferrous sulfide particles with a shell concentration ranging from 0.08 to 0.12 g / L are mixed with a buffer solution with a molar concentration ranging from 8 to 12 mM / L to obtain a target repair solution with a pH range of 6.5 to 7.8. In an optional embodiment, ferrous sulfide particles with a shell concentration of 0.1 g / L can be mixed with a buffer solution with a molar concentration ranging from 10 mM / L to prepare a target repair solution with a pH value of 6.9 to 7.5 and a mass concentration of 0.1 g / L. The buffer solution may include at least one of HEPES buffer, Tris-HCl buffer, and phosphate buffer.

[0037] Step S202: Inject the target remediation fluid into the medium to be treated based on the initial remediation parameters, and continuously monitor the real-time remediation index parameters in the medium to be treated.

[0038] Specifically, the injection method of the target repair fluid can be determined according to the type of the medium to be treated, and the target repair fluid can be injected into the medium to be treated based on the initial repair parameters, which include the initial injection pressure, the single pulse injection volume, and the initial pulse period.

[0039] In the specific implementation process, when the medium to be treated is soil, the target remediation fluid is injected using at least one of the following methods: surface spraying, deep pipe injection, and horizontal borehole injection, with an injection depth of 0-150cm; when the medium to be treated is groundwater, the target remediation fluid is injected using at least one of the following methods: well group injection, infiltration injection, and horizontal well injection, with a well spacing of 2-6m; when the medium to be treated is bottom mud or sediment, the target remediation fluid is injected using at least one of the following methods: surface spraying, underwater pipe injection, and stirring injection.

[0040] Correspondingly, the injection head can be at least one of a spray injection head, a cannula injection head, or a multi-hole injection head. Furthermore, a pulse pump can be used when injecting the target remediation solution, and the corresponding initial remediation parameters can be dynamically adjusted according to the degree of contamination. Specifically, the initial injection pressure range can be 0.08-0.35 MPa, the single-pulse injection volume range can be 4-12 L / m², and the initial pulse cycle can be 3-8 minutes for each injection followed by an 8-15 minute pause.

[0041] Compared to traditional continuous injection, the present invention uses pulse injection of the target remediation fluid, which can effectively reduce the filter cake effect. CT scans have confirmed that this method enables the target remediation fluid to migrate up to 80 cm in the soil, improving the migration efficiency by 433%, thus solving the problem of insufficient migration distance in existing injection methods.

[0042] Real-time remediation parameters, including hexavalent chromium concentration and pH value, are obtained by monitoring at least one point of the medium to be treated.

[0043] In practical implementation, at least one of the following detection modules—diphenylcarbazide colorimetric detection module, high-performance liquid chromatography detection module, and ion chromatography detection module—can be used to monitor the concentration of hexavalent chromium. The detection limit for hexavalent chromium concentration must be less than or equal to 0.005 mg / L. Alternatively, at least one of the following detection modules—graphite furnace atomic absorption spectrometry, inductively coupled plasma mass spectrometry, and atomic fluorescence spectrometry—can be used to monitor the total chromium concentration. The monitoring accuracy must be less than or equal to ±0.02 mg / L. The pH value is obtained by an online pH analyzer.

[0044] Step S203: Based on the preset modified adsorption model and real-time repair index parameters, determine the dynamic repair parameters, and use the dynamic repair parameters to repair the medium to be treated.

[0045] Specifically, a modified adsorption model was established based on the linear distribution coefficient, the reciprocal of cadmium concentration, and the Langmuir equation. Using the modified adsorption model and real-time remediation index parameters, the dynamic remediation parameters of the target remediation solution were determined.

[0046] In practical implementation, the expression for the modified adsorption model can be: in, To balance the adsorption amount, K d Q is the linear distribution coefficient. max The maximum adsorption capacity is represented by L and s, which are fitting parameters. The concentration of hexavalent chromium remaining in the solution when adsorption reaches equilibrium.

[0047] The concentration of residual hexavalent chromium at adsorption equilibrium under different initial concentrations of hexavalent chromium can be obtained in advance through batch experiments using ferrous sulfide particles to adsorb hexavalent chromium. ) and the corresponding equilibrium adsorption amount ( ) data. Q max A rough estimate can be made by referring to the maximum adsorption amount measured experimentally; K d The initial values ​​can be obtained by performing linear regression on low-concentration data points; L and s can usually be set to an initial range, such as 0.1-10.

[0048] Using software such as Origin, MATLAB, or Python, a nonlinear least squares method, such as the Levenberg-Marquardt algorithm, is employed for nonlinear fitting to determine the concentration of remaining hexavalent chromium at adsorption equilibrium. ) data, corresponding equilibrium adsorption capacity ( Input the data and the modified adsorption model equation, and iteratively adjust K. d Q max The parameters L and s are used to minimize the sum of squared residuals between the calculated and experimental values ​​of the modified adsorption model, thereby determining K. d Q max Find the optimal values ​​for the four unknown parameters: L, s, and s.

[0049] Among these, the closer the coefficient of determination R² of the modified adsorption model is to 1, the better; its residual distribution should be random; Q max It should be a positive number and consistent with the experimental trend.

[0050] To address the issue of fitting failure in traditional models at low concentrations of hexavalent chromium, especially when the chromium concentration is less than 2 mg / L, the modified adsorption model provided in this invention introduces the s / Ce parameter term to describe CMC-CrO4. 2- The affinity varies with chromium concentration, and the modified adsorption model provided in this embodiment fits R... 2 The R-value is 0.9954, with a standard error of 8.30, which is higher than that of the traditional Freundlich model. 2 =0.9411, the fitting accuracy was improved by 64%.

[0051] After establishing the modified adsorption model, dynamic remediation parameters are determined based on the modified adsorption model and real-time remediation index parameters. These dynamic remediation parameters are then used to remediate the medium to be treated. The dynamic remediation parameters include the amount of buffer solution replenished, the injection flow rate of the target remediation solution, and the injection concentration.

[0052] Based on real-time remediation index parameters, the modified adsorption model can predict a corresponding equilibrium adsorption amount, thereby determining the total amount of the target remediation solution. Then, by controlling the injection process of the target remediation solution through dynamic remediation parameters, it can achieve enhanced remediation of high-concentration chromium contamination areas and precise remediation of low-concentration chromium contamination areas, ultimately reducing the hexavalent chromium concentration to below the target value in the most optimized way.

[0053] The dynamic remediation parameters are mainly achieved by dynamically adjusting the injection flow rate and concentration of the target remediation solution. When the pH value deviates from the 6.9-7.5 range, the pH value of the target remediation solution can be adjusted by increasing or decreasing the HEPES buffer solution to ensure that the target remediation solution reacts within the optimal pH window. For example, when the hexavalent chromium concentration is >50 mg / L, the injection flow rate of the target remediation solution can be increased to 1.5 times the initial value to enhance the remediation intensity of hexavalent chromium; when the hexavalent chromium concentration is <2 mg / L, the injection flow rate of the target remediation solution can be reduced to 0.5 times the initial value to avoid wasting the target remediation solution.

[0054] In the specific implementation process, before injecting the target remediation fluid into the medium to be treated for remediation, in order to ensure that the target remediation fluid can work normally, the medium to be treated can be pretreated, such as removing large impurities with a particle size >5cm in the soil, and for groundwater pollution, clearing the blockages around the injection well.

[0055] During the remediation of the medium to be treated, if the real-time remediation index parameters meet the preset conditions, the injection of the target remediation solution can be stopped and the remediation can be deemed complete. Specifically, when the hexavalent chromium residue in the medium to be treated is detected to be ≤5.7mg / kg and the leaching concentration is ≤0.05mg / L for three consecutive tests, the real-time remediation index parameters can be deemed to meet the preset conditions, and the injection of the target remediation solution can be stopped.

[0056] After the treatment medium is repaired, it can be monitored for two years, with regular testing of its hexavalent chromium concentration and leaching risk to ensure that the repair effect is long-lasting and stable.

[0057] The ferrous sulfide particles with a shell provided in this invention effectively inhibit the aggregation and passivation of ferrous sulfide nanoparticles by adding carboxymethyl cellulose as a stabilizer shell, thus extending the reaction activity cycle of ferrous sulfide nanoparticles and solving the technical problem of rapid activity decay of traditional nano-ferrous sulfide.

[0058] More importantly, through in-situ X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) combined with density functional theory (DFT) calculations, the applicant believes that the reaction between the shelled ferrous sulfide particles and hexavalent chromium in the embodiments of this invention reveals for the first time a three-step synergistic reaction mechanism dominated by sulfur sites: "adsorption-electron relay-stabilization," overturning the traditional understanding of a single reaction mechanism of "direct reduction of hexavalent chromium by divalent iron." The specific reaction is as follows: The first step of the reaction is the targeted adsorption and configuration anchoring stage.

[0059] Hexavalent chromium mainly exists as CrO4 in environments with a pH of 5-9. 2- or HCrO4 - In its morphological form, the CMC molecules on the surface of ferrous sulfide particles with a shell construct a negatively charged chromophilic microenvironment through carboxyl groups, which can reduce CrO4 content. 2- ⁻ / HCrO4 - The diffusion barrier is reduced by 0.32 eV compared to unmodified FeS. At this point, hexavalent chromium preferentially anchors to the sulfur sites on the FeS surface in a bidentate bridge configuration, forming a ≡Fe-S-Cr-O surface complex. In this complex, the coordination number of the Cr atom changes from 4 to 6, the Cr-O bond length is 1.911 Å, and the Cr-S bond length is 2.32 Å. This configuration reduces the energy level difference between the highest occupied molecular orbital (HOMO) of hexavalent chromium and the lowest unoccupied molecular orbital (LUMO) of the S site to 0.85 eV, thereby creating thermodynamically favorable conditions for electron transfer.

[0060] The second step of the reaction is the electron relay stage mediated by sulfur sites.

[0061] DFT calculations and cyclic voltammetry tests show that the electron transfer path is not the traditional transfer from divalent iron to hexavalent chromium, but rather achieves efficient transfer through sulfur sites as electron relays: First, divalent iron in the FeS lattice transfers electrons to surface sulfur sites, causing divalent sulfur to be oxidized to zero-valent sulfur. Then, electrons are transferred along the S→O→Cr(VI) path to the d orbitals of hexavalent chromium, with a single-molecule transfer amount of 1.347e.

[0062] The relay stage mediated by this sulfur site lowered the reaction barrier to 0.85 ± 0.05 eV, a 44% reduction compared to the direct reduction of hexavalent chromium by divalent iron. Consequently, the reduction rate constant of hexavalent chromium increased by 2.7 times compared to the unmodified FeS, specifically to 0.032 min. -1 Meanwhile, the monolayer coating of FeS by CMC avoids the aggregation of zero-valent sulfur and can maintain the high activity of the sulfur sites in FeS, for example, stabilizing the sulfur vacancy density at 1.8 × 10⁻⁶. 14 sites / cm 2 above.

[0063] The third step is the stabilization and passivation protection stage of trivalent chromium.

[0064] Hexavalent chromium accepts electrons and is reduced to trivalent chromium. Trivalent chromium then forms stable chelates Cr(III)-O-Fe(III) and Cr(III)-O-CMC with the hydroxyl groups on the FeS surface and the carboxyl groups on CMC. Some trivalent chromium reacts with unreacted divalent sulfur to form Cr₂S₃ precipitate. The zero-valent sulfur generated in the reaction accumulates on the surface of the medium to be treated. When the zero-valent sulfur content reaches 41.3% or higher, a dense passivation protective layer is formed. This passivation protective layer physically blocks oxygen from contacting trivalent chromium, thereby inhibiting the re-oxidation of trivalent chromium to hexavalent chromium.

[0065] The use of ferrous sulfide particles with a shell in this embodiment of the invention to remediate hexavalent chromium pollution resulted in a remediation rate of trivalent chromium of ≥72.4% of the total chromium, a leaching concentration of trivalent chromium of <0.01 mg / L, and no rebound was observed during two years of follow-up monitoring.

[0066] In practical implementation, during the preparation of ferrous sulfide particles with a shell, nitrogen protection must be maintained until centrifugation to prevent oxidation of ferrous iron, which would reduce the reactivity of the particles. The injection head needs to be cleaned regularly, for example, every 3 days, to prevent soil particles and sediment from clogging the injection head's pores and affecting the uniformity of subsequent injection of the target remediation solution. During the remediation process, the pH value must be strictly controlled between 6.9 and 7.5. If the pH is less than 6.9, a small amount of HEPES buffer solution needs to be added; if the pH is greater than 7.5, a trace amount of dilute hydrochloric acid should be added for adjustment. When monitoring real-time remediation indicators, sampling points must cover both the edge and center of the contaminated area to ensure data representativeness.

[0067] To further highlight the hexavalent chromium treatment effect brought about by the shell-shaped ferrous sulfide particles provided in the embodiments of the present invention, please refer to the following experimental results to demonstrate the significant effects of the embodiments of the present invention: Experiment 1 The remediation of chromium-contaminated soil from a decommissioned electroplating plant covered an area of ​​2000 m². 2The soil contamination depth ranged from 0 to 80 cm. The initial hexavalent chromium concentration detected in the soil was 120-350 mg / kg, the pH value was 6.8, the soil moisture content was 18%, and the porosity was 25%. The corresponding remediation targets can be set as follows: hexavalent chromium residue ≤ 5.7 mg / kg, leaching concentration ≤ 0.05 mg / L, and no rebound within 2 years.

[0068] In the temporary work area, a 50L reactor with nitrogen protection and an ice-water bath, an 8000r / min high-speed centrifuge, and a -50℃ vacuum freeze dryer were used. Four high-pressure diaphragm pumps with injection pressures of 0.1-0.3MPa and corresponding flow controllers were evenly distributed in the soil contaminated area, along with 0.5mm diameter injection heads for deep soil insertion. A portable diphenylcarbazide colorimetric analyzer with a detection limit of 0.001mg / L and a graphite furnace atomic absorption spectrometer were used to conduct on-site testing of the contaminated soil, and corresponding soil samples were taken for laboratory retesting.

[0069] An embedded controller with a touch screen is installed in the control room. The embedded controller includes a microprocessor, a storage module, a communication module, and an execution drive module. The storage module stores the modified adsorption model and the database required for operation. The communication module is used to receive data sent by the diphenylcarbazide colorimetric detector and the graphite furnace atomic absorption spectrometer. The microprocessor processes the received data to generate corresponding control commands. The execution drive module responds to the control commands to generate corresponding control signals. The communication module then sends the control signals to the reactor, centrifuge, vacuum freeze dryer, high-pressure diaphragm pump, and corresponding flow controller.

[0070] In practical implementation, the embedded controller can dynamically adjust the injection flow rate, concentration, and pulse cycle of the target repair solution based on real-time chromium concentration data, ensuring precise and controllable repair process. The communication module can include at least one of WiFi, Bluetooth, ZigBee, LoRa, and 4G / 5G.

[0071] Before injecting the target remediation solution, an excavator was used to remove stones, construction waste, and other impurities with a particle size greater than 5cm from the soil. A grader was then used to level the contaminated area, dividing it into four remediation zones, each with an area of ​​500m². 2 per 100m 2 One sampling point was set up, and a total of 20 sampling points were set up to collect soil samples from a depth of 0-80cm. The initial hexavalent chromium concentration was detected by graphite furnace atomic absorption spectrometry, and the pH value was detected by an online pH meter to establish a pollution distribution map.

[0072] Prepare 30 L of 0.1 mol / L ferrous sulfate solution and 31.5 L of 0.1 mol / L sodium sulfide solution to achieve a ferrous ion to sulfide ion molar ratio of 1:1.05. Purge both solutions with nitrogen gas at a flow rate of 5 L / min for protection and place them in an ice-water bath at 0–4 °C. Start the reactor and stir at 400 rpm. Add sodium sulfide solution dropwise to the ferrous sulfate solution at a rate of 1.5 mL / min. After the addition is complete, continue the reaction for 18 min to generate a suspension of ferrous sulfide nanoparticles.

[0073] A 10 g / L sodium carboxymethyl cellulose solution was prepared. Based on a CMC to FeS molar ratio of 0.0010, 4.2 L of CMC solution was added to the ferrous sulfide nanoparticle suspension, and the mixture was stirred continuously for 35 min to form a monolayer-coated CMC-FeS nanoparticle with a coating thickness ranging from 1.1 to 1.3 nm. The reaction solution was then transferred to a centrifuge at 8000 rpm for 12 min. The precipitate was collected and washed three times with deionized water, then placed in a vacuum freeze dryer at -50°C and a vacuum degree ≤10 Pa for 12 h to obtain approximately 2.8 kg of CMC-FeS nanomaterial powder, i.e., solid ferrous sulfide particles with a shell. Finally, this powder was mixed with 10 mM / L HEPES buffer to prepare a target repair solution with a concentration of 0.1 g / L. The pH of the target repair solution was adjusted to 7.2 with dilute hydrochloric acid, and the total volume of the target repair solution was 28 m³. 3 .

[0074] Ten injection points were arranged in each remediation zone, with a spacing of 10m × 10m between each point. The injection head was inserted into the soil to a depth of 50cm. The injection pump was started, and the injection pressure was set to 0.2MPa, with a single-pulse injection rate of 8L / m. 2 The pulse cycle is 5 minutes on and 10 minutes off.

[0075] During the injection of the target repair solution, data was collected every 30 minutes. Three monitoring points were set up in each zone: a 20cm depth monitoring point, a 50cm depth monitoring point, and an 80cm depth monitoring point, to monitor the hexavalent chromium concentration and pH value in real time.

[0076] When the hexavalent chromium concentration was detected to be 80-250 mg / kg, the embedded controller automatically increased the injection flow rate of the target remediation solution by 1.5 times, from the initial injection flow rate of 10 L / h·m. 2 Increased to 15 L / h·m 2 The concentration of the target repair solution was kept constant at 0.1 g / L.

[0077] When the hexavalent chromium concentration dropped to 20-80 mg / kg, the initial repair parameters were restored, i.e., the injection flow rate was 10 L / h·m. 2 The concentration of the target remediation solution was 0.1 g / L. When the hexavalent chromium concentration was monitored to drop to 1-20 mg / kg, the injection flow rate of the target remediation solution was reduced by 0.5 times, i.e., the injection flow rate was reduced to 5 L / h·m. 2 If the pH value remains stable between 7.0 and 7.4 throughout the process, no additional buffer solution is required.

[0078] If soil sampling and testing are conducted at 24-hour intervals, and the results of three consecutive tests show that the hexavalent chromium residue is 2.5-5.5 mg / kg and the leaching concentration is 0.003-0.008 mg / L, then the remediation target has been achieved, and the injection of the target remediation solution can be stopped.

[0079] Soil samples were collected and tested at 6 months, 1 year, and 2 years after remediation. Hexavalent chromium residue remained between 1.8 and 5.4 mg / kg, with a leaching concentration of 0.002-0.007 mg / L. The content of zero-valent sulfur in the soil surface layer was 42.1%, indicating that the soil passivation protective layer was intact and there was no rebound in chromium concentration. Compared with traditional chromium pollution remediation methods, the specific effects are shown in Table 1 below. Table 1. Comparison of Results

[0080] Experiment 2 The remediation of groundwater contaminated with hexavalent chromium in a chemical industrial park, covering an area of ​​1500 m². 2 The groundwater level is 3-5m deep, with a permeability coefficient of 1.2×10⁻⁶. -4 The initial hexavalent chromium concentration was detected at cm / s, ranging from 8 to 25 mg / L, with a pH of 7.1 and a total chromium concentration of 10 to 28 mg / L. The corresponding remediation targets are set as follows: hexavalent chromium concentration ≤ 0.05 mg / L and total chromium concentration ≤ 0.5 mg / L, meeting the Class III standard of the Groundwater Quality Standard (GB / T14848-2017).

[0081] In the temporary work area, a 50L reactor with nitrogen protection and an ice-water bath, an 8000r / min high-speed centrifuge, and a -50℃ vacuum freeze dryer were used. Six injection wells and three pumping wells were employed, with each injection well having an injection pump pressure of 0.25MPa and a corresponding flow controller accuracy of ±1%. An online diphenylcarbazide colorimetric monitor was used to monitor chromium concentration and total chromium concentration in real time.

[0082] Before injecting the target remediation fluid, debris around the injection well and pumping well can be cleared, well pipes can be unblocked to ensure smooth water flow, and groundwater initial hexavalent chromium concentration, pH value and flow rate can be tested at multiple depths to determine the range of pollution sources.

[0083] 1.5 kg of CMC-FeS nanomaterial powder was prepared according to the method in Experiment 1, and 15 m³ of target remediation solution with a mass concentration of 0.1 g / L was prepared and the pH value was adjusted to 7.2. Six injection wells were arranged in an equilateral triangle with a well spacing of 4 m. The pumping well was located in the central area of ​​the pollution source. The injection pressure of the target remediation solution was controlled at 0.25 MPa, the single-pulse injection volume was 10 L / m², and the pulse cycle was 6 min on / 12 min off. The flow rate of the pumping well was matched with that of the injection well to maintain a stable groundwater level.

[0084] During the injection of the target remediation solution, the concentration of hexavalent chromium at the injection well outlet and pumping well inlet was collected every 2 hours, and the corresponding water samples were sent to the laboratory for total chromium testing. When the hexavalent chromium concentration was 5-18 mg / L, the injection flow rate of the target remediation solution was controlled at 8 L / h / well. When the hexavalent chromium concentration was 1-5 mg / L, the standard flow rate was maintained. When the hexavalent chromium concentration was 0.05-1 mg / kg, the injection flow rate of the target remediation solution was reduced to 4 L / h / well. Throughout the process, the pH value was monitored and maintained at 7.0-7.5 without fluctuation.

[0085] Three consecutive tests showed hexavalent chromium concentrations of 0.02-0.05 mg / L and total chromium concentrations of 0.2-0.5 mg / L, indicating that the remediation met water quality standards. Furthermore, one year after remediation, the hexavalent chromium concentration in the groundwater stabilized at 0.01-0.03 mg / L without rebound, demonstrating that the CMC-FeS nanomaterials did not affect other groundwater indicators such as COD and ammonia nitrogen.

[0086] Experiment 3 The remediation of riverbed sediment from electroplating wastewater discharge was planned. The contaminated sediment was 500m long, 10m wide, and 0.3-0.6m thick, with an initial hexavalent chromium concentration of 80-150 mg / kg, a pH of 7.3, and a moisture content of 40%. The corresponding remediation targets were set as follows: residual hexavalent chromium ≤ 5.7 mg / kg, leaching concentration ≤ 0.05 mg / L, without impacting the river's ecosystem.

[0087] In the temporary work area, a 50L reactor with nitrogen protection and an ice-water bath, an 8000r / min high-speed centrifuge, and a -50℃ vacuum freeze dryer were used. Underwater injection pumps with multi-hole injection heads (each hole diameter 0.3mm) and portable water / sediment analyzers and underwater samplers were employed for water quality monitoring. A small mixing boat with a rotation speed of 50r / min was used for auxiliary sediment disturbance.

[0088] Before injecting the target remediation solution, the top 0-10cm of sediment can be lightly stirred with a mixing boat and floating debris removed. Sampling points are set up every 50m to collect sediment samples to test the initial hexavalent chromium concentration and pH value.

[0089] 2.0 kg of CMC-FeS nanomaterial powder was prepared according to the method in Experiment 1, and 20 m³ of target remediation solution with a mass concentration of 0.1 g / L was prepared and the pH value was adjusted to 7.3. The underwater cannula injection head was inserted into the bottom sediment at a depth of 0-30 cm. The single-pulse injection volume of the target remediation solution was controlled at 9 L / m², the pulse cycle was 5 min on / 10 min off, and the injection pressure of the target remediation solution was 0.15 MPa.

[0090] After the target remediation solution is injected, it is gently stirred with a mixing vessel to ensure uniform mixing with the sediment. When the hexavalent chromium concentration is monitored at 60-120 mg / kg, the injection flow rate of the target remediation solution is increased to 1.5 times the initial value. When the hexavalent chromium concentration is monitored at 20-60 mg / kg, the standard injection flow rate is restored. When the hexavalent chromium concentration is monitored at 10-30 mg / kg, the injection flow rate of the target remediation solution is reduced to 0.5 times the initial value.

[0091] On the 24th day of remediation, the residual hexavalent chromium level dropped to 4.8-9.5 mg / kg, and the leaching concentration dropped to 0.004-0.009 mg / L. Three months after remediation, the microbial community in the riverbed sediment recovered to the unpolluted level, aquatic plants grew normally, and there was no secondary pollution.

[0092] Furthermore, some key parameters in the embodiments of this invention were verified and explained through certain experiments. One was the verification of the rationality of the molar ratio of CMC to FeS. Specifically, by setting the molar ratios of 0.0007, 0.0008, 0.0010, 0.0012, and 0.0013, ferrous sulfide particles with shells were prepared respectively, and the corresponding performance test results were as follows: When the molar ratio is 0.0010, the ferrous sulfide particles with a shell have a particle size of 161~171 nm, an adsorption capacity of 327.9 mg / g, and a sulfur vacancy density of 1.8 × 10⁻⁶. 14 sites / cm 2 When the molar ratio is 0.008, the particle size of the ferrous sulfide particles with shells is >200nm, and agglomeration occurs between the particles; when the molar ratio is greater than 0.0012, the active sites of the ferrous sulfide particles with shells are shielded, resulting in an adsorption capacity of less than 280mg / g, thus verifying the core advantage of a molar ratio of 0.0010.

[0093] The second aspect is the optimization and verification of the pulse injection method, which involves comparing the effects of setting the pulse period to 3min on / 8min off, 5min on / 10min off, and 8min on / 15min off with continuous injection. The corresponding test results are as follows: Under a pulse cycle of 5 min on / 10 min off, the soil pore blockage rate reached a minimum of 8%, and the migration distance reached a maximum of 80 cm. The migration efficiency was improved by 433% compared with continuous injection, which verified that the 5 min on / 10 min off pulse cycle is the optimal injection pulse cycle.

[0094] Thirdly, the modified adsorption model was validated by fitting the model using the hexavalent chromium concentration data from Experiment 1, ranging from 0.5 to 350 mg / L, and calculating R0. 2 The value is 0.9961, with a standard error of 7.8, which is lower than the R-squared value of the traditional Freundlich model. 2 =0.9402, the fitting accuracy improved by 64%, verifying the advanced nature of the modified adsorption model.

[0095] In summary, when remediating media contaminated with hexavalent chromium, the ferrous sulfide particles with a shell provided in this invention exhibit a 17.3% increase in adsorption capacity compared to unmodified FeS particles, significantly enhancing the remediation capacity for the same mass. The pulsed injection method effectively overcomes the filter cake effect, increasing the migration distance of the remediation material in contaminated soil. Compared to the traditional continuous injection method, the migration efficiency is improved by 433%, ensuring uniform remediation of deeply contaminated media and avoiding uneven or incomplete remediation. The overall remediation cycle can be shortened to 18-24 days, compared to 35-40 days for traditional chemical reduction methods, reducing the remediation time by 42.9%-55.0%. Furthermore, the energy consumption during the remediation process is reduced by more than 40%, and the remediation cost per unit area is reduced by 30%-35%, significantly lowering the actual application cost.

[0096] By coating ferrous sulfide particles with a CMC monolayer and preparing a target remediation solution in conjunction with a buffer solution, the carboxylation of CMC can inhibit Fe2+ even in an acidic environment with a pH of 5-6. 2+ The measured Fe dissolution rate is less than or equal to 30 mg / L, a 32.3% reduction compared to traditional chemical reduction methods. In an alkaline environment with a pH of 8-9, the steric hindrance effect of CMC can prevent the formation of Fe(OH)3 precipitation, ensuring that the exposure rate of FeS surface active sites is greater than 85%, thus guaranteeing stable remediation efficiency. This allows the remediation reaction to proceed stably within a wide pH range of 5-9, effectively covering the pH range of neutral, weakly acidic, and weakly alkaline contaminated media. This solves the core defects of traditional ferrous sulfide particles, such as surface passivation leading to a more than 40% decrease in reactivity at pH greater than 7, or excessively high Fe dissolution rates at pH less than 5.

[0097] Based on the sulfur site electron relay mechanism, hexavalent chromium is efficiently reduced to trivalent chromium, which exists in stable states of Cr(III)-O and Fe-O-Cr(III), accounting for over 72.4% of the total chromium. This is more than 20.7% higher than the proportion of stable chromium in traditional remediation methods, which is less than 60%, significantly reducing subsequent chromium migration. Furthermore, the zero-valent sulfur generated in the reaction can accumulate on the surface of the contaminated medium to form a dense passivation protective layer, physically blocking oxygen from contacting trivalent chromium and inhibiting its re-oxidation to hexavalent chromium. During a two-year follow-up study, the residual hexavalent chromium level remained below 10 mg / kg, the leaching concentration was below 1 mg / L, and there was no rebound phenomenon. This effectively meets the long-term stability requirements for contaminated site remediation and solves the problem of easy rebound after remediation using traditional techniques.

[0098] In this embodiment of the invention, the modified adsorption model also solves for the first time the problem of fitting the "S-shaped" adsorption behavior of the traditional Langmuir / Freundlich model in the low chromium concentration region, improving the fitting accuracy by 64% compared to the traditional model. It can accurately predict the adsorption capacity and reaction rate at different chromium concentrations. Furthermore, based on the modified adsorption model and real-time remediation index parameters, by dynamically adjusting the injection flow rate and concentration of the target remediation solution, the target remediation solution can be injected more accurately, increasing its utilization rate by more than 35% and avoiding waste and secondary pollution caused by over-injection.

[0099] It should be clarified that the present invention is not limited to the specific configurations and processes described above and shown in the figures. For the sake of brevity, detailed descriptions of known methods are omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present invention is not limited to the specific steps described and shown. Those skilled in the art can make various changes, modifications, and additions, or change the order of steps, after understanding the spirit of the present invention.

[0100] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0101] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0102] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0103] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0104] It should also be noted that the exemplary embodiments mentioned in this invention describe methods or systems based on a series of steps or apparatus. However, this invention is not limited to the order of the steps described above; that is, the steps can be performed in the order mentioned in the embodiments, or in a different order, or several steps can be performed simultaneously.

[0105] The above are merely specific embodiments of the present invention. Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, modules, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here. It should be understood that the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the protection scope of the present invention.

Claims

1. A ferrous sulfide particle with a shell, characterized in that, include: Ferrous sulfide particles and a stabilizer shell coating the surface of the ferrous sulfide particles; wherein the molar ratio of the stabilizer shell to the ferrous sulfide particles is in the range of 0.0006-0.002, and the stabilizer shell comprises carboxymethyl cellulose.

2. The ferrous sulfide particles with a shell as described in claim 1, characterized in that, The zeta potential of the ferrous sulfide particles with a shell ranges from -35mV to -42mV, the particle size of the ferrous sulfide particles with a shell ranges from 130nm to 200nm, and the thickness of the stabilizer shell ranges from 0.8nm to 2nm.

3. A method for preparing ferrous sulfide particles with a shell as described in claim 1 or 2, characterized in that, include: A suspension containing ferrous sulfide particles was prepared by mixing the ferrous salt solution and the sulfide solution based on the first molar ratio. A stabilizer solution is added to the suspension at a second molar ratio to obtain a target reaction solution, wherein the target reaction solution contains the ferrous sulfide particles with a shell, and the stabilizer solution comprises an aqueous solution of carboxymethyl cellulose. The shelled ferrous sulfide particles in the target reaction solution are concentrated to obtain solid shelled ferrous sulfide particles.

4. The method for preparing ferrous sulfide particles with a shell as described in claim 3, characterized in that, The preparation of a suspension containing ferrous sulfide particles by mixing the ferrous salt solution and the sulfide solution based on a first molar ratio includes: In an environment filled with inert gas, a ferrous salt solution with a concentration range of 0.05 mol to 0.2 mol / L and a sulfide solution with a concentration range of 0.05 mol to 0.2 mol / L are prepared. The first molar ratio is defined as the molar ratio of ferrous sulfide ions to sulfide ions. Based on the first molar ratio, the sulfide solution is added dropwise to the ferrous salt solution to prepare the suspension. The stirring speed is controlled within the range of 250~550 r / min, the dropping rate of the sulfide solution is controlled within the range of 0.8~2.5 ml / min, and the first molar ratio is controlled within the range of 1~1.

1.

5. The method for preparing ferrous sulfide particles with a shell as described in claim 3, characterized in that, The step of adding a stabilizer solution to the suspension based on a second molar ratio to obtain the target reaction solution includes: The molar ratio of carboxymethyl cellulose to ferrous sulfide particles is used as the second molar ratio, and the stabilizer solution is added to the suspension based on the second molar ratio. The stirring time is controlled within the range of 25 min to 45 min, and the second molar ratio ranges from 0.0006 to 0.

002.

6. The method for preparing ferrous sulfide particles with a shell as described in claim 3, characterized in that, The process of concentrating the shelled ferrous sulfide particles in the target reaction solution to obtain solid shelled ferrous sulfide particles includes: The target reaction solution is centrifuged to obtain a concentrated solution, and the centrifugation time is controlled within the range of 8 to 20 minutes, and the centrifugation speed is controlled within the range of 7000 to 12000 r / min. The concentrate is subjected to vacuum freeze-drying to obtain solid ferrous sulfide particles with a shell. The temperature range of the vacuum freeze-drying is controlled to be -60℃ to -30℃, and the vacuum degree of the vacuum freeze-drying is controlled to be less than or equal to 20Pa.

7. An application of ferrous sulfide particles with a shell as described in claim 1 or 2, characterized in that, include: The ferrous sulfide particles with shells are mixed with a buffer solution to prepare the target repair solution. The target repair fluid is injected into the medium to be treated based on the initial repair parameters, and the real-time repair index parameters in the medium to be treated are continuously monitored. Based on the preset modified adsorption model and the real-time repair index parameters, dynamic repair parameters are determined, and the media to be treated are repaired using the dynamic repair parameters.

8. The application of ferrous sulfide particles with a shell as described in claim 7, characterized in that, The step of mixing the shelled ferrous sulfide particles with a buffer solution to prepare the target repair solution includes: The shelled ferrous sulfide particles with a mass concentration range of 0.08~0.12 g / L are mixed with the buffer solution with a molar concentration range of 8~12 mM / L to obtain the target repair solution with a pH range of 6.5~7.

8.

9. The application of ferrous sulfide particles with a shell as described in claim 7, characterized in that, The process of injecting the target remediation fluid into the medium to be treated based on initial remediation parameters, and continuously monitoring the real-time remediation index parameters in the medium to be treated, includes: The injection method of the target repair fluid is determined according to the type of the medium to be treated, and the target repair fluid is injected into the medium to be treated based on the initial repair parameters, wherein the initial repair parameters include the initial injection pressure, the single pulse injection volume, and the initial pulse period; Monitor at least one point of the medium to be treated to obtain the real-time remediation index parameters, which include hexavalent chromium concentration and pH value.

10. The application of ferrous sulfide particles with a shell as described in claim 9, characterized in that, The process involves determining dynamic remediation parameters based on a preset modified adsorption model and real-time remediation index parameters, and then using these dynamic remediation parameters to remediate the medium to be treated, including: The modified adsorption model is established based on the linear partition coefficient, the reciprocal of cadmium concentration, and the Langmuir equation. The dynamic remediation parameters of the target remediation solution are determined using the modified adsorption model and the real-time remediation index parameters. The media to be treated is repaired using the dynamic repair parameters, wherein the dynamic repair parameters include the replenishment volume of the buffer solution, the injection flow rate of the target repair solution, and the injection concentration.

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