A slow-release functional material for repairing halogenated hydrocarbon contaminated groundwater and a preparation method and application thereof

Abstract

The application relates to the technical field of groundwater remediation, and discloses a preparation method of a slow-release functional material for repairing halogenated hydrocarbon-polluted groundwater. The method comprises the following steps: pre-treating sludge to obtain sludge powder; mixing cobalt salt, nickel salt and imidazole compounds with water, then adding a surfactant and the sludge powder, heating and then passing in carbon dioxide for calcination to obtain a biochar catalyst solid powder; mixing the biochar catalyst solid powder with an organic nitrogen source, and calcining to obtain a biochar catalyst / carbon nitride; mixing the biochar catalyst / carbon nitride with an iron salt, polyethylene glycol and a solvent, and adding a reducing agent to react to obtain a composite material powder; stirring and mixing the composite material powder, a polylactic acid solution and glycerol, and performing liquid nitrogen low-temperature quenching to obtain the slow-release functional material. The material integrates the effects of biochar adsorption and electrocatalytic reduction, and the removal effect of pollutants is strengthened; the material takes nanofiber microspheres as carriers, and the agglomeration effect of the material is further relieved.

Description

Technical Field

[0001] This invention relates to the field of groundwater remediation technology, specifically to a slow-release functional material for remediating groundwater contaminated with halogenated hydrocarbons, its preparation method, and its application. Background Technology

[0002] With the continuous progress and development of modern industry and agriculture, especially the continuous development of highly polluting industries such as petrochemicals, metallurgy, leather making, electronics, pharmaceuticals, and the processing and production of synthetic organic substances (detergents, plastics, etc.), coupled with the large-scale use of pesticides and insecticides in agriculture, more and more chlorinated hydrocarbon pollutants have entered the environment, leading to increasingly serious pollution of groundwater, one of the important sources of drinking water for humans.

[0003] Iron is a common and inexpensive metallic element, making its application in environmental remediation cost-effective and avoiding secondary pollution. Nano-zero-valent iron (nZVI), a novel environmental remediation material commonly used in recent years, is also a popular choice for the remediation of contaminated soil and groundwater. nZVI possesses a unique core-shell structure, offering advantages such as large specific surface area, low toxicity, low cost, and ease of preparation. It can remove various types of pollutants from groundwater through chemical reduction and adsorption-precipitation, attracting widespread attention in the field of groundwater remediation. nZVI primarily removes halogenated hydrocarbons through its strong reducing properties. Halogenated hydrocarbons act as electron acceptors, receiving electrons from nZVI and undergoing hydrogenolysis or dehalogenation to transform into non-toxic or low-toxic substances. However, nZVI exhibits limitations in groundwater remediation due to its tendency to aggregate, passivate, and leak, as well as poor electron selectivity.

[0004] Biochar typically refers to a loose, porous material with high carbon content, formed by the pyrolysis of biomass resources under anaerobic conditions, followed by dehydration, pyrolysis, and aromatization. It is mainly composed of elemental carbon, aromatized carbon, and graphitic carbon. Common raw materials for biochar production include straw, wood, sludge, and core shells. Existing research and applications have shown that biochar possesses numerous advantages, including a large specific surface area, well-developed pore structure, abundant surface functional groups, high cation exchange capacity, low bulk density, and strong chemical and thermal stability. It can be used simultaneously as an adsorbent and catalyst for pollutant control in the environment. Furthermore, its wide availability and low economic cost make it a widely used adsorbent and carrier material for treating various organic pollutants such as organic dyes, polycyclic aromatic hydrocarbons, antibiotics, pesticides, and insecticides. As a carrier material, biochar's surface can also support the growth of numerous microorganisms, increasing their quantity and activity, which is beneficial for the further degradation of halogenated hydrocarbon pollutants by microorganisms. Studies have also shown that biochar solidification has a significant passivating effect on U and Cd in soil. While biochar offers numerous advantages for environmental remediation, its adsorption capacity and kinetic rate are generally insufficient for the efficient removal of pollutants from the environment, especially for single-phase biochar. Biochar, with its large specific surface area and abundant functional groups, is commonly used as a mechanical loading material for dispersing, immobilizing, and stabilizing nanoparticles to improve material properties.

[0005] CN03816562.7 discloses a carrier catalyst for in-situ remediation of soil and / or groundwater contaminated with halogenated hydrocarbons, utilizing adsorbents and sulfate-reducing bacteria to adsorb and degrade halogenated hydrocarbons. CN202010752483.6 discloses a method for obtaining halogenated hydrocarbon-degrading microbial communities suitable for bioelectrochemical remediation systems, which utilizes hydrogen and oxygen generated from water electrolysis as electron donors and acceptors to promote the degradation of halogenated hydrocarbons by microorganisms. CN201010259924.5 discloses a permeable reactive barrier method for remediating groundwater contaminated with halogenated hydrocarbons and nitrates, which utilizes bark fermentation to provide co-metabolic carbon sources and nutrients for anaerobic microorganisms, promoting the degradation of halogenated hydrocarbons by anaerobic microorganisms. Summary of the Invention

[0006] The purpose of this invention is to overcome the problem that existing materials in the prior art do not meet the requirements for removing pollutants from the environment. This invention provides a slow-release functional material for remediating groundwater contaminated with halogenated hydrocarbons, its preparation method, and its application. This slow-release functional material integrates the functions of biochar adsorption and electrocatalytic reduction, thereby enhancing the removal effect of pollutants. Furthermore, the slow-release functional material uses nanofiber microspheres as a carrier, which further alleviates the aggregation effect of the material and improves the sustainability of the material's function.

[0007] To achieve the above objectives, the present invention provides a method for preparing a slow-release functional material for remediating groundwater contaminated with halohydrocarbons, the method comprising the following steps:

[0008] (1) The sludge is pretreated to obtain sludge powder;

[0009] (2) After mixing cobalt salt, nickel salt, imidazole compound and water under an inert atmosphere, a surfactant and the sludge powder are added to the mixed solution. After solid-liquid separation, the solid part is heated under an inert atmosphere and then calcined by passing carbon dioxide through it. After cooling under an inert atmosphere, a biochar catalyst solid powder is obtained.

[0010] (3) The biochar catalyst solid powder is mixed with an organic nitrogen source and calcined under an inert atmosphere. After cooling, biochar catalyst / carbon nitride is obtained.

[0011] (4) The biochar catalyst / carbon nitride is mixed with iron salt, polyethylene glycol and solvent under an inert atmosphere, and then a reducing agent is added under an inert atmosphere to react and obtain composite material powder.

[0012] (5) The composite material powder, polylactic acid solution and glycerol are stirred and mixed, and then the mixture is quenched at low temperature with liquid nitrogen to obtain a sustained-release functional material.

[0013] Preferably, in step (1), the pretreatment includes: subjecting the sludge to static sedimentation, solid-liquid separation, centrifugal separation, solid-liquid separation, drying, grinding and sieving in sequence.

[0014] Preferably, in step (1), the drying temperature is 60 to 100°C.

[0015] Preferably, in step (1), the mesh size of the sieve is ≥100 mesh.

[0016] Preferably, in step (2), the mass ratio of cobalt salt, nickel salt, water, imidazole compound, surfactant and sludge powder is 3-10:1:300-600:10-50:0.2-0.5:15-30.

[0017] Preferably, in step (2), the cobalt salt is selected from at least one of cobalt nitrate, cobalt sulfate and cobalt chloride.

[0018] Preferably, in step (2), the nickel salt is selected from at least one of nickel nitrate, nickel sulfate, and nickel chloride.

[0019] Preferably, in step (2), the imidazole compound is selected from at least one of 1-methylimidazole, 2-methylimidazole and 4-methylimidazole.

[0020] Preferably, in step (2), the surfactant is selected from at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and methylpentanol.

[0021] Preferably, in step (2), the mixing method is stirring.

[0022] Preferably, in step (2), the mixing conditions include: a rotation speed of 200-280 r / min, a temperature of 10-30°C, and a time of 12-24 h.

[0023] Preferably, step (2) further includes: constant temperature shaking under an inert atmosphere before solid-liquid separation; and drying the solid part after solid-liquid separation.

[0024] Preferably, the conditions for the isothermal oscillation include: a rotation speed of 200-280 times / min, a temperature of 5-25°C, and a time of 12-24 hours.

[0025] Preferably, the drying conditions include a temperature of 80–110°C and a time of 6–8 hours.

[0026] Preferably, in step (2), the calcination process includes: heating to 700-800°C under an inert atmosphere and then introducing carbon dioxide for calcination for 3-4 hours.

[0027] More preferably, the temperature is raised to 700-800°C at a heating rate of 2-5°C / min.

[0028] Preferably, step (2) further includes: sieving after cooling; more preferably, in step (2), the mesh number of the sieve is ≥100 mesh.

[0029] Preferably, in step (3), the mass ratio of the biochar catalyst solid powder to the organic nitrogen source is 1 to 3:1.

[0030] Preferably, in step (3), the organic nitrogen source is selected from at least one of dicyandiamide, melamine and thiourea.

[0031] Preferably, in step (3), the calcination conditions include: a heating rate of 2-6°C / min, more preferably 5-6°C / min; a temperature of 500-600°C, more preferably 500-550°C; and a time of 2-3 hours.

[0032] Preferably, in step (4), the mass ratio of the biochar catalyst / carbon nitride, the iron salt, and the polyethylene glycol is 15-30:15-30:1.

[0033] More preferably, in step (4), the mass ratio of the biochar catalyst / carbon nitride, the iron salt and the polyethylene glycol is 15-25:25:1.

[0034] Preferably, in step (4), the iron salt is a divalent iron salt and / or a trivalent iron salt.

[0035] Preferably, the ferrous salt is selected from at least one of ferrous sulfate, ferrous nitrate and ferrous chloride.

[0036] Preferably, the trivalent iron salt is selected from at least one of ferric sulfate, ferric nitrate, and ferric chloride.

[0037] Preferably, in step (4), the molecular weight of the polyethylene glycol is 3500 to 4500.

[0038] Preferably, in step (4), the solvent is a mixture of ethanol and water.

[0039] Preferably, the volume ratio of ethanol to water is 1:1 to 2, more preferably 1:1.

[0040] Preferably, in step (4), the mixing method is ultrasonic mixing.

[0041] Preferably, in step (4), the mixing time is 2 to 3 hours.

[0042] Preferably, in step (4), the reducing agent is NaBH4 solid or NaBH4 solution.

[0043] More preferably, the concentration of the NaBH4 solution is 10–20 mol / L, and even more preferably 12–16 mol / L.

[0044] More preferably, the pH value of the NaBH4 solution is 10 to 12.

[0045] Preferably, the amount of reducing agent can be based on a molar ratio of Fe element in the iron salt to NaBH4 in the reducing agent of 1:2 to 4.

[0046] Preferably, in step (4), the reaction time is 1 to 2 hours.

[0047] Preferably, step (4) further includes: performing solid-liquid separation after the reaction and washing, drying, grinding and sieving the solid part.

[0048] Preferably, the washing process includes washing multiple times with deionized water and deoxygenated anhydrous ethanol, more preferably washing 3 to 5 times.

[0049] More preferably, the drying conditions include: a temperature of 60–80°C and a time of 20–30 hours.

[0050] More preferably, the mesh size of the sieve is ≥100 mesh.

[0051] Preferably, in step (5), the mass ratio of the polylactic acid solution, the glycerol and the composite material powder is 1:1 to 9:1 to 6, and more preferably 1:2 to 4:1 to 2.

[0052] Preferably, in step (5), the preparation process of the polylactic acid solution includes: adding polylactic acid to tetrahydrofuran and stirring.

[0053] Preferably, the concentration of polylactic acid in the polylactic acid solution is 0.5 to 5% by weight, more preferably 2 to 4% by weight.

[0054] Preferably, the stirring conditions include: a temperature of 55–65°C and a time of 2–3 hours.

[0055] Preferably, in step (5), the mixing method is stirring.

[0056] Preferably, in step (5), the mixing conditions include a temperature of 48–53°C and a time of 2–3 hours.

[0057] Preferably, step (5) further includes: extraction, freeze-drying, grinding and sieving after liquid nitrogen cryogenic quenching.

[0058] More preferably, the extraction conditions include: water as the extractant, a temperature of 0–4°C, and a time of 2–3 days.

[0059] More preferably, the freeze-drying conditions include: a temperature of -40 to -60°C and a time of 24 to 36 hours.

[0060] More preferably, the mesh size of the sieve is ≥100 mesh.

[0061] Preferably, in steps (2), (3), and (4), the inert atmosphere is composed of one or more gases selected from nitrogen, helium, neon, and argon.

[0062] A second aspect of the present invention provides a sustained-release functional material prepared by the method described above.

[0063] A third aspect of the present invention provides the application of the aforementioned slow-release functional material in the remediation of groundwater contaminated with halogenated hydrocarbons.

[0064] Compared with the prior art, the present invention has the following advantages:

[0065] 1) Modified biochar has a higher specific surface area and pore volume, which can attach more microorganisms, and has higher catalytic activity and richer carboxyl and phenolic hydroxyl acidic functional groups, which can improve the adsorption capacity of pollutants and improve the catalytic reduction capacity.

[0066] 2) Loading nano-iron, Co, and Ni onto the surface of biochar can effectively prevent the agglomeration of nano-iron. The loaded material has a large specific surface area, rich pore structure, and surface functional groups. Among them, carbon dioxide modified biochar can improve the porosity and specific surface area of ​​biochar, reduce the surface oxygen content, improve the surface reduction capacity, increase the C=O / CO group ratio and carbon defects, which is beneficial to improving the catalytic reduction performance of the material.

[0067] 3) Compared with ordinary biochar, biochar loaded with nano-iron, Co, and Ni integrates multiple functions such as biochar adsorption, nano-iron providing electrons for dehalogenation, catalytic reduction of halogenated hydrocarbons, and micro-electrolysis, thereby enhancing the removal effect of pollutants.

[0068] 4) Using polylactic acid prepared by low-temperature quenching with liquid nitrogen as a carrier, a microporous membrane structure can be formed on the material surface, which can further inhibit material passivation, hardening and agglomeration, and improve the continuity of the material's function.

[0069] In addition to providing favorable conditions for anaerobic bacteria to degrade halogenated hydrocarbons by using zero-valent iron as an electron donor, the sustained-release functional material prepared by this invention can also degrade halogenated hydrocarbons through chemical reduction, catalytic reduction and micro-electrolysis. The sustained-release functional material prepared by this invention also has advantages in terms of structural stability and long-term degradation effect. Attached Figure Description

[0070] Figure 1 These are the trichloroethylene removal rates for Examples 1-3 and Comparative Examples 1-5;

[0071] Figure 2 This is a SEM image of material A1 prepared in Example 1. Detailed Implementation

[0072] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0073] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0074] In a first aspect, the present invention provides a method for preparing a slow-release functional material for remediating groundwater contaminated with halohydrocarbons, the method comprising the following steps:

[0075] (1) The sludge is pretreated to obtain sludge powder;

[0076] (2) After mixing cobalt salt, nickel salt, imidazole compound and water under an inert atmosphere, a surfactant and the sludge powder are added to the mixed solution. After solid-liquid separation, the solid part is heated under an inert atmosphere and then calcined by passing carbon dioxide through it. After cooling under an inert atmosphere, a biochar catalyst solid powder is obtained.

[0077] (3) The biochar catalyst solid powder is mixed with an organic nitrogen source and calcined under an inert atmosphere. After cooling, biochar catalyst / carbon nitride is obtained.

[0078] (4) The biochar catalyst / carbon nitride is mixed with iron salt, polyethylene glycol and solvent under an inert atmosphere, and then a reducing agent is added under an inert atmosphere to react and obtain composite material powder.

[0079] (5) The composite material powder, polylactic acid solution and glycerol are stirred and mixed, and then the mixture is quenched at low temperature with liquid nitrogen to obtain a sustained-release functional material.

[0080] The method of this invention utilizes sludge, cobalt nitrate, and nickel nitrate to prepare a biochar catalyst, and then modifies the biochar catalyst with CO2. Using cobalt and nickel as active centers, imidazole compounds as ligands, and biochar as a support, the catalyst is prepared. C-Co and C-Ni coordination bonds are formed on the surface of the biochar pores, improving the porosity and catalytic activity of the material. Carbon dioxide modification of biochar can increase its porosity and specific surface area, reduce surface oxygen content, enhance surface reducing capacity, increase the C=O / CO group ratio and carbon defects, which is beneficial to improving the catalytic reduction performance of the material. A biochar catalyst / carbon nitride composite material is prepared using the biochar catalyst and organic nitrogen source to produce carbon nitride. Then, zero-valent iron is negatively deposited onto the composite material using an in-situ liquid-phase precipitation method. Finally, polymer nanofiber microspheres are fabricated as the carrier of the composite material to form a slow-release functional material. This slow-release functional material can effectively prevent the agglomeration of nano-iron, has a large specific surface area, abundant pore structure and surface functional groups, and has a strengthening and promoting effect on the adsorption of halogenated hydrocarbons. Compared to ordinary biochar materials, this slow-release functional material integrates the adsorption and electrocatalytic reduction functions of biochar, thus enhancing the removal effect of pollutants. Using nanofiber microspheres as a carrier further mitigates the aggregation effect of the material and improves the sustainability of its function.

[0081] In this invention, sludge is used as the raw material for preparing biochar, and residual sludge from the secondary sedimentation tank of a domestic sewage treatment plant's biochemical treatment system can be used. The sludge can be pretreated before use. In a specific embodiment, in step (1), the pretreatment may include: subjecting the sludge to static sedimentation, solid-liquid separation, centrifugal separation, solid-liquid separation again, drying, grinding, and sieving in sequence. In a preferred embodiment, the sludge is allowed to settle for 1–6 hours, and solid-liquid separation is performed to obtain concentrated sludge. Then, the concentrated sludge is placed in a centrifuge for centrifugal separation at a speed of 5000–8000 r / min for 15–20 min. After centrifugation, the sludge undergoes solid-liquid separation to separate the mud and water. The separated sludge is then placed in an oven to dry to constant weight, ground, and sieved for later use.

[0082] In a preferred embodiment, in step (1), the drying temperature is 60–100°C, for example, 60°C, 70°C, 80°C, 90°C, or 100°C. In another preferred embodiment, in step (1), the mesh size of the sieve is ≥100 mesh.

[0083] In this invention, in order to obtain the biochar catalyst, in a specific embodiment, in step (2), the mass ratio of cobalt salt, nickel salt, water, imidazole compound, surfactant and sludge powder can be 3-10:1:300-600:10-50:0.2-0.5:15-30, for example 3:1:300:10:0.2:15, 4:1:370:15:0.3:20, 5:1:400:20:0.4:30, 6:1:500:30:0.5:18, 7:1:600:40:0.25:25, 8:1:380:35:0.35:25, 9:1:540:25:0.45:20 or 10:1:460:40:0.3:35.

[0084] In this invention, the cobalt salt and nickel salt can be conventionally selected in the art. In a specific embodiment, in step (2), the cobalt salt is selected from at least one of cobalt nitrate, cobalt sulfate, and cobalt chloride, preferably cobalt nitrate. In another specific embodiment, the nickel salt is selected from at least one of nickel nitrate, nickel sulfate, and nickel chloride, preferably nickel salt.

[0085] In this invention, the imidazole compound can be a conventional choice in the art, as long as it can form a metal-organic framework with cobalt salts or nickel salts. In a specific embodiment, in step (2), the imidazole compound is selected from at least one of 1-methylimidazole, 2-methylimidazole, and 4-methylimidazole, preferably 2-methylimidazole.

[0086] In this invention, the surfactant can be a conventional choice in the art, as long as it can uniformly disperse cobalt salt, cobalt salt, imidazole compound, and sludge powder. In a specific embodiment, in step (2), the surfactant is selected from at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and methylpentanol, preferably sodium dodecylbenzenesulfonate.

[0087] In this invention, the mixing method and conditions in step (2) can be conventionally selected in the art. In a specific embodiment, the mixing method in step (2) is stirring. In a preferred embodiment, the mixing conditions in step (2) include: a rotation speed of 200–280 r / min, for example 200 r / min, 220 r / min, 240 r / min, 260 r / min, or 280 r / min; a temperature of 10–30°C, for example 10°C, 15°C, 20°C, 25°C, or 30°C; and a time of 12–24 h, for example 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, or 24 h.

[0088] In this invention, step (2) may further include: constant-temperature shaking under an inert atmosphere before solid-liquid separation; and drying of the solid portion after solid-liquid separation. In a specific embodiment, the conditions for constant-temperature shaking include: a rotation speed of 200–280 times / min, for example, 200, 220, 240, 260, or 280 times / min; a temperature of 5–25°C, for example, 5°C, 10°C, 15°C, 20°C, or 25°C; and a time of 12–24 hours, for example, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, or 24 hours. In a specific embodiment, the drying conditions can be conventionally chosen in the art. In a preferred embodiment, the drying conditions in step (2) include: a temperature of 80–110°C, for example, 80°C, 90°C, 100°C, or 110°C; and a time of 6–8 hours, for example, 6 hours, 7 hours, or 8 hours.

[0089] In this invention, in order to obtain a biochar catalyst with strong adsorption capacity and strong catalytic reduction capacity, the calcination conditions need to be limited to an appropriate range.

[0090] In a preferred embodiment, in step (2), the calcination process includes: heating to 700–800°C (e.g., 700°C, 750°C, or 800°C) under an inert atmosphere, followed by calcination with carbon dioxide for 3–4 hours (e.g., 3 hours, 3.5 hours, or 4 hours). In a preferred embodiment, in step (2), the temperature is raised to 700–800°C at a heating rate of 2–5°C / min (e.g., 2°C / min, 2.5°C / min, 3°C / min, 3.5°C / min, 4°C / min, 4.5°C / min, or 5°C / min).

[0091] In this invention, step (2) may further include: sieving after cooling. In a specific embodiment, the mesh size of the sieve is ≥100 mesh, preferably, the mesh size of the sieve is 100 mesh.

[0092] In this invention, in order to improve the ability of the prepared material to remove halogenated hydrocarbons from organic compounds, the amounts of the biochar catalyst solid powder and the organic nitrogen source need to be limited to an appropriate range. In a specific embodiment, in step (3), the mass ratio of the biochar catalyst solid powder to the organic nitrogen source can be 1 to 3:1, for example, 1:1, 1.5:1, 2:1, 2.5:1 or 3:1.

[0093] In this invention, the organic nitrogen source can be conventionally selected in the art, as long as carbon nitride can be obtained. In a preferred embodiment, in step (3), the organic nitrogen source is selected from at least one of dicyandiamide, melamine, and thiourea.

[0094] In a specific embodiment, in step (3), the calcination conditions include: the heating rate can be 2 to 6℃ / min, for example 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min or 6℃ / min, preferably 5 to 6℃ / min; the temperature can be 500 to 600℃, for example 500℃, 520℃, 540℃, 550℃, 560℃, 580℃ or 600℃, preferably 500 to 550℃; and the time can be 2 to 3h, for example 2h, 2.5h or 3h.

[0095] In a specific embodiment, in step (4), the mass ratio of the biochar catalyst / carbon nitride, the iron salt, and the polyethylene glycol can be 15–30:15–30:1, for example 15:15:1, 20:20:1, 30:25:1, 25:30:1, 18:28:1, 28:25:1, 24:22:1, 27:22:1, or 20:25:1. In a preferred embodiment, in step (4), the mass ratio of the biochar catalyst / carbon nitride, the iron salt, and the polyethylene glycol is 15–25:25:1.

[0096] In the method described in this invention, the iron salt can be a conventional choice in the art. In a specific embodiment, in step (4), the iron salt can be a divalent iron salt and / or a trivalent iron salt. In a preferred embodiment, the divalent iron salt is selected from at least one of ferrous sulfate, ferrous nitrate, and ferrous chloride, more preferably ferrous sulfate. In a preferred embodiment, the trivalent iron salt is selected from at least one of ferric sulfate, ferric nitrate, and ferric chloride.

[0097] In a preferred embodiment, in step (4), the molecular weight of the polyethylene glycol can be 3500 to 4500, for example 3500, 4000 or 4500.

[0098] In the method described in this invention, in step (4), the solvent can be a conventional choice in the art. In a specific embodiment, in step (4), the solvent is a mixed solution of ethanol and water. In a preferred embodiment, the volume ratio of ethanol to water can be 1:1 to 2, for example 1:1, 1:2, 1:4, 1:6, 1:8 or 1:2, more preferably 1:1.

[0099] In this invention, the mixing method in step (4) is not limited and can be any conventional choice in the art. In a specific embodiment, the mixing method in step (4) is ultrasonic mixing. In a preferred embodiment, the mixing time is 2 to 3 hours, for example, 2 hours, 2.5 hours, or 3 hours.

[0100] In this invention, the reducing agent in step (4) can be a conventional choice in the art. In a preferred embodiment, the reducing agent in step (4) is solid NaBH4 or a NaBH4 solution. When using a NaBH4 solution as the reducing agent, the concentration of the NaBH4 solution can be 10–20 mol / L, for example, 10 mol / L, 15 mol / L, or 20 mol / L, preferably 12–16 mol / L. In a preferred embodiment, the pH value of the NaBH4 solution can be 10–12, for example, 10, 10.5, 11, 11.5, or 12. In this invention, the amount of the reducing agent can be based on a molar ratio of Fe in the iron salt to NaBH4 in the reducing agent of 1:2–4 (for example, 1:2, 1:2.5, 1:3, 1:3.5, or 1:4).

[0101] In a specific implementation, in step (4), the reaction time can be 1 to 2 hours, for example 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours or 2 hours.

[0102] In this invention, step (4) may further include: performing solid-liquid separation after the reaction and washing, drying, grinding, and sieving the solid portion. In specific embodiments, the washing can be performed using conventional operations in the art. In a preferred embodiment, in step (4), the washing includes: washing multiple times with deionized water and deoxygenated anhydrous ethanol, respectively. More preferably, the washing process is: washing 3 to 5 times with deionized water and deoxygenated anhydrous ethanol, respectively. In step (4), the drying conditions can be conventionally selected in the art. In a preferred embodiment, in step (4), the drying conditions include: a temperature of 60 to 80°C, for example, 60°C, 65°C, 70°C, 75°C, or 80°C; and a time of 20 to 30 hours, for example, 20 hours, 25 hours, or 30 hours. In a preferred embodiment, in step (4), the mesh size of the sieve is ≥100 mesh.

[0103] In a specific embodiment, in step (5), the mass ratio of the polylactic acid solution, the glycerol, and the composite material powder can be 1:1 to 9:1 to 6, for example, 1:1:1, 1:2:2, 1:2:1, 1:3:1, 1:3:3, 1:4:1, 1:4:2, 1:5:4, 1:6:5, 1:7:6, 1:8:2, 1:9:5, preferably 1:2 to 4:1 to 2. In this invention, in step (5), the glycerol can be preheated to 48 to 53°C before use, for example, 48°C, 49°C, 50°C, 51°C, 52°C, or 53°C.

[0104] In this invention, in step (5), the polylactic acid solution can be prepared according to conventional methods in the art. In a specific embodiment, the preparation process of the polylactic acid solution in step (5) includes: adding polylactic acid to tetrahydrofuran and stirring. In a preferred embodiment, the concentration of polylactic acid in the polylactic acid solution can be 0.5–5% by weight, for example, 0.5% by weight, 1% by weight, 2% by weight, 3% by weight, 4% by weight, or 5% by weight, more preferably 2–4% by weight. The stirring conditions can be conventionally selected in the art. In a preferred embodiment, the stirring conditions include: a temperature of 55–65°C, for example, 55°C, 60°C, or 65°C; and a time of 2–3 hours, for example, 2 hours, 2.5 hours, or 3 hours.

[0105] In this invention, the mixing method and conditions in step (5) can be conventionally selected in the art. In a specific embodiment, the mixing method can be stirring. In a preferred embodiment, the mixing conditions include: a temperature of 48–53°C, for example 48°C, 49°C, 50°C, 51°C, 52°C, or 53°C; and a time of 2–3 hours, for example 2 hours, 2.5 hours, or 3 hours.

[0106] In the method described in this invention, step (5) may further include: extraction, freeze-drying, grinding, and sieving after liquid nitrogen cryogenic quenching. In a specific embodiment, the extraction conditions in step (5) can be conventionally selected in the art. In a preferred embodiment, the extraction conditions in step (5) include: the extractant is water; the temperature is 0 to 4°C, for example, 0°C, 1°C, 2°C, 3°C, or 4°C; and the time is 2 to 3 days, for example, 2 days, 2.5 days, or 3 days. In a preferred embodiment, the freeze-drying conditions in step (5) include: the temperature is -40 to -60°C, for example, -40°C, -45°C, -50°C, -55°C, or -60°C; and the time is 24 to 36 hours, for example, 24 hours, 26 hours, 28 hours, 30 hours, 32 hours, 34 hours, or 36 hours. In a particularly preferred embodiment, in step (5), the mesh size of the sieve used for sieving is ≥100 mesh, more preferably, the mesh size of the sieve used for sieving is 100 mesh.

[0107] In the specific implementation, in steps (2), (3) and (4), the gas used in the inert atmosphere is independently selected from one or more of nitrogen, helium, neon and argon, preferably nitrogen.

[0108] A second aspect of the present invention provides a sustained-release functional material prepared by the method described above.

[0109] A third aspect of this invention provides an application of the aforementioned slow-release functional material in the remediation of groundwater contaminated with halohydrocarbons. Specifically, this slow-release functional material can be used to remediate groundwater contaminated with heavy metals and halohydrocarbons, and has broad application prospects.

[0110] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited thereto.

[0111] In this invention, benzene series compounds in groundwater are determined according to the "Determination of Benzene Series Compounds in Water by Headspace Gas Chromatography" (HJ1067-2019), and the pH value of groundwater is determined according to the "Determination of pH Value in Water by Glass Electrode Method" (HJ 1147-2020).

[0112] Example 1

[0113] (1) Take the residual sludge from the secondary sedimentation tank of the biochemical treatment system of the domestic sewage treatment plant, let it stand for 3 hours, filter it to obtain the lower layer of gravity concentrated sludge, take a certain amount of gravity concentrated sludge and put it into a centrifuge for centrifugation at a speed of 8000 r / min for 20 min, filter the sludge after centrifugation for mud-water separation, put the separated sludge in an oven and dry it at 80℃ to constant weight, grind it and pass it through a 100-mesh sieve to obtain sludge powder for later use.

[0114] (2) Dissolve 3g of cobalt nitrate and 0.5g of nickel nitrate in 250mL of deionized water, then slowly add 20g of 2-methylimidazole powder to the above solution. Under nitrogen protection and magnetic stirring at 260r / min, stir at 20℃ for 24h. Then add 0.2g of sodium dodecylbenzenesulfonate and 10g of the sludge powder in step (1) to the mixture. Under nitrogen protection, at 20℃, shake at 260 times / min for 24h. Then filter the mixed powder and place it in an oven to dry at 110℃ for 6h. Then put the mixed powder into a crucible and place it in a muffle furnace. Under nitrogen atmosphere, heat to 800℃ at a heating rate of 3℃ / min and then calcine with CO2 for 3h. Then cool to room temperature under nitrogen protection and pass through a 100-mesh sieve to obtain solid powder of biochar catalyst and place it in a centrifuge tube filled with inert gas for later use.

[0115] (3) Mix 10g of the biochar catalyst solid powder described in step (2) with 5g of dicyandiamide and add it to a crucible. Cover the crucible and seal it with aluminum foil. Place the crucible in a muffle furnace under a nitrogen atmosphere and heat it to 550°C at 5°C / min. Calcinate it at a constant temperature for 3 hours. After the muffle furnace cools down to room temperature, grind it through a 100-mesh sieve to obtain the biochar catalyst / carbon nitride. Place it in a centrifuge tube filled with inert gas for later use.

[0116] (4) Weigh 12g of the biochar catalyst / carbon nitride described in step (3) and add it to 200mL of ethanol-deionized water containing 12.5g of FeSO4·7H2O and 0.5g of polyethylene glycol (4000), V ethanol: V deionized water = 1:1. Then, ultrasonically mix for 3h under nitrogen protection. Then, immediately add 15mol / L NaBH4 solution with pH 11 dropwise to the above mixture under nitrogen protection and stir thoroughly. The Fe:NaBH4 molar ratio is 1:3. After reacting for 2h, the mixed solid obtained by vacuum filtration is washed 5 times with deoxygenated deionized water and deoxygenated anhydrous ethanol, and then placed in a vacuum drying oven and dried at 70℃ for 24h. After cooling to room temperature, grind through a 100-mesh sieve to obtain composite material powder and store it in a centrifuge tube filled with inert gas for later use.

[0117] (5) Dissolve 0.3g of polylactic acid in 9.7g of tetrahydrofuran and stir thoroughly at 60℃ for 2h to form a clear and transparent polylactic acid solution. Preheat 30g of glycerol to 50℃ and add it to the above solution, along with 15g of the composite material. Stir thoroughly at 50℃ for 2h. Then, add the mixture to a 300mL liquid nitrogen insulated container at -200℃. After the liquid nitrogen has completely evaporated, add 300mL of an ice-water mixture to extract the glycerol and tetrahydrofuran. Change the water every 8h for 2 days. Then, freeze-dry the mixture at -60℃ for 24h. Finally, grind the mixture and pass it through a 100-mesh sieve to obtain material A1. The SEM image of material A1 is shown below. Figure 2 As shown.

[0118] 100 mL of contaminated groundwater was taken from a monitoring well at a contaminated site. The groundwater had a pH of 7.6 and a trichloroethylene concentration of 102 mg / L. 5 g of material A1 was added to the water sample and mixed thoroughly. The mixed water sample was placed in a brown wide-mouth bottle and sealed and protected from light at 25°C for 60 days. After 60 days, the sample was taken for testing. The trichloroethylene concentration was 0.11 mg / kg, and the removal rate was 99.89%.

[0119] Example 2

[0120] (1) Take the residual sludge from the secondary sedimentation tank of the biochemical treatment system of the domestic sewage treatment plant, let it stand for 3 hours, filter it to obtain the lower layer of gravity concentrated sludge, take a certain amount of gravity concentrated sludge and put it into a centrifuge for centrifugation at a speed of 8000 r / min for 20 min, filter the sludge after centrifugation for mud-water separation, put the separated sludge in an oven and dry it at 80℃ to constant weight, grind it and pass it through a 100-mesh sieve to obtain sludge powder for later use.

[0121] (2) Dissolve 2.5g cobalt nitrate and 0.5g nickel nitrate in 220mL of deionized water, then slowly add 18g of 2-methylimidazole powder to the above solution. Under nitrogen protection and magnetic stirring at 260r / min, stir at 20℃ for 24h. Then add 0.2g sodium dodecylbenzenesulfonate and 8g sludge powder from step (1) to the mixture. Under nitrogen protection, at 20℃, shake at 260 times / min for 24h. Then filter the mixed powder and place it in an oven to dry at 110℃ for 6h. Then put the mixed powder into a crucible and place it in a muffle furnace. Under nitrogen atmosphere, heat to 800℃ at a heating rate of 3℃ / min and then calcine with CO2 for 3h. Then cool to room temperature under nitrogen protection and pass through a 100-mesh sieve to obtain solid biochar catalyst powder and place it in a centrifuge tube filled with inert gas for later use.

[0122] (3) Mix 10g of the biochar catalyst solid powder described in step (2) with 5g of dicyandiamide and add it to a crucible. Cover the crucible and seal it with aluminum foil. Place the crucible in a muffle furnace under a nitrogen atmosphere and heat it to 550°C at 5°C / min. Calcinate it at a constant temperature for 3 hours. After the muffle furnace cools down to room temperature, grind it through a 100-mesh sieve to obtain the biochar catalyst / carbon nitride. Place it in a centrifuge tube filled with inert gas for later use.

[0123] (4) Weigh 10g of the biochar catalyst / carbon nitride described in step (3) and add it to 200mL of ethanol-deionized water containing 12.5g of FeSO4·7H2O and 0.5g of polyethylene glycol (4000), V ethanol: V deionized water = 1:1. Then, ultrasonically mix for 3h under nitrogen protection. Then, immediately add 15mol / L NaBH4 solution with pH 11 dropwise to the above mixture under nitrogen protection and stir thoroughly. The Fe:NaBH4 molar ratio is 1:3. After reacting for 2h, the mixed solid obtained by vacuum filtration is washed 5 times with deoxygenated deionized water and deoxygenated anhydrous ethanol, and then placed in a vacuum drying oven and dried at 70℃ for 24h. After cooling to room temperature, grind through a 100-mesh sieve to obtain composite material powder and store it in a centrifuge tube filled with inert gas for later use.

[0124] (5) Dissolve 0.3g of polylactic acid in 9.7g of tetrahydrofuran and stir thoroughly at 60°C for 2 hours to form a clear and transparent polylactic acid solution. Preheat 30g of glycerol to 50°C and add it to the above solution. At the same time, add 15g of the composite material and stir thoroughly at 50°C for 2 hours. Then add the mixture to a 300mL liquid nitrogen insulated container at -200°C. After the liquid nitrogen has completely evaporated, add 300mL of ice water mixture to extract glycerol and tetrahydrofuran. Change the water every 8 hours for 2 days. Then freeze-dry the mixture at -60°C for 24 hours. Then grind the mixture and pass it through a 100-mesh sieve to obtain material A2.

[0125] 100 mL of contaminated groundwater was taken from a monitoring well at a contaminated site. The groundwater had a pH of 7.6 and a trichloroethylene concentration of 102 mg / L. 5 g of material A2 was added to the water sample and mixed thoroughly. The mixed water sample was placed in a brown wide-mouth bottle and sealed and protected from light at 25°C for 60 days. After 60 days, the sample was taken for testing. The trichloroethylene concentration was 1.40 mg / kg, and the removal rate was 98.63%.

[0126] Example 3

[0127] (1) Take the residual sludge from the secondary sedimentation tank of the biochemical treatment system of the domestic sewage treatment plant, let it stand for 3 hours, filter it to obtain the lower layer of gravity concentrated sludge, take a certain amount of gravity concentrated sludge and put it into a centrifuge for centrifugation at a speed of 8000 r / min for 20 min, filter the sludge after centrifugation for mud-water separation, put the separated sludge in an oven and dry it at 80℃ to constant weight, grind it and pass it through a 100-mesh sieve to obtain sludge powder for later use.

[0128] (2) Dissolve 3g of cobalt nitrate and 0.5g of nickel nitrate in 250mL of deionized water, then slowly add 18g of 2-methylimidazole powder to the above solution. Under nitrogen protection and magnetic stirring at 260r / min, stir at 20℃ for 24h. Then add 0.2g of sodium dodecylbenzenesulfonate and 9g of the sludge powder described in step (1) to the mixture. Under nitrogen protection, at 20℃, shake at 260 times / min for 24h. Then filter the mixed powder and place it in an oven to dry at 110℃ for 6h. Then put the mixed powder into a crucible and place it in a muffle furnace. Under nitrogen atmosphere, heat to 800℃ at a heating rate of 3℃ / min and then calcine with CO2 for 3h. Then cool to room temperature under nitrogen protection and pass through a 100-mesh sieve to obtain solid biochar catalyst powder and place it in a centrifuge tube filled with inert gas for later use.

[0129] (3) Mix 10g of the biochar catalyst solid powder described in step (2) with 5g of dicyandiamide and add it to a crucible. Cover the crucible and seal it with aluminum foil. Place the crucible in a muffle furnace under a nitrogen atmosphere and heat it to 550°C at 5°C / min. Calcinate it at a constant temperature for 3 hours. After the muffle furnace cools down to room temperature, grind it through a 100-mesh sieve to obtain the biochar catalyst / carbon nitride. Place it in a centrifuge tube filled with inert gas for later use.

[0130] (4) Weigh 7.5g of the biochar catalyst / carbon nitride described in step (3) and add it to 200mL of ethanol-deionized water containing 12.5g of FeSO4·7H2O and 0.5g of polyethylene glycol (4000), V ethanol: V deionized water = 1:1. Then, ultrasonically mix for 3h under nitrogen protection. Then, immediately add 15mol / L NaBH4 solution with pH 11 dropwise to the above mixture under nitrogen protection and stir thoroughly. The Fe:NaBH4 molar ratio is 1:3. After reacting for 2h, the mixed solid obtained by vacuum filtration is washed 5 times with deoxygenated deionized water and deoxygenated anhydrous ethanol, and then placed in a vacuum drying oven and dried at 70℃ for 24h. After cooling to room temperature, grind through a 100-mesh sieve to obtain composite material powder and store it in a centrifuge tube filled with inert gas for later use.

[0131] (5) Dissolve 0.3g of polylactic acid in 9.7g of tetrahydrofuran and stir thoroughly at 60°C for 2 hours to form a clear and transparent polylactic acid solution. Preheat 30g of glycerol to 50°C and add it to the above solution. At the same time, add 15g of the composite material and stir thoroughly at 50°C for 2 hours. Then add the mixture to a 300mL liquid nitrogen insulated container at -200°C. After the liquid nitrogen has completely evaporated, add 300mL of ice water mixture to extract glycerol and tetrahydrofuran. Change the water every 8 hours for 2 days. Then freeze-dry the mixture at -60°C for 24 hours. Then grind the mixture and pass it through a 100-mesh sieve to obtain material A3.

[0132] 100 mL of contaminated groundwater was taken from a monitoring well at a contaminated site. The groundwater had a pH of 7.6 and a trichloroethylene concentration of 102 mg / L. 5 g of material A3 was added to the water sample and mixed thoroughly. The mixed water sample was placed in a brown wide-mouth bottle and sealed and protected from light at 25°C for 60 days. After 60 days, the sample was taken for testing. The trichloroethylene concentration was 4.25 mg / kg, and the removal rate was 95.83%.

[0133] Comparative Example 1

[0134] (1) Take the residual sludge from the secondary sedimentation tank of the biochemical treatment system of the domestic sewage treatment plant, let it stand for 3 hours, filter it to obtain the lower layer of gravity concentrated sludge, put the gravity concentrated sludge into a centrifuge for centrifugation at 8000 r / min for 20 min; after centrifugation, the sludge is filtered to separate the mud and water, and the separated sludge is placed in an oven and dried at 80℃ to constant weight. After grinding, it is passed through a 100-mesh sieve to obtain sludge powder, which is then placed in a centrifuge tube filled with inert gas for later use.

[0135] (2) Mix 10g of the sludge powder described in step (1) with 5g of dicyandiamide and add it to a crucible. Cover the crucible and seal it with aluminum foil. Place the crucible in a muffle furnace under a nitrogen atmosphere and heat it to 550°C at 5°C / min. Calcinate it at a constant temperature for 3 hours. After the muffle furnace cools down to room temperature, grind it through a 100-mesh sieve to obtain biochar / carbon nitride powder and place it in a centrifuge tube filled with inert gas for later use.

[0136] (3) Weigh 11g of the biochar / carbon nitride powder described in step (2) and add it to 200mL of ethanol-deionized water containing 12.5g of FeSO4·7H2O and 0.5g of polyethylene glycol (4000), V ethanol: V deionized water = 1:1. Then, ultrasonically mix for 3h under nitrogen protection. Then, immediately add 15mol / L NaBH4 solution with pH 11 dropwise to the above mixture under nitrogen protection and stir thoroughly. The Fe:NaBH4 molar ratio is 1:3. After reacting for 2h, the mixed solid obtained by vacuum filtration is washed 5 times with deoxygenated deionized water and deoxygenated anhydrous ethanol, and then placed in a vacuum drying oven and dried at 70℃ for 24h. After cooling to room temperature, grind through a 100-mesh sieve to obtain composite material powder and store it in a centrifuge tube filled with inert gas for later use.

[0137] (4) Dissolve 0.3g polylactic acid in 9.7g tetrahydrofuran and stir thoroughly at 60℃ for 2h to form a clear and transparent solution. Preheat 30g glycerol to 50℃ and add it to the above solution. At the same time, add 15g composite material and stir thoroughly at 50℃ for 2h. Then add the mixture to a 300mL liquid nitrogen insulated container at -200℃. After the liquid nitrogen has completely evaporated, add 300mL ice water mixture to extract glycerol and tetrahydrofuran. Change the water every 8h during this period for 2 days. Then freeze-dry the mixture at -60℃ for 24h. Then grind the mixture and pass it through a 100-mesh sieve to obtain material B1.

[0138] 100 mL of contaminated groundwater was taken from a monitoring well at a contaminated site. The groundwater had a pH of 7.6 and a trichloroethylene concentration of 102 mg / L. 3 g of material B1 was added to the water sample and mixed thoroughly. The mixed water sample was placed in a brown wide-mouth bottle and sealed and protected from light at 25°C for 60 days. After 60 days, the sample was taken for testing. The trichloroethylene concentration was 10.70 mg / kg, and the removal rate was 89.51%.

[0139] Comparative Example 2

[0140] (1) Take the residual sludge from the secondary sedimentation tank of the biochemical treatment system of the domestic sewage treatment plant, let it stand for 3 hours, and filter it to obtain the lower layer of gravity concentrated sludge; take a certain amount of gravity concentrated sludge and put it into a centrifuge for centrifugation at a speed of 8000 r / min for 20 min. After centrifugation, the sludge is filtered to separate the mud and water. The separated sludge is placed in an oven and dried at 80℃ to constant weight. After grinding, it is passed through a 100-mesh sieve to obtain sludge powder for later use.

[0141] (2) Dissolve 3g of cobalt nitrate and 0.5g of nickel nitrate in 250mL of deionized water, then slowly add 20g of 2-methylimidazole powder to the above solution. Under nitrogen protection and magnetic stirring at 260r / min, stir at 20℃ for 24h. Then add 0.2g of sodium dodecylbenzenesulfonate and 10g of the sludge powder described in step (1) to the mixture. Under nitrogen protection, at 20℃, and constant temperature shaking at 260 times / min for 24h. Then filter the mixed powder and place it in an oven to dry at 110℃ for 6h. Then put the mixed powder into a crucible and place it in a muffle furnace. Under nitrogen atmosphere, heat it to 800℃ at a heating rate of 3℃ / min and then calcine it with CO2 for 3h. Then cool it to room temperature under nitrogen protection and pass it through a 100-mesh sieve to obtain solid biochar catalyst powder and place it in a centrifuge tube filled with inert gas for later use.

[0142] (3) Weigh 11g of the biochar catalyst solid powder described in step (3) and add it to 200mL of ethanol-deionized water containing 12.5g of FeSO4·7H2O and 0.5g of polyethylene glycol (4000), V ethanol: V deionized water = 1:1. Then, ultrasonically mix for 3h under nitrogen protection. Then, immediately add 15mol / L NaBH4 solution with pH 11 dropwise to the above mixture under nitrogen protection and stir thoroughly. The Fe:NaBH4 molar ratio is 1:3. After reacting for 2h, the mixed solid obtained by vacuum filtration is washed 5 times with deoxygenated deionized water and deoxygenated anhydrous ethanol, and then placed in a vacuum drying oven and dried at 70℃ for 24h. After cooling to room temperature, grind through a 100-mesh sieve to obtain composite material powder and store it in a centrifuge tube filled with inert gas for later use.

[0143] (4) Dissolve 0.3g polylactic acid in 9.7g tetrahydrofuran and stir thoroughly at 60℃ for 2h to form a clear and transparent solution. Preheat 30g glycerol to 50℃ and add it to the above solution. At the same time, add 15g composite material and stir thoroughly at 50℃ for 2h. Then add the mixture to a 300mL liquid nitrogen insulated container at -200℃. After the liquid nitrogen has completely evaporated, add 300mL ice water mixture to extract glycerol and tetrahydrofuran. Change the water every 8h during this period for 2 days. Then freeze-dry the mixture at -60℃ for 24h. Then grind the mixture and pass it through a 100-mesh sieve to obtain material B2.

[0144] 100 mL of contaminated groundwater was taken from a monitoring well at a contaminated site. The groundwater had a pH of 7.6 and a trichloroethylene concentration of 102 mg / L. 3 g of material B2 was added to the water sample and mixed thoroughly. The mixed water sample was placed in a brown wide-mouth bottle and sealed and protected from light at 25°C for 60 days. After 60 days, the sample was taken for testing. The trichloroethylene concentration was 8.56 mg / kg, and the removal rate was 91.61%.

[0145] Comparative Example 3

[0146] (1) Take the residual sludge from the secondary sedimentation tank of the biochemical treatment system of the domestic sewage treatment plant, let it settle for 3 hours, and filter it to obtain the lower layer of gravity concentrated sludge; take a certain amount of gravity concentrated sludge and put it into a centrifuge for centrifugation at a speed of 8000 r / min for 20 min. After centrifugation, the sludge is filtered to separate the mud and water. The separated sludge is placed in an oven and dried at 80℃ to constant weight. After grinding, it is passed through a 100-mesh sieve to obtain sludge powder. The sludge powder is placed in a crucible and placed in a muffle furnace. Under nitrogen atmosphere, the temperature is raised to 800℃ at a heating rate of 3℃ / min and calcined for 3 hours. Then, it is cooled to room temperature under nitrogen protection and passed through a 100-mesh sieve to obtain biochar powder, which is placed in a centrifuge tube filled with inert gas for later use.

[0147] (2) Weigh 11g of the biochar powder described in step (1) and add it to 200mL of ethanol-deionized water containing 12.5g of FeSO4·7H2O and 0.5g of polyethylene glycol (4000), V ethanol: V deionized water = 1:1. Then, ultrasonically mix for 3h under nitrogen protection. Then, immediately add 15mol / L NaBH4 solution with pH 11 dropwise to the above mixture under nitrogen protection and stir thoroughly. The Fe:NaBH4 molar ratio is 1:3. After reacting for 2h, the mixed solid obtained by vacuum filtration is washed 5 times with deoxygenated deionized water and deoxygenated anhydrous ethanol, and then placed in a vacuum drying oven and dried at 70℃ for 24h. After cooling to room temperature, grind through a 100-mesh sieve to obtain composite material powder and store it in a centrifuge tube filled with inert gas for later use.

[0148] (3) Dissolve 0.3g polylactic acid in 9.7g tetrahydrofuran and stir thoroughly at 60℃ for 2h to form a clear and transparent solution. Preheat 30g glycerol to 50℃ and add it to the above solution. At the same time, add 15g composite material and stir thoroughly at 50℃ for 2h. Then add the mixture to a 300mL liquid nitrogen insulated container at -200℃. After the liquid nitrogen has completely evaporated, add 300mL ice water mixture to extract glycerol and tetrahydrofuran. Change the water every 8h for 2 days. Then freeze-dry the mixture at -60℃ for 24h. Then grind the mixture and pass it through a 100-mesh sieve to obtain material B3.

[0149] 100 mL of contaminated groundwater was taken from a monitoring well at a contaminated site. The groundwater had a pH of 7.6 and a trichloroethylene concentration of 102 mg / L. 3 g of material B3 was added to the water sample and mixed thoroughly. The mixed water sample was placed in a brown wide-mouth bottle and sealed and protected from light at 25°C for 60 days. After 60 days, the sample was taken for testing. The trichloroethylene concentration was 15.25 mg / kg, and the removal rate was 85.05%.

[0150] Comparative Example 4

[0151] (1) Weigh 12.5g of FeSO4·7H2O and 0.5g of polyethylene glycol (4000) to prepare 200mL of ethanol-deionized water solution, Vethanol:Vdeionized water = 1:1. Then, under nitrogen protection, ultrasonically mix for 3h. Then, immediately under nitrogen protection, add 15mol / L NaBH4 solution with pH 11 dropwise to the above mixture and stir thoroughly. The Fe:NaBH4 molar ratio is 1:3. After reacting for 2h, filter the mixed solid and wash it 5 times with deoxygenated deionized water and deoxygenated anhydrous ethanol. Then, place it in a vacuum drying oven and dry it at 70℃ for 24h. After cooling to room temperature, grind it through a 100-mesh sieve to obtain nano zero-valent iron powder and store it in a centrifuge tube filled with inert gas for later use.

[0152] (2) Dissolve 0.3g polylactic acid in 9.7g tetrahydrofuran and stir thoroughly at 60°C for 2 hours to form a clear and transparent solution. Preheat 30g glycerol to 50°C and add it to the above solution. At the same time, add 15g of the nano zero-valent iron powder described in step (1). Stir thoroughly at 50°C for 2 hours. Then add the mixture to a 300mL liquid nitrogen insulated container at -200°C. After the liquid nitrogen has completely evaporated, add 300mL of ice water mixture to extract glycerol and tetrahydrofuran. Change the water every 8 hours for 2 days. Then freeze-dry the mixture at -60°C for 24 hours. Then grind the mixture and pass it through a 100-mesh sieve to obtain material B4.

[0153] 100 mL of contaminated groundwater was taken from a monitoring well at a contaminated site. The groundwater had a pH of 7.6 and a trichloroethylene concentration of 102 mg / L. 3 g of material B4 was added to the water sample and mixed thoroughly. The mixed water sample was placed in a brown wide-mouth bottle and sealed and protected from light at 25°C for 60 days. After 60 days, the sample was taken for testing. The trichloroethylene concentration was 29.93 mg / kg, and the removal rate was 70.66%.

[0154] Comparative Example 5

[0155] (1) Take the residual sludge from the secondary sedimentation tank of the biochemical treatment system of the domestic sewage treatment plant, let it stand for 3 hours, filter it to obtain the lower layer of gravity concentrated sludge, take a certain amount of gravity concentrated sludge and put it into a centrifuge for centrifugation at a speed of 8000 r / min for 20 min, filter the sludge after centrifugation for mud-water separation, put the separated sludge in an oven and dry it at 80℃ to constant weight, grind it and pass it through a 100-mesh sieve to obtain sludge powder for later use.

[0156] (2) Dissolve 3g of cobalt nitrate and 0.5g of nickel nitrate in 250mL of deionized water, then slowly add 20g of 2-methylimidazole powder to the above solution. Under nitrogen protection and magnetic stirring at 260r / min, stir at 20℃ for 24h. Then add 0.2g of sodium dodecylbenzenesulfonate and 10g of the sludge powder described in step (1) to the mixture. Under nitrogen protection, at 20℃, shake at 260 times / min for 24h. Then filter the mixed powder and place it in an oven to dry at 110℃ for 6h. Then put the mixed powder into a crucible and place it in a muffle furnace. Under nitrogen atmosphere, heat it to 800℃ at a heating rate of 3℃ / min and then calcine it with CO2 for 3h. Then cool it to room temperature under nitrogen protection and pass it through a 100-mesh sieve to obtain solid biochar catalyst powder and place it in a centrifuge tube filled with inert gas for later use.

[0157] (3) Dissolve 0.3g polylactic acid in 9.7g tetrahydrofuran and stir thoroughly at 60℃ for 2h to form a clear and transparent solution. Preheat 30g glycerol to 50℃ and add it to the above solution. At the same time, add 15g biochar catalyst and stir thoroughly at 50℃ for 2h. Then add the mixture to a 300mL liquid nitrogen insulated container at -200℃. After the liquid nitrogen has completely evaporated, add 300mL ice water mixture to extract glycerol and tetrahydrofuran. Change the water every 8h during this period for 2 days. Then freeze-dry the mixture at -60℃ for 24h. Then grind the mixture and pass it through a 100-mesh sieve to obtain material B5.

[0158] 100 mL of contaminated groundwater was taken from a monitoring well at a contaminated site. The groundwater had a pH of 7.6 and a trichloroethylene concentration of 102 mg / L. 3 g of material B5 was added to the water sample and mixed thoroughly. The mixed water sample was placed in a brown wide-mouth bottle and sealed and protected from light at 25°C for 60 days before sampling and testing. The trichloroethylene concentration was 34.45 mg / kg, and the removal rate was 66.23%.

[0159] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a slow-release functional material for remediating groundwater contaminated with halohydrocarbons, characterized in that, The method includes the following steps: (1) The sludge is pretreated to obtain sludge powder; (2) After mixing cobalt salt, nickel salt, imidazole compound and water under an inert atmosphere, a surfactant and the sludge powder are added to the mixed solution. After solid-liquid separation, the solid part is heated under an inert atmosphere and then calcined by passing carbon dioxide through it. After cooling under an inert atmosphere, a biochar catalyst solid powder is obtained. (3) The biochar catalyst solid powder is mixed with an organic nitrogen source and calcined under an inert atmosphere. After cooling, biochar catalyst / carbon nitride is obtained. (4) The biochar catalyst / carbon nitride is mixed with iron salt, polyethylene glycol and solvent under an inert atmosphere, and then a reducing agent is added under an inert atmosphere to react and obtain composite material powder; (5) The composite material powder, polylactic acid solution and glycerol are stirred and mixed, and then the mixture is subjected to liquid nitrogen low temperature quenching to obtain a sustained-release functional material.

2. The method according to claim 1, characterized in that, In step (1), the pretreatment includes: subjecting the sludge to static sedimentation, solid-liquid separation, centrifugal separation, solid-liquid separation, drying, grinding and sieving in sequence; The drying temperature is 60~100℃; The sieve mesh size is ≥100 mesh.

3. The method according to claim 1, characterized in that, In step (2), the mass ratio of cobalt salt, nickel salt, water, imidazole compound, surfactant and sludge powder is 3~10:1:300~600:10~50:0.2~0.5:15~30.

4. The method according to any one of claims 1-3, characterized in that, In step (2), the cobalt salt is selected from at least one of cobalt nitrate, cobalt sulfate and cobalt chloride.

5. The method according to claim 4, characterized in that, In step (2), the nickel salt is selected from at least one of nickel nitrate, nickel sulfate and nickel chloride.

6. The method according to claim 4, characterized in that, In step (2), the imidazole compound is selected from at least one of 1-methylimidazole, 2-methylimidazole and 4-methylimidazole.

7. The method according to claim 4, characterized in that, In step (2), the surfactant is selected from at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and methylpentanol.

8. The method according to claim 1, characterized in that, In step (2), the mixing method is stirring.

9. The method according to claim 8, characterized in that, In step (2), the mixing conditions include: a rotation speed of 200~280 r / min, a temperature of 10~30℃, and a time of 12~24h.

10. The method according to claim 1, characterized in that, Step (2) also includes: constant temperature shaking under an inert atmosphere before solid-liquid separation; drying the solid part after solid-liquid separation; The conditions for constant temperature oscillation include: rotation speed of 200~280 times / min, temperature of 5~25℃, and time of 12~24 hours; The drying conditions include a temperature of 80~110℃ and a time of 6~8h.

11. The method according to claim 1, characterized in that, In step (2), the calcination process includes heating the temperature to 700~800℃ under an inert atmosphere and then introducing carbon dioxide for calcination for 3~4 hours.

12. The method according to claim 11, characterized in that, The temperature is raised to 700-800℃ at a heating rate of 2-5℃ / min.

13. The method according to claim 1, characterized in that, Step (2) also includes: sieving after cooling; the mesh size of the sieve is ≥100 mesh.

14. The method according to claim 1, characterized in that, In step (3), the mass ratio of the biochar catalyst solid powder to the organic nitrogen source is 1~3:

1.

15. The method according to claim 1, characterized in that, In step (3), the organic nitrogen source is selected from at least one of dicyandiamide, melamine and thiourea.

16. The method according to claim 1, characterized in that, In step (3), the calcination conditions include: a heating rate of 2~6℃ / min; a temperature of 500~600℃; and a time of 2~3h.

17. The method according to claim 16, characterized in that, In step (3), the calcination conditions include a heating rate of 5~6℃ / min.

18. The method according to claim 16, characterized in that, In step (3), the calcination conditions include a temperature of 500~550℃.

19. The method according to claim 1, characterized in that, In step (4), the mass ratio of the biochar catalyst / carbon nitride, the iron salt and the polyethylene glycol is 15~30:15~30:

1.

20. The method according to claim 19, characterized in that, In step (4), the mass ratio of the biochar catalyst / carbon nitride, the iron salt and the polyethylene glycol is 15~25:25:

1.

21. The method according to claim 1, characterized in that, In step (4), the iron salt is a divalent iron salt and / or a trivalent iron salt.

22. The method according to claim 21, characterized in that, The ferrous salt is selected from at least one of ferrous sulfate, ferrous nitrate and ferrous chloride.

23. The method according to claim 21, characterized in that, The ferric salt is selected from at least one of ferric sulfate, ferric nitrate, and ferric chloride.

24. The method according to claim 1, characterized in that, In step (4), the molecular weight of the polyethylene glycol is 3500~4500.

25. The method according to claim 1, characterized in that, In step (4), the solvent is a mixture of ethanol and water; The volume ratio of ethanol to water is 1:1~2.

26. The method according to claim 1, characterized in that, In step (4), the mixing method is ultrasonic mixing.

27. The method according to claim 1 or 26, characterized in that, In step (4), the mixing time is 2 to 3 hours.

28. The method according to claim 1, characterized in that, In step (4), the reducing agent is NaBH4 solid or NaBH4 solution.

29. The method according to claim 28, characterized in that, The concentration of the NaBH4 solution is 10~20 mol / L.

30. The method according to claim 29, characterized in that, The concentration of the NaBH4 solution is 12~16 mol / L.

31. The method according to claim 28, characterized in that, The pH value of the NaBH4 solution is 10-12.

32. The method according to claim 28, characterized in that, The amount of reducing agent used is based on a molar ratio of Fe element in the iron salt to NaBH4 in the reducing agent of 1:2~4.

33. The method according to claim 1, characterized in that, In step (4), the reaction time is 1 to 2 hours.

34. The method according to claim 1, characterized in that, Step (4) also includes: performing solid-liquid separation after the reaction and washing, drying, grinding and sieving the solid part; The washing process includes: washing multiple times with deionized water and deoxygenated anhydrous ethanol, respectively; Drying conditions include: temperature of 60~80℃; time of 20~30h; The sieve mesh size is ≥100 mesh.

35. The method according to claim 1, characterized in that, In step (5), the mass ratio of the polylactic acid solution, the glycerol and the composite material powder is 1:1~9:1~6.

36. The method according to claim 35, characterized in that, The mass ratio of the polylactic acid solution, the glycerol, and the composite material powder is 1:2~4:1~2.

37. The method according to claim 1, characterized in that, In step (5), the preparation process of the polylactic acid solution includes: adding polylactic acid to tetrahydrofuran and stirring.

38. The method according to claim 1 or 37, characterized in that, In the polylactic acid solution, the concentration of polylactic acid is 0.5 to 5% by weight.

39. The method according to claim 38, characterized in that, In the polylactic acid solution, the concentration of polylactic acid is 2-4% by weight.

40. The method according to claim 37, characterized in that, The stirring conditions include a temperature of 55-65°C and a time of 2-3 hours.

41. The method according to claim 1, characterized in that, In step (5), the mixing method is stirring.

42. The method according to claim 1 or 41, characterized in that, In step (5), the mixing conditions include a temperature of 48~53℃ and a time of 2~3h.

43. The method according to claim 1, characterized in that, Step (5) also includes: extraction, freeze-drying, grinding and sieving after liquid nitrogen cryogenic quenching.

44. The method according to claim 43, characterized in that, Extraction conditions include: water as the extractant, a temperature of 0-4℃, and a time of 2-3 days.

45. The method according to claim 44, characterized in that, The freeze-drying conditions include: a temperature of -40 to -60°C and a time of 24 to 36 hours.

46. ​​The method according to claim 44, characterized in that, The sieve mesh size is ≥100 mesh.

47. The method according to claim 1, characterized in that, In steps (2), (3) and (4), the inert atmosphere is made of one or more of nitrogen, helium, neon and argon.

48. The sustained-release functional material prepared by the method of any one of claims 1-47.

49. The application of the slow-release functional material according to claim 48 in the remediation of groundwater contaminated with halogenated hydrocarbons.

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