A composite material for halogenated hydrocarbon-heavy metal contaminated site remediation and a preparation method and application thereof
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2022-07-18
- Publication Date
- 2026-05-29
AI Technical Summary
Existing technologies are not effective in degrading halogenated hydrocarbons and heavy metal pollution, and nano-zero valent iron is prone to agglomeration, passivation, and loss during application, making it difficult to achieve efficient removal.
By preparing biochar-supported nano-zero-valent iron and combining it with emulsified vegetable oil and sludge supernatant to form a composite material, the adsorption of biochar, the electrochemical effect of nano-zero-valent iron and the catalytic reduction of Co are utilized to promote microbial growth and achieve the synergistic degradation of halogenated hydrocarbons and heavy metals.
It achieves efficient removal of halogenated hydrocarbons and heavy metals. Biochar provides a large specific surface area and abundant pore structure, nano-zero valent iron provides electrochemical action, and emulsified oil and sludge supernatant provide carbon source and nutrients to promote microbial growth and achieve continuous and efficient pollutant degradation.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of contaminated soil and groundwater remediation technology, specifically to a composite material for the remediation of sites contaminated with halogenated hydrocarbons and heavy metals, 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 organics (detergents, plastics, etc.), as well as the large-scale use of pesticides and insecticides in agriculture, more and more chlorinated hydrocarbon pollutants are entering the environment, leading to increasingly serious pollution of groundwater, one of the important sources of drinking water for humans.
[0003] 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. 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 as an adsorbent and catalyst for controlling pollutants in the environment. Furthermore, its wide availability and low economic cost make it a high-performance adsorbent and carrier material. Biochar is widely used to treat 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.
[0004] Studies have also shown that biochar-stabilized microorganisms have a significant passivation effect on uranium and cadmium ions in soil. Although biochar has many advantages in the field of environmental remediation, for single-phase biochar, its adsorption capacity and kinetic rate are generally insufficient to meet the requirements for efficient removal of pollutants from the environment.
[0005] Iron is a common, inexpensive, and readily available metallic element, making its application in environmental remediation cost-effective and avoiding secondary pollution. Nano-zero-valent iron (nZVI) is a novel environmental remediation material that has gained popularity in recent years, and is also commonly used in 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.
[0006] Emulsified vegetable oil is usually made by mixing vegetable oil, water, emulsifier and other additives in a certain proportion and then dispersing them through a high-speed dispersion device to form an oil-in-water emulsion. Its main components as a carbon source for microorganisms are the long-chain fatty acids that make up the vegetable oil, such as oleic acid, linoleic acid, linolenic acid and palmitic acid, while the additives provide various nutrients for the growth of microorganisms.
[0007] Current research results indicate that emulsified vegetable oil, as a carbon source for in-situ microbial remediation of contaminated sites, has many advantages: (1) It has strong migration ability in aquifers, capable of migrating in coarse, medium, and fine sand, and has a large adsorption capacity on aquifer media, enabling it to form a bioreaction zone over a large area; (2) It has strong slow-release ability, as the triglycerides adsorbed on aquifer media can be slowly oxidized by microorganisms to produce acetic acid and hydrogen, which can provide long-term support for the growth of functional microorganisms, thereby removing contaminants; (3) The raw materials are inexpensive and readily available, the preparation process is simple, the engineering technology is mature, and the economics are good. In addition, during the migration of emulsified oil droplets in the contaminated area, hydrophobic halogenated hydrocarbons can enter the interior of the oil droplets, forming a new mixed non-aqueous phase. This mixed non-aqueous phase has both electron donors and electron acceptors, providing an ideal environment for the growth of target microorganisms. Once the mixed non-aqueous phase environment is formed, it can prevent other microorganisms at the remediation site from competing with the target pollutants for carbon sources.
[0008] CN104803486A discloses a permeable reactive wall material for remediating chromium contamination in groundwater. This material includes a reducing agent and an adsorption medium. Its composition and manufacturing method are complex. It is mainly used to reduce hexavalent chromium in groundwater, but it has great limitations in the remediation of organically contaminated groundwater.
[0009] CN104138745A discloses a method for preparing a biocarbon adsorbent for the remediation of organic pollution. Although the material has the function of adsorbing pollutants, it is difficult to completely degrade pollutants, and the removal effect of pollutants is limited after the material is saturated with adsorption, and it does not have the function of long-term degradation of pollutants.
[0010] CN107999531A discloses an in-situ remediation material and method for soil and groundwater in organically contaminated sites. This patent uses surfactants to increase the solubility and dispersibility of organic pollutants in groundwater and activates zero-valent iron to form a Fenton-like system for oxidative degradation of organic pollutants. However, this material is difficult to inhibit the aggregation, oxidation, and scaling of zero-valent iron, and it does not have a slow-release function or long-term effect. Summary of the Invention
[0011] The purpose of this invention is to solve the problem of poor degradation effect of heavy metals and chlorinated hydrocarbons in the existing technology.
[0012] To achieve the above objectives, a first aspect of the present invention provides a method for preparing a composite material for the remediation of sites contaminated with halohydrocarbons and heavy metals, the method comprising:
[0013] (1) Preparation of biochar-supported nano-zero-valent iron
[0014] S1: In the presence of water, CeCl3, RuCl3 and sodium dodecylbenzenesulfonate are first mixed to obtain mixture I;
[0015] S2: The sludge and straw are soaked in the mixture I and then mixed a second time to obtain mixture II;
[0016] S3: The dried mixture II is heated under nitrogen protection, then CO2 is introduced for modification, nitrogen is introduced again and heating is stopped to obtain modified biochar;
[0017] S4: In the presence of water and ethanol, the modified biochar is first contacted with ferrous sulfate and polyethylene glycol to obtain mixture A; the volume ratio of ethanol to water is 1:1-2.
[0018] S5: Under nitrogen protection, the mixture A is brought into a second contact with NaBH4 to obtain mixture B;
[0019] S6: Under nitrogen protection, the mixture B is brought into a third contact with cobalt sulfate to obtain the biochar-supported nano-zero-valent iron.
[0020] (2) Vegetable oil, polyoxyethylene sorbitan monooleate, dehydrated sorbitan monooleate, sludge supernatant, biochar-supported nano-zero valent iron and water in a mass ratio of 1:0.1~0.3:0.1~0.3:1~2:0.7~2:15~30 are emulsified to obtain a composite material.
[0021] The vegetable oil is selected from at least one of soybean oil, corn oil, rapeseed oil, and peanut oil.
[0022] A second aspect of the invention provides a composite material for the remediation of sites contaminated with halogenated hydrocarbons and heavy metals, prepared by the method described in the first aspect.
[0023] A third aspect of the invention provides the use of the composite material described in the second aspect in the degradation of halogenated hydrocarbons and / or heavy metals.
[0024] The composite material prepared by the method provided in this invention can promote the emulsification of vegetable oil and prevent the agglomeration of biochar-loaded nano-zero-valent iron particles by introducing polyoxyethylene sorbitan monooleate (Tween 80) and dehydrated sorbitan monooleate (Span 80) in a mass ratio of 0.1-0.3:0.1-0.3. This composite material utilizes the supernatant of residual sludge to provide nutrients for microorganisms and uses emulsified oil as a co-metabolic carbon source, enabling the degradation of halogenated hydrocarbons and reduced heavy metals during microbial growth and reproduction. Simultaneously, this composite material can utilize biochar to adsorb pollutants, and use nano-zero-valent iron and emulsified oil as continuous electron donors to achieve heavy metal reduction and halogenated hydrocarbon dehalogenation under the action of the catalyst Co.
[0025] Furthermore, the composite material provided by this invention can simultaneously utilize adsorption, biological, chemical, and electrochemical processes for contaminated site remediation, achieving a synergistic, continuous, and efficient removal of heavy metals and halogenated hydrocarbons. Detailed Implementation
[0026] 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.
[0027] As previously stated, a first aspect of the present invention provides a method for preparing a composite material for the remediation of sites contaminated with halogenated hydrocarbons and heavy metals, the method comprising:
[0028] (1) Preparation of biochar-supported nano-zero-valent iron
[0029] S1: In the presence of water, CeCl3, RuCl3 and sodium dodecylbenzenesulfonate are first mixed to obtain mixture I;
[0030] S2: The sludge and straw are soaked in the mixture I and then mixed a second time to obtain mixture II;
[0031] S3: The dried mixture II is heated under nitrogen protection, then CO2 is introduced for modification, nitrogen is introduced again and heating is stopped to obtain modified biochar;
[0032] S4: In the presence of water and ethanol, the modified biochar is first contacted with ferrous sulfate and polyethylene glycol to obtain mixture A; the volume ratio of ethanol to water is 1:1-2.
[0033] S5: Under nitrogen protection, the mixture A is brought into a second contact with NaBH4 to obtain mixture B;
[0034] S6: Under nitrogen protection, the mixture B is brought into a third contact with cobalt sulfate to obtain the biochar-supported nano-zero-valent iron.
[0035] (2) Vegetable oil, polyoxyethylene sorbitan monooleate, dehydrated sorbitan monooleate, sludge supernatant, biochar-supported nano-zero valent iron and water in a mass ratio of 1:0.1~0.3:0.1~0.3:1~2:0.7~2:15~30 are emulsified to obtain a composite material.
[0036] The vegetable oil is selected from at least one of soybean oil, corn oil, rapeseed oil, and peanut oil.
[0037] It should be noted that in the process of preparing biochar-supported nano-zero valent iron, the water and ethanol used in this invention are deoxygenated deionized water and deoxygenated anhydrous ethanol, respectively.
[0038] Preferably, in step (2), the sludge supernatant contains proteins, carbohydrates, lipids and organic acids.
[0039] In a preferred embodiment, in step (2), the sludge in the sludge supernatant is residual sludge from the secondary sedimentation tank of a domestic wastewater treatment plant's biochemical treatment system. The inventors of this invention have discovered that, in this preferred embodiment, waste resource recovery can be achieved, reducing the problems associated with sludge treatment.
[0040] Preferably, the sludge supernatant in step (2) is obtained by the following method: centrifuging the concentrated sludge to obtain sludge supernatant and centrifuged sludge; the centrifugation conditions are at least: rotation speed of 5000-8000 r / min and time of 15-20 min.
[0041] It should be noted that the method for preparing sludge supernatant also includes concentrating the sludge before centrifugation. The concentration method is not particularly limited, and those skilled in the art can choose according to their needs. For example, residual sludge from the secondary sedimentation tank of a domestic wastewater treatment plant's biochemical treatment system is allowed to settle for 12–24 hours, then filtered to obtain concentrated sludge.
[0042] Preferably, in step S2, the sludge is obtained by the following method: taking the residual sludge from the secondary sedimentation tank of the biochemical treatment system of a domestic sewage treatment plant, allowing it to settle for 12-24 hours, filtering it to obtain concentrated sludge; centrifuging the concentrated sludge at 5000-8000 r / min for 15-20 minutes to obtain sludge supernatant and centrifuged sludge; drying the centrifuged sludge at 60-100℃ to constant weight, grinding it, and passing it through a 90-100 mesh sieve to obtain sludge.
[0043] It should be noted that the aforementioned method for preparing biochar-supported nano-zero-valent iron of the present invention may also involve various post-processing operations known in the art, such as washing, filtering, drying, sieving, etc. The present invention does not have any particular limitations in this regard, and those skilled in the art should not understand it as a limitation of the present invention.
[0044] For example, the mixture II obtained in step S2 is dried at 80-110°C for 6-8 hours to obtain dried mixture II.
[0045] For example, the modified biochar obtained in step S3 is passed through a 90-100 mesh sieve.
[0046] For example, in step S5, after the second contact, the solid is filtered and washed 3 to 5 times with deoxygenated deionized water and deoxygenated anhydrous ethanol, and then filtered again to obtain mixture B.
[0047] For example, the product obtained after the third contact is filtered, and the solid product is washed 3 to 5 times with deoxygenated deionized water and deoxygenated anhydrous ethanol in sequence; then the washed product is dried at 60 to 80°C for 22 to 26 hours; ground, and passed through a 90-100 mesh sieve, and the sieved biochar-supported nano-zero valence is stored in a centrifuge tube filled with inert gas for later use; the inert gas is nitrogen and / or argon.
[0048] Preferably, in step S1, the mass ratio of the water, CeCl3, RuCl3, and sodium dodecylbenzenesulfonate is 100:5–30:1–10:0.1–2. The inventors have found through research that, under this preferred condition, the obtained composite material exhibits better pollutant removal performance.
[0049] In a preferred embodiment, in step S2, the mass ratio of the sludge to the straw is 1 to 5:1; and the average particle size of the straw is 70 to 150 μm.
[0050] In the absence of a specific limitation on the water used in this invention, it can be deionized water, ultrapure water, etc. Those skilled in the art can choose according to their needs, and this should not be construed as a limitation of the invention.
[0051] This invention does not impose any particular limitations on the type or moisture content of the straw, and those skilled in the art can select according to their needs. Corn straw with a moisture content of 23-27 wt% is preferred.
[0052] Preferably, in step S4, the mass ratio of the modified biochar, the ferrous sulfate, and the polyethylene glycol is 40-55:40-55:1.
[0053] Preferably, the number average molecular weight of the polyethylene glycol is 3500-4500.
[0054] According to a preferred embodiment, in step S5, the molar ratio of NaBH4 to the mixture A (calculated as iron) is 1.5 to 3:1.
[0055] According to another preferred embodiment, in step S6, the molar ratio of the mixture B (based on iron) to the cobalt sulfate is 1:0.05 to 0.5.
[0056] More preferably, in step S6, the molar ratio of the mixture B (based on iron content) to the cobalt sulfate is 1:0.2 to 0.4. The inventors have found through research that, under this preferred condition, the resulting composite material exhibits better pollutant removal performance.
[0057] It should be noted that the present invention does not impose any particular limitations on the conditions for the first mixing, as long as the CeCl3, RuCl3, and sodium dodecylbenzenesulfonate can be completely dissolved in water. For example, CeCl3, RuCl3, and sodium dodecylbenzenesulfonate are stirred at 500 rpm for 10 minutes in the presence of water.
[0058] In a preferred embodiment, in step S2, the conditions for the second mixing are at least: a temperature of 5–25°C, a stirring speed of 160–280 r / min, and a time of 10–40 min.
[0059] In a preferred embodiment, in step S3, the heating conditions are as follows: the temperature is increased to 700-800°C at a heating rate of 5-10°C / min.
[0060] Preferably, in step S3, the modification conditions are at least satisfied as follows: time is 2 to 3 hours, temperature is 700 to 800°C, and CO2 flow rate is 0.8 to 1.5 L / min.
[0061] In a preferred embodiment, in step S4, the conditions for the first contact are at least: a temperature of 5–35°C and a time of 2–3 hours. It should be noted that the first contact described in this invention is preferably performed under ultrasonic conditions.
[0062] Preferably, in step S5, the conditions for the second contact are at least: temperature of 5 to 25°C, stirring speed of 160 to 280 r / min, and time of 10 to 40 min.
[0063] According to a preferred embodiment, in step S6, the conditions for the third contact are at least: the stirring speed is 160-280 r / min and the time is 10-40 min.
[0064] According to another preferred embodiment, in step (2), the emulsification conditions must at least satisfy: a rotation speed of 2500-2800 r / min and a time of 30-40 min.
[0065] In the process of preparing composite materials in this invention, unless the reaction temperature is explicitly stated in each step, it is indicated that the process is carried out at room temperature (25±5℃).
[0066] As previously stated, a second aspect of the present invention provides a composite material for the remediation of sites contaminated with halogenated hydrocarbons and heavy metals, prepared by the method described in the first aspect.
[0067] As previously stated, a third aspect of the present invention provides the application of the composite material described in the second aspect in the degradation of halogenated hydrocarbons and / or heavy metals.
[0068] Preferably, the halogenated hydrocarbon is trichloroethylene, and the heavy metal is hexavalent chromium.
[0069] Compared with the prior art, the technical solution of the present invention has the following advantages:
[0070] (1) The composite material prepared by the present invention loads nano-zero valent iron and Co on the surface of modified biochar, which can effectively prevent the nano-zero valent iron from agglomerating. Moreover, the modified biochar provides a large specific surface area, rich pore structure and surface functional groups (C=C, C=O bonds), which can enhance and promote the adsorption of halogenated hydrocarbons.
[0071] (2) Compared with ordinary biochar, the biochar supported on nano-zero valent iron provided by the present invention can simultaneously utilize the adsorption effect of biochar, the electrochemical effect provided by nano-zero valent iron, and the catalytic reduction of heavy metals and halogenated hydrocarbons by Co to promote the degradation of pollutants.
[0072] (3) The composite material prepared by the present invention utilizes emulsified oil and supernatant of residual sludge to provide carbon source and nutrients to promote the growth of microorganisms, so that the growth and reproduction of microorganisms can promote the degradation of halogenated hydrocarbons and reduced heavy metals.
[0073] (4) The composite material prepared by the present invention can simultaneously apply adsorption, biological, chemical and electrochemical action to the remediation of halogenated hydrocarbon-heavy metal contaminated sites, achieving the effect of efficient removal of heavy metals and halogenated hydrocarbons.
[0074] The present invention will be described in detail below through examples. Unless otherwise specified, the instruments, reagents, materials, etc. involved in the following examples are all conventional instruments, reagents, materials, etc. that are already available in the prior art and can be obtained through legitimate commercial channels.
[0075] The main materials used in the examples and comparative examples are all commercially available, as shown in Table 1:
[0076] Table 1
[0077]
[0078]
[0079] Example 1
[0080] (1) Preparation of biochar-supported nano-zero-valent iron
[0081] S0: Take 2000 mL of residual sludge from the secondary sedimentation tank of the biochemical treatment system of Qingdao Municipal Wastewater Treatment Plant, let it settle for 24 h, filter it to obtain concentrated sludge; centrifuge the concentrated sludge at 8000 r / min for 20 min to obtain sludge supernatant and centrifuged sludge; seal and store the sludge supernatant for later use; dry the centrifuged sludge at 80℃ to constant weight, grind it, and pass it through a 100-mesh sieve to obtain sludge; seal and store the sludge for later use.
[0082] S1: In the presence of water, CeCl3, RuCl3 and sodium dodecylbenzenesulfonate were stirred at 500 r / min for 10 min to obtain mixture I;
[0083] The mass ratio of the water, CeCl3, RuCl3, and sodium dodecylbenzenesulfonate is 100:20:5:0.57, and the mass of the water is 53g.
[0084] S2: The sludge and straw are soaked in the mixture I and then mixed in a second way to obtain mixture II; the mixture II is dried at 110°C for 6 hours to obtain dried mixture II;
[0085] The mass ratio of the sludge to the straw is 1:1; the amount of sludge used is 10g; the particle size of the straw is 120μm; the straw is corn stalks harvested from a farm in Laixi City, and the moisture content of the straw is 25wt%.
[0086] The conditions for the second mixing were: temperature 10°C, stirring speed 260 r / min, and time 40 min.
[0087] S3: The dried mixture II is heated under nitrogen protection, then CO2 is introduced for modification, nitrogen is introduced again and heating is stopped to obtain modified biochar, and the modified biochar is passed through a 100-mesh sieve.
[0088] The heating conditions are: heating to 750℃ at a heating rate of 5℃ / min; the modification conditions are: time of 3h, temperature of 750℃, and CO2 flow rate of 1.5L / min.
[0089] S4: In the presence of water and ethanol, the modified biochar is subjected to ultrasonic first contact with ferrous sulfate and polyethylene glycol to obtain mixture A;
[0090] The volume ratio of ethanol to water is 1:1; the volume of water is 150 mL.
[0091] The modified biochar, ferrous sulfate, and polyethylene glycol are used in a mass ratio of 40:40:1, and the polyethylene glycol weighs 0.25g.
[0092] The conditions for the first contact were: temperature 30°C and time 2 hours.
[0093] S5: Under nitrogen protection, NaBH4 (concentration of 15mol / L) is added dropwise to the mixture A for a second contact, filtered, and the solid after filtration is washed 5 times with deoxygenated deionized water and deoxygenated anhydrous ethanol, and then filtered again to obtain mixture B.
[0094] The molar ratio of NaBH4 to the mixture A (based on iron content) is 2:1.
[0095] The conditions for the second contact were: temperature 20°C, stirring speed 200 r / min, and time 40 min.
[0096] S6: Under nitrogen protection, the mixture B is brought into a third contact with cobalt sulfate (concentration of 0.6 wt%);
[0097] The conditions for the third contact are: stirring speed of 200 r / min and time of 40 min;
[0098] The molar ratio of the mixture B, calculated as iron, to the cobalt sulfate is 1:0.35.
[0099] S7: The product obtained after the third contact was filtered and washed five times with deoxygenated deionized water and deoxygenated anhydrous ethanol. The washed product was then dried at 70°C for 24 hours. It was then ground and passed through a 100-mesh sieve to obtain biochar-supported nano-zero valent iron.
[0100] (2) Vegetable oil, Tween 80, Span 80, sludge supernatant, biochar-supported nano-zero valent iron and water in a mass ratio of 1:0.2:0.2:1:1.5:20 were emulsified to obtain composite material T1;
[0101] The vegetable oil is soybean oil, and the mass of the soybean oil is 10g;
[0102] The emulsification conditions were: rotation speed of 2800 r / min and time of 40 min.
[0103] Example 2
[0104] The preparation method of this embodiment is similar to that of embodiment 1, except that in step S2, the mass ratio of the sludge to the straw is 3:1; and the amount of sludge used is 15g.
[0105] The conditions for the second mixing were: temperature 25°C, stirring speed 180 r / min, and time 30 min.
[0106] In step S3, the heating conditions are: heating to 800℃ at a heating rate of 7℃ / min; the modification conditions are: time of 2h, temperature of 800℃, and CO2 flow rate of 1L / min.
[0107] In step S4, the conditions for the first contact are: temperature 20°C and time 3 hours.
[0108] In step (2), vegetable oil, Tween 80, Span 80, sludge supernatant, biochar-supported nano-zero valent iron, and water in a mass ratio of 1:0.2:0.2:1:0.7:20 are emulsified.
[0109] The emulsification conditions were: rotation speed of 2500 r / min and time of 30 min;
[0110] Composite material T2 was obtained.
[0111] Example 3
[0112] The preparation method of this embodiment is similar to that of Embodiment 1, except that in step S2, the conditions for the second mixing are: temperature of 15°C, stirring speed of 280 r / min, and time of 20 min.
[0113] In step S5, the conditions for the second contact are: temperature 25°C, stirring speed 260 r / min, and time 15 min.
[0114] In step S6, the conditions for the third contact are: stirring speed of 260 r / min and time of 15 min;
[0115] In step (2), vegetable oil, Tween 80, Span 80, sludge supernatant, biochar-supported nano-zero valent iron, and water in a mass ratio of 1:0.2:0.2:1:2:20 are emulsified.
[0116] Composite material T3 was prepared.
[0117] Example 4
[0118] The preparation method of this embodiment is similar to that of Example 1, except that in step S1, the mass ratio of water, CeCl3, RuCl3, and sodium dodecylbenzenesulfonate is 100:11.3:2.83:0.19, and the mass of water is 53g.
[0119] Composite material T4 was prepared.
[0120] Example 5
[0121] The preparation method of this embodiment is similar to that of Example 1, except that in step S4, the volume ratio of ethanol to water is 1:2; the volume of water is 200mL; the mass ratio of modified biochar, ferrous sulfate, and polyethylene glycol is 50:55:1; and the mass of polyethylene glycol is 0.25g.
[0122] Composite material T5 was obtained.
[0123] Example 6
[0124] The preparation method of this embodiment is similar to that of Example 1, except that in step S6, the molar ratio of the mixture B (calculated as iron) to the cobalt sulfate is 1:0.2.
[0125] Composite material T6 was prepared.
[0126] Example 7
[0127] The preparation method of this embodiment is similar to that of Example 1, except that in step S5, the molar ratio of NaBH4 to the mixture A (calculated as iron) is 3:1.
[0128] Composite material T7 was obtained.
[0129] Comparative Example 1
[0130] The preparation method of this comparative example is similar to that of Example 1, except that this method does not involve the addition of CeCl3, RuCl3, and sodium dodecylbenzenesulfonate to modify the sludge and straw; specifically,
[0131] In step S2, 10g of sludge and 10g of straw are mixed for the second time to obtain mixture II;
[0132] The composite material DT1 was prepared.
[0133] Comparative Example 2
[0134] The preparation method of this comparative example is similar to that of Example 1, except that cobalt sulfate is not added in step S6.
[0135] The composite material DT2 was prepared.
[0136] Comparative Example 3
[0137] The preparation method of this comparative example is similar to that of Example 1, except that the CO2 introduced in step S3 is replaced with nitrogen gas.
[0138] The composite material DT3 was prepared.
[0139] Comparative Example 4
[0140] The preparation method of this comparative example is similar to that of Example 1. The difference is that in step (2), vegetable oil, Tween 80, Span 80, sludge supernatant, biochar-supported nano-zero valent iron and water in a mass ratio of 1:0.4:0.7:3:4:20 are emulsified.
[0141] The composite material DT4 was prepared.
[0142] Comparative Example 5
[0143] The preparation method of this comparative example is similar to that of Example 1, except that in step (2), Tween 80 and Span 80 are not added, while other components remain unchanged;
[0144] The composite material DT5 was prepared.
[0145] Test case
[0146] Take 500g of soil from the aquifer of the contaminated site. The soil has a pH of 7.3 and a permeability coefficient of 7 × 10⁻⁶. -5 The soil concentration was 65 mg / kg, Cr(VI) concentration was 288 mg / kg, and the soil moisture content was 80%. 500 g of soil was thoroughly mixed with 10 g of the compound remediation agent. Deionized water was added to adjust the soil moisture content to 80%. The mixed soil was placed in a brown wide-mouth bottle and sealed and protected from light at 25℃ for 60 days. Samples were then taken for testing. The test results are shown in Table 2.
[0147] Removal rate = (C0 - C) / C0 × 100%
[0148] C0 represents the initial concentration of the pollutant, and C represents the final concentration of the pollutant, with the unit being mg / kg.
[0149] Table 2
[0150] Composite material number Cr(VI) removal rate / % Trichloroethylene removal rate / % T1 95.2 98.8 T2 93.2 96.9 T3 94.5 97.5 T4 92.9 95.6 T5 93.2 96.4 T6 93.1 95.5 T7 94.8 97.7 DT1 75.1 76.3 DT2 79.7 79.3 DT3 86.6 89.7 DT4 86.3 88.5 DT5 81.5 84.8
[0151] As can be seen from the results in Table 2, the composite materials prepared in the embodiments of the present invention have a removal rate of Cr(VI) in the aquifer soil of contaminated sites of more than 92% and a removal rate of trichloroethylene of more than 95%, which are obvious effects.
[0152] Comparing Example 1 with Comparative Example 1, it can be found that the addition of CeCl3, RuCl3 and sodium dodecylbenzenesulfonate to modify sludge and straw can make the modified biochar have higher catalytic activity, improve electron transport efficiency, promote the catalytic reduction of Cr(VI) and trichloroethylene, thereby improving the removal rate of Cr(VI) and trichloroethylene by the composite material.
[0153] Comparing Example 1 with Comparative Example 2, it can be found that adding cobalt sulfate for modification during the preparation of biochar-supported nano-zero-valent iron results in a composite material with higher catalytic activity, promoting the catalytic reduction of Cr(VI) and trichloroethylene, thereby improving the removal rate of Cr(VI) and trichloroethylene.
[0154] Comparing Example 1 with Comparative Example 3, it can be found that modifying biochar with CO2 can increase the porous structure of the biochar surface, increase the specific surface area of the biochar, and optimize the proportion of surface functional groups, thereby improving the adsorption capacity and catalytic degradation capacity of the prepared composite material for Cr(VI) and trichloroethylene.
[0155] Comparing Example 1 with Comparative Example 4, it can be seen that the composite material prepared by compounding vegetable oil, Tween 80, Span 80, sludge supernatant, biochar-supported nano-zero valent iron, and water in a mass ratio of 1:0.1-0.3:0.1-0.3:1-2:0.7-2:15-30 has a better synergistic effect and can remove Cr(VI) and trichloroethylene more efficiently.
[0156] Comparing Example 1 with Comparative Example 5, it can be seen that Tween 80 and Span 80 can improve the removal efficiency of the composite material for Cr(VI) and trichloroethylene. This is because the addition of Tween 80 and Span 80 can improve the emulsification and dispersion of vegetable oil, enhance the dispersibility and stability of biochar-supported nano-zero-valent iron in the mixed material, prevent the agglomeration of biochar-supported nano-zero-valent iron particles, and more fully utilize the synergistic effect of the composite material and microorganisms on the adsorption, Fenton-like catalytic reduction, and biocatalytic reduction of Cr(VI) and trichloroethylene.
[0157] 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 composite material for the remediation of sites contaminated with halohydrocarbons and heavy metals, characterized in that, The method includes: (1) Preparation of biochar-supported nano-zero-valent iron S1: In the presence of water, CeCl3, RuCl3 and sodium dodecylbenzenesulfonate are first mixed to obtain mixture I; S2: The sludge and straw are soaked in the mixture I and then mixed a second time to obtain mixture II; S3: The dried mixture II is heated under nitrogen protection, then CO2 is introduced for modification, nitrogen is introduced again and heating is stopped to obtain modified biochar; S4: In the presence of water and ethanol, the modified biochar is first contacted with ferrous sulfate and polyethylene glycol to obtain mixture A; the volume ratio of ethanol to water is 1:1-2. S5: Under nitrogen protection, the mixture A is brought into a second contact with NaBH4 to obtain mixture B; S6: Under nitrogen protection, the mixture B is brought into a third contact with cobalt sulfate to obtain the biochar-supported nano-zero-valent iron. (2) Vegetable oil, polyoxyethylene sorbitan monooleate, dehydrated sorbitan monooleate, sludge supernatant, biochar-supported nano-zero valent iron and water in a mass ratio of 1:0.1~0.3:0.1~0.3:1~2:0.7~2:15~30 are emulsified to obtain a composite material; The vegetable oil is selected from at least one of soybean oil, corn oil, rapeseed oil, and peanut oil; The sludge supernatant contains proteins, carbohydrates, lipids, and organic acids; the sludge in the sludge supernatant is the residual sludge from the secondary sedimentation tank of the biochemical treatment system in a domestic sewage treatment plant.
2. The method according to claim 1, wherein, The sludge supernatant obtained in step (2) is obtained by the following method: The concentrated sludge is centrifuged to obtain sludge supernatant and centrifuged sludge; the centrifugation conditions must at least meet the following: rotation speed of 5000~8000 r / min and time of 15~20 min.
3. The method according to claim 1 or 2, wherein, In step S1, the mass ratio of the water, CeCl3, RuCl3, and sodium dodecylbenzenesulfonate is 100:5~30:1~10:0.1~2.
4. The method according to claim 1 or 2, wherein, In step S2, the mass ratio of the sludge to the straw is 1~5:1; the average particle size of the straw is 70~150μm.
5. The method according to claim 1 or 2, wherein, In step S4, the mass ratio of the modified biochar, the ferrous sulfate, and the polyethylene glycol is 40~55:40~55:
1.
6. The method according to claim 1 or 2, wherein, In step S5, the molar ratio of NaBH4 to the mixture A (based on iron) is 1.5 to 3:
1.
7. The method according to claim 1 or 2, wherein, In step S6, the molar ratio of the mixture B (based on iron content) to the cobalt sulfate is 1:0.05~0.
5.
8. The method according to claim 1 or 2, wherein, In step S2, the conditions for the second mixing must at least satisfy: temperature of 5~25℃, stirring speed of 160~280 r / min, and time of 10~40 min; and / or In step S3, the modification conditions must at least satisfy: time of 2-3 hours, temperature of 700-800°C, and CO2 flow rate of 0.8-1.5 L / min; and / or In step S4, the conditions for the first contact are at least: a temperature of 5~35℃ and a time of 2~3 hours; and / or In step S5, the conditions for the second contact must at least satisfy: temperature of 5~25℃, stirring speed of 160~280 r / min, and time of 10~40 min; and / or In step S6, the conditions for the third contact must at least satisfy: a stirring speed of 160~280 r / min and a time of 10~40 min; and / or In step (2), the emulsification conditions must at least meet the following requirements: rotation speed of 2500~2800 r / min and time of 30~40 min.
9. A composite material for remediation of sites contaminated with halogenated hydrocarbons and heavy metals, prepared by the method according to any one of claims 1-8.
10. The application of the composite material of claim 9 in the degradation of halogenated hydrocarbons and / or heavy metals.