A composite material composition for groundwater remediation, a composite material and a preparation method and application thereof

Abstract

The present application relates to the technical field of sewage treatment, and discloses a composite material composition for groundwater remediation, a composite material, and a preparation method and application thereof.The composition contains modified nano zero-valent iron, cobalt chloride modified biochar, attapulgite, persulfate, and a binder; the mass ratio of the modified nano zero-valent iron, the cobalt chloride modified biochar, the attapulgite, the persulfate, and the binder is 1:2-6:0.5-1.5:1-3:16-40.The composite material provided by the present application forms a micro-electrolysis environment by using carbon nitride modified nano zero-valent iron and cobalt chloride modified biochar, can effectively improve the selectivity and removal rate of target pollutants, and can continuously play the roles of adsorption, Fenton-like catalytic oxidation, and micro-electrolysis in the process of treating contaminated groundwater after being embedded by the binder, so that the purpose of efficiently removing pollutants in groundwater is achieved.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a composite material composition for groundwater remediation, a composite material for groundwater remediation, its preparation method, and its application. Background Technology

[0002] Groundwater remediation technologies include ex-situ remediation and in-situ remediation. Ex-situ remediation primarily involves pumping groundwater to the surface and treating it using wastewater treatment technologies, requiring the construction of above-ground wastewater treatment facilities. In-situ remediation technologies include in-situ chemical oxidation, bioremediation, in-situ aeration, and permeable reactive barrier (PRB) technology. For operating industries and enterprises, due to limitations imposed by production operations and above-ground structures, in-situ remediation technologies are more suitable for controlling groundwater pollution risks. Permeable reactive barrier (PRB) technology, which originated in the United States in the 1980s, involves installing a permeable reactive barrier filled with reactive materials perpendicular to the direction of groundwater flow. When contaminants migrate along the water flow direction and pass through the PRB, they react with the filling material within the barrier, leading to the degradation or in-situ fixation of the contaminants. Since the contaminated water flows through the reactive barrier by gravity, no additional power or above-ground treatment systems are required. Therefore, selecting appropriate reactive materials for different contaminants in groundwater is crucial for groundwater remediation.

[0003] Iron is a common, inexpensive, and readily available metallic element. Its application in environmental remediation is not only cost-effective but also avoids secondary pollution. Nano-zero-valent iron (nZVI), a novel environmental remediation material commonly used in recent years, is one of the fillers frequently used in groundwater remediation (PRB). 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. 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, and is one of the commonly used fillers in biochar remediation (PRB). Common raw materials for biochar preparation 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. Although biochar has many advantages in environmental remediation, for single-phase biochar, its adsorption capacity and kinetic rate are generally insufficient to meet the requirements for efficient removal of organic pollutants from the environment. Furthermore, when biochar is used to adsorb organic pollutants, solid-liquid separation is difficult to achieve, and the long-term effectiveness and stability of pollutant removal also face some challenges. Therefore, the preparation of composite materials with unique remediation functions using biochar as a carrier or auxiliary catalyst is attracting increasing attention.

[0005] In-situ chemical oxidation remediation technology for organically contaminated sites has advantages such as broad applicability, good remediation effect, and short remediation cycle. Commonly used oxidants include Fenton's reagent, permanganate, persulfate, and ozone. Fenton's reagent can react with most organic matter and adsorbed pollutants, but its stability is relatively poor. Ozone can also react with most organic matter, but its treatment effect is easily limited by mass transfer and solubility, and it is also affected by the toxicity of byproducts. Permanganate is relatively stable in the underground environment, but its reaction is selective, and permanganate reacts rapidly with natural organic matter in the soil. The resulting manganese dioxide precipitate can clog soil pores and affect the transport of oxidants.

[0006] Persulfate, as a novel in-situ chemical oxidative remediation agent, exhibits advantages such as good stability, wide pH applicability, and being green and non-toxic. Its oxidation mechanism involves the cleavage of its -OO- groups under activation, generating highly oxidizing sulfate free radicals (SO₄²⁻). 4- ·, SO 4- The SO₂ contains a lone pair of electrons, giving it an oxidizing power exceeding that of persulfate itself and approaching that of the hydroxyl radical ·OH. 4- The long half-life of · allows for more complete contact with pollutants. In addition, persulfate can generate ·OH after activation, which can oxidize recalcitrant organic pollutants such as polychlorinated biphenyls.

[0007] CN104803486A discloses a permeable reactive wall material for remediating chromium contamination in groundwater. This material includes a reducing agent and an adsorption medium, and 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.

[0008] CN104138745A discloses a method for preparing a biocarbon adsorbent for the remediation of organic pollution. This material only has the function of adsorbing pollutants and is difficult to completely degrade pollutants. Moreover, 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.

[0009] 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 does not have a slow-release function or long-term effect. Summary of the Invention

[0010] The purpose of this invention is to solve the problem of poor removal effect of groundwater pollutants in the prior art, and to provide a composite material for groundwater remediation.

[0011] To achieve the above objectives, a first aspect of the present invention provides a composite material composition for groundwater remediation, the composition comprising modified nano-zero valent iron, cobalt chloride-modified biochar, attapulgite, persulfate, and a binder; wherein the mass ratio of the modified nano-zero valent iron, the cobalt chloride-modified biochar, the attapulgite, the persulfate, and the binder is 1:2-6:0.5-1.5:1-3:16-40;

[0012] The persulfate is sodium persulfate and / or potassium persulfate;

[0013] The modified nano-zero-valent iron is prepared by a method comprising the following steps:

[0014] S1: Under a protective atmosphere and in the presence of oxygen-free water, cobalt nitrate, manganese nitrate, copper nitrate, ammonium fluoride, and urea are mixed to obtain mixture A.

[0015] S2: Mix the mixture A with sodium percarbonate for a second time. The pH value of the resulting solution is greater than 10, thus obtaining the Co-Mn-Cu catalyst.

[0016] S3: In an ethanol-water solution, carbon nitride, Co-Mn-Cu catalyst, and FeCl3 are mixed for the third time to obtain mixture B. In the ethanol-water solution, the volume ratio of water to ethanol is 1:1-4.

[0017] S4: Under a protective atmosphere, the mixture B is mixed with NaBH4 for the fourth time to obtain the modified nano-zero valent iron.

[0018] A second aspect of the present invention provides a method for preparing a composite material for groundwater remediation, the method being carried out using the composite material composition for groundwater remediation described in the first aspect, comprising:

[0019] 1) Preparation of modified nano-zero-valent iron and cobalt chloride-modified biochar;

[0020] 2) Modified nano-zero valent iron, cobalt chloride-modified biochar, attapulgite, and persulfate were brought into first contact to obtain mixture I;

[0021] 3) The mixture I is brought into a second contact with the binder to obtain a composite material.

[0022] A third aspect of the present invention provides a composite material for groundwater remediation prepared by the method described in the second aspect.

[0023] The fourth aspect of the present invention provides the application of the composite material for groundwater remediation described in the third aspect in the removal of at least one of benzene and its derivatives.

[0024] The present invention can significantly improve the removal rate of the composite material obtained by applying the modified nano-zero valent iron, cobalt chloride modified biochar, attapulgite, persulfate and binder in a mass ratio of 1:2-6:0.5-1.5:1-3:16-40.

[0025] This invention prepares modified nano-zero-valent iron with catalytic function by adding a Co-Mn-Cu catalyst and carbon nitride. This modified nano-zero-valent iron is less prone to agglomeration, oxidation, and caking, possesses a larger specific surface area and higher conductivity, and provides more active reaction sites. This enhances the activation effect of nano-zero-valent iron on sodium persulfate, increases the generation efficiency of hydroxyl radicals, and thus improves the oxidation capacity for organic pollutants. The modified nano-zero-valent iron and cobalt chloride-modified biochar can form a strengthened micro-electrolysis environment, improving electron transport efficiency during the micro-electrolysis degradation of pollutants. Simultaneously, the cobalt chloride-modified biochar can enhance the activation effect on sodium persulfate, increasing the oxidation capacity of persulfate, thereby achieving the synergistic adsorption and oxidative degradation of different pollutants by the composite material.

[0026] Meanwhile, the slow-release composite material encapsulated with binder can exert long-term and continuous adsorption, Fenton-like catalytic oxidation and micro-electrolysis effects in the process of treating polluted groundwater, so as to achieve the purpose of efficiently removing pollutants from groundwater. Detailed Implementation

[0027] 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.

[0028] As previously stated, a first aspect of the present invention provides a composite material composition for groundwater remediation, the composition comprising modified nano-zero valent iron, cobalt chloride-modified biochar, attapulgite, persulfate, and a binder; wherein the mass ratio of the modified nano-zero valent iron, the cobalt chloride-modified biochar, the attapulgite, the persulfate, and the binder is 1:2-6:0.5-1.5:1-3:16-40;

[0029] The persulfate is sodium persulfate and / or potassium persulfate;

[0030] The modified nano-zero-valent iron is prepared by a method comprising the following steps:

[0031] S1: Under a protective atmosphere and in the presence of oxygen-free water, cobalt nitrate, manganese nitrate, copper nitrate, ammonium fluoride, and urea are mixed to obtain mixture A.

[0032] S2: Mix the mixture A with sodium percarbonate for a second time. The pH value of the resulting solution is greater than 10, thus obtaining the Co-Mn-Cu catalyst.

[0033] S3: In an ethanol-water solution, carbon nitride, Co-Mn-Cu catalyst, and FeCl3 are mixed for the third time to obtain mixture B. In the ethanol-water solution, the volume ratio of water to ethanol is 1:1-4.

[0034] S4: Under a protective atmosphere, the mixture B is mixed with NaBH4 for the fourth time to obtain the modified nano-zero valent iron.

[0035] In a preferred embodiment, the protective atmosphere is at least one of nitrogen and argon.

[0036] Preferably, the mass ratio of the modified nano-zero-valent iron, the cobalt chloride-modified biochar, the attapulgite, the persulfate, and the binder is 1:3-5:0.5-1.5:1-3:24-32. The inventors have found that, under this preferred condition, the obtained composite material exhibits better pollutant removal performance.

[0037] Preferably, the adhesive is formed from sodium alginate, polyvinyl alcohol and water in a mass ratio of 1:5-12:100-500.

[0038] More preferably, the binder is formed from sodium alginate, polyvinyl alcohol, and water in a mass ratio of 1:5-12:160-300. The inventors have found that, under this preferred condition, the resulting composite material exhibits better pollutant removal performance.

[0039] The present invention does not specifically limit the water used in the adhesive; it can be deionized water, ultrapure water, etc., and those skilled in the art should not understand this as a limitation of the present invention.

[0040] Unless otherwise specified in this invention, all ethanol used is anhydrous ethanol.

[0041] The attapulgite clay described in this invention is a hydrous magnesium aluminum silicate clay mineral with a layered chain structure; the average particle size of the attapulgite clay is 50-100 μm.

[0042] Preferably, in step S1, the mass ratio of copper nitrate, cobalt nitrate, manganese nitrate, ammonium fluoride, and urea is 1:2-5:1.5-2.5:9-11:4.5-5.5.

[0043] Preferably, in step S2, the amount of sodium percarbonate is controlled so that the pH value of the second mixed solution is greater than 10.

[0044] In a preferred embodiment, in step S3, the mass ratio of the carbon nitride, the Co-Mn-Cu catalyst, and the FeCl3 is 0.3-2:0.1-0.5:1.

[0045] More preferably, in step S3, the mass ratio of the carbon nitride, the Co-Mn-Cu catalyst, and the FeCl3 is 0.8-1.2:0.2-0.3:1. The inventors have found through research that, under this preferred condition, the obtained composite material exhibits better pollutant removal performance.

[0046] Preferably, in step S4, the molar ratio of NaBH4 to the molar ratio of the mixture B (calculated as iron) is 2-4:1.

[0047] According to a preferred embodiment, in step S1, the conditions for the first mixing are at least: the stirring speed is 180-260 r / min and the time is 20-40 min.

[0048] According to another preferred embodiment, in step S2, the conditions for the second mixing are at least: a temperature of 20-40°C and a time of 12-24 hours.

[0049] Preferably, in step S3, the conditions for the third mixing are at least: a stirring speed of 180-260 r / min and a time of 20-30 min.

[0050] In a preferred embodiment, in step S4, the conditions for the fourth mixing are at least: a stirring speed of 180-260 r / min and a time of 30-40 min.

[0051] According to a preferred embodiment, the method for preparing modified nano-zero-valent iron further includes: performing solid-liquid separation, washing, drying (I), and sieving the solution after the second mixing to obtain a Co-Mn-Cu catalyst; the drying (I) conditions are drying at 50-70°C for 11-13 hours. It should be noted that the present invention does not particularly limit the specific methods of solid-liquid separation and washing, and those skilled in the art can choose according to their needs. Exemplarily, the solution after the second mixing is subjected to vacuum filtration to achieve solid-liquid separation, the solid precipitate is collected, and the solid precipitate is washed alternately with deionized water and ethanol until neutral, then dried (I) and sieved through a 100-mesh sieve.

[0052] According to another preferred embodiment, the method for preparing modified nano-zero valent iron further includes: before the carbon nitride is mixed for the third time, the carbon nitride needs to be prepared, and the method for preparing the carbon nitride includes: calcining dicyandiamide under anaerobic conditions to obtain carbon nitride;

[0053] The calcination conditions must at least meet the following requirements: heating rate of 5-6℃ / min, temperature of 500-600℃, and time of 2-3h.

[0054] In a preferred embodiment, the method for preparing the carbon nitride further includes passing the obtained carbon nitride through a 90-100 mesh sieve.

[0055] In a preferred embodiment, the method for preparing modified nano-zero valent iron further includes: post-processing the product obtained after the fourth mixing.

[0056] It should be noted that the post-processing described in this invention may involve solid-liquid separation, washing, drying, grinding, sieving, etc., and this invention does not have any particular limitations in this regard. Those skilled in the art can choose according to their needs. For example, a magnet is used to separate the product obtained after the fourth mixing into solid and liquid phases to obtain modified nano-zero-valent iron solid; then the modified nano-zero-valent iron solid is washed 2-4 times with oxygen-free deionized water and anhydrous ethanol in sequence; the washed product is then placed in a vacuum drying oven and dried at 50-70°C for 6-8 hours; after cooling to room temperature, it is ground through a 100-mesh sieve, and finally the dried product is stored in a centrifuge tube filled with nitrogen gas for later use.

[0057] Preferably, the cobalt chloride-modified biochar is prepared by a method comprising the following steps:

[0058] SS1: The sludge, ammonia, cobalt chloride and solvent are mixed in a fifth step to obtain mixture C;

[0059] SS2: The mixture C is subjected to a hydrothermal reaction to obtain mixture D;

[0060] SS3: Under nitrogen protection, the dried mixture D is heated and pyrolyzed to obtain cobalt chloride modified biochar.

[0061] In a preferred embodiment, the sludge is the residual sludge discharged from the bottom of the secondary sedimentation tank of a municipal wastewater treatment plant.

[0062] In this invention, the method for preparing cobalt chloride modified biochar further includes: first pretreating the sludge from step SS1, and then mixing the sludge in a fifth step. It should be noted that this invention does not have specific requirements for the specific operation of the pretreatment; the pretreatment may involve static sedimentation, centrifugation, filtration, drying, grinding, sieving, etc., and those skilled in the art can choose according to their needs.

[0063] For example, the residual sludge discharged from the bottom of the secondary sedimentation tank of a municipal sewage treatment plant is taken, allowed to settle, and the lower sedimentation sludge is centrifuged at 3000-5000 r / min for 5-15 min; the centrifuged sludge is then filtered; the filtered sludge is then placed in an oven and dried at 80-120℃ to constant weight, ground, and passed through a 90-100 mesh sieve to obtain the sludge.

[0064] In a preferred embodiment, the method for preparing cobalt chloride-modified biochar further includes: solid-liquid separation, washing, and drying of the product obtained after the hydrothermal reaction. It should be noted that the present invention does not particularly limit the specific methods of solid-liquid separation, washing, and drying; those skilled in the art can use known techniques. For example, the product obtained after the hydrothermal reaction is subjected to solid-liquid separation by vacuum filtration, the mixed solid powder is collected, washed 3-5 times with isopropanol, centrifuged and filtered dry, and the resulting powder is dried in an oven at 80-100°C to constant weight.

[0065] Preferably, in step SS1, the solvent is at least one of isopropanol, ethylene glycol, propylene glycol, and glycerol.

[0066] Preferably, in step SS1, the mass ratio of the sludge, the ammonia water, the cobalt chloride, and the solvent is 1:1-2:0.05-0.3:30-40.

[0067] Preferably, in step SS1, the mass fraction of the ammonia water is 25%-28%.

[0068] In a preferred embodiment, in step SS1, the conditions for the fifth mixing are at least: a time of 60-120 min and a stirring speed of 180-260 r / min.

[0069] According to a preferred embodiment, in step SS2, the conditions for the hydrothermal reaction are at least: a temperature of 160-200°C and a time of 18-36 hours.

[0070] According to another preferred embodiment, in step SS3, the pyrolysis conditions must at least satisfy: a heating rate of 3-6℃ / min, a temperature of 750-850℃, and a time of 6-8h.

[0071] Preferably, the method for preparing cobalt chloride modified biochar further includes: cooling the solid powder after pyrolysis to room temperature under nitrogen protection, and then passing the solid powder through a 100-mesh sieve to obtain cobalt chloride modified biochar.

[0072] As previously described, a second aspect of the present invention provides a method for preparing a composite material for groundwater remediation, the method being carried out using the composite material composition for groundwater remediation described in the first aspect, comprising:

[0073] 1) Preparation of modified nano-zero-valent iron and cobalt chloride-modified biochar;

[0074] 2) Modified nano-zero valent iron, cobalt chloride-modified biochar, attapulgite, and persulfate were brought into first contact to obtain mixture I;

[0075] 3) The mixture I is brought into a second contact with the binder to obtain a composite material.

[0076] Unless otherwise specified, the definitions and amounts of the modified nano-zero valent iron, cobalt chloride modified biochar, attapulgite, persulfate, and binder described in the second aspect of this invention are the same as those of the corresponding components described in the first aspect. This invention will not repeat them here, and those skilled in the art should not understand them as limitations on this invention.

[0077] It should be noted that the present invention does not impose any particular restrictions on the conditions of the first contact in step 2). As long as the modified nano-zero valent iron, the cobalt chloride modified biochar, the attapulgite clay, and the persulfate can be mixed evenly, those skilled in the art can use known technical means.

[0078] According to a preferred embodiment, in step 3), the conditions for the second contact are at least: temperature of 20-25°C, stirring speed of 150-180 r / min, and time of 8-12 h.

[0079] According to another preferred embodiment, the method further includes: before step 3), preparing the adhesive, and then making a second contact between the prepared adhesive and the mixture I; the method for preparing the adhesive includes:

[0080] Sodium alginate, polyvinyl alcohol, and water are mixed and stirred to obtain an adhesive; the mass ratio of sodium alginate, polyvinyl alcohol, and water is 1:5-12:100-500.

[0081] More preferably, the mass ratio of sodium alginate, polyvinyl alcohol and water is 1:5-12:160-300.

[0082] Preferably, the mixing conditions should at least meet the following requirements: temperature of 5-25℃, stirring speed of 150-180 r / min, and time of 20-40 min.

[0083] In a preferred embodiment, the method further includes: extruding, granulating, and drying the product obtained after the second contact.

[0084] Preferably, the average particle size of the product obtained after granulation is 5-10 mm.

[0085] In a preferred embodiment, the drying conditions shall at least satisfy the following: time of 2-4 hours and temperature of 50-70°C.

[0086] As previously stated, a third aspect of the present invention provides a composite material for groundwater remediation prepared by the method described in the first aspect.

[0087] As previously stated, the fourth aspect of the present invention provides the application of the composite material for groundwater remediation described in the third aspect in the removal of at least one of benzene and its derivatives.

[0088] Preferably, the benzene derivative is at least one of toluene and ethylbenzene.

[0089] The present invention will be described in detail below through examples. Unless otherwise specified, the instruments, reagents, and materials involved in the following examples are all conventional instruments, reagents, and materials already existing in the prior art and can be obtained through legitimate commercial channels. Unless otherwise specified, the reaction temperature in the examples indicates that the reaction was carried out at room temperature (25±5℃).

[0090] The main materials used in the examples and comparative examples are all commercially available, as shown in Table 1:

[0091] Table 1

[0092]

[0093] Preparation Example 1: Preparation of modified nano-zero valent iron M1

[0094] S1: In the presence of nitrogen and under the condition of oxygen-free water, cobalt nitrate, manganese nitrate, copper nitrate, ammonium fluoride and urea are mixed for the first time to obtain mixture A;

[0095] The mass ratio of copper nitrate, cobalt nitrate, manganese nitrate, ammonium fluoride, and urea is 1:3:2:10:5; the mass of copper nitrate is 1g.

[0096] The conditions for the first mixing were: stirring speed of 180 r / min and time of 30 min.

[0097] S2: The mixture A and sodium percarbonate are mixed for the second time in a constant temperature water bath shaker. The pH value of the mixed solution is 11. The solution after mixing is filtered by vacuum to achieve solid-liquid separation. The solid precipitate is collected and washed with deionized water and ethanol alternately until neutral. The solid precipitate is then dried at 60°C for 12 hours and passed through a 100-mesh sieve to obtain the Co-Mn-Cu catalyst.

[0098] The conditions for the second mixing were: temperature 25°C and time 24 hours.

[0099] S3: 15g of dicyandiamide was calcined under anaerobic conditions and passed through a 100-mesh sieve to obtain carbon nitride.

[0100] The calcination conditions are as follows: heating rate of 5℃ / min, temperature of 550℃, and time of 2h.

[0101] S4: In an ethanol-water solution, carbon nitride, Co-Mn-Cu catalyst, and FeCl3 are mixed for the third time to obtain mixture B.

[0102] In the ethanol-water solution, the volume ratio of water to ethanol is 1:2; the volume of water is 100 mL.

[0103] The mass ratio of the carbon nitride, the Co-Mn-Cu catalyst, and the FeCl3 is 1:0.25:1, and the mass of the carbon nitride is 8g.

[0104] The conditions for the third mixing are: stirring speed of 220 r / min and time of 30 min.

[0105] S5: In the presence of nitrogen, the mixture B is mixed with NaBH4 (concentration of 15 mol / L) for the fourth time;

[0106] The molar ratio of NaBH4 to the molar ratio of the mixture B (calculated as iron) is 3:1.

[0107] The conditions for the fourth mixing are: stirring speed of 200 r / min and time of 30 min.

[0108] S6: Use a magnet to separate the solid and liquid components of the product obtained after the fourth mixing to obtain modified nano-zero valent iron solid; then wash the modified nano-zero valent iron solid three times with oxygen-free deionized water and anhydrous ethanol; then place the washed product in a vacuum drying oven and dry it at 60°C for 8 hours, cool it to room temperature, grind it, and pass it through a 100-mesh sieve to obtain the modified nano-zero valent iron M1.

[0109] Preparation Example 2: Preparation of modified nano-zero valent iron M2

[0110] This preparation example is similar to the method of preparing modified nano-zero valent iron in Preparation Example 1, except that in step S1, the conditions for the first mixing are: stirring speed of 260 r / min and time of 40 min.

[0111] In step S2, the conditions for the second mixing are: temperature 40°C and time 15 hours.

[0112] In step S3, the calcination conditions are: heating rate of 6℃ / min, temperature of 600℃, and time of 3h.

[0113] In step S4, in the ethanol-water solution, the volume ratio of water to ethanol is 1:4; the volume of water is 100 mL.

[0114] The mass ratio of the carbon nitride, the Co-Mn-Cu catalyst, and the FeCl3 is 1.2:0.3:1, and the mass of the carbon nitride is 8g.

[0115] In step S5, the ratio of the molar amount of NaBH4 to the molar amount of the mixture B (calculated as iron) is 4:1.

[0116] Modified nano-zero valent iron M2 was prepared.

[0117] Preparation Example 3: Preparation of modified nano-zero valent iron M3

[0118] This preparation example is similar to the method of preparing modified nano-zero valent iron in Preparation Example 1, except that in step S4, the conditions for the third mixing are: stirring speed of 260 r / min and time of 20 min.

[0119] The mass ratio of the carbon nitride, the Co-Mn-Cu catalyst, and the FeCl3 is 0.6:0.2:1, and the mass of the carbon nitride is 8g.

[0120] In step S5, the conditions for the fourth mixing are: stirring speed of 260 r / min and time of 40 min;

[0121] Modified nano-zero valent iron M3 was prepared.

[0122] Preparation Example 4: Preparation of cobalt chloride modified biochar N1

[0123] SS0: Take the residual sludge discharged from the bottom of the secondary sedimentation tank of Qingdao Municipal Wastewater Treatment Plant, let it settle, take the lower sedimentation sludge and centrifuge it at 5000 r / min for 10 min; filter the centrifuged sludge; then place the filtered 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.

[0124] SS1: The sludge, ammonia (26.5% by mass), cobalt chloride and isopropanol are mixed in a fifth step to obtain mixture C;

[0125] The mass ratio of the sludge, the ammonia water, the cobalt chloride, and the solvent is 1:1.6:0.1:35; the mass of the sludge is 10g.

[0126] The conditions for the fifth mixing process are: 80 min for the time and 260 r / min for the stirring speed.

[0127] SS2: The mixture C is subjected to a hydrothermal reaction to obtain mixture D;

[0128] The conditions for the hydrothermal reaction must at least be met: temperature 185℃ and time 24h.

[0129] SS3: The product obtained after the hydrothermal reaction is separated into solid and liquid by vacuum filtration. The mixed solid powder is collected, washed three times with isopropanol, centrifuged and filtered dry. The obtained powder is placed in an oven at 80°C and dried to constant weight to obtain a dry mixture D.

[0130] SS4: In the presence of nitrogen, the dry mixture D is heated and pyrolyzed, cooled to room temperature under nitrogen protection, and the solid powder is passed through a 100-mesh sieve to obtain cobalt chloride modified biochar N1.

[0131] The pyrolysis conditions are as follows: heating rate of 5℃ / min, pyrolysis temperature of 800℃, and time of 8h.

[0132] Preparation Example 5: Preparation of cobalt chloride modified biochar N2

[0133] This preparation example is similar to the method used in Preparation Example 4 for preparing cobalt chloride modified biochar, except that in step SS1, the mass ratio of the sludge, the ammonia water, the cobalt chloride, and the solvent is 1:1:0.2:30; and the mass of the sludge is 10g.

[0134] The conditions for the fifth mixing are: time 120 min, stirring speed 180 r / min;

[0135] In step SS2, the conditions for the hydrothermal reaction are: temperature 160°C and time 36 hours.

[0136] In step SS4, the pyrolysis conditions are: heating rate of 3℃ / min, pyrolysis temperature of 850℃, and time of 6h.

[0137] Cobalt chloride-modified biochar N2 was prepared.

[0138] Preparation Example 6: Preparation of cobalt chloride modified biochar N3

[0139] This preparation example is similar to the preparation example 4 in the method of preparing cobalt chloride modified biochar, except that in step SS1, the mass ratio of the sludge, the ammonia water, the cobalt chloride and the solvent is 1:2:0.3:40; and the mass of the sludge is 10g.

[0140] Cobalt chloride-modified biochar N3 was prepared.

[0141] Preparation Example 7: Preparation of zinc chloride modified biochar

[0142] This preparation example is similar to the preparation example 4 in the method of preparing cobalt chloride modified biochar, except that the cobalt chloride in step SS1 is replaced with an equal amount of zinc chloride;

[0143] Zinc chloride-modified biochar was prepared.

[0144] Preparation Example 8: Preparation of adhesive L1

[0145] 1g sodium alginate, 8g polyvinyl alcohol and 180g water were mixed and stirred to obtain adhesive L1;

[0146] The mixing conditions are: temperature 8℃, stirring speed 180r / min, and time 20min.

[0147] Preparation Example 9: Preparation of adhesive L2

[0148] 1g sodium alginate, 12g polyvinyl alcohol and 260g water were mixed and stirred to obtain adhesive L2;

[0149] The mixing conditions are: temperature 25℃, stirring speed 150r / min, and time 20min.

[0150] Comparative preparation example 1: Preparation of modified nano-zero valent iron D-M1

[0151] This preparation example is similar to the method of preparing modified nano-zero valent iron in Preparation Example 1, except that the Co-Mn-Cu catalyst is replaced with manganese dioxide in step S4.

[0152] Modified nano-zero valent iron D-M1 was prepared.

[0153] Comparative preparation example 2: Preparation of modified nano-zero valent iron D-M2

[0154] This preparation example is similar to the method used in Preparation Example 1 for preparing modified nano-zero valent iron, except that carbon nitride will not be added in step S4.

[0155] Modified nano-zero valent iron D-M2 was prepared.

[0156] Example 1

[0157] The formulation of the composite material composition is as follows: the mass ratio of modified nano zero-valent iron M1, cobalt chloride modified biochar N1, attapulgite, persulfate and binder L1 is 1:4:1:2:29, wherein the mass of modified nano zero-valent iron L1 is 2g.

[0158] Preparation of composite materials:

[0159] 1) Modified nano-zero valent iron, cobalt chloride-modified biochar, attapulgite, and sodium persulfate are brought into first contact to obtain mixture I;

[0160] 2) Place the mixture I and the binder in a constant temperature shaker for a second contact.

[0161] The conditions for the second mixing were: temperature 25°C, stirring speed 160 r / min, and time 10 h.

[0162] 3) The product obtained after the second contact is extruded, granulated, and dried to obtain composite material T1;

[0163] The average particle size of the product obtained after granulation is 8 mm, and the drying conditions are: time 2 h, temperature 60 °C.

[0164] Example 2

[0165] Formulation of the composite material composition: Similar to the formulation of the composite material composition in Example 1, except that modified nano-zero valent iron M1 is replaced with modified nano-zero valent iron M2, and in step 2), binder L1 is replaced with binder L2.

[0166] Preparation of composite materials:

[0167] This method is similar to the method for preparing composite materials in Example 1, except that the conditions for the second contact are: temperature of 20°C, stirring speed of 180 r / min, and time of 12 h.

[0168] Composite material T2 was obtained.

[0169] Example 3

[0170] Formulation of the composite material composition: Similar to the formulation of the composite material composition in Example 1, except that modified nano-zero valent iron M1 is replaced with modified nano-zero valent iron M3.

[0171] Preparation of composite materials:

[0172] This method is the same as the method for preparing composite materials in Example 1.

[0173] Composite material T3 was prepared.

[0174] Example 4

[0175] Formulation of the composite material composition: Similar to the formulation of the composite material composition in Example 1, except that cobalt chloride modified biochar N1 is replaced with cobalt chloride modified biochar N2.

[0176] Preparation of composite materials:

[0177] This method is the same as the method for preparing composite materials in Example 1.

[0178] Composite material T4 was prepared.

[0179] Example 5

[0180] Formulation of the composite material composition: Similar to the formulation of the composite material composition in Example 1, except that cobalt chloride modified biochar N1 is replaced with cobalt chloride modified biochar N3.

[0181] Preparation of composite materials:

[0182] This method is the same as the method for preparing composite materials in Example 1.

[0183] Composite material T5 was obtained.

[0184] Example 6

[0185] The formulation of the composite material composition is as follows: the mass ratio of modified nano-zero valent iron M1, cobalt chloride modified biochar N1, attapulgite, persulfate and binder L1 is 1:5:1.5:3:26.5.

[0186] Preparation of composite materials:

[0187] This method is the same as the method for preparing composite materials in Example 1.

[0188] Composite material T6 was prepared.

[0189] Example 7

[0190] The formulation of the composite material composition is as follows: the mass ratio of modified nano-zero valent iron M1, cobalt chloride modified biochar N1, attapulgite, persulfate and binder L1 is 1:4:1:2:40.

[0191] Preparation of composite materials:

[0192] This method is the same as the method for preparing composite materials in Example 1.

[0193] Composite material T7 was obtained.

[0194] Comparative Example 1

[0195] Formulation of the composite material composition: Similar to the formulation of the composite material composition in Example 1, except that the modified nano-zero valent iron M1 is replaced with modified nano-zero valent iron D-M1.

[0196] Preparation of composite materials:

[0197] This method is the same as the method for preparing composite materials in Example 1.

[0198] The composite material DT1 was prepared.

[0199] Comparative Example 2

[0200] Formulation of the composite material composition: Similar to the formulation of the composite material composition in Example 1, except that modified nano-zero valent iron M1 is replaced with modified nano-zero valent iron D-M2.

[0201] Preparation of composite materials:

[0202] This method is the same as the method for preparing composite materials in Example 1.

[0203] The composite material DT2 was prepared.

[0204] Comparative Example 3

[0205] Formulation of the composite material composition: Similar to the formulation of the composite material composition in Example 1, except that the modified nano zero-valent iron M1 is replaced with nano iron powder.

[0206] Preparation of composite materials:

[0207] This method is the same as the method for preparing composite materials in Example 1.

[0208] The composite material DT3 was prepared.

[0209] Comparative Example 4

[0210] Formulation of the composite material composition: Similar to the formulation of the composite material composition in Example 1, except that this composition does not contain sodium persulfate.

[0211] Preparation of composite materials:

[0212] This method is similar to the method for preparing composite materials in Example 1, except that sodium persulfate is not added in step 1).

[0213] The composite material DT4 was prepared.

[0214] Comparative Example 5

[0215] The formulation of the composite material composition is as follows: the mass ratio of modified nano-zero valent iron M1, cobalt chloride modified biochar N1, attapulgite, persulfate and binder L1 is 1:8:1:2:40.

[0216] Preparation of composite materials:

[0217] This method is the same as the method for preparing composite materials in Example 1.

[0218] The composite material DT5 was prepared.

[0219] Comparative Example 6

[0220] Formulation of the composite material composition: Similar to the formulation of the composite material composition in Example 1, except that cobalt chloride modified biochar N1 is replaced with zinc chloride modified biochar.

[0221] Preparation of composite materials:

[0222] This method is the same as the method for preparing composite materials in Example 1.

[0223] The composite material DT6 was prepared.

[0224] Test case

[0225] Groundwater contaminated with benzene and its derivatives was collected from a groundwater monitoring well at a chemical plant. The concentrations of pollutants in the groundwater were: benzene 189.7 mg / L, toluene 15.3 mg / L, and ethylbenzene 7.6 mg / L. The initial pH of the groundwater was 6.8. 300 mL of the contaminated groundwater and 8 g of the composite material prepared in the example were sealed in a brown wide-mouth bottle and then placed in a constant-temperature shaker at 25℃ and 150 r / min for 72 h. Samples were then taken for testing. The test results are shown in Table 2.

[0226] Removal rate = (C0 - C) / C0 × 100%

[0227] C0 represents the initial concentration of the pollutant, and C represents the final concentration of the pollutant, in mg / L.

[0228] Table 2

[0229]

[0230] As can be seen from the results in Table 2, the composite material prepared in the embodiments of the present invention has a significant removal effect on benzene and its derivatives in groundwater, with a removal rate of over 80%.

[0231] 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 composite material composition for groundwater remediation, characterized in that, The composition contains modified nano-zero valent iron, cobalt chloride modified biochar, attapulgite, persulfate, and a binder; the mass ratio of the modified nano-zero valent iron, the cobalt chloride modified biochar, the attapulgite, the persulfate, and the binder is 1:2-6:0.5-1.5:1-3:16-40. The persulfate is sodium persulfate and / or potassium persulfate; The modified nano-zero-valent iron is prepared by a method comprising the following steps: S1: Under a protective atmosphere and in the presence of oxygen-free water, cobalt nitrate, manganese nitrate, copper nitrate, ammonium fluoride, and urea are mixed to obtain mixture A. S2: Mix the mixture A with sodium percarbonate for a second time. The pH value of the resulting solution is greater than 10, thus obtaining a Co-Mn-Cu catalyst. S3: In an ethanol-water solution, carbon nitride, Co-Mn-Cu catalyst, and FeCl3 are mixed for the third time to obtain mixture B. In the ethanol-water solution, the volume ratio of water to ethanol is 1:1-4. S4: Under a protective atmosphere, the mixture B is mixed with NaBH4 for the fourth time to obtain the modified nano-zero valent iron.

2. The composition according to claim 1, wherein, The mass ratio of the modified nano-zero valent iron, the cobalt chloride modified biochar, the attapulgite, the persulfate, and the binder is 1:3-5:0.5-1.5:1-3:24-32.

3. The composition according to claim 1 or 2, wherein, The adhesive is formed from sodium alginate, polyvinyl alcohol and water in a mass ratio of 1:5-12:100-500.

4. The composition according to claim 1 or 2, wherein, In step S1, the mass ratio of copper nitrate, cobalt nitrate, manganese nitrate, ammonium fluoride, and urea is 1:2-5:1.5-2.5:9-11:4.5-5.

5.

5. The composition according to claim 1 or 2, wherein, In step S3, the mass ratio of the carbon nitride, the Co-Mn-Cu catalyst, and the FeCl3 is 0.3-2:0.1-0.5:

1.

6. The composition according to claim 1, wherein, In step S4, the molar ratio of NaBH4 to the molar ratio of the mixture B (calculated as iron) is 2-4:

1.

7. The composition according to claim 1 or 2, wherein, In step S1, the conditions for the first mixing must at least satisfy: a stirring speed of 180-260 r / min and a mixing time of 20-40 min; and / or, In step S2, the conditions for the second mixing must at least satisfy: a temperature of 20-40°C and a time of 12-24 hours; and / or, In step S3, the conditions for the third mixing must at least satisfy: a stirring speed of 180-260 r / min and a time of 20-30 min; and / or, In step S4, the conditions for the fourth mixing must at least satisfy: a stirring speed of 180-260 r / min and a time of 30-40 min.

8. The composition according to claim 1 or 2, wherein, Before the carbon nitride is mixed in the third stage, the carbon nitride needs to be prepared. The method for preparing the carbon nitride includes: calcining dicyandiamide under anaerobic conditions to obtain carbon nitride. The calcination conditions must at least meet the following requirements: heating rate of 5-6℃ / min, temperature of 500-600℃, and time of 2-3h.

9. The composition according to claim 1 or 2, wherein, The cobalt chloride-modified biochar is prepared by a method comprising the following steps: SS1: The sludge, ammonia, cobalt chloride and solvent are mixed in a fifth step to obtain mixture C; SS2: The mixture C is subjected to a hydrothermal reaction to obtain mixture D; SS3: Under nitrogen protection, the dried mixture D is heated and pyrolyzed to obtain cobalt chloride modified biochar.

10. The composition according to claim 9, wherein, In step SS1, the mass ratio of the sludge, the ammonia water, the cobalt chloride, and the solvent is 1:1-2:0.05-0.3:30-40.

11. The composition according to claim 9, wherein, In step SS1, the conditions for the fifth mixing must at least satisfy: a time of 60-120 min, a stirring speed of 180-260 r / min; and / or, In step SS2, the conditions for the hydrothermal reaction must at least satisfy: a temperature of 160-200°C and a time of 18-36 hours; and / or, In step SS3, the pyrolysis conditions must at least meet the following requirements: heating rate of 3-6℃ / min, temperature of 750-850℃, and time of 6-8h.

12. A method for preparing a composite material for groundwater remediation, characterized in that, This method is performed using the composition according to any one of claims 1-11, comprising: 1) Preparation of modified nano-zero-valent iron and cobalt chloride-modified biochar; 2) Modified nano-zero valent iron, cobalt chloride-modified biochar, attapulgite, and persulfate were brought into first contact to obtain mixture I; 3) The mixture I is brought into a second contact with the binder to obtain a composite material.

13. The method according to claim 12, wherein, In step 3), the conditions for the second contact must at least be: temperature of 20-25℃, stirring speed of 150-180r / min, and time of 8-12h.

14. A composite material for groundwater remediation prepared by the method of claim 12 or 13.

15. The use of the composite material for groundwater remediation according to claim 14 in the removal of at least one of benzene and its derivatives.

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