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

Abstract

The present invention relates to the field of sewage treatment technology, and discloses a composite material composition for groundwater remediation, a composite material, a preparation method thereof, and an application thereof. The composite material comprises nanometer zero-valent iron sulfide, ruthenium chloride-modified biochar, attapulgite, a persulfate, and a binder; the mass ratio of the nanometer zero-valent iron sulfide, the ruthenium 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 invention is resistant to clogging and scaling, has high permeability, and has a high removal rate of target pollutants in groundwater. It can be used as a filler in permeable reactive grids (PRBs) for treating contaminated groundwater.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a composite material composition for groundwater remediation, a composite material for groundwater remediation, and a preparation method and application thereof. Background Art

[0002] Groundwater remediation technologies include ex situ and in situ. For existing industrial enterprises, which are constrained by factors such as production operations and surface buildings, in situ remediation technologies are more suitable for preventing and controlling groundwater contamination risks. These technologies include in situ chemical oxidation, bioremediation, in situ aeration, and permeable reaction wall (PRB) technology. PRB technology, a type of in situ remediation technology developed in the United States in the 1980s, involves installing a permeable reaction wall filled with a reactive filler perpendicular to the direction of groundwater flow. As contaminants migrate through the permeable reaction wall, they interact with the filler material in the wall, causing degradation or in-situ fixation of the contaminants. Because contaminated water flows through the reaction wall by gravity, no additional power or surface treatment systems are required. Therefore, selecting the appropriate reactive filler for each contaminant in the groundwater is crucial for groundwater remediation.

[0003] Iron is a common metallic element that is inexpensive and readily available. Its application in environmental remediation is not only low-cost but also prevents secondary pollution. Nanoscale zero-valent iron (nZVI) is a new environmental remediation material commonly used in recent years. It possesses a unique core-shell structure and offers 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, and has garnered widespread attention in the field of groundwater environmental remediation. However, nZVI suffers from problems such as easy aggregation, passivation, loss, and poor electron selectivity during groundwater remediation, resulting in certain limitations in its application in in-situ groundwater remediation and storage.

[0004] Biochar generally refers to a highly carbonaceous, fluffy, porous material formed by the pyrolysis of biomass resources under anoxic conditions, followed by a series of processes including dehydration, cracking, and aromatization. It is primarily composed of elemental carbon, aromatized carbon, and graphitic carbon. Common raw materials for biochar production include straw, wood, sewage sludge, and core-shell materials. Due to its numerous advantages, including large surface area, well-developed pore structure, abundant surface functional groups, high cation exchange capacity, low bulk density, and strong chemical and thermal stability, biochar can be used as both an adsorbent and catalyst for environmental pollutant control. Furthermore, its wide availability and low cost make it a highly effective adsorbent and support material. While biochar offers numerous advantages for environmental remediation, single-phase biochar generally lacks the required adsorption capacity and kinetic rate to efficiently remove organic pollutants from the environment. Furthermore, its low bulk density makes solid-liquid separation difficult when used for adsorbing organic pollutants, and its long-term and stable removal performance also presents challenges. Consequently, the use of biochar as a support or co-catalyst to prepare composite materials with unique remediation properties has attracted increasing attention.

[0005] In-situ chemical oxidation remediation technology for organically contaminated sites has the advantages of strong universality, good remediation effects, and short remediation cycles. Commonly used oxidants include Fenton's reagent, permanganate, persulfate, and ozone. Fenton's reagent can react with most organic matter and can also react with 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 is also affected by the toxicity of by-products. Permanganate is relatively stable in underground environments, but its reaction is selective, and permanganate reacts rapidly with natural organic matter in the soil. The resulting manganese dioxide precipitate will clog soil pores and affect the transmission of oxidants.

[0006] As an emerging in-situ chemical oxidation repair agent, persulfate has the characteristics of good stability, wide pH range, and green and non-toxicity. The mechanism of its oxidation process is that under the action of activation mode, the -OO- bond breaks and produces sulfate free radicals SO with strong oxidizing properties. 4- ·, SO 4- · has a pair of lone electrons, and its oxidizing ability is stronger than that of persulfate, and is close to that of hydroxyl radical ·OH, SO 4- The half-life of persulfate is longer, allowing it to come into contact with pollutants more fully. In addition, persulfate can produce OH after activation, which can oxidize difficult-to-degrade organic pollutants such as polychlorinated biphenyls.

[0007] CN104803486A discloses a permeable reactive wall material for repairing chromium contaminated groundwater. The material includes a reducing agent and an adsorption medium. Its composition and preparation method are complex. It is mainly used to reduce hexavalent chromium in groundwater and has great limitations in the repair of organically contaminated groundwater.

[0008] CN104876321A discloses a method for treating chlorine-containing organic pollutants in groundwater using a slow-release composite remediation material. The slow-release material is made of biochar and nano-zero-valent iron, and uses adsorption and reduction to remove chlorine-containing organic matter in groundwater. However, it cannot use oxidation to remove other pollutants. The use of the method has great limitations, and since neither the biochar nor the zero-valent iron has been modified, the slow-release material is not effective in treating organic matter.

[0009] CN107999531A discloses a material and method for in-situ remediation of soil and groundwater in organically contaminated sites. This patent uses a surfactant to increase the solubility and dispersibility of organic pollutants in groundwater, activates zero-valent iron to form a Fenton-like system to oxidatively degrade the organic pollutants. However, this material has difficulty in inhibiting the aggregation, oxidation, and scaling of zero-valent iron, and does not have a sustained-release function or a long-lasting effect. Summary of the Invention

[0010] The purpose of the present 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] The inventors discovered that modified biochar not only effectively improves its specific surface area and adsorption properties, but also significantly enhances the catalytic activity of the biochar particles and the redox capacity of the oxidant, thereby achieving synergistic adsorption and oxidative degradation of different pollutants. Furthermore, the inventors discovered that compared to the outer shell of ordinary iron oxides, the surface of sulfided nano-zero-valent iron forms a sulfide shell with stronger conductivity, and that modifying it with (NH4)2MoO4 effectively inhibits the aggregation, oxidation, and scaling of the nano-zero-valent iron, as well as side reactions with non-target pollutants. In light of this, the inventors conducted in-depth research and found that by using the sulfided nano-zero-valent iron, the ruthenium chloride-modified biochar, the attapulgite, the persulfate, and the binder in a mass ratio of 1:2-6:0.5-1.5:1-3:16-40, the resulting composite material can significantly enhance the synergistic adsorption, oxidative degradation, and micro-electrolysis of pollutants, thereby improving the composite material's removal efficiency of target pollutants.

[0012] To achieve the above objectives, the first aspect of the present invention provides a composite material composition for groundwater remediation, comprising nano-zero-valent iron sulfide, ruthenium chloride-modified biochar, attapulgite, persulfate, and a binder; the mass ratio of the nano-zero-valent iron sulfide, the ruthenium chloride-modified biochar, the attapulgite, the persulfate, and the binder is 1:2-6:0.5-1.5:1-3:16-40;

[0013] The persulfate is sodium persulfate and / or potassium persulfate;

[0014] The sulfide nanometer zero-valent iron is prepared by a method comprising the following steps:

[0015] S1: Under an inert atmosphere, in the presence of water and ethanol, FeCl3 and NaBH4 are first contacted to obtain a mixed solution A; the volume ratio of the water to the ethanol is 1:1-3;

[0016] S2: Under an inert atmosphere, the mixed solution A is brought into contact with a sulfur-containing modifier for a second time to obtain a mixed solution B;

[0017] S3: Under an inert atmosphere, the mixed solution B is brought into contact with (NH 4 ) 2 MoO 4 for a third time to obtain the sulfide nano-zero-valent iron.

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

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

[0020] 2) first mixing the sulfide nano-zero-valent iron, the ruthenium chloride-modified biochar, attapulgite, and persulfate to obtain a mixture I;

[0021] 3) The mixture I is mixed with a binder for a second time.

[0022] The 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 use of the composite material for groundwater remediation described in the third aspect in removing at least one of benzene and its derivatives.

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

[0025] At the same time, the composite material provided by the present invention is not prone to clogging and scaling, has high permeability, and can be used as a filler for permeable reaction grids (PRBs) to treat contaminated groundwater. DETAILED DESCRIPTION

[0026] The endpoints of the ranges and any values 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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0027] As mentioned above, one aspect of the present invention provides a composite material composition for groundwater remediation, which contains nano-zero-valent iron sulfide, ruthenium chloride-modified biochar, attapulgite, persulfate, and a binder; the mass ratio of the nano-zero-valent iron sulfide, the ruthenium chloride-modified biochar, the attapulgite, the persulfate, and the binder is 1:2-6:0.5-1.5:1-3:16-40;

[0028] The persulfate is sodium persulfate and / or potassium persulfate;

[0029] The sulfide nanometer zero-valent iron is prepared by a method comprising the following steps:

[0030] S1: Under an inert atmosphere, in the presence of water and ethanol, FeCl3 and NaBH4 are first contacted to obtain a mixed solution A; the volume ratio of the water to the ethanol is 1:1-3;

[0031] S2: Under an inert atmosphere, the mixed solution A is brought into contact with a sulfur-containing modifier for a second time to obtain a mixed solution B;

[0032] S3: Under an inert atmosphere, the mixed solution B is brought into contact with (NH 4 ) 2 MoO 4 for a third time to obtain the sulfide nano-zero-valent iron.

[0033] Preferably, the mass ratio of the sulfided nano-zero-valent iron, the ruthenium 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 in this preferred embodiment, the resulting composite material has a better pollutant removal effect.

[0034] The present invention has no particular limitation on the water, which may be deionized water, ultrapure water, etc. Those skilled in the art should not understand this as a limitation to the present invention.

[0035] The attapulgite described in the present invention is a water-containing magnesium-rich aluminum silicate clay mineral with a layered chain structure; the average particle size of the attapulgite is 50-100 μm.

[0036] Preferably, the binder is formed by sodium alginate, polyvinyl alcohol and water in a mass ratio of 1:5-12:100-500.

[0037] More preferably, the binder is formed by sodium alginate, polyvinyl alcohol and water in a mass ratio of 1:8-10:160-300. The inventors have found that in this preferred embodiment, the obtained composite material has a higher efficiency in removing pollutants.

[0038] Preferably, in step S1, the mass ratio of the FeCl3 to the NaBH4 is 1:1.5-3.

[0039] Preferably, in step S2, the amounts of the mixed solution A and the sulfur-containing modifier are controlled so that the molar ratio of sulfur element to iron element in the mixed solution B is 0.01-0.3:1.

[0040] More preferably, in step S2, the amounts of the mixed solution A and the sulfur-containing modifier are controlled so that the molar ratio of sulfur element to iron element in the mixed solution B is 0.1-0.2:1.

[0041] Preferably, the sulfur-containing modifier is selected from at least one of Na2S, Na2S2O4, Na2S2O3, K2S6 and elemental sulfur.

[0042] Preferably, in step S3, the ratio of the molar amount of the (NH4)2MoO4 to the molar amount of the mixed solution B calculated as iron element is 0.01-0.5:1.

[0043] More preferably, in step S3, the ratio of the molar amount of (NH4)2MoO4 to the molar amount of the mixed solution B (calculated as elemental iron) is 0.1-0.3:1. The inventors have discovered that in this preferred embodiment, the resulting sulfide nano-zero-valent iron can better activate persulfate, further improving the composite material's pollutant removal efficiency.

[0044] Preferably, in steps S1, S2, and S3, the inert atmosphere is nitrogen and / or argon.

[0045] According to a preferred embodiment, in step S1, the conditions for the first contact at least meet the following requirements: temperature of 5-25°C, time of 20-40 min, and stirring speed of 150-180 r / min.

[0046] Preferably, in step S2, the second contacting conditions at least meet the following requirements: temperature of 20-40°C, time of 10-30 min, and stirring speed of 150-180 r / min.

[0047] Preferably, in step S3, the conditions for the third contact at least meet the following requirements: temperature of 20-40° C., time of 10-30 min, and stirring speed of 150-180 r / min.

[0048] More preferably, in step S2, the second contacting conditions at least meet the following requirements: temperature of 20-30°C, time of 15-20 min, and stirring speed of 150-180 r / min.

[0049] More preferably, in step S3, the conditions for the third contact at least meet the following requirements: temperature of 20-30°C, time of 15-20 min, and stirring speed of 150-180 r / min.

[0050] According to another preferred embodiment, the method for preparing sulfide nano-zero-valent iron further comprises: post-processing the product obtained after the third contact; the post-processing comprises solid-liquid separation, washing, and drying.

[0051] It should be noted that the present invention does not particularly require the specific methods of solid-liquid separation, washing, and drying; those skilled in the art may employ known techniques. For example, the product obtained after the third contacting step is subjected to solid-liquid separation using a magnet to obtain a sulfide nano-zero-valent iron solid. The sulfide nano-zero-valent iron solid is then washed 2-4 times with oxygen-free deionized water and then with anhydrous ethanol. The washed product is then dried in a vacuum drying oven at 50-70°C for 6-8 hours. Finally, the dried product is passed through a 100-mesh sieve and stored in a centrifuge tube filled with inert gas for later use.

[0052] Preferably, the ruthenium chloride modified biochar is prepared by a method comprising the following steps:

[0053] SS1: The sludge biochar is reacted with ruthenium chloride to obtain a mixture D;

[0054] SS2: The dried mixture D is heated under nitrogen protection, then CO2 is introduced for modification, nitrogen is introduced again and heating is stopped to obtain ruthenium chloride modified biochar.

[0055] Preferably, the method for preparing ruthenium chloride-modified biochar further comprises: before step SS1, pre-treating the sludge to obtain sludge biochar; the sludge is the residual sludge discharged from the bottom of the secondary sedimentation tank of the municipal sewage treatment plant.

[0056] Preferably, the pretreatment includes static sedimentation, centrifugation, filtration, drying, grinding, and sieving. It should be noted that the present invention has no particular requirements for the specific operation mode of the pretreatment, and those skilled in the art can use known technical means in the art to perform the pretreatment.

[0057] For example, the residual sludge discharged from the bottom of the secondary sedimentation tank of a municipal sewage treatment plant is taken, and after static sedimentation, the lower layer of precipitated sludge is taken out and centrifuged at 3000-5000r / min for 5-15min; the centrifuged sludge is filtered; the filtered sludge is then placed in an oven, dried at 100-120°C to constant weight, ground, and passed through a 90-100 mesh sieve to obtain sludge biochar.

[0058] Preferably, in step SS1, the mass ratio of the sludge biochar to the ruthenium chloride is 1:0.5-2.

[0059] Preferably, in step SS1, the conditions of the first reaction at least meet the following requirements: time of 12-36 h, temperature of 20-40° C., and stirring speed of 150-180 r / min.

[0060] It should be noted that the present invention has no particular requirements for the heating method described in step SS2, and those skilled in the art may select an appropriate method as needed. For example, the dried mixture D is placed in a tube furnace under nitrogen protection and heated at a heating rate of 1-6°C / min to 500-800°C.

[0061] Preferably, in step SS2, the modification conditions at least meet the following conditions: time of 60-120 min, temperature of 500-800° C., and CO 2 flow rate of 0.9-1.1 L / min.

[0062] Preferably, the method for preparing ruthenium chloride modified biochar further comprises: drying I the mixture D obtained after the first reaction to obtain a dry mixture D; the conditions of the drying I at least meet: a temperature of 120-150° C. and a time of 36-48 hours.

[0063] Preferably, the method for preparing ruthenium chloride-modified biochar further comprises cooling, washing, filtering, drying, and sieving the ruthenium chloride-modified biochar produced in step SS2. It should be noted that the present invention has no particular requirements for the specific operations of cooling, washing, centrifuging, filtering, and drying, and those skilled in the art can perform these operations according to techniques known in the art.

[0064] For example, the ruthenium chloride-modified biochar that has been introduced with nitrogen and heated is cooled to room temperature; then washed 3-5 times with 2-4 mol / L hydrochloric acid and washed with deionized water until the pH is neutral; the washed product is centrifuged at 3000-5000 r / min for 5-15 minutes, filtered, and then the filtered product is placed in an oven and dried at 100-110°C to constant weight, passed through a 90-100 mesh sieve, and placed in a centrifuge tube filled with inert gas for later use.

[0065] As mentioned above, the second aspect of the present invention provides a method for preparing a composite material for groundwater remediation, which is performed using the composite material composition for groundwater remediation described in the first aspect, comprising:

[0066] 1) Preparation of sulfided nano-zero-valent iron and ruthenium chloride modified biochar;

[0067] 2) first mixing the sulfide nano-zero-valent iron, the ruthenium chloride-modified biochar, attapulgite, and persulfate to obtain a mixture I;

[0068] 3) The mixture I is mixed with a binder for a second time.

[0069] Unless otherwise specified, the definitions and amounts of the sulfide nano zero-valent iron, ruthenium chloride modified biochar, attapulgite, persulfate and binder described in the second aspect of the present invention are the same as the definitions and amounts of the corresponding components described in the first aspect. The present invention will not be repeated here, and those skilled in the art should not understand it as a limitation of the present invention.

[0070] It should be noted that the present invention has no particular restrictions on the conditions of the first mixing in step 2), as long as the sulfide nano-zero-valent iron, the ruthenium chloride-modified biochar, the attapulgite, and the persulfate can be evenly mixed. Those skilled in the art can make the selection based on known technical means.

[0071] Preferably, in step 3), the second mixing conditions at least meet the following requirements: temperature of 20-25° C., stirring speed of 150-180 r / min, and time of 8-12 h.

[0072] According to a preferred embodiment, the method further comprises: in step 1), a binder needs to be prepared; the method for preparing the binder comprises:

[0073] Sodium alginate, polyvinyl alcohol and water are mixed and stirred in a mass ratio of 1:5-12:100-500 to obtain a binder.

[0074] More preferably, sodium alginate, polyvinyl alcohol and water are mixed and stirred in a mass ratio of 1:5-12:160-300.

[0075] Preferably, the mixing and stirring conditions at least meet the following requirements: temperature of 5-25° C., stirring speed of 150-180 r / min, and time of 20-40 min.

[0076] According to another preferred embodiment, the method further comprises: extruding, granulating, and drying II the product obtained after the second mixing to obtain a composite material.

[0077] Preferably, the average particle size of the product obtained after the granulation is 5-10 mm.

[0078] Preferably, the conditions of drying II at least meet the following requirements: a drying time of 2-4 hours and a temperature of 50-70°C.

[0079] As mentioned above, the third aspect of the present invention provides a composite material for groundwater remediation prepared by the method described in the second aspect.

[0080] The fourth aspect of the present invention provides the use of the composite material for groundwater remediation described in the third aspect in removing at least one of benzene and its derivatives.

[0081] Preferably, the benzene derivative described in the present invention is at least one of toluene and ethylbenzene.

[0082] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0083] (1) The present invention uses sludge from sewage treatment plants to prepare ruthenium chloride-modified biochar, which can realize waste resource utilization.

[0084] (2) Compared with the ordinary "iron / carbon" micro-electrolysis environment, the micro-electrolysis environment composed of sulfide nano-zero-valent iron and ruthenium chloride modified biochar provided by the present invention has a higher electron transfer ability and can transfer electrons to the reaction interface faster, thereby improving the selectivity of the composite material for target pollutants.

[0085] (3) The composite material prepared based on sulfide nano-zero-valent iron, ruthenium chloride-modified biochar, attapulgite, persulfate, binder and other components of the present invention can continuously play the role of synergistic adsorption, Fenton-like catalytic oxidation and micro-electrolysis in the treatment of contaminated groundwater to remove target pollutants in groundwater, thereby improving the efficiency of pollutant removal.

[0086] The present invention will be described in detail below through examples. In the following examples, the instruments, reagents, materials, etc. involved, unless otherwise specified, are conventional instruments, reagents, materials, etc. already available in the prior art and can be obtained through regular commercial channels.

[0087] The main materials used in the examples and comparative examples are all commercially available, as shown in Table 1:

[0088] Table 1

[0089]

[0090] Preparation Example 1: Preparation of sulfide nano-zero-valent iron A1

[0091] S1: Under nitrogen atmosphere, 5 g of FeCl3 was first contacted with NaBH4 (concentration of 15 mol / L) in the presence of 100 mL of water and 200 mL of ethanol to obtain a mixed solution A;

[0092] The mass ratio of the FeCl3 to the NaBH4 on a dry basis is 1:2

[0093] The conditions of the first contact are: temperature of 8°C, time of 30 min, stirring speed of 160 r / min;

[0094] S2: Under a nitrogen atmosphere, the mixed solution A is brought into contact with the sulfur-containing modifier in a constant temperature ultrasonic oscillator for a second time to obtain a mixed solution B;

[0095] The sulfur-containing modifier is Na2S, and the amounts of the mixed solution A and Na2S are controlled so that the molar ratio of sulfur element to iron element in the mixed solution B is 0.2:1;

[0096] The conditions of the second contact are: temperature of 25°C, time of 20 min, stirring speed of 160 r / min;

[0097] S3: Under a nitrogen atmosphere, the mixed solution B is brought into contact with (NH4)2MoO4 (concentration of 1.5 mol / L) in a constant temperature ultrasonic oscillator for a third time;

[0098] The ratio of the molar amount of (NH4)2MoO4 to the molar amount of the mixed solution B calculated as iron element is 0.3:1;

[0099] The conditions of the third contact are: temperature 25°C, time 20 min, stirring speed 160 r / min;

[0100] S4: using a magnet to perform solid-liquid separation on the product obtained after the third contact, to obtain sulfide nano-zero-valent iron solid;

[0101] S5: washing the sulfide nano-zero-valent iron solid with oxygen-free deionized water 3 times and with anhydrous ethanol 3 times;

[0102] S6: Place the washed product in a vacuum drying oven at 60°C and dry for 8 hours; pass the dried product through a 100-mesh sieve and store in a centrifuge tube filled with nitrogen for later use.

[0103] Preparation Example 2: Preparation of sulfide nano-zero-valent iron A2

[0104] The method for preparing sulfide nano zero-valent iron in this preparation example is similar to that in Preparation Example 1, except that:

[0105] In step S1, the conditions for the first contact are: temperature of 25°C, time of 20 min, and stirring speed of 150 r / min;

[0106] In step S2, the sulfur-containing modifier is Na2S2O3, and the amounts of the mixed solution A and Na2S2O3 are controlled so that the molar ratio of sulfur element to iron element in the mixed solution B is 0.1:1;

[0107] The conditions of the second contact are: temperature of 30°C, time of 15 min, stirring speed of 180 r / min;

[0108] In step S3, the ratio of the molar amount of the (NH4)2MoO4 calculated on a dry basis to the molar amount of the mixed solution B calculated on an iron element basis is 0.1:1;

[0109] The conditions of the third contact are: temperature 20°C, time 20 min, stirring speed 150 r / min;

[0110] Sulfide nano-zero-valent iron A2 was obtained.

[0111] Preparation Example 3: Preparation of sulfide nano-zero-valent iron A3

[0112] The method for preparing sulfide nano-zero-valent iron in this preparation example is similar to that in Preparation Example 1, except that in step S2, the amount of the mixed solution A and Na2S is controlled so that the molar ratio of the sulfur element to the iron element in the mixed solution B is 0.3:1, and in step S3, the ratio of the molar amount of (NH4)2MoO4 to the molar amount of the mixed solution B calculated as iron element is 0.5:1.

[0113] Sulfide nano-zero-valent iron A3 was obtained.

[0114] Preparation Example 4: Preparation of ruthenium chloride modified biochar B1

[0115] SS0: 2000 mL of residual sludge discharged from the bottom of the secondary sedimentation tank of Qingdao Municipal Wastewater Treatment Plant was collected. After static sedimentation, the lower layer of precipitated sludge was removed and centrifuged at 5000 rpm for 10 min. The centrifuged sludge was filtered. The filtered sludge was then dried in an oven at 110°C to constant weight, ground, and passed through a 100-mesh sieve to obtain sludge biochar.

[0116] SS1: 8 g of sludge biochar and ruthenium chloride (concentration: 3 mol / L) were subjected to a first reaction in a constant temperature ultrasonic oscillator to obtain a mixture D; the mixture D was then dried I to obtain a dry mixture D;

[0117] The mass ratio of the sludge biochar to the ruthenium chloride on a dry basis is 1:1;

[0118] The conditions of the first reaction are: time 24h, temperature 25°C, stirring speed 160r / min; the conditions of the drying I are: temperature 130°C, time 36h;

[0119] SS2: The dried mixture D was placed in a tube furnace and heated to 650°C at a heating rate of 5°C / min under nitrogen protection, and then CO2 was introduced for modification. Nitrogen was then introduced and heating was stopped to obtain ruthenium chloride-modified biochar;

[0120] The modification conditions are as follows: time 80 min, temperature 650°C, CO2 flow rate 1 L / min;

[0121] SS3: The ruthenium chloride-modified biochar, which has been introduced with nitrogen and stopped heating, was cooled to room temperature; then washed four times with 3 mol / L hydrochloric acid and washed with deionized water until the pH value reached 7; the washed product was centrifuged at 5000 r / min for 10 min, filtered, and then dried in an oven at 105°C to constant weight, passed through a 100-mesh sieve, and placed in a nitrogen-filled centrifuge tube for later use.

[0122] Preparation Example 5: Preparation of ruthenium chloride modified biochar B2

[0123] The method for preparing ruthenium chloride-modified biochar in this preparation example is similar to that in Preparation Example 4, except that in step SS1, the mass ratio of the sludge biochar to the ruthenium chloride on a dry basis is 1:0.5;

[0124] The conditions of the first reaction are: time 15h, temperature 40°C, stirring speed 180r / min; the conditions of the drying I are: temperature 150°C, time 48h;

[0125] In step SS2, the modification conditions are: time is 60 min, temperature is 800° C., and CO 2 flow rate is 1 L / min.

[0126] Ruthenium chloride modified biochar B2 was obtained.

[0127] Preparation Example 6: Preparation of ruthenium chloride modified biochar B3

[0128] The method for preparing ruthenium chloride-modified biochar in this preparation example is similar to that in Preparation Example 4, except that the mass ratio of the sludge biochar to the ruthenium chloride on a dry basis in step SS1 is 1:2.

[0129] Ruthenium chloride modified biochar B3 was obtained.

[0130] Preparation Example 7: Preparation of zinc chloride modified biochar

[0131] The method for preparing ruthenium chloride-modified biochar in this preparation example is similar to that in Preparation Example 4, except that the ruthenium chloride in step SS1 is replaced by an equal amount of zinc chloride.

[0132] Zinc chloride modified biochar was obtained.

[0133] Preparation Example 8: Preparation of binder C1

[0134] 1 g of sodium alginate, 8 g of polyvinyl alcohol, and 180 g of water were mixed and stirred to obtain a binder C1;

[0135] The mixing and stirring conditions are as follows: temperature of 8° C., stirring speed of 180 r / min, and time of 20 min.

[0136] Preparation Example 9: Preparation of binder C2

[0137] 1 g of sodium alginate, 12 g of polyvinyl alcohol, and 260 g of water were mixed and stirred to obtain a binder C2;

[0138] The mixing and stirring conditions are as follows: temperature of 25° C., stirring speed of 150 r / min, and time of 40 min.

[0139] Comparative Preparation Example 1: Preparation of sulfide nano-zero-valent iron D-A1

[0140] The method for preparing sulfide nano-zero-valent iron in this preparation example is similar to that in Preparation Example 1, except that (NH4)2MoO4 is not added in step S3.

[0141] Sulfide nano zero-valent iron D-A1 was obtained.

[0142] Example 1

[0143] The formula of the composite material composition is as follows: the mass ratio of sulfided nano-zero-valent iron A1, ruthenium chloride-modified biochar B1, attapulgite, persulfate, and binder C1 is 1:4:1:2:28, wherein the mass of sulfided nano-zero-valent iron A1 is 0.6 g;

[0144] Preparation of composite materials:

[0145] 1) Firstly mixing the sulfide nano-zero-valent iron, ruthenium chloride-modified biochar, attapulgite, and sodium persulfate to obtain a mixture I;

[0146] 2) The mixture I and the binder are placed in a constant temperature oscillator for a second mixing.

[0147] The second mixing conditions are as follows: temperature of 25° C., stirring speed of 160 r / min, and time of 10 h.

[0148] 3) Extruding, granulating, and drying the product obtained after the second mixing step II to obtain a composite material T1;

[0149] The average particle size of the product obtained after the granulation is 8 mm. The conditions of the drying II are: time is 2 h, and temperature is 60°C.

[0150] Example 2

[0151] Formula of the composite material composition: Similar to the formula of the composite material composition in Example 1, except that the sulfide nano zero-valent iron A1 is replaced by sulfide nano zero-valent iron A2, and in step 2), the binder C1 is replaced by the binder C2.

[0152] Preparation of composite materials:

[0153] This method is similar to the method for preparing the composite material in Example 1, except that:

[0154] The second mixing conditions are as follows: temperature of 20° C., stirring speed of 180 r / min, and time of 12 h.

[0155] The composite material T2 was obtained.

[0156] Example 3

[0157] Formula of the composite material composition: similar to the formula of the composite material composition in Example 1, except that the sulfide nano-zero-valent iron A1 is replaced by sulfide nano-zero-valent iron A3.

[0158] Preparation of composite materials:

[0159] This method is the same as the method for preparing the composite material in Example 1.

[0160] The composite material T3 was obtained.

[0161] Example 4

[0162] Formula of the composite material composition: Similar to the formula of the composite material composition in Example 1, except that the ruthenium chloride-modified biochar B1 is replaced by ruthenium chloride-modified biochar B2.

[0163] Preparation of composite materials:

[0164] This method is the same as the method for preparing the composite material in Example 1.

[0165] The composite material T4 was obtained.

[0166] Example 5

[0167] Formula of the composite material composition: Similar to the formula of the composite material composition in Example 1, except that the ruthenium chloride-modified biochar B1 is replaced by ruthenium chloride-modified biochar B3.

[0168] Preparation of composite materials:

[0169] This method is the same as the method for preparing the composite material in Example 1.

[0170] The composite material T5 was obtained.

[0171] Example 6

[0172] The formula of the composite material composition: the mass ratio of sulfide nano zero-valent iron A1, ruthenium chloride modified biochar B1, attapulgite, persulfate and binder C1 is 1:2:1.5:3:39, wherein the mass of sulfide nano zero-valent iron A1 is 0.6g.

[0173] Preparation of composite materials:

[0174] This method is the same as the method for preparing the composite material in Example 1.

[0175] The composite material T6 was obtained.

[0176] Comparative Example 1

[0177] The formula of the composite material composition is similar to that of the composite material composition in Example 1, except that the sulfide nano-zero-valent iron A1 is replaced by sulfide nano-zero-valent iron D-A1.

[0178] Preparation of composite materials:

[0179] This method is the same as the method for preparing the composite material in Example 1.

[0180] The composite material DT1 was obtained.

[0181] Comparative Example 2

[0182] The formula of the composite material composition is similar to that of the composite material composition in Example 1, except that the sulfide nano-zero-valent iron A1 is replaced by nano-iron powder.

[0183] Preparation of composite materials:

[0184] This method is the same as the method for preparing the composite material in Example 1.

[0185] The composite material DT2 was obtained.

[0186] Comparative Example 3

[0187] The formula of the composite material composition is similar to that of the composite material composition in Example 1, except that the composition does not contain sodium persulfate.

[0188] Preparation of composite materials:

[0189] This method is similar to the method for preparing the composite material in Example 1, except that sodium persulfate is not added in step 1).

[0190] The composite material DT3 was obtained.

[0191] Comparative Example 4

[0192] The formula of the composite material composition: the mass ratio of sulfide nano zero-valent iron A1, ruthenium chloride modified biochar B1, attapulgite, persulfate and binder C1 is 1:8:1:5:39, wherein the mass of sulfide nano zero-valent iron A1 is 0.6g.

[0193] Preparation of composite materials:

[0194] This method is the same as the method for preparing the composite material in Example 1.

[0195] The composite material DT4 was obtained.

[0196] Comparative Example 5

[0197] The formula of the composite material composition is similar to the formula of the composite material composition in Example 1, except that the ruthenium chloride modified biochar B1 is replaced by zinc chloride modified biochar.

[0198] Preparation of composite materials:

[0199] This method is the same as the method for preparing the composite material in Example 1.

[0200] The composite material DT5 was obtained.

[0201] Test Case

[0202] Groundwater contaminated with benzene and its derivatives was collected from a chemical company's groundwater monitoring well. The pH of the groundwater was 6.8, and the contaminant concentrations were: 189.7 mg / L benzene, 15.3 mg / L toluene, and 7.6 mg / L ethylbenzene. 300 mL of the contaminated groundwater and 7 g of the composite material prepared in Example 1 were sealed in a brown jar. The jar was then placed in a thermostatic shaker at 25°C and 150 rpm for 72 hours. Samples were then collected and tested. The test results are shown in Table 2.

[0203] Removal rate = (C0-C) / C0×100%

[0204] C0 represents the initial concentration of pollutants, and C represents the final concentration of pollutants, in mg / L.

[0205] Table 2

[0206]

[0207] It can be seen from the results in Table 2 that the composite material prepared in the embodiment of the present invention has a significant removal effect on benzene and its derivatives in groundwater, with a removal rate of more than 85%.

[0208] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A composite material composition for groundwater remediation, characterized in that: The composition contains sulfide nanometer zero-valent iron, ruthenium chloride modified biochar, attapulgite, persulfate and a binder; the mass ratio of the sulfide nanometer zero-valent iron, the ruthenium 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 sulfide nanometer zero-valent iron is prepared by a method comprising the following steps: S1: Under an inert atmosphere, in the presence of water and ethanol, FeCl3 and NaBH4 are first contacted to obtain a mixed solution A; the volume ratio of the water to the ethanol is 1:1-3; S2: Under an inert atmosphere, the mixed solution A is brought into contact with a sulfur-containing modifier for a second time to obtain a mixed solution B; S3: Under an inert atmosphere, the mixed solution B is brought into contact with (NH 4 ) 2 MoO 4 for a third time to obtain the sulfide nano-zero-valent iron.

2. The composition according to claim 1, wherein The mass ratio of the sulfide nano zero-valent iron, the ruthenium 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 binder is formed by 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 the FeCl3 to the NaBH4 is 1:1.5-3.

5. The composition according to claim 1 or 2, wherein In step S2, the amounts of the mixed solution A and the sulfur-containing modifier are controlled so that the molar ratio of sulfur element to iron element in the mixed solution B is 0.01-0.3:

1.

6. The composition according to claim 1 or 2, wherein In step S2, the sulfur-containing modifier is selected from at least one of Na2S, Na2S2O4, Na2S2O3, K2S6 and elemental sulfur.

7. The composition according to claim 1 or 2, wherein In step S3, the ratio of the molar amount of the (NH4)2MoO4 to the molar amount of the mixed solution B calculated as the iron element is 0.01-0.5:

1.

8. The composition according to claim 1 or 2, wherein In step S1, the first contacting conditions at least meet the following requirements: temperature of 5-25°C, time of 20-40 min, stirring speed of 150-180 r / min; and / or, In step S2, the second contacting conditions at least meet the following requirements: temperature of 20-40°C, time of 10-30 min, stirring speed of 150-180 r / min; and / or, In step S3, the conditions for the third contact at least meet the following requirements: temperature of 20-40°C, time of 10-30 min, and stirring speed of 150-180 r / min.

9. The composition according to claim 1 or 2, wherein In step S2, the second contacting conditions at least meet the following requirements: temperature of 20-30°C, time of 15-20 min, stirring speed of 150-180 r / min; and / or, In step S3, the conditions for the third contact at least meet the following requirements: temperature of 20-30°C, time of 15-20 min, and stirring speed of 150-180 r / min.

10. The composition according to claim 1 or 2, wherein The ruthenium chloride modified biochar is prepared by a method comprising the following steps: SS1: The sludge biochar is first reacted with ruthenium chloride to obtain a mixture D; SS2: The dried mixture D is heated under nitrogen protection, CO2 is introduced for modification, nitrogen is introduced again and heating is stopped to obtain ruthenium chloride modified biochar.

11. The composition according to claim 10, wherein In step SS1, the mass ratio of the sludge biochar to the ruthenium chloride is 1:0.5-2.

12. The composition according to claim 10, wherein In step SS1, the conditions of the first reaction at least meet the following requirements: time of 12-36 hours, temperature of 20-40° C., stirring speed of 150-180 r / min; and / or, In step SS2, the modification conditions at least meet the following requirements: time of 60-120 min, temperature of 500-800° C., and CO 2 flow rate of 0.9-1.1 L / min.

13. A method for preparing a composite material for groundwater remediation, characterized in that: The method is carried out using the composition according to any one of claims 1 to 12, comprising: 1) Preparation of sulfided nano-zero-valent iron and ruthenium chloride modified biochar; 2) first mixing the sulfide nano-zero-valent iron, the ruthenium chloride-modified biochar, attapulgite, and persulfate to obtain a mixture I; 3) The mixture I is mixed with a binder for a second time.

14. The method according to claim 13, wherein In step 3), the second mixing conditions at least meet the following requirements: temperature of 20-25° C., stirring speed of 150-180 r / min, and time of 8-12 h.

15. A composite material for groundwater remediation prepared by the method according to claim 13 or 14.

16. Use of the composite material for groundwater remediation according to claim 15 in removing at least one of benzene and its derivatives.

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