CN109909280B - medicament and method for synchronously fixing and reducing benzene in soil and/or underground water - Google Patents

Abstract

the invention discloses a medicament and a method for synchronously fixing and reducing trichloroethylene in soil and/or underground water. The agent adopts montmorillonite, slag, persulfate and water which are matched in a specific proportion, and simultaneously the montmorillonite adopts sodium-based montmorillonite with specific performance, and the sodium-based montmorillonite and the slag with the specific performance can effectively activate the persulfate to generate more SO with strong oxidizing property₄ ^·‑and OH, making use of SO₄ ^·‑and OH thoroughly oxidizes the benzene, thereby improving the benzene removal rate in the LNAPL polluted source region. Meanwhile, the sodium-based montmorillonite with specific performance can be matched with slag in the benzene removal process to maintain the pH stability of a reaction system, so that an alkali reagent is not required to be additionally added in the reaction process, and the pH value is not required to be adjusted. Through tests, the benzene removal rate reaches 93-98% within 15 days, the secondary pollution is low, the ecological environment risk is low, the safety is high, and the method has remarkable advantages in technical and environmental protection.

Description

Medicament and method for synchronously fixing and reducing benzene in soil and/or underground water

Technical Field

The invention belongs to the technical field of soil and underground water pollution risk management and control and remediation, and particularly relates to a medicament and a method for synchronously fixing and reducing benzene in soil and/or underground water, in particular to a medicament and a method for synchronously fixing and reducing benzene in a light non-aqueous phase liquid (LNAPL) pollution source region of soil and/or underground water by combining montmorillonite, slag and persulfate.

background

Benzene is one of the volatile organic compounds that are ubiquitous in soil and groundwater worldwide, and its pollution has caused serious environmental and health problems. Benzene in soil and underground water is mainly from leakage and seepage caused by damage of equipment and facilities in the links of petroleum production, use, storage and transportation. For example, the sewage leakage of a certain production plant of the Qilu petrochemical company causes the benzene content in the aeration zone to reach 138.64mg/kg and the benzene content in the soil layer of the oil tank area to reach 46.6mg/kg, so that the water quality safety of the aquifer is seriously threatened. The long-term benzene inhalation of the human body can damage the nervous system; short-term inhalation can produce nerve spasm, even coma and death; benzene can also damage the blood system, manifested as anemia, myelodysplasia, aplastic anemia and even leukemia. After benzene enters an underground water environment, because the density of the benzene is smaller than that of water, vertical migration is hindered by an underground water surface, a light non-aqueous phase liquid (LNAPL) pollution source area with relatively concentrated concentration is formed on the water surface, and benzene in the pollution source area can continuously and durably migrate and diffuse along the underground water surface in a transverse direction, so that secondary pollution in a larger range is caused.

At present, the in-situ risk management and control and treatment repair technology for benzene in a soil and underground water LNAPL pollution source area mainly comprises a blocking technology, a pumping treatment technology, a biodegradation permeable reactive barrier technology and the like. The blocking technology is one of risk control technologies, and mainly depends on clay, cement, mixed fly ash and other non-permeable materials to construct a blocking wall to block the downstream migration and diffusion of a pollution source. The blocking technology can only cut off the exposure path and limit the migration of the pollution plume, but cannot reduce the concentration of the pollutants and has the risk of leakage of the pollutants. In most cases, the barrier technology is used as a temporary control method only in the early stage of groundwater pollution control. Often, barrier technologies need to be used in conjunction with other repair technologies to achieve repair.

The pumping treatment technology is a traditional polluted underground water treatment mode, is very effective in treating LNAPL polluted source areas in underground water, and can avoid disasters such as ground settlement, seawater invasion and the like caused by pumping a large amount of water. In the 80 s of the 20 th century, the technology is applied to 73 percent of underground water pollution treatment projects in the United states. However, in the later-stage restoration of the polluted site, because the pollutants and the aquifer medium have the effects of desorption, dissolution and the like, a tailing effect and a rebound effect are generated, so that the restoration time is prolonged, the efficiency is poor, and the technology is high in cost and energy consumption due to the fact that extraction and injection systems are needed.

the permeable reactive grille technology is a structure composed of active fillers, is perpendicular to the direction of underground water flow, and effectively removes pollutants through reactions such as physical adsorption, chemical reduction, biodegradation and the like when underground water flows through the grille. Benzene series has strong chemical inertness to metals, but is easy to be used as a carbon source and an energy source of microorganisms. Therefore, most of the existing indoor researches and engineering practices adopt a biodegradable grating to treat the benzene series on the basis of screening and enriching functional flora. The existing research shows that under the denitrification condition, the microorganisms can degrade benzene and toluene in the underground water by using nitrate as an electron acceptor. In aromatic hydrocarbon polluted soil and groundwater, the lack of electron acceptors is one of the important reasons for the long-term existence of benzene in the polluted source region, and the acid-base conditions, aerobic conditions and other chemical components of the environment have great influence on the activity of microorganisms, such as the inhibition of the biochemical degradation of microorganisms due to the over-high pH value (pH >10) or the under-low pH value (pH < 4).

in practical application, the technology has the defects of large pH change, low benzene removal rate, high barrier wall permeability coefficient and high service life technical requirement in the benzene process in the fixed soil and/or underground water light non-aqueous phase liquid (LNAPL) pollution reduction source region.

Disclosure of Invention

therefore, the invention aims to solve the defects of large pH change, low benzene removal rate, high barrier wall permeability coefficient and high service life technical requirement in the process of fixing and reducing benzene in a light water-insoluble phase liquid pollution source region of soil and/or underground water in the prior art, and further provides a medicament and a method for synchronously fixing and reducing benzene in soil and/or underground water.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

The medicament for synchronously fixing and reducing benzene in soil and/or underground water comprises montmorillonite, slag, persulfate and water, wherein the mass ratio of the montmorillonite to the slag to the persulfate is 3000-5000: 100-1000 parts of: 300-400, wherein the mass ratio of the total mass of the montmorillonite and the slag to the water is 1-3: 40-60;

The montmorillonite is sodium-based montmorillonite, and Na in the sodium-based montmorillonite⁺The content is 2 to 4 weight percent, and the total organic carbon content is 10 to 15mg/Lthe pH is 10.0 to 11.0, and the particle size is 75 to 180 μm.

further, the mass ratio of the montmorillonite to the slag to the persulfate is 3500-4500: 150-850: 350-400;

na in the sodium-based montmorillonite⁺The content is 2.5 wt% -3 wt%, the total organic carbon content is 13-14 mg/L, the pH is 10.3-10.8, and the particle size is 120-150 mu m.

Further, the furnace slag is lignite furnace slag, wherein the content of calcium oxide in the lignite furnace slag is 35 wt% -41 wt%, the content of sodium oxide is 1 wt% -3 wt%, the content of potassium oxide is 0.1 wt% -1 wt%, the pH value is 9.0-10.5, and the particle size is 75-120 mu m;

The persulfate is potassium persulfate and/or sodium persulfate, and the purity of the persulfate is more than or equal to 98 wt%.

Further, the persulfate is potassium persulfate and sodium persulfate, and the mass ratio of the potassium persulfate to the sodium persulfate is 1: (4-5).

in addition, the pH test method of the sodium montmorillonite is as follows: adding ultrapure water into sodium-based montmorillonite, and controlling the mass ratio of the sodium-based montmorillonite to the ultrapure water to be 1: and 50, after stirring for more than 24 hours by the stirrer, measuring the pH value of the water, wherein the pH value is the pH value of the sodium montmorillonite.

The method for testing the pH value of the lignite slag comprises the following steps: adding ultrapure water into the lignite slag, and controlling the mass ratio of the lignite slag to the ultrapure water to be 1: and 50, measuring the pH value of the water after the stirrer stirs for more than 24 hours, wherein the pH value is the pH value of the lignite slag.

The preparation method of the medicament comprises the following steps: the montmorillonite, the slag, the persulfate and the water are weighed according to the mass ratio and are uniformly stirred at room temperature, so that the montmorillonite and the slag are in a suspended state, and the medicament is prepared.

In addition, the invention also provides a method for synchronously fixing and reducing benzene in soil and/or underground water by adopting the medicament, which comprises the following steps:

S1, mixing montmorillonite with water to prepare slurry;

s2, pouring the slurry obtained in the step S1 into soil and underground water media around the LNAPL pollution source area by adopting a cofferdam or high-pressure spraying mode to form a vertical barrier wall and/or a horizontal barrier wall, blocking migration and diffusion of the LNAPL pollution source, and fixing benzene;

s3, injecting the medicament into the LNAPL pollution source area, and degrading benzene in the LNAPL pollution source area.

Further, in step S1, the mass ratio of montmorillonite to water is 1-3: 40-60.

Further, in step S2, the permeability coefficient of the vertical barrier wall is less than or equal to 1 × 10^-7cm/s and the thickness is 9-19 cm;

The permeability coefficient of the horizontal barrier wall is less than or equal to 1 multiplied by 10^-7cm/s and a thickness of 9-19 cm.

Further, in step S3, the mass ratio of the persulfate in the chemical to the benzene in the LNAPLL-contaminated source region is 300-500: 1 to 5.

Further, in step S2, when the buried depth of the LNAPL contamination source region is less than 10m, the method is implemented by using a bank; or the like, or, alternatively,

in step S2, when the buried depth of the LNAPL polluted source region is 10-30 m, a high-pressure injection mode is adopted.

further, the slurry in the step S1 is poured into the aeration zone around the LNAPL polluted source area, and vertical and horizontal barrier walls are formed in the aeration zone and around the LNAPL polluted source area; or the like, or, alternatively,

And (5) pouring the slurry in the step S1 into an aquifer downstream of the LNAPL polluted source region to form a vertical barrier wall.

Compared with the prior art, the invention has the following beneficial effects:

(1) the medicament for synchronously fixing and reducing benzene in soil and/or underground water provided by the invention adopts montmorillonite, slag, persulfate and water to be matched in a specific proportion, and simultaneously the montmorillonite adopts sodium-based montmorillonite with specific performance, and the sodium-based montmorillonite and the slag with specific performance can effectively activate the persulfate to generate more SO with strong oxidizing property₄ ^·-And OH, making use of SO₄ ^·-And OH thoroughly oxidizes the benzene, thereby improving the benzene removal rate in the LNAPL polluted source region. Meanwhile, the sodium-based montmorillonite with specific properties can remove benzeneThe catalyst is matched with slag to maintain the pH value of a reaction system to be stable, so that the pH value of the reaction system can be kept to be more than 9.7 for a long time without additionally adding an alkali reagent and regulating the pH value in the reaction process, and an alkali activated persulfate system is promoted to be formed. Through tests, the benzene removal rate reaches 93-98% within 15 days, the secondary pollution is low, the ecological environment risk is low, the safety is high, and the method has remarkable advantages in technical and environmental protection.

(2) The medicament for synchronously fixing and reducing benzene in soil and/or underground water provided by the invention adopts sodium-based montmorillonite and optimizes Na in the sodium-based montmorillonite⁺The content, the total organic carbon content, the pH value and the particle size can improve the properties of the sodium-based montmorillonite such as thixotropy, expansibility, cohesiveness and the like, so that the sodium-based montmorillonite can effectively fill the gaps of soil, an aeration zone and a groundwater medium, and finally can effectively block the migration and diffusion of benzene for a long time;

meanwhile, the stabilizing effect of the lignite slag on the pH value of a reaction system can be effectively improved by optimizing the content of calcium oxide, the content of sodium oxide, the content of potassium oxide, the pH value and the particle size in the lignite slag.

(3) The invention provides a medicament for synchronously fixing and reducing benzene in soil and/or underground water, wherein persulfate is potassium persulfate and sodium persulfate, and the mass ratio of the potassium persulfate to the sodium persulfate is 1: and (4-5), the removal rate of benzene in the LNAPL polluted source region is improved by matching different types of persulfate according to a specific proportion.

(4) The method for synchronously fixing and reducing benzene in soil and/or underground water provided by the invention comprises the steps of mixing montmorillonite with water to prepare slurry; then, pouring the slurry into soil and underground water medium around the LNAPL pollution source area by adopting a cofferdam or high-pressure spraying mode to form a vertical barrier wall and/or a horizontal barrier wall, blocking migration and diffusion of the LNAPL pollution source, and fixing benzene; and finally, injecting the medicament into an LNAPL (low-permeability alkaline peroxide solution) polluted source region, filling montmorillonite in the medicament into gaps of soil and underground water media, dispersing persulfate in the polluted source region by virtue of the action of gravity and the capillary phenomenon to form a low-permeability reaction region, and prolonging the retention time of benzene in the reaction region so as to completely oxidize and degrade the benzene.

(5) The method for synchronously fixing and reducing benzene in soil and/or underground water provided by the invention is characterized in that montmorillonite and water are mixed according to a specific mass ratio to form slurry, and the slurry is suitable for being poured into soil and underground water media around an LNAPL pollution source area to form a vertical barrier wall and/or a horizontal barrier wall; blocking the migration and diffusion of benzene by optimizing the permeability coefficient and thickness of the vertical barrier and/or the horizontal barrier; the mass ratio of persulfate in the medicament to benzene in the LNAPL polluted source region is limited, so that the benzene removal rate in the LNAPL polluted source region can be improved.

(6) The method for synchronously fixing and reducing benzene in soil and/or underground water provided by the invention can be carried out at normal temperature and normal pressure without heating, ultraviolet irradiation, transition metal ions, hydrogen peroxide and the like, and has the advantages of simple reaction system, mild reaction conditions and low operation, maintenance and management costs. By using the method, the technical requirements on the thickness and service life (at least 10 years) of the existing barrier wall can be obviously reduced, and further the construction cost of the barrier wall is reduced. Meanwhile, the in-situ fixation, treatment and restoration of soil and underground water, particularly deep underground water pollutants, and emergent pollution treatment can be realized, and the application range is wide.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a diagram showing a structure and a layout state of montmorillonite, slag and persulfate which are combined to synchronously fix in situ and reduce benzene in an underground water LNAPL pollution source region in the embodiment of the invention;

FIG. 2 is a diagram showing a structure and a layout state of synchronous in-situ fixation and reduction of benzene in a soil LNAPL (Low-grade aluminum chloride) polluted source region by combining montmorillonite, slag and persulfate in the embodiment of the invention;

FIG. 3 is a graph showing the change of the benzene removal rate with the reaction time, which is caused by the combination of montmorillonite, slag and persulfate in the example of the present invention;

FIG. 4 is a linear fit graph of the kinetics of oxidative degradation of benzene with a combination of montmorillonite, slag, and persulfate in an embodiment of the invention;

FIG. 5 is a graph showing the change of pH with respect to the reaction time in the combined reaction system of montmorillonite, slag and persulfate in the example of the present invention.

FIG. 6 shows a reaction system S caused by the combination of montmorillonite, slag and persulfate in the example of the present invention₂O₈ ^2-Graph of residual amount as a function of reaction time;

FIG. 7 is a graph showing the change of the benzene removal rate with reaction time, which is caused by the combination of montmorillonite, slag and persulfate under the coexistence of TCE in the example of the present invention.

FIG. 8 is a linear fit graph of the kinetics of the oxidative degradation of benzene by the combination of montmorillonite, slag, and persulfate under the coexistence of TCE in the example of the present invention;

FIG. 9 is a graph showing the effect of different inorganic ions on the removal rate of benzene in benzene-TCE combined contamination caused by the combined use of montmorillonite, slag, and persulfate in examples of the present invention;

FIG. 10 is a graph showing the pH change of a benzene-TCE combined oxidative degradation reaction system by montmorillonite, slag and persulfate under different inorganic ion conditions in the example of the present invention;

FIG. 11 is a graph showing the change of Eh of a benzene-TCE combined oxidative degradation reaction system by montmorillonite, slag and persulfate under different inorganic ion conditions in the example of the present invention.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

the term "montmorillonite" in the present invention is a layered mineral formed in an alkaline medium, consisting of finely divided aqueous aluminosilicates, belonging to the group consisting of 2: the crystal structure of the type 1 is formed by sandwiching a layer of aluminum oxygen octahedron between two silicon-oxygen tetrahedrons, the main chemical components are silicon dioxide, aluminum oxide and water, the crystal structure also contains elements such as iron, magnesium, calcium, sodium, potassium and the like, the hardness is 1-2, the relative density is 2-3, the crystal structure is white, light gray, pink, light green and the like, and the crystal structure has high ion exchange capacity and water absorption expansion capacity.

The term "slag" in the invention is the melt discharged from coal burning of thermal power plants, industrial and civil boilers and other equipment, the main components are silicon dioxide, alumina, ferric oxide, calcium oxide and a small amount of magnesium, sulfur, carbon and the like, the mineral composition mainly comprises anorthite, quartz, mullite, magnetite, pyrite and the like, the slag is in a porous structure, and various alkaline substances can be dissolved out under the soaking condition.

the term "light non-aqueous phase liquid (LNAPL)" as used herein refers to a generic term for all water-insoluble liquid contaminants in soil and groundwater, such as gasoline, diesel oil, fuel oil, crude oil, etc., which have low solubility and high interfacial tension.

The term "benzene" in the present invention is of the formula C₆H₆The LNAPL is one of pollutants represented by LNAPL, and has the advantages of colorless, sweet and flammable transparent liquid at normal temperature, 80.1 ℃ of relative molecular weight, 5.5 ℃ of melting point and 0.866 of relative density, difficult water solubility, easy organic solvent solubility, strong capability of dissolving organic molecules and nonpolar inorganic molecules, capability of being miscible with most organic solvents except glycerol, glycol and other polyols.

The term "Trichloroethylene (TCE) in the present invention is of the formula C₂HCl₃The organic solvent has the relative molecular weight of 131.39, the boiling point of 87.1 ℃, the melting point of-86 ℃, and is colorless, flammable and volatile liquid with the smell similar to chloroform, insoluble in water, soluble in ethanol, ether and the like, and soluble in most organic solvents.

In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Example 1

This implementationthe embodiment provides a medicament for synchronously fixing and reducing benzene in soil and/or underground water, which comprises 4000g of montmorillonite, 800g of slag, 384g of persulfate and water, wherein the mass ratio of the total mass of the montmorillonite and the slag to the water is 1: 50; wherein the montmorillonite is sodium-based montmorillonite, and Na in sodium-based montmorillonite⁺The content is 2.6 wt%, the total organic carbon content is 13.7mg/L, the pH value is 10.5, and the particle size is 150 mu m; the persulfate is sodium persulfate; the slag is lignite slag, the content of calcium oxide in the lignite slag is 35 wt%, the content of sodium oxide is 2 wt%, the content of potassium oxide is 0.5 wt%, the pH value is 9.5, and the particle size is 75 micrometers;

In the embodiment, the surface of the sodium-based montmorillonite is irregular polygon, smooth and angular; it is mainly composed of oxygen, silicon and aluminum and contains a small amount of sodium, potassium, iron, calcium, magnesium and the like, and is in accordance with 2: a type 1 crystal structure;

The application environment is simulated, and the medicament in the embodiment is applied to 10mg/L of underground water containing benzene, and the specific application method is as follows: adding persulfate and water in the medicament into 10mg/L of benzene-containing groundwater, and then adding sodium-based montmorillonite and slag to ensure that the mass ratio of the persulfate in the medicament to the benzene in the benzene-containing groundwater is 384: 2, after reacting for 15 days under the conditions of normal temperature, normal pressure and oscillation (250rpm), the benzene removal rate in the benzene-containing groundwater reaches 98 percent.

example 2

The embodiment provides a medicament for synchronously fixing and reducing benzene in soil and/or underground water, which comprises 4000g of montmorillonite, 800g of slag, 384g of persulfate and water, wherein the mass ratio of the montmorillonite to the water is 1: 50; wherein the montmorillonite is sodium-based montmorillonite, and Na in sodium-based montmorillonite⁺The content is 2.6 wt%, the total organic carbon content is 13.7mg/L, the pH value is 10.6, the particle size is 120 mu m, and the persulfate is potassium persulfate; the slag is lignite slag, the content of calcium oxide in the lignite slag is 40 wt%, the content of sodium oxide is 1.5 wt%, the content of potassium oxide is 0.5 wt%, the pH value is 9.3, and the particle size is 75 micrometers;

the application environment is simulated, and the medicament in the embodiment is applied to 10mg/kg of soil containing benzene, and the specific application method is as follows: adding persulfate in the medicament into 10mg/kg of benzene-containing soil, and then adding montmorillonite, slag and water in the medicament to ensure that the mass ratio of persulfate in the medicament to benzene in the benzene-containing groundwater is 384: 2, after reacting for 15 days under the conditions of normal temperature, normal pressure and oscillation (250rpm), the benzene removal rate in the benzene-containing groundwater reaches 74%, and after reacting for 50 days, the benzene removal rate in the benzene-containing anaerobic groundwater reaches 95%.

example 3

The embodiment provides a medicament for synchronously fixing and reducing benzene in soil and/or underground water, which comprises 3500g of montmorillonite, 850g of slag, 350g of persulfate and water, wherein the mass ratio of the total mass of the montmorillonite and the slag to the water is 1: 55; wherein the montmorillonite is sodium-based montmorillonite, and Na in sodium-based montmorillonite⁺The content is 2.5 wt%, the total organic carbon content is 14mg/L, the pH value is 10.3, the particle size is 150 mu m, and the persulfate is sodium persulfate; the slag is brown coal slag, the calcium oxide content in the brown coal slag is 41 wt%, the sodium oxide content is 1 wt%, the potassium oxide content is 1 wt%, the pH value is 9.0, and the particle size is 120 mu m;

The application environment is simulated, and the medicament in the embodiment is applied to 10mg/L of underground water containing benzene, and the specific application method is as follows: adding persulfate and water in the medicament into 10mg/L of benzene-containing groundwater, and then adding montmorillonite and furnace slag to ensure that the mass ratio of the persulfate to the benzene in the benzene-containing groundwater in the medicament is 350: 2, after reacting for 15 days under the conditions of normal temperature, normal pressure and oscillation (250rpm), the benzene removal rate in the benzene-containing groundwater reaches 96.7 percent.

Example 4

The embodiment provides a medicament for synchronously fixing and reducing benzene in soil and/or underground water, which comprises 4500g of montmorillonite, 350g of slag, 400g of persulfate and water, wherein the mass ratio of the total mass of the montmorillonite and the slag to the water is 2: 45, a first step of; wherein the montmorillonite is sodium-based montmorillonite, and Na in sodium-based montmorillonite⁺The content is 3 wt%, the total organic carbon content is 13mg/L, the pH value is 10.5, the particle size is 140 mu m, and the persulfate is potassium persulfate; the furnace slag is brown coal furnace slag, and the calcium oxide content in the brown coal furnace slag35 wt%, sodium oxide content 3 wt%, potassium oxide content 0.1 wt%, pH 10.5, particle size 75 μm;

the application environment is simulated, and the medicament in the embodiment is applied to 10mg/L of underground water containing benzene, and the specific application method is as follows: adding persulfate and water in the medicament into 10mg/L of benzene-containing groundwater, and then adding montmorillonite and furnace slag to ensure that the mass ratio of the persulfate to the benzene in the benzene-containing groundwater in the medicament is 400: 2, after reacting for 15 days under the conditions of normal temperature, normal pressure and oscillation (250rpm), the benzene removal rate in the benzene-containing groundwater reaches 97 percent.

Example 5

The embodiment provides a medicament for synchronously fixing and reducing benzene in soil and/or underground water, which comprises 3000g of montmorillonite, 1000g of slag, 300g of persulfate and water, wherein the mass ratio of the total mass of the montmorillonite and the slag to the water is 1: 60, adding a solvent to the mixture; wherein the montmorillonite is sodium-based montmorillonite, and Na in sodium-based montmorillonite⁺the content is 4 wt%, the total organic carbon content is 10mg/L, the pH value is 11, the particle size is 75 mu m, and the persulfate is sodium persulfate; the slag is brown coal slag, the calcium oxide content in the brown coal slag is 38 wt%, the sodium oxide content is 2 wt%, the potassium oxide content is 0.8 wt%, the pH value is 9.6, and the particle size is 110 mu m;

The application environment is simulated, and the medicament in the embodiment is applied to 10mg/L of underground water containing benzene, and the specific application method is as follows: adding persulfate and water in the medicament into 10mg/L of benzene-containing anaerobic underground water, and then adding montmorillonite and furnace slag to ensure that the mass ratio of the persulfate to the benzene in the benzene-containing underground water in the medicament is 300: 2, after reacting for 15 days under the conditions of normal temperature, normal pressure and oscillation (250rpm), the benzene removal rate in the benzene-containing groundwater reaches 93 percent.

Example 6

The embodiment provides a medicament for synchronously fixing and reducing benzene in soil and/or underground water, which comprises 5000g of montmorillonite, 100g of slag, 400g of persulfate and water, wherein the mass ratio of the total mass of the montmorillonite and the slag to the water is 2: 40; wherein the montmorillonite is sodium-based montmorillonite, and Na in sodium-based montmorillonite⁺The content is 2wtPercent, total organic carbon content is 15mg/L, pH is 10, particle size is 180 mu m, persulfate is potassium persulfate; the slag is lignite slag, the content of calcium oxide in the lignite slag is 39 wt%, the content of sodium oxide is 2.5 wt%, the content of potassium oxide is 0.3 wt%, the pH value is 10.2, and the particle size is 90 mu m;

The application environment is simulated, and the medicament in the embodiment is applied to 10mg/L of underground water containing benzene, and the specific application method is as follows: adding persulfate and water in the medicament into 10mg/L of benzene-containing groundwater, and then adding montmorillonite and furnace slag to ensure that the mass ratio of the persulfate to the benzene in the benzene-containing groundwater in the medicament is 400: 2, after reacting for 15 days under the conditions of normal temperature, normal pressure and oscillation (250rpm), the benzene removal rate in the benzene-containing groundwater reaches 94 percent.

Example 7

The embodiment provides a medicament for synchronously fixing and reducing benzene in soil and/or underground water, which is the same as the embodiment 2, and has the only difference that: in this embodiment, the persulfate is a mixture of potassium persulfate and sodium persulfate, wherein the mass ratio of potassium persulfate to sodium persulfate is 1: 4.5;

according to the test method in the example 2, after the reaction is carried out for 15 days under the conditions of normal temperature, normal pressure and oscillation (250rpm), the benzene removal rate in the anaerobic underground water containing the benzene reaches 97 percent.

Example 8

The present embodiment provides a method for simultaneously fixing and cutting benzene in soil and/or groundwater, as shown in fig. 1, comprising the following steps:

s1, mixing montmorillonite and water, wherein the mass ratio of the montmorillonite to the water is 1.5: 50, preparing slurry;

S2, filling the slurry in the step S1 into a water-bearing stratum at the downstream of the LNAPL polluted source region in a high-pressure spraying mode, wherein the burial depth of the LNAPL polluted source region is 10-30 m, so that a vertical partition wall is formed, and the permeability coefficient of the vertical partition wall is 1 multiplied by 10^-7cm/s and the thickness of 13cm, and is vertical to the bottom of the barrier wall to the water-resisting layer, so that the migration and diffusion of an LNAPL pollution source are blocked, and benzene is fixed;

s3, injecting the medicament in the embodiment 1 into an LNAPL pollution source region, and controlling the mass ratio of persulfate in the medicament to benzene in the LNAPL pollution source region to be 300: 4, degrading benzene therein;

Tests show that after the reaction is carried out for 15 days, the benzene removal rate in the LNAPL polluted source region reaches more than 95%.

Example 9

The embodiment provides a method for synchronously fixing and reducing benzene in soil and/or underground water, which comprises the following steps:

s1, mixing montmorillonite and water, wherein the mass ratio of the montmorillonite to the water is 1: 60, preparing slurry;

S2, filling the slurry in the step S1 into a water-bearing stratum at the downstream of the LNAPL polluted source region in a high-pressure spraying mode, wherein the burial depth of the LNAPL polluted source region is 10-30 m, so that a vertical partition wall is formed, and the permeability coefficient of the vertical partition wall is 1 multiplied by 10^-8cm/s, the thickness is 19cm, the vertical barrier wall is perpendicular to the bottom of the water-resisting layer, the migration and the diffusion of an LNAPL pollution source are blocked, and benzene is fixed;

S3, injecting the medicament in the embodiment 2 into an LNAPL pollution source region, and controlling the mass ratio of persulfate in the medicament to benzene in the LNAPL pollution source region to be 400: 1, degrading benzene therein;

Tests show that after the reaction is carried out for 15 days, the benzene removal rate in the LNAPL polluted source region reaches more than 95%.

Example 10

the embodiment provides a method for synchronously fixing and reducing benzene in soil and/or underground water, which comprises the following steps:

S1, mixing montmorillonite and water, wherein the mass ratio of the montmorillonite to the water is 2: 40, preparing slurry;

S2, filling the slurry in the step S1 into a water-bearing stratum at the downstream of the LNAPL polluted source region in a high-pressure spraying mode, wherein the burial depth of the LNAPL polluted source region is 10-30 m, so that a vertical partition wall is formed, and the permeability coefficient of the vertical partition wall is 1 multiplied by 10^-9cm/s and the thickness of 9cm, and is vertical to the bottom of the barrier wall to the water-resisting layer, so that the migration and diffusion of an LNAPL pollution source are blocked, and benzene is fixed;

S3, injecting the medicament in the embodiment 3 into an LNAPL pollution source region, and controlling the mass ratio of persulfate in the medicament to benzene in the LNAPL pollution source region to be 350: 1, degrading benzene therein;

Tests show that after the reaction is carried out for 15 days, the benzene removal rate in the LNAPL polluted source region reaches more than 95%.

Example 11

the present embodiment provides a method for synchronously fixing and cutting benzene in soil and/or groundwater, as shown in fig. 2, comprising the following steps:

S1, mixing montmorillonite and water, wherein the mass ratio of the montmorillonite to the water is 1.5: 55, preparing slurry;

S2 and LNAPL pollution source region buried depth<10m, pouring the slurry obtained in the step S1 into an air-entrapping zone around the LNAPL pollution source area by adopting a cofferdam mode, forming a vertical barrier wall and a horizontal barrier wall around the air-entrapping zone and the LNAPL pollution source area, wherein the permeability coefficient of the vertical barrier wall is 1 multiplied by 10^-7cm/s, thickness of 16cm, and permeability coefficient of 1 × 10^-7cm/s, the thickness is 16cm, migration and diffusion of LNAPL pollution sources are blocked, and benzene is fixed;

S3, injecting the medicament in the embodiment 4 into an LNAPL pollution source area, and controlling the mass ratio of persulfate in the medicament to benzene in the LNAPL pollution source area to be 400: 3, degrading benzene therein;

Tests show that after the reaction is carried out for 15 days, the benzene removal rate in the LNAPL polluted source region reaches more than 95%.

Example 12

The embodiment provides a method for synchronously fixing and reducing benzene in soil and/or underground water, which comprises the following steps:

S1, mixing montmorillonite and water, wherein the mass ratio of the montmorillonite to the water is 2: 50, preparing slurry;

S2 and LNAPL pollution source region buried depth<10m, pouring the slurry obtained in the step S1 into an air-entrapping zone around the LNAPL pollution source area by adopting a cofferdam mode, forming a vertical barrier wall and a horizontal barrier wall around the air-entrapping zone and the LNAPL pollution source area, wherein the permeability coefficient of the vertical barrier wall is 1 multiplied by 10^-8cm/s, thickness of 14cm, and permeability coefficient of 1 × 10^-8cm/s and a thickness of 14cm, blocking migration and diffusion of an LNAPL pollution source, and fixing benzene;

s3, injecting the medicament in the embodiment 5 into an LNAPL pollution source region, and controlling the mass ratio of persulfate in the medicament to benzene in the LNAPL pollution source region to be 340: 3, degrading benzene therein;

Tests show that after the reaction is carried out for 15 days, the benzene removal rate in the LNAPL polluted source region reaches more than 94 percent.

Comparative example 1

This comparative example provides an agent for simultaneous fixation and reduction of benzene in soil and/or groundwater, the only difference being that in example 1: in the comparative example, the montmorillonite is calcium-based montmorillonite, and is purchased from Xinglong Bentonite factory in the mill district of Gallery in Shandong province;

The application environment is simulated, and the medicament in the comparative example is applied to 10mg/L of underground water containing benzene, and the specific application method is as follows: adding persulfate and water in the medicament into 10mg/L of benzene-containing groundwater, and then adding calcium-based montmorillonite to ensure that the mass ratio of the calcium-based montmorillonite, slag and persulfate in the medicament to the benzene in the benzene-containing anaerobic groundwater is 4000: 800: 384: 2, after reacting for 15 days under the conditions of normal temperature, normal pressure and oscillation (250rpm), the benzene removal rate in the benzene-containing groundwater reaches 72 percent.

Comparative example 2

This comparative example provides an agent for simultaneous fixation and reduction of benzene in soil and/or groundwater, the only difference being that in example 1: in the comparative example, the montmorillonite is sodium montmorillonite, and Na in the sodium montmorillonite⁺the content is 5 wt%, the total organic carbon content is 9mg/L, the pH value is 10.6, and the particle size is 150 mu m;

The application environment is simulated, and the medicament in the comparative example is applied to 10mg/L of underground water containing benzene, and the specific application method is as follows: adding persulfate and water in the medicament into 10mg/L of benzene-containing groundwater, and then adding montmorillonite and slag to ensure that the mass ratio of the montmorillonite and slag persulfate in the medicament to benzene in the benzene-containing anaerobic groundwater is 4000: 800: 384: 2, after reacting for 15 days under the conditions of normal temperature, normal pressure and oscillation (250rpm), the benzene removal rate in the anaerobic underground water containing benzene reaches 78 percent.

Test example 1: application of montmorillonite, slag and persulfate in combination to reduction of benzene in underground water pollution source region

1. experimental materials and instruments: TCE: beijing chemical plant (purity is more than or equal to 99.5%); benzene: beijing chemical plant (analytical grade); sodium persulfate: beijing chemical plant (analytical grade); potassium iodide: beijing chemical plant (analytical grade); sodium bicarbonate: beijing chemical plant (analytical grade); sodium chloride: beijing chemical plant (analytical grade); potassium sulfate: beijing chemical plant (analytical grade); magnesium sulfate: beijing chemical plant (analytical grade); calcium sulfate: beijing chemical plant (analytical grade); methanol: DIKMA (purity is more than or equal to 99.9%), Honeywell in USA (chromatographic purity); alternative standard mixtures: chem Service Inc. USA (2000. mu.g/mL in methanol); mixing 54 components of volatile organic compounds: chem Service Inc. USA (2000. mu.g/mL in methanol); montmorillonite: national chemical group chemical reagents ltd (sodium-based); slag: beijing Ershangmeng meat products Ltd; water for experiment: ultrapure water; helium gas: beijing Huayuan gas Co., Ltd. (purity 99.999%); gas chromatography-mass spectrometer: agilent, 6890/5973N, USA; headspace autosampler: agilent, G1888, usa; constant temperature cultivation shaking table: fuma, QYC-2102C, china; desk-top low-speed centrifuge: hunan instrument, L550, china; a desk-top high-speed centrifuge: jingli, LG16-W (I), China; ultraviolet spectrophotometer: shimadzu, UV-1800, Japan; anaerobic box glove box: COY, 14500 cov Drive, usa; a pH meter: sartorius, PB-10, germany; oxidation-reduction potentiometer: clean, ORP30, usa; a micro sample injection needle: hamilton, 10, 25, 100, 1000 μ L, switzerland;

2. Experiment:

(1) Montmorillonite, slag and persulfuric acid properties to reduce benzene in groundwater:

0.4g of montmorillonite and 0.08g of slag are respectively put into a series of 20mL threaded-mouth brown glass bottles with covers (lined with polytetrafluoroethylene/silica gel spacers); adding 20mL of oxygen-driving ultrapure water; adding 100 mu L of 476g/L of sodium persulfate mother liquor to ensure that the initial concentration of persulfate is 1.9 g/L; adding 5 mu L of 40.0g/L benzene mother liquor to ensure that the initial concentration of benzene is 10 mg/L; placing the glass bottle in a constant temperature oscillator (250rpm, 25 + -1.0 deg.C), taking out periodically for 15 days, and centrifuging (3000rpm, 20 min); taking supernatant to detect benzene, pH and S₂O₈ ^2-(ii) a Each set of experiments was set to 3 replicates.

The effect of benzene removal by the combination of montmorillonite, slag and persulfate as mentioned in example 1 is shown in FIG. 3, the linear fit on the kinetics is shown in FIG. 4, the pH of the system is shown as a function of time in FIG. 5, and the S in the system is shown as₂O₈ ^2-The residual ratio of (D) is shown in FIG. 6. When the reaction lasts for 15 days, the removal rate of the montmorillonite, the slag and the persulfate which are combined with one another reaches 98 percent (figure 3), which shows that the combination of the montmorillonite, the slag and the persulfate can effectively promote the oxidative degradation of benzene. Releasing OH from montmorillonite and slag when it meets water^-To make the system alkaline. Under alkaline conditions, S₂O₈ ^2-preferably with OH^-reaction to HO₂ ^-Then HO follows₂ ^-And S₂O₈ ^2-Acting to break its-O-O-bond to produce SO₄ ^·-And SO finally generated₄ ^·-with OH^-The reaction produces OH (see formula 1, formula 2, formula 3, and formula 4).

S₂O₈ ^2-+2H₂O(OH^-)→HO₂ ^-+2SO₄ ^2-+3H⁺ (1)

HO₂ ^-+S₂O₈ ^2–→SO₄ ^·-+SO₄ ^2-+H⁺+O₂ ^·- (2)

S₂O₈ ^2-+2H₂O→3SO₄ ^2-+SO₄ ^·-+H⁺+O₂ ^·- (3)

SO₄ ^·-+OH^-→SO₄ ^2-+·OH (4)

The oxidative degradation of the montmorillonite, slag and persulfate in combination with the benzene is fitted to conform to the quasi-first order reaction kinetics, and the degradation rate constant is 0.24 (d)^-1) (FIG. 4). At an initial pH of 10.7, the pH of the system decreased by only 1 unit after 15 days to 9.7 (fig. 5). Therefore, the change of the system pH along with the reaction time is not large, which indicates that the montmorillonite and the slag can maintain the system in a stable alkaline environment, and further, the alkali activation effect is facilitated. The reaction is carried out for 15 daysA large amount of persulfate still remains in the latter system (residual rate)>94%) (fig. 6), which shows that the system still has strong capacity for oxidizing and degrading pollutants.

(2) the performance of montmorillonite, slag and persulfate on benzene reduction under the coexistence of trichloroethylene in underground water is as follows:

0.4g of montmorillonite and 0.08g of slag are respectively put into a series of 20mL threaded-mouth brown glass bottles with covers (lined with polytetrafluoroethylene/silica gel spacers); adding 20mL of oxygen-driving ultrapure water; adding 100 mu L of 476g/L of sodium persulfate mother liquor to ensure that the initial concentration of persulfate is 1.9 g/L; adding 5 mu L of mother liquor containing 40.0g/L of TCE and 40.0g/L of benzene to ensure that the initial concentrations of TCE and benzene are both 10 mg/L; placing the glass bottle in a constant temperature oscillator (250rpm, 25 + -1.0 deg.C), taking out periodically for 15 days, and centrifuging (3000rpm, 20 min); taking supernatant to detect benzene; each set of experiments was set to 3 replicates.

The change of the benzene removal rate caused by the combination of montmorillonite, slag and persulfate under the condition of coexistence of benzene and TCE is shown in FIG. 7, and the linear fit of the kinetics of the oxidative degradation of benzene is shown in FIG. 8. The combined use of montmorillonite, slag and persulfate caused a gradual increase in benzene removal to 93% with increasing reaction time to 15 days in the presence of benzene with TCE (figure 7), below the removal of oxidatively degraded benzene alone (98%) (figure 3). The oxidative degradation process still follows the quasi-first order reaction kinetics, and the degradation rate constant is 0.19 (d)^-1) (FIG. 8), but it is less than the rate constant for oxidative degradation of benzene alone (0.24 (d)^-1) (FIG. 4). The decrease in removal rate and degradation rate constants is due to the competition of TCE and benzene for the presence of free radicals.

(3) the influence of the inorganic components of the underground water on the performance of benzene reduction by montmorillonite, slag and persulfate under the coexistence of trichloroethylene:

0.4g of montmorillonite and 0.08g of slag are respectively put into a series of 20mL threaded-mouth brown glass bottles with covers (lined with polytetrafluoroethylene/silica gel spacers); 20mL of 568mg/L Cl solution was added^-、768mg/L SO₄ ^2-、320mg/L Ca²⁺、194.4mg/L Mg²⁺an oxygen-scavenging ultrapure aqueous solution; adding 100 mu L of 476g/L of sodium persulfate mother liquor to ensure that the initial concentration of persulfate is 1.9 g/L; 5 μ L of mother liquor containing 40.0g/L TCE and 40.0g/L benzene was added to ensure TThe initial concentrations of CE and benzene are both 10 mg/L; placing the glass bottle in a constant temperature oscillator (250rpm, 25 + -1.0 deg.C), taking out periodically for 12 days, and centrifuging (3000rpm, 20 min); taking the supernatant to detect benzene, pH and Eh; does not contain Cl^-、SO₄ ^2-、Ca²⁺and Mg²⁺oxygen-driving ultrapure water is used as a reference; each set of experiments was set to 3 replicates.

The change of the benzene removal rate caused by the combined use of montmorillonite, slag and persulfate in the coexistence of the inorganic components of the underground water and trichloroethylene is shown in figure 9, the change of the pH of the reaction system is shown in figure 10, and the change of the Eh of the reaction system is shown in figure 11. In the presence of benzene and TCE, Cl alone^-、SO₄ ^2-、Ca²⁺And Mg²⁺All obviously cause the reduction of benzene removal rate, and Cl is generated in 12 days^-、Ca²⁺、Mg²⁺、SO₄ ^2-The corresponding removal rate is reduced by 50, 21, 18 and 7 percentage points compared with the removal rate in the case of no inorganic component, which indicates that the inhibition capacity is Cl^->Ca²⁺≈Mg²⁺>SO₄ ^2-(FIG. 9). Cl^-、SO₄ ^2-The influence on the pH of a reaction system is small; and Ca²⁺、Mg²⁺The influence of (1) was large (pH was lowered by 0.5 to 1.3 units at any time) (FIG. 10), and Ca was estimated²⁺、Mg²⁺By generating Ca (OH)₂Or Mg (OH)₂the pH of the system is reduced. Single Cl^-、Ca²⁺、Mg²⁺and SO₄ ^2-all resulted in an increase in Eh of the reaction system (fig. 11).

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.

Claims (10)

1. A medicament for synchronously fixing and reducing benzene in soil and/or underground water comprises montmorillonite, slag, persulfate and water, wherein the mass ratio of the montmorillonite to the slag to the persulfate is 3000-5000: 100-1000 parts of: 300-400, wherein the mass ratio of the total mass of the montmorillonite and the slag to the water is 1-3: 40-60;

the montmorillonite is sodium-based montmorillonite, and Na in the sodium-based montmorillonite⁺The content is 2 wt% -4 wt%, the total organic carbon content is 10-15 mg/L, the pH is 10.0-11.0, and the particle size is 75-180 mu m.

2. The agent according to claim 1, wherein the mass ratio of montmorillonite, slag and persulfate is 3500-4500: 150-850: 350-400;

Na in the sodium-based montmorillonite⁺The content is 2.5 wt% -3 wt%, the total organic carbon content is 13-14 mg/L, the pH is 10.3-10.8, and the particle size is 120-150 mu m.

3. The agent according to claim 1 or 2, wherein the slag is lignite slag, the content of calcium oxide in the lignite slag is 35-41 wt%, the content of sodium oxide is 1-3 wt%, the content of potassium oxide is 0.1-1 wt%, the pH value is 9.0-10.5, and the particle size is 75-120 μm;

The persulfate is potassium persulfate and/or sodium persulfate, and the purity of the persulfate is more than or equal to 98 wt%.

4. The agent according to claim 3, wherein the persulfate is potassium persulfate and sodium persulfate, and the mass ratio of the potassium persulfate to the sodium persulfate is 1: (4-5).

5. A method for simultaneous fixation and reduction of benzene in soil and/or groundwater using the agent of any of claims 1-4, comprising the steps of:

S1, mixing montmorillonite with water to prepare slurry;

s2, pouring the slurry obtained in the step S1 into soil and underground water media around the LNAPL pollution source area by adopting a cofferdam or high-pressure spraying mode to form a vertical barrier wall and/or a horizontal barrier wall, blocking migration and diffusion of the LNAPL pollution source, and fixing benzene;

S3, injecting the medicament into the LNAPL pollution source area, and degrading benzene in the LNAPL pollution source area.

6. the method according to claim 5, wherein in step S1, the mass ratio of montmorillonite to water is 1-3: 40-60.

7. the method as claimed in claim 5 or 6, wherein the permeability coefficient of the vertical barrier wall is ≦ 1 × 10 in step S2^-7cm/s and the thickness is 9-19 cm;

the permeability coefficient of the horizontal barrier wall is less than or equal to 1 multiplied by 10^-7cm/s and a thickness of 9-19 cm.

8. The method according to claim 5 or 6, wherein in step S3, the mass ratio of the persulfate in the agent to the benzene in the LNAPL-contaminated source region is 300-400: 1 to 4.

9. the method according to claim 5 or 6, wherein in step S2, when the LNAPL contamination source region burial depth is less than 10m, the method is implemented by using a cofferdam; or the like, or, alternatively,

in step S2, when the buried depth of the LNAPL polluted source region is 10-30 m, a high-pressure injection mode is adopted.

10. The method of claim 5 or 6 wherein the slurry of step S1 is poured into the aeration zone around the LNAPL contaminated source zone to form vertical and horizontal barriers around the aeration zone and around the LNAPL contaminated source zone; or the like, or, alternatively,

And (5) pouring the slurry in the step S1 into an aquifer downstream of the LNAPL polluted source region to form a vertical barrier wall.